Velocity potential formulations of highly accurate Boussinesq-type models
DEFF Research Database (Denmark)
Bingham, Harry B.; Madsen, Per A.; Fuhrman, David R.
2009-01-01
, B., 2006. A Boussinesq-type method for fully nonlinear waves interacting with a rapidly varying bathymetry. Coast. Eng. 53, 487-504); Jamois et al. (Jamois, E., Fuhrman, D.R., Bingham, H.B., Molin, B., 2006. Wave-structure interactions and nonlinear wave processes on the weather side of reflective...... is of interest because it reduces the computational effort by approximately a factor of two and facilitates a coupling to other potential flow solvers. A new shoaling enhancement operator is introduced to derive new models (in both formulations) with a velocity profile which is always consistent...... processes on the weather side of reflective structures. Coast. Eng. 53, 929-945). An exact infinite series solution for the potential is obtained via a Taylor expansion about an arbitrary vertical position z=(z) over cap. For practical implementation however, the solution is expanded based on a slow...
A Study of Enhanced, Higher Order Boussinesq-Type Equations and Their Numerical Modelling
DEFF Research Database (Denmark)
Banijamali, Babak
This project has encompassed efforts in two separate veins: on the one hand, the acquiring of highly accurate model equations of the Boussinesq-type, and on the other hand, the theoretical and practical work in implementing such equations in the form of conventional numerical models, with obvious...... potential for applications to the realm of numerical modelling in coastal engineering. The derivation and analysis of several forms of higher-order in dispersion and non-linearity Boussinesq-type equations have been undertaken, obtaining and investigating the properties of a new and generalised class...... of Boussinesq-type equations. The equations emerge from a study of arbitrarily higher-order Boussinesq-type equations in several customary choices of velocity variables. In doing so, a generalised horizontal velocity variable is defined corresponding to optimal properties, in the sense of the Padé...
A double-layer Boussinesq-type model for highly nonlinear and dispersive waves
Chazel, Florent; Benoit, Michel; Ern, Alexandre; Piperno, Serge
2009-01-01
28 pages, 5 figures. Soumis à Proceedings of the Royal Society of London A. We derive and analyze in the framework of the mild-slope approximation a new double-layer Boussinesq-type model which is linearly and nonlinearly accurate up to deep water. Assuming the flow to be irrotational, we formulate the problem in terms of the velocity potential thereby lowering the number of unknowns. The model derivation combines two approaches, namely the method proposed by Agnon et al. (Agnon et al. 199...
Brocchini, Maurizio
2013-01-01
This paper, which is largely the fruit of an invited talk on the topic at the latest International Conference on Coastal Engineering, describes the state of the art of modelling by means of Boussinesq-type models (BTMs). Motivations for using BTMs as well as their fundamentals are illustrated, with special attention to the interplay between the physics to be described, the chosen model equations and the numerics in use. The perspective of the analysis is that of a physicist/engineer rather th...
Brocchini, Maurizio
2013-12-01
This paper, which is largely the fruit of an invited talk on the topic at the latest International Conference on Coastal Engineering, describes the state of the art of modelling by means of Boussinesq-type models (BTMs). Motivations for using BTMs as well as their fundamentals are illustrated, with special attention to the interplay between the physics to be described, the chosen model equations and the numerics in use. The perspective of the analysis is that of a physicist/engineer rather than of an applied mathematician. The chronological progress of the currently available BTMs from the pioneering models of the late 1960s is given. The main applications of BTMs are illustrated, with reference to specific models and methods. The evolution in time of the numerical methods used to solve BTMs (e.g. finite differences, finite elements, finite volumes) is described, with specific focus on finite volumes. Finally, an overview of the most important BTMs currently available is presented, as well as some indications on improvements required and fields of applications that call for attention. PMID:24353475
Brocchini, Maurizio
2013-12-01
This paper, which is largely the fruit of an invited talk on the topic at the latest International Conference on Coastal Engineering, describes the state of the art of modelling by means of Boussinesq-type models (BTMs). Motivations for using BTMs as well as their fundamentals are illustrated, with special attention to the interplay between the physics to be described, the chosen model equations and the numerics in use. The perspective of the analysis is that of a physicist/engineer rather than of an applied mathematician. The chronological progress of the currently available BTMs from the pioneering models of the late 1960s is given. The main applications of BTMs are illustrated, with reference to specific models and methods. The evolution in time of the numerical methods used to solve BTMs (e.g. finite differences, finite elements, finite volumes) is described, with specific focus on finite volumes. Finally, an overview of the most important BTMs currently available is presented, as well as some indications on improvements required and fields of applications that call for attention.
NUMERICAL SIMULATION OF SOLITARY WAVE RUN-UP AND OVERTOPPING USING BOUSSINESQ-TYPE MODEL
Institute of Scientific and Technical Information of China (English)
TSUNG Wen-Shuo; HSIAO Shih-Chun; LIN Ting-Chieh
2012-01-01
In this article,the use of a high-order Boussinesq-type model and sets of laboratory experiments in a large scale flume of breaking solitary waves climbing up slopes with two inclinations are presented to study the shoreline behavior of breaking and non-breaking solitary waves on plane slopes.The scale effect on run-up height is briefly discussed.The model simulation capability is well validated against the available laboratory data and present experiments.Then,serial numerical tests are conducted to study the shoreline motion correlated with the effects of beach slope and wave nonlinearity for breaking and non-breaking waves.The empirical formula proposed by Hsiao et al.for predicting the maximum run-up height of a breaking solitary wave on plane slopes with a wide range of slope inclinations is confirmed to be cautious.Furthermore,solitary waves impacting and overtopping an impermeable sloping seawall at various water depths are investigated.Laboratory data of run-up height,shoreline motion,free surface elevation and overtopping discharge are presented.Comparisons of run-up,run-down,shoreline trajectory and wave overtopping discharge are made.A fairly good agreement is seen between numerical results and experimental data.It elucidates that the present depth-integrated model can be used as an efficient tool for predicting a wide spectrum of coastal problems.
On devising Boussinesq-type models with bounded eigenspectra: One horizontal dimension
DEFF Research Database (Denmark)
Eskilsson, Claes; Engsig-Karup, Allan Peter
2014-01-01
The propagation of water waves in the nearshore region can be described by depth-integrated Boussinesq-type equations. The dispersive and nonlinear characteristics of the equations are governed by tuneable parameters. We examine the associated linear eigenproblem both analytically and numerically...... requires Δt∝p−2. We derive and present conditions on the parameters under which implicitly-implicit Boussinesq-type equations will exhibit bounded eigenspectra. Two new bounded versions having comparable nonlinear and dispersive properties as the equations of Nwogu (1993) and Schäffer and Madsen (1995) are...
A hybrid finite-volume finite-difference rotational Boussinesq-type model of surf-zone hydrodynamics
Tatlock, Benjamin
2015-01-01
An investigation into the numerical and physical behaviour of a hybrid finite-volume finite-difference Boussinesq-type model, using a rotational surface roller approach in the surf-zone is presented. The relevant theory for the required development of a numerical model implementing this technique is outlined. The proposed method looks to achieve a more physically realistic description of the hydrodynamics by considering the rotational nature of the highly turbulent flow found during wave br...
High-order Boussinesq-type modelling of nonlinear wave phenomena in deep and shallow water
DEFF Research Database (Denmark)
Madsen, Per A.; Fuhrman, David R.
2010-01-01
In this work, we start with a review of the development of Boussinesq theory for water waves covering the period from 1872 to date. Previous reviews have been given by Dingemans,1 Kirby,2,3 and Madsen & Schäffer.4 Next, we present our most recent high-order Boussinesq-type formulation valid for f...... from an undular sea bed; (8) Run-up of non-breaking solitary waves on a beach; and (9) Tsunami generation from submerged landslides....
Institute of Scientific and Technical Information of China (English)
HE Hailun; SONG Jinbao; Patrick J. Lynett; LI Shuang
2009-01-01
Fractional energy losses of waves due to wave breaking when passing over a submerged bar are studied systematically using a modified numerical code that is based on the high-order Boussinesq-type equations. The model is first tested by the additional experimental data, and the model's capability of simulating the wave transformation over both gentle slope and steep slope is demonstrated. Then, the model's breaking index is replaced and tested. The new breaking index, which is optimized from the several breaking indices, is not sensitive to the spatial grid length and includes the bottom slopes. Numerical tests show that the modified model with the new breaking index is more stable and efficient for the shallow-water wave breaking. Finally, the modified model is used to study the fractional energy losses for the regular waves propagating and breaking over a submerged bar. Our results have revealed that how the nonlinearity and the dispersion of the incident waves as well as the dimensionless bar height (normalized by water depth) dominate the fractional energy losses. It is also found that the bar slope (limited to gentle slopes that less than 1:10) and the dimensionless bar length (normalized by incident wave length) have negligible effects on the fractional energy losses.
DG-FEM solution for nonlinear wave-structure interaction using Boussinesq-type equations
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Hesthaven, Jan; Bingham, Harry B.;
2008-01-01
waters within the breaking limit. To demonstrate the current applicability of the model both linear and mildly nonlinear test cases are considered in two horizontal dimensions where the water waves interact with bottom-mounted fully reflecting structures. It is established that, by simple symmetry......We present a high-order nodal Discontinuous Galerkin Finite Element Method (DG-FEM) solution based on a set of highly accurate Boussinesq-type equations for solving general water-wave problems in complex geometries. A nodal DG-FEM is used for the spatial discretization to solve the Boussinesq...... equations in complex and curvilinear geometries which amends the application range of previous numerical models that have been based on structured Cartesian grids. The Boussinesq method provides the basis for the accurate description of fully nonlinear and dispersive water waves in both shallow and deep...
Unstructured nodal DG-FEM solution of high-order Boussinesq-type equations
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter
2007-01-01
of today, the high-order Boussinesq equations represent the most advanced set of Boussinesq-type equations capable of modelling nonlinear and dispersive waves from shallow to deep water without the practical limitations of classical Boussinesq-type equations. The high-order Boussinesq equations constitute...... time-dependent linear system; and the numerical treatment of high-order and cross-differential derivatives. The suggested solution strategy of the current work is based on a collocation approach where the DG-FEM is used to approximate spatial derivatives and the boundary conditions are imposed weakly...... using a symmetry technique. Since collocation methods are prone to aliasing errors, various anti-aliasing strategies are applied for the stabilization of the models. A practical and relatively straightforward discretization is applied, which is based on a simple treatment of slip boundary conditions...
Nonhydrostatic granular flow over 3-D terrain: New Boussinesq-type gravity waves?
Castro-Orgaz, Oscar; Hutter, Kolumban; Giraldez, Juan V.; Hager, Willi H.
2015-01-01
granular mass flow is a basic step in the prediction and control of natural or man-made disasters related to avalanches on the Earth. Savage and Hutter (1989) pioneered the mathematical modeling of these geophysical flows introducing Saint-Venant-type mass and momentum depth-averaged hydrostatic equations using the continuum mechanics approach. However, Denlinger and Iverson (2004) found that vertical accelerations in granular mass flows are of the same order as the gravity acceleration, requiring the consideration of nonhydrostatic modeling of granular mass flows. Although free surface water flow simulations based on nonhydrostatic depth-averaged models are commonly used since the works of Boussinesq (1872, 1877), they have not yet been applied to the modeling of debris flow. Can granular mass flow be described by Boussinesq-type gravity waves? This is a fundamental question to which an answer is required, given the potential to expand the successful Boussinesq-type water theory to granular flow over 3-D terrain. This issue is explored in this work by generalizing the basic Boussinesq-type theory used in civil and coastal engineering for more than a century to an arbitrary granular mass flow using the continuum mechanics approach. Using simple test cases, it is demonstrated that the above question can be answered in the affirmative way, thereby opening a new framework for the physical and mathematical modeling of granular mass flow in geophysics, whereby the effect of vertical motion is mathematically included without the need of ad hoc assumptions.
Nodal DG-FEM solution of high-order Boussinesq-type equations
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter; Hesthaven, Jan S.; Bingham, Harry B.;
2006-01-01
We present a discontinuous Galerkin finite element method (DG-FEM) solution to a set of high-order Boussinesq-type equations for modelling highly nonlinear and dispersive water waves in one and two horizontal dimensions. The continuous equations are discretized using nodal polynomial basis...... and convergence of the model with both h (grid size) and p (order) refinement are verified for the linearized equations, and calculations are provided for two nonlinear test cases in one horizontal dimension: harmonic generation over a submerged bar; and reflection of a steep solitary wave from a vertical wall...
Unstructured nodal DG-FEM solution of high-order Boussinesq-type equations
Engsig-Karup, Allan Peter; Madsen, Per A.; Bingham, Harry B.; Thomsen, Per Grove
2007-01-01
The main objective of the present study has been to develop a numerical model and investigate solution techniques for solving the recently derived high-order Boussinesq equations of \\cite{MBL02} in irregular domains in one and two horizontal dimensions. The Boussinesq-type methods are the simplest alternative to solving full three-dimensional wave problems by e.g. Navier-Stokes equations, which can capture all the important wave phenomena such as diffraction, refraction, nonlinear wave-wave i...
Boundary Conditions for 2D Boussinesq-type Wave-Current Interaction Equations
Directory of Open Access Journals (Sweden)
Mera M.
2011-01-01
Full Text Available This research focuses on the development of a set of two-dimensional boundary conditions for specific governing equations. The governing equations are existing Boussinesqtype equations which is capable of simulating wave-current interaction. The present boundary conditions consist of for waves only case and for currents only case. To simulate wave-current interaction, the two kinds of the present boundary conditions are then combined. A numerical model based on both the existing governing equations and the present boundary conditions is applied to simulation of currents only and of wave-current interaction propagating over a basin with a submerged shoal. The results of the numerical model show that the present boundary conditions go well with the existing Boussinesq-type wave-current interaction equations.
Fully Nonlinear Boussinesq-Type Equations with Optimized Parameters for Water Wave Propagation
Institute of Scientific and Technical Information of China (English)
荆海晓; 刘长根; 龙文; 陶建华
2015-01-01
For simulating water wave propagation in coastal areas, various Boussinesq-type equations with improved properties in intermediate or deep water have been presented in the past several decades. How to choose proper Boussinesq-type equations has been a practical problem for engineers. In this paper, approaches of improving the characteristics of the equations, i.e. linear dispersion, shoaling gradient and nonlinearity, are reviewed and the advantages and disadvantages of several different Boussinesq-type equations are compared for the applications of these Boussinesq-type equations in coastal engineering with relatively large sea areas. Then for improving the properties of Boussinesq-type equations, a new set of fully nonlinear Boussinseq-type equations with modified representative velocity are derived, which can be used for better linear dispersion and nonlinearity. Based on the method of minimizing the overall error in different ranges of applications, sets of parameters are determined with optimized linear dispersion, linear shoaling and nonlinearity, respectively. Finally, a test example is given for validating the results of this study. Both results show that the equations with optimized parameters display better characteristics than the ones obtained by matching with padé approximation.
The consistent Riccati expansion and new interaction solution for a Boussinesq-type coupled system
Ruan, Shao-Qing; Yu, Wei-Feng; Yu, Jun; Yu, Guo-Xiang
2015-06-01
Starting from the Davey-Stewartson equation, a Boussinesq-type coupled equation system is obtained by using a variable separation approach. For the Boussinesq-type coupled equation system, its consistent Riccati expansion (CRE) solvability is studied with the help of a Riccati equation. It is significant that the soliton-cnoidal wave interaction solution, expressed explicitly by Jacobi elliptic functions and the third type of incomplete elliptic integral, of the system is also given. Project supported by the National Natural Science Foundation of China (Grant No. 11275129).
Coastal zone simulations with variational Boussinesq modelling
Adytia, Didit
2012-01-01
The main challenge in deriving a Boussinesq model for water wave is to model accurately the dispersion and nonlinearity of waves. The dispersion is a depth-dependent relation between the wave speed and the wavelength. A Boussinesq-type model can be derived from the so-called variational principle
Tissier, M.F.S.; Bonneton, P.; Ruessink, B.G.; Marche, F.; Chazel, F.; Lannes, D.
2012-01-01
Recent field studies over low sloping beaches have shown that infragravity waves could dissipate a significant part of their energy in the inner surf zone. This phenomenon and the associated short- and long-wave transformations are not well-understood. In this paper, we assess the ability of the ful
Accurate Modeling of Advanced Reflectarrays
DEFF Research Database (Denmark)
Zhou, Min
Analysis and optimization methods for the design of advanced printed re ectarrays have been investigated, and the study is focused on developing an accurate and efficient simulation tool. For the analysis, a good compromise between accuracy and efficiency can be obtained using the spectral domain...
A Boussinesq-type method for fully nonlinear waves interacting with a rapidly varying bathymetry
DEFF Research Database (Denmark)
Madsen, Per A.; Fuhrman, David R.; Wang, Benlong
2006-01-01
class II Bragg scattering from an undular sea bottom. The computations are verified against measurements, theoretical solutions and numerical models from the literature. Finally, we make a detailed investigation of nonlinear class III Bragg scattering and results are given for the sub-harmonic and super......-harmonic interactions with the sea bed. We provide a new explanation and a prediction of the resulting downshift/upshift of the peak reflection/transmission as a function of wave steepness. (C) 2005 Elsevier B.V. All rights reserved....
Universality: Accurate Checks in Dyson's Hierarchical Model
Godina, J. J.; Meurice, Y.; Oktay, M. B.
2003-06-01
In this talk we present high-accuracy calculations of the susceptibility near βc for Dyson's hierarchical model in D = 3. Using linear fitting, we estimate the leading (γ) and subleading (Δ) exponents. Independent estimates are obtained by calculating the first two eigenvalues of the linearized renormalization group transformation. We found γ = 1.29914073 ± 10 -8 and, Δ = 0.4259469 ± 10-7 independently of the choice of local integration measure (Ising or Landau-Ginzburg). After a suitable rescaling, the approximate fixed points for a large class of local measure coincide accurately with a fixed point constructed by Koch and Wittwer.
Accurate Electromagnetic Modeling Methods for Integrated Circuits
Sheng, Z.
2010-01-01
The present development of modern integrated circuits (IC’s) is characterized by a number of critical factors that make their design and verification considerably more difficult than before. This dissertation addresses the important questions of modeling all electromagnetic behavior of features on t
Przybylski, D; Cally, P S
2015-01-01
We present a technique to construct a spectropolarimetrically accurate magneto-hydrostatic model of a large-scale solar magnetic field concentration, mimicking a sunspot. Using the constructed model we perform a simulation of acoustic wave propagation, conversion and absorption in the solar interior and photosphere with the sunspot embedded into it. With the $6173\\mathrm{\\AA}$ magnetically sensitive photospheric absorption line of neutral iron, we calculate observable quantities such as continuum intensities, Doppler velocities, as well as full Stokes vector for the simulation at various positions at the solar disk, and analyse the influence of non-locality of radiative transport in the solar photosphere on helioseismic measurements. Bisector shapes were used to perform multi-height observations. The differences in acoustic power at different heights within the line formation region at different positions at the solar disk were simulated and characterised. An increase in acoustic power in the simulated observ...
A new, accurate predictive model for incident hypertension
DEFF Research Database (Denmark)
Völzke, Henry; Fung, Glenn; Ittermann, Till;
2013-01-01
Data mining represents an alternative approach to identify new predictors of multifactorial diseases. This work aimed at building an accurate predictive model for incident hypertension using data mining procedures....
Accurate Load Modeling Based on Analytic Hierarchy Process
Directory of Open Access Journals (Sweden)
Zhenshu Wang
2016-01-01
Full Text Available Establishing an accurate load model is a critical problem in power system modeling. That has significant meaning in power system digital simulation and dynamic security analysis. The synthesis load model (SLM considers the impact of power distribution network and compensation capacitor, while randomness of power load is more precisely described by traction power system load model (TPSLM. On the basis of these two load models, a load modeling method that combines synthesis load with traction power load is proposed in this paper. This method uses analytic hierarchy process (AHP to interact with two load models. Weight coefficients of two models can be calculated after formulating criteria and judgment matrixes and then establishing a synthesis model by weight coefficients. The effectiveness of the proposed method was examined through simulation. The results show that accurate load modeling based on AHP can effectively improve the accuracy of load model and prove the validity of this method.
An accurate RLGC circuit model for dual tapered TSV structure
International Nuclear Information System (INIS)
A fast RLGC circuit model with analytical expression is proposed for the dual tapered through-silicon via (TSV) structure in three-dimensional integrated circuits under different slope angles at the wide frequency region. By describing the electrical characteristics of the dual tapered TSV structure, the RLGC parameters are extracted based on the numerical integration method. The RLGC model includes metal resistance, metal inductance, substrate resistance, outer inductance with skin effect and eddy effect taken into account. The proposed analytical model is verified to be nearly as accurate as the Q3D extractor but more efficient. (semiconductor integrated circuits)
Bayesian calibration of power plant models for accurate performance prediction
International Nuclear Information System (INIS)
Highlights: • Bayesian calibration is applied to power plant performance prediction. • Measurements from a plant in operation are used for model calibration. • A gas turbine performance model and steam cycle model are calibrated. • An integrated plant model is derived. • Part load efficiency is accurately predicted as a function of ambient conditions. - Abstract: Gas turbine combined cycles are expected to play an increasingly important role in the balancing of supply and demand in future energy markets. Thermodynamic modeling of these energy systems is frequently applied to assist in decision making processes related to the management of plant operation and maintenance. In most cases, model inputs, parameters and outputs are treated as deterministic quantities and plant operators make decisions with limited or no regard of uncertainties. As the steady integration of wind and solar energy into the energy market induces extra uncertainties, part load operation and reliability are becoming increasingly important. In the current study, methods are proposed to not only quantify various types of uncertainties in measurements and plant model parameters using measured data, but to also assess their effect on various aspects of performance prediction. The authors aim to account for model parameter and measurement uncertainty, and for systematic discrepancy of models with respect to reality. For this purpose, the Bayesian calibration framework of Kennedy and O’Hagan is used, which is especially suitable for high-dimensional industrial problems. The article derives a calibrated model of the plant efficiency as a function of ambient conditions and operational parameters, which is also accurate in part load. The article shows that complete statistical modeling of power plants not only enhances process models, but can also increases confidence in operational decisions
More-Accurate Model of Flows in Rocket Injectors
Hosangadi, Ashvin; Chenoweth, James; Brinckman, Kevin; Dash, Sanford
2011-01-01
An improved computational model for simulating flows in liquid-propellant injectors in rocket engines has been developed. Models like this one are needed for predicting fluxes of heat in, and performances of, the engines. An important part of predicting performance is predicting fluctuations of temperature, fluctuations of concentrations of chemical species, and effects of turbulence on diffusion of heat and chemical species. Customarily, diffusion effects are represented by parameters known in the art as the Prandtl and Schmidt numbers. Prior formulations include ad hoc assumptions of constant values of these parameters, but these assumptions and, hence, the formulations, are inaccurate for complex flows. In the improved model, these parameters are neither constant nor specified in advance: instead, they are variables obtained as part of the solution. Consequently, this model represents the effects of turbulence on diffusion of heat and chemical species more accurately than prior formulations do, and may enable more-accurate prediction of mixing and flows of heat in rocket-engine combustion chambers. The model has been implemented within CRUNCH CFD, a proprietary computational fluid dynamics (CFD) computer program, and has been tested within that program. The model could also be implemented within other CFD programs.
On the importance of having accurate data for astrophysical modelling
Lique, Francois
2016-06-01
The Herschel telescope and the ALMA and NOEMA interferometers have opened new windows of observation for wavelengths ranging from far infrared to sub-millimeter with spatial and spectral resolutions previously unmatched. To make the most of these observations, an accurate knowledge of the physical and chemical processes occurring in the interstellar and circumstellar media is essential.In this presentation, I will discuss what are the current needs of astrophysics in terms of molecular data and I will show that accurate molecular data are crucial for the proper determination of the physical conditions in molecular clouds.First, I will focus on collisional excitation studies that are needed for molecular lines modelling beyond the Local Thermodynamic Equilibrium (LTE) approach. In particular, I will show how new collisional data for the HCN and HNC isomers, two tracers of star forming conditions, have allowed solving the problem of their respective abundance in cold molecular clouds. I will also present the last collisional data that have been computed in order to analyse new highly resolved observations provided by the ALMA interferometer.Then, I will present the calculation of accurate rate constants for the F+H2 → HF+H and Cl+H2 ↔ HCl+H reactions, which have allowed a more accurate determination of the physical conditions in diffuse molecular clouds. I will also present the recent work on the ortho-para-H2 conversion due to hydrogen exchange that allow more accurate determination of the ortho-to-para-H2 ratio in the universe and that imply a significant revision of the cooling mechanism in astrophysical media.
Accurate macroscale modelling of spatial dynamics in multiple dimensions
Roberts, A ~J; Bunder, J ~E
2011-01-01
Developments in dynamical systems theory provides new support for the macroscale modelling of pdes and other microscale systems such as Lattice Boltzmann, Monte Carlo or Molecular Dynamics simulators. By systematically resolving subgrid microscale dynamics the dynamical systems approach constructs accurate closures of macroscale discretisations of the microscale system. Here we specifically explore reaction-diffusion problems in two spatial dimensions as a prototype of generic systems in multiple dimensions. Our approach unifies into one the modelling of systems by a type of finite elements, and the `equation free' macroscale modelling of microscale simulators efficiently executing only on small patches of the spatial domain. Centre manifold theory ensures that a closed model exist on the macroscale grid, is emergent, and is systematically approximated. Dividing space either into overlapping finite elements or into spatially separated small patches, the specially crafted inter-element\\slash patch coupling als...
Simple Mathematical Models Do Not Accurately Predict Early SIV Dynamics
Directory of Open Access Journals (Sweden)
Cecilia Noecker
2015-03-01
Full Text Available Upon infection of a new host, human immunodeficiency virus (HIV replicates in the mucosal tissues and is generally undetectable in circulation for 1–2 weeks post-infection. Several interventions against HIV including vaccines and antiretroviral prophylaxis target virus replication at this earliest stage of infection. Mathematical models have been used to understand how HIV spreads from mucosal tissues systemically and what impact vaccination and/or antiretroviral prophylaxis has on viral eradication. Because predictions of such models have been rarely compared to experimental data, it remains unclear which processes included in these models are critical for predicting early HIV dynamics. Here we modified the “standard” mathematical model of HIV infection to include two populations of infected cells: cells that are actively producing the virus and cells that are transitioning into virus production mode. We evaluated the effects of several poorly known parameters on infection outcomes in this model and compared model predictions to experimental data on infection of non-human primates with variable doses of simian immunodifficiency virus (SIV. First, we found that the mode of virus production by infected cells (budding vs. bursting has a minimal impact on the early virus dynamics for a wide range of model parameters, as long as the parameters are constrained to provide the observed rate of SIV load increase in the blood of infected animals. Interestingly and in contrast with previous results, we found that the bursting mode of virus production generally results in a higher probability of viral extinction than the budding mode of virus production. Second, this mathematical model was not able to accurately describe the change in experimentally determined probability of host infection with increasing viral doses. Third and finally, the model was also unable to accurately explain the decline in the time to virus detection with increasing viral
Accurate Modeling of Buck Converters with Magnetic-Core Inductors
DEFF Research Database (Denmark)
Astorino, Antonio; Antonini, Giulio; Swaminathan, Madhavan
2015-01-01
In this paper, a modeling approach for buck converters with magnetic-core inductors is presented. Due to the high nonlinearity of magnetic materials, the frequency domain analysis of such circuits is not suitable for an accurate description of their behaviour. Hence, in this work, a timedomain...... model of buck converters with magnetic-core inductors in a SimulinkR environment is proposed. As an example, the presented approach is used to simulate an eight-phase buck converter. The simulation results show that an unexpected system behaviour in terms of current ripple amplitude needs the inductor core...
Accurate, low-cost 3D-models of gullies
Onnen, Nils; Gronz, Oliver; Ries, Johannes B.; Brings, Christine
2015-04-01
Soil erosion is a widespread problem in arid and semi-arid areas. The most severe form is the gully erosion. They often cut into agricultural farmland and can make a certain area completely unproductive. To understand the development and processes inside and around gullies, we calculated detailed 3D-models of gullies in the Souss Valley in South Morocco. Near Taroudant, we had four study areas with five gullies different in size, volume and activity. By using a Canon HF G30 Camcorder, we made varying series of Full HD videos with 25fps. Afterwards, we used the method Structure from Motion (SfM) to create the models. To generate accurate models maintaining feasible runtimes, it is necessary to select around 1500-1700 images from the video, while the overlap of neighboring images should be at least 80%. In addition, it is very important to avoid selecting photos that are blurry or out of focus. Nearby pixels of a blurry image tend to have similar color values. That is why we used a MATLAB script to compare the derivatives of the images. The higher the sum of the derivative, the sharper an image of similar objects. MATLAB subdivides the video into image intervals. From each interval, the image with the highest sum is selected. E.g.: 20min. video at 25fps equals 30.000 single images. The program now inspects the first 20 images, saves the sharpest and moves on to the next 20 images etc. Using this algorithm, we selected 1500 images for our modeling. With VisualSFM, we calculated features and the matches between all images and produced a point cloud. Then, MeshLab has been used to build a surface out of it using the Poisson surface reconstruction approach. Afterwards we are able to calculate the size and the volume of the gullies. It is also possible to determine soil erosion rates, if we compare the data with old recordings. The final step would be the combination of the terrestrial data with the data from our aerial photography. So far, the method works well and we
An accurate and simple quantum model for liquid water.
Paesani, Francesco; Zhang, Wei; Case, David A; Cheatham, Thomas E; Voth, Gregory A
2006-11-14
The path-integral molecular dynamics and centroid molecular dynamics methods have been applied to investigate the behavior of liquid water at ambient conditions starting from a recently developed simple point charge/flexible (SPC/Fw) model. Several quantum structural, thermodynamic, and dynamical properties have been computed and compared to the corresponding classical values, as well as to the available experimental data. The path-integral molecular dynamics simulations show that the inclusion of quantum effects results in a less structured liquid with a reduced amount of hydrogen bonding in comparison to its classical analog. The nuclear quantization also leads to a smaller dielectric constant and a larger diffusion coefficient relative to the corresponding classical values. Collective and single molecule time correlation functions show a faster decay than their classical counterparts. Good agreement with the experimental measurements in the low-frequency region is obtained for the quantum infrared spectrum, which also shows a higher intensity and a redshift relative to its classical analog. A modification of the original parametrization of the SPC/Fw model is suggested and tested in order to construct an accurate quantum model, called q-SPC/Fw, for liquid water. The quantum results for several thermodynamic and dynamical properties computed with the new model are shown to be in a significantly better agreement with the experimental data. Finally, a force-matching approach was applied to the q-SPC/Fw model to derive an effective quantum force field for liquid water in which the effects due to the nuclear quantization are explicitly distinguished from those due to the underlying molecular interactions. Thermodynamic and dynamical properties computed using standard classical simulations with this effective quantum potential are found in excellent agreement with those obtained from significantly more computationally demanding full centroid molecular dynamics
Accurate energy model for WSN node and its optimal design
Institute of Scientific and Technical Information of China (English)
Kan Baoqiang; Cai Li; Zhu Hongsong; Xu Yongjun
2008-01-01
With the development of CMOS and MEMS technologies, the implementation of a large number of wireless distributed micro-sensors that can be easily and rapidly deployed to form highly redundant, self-configuring, and ad hoc sensor networks. To facilitate ease of deployment, these sensors operate on battery for extended periods of time. A particular challenge in maintaining extended battery lifetime lies in achieving communications with low power. For better understanding of the design tradeoffs of wireless sensor network (WSN), a more accurate energy model for wireless sensor node is proposed, and an optimal design method of energy efficient wireless sensor node is described as well. Different from power models ever shown which assume the power cost of each component in WSN node is constant, the new one takes into account the energy dissipation of circuits in practical physical layer. It shows that there are some parameters, such as data rate, carrier frequency, bandwidth, Tsw, etc, which have a significant effect on the WSN node energy consumption per useful bit (EPUB). For a given quality specification, how energy consumption can be reduced by adjusting one or more of these parameters is shown.
Embedded wave generation for dispersive surface wave models
She Liam, L.; Adytia, D.; Groesen, van E.
2014-01-01
This paper generalizes previous research on embedded wave generation in Boussinesq-type of equations for multi-directional surface water waves; the generation takes place by adding a suitable source term to the equations. Accurate generation is important to prevent influx errors in simulated waves d
An accurate and simple large signal model of HEMT
DEFF Research Database (Denmark)
Liu, Qing
1989-01-01
A large-signal model of discrete HEMTs (high-electron-mobility transistors) has been developed. It is simple and suitable for SPICE simulation of hybrid digital ICs. The model parameters are extracted by using computer programs and data provided by the manufacturer. Based on this model, a hybrid...
Coupling Efforts to the Accurate and Efficient Tsunami Modelling System
Son, S.
2015-12-01
In the present study, we couple two different types of tsunami models, i.e., nondispersive shallow water model of characteristic form(MOST ver.4) and dispersive Boussinesq model of non-characteristic form(Son et al. (2011)) in an attempt to improve modelling accuracy and efficiency. Since each model deals with different type of primary variables, additional care on matching boundary condition is required. Using an absorbing-generating boundary condition developed by Van Dongeren and Svendsen(1997), model coupling and integration is achieved. Characteristic variables(i.e., Riemann invariants) in MOST are converted to non-characteristic variables for Boussinesq solver without any loss of physical consistency. Established modelling system has been validated through typical test problems to realistic tsunami events. Simulated results reveal good performance of developed modelling system. Since coupled modelling system provides advantageous flexibility feature during implementation, great efficiencies and accuracies are expected to be gained through spot-focusing application of Boussinesq model inside the entire domain of tsunami propagation.
A Simple and Accurate Closed-Form EGN Model Formula
Poggiolini, P; Carena, A; Forghieri, F
2015-01-01
The GN model of non-linear fiber propagation has been shown to overestimate the variance of non-linearity due to the signal Gaussianity approximation, leading to maximum reach predictions for typical optical systems which may be pessimistic by about 5% to 15%, depending on fiber type and system set-up. Various models have been proposed which improve over the GN model accuracy. One of them is the EGN model, which completely removes the Gaussianity approximation from all non-linear interference (NLI) components. The EGN model is, however, substantially more complex than the GN model. Recently, we proposed a simple closed-form formula which permits to approximate the EGN model, starting from the GN. It was however limited to all-identical, equispaced channels, and did not correct single-channel NLI (also called SCI). In this follow-up contribution, we propose an improved version which both allows to address non-identical channels and corrects the SCI contribution as well. Extensive simulative testing shows the n...
A more accurate model of wetting transitions with liquid helium
International Nuclear Information System (INIS)
Up to now the analysis of the liquid helium prewetting line on alkali metal substrates have been made using the simple model proposed by Saam et al. Some improvements on this model are considered within a mean field, sharp kink model. The temperature variations of the substrate-liquid interface energy and that of the liquid density are considered, as well as a more realistic effective potential for the film-substrate interaction. A comparison is made with the experimental data on rubidium and cesium
Visual texture accurate material appearance measurement, representation and modeling
Haindl, Michal
2013-01-01
This book surveys the state of the art in multidimensional, physically-correct visual texture modeling. Features: reviews the entire process of texture synthesis, including material appearance representation, measurement, analysis, compression, modeling, editing, visualization, and perceptual evaluation; explains the derivation of the most common representations of visual texture, discussing their properties, advantages, and limitations; describes a range of techniques for the measurement of visual texture, including BRDF, SVBRDF, BTF and BSSRDF; investigates the visualization of textural info
Accurate wind farm development and operation. Advanced wake modelling
Energy Technology Data Exchange (ETDEWEB)
Brand, A.; Bot, E.; Ozdemir, H. [ECN Unit Wind Energy, P.O. Box 1, NL 1755 ZG Petten (Netherlands); Steinfeld, G.; Drueke, S.; Schmidt, M. [ForWind, Center for Wind Energy Research, Carl von Ossietzky Universitaet Oldenburg, D-26129 Oldenburg (Germany); Mittelmeier, N. REpower Systems SE, D-22297 Hamburg (Germany))
2013-11-15
The ability is demonstrated to calculate wind farm wakes on the basis of ambient conditions that were calculated with an atmospheric model. Specifically, comparisons are described between predicted and observed ambient conditions, and between power predictions from three wind farm wake models and power measurements, for a single and a double wake situation. The comparisons are based on performance indicators and test criteria, with the objective to determine the percentage of predictions that fall within a given range about the observed value. The Alpha Ventus site is considered, which consists of a wind farm with the same name and the met mast FINO1. Data from the 6 REpower wind turbines and the FINO1 met mast were employed. The atmospheric model WRF predicted the ambient conditions at the location and the measurement heights of the FINO1 mast. May the predictability of the wind speed and the wind direction be reasonable if sufficiently sized tolerances are employed, it is fairly impossible to predict the ambient turbulence intensity and vertical shear. Three wind farm wake models predicted the individual turbine powers: FLaP-Jensen and FLaP-Ainslie from ForWind Oldenburg, and FarmFlow from ECN. The reliabilities of the FLaP-Ainslie and the FarmFlow wind farm wake models are of equal order, and higher than FLaP-Jensen. Any difference between the predictions from these models is most clear in the double wake situation. Here FarmFlow slightly outperforms FLaP-Ainslie.
Mead, Alexander; Heymans, Catherine; Joudaki, Shahab; Heavens, Alan
2015-01-01
We present an optimised variant of the halo model, designed to produce accurate matter power spectra well into the non-linear regime for a wide range of cosmological models. To do this, we introduce physically-motivated free parameters into the halo-model formalism and fit these to data from high-resolution N-body simulations. For a variety of $\\Lambda$CDM and $w$CDM models the halo-model power is accurate to $\\simeq 5$ per cent for $k\\leq 10h\\,\\mathrm{Mpc}^{-1}$ and $z\\leq 2$. We compare our results with recent revisions of the popular HALOFIT model and show that our predictions are more accurate. An advantage of our new halo model is that it can be adapted to account for the effects of baryonic feedback on the power spectrum. We demonstrate this by fitting the halo model to power spectra from the OWLS hydrodynamical simulation suite via parameters that govern halo internal structure. We are able to fit all feedback models investigated at the 5 per cent level using only two free parameters, and we place limi...
Accurate modelling of flow induced stresses in rigid colloidal aggregates
Vanni, Marco
2015-07-01
A method has been developed to estimate the motion and the internal stresses induced by a fluid flow on a rigid aggregate. The approach couples Stokesian dynamics and structural mechanics in order to take into account accurately the effect of the complex geometry of the aggregates on hydrodynamic forces and the internal redistribution of stresses. The intrinsic error of the method, due to the low-order truncation of the multipole expansion of the Stokes solution, has been assessed by comparison with the analytical solution for the case of a doublet in a shear flow. In addition, it has been shown that the error becomes smaller as the number of primary particles in the aggregate increases and hence it is expected to be negligible for realistic reproductions of large aggregates. The evaluation of internal forces is performed by an adaptation of the matrix methods of structural mechanics to the geometric features of the aggregates and to the particular stress-strain relationship that occurs at intermonomer contacts. A preliminary investigation on the stress distribution in rigid aggregates and their mode of breakup has been performed by studying the response to an elongational flow of both realistic reproductions of colloidal aggregates (made of several hundreds monomers) and highly simplified structures. A very different behaviour has been evidenced between low-density aggregates with isostatic or weakly hyperstatic structures and compact aggregates with highly hyperstatic configuration. In low-density clusters breakup is caused directly by the failure of the most stressed intermonomer contact, which is typically located in the inner region of the aggregate and hence originates the birth of fragments of similar size. On the contrary, breakup of compact and highly cross-linked clusters is seldom caused by the failure of a single bond. When this happens, it proceeds through the removal of a tiny fragment from the external part of the structure. More commonly, however
Simulation model accurately estimates total dietary iodine intake
Verkaik-Kloosterman, J.; Veer, van 't P.; Ocke, M.C.
2009-01-01
One problem with estimating iodine intake is the lack of detailed data about the discretionary use of iodized kitchen salt and iodization of industrially processed foods. To be able to take into account these uncertainties in estimating iodine intake, a simulation model combining deterministic and p
Compact and Accurate Turbocharger Modelling for Engine Control
DEFF Research Database (Denmark)
Sorenson, Spencer C; Hendricks, Elbert; Magnússon, Sigurjón;
2005-01-01
With the current trend towards engine downsizing, the use of turbochargers to obtain extra engine power has become common. A great díffuculty in the use of turbochargers is in the modelling of the compressor map. In general this is done by inserting the compressor map directly into the engine ECU...
Double Layered Sheath in Accurate HV XLPE Cable Modeling
DEFF Research Database (Denmark)
Gudmundsdottir, Unnur Stella; Silva, J. De; Bak, Claus Leth;
2010-01-01
This paper discusses modelling of high voltage AC underground cables. For long cables, when crossbonding points are present, not only the coaxial mode of propagation is excited during transient phenomena, but also the intersheath mode. This causes inaccurate simulation results for high frequency...... studies of crossbonded cables. For the intersheath mode, the correct physical representation of the cables sheath as well as proximity affect play a large role and will ensure correct calculations of the series impedance matrix and therefore a correct simulation for the actual cable. This paper gives...... a new, more correct method for modelling the actual physical layout of the sheath. It is shown by comparison to field measurements how the new method of simulating the cable's sheath results in simulations with less deviation from field test results....
Simulation model accurately estimates total dietary iodine intake.
Verkaik-Kloosterman, Janneke; van 't Veer, Pieter; Ocké, Marga C
2009-07-01
One problem with estimating iodine intake is the lack of detailed data about the discretionary use of iodized kitchen salt and iodization of industrially processed foods. To be able to take into account these uncertainties in estimating iodine intake, a simulation model combining deterministic and probabilistic techniques was developed. Data from the Dutch National Food Consumption Survey (1997-1998) and an update of the Food Composition database were used to simulate 3 different scenarios: Dutch iodine legislation until July 2008, Dutch iodine legislation after July 2008, and a potential future situation. Results from studies measuring iodine excretion during the former legislation are comparable with the iodine intakes estimated with our model. For both former and current legislation, iodine intake was adequate for a large part of the Dutch population, but some young children (iodine levels, the percentage of the Dutch population with intakes that were too low increased (almost 10% of young children). To keep iodine intakes adequate, salt iodine levels should not be decreased, unless many more foods will contain iodized salt. Our model should be useful in predicting the effects of food reformulation or fortification on habitual nutrient intakes.
Accurate numerical solutions for elastic-plastic models
International Nuclear Information System (INIS)
The accuracy of two integration algorithms is studied for the common engineering condition of a von Mises, isotropic hardening model under plane stress. Errors in stress predictions for given total strain increments are expressed with contour plots of two parameters: an angle in the pi plane and the difference between the exact and computed yield-surface radii. The two methods are the tangent-predictor/radial-return approach and the elastic-predictor/radial-corrector algorithm originally developed by Mendelson. The accuracy of a combined tangent-predictor/radial-corrector algorithm is also investigated
Mead, A. J.; Peacock, J. A.; Heymans, C.; Joudaki, S.; Heavens, A. F.
2015-12-01
We present an optimized variant of the halo model, designed to produce accurate matter power spectra well into the non-linear regime for a wide range of cosmological models. To do this, we introduce physically motivated free parameters into the halo-model formalism and fit these to data from high-resolution N-body simulations. For a variety of Λ cold dark matter (ΛCDM) and wCDM models, the halo-model power is accurate to ≃ 5 per cent for k ≤ 10h Mpc-1 and z ≤ 2. An advantage of our new halo model is that it can be adapted to account for the effects of baryonic feedback on the power spectrum. We demonstrate this by fitting the halo model to power spectra from the OWLS (OverWhelmingly Large Simulations) hydrodynamical simulation suite via parameters that govern halo internal structure. We are able to fit all feedback models investigated at the 5 per cent level using only two free parameters, and we place limits on the range of these halo parameters for feedback models investigated by the OWLS simulations. Accurate predictions to high k are vital for weak-lensing surveys, and these halo parameters could be considered nuisance parameters to marginalize over in future analyses to mitigate uncertainty regarding the details of feedback. Finally, we investigate how lensing observables predicted by our model compare to those from simulations and from HALOFIT for a range of k-cuts and feedback models and quantify the angular scales at which these effects become important. Code to calculate power spectra from the model presented in this paper can be found at https://github.com/alexander-mead/hmcode.
Modelling of nonlinear shoaling based on stochastic evolution equations
DEFF Research Database (Denmark)
Kofoed-Hansen, Henrik; Rasmussen, Jørgen Hvenekær
1998-01-01
A one-dimensional stochastic model is derived to simulate the transformation of wave spectra in shallow water including generation of bound sub- and super-harmonics, near-resonant triad wave interaction and wave breaking. Boussinesq type equations with improved linear dispersion characteristics a...
Study on Solitary Waves of a General Boussinesq Model
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In this paper, we employ the bifurcation method of dynamical systems to study the solitary waves and periodic waves of a generalized Boussinesq equations. All possible phase portraits in the parameter plane for the travelling wave systems are obtained. The possible solitary wave solutions, periodic wave solutions and cusp waves for the general Boussinesq type fluid model are also investigated.
Accurate mask model implementation in OPC model for 14nm nodes and beyond
Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Farys, Vincent; Huguennet, Frederic; Armeanu, Ana-Maria; Bork, Ingo; Chomat, Michael; Buck, Peter; Schanen, Isabelle
2015-10-01
In a previous work [1] we demonstrated that current OPC model assuming the mask pattern to be analogous to the designed data is no longer valid. Indeed as depicted in figure 1, an extreme case of line-end shortening shows a gap up to 10 nm difference (at mask level). For that reason an accurate mask model, for a 14nm logic gate level has been calibrated. A model with a total RMS of 1.38nm at mask level was obtained. 2D structures such as line-end shortening and corner rounding were well predicted using SEM pictures overlaid with simulated contours. The first part of this paper is dedicated to the implementation of our improved model in current flow. The improved model consists of a mask model capturing mask process and writing effects and a standard optical and resist model addressing the litho exposure and development effects at wafer level. The second part will focus on results from the comparison of the two models, the new and the regular, as depicted in figure 2.
Accurate mask model implementation in optical proximity correction model for 14-nm nodes and beyond
Zine El Abidine, Nacer; Sundermann, Frank; Yesilada, Emek; Farys, Vincent; Huguennet, Frederic; Armeanu, Ana-Maria; Bork, Ingo; Chomat, Michael; Buck, Peter; Schanen, Isabelle
2016-04-01
In a previous work, we demonstrated that the current optical proximity correction model assuming the mask pattern to be analogous to the designed data is no longer valid. An extreme case of line-end shortening shows a gap up to 10 nm difference (at mask level). For that reason, an accurate mask model has been calibrated for a 14-nm logic gate level. A model with a total RMS of 1.38 nm at mask level was obtained. Two-dimensional structures, such as line-end shortening and corner rounding, were well predicted using scanning electron microscopy pictures overlaid with simulated contours. The first part of this paper is dedicated to the implementation of our improved model in current flow. The improved model consists of a mask model capturing mask process and writing effects, and a standard optical and resist model addressing the litho exposure and development effects at wafer level. The second part will focus on results from the comparison of the two models, the new and the regular.
The next step in coastal numerical models: spectral/hp element methods?
DEFF Research Database (Denmark)
Eskilsson, Claes; Engsig-Karup, Allan Peter; Sherwin, Spencer J.;
2005-01-01
In this paper we outline the application of spectral/hp element methods for modelling nonlinear and dispersive waves. We present one- and two-dimensional test cases for the shallow water equations and Boussinesqtype equations – including highly dispersive Boussinesq-type equations....
Energy Technology Data Exchange (ETDEWEB)
Leng, Wei [Chinese Academy of Sciences; Ju, Lili [University of South Carolina; Gunzburger, Max [Florida State University; Price, Stephen [Los Alamos National Laboratory; Ringler, Todd [Los Alamos National Laboratory,
2012-01-01
The numerical modeling of glacier and ice sheet evolution is a subject of growing interest, in part because of the potential for models to inform estimates of global sea level change. This paper focuses on the development of a numerical model that determines the velocity and pressure fields within an ice sheet. Our numerical model features a high-fidelity mathematical model involving the nonlinear Stokes system and combinations of no-sliding and sliding basal boundary conditions, high-order accurate finite element discretizations based on variable resolution grids, and highly scalable parallel solution strategies, all of which contribute to a numerical model that can achieve accurate velocity and pressure approximations in a highly efficient manner. We demonstrate the accuracy and efficiency of our model by analytical solution tests, established ice sheet benchmark experiments, and comparisons with other well-established ice sheet models.
Energy Technology Data Exchange (ETDEWEB)
Blank, Frederic; Roth-Stielow, Joerg [Stuttgart Univ. (Germany). Inst. fuer Leistungselektronik und Elektrische Antriebe
2011-07-01
For the evaluation of the energy efficiency of electrical drive systems in start-stop operations, the amount of energy per cycle is used. This variable of comparison ''energy'' is determined by simulating the whole drive system with special simulation models. These models have to be energy-accurate in order to implement the significant losses. Two simulation models are presented, which were optimized for these simulations: models of a permanent synchronous motor and a frequency inverter. The models are parameterized with measurements and the calculations are verified. Using these models, motion cycles can be simulated and the necessary energy per cycle can be determined. (orig.)
Development of an accurate cavitation coupled spray model for diesel engine simulation
International Nuclear Information System (INIS)
Highlights: • A new hybrid spray model was implemented into KIVA4 CFD code. • Cavitation sub model was coupled with classic KHRT model. • New model predicts better than classical spray models. • New model predicts spray and combustion characteristics with accuracy. - Abstract: The combustion process in diesel engines is essentially controlled by the dynamics of the fuel spray. Thus accurate modeling of spray process is vital to accurately model the combustion process in diesel engines. In this work, a new hybrid spray model was developed by coupling the cavitation induced spray sub model to KHRT spray model. This new model was implemented into KIVA4 CFD code. The new developed spray model was extensively validated against the experimental data of non-vaporizing and vaporizing spray obtained from constant volume combustion chamber (CVCC) available in literature. The results were compared on the basis of liquid length, spray penetration and spray images. The model was also validated against the engine combustion characteristics data like in-cylinder pressure and heat release rate. The new spray model very well captures both spray characteristics and combustion characteristics
Efficient and Accurate Log-Levy Approximations of Levy-Driven LIBOR Models
DEFF Research Database (Denmark)
Papapantoleon, Antonis; Schoenmakers, John; Skovmand, David
2012-01-01
-driven LIBOR model and aim to develop accurate and efficient log-Lévy approximations for the dynamics of the rates. The approximations are based on the truncation of the drift term and on Picard approximation of suitable processes. Numerical experiments for forward-rate agreements, caps, swaptions and sticky...
In-situ measurements of material thermal parameters for accurate LED lamp thermal modelling
Vellvehi, M.; Perpina, X.; Jorda, X.; Werkhoven, R.J.; Kunen, J.M.G.; Jakovenko, J.; Bancken, P.; Bolt, P.J.
2013-01-01
This work deals with the extraction of key thermal parameters for accurate thermal modelling of LED lamps: air exchange coefficient around the lamp, emissivity and thermal conductivity of all lamp parts. As a case study, an 8W retrofit lamp is presented. To assess simulation results, temperature is
Utilizing anisotropic Preisach-type models in the accurate simulation of magnetostriction
Energy Technology Data Exchange (ETDEWEB)
Adly, A.A. [Cairo Univ., Giza (Egypt). Electrical Power and Machines Dept.; Mayergoyz, I.D. [Univ. of Maryland, College Park, MD (United States). Electrical Engineering Dept.; Bergqvist, A. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Electrical Power Engineering
1997-09-01
Magnetostriction models are being widely used in the development of fine positioning and active vibration damping devices. This paper presents a new approach for simulating 1-D magnetostriction using 2-D anisotropic Preisach-type models. In this approach, identification of the model takes into account measured flux density versus field and strain versus field curves for different stress values. Consequently, a more accurate magnetostriction model may be obtained. Details of the identification procedure as well as experimental testing of the proposed model are given.
Accurate Modeling of the Spiral Bevel and Hypoid Gear with a New Tooth Profile
Institute of Scientific and Technical Information of China (English)
LI Yun-song; ADAYI Xieeryazidan; DING Han
2014-01-01
Distinguishing with traditional tooth profile of spiral bevel and hypoid gear, it proposed a new tooth profile namely the spherical involute. Firstly, a new theory of forming the spherical involute tooth profile was proposed. Then, this theory was applied to complete parametric derivation of each part of its tooth profile. For enhancing the precision, the SWEEP method used for formation of each part of tooth surface and G1 stitching schema for obtaining a unified tooth surface are put forward and made the application in the accurate modeling. Lastly, owing to the higher accuracy of tooth surface of outputted model, it gave some optimization approaches. Given numerical example about the model can show that this designed gear with spherical involute tooth profile can achieve fast and accurate parametric modeling and provide a foundation for tooth contact analysis (TCA) in digitized design and manufacture.
Institute of Scientific and Technical Information of China (English)
Tomosato Takada; Kazuo Kashiyama
2008-01-01
This paper presents an urban modeling system using CAD/GIS data for atmosphere environ- mental simulation, such as wind flow and contaminant spread in urban area. The CAD data is used for the shape modeling for the high-storied buildings and civil structures with complicated shape since the data for that is not included in the 3D-GIS data accurately. The unstructured mesh based on the tetrahedron element is employed in order to express the urban structures with complicated shape accurately. It is difficult to un- derstand the quality of shape model and mesh by the conventional visualization technique. In this paper, the stereoscopic visualization using virtual reality (VR) technology is employed for the vedfication of the quality of shape model and mesh. The present system is applied to the atmosphere environmental simulation in ur- ban area and is shown to be an useful planning and design tool to investigate the atmosphere environmental problem.
A Method to Build a Super Small but Practically Accurate Language Model for Handheld Devices
Institute of Scientific and Technical Information of China (English)
WU GenQing (吴根清); ZHENG Fang (郑方)
2003-01-01
In this paper, an important question, whether a small language model can be practically accurate enough, is raised. Afterwards, the purpose of a language model, the problems that a language model faces, and the factors that affect the performance of a language model,are analyzed. Finally, a novel method for language model compression is proposed, which makes the large language model usable for applications in handheld devices, such as mobiles, smart phones, personal digital assistants (PDAs), and handheld personal computers (HPCs). In the proposed language model compression method, three aspects are included. First, the language model parameters are analyzed and a criterion based on the importance measure of n-grams is used to determine which n-grams should be kept and which removed. Second, a piecewise linear warping method is proposed to be used to compress the uni-gram count values in the full language model. And third, a rank-based quantization method is adopted to quantize the bi-gram probability values. Experiments show that by using this compression method the language model can be reduced dramatically to only about 1M bytes while the performance almost does not decrease. This provides good evidence that a language model compressed by means of a well-designed compression technique is practically accurate enough, and it makes the language model usable in handheld devices.
Automated Image-Based Procedures for Accurate Artifacts 3D Modeling and Orthoimage Generation
Directory of Open Access Journals (Sweden)
Marc Pierrot-Deseilligny
2011-12-01
Full Text Available The accurate 3D documentation of architectures and heritages is getting very common and required in different application contexts. The potentialities of the image-based approach are nowadays very well-known but there is a lack of reliable, precise and flexible solutions, possibly open-source, which could be used for metric and accurate documentation or digital conservation and not only for simple visualization or web-based applications. The article presents a set of photogrammetric tools developed in order to derive accurate 3D point clouds and orthoimages for the digitization of archaeological and architectural objects. The aim is also to distribute free solutions (software, methodologies, guidelines, best practices, etc. based on 3D surveying and modeling experiences, useful in different application contexts (architecture, excavations, museum collections, heritage documentation, etc. and according to several representations needs (2D technical documentation, 3D reconstruction, web visualization, etc..
Applying an accurate spherical model to gamma-ray burst afterglow observations
Leventis, Konstantinos; van Eerten, Hendrik J; Wijers, Ralph A M J
2013-01-01
We present results of model fits to afterglow data sets of GRB970508, GRB980703 and GRB070125, characterized by long and broadband coverage. The model assumes synchrotron radiation (including self-absorption) from a spherical adiabatic blast wave and consists of analytic flux prescriptions based on numerical results. For the first time it combines the accuracy of hydrodynamic simulations through different stages of the outflow dynamics with the flexibility of simple heuristic formulas. The prescriptions are especially geared towards accurate description of the dynamical transition of the outflow from relativistic to Newtonian velocities in an arbitrary power-law density environment. We show that the spherical model can accurately describe the data only in the case of GRB970508, for which we find a circumburst medium density consistent with a stellar wind. We investigate in detail the implied spectra and physical parameters of that burst. For the microphysics we show evidence for equipartition between the frac...
The accurate and comprehensive model of thin fluid flows with inertia on curved substrates
Roberts, A J; Li, Zhenquan
1999-01-01
Consider the 3D flow of a viscous Newtonian fluid upon a curved 2D substrate when the fluid film is thin as occurs in many draining, coating and biological flows. We derive a comprehensive model of the dynamics of the film, the model being expressed in terms of the film thickness and the average lateral velocity. Based upon centre manifold theory, we are assured that the model accurately includes the effects of the curvature of substrate, gravitational body force, fluid inertia and dissipatio...
Impact of an accurate modeling of primordial chemistry in high resolution studies
Bovino, S; Latif, M A; Schleicher, D R G
2013-01-01
The formation of the first stars in the Universe is regulated by a sensitive interplay of chemistry and cooling with the dynamics of a self-gravitating system. As the outcome of the collapse and the final stellar masses depend sensitively on the thermal evolution, it is necessary to accurately model the thermal evolution in high resolution simulations. As previous investigations raised doubts regarding the convergence of the temperature at high resolution, we investigate the role of the numerical method employed to model the chemistry and the thermodynamics. Here we compare the standard implementation in the adaptive-mesh refinement code \\verb|ENZO|, employing a first order backward differentiation formula (BDF), with the 5th order accurate BDF solver \\verb|DLSODES|. While the standard implementation in \\verb|ENZO| shows a strong dependence on the employed resolution, the results obtained with \\verb|DLSODES| are considerably more robust, both with respect to the chemistry and thermodynamics, but also for dyna...
Energy Technology Data Exchange (ETDEWEB)
Seth A Veitzer
2008-10-21
Effects of stray electrons are a main factor limiting performance of many accelerators. Because heavy-ion fusion (HIF) accelerators will operate in regimes of higher current and with walls much closer to the beam than accelerators operating today, stray electrons might have a large, detrimental effect on the performance of an HIF accelerator. A primary source of stray electrons is electrons generated when halo ions strike the beam pipe walls. There is some research on these types of secondary electrons for the HIF community to draw upon, but this work is missing one crucial ingredient: the effect of grazing incidence. The overall goal of this project was to develop the numerical tools necessary to accurately model the effect of grazing incidence on the behavior of halo ions in a HIF accelerator, and further, to provide accurate models of heavy ion stopping powers with applications to ICF, WDM, and HEDP experiments.
Qingwen Li; Lan Qiao; Gautam Dasgupta; Siwei Ma; Liping Wang; Jianghui Dong
2015-01-01
In the tunnel and underground space engineering, the blasting wave will attenuate from shock wave to stress wave to elastic seismic wave in the host rock. Also, the host rock will form crushed zone, fractured zone, and elastic seismic zone under the blasting loading and waves. In this paper, an accurate mathematical dynamic loading model was built. And the crushed zone as well as fractured zone was considered as the blasting vi...
Oksel, Ceyda; Winkler, David A; Ma, Cai Y; Wilkins, Terry; Wang, Xue Z
2016-09-01
The number of engineered nanomaterials (ENMs) being exploited commercially is growing rapidly, due to the novel properties they exhibit. Clearly, it is important to understand and minimize any risks to health or the environment posed by the presence of ENMs. Data-driven models that decode the relationships between the biological activities of ENMs and their physicochemical characteristics provide an attractive means of maximizing the value of scarce and expensive experimental data. Although such structure-activity relationship (SAR) methods have become very useful tools for modelling nanotoxicity endpoints (nanoSAR), they have limited robustness and predictivity and, most importantly, interpretation of the models they generate is often very difficult. New computational modelling tools or new ways of using existing tools are required to model the relatively sparse and sometimes lower quality data on the biological effects of ENMs. The most commonly used SAR modelling methods work best with large datasets, are not particularly good at feature selection, can be relatively opaque to interpretation, and may not account for nonlinearity in the structure-property relationships. To overcome these limitations, we describe the application of a novel algorithm, a genetic programming-based decision tree construction tool (GPTree) to nanoSAR modelling. We demonstrate the use of GPTree in the construction of accurate and interpretable nanoSAR models by applying it to four diverse literature datasets. We describe the algorithm and compare model results across the four studies. We show that GPTree generates models with accuracies equivalent to or superior to those of prior modelling studies on the same datasets. GPTree is a robust, automatic method for generation of accurate nanoSAR models with important advantages that it works with small datasets, automatically selects descriptors, and provides significantly improved interpretability of models. PMID:26956430
A rapid and accurate two-point ray tracing method in horizontally layered velocity model
Institute of Scientific and Technical Information of China (English)
TIAN Yue; CHEN Xiao-fei
2005-01-01
A rapid and accurate method for two-point ray tracing in horizontally layered velocity model is presented in this paper. Numerical experiments show that this method provides stable and rapid convergence with high accuracies, regardless of various 1-D velocity structures, takeoff angles and epicentral distances. This two-point ray tracing method is compared with the pseudobending technique and the method advanced by Kim and Baag (2002). It turns out that the method in this paper is much more efficient and accurate than the pseudobending technique, but is only applicable to 1-D velocity model. Kim(s method is equivalent to ours for cases without large takeoff angles, but it fails to work when the takeoff angle is close to 90o. On the other hand, the method presented in this paper is applicable to cases with any takeoff angles with rapid and accurate convergence. Therefore, this method is a good choice for two-point ray tracing problems in horizontally layered velocity model and is efficient enough to be applied to a wide range of seismic problems.
