WorldWideScience

Sample records for variational surface modeling

  1. Modeling seasonal surface temperature variations in secondary tropical dry forests

    Science.gov (United States)

    Cao, Sen; Sanchez-Azofeifa, Arturo

    2017-10-01

    Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15-20 K higher than in the wet season at SRNP. We found that the early successional stages were about 6-8 K warmer than the intermediate successional stages and were 9-10 K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0-1 K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

  2. A Variational Model for Two-Phase Immiscible Electroosmotic Flow at Solid Surfaces

    KAUST Repository

    Shao, Sihong; Qian, Tiezheng

    2012-01-01

    We develop a continuum hydrodynamic model for two-phase immiscible flows that involve electroosmotic effect in an electrolyte and moving contact line at solid surfaces. The model is derived through a variational approach based on the Onsager

  3. Core surface flow modelling from high-resolution secular variation

    DEFF Research Database (Denmark)

    Holme, R.; Olsen, Nils

    2006-01-01

    -flux hypothesis, but the spectrum of the SV implies that a conclusive test of frozen-flux is not possible. We parametrize the effects of diffusion as an expected misfit in the flow prediction due to departure from the frozen-flux hypothesis; at low spherical harmonic degrees, this contribution dominates...... the expected departure of the SV predictions from flow to the observed SV, while at high degrees the SV model uncertainty is dominant. We construct fine-scale core surface flows to model the SV. Flow non-uniqueness is a serious problem because the flows are sufficiently small scale to allow flow around non......-series of magnetic data and better parametrization of the external magnetic field....

  4. On Geometric Variational Models for Inpainting Surface Holes (PREPRINT)

    Science.gov (United States)

    2006-01-01

    email: haro@ima.umn.edu Phone: (612) 626-1501 Fax: (612) 626-7370 Affiliations: 1 Dept. de Tecnologia , University of Pompeu-Fabra, Passeig de...regions where the 3D model is incomplete. The main cause of holes are occlusions, but these can also be due to low reflectance, constraints in the...major areas where range scanners are used. With the increasing popularity of range scanners as 3D shape acquisition devices, with applications in

  5. A variational model of disjoining pressure: Liquid film on a nonplanar surface

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Virnovsky, G.

    2009-06-01

    Variational methods have been successfully used in modelling thin liquid films in numerous theoretical studies of wettability. In this paper, the variational model of the disjoining pressure is extended to the general case of a two-dimensional solid surface. The Helmgoltz free energy functional depends both on the disjoining pressure isotherm and the shape of the solid surface. The augmented Young-Laplace equation (AYLE) is a nonlinear second-order partial differential equation. A number of solutions describing wetting films on spherical grains have been obtained. In the case of cylindrical films, the phase portrait technique describes the entire variety of mathematically feasible solutions. It turns out that a periodic solution, which would describe wave-like wetting films, does not satisfy the Jacobi's condition of the classical calculus of variations. Therefore, such a solution is nonphysical. The roughness of the solid surface significantly affects liquid film stability. AYLE solutions suggest that film rupture is more likely at a location where the pore-wall surface is most exposed into the pore space and the curvature is positive.

  6. A Variational Model for Two-Phase Immiscible Electroosmotic Flow at Solid Surfaces

    KAUST Repository

    Shao, Sihong

    2012-01-01

    We develop a continuum hydrodynamic model for two-phase immiscible flows that involve electroosmotic effect in an electrolyte and moving contact line at solid surfaces. The model is derived through a variational approach based on the Onsager principle of minimum energy dissipation. This approach was first presented in the derivation of a continuum hydrodynamic model for moving contact line in neutral two-phase immiscible flows (Qian, Wang, and Sheng, J. Fluid Mech. 564, 333-360 (2006)). Physically, the electroosmotic effect can be formulated by the Onsager principle as well in the linear response regime. Therefore, the same variational approach is applied here to the derivation of the continuum hydrodynamic model for charged two-phase immiscible flows where one fluid component is an electrolyte exhibiting electroosmotic effect on a charged surface. A phase field is employed to model the diffuse interface between two immiscible fluid components, one being the electrolyte and the other a nonconductive fluid, both allowed to slip at solid surfaces. Our model consists of the incompressible Navier-Stokes equation for momentum transport, the Nernst-Planck equation for ion transport, the Cahn-Hilliard phase-field equation for interface motion, and the Poisson equation for electric potential, along with all the necessary boundary conditions. In particular, all the dynamic boundary conditions at solid surfaces, including the generalized Navier boundary condition for slip, are derived together with the equations of motion in the bulk region. Numerical examples in two-dimensional space, which involve overlapped electric double layer fields, have been presented to demonstrate the validity and applicability of the model, and a few salient features of the two-phase immiscible electroosmotic flows at solid surface. The wall slip in the vicinity of moving contact line and the Smoluchowski slip in the electric double layer are both investigated. © 2012 Global-Science Press.

  7. Diffusion Filters for Variational Data Assimilation of Sea Surface Temperature in an Intermediate Climate Model

    Directory of Open Access Journals (Sweden)

    Xuefeng Zhang

    2015-01-01

    Full Text Available Sequential, adaptive, and gradient diffusion filters are implemented into spatial multiscale three-dimensional variational data assimilation (3DVAR as alternative schemes to model background error covariance matrix for the commonly used correction scale method, recursive filter method, and sequential 3DVAR. The gradient diffusion filter (GDF is verified by a two-dimensional sea surface temperature (SST assimilation experiment. Compared to the existing DF, the new GDF scheme shows a superior performance in the assimilation experiment due to its success in extracting the spatial multiscale information. The GDF can retrieve successfully the longwave information over the whole analysis domain and the shortwave information over data-dense regions. After that, a perfect twin data assimilation experiment framework is designed to study the effect of the GDF on the state estimation based on an intermediate coupled model. In this framework, the assimilation model is subject to “biased” initial fields from the “truth” model. While the GDF reduces the model bias in general, it can enhance the accuracy of the state estimation in the region that the observations are removed, especially in the South Ocean. In addition, the higher forecast skill can be obtained through the better initial state fields produced by the GDF.

  8. Surface Temperature Variation Prediction Model Using Real-Time Weather Forecasts

    Science.gov (United States)

    Karimi, M.; Vant-Hull, B.; Nazari, R.; Khanbilvardi, R.

    2015-12-01

    Combination of climate change and urbanization are heating up cities and putting the lives of millions of people in danger. More than half of the world's total population resides in cities and urban centers. Cities are experiencing urban Heat Island (UHI) effect. Hotter days are associated with serious health impacts, heart attaches and respiratory and cardiovascular diseases. Densely populated cities like Manhattan, New York can be affected by UHI impact much more than less populated cities. Even though many studies have been focused on the impact of UHI and temperature changes between urban and rural air temperature, not many look at the temperature variations within a city. These studies mostly use remote sensing data or typical measurements collected by local meteorological station networks. Local meteorological measurements only have local coverage and cannot be used to study the impact of UHI in a city and remote sensing data such as MODIS, LANDSAT and ASTER have with very low resolution which cannot be used for the purpose of this study. Therefore, predicting surface temperature in urban cities using weather data can be useful.Three months of Field campaign in Manhattan were used to measure spatial and temporal temperature variations within an urban setting by placing 10 fixed sensors deployed to measure temperature, relative humidity and sunlight. Fixed instrument shelters containing relative humidity, temperature and illumination sensors were mounted on lampposts in ten different locations in Manhattan (Vant-Hull et al, 2014). The shelters were fixed 3-4 meters above the ground for the period of three months from June 23 to September 20th of 2013 making measurements with the interval of 3 minutes. These high resolution temperature measurements and three months of weather data were used to predict temperature variability from weather forecasts. This study shows that the amplitude of spatial and temporal variation in temperature for each day can be predicted

  9. A three-layer model of self-assembly induced surface-energy variation experimentally extracted by using nanomechanically sensitive cantilevers

    International Nuclear Information System (INIS)

    Zuo Guomin; Li Xinxin

    2011-01-01

    This research is aimed at elucidating surface-energy (or interfacial energy) variation during the process of molecule-layer self-assembly on a solid surface. A quasi-quantitative plotting model is proposed and established to distinguish the surface-energy variation contributed by the three characteristic layers of a thiol-on-gold self-assembled monolayer (SAM), namely the assembly-medium correlative gold/head-group layer, the chain/chain interaction layer and the tail/medium layer, respectively. The data for building the model are experimentally extracted from a set of correlative thiol self-assemblies in different media. The variation in surface-energy during self-assembly is obtained by in situ recording of the self-assembly induced nanomechanical surface-stress using integrated micro-cantilever sensors. Based on the correlative self-assembly experiment, and by using the nanomechanically sensitive self-sensing cantilevers to monitor the self-assembly induced surface-stressin situ, the experimentally extracted separate contributions of the three layers to the overall surface-energy change aid a comprehensive understanding of the self-assembly mechanism. Moreover, the quasi-quantitative modeling method is helpful for optimal design, molecule synthesis and performance evaluation of molecule self-assembly for application-specific surface functionalization.

  10. Upper mantle compositional variations and discontinuity topography imaged beneath Australia from Bayesian inversion of surface-wave phase velocities and thermochemical modeling

    DEFF Research Database (Denmark)

    Khan, A.; Zunino, Andrea; Deschamps, F.

    2013-01-01

    Here we discuss the nature of velocity heterogeneities seen in seismic tomography images of Earth's mantle whose origins and relation to thermochemical variations are yet to be understood. We illustrate this by inverting fundamental-mode and higher-order surface-wave phase velocities for radial....../Fe and Mg/Si values relative to surrounding mantle. Correlated herewith are thermal variations that closely follow surface tectonics. We also observe a strong contribution to lateral variations in structure and topography across the “410 km” seismic discontinuity from thermochemically induced phase......-wave tomography models with other regional models is encouraging. Radial anisotropy is strongest at 150/200 km depth beneath oceanic/continental areas, respectively, and appears weak and homogeneous below. Finally, geoid anomalies are computed for a subset of sampled model and compared to observations....

  11. Effects of meteorological models on the solution of the surface energy balance and soil temperature variations in bare soils

    Science.gov (United States)

    Saito, Hirotaka; Šimůnek, Jiri

    2009-07-01

    SummaryA complete evaluation of the soil thermal regime can be obtained by evaluating the movement of liquid water, water vapor, and thermal energy in the subsurface. Such an evaluation requires the simultaneous solution of the system of equations for the surface water and energy balance, and subsurface heat transport and water flow. When only daily climatic data is available, one needs not only to estimate diurnal cycles of climatic data, but to calculate the continuous values of various components in the energy balance equation, using different parameterization methods. The objective of this study is to quantify the impact of the choice of different estimation and parameterization methods, referred together to as meteorological models in this paper, on soil temperature predictions in bare soils. A variety of widely accepted meteorological models were tested on the dataset collected at a proposed low-level radioactive-waste disposal site in the Chihuahua Desert in West Texas. As the soil surface was kept bare during the study, no vegetation effects were evaluated. A coupled liquid water, water vapor, and heat transport model, implemented in the HYDRUS-1D program, was used to simulate diurnal and seasonal soil temperature changes in the engineered cover installed at the site. The modified version of HYDRUS provides a flexible means for using various types of information and different models to evaluate surface mass and energy balance. Different meteorological models were compared in terms of their prediction errors for soil temperatures at seven observation depths. The results obtained indicate that although many available meteorological models can be used to solve the energy balance equation at the soil-atmosphere interface in coupled water, vapor, and heat transport models, their impact on overall simulation results varies. For example, using daily average climatic data led to greater prediction errors, while relatively simple meteorological models may

  12. Overlapping constraint for variational surface reconstruction

    DEFF Research Database (Denmark)

    Aanæs, Henrik; Solem, J.E.

    2005-01-01

    In this paper a counter example, illustrating a shortcoming in most variational formulations for 3D surface estimation, is presented. The nature of this shortcoming is a lack of an overlapping constraint. A remedy for this shortcoming is presented in the form of a penalty function with an analysi...... of the effects of this function on surface motion. For practical purposes, this will only have minor influence on current methods. However, the insight provided in the analysis is likely to influence future developments in the field of variational surface reconstruction....

  13. Estimating Trends and Variation of Net Biome Productivity in India for 1980-2012 Using a Land Surface Model

    Science.gov (United States)

    Gahlot, Shilpa; Shu, Shijie; Jain, Atul K.; Baidya Roy, Somnath

    2017-11-01

    In this paper we explore the trend in net biome productivity (NBP) over India for the period 1980-2012 and quantify the impact of different environmental factors, including atmospheric CO2 concentrations ([CO2]), land use and land cover change, climate, and nitrogen deposition on carbon fluxes using a land surface model, Integrated Science Assessment Model. Results show that terrestrial ecosystems of India have been a carbon sink for this period. Driven by a strong CO2 fertilization effect, magnitude of NBP increased from 27.17 TgC/yr in the 1980s to 34.39 TgC/yr in the 1990s but decreased to 23.70 TgC/yr in the 2000s due to change in climate. Adoption of forest conservation, management, and reforestation policies in the past decade has promoted carbon sequestration in the ecosystems, but this effect has been offset by loss of carbon from ecosystems due to rising temperatures and decrease in precipitation.

  14. Variational mesh segmentation via quadric surface fitting

    KAUST Repository

    Yan, Dongming

    2012-11-01

    We present a new variational method for mesh segmentation by fitting quadric surfaces. Each component of the resulting segmentation is represented by a general quadric surface (including plane as a special case). A novel energy function is defined to evaluate the quality of the segmentation, which combines both L2 and L2 ,1 metrics from a triangle to a quadric surface. The Lloyd iteration is used to minimize the energy function, which repeatedly interleaves between mesh partition and quadric surface fitting. We also integrate feature-based and simplification-based techniques in the segmentation framework, which greatly improve the performance. The advantages of our algorithm are demonstrated by comparing with the state-of-the-art methods. © 2012 Elsevier Ltd. All rights reserved.

  15. Variational mesh segmentation via quadric surface fitting

    KAUST Repository

    Yan, Dongming; Wang, Wen Ping; Liu, Yang; Yang, Zhouwang

    2012-01-01

    We present a new variational method for mesh segmentation by fitting quadric surfaces. Each component of the resulting segmentation is represented by a general quadric surface (including plane as a special case). A novel energy function is defined to evaluate the quality of the segmentation, which combines both L2 and L2 ,1 metrics from a triangle to a quadric surface. The Lloyd iteration is used to minimize the energy function, which repeatedly interleaves between mesh partition and quadric surface fitting. We also integrate feature-based and simplification-based techniques in the segmentation framework, which greatly improve the performance. The advantages of our algorithm are demonstrated by comparing with the state-of-the-art methods. © 2012 Elsevier Ltd. All rights reserved.

  16. 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

  17. Variational reconstruction using subdivision surfaces with continuous sharpness control

    Institute of Scientific and Technical Information of China (English)

    Xiaoqun Wu; Jianmin Zheng; Yiyu Cai; Haisheng Li

    2017-01-01

    We present a variational method for subdivision surface reconstruction from a noisy dense mesh.A new set of subdivision rules with continuous sharpness control is introduced into Loop subdivision for better modeling subdivision surface features such as semi-sharp creases,creases,and corners.The key idea is to assign a sharpness value to each edge of the control mesh to continuously control the surface features.Based on the new subdivision rules,a variational model with L1 norm is formulated to find the control mesh and the corresponding sharpness values of the subdivision surface that best fits the input mesh.An iterative solver based on the augmented Lagrangian method and particle swarm optimization is used to solve the resulting non-linear,non-differentiable optimization problem.Our experimental results show that our method can handle meshes well with sharp/semi-sharp features and noise.

  18. Reactive solid surface morphology variation via ionic diffusion.

    Science.gov (United States)

    Sun, Zhenchao; Zhou, Qiang; Fan, Liang-Shih

    2012-08-14

    In gas-solid reactions, one of the most important factors that determine the overall reaction rate is the solid morphology, which can be characterized by a combination of smooth, convex and concave structures. Generally, the solid surface structure varies in the course of reactions, which is classically noted as being attributed to one or more of the following three mechanisms: mechanical interaction, molar volume change, and sintering. Here we show that if a gas-solid reaction involves the outward ionic diffusion of a solid-phase reactant then this outward ionic diffusion could eventually smooth the surface with an initial concave and/or convex structure. Specifically, the concave surface is filled via a larger outward diffusing surface pointing to the concave valley, whereas the height of the convex surface decreases via a lower outward diffusion flux in the vertical direction. A quantitative 2-D continuum diffusion model is established to analyze these two morphological variation processes, which shows consistent results with the experiments. This surface morphology variation by solid-phase ionic diffusion serves to provide a fourth mechanism that supplements the traditionally acknowledged solid morphology variation or, in general, porosity variation mechanisms in gas-solid reactions.

  19. Effects of sea surface temperature, cloud radiative and microphysical processes, and diurnal variations on rainfall in equilibrium cloud-resolving model simulations

    International Nuclear Information System (INIS)

    Jiang Zhe; Li Xiao-Fan; Zhou Yu-Shu; Gao Shou-Ting

    2012-01-01

    The effects of sea surface temperature (SST), cloud radiative and microphysical processes, and diurnal variations on rainfall statistics are documented with grid data from the two-dimensional equilibrium cloud-resolving model simulations. For a rain rate of higher than 3 mm·h −1 , water vapor convergence prevails. The rainfall amount decreases with the decrease of SST from 29 °C to 27 °C, the inclusion of diurnal variation of SST, or the exclusion of microphysical effects of ice clouds and radiative effects of water clouds, which are primarily associated with the decreases in water vapor convergence. However, the amount of rainfall increases with the increase of SST from 29 °C to 31 °C, the exclusion of diurnal variation of solar zenith angle, and the exclusion of the radiative effects of ice clouds, which are primarily related to increases in water vapor convergence. For a rain rate of less than 3 mm·h −1 , water vapor divergence prevails. Unlike rainfall statistics for rain rates of higher than 3 mm·h −1 , the decrease of SST from 29 °C to 27 °C and the exclusion of radiative effects of water clouds in the presence of radiative effects of ice clouds increase the rainfall amount, which corresponds to the suppression in water vapor divergence. The exclusion of microphysical effects of ice clouds decreases the amount of rainfall, which corresponds to the enhancement in water vapor divergence. The amount of rainfall is less sensitive to the increase of SST from 29 °C to 31 °C and to the radiative effects of water clouds in the absence of the radiative effects of ice clouds. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  20. Rock discontinuity surface roughness variation with scale

    Science.gov (United States)

    Bitenc, Maja; Kieffer, D. Scott; Khoshelham, Kourosh

    2017-04-01

    hypothesize that roughness can increase or decrease with the joint size, depending on the large scale roughness (or waviness), which is entering the roughness calculation once the discontinuity size increases. Therefore, our objective is to characterize roughness at various spatial scales, rather than at changing surface size. Firstly, the rock surface is interpolated into a grid on which a Discrete Wavelet Transform (DWT) is applied. The resulting surface components have different frequencies, or in other words, they have a certain physical scale depending on the decomposition level and input grid resolution. Secondly, the Grasselli Parameter is computed for the original and each decomposed surface. Finally, the relative roughness change is analyzed with respect to increasing roughness wavelength for four different rock samples. The scale variation depends on the sample itself and thus indicates its potential mechanical behavior. References: - Barton, N. and V. Choubey (1977). "The shear strength of rock joints in theory and practice." Rock Mechanics and Rock Engineering 10(1): 1-54. - Grasselli, G. (2001). Shear strength of rock joints based on quantified surface description. École Polytechnique Fédérale de Lausanne. Lausanne, EPFL. - Tatone, B. S. A. and G. Grasselli (2009). "A method to evaluate the three-dimensional roughness of fracture surfaces in brittle geomaterials." Review of Scientific Instruments 80(12) - Tatone, B. and G. Grasselli (2012). "An Investigation of Discontinuity Roughness Scale Dependency Using High-Resolution Surface Measurements." Rock Mechanics and Rock Engineering: 1-25.

  1. (90377) SEDNA: INVESTIGATION OF SURFACE COMPOSITIONAL VARIATION

    International Nuclear Information System (INIS)

    Barucci, M. A.; De Bergh, C.; Merlin, F.; Morea Dalle Ore, C.; Cruikshank, D.; Alvarez-Candal, A.; Dumas, C.

    2010-01-01

    The dwarf planet (90377) Sedna is one of the most remote solar system objects accessible to investigations. To better constrain its surface composition and to investigate the possible heterogeneity of the surface of Sedna, several observations have been carried out at ESO-VLT with the powerful spectrometer SINFONI observing simultaneously the H and K bands. The analyzed spectra (obtained in 2005, 2007, and 2008) show a non-uniform spectral signature, particularly in the K band. Spectral modeling using the Shkuratov radiative transfer code for surface scattering has been performed using the various sets of data, including previous observations at visible wavelengths and photometry at 3.6 and 4.5 μm by the Spitzer Space Telescope. The visible and near-infrared spectra can be modeled with organic materials (triton and titan tholin), serpentine, and H 2 O ice in fairly significant amounts, and CH 4 , N 2 , and C 2 H 6 in varying trace amounts. One of the spectra obtained in 2005 October shows a different signature in the K band and is best modeled with CH 3 OH in place of CH 4 , with reduced amounts of serpentine and with the addition of olivine. The compositional surface heterogeneity can give input on the past history as well clues to the origin of this peculiar, distant object.

  2. Variational methods in molecular modeling

    CERN Document Server

    2017-01-01

    This book presents tutorial overviews for many applications of variational methods to molecular modeling. Topics discussed include the Gibbs-Bogoliubov-Feynman variational principle, square-gradient models, classical density functional theories, self-consistent-field theories, phase-field methods, Ginzburg-Landau and Helfrich-type phenomenological models, dynamical density functional theory, and variational Monte Carlo methods. Illustrative examples are given to facilitate understanding of the basic concepts and quantitative prediction of the properties and rich behavior of diverse many-body systems ranging from inhomogeneous fluids, electrolytes and ionic liquids in micropores, colloidal dispersions, liquid crystals, polymer blends, lipid membranes, microemulsions, magnetic materials and high-temperature superconductors. All chapters are written by leading experts in the field and illustrated with tutorial examples for their practical applications to specific subjects. With emphasis placed on physical unders...

  3. Deterministic prediction of surface wind speed variations

    Directory of Open Access Journals (Sweden)

    G. V. Drisya

    2014-11-01

    Full Text Available Accurate prediction of wind speed is an important aspect of various tasks related to wind energy management such as wind turbine predictive control and wind power scheduling. The most typical characteristic of wind speed data is its persistent temporal variations. Most of the techniques reported in the literature for prediction of wind speed and power are based on statistical methods or probabilistic distribution of wind speed data. In this paper we demonstrate that deterministic forecasting methods can make accurate short-term predictions of wind speed using past data, at locations where the wind dynamics exhibit chaotic behaviour. The predictions are remarkably accurate up to 1 h with a normalised RMSE (root mean square error of less than 0.02 and reasonably accurate up to 3 h with an error of less than 0.06. Repeated application of these methods at 234 different geographical locations for predicting wind speeds at 30-day intervals for 3 years reveals that the accuracy of prediction is more or less the same across all locations and time periods. Comparison of the results with f-ARIMA model predictions shows that the deterministic models with suitable parameters are capable of returning improved prediction accuracy and capturing the dynamical variations of the actual time series more faithfully. These methods are simple and computationally efficient and require only records of past data for making short-term wind speed forecasts within practically tolerable margin of errors.

  4. Equilibrium models and variational inequalities

    CERN Document Server

    Konnov, Igor

    2007-01-01

    The concept of equilibrium plays a central role in various applied sciences, such as physics (especially, mechanics), economics, engineering, transportation, sociology, chemistry, biology and other fields. If one can formulate the equilibrium problem in the form of a mathematical model, solutions of the corresponding problem can be used for forecasting the future behavior of very complex systems and, also, for correcting the the current state of the system under control. This book presents a unifying look on different equilibrium concepts in economics, including several models from related sciences.- Presents a unifying look on different equilibrium concepts and also the present state of investigations in this field- Describes static and dynamic input-output models, Walras, Cassel-Wald, spatial price, auction market, oligopolistic equilibrium models, transportation and migration equilibrium models- Covers the basics of theory and solution methods both for the complementarity and variational inequality probl...

  5. Variational multiscale models for charge transport.

    Science.gov (United States)

    Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin

    2012-01-01

    This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle

  6. Variational multiscale models for charge transport

    Science.gov (United States)

    Wei, Guo-Wei; Zheng, Qiong; Chen, Zhan; Xia, Kelin

    2012-01-01

    This work presents a few variational multiscale models for charge transport in complex physical, chemical and biological systems and engineering devices, such as fuel cells, solar cells, battery cells, nanofluidics, transistors and ion channels. An essential ingredient of the present models, introduced in an earlier paper (Bulletin of Mathematical Biology, 72, 1562-1622, 2010), is the use of differential geometry theory of surfaces as a natural means to geometrically separate the macroscopic domain from the microscopic domain, meanwhile, dynamically couple discrete and continuum descriptions. Our main strategy is to construct the total energy functional of a charge transport system to encompass the polar and nonpolar free energies of solvation, and chemical potential related energy. By using the Euler-Lagrange variation, coupled Laplace-Beltrami and Poisson-Nernst-Planck (LB-PNP) equations are derived. The solution of the LB-PNP equations leads to the minimization of the total free energy, and explicit profiles of electrostatic potential and densities of charge species. To further reduce the computational complexity, the Boltzmann distribution obtained from the Poisson-Boltzmann (PB) equation is utilized to represent the densities of certain charge species so as to avoid the computationally expensive solution of some Nernst-Planck (NP) equations. Consequently, the coupled Laplace-Beltrami and Poisson-Boltzmann-Nernst-Planck (LB-PBNP) equations are proposed for charge transport in heterogeneous systems. A major emphasis of the present formulation is the consistency between equilibrium LB-PB theory and non-equilibrium LB-PNP theory at equilibrium. Another major emphasis is the capability of the reduced LB-PBNP model to fully recover the prediction of the LB-PNP model at non-equilibrium settings. To account for the fluid impact on the charge transport, we derive coupled Laplace-Beltrami, Poisson-Nernst-Planck and Navier-Stokes equations from the variational principle

  7. Hydrological land surface modelling

    DEFF Research Database (Denmark)

    Ridler, Marc-Etienne Francois

    Recent advances in integrated hydrological and soil-vegetation-atmosphere transfer (SVAT) modelling have led to improved water resource management practices, greater crop production, and better flood forecasting systems. However, uncertainty is inherent in all numerical models ultimately leading...... temperature are explored in a multi-objective calibration experiment to optimize the parameters in a SVAT model in the Sahel. The two satellite derived variables were effective at constraining most land-surface and soil parameters. A data assimilation framework is developed and implemented with an integrated...... and disaster management. The objective of this study is to develop and investigate methods to reduce hydrological model uncertainty by using supplementary data sources. The data is used either for model calibration or for model updating using data assimilation. Satellite estimates of soil moisture and surface...

  8. Surface texture generation during cylindrical milling in the aspect of cutting force variations

    International Nuclear Information System (INIS)

    Wojciechowski, S; Twardowski, P; Pelic, M

    2014-01-01

    The work presented here concentrates on surface texture analysis, after cylindrical milling of hardened steel. Cutting force variations occurring in the machining process have direct influence on the cutter displacements and thus on the generated surface texture. Therefore, in these experiments, the influence of active number of teeth (z c ) on the cutting force variations was investigated. Cutting forces and cutter displacements were measured during machining process (online) using, namely piezoelectric force dynamometer and 3D laser vibrometer. Surface roughness parameters were measured using stylus surface profiler. The surface roughness model including cutting parameters (f z , D) and cutting force variations was also developed. The research revealed that in cylindrical milling process, cutting force variations have immediate influence on surface texture generation

  9. Diurnal Variations of Titan's Surface Temperatures From Cassini -CIRS Observations

    Science.gov (United States)

    Cottini, Valeria; Nixon, Conor; Jennings, Don; Anderson, Carrie; Samuelson, Robert; Irwin, Patrick; Flasar, F. Michael

    The Cassini Composite Infrared Spectrometer (CIRS) observations of Saturn's largest moon, Titan, are providing us with the ability to detect the surface temperature of the planet by studying its outgoing radiance through a spectral window in the thermal infrared at 19 m (530 cm-1) characterized by low opacity. Since the first acquisitions of CIRS Titan data the in-strument has gathered a large amount of spectra covering a wide range of latitudes, longitudes and local times. We retrieve the surface temperature and the atmospheric temperature pro-file by modeling proper zonally averaged spectra of nadir observations with radiative transfer computations. Our forward model uses the correlated-k approximation for spectral opacity to calculate the emitted radiance, including contributions from collision induced pairs of CH4, N2 and H2, haze, and gaseous emission lines (Irwin et al. 2008). The retrieval method uses a non-linear least-squares optimal estimation technique to iteratively adjust the model parameters to achieve a spectral fit (Rodgers 2000). We show an accurate selection of the wide amount of data available in terms of footprint diameter on the planet and observational conditions, together with the retrieved results. Our results represent formal retrievals of surface brightness temperatures from the Cassini CIRS dataset using a full radiative transfer treatment, and we compare to the earlier findings of Jennings et al. (2009). The application of our methodology over wide areas has increased the planet coverage and accuracy of our knowledge of Titan's surface brightness temperature. In particular we had the chance to look for diurnal variations in surface temperature around the equator: a trend with slowly increasing temperature toward the late afternoon reveals that diurnal temperature changes are present on Titan surface. References: Irwin, P.G.J., et al.: "The NEMESIS planetary atmosphere radiative transfer and retrieval tool" (2008). JQSRT, Vol. 109, pp

  10. Predictive Surface Complexation Modeling

    Energy Technology Data Exchange (ETDEWEB)

    Sverjensky, Dimitri A. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Earth and Planetary Sciences

    2016-11-29

    Surface complexation plays an important role in the equilibria and kinetics of processes controlling the compositions of soilwaters and groundwaters, the fate of contaminants in groundwaters, and the subsurface storage of CO2 and nuclear waste. Over the last several decades, many dozens of individual experimental studies have addressed aspects of surface complexation that have contributed to an increased understanding of its role in natural systems. However, there has been no previous attempt to develop a model of surface complexation that can be used to link all the experimental studies in order to place them on a predictive basis. Overall, my research has successfully integrated the results of the work of many experimentalists published over several decades. For the first time in studies of the geochemistry of the mineral-water interface, a practical predictive capability for modeling has become available. The predictive correlations developed in my research now enable extrapolations of experimental studies to provide estimates of surface chemistry for systems not yet studied experimentally and for natural and anthropogenically perturbed systems.

  11. Urbanization Process and Variation of Energy Budget of Land Surfaces

    Directory of Open Access Journals (Sweden)

    Ciro Gardi

    2007-06-01

    Full Text Available Urban areas are increasing at a rate much higher than human population growth in many part of the world; actually more than 73 towns in the world are larger than 1000 km2. The European Environmental Agency indicates an urban area average growth rate, over the last 20 years, of 20%. The urbanization process, and the consequent soil sealing, determines not only the losses of the ecological functions of the soil, but also a variation of the energy budget of land surfaces, that affect the microclimatic conditions (heat islands. The alteration of the energy budget are determined by the variations of albedo and roughness of surfaces, but especially by the net losses of evapotranspirating areas. In the present research we have assessed the variation of Parma territory energy budget, induced by the change in land use over the last 122 years. The urban area increase between 1881 and 2003 was 535%.

  12. Modeling Per Capita State Health Expenditure Variat...

    Data.gov (United States)

    U.S. Department of Health & Human Services — Modeling Per Capita State Health Expenditure Variation State-Level Characteristics Matter, published in Volume 3, Issue 4, of the Medicare and Medicaid Research...

  13. Surface Flux Modeling for Air Quality Applications

    Directory of Open Access Journals (Sweden)

    Limei Ran

    2011-08-01

    Full Text Available For many gasses and aerosols, dry deposition is an important sink of atmospheric mass. Dry deposition fluxes are also important sources of pollutants to terrestrial and aquatic ecosystems. The surface fluxes of some gases, such as ammonia, mercury, and certain volatile organic compounds, can be upward into the air as well as downward to the surface and therefore should be modeled as bi-directional fluxes. Model parameterizations of dry deposition in air quality models have been represented by simple electrical resistance analogs for almost 30 years. Uncertainties in surface flux modeling in global to mesoscale models are being slowly reduced as more field measurements provide constraints on parameterizations. However, at the same time, more chemical species are being added to surface flux models as air quality models are expanded to include more complex chemistry and are being applied to a wider array of environmental issues. Since surface flux measurements of many of these chemicals are still lacking, resistances are usually parameterized using simple scaling by water or lipid solubility and reactivity. Advances in recent years have included bi-directional flux algorithms that require a shift from pre-computation of deposition velocities to fully integrated surface flux calculations within air quality models. Improved modeling of the stomatal component of chemical surface fluxes has resulted from improved evapotranspiration modeling in land surface models and closer integration between meteorology and air quality models. Satellite-derived land use characterization and vegetation products and indices are improving model representation of spatial and temporal variations in surface flux processes. This review describes the current state of chemical dry deposition modeling, recent progress in bi-directional flux modeling, synergistic model development research with field measurements, and coupling with meteorological land surface models.

  14. Spatial-temporal variations in surface ozone over Ushuaia and the Antarctic region: observations from in situ measurements, satellite data, and global models.

    Science.gov (United States)

    Nadzir, Mohd Shahrul Mohd; Ashfold, Matthew J; Khan, Md Firoz; Robinson, Andrew D; Bolas, Conor; Latif, Mohd Talib; Wallis, Benjamin M; Mead, Mohammed Iqbal; Hamid, Haris Hafizal Abdul; Harris, Neil R P; Ramly, Zamzam Tuah Ahmad; Lai, Goh Thian; Liew, Ju Neng; Ahamad, Fatimah; Uning, Royston; Samah, Azizan Abu; Maulud, Khairul Nizam; Suparta, Wayan; Zainudin, Siti Khalijah; Wahab, Muhammad Ikram Abdul; Sahani, Mazrura; Müller, Moritz; Yeok, Foong Swee; Rahman, Nasaruddin Abdul; Mujahid, Aazani; Morris, Kenobi Isima; Sasso, Nicholas Dal

    2018-01-01

    The Antarctic continent is known to be an unpopulated region due to its extreme weather and climate conditions. However, the air quality over this continent can be affected by long-lived anthropogenic pollutants from the mainland. The Argentinian region of Ushuaia is often the main source area of accumulated hazardous gases over the Antarctic Peninsula. The main objective of this study is to report the first in situ observations yet known of surface ozone (O 3 ) over Ushuaia, the Drake Passage, and Coastal Antarctic Peninsula (CAP) on board the RV Australis during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC'16). Hourly O 3 data was measured continuously for 23 days using an EcoTech O 3 analyzer. To understand more about the distribution of surface O 3 over the Antarctic, we present the spatial and temporal of surface O 3 of long-term data (2009-2015) obtained online from the World Meteorology Organization of World Data Centre for greenhouse gases (WMO WDCGG). Furthermore, surface O 3 satellite data from the free online NOAA-Atmospheric Infrared Sounder (AIRS) database and online data assimilation from the European Centre for Medium-Range Weather Forecasts (ECMWF)-Monitoring Atmospheric Composition and Climate (MACC) were used. The data from both online products are compared to document the data sets and to give an indication of its quality towards in situ data. Finally, we used past carbon monoxide (CO) data as a proxy of surface O 3 formation over Ushuaia and the Antarctic region. Our key findings were that the surface O 3 mixing ratio during MASEC'16 increased from a minimum of 5 ppb to ~ 10-13 ppb approaching the Drake Passage and the Coastal Antarctic Peninsula (CAP) region. The anthropogenic and biogenic O 3 precursors from Ushuaia and the marine region influenced the mixing ratio of surface O 3 over the Drake Passage and CAP region. The past data from WDCGG showed that the annual O 3 cycle has a maximum during the winter of 30 to 35

  15. Variational Boussinesq model for simulation of coastal waves and tsunamis

    NARCIS (Netherlands)

    Adytia, D.; Adytia, Didit; van Groesen, Embrecht W.C.; Tan, Soon Keat; Huang, Zhenhua

    2009-01-01

    In this paper we describe the basic ideas of a so-called Variational Boussinesq Model which is based on the Hamiltonian structure of gravity surface waves. By using a rather simple approach to prescribe the profile of vertical fluid potential in the expression for the kinetic energy, we obtain a set

  16. A variational void coalescence model for ductile metals

    KAUST Repository

    Siddiq, Amir

    2011-08-17

    We present a variational void coalescence model that includes all the essential ingredients of failure in ductile porous metals. The model is an extension of the variational void growth model by Weinberg et al. (Comput Mech 37:142-152, 2006). The extended model contains all the deformation phases in ductile porous materials, i.e. elastic deformation, plastic deformation including deviatoric and volumetric (void growth) plasticity followed by damage initiation and evolution due to void coalescence. Parametric studies have been performed to assess the model\\'s dependence on the different input parameters. The model is then validated against uniaxial loading experiments for different materials. We finally show the model\\'s ability to predict the damage mechanisms and fracture surface profile of a notched round bar under tension as observed in experiments. © Springer-Verlag 2011.

  17. Use of AMSR-E microwave satellite data for land surface characteristics and snow cover variation

    Directory of Open Access Journals (Sweden)

    Mukesh Singh Boori

    2016-12-01

    Full Text Available This data article contains data related to the research article entitled “Global land cover classification based on microwave polarization and gradient ratio (MPGR” [1] and “Microwave polarization and gradient ratio (MPGR for global land surface phenology” [2]. This data article presents land surface characteristics and snow cover variation information from sensors like EOS Advanced Microwave Scanning Radiometer (AMSR-E. This data article use the HDF Explorer, Matlab, and ArcGIS software to process the pixel latitude, longitude, snow water equivalent (SWE, digital elevation model (DEM and Brightness Temperature (BT information from AMSR-E satellite data to provide land surface characteristics and snow cover variation data in all-weather condition at any time. This data information is useful to discriminate different land surface cover types and snow cover variation, which is turn, will help to improve monitoring of weather, climate and natural disasters.

  18. Variations of surface ozone concentration across the Klang Valley, Malaysia

    Science.gov (United States)

    Latif, Mohd Talib; Huey, Lim Shun; Juneng, Liew

    2012-12-01

    Hourly air quality data covering the period 2004-2008 was obtained from the Air Quality Division, the Department of Environment (DOE) through long-term monitoring by Alam Sekitar Sdn. Bhd. (ASMA) were analysed to investigate the variations of surface ozone (O3) in the Klang Valley, Malaysia. A total of nine monitoring stations were selected for analysis in this study and the results show that there are distinct seasonal patterns in the surface O3 across the Klang Valley. A high surface O3 concentration is usually observed between January and April, while a low surface O3 concentration is found between June and August. Analysis of daily variations in surface O3 and the precursors - NO, NO2, CO, NMHC and UVb, indicate that the surface O3 photochemistry in this study area exhibits a positive response to the intensity and wavelength in UVb while being influenced by the concentration of NOx, particularly through tritration processes. Although results from our study suggested that NMHCs may influence the maximum O3 concentration, further investigation is required. Wind direction during different monsoons was found to influence the concentration of O3 around the Klang Valley. HYSPLIT back trajectories (-72 h) were used to indicate the air-mass transport patterns on days with high concentrations of surface O3 in the study area. Results show that 47% of the high O3 days was associated with the localized circulation. The remaining 32% and 22% were associated with mid-range and long-range transport across the South China Sea from the northeast.

  19. Delay Variation Model with Two Service Queues

    Directory of Open Access Journals (Sweden)

    Filip Rezac

    2010-01-01

    Full Text Available Delay in VoIP technology is very unpleasant issue and therefore a voice packets prioritization must be ensured. To maintain the high call quality a maximum information delivery time from the sender to the recipient is set to 150 ms. This paper focuses on the design of a mathematical model of end-to-end delay of a VoIP connection, in particular on a delay variation. It describes all partial delay components and mechanisms, their generation, facilities and mathematical formulations. A new approach to the delay variation model is presented and its validation has been done by experimention.

  20. Genetic variation and significance of hepatitis B surface antigen

    Directory of Open Access Journals (Sweden)

    ZHANG Zhenhua

    2013-11-01

    Full Text Available Hepatitis B virus (HBV is prone to genetic variation because there is reverse transcription in the process of HBV replication. The gene mutation of hepatitis B surface antigen may affect clinical diagnosis of HBV infection, viral replication, and vaccine effect. The current research and existing problems are discussed from the following aspects: the mechanism and biological and clinical significance of S gene mutation. Most previous studies focused on S gene alone, so S gene should be considered as part of HBV DNA in the future research on S gene mutation.

  1. Variational approach to chiral quark models

    Energy Technology Data Exchange (ETDEWEB)

    Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira

    1987-03-01

    A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation.

  2. A variational approach to chiral quark models

    International Nuclear Information System (INIS)

    Futami, Yasuhiko; Odajima, Yasuhiko; Suzuki, Akira.

    1987-01-01

    A variational approach is applied to a chiral quark model to test the validity of the perturbative treatment of the pion-quark interaction based on the chiral symmetry principle. It is indispensably related to the chiral symmetry breaking radius if the pion-quark interaction can be regarded as a perturbation. (author)

  3. Alternative model of random surfaces

    International Nuclear Information System (INIS)

    Ambartzumian, R.V.; Sukiasian, G.S.; Savvidy, G.K.; Savvidy, K.G.

    1992-01-01

    We analyse models of triangulated random surfaces and demand that geometrically nearby configurations of these surfaces must have close actions. The inclusion of this principle drives us to suggest a new action, which is a modified Steiner functional. General arguments, based on the Minkowski inequality, shows that the maximal distribution to the partition function comes from surfaces close to the sphere. (orig.)

  4. Unexpected and Unexplained Surface Temperature Variations on Mimas

    Science.gov (United States)

    Howett, C.; Spencer, J. R.; Pearl, J. C.; Hurford, T. A.; Segura, M.; Cassini Cirs Team

    2010-12-01

    Until recently it was thought one of the most interesting things about Mimas, Saturn’s innermost classical icy moon, was its resemblance to Star Wars’ Death Star. However, a bizarre pattern of daytime surface temperatures was observed on Mimas using data obtained by Cassini’s Composite Infrared Spectrometer (CIRS) in February 2010. The observations were taken during Cassini’s closest ever encounter with Mimas (<10,000 km) and cover the daytime anti-Saturn hemisphere centered on longitude ~145° W. Instead of surface temperatures smoothly increasing throughout the morning and early afternoon, then cooling in the evening, as expected, a sharp V-shaped boundary is observed separating cooler midday and afternoon temperatures (~77 K) on the leading side from warmer morning temperatures (~92 K) on the trailing side. The boundary’s apex is centered at equatorial latitudes near the anti-Saturn point and extends to low north and south latitudes on the trailing side. Subtle differences in the surface colors have been observed that are roughly spatially correlated with the observed extent of the temperature anomaly, with the cooler regions tending to be bluer (Schenk et al., Submitted). However, visible-wavelength albedo is similar in the two regions, so albedo variations are probably not directly responsible for the thermal anomaly. It is more likely that thermal inertia variations produce the anomaly, with thermal inertia being unusually high in the region with anomalously low daytime temperatures. Comparison of the February 2010 CIRS data to previous lower spatial resolution data taken at different local times tentatively confirm that the cooler regions do indeed display higher thermal inertias. Bombardment of the surface by high energy electrons from Saturn’s radiation belts has been proposed to explain the observed color variations (Schenk et al., Submitted). Electrons above ~1 MeV preferentially impact Mimas’ leading hemisphere at low latitudes where they

  5. Interannual Variation of Surface Circulation in the Japan/East Sea due to External Forcings and Intrinsic Variability

    Science.gov (United States)

    Choi, Byoung-Ju; Cho, Seong Hun; Jung, Hee Seok; Lee, Sang-Ho; Byun, Do-Seong; Kwon, Kyungman

    2018-03-01

    The interannual variation of surface ocean currents can be as large as seasonal variation in the Japan/East Sea (JES). To identify the major factors that cause such interannual variability of surface ocean circulation in the JES, surface circulation was simulated from 1998 to 2009 using a three-dimensional model. Contributions of atmospheric forcing (ATM), open boundary data (OBC), and intrinsic variability (ITV) of the surface flow in the JES on the interannual variability of surface ocean circulation were separately examined using numerical simulations. Variability in surface circulation was quantified in terms of variance in sea surface height, 100-m depth water temperature, and surface currents. ITV was found to be the dominant factor that induced interannual variabilities of surface circulation, the main path of the East Korea Warm Current (EKWC), and surface kinetic energy on a time scale of 2-4 years. OBC and ATM were secondary factors contributing to the interannual variation of surface circulation. Interannual variation of ATM changed the separation latitude of EKWC and increased the variability of surface circulation in the Ulleung Basin. Interannual variation of OBC enhanced low-frequency changes in surface circulation and eddies in the Yamato Basin. It also modulated basin-wide uniform oscillations of sea level. This study suggests that precise estimation of initial conditions using data assimilation is essential for long-term prediction of surface circulation in the JES.

  6. Modeling radon flux from the earth's surface

    International Nuclear Information System (INIS)

    Schery, S.D.; Wasiolek, M.A.

    1998-01-01

    We report development of a 222 Rn flux density model and its use to estimate the 222 Rn flux density over the earth's land surface. The resulting maps are generated on a grid spacing of 1 0 x 1 0 using as input global data for soil radium, soil moisture, and surface temperature. While only a first approximation, the maps suggest a significant regional variation (a factor of three is not uncommon) and a significant seasonal variation (a factor of two is not uncommon) in 222 Rn flux density over the earth's surface. The estimated average global flux density from ice-free land is 34 ± 9 mBq m -2 s -1 . (author)

  7. Variations in sea surface roughness induced by the 2004 Sumatra-Andaman tsunami

    Directory of Open Access Journals (Sweden)

    O. A. Godin

    2009-07-01

    Full Text Available Observations of tsunamis away from shore are critically important for improving early warning systems and understanding of tsunami generation and propagation. Tsunamis are difficult to detect and measure in the open ocean because the wave amplitude there is much smaller than it is close to shore. Currently, tsunami observations in deep water rely on measurements of variations in the sea surface height or bottom pressure. Here we demonstrate that there exists a different observable, specifically, ocean surface roughness, which can be used to reveal tsunamis away from shore. The first detailed measurements of the tsunami effect on sea surface height and radar backscattering strength in the open ocean were obtained from satellite altimeters during passage of the 2004 Sumatra-Andaman tsunami. Through statistical analyses of satellite altimeter observations, we show that the Sumatra-Andaman tsunami effected distinct, detectable changes in sea surface roughness. The magnitude and spatial structure of the observed variations in radar backscattering strength are consistent with hydrodynamic models predicting variations in the near-surface wind across the tsunami wave front. Tsunami-induced changes in sea surface roughness can be potentially used for early tsunami detection by orbiting microwave radars and radiometers, which have broad surface coverage across the satellite ground track.

  8. Surface Tension of Multi-phase Flow with Multiple Junctions Governed by the Variational Principle

    International Nuclear Information System (INIS)

    Matsutani, Shigeki; Nakano, Kota; Shinjo, Katsuhiko

    2011-01-01

    We explore a computational model of an incompressible fluid with a multi-phase field in three-dimensional Euclidean space. By investigating an incompressible fluid with a two-phase field geometrically, we reformulate the expression of the surface tension for the two-phase field found by Lafaurie et al. (J Comput Phys 113:134–147, 1994) as a variational problem related to an infinite dimensional Lie group, the volume-preserving diffeomorphism. The variational principle to the action integral with the surface energy reproduces their Euler equation of the two-phase field with the surface tension. Since the surface energy of multiple interfaces even with singularities is not difficult to be evaluated in general and the variational formulation works for every action integral, the new formulation enables us to extend their expression to that of a multi-phase (N-phase, N ≥ 2) flow and to obtain a novel Euler equation with the surface tension of the multi-phase field. The obtained Euler equation governs the equation for motion of the multi-phase field with different surface tension coefficients without any difficulties for the singularities at multiple junctions. In other words, we unify the theory of multi-phase fields which express low dimensional interface geometry and the theory of the incompressible fluid dynamics on the infinite dimensional geometry as a variational problem. We apply the equation to the contact angle problems at triple junctions. We computed the fluid dynamics for a two-phase field with a wall numerically and show the numerical computational results that for given surface tension coefficients, the contact angles are generated by the surface tension as results of balances of the kinematic energy and the surface energy.

  9. Nonlinear (MARS modeling of long-term variations of surface UV-B radiation as revealed from the analysis of Belsk, Poland data for the period 1976–2000

    Directory of Open Access Journals (Sweden)

    J. W. Krzyścin

    Full Text Available A new, powerful statistical technique, multivariate adaptive regression splines (MARS, is applied to reproduce monthly fractional deviations of UV-B doses over Belsk, Poland, during the snowless (May–October part of the year in the period 1976–2000. Two kinds of regressors were used: local ones (total ozone, percentage of sky covered by low-, mid-, high-level clouds or total solar radiation over Belsk and non-local ones, i.e. those describing the long-distance forcings on the surface UV-B due to changes in the global atmospheric circulation. Standard indices of the Quasi-Biennial, North Atlantic, El Niño-Southern Oscillations, and the 11-year solar activity were used as non-local regressors. The results there indicate that the MARS procedure is able to reproduce the observed year-to-year and decadal oscillations in the UV data. The MARS model yields better model-observation agreement than an ordinary least-squares fit based on the same set of regressors. It is found that MARS is capable of handling interactions between the local and non-local regressors, suggesting a possible nonlinear nature of connections between variables characterizing the atmospheric transparency over Belsk and the long-distance forcings. MARS enables a reconstruction of the surface UV-B variations over any site based on the cloud and ozone data presently stored on web pages.

    Key words. Atmospheric composition and structure (aerosols and particles; biosphere-atmosphere interactions

  10. Modeling response variation for radiometric calorimeters

    International Nuclear Information System (INIS)

    Mayer, R.L. II.

    1986-01-01

    Radiometric calorimeters are widely used in the DOE complex for accountability measurements of plutonium and tritium. Proper characterization of response variation for these instruments is, therefore, vital for accurate assessment of measurement control as well as for propagation of error calculations. This is not difficult for instruments used to measure items within a narrow range of power values; however, when a single instrument is used to measure items over a wide range of power values, improper estimates of uncertainty can result since traditional error models for radiometric calorimeters assume that uncertainty is not a function of sample power. This paper describes methods which can be used to accurately estimate random response variation for calorimeters used to measure items over a wide range of sample powers. The model is applicable to the two most common modes of calorimeter operation: heater replacement and servo control. 5 refs., 4 figs., 1 tab

  11. Modelling land surface - atmosphere interactions

    DEFF Research Database (Denmark)

    Rasmussen, Søren Højmark

    representation of groundwater in the hydrological model is found to important and this imply resolving the small river valleys. Because, the important shallow groundwater is found in the river valleys. If the model does not represent the shallow groundwater then the area mean surface flux calculation......The study is investigates modelling of land surface – atmosphere interactions in context of fully coupled climatehydrological model. With a special focus of under what condition a fully coupled model system is needed. Regional climate model inter-comparison projects as ENSEMBLES have shown bias...... by the hydrological model is found to be insensitive to model resolution. Furthermore, this study highlights the effect of bias precipitation by regional climate model and it implications for hydrological modelling....

  12. Mars Surface Heterogeneity From Variations in Apparent Thermal Inertia

    Science.gov (United States)

    Putzig, N. E.; Mellon, M. T.

    2005-12-01

    Current techniques used in the calculation of thermal inertia from observed brightness temperatures typically assume that planetary surface properties are uniform on the scale of the instrument's observational footprint. Mixed or layered surfaces may yield different apparent thermal inertia values at different seasons or times of day due to the nonlinear relationship between temperature and thermal inertia. To obtain sufficient data coverage for investigating temporal changes, we processed three Mars years of observations from the Mars Global Surveyor Thermal Emission Spectrometer and produced seasonal nightside and dayside maps of apparent thermal inertia. These maps show broad regions with seasonal and diurnal differences as large as 200 J m-2 K-1 s-½ at mid-latitudes (60°S to 60°N) and ranging up to 600 J m-2 K-1 s-½ or greater in the polar regions. Comparison of the maps with preliminary results from forward-modeling of heterogeneous surfaces indicates that much of the martian surface may be dominated by (1) horizontally mixed surfaces, such as those containing differing proportions of rocks, sand, dust, duricrust, and localized frosts; (2) higher thermal inertia layers over lower thermal inertia substrates, such as duricrust or desert pavements; and (3) lower thermal inertia layers over higher thermal inertia substrates, such as dust over sand or rocks and soils with an ice table at depth.

  13. A variational approach to closed bosonic strings on bordered Riemann surfaces

    International Nuclear Information System (INIS)

    Ohrndorf, T.

    1987-01-01

    Polyakov's path integral for bosonic closed strings defined on a bordered Riemann surface is investigated by variational methods. It is demonstrated that boundary variations are generated by the Virasoro operators. The investigation is performed for both, simply connected Riemann surfaces as well as ringlike domains. It is shown that the form of the variational operator is the same on both kinds of surfaces. The Virasoro algebra arises as a consistency condition for the variation. (orig.)

  14. Pavement Aging Model by Response Surface Modeling

    Directory of Open Access Journals (Sweden)

    Manzano-Ramírez A.

    2011-10-01

    Full Text Available In this work, surface course aging was modeled by Response Surface Methodology (RSM. The Marshall specimens were placed in a conventional oven for time and temperature conditions established on the basis of the environment factors of the region where the surface course is constructed by AC-20 from the Ing. Antonio M. Amor refinery. Volatilized material (VM, load resistance increment (ΔL and flow resistance increment (ΔF models were developed by the RSM. Cylindrical specimens with real aging were extracted from the surface course pilot to evaluate the error of the models. The VM model was adequate, in contrast (ΔL and (ΔF models were almost adequate with an error of 20 %, that was associated with the other environmental factors, which were not considered at the beginning of the research.

  15. Modelling nanostructures with vicinal surfaces

    International Nuclear Information System (INIS)

    Mugarza, A; Schiller, F; Kuntze, J; Cordon, J; Ruiz-Oses, M; Ortega, J E

    2006-01-01

    Vicinal surfaces of the (111) plane of noble metals are characterized by free-electron-like surface states that scatter at one-dimensional step edges, making them ideal model systems to test the electronic properties of periodic lateral nanostructures. Here we use high-resolution, angle-resolved photoemission to analyse the evolution of the surface state on a variety of vicinal surface structures where both the step potential barrier and the superlattice periodicity can vary. A transition in the electron dimensionality is found as we vary the terrace size in single-phase step arrays. In double-phase, periodic faceted surfaces, we observe surface states that characterize each of the phases

  16. Variational study of the pair hopping model

    International Nuclear Information System (INIS)

    Fazekas, P.

    1990-01-01

    We study the ground state of a Hamiltonian introduced by Kolb and Penson for modelling situations in which small electron pairs are formed. The Hamiltonian consists of a tight binding band term, and a term describing the nearest neighbour hopping of electron pairs. We give a Gutzwiller-type variational treatment, first with a single-parameter Ansatz treated in the single site Gutzwiller approximation, and then with more complicated trial wave functions, and an improved Gutzwiller approximation. The calculation yields a transition from a partially paired normal state, in which the spin susceptibility has a diminished value, into a fully paired state. (author). 16 refs, 2 figs

  17. Surface adhesion and confinement variation of Staphylococcus aurius on SAM surfaces

    Science.gov (United States)

    Amroski, Alicia; Olsen, Morgan; Calabrese, Joseph; Senevirathne, Reshani; Senevirathne, Indrajith

    2012-02-01

    Controlled surface adhesion of non - pathogenic gram positive strain, Staphylococcus aureus is interesting as a model system due to possible development of respective biosensors for prevention and detection of the pathogenic strain methicillin resistant Staphylococcus aureus (MRSA) and further as a study for bio-machine interfacing. Self Assembled Monolayers (SAM) with engineered surfaces of linear thiols on Au(111) were used as the substrate. Sub cultured S. aureus were used for the analysis. The SAM layered surfaces were dipped in 2 -- 4 Log/ml S. aureus solution. Subsequent surface adhesion at different bacterial dilutions on surfaces will be discussed, and correlated with quantitative and qualitative adhesion properties of bacteria on the engineered SAM surfaces. The bacteria adhered SAM surfaces were investigated using intermittent contact, noncontact, lateral force and contact modes of Atomic Force Microscopy (AFM).

  18. Modeling Individual Cyclic Variation in Human Behavior.

    Science.gov (United States)

    Pierson, Emma; Althoff, Tim; Leskovec, Jure

    2018-04-01

    Cycles are fundamental to human health and behavior. Examples include mood cycles, circadian rhythms, and the menstrual cycle. However, modeling cycles in time series data is challenging because in most cases the cycles are not labeled or directly observed and need to be inferred from multidimensional measurements taken over time. Here, we present Cyclic Hidden Markov Models (CyH-MMs) for detecting and modeling cycles in a collection of multidimensional heterogeneous time series data. In contrast to previous cycle modeling methods, CyHMMs deal with a number of challenges encountered in modeling real-world cycles: they can model multivariate data with both discrete and continuous dimensions; they explicitly model and are robust to missing data; and they can share information across individuals to accommodate variation both within and between individual time series. Experiments on synthetic and real-world health-tracking data demonstrate that CyHMMs infer cycle lengths more accurately than existing methods, with 58% lower error on simulated data and 63% lower error on real-world data compared to the best-performing baseline. CyHMMs can also perform functions which baselines cannot: they can model the progression of individual features/symptoms over the course of the cycle, identify the most variable features, and cluster individual time series into groups with distinct characteristics. Applying CyHMMs to two real-world health-tracking datasets-of human menstrual cycle symptoms and physical activity tracking data-yields important insights including which symptoms to expect at each point during the cycle. We also find that people fall into several groups with distinct cycle patterns, and that these groups differ along dimensions not provided to the model. For example, by modeling missing data in the menstrual cycles dataset, we are able to discover a medically relevant group of birth control users even though information on birth control is not given to the model.

  19. Inter-fraction variations in respiratory motion models

    Energy Technology Data Exchange (ETDEWEB)

    McClelland, J R; Modat, M; Ourselin, S; Hawkes, D J [Centre for Medical Image Computing, University College London (United Kingdom); Hughes, S; Qureshi, A; Ahmad, S; Landau, D B, E-mail: j.mcclelland@cs.ucl.ac.uk [Department of Oncology, Guy' s and St Thomas' s Hospitals NHS Trust, London (United Kingdom)

    2011-01-07

    Respiratory motion can vary dramatically between the planning stage and the different fractions of radiotherapy treatment. Motion predictions used when constructing the radiotherapy plan may be unsuitable for later fractions of treatment. This paper presents a methodology for constructing patient-specific respiratory motion models and uses these models to evaluate and analyse the inter-fraction variations in the respiratory motion. The internal respiratory motion is determined from the deformable registration of Cine CT data and related to a respiratory surrogate signal derived from 3D skin surface data. Three different models for relating the internal motion to the surrogate signal have been investigated in this work. Data were acquired from six lung cancer patients. Two full datasets were acquired for each patient, one before the course of radiotherapy treatment and one at the end (approximately 6 weeks later). Separate models were built for each dataset. All models could accurately predict the respiratory motion in the same dataset, but had large errors when predicting the motion in the other dataset. Analysis of the inter-fraction variations revealed that most variations were spatially varying base-line shifts, but changes to the anatomy and the motion trajectories were also observed.

  20. Surface tension modelling of liquid Cd-Sn-Zn alloys

    Science.gov (United States)

    Fima, Przemyslaw; Novakovic, Rada

    2018-06-01

    The thermodynamic model in conjunction with Butler equation and the geometric models were used for the surface tension calculation of Cd-Sn-Zn liquid alloys. Good agreement was found between the experimental data for limiting binaries and model calculations performed with Butler model. In the case of ternary alloys, the surface tension variation with Cd content is better reproduced in the case of alloys lying on vertical sections defined by high Sn to Zn molar fraction ratio. The calculated surface tension is in relatively good agreement with the available experimental data. In addition, the surface segregation of liquid ternary Cd-Sn-Zn and constituent binaries has also been calculated.

  1. Understanding the Effect of Atmospheric Density on the Cosmic Ray Flux Variations at the Earth Surface

    OpenAIRE

    Dayananda, Mathes; Zhang, Xiaohang; Butler, Carola; He, Xiaochun

    2013-01-01

    We report in this letter for the first time the numerical simulations of muon and neutron flux variations at the surface of the earth with varying air densities in the troposphere and stratosphere. The simulated neutron and muon flux variations are in very good agreement with the measured neutron flux variation in Oulu and the muon flux variation in Atlanta. We conclude from this study that the stratosphere air density variation dominates the effects on the muon flux changes while the density...

  2. Simplified models for surface hyperchannelling

    International Nuclear Information System (INIS)

    Evdokimov, I.N.; Webb, R.; Armour, D.G.; Karpuzov, D.S.

    1979-01-01

    Experimental and detailed, three-dimensional computer simulation studies of the scattering of low energy argon ions incident at grazing angles onto a nickel single crystal have shown that under certain, well defined conditions, surface hyperchannelling dominates the reflection process. The applicability of simple computer simulation models to the study of this type of scattering has been investigated by comparing the results obtained using a 'summation of binary collisions' model and a continuous string model with both the experimental observations and the three dimensional model calculations. It has been shown that all the major features of the phenomenon can be reproduced in a qualitative way using the simple models and that the continuous string represents a good approximation to the 'real' crystal over a wide range of angles. The saving in computer time compared with the more complex model makes it practicable to use the simple models to calculate cross-sections and overall scattering intensities for a wide range of geometries. The results of these calculations suggest that the critical angle for the onset of surface hyperchannelling, which is associated with a reduction in scattering intensity and which is thus not too sensitive to the parameters of experimental apparatus is a useful quantity from the point of view of comparison of theoretical calculations with experimental measurements. (author)

  3. Surface EXAFS - A mathematical model

    International Nuclear Information System (INIS)

    Bateman, J.E.

    2002-01-01

    Extended X-ray absorption fine structure (EXAFS) studies are a powerful technique for studying the chemical environment of specific atoms in a molecular or solid matrix. The study of the surface layers of 'thick' materials introduces special problems due to the different escape depths of the various primary and secondary emission products which follow X-ray absorption. The processes are governed by the properties of the emitted fluorescent photons or electrons and of the material. Their interactions can easily destroy the linear relation between the detected signal and the absorption cross-section. Also affected are the probe depth within the surface and the background superimposed on the detected emission signal. A general mathematical model of the escape processes is developed which permits the optimisation of the detection modality (X-rays or electrons) and the experimental variables to suit the composition of any given surface under study

  4. Impact of Water Withdrawals from Groundwater and Surface Water on Continental Water Storage Variations

    Science.gov (United States)

    Doell, Petra; Hoffmann-Dobrev, Heike; Portmann, Felix T.; Siebert, Stefan; Eicker, Annette; Rodell, Matthew; Strassberg, Gil

    2011-01-01

    Humans have strongly impacted the global water cycle, not only water flows but also water storage. We have performed a first global-scale analysis of the impact of water withdrawals on water storage variations, using the global water resources and use model WaterGAP. This required estimation of fractions of total water withdrawals from groundwater, considering five water use sectors. According to our assessment, the source of 35% of the water withdrawn worldwide (4300 cubic km/yr during 1998-2002) is groundwater. Groundwater contributes 42%, 36% and 27% of water used for irrigation, households and manufacturing, respectively, while we assume that only surface water is used for livestock and for cooling of thermal power plants. Consumptive water use was 1400 cubic km/yr during 1998-2002. It is the sum of the net abstraction of 250 cubic km/yr of groundwater (taking into account evapotranspiration and return flows of withdrawn surface water and groundwater) and the net abstraction of 1150 km3/yr of surface water. Computed net abstractions indicate, for the first time at the global scale, where and when human water withdrawals decrease or increase groundwater or surface water storage. In regions with extensive surface water irrigation, such as Southern China, net abstractions from groundwater are negative, i.e. groundwater is recharged by irrigation. The opposite is true for areas dominated by groundwater irrigation, such as in the High Plains aquifer of the central USA, where net abstraction of surface water is negative because return flow of withdrawn groundwater recharges the surface water compartments. In intensively irrigated areas, the amplitude of seasonal total water storage variations is generally increased due to human water use; however, in some areas, it is decreased. For the High Plains aquifer and the whole Mississippi basin, modeled groundwater and total water storage variations were compared with estimates of groundwater storage variations based on

  5. Color Variation on the Surfaces of Jupiter’s Greek and Trojan Asteroids

    Science.gov (United States)

    Chatelain, Joseph; Trilling, David E.; Emery, Joshua P.

