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
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...... variation of (z) over cap and terms are retained to first-order. With shoaling enhancement, the new models obtain a comparable accuracy in linear shoaling to the original velocity formulation. General consistency relations are also derived which are convenient for verifying that the differential operators...
On the Range of Validity and Accuracy of Boussinesq-Type Models
Institute of Scientific and Technical Information of China (English)
许泰文; 杨炳达; 曾以帆
2004-01-01
In this paper the range of validity and comparison of accuracy of three Boussinesq-type models (Madsen and Sφrensen, 1992; Nwogu, 1993; Wei et al., 1995; referred to as MS, NW and WKGS, respectively) are analyzed and discussed. The governing equations are extended to the second-order approximations to keep higher-order nonlinear terms. Two key parameters ε andμ representing wave nonlinear and frequency dispersive properties are used to demarcate the limit of applicability for these three models. The accuracy of predictions by each model is compared by the relative errors with and without higher-order nonlinear terms in Boussinesq equations. A numerical model is developed based on one-dimensional Boussinesq equations and applied to the case of waves propagating over a submerged bar. The performance and feasibility of each model are tested against laboratory data.
A Study of Enhanced, Higher Order Boussinesq-Type Equations and Their Numerical Modelling
DEFF Research Database (Denmark)
Banijamali, Babak
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...... discretisation methods. The analysis categorises the errors of the semidiscretised and the fully-discretised equations into the categories of spurious dispersion and spurious diffusion. In particular, issues of numerical wave refraction and numerical wave blocking are introduced and addressed in the contexts...... is realizable. These tests also provided a venue for the practical investigation of the linear and nonlinear properties of the numerical models in the sense of the type of discretisations. Similarly, the applications to the propagation over the focusing bathymetry of Whalin (1971) was a similar venue...
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 fully nonlinear and highly dispersive waves traveling over a rapidly varying bathymetry. Finally, we cover applications of this Boussinesq model, and we study a number of nonlinear wave phenomena in deep and shallow water. These include (1) Kinematics in highly nonlinear progressive deep-water waves; (2......) Kinematics in progressive solitary waves; (3) Reflection of solitary waves from a vertical wall; (4) Reflection and diffraction around a vertical plate; (5) Quartet and quintet interactions and class I and II instabilities; (6) Extreme events from focused directionally spread waveelds; (7) Bragg scattering...
Brocchini, Maurizio
2013-12-08
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 introduced. Using spectral element simulations of stream function waves it is illustrated that (i) the bounded equations capture the physics of the wave motion as well as the standard unbounded equations, and (ii) the bounded equations are computationally more efficient when explicit time-stepping schemes...
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.
A variational model for fully non-linear water waves of Boussinesq type
Klopman, Gert; Dingemans, Maarten W.; Groesen, van Brenny; Grue, J.
2005-01-01
Using a variational principle and a parabolic approximation to the vertical structure of the velocity potential, the equations of motion for surface gravity waves over mildly sloping bathymetry are derived. No approximations are made concerning the non-linearity of the waves. The resulting model equ
Finite volume schemes for Boussinesq type equations
2011-01-01
6 pages, 2 figures, 18 references. Published in proceedings of Colloque EDP-Normandie held at Caen (France), on 28 & 29 October 2010. Other author papers can be dowloaded at http://www.lama.univ-savoie.fr/~dutykh/; Finite volume schemes are commonly used to construct approximate solutions to conservation laws. In this study we extend the framework of the finite volume methods to dispersive water wave models, in particular to Boussinesq type systems. We focus mainly on the application of the m...
Finite volume schemes for Boussinesq type equations
Dutykh, Denys; Mitsotakis, Dimitrios
2011-01-01
Finite volume schemes are commonly used to construct approximate solutions to conservation laws. In this study we extend the framework of the finite volume methods to dispersive water wave models, in particular to Boussinesq type systems. We focus mainly on the application of the method to bidirectional nonlinear, dispersive wave propagation in one space dimension. Special emphasis is given to important nonlinear phenomena such as solitary waves interactions.
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
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...... considerations combined with a mirror principle, it is possible to impose weak slip boundary conditions for both structured and general curvilinear wall boundaries while maintaining the accuracy of the scheme. As is standard for current high-order Boussinesq-type models, arbitrary waves can be generated...... 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...
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.
Jeschke, Anja; Behrens, Jörn
2015-04-01
In tsunami modeling, two different systems of dispersive long wave equations are common: The nonhydrostatic pressure correction for the shallow water equations derived out of the depth-integrated 3D Reynolds-averaged Navier-Stokes equations, and the category of Boussinesq-type equations obtained by an expansion in the nondimensional parameters for nonlinearity and dispersion in the Euler equations. The first system uses as an assumption a linear vertical interpolation of the nonhydrostatic pressure, whereas the second system's derivation includes an quadratic vertical interpolation for the nonhydrostatic pressure. In this case the analytical dispersion relations do not coincide. We show that the nonhydrostatic correction with a quadratic vertical interpolation yields an equation set equivalent to the Serre equations, which are 1D Boussinesq-type equations for the case of a horizontal bottom. Now, both systems yield the same analytical dispersion relation according up to the first order with the reference dispersion relation of the linear wave theory. The adjusted model is also compared to other Boussinesq-type equations. The numerical model with the nonhydrostatic correction for the shallow water equations uses Leapfrog timestepping stabilized with the Asselin filter and the P1-PNC1 finite element space discretization. The numerical dispersion relations are computed and compared by employing a testcase of a standing wave in a closed basin. All numerical values match their theoretical expectations. This work is funded by project ASTARTE - Assessment, Strategy And Risk Reduction for Tsunamis in Europe - FP7-ENV2013 6.4-3, Grant 603839. We acknowledge the support given by Geir K. Petersen from the University of Oslo.
Boundary Value Problems for Boussinesq Type Systems
Energy Technology Data Exchange (ETDEWEB)
Fokas, A. S. [Cambridge University, Department of Applied Mathematics and Theoretical Physics (United Kingdom)], E-mail: t.fokas@damtp.cam.ac.uk; Pelloni, B. [University of Reading, Department of Mathematics (United Kingdom)], E-mail: b.pelloni@rdg.ac.uk
2005-02-15
We characterise the boundary conditions that yield a linearly well posed problem for the so-called KdV-KdV system and for the classical Boussinesq system. Each of them is a system of two evolution PDEs modelling two-way propagation of water waves. We study these problems with the spatial variable in either the half-line or in a finite interval. The results are obtained by extending a spectral transform approach, recently developed for the analysis of scalar evolution PDEs, to the case of systems of PDEs.The knowledge of the boundary conditions that should be imposed in order for the problem to be linearly well posed can be used to obtain an integral representation of the solution. This knowledge is also necessary in order to conduct numerical simulations for the fully nonlinear systems.
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.
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...... functions of arbitrary order in space on each element of an unstructured computational domain. A fourth order explicit Runge-Kutta scheme is used to advance the solution in time. Methods for introducing artificial damping to control mild nonlinear instabilities are also discussed. The accuracy...... 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
DEFF Research Database (Denmark)
Engsig-Karup, Allan Peter
2007-01-01
is not subject to severe restrictions which can affect the performance of the scheme. It is demonstrated that the discrete properties of both DG-FEM and finite difference methods can be discretized to mimic the analytical properties. It is investigated mathematically and demonstrated numerically how......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 interactions and interaction with structures. The main goal can be reached by using multi-domain methods...
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.
Fully nonlinear Boussinesq-type equations with optimized parameters for water wave propagation
Jing, Hai-xiao; Liu, Chang-gen; Long, Wen; Tao, Jian-hua
2015-06-01
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.
Kazolea, M.; Delis, A. I.; Synolakis, C. E.
2014-08-01
A new methodology is presented to handle wave breaking over complex bathymetries in extended two-dimensional Boussinesq-type (BT) models which are solved by an unstructured well-balanced finite volume (FV) scheme. The numerical model solves the 2D extended BT equations proposed by Nwogu (1993), recast in conservation law form with a hyperbolic flux identical to that of the Non-linear Shallow Water (NSW) equations. Certain criteria, along with their proper implementation, are established to characterize breaking waves. Once breaking waves are recognized, we switch locally in the computational domain from the BT to NSW equations by suppressing the dispersive terms in the vicinity of the wave fronts. Thus, the shock-capturing features of the FV scheme enable an intrinsic representation of the breaking waves, which are handled as shocks by the NSW equations. An additional methodology is presented on how to perform a stable switching between the BT and NSW equations within the unstructured FV framework. Extensive validations are presented, demonstrating the performance of the proposed wave breaking treatment, along with some comparisons with other well-established wave breaking mechanisms that have been proposed for BT models.
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).
Feng, Wei; Zhao, Song-lin
2016-10-01
In this paper, we investigate the nonautonomous extended lattice Boussinesq-type equations in terms of generalized Cauchy matrix approach. Several kinds of solutions more than multi-soliton solutions to these equations are derived by solving determining equation set. Three-dimensional consistency of these equations is also studied.
Global behavior of the solutions to Boussinesq type equation with linear restoring force
Kutev, N.; Kolkovska, N.; Dimova, M.
2014-11-01
Global existence or finite time blow up of the weak solutions to Boussinesq type equation with linear restoring force is proved. For subcritical initial energy the potential well method is applied. Finite time blow up of the solutions with arbitrary high positive initial energy is proved under general structural conditions for the initial data. Numerical experiments illustrating the theoretical results are presented.
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
On Devising Boussinesq-type Equations with Bounded Eigenspectra: Two Horizontal Dimensions
DEFF Research Database (Denmark)
Eskilsson, Claes; Engsig-Karup, Allan Peter
2015-01-01
Boussinesq-type equations are used to describe the propagation and transformation of free-surface waves in the nearshore region. The nonlinear and dispersive performance of the equations are determined by tunable parameters. Recently the authors presented conditions on the free parameters under...... which a Nwogu-type equations would yield bounded eigenspectra [5]. This leads to a global conditional CFL time-step restriction which is shown to not be affected by the discretisation method and in this sense the CFL condition is tamed to impose a minimal constraint. In this paper we extend the previous...
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...... to the POT. The GDOT can optimize for the size as well as the orientation and position of arbitrarily shaped array elements. Both co- and cross-polar radiation can be optimized for multiple frequencies, dual polarization, and several feed illuminations. Several contoured beam reflectarrays have been designed...... using the GDOT to demonstrate its capabilities. To verify the accuracy of the GDOT, two offset contoured beam reflectarrays that radiate a high-gain beam on a European coverage have been designed and manufactured, and subsequently measured at the DTU-ESA Spherical Near-Field Antenna Test Facility...
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
Domain walls to Boussinesq-type equations in (2 + 1)-dimensions
Triki, H.; Kara, A. H.; Biswas, A.
2014-07-01
In this paper, two models with fourth-order dispersion in 2 + 1 dimensions are investigated. Based on Ansatz method, exact domain wall solutions are derived. Parametric conditions for the existence of the domain wall solutions are given. Lie symmetry analysis also retrieves conserved densities of governing nonlinear evolution equations.
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
and 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...
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.
Towards Accurate Modeling of Moving Contact Lines
Holmgren, Hanna
2015-01-01
A main challenge in numerical simulations of moving contact line problems is that the adherence, or no-slip boundary condition leads to a non-integrable stress singularity at the contact line. In this report we perform the first steps in developing the macroscopic part of an accurate multiscale model for a moving contact line problem in two space dimensions. We assume that a micro model has been used to determine a relation between the contact angle and the contact line velocity. An intermediate region is introduced where an analytical expression for the velocity exists. This expression is used to implement boundary conditions for the moving contact line at a macroscopic scale, along a fictitious boundary located a small distance away from the physical boundary. Model problems where the shape of the interface is constant thought the simulation are introduced. For these problems, experiments show that the errors in the resulting contact line velocities converge with the grid size $h$ at a rate of convergence $...
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...
Tsunami generation, propagation, and run-up with a high-order Boussinesq model
DEFF Research Database (Denmark)
Fuhrman, David R.; Madsen, Per A.
2009-01-01
In this work we extend a high-order Boussinesq-type (finite difference) model, capable of simulating waves out to wavenumber times depth kh landslide-induced tsunamis. The extension is straight forward, requiring only....... The Boussinesq-type model is then used to simulate numerous tsunami-type events generated from submerged landslides, in both one and two horizontal dimensions. The results again compare well against previous experiments and/or numerical simulations. The new extension compliments recently developed run...
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.
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
Inverter Modeling For Accurate Energy Predictions Of Tracking HCPV Installations
Bowman, J.; Jensen, S.; McDonald, Mark
2010-10-01
High efficiency high concentration photovoltaic (HCPV) solar plants of megawatt scale are now operational, and opportunities for expanded adoption are plentiful. However, effective bidding for sites requires reliable prediction of energy production. HCPV module nameplate power is rated for specific test conditions; however, instantaneous HCPV power varies due to site specific irradiance and operating temperature, and is degraded by soiling, protective stowing, shading, and electrical connectivity. These factors interact with the selection of equipment typically supplied by third parties, e.g., wire gauge and inverters. We describe a time sequence model accurately accounting for these effects that predicts annual energy production, with specific reference to the impact of the inverter on energy output and interactions between system-level design decisions and the inverter. We will also show two examples, based on an actual field design, of inverter efficiency calculations and the interaction between string arrangements and inverter selection.
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
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.
Modeling Battery Behavior for Accurate State-of-Charge Indication
Pop, V.; Bergveld, H.J.; Veld, op het J.H.G.; Regtien, P.P.L.; Danilov, D.; Notten, P.H.L.
2006-01-01
Li-ion is the most commonly used battery chemistry in portable applications nowadays. Accurate state-of-charge (SOC) and remaining run-time indication for portable devices is important for the user's convenience and to prolong the lifetime of batteries. A new SOC indication system, combining the ele
Artificial Intelligence for Constructing Accurate, Low-Cost Models and
2005-01-01
0.5 1 1.5 2 2.5 -12 -7 -2 3 8 13 AOA C l Equation Model Human Predicition Machine Learning Test Data Figure C-14 NACA 4421 Model Comparison...Natrajan, Anand, and Srinivasan, Sudhir, (1997) “Consistency Maintenance in Multiresolution Simulation”, ACM Transactions on Modeling and
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...
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...
Towards an Accurate Performance Modeling of Parallel SparseFactorization
Energy Technology Data Exchange (ETDEWEB)
Grigori, Laura; Li, Xiaoye S.
2006-05-26
We present a performance model to analyze a parallel sparseLU factorization algorithm on modern cached-based, high-end parallelarchitectures. Our model characterizes the algorithmic behavior bytakingaccount the underlying processor speed, memory system performance, aswell as the interconnect speed. The model is validated using theSuperLU_DIST linear system solver, the sparse matrices from realapplications, and an IBM POWER3 parallel machine. Our modelingmethodology can be easily adapted to study performance of other types ofsparse factorizations, such as Cholesky or QR.
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 Low-Mass Stellar Models of KOI-126
Feiden, Gregory A; Dotter, Aaron
2011-01-01
The recent discovery of an eclipsing hierarchical triple system with two low-mass stars in a close orbit (KOI-126) by Carter et al. (2011) appeared to reinforce the evidence that theoretical stellar evolution models are not able to reproduce the observational mass-radius relation for low-mass stars. We present a set of stellar models for the three stars in the KOI-126 system that show excellent agreement with the observed radii. This agreement appears to be due to the equation of state implemented by our code. A significant dispersion in the observed mass-radius relation for fully convective stars is demonstrated; indicative of the influence of physics currently not incorporated in standard stellar evolution models. We also predict apsidal motion constants for the two M-dwarf companions. These values should be observationally determined to within 1% by the end of the Kepler mission.
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 ...
Accurate Modeling of Buck Converters with Magnetic-Core Inductors
DEFF Research Database (Denmark)
Astorino, Antonio; Antonini, Giulio; Swaminathan, Madhavan
2015-01-01
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...
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...
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 modelling of fabricated hollow-core photonic bandgap fibers.
Fokoua, Eric Numkam; Sandoghchi, Seyed Reza; Chen, Yong; Jasion, Gregory T; Wheeler, Natalie V; Baddela, Naveen K; Hayes, John R; Petrovich, Marco N; Richardson, David J; Poletti, Francesco
2015-09-07
We report a novel approach to reconstruct the cross-sectional profile of fabricated hollow-core photonic bandgap fibers from scanning electron microscope images. Finite element simulations on the reconstructed geometries achieve a remarkable match with the measured transmission window, surface mode position and attenuation. The agreement between estimated scattering loss from surface roughness and measured loss values indicates that structural distortions, in particular the uneven distribution of glass across the thin silica struts on the core boundary, have a strong impact on the loss. This provides insight into the differences between idealized models and fabricated fibers, which could be key to further fiber loss reduction.
Accurate Force Field Development for Modeling Conjugated Polymers.
DuBay, Kateri H; Hall, Michelle Lynn; Hughes, Thomas F; Wu, Chuanjie; Reichman, David R; Friesner, Richard A
2012-11-13
The modeling of the conformational properties of conjugated polymers entails a unique challenge for classical force fields. Conjugation imposes strong constraints upon bond rotation. Planar configurations are favored, but the concomitantly shortened bond lengths result in moieties being brought into closer proximity than usual. The ensuing steric repulsions are particularly severe in the presence of side chains, straining angles, and stretching bonds to a degree infrequently found in nonconjugated systems. We herein demonstrate the resulting inaccuracies by comparing the LMP2-calculated inter-ring torsion potentials for a series of substituted stilbenes and bithiophenes to those calculated using standard classical force fields. We then implement adjustments to the OPLS-2005 force field in order to improve its ability to model such systems. Finally, we show the impact of these changes on the dihedral angle distributions, persistence lengths, and conjugation length distributions observed during molecular dynamics simulations of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) and poly 3-hexylthiophene (P3HT), two of the most widely used conjugated polymers.
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.
Tavakkol, Sasan
2016-01-01
In this paper, we introduce an interactive coastal wave simulation and visualization software, called Celeris. Celeris is an open source software which needs minimum preparation to run on a Windows machine. The software solves the extended Boussinesq equations using a hybrid finite volume - finite difference method and supports moving shoreline boundaries. The simulation and visualization are performed on the GPU using Direct3D libraries, which enables the software to run faster than real-time. Celeris provides a first-of-its-kind interactive modeling platform for coastal wave applications and it supports simultaneous visualization with both photorealistic and colormapped rendering capabilities. We validate our software through comparison with three standard benchmarks for non-breaking and breaking waves.
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....
Fast and accurate calculation of dilute quantum gas using Uehling-Uhlenbeck model equation
Yano, Ryosuke
2017-02-01
The Uehling-Uhlenbeck (U-U) model equation is studied for the fast and accurate calculation of a dilute quantum gas. In particular, the direct simulation Monte Carlo (DSMC) method is used to solve the U-U model equation. DSMC analysis based on the U-U model equation is expected to enable the thermalization to be accurately obtained using a small number of sample particles and the dilute quantum gas dynamics to be calculated in a practical time. Finally, the applicability of DSMC analysis based on the U-U model equation to the fast and accurate calculation of a dilute quantum gas is confirmed by calculating the viscosity coefficient of a Bose gas on the basis of the Green-Kubo expression and the shock layer of a dilute Bose gas around a cylinder.
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.
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
Fast and accurate exercise policies for Bermudan swaptions in the LIBOR market model
Karlsson, P.K.; Jain, S.; Oosterlee, C.W.