Blackman, Jonathan; Galley, Chad R; Szilagyi, Bela; Scheel, Mark A; Tiglio, Manuel; Hemberger, Daniel A
2015-01-01
Simulating a binary black hole coalescence by solving Einstein's equations is computationally expensive, requiring days to months of supercomputing time. In this paper, we construct an accurate and fast-to-evaluate surrogate model for numerical relativity (NR) waveforms from non-spinning binary black hole coalescences with mass ratios from $1$ to $10$ and durations corresponding to about $15$ orbits before merger. Our surrogate, which is built using reduced order modeling techniques, is distinct from traditional modeling efforts. We find that the full multi-mode surrogate model agrees with waveforms generated by NR to within the numerical error of the NR code. In particular, we show that our modeling strategy produces surrogates which can correctly predict NR waveforms that were {\\em not} used for the surrogate's training. For all practical purposes, then, the surrogate waveform model is equivalent to the high-accuracy, large-scale simulation waveform but can be evaluated in a millisecond to a second dependin...
Accurate Analytic Results for the Steady State Distribution of the Eigen Model
Huang, Guan-Rong; Saakian, David B.; Hu, Chin-Kun
2016-04-01
Eigen model of molecular evolution is popular in studying complex biological and biomedical systems. Using the Hamilton-Jacobi equation method, we have calculated analytic equations for the steady state distribution of the Eigen model with a relative accuracy of O(1/N), where N is the length of genome. Our results can be applied for the case of small genome length N, as well as the cases where the direct numerics can not give accurate result, e.g., the tail of distribution.
DEFF Research Database (Denmark)
Blurton, Steven Paul; Kesselmeier, M.; Gondan, Matthias
2012-01-01
We propose an improved method for calculating the cumulative first-passage time distribution in Wiener diffusion models with two absorbing barriers. This distribution function is frequently used to describe responses and error probabilities in choice reaction time tasks. The present work extends...... related work on the density of first-passage times [Navarro, D.J., Fuss, I.G. (2009). Fast and accurate calculations for first-passage times in Wiener diffusion models. Journal of Mathematical Psychology, 53, 222-230]. Two representations exist for the distribution, both including infinite series. We...
Directory of Open Access Journals (Sweden)
Marco Paggi
2015-01-01
Full Text Available The thermoviscoelastic rheological properties of ethylene vinyl acetate (EVA used to embed solar cells have to be accurately described to assess the deformation and the stress state of photovoltaic (PV modules and their durability. In the present work, considering the stress as dependent on a noninteger derivative of the strain, a two-parameter model is proposed to approximate the power-law relation between the relaxation modulus and time for a given temperature level. Experimental validation with EVA uniaxial relaxation data at different constant temperatures proves the great advantage of the proposed approach over classical rheological models based on exponential solutions.
Mead, A. J.; Heymans, C.; Lombriser, L.; Peacock, J. A.; Steele, O. I.; Winther, H. A.
2016-06-01
We present an accurate non-linear matter power spectrum prediction scheme for a variety of extensions to the standard cosmological paradigm, which uses the tuned halo model previously developed in Mead et al. We consider dark energy models that are both minimally and non-minimally coupled, massive neutrinos and modified gravitational forces with chameleon and Vainshtein screening mechanisms. In all cases, we compare halo-model power spectra to measurements from high-resolution simulations. We show that the tuned halo-model method can predict the non-linear matter power spectrum measured from simulations of parametrized w(a) dark energy models at the few per cent level for k 0.5 h Mpc-1. An updated version of our publicly available HMCODE can be found at https://github.com/alexander-mead/hmcode.
Mead, Alexander; Lombriser, Lucas; Peacock, John; Steele, Olivia; Winther, Hans
2016-01-01
We present an accurate non-linear matter power spectrum prediction scheme for a variety of extensions to the standard cosmological paradigm, which uses the tuned halo model previously developed in Mead (2015b). We consider dark energy models that are both minimally and non-minimally coupled, massive neutrinos and modified gravitational forces with chameleon and Vainshtein screening mechanisms. In all cases we compare halo-model power spectra to measurements from high-resolution simulations. We show that the tuned halo model method can predict the non-linear matter power spectrum measured from simulations of parameterised $w(a)$ dark energy models at the few per cent level for $k0.5\\,h\\mathrm{Mpc}^{-1}$. An updated version of our publicly available HMcode can be found at https://github.com/alexander-mead/HMcode
An Accurate Multimoment Constrained Finite Volume Transport Model on Yin-Yang Grids
Institute of Scientific and Technical Information of China (English)
LI Xingliang; SHEN Xueshun; PENG Xindong; XIAO Feng; ZHUANG Zhaorong; CHEN Chungang
2013-01-01
A global transport model is proposed in which a multimoment constrained finite volume (MCV) scheme is applied to a Yin-Yang overset grid.The MCV scheme defines 16 degrees of freedom (DOFs) within each element to build a 2D cubic reconstruction polynomial.The time evolution equations for DOFs are derived from constraint conditions on moments of line-integrated averages (LIA),point values (PV),and values of first-order derivatives (DV).The Yin-Yang grid eliminates polar singularities and results in a quasi-uniform mesh.A limiting projection is designed to remove nonphysical oscillations around discontinuities.Our model was tested against widely used benchmarks; the competitive results reveal that the model is accurate and promising for developing general circulation models.
An Accurate and Computationally Efficient Model for Membrane-Type Circular-Symmetric Micro-Hotplates
Directory of Open Access Journals (Sweden)
Usman Khan
2014-04-01
Full Text Available Ideally, the design of high-performance micro-hotplates would require a large number of simulations because of the existence of many important design parameters as well as the possibly crucial effects of both spread and drift. However, the computational cost of FEM simulations, which are the only available tool for accurately predicting the temperature in micro-hotplates, is very high. As a result, micro-hotplate designers generally have no effective simulation-tools for the optimization. In order to circumvent these issues, here, we propose a model for practical circular-symmetric micro-hot-plates which takes advantage of modified Bessel functions, computationally efficient matrix-approach for considering the relevant boundary conditions, Taylor linearization for modeling the Joule heating and radiation losses, and external-region-segmentation strategy in order to accurately take into account radiation losses in the entire micro-hotplate. The proposed model is almost as accurate as FEM simulations and two to three orders of magnitude more computationally efficient (e.g., 45 s versus more than 8 h. The residual errors, which are mainly associated to the undesired heating in the electrical contacts, are small (e.g., few degrees Celsius for an 800 °C operating temperature and, for important analyses, almost constant. Therefore, we also introduce a computationally-easy single-FEM-compensation strategy in order to reduce the residual errors to about 1 °C. As illustrative examples of the power of our approach, we report the systematic investigation of a spread in the membrane thermal conductivity and of combined variations of both ambient and bulk temperatures. Our model enables a much faster characterization of micro-hotplates and, thus, a much more effective optimization prior to fabrication.
Dintwa, Edward
2006-01-01
This thesis is primarily concerned with the development of accurate, simplified and validated contact force models for the discrete element modelling (DEM) of fruit bulk handling systems. The DEM is essentially a numerical technique to model a system of particles interacting with one another and with the system boundaries through collisions. The specific area of application envisaged is in postharvest agriculture, where DEM could be used in simulation of many unit operations with bulk fruit,...
Towards an accurate model of the redshift space clustering of halos in the quasilinear regime
Reid, Beth A
2011-01-01
Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for measuring the build-up of cosmological structure, which depends both on the expansion rate of the Universe and our theory of gravity. Galaxies occupy dark matter halos, whose redshift space clustering has a complex dependence on bias that cannot be inferred from the behavior of matter. We identify two distinct corrections on quasilinear scales (~ 30-80 Mpc/h): the non-linear mapping between real and redshift space positions, and the non-linear suppression of power in the velocity divergence field. We model the first non-perturbatively using the scale-dependent Gaussian streaming model, which we show is accurate at the 10 (s>25) Mpc/h for the monopole (quadrupole) halo correlation functions. We use perturbation theory to predict the real space pairwise halo velocity statistics. Our fully analytic model is accurate at the 2 per cent level only on scales s > 40 Mpc/h. Recent models that neglect the correctio...
Beekhuizen, Johan; Kromhout, Hans; Bürgi, Alfred; Huss, Anke; Vermeulen, Roel
2015-01-01
The increase in mobile communication technology has led to concern about potential health effects of radio frequency electromagnetic fields (RF-EMFs) from mobile phone base stations. Different RF-EMF prediction models have been applied to assess population exposure to RF-EMF. Our study examines what input data are needed to accurately model RF-EMF, as detailed data are not always available for epidemiological studies. We used NISMap, a 3D radio wave propagation model, to test models with various levels of detail in building and antenna input data. The model outcomes were compared with outdoor measurements taken in Amsterdam, the Netherlands. Results showed good agreement between modelled and measured RF-EMF when 3D building data and basic antenna information (location, height, frequency and direction) were used: Spearman correlations were >0.6. Model performance was not sensitive to changes in building damping parameters. Antenna-specific information about down-tilt, type and output power did not significantly improve model performance compared with using average down-tilt and power values, or assuming one standard antenna type. We conclude that 3D radio wave propagation modelling is a feasible approach to predict outdoor RF-EMF levels for ranking exposure levels in epidemiological studies, when 3D building data and information on the antenna height, frequency, location and direction are available. PMID:24472756
Beekhuizen, Johan; Kromhout, Hans; Bürgi, Alfred; Huss, Anke; Vermeulen, Roel
2015-01-01
The increase in mobile communication technology has led to concern about potential health effects of radio frequency electromagnetic fields (RF-EMFs) from mobile phone base stations. Different RF-EMF prediction models have been applied to assess population exposure to RF-EMF. Our study examines what input data are needed to accurately model RF-EMF, as detailed data are not always available for epidemiological studies. We used NISMap, a 3D radio wave propagation model, to test models with various levels of detail in building and antenna input data. The model outcomes were compared with outdoor measurements taken in Amsterdam, the Netherlands. Results showed good agreement between modelled and measured RF-EMF when 3D building data and basic antenna information (location, height, frequency and direction) were used: Spearman correlations were >0.6. Model performance was not sensitive to changes in building damping parameters. Antenna-specific information about down-tilt, type and output power did not significantly improve model performance compared with using average down-tilt and power values, or assuming one standard antenna type. We conclude that 3D radio wave propagation modelling is a feasible approach to predict outdoor RF-EMF levels for ranking exposure levels in epidemiological studies, when 3D building data and information on the antenna height, frequency, location and direction are available.
Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis
DEFF Research Database (Denmark)
Hosseini, Seyedmohsen; Moghani, Javad Shokrollahi; Jensen, Bogi Bech
2011-01-01
This paper presents an accurate modeling method that is applied to a single-sided outer-rotor transverse flux permanent magnet generator. The inductances and the induced electromotive force for a typical generator are calculated using the magnetostatic three-dimensional finite element method. A new...... method is then proposed that reveals the behavior of the generator under any load. Finally, torque calculations are carried out using three dimensional finite element analyses. It is shown that although in the single-phase generator the cogging torque is very high, this can be improved significantly by...... combining three single-phase modules into a three-phase generator....
Applying an accurate spherical model to gamma-ray burst afterglow observations
Leventis, K.; van der Horst, A. J.; van Eerten, H. J.; Wijers, R. A. M. J.
2013-05-01
We present results of model fits to afterglow data sets of GRB 970508, GRB 980703 and GRB 070125, characterized by long and broad-band coverage. The model assumes synchrotron radiation (including self-absorption) from a spherical adiabatic blast wave and consists of analytic flux prescriptions based on numerical results. For the first time it combines the accuracy of hydrodynamic simulations through different stages of the outflow dynamics with the flexibility of simple heuristic formulas. The prescriptions are especially geared towards accurate description of the dynamical transition of the outflow from relativistic to Newtonian velocities in an arbitrary power-law density environment. We show that the spherical model can accurately describe the data only in the case of GRB 970508, for which we find a circumburst medium density n ∝ r-2. We investigate in detail the implied spectra and physical parameters of that burst. For the microphysics we show evidence for equipartition between the fraction of energy density carried by relativistic electrons and magnetic field. We also find that for the blast wave to be adiabatic, the fraction of electrons accelerated at the shock has to be smaller than 1. We present best-fitting parameters for the afterglows of all three bursts, including uncertainties in the parameters of GRB 970508, and compare the inferred values to those obtained by different authors.
Zhang, Shunli; Zhang, Dinghua; Gong, Hao; Ghasemalizadeh, Omid; Wang, Ge; Cao, Guohua
2014-11-01
Iterative algorithms, such as the algebraic reconstruction technique (ART), are popular for image reconstruction. For iterative reconstruction, the area integral model (AIM) is more accurate for better reconstruction quality than the line integral model (LIM). However, the computation of the system matrix for AIM is more complex and time-consuming than that for LIM. Here, we propose a fast and accurate method to compute the system matrix for AIM. First, we calculate the intersection of each boundary line of a narrow fan-beam with pixels in a recursive and efficient manner. Then, by grouping the beam-pixel intersection area into six types according to the slopes of the two boundary lines, we analytically compute the intersection area of the narrow fan-beam with the pixels in a simple algebraic fashion. Overall, experimental results show that our method is about three times faster than the Siddon algorithm and about two times faster than the distance-driven model (DDM) in computation of the system matrix. The reconstruction speed of our AIM-based ART is also faster than the LIM-based ART that uses the Siddon algorithm and DDM-based ART, for one iteration. The fast reconstruction speed of our method was accomplished without compromising the image quality.
Rumple, C.; Richter, J.; Craven, B. A.; Krane, M.
2012-11-01
A summary of the research being carried out by our multidisciplinary team to better understand the form and function of the nose in different mammalian species that include humans, carnivores, ungulates, rodents, and marine animals will be presented. The mammalian nose houses a convoluted airway labyrinth, where two hallmark features of mammals occur, endothermy and olfaction. Because of the complexity of the nasal cavity, the anatomy and function of these upper airways remain poorly understood in most mammals. However, recent advances in high-resolution medical imaging, computational modeling, and experimental flow measurement techniques are now permitting the study of airflow and respiratory and olfactory transport phenomena in anatomically-accurate reconstructions of the nasal cavity. Here, we focus on efforts to manufacture transparent, anatomically-accurate models for stereo particle image velocimetry (SPIV) measurements of nasal airflow. Challenges in the design and manufacture of index-matched anatomical models are addressed and preliminary SPIV measurements are presented. Such measurements will constitute a validation database for concurrent computational fluid dynamics (CFD) simulations of mammalian respiration and olfaction. Supported by the National Science Foundation.
A Multilayer Recurrent Fuzzy Neural Network for Accurate Dynamic System Modeling
Institute of Scientific and Technical Information of China (English)
LIU He; HUANG Dao
2008-01-01
A muitilayer recurrent fuzzy neural network (MRFNN)is proposed for accurate dynamic system modeling.The proposed MRFNN has six layers combined with T-S fuzzy model.The recurrent structures are formed by local feedback connections in the membership layer and the rule layer.With these feedbacks,the fuzzy sets are time-varying and the temporal problem of dynamic system can he solved well.The parameters of MRFNN are learned by chaotic search(CS)and least square estimation(LSE)simultaneously,where CS is for tuning the premise parameters and LSE is for updating the consequent coefficients accordingly.Results of simulations show the proposed approach is effective for dynamic system modeling with high accuracy.
Digitalized accurate modeling of SPCB with multi-spiral surface based on CPC algorithm
Huang, Yanhua; Gu, Lizhi
2015-09-01
The main methods of the existing multi-spiral surface geometry modeling include spatial analytic geometry algorithms, graphical method, interpolation and approximation algorithms. However, there are some shortcomings in these modeling methods, such as large amount of calculation, complex process, visible errors, and so on. The above methods have, to some extent, restricted the design and manufacture of the premium and high-precision products with spiral surface considerably. This paper introduces the concepts of the spatially parallel coupling with multi-spiral surface and spatially parallel coupling body. The typical geometry and topological features of each spiral surface forming the multi-spiral surface body are determined, by using the extraction principle of datum point cluster, the algorithm of coupling point cluster by removing singular point, and the "spatially parallel coupling" principle based on the non-uniform B-spline for each spiral surface. The orientation and quantitative relationships of datum point cluster and coupling point cluster in Euclidean space are determined accurately and in digital description and expression, coupling coalescence of the surfaces with multi-coupling point clusters under the Pro/E environment. The digitally accurate modeling of spatially parallel coupling body with multi-spiral surface is realized. The smooth and fairing processing is done to the three-blade end-milling cutter's end section area by applying the principle of spatially parallel coupling with multi-spiral surface, and the alternative entity model is processed in the four axis machining center after the end mill is disposed. And the algorithm is verified and then applied effectively to the transition area among the multi-spiral surface. The proposed model and algorithms may be used in design and manufacture of the multi-spiral surface body products, as well as in solving essentially the problems of considerable modeling errors in computer graphics and
Quinci, Federico; Dressler, Matthew; Strickland, Anthony M; Limbert, Georges
2014-04-01
Considerable progress has been made in understanding implant wear and developing numerical models to predict wear for new orthopaedic devices. However any model of wear could be improved through a more accurate representation of the biomaterial mechanics, including time-varying dynamic and inelastic behaviour such as viscosity and plastic deformation. In particular, most computational models of wear of UHMWPE implement a time-invariant version of Archard's law that links the volume of worn material to the contact pressure between the metal implant and the polymeric tibial insert. During in-vivo conditions, however, the contact area is a time-varying quantity and is therefore dependent upon the dynamic deformation response of the material. From this observation one can conclude that creep deformations of UHMWPE may be very important to consider when conducting computational wear analyses, in stark contrast to what can be found in the literature. In this study, different numerical modelling techniques are compared with experimental creep testing on a unicondylar knee replacement system in a physiologically representative context. Linear elastic, plastic and time-varying visco-dynamic models are benchmarked using literature data to predict contact deformations, pressures and areas. The aim of this study is to elucidate the contributions of viscoelastic and plastic effects on these surface quantities. It is concluded that creep deformations have a significant effect on the contact pressure measured (experiment) and calculated (computational models) at the surface of the UHMWPE unicondylar insert. The use of a purely elastoplastic constitutive model for UHMWPE lead to compressive deformations of the insert which are much smaller than those predicted by a creep-capturing viscoelastic model (and those measured experimentally). This shows again the importance of including creep behaviour into a constitutive model in order to predict the right level of surface deformation
Quinci, Federico; Dressler, Matthew; Strickland, Anthony M; Limbert, Georges
2014-04-01
Considerable progress has been made in understanding implant wear and developing numerical models to predict wear for new orthopaedic devices. However any model of wear could be improved through a more accurate representation of the biomaterial mechanics, including time-varying dynamic and inelastic behaviour such as viscosity and plastic deformation. In particular, most computational models of wear of UHMWPE implement a time-invariant version of Archard's law that links the volume of worn material to the contact pressure between the metal implant and the polymeric tibial insert. During in-vivo conditions, however, the contact area is a time-varying quantity and is therefore dependent upon the dynamic deformation response of the material. From this observation one can conclude that creep deformations of UHMWPE may be very important to consider when conducting computational wear analyses, in stark contrast to what can be found in the literature. In this study, different numerical modelling techniques are compared with experimental creep testing on a unicondylar knee replacement system in a physiologically representative context. Linear elastic, plastic and time-varying visco-dynamic models are benchmarked using literature data to predict contact deformations, pressures and areas. The aim of this study is to elucidate the contributions of viscoelastic and plastic effects on these surface quantities. It is concluded that creep deformations have a significant effect on the contact pressure measured (experiment) and calculated (computational models) at the surface of the UHMWPE unicondylar insert. The use of a purely elastoplastic constitutive model for UHMWPE lead to compressive deformations of the insert which are much smaller than those predicted by a creep-capturing viscoelastic model (and those measured experimentally). This shows again the importance of including creep behaviour into a constitutive model in order to predict the right level of surface deformation
LogGPO: An accurate communication model for performance prediction of MPI programs
Institute of Scientific and Technical Information of China (English)
CHEN WenGuang; ZHAI JiDong; ZHANG Jin; ZHENG WeiMin
2009-01-01
Message passing interface (MPI) is the de facto standard in writing parallel scientific applications on distributed memory systems. Performance prediction of MPI programs on current or future parallel sys-terns can help to find system bottleneck or optimize programs. To effectively analyze and predict per-formance of a large and complex MPI program, an efficient and accurate communication model is highly needed. A series of communication models have been proposed, such as the LogP model family, which assume that the sending overhead, message transmission, and receiving overhead of a communication is not overlapped and there is a maximum overlap degree between computation and communication. However, this assumption does not always hold for MPI programs because either sending or receiving overhead introduced by MPI implementations can decrease potential overlap for large messages. In this paper, we present a new communication model, named LogGPO, which captures the potential overlap between computation with communication of MPI programs. We design and implement a trace-driven simulator to verify the LogGPO model by predicting performance of point-to-point communication and two real applications CG and Sweep3D. The average prediction errors of LogGPO model are 2.4% and 2.0% for these two applications respectively, while the average prediction errors of LogGP model are 38.3% and 9.1% respectively.
Physical modeling of real-world slingshots for accurate speed predictions
Yeats, Bob
2016-01-01
We discuss the physics and modeling of latex-rubber slingshots. The goal is to get accurate speed predictions inspite of the significant real world difficulties of force drift, force hysteresis, rubber ageing, and the very non- linear, non-ideal, force vs. pull distance curves of slingshot rubber bands. Slingshots are known to shoot faster under some circumstances when the bands are tapered rather than having constant width and stiffness. We give both qualitative understanding and numerical predictions of this effect. We consider two models. The first is based on conservation of energy and is easier to implement, but cannot determine the speeds along the rubber bands without making assumptions. The second, treats the bands as a series of mass points subject to being pulled by immediately adjacent mass points according to how much the rubber has been stretched on the two adjacent sides. This is a classic many-body F=ma problem but convergence requires using a particular numerical technique. It gives accurate p...
O'Connor, James P B; Boult, Jessica K R; Jamin, Yann; Babur, Muhammad; Finegan, Katherine G; Williams, Kaye J; Little, Ross A; Jackson, Alan; Parker, Geoff J M; Reynolds, Andrew R; Waterton, John C; Robinson, Simon P
2016-02-15
There is a clinical need for noninvasive biomarkers of tumor hypoxia for prognostic and predictive studies, radiotherapy planning, and therapy monitoring. Oxygen-enhanced MRI (OE-MRI) is an emerging imaging technique for quantifying the spatial distribution and extent of tumor oxygen delivery in vivo. In OE-MRI, the longitudinal relaxation rate of protons (ΔR1) changes in proportion to the concentration of molecular oxygen dissolved in plasma or interstitial tissue fluid. Therefore, well-oxygenated tissues show positive ΔR1. We hypothesized that the fraction of tumor tissue refractory to oxygen challenge (lack of positive ΔR1, termed "Oxy-R fraction") would be a robust biomarker of hypoxia in models with varying vascular and hypoxic features. Here, we demonstrate that OE-MRI signals are accurate, precise, and sensitive to changes in tumor pO2 in highly vascular 786-0 renal cancer xenografts. Furthermore, we show that Oxy-R fraction can quantify the hypoxic fraction in multiple models with differing hypoxic and vascular phenotypes, when used in combination with measurements of tumor perfusion. Finally, Oxy-R fraction can detect dynamic changes in hypoxia induced by the vasomodulator agent hydralazine. In contrast, more conventional biomarkers of hypoxia (derived from blood oxygenation-level dependent MRI and dynamic contrast-enhanced MRI) did not relate to tumor hypoxia consistently. Our results show that the Oxy-R fraction accurately quantifies tumor hypoxia noninvasively and is immediately translatable to the clinic.
Directory of Open Access Journals (Sweden)
Ajay Seth
Full Text Available The complexity of shoulder mechanics combined with the movement of skin relative to the scapula makes it difficult to measure shoulder kinematics with sufficient accuracy to distinguish between symptomatic and asymptomatic individuals. Multibody skeletal models can improve motion capture accuracy by reducing the space of possible joint movements, and models are used widely to improve measurement of lower limb kinematics. In this study, we developed a rigid-body model of a scapulothoracic joint to describe the kinematics of the scapula relative to the thorax. This model describes scapular kinematics with four degrees of freedom: 1 elevation and 2 abduction of the scapula on an ellipsoidal thoracic surface, 3 upward rotation of the scapula normal to the thoracic surface, and 4 internal rotation of the scapula to lift the medial border of the scapula off the surface of the thorax. The surface dimensions and joint axes can be customized to match an individual's anthropometry. We compared the model to "gold standard" bone-pin kinematics collected during three shoulder tasks and found modeled scapular kinematics to be accurate to within 2 mm root-mean-squared error for individual bone-pin markers across all markers and movement tasks. As an additional test, we added random and systematic noise to the bone-pin marker data and found that the model reduced kinematic variability due to noise by 65% compared to Euler angles computed without the model. Our scapulothoracic joint model can be used for inverse and forward dynamics analyses and to compute joint reaction loads. The computational performance of the scapulothoracic joint model is well suited for real-time applications; it is freely available for use with OpenSim 3.2, and is customizable and usable with other OpenSim models.
Seth, Ajay; Matias, Ricardo; Veloso, António P; Delp, Scott L
2016-01-01
The complexity of shoulder mechanics combined with the movement of skin relative to the scapula makes it difficult to measure shoulder kinematics with sufficient accuracy to distinguish between symptomatic and asymptomatic individuals. Multibody skeletal models can improve motion capture accuracy by reducing the space of possible joint movements, and models are used widely to improve measurement of lower limb kinematics. In this study, we developed a rigid-body model of a scapulothoracic joint to describe the kinematics of the scapula relative to the thorax. This model describes scapular kinematics with four degrees of freedom: 1) elevation and 2) abduction of the scapula on an ellipsoidal thoracic surface, 3) upward rotation of the scapula normal to the thoracic surface, and 4) internal rotation of the scapula to lift the medial border of the scapula off the surface of the thorax. The surface dimensions and joint axes can be customized to match an individual's anthropometry. We compared the model to "gold standard" bone-pin kinematics collected during three shoulder tasks and found modeled scapular kinematics to be accurate to within 2 mm root-mean-squared error for individual bone-pin markers across all markers and movement tasks. As an additional test, we added random and systematic noise to the bone-pin marker data and found that the model reduced kinematic variability due to noise by 65% compared to Euler angles computed without the model. Our scapulothoracic joint model can be used for inverse and forward dynamics analyses and to compute joint reaction loads. The computational performance of the scapulothoracic joint model is well suited for real-time applications; it is freely available for use with OpenSim 3.2, and is customizable and usable with other OpenSim models. PMID:26734761
Accurate calibration of the velocity-dependent one-scale model for domain walls
Energy Technology Data Exchange (ETDEWEB)
Leite, A.M.M., E-mail: up080322016@alunos.fc.up.pt [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Ecole Polytechnique, 91128 Palaiseau Cedex (France); Martins, C.J.A.P., E-mail: Carlos.Martins@astro.up.pt [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Shellard, E.P.S., E-mail: E.P.S.Shellard@damtp.cam.ac.uk [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
2013-01-08
We study the asymptotic scaling properties of standard domain wall networks in several cosmological epochs. We carry out the largest field theory simulations achieved to date, with simulation boxes of size 2048{sup 3}, and confirm that a scale-invariant evolution of the network is indeed the attractor solution. The simulations are also used to obtain an accurate calibration for the velocity-dependent one-scale model for domain walls: we numerically determine the two free model parameters to have the values c{sub w}=0.34{+-}0.16 and k{sub w}=0.98{+-}0.07, which are of higher precision than (but in agreement with) earlier estimates.
Smith, Rory; Candlish, Graeme N; Fellhauer, Michael; Gibson, Bradley K
2015-01-01
We present accurate models of the gravitational potential produced by a radially exponential disk mass distribution. The models are produced by combining three separate Miyamoto-Nagai disks. Such models have been used previously to model the disk of the Milky Way, but here we extend this framework to allow its application to disks of any mass, scalelength, and a wide range of thickness from infinitely thin to near spherical (ellipticities from 0 to 0.9). The models have the advantage of simplicity of implementation, and we expect faster run speeds over a double exponential disk treatment. The potentials are fully analytical, and differentiable at all points. The mass distribution of our models deviates from the radial mass distribution of a pure exponential disk by <0.4% out to 4 disk scalelengths, and <1.9% out to 10 disk scalelengths. We tabulate fitting parameters which facilitate construction of exponential disks for any scalelength, and a wide range of disk thickness (a user-friendly, web-based int...
Fitmunk: improving protein structures by accurate, automatic modeling of side-chain conformations.
Porebski, Przemyslaw Jerzy; Cymborowski, Marcin; Pasenkiewicz-Gierula, Marta; Minor, Wladek
2016-02-01
Improvements in crystallographic hardware and software have allowed automated structure-solution pipelines to approach a near-`one-click' experience for the initial determination of macromolecular structures. However, in many cases the resulting initial model requires a laborious, iterative process of refinement and validation. A new method has been developed for the automatic modeling of side-chain conformations that takes advantage of rotamer-prediction methods in a crystallographic context. The algorithm, which is based on deterministic dead-end elimination (DEE) theory, uses new dense conformer libraries and a hybrid energy function derived from experimental data and prior information about rotamer frequencies to find the optimal conformation of each side chain. In contrast to existing methods, which incorporate the electron-density term into protein-modeling frameworks, the proposed algorithm is designed to take advantage of the highly discriminatory nature of electron-density maps. This method has been implemented in the program Fitmunk, which uses extensive conformational sampling. This improves the accuracy of the modeling and makes it a versatile tool for crystallographic model building, refinement and validation. Fitmunk was extensively tested on over 115 new structures, as well as a subset of 1100 structures from the PDB. It is demonstrated that the ability of Fitmunk to model more than 95% of side chains accurately is beneficial for improving the quality of crystallographic protein models, especially at medium and low resolutions. Fitmunk can be used for model validation of existing structures and as a tool to assess whether side chains are modeled optimally or could be better fitted into electron density. Fitmunk is available as a web service at http://kniahini.med.virginia.edu/fitmunk/server/ or at http://fitmunk.bitbucket.org/. PMID:26894674
Fitmunk: improving protein structures by accurate, automatic modeling of side-chain conformations.
Porebski, Przemyslaw Jerzy; Cymborowski, Marcin; Pasenkiewicz-Gierula, Marta; Minor, Wladek
2016-02-01
Improvements in crystallographic hardware and software have allowed automated structure-solution pipelines to approach a near-`one-click' experience for the initial determination of macromolecular structures. However, in many cases the resulting initial model requires a laborious, iterative process of refinement and validation. A new method has been developed for the automatic modeling of side-chain conformations that takes advantage of rotamer-prediction methods in a crystallographic context. The algorithm, which is based on deterministic dead-end elimination (DEE) theory, uses new dense conformer libraries and a hybrid energy function derived from experimental data and prior information about rotamer frequencies to find the optimal conformation of each side chain. In contrast to existing methods, which incorporate the electron-density term into protein-modeling frameworks, the proposed algorithm is designed to take advantage of the highly discriminatory nature of electron-density maps. This method has been implemented in the program Fitmunk, which uses extensive conformational sampling. This improves the accuracy of the modeling and makes it a versatile tool for crystallographic model building, refinement and validation. Fitmunk was extensively tested on over 115 new structures, as well as a subset of 1100 structures from the PDB. It is demonstrated that the ability of Fitmunk to model more than 95% of side chains accurately is beneficial for improving the quality of crystallographic protein models, especially at medium and low resolutions. Fitmunk can be used for model validation of existing structures and as a tool to assess whether side chains are modeled optimally or could be better fitted into electron density. Fitmunk is available as a web service at http://kniahini.med.virginia.edu/fitmunk/server/ or at http://fitmunk.bitbucket.org/.
A Simple and Accurate Model to Predict Responses to Multi-electrode Stimulation in the Retina.
Directory of Open Access Journals (Sweden)
Matias I Maturana
2016-04-01
Full Text Available Implantable electrode arrays are widely used in therapeutic stimulation of the nervous system (e.g. cochlear, retinal, and cortical implants. Currently, most neural prostheses use serial stimulation (i.e. one electrode at a time despite this severely limiting the repertoire of stimuli that can be applied. Methods to reliably predict the outcome of multi-electrode stimulation have not been available. Here, we demonstrate that a linear-nonlinear model accurately predicts neural responses to arbitrary patterns of stimulation using in vitro recordings from single retinal ganglion cells (RGCs stimulated with a subretinal multi-electrode array. In the model, the stimulus is projected onto a low-dimensional subspace and then undergoes a nonlinear transformation to produce an estimate of spiking probability. The low-dimensional subspace is estimated using principal components analysis, which gives the neuron's electrical receptive field (ERF, i.e. the electrodes to which the neuron is most sensitive. Our model suggests that stimulation proportional to the ERF yields a higher efficacy given a fixed amount of power when compared to equal amplitude stimulation on up to three electrodes. We find that the model captures the responses of all the cells recorded in the study, suggesting that it will generalize to most cell types in the retina. The model is computationally efficient to evaluate and, therefore, appropriate for future real-time applications including stimulation strategies that make use of recorded neural activity to improve the stimulation strategy.
A Simple and Accurate Model to Predict Responses to Multi-electrode Stimulation in the Retina.
Maturana, Matias I; Apollo, Nicholas V; Hadjinicolaou, Alex E; Garrett, David J; Cloherty, Shaun L; Kameneva, Tatiana; Grayden, David B; Ibbotson, Michael R; Meffin, Hamish
2016-04-01
Implantable electrode arrays are widely used in therapeutic stimulation of the nervous system (e.g. cochlear, retinal, and cortical implants). Currently, most neural prostheses use serial stimulation (i.e. one electrode at a time) despite this severely limiting the repertoire of stimuli that can be applied. Methods to reliably predict the outcome of multi-electrode stimulation have not been available. Here, we demonstrate that a linear-nonlinear model accurately predicts neural responses to arbitrary patterns of stimulation using in vitro recordings from single retinal ganglion cells (RGCs) stimulated with a subretinal multi-electrode array. In the model, the stimulus is projected onto a low-dimensional subspace and then undergoes a nonlinear transformation to produce an estimate of spiking probability. The low-dimensional subspace is estimated using principal components analysis, which gives the neuron's electrical receptive field (ERF), i.e. the electrodes to which the neuron is most sensitive. Our model suggests that stimulation proportional to the ERF yields a higher efficacy given a fixed amount of power when compared to equal amplitude stimulation on up to three electrodes. We find that the model captures the responses of all the cells recorded in the study, suggesting that it will generalize to most cell types in the retina. The model is computationally efficient to evaluate and, therefore, appropriate for future real-time applications including stimulation strategies that make use of recorded neural activity to improve the stimulation strategy. PMID:27035143
Optimal Cluster Mill Pass Scheduling With an Accurate and Rapid New Strip Crown Model
Malik, Arif S.; Grandhi, Ramana V.; Zipf, Mark E.
2007-05-01
Besides the requirement to roll coiled sheet at high levels of productivity, the optimal pass scheduling of cluster-type reversing cold mills presents the added challenge of assigning mill parameters that facilitate the best possible strip flatness. The pressures of intense global competition, and the requirements for increasingly thinner, higher quality specialty sheet products that are more difficult to roll, continue to force metal producers to commission innovative flatness-control technologies. This means that during the on-line computerized set-up of rolling mills, the mathematical model should not only determine the minimum total number of passes and maximum rolling speed, it should simultaneously optimize the pass-schedule so that desired flatness is assured, either by manual or automated means. In many cases today, however, on-line prediction of strip crown and corresponding flatness for the complex cluster-type rolling mills is typically addressed either by trial and error, by approximate deflection models for equivalent vertical roll-stacks, or by non-physical pattern recognition style models. The abundance of the aforementioned methods is largely due to the complexity of cluster-type mill configurations and the lack of deflection models with sufficient accuracy and speed for on-line use. Without adequate assignment of the pass-schedule set-up parameters, it may be difficult or impossible to achieve the required strip flatness. In this paper, we demonstrate optimization of cluster mill pass-schedules using a new accurate and rapid strip crown model. This pass-schedule optimization includes computations of the predicted strip thickness profile to validate mathematical constraints. In contrast to many of the existing methods for on-line prediction of strip crown and flatness on cluster mills, the demonstrated method requires minimal prior tuning and no extensive training with collected mill data. To rapidly and accurately solve the multi-contact problem
Fast and accurate analytical model to solve inverse problem in SHM using Lamb wave propagation
Poddar, Banibrata; Giurgiutiu, Victor
2016-04-01
Lamb wave propagation is at the center of attention of researchers for structural health monitoring of thin walled structures. This is due to the fact that Lamb wave modes are natural modes of wave propagation in these structures with long travel distances and without much attenuation. This brings the prospect of monitoring large structure with few sensors/actuators. However the problem of damage detection and identification is an "inverse problem" where we do not have the luxury to know the exact mathematical model of the system. On top of that the problem is more challenging due to the confounding factors of statistical variation of the material and geometric properties. Typically this problem may also be ill posed. Due to all these complexities the direct solution of the problem of damage detection and identification in SHM is impossible. Therefore an indirect method using the solution of the "forward problem" is popular for solving the "inverse problem". This requires a fast forward problem solver. Due to the complexities involved with the forward problem of scattering of Lamb waves from damages researchers rely primarily on numerical techniques such as FEM, BEM, etc. But these methods are slow and practically impossible to be used in structural health monitoring. We have developed a fast and accurate analytical forward problem solver for this purpose. This solver, CMEP (complex modes expansion and vector projection), can simulate scattering of Lamb waves from all types of damages in thin walled structures fast and accurately to assist the inverse problem solver.
Accurate modeling of vector hysteresis using a superposition of Preisach-type models
Energy Technology Data Exchange (ETDEWEB)
Adly, A.A. [Cairo Univ., Giza (Egypt). Electrical Power and Machines Dept.; Mayergoyz, I.D. [Univ. of Maryland, College Park, MD (United States). Electrical Engineering Dept.
1997-09-01
Vector hysteresis models are basically regarded as helpful tools that can be utilized in simulating and/or predicting multi-dimensional field-media interactions. Simulations of energy loss in power devices having unoriented magnetic cores, read/write recording processes as well as tape and disk erasure approaches are examples of such interactions that are currently of considerable interest. Vector hysteresis models are generally regarded as helpful tools that can be utilized in simulating multi-dimensional field-media interactions. In this paper, simulation of vector hysteresis is proposed by using a superposition of isotropic Preisach-type models. This approach gives the opportunity to fully incorporate rotational experimental results in its identification procedure, thus leading to higher simulation accuracy. Detailed solution of the model identification problem and some experimental testing results are given in the paper.
An accurate and efficient Lagrangian sub-grid model for multi-particle dispersion
Toschi, Federico; Mazzitelli, Irene; Lanotte, Alessandra S.
2014-11-01
Many natural and industrial processes involve the dispersion of particle in turbulent flows. Despite recent theoretical progresses in the understanding of particle dynamics in simple turbulent flows, complex geometries often call for numerical approaches based on eulerian Large Eddy Simulation (LES). One important issue related to the Lagrangian integration of tracers in under-resolved velocity fields is connected to the lack of spatial correlations at unresolved scales. Here we propose a computationally efficient Lagrangian model for the sub-grid velocity of tracers dispersed in statistically homogeneous and isotropic turbulent flows. The model incorporates the multi-scale nature of turbulent temporal and spatial correlations that are essential to correctly reproduce the dynamics of multi-particle dispersion. The new model is able to describe the Lagrangian temporal and spatial correlations in clouds of particles. In particular we show that pairs and tetrads dispersion compare well with results from Direct Numerical Simulations of statistically isotropic and homogeneous 3d turbulence. This model may offer an accurate and efficient way to describe multi-particle dispersion in under resolved turbulent velocity fields such as the one employed in eulerian LES. This work is part of the research programmes FP112 of the Foundation for Fundamental Research on Matter (FOM), which is part of the Netherlands Organisation for Scientific Research (NWO). We acknowledge support from the EU COST Action MP0806.
Pagán, Josué; Risco-Martín, José L; Moya, José M; Ayala, José L
2016-08-01
Prediction of symptomatic crises in chronic diseases allows to take decisions before the symptoms occur, such as the intake of drugs to avoid the symptoms or the activation of medical alarms. The prediction horizon is in this case an important parameter in order to fulfill the pharmacokinetics of medications, or the time response of medical services. This paper presents a study about the prediction limits of a chronic disease with symptomatic crises: the migraine. For that purpose, this work develops a methodology to build predictive migraine models and to improve these predictions beyond the limits of the initial models. The maximum prediction horizon is analyzed, and its dependency on the selected features is studied. A strategy for model selection is proposed to tackle the trade off between conservative but robust predictive models, with respect to less accurate predictions with higher horizons. The obtained results show a prediction horizon close to 40min, which is in the time range of the drug pharmacokinetics. Experiments have been performed in a realistic scenario where input data have been acquired in an ambulatory clinical study by the deployment of a non-intrusive Wireless Body Sensor Network. Our results provide an effective methodology for the selection of the future horizon in the development of prediction algorithms for diseases experiencing symptomatic crises. PMID:27260782
Directory of Open Access Journals (Sweden)
Marc Santolini
Full Text Available The identification of transcription factor binding sites (TFBSs on genomic DNA is of crucial importance for understanding and predicting regulatory elements in gene networks. TFBS motifs are commonly described by Position Weight Matrices (PWMs, in which each DNA base pair contributes independently to the transcription factor (TF binding. However, this description ignores correlations between nucleotides at different positions, and is generally inaccurate: analysing fly and mouse in vivo ChIPseq data, we show that in most cases the PWM model fails to reproduce the observed statistics of TFBSs. To overcome this issue, we introduce the pairwise interaction model (PIM, a generalization of the PWM model. The model is based on the principle of maximum entropy and explicitly describes pairwise correlations between nucleotides at different positions, while being otherwise as unconstrained as possible. It is mathematically equivalent to considering a TF-DNA binding energy that depends additively on each nucleotide identity at all positions in the TFBS, like the PWM model, but also additively on pairs of nucleotides. We find that the PIM significantly improves over the PWM model, and even provides an optimal description of TFBS statistics within statistical noise. The PIM generalizes previous approaches to interdependent positions: it accounts for co-variation of two or more base pairs, and predicts secondary motifs, while outperforming multiple-motif models consisting of mixtures of PWMs. We analyse the structure of pairwise interactions between nucleotides, and find that they are sparse and dominantly located between consecutive base pairs in the flanking region of TFBS. Nonetheless, interactions between pairs of non-consecutive nucleotides are found to play a significant role in the obtained accurate description of TFBS statistics. The PIM is computationally tractable, and provides a general framework that should be useful for describing and predicting
McKemmish, Laura K; Tennyson, Jonathan
2016-01-01
Accurate knowledge of the rovibronic near-infrared and visible spectra of vanadium monoxide (VO) is very important for studies of cool stellar and hot planetary atmospheres. Here, the required ab initio dipole moment and spin-orbit coupling curves for VO are produced. This data forms the basis of a new VO line list considering 13 different electronic states and containing over 277 million transitions. Open shell transition, metal diatomics are challenging species to model through ab initio quantum mechanics due to the large number of low-lying electronic states, significant spin-orbit coupling and strong static and dynamic electron correlation. Multi-reference configuration interaction methodologies using orbitals from a complete active space self-consistent-field (CASSCF) calculation are the standard technique for these systems. We use different state-specific or minimal-state CASSCF orbitals for each electronic state to maximise the calculation accuracy. The off-diagonal dipole moment controls the intensity...
An Accurately Stable Thermo-Hydro-Mechanical Model for Geo-Environmental Simulations
Gambolati, G.; Castelletto, N.; Ferronato, M.
2011-12-01
In real-world applications involving complex 3D heterogeneous domains the use of advanced numerical algorithms is of paramount importance to stabily, accurately and efficiently solve the coupled system of partial differential equations governing the mass and the energy balance in deformable porous media. The present communication discusses a novel coupled 3-D numerical model based on a suitable combination of Finite Elements (FEs), Mixed FEs (MFEs), and Finite Volumes (FVs) developed with the aim at stabilizing the numerical solution. Elemental pressures and temperatures, nodal displacements and face normal Darcy and Fourier fluxes are the selected primary variables. Such an approach provides an element-wise conservative velocity field, with both pore pressure and stress having the same order of approximation, and allows for the accurate prediction of sharp temperature convective fronts. In particular, the flow-deformation problem is addressed jointly by FEs and MFEs and is coupled to the heat transfer equation using an ad hoc time splitting technique that separates the time temperature evolution into two partial differential equations, accounting for the convective and the diffusive contribution, respectively. The convective part is addressed by a FV scheme which proves effective in treating sharp convective fronts, while the diffusive part is solved by a MFE formulation. A staggered technique is then implemented for the global solution of the coupled thermo-hydro-mechanical problem, solving iteratively the flow-deformation and the heat transport at each time step. Finally, the model is successfully experimented with in realistic applications dealing with geothermal energy extraction and injection.
Nielsen, Jens; d'Avezac, Mayeul; Hetherington, James; Stamatakis, Michail
2013-12-01
Ab initio kinetic Monte Carlo (KMC) simulations have been successfully applied for over two decades to elucidate the underlying physico-chemical phenomena on the surfaces of heterogeneous catalysts. These simulations necessitate detailed knowledge of the kinetics of elementary reactions constituting the reaction mechanism, and the energetics of the species participating in the chemistry. The information about the energetics is encoded in the formation energies of gas and surface-bound species, and the lateral interactions between adsorbates on the catalytic surface, which can be modeled at different levels of detail. The majority of previous works accounted for only pairwise-additive first nearest-neighbor interactions. More recently, cluster-expansion Hamiltonians incorporating long-range interactions and many-body terms have been used for detailed estimations of catalytic rate [C. Wu, D. J. Schmidt, C. Wolverton, and W. F. Schneider, J. Catal. 286, 88 (2012)]. In view of the increasing interest in accurate predictions of catalytic performance, there is a need for general-purpose KMC approaches incorporating detailed cluster expansion models for the adlayer energetics. We have addressed this need by building on the previously introduced graph-theoretical KMC framework, and we have developed Zacros, a FORTRAN2003 KMC package for simulating catalytic chemistries. To tackle the high computational cost in the presence of long-range interactions we introduce parallelization with OpenMP. We further benchmark our framework by simulating a KMC analogue of the NO oxidation system established by Schneider and co-workers [J. Catal. 286, 88 (2012)]. We show that taking into account only first nearest-neighbor interactions may lead to large errors in the prediction of the catalytic rate, whereas for accurate estimates thereof, one needs to include long-range terms in the cluster expansion.
An Efficient Hybrid DSMC/MD Algorithm for Accurate Modeling of Micro Gas Flows
Liang, Tengfei
2013-01-01
Aiming at simulating micro gas flows with accurate boundary conditions, an efficient hybrid algorithmis developed by combining themolecular dynamics (MD) method with the direct simulationMonte Carlo (DSMC)method. The efficiency comes from the fact that theMD method is applied only within the gas-wall interaction layer, characterized by the cut-off distance of the gas-solid interaction potential, to resolve accurately the gas-wall interaction process, while the DSMC method is employed in the remaining portion of the flow field to efficiently simulate rarefied gas transport outside the gas-wall interaction layer. A unique feature about the present scheme is that the coupling between the two methods is realized by matching the molecular velocity distribution function at the DSMC/MD interface, hence there is no need for one-toone mapping between a MD gas molecule and a DSMC simulation particle. Further improvement in efficiency is achieved by taking advantage of gas rarefaction inside the gas-wall interaction layer and by employing the "smart-wall model" proposed by Barisik et al. The developed hybrid algorithm is validated on two classical benchmarks namely 1-D Fourier thermal problem and Couette shear flow problem. Both the accuracy and efficiency of the hybrid algorithm are discussed. As an application, the hybrid algorithm is employed to simulate thermal transpiration coefficient in the free-molecule regime for a system with atomically smooth surface. Result is utilized to validate the coefficients calculated from the pure DSMC simulation with Maxwell and Cercignani-Lampis gas-wall interaction models. ©c 2014 Global-Science Press.
Directory of Open Access Journals (Sweden)
Kostelich Eric J
2011-12-01
Full Text Available Abstract Background Data assimilation refers to methods for updating the state vector (initial condition of a complex spatiotemporal model (such as a numerical weather model by combining new observations with one or more prior forecasts. We consider the potential feasibility of this approach for making short-term (60-day forecasts of the growth and spread of a malignant brain cancer (glioblastoma multiforme in individual patient cases, where the observations are synthetic magnetic resonance images of a hypothetical tumor. Results We apply a modern state estimation algorithm (the Local Ensemble Transform Kalman Filter, previously developed for numerical weather prediction, to two different mathematical models of glioblastoma, taking into account likely errors in model parameters and measurement uncertainties in magnetic resonance imaging. The filter can accurately shadow the growth of a representative synthetic tumor for 360 days (six 60-day forecast/update cycles in the presence of a moderate degree of systematic model error and measurement noise. Conclusions The mathematical methodology described here may prove useful for other modeling efforts in biology and oncology. An accurate forecast system for glioblastoma may prove useful in clinical settings for treatment planning and patient counseling. Reviewers This article was reviewed by Anthony Almudevar, Tomas Radivoyevitch, and Kristin Swanson (nominated by Georg Luebeck.
The propagation of a solitary wave over seabed mud of the Voigt model
Xia, YueZhang; Zhu, KeQin
2012-01-01
In shallow water, seabed mud can dissipate the energy of surface gravity waves effectively. In this paper, solitary wave attenuation induced by seabed mud is studied based on a two-layered system, in which the water is assumed to be inviscid and the mud layer is described by the Voigt model. A set of Boussinesq-type equations suitable for solitary waves over the mud of the Voigt model is established, by combining the perturbation analysis and the Laplace transformation. Degenerating into the case of Newtonian model, our Boussinesq-type equations are equivalent to those of Liu and Chan (2007), while the term indicating mud influence is greatly simplified. Based on the equations, the attenuation of solitary waves is studied. An evolution equation of wave amplitude is obtained and the development of mud velocity profiles is discussed. The modal analysis shows that the first mode always dominates mud dynamics. The results are also compared with those of the Maxwell model.
Kopparla, P.; Natraj, V.; Shia, R. L.; Spurr, R. J. D.; Crisp, D.; Yung, Y. L.
2015-12-01
Radiative transfer (RT) computations form the engine of atmospheric retrieval codes. However, full treatment of RT processes is computationally expensive, prompting usage of two-stream approximations in current exoplanetary atmospheric retrieval codes [Line et al., 2013]. Natraj et al. [2005, 2010] and Spurr and Natraj [2013] demonstrated the ability of a technique using principal component analysis (PCA) to speed up RT computations. In the PCA method for RT performance enhancement, empirical orthogonal functions are developed for binned sets of inherent optical properties that possess some redundancy; costly multiple-scattering RT calculations are only done for those few optical states corresponding to the most important principal components, and correction factors are applied to approximate radiation fields. Kopparla et al. [2015, in preparation] extended the PCA method to a broadband spectral region from the ultraviolet to the shortwave infrared (0.3-3 micron), accounting for major gas absorptions in this region. Here, we apply the PCA method to a some typical (exo-)planetary retrieval problems. Comparisons between the new model, called Universal Principal Component Analysis Radiative Transfer (UPCART) model, two-stream models and line-by-line RT models are performed, for spectral radiances, spectral fluxes and broadband fluxes. Each of these are calculated at the top of the atmosphere for several scenarios with varying aerosol types, extinction and scattering optical depth profiles, and stellar and viewing geometries. We demonstrate that very accurate radiance and flux estimates can be obtained, with better than 1% accuracy in all spectral regions and better than 0.1% in most cases, as compared to a numerically exact line-by-line RT model. The accuracy is enhanced when the results are convolved to typical instrument resolutions. The operational speed and accuracy of UPCART can be further improved by optimizing binning schemes and parallelizing the codes, work
Directory of Open Access Journals (Sweden)
Qingwen Li
2015-01-01
Full Text Available In the tunnel and underground space engineering, the blasting wave will attenuate from shock wave to stress wave to elastic seismic wave in the host rock. Also, the host rock will form crushed zone, fractured zone, and elastic seismic zone under the blasting loading and waves. In this paper, an accurate mathematical dynamic loading model was built. And the crushed zone as well as fractured zone was considered as the blasting vibration source thus deducting the partial energy for cutting host rock. So this complicated dynamic problem of segmented differential blasting was regarded as an equivalent elastic boundary problem by taking advantage of Saint-Venant’s Theorem. At last, a 3D model in finite element software FLAC3D accepted the constitutive parameters, uniformly distributed mutative loading, and the cylindrical attenuation law to predict the velocity curves and effective tensile curves for calculating safety criterion formulas of surrounding rock and tunnel liner after verifying well with the in situ monitoring data.
Walter, Johannes; Thajudeen, Thaseem; Süß, Sebastian; Segets, Doris; Peukert, Wolfgang
2015-04-01
Analytical centrifugation (AC) is a powerful technique for the characterisation of nanoparticles in colloidal systems. As a direct and absolute technique it requires no calibration or measurements of standards. Moreover, it offers simple experimental design and handling, high sample throughput as well as moderate investment costs. However, the full potential of AC for nanoparticle size analysis requires the development of powerful data analysis techniques. In this study we show how the application of direct boundary models to AC data opens up new possibilities in particle characterisation. An accurate analysis method, successfully applied to sedimentation data obtained by analytical ultracentrifugation (AUC) in the past, was used for the first time in analysing AC data. Unlike traditional data evaluation routines for AC using a designated number of radial positions or scans, direct boundary models consider the complete sedimentation boundary, which results in significantly better statistics. We demonstrate that meniscus fitting, as well as the correction of radius and time invariant noise significantly improves the signal-to-noise ratio and prevents the occurrence of false positives due to optical artefacts. Moreover, hydrodynamic non-ideality can be assessed by the residuals obtained from the analysis. The sedimentation coefficient distributions obtained by AC are in excellent agreement with the results from AUC. Brownian dynamics simulations were used to generate numerical sedimentation data to study the influence of diffusion on the obtained distributions. Our approach is further validated using polystyrene and silica nanoparticles. In particular, we demonstrate the strength of AC for analysing multimodal distributions by means of gold nanoparticles.
SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
Lelli, Federico; Schombert, James M
2016-01-01
We introduce SPARC (Spitzer Photometry & Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 um and high-quality rotation curves from previous HI/Halpha studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (~5 dex), and surface brightnesses (~4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass-HI mass relation and the stellar radius-HI radius relation have significant intrinsic scatter, while the HI mass-radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic-to-observed velocity (Vbar/Vobs) for different characteristic radii and values of the stellar mass-to-light ratio (M/L) at [3.6]. Assuming M/L=0.5 Msun/Lsun (as suggested by stellar population models) we find that (i) the gas fraction linearly correlates with total luminosity, (ii) the transition from star-dominated to gas-dominated galaxies roughly correspond...
ACCURATE UNIVERSAL MODELS FOR THE MASS ACCRETION HISTORIES AND CONCENTRATIONS OF DARK MATTER HALOS
International Nuclear Information System (INIS)
A large amount of observations have constrained cosmological parameters and the initial density fluctuation spectrum to a very high accuracy. However, cosmological parameters change with time and the power index of the power spectrum dramatically varies with mass scale in the so-called concordance ΛCDM cosmology. Thus, any successful model for its structural evolution should work well simultaneously for various cosmological models and different power spectra. We use a large set of high-resolution N-body simulations of a variety of structure formation models (scale-free, standard CDM, open CDM, and ΛCDM) to study the mass accretion histories, the mass and redshift dependence of concentrations, and the concentration evolution histories of dark matter halos. We find that there is significant disagreement between the much-used empirical models in the literature and our simulations. Based on our simulation results, we find that the mass accretion rate of a halo is tightly correlated with a simple function of its mass, the redshift, parameters of the cosmology, and of the initial density fluctuation spectrum, which correctly disentangles the effects of all these factors and halo environments. We also find that the concentration of a halo is strongly correlated with the universe age when its progenitor on the mass accretion history first reaches 4% of its current mass. According to these correlations, we develop new empirical models for both the mass accretion histories and the concentration evolution histories of dark matter halos, and the latter can also be used to predict the mass and redshift dependence of halo concentrations. These models are accurate and universal: the same set of model parameters works well for different cosmological models and for halos of different masses at different redshifts, and in the ΛCDM case the model predictions match the simulation results very well even though halo mass is traced to about 0.0005 times the final mass, when
The accurate simulation of the tension test for stainless steel sheet: the plasticity model
International Nuclear Information System (INIS)
Full text: The overall aim of this research project is to achieve the accurate simulation of a hydroforming process chain, in this case the manufacturing of a metal bellow. The work is done in cooperation with the project group for numerical research at the computer centre of the University of Karlsruhe, which is responsible for the simulation itself, while the Institute for Metal Forming Technology (IFU) of the University of Stuttgart is responsible for the material modeling and the resulting differential equations to describe the material behavior. Hydroforming technology uses highly compressed fluid media (up to 4200 bar) to form the basic, mostly metallic material. One hydroforming field is tube hydroforming (THF), which uses tubes or extrusions as basic material. The forming conditions created by hydroforming are quite different from those originated by other processes as for example deep drawing. That's why today's available simulation software is not always able to show satisfying results when a hydroforming process is simulated. The partners of this project try to solve this problem with the FDEM simulation software, developed by W. Schoenauer at the University of Karlsruhe, Germany. It was designed to solve systems of partial differential equations, which in this project are delivered by the IFU. The manufacturing of a metal bellow by hydroforming leads to tensile stress in longitudinal and tangential direction and to bend load due to the shifting and rollforming process. Therefore as a first step, the standardized tensile test is simulated. For plastic deformation a material model developed by D. Banabic is used. It describes the plastic behavior of orthotropic sheet metal. For elastic deformation Hooke's law for isotropic materials is used. In permanent iteration with the simulation the used material model has to be checked for its validity and must be modified if necessary. Refs. 3 (author)
Warm gas in the rotating disk of the Red Rectangle: accurate models of molecular line emission
Bujarrabal, V
2013-01-01
We aim to study the excitation conditions of the molecular gas in the rotating disk of the Red Rectangle, the only post-Asymptotic-Giant-Branch object in which the existence of an equatorial rotating disk has been demonstrated. For this purpose, we developed a complex numerical code that accurately treats radiative transfer in 2-D, adapted to the study of molecular lines from rotating disks. We present far-infrared Herschel/HIFI observations of the 12CO and 13CO J=6-5, J=10-9, and J=16-15 transitions in the Red Rectangle. We also present our code in detail and discuss the accuracy of its predictions, from comparison with well-tested codes. Theoretical line profiles are compared with the empirical data to deduce the physical conditions in the disk by means of model fitting. We conclude that our code is very efficient and produces reliable results. The comparison of the theoretical predictions with our observations reveals that the temperature of the Red Rectangle disk is typically ~ 100-150 K, about twice as h...
Dai, Daoxin; He, Sailing
2004-12-01
An accurate two-dimensional (2D) model is introduced for the simulation of an arrayed-waveguide grating (AWG) demultiplexer by integrating the field distribution along the vertical direction. The equivalent 2D model has almost the same accuracy as the original three-dimensional model and is more accurate for the AWG considered here than the conventional 2D model based on the effective-index method. To further improve the computational efficiency, the reciprocity theory is applied to the optimal design of a flat-top AWG demultiplexer with a special input structure.
Accurate modeling of cache replacement policies in a Data-Grid.
Energy Technology Data Exchange (ETDEWEB)
Otoo, Ekow J.; Shoshani, Arie
2003-01-23
Caching techniques have been used to improve the performance gap of storage hierarchies in computing systems. In data intensive applications that access large data files over wide area network environment, such as a data grid,caching mechanism can significantly improve the data access performance under appropriate workloads. In a data grid, it is envisioned that local disk storage resources retain or cache the data files being used by local application. Under a workload of shared access and high locality of reference, the performance of the caching techniques depends heavily on the replacement policies being used. A replacement policy effectively determines which set of objects must be evicted when space is needed. Unlike cache replacement policies in virtual memory paging or database buffering, developing an optimal replacement policy for data grids is complicated by the fact that the file objects being cached have varying sizes and varying transfer and processing costs that vary with time. We present an accurate model for evaluating various replacement policies and propose a new replacement algorithm referred to as ''Least Cost Beneficial based on K backward references (LCB-K).'' Using this modeling technique, we compare LCB-K with various replacement policies such as Least Frequently Used (LFU), Least Recently Used (LRU), Greedy DualSize (GDS), etc., using synthetic and actual workload of accesses to and from tertiary storage systems. The results obtained show that (LCB-K) and (GDS) are the most cost effective cache replacement policies for storage resource management in data grids.
Stable, accurate and efficient computation of normal modes for horizontal stratified models
Wu, Bo; Chen, Xiaofei
2016-08-01
We propose an adaptive root-determining strategy that is very useful when dealing with trapped modes or Stoneley modes whose energies become very insignificant on the free surface in the presence of low-velocity layers or fluid layers in the model. Loss of modes in these cases or inaccuracy in the calculation of these modes may then be easily avoided. Built upon the generalized reflection/transmission coefficients, the concept of `family of secular functions' that we herein call `adaptive mode observers' is thus naturally introduced to implement this strategy, the underlying idea of which has been distinctly noted for the first time and may be generalized to other applications such as free oscillations or applied to other methods in use when these cases are encountered. Additionally, we have made further improvements upon the generalized reflection/transmission coefficient method; mode observers associated with only the free surface and low-velocity layers (and the fluid/solid interface if the model contains fluid layers) are adequate to guarantee no loss and high precision at the same time of any physically existent modes without excessive calculations. Finally, the conventional definition of the fundamental mode is reconsidered, which is entailed in the cases under study. Some computational aspects are remarked on. With the additional help afforded by our superior root-searching scheme and the possibility of speeding calculation using a less number of layers aided by the concept of `turning point', our algorithm is remarkably efficient as well as stable and accurate and can be used as a powerful tool for widely related applications.