    2017-10-01

    The L4 and L5 Lagrange points of Jupiter are populated with thousands of known, and possibly hundreds of thousands of unknown, Greek and Trojan Asteroids. Understanding the environmental and weathering conditions experienced by these objects over their lifetimes could constrain formation models for the Solar System. In an effort to shine some light on this issue, we have collected partial, simultaneous, lightcurves in both Johnson-Cousins V and I filters for a dozen large Jupiter Trojans. We found significant signs of color variation over the surfaces of four of these objects, and more subtle signs on an additional four. The most convincing examples of variation occur on (4709) Ennomos and (4833) Meges. Such a variation in color with rotation likely implies a large surface feature such as a recent crater. That such a high fraction of observed Trojans display these signatures could imply a more active collisional history for Jupiter Trojans than previously thought. It is therefore likely that one or more of the targets for the Lucy mission will have experienced a large, relatively recent, cratering event. This may help us obtain a much more in-depth understanding of the evolutionary processes ongoing for the Jupiter Trojan populations.

  6. Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

    Science.gov (United States)

    Yin, Xiufeng; Kang, Shichang; de Foy, Benjamin; Cong, Zhiyuan; Luo, Jiali; Zhang, Lang; Ma, Yaoming; Zhang, Guoshuai; Rupakheti, Dipesh; Zhang, Qianggong

    2017-09-01

    Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of ˜ 5 years (January 2011 to October 2015), which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation) was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau. This work may provide a

  7. A variational void coalescence model for ductile metals

    KAUST Repository

    Siddiq, Amir; Arciniega, Roman; El Sayed, Tamer

    2011-01-01

    We present a variational void coalescence model that includes all the essential ingredients of failure in ductile porous metals. The model is an extension of the variational void growth model by Weinberg et al. (Comput Mech 37:142-152, 2006

  8. The variational 2D Boussinesq model for wave propagation over a shoal

    NARCIS (Netherlands)

    Adytia, D.; van Groesen, Embrecht W.C.

    2011-01-01

    The Variational Boussinesq Model (VBM) for waves (Klopman et al. 2010) is based on the Hamiltonian structure of gravity surface waves. In its approximation, the fluid potential in the kinetic energy is approximated by the sum of its value at the free surface and a linear combination of vertical

  9. 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.

  10. Axelrod's model with surface tension

    Science.gov (United States)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  11. Modeling Wettability Variation during Long-Term Water Flooding

    Directory of Open Access Journals (Sweden)

    Renyi Cao

    2015-01-01

    Full Text Available Surface property of rock affects oil recovery during water flooding. Oil-wet polar substances adsorbed on the surface of the rock will gradually be desorbed during water flooding, and original reservoir wettability will change towards water-wet, and the change will reduce the residual oil saturation and improve the oil displacement efficiency. However there is a lack of an accurate description of wettability alternation model during long-term water flooding and it will lead to difficulties in history match and unreliable forecasts using reservoir simulators. This paper summarizes the mechanism of wettability variation and characterizes the adsorption of polar substance during long-term water flooding from injecting water or aquifer and relates the residual oil saturation and relative permeability to the polar substance adsorbed on clay and pore volumes of flooding water. A mathematical model is presented to simulate the long-term water flooding and the model is validated with experimental results. The simulation results of long-term water flooding are also discussed.

  12. Variation on wettability of anodic zirconium oxide nanotube surface

    International Nuclear Information System (INIS)

    Wang, Lu-Ning; Shen, Chen; Shinbine, Alyssa; Luo, Jing-Li

    2013-01-01

    The present study reports the effect of fabrication conditions and environmental conditions, such as anodization voltage and aging period, on the wetting of zirconium dioxide nanotube (ZrNT) surfaces. Comparing with intact zirconium foil, which was inherently less hydrophilic, possessing an approximate contact angle of 60–70°, the as-formed ZrNT surfaces were much hydrophilic with an approximate contact angle of 18°. However, the hydrophilicity of the surfaces exhibited a decrease when the nanotubular opening diameters decreased while maintaining the nanotubular layer thickness. This phenomenon was attributed to the balance of capillary force and force generated by compressed air in the ZrNTs. The annealing treatment further increased the hydrophilic property of the ZrNTs. In addition, it was found that the wettability of ZrNTs, when aged in air over a period of 105 days, demonstrated a decrease in hydrophilic characteristics and exhibited, to some extent, an increase in hydrophobic characteristics. It was believed that the surface wettability was able to be changed due to the decreasing content of hydroxyl groups in ambient atmosphere. This work can provide guidelines for improving the structural and environmental conditions responsible for changing surface wettability of ZrNT surfaces for biomedical application. - Highlights: ► Wettability of zirconium oxide nanotubes (ZrNTs) was observed and characterized. ► Increasing of nanotubular diameter decreased the hydrophilicity of ZrNTs. ► Annealing processes enhanced the hydrophilicity of ZrNTs. ► Long term aging resulted in the hydrophobicity of ZrNTs

  13. Variation in skin surface lipid composition among the Equidae.

    Science.gov (United States)

    Colton, S W; Downing, D T

    1983-01-01

    Skin surface lipids from Equus caballus, E. przewalskii, E. asinus, E. grevyi, E. hemionus onager and a mule (E. asinus/E. caballus) were analyzed in detail. In all species the surface lipid mixtures consisted of giant-ring lactones, cholesterol, cholesteryl esters and minor amounts of wax diesters. In E. caballus, the lactone hydroxyacids were entirely branched chained, while in E. asinus and E. grevyi they were almost exclusively straight chained. In E. przewalskii, the onager and the mule there were both straight and branched chain hydroxyacid lactones. These results are in harmony with published interpretations of the evolutionary relationships among Equus species.

  14. Geomagnetic Core Field Secular Variation Models

    DEFF Research Database (Denmark)

    Gillet, N.; Lesur, V.; Olsen, Nils

    2010-01-01

    highlight the difficulty of resolving the time variability of the high degree secular variation coefficients (i.e. the secular acceleration), arising for instance from the challenge to properly separate sources of internal and of external origin. In addition, the regularisation process may also result...

  15. Performance verification of focus variation and confocal microscopes measuring tilted ultra-fine surfaces

    DEFF Research Database (Denmark)

    Quagliotti, Danilo; Baruffi, Federico; Tosello, Guido

    2016-01-01

    The behaviour of two optical instruments, scilicet a laser scanning confocal microscope and a focus-variation microscope, was investigated considering measurements of tilted surfaces. The measured samples were twelve steel artefacts for mould surface finish reference, covering Sa roughness...... parameter in the range (101—103) nm. The 3D surface texture parameters considered were Sa, Sq and Sdq. The small working distance of the confocal microscope objectives influenced the measurement setup, preventing from selecting a high tilting angle. The investigation was carried out comparing measurements...... of flat surfaces (0° tilt) with measurements of 12.5° tilted surfaces. The confocal microscope results showed a high sensitivity to tilting due to the laser beam reflection on the metal surfaces. The focus variation microscope results were more robust with respect to the considered angular variation...

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

    Energy Technology Data Exchange (ETDEWEB)

    Lindsey, Sloan J. [Institute of Solid-State Electronics, TU Wien, Floragasse 7, A-1040 Wien (Austria); Hobler, Gerhard, E-mail: gerhard.hobler@tuwien.ac.at [Institute of Solid-State Electronics, TU Wien, Floragasse 7, A-1040 Wien (Austria); Maciążek, Dawid; Postawa, Zbigniew [Institute of Physics, Jagiellonian University, ul. Lojasiewicza 11, 30348 Kraków (Poland)

    2017-02-15

    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.

  17. 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.

  18. Frost behavior of a fin surface with temperature variation along heat exchanger fins

    International Nuclear Information System (INIS)

    Kim, Jung Soo; Kim, Min Soo; Lee, Kwan Soo; Kim, Ook Joong

    2007-01-01

    This paper presents a mathematical model for predicting the frost behavior formed on heat exchanger fins, considering fin heat conduction under frosting condition. The model is composed of air-side, the frost layer, and fin region, and they are coupled to the frost layer. The frost behavior is more accurately predicted with fin heat conduction considered (Case A) than with a constant fin surface temperature assumed (Case B). The results indicate that the frost thickness and heat transfer rate for Case B are over-predicted in most regions of the fin, as compared to those for Case A. Also, for Case A, the maximum frost thickness varies little with the fin length variations, and the extension of the fin length over 30 mm contributes insignificantly to heat transfer

  19. On well-posedness of variational models of charged drops.

    Science.gov (United States)

    Muratov, Cyrill B; Novaga, Matteo

    2016-03-01

    Electrified liquids are well known to be prone to a variety of interfacial instabilities that result in the onset of apparent interfacial singularities and liquid fragmentation. In the case of electrically conducting liquids, one of the basic models describing the equilibrium interfacial configurations and the onset of instability assumes the liquid to be equipotential and interprets those configurations as local minimizers of the energy consisting of the sum of the surface energy and the electrostatic energy. Here we show that, surprisingly, this classical geometric variational model is mathematically ill-posed irrespective of the degree to which the liquid is electrified. Specifically, we demonstrate that an isolated spherical droplet is never a local minimizer, no matter how small is the total charge on the droplet, as the energy can always be lowered by a smooth, arbitrarily small distortion of the droplet's surface. This is in sharp contrast to the experimental observations that a critical amount of charge is needed in order to destabilize a spherical droplet. We discuss several possible regularization mechanisms for the considered free boundary problem and argue that well-posedness can be restored by the inclusion of the entropic effects resulting in finite screening of free charges.

  20. Spatiotemporal Variation in Surface Urban Heat Island Intensity and Associated Determinants across Major Chinese Cities

    Directory of Open Access Journals (Sweden)

    Juan Wang

    2015-03-01

    Full Text Available Urban heat islands (UHIs created through urbanization can have negative impacts on the lives of people living in cities. They may also vary spatially and temporally over a city. There is, thus, a need for greater understanding of these patterns and their causes. While previous UHI studies focused on only a few cities and/or several explanatory variables, this research provides a comprehensive and comparative characterization of the diurnal and seasonal variation in surface UHI intensities (SUHIIs across 67 major Chinese cities. The factors associated with the SUHII were assessed by considering a variety of related social, economic and natural factors using a regression tree model. Obvious seasonal variation was observed for the daytime SUHII, and the diurnal variation in SUHII varied seasonally across China. Interestingly, the SUHII varied significantly in character between northern and southern China. Southern China experienced more intense daytime SUHIIs, while the opposite was true for nighttime SUHIIs. Vegetation had the greatest effect in the day time in northern China. In southern China, annual electricity consumption and the number of public buses were found to be important. These results have important theoretical significance and may be of use to mitigate UHI effects.

  1. Modeling Density Variation in the Thermosphere

    Science.gov (United States)

    2011-04-29

    static electromagnetic fields as follows: when a volume of the ionosphere is bounded on the sides by an equipotential surface and on the bottom by the...generation of electromagnetic energy along that geomagnetic-field line. An Equipotential -Boundary Poynting-Flux (EBPF) theorem was presented for quasi

  2. OSOAA: A Vector Radiative Transfer Model of Coupled Atmosphere-Ocean System for a Rough Sea Surface Application to the Estimates of the Directional Variations of the Water Leaving Reflectance to Better Process Multi-angular Satellite Sensors Data Over the Ocean

    Science.gov (United States)

    Chami, Malik; LaFrance, Bruno; Fougnie, Bertrand; Chowdhary, Jacek; Harmel, Tristan; Waquet, Fabien

    2015-01-01

    In this study, we present a radiative transfer model, so-called OSOAA, that is able to predict the radiance and degree of polarization within the coupled atmosphere-ocean system in the presence of a rough sea surface. The OSOAA model solves the radiative transfer equation using the successive orders of scattering method. Comparisons with another operational radiative transfer model showed a satisfactory agreement within 0.8%. The OSOAA model has been designed with a graphical user interface to make it user friendly for the community. The radiance and degree of polarization are provided at any level, from the top of atmosphere to the ocean bottom. An application of the OSOAA model is carried out to quantify the directional variations of the water leaving reflectance and degree of polarization for phytoplankton and mineral-like dominated waters. The difference between the water leaving reflectance at a given geometry and that obtained for the nadir direction could reach 40%, thus questioning the Lambertian assumption of the sea surface that is used by inverse satellite algorithms dedicated to multi-angular sensors. It is shown as well that the directional features of the water leaving reflectance are weakly dependent on wind speed. The quantification of the directional variations of the water leaving reflectance obtained in this study should help to correctly exploit the satellite data that will be acquired by the current or forthcoming multi-angular satellite sensors.

  3. Modeling of Craniofacial Anatomy, Variation, and Growth

    DEFF Research Database (Denmark)

    Thorup, Signe Strann

    The topic of this thesis is automatic analysis of craniofacial images with respect to changes due to growth and surgery, inter-subject variation and intracranial volume estimation. The methods proposed contribute to the knowledge about specific craniofacial anomalies, as well as provide a tool...... for detailed analyses for clinical and research purposes. Most of the applications in this thesis rely on non-rigid image registration by the means of warping one image into the coordinate system of another image. This warping results in a deformation field that describes the anatomical correspondence between......, thus creating a personalized atlas. The knowledge built into the atlas is e.g. location of anatomical regions and landmarks of importance to surgery planning and evaluation or population studies. With these correspondences, various analyses could be carried out e.g. quantification of growth, inter...

  4. Modeling Cyclic Variation of Intracranial Pressure

    National Research Council Canada - National Science Library

    Daley, M

    2001-01-01

    ...) recording during mechanical ventilation are due to cyclic extravascular compressional modulation primarily of the cerebral venous bed, an established isovolumetric model of cerebrospinal fluid...

  5. Surface ozone at Nam Co in the inland Tibetan Plateau: variation, synthesis comparison and regional representativeness

    Directory of Open Access Journals (Sweden)

    X. Yin

    2017-09-01

    Full Text Available Ozone is an important pollutant and greenhouse gas, and tropospheric ozone variations are generally associated with both natural and anthropogenic processes. As one of the most pristine and inaccessible regions in the world, the Tibetan Plateau has been considered as an ideal region for studying processes of the background atmosphere. Due to the vast area of the Tibetan Plateau, sites in the southern, northern and central regions exhibit different patterns of variation in surface ozone. Here, we present continuous measurements of surface ozone mixing ratios at Nam Co Station over a period of  ∼ 5 years (January 2011 to October 2015, which is a background site in the inland Tibetan Plateau. An average surface ozone mixing ratio of 47.6 ± 11.6 ppb (mean ± standard deviation was recorded, and a large annual cycle was observed with maximum ozone mixing ratios in the spring and minimum ratios during the winter. The diurnal cycle is characterized by a minimum in the early morning and a maximum in the late afternoon. Nam Co Station represents a background region where surface ozone receives negligible local anthropogenic emissions inputs, and the anthropogenic contribution from South Asia in spring and China in summer may affect Nam Co Station occasionally. Surface ozone at Nam Co Station is mainly dominated by natural processes involving photochemical reactions, vertical mixing and downward transport of stratospheric air mass. Model results indicate that the study site is affected differently by the surrounding areas in different seasons: air masses from the southern Tibetan Plateau contribute to the high ozone levels in the spring, and enhanced ozone levels in the summer are associated with air masses from the northern Tibetan Plateau. By comparing measurements at Nam Co Station with those from other sites on the Tibetan Plateau, we aim to expand the understanding of ozone cycles and transport processes over the Tibetan Plateau

  6. Seasonal Variations of the Surface Urban Heat Island in a Semi-Arid City

    Directory of Open Access Journals (Sweden)

    Sirous Haashemi

    2016-04-01

    Full Text Available The process of the surface urban heat island (SUHI varies with latitude, climate, topography and meteorological conditions. This study investigated the seasonal variability of SUHI in the Tehran metropolitan area, Iran, with respect to selected surface biophysical variables. Terra Moderate Resolution Imaging Spectroradiometer (MODIS Land Surface Temperature (LST was retrieved as nighttime LST data, while daytime LST was retrieved from Landsat 8 Thermal Infrared Sensor (TIRS using the split-window algorithm. Both data covered the time period from September 2013 to September 2015. To assess SUHI intensity, we employed three SUHI indicators, i.e., the LST difference of urban-rural, that of urban-agriculture and that of urban-water. Physical and biophysical surface variables, including land use and land cover (LULC, elevation, impervious surface (IS, fractional vegetation cover (FVC and albedo, were selected to estimate the relationship between LST seasonal variability and the surface properties. Results show that an inversion of the SUHI phenomenon (i.e., surface urban cool island existed at daytime with the maximal value of urban-rural LST difference of −4 K in March; whereas the maximal value of SUHI at nighttime yielded 3.9 K in May. When using the indicators of urban-agriculture and urban-water LST differences, the maximal value of SUHI was found to be 8.2 K and 15.5 K, respectively. Both results were observed at daytime, suggesting the role of bare soils in the inversion of the SUHI phenomenon with the urban-rural indicator. Maximal correlation was observed in the relationship between night LST and elevation in spring (coefficient: −0.76, night LST and IS in spring (0.60, night LST and albedo in winter (−0.53 and day LST with fractional vegetation cover in summer (−0.41. The relationship between all surface properties with LST possessed large seasonal variations, and thus, using these relationships for SUHI modeling may not be

  7. Surface-complexation models for sorption onto heterogeneous surfaces

    International Nuclear Information System (INIS)

    Harvey, K.B.

    1997-10-01

    This report provides a description of the discrete-logK spectrum model, together with a description of its derivation, and of its place in the larger context of surface-complexation modelling. The tools necessary to apply the discrete-logK spectrum model are discussed, and background information appropriate to this discussion is supplied as appendices. (author)

  8. Variational Ridging in Sea Ice Models

    Science.gov (United States)

    Roberts, A.; Hunke, E. C.; Lipscomb, W. H.; Maslowski, W.; Kamal, S.

    2017-12-01

    This work presents the results of a new development to make basin-scale sea ice models aware of the shape, porosity and extent of individual ridges within the pack. We have derived an analytic solution for the Euler-Lagrange equation of individual ridges that accounts for non-conservative forces, and therefore the compressive strength of individual ridges. Because a region of the pack is simply a collection of paths of individual ridges, we are able to solve the Euler-Lagrange equation for a large-scale sea ice field also, and therefore the compressive strength of a region of the pack that explicitly accounts for the macro-porosity of ridged debris. We make a number of assumptions that have simplified the problem, such as treating sea ice as a granular material in ridges, and assuming that bending moments associated with ridging are perturbations around an isostatic state. Regardless of these simplifications, the ridge model is remarkably predictive of macro-porosity and ridge shape, and, because our equations are analytic, they do not require costly computations to solve the Euler-Lagrange equation of ridges on the large scale. The new ridge model is therefore applicable to large-scale sea ice models. We present results from this theoretical development, as well as plans to apply it to the Regional Arctic System Model and a community sea ice code. Most importantly, the new ridging model is particularly useful for pinpointing gaps in our observational record of sea ice ridges, and points to the need for improved measurements of the evolution of porosity of deformed ice in the Arctic and Antarctic. Such knowledge is not only useful for improving models, but also for improving estimates of sea ice volume derived from altimetric measurements of sea ice freeboard.

  9. A Proposed Conceptual Model to Measure Unwarranted Practice Variation

    National Research Council Canada - National Science Library

    Barr, Andrew M

    2007-01-01

    .... Employing a unit of analysis of the U.S. Army healthcare system and utilizing research by Wennberg and the Institute of Medicine, a model describing healthcare quality in terms of unwarranted practice variation and healthcare outcomes...

  10. Target Selection Models with Preference Variation Between Offenders

    NARCIS (Netherlands)

    Townsley, Michael; Birks, Daniel; Ruiter, Stijn; Bernasco, Wim; White, Gentry

    2016-01-01

    Objectives: This study explores preference variation in location choice strategies of residential burglars. Applying a model of offender target selection that is grounded in assertions of the routine activity approach, rational choice perspective, crime pattern and social disorganization theories,

  11. Ultrasonic-assisted manufacturing processes: Variational model and numerical simulations

    KAUST Repository

    Siddiq, Amir; El Sayed, Tamer

    2012-01-01

    We present a computational study of ultrasonic assisted manufacturing processes including sheet metal forming, upsetting, and wire drawing. A fully variational porous plasticity model is modified to include ultrasonic softening effects

  12. A variational approach to the Gross-Neveu model

    International Nuclear Information System (INIS)

    Mishra, H.; Misra, P.; Mishra, A.

    1988-01-01

    The authors solve the instability of perturbative vacuum of Gross-Neveu model. They use a variational method. The analysis is nonperturbative as it uses only equal time commmutator/anticommutator algebra

  13. Validity of covariance models for the analysis of geographical variation

    DEFF Research Database (Denmark)

    Guillot, Gilles; Schilling, Rene L.; Porcu, Emilio

    2014-01-01

    1. Due to the availability of large molecular data-sets, covariance models are increasingly used to describe the structure of genetic variation as an alternative to more heavily parametrised biological models. 2. We focus here on a class of parametric covariance models that received sustained att...

  14. Influences of the variation in inflow to East Asia on surface ozone over Japan during 1996–2005

    Directory of Open Access Journals (Sweden)

    S. Chatani

    2011-08-01

    Full Text Available Air quality simulations in which the global chemical transport model CHASER and the regional chemical transport model WRF/chem are coupled have been developed to consider the dynamic transport of chemical species across the boundaries of the domain of the regional chemical transport model. The simulation captures the overall seasonal variations of surface ozone, but overestimates its concentration over Japanese populated areas by approximately 20 ppb from summer to early winter. It is deduced that ozone formation around Northeast China and Japan in summer is overestimated in the simulation. On the other hand, the simulation well reproduces the interannual variability and the long-term trend of observed surface ozone over Japan. Sensitivity experiments have been performed to investigate the influence of the variation in inflow to East Asia on the interannual variability and the long-term trend of surface ozone over Japan during 1996–2005. The inflow defined in this paper includes the recirculation of species with sources within the East Asian region as well as the transport of species with sources out of the East Asian region. Results of sensitivity experiments suggest that inflow to East Asia accounts for approximately 30 % of the increasing trend of surface ozone, whereas it has much less influence on the interannual variability of observed surface ozone compared to meteorological processes within East Asia.

  15. Temporal variation of optimal UV exposure time over Korea: risks and benefits of surface UV radiation

    Science.gov (United States)

    Lee, Y. G.; Koo, J. H.

    2015-12-01

    Solar UV radiation in a wavelength range between 280 to 400 nm has both positive and negative influences on human body. Surface UV radiation is the main natural source of vitamin D, providing the promotion of bone and musculoskeletal health and reducing the risk of a number of cancers and other medical conditions. However, overexposure to surface UV radiation is significantly related with the majority of skin cancer, in addition other negative health effects such as sunburn, skin aging, and some forms of eye cataracts. Therefore, it is important to estimate the optimal UV exposure time, representing a balance between reducing negative health effects and maximizing sufficient vitamin D production. Previous studies calculated erythemal UV and vitamin-D UV from the measured and modelled spectral irradiances, respectively, by weighting CIE Erythema and Vitamin D3 generation functions (Kazantzidis et al., 2009; Fioletov et al., 2010). In particular, McKenzie et al. (2009) suggested the algorithm to estimate vitamin-D production UV from erythemal UV (or UV index) and determined the optimum conditions of UV exposure based on skin type Ⅱ according to the Fitzpatrick (1988). Recently, there are various demands for risks and benefits of surface UV radiation on public health over Korea, thus it is necessary to estimate optimal UV exposure time suitable to skin type of East Asians. This study examined the relationship between erythemally weighted UV (UVEry) and vitamin D weighted UV (UVVitD) over Korea during 2004-2012. The temporal variations of the ratio (UVVitD/UVEry) were also analyzed and the ratio as a function of UV index was applied in estimating the optimal UV exposure time. In summer with high surface UV radiation, short exposure time leaded to sufficient vitamin D and erythema and vice versa in winter. Thus, the balancing time in winter was enough to maximize UV benefits and minimize UV risks.

  16. Variational Data Assimilative Modeling of the Gulf of Maine Circulation in Spring and Summer 2010

    OpenAIRE

    Li, Yizhen; He, Ruoying; Chen, Ke; McGillicuddy, Dennis J.

    2015-01-01

    A data assimilative ocean circulation model is used to hindcast the Gulf of Maine (GOM) circulation in spring and summer 2010. Using the recently developed incremental strong constraint 4D Variational data assimilation algorithm, the model assimilates satellite sea surface temperature and in situ temperature and salinity profiles measured by expendable bathythermograph, Argo floats, and shipboard CTD casts. Validation against independent observations shows that the model skill is significantl...

  17. 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.

  18. Dynamical modeling of surface tension

    International Nuclear Information System (INIS)

    Brackbill, J.U.; Kothe, D.B.

    1996-01-01

    In a recent review it is said that free-surface flows ''represent some of the difficult remaining challenges in computational fluid dynamics''. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin. This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin are discussed

  19. Modeling of ion beam surface treatment

    Energy Technology Data Exchange (ETDEWEB)

    Stinnett, R W [Quantum Manufacturing Technologies, Inc., Albuquerque, NM (United States); Maenchen, J E; Renk, T J [Sandia National Laboratories, Albuquerque, NM (United States); Struve, K W [Mission Research Corporation, Albuquerque, NM (United States); Campbell, M M [PASTDCO, Albuquerque, NM (United States)

    1997-12-31

    The use of intense pulsed ion beams is providing a new capability for surface engineering based on rapid thermal processing of the top few microns of metal, ceramic, and glass surfaces. The Ion Beam Surface Treatment (IBEST) process has been shown to produce enhancements in the hardness, corrosion, wear, and fatigue properties of surfaces by rapid melt and re-solidification. A new code called IBMOD was created, enabling the modeling of intense ion beam deposition and the resulting rapid thermal cycling of surfaces. This code was used to model the effect of treatment of aluminum, iron, and titanium using different ion species and pulse durations. (author). 3 figs., 4 refs.

  20. Surface Freshwater Storage Variations in the Orinoco Floodplains Using Multi-Satellite Observations

    Directory of Open Access Journals (Sweden)

    Frédéric Frappart

    2014-12-01

    Full Text Available Variations in surface water extent and storage are poorly characterized from regional to global scales. In this study, a multi-satellite approach is proposed to estimate the water stored in the floodplains of the Orinoco Basin at a monthly time-scale using remotely-sensed observations of surface water from the Global Inundation Extent Multi-Satellite (GIEMS and stages from Envisat radar altimetry. Surface water storage variations over 2003–2007 exhibit large interannual variability and a strong seasonal signal, peaking during summer, and associated with the flood pulse. The volume of surface water storage in the Orinoco Basin was highly correlated with the river discharge at Ciudad Bolivar (R = 0.95, the closest station to the mouth where discharge was estimated, although discharge lagged one month behind storage. The correlation remained high (R = 0.73 after removing seasonal effects. Mean annual variations in surface water volume represented ~170 km3, contributing to ~45% of the Gravity Recovery and Climate Experiment (GRACE-derived total water storage variations and representing ~13% of the total volume of water that flowed out of the Orinoco Basin to the Atlantic Ocean.

  1. Dynamic Factor Models for the Volatility Surface

    DEFF Research Database (Denmark)

    van der Wel, Michel; Ozturk, Sait R.; Dijk, Dick van

    The implied volatility surface is the collection of volatilities implied by option contracts for different strike prices and time-to-maturity. We study factor models to capture the dynamics of this three-dimensional implied volatility surface. Three model types are considered to examine desirable...

  2. An analytical model for the description of the full-polarimetric sea surface Doppler signature

    NARCIS (Netherlands)

    Fois, F.; Hoogeboom, P.; Le Chevalier, F.; Stoffelen, A.

    2015-01-01

    This paper describes an analytical model of the full-polarimetric sea surface scattering and Doppler signature. The model combines the small-slope-approximation theory (at the second order) with a weak nonlinear sea surface representation. Such a model is used to examine the variation of the Doppler

  3. Variational analysis of topological stationary barotropic MHD in the case of single-valued magnetic surfaces

    International Nuclear Information System (INIS)

    Yahalom, A

    2014-01-01

    Variational principles for magnetohydrodynamics have been introduced by previous authors both in Lagrangian and Eulerian form. Yahalom and Lynden-Bell (2008) have previously introduced simpler Eulerian variational principles from which all the relevant equations of barotropic magnetohydrodynamics can be derived. These variational principles were given in terms of six independent functions for non-stationary barotropic flows with given topologies and three independent functions for stationary barotropic flows. This is less then the seven variables which appear in the standard equations of barotropic magnetohydrodynamics which are the magnetic field B-vector the velocity field v-vector and the density ρ. Later, Yahalom (2010) introduced a simpler variational principle in terms of four functions for non-stationary barotropic magnetohydrodynamics. It was shown that the above variational principles are also relevant for flows of non-trivial topologies and in fact using those variational variables one arrives at additional topological conservation laws in terms of cuts of variables which have close resemblance to the Aharonov- Bohm phase (Yahalom (2013)). In previous examples (Yahalom and Lynden-Bell (2008); Yahalom (2013)) the magnetic field lines with non-trivial topology were at the intersection of two surface one of which was always multivalued; in this paper an example is introduced in which the magnetic helicity is not zero yet both surfaces are single-valued

  4. Super-quasi-conformal transformation and Schiffer variation on super-Riemann surface

    International Nuclear Information System (INIS)

    Takahasi, Wataru

    1990-01-01

    A set of equations which characterizes the super-Teichmueller deformations is proposed. It is a supersymmetric extension of the Beltrami equation. Relations between the set of equations and the Schiffer variations with the KN bases are discussed. This application of the KN bases shows the powerfulness of the KN theory in the study of super-Riemann surfaces. (author)

  5. Spatial and temporal variation of surface waves in shallow waters along the eastern Arabian Sea.

    Digital Repository Service at National Institute of Oceanography (India)

    Anoop, T.R.; SanilKumar, V.; Shanas, P.R.

    We studied the spatial and temporal variation of surface waves along the eastern Arabian Sea during 2011 and 2012. Measured directional wave data at two shallow water locations and re-analysis datasets (ERA-Interim) at 0.751 intervals at four...

  6. Variations of surface temparature with solar activity at two stations in ...

    African Journals Online (AJOL)

    Nigeria Journal of Pure and Applied Physics ... A consistent and persistent diurnal variation in surface air temperature exists which shows an almost constant level in the early morning hours (0000 0600 hours LT.); a rise at sunrise till about 1500 hr LT., a subsequent fall to the constant level by about 1900 hr LT. at sunset.

  7. Bag model with diffuse surface

    International Nuclear Information System (INIS)

    Phatak, S.C.

    1986-01-01

    The constraint of a sharp bag boundary in the bag model is relaxed in the present work. This has been achieved by replacing the square-well potential of the bag model by a smooth scalar potential and introducing a term similar to the bag pressure term. The constraint of the conservation of the energy-momentum tensor is used to obtain an expression for the added bag pressure term. The model is then used to determine the static properties of the nucleon. The calculation shows that the rms charge radius and the nucleon magnetic moment are larger than the corresponding bag model values. Also, the axial vector coupling constant and the πNN coupling constant are in better agreement with the experimental values

  8. Single-layer model for surface roughness.

    Science.gov (United States)

    Carniglia, C K; Jensen, D G

    2002-06-01

    Random roughness of an optical surface reduces its specular reflectance and transmittance by the scattering of light. The reduction in reflectance can be modeled by a homogeneous layer on the surface if the refractive index of the layer is intermediate to the indices of the media on either side of the surface. Such a layer predicts an increase in the transmittance of the surface and therefore does not provide a valid model for the effects of scatter on the transmittance. Adding a small amount of absorption to the layer provides a model that predicts a reduction in both reflectance and transmittance. The absorbing layer model agrees with the predictions of a scalar scattering theory for a layer with a thickness that is twice the rms roughness of the surface. The extinction coefficient k for the layer is proportional to the thickness of the layer.

  9. Surface chemistry of cellulose : from natural fibres to model surfaces

    NARCIS (Netherlands)

    Kontturi, E.J.

    2005-01-01

    The theme of the thesis was to link together the research aspects of cellulose occurring in nature (in natural wood fibres) and model surfaces of cellulose. Fundamental changes in cellulose (or fibre) during recycling of paper was a pragmatic aspect which was retained throughout the thesis with

  10. Digital Modeling Phenomenon Of Surface Ground Movement

    Directory of Open Access Journals (Sweden)

    Ioan Voina

    2016-11-01

    Full Text Available With the development of specialized software applications it was possible to approach and resolve complex problems concerning automating and process optimization for which are being used field data. Computerized representation of the shape and dimensions of the Earth requires a detailed mathematical modeling, known as "digital terrain model". The paper aims to present the digital terrain model of Vulcan mining, Hunedoara County, Romania. Modeling consists of a set of mathematical equations that define in detail the surface of Earth and has an approximate surface rigorously and mathematical, that calculated the land area. Therefore, the digital terrain model means a digital representation of the earth's surface through a mathematical model that approximates the land surface modeling, which can be used in various civil and industrial applications in. To achieve the digital terrain model of data recorded using linear and nonlinear interpolation method based on point survey which highlights the natural surface studied. Given the complexity of this work it is absolutely necessary to know in detail of all topographic elements of work area, without the actions to be undertaken to project and manipulate would not be possible. To achieve digital terrain model, within a specialized software were set appropriate parameters required to achieve this case study. After performing all steps we obtained digital terrain model of Vulcan Mine. Digital terrain model is the complex product, which has characteristics that are equivalent to the specialists that use satellite images and information stored in a digital model, this is easier to use.

  11. A variational formulation for linear models in coupled dynamic thermoelasticity

    International Nuclear Information System (INIS)

    Feijoo, R.A.; Moura, C.A. de.

    1981-07-01

    A variational formulation for linear models in coupled dynamic thermoelasticity which quite naturally motivates the design of a numerical scheme for the problem, is studied. When linked to regularization or penalization techniques, this algorithm may be applied to more general models, namely, the ones that consider non-linear constraints associated to variational inequalities. The basic postulates of Mechanics and Thermodynamics as well as some well-known mathematical techniques are described. A thorough description of the algorithm implementation with the finite-element method is also provided. Proofs for existence and uniqueness of solutions and for convergence of the approximations are presented, and some numerical results are exhibited. (Author) [pt

  12. Internal Physical Features of a Land Surface Model Employing a Tangent Linear Model

    Science.gov (United States)

    Yang, Runhua; Cohn, Stephen E.; daSilva, Arlindo; Joiner, Joanna; Houser, Paul R.

    1997-01-01

    The Earth's land surface, including its biomass, is an integral part of the Earth's weather and climate system. Land surface heterogeneity, such as the type and amount of vegetative covering., has a profound effect on local weather variability and therefore on regional variations of the global climate. Surface conditions affect local weather and climate through a number of mechanisms. First, they determine the re-distribution of the net radiative energy received at the surface, through the atmosphere, from the sun. A certain fraction of this energy increases the surface ground temperature, another warms the near-surface atmosphere, and the rest evaporates surface water, which in turn creates clouds and causes precipitation. Second, they determine how much rainfall and snowmelt can be stored in the soil and how much instead runs off into waterways. Finally, surface conditions influence the near-surface concentration and distribution of greenhouse gases such as carbon dioxide. The processes through which these mechanisms interact with the atmosphere can be modeled mathematically, to within some degree of uncertainty, on the basis of underlying physical principles. Such a land surface model provides predictive capability for surface variables including ground temperature, surface humidity, and soil moisture and temperature. This information is important for agriculture and industry, as well as for addressing fundamental scientific questions concerning global and local climate change. In this study we apply a methodology known as tangent linear modeling to help us understand more deeply, the behavior of the Mosaic land surface model, a model that has been developed over the past several years at NASA/GSFC. This methodology allows us to examine, directly and quantitatively, the dependence of prediction errors in land surface variables upon different vegetation conditions. The work also highlights the importance of accurate soil moisture information. Although surface

  13. Modelling basin-wide variations in Amazon forest photosynthesis

    Science.gov (United States)

    Mercado, Lina; Lloyd, Jon; Domingues, Tomas; Fyllas, Nikolaos; Patino, Sandra; Dolman, Han; Sitch, Stephen

    2010-05-01

    Given the importance of Amazon rainforest in the global carbon and hydrological cycles, there is a need to use parameterized and validated ecosystem gas exchange and vegetation models for this region in order to adequately simulate present and future carbon and water balances. Recent research has found major differences in above-ground net primary productivity (ANPP), above ground biomass and tree dynamics across Amazonia. West Amazonia is more dynamic, with younger trees, higher stem growth rates and lower biomass than central and eastern Amazon (Baker et al. 2004; Malhi et al. 2004; Phillips et al. 2004). A factor of three variation in above-ground net primary productivity has been estimated across Amazonia by Malhi et al. (2004). Different hypotheses have been proposed to explain the observed spatial variability in ANPP (Malhi et al. 2004). First, due to the proximity to the Andes, sites from western Amazonia tend to have richer soils than central and eastern Amazon and therefore soil fertility could possibly be highly related to the high wood productivity found in western sites. Second, if GPP does not vary across the Amazon basin then different patterns of carbon allocation to respiration could also explain the observed ANPP gradient. However since plant growth depends on the interaction between photosynthesis, transport of assimilates, plant respiration, water relations and mineral nutrition, variations in plant gross photosynthesis (GPP) could also explain the observed variations in ANPP. In this study we investigate whether Amazon GPP can explain variations of observed ANPP. We use a sun and shade canopy gas exchange model that has been calibrated and evaluated at five rainforest sites (Mercado et al. 2009) to simulate gross primary productivity of 50 sites across the Amazon basin during the period 1980-2001. Such simulation differs from the ones performed with global vegetation models (Cox et al. 1998; Sitch et al. 2003) where i) single plant functional

  14. An Improved MUSIC Model for Gibbsite Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Scott C.; Bickmore, Barry R.; Tadanier, Christopher J.; Rosso, Kevin M.

    2004-06-01

    Here we use gibbsite as a model system with which to test a recently published, bond-valence method for predicting intrinsic pKa values for surface functional groups on oxides. At issue is whether the method is adequate when valence parameters for the functional groups are derived from ab initio structure optimization of surfaces terminated by vacuum. If not, ab initio molecular dynamics (AIMD) simulations of solvated surfaces (which are much more computationally expensive) will have to be used. To do this, we had to evaluate extant gibbsite potentiometric titration data that where some estimate of edge and basal surface area was available. Applying BET and recently developed atomic force microscopy methods, we found that most of these data sets were flawed, in that their surface area estimates were probably wrong. Similarly, there may have been problems with many of the titration procedures. However, one data set was adequate on both counts, and we applied our method of surface pKa int prediction to fitting a MUSIC model to this data with considerable success—several features of the titration data were predicted well. However, the model fit was certainly not perfect, and we experienced some difficulties optimizing highly charged, vacuum-terminated surfaces. Therefore, we conclude that we probably need to do AIMD simulations of solvated surfaces to adequately predict intrinsic pKa values for surface functional groups.

  15. Variational Boussinesq model for strongly nonlinear dispersive waves

    NARCIS (Netherlands)

    Lawrence, C.; Adytia, D.; van Groesen, E.

    2018-01-01

    For wave tank, coastal and oceanic applications, a fully nonlinear Variational Boussinesq model with optimized dispersion is derived and a simple Finite Element implementation is described. Improving a previous weakly nonlinear version, high waves over flat and varying bottom are shown to be

  16. Analysis of spin and gauge models with variational methods

    International Nuclear Information System (INIS)

    Dagotto, E.; Masperi, L.; Moreo, A.; Della Selva, A.; Fiore, R.

    1985-01-01

    Since independent-site (link) or independent-link (plaquette) variational states enhance the order or the disorder, respectively, in the treatment of spin (gauge) models, we prove that mixed states are able to improve the critical coupling while giving the qualitatively correct behavior of the relevant parameters

  17. The variational approach to the Glashow-Weinberg-Salam model

    International Nuclear Information System (INIS)

    Manka, R.; Sladkowski, J.

    1987-01-01

    The variational approach to the Glashow-Weinberg-Salam model, based on canonical quantization, is presented. It is shown that taking into consideration the Becchi-Rouet-Stora symmetry leads to the correct, temperature-dependent, effective potential. This generalization of the Weinberg-Coleman potential leads to a phase transition of the first kind

  18. Modeling stimulus variation in three common implicit attitude tasks.

    Science.gov (United States)

    Wolsiefer, Katie; Westfall, Jacob; Judd, Charles M

    2017-08-01

    We explored the consequences of ignoring the sampling variation due to stimuli in the domain of implicit attitudes. A large literature in psycholinguistics has examined the statistical treatment of random stimulus materials, but the recommendations from this literature have not been applied to the social psychological literature on implicit attitudes. This is partly because of inherent complications in applying crossed random-effect models to some of the most common implicit attitude tasks, and partly because no work to date has demonstrated that random stimulus variation is in fact consequential in implicit attitude measurement. We addressed this problem by laying out statistically appropriate and practically feasible crossed random-effect models for three of the most commonly used implicit attitude measures-the Implicit Association Test, affect misattribution procedure, and evaluative priming task-and then applying these models to large datasets (average N = 3,206) that assess participants' implicit attitudes toward race, politics, and self-esteem. We showed that the test statistics from the traditional analyses are substantially (about 60 %) inflated relative to the more-appropriate analyses that incorporate stimulus variation. Because all three tasks used the same stimulus words and faces, we could also meaningfully compare the relative contributions of stimulus variation across the tasks. In an appendix, we give syntax in R, SAS, and SPSS for fitting the recommended crossed random-effects models to data from all three tasks, as well as instructions on how to structure the data file.

  19. Sensitivity of hydrological performance assessment analysis to variations in material properties, conceptual models, and ventilation models

    Energy Technology Data Exchange (ETDEWEB)

    Sobolik, S.R.; Ho, C.K.; Dunn, E. [Sandia National Labs., Albuquerque, NM (United States); Robey, T.H. [Spectra Research Inst., Albuquerque, NM (United States); Cruz, W.T. [Univ. del Turabo, Gurabo (Puerto Rico)

    1996-07-01

    The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface- based and underground testing. Analyses have been performed to support the design of an Exploratory Studies Facility (ESF) and the design of the tests performed as part of the characterization process, in order to ascertain that they have minimal impact on the natural ability of the site to isolate waste. The information in this report pertains to sensitivity studies evaluating previous hydrological performance assessment analyses to variation in the material properties, conceptual models, and ventilation models, and the implications of this sensitivity on previous recommendations supporting ESF design. This document contains information that has been used in preparing recommendations for Appendix I of the Exploratory Studies Facility Design Requirements document.

  20. Sensitivity of hydrological performance assessment analysis to variations in material properties, conceptual models, and ventilation models

    International Nuclear Information System (INIS)

    Sobolik, S.R.; Ho, C.K.; Dunn, E.; Robey, T.H.; Cruz, W.T.

    1996-07-01

    The Yucca Mountain Site Characterization Project is studying Yucca Mountain in southwestern Nevada as a potential site for a high-level nuclear waste repository. Site characterization includes surface- based and underground testing. Analyses have been performed to support the design of an Exploratory Studies Facility (ESF) and the design of the tests performed as part of the characterization process, in order to ascertain that they have minimal impact on the natural ability of the site to isolate waste. The information in this report pertains to sensitivity studies evaluating previous hydrological performance assessment analyses to variation in the material properties, conceptual models, and ventilation models, and the implications of this sensitivity on previous recommendations supporting ESF design. This document contains information that has been used in preparing recommendations for Appendix I of the Exploratory Studies Facility Design Requirements document

  1. Storm surge model based on variational data assimilation method

    Directory of Open Access Journals (Sweden)

    Shi-li Huang

    2010-06-01

    Full Text Available By combining computation and observation information, the variational data assimilation method has the ability to eliminate errors caused by the uncertainty of parameters in practical forecasting. It was applied to a storm surge model based on unstructured grids with high spatial resolution meant for improving the forecasting accuracy of the storm surge. By controlling the wind stress drag coefficient, the variation-based model was developed and validated through data assimilation tests in an actual storm surge induced by a typhoon. In the data assimilation tests, the model accurately identified the wind stress drag coefficient and obtained results close to the true state. Then, the actual storm surge induced by Typhoon 0515 was forecast by the developed model, and the results demonstrate its efficiency in practical application.

  2. Insights into pre-reversal paleosecular variation from stochastic models

    Directory of Open Access Journals (Sweden)

    Klaudio ePeqini

    2015-09-01

    Full Text Available To provide insights on the paleosecular variation of the geomagnetic field and the mechanism of reversals, long time series of the dipolar magnetic moment are generated by two different stochastic models, known as the domino model and the inhomogeneous Lebovitz disk dynamo model, with initial values taken from the from paleomagnetic data. The former model considers mutual interactions of N macrospins embedded in a uniformly rotating medium, where random forcing and dissipation act on each macrospin. With an appropriate set of the model’s parameters values, the series generated by this model have similar statistical behaviour to the time series of the SHA.DIF.14K model. The latter model is an extension of the classical two-disk Rikitake model, considering N dynamo elements with appropriate interactions between them.We varied the parameters set of both models aiming at generating suitable time series with behaviour similar to the long time series of recent secular variation (SV. Such series are then extended to the near future, obtaining reversals in both cases of models. The analysis of the time series generated by simulating the models show that the reversals appears after a persistent period of low intensity geomagnetic field, as it is occurring in the present times.

  3. Ultrasonic-assisted manufacturing processes: Variational model and numerical simulations

    KAUST Repository

    Siddiq, Amir

    2012-04-01

    We present a computational study of ultrasonic assisted manufacturing processes including sheet metal forming, upsetting, and wire drawing. A fully variational porous plasticity model is modified to include ultrasonic softening effects and then utilized to account for instantaneous softening when ultrasonic energy is applied during deformation. Material model parameters are identified via inverse modeling, i.e. by using experimental data. The versatility and predictive ability of the model are demonstrated and the effect of ultrasonic intensity on the manufacturing process at hand is investigated and compared qualitatively with experimental results reported in the literature. © 2011 Elsevier B.V. All rights reserved.

  4. Impact of Surface Soil Moisture Variations on Radar Altimetry Echoes at Ku and Ka Bands in Semi-Arid Areas

    Directory of Open Access Journals (Sweden)

    Christophe Fatras

    2018-04-01

    Full Text Available Radar altimetry provides information on the topography of the Earth surface. It is commonly used for the monitoring not only sea surface height but also ice sheets topography and inland water levels. The radar altimetry backscattering coefficient, which depends on surface roughness and water content, can be related to surface properties such as surface soil moisture content. In this study, the influence of surface soil moisture on the radar altimetry echo and backscattering coefficient is analyzed over semi-arid areas. A semi-empirical model of the soil’s complex dielectric permittivity that takes into account that small-scale roughness and large-scale topography was developed to simulate the radar echoes. It was validated using waveforms acquired at Ku and Ka-bands by ENVISAT RA-2 and SARAL AltiKa respectively over several sites in Mali. Correlation coefficients ranging from 0.66 to 0.94 at Ku-band and from 0.27 to 0.96 at Ka-band were found. The increase in surface soil moisture from 0.02 to 0.4 (i.e., the typical range of variations in semi-arid areas increase the backscattering from 10 to 15 dB between the core of the dry and the maximum of the rainy seasons.

  5. Minimal model for spoof acoustoelastic surface states

    Directory of Open Access Journals (Sweden)

    J. Christensen

    2014-12-01

    Full Text Available Similar to textured perfect electric conductors for electromagnetic waves sustaining artificial or spoof surface plasmons we present an equivalent phenomena for the case of sound. Aided by a minimal model that is able to capture the complex wave interaction of elastic cavity modes and airborne sound radiation in perfect rigid panels, we construct designer acoustoelastic surface waves that are entirely controlled by the geometrical environment. Comparisons to results obtained by full-wave simulations confirm the feasibility of the model and we demonstrate illustrative examples such as resonant transmissions and waveguiding to show a few examples of many where spoof elastic surface waves are useful.

  6. Foundations of elastoplasticity subloading surface model

    CERN Document Server

    Hashiguchi, Koichi

    2017-01-01

    This book is the standard text book of elastoplasticity in which the elastoplasticity theory is comprehensively described from the conventional theory for the monotonic loading to the unconventional theory for the cyclic loading behavior. Explanations of vector-tensor analysis and continuum mechanics are provided first as a foundation for elastoplasticity theory, covering various strain and stress measures and their rates with their objectivities. Elastoplasticity has been highly developed by the creation and formulation of the subloading surface model which is the unified fundamental law for irreversible mechanical phenomena in solids. The assumption that the interior of the yield surface is an elastic domain is excluded in order to describe the plastic strain rate due to the rate of stress inside the yield surface in this model aiming at the prediction of cyclic loading behavior, although the yield surface enclosing the elastic domain is assumed in all the elastoplastic models other than the subloading surf...

  7. Variations and asymmetries in regional brain surface in the genus Homo.

    Science.gov (United States)

    Balzeau, Antoine; Holloway, Ralph L; Grimaud-Hervé, Dominique

    2012-06-01

    Paleoneurology is an important field of research within human evolution studies. Variations in size and shape of an endocast help to differentiate among fossil hominin species whereas endocranial asymmetries are related to behavior and cognitive function. Here we analyse variations of the surface of the frontal, parieto-temporal and occipital lobes among different species of Homo, including 39 fossil hominins, ten fossil anatomically modern Homo sapiens and 100 endocasts of extant modern humans. We also test for the possible asymmetries of these features in a large sample of modern humans and observe individual particularities in the fossil specimens. This study contributes important new information about the brain evolution in the genus Homo. Our results show that the general pattern of surface asymmetry for the different regional brain surfaces in fossil species of Homo does not seem to be different from the pattern described in a large sample of anatomically modern H. sapiens, i.e., the right hemisphere has a larger surface than the left, as do the right frontal, the right parieto-temporal and the left occipital lobes compared with the contra-lateral side. It also appears that Asian Homo erectus specimens are discriminated from all other samples of Homo, including African and Georgian specimens that are also sometimes included in that taxon. The Asian fossils show a significantly smaller relative size of the parietal and temporal lobes. Neandertals and anatomically modern H. sapiens, who share the largest endocranial volume of all hominins, show differences when considering the relative contribution of the frontal, parieto-temporal and occipital lobes. These results illustrate an original variation in the pattern of brain organization in hominins independent of variations in total size. The globularization of the brain and the enlargement of the parietal lobes could be considered derived features observed uniquely in anatomically modern H. sapiens. Copyright

  8. Variation of air--water gas transfer with wind stress and surface viscoelasticity

    OpenAIRE

    Frew, Nelson M.; Bock, Erik J.; McGillis, Wade R.; Karachintsev, Andrey V.; Hara, Tetsu; Münsterer, Thomas; Jähne, Bernd

    1995-01-01

    Previous parameterizations of gas transfer velocity have attempted to cast this quantity as a function of wind speed or wind-stress. This study demonstrates that the presence of a surface film is effective at reducing the gas transfer velocity at constant wind-stress. Gas exchange experiments were performed at WHOI and UH using annular wind-wave tanks of different scales. Systematic variations of wind-stress and surfactant concentration (Triton-X-100) were explored to determ...

  9. Surface Adsorption in Nonpolarizable Atomic Models.

    Science.gov (United States)

    Whitmer, Jonathan K; Joshi, Abhijeet A; Carlton, Rebecca J; Abbott, Nicholas L; de Pablo, Juan J

    2014-12-09

    Many ionic solutions exhibit species-dependent properties, including surface tension and the salting-out of proteins. These effects may be loosely quantified in terms of the Hofmeister series, first identified in the context of protein solubility. Here, our interest is to develop atomistic models capable of capturing Hofmeister effects rigorously. Importantly, we aim to capture this dependence in computationally cheap "hard" ionic models, which do not exhibit dynamic polarization. To do this, we have performed an investigation detailing the effects of the water model on these properties. Though incredibly important, the role of water models in simulation of ionic solutions and biological systems is essentially unexplored. We quantify this via the ion-dependent surface attraction of the halide series (Cl, Br, I) and, in so doing, determine the relative importance of various hypothesized contributions to ionic surface free energies. Importantly, we demonstrate surface adsorption can result in hard ionic models combined with a thermodynamically accurate representation of the water molecule (TIP4Q). The effect observed in simulations of iodide is commensurate with previous calculations of the surface potential of mean force in rigid molecular dynamics and polarizable density-functional models. Our calculations are direct simulation evidence of the subtle but sensitive role of water thermodynamics in atomistic simulations.

  10. A physically based model of global freshwater surface temperature

    Science.gov (United States)

    van Beek, Ludovicus P. H.; Eikelboom, Tessa; van Vliet, Michelle T. H.; Bierkens, Marc F. P.

    2012-09-01

    the Arctic rivers because the timing of ice breakup is predicted too late in the year due to the lack of including a mechanical breakup mechanism. Moreover, surface water temperatures for tropical rivers were overestimated, most likely due to an overestimation of rainfall temperature and incoming shortwave radiation. The spatiotemporal variation of water temperature reveals large temperature differences between water and atmosphere for the higher latitudes, while considerable lateral transport of heat can be observed for rivers crossing hydroclimatic zones, such as the Nile, the Mississippi, and the large rivers flowing to the Arctic. Overall, our model results show promise for future projection of global surface freshwater temperature under global change.

  11. Impurities and Electronic Property Variations of Natural MoS 2 Crystal Surfaces

    KAUST Repository

    Addou, Rafik; McDonnell, Stephen; Barrera, Diego; Guo, Zaibing; Azcatl, Angelica; Wang, Jian; Zhu, Hui; Hinkle, Christopher L.; Quevedo-Lopez, Manuel; Alshareef, Husam N.; Colombo, Luigi; Hsu, Julia W P; Wallace, Robert M.

    2015-01-01

    Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication. © 2015 American Chemical Society.

  12. Impurities and Electronic Property Variations of Natural MoS 2 Crystal Surfaces

    KAUST Repository

    Addou, Rafik

    2015-09-22

    Room temperature X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICPMS), high resolution Rutherford backscattering spectrometry (HR-RBS), Kelvin probe method, and scanning tunneling microscopy (STM) are employed to study the properties of a freshly exfoliated surface of geological MoS2 crystals. Our findings reveal that the semiconductor 2H-MoS2 exhibits both n- and p-type behavior, and the work function as measured by the Kelvin probe is found to vary from 4.4 to 5.3 eV. The presence of impurities in parts-per-million (ppm) and a surface defect density of up to 8% of the total area could explain the variation of the Fermi level position. High resolution RBS data also show a large variation in the MoSx composition (1.8 < x < 2.05) at the surface. Thus, the variation in the conductivity, the work function, and stoichiometry across small areas of MoS2 will have to be controlled during crystal growth in order to provide high quality uniform materials for future device fabrication. © 2015 American Chemical Society.

  13. Use of upscaled elevation and surface roughness data in two-dimensional surface water models

    Science.gov (United States)

    Hughes, J.D.; Decker, J.D.; Langevin, C.D.

    2011-01-01

    In this paper, we present an approach that uses a combination of cell-block- and cell-face-averaging of high-resolution cell elevation and roughness data to upscale hydraulic parameters and accurately simulate surface water flow in relatively low-resolution numerical models. The method developed allows channelized features that preferentially connect large-scale grid cells at cell interfaces to be represented in models where these features are significantly smaller than the selected grid size. The developed upscaling approach has been implemented in a two-dimensional finite difference model that solves a diffusive wave approximation of the depth-integrated shallow surface water equations using preconditioned Newton–Krylov methods. Computational results are presented to show the effectiveness of the mixed cell-block and cell-face averaging upscaling approach in maintaining model accuracy, reducing model run-times, and how decreased grid resolution affects errors. Application examples demonstrate that sub-grid roughness coefficient variations have a larger effect on simulated error than sub-grid elevation variations.

  14. Seasonal Gravity Field Variations from GRACE and Hydrological Models

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.

    2004-01-01

    . Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... µGal or nearly 5 cm equivalent water storage in selected regions. Integrated over all land masses the standard deviation among the annual signal from the four hydrological models are 0.6 µGal equivalent to around 1.4 cm in equivalent water layer thickness. The estimated accuracy of the annual...

  15. Biosphere modelling for a HLW repository - scenario and parameter variations

    International Nuclear Information System (INIS)

    Grogan, H.

    1985-03-01

    In Switzerland high-level radioactive wastes have been considered for disposal in deep-lying crystalline formations. The individual doses to man resulting from radionuclides entering the biosphere via groundwater transport are calculated. The main recipient area modelled, which constitutes the base case, is a broad gravel terrace sited along the south bank of the river Rhine. An alternative recipient region, a small valley with a well, is also modelled. A number of parameter variations are performed in order to ascertain their impact on the doses. Finally two scenario changes are modelled somewhat simplistically, these consider different prevailing climates, namely tundra and a warmer climate than present. In the base case negligibly low doses to man in the long term, resulting from the existence of a HLW repository have been calculated. Cs-135 results in the largest dose (8.4E-7 mrem/y at 6.1E+6 y) while Np-237 gives the largest dose from the actinides (3.6E-8 mrem/y). The response of the model to parameter variations cannot be easily predicted due to non-linear coupling of many of the parameters. However, the calculated doses were negligibly low in all cases as were those resulting from the two scenario variations. (author)

  16. Land-surface modelling in hydrological perspective

    DEFF Research Database (Denmark)

    Overgaard, Jesper; Rosbjerg, Dan; Butts, M.B.

    2006-01-01

    The purpose of this paper is to provide a review of the different types of energy-based land-surface models (LSMs) and discuss some of the new possibilities that will arise when energy-based LSMs are combined with distributed hydrological modelling. We choose to focus on energy-based approaches......, and the difficulties inherent in various evaluation procedures are presented. Finally, the dynamic coupling of hydrological and atmospheric models is explored, and the perspectives of such efforts are discussed......., because in comparison to the traditional potential evapotranspiration models, these approaches allow for a stronger link to remote sensing and atmospheric modelling. New opportunities for evaluation of distributed land-surface models through application of remote sensing are discussed in detail...

  17. Menu variations for diabetes mellitus patients using Goal Programming model

    Science.gov (United States)

    Dhoruri, Atmini; Lestari, Dwi; Ratnasari, Eminugroho

    2017-08-01

    Diabetes mellitus (DM) was a chronic metabolic disease characterized by higher than normal blood glucose level (normal blood glucose level = = 80 -120 mg/dl). In this study, type 2 DM which mostly caused by unhealthy eating habits would be investigated. Related to eating habit, DM patients needed dietary menu planning with an extracare regarding their nutrients intake (energy, protein, fat and carbohydrate). Therefore, the measures taken were by organizing nutritious dietary menu for diabetes mellitus patients. Dietary menu with appropriate amount of nutrients was organized by considering the amount of calories, proteins, fats and carbohydrates. In this study, Goal Programming model was employed to determine optimal dietary menu variations for diabetes mellitus patients by paying attention to optimal expenses. According to the data obtained from hospitals in Yogyakarta, optimal menu variations would be analyzed by using Goal Programming model and would be completed by using LINGO computer program.

  18. Discrete gradient methods for solving variational image regularisation models

    International Nuclear Information System (INIS)

    Grimm, V; McLachlan, Robert I; McLaren, David I; Quispel, G R W; Schönlieb, C-B

    2017-01-01

    Discrete gradient methods are well-known methods of geometric numerical integration, which preserve the dissipation of gradient systems. In this paper we show that this property of discrete gradient methods can be interesting in the context of variational models for image processing, that is where the processed image is computed as a minimiser of an energy functional. Numerical schemes for computing minimisers of such energies are desired to inherit the dissipative property of the gradient system associated to the energy and consequently guarantee a monotonic decrease of the energy along iterations, avoiding situations in which more computational work might lead to less optimal solutions. Under appropriate smoothness assumptions on the energy functional we prove that discrete gradient methods guarantee a monotonic decrease of the energy towards stationary states, and we promote their use in image processing by exhibiting experiments with convex and non-convex variational models for image deblurring, denoising, and inpainting. (paper)

  19. Surface physics theoretical models and experimental methods

    CERN Document Server

    Mamonova, Marina V; Prudnikova, I A

    2016-01-01

    The demands of production, such as thin films in microelectronics, rely on consideration of factors influencing the interaction of dissimilar materials that make contact with their surfaces. Bond formation between surface layers of dissimilar condensed solids-termed adhesion-depends on the nature of the contacting bodies. Thus, it is necessary to determine the characteristics of adhesion interaction of different materials from both applied and fundamental perspectives of surface phenomena. Given the difficulty in obtaining reliable experimental values of the adhesion strength of coatings, the theoretical approach to determining adhesion characteristics becomes more important. Surface Physics: Theoretical Models and Experimental Methods presents straightforward and efficient approaches and methods developed by the authors that enable the calculation of surface and adhesion characteristics for a wide range of materials: metals, alloys, semiconductors, and complex compounds. The authors compare results from the ...

  20. Assessment of broiler surface temperature variation when exposed to different air temperatures

    Directory of Open Access Journals (Sweden)

    GR Nascimento

    2011-12-01

    Full Text Available This study was conducted to determine the effect of the air temperature variation on the mean surface temperature (MST of 7- to 35-day-old broiler chickens using infrared thermometry to estimate MST, and to study surface temperature variation of the wings, head, legs, back and comb as affected by air temperature and broiler age. One hundred Cobb® broilers were used in the experiment. Starting on day 7, 10 birds were weekly selected at random, housed in an environmental chamber and reared under three distinct temperatures (18, 25 and 32 ºC to record their thermal profile using an infrared thermal camera. The recorded images were processed to estimate MST by selecting the whole area of the bird within the picture and comparing it with the values obtained using selected equations in literature, and to record the surface temperatures of the body parts. The MST estimated by infrared images were not statistically different (p > 0.05 from the values obtained by the equations. MST values significantly increased (p < 0.05 when the air temperature increased, but were not affected by bird age. However, age influenced the difference between MST and air temperature, which was highest on day 14. The technique of infrared thermal image analysis was useful to estimate the mean surface temperature of broiler chickens.

  1. Diurnal and seasonal variations in surface methane at a tropical coastal station: Role of mesoscale meteorology.

    Science.gov (United States)

    Kavitha, M; Nair, Prabha R; Girach, I A; Aneesh, S; Sijikumar, S; Renju, R

    2018-08-01

    In view of the large uncertainties in the methane (CH 4 ) emission estimates and the large spatial gaps in its measurements, studies on near-surface CH 4 on regional basis become highly relevant. This paper presents the first time observational results of a study on the impacts of mesoscale meteorology on the temporal variations of near-surface CH 4 at a tropical coastal station, in India. It is based on the in-situ measurements conducted during January 2014 to August 2016, using an on-line CH 4 analyzer working on the principle of gas chromatography. The diurnal variation shows a daytime low (1898-1925ppbv) and nighttime high (1936-2022ppbv) extending till early morning hours. These changes are closely associated with the mesoscale circulations, namely Sea Breeze (SB) and Land Breeze (LB), as obtained through the meteorological observations, WRF simulations of the circulations and the diurnal variation of boundary layer height as observed by the Microwave Radiometer Profiler. The diurnal enhancement always coincides with the onset of LB. Several cases of different onset timings of LB were examined and results presented. The CH 4 mixing ratio also exhibits significant seasonal patterns being maximum in winter and minimum in pre-monsoon/monsoon with significant inter-annual variations, which is also reflected in diurnal patterns, and are associated with changing synoptic meteorology. This paper also presents an analysis of in-situ measured near-surface CH 4 , column averaged and upper tropospheric CH 4 retrieved by Atmospheric Infrared Sounder (AIRS) onboard Earth Observing System (EOS)/Aqua which gives insight into the vertical distribution of the CH 4 over the location. An attempt is also made to estimate the instantaneous radiative forcing for the measured CH 4 mixing ratio. Copyright © 2018 Elsevier B.V. All rights reserved.

  2. Modelling the appearance of heritage metallic surfaces

    Directory of Open Access Journals (Sweden)

    L. MacDonald

    2014-06-01

    Full Text Available Polished metallic surfaces exhibit a high degree of specularity, which makes them difficult to reproduce accurately. We have applied two different techniques for modelling a heritage object known as the Islamic handbag. Photogrammetric multi-view stereo enabled a dense point cloud to be extracted from a set of photographs with calibration targets, and a geometrically accurate 3D model produced. A new method based on photometric stereo from a set of images taken in an illumination dome enabled surface normals to be generated for each face of the object and its appearance to be rendered, to a high degree of visual realism, when illuminated by one or more light sources from any angles. The specularity of the reflection from the metal surface was modelled by a modified Lorentzian function.

  3. Small velocity and finite temperature variations in kinetic relaxation models

    KAUST Repository

    Markowich, Peter; Jü ngel, Ansgar; Aoki, Kazuo

    2010-01-01

    A small Knuden number analysis of a kinetic equation in the diffusive scaling is performed. The collision kernel is of BGK type with a general local Gibbs state. Assuming that the flow velocity is of the order of the Knudsen number, a Hilbert expansion yields a macroscopic model with finite temperature variations, whose complexity lies in between the hydrodynamic and the energy-transport equations. Its mathematical structure is explored and macroscopic models for specific examples of the global Gibbs state are presented. © American Institute of Mathematical Sciences.