2016-01-01
This paper describes an American Monte Carlo approach for obtaining fast and accurate exercise policies for pricing of callable LIBOR Exotics (e.g., Bermudan swaptions) in the LIBOR market model using the Stochastic Grid Bundling Method (SGBM). SGBM is a bundling and regression based Monte Carlo met
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.
Gay, Guillaume; Courtheoux, Thibault; Reyes, Céline; Tournier, Sylvie; Gachet, Yannick
2012-01-01
In fission yeast, erroneous attachments of spindle microtubules to kinetochores are frequent in early mitosis. Most are corrected before anaphase onset by a mechanism involving the protein kinase Aurora B, which destabilizes kinetochore microtubules (ktMTs) in the absence of tension between sister chromatids. In this paper, we describe a minimal mathematical model of fission yeast chromosome segregation based on the stochastic attachment and detachment of ktMTs. The model accurately reproduce...
Accurate Cure Modeling for Isothermal Processing of Fast Curing Epoxy Resins
Directory of Open Access Journals (Sweden)
Alexander Bernath
2016-11-01
Full Text Available In this work a holistic approach for the characterization and mathematical modeling of the reaction kinetics of a fast epoxy resin is shown. Major composite manufacturing processes like resin transfer molding involve isothermal curing at temperatures far below the ultimate glass transition temperature. Hence, premature vitrification occurs during curing and consequently has to be taken into account by the kinetic model. In order to show the benefit of using a complex kinetic model, the Kamal-Malkin kinetic model is compared to the Grindling kinetic model in terms of prediction quality for isothermal processing. From the selected models, only the Grindling kinetic is capable of taking into account vitrification. Non-isothermal, isothermal and combined differential scanning calorimetry (DSC measurements are conducted and processed for subsequent use for model parametrization. In order to demonstrate which DSC measurements are vital for proper cure modeling, both models are fitted to varying sets of measurements. Special attention is given to the evaluation of isothermal DSC measurements which are subject to deviations arising from unrecorded cross-linking prior to the beginning of the measurement as well as from physical aging effects. It is found that isothermal measurements are vital for accurate modeling of isothermal cure and cannot be neglected. Accurate cure predictions are achieved using the Grindling kinetic model.
A Verilog-A Based Fractional Frequency Synthesizer Model for Fast and Accurate Noise Assessment
Directory of Open Access Journals (Sweden)
V. R. Gonzalez-Diaz
2016-04-01
Full Text Available This paper presents a new strategy to simulate fractional frequency synthesizer behavioral models with better performance and reduced simulation time. The models are described in Verilog-A with accurate phase noise predictions and they are based on a time jitter to power spectral density transformation of the principal noise sources in a synthesizer. The results of a fractional frequency synthesizer simulation is compared with state of the art Verilog-A descriptions showing a reduction of nearly 20 times. In addition, experimental results of a fractional frequency synthesizer are compared to the simulation results to validate the proposed model.
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...
Accurate Modeling of a Transverse Flux Permanent Magnet Generator Using 3D Finite Element Analysis
S. Hosseini; MOGHANI, J. S.; Jensen, B B
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...
Li, Rui; Ye, Hongfei; Zhang, Weisheng; Ma, Guojun; Su, Yewang
2015-10-29
Spring constant calibration of the atomic force microscope (AFM) cantilever is of fundamental importance for quantifying the force between the AFM cantilever tip and the sample. The calibration within the framework of thin plate theory undoubtedly has a higher accuracy and broader scope than that within the well-established beam theory. However, thin plate theory-based accurate analytic determination of the constant has been perceived as an extremely difficult issue. In this paper, we implement the thin plate theory-based analytic modeling for the static behavior of rectangular AFM cantilevers, which reveals that the three-dimensional effect and Poisson effect play important roles in accurate determination of the spring constants. A quantitative scaling law is found that the normalized spring constant depends only on the Poisson's ratio, normalized dimension and normalized load coordinate. Both the literature and our refined finite element model validate the present results. The developed model is expected to serve as the benchmark for accurate calibration of rectangular AFM cantilevers.
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.
Directory of Open Access Journals (Sweden)
Péter Fülöp
2009-01-01
Full Text Available The efficient dimensioning of cellular wireless access networks depends highly on the accuracy of the underlying mathematical models of user distribution and traffic estimations. Mobility prediction also considered as an effective method contributing to the accuracy of IP multicast based multimedia transmissions, and ad hoc routing algorithms. In this paper we focus on the tradeoff between the accuracy and the complexity of the mathematical models used to describe user movements in the network. We propose mobility model extension, in order to utilize user's movement history thus providing more accurate results than other widely used models in the literature. The new models are applicable in real-life scenarios, because these rely on additional information effectively available in cellular networks (e.g. handover history, too. The complexity of the proposed models is analyzed, and the accuracy is justified by means of simulation.
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...
Yield-Ensuring DAC-Embedded Opamp Design Based on Accurate Behavioral Model Development
Jang, Yeong-Shin; Nguyen, Hoai-Nam; Ryu, Seung-Tak; Lee, Sang-Gug
An accurate behavioral model of a DAC-embedded opamp (DAC-opamp) is developed for a yield-ensuring LCD column driver design. A lookup table for the V-I curve of the unit differential pair in the DAC-opamp is extracted from a circuit simulation and is later manipulated through a random error insertion. Virtual ground assumption simplifies the output voltage estimation algorithm. The developed behavioral model of a 5-bit DAC-opamp shows good agreement with the circuit level simulation with less than 5% INL difference.
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
Body charge modelling for accurate simulation of small-signal behaviour in floating body SOI
Benson, James; Redman-White, William; D'Halleweyn, Nele V.; Easson, Craig A.; Uren, Michael J.
2002-04-01
We show that careful modelling of body node elements in floating body PD-SOI MOSFET compact models is required in order to obtain accurate small-signal simulation results in the saturation region. The body network modifies the saturation output conductance of the device via the body-source transconductance, resulting in a pole/zero pair being introduced in the conductance-frequency response. We show that neglecting the presence of body charge in the saturation region can often yield inaccurate values for the body capacitances, which in turn can adversely affect the modelling of the output conductance above the pole/zero frequency. We conclude that the underlying cause of this problem is the use of separate models for the intrinsic and extrinsic capacitances. Finally, we present a simple saturation body charge model which can greatly improve small-signal simulation accuracy for floating body devices.
OPUS-Rota: a fast and accurate method for side-chain modeling.
Lu, Mingyang; Dousis, Athanasios D; Ma, Jianpeng
2008-09-01
In this paper, we introduce a fast and accurate side-chain modeling method, named OPUS-Rota. In a benchmark comparison with the methods SCWRL, NCN, LGA, SPRUCE, Rosetta, and SCAP, OPUS-Rota is shown to be much faster than all the methods except SCWRL, which is comparably fast. In terms of overall chi (1) and chi (1+2) accuracies, however, OPUS-Rota is 5.4 and 8.8 percentage points better, respectively, than SCWRL. Compared with NCN, which has the best accuracy in the literature, OPUS-Rota is 1.6 percentage points better for overall chi (1+2) but 0.3 percentage points weaker for overall chi (1). Hence, our algorithm is much more accurate than SCWRL with similar execution speed, and it has accuracy comparable to or better than the most accurate methods in the literature, but with a runtime that is one or two orders of magnitude shorter. In addition, OPUS-Rota consistently outperforms SCWRL on the Wallner and Elofsson homology-modeling benchmark set when the sequence identity is greater than 40%. We hope that OPUS-Rota will contribute to high-accuracy structure refinement, and the computer program is freely available for academic users.
Accurate neural network-based modeling for RF MEMS component synthesizing
Mohamed, Firas; Affour, Bachar
2004-01-01
Contrary to traditional analysis flows as expensive FEM simulation tools or inaccurate electrical models extractors, we developed MemsCompiler that implements a new real synthesis approach for RF MEMS. The new flow starts from system designer requirements and generates, in a one-click operation, a ready-to-fabricate layout (GDSII) and a passive fitted equivalent Spice circuit. Concerning the circuit, physical considerations give us an equivalent schematic in which circuit parameters values must be adjusted to fit the required performances. As to the GDSII, which constitutes the main contribution of this work, Design Of Experiment technique, used in the first version of the synthesizer, gave about 11% of dispersion and found to be unsatisfactory in some cases. A more accurate modeling was indispensable. Thus, we developed a neural networks-based modeling for circular inductors, which are considered by designers among the most stubborn components. This new modeling has shown to be very accurate: MemsCompiler produced about 3% of dispersion compared to the equivalent circuit and about 6% of dispersion for generated geometries. This modeling is flexible and could be rapidly generalized to other components.
Modeling the Non-Linear Behavior of Library Cells for an Accurate Static Noise Analysis
Forzan, Cristiano
2011-01-01
In signal integrity analysis, the joint effect of propagated noise through library cells, and of the noise injected on a quiet net by neighboring switching nets through coupling capacitances, must be considered in order to accurately estimate the overall noise impact on design functionality and performances. In this work the impact of the cell non-linearity on the noise glitch waveform is analyzed in detail, and a new macromodel that allows to accurately and efficiently modeling the non-linear effects of the victim driver in noise analysis is presented. Experimental results demonstrate the effectiveness of our method, and confirm that existing noise analysis approaches based on linear superposition of the propagated and crosstalk-injected noise can be highly inaccurate, thus impairing the sign-off functional verification phase.
Qiuyang, He; Yue, Xu; Feifei, Zhao
2013-10-01
An accurate and complete circuit simulation model for single-photon avalanche diodes (SPADs) is presented. The derived model is not only able to simulate the static DC and dynamic AC behaviors of an SPAD operating in Geiger-mode, but also can emulate the second breakdown and the forward bias behaviors. In particular, it considers important statistical effects, such as dark-counting and after-pulsing phenomena. The developed model is implemented using the Verilog-A description language and can be directly performed in commercial simulators such as Cadence Spectre. The Spectre simulation results give a very good agreement with the experimental results reported in the open literature. This model shows a high simulation accuracy and very fast simulation rate.
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.
A hamster model for Marburg virus infection accurately recapitulates Marburg hemorrhagic fever
Marzi, Andrea; Banadyga, Logan; Haddock, Elaine; Thomas, Tina; Shen, Kui; Horne, Eva J.; Scott, Dana P.; Feldmann, Heinz; Ebihara, Hideki
2016-01-01
Marburg virus (MARV), a close relative of Ebola virus, is the causative agent of a severe human disease known as Marburg hemorrhagic fever (MHF). No licensed vaccine or therapeutic exists to treat MHF, and MARV is therefore classified as a Tier 1 select agent and a category A bioterrorism agent. In order to develop countermeasures against this severe disease, animal models that accurately recapitulate human disease are required. Here we describe the development of a novel, uniformly lethal Syrian golden hamster model of MHF using a hamster-adapted MARV variant Angola. Remarkably, this model displayed almost all of the clinical features of MHF seen in humans and non-human primates, including coagulation abnormalities, hemorrhagic manifestations, petechial rash, and a severely dysregulated immune response. This MHF hamster model represents a powerful tool for further dissecting MARV pathogenesis and accelerating the development of effective medical countermeasures against human MHF. PMID:27976688
Accurate modeling of switched reluctance machine based on hybrid trained WNN
Song, Shoujun; Ge, Lefei; Ma, Shaojie; Zhang, Man
2014-04-01
According to the strong nonlinear electromagnetic characteristics of switched reluctance machine (SRM), a novel accurate modeling method is proposed based on hybrid trained wavelet neural network (WNN) which combines improved genetic algorithm (GA) with gradient descent (GD) method to train the network. In the novel method, WNN is trained by GD method based on the initial weights obtained per improved GA optimization, and the global parallel searching capability of stochastic algorithm and local convergence speed of deterministic algorithm are combined to enhance the training accuracy, stability and speed. Based on the measured electromagnetic characteristics of a 3-phase 12/8-pole SRM, the nonlinear simulation model is built by hybrid trained WNN in Matlab. The phase current and mechanical characteristics from simulation under different working conditions meet well with those from experiments, which indicates the accuracy of the model for dynamic and static performance evaluation of SRM and verifies the effectiveness of the proposed modeling method.
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.
A pairwise maximum entropy model accurately describes resting-state human brain networks.
Watanabe, Takamitsu; Hirose, Satoshi; Wada, Hiroyuki; Imai, Yoshio; Machida, Toru; Shirouzu, Ichiro; Konishi, Seiki; Miyashita, Yasushi; Masuda, Naoki
2013-01-01
The resting-state human brain networks underlie fundamental cognitive functions and consist of complex interactions among brain regions. However, the level of complexity of the resting-state networks has not been quantified, which has prevented comprehensive descriptions of the brain activity as an integrative system. Here, we address this issue by demonstrating that a pairwise maximum entropy model, which takes into account region-specific activity rates and pairwise interactions, can be robustly and accurately fitted to resting-state human brain activities obtained by functional magnetic resonance imaging. Furthermore, to validate the approximation of the resting-state networks by the pairwise maximum entropy model, we show that the functional interactions estimated by the pairwise maximum entropy model reflect anatomical connexions more accurately than the conventional functional connectivity method. These findings indicate that a relatively simple statistical model not only captures the structure of the resting-state networks but also provides a possible method to derive physiological information about various large-scale brain networks.
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.
Calculation of accurate small angle X-ray scattering curves from coarse-grained protein models
Directory of Open Access Journals (Sweden)
Stovgaard Kasper
2010-08-01
Full Text Available Abstract Background Genome sequencing projects have expanded the gap between the amount of known protein sequences and structures. The limitations of current high resolution structure determination methods make it unlikely that this gap will disappear in the near future. Small angle X-ray scattering (SAXS is an established low resolution method for routinely determining the structure of proteins in solution. The purpose of this study is to develop a method for the efficient calculation of accurate SAXS curves from coarse-grained protein models. Such a method can for example be used to construct a likelihood function, which is paramount for structure determination based on statistical inference. Results We present a method for the efficient calculation of accurate SAXS curves based on the Debye formula and a set of scattering form factors for dummy atom representations of amino acids. Such a method avoids the computationally costly iteration over all atoms. We estimated the form factors using generated data from a set of high quality protein structures. No ad hoc scaling or correction factors are applied in the calculation of the curves. Two coarse-grained representations of protein structure were investigated; two scattering bodies per amino acid led to significantly better results than a single scattering body. Conclusion We show that the obtained point estimates allow the calculation of accurate SAXS curves from coarse-grained protein models. The resulting curves are on par with the current state-of-the-art program CRYSOL, which requires full atomic detail. Our method was also comparable to CRYSOL in recognizing native structures among native-like decoys. As a proof-of-concept, we combined the coarse-grained Debye calculation with a previously described probabilistic model of protein structure, TorusDBN. This resulted in a significant improvement in the decoy recognition performance. In conclusion, the presented method shows great promise for
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....
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.
AN ACCURATE MODEL FOR CALCULATING CORRECTION OF PATH FLEXURE OF SATELLITE SIGNALS
Institute of Scientific and Technical Information of China (English)
LiYanxing; HuXinkang; ShuaiPing; ZhangZhongfu
2003-01-01
The propagation path of satellite signals in the atmosphere is a curve thus it,is very difficult to calculate its flexure correction accurately, a strict calculating expressions has so far not been derived. In this study, the flexure correction of the refraction curve is divided into two parts and their strict calculating expressions are derived. By use of the standard atmospheric model, the accurate flexure correction of the refraction curve is calculated for different zenith distance Z. On this basis, a calculation model is structured. This model is very simple in structure, convenient in use and high in accuracy. When Z is smaller than 85°,the accuracy of the correction exceeds 0.06mm. The flexure correction is basically proportional to tan2Z and increases rapidly with the increase of Z When Z＞50°,the correction is smaller than 0.5 mm and can be neglected. When Z＞50°, the correction must be made. When Z is 85°, 88° and 89° , the corrections are 198mm, 8.911m and 28.497 km, respectively. The calculation results shows that the correction estimate by Hopfield is correct when Z≤80°, but too small when Z=89°. The expression in this paper is applicable to any satellite.
AN ACCURATE MODEL FOR CALCULATING CORRECTION OF PATH FLEXURE OF SATELLITE SIGNALS
Institute of Scientific and Technical Information of China (English)
Li Yanxing; Hu Xinkang; Shuai Ping; Zhang Zhongfu
2003-01-01
The propagation path of satellite signals in the atmosphere is a curve thus it.is very difficult to calculate its flexure correction accurately, a strict calculating expressions has so far not been derived. In this study, the flexure correction of the refraction curve is divided into two parts and their strict calculating expressions are derived. By use of the standard atmospheric model, the accurate flexure correction of the refraction curve is calculated for different zenith distance Z. On this basis, a calculation model is structured. This model is very simple in structure, convenient in use and high in accuracy. When Z is smaller than 85°, the accuracy of the correction exceeds 0.06 mm. The flexure correction is basically proportional to tan2Z and increases rapidly with the increase of Z When Z＞50°,the correction is smaller than 0.5 mm and can be neglected.When Z＞50°, the correction must be made. When Z is 85° , 88° and 89° , the corrections are 198mm, 8. 911 m and 28. 497 km, respectively. The calculation results shows that the correction estimate by Hopfield is correct when Z≤80 °, but too small when Z=89°. The expression in this paper is applicable to any satellite.
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.
Sokalski, W. A.; Shibata, M.; Ornstein, R. L.; Rein, R.
1992-01-01
The quality of several atomic charge models based on different definitions has been analyzed using cumulative atomic multipole moments (CAMM). This formalism can generate higher atomic moments starting from any atomic charges, while preserving the corresponding molecular moments. The atomic charge contribution to the higher molecular moments, as well as to the electrostatic potentials, has been examined for CO and HCN molecules at several different levels of theory. The results clearly show that the electrostatic potential obtained from CAMM expansion is convergent up to R-5 term for all atomic charge models used. This illustrates that higher atomic moments can be used to supplement any atomic charge model to obtain more accurate description of electrostatic properties.
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.
Gay, Guillaume; Courtheoux, Thibault; Reyes, Céline; Tournier, Sylvie; Gachet, Yannick
2012-03-19
In fission yeast, erroneous attachments of spindle microtubules to kinetochores are frequent in early mitosis. Most are corrected before anaphase onset by a mechanism involving the protein kinase Aurora B, which destabilizes kinetochore microtubules (ktMTs) in the absence of tension between sister chromatids. In this paper, we describe a minimal mathematical model of fission yeast chromosome segregation based on the stochastic attachment and detachment of ktMTs. The model accurately reproduces the timing of correct chromosome biorientation and segregation seen in fission yeast. Prevention of attachment defects requires both appropriate kinetochore orientation and an Aurora B-like activity. The model also reproduces abnormal chromosome segregation behavior (caused by, for example, inhibition of Aurora B). It predicts that, in metaphase, merotelic attachment is prevented by a kinetochore orientation effect and corrected by an Aurora B-like activity, whereas in anaphase, it is corrected through unbalanced forces applied to the kinetochore. These unbalanced forces are sufficient to prevent aneuploidy.
Gröning, Flora; Jones, Marc E. H.; Curtis, Neil; Herrel, Anthony; O'Higgins, Paul; Evans, Susan E.; Fagan, Michael J.