Lachaume, Regis; Rabus, Markus; Jordan, Andres
2015-08-01
In stellar interferometry, the assumption that the observables can be seen as Gaussian, independent variables is the norm. In particular, neither the optical interferometry FITS (OIFITS) format nor the most popular fitting software in the field, LITpro, offer means to specify a covariance matrix or non-Gaussian uncertainties. Interferometric observables are correlated by construct, though. Also, the calibration by an instrumental transfer function ensures that the resulting observables are not Gaussian, even if uncalibrated ones happened to be so.While analytic frameworks have been published in the past, they are cumbersome and there is no generic implementation available. We propose here a relatively simple way of dealing with correlated errors without the need to extend the OIFITS specification or making some Gaussian assumptions. By repeatedly picking at random which interferograms, which calibrator stars, and which are the errors on their diameters, and performing the data processing on the bootstrapped data, we derive a sampling of p(O), the multivariate probability density function (PDF) of the observables O. The results can be stored in a normal OIFITS file. Then, given a model m with parameters P predicting observables O = m(P), we can estimate the PDF of the model parameters f(P) = p(m(P)) by using a density estimation of the observables' PDF p.With observations repeated over different baselines, on nights several days apart, and with a significant set of calibrators systematic errors are de facto taken into account. We apply the technique to a precise and accurate assessment of stellar diameters obtained at the Very Large Telescope Interferometer with PIONIER.
Towards more accurate wind and solar power prediction by improving NWP model physics
Steiner, Andrea; Köhler, Carmen; von Schumann, Jonas; Ritter, Bodo
2014-05-01
nighttime to well mixed conditions during the day presents a big challenge to NWP models. Fast decrease and successive increase in hub-height wind speed after sunrise, and the formation of nocturnal low level jets will be discussed. For PV, the life cycle of low stratus clouds and fog is crucial. Capturing these processes correctly depends on the accurate simulation of diffusion or vertical momentum transport and the interaction with other atmospheric and soil processes within the numerical weather model. Results from Single Column Model simulations and 3d case studies will be presented. Emphasis is placed on wind forecasts; however, some references to highlights concerning the PV-developments will also be given. *) ORKA: Optimierung von Ensembleprognosen regenerativer Einspeisung für den Kürzestfristbereich am Anwendungsbeispiel der Netzsicherheitsrechnungen **) EWeLiNE: Erstellung innovativer Wetter- und Leistungsprognosemodelle für die Netzintegration wetterabhängiger Energieträger, www.projekt-eweline.de
Wheeler, M.F.
2010-09-06
For many years there have been formulations considered for modeling single phase ow on general hexahedra grids. These include the extended mixed nite element method, and families of mimetic nite di erence methods. In most of these schemes either no rate of convergence of the algorithm has been demonstrated both theoret- ically and computationally or a more complicated saddle point system needs to be solved for an accurate solution. Here we describe a multipoint ux mixed nite element (MFMFE) method [5, 2, 3]. This method is motivated from the multipoint ux approximation (MPFA) method [1]. The MFMFE method is locally conservative with continuous ux approximations and is a cell-centered scheme for the pressure. Compared to the MPFA method, the MFMFE has a variational formulation, since it can be viewed as a mixed nite element with special approximating spaces and quadrature rules. The framework allows han- dling of hexahedral grids with non-planar faces by applying trilinear mappings from physical elements to reference cubic elements. In addition, there are several multi- scale and multiphysics extensions such as the mortar mixed nite element method that allows the treatment of non-matching grids [4]. Extensions to the two-phase oil-water ow are considered. We reformulate the two- phase model in terms of total velocity, capillary velocity, water pressure, and water saturation. We choose water pressure and water saturation as primary variables. The total velocity is driven by the gradient of the water pressure and total mobility. Iterative coupling scheme is employed for the coupled system. This scheme allows treatments of di erent time scales for the water pressure and water saturation. In each time step, we rst solve the pressure equation using the MFMFE method; we then Center for Subsurface Modeling, The University of Texas at Austin, Austin, TX 78712; mfw@ices.utexas.edu. yCenter for Subsurface Modeling, The University of Texas at Austin, Austin, TX 78712; gxue
Toward accurate tooth segmentation from computed tomography images using a hybrid level set model
Energy Technology Data Exchange (ETDEWEB)
Gan, Yangzhou; Zhao, Qunfei [Department of Automation, Shanghai Jiao Tong University, and Key Laboratory of System Control and Information Processing, Ministry of Education of China, Shanghai 200240 (China); Xia, Zeyang, E-mail: zy.xia@siat.ac.cn, E-mail: jing.xiong@siat.ac.cn; Hu, Ying [Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, and The Chinese University of Hong Kong, Shenzhen 518055 (China); Xiong, Jing, E-mail: zy.xia@siat.ac.cn, E-mail: jing.xiong@siat.ac.cn [Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 510855 (China); Zhang, Jianwei [TAMS, Department of Informatics, University of Hamburg, Hamburg 22527 (Germany)
2015-01-15
Purpose: A three-dimensional (3D) model of the teeth provides important information for orthodontic diagnosis and treatment planning. Tooth segmentation is an essential step in generating the 3D digital model from computed tomography (CT) images. The aim of this study is to develop an accurate and efficient tooth segmentation method from CT images. Methods: The 3D dental CT volumetric images are segmented slice by slice in a two-dimensional (2D) transverse plane. The 2D segmentation is composed of a manual initialization step and an automatic slice by slice segmentation step. In the manual initialization step, the user manually picks a starting slice and selects a seed point for each tooth in this slice. In the automatic slice segmentation step, a developed hybrid level set model is applied to segment tooth contours from each slice. Tooth contour propagation strategy is employed to initialize the level set function automatically. Cone beam CT (CBCT) images of two subjects were used to tune the parameters. Images of 16 additional subjects were used to validate the performance of the method. Volume overlap metrics and surface distance metrics were adopted to assess the segmentation accuracy quantitatively. The volume overlap metrics were volume difference (VD, mm{sup 3}) and Dice similarity coefficient (DSC, %). The surface distance metrics were average symmetric surface distance (ASSD, mm), RMS (root mean square) symmetric surface distance (RMSSSD, mm), and maximum symmetric surface distance (MSSD, mm). Computation time was recorded to assess the efficiency. The performance of the proposed method has been compared with two state-of-the-art methods. Results: For the tested CBCT images, the VD, DSC, ASSD, RMSSSD, and MSSD for the incisor were 38.16 ± 12.94 mm{sup 3}, 88.82 ± 2.14%, 0.29 ± 0.03 mm, 0.32 ± 0.08 mm, and 1.25 ± 0.58 mm, respectively; the VD, DSC, ASSD, RMSSSD, and MSSD for the canine were 49.12 ± 9.33 mm{sup 3}, 91.57 ± 0.82%, 0.27 ± 0.02 mm, 0
Applicability of CFD Modelling in Determining Accurate Weir Discharge: Water Level Relationships
Rombouts, P.M.M.; Tralli, A.; Langeveld, J.G.; Verhaart, F.; Clemens, F.H.L.R.
2014-01-01
Being able to accurately determine weir discharges is of key importance in urban water management. The most common method is performing a level measurement and calculating the discharge using the standard weir equation. Since this equation is only valid in certain conditions, this can lead to large
Fast and accurate conversion of atomic models into electron density maps
Directory of Open Access Journals (Sweden)
Carlos O.S. Sorzano
2015-03-01
Full Text Available New image processing methodologies and algorithms have greatly contributed to the signi cant progress in three-dimensional electron microscopy (3DEM of biological complexes we have seen over the last decades. Naturally, the availability of accurate procedures for the objective testing of new algorithms is a crucial requirement for the further advancement of the eld. A good and accepted testing work ow involves the generation of realistic 3DEM-like maps of biological macromolecules from which some measure of ground truth can be derived, ideally because their 3D atomic structure is already known. In this work we propose a very accurate generation of maps using atomic form factors for electron scattering. We thoroughly review current approaches in the eld, quantitatively demonstrating the bene ts of the new methodology. Additionally, we study a concrete example of the use of this approach for hypothesis testing in 3D Electron Microscopy.
A simple and accurate model for Love wave based sensors: Dispersion equation and mass sensitivity
Jiansheng Liu
2014-01-01
Dispersion equation is an important tool for analyzing propagation properties of acoustic waves in layered structures. For Love wave (LW) sensors, the dispersion equation with an isotropic-considered substrate is too rough to get accurate solutions; the full dispersion equation with a piezoelectric-considered substrate is too complicated to get simple and practical expressions for optimizing LW-based sensors. In this work, a dispersion equation is introduced for Love waves in a layered struct...
Energy Technology Data Exchange (ETDEWEB)
Dunn, Nicholas J. H.; Noid, W. G., E-mail: wnoid@chem.psu.edu [Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)
2015-12-28
The present work investigates the capability of bottom-up coarse-graining (CG) methods for accurately modeling both structural and thermodynamic properties of all-atom (AA) models for molecular liquids. In particular, we consider 1, 2, and 3-site CG models for heptane, as well as 1 and 3-site CG models for toluene. For each model, we employ the multiscale coarse-graining method to determine interaction potentials that optimally approximate the configuration dependence of the many-body potential of mean force (PMF). We employ a previously developed “pressure-matching” variational principle to determine a volume-dependent contribution to the potential, U{sub V}(V), that approximates the volume-dependence of the PMF. We demonstrate that the resulting CG models describe AA density fluctuations with qualitative, but not quantitative, accuracy. Accordingly, we develop a self-consistent approach for further optimizing U{sub V}, such that the CG models accurately reproduce the equilibrium density, compressibility, and average pressure of the AA models, although the CG models still significantly underestimate the atomic pressure fluctuations. Additionally, by comparing this array of models that accurately describe the structure and thermodynamic pressure of heptane and toluene at a range of different resolutions, we investigate the impact of bottom-up coarse-graining upon thermodynamic properties. In particular, we demonstrate that U{sub V} accounts for the reduced cohesion in the CG models. Finally, we observe that bottom-up coarse-graining introduces subtle correlations between the resolution, the cohesive energy density, and the “simplicity” of the model.
Dunn, Nicholas J. H.; Noid, W. G.
2015-12-01
The present work investigates the capability of bottom-up coarse-graining (CG) methods for accurately modeling both structural and thermodynamic properties of all-atom (AA) models for molecular liquids. In particular, we consider 1, 2, and 3-site CG models for heptane, as well as 1 and 3-site CG models for toluene. For each model, we employ the multiscale coarse-graining method to determine interaction potentials that optimally approximate the configuration dependence of the many-body potential of mean force (PMF). We employ a previously developed "pressure-matching" variational principle to determine a volume-dependent contribution to the potential, UV(V), that approximates the volume-dependence of the PMF. We demonstrate that the resulting CG models describe AA density fluctuations with qualitative, but not quantitative, accuracy. Accordingly, we develop a self-consistent approach for further optimizing UV, such that the CG models accurately reproduce the equilibrium density, compressibility, and average pressure of the AA models, although the CG models still significantly underestimate the atomic pressure fluctuations. Additionally, by comparing this array of models that accurately describe the structure and thermodynamic pressure of heptane and toluene at a range of different resolutions, we investigate the impact of bottom-up coarse-graining upon thermodynamic properties. In particular, we demonstrate that UV accounts for the reduced cohesion in the CG models. Finally, we observe that bottom-up coarse-graining introduces subtle correlations between the resolution, the cohesive energy density, and the "simplicity" of the model.
Surface electron density models for accurate ab initio molecular dynamics with electronic friction
Novko, D.; Blanco-Rey, M.; Alducin, M.; Juaristi, J. I.
2016-06-01
Ab initio molecular dynamics with electronic friction (AIMDEF) is a valuable methodology to study the interaction of atomic particles with metal surfaces. This method, in which the effect of low-energy electron-hole (e-h) pair excitations is treated within the local density friction approximation (LDFA) [Juaristi et al., Phys. Rev. Lett. 100, 116102 (2008), 10.1103/PhysRevLett.100.116102], can provide an accurate description of both e-h pair and phonon excitations. In practice, its applicability becomes a complicated task in those situations of substantial surface atoms displacements because the LDFA requires the knowledge at each integration step of the bare surface electron density. In this work, we propose three different methods of calculating on-the-fly the electron density of the distorted surface and we discuss their suitability under typical surface distortions. The investigated methods are used in AIMDEF simulations for three illustrative adsorption cases, namely, dissociated H2 on Pd(100), N on Ag(111), and N2 on Fe(110). Our AIMDEF calculations performed with the three approaches highlight the importance of going beyond the frozen surface density to accurately describe the energy released into e-h pair excitations in case of large surface atom displacements.
Ustinov, E A
2014-10-01
Commensurate-incommensurate (C-IC) transition of krypton molecular layer on graphite received much attention in recent decades in theoretical and experimental researches. However, there still exists a possibility of generalization of the phenomenon from thermodynamic viewpoint on the basis of accurate molecular simulation. Recently, a new technique was developed for analysis of two-dimensional (2D) phase transitions in systems involving a crystalline phase, which is based on accounting for the effect of temperature and the chemical potential on the lattice constant of the 2D layer using the Gibbs-Duhem equation [E. A. Ustinov, J. Chem. Phys. 140, 074706 (2014)]. The technique has allowed for determination of phase diagrams of 2D argon layers on the uniform surface and in slit pores. This paper extends the developed methodology on systems accounting for the periodic modulation of the substrate potential. The main advantage of the developed approach is that it provides highly accurate evaluation of the chemical potential of crystalline layers, which allows reliable determination of temperature and other parameters of various 2D phase transitions. Applicability of the methodology is demonstrated on the krypton-graphite system. Analysis of phase diagram of the krypton molecular layer, thermodynamic functions of coexisting phases, and a method of prediction of adsorption isotherms is considered accounting for a compression of the graphite due to the krypton-carbon interaction. The temperature and heat of C-IC transition has been reliably determined for the gas-solid and solid-solid system.
International Nuclear Information System (INIS)
Accurate modeling of the photon acquisition process in pinhole SPECT is essential for optimizing resolution. In this work, the authors develop an accurate system model in which pinhole finite aperture and depth-dependent geometric sensitivity are explicitly included. To achieve high-resolution pinhole SPECT, the voxel size is usually set in the range of sub-millimeter so that the total number of image voxels increase accordingly. It is inevitably that a system matrix that models a variety of favorable physical factors will become extremely sophisticated. An efficient implementation for such an accurate system model is proposed in this research. We first use the geometric symmetries to reduce redundant entries in the matrix. Due to the sparseness of the matrix, only non-zero terms are stored. A novel center-to-radius recording rule is also developed to effectively describe the relation between a voxel and its related detectors at every projection angle. The proposed system matrix is also suitable for multi-threaded computing. Finally, the accuracy and effectiveness of the proposed system model is evaluated in a workstation equipped with two Quad-Core Intel X eon processors.
Accurate and fast table look-up models for leakage current analysis in 65 nm CMOS technology
Institute of Scientific and Technical Information of China (English)
薛冀颖; 李涛; 余志平
2009-01-01
Novel physical models for leakage current analysis in 65 nm technology are proposed. Taking into con-sideration the process variations and emerging effects in nano-scaled technology, the presented models are capable of accurately estimating the subthreshold leakage current and junction tunneling leakage current in 65 nm technol-ogy. Based on the physical models, new table look-up models are developed and first applied to leakage current analysis in pursuit of higher simulation speed. Simulation results show that the novel physical models are in ex-cellent agreement with the data measured from the foundry in the 65 nm process, and the proposed table look-up models can provide great computational efficiency by using suitable interpolation techniques. Compared with the traditional physical-based models, the table look-up models can achieve 2.5X speedup on average on a variety of industry circuits.
Can crop-climate models be accurate and precise? A case study for wheat production in Denmark
DEFF Research Database (Denmark)
Montesino San Martin, Manuel; Olesen, Jørgen E.; Porter, John Roy
2015-01-01
and mechanistic wheat models to assess how differences in the extent of process understanding in models affects uncertainties in projected impact. Predictive power of the models was tested via both accuracy (bias) and precision (or tightness of grouping) of yield projections for extrapolated weather conditions....... Yields predicted by the mechanistic model were generally more accurate than the empirical models for extrapolated conditions. This trend does not hold for all extrapolations; mechanistic and empirical models responded differently due to their sensitivities to distinct weather features. However, higher...... accuracy comes at the cost of precision of the mechanistic model to embrace all observations within given boundaries. The approaches showed complementarity in sensitivity to weather variables and in accuracy for different extrapolation domains. Their differences in model precision and accuracy make them...
Zhang, Xiang; Vu-Quoc, Loc
2007-07-01
We present in this paper the displacement-driven version of a tangential force-displacement (TFD) model that accounts for both elastic and plastic deformations together with interfacial friction occurring in collisions of spherical particles. This elasto-plastic frictional TFD model, with its force-driven version presented in [L. Vu-Quoc, L. Lesburg, X. Zhang. An accurate tangential force-displacement model for granular-flow simulations: contacting spheres with plastic deformation, force-driven formulation, Journal of Computational Physics 196(1) (2004) 298-326], is consistent with the elasto-plastic frictional normal force-displacement (NFD) model presented in [L. Vu-Quoc, X. Zhang. An elasto-plastic contact force-displacement model in the normal direction: displacement-driven version, Proceedings of the Royal Society of London, Series A 455 (1991) 4013-4044]. Both the NFD model and the present TFD model are based on the concept of additive decomposition of the radius of contact area into an elastic part and a plastic part. The effect of permanent indentation after impact is represented by a correction to the radius of curvature. The effect of material softening due to plastic flow is represented by a correction to the elastic moduli. The proposed TFD model is accurate, and is validated against nonlinear finite element analyses involving plastic flows in both the loading and unloading conditions. The proposed consistent displacement-driven, elasto-plastic NFD and TFD models are designed for implementation in computer codes using the discrete-element method (DEM) for granular-flow simulations. The model is shown to be accurate and is validated against nonlinear elasto-plastic finite-element analysis.
Multi Sensor Data Integration for AN Accurate 3d Model Generation
Chhatkuli, S.; Satoh, T.; Tachibana, K.
2015-05-01
The aim of this paper is to introduce a novel technique of data integration between two different data sets, i.e. laser scanned RGB point cloud and oblique imageries derived 3D model, to create a 3D model with more details and better accuracy. In general, aerial imageries are used to create a 3D city model. Aerial imageries produce an overall decent 3D city models and generally suit to generate 3D model of building roof and some non-complex terrain. However, the automatically generated 3D model, from aerial imageries, generally suffers from the lack of accuracy in deriving the 3D model of road under the bridges, details under tree canopy, isolated trees, etc. Moreover, the automatically generated 3D model from aerial imageries also suffers from undulated road surfaces, non-conforming building shapes, loss of minute details like street furniture, etc. in many cases. On the other hand, laser scanned data and images taken from mobile vehicle platform can produce more detailed 3D road model, street furniture model, 3D model of details under bridge, etc. However, laser scanned data and images from mobile vehicle are not suitable to acquire detailed 3D model of tall buildings, roof tops, and so forth. Our proposed approach to integrate multi sensor data compensated each other's weakness and helped to create a very detailed 3D model with better accuracy. Moreover, the additional details like isolated trees, street furniture, etc. which were missing in the original 3D model derived from aerial imageries could also be integrated in the final model automatically. During the process, the noise in the laser scanned data for example people, vehicles etc. on the road were also automatically removed. Hence, even though the two dataset were acquired in different time period the integrated data set or the final 3D model was generally noise free and without unnecessary details.
Minimum required number of specimen records to develop accurate species distribution models
Proosdij, van A.S.J.; Sosef, M.S.M.; Wieringa, J.J.; Raes, N.
2016-01-01
Species distribution models (SDMs) are widely used to predict the occurrence of species. Because SDMs generally use presence-only data, validation of the predicted distribution and assessing model accuracy is challenging. Model performance depends on both sample size and species’ prevalence, being t
Minimum required number of specimen records to develop accurate species distribution models
Proosdij, van A.S.J.; Sosef, M.S.M.; Wieringa, J.J.; Raes, N.
2015-01-01
Species Distribution Models (SDMs) are widely used to predict the occurrence of species. Because SDMs generally use presence-only data, validation of the predicted distribution and assessing model accuracy is challenging. Model performance depends on both sample size and species’ prevalence, being t
MULTI SENSOR DATA INTEGRATION FOR AN ACCURATE 3D MODEL GENERATION
S. Chhatkuli; Satoh, T; Tachibana, K
2015-01-01
The aim of this paper is to introduce a novel technique of data integration between two different data sets, i.e. laser scanned RGB point cloud and oblique imageries derived 3D model, to create a 3D model with more details and better accuracy. In general, aerial imageries are used to create a 3D city model. Aerial imageries produce an overall decent 3D city models and generally suit to generate 3D model of building roof and some non-complex terrain. However, the automatically generated 3D mod...
West, J. B.; Ehleringer, J. R.; Cerling, T.
2006-12-01
Understanding how the biosphere responds to change it at the heart of biogeochemistry, ecology, and other Earth sciences. The dramatic increase in human population and technological capacity over the past 200 years or so has resulted in numerous, simultaneous changes to biosphere structure and function. This, then, has lead to increased urgency in the scientific community to try to understand how systems have already responded to these changes, and how they might do so in the future. Since all biospheric processes exhibit some patchiness or patterns over space, as well as time, we believe that understanding the dynamic interactions between natural systems and human technological manipulations can be improved if these systems are studied in an explicitly spatial context. We present here results of some of our efforts to model the spatial variation in the stable isotope ratios (δ2H and δ18O) of plants over large spatial extents, and how these spatial model predictions compare to spatially explicit data. Stable isotopes trace and record ecological processes and as such, if modeled correctly over Earth's surface allow us insights into changes in biosphere states and processes across spatial scales. The data-model comparisons show good agreement, in spite of the remaining uncertainties (e.g., plant source water isotopic composition). For example, inter-annual changes in climate are recorded in wine stable isotope ratios. Also, a much simpler model of leaf water enrichment driven with spatially continuous global rasters of precipitation and climate normals largely agrees with complex GCM modeling that includes leaf water δ18O. Our results suggest that modeling plant stable isotope ratios across large spatial extents may be done with reasonable accuracy, including over time. These spatial maps, or isoscapes, can now be utilized to help understand spatially distributed data, as well as to help guide future studies designed to understand ecological change across
International Nuclear Information System (INIS)
Model error is one of the key factors restricting the accuracy of numerical weather prediction (NWP). Considering the continuous evolution of the atmosphere, the observed data (ignoring the measurement error) can be viewed as a series of solutions of an accurate model governing the actual atmosphere. Model error is represented as an unknown term in the accurate model, thus NWP can be considered as an inverse problem to uncover the unknown error term. The inverse problem models can absorb long periods of observed data to generate model error correction procedures. They thus resolve the deficiency and faultiness of the NWP schemes employing only the initial-time data. In this study we construct two inverse problem models to estimate and extrapolate the time-varying and spatial-varying model errors in both the historical and forecast periods by using recent observations and analogue phenomena of the atmosphere. Numerical experiment on Burgers' equation has illustrated the substantial forecast improvement using inverse problem algorithms. The proposed inverse problem methods of suppressing NWP errors will be useful in future high accuracy applications of NWP. (geophysics, astronomy, and astrophysics)
The Impact of Accurate Extinction Measurements for X-ray Spectral Models
Smith, Randall K; Corrales, Lia
2016-01-01
Interstellar extinction includes both absorption and scattering of photons from interstellar gas and dust grains, and it has the effect of altering a source's spectrum and its total observed intensity. However, while multiple absorption models exist, there are no useful scattering models in standard X-ray spectrum fitting tools, such as XSPEC. Nonetheless, X-ray halos, created by scattering from dust grains, are detected around even moderately absorbed sources and the impact on an observed source spectrum can be significant, if modest, compared to direct absorption. By convolving the scattering cross section with dust models, we have created a spectral model as a function of energy, type of dust, and extraction region that can be used with models of direct absorption. This will ensure the extinction model is consistent and enable direct connections to be made between a source's X-ray spectral fits and its UV/optical extinction.
Efficient and accurate approach to modeling the microstructure and defect properties of LaCoO3
Buckeridge, J.; Taylor, F. H.; Catlow, C. R. A.
2016-04-01
Complex perovskite oxides are promising materials for cathode layers in solid oxide fuel cells. Such materials have intricate electronic, magnetic, and crystalline structures that prove challenging to model accurately. We analyze a wide range of standard density functional theory approaches to modeling a highly promising system, the perovskite LaCoO3, focusing on optimizing the Hubbard U parameter to treat the self-interaction of the B-site cation's d states, in order to determine the most appropriate method to study defect formation and the effect of spin on local structure. By calculating structural and electronic properties for different magnetic states we determine that U =4 eV for Co in LaCoO3 agrees best with available experiments. We demonstrate that the generalized gradient approximation (PBEsol +U ) is most appropriate for studying structure versus spin state, while the local density approximation (LDA +U ) is most appropriate for determining accurate energetics for defect properties.
GLOBAL THRESHOLD AND REGION-BASED ACTIVE CONTOUR MODEL FOR ACCURATE IMAGE SEGMENTATION
Nuseiba M. Altarawneh; Suhuai Luo; Brian Regan; Changming Sun; Fucang Jia
2014-01-01
In this contribution, we develop a novel global threshold-based active contour model. This model deploys a new edge-stopping function to control the direction of the evolution and to stop the evolving contour at weak or blurred edges. An implementation of the model requires the use of selective binary and Gaussian filtering regularized level set (SBGFRLS) method. The method uses either a selective local or global segmentation property. It penalizes the level set function to force ...
Seth, Ajay; Matias, Ricardo; António P Veloso; Delp, Scott L.
2016-01-01
The complexity of shoulder mechanics combined with the movement of skin relative to the scapula makes it difficult to measure shoulder kinematics with sufficient accuracy to distinguish between symptomatic and asymptomatic individuals. Multibody skeletal models can improve motion capture accuracy by reducing the space of possible joint movements, and models are used widely to improve measurement of lower limb kinematics. In this study, we developed a rigid-body model of a scapulothoracic join...
EXAMINING THE MOVEMENTS OF MOBILE NODES IN THE REAL WORLD TO PRODUCE ACCURATE MOBILITY MODELS
Directory of Open Access Journals (Sweden)
TANWEER ALAM
2010-09-01
Full Text Available All communication occurs through a wireless median in an ad hoc network. Ad hoc networks are dynamically created and maintained by the individual nodes comprising the network. Random Waypoint Mobility Model is a model that includes pause times between changes in destination and speed. To produce a real-world environment within which an ad hoc network can be formed among a set of nodes, there is a need for the development of realistic, generic and comprehensive mobility models. In this paper, we examine the movements of entities in the real world and present the production of mobility model in an ad hoc network.
Patel, Utkarsh R.; Triverio, Piero
2015-01-01
An accurate knowledge of the per-unit length impedance of power cables is necessary to correctly predict electromagnetic transients in power systems. In particular, skin, proximity, and ground return effects must be properly estimated. In many applications, the medium that surrounds the cable is not uniform and can consist of multiple layers of different conductivity, such as dry and wet soil, water, or air. We introduce a multilayer ground model for the recently-proposed MoM-SO method, suita...
Fault Tolerance for Industrial Actuators in Absence of Accurate Models and Hardware Redundancy
DEFF Research Database (Denmark)
Papageorgiou, Dimitrios; Blanke, Mogens; Niemann, Hans Henrik;
2015-01-01
This paper investigates Fault-Tolerant Control for closed-loop systems where only coarse models are available and there is lack of actuator and sensor redundancies. The problem is approached in the form of a typical servomotor in closed-loop. A linear model is extracted from input/output data to ...
Active appearance model and deep learning for more accurate prostate segmentation on MRI
Cheng, Ruida; Roth, Holger R.; Lu, Le; Wang, Shijun; Turkbey, Baris; Gandler, William; McCreedy, Evan S.; Agarwal, Harsh K.; Choyke, Peter; Summers, Ronald M.; McAuliffe, Matthew J.
2016-03-01
Prostate segmentation on 3D MR images is a challenging task due to image artifacts, large inter-patient prostate shape and texture variability, and lack of a clear prostate boundary specifically at apex and base levels. We propose a supervised machine learning model that combines atlas based Active Appearance Model (AAM) with a Deep Learning model to segment the prostate on MR images. The performance of the segmentation method is evaluated on 20 unseen MR image datasets. The proposed method combining AAM and Deep Learning achieves a mean Dice Similarity Coefficient (DSC) of 0.925 for whole 3D MR images of the prostate using axial cross-sections. The proposed model utilizes the adaptive atlas-based AAM model and Deep Learning to achieve significant segmentation accuracy.
Accurate characterization and modeling of transmission lines for GaAs MMIC's
Finlay, Hugh J.; Jansen, Rolf H.; Jenkins, John A.; Eddison, Ian G.
1988-06-01
The authors discuss computer-aided design (CAD) tools together with high-accuracy microwave measurements to realize improved design data for GaAs monolithic microwave integrated circuits (MMICs). In particular, a combined theoretical and experimental approach to the generation of an accurate design database for transmission lines on GaAs MMICs is presented. The theoretical approach is based on an improved transmission-line theory which is part of the spectral-domain hybrid-mode computer program MCLINE. The benefit of this approach in the design of multidielectric-media transmission lines is described. The program was designed to include loss mechanisms in all dielectric layers and to include conductor and surface roughness loss contributions. As an example, using GaAs ring resonator techniques covering 2 to 24 GHz, accuracies in effective dielectric constant and loss of 1 percent and 15 percent respectively, are presented. By combining theoretical and experimental techniques, a generalized MMIC microstrip design database is outlined.
Highly Accurate Tree Models Derived from Terrestrial Laser Scan Data: A Method Description
Directory of Open Access Journals (Sweden)
Jan Hackenberg
2014-05-01
Full Text Available This paper presents a method for fitting cylinders into a point cloud, derived from a terrestrial laser-scanned tree. Utilizing high scan quality data as the input, the resulting models describe the branching structure of the tree, capable of detecting branches with a diameter smaller than a centimeter. The cylinders are stored as a hierarchical tree-like data structure encapsulating parent-child neighbor relations and incorporating the tree’s direction of growth. This structure enables the efficient extraction of tree components, such as the stem or a single branch. The method was validated both by applying a comparison of the resulting cylinder models with ground truth data and by an analysis between the input point clouds and the models. Tree models were accomplished representing more than 99% of the input point cloud, with an average distance from the cylinder model to the point cloud within sub-millimeter accuracy. After validation, the method was applied to build two allometric models based on 24 tree point clouds as an example of the application. Computation terminated successfully within less than 30 min. For the model predicting the total above ground volume, the coefficient of determination was 0.965, showing the high potential of terrestrial laser-scanning for forest inventories.
A new geometric-based model to accurately estimate arm and leg inertial estimates.
Wicke, Jason; Dumas, Geneviève A
2014-06-01
Segment estimates of mass, center of mass and moment of inertia are required input parameters to analyze the forces and moments acting across the joints. The objectives of this study were to propose a new geometric model for limb segments, to evaluate it against criterion values obtained from DXA, and to compare its performance to five other popular models. Twenty five female and 24 male college students participated in the study. For the criterion measures, the participants underwent a whole body DXA scan, and estimates for segment mass, center of mass location, and moment of inertia (frontal plane) were directly computed from the DXA mass units. For the new model, the volume was determined from two standing frontal and sagittal photographs. Each segment was modeled as a stack of slices, the sections of which were ellipses if they are not adjoining another segment and sectioned ellipses if they were adjoining another segment (e.g. upper arm and trunk). Length of axes of the ellipses was obtained from the photographs. In addition, a sex-specific, non-uniform density function was developed for each segment. A series of anthropometric measurements were also taken by directly following the definitions provided of the different body segment models tested, and the same parameters determined for each model. Comparison of models showed that estimates from the new model were consistently closer to the DXA criterion than those from the other models, with an error of less than 5% for mass and moment of inertia and less than about 6% for center of mass location. PMID:24735506
Telfer, Scott; Erdemir, Ahmet; Woodburn, James; Cavanagh, Peter R
2016-01-25
Integration of patient-specific biomechanical measurements into the design of therapeutic footwear has been shown to improve clinical outcomes in patients with diabetic foot disease. The addition of numerical simulations intended to optimise intervention design may help to build on these advances, however at present the time and labour required to generate and run personalised models of foot anatomy restrict their routine clinical utility. In this study we developed second-generation personalised simple finite element (FE) models of the forefoot with varying geometric fidelities. Plantar pressure predictions from barefoot, shod, and shod with insole simulations using simplified models were compared to those obtained from CT-based FE models incorporating more detailed representations of bone and tissue geometry. A simplified model including representations of metatarsals based on simple geometric shapes, embedded within a contoured soft tissue block with outer geometry acquired from a 3D surface scan was found to provide pressure predictions closest to the more complex model, with mean differences of 13.3kPa (SD 13.4), 12.52kPa (SD 11.9) and 9.6kPa (SD 9.3) for barefoot, shod, and insole conditions respectively. The simplified model design could be produced in 3h in the case of the more detailed model, and solved on average 24% faster. FE models of the forefoot based on simplified geometric representations of the metatarsal bones and soft tissue surface geometry from 3D surface scans may potentially provide a simulation approach with improved clinical utility, however further validity testing around a range of therapeutic footwear types is required.
Accurate Modeling of Multilayer Transmission Lines for High-Speed Digital Interconnects
Directory of Open Access Journals (Sweden)
Sarhan M. Musa
2014-03-01
Full Text Available In this paper, we consider the finite element modeling of multilayer transmission lines for high-speed digital interconnects. We mainly focused on the modeling of the transmission structures with both cases of symmetric and asymmetric geometries. We specifically designed asymmetric coupled microstrips and four-line symmetric coupled microstrips with a two-layer substrate. We computed the capacitance matrix for asymmetric coupled microstrips and the capacitance, and inductance matrices for four-line symmetric coupled microstrips on a twolayer substrate. We also provide the potential distribution spectrums of the models.
Energy Technology Data Exchange (ETDEWEB)
Maeda, Chiaki; Tasaki, Satoko; Kirihara, Soshu, E-mail: c-maeda@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11-1 Mihogaoka, Ibaraki City, Osaka 567-0047 (Japan)
2011-05-15
Computer graphic models of bioscaffolds with four-coordinate lattice structures of solid rods in artificial bones were designed by using a computer aided design. The scaffold models composed of acryl resin with hydroxyapatite particles at 45vol. % were fabricated by using stereolithography of a computer aided manufacturing. After dewaxing and sintering heat treatment processes, the ceramics scaffold models with four-coordinate lattices and fine hydroxyapatite microstructures were obtained successfully. By using a computer aided analysis, it was found that bio-fluids could flow extensively inside the sintered scaffolds. This result shows that the lattice structures will realize appropriate bio-fluid circulations and promote regenerations of new bones.
HIGH ACCURATE LOW COMPLEX FACE DETECTION BASED ON KL TRANSFORM AND YCBCR GAUSSIAN MODEL
Directory of Open Access Journals (Sweden)
Epuru Nithish Kumar
2013-05-01
Full Text Available This paper presents a skin color model for face detection based on YCbCr Gauss model and KL transform. The simple gauss model and the region model of the skin color are designed in both KL color space and YCbCr space according to clustering. Skin regions are segmented using optimal threshold value obtained from adaptive algorithm. The segmentation results are then used to eliminate likely skin region in the gauss-likelihood image. Different morphological processes are then used to eliminate noise from binary image. In order to locate the face, the obtained regions are grouped out with simple detection algorithms. The proposed algorithm works well for complex background and many faces.
Dale, Andy; Stolpovsky, Konstantin; Wallmann, Klaus
2016-04-01
The recycling and burial of biogenic material in the sea floor plays a key role in the regulation of ocean chemistry. Proper consideration of these processes in ocean biogeochemical models is becoming increasingly recognized as an important step in model validation and prediction. However, the rate of organic matter remineralization in sediments and the benthic flux of redox-sensitive elements are difficult to predict a priori. In this communication, examples of empirical benthic flux models that can be coupled to earth system models to predict sediment-water exchange in the open ocean are presented. Large uncertainties hindering further progress in this field include knowledge of the reactivity of organic carbon reaching the sediment, the importance of episodic variability in bottom water chemistry and particle rain rates (for both the deep-sea and margins) and the role of benthic fauna. How do we meet the challenge?
A tri-stage cluster identification model for accurate analysis of seismic catalogs
Directory of Open Access Journals (Sweden)
S. J. Nanda
2013-02-01
Full Text Available In this paper we propose a tri-stage cluster identification model that is a combination of a simple single iteration distance algorithm and an iterative K-means algorithm. In this study of earthquake seismicity, the model considers event location, time and magnitude information from earthquake catalog data to efficiently classify events as either background or mainshock and aftershock sequences. Tests on a synthetic seismicity catalog demonstrate the efficiency of the proposed model in terms of accuracy percentage (94.81% for background and 89.46% for aftershocks. The close agreement between lambda and cumulative plots for the ideal synthetic catalog and that generated by the proposed model also supports the accuracy of the proposed technique. There is flexibility in the model design to allow for proper selection of location and magnitude ranges, depending upon the nature of the mainshocks present in the catalog. The effectiveness of the proposed model also is evaluated by the classification of events in three historic catalogs: California, Japan and Indonesia. As expected, for both synthetic and historic catalog analysis it is observed that the density of events classified as background is almost uniform throughout the region, whereas the density of aftershock events are higher near the mainshocks.
Directory of Open Access Journals (Sweden)
Xuemiao Xu
2016-04-01
Full Text Available Exterior orientation parameters’ (EOP estimation using space resection plays an important role in topographic reconstruction for push broom scanners. However, existing models of space resection are highly sensitive to errors in data. Unfortunately, for lunar imagery, the altitude data at the ground control points (GCPs for space resection are error-prone. Thus, existing models fail to produce reliable EOPs. Motivated by a finding that for push broom scanners, angular rotations of EOPs can be estimated independent of the altitude data and only involving the geographic data at the GCPs, which are already provided, hence, we divide the modeling of space resection into two phases. Firstly, we estimate the angular rotations based on the reliable geographic data using our proposed mathematical model. Then, with the accurate angular rotations, the collinear equations for space resection are simplified into a linear problem, and the global optimal solution for the spatial position of EOPs can always be achieved. Moreover, a certainty term is integrated to penalize the unreliable altitude data for increasing the error tolerance. Experimental results evidence that our model can obtain more accurate EOPs and topographic maps not only for the simulated data, but also for the real data from Chang’E-1, compared to the existing space resection model.
Xu, Xuemiao; Zhang, Huaidong; Han, Guoqiang; Kwan, Kin Chung; Pang, Wai-Man; Fang, Jiaming; Zhao, Gansen
2016-01-01
Exterior orientation parameters' (EOP) estimation using space resection plays an important role in topographic reconstruction for push broom scanners. However, existing models of space resection are highly sensitive to errors in data. Unfortunately, for lunar imagery, the altitude data at the ground control points (GCPs) for space resection are error-prone. Thus, existing models fail to produce reliable EOPs. Motivated by a finding that for push broom scanners, angular rotations of EOPs can be estimated independent of the altitude data and only involving the geographic data at the GCPs, which are already provided, hence, we divide the modeling of space resection into two phases. Firstly, we estimate the angular rotations based on the reliable geographic data using our proposed mathematical model. Then, with the accurate angular rotations, the collinear equations for space resection are simplified into a linear problem, and the global optimal solution for the spatial position of EOPs can always be achieved. Moreover, a certainty term is integrated to penalize the unreliable altitude data for increasing the error tolerance. Experimental results evidence that our model can obtain more accurate EOPs and topographic maps not only for the simulated data, but also for the real data from Chang'E-1, compared to the existing space resection model. PMID:27077855
Accurate modeling of a DOI capable small animal PET scanner using GATE
International Nuclear Information System (INIS)
In this work we developed a Monte Carlo (MC) model of the Sedecal Argus pre-clinical PET scanner, using GATE (Geant4 Application for Tomographic Emission). This is a dual-ring scanner which features DOI compensation by means of two layers of detector crystals (LYSO and GSO). Geometry of detectors and sources, pulses readout and selection of coincidence events were modeled with GATE, while a separate code was developed in order to emulate the processing of digitized data (for example, customized time windows and data flow saturation), the final binning of the lines of response and to reproduce the data output format of the scanner's acquisition software. Validation of the model was performed by modeling several phantoms used in experimental measurements, in order to compare the results of the simulations. Spatial resolution, sensitivity, scatter fraction, count rates and NECR were tested. Moreover, the NEMA NU-4 phantom was modeled in order to check for the image quality yielded by the model. Noise, contrast of cold and hot regions and recovery coefficient were calculated and compared using images of the NEMA phantom acquired with our scanner. The energy spectrum of coincidence events due to the small amount of 176Lu in LYSO crystals, which was suitably included in our model, was also compared with experimental measurements. Spatial resolution, sensitivity and scatter fraction showed an agreement within 7%. Comparison of the count rates curves resulted satisfactory, being the values within the uncertainties, in the range of activities practically used in research scans. Analysis of the NEMA phantom images also showed a good agreement between simulated and acquired data, within 9% for all the tested parameters. This work shows that basic MC modeling of this kind of system is possible using GATE as a base platform; extension through suitably written customized code allows for an adequate level of accuracy in the results. Our careful validation against experimental
Toward Accurate Modeling of the Effect of Ion-Pair Formation on Solute Redox Potential.
Qu, Xiaohui; Persson, Kristin A
2016-09-13
A scheme to model the dependence of a solute redox potential on the supporting electrolyte is proposed, and the results are compared to experimental observations and other reported theoretical models. An improved agreement with experiment is exhibited if the effect of the supporting electrolyte on the redox potential is modeled through a concentration change induced via ion pair formation with the salt, rather than by only considering the direct impact on the redox potential of the solute itself. To exemplify the approach, the scheme is applied to the concentration-dependent redox potential of select molecules proposed for nonaqueous flow batteries. However, the methodology is general and enables rational computational electrolyte design through tuning of the operating window of electrochemical systems by shifting the redox potential of its solutes; including potentially both salts as well as redox active molecules. PMID:27500744
DEFF Research Database (Denmark)
Kiil, Søren; Johnsson, Jan Erik; Dam-Johansen, Kim
1999-01-01
In wet flue gas desulphurisation (FGD) plants, the most common sorbent is limestone. Over the past 25 years, many attempts to model the transient dissolution of limestone particles in aqueous solutions have been performed, due to the importance for the development of reliable FGD simu-lation tools...... Danish limestone types with very different particle size distributions (PSDs). All limestones were of a high purity. Model predictions were found to be qualitatively in good agreement with experimental data without any use of adjustable parameters. Deviations between measurements and simulations were...... attributed primarily to the PSD measurements of the limestone particles, which were used as model inputs. The PSDs, measured using a laser diffrac-tion-based Malvern analyser, were probably not representative of the limestone samples because agglomeration phenomena took place when the particles were...
Inflation model building with an accurate measure of e-folding
Chongchitnan, Sirichai
2016-01-01
We revisit the problem of measuring the number of e-folding during inflation. It has become standard practice to take the logarithmic growth of the scale factor as a measure of the amount of inflation. However, this is only an approximation for the true amount of inflation required to solve the horizon and flatness problems. The aim of this work is to quantify the error in this approximation, and show how it can be avoided. We present an alternative framework for inflation model building using the inverse Hubble radius, aH, as the key parameter. We show that in this formalism, the correct number of e-folding arises naturally as a measure of inflation. As an application, we present an interesting model in which the entire inflationary dynamics can be solved analytically and exactly, and, in special cases, reduces to the familiar class of power-law models.
Fast and Accurate Modeling of Molecular Atomization Energies with Machine Learning
Rupp, Matthias; Müller, Klaus-Robert; von Lilienfeld, O Anatole
2011-01-01
We introduce a machine learning model to predict atomization energies of a diverse set of organic molecules, based on nuclear charges and atomic positions only. The problem of solving the molecular Schr\\"odinger equation is mapped onto a non-linear statistical regression problem of reduced complexity. Regression models are trained on and compared to atomization energies computed with hybrid density-functional theory. Cross-validation over more than seven thousand small organic molecules yields a mean absolute error of ~10 kcal/mol. Applicability is demonstrated for the prediction of molecular atomization potential energy curves.
Engwirda, Darren; Marshall, John
2016-01-01
The development of a set of high-order accurate finite-volume formulations for evaluation of the pressure gradient force in layered ocean models is described. A pair of new schemes are presented, both based on an integration of the contact pressure force about the perimeter of an associated momentum control-volume. The two proposed methods differ in their choice of control-volume geometries. High-order accurate numerical integration techniques are employed in both schemes to account for non-linearities in the underlying equation-of-state definitions and thermodynamic profiles, and details of an associated vertical interpolation and quadrature scheme are discussed in detail. Numerical experiments are used to confirm the consistency of the two formulations, and it is demonstrated that the new methods maintain hydrostatic and thermobaric equilibrium in the presence of strongly-sloping layer-wise geometry, non-linear equation-of-state definitions and non-uniform vertical stratification profiles. Additionally, one...
Accurate Finite Element Modelling of Chipboard Single-Stud Floor Panels subjected to Dynamic Loads
DEFF Research Database (Denmark)
Sjöström, A.; Flodén, O.; Persson, K.;
2012-01-01
in constructing a building compliant with building codes vis-a-vis the propagation of sound and vibrations within the structure is a challenge. Focusing on junctions in a multi-storey lightweight buildings, a modular finite element model is developed to be used for analyses of vibration transmission...
Analysis of computational models for an accurate study of electronic excitations in GFP
DEFF Research Database (Denmark)
Schwabe, Tobias; Beerepoot, Maarten; Olsen, Jógvan Magnus Haugaard;
2015-01-01
Using the chromophore of the green fluorescent protein (GFP), the performance of a hybrid RI-CC2 / polarizable embedding (PE) model is tested against a quantum chemical cluster pproach. Moreover, the effect of the rest of the protein environment is studied by systematically increasing the size...
Beekhuizen, Johan; Kromhout, Hans; Bürgi, Alfred; Huss, Anke; Vermeulen, Roel
2015-01-01
The increase in mobile communication technology has led to concern about potential health effects of radio frequency electromagnetic fields (RF-EMFs) from mobile phone base stations. Different RF-EMF prediction models have been applied to assess population exposure to RF-EMF. Our study examines what
A fast and accurate SystemC-AMS model for PLL
Ma, K.; Leuken, R. van; Vidojkovic, M.; Romme, J.; Rampu, S.; Pflug, H.; Huang, L.; Dolmans, G.
2011-01-01
PLLs have become an important part of electrical systems. When designing a PLL, an efficient and reliable simulation platform for system evaluation is needed. However, the closed loop simulation of a PLL is time consuming. To address this problem, in this paper, a new PLL model containing both digit
DEFF Research Database (Denmark)
Chon, K H; Cohen, R J; Holstein-Rathlou, N H
1997-01-01
A linear and nonlinear autoregressive moving average (ARMA) identification algorithm is developed for modeling time series data. The algorithm uses Laguerre expansion of kernals (LEK) to estimate Volterra-Wiener kernals. However, instead of estimating linear and nonlinear system dynamics via movi...
Energy Technology Data Exchange (ETDEWEB)
Pino, Francisco [Unitat de Biofísica, Facultat de Medicina, Universitat de Barcelona, Barcelona 08036, Spain and Servei de Física Mèdica i Protecció Radiològica, Institut Català d’Oncologia, L’Hospitalet de Llobregat 08907 (Spain); Roé, Nuria [Unitat de Biofísica, Facultat de Medicina, Universitat de Barcelona, Barcelona 08036 (Spain); Aguiar, Pablo, E-mail: pablo.aguiar.fernandez@sergas.es [Fundación Ramón Domínguez, Complexo Hospitalario Universitario de Santiago de Compostela 15706, Spain and Grupo de Imagen Molecular, Instituto de Investigacións Sanitarias de Santiago de Compostela (IDIS), Galicia 15782 (Spain); Falcon, Carles; Ros, Domènec [Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona 08036, Spain and CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Barcelona 08036 (Spain); Pavía, Javier [Institut d’Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Barcelona 080836 (Spain); CIBER en Bioingeniería, Biomateriales y Nanomedicina (CIBER-BBN), Barcelona 08036 (Spain); and Servei de Medicina Nuclear, Hospital Clínic, Barcelona 08036 (Spain)
2015-02-15
Purpose: Single photon emission computed tomography (SPECT) has become an important noninvasive imaging technique in small-animal research. Due to the high resolution required in small-animal SPECT systems, the spatially variant system response needs to be included in the reconstruction algorithm. Accurate modeling of the system response should result in a major improvement in the quality of reconstructed images. The aim of this study was to quantitatively assess the impact that an accurate modeling of spatially variant collimator/detector response has on image-quality parameters, using a low magnification SPECT system equipped with a pinhole collimator and a small gamma camera. Methods: Three methods were used to model the point spread function (PSF). For the first, only the geometrical pinhole aperture was included in the PSF. For the second, the septal penetration through the pinhole collimator was added. In the third method, the measured intrinsic detector response was incorporated. Tomographic spatial resolution was evaluated and contrast, recovery coefficients, contrast-to-noise ratio, and noise were quantified using a custom-built NEMA NU 4–2008 image-quality phantom. Results: A high correlation was found between the experimental data corresponding to intrinsic detector response and the fitted values obtained by means of an asymmetric Gaussian distribution. For all PSF models, resolution improved as the distance from the point source to the center of the field of view increased and when the acquisition radius diminished. An improvement of resolution was observed after a minimum of five iterations when the PSF modeling included more corrections. Contrast, recovery coefficients, and contrast-to-noise ratio were better for the same level of noise in the image when more accurate models were included. Ring-type artifacts were observed when the number of iterations exceeded 12. Conclusions: Accurate modeling of the PSF improves resolution, contrast, and recovery
A semi-implicit, second-order-accurate numerical model for multiphase underexpanded volcanic jets
Directory of Open Access Journals (Sweden)
S. Carcano
2013-11-01
Full Text Available An improved version of the PDAC (Pyroclastic Dispersal Analysis Code, Esposti Ongaro et al., 2007 numerical model for the simulation of multiphase volcanic flows is presented and validated for the simulation of multiphase volcanic jets in supersonic regimes. The present version of PDAC includes second-order time- and space discretizations and fully multidimensional advection discretizations in order to reduce numerical diffusion and enhance the accuracy of the original model. The model is tested on the problem of jet decompression in both two and three dimensions. For homogeneous jets, numerical results are consistent with experimental results at the laboratory scale (Lewis and Carlson, 1964. For nonequilibrium gas–particle jets, we consider monodisperse and bidisperse mixtures, and we quantify nonequilibrium effects in terms of the ratio between the particle relaxation time and a characteristic jet timescale. For coarse particles and low particle load, numerical simulations well reproduce laboratory experiments and numerical simulations carried out with an Eulerian–Lagrangian model (Sommerfeld, 1993. At the volcanic scale, we consider steady-state conditions associated with the development of Vulcanian and sub-Plinian eruptions. For the finest particles produced in these regimes, we demonstrate that the solid phase is in mechanical and thermal equilibrium with the gas phase and that the jet decompression structure is well described by a pseudogas model (Ogden et al., 2008. Coarse particles, on the other hand, display significant nonequilibrium effects, which associated with their larger relaxation time. Deviations from the equilibrium regime, with maximum velocity and temperature differences on the order of 150 m s−1 and 80 K across shock waves, occur especially during the rapid acceleration phases, and are able to modify substantially the jet dynamics with respect to the homogeneous case.
Energy Technology Data Exchange (ETDEWEB)
Yu, Victoria Y.; Tran, Angelia; Nguyen, Dan; Cao, Minsong; Ruan, Dan; Low, Daniel A.; Sheng, Ke, E-mail: ksheng@mednet.ucla.edu [Department of Radiation Oncology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California 90024 (United States)
2015-11-15
Purpose: Significant dosimetric benefits had been previously demonstrated in highly noncoplanar treatment plans. In this study, the authors developed and verified an individualized collision model for the purpose of delivering highly noncoplanar radiotherapy and tested the feasibility of total delivery automation with Varian TrueBeam developer mode. Methods: A hand-held 3D scanner was used to capture the surfaces of an anthropomorphic phantom and a human subject, which were positioned with a computer-aided design model of a TrueBeam machine to create a detailed virtual geometrical collision model. The collision model included gantry, collimator, and couch motion degrees of freedom. The accuracy of the 3D scanner was validated by scanning a rigid cubical phantom with known dimensions. The collision model was then validated by generating 300 linear accelerator orientations corresponding to 300 gantry-to-couch and gantry-to-phantom distances, and comparing the corresponding distance measurements to their corresponding models. The linear accelerator orientations reflected uniformly sampled noncoplanar beam angles to the head, lung, and prostate. The distance discrepancies between measurements on the physical and virtual systems were used to estimate treatment-site-specific safety buffer distances with 0.1%, 0.01%, and 0.001% probability of collision between the gantry and couch or phantom. Plans containing 20 noncoplanar beams to the brain, lung, and prostate optimized via an in-house noncoplanar radiotherapy platform were converted into XML script for automated delivery and the entire delivery was recorded and timed to demonstrate the feasibility of automated delivery. Results: The 3D scanner measured the dimension of the 14 cm cubic phantom within 0.5 mm. The maximal absolute discrepancy between machine and model measurements for gantry-to-couch and gantry-to-phantom was 0.95 and 2.97 cm, respectively. The reduced accuracy of gantry-to-phantom measurements was
Otomo, Hiroshi; Li, Yong; Dressler, Marco; Staroselsky, Ilya; Zhang, Raoyang; Chen, Hudong
2016-01-01
We present recent developments in lattice Boltzmann modeling for multi-component flows, implemented on the platform of a general purpose, arbitrary geometry solver PowerFLOW. Presented benchmark cases demonstrate the method's accuracy and robustness necessary for handling real world engineering applications at practical resolution and computational cost. The key requirements for such approach are that the relevant physical properties and flow characteristics do not strongly depend on numerics. In particular, the strength of surface tension obtained using our new approach is independent of viscosity and resolution, while the spurious currents are significantly suppressed. Using a much improved surface wetting model, undesirable numerical artifacts including thin film and artificial droplet movement on inclined wall are significantly reduced.
An accurate two-phase approximate solution to the acute viral infection model
Energy Technology Data Exchange (ETDEWEB)
Perelson, Alan S [Los Alamos National Laboratory
2009-01-01
During an acute viral infection, virus levels rise, reach a peak and then decline. Data and numerical solutions suggest the growth and decay phases are linear on a log scale. While viral dynamic models are typically nonlinear with analytical solutions difficult to obtain, the exponential nature of the solutions suggests approximations can be found. We derive a two-phase approximate solution to the target cell limited influenza model and illustrate the accuracy using data and previously established parameter values of six patients infected with influenza A. For one patient, the subsequent fall in virus concentration was not consistent with our predictions during the decay phase and an alternate approximation is derived. We find expressions for the rate and length of initial viral growth in terms of the parameters, the extent each parameter is involved in viral peaks, and the single parameter responsible for virus decay. We discuss applications of this analysis in antiviral treatments and investigating host and virus heterogeneities.
Accurate Simulation of 802.11 Indoor Links: A "Bursty" Channel Model Based on Real Measurements
Directory of Open Access Journals (Sweden)
Agüero Ramón
2010-01-01
Full Text Available We propose a novel channel model to be used for simulating indoor wireless propagation environments. An extensive measurement campaign was carried out to assess the performance of different transport protocols over 802.11 links. This enabled us to better adjust our approach, which is based on an autoregressive filter. One of the main advantages of this proposal lies in its ability to reflect the "bursty" behavior which characterizes indoor wireless scenarios, having a great impact on the behavior of upper layer protocols. We compare this channel model, integrated within the Network Simulator (ns-2 platform, with other traditional approaches, showing that it is able to better reflect the real behavior which was empirically assessed.
Features of creation of highly accurate models of triumphal pylons for archaeological reconstruction
Grishkanich, A. S.; Sidorov, I. S.; Redka, D. N.
2015-12-01
Cited a measuring operation for determining the geometric characteristics of objects in space and geodetic survey objects on the ground. In the course of the work, data were obtained on a relative positioning of the pylons in space. There are deviations from verticality. In comparison with traditional surveying this testing method is preferable because it allows you to get in semi-automated mode, the CAD model of the object is high for subsequent analysis that is more economical-ly advantageous.
Naumenko, Mikhail; Guzivaty, Vadim; Sapelko, Tatiana
2016-04-01
Lake morphometry refers to physical factors (shape, size, structure, etc) that determine the lake depression. Morphology has a great influence on lake ecological characteristics especially on water thermal conditions and mixing depth. Depth analyses, including sediment measurement at various depths, volumes of strata and shoreline characteristics are often critical to the investigation of biological, chemical and physical properties of fresh waters as well as theoretical retention time. Management techniques such as loading capacity for effluents and selective removal of undesirable components of the biota are also dependent on detailed knowledge of the morphometry and flow characteristics. During the recent years a lake bathymetric surveys were carried out by using echo sounder with a high bottom depth resolution and GPS coordinate determination. Few digital bathymetric models have been created with 10*10 m spatial grid for some small lakes of Russian Plain which the areas not exceed 1-2 sq. km. The statistical characteristics of the depth and slopes distribution of these lakes calculated on an equidistant grid. It will provide the level-surface-volume variations of small lakes and reservoirs, calculated through combination of various satellite images. We discuss the methodological aspects of creating of morphometric models of depths and slopes of small lakes as well as the advantages of digital models over traditional methods.
Accurate 3d Textured Models of Vessels for the Improvement of the Educational Tools of a Museum
Soile, S.; Adam, K.; Ioannidis, C.; Georgopoulos, A.
2013-02-01
Besides the demonstration of the findings, modern museums organize educational programs which aim to experience and knowledge sharing combined with entertainment rather than to pure learning. Toward that effort, 2D and 3D digital representations are gradually replacing the traditional recording of the findings through photos or drawings. The present paper refers to a project that aims to create 3D textured models of two lekythoi that are exhibited in the National Archaeological Museum of Athens in Greece; on the surfaces of these lekythoi scenes of the adventures of Odysseus are depicted. The project is expected to support the production of an educational movie and some other relevant interactive educational programs for the museum. The creation of accurate developments of the paintings and of accurate 3D models is the basis for the visualization of the adventures of the mythical hero. The data collection was made by using a structured light scanner consisting of two machine vision cameras that are used for the determination of geometry of the object, a high resolution camera for the recording of the texture, and a DLP projector. The creation of the final accurate 3D textured model is a complicated and tiring procedure which includes the collection of geometric data, the creation of the surface, the noise filtering, the merging of individual surfaces, the creation of a c-mesh, the creation of the UV map, the provision of the texture and, finally, the general processing of the 3D textured object. For a better result a combination of commercial and in-house software made for the automation of various steps of the procedure was used. The results derived from the above procedure were especially satisfactory in terms of accuracy and quality of the model. However, the procedure was proved to be time consuming while the use of various software packages presumes the services of a specialist.
Energy Technology Data Exchange (ETDEWEB)
Jha, D.K., E-mail: dkjha@barc.gov.in [Civil Engineering Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Kant, Tarun [Department of Civil Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400 076 (India); Srinivas, K. [Civil Engineering Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Singh, R.K. [Reactor Safety Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India)
2013-12-15
Highlights: • We model through-thickness variation of material properties in functionally graded (FG) plates. • Effect of material grading index on deformations, stresses and natural frequency of FG plates is studied. • Effect of higher order terms in displacement models is studied for plate statics. • The benchmark solutions for the static analysis and free vibration of thick FG plates are presented. -- Abstract: Functionally graded materials (FGMs) are the potential candidates under consideration for designing the first wall of fusion reactors with a view to make best use of potential properties of available materials under severe thermo-mechanical loading conditions. A higher order shear and normal deformations plate theory is employed for stress and free vibration analyses of functionally graded (FG) elastic, rectangular, and simply (diaphragm) supported plates. Although FGMs are highly heterogeneous in nature, they are generally idealized as continua with mechanical properties changing smoothly with respect to spatial coordinates. The material properties of FG plates are assumed here to vary through thickness of plate in a continuous manner. Young's modulii and material densities are considered to be varying continuously in thickness direction according to volume fraction of constituents which are mathematically modeled here as exponential and power law functions. The effects of variation of material properties in terms of material gradation index on deformations, stresses and natural frequency of FG plates are investigated. The accuracy of present numerical solutions has been established with respect to exact three-dimensional (3D) elasticity solutions and the other models’ solutions available in literature.
Reynolds, Andrew M; Lihoreau, Mathieu; Chittka, Lars
2013-01-01
Pollinating bees develop foraging circuits (traplines) to visit multiple flowers in a manner that minimizes overall travel distance, a task analogous to the travelling salesman problem. We report on an in-depth exploration of an iterative improvement heuristic model of bumblebee traplining previously found to accurately replicate the establishment of stable routes by bees between flowers distributed over several hectares. The critical test for a model is its predictive power for empirical data for which the model has not been specifically developed, and here the model is shown to be consistent with observations from different research groups made at several spatial scales and using multiple configurations of flowers. We refine the model to account for the spatial search strategy of bees exploring their environment, and test several previously unexplored predictions. We find that the model predicts accurately 1) the increasing propensity of bees to optimize their foraging routes with increasing spatial scale; 2) that bees cannot establish stable optimal traplines for all spatial configurations of rewarding flowers; 3) the observed trade-off between travel distance and prioritization of high-reward sites (with a slight modification of the model); 4) the temporal pattern with which bees acquire approximate solutions to travelling salesman-like problems over several dozen foraging bouts; 5) the instability of visitation schedules in some spatial configurations of flowers; 6) the observation that in some flower arrays, bees' visitation schedules are highly individually different; 7) the searching behaviour that leads to efficient location of flowers and routes between them. Our model constitutes a robust theoretical platform to generate novel hypotheses and refine our understanding about how small-brained insects develop a representation of space and use it to navigate in complex and dynamic environments.