  4. Variational approach to thermal masses in compactified models

    Energy Technology Data Exchange (ETDEWEB)

    Dominici, Daniele [Dipartimento di Fisica e Astronomia Università di Firenze and INFN - Sezione di Firenze,Via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Roditi, Itzhak [Centro Brasileiro de Pesquisas Físicas - CBPF/MCT,Rua Dr. Xavier Sigaud 150, 22290-180, Rio de Janeiro, RJ (Brazil)

    2015-08-20

    We investigate by means of a variational approach the effective potential of a 5DU(1) scalar model at finite temperature and compactified on S{sup 1} and S{sup 1}/Z{sub 2} as well as the corresponding 4D model obtained through a trivial dimensional reduction. We are particularly interested in the behavior of the thermal masses of the scalar field with respect to the Wilson line phase and the results obtained are compared with those coming from a one-loop effective potential calculation. We also explore the nature of the phase transition.

  5. Spatial variation in spoil and vegetative characteristics of pastures on reclaimed surface mined land

    International Nuclear Information System (INIS)

    Teutsch, C.D.; Collins, M.; Ditsch, D.C.

    1999-01-01

    Kentucky has large areas of reclaimed surface mined land that could provide grazing for livestock. Research is needed to determine optimal stocking densities and to evaluate the sustainability of such grazing systems for this region. A long-term grazing study was initiated in 1997 on 151 ha of reclaimed land near Chavies, KY to determine spatial and temporal variation with stocking densities of 0, 0.28, 0.42, or 0.83 beef cow-calf units/ha. Global Positioning System and GIS technologies were used to establish pasture boundaries, locate permanent sampling markers at a density of 1 per 0.4 ha, and interpolate maps of physical, spoil, and vegetable pasture characteristics. Herbage and spoil samples were collected around the permanent markers in May of 1997. Stepwise regression was used to determine factors affecting the vegetative characteristics of the sites. Biomass density ranged from 0 to 2500 kg/ha with a mean of 570 kg/ha. Factors affecting biomass included legume and weed proportions in the sward, grazing activity, soil potassium, elevation, and potential acidity, cumulatively accounting for 32% of the variation. Ground cover ranged from 10 to 100% with an average of 74%. Soil pH, potassium, and grass in the sward accounted for 14% of the variation in ground cover. Legumes made up 0 to 61% of the sward with a mean of 13% over the pasture area. Variables affecting the amount of legume in the sward included biomass density, slope, elevation, pH, and stocking density, together accounting for 21% of the variation. Spatial variation in the physical, spoil, and vegetative characteristics of the pastures was large. Overall, regression accounted for a limited amount of the variation in the vegetative characteristics of the site indicating that other important variables exist

  6. Temporal variation of 228Ra in the near-surface Gulf of Mexico

    International Nuclear Information System (INIS)

    Reid, F.D.; Moore, W.S.; Sackett, W.M.

    1979-01-01

    The Mn-fiber technique for extracting radium from seawater has proved useful for studying the marine geochemistry of 228 Ra. In the Gulf of Mexico, this technique was used to measure the surface and near-surface distribution of 226 Ra and 228 Ra. The observed surface distribution of 228 Ra, and particularly the radium activity ratio (228/226) can be explained by known circulation patterns, or, when local surface currents are not well understood, may provide insight into their general characteristics. The radium activity ratio has increased from 0.5 in 1968 to 0.7 in 1973 in the surface Gulf of Mexico. This observed increase cannot be attributed to known anthropogenic or natural source perturbations within the Caribbean Sea-Gulf of Mexico system. Possible causes include a change in the residence time for near-surface water, or variations in the relative dominance of the two eastern Caribbean; the North Equatorial Current and the Guiana Current. The temporal distribution of 228 Ra is unstable and naturally variable over a time period less than or equal to five years in the Gulf of Mexico and by extrapolation, the Caribbean Sea. Therefore, its usefulness in calculations of eddy diffusion coefficients for these regions is greatly diminished. (Auth.)

  7. Lateral variation in crustal and mantle structure in Bay of Bengal based on surface wave data

    Science.gov (United States)

    Kumar, Amit; Mukhopadhyay, Sagarika; Kumar, Naresh; Baidya, P. R.

    2018-01-01

    Surface waves generated by earthquakes that occurred near Sumatra, Andaman-Nicobar Island chain and Sunda arc are used to estimate crustal and upper mantle S wave velocity structure of Bay of Bengal. Records of these seismic events at various stations located along the eastern coast of India and a few stations in the north eastern part of India are selected for such analysis. These stations lie within regional distance of the selected earthquakes. The selected events are shallow focused with magnitude greater than 5.5. Data of 65, 37, 36, 53 and 36 events recorded at Shillong, Bokaro, Visakhapatnam, Chennai and Trivandrum stations respectively are used for this purpose. The ray paths from the earthquake source to the recording stations cover different parts of the Bay of Bengal. Multiple Filtering Technique (MFT) is applied to compute the group velocities of surface waves from the available data. The dispersion curves thus obtained for this data set are within the period range of 15-120 s. Joint inversion of Rayleigh and Love wave group velocity is carried out to obtain the subsurface information in terms of variation of S wave velocity with depth. The estimated S wave velocity at a given depth and layer thickness can be considered to be an average value for the entire path covered by the corresponding ray paths. However, we observe variation in the value of S wave velocity and layer thickness from data recorded at different stations, indicating lateral variation in these two parameters. Thick deposition of sediments is observed along the paths followed by surface waves to Shillong and Bokaro stations. Sediment thickness keeps on decreasing as the surface wave paths move further south. Based on velocity variation the sedimentary layer is further divided in to three parts; on top lay unconsolidated sediment, underlain by consolidated sediment. Below this lies a layer which we consider as meta-sediments. The thickness and velocity of these layers decrease from north

  8. [Modeling polarimetric BRDF of leaves surfaces].

    Science.gov (United States)

    Xie, Dong-Hui; Wang, Pei-Juan; Zhu, Qi-Jiang; Zhou, Hong-Min

    2010-12-01

    The purpose of the present paper is to model a physical polarimetric bidirectional reflectance distribution function (pBRDF), which can character not only the non-Lambertian but also the polarized features in order that the pBRDF can be applied to analyze the relationship between the degree of polarization and the physiological and biochemical parameters of leaves quantitatively later. Firstly, the bidirectional polarized reflectance distributions from several leaves surfaces were measured by the polarized goniometer developed by Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences. The samples of leaves include two pieces of zea mays L. leaves (young leaf and mature leaf) and a piece of E. palcherrima wild leaf. Non-Lambertian characteristics of directional reflectance from the surfaces of these three leaves are obvious. A Cook-Torrance model was modified by coupling the polarized Fresnel equations to simulate the bidirectional polarized reflectance properties of leaves surfaces. The three parameters in the modified pBRDF model, such as diffuse reflectivity, refractive index and roughness of leaf surface were inversed with genetic algorithm (GA). It was found that the pBRDF model can fit with the measured data well. In addition, these parameters in the model are related with both the physiological and biochemical properties and the polarized characteristics of leaves, therefore it is possible to build the relationships between them later.

  9. Role of Surface Wind and Vegetation Cover in Multi-decadal Variations of Dust Emission in the Sahara and Sahel

    Science.gov (United States)

    Kim, Dong; Chin, Mian; Remer, Lorraine A.; Diehl, Thomas L.; Bian, Huisheng; Yu, Hongbin; Brown, Molly E.; Stockwell, William R.

    2016-01-01

    North Africa, the world's largest dust source, is non-uniform, consisting of a permanently arid region (Sahara), a semi-arid region (Sahel), and a relatively moist vegetated region (Savanna), each with very different rainfall patterns and surface conditions. This study aims to better understand the controlling factors that determine the variation of dust emission in North Africa over a 27-year period from 1982 to 2008, using observational data and model simulations. The results show that the model-derived Saharan dust emission is only correlated with the 10-m winds (W10m) obtained from reanalysis data, but the model-derived Sahel dust emission is correlated with both W10m and the Normalized Difference Vegetation Index (NDVI) that is obtained from satellite. While the Saharan dust accounts for 82 of the continental North Africa dust emission (1340-1570 Tg year(exp -1) in the 27-year average, the Sahel accounts for 17 with a larger seasonal and inter-annual variation (230-380 Tg year(exp -1), contributing about a quarter of the transatlantic dust transported to the northern part of South America. The decreasing dust emission trend over the 27-year period is highly correlated with W10m over the Sahara (R equals 0.92). Over the Sahel, the dust emission is correlated with W10m (R 0.69) but is also anti-correlated with the trend of NDVI (R equals 0.65). W10m is decreasing over both the Sahara and the Sahel between 1982 and 2008, and the trends are correlated (R equals 0.53), suggesting that Saharan Sahelian surface winds are a coupled system, driving the inter-annual variation of dust emission.

  10. Modeling of hydrogen desorption from tungsten surface

    Energy Technology Data Exchange (ETDEWEB)

    Guterl, J., E-mail: jguterl@ucsd.edu [University of California, San Diego, La Jolla, CA 92093 (United States); Smirnov, R.D. [University of California, San Diego, La Jolla, CA 92093 (United States); Krasheninnikov, S.I. [University of California, San Diego, La Jolla, CA 92093 (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation); Uberuaga, B.; Voter, A.F.; Perez, D. [Los Alamos National Laboratory, Los Alamos, NM 8754 (United States)

    2015-08-15

    Hydrogen retention in metallic plasma-facing components is among key-issues for future fusion devices. For tungsten, which has been chosen as divertor material in ITER, hydrogen desorption parameters experimentally measured for fusion-related conditions show large discrepancies. In this paper, we therefore investigate hydrogen recombination and desorption on tungsten surfaces using molecular dynamics simulations and accelerated molecular dynamics simulations to analyze adsorption states, diffusion, hydrogen recombination into molecules, and clustering of hydrogen on tungsten surfaces. The quality of tungsten hydrogen interatomic potential is discussed in the light of MD simulations results, showing that three body interactions in current interatomic potential do not allow to reproduce hydrogen molecular recombination and desorption. Effects of surface hydrogen clustering on hydrogen desorption are analyzed by introducing a kinetic model describing the competition between surface diffusion, clustering and recombination. Different desorption regimes are identified and reproduce some aspects of desorption regimes experimentally observed.

  11. Variational cluster perturbation theory for Bose-Hubbard models

    International Nuclear Information System (INIS)

    Koller, W; Dupuis, N

    2006-01-01

    We discuss the application of the variational cluster perturbation theory (VCPT) to the Mott-insulator-to-superfluid transition in the Bose-Hubbard model. We show how the VCPT can be formulated in such a way that it gives a translation invariant excitation spectrum-free of spurious gaps-despite the fact that it formally breaks translation invariance. The phase diagram and the single-particle Green function in the insulating phase are obtained for one-dimensional systems. When the chemical potential of the cluster is taken as a variational parameter, the VCPT reproduces the dimensional dependence of the phase diagram even for one-site clusters. We find a good quantitative agreement with the results of the density-matrix renormalization group when the number of sites in the cluster becomes of order 10. The extension of the method to the superfluid phase is discussed

  12. Variation in Pockels constants of silicate glass-ceramics prepared by perfect surface crystallization

    Science.gov (United States)

    Takano, Kazuya; Takahashi, Yoshihiro; Miyazaki, Takamichi; Terakado, Nobuaki; Fujiwara, Takumi

    2018-01-01

    We investigated the Pockels effect in polycrystalline materials consisting of highly oriented polar fresnoite-type Sr2TiSi2O8 fabricated using perfectly surface-crystallized glass-ceramics (PSC-GCs). The chemical composition of the precursor glass was shown to significantly affect the crystallized texture, e.g., the crystal orientation and appearance of amorphous nanoparasites in the domains, resulting in variations in the Pockels constants. Single crystals exhibiting spontaneous polarization possessed large structural anisotropy, leading to a strong dependence of the nonlinear-optical properties on the direction of polarized light. This study suggests that variations in the Pockels constants (r13 and r33) and tuning of the r13/r33 ratio can be realized in PSC-GC materials.

  13. Seasonal Variations in Surface Metabolite Composition of Fucus vesiculosus and Fucus serratus from the Baltic Sea.

    Directory of Open Access Journals (Sweden)

    Esther Rickert

    Full Text Available Perennial macroalgae within the genus Fucus are known to exude metabolites through their outer thallus surface. Some of these metabolites have pro- and/or antifouling properties. Seasonal fluctuations of natural fouling pressure and chemical fouling control strength against micro- and macrofoulers have previously been observed in Fucus, suggesting that control strength varies with threat. To date, a study on the seasonal composition of surface associated metabolites, responsible for much of the fouling control, has not been done. We sampled individuals of the two co-occurring species F. vesiculosus and F. serratus at monthly intervals (six per species and month during a one-year field study. We analysed the chemical composition of surface associated metabolites of both Fucus species by means of gas chromatography-mass spectrometry (GC-MS to describe temporal patterns in chemical surface composition. Additionally, we correlated abiotic and biotic parameters recorded monthly within the sampled habitat with the variation in the chemical surface landscape of Fucus. Our study revealed that the chemical surface composition of both Fucus species exhibits substantial seasonal differences between spring/summer and autumn/winter months. Light and temperature explained most of the seasonal variability in surface metabolite composition of both Fucus species. A strong summerly up-regulation of eighteen saccharides and two hydroxy acids in F. vesiculosus as well as of four fatty acids and two saccharides in F. serratus was observed. We discuss how these up-regulated molecules may have a complex effect on associated microfoulers, both promoting or decreasing fouling depending on metabolite and bacterial identity. These seasonal shifts in the surface metabolome seem to exert a compound control of density and composition of the Fucus associated biofilm.

  14. Modeling surface roughness scattering in metallic nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Moors, Kristof, E-mail: kristof@itf.fys.kuleuven.be [KU Leuven, Institute for Theoretical Physics, Celestijnenlaan 200D, B-3001 Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Sorée, Bart [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Physics Department, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); KU Leuven, Electrical Engineering (ESAT) Department, Kasteelpark Arenberg 10, B-3001 Leuven (Belgium); Magnus, Wim [IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Physics Department, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium)

    2015-09-28

    Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.

  15. Quantitative Modeling of Earth Surface Processes

    Science.gov (United States)

    Pelletier, Jon D.

    This textbook describes some of the most effective and straightforward quantitative techniques for modeling Earth surface processes. By emphasizing a core set of equations and solution techniques, the book presents state-of-the-art models currently employed in Earth surface process research, as well as a set of simple but practical research tools. Detailed case studies demonstrate application of the methods to a wide variety of processes including hillslope, fluvial, aeolian, glacial, tectonic, and climatic systems. Exercises at the end of each chapter begin with simple calculations and then progress to more sophisticated problems that require computer programming. All the necessary computer codes are available online at www.cambridge.org/9780521855976. Assuming some knowledge of calculus and basic programming experience, this quantitative textbook is designed for advanced geomorphology courses and as a reference book for professional researchers in Earth and planetary science looking for a quantitative approach to Earth surface processes. More details...

  16. Towards predictive models for transitionally rough surfaces

    Science.gov (United States)

    Abderrahaman-Elena, Nabil; Garcia-Mayoral, Ricardo

    2017-11-01

    We analyze and model the previously presented decomposition for flow variables in DNS of turbulence over transitionally rough surfaces. The flow is decomposed into two contributions: one produced by the overlying turbulence, which has no footprint of the surface texture, and one induced by the roughness, which is essentially the time-averaged flow around the surface obstacles, but modulated in amplitude by the first component. The roughness-induced component closely resembles the laminar steady flow around the roughness elements at the same non-dimensional roughness size. For small - yet transitionally rough - textures, the roughness-free component is essentially the same as over a smooth wall. Based on these findings, we propose predictive models for the onset of the transitionally rough regime. Project supported by the Engineering and Physical Sciences Research Council (EPSRC).

  17. Learning-based stochastic object models for characterizing anatomical variations

    Science.gov (United States)

    Dolly, Steven R.; Lou, Yang; Anastasio, Mark A.; Li, Hua

    2018-03-01

    It is widely known that the optimization of imaging systems based on objective, task-based measures of image quality via computer-simulation requires the use of a stochastic object model (SOM). However, the development of computationally tractable SOMs that can accurately model the statistical variations in human anatomy within a specified ensemble of patients remains a challenging task. Previously reported numerical anatomic models lack the ability to accurately model inter-patient and inter-organ variations in human anatomy among a broad patient population, mainly because they are established on image data corresponding to a few of patients and individual anatomic organs. This may introduce phantom-specific bias into computer-simulation studies, where the study result is heavily dependent on which phantom is used. In certain applications, however, databases of high-quality volumetric images and organ contours are available that can facilitate this SOM development. In this work, a novel and tractable methodology for learning a SOM and generating numerical phantoms from a set of volumetric training images is developed. The proposed methodology learns geometric attribute distributions (GAD) of human anatomic organs from a broad patient population, which characterize both centroid relationships between neighboring organs and anatomic shape similarity of individual organs among patients. By randomly sampling the learned centroid and shape GADs with the constraints of the respective principal attribute variations learned from the training data, an ensemble of stochastic objects can be created. The randomness in organ shape and position reflects the learned variability of human anatomy. To demonstrate the methodology, a SOM of an adult male pelvis is computed and examples of corresponding numerical phantoms are created.

  18. Mechanisms of Surface Antigenic Variation in the Human Pathogenic Fungus Pneumocystis jirovecii.

    Science.gov (United States)

    Schmid-Siegert, Emanuel; Richard, Sophie; Luraschi, Amanda; Mühlethaler, Konrad; Pagni, Marco; Hauser, Philippe M

    2017-11-07

    Microbial pathogens commonly escape the human immune system by varying surface proteins. We investigated the mechanisms used for that purpose by Pneumocystis jirovecii This uncultivable fungus is an obligate pulmonary pathogen that in immunocompromised individuals causes pneumonia, a major life-threatening infection. Long-read PacBio sequencing was used to assemble a core of subtelomeres of a single P. jirovecii strain from a bronchoalveolar lavage fluid specimen from a single patient. A total of 113 genes encoding surface proteins were identified, including 28 pseudogenes. These genes formed a subtelomeric gene superfamily, which included five families encoding adhesive glycosylphosphatidylinositol (GPI)-anchored glycoproteins and one family encoding excreted glycoproteins. Numerical analyses suggested that diversification of the glycoproteins relies on mosaic genes created by ectopic recombination and occurs only within each family. DNA motifs suggested that all genes are expressed independently, except those of the family encoding the most abundant surface glycoproteins, which are subject to mutually exclusive expression. PCR analyses showed that exchange of the expressed gene of the latter family occurs frequently, possibly favored by the location of the genes proximal to the telomere because this allows concomitant telomere exchange. Our observations suggest that (i) the P. jirovecii cell surface is made of a complex mixture of different surface proteins, with a majority of a single isoform of the most abundant glycoprotein, (ii) genetic mosaicism within each family ensures variation of the glycoproteins, and (iii) the strategy of the fungus consists of the continuous production of new subpopulations composed of cells that are antigenically different. IMPORTANCE Pneumocystis jirovecii is a fungus causing severe pneumonia in immunocompromised individuals. It is the second most frequent life-threatening invasive fungal infection. We have studied the mechanisms

  19. Detection of a surface breaking crack by using the centroid variations of laser ultrasonic spectrums

    International Nuclear Information System (INIS)

    Park, Seung Kyu; Baik, Sung Hoon; Lim, Chang Hwan; Joo, Young Sang; Jung, Hyun Kyu; Cha, Hyung Ki; Kang, Young June

    2006-01-01

    A laser ultrasonic system is a non-contact inspection device with a wide-band spectrum and a high spatial resolution. It provides absolute measurements of the moving distance and it can be applied to hard-to-access locations including curved or rough surfaces like in a nuclear power plant. In this paper, we have investigated the detection methods of the depth of a surface-breaking crack by using the surface wave of a laser ultrasound. The filtering function of a surface-breaking crack is a kind of a low-pass filter. The higher frequency components are more highly decreased in proportion to the crack depth. Also, the center frequency value of each ultrasound spectrum is decreased in proportion to the crack depth. We extracted the depth information of a surface-breaking crack by observing the centroid variation of the frequency spectrum. We describe the experimental results to detect the crack depth information by using the peak-to-valley values in the time domain and the center frequency values in the frequency domain.

  20. Enhancing the representation of subgrid land surface characteristics in land surface models

    Directory of Open Access Journals (Sweden)

    Y. Ke

    2013-09-01

    Full Text Available Land surface heterogeneity has long been recognized as important to represent in the land surface models. In most existing land surface models, the spatial variability of surface cover is represented as subgrid composition of multiple surface cover types, although subgrid topography also has major controls on surface processes. In this study, we developed a new subgrid classification method (SGC that accounts for variability of both topography and vegetation cover. Each model grid cell was represented with a variable number of elevation classes and each elevation class was further described by a variable number of vegetation types optimized for each model grid given a predetermined total number of land response units (LRUs. The subgrid structure of the Community Land Model (CLM was used to illustrate the newly developed method in this study. Although the new method increases the computational burden in the model simulation compared to the CLM subgrid vegetation representation, it greatly reduced the variations of elevation within each subgrid class and is able to explain at least 80% of the total subgrid plant functional types (PFTs. The new method was also evaluated against two other subgrid methods (SGC1 and SGC2 that assigned fixed numbers of elevation and vegetation classes for each model grid (SGC1: M elevation bands–N PFTs method; SGC2: N PFTs–M elevation bands method. Implemented at five model resolutions (0.1°, 0.25°, 0.5°, 1.0°and 2.0° with three maximum-allowed total number of LRUs (i.e., NLRU of 24, 18 and 12 over North America (NA, the new method yielded more computationally efficient subgrid representation compared to SGC1 and SGC2, particularly at coarser model resolutions and moderate computational intensity (NLRU = 18. It also explained the most PFTs and elevation variability that is more homogeneously distributed spatially. The SGC method will be implemented in CLM over the NA continent to assess its impacts on

  1. Global modelling of Cryptosporidium in surface water

    Science.gov (United States)

    Vermeulen, Lucie; Hofstra, Nynke

    2016-04-01

    Introduction Waterborne pathogens that cause diarrhoea, such as Cryptosporidium, pose a health risk all over the world. In many regions quantitative information on pathogens in surface water is unavailable. Our main objective is to model Cryptosporidium concentrations in surface waters worldwide. We present the GloWPa-Crypto model and use the model in a scenario analysis. A first exploration of global Cryptosporidium emissions to surface waters has been published by Hofstra et al. (2013). Further work has focused on modelling emissions of Cryptosporidium and Rotavirus to surface waters from human sources (Vermeulen et al 2015, Kiulia et al 2015). A global waterborne pathogen model can provide valuable insights by (1) providing quantitative information on pathogen levels in data-sparse regions, (2) identifying pathogen hotspots, (3) enabling future projections under global change scenarios and (4) supporting decision making. Material and Methods GloWPa-Crypto runs on a monthly time step and represents conditions for approximately the year 2010. The spatial resolution is a 0.5 x 0.5 degree latitude x longitude grid for the world. We use livestock maps (http://livestock.geo-wiki.org/) combined with literature estimates to calculate spatially explicit livestock Cryptosporidium emissions. For human Cryptosporidium emissions, we use UN population estimates, the WHO/UNICEF JMP sanitation country data and literature estimates of wastewater treatment. We combine our emissions model with a river routing model and data from the VIC hydrological model (http://vic.readthedocs.org/en/master/) to calculate concentrations in surface water. Cryptosporidium survival during transport depends on UV radiation and water temperature. We explore pathogen emissions and concentrations in 2050 with the new Shared Socio-economic Pathways (SSPs) 1 and 3. These scenarios describe plausible future trends in demographics, economic development and the degree of global integration. Results and

  2. Variational Assimilation of Sparse and Uncertain Satellite Data For 1D Saint-Venant River Models

    Science.gov (United States)

    Garambois, P. A.; Brisset, P.; Monnier, J.; Roux, H.

    2016-12-01

    Profusion of satellites are providing increasingly accurate measurements of continental water cyle, and water bodies variations while in situ observability is declining. The future Surface Water and Ocean Topography (SWOT) mission will provide maps of river surface elevations widths and slopes with an almost global coverage and temporal revisits. This will offer the possibility to address a larger variety of inverse problems in surface hydrology. Data assimilation techniques, that are broadly used in several scientific fields, aim to optimally combine models, system observations and prior information. Variational assimilation consists in iterative minimization of a discrepency measure between model outputs and observations, here for retrieving boundary conditions and parameters of a 1D Saint Venant model. Nevertheless, inferring river discharge and hydraulic parameters thanks to the observation of river surface is not straightforward. This is particularly true in the case of sparse and uncertain observations of flow state variables since they are governed by nonlinear physical processes. This paper investigates the identifiability of hydraulic controls given sparse and uncertain satellite observations of a river. The identifiability of river discharge alone and with roughness is tested for several spatio temporal patterns of river observations, including SWOT like observations. A new 1D Shallow water model with variational data assimilation, within the DassFlow chain is presented as well as postprocessing and observation operator dedicated to the future SWOT and SWOT simulator data. In view to decrease inverse problem dimensionality discharge is represented in a reduced basis. Moreover we introduce an original and reduced parametrization of the flow resistance that can account for various flow regimes along with a cross section design dedicated to remote sensing. We show which discharge temporal frequencies can be identified w.r.t observation ones and at which

  3. Olkiluoto surface and near-surface hydrological modelling in 2010

    International Nuclear Information System (INIS)

    Karvonen, T.

    2011-08-01

    The modeling approaches carried out with the Olkiluoto surface hydrological model (SHYD) include palaeohydrological evolution of the Olkiluoto Island, examination of the boundary condition at the geosphere-biosphere interface zone, simulations related to infiltration experiment, prediction of the influence of ONKALO on hydraulic head in shallow and deep bedrock and optimisation of the shallow monitoring network. A so called short-term prediction system was developed for continuous updating of the estimated drawdowns caused by ONKALO. The palaeohydrological simulations were computed for a period starting from the time when the highest hills on Olkiluoto Island rose above sea level around 2 500 years ago. The input data needed in the model were produced by the UNTAMO-toolbox. The groundwater flow evolution is primarily driven by the postglacial land uplift and the uncertainty in the land uplift model is the biggest single factor that influences the accuracy of the results. The consistency of the boundary condition at the geosphere-biosphere interface zone (GBIZ) was studied during 2010. The comparison carried out during 2010 showed that pressure head profiles computed with the SHYD model and deep groundwater flow model FEFTRA are in good agreement with each other in the uppermost 100 m of the bedrock. This implies that flux profiles computed with the two approaches are close to each other and hydraulic heads computed at level z=0 m with the SHYD can be used as head boundary condition in the deep groundwater flow model FEFTRA. The surface hydrological model was used to analyse the results of the infiltration experiment. Increase in bedrock recharge inside WCA explains around 60-63 % from the amount of water pumped from OL-KR14 and 37-40 % of the water pumped from OL-KR14 flows towards pumping section via the hydrogeological zones. Pumping from OL-KR14 has only a minor effect on heads and fluxes in zones HZ19A and HZ19C compared to responses caused by leakages into

  4. Does quality control matter? Surface urban heat island intensity variations estimated by satellite-derived land surface temperature products

    Science.gov (United States)

    Lai, Jiameng; Zhan, Wenfeng; Huang, Fan; Quan, Jinling; Hu, Leiqiu; Gao, Lun; Ju, Weimin

    2018-05-01

    The temporally regular and spatially comprehensive monitoring of surface urban heat islands (SUHIs) have been extremely difficult, until the advent of satellite-based land surface temperature (LST) products. However, these LST products have relatively higher errors compared to in situ measurements. This has resulted in comparatively inaccurate estimations of SUHI indicators and, consequently, may have distorted interpretations of SUHIs. Although reports have shown that LST qualities are important for SUHI interpretations, systematic investigations of the response of SUHI indicators to LST qualities across cities with dissimilar bioclimates are rare. To address this issue, we chose eighty-six major cities across mainland China and analyzed SUHI intensity (SUHII) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) LST data. The LST-based SUHII differences due to inclusion or exclusion of MODIS quality control (QC) flags (i.e., ΔSUHII) were evaluated. Our major findings included, but are not limited to, the following four aspects: (1) SUHIIs can be significantly impacted by MODIS QC flags, and the associated QC-induced ΔSUHIIs generally accounted for 24.3% (29.9%) of the total SUHII value during the day (night); (2) the ΔSUHIIs differed between seasons, with considerable differences between transitional (spring and autumn) and extreme (summer and winter) seasons; (3) significant discrepancies also appeared among cities located in northern and southern regions, with northern cities often possessing higher annual mean ΔSUHIIs. The internal variations of ΔSUHIIs within individual cities also showed high heterogeneity, with ΔSUHII variations that generally exceeded 5.0 K (3.0 K) in northern (southern) cities; (4) ΔSUHIIs were negatively related to SUHIIs and cloud cover percentages (mostly in transitional seasons). No significant relationship was found in the extreme seasons. Our findings highlight the need to be extremely cautious when using LST

  5. On Geometric Variational Models for Inpainting Surface Holes (PREPRINT)

    National Research Council Canada - National Science Library

    Caselles, Vicent; Haro, Gloria; Sapiro, Guillermo; Verdera, Joan

    2006-01-01

    .... These equations include a system for the joint interpolation of scalar and vector fields, a Laplacian-based minimization, a mean curvature diffusion flow, and an absolutely minimizing Lipschitz extension...

  6. Modeling of electron time variations in the radiation belts

    International Nuclear Information System (INIS)

    Chan, K.W.; Teague, M.J.; Schofield, N.J.; Vette, J.I.

    1979-01-01

    A review of the temporal variation in the trapped electron population of the inner and outer radiation zones is presented. Techniques presently used for modeling these zones are discussed and their deficiencies identified. An intermediate region is indicated between the zones in which the present modeling techniques are inadequate due to the magnitude and frequency of magnetic storms. Future trends are examined, and it is suggested that modeling of individual magnetic storms may be required in certain L bands. An analysis of seven magnetic storms is presented, establishing the independence of the depletion time of the storm flux and the storm magnitude. Provisional correlation between the storm magnitude and the Dst index is demonstrated

  7. Nuclear surface vibrations in bag models

    International Nuclear Information System (INIS)

    Tomio, L.

    1984-01-01

    The main difficulties found in the hadron bag models are reviewed from the original version of the MIT bag model. Following, with the aim to answer two of the main difficulties in bag models, viz., the parity and the divergence illness, a dynamical model is presented. In the model, the confinement surface of the quarks (bag) is treated like a real physical object which interacts with the quarks and is exposed to vibrations. The model is applied to the nucleon, being observed that his spectrum, in the first excited levels, can be reproduced with resonable precision and obeying to the correct parity order. In the same way that in a similar work of Brown et al., it is observed to be instrumental the inclusion of the effect due to pions. (L.C.) [pt

  8. Variations of little Higgs models and their electroweak constraints

    International Nuclear Information System (INIS)

    Csaki, Csaba; Hubisz, Jay; Meade, Patrick; Kribs, Graham D.; Terning, John

    2003-01-01

    We calculate the tree-level electroweak precision constraints on a wide class of little Higgs models including variations of the littlest Higgs SU(5)/SO(5), SU(6)/Sp(6), and SU(4) 4 /SU(3) 4 models. By performing a global fit to the precision data we find that for generic regions of the parameter space the bound on the symmetry breaking scale f is several TeV, where we have kept the normalization of f constant in the different models. For example, the 'minimal' implementation of SU(6)/Sp(6) is bounded by f>3.0 TeV throughout most of the parameter space, and SU(4) 4 /SU(3) 4 is bounded by f 2 ≡f 1 2 +f 2 2 >(4.2 TeV) 2 . In certain models, such as SU(4) 4 /SU(3) 4 , a large f does not directly imply a large amount of fine-tuning since the heavy-fermion masses that contribute to the Higgs boson mass can be lowered below f for a carefully chosen set of parameters. We also find that for certain models (or variations) there exist regions of parameter space in which the bound on f can be lowered into the range 1-2 TeV. These regions are typically characterized by a small mixing between heavy and standard model gauge bosons and a small (or vanishing) coupling between heavy U(1) gauge bosons and light fermions. Whether such a region of parameter space is natural or not is ultimately contingent on the UV completion

  9. Residential radon in Finland: sources, variation, modelling and dose comparisons

    Energy Technology Data Exchange (ETDEWEB)

    Arvela, H

    1995-09-01

    The study deals with sources of indoor radon in Finland, seasonal variations in radon concentration, the effect of house construction and ventilation and also with the radiation dose from indoor radon and terrestrial gamma radiation. The results are based on radon measurements in approximately 4000 dwellings and on air exchange measurements in 250 dwellings as well as on model calculations. The results confirm that convective soil air flow is by far the most important source of indoor radon in Finnish low-rise residential housing. (97 refs., 61 figs., 30 tabs.).

  10. Residential radon in Finland: sources, variation, modelling and dose comparisons

    International Nuclear Information System (INIS)

    Arvela, H.

    1995-09-01

    The study deals with sources of indoor radon in Finland, seasonal variations in radon concentration, the effect of house construction and ventilation and also with the radiation dose from indoor radon and terrestrial gamma radiation. The results are based on radon measurements in approximately 4000 dwellings and on air exchange measurements in 250 dwellings as well as on model calculations. The results confirm that convective soil air flow is by far the most important source of indoor radon in Finnish low-rise residential housing. (97 refs., 61 figs., 30 tabs.)

  11. Surface and near-surface hydrological model of Olkiluoto island

    International Nuclear Information System (INIS)

    Karvonen, T.

    2008-04-01

    The aim of the study was to develop a 3D-model that calculates the overall water balance components of Olkiluoto Island in the present-day condition utilizing the existing extensive data sets available. The model links the unsaturated and saturated soil water in the overburden and groundwater in bedrock to a continuous pressure system. The parameterization of land use and vegetation was done in such a way that the model can later on be used for description of the past evolution of the overburden hydrology at the site and overburden's hydrological evolution in the future. Measured groundwater level in overburden tubes, pressure heads in shallow bedrock holes, snow depth, soil temperature, frost depth and discharge measurements were used in assessing the performance of the models in the calibration period (01.05.2001- 31.12.2005). Computed groundwater level variation can be characterized by variables ΔH MEAS and ΔH COMP , which are the difference between maximum and minimum measured and computed groundwater level value during the calibration period. Average ΔH MEAS for all tubes located in fine-textured till soil was 1.99 m and the corresponding computed value ΔH COMP was 1.83 m. Average ΔH MEAS for all tubes located in sandy till soil was 2.12 m and the corresponding computed value ΔH COMP was 1.93 m. The computed results indicate that in future studies it is necessary to divide the two most important soil types into several subclasses. In the present study the uncertainty and sensitivity analysis was carried out through a parameter uncertainty framework known as GLUE. According to the uncertainty analysis the average yearly runoff was around 175 mm a -1 and 50 % confidence limits were 155 and 195 mm a -1 . Measured average yearly runoff during the calibration period was 190 mm a -1 . Average yearly evapotranspiration estimate was 310 mm a -1 and the 50 % confidence limits were 290 and 330 mm a -1 . Average value for recharge through the bedrock system was 1

  12. A variational multiscale constitutive model for nanocrystalline materials

    KAUST Repository

    Gurses, Ercan

    2011-03-01

    This paper presents a variational multi-scale constitutive model in the finite deformation regime capable of capturing the mechanical behavior of nanocrystalline (nc) fcc metals. The nc-material is modeled as a two-phase material consisting of a grain interior phase and a grain boundary effected zone (GBAZ). A rate-independent isotropic porous plasticity model is employed to describe the GBAZ, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full dislocation mediated plasticity is employed for the grain interior. The constitutive models of both phases are formulated in a small strain framework and extended to finite deformation by use of logarithmic and exponential mappings. Assuming the rule of mixtures, the overall behavior of a given grain is obtained via volume averaging. The scale transition from a single grain to a polycrystal is achieved by Taylor-type homogenization where a log-normal grain size distribution is assumed. It is shown that the proposed model is able to capture the inverse HallPetch effect, i.e., loss of strength with grain size refinement. Finally, the predictive capability of the model is validated against experimental results on nanocrystalline copper and nickel. © 2010 Elsevier Ltd. All rights reserved.

  13. INTEGRATION OF HETEROGENOUS DIGITAL SURFACE MODELS

    Directory of Open Access Journals (Sweden)

    R. Boesch

    2012-08-01

    Full Text Available The application of extended digital surface models often reveals, that despite an acceptable global accuracy for a given dataset, the local accuracy of the model can vary in a wide range. For high resolution applications which cover the spatial extent of a whole country, this can be a major drawback. Within the Swiss National Forest Inventory (NFI, two digital surface models are available, one derived from LiDAR point data and the other from aerial images. Automatic photogrammetric image matching with ADS80 aerial infrared images with 25cm and 50cm resolution is used to generate a surface model (ADS-DSM with 1m resolution covering whole switzerland (approx. 41000 km2. The spatially corresponding LiDAR dataset has a global point density of 0.5 points per m2 and is mainly used in applications as interpolated grid with 2m resolution (LiDAR-DSM. Although both surface models seem to offer a comparable accuracy from a global view, local analysis shows significant differences. Both datasets have been acquired over several years. Concerning LiDAR-DSM, different flight patterns and inconsistent quality control result in a significantly varying point density. The image acquisition of the ADS-DSM is also stretched over several years and the model generation is hampered by clouds, varying illumination and shadow effects. Nevertheless many classification and feature extraction applications requiring high resolution data depend on the local accuracy of the used surface model, therefore precise knowledge of the local data quality is essential. The commercial photogrammetric software NGATE (part of SOCET SET generates the image based surface model (ADS-DSM and delivers also a map with figures of merit (FOM of the matching process for each calculated height pixel. The FOM-map contains matching codes like high slope, excessive shift or low correlation. For the generation of the LiDAR-DSM only first- and last-pulse data was available. Therefore only the point

  14. [Ciliate diversity and spatiotemporal variation in surface sediments of Yangtze River estuary hypoxic zone].

    Science.gov (United States)

    Feng, Zhao; Kui-Dong, Xu; Zhao-Cui, Meng

    2012-12-01

    By using denaturing gradient gel electrophoresis (DGGE) and sequencing as well as Ludox-QPS method, an investigation was made on the ciliate diversity and its spatiotemporal variation in the surface sediments at three sites of Yangtze River estuary hypoxic zone in April and August 2011. The ANOSIM analysis indicated that the ciliate diversity had significant difference among the sites (R = 0.896, P = 0.0001), but less difference among seasons (R = 0.043, P = 0.207). The sequencing of 18S rDNA DGGE bands revealed that the most predominant groups were planktonic Choreotrichia and Oligotrichia. The detection by Ludox-QPS method showed that the species number and abundance of active ciliates were maintained at a higher level, and increased by 2-5 times in summer, as compared with those in spring. Both the Ludox-QPS method and the DGGE technique detected that the ciliate diversity at the three sites had the similar variation trend, and the Ludox-QPS method detected that there was a significant variation in the ciliate species number and abundance between different seasons. The species number detected by Ludox-QPS method was higher than that detected by DGGE bands. Our study indicated that the ciliates in Yangtze River estuary hypoxic zone had higher diversity and abundance, with the potential to supply food for the polyps of jellyfish.

  15. GEOQUIMICO : an interactive tool for comparing sorption conceptual models (surface complexation modeling versus K[D])

    International Nuclear Information System (INIS)

    Hammond, Glenn E.; Cygan, Randall Timothy

    2007-01-01

    Within reactive geochemical transport, several conceptual models exist for simulating sorption processes in the subsurface. Historically, the K D approach has been the method of choice due to ease of implementation within a reactive transport model and straightforward comparison with experimental data. However, for modeling complex sorption phenomenon (e.g. sorption of radionuclides onto mineral surfaces), this approach does not systematically account for variations in location, time, or chemical conditions, and more sophisticated methods such as a surface complexation model (SCM) must be utilized. It is critical to determine which conceptual model to use; that is, when the material variation becomes important to regulatory decisions. The geochemical transport tool GEOQUIMICO has been developed to assist in this decision-making process. GEOQUIMICO provides a user-friendly framework for comparing the accuracy and performance of sorption conceptual models. The model currently supports the K D and SCM conceptual models. The code is written in the object-oriented Java programming language to facilitate model development and improve code portability. The basic theory underlying geochemical transport and the sorption conceptual models noted above is presented in this report. Explanations are provided of how these physicochemical processes are instrumented in GEOQUIMICO and a brief verification study comparing GEOQUIMICO results to data found in the literature is given

  16. An assessment of surface emissivity variation effects on plasma uniformity analysis using IR cameras

    Science.gov (United States)

    Greenhalgh, Abigail; Showers, Melissa; Biewer, Theodore

    2017-10-01

    The Prototype-Material Plasma Exposure eXperiment (Proto-MPEX) is a linear plasma device operating at Oak Ridge National Laboratory (ORNL). Its purpose is to test plasma source and heating concepts for the planned Material Plasma Exposure eXperiment (MPEX), which has the mission to test the plasma-material interactions under fusion reactor conditions. In this device material targets will be exposed to high heat fluxes (>10 MW/m2). To characterize the heat fluxes to the target a IR thermography system is used taking up to 432 frames per second videos. The data is analyzed to determine the surface temperature on the target in specific regions of interest. The IR analysis has indicated a low level of plasma uniformity; the plasma often deposits more heat to the edge of the plate than the center. An essential parameter for IR temperature calculation is the surface emissivity of the plate (stainless steel). A study has been performed to characterize the variation in the surface emissivity of the plate as its temperature changes and its surface finish is modified by plasma exposure.

  17. SPATIAL AND TEMPORAL VARIATION OF LAND SURFACE TEMPERATURE IN FUJIAN PROVINCE FROM 2001 TO 2015

    Directory of Open Access Journals (Sweden)

    Y. Li

    2018-04-01

    Full Text Available Land surface temperature (LST is an essential parameter in the physics of land surface processes. The spatiotemporal variations of LST on the Fujian province were studied using AQUA Moderate Resolution Imaging Spectroradiometer LST data. Considering the data gaps in remotely sensed LST products caused by cloud contamination, the Savitzky-Golay (S-G filter method was used to eliminate the influence of cloud cover and to describe the periodical signals of LST. Observed air temperature data from 27 weather stations were employed to evaluate the fitting performance of the S-G filter method. Results indicate that S-G can effectively fit the LST time series and remove the influence of cloud cover. Based on the S-G-derived result, Spatial and temporal Variations of LST in Fujian province from 2001 to 2015 are analysed through slope analysis. The results show that: 1 the spatial distribution of annual mean LST generally exhibits consistency with altitude in the study area and the average of LST was much higher in the east than in the west. 2 The annual mean temperature of LST declines slightly among 15 years in Fujian. 3 Slope analysis reflects the spatial distribution characteristics of LST changing trend in Fujian.Improvement areas of LST are mainly concentrated in the urban areas of Fujian, especially in the eastern urban areas. Apparent descent areas are mainly distributed in the area of Zhangzhou and eastern mountain area.

  18. Spatial and Temporal Variation of Land Surface Temperature in Fujian Province from 2001 TO 2015

    Science.gov (United States)

    Li, Y.; Wang, X.; Ding, Z.

    2018-04-01

    Land surface temperature (LST) is an essential parameter in the physics of land surface processes. The spatiotemporal variations of LST on the Fujian province were studied using AQUA Moderate Resolution Imaging Spectroradiometer LST data. Considering the data gaps in remotely sensed LST products caused by cloud contamination, the Savitzky-Golay (S-G) filter method was used to eliminate the influence of cloud cover and to describe the periodical signals of LST. Observed air temperature data from 27 weather stations were employed to evaluate the fitting performance of the S-G filter method. Results indicate that S-G can effectively fit the LST time series and remove the influence of cloud cover. Based on the S-G-derived result, Spatial and temporal Variations of LST in Fujian province from 2001 to 2015 are analysed through slope analysis. The results show that: 1) the spatial distribution of annual mean LST generally exhibits consistency with altitude in the study area and the average of LST was much higher in the east than in the west. 2) The annual mean temperature of LST declines slightly among 15 years in Fujian. 3) Slope analysis reflects the spatial distribution characteristics of LST changing trend in Fujian.Improvement areas of LST are mainly concentrated in the urban areas of Fujian, especially in the eastern urban areas. Apparent descent areas are mainly distributed in the area of Zhangzhou and eastern mountain area.

  19. Spatiotemporal variation of surface shortwave forcing from fire-induced albedo change in interior Alaska

    Science.gov (United States)

    Huang, Shengli; Dahal, Devendra; Liu, Heping; Jin, Suming; Young, Claudia J.; Liu, Shuang; Liu, Shu-Guang

    2015-01-01

    The albedo change caused by both fires and subsequent succession is spatially heterogeneous, leading to the need to assess the spatiotemporal variation of surface shortwave forcing (SSF) as a component to quantify the climate impacts of high-latitude fires. We used an image reconstruction approach to compare postfire albedo with the albedo assuming fires had not occurred. Combining the fire-caused albedo change from the 2001-2010 fires in interior Alaska and the monthly surface incoming solar radiation, we examined the spatiotemporal variation of SSF in the early successional stage of around 10 years. Our results showed that while postfire albedo generally increased in fall, winter, and spring, some burned areas could show an albedo decrease during these seasons. In summer, the albedo increased for several years and then declined again. The spring SSF distribution did not show a latitudinal decrease from south to north as previously reported. The results also indicated that although the SSF is usually largely negative in the early successional years, it may not be significant during the first postfire year. The annual 2005-2010 SSF for the 2004 fire scars was -1.30, -4.40, -3.31, -4.00, -3.42, and -2.47 Wm-2. The integrated annual SSF map showed significant spatial variation with a mean of -3.15 Wm-2 and a standard deviation of 3.26 Wm-2, 16% of burned areas having positive SSF. Our results suggest that boreal deciduous fires would be less positive for climate change than boreal evergreen fires. Future research is needed to comprehensively investigate the spatiotemporal radiative and non-radiative forcings to determine the effect of boreal fires on climate.

  20. Sparse linear models: Variational approximate inference and Bayesian experimental design

    International Nuclear Information System (INIS)

    Seeger, Matthias W

    2009-01-01

    A wide range of problems such as signal reconstruction, denoising, source separation, feature selection, and graphical model search are addressed today by posterior maximization for linear models with sparsity-favouring prior distributions. The Bayesian posterior contains useful information far beyond its mode, which can be used to drive methods for sampling optimization (active learning), feature relevance ranking, or hyperparameter estimation, if only this representation of uncertainty can be approximated in a tractable manner. In this paper, we review recent results for variational sparse inference, and show that they share underlying computational primitives. We discuss how sampling optimization can be implemented as sequential Bayesian experimental design. While there has been tremendous recent activity to develop sparse estimation, little attendance has been given to sparse approximate inference. In this paper, we argue that many problems in practice, such as compressive sensing for real-world image reconstruction, are served much better by proper uncertainty approximations than by ever more aggressive sparse estimation algorithms. Moreover, since some variational inference methods have been given strong convex optimization characterizations recently, theoretical analysis may become possible, promising new insights into nonlinear experimental design.

  1. Sparse linear models: Variational approximate inference and Bayesian experimental design

    Energy Technology Data Exchange (ETDEWEB)

    Seeger, Matthias W [Saarland University and Max Planck Institute for Informatics, Campus E1.4, 66123 Saarbruecken (Germany)

    2009-12-01

    A wide range of problems such as signal reconstruction, denoising, source separation, feature selection, and graphical model search are addressed today by posterior maximization for linear models with sparsity-favouring prior distributions. The Bayesian posterior contains useful information far beyond its mode, which can be used to drive methods for sampling optimization (active learning), feature relevance ranking, or hyperparameter estimation, if only this representation of uncertainty can be approximated in a tractable manner. In this paper, we review recent results for variational sparse inference, and show that they share underlying computational primitives. We discuss how sampling optimization can be implemented as sequential Bayesian experimental design. While there has been tremendous recent activity to develop sparse estimation, little attendance has been given to sparse approximate inference. In this paper, we argue that many problems in practice, such as compressive sensing for real-world image reconstruction, are served much better by proper uncertainty approximations than by ever more aggressive sparse estimation algorithms. Moreover, since some variational inference methods have been given strong convex optimization characterizations recently, theoretical analysis may become possible, promising new insights into nonlinear experimental design.

  2. Modeling superhydrophobic surfaces comprised of random roughness

    Science.gov (United States)

    Samaha, M. A.; Tafreshi, H. Vahedi; Gad-El-Hak, M.

    2011-11-01

    We model the performance of superhydrophobic surfaces comprised of randomly distributed roughness that resembles natural surfaces, or those produced via random deposition of hydrophobic particles. Such a fabrication method is far less expensive than ordered-microstructured fabrication. The present numerical simulations are aimed at improving our understanding of the drag reduction effect and the stability of the air-water interface in terms of the microstructure parameters. For comparison and validation, we have also simulated the flow over superhydrophobic surfaces made up of aligned or staggered microposts for channel flows as well as streamwise or spanwise ridge configurations for pipe flows. The present results are compared with other theoretical and experimental studies. The numerical simulations indicate that the random distribution of surface roughness has a favorable effect on drag reduction, as long as the gas fraction is kept the same. The stability of the meniscus, however, is strongly influenced by the average spacing between the roughness peaks, which needs to be carefully examined before a surface can be recommended for fabrication. Financial support from DARPA, contract number W91CRB-10-1-0003, is acknowledged.

  3. A Variational Approach to the Modeling of MIMO Systems

    Directory of Open Access Journals (Sweden)

    Jraifi A

    2007-01-01

    Full Text Available Motivated by the study of the optimization of the quality of service for multiple input multiple output (MIMO systems in 3G (third generation, we develop a method for modeling MIMO channel . This method, which uses a statistical approach, is based on a variational form of the usual channel equation. The proposed equation is given by with scalar variable . Minimum distance of received vectors is used as the random variable to model MIMO channel. This variable is of crucial importance for the performance of the transmission system as it captures the degree of interference between neighbors vectors. Then, we use this approach to compute numerically the total probability of errors with respect to signal-to-noise ratio (SNR and then predict the numbers of antennas. By fixing SNR variable to a specific value, we extract informations on the optimal numbers of MIMO antennas.

  4. Stochastic models for surface diffusion of molecules

    Energy Technology Data Exchange (ETDEWEB)

    Shea, Patrick, E-mail: patrick.shea@dal.ca; Kreuzer, Hans Jürgen [Department of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada)

    2014-07-28

    We derive a stochastic model for the surface diffusion of molecules, starting from the classical equations of motion for an N-atom molecule on a surface. The equation of motion becomes a generalized Langevin equation for the center of mass of the molecule, with a non-Markovian friction kernel. In the Markov approximation, a standard Langevin equation is recovered, and the effect of the molecular vibrations on the diffusion is seen to lead to an increase in the friction for center of mass motion. This effective friction has a simple form that depends on the curvature of the lowest energy diffusion path in the 3N-dimensional coordinate space. We also find that so long as the intramolecular forces are sufficiently strong, memory effects are usually not significant and the Markov approximation can be employed, resulting in a simple one-dimensional model that can account for the effect of the dynamics of the molecular vibrations on the diffusive motion.

  5. The global mean sea surface model WHU2013

    Directory of Open Access Journals (Sweden)

    Taoyong Jin

    2016-05-01

    Full Text Available The mean sea surface (MSS model is an important reference for the study of charting datum and sea level change. A global MSS model named WHU2013, with 2′ × 2′ spatial resolution between 80°S and 84°N, is established in this paper by combining nearly 20 years of multi-satellite altimetric data that include Topex/Poseidon (T/P, Jason-1, Jason-2, ERS-2, ENVISAT and GFO Exact Repeat Mission (ERM data, ERS-1/168, Jason-1/C geodetic mission data and Cryosat-2 low resolution mode (LRM data. All the ERM data are adjusted by the collinear method to achieve the mean along-track sea surface height (SSH, and the combined dataset of T/P, Jason-1 and Jason-2 from 1993 to 2012 after collinear adjustment is used as the reference data. The sea level variations in the non-ERM data (geodetic mission data and LRM data are mainly investigated, and a combined method is proposed to correct the sea level variations between 66°S and 66°N by along-track sea level variation time series and beyond 66°S or 66°N by seasonal sea level variations. In the crossover adjustment between multi-altimetric data, a stepwise method is used to solve the problem of inconsistency in the reference data between the high and low latitude regions. The proposed model is compared with the CNES-CLS2011 and DTU13 MSS models, and the standard derivation (STD of the differences between the models is about 5 cm between 80°S and 84°N, less than 3 cm between 66°S and 66°N, and less than 4 cm in the China Sea and its adjacent sea. Furthermore, the three models exhibit a good agreement in the SSH differences and the along-track gradient of SSH following comparisons with satellite altimetry data.

  6. Variation with age of anisotropy under oceans, from great circle surface waves

    International Nuclear Information System (INIS)

    Journet, B.; Jobert, N.

    1982-01-01

    Global great circle measurements of regionalized mantle Love wave phase velocities are interpreted in terms of regional models. The same study had been made by J. J. Leveque (1980) for Rayleigh waves, and the resulting models for the two oceanic regions of different ages are used as a basis for comparison: the observed Love wave dispersion cannot be explained with these models if isotropic. The models obtained by inversion of Love wave data are compared with the models mentioned; the discrepancy appearing in the 250 km depth range between the velocities β/sub H/ and β/sub V/ of respectively SH and SV waves is indicative of polarization anisotropy. Moreover, we put forward a significant variation from young to old oceans: the difference between β/sub H/, and β/sub V/ is of the order of 1% for the former, compared to 3% for the latter. This variation can bring information about the behaviour of upper mantle materials in connection with the motion of oceanic plates

  7. Cohesive zone modelling of wafer bonding and fracture: effect of patterning and toughness variations

    Science.gov (United States)

    Kubair, D. V.; Spearing, S. M.

    2006-03-01

    Direct wafer bonding has increasingly become popular in the manufacture of microelectromechanical systems and semiconductor microelectronics components. The success of the bonding process is controlled by variables such as wafer flatness and surface preparation. In order to understand the effects of these variables, spontaneous planar crack propagation simulations were performed using the spectral scheme in conjunction with a cohesive zone model. The fracture-toughness on the bond interface is varied to simulate the effect of surface roughness (nanotopography) and patterning. Our analysis indicated that the energetics of crack propagation is sensitive to the local surface property variations. The patterned wafers are tougher (well bonded) than the unpatterned ones of the same average fracture-toughness.

  8. BUILDING DETECTION USING AERIAL IMAGES AND DIGITAL SURFACE MODELS

    Directory of Open Access Journals (Sweden)

    J. Mu

    2017-05-01

    Full Text Available In this paper a method for building detection in aerial images based on variational inference of logistic regression is proposed. It consists of three steps. In order to characterize the appearances of buildings in aerial images, an effective bag-of-Words (BoW method is applied for feature extraction in the first step. In the second step, a classifier of logistic regression is learned using these local features. The logistic regression can be trained using different methods. In this paper we adopt a fully Bayesian treatment for learning the classifier, which has a number of obvious advantages over other learning methods. Due to the presence of hyper prior in the probabilistic model of logistic regression, approximate inference methods have to be applied for prediction. In order to speed up the inference, a variational inference method based on mean field instead of stochastic approximation such as Markov Chain Monte Carlo is applied. After the prediction, a probabilistic map is obtained. In the third step, a fully connected conditional random field model is formulated and the probabilistic map is used as the data term in the model. A mean field inference is utilized in order to obtain a binary building mask. A benchmark data set consisting of aerial images and digital surfaced model (DSM released by ISPRS for 2D semantic labeling is used for performance evaluation. The results demonstrate the effectiveness of the proposed method.

  9. SEMIC: an efficient surface energy and mass balance model applied to the Greenland ice sheet

    Directory of Open Access Journals (Sweden)

    M. Krapp

    2017-07-01

    Full Text Available We present SEMIC, a Surface Energy and Mass balance model of Intermediate Complexity for snow- and ice-covered surfaces such as the Greenland ice sheet. SEMIC is fast enough for glacial cycle applications, making it a suitable replacement for simpler methods such as the positive degree day (PDD method often used in ice sheet modelling. Our model explicitly calculates the main processes involved in the surface energy and mass balance, while maintaining a simple interface and requiring minimal data input to drive it. In this novel approach, we parameterise diurnal temperature variations in order to more realistically capture the daily thaw–freeze cycles that characterise the ice sheet mass balance. We show how to derive optimal model parameters for SEMIC specifically to reproduce surface characteristics and day-to-day variations similar to the regional climate model MAR (Modèle Atmosphérique Régional, version 2 and its incorporated multilayer snowpack model SISVAT (Soil Ice Snow Vegetation Atmosphere Transfer. A validation test shows that SEMIC simulates future changes in surface temperature and surface mass balance in good agreement with the more sophisticated multilayer snowpack model SISVAT included in MAR. With this paper, we present a physically based surface model to the ice sheet modelling community that is general enough to be used with in situ observations, climate model, or reanalysis data, and that is at the same time computationally fast enough for long-term integrations, such as glacial cycles or future climate change scenarios.

  10. Modelling of the dose-rate variations with depth in the Martian regolith using GEANT4

    International Nuclear Information System (INIS)

    Morthekai, P.; Jain, M.; Dartnell, L.; Murray, A.S.; Botter-Jensen, L.; Desorgher, L.

    2007-01-01

    The environmental radiation field at the Martian surface consists mainly of Galactic Cosmic Rays (GCR) and charged particles ejected during the Solar Particle Events (SPE). Interactions between these radiation fluxes and the regolith result in a complex radiation field that varies both as a function of depth and time and can only be quantified using radiation transport models. We first describe here the main issues and constraints in deriving Martian dose rates. Preliminary results, obtained using the GEANT4 Monte Carlo simulation tool kit, suggest the surface dose rate is ∼63 mGy a -1 during quiet periods in solar activity. The accuracy of the model predictions has been tested by comparison with published observations of cosmic ray dose-rate variation in the Earth's atmosphere

  11. Modeling temperature variations in a pilot plant thermophilic anaerobic digester.

    Science.gov (United States)

    Valle-Guadarrama, Salvador; Espinosa-Solares, Teodoro; López-Cruz, Irineo L; Domaschko, Max

    2011-05-01

    A model that predicts temperature changes in a pilot plant thermophilic anaerobic digester was developed based on fundamental thermodynamic laws. The methodology utilized two simulation strategies. In the first, model equations were solved through a searching routine based on a minimal square optimization criterion, from which the overall heat transfer coefficient values, for both biodigester and heat exchanger, were determined. In the second, the simulation was performed with variable values of these overall coefficients. The prediction with both strategies allowed reproducing experimental data within 5% of the temperature span permitted in the equipment by the system control, which validated the model. The temperature variation was affected by the heterogeneity of the feeding and extraction processes, by the heterogeneity of the digestate recirculation through the heating system and by the lack of a perfect mixing inside the biodigester tank. The use of variable overall heat transfer coefficients improved the temperature change prediction and reduced the effect of a non-ideal performance of the pilot plant modeled.

  12. Discrete Variational Approach for Modeling Laser-Plasma Interactions

    Science.gov (United States)

    Reyes, J. Paxon; Shadwick, B. A.

    2014-10-01

    The traditional approach for fluid models of laser-plasma interactions begins by approximating fields and derivatives on a grid in space and time, leading to difference equations that are manipulated to create a time-advance algorithm. In contrast, by introducing the spatial discretization at the level of the action, the resulting Euler-Lagrange equations have particular differencing approximations that will exactly satisfy discrete versions of the relevant conservation laws. For example, applying a spatial discretization in the Lagrangian density leads to continuous-time, discrete-space equations and exact energy conservation regardless of the spatial grid resolution. We compare the results of two discrete variational methods using the variational principles from Chen and Sudan and Brizard. Since the fluid system conserves energy and momentum, the relative errors in these conserved quantities are well-motivated physically as figures of merit for a particular method. This work was supported by the U. S. Department of Energy under Contract No. DE-SC0008382 and by the National Science Foundation under Contract No. PHY-1104683.

  13. A moving boundary problem for the Stokes equations involving osmosis : Variational modelling and short-time well-posedness

    NARCIS (Netherlands)

    Lippoth, F.; Peletier, M.A.; Prokert, G.

    2016-01-01

    Within the framework of variational modelling we derive a one-phase moving boundary problem describing the motion of a semipermeable membrane enclosing a viscous liquid, driven by osmotic pressure and surface tension of the membrane. For this problem we prove the existence of classical solutions for

  14. Two-dimensional strain gradient damage modeling: a variational approach

    Science.gov (United States)

    Placidi, Luca; Misra, Anil; Barchiesi, Emilio

    2018-06-01

    In this paper, we formulate a linear elastic second gradient isotropic two-dimensional continuum model accounting for irreversible damage. The failure is defined as the condition in which the damage parameter reaches 1, at least in one point of the domain. The quasi-static approximation is done, i.e., the kinetic energy is assumed to be negligible. In order to deal with dissipation, a damage dissipation term is considered in the deformation energy functional. The key goal of this paper is to apply a non-standard variational procedure to exploit the damage irreversibility argument. As a result, we derive not only the equilibrium equations but, notably, also the Karush-Kuhn-Tucker conditions. Finally, numerical simulations for exemplary problems are discussed as some constitutive parameters are varying, with the inclusion of a mesh-independence evidence. Element-free Galerkin method and moving least square shape functions have been employed.

  15. Modeling Geomagnetic Variations using a Machine Learning Framework

    Science.gov (United States)

    Cheung, C. M. M.; Handmer, C.; Kosar, B.; Gerules, G.; Poduval, B.; Mackintosh, G.; Munoz-Jaramillo, A.; Bobra, M.; Hernandez, T.; McGranaghan, R. M.

    2017-12-01

    We present a framework for data-driven modeling of Heliophysics time series data. The Solar Terrestrial Interaction Neural net Generator (STING) is an open source python module built on top of state-of-the-art statistical learning frameworks (traditional machine learning methods as well as deep learning). To showcase the capability of STING, we deploy it for the problem of predicting the temporal variation of geomagnetic fields. The data used includes solar wind measurements from the OMNI database and geomagnetic field data taken by magnetometers at US Geological Survey observatories. We examine the predictive capability of different machine learning techniques (recurrent neural networks, support vector machines) for a range of forecasting times (minutes to 12 hours). STING is designed to be extensible to other types of data. We show how STING can be used on large sets of data from different sensors/observatories and adapted to tackle other problems in Heliophysics.

  16. Seasonal and spatial variation in broadleaf forest model parameters

    Science.gov (United States)

    Groenendijk, M.; van der Molen, M. K.; Dolman, A. J.

    2009-04-01

    Process based, coupled ecosystem carbon, energy and water cycle models are used with the ultimate goal to project the effect of future climate change on the terrestrial carbon cycle. A typical dilemma in such exercises is how much detail the model must be given to describe the observations reasonably realistic while also be general. We use a simple vegetation model (5PM) with five model parameters to study the variability of the parameters. These parameters are derived from the observed carbon and water fluxes from the FLUXNET database. For 15 broadleaf forests the model parameters were derived for different time resolutions. It appears that in general for all forests, the correlation coefficient between observed and simulated carbon and water fluxes improves with a higher parameter time resolution. The quality of the simulations is thus always better when a higher time resolution is used. These results show that annual parameters are not capable of properly describing weather effects on ecosystem fluxes, and that two day time resolution yields the best results. A first indication of the climate constraints can be found by the seasonal variation of the covariance between Jm, which describes the maximum electron transport for photosynthesis, and climate variables. A general seasonality we found is that during winter the covariance with all climate variables is zero. Jm increases rapidly after initial spring warming, resulting in a large covariance with air temperature and global radiation. During summer Jm is less variable, but co-varies negatively with air temperature and vapour pressure deficit and positively with soil water content. A temperature response appears during spring and autumn for broadleaf forests. This shows that an annual model parameter cannot be representative for the entire year. And relations with mean annual temperature are not possible. During summer the photosynthesis parameters are constrained by water availability, soil water content and

  17. Liquid surface model for carbon nanotube energetics

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Mathew, Maneesh; Solov'yov, Andrey V.

    2008-01-01

    an important insight in the energetics and stability of nanotubes of different chirality and might be important for the understanding of nanotube growth process. For the computations we use empirical Brenner and Tersoff potentials and discuss their applicability to the study of carbon nanotubes. From......In the present paper we developed a model for calculating the energy of single-wall carbon nanotubes of arbitrary chirality. This model, which we call as the liquid surface model, predicts the energy of a nanotube with relative error less than 1% once its chirality and the total number of atoms...... the calculated energies we determine the elastic properties of the single-wall carbon nanotubes (Young modulus, curvature constant) and perform a comparison with available experimental measurements and earlier theoretical predictions....

  18. Regional variations of cell surface carbohydrates in human oral stratified epithelium

    DEFF Research Database (Denmark)

    Vedtofte, P; Dabelsteen, Erik; Hakomori, S

    1984-01-01

    The distribution of blood group carbohydrate chains with antigen A, B, H type 2 chain (A and B precursor), and N-acetyllactosamine (H type 2 precursor) specificity was studied in human oral epithelium from different anatomical regions. These represented various epithelial differentiation patterns...... epithelium from nine blood group A, two blood group B, and nine blood group O individuals. The blood group carbohydrate chains were examined in tissue sections by immunofluorescence microscopy. The A and B blood group antigens were detected by human blood group sera, and antigen H type 2 chains and N...... antigen H type 2 chains in metaplastically keratinized buccal epithelium was found to differ significantly from that seen in normal non-keratinized buccal epithelium. The regional variations demonstrated in cell surface carbohydrates are suggested to reflect differences in tissue differentiation....