2013-01-01
Computer-based simulation techniques such as multi-body dynamics analysis are becoming increasingly popular in the field of skull mechanics. Multi-body models can be used for studying the relationships between skull architecture, muscle morphology and feeding performance. However, to be confident in the modelling results, models need to be validated against experimental data, and the effects of uncertainties or inaccuracies in the chosen model attributes need to be assessed with sensitivity analyses. Here, we compare the bite forces predicted by a multi-body model of a lizard (Tupinambis merianae) with in vivo measurements, using anatomical data collected from the same specimen. This subject-specific model predicts bite forces that are very close to the in vivo measurements and also shows a consistent increase in bite force as the bite position is moved posteriorly on the jaw. However, the model is very sensitive to changes in muscle attributes such as fibre length, intrinsic muscle strength and force orientation, with bite force predictions varying considerably when these three variables are altered. We conclude that accurate muscle measurements are crucial to building realistic multi-body models and that subject-specific data should be used whenever possible. PMID:23614944
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
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...
Directory of Open Access Journals (Sweden)
Suzhi Xiao
2016-04-01
Full Text Available In order to acquire an accurate three-dimensional (3D measurement, the traditional fringe projection technique applies complex and laborious procedures to compensate for the errors that exist in the vision system. However, the error sources in the vision system are very complex, such as lens distortion, lens defocus, and fringe pattern nonsinusoidality. Some errors cannot even be explained or rendered with clear expressions and are difficult to compensate directly as a result. In this paper, an approach is proposed that avoids the complex and laborious compensation procedure for error sources but still promises accurate 3D measurement. It is realized by the mathematical model extension technique. The parameters of the extended mathematical model for the ’phase to 3D coordinates transformation’ are derived using the least-squares parameter estimation algorithm. In addition, a phase-coding method based on a frequency analysis is proposed for the absolute phase map retrieval to spatially isolated objects. The results demonstrate the validity and the accuracy of the proposed flexible fringe projection vision system on spatially continuous and discontinuous objects for 3D measurement.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Wiegman, H.L.N. [General Electric Corporate Research and Development, Schenectady, NY (United States)
2000-07-01
Some recent advances in battery modeling were discussed with reference to on-line impedance estimates and power performance predictions for aqueous solution, porous electrode cell structures. The objective was to determine which methods accurately estimate a battery's internal state and power capability while operating a charge and sustaining a hybrid electric vehicle (HEV) over a wide range of driving conditions. The enhancements to the Randles-Ershler equivalent electrical model of common cells with lead-acid, nickel-cadmium and nickel-metal hydride chemistries were described. This study also investigated which impedances are sensitive to boundary layer charge concentrations and mass transport limitations. Non-linear impedances were shown to significantly affect the battery's ability to process power. The main advantage of on-line estimating a battery's impedance state and power capability is that the battery can be optimally sized for any application. refs., tabs., figs., append.
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...... suspended in a liquid solution. The measured PSDs were sensitive to the addition of a dispersing agent, the dispersion time, and the presence of ultrasound. It was found that the different PSDs influenced the simulated rate of dis-solution significantly (i.e. from below to above the measured dissolution...... rate). The results of this work show that a representative PSD is essential in order to model the rate of dissolution of lime-stone particles accurately....
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.
Directory of Open Access Journals (Sweden)
Apratim Roy
2014-05-01
Full Text Available This paper proposes a technique to accurately estimate radio frequency behaviour of low-power 90 nm amplifier circuits with geometry scalable discrete complementary metal oxide semiconductor (CMOS modelling. Rather than characterising individual elements, the scheme is able to predict gain, noise and reflection loss of low-noise amplifier (LNA architectures made with bias, active and passive components. It reduces number of model parameters by formulating dependent functions in symmetric distributed modelling and shows that simple fitting factors can account for extraneous (interconnect effects in LNA structure. Equivalent-circuit model equations based on physical structure and describing layout parasites are developed for major amplifier elements like metal–insulator–metal (MIM capacitor, spiral symmetric inductor, polysilicon (PS resistor and bulk RF transistor. The models are geometry scalable with respect to feature dimensions, i.e. MIM/PS width and length, outer-dimension/turns of planar inductor and channel-width/fingers of active device. Results obtained with the CMOS models are compared against measured literature data for two 1.2 V amplifier circuits where prediction accuracy for RF parameters (S(21, noise figure, S(11, S(22 lies within the range of 92–99%.
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/.
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
Whittleton, Sarah R; Otero-de-la-Roza, A; Johnson, Erin R
2017-02-14
Accurate energy ranking is a key facet to the problem of first-principles crystal-structure prediction (CSP) of molecular crystals. This work presents a systematic assessment of B86bPBE-XDM, a semilocal density functional combined with the exchange-hole dipole moment (XDM) dispersion model, for energy ranking using 14 compounds from the first five CSP blind tests. Specifically, the set of crystals studied comprises 11 rigid, planar compounds and 3 co-crystals. The experimental structure was correctly identified as the lowest in lattice energy for 12 of the 14 total crystals. One of the exceptions is 4-hydroxythiophene-2-carbonitrile, for which the experimental structure was correctly identified once a quasi-harmonic estimate of the vibrational free-energy contribution was included, evidencing the occasional importance of thermal corrections for accurate energy ranking. The other exception is an organic salt, where charge-transfer error (also called delocalization error) is expected to cause the base density functional to be unreliable. Provided the choice of base density functional is appropriate and an estimate of temperature effects is used, XDM-corrected density-functional theory is highly reliable for the energetic ranking of competing crystal structures.
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.
Accurate integral equation theory for the central force model of liquid water and ionic solutions
Ichiye, Toshiko; Haymet, A. D. J.
1988-10-01
The atom-atom pair correlation functions and thermodynamics of the central force model of water, introduced by Lemberg, Stillinger, and Rahman, have been calculated accurately by an integral equation method which incorporates two new developments. First, a rapid new scheme has been used to solve the Ornstein-Zernike equation. This scheme combines the renormalization methods of Allnatt, and Rossky and Friedman with an extension of the trigonometric basis-set solution of Labik and co-workers. Second, by adding approximate ``bridge'' functions to the hypernetted-chain (HNC) integral equation, we have obtained predictions for liquid water in which the hydrogen bond length and number are in good agreement with ``exact'' computer simulations of the same model force laws. In addition, for dilute ionic solutions, the ion-oxygen and ion-hydrogen coordination numbers display both the physically correct stoichiometry and good agreement with earlier simulations. These results represent a measurable improvement over both a previous HNC solution of the central force model and the ex-RISM integral equation solutions for the TIPS and other rigid molecule models of water.
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
Application of thin plate splines for accurate regional ionosphere modeling with multi-GNSS data
Krypiak-Gregorczyk, Anna; Wielgosz, Pawel; Borkowski, Andrzej
2016-04-01
GNSS-derived regional ionosphere models are widely used in both precise positioning, ionosphere and space weather studies. However, their accuracy is often not sufficient to support precise positioning, RTK in particular. In this paper, we presented new approach that uses solely carrier phase multi-GNSS observables and thin plate splines (TPS) for accurate ionospheric TEC modeling. TPS is a closed solution of a variational problem minimizing both the sum of squared second derivatives of a smoothing function and the deviation between data points and this function. This approach is used in UWM-rt1 regional ionosphere model developed at UWM in Olsztyn. The model allows for providing ionospheric TEC maps with high spatial and temporal resolutions - 0.2x0.2 degrees and 2.5 minutes, respectively. For TEC estimation, EPN and EUPOS reference station data is used. The maps are available with delay of 15-60 minutes. In this paper we compare the performance of UWM-rt1 model with IGS global and CODE regional ionosphere maps during ionospheric storm that took place on March 17th, 2015. During this storm, the TEC level over Europe doubled comparing to earlier quiet days. The performance of the UWM-rt1 model was validated by (a) comparison to reference double-differenced ionospheric corrections over selected baselines, and (b) analysis of post-fit residuals to calibrated carrier phase geometry-free observational arcs at selected test stations. The results show a very good performance of UWM-rt1 model. The obtained post-fit residuals in case of UWM maps are lower by one order of magnitude comparing to IGS maps. The accuracy of UWM-rt1 -derived TEC maps is estimated at 0.5 TECU. This may be directly translated to the user positioning domain.
Brandenburg, Jan Gerit; Grimme, Stefan
2014-06-05
The ambitious goal of organic crystal structure prediction challenges theoretical methods regarding their accuracy and efficiency. Dispersion-corrected density functional theory (DFT-D) in principle is applicable, but the computational demands, for example, to compute a huge number of polymorphs, are too high. Here, we demonstrate that this task can be carried out by a dispersion-corrected density functional tight binding (DFTB) method. The semiempirical Hamiltonian with the D3 correction can accurately and efficiently model both solid- and gas-phase inter- and intramolecular interactions at a speed up of 2 orders of magnitude compared to DFT-D. The mean absolute deviations for interaction (lattice) energies for various databases are typically 2-3 kcal/mol (10-20%), that is, only about two times larger than those for DFT-D. For zero-point phonon energies, small deviations of <0.5 kcal/mol compared to DFT-D are obtained.
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 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.
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 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.
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.
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)
Mohammed Moulay
2015-01-01
Full Text Available A novel configuration of quad-band bowtie antenna suitable for wireless application is proposed based on accurate equivalent circuit model. The simple configuration and low profile nature of the proposed antenna lead to easy multifrequency operation. The proposed antenna is designed to satisfy specific bandwidth specifications for current communication systems including the Bluetooth (frequency range 2.4–2.485 GHz and bands of the Unlicensed National Information Infrastructure (U-NII low band (frequency range 5.15–5.35 GHz and U-NII mid band (frequency range 5.47–5.725 GHz and used for mobile WiMAX (frequency range 3.3–3.6 GHz. To validate the proposed equivalent circuit model, the simulation results are compared with those obtained by the moments method of Momentum software, the finite integration technique of CST Microwave studio, and the finite element method of HFSS software. An excellent agreement is achieved for all the designed antennas. The analysis of the simulated results confirms the successful design of quad-band bowtie antenna.
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.
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 De Novo Prediction of Protein Contact Map by Ultra-Deep Learning Model
Li, Zhen; Zhang, Renyu
2017-01-01
Motivation Protein contacts contain key information for the understanding of protein structure and function and thus, contact prediction from sequence is an important problem. Recently exciting progress has been made on this problem, but the predicted contacts for proteins without many sequence homologs is still of low quality and not very useful for de novo structure prediction. Method This paper presents a new deep learning method that predicts contacts by integrating both evolutionary coupling (EC) and sequence conservation information through an ultra-deep neural network formed by two deep residual neural networks. The first residual network conducts a series of 1-dimensional convolutional transformation of sequential features; the second residual network conducts a series of 2-dimensional convolutional transformation of pairwise information including output of the first residual network, EC information and pairwise potential. By using very deep residual networks, we can accurately model contact occurrence patterns and complex sequence-structure relationship and thus, obtain higher-quality contact prediction regardless of how many sequence homologs are available for proteins in question. Results Our method greatly outperforms existing methods and leads to much more accurate contact-assisted folding. Tested on 105 CASP11 targets, 76 past CAMEO hard targets, and 398 membrane proteins, the average top L long-range prediction accuracy obtained by our method, one representative EC method CCMpred and the CASP11 winner MetaPSICOV is 0.47, 0.21 and 0.30, respectively; the average top L/10 long-range accuracy of our method, CCMpred and MetaPSICOV is 0.77, 0.47 and 0.59, respectively. Ab initio folding using our predicted contacts as restraints but without any force fields can yield correct folds (i.e., TMscore>0.6) for 203 of the 579 test proteins, while that using MetaPSICOV- and CCMpred-predicted contacts can do so for only 79 and 62 of them, respectively. Our contact
SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves
Lelli, Federico; McGaugh, Stacy S.; Schombert, James M.
2016-12-01
We introduce SPARC (Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 μm and high-quality rotation curves from previous H i/Hα 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–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i mass–radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic to observed velocity (V bar/V obs) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ⋆) at [3.6]. Assuming ϒ⋆ ≃ 0.5 M ⊙/L ⊙ (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 corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii) V bar/V obs varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ⋆ ≃ 0.2 M ⊙/L ⊙ as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ⋆ ≃ 0.7 M ⊙/L ⊙ at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.
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...
Accurate prediction of DnaK-peptide binding via homology modelling and experimental data.
Directory of Open Access Journals (Sweden)
Joost Van Durme
2009-08-01
Full Text Available Molecular chaperones are essential elements of the protein quality control machinery that governs translocation and folding of nascent polypeptides, refolding and degradation of misfolded proteins, and activation of a wide range of client proteins. The prokaryotic heat-shock protein DnaK is the E. coli representative of the ubiquitous Hsp70 family, which specializes in the binding of exposed hydrophobic regions in unfolded polypeptides. Accurate prediction of DnaK binding sites in E. coli proteins is an essential prerequisite to understand the precise function of this chaperone and the properties of its substrate proteins. In order to map DnaK binding sites in protein sequences, we have developed an algorithm that combines sequence information from peptide binding experiments and structural parameters from homology modelling. We show that this combination significantly outperforms either single approach. The final predictor had a Matthews correlation coefficient (MCC of 0.819 when assessed over the 144 tested peptide sequences to detect true positives and true negatives. To test the robustness of the learning set, we have conducted a simulated cross-validation, where we omit sequences from the learning sets and calculate the rate of repredicting them. This resulted in a surprisingly good MCC of 0.703. The algorithm was also able to perform equally well on a blind test set of binders and non-binders, of which there was no prior knowledge in the learning sets. The algorithm is freely available at http://limbo.vib.be.
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.
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.
A simple and accurate model for Love wave based sensors: Dispersion equation and mass sensitivity
Directory of Open Access Journals (Sweden)
Jiansheng Liu
2014-07-01
Full Text Available 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 structure with an anisotropic-considered substrate and an isotropic guiding layer; an intuitive expression for mass sensitivity is also derived based on the dispersion equation. The new equations are in simple forms similar to the previously reported simplified model with an isotropic substrate. By introducing the Maxwell-Weichert model, these equations are also applicable to the LW device incorporating a viscoelastic guiding layer; the mass velocity sensitivity and the mass propagation loss sensitivity are obtained from the real part and the imaginary part of the complex mass sensitivity, respectively. With Love waves in an elastic SiO2 layer on an ST-90°X quartz structure, for example, comparisons are carried out between the velocities and normalized sensitivities calculated by using different dispersion equations and corresponding mass sensitivities. Numerical results of the method presented in this work are very close to those of the method with a piezoelectric-considered substrate. Another numerical calculation is carried out for the case of a LW sensor with a viscoelastic guiding layer. If the viscosity of the layer is not too big, the effect on the real part of the velocity and the mass velocity sensitivity is relatively small; the propagation loss and the mass loss sensitivity are proportional to the viscosity of the guiding layer.
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
Watson, Charles M; Francis, Gamal R
2015-07-01
Hollow copper models painted to match the reflectance of the animal subject are standard in thermal ecology research. While the copper electroplating process results in accurate models, it is relatively time consuming, uses caustic chemicals, and the models are often anatomically imprecise. Although the decreasing cost of 3D printing can potentially allow the reproduction of highly accurate models, the thermal performance of 3D printed models has not been evaluated. We compared the cost, accuracy, and performance of both copper and 3D printed lizard models and found that the performance of the models were statistically identical in both open and closed habitats. We also find that 3D models are more standard, lighter, durable, and inexpensive, than the copper electroformed models.
Oosten, J.J.M. van; Pacejka, H.B.
2000-01-01
As is well known, Magic Formula tyre modelling (MF-Tyre is a part of ADAMS/Tire) allows an accurate and efficient description of tyre-road interaction forces required for any usual vehicle handling simulation. When it comes to modelling of tyre behaviour at higher frequencies and short road obstacle
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
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...
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.
Directory of Open Access Journals (Sweden)
Sun Lijie
2015-01-01
Full Text Available In this paper, the SPICE model of poly resistor is accurately developed based on silicon data. To describe the non-linear R-V trend, the new correlation in temperature and voltage is found in non-silicide poly-silicon resistor. A scalable model is developed on the temperature-dependent characteristics (TDC and the temperature-dependent voltage characteristics (TDVC from the R-V data. Besides, the parasitic capacitance between poly and substrate are extracted from real silicon structure in replacing conventional simulation data. The capacitance data are tested through using on-wafer charge-induced-injection error-free charge-based capacitance measurement (CIEF-CBCM technique which is driven by non-overlapping clock generation circuit. All modeling test structures are designed and fabricated through using 40nm CMOS technology process. The new SPICE model of poly-silicon resistor is more accurate to silicon for analog circuit simulation.
Alanazi, Hamdan O; Abdullah, Abdul Hanan; Qureshi, Kashif Naseer
2017-04-01
Recently, Artificial Intelligence (AI) has been used widely in medicine and health care sector. In machine learning, the classification or prediction is a major field of AI. Today, the study of existing predictive models based on machine learning methods is extremely active. Doctors need accurate predictions for the outcomes of their patients' diseases. In addition, for accurate predictions, timing is another significant factor that influences treatment decisions. In this paper, existing predictive models in medicine and health care have critically reviewed. Furthermore, the most famous machine learning methods have explained, and the confusion between a statistical approach and machine learning has clarified. A review of related literature reveals that the predictions of existing predictive models differ even when the same dataset is used. Therefore, existing predictive models are essential, and current methods must be improved.
Derakhti, Morteza; Kirby, James T.; Shi, Fengyan; Ma, Gangfeng
2016-11-01
Field-scale modeling of wave-breaking-induced turbulence and mean circulation is still challenging. Although Boussinesq-type models have been successfully used to study field-scale wave transformation and wave-breaking-driven circulation, they cannot provide turbulence or the vertical structure of the velocity field. In addition, the applicability of such models is limited to shallow water. In Part 1 (Derakhti et al., 2016b) of this study, we showed that the non-hydrostatic σ-coordinate RANS model NHWAVE, as described by Derakhti et al. (2016a), accurately predicts organized wave motions and total wave-breaking-induced energy dissipation from deep-water up to the swash zone using a few vertical σ-layers. In this paper, our goal is to examine what level of detail of wave-breaking-induced turbulence and mean circulation, both in depth- and steepness-limited breaking waves, can be reproduced by NHWAVE. Further, effects of modeled turbulent eddy viscosity on the predicted time-averaged velocity distribution is discussed. We establish that NHWAVE is capable of predicting the structure of the mean velocity and vorticity fields including large-scale breaking-induced coherent vortices in deep-water breaking events; where the absence of turbulence-induced eddy viscosity results in the overprediction of the velocity and vorticity field in the breaking region. We show that NHWAVE reduces the required CPU time up to two orders of magnitude in comparison with a comparable VOF-based simulation.
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.
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.
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.
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
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
Toyokuni, Genti; Takenaka, Hiroshi
2012-06-01
We propose a method for modeling global seismic wave propagation through an attenuative Earth model including the center. This method enables accurate and efficient computations since it is based on the 2.5-D approach, which solves wave equations only on a 2-D cross section of the whole Earth and can correctly model 3-D geometrical spreading. We extend a numerical scheme for the elastic waves in spherical coordinates using the finite-difference method (FDM), to solve the viscoelastodynamic equation. For computation of realistic seismic wave propagation, incorporation of anelastic attenuation is crucial. Since the nature of Earth material is both elastic solid and viscous fluid, we should solve stress-strain relations of viscoelastic material, including attenuative structures. These relations represent the stress as a convolution integral in time, which has had difficulty treating viscoelasticity in time-domain computation such as the FDM. However, we now have a method using so-called memory variables, invented in the 1980s, followed by improvements in Cartesian coordinates. Arbitrary values of the quality factor (Q) can be incorporated into the wave equation via an array of Zener bodies. We also introduce the multi-domain, an FD grid of several layers with different grid spacings, into our FDM scheme. This allows wider lateral grid spacings with depth, so as not to perturb the FD stability criterion around the Earth center. In addition, we propose a technique to avoid the singularity problem of the wave equation in spherical coordinates at the Earth center. We develop a scheme to calculate wavefield variables on this point, based on linear interpolation for the velocity-stress, staggered-grid FDM. This scheme is validated through a comparison of synthetic seismograms with those obtained by the Direct Solution Method for a spherically symmetric Earth model, showing excellent accuracy for our FDM scheme. As a numerical example, we apply the method to simulate seismic
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.