A simple and accurate numerical network flow model for bionic micro heat exchangers
Energy Technology Data Exchange (ETDEWEB)
Pieper, M.; Klein, P. [Fraunhofer Institute (ITWM), Kaiserslautern (Germany)
2011-05-15
Heat exchangers are often associated with drawbacks like a large pressure drop or a non-uniform flow distribution. Recent research shows that bionic structures can provide possible improvements. We considered a set of such structures that were designed with M. Hermann's FracTherm {sup registered} algorithm. In order to optimize and compare them with conventional heat exchangers, we developed a numerical method to determine their performance. We simulated the flow in the heat exchanger applying a network model and coupled these results with a finite volume method to determine the heat distribution in the heat exchanger. (orig.)
Considering mask pellicle effect for more accurate OPC model at 45nm technology node
Wang, Ching-Heng; Liu, Qingwei; Zhang, Liguo
2008-11-01
Now it comes to the 45nm technology node, which should be the first generation of the immersion micro-lithography. And the brand-new lithography tool makes many optical effects, which can be ignored at 90nm and 65nm nodes, now have significant impact on the pattern transmission process from design to silicon. Among all the effects, one that needs to be pay attention to is the mask pellicle effect's impact on the critical dimension variation. With the implement of hyper-NA lithography tools, light transmits the mask pellicle vertically is not a good approximation now, and the image blurring induced by the mask pellicle should be taken into account in the computational microlithography. In this works, we investigate how the mask pellicle impacts the accuracy of the OPC model. And we will show that considering the extremely tight critical dimension control spec for 45nm generation node, to take the mask pellicle effect into the OPC model now becomes necessary.
A new method based on the subpixel Gaussian model for accurate estimation of asteroid coordinates
Savanevych, V E; Sokovikova, N S; Bezkrovny, M M; Vavilova, I B; Ivashchenko, Yu M; Elenin, L V; Khlamov, S V; Movsesian, Ia S; Dashkova, A M; Pogorelov, A V
2015-01-01
We describe a new iteration method to estimate asteroid coordinates, which is based on the subpixel Gaussian model of a discrete object image. The method operates by continuous parameters (asteroid coordinates) in a discrete observational space (the set of pixels potential) of the CCD frame. In this model, a kind of the coordinate distribution of the photons hitting a pixel of the CCD frame is known a priori, while the associated parameters are determined from a real digital object image. The developed method, being more flexible in adapting to any form of the object image, has a high measurement accuracy along with a low calculating complexity due to a maximum likelihood procedure, which is implemented to obtain the best fit instead of a least-squares method and Levenberg-Marquardt algorithm for the minimisation of the quadratic form. Since 2010, the method was tested as the basis of our CoLiTec (Collection Light Technology) software, which has been installed at several observatories of the world with the ai...
Extrapolation of Urn Models via Poissonization: Accurate Measurements of the Microbial Unknown
Lladser, Manuel; Reeder, Jens; 10.1371/journal.pone.0021105
2011-01-01
The availability of high-throughput parallel methods for sequencing microbial communities is increasing our knowledge of the microbial world at an unprecedented rate. Though most attention has focused on determining lower-bounds on the alpha-diversity i.e. the total number of different species present in the environment, tight bounds on this quantity may be highly uncertain because a small fraction of the environment could be composed of a vast number of different species. To better assess what remains unknown, we propose instead to predict the fraction of the environment that belongs to unsampled classes. Modeling samples as draws with replacement of colored balls from an urn with an unknown composition, and under the sole assumption that there are still undiscovered species, we show that conditionally unbiased predictors and exact prediction intervals (of constant length in logarithmic scale) are possible for the fraction of the environment that belongs to unsampled classes. Our predictions are based on a P...
How to build accurate macroscopic models of actinide ions in aqueous solvents?
International Nuclear Information System (INIS)
Classical molecular dynamics (MD) based on parameterized force fields allow one to simulate large molecular systems on significantly long simulation times (usually, at the ns scale and above). Hence, they provide statistically relevant sampled sets of data, which may then be post-processed to estimate specific properties. However, the study of the ligand coordination dynamics around heavy ions requires the use of sophisticated force fields accounting for in particular polarization phenomena, as well as for the charge-transfer effects affecting ion/ligand interactions, which are shown to be significant in several heavy element systems. Our current efforts focus on the development of force-field models for radionuclides, with the intention of pushing as far as possible the accuracy of all competing interactions between the various elements present in solution, that is the metal, the ligands, the solvent, and the counter-ions
Energy Technology Data Exchange (ETDEWEB)
Sever, M.; Lipovsek, B.; Krc, J.; Campa, A.; Topic, M. [University of Ljubljana, Faculty of Electrical Engineering Trzaska cesta 25, Ljubljana 1000 (Slovenia); Sanchez Plaza, G. [Technical University of Valencia, Valencia Nanophotonics Technology Center (NTC) Valencia 46022 (Spain); Haug, F.J. [Ecole Polytechnique Federale de Lausanne EPFL, Institute of Microengineering IMT, Photovoltaics and Thin-Film Electronics Laboratory, Neuchatel 2000 (Switzerland); Duchamp, M. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons Institute for Microstructure Research, Research Centre Juelich, Juelich D-52425 (Germany); Soppe, W. [ECN-Solliance, High Tech Campus 5, Eindhoven 5656 AE (Netherlands)
2013-12-15
In thin-film silicon solar cells textured interfaces are introduced, leading to improved antireflection and light trapping capabilities of the devices. Thin-layers are deposited on surface-textured substrates or superstrates and the texture is translated to internal interfaces. For accurate optical modelling of the thin-film silicon solar cells it is important to define and include the morphology of textured interfaces as realistic as possible. In this paper we present a model of thin-layer growth on textured surfaces which combines two growth principles: conformal and isotropic one. With the model we can predict the morphology of subsequent internal interfaces in thin-film silicon solar cells based on the known morphology of the substrate or superstrate. Calibration of the model for different materials grown under certain conditions is done on various cross-sectional scanning electron microscopy images of realistic devices. Advantages over existing growth modelling approaches are demonstrated - one of them is the ability of the model to predict and omit the textures with high possibility of defective regions formation inside the Si absorber layers. The developed model of layer growth is used in rigorous 3-D optical simulations employing the COMSOL simulator. A sinusoidal texture of the substrate is optimised for the case of a micromorph silicon solar cell. More than a 50 % increase in short-circuit current density of the bottom cell with respect to the flat case is predicted, considering the defect-free absorber layers. The developed approach enables accurate prediction and powerful design of current-matched top and bottom cell.
International Nuclear Information System (INIS)
Due to the absence of the long-range van der Waals (vdW) interaction, conventional density functional theory (DFT) often fails in the description of molecular complexes and solids. In recent years, considerable progress has been made in the development of the vdW correction. However, the vdW correction based on the leading-order coefficient C6 alone can only achieve limited accuracy, while accurate modeling of higher-order coefficients remains a formidable task, due to the strong non-additivity effect. Here, we apply a model dynamic multipole polarizability within a modified single-frequency approximation to calculate C8 and C10 between small molecules. We find that the higher-order vdW coefficients from this model can achieve remarkable accuracy, with mean absolute relative deviations of 5% for C8 and 7% for C10. Inclusion of accurate higher-order contributions in the vdW correction will effectively enhance the predictive power of DFT in condensed matter physics and quantum chemistry
Energy Technology Data Exchange (ETDEWEB)
Hoffman, C.; Fritz, B. [United States Dept. of Agriculture, College Station, TX (United States); Nedwed, T. [ExxonMobil Upstream Research Co., Houston, TX (United States); Coolbaugh, T. [ExxonMobil Research and Engineering Co., Fairfax, VA (United States); Huber, C.A. [CAH Inc., Williamsburg, VA (United States)
2009-07-01
Oil dispersants are used to accelerate the dispersion of floating oil slicks. This study was conducted to select application equipment that will help to optimize the application oil dispersants from aircraft. Oil spill responders have a broad range of oil dispersants at their disposal because the physical and chemical interaction between the oil and dispersant is critical to successful mitigation. In order to make efficient use of dispersants, it is important to evaluate how each one atomizes once released from an aircraft. The specific goal of this study was to evaluate current spray nozzles used to spray oil dispersants from aircraft. The United States Department of Agriculture's high-speed wind tunnel facility in College Station, Texas was used to determine droplet size distributions generated by dispersant delivery nozzles at wind speeds similar to those used in aerial dispersant applications. Droplet distribution was quantified using a laser particle size analyzer. Wind-tunnel tests were conducted using water, Corexit 9500 and 9527 as well as a new dispersant gel being developed by ExxonMobil. The measured drop-size distributions were then used in an agriculture spray model to predict the delivery efficiency and swath width of dispersant delivered at flight speeds and altitudes commonly used for dispersant application. It was concluded that current practices for aerial application of dispersants lead to very efficient application. 19 refs., 5 tabs., 10 figs.
Indian Academy of Sciences (India)
G Sasibhushana Rao
2007-10-01
The positional accuracy of the Global Positioning System (GPS)is limited due to several error sources.The major error is ionosphere.By augmenting the GPS,the Category I (CAT I)Precision Approach (PA)requirements can be achieved.The Space-Based Augmentation System (SBAS)in India is known as GPS Aided Geo Augmented Navigation (GAGAN).One of the prominent errors in GAGAN that limits the positional accuracy is instrumental biases.Calibration of these biases is particularly important in achieving the CAT I PA landings.In this paper,a new algorithm is proposed to estimate the instrumental biases by modelling the TEC using 4th order polynomial.The algorithm uses values corresponding to a single station for one month period and the results conﬁrm the validity of the algorithm.The experimental results indicate that the estimation precision of the satellite-plus-receiver instrumental bias is of the order of ± 0.17 nsec.The observed mean bias error is of the order − 3.638 nsec and − 4.71 nsec for satellite 1 and 31 respectively.It is found that results are consistent over the period.
Slodownik, Dan; Grinberg, Igor; Spira, Ram M; Skornik, Yehuda; Goldstein, Ronald S
2009-04-01
The current standard method for predicting contact allergenicity is the murine local lymph node assay (LLNA). Public objection to the use of animals in testing of cosmetics makes the development of a system that does not use sentient animals highly desirable. The chorioallantoic membrane (CAM) of the chick egg has been extensively used for the growth of normal and transformed mammalian tissues. The CAM is not innervated, and embryos are sacrificed before the development of pain perception. The aim of this study was to determine whether the sensitization phase of contact dermatitis to known cosmetic allergens can be quantified using CAM-engrafted human skin and how these results compare with published EC3 data obtained with the LLNA. We studied six common molecules used in allergen testing and quantified migration of epidermal Langerhans cells (LC) as a measure of their allergic potency. All agents with known allergic potential induced statistically significant migration of LC. The data obtained correlated well with published data for these allergens generated using the LLNA test. The human-skin CAM model therefore has great potential as an inexpensive, non-radioactive, in vivo alternative to the LLNA, which does not require the use of sentient animals. In addition, this system has the advantage of testing the allergic response of human, rather than animal skin. PMID:19054059
Institute of Scientific and Technical Information of China (English)
F. Djeffal; A. Ferdi; M. Chahdi
2012-01-01
The double gate (DG) silicon MOSFET with an extremely short-channel length has the appropriate features to constitute the devices for nanoscale circuit design.To develop a physical model for extremely scaled DG MOSFETs,the drain current in the channel must be accurately determined under the application of drain and gate voltages.However,modeling the transport mechanism for the nanoscale structures requires the use of overkill methods and models in terms of their complexity and computation time (self-consistent,quantum computations ).Therefore,new methods and techniques are required to overcome these constraints.In this paper,a new approach based on the fuzzy logic computation is proposed to investigate nanoscale DG MOSFETs.The proposed approach has been implemented in a device simulator to show the impact of the proposed approach on the nanoelectronic circuit design.The approach is general and thus is suitable for any type ofnanoscale structure investigation problems in the nanotechnology industry.
van Wyk, Marnus J; Bingle, Marianne; Meyer, Frans J C
2005-09-01
International bodies such as International Commission on Non-Ionizing Radiation Protection (ICNIRP) and the Institute for Electrical and Electronic Engineering (IEEE) make provision for human exposure assessment based on SAR calculations (or measurements) and basic restrictions. In the case of base station exposure this is mostly applicable to occupational exposure scenarios in the very near field of these antennas where the conservative reference level criteria could be unnecessarily restrictive. This study presents a variety of critical aspects that need to be considered when calculating SAR in a human body close to a mobile phone base station antenna. A hybrid FEM/MoM technique is proposed as a suitable numerical method to obtain accurate results. The verification of the FEM/MoM implementation has been presented in a previous publication; the focus of this study is an investigation into the detail that must be included in a numerical model of the antenna, to accurately represent the real-world scenario. This is accomplished by comparing numerical results to measurements for a generic GSM base station antenna and appropriate, representative canonical and human phantoms. The results show that it is critical to take the disturbance effect of the human phantom (a large conductive body) on the base station antenna into account when the antenna-phantom spacing is less than 300 mm. For these small spacings, the antenna structure must be modeled in detail. The conclusion is that it is feasible to calculate, using the proposed techniques and methodology, accurate occupational compliance zones around base station antennas based on a SAR profile and basic restriction guidelines. PMID:15931680
Panagiotopoulou, O; Wilshin, S D; Rayfield, E J; Shefelbine, S J; Hutchinson, J R
2012-02-01
Finite element modelling is well entrenched in comparative vertebrate biomechanics as a tool to assess the mechanical design of skeletal structures and to better comprehend the complex interaction of their form-function relationships. But what makes a reliable subject-specific finite element model? To approach this question, we here present a set of convergence and sensitivity analyses and a validation study as an example, for finite element analysis (FEA) in general, of ways to ensure a reliable model. We detail how choices of element size, type and material properties in FEA influence the results of simulations. We also present an empirical model for estimating heterogeneous material properties throughout an elephant femur (but of broad applicability to FEA). We then use an ex vivo experimental validation test of a cadaveric femur to check our FEA results and find that the heterogeneous model matches the experimental results extremely well, and far better than the homogeneous model. We emphasize how considering heterogeneous material properties in FEA may be critical, so this should become standard practice in comparative FEA studies along with convergence analyses, consideration of element size, type and experimental validation. These steps may be required to obtain accurate models and derive reliable conclusions from them. PMID:21752810
Malik, Arif Sultan
This work presents improved technology for attaining high-quality rolled metal strip. The new technology is based on an innovative method to model both the static and dynamic characteristics of rolling mill deflection, and it applies equally to both cluster-type and non cluster-type rolling mill configurations. By effectively combining numerical Finite Element Analysis (FEA) with analytical solid mechanics, the devised approach delivers a rapid, accurate, flexible, high-fidelity model useful for optimizing many important rolling parameters. The associated static deflection model enables computation of the thickness profile and corresponding flatness of the rolled strip. Accurate methods of predicting the strip thickness profile and strip flatness are important in rolling mill design, rolling schedule set-up, control of mill flatness actuators, and optimization of ground roll profiles. The corresponding dynamic deflection model enables solution of the standard eigenvalue problem to determine natural frequencies and modes of vibration. The presented method for solving the roll-stack deflection problem offers several important advantages over traditional methods. In particular, it includes continuity of elastic foundations, non-iterative solution when using pre-determined elastic foundation moduli, continuous third-order displacement fields, simple stress-field determination, the ability to calculate dynamic characteristics, and a comparatively faster solution time. Consistent with the most advanced existing methods, the presented method accommodates loading conditions that represent roll crowning, roll bending, roll shifting, and roll crossing mechanisms. Validation of the static model is provided by comparing results and solution time with large-scale, commercial finite element simulations. In addition to examples with the common 4-high vertical stand rolling mill, application of the presented method to the most complex of rolling mill configurations is demonstrated
Research of Gear Accurate Modeling Based on UG%基于UG的齿轮精确建模研究
Institute of Scientific and Technical Information of China (English)
张磊; 赵韩; 刘迪祥; 崔港
2011-01-01
In the analysis of equations about transition curve,the research on gear accurate parametric modeling was done.The mixed technology of UG/Open API,UG/Open GRIP and MFC was used to accomplish gear accurate parametric modeling system.It makes preparations for subsequent finite element analysis and dynamic simulation,and has a practical engineering significance.%在分析了齿轮两种过渡曲线方程的基础之上,对齿轮的精确参数化建模方法进行了研究,并利用UG/OpenAPI、UG/Open GR IP及MFC的混合开发技术实现了渐开线齿轮精确参数化建模系统的设计。为齿轮后续有限元分析和运动仿真的准确进行做准备,具有实际工程意义。
Gao, Yaozong; Shao, Yeqin; Lian, Jun; Wang, Andrew Z; Chen, Ronald C; Shen, Dinggang
2016-06-01
Segmenting male pelvic organs from CT images is a prerequisite for prostate cancer radiotherapy. The efficacy of radiation treatment highly depends on segmentation accuracy. However, accurate segmentation of male pelvic organs is challenging due to low tissue contrast of CT images, as well as large variations of shape and appearance of the pelvic organs. Among existing segmentation methods, deformable models are the most popular, as shape prior can be easily incorporated to regularize the segmentation. Nonetheless, the sensitivity to initialization often limits their performance, especially for segmenting organs with large shape variations. In this paper, we propose a novel approach to guide deformable models, thus making them robust against arbitrary initializations. Specifically, we learn a displacement regressor, which predicts 3D displacement from any image voxel to the target organ boundary based on the local patch appearance. This regressor provides a non-local external force for each vertex of deformable model, thus overcoming the initialization problem suffered by the traditional deformable models. To learn a reliable displacement regressor, two strategies are particularly proposed. 1) A multi-task random forest is proposed to learn the displacement regressor jointly with the organ classifier; 2) an auto-context model is used to iteratively enforce structural information during voxel-wise prediction. Extensive experiments on 313 planning CT scans of 313 patients show that our method achieves better results than alternative classification or regression based methods, and also several other existing methods in CT pelvic organ segmentation. PMID:26800531
Energy Technology Data Exchange (ETDEWEB)
Vial, A.; Dridi, M.; Cunff, L. le [Universite de Technologie de Troyes, Institut Charles Delaunay, CNRS UMR 6279, Laboratoire de Nanotechnologie et d' Instrumentation Optique, 12, rue Marie Curie, BP-2060, Troyes Cedex (France); Laroche, T. [Universite de Franche-Comte, Institut FEMTO-ST, CNRS UMR 6174, Departement de Physique et de Metrologie des Oscillateurs, Besancon Cedex (France)
2011-06-15
We present FDTD simulations results obtained using the Drude critical points model. This model enables spectroscopic studies of metallic structures over wider wavelength ranges than usually used, and it facilitates the study of structures made of several metals. (orig.)
Energy Technology Data Exchange (ETDEWEB)
Chen, Y; Mo, X; Chen, M; Olivera, G; Parnell, D; Key, S; Lu, W [21st Century Oncology, Madison, WI (United States); Reeher, M [21st Century Oncology, Naples, FL (United States); Galmarini, D [21st Century Oncology, Fort Myers, FL (United States)
2014-06-01
Purpose: An accurate leaf fluence model can be used in applications such as patient specific delivery QA and in-vivo dosimetry for TomoTherapy systems. It is known that the total fluence is not a linear combination of individual leaf fluence due to leakage-transmission, tongue-and-groove, and source occlusion effect. Here we propose a method to model the nonlinear effects as linear terms thus making the MLC-detector system a linear system. Methods: A leaf pattern basis (LPB) consisting of no-leaf-open, single-leaf-open, double-leaf-open and triple-leaf-open patterns are chosen to represent linear and major nonlinear effects of leaf fluence as a linear system. An arbitrary leaf pattern can be expressed as (or decomposed to) a linear combination of the LPB either pulse by pulse or weighted by dwelling time. The exit detector responses to the LPB are obtained by processing returned detector signals resulting from the predefined leaf patterns for each jaw setting. Through forward transformation, detector signal can be predicted given a delivery plan. An equivalent leaf open time (LOT) sinogram containing output variation information can also be inversely calculated from the measured detector signals. Twelve patient plans were delivered in air. The equivalent LOT sinograms were compared with their planned sinograms. Results: The whole calibration process was done in 20 minutes. For two randomly generated leaf patterns, 98.5% of the active channels showed differences within 0.5% of the local maximum between the predicted and measured signals. Averaged over the twelve plans, 90% of LOT errors were within +/−10 ms. The LOT systematic error increases and shows an oscillating pattern when LOT is shorter than 50 ms. Conclusion: The LPB method models the MLC-detector response accurately, which improves patient specific delivery QA and in-vivo dosimetry for TomoTherapy systems. It is sensitive enough to detect systematic LOT errors as small as 10 ms.
International Nuclear Information System (INIS)
Huffaker and Cohen (ref.1) claim that the perturbed-Morse-oscillator (PMO) model, for the potential energy function for hydrogen, gives very high accuracy results; surpassing that of the RKR potential. A more efficient approach to formulating analytical functions based on the PMO model is given, and some defects of the PMO model are discussed
Bhaskara, Ramachandra M; Padhi, Amrita; Srinivasan, Narayanaswamy
2014-07-01
With the preponderance of multidomain proteins in eukaryotic genomes, it is essential to recognize the constituent domains and their functions. Often function involves communications across the domain interfaces, and the knowledge of the interacting sites is essential to our understanding of the structure-function relationship. Using evolutionary information extracted from homologous domains in at least two diverse domain architectures (single and multidomain), we predict the interface residues corresponding to domains from the two-domain proteins. We also use information from the three-dimensional structures of individual domains of two-domain proteins to train naïve Bayes classifier model to predict the interfacial residues. Our predictions are highly accurate (∼85%) and specific (∼95%) to the domain-domain interfaces. This method is specific to multidomain proteins which contain domains in at least more than one protein architectural context. Using predicted residues to constrain domain-domain interaction, rigid-body docking was able to provide us with accurate full-length protein structures with correct orientation of domains. We believe that these results can be of considerable interest toward rational protein and interaction design, apart from providing us with valuable information on the nature of interactions.
Bhaskara, Ramachandra M; Padhi, Amrita; Srinivasan, Narayanaswamy
2014-07-01
With the preponderance of multidomain proteins in eukaryotic genomes, it is essential to recognize the constituent domains and their functions. Often function involves communications across the domain interfaces, and the knowledge of the interacting sites is essential to our understanding of the structure-function relationship. Using evolutionary information extracted from homologous domains in at least two diverse domain architectures (single and multidomain), we predict the interface residues corresponding to domains from the two-domain proteins. We also use information from the three-dimensional structures of individual domains of two-domain proteins to train naïve Bayes classifier model to predict the interfacial residues. Our predictions are highly accurate (∼85%) and specific (∼95%) to the domain-domain interfaces. This method is specific to multidomain proteins which contain domains in at least more than one protein architectural context. Using predicted residues to constrain domain-domain interaction, rigid-body docking was able to provide us with accurate full-length protein structures with correct orientation of domains. We believe that these results can be of considerable interest toward rational protein and interaction design, apart from providing us with valuable information on the nature of interactions. PMID:24375512
Wang, Guotai; Zhang, Shaoting; Xie, Hongzhi; Metaxas, Dimitris N; Gu, Lixu
2015-01-01
Shape prior plays an important role in accurate and robust liver segmentation. However, liver shapes have complex variations and accurate modeling of liver shapes is challenging. Using large-scale training data can improve the accuracy but it limits the computational efficiency. In order to obtain accurate liver shape priors without sacrificing the efficiency when dealing with large-scale training data, we investigate effective and scalable shape prior modeling method that is more applicable in clinical liver surgical planning system. We employed the Sparse Shape Composition (SSC) to represent liver shapes by an optimized sparse combination of shapes in the repository, without any assumptions on parametric distributions of liver shapes. To leverage large-scale training data and improve the computational efficiency of SSC, we also introduced a homotopy-based method to quickly solve the L1-norm optimization problem in SSC. This method takes advantage of the sparsity of shape modeling, and solves the original optimization problem in SSC by continuously transforming it into a series of simplified problems whose solution is fast to compute. When new training shapes arrive gradually, the homotopy strategy updates the optimal solution on the fly and avoids re-computing it from scratch. Experiments showed that SSC had a high accuracy and efficiency in dealing with complex liver shape variations, excluding gross errors and preserving local details on the input liver shape. The homotopy-based SSC had a high computational efficiency, and its runtime increased very slowly when repository's capacity and vertex number rose to a large degree. When repository's capacity was 10,000, with 2000 vertices on each shape, homotopy method cost merely about 11.29 s to solve the optimization problem in SSC, nearly 2000 times faster than interior point method. The dice similarity coefficient (DSC), average symmetric surface distance (ASD), and maximum symmetric surface distance measurement
Somerville, W R C; Ru, E C Le
2015-01-01
We provide a detailed user guide for SMARTIES, a suite of Matlab codes for the calculation of the optical properties of oblate and prolate spheroidal particles, with comparable capabilities and ease-of-use as Mie theory for spheres. SMARTIES is a Matlab implementation of an improved T-matrix algorithm for the theoretical modelling of electromagnetic scattering by particles of spheroidal shape. The theory behind the improvements in numerical accuracy and convergence is briefly summarised, with reference to the original publications. Instructions of use, and a detailed description of the code structure, its range of applicability, as well as guidelines for further developments by advanced users are discussed in separate sections of this user guide. The code may be useful to researchers seeking a fast, accurate and reliable tool to simulate the near-field and far-field optical properties of elongated particles, but will also appeal to other developers of light-scattering software seeking a reliable benchmark for...
Energy Technology Data Exchange (ETDEWEB)
Ueda, T. [Chubu Electric Power Co. Inc., Nagoya (Japan); Funabashi, T.; Hagiwara, T.; Watanabe, H. [Meidensha Corp., Tokyo (Japan)
1998-12-28
Introduced herein are a dynamic behavior model for lightning arresters designed for power stations and substations and a flashover model for a lightning arresting device designed for transmission, both developed by the author et al. The author et al base their zinc oxide type lightning arrester model on the conventional static V-I characteristics, and supplement them with difference in voltage between static and dynamic characteristics. The model is easily simulated using EMTP (Electromagnetic Transients Program) etc. There is good agreement between the results of calculation performed using this model and actually measured values. Lightning arresting devices for transmission have come into practical use, and their effectiveness is introduced on various occasions. For the proper application of such devices, an analysis model capable of faithfully describing the flashover characteristics of arcing horns installed in great numbers along transmission lines, and of lightning arresting devices for transmission, are required. The author et al have newly developed a flashover model for the devices and uses the model for the analysis of lightning surges. It is found that the actually measured values of discharge characteristics of lightning arresting devices for transmission agree well with the values calculated by use of the model. (NEDO)
Towards an accurate model of the redshift-space clustering of haloes in the quasi-linear regime
Reid, Beth A.; White, Martin
2011-11-01
Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for measuring the build-up of cosmological structure, which depends both on the expansion rate of the Universe and on our theory of gravity. The statistical precision with which redshift-space distortions can now be measured demands better control of our theoretical systematic errors. While many recent studies focus on understanding dark matter clustering in redshift space, galaxies occupy special places in the universe: dark matter haloes. In our detailed study of halo clustering and velocity statistics in 67.5 h-3 Gpc3 of N-body simulations, we uncover a complex dependence of redshift-space clustering on halo bias. We identify two distinct corrections which affect the halo redshift-space correlation function on quasi-linear scales (˜30-80 h-1 Mpc): the non-linear mapping between real-space and redshift-space positions, and the non-linear suppression of power in the velocity divergence field. We model the first non-perturbatively using the scale-dependent Gaussian streaming model, which we show is accurate at the 10 (s > 25) h-1 Mpc for the monopole (quadrupole) halo correlation functions. The dominant correction to the Kaiser limit in this model scales like b3. We use standard perturbation theory to predict the real-space pairwise halo velocity statistics. Our fully analytic model is accurate at the 2 per cent level only on scales s > 40 h-1 Mpc for the range of halo masses we studied (with b= 1.4-2.8). We find that recent models of halo redshift-space clustering that neglect the corrections from the bispectrum and higher order terms from the non-linear real-space to redshift-space mapping will not have the accuracy required for current and future observational analyses. Finally, we note that our simulation results confirm the essential but non-trivial assumption that on large scales, the bias inferred from the real-space clustering of haloes is the same as the
Cisonni, Julien; Lucey, Anthony D; King, Andrew J C; Islam, Syed Mohammed Shamsul; Lewis, Richard; Goonewardene, Mithran S
2015-11-01
Repetitive brief episodes of soft-tissue collapse within the upper airway during sleep characterize obstructive sleep apnea (OSA), an extremely common and disabling disorder. Failure to maintain the patency of the upper airway is caused by the combination of sleep-related loss of compensatory dilator muscle activity and aerodynamic forces promoting closure. The prediction of soft-tissue movement in patient-specific airway 3D mechanical models is emerging as a useful contribution to clinical understanding and decision making. Such modeling requires reliable estimations of the pharyngeal wall pressure forces. While nasal obstruction has been recognized as a risk factor for OSA, the need to include the nasal cavity in upper-airway models for OSA studies requires consideration, as it is most often omitted because of its complex shape. A quantitative analysis of the flow conditions generated by the nasal cavity and the sinuses during inspiration upstream of the pharynx is presented. Results show that adequate velocity boundary conditions and simple artificial extensions of the flow domain can reproduce the essential effects of the nasal cavity on the pharyngeal flow field. Therefore, the overall complexity and computational cost of accurate flow predictions can be reduced.
Energy Technology Data Exchange (ETDEWEB)
Balzar, D. [Ruder Boskovic Inst., Zagreb (Croatia); Ledbetter, H. [National Inst. of Standards and Technology, Boulder, CO (United States)
1995-12-31
In the {open_quotes}double-Voigt{close_quotes} approach, an exact Voigt function describes both size- and strain-broadened profiles. The lattice strain is defined in terms of physically credible mean-square strain averaged over a distance in the diffracting domains. Analysis of Fourier coefficients in a harmonic approximation for strain coefficients leads to the Warren-Averbach method for the separation of size and strain contributions to diffraction line broadening. The model is introduced in the Rietveld refinement program in the following way: Line widths are modeled with only four parameters in the isotropic case. Varied parameters are both surface- and volume-weighted domain sizes and root-mean-square strains averaged over two distances. Refined parameters determine the physically broadened Voigt line profile. Instrumental Voigt line profile parameters are added to obtain the observed (Voigt) line profile. To speed computation, the corresponding pseudo-Voigt function is calculated and used as a fitting function in refinement. This approach allows for both fast computer code and accurate modeling in terms of physically identifiable parameters.
BOUSSINESQ MODELLING OF NEARSHORE WAVES UNDER BODY FITTED COORDINATE
Institute of Scientific and Technical Information of China (English)
FANG Ke-zhao; ZOU Zhi-li; LIU Zhong-bo; YIN Ji-wei
2012-01-01
A set of nonlinear Boussinesq equations with fully nonlinearity property is solved numerically in generalized coordinates,to develop a Boussinesq-type wave model in dealing with irregular computation boundaries in complex nearshore regions and to facilitate the grid refinements in simulations.The governing equations expressed in contravariant components of velocity vectors under curv ilinear coordinates are derived and a high order finite difference scheme on a staggered grid is employed for the numerical implementation.The developed model is used to simulate nearshore wave propagations under curvilinear coordinates,the numerical results are compared against analytical or experimental data with a good agreement.
Directory of Open Access Journals (Sweden)
Hang Zhang
Full Text Available In many motor tasks, optimal performance presupposes that human movement planning is based on an accurate internal model of the subject's own motor error. We developed a motor choice task that allowed us to test whether the internal model implicit in a subject's choices differed from the actual in isotropy (elongation and variance. Subjects were first trained to hit a circular target on a touch screen within a time limit. After training, subjects were repeatedly shown pairs of targets differing in size and shape and asked to choose the target that was easier to hit. On each trial they simply chose a target - they did not attempt to hit the chosen target. For each subject, we tested whether the internal model implicit in her target choices was consistent with her true error distribution in isotropy and variance. For all subjects, movement end points were anisotropic, distributed as vertically elongated bivariate Gaussians. However, in choosing targets, almost all subjects effectively assumed an isotropic distribution rather than their actual anisotropic distribution. Roughly half of the subjects chose as though they correctly estimated their own variance and the other half effectively assumed a variance that was more than four times larger than the actual, essentially basing their choices merely on the areas of the targets. The task and analyses we developed allowed us to characterize the internal model of motor error implicit in how humans plan reaching movements. In this task, human movement planning - even after extensive training - is based on an internal model of human motor error that includes substantial and qualitative inaccuracies.
Energy Technology Data Exchange (ETDEWEB)
Martin, Katherine J.; Patrick, Denis R.; Bissell, Mina J.; Fournier, Marcia V.
2008-10-20
One of the major tenets in breast cancer research is that early detection is vital for patient survival by increasing treatment options. To that end, we have previously used a novel unsupervised approach to identify a set of genes whose expression predicts prognosis of breast cancer patients. The predictive genes were selected in a well-defined three dimensional (3D) cell culture model of non-malignant human mammary epithelial cell morphogenesis as down-regulated during breast epithelial cell acinar formation and cell cycle arrest. Here we examine the ability of this gene signature (3D-signature) to predict prognosis in three independent breast cancer microarray datasets having 295, 286, and 118 samples, respectively. Our results show that the 3D-signature accurately predicts prognosis in three unrelated patient datasets. At 10 years, the probability of positive outcome was 52, 51, and 47 percent in the group with a poor-prognosis signature and 91, 75, and 71 percent in the group with a good-prognosis signature for the three datasets, respectively (Kaplan-Meier survival analysis, p<0.05). Hazard ratios for poor outcome were 5.5 (95% CI 3.0 to 12.2, p<0.0001), 2.4 (95% CI 1.6 to 3.6, p<0.0001) and 1.9 (95% CI 1.1 to 3.2, p = 0.016) and remained significant for the two larger datasets when corrected for estrogen receptor (ER) status. Hence the 3D-signature accurately predicts breast cancer outcome in both ER-positive and ER-negative tumors, though individual genes differed in their prognostic ability in the two subtypes. Genes that were prognostic in ER+ patients are AURKA, CEP55, RRM2, EPHA2, FGFBP1, and VRK1, while genes prognostic in ER patients include ACTB, FOXM1 and SERPINE2 (Kaplan-Meier p<0.05). Multivariable Cox regression analysis in the largest dataset showed that the 3D-signature was a strong independent factor in predicting breast cancer outcome. The 3D-signature accurately predicts breast cancer outcome across multiple datasets and holds prognostic
Skorupski, Krzysztof; Mroczka, Janusz; Wriedt, Thomas; Riefler, Norbert
2014-06-01
In many branches of science experiments are expensive, require specialist equipment or are very time consuming. Studying the light scattering phenomenon by fractal aggregates can serve as an example. Light scattering simulations can overcome these problems and provide us with theoretical, additional data which complete our study. For this reason a fractal-like aggregate model as well as fast aggregation codes are needed. Until now various computer models, that try to mimic the physics behind this phenomenon, have been developed. However, their implementations are mostly based on a trial-and-error procedure. Such approach is very time consuming and the morphological parameters of resulting aggregates are not exact because the postconditions (e.g. the position error) cannot be very strict. In this paper we present a very fast and accurate implementation of a tunable aggregation algorithm based on the work of Filippov et al. (2000). Randomization is reduced to its necessary minimum (our technique can be more than 1000 times faster than standard algorithms) and the position of a new particle, or a cluster, is calculated with algebraic methods. Therefore, the postconditions can be extremely strict and the resulting errors negligible (e.g. the position error can be recognized as non-existent). In our paper two different methods, which are based on the particle-cluster (PC) and the cluster-cluster (CC) aggregation processes, are presented.
An accurate locally active memristor model for S-type negative differential resistance in NbOx
Gibson, Gary A.; Musunuru, Srinitya; Zhang, Jiaming; Vandenberghe, Ken; Lee, James; Hsieh, Cheng-Chih; Jackson, Warren; Jeon, Yoocharn; Henze, Dick; Li, Zhiyong; Stanley Williams, R.
2016-01-01
A number of important commercial applications would benefit from the introduction of easily manufactured devices that exhibit current-controlled, or "S-type," negative differential resistance (NDR). A leading example is emerging non-volatile memory based on crossbar array architectures. Due to the inherently linear current vs. voltage characteristics of candidate non-volatile memristor memory elements, individual memory cells in these crossbar arrays can be addressed only if a highly non-linear circuit element, termed a "selector," is incorporated in the cell. Selectors based on a layer of niobium oxide sandwiched between two electrodes have been investigated by a number of groups because the NDR they exhibit provides a promisingly large non-linearity. We have developed a highly accurate compact dynamical model for their electrical conduction that shows that the NDR in these devices results from a thermal feedback mechanism. A series of electrothermal measurements and numerical simulations corroborate this model. These results reveal that the leakage currents can be minimized by thermally isolating the selector or by incorporating materials with larger activation energies for electron motion.
Energy Technology Data Exchange (ETDEWEB)
Gray, Alan [The University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom); Harlen, Oliver G. [University of Leeds, Leeds LS2 9JT (United Kingdom); Harris, Sarah A., E-mail: s.a.harris@leeds.ac.uk [University of Leeds, Leeds LS2 9JT (United Kingdom); University of Leeds, Leeds LS2 9JT (United Kingdom); Khalid, Syma; Leung, Yuk Ming [University of Southampton, Southampton SO17 1BJ (United Kingdom); Lonsdale, Richard [Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr (Germany); Philipps-Universität Marburg, Hans-Meerwein Strasse, 35032 Marburg (Germany); Mulholland, Adrian J. [University of Bristol, Bristol BS8 1TS (United Kingdom); Pearson, Arwen R. [University of Leeds, Leeds LS2 9JT (United Kingdom); University of Hamburg, Hamburg (Germany); Read, Daniel J.; Richardson, Robin A. [University of Leeds, Leeds LS2 9JT (United Kingdom); The University of Edinburgh, Edinburgh EH9 3JZ, Scotland (United Kingdom)
2015-01-01
The current computational techniques available for biomolecular simulation are described, and the successes and limitations of each with reference to the experimental biophysical methods that they complement are presented. Despite huge advances in the computational techniques available for simulating biomolecules at the quantum-mechanical, atomistic and coarse-grained levels, there is still a widespread perception amongst the experimental community that these calculations are highly specialist and are not generally applicable by researchers outside the theoretical community. In this article, the successes and limitations of biomolecular simulation and the further developments that are likely in the near future are discussed. A brief overview is also provided of the experimental biophysical methods that are commonly used to probe biomolecular structure and dynamics, and the accuracy of the information that can be obtained from each is compared with that from modelling. It is concluded that progress towards an accurate spatial and temporal model of biomacromolecules requires a combination of all of these biophysical techniques, both experimental and computational.
Stecca, Guglielmo; Siviglia, Annunziato; Blom, Astrid
2016-07-01
We present an accurate numerical approximation to the Saint-Venant-Hirano model for mixed-sediment morphodynamics in one space dimension. Our solution procedure originates from the fully-unsteady matrix-vector formulation developed in [54]. The principal part of the problem is solved by an explicit Finite Volume upwind method of the path-conservative type, by which all the variables are updated simultaneously in a coupled fashion. The solution to the principal part is embedded into a splitting procedure for the treatment of frictional source terms. The numerical scheme is extended to second-order accuracy and includes a bookkeeping procedure for handling the evolution of size stratification in the substrate. We develop a concept of balancedness for the vertical mass flux between the substrate and active layer under bed degradation, which prevents the occurrence of non-physical oscillations in the grainsize distribution of the substrate. We suitably modify the numerical scheme to respect this principle. We finally verify the accuracy in our solution to the equations, and its ability to reproduce one-dimensional morphodynamics due to streamwise and vertical sorting, using three test cases. In detail, (i) we empirically assess the balancedness of vertical mass fluxes under degradation; (ii) we study the convergence to the analytical linearised solution for the propagation of infinitesimal-amplitude waves [54], which is here employed for the first time to assess a mixed-sediment model; (iii) we reproduce Ribberink's E8-E9 flume experiment [46].
An accurate locally active memristor model for S-type negative differential resistance in NbO{sub x}
Energy Technology Data Exchange (ETDEWEB)
Gibson, Gary A.; Musunuru, Srinitya; Zhang, Jiaming; Lee, James; Hsieh, Cheng-Chih; Jackson, Warren; Jeon, Yoocharn; Henze, Dick; Li, Zhiyong; Stanley Williams, R. [Hewlett-Packard Laboratories, 1501 Page Mill Road, Palo Alto, California 94304 (United States); Vandenberghe, Ken [PTD-PPS, Hewlett-Packard Company, 1070 NE Circle Boulevard, Corvallis, Oregon 97330 (United States)
2016-01-11
A number of important commercial applications would benefit from the introduction of easily manufactured devices that exhibit current-controlled, or “S-type,” negative differential resistance (NDR). A leading example is emerging non-volatile memory based on crossbar array architectures. Due to the inherently linear current vs. voltage characteristics of candidate non-volatile memristor memory elements, individual memory cells in these crossbar arrays can be addressed only if a highly non-linear circuit element, termed a “selector,” is incorporated in the cell. Selectors based on a layer of niobium oxide sandwiched between two electrodes have been investigated by a number of groups because the NDR they exhibit provides a promisingly large non-linearity. We have developed a highly accurate compact dynamical model for their electrical conduction that shows that the NDR in these devices results from a thermal feedback mechanism. A series of electrothermal measurements and numerical simulations corroborate this model. These results reveal that the leakage currents can be minimized by thermally isolating the selector or by incorporating materials with larger activation energies for electron motion.
Długosz, Maciej; Antosiewicz, Jan M
2015-07-01
Proper treatment of hydrodynamic interactions is of importance in evaluation of rigid-body mobility tensors of biomolecules in Stokes flow and in simulations of their folding and solution conformation, as well as in simulations of the translational and rotational dynamics of either flexible or rigid molecules in biological systems at low Reynolds numbers. With macromolecules conveniently modeled in calculations or in dynamic simulations as ensembles of spherical frictional elements, various approximations to hydrodynamic interactions, such as the two-body, far-field Rotne-Prager approach, are commonly used, either without concern or as a compromise between the accuracy and the numerical complexity. Strikingly, even though the analytical Rotne-Prager approach fails to describe (both in the qualitative and quantitative sense) mobilities in the simplest system consisting of two spheres, when the distance between their surfaces is of the order of their size, it is commonly applied to model hydrodynamic effects in macromolecular systems. Here, we closely investigate hydrodynamic effects in two and three-body systems, consisting of bead-shell molecular models, using either the analytical Rotne-Prager approach, or an accurate numerical scheme that correctly accounts for the many-body character of hydrodynamic interactions and their short-range behavior. We analyze mobilities, and translational and rotational velocities of bodies resulting from direct forces acting on them. We show, that with the sufficient number of frictional elements in hydrodynamic models of interacting bodies, the far-field approximation is able to provide a description of hydrodynamic effects that is in a reasonable qualitative as well as quantitative agreement with the description resulting from the application of the virtually exact numerical scheme, even for small separations between bodies. PMID:26068580
Jolivet, L.; Cohen, M.; Ruas, A.
2015-08-01
Landscape influences fauna movement at different levels, from habitat selection to choices of movements' direction. Our goal is to provide a development frame in order to test simulation functions for animal's movement. We describe our approach for such simulations and we compare two types of functions to calculate trajectories. To do so, we first modelled the role of landscape elements to differentiate between elements that facilitate movements and the ones being hindrances. Different influences are identified depending on landscape elements and on animal species. Knowledge were gathered from ecologists, literature and observation datasets. Second, we analysed the description of animal movement recorded with GPS at fine scale, corresponding to high temporal frequency and good location accuracy. Analysing this type of data provides information on the relation between landscape features and movements. We implemented an agent-based simulation approach to calculate potential trajectories constrained by the spatial environment and individual's behaviour. We tested two functions that consider space differently: one function takes into account the geometry and the types of landscape elements and one cost function sums up the spatial surroundings of an individual. Results highlight the fact that the cost function exaggerates the distances travelled by an individual and simplifies movement patterns. The geometry accurate function represents a good bottom-up approach for discovering interesting areas or obstacles for movements.
Directory of Open Access Journals (Sweden)
L. Jolivet
2015-08-01
Full Text Available Landscape influences fauna movement at different levels, from habitat selection to choices of movements’ direction. Our goal is to provide a development frame in order to test simulation functions for animal’s movement. We describe our approach for such simulations and we compare two types of functions to calculate trajectories. To do so, we first modelled the role of landscape elements to differentiate between elements that facilitate movements and the ones being hindrances. Different influences are identified depending on landscape elements and on animal species. Knowledge were gathered from ecologists, literature and observation datasets. Second, we analysed the description of animal movement recorded with GPS at fine scale, corresponding to high temporal frequency and good location accuracy. Analysing this type of data provides information on the relation between landscape features and movements. We implemented an agent-based simulation approach to calculate potential trajectories constrained by the spatial environment and individual’s behaviour. We tested two functions that consider space differently: one function takes into account the geometry and the types of landscape elements and one cost function sums up the spatial surroundings of an individual. Results highlight the fact that the cost function exaggerates the distances travelled by an individual and simplifies movement patterns. The geometry accurate function represents a good bottom-up approach for discovering interesting areas or obstacles for movements.
Augustin, Christoph M.; Neic, Aurel; Liebmann, Manfred; Prassl, Anton J.; Niederer, Steven A.; Haase, Gundolf; Plank, Gernot
2016-01-01
Electromechanical (EM) models of the heart have been used successfully to study fundamental mechanisms underlying a heart beat in health and disease. However, in all modeling studies reported so far numerous simplifications were made in terms of representing biophysical details of cellular function and its heterogeneity, gross anatomy and tissue microstructure, as well as the bidirectional coupling between electrophysiology (EP) and tissue distension. One limiting factor is the employed spatial discretization methods which are not sufficiently flexible to accommodate complex geometries or resolve heterogeneities, but, even more importantly, the limited efficiency of the prevailing solver techniques which is not sufficiently scalable to deal with the incurring increase in degrees of freedom (DOF) when modeling cardiac electromechanics at high spatio-temporal resolution. This study reports on the development of a novel methodology for solving the nonlinear equation of finite elasticity using human whole organ models of cardiac electromechanics, discretized at a high para-cellular resolution. Three patient-specific, anatomically accurate, whole heart EM models were reconstructed from magnetic resonance (MR) scans at resolutions of 220 μm, 440 μm and 880 μm, yielding meshes of approximately 184.6, 24.4 and 3.7 million tetrahedral elements and 95.9, 13.2 and 2.1 million displacement DOF, respectively. The same mesh was used for discretizing the governing equations of both electrophysiology (EP) and nonlinear elasticity. A novel algebraic multigrid (AMG) preconditioner for an iterative Krylov solver was developed to deal with the resulting computational load. The AMG preconditioner was designed under the primary objective of achieving favorable strong scaling characteristics for both setup and solution runtimes, as this is key for exploiting current high performance computing hardware. Benchmark results using the 220 μm, 440 μm and 880 μm meshes demonstrate
Infantino, Angelo; Marengo, Mario; Baschetti, Serafina; Cicoria, Gianfranco; Longo Vaschetto, Vittorio; Lucconi, Giulia; Massucci, Piera; Vichi, Sara; Zagni, Federico; Mostacci, Domiziano
2015-11-01
Biomedical cyclotrons for production of Positron Emission Tomography (PET) radionuclides and radiotherapy with hadrons or ions are widely diffused and established in hospitals as well as in industrial facilities and research sites. Guidelines for site planning and installation, as well as for radiation protection assessment, are given in a number of international documents; however, these well-established guides typically offer analytic methods of calculation of both shielding and materials activation, in approximate or idealized geometry set up. The availability of Monte Carlo codes with accurate and up-to-date libraries for transport and interactions of neutrons and charged particles at energies below 250 MeV, together with the continuously increasing power of nowadays computers, makes systematic use of simulations with realistic geometries possible, yielding equipment and site specific evaluation of the source terms, shielding requirements and all quantities relevant to radiation protection. In this work, the well-known Monte Carlo code FLUKA was used to simulate two representative models of cyclotron for PET radionuclides production, including their targetry; and one type of proton therapy cyclotron including the energy selection system. Simulations yield estimates of various quantities of radiological interest, including the effective dose distribution around the equipment, the effective number of neutron produced per incident proton and the activation of target materials, the structure of the cyclotron, the energy degrader, the vault walls and the soil. The model was validated against experimental measurements and comparison with well-established reference data. Neutron ambient dose equivalent H*(10) was measured around a GE PETtrace cyclotron: an average ratio between experimental measurement and simulations of 0.99±0.07 was found. Saturation yield of 18F, produced by the well-known 18O(p,n)18F reaction, was calculated and compared with the IAEA recommended
Cerfontaine, Benjamin; Radioti, Georgia; Collin, Frédéric; Charlier, Robert
2016-01-01
This paper presents a comprehensive formulation of a finite element for the modelling of borehole heat exchangers. This work focuses on the accurate modelling of the grouting and the field of temperature near a single borehole. Therefore the grouting of the BHE is explicitly modelled. The purpose of this work is to provide tools necessary to the further modelling of thermo-mechanical couplings. The finite element discretises the classical governing equation of advection-diffusion of heat w...
DEFF Research Database (Denmark)
Wu, Rui; Iannuzzo, Francesco; Wang, Huai;
2014-01-01
A basic problem in the IGBT short-circuit failure mechanism study is to obtain realistic temperature distribution inside the chip, which demands accurate electrical simulation to obtain power loss distribution as well as detailed IGBT geometry and material information. This paper describes an unp...
Feldgus, Steven; Shields, George C.
2001-10-01
The Bergman cyclization of large polycyclic enediyne systems that mimic the cores of the enediyne anticancer antibiotics was studied using the ONIOM hybrid method. Tests on small enediynes show that ONIOM can accurately match experimental data. The effect of the triggering reaction in the natural products is investigated, and we support the argument that it is strain effects that lower the cyclization barrier. The barrier for the triggered molecule is very low, leading to a reasonable half-life at biological temperatures. No evidence is found that would suggest a concerted cyclization/H-atom abstraction mechanism is necessary for DNA cleavage.
Chowdhury, Amor; Sarjaš, Andrej
2016-01-01
The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation. PMID:27649197
Chowdhury, Amor; Sarjaš, Andrej
2016-09-15
The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation.
Chowdhury, Amor; Sarjaš, Andrej
2016-01-01
The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation. PMID:27649197
Directory of Open Access Journals (Sweden)
Amor Chowdhury
2016-09-01
Full Text Available The presented paper describes accurate distance measurement for a field-sensed magnetic suspension system. The proximity measurement is based on a Hall effect sensor. The proximity sensor is installed directly on the lower surface of the electro-magnet, which means that it is very sensitive to external magnetic influences and disturbances. External disturbances interfere with the information signal and reduce the usability and reliability of the proximity measurements and, consequently, the whole application operation. A sensor fusion algorithm is deployed for the aforementioned reasons. The sensor fusion algorithm is based on the Unscented Kalman Filter, where a nonlinear dynamic model was derived with the Finite Element Modelling approach. The advantage of such modelling is a more accurate dynamic model parameter estimation, especially in the case when the real structure, materials and dimensions of the real-time application are known. The novelty of the paper is the design of a compact electro-magnetic actuator with a built-in low cost proximity sensor for accurate proximity measurement of the magnetic object. The paper successively presents a modelling procedure with the finite element method, design and parameter settings of a sensor fusion algorithm with Unscented Kalman Filter and, finally, the implementation procedure and results of real-time operation.
Li, Yanjun; Nguyen, M. Hong; Cheng, Shaoji; Schmidt, Stephan; Zhong, Li; Derendorf, Hartmut; Clancy, Cornelius J.
2008-01-01
We developed a pharmacokinetic/pharmacodynamic (PK/PD) mathematical model that fits voriconazole time–kill data against Candida isolates in vitro and used the model to simulate the expected kill curves for typical intravenous and oral dosing regimens. A series of Emax mathematical models were used to fit time–kill data for two isolates each of Candida albicans, Candida glabrata and Candida parapsilosis. PK parameters extracted from human data sets were used in the model to simulate kill curve...
Directory of Open Access Journals (Sweden)
Mohamed H. Abdel Meniem
2012-03-01
Full Text Available In this paper, we consider problem of positioning of mobile phones, different approaches were produced for these targets using GPS, WiFi, GSM, UMTS and other sensors, which exist in today smart phone sensors. Location awareness in gen-eral is emerging a tremendous interest in different fields and scopes. Position is the key element of context awareness. How-ever GPS produces an accurate position, it requires open sky and does not work indoors. We produce an innovative robust tech-nique for positioning which could be applied on terminal-based or network-based architecture. It depends only on Received Sig-nal Strength (RSS and location of Base Transceiver Station (BTS. This work has been completely tested and analyzed in Egypt1 roads using realistic data and commercial android smart phone. In general, all performance evaluation results were good. Mean positioning error was about 120 m in urban and 394 m in rural.
DEFF Research Database (Denmark)
Brandt, J.; Bastrup-Birk, A.; Christensen, J.H.;
1998-01-01
transport and dispersion of air pollutants caused by a single but strong source as, e.g. an accidental release from a nuclear power plant. The model system including the coupling of the Lagrangian model with the Eulerian model are described. Various simple and comprehensive parameterizations of the mixing...
Swennen, G R J; Barth, E-L; Eulzer, C; Schutyser, F
2007-02-01
Three-dimensional (3D) virtual planning of orthognathic surgery requires detailed visualization of the interocclusal relationship. The purpose of this study was to introduce the modification of the double computed tomography (CT) scan procedure using a newly designed 3D splint in order to obtain a detailed anatomic 3D virtual augmented model of the skull. A total of 10 dry adult human cadaver skulls were used to evaluate the accuracy of the automatic rigid registration method for fusion of both CT datasets (Maxilim, version 1.3.0). The overall mean registration error was 0.1355+/-0.0323 mm (range 0.0760-0.1782 mm). Analysis of variance showed a registration method error of 0.0564 mm (P 3D splint with the double CT scan procedure allowed accurate registration and the set-up of an accurate anatomic 3D virtual augmented model of the skull with detailed dental surface.
Shiyao Wang; Zhidong Deng; Gang Yin
2016-01-01
A high-performance differential global positioning system (GPS) receiver with real time kinematics provides absolute localization for driverless cars. However, it is not only susceptible to multipath effect but also unable to effectively fulfill precise error correction in a wide range of driving areas. This paper proposes an accurate GPS–inertial measurement unit (IMU)/dead reckoning (DR) data fusion method based on a set of predictive models and occupancy grid constraints. First, we employ...
M.J. Kehoe; K. O’ Brien; A. Grinham; D. Rissik; K.S. Ahern; P. Maxwell
2012-01-01
It is shown that targeted high frequency monitoring and modern machine learning methods lead to highly predictive models of benthic light flux. A state-of-the-art machine learning technique was used in conjunction with a high frequency data set to calibrate and test predictive benthic lights models
Antonelli, Cristian; Li, Wangzhe; Coldren, Larry
2015-01-01
We present a model for multi-wavelength mixing in semiconductor optical amplifiers (SOAs) based on coupled-mode equations. The proposed model applies to all kinds of SOA structures, takes into account the longitudinal dependence of carrier density caused by saturation, it accommodates an arbitrary functional dependencies of the material gain and carrier recombination rate on the local value of carrier density, and is computationally more efficient by orders of magnitude as compared with the standard full model based on space-time equations. We apply the coupled-mode equations model to a recently demonstrated phase-sensitive amplifier based on an integrated SOA and prove its results to be consistent with the experimental data. The accuracy of the proposed model is certified by means of a meticulous comparison with the results obtained by integrating the space-time equations.
Directory of Open Access Journals (Sweden)
Nada Chendeb Taher
2011-01-01
Full Text Available Extensive research addressing IEEE 802.11e enhanced distributed channel access (EDCA performance analysis, by means of analytical models, exist in the literature. Unfortunately, the currently proposed models, even though numerous, do not reach this accuracy due to the great number of simplifications that have been done. Particularly, none of these models considers the 802.11e contention free burst (CFB mode which allows a given station to transmit a burst of frames without contention during a given transmission opportunity limit (TXOPLimit time interval. Despite its influence on the global performance, TXOPLimit is ignored in almost all existing models. To fill in this gap, we develop in this paper a new and complete analytical model that (i reflects the correct functioning of EDCA, (ii includes all the 802.11e EDCA differentiation parameters, (iii takes into account all the features of the protocol, and (iv can be applied to all network conditions, going from nonsaturation to saturation conditions. Additionally, this model is developed in order to be used in admission control procedure, so it was designed to have a low complexity and an acceptable response time. The proposed model is validated by means of both calculations and extensive simulations.
Neufeld, Susan M; Newburn-Cook, Christine V; Drummond, Jane E
2008-10-01
Postoperative nausea and vomiting (PONV) is a problem for many children after craniotomy. Prognostic models and risk scores help identify who is at risk for an adverse event such as PONV to help guide clinical care. The purpose of this article is to assess whether an existing prognostic model or risk score can predict PONV in children after craniotomy. The concepts of transportability, calibration, and discrimination are presented to identify what is required to have a valid tool for clinical use. Although previous work may inform clinical practice and guide future research, existing prognostic models and risk scores do not appear to be options for predicting PONV in children undergoing craniotomy. However, until risk factors are further delineated, followed by the development and validation of prognostic models and risk scores that include children after craniotomy, clinical judgment in the context of current research may serve as a guide for clinical care in this population. PMID:18939320
Panagiotopoulou, O.; Wilshin, S. D.; Rayfield, E J; Shefelbine, S. J.; Hutchinson, J. R.
2014-01-01
Finite element modelling is well entrenched in comparative vertebrate biomechanics as a tool to assess the mechanical design of skeletal structures and to better comprehend the complex interaction of their form–function relationships. But what makes a reliable subject-specific finite element model? To approach this question, we here present a set of convergence and sensitivity analyses and a validation study as an example, for finite element analysis (FEA) in general, of ways to ensure a reli...
Immonen, Taina; Gibson, Richard; Leitner, Thomas; Miller, Melanie A; Arts, Eric J; Somersalo, Erkki; Calvetti, Daniela
2012-11-01
We present a new hybrid stochastic-deterministic, spatially distributed computational model to simulate growth competition assays on a relatively immobile monolayer of peripheral blood mononuclear cells (PBMCs), commonly used for determining ex vivo fitness of human immunodeficiency virus type-1 (HIV-1). The novel features of our approach include incorporation of viral diffusion through a deterministic diffusion model while simulating cellular dynamics via a stochastic Markov chain model. The model accounts for multiple infections of target cells, CD4-downregulation, and the delay between the infection of a cell and the production of new virus particles. The minimum threshold level of infection induced by a virus inoculum is determined via a series of dilution experiments, and is used to determine the probability of infection of a susceptible cell as a function of local virus density. We illustrate how this model can be used for estimating the distribution of cells infected by either a single virus type or two competing viruses. Our model captures experimentally observed variation in the fitness difference between two virus strains, and suggests a way to minimize variation and dual infection in experiments.
Orenstein, Yaron; Wang, Yuhao; Berger, Bonnie
2016-01-01
Motivation: Protein–RNA interactions, which play vital roles in many processes, are mediated through both RNA sequence and structure. CLIP-based methods, which measure protein–RNA binding in vivo, suffer from experimental noise and systematic biases, whereas in vitro experiments capture a clearer signal of protein RNA-binding. Among them, RNAcompete provides binding affinities of a specific protein to more than 240 000 unstructured RNA probes in one experiment. The computational challenge is to infer RNA structure- and sequence-based binding models from these data. The state-of-the-art in sequence models, Deepbind, does not model structural preferences. RNAcontext models both sequence and structure preferences, but is outperformed by GraphProt. Unfortunately, GraphProt cannot detect structural preferences from RNAcompete data due to the unstructured nature of the data, as noted by its developers, nor can it be tractably run on the full RNACompete dataset. Results: We develop RCK, an efficient, scalable algorithm that infers both sequence and structure preferences based on a new k-mer based model. Remarkably, even though RNAcompete data is designed to be unstructured, RCK can still learn structural preferences from it. RCK significantly outperforms both RNAcontext and Deepbind in in vitro binding prediction for 244 RNAcompete experiments. Moreover, RCK is also faster and uses less memory, which enables scalability. While currently on par with existing methods in in vivo binding prediction on a small scale test, we demonstrate that RCK will increasingly benefit from experimentally measured RNA structure profiles as compared to computationally predicted ones. By running RCK on the entire RNAcompete dataset, we generate and provide as a resource a set of protein–RNA structure-based models on an unprecedented scale. Availability and Implementation: Software and models are freely available at http://rck.csail.mit.edu/ Contact: bab@mit.edu Supplementary information
Directory of Open Access Journals (Sweden)
Rajib Kar
2010-09-01
Full Text Available This work presents an accurate and efficient model to compute the delay and slew metric of on-chip interconnect of high speed CMOS circuits foe ramp input. Our metric assumption is based on the Burr’s Distribution function. The Burr’s distribution is used to characterize the normalized homogeneous portion of the step response. We used the PERI (Probability distribution function Extension for Ramp Inputs technique that extends delay metrics and slew metric for step inputs to the more general and realistic non-step inputs. The accuracy of our models is justified with the results compared with that of SPICE simulations.