  19. Variational analysis for simulating free-surface flows in a porous medium

    Directory of Open Access Journals (Sweden)

    Shabbir Ahmed

    2003-01-01

    is used to obtain a discrete form of equations for a two-dimensional domain. The matrix characteristics and the stability criteria have been investigated to develop a stable numerical algorithm for solving the governing equation. A computer programme has been written to solve a symmetric positive definite system obtained from the variational finite element analysis. The system of equations is solved using the conjugate gradient method. The solution generates time-varying hydraulic heads in the subsurface. The interfacing free surface between the unsaturated and saturated zones in the variably saturated domain is located, based on the computed hydraulic heads. Example problems are investigated. The finite element solutions are compared with the exact solutions for the example problems. The numerical characteristics of the finite element solution method are also investigated using the example problems.

  20. Convergence of surface diffusion parameters with model crystal size

    Science.gov (United States)

    Cohen, Jennifer M.; Voter, Arthur F.

    1994-07-01

    A study of the variation in the calculated quantities for adatom diffusion with respect to the size of the model crystal is presented. The reported quantities include surface diffusion barrier heights, pre-exponential factors, and dynamical correction factors. Embedded atom method (EAM) potentials were used throughout this effort. Both the layer size and the depth of the crystal were found to influence the values of the Arrhenius factors significantly. In particular, exchange type mechanisms required a significantly larger model than standard hopping mechanisms to determine adatom diffusion barriers of equivalent accuracy. The dynamical events that govern the corrections to transition state theory (TST) did not appear to be as sensitive to crystal depth. Suitable criteria for the convergence of the diffusion parameters with regard to the rate properties are illustrated.

  1. Annual and latitudinal variations of surface fluxes and meteorological variables at Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey; Uttal, Taneil; Persson, Ola; Konopleva-Akish, Elena; Crepinsek, Sara; Cox, Christopher; Fairall, Christopher; Makshtas, Alexander; Repina, Irina

    2016-04-01

    This study analyzes and discusses seasonal and latitudinal variations of surface fluxes (turbulent, radiative, and soil ground heat) and other ancillary surface/snow/permafrost data based on in-situ measurements made at two long-term research observatories near the coast of the Arctic Ocean located in Canada and Russia. The hourly averaged data collected at Eureka (Canadian territory of Nunavut) and Tiksi (East Siberia) located at two quite different latitudes (80.0 N and 71.6 N respectively) are analyzed in details to describe the seasons in the Arctic. Although Eureka and Tiksi are located at the different continents and at the different latitudes, the annual course of the surface meteorology and the surface fluxes are qualitatively very similar. The air and soil temperatures display the familiar strong seasonal trend with maximum of measured temperatures in mid-summer and minimum during winter. According to our data, variation in incoming short-wave solar radiation led the seasonal pattern of the air and soil temperatures, and the turbulent fluxes. During the dark Polar nights, air and ground temperatures are strongly controlled by long-wave radiation associated generally with cloud cover. Due to the fact that in average the higher latitudes receive less solar radiation than lower latitudes, a length of the convective atmospheric boundary layer (warm season) is shorter and middle-summer amplitude of the turbulent fluxes is generally less in Eureka than in Tiksi. However, since solar elevation angle at local midnight in the middle of Arctic summer is higher for Eureka as compared to Tiksi, stable stratification and upward turbulent flux for carbon dioxide is generally did not observed at Eureka site during summer seasons. It was found a high correlation between the turbulent fluxes of sensible and latent heat, carbon dioxide and the net solar radiation. A comprehensive evaluation of energy balance closure problem is performed based on the multi-year data sets

  2. Seasonal variation in aragonite saturation in surface waters of Puget Sound – a pilot study

    Directory of Open Access Journals (Sweden)

    Gregory Pelletier

    2018-01-01

    Full Text Available A pilot study of sampling, using monthly marine flights over spatially distributed stations, was conducted with the aim to characterize the carbonate system in Puget Sound over a full year-long period. Surface waters of Puget Sound were found to be under-saturated with respect to aragonite during October–March, and super-saturated during April–September. Highest pCO2 and lowest pH occurred during the corrosive October–March period. Lowest pCO2 and highest pH occurred during the super-saturated April–September period. The monthly variations in pCO2 , pH, and aragonite saturation state closely followed the variations in monthly average chlorophyll a. Super-saturated conditions during April–September are likely strongly influenced by photosynthetic uptake of CO2 during the phytoplankton growing season. The relationship between phytoplankton production, the carbonate system, and aragonite saturation state suggests that long-term trends in eutrophication processes may contribute to trends in ocean acidification in Puget Sound

  3. Distribution and temporal variation of trace metal enrichment in surface sediments of San Jorge Bay, Chile.

    Science.gov (United States)

    Valdés, Jorge; Román, Domingo; Guiñez, Marcos; Rivera, Lidia; Morales, Tatiana; Morales, Tomás; Avila, Juan; Cortés, Pedro

    2010-08-01

    Cu, Pb, and Hg concentrations were determined in surface sediment samples collected at three sites in San Jorge Bay, northern Chile. This study aims to evaluate differences in their spatial distribution and temporal variability. The highest metal concentrations were found at the site "Puerto", where minerals (Cu and Pb) have been loaded for more than 60 years. On the other hand, Hg does not pose a contamination problem in this bay. Cu and Pb concentrations showed significant variations from 1 year to another. These variations seem to be a consequence of the combination of several factors, including changes in the loading and/or storage of minerals in San Jorge Bay, the dredging of bottom sediments (especially at Puerto), and seasonal changes in physical-chemical properties of the water column that modify the exchange of metals at the sediment-water interface. Differences in the contamination factor and geoaccumulation index suggest that pre-industrial concentrations measured in marine sediments of this geographical zone, were better than geological values (average shale, continental crust average) for evaluating the degree of contamination in this coastal system. Based on these last two indexes, San Jorge Bay has a serious problem of Cu and Pb pollution at the three sampling locations. However, only Cu exceeds the national maximum values used to evaluate ecological risk and the health of marine environments. It is suggested that Chilean environmental legislation for marine sediment quality--presently under technical discussion--is not an efficient tool for protecting the marine ecosystem.

  4. Interannual Variation of the Surface Temperature of Tropical Forests from Satellite Observations

    Directory of Open Access Journals (Sweden)

    Huilin Gao

    2016-01-01

    Full Text Available Land surface temperatures (LSTs within tropical forests contribute to climate variations. However, observational data are very limited in such regions. This study used passive microwave remote sensing data from the Special Sensor Microwave/Imager (SSM/I and the Special Sensor Microwave Imager Sounder (SSMIS, providing observations under all weather conditions, to investigate the LST over the Amazon and Congo rainforests. The SSM/I and SSMIS data were collected from 1996 to 2012. The morning and afternoon observations from passive microwave remote sensing facilitate the investigation of the interannual changes of LST anomalies on a diurnal basis. As a result of the variability of cloud cover and the corresponding reduction of solar radiation, the afternoon LST anomalies tend to vary more than the morning LST anomalies. The dominant spatial and temporal patterns for interseasonal variations of the LST anomalies over the tropical rainforest were analyzed. The impacts of droughts and El Niños on this LST were also investigated. Differences between early morning and late afternoon LST anomalies were identified by the remote sensing product, with the morning LST anomalies controlled by humidity (according to comparisons with the National Centers for Environmental Prediction (NCEP reanalysis data.

  5. Increasing the reliability of the Olkiluoto surface and near-surface hydrological model

    International Nuclear Information System (INIS)

    Karvonen, T.

    2009-05-01

    The aim of the study was to improve the reliability of the Olkiluoto surface hydrological model that calculates the overall water balance components of Olkiluoto Island. ONKALO and Korvensuo reservoir were added as explicit structures to the model. The model links the unsaturated and saturated soil water in the overburden and groundwater in bedrock to a continuous pressure system. With the model it is possible to evaluate the influence of water leaking to ONKALO on groundwater level in overburden soils and pressure head in shallow bedrock drillholes. Anisotropy was added to the surface hydrological model and several model runs were carried out using anisotropy factors 1, 5 and 10. Anisotropy factor of 10 is used in the 2008 version of the deep hydrogeological model and the same anisotropy will be used in future calculations of the surface hydrological model to ensure consistency of the parameter values in the two models. The correspondence between measured and computed groundwater levels has been improved due to new soil type delineation and the calibration of the soil water retention curve parameters. Computed groundwater level variation can be characterized by a measure ΔH COMP , which is difference between maximum and minimum value during the calibration period. Average ΔH COMP in groundwater tubes was 1.98 m and the corresponding measured value ΔH MEAS was 2.08 m, i.e. the difference between measured and computed value was around 0.1 m (0.16 m in the 2007 version). Temporal variation (difference between maximum and minimum pressure head) was simulated well also in most of the shallow bedrock drillholes. ONKALO was added to the 2008 version of the Olkiluoto surface hydrological model. Influence of ONKALO is taken into account by giving the total discharge as input data from existing measurements or from calculations of the deep hydrogeological model of the Olkiluoto Island. The computed results show that ONKALO has a temporal effect on groundwater level in

  6. Seasonal and latitudinal variations of surface fluxes at two Arctic terrestrial sites

    Science.gov (United States)

    Grachev, Andrey A.; Persson, P. Ola G.; Uttal, Taneil; Akish, Elena A.; Cox, Christopher J.; Morris, Sara M.; Fairall, Christopher W.; Stone, Robert S.; Lesins, Glen; Makshtas, Alexander P.; Repina, Irina A.

    2017-11-01

    This observational study compares seasonal variations of surface fluxes (turbulent, radiative, and soil heat) and other ancillary atmospheric/surface/permafrost data based on in-situ measurements made at terrestrial research observatories located near the coast of the Arctic Ocean. Hourly-averaged multiyear data sets collected at Eureka (Nunavut, Canada) and Tiksi (East Siberia, Russia) are analyzed in more detail to elucidate similarities and differences in the seasonal cycles at these two Arctic stations, which are situated at significantly different latitudes (80.0°N and 71.6°N, respectively). While significant gross similarities exist in the annual cycles of various meteorological parameters and fluxes, the differences in latitude, local topography, cloud cover, snowfall, and soil characteristics produce noticeable differences in fluxes and in the structures of the atmospheric boundary layer and upper soil temperature profiles. An important factor is that even though higher latitude sites (in this case Eureka) generally receive less annual incoming solar radiation but more total daily incoming solar radiation throughout the summer months than lower latitude sites (in this case Tiksi). This leads to a counter-intuitive state where the average active layer (or thaw line) is deeper and the topsoil temperature in midsummer are higher in Eureka which is located almost 10° north of Tiksi. The study further highlights the differences in the seasonal and latitudinal variations of the incoming shortwave and net radiation as well as the moderating cloudiness effects that lead to temporal and spatial differences in the structure of the atmospheric boundary layer and the uppermost ground layer. Specifically the warm season (Arctic summer) is shorter and mid-summer amplitude of the surface fluxes near solar noon is generally less in Eureka than in Tiksi. During the dark Polar night and cold seasons (Arctic winter) when the ground is covered with snow and air temperatures

  7. Spectroscopic study on variations in illite surface properties after acid-base titration.

    Science.gov (United States)

    Liu, Wen-xin; Coveney, R M; Tang, Hong-xiao

    2003-07-01

    FT-IR, Raman microscopy, XRD, 29Si and 27Al MAS NMR, were used to investigate changes in surface properties of a natural illite sample after acid-base potentiometric titration. The characteristic XRD lines indicated the presence of surface Al-Si complexes, preferable to Al(OH)3 precipitates. In the microscopic Raman spectra, the vibration peaks of Si-O and Al-O bonds diminished as a result of treatment with acid, then increased after hydroxide back titration. The varied ratio of signal intensity between (IV)Al and (VI)Al species in 27Al MAS NMR spectra, together with the stable BET surface area after acidimetric titration, suggested that edge faces and basal planes in the layer structure of illite participated in dissolution of structural components. The combined spectroscopic evidence demonstrated that the reactions between illite surfaces and acid-leaching silicic acid and aluminum ions should be considered in the model description of surface acid-base properties of the aqueous illite.

  8. Temporal aspects of surface water quality variation using robust statistical tools.

    Science.gov (United States)

    Mustapha, Adamu; Aris, Ahmad Zaharin; Ramli, Mohammad Firuz; Juahir, Hafizan

    2012-01-01

    Robust statistical tools were applied on the water quality datasets with the aim of determining the most significance parameters and their contribution towards temporal water quality variation. Surface water samples were collected from four different sampling points during dry and wet seasons and analyzed for their physicochemical constituents. Discriminant analysis (DA) provided better results with great discriminatory ability by using five parameters with (P < 0.05) for dry season affording more than 96% correct assignation and used five and six parameters for forward and backward stepwise in wet season data with P-value (P < 0.05) affording 68.20% and 82%, respectively. Partial correlation results revealed that there are strong (r(p) = 0.829) and moderate (r(p) = 0.614) relationships between five-day biochemical oxygen demand (BOD(5)) and chemical oxygen demand (COD), total solids (TS) and dissolved solids (DS) controlling for the linear effect of nitrogen in the form of ammonia (NH(3)) and conductivity for dry and wet seasons, respectively. Multiple linear regression identified the contribution of each variable with significant values r = 0.988, R(2) = 0.976 and r = 0.970, R(2) = 0.942 (P < 0.05) for dry and wet seasons, respectively. Repeated measure t-test confirmed that the surface water quality varies significantly between the seasons with significant value P < 0.05.

  9. Charging effects and surface potential variations of Cu-based nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Nunes, D., E-mail: daniela.gomes@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Calmeiro, T.R.; Nandy, S.; Pinto, J.V.; Pimentel, A.; Barquinha, P. [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Carvalho, P.A. [SINTEF Materials and Chemistry, PB 124 Blindern, NO-0314, Oslo (Norway); CeFEMA, Instituto Superior Técnico, Universidade de Lisboa, 1049-001, Lisboa (Portugal); Walmsley, J.C. [SINTEF Materials and Chemistry, Materials and Nanotechnology, Høgskoleringen 5, 7034 Trondheim (Norway); Fortunato, E., E-mail: emf@fct.unl.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Martins, R., E-mail: rm@uninova.pt [i3N/CENIMAT, Department of Materials Science, Faculty of Science and Technology, Universidade NOVA de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

    2016-02-29

    The present work reports charging effects and surface potential variations in pure copper, cuprous oxide and cupric oxide nanowires observed by electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM). The copper nanowires were produced by wet synthesis, oxidation into cuprous oxide nanowires was achieved through microwave irradiation and cupric oxide nanowires were obtained via furnace annealing in atmospheric conditions. Structural characterization of the nanowires was carried out by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. During the EFM experiments the electrostatic field of the positive probe charged negatively the Cu-based nanowires, which in turn polarized the SiO{sub 2} dielectric substrate. Both the probe/nanowire capacitance as well as the substrate polarization increased with the applied bias. Cu{sub 2}O and CuO nanowires behaved distinctively during the EFM measurements in accordance with their band gap energies. The work functions (WF) of the Cu-based nanowires, obtained by KPFM measurements, yielded WF{sub CuO} > WF{sub Cu} > WF{sub Cu{sub 2O}}. - Highlights: • Charge distribution study in Cu, Cu{sub 2}O and CuO nanowires through electrostatic force microscopy • Structural/surface defect role on the charge distribution along the Cu nanowires • Determination of the nanowire work functions by Kelvin probe force microscopy • Three types of nanowires give a broad idea of charge behavior on Cu based-nanowires.

  10. Interannual variations and trends in global land surface phenology derived from enhanced vegetation index during 1982-2010

    Science.gov (United States)

    Zhang, Xiaoyang; Tan, Bin; Yu, Yunyue

    2014-05-01

    Land surface phenology is widely retrieved from satellite observations at regional and global scales, and its long-term record has been demonstrated to be a valuable tool for reconstructing past climate variations, monitoring the dynamics of terrestrial ecosystems in response to climate impacts, and predicting biological responses to future climate scenarios. This study detected global land surface phenology from the advanced very high resolution radiometer (AVHRR) and the Moderate Resolution Imaging Spectroradiometer (MODIS) data from 1982 to 2010. Based on daily enhanced vegetation index at a spatial resolution of 0.05 degrees, we simulated the seasonal vegetative trajectory for each individual pixel using piecewise logistic models, which was then used to detect the onset of greenness increase (OGI) and the length of vegetation growing season (GSL). Further, both overall interannual variations and pixel-based trends were examined across Koeppen's climate regions for the periods of 1982-1999 and 2000-2010, respectively. The results show that OGI and GSL varied considerably during 1982-2010 across the globe. Generally, the interannual variation could be more than a month in precipitation-controlled tropical and dry climates while it was mainly less than 15 days in temperature-controlled temperate, cold, and polar climates. OGI, overall, shifted early, and GSL was prolonged from 1982 to 2010 in most climate regions in North America and Asia while the consistently significant trends only occurred in cold climate and polar climate in North America. The overall trends in Europe were generally insignificant. Over South America, late OGI was consistent (particularly from 1982 to 1999) while either positive or negative GSL trends in a climate region were mostly reversed between the periods of 1982-1999 and 2000-2010. In the Northern Hemisphere of Africa, OGI trends were mostly insignificant, but prolonged GSL was evident over individual climate regions during the last 3

  11. A generalized regression model of arsenic variations in the shallow groundwater of Bangladesh

    Science.gov (United States)

    Taylor, Richard G.; Chandler, Richard E.

    2015-01-01

    Abstract Localized studies of arsenic (As) in Bangladesh have reached disparate conclusions regarding the impact of irrigation‐induced recharge on As concentrations in shallow (≤50 m below ground level) groundwater. We construct generalized regression models (GRMs) to describe observed spatial variations in As concentrations in shallow groundwater both (i) nationally, and (ii) regionally within Holocene deposits where As concentrations in groundwater are generally high (>10 μg L−1). At these scales, the GRMs reveal statistically significant inverse associations between observed As concentrations and two covariates: (1) hydraulic conductivity of the shallow aquifer and (2) net increase in mean recharge between predeveloped and developed groundwater‐fed irrigation periods. Further, the GRMs show that the spatial variation of groundwater As concentrations is well explained by not only surface geology but also statistical interactions (i.e., combined effects) between surface geology and mean groundwater recharge, thickness of surficial silt and clay, and well depth. Net increases in recharge result from intensive groundwater abstraction for irrigation, which induces additional recharge where it is enabled by a permeable surface geology. Collectively, these statistical associations indicate that irrigation‐induced recharge serves to flush mobile As from shallow groundwater. PMID:27524841

  12. A new MRI land surface model HAL

    Science.gov (United States)

    Hosaka, M.

    2011-12-01

    A land surface model HAL is newly developed for MRI-ESM1. It is used for the CMIP simulations. HAL consists of three submodels: SiByl (vegetation), SNOWA (snow) and SOILA (soil) in the current version. It also contains a land coupler LCUP which connects some submodels and an atmospheric model. The vegetation submodel SiByl has surface vegetation processes similar to JMA/SiB (Sato et al. 1987, Hirai et al. 2007). SiByl has 2 vegetation layers (canopy and grass) and calculates heat, moisture, and momentum fluxes between the land surface and the atmosphere. The snow submodel SNOWA can have any number of snow layers and the maximum value is set to 8 for the CMIP5 experiments. Temperature, SWE, density, grain size and the aerosol deposition contents of each layer are predicted. The snow properties including the grain size are predicted due to snow metamorphism processes (Niwano et al., 2011), and the snow albedo is diagnosed from the aerosol mixing ratio, the snow properties and the temperature (Aoki et al., 2011). The soil submodel SOILA can also have any number of soil layers, and is composed of 14 soil layers in the CMIP5 experiments. The temperature of each layer is predicted by solving heat conduction equations. The soil moisture is predicted by solving the Darcy equation, in which hydraulic conductivity depends on the soil moisture. The land coupler LCUP is designed to enable the complicated constructions of the submidels. HAL can include some competing submodels (precise and detailed ones, and simpler ones), and they can run at the same simulations. LCUP enables a 2-step model validation, in which we compare the results of the detailed submodels with the in-situ observation directly at the 1st step, and follows the comparison between them and those of the simpler ones at the 2nd step. When the performances of the detailed ones are good, we can improve the simpler ones by using the detailed ones as reference models.

  13. Causes of global mean surface temperature slowdowns, trends and variations from months to a century, 1891-2015

    Science.gov (United States)

    Folland, C. K.; Boucher, O.; Colman, A.; Parker, D. E.

    2017-12-01

    The recent slowdown in the warming of global mean surface temperature (GST) has highlighted the influences of natural variability. This talk discusses reconstructions of the variations of GST down to the monthly time scale since 1891 using monthly forcing data. We show that most of the variations in annual, and to some extent sub-annual, GST since 1891 can be reproduced skillfully from known forcing factors external and internal to the climate system. This includes the slowdown in warming over about 1998-2013 where reconstruction skill is particularly high down to the multi-monthly time scale. The relative contributions of the several key forcing factors to GST continually vary, but most of the net warming since 1891 is reconstructed to be attributable to the net forcing due to increasing greenhouse gases and anthropogenic aerosols. Separate analyses are carried out for three periods of GST slowdown:- 1896-1910, 1941-1976, together with 1998-2013 and some of its sub periods. We also study two periods where strong warming occurred, 1911-1940 and 1977-1997. Comparisons are made with the skill of average GST provided by 40 CMIP5 models. In the recent 1998-2013 slowdown, TSI forcing appears to have caused significant cooling, particularly over 2001-2010. This is additional to well documented cooling effects of an increased frequency of La Nina events, a negative Interdecadal Pacific Oscillation and some increases in volcanic forcing. Although there are short-term features of the GST curve since 1891 that cannot be fully explained, the most serious disagreements between the reconstructions and observations occur in the Second World War, especially in 1944-1945. Here observed near worldwide SSTs may be biased significantly too warm. Despite this, our generally high reconstruction skill is consistent with a good understanding of the multiple causes of observed GST variations and the general veracity of the GST record since 1891.

  14. Origins of Tropospheric Ozone Interannual Variation (IAV) over Reunion: A Model Investigation

    Science.gov (United States)

    Liu, Junhua; Rodriguez, Jose M.; Thompson, Anne M.; Logan, Jennifer A.; Douglass, Anne R.; Olsen, Mark A.; Steenrod, Stephen D.; Posny, Francoise

    2016-01-01

    Observations from long-term ozonesonde measurements show robust variations and trends in the evolution of ozone in the middle and upper troposphere over Reunion Island (21.1 degrees South Latitude, 55.5 degrees East Longitude) in June-August. Here we examine possible causes of the observed ozone variation at Reunion Island using hindcast simulations by the stratosphere-troposphere Global Modeling Initiative chemical transport model for 1992-2014, driven by assimilated Modern-Era Retrospective Analysis for Research and Applications (MERRA) meteorological fields. Reunion Island is at the edge of the subtropical jet, a region of strong stratospheric-tropospheric exchange. Our analysis implies that the large interannual variation (IAV) of upper tropospheric ozone over Reunion is driven by the large IAV of the stratospheric influence. The IAV of the large-scale, quasi-horizontal wind patterns also contributes to the IAV of ozone in the upper troposphere. Comparison to a simulation with constant emissions indicates that increasing emissions do not lead to the maximum trend in the middle and upper troposphere over Reunion during austral winter implied by the sonde data. The effects of increasing emission over southern Africa are limited tothe lower troposphere near the surface in August-September.

  15. A four-dimensional variational chemistry data assimilation scheme for Eulerian chemistry transport modeling

    Science.gov (United States)

    Eibern, Hendrik; Schmidt, Hauke

    1999-08-01

    The inverse problem of data assimilation of tropospheric trace gas observations into an Eulerian chemistry transport model has been solved by the four-dimensional variational technique including chemical reactions, transport, and diffusion. The University of Cologne European Air Pollution Dispersion Chemistry Transport Model 2 with the Regional Acid Deposition Model 2 gas phase mechanism is taken as the basis for developing a full four-dimensional variational data assimilation package, on the basis of the adjoint model version, which includes the adjoint operators of horizontal and vertical advection, implicit vertical diffusion, and the adjoint gas phase mechanism. To assess the potential and limitations of the technique without degrading the impact of nonperfect meteorological analyses and statistically not established error covariance estimates, artificial meteorological data and observations are used. The results are presented on the basis of a suite of experiments, where reduced records of artificial "observations" are provided to the assimilation procedure, while other "data" is retained for performance control of the analysis. The paper demonstrates that the four-dimensional variational technique is applicable for a comprehensive chemistry transport model in terms of computational and storage requirements on advanced parallel platforms. It is further shown that observed species can generally be analyzed, even if the "measurements" have unbiased random errors. More challenging experiments are presented, aiming to tax the skill of the method (1) by restricting available observations mostly to surface ozone observations for a limited assimilation interval of 6 hours and (2) by starting with poorly chosen first guess values. In this first such application to a three-dimensional chemistry transport model, success was also achieved in analyzing not only observed but also chemically closely related unobserved constituents.

  16. Merging Digital Surface Models Implementing Bayesian Approaches

    Science.gov (United States)

    Sadeq, H.; Drummond, J.; Li, Z.

    2016-06-01

    In this research different DSMs from different sources have been merged. The merging is based on a probabilistic model using a Bayesian Approach. The implemented data have been sourced from very high resolution satellite imagery sensors (e.g. WorldView-1 and Pleiades). It is deemed preferable to use a Bayesian Approach when the data obtained from the sensors are limited and it is difficult to obtain many measurements or it would be very costly, thus the problem of the lack of data can be solved by introducing a priori estimations of data. To infer the prior data, it is assumed that the roofs of the buildings are specified as smooth, and for that purpose local entropy has been implemented. In addition to the a priori estimations, GNSS RTK measurements have been collected in the field which are used as check points to assess the quality of the DSMs and to validate the merging result. The model has been applied in the West-End of Glasgow containing different kinds of buildings, such as flat roofed and hipped roofed buildings. Both quantitative and qualitative methods have been employed to validate the merged DSM. The validation results have shown that the model was successfully able to improve the quality of the DSMs and improving some characteristics such as the roof surfaces, which consequently led to better representations. In addition to that, the developed model has been compared with the well established Maximum Likelihood model and showed similar quantitative statistical results and better qualitative results. Although the proposed model has been applied on DSMs that were derived from satellite imagery, it can be applied to any other sourced DSMs.

  17. MERGING DIGITAL SURFACE MODELS IMPLEMENTING BAYESIAN APPROACHES

    Directory of Open Access Journals (Sweden)

    H. Sadeq

    2016-06-01

    Full Text Available In this research different DSMs from different sources have been merged. The merging is based on a probabilistic model using a Bayesian Approach. The implemented data have been sourced from very high resolution satellite imagery sensors (e.g. WorldView-1 and Pleiades. It is deemed preferable to use a Bayesian Approach when the data obtained from the sensors are limited and it is difficult to obtain many measurements or it would be very costly, thus the problem of the lack of data can be solved by introducing a priori estimations of data. To infer the prior data, it is assumed that the roofs of the buildings are specified as smooth, and for that purpose local entropy has been implemented. In addition to the a priori estimations, GNSS RTK measurements have been collected in the field which are used as check points to assess the quality of the DSMs and to validate the merging result. The model has been applied in the West-End of Glasgow containing different kinds of buildings, such as flat roofed and hipped roofed buildings. Both quantitative and qualitative methods have been employed to validate the merged DSM. The validation results have shown that the model was successfully able to improve the quality of the DSMs and improving some characteristics such as the roof surfaces, which consequently led to better representations. In addition to that, the developed model has been compared with the well established Maximum Likelihood model and showed similar quantitative statistical results and better qualitative results. Although the proposed model has been applied on DSMs that were derived from satellite imagery, it can be applied to any other sourced DSMs.

  18. Variations of uranium concentrations in a multi-aquifer system under the impact of surface water-groundwater interaction

    Science.gov (United States)

    Wu, Ya; Li, Junxia; Wang, Yanxin; Xie, Xianjun

    2018-04-01

    Understanding uranium (U) mobility is vital to minimizing its concentrations in potential drinking water sources. In this study, we report spatial-seasonal variations in U speciation and concentrations in a multi-aquifer system under the impact of Sanggan River in Datong basin, northern China. Hydrochemical and H, O, Sr isotopic data, thermodynamic calculations, and geochemical modeling are used to investigate the mechanisms of surface water-groundwater mixing-induced mobilization and natural attenuation of U. In the study site, groundwater U concentrations are up to 30.2 μg/L, and exhibit strong spatial-seasonal variations that are related to pH and Eh values, as well as dissolved Ca2+, HCO3-, and Fe(III) concentrations. For the alkaline aquifers of this site (pH 7.02-8.44), U mobilization is due to the formation and desorption of Ca2UO2(CO3)30 and CaUO2(CO3)32- caused by groundwater Ca2+ elevation via mineral weathering and Na-Ca exchange, incorporated U(VI) release from calcite, and U(IV) oxidation by Fe(OH)3. U immobilization is linked to the adsorption of CaUO2(CO3)32- and UO2(CO3)34- shifted from Ca2UO2(CO3)30 because of HCO3- elevation and Ca2+ depletion, U(VI) co-precipitation with calcite, and U(VI) reduction by adsorbed Fe2+ and FeS. Those results are of great significance for the groundwater resource management of this and similar other surface water-groundwater interaction zones.

  19. Toward Spectroscopically Detecting the Global Latitudinal Temperature Variation on the Solar Surface

    Science.gov (United States)

    Takeda, Y.; UeNo, S.

    2017-09-01

    A very slight rotation-induced latitudinal temperature variation (presumably on the order of several kelvin) on the solar surface is theoretically expected. While recent high-precision solar brightness observations reported its detection, confirmation by an alternative approach using the strengths of spectral lines is desirable, for which reducing the noise due to random fluctuation caused by atmospheric inhomogeneity is critical. Toward this difficult task, we carried out a pilot study of spectroscopically investigating the relative variation of temperature (T) at a number of points in the solar circumference region near to the limb (where latitude dependence should be detectable, if any exists) based on the equivalent widths (W) of 28 selected lines in the 5367 - 5393 Å and 6075 - 6100 Å regions. We paid special attention to i) clarifying which types of lines should be employed and ii) how much precision is attainable in practice. We found that lines with strong T-sensitivity (|log W/log T|) should be used and that very weak lines should be avoided because they inevitably suffer strong relative fluctuations (Δ W/W). Our analysis revealed that a precision of Δ T/T ≈ 0.003 (corresponding to ≈ 15 K) can be achieved at best by a spectral line with comparatively large |log W/log T|, although this can possibly be further improved When a number of lines are used all together. Accordingly, if many such favorable lines could be measured with subpercent precision of Δ W/W and by averaging the resulting Δ T/T from each line, the random noise would eventually be reduced to ≲ 1 K and detection of a very subtle amount of global T-gradient might be possible.

  20. The contact binary VW Cephei revisited: surface activity and period variation

    Science.gov (United States)

    Mitnyan, T.; Bódi, A.; Szalai, T.; Vinkó, J.; Szatmáry, K.; Borkovits, T.; Bíró, B. I.; Hegedüs, T.; Vida, K.; Pál, A.

    2018-05-01

    Context. Despite the fact that VW Cephei is one of the most well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of this system. Aims: Our aims are to obtain new spectra along with photometric measurements, to analyze what kind of changes may have happened in the system in the past two decades, and to propose new ideas for explaining them. Methods: For the period analysis we determined ten new times of minima from our light curves, and constructed a new O-C diagram of the system. Radial velocities of the components were determined using the cross-correlation technique. The light curves and radial velocities were modeled simultaneously with the PHOEBE code. All observed spectra were compared to synthetic spectra and equivalent widths (EWs) of the Hα line were measured on their differences. Results: We re-determine the physical parameters of the system according to our new light curve and spectral models. We confirm that the primary component is more active than the secondary, and there is a correlation between spottedness and the chromospheric activity. We propose that the flip-flop phenomenon occurring on the primary component could be a possible explanation of the observed nature of the activity. To explain the period variation of VW Cep, we test two previously suggested scenarios: the presence of a fourth body in the system, and the Applegate-mechanism caused by periodic magnetic activity. We conclude that although none of these mechanisms can be ruled out entirely, the available data suggest that mass transfer with a slowly decreasing rate provides the most likely explanation for the period variation of VW Cep.

  1. Accuracy Assessment of Different Digital Surface Models

    Directory of Open Access Journals (Sweden)

    Ugur Alganci

    2018-03-01

    Full Text Available Digital elevation models (DEMs, which can occur in the form of digital surface models (DSMs or digital terrain models (DTMs, are widely used as important geospatial information sources for various remote sensing applications, including the precise orthorectification of high-resolution satellite images, 3D spatial analyses, multi-criteria decision support systems, and deformation monitoring. The accuracy of DEMs has direct impacts on specific calculations and process chains; therefore, it is important to select the most appropriate DEM by considering the aim, accuracy requirement, and scale of each study. In this research, DSMs obtained from a variety of satellite sensors were compared to analyze their accuracy and performance. For this purpose, freely available Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER 30 m, Shuttle Radar Topography Mission (SRTM 30 m, and Advanced Land Observing Satellite (ALOS 30 m resolution DSM data were obtained. Additionally, 3 m and 1 m resolution DSMs were produced from tri-stereo images from the SPOT 6 and Pleiades high-resolution (PHR 1A satellites, respectively. Elevation reference data provided by the General Command of Mapping, the national mapping agency of Turkey—produced from 30 cm spatial resolution stereo aerial photos, with a 5 m grid spacing and ±3 m or better overall vertical accuracy at the 90% confidence interval (CI—were used to perform accuracy assessments. Gross errors and water surfaces were removed from the reference DSM. The relative accuracies of the different DSMs were tested using a different number of checkpoints determined by different methods. In the first method, 25 checkpoints were selected from bare lands to evaluate the accuracies of the DSMs on terrain surfaces. In the second method, 1000 randomly selected checkpoints were used to evaluate the methods’ accuracies for the whole study area. In addition to the control point approach, vertical cross

  2. Models of Solar Irradiance Variations: Current Status Natalie A ...

    Indian Academy of Sciences (India)

    Abstract. Regular monitoring of solar irradiance has been carried out since 1978 to show that solar total and spectral irradiance varies at different time scales. Whereas variations on time scales of minutes to hours are due to solar oscillations and granulation, variations on longer time scales are driven by the evolution of the ...

  3. Possible variations on the calcrete-gypcrete uranium model

    International Nuclear Information System (INIS)

    Carlisle, D.

    1980-01-01

    Genetic models and favorability criteria for calcrete and gypcrete uranium deposits based upon Yeelirrie and other occurrences in Western Australia and upon Langer Henirich and others in Namibia-South West Africa are summarized. Viable analogues of these world-class deposits have not yet been found in USA even though several of the favorable conditions occur in the southwest. A principal deterrent to economic concentration has been tectonic instability. But even in the most favorable areas it is not clear that climates have ever been sufficiently similar to that of the valley-calcrete region of Western Australia. Extensive, thick valley (nonpedogenic) calcretes such as those which host the carnotite in Australia and in Namibia have not been documented here. Nevertheless, submarginal occurrances of carnotite have been found in southwestern United States in small bodies of nonpedogenic and mixed pedogenic-nonpedogenic calcrete. Much of the study is based upon occurrences of carnotite-bearing calcrete and calcrete-gypcrete in the Republic of South Africa. Several of these are described briefly. Some reference is also made to new occurrences and to new data on previously described occurrences on the Namib Desert. Possible variations on the Western Australian and Namibia-South West Africa models which are considered are capillary rise of U in solution, addition of new uraniferous sediment over a calcrete, lateral access of U into a pedogenic calcrete, reworking of U from a weekly mineralized pedogenic calcrete or gypcrete into a new or reconstituted calcrete, or into an unrelated environment for fixation of U

  4. Possible variations on the calcrete-gypcrete uranium model

    Energy Technology Data Exchange (ETDEWEB)

    Carlisle, D.

    1980-01-01

    Genetic models and favorability criteria for calcrete and gypcrete uranium deposits based upon Yeelirrie and other occurrences in Western Australia and upon Langer Henirich and others in Namibia-South West Africa are summarized. Viable analogues of these world-class deposits have not yet been found in USA even though several of the favorable conditions occur in the southwest. A principal deterrent to economic concentration has been tectonic instability. But even in the most favorable areas it is not clear that climates have ever been sufficiently similar to that of the valley-calcrete region of Western Australia. Extensive, thick valley (nonpedogenic) calcretes such as those which host the carnotite in Australia and in Namibia have not been documented here. Nevertheless, submarginal occurrances of carnotite have been found in southwestern United States in small bodies of nonpedogenic and mixed pedogenic-nonpedogenic calcrete. Much of the study is based upon occurrences of carnotite-bearing calcrete and calcrete-gypcrete in the Republic of South Africa. Several of these are described briefly. Some reference is also made to new occurrences and to new data on previously described occurrences on the Namib Desert. Possible variations on the Western Australian and Namibia-South West Africa models which are considered are capillary rise of U in solution, addition of new uraniferous sediment over a calcrete, lateral access of U into a pedogenic calcrete, reworking of U from a weekly mineralized pedogenic calcrete or gypcrete into a new or reconstituted calcrete, or into an unrelated environment for fixation of U.

  5. Interannual Variations of Surface Currents and Transports in the Sicily Channel Derived From Coastal Altimetry

    Science.gov (United States)

    Jebri, Fatma; Zakardjian, Bruno; Birol, Florence; Bouffard, Jérôme; Jullion, Loïc.; Sammari, Cherif

    2017-11-01

    A 20 year coastal altimetry data set (X-TRACK) is used, for the first time, to gain insight into the long-term interannual variations of the surface circulation in the Sicily Channel. First, a spectral along with a time/space diagram analysis are applied to the monthly means. They reveal a regionally coherent current patterns from track to track with a marked interannual variability that is unequally shared between the Atlantic Tunisian Current and Atlantic Ionian Stream inflows in the Sicily Channel and the Bifurcation Tyrrhenian Current outflow northeast of Sicily. Second, an empirical altimetry-based transport-like technique is proposed to quantify volume budgets inside the closed boxes formed by the crossing of the altimetry tracks and coastlines over the study area. A set of hydrographic measurements is used to validate the method. The inferred altimetry transports give a well-balanced mean eastward Atlantic Waters baroclinic flow of 0.4 Sv and standard deviations of 0.2 Sv on a yearly basis throughout the Sicily Channel and toward the Ionian Sea, which is fairly coherent with those found in the literature. Furthermore, the analysis allows to quantify the intrusions of Atlantic Waters over the Tunisian Shelf (0.12 ± 0.1 Sv) and highlights two main modes of variability of the main surface waters path over the Sicily Channel through the Bifurcation Atlantic Tunisian Current and Atlantic Ionian Stream systems. Some physical mechanisms are finally discussed with regards to changes in the observed currents and transports.

  6. Roof planes detection via a second-order variational model

    Science.gov (United States)

    Benciolini, Battista; Ruggiero, Valeria; Vitti, Alfonso; Zanetti, Massimo

    2018-04-01

    proposed procedure is demonstrated by means of its application to urban digital surface models characterized by different spatial resolutions. Results are presented and discussed along with some promising developments.

  7. Seasonal variations of seismicity and geodetic strain in the Himalaya induced by surface hydrology

    OpenAIRE

    Bettinelli, Pierre; Avouac, Jean-Philippe; Flouzat, Mireille; Bollinger, Laurent; Ramillien, Guillaume; Rajaure, Sudhir; Sapkota, Som

    2008-01-01

    One way to probe earthquake nucleation processes and the relation between stress buildup and seismicity is to analyze the sensitivity of seismicity to stress perturbations. Here, we report evidence for seasonal strain and stress (~ 2–4 kPa) variations in the Nepal Himalaya, induced by water storage variations which correlate with seasonal variations of seismicity. The seismicity rate is twice as high in the winter as in the summer, and correlates with stress rate variations. We infer ~ 10–20 ...

  8. Hyper-Resolution Global Land Surface Model at Regional-to-Local Scales with observed Groundwater data assimilation

    OpenAIRE

    Singh, Raj Shekhar

    2014-01-01

    Modeling groundwater is challenging: it is not readily visible and is difficult to measure, with limited sets of observations available. Even though groundwater models can reproduce water table and head variations, considerable drift in modeled land surface states can nonetheless result from partially known geologic structure, errors in the input forcing fields, and imperfect Land Surface Model (LSM) parameterizations. These models frequently have biased results that are very different from o...

  9. 4D RECONSTRUCTIONS FROM LOW-COUNT SPECT DATA USING DEFORMABLE MODELS WITH SMOOTH INTERIOR INTENSITY VARIATIONS

    International Nuclear Information System (INIS)

    Cunningham, G. S.; Lehovich, A.

    2000-01-01

    The Bayes Inference Engine (BIE) has been used to perform a 4D reconstruction of a first-pass radiotracer bolus distribution inside a CardioWest Total Artificial Heart, imaged with the University of Arizona's FastSPECT system. The BIE estimates parameter values that define the 3D model of the radiotracer distribution at each of 41 times spanning about two seconds. The 3D models have two components: a closed surface, composed of hi-quadratic Bezier triangular surface patches, that defines the interface between the part of the blood pool that contains radiotracer and the part that contains no radiotracer, and smooth voxel-to-voxel variations in intensity within the closed surface. Ideally, the surface estimates the ventricular wall location where the bolus is infused throughout the part of the blood pool contained by the right ventricle. The voxel-to-voxel variations are needed to model an inhomogeneously-mixed bolus. Maximum a posterior (MAP) estimates of the Bezier control points and voxel values are obtained for each time frame. We show new reconstructions using the Bezier surface models, and discuss estimates of ventricular volume as a function of time, ejection fraction, and wall motion. The computation time for our reconstruction process, which directly estimates complex 3D model parameters from the raw data, is performed in a time that is competitive with more traditional voxel-based methods (ML-EM, e.g.)

  10. Spatial Variation of Soil Type and Soil Moisture in the Regional Atmospheric Modeling System

    Energy Technology Data Exchange (ETDEWEB)

    Buckley, R.

    2001-06-27

    Soil characteristics (texture and moisture) are typically assumed to be initially constant when performing simulations with the Regional Atmospheric Modeling System (RAMS). Soil texture is spatially homogeneous and time-independent, while soil moisture is often spatially homogeneous initially, but time-dependent. This report discusses the conversion of a global data set of Food and Agriculture Organization (FAO) soil types to RAMS soil texture and the subsequent modifications required in RAMS to ingest this information. Spatial variations in initial soil moisture obtained from the National Center for Environmental Predictions (NCEP) large-scale models are also introduced. Comparisons involving simulations over the southeastern United States for two different time periods, one during warmer, more humid summer conditions, and one during cooler, dryer winter conditions, reveals differences in surface conditions related to increases or decreases in near-surface atmospheric moisture con tent as a result of different soil properties. Three separate simulation types were considered. The base case assumed spatially homogeneous soil texture and initial soil moisture. The second case assumed variable soil texture and constant initial soil moisture, while the third case allowed for both variable soil texture and initial soil moisture. The simulation domain was further divided into four geographically distinct regions. It is concluded there is a more dramatic impact on thermodynamic variables (surface temperature and dewpoint) than on surface winds, and a more pronounced variability in results during the summer period. While no obvious trends in surface winds or dewpoint temperature were found relative to observations covering all regions and times, improvement in surface temperatures in most regions and time periods was generally seen with the incorporation of variable soil texture and initial soil moisture.

  11. A new dry-surface biofilm model: An essential tool for efficacy testing of hospital surface decontamination procedures.

    Science.gov (United States)

    Almatroudi, Ahmad; Hu, Honghua; Deva, Anand; Gosbell, Iain B; Jacombs, Anita; Jensen, Slade O; Whiteley, Greg; Glasbey, Trevor; Vickery, Karen

    2015-10-01

    The environment has been shown to be a source of pathogens causing infections in hospitalised patients. Incorporation of pathogens into biofilms, contaminating dry hospital surfaces, prolongs their survival and renders them tolerant to normal hospital cleaning and disinfection procedures. Currently there is no standard method for testing efficacy of detergents and disinfectants against biofilm formed on dry surfaces. The aim of this study was to develop a reproducible method of producing Staphylococcus aureus biofilm with properties similar to those of biofilm obtained from dry hospital clinical surfaces, for use in efficacy testing of decontamination products. The properties (composition, architecture) of model biofilm and biofilm obtained from clinical dry surfaces within an intensive care unit were compared. The CDC Biofilm Reactor was adapted to create a dry surface biofilm model. S. aureus ATCC 25923 was grown on polycarbonate coupons. Alternating cycles of dehydration and hydration in tryptone soy broth (TSB) were performed over 12 days. Number of biofilm bacteria attached to individual coupons was determined by plate culture and the coefficient of variation (CV%) calculated. The DNA, glycoconjugates and protein content of the biofilm were determined by analysing biofilm stained with SYTO 60, Alexa-488-labelled Aleuria aurantia lectin and SyproOrange respectively using Image J and Imaris software. Biofilm architecture was analysed using live/dead staining and confocal microscopy (CM) and scanning electron microscopy (SEM). Model biofilm was compared to naturally formed biofilm containing S. aureus on dry clinical surfaces. The CDC Biofilm reactor reproducibly formed a multi-layered, biofilm containing about 10(7) CFU/coupon embedded in thick extracellular polymeric substances. Within run CV was 9.5% and the between run CV was 10.1%. Protein was the principal component of both the in vitro model biofilm and the biofilms found on clinical surfaces. Continued

  12. Empirical Mode Decomposition on the sphere: application to the spatial scales of surface temperature variations

    Directory of Open Access Journals (Sweden)

    N. Fauchereau

    2008-06-01

    Full Text Available Empirical Mode Decomposition (EMD is applied here in two dimensions over the sphere to demonstrate its potential as a data-adaptive method of separating the different scales of spatial variability in a geophysical (climatological/meteorological field. After a brief description of the basics of the EMD in 1 then 2 dimensions, the principles of its application on the sphere are explained, in particular via the use of a zonal equal area partitioning. EMD is first applied to an artificial dataset, demonstrating its capability in extracting the different (known scales embedded in the field. The decomposition is then applied to a global mean surface temperature dataset, and we show qualitatively that it extracts successively larger scales of temperature variations related, for example, to topographic and large-scale, solar radiation forcing. We propose that EMD can be used as a global data-adaptive filter, which will be useful in analysing geophysical phenomena that arise as the result of forcings at multiple spatial scales.

  13. Stratified turbulent Bunsen flames: flame surface analysis and flame surface density modelling

    Science.gov (United States)

    Ramaekers, W. J. S.; van Oijen, J. A.; de Goey, L. P. H.

    2012-12-01

    In this paper it is investigated whether the Flame Surface Density (FSD) model, developed for turbulent premixed combustion, is also applicable to stratified flames. Direct Numerical Simulations (DNS) of turbulent stratified Bunsen flames have been carried out, using the Flamelet Generated Manifold (FGM) reduction method for reaction kinetics. Before examining the suitability of the FSD model, flame surfaces are characterized in terms of thickness, curvature and stratification. All flames are in the Thin Reaction Zones regime, and the maximum equivalence ratio range covers 0.1⩽φ⩽1.3. For all flames, local flame thicknesses correspond very well to those observed in stretchless, steady premixed flamelets. Extracted curvature radii and mixing length scales are significantly larger than the flame thickness, implying that the stratified flames all burn in a premixed mode. The remaining challenge is accounting for the large variation in (subfilter) mass burning rate. In this contribution, the FSD model is proven to be applicable for Large Eddy Simulations (LES) of stratified flames for the equivalence ratio range 0.1⩽φ⩽1.3. Subfilter mass burning rate variations are taken into account by a subfilter Probability Density Function (PDF) for the mixture fraction, on which the mass burning rate directly depends. A priori analysis point out that for small stratifications (0.4⩽φ⩽1.0), the replacement of the subfilter PDF (obtained from DNS data) by the corresponding Dirac function is appropriate. Integration of the Dirac function with the mass burning rate m=m(φ), can then adequately model the filtered mass burning rate obtained from filtered DNS data. For a larger stratification (0.1⩽φ⩽1.3), and filter widths up to ten flame thicknesses, a β-function for the subfilter PDF yields substantially better predictions than a Dirac function. Finally, inclusion of a simple algebraic model for the FSD resulted only in small additional deviations from DNS data

  14. Variation and Trends of Landscape Dynamics, Land Surface Phenology and Net Primary Production of the Appalachian Mountains

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yeqiao; Zhao, Jianjun; Zhou, Yuyu; Zhang, Hongyan

    2012-12-15

    The gradients of the Appalachian Mountains in elevations and latitudes provide a unique regional perspective of landscape variations in the eastern United States and a section of the southeastern Canada. This study reveals patterns and trends of landscape dynamics, land surface phenology and ecosystem production along the Appalachian Mountains using time series data from Global Inventory Modeling and Mapping Studies (GIMMS) and AVHRR Global Production Efficiency Model (GloPEM) datasets. We analyzed the spatial and temporal patterns of Normalized Difference Vegetation Index (NDVI), length of growing season (LOS) and net primary production (NPP) of selected ecoregions along the Appalachian Mountains regions. We compared the results out of the Appalachian Mountains regions in different spatial contexts including the North America and the Appalachian Trail corridor area. To reveal latitudinal variations we analyzed data and compared the results between 30°N-40°N and 40°N-50°N latitudes. The result revealed significant decreases in annual peak NDVI in the Appalachian Mountains regions. The trend for the Appalachian Mountains regions was -0.0018 (R2=0.55, P<0.0001) NDVI unit decrease per year during 25 years between 1982 and 2006. The LOS had prolonged 0.3 day yr-1 during 25 years over the Appalachian Mountains regions. The NPP increased by 2.68 gC m-2yr-2 in Appalachian Mountains regions from 1981 to 2000. The comparison with the North America reveals the effects of topography and ecosystem compositions of the Appalachian Mountains. The comparison with the Appalachian Trail corridor area provides a regional mega-transect view of the measured variables.

  15. A surface hydrology model for regional vector borne disease models

    Science.gov (United States)

    Tompkins, Adrian; Asare, Ernest; Bomblies, Arne; Amekudzi, Leonard

    2016-04-01

    Small, sun-lit temporary pools that form during the rainy season are important breeding sites for many key mosquito vectors responsible for the transmission of malaria and other diseases. The representation of this surface hydrology in mathematical disease models is challenging, due to their small-scale, dependence on the terrain and the difficulty of setting soil parameters. Here we introduce a model that represents the temporal evolution of the aggregate statistics of breeding sites in a single pond fractional coverage parameter. The model is based on a simple, geometrical assumption concerning the terrain, and accounts for the processes of surface runoff, pond overflow, infiltration and evaporation. Soil moisture, soil properties and large-scale terrain slope are accounted for using a calibration parameter that sets the equivalent catchment fraction. The model is calibrated and then evaluated using in situ pond measurements in Ghana and ultra-high (10m) resolution explicit simulations for a village in Niger. Despite the model's simplicity, it is shown to reproduce the variability and mean of the pond aggregate water coverage well for both locations and validation techniques. Example malaria simulations for Uganda will be shown using this new scheme with a generic calibration setting, evaluated using district malaria case data. Possible methods for implementing regional calibration will be briefly discussed.

  16. Variational model for one-dimensional quantum magnets

    Science.gov (United States)

    Kudasov, Yu. B.; Kozabaranov, R. V.

    2018-04-01

    A new variational technique for investigation of the ground state and correlation functions in 1D quantum magnets is proposed. A spin Hamiltonian is reduced to a fermionic representation by the Jordan-Wigner transformation. The ground state is described by a new non-local trial wave function, and the total energy is calculated in an analytic form as a function of two variational parameters. This approach is demonstrated with an example of the XXZ-chain of spin-1/2 under a staggered magnetic field. Generalizations and applications of the variational technique for low-dimensional magnetic systems are discussed.

  17. Variational data assimilation problem for the thermodynamics model with displaced pole

    Science.gov (United States)

    Parmuzin, Eugene; Agosgkov, Valery; Zakharova, Natalia

    2017-04-01

    The most versatile and promising technology for solving problems of monitoring and analysis of the natural environment is a four-dimensional variational data assimilation of observation data. The development of computational algorithms for the solution of data assimilation problems in geophysical hydrodynamics is important in the contemporary computation and informational science to improve the quality of long-term prediction by using the hydrodynamics sea model. These problems are applied to close and solve in practice the appropriate inverse problems of the geophysical hydrodynamics. In this work the variational data assimilation problems in the Baltic Sea water area with displaced pole were formulated and studied [1]. We assume, that the unique function which is obtained by observation data processing is the function and we permit that the function is known only on a part of considering area (for example, on a part of the Baltic Sea). Numerical experiments on restoring the ocean heat flux and obtaining solution of the system (temperature, salinity, velocity, and sea surface height) in the Baltic Sea primitive equation hydrodynamics model [2] with assimilation procedure were carried out. In the calculations we used daily sea surface temperature observation from Danish meteorological Institute, prepared on the basis of measurements of the radiometer (AVHRR, AATSR and AMSRE) and spectroradiometer (SEVIRI and MODIS). The spatial resolution of the model grid with respect to the horizontal variables is uniform on latitude (0.2 degree) and varies on longitude from 0.04 to 0.0004 degree . The results of the numerical experiments are presented. This study was supported by the Russian Foundation for Basic Research (project №16-01-00548) and project №14-11-00609 by the Russian Science Foundation. References: [1] Agoshkov V.I., Parmuzin E.I., Zakharova N.B., Zalesny V.B., Shutyaev V.P., Gusev A.V. Variational assimilation of observation data in the mathematical model of

  18. Does the hybrid light source (LED/laser) influence temperature variation on the enamel surface during 35% hydrogen peroxide bleaching? A randomized clinical trial.

    Science.gov (United States)

    de Freitas, Patricia Moreira; Menezes, Andressa Nery; da Mota, Ana Carolina Costa; Simões, Alyne; Mendes, Fausto Medeiros; Lago, Andrea Dias Neves; Ferreira, Leila Soares; Ramos-Oliveira, Thayanne Monteiro

    2016-01-01

    The present study investigated how a hybrid light source (LED/laser) influences temperature variation on the enamel surfaces during 35% hydrogen peroxide (HP) bleaching. Effects on the whitening effectiveness and tooth sensitivity were analyzed. Twenty-two volunteers were randomly assigned to two different treatments in a split-mouth experimental model: group 1 (control), 35% HP; group 2 (experimental), 35% HP + LED/laser. Color evaluation was performed before treatment, and 7 and 14 days after completion of bleaching, using a color shade scale. Tooth sensitivity was assessed using a visual analog scale (VAS; before, immediately, and 24 hours after bleaching). During the bleaching treatment, thermocouple channels positioned on the tooth surfaces recorded the temperature. Data on color and temperature changes were subjected to statistical analysis (α = 5%). Tooth sensitivity data were evaluated descriptively. Groups 1 and 2 showed mean temperatures (± standard deviation) of 30.7 ± 1.2 °C and 34.1 ± 1.3 °C, respectively. It was found that there were statistically significant differences between the groups, with group 2 showing higher mean variation (P enamel surface. The color change results showed no differences in bleaching between the two treatment groups (P = .177). The variation of the average temperature during the treatments was not statistically associated with color variation (P = .079). Immediately after bleaching, it was found that 36.4% of the subjects in group 2 had mild to moderate sensitivity. In group 1, 45.5% showed moderate sensitivity. In both groups, the sensitivity ceased within 24 hours. Hybrid light source (LED/ laser) influences temperature variation on the enamel surface during 35% HP bleaching and is not related to greater tooth sensitivity.

  19. Forcing Mechanisms for the Variations of Near-surface Temperature Lapse Rates along the Himalayas, Tibetan Plateau (HTP) and Their Surroundings

    Science.gov (United States)

    Kattel, D. B.; Yao, T.; Ullah, K.; Islam, G. M. T.

    2016-12-01

    This study investigates the monthly characteristics of near-surface temperature lapse rates (TLRs) (i.e., governed by surface energy balance) based on the 176 stations 30-year (1980 to 2010) dataset covering a wide range of topography, climatic regime and relief (4801 m) in the HTP and its surroundings. Empirical analysis based on techniques in thermodynamics and hydrostatic system were used to obtain the results. Steepest TLRs in summer is due to strong dry convection and shallowest in winter is due to inversion effect is the general pattern of TLR that reported in previous studies in other mountainous region. Result of this study reports a contrast variation of TLRs from general patterns, and suggest distinct forcing mechanisms in an annual cycle. Shallower lapse rate occurs in summer throughout the regions is due to strong heat exchange process within the boundary layer, corresponding to the warm and moist atmospheric conditions. There is a systematic differences of TLRs in winter between the northern and southern slopes the Himalayas. Steeper TLRs in winter on the northern slopes is due to intense cooling at higher elevations, corresponding to the continental dry and cold air surges, and considerable snow-temperature feedback. The differences in elevation and topography, as well as the distinct variation of turbulent heating and cooling, explain the contrast TLRs (shallower) values in winter on the southern slopes. Distinct diurnal variations of TLRs and its magnitudes between alpine, dry, humid and coastal regions is due to the variations of adiabatic mixing during the daytime in the boundary layer i.e., associated with the variations in net radiations, elevation, surface roughness and sea surface temperature. The findings of this study is useful to determine the temperature range for accurately modelling in various field such as hydrology, glaciology, ecology, forestry, agriculture, as well as inevitable for climate downscaling in complex mountainous terrain.

  20. Model of Dipole Field Variations in the LEP Bending Magnets

    CERN Document Server

    Bravin, Enrico; Drees, A; Mugnai, G

    1998-01-01

    The determination of the Z mass at LEP requires a knowledge of the relative beam energy in the order of 10 ppm, therefore it is essential to understand the dipole field variations to the same level of accuracy. In LEP the bending magnet field shows a relative increase of the order of 100 ppm over 10 hours, which was found to be caused by leakage currents from railways flowing along the vacuum cham ber and temperature variations. A LEP dipole test bench was set up for systematic investigations. Field variations were monitored with NMR probes while the cooling water temperature of both coil and vacuum chamber was kept under control. The results lead to a parametrisation of the magnetic field variation as a function of the vacuum chamber current and temperature.

  1. Model-assisted analysis of spatial and temporal variations in fruit temperature and transpiration highlighting the role of fruit development.

    Science.gov (United States)

    Nordey, Thibault; Léchaudel, Mathieu; Saudreau, Marc; Joas, Jacques; Génard, Michel

    2014-01-01

    Fruit physiology is strongly affected by both fruit temperature and water losses through transpiration. Fruit temperature and its transpiration vary with environmental factors and fruit characteristics. In line with previous studies, measurements of physical and thermal fruit properties were found to significantly vary between fruit tissues and maturity stages. To study the impact of these variations on fruit temperature and transpiration, a modelling approach was used. A physical model was developed to predict the spatial and temporal variations of fruit temperature and transpiration according to the spatial and temporal variations of environmental factors and thermal and physical fruit properties. Model predictions compared well to temperature measurements on mango fruits, making it possible to accurately simulate the daily temperature variations of the sunny and shaded sides of fruits. Model simulations indicated that fruit development induced an increase in both the temperature gradient within the fruit and fruit water losses, mainly due to fruit expansion. However, the evolution of fruit characteristics has only a very slight impact on the average temperature and the transpiration per surface unit. The importance of temperature and transpiration gradients highlighted in this study made it necessary to take spatial and temporal variations of environmental factors and fruit characteristics into account to model fruit physiology.

  2. Model-assisted analysis of spatial and temporal variations in fruit temperature and transpiration highlighting the role of fruit development.

    Directory of Open Access Journals (Sweden)

    Thibault Nordey

    Full Text Available Fruit physiology is strongly affected by both fruit temperature and water losses through transpiration. Fruit temperature and its transpiration vary with environmental factors and fruit characteristics. In line with previous studies, measurements of physical and thermal fruit properties were found to significantly vary between fruit tissues and maturity stages. To study the impact of these variations on fruit temperature and transpiration, a modelling approach was used. A physical model was developed to predict the spatial and temporal variations of fruit temperature and transpiration according to the spatial and temporal variations of environmental factors and thermal and physical fruit properties. Model predictions compared well to temperature measurements on mango fruits, making it possible to accurately simulate the daily temperature variations of the sunny and shaded sides of fruits. Model simulations indicated that fruit development induced an increase in both the temperature gradient within the fruit and fruit water losses, mainly due to fruit expansion. However, the evolution of fruit characteristics has only a very slight impact on the average temperature and the transpiration per surface unit. The importance of temperature and transpiration gradients highlighted in this study made it necessary to take spatial and temporal variations of environmental factors and fruit characteristics into account to model fruit physiology.

  3. The Variations of Land Surface Phenology in Northeast China and Its Responses to Climate Change from 1982 to 2013

    Directory of Open Access Journals (Sweden)

    Jianjun Zhao

    2016-05-01

    Full Text Available Northeast China is located at high northern latitudes and is a typical region of relatively high sensitivity to global climate change. Studies of the land surface phenology in Northeast China and its response to climate change are important for understanding global climate change. In this study, the land surface phenology parameters were calculated using the third generation dataset from the Global Inventory Modeling and Mapping Studies (GIMMS 3g that was collected from 1982 to 2013 were estimated to analyze the variations of the land surface phenology in Northeast China at different scales and to discuss the internal relationships between phenology and climate change. We examined the phonological changes of all ecoregions. The average start of the growing season (SOS did not exhibit a significant trend throughout the study area; however, the end of the growing season (EOS was significantly delayed by 4.1 days or 0.13 days/year (p < 0.05 over the past 32 years. The SOS for the Hulunbuir Plain, Greater Khingan Mountains and Lesser Khingan Mountains was earlier, and the SOS for the Sanjing, Songnen and Liaohe Plains was later. In addition, the EOS of the Greater Khingan Mountains, Lesser Khingan Mountains and Changbai Mountains was later than the EOS of the Liaohe Plain. The spring temperature had the greatest impact on the SOS. Precipitation had an insignificant impact on forest SOS and a relatively large impact on grassland SOS. The EOS was affected by both temperature and precipitation. Furthermore, although temperature had a lag effect on the EOS, no significant lag effect was observed for the SOS.

  4. Variational methods and effective actions in string models

    International Nuclear Information System (INIS)

    Dereli, T.; Tucker, R.W.

    1987-01-01

    Effective actions motivated by zero-order and first-order actions are examined. Particular attention is devoted to a variational procedure that is consistent with the structure equations involving the Lorentz connection. Attention is drawn to subtleties that can arise in varying higher-order actions and an efficient procedure developed to handle these cases using the calculus of forms. The effect of constrained variations on the field equations is discussed. (author)

  5. Testing the Processing Hypothesis of word order variation using a probabilistic language model

    NARCIS (Netherlands)

    Bloem, J.

    2016-01-01

    This work investigates the application of a measure of surprisal to modeling a grammatical variation phenomenon between near-synonymous constructions. We investigate a particular variation phenomenon, word order variation in Dutch two-verb clusters, where it has been established that word order

  6. Assessing modeled Greenland surface mass balance in the GISS Model E2 and its sensitivity to surface albedo

    Science.gov (United States)

    Alexander, Patrick; LeGrande, Allegra N.; Koenig, Lora S.; Tedesco, Marco; Moustafa, Samiah E.; Ivanoff, Alvaro; Fischer, Robert P.; Fettweis, Xavier

    2016-04-01

    The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) plays an important role in global sea level change. Regional Climate Models (RCMs) such as the Modèle Atmosphérique Régionale (MAR) have been employed at high spatial resolution with relatively complex physics to simulate ice sheet SMB. Global climate models (GCMs) incorporate less sophisticated physical schemes and provide outputs at a lower spatial resolution, but have the advantage of modeling the interaction between different components of the earth's oceans, climate, and land surface at a global scale. Improving the ability of GCMs to represent ice sheet SMB is important for making predictions of future changes in global sea level. With the ultimate goal of improving SMB simulated by the Goddard Institute for Space Studies (GISS) Model E2 GCM, we compare simulated GrIS SMB against the outputs of the MAR model and radar-derived estimates of snow accumulation. In order to reproduce present-day climate variability in the Model E2 simulation, winds are constrained to match the reanalysis datasets used to force MAR at the lateral boundaries. We conduct a preliminary assessment of the sensitivity of the simulated Model E2 SMB to surface albedo, a parameter that is known to strongly influence SMB. Model E2 albedo is set to a fixed value of 0.8 over the entire ice sheet in the initial configuration of the model (control case). We adjust this fixed value in an ensemble of simulations over a range of 0.4 to 0.8 (roughly the range of observed summer GrIS albedo values) to examine the sensitivity of ice-sheet-wide SMB to albedo. We prescribe albedo from the Moderate Resolution Imaging Spectroradiometer (MODIS) MCD43A3 v6 to examine the impact of a more realistic spatial and temporal variations in albedo. An age-dependent snow albedo parameterization is applied, and its impact on SMB relative to observations and the RCM is assessed.

  7. Variational data assimilative modeling of the Gulf of Maine in spring and summer 2010

    Science.gov (United States)

    Li, Yizhen; He, Ruoying; Chen, Ke; McGillicuddy, Dennis J.