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.
Arpaia, P; Spiezia, G; Tiso, S
2007-01-01
A statistical approach to behavioral modeling for assessing dynamic metrological performance during the concept design of accurate digitizers is proposed. A surface-response approach based on statistical experiment design is exploited for avoiding unrealistic hypothesis of linearity, optimizing simulation, exploring operating conditions systematically, as well as verifying identification and validation uncertainty. An actual case study on the dynamic metrological characterization of a Fast Digital Integrator for high-performance magnetic measurements at the European Organization for Nuclear Research (CERN) is presented.
Accurate 3D modeling of Cable in Conduit Conductor type superconductors by X-ray microtomography
Energy Technology Data Exchange (ETDEWEB)
Tiseanu, Ion, E-mail: tiseanu@infim.ro [National Institute for Laser, Plasma and Radiation Physics (INFLPR), Bucharest-Magurele (Romania); Zani, Louis [CEA/Cadarache – Institut de Recherche sur la Fusion Magnetique, St Paul-lez-Durance Cedex (France); Tiseanu, Catalin-Stefan [University of Bucharest, Faculty of Mathematics and Computer Science (Romania); Craciunescu, Teddy; Dobrea, Cosmin [National Institute for Laser, Plasma and Radiation Physics (INFLPR), Bucharest-Magurele (Romania)
2015-10-15
Graphical abstract: - Highlights: • Quality controls monitoring of Cable in Conduit Conductor (CICC) by X-ray tomography. • High resolution (≈40 μm) X-ray tomography images of CICC section up to 300 mm long. • Assignment of vast majority of strand trajectories over relevant section of CICC. • Non-invasive accurate measurements of local void fraction statistics. - Abstract: Operation and data acquisition of an X-ray microtomography developed at INFLPR are optimized to produce stacks of 2-D high-resolution tomographic sections of Cable in Conduit Conductor (CICC) type superconductors demanded in major fusion projects. High-resolution images for CCIC samples (486 NbTi&Cu strands of 0.81 mm diameter, jacketed in rectangular stainless steel pipes of 22 × 26 mm{sup 2}) are obtained by a combination of high energy/intensity and small focus spot X-ray source and high resolution/efficiency detector array. The stack of reconstructed slices is then used for quantitative analysis consisting of accurate strand positioning, determination of the local and global void fraction and 3D strand trajectory assignment for relevant fragments of cable (∼300 mm). The strand positioning algorithm is based on the application of Gabor Annular filtering followed by local maxima detection. The local void fraction is extensively mapped by employing local segmentation methods at a space resolution of about 50 sub-cells sized to be relevant to the triplet of triplet twisting pattern. For the strand trajectory assignment part we developed a global algorithm of the linear programing type which provides the vast majority of correct strand trajectories for most practical applications. For carefully manufactured benchmark CCIC samples over 99% of the trajectories are correctly assigned. For production samples the efficiency of the algorithm is around 90%. Trajectory assignment of a high proportion of the strands is a crucial factor for the derivation of statistical properties of the cable
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Cimpoesu, Dorin, E-mail: cdorin@uaic.ro; Stoleriu, Laurentiu; Stancu, Alexandru [Department of Physics, Alexandru Ioan Cuza University of Iasi, Iasi 700506 (Romania)
2013-12-14
We propose a generalized Stoner-Wohlfarth (SW) type model to describe various experimentally observed angular dependencies of the switching field in non-single-domain magnetic particles. Because the nonuniform magnetic states are generally characterized by complicated spin configurations with no simple analytical description, we maintain the macrospin hypothesis and we phenomenologically include the effects of nonuniformities only in the anisotropy energy, preserving as much as possible the elegance of SW model, the concept of critical curve and its geometric interpretation. We compare the results obtained with our model with full micromagnetic simulations in order to evaluate the performance and limits of our approach.
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.
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 moving...... average models, as is the case for the Volterra-Wiener analysis, we propose an ARMA model-based approach. The proposed algorithm is essentially the same as LEK, but this algorithm is extended to include past values of the output as well. Thus, all of the advantages associated with using the Laguerre...... function remain with our algorithm; but, by extending the algorithm to the linear and nonlinear ARMA model, a significant reduction in the number of Laguerre functions can be made, compared with the Volterra-Wiener approach. This translates into a more compact system representation and makes...
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?
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.
Accurate model annotation of a near-atomic resolution cryo-EM map.
Hryc, Corey F; Chen, Dong-Hua; Afonine, Pavel V; Jakana, Joanita; Wang, Zhao; Haase-Pettingell, Cameron; Jiang, Wen; Adams, Paul D; King, Jonathan A; Schmid, Michael F; Chiu, Wah
2017-03-21
Electron cryomicroscopy (cryo-EM) has been used to determine the atomic coordinates (models) from density maps of biological assemblies. These models can be assessed by their overall fit to the experimental data and stereochemical information. However, these models do not annotate the actual density values of the atoms nor their positional uncertainty. Here, we introduce a computational procedure to derive an atomic model from a cryo-EM map with annotated metadata. The accuracy of such a model is validated by a faithful replication of the experimental cryo-EM map computed using the coordinates and associated metadata. The functional interpretation of any structural features in the model and its utilization for future studies can be made in the context of its measure of uncertainty. We applied this protocol to the 3.3-Å map of the mature P22 bacteriophage capsid, a large and complex macromolecular assembly. With this protocol, we identify and annotate previously undescribed molecular interactions between capsid subunits that are crucial to maintain stability in the absence of cementing proteins or cross-linking, as occur in other bacteriophages.
Statistical tests with accurate size and power for balanced linear mixed models.
Muller, Keith E; Edwards, Lloyd J; Simpson, Sean L; Taylor, Douglas J
2007-08-30
The convenience of linear mixed models for Gaussian data has led to their widespread use. Unfortunately, standard mixed model tests often have greatly inflated test size in small samples. Many applications with correlated outcomes in medical imaging and other fields have simple properties which do not require the generality of a mixed model. Alternately, stating the special cases as a general linear multivariate model allows analysing them with either the univariate or multivariate approach to repeated measures (UNIREP, MULTIREP). Even in small samples, an appropriate UNIREP or MULTIREP test always controls test size and has a good power approximation, in sharp contrast to mixed model tests. Hence, mixed model tests should never be used when one of the UNIREP tests (uncorrected, Huynh-Feldt, Geisser-Greenhouse, Box conservative) or MULTIREP tests (Wilks, Hotelling-Lawley, Roy's, Pillai-Bartlett) apply. Convenient methods give exact power for the uncorrected and Box conservative tests. Simulations demonstrate that new power approximations for all four UNIREP tests eliminate most inaccuracy in existing methods. In turn, free software implements the approximations to give a better choice of sample size. Two repeated measures power analyses illustrate the methods. The examples highlight the advantages of examining the entire response surface of power as a function of sample size, mean differences, and variability.
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.
Krokhotin, Andrey; Dokholyan, Nikolay V
2015-01-01
Computational methods can provide significant insights into RNA structure and dynamics, bridging the gap in our understanding of the relationship between structure and biological function. Simulations enrich and enhance our understanding of data derived on the bench, as well as provide feasible alternatives to costly or technically challenging experiments. Coarse-grained computational models of RNA are especially important in this regard, as they allow analysis of events occurring in timescales relevant to RNA biological function, which are inaccessible through experimental methods alone. We have developed a three-bead coarse-grained model of RNA for discrete molecular dynamics simulations. This model is efficient in de novo prediction of short RNA tertiary structure, starting from RNA primary sequences of less than 50 nucleotides. To complement this model, we have incorporated additional base-pairing constraints and have developed a bias potential reliant on data obtained from hydroxyl probing experiments that guide RNA folding to its correct state. By introducing experimentally derived constraints to our computer simulations, we are able to make reliable predictions of RNA tertiary structures up to a few hundred nucleotides. Our refined model exemplifies a valuable benefit achieved through integration of computation and experimental methods.
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.
Jalas, S.; Dornmair, I.; Lehe, R.; Vincenti, H.; Vay, J.-L.; Kirchen, M.; Maier, A. R.
2017-03-01
Particle in Cell (PIC) simulations are a widely used tool for the investigation of both laser- and beam-driven plasma acceleration. It is a known issue that the beam quality can be artificially degraded by numerical Cherenkov radiation (NCR) resulting primarily from an incorrectly modeled dispersion relation. Pseudo-spectral solvers featuring infinite order stencils can strongly reduce NCR—or even suppress it—and are therefore well suited to correctly model the beam properties. For efficient parallelization of the PIC algorithm, however, localized solvers are inevitable. Arbitrary order pseudo-spectral methods provide this needed locality. Yet, these methods can again be prone to NCR. Here, we show that acceptably low solver orders are sufficient to correctly model the physics of interest, while allowing for parallel computation by domain decomposition.
Jalas, Sören; Lehe, Rémi; Vincenti, Henri; Vay, Jean-Luc; Kirchen, Manuel; Maier, Andreas R
2016-01-01
Particle in Cell (PIC) simulations are a widely used tool for the investigation of both laser- and beam-driven plasma acceleration. It is a known issue that the beam quality can be artificially degraded by numerical Cherenkov radiation (NCR) resulting primarily from an incorrectly modeled dispersion relation. Pseudo-spectral solvers featuring infinite order stencils can strongly reduce NCR -- or even suppress it -- and are therefore well suited to correctly model the beam properties. For efficient parallelization of the PIC algorithm, however, localized solvers are inevitable. Arbitrary order pseudo-spectral methods provide this needed locality. Yet, these methods can again be prone to NCR. Here, we show that acceptably low solver orders are sufficient to correctly model the physics of interest, while allowing for efficient parallelization.
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.
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...... that the treatment of only a small region around the chromophore is only by coincidence a good approximation. Therefore, such cluster approaches should be used with care. Based on our results, we suggest that polarizable embedding models, including a large part of the environment to describe its effect...
Mithen, James P; Crowley, Basil J B; Gregori, Gianluca
2011-01-01
Using numerical simulations, we investigate the equilibrium dynamics of a single component fluid with Yukawa interaction potential. We show that, for a wide range of densities and temperatures, the dynamics of the system are in striking agreement with a simple model of generalized hydrodynamics. Since the Yukawa potential can describe the ion-ion interactions in a plasma, the model has significant applicability for both analyzing and interpreting the results of x-ray scattering data from high power lasers and fourth generation light sources.
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...
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
Towards Relaxing the Spherical Solar Radiation Pressure Model for Accurate Orbit Predictions
Lachut, M.; Bennett, J.
2016-09-01
The well-known cannonball model has been used ubiquitously to capture the effects of atmospheric drag and solar radiation pressure on satellites and/or space debris for decades. While it lends itself naturally to spherical objects, its validity in the case of non-spherical objects has been debated heavily for years throughout the space situational awareness community. One of the leading motivations to improve orbit predictions by relaxing the spherical assumption, is the ongoing demand for more robust and reliable conjunction assessments. In this study, we explore the orbit propagation of a flat plate in a near-GEO orbit under the influence of solar radiation pressure, using a Lambertian BRDF model. Consequently, this approach will account for the spin rate and orientation of the object, which is typically determined in practice using a light curve analysis. Here, simulations will be performed which systematically reduces the spin rate to demonstrate the point at which the spherical model no longer describes the orbital elements of the spinning plate. Further understanding of this threshold would provide insight into when a higher fidelity model should be used, thus resulting in improved orbit propagations. Therefore, the work presented here is of particular interest to organizations and researchers that maintain their own catalog, and/or perform conjunction analyses.
Developing an Accurate CFD Based Gust Model for the Truss Braced Wing Aircraft
Bartels, Robert E.
2013-01-01
The increased flexibility of long endurance aircraft having high aspect ratio wings necessitates attention to gust response and perhaps the incorporation of gust load alleviation. The design of civil transport aircraft with a strut or truss-braced high aspect ratio wing furthermore requires gust response analysis in the transonic cruise range. This requirement motivates the use of high fidelity nonlinear computational fluid dynamics (CFD) for gust response analysis. This paper presents the development of a CFD based gust model for the truss braced wing aircraft. A sharp-edged gust provides the gust system identification. The result of the system identification is several thousand time steps of instantaneous pressure coefficients over the entire vehicle. This data is filtered and downsampled to provide the snapshot data set from which a reduced order model is developed. A stochastic singular value decomposition algorithm is used to obtain a proper orthogonal decomposition (POD). The POD model is combined with a convolution integral to predict the time varying pressure coefficient distribution due to a novel gust profile. Finally the unsteady surface pressure response of the truss braced wing vehicle to a one-minus-cosine gust, simulated using the reduced order model, is compared with the full CFD.
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
Accurate 2D/3D electromagnetic modeling for time-domain airborne EM systems
Yin, C.; Hodges, G.
2012-12-01
The existing industry software cannot deliver correct results for 3D time-domain airborne EM responses. In this paper, starting from the Fourier transform and convolution, we compare the stability of different modeling techniques and analyze the reason for instable calculations of the time-domain airborne EM responses. We find that the singularity of the impulse responses of EM systems at very early time that are used in the convolution is responsible for the instability of the modeling (Fig.1). Based on this finding, we put forward an algorithm that uses step response rather than impulse response of the airborne EM system for the convolution and create a stable algorithm that delivers precise results and maintains well the integral/derivative relationship between the magnetic field B and the magnetic induction dB/dt. A three-step transformation procedure for the modeling is proposed: 1) output the frequency-domain EM response data from the existing software; 2) transform into step-response by digital Fourier/Hankel transform; 3) convolve the step response with the transmitting current or its derivatives. The method has proved to be working very well (Fig. 2). The algorithm can be extended to the modeling of other time-domain ground and airborne EM system responses.Fig. 1: Comparison of impulse and step responses for an airborne EM system Fig. 2: Bz and dBz/dt calculated from step (middle panel) and impulse responses (lower panel) for the same 3D model as in Fig.1.
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
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.
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.
Robust and Accurate Modeling Approaches for Migraine Per-Patient Prediction from Ambulatory Data
Pagán, Josué; Irene De Orbe, M.; Gago, Ana; Sobrado, Mónica; Risco-Martín, José L.; Vivancos Mora, J.; Moya, José M.; Ayala, José L.
2015-01-01
Migraine is one of the most wide-spread neurological disorders, and its medical treatment represents a high percentage of the costs of health systems. In some patients, characteristic symptoms that precede the headache appear. However, they are nonspecific, and their prediction horizon is unknown and pretty variable; hence, these symptoms are almost useless for prediction, and they are not useful to advance the intake of drugs to be effective and neutralize the pain. To solve this problem, this paper sets up a realistic monitoring scenario where hemodynamic variables from real patients are monitored in ambulatory conditions with a wireless body sensor network (WBSN). The acquired data are used to evaluate the predictive capabilities and robustness against noise and failures in sensors of several modeling approaches. The obtained results encourage the development of per-patient models based on state-space models (N4SID) that are capable of providing average forecast windows of 47 min and a low rate of false positives. PMID:26134103
Robust and Accurate Modeling Approaches for Migraine Per-Patient Prediction from Ambulatory Data
Directory of Open Access Journals (Sweden)
Josué Pagán
2015-06-01
Full Text Available Migraine is one of the most wide-spread neurological disorders, and its medical treatment represents a high percentage of the costs of health systems. In some patients, characteristic symptoms that precede the headache appear. However, they are nonspecific, and their prediction horizon is unknown and pretty variable; hence, these symptoms are almost useless for prediction, and they are not useful to advance the intake of drugs to be effective and neutralize the pain. To solve this problem, this paper sets up a realistic monitoring scenario where hemodynamic variables from real patients are monitored in ambulatory conditions with a wireless body sensor network (WBSN. The acquired data are used to evaluate the predictive capabilities and robustness against noise and failures in sensors of several modeling approaches. The obtained results encourage the development of per-patient models based on state-space models (N4SID that are capable of providing average forecast windows of 47 min and a low rate of false positives.
Towards a More Accurate Solar Power Forecast By Improving NWP Model Physics
Köhler, C.; Lee, D.; Steiner, A.; Ritter, B.
2014-12-01
The growing importance and successive expansion of renewable energies raise new challenges for decision makers, transmission system operators, scientists and many more. In this interdisciplinary field, the role of Numerical Weather Prediction (NWP) is to reduce the uncertainties associated with the large share of weather-dependent power sources. Precise power forecast, well-timed energy trading on the stock market, and electrical grid stability can be maintained. The research project EWeLiNE is a collaboration of the German Weather Service (DWD), the Fraunhofer Institute (IWES) and three German transmission system operators (TSOs). Together, wind and photovoltaic (PV) power forecasts shall be improved by combining optimized NWP and enhanced power forecast models. The conducted work focuses on the identification of critical weather situations and the associated errors in the German regional NWP model COSMO-DE. Not only the representation of the model cloud characteristics, but also special events like Sahara dust over Germany and the solar eclipse in 2015 are treated and their effect on solar power accounted for. An overview of the EWeLiNE project and results of the ongoing research will be presented.
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.
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.
Directory of Open Access Journals (Sweden)
Andrew M Reynolds
Full Text Available 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.
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.
Highly accurate SVM model with automatic feature selection for word sense disambiguation
Institute of Scientific and Technical Information of China (English)
王浩; 陈贵林; 吴连献
2004-01-01
A novel algorithm for word sense disambiguation(WSD) that is based on SVM model improved with automatic feature selection is introduced. This learning method employs rich contextual features to predict the proper senses for specific words. Experimental results show that this algorithm can achieve an execellent performance on the set of data released during the SENSEEVAL-2 competition. We present the results obtained and discuss the transplantation of this algorithm to other languages such as Chinese. Experimental results on Chinese corpus show that our algorithm achieves an accuracy of 70.0 % even with small training data.
2010-01-01
Mateger, Herley E. Hurlburt, Alan J. Walloraft H a inleficed to offer this paper to the (Nanm of Confe ounce) (Dafe. P/ace and Classification of...temperature during ENSO events? By A. BIROL KARA.HARLEY E. HURLBURT*. CHARLIE N. BARRON. ALAN J. WALLCRAFT andE. JOSEPH METZGER, Naval Research...Quantifying SST errors from an OGCM in relation to atmospheric forcing variables. Ocean Modell. 29, 43-57. Urge. W. G., McWilliams , J. C. and Doney. S. C
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 multi-storey buildings, the use of lightweight material has many advantages. The low weight, the low energy consumption and the sustainability of the material are some attractive benefits from using lightweight materials. Compared with heavier structures i.e. concrete the challenge...... 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...... in lightweight buildings subjected to different types of loads....
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...