International Nuclear Information System (INIS)
In this paper, a reformulation for the recently published dielectric properties dispersion models of the breast tissues is carried out to be used by CST simulation tool. The reformulation includes tabulation of the real and imaginary parts versus frequency on ultra-wideband (UWB) for these models by MATLAB programs. The tables are imported and fitted by CST simulation tool to second or first order general equations. The results have shown good agreement between the original and the imported data. The MATLAB programs written in MATLAB code are included in the appendix.
Fast and accurate two-dimensional modelling of high-current, high-voltage air-cored transformers
International Nuclear Information System (INIS)
This paper presents a detailed two-dimensional model for high-voltage air-cored pulse transformers of two quite different designs. A filamentary technique takes magnetic diffusion fully into account and enables the resistances and self and mutual inductances that are effective under fast transient conditions to be calculated. Very good agreement between calculated and measured results for typical transformers has been obtained in several cases, and the model is now regularly used in the design of compact high-power sources
Grassi, Lorenzo; Väänänen, Sami P; Ristinmaa, Matti; Jurvelin, Jukka S; Isaksson, Hanna
2016-03-21
Subject-specific finite element models have been proposed as a tool to improve fracture risk assessment in individuals. A thorough laboratory validation against experimental data is required before introducing such models in clinical practice. Results from digital image correlation can provide full-field strain distribution over the specimen surface during in vitro test, instead of at a few pre-defined locations as with strain gauges. The aim of this study was to validate finite element models of human femora against experimental data from three cadaver femora, both in terms of femoral strength and of the full-field strain distribution collected with digital image correlation. The results showed a high accuracy between predicted and measured principal strains (R(2)=0.93, RMSE=10%, 1600 validated data points per specimen). Femoral strength was predicted using a rate dependent material model with specific strain limit values for yield and failure. This provided an accurate prediction (strain accuracy was comparable to that obtained in state-of-the-art studies which validated their prediction accuracy against 10-16 strain gauge measurements. Fracture force was accurately predicted, with the predicted failure location being very close to the experimental fracture rim. Despite the low sample size and the single loading condition tested, the present combined numerical-experimental method showed that finite element models can predict femoral strength by providing a thorough description of the local bone mechanical response. PMID:26944687
DEFF Research Database (Denmark)
Gondan, Matthias; Blurton, Steven Paul; Kesselmeier, Miriam
2014-01-01
The Wiener diffusion model with two absorbing barriers is often used to describe response times and error probabilities in two-choice decisions. Different representations exist for the density and cumulative distribution of first-passage times, all including infinite series, but with different...
Basso, Bruno; Hyndman, David W; Kendall, Anthony D; Grace, Peter R; Robertson, G Philip
2015-01-01
Estimates of climate change impacts on global food production are generally based on statistical or process-based models. Process-based models can provide robust predictions of agricultural yield responses to changing climate and management. However, applications of these models often suffer from bias due to the common practice of re-initializing soil conditions to the same state for each year of the forecast period. If simulations neglect to include year-to-year changes in initial soil conditions and water content related to agronomic management, adaptation and mitigation strategies designed to maintain stable yields under climate change cannot be properly evaluated. We apply a process-based crop system model that avoids re-initialization bias to demonstrate the importance of simulating both year-to-year and cumulative changes in pre-season soil carbon, nutrient, and water availability. Results are contrasted with simulations using annual re-initialization, and differences are striking. We then demonstrate the potential for the most likely adaptation strategy to offset climate change impacts on yields using continuous simulations through the end of the 21st century. Simulations that annually re-initialize pre-season soil carbon and water contents introduce an inappropriate yield bias that obscures the potential for agricultural management to ameliorate the deleterious effects of rising temperatures and greater rainfall variability.
Zakrzewski, Jakub; Delande, Dominique
2007-01-01
The quantum phase transition point between the insulator and the superfluid phase at unit filling factor of the infinite one-dimensional Bose-Hubbard model is numerically computed with a high accuracy, better than current state of the art calculations. The method uses the infinite system version of the time evolving block decimation algorithm, here tested in a challenging case.
Institute of Scientific and Technical Information of China (English)
LIU Weiyi; QIU Jinhuan
2012-01-01
A parameterized transmittance model (PTR) for ozone and water vapor monochromatic transmittance calculation in the solar-to-near-infrared spectrum 0.3-4 μm with a spectral resolution of 5 cm-1 was developed based on the transmittance data calculated by Moderate-resolution Transmittance model (MODTRAN).Polynomial equations were derived to represent the transmittance as functions of path length and airmass for every wavelength based on the least-squares method.Comparisons between the transmittances calculated using PTR and MODTRAN were made,using the results of MODTRAN as a reference.Relative root-mean-square error (RMSre) was 0.823％ for ozone transmittance.RMSre values were 8.84％ and 3.48％ for water vapor transmittance ranges of 1-1 × 10-18and 1-1× 10-3,respectively.In addition,the Stratospheric Aerosol and Gas Experiment II (SAGEII) ozone profiles and University of Wyoming (UWYO)water vapor profiles were applied to validate the applicability of PTR model.RMSre was 0.437％ for ozone transmittance.RMSre values were 8.89％ and 2.43％ for water vapor transmittance ranges of 1-1 × 10-18and 1-1 × 10-6,respectively.Furthermore,the optical depth profiles calculated using the PTR model were compared to the results of MODTRAN.Absolute RMS errors (RMSab) for ozone optical depths were within 0.0055 and 0.0523 for water vapor at all of the tested altitudes.Finally,the comparison between the solar heating rate calculated from the transmittance of PTR and Line-by-Line radiative transfer model (LBLRTM) was performed,showing a maximum deviation of 0.238 K d-1 (6％ of the corresponding solar heating rate calculated using LBLRTM).In the troposphere all of the deviations were within 0.08 K d-1.The computational speed of PTR model is nearly two orders of magnitude faster than that of MODTRAN.
ACCURATE 3D TEXTURED MODELS OF VESSELS FOR THE IMPROVEMENT OF THE EDUCATIONAL TOOLS OF A MUSEUM
S. Soile; Adam, K.; C. Ioannidis; A. Georgopoulos
2013-01-01
Besides the demonstration of the findings, modern museums organize educational programs which aim to experience and knowledge sharing combined with entertainment rather than to pure learning. Toward that effort, 2D and 3D digital representations are gradually replacing the traditional recording of the findings through photos or drawings. The present paper refers to a project that aims to create 3D textured models of two lekythoi that are exhibited in the National Archaeological Museu...
Energy Technology Data Exchange (ETDEWEB)
Nguyen, Hung T. [BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854 (United States); Pabit, Suzette A.; Meisburger, Steve P.; Pollack, Lois [School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853 (United States); Case, David A., E-mail: case@biomaps.rutgers.edu [BioMaPS Institute for Quantitative Biology, Rutgers University, Piscataway, New Jersey 08854 (United States); Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854 (United States)
2014-12-14
A new method is introduced to compute X-ray solution scattering profiles from atomic models of macromolecules. The three-dimensional version of the Reference Interaction Site Model (RISM) from liquid-state statistical mechanics is employed to compute the solvent distribution around the solute, including both water and ions. X-ray scattering profiles are computed from this distribution together with the solute geometry. We describe an efficient procedure for performing this calculation employing a Lebedev grid for the angular averaging. The intensity profiles (which involve no adjustable parameters) match experiment and molecular dynamics simulations up to wide angle for two proteins (lysozyme and myoglobin) in water, as well as the small-angle profiles for a dozen biomolecules taken from the BioIsis.net database. The RISM model is especially well-suited for studies of nucleic acids in salt solution. Use of fiber-diffraction models for the structure of duplex DNA in solution yields close agreement with the observed scattering profiles in both the small and wide angle scattering (SAXS and WAXS) regimes. In addition, computed profiles of anomalous SAXS signals (for Rb{sup +} and Sr{sup 2+}) emphasize the ionic contribution to scattering and are in reasonable agreement with experiment. In cases where an absolute calibration of the experimental data at q = 0 is available, one can extract a count of the excess number of waters and ions; computed values depend on the closure that is assumed in the solution of the Ornstein–Zernike equations, with results from the Kovalenko–Hirata closure being closest to experiment for the cases studied here.
Koesters, Thomas; Friedman, Kent P.; Fenchel, Matthias; Zhan, Yiqiang; Hermosillo, Gerardo; Babb, James; Jelescu, Ileana O.; Faul, David; Boada, Fernando E.; Shepherd, Timothy M.
2016-01-01
Simultaneous PET/MR of the brain is a promising new technology for characterizing patients with suspected cognitive impairment or epilepsy. Unlike CT though, MR signal intensities do not provide a direct correlate to PET photon attenuation correction (AC) and inaccurate radiotracer standard uptake value (SUV) estimation could limit future PET/MR clinical applications. We tested a novel AC method that supplements standard Dixon-based tissue segmentation with a superimposed model-based bone com...
Takemiya, Takako; Takeuchi, Chisen
2013-01-01
Multiple sclerosis (MS) is a common central nervous system disease associated with progressive physical impairment. To study the mechanisms of the disease, we used experimental autoimmune encephalomyelitis (EAE), an animal model of MS. EAE is induced by myelin oligodendrocyte glycoprotein35–55 peptide, and the severity of paralysis in the disease is generally measured using the EAE score. Here, we compared EAE scores and traveled distance using the open-field test for an assessment of EAE pro...
Laub, Bernard; Grinstead, Jay; Dyakonov, Artem; Venkatapathy, Ethiraj
2011-01-01
Though arc jet testing has been the proven method employed for development testing and certification of TPS and TPS instrumentation, the operational aspects of arc jets limit testing to selected, but constant, conditions. Flight, on the other hand, produces timevarying entry conditions in which the heat flux increases, peaks, and recedes as a vehicle descends through an atmosphere. As a result, we are unable to "test as we fly." Attempts to replicate the time-dependent aerothermal environment of atmospheric entry by varying the arc jet facility operating conditions during a test have proven to be difficult, expensive, and only partially successful. A promising alternative is to rotate the test model exposed to a constant-condition arc jet flow to yield a time-varying test condition at a point on a test article (Fig. 1). The model shape and rotation rate can be engineered so that the heat flux at a point on the model replicates the predicted profile for a particular point on a flight vehicle. This simple concept will enable, for example, calibration of the TPS sensors on the Mars Science Laboratory (MSL) aeroshell for anticipated flight environments.
Oliver-Rodríguez, B; Zafra-Gómez, A; Reis, M S; Duarte, B P M; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L
2015-11-01
In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results.
Oliver-Rodríguez, B; Zafra-Gómez, A; Reis, M S; Duarte, B P M; Verge, C; de Ferrer, J A; Pérez-Pascual, M; Vílchez, J L
2015-11-01
In this paper, rigorous data and adequate models about linear alkylbenzene sulfonate (LAS) adsorption/desorption on agricultural soil are presented, contributing with a substantial improvement over available adsorption works. The kinetics of the adsorption/desorption phenomenon and the adsorption/desorption equilibrium isotherms were determined through batch studies for total LAS amount and also for each homologue series: C10, C11, C12 and C13. The proposed multiple pseudo-first order kinetic model provides the best fit to the kinetic data, indicating the presence of two adsorption/desorption processes in the general phenomenon. Equilibrium adsorption and desorption data have been properly fitted by a model consisting of a Langmuir plus quadratic term, which provides a good integrated description of the experimental data over a wide range of concentrations. At low concentrations, the Langmuir term explains the adsorption of LAS on soil sites which are highly selective of the n-alkyl groups and cover a very small fraction of the soil surface area, whereas the quadratic term describes adsorption on the much larger part of the soil surface and on LAS retained at moderate to high concentrations. Since adsorption/desorption phenomenon plays a major role in the LAS behavior in soils, relevant conclusions can be drawn from the obtained results. PMID:26070080
DEFF Research Database (Denmark)
Mihet-Popa, Lucian; Camacho, Oscar Mauricio Forero; Nørgård, Per Bromand
2013-01-01
This paper presents a battery test platform including two Li-ion battery designed for hybrid and EV applications, and charging/discharging tests under different operating conditions carried out for developing an accurate dynamic electro-thermal model of a high power Li-ion battery pack system....... The aim of the tests has been to study the impact of the battery degradation and to find out the dynamic characteristics of the cells including nonlinear open circuit voltage, series resistance and parallel transient circuit at different charge/discharge currents and cell temperature. An equivalent...... circuit model, based on the runtime battery model and the Thevenin circuit model, with parameters obtained from the tests and depending on SOC, current and temperature has been implemented in MATLAB/Simulink and Power Factory. A good alignment between simulations and measurements has been found....
Eissa, Y.; Blanc, P.; Wald, L.; Ghedira, H.
2015-12-01
Routine measurements of the beam irradiance at normal incidence include the irradiance originating from within the extent of the solar disc only (DNIS), whose angular extent is 0.266° ± 1.7 %, and from a larger circumsolar region, called the circumsolar normal irradiance (CSNI). This study investigates whether the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and the collocated Sun and Aureole Measurement instrument which offers reference measurements of the monochromatic profile of solar radiance were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE) of 6 % and a coefficient of determination greater than 0.96. The observed relative bias obtained with libRadtran is +2 %, while that obtained with SMARTS is -1 %. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a two-term Henyey-Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 27 and -24 % and a coefficient of determination of 0.882. Therefore, AERONET data may very well be used to model the monochromatic DNIS and the monochromatic CSNI. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard measurements of the beam irradiance.
Safaei, B; Naseradinmousavi, P; Rahmani, A
2016-04-01
In the present paper, an analytical solution based on a molecular mechanics model is developed to evaluate the elastic critical axial buckling strain of chiral multi-walled carbon nanotubes (MWCNTs). To this end, the total potential energy of the system is calculated with the consideration of the both bond stretching and bond angular variations. Density functional theory (DFT) in the form of generalized gradient approximation (GGA) is implemented to evaluate force constants used in the molecular mechanics model. After that, based on the principle of molecular mechanics, explicit expressions are proposed to obtain elastic surface Young's modulus and Poisson's ratio of the single-walled carbon nanotubes corresponding to different types of chirality. Selected numerical results are presented to indicate the influence of the type of chirality, tube diameter, and number of tube walls in detailed. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. It is found that the value of critical axial buckling strain exhibit significant dependency on the type of chirality and number of tube walls.
A new expression of Ns versus Ef to an accurate control charge model for AlGaAs/GaAs
Bouneb, I.; Kerrour, F.
2016-03-01
Semi-conductor components become the privileged support of information and communication, particularly appreciation to the development of the internet. Today, MOS transistors on silicon dominate largely the semi-conductors market, however the diminution of transistors grid length is not enough to enhance the performances and respect Moore law. Particularly, for broadband telecommunications systems, where faster components are required. For this reason, alternative structures proposed like hetero structures IV-IV or III-V [1] have been.The most effective components in this area (High Electron Mobility Transistor: HEMT) on IIIV substrate. This work investigates an approach for contributing to the development of a numerical model based on physical and numerical modelling of the potential at heterostructure in AlGaAs/GaAs interface. We have developed calculation using projective methods allowed the Hamiltonian integration using Green functions in Schrodinger equation, for a rigorous resolution “self coherent” with Poisson equation. A simple analytical approach for charge-control in quantum well region of an AlGaAs/GaAs HEMT structure was presented. A charge-control equation, accounting for a variable average distance of the 2-DEG from the interface was introduced. Our approach which have aim to obtain ns-Vg characteristics is mainly based on: A new linear expression of Fermi-level variation with two-dimensional electron gas density in high electron mobility and also is mainly based on the notion of effective doping and a new expression of AEc
Tao, Liang; Xinzhang, Jia; Junfeng, Chen
2009-11-01
Techniques for constructing metamodels of device parameters at BSIM3v3 level accuracy are presented to improve knowledge-based circuit sizing optimization. Based on the analysis of the prediction error of analytical performance expressions, operating point driven (OPD) metamodels of MOSFETs are introduced to capture the circuit's characteristics precisely. In the algorithm of metamodel construction, radial basis functions are adopted to interpolate the scattered multivariate data obtained from a well tailored data sampling scheme designed for MOSFETs. The OPD metamodels can be used to automatically bias the circuit at a specific DC operating point. Analytical-based performance expressions composed by the OPD metamodels show obvious improvement for most small-signal performances compared with simulation-based models. Both operating-point variables and transistor dimensions can be optimized in our nesting-loop optimization formulation to maximize design flexibility. The method is successfully applied to a low-voltage low-power amplifier.
Energy Technology Data Exchange (ETDEWEB)
Myint, P. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hao, Y. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Firoozabadi, A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-03-27
Thermodynamic property calculations of mixtures containing carbon dioxide (CO_{2}) and water, including brines, are essential in theoretical models of many natural and industrial processes. The properties of greatest practical interest are density, solubility, and enthalpy. Many models for density and solubility calculations have been presented in the literature, but there exists only one study, by Spycher and Pruess, that has compared theoretical molar enthalpy predictions with experimental data [1]. In this report, we recommend two different models for enthalpy calculations: the CPA equation of state by Li and Firoozabadi [2], and the CO_{2} activity coefficient model by Duan and Sun [3]. We show that the CPA equation of state, which has been demonstrated to provide good agreement with density and solubility data, also accurately calculates molar enthalpies of pure CO_{2}, pure water, and both CO_{2}-rich and aqueous (H_{2}O-rich) mixtures of the two species. It is applicable to a wider range of conditions than the Spycher and Pruess model. In aqueous sodium chloride (NaCl) mixtures, we show that Duan and Sun’s model yields accurate results for the partial molar enthalpy of CO_{2}. It can be combined with another model for the brine enthalpy to calculate the molar enthalpy of H_{2}O-CO_{2}-NaCl mixtures. We conclude by explaining how the CPA equation of state may be modified to further improve agreement with experiments. This generalized CPA is the basis of our future work on this topic.
Directory of Open Access Journals (Sweden)
Y. Eissa
2015-07-01
Full Text Available Routine measurements of the beam irradiance at normal incidence (DNI include the irradiance originating from within the extent of the solar disc only (DNIS whose angular extent is 0.266° ± 1.7 %, and that from a larger circumsolar region, called the circumsolar normal irradiance (CSNI. This study investigates if the spectral aerosol optical properties of the AERONET stations are sufficient for an accurate modelling of the monochromatic DNIS and CSNI under cloud-free conditions in a desert environment. The data from an AERONET station in Abu Dhabi, United Arab Emirates, and a collocated Sun and Aureole Measurement (SAM instrument which offers reference measurements of the monochromatic profile of solar radiance, were exploited. Using the AERONET data both the radiative transfer models libRadtran and SMARTS offer an accurate estimate of the monochromatic DNIS, with a relative root mean square error (RMSE of 5 %, a relative bias of +1 % and acoefficient of determination greater than 0.97. After testing two configurations in SMARTS and three in libRadtran for modelling the monochromatic CSNI, libRadtran exhibits the most accurate results when the AERONET aerosol phase function is presented as a Two Term Henyey–Greenstein phase function. In this case libRadtran exhibited a relative RMSE and a bias of respectively 22 and −19 % and a coefficient of determination of 0.89. The results are promising and pave the way towards reporting the contribution of the broadband circumsolar irradiance to standard DNI measurements.
A Hybrid Mode Model of the Blazhko Effect, Shown to Accurately Fit Kepler Data for RR Lyr
Bryant, Paul H
2013-01-01
A new hypothesis is presented for the Blazhko effect in RRab stars. A nonlinear model is developed for the first overtone mode, which, if excited to large amplitude, is found to drop strongly in frequency while becoming highly nonsinusoidal. Its frequency is shown to drop sufficiently to become equal that of the fundamental mode. It is proposed that this may lead to phase-locking between the fundamental and the overtone forming a hybrid mode at the fundamental frequency. The fundamental mode, excited less strongly than the overtone, remains nearly sinusoidal and constant in frequency. By varying the fundamental's peak amplitude and its phase relative to the overtone, the hybrid mode can produce a variety of forms that match those observed in various parts of the Blazhko cycle. The presence of the fundamental also serves to stabilize the period of the hybrid which is found in real Blazhko data to be extremely stable. It is proposed that the variations in amplitude and phase might result from a nonlinear intera...
Energy Technology Data Exchange (ETDEWEB)
Dall' Ora, M.; Botticella, M. T.; Della Valle, M. [INAF, Osservatorio Astronomico di Capodimonte, Napoli (Italy); Pumo, M. L.; Zampieri, L.; Tomasella, L.; Cappellaro, E.; Benetti, S. [INAF, Osservatorio Astronomico di Padova, I-35122 Padova (Italy); Pignata, G.; Bufano, F. [Departamento de Ciencias Fisicas, Universidad Andres Bello, Avda. Republica 252, Santiago (Chile); Bayless, A. J. [Southwest Research Institute, Department of Space Science, 6220 Culebra Road, San Antonio, TX 78238 (United States); Pritchard, T. A. [Department of Astronomy and Astrophysics, Penn State University, 525 Davey Lab, University Park, PA 16802 (United States); Taubenberger, S.; Benitez, S. [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany); Kotak, R.; Inserra, C.; Fraser, M. [Astrophysics Research Centre, School of Mathematics and Physics, Queen' s University Belfast, Belfast, BT7 1NN (United Kingdom); Elias-Rosa, N. [Institut de Ciències de l' Espai (CSIC-IEEC) Campus UAB, Torre C5, Za plata, E-08193 Bellaterra, Barcelona (Spain); Haislip, J. B. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, 120 E. Cameron Ave., Chapel Hill, NC 27599 (United States); Harutyunyan, A. [Fundación Galileo Galilei - Telescopio Nazionale Galileo, Rambla José Ana Fernández Pérez 7, E-38712 Breña Baja, TF - Spain (Spain); and others
2014-06-01
We present an extensive optical and near-infrared photometric and spectroscopic campaign of the Type IIP supernova SN 2012aw. The data set densely covers the evolution of SN 2012aw shortly after the explosion through the end of the photospheric phase, with two additional photometric observations collected during the nebular phase, to fit the radioactive tail and estimate the {sup 56}Ni mass. Also included in our analysis is the previously published Swift UV data, therefore providing a complete view of the ultraviolet-optical-infrared evolution of the photospheric phase. On the basis of our data set, we estimate all the relevant physical parameters of SN 2012aw with our radiation-hydrodynamics code: envelope mass M {sub env} ∼ 20 M {sub ☉}, progenitor radius R ∼ 3 × 10{sup 13} cm (∼430 R {sub ☉}), explosion energy E ∼ 1.5 foe, and initial {sup 56}Ni mass ∼0.06 M {sub ☉}. These mass and radius values are reasonably well supported by independent evolutionary models of the progenitor, and may suggest a progenitor mass higher than the observational limit of 16.5 ± 1.5 M {sub ☉} of the Type IIP events.
Zuñiga, Cristal; Li, Chien-Ting; Huelsman, Tyler; Levering, Jennifer; Zielinski, Daniel C; McConnell, Brian O; Long, Christopher P; Knoshaug, Eric P; Guarnieri, Michael T; Antoniewicz, Maciek R; Betenbaugh, Michael J; Zengler, Karsten
2016-09-01
The green microalga Chlorella vulgaris has been widely recognized as a promising candidate for biofuel production due to its ability to store high lipid content and its natural metabolic versatility. Compartmentalized genome-scale metabolic models constructed from genome sequences enable quantitative insight into the transport and metabolism of compounds within a target organism. These metabolic models have long been utilized to generate optimized design strategies for an improved production process. Here, we describe the reconstruction, validation, and application of a genome-scale metabolic model for C. vulgaris UTEX 395, iCZ843. The reconstruction represents the most comprehensive model for any eukaryotic photosynthetic organism to date, based on the genome size and number of genes in the reconstruction. The highly curated model accurately predicts phenotypes under photoautotrophic, heterotrophic, and mixotrophic conditions. The model was validated against experimental data and lays the foundation for model-driven strain design and medium alteration to improve yield. Calculated flux distributions under different trophic conditions show that a number of key pathways are affected by nitrogen starvation conditions, including central carbon metabolism and amino acid, nucleotide, and pigment biosynthetic pathways. Furthermore, model prediction of growth rates under various medium compositions and subsequent experimental validation showed an increased growth rate with the addition of tryptophan and methionine. PMID:27372244
Directory of Open Access Journals (Sweden)
Younak Choi
Full Text Available Neutrophil to lymphocyte ratio (NLR and standard uptake value (SUV by 18F-FDG PET represent host immunity and tumor metabolic activity, respectively. We investigated NLR and maximum SUV (SUVmax as prognostic markers in metastatic pancreatic cancer (MPC patients who receive palliative chemotherapy.We reviewed 396 MPC patients receiving palliative chemotherapy. NLR was obtained before and after the first cycle of chemotherapy. In 118 patients with PET prior to chemotherapy, SUVmax was collected. Cut-off values were determined by ROC curve.In multivariate analysis of all patients, NLR and change in NLR after the first cycle of chemotherapy (ΔNLR were independent prognostic factors for overall survival (OS. We scored the risk considering NLR and ΔNLR and identified 4 risk groups with different prognosis (risk score 0 vs 1 vs 2 vs 3: OS 9.7 vs 7.9 vs 5.7 vs 2.6 months, HR 1 vs 1.329 vs 2.137 vs 7.915, respectively; P<0.001. In PET cohort, NLR and SUVmax were independently prognostic for OS. Prognostication model using both NLR and SUVmax could define 4 risk groups with different OS (risk score 0 vs 1 vs 2 vs 3: OS 11.8 vs 9.8 vs 7.2 vs 4.6 months, HR 1 vs 1.536 vs 2.958 vs 5.336, respectively; P<0.001.NLR and SUVmax as simple parameters of host immunity and metabolic activity of tumor cell, respectively, are independent prognostic factors for OS in MPC patients undergoing palliative chemotherapy.
Wang, Shiyao; Deng, Zhidong; Yin, Gang
2016-01-01
A high-performance differential global positioning system (GPS) receiver with real time kinematics provides absolute localization for driverless cars. However, it is not only susceptible to multipath effect but also unable to effectively fulfill precise error correction in a wide range of driving areas. This paper proposes an accurate GPS-inertial measurement unit (IMU)/dead reckoning (DR) data fusion method based on a set of predictive models and occupancy grid constraints. First, we employ a set of autoregressive and moving average (ARMA) equations that have different structural parameters to build maximum likelihood models of raw navigation. Second, both grid constraints and spatial consensus checks on all predictive results and current measurements are required to have removal of outliers. Navigation data that satisfy stationary stochastic process are further fused to achieve accurate localization results. Third, the standard deviation of multimodal data fusion can be pre-specified by grid size. Finally, we perform a lot of field tests on a diversity of real urban scenarios. The experimental results demonstrate that the method can significantly smooth small jumps in bias and considerably reduce accumulated position errors due to DR. With low computational complexity, the position accuracy of our method surpasses existing state-of-the-arts on the same dataset and the new data fusion method is practically applied in our driverless car. PMID:26927108
Wang, Shiyao; Deng, Zhidong; Yin, Gang
2016-01-01
A high-performance differential global positioning system (GPS) receiver with real time kinematics provides absolute localization for driverless cars. However, it is not only susceptible to multipath effect but also unable to effectively fulfill precise error correction in a wide range of driving areas. This paper proposes an accurate GPS–inertial measurement unit (IMU)/dead reckoning (DR) data fusion method based on a set of predictive models and occupancy grid constraints. First, we employ a set of autoregressive and moving average (ARMA) equations that have different structural parameters to build maximum likelihood models of raw navigation. Second, both grid constraints and spatial consensus checks on all predictive results and current measurements are required to have removal of outliers. Navigation data that satisfy stationary stochastic process are further fused to achieve accurate localization results. Third, the standard deviation of multimodal data fusion can be pre-specified by grid size. Finally, we perform a lot of field tests on a diversity of real urban scenarios. The experimental results demonstrate that the method can significantly smooth small jumps in bias and considerably reduce accumulated position errors due to DR. With low computational complexity, the position accuracy of our method surpasses existing state-of-the-arts on the same dataset and the new data fusion method is practically applied in our driverless car. PMID:26927108
精确动力学模型下的火星探测轨道设计%Orbit Design for Mars Exploration by the Accurate Dynamic Model
Institute of Scientific and Technical Information of China (English)
陈杨; 赵国强; 宝音贺西; 李俊峰
2011-01-01
The precision orbit design for Mars exploration by the accurate dynamic model was studied. The launch window and trans-Mars orbit was determined through the partical swarm optimization (PSO) algorithm within the heliocentric two-body restriction. The patched conics method was introduced to design the earth-centred parking orbit and departure hyperbolic orbit. The solution of two-body Lambert problem was input as initial value for precision orbit design, and the preliminary orbit was corrected with the restrictions of the Mars B-plane parameters and flight time by the accurate dynamic model. Finally the designed orbit was simulated with the STK softwares.%首先在二体意义下采用粒子群优化算法(PSO)求解Lambert问题,确定发射窗口和二体地火转移轨道.使用圆锥曲线拼接法设计地心停泊轨道、逃逸轨道,并作为轨道精确设计的初值,以建立在火星的B平面参数和地火转移时间为约束,在精确动力学模型下进行微分迭代修正,最终得到满足约束的精确轨道.将设计轨道在STK软件中仿真,结果吻合.
International Nuclear Information System (INIS)
Diabetes is one of the biggest health challenges of the 21st century. The obesity epidemic, sedentary lifestyles and an ageing population mean prevalence of the condition is currently doubling every generation. Diabetes is associated with serious chronic ill health, disability and premature mortality. Long-term complications including heart disease, stroke, blindness, kidney disease and amputations, make the greatest contribution to the costs of diabetes care. Many of these long-term effects could be avoided with earlier, more effective monitoring and treatment. Currently, blood glucose can only be monitored through the use of invasive techniques. To date there is no widely accepted and readily available non-invasive monitoring technique to measure blood glucose despite the many attempts. This paper challenges one of the most difficult non-invasive monitoring techniques, that of blood glucose, and proposes a new novel approach that will enable the accurate, and calibration free estimation of glucose concentration in blood. This approach is based on spectroscopic techniques and a new adaptive modelling scheme. The theoretical implementation and the effectiveness of the adaptive modelling scheme for this application has been described and a detailed mathematical evaluation has been employed to prove that such a scheme has the capability of extracting accurately the concentration of glucose from a complex biological media
Directory of Open Access Journals (Sweden)
Shiyao Wang
2016-02-01
Full Text Available A high-performance differential global positioning system (GPS receiver with real time kinematics provides absolute localization for driverless cars. However, it is not only susceptible to multipath effect but also unable to effectively fulfill precise error correction in a wide range of driving areas. This paper proposes an accurate GPS–inertial measurement unit (IMU/dead reckoning (DR data fusion method based on a set of predictive models and occupancy grid constraints. First, we employ a set of autoregressive and moving average (ARMA equations that have different structural parameters to build maximum likelihood models of raw navigation. Second, both grid constraints and spatial consensus checks on all predictive results and current measurements are required to have removal of outliers. Navigation data that satisfy stationary stochastic process are further fused to achieve accurate localization results. Third, the standard deviation of multimodal data fusion can be pre-specified by grid size. Finally, we perform a lot of field tests on a diversity of real urban scenarios. The experimental results demonstrate that the method can significantly smooth small jumps in bias and considerably reduce accumulated position errors due to DR. With low computational complexity, the position accuracy of our method surpasses existing state-of-the-arts on the same dataset and the new data fusion method is practically applied in our driverless car.
Directory of Open Access Journals (Sweden)
B Zeinali-Rafsanjani
2015-01-01
Full Text Available To accurately recompute dose distributions in chest-wall radiotherapy with 120 kVp kilovoltage X-rays, an MCNP4C Monte Carlo model is presented using a fast method that obviates the need to fully model the tube components. To validate the model, half-value layer (HVL, percentage depth doses (PDDs and beam profiles were measured. Dose measurements were performed for a more complex situation using thermoluminescence dosimeters (TLDs placed within a Rando phantom. The measured and computed first and second HVLs were 3.8, 10.3 mm Al and 3.8, 10.6 mm Al, respectively. The differences between measured and calculated PDDs and beam profiles in water were within 2 mm/2% for all data points. In the Rando phantom, differences for majority of data points were within 2%. The proposed model offered an approximately 9500-fold reduced run time compared to the conventional full simulation. The acceptable agreement, based on international criteria, between the simulations and the measurements validates the accuracy of the model for its use in treatment planning and radiobiological modeling studies of superficial therapies including chest-wall irradiation using kilovoltage beam.
Blaclard, G; Lehe, R; Vay, J L
2016-01-01
With the advent of PW class lasers, the very large laser intensities attainable on-target should enable the production of intense high order Doppler harmonics from relativistic laser-plasma mirrors interactions. At present, the modeling of these harmonics with Particle-In-Cell (PIC) codes is extremely challenging as it implies an accurate description of tens of harmonic orders on a a broad range of angles. In particular, we show here that standard Finite Difference Time Domain (FDTD) Maxwell solvers used in most PIC codes partly fail to model Doppler harmonic generation because they induce numerical dispersion of electromagnetic waves in vacuum which is responsible for a spurious angular deviation of harmonic beams. This effect was extensively studied and a simple toy-model based on Snell-Descartes law was developed that allows us to finely predict the angular deviation of harmonics depending on the spatio-temporal resolution and the Maxwell solver used in the simulations. Our model demonstrates that the miti...
Wlodarczyk, Natalie
2010-01-01
The purpose of this research was to determine the effect of audio and visual modeling on music and nonmusic majors' ability to accurately sing and accompany a familiar melody on guitar by ear. Two studies were run to investigate the impact of musical training on the ability to play by ear. All participants were student volunteers enrolled in sections of a beginning class guitar course and were randomly assigned to one of three groups: control, audio modeling only, or audio and visual modeling. All participants were asked to sing the same familiar song in the same key and accompany on guitar. Study 1 compared music majors with nonmusic majors and showed no significant difference between treatment conditions, however, there was a significant difference between music majors and nonmusic majors across all conditions. There was no significant interaction between groups and treatment conditions. Study 2 investigated the operational definition of "musically trained" and compared musically trained with nonmusically trained participants across the same three conditions. Results of Study 2 showed no significant difference between musically trained and nonmusically trained participants; however, there was a significant difference between treatment conditions with the audio-visual group completing the task in the shortest amount of time. There was no significant interaction between groups and treatment conditions. Results of these analyses support the use of instructor modeling for beginning guitar students and suggest that previous musical knowledge does not play a role in guitar skills acquisition at the beginning level. PMID:21141772
International Nuclear Information System (INIS)
A significant fraction of anthropogenic CO2 emissions is assimilated by tropical forests and stored as biomass, slowing the accumulation of CO2 in the atmosphere. Because different plant tissues have different functional roles and turnover times, predictions of carbon balance of tropical forests depend on how earth system models (ESMs) represent the dynamic allocation of productivity to different tree compartments. This study shows that observed allocation of productivity, biomass, and turnover times of main tree compartments (leaves, wood, and roots) are not accurately represented in Coupled Model Intercomparison Project Phase 5 ESMs. In particular, observations indicate that biomass saturates with increasing productivity. In contrast, most models predict continuous increases in biomass with increases in productivity. This bias may lead to an over-prediction of carbon uptake in response to CO2 or climate-driven changes in productivity. Compartment-specific productivity and biomass are useful benchmarks to assess terrestrial ecosystem model performance. Improvements in the predicted allocation patterns and turnover times by ESMs will reduce uncertainties in climate predictions. (letter)
Institute of Scientific and Technical Information of China (English)
Jin Xuesong; Tsai Hailung
1994-01-01
This paper is a continuation of Ref. [1]. It employs frist-order accurate Taylor-Galerkin-based finite element approach for casting solidification. The approach is based on expressing the finite-difference approximation of the transient time derivative of temperature, while the expressions of the governing equations are discretized in space via the classical Galerkin scheme using finiteelement formulations. The detailed technique is reported in this study. Several casting solidification examples are solved to demonstrate the excellent agreements in comparison with the results obtained by using the control volume method, and to show the availability of combination of the finite element method and the finite difference method in multi-dimensional modeling of casting solidification.
Numerical modeling of surf beat generated by moving breakpoint
Institute of Scientific and Technical Information of China (English)
DONG GuoHai; MA XiaoZhou; TENG Bin
2009-01-01
As an important hydrodynamic phenomenon in the nearshore zone, the cross-shore surf beat is nu-merically studied in this paper with a fully nonlinear Boussinesq-type model, which resolves the pri-mary wave motion as well as the long waves. Compared with the classical Boussinesq equations, the equations adopted here allow for improved linear dispersion characteristics. Wave breaking and run-up in the swash zone are included in the numerical model. Mutual interactions between short waves and long waves are inherent in the model. The numerical study of long waves is based on bichromatic wave groups with a wide range of mean frequencies, group frequencies and modulation rates. The cross-shore variation in the amplitudes of short waves and long waves is investigated. The model results are compared with laboratory experiments from the literature and good agreement is found.
Numerical modeling of surf beat generated by moving breakpoint
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
As an important hydrodynamic phenomenon in the nearshore zone, the cross-shore surf beat is numerically studied in this paper with a fully nonlinear Boussinesq-type model, which resolves the primary wave motion as well as the long waves. Compared with the classical Boussinesq equations, the equations adopted here allow for improved linear dispersion characteristics. Wave breaking and run-up in the swash zone are included in the numerical model. Mutual interactions between short waves and long waves are inherent in the model. The numerical study of long waves is based on bichromatic wave groups with a wide range of mean frequencies, group frequencies and modulation rates. The cross-shore variation in the amplitudes of short waves and long waves is investigated. The model results are compared with laboratory experiments from the literature and good agreement is found.
Alós, Josep; Palmer, Miquel; Balle, Salvador; Arlinghaus, Robert
2016-01-01
State-space models (SSM) are increasingly applied in studies involving biotelemetry-generated positional data because they are able to estimate movement parameters from positions that are unobserved or have been observed with non-negligible observational error. Popular telemetry systems in marine coastal fish consist of arrays of omnidirectional acoustic receivers, which generate a multivariate time-series of detection events across the tracking period. Here we report a novel Bayesian fitting of a SSM application that couples mechanistic movement properties within a home range (a specific case of random walk weighted by an Ornstein-Uhlenbeck process) with a model of observational error typical for data obtained from acoustic receiver arrays. We explored the performance and accuracy of the approach through simulation modelling and extensive sensitivity analyses of the effects of various configurations of movement properties and time-steps among positions. Model results show an accurate and unbiased estimation of the movement parameters, and in most cases the simulated movement parameters were properly retrieved. Only in extreme situations (when fast swimming speeds are combined with pooling the number of detections over long time-steps) the model produced some bias that needs to be accounted for in field applications. Our method was subsequently applied to real acoustic tracking data collected from a small marine coastal fish species, the pearly razorfish, Xyrichtys novacula. The Bayesian SSM we present here constitutes an alternative for those used to the Bayesian way of reasoning. Our Bayesian SSM can be easily adapted and generalized to any species, thereby allowing studies in freely roaming animals on the ecological and evolutionary consequences of home ranges and territory establishment, both in fishes and in other taxa. PMID:27119718
Directory of Open Access Journals (Sweden)
Josep Alós
Full Text Available State-space models (SSM are increasingly applied in studies involving biotelemetry-generated positional data because they are able to estimate movement parameters from positions that are unobserved or have been observed with non-negligible observational error. Popular telemetry systems in marine coastal fish consist of arrays of omnidirectional acoustic receivers, which generate a multivariate time-series of detection events across the tracking period. Here we report a novel Bayesian fitting of a SSM application that couples mechanistic movement properties within a home range (a specific case of random walk weighted by an Ornstein-Uhlenbeck process with a model of observational error typical for data obtained from acoustic receiver arrays. We explored the performance and accuracy of the approach through simulation modelling and extensive sensitivity analyses of the effects of various configurations of movement properties and time-steps among positions. Model results show an accurate and unbiased estimation of the movement parameters, and in most cases the simulated movement parameters were properly retrieved. Only in extreme situations (when fast swimming speeds are combined with pooling the number of detections over long time-steps the model produced some bias that needs to be accounted for in field applications. Our method was subsequently applied to real acoustic tracking data collected from a small marine coastal fish species, the pearly razorfish, Xyrichtys novacula. The Bayesian SSM we present here constitutes an alternative for those used to the Bayesian way of reasoning. Our Bayesian SSM can be easily adapted and generalized to any species, thereby allowing studies in freely roaming animals on the ecological and evolutionary consequences of home ranges and territory establishment, both in fishes and in other taxa.
Alós, Josep; Palmer, Miquel; Balle, Salvador; Arlinghaus, Robert
2016-01-01
State-space models (SSM) are increasingly applied in studies involving biotelemetry-generated positional data because they are able to estimate movement parameters from positions that are unobserved or have been observed with non-negligible observational error. Popular telemetry systems in marine coastal fish consist of arrays of omnidirectional acoustic receivers, which generate a multivariate time-series of detection events across the tracking period. Here we report a novel Bayesian fitting of a SSM application that couples mechanistic movement properties within a home range (a specific case of random walk weighted by an Ornstein-Uhlenbeck process) with a model of observational error typical for data obtained from acoustic receiver arrays. We explored the performance and accuracy of the approach through simulation modelling and extensive sensitivity analyses of the effects of various configurations of movement properties and time-steps among positions. Model results show an accurate and unbiased estimation of the movement parameters, and in most cases the simulated movement parameters were properly retrieved. Only in extreme situations (when fast swimming speeds are combined with pooling the number of detections over long time-steps) the model produced some bias that needs to be accounted for in field applications. Our method was subsequently applied to real acoustic tracking data collected from a small marine coastal fish species, the pearly razorfish, Xyrichtys novacula. The Bayesian SSM we present here constitutes an alternative for those used to the Bayesian way of reasoning. Our Bayesian SSM can be easily adapted and generalized to any species, thereby allowing studies in freely roaming animals on the ecological and evolutionary consequences of home ranges and territory establishment, both in fishes and in other taxa. PMID:27119718
International Nuclear Information System (INIS)
Adsorption of biomolecules and polymers to inorganic nanostructures plays a major role in the design of novel materials and therapeutics. The behavior of flexible molecules on solid surfaces at a scale of 1–1000 nm remains difficult and expensive to monitor using current laboratory techniques, while playing a critical role in energy conversion and composite materials as well as in understanding the origin of diseases. Approaches to implement key surface features and pH in molecular models of solids are explained, and distinct mechanisms of peptide recognition on metal nanostructures, silica and apatite surfaces in solution are described as illustrative examples. The influence of surface energies, specific surface features and protonation states on the structure of aqueous interfaces and selective biomolecular adsorption is found to be critical, comparable to the well-known influence of the charge state and pH of proteins and surfactants on their conformations and assembly. The representation of such details in molecular models according to experimental data and available chemical knowledge enables accurate simulations of unknown complex interfaces in atomic resolution in quantitative agreement with independent experimental measurements. In this context, the benefits of a uniform force field for all material classes and of a mineral surface structure database are discussed. (paper)
Speaking Fluently And Accurately
Institute of Scientific and Technical Information of China (English)
JosephDeVeto
2004-01-01
Even after many years of study,students make frequent mistakes in English. In addition, many students still need a long time to think of what they want to say. For some reason, in spite of all the studying, students are still not quite fluent.When I teach, I use one technique that helps students not only speak more accurately, but also more fluently. That technique is dictations.
Accurate Finite Difference Algorithms
Goodrich, John W.
1996-01-01
Two families of finite difference algorithms for computational aeroacoustics are presented and compared. All of the algorithms are single step explicit methods, they have the same order of accuracy in both space and time, with examples up to eleventh order, and they have multidimensional extensions. One of the algorithm families has spectral like high resolution. Propagation with high order and high resolution algorithms can produce accurate results after O(10(exp 6)) periods of propagation with eight grid points per wavelength.
Zarpalas, Dimitrios; Gkontra, Polyxeni; Daras, Petros; Maglaveras, Nicos
2014-01-01
Assessing the structural integrity of the hippocampus (HC) is an essential step toward prevention, diagnosis, and follow-up of various brain disorders due to the implication of the structural changes of the HC in those disorders. In this respect, the development of automatic segmentation methods that can accurately, reliably, and reproducibly segment the HC has attracted considerable attention over the past decades. This paper presents an innovative 3-D fully automatic method to be used on top of the multiatlas concept for the HC segmentation. The method is based on a subject-specific set of 3-D optimal local maps (OLMs) that locally control the influence of each energy term of a hybrid active contour model (ACM). The complete set of the OLMs for a set of training images is defined simultaneously via an optimization scheme. At the same time, the optimal ACM parameters are also calculated. Therefore, heuristic parameter fine-tuning is not required. Training OLMs are subsequently combined, by applying an extended multiatlas concept, to produce the OLMs that are anatomically more suitable to the test image. The proposed algorithm was tested on three different and publicly available data sets. Its accuracy was compared with that of state-of-the-art methods demonstrating the efficacy and robustness of the proposed method. PMID:27170866
Grillo, C; Rosati, P; Mercurio, A; Balestra, I; Munari, E; Nonino, M; Caminha, G B; Lombardi, M; De Lucia, G; Borgani, S; Gobat, R; Biviano, A; Girardi, M; Umetsu, K; Coe, D; Koekemoer, A M; Postman, M; Zitrin, A; Halkola, A; Broadhurst, T; Sartoris, B; Presotto, V; Annunziatella, M; Maier, C; Fritz, A; Vanzella, E; Frye, B
2014-01-01
We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the CLASH and Frontier Fields galaxy cluster MACS J0416.1-2403. We show and employ our extensive spectroscopic data set taken with the VIMOS instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log(M_*/M_Sun) ~ 8.6. We reproduce the measured positions of 30 multiple images with a remarkable median offset of only 0.3" by means of a comprehensive strong lensing model comprised of 2 cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ~5%, including systematic uncertainties. We emphasize that the use of multip...
Baines, Kevin; Sromovsky, Lawrence A.; Fry, Patrick M.; Carlson, Robert W.; Momary, Thomas W.
2016-10-01
We report results incorporating the red-tinted photochemically-generated aerosols of Carlson et al (2016, Icarus 274, 106-115) in spectral models of Jupiter's Great Red Spot (GRS). Spectral models of the 0.35-1.0-micron spectrum show good agreement with Cassini/VIMS near-center-meridian and near-limb GRS spectra for model morphologies incorporating an optically-thin layer of Carlson (2016) aerosols at high altitudes, either at the top of the tropospheric GRS cloud, or in a distinct stratospheric haze layer. Specifically, a two-layer "crème brûlée" structure of the Mie-scattering Carlson et al (2016) chromophore attached to the top of a conservatively scattering (hereafter, "white") optically-thick cloud fits the spectra well. Currently, best agreement (reduced χ2 of 0.89 for the central-meridian spectrum) is found for a 0.195-0.217-bar, 0.19 ± 0.02 opacity layer of chromophores with mean particle radius of 0.14 ± 0.01 micron. As well, a structure with a detached stratospheric chromophore layer ~0.25 bar above a white tropospheric GRS cloud provides a good spectral match (reduced χ2 of 1.16). Alternatively, a cloud morphology with the chromophore coating white particles in a single optically- and physically-thick cloud (the "coated-shell model", initially explored by Carlson et al 2016) was found to give significantly inferior fits (best reduced χ2 of 2.9). Overall, we find that models accurately fit the GRS spectrum if (1) most of the optical depth of the chromophore is in a layer near the top of the main cloud or in a distinct separated layer above it, but is not uniformly distributed within the main cloud, (2) the chromophore consists of relatively small, 0.1-0.2-micron-radius particles, and (3) the chromophore layer optical depth is small, ~ 0.1-0.2. Thus, our analysis supports the exogenic origin of the red chromophore consistent with the Carlson et al (2016) photolytic production mechanism rather than an endogenic origin, such as upwelling of material
Howdeshell, Kembra L; Rider, Cynthia V; Wilson, Vickie S; Furr, Johnathan R; Lambright, Christy R; Gray, L Earl
2015-12-01
Challenges in cumulative risk assessment of anti-androgenic phthalate mixtures include a lack of data on all the individual phthalates and difficulty determining the biological relevance of reduction in fetal testosterone (T) on postnatal development. The objectives of the current study were 2-fold: (1) to test whether a mixture model of dose addition based on the fetal T production data of individual phthalates would predict the effects of a 5 phthalate mixture on androgen-sensitive postnatal male reproductive tract development, and (2) to determine the biological relevance of the reductions in fetal T to induce abnormal postnatal reproductive tract development using data from the mixture study. We administered a dose range of the mixture (60, 40, 20, 10, and 5% of the top dose used in the previous fetal T production study consisting of 300 mg/kg per chemical of benzyl butyl (BBP), di(n)butyl (DBP), diethyl hexyl phthalate (DEHP), di-isobutyl phthalate (DiBP), and 100 mg dipentyl (DPP) phthalate/kg; the individual phthalates were present in equipotent doses based on their ability to reduce fetal T production) via gavage to Sprague Dawley rat dams on GD8-postnatal day 3. We compared observed mixture responses to predictions of dose addition based on the previously published potencies of the individual phthalates to reduce fetal T production relative to a reference chemical and published postnatal data for the reference chemical (called DAref). In addition, we predicted DA (called DAall) and response addition (RA) based on logistic regression analysis of all 5 individual phthalates when complete data were available. DA ref and DA all accurately predicted the observed mixture effect for 11 of 14 endpoints. Furthermore, reproductive tract malformations were seen in 17-100% of F1 males when fetal T production was reduced by about 25-72%, respectively. PMID:26350170
International Nuclear Information System (INIS)
Background: PET allows non-invasive mapping of tumor hypoxia, but the combination of low resolution, slow tracer adduct-formation and slow clearance of unbound tracer remains problematic. Using a murine tumor with a hypoxic fraction within the clinical range and a tracer post-injection sampling time that results in clinically obtainable tumor-to-reference tissue activity ratios, we have analyzed to what extent inherent limitations actually compromise the validity of PET-generated hypoxia maps. Materials and methods: Mice bearing SCCVII tumors were injected with the PET hypoxia-marker fluoroazomycin arabinoside (FAZA), and the immunologically detectable hypoxia marker, pimonidazole. Tumors and reference tissue (muscle, blood) were harvested 0.5, 2 and 4 h after FAZA administration. Tumors were analyzed for global (well counter) and regional (autoradiography) tracer distribution and compared to pimonidazole as visualized using immunofluorescence microscopy. Results: Hypoxic fraction as measured by pimonidazole staining ranged from 0.09 to 0.32. FAZA tumor to reference tissue ratios were close to unity 0.5 h post-injection but reached values of 2 and 6 when tracer distribution time was prolonged to 2 and 4 h, respectively. A fine-scale pixel-by-pixel comparison of autoradiograms and immunofluorescence images revealed a clear spatial link between FAZA and pimonidazole-adduct signal intensities at 2 h and later. Furthermore, when using a pixel size that mimics the resolution in PET, an excellent correlation between pixel FAZA mean intensity and density of hypoxic cells was observed already at 2 h post-injection. Conclusions: Despite inherent weaknesses, PET-hypoxia imaging is able to generate quantitative tumor maps that accurately reflect the underlying microscopic reality (i.e., hypoxic cell density) in an animal model with a clinical realistic image contrast.
Energy Technology Data Exchange (ETDEWEB)
Grillo, C. [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Suyu, S. H.; Umetsu, K. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China); Rosati, P.; Caminha, G. B. [Dipartimento di Fisica e Scienze della Terra, Università degli Studi di Ferrara, Via Saragat 1, I-44122 Ferrara (Italy); Mercurio, A. [INAF - Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131 Napoli (Italy); Balestra, I.; Munari, E.; Nonino, M.; De Lucia, G.; Borgani, S.; Biviano, A.; Girardi, M. [INAF - Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, I-34143, Trieste (Italy); Lombardi, M. [Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, I-20133 Milano (Italy); Gobat, R. [Laboratoire AIM-Paris-Saclay, CEA/DSM-CNRS-Universitè Paris Diderot, Irfu/Service d' Astrophysique, CEA Saclay, Orme des Merisiers, F-91191 Gif sur Yvette (France); Coe, D.; Koekemoer, A. M.; Postman, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21208 (United States); Zitrin, A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, MS 249-17, Pasadena, CA 91125 (United States); Halkola, A., E-mail: grillo@dark-cosmology.dk; and others
2015-02-10
We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy cluster MACS J0416.1–2403. We show and employ our extensive spectroscopic data set taken with the VIsible Multi-Object Spectrograph instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log (M {sub *}/M {sub ☉}) ≅ 8.6. We reproduce the measured positions of a set of 30 multiple images with a remarkable median offset of only 0.''3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ∼5%, including the systematic uncertainties estimated from six distinct mass models. We emphasize that the use of multiple-image systems with spectroscopic redshifts and knowledge of cluster membership based on extensive spectroscopic information is key to constructing robust high-resolution mass maps. We also produce magnification maps over the central area that is covered with HST observations. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. When compared with the outcomes of cosmological N-body simulations, our results point to a lack of massive subhalos in the inner regions of simulated clusters with total masses similar to that of MACS J0416.1–2403. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide
A study of a hamiltonian model for martensitic phase transformations including microkinetic energy
Theil, F
1998-01-01
How can a system in a macroscopically stable state explore energetically more favorable states, which are far away from the current equilibrium state? Based on continuum mechanical considerations we derive a Boussinesq-type equation which models the dynamics of martensitic phase transformations. The solutions of the system, which we refer to as microkinetically regularized wave equation exhibit strong oscillations after short times, thermalization can be confirmed. That means that macroscopic fluctuations of the solutions decay at the benefit of microscopic fluctuations. First analytical and numerical results on the propagation of phase boundaries and thermalization effects are presented. Despite the fact that model is conservative, it exhibits the hysteretic behavior. Such a behavior is usually interpreted in macroscopic models in terms of dissipative threshold which the driving force has to overcome to ensure that the phase transformation proceeds. The threshold value depends on the amount of the transforme...
International Nuclear Information System (INIS)
Investigation has been made to discuss how the accurate scientific information affects the perception of risk. To verify this investigation, dialogue seminars have been held. Based upon the outcomes of these investigations, the analysis of attribution was done to verify the factors affecting the risk perception and acceptance relevant to the consensus-building for HLW geological disposal site determination. (author)
ZARPALAS, Dimitrios; Gkontra, Polyxeni; Daras, Petros; Maglaveras, Nicos
2014-01-01
Assessing the structural integrity of the hippocampus (HC) is an essential step toward prevention, diagnosis, and follow-up of various brain disorders due to the implication of the structural changes of the HC in those disorders. In this respect, the development of automatic segmentation methods that can accurately, reliably, and reproducibly segment the HC has attracted considerable attention over the past decades. This paper presents an innovative 3-D fully automatic method to be used on to...
Accurate tracking control in LOM application
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
The fabrication of accurate prototype from CAD model directly in short time depends on the accurate tracking control and reference trajectory planning in (Laminated Object Manufacture) LOM application. An improvement on contour accuracy is acquired by the introduction of a tracking controller and a trajectory generation policy. A model of the X-Y positioning system of LOM machine is developed as the design basis of tracking controller. The ZPETC (Zero Phase Error Tracking Controller) is used to eliminate single axis following error, thus reduce the contour error. The simulation is developed on a Maltab model based on a retrofitted LOM machine and the satisfied result is acquired.
Energy Technology Data Exchange (ETDEWEB)
Mezey, P.G.; Zimpel, Z.; Warburton, P.; Walker, P.D.; Irvine, D.G. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada); Huang, X.D.; Dixon, D.G.; Greenberg, B.M. [Univ. of Waterloo, Ontario (Canada). Dept. of Biology
1998-07-01
The quantitative shape-activity relationship (QShAR) methodology, based on accurate three-dimensional electron densities and detailed shape analysis methods, has been applied to a Lemna gibba photoinduced toxicity data set of 16 polycyclic aromatic hydrocarbon (PAH) molecules. In the first phase of the studies, a shape fragment QShAR database of PAHs was developed. The results provide a very good match to toxicity based on a combination of the local shape features of single rings in comparison to the central ring of anthracene and a more global shape feature involving larger molecular fragments. The local shape feature appears as a descriptor of the susceptibility of PAHs to photomodification and the global shape feature is probably related to photosensitization activity.
Efficient Accurate Context-Sensitive Anomaly Detection
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
For program behavior-based anomaly detection, the only way to ensure accurate monitoring is to construct an efficient and precise program behavior model. A new program behavior-based anomaly detection model,called combined pushdown automaton (CPDA) model was proposed, which is based on static binary executable analysis. The CPDA model incorporates the optimized call stack walk and code instrumentation technique to gain complete context information. Thereby the proposed method can detect more attacks, while retaining good performance.
Wang, Yong; Goh, Wang Ling; Chai, Kevin T.-C.; Mu, Xiaojing; Hong, Yan; Kropelnicki, Piotr; Je, Minkyu
2016-04-01
The parasitic effects from electromechanical resonance, coupling, and substrate losses were collected to derive a new two-port equivalent-circuit model for Lamb wave resonators, especially for those fabricated on silicon technology. The proposed model is a hybrid π-type Butterworth-Van Dyke (PiBVD) model that accounts for the above mentioned parasitic effects which are commonly observed in Lamb-wave resonators. It is a combination of interdigital capacitor of both plate capacitance and fringe capacitance, interdigital resistance, Ohmic losses in substrate, and the acoustic motional behavior of typical Modified Butterworth-Van Dyke (MBVD) model. In the case studies presented in this paper using two-port Y-parameters, the PiBVD model fitted significantly better than the typical MBVD model, strengthening the capability on characterizing both magnitude and phase of either Y11 or Y21. The accurate modelling on two-port Y-parameters makes the PiBVD model beneficial in the characterization of Lamb-wave resonators, providing accurate simulation to Lamb-wave resonators and oscillators.
McMillan, K; Bostani, M; McCollough, C; McNitt-Gray, M
2015-01-01
PURPOSE: Most patient models used in Monte Carlo-based estimates of CT dose, including computational phantoms, do not have tube current modulation (TCM) data associated with them. While not a problem for fixed tube current simulations, this is a limitation when modeling the effects of TCM. Therefore, the purpose of this work was to develop and validate methods to estimate TCM schemes for any voxelized patient model. METHODS: For 10 patients who received clinically-indicated chest (n=5) and ab...
Marvin, Esra
2013-01-01
The purpose of this thesis was to calibrate a combined glass electrode to obtain accurate pH measurements in high ionic strength brines. pH measurements in high ionic strength brines are susceptible to significant errors when measured with standard calibrated electrodes. The work done in this thesis was part of a larger project carried out at the Israel Institute of Technology, where a new single pass boron removal process is being developed and modeled. The goal for the calibration was...
Directory of Open Access Journals (Sweden)
Hitinder S Gurm
Full Text Available BACKGROUND: Transfusion is a common complication of Percutaneous Coronary Intervention (PCI and is associated with adverse short and long term outcomes. There is no risk model for identifying patients most likely to receive transfusion after PCI. The objective of our study was to develop and validate a tool for predicting receipt of blood transfusion in patients undergoing contemporary PCI. METHODS: Random forest models were developed utilizing 45 pre-procedural clinical and laboratory variables to estimate the receipt of transfusion in patients undergoing PCI. The most influential variables were selected for inclusion in an abbreviated model. Model performance estimating transfusion was evaluated in an independent validation dataset using area under the ROC curve (AUC, with net reclassification improvement (NRI used to compare full and reduced model prediction after grouping in low, intermediate, and high risk categories. The impact of procedural anticoagulation on observed versus predicted transfusion rates were assessed for the different risk categories. RESULTS: Our study cohort was comprised of 103,294 PCI procedures performed at 46 hospitals between July 2009 through December 2012 in Michigan of which 72,328 (70% were randomly selected for training the models, and 30,966 (30% for validation. The models demonstrated excellent calibration and discrimination (AUC: full model = 0.888 (95% CI 0.877-0.899, reduced model AUC = 0.880 (95% CI, 0.868-0.892, p for difference 0.003, NRI = 2.77%, p = 0.007. Procedural anticoagulation and radial access significantly influenced transfusion rates in the intermediate and high risk patients but no clinically relevant impact was noted in low risk patients, who made up 70% of the total cohort. CONCLUSIONS: The risk of transfusion among patients undergoing PCI can be reliably calculated using a novel easy to use computational tool (https://bmc2.org/calculators/transfusion. This risk prediction
Energy Technology Data Exchange (ETDEWEB)
Zechner, Christoph [Synopsys Switzerland LLC., Affolternstr. 52, CH-8050 Zurich-Oerlikon (Switzerland)]. E-mail: zechner@synopsys.com; Zographos, Nikolas [Synopsys Switzerland LLC., Affolternstr. 52, CH-8050 Zurich-Oerlikon (Switzerland); Matveev, Dmitri [Synopsys Switzerland LLC., Affolternstr. 52, CH-8050 Zurich-Oerlikon (Switzerland); Erlebach, Axel [Synopsys Switzerland LLC., Affolternstr. 52, CH-8050 Zurich-Oerlikon (Switzerland)
2005-12-05
In recent years, physics-based models have been developed for the time evolution of defects formed by Si self-interstitials in ion-implanted Si. The accuracy of these models is crucial for a predictive process simulation of deep sub micron devices. However, the most complete models are usually not considered in applied process simulation, because they use too many equations. In this work, a new model is presented in which the essential physics behind the formation and dissolution of small interstitial clusters and {l_brace}3 1 1{r_brace} defects is described by a minimum set of five reaction equations. Three equations describe the kinetics of small interstitial clusters which governs the initial phase of implantation damage annealing. Two equations describe the formation and Ostwald ripening of {l_brace}3 1 1{r_brace} defects. The model is capable to reproduce experimental data over a wide range of implantation energies, doses and anneal temperatures. It allows predictive simulations of interstitial cluster kinetics at a minimum computational cost.