    2015-05-01

    A data assimilative ocean circulation model is used to hindcast the Gulf of Maine [GOM) circulation in spring and summer 2010. Using the recently developed incremental strong constraint 4D Variational data assimilation algorithm, the model assimilates satellite sea surface temperature and in situ temperature and salinity profiles measured by expendable bathythermograph, Argo floats, and shipboard CTD casts. Validation against independent observations shows that the model skill is significantly improved after data assimilation. The data-assimilative model hindcast reproduces the temporal and spatial evolution of the ocean state, showing that a sea level depression southwest of the Scotian Shelf played a critical role in shaping the gulf-wide circulation. Heat budget analysis further demonstrates that both advection and surface heat flux contribute to temperature variability. The estimated time scale for coastal water to travel from the Scotian Shelf to the Jordan Basin is around 60 days, which is consistent with previous estimates based on in situ observations. Our study highlights the importance of resolving upstream and offshore forcing conditions in predicting the coastal circulation in the GOM.

  8. Variations in pCO2 during summer in the surface water of an unproductive lake in northern Sweden

    International Nuclear Information System (INIS)

    Jonsson, A.; Aaberg, J.; Jansson, M.

    2007-01-01

    Unproductive lakes are generally supersaturated with carbon dioxide (CO 2 ) and emit CO 2 to the atmosphere continuously during ice-free periods. However, temporal variation of the partial pressure of CO 2 (pCO 2 ) and thus of CO 2 evasion to atmosphere is poorly documented. We therefore carried out temporally high-resolution (every 6 h) measurements of the pCO 2 using an automated logger system in the surface water of a subarctic, unproductive, lake in the birch forest belt. The study period was June-September 2004. We found that the pCO 2 showed large seasonal variation, but low daily variation. The seasonal variation was likely mainly caused by variations in input and mineralization of allochthonous organic matter. Stratification depth probably also influenced pCO 2 of the surface water by controlling the volume in which mineralization of dissolved organic carbon (DOC) occurred. In lakes, with large variations in pCO 2 , as in our study lake a high (weekly) sampling intensity is recommended for obtaining accurate estimates of the evasion of CO 2

  9. Variations in pCO{sub 2} during summer in the surface water of an unproductive lake in northern Sweden

    Energy Technology Data Exchange (ETDEWEB)

    Jonsson, A.; Aaberg, J.; Jansson, M. [Dept. of Ecology and Environmental Sci ence, Umeaa Univ., 901 87 Umeaa (Sweden)]. e-mail: anders.jonsson@emg.umu.se

    2007-11-15

    Unproductive lakes are generally supersaturated with carbon dioxide (CO{sub 2}) and emit CO{sub 2} to the atmosphere continuously during ice-free periods. However, temporal variation of the partial pressure of CO{sub 2} (pCO{sub 2}) and thus of CO{sub 2} evasion to atmosphere is poorly documented. We therefore carried out temporally high-resolution (every 6 h) measurements of the pCO{sub 2} using an automated logger system in the surface water of a subarctic, unproductive, lake in the birch forest belt. The study period was June-September 2004. We found that the pCO{sub 2} showed large seasonal variation, but low daily variation. The seasonal variation was likely mainly caused by variations in input and mineralization of allochthonous organic matter. Stratification depth probably also influenced pCO{sub 2} of the surface water by controlling the volume in which mineralization of dissolved organic carbon (DOC) occurred. In lakes, with large variations in pCO{sub 2}, as in our study lake a high (weekly) sampling intensity is recommended for obtaining accurate estimates of the evasion of CO{sub 2}.

  10. Effect of surface roughness variation on the transmission characteristics of D-shaped fibers with ambient index change

    International Nuclear Information System (INIS)

    Kim, Hyun-Joo; Kwon, Oh-Jang; Han, Young-Geun

    2010-01-01

    The influence of surface roughness on the sensitivity of D-shaped fibers to changes in the ambient index was investigated. In order to obtain D-shaped fibers with different surface roughness, we polished one side of the fibers by using different abrasive grits. The topographies of the surfaces of the polished D-shaped fibers were then observed by using atomic force microscopy (AFM). The light scattered from the rough surfaces of the D-shaped fibers was measured by using optical microscopy. The effect of an ambient index change on the transmission characteristics of D-shaped fibers was measured for various values of the surface roughness. The experimental results indicate that variations in the surface roughness have a considerable influence on the sensitivity of the transmission characteristics of D-shaped fibers to changes in the ambient index.

  11. Influence of cloud fraction and snow cover to the variation of surface UV radiation at King Sejong station, Antarctica

    Science.gov (United States)

    Lee, Yun Gon; Koo, Ja-Ho; Kim, Jhoon

    2015-10-01

    This study investigated how cloud fraction and snow cover affect the variation of surface ultraviolet (UV) radiation by using surface Erythemal UV (EUV) and Near UV (NUV) observed at the King Sejong Station, Antarctica. First the Radiative Amplification Factor (RAF), the relative change of surface EUV according to the total-column ozone amount, is compared for different cloud fractions and solar zenith angles (SZAs). Generally, all cloudy conditions show that the increase of RAF as SZA becomes larger, showing the larger effects of vertical columnar ozone. For given SZA cases, the EUV transmission through mean cloud layer gradually decreases as cloud fraction increases, but sometimes the maximum of surface EUV appears under partly cloudy conditions. The high surface EUV transmittance under broken cloud conditions seems due to the re-radiation of scattered EUV by cloud particles. NUV transmission through mean cloud layer also decreases as cloud amount increases but the sensitivity to the cloud fraction is larger than EUV. Both EUV and NUV radiations at the surface are also enhanced by the snow cover, and their enhancement becomes higher as SZA increases implying the diurnal variation of surface albedo. This effect of snow cover seems large under the overcast sky because of the stronger interaction between snow surface and cloudy sky.

  12. Variation in nutrient characteristics of surface soils from the Luquillo Experimental Forest of Puerto Rico: A multivariate perspective.

    Science.gov (United States)

    S. B. Cox; M. R. Willig; F. N. Scatena

    2002-01-01

    We assessed the effects of landscape features (vegetation type and topography), season, and spatial hierarchy on the nutrient content of surface soils in the Luquillo Experimental Forest (LEF) of Puerto Rico. Considerable spatial variation characterized the soils of the LEF, and differences between replicate sites within each combination of vegetation type (tabonuco vs...

  13. Radiation balance at the surface in the city of São Paulo, Brazil: diurnal and seasonal variations

    NARCIS (Netherlands)

    Ferreira, M.J.; Oliveira, de A.P.; Soares, J.; Codato, G.; Wilde Barbaro, E.; Escobedo, J.F.

    2012-01-01

    The main goal of this work is to describe the diurnal and seasonal variations of the radiation balance components at the surface in the city of São Paulo based on observations carried out during 2004. Monthly average hourly values indicate that the amplitudes of the diurnal cycles of net radiation

  14. Seasonal Variations of the Earth's Gravitational Field: An Analysis of Atmospheric Pressure, Ocean Tidal, and Surface Water Excitation

    Science.gov (United States)

    Dong, D,; Gross, R.S.; Dickey, J.

    1996-01-01

    Monthly mean gravitational field parameters (denoted here as C(sub even)) that represent linear combinations of the primarily even degree zonal spherical harmonic coefficients of the Earth's gravitational field have been recovered using LAGEOS I data and are compared with those derived from gridded global surface pressure data of the National meteorological center (NMC) spanning 1983-1992. The effect of equilibrium ocean tides and surface water variations are also considered. Atmospheric pressure and surface water fluctuations are shown to be the dominant cause of observed annual C(sub even) variations. Closure with observations is seen at the 1sigma level when atmospheric pressure, ocean tide and surface water effects are include. Equilibrium ocean tides are shown to be the main source of excitation at the semiannual period with closure at the 1sigma level seen when both atmospheric pressure and ocean tide effects are included. The inverted barometer (IB) case is shown to give the best agreement with the observation series. The potential of the observed C(sub even) variations for monitoring mass variations in the polar regions of the Earth and the effect of the land-ocean mask in the IB calculation are discussed.

  15. Modelling the Probability Density Function of IPTV Traffic Packet Delay Variation

    Directory of Open Access Journals (Sweden)

    Michal Halas

    2012-01-01

    Full Text Available This article deals with modelling the Probability density function of IPTV traffic packet delay variation. The use of this modelling is in an efficient de-jitter buffer estimation. When an IP packet travels across a network, it experiences delay and its variation. This variation is caused by routing, queueing systems and other influences like the processing delay of the network nodes. When we try to separate these at least three types of delay variation, we need a way to measure these types separately. This work is aimed to the delay variation caused by queueing systems which has the main implications to the form of the Probability density function.

  16. Bayesian estimation of regularization parameters for deformable surface models

    International Nuclear Information System (INIS)

    Cunningham, G.S.; Lehovich, A.; Hanson, K.M.

    1999-01-01

    In this article the authors build on their past attempts to reconstruct a 3D, time-varying bolus of radiotracer from first-pass data obtained by the dynamic SPECT imager, FASTSPECT, built by the University of Arizona. The object imaged is a CardioWest total artificial heart. The bolus is entirely contained in one ventricle and its associated inlet and outlet tubes. The model for the radiotracer distribution at a given time is a closed surface parameterized by 482 vertices that are connected to make 960 triangles, with nonuniform intensity variations of radiotracer allowed inside the surface on a voxel-to-voxel basis. The total curvature of the surface is minimized through the use of a weighted prior in the Bayesian framework, as is the weighted norm of the gradient of the voxellated grid. MAP estimates for the vertices, interior intensity voxels and background count level are produced. The strength of the priors, or hyperparameters, are determined by maximizing the probability of the data given the hyperparameters, called the evidence. The evidence is calculated by first assuming that the posterior is approximately normal in the values of the vertices and voxels, and then by evaluating the integral of the multi-dimensional normal distribution. This integral (which requires evaluating the determinant of a covariance matrix) is computed by applying a recent algorithm from Bai et. al. that calculates the needed determinant efficiently. They demonstrate that the radiotracer is highly inhomogeneous in early time frames, as suspected in earlier reconstruction attempts that assumed a uniform intensity of radiotracer within the closed surface, and that the optimal choice of hyperparameters is substantially different for different time frames

  17. Spatial distribution, temporal variation and risks of parabens and their chlorinated derivatives in urban surface water in Beijing, China

    International Nuclear Information System (INIS)

    Li, Wenhui; Gao, Lihong; Shi, Yali; Wang, Yuan; Liu, Jiemin; Cai, Yaqi

    2016-01-01

    The occurrence and distribution of 13 target compounds, including eight parabens, four chlorinated parabens and p-hydroxybenzoic acid (PHBA), were detected in surface water samples at 35 sampling sites in the Beijing River system, China. The surface water samples were collected from the main rivers and lakes in the urban area monthly from July 2013 to June 2014 (except the frozen period). Laboratory analyses revealed that parabens were ubiquitous in the surface water of Beijing. PHBA was the predominant compound in the surface water samples, with the average concentration of 239 ng L −1 , followed by the total amount of chlorinated parabens (average 50.1 ng/L) and parabens (average 44.3 ng/L). It is noteworthy that octylparaben with longer chain was firstly detected in the surface water. Significant difference was observed for paraben concentrations from different sampling sites, and the highest level of parabens was found in the Xiaotaihou River, which was mainly due to the untreated sewage discharge. Seasonal variation of target compounds in the urban surface water was also studied, and parabens exhibited a different temporal variation from chlorinated derivatives. A combination of factors including high residual chlorine level and water temperature as well as intense ultraviolet radiation might enhance the persistence of chlorinated parabens in chlorinated water during the wet season. Risk assessment showed that parabens and their chlorinated derivatives are not likely to produce biological effects on aquatic ecosystems at current levels in the surface water of Beijing. - Highlights: • Parabens and chlorinated parabens are ubiquitous in surface water in Beijing. • Octylparaben with longer chain was firstly detected in surface water. • Untreated sewage discharge was the main source of parabens in river. • Parabens exhibited a different seasonal variation from chlorinated derivatives. • The risks of target compounds are negligible at environmentally

  18. Spatial distribution, temporal variation and risks of parabens and their chlorinated derivatives in urban surface water in Beijing, China

    Energy Technology Data Exchange (ETDEWEB)

    Li, Wenhui; Gao, Lihong [School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Shi, Yali; Wang, Yuan [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085 (China); Liu, Jiemin, E-mail: liujm@ustb.edu.cn [School of Chemistry and Biological Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Cai, Yaqi, E-mail: caiyaqi@rcees.ac.cn [State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085 (China)

    2016-01-01

    The occurrence and distribution of 13 target compounds, including eight parabens, four chlorinated parabens and p-hydroxybenzoic acid (PHBA), were detected in surface water samples at 35 sampling sites in the Beijing River system, China. The surface water samples were collected from the main rivers and lakes in the urban area monthly from July 2013 to June 2014 (except the frozen period). Laboratory analyses revealed that parabens were ubiquitous in the surface water of Beijing. PHBA was the predominant compound in the surface water samples, with the average concentration of 239 ng L{sup −1}, followed by the total amount of chlorinated parabens (average 50.1 ng/L) and parabens (average 44.3 ng/L). It is noteworthy that octylparaben with longer chain was firstly detected in the surface water. Significant difference was observed for paraben concentrations from different sampling sites, and the highest level of parabens was found in the Xiaotaihou River, which was mainly due to the untreated sewage discharge. Seasonal variation of target compounds in the urban surface water was also studied, and parabens exhibited a different temporal variation from chlorinated derivatives. A combination of factors including high residual chlorine level and water temperature as well as intense ultraviolet radiation might enhance the persistence of chlorinated parabens in chlorinated water during the wet season. Risk assessment showed that parabens and their chlorinated derivatives are not likely to produce biological effects on aquatic ecosystems at current levels in the surface water of Beijing. - Highlights: • Parabens and chlorinated parabens are ubiquitous in surface water in Beijing. • Octylparaben with longer chain was firstly detected in surface water. • Untreated sewage discharge was the main source of parabens in river. • Parabens exhibited a different seasonal variation from chlorinated derivatives. • The risks of target compounds are negligible at

  19. A statistical model for the wettability of surfaces with heterogeneous pore geometries

    Science.gov (United States)

    Brockway, Lance; Taylor, Hayden

    2016-10-01

    We describe a new approach to modeling the wetting behavior of micro- and nano-textured surfaces with varying degrees of geometrical heterogeneity. Surfaces are modeled as pore arrays with a Gaussian distribution of sidewall reentrant angles and a characteristic wall roughness. Unlike conventional wettability models, our model considers the fraction of a surface’s pores that are filled at any time, allowing us to capture more subtle dependences of a liquid’s apparent contact angle on its surface tension. The model has four fitting parameters and is calibrated for a particular surface by measuring the apparent contact angles between the surface and at least four probe liquids. We have calibrated the model for three heterogeneous nanoporous surfaces that we have fabricated: a hydrothermally grown zinc oxide, a film of polyvinylidene fluoride (PVDF) microspheres formed by spinodal decomposition, and a polytetrafluoroethylene (PTFE) film with pores defined by sacrificial polystyrene microspheres. These three surfaces show markedly different dependences of a liquid’s apparent contact angle on the liquid’s surface tension, and the results can be explained by considering geometric variability. The highly variable PTFE pores yield the most gradual variation of apparent contact angle with probe liquid surface tension. The PVDF microspheres are more regular in diameter and, although connected in an irregular manner, result in a much sharper transition from non-wetting to wetting behavior as surface tension reduces. We also demonstrate, by terminating porous zinc oxide with three alternative hydrophobic molecules, that a single geometrical model can capture a structure’s wetting behavior for multiple surface chemistries and liquids. Finally, we contrast our results with those from a highly regular, lithographically-produced structure which shows an extremely sharp dependence of wettability on surface tension. This new model could be valuable in designing and

  20. High cloud variations with surface temperature from 2002 to 2015: Contributions to atmospheric radiative cooling rate and precipitation changes

    Science.gov (United States)

    Liu, Run; Liou, Kuo-Nan; Su, Hui; Gu, Yu; Zhao, Bin; Jiang, Jonathan H.; Liu, Shaw Chen

    2017-05-01

    The global mean precipitation is largely constrained by atmospheric radiative cooling rates (Qr), which are sensitive to changes in high cloud fraction. We investigate variations of high cloud fraction with surface temperature (Ts) from July 2002 to June 2015 and compute their radiative effects on Qr using the Fu-Liou-Gu plane-parallel radiation model. We find that the tropical mean (30°S-30°N) high cloud fraction decreases with increasing Ts at a rate of about -1.0 ± 0.34% K-1 from 2002 to 2015, which leads to an enhanced atmospheric cooling around 0.86 W m-2 K-1. On the other hand, the northern midlatitudes (30°N-60°N) high cloud fraction increases with surface warming at a rate of 1.85 ± 0.65% K-1 and the near-global mean (60°S-60°N) high cloud fraction shows a statistically insignificant decreasing trend with increasing Ts over the analysis period. Dividing high clouds into cirrus, cirrostratus, and deep convective clouds, we find that cirrus cloud fraction increases with surface warming at a rate of 0.32 ± 0.11% K-1 (0.01 ± 0.17% K-1) for the near-global mean (tropical mean), while cirrostratus and deep convective clouds decrease with surface warming at a rate of -0.02 ± 0.18% K-1 and -0.33 ± 0.18% K-1 for the near-global mean and -0.64 ± 0.23% K-1 and -0.37 ± 0.13% K-1 for the tropical mean, respectively. High cloud fraction response to feedback to Ts accounts for approximately 1.9 ± 0.7% and 16.0 ± 6.1% of the increase in precipitation per unit surface warming over the period of 2002-2015 for the near-global mean and the tropical mean, respectively.

  1. Leishmania-specific surface antigens show sub-genus sequence variation and immune recognition.

    Directory of Open Access Journals (Sweden)

    Daniel P Depledge

    2010-09-01

    Full Text Available A family of hydrophilic acylated surface (HASP proteins, containing extensive and variant amino acid repeats, is expressed at the plasma membrane in infective extracellular (metacyclic and intracellular (amastigote stages of Old World Leishmania species. While HASPs are antigenic in the host and can induce protective immune responses, the biological functions of these Leishmania-specific proteins remain unresolved. Previous genome analysis has suggested that parasites of the sub-genus Leishmania (Viannia have lost HASP genes from their genomes.We have used molecular and cellular methods to analyse HASP expression in New World Leishmania mexicana complex species and show that, unlike in L. major, these proteins are expressed predominantly following differentiation into amastigotes within macrophages. Further genome analysis has revealed that the L. (Viannia species, L. (V. braziliensis, does express HASP-like proteins of low amino acid similarity but with similar biochemical characteristics, from genes present on a region of chromosome 23 that is syntenic with the HASP/SHERP locus in Old World Leishmania species and the L. (L. mexicana complex. A related gene is also present in Leptomonas seymouri and this may represent the ancestral copy of these Leishmania-genus specific sequences. The L. braziliensis HASP-like proteins (named the orthologous (o HASPs are predominantly expressed on the plasma membrane in amastigotes and are recognised by immune sera taken from 4 out of 6 leishmaniasis patients tested in an endemic region of Brazil. Analysis of the repetitive domains of the oHASPs has shown considerable genetic variation in parasite isolates taken from the same patients, suggesting that antigenic change may play a role in immune recognition of this protein family.These findings confirm that antigenic hydrophilic acylated proteins are expressed from genes in the same chromosomal region in species across the genus Leishmania. These proteins are

  2. Genetic diversity and antigenicity variation of Babesia bovis merozoite surface antigen-1 (MSA-1) in Thailand.

    Science.gov (United States)

    Tattiyapong, Muncharee; Sivakumar, Thillaiampalam; Takemae, Hitoshi; Simking, Pacharathon; Jittapalapong, Sathaporn; Igarashi, Ikuo; Yokoyama, Naoaki

    2016-07-01

    Babesia bovis, an intraerythrocytic protozoan parasite, causes severe clinical disease in cattle worldwide. The genetic diversity of parasite antigens often results in different immune profiles in infected animals, hindering efforts to develop immune control methodologies against the B. bovis infection. In this study, we analyzed the genetic diversity of the merozoite surface antigen-1 (msa-1) gene using 162 B. bovis-positive blood DNA samples sourced from cattle populations reared in different geographical regions of Thailand. The identity scores shared among 93 msa-1 gene sequences isolated by PCR amplification were 43.5-100%, and the similarity values among the translated amino acid sequences were 42.8-100%. Of 23 total clades detected in our phylogenetic analysis, Thai msa-1 gene sequences occurred in 18 clades; seven among them were composed of sequences exclusively from Thailand. To investigate differential antigenicity of isolated MSA-1 proteins, we expressed and purified eight recombinant MSA-1 (rMSA-1) proteins, including an rMSA-1 from B. bovis Texas (T2Bo) strain and seven rMSA-1 proteins based on the Thai msa-1 sequences. When these antigens were analyzed in a western blot assay, anti-T2Bo cattle serum strongly reacted with the rMSA-1 from T2Bo, as well as with three other rMSA-1 proteins that shared 54.9-68.4% sequence similarity with T2Bo MSA-1. In contrast, no or weak reactivity was observed for the remaining rMSA-1 proteins, which shared low sequence similarity (35.0-39.7%) with T2Bo MSA-1. While demonstrating the high genetic diversity of the B. bovis msa-1 gene in Thailand, the present findings suggest that the genetic diversity results in antigenicity variations among the MSA-1 antigens of B. bovis in Thailand. Copyright © 2016 Elsevier B.V. All rights reserved.

  3. Variations in global land surface phenology: a comparison of satellite optical and passive microwave data

    Science.gov (United States)

    Tong, X.; Tian, F.; Brandt, M.; Zhang, W.; Liu, Y.; Fensholt, R.

    2017-12-01

    Changes in vegetation phenological events are among the most sensitive biological responses to climate change. In last decades, facilitating by satellite remote sensing techniques, land surface phenology (LSP) have been monitored at global scale using proxy approaches as tracking the temporal change of a satellite-derived vegetation index. However, the existing global assessments of changes in LSP are all established on the basis of leaf phenology using NDVI derived from optical sensors, being responsive to vegetation canopy cover and greenness. Instead, the vegetation optical depth (VOD) parameter from passive microwave sensors, which is sensitive to the aboveground vegetation water content by including as well the woody components in the observations, provides an alternative, independent and comprehensive means for global vegetation phenology monitoring. We used the unique long-term global VOD record available for the period 1992-2012 to monitoring the dynamics of LSP metrics (length of season, start of season and end of season) in comparison with the dynamics of LSP metrics derived from the latest GIMMS NDVI3G V1. We evaluated the differences in the linear trends of LSP metrics between two datasets. Currently, our results suggest that the level of seasonality variation of vegetation water content is less than the vegetation greenness. We found significant phenological changes in vegetation water content in African woodlands, where has been reported with little leaf phenological change regardless of the delays in rainfall onset. Therefore, VOD might allow us to detect temporal shifts in the timing difference of vegetation water storage vs. leaf emergence and to see if some ecophysiological thresholds seem to be reached, that could cause species turnover as climate change-driven alterations to the African monsoon proceed.

  4. Comment on 'Modelling of surface energies of elemental crystals'

    International Nuclear Information System (INIS)

    Li Jinping; Luo Xiaoguang; Hu Ping; Dong Shanliang

    2009-01-01

    Jiang et al (2004 J. Phys.: Condens. Matter 16 521) present a model based on the traditional broken-bond model for predicting surface energies of elemental crystals. It is found that bias errors can be produced in calculating the coordination numbers of surface atoms, especially in the prediction of high-Miller-index surface energies. (comment)

  5. Occurrence, distribution and seasonal variation of organophosphate flame retardants and plasticizers in urban surface water in Beijing, China

    International Nuclear Information System (INIS)

    Shi, Yali; Gao, Lihong; Li, Wenhui; Wang, Yuan; Liu, Jiemin; Cai, Yaqi

    2016-01-01

    The occurrence, spatial distribution and seasonal variation of 14 organophosphate esters (OPEs) were investigated in urban surface water (river and lake water) from July 2013 to June 2014 in Beijing, China. Sewage influent and effluent samples, as well as rainwater and road runoff samples were also analyzed as the potential sources of OPEs in surface water. Tris(2-chloro-1-methylethyl) phosphate (TCPP) and tris(2-chloroethyl) phosphate (TCEP) were the most abundant OPEs with the average concentrations of 291 ng L"−"1 and 219 ng L"−"1, respectively. Relatively high concentrations of OPEs were detected in rivers located at southern and eastern urban of Beijing, which was probably attributed to the treated and untreated sewage discharge. Besides, higher levels of OPEs were observed in urban surface water in the summer, and the wet deposition (rainfall) was confirmed to be an important factor for this observation. Risk assessment showed low or medium risk of OPEs for the organisms (algae, crustacean and fish). - Highlights: • High levels of OPEs were detected in urban surface water of Beijing, China. • Seasonal variation revealed higher levels of OPEs in the summer. • Wastewater, rainwater and road runoff samples were analyzed as sources of OPEs. • The risks of OPEs to the organisms (algae, crustacean and fish) were assessed. - The occurrence, spatial distribution and seasonal variation of OPEs in urban surface water were investigated from densely populated big city (Beijing, China).

  6. Understanding Surface Adhesion in Nature: A Peeling Model.

    Science.gov (United States)

    Gu, Zhen; Li, Siheng; Zhang, Feilong; Wang, Shutao

    2016-07-01

    Nature often exhibits various interesting and unique adhesive surfaces. The attempt to understand the natural adhesion phenomena can continuously guide the design of artificial adhesive surfaces by proposing simplified models of surface adhesion. Among those models, a peeling model can often effectively reflect the adhesive property between two surfaces during their attachment and detachment processes. In the context, this review summarizes the recent advances about the peeling model in understanding unique adhesive properties on natural and artificial surfaces. It mainly includes four parts: a brief introduction to natural surface adhesion, the theoretical basis and progress of the peeling model, application of the peeling model, and finally, conclusions. It is believed that this review is helpful to various fields, such as surface engineering, biomedicine, microelectronics, and so on.

  7. Surface effects in solid mechanics models, simulations and applications

    CERN Document Server

    Altenbach, Holm

    2013-01-01

    This book reviews current understanding, and future trends, of surface effects in solid mechanics. Covers elasticity, plasticity and viscoelasticity, modeling based on continuum theories and molecular modeling and applications of different modeling approaches.

  8. Surface CUrrents from a Diagnostic model (SCUD): Pacific

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The SCUD data product is an estimate of upper-ocean velocities computed from a diagnostic model (Surface CUrrents from a Diagnostic model). This model makes daily...

  9. Influence of World and Gravity Model Selection on Surface Interacting Vehicle Simulations

    Science.gov (United States)

    Madden, Michael M.

    2007-01-01

    A vehicle simulation is surface-interacting if the state of the vehicle (position, velocity, and acceleration) relative to the surface is important. Surface-interacting simulations perform ascent, entry, descent, landing, surface travel, or atmospheric flight. Modeling of gravity is an influential environmental factor for surface-interacting simulations. Gravity is the free-fall acceleration observed from a world-fixed frame that rotates with the world. Thus, gravity is the sum of gravitation and the centrifugal acceleration due to the world s rotation. In surface-interacting simulations, the fidelity of gravity at heights above the surface is more significant than gravity fidelity at locations in inertial space. A surface-interacting simulation cannot treat the gravity model separately from the world model, which simulates the motion and shape of the world. The world model's simulation of the world's rotation, or lack thereof, produces the centrifugal acceleration component of gravity. The world model s reproduction of the world's shape will produce different positions relative to the world center for a given height above the surface. These differences produce variations in the gravitation component of gravity. This paper examines the actual performance of world and gravity/gravitation pairs in a simulation using the Earth.

  10. Multiwalled Carbon Nanotube Deposition on Model Environmental Surfaces

    Science.gov (United States)

    Deposition of multiwalled carbon nanotubes (MWNTs) on model environmental surfaces was investigated using a quartz crystal microbalance with dissipation monitoring (QCM-D). Deposition behaviors of MWNTs on positively and negatively charged surfaces were in good agreement with Der...

  11. Empirical model for estimating the surface roughness of machined ...

    African Journals Online (AJOL)

    Empirical model for estimating the surface roughness of machined ... as well as surface finish is one of the most critical quality measure in mechanical products. ... various cutting speed have been developed using regression analysis software.

  12. Variational cellular model of the molecular and crystal electronic structure

    International Nuclear Information System (INIS)

    Ferreira, L.G.; Leite, J.R.

    1977-12-01

    A variational version of the cellular method is developed to calculate the electronic structure of molecules and crystals. Due to the simplicity of the secular equation, the method is easy to be implemented. Preliminary calculations on the hydrogen molecular ion suggest that it is also accurate and of fast convergence [pt

  13. Towards Modelling Variation in Music as Foundation for Similarity

    NARCIS (Netherlands)

    Volk, A.; de Haas, W.B.; van Kranenburg, P.; Cambouropoulos, E.; Tsougras, C.; Mavromatis, P.; Pastiadis, K.

    2012-01-01

    This paper investigates the concept of variation in music from the perspective of music similarity. Music similarity is a central concept in Music Information Retrieval (MIR), however there exists no comprehensive approach to music similarity yet. As a consequence, MIR faces the challenge on how to

  14. Surfaces foliated by planar geodesics: a model forcurved wood design

    DEFF Research Database (Denmark)

    Brander, David; Gravesen, Jens

    2017-01-01

    Surfaces foliated by planar geodesics are a natural model for surfaces made from wood strips. We outline how to construct all solutions, and produce non-trivial examples, such as a wood-strip Klein bottle......Surfaces foliated by planar geodesics are a natural model for surfaces made from wood strips. We outline how to construct all solutions, and produce non-trivial examples, such as a wood-strip Klein bottle...

  15. Poloidal density variation of impurities in a rotating tokamak plasma - flux surface coordinates and effect on transport coefficients

    International Nuclear Information System (INIS)

    Romanelli, M.

    1999-09-01

    The poloidal variation of impurity densities over magnetic surfaces brings about an enhancement of neoclassical transport coefficients, as shown by Romanelli and Ottaviani for impurities in the Pfirsch Schlueter regime and by Helander for particles in the banana-plateau regime, both in a large aspect ratio tokamak. The same effect will occur in a finite aspect ratio tokamak and therefore it is considered to be relevant for inclusion in transport codes for comparison with the experimental measurements of impurity transport. Here an expression for the impurity-density poloidal-variation generated by the fast toroidal rotation of the plasma column is presented in general coordinates. (author)

  16. Delay Variation Model with RTP Flows Behavior in Accordance with M/D/1 Kendall's Notation

    Directory of Open Access Journals (Sweden)

    Miroslav Voznak

    2010-01-01

    Full Text Available This paper focuses on the design of a mathematical model of end-to-end delay of a VoIP connection, in particular on a delay variation. It describes all partial delay components and mechanisms, its generation, facilities and its mathematical formulations. A new approach to the delay variation model is presented; its validation has been done by an experiment.

  17. Hydrologically induced orientation variations of a tri-axial Earth's principal axes based on satellite-gravimetric and hydrological models

    Directory of Open Access Journals (Sweden)

    Shen Wenbin

    2013-05-01

    Full Text Available The Earth is a tri-axial body, with unequal principal inertia moments, A, B and C. The corresponding principal axes a, b and c are determined by the mass distribution of the Earth, and their orientations vary with the mass redistribution. In this study, the hydrologically induced variations are estimated on the basis of satellite gravimetric data, including those from satellite laser ranging (SLR and gravity recovery and climate experiment (GRACE, and hydrological models from global land data assimilation system (GLDAS. The longitude variations of a and b are mainly related to the variations of the spherical harmonic coefficients C¯22 and S¯22, which have been estimated to be consisting annual variations of about 1. 6 arc seconds and 1. 8 arc seconds, respectively, from gravity data. This result is confirmed by land surface water storage provided by the GLDAS model. If the atmospheric and oceanic signals are removed from the spherical harmonic coefficients C¯21 and S¯21, the agreement of the orientation series for c becomes poor, possibly due to the inaccurate background models used in pre-processing of the satellite gravimetric data. Determination of the orientation variations may provide a better understanding of various phenomena in the study of the rotation of a tri-axial Earth.

  18. Modelling of energetic molecule-surface interactions

    International Nuclear Information System (INIS)

    Kerford, M.

    2000-09-01

    This thesis contains the results of molecular dynamics simulations of molecule-surface interactions, looking particularly at fullerene molecules and carbon surfaces. Energetic impacts of fullerene molecules on graphite create defect craters. The relationship between the parameters of the impacting molecule and the parameters of the crater axe examined and found to be a function of the energy and velocity of the impacting molecule. Less energetic fullerene molecules can be scattered from a graphite surface and the partitioning of energy after a scattering event is investigated. It is found that a large fraction of the kinetic energy retained after impact is translational energy, with a small fraction of rotational energy and a number of vibrational modes. At impact energies where the surface is not broken and at normal incidence, surface waves axe seen to occur. These waves axe used to develop a method of desorbing molecules from a graphite surface without damage to either the surface or the molecules being desorbed. A number of fullerene molecules are investigated and ways to increase the desorption yield are examined. It is found that this is a successful technique for desorbing large numbers of intact molecules from graphite. This technique could be used for desorbing intact molecules into a gas phase for mass spectrometric analysis. (author)

  19. Decadal variations in estimated surface solar radiation over Switzerland since the late 19th century

    Directory of Open Access Journals (Sweden)

    A. Sanchez-Lorenzo

    2012-09-01

    Full Text Available Our knowledge on trends in surface solar radiation (SSR involves uncertainties due to the scarcity of long-term time series of SSR, especially with records before the second half of the 20th century. Here we study the trends of all-sky SSR from 1885 to 2010 in Switzerland, which have been estimated using a homogenous dataset of sunshine duration series. This variable is shown to be a useful proxy data of all-sky SSR, which can help to solve some of the current open issues in the dimming/brightening phenomenon. All-sky SSR has been fairly stable with little variations in the first half of the 20th century, unlike the second half of the 20th century that is characterized also in Switzerland by a dimming from the 1950s to the 1980s and a subsequent brightening. Cloud cover changes seem to explain the major part of the decadal variability observed in all-sky SSR, at least from 1885 to the 1970s; at this point, a discrepancy in the sign of the trend is visible in the all-sky SSR and cloud cover series from the 1970s to the present. Finally, an attempt to estimate SSR series for clear-sky conditions, based also on sunshine duration records since the 1930s, has been made for the first time. The mean clear-sky SSR series shows no relevant changes between the 1930s to the 1950s, then a decrease, smaller than the observed in the all-sky SSR, from the 1960s to 1970s, and ends with a strong increase from the 1980s up to the present. During the three decades from 1981 to 2010 the estimated clear-sky SSR trends reported in this study are in line with previous findings over Switzerland based on direct radiative flux measurements. Moreover, the signal of the El Chichón and Pinatubo volcanic eruption visible in the estimated clear-sky SSR records further demonstrates the potential to infer aerosol-induced radiation changes from sunshine duration observations.

  20. Predicting Indian Summer Monsoon onset through variations of surface air temperature and relative humidity

    Science.gov (United States)

    Stolbova, Veronika; Surovyatkina, Elena; Kurths, Jurgen

    2015-04-01

    Indian Summer Monsoon (ISM) rainfall has an enormous effect on Indian agriculture, economy, and, as a consequence, life and prosperity of more than one billion people. Variability of the monsoonal rainfall and its onset have a huge influence on food production, agricultural planning and GDP of the country, which on 22% is determined by agriculture. Consequently, successful forecasting of the ISM onset is a big challenge and large efforts are being put into it. Here, we propose a novel approach for predictability of the ISM onset, based on critical transition theory. The ISM onset is defined as an abrupt transition from sporadious rainfall to spatially organized and temporally sustained rainfall. Taking this into account, we consider the ISM onset as is a critical transition from pre-monsoon to monsoon, which take place in time and also in space. It allows us to suggest that before the onset of ISM on the Indian subcontinent should be areas of critical behavior where indicators of the critical transitions can be detected through an analysis of observational data. First, we identify areas with such critical behavior. Second, we use detected areas as reference points for observation locations for the ISM onset prediction. Third, we derive a precursor for the ISM onset based on the analysis of surface air temperature and relative humidity variations in these reference points. Finally, we demonstrate the performance of this precursor on two observational data sets. The proposed approach allows to determine ISM onset in advance in 67% of all considered years. Our proposed approach is less effective during the anomalous years, which are associated with weak/strong monsoons, e.g. El-Nino, La-Nina or positive Indian Ocean Dipole events. The ISM onset is predicted for 23 out of 27 normal monsoon years (85%) during the past 6 decades. In the anomalous years, we show that time series analysis in both areas during the pre-monsoon period reveals indicators whether the

  1. Mixed Higher Order Variational Model for Image Recovery

    Directory of Open Access Journals (Sweden)

    Pengfei Liu

    2014-01-01

    Full Text Available A novel mixed higher order regularizer involving the first and second degree image derivatives is proposed in this paper. Using spectral decomposition, we reformulate the new regularizer as a weighted L1-L2 mixed norm of image derivatives. Due to the equivalent formulation of the proposed regularizer, an efficient fast projected gradient algorithm combined with monotone fast iterative shrinkage thresholding, called, FPG-MFISTA, is designed to solve the resulting variational image recovery problems under majorization-minimization framework. Finally, we demonstrate the effectiveness of the proposed regularization scheme by the experimental comparisons with total variation (TV scheme, nonlocal TV scheme, and current second degree methods. Specifically, the proposed approach achieves better results than related state-of-the-art methods in terms of peak signal to ratio (PSNR and restoration quality.

  2. Explained variation and predictive accuracy in general parametric statistical models: the role of model misspecification

    DEFF Research Database (Denmark)

    Rosthøj, Susanne; Keiding, Niels

    2004-01-01

    When studying a regression model measures of explained variation are used to assess the degree to which the covariates determine the outcome of interest. Measures of predictive accuracy are used to assess the accuracy of the predictions based on the covariates and the regression model. We give a ...... a detailed and general introduction to the two measures and the estimation procedures. The framework we set up allows for a study of the effect of misspecification on the quantities estimated. We also introduce a generalization to survival analysis....

  3. Exactly soluble models for surface partition of large clusters

    International Nuclear Information System (INIS)

    Bugaev, K.A.; Bugaev, K.A.; Elliott, J.B.

    2007-01-01

    The surface partition of large clusters is studied analytically within a framework of the 'Hills and Dales Model'. Three formulations are solved exactly by using the Laplace-Fourier transformation method. In the limit of small amplitude deformations, the 'Hills and Dales Model' gives the upper and lower bounds for the surface entropy coefficient of large clusters. The found surface entropy coefficients are compared with those of large clusters within the 2- and 3-dimensional Ising models

  4. A Surface Modeling Paradigm for Electromagnetic Applications in Aerospace Structures

    OpenAIRE

    Jha, RM; Bokhari, SA; Sudhakar, V; Mahapatra, PR

    1989-01-01

    A systematic approach has been developed to model the surfaces encountered in aerospace engineering for EM applications. The basis of this modeling is the quadric canonical shapes which are the coordinate surfaces of the Eisenhart Coordinate systems. The building blocks are visualized as sections of quadric cylinders and surfaces of revolution. These truncated quadrics can successfully model realistic aerospace structures which are termed a s hybrid quadrics, of which the satellite launch veh...

  5. Model for the Evolving Bed Surface around an Offshore Monopile

    DEFF Research Database (Denmark)

    Hartvig, Peres Akrawi

    2012-01-01

    This paper presents a model for the bed surface around an offshore monopile. The model has been designed from measured laboratory bed surfaces and is shown to reproduce these satisfactorily for both scouring and backfilling. The local rate of the bed elevation is assumed to satisfy a certain...... general parametrized surface. The model also accounts for sliding of sediment particles when the angle of the local bed slope exceeds the angle of repose....

  6. A surface diffuse scattering model for the mobility of electrons in surface charge coupled devices

    International Nuclear Information System (INIS)

    Ionescu, M.

    1977-01-01

    An analytical model for the mobility of electrons in surface charge coupled devices is studied on the basis of the results previously obtained, considering a surface diffuse scattering; the importance of the results obtained for a better understanding of the influence of the fringing field in surface charge coupled devices is discussed. (author)

  7. Modelling global fresh surface water temperature

    NARCIS (Netherlands)

    Beek, L.P.H. van; Eikelboom, T.; Vliet, M.T.H. van; Bierkens, M.F.P.

    2011-01-01

    Temperature directly determines a range of water physical properties including vapour pressure, surface tension, density and viscosity, and the solubility of oxygen and other gases. Indirectly water temperature acts as a strong control on fresh water biogeochemistry, influencing sediment

  8. Radiative Transfer Model for Contaminated Rough Surfaces

    Science.gov (United States)

    2013-02-01

    reflectance of potassium chlorate and ammonium nitrate contaminated surfaces in mid-wavelength and long-wavelength infrared for detection. Our framework...obtained excellent or good results for lab measurements of potassium chlorate on most aluminum surfaces; however, ammonium nitrate on painted aluminum...misidentify potassium chlorate as ammonium nitrate and vice versa). We also observed moderate success on field data. 15. SUBJECT TERMS radiative

  9. High-frequency pressure variations in the vicinity of a surface CO2 flux chamber

    Science.gov (United States)

    Eugene S. Takle; James R. Brandle; R. A. Schmidt; Rick Garcia; Irina V. Litvina; William J. Massman; Xinhua Zhou; Geoffrey Doyle; Charles W. Rice

    2003-01-01

    We report measurements of 2Hz pressure fluctuations at and below the soil surface in the vicinity of a surface-based CO2 flux chamber. These measurements were part of a field experiment to examine the possible role of pressure pumping due to atmospheric pressure fluctuations on measurements of surface fluxes of CO2. Under the moderate wind speeds, warm temperatures,...

  10. Assessment of spatio-temporal variations in surface water quality of ...

    African Journals Online (AJOL)

    MANN

    2012-10-02

    Oct 2, 2012 ... 1School of Biological and Environmental Sciences, Shoolini University, Solan, H.P.- 173229, India. 2Department ... variation. Of late, multivariate statistical techniques such ..... Statistical Package for the Social Sciences 10.0.

  11. Genetic variation of hepatitis B surface antigen among acute and chronic hepatitis B virus infections in The Netherlands.

    Science.gov (United States)

    Cremer, Jeroen; Hofstraat, Sanne H I; van Heiningen, Francoise; Veldhuijzen, Irene K; van Benthem, Birgit H B; Benschop, Kimberley S M

    2018-05-24

    Genetic variation within hepatitis B surface antigen (HBsAg), in particular within the major hydrophobic region (MHR), is related to immune/vaccine and test failures and can have a significant impact on the vaccination and diagnosis of acute infection. This study shows, for the first time, variation among acute cases and compares the amino acid variation within the HBsAg between acute and chronic infections. We analyzed the virus isolated from 1231 acute and 585 chronic cases reported to an anonymized public health surveillance database between 2004 and 2014 in The Netherlands. HBsAg analysis revealed the circulation of 6 genotypes (Gt); GtA was the dominant genotype followed by GtD among both acute (68.2% and 17.4%, respectively) and chronic (34.9% and 34.2%, respectively) cases. Variation was the highest among chronic strains compared to that among acute strains. Both acute and chronic GtD showed the highest variation compared to that of other genotypes (P < .01). Substitutions within the MHR were found in 8.5% of the acute strains and 18.6% of the chronic strains. Specific MHR substitutions described to have an impact on vaccine/immune escape and/or HBsAg test failure were found among 4.1% of the acute strains and 7.0% of the chronic strains. In conclusion, we show a high variation of HBsAg among acute and chronic hepatitis B virus-infected cases in The Netherlands, in particular among those infected with GtD, and compare, for the first time, variation in frequencies between acute and chronic cases. Additional studies on the impact of these variations on vaccination and test failure need to be conducted, as well as whether HBsAg false-negative variants have been missed. © 2018 The Authors. Journal of Medical Virology Published by Wiley Periodicals, Inc.

  12. Analytical fitting model for rough-surface BRDF.

    Science.gov (United States)

    Renhorn, Ingmar G E; Boreman, Glenn D

    2008-08-18

    A physics-based model is developed for rough surface BRDF, taking into account angles of incidence and scattering, effective index, surface autocovariance, and correlation length. Shadowing is introduced on surface correlation length and reflectance. Separate terms are included for surface scatter, bulk scatter and retroreflection. Using the FindFit function in Mathematica, the functional form is fitted to BRDF measurements over a wide range of incident angles. The model has fourteen fitting parameters; once these are fixed, the model accurately describes scattering data over two orders of magnitude in BRDF without further adjustment. The resulting analytical model is convenient for numerical computations.

  13. Surface quality prediction model of nano-composite ceramics in ultrasonic vibration-assisted ELID mirror grinding

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Bo; Chen, Fan; Jia, Xiao-feng; Zhao, Chong-yang; Wang, Xiao-bo [Henan Polytechnic University, Jiaozuo (China)

    2017-04-15

    Ultrasonic vibration-assisted Electrolytic in-process dressing (ELID) grinding is a highly efficient and highly precise machining method. The surface quality prediction model in ultrasonic vibration-assisted ELID mirror grinding was studied. First, the interaction between grits and workpiece surface was analyzed according to kinematic mechanics, and the surface roughness model was developed. The variations in surface roughness under different parameters was subsequently calculated and analyzed by MATLAB. Results indicate that compared with the ordinary ELID grinding, ultrasonic vibration-assisted ELID grinding is superior, because it has more stable and better surface quality and has an improved range of ductile machining.

  14. Modeling of circular-grating surface-emitting lasers

    Science.gov (United States)

    Shams-Zadeh-Amiri, Ali M.

    Grating-coupled surface-emitting lasers became an area of growing interest due to their salient features. Emission from a broad area normal to the wafer surface, makes them very well suited in high power applications and two- dimensional laser arrays. These new possibilities have caused an interest in different geometries to fully develop their potential. Among them, circular-grating lasers have the additional advantage of producing a narrow beam with a circular cross section. This special feature makes them ideal for coupling to optical fibers. All existing theoretical models dealing with circular- grating lasers only consider first-order gratings, or second-order gratings, neglecting surface emission. In this thesis, the emphasis is to develop accurate models describing the laser performance by considering the radiation field. Toward this aim, and due to the importance of the radiation modes in surface-emitting structures, a theoretical study of these modes in multilayer planar structures has been done in a rigorous and systematic fashion. Problems like orthogonality of the radiation modes have been treated very accurately. We have considered the inner product of radiation modes using the distribution theory. Orthogonality of degenerate radiation modes is an important issue. We have examined its validity using the transfer matrix method. It has been shown that orthogonality of degenerate radiation modes in a very special case leads to the Brewster theorem. In addition, simple analytical formulas for the normalization of radiation modes have been derived. We have shown that radiation modes can be handled in a much easier way than has been thought before. A closed-form spectral dyadic Green's function formulation of multilayer planar structures has been developed. In this formulation, both rectangular and cylindrical structures can be treated within the same mathematical framework. The Hankel transform of some auxiliary functions defined on a circular aperture has

  15. Empirical model of subdaily variations in the Earth rotation from GPS and its stability

    Science.gov (United States)

    Panafidina, N.; Kurdubov, S.; Rothacher, M.

    2012-12-01

    The model recommended by the IERS for these variations at diurnal and semidiurnal periods has been computed from an ocean tide model and comprises 71 terms in polar motion and Universal Time. In the present study we compute an empirical model of variations in the Earth rotation on tidal frequencies from homogeneously re-processed GPS-observations over 1994-2007 available as free daily normal equations. We discuss the reliability of the obtained amplitudes of the ERP variations and compare results from GPS and VLBI data to identify technique-specific problems and instabilities of the empirical tidal models.

  16. Introductory Biology Students’ Conceptual Models and Explanations of the Origin of Variation

    Science.gov (United States)

    Shaw, Neil; Momsen, Jennifer; Reinagel, Adam; Le, Paul; Taqieddin, Ranya; Long, Tammy

    2014-01-01

    Mutation is the key molecular mechanism generating phenotypic variation, which is the basis for evolution. In an introductory biology course, we used a model-based pedagogy that enabled students to integrate their understanding of genetics and evolution within multiple case studies. We used student-generated conceptual models to assess understanding of the origin of variation. By midterm, only a small percentage of students articulated complete and accurate representations of the origin of variation in their models. Targeted feedback was offered through activities requiring students to critically evaluate peers’ models. At semester's end, a substantial proportion of students significantly improved their representation of how variation arises (though one-third still did not include mutation in their models). Students’ written explanations of the origin of variation were mostly consistent with their models, although less effective than models in conveying mechanistic reasoning. This study contributes evidence that articulating the genetic origin of variation is particularly challenging for learners and may require multiple cycles of instruction, assessment, and feedback. To support meaningful learning of the origin of variation, we advocate instruction that explicitly integrates multiple scales of biological organization, assessment that promotes and reveals mechanistic and causal reasoning, and practice with explanatory models with formative feedback. PMID:25185235

  17. Measuring variation of indoor radon concentration using bare nuclear tracks detectors, scintillation counters and surface barrier detectors

    International Nuclear Information System (INIS)

    Ishak, I.; Mahat, R.H.; Amin, Y.M.

    1996-01-01

    Bare LRI 15 nuclear track detectors , scintillators counter and surface barrier detectors were used to measured the indoor radon concentration in various location within two rooms. Spatial variation of the radon concentration is caused by positioning of the door, windows, furniture, cracks in the building and also distances from floor, wall and ceiling. It is found that the change in temperature are causing radon concentration to increase at certain time of the day

  18. Despeckling Polsar Images Based on Relative Total Variation Model

    Science.gov (United States)

    Jiang, C.; He, X. F.; Yang, L. J.; Jiang, J.; Wang, D. Y.; Yuan, Y.

    2018-04-01

    Relatively total variation (RTV) algorithm, which can effectively decompose structure information and texture in image, is employed in extracting main structures of the image. However, applying the RTV directly to polarimetric SAR (PolSAR) image filtering will not preserve polarimetric information. A new RTV approach based on the complex Wishart distribution is proposed considering the polarimetric properties of PolSAR. The proposed polarization RTV (PolRTV) algorithm can be used for PolSAR image filtering. The L-band Airborne SAR (AIRSAR) San Francisco data is used to demonstrate the effectiveness of the proposed algorithm in speckle suppression, structural information preservation, and polarimetric property preservation.

  19. A variational multiscale constitutive model for nanocrystalline materials

    KAUST Repository

    Gurses, Ercan; El Sayed, Tamer S.

    2011-01-01

    grain interior phase and a grain boundary effected zone (GBAZ). A rate-independent isotropic porous plasticity model is employed to describe the GBAZ, whereas a crystal-plasticity model which accounts for the transition from partial dislocation to full

  20. Seasonal and Spatial Variation of Surface Urban Heat Island Intensity in a Small Urban Agglomerate in Brazil

    Directory of Open Access Journals (Sweden)

    Elis Dener Lima Alves

    2016-12-01

    Full Text Available In recent years, SUHIs (surface urban heat islands have been greatly emphasized in urban climate studies, since it is one of the climate phenomena most influenced by human action. In this study, temporal and spatial variations of SUHIs in the cities of Ceres and Rialma (Brazil were investigated; satellite Landsat 8 TIRS/OLI images from 2013 to 2016 were used for this purpose. The results showed that in all seasons, two relationships were observed, one positive and one negative. An N D V I (Normalized Difference Vegetation Index of 0.2 is the divider of this relationship: up to this value, the relationship is positive, that is, the higher the N D V I value, the higher the surface temperature, while the relationship is negative at an N D V I greater than 0.2. There was high seasonal variation in the SUHIs, with the highest intensities recorded in the spring and summer (±12 °C, and the lowest in the winter. These temporal variations were attributed to the annual cycle of precipitation, which directly involves the robustness of the Cerrado vegetation. SUHIs occupied, on average, an area three times larger than the area of SUCIs (surface urban cool islands. The highest values of SUCIs were observed in water bodies and in valley bottoms. Overall, SUHIs showed high intensities; however, a more intense core area, such as in large cities, was not observed.

  1. Natural variation of model mutant phenotypes in Ciona intestinalis.

    Directory of Open Access Journals (Sweden)

    Paolo Sordino

    Full Text Available BACKGROUND: The study of ascidians (Chordata, Tunicata has made a considerable contribution to our understanding of the origin and evolution of basal chordates. To provide further information to support forward genetics in Ciona intestinalis, we used a combination of natural variation and neutral population genetics as an approach for the systematic identification of new mutations. In addition to the significance of developmental variation for phenotype-driven studies, this approach can encompass important implications in evolutionary and population biology. METHODOLOGY/PRINCIPAL FINDINGS: Here, we report a preliminary survey for naturally occurring mutations in three geographically interconnected populations of C. intestinalis. The influence of historical, geographical and environmental factors on the distribution of abnormal phenotypes was assessed by means of 12 microsatellites. We identified 37 possible mutant loci with stereotyped defects in embryonic development that segregate in a way typical of recessive alleles. Local populations were found to differ in genetic organization and frequency distribution of phenotypic classes. CONCLUSIONS/SIGNIFICANCE: Natural genetic polymorphism of C. intestinalis constitutes a valuable source of phenotypes for studying embryonic development in ascidians. Correlating genetic structure and the occurrence of abnormal phenotypes is a crucial focus for understanding the selective forces that shape natural finite populations, and may provide insights of great importance into the evolutionary mechanisms that generate animal diversity.

  2. Natural Variation of Model Mutant Phenotypes in Ciona intestinalis

    Science.gov (United States)

    Brown, Euan R.; Leccia, Nicola I.; Squarzoni, Paola; Tarallo, Raffaella; Alfano, Christian; Caputi, Luigi; D'Ambrosio, Palmira; Daniele, Paola; D'Aniello, Enrico; D'Aniello, Salvatore; Maiella, Sylvie; Miraglia, Valentina; Russo, Monia Teresa; Sorrenti, Gerarda; Branno, Margherita; Cariello, Lucio; Cirino, Paola; Locascio, Annamaria; Spagnuolo, Antonietta; Zanetti, Laura; Ristoratore, Filomena

    2008-01-01

    Background The study of ascidians (Chordata, Tunicata) has made a considerable contribution to our understanding of the origin and evolution of basal chordates. To provide further information to support forward genetics in Ciona intestinalis, we used a combination of natural variation and neutral population genetics as an approach for the systematic identification of new mutations. In addition to the significance of developmental variation for phenotype-driven studies, this approach can encompass important implications in evolutionary and population biology. Methodology/Principal Findings Here, we report a preliminary survey for naturally occurring mutations in three geographically interconnected populations of C. intestinalis. The influence of historical, geographical and environmental factors on the distribution of abnormal phenotypes was assessed by means of 12 microsatellites. We identified 37 possible mutant loci with stereotyped defects in embryonic development that segregate in a way typical of recessive alleles. Local populations were found to differ in genetic organization and frequency distribution of phenotypic classes. Conclusions/Significance Natural genetic polymorphism of C. intestinalis constitutes a valuable source of phenotypes for studying embryonic development in ascidians. Correlating genetic structure and the occurrence of abnormal phenotypes is a crucial focus for understanding the selective forces that shape natural finite populations, and may provide insights of great importance into the evolutionary mechanisms that generate animal diversity. PMID:18523552

  3. Digital Modeling Phenomenon Of Surface Ground Movement

    OpenAIRE

    Ioan Voina; Maricel Palamariu; Iohan Neuner; Tudor Salagean; Dumitru Onose; Mircea Ortelecan; Anca Maria Moscovici; Mariana Calin

    2016-01-01

    With the development of specialized software applications it was possible to approach and resolve complex problems concerning automating and process optimization for which are being used field data. Computerized representation of the shape and dimensions of the Earth requires a detailed mathematical modeling, known as "digital terrain model". The paper aims to present the digital terrain model of Vulcan mining, Hunedoara County, Romania. Modeling consists of a set of mathematical equations th...

  4. Impact of Dust on Mars Surface Albedo and Energy Flux with LMD General Circulation Model

    Science.gov (United States)

    Singh, D.; Flanner, M.; Millour, E.; Martinez, G.

    2015-12-01

    Mars, just like Earth experience different seasons because of its axial tilt (about 25°). This causes growth and retreat of snow cover (primarily CO2) in Martian Polar regions. The perennial caps are the only place on the planet where condensed H2O is available at surface. On Mars, as much as 30% atmospheric CO2 deposits in each hemisphere depending upon the season. This leads to a significant variation on planet's surface albedo and hence effecting the amount of solar flux absorbed or reflected at the surface. General Circulation Model (GCM) of Laboratoire de Météorologie Dynamique (LMD) currently uses observationally derived surface albedo from Thermal Emission Spectrometer (TES) instrument for the polar caps. These TES albedo values do not have any inter-annual variability, and are independent of presence of any dust/impurity on surface. Presence of dust or other surface impurities can significantly reduce the surface albedo especially during and right after a dust storm. This change will also be evident in the surface energy flux interactions. Our work focuses on combining earth based Snow, Ice, and Aerosol Radiation (SNICAR) model with current state of GCM to incorporate the impact of dust on Martian surface albedo, and hence the energy flux. Inter-annual variability of surface albedo and planet's top of atmosphere (TOA) energy budget along with their correlation with currently available mission data will be presented.

  5. Methanol Oxidation on Model Elemental and Bimetallic Transition Metal Surfaces

    DEFF Research Database (Denmark)

    Tritsaris, G. A.; Rossmeisl, J.

    2012-01-01

    Direct methanol fuel cells are a key enabling technology for clean energy conversion. Using density functional theory calculations, we study the methanol oxidation reaction on model electrodes. We discuss trends in reactivity for a set of monometallic and bimetallic transition metal surfaces, flat...... sites on the surface and to screen for novel bimetallic surfaces of enhanced activity. We suggest platinum copper surfaces as promising anode catalysts for direct methanol fuel cells....

  6. Accurate Modelling of Surface Currents and Internal Tides in a Semi-enclosed Coastal Sea

    Science.gov (United States)

    Allen, S. E.; Soontiens, N. K.; Dunn, M. B. H.; Liu, J.; Olson, E.; Halverson, M. J.; Pawlowicz, R.

    2016-02-01

    The Strait of Georgia is a deep (400 m), strongly stratified, semi-enclosed coastal sea on the west coast of North America. We have configured a baroclinic model of the Strait of Georgia and surrounding coastal waters using the NEMO ocean community model. We run daily nowcasts and forecasts and publish our sea-surface results (including storm surge warnings) to the web (salishsea.eos.ubc.ca/storm-surge). Tides in the Strait of Georgia are mixed and large. The baroclinic model and previous barotropic models accurately represent tidal sea-level variations and depth mean currents. The baroclinic model reproduces accurately the diurnal but not the semi-diurnal baroclinic tidal currents. In the Southern Strait of Georgia, strong internal tidal currents at the semi-diurnal frequency are observed. Strong semi-diurnal tides are also produced in the model, but are almost 180 degrees out of phase with the observations. In the model, in the surface, the barotropic and baroclinic tides reinforce, whereas the observations show that at the surface the baroclinic tides oppose the barotropic. As such the surface currents are very poorly modelled. Here we will present evidence of the internal tidal field from observations. We will discuss the generation regions of the tides, the necessary modifications to the model required to correct the phase, the resulting baroclinic tides and the improvements in the surface currents.

  7. Viscosity of dilute suspensions of rigid bead arrays at low shear: accounting for the variation in hydrodynamic stress over the bead surfaces.

    Science.gov (United States)

    Allison, Stuart A; Pei, Hongxia

    2009-06-11

    In this work, we examine the viscosity of a dilute suspension of irregularly shaped particles at low shear. A particle is modeled as a rigid array of nonoverlapping beads of variable size and geometry. Starting from a boundary element formalism, approximate account is taken of the variation in hydrodynamic stress over the surface of the individual beads. For a touching dimer of two identical beads, the predicted viscosity is lower than the exact value by 5.2%. The methodology is then applied to several other model systems including tetramers of variable conformation and linear strings of touching beads. An analysis is also carried out of the viscosity and translational diffusion of several dilute amino acids and diglycine in water. It is concluded that continuum hydrodynamic modeling with stick boundary conditions is unable to account for the experimental viscosity and diffusion data simultaneously. A model intermediate between "stick" and "slip" could possibly reconcile theory and experiment.

  8. Two levels ARIMAX and regression models for forecasting time series data with calendar variation effects

    Science.gov (United States)

    Suhartono, Lee, Muhammad Hisyam; Prastyo, Dedy Dwi

    2015-12-01

    The aim of this research is to develop a calendar variation model for forecasting retail sales data with the Eid ul-Fitr effect. The proposed model is based on two methods, namely two levels ARIMAX and regression methods. Two levels ARIMAX and regression models are built by using ARIMAX for the first level and regression for the second level. Monthly men's jeans and women's trousers sales in a retail company for the period January 2002 to September 2009 are used as case study. In general, two levels of calendar variation model yields two models, namely the first model to reconstruct the sales pattern that already occurred, and the second model to forecast the effect of increasing sales due to Eid ul-Fitr that affected sales at the same and the previous months. The results show that the proposed two level calendar variation model based on ARIMAX and regression methods yields better forecast compared to the seasonal ARIMA model and Neural Networks.

  9. Towards a Revised Monte Carlo Neutral Particle Surface Interaction Model

    International Nuclear Information System (INIS)

    Stotler, D.P.

    2005-01-01

    The components of the neutral- and plasma-surface interaction model used in the Monte Carlo neutral transport code DEGAS 2 are reviewed. The idealized surfaces and processes handled by that model are inadequate for accurately simulating neutral transport behavior in present day and future fusion devices. We identify some of the physical processes missing from the model, such as mixed materials and implanted hydrogen, and make some suggestions for improving the model

  10. Surface science models of CoMoS hydrodesulfurisation catalysts

    NARCIS (Netherlands)

    Jong, de A.M.; Beer, de V.H.J.; Veen, van J.A.R.; Niemantsverdriet, J.W.; Froment, G.F.; Delmon, B.; Grange, P.

    1997-01-01

    Characterization of supported catalysts with surface spectroscopic techniques is often limited due to restraints imposed by the support material. The use of flat conducting substrates as a model support offers a way to apply these techniques to their full potential. Such surface science models of

  11. Mathematical modeling of rainwater runoff over catchment surface ...

    African Journals Online (AJOL)

    The subject of an article is the mathematical modeling of the rainwater runoff along the surface catchment taking account the transport of pollution which permeates into the water flow from a porous media of soil at the certain areas of this surface. The developed mathematical model consists of two types of equations: the ...

  12. ANALYSIS OF THE INTRA-CITY VARIATION OF URBAN HEAT ISLAND AND ITS RELATION TO LAND SURFACE/COVER PARAMETERS

    Directory of Open Access Journals (Sweden)

    D. Gerçek

    2016-06-01

    Full Text Available Along with urbanization, sealing of vegetated land and evaporation surfaces by impermeable materials, lead to changes in urban climate. This phenomenon is observed as temperatures several degrees higher in densely urbanized areas compared to the rural land at the urban fringe particularly at nights, so-called Urban Heat Island. Urban Heat Island (UHI effect is related with urban form, pattern and building materials so far as it is associated with meteorological conditions, air pollution, excess heat from cooling. UHI effect has negative influences on human health, as well as other environmental problems such as higher energy demand, air pollution, and water shortage. Urban Heat Island (UHI effect has long been studied by observations of air temperature from thermometers. However, with the advent and proliferation of remote sensing technology, synoptic coverage and better representations of spatial variation of surface temperature became possible. This has opened new avenues for the observation capabilities and research of UHIs. In this study, "UHI effect and its relation to factors that cause it" is explored for İzmit city which has been subject to excess urbanization and industrialization during the past decades. Spatial distribution and variation of UHI effect in İzmit is analysed using Landsat 8 and ASTER day & night images of 2015 summer. Surface temperature data derived from thermal bands of the images were analysed for UHI effect. Higher temperatures were classified into 4 grades of UHIs and mapped both for day and night. Inadequate urban form, pattern, density, high buildings and paved surfaces at the expanse of soil ground and vegetation cover are the main factors that cause microclimates giving rise to spatial variations in temperatures across cities. These factors quantified as land surface/cover parameters for the study include vegetation index (NDVI, imperviousness (NDISI, albedo, solar insolation, Sky View Factor (SVF, building

  13. Analysis of the Intra-City Variation of Urban Heat Island and its Relation to Land Surface/cover Parameters

    Science.gov (United States)

    Gerçek, D.; Güven, İ. T.; Oktay, İ. Ç.