Flow Modeling in Pelton Turbines by an Accurate Eulerian and a Fast Lagrangian Evaluation Method
Directory of Open Access Journals (Sweden)
A. Panagiotopoulos
2015-01-01
Full Text Available The recent development of CFD has allowed the flow modeling in impulse hydro turbines that includes complex phenomena like free surface flow, multifluid interaction, and unsteady, time dependent flow. Some commercial and open-source CFD codes, which implement Eulerian methods, have been validated against experimental results showing satisfactory accuracy. Nevertheless, further improvement of accuracy is still a challenge, while the computational cost is very high and unaffordable for multiparametric design optimization of the turbine’s runner. In the present work a CFD Eulerian approach is applied at first, in order to simulate the flow in the runner of a Pelton turbine model installed at the laboratory. Then, a particulate method, the Fast Lagrangian Simulation (FLS, is used for the same case, which is much faster and hence potentially suitable for numerical design optimization, providing that it can achieve adequate accuracy. The results of both methods for various turbine operation conditions, as also for modified runner and bucket designs, are presented and discussed in the paper. In all examined cases the FLS method shows very good accuracy in predicting the hydraulic efficiency of the runner, although the computed flow evolution and the torque curve exhibit some systematic differences from the Eulerian results.
Boussinesq-type equations from nonlinear realizations of $W_3$
Ivanov, E; Malik, R P
1993-01-01
We construct new coset realizations of infinite-dimensional linear $W_3^{\\infty}$ symmetry associated with Zamolodchikov's $W_3$ algebra which are different from the previously explored $sl_3$ Toda realization of $W_3^{\\infty}$. We deduce the Boussinesq and modified Boussinesq equations as constraints on the geometry of the corresponding coset manifolds.The main characteristic features of these realizations are:i. Among the coset parameters there are the space and time coordinates $x$ and $t$ which enter the Boussinesq equations, all other coset parameters are regarded as fields depending on these coordinates;ii. The spin 2 and 3 currents of $W_3$ and two spin 1 $U(1)$ Kac- Moody currents as well as two spin 0 fields related to the $W_3$currents via Miura maps, come out as the only essential parameters-fields of these cosets. The remaining coset fields are covariantly expressed through them;iii.The Miura maps get a new geometric interpretation as $W_3^{\\infty}$ covariant constraints which relate the above fie...
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...
Modified Poisson-Nernst-Planck model with accurate Coulomb correlation in variable media
Liu, Pei; Xu, Zhenli
2016-01-01
We derive a set of modified Poisson-Nernst-Planck (PNP) equations for ion transport from the variation of the free energy functional which includes the many-body Coulomb correlation in media of variable dielectric coefficient. The correlation effects are considered through the Debye charging process in which the self energy of an ion is governed by the generalized Debye-H\\"uckel equation. We develop the asymptotic expansions of the self energy taking the ion radius as the small parameter such that the multiscale model can be solved efficiently by numerical methods. We show that the variations of the energy functional give the self-energy-modified PNP equations which satisfy a proper energy law. We present the numerical results from different asymptotic expansions with a semi-implicit conservative numerical method and investigate the effect of the Coulomb correlation.
A new method based on the subpixel Gaussian model for accurate estimation of asteroid coordinates
Savanevych, V. E.; Briukhovetskyi, O. B.; 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.
2015-08-01
We describe a new iteration method to estimate asteroid coordinates, based on a subpixel Gaussian model of the discrete object image. The method operates by continuous parameters (asteroid coordinates) in a discrete observational space (the set of pixel potentials) of the CCD frame. In this model, the kind of 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 method that is developed, which is flexible in adapting to any form of object image, has a high measurement accuracy along with a low calculating complexity, due to the maximum-likelihood procedure that is implemented to obtain the best fit instead of a least-squares method and Levenberg-Marquardt algorithm for minimization of the quadratic form. Since 2010, the method has been tested as the basis of our Collection Light Technology (COLITEC) software, which has been installed at several observatories across the world with the aim of the automatic discovery of asteroids and comets in sets of CCD frames. As a result, four comets (C/2010 X1 (Elenin), P/2011 NO1(Elenin), C/2012 S1 (ISON) and P/2013 V3 (Nevski)) as well as more than 1500 small Solar system bodies (including five near-Earth objects (NEOs), 21 Trojan asteroids of Jupiter and one Centaur object) have been discovered. We discuss these results, which allowed us to compare the accuracy parameters of the new method and confirm its efficiency. In 2014, the COLITEC software was recommended to all members of the Gaia-FUN-SSO network for analysing observations as a tool to detect faint moving objects in frames.
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.
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.
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.
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
El-Mellouhi, Fadwa; Lucero, Melissa J; Scuseria, Gustavo E
2011-01-01
We have calculated the properties of SrTiO3 (STO) using a wide array of density functionals ranging from standard semi-local functionals to modern range-separated hybrids, combined with several basis sets of varying size/quality. We show how these combination's predictive ability varies signi?cantly, both for STO's cubic and antiferrodistortive (AFD) phases, with the greatest variation in functional/basis set e?cacy seen in modeling the AFD phase. The screened hybrid functionals we utilized predict the structural properties of both phases in very good agreement with experiment, especially if used with large (but still computationally tractable) basis sets. The most accurate results presented in this study, namely those from HSE06/modi?ed-def2-TZVP, stand as the most accurate modeling of STO to date when compared to the literature; these results agree well with experimental structural and electronic properties as well as providing insight into the band structure alteration during the phase transition.
Accurate Time-Dependent Traveling-Wave Tube Model Developed for Computational Bit-Error-Rate Testing
Kory, Carol L.
2001-01-01
The phenomenal growth of the satellite communications industry has created a large demand for traveling-wave tubes (TWT's) operating with unprecedented specifications requiring the design and production of many novel devices in record time. To achieve this, the TWT industry heavily relies on computational modeling. However, the TWT industry's computational modeling capabilities need to be improved because there are often discrepancies between measured TWT data and that predicted by conventional two-dimensional helical TWT interaction codes. This limits the analysis and design of novel devices or TWT's with parameters differing from what is conventionally manufactured. In addition, the inaccuracy of current computational tools limits achievable TWT performance because optimized designs require highly accurate models. To address these concerns, a fully three-dimensional, time-dependent, helical TWT interaction model was developed using the electromagnetic particle-in-cell code MAFIA (Solution of MAxwell's equations by the Finite-Integration-Algorithm). The model includes a short section of helical slow-wave circuit with excitation fed by radiofrequency input/output couplers, and an electron beam contained by periodic permanent magnet focusing. A cutaway view of several turns of the three-dimensional helical slow-wave circuit with input/output couplers is shown. This has been shown to be more accurate than conventionally used two-dimensional models. The growth of the communications industry has also imposed a demand for increased data rates for the transmission of large volumes of data. To achieve increased data rates, complex modulation and multiple access techniques are employed requiring minimum distortion of the signal as it is passed through the TWT. Thus, intersymbol interference (ISI) becomes a major consideration, as well as suspected causes such as reflections within the TWT. To experimentally investigate effects of the physical TWT on ISI would be
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.
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.)
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.
Yu, Xiaolin; Zhang, Shaoqing; Lin, Xiaopei; Li, Mingkui
2017-03-01
The uncertainties in values of coupled model parameters are an important source of model bias that causes model climate drift. The values can be calibrated by a parameter estimation procedure that projects observational information onto model parameters. The signal-to-noise ratio of error covariance between the model state and the parameter being estimated directly determines whether the parameter estimation succeeds or not. With a conceptual climate model that couples the stochastic atmosphere and slow-varying ocean, this study examines the sensitivity of state-parameter covariance on the accuracy of estimated model states in different model components of a coupled system. Due to the interaction of multiple timescales, the fast-varying atmosphere with a chaotic nature is the major source of the inaccuracy of estimated state-parameter covariance. Thus, enhancing the estimation accuracy of atmospheric states is very important for the success of coupled model parameter estimation, especially for the parameters in the air-sea interaction processes. The impact of chaotic-to-periodic ratio in state variability on parameter estimation is also discussed. This simple model study provides a guideline when real observations are used to optimize model parameters in a coupled general circulation model for improving climate analysis and predictions.
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)
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.
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.
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.
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.
Gritsyk, P. A.; Somov, B. V.
2016-08-01
The M7.7 solar flare of July 19, 2012, at 05:58 UT was observed with high spatial, temporal, and spectral resolutions in the hard X-ray and optical ranges. The flare occurred at the solar limb, which allowed us to see the relative positions of the coronal and chromospheric X-ray sources and to determine their spectra. To explain the observations of the coronal source and the chromospheric one unocculted by the solar limb, we apply an accurate analytical model for the kinetic behavior of accelerated electrons in a flare. We interpret the chromospheric hard X-ray source in the thick-target approximation with a reverse current and the coronal one in the thin-target approximation. Our estimates of the slopes of the hard X-ray spectra for both sources are consistent with the observations. However, the calculated intensity of the coronal source is lower than the observed one by several times. Allowance for the acceleration of fast electrons in a collapsing magnetic trap has enabled us to remove this contradiction. As a result of our modeling, we have estimated the flux density of the energy transferred by electrons with energies above 15 keV to be ˜5 × 1010 erg cm-2 s-1, which exceeds the values typical of the thick-target model without a reverse current by a factor of ˜5. To independently test the model, we have calculated the microwave spectrum in the range 1-50 GHz that corresponds to the available radio observations.
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.
Chang, Chih-Hao; Liou, Meng-Sing
2007-07-01
In this paper, we propose a new approach to compute compressible multifluid equations. Firstly, a single-pressure compressible multifluid model based on the stratified flow model is proposed. The stratified flow model, which defines different fluids in separated regions, is shown to be amenable to the finite volume method. We can apply the conservation law to each subregion and obtain a set of balance equations . Secondly, the AUSM + scheme, which is originally designed for the compressible gas flow, is extended to solve compressible liquid flows. By introducing additional dissipation terms into the numerical flux, the new scheme, called AUSM +-up, can be applied to both liquid and gas flows. Thirdly, the contribution to the numerical flux due to interactions between different phases is taken into account and solved by the exact Riemann solver. We will show that the proposed approach yields an accurate and robust method for computing compressible multiphase flows involving discontinuities, such as shock waves and fluid interfaces. Several one-dimensional test problems are used to demonstrate the capability of our method, including the Ransom's water faucet problem and the air-water shock tube problem. Finally, several two dimensional problems will show the capability to capture enormous details and complicated wave patterns in flows having large disparities in the fluid density and velocities, such as interactions between water shock wave and air bubble, between air shock wave and water column(s), and underwater explosion. However, conservative form is lost in these balance equations when considering each individual phase; in fact, the interactions that exist simultaneously in both phases manifest themselves as nonconservative terms.
Directory of Open Access Journals (Sweden)
M. Montes-Hugo
2014-06-01
Full Text Available The understanding of phytoplankton dynamics in the Gulf of the Saint Lawrence (GSL is critical for managing major fisheries off the Canadian East coast. In this study, the accuracy of two atmospheric correction techniques (NASA standard algorithm, SA, and Kuchinke's spectral optimization, KU and three ocean color inversion models (Carder's empirical for SeaWiFS (Sea-viewing Wide Field-of-View Sensor, EC, Lee's quasi-analytical, QAA, and Garver- Siegel-Maritorena semi-empirical, GSM for estimating the phytoplankton absorption coefficient at 443 nm (aph(443 and the chlorophyll concentration (chl in the GSL is examined. Each model was validated based on SeaWiFS images and shipboard measurements obtained during May of 2000 and April 2001. In general, aph(443 estimates derived from coupling KU and QAA models presented the smallest differences with respect to in situ determinations as measured by High Pressure liquid Chromatography measurements (median absolute bias per cruise up to 0.005, RMSE up to 0.013. A change on the inversion approach used for estimating aph(443 values produced up to 43.4% increase on prediction error as inferred from the median relative bias per cruise. Likewise, the impact of applying different atmospheric correction schemes was secondary and represented an additive error of up to 24.3%. By using SeaDAS (SeaWiFS Data Analysis System default values for the optical cross section of phytoplankton (i.e., aph(443 = aph(443/chl = 0.056 m2mg−1, the median relative bias of our chl estimates as derived from the most accurate spaceborne aph(443 retrievals and with respect to in situ determinations increased up to 29%.
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.
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
Kim, Jibeom; Jeon, Joonhyeon
2015-01-01
Recently, related studies on Equation Of State (EOS) have reported that generalized van der Waals (GvdW) shows poor representations in the near critical region for non-polar and non-sphere molecules. Hence, there are still remains a problem of GvdW parameters to minimize loss in describing saturated vapor densities and vice versa. This paper describes a recursive model GvdW (rGvdW) for an accurate representation of pure fluid materials in the near critical region. For the performance evaluation of rGvdW in the near critical region, other EOS models are also applied together with two pure molecule group: alkane and amine. The comparison results show rGvdW provides much more accurate and reliable predictions of pressure than the others. The calculating model of EOS through this approach gives an additional insight into the physical significance of accurate prediction of pressure in the nearcritical region.
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...
Paricaud, Patrice; Predota, Milan; Chialvo, Ariel A; Cummings, Peter T
2005-06-22
Water exhibits many unusual properties that are essential for the existence of life. Water completely changes its character from ambient to supercritical conditions in a way that makes it possible to sustain life at extreme conditions, leading to conjectures that life may have originated in deep-sea vents. Molecular simulation can be very useful in exploring biological and chemical systems, particularly at extreme conditions for which experiments are either difficult or impossible; however this scenario entails an accurate molecular model for water applicable over a wide range of state conditions. Here, we present a Gaussian charge polarizable model (GCPM) based on the model developed earlier by Chialvo and Cummings [Fluid Phase Equilib. 150, 73 (1998)] which is, to our knowledge, the first that satisfies the water monomer and dimer properties, and simultaneously yields very accurate predictions of dielectric, structural, vapor-liquid equilibria, and transport properties, over the entire fluid range. This model would be appropriate for simulating biological and chemical systems at both ambient and extreme conditions. The particularity of the GCPM model is the use of Gaussian distributions instead of points to represent the partial charges on the water molecules. These charge distributions combined with a dipole polarizability and a Buckingham exp-6 potential are found to play a crucial role for the successful and simultaneous predictions of a variety of water properties. This work not only aims at presenting an accurate model for water, but also at proposing strategies to develop classical accurate models for the predictions of structural, dynamic, and thermodynamic properties.
Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard; Jiang, Xueping; Kharche, Neerav; Zhou, Yu; Nayak, Saroj K
2011-01-01
Accurate modeling of the pi-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional ...
Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard; Jiang, Xueping; Kharche, Neerav; Zhou, Yu; Nayak, Saroj K
2011-01-01
Accurate modeling of the ␣-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional t...
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.
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.
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...
Davtyan, Aram; Voth, Gregory A.; Andersen, Hans C.
2016-12-01
We recently developed a dynamic force matching technique for converting a coarse-grained (CG) model of a molecular system, with a CG potential energy function, into a dynamic CG model with realistic dynamics [A. Davtyan et al., J. Chem. Phys. 142, 154104 (2015)]. This is done by supplementing the model with additional degrees of freedom, called "fictitious particles." In that paper, we tested the method on CG models in which each molecule is coarse-grained into one CG point particle, with very satisfactory results. When the method was applied to a CG model of methanol that has two CG point particles per molecule, the results were encouraging but clearly required improvement. In this paper, we introduce a new type (called type-3) of fictitious particle that exerts forces on the center of mass of two CG sites. A CG model constructed using type-3 fictitious particles (as well as type-2 particles previously used) gives a much more satisfactory dynamic model for liquid methanol. In particular, we were able to construct a CG model that has the same self-diffusion coefficient and the same rotational relaxation time as an all-atom model of liquid methanol. Type-3 particles and generalizations of it are likely to be useful in converting more complicated CG models into dynamic CG models.
Perassi, Eduardo M; Hernandez-Garrido, Juan C; Moreno, M Sergio; Encina, Ezequiel R; Coronado, Eduardo A; Midgley, Paul A
2010-06-09
The realization of materials at the nanometer scale creates new challenges for quantitative characterization and modeling as many physical and chemical properties at the nanoscale are highly size and shape-dependent. In particular, the accurate nanometrological characterization of noble metal nanoparticles (NPs) is crucial for understanding their optical response that is determined by the collective excitation of conduction electrons, known as localized surface plasmons. Its manipulation gives place to a variety of applications in ultrasensitive spectroscopies, photonics, improved photovoltaics, imaging, and cancer therapy. Here we show that by combining electron tomography with electrodynamic simulations an accurate optical model of a highly irregular gold NP synthesized by chemical methods could be achieved. This constitutes a novel and rigorous tool for understanding the plasmonic properties of real three-dimensional nano-objects.
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.
Boykin, Timothy B.; Luisier, Mathieu; Klimeck, Gerhard; Jiang, Xueping; Kharche, Neerav; Zhou, Yu; Nayak, Saroj K.
2011-05-01
Accurate modeling of the π-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands, as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional theory -based calculations as well as to those based on the many-body Green's function and screened-exchange formalism, giving excellent agreement with the ab initio AGNR bands. We employ this model to calculate the current-voltage characteristics of an AGNR MOSFET and the conductance of rough-edge AGNRs, finding significant differences versus the single-pz model. These results show that an accurate band structure model is essential for predicting the performance of graphene-based nanodevices.
Kehoe, M.J.; O’ Brien, K.; Grinham, A.; Rissik, D.; Ahern, K.S.; Maxwell, P.
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
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.
Highly compact and accurate circuit-level macro modeling of gate-all-around charge-trap flash memory
Kim, Seunghyun; Lee, Sang-Ho; Kim, Young-Goan; Cho, Seongjae; Park, Byung-Gook
2017-01-01
In this paper, a highly reliable circuit model of gate-all-around (GAA) charge-trap flash (CTF) memory cell is proposed, considering the transient behaviors for describing the program operations with improved accuracy. Although several compact models have been reported in the previous literature, time-dependent behaviors have not been precisely reflected and the failures tend to get worse as the operation time elapses. Furthermore, the developed SPICE models in this work have been verified by the measurement results of the fabricated flash memory cells having silicon-oxide-nitride-oxide-silicon (SONOS). This more realistic model would be beneficial in designing the system architectures and setting up the operation schemes for the leading three-dimensional (3D) stack CTF memory.
Fischer, A.; Hoffmann, K.-H.
2004-03-01
In this case study a complex Otto engine simulation provides data including, but not limited to, effects from losses due to heat conduction, exhaust losses and frictional losses. This data is used as a benchmark to test whether the Novikov engine with heat leak, a simple endoreversible model, can reproduce the complex engine behavior quantitatively by an appropriate choice of model parameters. The reproduction obtained proves to be of high quality.
Vinyard, David J; Zachary, Chase E; Ananyev, Gennady; Dismukes, G Charles
2013-07-01
Forty-three years ago, Kok and coworkers introduced a phenomenological model describing period-four oscillations in O2 flash yields during photosynthetic water oxidation (WOC), which had been first reported by Joliot and coworkers. The original two-parameter Kok model was subsequently extended in its level of complexity to better simulate diverse data sets, including intact cells and isolated PSII-WOCs, but at the expense of introducing physically unrealistic assumptions necessary to enable numerical solutions. To date, analytical solutions have been found only for symmetric Kok models (inefficiencies are equally probable for all intermediates, called "S-states"). However, it is widely accepted that S-state reaction steps are not identical and some are not reversible (by thermodynamic restraints) thereby causing asymmetric cycles. We have developed a mathematically more rigorous foundation that eliminates unphysical assumptions known to be in conflict with experiments and adopts a new experimental constraint on solutions. This new algorithm termed STEAMM for S-state Transition Eigenvalues of Asymmetric Markov Models enables solutions to models having fewer adjustable parameters and uses automated fitting to experimental data sets, yielding higher accuracy and precision than the classic Kok or extended Kok models. This new tool provides a general mathematical framework for analyzing damped oscillations arising from any cycle period using any appropriate Markov model, regardless of symmetry. We illustrate applications of STEAMM that better describe the intrinsic inefficiencies for photon-to-charge conversion within PSII-WOCs that are responsible for damped period-four and period-two oscillations of flash O2 yields across diverse species, while using simpler Markov models free from unrealistic assumptions.