Directory of Open Access Journals (Sweden)
Sakaros Bogning Dongue
2013-01-01
Full Text Available This paper presents the modelling of electrical I-V response of illuminated photovoltaic crystalline modules. As an alternative method to the linear five-parameter model, our strategy uses advantages of a nonlinear analytical five-point model to take into account the effects of nonlinear variations of current with respect to solar irradiance and of voltage with respect to cells temperature. We succeeded in this work to predict with great accuracy the I-V characteristics of monocrystalline shell SP75 and polycrystalline GESOLAR GE-P70 photovoltaic modules. The good comparison of our calculated results to experimental data provided by the modules manufacturers makes it possible to appreciate the contribution of taking into account the nonlinear effect of operating conditions data on I-V characteristics of photovoltaic modules.
Directory of Open Access Journals (Sweden)
Zheng Wei
2016-05-01
Full Text Available Firstly, the new single and combined error models applied to estimate the cumulative geoid height error are efficiently produced by the dominating error sources consisting of the gravity gradient of the satellite-equipped gradiometer and the orbital position of the space-borne GPS/GLONASS receiver using the power spectral principle. At degree 250, the cumulative geoid height error is 1.769 × 10–1 m based on the new combined error model, which preferably accords with a recovery accuracy of 1.760 × 10–1 m from the GOCE-only Earth gravity field model GO_CONS_GCF_2_TIM_R2 released in Germany. Therefore, the new combined error model of the cumulative geoid height is correct and reliable in this study. Secondly, the requirements analysis for the future GOCE Follow-On satellite system is carried out in respect of the preferred design of the matching measurement accuracy of key payloads comprising the gravity gradient and orbital position and the optimal selection of the orbital altitude of the satellite. We recommend the gravity gradient with an accuracy of 10–13-10–15/s2, the orbital position with a precision of 1-0.1 cm and the orbital altitude of 200-250 km in the future GOCE Follow-On mission.
Okeme, Joseph O; Parnis, J Mark; Poole, Justen; Diamond, Miriam L; Jantunen, Liisa M
2016-08-01
Polydimethylsiloxane (PDMS) shows promise for use as a passive air sampler (PAS) for semi-volatile organic compounds (SVOCs). To use PDMS as a PAS, knowledge of its chemical-specific partitioning behaviour and time to equilibrium is needed. Here we report on the effectiveness of two approaches for estimating the partitioning properties of polydimethylsiloxane (PDMS), values of PDMS-to-air partition ratios or coefficients (KPDMS-Air), and time to equilibrium of a range of SVOCs. Measured values of KPDMS-Air, Exp' at 25 °C obtained using the gas chromatography retention method (GC-RT) were compared with estimates from a poly-parameter free energy relationship (pp-FLER) and a COSMO-RS oligomer-based model. Target SVOCs included novel flame retardants (NFRs), polybrominated diphenyl ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), organophosphate flame retardants (OPFRs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). Significant positive relationships were found between log KPDMS-Air, Exp' and estimates made using the pp-FLER model (log KPDMS-Air, pp-LFER) and the COSMOtherm program (log KPDMS-Air, COSMOtherm). The discrepancy and bias between measured and predicted values were much higher for COSMO-RS than the pp-LFER model, indicating the anticipated better performance of the pp-LFER model than COSMO-RS. Calculations made using measured KPDMS-Air, Exp' values show that a PDMS PAS of 0.1 cm thickness will reach 25% of its equilibrium capacity in ∼1 day for alpha-hexachlorocyclohexane (α-HCH) to ∼ 500 years for tris (4-tert-butylphenyl) phosphate (TTBPP), which brackets the volatility range of all compounds tested. The results presented show the utility of GC-RT method for rapid and precise measurements of KPDMS-Air. PMID:27179237
Lagi, Marco; Bar-Yam, Yavni; Bertrand, Karla Z; Bar-Yam, Yaneer
2015-11-10
Recent increases in basic food prices are severely affecting vulnerable populations worldwide. Proposed causes such as shortages of grain due to adverse weather, increasing meat consumption in China and India, conversion of corn to ethanol in the United States, and investor speculation on commodity markets lead to widely differing implications for policy. A lack of clarity about which factors are responsible reinforces policy inaction. Here, for the first time to our knowledge, we construct a dynamic model that quantitatively agrees with food prices. The results show that the dominant causes of price increases are investor speculation and ethanol conversion. Models that just treat supply and demand are not consistent with the actual price dynamics. The two sharp peaks in 2007/2008 and 2010/2011 are specifically due to investor speculation, whereas an underlying upward trend is due to increasing demand from ethanol conversion. The model includes investor trend following as well as shifting between commodities, equities, and bonds to take advantage of increased expected returns. Claims that speculators cannot influence grain prices are shown to be invalid by direct analysis of price-setting practices of granaries. Both causes of price increase, speculative investment and ethanol conversion, are promoted by recent regulatory changes-deregulation of the commodity markets, and policies promoting the conversion of corn to ethanol. Rapid action is needed to reduce the impacts of the price increases on global hunger. PMID:26504216
Directory of Open Access Journals (Sweden)
Julia Lambret-Frotté
Full Text Available Employing reference genes to normalize the data generated with quantitative PCR (qPCR can increase the accuracy and reliability of this method. Previous results have shown that no single housekeeping gene can be universally applied to all experiments. Thus, the identification of a suitable reference gene represents a critical step of any qPCR analysis. Setaria viridis has recently been proposed as a model system for the study of Panicoid grasses, a crop family of major agronomic importance. Therefore, this paper aims to identify suitable S. viridis reference genes that can enhance the analysis of gene expression in this novel model plant. The first aim of this study was the identification of a suitable RNA extraction method that could retrieve a high quality and yield of RNA. After this, two distinct algorithms were used to assess the gene expression of fifteen different candidate genes in eighteen different samples, which were divided into two major datasets, the developmental and the leaf gradient. The best-ranked pair of reference genes from the developmental dataset included genes that encoded a phosphoglucomutase and a folylpolyglutamate synthase; genes that encoded a cullin and the same phosphoglucomutase as above were the most stable genes in the leaf gradient dataset. Additionally, the expression pattern of two target genes, a SvAP3/PI MADS-box transcription factor and the carbon-fixation enzyme PEPC, were assessed to illustrate the reliability of the chosen reference genes. This study has shown that novel reference genes may perform better than traditional housekeeping genes, a phenomenon which has been previously reported. These results illustrate the importance of carefully validating reference gene candidates for each experimental set before employing them as universal standards. Additionally, the robustness of the expression of the target genes may increase the utility of S. viridis as a model for Panicoid grasses.
Chuang, Chia-Hsun; Rodríguez-Torres, Sergio; Ross, Ashley J; Zhao, Gong-bo; Wang, Yuting; Cuesta, Antonio J; Rubiño-Martín, J A; Prada, Francisco; Alam, Shadab; Beutler, Florian; Eisenstein, Daniel J; Gil-Marín, Héctor; Grieb, Jan Niklas; Ho, Shirley; Kitaura, Francisco-Shu; Percival, Will J; Rossi, Graziano; Salazar-Albornoz, Salvador; Samushia, Lado; Sánchez, Ariel G; Satpathy, Siddharth; Slosar, Anže; Tinker, Jeremy L; Tojeiro, Rita; Vargas-Magaña, Mariana; Vazquez, Jose A; Brownstein, Joel R; Nichol, Robert C; Olmstead, Matthew D
2016-01-01
We analyse the broad-range shape of the monopole and quadrupole correlation functions of the BOSS Data Release 12 (DR12) CMASS and LOWZ galaxy sample to obtain constraints on the Hubble expansion rate $H(z)$, the angular-diameter distance $D_A(z)$, the normalised growth rate $f(z)\\sigma_8(z)$, and the physical matter density $\\Omega_mh^2$. We adopt wide and flat priors on all model parameters in order to ensure the results are those of a `single-probe' galaxy clustering analysis. We also marginalise over three nuisance terms that account for potential observational systematics affecting the measured monopole. However, such Monte Carlo Markov Chain analysis is computationally expensive for advanced theoretical models, thus we develop a new methodology to speed up our analysis. We obtain $\\{D_A(z)r_{s,fid}/r_s$Mpc, $H(z)r_s/r_{s,fid}$kms$^{-1}$Mpc$^{-1}$, $f(z)\\sigma_8(z)$, $\\Omega_m h^2\\}$ = $\\{956\\pm28$ , $75.0\\pm4.0$ , $0.397 \\pm 0.073$, $0.143\\pm0.017\\}$ at $z=0.32$ and $\\{1421\\pm23$, $96.7\\pm2.7$ , $0.497 ...
Rosati, Dora P.; Molina, Chai; Earn, David J. D.
2015-12-01
Human behaviour and disease dynamics can greatly influence each other. In particular, people often engage in self-protective behaviours that affect epidemic patterns (e.g., vaccination, use of barrier precautions, isolation, etc.). Self-protective measures usually have a mitigating effect on an epidemic [16], but can in principle have negative impacts at the population level [12,15,18]. The structure of underlying social and biological contact networks can significantly influence the specific ways in which population-level effects are manifested. Using a different contact network in a disease dynamics model-keeping all else equal-can yield very different epidemic patterns. For example, it has been shown that when individuals imitate their neighbours' vaccination decisions with some probability, this can lead to herd immunity in some networks [9], yet for other networks it can preserve clusters of susceptible individuals that can drive further outbreaks of infectious disease [12].
Ishikawa, Atsushi; Nakatsuji, Hiroshi
2013-08-01
O1s core-electron binding energies (CEBE) of the atomic oxygens on different Ag surfaces were investigated by the symmetry adapted cluster-configuration interaction (SAC-CI) method combined with the dipped adcluster model, in which the electron exchange between bulk metal and adsorbate is taken into account properly. Electrophilic and nucleophilic oxygens (O(elec) and O(nuc)) that might be important for olefin epoxidation in a low-oxygen coverage condition were focused here. We consider the O1s CEBE as a key property to distinguish the surface oxygen states, and series of calculation was carried out by the Hartree-Fock, Density functional theory, and SAC/SAC-CI methods. The experimental information and our SAC/SAC-CI results indicate that O(elec) is the atomic oxygen adsorbed on the fcc site of Ag(111) and that O(nuc) is the one on the reconstructed added-row site of Ag(110) and that one- and two-electron transfers occur, respectively, to the O(elec) and O(nuc) adclusters from the silver surface.
Fernández-Colino, A; Bermudez, J M; Arias, F J; Quinteros, D; Gonzo, E
2016-04-01
Transversality between mathematical modeling, pharmacology, and materials science is essential in order to achieve controlled-release systems with advanced properties. In this regard, the area of biomaterials provides a platform for the development of depots that are able to achieve controlled release of a drug, whereas pharmacology strives to find new therapeutic molecules and mathematical models have a connecting function, providing a rational understanding by modeling the parameters that influence the release observed. Herein we present a mechanism which, based on reasonable assumptions, explains the experimental data obtained very well. In addition, we have developed a simple and accurate “lumped” kinetics model to correctly fit the experimentally observed drug-release behavior. This lumped model allows us to have simple analytic solutions for the mass and rate of drug release as a function of time without limitations of time or mass of drug released, which represents an important step-forward in the area of in vitro drug delivery when compared to the current state of the art in mathematical modeling. As an example, we applied the mechanism and model to the release data for acetazolamide from a recombinant polymer. Both materials were selected because of a need to develop a suitable ophthalmic formulation for the treatment of glaucoma. The in vitro release model proposed herein provides a valuable predictive tool for ensuring product performance and batch-to-batch reproducibility, thus paving the way for the development of further pharmaceutical devices. PMID:26838852
Energy Technology Data Exchange (ETDEWEB)
May, M; Beiersdorfer, P; Dunn, J; Jordan, N; Osterheld, A; Faenov, A; Pikuz, T; Skobelev, I; Fora, F; Bollanti, S; Lazzaro, P D; Murra, D; Reale, A; Reale, L; Tomassetti, G; Ritucci, A; Francucci, M; Martellucci, S; Petrocelli, G
2004-09-28
Iron spectra have been recorded from plasmas created at three different laser plasma facilities, the Tor Vergata University laser in Rome (Italy), the Hercules laser at ENEA in Frascati (Italy), and the Compact Multipulse Terawatt (COMET) laser at LLNL in California (USA). The measurements provide a means of identifying dielectronic satellite lines from FeXVI and FeXV in the vicinity of the strong 2p {yields} 3d transitions of FeXVII. About 80 {Delta}n {ge} 1 lines of FeXV (Mg-like) to FeXIX (O-like) were recorded between 13.8 to 17.1 {angstrom} with a high spectral resolution ({lambda}/{Delta}{lambda} {approx} 4000), about thirty of these lines are from FeXVI and FeXV. The laser produced plasmas had electron temperatures between 100 to 500 eV and electron densities between 10{sup 20} to 10{sup 22} cm{sup -3}. The Hebrew University Lawrence Livermore Atomic Code (HULLAC) was used to calculate the atomic structure and atomic rates for FeXV to FeXIX. HULLAC was used to calculate synthetic line intensities at T{sub e} = 200 eV and n{sub e} = 10{sup 21}cm{sup -3} for three different conditions to illustrate the role of opacity: optically thin plasmas with no excitation-autoionization/dielectronic recombination (EA/DR) contributions to the line intensities, optically thin plasmas that included EA/DR contributions to the line intensities, and optically thick plasmas (optical depth {approx} 200 {micro}m) that included EA/DR contributions to the line intensities. The optically thick simulation best reproduced the recorded spectrum from the Hercules laser. However some discrepancies between the modeling and the recorded spectra remain.
Towards accurate emergency response behavior
International Nuclear Information System (INIS)
Nuclear reactor operator emergency response behavior has persisted as a training problem through lack of information. The industry needs an accurate definition of operator behavior in adverse stress conditions, and training methods which will produce the desired behavior. Newly assembled information from fifty years of research into human behavior in both high and low stress provides a more accurate definition of appropriate operator response, and supports training methods which will produce the needed control room behavior. The research indicates that operator response in emergencies is divided into two modes, conditioned behavior and knowledge based behavior. Methods which assure accurate conditioned behavior, and provide for the recovery of knowledge based behavior, are described in detail
Institute of Scientific and Technical Information of China (English)
周建永
2014-01-01
In traditional estimating method, the linear method was used and the budget estimating result was poor. An accu-rately model of project estimated budget based on SVM-PCA and chaos post processing was proposed, In the SVM model, the PCA method was used for clear and filter the number of redundant information, to ensure the contribution of the input information data, the data was output to the post-processing model, and with the chaos mixed characteristics of the data smoothing, the accuracy model of systems engineering estimated budget was achieved. Finally a team of 5 projects with 10 elements were taken as target to do experiment, the result shows that with the accurately model of project estimated budget based on SVM-PCA and chaos post processing, each engineering accurate estimates of consumption estimated core out, it has good application value.%传统的估计模型采用线性方法，预算估计结果差。提出一种基于混沌后处理的SVM-PCA精确工程预算估计模型。在SVM模型的基础上，采用PCA方法，对输入系统的一些冗余信息进行清除过滤，保证输入信息数据的贡献率，数据输出后，采用混沌后处理的方法对数据参差特性进行平滑处理，保证系统工程预算估计模型的精确性。最后采用一组10大类元素的5个工程进行预算估计实验，结果显示，采用基于混沌后处理的SVM-PCA精确工程预算估计模型后，每个工程中的核心消耗均被精确的估计出来，具有很好的工程应用价值。
An Accurate Macro Model of Organic Light Emitting Diode for Circuit Simulation%一种有机发光二极管的电路仿真宏模型
Institute of Scientific and Technical Information of China (English)
王颖
2011-01-01
文章介绍了一种有机发光二极管的电路仿真宏模型及其元件参数数值的提取方法。该电路仿真宏模型不但表征了有机发光二极管的全固态多层结构,而且表征有机发光二极管发光的物理过程。同时还提出了采用交流阻抗法提取该有机发光二极管电路仿真宏模型的元件参数的方法。该有机发光二极管的电路仿真宏模型可用于有源二极管显示器的背板电路设计过程中,背板电路与有机发光二极管器件的联合电路功能仿真,从而实现更准确的背板电路性能评估。%In this paper,an accurate macro mode of organic light emitting diode（OLED） is proposed and the model parameter extraction is implemented for active matrix OLED（AMOLED） display panel design.This macro model of OLED presents the solid multi-layer structure of OLED device,as well as the physical mechanism of OLED light procedure.AC impedance method is used to extract the elements parameter of this macro model.This macro model of OLED device is used for AMOLED display panel design in order to evaluate the performance of panel circuit accurately.
Accurate modelling of UV written waveguide components
DEFF Research Database (Denmark)
Svalgaard, Mikael
BPM simulation results of UV written waveguide components that are indistinguishable from measurements can be achieved on the basis of trajectory scan data and an equivalent step index profile that is very easy to measure.......BPM simulation results of UV written waveguide components that are indistinguishable from measurements can be achieved on the basis of trajectory scan data and an equivalent step index profile that is very easy to measure....
Accurate modeling of UV written waveguide components
DEFF Research Database (Denmark)
Svalgaard, Mikael
BPM simulation results of UV written waveguide components that are indistinguishable from measurements can be achieved on the basis of trajectory scan data and an equivalent step index profile that is very easy to measure.......BPM simulation results of UV written waveguide components that are indistinguishable from measurements can be achieved on the basis of trajectory scan data and an equivalent step index profile that is very easy to measure....
Efficient and accurate modelling of quantum nanostructures
Ayad, Marina; Obayya, Salah S. A.; Swillam, Mohamed A.
2016-03-01
An efficient sensitivity analysis approach for quantum nanostructures is proposed. The imaginary time propagation method (ITP) is utilized to solve the Time Dependent Schrödinger's Equation (TDSE). Using this method, an extraction of all the modes and their sensitivity with respect to all the design parameters have been performed with minimal computational effort. The sensitivity analysis is performed using the Adjoint Variable Method (AVM) and results are comparable to those obtained using Central Finite Difference Method (CFD) applied directly on the response level.
Accurate atomic data for industrial plasma applications
Energy Technology Data Exchange (ETDEWEB)
Griesmann, U.; Bridges, J.M.; Roberts, J.R.; Wiese, W.L.; Fuhr, J.R. [National Inst. of Standards and Technology, Gaithersburg, MD (United States)
1997-12-31
Reliable branching fraction, transition probability and transition wavelength data for radiative dipole transitions of atoms and ions in plasma are important in many industrial applications. Optical plasma diagnostics and modeling of the radiation transport in electrical discharge plasmas (e.g. in electrical lighting) depend on accurate basic atomic data. NIST has an ongoing experimental research program to provide accurate atomic data for radiative transitions. The new NIST UV-vis-IR high resolution Fourier transform spectrometer has become an excellent tool for accurate and efficient measurements of numerous transition wavelengths and branching fractions in a wide wavelength range. Recently, the authors have also begun to employ photon counting techniques for very accurate measurements of branching fractions of weaker spectral lines with the intent to improve the overall accuracy for experimental branching fractions to better than 5%. They have now completed their studies of transition probabilities of Ne I and Ne II. The results agree well with recent calculations and for the first time provide reliable transition probabilities for many weak intercombination lines.
Arockia Bazil Raj, A.; Padmavathi, S.
2016-07-01
Atmospheric parameters strongly affect the performance of Free Space Optical Communication (FSOC) system when the optical wave is propagating through the inhomogeneous turbulent medium. Developing a model to get an accurate prediction of optical attenuation according to meteorological parameters becomes significant to understand the behaviour of FSOC channel during different seasons. A dedicated free space optical link experimental set-up is developed for the range of 0.5 km at an altitude of 15.25 m. The diurnal profile of received power and corresponding meteorological parameters are continuously measured using the developed optoelectronic assembly and weather station, respectively, and stored in a data logging computer. Measured meteorological parameters (as input factors) and optical attenuation (as response factor) of size [177147 × 4] are used for linear regression analysis and to design the mathematical model that is more suitable to predict the atmospheric optical attenuation at our test field. A model that exhibits the R2 value of 98.76% and average percentage deviation of 1.59% is considered for practical implementation. The prediction accuracy of the proposed model is investigated along with the comparative results obtained from some of the existing models in terms of Root Mean Square Error (RMSE) during different local seasons in one-year period. The average RMSE value of 0.043-dB/km is obtained in the longer range dynamic of meteorological parameters variations.
Profitable capitation requires accurate costing.
West, D A; Hicks, L L; Balas, E A; West, T D
1996-01-01
In the name of costing accuracy, nurses are asked to track inventory use on per treatment basis when more significant costs, such as general overhead and nursing salaries, are usually allocated to patients or treatments on an average cost basis. Accurate treatment costing and financial viability require analysis of all resources actually consumed in treatment delivery, including nursing services and inventory. More precise costing information enables more profitable decisions as is demonstrated by comparing the ratio-of-cost-to-treatment method (aggregate costing) with alternative activity-based costing methods (ABC). Nurses must participate in this costing process to assure that capitation bids are based upon accurate costs rather than simple averages. PMID:8788799
Institute of Scientific and Technical Information of China (English)
左文全; 吕艳博; 付向东; 潘伟; 朱熀秋
2012-01-01
Bearingless slice motors（BSM） have a wide application prospect as the special structure of its slice rotor.It is the focus in getting accurate mathematical model of radial suspension force to levitate the rotor stably by directly and effectively controlling rotor eccentric displacement.Firstly,air-gap flux density distributions of BSM are analyzed in detail.Then,an accurate mathematical model of radial suspension force is deduced by using the Maxwell stress tensor method,and it is verified by the finite element method（FEM）.Results both by the radial suspension force mathematical model of BSM and by FEM are consistent.%无轴承永磁薄片电机具有薄片转子的特殊结构,为了采取有效方法控制转子偏心位移、使转子稳定悬浮,研究的关键在于获得无轴承永磁薄片电机精确的径向悬浮力数学模型。在介绍无轴承永磁薄片电机的结构和工作原理基础上,对无轴承永磁薄片电机气隙磁场进行了详细分析,基于麦克斯韦应力张量法推导了其径向悬浮力数学模型,最后对比验证了利用有限元方法的计算结果和样机实验对数学模型的理论计算结果。验证结果表明,该方法建立的径向悬浮力数学模型误差小、精确度髙。
Accurate phase-shift velocimetry in rock
Shukla, Matsyendra Nath; Vallatos, Antoine; Phoenix, Vernon R.; Holmes, William M.
2016-06-01
Spatially resolved Pulsed Field Gradient (PFG) velocimetry techniques can provide precious information concerning flow through opaque systems, including rocks. This velocimetry data is used to enhance flow models in a wide range of systems, from oil behaviour in reservoir rocks to contaminant transport in aquifers. Phase-shift velocimetry is the fastest way to produce velocity maps but critical issues have been reported when studying flow through rocks and porous media, leading to inaccurate results. Combining PFG measurements for flow through Bentheimer sandstone with simulations, we demonstrate that asymmetries in the molecular displacement distributions within each voxel are the main source of phase-shift velocimetry errors. We show that when flow-related average molecular displacements are negligible compared to self-diffusion ones, symmetric displacement distributions can be obtained while phase measurement noise is minimised. We elaborate a complete method for the production of accurate phase-shift velocimetry maps in rocks and low porosity media and demonstrate its validity for a range of flow rates. This development of accurate phase-shift velocimetry now enables more rapid and accurate velocity analysis, potentially helping to inform both industrial applications and theoretical models.
Accurate determination of antenna directivity
DEFF Research Database (Denmark)
Dich, Mikael
1997-01-01
The derivation of a formula for accurate estimation of the total radiated power from a transmitting antenna for which the radiated power density is known in a finite number of points on the far-field sphere is presented. The main application of the formula is determination of directivity from power......-pattern measurements. The derivation is based on the theory of spherical wave expansion of electromagnetic fields, which also establishes a simple criterion for the required number of samples of the power density. An array antenna consisting of Hertzian dipoles is used to test the accuracy and rate of convergence...
Parameters for accurate genome alignment
Directory of Open Access Journals (Sweden)
Hamada Michiaki
2010-02-01
Full Text Available Abstract Background Genome sequence alignments form the basis of much research. Genome alignment depends on various mundane but critical choices, such as how to mask repeats and which score parameters to use. Surprisingly, there has been no large-scale assessment of these choices using real genomic data. Moreover, rigorous procedures to control the rate of spurious alignment have not been employed. Results We have assessed 495 combinations of score parameters for alignment of animal, plant, and fungal genomes. As our gold-standard of accuracy, we used genome alignments implied by multiple alignments of proteins and of structural RNAs. We found the HOXD scoring schemes underlying alignments in the UCSC genome database to be far from optimal, and suggest better parameters. Higher values of the X-drop parameter are not always better. E-values accurately indicate the rate of spurious alignment, but only if tandem repeats are masked in a non-standard way. Finally, we show that γ-centroid (probabilistic alignment can find highly reliable subsets of aligned bases. Conclusions These results enable more accurate genome alignment, with reliability measures for local alignments and for individual aligned bases. This study was made possible by our new software, LAST, which can align vertebrate genomes in a few hours http://last.cbrc.jp/.
Accurate structural correlations from maximum likelihood superpositions.
Directory of Open Access Journals (Sweden)
Douglas L Theobald
2008-02-01
Full Text Available The cores of globular proteins are densely packed, resulting in complicated networks of structural interactions. These interactions in turn give rise to dynamic structural correlations over a wide range of time scales. Accurate analysis of these complex correlations is crucial for understanding biomolecular mechanisms and for relating structure to function. Here we report a highly accurate technique for inferring the major modes of structural correlation in macromolecules using likelihood-based statistical analysis of sets of structures. This method is generally applicable to any ensemble of related molecules, including families of nuclear magnetic resonance (NMR models, different crystal forms of a protein, and structural alignments of homologous proteins, as well as molecular dynamics trajectories. Dominant modes of structural correlation are determined using principal components analysis (PCA of the maximum likelihood estimate of the correlation matrix. The correlations we identify are inherently independent of the statistical uncertainty and dynamic heterogeneity associated with the structural coordinates. We additionally present an easily interpretable method ("PCA plots" for displaying these positional correlations by color-coding them onto a macromolecular structure. Maximum likelihood PCA of structural superpositions, and the structural PCA plots that illustrate the results, will facilitate the accurate determination of dynamic structural correlations analyzed in diverse fields of structural biology.
Accurate ab initio spin densities
Boguslawski, Katharina; Legeza, Örs; Reiher, Markus
2012-01-01
We present an approach for the calculation of spin density distributions for molecules that require very large active spaces for a qualitatively correct description of their electronic structure. Our approach is based on the density-matrix renormalization group (DMRG) algorithm to calculate the spin density matrix elements as basic quantity for the spatially resolved spin density distribution. The spin density matrix elements are directly determined from the second-quantized elementary operators optimized by the DMRG algorithm. As an analytic convergence criterion for the spin density distribution, we employ our recently developed sampling-reconstruction scheme [J. Chem. Phys. 2011, 134, 224101] to build an accurate complete-active-space configuration-interaction (CASCI) wave function from the optimized matrix product states. The spin density matrix elements can then also be determined as an expectation value employing the reconstructed wave function expansion. Furthermore, the explicit reconstruction of a CA...
The Accurate Particle Tracer Code
Wang, Yulei; Qin, Hong; Yu, Zhi
2016-01-01
The Accurate Particle Tracer (APT) code is designed for large-scale particle simulations on dynamical systems. Based on a large variety of advanced geometric algorithms, APT possesses long-term numerical accuracy and stability, which are critical for solving multi-scale and non-linear problems. Under the well-designed integrated and modularized framework, APT serves as a universal platform for researchers from different fields, such as plasma physics, accelerator physics, space science, fusion energy research, computational mathematics, software engineering, and high-performance computation. The APT code consists of seven main modules, including the I/O module, the initialization module, the particle pusher module, the parallelization module, the field configuration module, the external force-field module, and the extendible module. The I/O module, supported by Lua and Hdf5 projects, provides a user-friendly interface for both numerical simulation and data analysis. A series of new geometric numerical methods...
Accurate thickness measurement of graphene
Shearer, Cameron J.; Slattery, Ashley D.; Stapleton, Andrew J.; Shapter, Joseph G.; Gibson, Christopher T.
2016-03-01
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Accurate thickness measurement of graphene.
Shearer, Cameron J; Slattery, Ashley D; Stapleton, Andrew J; Shapter, Joseph G; Gibson, Christopher T
2016-03-29
Graphene has emerged as a material with a vast variety of applications. The electronic, optical and mechanical properties of graphene are strongly influenced by the number of layers present in a sample. As a result, the dimensional characterization of graphene films is crucial, especially with the continued development of new synthesis methods and applications. A number of techniques exist to determine the thickness of graphene films including optical contrast, Raman scattering and scanning probe microscopy techniques. Atomic force microscopy (AFM), in particular, is used extensively since it provides three-dimensional images that enable the measurement of the lateral dimensions of graphene films as well as the thickness, and by extension the number of layers present. However, in the literature AFM has proven to be inaccurate with a wide range of measured values for single layer graphene thickness reported (between 0.4 and 1.7 nm). This discrepancy has been attributed to tip-surface interactions, image feedback settings and surface chemistry. In this work, we use standard and carbon nanotube modified AFM probes and a relatively new AFM imaging mode known as PeakForce tapping mode to establish a protocol that will allow users to accurately determine the thickness of graphene films. In particular, the error in measuring the first layer is reduced from 0.1-1.3 nm to 0.1-0.3 nm. Furthermore, in the process we establish that the graphene-substrate adsorbate layer and imaging force, in particular the pressure the tip exerts on the surface, are crucial components in the accurate measurement of graphene using AFM. These findings can be applied to other 2D materials.
Directory of Open Access Journals (Sweden)
Susana Borruel
Full Text Available Surrogate indexes of visceral adiposity, a major risk factor for metabolic and cardiovascular disorders, are routinely used in clinical practice because objective measurements of visceral adiposity are expensive, may involve exposure to radiation, and their availability is limited. We compared several surrogate indexes of visceral adiposity with ultrasound assessment of subcutaneous and visceral adipose tissue depots in 99 young Caucasian adults, including 20 women without androgen excess, 53 women with polycystic ovary syndrome, and 26 men. Obesity was present in 7, 21, and 7 subjects, respectively. We obtained body mass index (BMI, waist circumference (WC, waist-hip ratio (WHR, model of adipose distribution (MOAD, visceral adiposity index (VAI, and ultrasound measurements of subcutaneous and visceral adipose tissue depots and hepatic steatosis. WC and BMI showed the strongest correlations with ultrasound measurements of visceral adiposity. Only WHR correlated with sex hormones. Linear stepwise regression models including VAI were only slightly stronger than models including BMI or WC in explaining the variability in the insulin sensitivity index (yet BMI and WC had higher individual standardized coefficients of regression, and these models were superior to those including WHR and MOAD. WC showed 0.94 (95% confidence interval 0.88-0.99 and BMI showed 0.91 (0.85-0.98 probability of identifying the presence of hepatic steatosis according to receiver operating characteristic curve analysis. In conclusion, WC and BMI not only the simplest to obtain, but are also the most accurate surrogate markers of visceral adiposity in young adults, and are good indicators of insulin resistance and powerful predictors of the presence of hepatic steatosis.
How Accurately can we Calculate Thermal Systems?
Energy Technology Data Exchange (ETDEWEB)
Cullen, D; Blomquist, R N; Dean, C; Heinrichs, D; Kalugin, M A; Lee, M; Lee, Y; MacFarlan, R; Nagaya, Y; Trkov, A
2004-04-20
I would like to determine how accurately a variety of neutron transport code packages (code and cross section libraries) can calculate simple integral parameters, such as K{sub eff}, for systems that are sensitive to thermal neutron scattering. Since we will only consider theoretical systems, we cannot really determine absolute accuracy compared to any real system. Therefore rather than accuracy, it would be more precise to say that I would like to determine the spread in answers that we obtain from a variety of code packages. This spread should serve as an excellent indicator of how accurately we can really model and calculate such systems today. Hopefully, eventually this will lead to improvements in both our codes and the thermal scattering models that they use in the future. In order to accomplish this I propose a number of extremely simple systems that involve thermal neutron scattering that can be easily modeled and calculated by a variety of neutron transport codes. These are theoretical systems designed to emphasize the effects of thermal scattering, since that is what we are interested in studying. I have attempted to keep these systems very simple, and yet at the same time they include most, if not all, of the important thermal scattering effects encountered in a large, water-moderated, uranium fueled thermal system, i.e., our typical thermal reactors.
Accurate determination of characteristic relative permeability curves
Krause, Michael H.; Benson, Sally M.
2015-09-01
A recently developed technique to accurately characterize sub-core scale heterogeneity is applied to investigate the factors responsible for flowrate-dependent effective relative permeability curves measured on core samples in the laboratory. The dependency of laboratory measured relative permeability on flowrate has long been both supported and challenged by a number of investigators. Studies have shown that this apparent flowrate dependency is a result of both sub-core scale heterogeneity and outlet boundary effects. However this has only been demonstrated numerically for highly simplified models of porous media. In this paper, flowrate dependency of effective relative permeability is demonstrated using two rock cores, a Berea Sandstone and a heterogeneous sandstone from the Otway Basin Pilot Project in Australia. Numerical simulations of steady-state coreflooding experiments are conducted at a number of injection rates using a single set of input characteristic relative permeability curves. Effective relative permeability is then calculated from the simulation data using standard interpretation methods for calculating relative permeability from steady-state tests. Results show that simplified approaches may be used to determine flowrate-independent characteristic relative permeability provided flow rate is sufficiently high, and the core heterogeneity is relatively low. It is also shown that characteristic relative permeability can be determined at any typical flowrate, and even for geologically complex models, when using accurate three-dimensional models.
Accurate renormalization group analyses in neutrino sector
Energy Technology Data Exchange (ETDEWEB)
Haba, Naoyuki [Graduate School of Science and Engineering, Shimane University, Matsue 690-8504 (Japan); Kaneta, Kunio [Kavli IPMU (WPI), The University of Tokyo, Kashiwa, Chiba 277-8568 (Japan); Takahashi, Ryo [Graduate School of Science and Engineering, Shimane University, Matsue 690-8504 (Japan); Yamaguchi, Yuya [Department of Physics, Faculty of Science, Hokkaido University, Sapporo 060-0810 (Japan)
2014-08-15
We investigate accurate renormalization group analyses in neutrino sector between ν-oscillation and seesaw energy scales. We consider decoupling effects of top quark and Higgs boson on the renormalization group equations of light neutrino mass matrix. Since the decoupling effects are given in the standard model scale and independent of high energy physics, our method can basically apply to any models beyond the standard model. We find that the decoupling effects of Higgs boson are negligible, while those of top quark are not. Particularly, the decoupling effects of top quark affect neutrino mass eigenvalues, which are important for analyzing predictions such as mass squared differences and neutrinoless double beta decay in an underlying theory existing at high energy scale.
A More Accurate Fourier Transform
Courtney, Elya
2015-01-01
Fourier transform methods are used to analyze functions and data sets to provide frequencies, amplitudes, and phases of underlying oscillatory components. Fast Fourier transform (FFT) methods offer speed advantages over evaluation of explicit integrals (EI) that define Fourier transforms. This paper compares frequency, amplitude, and phase accuracy of the two methods for well resolved peaks over a wide array of data sets including cosine series with and without random noise and a variety of physical data sets, including atmospheric $\\mathrm{CO_2}$ concentrations, tides, temperatures, sound waveforms, and atomic spectra. The FFT uses MIT's FFTW3 library. The EI method uses the rectangle method to compute the areas under the curve via complex math. Results support the hypothesis that EI methods are more accurate than FFT methods. Errors range from 5 to 10 times higher when determining peak frequency by FFT, 1.4 to 60 times higher for peak amplitude, and 6 to 10 times higher for phase under a peak. The ability t...
Institute of Scientific and Technical Information of China (English)
刘成; 周立; 屠晓杰; 王彤
2013-01-01
Avionics Full Duplex Switched Ethernet ( AFDX ) standardized as ARINC 664 is an upgrade from Ethernet for avionics demand .AFDX adopts the mechanisms such as Virtual Link ( VL) and traffic policing for the determinacy of communication task .Network calculus approach is a basic tool to compute the upper bound of end-to-end delay for VL in AFDX network,which give AFDX a useful method to research the real-time performance .However,the network calculus approach used a simple flow model of VL .Based on that model,the result got by network calculus approach is pessimistic .An accurate flow model of VL is adopted in the network calculus approach in this paper,and it helps the network calculus approach to get a tighter upper bound of delay for VL .%航空电子全双工交换式以太网（ AFDX）是针对航空电子应用从工业交换式以太网升级而来的。其中，引入的虚拟链路（ VL）和流量管制机制为网络通信任务提供了确定性的保障。网络演算是AFDX中常用的VL延时上界计算工具，为AFDX网络的实时性研究提供了理论依据。但是网络演算采用了VL简单流模型，计算得到的延时上界比较悲观。将VL精确流模型应用在网络演算工具中，并展示了基于精确流模型的网络演算能够得到更紧的延时上界计算结果。
Institute of Scientific and Technical Information of China (English)
姜俊泽; 张伟明
2012-01-01
分析了水平管内气液两相段塞流的运动特性和形态特征以及段塞单元内部的速度分布规律,建立了水平管路气液两相段塞单元的物理模型.将一个完整的段塞流单元分为液相段塞区和液层/气泡区,建立了液相段塞区的质量和动量守恒方程,计算了其压降和持液率;对液层区,模型考虑液层厚度分布不均(坡状液层)对参数计算的影响,通过建立局部控制方程,推导了液层高度随流动方向坐标变化的表达式,并将持液率和湿周写成液层高度的函数.通过与实验和其他模型的计算结果对比,本文建立的模型可以对压降和持液率有更准确的预测结果.%The paper analyzes the flow mechanism,shape characteristics and inner velocity distribution of gas-liquid slug flow in a horizontal pipe,and develops a physical model for the horizontal pipe. In a steady slug unit,lift velocity is always equal to shedding velocity,so the slug can keep an established shape. The model divides the slug into two parts: liquid-slug and film/bubble zone. For the liquid-slug zone,mass conservation and momentum conservation equations are built up to compute the local liquid-holdup and pressure-drop. For the film area,the model takes film height variation into consideration,assuming the height is only varying along the flow direction but not in the radial direction. The paper deduces a film height variation expression by building local control equations,and then develops a film height via liquid-holdup function and a film height via wet-diameter function. By comparing with test data and some other models,this model presents more accurate prediction results of liquid-holdup and pressure-drop.
Accurate measurement of unsteady state fluid temperature
Jaremkiewicz, Magdalena
2016-07-01
In this paper, two accurate methods for determining the transient fluid temperature were presented. Measurements were conducted for boiling water since its temperature is known. At the beginning the thermometers are at the ambient temperature and next they are immediately immersed into saturated water. The measurements were carried out with two thermometers of different construction but with the same housing outer diameter equal to 15 mm. One of them is a K-type industrial thermometer widely available commercially. The temperature indicated by the thermometer was corrected considering the thermometers as the first or second order inertia devices. The new design of a thermometer was proposed and also used to measure the temperature of boiling water. Its characteristic feature is a cylinder-shaped housing with the sheath thermocouple located in its center. The temperature of the fluid was determined based on measurements taken in the axis of the solid cylindrical element (housing) using the inverse space marching method. Measurements of the transient temperature of the air flowing through the wind tunnel using the same thermometers were also carried out. The proposed measurement technique provides more accurate results compared with measurements using industrial thermometers in conjunction with simple temperature correction using the inertial thermometer model of the first or second order. By comparing the results, it was demonstrated that the new thermometer allows obtaining the fluid temperature much faster and with higher accuracy in comparison to the industrial thermometer. Accurate measurements of the fast changing fluid temperature are possible due to the low inertia thermometer and fast space marching method applied for solving the inverse heat conduction problem.
Accurate pose estimation for forensic identification
Merckx, Gert; Hermans, Jeroen; Vandermeulen, Dirk
2010-04-01
In forensic authentication, one aims to identify the perpetrator among a series of suspects or distractors. A fundamental problem in any recognition system that aims for identification of subjects in a natural scene is the lack of constrains on viewing and imaging conditions. In forensic applications, identification proves even more challenging, since most surveillance footage is of abysmal quality. In this context, robust methods for pose estimation are paramount. In this paper we will therefore present a new pose estimation strategy for very low quality footage. Our approach uses 3D-2D registration of a textured 3D face model with the surveillance image to obtain accurate far field pose alignment. Starting from an inaccurate initial estimate, the technique uses novel similarity measures based on the monogenic signal to guide a pose optimization process. We will illustrate the descriptive strength of the introduced similarity measures by using them directly as a recognition metric. Through validation, using both real and synthetic surveillance footage, our pose estimation method is shown to be accurate, and robust to lighting changes and image degradation.
38 CFR 4.46 - Accurate measurement.
2010-07-01
... 38 Pensions, Bonuses, and Veterans' Relief 1 2010-07-01 2010-07-01 false Accurate measurement. 4... RATING DISABILITIES Disability Ratings The Musculoskeletal System § 4.46 Accurate measurement. Accurate measurement of the length of stumps, excursion of joints, dimensions and location of scars with respect...
Toward Accurate and Quantitative Comparative Metagenomics
Nayfach, Stephen; Pollard, Katherine S.
2016-01-01
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
Toward Accurate and Quantitative Comparative Metagenomics.
Nayfach, Stephen; Pollard, Katherine S
2016-08-25
Shotgun metagenomics and computational analysis are used to compare the taxonomic and functional profiles of microbial communities. Leveraging this approach to understand roles of microbes in human biology and other environments requires quantitative data summaries whose values are comparable across samples and studies. Comparability is currently hampered by the use of abundance statistics that do not estimate a meaningful parameter of the microbial community and biases introduced by experimental protocols and data-cleaning approaches. Addressing these challenges, along with improving study design, data access, metadata standardization, and analysis tools, will enable accurate comparative metagenomics. We envision a future in which microbiome studies are replicable and new metagenomes are easily and rapidly integrated with existing data. Only then can the potential of metagenomics for predictive ecological modeling, well-powered association studies, and effective microbiome medicine be fully realized. PMID:27565341
Accurate Weather Forecasting for Radio Astronomy
Maddalena, Ronald J.
2010-01-01
The NRAO Green Bank Telescope routinely observes at wavelengths from 3 mm to 1 m. As with all mm-wave telescopes, observing conditions depend upon the variable atmospheric water content. The site provides over 100 days/yr when opacities are low enough for good observing at 3 mm, but winds on the open-air structure reduce the time suitable for 3-mm observing where pointing is critical. Thus, to maximum productivity the observing wavelength needs to match weather conditions. For 6 years the telescope has used a dynamic scheduling system (recently upgraded; www.gb.nrao.edu/DSS) that requires accurate multi-day forecasts for winds and opacities. Since opacity forecasts are not provided by the National Weather Services (NWS), I have developed an automated system that takes available forecasts, derives forecasted opacities, and deploys the results on the web in user-friendly graphical overviews (www.gb.nrao.edu/ rmaddale/Weather). The system relies on the "North American Mesoscale" models, which are updated by the NWS every 6 hrs, have a 12 km horizontal resolution, 1 hr temporal resolution, run to 84 hrs, and have 60 vertical layers that extend to 20 km. Each forecast consists of a time series of ground conditions, cloud coverage, etc, and, most importantly, temperature, pressure, humidity as a function of height. I use the Liebe's MWP model (Radio Science, 20, 1069, 1985) to determine the absorption in each layer for each hour for 30 observing wavelengths. Radiative transfer provides, for each hour and wavelength, the total opacity and the radio brightness of the atmosphere, which contributes substantially at some wavelengths to Tsys and the observational noise. Comparisons of measured and forecasted Tsys at 22.2 and 44 GHz imply that the forecasted opacities are good to about 0.01 Nepers, which is sufficient for forecasting and accurate calibration. Reliability is high out to 2 days and degrades slowly for longer-range forecasts.
Towards an accurate bioimpedance identification
Sanchez, B.; Louarroudi, E.; Bragos, R.; Pintelon, R.
2013-04-01
This paper describes the local polynomial method (LPM) for estimating the time-invariant bioimpedance frequency response function (FRF) considering both the output-error (OE) and the errors-in-variables (EIV) identification framework and compare it with the traditional cross— and autocorrelation spectral analysis techniques. The bioimpedance FRF is measured with the multisine electrical impedance spectroscopy (EIS) technique. To show the overwhelming accuracy of the LPM approach, both the LPM and the classical cross— and autocorrelation spectral analysis technique are evaluated through the same experimental data coming from a nonsteady-state measurement of time-varying in vivo myocardial tissue. The estimated error sources at the measurement frequencies due to noise, σnZ, and the stochastic nonlinear distortions, σZNL, have been converted to Ω and plotted over the bioimpedance spectrum for each framework. Ultimately, the impedance spectra have been fitted to a Cole impedance model using both an unweighted and a weighted complex nonlinear least square (CNLS) algorithm. A table is provided with the relative standard errors on the estimated parameters to reveal the importance of which system identification frameworks should be used.
Towards an accurate bioimpedance identification
International Nuclear Information System (INIS)
This paper describes the local polynomial method (LPM) for estimating the time-invariant bioimpedance frequency response function (FRF) considering both the output-error (OE) and the errors-in-variables (EIV) identification framework and compare it with the traditional cross— and autocorrelation spectral analysis techniques. The bioimpedance FRF is measured with the multisine electrical impedance spectroscopy (EIS) technique. To show the overwhelming accuracy of the LPM approach, both the LPM and the classical cross— and autocorrelation spectral analysis technique are evaluated through the same experimental data coming from a nonsteady-state measurement of time-varying in vivo myocardial tissue. The estimated error sources at the measurement frequencies due to noise, σnZ, and the stochastic nonlinear distortions, σZNL, have been converted to Ω and plotted over the bioimpedance spectrum for each framework. Ultimately, the impedance spectra have been fitted to a Cole impedance model using both an unweighted and a weighted complex nonlinear least square (CNLS) algorithm. A table is provided with the relative standard errors on the estimated parameters to reveal the importance of which system identification frameworks should be used.
New advance on non-hydrostatic shallow granular flow model in a global Cartesian coordinate system
Yuan, L; Zhai, J; Wu, S F; Patra, A K; Pitman, E B
2016-01-01
Mathematical modeling of granular avalanche flows over a general topography needs appropriate forms of shallow granular flow models. Current shallow granular flow models suited to arbitrary topography can be grossly divided into two types, those formulated in bed-fitted curvilinear coordinates (e.g., Ref.~\\cite{{Puda2003}}), and those formulated in global Cartesian coordinates (e.g., Refs.~\\cite{{Bouchut2004},{Denlinger2004},{Castro2014}}). In the recent years, several improvements have been made in global Cartesian formulations for shallow granular flows. In this paper, we first perform a review of the Cartesian model of Denlinger and Iverson \\cite{Denlinger2004} and the Cartesian Boussinesq-type granular flow theory of Castr-Ogaz \\emph{et al.} \\cite{Castro2014}. Both formulations account for the effect of nonzero vertical acceleration on depth-averaged momentum fluxes and stress states. We then further calculate the vertical normal stress of Castr-Ogaz \\emph{et al.}~\\cite{Castro2014} and the basal normal st...
Simple and accurate analytical calculation of shortest path lengths
Melnik, Sergey
2016-01-01
We present an analytical approach to calculating the distribution of shortest paths lengths (also called intervertex distances, or geodesic paths) between nodes in unweighted undirected networks. We obtain very accurate results for synthetic random networks with specified degree distribution (the so-called configuration model networks). Our method allows us to accurately predict the distribution of shortest path lengths on real-world networks using their degree distribution, or joint degree-degree distribution. Compared to some other methods, our approach is simpler and yields more accurate results. In order to obtain the analytical results, we use the analogy between an infection reaching a node in $n$ discrete time steps (i.e., as in the susceptible-infected epidemic model) and that node being at a distance $n$ from the source of the infection.
Accurate paleointensities - the multi-method approach
de Groot, Lennart
2016-04-01
The accuracy of models describing rapid changes in the geomagnetic field over the past millennia critically depends on the availability of reliable paleointensity estimates. Over the past decade methods to derive paleointensities from lavas (the only recorder of the geomagnetic field that is available all over the globe and through geologic times) have seen significant improvements and various alternative techniques were proposed. The 'classical' Thellier-style approach was optimized and selection criteria were defined in the 'Standard Paleointensity Definitions' (Paterson et al, 2014). The Multispecimen approach was validated and the importance of additional tests and criteria to assess Multispecimen results must be emphasized. Recently, a non-heating, relative paleointensity technique was proposed -the pseudo-Thellier protocol- which shows great potential in both accuracy and efficiency, but currently lacks a solid theoretical underpinning. Here I present work using all three of the aforementioned paleointensity methods on suites of young lavas taken from the volcanic islands of Hawaii, La Palma, Gran Canaria, Tenerife, and Terceira. Many of the sampled cooling units are <100 years old, the actual field strength at the time of cooling is therefore reasonably well known. Rather intuitively, flows that produce coherent results from two or more different paleointensity methods yield the most accurate estimates of the paleofield. Furthermore, the results for some flows pass the selection criteria for one method, but fail in other techniques. Scrutinizing and combing all acceptable results yielded reliable paleointensity estimates for 60-70% of all sampled cooling units - an exceptionally high success rate. This 'multi-method paleointensity approach' therefore has high potential to provide the much-needed paleointensities to improve geomagnetic field models for the Holocene.
Accurately Detecting Students' Lies regarding Relational Aggression by Correctional Instructions
Dickhauser, Oliver; Reinhard, Marc-Andre; Marksteiner, Tamara
2012-01-01
This study investigates the effect of correctional instructions when detecting lies about relational aggression. Based on models from the field of social psychology, we predict that correctional instruction will lead to a less pronounced lie bias and to more accurate lie detection. Seventy-five teachers received videotapes of students' true denial…
Laboratory Building for Accurate Determination of Plutonium
Institute of Scientific and Technical Information of China (English)
2008-01-01
<正>The accurate determination of plutonium is one of the most important assay techniques of nuclear fuel, also the key of the chemical measurement transfer and the base of the nuclear material balance. An
Invariant Image Watermarking Using Accurate Zernike Moments
Directory of Open Access Journals (Sweden)
Ismail A. Ismail
2010-01-01
Full Text Available problem statement: Digital image watermarking is the most popular method for image authentication, copyright protection and content description. Zernike moments are the most widely used moments in image processing and pattern recognition. The magnitudes of Zernike moments are rotation invariant so they can be used just as a watermark signal or be further modified to carry embedded data. The computed Zernike moments in Cartesian coordinate are not accurate due to geometrical and numerical error. Approach: In this study, we employed a robust image-watermarking algorithm using accurate Zernike moments. These moments are computed in polar coordinate, where both approximation and geometric errors are removed. Accurate Zernike moments are used in image watermarking and proved to be robust against different kind of geometric attacks. The performance of the proposed algorithm is evaluated using standard images. Results: Experimental results show that, accurate Zernike moments achieve higher degree of robustness than those approximated ones against rotation, scaling, flipping, shearing and affine transformation. Conclusion: By computing accurate Zernike moments, the embedded bits watermark can be extracted at low error rate.
Hydraulic Modeling of A Curtain-Walled Dissipater by the Coupling of RANS and Boussinesq Equations
Institute of Scientific and Technical Information of China (English)
齐鹏; 王永学
2002-01-01
A hybrid numerical method for the hydraulic modeling of a curtain-walled dissipater of reflected waves from breakwa-ters is presented. In this method, a zonal approach that combines a nonlinear weakly dispersive wave (Boussinesq-typeequation) method and a Reynolds-Averaged Navier-Stokes (RANS) method is used. The Boussinesq-type equation issolved in the far field to describe wave transformation in shallow water. The RANS method is used in the near field to re-solve the turbulent boundary layer and vortex flows around the structure. Suitable matching conditions are enforced at theinterface between the viscous and the Boussinesq region. The Coupled RANS and Boussinesq method successfully resolvesthe vortex characteristics of flow in the vicinity of the structure, while unexpected phenomena like wave re-reflection areeffectively controlled by lengthening the Boussinesq region. Extensive results on hydraulic performance of a curtain-walleddissipater and the mechanism of dissipation of reflected waves are presented, providing a reference for minimization of thebreadth of the water chamber and for determination of the submerged depth of the curtain wall.
The FLUKA code: An accurate simulation tool for particle therapy
Battistoni, Giuseppe; Böhlen, Till T; Cerutti, Francesco; Chin, Mary Pik Wai; Dos Santos Augusto, Ricardo M; Ferrari, Alfredo; Garcia Ortega, Pablo; Kozlowska, Wioletta S; Magro, Giuseppe; Mairani, Andrea; Parodi, Katia; Sala, Paola R; Schoofs, Philippe; Tessonnier, Thomas; Vlachoudis, Vasilis
2016-01-01
Monte Carlo (MC) codes are increasingly spreading in the hadrontherapy community due to their detailed description of radiation transport and interaction with matter. The suitability of a MC code for application to hadrontherapy demands accurate and reliable physical models capable of handling all components of the expected radiation field. This becomes extremely important for correctly performing not only physical but also biologically-based dose calculations, especially in cases where ions heavier than protons are involved. In addition, accurate prediction of emerging secondary radiation is of utmost importance in innovative areas of research aiming at in-vivo treatment verification. This contribution will address the recent developments of the FLUKA MC code and its practical applications in this field. Refinements of the FLUKA nuclear models in the therapeutic energy interval lead to an improved description of the mixed radiation field as shown in the presented benchmarks against experimental data with bot...
Fixed-Wing Micro Aerial Vehicle for Accurate Corridor Mapping
Rehak, M.; Skaloud, J.
2015-08-01
In this study we present a Micro Aerial Vehicle (MAV) equipped with precise position and attitude sensors that together with a pre-calibrated camera enables accurate corridor mapping. The design of the platform is based on widely available model components to which we integrate an open-source autopilot, customized mass-market camera and navigation sensors. We adapt the concepts of system calibration from larger mapping platforms to MAV and evaluate them practically for their achievable accuracy. We present case studies for accurate mapping without ground control points: first for a block configuration, later for a narrow corridor. We evaluate the mapping accuracy with respect to checkpoints and digital terrain model. We show that while it is possible to achieve pixel (3-5 cm) mapping accuracy in both cases, precise aerial position control is sufficient for block configuration, the precise position and attitude control is required for corridor mapping.
Coupling of unstructured TLM and BEM for accurate 2D electromagnetic simulation
Simmons, Daniel; Cools, Kristof; Sewell, Phillip
2015-01-01
In this paper the hybridisation of the 2D time-domain boundary element method (BEM) with the unstructured transmission line method (UTLM) will be introduced, which enables accurate modeling of radiating boundary conditions and plane wave excitations of uniform and non-uniform targets modelled by geometrically accurate unstructured meshes. The method is demonstrated by comparing numerical results against analytical results.
Accurate calculation of thermal noise in multilayer coating
Gurkovsky, Alexey; Vyatchanin, Sergey
2010-01-01
We derive accurate formulas for thermal fluctuations in multilayer interferometric coating taking into account light propagation inside the coating. In particular, we calculate the reflected wave phase as a function of small displacements of the boundaries between the layers using transmission line model for interferometric coating and derive formula for spectral density of reflected phase in accordance with Fluctuation-Dissipation Theorem. We apply the developed approach for calculation of t...
Building with Drones: Accurate 3D Facade Reconstruction using MAVs
Daftry, Shreyansh; Hoppe, Christof; Bischof, Horst
2015-01-01
Automatic reconstruction of 3D models from images using multi-view Structure-from-Motion methods has been one of the most fruitful outcomes of computer vision. These advances combined with the growing popularity of Micro Aerial Vehicles as an autonomous imaging platform, have made 3D vision tools ubiquitous for large number of Architecture, Engineering and Construction applications among audiences, mostly unskilled in computer vision. However, to obtain high-resolution and accurate reconstruc...
Interactive Isogeometric Volume Visualization with Pixel-Accurate Geometry
Fuchs, Franz G.; Hjelmervik, Jon M.
2014-01-01
A recent development, called isogeometric analysis, provides a unified approach for design, analysis and optimization of functional products in industry. Traditional volume rendering methods for inspecting the results from the numerical simulations cannot be applied directly to isogeometric models. We present a novel approach for interactive visualization of isogeometric analysis results, ensuring correct, i.e., pixel-accurate geometry of the volume including its bounding surfaces. The entire...
Efficient and accurate sound propagation using adaptive rectangular decomposition.
Raghuvanshi, Nikunj; Narain, Rahul; Lin, Ming C
2009-01-01
Accurate sound rendering can add significant realism to complement visual display in interactive applications, as well as facilitate acoustic predictions for many engineering applications, like accurate acoustic analysis for architectural design. Numerical simulation can provide this realism most naturally by modeling the underlying physics of wave propagation. However, wave simulation has traditionally posed a tough computational challenge. In this paper, we present a technique which relies on an adaptive rectangular decomposition of 3D scenes to enable efficient and accurate simulation of sound propagation in complex virtual environments. It exploits the known analytical solution of the Wave Equation in rectangular domains, and utilizes an efficient implementation of the Discrete Cosine Transform on Graphics Processors (GPU) to achieve at least a 100-fold performance gain compared to a standard Finite-Difference Time-Domain (FDTD) implementation with comparable accuracy, while also being 10-fold more memory efficient. Consequently, we are able to perform accurate numerical acoustic simulation on large, complex scenes in the kilohertz range. To the best of our knowledge, it was not previously possible to perform such simulations on a desktop computer. Our work thus enables acoustic analysis on large scenes and auditory display for complex virtual environments on commodity hardware. PMID:19590105
Badami, Rokhsareh; VaezMousavi, Mohammad; Wulf, Gabriele; Namazizadeh, Mahdi
2012-06-01
One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected byfeedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On day 1, participants performed a golf putting task under one of two conditions: one group received feedback on the most accurate trials, whereas another group received feedback on the least accurate trials. On day 2, participants completed an anxiety questionnaire and performed a retention test. Shin conductance level, as a measure of arousal, was determined. The results indicated that feedback about more accurate trials resulted in more effective learning as well as increased self-confidence. Also, activation was a predictor of performance. PMID:22808705
Accurate estimation of indoor travel times
DEFF Research Database (Denmark)
Prentow, Thor Siiger; Blunck, Henrik; Stisen, Allan;
2014-01-01
are collected within the building complex. Results indicate that InTraTime is superior with respect to metrics such as deployment cost, maintenance cost and estimation accuracy, yielding an average deviation from actual travel times of 11.7 %. This accuracy was achieved despite using a minimal-effort setup......The ability to accurately estimate indoor travel times is crucial for enabling improvements within application areas such as indoor navigation, logistics for mobile workers, and facility management. In this paper, we study the challenges inherent in indoor travel time estimation, and we propose...... the InTraTime method for accurately estimating indoor travel times via mining of historical and real-time indoor position traces. The method learns during operation both travel routes, travel times and their respective likelihood---both for routes traveled as well as for sub-routes thereof. In...
Accurate guitar tuning by cochlear implant musicians.
Directory of Open Access Journals (Sweden)
Thomas Lu
Full Text Available Modern cochlear implant (CI users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task.
Accurate Finite Difference Methods for Option Pricing
Persson, Jonas
2006-01-01
Stock options are priced numerically using space- and time-adaptive finite difference methods. European options on one and several underlying assets are considered. These are priced with adaptive numerical algorithms including a second order method and a more accurate method. For American options we use the adaptive technique to price options on one stock with and without stochastic volatility. In all these methods emphasis is put on the control of errors to fulfill predefined tolerance level...
Accurate variational forms for multiskyrmion configurations
Energy Technology Data Exchange (ETDEWEB)
Jackson, A.D.; Weiss, C.; Wirzba, A.; Lande, A.
1989-04-17
Simple variational forms are suggested for the fields of a single skyrmion on a hypersphere, S/sub 3/(L), and of a face-centered cubic array of skyrmions in flat space, R/sub 3/. The resulting energies are accurate at the level of 0.2%. These approximate field configurations provide a useful alternative to brute-force solutions of the corresponding Euler equations.
High Frequency QRS ECG Accurately Detects Cardiomyopathy
Schlegel, Todd T.; Arenare, Brian; Poulin, Gregory; Moser, Daniel R.; Delgado, Reynolds
2005-01-01
High frequency (HF, 150-250 Hz) analysis over the entire QRS interval of the ECG is more sensitive than conventional ECG for detecting myocardial ischemia. However, the accuracy of HF QRS ECG for detecting cardiomyopathy is unknown. We obtained simultaneous resting conventional and HF QRS 12-lead ECGs in 66 patients with cardiomyopathy (EF = 23.2 plus or minus 6.l%, mean plus or minus SD) and in 66 age- and gender-matched healthy controls using PC-based ECG software recently developed at NASA. The single most accurate ECG parameter for detecting cardiomyopathy was an HF QRS morphological score that takes into consideration the total number and severity of reduced amplitude zones (RAZs) present plus the clustering of RAZs together in contiguous leads. This RAZ score had an area under the receiver operator curve (ROC) of 0.91, and was 88% sensitive, 82% specific and 85% accurate for identifying cardiomyopathy at optimum score cut-off of 140 points. Although conventional ECG parameters such as the QRS and QTc intervals were also significantly longer in patients than controls (P less than 0.001, BBBs excluded), these conventional parameters were less accurate (area under the ROC = 0.77 and 0.77, respectively) than HF QRS morphological parameters for identifying underlying cardiomyopathy. The total amplitude of the HF QRS complexes, as measured by summed root mean square voltages (RMSVs), also differed between patients and controls (33.8 plus or minus 11.5 vs. 41.5 plus or minus 13.6 mV, respectively, P less than 0.003), but this parameter was even less accurate in distinguishing the two groups (area under ROC = 0.67) than the HF QRS morphologic and conventional ECG parameters. Diagnostic accuracy was optimal (86%) when the RAZ score from the HF QRS ECG and the QTc interval from the conventional ECG were used simultaneously with cut-offs of greater than or equal to 40 points and greater than or equal to 445 ms, respectively. In conclusion 12-lead HF QRS ECG employing
快速准确的多分辨率地形模型误差计算%Rapid and Accurate Error Calculation for Multi-resolution Terrain Models
Institute of Scientific and Technical Information of China (English)
钮小琳; 慕晓冬; 时少旺; 韩晓峰
2014-01-01
Massive terrain rendering methods have improved considerably with the great development of graphics hardware. But the error calculation methods for terrain models do not pick up the pace. Most rendering methods still use the traditional recursive errors,which are not compatible with current rendering methods. This paper proposes a new error calculation method for this issue. The proposed error metric directly describes the simplified model’s deviation from the original model,thus it is more precise than the previous methods. By using the linear interpolation ability of current graphics hardware,a high calculation performance is achieved,large terrain models can be processed promptly with the proposed method.%随着图形硬件的高速发展，大规模地形的可视化技术相比传统方法发生了很大变化，但是地形的误差计算方法却没有作出相应的改进，大多算法依然使用保守的迭代式误差，不能很好地与当前绘制算法相适应。针对这个问题，提出一种新的误差定义和计算方式。该误差直接描述简化模型同原始模型之间的差异，比以前的算法更为准确。误差的计算利用图形硬件的插值能力进行加速，大规模地形数据的误差计算能够在较短时间内完成。
Molodenskii, S. M.; Molodenskii, M. S.; Begitova, T. A.