    2016-06-01

    Along with urbanization, sealing of vegetated land and evaporation surfaces by impermeable materials, lead to changes in urban climate. This phenomenon is observed as temperatures several degrees higher in densely urbanized areas compared to the rural land at the urban fringe particularly at nights, so-called Urban Heat Island. Urban Heat Island (UHI) effect is related with urban form, pattern and building materials so far as it is associated with meteorological conditions, air pollution, excess heat from cooling. UHI effect has negative influences on human health, as well as other environmental problems such as higher energy demand, air pollution, and water shortage. Urban Heat Island (UHI) effect has long been studied by observations of air temperature from thermometers. However, with the advent and proliferation of remote sensing technology, synoptic coverage and better representations of spatial variation of surface temperature became possible. This has opened new avenues for the observation capabilities and research of UHIs. In this study, "UHI effect and its relation to factors that cause it" is explored for İzmit city which has been subject to excess urbanization and industrialization during the past decades. Spatial distribution and variation of UHI effect in İzmit is analysed using Landsat 8 and ASTER day & night images of 2015 summer. Surface temperature data derived from thermal bands of the images were analysed for UHI effect. Higher temperatures were classified into 4 grades of UHIs and mapped both for day and night. Inadequate urban form, pattern, density, high buildings and paved surfaces at the expanse of soil ground and vegetation cover are the main factors that cause microclimates giving rise to spatial variations in temperatures across cities. These factors quantified as land surface/cover parameters for the study include vegetation index (NDVI), imperviousness (NDISI), albedo, solar insolation, Sky View Factor (SVF), building envelope

  14. A new class of actuator surface models for wind turbines

    Science.gov (United States)

    Yang, Xiaolei; Sotiropoulos, Fotis

    2018-05-01

    Actuator line model has been widely employed in wind turbine simulations. However, the standard actuator line model does not include a model for the turbine nacelle which can significantly impact turbine wake characteristics as shown in the literature. Another disadvantage of the standard actuator line model is that more geometrical features of turbine blades cannot be resolved on a finer mesh. To alleviate these disadvantages of the standard model, we develop a new class of actuator surface models for turbine blades and nacelle to take into account more geometrical details of turbine blades and include the effect of turbine nacelle. In the actuator surface model for blade, the aerodynamic forces calculated using the blade element method are distributed from the surface formed by the foil chords at different radial locations. In the actuator surface model for nacelle, the forces are distributed from the actual nacelle surface with the normal force component computed in the same way as in the direct forcing immersed boundary method and the tangential force component computed using a friction coefficient and a reference velocity of the incoming flow. The actuator surface model for nacelle is evaluated by simulating the flow over periodically placed nacelles. Both the actuator surface simulation and the wall-resolved large-eddy simulation are carried out. The comparison shows that the actuator surface model is able to give acceptable results especially at far wake locations on a very coarse mesh. It is noted that although this model is employed for the turbine nacelle in this work, it is also applicable to other bluff bodies. The capability of the actuator surface model in predicting turbine wakes is assessed by simulating the flow over the MEXICO (Model experiments in Controlled Conditions) turbine and a hydrokinetic turbine.

  15. Influence of spatial variations of microtopography and infiltration on surface runoff and field scale hydrological connectivity

    NARCIS (Netherlands)

    Appels, W.M.; Bogaart, P.W.; Zee, van der S.E.A.T.M.

    2011-01-01

    Surface runoff on agricultural fields arises when rainfall exceeds infiltration. Excess water ponding in and flowing through local microtopography increases the hydrological connectivity of fields. In turn, an increased level of hydrological connectivity leads to a higher surface runoff flux at the

  16. Greenland ice sheet surface mass-balance modeling in a 131-Yr perspective, 1950-2080

    DEFF Research Database (Denmark)

    Mernild, Sebastian H.; Liston, Glen E.; Hiemstra, Christopher A.

    2010-01-01

    to simulate variations in theGrISmelt extent, surfacewater balance components, changes inSMB, and freshwater influx to the ocean. The simulations are based on the Intergovernmental Panel on Climate Change scenario A1B modeled by the HIRHAM4 regional climate model (RCM) using boundary conditions from the ECHAM...... and correct RCM output data before they were used as input for SnowModel. Satellite observations and independent SMB studies were used to validate the SnowModel output and confirmthemodel's robustness. The authors simulated an ~90% increase in end-of-summer surface melt extent (0.483 × 106 km2) from 1950...

  17. Phase-field modelling of ductile fracture: a variational gradient-extended plasticity-damage theory and its micromorphic regularization.

    Science.gov (United States)

    Miehe, C; Teichtmeister, S; Aldakheel, F

    2016-04-28

    This work outlines a novel variational-based theory for the phase-field modelling of ductile fracture in elastic-plastic solids undergoing large strains. The phase-field approach regularizes sharp crack surfaces within a pure continuum setting by a specific gradient damage modelling. It is linked to a formulation of gradient plasticity at finite strains. The framework includes two independent length scales which regularize both the plastic response as well as the crack discontinuities. This ensures that the damage zones of ductile fracture are inside of plastic zones, and guarantees on the computational side a mesh objectivity in post-critical ranges. © 2016 The Author(s).

  18. Numerical modelling of surface plasmonic polaritons

    Science.gov (United States)

    Mansoor, Riyadh; AL-Khursan, Amin Habbeb

    2018-06-01

    Extending optoelectronics into the nano-regime seems problematic due to the relatively long wavelengths of light. The conversion of light into plasmons is a possible way to overcome this problem. Plasmon's wavelengths are much shorter than that of light which enables the propagation of signals in small size components. In this paper, a 3D simulation of surface plasmon polariton (SPP) excitation is performed. The Finite integration technique was used to solve Maxwell's equations in the dielectric-metal interface. The results show how the surface plasmon polariton was generated at the grating assisted dielectric-metal interface. SPP is a good candidate for signal confinement in small size optoelectronics which allow high density optical integrated circuits in all optical networks.

  19. A variational integrators approach to second order modeling and identification of linear mechanical systems

    NARCIS (Netherlands)

    Bruschetta, M.; Saccon, A.; Picci, G.

    2014-01-01

    The theory of variational integration provides a systematic procedure to discretize the equations of motion of a mechanical system, preserving key properties of the continuous time flow. The discrete-time model obtained by variational integration theory inherits structural conditions which in

  20. The influence of climatically-driven surface loading variations on continental strain and seismicity

    Science.gov (United States)

    Craig, Tim; Calais, Eric; Fleitout, Luce; Bollinger, Laurent; Scotti, Oona

    2016-04-01

    In slowly deforming regions of plate interiors, secondary sources of stress and strain can result in transient deformation rates comparable to, or greater than, the background tectonic rates. Highly variable in space and time, these transients have the potential to influence the spatio-temporal distribution of seismicity, interfering with any background tectonic effects to either promote or inhibit the failure of pre-existing faults, and potentially leading to a clustered, or 'pulse-like', seismic history. Here, we investigate the ways in which the large-scale deformation field resulting from climatically-controlled changes in surface ice mass over the Pleistocene and Holocene may have influenced not only the seismicity of glaciated regions, but also the wider seismicity around the ice periphery. We first use a set of geodynamic models to demonstrate that a major pulse of seismic activity occurring in Fennoscandia, coincident with the time of end-glaciation, occurred in a setting where the contemporaneous horizontal strain-rate resulting from the changing ice mass, was extensional - opposite to the reverse sense of coseismic displacement accommodated on these faults. Therefore, faulting did not release extensional elastic strain that was building up at the time of failure, but compressional elastic strain that had accumulated in the lithosphere on timescales longer than the glacial cycle, illustrating the potential for a non-tectonic trigger to tap in to the background tectonic stress-state. We then move on to investigate the more distal influence that changing ice (and ocean) volumes may have had on the evolving strain field across intraplate Europe, how this is reflected in the seismicity across intraplate Europe, and what impact this might have on the paleoseismic record.

  1. Modeling wind adjustment factor and midflame wind speed for Rothermel's surface fire spread model

    Science.gov (United States)

    Patricia L. Andrews

    2012-01-01

    Rothermel's surface fire spread model was developed to use a value for the wind speed that affects surface fire, called midflame wind speed. Models have been developed to adjust 20-ft wind speed to midflame wind speed for sheltered and unsheltered surface fuel. In this report, Wind Adjustment Factor (WAF) model equations are given, and the BehavePlus fire modeling...

  2. Olkiluoto surface hydrological modelling: Update 2012 including salt transport modelling

    International Nuclear Information System (INIS)

    Karvonen, T.

    2013-11-01

    Posiva Oy is responsible for implementing a final disposal program for spent nuclear fuel of its owners Teollisuuden Voima Oyj and Fortum Power and Heat Oy. The spent nuclear fuel is planned to be disposed at a depth of about 400-450 meters in the crystalline bedrock at the Olkiluoto site. Leakages located at or close to spent fuel repository may give rise to the upconing of deep highly saline groundwater and this is a concern with regard to the performance of the tunnel backfill material after the closure of the tunnels. Therefore a salt transport sub-model was added to the Olkiluoto surface hydrological model (SHYD). The other improvements include update of the particle tracking algorithm and possibility to estimate the influence of open drillholes in a case where overpressure in inflatable packers decreases causing a hydraulic short-circuit between hydrogeological zones HZ19 and HZ20 along the drillhole. Four new hydrogeological zones HZ056, HZ146, BFZ100 and HZ039 were added to the model. In addition, zones HZ20A and HZ20B intersect with each other in the new structure model, which influences salinity upconing caused by leakages in shafts. The aim of the modelling of long-term influence of ONKALO, shafts and repository tunnels provide computational results that can be used to suggest limits for allowed leakages. The model input data included all the existing leakages into ONKALO (35-38 l/min) and shafts in the present day conditions. The influence of shafts was computed using eight different values for total shaft leakage: 5, 11, 20, 30, 40, 50, 60 and 70 l/min. The selection of the leakage criteria for shafts was influenced by the fact that upconing of saline water increases TDS-values close to the repository areas although HZ20B does not intersect any deposition tunnels. The total limit for all leakages was suggested to be 120 l/min. The limit for HZ20 zones was proposed to be 40 l/min: about 5 l/min the present day leakages to access tunnel, 25 l/min from

  3. Olkiluoto surface hydrological modelling: Update 2012 including salt transport modelling

    Energy Technology Data Exchange (ETDEWEB)

    Karvonen, T. [WaterHope, Helsinki (Finland)

    2013-11-15

    Posiva Oy is responsible for implementing a final disposal program for spent nuclear fuel of its owners Teollisuuden Voima Oyj and Fortum Power and Heat Oy. The spent nuclear fuel is planned to be disposed at a depth of about 400-450 meters in the crystalline bedrock at the Olkiluoto site. Leakages located at or close to spent fuel repository may give rise to the upconing of deep highly saline groundwater and this is a concern with regard to the performance of the tunnel backfill material after the closure of the tunnels. Therefore a salt transport sub-model was added to the Olkiluoto surface hydrological model (SHYD). The other improvements include update of the particle tracking algorithm and possibility to estimate the influence of open drillholes in a case where overpressure in inflatable packers decreases causing a hydraulic short-circuit between hydrogeological zones HZ19 and HZ20 along the drillhole. Four new hydrogeological zones HZ056, HZ146, BFZ100 and HZ039 were added to the model. In addition, zones HZ20A and HZ20B intersect with each other in the new structure model, which influences salinity upconing caused by leakages in shafts. The aim of the modelling of long-term influence of ONKALO, shafts and repository tunnels provide computational results that can be used to suggest limits for allowed leakages. The model input data included all the existing leakages into ONKALO (35-38 l/min) and shafts in the present day conditions. The influence of shafts was computed using eight different values for total shaft leakage: 5, 11, 20, 30, 40, 50, 60 and 70 l/min. The selection of the leakage criteria for shafts was influenced by the fact that upconing of saline water increases TDS-values close to the repository areas although HZ20B does not intersect any deposition tunnels. The total limit for all leakages was suggested to be 120 l/min. The limit for HZ20 zones was proposed to be 40 l/min: about 5 l/min the present day leakages to access tunnel, 25 l/min from

  4. Modeling and analysis of surface roughness effects on sputtering, reflection, and sputtered particle transport

    International Nuclear Information System (INIS)

    Brooks, J.N.; Ruzic, D.N.

    1990-01-01

    The microstructure of the redeposited surface in tokamaks may affect sputtering and reflection properties and subsequent particle transport. This subject has been studied numerically using coupled models/codes for near-surface plasma particle kinetic transport (WBC code) and rough surface sputtering (fractal-TRIM). The coupled codes provide an overall Monte Carlo calculation of the sputtering cascade resulting from an initial flux of hydrogen ions. Beryllium, carbon, and tungsten surfaces are analyzed for typical high recycling, oblique magnetic field, divertor conditions. Significant variations in computed sputtering rates are found with surface roughness. Beryllium exhibits high D-T and self-sputtering coefficients for the plasma regime studied (T e = 30-75 eV). Carbon and tungsten sputtering is significantly lower. 9 refs., 6 figs., 1 tab

  5. On a free-surface problem with moving contact line: From variational principles to stable numerical approximations

    Science.gov (United States)

    Fumagalli, Ivan; Parolini, Nicola; Verani, Marco

    2018-02-01

    We analyze a free-surface problem described by time-dependent Navier-Stokes equations. Surface tension, capillary effects and wall friction are taken into account in the evolution of the system, influencing the motion of the contact line - where the free surface hits the wall - and of the dynamics of the contact angle. The differential equations governing the phenomenon are first derived from the variational principle of minimum reduced dissipation, and then discretized by means of the ALE approach. The numerical properties of the resulting scheme are investigated, drawing a parallel with the physical properties holding at the continuous level. Some instability issues are addressed in detail, in the case of an explicit treatment of the geometry, and novel additional terms are introduced in the discrete formulation in order to damp the instabilities. Numerical tests assess the suitability of the approach, the influence of the parameters, and the effectiveness of the new stabilizing terms.

  6. Bacterial community diversity and variation in spray water sources and the tomato fruit surface.

    Science.gov (United States)

    Telias, Adriana; White, James R; Pahl, Donna M; Ottesen, Andrea R; Walsh, Christopher S

    2011-04-21

    Tomato (Solanum lycopersicum) consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water) when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production. The two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant. Despite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an important step forward towards the development of science

  7. Bacterial community diversity and variation in spray water sources and the tomato fruit surface

    Directory of Open Access Journals (Sweden)

    Ottesen Andrea R

    2011-04-01

    Full Text Available Abstract Background Tomato (Solanum lycopersicum consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production. Results The two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant. Conclusions Despite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an

  8. Long-Term Evaluation of Ocean Tidal Variation Models of Polar Motion and UT1

    Science.gov (United States)

    Karbon, Maria; Balidakis, Kyriakos; Belda, Santiago; Nilsson, Tobias; Hagedoorn, Jan; Schuh, Harald

    2018-04-01

    Recent improvements in the development of VLBI (very long baseline interferometry) and other space geodetic techniques such as the global navigation satellite systems (GNSS) require very precise a-priori information of short-period (daily and sub-daily) Earth rotation variations. One significant contribution to Earth rotation is caused by the diurnal and semi-diurnal ocean tides. Within this work, we developed a new model for the short-period ocean tidal variations in Earth rotation, where the ocean tidal angular momentum model and the Earth rotation variation have been setup jointly. Besides the model of the short-period variation of the Earth's rotation parameters (ERP), based on the empirical ocean tide model EOT11a, we developed also ERP models, that are based on the hydrodynamic ocean tide models FES2012 and HAMTIDE. Furthermore, we have assessed the effect of uncertainties in the elastic Earth model on the resulting ERP models. Our proposed alternative ERP model to the IERS 2010 conventional model considers the elastic model PREM and 260 partial tides. The choice of the ocean tide model and the determination of the tidal velocities have been identified as the main uncertainties. However, in the VLBI analysis all models perform on the same level of accuracy. From these findings, we conclude that the models presented here, which are based on a re-examined theoretical description and long-term satellite altimetry observation only, are an alternative for the IERS conventional model but do not improve the geodetic results.

  9. Joint surface modeling with thin-plate splines.

    Science.gov (United States)

    Boyd, S K; Ronsky, J L; Lichti, D D; Salkauskas, K; Chapman, M A; Salkauskas, D

    1999-10-01

    Mathematical joint surface models based on experimentally determined data points can be used to investigate joint characteristics such as curvature, congruency, cartilage thickness, joint contact areas, as well as to provide geometric information well suited for finite element analysis. Commonly, surface modeling methods are based on B-splines, which involve tensor products. These methods have had success; however, they are limited due to the complex organizational aspect of working with surface patches, and modeling unordered, scattered experimental data points. An alternative method for mathematical joint surface modeling is presented based on the thin-plate spline (TPS). It has the advantage that it does not involve surface patches, and can model scattered data points without experimental data preparation. An analytical surface was developed and modeled with the TPS to quantify its interpolating and smoothing characteristics. Some limitations of the TPS include discontinuity of curvature at exactly the experimental surface data points, and numerical problems dealing with data sets in excess of 2000 points. However, suggestions for overcoming these limitations are presented. Testing the TPS with real experimental data, the patellofemoral joint of a cat was measured with multistation digital photogrammetry and modeled using the TPS to determine cartilage thicknesses and surface curvature. The cartilage thickness distribution ranged between 100 to 550 microns on the patella, and 100 to 300 microns on the femur. It was found that the TPS was an effective tool for modeling joint surfaces because no preparation of the experimental data points was necessary, and the resulting unique function representing the entire surface does not involve surface patches. A detailed algorithm is presented for implementation of the TPS.

  10. mathematical model of thermal explosion, the dual variational formulation of nonlinear problem, alternative functional

    Directory of Open Access Journals (Sweden)

    V. S. Zarubin

    2016-01-01

    Full Text Available A temperature state of the solid body may depend both on the conditions of heat exchange with external environment surrounding its surface and on the energy release within the body volume, caused, for example, by the processes in nuclear reactor elements or exothermic chemical reactions, absorption of penetrating radiation energy or transformation of a part of the electrical power into heat with flowing electric current (so-called Joule heat.If with growing temperature the intensity of bulk power density increases, a limited steady temperature state can emerge at which heat extracted to the body surface and released within its volume reaches maximum. Thus, small increments of temperature lead to an increase of heat release, which can not be extracted to the body surface by conduction without further temperature increase. As a result, the steady temperature distribution in the body becomes impossible that determines the state of the thermal explosion, so named due to the fact that in this case the appropriate mathematical model predicts an unlimited temperature increase.A lot of published papers and monographs concerning the study of the combustion and explosion processes in a stationary medium analyse the thermal explosion state. The most famous papers consider a mathematical model to describe a temperature distribution in the case when heat release is because of exothermic chemical reactions the rate of which increases with temperature growth. The dependence of the chemical reaction rate on temperature is usually described by the exponential Arrhenius law, which makes it necessary to consider an essentially nonlinear mathematical model containing differential equation, which includes the term, nonlinearly rising with increasing temperature. Even with simplifying assumptions, this model allows an exact closed form solution only in the case of one-dimensional temperature distributions in the two areas of the canonical form: in the plate, infinite

  11. Variations within simple models for structure-soil interaction

    DEFF Research Database (Denmark)

    Peplow, Andrew; Andersen, Lars Vabbersgaard; Bucinskas, Paulius

    , obstacles such as concrete blocks lead to wave scattering that may be beneficial or unfavourable for the response of a building close to, for example, a railway. To account for this dynamic cross coupling via the soil, a model must be accurate enough to provide the correct overall behaviour of the scattered...... wave field. However, simplicity is also important when a model should be used for design purposes, especially in the early stages of design and feasibility studies. The paper addresses two models in 2D and 3D based on different methodologies. Results are discussed regarding their capability to quantify...

  12. Modeling noncontact atomic force microscopy resolution on corrugated surfaces

    Directory of Open Access Journals (Sweden)

    Kristen M. Burson

    2012-03-01

    Full Text Available Key developments in NC-AFM have generally involved atomically flat crystalline surfaces. However, many surfaces of technological interest are not atomically flat. We discuss the experimental difficulties in obtaining high-resolution images of rough surfaces, with amorphous SiO2 as a specific case. We develop a quasi-1-D minimal model for noncontact atomic force microscopy, based on van der Waals interactions between a spherical tip and the surface, explicitly accounting for the corrugated substrate (modeled as a sinusoid. The model results show an attenuation of the topographic contours by ~30% for tip distances within 5 Å of the surface. Results also indicate a deviation from the Hamaker force law for a sphere interacting with a flat surface.

  13. Conformally parametrized surfaces associated with CPN-1 sigma models

    International Nuclear Information System (INIS)

    Grundland, A M; Hereman, W A; Yurdusen, I-dot

    2008-01-01

    Two-dimensional parametrized surfaces immersed in the su(N) algebra are investigated. The focus is on surfaces parametrized by solutions of the equations for the CP N-1 sigma model. The Lie-point symmetries of the CP N-1 model are computed for arbitrary N. The Weierstrass formula for immersion is determined and an explicit formula for a moving frame on a surface is constructed. This allows us to determine the structural equations and geometrical properties of surfaces in R N 2 -1 . The fundamental forms, Gaussian and mean curvatures, Willmore functional and topological charge of surfaces are given explicitly in terms of any holomorphic solution of the CP 2 model. The approach is illustrated through several examples, including surfaces immersed in low-dimensional su(N) algebras

  14. Modeling the dependency of radon concentration levels inside ancient Egyptian tombs on the ambient temperature variations

    Energy Technology Data Exchange (ETDEWEB)

    Metwally, S M; Abo-Elmagdb, M [Faculty of Science, Department of Physics, Ain Shams University, P. O. Box 11566, Cairo (Egypt); Salamaa, E [National Institute for Standard, Radiation Measurements Department, Cairo (Egypt)

    2007-06-15

    Radon concentration inside partially closed places like dwellings, caves and tombs, depends on many parameters. Some parameters are known quantitatively as radon exhalation rate for walls, decay constant, surface to volume ratio and outdoor concentration while other parameters as ventilation rate is in common known qualitatively due to useless of traditional methods (tracer gases) in many places as ancient Egyptian tombs. This work introduces a derived mathematical model to evaluate the sensitivity of radon concentration levels inside single sided opening places as ancient Egyptian tombs on the ambient temperature differences. The obtained formula for the natural ventilation rate depends on the indoor and outdoor temperature difference and the geometrical dimensions of the doorway. The effects of in and out flow mixing, air viscosity, streamline contraction, swirling flow and turbulence, were taken into consideration in terms of an empirical correction factor. According UNSCEAR reports, the exhalation rate {phi}=C{sub ra}{lambda}{sub rn} f{rho}{sub s}(1-{epsilon})L; C{sub ra} the effective radium content, {lambda}{sub rn} decay constant, f emanation fraction, {rho}{sub s} soil grain density, {epsilon} porosity and L diffusion length, these are approximately static parameters but the variability of ambient temperature introduces a source of energy of fluctuating strength to radon atoms in rocks which controls the flow rate and the ambient content of radon. Therefore, the change of outdoor and indoor temperature difference causes fluctuation of value and direction of volume flow rate in such places consequently causes the daily variation and on average the seasonal variation of radon concentration. Therefore according to the present model, the daily accurate expectation of radon concentrations inside ancient Egyptian tombs, require precise measurements of indoor and outdoor temperatures.

  15. Modeling the dependency of radon concentration levels inside ancient Egyptian tombs on the ambient temperature variations

    International Nuclear Information System (INIS)

    Metwally, S.M.; Abo-Elmagdb, M.; Salamaa, E.

    2007-01-01

    Radon concentration inside partially closed places like dwellings, caves and tombs, depends on many parameters. Some parameters are known quantitatively as radon exhalation rate for walls, decay constant, surface to volume ratio and outdoor concentration while other parameters as ventilation rate is in common known qualitatively due to useless of traditional methods (tracer gases) in many places as ancient Egyptian tombs. This work introduces a derived mathematical model to evaluate the sensitivity of radon concentration levels inside single sided opening places as ancient Egyptian tombs on the ambient temperature differences. The obtained formula for the natural ventilation rate depends on the indoor and outdoor temperature difference and the geometrical dimensions of the doorway. The effects of in and out flow mixing, air viscosity, streamline contraction, swirling flow and turbulence, were taken into consideration in terms of an empirical correction factor. According UNSCEAR reports, the exhalation rate Φ=C ra λ rn fρ s (1-ε)L; C ra the effective radium content, λ rn decay constant, f emanation fraction, ρ s soil grain density, ε porosity and L diffusion length, these are approximately static parameters but the variability of ambient temperature introduces a source of energy of fluctuating strength to radon atoms in rocks which controls the flow rate and the ambient content of radon. Therefore, the change of outdoor and indoor temperature difference causes fluctuation of value and direction of volume flow rate in such places consequently causes the daily variation and on average the seasonal variation of radon concentration. Therefore according to the present model, the daily accurate expectation of radon concentrations inside ancient Egyptian tombs, require precise measurements of indoor and outdoor temperatures

  16. Influence of ozone precursors and particulate matter on the variation of surface ozone at an urban site of Delhi, India

    Directory of Open Access Journals (Sweden)

    Ashima Sharma

    2016-03-01

    Full Text Available Continuous measurements of surface O3 and its precursors (NO, NO2, CO, CH4 and NMHCs at an urban site of Delhi, India during January 2012 to December 2013 are presented. In the present study, the annual average mixing ratios of surface O3, NO, NO2, CO, CH4 and NMHC were 30 ± 6 ppb, 24 ± 6 ppb, 15 ± 4 ppb, 1.5 ± 0.4 ppm, 2.4 ± 0.4 ppm and 0.4 ± 0.1 ppm, respectively. The maximum average mixing ratios of surface O3, NO and NO2 were observed during the summer, whereas, the minimum average mixing ratios of ambient NO and NO2 were during monsoon seasons. The surface O3, NO and NO2 have shown the prominent diurnal variations during all the seasons at the observational site of Delhi. The result reveals that the surface O3 was negatively correlated with NOx and CO during the study. The linear scatter plot analysis shows that the PM2.5 and PM10 present in the ambient air of Delhi influence the production of surface O3 at observational site.

  17. The investigation of spatiotemporal variations of land surface temperature based on land use changes using NDVI in southwest of Iran

    Science.gov (United States)

    Fathizad, Hassan; Tazeh, Mahdi; Kalantari, Saeideh; Shojaei, Saeed

    2017-10-01

    Land use changes can bring about changes in land surface temperature (LST) which is influenced by climatic conditions and physical characteristics of the land surface. In this study, spatiotemporal variations of land surface temperature have been investigated in the desert area of Dasht-e-Abbas, Ilam, based on a variety of land use changes. The investigated periods for the study include 1990, 2000 and 2010 using Landsat image data. First, in mapping land use we used the Fuzzy ARTMAP Neural Network Classification method followed by determination of the NDVI Index to estimate land surface temperature. The results show an increase in LST in areas where degradation, land use and land cover changes have occurred. In 1990, 2000 and 2010, the average land surface temperature of the Fair Rangelands was 26.72 °C, 30.06 °C and 30.95 °C, respectively. This rangeland has been reduced by about 5%. For poor rangelands, the average LSTs were 26.95, 32.83 and 34.49 Cº, respectively which had a 18% reduction. In 1990, 2000 and 2010, the average land surface temperatures of agricultural lands were 24.31 °C, 27.87 °C and 28.61 °C, respectively which has been an increasing trend. The reason can be attributed to changes in cropping patterns of the study area.

  18. Tides and lake-level variations in the great Patagonian lakes: Observations, modelling and geophysical implications.

    Science.gov (United States)

    Marderwald, Eric; Richter, Andreas; Horwath, Martin; Hormaechea, Jose Luis; Groh, Andreas

    2016-04-01

    In Patagonia, the glacial-isostatic adjustment (GIA) to past ice-mass changes (Ivins & James 2004; Klemann et al. 2007) is of particular interest in the context of the determination of the complex regional rheology related to plate subduction in a triple-junction constellation. To further complicate the situation, GIA is overlaid with load deformation not only due to present ice mass changes but also due to water-level changes in the lakes surrounding the icefields and the ocean surrounding Patagonia. These elastic deformations affect the determination of glacial-isostatic uplift rates from GPS observations (Dietrich et al. 2010; Lange et al. 2014). Observations of lake tides and their comparison with the theoretical tidal signal have been used previously to validate predictions of ocean tidal loading and have revealed regional deviations from conventional global elastic earth models (Richter et al. 2009). In this work we investigate the tides and lake-level variations in Lago Argentino, Lago Viedma, Lago San Martín/O'Higgins and Lago Buenos Aires/General Carrera. This allows us to test, among other things, the validity of tidal loading models. We present pressure tide-gauge records from two sites in Lago Argentino extending over 2.5 years (Richter et al. 2015). These observations are complemented by lake-level records provided by the Argentine National Hydrometeorological Network. Based on these lake-level time series the principal processes affecting the lake level are identified and quantified. Lake-level changes reflecting variations in lake volume are dominated by a seasonal cycle exceeding 1 m in amplitude. Lake-volume changes occur in addition with a daily period in response to melt water influx from surrounding glaciers. In Lago Argentino sporadic lake-volume jumps are caused by bursting of the ice dam of Perito Moreno glacier. Water movements in these lakes are dominated by surface seiches reaching 20 cm in amplitude. A harmonic tidal analysis of the lake

  19. Navier-Stokes Computations With One-Equation Turbulence Model for Flows Along Concave Wall Surfaces

    Science.gov (United States)

    Wang, Chi R.

    2005-01-01

    This report presents the use of a time-marching three-dimensional compressible Navier-Stokes equation numerical solver with a one-equation turbulence model to simulate the flow fields developed along concave wall surfaces without and with a downstream extension flat wall surface. The 3-D Navier- Stokes numerical solver came from the NASA Glenn-HT code. The one-equation turbulence model was derived from the Spalart and Allmaras model. The computational approach was first calibrated with the computations of the velocity and Reynolds shear stress profiles of a steady flat plate boundary layer flow. The computational approach was then used to simulate developing boundary layer flows along concave wall surfaces without and with a downstream extension wall. The author investigated the computational results of surface friction factors, near surface velocity components, near wall temperatures, and a turbulent shear stress component in terms of turbulence modeling, computational mesh configurations, inlet turbulence level, and time iteration step. The computational results were compared with existing measurements of skin friction factors, velocity components, and shear stresses of the developing boundary layer flows. With a fine computational mesh and a one-equation model, the computational approach could predict accurately the skin friction factors, near surface velocity and temperature, and shear stress within the flows. The computed velocity components and shear stresses also showed the vortices effect on the velocity variations over a concave wall. The computed eddy viscosities at the near wall locations were also compared with the results from a two equation turbulence modeling technique. The inlet turbulence length scale was found to have little effect on the eddy viscosities at locations near the concave wall surface. The eddy viscosities, from the one-equation and two-equation modeling, were comparable at most stream-wise stations. The present one

  20. Temporal and spatial variations in sand and dust storm events in East Asia from 2007 to 2016: Relationships with surface conditions and climate change.

    Science.gov (United States)

    An, Linchang; Che, Huizheng; Xue, Min; Zhang, Tianhang; Wang, Hong; Wang, Yaqiang; Zhou, Chunhong; Zhao, Hujia; Gui, Ke; Zheng, Yu; Sun, Tianze; Liang, Yuanxin; Sun, Enwei; Zhang, Hengde; Zhang, Xiaoye

    2018-08-15

    We analyzed the frequency and intensity of sand and dust storms (SDSs) in East Asia from 2007 to 2016 using observational data from ground stations, numerical modeling, and vegetation indices obtained from both satellite and reanalysis data. The relationships of SDSs with surface conditions and the synoptic circulation pattern were also analyzed. The statistical analyses demonstrated that the number and intensity of SDS events recorded in spring during 2007 to 2016 showed a decreasing trend. The total number of spring SDSs decreased from at least ten events per year before 2011 to less than ten events per year after 2011. The overall average annual variation of the surface dust concentration in the main dust source regions decreased 33.24μg/m 3 (-1.75%) annually. The variation in the temperatures near and below the ground surface and the amount of precipitation and soil moisture all favored an improvement in vegetation coverage, which reduced the intensity and frequency of SDSs. The strong winds accompanying the influx of cold air from high latitudes showed a decreasing trend, leading to a decrease in the number of SDSs and playing a key role in the decadal decrease of SDSs. The decrease in the intensity of the polar vortex during study period was closely related to the decrease in the intensity and frequency of SDSs. Copyright © 2018 Elsevier B.V. All rights reserved.

  1. Fractal modeling of fluidic leakage through metal sealing surfaces

    Science.gov (United States)

    Zhang, Qiang; Chen, Xiaoqian; Huang, Yiyong; Chen, Yong

    2018-04-01

    This paper investigates the fluidic leak rate through metal sealing surfaces by developing fractal models for the contact process and leakage process. An improved model is established to describe the seal-contact interface of two metal rough surface. The contact model divides the deformed regions by classifying the asperities of different characteristic lengths into the elastic, elastic-plastic and plastic regimes. Using the improved contact model, the leakage channel under the contact surface is mathematically modeled based on the fractal theory. The leakage model obtains the leak rate using the fluid transport theory in porous media, considering that the pores-forming percolation channels can be treated as a combination of filled tortuous capillaries. The effects of fractal structure, surface material and gasket size on the contact process and leakage process are analyzed through numerical simulations for sealed ring gaskets.

  2. Variations in land surface temperature and cooling efficiency of green space in rapid urbanization

    DEFF Research Database (Denmark)

    Yu, Zhaowu; Guo, Xieying; Zeng, Yuxi

    2018-01-01

    understood. Additionally, a strategy to optimize the most significant decreased land cover type in order to maximize the cooling effect is still lacking. Therefore, in this study, we selected the rapidly urbanizing and ‘hottest’ city in China, Fuzhou, as a case study. Two algorithms were selected to compare....... This study extends the current understanding of LCC dynamics and LST variation. The concepts of the CE and TVoE are meaningful for landscape planning practice and can be used in other cases....... and obtain reliable LST data. A land use transfer matrix was used to detect critical contributions leading to the LST variations. The concept of cooling efficiency (CE) and the threshold value of efficiency (TVoE) are also proposed, defined, and calculated. The results show that LST values increased...

  3. A diffuse radar scattering model from Martian surface rocks

    Science.gov (United States)

    Calvin, W. M.; Jakosky, B. M.; Christensen, P. R.

    1987-01-01

    Remote sensing of Mars has been done with a variety of instrumentation at various wavelengths. Many of these data sets can be reconciled with a surface model of bonded fines (or duricrust) which varies widely across the surface and a surface rock distribution which varies less so. A surface rock distribution map from -60 to +60 deg latitude has been generated by Christensen. Our objective is to model the diffuse component of radar reflection based on this surface distribution of rocks. The diffuse, rather than specular, scattering is modeled because the diffuse component arises due to scattering from rocks with sizes on the order of the wavelength of the radar beam. Scattering for radio waves of 12.5 cm is then indicative of the meter scale and smaller structure of the surface. The specular term is indicative of large scale surface undulations and should not be causally related to other surface physical properties. A simplified model of diffuse scattering is described along with two rock distribution models. The results of applying the models to a planet of uniform fractional rock coverage with values ranging from 5 to 20% are discussed.

  4. A phenomenological variational multiscale constitutive model for intergranular failure in nanocrystalline materials

    KAUST Repository

    Siddiq, A.; El Sayed, Tamer S.

    2013-01-01

    We present a variational multiscale constitutive model that accounts for intergranular failure in nanocrystalline fcc metals due to void growth and coalescence in the grain boundary region. Following previous work by the authors, a nanocrystalline

  5. Limitations Of The Current State Space Modelling Approach In Multistage Machining Processes Due To Operation Variations

    Science.gov (United States)

    Abellán-Nebot, J. V.; Liu, J.; Romero, F.

    2009-11-01

    The State Space modelling approach has been recently proposed as an engineering-driven technique for part quality prediction in Multistage Machining Processes (MMP). Current State Space models incorporate fixture and datum variations in the multi-stage variation propagation, without explicitly considering common operation variations such as machine-tool thermal distortions, cutting-tool wear, cutting-tool deflections, etc. This paper shows the limitations of the current State Space model through an experimental case study where the effect of the spindle thermal expansion, cutting-tool flank wear and locator errors are introduced. The paper also discusses the extension of the current State Space model to include operation variations and its potential benefits.

  6. Explanatory models for ecological response surfaces

    International Nuclear Information System (INIS)

    Jager, H.I.; Overton, W.S.

    1991-01-01

    Understanding the spatial organization of ecological systems is a fundamental part of ecosystem study. While discovering the causal relationships of this organization is an important goal, our purpose of spatial description on a regional scale is best met by use of explanatory variables that are somewhat removed from the mechanistic causal level. Regional level understanding is best obtained from explanatory variables that reflect spatial gradients at the regional scale and from categorical variables that describe the discrete constituents of (statistical) populations, such as lakes. In this paper, we use a regression model to predict lake acid neutralizing capacity (ANC) based on environmental predictor variables over a large region. These predictions are used to produce model-based population estimates. Two key features of our modeling approach are that is honors the spatial context and the design of the sample data. The spatial context of the data are brought into the analysis of model residuals through the interpretation of residual maps and semivariograms. The sampling design is taken into account by including stratification variables from the design in the model. This ensures that the model applies to a real population of lakes (the target population), rather than whatever hypothetical population the sample is a random sample of

  7. Gutzwiller variational wave function for a two-orbital Hubbard model on a square lattice

    Energy Technology Data Exchange (ETDEWEB)

    Muenster, Kevin Torben zu

    2015-07-01

    freedom of the Gutzwiller correlator. Furthermore, we discussed the implications of this parameter gauge for a more general setup. The big advantage of our diagrammatic approach lies in the fact that it simplifies decisively in the limit of infinite spatial dimensions. We obtain the exact result for Gutzwiller expectation values of single-site and two-site operators without calculating a single, non-trivial diagram. Of course, the diagrams with internal vertices contribute in finite dimensions, and their importance for phase transitions and the Fermi surface has to be studied. In the chapter 3, we therefore investigated a two-band Hubbard model on a square lattice. We introduced the Hamiltonian for two degenerate p{sub x}-p{sub y} (or d{sub xy}-d{sub yz}) orbitals where we considered electron transfers between nearest neighbors and next-nearest neighbors. The orbital degeneracy reduces the number of different hopping parameters but transitions between the two orbitals are still permitted, i.e., the local orbital quantum number is not conserved in the lattice. For two degenerate orbitals, all local Coulomb interactions can be expressed in terms of the Hubbard interaction U and the Hund's-rule coupling J. The Hubbard interaction suppresses charge fluctuations in the lattice, and the Hund's rule coupling tends to maximize the local spin. We incorporated the symmetry constraints in the Gutzwiller variational states. As our first application, we studied the ferromagnetic phase transition as a function of the model parameters for various band fillings. In general, a large density of states and a strong Hund's-rule exchange favor ferromagnetism. In the Gutzwiller wave function, the ferromagnetic order is strongly suppressed so that much larger interaction strength are needed than predicted by the Hartree-Fock solution. Moreover, the regions in parameter space where non-saturated ferromagnetism occurs are much broader in Gutzwiller theory. As shown in earlier

  8. Solar Luminosity on the Main Sequence, Standard Model and Variations

    Science.gov (United States)

    Ayukov, S. V.; Baturin, V. A.; Gorshkov, A. B.; Oreshina, A. V.

    2017-05-01

    Our Sun became Main Sequence star 4.6 Gyr ago according Standard Solar Model. At that time solar luminosity was 30% lower than current value. This conclusion is based on assumption that Sun is fueled by thermonuclear reactions. If Earth's albedo and emissivity in infrared are unchanged during Earth history, 2.3 Gyr ago oceans had to be frozen. This contradicts to geological data: there was liquid water 3.6-3.8 Gyr ago on Earth. This problem is known as Faint Young Sun Paradox. We analyze luminosity change in standard solar evolution theory. Increase of mean molecular weight in the central part of the Sun due to conversion of hydrogen to helium leads to gradual increase of luminosity with time on the Main Sequence. We also consider several exotic models: fully mixed Sun; drastic change of pp reaction rate; Sun consisting of hydrogen and helium only. Solar neutrino observations however exclude most non-standard solar models.

  9. Parametric modelling of temporal variations in radon concentrations in homes

    International Nuclear Information System (INIS)

    Revzan, K.L.; Turk, B.H.; Harrison, J.; Nero, A.V.; Sextro, R.G.

    1988-01-01

    The 222 Rn concentrations in the living area, the basement, and the undelying soil of a New Jersey home have been measured at half-hour intervals over the course of a year, as have indoor and outdoor temperatures, wind speed and direction, and indoor-outdoor and basement-subslab pressures; in addition, periods of furnace opration have been logged. We generalize and extend an existing radon entry model in order to demonstrate the dependence of the radon concentration on the environmental variales and the extent of furnace use. The model contains parameters which are dependent on geological and structural factors which have not been measured or otherwise determined; statistical methods are used to find the best values of the parameters. The non-linear regression of the model predictions (over time) on the measured living area radon concentrations yields an R/aup 2/ of 0.88. 9 refs., 2 figs

  10. Sparse Decomposition and Modeling of Anatomical Shape Variation

    DEFF Research Database (Denmark)

    Sjöstrand, Karl; Rostrup, Egill; Ryberg, Charlotte

    2007-01-01

    counterparts if constructed carefully. In most medical applications, models are required to have both good statistical performance and a relevant clinical interpretation to be of value. Morphometry of the corpus callosum is one illustrative example. This paper presents a method for relating spatial features...... to clinical outcome data. A set of parsimonious variables is extracted using sparse principal component analysis, producing simple yet characteristic features. The relation of these variables with clinical data is then established using a regression model. The result may be visualized as patterns...... two alternative techniques, one where features are derived using a model-based wavelet approach, and one where the original variables are regressed directly on the outcome....

  11. Variational theory of valence fluctuations: Ground states and quasiparticle excitations of the Anderson lattice model

    Science.gov (United States)

    Brandow, B. H.

    1986-01-01

    A variational study of ground states of the orbitally nondegenerate Anderson lattice model, using a wave function with one variational parameter per Bloch state k, has been extended to deal with essentially metallic systems having a nonintegral number of electrons per site. Quasiparticle excitations are obtained by direct appeal to Landau's original definition for interacting Fermi liquids, scrEqp(k,σ)=δEtotal/δn qp(k,σ). This approach provides a simple and explicit realization of the Luttinger picture of a periodic Fermi liquid. A close correspondence is maintained between the ``interacting'' (U=∞) system and the corresponding ``noninteracting'' (U=0) case, i.e., ordinary band theory; the result can be described as a renormalized band or renormalized hybridization theory. The occupation-number distribution for the conduction orbitals displays a finite discontinuity at the Fermi surface. If the d-f hybridization is nonzero throughout the Brillouin zone, the quasiparticle spectrum will always exhibit a gap, although this gap becomes exponentially small (i.e., of order TK) in the Kondo-lattice regime. In the ``ionic'' case with precisely two electrons per site, such a system may therefore exhibit an insulating (semiconducting) gap. The quasiparticle state density exhibits a prominent spike on each side of the spectral gap, just as in the elementary hybridization model (the U=0 case). For the metallic case, with a nonintegral number of electrons per site, the Fermi level falls within one of the two sharp density peaks. The effective mass at the Fermi surface tends to be very large; enhancements by a factor >~102 are quite feasible. The foregoing variational theory has also been refined by means of a trial wave function having two variational parameters per Bloch state k. The above qualitative features are all retained, with some quantitative differences, but there are also some qualitatively new features. The most interesting of these is the appearance, within

  12. Sensitivity of euphotic zone properties to CDOM variations in marine ecosystem models

    OpenAIRE

    Urtizberea, Agurtzane; Dupont, Nicolas; Rosland, Rune; Aksnes, Dag L.

    2013-01-01

    In marine ecosystem models, the underwater light intensity is commonly characterized by the shading of phytoplankton in addition to a background light attenuation coefficient. Colour dissolved organic matter (CDOM) is an important component of the background light attenuation, and we investigate how variation in CDOM attenuation affects euphotic zone properties in a general marine ecosystem model. Our results suggest that euphotic zone properties are highly sensitive to CDOM variations occurr...

  13. On numerical heat transfer characteristic study of flat surface subjected to variation in geometric thickness

    Science.gov (United States)

    Umair, Siddique Mohammed; Kolawale, Abhijeet Rangnath; Bhise, Ganesh Anurath; Gulhane, Nitin Parashram

    Thermal management in the looming world of electronic packaging system is the most prior and conspicuous issue as far as the working efficiency of the system is concerned. The cooling in such systems can be achieved by impinging air jet over the heat sink as jet impingement cooling is one of the cooling technologies which are widely studied now. Here the modulation in impinging and geometric parameters results in the establishment of the characteristic cooling rate over the target surface. The characteristic cooling curve actually resembles non-uniformity in cooling rate. This non-uniformity favors the area average heat dissipation rate. In order to study the non-uniformity in cooling characteristic, the present study takes an initiative in plotting the local Nusselt number magnitude against the non-dimensional radial distance of the different thickness of target surfaces. For this, the steady temperature distribution over the target surface under the impingement of air jet is being determined numerically. The work is completely inclined towards the determination of critical value of geometric thickness below which the non-uniformity in the Nusselt profile starts. This is done by numerically examining different target surfaces under constant Reynolds number and nozzle-target spacing. The occurrences of non-uniformity in Nusselt profile contributes to over a 42% enhancement in area average Nusselt magnitude. The critical value of characteristic thickness (t/d) reported in the present investigation approximate to 0.05. Below this value, the impingement of air jet generates a discrete pressure zones over the target surface in the form of pressure spots. As a result of this, the air flowing in contact with the target surface experiences a damping potential, in due of which it gets more time and contact with the surface to dissipate heat.

  14. Prospect of Using Numerical Dynamo Model for Prediction of Geomagnetic Secular Variation

    Science.gov (United States)

    Kuang, Weijia; Tangborn, Andrew

    2003-01-01

    Modeling of the Earth's core has reached a level of maturity to where the incorporation of observations into the simulations through data assimilation has become feasible. Data assimilation is a method by which observations of a system are combined with a model output (or forecast) to obtain a best guess of the state of the system, called the analysis. The analysis is then used as an initial condition for the next forecast. By doing assimilation, not only we shall be able to predict partially secular variation of the core field, we could also use observations to further our understanding of dynamical states in the Earth's core. One of the first steps in the development of an assimilation system is a comparison between the observations and the model solution. The highly turbulent nature of core dynamics, along with the absence of any regular external forcing and constraint (which occurs in atmospheric dynamics, for example) means that short time comparisons (approx. 1000 years) cannot be made between model and observations. In order to make sensible comparisons, a direct insertion assimilation method has been implemented. In this approach, magnetic field observations at the Earth's surface have been substituted into the numerical model, such that the ratio of the multiple components and the dipole component from observation is adjusted at the core-mantle boundary and extended to the interior of the core, while the total magnetic energy remains unchanged. This adjusted magnetic field is then used as the initial field for a new simulation. In this way, a time tugged simulation is created which can then be compared directly with observations. We present numerical solutions with and without data insertion and discuss their implications for the development of a more rigorous assimilation system.

  15. The nicolet lettuce model : a theme with variations

    NARCIS (Netherlands)

    Seginer, I.; Linker, F.; Buwalda, F.; Straten, van G.

    2004-01-01

    The NICOLET model has been developed to predict the growth and nitrate content of greenhouse lettuce. Four single-organ versions have been developed: [1] abundant supply of nitrogen (1998), [2] mild N-stress (1999), [3] severe N-stress (2003), and [4] ontogenetic changes of organic-N and water

  16. Variation in PAH inputs and microbial community in surface sediments of Hamilton Harbour: Implications to remediation and monitoring

    International Nuclear Information System (INIS)

    Slater, G.F.; Cowie, B.R.; Harper, N.; Droppo, I.G.

    2008-01-01

    Variations in concentrations of polycyclic aromatic hydrocarbons (PAHs) and microbial community indicators were investigated in representative highly contaminated and less contaminated surface sediment sites of Hamilton Harbour. Inputs of PAH to the upper 3 cm of sediments up to four times the average upper sediment concentrations were observed. Associated PAH fingerprint profiles indicated that the source was consistent with the PAH source to the industrial region of the harbour. Increased PAH loadings were associated with decreased bacterial populations as indicated by phospholipid fatty acid (PLFA) concentrations. However, relatively minor impacts on overall community composition were indicated. Porewater methane concentrations and isotopic data indicated a difference in the occurrence of methane oxidation between the two sites. This study confirms temporally limited transport of contaminants from highly impacted regions as a vector for contaminants within the harbour and the impact on microbial carbon cycling and bed stability. - Variations in PAH inputs to harbour sediments have implications to implementation and monitoring of mitigation/remediation efforts

  17. Unusual shapes for a catenary under the effects of surface tension and gravity: A variational treatment

    International Nuclear Information System (INIS)

    Behroozi, F.; Mohazzabi, P.; McCrickard, J.

    1995-01-01

    The familiar catenary is the shape assumed by a chain or string as it hangs from two points. The mathematical equation of the catenary was first published more than three hundred years ago by Leibnitz and Huygen, among others. Here we consider the shapes assumed by a hanging string in the presence of gravity and surface tension. The surface tension is introduced by suspending the string from a thin horizontal rod while the area bounded by the string and the rod is covered with a soap film. The string then assumes new and wonderful shapes depending on the relative strength of the surface tension and the weight per unit length of the string. When surface tension dominates, the string is pulled inward, assuming a convex shape similar to the Greek letter γ. On the other hand, when gravity is dominant the string is pulled outward and assumes a concave shape best described as a distorted catenary. However, when the gravitational force normal to the string matches the surface tension, the string takes a linear configuration similar to the letter V. Under suitable conditions, the string can be made to assume any of the three configurations by adjusting the separation of its end points. The equations that describe the shape of the string are derived by minimizing the total energy of the system and are presented for the three principal configurations

  18. Modeling Surface Roughness to Estimate Surface Moisture Using Radarsat-2 Quad Polarimetric SAR Data

    Science.gov (United States)

    Nurtyawan, R.; Saepuloh, A.; Budiharto, A.; Wikantika, K.

    2016-08-01

    Microwave backscattering from the earth's surface depends on several parameters such as surface roughness and dielectric constant of surface materials. The two parameters related to water content and porosity are crucial for estimating soil moisture. The soil moisture is an important parameter for ecological study and also a factor to maintain energy balance of land surface and atmosphere. Direct roughness measurements to a large area require extra time and cost. Heterogeneity roughness scale for some applications such as hydrology, climate, and ecology is a problem which could lead to inaccuracies of modeling. In this study, we modeled surface roughness using Radasat-2 quad Polarimetric Synthetic Aperture Radar (PolSAR) data. The statistical approaches to field roughness measurements were used to generate an appropriate roughness model. This modeling uses a physical SAR approach to predicts radar backscattering coefficient in the parameter of radar configuration (wavelength, polarization, and incidence angle) and soil parameters (surface roughness and dielectric constant). Surface roughness value is calculated using a modified Campbell and Shepard model in 1996. The modification was applied by incorporating the backscattering coefficient (σ°) of quad polarization HH, HV and VV. To obtain empirical surface roughness model from SAR backscattering intensity, we used forty-five sample points from field roughness measurements. We selected paddy field in Indramayu district, West Java, Indonesia as the study area. This area was selected due to intensive decreasing of rice productivity in the Northern Coast region of West Java. Third degree polynomial is the most suitable data fitting with coefficient of determination R2 and RMSE are about 0.82 and 1.18 cm, respectively. Therefore, this model is used as basis to generate the map of surface roughness.

  19. Comparison of Surface and Column Variations of CO2 Over Urban Areas for Future Active Remote CO2 Sensors

    Science.gov (United States)

    Choi, Yonghoon; Yang, Melissa; Kooi, Susan; Browell, Edward

    2015-01-01

    High resolution in-situ CO2 measurements were recorded onboard the NASA P-3B during the DISCOVER-AQ (Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality) Field Campaign, to investigate the ability of space-based observations to accurately assess near surface conditions related to air quality. This campaign includes, Washington DC/Baltimore, MD (July 2011), San Joaquin Valley, CA (January - February 2013), Houston, TX (September 2013), and Denver, CO (July-August 2014). Each of these campaigns consisted of missed approaches and approximately two hundred vertical soundings of CO2 within the lower troposphere (surface to about 5 km). In this study, surface (0 - 1 km) and column-averaged (0 - 3.5 km) CO2 mixing ratio values from the vertical soundings in the four geographically different urban areas are used to investigate the temporal and spatial variability of CO2 within the different urban atmospheric emission environments. Tracers such as CO, CH2O, NOx, and NMHCs are used to identify the source of CO2 variations in the urban sites. Additionally, we apply nominal CO2 column weighting functions for potential future active remote CO2 sensors operating in the 1.57-microns and 2.05-microns measurement regions to convert the in situ CO2 vertical mixing ratio profiles to variations in CO2 column optical depths, which is what the active remote sensors actually measure. Using statistics calculated from the optical depths at each urban site measured during the DISCOVER-AQ field campaign and for each nominal weighting function, we investigate the natural variability of CO2 columns in the lower troposphere; relate the CO2 column variability to the urban surface emissions; and show the measurement requirements for the future ASCENDS (Active Sensing of CO2 Emissions over Nights, Days, and Seasons) in the continental U.S. urban areas.

  20. Creating historical range of variation (HRV) time series using landscape modeling: Overview and issues [Chapter 8

    Science.gov (United States)

    Robert E. Keane

    2012-01-01

    Simulation modeling can be a powerful tool for generating information about historical range of variation (HRV) in landscape conditions. In this chapter, I will discuss several aspects of the use of simulation modeling to generate landscape HRV data, including (1) the advantages and disadvantages of using simulation, (2) a brief review of possible landscape models. and...

  1. MODELING THE INTERACTION OF AGROCHEMICALS WITH ENVIRONMENTAL SURFACES: PESTICIDES ON RUTILE AND ORGANO-RUTILE SURFACES

    Science.gov (United States)

    Non-bonded interactions between model pesticides and organo-mineral surfaces have been studied using molecular mechanical conformational calculations and molecular dynamics simulations. The minimum energy conformations and relative binding energies for the interaction of atrazine...

  2. Measuring and modeling surface sorption dynamics of organophosphate flame retardants on impervious surfaces

    Data.gov (United States)

    U.S. Environmental Protection Agency — The data presented in this data file is a product of a journal publication. The dataset contains measured and model predicted OPFRs gas-phase and surface-phase...

  3. Feasibility Study of Ex Ovo Chick Chorioallantoic Artery Model for Investigating Pulsatile Variation of Arterial Geometry.

    Directory of Open Access Journals (Sweden)

    Kweon-Ho Nam

    Full Text Available Despite considerable research efforts on the relationship between arterial geometry and cardiovascular pathology, information is lacking on the pulsatile geometrical variation caused by arterial distensibility and cardiomotility because of the lack of suitable in vivo experimental models and the methodological difficulties in examining the arterial dynamics. We aimed to investigate the feasibility of using a chick embryo system as an experimental model for basic research on the pulsatile variation of arterial geometry. Optical microscope video images of various arterial shapes in chick chorioallantoic circulation were recorded from different locations and different embryo samples. The high optical transparency of the chorioallantoic membrane (CAM allowed clear observation of tiny vessels and their movements. Systolic and diastolic changes in arterial geometry were visualized by detecting the wall boundaries from binary images. Several to hundreds of microns of wall displacement variations were recognized during a pulsatile cycle. The spatial maps of the wall motion harmonics and magnitude ratio of harmonic components were obtained by analyzing the temporal brightness variation at each pixel in sequential grayscale images using spectral analysis techniques. The local variations in the spectral characteristics of the arterial wall motion were reflected well in the analysis results. In addition, mapping the phase angle of the fundamental frequency identified the regional variations in the wall motion directivity and phase shift. Regional variations in wall motion phase angle and fundamental-to-second harmonic ratio were remarkable near the bifurcation area. In summary, wall motion in various arterial geometry including straight, curved and bifurcated shapes was well observed in the CAM artery model, and their local and cyclic variations could be characterized by Fourier and wavelet transforms of the acquired video images. The CAM artery model with

  4. Surface system Forsmark. Site descriptive modelling SDM-Site Forsmark

    International Nuclear Information System (INIS)

    Lindborg, Tobias

    2008-12-01

    SKB has undertaken site characterization of two different areas, Forsmark and Laxemar-Simpevarp, in order to find a suitable location for a geological repository for spent nuclear fuel. This report focuses on the site descriptive modelling of the surface system at Forsmark. The characterization of the surface system at the site was primarily made by identifying and describing important properties in different parts of the surface system, properties concerning e.g. hydrology and climate, Quaternary deposits and soils, hydrochemistry, vegetation, ecosystem functions, but also current and historical land use. The report presents available input data, methodology for data evaluation and modelling, and resulting models for each of the different disciplines. Results from the modelling of the surface system are also integrated with results from modelling of the deep bedrock system. The Forsmark site is located within the municipality of Oesthammar, about 120 km north of Stockholm. The investigated area is located along the shoreline of Oeregrundsgrepen, a funnel-shaped bay of the Baltic Sea. The area is characterized by small-scale topographic variations and is almost entirely located at altitudes lower than 20 metres above sea level. The Quaternary deposits in the area are dominated by till, characterized by a rich content of calcite which was transported by the glacier ice to the area from the sedimentary bedrock of Gaevlebukten about 100 km north of Forsmark. As a result, the surface waters and shallow groundwater at Forsmark are characterized by high pH values and high concentrations of certain major constituents, especially calcium and bicarbonate. The annual precipitation and runoff are 560 and 150 mm, respectively. The lakes are small and shallow, with mean and maximum depths ranging from approximately 0.1 to 1 m and 0.4 to 2 m. Sea water flows into the most low-lying lakes during events giving rise to very high sea levels. Wetlands are frequent and cover 25 to 35

  5. Surface modification induced phase transformation and structure variation on the rapidly solidified recast layer of titanium

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Ming-Hung [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Haung, Chiung-Fang [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Division of Family and Operative Dentistry, Department of Dentistry, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Shyu, Shih-Shiun [Department of Dentistry, Taipei Tzu Chi Hospital, Buddhist Tzu Chi Medical Foundation, New Taipei City 231, Taiwan (China); Chou, Yen-Ru [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 110, Taiwan (China); Graduate Institute of Biomedical Materials and Tissue Engineering, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Lin, Ming-Hong [Department of Mechanical Engineering and Graduate Institute of Mechanical and Precision Engineering, National Kaoshiung University of Applied Sciences, Kaoshiung 807, Taiwan (China); Peng, Pei-Wen, E-mail: apon@tmu.edu.tw [School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 110, Taiwan (China); and others

    2015-08-15

    In this study, neodymium-doped yttrium orthovanadate (Nd:YVO{sub 4}) as a laser source with different scanning speeds was used on biomedical Ti surface. The microstructural and biological properties of laser-modified samples were investigated by means of optical microscope, electron microscope, X-ray diffraction, surface roughness instrument, contact angle and cell cytotoxicity assay. After laser modification, the rough volcano-like recast layer with micro-/nanoporous structure and wave-like recast layer with nanoporous structure were generated on the surfaces of laser-modified samples, respectively. It was also found out that, an α → (α + rutile-TiO{sub 2}) phase transition occurred on the recast layers of laser-modified samples. The Ti surface becomes hydrophilic at a high speed laser scanning. Moreover, the cell cytotoxicity assay demonstrated that laser-modified samples did not influence the cell adhesion and proliferation behaviors of osteoblast (MG-63) cell. The laser with 50 mm/s scanning speed induced formation of rough volcano-like recast layer accompanied with micro-/nanoporous structure, which can promote cell adhesion and proliferation of MG-63 cell on Ti surface. The results indicated that the laser treatment was a potential technology to enhance the biocompatibility for titanium. - Highlights: • Laser induced the formation of recast layer with micro-/nanoporous structure on Ti. • An α → (α + rutile-TiO{sub 2}) phase transition was observed within the recast layer. • The Ti surface becomes hydrophilic at a high speed laser scanning. • Laser-modified samples exhibit good biocompatibility to osteoblast (MG-63) cell.

  6. Numerical Study of Wind Turbine Wake Modeling Based on a Actuator Surface Model

    DEFF Research Database (Denmark)

    Zhou, Huai-yang; Xu, Chang; Han, Xing Xing

    2017-01-01

    In the Actuator Surface Model (ALM), the turbine blades are represented by porous surfaces of velocity and pressure discontinuities to model the action of lifting surfaces on the flow. The numerical simulation is implemented on FLUENT platform combined with N-S equations. This model is improved o...

  7. Factoring variations in natural images with deep Gaussian mixture models

    OpenAIRE

    van den Oord, Aäron; Schrauwen, Benjamin

    2014-01-01

    Generative models can be seen as the swiss army knives of machine learning, as many problems can be written probabilistically in terms of the distribution of the data, including prediction, reconstruction, imputation and simulation. One of the most promising directions for unsupervised learning may lie in Deep Learning methods, given their success in supervised learning. However, one of the cur- rent problems with deep unsupervised learning methods, is that they often are harder to scale. As ...

  8. Potential of electrical resistivity tomography and muon density imaging to study spatio-temporal variations in the sub-surface

    Science.gov (United States)

    Lesparre, Nolwenn; Cabrera, Justo; Courbet, Christelle

    2015-04-01

    We explore the capacity of electrical resistivity tomography and muon density imaging to detect spatio-temporal variations of the medium surrounding a regional fault crossing the underground platform of Tournemire (Aveyron, France). The studied Cernon fault is sub-vertical and intersects perpendicularly the tunnel of Tournemire and extends to surface. The fault separates clay and limestones layers of the Dogger from limestones layers of the Lias. The Cernon fault presents a thickness of a ten of meters and drives water from an aquifer circulating at the top of the Dogger clay layer to the tunnel. An experiment combining electrical resistivity imaging and muon density imaging was setup taking advantage of the tunnel presence. A specific array of electrodes were set up, adapted for the characterization of the fault. Electrodes were placed along the tunnel as well as at the surface above the tunnel on both sides of the fault in order to acquire data in transmission across the massif to better cover the sounded medium. Electrical resistivity is particularly sensitive to water presence in the medium and thus carry information on the main water flow paths and on the pore space saturation. At the same time a muon sensor was placed in the tunnel under the fault region to detect muons coming from the sky after their crossing of the rock medium. Since the muon flux is attenuated as function of the quantity of matter crossed, muons flux measurements supply information on the medium average density along muons paths. The sensor presents 961 angles of view so measurements performed from one station allows a comparison of the muon flux temporal variations along the fault as well as in the medium surrounding the fault. As the water saturation of the porous medium fluctuates through time the medium density might indeed present sensible variations as shown by gravimetric studies. During the experiment important rainfalls occurred leading variations of the medium properties

  9. Modelling of surface evolution of rough surface on divertor target in fusion devices

    International Nuclear Information System (INIS)

    Dai, Shuyu; Liu, Shengguang; Sun, Jizhong; Kirschner, A.; Kawamura, G.; Tskhakaya, D.; Ding, Rui; Luo, Guangnan; Wang, Dezhen

    2015-01-01

    Highlights: • We study the surface evolution of rough surface on divertor target in fusion devices. • The effects of gyration motion and E × B drift affect 3D angular distribution. • A larger magnetic field angle leads to a reduced net eroded areal density. • The rough surface evolution affects the physical sputtering yield. - Abstract: The 3D Monte-Carlo code SURO has been used to study the surface evolution of rough surface on the divertor target in fusion devices. The edge plasma at divertor region is modelled by the SDPIC code and used as input data for SURO. Coupled with SDPIC, SURO can perform more sophisticated simulations to calculate the local angle and surface evolution of rough surface. The simulation results show that the incident direction of magnetic field, gyration and E × B force has a significant impact on 3D angular distribution of background plasma and accordingly on the erosion of rough surface. The net eroded areal density of rough surface is studied by varying the magnetic field angle with surface normal. The evolution of the microscopic morphology of rough surface can lead to a significant change in the physical sputtering yield

  10. Modeling the Acceleration of Global Surface Temperture

    Science.gov (United States)

    Jones, B.

    2017-12-01

    A mathematical projection focusing on the changing rate of acceleration of Global Surface Temperatures. Using historical trajectory and informed expert near-term prediction, it is possible to extend this further forward drawing a reference arc of acceleration. Presented here is an example of this technique based on data found in the Summary of Findings of A New Estimate of the Average Earth Surface Land Temperature Spanning 1753 to 2011 and that same team's stated prediction to 2050. With this, we can project a curve showing future acceleration: Decade (midpoint) Change in Global Land Temp Degrees C Known Slope Projected Trend 1755 0.000 1955 0.600 0.0030 2005 1.500 0.0051 2045 3.000 0.0375 2095 5.485 0.0497 2145 8.895 0.0682 2195 13.488 0.0919 Observations: Slopes are getting steeper and doing so faster in an "acceleration of the acceleration" or an "arc of acceleration". This is consistent with the non-linear accelerating feedback loops of global warming. Such projected temperatures threaten human civilization and human life. This `thumbnail' projection is consistent with the other long term predictions based on anthropogenic greenhouse gases. This projection is low when compared to those whose forecasts include greenhouse gases released from thawing permafrost and clathrate hydrates. A reference line: This curve should be considered a point of reference. In the near term and absent significant drawdown of greenhouse gases, my "bet" for this AGU session is that future temperatures will generally be above this reference curve. For example, the decade ending 2020 - more than 1.9C and the decade ending 2030 - more than 2.3C - again measured from the 1750 start point. *Caveat: The long term curve and prediction assumes that mankind does not move quickly away from high cost fossil fuels and does not invent, mobilize and take actions drawing down greenhouse gases. Those seeking a comprehensive action plan are directed to drawdown.org

  11. 30th International School of Mathematics "G Stampacchia" : Equilibrium Problems and Variational Models "Ettore Majorana"

    CERN Document Server

    Giannessi, Franco; Maugeri, Antonino; Equilibrium Problems and Variational Models

    2000-01-01

    The volume, devoted to variational analysis and its applications, collects selected and refereed contributions, which provide an outline of the field. The meeting of the title "Equilibrium Problems and Variational Models", which was held in Erice (Sicily) in the period June 23 - July 2 2000, was the occasion of the presentation of some of these papers; other results are a consequence of a fruitful and constructive atmosphere created during the meeting. New results, which enlarge the field of application of variational analysis, are presented in the book; they deal with the vectorial analysis, time dependent variational analysis, exact penalization, high order deriva­ tives, geometric aspects, distance functions and log-quadratic proximal methodology. The new theoretical results allow one to improve in a remarkable way the study of significant problems arising from the applied sciences, as continuum model of transportation, unilateral problems, multicriteria spatial price models, network equilibrium...