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.
Brauchle, J.; Hein, D.; Berger, R.
2015-04-01
Remote sensing in areas with extreme altitude differences is particularly challenging. In high mountain areas specifically, steep slopes result in reduced ground pixel resolution and degraded quality in the DEM. Exceptionally high brightness differences can in part no longer be imaged by the sensors. Nevertheless, detailed information about mountainous regions is highly relevant: time and again glacier lake outburst floods (GLOFs) and debris avalanches claim dozens of victims. Glaciers are sensitive to climate change and must be carefully monitored. Very detailed and accurate 3D maps provide a basic tool for the analysis of natural hazards and the monitoring of glacier surfaces in high mountain areas. There is a gap here, because the desired accuracies are often not achieved. It is for this reason that the DLR Institute of Optical Sensor Systems has developed a new aerial camera, the MACS-Himalaya. The measuring unit comprises four camera modules with an overall aperture angle of 116° perpendicular to the direction of flight. A High Dynamic Range (HDR) mode was introduced so that within a scene, bright areas such as sun-flooded snow and dark areas such as shaded stone can be imaged. In 2014, a measuring survey was performed on the Nepalese side of the Himalayas. The remote sensing system was carried by a Stemme S10 motor glider. Amongst other targets, the Seti Valley, Kali-Gandaki Valley and the Mt. Everest/Khumbu Region were imaged at heights up to 9,200 m. Products such as dense point clouds, DSMs and true orthomosaics with a ground pixel resolution of up to 15 cm were produced. Special challenges and gaps in the investigation of high mountain areas, approaches for resolution of these problems, the camera system and the state of evaluation are presented with examples.
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.
Energy Technology Data Exchange (ETDEWEB)
Carrington, David Bradley [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Waters, Jiajia [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2017-01-05
KIVA-hpFE is a high performance computer software for solving the physics of multi-species and multiphase turbulent reactive flow in complex geometries having immersed moving parts. The code is written in Fortran 90/95 and can be used on any computer platform with any popular complier. The code is in two versions, a serial version and a parallel version utilizing MPICH2 type Message Passing Interface (MPI or Intel MPI) for solving distributed domains. The parallel version is at least 30x faster than the serial version and much faster than our previous generation of parallel engine modeling software, by many factors. The 5th generation algorithm construction is a Galerkin type Finite Element Method (FEM) solving conservative momentum, species, and energy transport equations along with two-equation turbulent model k-ω Reynolds Averaged Navier-Stokes (RANS) model and a Vreman type dynamic Large Eddy Simulation (LES) method. The LES method is capable modeling transitional flow from laminar to fully turbulent; therefore, this LES method does not require special hybrid or blending to walls. The FEM projection method also uses a Petrov-Galerkin (P-G) stabilization along with pressure stabilization. We employ hierarchical basis sets, constructed on the fly with enrichment in areas associated with relatively larger error as determined by error estimation methods. In addition, when not using the hp-adaptive module, the code employs Lagrangian basis or shape functions. The shape functions are constructed for hexahedral, prismatic and tetrahedral elements. The software is designed to solve many types of reactive flow problems, from burners to internal combustion engines and turbines. In addition, the formulation allows for direct integration of solid bodies (conjugate heat transfer), as in heat transfer through housings, parts, cylinders. It can also easily be extended to stress modeling of solids, used in fluid structure interactions problems, solidification, porous media
Zheng, Wenjun; Tekpinar, Mustafa
2011-12-21
Small-angle x-ray scattering (SAXS) is a powerful technique widely used to explore conformational states and transitions of biomolecular assemblies in solution. For accurate model reconstruction from SAXS data, one promising approach is to flexibly fit a known high-resolution protein structure to low-resolution SAXS data by computer simulations. This is a highly challenging task due to low information content in SAXS data. To meet this challenge, we have developed what we believe to be a novel method based on a coarse-grained (one-bead-per-residue) protein representation and a modified form of the elastic network model that allows large-scale conformational changes while maintaining pseudobonds and secondary structures. Our method optimizes a pseudoenergy that combines the modified elastic-network model energy with a SAXS-fitting score and a collision energy that penalizes steric collisions. Our method uses what we consider a new implicit hydration shell model that accounts for the contribution of hydration shell to SAXS data accurately without explicitly adding waters to the system. We have rigorously validated our method using five test cases with simulated SAXS data and three test cases with experimental SAXS data. Our method has successfully generated high-quality structural models with root mean-squared deviation of 1 ∼ 3 Å from the target structures.
Energy Technology Data Exchange (ETDEWEB)
Esfandiar, Habib; KoraYem, Moharam Habibnejad [Islamic Azad University, Tehran (Iran, Islamic Republic of)
2015-09-15
In this study, the researchers try to examine nonlinear dynamic analysis and determine Dynamic load carrying capacity (DLCC) in flexible manipulators. Manipulator modeling is based on Timoshenko beam theory (TBT) considering the effects of shear and rotational inertia. To get rid of the risk of shear locking, a new procedure is presented based on mixed finite element formulation. In the method proposed, shear deformation is free from the risk of shear locking and independent of the number of integration points along the element axis. Dynamic modeling of manipulators will be done by taking into account small and large deformation models and using extended Hamilton method. System motion equations are obtained by using nonlinear relationship between displacements-strain and 2nd PiolaKirchoff stress tensor. In addition, a comprehensive formulation will be developed to calculate DLCC of the flexible manipulators during the path determined considering the constraints end effector accuracy, maximum torque in motors and maximum stress in manipulators. Simulation studies are conducted to evaluate the efficiency of the method proposed taking two-link flexible and fixed base manipulators for linear and circular paths into consideration. Experimental results are also provided to validate the theoretical model. The findings represent the efficiency and appropriate performance of the method proposed.
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.
Yu, J S; Xue, A Y; Redei, E E; Bagheri, N
2016-01-01
Major depressive disorder (MDD) is a critical cause of morbidity and disability with an economic cost of hundreds of billions of dollars each year, necessitating more effective treatment strategies and novel approaches to translational research. A notable barrier in addressing this public health threat involves reliable identification of the disorder, as many affected individuals remain undiagnosed or misdiagnosed. An objective blood-based diagnostic test using transcript levels of a panel of markers would provide an invaluable tool for MDD as the infrastructure—including equipment, trained personnel, billing, and governmental approval—for similar tests is well established in clinics worldwide. Here we present a supervised classification model utilizing support vector machines (SVMs) for the analysis of transcriptomic data readily obtained from a peripheral blood specimen. The model was trained on data from subjects with MDD (n=32) and age- and gender-matched controls (n=32). This SVM model provides a cross-validated sensitivity and specificity of 90.6% for the diagnosis of MDD using a panel of 10 transcripts. We applied a logistic equation on the SVM model and quantified a likelihood of depression score. This score gives the probability of a MDD diagnosis and allows the tuning of specificity and sensitivity for individual patients to bring personalized medicine closer in psychiatry. PMID:27779627
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.
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.
Accurate simulation of 802.11 indoor links: a “bursty” channel model based on real measurements
Luis Muñoz; Ramón Agüero; Marta García-Arranz
2010-01-01
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...
Directory of Open Access Journals (Sweden)
Juliann E Kosovec
Full Text Available OBJECTIVE: To assess the reliability of magnetic resonance imaging (MRI for detection of esophageal cancer in the Levrat model of end-to-side esophagojejunostomy. BACKGROUND: The Levrat model has proven utility in terms of its ability to replicate Barrett's carcinogenesis by inducing gastroduodenoesophageal reflux (GDER. Due to lack of data on the utility of non-invasive methods for detection of esophageal cancer, treatment efficacy studies have been limited, as adenocarcinoma histology has only been validated post-mortem. It would therefore be of great value if the validity and reliability of MRI could be established in this setting. METHODS: Chronic GDER reflux was induced in 19 male Sprague-Dawley rats using the modified Levrat model. At 40 weeks post-surgery, all animals underwent endoscopy, MRI scanning, and post-mortem histological analysis of the esophagus and anastomosis. With post-mortem histology serving as the gold standard, assessment of presence of esophageal cancer was made by five esophageal specialists and five radiologists on endoscopy and MRI, respectively. RESULTS: The accuracy of MRI and endoscopic analysis to correctly identify cancer vs. no cancer was 85.3% and 50.5%, respectively. ROC curves demonstrated that MRI rating had an AUC of 0.966 (p<0.001 and endoscopy rating had an AUC of 0.534 (p = 0.804. The sensitivity and specificity of MRI for identifying cancer vs. no-cancer was 89.1% and 80% respectively, as compared to 45.5% and 57.5% for endoscopy. False positive rates of MRI and endoscopy were 20% and 42.5%, respectively. CONCLUSIONS: MRI is a more reliable diagnostic method than endoscopy in the Levrat model. The non-invasiveness of the tool and its potential to volumetrically quantify the size and number of tumors likely makes it even more useful in evaluating novel agents and their efficacy in treatment studies of esophageal cancer.
Jolivet, L.; Cohen, M.; Ruas, A.
2015-01-01
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 influe...
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.
De Backer, A; van den Bos, K H W; Van den Broek, W; Sijbers, J; Van Aert, S
2016-12-01
An efficient model-based estimation algorithm is introduced to quantify the atomic column positions and intensities from atomic resolution (scanning) transmission electron microscopy ((S)TEM) images. This algorithm uses the least squares estimator on image segments containing individual columns fully accounting for overlap between neighbouring columns, enabling the analysis of a large field of view. For this algorithm, the accuracy and precision with which measurements for the atomic column positions and scattering cross-sections from annular dark field (ADF) STEM images can be estimated, has been investigated. The highest attainable precision is reached even for low dose images. Furthermore, the advantages of the model-based approach taking into account overlap between neighbouring columns are highlighted. This is done for the estimation of the distance between two neighbouring columns as a function of their distance and for the estimation of the scattering cross-section which is compared to the integrated intensity from a Voronoi cell. To provide end-users this well-established quantification method, a user friendly program, StatSTEM, is developed which is freely available under a GNU public license.
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
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.
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.
Institute of Scientific and Technical Information of China (English)
GUO Xia; L(U) Daren; L(U) Yao
2007-01-01
Here we present a study focusing on atmospheric limb-scattered radiative characteristics in the ultraviolet band by using a limb-scan spherically-layered radiative-transfer-model based on the single-scattering approximation, which was developed by the present authors. We have applied an accurate numerical integration technique involving an auto-adaptive modified-space step, which assured high accuracy and simplification.Comparisons were made to the newly released spherical radiative transfer model, SCIATRAN2.0, which was developed by Institute of Remote Sensing/Institute of Environmental Physics (IUP/IFE) at University of Bremen and to measurements collected via an ultraviolet spectrometer on the Solar Mesospheric Explorer (SME) satellite, which was launched in October, 1981. Preliminary results indicate that the present model provides a good interpretation of the earth-limb scattered ultraviolet radiance, and thus, is suitable for the study of the ultraviolet-limb radiative-transfer problem with high accuracy.
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.
Directory of Open Access Journals (Sweden)
Carlo Baldassi
Full Text Available In the course of evolution, proteins show a remarkable conservation of their three-dimensional structure and their biological function, leading to strong evolutionary constraints on the sequence variability between homologous proteins. Our method aims at extracting such constraints from rapidly accumulating sequence data, and thereby at inferring protein structure and function from sequence information alone. Recently, global statistical inference methods (e.g. direct-coupling analysis, sparse inverse covariance estimation have achieved a breakthrough towards this aim, and their predictions have been successfully implemented into tertiary and quaternary protein structure prediction methods. However, due to the discrete nature of the underlying variable (amino-acids, exact inference requires exponential time in the protein length, and efficient approximations are needed for practical applicability. Here we propose a very efficient multivariate Gaussian modeling approach as a variant of direct-coupling analysis: the discrete amino-acid variables are replaced by continuous Gaussian random variables. The resulting statistical inference problem is efficiently and exactly solvable. We show that the quality of inference is comparable or superior to the one achieved by mean-field approximations to inference with discrete variables, as done by direct-coupling analysis. This is true for (i the prediction of residue-residue contacts in proteins, and (ii the identification of protein-protein interaction partner in bacterial signal transduction. An implementation of our multivariate Gaussian approach is available at the website http://areeweb.polito.it/ricerca/cmp/code.
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.
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.
Dobrev, Plamen; Donnini, Serena; Groenhof, Gerrit; Grubmüller, Helmut
2017-01-10
Correct protonation of titratable groups in biomolecules is crucial for their accurate description by molecular dynamics simulations. In the context of constant pH simulations, an additional protonation degree of freedom is introduced for each titratable site, allowing the protonation state to change dynamically with changing structure or electrostatics. Here, we extend previous approaches for an accurate description of chemically coupled titrating sites. A second reaction coordinate is used to switch between two tautomeric states of an amino acid with chemically coupled titratable sites, such as aspartate (Asp), glutamate (Glu), and histidine (His). To this aim, we test a scheme involving three protonation states. To facilitate charge neutrality as required for periodic boundary conditions and Particle Mesh Ewald (PME) electrostatics, titration of each respective amino acid is coupled to a "water" molecule that is charged in the opposite direction. Additionally, a force field modification for Amber99sb is introduced and tested for the description of carboxyl group protonation. Our three states model is tested by titration simulations of Asp, Glu, and His, yielding a good agreement, reproducing the correct geometry of the groups in their different protonation forms. We further show that the ion concentration change due to the neutralizing "water" molecules does not significantly affect the protonation free energies of the titratable groups, suggesting that the three states model provides a good description of biomolecular dynamics at constant pH.
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
Energy Technology Data Exchange (ETDEWEB)
Rybynok, V O; Kyriacou, P A [City University, London (United Kingdom)
2007-10-15
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.
Wang, Shiyao; Deng, Zhidong; Yin, Gang
2016-02-24
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)
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.
Reynolds, Sheila M; Bilmes, Jeff A; Noble, William Stafford
2010-07-08
DNA in eukaryotes is packaged into a chromatin complex, the most basic element of which is the nucleosome. The precise positioning of the nucleosome cores allows for selective access to the DNA, and the mechanisms that control this positioning are important pieces of the gene expression puzzle. We describe a large-scale nucleosome pattern that jointly characterizes the nucleosome core and the adjacent linkers and is predominantly characterized by long-range oscillations in the mono, di- and tri-nucleotide content of the DNA sequence, and we show that this pattern can be used to predict nucleosome positions in both Homo sapiens and Saccharomyces cerevisiae more accurately than previously published methods. Surprisingly, in both H. sapiens and S. cerevisiae, the most informative individual features are the mono-nucleotide patterns, although the inclusion of di- and tri-nucleotide features results in improved performance. Our approach combines a much longer pattern than has been previously used to predict nucleosome positioning from sequence-301 base pairs, centered at the position to be scored-with a novel discriminative classification approach that selectively weights the contributions from each of the input features. The resulting scores are relatively insensitive to local AT-content and can be used to accurately discriminate putative dyad positions from adjacent linker regions without requiring an additional dynamic programming step and without the attendant edge effects and assumptions about linker length modeling and overall nucleosome density. Our approach produces the best dyad-linker classification results published to date in H. sapiens, and outperforms two recently published models on a large set of S. cerevisiae nucleosome positions. Our results suggest that in both genomes, a comparable and relatively small fraction of nucleosomes are well-positioned and that these positions are predictable based on sequence alone. We believe that the bulk of the
Directory of Open Access Journals (Sweden)
Sheila M Reynolds
Full Text Available DNA in eukaryotes is packaged into a chromatin complex, the most basic element of which is the nucleosome. The precise positioning of the nucleosome cores allows for selective access to the DNA, and the mechanisms that control this positioning are important pieces of the gene expression puzzle. We describe a large-scale nucleosome pattern that jointly characterizes the nucleosome core and the adjacent linkers and is predominantly characterized by long-range oscillations in the mono, di- and tri-nucleotide content of the DNA sequence, and we show that this pattern can be used to predict nucleosome positions in both Homo sapiens and Saccharomyces cerevisiae more accurately than previously published methods. Surprisingly, in both H. sapiens and S. cerevisiae, the most informative individual features are the mono-nucleotide patterns, although the inclusion of di- and tri-nucleotide features results in improved performance. Our approach combines a much longer pattern than has been previously used to predict nucleosome positioning from sequence-301 base pairs, centered at the position to be scored-with a novel discriminative classification approach that selectively weights the contributions from each of the input features. The resulting scores are relatively insensitive to local AT-content and can be used to accurately discriminate putative dyad positions from adjacent linker regions without requiring an additional dynamic programming step and without the attendant edge effects and assumptions about linker length modeling and overall nucleosome density. Our approach produces the best dyad-linker classification results published to date in H. sapiens, and outperforms two recently published models on a large set of S. cerevisiae nucleosome positions. Our results suggest that in both genomes, a comparable and relatively small fraction of nucleosomes are well-positioned and that these positions are predictable based on sequence alone. We believe that the
Nir, Oded; Marvin, Esra; Lahav, Ori
2014-11-01
Measuring and modeling pH in concentrated aqueous solutions in an accurate and consistent manner is of paramount importance to many R&D and industrial applications, including RO desalination. Nevertheless, unified definitions and standard procedures have yet to be developed for solutions with ionic strength higher than ∼0.7 M, while implementation of conventional pH determination approaches may lead to significant errors. In this work a systematic yet simple methodology for measuring pH in concentrated solutions (dominated by Na(+)/Cl(-)) was developed and evaluated, with the aim of achieving consistency with the Pitzer ion-interaction approach. Results indicate that the addition of 0.75 M of NaCl to NIST buffers, followed by assigning a new standard pH (calculated based on the Pitzer approach), enabled reducing measured errors to below 0.03 pH units in seawater RO brines (ionic strength up to 2 M). To facilitate its use, the method was developed to be both conceptually and practically analogous to the conventional pH measurement procedure. The method was used to measure the pH of seawater RO retentates obtained at varying recovery ratios. The results matched better the pH values predicted by an accurate RO transport model. Calibrating the model by the measured pH values enabled better boron transport prediction. A Donnan-induced phenomenon, affecting pH in both retentate and permeate streams, was identified and quantified.
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...
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.
Arbabi, Vahid; Pouran, Behdad; Weinans, Harrie; Zadpoor, Amir A
2016-09-06
Analytical and numerical methods have been used to extract essential engineering parameters such as elastic modulus, Poisson׳s ratio, permeability and diffusion coefficient from experimental data in various types of biological tissues. The major limitation associated with analytical techniques is that they are often only applicable to problems with simplified assumptions. Numerical multi-physics methods, on the other hand, enable minimizing the simplified assumptions but require substantial computational expertise, which is not always available. In this paper, we propose a novel approach that combines inverse and forward artificial neural networks (ANNs) which enables fast and accurate estimation of the diffusion coefficient of cartilage without any need for computational modeling. In this approach, an inverse ANN is trained using our multi-zone biphasic-solute finite-bath computational model of diffusion in cartilage to estimate the diffusion coefficient of the various zones of cartilage given the concentration-time curves. Robust estimation of the diffusion coefficients, however, requires introducing certain levels of stochastic variations during the training process. Determining the required level of stochastic variation is performed by coupling the inverse ANN with a forward ANN that receives the diffusion coefficient as input and returns the concentration-time curve as output. Combined together, forward-inverse ANNs enable computationally inexperienced users to obtain accurate and fast estimation of the diffusion coefficients of cartilage zones. The diffusion coefficients estimated using the proposed approach are compared with those determined using direct scanning of the parameter space as the optimization approach. It has been shown that both approaches yield comparable results.