2016-09-01
Constructing detailed models for postseismic and coseismic deformations of the Earth's surface has become particularly important because of the recently established possibility to continuously monitor the tectonic stresses in the source zones based on the data on the time variations in the tidal tilt amplitudes. Below, a new method is suggested for solving the inverse problem about the coseismic and postseismic deformations in the real non-ideally elastic, radially and horizontally heterogeneous, self-gravitating Earth with a hydrostatic distribution of the initial stresses from the satellite data on the ground surface displacements. The solution of this problem is based on decomposing the parameters determining the geometry of the fault surface and the distribution of the dislocation vector on this surface and elastic modules in the source in the orthogonal bases. The suggested approach includes four steps: 1. Calculating (by the perturbation method) the variations in Green's function for the radial and tangential ground surface displacements with small 3D variations in the mechanical parameters and geometry of the source area (i.e., calculating the functional derivatives of the three components of Green's function on the surface from the distributions of the elastic moduli and creep function within the volume of the source area and Burgers' vector on the surface of the dislocations); 2. Successive orthogonalization of the functional derivatives; 3. Passing from the decompositions of the residuals between the observed and modeled surface displacements in the system of nonorthogonalized functional derivatives to their decomposition in the system of orthogonalized derivatives; finding the corrections to the distributions of the sought parameters from the coefficients of their decompositions in the orthogonalized basis; and 4. Analyzing the ambiguity of the inverse problem solution by constructing the orthogonal complement to the obtained basis. The described
Accurate genome relative abundance estimation based on shotgun metagenomic reads.
Directory of Open Access Journals (Sweden)
Li C Xia
Full Text Available Accurate estimation of microbial community composition based on metagenomic sequencing data is fundamental for subsequent metagenomics analysis. Prevalent estimation methods are mainly based on directly summarizing alignment results or its variants; often result in biased and/or unstable estimates. We have developed a unified probabilistic framework (named GRAMMy by explicitly modeling read assignment ambiguities, genome size biases and read distributions along the genomes. Maximum likelihood method is employed to compute Genome Relative Abundance of microbial communities using the Mixture Model theory (GRAMMy. GRAMMy has been demonstrated to give estimates that are accurate and robust across both simulated and real read benchmark datasets. We applied GRAMMy to a collection of 34 metagenomic read sets from four metagenomics projects and identified 99 frequent species (minimally 0.5% abundant in at least 50% of the data-sets in the human gut samples. Our results show substantial improvements over previous studies, such as adjusting the over-estimated abundance for Bacteroides species for human gut samples, by providing a new reference-based strategy for metagenomic sample comparisons. GRAMMy can be used flexibly with many read assignment tools (mapping, alignment or composition-based even with low-sensitivity mapping results from huge short-read datasets. It will be increasingly useful as an accurate and robust tool for abundance estimation with the growing size of read sets and the expanding database of reference genomes.
Accurate Multisteps Traffic Flow Prediction Based on SVM
Directory of Open Access Journals (Sweden)
Zhang Mingheng
2013-01-01
Full Text Available Accurate traffic flow prediction is prerequisite and important for realizing intelligent traffic control and guidance, and it is also the objective requirement for intelligent traffic management. Due to the strong nonlinear, stochastic, time-varying characteristics of urban transport system, artificial intelligence methods such as support vector machine (SVM are now receiving more and more attentions in this research field. Compared with the traditional single-step prediction method, the multisteps prediction has the ability that can predict the traffic state trends over a certain period in the future. From the perspective of dynamic decision, it is far important than the current traffic condition obtained. Thus, in this paper, an accurate multi-steps traffic flow prediction model based on SVM was proposed. In which, the input vectors were comprised of actual traffic volume and four different types of input vectors were compared to verify their prediction performance with each other. Finally, the model was verified with actual data in the empirical analysis phase and the test results showed that the proposed SVM model had a good ability for traffic flow prediction and the SVM-HPT model outperformed the other three models for prediction.
The economic value of accurate wind power forecasting to utilities
Energy Technology Data Exchange (ETDEWEB)
Watson, S.J. [Rutherford Appleton Lab., Oxfordshire (United Kingdom); Giebel, G.; Joensen, A. [Risoe National Lab., Dept. of Wind Energy and Atmospheric Physics, Roskilde (Denmark)
1999-03-01
With increasing penetrations of wind power, the need for accurate forecasting is becoming ever more important. Wind power is by its very nature intermittent. For utility schedulers this presents its own problems particularly when the penetration of wind power capacity in a grid reaches a significant level (>20%). However, using accurate forecasts of wind power at wind farm sites, schedulers are able to plan the operation of conventional power capacity to accommodate the fluctuating demands of consumers and wind farm output. The results of a study to assess the value of forecasting at several potential wind farm sites in the UK and in the US state of Iowa using the Reading University/Rutherford Appleton Laboratory National Grid Model (NGM) are presented. The results are assessed for different types of wind power forecasting, namely: persistence, optimised numerical weather prediction or perfect forecasting. In particular, it will shown how the NGM has been used to assess the value of numerical weather prediction forecasts from the Danish Meteorological Institute model, HIRLAM, and the US Nested Grid Model, which have been `site tailored` by the use of the linearized flow model WA{sup s}P and by various Model output Statistics (MOS) and autoregressive techniques. (au)
Accurate parameter estimation for unbalanced three-phase system.
Chen, Yuan; So, Hing Cheung
2014-01-01
Smart grid is an intelligent power generation and control console in modern electricity networks, where the unbalanced three-phase power system is the commonly used model. Here, parameter estimation for this system is addressed. After converting the three-phase waveforms into a pair of orthogonal signals via the α β-transformation, the nonlinear least squares (NLS) estimator is developed for accurately finding the frequency, phase, and voltage parameters. The estimator is realized by the Newton-Raphson scheme, whose global convergence is studied in this paper. Computer simulations show that the mean square error performance of NLS method can attain the Cramér-Rao lower bound. Moreover, our proposal provides more accurate frequency estimation when compared with the complex least mean square (CLMS) and augmented CLMS.
地震模拟振动台阵系统的精细化建模与频响仿真%Accurate Modeling and Frequency Simulation of Shaking Table Array
Institute of Scientific and Technical Information of China (English)
高春华; 纪金豹; 闫维明; 王巨科; 李娜
2015-01-01
为解决地震模拟振动台建模中的非线性问题，采用Matlab/Simulink中的SimHydraulics、SimMechanics模块对北京工业大学地震模拟振动台九子台阵进行了精细化建模与仿真，分析了伺服阀特性、台面质量及油源压力对系统频响特性的影响，给出了振动台建设中合理的台面质量范围，得出了试验中通常应该采用的理想油源压力。研究结果表明：伺服阀频率对振动台系统频响特性的影响较大而伺服阀的阻尼比对此几乎没有影响。%In order to solve the nonlinear problems in the modeling of shaking table array system, refined modeling and simulation of shaking table 9 -sub array system of Beijing university of technology were carried out using Matlab/Simulink, the characteristics of servo valve, mesa quality and the effect of oil source pressure on the system frequency response characteristics were analyzed. The study shows that the servo valve frequency exerts great influence on the frequency response characteristics of shaking table system while servo valve damping ratio has little impact on the system frequency response characteristics.
New law requires 'medically accurate' lesson plans.
1999-09-17
The California Legislature has passed a bill requiring all textbooks and materials used to teach about AIDS be medically accurate and objective. Statements made within the curriculum must be supported by research conducted in compliance with scientific methods, and published in peer-reviewed journals. Some of the current lesson plans were found to contain scientifically unsupported and biased information. In addition, the bill requires material to be "free of racial, ethnic, or gender biases." The legislation is supported by a wide range of interests, but opposed by the California Right to Life Education Fund, because they believe it discredits abstinence-only material.
Niche Genetic Algorithm with Accurate Optimization Performance
Institute of Scientific and Technical Information of China (English)
LIU Jian-hua; YAN De-kun
2005-01-01
Based on crowding mechanism, a novel niche genetic algorithm was proposed which can record evolutionary direction dynamically during evolution. After evolution, the solutions's precision can be greatly improved by means of the local searching along the recorded direction. Simulation shows that this algorithm can not only keep population diversity but also find accurate solutions. Although using this method has to take more time compared with the standard GA, it is really worth applying to some cases that have to meet a demand for high solution precision.
Investigations on Accurate Analysis of Microstrip Reflectarrays
DEFF Research Database (Denmark)
Zhou, Min; Sørensen, S. B.; Kim, Oleksiy S.;
2011-01-01
An investigation on accurate analysis of microstrip reflectarrays is presented. Sources of error in reflectarray analysis are examined and solutions to these issues are proposed. The focus is on two sources of error, namely the determination of the equivalent currents to calculate the radiation...... pattern, and the inaccurate mutual coupling between array elements due to the lack of periodicity. To serve as reference, two offset reflectarray antennas have been designed, manufactured and measured at the DTUESA Spherical Near-Field Antenna Test Facility. Comparisons of simulated and measured data are...
Accurate diagnosis is essential for amebiasis
Institute of Scientific and Technical Information of China (English)
无
2004-01-01
@@ Amebiasis is one of the three most common causes of death from parasitic disease, and Entamoeba histolytica is the most widely distributed parasites in the world. Particularly, Entamoeba histolytica infection in the developing countries is a significant health problem in amebiasis-endemic areas with a significant impact on infant mortality[1]. In recent years a world wide increase in the number of patients with amebiasis has refocused attention on this important infection. On the other hand, improving the quality of parasitological methods and widespread use of accurate tecniques have improved our knowledge about the disease.
Chimot, J.; Vlemmix, T.; Veefkind, J. P.; de Haan, J. F.; Levelt, P. F.
2016-02-01
The Ozone Monitoring Instrument (OMI) has provided daily global measurements of tropospheric NO2 for more than a decade. Numerous studies have drawn attention to the complexities related to measurements of tropospheric NO2 in the presence of aerosols. Fine particles affect the OMI spectral measurements and the length of the average light path followed by the photons. However, they are not explicitly taken into account in the current operational OMI tropospheric NO2 retrieval chain (DOMINO - Derivation of OMI tropospheric NO2) product. Instead, the operational OMI O2 - O2 cloud retrieval algorithm is applied both to cloudy and to cloud-free scenes (i.e. clear sky) dominated by the presence of aerosols. This paper describes in detail the complex interplay between the spectral effects of aerosols in the satellite observation and the associated response of the OMI O2 - O2 cloud retrieval algorithm. Then, it evaluates the impact on the accuracy of the tropospheric NO2 retrievals through the computed Air Mass Factor (AMF) with a focus on cloud-free scenes. For that purpose, collocated OMI NO2 and MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua aerosol products are analysed over the strongly industrialized East China area. In addition, aerosol effects on the tropospheric NO2 AMF and the retrieval of OMI cloud parameters are simulated. Both the observation-based and the simulation-based approach demonstrate that the retrieved cloud fraction increases with increasing Aerosol Optical Thickness (AOT), but the magnitude of this increase depends on the aerosol properties and surface albedo. This increase is induced by the additional scattering effects of aerosols which enhance the scene brightness. The decreasing effective cloud pressure with increasing AOT primarily represents the shielding effects of the O2 - O2 column located below the aerosol layers. The study cases show that the aerosol correction based on the implemented OMI cloud model results in biases
Accurate radiative transfer calculations for layered media.
Selden, Adrian C
2016-07-01
Simple yet accurate results for radiative transfer in layered media with discontinuous refractive index are obtained by the method of K-integrals. These are certain weighted integrals applied to the angular intensity distribution at the refracting boundaries. The radiative intensity is expressed as the sum of the asymptotic angular intensity distribution valid in the depth of the scattering medium and a transient term valid near the boundary. Integrated boundary equations are obtained, yielding simple linear equations for the intensity coefficients, enabling the angular emission intensity and the diffuse reflectance (albedo) and transmittance of the scattering layer to be calculated without solving the radiative transfer equation directly. Examples are given of half-space, slab, interface, and double-layer calculations, and extensions to multilayer systems are indicated. The K-integral method is orders of magnitude more accurate than diffusion theory and can be applied to layered scattering media with a wide range of scattering albedos, with potential applications to biomedical and ocean optics. PMID:27409700
Accurate basis set truncation for wavefunction embedding
Barnes, Taylor A.; Goodpaster, Jason D.; Manby, Frederick R.; Miller, Thomas F.
2013-07-01
Density functional theory (DFT) provides a formally exact framework for performing embedded subsystem electronic structure calculations, including DFT-in-DFT and wavefunction theory-in-DFT descriptions. In the interest of efficiency, it is desirable to truncate the atomic orbital basis set in which the subsystem calculation is performed, thus avoiding high-order scaling with respect to the size of the MO virtual space. In this study, we extend a recently introduced projection-based embedding method [F. R. Manby, M. Stella, J. D. Goodpaster, and T. F. Miller III, J. Chem. Theory Comput. 8, 2564 (2012)], 10.1021/ct300544e to allow for the systematic and accurate truncation of the embedded subsystem basis set. The approach is applied to both covalently and non-covalently bound test cases, including water clusters and polypeptide chains, and it is demonstrated that errors associated with basis set truncation are controllable to well within chemical accuracy. Furthermore, we show that this approach allows for switching between accurate projection-based embedding and DFT embedding with approximate kinetic energy (KE) functionals; in this sense, the approach provides a means of systematically improving upon the use of approximate KE functionals in DFT embedding.
Accurate pattern registration for integrated circuit tomography
Energy Technology Data Exchange (ETDEWEB)
Levine, Zachary H.; Grantham, Steven; Neogi, Suneeta; Frigo, Sean P.; McNulty, Ian; Retsch, Cornelia C.; Wang, Yuxin; Lucatorto, Thomas B.
2001-07-15
As part of an effort to develop high resolution microtomography for engineered structures, a two-level copper integrated circuit interconnect was imaged using 1.83 keV x rays at 14 angles employing a full-field Fresnel zone plate microscope. A major requirement for high resolution microtomography is the accurate registration of the reference axes in each of the many views needed for a reconstruction. A reconstruction with 100 nm resolution would require registration accuracy of 30 nm or better. This work demonstrates that even images that have strong interference fringes can be used to obtain accurate fiducials through the use of Radon transforms. We show that we are able to locate the coordinates of the rectilinear circuit patterns to 28 nm. The procedure is validated by agreement between an x-ray parallax measurement of 1.41{+-}0.17 {mu}m and a measurement of 1.58{+-}0.08 {mu}m from a scanning electron microscope image of a cross section.
Directory of Open Access Journals (Sweden)
F. Løvholt
2013-06-01
Full Text Available Tsunamis induced by rock slides plunging into fjords constitute a severe threat to local coastal communities. The rock slide impact may give rise to highly non-linear waves in the near field, and because the wave lengths are relatively short, frequency dispersion comes into play. Fjord systems are rugged with steep slopes, and modeling non-linear dispersive waves in this environment with simultaneous run-up is demanding. We have run an operational Boussinesq-type TVD (total variation diminishing model using different run-up formulations. Two different tests are considered, inundation on steep slopes and propagation in a trapezoidal channel. In addition, a set of Lagrangian models serves as reference models. Demanding test cases with solitary waves with amplitudes ranging from 0.1 to 0.5 were applied, and slopes were ranging from 10 to 50°. Different run-up formulations yielded clearly different accuracy and stability, and only some provided similar accuracy as the reference models. The test cases revealed that the model was prone to instabilities for large non-linearity and fine resolution. Some of the instabilities were linked with false breaking during the first positive inundation, which was not observed for the reference models. None of the models were able to handle the bore forming during drawdown, however. The instabilities are linked to short-crested undulations on the grid scale, and appear on fine resolution during inundation. As a consequence, convergence was not always obtained. It is reason to believe that the instability may be a general problem for Boussinesq models in fjords.
Energy Technology Data Exchange (ETDEWEB)
Puckett, Elbridge Gerry [U.C. Davis, Department of Mathematics; Miller, Gregory Hale [.C. Davis, Department of Chemical Engineering
2012-10-14
published by Dr. Phillip Colella, the head of ANAG, and some of his colleagues. Chris Algieri is now employed as a staff member in Dr. Bill Collins' Climate Science Department in the Earth Sciences Division at LBNL working with computational models of climate change. Finally, it should be noted that the work conducted by Professor Puckett and his students Sarah Williams and Chris Algieri and described in this final report for DOE grant # DE-FC02-03ER25579 is closely related to work performed by Professor Puckett and his students under the auspices of Professor Puckett's DOE SciDAC grant DE-FC02-01ER25473 An Algorithmic and Software Framework for Applied Partial Differential Equations: A DOE SciDAC Integrated Software Infrastructure Center (ISIC). Dr. Colella was the lead PI for this SciDAC grant, which was comprised of several research groups from DOE national laboratories and five university PI's from five different universities. In theory Professor Puckett tried to use funds from the SciDAC grant to support work directly involved in implementing algorithms developed by members of his research group at UCD as software that might be of use to Puckett's SciDAC CoPIs. (For example, see the work reported in Section 2.2.2 of this final report.) However, since there is considerable lead time spent developing such algorithms before they are ready to become `software' and research plans and goals change as the research progresses, Professor Puckett supported each member of his research group partially with funds from the SciDAC APDEC ISIC DE-FC02-01ER25473 and partially with funds from this DOE MICS grant DE-FC02-03ER25579. This has necessarily resulted in a significant overlap of project areas that were funded by both grants. In particular, both Sarah Williams and Chris Algieri were supported partially with funds from grant # DE-FG02-03ER25579, for which this is the final report, and in part with funds from Professor Puckett's DOE SciDAC grant # DE
Accurate guitar tuning by cochlear implant musicians.
Lu, Thomas; Huang, Juan; Zeng, Fan-Gang
2014-01-01
Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081
How accurate are SuperCOSMOS positions?
Schaefer, Adam; Johnston, Helen
2014-01-01
Optical positions from the SuperCOSMOS Sky Survey have been compared in detail with accurate radio positions that define the second realisation of the International Celestial Reference Frame (ICRF2). The comparison was limited to the IIIaJ plates from the UK/AAO and Oschin (Palomar) Schmidt telescopes. A total of 1373 ICRF2 sources was used, with the sample restricted to stellar objects brighter than $B_J=20$ and Galactic latitudes $|b|>10^{\\circ}$. Position differences showed an rms scatter of $0.16''$ in right ascension and declination. While overall systematic offsets were $<0.1''$ in each hemisphere, both the systematics and scatter were greater in the north.
Accurate Telescope Mount Positioning with MEMS Accelerometers
Mészáros, László; Pál, András; Csépány, Gergely
2014-01-01
This paper describes the advantages and challenges of applying microelectromechanical accelerometer systems (MEMS accelerometers) in order to attain precise, accurate and stateless positioning of telescope mounts. This provides a completely independent method from other forms of electronic, optical, mechanical or magnetic feedback or real-time astrometry. Our goal is to reach the sub-arcminute range which is well smaller than the field-of-view of conventional imaging telescope systems. Here we present how this sub-arcminute accuracy can be achieved with very cheap MEMS sensors and we also detail how our procedures can be extended in order to attain even finer measurements. In addition, our paper discusses how can a complete system design be implemented in order to be a part of a telescope control system.
A robust and accurate formulation of molecular and colloidal electrostatics
Sun, Qiang; Klaseboer, Evert; Chan, Derek Y. C.
2016-08-01
This paper presents a re-formulation of the boundary integral method for the Debye-Hückel model of molecular and colloidal electrostatics that removes the mathematical singularities that have to date been accepted as an intrinsic part of the conventional boundary integral equation method. The essence of the present boundary regularized integral equation formulation consists of subtracting a known solution from the conventional boundary integral method in such a way as to cancel out the singularities associated with the Green's function. This approach better reflects the non-singular physical behavior of the systems on boundaries with the benefits of the following: (i) the surface integrals can be evaluated accurately using quadrature without any need to devise special numerical integration procedures, (ii) being able to use quadratic or spline function surface elements to represent the surface more accurately and the variation of the functions within each element is represented to a consistent level of precision by appropriate interpolation functions, (iii) being able to calculate electric fields, even at boundaries, accurately and directly from the potential without having to solve hypersingular integral equations and this imparts high precision in calculating the Maxwell stress tensor and consequently, intermolecular or colloidal forces, (iv) a reliable way to handle geometric configurations in which different parts of the boundary can be very close together without being affected by numerical instabilities, therefore potentials, fields, and forces between surfaces can be found accurately at surface separations down to near contact, and (v) having the simplicity of a formulation that does not require complex algorithms to handle singularities will result in significant savings in coding effort and in the reduction of opportunities for coding errors. These advantages are illustrated using examples drawn from molecular and colloidal electrostatics.
D-BRAIN: Anatomically Accurate Simulated Diffusion MRI Brain Data.
Perrone, Daniele; Jeurissen, Ben; Aelterman, Jan; Roine, Timo; Sijbers, Jan; Pizurica, Aleksandra; Leemans, Alexander; Philips, Wilfried
2016-01-01
Diffusion Weighted (DW) MRI allows for the non-invasive study of water diffusion inside living tissues. As such, it is useful for the investigation of human brain white matter (WM) connectivity in vivo through fiber tractography (FT) algorithms. Many DW-MRI tailored restoration techniques and FT algorithms have been developed. However, it is not clear how accurately these methods reproduce the WM bundle characteristics in real-world conditions, such as in the presence of noise, partial volume effect, and a limited spatial and angular resolution. The difficulty lies in the lack of a realistic brain phantom on the one hand, and a sufficiently accurate way of modeling the acquisition-related degradation on the other. This paper proposes a software phantom that approximates a human brain to a high degree of realism and that can incorporate complex brain-like structural features. We refer to it as a Diffusion BRAIN (D-BRAIN) phantom. Also, we propose an accurate model of a (DW) MRI acquisition protocol to allow for validation of methods in realistic conditions with data imperfections. The phantom model simulates anatomical and diffusion properties for multiple brain tissue components, and can serve as a ground-truth to evaluate FT algorithms, among others. The simulation of the acquisition process allows one to include noise, partial volume effects, and limited spatial and angular resolution in the images. In this way, the effect of image artifacts on, for instance, fiber tractography can be investigated with great detail. The proposed framework enables reliable and quantitative evaluation of DW-MR image processing and FT algorithms at the level of large-scale WM structures. The effect of noise levels and other data characteristics on cortico-cortical connectivity and tractography-based grey matter parcellation can be investigated as well. PMID:26930054
International Nuclear Information System (INIS)
Atmospheric transport of air pollutants is, in principle, a well understood process. If information about the state of the atmosphere is given in all details (infinitely accurate information about wind speed, etc.) and infinitely fast computers are available then the advection equation could in principle be solved exactly. This is, however, not the case: discretization of the equations and input data introduces some uncertainties and errors in the results. Therefore many different issues have to be carefully studied in order to diminish these uncertainties and to develop an accurate transport model. Some of these are e.g. the numerical treatment of the transport equation, accuracy of the mean meteorological input fields and parameterizations of sub-grid scale phenomena (as e.g. parameterizations of the 2 nd and higher order turbulence terms in order to reach closure in the perturbation equation). A tracer model for studying transport and dispersion of air pollution caused by a single but strong source is under development. The model simulations from the first ETEX release illustrate the differences caused by using various analyzed fields directly in the tracer model or using a meteorological driver. Also different parameterizations of the mixing height and the vertical exchange are compared. (author)
Calibration Techniques for Accurate Measurements by Underwater Camera Systems.
Shortis, Mark
2015-12-07
Calibration of a camera system is essential to ensure that image measurements result in accurate estimates of locations and dimensions within the object space. In the underwater environment, the calibration must implicitly or explicitly model and compensate for the refractive effects of waterproof housings and the water medium. This paper reviews the different approaches to the calibration of underwater camera systems in theoretical and practical terms. The accuracy, reliability, validation and stability of underwater camera system calibration are also discussed. Samples of results from published reports are provided to demonstrate the range of possible accuracies for the measurements produced by underwater camera systems.
Zhao, Xiao-mei; Xie, Dong-fan; Li, Qi
2015-02-01
With the development of intelligent transport system, advanced information feedback strategies have been developed to reduce traffic congestion and enhance the capacity. However, previous strategies provide accurate information to travelers and our simulation results show that accurate information brings negative effects, especially in delay case. Because travelers prefer to the best condition route with accurate information, and delayed information cannot reflect current traffic condition but past. Then travelers make wrong routing decisions, causing the decrease of the capacity and the increase of oscillations and the system deviating from the equilibrium. To avoid the negative effect, bounded rationality is taken into account by introducing a boundedly rational threshold BR. When difference between two routes is less than the BR, routes have equal probability to be chosen. The bounded rationality is helpful to improve the efficiency in terms of capacity, oscillation and the gap deviating from the system equilibrium.
Accurate Modeling of X-ray Extinction by Interstellar Grains
Hoffman, John; Draine, B. T.
2016-02-01
Interstellar abundance determinations from fits to X-ray absorption edges often rely on the incorrect assumption that scattering is insignificant and can be ignored. We show instead that scattering contributes significantly to the attenuation of X-rays for realistic dust grain size distributions and substantially modifies the spectrum near absorption edges of elements present in grains. The dust attenuation modules used in major X-ray spectral fitting programs do not take this into account. We show that the consequences of neglecting scattering on the determination of interstellar elemental abundances are modest; however, scattering (along with uncertainties in the grain size distribution) must be taken into account when near-edge extinction fine structure is used to infer dust mineralogy. We advertise the benefits and accuracy of anomalous diffraction theory for both X-ray halo analysis and near edge absorption studies. We present an open source Fortran suite, General Geometry Anomalous Diffraction Theory (GGADT), that calculates X-ray absorption, scattering, and differential scattering cross sections for grains of arbitrary geometry and composition.
Leidenfrost effect: Accurate drop shape modeling and refined scaling laws.
Sobac, B; Rednikov, A; Dorbolo, S; Colinet, P
2014-11-01
We here present a simple fitting-parameter-free theory of the Leidenfrost effect (droplet levitation above a superheated plate) covering the full range of stable shapes, i.e., from small quasispherical droplets to larger puddles floating on a pocketlike vapor film. The geometry of this film is found to be in excellent quantitative agreement with the interferometric measurements of Burton et al. [Phys. Rev. Lett. 109, 074301 (2012)PRLTAO0031-900710.1103/PhysRevLett.109.074301]. We also obtain new scalings generalizing classical ones derived by Biance et al. [Phys. Fluids 15, 1632 (2003)PHFLE61070-663110.1063/1.1572161] as far as the effect of plate superheat is concerned and highlight the relative role of evaporation, gravity, and capillarity in the vapor film. To further substantiate these findings, a treatment of the problem by matched asymptotic expansions is also presented. PMID:25493885
Accurate and stable time stepping in ice sheet modeling
Cheng, Gong; von Sydow, Lina
2016-01-01
In this paper we introduce adaptive time step control for simulation of evolution of ice sheets. The discretization error in the approximations is estimated using "Milne's device" by comparing the result from two different methods in a predictor-corrector pair. Using a predictor-corrector pair the expensive part of the procedure, the solution of the velocity and pressure equations, is performed only once per time step and an estimate of the local error is easily obtained. The stability of the numerical solution is maintained and the accuracy is controlled by keeping the local error below a given threshold using PI-control. Depending on the threshold, the time step $\\Delta t$ is bound by stability requirements or accuracy requirements. Our method takes a shorter $\\Delta t$ than an implicit method but with less work in each time step and the solver is simpler. The method is analyzed theoretically with respect to stability and applied to the simulation of a 2D ice slab and a 3D circular ice sheet. %The automatic...
Accurate Antenna Models in Ground Penetrating Radar Diffraction Tomography
DEFF Research Database (Denmark)
Meincke, Peter; Kim, Oleksiy S.
2002-01-01
Linear inversion schemes based on the concept of diffraction tomography have proven successful for ground penetrating radar (GPR) imaging. In many GPR surveys, the antennas of the GPR are located close to the air-soil interface and, therefore, it is important to incorporate the presence of this i......Linear inversion schemes based on the concept of diffraction tomography have proven successful for ground penetrating radar (GPR) imaging. In many GPR surveys, the antennas of the GPR are located close to the air-soil interface and, therefore, it is important to incorporate the presence...
Accurate Sliding-Mode Control System Modeling for Buck Converters
DEFF Research Database (Denmark)
Høyerby, Mikkel Christian Wendelboe; Andersen, Michael Andreas E.
2007-01-01
This paper shows that classical sliding mode theory fails to correctly predict the output impedance of the highly useful sliding mode PID compensated buck converter. The reason for this is identified as the assumption of the sliding variable being held at zero during sliding mode, effectively...... approach also predicts the self-oscillating switching action of the sliding-mode control system correctly. Analytical findings are verified by simulation as well as experimentally in a 10-30V/3A buck converter....
The FLUKA Code: An Accurate Simulation Tool for Particle Therapy.
Battistoni, Giuseppe; Bauer, Julia; Boehlen, Till T; Cerutti, Francesco; Chin, Mary P W; Dos Santos Augusto, Ricardo; Ferrari, Alfredo; Ortega, Pablo G; Kozłowska, Wioletta; Magro, Giuseppe; Mairani, Andrea; Parodi, Katia; Sala, Paola R; Schoofs, Philippe; Tessonnier, Thomas; Vlachoudis, Vasilis
2016-01-01
Monte Carlo (MC) codes are increasingly spreading in the hadrontherapy community due to their detailed description of radiation transport and interaction with matter. The suitability of a MC code for application to hadrontherapy demands accurate and reliable physical models capable of handling all components of the expected radiation field. This becomes extremely important for correctly performing not only physical but also biologically based dose calculations, especially in cases where ions heavier than protons are involved. In addition, accurate prediction of emerging secondary radiation is of utmost importance in innovative areas of research aiming at in vivo treatment verification. This contribution will address the recent developments of the FLUKA MC code and its practical applications in this field. Refinements of the FLUKA nuclear models in the therapeutic energy interval lead to an improved description of the mixed radiation field as shown in the presented benchmarks against experimental data with both (4)He and (12)C ion beams. Accurate description of ionization energy losses and of particle scattering and interactions lead to the excellent agreement of calculated depth-dose profiles with those measured at leading European hadron therapy centers, both with proton and ion beams. In order to support the application of FLUKA in hospital-based environments, Flair, the FLUKA graphical interface, has been enhanced with the capability of translating CT DICOM images into voxel-based computational phantoms in a fast and well-structured way. The interface is capable of importing also radiotherapy treatment data described in DICOM RT standard. In addition, the interface is equipped with an intuitive PET scanner geometry generator and automatic recording of coincidence events. Clinically, similar cases will be presented both in terms of absorbed dose and biological dose calculations describing the various available features. PMID:27242956
Accurate free energy calculation along optimized paths.
Chen, Changjun; Xiao, Yi
2010-05-01
The path-based methods of free energy calculation, such as thermodynamic integration and free energy perturbation, are simple in theory, but difficult in practice because in most cases smooth paths do not exist, especially for large molecules. In this article, we present a novel method to build the transition path of a peptide. We use harmonic potentials to restrain its nonhydrogen atom dihedrals in the initial state and set the equilibrium angles of the potentials as those in the final state. Through a series of steps of geometrical optimization, we can construct a smooth and short path from the initial state to the final state. This path can be used to calculate free energy difference. To validate this method, we apply it to a small 10-ALA peptide and find that the calculated free energy changes in helix-helix and helix-hairpin transitions are both self-convergent and cross-convergent. We also calculate the free energy differences between different stable states of beta-hairpin trpzip2, and the results show that this method is more efficient than the conventional molecular dynamics method in accurate free energy calculation.
Accurate fission data for nuclear safety
Solders, A; Jokinen, A; Kolhinen, V S; Lantz, M; Mattera, A; Penttila, H; Pomp, S; Rakopoulos, V; Rinta-Antila, S
2013-01-01
The Accurate fission data for nuclear safety (AlFONS) project aims at high precision measurements of fission yields, using the renewed IGISOL mass separator facility in combination with a new high current light ion cyclotron at the University of Jyvaskyla. The 30 MeV proton beam will be used to create fast and thermal neutron spectra for the study of neutron induced fission yields. Thanks to a series of mass separating elements, culminating with the JYFLTRAP Penning trap, it is possible to achieve a mass resolving power in the order of a few hundred thousands. In this paper we present the experimental setup and the design of a neutron converter target for IGISOL. The goal is to have a flexible design. For studies of exotic nuclei far from stability a high neutron flux (10^12 neutrons/s) at energies 1 - 30 MeV is desired while for reactor applications neutron spectra that resembles those of thermal and fast nuclear reactors are preferred. It is also desirable to be able to produce (semi-)monoenergetic neutrons...
Fast and Provably Accurate Bilateral Filtering.
Chaudhury, Kunal N; Dabhade, Swapnil D
2016-06-01
The bilateral filter is a non-linear filter that uses a range filter along with a spatial filter to perform edge-preserving smoothing of images. A direct computation of the bilateral filter requires O(S) operations per pixel, where S is the size of the support of the spatial filter. In this paper, we present a fast and provably accurate algorithm for approximating the bilateral filter when the range kernel is Gaussian. In particular, for box and Gaussian spatial filters, the proposed algorithm can cut down the complexity to O(1) per pixel for any arbitrary S . The algorithm has a simple implementation involving N+1 spatial filterings, where N is the approximation order. We give a detailed analysis of the filtering accuracy that can be achieved by the proposed approximation in relation to the target bilateral filter. This allows us to estimate the order N required to obtain a given accuracy. We also present comprehensive numerical results to demonstrate that the proposed algorithm is competitive with the state-of-the-art methods in terms of speed and accuracy. PMID:27093722
An accurate bound on tensor-to-scalar ratio and the scale of inflation
Choudhury, Sayantan
2014-01-01
In this paper we provide an accurate bound on tensor-to-scalar ratio (r) for class of models where inflation always occurs below the Planck scale, and the field displacement during inflation remains sub-Planckian.
Machine learning of parameters for accurate semiempirical quantum chemical calculations
International Nuclear Information System (INIS)
We investigate possible improvements in the accuracy of semiempirical quantum chemistry (SQC) methods through the use of machine learning (ML) models for the parameters. For a given class of compounds, ML techniques require sufficiently large training sets to develop ML models that can be used for adapting SQC parameters to reflect changes in molecular composition and geometry. The ML-SQC approach allows the automatic tuning of SQC parameters for individual molecules, thereby improving the accuracy without deteriorating transferability to molecules with molecular descriptors very different from those in the training set. The performance of this approach is demonstrated for the semiempirical OM2 method using a set of 6095 constitutional isomers C7H10O2, for which accurate ab initio atomization enthalpies are available. The ML-OM2 results show improved average accuracy and a much reduced error range compared with those of standard OM2 results, with mean absolute errors in atomization enthalpies dropping from 6.3 to 1.7 kcal/mol. They are also found to be superior to the results from specific OM2 reparameterizations (rOM2) for the same set of isomers. The ML-SQC approach thus holds promise for fast and reasonably accurate high-throughput screening of materials and molecules
Accurate 3D quantification of the bronchial parameters in MDCT
Saragaglia, A.; Fetita, C.; Preteux, F.; Brillet, P. Y.; Grenier, P. A.
2005-08-01
The assessment of bronchial reactivity and wall remodeling in asthma plays a crucial role in better understanding such a disease and evaluating therapeutic responses. Today, multi-detector computed tomography (MDCT) makes it possible to perform an accurate estimation of bronchial parameters (lumen and wall areas) by allowing a quantitative analysis in a cross-section plane orthogonal to the bronchus axis. This paper provides the tools for such an analysis by developing a 3D investigation method which relies on 3D reconstruction of bronchial lumen and central axis computation. Cross-section images at bronchial locations interactively selected along the central axis are generated at appropriate spatial resolution. An automated approach is then developed for accurately segmenting the inner and outer bronchi contours on the cross-section images. It combines mathematical morphology operators, such as "connection cost", and energy-controlled propagation in order to overcome the difficulties raised by vessel adjacencies and wall irregularities. The segmentation accuracy was validated with respect to a 3D mathematically-modeled phantom of a pair bronchus-vessel which mimics the characteristics of real data in terms of gray-level distribution, caliber and orientation. When applying the developed quantification approach to such a model with calibers ranging from 3 to 10 mm diameter, the lumen area relative errors varied from 3.7% to 0.15%, while the bronchus area was estimated with a relative error less than 5.1%.
Towards Accurate Application Characterization for Exascale (APEX)
Energy Technology Data Exchange (ETDEWEB)
Hammond, Simon David [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2015-09-01
Sandia National Laboratories has been engaged in hardware and software codesign activities for a number of years, indeed, it might be argued that prototyping of clusters as far back as the CPLANT machines and many large capability resources including ASCI Red and RedStorm were examples of codesigned solutions. As the research supporting our codesign activities has moved closer to investigating on-node runtime behavior a nature hunger has grown for detailed analysis of both hardware and algorithm performance from the perspective of low-level operations. The Application Characterization for Exascale (APEX) LDRD was a project concieved of addressing some of these concerns. Primarily the research was to intended to focus on generating accurate and reproducible low-level performance metrics using tools that could scale to production-class code bases. Along side this research was an advocacy and analysis role associated with evaluating tools for production use, working with leading industry vendors to develop and refine solutions required by our code teams and to directly engage with production code developers to form a context for the application analysis and a bridge to the research community within Sandia. On each of these accounts significant progress has been made, particularly, as this report will cover, in the low-level analysis of operations for important classes of algorithms. This report summarizes the development of a collection of tools under the APEX research program and leaves to other SAND and L2 milestone reports the description of codesign progress with Sandia’s production users/developers.
Accurate hydrocarbon estimates attained with radioactive isotope
International Nuclear Information System (INIS)
To make accurate economic evaluations of new discoveries, an oil company needs to know how much gas and oil a reservoir contains. The porous rocks of these reservoirs are not completely filled with gas or oil, but contain a mixture of gas, oil and water. It is extremely important to know what volume percentage of this water--called connate water--is contained in the reservoir rock. The percentage of connate water can be calculated from electrical resistivity measurements made downhole. The accuracy of this method can be improved if a pure sample of connate water can be analyzed or if the chemistry of the water can be determined by conventional logging methods. Because of the similarity of the mud filtrate--the water in a water-based drilling fluid--and the connate water, this is not always possible. If the oil company cannot distinguish between connate water and mud filtrate, its oil-in-place calculations could be incorrect by ten percent or more. It is clear that unless an oil company can be sure that a sample of connate water is pure, or at the very least knows exactly how much mud filtrate it contains, its assessment of the reservoir's water content--and consequently its oil or gas content--will be distorted. The oil companies have opted for the Repeat Formation Tester (RFT) method. Label the drilling fluid with small doses of tritium--a radioactive isotope of hydrogen--and it will be easy to detect and quantify in the sample
How flatbed scanners upset accurate film dosimetry.
van Battum, L J; Huizenga, H; Verdaasdonk, R M; Heukelom, S
2016-01-21
Film is an excellent dosimeter for verification of dose distributions due to its high spatial resolution. Irradiated film can be digitized with low-cost, transmission, flatbed scanners. However, a disadvantage is their lateral scan effect (LSE): a scanner readout change over its lateral scan axis. Although anisotropic light scattering was presented as the origin of the LSE, this paper presents an alternative cause. Hereto, LSE for two flatbed scanners (Epson 1680 Expression Pro and Epson 10000XL), and Gafchromic film (EBT, EBT2, EBT3) was investigated, focused on three effects: cross talk, optical path length and polarization. Cross talk was examined using triangular sheets of various optical densities. The optical path length effect was studied using absorptive and reflective neutral density filters with well-defined optical characteristics (OD range 0.2-2.0). Linear polarizer sheets were used to investigate light polarization on the CCD signal in absence and presence of (un)irradiated Gafchromic film. Film dose values ranged between 0.2 to 9 Gy, i.e. an optical density range between 0.25 to 1.1. Measurements were performed in the scanner's transmission mode, with red-green-blue channels. LSE was found to depend on scanner construction and film type. Its magnitude depends on dose: for 9 Gy increasing up to 14% at maximum lateral position. Cross talk was only significant in high contrast regions, up to 2% for very small fields. The optical path length effect introduced by film on the scanner causes 3% for pixels in the extreme lateral position. Light polarization due to film and the scanner's optical mirror system is the main contributor, different in magnitude for the red, green and blue channel. We concluded that any Gafchromic EBT type film scanned with a flatbed scanner will face these optical effects. Accurate dosimetry requires correction of LSE, therefore, determination of the LSE per color channel and dose delivered to the film.
Accurate object tracking system by integrating texture and depth cues
Chen, Ju-Chin; Lin, Yu-Hang
2016-03-01
A robust object tracking system that is invariant to object appearance variations and background clutter is proposed. Multiple instance learning with a boosting algorithm is applied to select discriminant texture information between the object and background data. Additionally, depth information, which is important to distinguish the object from a complicated background, is integrated. We propose two depth-based models that can compensate texture information to cope with both appearance variants and background clutter. Moreover, in order to reduce the risk of drifting problem increased for the textureless depth templates, an update mechanism is proposed to select more precise tracking results to avoid incorrect model updates. In the experiments, the robustness of the proposed system is evaluated and quantitative results are provided for performance analysis. Experimental results show that the proposed system can provide the best success rate and has more accurate tracking results than other well-known algorithms.
Interactive Isogeometric Volume Visualization with Pixel-Accurate Geometry.
Fuchs, Franz G; Hjelmervik, Jon M
2016-02-01
A recent development, called isogeometric analysis, provides a unified approach for design, analysis and optimization of functional products in industry. Traditional volume rendering methods for inspecting the results from the numerical simulations cannot be applied directly to isogeometric models. We present a novel approach for interactive visualization of isogeometric analysis results, ensuring correct, i.e., pixel-accurate geometry of the volume including its bounding surfaces. The entire OpenGL pipeline is used in a multi-stage algorithm leveraging techniques from surface rendering, order-independent transparency, as well as theory and numerical methods for ordinary differential equations. We showcase the efficiency of our approach on different models relevant to industry, ranging from quality inspection of the parametrization of the geometry, to stress analysis in linear elasticity, to visualization of computational fluid dynamics results.
Accurate mass measurements on neutron-deficient krypton isotopes
Rodríguez, D; Äystö, J; Beck, D
2006-01-01
The masses of $^{72–78,80,82,86}$Kr were measured directly with the ISOLTRAP Penning trap mass spectrometer at ISOLDE/CERN. For all these nuclides, the measurements yielded mass uncertainties below 10 keV. The ISOLTRAP mass values for $^{72–75}$Kr being more precise than the previous results obtained by means of other techniques, and thus completely determine the new values in the Atomic-Mass Evaluation. Besides the interest of these masses for nuclear astrophysics, nuclear structure studies, and Standard Model tests, these results constitute a valuable and accurate input to improve mass models. In this paper, we present the mass measurements and discuss the mass evaluation for these Kr isotopes.
Fast and Accurate Construction of Confidence Intervals for Heritability.
Schweiger, Regev; Kaufman, Shachar; Laaksonen, Reijo; Kleber, Marcus E; März, Winfried; Eskin, Eleazar; Rosset, Saharon; Halperin, Eran
2016-06-01
Estimation of heritability is fundamental in genetic studies. Recently, heritability estimation using linear mixed models (LMMs) has gained popularity because these estimates can be obtained from unrelated individuals collected in genome-wide association studies. Typically, heritability estimation under LMMs uses the restricted maximum likelihood (REML) approach. Existing methods for the construction of confidence intervals and estimators of SEs for REML rely on asymptotic properties. However, these assumptions are often violated because of the bounded parameter space, statistical dependencies, and limited sample size, leading to biased estimates and inflated or deflated confidence intervals. Here, we show that the estimation of confidence intervals by state-of-the-art methods is inaccurate, especially when the true heritability is relatively low or relatively high. We further show that these inaccuracies occur in datasets including thousands of individuals. Such biases are present, for example, in estimates of heritability of gene expression in the Genotype-Tissue Expression project and of lipid profiles in the Ludwigshafen Risk and Cardiovascular Health study. We also show that often the probability that the genetic component is estimated as 0 is high even when the true heritability is bounded away from 0, emphasizing the need for accurate confidence intervals. We propose a computationally efficient method, ALBI (accurate LMM-based heritability bootstrap confidence intervals), for estimating the distribution of the heritability estimator and for constructing accurate confidence intervals. Our method can be used as an add-on to existing methods for estimating heritability and variance components, such as GCTA, FaST-LMM, GEMMA, or EMMAX. PMID:27259052
Accurate LAI retrieval method based on PROBA/CHRIS data
Directory of Open Access Journals (Sweden)
W. Fan
2009-11-01
Full Text Available Leaf area index (LAI is one of the key structural variables in terrestrial vegetation ecosystems. Remote sensing offers a chance to derive LAI in regional scales accurately. Variations of background, atmospheric conditions and the anisotropy of canopy reflectance are three factors that can strongly restrain the accuracy of retrieved LAI. Based on the hybrid canopy reflectance model, a new hyperspectral directional second derivative method (DSD is proposed in this paper. This method can estimate LAI accurately through analyzing the canopy anisotropy. The effect of the background can also be effectively removed. So the inversion precision and the dynamic range can be improved remarkably, which has been proved by numerical simulations. As the derivative method is very sensitive to the random noise, we put forward an innovative filtering approach, by which the data can be de-noised in spectral and spatial dimensions synchronously. It shows that the filtering method can remove the random noise effectively; therefore, the method can be performed to the remotely sensed hyperspectral image. The study region is situated in Zhangye, Gansu Province, China; the hyperspectral and multi-angular image of the study region has been acquired from Compact High-Resolution Imaging Spectrometer/Project for On-Board Autonomy (CHRIS/PROBA, on 4 and 14 June 2008. After the pre-processing procedures, the DSD method was applied, and the retrieve LAI was validated by the ground truth of 11 sites. It shows that by applying innovative filtering method, the new LAI inversion method is accurate and effective.
Accurate measurement of streamwise vortices using dual-plane PIV
Energy Technology Data Exchange (ETDEWEB)
Waldman, Rye M.; Breuer, Kenneth S. [Brown University, School of Engineering, Providence, RI (United States)
2012-11-15
Low Reynolds number aerodynamic experiments with flapping animals (such as bats and small birds) are of particular interest due to their application to micro air vehicles which operate in a similar parameter space. Previous PIV wake measurements described the structures left by bats and birds and provided insight into the time history of their aerodynamic force generation; however, these studies have faced difficulty drawing quantitative conclusions based on said measurements. The highly three-dimensional and unsteady nature of the flows associated with flapping flight are major challenges for accurate measurements. The challenge of animal flight measurements is finding small flow features in a large field of view at high speed with limited laser energy and camera resolution. Cross-stream measurement is further complicated by the predominately out-of-plane flow that requires thick laser sheets and short inter-frame times, which increase noise and measurement uncertainty. Choosing appropriate experimental parameters requires compromise between the spatial and temporal resolution and the dynamic range of the measurement. To explore these challenges, we do a case study on the wake of a fixed wing. The fixed model simplifies the experiment and allows direct measurements of the aerodynamic forces via load cell. We present a detailed analysis of the wake measurements, discuss the criteria for making accurate measurements, and present a solution for making quantitative aerodynamic load measurements behind free-flyers. (orig.)
Accurate Robot Simulation Through System Identification
Kyriacou, T; Nehmzow, U.; Inglesias, R.; Billings, S. A.
2008-01-01
Robot simulators are useful tools for developing robot behaviours. They provide a fast and efficient means to test robot control code at the convenience of the office desk. In all but the simplest cases though, due to the complexities of the physical systems modelled in the simulator, there are considerable differences between the behaviour of the robot in the simulator and that in the real world environment. In this paper we present a novel method to create a robot simulator using real...
Building Accurate 3D Spatial Networks to Enable Next Generation Intelligent Transportation Systems
DEFF Research Database (Denmark)
Kaul, Manohar; Yang, Bin; Jensen, Christian S.
2013-01-01
model with elevation information extracted from massive aerial laser scan data and thus yields an accurate 3D model. We present a filtering technique that is capable of pruning irrelevant laser scan points in a single pass, but assumes that the 2D network fits in internal memory and that the points......The use of accurate 3D spatial network models can enable substantial improvements in vehicle routing. Notably, such models enable eco-routing, which reduces the environmental impact of transportation. We propose a novel filtering and lifting framework that augments a standard 2D spatial network...
Are National HFC Inventory Reports Accurate?
Lunt, M. F.; Rigby, M. L.; Ganesan, A.; Manning, A.; O'Doherty, S.; Prinn, R. G.; Saito, T.; Harth, C. M.; Muhle, J.; Weiss, R. F.; Salameh, P.; Arnold, T.; Yokouchi, Y.; Krummel, P. B.; Steele, P.; Fraser, P. J.; Li, S.; Park, S.; Kim, J.; Reimann, S.; Vollmer, M. K.; Lunder, C. R.; Hermansen, O.; Schmidbauer, N.; Young, D.; Simmonds, P. G.
2014-12-01
Hydrofluorocarbons (HFCs) were introduced as replacements for ozone depleting chlorinated gases due to their negligible ozone depletion potential. As a result, these potent greenhouse gases are now rapidly increasing in atmospheric mole fraction. However, at present, less than 50% of HFC emissions, as inferred from models combined with atmospheric measurements (top-down methods), can be accounted for by the annual national reports to the United Nations Framework Convention on Climate Change (UNFCCC). There are at least two possible reasons for the discrepancy. Firstly, significant emissions could be originating from countries not required to report to the UNFCCC ("non-Annex 1" countries). Secondly, emissions reports themselves may be subject to inaccuracies. For example the HFC emission factors used in the 'bottom-up' calculation of emissions tend to be technology-specific (refrigeration, air conditioning etc.), but not tuned to the properties of individual HFCs. To provide a new top-down perspective, we inferred emissions using high frequency HFC measurements from the Advanced Global Atmospheric Gases Experiment (AGAGE) and the National Institute for Environmental Studies (NIES) networks. Global and regional emissions information was inferred from these measurements using a coupled Eulerian and Lagrangian system, based on NCAR's MOZART model and the UK Met Office NAME model. Uncertainties in this measurement and modelling framework were investigated using a hierarchical Bayesian inverse method. Global and regional emissions estimates for five of the major HFCs (HFC-134a, HFC-125, HFC-143a, HFC-32, HFC-152a) from 2004-2012 are presented. It was found that, when aggregated, the top-down estimates from Annex 1 countries agreed remarkably well with the reported emissions, suggesting the non-Annex 1 emissions make up the difference with the top-down global estimate. However, when these HFC species are viewed individually we find that emissions of HFC-134a are over
Accurate and efficient waveforms for compact binaries on eccentric orbits
Huerta, E A; McWilliams, Sean T; O'Shaughnessy, Richard; Yunes, Nicolas
2014-01-01
Compact binaries that emit gravitational waves in the sensitivity band of ground-based detectors can have non-negligible eccentricities just prior to merger, depending on the formation scenario. We develop a purely analytic, frequency-domain model for gravitational waves emitted by compact binaries on orbits with small eccentricity, which reduces to the quasi-circular post-Newtonian approximant TaylorF2 at zero eccentricity and to the post-circular approximation of Yunes et al. (2009) at small eccentricity. Our model uses a spectral approximation to the (post-Newtonian) Kepler problem to model the orbital phase as a function of frequency, accounting for eccentricity effects up to ${\\cal{O}}(e^8)$ at each post-Newtonian order. Our approach accurately reproduces an alternative time-domain eccentric waveform model for eccentricities $e\\in [0, 0.4]$ and binaries with total mass less than 12 solar masses. As an application, we evaluate the signal amplitude that eccentric binaries produce in different networks of e...
Analytical method to accurately predict LMFBR core flow distribution
International Nuclear Information System (INIS)
An accurate and detailed representation of the flow distribution in LMFBR cores is very important as the starting point and basis of the thermal and structural core design. Previous experience indicated that the steady state and transient core design is as good as the core orificing; thus, a new orificing philosophy satisfying a priori all design constraints was developd. However, optimized orificing is a necessary, but not sufficient condition for achieving the optimum core flow distribution, which is affected by the hydraulic characteristics of the remainder of the primary system. Consequently, an analytical model of the overall primary system was developed, resulting in the CATFISH computer code, which, even though specifically written for LMFBRs, can be used for any reactor employing ducted assemblies
Accurate molecular classification of cancer using simple rules
Directory of Open Access Journals (Sweden)
Gotoh Osamu
2009-10-01
Full Text Available Abstract Background One intractable problem with using microarray data analysis for cancer classification is how to reduce the extremely high-dimensionality gene feature data to remove the effects of noise. Feature selection is often used to address this problem by selecting informative genes from among thousands or tens of thousands of genes. However, most of the existing methods of microarray-based cancer classification utilize too many genes to achieve accurate classification, which often hampers the interpretability of the models. For a better understanding of the classification results, it is desirable to develop simpler rule-based models with as few marker genes as possible. Methods We screened a small number of informative single genes and gene pairs on the basis of their depended degrees proposed in rough sets. Applying the decision rules induced by the selected genes or gene pairs, we constructed cancer classifiers. We tested the efficacy of the classifiers by leave-one-out cross-validation (LOOCV of training sets and classification of independent test sets. Results We applied our methods to five cancerous gene expression datasets: leukemia (acute lymphoblastic leukemia [ALL] vs. acute myeloid leukemia [AML], lung cancer, prostate cancer, breast cancer, and leukemia (ALL vs. mixed-lineage leukemia [MLL] vs. AML. Accurate classification outcomes were obtained by utilizing just one or two genes. Some genes that correlated closely with the pathogenesis of relevant cancers were identified. In terms of both classification performance and algorithm simplicity, our approach outperformed or at least matched existing methods. Conclusion In cancerous gene expression datasets, a small number of genes, even one or two if selected correctly, is capable of achieving an ideal cancer classification effect. This finding also means that very simple rules may perform well for cancerous class prediction.
Energy functions for protein design I: Efficient and accurate continuum electrostatics and solvation
Pokala, Navin; Handel, Tracy M.
2004-01-01
Electrostatics and solvation energies are important for defining protein stability, structural specificity, and molecular recognition. Because these energies are difficult to compute quickly and accurately, they are often ignored or modeled very crudely in computational protein design. To address this problem, we have developed a simple, fast, and accurate approximation for calculating Born radii in the context of protein design calculations. When these approximate Born radii are used with th...
Accurate Segmentation for Infrared Flying Bird Tracking
Institute of Scientific and Technical Information of China (English)
ZHENG Hong; HUANG Ying; LING Haibin; ZOU Qi; YANG Hao
2016-01-01
Bird strikes present a huge risk for air ve-hicles, especially since traditional airport bird surveillance is mainly dependent on ineﬃcient human observation. For improving the effectiveness and eﬃciency of bird monitor-ing, computer vision techniques have been proposed to detect birds, determine bird flying trajectories, and pre-dict aircraft takeoff delays. Flying bird with a huge de-formation causes a great challenge to current tracking al-gorithms. We propose a segmentation based approach to enable tracking can adapt to the varying shape of bird. The approach works by segmenting object at a region of inter-est, where is determined by the object localization method and heuristic edge information. The segmentation is per-formed by Markov random field, which is trained by fore-ground and background mixture Gaussian models. Exper-iments demonstrate that the proposed approach provides the ability to handle large deformations and outperforms the m ost state-of-the-art tracker in the infrared flying bird tracking problem.
Accurate simulation of optical properties in dyes.
Jacquemin, Denis; Perpète, Eric A; Ciofini, Ilaria; Adamo, Carlo
2009-02-17
Since Antiquity, humans have produced and commercialized dyes. To this day, extraction of natural dyes often requires lengthy and costly procedures. In the 19th century, global markets and new industrial products drove a significant effort to synthesize artificial dyes, characterized by low production costs, huge quantities, and new optical properties (colors). Dyes that encompass classes of molecules absorbing in the UV-visible part of the electromagnetic spectrum now have a wider range of applications, including coloring (textiles, food, paintings), energy production (photovoltaic cells, OLEDs), or pharmaceuticals (diagnostics, drugs). Parallel to the growth in dye applications, researchers have increased their efforts to design and synthesize new dyes to customize absorption and emission properties. In particular, dyes containing one or more metallic centers allow for the construction of fairly sophisticated systems capable of selectively reacting to light of a given wavelength and behaving as molecular devices (photochemical molecular devices, PMDs).Theoretical tools able to predict and interpret the excited-state properties of organic and inorganic dyes allow for an efficient screening of photochemical centers. In this Account, we report recent developments defining a quantitative ab initio protocol (based on time-dependent density functional theory) for modeling dye spectral properties. In particular, we discuss the importance of several parameters, such as the methods used for electronic structure calculations, solvent effects, and statistical treatments. In addition, we illustrate the performance of such simulation tools through case studies. We also comment on current weak points of these methods and ways to improve them. PMID:19113946
A numerical study of nonlinear wave run-up on a vertical plate
DEFF Research Database (Denmark)
Jamois, Eric; Fuhrman, David R.; Bingham, Harry;
2006-01-01
A finite difference model based on a recently derived highly-accurate Boussinesq-type formulation is presented. Up to the third-order space derivatives in terms of the velocity variables are retained, and the horizontal velocity variables are re-formulated in terms of a velocity potential....... This decreases the total number of unknowns in two horizontal dimensions from seven to five, simplifying the implementation, and leading to increased computational efficiency. Analysis of the embedded properties demonstrates that the resulting model has applications with errors of 2 to 3% for (wavenumber times...... depth) kh $LSEQ 10 in terms of dispersion and kh $LSEQ 4 in terms of internal kinematics. The stability and accuracy of the discrete linearised systems are also analysed for both potential and velocity formulations and the advantages and disadvantages of each are discussed. The velocity potential model...
Accurate, fully-automated NMR spectral profiling for metabolomics.
Directory of Open Access Journals (Sweden)
Siamak Ravanbakhsh
Full Text Available Many diseases cause significant changes to the concentrations of small molecules (a.k.a. metabolites that appear in a person's biofluids, which means such diseases can often be readily detected from a person's "metabolic profile"-i.e., the list of concentrations of those metabolites. This information can be extracted from a biofluids Nuclear Magnetic Resonance (NMR spectrum. However, due to its complexity, NMR spectral profiling has remained manual, resulting in slow, expensive and error-prone procedures that have hindered clinical and industrial adoption of metabolomics via NMR. This paper presents a system, BAYESIL, which can quickly, accurately, and autonomously produce a person's metabolic profile. Given a 1D 1H NMR spectrum of a complex biofluid (specifically serum or cerebrospinal fluid, BAYESIL can automatically determine the metabolic profile. This requires first performing several spectral processing steps, then matching the resulting spectrum against a reference compound library, which contains the "signatures" of each relevant metabolite. BAYESIL views spectral matching as an inference problem within a probabilistic graphical model that rapidly approximates the most probable metabolic profile. Our extensive studies on a diverse set of complex mixtures including real biological samples (serum and CSF, defined mixtures and realistic computer generated spectra; involving > 50 compounds, show that BAYESIL can autonomously find the concentration of NMR-detectable metabolites accurately (~ 90% correct identification and ~ 10% quantification error, in less than 5 minutes on a single CPU. These results demonstrate that BAYESIL is the first fully-automatic publicly-accessible system that provides quantitative NMR spectral profiling effectively-with an accuracy on these biofluids that meets or exceeds the performance of trained experts. We anticipate this tool will usher in high-throughput metabolomics and enable a wealth of new applications of
Population variability complicates the accurate detection of climate change responses.
McCain, Christy; Szewczyk, Tim; Bracy Knight, Kevin
2016-06-01
The rush to assess species' responses to anthropogenic climate change (CC) has underestimated the importance of interannual population variability (PV). Researchers assume sampling rigor alone will lead to an accurate detection of response regardless of the underlying population fluctuations of the species under consideration. Using population simulations across a realistic, empirically based gradient in PV, we show that moderate to high PV can lead to opposite and biased conclusions about CC responses. Between pre- and post-CC sampling bouts of modeled populations as in resurvey studies, there is: (i) A 50% probability of erroneously detecting the opposite trend in population abundance change and nearly zero probability of detecting no change. (ii) Across multiple years of sampling, it is nearly impossible to accurately detect any directional shift in population sizes with even moderate PV. (iii) There is up to 50% probability of detecting a population extirpation when the species is present, but in very low natural abundances. (iv) Under scenarios of moderate to high PV across a species' range or at the range edges, there is a bias toward erroneous detection of range shifts or contractions. Essentially, the frequency and magnitude of population peaks and troughs greatly impact the accuracy of our CC response measurements. Species with moderate to high PV (many small vertebrates, invertebrates, and annual plants) may be inaccurate 'canaries in the coal mine' for CC without pertinent demographic analyses and additional repeat sampling. Variation in PV may explain some idiosyncrasies in CC responses detected so far and urgently needs more careful consideration in design and analysis of CC responses. PMID:26725404
Accurate Jones Matrix of the Practical Faraday Rotator
Institute of Scientific and Technical Information of China (English)
王林斗; 祝昇翔; 李玉峰; 邢文烈; 魏景芝
2003-01-01
The Jones matrix of practical Faraday rotators is often used in the engineering calculation of non-reciprocal optical field. Nevertheless, only the approximate Jones matrix of practical Faraday rotators has been presented by now. Based on the theory of polarized light, this paper presents the accurate Jones matrix of practical Faraday rotators. In addition, an experiment has been carried out to verify the validity of the accurate Jones matrix. This matrix accurately describes the optical characteristics of practical Faraday rotators, including rotation, loss and depolarization of the polarized light. The accurate Jones matrix can be used to obtain the accurate results for the practical Faraday rotator to transform the polarized light, which paves the way for the accurate analysis and calculation of practical Faraday rotators in relevant engineering applications.