  12. Modeling the Acid-Base Properties of Montmorillonite Edge Surfaces.

    Science.gov (United States)

    Tournassat, Christophe; Davis, James A; Chiaberge, Christophe; Grangeon, Sylvain; Bourg, Ian C

    2016-12-20

    The surface reactivity of clay minerals remains challenging to characterize because of a duality of adsorption surfaces and mechanisms that does not exist in the case of simple oxide surfaces: edge surfaces of clay minerals have a variable proton surface charge arising from hydroxyl functional groups, whereas basal surfaces have a permanent negative charge arising from isomorphic substitutions. Hence, the relationship between surface charge and surface potential on edge surfaces cannot be described using the Gouy-Chapman relation, because of a spillover of negative electrostatic potential from the basal surface onto the edge surface. While surface complexation models can be modified to account for these features, a predictive fit of experimental data was not possible until recently, because of uncertainty regarding the densities and intrinsic pK a values of edge functional groups. Here, we reexamine this problem in light of new knowledge on intrinsic pK a values obtained over the past decade using ab initio molecular dynamics simulations, and we propose a new formalism to describe edge functional groups. Our simulation results yield reasonable predictions of the best available experimental acid-base titration data.

  13. Modeling marine surface microplastic transport to assess optimal removal locations

    OpenAIRE

    Sherman, Peter; Van Sebille, Erik

    2016-01-01

    Marine plastic pollution is an ever-increasing problem that demands immediate mitigation and reduction plans. Here, a model based on satellite-tracked buoy observations and scaled to a large data set of observations on microplastic from surface trawls was used to simulate the transport of plastics floating on the ocean surface from 2015 to 2025, with the goal to assess the optimal marine microplastic removal locations for two scenarios: removing the most surface microplastic and reducing the ...

  14. Using semi-variogram analysis for providing spatially distributed information on soil surface condition for land surface modeling

    Science.gov (United States)

    Croft, Holly; Anderson, Karen; Kuhn, Nikolaus J.

    2010-05-01

    the change in soil surface structure during crusting. The laser data were also used to create digital surface models (DSM) of the soil states for visual comparison. This research has shown that aggregate breakdown and soil crusting can be shown quantitatively by a decrease in sill variance (silt soil: 11.67 (control) to 1.08 (after 90 mins rainfall)). Features present within semi-variograms were spatially linked to features at the soil surface, such as soil cracks, tillage lines and areas of deposition. Directional semi-variograms were used to provide a spatially orientated component, where the directional sill variance associated with a soil crack was shown to increase from 7.95 to 19.33. Periodicity within semi-variogram was also shown to quantify the spatial scale of soil cracking networks and potentially surface flowpaths; an average distance between soil cracks of 37 mm closely corresponded to the distance of 38 mm shown in the semi-variogram. The results provide a strong basis for the future retrieval of spatio-temporal variations in soil surface condition. Furthermore, the presence of process-based information on hydrological pathways within semi-variograms may work towards an inclusion of geostatisically-derived information in land surface models and the understanding of complex surface processes at different spatial scales.

  15. A Different View of Solar Spectral Irradiance Variations: Modeling Total Energy over Six-Month Intervals.

    Science.gov (United States)

    Woods, Thomas N; Snow, Martin; Harder, Jerald; Chapman, Gary; Cookson, Angela

    A different approach to studying solar spectral irradiance (SSI) variations, without the need for long-term (multi-year) instrument degradation corrections, is examining the total energy of the irradiance variation during 6-month periods. This duration is selected because a solar active region typically appears suddenly and then takes 5 to 7 months to decay and disperse back into the quiet-Sun network. The solar outburst energy, which is defined as the irradiance integrated over the 6-month period and thus includes the energy from all phases of active region evolution, could be considered the primary cause for the irradiance variations. Because solar cycle variation is the consequence of multiple active region outbursts, understanding the energy spectral variation may provide a reasonable estimate of the variations for the 11-year solar activity cycle. The moderate-term (6-month) variations from the Solar Radiation and Climate Experiment (SORCE) instruments can be decomposed into positive (in-phase with solar cycle) and negative (out-of-phase) contributions by modeling the variations using the San Fernando Observatory (SFO) facular excess and sunspot deficit proxies, respectively. These excess and deficit variations are fit over 6-month intervals every 2 months over the mission, and these fitted variations are then integrated over time for the 6-month energy. The dominant component indicates which wavelengths are in-phase and which are out-of-phase with solar activity. The results from this study indicate out-of-phase variations for the 1400 - 1600 nm range, with all other wavelengths having in-phase variations.

  16. Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations

    NARCIS (Netherlands)

    Schrama, E.J.O.; Wouters, B.; Lavallée, D.A.

    2007-01-01

    The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing

  17. Quantitative estimation of Holocene surface salinity variation in the Black Sea using dinoflagellate cyst process length

    DEFF Research Database (Denmark)

    Mertens, Kenneth Neil; Bradley, Lee R.; Takano, Yoshihito

    2012-01-01

    Reconstruction of salinity in the Holocene Black Sea has been an ongoing debate over the past four decades. Here we calibrate summer surface water salinity in the Black Sea, Sea of Azov and Caspian Sea with the process length of the dinoflagellate cyst Lingulodinium machaerophorum. We then apply ...

  18. Hydration dynamics near a model protein surface

    International Nuclear Information System (INIS)

    Russo, Daniela; Hura, Greg; Head-Gordon, Teresa

    2003-01-01

    The evolution of water dynamics from dilute to very high concentration solutions of a prototypical hydrophobic amino acid with its polar backbone, N-acetyl-leucine-methylamide (NALMA), is studied by quasi-elastic neutron scattering and molecular dynamics simulation for both the completely deuterated and completely hydrogenated leucine monomer. We observe several unexpected features in the dynamics of these biological solutions under ambient conditions. The NALMA dynamics shows evidence of de Gennes narrowing, an indication of coherent long timescale structural relaxation dynamics. The translational water dynamics are analyzed in a first approximation with a jump diffusion model. At the highest solute concentrations, the hydration water dynamics is significantly suppressed and characterized by a long residential time and a slow diffusion coefficient. The analysis of the more dilute concentration solutions takes into account the results of the 2.0M solution as a model of the first hydration shell. Subtracting the first hydration layer based on the 2.0M spectra, the translational diffusion dynamics is still suppressed, although the rotational relaxation time and residential time are converged to bulk-water values. Molecular dynamics analysis shows spatially heterogeneous dynamics at high concentration that becomes homogeneous at more dilute concentrations. We discuss the hydration dynamics results of this model protein system in the context of glassy systems, protein function, and protein-protein interfaces

  19. Image Restoration Based on the Hybrid Total-Variation-Type Model

    OpenAIRE

    Shi, Baoli; Pang, Zhi-Feng; Yang, Yu-Fei

    2012-01-01

    We propose a hybrid total-variation-type model for the image restoration problem based on combining advantages of the ROF model with the LLT model. Since two ${L}^{1}$ -norm terms in the proposed model make it difficultly solved by using some classically numerical methods directly, we first employ the alternating direction method of multipliers (ADMM) to solve a general form of the proposed model. Then, based on the ADMM and the Moreau-Yosida decomposition theory, a more efficient method call...

  20. Solar activity variations of ionosonde measurements and modeling results

    Czech Academy of Sciences Publication Activity Database

    Altadill, D.; Arrazola, D.; Blanch, E.; Burešová, Dalia

    2008-01-01

    Roč. 42, č. 4 (2008), s. 610-616 ISSN 0273-1177 R&D Projects: GA AV ČR 1QS300120506 Grant - others:MCYT(ES) REN2003-08376-C02-02; CSIC(XE) 2004CZ0002; AGAUR(XE) 2006BE00112; AF Research Laboratory(XE) FA8718-L-0072 Institutional research plan: CEZ:AV0Z30420517 Keywords : mid-latitude ionosphere * bottomside modeling * ionospheric variability Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 0.860, year: 2008 http://www.sciencedirect.com/science/journal/02731177

  1. Short-term variations in core surface flow resolved from an improved method of calculating observatory monthly means

    Science.gov (United States)

    Olsen, Nils; Whaler, Kathryn A.; Finlay, Christopher C.

    2014-05-01

    Monthly means of the magnetic field measurements taken by ground observatories are a useful data source for studying temporal changes of the core magnetic field and the underlying core flow. However, the usual way of calculating monthly means as the arithmetic mean of all days (geomagnetic quiet as well as disturbed) and all local times (day and night) may result in contributions from external (magnetospheric and ionospheric) origin in the (ordinary, omm) monthly means. Such contamination makes monthly means less favourable for core studies. We calculated revised monthly means (rmm), and their uncertainties, from observatory hourly means using robust means and after removal of external field predictions, using an improved method for characterising the magnetospheric ring current. The utility of the new method for calculating observatory monthly means is demonstrated by inverting their first differences for core surface advective flows. The flow is assumed steady over three consecutive months to ensure uniqueness; the effects of more rapid changes should be attenuated by the weakly conducting mantle. Observatory data are inverted directly for a regularised core flow, rather than deriving it from a secular variation spherical harmonic model. The main field is specified by the CHAOS-4 model. Data from up to 128 observatories between 1997 and 2013 were used to calculate 185 flow models from the omm and rmm, for each possible set of three consecutive months. The full 3x3 (non-diagonal) data covariance matrix was used, and two-norm (least squares) minimisation performed. We are able to fit the data to the target (weighted) misfit of 1, for both omm and rmm inversions, provided we incorporate the full data covariance matrix, and produce consistent, plausible flows. Fits are better for rmm flows. The flows exhibit noticeable changes over timescales of a few months. However, they follow rapid excursions in the omm that we suspect result from external field contamination

  2. Specification for a surface-search radar-detection-range model

    Science.gov (United States)

    Hattan, Claude P.

    1990-09-01

    A model that predicts surface-search radar detection range versus a variety of combatants has been developed at the Naval Ocean Systems Center. This model uses a simplified ship radar cross section (RCS) model and the U.S. Navy Oceanographic and Atmospheric Mission Library Standard Electromagnetic Propagation Model. It provides the user with a method of assessing the effects of the environment of the performance of a surface-search radar system. The software implementation of the model is written in ANSI FORTRAN 77, with MIL-STD-1753 extensions. The program provides the user with a table of expected detection ranges when the model is supplied with the proper environmental radar system inputs. The target model includes the variation in RCS as a function of aspect angle and the distribution of reflected radar energy as a function of height above the waterline. The modeled propagation effects include refraction caused by a multisegmented refractivity profile, sea-surface roughness caused by local winds, evaporation ducting, and surface-based ducts caused by atmospheric layering.

  3. Integrating Surface Modeling into the Engineering Design Graphics Curriculum

    Science.gov (United States)

    Hartman, Nathan W.

    2006-01-01

    It has been suggested there is a knowledge base that surrounds the use of 3D modeling within the engineering design process and correspondingly within engineering design graphics education. While solid modeling receives a great deal of attention and discussion relative to curriculum efforts, and rightly so, surface modeling is an equally viable 3D…

  4. Land Surface Verification Toolkit (LVT) - A Generalized Framework for Land Surface Model Evaluation

    Science.gov (United States)

    Kumar, Sujay V.; Peters-Lidard, Christa D.; Santanello, Joseph; Harrison, Ken; Liu, Yuqiong; Shaw, Michael

    2011-01-01

    Model evaluation and verification are key in improving the usage and applicability of simulation models for real-world applications. In this article, the development and capabilities of a formal system for land surface model evaluation called the Land surface Verification Toolkit (LVT) is described. LVT is designed to provide an integrated environment for systematic land model evaluation and facilitates a range of verification approaches and analysis capabilities. LVT operates across multiple temporal and spatial scales and employs a large suite of in-situ, remotely sensed and other model and reanalysis datasets in their native formats. In addition to the traditional accuracy-based measures, LVT also includes uncertainty and ensemble diagnostics, information theory measures, spatial similarity metrics and scale decomposition techniques that provide novel ways for performing diagnostic model evaluations. Though LVT was originally designed to support the land surface modeling and data assimilation framework known as the Land Information System (LIS), it also supports hydrological data products from other, non-LIS environments. In addition, the analysis of diagnostics from various computational subsystems of LIS including data assimilation, optimization and uncertainty estimation are supported within LVT. Together, LIS and LVT provide a robust end-to-end environment for enabling the concepts of model data fusion for hydrological applications. The evolving capabilities of LVT framework are expected to facilitate rapid model evaluation efforts and aid the definition and refinement of formal evaluation procedures for the land surface modeling community.

  5. Land surface Verification Toolkit (LVT) - a generalized framework for land surface model evaluation

    Science.gov (United States)

    Kumar, S. V.; Peters-Lidard, C. D.; Santanello, J.; Harrison, K.; Liu, Y.; Shaw, M.

    2012-06-01

    Model evaluation and verification are key in improving the usage and applicability of simulation models for real-world applications. In this article, the development and capabilities of a formal system for land surface model evaluation called the Land surface Verification Toolkit (LVT) is described. LVT is designed to provide an integrated environment for systematic land model evaluation and facilitates a range of verification approaches and analysis capabilities. LVT operates across multiple temporal and spatial scales and employs a large suite of in-situ, remotely sensed and other model and reanalysis datasets in their native formats. In addition to the traditional accuracy-based measures, LVT also includes uncertainty and ensemble diagnostics, information theory measures, spatial similarity metrics and scale decomposition techniques that provide novel ways for performing diagnostic model evaluations. Though LVT was originally designed to support the land surface modeling and data assimilation framework known as the Land Information System (LIS), it supports hydrological data products from non-LIS environments as well. In addition, the analysis of diagnostics from various computational subsystems of LIS including data assimilation, optimization and uncertainty estimation are supported within LVT. Together, LIS and LVT provide a robust end-to-end environment for enabling the concepts of model data fusion for hydrological applications. The evolving capabilities of LVT framework are expected to facilitate rapid model evaluation efforts and aid the definition and refinement of formal evaluation procedures for the land surface modeling community.

  6. Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

    Science.gov (United States)

    Yueh, Simon H.

    2004-01-01

    Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

  7. Introductory biology students' conceptual models and explanations of the origin of variation.

    Science.gov (United States)

    Speth, Elena Bray; Shaw, Neil; Momsen, Jennifer; Reinagel, Adam; Le, Paul; Taqieddin, Ranya; Long, Tammy

    2014-01-01

    Mutation is the key molecular mechanism generating phenotypic variation, which is the basis for evolution. In an introductory biology course, we used a model-based pedagogy that enabled students to integrate their understanding of genetics and evolution within multiple case studies. We used student-generated conceptual models to assess understanding of the origin of variation. By midterm, only a small percentage of students articulated complete and accurate representations of the origin of variation in their models. Targeted feedback was offered through activities requiring students to critically evaluate peers' models. At semester's end, a substantial proportion of students significantly improved their representation of how variation arises (though one-third still did not include mutation in their models). Students' written explanations of the origin of variation were mostly consistent with their models, although less effective than models in conveying mechanistic reasoning. This study contributes evidence that articulating the genetic origin of variation is particularly challenging for learners and may require multiple cycles of instruction, assessment, and feedback. To support meaningful learning of the origin of variation, we advocate instruction that explicitly integrates multiple scales of biological organization, assessment that promotes and reveals mechanistic and causal reasoning, and practice with explanatory models with formative feedback. © 2014 E. Bray Speth et al. CBE—Life Sciences Education © 2014 The American Society for Cell Biology. This article is distributed by The American Society for Cell Biology under license from the author(s). It is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).

  8. Significant Variation of Post-critical SsPmp Amplitude as a Result of Variation in Near-surface Velocity: Observations from the Yellowknife Array

    Science.gov (United States)

    Ferragut, G.; Liu, T.; Klemperer, S. L.

    2017-12-01

    In recent years Virtual Deep Seismic Sounding (VDSS) emerged as a novel method to image the Moho, which uses the post-critical reflection P waves at the Moho generated by teleseismic S waves at the free surface near the receivers (SsPmp). However, observed SsPmp sometimes have significantly lower amplitude than predicted, raising doubts among the seismic community on the theoretical basis of the method. With over two decades of continuous digital broadband records and major subduction zones in the range of 30-50 degrees, the Yellowknife Array in northern Canada provides a rich opportunity for observation of post-critical SsPmp. We analyze S wave coda of events with epicenter distances of 30-50°, and pay special attention to earthquakes in a narrow azimuth range that ­­­encompasses the Kamchatka Peninsula. Among 21 events with strong direct S energy on the radial components, we observe significant variation of SsPmp energy. After associating the SsPmp energy with the virtual source location of each event, we observe a general trend of decreasing SsPmp energy from NE to SW. As the trend coincides with the transition from exposed basement of the Slave Craton to Paleozoic platform covered by Phanerozoic sediment, we interpret the decreasing SsPmp energy as a result of lower S velocity at the virtual sources, which reduces S-to-P reflection coefficients. We plan to include more events from the Aleutian Islands, the virtual sources of which are primarily located in the Paleozoic platform. This will allow us to further investigate the relationship between SsPmp amplitude and near-surface velocity.

  9. 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.

  10. Modelled long term trends of surface ozone over South Africa

    CSIR Research Space (South Africa)

    Naidoo, M

    2011-09-01

    Full Text Available focused on SA Highveld, 2006 ? Keeping all CAMx inputs ?standardized?, leaving only meteorology as a variable ? CSIR 2010 Slide 11 CAMx data flow CAMx Met model USGS surface data Emissions Initial & boundary Haze & albedo Photolysis rates...

  11. The ising model on the dynamical triangulated random surface

    International Nuclear Information System (INIS)

    Aleinov, I.D.; Migelal, A.A.; Zmushkow, U.V.

    1990-01-01

    The critical properties of Ising model on the dynamical triangulated random surface embedded in D-dimensional Euclidean space are investigated. The strong coupling expansion method is used. The transition to thermodynamical limit is performed by means of continuous fractions

  12. Source Term Model for Fine Particle Resuspension from Indoor Surfaces

    National Research Council Canada - National Science Library

    Kim, Yoojeong; Gidwani, Ashok; Sippola, Mark; Sohn, Chang W

    2008-01-01

    This Phase I effort developed a source term model for particle resuspension from indoor surfaces to be used as a source term boundary condition for CFD simulation of particle transport and dispersion in a building...

  13. Empirical model for estimating the surface roughness of machined ...

    African Journals Online (AJOL)

    Michael Horsfall

    one of the most critical quality measure in mechanical products. In the ... Keywords: cutting speed, centre lathe, empirical model, surface roughness, Mean absolute percentage deviation ... The factors considered were work piece properties.

  14. A model of the ground surface temperature for micrometeorological analysis

    Science.gov (United States)

    Leaf, Julian S.; Erell, Evyatar

    2017-07-01

    Micrometeorological models at various scales require ground surface temperature, which may not always be measured in sufficient spatial or temporal detail. There is thus a need for a model that can calculate the surface temperature using only widely available weather data, thermal properties of the ground, and surface properties. The vegetated/permeable surface energy balance (VP-SEB) model introduced here requires no a priori knowledge of soil temperature or moisture at any depth. It combines a two-layer characterization of the soil column following the heat conservation law with a sinusoidal function to estimate deep soil temperature, and a simplified procedure for calculating moisture content. A physically based solution is used for each of the energy balance components allowing VP-SEB to be highly portable. VP-SEB was tested using field data measuring bare loess desert soil in dry weather and following rain events. Modeled hourly surface temperature correlated well with the measured data (r 2 = 0.95 for a whole year), with a root-mean-square error of 2.77 K. The model was used to generate input for a pedestrian thermal comfort study using the Index of Thermal Stress (ITS). The simulation shows that the thermal stress on a pedestrian standing in the sun on a fully paved surface, which may be over 500 W on a warm summer day, may be as much as 100 W lower on a grass surface exposed to the same meteorological conditions.

  15. Fringe projection application for surface variation analysis on helical shaped silicon breast

    Science.gov (United States)

    Vairavan, R.; Ong, N. R.; Sauli, Z.; Shahimin, M. M.; Kirtsaeng, S.; Sakuntasathien, S.; Alcain, J. B.; Paitong, P.; Retnasamy, V.

    2017-09-01

    Breast carcinoma is rated as a second collective cause of cancer associated death among adult females. Detection of the disease at an early stage would enhance the chance for survival. Established detection methods such as mammography, ultrasound and MRI are classified as non invasive breast cancer detection modality, but however they are not entire non-invasive as physical contact still occurs to the breast. Thus requirement for a complete non invasive and non contact is evident. Therefore, in this work, a novel application of digital fringe projection for early detection of breast cancer based on breast surface analysis is reported. Phase shift fringe projection technique and pixel tracing method was utilized to analyze the breast surface change due to the incidence of breast lump. Results have shown that the digital fringe projection is capable in detecting the existence of 1 cm sized lump within the breast sample.

  16. A Combined EOF/Variational Approach for Mapping Radar-Derived Sea Surface Currents

    Science.gov (United States)

    2011-01-01

    gaps in the gridded SST images, which was successfully applied in Adriatic ( Alvera - Azcarate et al., 2005). Kondrashov and Chil (2006) developed...velocities. Similar to SST analysis (Beckers and Rixen, 2003: Alvera -Azcarate et al.. 2005), these modes are used to fill the gaps in HFR...and selection of the time interval for estimating the covariances becomes important. In the present study the sea surface velocity Alvera -Azcarate

  17. Variation in surface water-groundwater exchange with land use in an urban stream

    Science.gov (United States)

    Ryan, Robert J.; Welty, Claire; Larson, Philip C.

    2010-10-01

    SummaryA suite of methods is being utilized in the Baltimore metropolitan area to develop an understanding of the interaction between groundwater and surface water at multiple space and time scales. As part of this effort, bromide tracer experiments were conducted over two 10-day periods in August 2007 and May 2008 along two sections (each approximately 900 m long) of Dead Run, a small urban stream located in Baltimore County, Maryland, to investigate the influence of distinct zones of riparian land cover on surface-subsurface exchange and transient storage under low and high baseflow conditions. Riparian land cover varied by reach along a gradient of land use spanning parkland, suburban/residential, commercial, institutional, and transportation, and included wooded, meadow, turf grass, and impervious cover. Under summer low baseflow conditions, surface water-groundwater exchange, defined by gross inflow and gross outflow, was larger and net inflow (gross inflow minus gross outflow) had greater spatial variability, than was observed under spring high baseflow conditions. In addition, the fraction of nominal travel time attributable to transient storage ( Fmed) was lower and was more spatially variable under high baseflow conditions than under low baseflow conditions. The influence of baseflow condition on surface water-ground water exchange and transient storage was most evident in the subreaches with the least riparian forest cover and these effects are attributed to a lack of shading in reaches with little riparian forest cover. We suggest that under summer low baseflow conditions, the lack of shading allowed excess in-channel vegetation growth which acted as a transient storage zone and a conduit for outflow (i.e. uptake and evapotranspiration). Under spring high baseflow conditions the transient storage capacity of the channel was reduced because there was little in-channel vegetation.

  18. Atmospheric summer teleconnections and Greenland Ice Sheet surface mass variations: insights from MERRA-2

    International Nuclear Information System (INIS)

    Lim, Young-Kwon; Schubert, Siegfried D; Molod, Andrea M; Cullather, Richard I; Zhao, Bin; Nowicki, Sophie M J; Lee, Jae N; Velicogna, Isabella

    2016-01-01

    The relationship between leading atmospheric teleconnection patterns and Greenland Ice Sheet (GrIS) temperature, precipitation, and surface mass balance (SMB) are investigated for the last 36 summers (1979–2014) based on Modern-Era Retrospective analysis for Research and Applications version 2 reanalyses. The results indicate that the negative phase of both the North Atlantic Oscillation (NAO) and Arctic Oscillation, associated with warm and dry conditions for the GrIS, lead to SMB decreases within 0–1 months. Furthermore, the positive phase of the East Atlantic (EA) pattern often lags the negative NAO, reflecting a dynamical linkage between these modes that acts to further enhance the warm and dry conditions over the GrIS, leading to a favorable environment for enhanced surface mass loss. The development of a strong negative NAO in combination with a strong positive EA in recent years leads to significantly larger GrIS warming compared to when the negative NAO occurs in combination with a negative or weak positive EA (0.69 K versus 0.13 K anomaly). During 2009 and 2011, weakened (as compared to conditions during the severe surface melt cases of 2010 and 2012) local high pressure blocking produced colder northerly flow over the GrIS inhibiting warming despite the occurrence of a strong negative NAO, reflecting an important role for the EA during those years. In particular, the EA acts with the NAO to enhance warming in 2010 and 2012, and weaken high pressure blocking in 2009 and 2011. In general, high pressure blocking primarily impacts the western areas of the GrIS via advective temperature increases, while changes in net surface radiative fluxes account for both western and eastern GrIS temperature changes. (letter)

  19. The Role of Meteorology and Surface Condition to Multi-Decadal Variations of Dust Emission in Sahara and Sahel

    Science.gov (United States)

    Kim, D.; Chin, M.; Diehl, T. L.; Bian, H.; Brown, M. E.; Remer, L. A.; Stockwell, W. R.

    2014-12-01

    North Africa is the world's largest dust source region influencing regional and global climate, human health, and even the local economy. However North Africa as a dust source is not uniform but it consists of the arid region (Sahara) and the semi-arid region (Sahel) with emission rates depending on meteorological and surface conditions. Several recent studies have shown that dust from North Africa seems to have a decreasing trend in the past three decades. The goal of this study is to better understand the controlling factors that determine the change of dust in North Africa using observational data and model simulations. First we analyze surface bareness conditions determined from a long-term satellite observed Normalized Difference Vegetation Index for 1980-2008. Then we examine the key meteorological variables of precipitation and surface winds. Modeling experiments were conducted using the NASA Goddard Chemistry Aerosol Radiation and Transport (GOCART) model, which has been recently updated with a dynamic dust source function. Using the method we separate the dust originating from the Sahel from that of the Sahara desert. We find that the surface wind speed is the most dominant factor affecting Sahelian dust emission while vegetation has a modulating effect. We will show regional differences in meteorological variables, surface conditions, dust emission, and dust distribution and address the relationships among meteorology, surface conditions, and dust emission/loading in the past three decades (1980-2008).

  20. Seasonal variation of monomethylmercury concentrations in surface sediments of the Tagus Estuary (Portugal)

    International Nuclear Information System (INIS)

    Canario, Joao; Branco, Vasco; Vale, Carlos

    2007-01-01

    Surface sediments (0-2 cm) were collected at 40 sites along the Tagus Estuary in July and December 2004. The sediments were analysed for total mercury, monomethylmercury (MMHg) and interpretative parameters (e.g. redox potential, pH, C org ). No significant differences in total Hg, pH, Al, Fe, Mn and C org were found between sediments collected in the two periods, but MMHg concentrations were higher in July. On average sediments were warmer and more reducing in summer. On the basis of these results, an increase of 7 kg of MMHg (+37%) in surface sediments of the Tagus Estuary was estimated. Presumably higher temperatures in summer promote the increase of microbial activity and higher methylation rates. The alterations observed in this study point to the potential importance of seasonal changes in MMHg production at surface sediments with eventual changes in the MMHg uptake by benthic invertebrates and other organisms in the food web. - Seasonal changes in monomethylmercury production in sediments may increase its uptake by benthic invertebrates and other organisms in the food web

  1. Evolution of Mars’ Northern Polar Seasonal CO2 deposits: variations in surface brightness and bulk density

    Science.gov (United States)

    Mount, Christopher P.; Titus, Timothy N.

    2015-01-01

    Small scale variations of seasonal ice are explored at different geomorphic units on the Northern Polar Seasonal Cap (NPSC). We use seasonal rock shadow measurements, combined with visible and thermal observations, to calculate density over time. The coupling of volume density and albedo allows us to determine the microphysical state of the seasonal CO2 ice. We find two distinct endmembers across the NPSC: 1) Snow deposits may anneal to form an overlying slab layer that fractures. These low density deposits maintain relatively constant densities over springtime. 2) Porous slab deposits likely anneal rapidly in early spring and fracture in late spring. These high density deposits dramatically increase in density over time. The endmembers appear to be correlated with latitude.

  2. Causes of seasonal variations of Cs-134/137 activity concentrations in surface air

    International Nuclear Information System (INIS)

    Hoetzl, H.; Winkler, R.

    1993-01-01

    In winter months maxima of Cs-134/137 activity concentrations in air are observed at several locations in Europe. To clarify this phenomenon, from October 1991 to November 1992 we performed a program for aerosol collection on a short-term scale based on collecting intervals of 48-72 hours. The local meteorological parameters were determined simultaneously. Statistical analysis of these observations reveiled a highly significant positive correlation between Cs-137 activity concentration and the so-called 'Stagnationsindex'. Based on this relationship the seasonal variations of Cs-134/137 concentrations in ground-level air can be explained by atmospheric inversion conditions frequently occurring during fall- and wintermonths. (orig.) [de

  3. A numerical analysis of antithetic variates in Monte Carlo radiation transport with geometrical surface splitting

    International Nuclear Information System (INIS)

    Sarkar, P.K.; Prasad, M.A.

    1989-01-01

    A numerical study for effective implementation of the antithetic variates technique with geometric splitting/Russian roulette in Monte Carlo radiation transport calculations is presented. The study is based on the theory of Monte Carlo errors where a set of coupled integral equations are solved for the first and second moments of the score and for the expected number of flights per particle history. Numerical results are obtained for particle transmission through an infinite homogeneous slab shield composed of an isotropically scattering medium. Two types of antithetic transformations are considered. The results indicate that the antithetic transformations always lead to reduction in variance and increase in efficiency provided optimal antithetic parameters are chosen. A substantial gain in efficiency is obtained by incorporating antithetic transformations in rule of thumb splitting. The advantage gained for thick slabs (∼20 mfp) with low scattering probability (0.1-0.5) is attractively large . (author). 27 refs., 9 tabs

  4. A variational approach to a differential equation modeling thin-film flows and pertinent to Tanner's Law

    International Nuclear Information System (INIS)

    Khuri, S A; Sayfy, Ali

    2013-01-01

    This study is intended to provide a modified variational algorithm for the numerical solution of the third-order ordinary differential equation y″′ = y -2 which arises in the modeling of thin viscous films with surface tension. The resulting solution is used to solve a problem relevant to Tanner's Law for the speed of a moving three-phase contact line. Numerical results, computational comparisons, suitable error measures and illustrations are provided to testify and demonstrate the convergence and efficiency of the method.

  5. SIMULATING THE TIMESCALE-DEPENDENT COLOR VARIATION IN QUASARS WITH A REVISED INHOMOGENEOUS DISK MODEL

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Zhen-Yi; Wang, Jun-Xian; Sun, Yu-Han; Wu, Mao-Chun; Huang, Xing-Xing; Chen, Xiao-Yang [CAS Key Laboratory for Researches in Galaxies and Cosmology, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026 (China); Gu, Wei-Min, E-mail: zcai@ustc.edu.cn, E-mail: jxw@ustc.edu.cn [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)

    2016-07-20

    The UV–optical variability of active galactic nuclei and quasars is useful for understanding the physics of the accretion disk and is gradually being attributed to stochastic fluctuations over the accretion disk. Quasars generally appear bluer when they brighten in the UV–optical bands; the nature of this phenomenon remains controversial. Recently, Sun et al. discovered that the color variation of quasars is timescale-dependent, in the way that faster variations are even bluer than longer term ones. While this discovery can directly rule out models that simply attribute the color variation to contamination from the host galaxies, or to changes in the global accretion rates, it favors the stochastic disk fluctuation model as fluctuations in the inner-most hotter disk could dominate the short-term variations. In this work, we show that a revised inhomogeneous disk model, where the characteristic timescales of thermal fluctuations in the disk are radius-dependent (i.e., τ ∼ r ; based on that originally proposed by Dexter and Agol), can reproduce well a timescale-dependent color variation pattern, similar to the observed one and unaffected by the uneven sampling and photometric error. This demonstrates that one may statistically use variation emission at different timescales to spatially resolve the accretion disk in quasars, thus opening a new window with which to probe and test the accretion disk physics in the era of time domain astronomy. Caveats of the current model, which ought to be addressed in future simulations, are discussed.

  6. Modeling of Thermospheric Neutral Density Variations in Response to Geomagnetic Forcing using GRACE Accelerometer Data

    Science.gov (United States)

    Calabia, A.; Matsuo, T.; Jin, S.

    2017-12-01

    The upper atmospheric expansion refers to an increase in the temperature and density of Earth's thermosphere due to increased geomagnetic and space weather activities, producing anomalous atmospheric drag on LEO spacecraft. Increased drag decelerates satellites, moving their orbit closer to Earth, decreasing the lifespan of satellites, and making satellite orbit determination difficult. In this study, thermospheric neutral density variations due to geomagnetic forcing are investigated from 10 years (2003-2013) of GRACE's accelerometer-based estimates. In order to isolate the variations produced by geomagnetic forcing, 99.8% of the total variability has been modeled and removed through the parameterization of annual, LST, and solar-flux variations included in the primary Empirical Orthogonal Functions. The residual disturbances of neutral density variations have been investigated further in order to unravel their relationship to several geomagnetic indices and space weather activity indicators. Stronger fluctuations have been found in the southern polar cap, following the dipole-tilt angle variations. While the parameterization of the residual disturbances in terms of Dst index results in the best fit to training data, the use of merging electric field as a predictor leads to the best forecasting performance. An important finding is that modeling of neutral density variations in response geomagnetic forcing can be improved by accounting for the latitude-dependent delay. Our data-driven modeling results are further compared to modeling with TIEGCM.

  7. Modeled Watershed Runoff Associated with Variations in Precipitation Data with Implications for Contaminant Fluxes

    Science.gov (United States)

    Watershed-scale fate and transport models are important tools for estimating the sources, transformation, and transport of contaminants to surface water systems. Precipitation is one of the primary inputs to watershed biogeochemical models, influencing changes in the water budge...

  8. Surface variations affecting human dental enamel studied using nanomechanical and chemical analysis

    Science.gov (United States)

    Dickinson, Michelle Emma

    The enamel surface is the interface between the tooth and its ever changing oral environment. Cavity (caries) formation and extrinsic tooth staining are due, respectively, to degradation of the enamel structure under low pH conditions and interactions between salivary pellicle and dietary elements. Both of these occur at the enamel surface and are caused by the local environment changing the chemistry of the surface. The results can be detrimental to the enamel's mechanical integrity and aesthetics. Incipient carious lesions are the precursor to caries and form due to demineralisation of enamel. These carious lesions are a reversible structure where ions (e.g. Ca2+, F -) can diffuse in (remineralisation) to preserve the tooth's structural integrity. This investigation used controlled in vitro demineralisation and remineralisation to study artificial carious lesion formation and repair. The carious lesions were cross-sectioned and characterised using nanoindentation, electron probe micro-analysis and time of flight secondary ion mass spectrometry. Mechanical and chemical maps showed the carious lesion had a significantly reduced hardness and elastic modulus, and the calcium and phosphate content was lower than in sound enamel. Fluoride based remineralisation treatments gave a new phase (possibly fluorohydroxyapatite) within the lesion with mechanical properties higher than sound enamel. The acquired salivary pellicle is a protein-rich film formed by the physisorption of organic molecules in saliva onto the enamel surface. Its functions include lubrication during mastication and chemical protection. However, pellicle proteins react with dietary elements such as polyphenols (tannins in tea) causing a brown stain. This study has used in vitro dynamic nanoindentation and atomic force microscopy to examine normal and stained pellicles formed in vivo. The effects of polyphenols on the pellicle's mechanical properties and morphology have been studied. It was found that the

  9. Modeling pH variation in reverse osmosis.

    Science.gov (United States)

    Nir, Oded; Bishop, Noga Fridman; Lahav, Ori; Freger, Viatcheslav

    2015-12-15

    The transport of hydronium and hydroxide ions through reverse osmosis membranes constitutes a unique case of ionic species characterized by uncommonly high permeabilities. Combined with electromigration, this leads to complex behavior of permeate pH, e.g., negative rejection, as often observed for monovalent ions in nanofiltration of salt mixtures. In this work we employed a rigorous phenomenological approach combined with chemical equilibrium to describe the trans-membrane transport of hydronium and hydroxide ions along with salt transport and calculate the resulting permeate pH. Starting from the Nernst-Planck equation, a full non-linear transport equation was derived, for which an approximate solution was proposed based on the analytical solution previously developed for trace ions in a dominant salt. Using the developed approximate equation, transport coefficients were deduced from experimental results obtained using a spiral wound reverse osmosis module operated under varying permeate flux (2-11 μm/s), NaCl feed concentrations (0.04-0.18 M) and feed pH values (5.5-9.0). The approximate equation agreed well with the experimental results, corroborating the finding that diffusion and electromigration, rather than a priori neglected convection, were the major contributors to the transport of hydronium and hydroxide. The approach presented here has the potential to improve the predictive capacity of reverse osmosis transport models for acid-base species, thereby improving process design/control. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Surface system Forsmark. Site descriptive modelling SDM-Site Forsmark

    Energy Technology Data Exchange (ETDEWEB)

    Lindborg, Tobias [ed.

    2008-12-15

    SKB has undertaken site characterization of two different areas, Forsmark and Laxemar-Simpevarp, in order to find a suitable location for a geological repository for spent nuclear fuel. This report focuses on the site descriptive modelling of the surface system at Forsmark. The characterization of the surface system at the site was primarily made by identifying and describing important properties in different parts of the surface system, properties concerning e.g. hydrology and climate, Quaternary deposits and soils, hydrochemistry, vegetation, ecosystem functions, but also current and historical land use. The report presents available input data, methodology for data evaluation and modelling, and resulting models for each of the different disciplines. Results from the modelling of the surface system are also integrated with results from modelling of the deep bedrock system. The Forsmark site is located within the municipality of Oesthammar, about 120 km north of Stockholm. The investigated area is located along the shoreline of Oeregrundsgrepen, a funnel-shaped bay of the Baltic Sea. The area is characterized by small-scale topographic variations and is almost entirely located at altitudes lower than 20 metres above sea level. The Quaternary deposits in the area are dominated by till, characterized by a rich content of calcite which was transported by the glacier ice to the area from the sedimentary bedrock of Gaevlebukten about 100 km north of Forsmark. As a result, the surface waters and shallow groundwater at Forsmark are characterized by high pH values and high concentrations of certain major constituents, especially calcium and bicarbonate. The annual precipitation and runoff are 560 and 150 mm, respectively. The lakes are small and shallow, with mean and maximum depths ranging from approximately 0.1 to 1 m and 0.4 to 2 m. Sea water flows into the most low-lying lakes during events giving rise to very high sea levels. Wetlands are frequent and cover 25 to 35

  11. Hydrological storage variations in a lake water balance, observed from multi-sensor satellite data and hydrological models.

    Science.gov (United States)

    Singh, Alka; Seitz, Florian; Schwatke, Christian; Guentner, Andreas

    2013-04-01

    Freshwater lakes and reservoirs account for 74.5% of continental water storage in surface water bodies and only 1.8% resides in rivers. Lakes and reservoirs are a key component of the continental hydrological cycle but in-situ monitoring networks are very limited either because of sparse spatial distribution of gauges or national data policy. Monitoring and predicting extreme events is very challenging in that case. In this study we demonstrate the use of optical remote sensing, satellite altimetry and the GRACE gravity field mission to monitor the lake water storage variations in the Aral Sea. Aral Sea is one of the most unfortunate examples of a large anthropogenic catastrophe. The 4th largest lake of 1960s has been decertified for more than 75% of its area due to the diversion of its primary rivers for irrigation purposes. Our study is focused on the time frame of the GRACE mission; therefore we consider changes from 2002 onwards. Continuous monthly time series of water masks from Landsat satellite data and water level from altimetry missions were derived. Monthly volumetric variations of the lake water storage were computed by intersecting a digital elevation model of the lake with respective water mask and altimetry water level. With this approach we obtained volume from two independent remote sensing methods to reduce the error in the estimated volume through least square adjustment. The resultant variations were then compared with mass variability observed by GRACE. In addition, GARCE estimates of water storage variations were compared with simulation results of the Water Gap Hydrology Model (WGHM). The different observations from all missions agree that the lake reached an absolute minimum in autumn 2009. A marked reversal of the negative trend occured in 2010 but water storage in the lake decreased again afterwards. The results reveal that water storage variations in the Aral Sea are indeed the principal, but not the only contributor to the GRACE signal of

  12. Characterizing bacterial communities in tilapia pond surface sediment and their responses to pond differences and temporal variations.

    Science.gov (United States)

    Fan, Limin; Barry, Kamira; Hu, Gengdong; Meng, Shunlong; Song, Chao; Qiu, Liping; Zheng, Yao; Wu, Wei; Qu, Jianhong; Chen, Jiazhang; Xu, Pao

    2017-01-01

    Bacterial community compositions in the surface sediment of tilapia ponds and their responses to pond characteristics or seasonal variations were investigated. For that, three ponds with different stocking densities were selected to collect the samples. And the method of Illumina high-throughput sequencing was used to amplify the bacterial 16S rRNA genes. A total of 662, 876 valid reads and 5649 operational taxonomic units were obtained. Further analysis showed that the dominant phyla in all three ponds were Proteobacteria, Bacteroidetes, Chloroflexi, and Acidobacteria. The phyla Planctomycetes, Firmicutes, Chlorobi, and Spirochaetae were also relatively abundant. Among the eight phyla, the abundances of only Proteobacteria, Bacteroidetes, Firmicutes, and Spirochaetae were affected by seasonal variations, while seven of these (with the exception of Acidobacteria) were affected by pond differences. A comprehensive analysis of the richness and diversity of the bacterial 16S rRNA gene, and of the similarity in bacterial community composition in sediment also showed that the communities in tilapia pond sediment were shaped more by pond differences than by seasonal variations. Linear discriminant analysis further indicated that the influences of pond characteristics on sediment bacterial communities might be related to feed coefficients and stocking densities of genetically improved farmed tilapia (GIFT).

  13. MODELING THE VARIATIONS OF DOSE RATE MEASURED BY RAD DURING THE FIRST MSL MARTIAN YEAR: 2012–2014

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Jingnan; Wimmer-Schweingruber, Robert F.; Heber, Bernd; Köhler, Jan; Appel, Jan K.; Böhm, Eckart; Böttcher, Stephan; Burmeister, Sönke; Lohf, Henning; Martin, Cesar [Institute of Experimental and Applied Physics, Christian-Albrechts-University, Kiel (Germany); Zeitlin, Cary [Southwest Research Institute, Earth, Oceans and Space Department, Durham, NH (United States); Rafkin, Scot; Hassler, Donald M.; Ehresmann, Bent [Southwest Research Institute, Space Science and Engineering Division, Boulder, CO (United States); Posner, Arik [NASA Headquarters, Science Mission Directorate, Washington, DC (United States); Brinza, David E. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA (United States); Kahanpää, H. [Finnish Meteorological Institute, Helsinki (Finland); Reitz, Günther, E-mail: guo@physik.uni-kiel.de [Aerospace Medicine, Deutsches Zentrum für Luft- und Raumfahrt, Köln (Germany)

    2015-09-01

    The Radiation Assessment Detector (RAD), on board Mars Science Laboratory’s (MSL) rover Curiosity, measures the energy spectra of both energetic charged and neutral particles along with the radiation dose rate at the surface of Mars. With these first-ever measurements on the Martian surface, RAD observed several effects influencing the galactic cosmic-ray (GCR) induced surface radiation dose concurrently: (a) short-term diurnal variations of the Martian atmospheric pressure caused by daily thermal tides, (b) long-term seasonal pressure changes in the Martian atmosphere, and (c) the modulation of the primary GCR flux by the heliospheric magnetic field, which correlates with long-term solar activity and the rotation of the Sun. The RAD surface dose measurements, along with the surface pressure data and the solar modulation factor, are analyzed and fitted to empirical models that quantitatively demonstrate how the long-term influences ((b) and (c)) are related to the measured dose rates. Correspondingly, we can estimate dose rate and dose equivalents under different solar modulations and different atmospheric conditions, thus allowing empirical predictions of the Martian surface radiation environment.

  14. Temporal variations of surface water quality in urban, suburban and rural areas during rapid urbanization in Shanghai, China

    International Nuclear Information System (INIS)

    Wang Junying; Da Liangjun; Song Kun; Li Bailian

    2008-01-01

    As the economic and financial center of China, Shanghai has experienced an extensive urban expansion since the early 1980s, with an attendant cost in environmental degradation. We use an integrated pollution index to study the temporal variations of surface water quality in urban, suburban and rural areas between 1982 and 2005. Data on monitored cross-sections were collected from the Shanghai Environmental Monitoring Center. The results indicated that the spatial pattern of surface water quality was determined by the level of urbanization. Surface water qualities in urban and suburban areas were improved by strengthening the environmental policies and management, but were worsening in rural areas. The relationship between economic growth and surface water quality in Shanghai showed an inversed-U-shaped curve, which reflected a similar pattern in most developed countries. This research suggests that decision makers and city officials should be more aware of the recent pollution increases in Shanghai. - An integrated pollution index documents the deterioration of water quality in greater Shanghai, recently most serious in rural sections

  15. Variations in Modeled Dengue Transmission over Puerto Rico Using a Climate Driven Dynamic Model

    Science.gov (United States)

    Morin, Cory; Monaghan, Andrew; Crosson, William; Quattrochi, Dale; Luvall, Jeffrey

    2014-01-01

    Dengue fever is a mosquito-borne viral disease reemerging throughout much of the tropical Americas. Dengue virus transmission is explicitly influenced by climate and the environment through its primary vector, Aedes aegypti. Temperature regulates Ae. aegypti development, survival, and replication rates as well as the incubation period of the virus within the mosquito. Precipitation provides water for many of the preferred breeding habitats of the mosquito, including buckets, old tires, and other places water can collect. Because of variations in topography, ocean influences and atmospheric processes, temperature and rainfall patterns vary across Puerto Rico and so do dengue virus transmission rates. Using NASA's TRMM (Tropical Rainfall Measuring Mission) satellite for precipitation input, ground-based observations for temperature input, and laboratory confirmed dengue cases reported by the Centers for Disease Control and Prevention for parameter calibration, we modeled dengue transmission at the county level across Puerto Rico from 2010-2013 using a dynamic dengue transmission model that includes interacting vector ecology and epidemiological components. Employing a Monte Carlo approach, we performed ensembles of several thousands of model simulations for each county in order to resolve the model uncertainty arising from using different combinations of parameter values that are not well known. The top 1% of model simulations that best reproduced the reported dengue case data were then analyzed to determine the most important parameters for dengue virus transmission in each county, as well as the relative influence of climate variability on transmission. These results can be used by public health workers to implement dengue control methods that are targeted for specific locations and climate conditions.

  16. Rapid core field variations during the satellite era: Investigations using stochastic process based field models

    DEFF Research Database (Denmark)

    Finlay, Chris; Olsen, Nils; Gillet, Nicolas

    We present a new ensemble of time-dependent magnetic field models constructed from satellite and observatory data spanning 1997-2013 that are compatible with prior information concerning the temporal spectrum of core field variations. These models allow sharper field changes compared to tradition...... physical hypotheses can be tested by asking questions of the entire ensemble of core field models, rather than by interpreting any single model.......We present a new ensemble of time-dependent magnetic field models constructed from satellite and observatory data spanning 1997-2013 that are compatible with prior information concerning the temporal spectrum of core field variations. These models allow sharper field changes compared to traditional...... regularization methods based on minimizing the square of second or third time derivative. We invert satellite and observatory data directly by adopting the external field and crustal field modelling framework of the CHAOS model, but apply the stochastic process method of Gillet et al. (2013) to the core field...

  17. Integrated Surface/subsurface flow modeling in PFLOTRAN

    Energy Technology Data Exchange (ETDEWEB)

    Painter, Scott L [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2016-10-01

    Understanding soil water, groundwater, and shallow surface water dynamics as an integrated hydrological system is critical for understanding the Earth’s critical zone, the thin outer layer at our planet’s surface where vegetation, soil, rock, and gases interact to regulate the environment. Computational tools that take this view of soil moisture and shallow surface flows as a single integrated system are typically referred to as integrated surface/subsurface hydrology models. We extend the open-source, highly parallel, subsurface flow and reactive transport simulator PFLOTRAN to accommodate surface flows. In contrast to most previous implementations, we do not represent a distinct surface system. Instead, the vertical gradient in hydraulic head at the land surface is neglected, which allows the surface flow system to be eliminated and incorporated directly into the subsurface system. This tight coupling approach leads to a robust capability and also greatly simplifies implementation in existing subsurface simulators such as PFLOTRAN. Successful comparisons to independent numerical solutions build confidence in the approximation and implementation. Example simulations of the Walker Branch and East Fork Poplar Creek watersheds near Oak Ridge, Tennessee demonstrate the robustness of the approach in geometrically complex applications. The lack of a robust integrated surface/subsurface hydrology capability had been a barrier to PFLOTRAN’s use in critical zone studies. This work addresses that capability gap, thus enabling PFLOTRAN as a community platform for building integrated models of the critical zone.

  18. Contribution to the modeling of the anisotropic damage and the variation of the permeability of the brittle rocks

    International Nuclear Information System (INIS)

    Zhou, J.

    2006-03-01

    This work deals with a modeling of the mechanical and hydro-mechanical behaviour of saturated rocks taking into account the variation of the permeability with damage. At first is established a function of the free enthalpy by a direct micro-mechanical approach in taking into account the distribution of the microcrack length. The opening of the closed microcracks due to the tangential gliding is taken into account because of the roughness of the cracks surfaces. This opening contributes directly to the volume expansion and to the variation of the macroscopic permeability of the material. A phenomenological approach with an approximation by a damage tensor of two order is shown too. Then, an extension of the model is proposed for describing the poro-mechanical behaviour of saturated rocks. The poro-mechanical answers in drained and undrained conditions of the Vosges sandstone have been studied. In the last part, a coupled model describing the behaviour of the coupling between the induced damage and the variation of the rocks permeability is proposed. (O.M.)

  19. Comparison on the forecast model of landfill surface

    International Nuclear Information System (INIS)

    Zhou Xiaozhi; Sang Shuxun; Cao Liwen; Ji Xiaoyan

    2010-01-01

    Using four large-scale simulated landfill equipments, indoor parallel simulation landfill experiment was carried out. By monitoring the cumulative settlement of MSW, comparable researches indicate the actual effects of 'empirical model' and 'biodegradation model' on landfill surface settlement forecast, and the optimization measures are proposed on the basis of model defects analysis. Research leaded to following results: To the short-term prediction of MSW settlement, two types of models all have satisfactory predictive validity. When performing medium and long-term prediction, 'empirical model' predicted a significant deviation from the actual, and the forecasting error of 'biodegradation model' is also gradually enlarge with the extending forecast period. For optimizing these two types of model, long-term surface settlement monitoring is fundamental method, and constantly modify the model parameters is the key according to the dynamic monitoring data. (authors)

  20. The continuing challenge of understanding and modeling hemodynamic variation in fMRI

    OpenAIRE

    Handwerker, Daniel A.; Gonzalez-Castillo, Javier; D’Esposito, Mark; Bandettini, Peter A.

    2012-01-01

    Interpretation of fMRI data depends on our ability to understand or model the shape of the hemodynamic response (HR) to a neural event. Although the HR has been studied almost since the beginning of fMRI, we are still far from having robust methods to account for the full range of known HR variation in typical fMRI analyses. This paper reviews how the authors and others contributed to our understanding of HR variation. We present an overview of studies that describe HR variation across voxels...

  1. Near-surface density profiling of Fe ion irradiated Si (100) using extremely asymmetric x-ray diffraction by variation of the wavelength

    Energy Technology Data Exchange (ETDEWEB)

    Khanbabaee, B., E-mail: khanbabaee@physik.uni-siegen.de; Pietsch, U. [Solid State Physics, University of Siegen, D-57068 Siegen (Germany); Facsko, S. [Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden (Germany); Doyle, S. [Synchrotron Light Source ANKA, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen (Germany)

    2014-10-20

    In this work, we report on correlations between surface density variations and ion parameters during ion beam-induced surface patterning process. The near-surface density variations of irradiated Si(100) surfaces were investigated after off-normal irradiation with 5 keV Fe ions at different fluences. In order to reduce the x-ray probing depth to a thickness below 5 nm, the extremely asymmetrical x-ray diffraction by variation of wavelength was applied, exploiting x-ray refraction at the air-sample interface. Depth profiling was achieved by measuring x-ray rocking curves as function of varying wavelengths providing incidence angles down to 0°. The density variation was extracted from the deviations from kinematical Bragg angle at grazing incidence angles due to refraction of the x-ray beam at the air-sample interface. The simulations based on the dynamical theory of x-ray diffraction revealed that while a net near-surface density decreases with increasing ion fluence which is accompanied by surface patterning, there is a certain threshold of ion fluence to surface density modulation. Our finding suggests that the surface density variation can be relevant with the mechanism of pattern formation.

  2. Spatial Representativeness of Surface-Measured Variations of Downward Solar Radiation

    Science.gov (United States)

    Schwarz, M.; Folini, D.; Hakuba, M. Z.; Wild, M.

    2017-12-01

    When using time series of ground-based surface solar radiation (SSR) measurements in combination with gridded data, the spatial and temporal representativeness of the point observations must be considered. We use SSR data from surface observations and high-resolution (0.05°) satellite-derived data to infer the spatiotemporal representativeness of observations for monthly and longer time scales in Europe. The correlation analysis shows that the squared correlation coefficients (R2) between SSR times series decrease linearly with increasing distance between the surface observations. For deseasonalized monthly mean time series, R2 ranges from 0.85 for distances up to 25 km between the stations to 0.25 at distances of 500 km. A decorrelation length (i.e., the e-folding distance of R2) on the order of 400 km (with spread of 100-600 km) was found. R2 from correlations between point observations and colocated grid box area means determined from satellite data were found to be 0.80 for a 1° grid. To quantify the error which arises when using a point observation as a surrogate for the area mean SSR of larger surroundings, we calculated a spatial sampling error (SSE) for a 1° grid of 8 (3) W/m2 for monthly (annual) time series. The SSE based on a 1° grid, therefore, is of the same magnitude as the measurement uncertainty. The analysis generally reveals that monthly mean (or longer temporally aggregated) point observations of SSR capture the larger-scale variability well. This finding shows that comparing time series of SSR measurements with gridded data is feasible for those time scales.

  3. Statistical metrology - measurement and modeling of variation for advanced process development and design rule generation

    International Nuclear Information System (INIS)

    Boning, Duane S.; Chung, James E.

    1998-01-01

    Advanced process technology will require more detailed understanding and tighter control of variation in devices and interconnects. The purpose of statistical metrology is to provide methods to measure and characterize variation, to model systematic and random components of that variation, and to understand the impact of variation on both yield and performance of advanced circuits. Of particular concern are spatial or pattern-dependencies within individual chips; such systematic variation within the chip can have a much larger impact on performance than wafer-level random variation. Statistical metrology methods will play an important role in the creation of design rules for advanced technologies. For example, a key issue in multilayer interconnect is the uniformity of interlevel dielectric (ILD) thickness within the chip. For the case of ILD thickness, we describe phases of statistical metrology development and application to understanding and modeling thickness variation arising from chemical-mechanical polishing (CMP). These phases include screening experiments including design of test structures and test masks to gather electrical or optical data, techniques for statistical decomposition and analysis of the data, and approaches to calibrating empirical and physical variation models. These models can be integrated with circuit CAD tools to evaluate different process integration or design rule strategies. One focus for the generation of interconnect design rules are guidelines for the use of 'dummy fill' or 'metal fill' to improve the uniformity of underlying metal density and thus improve the uniformity of oxide thickness within the die. Trade-offs that can be evaluated via statistical metrology include the improvements to uniformity possible versus the effect of increased capacitance due to additional metal

  4. Modelling the quiet-time geomagnetic daily variations using observatory data

    OpenAIRE

    Hamilton, Brian; Macmillan, Susan

    2008-01-01

    We present on-going work towards building a global model of the quiet-time geomagnetic daily variation using bservatory data. We select hourly mean data during June 2006 (solar minimum). We fit Fourier series in time, with a fundamental period of 24 hours, to the data at each observatory. We then use global spherical harmonic expansions to separate the daily variation signal, as characterised by the Fourier coefficients in time, into external and induced internal contributions. The mode...

  5. Inter-temporal variation in the travel time and travel cost parameters of transport models

    OpenAIRE

    Börjesson, Maria

    2012-01-01

    The parameters for travel time and travel cost are central in travel demand forecasting models. Since valuation of infrastructure investments requires prediction of travel demand for future evaluation years, inter-temporal variation of the travel time and travel cost parameters is a key issue in forecasting. Using two identical stated choice experiments conducted among Swedish drivers with an interval of 13 years, 1994 and 2007, this paper estimates the inter-temporal variation in travel time...

  6. The Kadanoff lower-bound variational renormalization group applied to an SU(2) lattice spin model

    International Nuclear Information System (INIS)

    Thorleifsson, G.; Damgaard, P.H.

    1990-07-01

    We apply the variational lower-bound Renormalization Group transformation of Kadanoff to an SU(2) lattice spin model in 2 and 3 dimensions. Even in the one-hypercube framework of this renormalization group transformation the present model is characterised by having an infinite basis of fundamental operators. We investigate whether the lower-bound variational renormalization group transformation yields results stable under truncations of this operator basis. Our results show that for this particular spin model this is not the case. (orig.)

  7. Land-surface modelling in hydrological perspective ? a review

    OpenAIRE

    Overgaard , J.; Rosbjerg , D.; Butts , M. B.

    2006-01-01

    International audience; The purpose of this paper is to provide a review of the different types of energy-based land-surface models (LSMs) and discuss some of the new possibilities that will arise when energy-based LSMs are combined with distributed hydrological modelling. We choose to focus on energy-based approaches, because in comparison to the traditional potential evapotranspiration models, these approaches allow for a stronger link to remote sensing and atmospheric modelling. New opport...

  8. Modeling Apple Surface Temperature Dynamics Based on Weather Data

    Directory of Open Access Journals (Sweden)

    Lei Li

    2014-10-01

    Full Text Available The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed was recorded for seven hours between 11:00–18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of “Fuji” apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management.

  9. Modeling apple surface temperature dynamics based on weather data.

    Science.gov (United States)

    Li, Lei; Peters, Troy; Zhang, Qin; Zhang, Jingjin; Huang, Danfeng

    2014-10-27

    The exposure of fruit surfaces to direct sunlight during the summer months can result in sunburn damage. Losses due to sunburn damage are a major economic problem when marketing fresh apples. The objective of this study was to develop and validate a model for simulating fruit surface temperature (FST) dynamics based on energy balance and measured weather data. A series of weather data (air temperature, humidity, solar radiation, and wind speed) was recorded for seven hours between 11:00-18:00 for two months at fifteen minute intervals. To validate the model, the FSTs of "Fuji" apples were monitored using an infrared camera in a natural orchard environment. The FST dynamics were measured using a series of thermal images. For the apples that were completely exposed to the sun, the RMSE of the model for estimating FST was less than 2.0 °C. A sensitivity analysis of the emissivity of the apple surface and the conductance of the fruit surface to water vapour showed that accurate estimations of the apple surface emissivity were important for the model. The validation results showed that the model was capable of accurately describing the thermal performances of apples under different solar radiation intensities. Thus, this model could be used to more accurately estimate the FST relative to estimates that only consider the air temperature. In addition, this model provides useful information for sunburn protection management.

  10. Adhesion of perfume-filled microcapsules to model fabric surfaces.

    Science.gov (United States)

    He, Yanping; Bowen, James; Andrews, James W; Liu, Min; Smets, Johan; Zhang, Zhibing

    2014-01-01

    The retention and adhesion of melamine formaldehyde (MF) microcapsules on a model fabric surface in aqueous solution were investigated using a customised flow chamber technique and atomic force microscopy (AFM). A cellulose film was employed as a model fabric surface. Modification of the cellulose with chitosan was found to increase the retention and adhesion of microcapsules on the model fabric surface. The AFM force-displacement data reveal that bridging forces resulting from the extension of cellulose chains dominate the adhesion between the microcapsule and the unmodified cellulose film, whereas electrostatic attraction helps the microcapsules adhere to the chitosan-modified cellulose film. The correlation between results obtained using these two complementary techniques suggests that the flow chamber device can be potentially used for rapid screening of the effect of chemical modification on the adhesion of microparticles to surfaces, reducing the time required to achieve an optimal formulation.

  11. Modeling the microstructure of surface by applying BRDF function

    Science.gov (United States)

    Plachta, Kamil

    2017-06-01

    The paper presents the modeling of surface microstructure using a bidirectional reflectance distribution function. This function contains full information about the reflectance properties of the flat surfaces - it is possible to determine the share of the specular, directional and diffuse components in the reflected luminous stream. The software is based on the authorial algorithm that uses selected elements of this function models, which allows to determine the share of each component. Basing on obtained data, the surface microstructure of each material can be modeled, which allows to determine the properties of this materials. The concentrator directs the reflected solar radiation onto the photovoltaic surface, increasing, at the same time, the value of the incident luminous stream. The paper presents an analysis of selected materials that can be used to construct the solar concentrator system. The use of concentrator increases the power output of the photovoltaic system by up to 17% as compared to the standard solution.

  12. THE HUBBLE WIDE FIELD CAMERA 3 TEST OF SURFACES IN THE OUTER SOLAR SYSTEM: SPECTRAL VARIATION ON KUIPER BELT OBJECTS

    International Nuclear Information System (INIS)

    Fraser, Wesley C.; Brown, Michael E.; Glass, Florian

    2015-01-01

    Here, we present additional photometry of targets observed as part of the Hubble Wide Field Camera 3 (WFC3) Test of Surfaces in the Outer Solar System. Twelve targets were re-observed with the WFC3 in the optical and NIR wavebands designed to complement those used during the first visit. Additionally, all of the observations originally presented by Fraser and Brown were reanalyzed through the same updated photometry pipeline. A re-analysis of the optical and NIR color distribution reveals a bifurcated optical color distribution and only two identifiable spectral classes, each of which occupies a broad range of colors and has correlated optical and NIR colors, in agreement with our previous findings. We report the detection of significant spectral variations on five targets which cannot be attributed to photometry errors, cosmic rays, point-spread function or sensitivity variations, or other image artifacts capable of explaining the magnitude of the variation. The spectrally variable objects are found to have a broad range of dynamical classes and absolute magnitudes, exhibit a broad range of apparent magnitude variations, and are found in both compositional classes. The spectrally variable objects with sufficiently accurate colors for spectral classification maintain their membership, belonging to the same class at both epochs. 2005 TV189 exhibits a sufficiently broad difference in color at the two epochs that span the full range of colors of the neutral class. This strongly argues that the neutral class is one single class with a broad range of colors, rather than the combination of multiple overlapping classes

  13. Modelling the variation in rectal dose due to inter-fraction rectal wall deformation in external beam prostate treatments

    International Nuclear Information System (INIS)

    Booth, Jeremy; Zavgorodni, Sergei

    2005-01-01

    Prostate radiotherapy inevitably deposits radiation dose in the rectal wall, and the dose delivered to prostate is limited by the expected rectal complications. Accurate evaluation of the rectal dose is non-trivial due to a number of factors. One of these is variation of the shape and position of the rectal wall (with respect to the clinical target volume (CTV)), which may differ daily from that taken during planning CT acquisition. This study uses data currently available in the literature on rectal wall motion to provide estimates of mean population rectal wall dose. The rectal wall geometry is characterized by a population mean radius of the rectum as well as inter-patient and inter-fraction standard deviations in rectum radius. The model is used to evaluate the range of inter-fraction and inter-patient rectal dose variations. The simulation of individual patients with full and empty rectum in the planning CT scan showed that large variations in rectal dose (>15 Gy) are possible. Mean calculated dose accounting for treatment and planning uncertainties in the rectal wall surface was calculated as well as the map of planning dose over/underpredictions. It was found that accuracy of planning dose is dependent on the CTV-PTV margin size with larger margins producing more accurate estimates. Over a patient population, the variation in rectal dose is reduced by increasing the number of pre-treatment CT scans

  14. MODELING THE ROSSITER–MCLAUGHLIN EFFECT: IMPACT OF THE CONVECTIVE CENTER-TO-LIMB VARIATIONS IN THE STELLAR PHOTOSPHERE

    Energy Technology Data Exchange (ETDEWEB)

    Cegla, H. M.; Watson, C. A. [Astrophysics Research Centre, School of Mathematics and Physics, Queen’s University Belfast, University Road, Belfast BT7 1NN (United Kingdom); Oshagh, M.; Figueira, P.; Santos, N. C. [Instituto de Astrofisica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, PT4150-762 Porto (Portugal); Shelyag, S., E-mail: h.cegla@qub.ac.uk [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Clayton, Victoria, 3800 (Australia)

    2016-03-01

    Observations of the Rossiter–McLaughlin (RM) effect provide information on star–planet alignments, which can inform planetary migration and evolution theories. Here, we go beyond the classical RM modeling and explore the impact of a convective blueshift that varies across the stellar disk and non-Gaussian stellar photospheric profiles. We simulated an aligned hot Jupiter with a four-day orbit about a Sun-like star and injected center-to-limb velocity (and profile shape) variations based on radiative 3D magnetohydrodynamic simulations of solar surface convection. The residuals between our modeling and classical RM modeling were dependent on the intrinsic profile width and v sin i; the amplitude of the residuals increased with increasing v sin i and with decreasing intrinsic profile width. For slowly rotating stars the center-to-limb convective variation dominated the residuals (with amplitudes of 10 s of cm s{sup −1} to ∼1 m s{sup −1}); however, for faster rotating stars the dominant residual signature was due a non-Gaussian intrinsic profile (with amplitudes from 0.5 to 9 m s{sup −1}). When the impact factor was 0, neglecting to account for the convective center-to-limb variation led to an uncertainty in the obliquity of ∼10°–20°, even though the true v sin i was known. Additionally, neglecting to properly model an asymmetric intrinsic profile had a greater impact for more rapidly rotating stars (e.g., v sin i = 6 km s{sup −1}) and caused systematic errors on the order of ∼20° in the measured obliquities. Hence, neglecting the impact of stellar surface convection may bias star–planet alignment measurements and consequently theories on planetary migration and evolution.