基于ESL快速精确的处理器混合模型%Fast and Accurate Processor Hybrid Model Based on ESL
Institute of Scientific and Technical Information of China (English)
鲁超; 魏继增; 常轶松
2012-01-01
For RTL design cannot meet the requirement of the speed of System on Chip(SoC), this paper presents a fast and accurate processor hybrid model based on Electronic System Level(ESL). It uses the proprietary 32 bit embedded microprocessor C*CORE340 based on ESL design methodology. For this target the Instruction Set Simulator(ISS) and Cache adopt the different abstraction layers to construct. Experimental results show that the simulation speeds of hybrid model is a least 10 times faster than that of RTL model, and the less than 10% error rate simulation accuracy is gotten.%RTL设计不能满足片上系统对仿真速度的要求.为此,提出一种基于电子系统级快速精确的处理器混合模型.以32位嵌入式微处理器C*CORE340为例,采用不同的抽象层次对指令集仿真器和Cache进行构建.实验结果表明,与RTL级模型相比,该模型的仿真速度至少快10倍,仿真精度误差率低于10％.
Wu, Chao; Zhang, Xiaojuan; Fang, Guangyou; Shi, Jiancheng; Liu, Shiyin
2015-03-01
We develop an accurate and fast forward model for calculating the compact closed-form high-order perturbative solutions of the problem of three-dimensional (3-D) radiation and propagation electromagnetic fields in a layered structure with multilayer rough interfaces. The proposed method for the fast forward model is first demonstrated by strictly theoretical formulas derivation in the framework of classical small perturbation method (SPM) without other else approximation and equivalent process. The kernel functions of high order are proposed for calculating the radar cross sections with more efficiency and clear physical meanings for better use in practice. What is more, we give the clear physical interpretation of the first-order fully polarimetric electromagnetic wave scattering mechanism in the layered structure with multilayer rough interfaces. The proposed forward model is necessary to insure a successful inversion process. Furthermore, the high-order SPM solutions derived by employing the proposed method are validated with existing methods and numerical results. Finally, we study the performance of the high-order fully polarimetric electromagnetic wave scattering according to the numerical results and analyze the scattering enhancement phenomena.
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
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.
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...... are recast into evolution equations for the complex amplitudes, and serve as the underlying deterministic model. Next, a set of evolution equations for the cumulants is derived. By formally introducing the well-known Gaussian closure hypothesis, nonlinear evolution equations for the power spectrum...... and bispectrum are derived. A simple description of depth-induced wave breaking is incorporated in the model equations, assuming that the total rate of dissipation may be distributed in proportion to the spectral energy density on each discrete frequency. The proposed phase-averaged model is compared...
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.
Energy Technology Data Exchange (ETDEWEB)
Guo, En-Yu [Key Laboratory for Advanced Materials Processing Technology, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Materials Science and Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287 (United States); Chawla, Nikhilesh [Materials Science and Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287 (United States); Jing, Tao [Key Laboratory for Advanced Materials Processing Technology, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Torquato, Salvatore [Department of Chemistry, Princeton University, Princeton, NJ 08544 (United States); Department of Physics, Princeton University, Princeton, NJ 08544 (United States); Princeton Institute for the Science and Technology of Materials, Princeton University, Princeton, NJ 08544 (United States); Program in Applied and Computational Mathematics, Princeton University, Princeton, NJ 08544 (United States); Jiao, Yang, E-mail: yang.jiao.2@asu.edu [Materials Science and Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287 (United States)
2014-03-01
Heterogeneous materials are ubiquitous in nature and synthetic situations and have a wide range of important engineering applications. Accurate modeling and reconstructing three-dimensional (3D) microstructure of topologically complex materials from limited morphological information such as a two-dimensional (2D) micrograph is crucial to the assessment and prediction of effective material properties and performance under extreme conditions. Here, we extend a recently developed dilation–erosion method and employ the Yeong–Torquato stochastic reconstruction procedure to model and generate 3D austenitic–ferritic cast duplex stainless steel microstructure containing percolating filamentary ferrite phase from 2D optical micrographs of the material sample. Specifically, the ferrite phase is dilated to produce a modified target 2D microstructure and the resulting 3D reconstruction is eroded to recover the percolating ferrite filaments. The dilation–erosion reconstruction is compared with the actual 3D microstructure, obtained from serial sectioning (polishing), as well as the standard stochastic reconstructions incorporating topological connectedness information. The fact that the former can achieve the same level of accuracy as the latter suggests that the dilation–erosion procedure is tantamount to incorporating appreciably more topological and geometrical information into the reconstruction while being much more computationally efficient. - Highlights: • Spatial correlation functions used to characterize filamentary ferrite phase • Clustering information assessed from 3D experimental structure via serial sectioning • Stochastic reconstruction used to generate 3D virtual structure 2D micrograph • Dilation–erosion method to improve accuracy of 3D reconstruction.
Heinz, Hendrik
2014-06-18
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.
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.
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...
Directory of Open Access Journals (Sweden)
Feng Chai
2016-10-01
Full Text Available High power density outer-rotor motors commonly use water or oil cooling. A reasonable thermal design for outer-rotor air-cooling motors can effectively enhance the power density without the fluid circulating device. Research on the heat dissipation mechanism of an outer-rotor air-cooling motor can provide guidelines for the selection of the suitable cooling mode and the design of the cooling structure. This study investigates the temperature field of the motor through computational fluid dynamics (CFD and presents a method to overcome the difficulties in building an accurate temperature field model. The proposed method mainly includes two aspects: a new method for calculating the equivalent thermal conductivity (ETC of the air-gap in the laminar state and an equivalent treatment to the thermal circuit that comprises a hub, shaft, and bearings. Using an outer-rotor air-cooling in-wheel motor as an example, the temperature field of this motor is calculated numerically using the proposed method; the results are experimentally verified. The heat transfer rate (HTR of each cooling path is obtained using the numerical results and analytic formulas. The influences of the structural parameters on temperature increases and the HTR of each cooling path are analyzed. Thereafter, the overload capability of the motor is analyzed in various overload conditions.
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
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...
Efficient and accurate fragmentation methods.
Pruitt, Spencer R; Bertoni, Colleen; Brorsen, Kurt R; Gordon, Mark S
2014-09-16
Conspectus Three novel fragmentation methods that are available in the electronic structure program GAMESS (general atomic and molecular electronic structure system) are discussed in this Account. The fragment molecular orbital (FMO) method can be combined with any electronic structure method to perform accurate calculations on large molecular species with no reliance on capping atoms or empirical parameters. The FMO method is highly scalable and can take advantage of massively parallel computer systems. For example, the method has been shown to scale nearly linearly on up to 131 000 processor cores for calculations on large water clusters. There have been many applications of the FMO method to large molecular clusters, to biomolecules (e.g., proteins), and to materials that are used as heterogeneous catalysts. The effective fragment potential (EFP) method is a model potential approach that is fully derived from first principles and has no empirically fitted parameters. Consequently, an EFP can be generated for any molecule by a simple preparatory GAMESS calculation. The EFP method provides accurate descriptions of all types of intermolecular interactions, including Coulombic interactions, polarization/induction, exchange repulsion, dispersion, and charge transfer. The EFP method has been applied successfully to the study of liquid water, π-stacking in substituted benzenes and in DNA base pairs, solvent effects on positive and negative ions, electronic spectra and dynamics, non-adiabatic phenomena in electronic excited states, and nonlinear excited state properties. The effective fragment molecular orbital (EFMO) method is a merger of the FMO and EFP methods, in which interfragment interactions are described by the EFP potential, rather than the less accurate electrostatic potential. The use of EFP in this manner facilitates the use of a smaller value for the distance cut-off (Rcut). Rcut determines the distance at which EFP interactions replace fully quantum
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.
Sekerzh-Zen'kovich, S. Ya.
2015-10-01
The Cauchy problem for the wave equations of Boussinesq type is treated by considering the initial conditions taken from the solution of generalized Cauchy problem for the potential model of tsunami with some "simple" impulsive source under the assumption that the depth of the liquid is constant. The solutions of the problem under consideration are derived in the form of a single integral giving the wave height at every point of observation at any time moment after the pulsed action of the source. The results of comparing the time history of the the height of tsunami waves at different distances from the source for different values of its characteristic radius (these histories are calculated using two solutions, namely, the solution derived here and the solution known for the potential tsunami model) are described. Conclusions concerning the accuracy of the tested solutions are made.
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.
DEFF Research Database (Denmark)
Mihet-Popa, Lucian; Camacho, Oscar Mauricio Forero; Nørgård, Per Bromand
2013-01-01
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....
Ma, Zelan; Chen, Xin; Huang, Yanqi; He, Lan; Liang, Cuishan; Liang, Changhong; Liu, Zaiyi
2015-01-01
Accurate and repeatable measurement of the gross tumour volume(GTV) of subcutaneous xenografts is crucial in the evaluation of anti-tumour therapy. Formula and image-based manual segmentation methods are commonly used for GTV measurement but are hindered by low accuracy and reproducibility. 3D Slicer is open-source software that provides semiautomatic segmentation for GTV measurements. In our study, subcutaneous GTVs from nude mouse xenografts were measured by semiautomatic segmentation with 3D Slicer based on morphological magnetic resonance imaging(mMRI) or diffusion-weighted imaging(DWI)(b = 0,20,800 s/mm2) . These GTVs were then compared with those obtained via the formula and image-based manual segmentation methods with ITK software using the true tumour volume as the standard reference. The effects of tumour size and shape on GTVs measurements were also investigated. Our results showed that, when compared with the true tumour volume, segmentation for DWI(P = 0.060–0.671) resulted in better accuracy than that mMRI(P < 0.001) and the formula method(P < 0.001). Furthermore, semiautomatic segmentation for DWI(intraclass correlation coefficient, ICC = 0.9999) resulted in higher reliability than manual segmentation(ICC = 0.9996–0.9998). Tumour size and shape had no effects on GTV measurement across all methods. Therefore, DWI-based semiautomatic segmentation, which is accurate and reproducible and also provides biological information, is the optimal GTV measurement method in the assessment of anti-tumour treatments. PMID:26489359
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.
Huerta, E A; Brown, Duncan A
2012-01-01
The LIGO detector is undergoing a major upgrade that will increase its sensitivity by a factor of 10, and extend its bandwidth from 40 Hz to 10 Hz on the lower frequency end, while also allowing for high-frequency operation due to its tunability. This advanced LIGO (aLIGO) detector will extend the mass range at which compact mass binaries may be detected by a factor of four or more at a fixed signal-to-noise ratio [1]. The inspirals of stellar-mass compact objects into intermediate-mass black holes (IMBHs) of 50-350 solar masses will lie in the frequency band of aLIGO [2]. GW searches for these type of events will provide conclusive evidence for the existence of IMBHs and explore the dynamics of cluster environments. To realize this science we need to develop waveform templates that accurately capture the dynamical evolution of these type of events before aLIGO begins observations. Implementing gravitational self-force (SF) corrections in templates for compact binaries with mass-ratios 1:10-1:1000 will be ess...
六安市旅游精准扶贫模式研究%Study on the Model of Tourism Accurate Poverty Alleviation in Lu’an City
Institute of Scientific and Technical Information of China (English)
杨祎; 梁宜人; 黄润
2016-01-01
An important symbol of the realization of a comprehensive well‐off society is China’s rural poor population are all out of poverty under the current standard by 2020 ,and China solve regional overall poverty .With the deepening of poverty alleviation and development work ,pro‐poor tourism also enters into the stage of accurate poverty alleviation .On the base of the review of theory and practice of tourism poverty alleviation ,and Combining with the case of tourism poverty alleviation in Lu’an city ,Anhui Province ,The paper analyzes the object of precise tourism poverty alleviation ,and puts forward four kinds of modes ,namely the government’s leading ,market‐oriented ,neighborhood assistance and scenic spot support .This study provides the theoretical basis and decision‐making reference in a new era of precise poverty .%随着我国扶贫开发工作进入攻坚克难阶段，旅游扶贫也进入精准扶贫阶段。在回顾总结国内外旅游扶贫理论和实践的基础上，对新时期我国旅游扶贫面临的问题进行探讨，并结合安徽省六安市旅游扶贫案例，对旅游扶贫对象的精准识别问题进行分析，在此基础上提出政府主导型、市场主导型、邻里互助型和景区帮扶型四种旅游精准扶贫模式。本文研究为新时期旅游精准扶贫提供理论依据和决策参考。
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
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.
This study assesses the ability of 21 crop models to capture the impact of elevated CO2 concentration ([CO218 ]) on maize yield and water use as measured in a 2-year Free Air Carbon dioxide Enrichment experiment conducted at the Thünen Institute in Braunschweig, Germany (Manderscheid et al. 2014). D...
Energy Technology Data Exchange (ETDEWEB)
Qafoku, Odeta; Felmy, Andrew R.
2007-01-01
The development of an accurate aqueous thermodynamic model is described for oxalate species in the Na-Ba-Ca-Mn-Sr-Cl-NO3-PO4-SO4-H2O system at 25°C. The model is valid to high ionic strength (as high as 10m) and from very acid (10m H2SO4) to neutral and basic conditions. The model is based upon the equations of Pitzer and co-workers. The necessary ion-interaction parameters are determined by comparison with experimental data taken from the literature or determined in this study. The proposed aqueous activity and solubility model is valid for a range of applications from interpretation of studies on mineral dissolution at circumneutral pH to the dissolution of high-level waste tank sludges under acidic conditions.
Directory of Open Access Journals (Sweden)
Sinem Oktem-Okullu
Full Text Available The outcome of H. pylori infection is closely related with bacteria's virulence factors and host immune response. The association between T cells and H. pylori infection has been identified, but the effects of the nine major H. pylori specific virulence factors; cagA, vacA, oipA, babA, hpaA, napA, dupA, ureA, ureB on T cell response in H. pylori infected patients have not been fully elucidated. We developed a multiplex- PCR assay to detect nine H. pylori virulence genes with in a three PCR reactions. Also, the expression levels of Th1, Th17 and Treg cell specific cytokines and transcription factors were detected by using qRT-PCR assays. Furthermore, a novel expert derived model is developed to identify set of factors and rules that can distinguish the ulcer patients from gastritis patients. Within all virulence factors that we tested, we identified a correlation between the presence of napA virulence gene and ulcer disease as a first data. Additionally, a positive correlation between the H. pylori dupA virulence factor and IFN-γ, and H. pylori babA virulence factor and IL-17 was detected in gastritis and ulcer patients respectively. By using computer-based models, clinical outcomes of a patients infected with H. pylori can be predicted by screening the patient's H. pylori vacA m1/m2, ureA and cagA status and IFN-γ (Th1, IL-17 (Th17, and FOXP3 (Treg expression levels. Herein, we report, for the first time, the relationship between H. pylori virulence factors and host immune responses for diagnostic prediction of gastric diseases using computer-based models.
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 ...
Abu-Al-Saud, Moataz O.; Riaz, Amir; Tchelepi, Hamdi A.
2017-03-01
We developed a multiscale sharp-interface level-set method for immiscible two-phase flow with a pre-existing thin film on solid surfaces. The lubrication approximation theory is used to model the thin-film equation efficiently. The incompressible Navier-Stokes, level-set, and thin-film evolution equations are coupled sequentially to capture the dynamics occurring at multiple length scales. The Hamilton-Jacobi level-set reinitialization is employed to construct the signed-distance function, which takes into account the deposited thin-film on the solid surface. The proposed multiscale method is validated and shown to match the augmented Young-Laplace equation for a static meniscus in a capillary tube. Viscous bending of the advancing interface over the precursor film is captured by the proposed level-set method and agrees with the Cox-Voinov theory. The advancing bubble surrounded by a wetting film inside a capillary tube is considered, and the predicted film thickness compares well with both theory and experiments. We also demonstrate that the multiscale level-set approach can model immiscible two-phase flow with a capillary number as low as 10-6.
Institute of Scientific and Technical Information of China (English)
王冰清; 曾国宏; 童亦斌; 张勇波
2013-01-01
The research on output characteristics of photovoltaic (PV) module is the foundation to determine the voltage range at maximum power point (MPP) of grid-connected PV inverter. The mathematical model of PV module is of high accuracy, however considering such disadvantages of the mathematical model such as concerning in transcendental equation, complex solving process and too much input parameters, it is not suitable for engineering design; the calculation of simplified model of PV module is simple, however by which the output characteristics of PV module under low light condition cannot be accurately described. Based on contrastive analysis on the mathematical model and simplified model, an accurate engineering model of PV module, which is benchmarked in the mathematical model, is proposed. The compensation parameters of the simplified model is fitted and modified, meanwhile both accuracy and complexity of engineering model are taken into account. The MathCad program is utilized to built the simulation model of PV module, and the output results of the simulation model is contrasted with the output of the mathematical model to verify the accuracy of accurate engineering model. Based on the proposed engineering model, through analyzing the impacts of external conditions such as illumination, temperature and so on, the voltage range traced at MPP of grid-connected PV inverter can be accurately determined, and the correctness of this conclusion is validated by experimental results.%光伏并网变流器最大功率点(maximum power point， MPP)电压范围的确定是以组件的输出特性研究为基础的。组件的数学模型精确度较高，但涉及到超越方程，求解复杂且输入参数多，不适用于工程设计。简化模型计算过程简单但不能准确表述弱光条件下的组件输出特性。基于对数学模型及简化模型的对比分析，提出了一种精确的工程模型，该模型以数学模型为基准，对简化模型的
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].
Directory of Open Access Journals (Sweden)
Vaisman Iosif I
2010-10-01
Full Text Available Abstract Background HIV-1 targets human cells expressing both the CD4 receptor, which binds the viral envelope glycoprotein gp120, as well as either the CCR5 (R5 or CXCR4 (X4 co-receptors, which interact primarily with the third hypervariable loop (V3 loop of gp120. Determination of HIV-1 affinity for either the R5 or X4 co-receptor on host cells facilitates the inclusion of co-receptor antagonists as a part of patient treatment strategies. A dataset of 1193 distinct gp120 V3 loop peptide sequences (989 R5-utilizing, 204 X4-capable is utilized to train predictive classifiers based on implementations of random forest, support vector machine, boosted decision tree, and neural network machine learning algorithms. An in silico mutagenesis procedure employing multibody statistical potentials, computational geometry, and threading of variant V3 sequences onto an experimental structure, is used to generate a feature vector representation for each variant whose components measure environmental perturbations at corresponding structural positions. Results Classifier performance is evaluated based on stratified 10-fold cross-validation, stratified dataset splits (2/3 training, 1/3 validation, and leave-one-out cross-validation. Best reported values of sensitivity (85%, specificity (100%, and precision (98% for predicting X4-capable HIV-1 virus, overall accuracy (97%, Matthew's correlation coefficient (89%, balanced error rate (0.08, and ROC area (0.97 all reach critical thresholds, suggesting that the models outperform six other state-of-the-art methods and come closer to competing with phenotype assays. Conclusions The trained classifiers provide instantaneous and reliable predictions regarding HIV-1 co-receptor usage, requiring only translated V3 loop genotypes as input. Furthermore, the novelty of these computational mutagenesis based predictor attributes distinguishes the models as orthogonal and complementary to previous methods that utilize sequence
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.