Progress in Fast, Accurate Multi-scale Climate Simulations
Energy Technology Data Exchange (ETDEWEB)
Collins, William D [Lawrence Berkeley National Laboratory (LBNL); Johansen, Hans [Lawrence Berkeley National Laboratory (LBNL); Evans, Katherine J [ORNL; Woodward, Carol S. [Lawrence Livermore National Laboratory (LLNL); Caldwell, Peter [Lawrence Livermore National Laboratory (LLNL)
2015-01-01
We present a survey of physical and computational techniques that have the potential to con- tribute to the next generation of high-fidelity, multi-scale climate simulations. Examples of the climate science problems that can be investigated with more depth include the capture of remote forcings of localized hydrological extreme events, an accurate representation of cloud features over a range of spatial and temporal scales, and parallel, large ensembles of simulations to more effectively explore model sensitivities and uncertainties. Numerical techniques, such as adaptive mesh refinement, implicit time integration, and separate treatment of fast physical time scales are enabling improved accuracy and fidelity in simulation of dynamics and allow more complete representations of climate features at the global scale. At the same time, part- nerships with computer science teams have focused on taking advantage of evolving computer architectures, such as many-core processors and GPUs, so that these approaches which were previously considered prohibitively costly have become both more efficient and scalable. In combination, progress in these three critical areas is poised to transform climate modeling in the coming decades.
An accurately fast algorithm of calculating reflection/transmission coefficients
Institute of Scientific and Technical Information of China (English)
CASTAGNA; J; P
2008-01-01
For the boundary between transversely isotropic media with a vertical axis of symmetry (VTI media), the interface between a liquid and a VTI medium, and the free-surface of an elastic half-space of a VTI medium, an accurately fast algorithm was presented for calculating reflection/transmission (R/T) coefficients. Specially, the case of post-critical angle incidence was considered. Although we only performed the numerical calculation for the models of the VTI media, the calculated results can be extended to the models of transversely isotropic media with a horizontal axis of rotation symmetry (HTI media). Compared to previous work, this algorithm can be used not only for the calculation of R/T coefficients of the boundary between ellipsoidally anisotropic media, but also for that between generally anisotropic media, and the speed and accuracy of this algorithm are faster and higher. According to the anisotropic parameters of some rocks given by the published literature, we performed the calculation of R/T coefficients by using this algorithm and analyzed the effect of the rock anisotropy on R/T coefficients. We used Snell’s law and the energy balance principle to perform verification for the calculated results.
How accurate are the weather forecasts for Bierun (southern Poland)?
Gawor, J.
2012-04-01
Weather forecast accuracy has increased in recent times mainly thanks to significant development of numerical weather prediction models. Despite the improvements, the forecasts should be verified to control their quality. The evaluation of forecast accuracy can also be an interesting learning activity for students. It joins natural curiosity about everyday weather and scientific process skills: problem solving, database technologies, graph construction and graphical analysis. The examination of the weather forecasts has been taken by a group of 14-year-old students from Bierun (southern Poland). They participate in the GLOBE program to develop inquiry-based investigations of the local environment. For the atmospheric research the automatic weather station is used. The observed data were compared with corresponding forecasts produced by two numerical weather prediction models, i.e. COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) developed by Naval Research Laboratory Monterey, USA; it runs operationally at the Interdisciplinary Centre for Mathematical and Computational Modelling in Warsaw, Poland and COSMO (The Consortium for Small-scale Modelling) used by the Polish Institute of Meteorology and Water Management. The analysed data included air temperature, precipitation, wind speed, wind chill and sea level pressure. The prediction periods from 0 to 24 hours (Day 1) and from 24 to 48 hours (Day 2) were considered. The verification statistics that are commonly used in meteorology have been applied: mean error, also known as bias, for continuous data and a 2x2 contingency table to get the hit rate and false alarm ratio for a few precipitation thresholds. The results of the aforementioned activity became an interesting basis for discussion. The most important topics are: 1) to what extent can we rely on the weather forecasts? 2) How accurate are the forecasts for two considered time ranges? 3) Which precipitation threshold is the most predictable? 4) Why
Biomimetic Approach for Accurate, Real-Time Aerodynamic Coefficients Project
National Aeronautics and Space Administration — Aerodynamic and structural reliability and efficiency depends critically on the ability to accurately assess the aerodynamic loads and moments for each lifting...
Simple and Accurate Analytical Solutions of the Electrostatically Actuated Curled Beam Problem
Younis, Mohammad I.
2014-08-17
We present analytical solutions of the electrostatically actuated initially deformed cantilever beam problem. We use a continuous Euler-Bernoulli beam model combined with a single-mode Galerkin approximation. We derive simple analytical expressions for two commonly observed deformed beams configurations: the curled and tilted configurations. The derived analytical formulas are validated by comparing their results to experimental data in the literature and numerical results of a multi-mode reduced order model. The derived expressions do not involve any complicated integrals or complex terms and can be conveniently used by designers for quick, yet accurate, estimations. The formulas are found to yield accurate results for most commonly encountered microbeams of initial tip deflections of few microns. For largely deformed beams, we found that these formulas yield less accurate results due to the limitations of the single-mode approximations they are based on. In such cases, multi-mode reduced order models need to be utilized.
DEFF Research Database (Denmark)
Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron L. C.;
2014-01-01
In the past decade, photonic crystal resonant reflectors have been increasingly used as the basis for label-free biochemical assays in lab-on-a-chip applications. In both designing and interpreting experimental results, an accurate model describing the optical behavior of such structures is essen......In the past decade, photonic crystal resonant reflectors have been increasingly used as the basis for label-free biochemical assays in lab-on-a-chip applications. In both designing and interpreting experimental results, an accurate model describing the optical behavior of such structures...
78 FR 34604 - Submitting Complete and Accurate Information
2013-06-10
... COMMISSION 10 CFR Part 50 Submitting Complete and Accurate Information AGENCY: Nuclear Regulatory Commission... accurate information as would a licensee or an applicant for a license.'' DATES: Submit comments by August... may submit comments by any of the following methods (unless this document describes a different...
Institute of Scientific and Technical Information of China (English)
邱金桓
2002-01-01
A simple yet more accurate semiempirical model is developed to calculate solar radiative flux in the optically inhomogeneous atmosphere. In the model a parameterized expression of spherical reflectance and transmitance of the atmosphere is confirmed, and the weighted single scatter albedo and weighted asymmetric factor are introduced to fit four empirical correction factors responsible for radiative fluxes in the inhomogeneous atmosphere. For both clean and turbid models, there are 120060 sets of radiative flux simulations for accuracy checks of the model, which cover 0-50 cloud optical depths, 0-0.8 surface reflectance, Junge and Log-normal aerosol size distributions, and 0-0.05 imaginary parts of aerosol refractive indexes. In case of the homogeneous atmosphere, standard errors of the 120060 upward fluxes from the present model are 1.08% and 1.04% for clean and turbid aerosol models, respectively; and those of the downward fluxes are 4.12% and 3.31%. In case of the inhomogeneous atmosphere, standard errors of the upw ard fluxes from the present model are 3.01% and 3.48% for clean and turbid aerosol models.respectively; and those of the downward fluxes are 4.54% and 4.89%, showing a much better accuracy than the results calculated by using an assumption of the homogeneous atmosphere.%发展了一个计算非均一大气条件下太阳辐射通量的一个简单而又精确的模式,其中包括关于大气球反射率与透过率的一个参数化表达式,并引入加权一次散射反照率和加权不对称因子,用于拟合非均一大气条件下计算辐射通量的四个经验订正因子.对清洁和浑浊的两类大气,都具有120060组的辐射通量模拟试验,以检验本模式的精度.这些模拟试验覆盖0-50的云光学厚度、0-0 8地表反射率、Junge和对数正态的气溶胶谱分布、0-0.05气溶胶折射率虚部.在均一大气条件下,由本模式计算的120060组向上通量的标准差对清洁和浑浊两类大气分别为1
Speed-of-sound compensated photoacoustic tomography for accurate imaging
Jose, Jithin; Steenbergen, Wiendelt; Slump, Cornelis H; van Leeuwen, Ton G; Manohar, Srirang
2012-01-01
In most photoacoustic (PA) measurements, variations in speed-of-sound (SOS) of the subject are neglected under the assumption of acoustic homogeneity. Biological tissue with spatially heterogeneous SOS cannot be accurately reconstructed under this assumption. We present experimental and image reconstruction methods with which 2-D SOS distributions can be accurately acquired and reconstructed, and with which the SOS map can be used subsequently to reconstruct highly accurate PA tomograms. We begin with a 2-D iterative reconstruction approach in an ultrasound transmission tomography (UTT) setting, which uses ray refracted paths instead of straight ray paths to recover accurate SOS images of the subject. Subsequently, we use the SOS distribution in a new 2-D iterative approach, where refraction of rays originating from PA sources are accounted for in accurately retrieving the distribution of these sources. Both the SOS reconstruction and SOS-compensated PA reconstruction methods utilize the Eikonal equation to m...
Institute of Scientific and Technical Information of China (English)
JIANG Min; FANG Zhen-Yun; SANG Wen-Long; GAO Fei
2006-01-01
@@ In the minimum electromagnetism coupling model of interaction between photon and electron (positron), we accurately calculate photon chain renormalized propagator and obtain the accurate result of differential cross section of Bhabha scattering with a photon chain renormalized propagator in quantum electrodynamics. The related radiative corrections are briefly reviewed and discussed.
Accurate mass measurements of very short-lived nuclei
Herfurth, F; Ames, F; Audi, G; Beck, D; Blaum, K; Bollen, G; Engels, O; Kluge, H J; Lunney, M D; Moores, R B; Oinonen, M; Sauvan, E; Bolle, C A; Scheidenberger, C; Schwarz, S; Sikler, G; Weber, C
2002-01-01
Mass measurements of /sup 34/Ar, /sup 73-78/Kr, and /sup 74,76/Rb were performed with the Penning-trap mass spectrometer ISOLTRAP. Very accurate Q/sub EC/-values are needed for the investigations of the F /sub t/-value of 0/sup +/ to 0/sup +/ nuclear beta -decays used to test the standard model predictions for weak interactions. The necessary accuracy on the Q/sub EC/-value requires the mass of mother and daughter nuclei to be measured with delta m/m
Faster and More Accurate Sequence Alignment with SNAP
Zaharia, Matei; Curtis, Kristal; Fox, Armando; Patterson, David; Shenker, Scott; Stoica, Ion; Karp, Richard M; Sittler, Taylor
2011-01-01
We present the Scalable Nucleotide Alignment Program (SNAP), a new short and long read aligner that is both more accurate (i.e., aligns more reads with fewer errors) and 10-100x faster than state-of-the-art tools such as BWA. Unlike recent aligners based on the Burrows-Wheeler transform, SNAP uses a simple hash index of short seed sequences from the genome, similar to BLAST's. However, SNAP greatly reduces the number and cost of local alignment checks performed through several measures: it uses longer seeds to reduce the false positive locations considered, leverages larger memory capacities to speed index lookup, and excludes most candidate locations without fully computing their edit distance to the read. The result is an algorithm that scales well for reads from one hundred to thousands of bases long and provides a rich error model that can match classes of mutations (e.g., longer indels) that today's fast aligners ignore. We calculate that SNAP can align a dataset with 30x coverage of a human genome in le...
Accurate measurement of streamwise vortices in low speed aerodynamic flows
Waldman, Rye M.; Kudo, Jun; Breuer, Kenneth S.
2010-11-01
Low Reynolds number experiments with flapping animals (such as bats and small birds) are of current interest in understanding biological flight mechanics, and due to their application to Micro Air Vehicles (MAVs) which operate in a similar parameter space. Previous PIV wake measurements have described the structures left by bats and birds, and provided insight to the time history of their aerodynamic force generation; however, these studies have faced difficulty drawing quantitative conclusions due to significant experimental challenges associated with the highly three-dimensional and unsteady nature of the flows, and the low wake velocities associated with lifting bodies that only weigh a few grams. This requires the high-speed resolution of small flow features in a large field of view using limited laser energy and finite camera resolution. Cross-stream measurements are further complicated by the high out-of-plane flow which requires thick laser sheets and short interframe times. To quantify and address these challenges we present data from a model study on the wake behind a fixed wing at conditions comparable to those found in biological flight. We present a detailed analysis of the PIV wake measurements, discuss the criteria necessary for accurate measurements, and present a new dual-plane PIV configuration to resolve these issues.
An Accurate Projector Calibration Method Based on Polynomial Distortion Representation
Directory of Open Access Journals (Sweden)
Miao Liu
2015-10-01
Full Text Available In structure light measurement systems or 3D printing systems, the errors caused by optical distortion of a digital projector always affect the precision performance and cannot be ignored. Existing methods to calibrate the projection distortion rely on calibration plate and photogrammetry, so the calibration performance is largely affected by the quality of the plate and the imaging system. This paper proposes a new projector calibration approach that makes use of photodiodes to directly detect the light emitted from a digital projector. By analyzing the output sequence of the photoelectric module, the pixel coordinates can be accurately obtained by the curve fitting method. A polynomial distortion representation is employed to reduce the residuals of the traditional distortion representation model. Experimental results and performance evaluation show that the proposed calibration method is able to avoid most of the disadvantages in traditional methods and achieves a higher accuracy. This proposed method is also practically applicable to evaluate the geometric optical performance of other optical projection system.
Accurate Complex Systems Design: Integrating Serious Games with Petri Nets
Directory of Open Access Journals (Sweden)
Kirsten Sinclair
2016-03-01
Full Text Available Difficulty understanding the large number of interactions involved in complex systems makes their successful engineering a problem. Petri Nets are one graphical modelling technique used to describe and check proposed designs of complex systems thoroughly. While automatic analysis capabilities of Petri Nets are useful, their visual form is less so, particularly for communicating the design they represent. In engineering projects, this can lead to a gap in communications between people with different areas of expertise, negatively impacting achieving accurate designs.In contrast, although capable of representing a variety of real and imaginary objects effectively, behaviour of serious games can only be analysed manually through interactive simulation. This paper examines combining the complementary strengths of Petri Nets and serious games. The novel contribution of this work is a serious game prototype of a complex system design that has been checked thoroughly. Underpinned by Petri Net analysis, the serious game can be used as a high-level interface to communicate and refine the design.Improvement of a complex system design is demonstrated by applying the integration to a proof-of-concept case study.
AUTOMATED, HIGHLY ACCURATE VERIFICATION OF RELAP5-3D
Energy Technology Data Exchange (ETDEWEB)
George L Mesina; David Aumiller; Francis Buschman
2014-07-01
Computer programs that analyze light water reactor safety solve complex systems of governing, closure and special process equations to model the underlying physics. In addition, these programs incorporate many other features and are quite large. RELAP5-3D[1] has over 300,000 lines of coding for physics, input, output, data management, user-interaction, and post-processing. For software quality assurance, the code must be verified and validated before being released to users. Verification ensures that a program is built right by checking that it meets its design specifications. Recently, there has been an increased importance on the development of automated verification processes that compare coding against its documented algorithms and equations and compares its calculations against analytical solutions and the method of manufactured solutions[2]. For the first time, the ability exists to ensure that the data transfer operations associated with timestep advancement/repeating and writing/reading a solution to a file have no unintended consequences. To ensure that the code performs as intended over its extensive list of applications, an automated and highly accurate verification method has been modified and applied to RELAP5-3D. Furthermore, mathematical analysis of the adequacy of the checks used in the comparisons is provided.
Accurate measurement method for tube's endpoints based on machine vision
Liu, Shaoli; Jin, Peng; Liu, Jianhua; Wang, Xiao; Sun, Peng
2016-08-01
Tubes are used widely in aerospace vehicles, and their accurate assembly can directly affect the assembling reliability and the quality of products. It is important to measure the processed tube's endpoints and then fix any geometric errors correspondingly. However, the traditional tube inspection method is time-consuming and complex operations. Therefore, a new measurement method for a tube's endpoints based on machine vision is proposed. First, reflected light on tube's surface can be removed by using photometric linearization. Then, based on the optimization model for the tube's endpoint measurements and the principle of stereo matching, the global coordinates and the relative distance of the tube's endpoint are obtained. To confirm the feasibility, 11 tubes are processed to remove the reflected light and then the endpoint's positions of tubes are measured. The experiment results show that the measurement repeatability accuracy is 0.167 mm, and the absolute accuracy is 0.328 mm. The measurement takes less than 1 min. The proposed method based on machine vision can measure the tube's endpoints without any surface treatment or any tools and can realize on line measurement.
AN ACCURATE FLUX DENSITY SCALE FROM 1 TO 50 GHz
Energy Technology Data Exchange (ETDEWEB)
Perley, R. A.; Butler, B. J., E-mail: RPerley@nrao.edu, E-mail: BButler@nrao.edu [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)
2013-02-15
We develop an absolute flux density scale for centimeter-wavelength astronomy by combining accurate flux density ratios determined by the Very Large Array between the planet Mars and a set of potential calibrators with the Rudy thermophysical emission model of Mars, adjusted to the absolute scale established by the Wilkinson Microwave Anisotropy Probe. The radio sources 3C123, 3C196, 3C286, and 3C295 are found to be varying at a level of less than {approx}5% per century at all frequencies between 1 and 50 GHz, and hence are suitable as flux density standards. We present polynomial expressions for their spectral flux densities, valid from 1 to 50 GHz, with absolute accuracy estimated at 1%-3% depending on frequency. Of the four sources, 3C286 is the most compact and has the flattest spectral index, making it the most suitable object on which to establish the spectral flux density scale. The sources 3C48, 3C138, 3C147, NGC 7027, NGC 6542, and MWC 349 show significant variability on various timescales. Polynomial coefficients for the spectral flux density are developed for 3C48, 3C138, and 3C147 for each of the 17 observation dates, spanning 1983-2012. The planets Venus, Uranus, and Neptune are included in our observations, and we derive their brightness temperatures over the same frequency range.
An Accurate Flux Density Scale from 1 to 50 GHz
Perley, Rick A
2012-01-01
We develop an absolute flux density scale for cm-wavelength astronomy by combining accurate flux density ratios determined by the VLA between the planet Mars and a set of potential calibrators with the Rudy thermophysical emission model of Mars, adjusted to the absolute scale established by WMAP. The radio sources 3C123, 3C196, 3C286 and 3C295 are found to be varying at a level of less than ~5% per century at all frequencies between 1 and 50 GHz, and hence are suitable as flux density standards. We present polynomial expressions for their spectral flux densities, valid from 1 to 50 GHz, with absolute accuracy estimated at 1-3% depending on frequency. Of the four sources, 3C286 is the most compact and has the flattest spectral index, making it the most suitable object on which to establish the spectral flux density scale. The sources 3C48, 3C138, 3C147, NGC7027, NGC6542, and MWC349 show significant variability on various timescales. Polynomial coefficients for the spectral flux density are developed for 3C48, ...
Accurate, robust and reliable calculations of Poisson-Boltzmann solvation energies
Wang, Bao
2016-01-01
Developing accurate solvers for the Poisson Boltzmann (PB) model is the first step to make the PB model suitable for implicit solvent simulation. Reducing the grid size influence on the performance of the solver benefits to increasing the speed of solver and providing accurate electrostatics analysis for solvated molecules. In this work, we explore the accurate coarse grid PB solver based on the Green's function treatment of the singular charges, matched interface and boundary (MIB) method for treating the geometric singularities, and posterior electrostatic potential field extension for calculating the reaction field energy. We made our previous PB software, MIBPB, robust and provides almost grid size independent reaction field energy calculation. Large amount of the numerical tests verify the grid size independence merit of the MIBPB software. The advantage of MIBPB software directly make the acceleration of the PB solver from the numerical algorithm instead of utilization of advanced computer architectures...
Institute of Scientific and Technical Information of China (English)
刘畅
2015-01-01
目前，社会计算和面向网络化社会的研究在许多国家都被提升到了国家战略层次，成为了学术界的研究热点和前沿课题。社会信息网络(SIN)作为社会计算的重要研究内容也是我们应该关注的对象。内容包括数据精准感知型核协同SIN构建、多维协同感知型SIN演化分析、动态SIN建模和SIN上的突发检测进行了系统描述，不但可以为SIN研究提供理论支持，而且也可为涉及社会和谐发展的SIN上的突发检测应用提供新方法。%At present,the research on social computing and network oriented society, which has been elevated to the national strategic level in many countries,has become the focus and advanced subject of academic.Social information network (SIN) should be paid more attention to,as the object of important research contents of social computing. SIN,including the data accurate perception of nuclear burst detection,collaborative SIN build multidimensional cooperative sensing type SIN evolution analysis, the burst detection of dynamic SIN modeling and SIN of the system description, can not only provide theoretical support for SIN research, but also provide a new method for relates to the harmonious development of society on the SIN burst detection application.
Accurate source location from P waves scattered by surface topography
Wang, N.; Shen, Y.
2015-12-01
Accurate source locations of earthquakes and other seismic events are fundamental in seismology. The location accuracy is limited by several factors, including velocity models, which are often poorly known. In contrast, surface topography, the largest velocity contrast in the Earth, is often precisely mapped at the seismic wavelength (> 100 m). In this study, we explore the use of P-coda waves generated by scattering at surface topography to obtain high-resolution locations of near-surface seismic events. The Pacific Northwest region is chosen as an example. The grid search method is combined with the 3D strain Green's tensor database type method to improve the search efficiency as well as the quality of hypocenter solution. The strain Green's tensor is calculated by the 3D collocated-grid finite difference method on curvilinear grids. Solutions in the search volume are then obtained based on the least-square misfit between the 'observed' and predicted P and P-coda waves. A 95% confidence interval of the solution is also provided as a posterior error estimation. We find that the scattered waves are mainly due to topography in comparison with random velocity heterogeneity characterized by the von Kάrmάn-type power spectral density function. When only P wave data is used, the 'best' solution is offset from the real source location mostly in the vertical direction. The incorporation of P coda significantly improves solution accuracy and reduces its uncertainty. The solution remains robust with a range of random noises in data, un-modeled random velocity heterogeneities, and uncertainties in moment tensors that we tested.
Spectroscopically Accurate Line Lists for Application in Sulphur Chemistry
Underwood, D. S.; Azzam, A. A. A.; Yurchenko, S. N.; Tennyson, J.
2013-09-01
Monitoring sulphur chemistry is thought to be of great importance for exoplanets. Doing this requires detailed knowledge of the spectroscopic properties of sulphur containing molecules such as hydrogen sulphide (H2S) [1], sulphur dioxide (SO2), and sulphur trioxide (SO3). Each of these molecules can be found in terrestrial environments, produced in volcano emissions on Earth, and analysis of their spectroscopic data can prove useful to the characterisation of exoplanets, as well as the study of planets in our own solar system, with both having a possible presence on Venus. A complete, high temperature list of line positions and intensities for H32 2 S is presented. The DVR3D program suite is used to calculate the bound ro-vibration energy levels, wavefunctions, and dipole transition intensities using Radau coordinates. The calculations are based on a newly determined, spectroscopically refined potential energy surface (PES) and a new, high accuracy, ab initio dipole moment surface (DMS). Tests show that the PES enables us to calculate the line positions accurately and the DMS gives satisfactory results for line intensities. Comparisons with experiment as well as with previous theoretical spectra will be presented. The results of this study will form an important addition to the databases which are considered as sources of information for space applications; especially, in analysing the spectra of extrasolar planets, and remote sensing studies for Venus and Earth, as well as laboratory investigations and pollution studies. An ab initio line list for SO3 was previously computed using the variational nuclear motion program TROVE [2], and was suitable for modelling room temperature SO3 spectra. The calculations considered transitions in the region of 0-4000 cm-1 with rotational states up to J = 85, and includes 174,674,257 transitions. A list of 10,878 experimental transitions had relative intensities placed on an absolute scale, and were provided in a form suitable
Accurate and Timely Forecasting of CME-Driven Geomagnetic Storms
Chen, J.; Kunkel, V.; Skov, T. M.
2015-12-01
Wide-spread and severe geomagnetic storms are primarily caused by theejecta of coronal mass ejections (CMEs) that impose long durations ofstrong southward interplanetary magnetic field (IMF) on themagnetosphere, the duration and magnitude of the southward IMF (Bs)being the main determinants of geoeffectiveness. Another importantquantity to forecast is the arrival time of the expected geoeffectiveCME ejecta. In order to accurately forecast these quantities in atimely manner (say, 24--48 hours of advance warning time), it isnecessary to calculate the evolving CME ejecta---its structure andmagnetic field vector in three dimensions---using remote sensing solardata alone. We discuss a method based on the validated erupting fluxrope (EFR) model of CME dynamics. It has been shown using STEREO datathat the model can calculate the correct size, magnetic field, and theplasma parameters of a CME ejecta detected at 1 AU, using the observedCME position-time data alone as input (Kunkel and Chen 2010). Onedisparity is in the arrival time, which is attributed to thesimplified geometry of circular toroidal axis of the CME flux rope.Accordingly, the model has been extended to self-consistently includethe transverse expansion of the flux rope (Kunkel 2012; Kunkel andChen 2015). We show that the extended formulation provides a betterprediction of arrival time even if the CME apex does not propagatedirectly toward the earth. We apply the new method to a number of CMEevents and compare predicted flux ropes at 1 AU to the observed ejectastructures inferred from in situ magnetic and plasma data. The EFRmodel also predicts the asymptotic ambient solar wind speed (Vsw) foreach event, which has not been validated yet. The predicted Vswvalues are tested using the ENLIL model. We discuss the minimum andsufficient required input data for an operational forecasting systemfor predicting the drivers of large geomagnetic storms.Kunkel, V., and Chen, J., ApJ Lett, 715, L80, 2010. Kunkel, V., Ph
Reinbolt, Jeffrey A; Haftka, Raphael T; Chmielewski, Terese L; Fregly, Benjamin J
2007-05-01
Variations in joint parameter (JP) values (axis positions and orientations in body segments) and inertial parameter (IP) values (segment masses, mass centers, and moments of inertia) as well as kinematic noise alter the results of inverse dynamics analyses of gait. Three-dimensional linkage models with joint constraints have been proposed as one way to minimize the effects of noisy kinematic data. Such models can also be used to perform gait optimizations to predict post-treatment function given pre-treatment gait data. This study evaluates whether accurate patient-specific JP and IP values are needed in three-dimensional linkage models to produce accurate inverse dynamics results for gait. The study was performed in two stages. First, we used optimization analyses to evaluate whether patient-specific JP and IP values can be calibrated accurately from noisy kinematic data, and second, we used Monte Carlo analyses to evaluate how errors in JP and IP values affect inverse dynamics calculations. Both stages were performed using a dynamic, 27 degrees-of-freedom, full-body linkage model and synthetic (i.e., computer generated) gait data corresponding to a nominal experimental gait motion. In general, JP but not IP values could be found accurately from noisy kinematic data. Root-mean-square (RMS) errors were 3 degrees and 4 mm for JP values and 1 kg, 22 mm, and 74 500 kg * mm2 for IP values. Furthermore, errors in JP but not IP values had a significant effect on calculated lower-extremity inverse dynamics joint torques. The worst RMS torque error averaged 4% bodyweight * height (BW * H) due to JP variations but less than 0.25% (BW * H) due to IP variations. These results suggest that inverse dynamics analyses of gait utilizing linkage models with joint constraints should calibrate the model's JP values to obtain accurate joint torques.
Accurate Fitting of Noisy Irregular Beam Data for the Planck Space Telescope
DEFF Research Database (Denmark)
Borries, Oscar; Nielsen, Per Heighwood; Tauber, Jan;
2011-01-01
the noise and the size of the dataset a spatial filter is applied, without reducing the amount of pattern information. Thereafter, a Kriging [2], [3] fitting is performed, providing a smooth model with a significant noise level reduction. As a result, this algorithm provides a much more accurate and...
A Fast and Accurate Universal Kepler Solver with Stumpff Series
Wisdom, Jack
2015-01-01
We derive and present a fast and accurate solution of the initial value problem for Keplerian motion in universal variables that does not use the Stumpff series. We find that it performs better than methods based on the Stumpff series.
Highly Accurate Sensor for High-Purity Oxygen Determination Project
National Aeronautics and Space Administration — In this STTR effort, Los Gatos Research (LGR) and the University of Wisconsin (UW) propose to develop a highly-accurate sensor for high-purity oxygen determination....
ACCURATE ESTIMATES OF CHARACTERISTIC EXPONENTS FOR SECOND ORDER DIFFERENTIAL EQUATION
Institute of Scientific and Technical Information of China (English)
无
2009-01-01
In this paper, a second order linear differential equation is considered, and an accurate estimate method of characteristic exponent for it is presented. Finally, we give some examples to verify the feasibility of our result.
Accurate wall thickness measurement using autointerference of circumferential Lamb wave
International Nuclear Information System (INIS)
In this paper, a method of accurately measuring the pipe wall thickness by using noncontact air-coupled ultrasonic transducer (NAUT) was presented. In this method, accurate measurement of angular wave number (AWN) is a key technique because the AWN is changes minutely with the wall thickness. An autointerference of the circumferential (C-) Lamb wave was used for accurate measurements of the AWN. Principle of the method was first explained. Modified method for measuring the wall thickness near a butt weld line was also proposed and its accuracy was evaluated within 6 μm error. It was also shown in the paper that wall thickness measurement was accurately carried out beyond the difference among the sensors by calibrating the frequency response of the sensors. (author)
Accurate backgrounds to Higgs production at the LHC
Kauer, N
2007-01-01
Corrections of 10-30% for backgrounds to the H --> WW --> l^+l^-\\sla{p}_T search in vector boson and gluon fusion at the LHC are reviewed to make the case for precise and accurate theoretical background predictions.
Strauss, Michael J.; Levine, Shellie H.
1985-01-01
Describes an extremely simple technique (using only Dreiding or Framework molecular models, a flashlight, small sheets of glass, and a piece of cardboard) which produces extremely accurate line drawings of stereoscopic images. Advantages of using the system are noted. (JN)
An efficient and accurate method for calculating nonlinear diffraction beam fields
Energy Technology Data Exchange (ETDEWEB)
Jeong, Hyun Jo; Cho, Sung Jong; Nam, Ki Woong; Lee, Jang Hyun [Division of Mechanical and Automotive Engineering, Wonkwang University, Iksan (Korea, Republic of)
2016-04-15
This study develops an efficient and accurate method for calculating nonlinear diffraction beam fields propagating in fluids or solids. The Westervelt equation and quasilinear theory, from which the integral solutions for the fundamental and second harmonics can be obtained, are first considered. A computationally efficient method is then developed using a multi-Gaussian beam (MGB) model that easily separates the diffraction effects from the plane wave solution. The MGB models provide accurate beam fields when compared with the integral solutions for a number of transmitter-receiver geometries. These models can also serve as fast, powerful modeling tools for many nonlinear acoustics applications, especially in making diffraction corrections for the nonlinearity parameter determination, because of their computational efficiency and accuracy.
CgWind: A high-order accurate simulation tool for wind turbines and wind farms
Energy Technology Data Exchange (ETDEWEB)
Chand, K K; Henshaw, W D; Lundquist, K A; Singer, M A
2010-02-22
CgWind is a high-fidelity large eddy simulation (LES) tool designed to meet the modeling needs of wind turbine and wind park engineers. This tool combines several advanced computational technologies in order to model accurately the complex and dynamic nature of wind energy applications. The composite grid approach provides high-quality structured grids for the efficient implementation of high-order accurate discretizations of the incompressible Navier-Stokes equations. Composite grids also provide a natural mechanism for modeling bodies in relative motion and complex geometry. Advanced algorithms such as matrix-free multigrid, compact discretizations and approximate factorization will allow CgWind to perform highly resolved calculations efficiently on a wide class of computing resources. Also in development are nonlinear LES subgrid-scale models required to simulate the many interacting scales present in large wind turbine applications. This paper outlines our approach, the current status of CgWind and future development plans.
Kainmueller, Dagmar
2014-01-01
? Segmentation of anatomical structures in medical image data is an essential task in clinical practice. Dagmar Kainmueller introduces methods for accurate fully automatic segmentation of anatomical structures in 3D medical image data. The author's core methodological contribution is a novel deformation model that overcomes limitations of state-of-the-art Deformable Surface approaches, hence allowing for accurate segmentation of tip- and ridge-shaped features of anatomical structures. As for practical contributions, she proposes application-specific segmentation pipelines for a range of anatom
Artificial neural network accurately predicts hepatitis B surface antigen seroclearance.
Directory of Open Access Journals (Sweden)
Ming-Hua Zheng
Full Text Available BACKGROUND & AIMS: Hepatitis B surface antigen (HBsAg seroclearance and seroconversion are regarded as favorable outcomes of chronic hepatitis B (CHB. This study aimed to develop artificial neural networks (ANNs that could accurately predict HBsAg seroclearance or seroconversion on the basis of available serum variables. METHODS: Data from 203 untreated, HBeAg-negative CHB patients with spontaneous HBsAg seroclearance (63 with HBsAg seroconversion, and 203 age- and sex-matched HBeAg-negative controls were analyzed. ANNs and logistic regression models (LRMs were built and tested according to HBsAg seroclearance and seroconversion. Predictive accuracy was assessed with area under the receiver operating characteristic curve (AUROC. RESULTS: Serum quantitative HBsAg (qHBsAg and HBV DNA levels, qHBsAg and HBV DNA reduction were related to HBsAg seroclearance (P<0.001 and were used for ANN/LRM-HBsAg seroclearance building, whereas, qHBsAg reduction was not associated with ANN-HBsAg seroconversion (P = 0.197 and LRM-HBsAg seroconversion was solely based on qHBsAg (P = 0.01. For HBsAg seroclearance, AUROCs of ANN were 0.96, 0.93 and 0.95 for the training, testing and genotype B subgroups respectively. They were significantly higher than those of LRM, qHBsAg and HBV DNA (all P<0.05. Although the performance of ANN-HBsAg seroconversion (AUROC 0.757 was inferior to that for HBsAg seroclearance, it tended to be better than those of LRM, qHBsAg and HBV DNA. CONCLUSIONS: ANN identifies spontaneous HBsAg seroclearance in HBeAg-negative CHB patients with better accuracy, on the basis of easily available serum data. More useful predictors for HBsAg seroconversion are still needed to be explored in the future.
Accurate source location from waves scattered by surface topography
Wang, Nian; Shen, Yang; Flinders, Ashton; Zhang, Wei
2016-06-01
Accurate source locations of earthquakes and other seismic events are fundamental in seismology. The location accuracy is limited by several factors, including velocity models, which are often poorly known. In contrast, surface topography, the largest velocity contrast in the Earth, is often precisely mapped at the seismic wavelength (>100 m). In this study, we explore the use of P coda waves generated by scattering at surface topography to obtain high-resolution locations of near-surface seismic events. The Pacific Northwest region is chosen as an example to provide realistic topography. A grid search algorithm is combined with the 3-D strain Green's tensor database to improve search efficiency as well as the quality of hypocenter solutions. The strain Green's tensor is calculated using a 3-D collocated-grid finite difference method on curvilinear grids. Solutions in the search volume are obtained based on the least squares misfit between the "observed" and predicted P and P coda waves. The 95% confidence interval of the solution is provided as an a posteriori error estimation. For shallow events tested in the study, scattering is mainly due to topography in comparison with stochastic lateral velocity heterogeneity. The incorporation of P coda significantly improves solution accuracy and reduces solution uncertainty. The solution remains robust with wide ranges of random noises in data, unmodeled random velocity heterogeneities, and uncertainties in moment tensors. The method can be extended to locate pairs of sources in close proximity by differential waveforms using source-receiver reciprocity, further reducing errors caused by unmodeled velocity structures.
TOWARDS MORE ACCURATE CLUSTERING METHOD BY USING DYNAMIC TIME WARPING
Directory of Open Access Journals (Sweden)
Khadoudja Ghanem
2013-03-01
Full Text Available An intrinsic problem of classifiers based on machine learning (ML methods is that their learning time grows as the size and complexity of the training dataset increases. For this reason, it is important to have efficient computational methods and algorithms that can be applied on large datasets, such that it is still possible to complete the machine learning tasks in reasonable time. In this context, we present in this paper a more accurate simple process to speed up ML methods. An unsupervised clustering algorithm is combined with Expectation, Maximization (EM algorithm to develop an efficient Hidden Markov Model (HMM training. The idea of the proposed process consists of two steps. In the first step, training instances with similar inputs are clustered and a weight factor which represents the frequency of these instances is assigned to each representative cluster. Dynamic Time Warping technique is used as a dissimilarity function to cluster similar examples. In the second step, all formulas in the classical HMM training algorithm (EM associated with the number of training instances are modified to include the weight factor in appropriate terms. This process significantly accelerates HMM training while maintaining the same initial, transition and emission probabilities matrixes as those obtained with the classical HMM training algorithm. Accordingly, the classification accuracy is preserved. Depending on the size of the training set, speedups of up to 2200 times is possible when the size is about 100.000 instances. The proposed approach is not limited to training HMMs, but it can be employed for a large variety of MLs methods.
Towards More Accurate Clutering Method by Using Dynamic Time Warping
Directory of Open Access Journals (Sweden)
Khadoudja Ghanem
2013-04-01
Full Text Available An intrinsic problem of classifiers based on machine learning (ML methods is that their learning timegrows as the size and complexity of the training dataset increases. For this reason, it is important to have efficient computational methods and algorithms that can be applied on large datasets, such that it is still possible to complete the machine learning tasks in reasonable time. In this context, we present in this paper a more accurate simple process to speed up ML methods. An unsupervised clustering algorithm is combined with Expectation, Maximization (EM algorithm to develop an efficient Hidden Markov Model (HMM training. The idea of the proposed process consists of two steps. In the first step, training instances with similar inputs are clustered and a weight factor which represents the frequency of these instances is assigned to each representative cluster. Dynamic Time Warping technique is used as a dissimilarity function to cluster similar examples. In the second step, all formulas in the classical HMM training algorithm (EM associated with the number of training instances are modified to include the weight factor in appropriate terms. This process significantly accelerates HMM training while maintaining the same initial, transition and emission probabilities matrixes as those obtained with the classical HMM training algorithm. Accordingly, the classification accuracy is preserved. Depending on the size of the training set, speedups of up to 2200 times is possible when the size is about 100.000 instances. The proposed approach is not limited to training HMMs, but it can be employed for a large variety of MLs methods
Chen, Yu-Wen; Tseng, Sheng-Hao
2015-01-01
In general, diffuse reflectance spectroscopy (DRS) systems work with photon diffusion models to determine the absorption coefficient μa and reduced scattering coefficient μs' of turbid samples. However, in some DRS measurement scenarios, such as using short source-detector separations to investigate superficial tissues with comparable μa and μs', photon diffusion models might be invalid or might not have analytical solutions. In this study, a systematic workflow of constructing a rapid, accur...
Smalter, Aaron; Huan, Jun; Jia, Yi; Lushington, Gerald
2010-01-01
Graph data mining is an active research area. Graphs are general modeling tools to organize information from heterogeneous sources and have been applied in many scientific, engineering, and business fields. With the fast accumulation of graph data, building highly accurate predictive models for graph data emerges as a new challenge that has not been fully explored in the data mining community. In this paper, we demonstrate a novel technique called graph pattern diffusion (GPD) kernel. Our ide...
An Accurate Arabic Root-Based Lemmatizer for Information Retrieval Purposes
El-Shishtawy, Tarek
2012-01-01
In spite of its robust syntax, semantic cohesion, and less ambiguity, lemma level analysis and generation does not yet focused in Arabic NLP literatures. In the current research, we propose the first non-statistical accurate Arabic lemmatizer algorithm that is suitable for information retrieval (IR) systems. The proposed lemmatizer makes use of different Arabic language knowledge resources to generate accurate lemma form and its relevant features that support IR purposes. As a POS tagger, the experimental results show that, the proposed algorithm achieves a maximum accuracy of 94.8%. For first seen documents, an accuracy of 89.15% is achieved, compared to 76.7% of up to date Stanford accurate Arabic model, for the same, dataset.
An Accurate Arabic Root-Based Lemmatizer for Information Retrieval Purposes
Directory of Open Access Journals (Sweden)
Tarek El-Shishtawy
2012-01-01
Full Text Available In spite of its robust syntax, semantic cohesion, and less ambiguity, lemma level analysis and generation does not yet focused in Arabic NLP literatures. In the current research, we propose the first non-statistical accurate Arabic lemmatizer algorithm that is suitable for information retrieval (IR systems. The proposed lemmatizer makes use of different Arabic language knowledge resources to generate accurate lemma form and its relevant features that support IR purposes. As a POS tagger, the experimental results show that, the proposed algorithm achieves a maximum accuracy of 94.8%. For first seen documents, an accuracy of 89.15% is achieved, compared to 76.7% of up to date Stanford accurate Arabic model, for the same, dataset.
Second-order accurate finite volume method for well-driven flows
Dotlić, Milan; Pokorni, Boris; Pušić, Milenko; Dimkić, Milan
2013-01-01
We consider a finite volume method for a well-driven fluid flow in a porous medium. Due to the singularity of the well, modeling in the near-well region with standard numerical schemes results in a completely wrong total well flux and an inaccurate hydraulic head. Local grid refinement can help, but it comes at computational cost. In this article we propose two methods to address well singularity. In the first method the flux through well faces is corrected using a logarithmic function, in a way related to the Peaceman correction. Coupling this correction with a second-order accurate two-point scheme gives a greatly improved total well flux, but the resulting scheme is still not even first order accurate on coarse grids. In the second method fluxes in the near-well region are corrected by representing the hydraulic head as a sum of a logarithmic and a linear function. This scheme is second-order accurate.
The MIDAS touch for Accurately Predicting the Stress-Strain Behavior of Tantalum
Energy Technology Data Exchange (ETDEWEB)
Jorgensen, S. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2016-03-02
Testing the behavior of metals in extreme environments is not always feasible, so material scientists use models to try and predict the behavior. To achieve accurate results it is necessary to use the appropriate model and material-specific parameters. This research evaluated the performance of six material models available in the MIDAS database [1] to determine at which temperatures and strain-rates they perform best, and to determine to which experimental data their parameters were optimized. Additionally, parameters were optimized for the Johnson-Cook model using experimental data from Lassila et al [2].
Accurate Fiber Length Measurement Using Time-of-Flight Technique
Terra, Osama; Hussein, Hatem
2016-06-01
Fiber artifacts of very well-measured length are required for the calibration of optical time domain reflectometers (OTDR). In this paper accurate length measurement of different fiber lengths using the time-of-flight technique is performed. A setup is proposed to measure accurately lengths from 1 to 40 km at 1,550 and 1,310 nm using high-speed electro-optic modulator and photodetector. This setup offers traceability to the SI unit of time, the second (and hence to meter by definition), by locking the time interval counter to the Global Positioning System (GPS)-disciplined quartz oscillator. Additionally, the length of a recirculating loop artifact is measured and compared with the measurement made for the same fiber by the National Physical Laboratory of United Kingdom (NPL). Finally, a method is proposed to relatively correct the fiber refractive index to allow accurate fiber length measurement.
Highly Accurate Measurement of the Electron Orbital Magnetic Moment
Awobode, A M
2015-01-01
We propose to accurately determine the orbital magnetic moment of the electron by measuring, in a Magneto-Optical or Ion trap, the ratio of the Lande g-factors in two atomic states. From the measurement of (gJ1/gJ2), the quantity A, which depends on the corrections to the electron g-factors can be extracted, if the states are LS coupled. Given that highly accurate values of the correction to the spin g-factor are currently available, accurate values of the correction to the orbital g-factor may also be determined. At present, (-1.8 +/- 0.4) x 10-4 has been determined as a correction to the electron orbital g-factor, by using earlier measurements of the ratio gJ1/gJ2, made on the Indium 2P1/2 and 2P3/2 states.
Accurate level set method for simulations of liquid atomization☆
Institute of Scientific and Technical Information of China (English)
Changxiao Shao; Kun Luo; Jianshan Yang; Song Chen; Jianren Fan
2015-01-01
Computational fluid dynamics is an efficient numerical approach for spray atomization study, but it is chal enging to accurately capture the gas–liquid interface. In this work, an accurate conservative level set method is intro-duced to accurately track the gas–liquid interfaces in liquid atomization. To validate the capability of this method, binary drop collision and drop impacting on liquid film are investigated. The results are in good agreement with experiment observations. In addition, primary atomization (swirling sheet atomization) is studied using this method. To the swirling sheet atomization, it is found that Rayleigh–Taylor instability in the azimuthal direction causes the primary breakup of liquid sheet and complex vortex structures are clustered around the rim of the liq-uid sheet. The effects of central gas velocity and liquid–gas density ratio on atomization are also investigated. This work lays a solid foundation for further studying the mechanism of spray atomization.
An, Zhe; Abarbanel, Henry D I
2014-01-01
Utilizing the information in observations of a complex system to make accurate predictions through a quantitative model when observations are completed at time $T$, requires an accurate estimate of the full state of the model at time $T$. When the number of measurements $L$ at each observation time within the observation window is larger than a sufficient minimum value $L_s$, the impediments in the estimation procedure are removed. As the number of available observations is typically such that $L \\ll L_s$, additional information from the observations must be presented to the model. We show how, using the time delays of the measurements at each observation time, one can augment the information transferred from the data to the model, removing the impediments to accurate estimation and permitting dependable prediction. We do this in a core geophysical fluid dynamics model, the shallow water equations, at the heart of numerical weather prediction. The method is quite general, however, and can be utilized in the a...
Extracting Time-Accurate Acceleration Vectors From Nontrivial Accelerometer Arrangements.
Franck, Jennifer A; Blume, Janet; Crisco, Joseph J; Franck, Christian
2015-09-01
Sports-related concussions are of significant concern in many impact sports, and their detection relies on accurate measurements of the head kinematics during impact. Among the most prevalent recording technologies are videography, and more recently, the use of single-axis accelerometers mounted in a helmet, such as the HIT system. Successful extraction of the linear and angular impact accelerations depends on an accurate analysis methodology governed by the equations of motion. Current algorithms are able to estimate the magnitude of acceleration and hit location, but make assumptions about the hit orientation and are often limited in the position and/or orientation of the accelerometers. The newly formulated algorithm presented in this manuscript accurately extracts the full linear and rotational acceleration vectors from a broad arrangement of six single-axis accelerometers directly from the governing set of kinematic equations. The new formulation linearizes the nonlinear centripetal acceleration term with a finite-difference approximation and provides a fast and accurate solution for all six components of acceleration over long time periods (>250 ms). The approximation of the nonlinear centripetal acceleration term provides an accurate computation of the rotational velocity as a function of time and allows for reconstruction of a multiple-impact signal. Furthermore, the algorithm determines the impact location and orientation and can distinguish between glancing, high rotational velocity impacts, or direct impacts through the center of mass. Results are shown for ten simulated impact locations on a headform geometry computed with three different accelerometer configurations in varying degrees of signal noise. Since the algorithm does not require simplifications of the actual impacted geometry, the impact vector, or a specific arrangement of accelerometer orientations, it can be easily applied to many impact investigations in which accurate kinematics need to
Method of accurate grinding for single enveloping TI worm
Institute of Scientific and Technical Information of China (English)
SUN Yuehai; ZHENG Huijiang; BI Qingzhen; WANG Shuren
2005-01-01
TI worm drive consists of involute helical gear and its enveloping Hourglass worm. Accurate grinding for TI worm is the key manufacture technology for TI worm gearing being popularized and applied. According to the theory of gear mesh, the equations of tooth surface of worm drive are gained, and the equation of the axial section profile of grinding wheel that can accurately grind TI worm is extracted. Simultaneously,the relation of position and motion between TI worm and grinding wheel are expounded.The method for precisely grinding single enveloping TI worm is obtained.
Equivalent method for accurate solution to linear interval equations
Institute of Scientific and Technical Information of China (English)
王冲; 邱志平
2013-01-01
Based on linear interval equations, an accurate interval finite element method for solving structural static problems with uncertain parameters in terms of optimization is discussed. On the premise of ensuring the consistency of solution sets, the original interval equations are equivalently transformed into some deterministic inequations. On this basis, calculating the structural displacement response with interval parameters is predigested to a number of deterministic linear optimization problems. The results are proved to be accurate to the interval governing equations. Finally, a numerical example is given to demonstrate the feasibility and eﬃciency of the proposed method.
Energy Technology Data Exchange (ETDEWEB)
Nakhleh, Luay
2014-03-12
I proposed to develop computationally efficient tools for accurate detection and reconstruction of microbes' complex evolutionary mechanisms, thus enabling rapid and accurate annotation, analysis and understanding of their genomes. To achieve this goal, I proposed to address three aspects. (1) Mathematical modeling. A major challenge facing the accurate detection of HGT is that of distinguishing between these two events on the one hand and other events that have similar "effects." I proposed to develop a novel mathematical approach for distinguishing among these events. Further, I proposed to develop a set of novel optimization criteria for the evolutionary analysis of microbial genomes in the presence of these complex evolutionary events. (2) Algorithm design. In this aspect of the project, I proposed to develop an array of e cient and accurate algorithms for analyzing microbial genomes based on the formulated optimization criteria. Further, I proposed to test the viability of the criteria and the accuracy of the algorithms in an experimental setting using both synthetic as well as biological data. (3) Software development. I proposed the nal outcome to be a suite of software tools which implements the mathematical models as well as the algorithms developed.
Technological Basis and Scientific Returns for Absolutely Accurate Measurements
Dykema, J. A.; Anderson, J.
2011-12-01
The 2006 NRC Decadal Survey fostered a new appreciation for societal objectives as a driving motivation for Earth science. Many high-priority societal objectives are dependent on predictions of weather and climate. These predictions are based on numerical models, which derive from approximate representations of well-founded physics and chemistry on space and timescales appropriate to global and regional prediction. These laws of chemistry and physics in turn have a well-defined quantitative relationship with physical measurement units, provided these measurement units are linked to international measurement standards that are the foundation of contemporary measurement science and standards for engineering and commerce. Without this linkage, measurements have an ambiguous relationship to scientific principles that introduces avoidable uncertainty in analyses, predictions, and improved understanding of the Earth system. Since the improvement of climate and weather prediction is fundamentally dependent on the improvement of the representation of physical processes, measurement systems that reduce the ambiguity between physical truth and observations represent an essential component of a national strategy for understanding and living with the Earth system. This paper examines the technological basis and potential science returns of sensors that make measurements that are quantitatively tied on-orbit to international measurement standards, and thus testable to systematic errors. This measurement strategy provides several distinct benefits. First, because of the quantitative relationship between these international measurement standards and fundamental physical constants, measurements of this type accurately capture the true physical and chemical behavior of the climate system and are not subject to adjustment due to excluded measurement physics or instrumental artifacts. In addition, such measurements can be reproduced by scientists anywhere in the world, at any time
Measurement of Fracture Geometry for Accurate Computation of Hydraulic Conductivity
Chae, B.; Ichikawa, Y.; Kim, Y.
2003-12-01
Fluid flow in rock mass is controlled by geometry of fractures which is mainly characterized by roughness, aperture and orientation. Fracture roughness and aperture was observed by a new confocal laser scanning microscope (CLSM; Olympus OLS1100). The wavelength of laser is 488nm, and the laser scanning is managed by a light polarization method using two galvano-meter scanner mirrors. The system improves resolution in the light axis (namely z) direction because of the confocal optics. The sampling is managed in a spacing 2.5 μ m along x and y directions. The highest measurement resolution of z direction is 0.05 μ m, which is the more accurate than other methods. For the roughness measurements, core specimens of coarse and fine grained granites were provided. Measurements were performed along three scan lines on each fracture surface. The measured data were represented as 2-D and 3-D digital images showing detailed features of roughness. Spectral analyses by the fast Fourier transform (FFT) were performed to characterize on the roughness data quantitatively and to identify influential frequency of roughness. The FFT results showed that components of low frequencies were dominant in the fracture roughness. This study also verifies that spectral analysis is a good approach to understand complicate characteristics of fracture roughness. For the aperture measurements, digital images of the aperture were acquired under applying five stages of uniaxial normal stresses. This method can characterize the response of aperture directly using the same specimen. Results of measurements show that reduction values of aperture are different at each part due to rough geometry of fracture walls. Laboratory permeability tests were also conducted to evaluate changes of hydraulic conductivities related to aperture variation due to different stress levels. The results showed non-uniform reduction of hydraulic conductivity under increase of the normal stress and different values of
Improved management of radiotherapy departments through accurate cost data
International Nuclear Information System (INIS)
Escalating health care expenses urge Governments towards cost containment. More accurate data on the precise costs of health care interventions are needed. We performed an aggregate cost calculation of radiation therapy departments and treatments and discussed the different cost components. The costs of a radiotherapy department were estimated, based on accreditation norms for radiotherapy departments set forth in the Belgian legislation. The major cost components of radiotherapy are the cost of buildings and facilities, equipment, medical and non-medical staff, materials and overhead. They respectively represent around 3, 30, 50, 4 and 13% of the total costs, irrespective of the department size. The average cost per patient lowers with increasing department size and optimal utilization of resources. Radiotherapy treatment costs vary in a stepwise fashion: minor variations of patient load do not affect the cost picture significantly due to a small impact of variable costs. With larger increases in patient load however, additional equipment and/or staff will become necessary, resulting in additional semi-fixed costs and an important increase in costs. A sensitivity analysis of these two major cost inputs shows that a decrease in total costs of 12-13% can be obtained by assuming a 20% less than full time availability of personnel; that due to evolving seniority levels, the annual increase in wage costs is estimated to be more than 1%; that by changing the clinical life-time of buildings and equipment with unchanged interest rate, a 5% reduction of total costs and cost per patient can be calculated. More sophisticated equipment will not have a very large impact on the cost (±4000 BEF/patient), provided that the additional equipment is adapted to the size of the department. That the recommendations we used, based on the Belgian legislation, are not outrageous is shown by replacing them by the USA Blue book recommendations. Depending on the department size, costs in
Accurate momentum transfer cross section for the attractive Yukawa potential
Khrapak, Sergey
2014-01-01
Accurate expression for the momentum transfer cross section for the attractive Yukawa potential is proposed. This simple analytic expression agrees with the numerical results better than to within 2% in the regime relevant for ion-particle collisions in complex (dusty) plasmas.
Accurate momentum transfer cross section for the attractive Yukawa potential
Khrapak, S. A.
2014-01-01
Accurate expression for the momentum transfer cross section for the attractive Yukawa potential is proposed. This simple analytic expression agrees with the numerical results better than to within $\\pm 2\\%$ in the regime relevant for ion-particle collisions in complex (dusty) plasmas.
$H_{2}^{+}$ ion in strong magnetic field an accurate calculation
López, J C; Turbiner, A V
1997-01-01
Using a unique trial function we perform an accurate calculation of the ground state $1\\sigma_g$ of the hydrogenic molecular ion $H^+_2$ in a constant uniform magnetic field ranging $0-10^{13}$ G. We show that this trial function also makes it possible to study the negative parity ground state $1\\sigma_u$.
Is a Writing Sample Necessary for "Accurate Placement"?
Sullivan, Patrick; Nielsen, David
2009-01-01
The scholarship about assessment for placement is extensive and notoriously ambiguous. Foremost among the questions that continue to be unresolved in this scholarship is this one: Is a writing sample necessary for "accurate placement"? Using a robust data sample of student assessment essays and ACCUPLACER test scores, we put this question to the…
A Simple and Accurate Method for Measuring Enzyme Activity.
Yip, Din-Yan
1997-01-01
Presents methods commonly used for investigating enzyme activity using catalase and presents a new method for measuring catalase activity that is more reliable and accurate. Provides results that are readily reproduced and quantified. Can also be used for investigations of enzyme properties such as the effects of temperature, pH, inhibitors,…
Accurate Period Approximation for Any Simple Pendulum Amplitude
Institute of Scientific and Technical Information of China (English)
XUE De-Sheng; ZHOU Zhao; GAO Mei-Zhen
2012-01-01
Accurate approximate analytical formulae of the pendulum period composed of a few elementary functions for any amplitude are constructed.Based on an approximation of the elliptic integral,two new logarithmic formulae for large amplitude close to 180° are obtained.Considering the trigonometric function modulation results from the dependence of relative error on the amplitude,we realize accurate approximation period expressions for any amplitude between 0 and 180°.A relative error less than 0.02％ is achieved for any amplitude.This kind of modulation is also effective for other large-amplitude logarithmic approximation expressions.%Accurate approximate analytical formulae of the pendulum period composed of a few elementary functions for any amplitude are constructed. Based on an approximation of the elliptic integral, two new logarithmic formulae for large amplitude close to 180° are obtained. Considering the trigonometric function modulation results from the dependence of relative error on the amplitude, we realize accurate approximation period expressions for any amplitude between 0 and 180°. A relative error less than 0.02% is achieved for any amplitude. This kind of modulation is also effective for other large-amplitude logarithmic approximation expressions.
Fast and Accurate Residential Fire Detection Using Wireless Sensor Networks
Bahrepour, Majid; Meratnia, Nirvana; Havinga, Paul J.M.
2010-01-01
Prompt and accurate residential fire detection is important for on-time fire extinguishing and consequently reducing damages and life losses. To detect fire sensors are needed to measure the environmental parameters and algorithms are required to decide about occurrence of fire. Recently, wireless s
Accurate momentum transfer cross section for the attractive Yukawa potential
Energy Technology Data Exchange (ETDEWEB)
Khrapak, S. A., E-mail: Sergey.Khrapak@dlr.de [Forschungsgruppe Komplexe Plasmen, Deutsches Zentrum für Luft- und Raumfahrt, Oberpfaffenhofen (Germany)
2014-04-15
Accurate expression for the momentum transfer cross section for the attractive Yukawa potential is proposed. This simple analytic expression agrees with the numerical results better than to within ±2% in the regime relevant for ion-particle collisions in complex (dusty) plasmas.
Novel multi-beam radiometers for accurate ocean surveillance
DEFF Research Database (Denmark)
Cappellin, C.; Pontoppidan, K.; Nielsen, P. H.;
2014-01-01
Novel antenna architectures for real aperture multi-beam radiometers providing high resolution and high sensitivity for accurate sea surface temperature (SST) and ocean vector wind (OVW) measurements are investigated. On the basis of the radiometer requirements set for future SST/OVW missions...
Accurate analysis of planar metamaterials using the RLC theory
DEFF Research Database (Denmark)
Malureanu, Radu; Lavrinenko, Andrei
2008-01-01
In this work we will present an accurate description of metallic pads response using RLC theory. In order to calculate such response we take into account several factors including the mutual inductances, precise formula for determining the capacitance and also the pads’ resistance considering the...
Accurate segmentation of dense nanoparticles by partially discrete electron tomography
Energy Technology Data Exchange (ETDEWEB)
Roelandts, T., E-mail: tom.roelandts@ua.ac.be [IBBT-Vision Lab University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); Batenburg, K.J. [IBBT-Vision Lab University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium); Centrum Wiskunde and Informatica, Science Park 123, 1098 XG Amsterdam (Netherlands); Biermans, E. [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Kuebel, C. [Institute of Nanotechnology, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen (Germany); Bals, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Sijbers, J. [IBBT-Vision Lab University of Antwerp, Universiteitsplein 1, 2610 Wilrijk (Belgium)
2012-03-15
Accurate segmentation of nanoparticles within various matrix materials is a difficult problem in electron tomography. Due to artifacts related to image series acquisition and reconstruction, global thresholding of reconstructions computed by established algorithms, such as weighted backprojection or SIRT, may result in unreliable and subjective segmentations. In this paper, we introduce the Partially Discrete Algebraic Reconstruction Technique (PDART) for computing accurate segmentations of dense nanoparticles of constant composition. The particles are segmented directly by the reconstruction algorithm, while the surrounding regions are reconstructed using continuously varying gray levels. As no properties are assumed for the other compositions of the sample, the technique can be applied to any sample where dense nanoparticles must be segmented, regardless of the surrounding compositions. For both experimental and simulated data, it is shown that PDART yields significantly more accurate segmentations than those obtained by optimal global thresholding of the SIRT reconstruction. -- Highlights: Black-Right-Pointing-Pointer We present a novel reconstruction method for partially discrete electron tomography. Black-Right-Pointing-Pointer It accurately segments dense nanoparticles directly during reconstruction. Black-Right-Pointing-Pointer The gray level to use for the nanoparticles is determined objectively. Black-Right-Pointing-Pointer The method expands the set of samples for which discrete tomography can be applied.
Practical schemes for accurate forces in quantum Monte Carlo
Moroni, S.; Saccani, S.; Filippi, C.
2014-01-01
While the computation of interatomic forces has become a well-established practice within variational Monte Carlo (VMC), the use of the more accurate Fixed-Node Diffusion Monte Carlo (DMC) method is still largely limited to the computation of total energies on structures obtained at a lower level of