  15. A Convex Variational Model for Restoring Blurred Images with Multiplicative Noise

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Tieyong Zeng

    2013-01-01

    In this paper, a new variational model for restoring blurred images with multiplicative noise is proposed. Based on the statistical property of the noise, a quadratic penalty function technique is utilized in order to obtain a strictly convex model under a mild condition, which guarantees...

  16. New Hybrid Variational Recovery Model for Blurred Images with Multiplicative Noise

    DEFF Research Database (Denmark)

    Dong, Yiqiu; Zeng, Tieyong

    2013-01-01

    A new hybrid variational model for recovering blurred images in the presence of multiplicative noise is proposed. Inspired by previous work on multiplicative noise removal, an I-divergence technique is used to build a strictly convex model under a condition that ensures the uniqueness...

  17. A variation method in the optimization problem of the minority game model

    International Nuclear Information System (INIS)

    Blazhyijevs'kij, L.; Yanyishevs'kij, V.

    2009-01-01

    This article contains the results of applying a variation method in the investigation of the optimization problem in the minority game model. That suggested approach is shown to give relevant results about phase transition in the model. Other methods pertinent to the problem have also been assessed.

  18. Fatty Alcohol Variations in Surface Sediments of Sungai Sepang Besar, Sepang, Selangor

    International Nuclear Information System (INIS)

    Masni Mohd Ali; Norfariza Humrawali; Ying, P.Q.; Mohd Talib Latif; Mohamad Pauzi Zakaria

    2011-01-01

    Composition of fatty alcohols from 19 surface sediment samples collected along Sungai Sepang Besar, Sepang, Selangor were determined. The sediments were extracted and analysed using the Gas Chromatography-Mass Spectrometry (GC-MS) technique. A total of 19 fatty alcohols from C 12 to C 30 including 4 branched compounds were identified with concentrations in the range 0.02 μg/ g - 9.01 μg/ g dry weight. C 26 fatty alcohols dominated most sampling stations with concentrations ranging from 0.29 to 5.43 μg/ g dry weight and constituted 15.5 % of total fatty alcohols. According to individual compounds of fatty alcohols and the [Σ(C 12 - C 20 )/ Σ(C 22 - C 30 )] ratio, Sungai Sepang Besar has a high composition of short-chain fatty alcohols (C 12 - C 20 ) which mainly originate from marine organisms. However, the Alcohol Sources Index (ASI) showed that terrestrial derived fatty alcohols dominated the area due to high concentration of C 26 compounds in most sampling stations. The value of (odd chain length)/ (even chain length) ratios were high for almost all the sampling stations due to high bacterial activities. It can be concluded that the surface sediments of Sungai Sepang Besar contained organic materials from marine, terrestrial and bacterial sources. (author)

  19. Analysis of surface air temperature variations and local urbanization effects on central Yunnan Plateau, SW China

    Science.gov (United States)

    He, Yunling; Wu, Zhijie; Liu, Xuelian; Deng, Fuying

    2018-01-01

    With the surface air temperature (SAT) data at 37 stations on Central Yunnan Plateau (CYP) for 1961-2010 and the Defense Meteorological Satellite Program/Operational Linescan System (DMSP/OLS) nighttime light data, the temporal-spatial patterns of the SAT trends are detected using Sen's Nonparametric Estimator of Slope approach and MK test, and the impact of urbanization on surface warming is analyzed by comparing the differences between the air temperature change trends of urban stations and their corresponding rural stations. Results indicated that annual mean air temperature showed a significant warming trend, which is equivalent to a rate of 0.17 °C/decade during the past 50 years. Seasonal mean air temperature presents a rising trend, and the trend was more significant in winter (0.31 °C/decade) than in other seasons. Annual/seasonal mean air temperature tends to increase in most areas, and higher warming trend appeared in urban areas, notably in Kunming city. The regional mean air temperature series was significantly impacted by urban warming, and the urbanization-induced warming contributed to approximately 32.3-62.9 % of the total regional warming during the past 50 years. Meantime, the urbanization-induced warming trend in winter and spring was more significant than that in summer and autumn. Since 1985, the urban heat island (UHI) intensity has gradually increased. And the urban temperatures always rise faster than rural temperatures on the CYP.

  20. Does litter size variation affect models of terrestrial carnivore extinction risk and management?

    Directory of Open Access Journals (Sweden)

    Eleanor S Devenish-Nelson

    Full Text Available Individual variation in both survival and reproduction has the potential to influence extinction risk. Especially for rare or threatened species, reliable population models should adequately incorporate demographic uncertainty. Here, we focus on an important form of demographic stochasticity: variation in litter sizes. We use terrestrial carnivores as an example taxon, as they are frequently threatened or of economic importance. Since data on intraspecific litter size variation are often sparse, it is unclear what probability distribution should be used to describe the pattern of litter size variation for multiparous carnivores.We used litter size data on 32 terrestrial carnivore species to test the fit of 12 probability distributions. The influence of these distributions on quasi-extinction probabilities and the probability of successful disease control was then examined for three canid species - the island fox Urocyon littoralis, the red fox Vulpes vulpes, and the African wild dog Lycaon pictus. Best fitting probability distributions differed among the carnivores examined. However, the discretised normal distribution provided the best fit for the majority of species, because variation among litter-sizes was often small. Importantly, however, the outcomes of demographic models were generally robust to the distribution used.These results provide reassurance for those using demographic modelling for the management of less studied carnivores in which litter size variation is estimated using data from species with similar reproductive attributes.

  1. Analysis of the Diurnal Variation of the Global Electric Circuit Obtained From Different Numerical Models

    Science.gov (United States)

    Jánský, Jaroslav; Lucas, Greg M.; Kalb, Christina; Bayona, Victor; Peterson, Michael J.; Deierling, Wiebke; Flyer, Natasha; Pasko, Victor P.

    2017-12-01

    This work analyzes different current source and conductivity parameterizations and their influence on the diurnal variation of the global electric circuit (GEC). The diurnal variations of the current source parameterizations obtained using electric field and conductivity measurements from plane overflights combined with global Tropical Rainfall Measuring Mission satellite data give generally good agreement with measured diurnal variation of the electric field at Vostok, Antarctica, where reference experimental measurements are performed. An approach employing 85 GHz passive microwave observations to infer currents within the GEC is compared and shows the best agreement in amplitude and phase with experimental measurements. To study the conductivity influence, GEC models solving the continuity equation in 3-D are used to calculate atmospheric resistance using yearly averaged conductivity obtained from the global circulation model Community Earth System Model (CESM). Then, using current source parameterization combining mean currents and global counts of electrified clouds, if the exponential conductivity is substituted by the conductivity from CESM, the peak to peak diurnal variation of the ionospheric potential of the GEC decreases from 24% to 20%. The main reason for the change is the presence of clouds while effects of 222Rn ionization, aerosols, and topography are less pronounced. The simulated peak to peak diurnal variation of the electric field at Vostok is increased from 15% to 18% from the diurnal variation of the global current in the GEC if conductivity from CESM is used.

  2. Simultaneous observation of seasonal variations of beryllium-7 and typical POPs in near-surface atmospheric aerosols in Guangzhou, China

    Science.gov (United States)

    Pan, Jing; Yang, Yong-Liang; Zhang, Gan; Shi, Jing-Lei; Zhu, Xiao-Hua; Li, Yong; Yu, Han-Qing

    2011-07-01

    Near-surface atmospheric aerosol samples were collected at the sampling frequency of 2-3 d per week for one year from August 2006 to August 2007 at a low latitude station in Tianhe District, Guangzhou, Guangdong Province of southern China. The samples were analyzed for cosmogenic nuclide 7Be and persistent organic pollutants, i.e. organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs). The annual average 7Be concentration was 2.59 mBq m -3, with the maximum occurred in May (8.45 mBq m -3) and minimum in late August and early September (0.07 mBq m -3). Winter and spring were the seasons in which the 7Be concentrations were high while summer and autumn were the lower 7Be seasons. Spring peaks in 7Be in the near-surface atmospheric aerosols may have associated with the "spring leak maximum" episode. The annual average ∑OCPs concentration was 345.6 pg m -3, ∑ 33PCBs 317.6 pg m -3, and ∑ 31PBDEs 609.0 pg m -3. The variation trends in the time-series of 7Be, OCPs, PCBs, and PBDEs in near-surface atmospheric aerosol showed both common features and differences. Significant correlations ( R2 = 0.957 and 0.811. respectively, p = 0.01) were observed between the monthly average 7Be concentrations and those of ∑PCBs and ∑PBDEs in summer, autumn, and early winter. The difference between the seasonal variation features of OCPs and PCBs (and PBDEs) could be attributed to the different source functions and physical-chemical properties which could control the behaviors of these compounds in air-aerosol partitions as well as atmospheric transport.

  3. Understanding Long-Term Variations in Surface Ozone in United States (U.S. National Parks

    Directory of Open Access Journals (Sweden)

    Deborah McGlynn

    2018-03-01

    Full Text Available Long-term surface ozone observations at 25 National Park Service sites across the United States were analyzed for processes on varying time scales using a time scale decomposition technique, the Ensemble Empirical Mode Decomposition (EEMD. Time scales of interest include the seasonal cycle, large-scale climate oscillations, and long-term (>10 years trends. Emission reductions were found to have a greater impact on sites that are nearest major urban areas. Multidecadal trends in surface ozone were increasing at a rate of 0.07 to 0.37 ppbv year−1 before 2004 and decreasing at a rate of −0.08 to −0.60 ppbv year−1 after 2004 for sites in the East, Southern California, and Northwestern Washington. Sites in the Intermountain West did not experience a reversal of trends from positive to negative until the mid- to late 2000s. The magnitude of the annual amplitude (=annual maximum–minimum decreased at eight sites, two in the West, two in the Intermountain West, and four in the East, by 5–20 ppbv and significantly increased at three sites; one in Alaska, one in the West, and one in the Intermountain West, by 3–4 ppbv. Stronger decreases in the annual amplitude occurred at a greater proportion of sites in the East (4/6 sites than in the West/Intermountain West (4/19 sites. The date of annual maximums and/or minimums has changed at 12 sites, occurring 10–60 days earlier in the year. There appeared to be a link between the timing of the annual maximum and the decrease in the annual amplitude, which was hypothesized to be related to a decrease in ozone titration resulting from NOx emission reductions. Furthermore, it was found that a phase shift of the Pacific Decadal Oscillation (PDO, from positive to negative, in 1998–1999 resulted in increased occurrences of La Niña-like conditions. This shift had the effect of directing more polluted air masses from East Asia to higher latitudes over the North American continent. The change in the

  4. Finsler Geometry Modeling of an Orientation-Asymmetric Surface Model for Membranes

    Science.gov (United States)

    Proutorov, Evgenii; Koibuchi, Hiroshi

    2017-12-01

    In this paper, a triangulated surface model is studied in the context of Finsler geometry (FG) modeling. This FG model is an extended version of a recently reported model for two-component membranes, and it is asymmetric under surface inversion. We show that the definition of the model is independent of how the Finsler length of a bond is defined. This leads us to understand that the canonical (or Euclidean) surface model is obtained from the FG model such that it is uniquely determined as a trivial model from the viewpoint of well definedness.

  5. A radiosity-based model to compute the radiation transfer of soil surface

    Science.gov (United States)

    Zhao, Feng; Li, Yuguang

    2011-11-01

    A good understanding of interactions of electromagnetic radiation with soil surface is important for a further improvement of remote sensing methods. In this paper, a radiosity-based analytical model for soil Directional Reflectance Factor's (DRF) distributions was developed and evaluated. The model was specifically dedicated to the study of radiation transfer for the soil surface under tillage practices. The soil was abstracted as two dimensional U-shaped or V-shaped geometric structures with periodic macroscopic variations. The roughness of the simulated surfaces was expressed as a ratio of the height to the width for the U and V-shaped structures. The assumption was made that the shadowing of soil surface, simulated by U or V-shaped grooves, has a greater influence on the soil reflectance distribution than the scattering properties of basic soil particles of silt and clay. Another assumption was that the soil is a perfectly diffuse reflector at a microscopic level, which is a prerequisite for the application of the radiosity method. This radiosity-based analytical model was evaluated by a forward Monte Carlo ray-tracing model under the same structural scenes and identical spectral parameters. The statistics of these two models' BRF fitting results for several soil structures under the same conditions showed the good agreements. By using the model, the physical mechanism of the soil bidirectional reflectance pattern was revealed.

  6. Comparison of Transmission Line Methods for Surface Acoustic Wave Modeling

    Science.gov (United States)

    Wilson, William; Atkinson, Gary

    2009-01-01

    Surface Acoustic Wave (SAW) technology is low cost, rugged, lightweight, extremely low power and can be used to develop passive wireless sensors. For these reasons, NASA is investigating the use of SAW technology for Integrated Vehicle Health Monitoring (IVHM) of aerospace structures. To facilitate rapid prototyping of passive SAW sensors for aerospace applications, SAW models have been developed. This paper reports on the comparison of three methods of modeling SAWs. The three models are the Impulse Response Method (a first order model), and two second order matrix methods; the conventional matrix approach, and a modified matrix approach that is extended to include internal finger reflections. The second order models are based upon matrices that were originally developed for analyzing microwave circuits using transmission line theory. Results from the models are presented with measured data from devices. Keywords: Surface Acoustic Wave, SAW, transmission line models, Impulse Response Method.

  7. Modifying a dynamic global vegetation model for simulating large spatial scale land surface water balance

    Science.gov (United States)

    Tang, G.; Bartlein, P. J.

    2012-01-01

    Water balance models of simple structure are easier to grasp and more clearly connect cause and effect than models of complex structure. Such models are essential for studying large spatial scale land surface water balance in the context of climate and land cover change, both natural and anthropogenic. This study aims to (i) develop a large spatial scale water balance model by modifying a dynamic global vegetation model (DGVM), and (ii) test the model's performance in simulating actual evapotranspiration (ET), soil moisture and surface runoff for the coterminous United States (US). Toward these ends, we first introduced development of the "LPJ-Hydrology" (LH) model by incorporating satellite-based land covers into the Lund-Potsdam-Jena (LPJ) DGVM instead of dynamically simulating them. We then ran LH using historical (1982-2006) climate data and satellite-based land covers at 2.5 arc-min grid cells. The simulated ET, soil moisture and surface runoff were compared to existing sets of observed or simulated data for the US. The results indicated that LH captures well the variation of monthly actual ET (R2 = 0.61, p 0.46, p 0.52) with observed values over the years 1982-2006, respectively. The modeled spatial patterns of annual ET and surface runoff are in accordance with previously published data. Compared to its predecessor, LH simulates better monthly stream flow in winter and early spring by incorporating effects of solar radiation on snowmelt. Overall, this study proves the feasibility of incorporating satellite-based land-covers into a DGVM for simulating large spatial scale land surface water balance. LH developed in this study should be a useful tool for studying effects of climate and land cover change on land surface hydrology at large spatial scales.

  8. Hybrid model for forecasting time series with trend, seasonal and salendar variation patterns

    Science.gov (United States)

    Suhartono; Rahayu, S. P.; Prastyo, D. D.; Wijayanti, D. G. P.; Juliyanto

    2017-09-01

    Most of the monthly time series data in economics and business in Indonesia and other Moslem countries not only contain trend and seasonal, but also affected by two types of calendar variation effects, i.e. the effect of the number of working days or trading and holiday effects. The purpose of this research is to develop a hybrid model or a combination of several forecasting models to predict time series that contain trend, seasonal and calendar variation patterns. This hybrid model is a combination of classical models (namely time series regression and ARIMA model) and/or modern methods (artificial intelligence method, i.e. Artificial Neural Networks). A simulation study was used to show that the proposed procedure for building the hybrid model could work well for forecasting time series with trend, seasonal and calendar variation patterns. Furthermore, the proposed hybrid model is applied for forecasting real data, i.e. monthly data about inflow and outflow of currency at Bank Indonesia. The results show that the hybrid model tend to provide more accurate forecasts than individual forecasting models. Moreover, this result is also in line with the third results of the M3 competition, i.e. the hybrid model on average provides a more accurate forecast than the individual model.

  9. Mesoscale model response to random, surface-based perturbations — A sea-breeze experiment

    Science.gov (United States)

    Garratt, J. R.; Pielke, R. A.; Miller, W. F.; Lee, T. J.

    1990-09-01

    The introduction into a mesoscale model of random (in space) variations in roughness length, or random (in space and time) surface perturbations of temperature and friction velocity, produces a measurable, but barely significant, response in the simulated flow dynamics of the lower atmosphere. The perturbations are an attempt to include the effects of sub-grid variability into the ensemble-mean parameterization schemes used in many numerical models. Their magnitude is set in our experiments by appeal to real-world observations of the spatial variations in roughness length and daytime surface temperature over the land on horizontal scales of one to several tens of kilometers. With sea-breeze simulations, comparisons of a number of realizations forced by roughness-length and surface-temperature perturbations with the standard simulation reveal no significant change in ensemble mean statistics, and only small changes in the sea-breeze vertical velocity. Changes in the updraft velocity for individual runs, of up to several cms-1 (compared to a mean of 14 cms-1), are directly the result of prefrontal temperature changes of 0.1 to 0.2K, produced by the random surface forcing. The correlation and magnitude of the changes are entirely consistent with a gravity-current interpretation of the sea breeze.

  10. Spatial and temporal modeling of wetland surface temperature using Landsat-8 imageries in Sulduz, Iran

    Directory of Open Access Journals (Sweden)

    Vahid Eisavi

    2016-01-01

    Full Text Available Wetland Surface Temperature (WST maps are an increasingly important parameter to understand the extensive range of existing processes in wetlands. The Wetlands placed in neighborhoods of agricultural and industrial lands are exposed to more chemical pollutants and pesticides that can lead to spatial and temporal variations of their surface temperature. Therefore, more studies are required for temperature modeling and the management and conservation of these variations in their ecosystem. Landsat 8 time series data of Sulduz region, Western Azerbaijan province, Iran were used in this study. The WST was derived using a mono-window algorithm after implementation of atmospheric correction. The NDVI (Normalized Differential Vegetation Index threshold method was also employed to determine the surface emissivity. Our findings show that the WST experienced extensive spatial and temporal variations. It reached its maximum value in June and also experienced the highest mean in the same month. In this research, August (2013.12.08 had a lowest spatial standard deviation regarding surface temperature and June (2013.06.28 had the highest one. Wetlands' watersides adjacent to industrial zones have a higher surface temperature than the middle lands of these places. The map obtained from the WST variance over time can be exploited to reveal thermal stable and unstable zones. The outcome demonstrates that land use, land cover effectively contribute to wetland ecosystem health. The results are useful in the water management, preventive efforts against drying of wetland and evapotranspiration modeling. The approach employed in this research indicates that remote sensing is a valuable, low-cost and stable tool for thermal monitoring of wetlands health.

  11. Novel Complete Probabilistic Models of Random Variation in High Frequency Performance of Nanoscale MOSFET

    Directory of Open Access Journals (Sweden)

    Rawid Banchuin

    2013-01-01

    Full Text Available The novel probabilistic models of the random variations in nanoscale MOSFET's high frequency performance defined in terms of gate capacitance and transition frequency have been proposed. As the transition frequency variation has also been considered, the proposed models are considered as complete unlike the previous one which take only the gate capacitance variation into account. The proposed models have been found to be both analytic and physical level oriented as they are the precise mathematical expressions in terms of physical parameters. Since the up-to-date model of variation in MOSFET's characteristic induced by physical level fluctuation has been used, part of the proposed models for gate capacitance is more accurate and physical level oriented than its predecessor. The proposed models have been verified based on the 65 nm CMOS technology by using the Monte-Carlo SPICE simulations of benchmark circuits and Kolmogorov-Smirnov tests as highly accurate since they fit the Monte-Carlo-based analysis results with 99% confidence. Hence, these novel models have been found to be versatile for the statistical/variability aware analysis/design of nanoscale MOSFET-based analog/mixed signal circuits and systems.

  12. Modeling Alaska boreal forests with a controlled trend surface approach

    Science.gov (United States)

    Mo Zhou; Jingjing Liang

    2012-01-01

    An approach of Controlled Trend Surface was proposed to simultaneously take into consideration large-scale spatial trends and nonspatial effects. A geospatial model of the Alaska boreal forest was developed from 446 permanent sample plots, which addressed large-scale spatial trends in recruitment, diameter growth, and mortality. The model was tested on two sets of...

  13. Modeling and analysis for surface roughness and material removal ...

    African Journals Online (AJOL)

    The cutting parameters considered were tool nose radius, tool rake angle, feed rate, cutting speed, depth of cut and cutting environment (dry, wet and cooled) on the surface roughness and material removal ... A second order mathematical model in terms of cutting parameters is also developed using regression modeling.

  14. Variational Monte Carlo Method with Dirichlet Boundary Conditions: Application to the Study of Confined Systems by Impenetrable Surfaces with Different Symmetries.

    Science.gov (United States)

    Sarsa, Antonio; Le Sech, Claude

    2011-09-13

    Variational Monte Carlo method is a powerful tool to determine approximate wave functions of atoms, molecules, and solids up to relatively large systems. In the present work, we extend the variational Monte Carlo approach to study confined systems. Important properties of the atoms, such as the spatial distribution of the electronic charge, the energy levels, or the filling of electronic shells, are modified under confinement. An expression of the energy very similar to the estimator used for free systems is derived. This opens the possibility to study confined systems with little changes in the solution of the corresponding free systems. This is illustrated by the study of helium atom in its ground state (1)S and the first (3)S excited state confined by spherical, cylindrical, and plane impenetrable surfaces. The average interelectronic distances are also calculated. They decrease in general when the confinement is stronger; however, it is seen that they present a minimum for excited states under confinement by open surfaces (cylindrical, planes) around the radii values corresponding to ionization. The ground (2)S and the first (2)P and (2)D excited states of the lithium atom are calculated under spherical constraints for different confinement radii. A crossing between the (2)S and (2)P states is observed around rc = 3 atomic units, illustrating the modification of the atomic energy level under confinement. Finally the carbon atom is studied in the spherical symmetry by using both variational and diffusion Monte Carlo methods. It is shown that the hybridized state sp(3) becomes lower in energy than the ground state (3)P due to a modification and a mixing of the atomic orbitals s, p under strong confinement. This result suggests a model, at least of pedagogical interest, to interpret the basic properties of carbon atom in chemistry.

  15. Analysis of Surface Heterogeneity Effects with Mesoscale Terrestrial Modeling Platforms

    Science.gov (United States)

    Simmer, C.

    2015-12-01

    An improved understanding of the full variability in the weather and climate system is crucial for reducing the uncertainty in weather forecasting and climate prediction, and to aid policy makers to develop adaptation and mitigation strategies. A yet unknown part of uncertainty in the predictions from the numerical models is caused by the negligence of non-resolved land surface heterogeneity and the sub-surface dynamics and their potential impact on the state of the atmosphere. At the same time, mesoscale numerical models using finer horizontal grid resolution [O(1)km] can suffer from inconsistencies and neglected scale-dependencies in ABL parameterizations and non-resolved effects of integrated surface-subsurface lateral flow at this scale. Our present knowledge suggests large-eddy-simulation (LES) as an eventual solution to overcome the inadequacy of the physical parameterizations in the atmosphere in this transition scale, yet we are constrained by the computational resources, memory management, big-data, when using LES for regional domains. For the present, there is a need for scale-aware parameterizations not only in the atmosphere but also in the land surface and subsurface model components. In this study, we use the recently developed Terrestrial Systems Modeling Platform (TerrSysMP) as a numerical tool to analyze the uncertainty in the simulation of surface exchange fluxes and boundary layer circulations at grid resolutions of the order of 1km, and explore the sensitivity of the atmospheric boundary layer evolution and convective rainfall processes on land surface heterogeneity.

  16. Four-dimensional variational data assimilation for inverse modelling of atmospheric methane emissions: method and comparison with synthesis inversion

    Directory of Open Access Journals (Sweden)

    J. F. Meirink

    2008-11-01

    Full Text Available A four-dimensional variational (4D-Var data assimilation system for inverse modelling of atmospheric methane emissions is presented. The system is based on the TM5 atmospheric transport model. It can be used for assimilating large volumes of measurements, in particular satellite observations and quasi-continuous in-situ observations, and at the same time it enables the optimization of a large number of model parameters, specifically grid-scale emission rates. Furthermore, the variational method allows to estimate uncertainties in posterior emissions. Here, the system is applied to optimize monthly methane emissions over a 1-year time window on the basis of surface observations from the NOAA-ESRL network. The results are rigorously compared with an analogous inversion by Bergamaschi et al. (2007, which was based on the traditional synthesis approach. The posterior emissions as well as their uncertainties obtained in both inversions show a high degree of consistency. At the same time we illustrate the advantage of 4D-Var in reducing aggregation errors by optimizing emissions at the grid scale of the transport model. The full potential of the assimilation system is exploited in Meirink et al. (2008, who use satellite observations of column-averaged methane mixing ratios to optimize emissions at high spatial resolution, taking advantage of the zooming capability of the TM5 model.

  17. Scale-adaptive surface modeling of vascular structures

    Directory of Open Access Journals (Sweden)

    Ma Xin

    2010-11-01

    Full Text Available Abstract Background The effective geometric modeling of vascular structures is crucial for diagnosis, therapy planning and medical education. These applications require good balance with respect to surface smoothness, surface accuracy, triangle quality and surface size. Methods Our method first extracts the vascular boundary voxels from the segmentation result, and utilizes these voxels to build a three-dimensional (3D point cloud whose normal vectors are estimated via covariance analysis. Then a 3D implicit indicator function is computed from the oriented 3D point cloud by solving a Poisson equation. Finally the vessel surface is generated by a proposed adaptive polygonization algorithm for explicit 3D visualization. Results Experiments carried out on several typical vascular structures demonstrate that the presented method yields both a smooth morphologically correct and a topologically preserved two-manifold surface, which is scale-adaptive to the local curvature of the surface. Furthermore, the presented method produces fewer and better-shaped triangles with satisfactory surface quality and accuracy. Conclusions Compared to other state-of-the-art approaches, our method reaches good balance in terms of smoothness, accuracy, triangle quality and surface size. The vessel surfaces produced by our method are suitable for applications such as computational fluid dynamics simulations and real-time virtual interventional surgery.

  18. 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.

  19. Investigation of Primary Factors Affecting the Variation of Modeled Oak Pollen Concentrations: A Case Study for Southeast Texas in 2010

    Science.gov (United States)

    Jeon, Wonbae; Choi, Yunsoo; Roy, Anirban; Pan, Shuai; Price, Daniel; Hwang, Mi-Kyoung; Kim, Kyu Rang; Oh, Inbo

    2018-02-01

    Oak pollen concentrations over the Houston-Galveston-Brazoria (HGB) area in southeastern Texas were modeled and evaluated against in-situ data. We modified the Community Multi-scale Air Quality (CMAQ) model to include oak pollen emission, dispersion, and deposition. The Oak Pollen Emission Model (OPEM) calculated gridded oak pollen emissions, which are based on a parameterized equation considering a plant-specific factor ( C e ), surface characteristics, and meteorology. The simulation period was chosen to be February 21 to April 30 in the spring of 2010, when the observed monthly mean oak pollen concentrations were the highest in six years (2009-2014). The results indicated C e and meteorology played an important role in the calculation of oak pollen emissions. While C e was critical in determining the magnitude of oak pollen emissions, meteorology determined their variability. In particular, the contribution of the meteorology to the variation in oak pollen emissions increased with the oak pollen emission rate. The evaluation results using in-situ surface data revealed that the model underestimated pollen concentrations and was unable to accurately reproduce the peak pollen episodes. The model error was likely due to uncertainty in climatology-based C e used for the estimation of oak pollen emissions and inaccuracy in the wind fields from the Weather Research and Forecast (WRF) model.

  20. Surface Winds and Dust Biases in Climate Models

    Science.gov (United States)

    Evan, A. T.

    2018-01-01

    An analysis of North African dust from models participating in the Fifth Climate Models Intercomparison Project (CMIP5) suggested that, when forced by observed sea surface temperatures, these models were unable to reproduce any aspects of the observed year-to-year variability in dust from North Africa. Consequently, there would be little reason to have confidence in the models' projections of changes in dust over the 21st century. However, no subsequent study has elucidated the root causes of the disagreement between CMIP5 and observed dust. Here I develop an idealized model of dust emission and then use this model to show that, over North Africa, such biases in CMIP5 models are due to errors in the surface wind fields and not due to the representation of dust emission processes. These results also suggest that because the surface wind field over North Africa is highly spatially autocorrelated, intermodel differences in the spatial structure of dust emission have little effect on the relative change in year-to-year dust emission over the continent. I use these results to show that similar biases in North African dust from the NASA Modern Era Retrospective analysis for Research and Applications (MERRA) version 2 surface wind field biases but that these wind biases were not present in the first version of MERRA.

  1. Digital fringe projection for hand surface coordinate variation analysis caused by osteoarthritis

    Science.gov (United States)

    Nor Haimi, Wan Mokhdzani Wan; Hau Tan, Cheek; Retnasamy, Vithyacharan; Vairavan, Rajendaran; Sauli, Zaliman; Roshidah Yusof, Nor; Hambali, Nor Azura Malini Ahmad; Aziz, Muhammad Hafiz Ab; Bakhit, Ahmad Syahir Ahmad

    2017-11-01

    Hand osteoarthritis is one of the most common forms of arthritis which impact millions of people worldwide. The disabling problem occurs when the protective cartilage on the boundaries of bones wear off over time. Currently, in order to identify hand osteoarthritis, special instruments namely X-ray scanning and MRI are used for the detection but it also has its limitations such as radiation exposure and can be quite costly. In this work, an optical metrology system based on digital fringe projection which comprises of an LCD projector, CCD camera and a personal computer has been developed to anticipate abnormal growth or deformation on the joints of the hand which are common symptoms of osteoarthritis. The main concept of this optical metrology system is to apply structured light as imaging source for surface change detection. The imaging source utilizes fringe patterns generated by C++ programming and is shifted by 3 phase shifts based on the 3 steps 2 shifts method. Phase wrapping technique and analysis were applied in order to detect the deformation of live subjects. The result has demonstrated a successful method of hand deformation detection based on the pixel tracking differences of a normal and deformed state.

  2. Late Holocene variations in Pacific surface circulation and biogeochemistry inferred from proteinaceous deep-sea corals

    Directory of Open Access Journals (Sweden)

    T. P. Guilderson

    2013-09-01

    Full Text Available δ15N and δ13C data obtained from samples of proteinaceous deep-sea corals collected from the North Pacific Subtropical Gyre (Hawaiian Archipelago and the central equatorial Pacific (Line Islands document multidecadal to century-scale variability in the isotopic composition of surface-produced particulate organic matter exported to the deep sea. Comparison of the δ13C data, where Line Islands samples are 0.6‰ more positive than the Hawaiian samples, supports the contention that the North Pacific Subtropical Gyre is more efficient than the tropical upwelling system at trapping and/or recycling nutrients within the mixed layer. δ15N values from the Line Islands samples are also more positive than those from the central gyre, and within the Hawaiian samples there is a gradient with more positive δ15N values in samples from the main Hawaiian Islands versus the French Frigate Shoals in the Northwestern Hawaiian Islands. The gradient in the Hawaiian samples likely reflects the relative importance of algal acquisition of metabolic N via dissolved seawater nitrate uptake versus nitrogen fixation. The Hawaiian sample set also exhibits a strong decrease in δ15N values from the mid-Holocene to present. We hypothesize that this decrease is most likely the result of decreasing trade winds, and possibly a commensurate decrease in entrainment of more positive δ15N-NO3 subthermocline water masses.

  3. A Statistical Model of the Fluctuations in the Geomagnetic Field from Paleosecular Variation to Reversal

    Science.gov (United States)

    Camps; Prevot

    1996-08-09

    The statistical characteristics of the local magnetic field of Earth during paleosecular variation, excursions, and reversals are described on the basis of a database that gathers the cleaned mean direction and average remanent intensity of 2741 lava flows that have erupted over the last 20 million years. A model consisting of a normally distributed axial dipole component plus an independent isotropic set of vectors with a Maxwellian distribution that simulates secular variation fits the range of geomagnetic fluctuations, in terms of both direction and intensity. This result suggests that the magnitude of secular variation vectors is independent of the magnitude of Earth's axial dipole moment and that the amplitude of secular variation is unchanged during reversals.

  4. A theoretical model of semi-elliptic surface crack growth

    Directory of Open Access Journals (Sweden)

    Shi Kaikai

    2014-06-01

    Full Text Available A theoretical model of semi-elliptic surface crack growth based on the low cycle strain damage accumulation near the crack tip along the cracking direction and the Newman–Raju formula is developed. The crack is regarded as a sharp notch with a small curvature radius and the process zone is assumed to be the size of cyclic plastic zone. The modified Hutchinson, Rice and Rosengren (HRR formulations are used in the presented study. Assuming that the shape of surface crack front is controlled by two critical points: the deepest point and the surface point. The theoretical model is applied to semi-elliptic surface cracked Al 7075-T6 alloy plate under cyclic loading, and five different initial crack shapes are discussed in present study. Good agreement between experimental and theoretical results is obtained.

  5. Analysis and Comprehensive Analytical Modeling of Statistical Variations in Subthreshold MOSFET's High Frequency Characteristics

    Directory of Open Access Journals (Sweden)

    Rawid Banchuin

    2014-01-01

    Full Text Available In this research, the analysis of statistical variations in subthreshold MOSFET's high frequency characteristics defined in terms of gate capacitance and transition frequency, have been shown and the resulting comprehensive analytical models of such variations in terms of their variances have been proposed. Major imperfection in the physical level properties including random dopant fluctuation and effects of variations in MOSFET's manufacturing process, have been taken into account in the proposed analysis and modeling. The up to dated comprehensive analytical model of statistical variation in MOSFET's parameter has been used as the basis of analysis and modeling. The resulting models have been found to be both analytic and comprehensive as they are the precise mathematical expressions in terms of physical level variables of MOSFET. Furthermore, they have been verified at the nanometer level by using 65~nm level BSIM4 based benchmarks and have been found to be very accurate with smaller than 5 % average percentages of errors. Hence, the performed analysis gives the resulting models which have been found to be the potential mathematical tool for the statistical and variability aware analysis and design of subthreshold MOSFET based VHF circuits, systems and applications.

  6. Market Microstructure Model: study of variations of exchange rate for Asia and Latin America

    OpenAIRE

    Lima, Antonieta; Salazar Soares , Vasco

    2008-01-01

    The paper studies the commercial relations between Europe and its principal commercial partners, such as Asia and Latin America, for the period of 1999 to 2007. The methodology appeals to the correlation analysis of the variables of the model and the autocorrelation of the exchange rate variation variable, to the Augmented DickeyFuller (1979) and Philips Perron tests (1988), and finally, to the market microstructure model suggested by Medeiros(2005). Medeiros(2005) model, when applied to the ...

  7. Probabilistic modelling in urban drainage – two approaches that explicitly account for temporal variation of model errors

    DEFF Research Database (Denmark)

    Löwe, Roland; Del Giudice, Dario; Mikkelsen, Peter Steen

    of input uncertainties observed in the models. The explicit inclusion of such variations in the modelling process will lead to a better fulfilment of the assumptions made in formal statistical frameworks, thus reducing the need to resolve to informal methods. The two approaches presented here...

  8. APPLICATION OF LEARNING CYCLE MODEL (5E LEARNING WITH CHART VARIATION TOWARDSTUDENTS’ CREATIVITY

    Directory of Open Access Journals (Sweden)

    Suciati -

    2015-04-01

    Full Text Available This study aims to determine the differences in the application of the model LC (5E with a technique variation (interrelationship diagram / ID and affinity diagrams / AD of two classes of different school (XIPA-8 class of SMAN 3 Surakarta and class XIPA-6 of SMAN 3 Boyolali, toward the increase of students’ creativity. This research is a qualitative descriptive study. The results of this study, we can conclude that the application of the model LC (5E with a technique variation at two schools can improve students' creativity despite different levels of improvement.

  9. Variational solution of the Gross-Neveu model; 2, finite-N and renormalization

    CERN Document Server

    Arvanitis, C; Iacomi, M; Kneur, J L; Neveu, A

    1995-01-01

    We show how to perform systematically improvable variational calculations in the O(2N) Gross-Neveu model for generic N, in such a way that all infinities usually plaguing such calculations are accounted for in a way compatible with the renormalization group. The final point is a general framework for the calculation of non-perturbative quantities like condensates, masses, etc..., in an asymptotically free field theory. For the Gross-Neveu model, the numerical results obtained from a "two-loop" variational calculation are in very good agreement with exact quantities down to low values of N.

  10. Application and Analysis of Measurement Model for Calibrating Spatial Shear Surface in Triaxial Test

    Science.gov (United States)

    Zhang, Zhihua; Qiu, Hongsheng; Zhang, Xiedong; Zhang, Hang

    2017-12-01

    Discrete element method has great advantages in simulating the contacts, fractures, large displacement and deformation between particles. In order to analyze the spatial distribution of the shear surface in the three-dimensional triaxial test, a measurement model is inserted in the numerical triaxial model which is generated by weighted average assembling method. Due to the non-visibility of internal shear surface in laboratory, it is largely insufficient to judge the trend of internal shear surface only based on the superficial cracks of sheared sample, therefore, the measurement model is introduced. The trend of the internal shear zone is analyzed according to the variations of porosity, coordination number and volumetric strain in each layer. It shows that as a case study on confining stress of 0.8 MPa, the spatial shear surface is calibrated with the results of the rotated particle distribution and the theoretical value with the specific characteristics of the increase of porosity, the decrease of coordination number, and the increase of volumetric strain, which represents the measurement model used in three-dimensional model is applicable.

  11. Geometry of surfaces associated to Grassmannian sigma models

    International Nuclear Information System (INIS)

    Delisle, L; Hussin, V; Zakrzewski, W J

    2015-01-01

    We investigate the geometric characteristics of constant Gaussian curvature surfaces obtained from solutions of the G(m, n) sigma model. Most of these solutions are related to the Veronese sequence. We show that we can distinguish surfaces with the same Gaussian curvature using additional quantities like the topological charge and the mean curvature. The cases of G(1,n) = CP n-1 and G(2,n) are used to illustrate these characteristics. (paper)

  12. ANFIS Modeling of the Surface Roughness in Grinding Process

    OpenAIRE

    H. Baseri; G. Alinejad

    2011-01-01

    The objective of this study is to design an adaptive neuro-fuzzy inference system (ANFIS) for estimation of surface roughness in grinding process. The Used data have been generated from experimental observations when the wheel has been dressed using a rotary diamond disc dresser. The input parameters of model are dressing speed ratio, dressing depth and dresser cross-feed rate and output parameter is surface roughness. In the experimental procedure the grinding conditions...

  13. Variations of Sea Surface Temperature, Wind Stress, and Rainfall over the Tropical Atlantic and South America.

    Science.gov (United States)

    Nobre, Paulo; Srukla, J.

    1996-10-01

    Empirical orthogonal functions (E0Fs) and composite analyses are used to investigate the development of sea surface temperature (SST) anomaly patterns over the tropical Atlantic. The evolution of large-scale rainfall anomaly patterns over the equatorial Atlantic and South America are also investigated. 71e EOF analyses revealed that a pattern of anomalous SST and wind stress asymmetric relative to the equator is the dominant mode of interannual and longer variability over the tropical Atlantic. The most important findings of this study are as follows.Atmospheric circulation anomalies precede the development of basinwide anomalous SST patterns over the tropical Atlantic. Anomalous SST originate off the African coast simultaneously with atmospheric circulation anomalies and expand westward afterward. The time lag between wind stress relaxation (strengthening) and maximum SST warming (cooling) is about two months.Anomalous atmospheric circulation patterns over northern tropical Atlantic are phase locked to the seasonal cycle. Composite fields of SLP and wind stress over northern tropical Atlantic can be distinguished from random only within a few months preceding the March-May (MAM) season. Observational evidence is presented to show that the El Niño-Southern Oscillation phenomenon in the Pacific influences atmospheric circulation and SST anomalies over northern tropical Atlantic through atmospheric teleconnection patterns into higher latitudes of the Northern Hemisphere.The well-known droughts over northeastern Brazil (Nordeste) are a local manifestation of a much larger-scale rainfall anomaly pattern encompassing the whole equatorial Atlantic and Amazon region. Negative rainfall anomalies to the south of the equator during MAM, which is the rainy season for the Nordeste region, are related to an early withdrawal of the intertropical convergence zone toward the warm SST anomalies over the northern tropical Atlantic. Also, it is shown that precipitation anomalies

  14. Edge-wave-driven durable variations in the thickness of the surfactant film and concentration of surface floats

    Energy Technology Data Exchange (ETDEWEB)

    Averbukh, Elena [Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Minin St. 24, 603950 Nizhny Novgorod (Russian Federation); Kurkina, Oksana, E-mail: okurkina@hse.ru [Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Minin St. 24, 603950 Nizhny Novgorod (Russian Federation); National Research University Higher School of Economics, 25/12 Bol' shaya Pecherskaya St., 603155 Nizhny Novgorod (Russian Federation); Kurkin, Andrey [Nizhny Novgorod State Technical University n.a. R.E. Alekseev, Minin St. 24, 603950 Nizhny Novgorod (Russian Federation); Soomere, Tarmo, E-mail: soomere@cs.ioc.ee [Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn (Estonia)

    2014-01-03

    By employing a simple model for small-scale linear edge waves propagating along a homogeneous sloping beach, we demonstrate that certain combinations of linear wave components may lead to durable changes in the thickness of the surfactant film, equivalently, in the concentration of various substances (debris, litter) floating on the water surface. Such changes are caused by high-amplitude transient elevations that resemble rogue waves and occur during dispersive focusing of wave fields with a continuous spectrum. This process can be treated as an intrinsic mechanism of production of patches in the surface layer of an otherwise homogeneous coastal environment impacted by linear edge waves.

  15. A Torque Error Compensation Algorithm for Surface Mounted Permanent Magnet Synchronous Machines with Respect to Magnet Temperature Variations

    Directory of Open Access Journals (Sweden)

    Chang-Seok Park

    2017-09-01

    Full Text Available This paper presents a torque error compensation algorithm for a surface mounted permanent magnet synchronous machine (SPMSM through real time permanent magnet (PM flux linkage estimation at various temperature conditions from medium to rated speed. As known, the PM flux linkage in SPMSMs varies with the thermal conditions. Since a maximum torque per ampere look up table, a control method used for copper loss minimization, is developed based on estimated PM flux linkage, variation of PM flux linkage results in undesired torque development of SPMSM drives. In this paper, PM flux linkage is estimated through a stator flux linkage observer and the torque error is compensated in real time using the estimated PM flux linkage. In this paper, the proposed torque error compensation algorithm is verified in simulation and experiment.

  16. A GIS Approach to Wind,SST(Sea Surface Temperature) and CHL(Chlorophyll) variations in the Caspian Sea

    Science.gov (United States)

    Mirkhalili, Seyedhamzeh

    2016-07-01

    Chlorophyll is an extremely important bio-molecule, critical in photosynthesis, which allows plants to absorb energy from light. At the base of the ocean food web are single-celled algae and other plant-like organisms known as Phytoplankton. Like plants on land, Phytoplankton use chlorophyll and other light-harvesting pigments to carry out photosynthesis. Where Phytoplankton grow depends on available sunlight, temperature, and nutrient levels. In this research a GIS Approach using ARCGIS software and QuikSCAT satellite data was applied to visualize WIND,SST(Sea Surface Temperature) and CHL(Chlorophyll) variations in the Caspian Sea.Results indicate that increase in chlorophyll concentration in coastal areas is primarily driven by terrestrial nutrients and does not imply that warmer SST will lead to an increase in chlorophyll concentration and consequently Phytoplankton abundance.

  17. Seasonal and spatial variations in microbial activity at various phylogenetic resolutions at a groundwater – surface water interface

    DEFF Research Database (Denmark)

    Yu, Ran; Smets, Barth F.; Gan, Ping

    2014-01-01

    analysis. Consistently higher microbial activities with less variation in depth were measured in the AIMC traps than in the ambient sediments. Flood disturbance appeared to control AIMC activity distributions at the gradually elevated GSI. The highest AIMC activities were generally obtained from locations...... closest to the free surface water boundary except during the dry season when microbial activities were similar across the entire GSI. A clone library of AIMC 16S rRNA genes was constructed, and it confirmed the predominant role of the targeted alphaproteobacterial group in AIMC activity and composition...... phylogenetically related to putative IOB, supporting the occurrence and persistence of active microbial iron oxidation across the studied iron-rich GSI ecosystem....

  18. Surface photovoltage measurements and finite element modeling of SAW devices.

    Energy Technology Data Exchange (ETDEWEB)

    Donnelly, Christine

    2012-03-01

    Over the course of a Summer 2011 internship with the MEMS department of Sandia National Laboratories, work was completed on two major projects. The first and main project of the summer involved taking surface photovoltage measurements for silicon samples, and using these measurements to determine surface recombination velocities and minority carrier diffusion lengths of the materials. The SPV method was used to fill gaps in the knowledge of material parameters that had not been determined successfully by other characterization methods. The second project involved creating a 2D finite element model of a surface acoustic wave device. A basic form of the model with the expected impedance response curve was completed, and the model is ready to be further developed for analysis of MEMS photonic resonator devices.

  19. The variation in visibility and its relationship with surface wind speed in China from 1960 to 2009

    Science.gov (United States)

    Sun, Tianze; Che, Huizheng; Wu, Jian; Wang, Hong; Wang, Yaqiang; Zhang, Xiaoye

    2018-01-01

    This study used daily visibility and surface wind speed observational data over the 50-year period from 1960 to 2009, from 464 national meteorological stations in China, to examine the relationship between these two variables. Specifically, using the statistical methods of empirical orthogonal function (EOF) analysis and wavelet analysis, the data were processed into anomaly data to study their spatial and temporal distributions and the characteristics of each pattern's periodicity after EOF analysis of the whole country's visibility and surface wind speed. Correlation analysis and composite analysis were then used to elucidate the relationship between the two variables on different time scales. The results showed a gradual reduction in visibility nationally, with the nine-point moving mean implying decadal variability of the visibility with a downward trend. However, an irregular oscillation was found for the inter-annual variability of visibility. For the anomaly series of visibility during the 50-year period, a long-period oscillation of around 32 years was apparent. Up until the 1990s, there was an approximate 16-year medium-term oscillation period, whereas, after the 1990s, an approximate 8-year oscillation period was generated. In terms of high correlation between the two variables, for the decadal variability, the changes in visibility and surface wind speed at this time scale were almost in agreement. Meanwhile, with respect to the serious pollution in the Yangtze River Delta Economic Zone, the correlation between the two variables was reasonably high, suggesting that surface wind had a significant influence on the scattering of aerosol particles. However, in the Sichuan Basin, the correlation was relatively low, possibly on account of its landscape limiting the variation of wind speed.

  20. Spatial variations of prokaryotic communities in surface water from India Ocean to Chinese marginal seas and their underlining environmental determinants

    Directory of Open Access Journals (Sweden)

    Xiaowei eZheng

    2016-02-01

    Full Text Available To illustrate the biogeographic patterns of prokaryotic communities in surface sea water, 24 samples were systematically collected across a large distance from Indian Ocean to Chinese marginal seas, with an average distance of 453 km between two adjacent stations. A total of 841,364 quality reads was produced by the high throughput DNA sequencing of the 16S rRNA genes. Phylogenetic analysis showed that Proteobacteria were predominant in all samples, with Alphaproteobacteria and Gammaproteobacteria being the two most abundant components. Cyanobacteria represented the second largest fraction of the total quality reads, and mainly included Prochlorococcus and Synechococcus. The semi-closed marginal seas, including South China Sea (SCS and nearby regions, exhibited a transition in community composition between oceanic and coastal seas, based on the distribution patterns of Prochlorococcus and Synechococcus as well as a non-metric multidimensional scaling (NMDS analysis. Distinct clusters of prokaryotes from coastal and open seas, and from different water masses in Indian Ocean were obtained by Bray-Curtis dissimilarity analysis at the OTU level, revealing a clear spatial heterogeneity. The major environmental factors correlated with the community variation in this broad scale were identified as salinity, temperature and geographic distance. Community comparison among regions shows that anthropogenic contamination is another dominant factor in shaping the biogeographic patterns of the microorganisms. These results suggest that environmental factors involved in complex interactions between land and sea act synergistically in driving spatial variations in coastal areas.

  1. Limited variation in vaccine candidate Plasmodium falciparum Merozoite Surface Protein-6 over multiple transmission seasons

    Directory of Open Access Journals (Sweden)

    Branch OraLee H

    2010-05-01

    Full Text Available Abstract Background Plasmodium falciparum Merozoite Surface Protein-6 (PfMSP6 is a component of the complex proteinacious coat that surrounds P. falciparum merozoites. This location, and the presence of anti-PfMSP6 antibodies in P. falciparum-exposed individuals, makes PfMSP6 a potential blood stage vaccine target. However, genetic diversity has proven to be a major hurdle for vaccines targeting other blood stage P. falciparum antigens, and few endemic field studies assessing PfMSP6 gene diversity have been conducted. This study follows PfMSP6 diversity in the Peruvian Amazon from 2003 to 2006 and is the first longitudinal assessment of PfMSP6 sequence dynamics. Methods Parasite DNA was extracted from 506 distinct P. falciparum infections spanning the transmission seasons from 2003 to 2006 as part of the Malaria Immunology and Genetics in the Amazon (MIGIA cohort study near Iquitos, Peru. PfMSP6 was amplified from each sample using a nested PCR protocol, genotyped for allele class by agarose gel electrophoresis, and sequenced to detect diversity. Allele frequencies were analysed using JMP v.8.0.1.0 and correlated with clinical and epidemiological data collected as part of the MIGIA project. Results Both PfMSP6 allele classes, K1-like and 3D7-like, were detected at the study site, confirming that both are globally distributed. Allele frequencies varied significantly between transmission seasons, with 3D7-class alleles dominating and K1-class alleles nearly disappearing in 2005 and 2006. There was a significant association between allele class and village location (p-value = 0.0008, but no statistically significant association between allele class and age, sex, or symptom status. No intra-allele class sequence diversity was detected. Conclusions Both PfMSP6 allele classes are globally distributed, and this study shows that allele frequencies can fluctuate significantly between communities separated by only a few kilometres, and over time in the

  2. Modeling per capita state health expenditure variation: state-level characteristics matter.

    Science.gov (United States)

    Cuckler, Gigi; Sisko, Andrea

    2013-01-01

    In this paper, we describe the methods underlying the econometric model developed by the Office of the Actuary in the Centers for Medicare & Medicaid Services, to explain differences in per capita total personal health care spending by state, as described in Cuckler, et al. (2011). Additionally, we discuss many alternative model specifications to provide additional insights for valid interpretation of the model. We study per capita personal health care spending as measured by the State Health Expenditures, by State of Residence for 1991-2009, produced by the Centers for Medicare & Medicaid Services' Office of the Actuary. State-level demographic, health status, economic, and health economy characteristics were gathered from a variety of U.S. government sources, such as the Census Bureau, Bureau of Economic Analysis, the Centers for Disease Control, the American Hospital Association, and HealthLeaders-InterStudy. State-specific factors, such as income, health care capacity, and the share of elderly residents, are important factors in explaining the level of per capita personal health care spending variation among states over time. However, the slow-moving nature of health spending per capita and close relationships among state-level factors create inefficiencies in modeling this variation, likely resulting in incorrectly estimated standard errors. In addition, we find that both pooled and fixed effects models primarily capture cross-sectional variation rather than period-specific variation.

  3. Modeling fish community dynamics in Florida Everglades: Role of temperature variation

    Science.gov (United States)

    Al-Rabai'ah, H. A.; Koh, H. L.; DeAngelis, Donald L.; Lee, Hooi-Ling

    2002-01-01

    Temperature variation is an important factor in Everglade wetlands ecology. A temperature fluctuation from 17°C to 32°C recorded in the Everglades may have significant impact on fish dynamics. The short life cycles of some of Everglade fishes has rendered this temperature variation to have even more impacts on the ecosystem. Fish population dynamic models, which do not explicitly consider seasonal oscillations in temperature, may fail to describe the details of such a population. Hence, a model for fish in freshwater marshes of the Florida Everglades that explicitly incorporates seasonal temperature variations is developed. The model's main objective is to assess the temporal pattern of fish population and densities through time subject to temperature variations. Fish population is divided into 2 functional groups (FGs) consisting of small fishes; each group is subdivided into 5-day age classes during their life cycles. Many governing sub-modules are set directly or indirectly to be temperature dependent. Growth, fecundity, prey availability, consumption rates and mortality are examples. Several mortality sub-modules are introduced in the model, of which starvation mortality is set to be proportional to the ratio of prey needed to prey available at that particular time step. As part of the calibration process, the model is run for 50 years to ensure that fish densities do not go to extinction, while the simulation period is about 8 years.

  4. Analysis of dynamic Cournot learning models for generation companies based on conjectural variations and forward expectation

    International Nuclear Information System (INIS)

    Gutierrez-Alcaraz, G.; Tovar-Hernandez, Jose H.; Moreno-Goytia, Edgar L.

    2009-01-01

    Electricity spot markets generally operate on an hourly basis; under this condition GENCOs can closely observe their competitors' market behavior. For this purposes, a detailed dynamic model is one of the tools used by GENCOs to understand the behavioral variations of competitors over time. The required abilities to rapidly adjust one's own decision-making create a need for new learning procedures and models. Conjectural variations (CV) have been proposed as a learning approach. In this paper a model based on forward expectations (FE) is proposed as a learning approach, and through illustrative examples it is shown that the market equilibria found by the CV model are also obtained by the FE model. (author)

  5. Feedforward Object-Vision Models Only Tolerate Small Image Variations Compared to Human

    Directory of Open Access Journals (Sweden)

    Masoud eGhodrati

    2014-07-01

    Full Text Available Invariant object recognition is a remarkable ability of primates' visual system that its underlying mechanism has constantly been under intense investigations. Computational modelling is a valuable tool toward understanding the processes involved in invariant object recognition. Although recent computational models have shown outstanding performances on challenging image databases, they fail to perform well when images with more complex variations of the same object are applied to them. Studies have shown that making sparse representation of objects by extracting more informative visual features through a feedforward sweep can lead to higher recognition performances. Here, however, we show that when the complexity of image variations is high, even this approach results in poor performance compared to humans. To assess the performance of models and humans in invariant object recognition tasks, we built a parametrically controlled image database consisting of several object categories varied in different dimensions and levels, rendered from 3D planes. Comparing the performance of several object recognition models with human observers shows that only in low-level image variations the models perform similar to humans in categorization tasks. Furthermore, the results of our behavioral experiments demonstrate that, even under difficult experimental conditions (i.e. briefly presented masked stimuli with complex image variations, human observers performed outstandingly well, suggesting that the models are still far from resembling humans in invariant object recognition. Taken together, we suggest that learning sparse informative visual features, although desirable, is not a complete solution for future progresses in object-vision modelling. We show that this approach is not of significant help in solving the computational crux of object recognition (that is invariant object recognition when the identity-preserving image variations become more complex.

  6. Temporal–spatial variation and partitioning prediction of antibiotics in surface water and sediments from the intertidal zones of the Yellow River Delta, China

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Shengnan [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Liu, Xinhui, E-mail: xhliu@bnu.edu.cn [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China); Cheng, Dengmiao [Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture, Beijing 100081 (China); Liu, Guannan [MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, CAGS, Beijing 100037 (China); Liang, Baocui; Cui, Baoshan; Bai, Junhong [State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875 (China)

    2016-11-01

    As special zones, the intertidal zones of the Yellow River Delta (YRD) are highly variable along with time and space. Fluvial–marine and land–ocean interactions which frequently occur in these areas have a great impact on the fate of pollutants. Antibiotics, which contribute to antibiotic-resistant genes (ARGs), are widely detected in wastewater, natural water, soil, sediments, and even drinking water. Therefore, it is meaningful to investigate the occurrence and fate of antibiotics in these special zones. In this study, eight antibiotics belonging to tetracyclines (TCs), fluoroquinolones (FQs), and macrolides (MLs) were detected in the surface water and sediments from the intertidal zones of YRD during two seasons. Two models were established to predict the partitioning coefficients of norfloxacin (NOR) and erythromycin (ETM) using physicochemical properties of sediments, respectively. The total concentrations of these antibiotics were 82.94–230.96 ng·L{sup −} {sup 1} and 40.97–207.44 ng·g{sup −} {sup 1}, respectively, in the surface water and sediments. Seasonal variation was mainly influenced by the frequency of antibiotics use and environment factors. The regions with river supply exhibited the highest concentrations of antibiotics in surface water and sediments. Meanwhile, particle-size fractions, cation exchange capability (CEC), and metal ions content played dominant roles in the partitioning behaviors of NOR and ETM between the surface water and sediments. Both models established in this study featured accuracy and feasibility, which provided the methods for predicting the partitioning coefficients of emerging contaminants similar in structures to NOR and ETM in the intertidal zones. - Highlights: • The intertidal zones of YRD were polluted by antibiotics to some extent. • The river supply was a major pathway for the antibiotic pollution of the intertidal zones of YRD. • The partitioning coefficients of NOR and ETM can be predicted using

  7. Temporal–spatial variation and partitioning prediction of antibiotics in surface water and sediments from the intertidal zones of the Yellow River Delta, China

    International Nuclear Information System (INIS)

    Zhao, Shengnan; Liu, Xinhui; Cheng, Dengmiao; Liu, Guannan; Liang, Baocui; Cui, Baoshan; Bai, Junhong

    2016-01-01

    As special zones, the intertidal zones of the Yellow River Delta (YRD) are highly variable along with time and space. Fluvial–marine and land–ocean interactions which frequently occur in these areas have a great impact on the fate of pollutants. Antibiotics, which contribute to antibiotic-resistant genes (ARGs), are widely detected in wastewater, natural water, soil, sediments, and even drinking water. Therefore, it is meaningful to investigate the occurrence and fate of antibiotics in these special zones. In this study, eight antibiotics belonging to tetracyclines (TCs), fluoroquinolones (FQs), and macrolides (MLs) were detected in the surface water and sediments from the intertidal zones of YRD during two seasons. Two models were established to predict the partitioning coefficients of norfloxacin (NOR) and erythromycin (ETM) using physicochemical properties of sediments, respectively. The total concentrations of these antibiotics were 82.94–230.96 ng·L"− "1 and 40.97–207.44 ng·g"− "1, respectively, in the surface water and sediments. Seasonal variation was mainly influenced by the frequency of antibiotics use and environment factors. The regions with river supply exhibited the highest concentrations of antibiotics in surface water and sediments. Meanwhile, particle-size fractions, cation exchange capability (CEC), and metal ions content played dominant roles in the partitioning behaviors of NOR and ETM between the surface water and sediments. Both models established in this study featured accuracy and feasibility, which provided the methods for predicting the partitioning coefficients of emerging contaminants similar in structures to NOR and ETM in the intertidal zones. - Highlights: • The intertidal zones of YRD were polluted by antibiotics to some extent. • The river supply was a major pathway for the antibiotic pollution of the intertidal zones of YRD. • The partitioning coefficients of NOR and ETM can be predicted using the physicochemical

  8. A surface-renewal model of cross-flow microfiltration

    Directory of Open Access Journals (Sweden)

    A. Hasan

    2013-03-01

    Full Text Available A mathematical model using classical cake-filtration theory and the surface-renewal concept is formulated for describing cross-flow microfiltration under dynamic and steady-state conditions. The model can predict the permeate flux and cake buildup in the filter. The three basic parameters of the model are the membrane resistance, specific cake resistance and rate of surface renewal. The model is able to correlate experimental permeate flow rate data in the microfiltration of fermentation broths in laboratory- and pilot-scale units with an average root-mean-square (RMS error of 4.6%. The experimental data are also compared against the critical-flux model of cross-flow microfiltration, which has average RMS errors of 6.3, 5.5 and 6.1% for the cases of cake filtration, intermediate blocking and complete blocking mechanisms, respectively.

  9. Improvement of a land surface model for accurate prediction of surface energy and water balances

    International Nuclear Information System (INIS)

    Katata, Genki

    2009-02-01

    In order to predict energy and water balances between the biosphere and atmosphere accurately, sophisticated schemes to calculate evaporation and adsorption processes in the soil and cloud (fog) water deposition on vegetation were implemented in the one-dimensional atmosphere-soil-vegetation model including CO 2 exchange process (SOLVEG2). Performance tests in arid areas showed that the above schemes have a significant effect on surface energy and water balances. The framework of the above schemes incorporated in the SOLVEG2 and instruction for running the model are documented. With further modifications of the model to implement the carbon exchanges between the vegetation and soil, deposition processes of materials on the land surface, vegetation stress-growth-dynamics etc., the model is suited to evaluate an effect of environmental loads to ecosystems by atmospheric pollutants and radioactive substances under climate changes such as global warming and drought. (author)

  10. A laminar cortical model of stereopsis and 3D surface perception: closure and da Vinci stereopsis.

    Science.gov (United States)

    Cao, Yongqiang; Grossberg, Stephen

    2005-01-01

    A laminar cortical model of stereopsis and 3D surface perception is developed and simulated. The model describes how monocular and binocular oriented filtering interact with later stages of 3D boundary formation and surface filling-in in the LGN and cortical areas V1, V2, and V4. It proposes how interactions between layers 4, 3B, and 2/3 in V1 and V2 contribute to stereopsis, and how binocular and monocular information combine to form 3D boundary and surface representations. The model includes two main new developments: (1) It clarifies how surface-to-boundary feedback from V2 thin stripes to pale stripes helps to explain data about stereopsis. This feedback has previously been used to explain data about 3D figure-ground perception. (2) It proposes that the binocular false match problem is subsumed under the Gestalt grouping problem. In particular, the disparity filter, which helps to solve the correspondence problem by eliminating false matches, is realized using inhibitory interneurons as part of the perceptual grouping process by horizontal connections in layer 2/3 of cortical area V2. The enhanced model explains all the psychophysical data previously simulated by Grossberg and Howe (2003), such as contrast variations of dichoptic masking and the correspondence problem, the effect of interocular contrast differences on stereoacuity, Panum's limiting case, the Venetian blind illusion, stereopsis with polarity-reversed stereograms, and da Vinci stereopsis. It also explains psychophysical data about perceptual closure and variations of da Vinci stereopsis that previous models cannot yet explain.

  11. Bilinear models for inter- and intra-patient variation of the prostate

    International Nuclear Information System (INIS)

    Jeong, Y; Radke, R J; Lovelock, D M

    2010-01-01

    We propose bilinear models for capturing and effectively decoupling the expected shape variations of an organ both across the patient population and within a specific patient. Bilinear models have been successfully introduced in other areas of computer vision, but they have rarely been used in medical imaging applications. Our particular interest is in modeling the shape variation of the prostate for potential use in radiation therapy treatment planning. Using a dataset of 204 prostate shapes contoured from CT imagery of 12 different patients, we build bilinear models and show that they can fit both training and testing shapes accurately. We also show how the bilinear model can adapt to a new patient using only a few example shapes, producing a patient-specific model that also reflects expected content variation learnt from a broader population. Finally, we evaluate the training and testing projection error, adaptation performance and image segmentation accuracy of the bilinear model compared to linear principal component analysis and hierarchical point distribution models with the same number of parameters.