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....
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.
西部脱贫攻坚小康化医疗卫生精准脱贫模式研究%Study on Accurate Poverty Alleviation Model through Health Care in West China
Institute of Scientific and Technical Information of China (English)
赵韡; 焦建彬
2016-01-01
Health care accurate poverty alleviation is an arduous and onerous task that alleviates poverty in the western region to implement welfare. According to the targets requirements task to shake off poverty to perform western welfare in the 13th Five-Year Plan period, this paper explores in depth “analytical framework, practical foundation and policy basis”. Then on this basis, the paper creates a new model, called “Western GASE health care accurate poverty alleviation model”. The new model can overcome all kinds of drawbacks in traditional health care Poverty Reducing Model and contribute to ensuring victory of western help-the-poor battle, to achieve western health care synchronous welfare.%医疗卫生精准脱贫是西部脱贫攻坚小康化一项艰巨繁重的任务。本文根据“十三五”时期西部脱贫攻坚小康化的目标任务要求，在深入探讨医疗卫生精准脱贫的“分析框架、实践基础与政策依据”的基础上，创新构建了一种新型的模式———“西部GASE医疗卫生精准脱贫模式”。这一新型模式能够克服西部“传统医疗卫生扶贫模式”的种种弊端，有助于确保2020年打赢西部脱贫攻坚战，实现西部医疗卫生同步小康化。
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。
Institute of Scientific and Technical Information of China (English)
许丽君
2016-01-01
The development of the big data era and the continuous progress of the data analysis technology, has brought a new idea for the government decision-making optimization. The government’s“accurate decision-making” model under the background of big data will become the new development direction of government decision-making. This paper will focus on to explore the sufficient conditions of our country, the significance of the mode construction and the measures for the development, is committed to improve the government’s decision-making level, make decision-making more scientific, efficient, accurate.%大数据时代的发展和数据分析技术的不断进步，为政府决策优化带来了新的思路。基于大数据背景下的政府“精准决策”模式将成为政府决策发展的新方向，本文将注重探讨该模式在我国发展的充分性条件、模式建设的意义和发展措施，致力于提高政府部门的决策水平，使决策更加科学、高效、精准。
Accurate colorimetric feedback for RGB LED clusters
Man, Kwong; Ashdown, Ian
2006-08-01
We present an empirical model of LED emission spectra that is applicable to both InGaN and AlInGaP high-flux LEDs, and which accurately predicts their relative spectral power distributions over a wide range of LED junction temperatures. We further demonstrate with laboratory measurements that changes in LED spectral power distribution with temperature can be accurately predicted with first- or second-order equations. This provides the basis for a real-time colorimetric feedback system for RGB LED clusters that can maintain the chromaticity of white light at constant intensity to within +/-0.003 Δuv over a range of 45 degrees Celsius, and to within 0.01 Δuv when dimmed over an intensity range of 10:1.
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...
Institute of Scientific and Technical Information of China (English)
郭思源; 周理兵; 曲荣海; 凌在汛
2013-01-01
游标永磁电机是一种基于磁场调制原理的新型电磁传动装置，适用于船舶推进、风力发电等低速大转矩的应用场合。准确计算游标永磁电机的磁场分布是设计、优化电磁性能的关键。关于电机解析磁场计算，该文讨论和比较了一极一槽模型和精确子域模型。以表贴式游标永磁电机为研究对象，在气隙子域建立拉普拉斯方程，在槽子域和永磁体子域建立泊松方程，根据分离变量法直接求解。模型建立在二维%Vernier permanent-magnet machines are novel magnetic force transmission devices, and are becoming promising candidate for low-speed high-torque applications such as ship propulsion and wind power generation. Accurate calculation of the magnetic field is a key to design and optimize vernier permanent-magnet machines. The one slot per pole machine model and the accurate subdomain model are discussed and compared. The Laplace's equations in the airgap subdomain, Poisson's equations in the permanent magnet subdomain and the slot subdomain are solved by the variable separation method. The analytical model is set up in 2D polar coordinates and accounts for the influence of radial/parallel/Halbach magnetization, single/double layer winding configurations, internal/external rotor topologies, which can be used to predict the open-circuit, armature reaction and on-load magnetic field distribution. Based on this field model, the electromagnetic performances, such as the airgap magnetic field density, back-EMF and winding inductances is calculated. The analytical model is validated by the corresponding finite-element results.
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.
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 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...
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.
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.
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.
Institute of Scientific and Technical Information of China (English)
徐文博; 刘世军; 李志胜; 黄红涛
2013-01-01
基于SolidWorks操作平台介绍了双圆弧齿轮的三维精确建模的方法,并可以使用VBA语言对其端面齿廓参数化,建立的三维模型导入到Ansys/LS-DYNA中,运用其显式非线性动力分析程序,对其进行动态接触分析,对双圆弧齿轮的设计计算具有一定的参考意义.%Based on SolidWorks operation platform, the accurate 3d modeling method due to the complexity of the double circular arc gear is introduced. Using VBA language, the gear surface is parametered. Then a 3d model is established and imported into the Ansys/ls - dyna. And using its explicit nonlinear dynamic analysis program, the dynamic contact analysis carried out, it has the certain reference significance to design and calculation.
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.
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...
Dixit, V. K.; Porwal, S.; Singh, S. D.; Sharma, T. K.; Ghosh, Sandip; Oak, S. M.
2014-02-01
Temperature dependence of the photoluminescence (PL) peak energy of bulk and quantum well (QW) structures is studied by using a new phenomenological model for including the effect of localized states. In general an anomalous S-shaped temperature dependence of the PL peak energy is observed for many materials which is usually associated with the localization of excitons in band-tail states that are formed due to potential fluctuations. Under such conditions, the conventional models of Varshni, Viña and Passler fail to replicate the S-shaped temperature dependence of the PL peak energy and provide inconsistent and unrealistic values of the fitting parameters. The proposed formalism persuasively reproduces the S-shaped temperature dependence of the PL peak energy and provides an accurate determination of the exciton localization energy in bulk and QW structures along with the appropriate values of material parameters. An example of a strained InAs0.38P0.62/InP QW is presented by performing detailed temperature and excitation intensity dependent PL measurements and subsequent in-depth analysis using the proposed model. Versatility of the new formalism is tested on a few other semiconductor materials, e.g. GaN, nanotextured GaN, AlGaN and InGaN, which are known to have a significant contribution from the localized states. A quantitative evaluation of the fractional contribution of the localized states is essential for understanding the temperature dependence of the PL peak energy of bulk and QW well structures having a large contribution of the band-tail states.
Accurate measurement of unsteady state fluid temperature
Jaremkiewicz, Magdalena
2017-03-01
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.
Institute of Scientific and Technical Information of China (English)
陈雷刚; 朱熀秋
2012-01-01
建立精确的径向悬浮力数学模型,对降低无轴承无刷直流电机系统复杂性、提高控制精度很有帮助.从无轴承无刷直流电机结构出发,详细阐述了其工作原理并建立了等效磁路.将永磁体磁动势等效为悬浮力绕组上的虚拟电流,进而推导了单自由度径向悬浮力的数学模型.最后对有限元分析得到的仿真结果和理论值进行了比较.为了得到更准确的结果,为位移刚度系数引入了修正系数,并再次对其进行了有限元验证.结果表明,所提出的无轴承无刷直流电机的径向悬浮力数学模型具有可行性和较高的精确性.%An accurate mathematical model of radial suspension force in a bearingless brushless DC motor is of great significance to reduce the complexity of system and to improve the control accuracy. This paper began with the structure of the bearingless brushless DC motor, then elaborated on the working principle and established the equivalent circuit. The magnetomotive force of permanent magnets was equivalent to virtual currents in suspension windings, and then a mathematical model with single degree of freedoms for radial suspension force was derived. Finally, results by finite element analysis and theoretical values were compared. In order to get more convincing results, the correction factor was introduced for the displacement stiffness coefficient, and then the finite element analysis was carried out again. The ultimate results show that the proposed mathematical model of radial suspension force of the bearingless brushless DC motor has feasibility and high accuracy.
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...
Optimal strategies for throwing accurately
Venkadesan, Madhusudhan
2010-01-01
Accuracy of throwing in games and sports is governed by how errors at projectile release are propagated by flight dynamics. To address the question of what governs the choice of throwing strategy, we use a simple model of throwing with an arm modelled as a hinged bar of fixed length that can release a projectile at any angle and angular velocity. We show that the amplification of deviations in launch parameters from a one parameter family of solution curves is quantified by the largest singular value of an appropriate Jacobian. This allows us to predict a preferred throwing style in terms of this singular value, which itself depends on target location and the target shape. Our analysis also allows us to characterize the trade-off between speed and accuracy despite not including any effects of signal-dependent noise. Using nonlinear calculations for propagating finite input-noise, we find that an underarm throw to a target leads to an undershoot, but an overarm throw does not. Finally, we consider the limit of...
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
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.
Does a pneumotach accurately characterize voice function?
Walters, Gage; Krane, Michael
2016-11-01
A study is presented which addresses how a pneumotach might adversely affect clinical measurements of voice function. A pneumotach is a device, typically a mask, worn over the mouth, in order to measure time-varying glottal volume flow. By measuring the time-varying difference in pressure across a known aerodynamic resistance element in the mask, the glottal volume flow waveform is estimated. Because it adds aerodynamic resistance to the vocal system, there is some concern that using a pneumotach may not accurately portray the behavior of the voice. To test this hypothesis, experiments were performed in a simplified airway model with the principal dimensions of an adult human upper airway. A compliant constriction, fabricated from silicone rubber, modeled the vocal folds. Variations of transglottal pressure, time-averaged volume flow, model vocal fold vibration amplitude, and radiated sound with subglottal pressure were performed, with and without the pneumotach in place, and differences noted. Acknowledge support of NIH Grant 2R01DC005642-10A1.
Accurate lineshape spectroscopy and the Boltzmann constant.
Truong, G-W; Anstie, J D; May, E F; Stace, T M; Luiten, A N
2015-10-14
Spectroscopy has an illustrious history delivering serendipitous discoveries and providing a stringent testbed for new physical predictions, including applications from trace materials detection, to understanding the atmospheres of stars and planets, and even constraining cosmological models. Reaching fundamental-noise limits permits optimal extraction of spectroscopic information from an absorption measurement. Here, we demonstrate a quantum-limited spectrometer that delivers high-precision measurements of the absorption lineshape. These measurements yield a very accurate measurement of the excited-state (6P1/2) hyperfine splitting in Cs, and reveals a breakdown in the well-known Voigt spectral profile. We develop a theoretical model that accounts for this breakdown, explaining the observations to within the shot-noise limit. Our model enables us to infer the thermal velocity dispersion of the Cs vapour with an uncertainty of 35 p.p.m. within an hour. This allows us to determine a value for Boltzmann's constant with a precision of 6 p.p.m., and an uncertainty of 71 p.p.m.
Institute of Scientific and Technical Information of China (English)
王源; 徐金辉; 陈嵘; 肖杰灵; 王平
2015-01-01
弦测法是测量轨道不平顺的一种基本方法，原理简单，使用方便，高效迅捷。传统观点是直接将弦测值作为轨道不平顺的近似描述，这会不可避免地因基准线变动而产生较大误差。针对该问题建立了一个描述中点弦测法本质的数学模型，分析了轨道不平顺与其弦测值之间的关系，构造了一种计算轨道不平顺精确值的迭代算法与快速算法，并采用数值仿真对弦测过程进行模拟。结果显示：迭代算法总体误差较小，传递函数较好，但由于迭代次数等原因会产生端点误差；快速算法以牺牲计算内存为代价能达到较高精度，绝对误差在1μm以内，传递函数效果极好，从而证明了所建立的数学模型的正确性与计算结果的精确性。%Chord measuring method is a basic method for measuring track irregularity,its theory is easily understood and it is convenient,quick and effective. T raditional method is considering the chord measuring value as approximate track irregularity,which inevitably leads to the big error because of the base line changing. In order to solve this problem,a mathematical model describing the nature of midpoint chord measuring method was established,the relationship between track irregularity and the chord measuring value was discussed,an iterative algorithm and a fast algorithm for calculating accurate track irregularity value were designed,the chord measuring process was simulated by numerical simulation. T he results showed that the iterative algorithm has less overall error,the transfer function is good and the endpoint error occurs because of such reasons as number of iterations,while the fast algorithm achieves a high accuracy at the expense of computing memory,the absolute error of which is less than 1 μm,the effect of transfer function is excellent,which proves the correctness of the mathematical model and the accuracy of the calculation results.
Analytical solution of Boussinesq equations as a model of wave generation
Wiryanto, L. H.; Mungkasi, S.
2016-02-01
When a uniform stream on an open channel is disturbed by existing of a bump at the bottom of the channel, the surface boundary forms waves growing splitting and propagating. The model of the wave generation can be a forced Korteweg de Vries (fKdV) equation or Boussinesq-type equations. In case the governing equations are approximated from steady problem, the fKdV equation is obtained. The model gives two solutions representing solitary-like wave, with different amplitude. However, phyically there is only one profile generated from that process. Which solution is occured, we confirm from unsteady model. The Boussinesq equations are proposed to determine the stabil solution of the fKdV equation. From the linear and steady model, its solution is developed to determine the analytical solution of the unsteady equations, so that it can explain the physical phenomena, i.e. the process of the wave generation, wave splitting and wave propagation. The solution can also determine the amplitude and wave speed of the waves.
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.
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
Understanding the Code: keeping accurate records.
Griffith, Richard
2015-10-01
In his continuing series looking at the legal and professional implications of the Nursing and Midwifery Council's revised Code of Conduct, Richard Griffith discusses the elements of accurate record keeping under Standard 10 of the Code. This article considers the importance of accurate record keeping for the safety of patients and protection of district nurses. The legal implications of records are explained along with how district nurses should write records to ensure these legal requirements are met.
Memory conformity affects inaccurate memories more than accurate memories.
Wright, Daniel B; Villalba, Daniella K
2012-01-01
After controlling for initial confidence, inaccurate memories were shown to be more easily distorted than accurate memories. In two experiments groups of participants viewed 50 stimuli and were then presented with these stimuli plus 50 fillers. During this test phase participants reported their confidence that each stimulus was originally shown. This was followed by computer-generated responses from a bogus participant. After being exposed to this response participants again rated the confidence of their memory. The computer-generated responses systematically distorted participants' responses. Memory distortion depended on initial memory confidence, with uncertain memories being more malleable than confident memories. This effect was moderated by whether the participant's memory was initially accurate or inaccurate. Inaccurate memories were more malleable than accurate memories. The data were consistent with a model describing two types of memory (i.e., recollective and non-recollective memories), which differ in how susceptible these memories are to memory distortion.
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.
Accurate Switched-Voltage voltage averaging circuit
金光, 一幸; 松本, 寛樹
2006-01-01
Abstract ###This paper proposes an accurate Switched-Voltage (SV) voltage averaging circuit. It is presented ###to compensated for NMOS missmatch error at MOS differential type voltage averaging circuit. ###The proposed circuit consists of a voltage averaging and a SV sample/hold (S/H) circuit. It can ###operate using nonoverlapping three phase clocks. Performance of this circuit is verified by PSpice ###simulations.
Accurate overlaying for mobile augmented reality
Pasman, W; van der Schaaf, A; Lagendijk, RL; Jansen, F.W.
1999-01-01
Mobile augmented reality requires accurate alignment of virtual information with objects visible in the real world. We describe a system for mobile communications to be developed to meet these strict alignment criteria using a combination of computer vision. inertial tracking and low-latency renderi
FIXED-WING MICRO AERIAL VEHICLE FOR ACCURATE CORRIDOR MAPPING
Directory of Open Access Journals (Sweden)
M. Rehak
2015-08-01
Full Text Available 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.
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...
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...
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.
On accurate determination of contact angle
Concus, P.; Finn, R.
1992-01-01
Methods are proposed that exploit a microgravity environment to obtain highly accurate measurement of contact angle. These methods, which are based on our earlier mathematical results, do not require detailed measurement of a liquid free-surface, as they incorporate discontinuous or nearly-discontinuous behavior of the liquid bulk in certain container geometries. Physical testing is planned in the forthcoming IML-2 space flight and in related preparatory ground-based experiments.
Accurate Control of Josephson Phase Qubits
2016-04-14
61 ~1986!. 23 K. Kraus, States, Effects, and Operations: Fundamental Notions of Quantum Theory, Lecture Notes in Physics , Vol. 190 ~Springer-Verlag... PHYSICAL REVIEW B 68, 224518 ~2003!Accurate control of Josephson phase qubits Matthias Steffen,1,2,* John M. Martinis,3 and Isaac L. Chuang1 1Center...for Bits and Atoms and Department of Physics , MIT, Cambridge, Massachusetts 02139, USA 2Solid State and Photonics Laboratory, Stanford University
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 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.
Synthesizing Accurate Floating-Point Formulas
Ioualalen, Arnault; Martel, Matthieu
2013-01-01
International audience; Many critical embedded systems perform floating-point computations yet their accuracy is difficult to assert and strongly depends on how formulas are written in programs. In this article, we focus on the synthesis of accurate formulas mathematically equal to the original formulas occurring in source codes. In general, an expression may be rewritten in many ways. To avoid any combinatorial explosion, we use an intermediate representation, called APEG, enabling us to rep...
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.
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 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.
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.
Accurate estimation of indoor travel times
DEFF Research Database (Denmark)
Prentow, Thor Siiger; Blunck, Henrik; Stisen, Allan
2014-01-01
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...... 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...
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.
The first accurate description of an aurora
Schröder, Wilfried
2006-12-01
As technology has advanced, the scientific study of auroral phenomena has increased by leaps and bounds. A look back at the earliest descriptions of aurorae offers an interesting look into how medieval scholars viewed the subjects that we study.Although there are earlier fragmentary references in the literature, the first accurate description of the aurora borealis appears to be that published by the German Catholic scholar Konrad von Megenberg (1309-1374) in his book Das Buch der Natur (The Book of Nature). The book was written between 1349 and 1350.
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.
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.
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 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.
Accurate taxonomic assignment of short pyrosequencing reads.
Clemente, José C; Jansson, Jesper; Valiente, Gabriel
2010-01-01
Ambiguities in the taxonomy dependent assignment of pyrosequencing reads are usually resolved by mapping each read to the lowest common ancestor in a reference taxonomy of all those sequences that match the read. This conservative approach has the drawback of mapping a read to a possibly large clade that may also contain many sequences not matching the read. A more accurate taxonomic assignment of short reads can be made by mapping each read to the node in the reference taxonomy that provides the best precision and recall. We show that given a suffix array for the sequences in the reference taxonomy, a short read can be mapped to the node of the reference taxonomy with the best combined value of precision and recall in time linear in the size of the taxonomy subtree rooted at the lowest common ancestor of the matching sequences. An accurate taxonomic assignment of short reads can thus be made with about the same efficiency as when mapping each read to the lowest common ancestor of all matching sequences in a reference taxonomy. We demonstrate the effectiveness of our approach on several metagenomic datasets of marine and gut microbiota.
A variational approach to Boussinesq modelling of fully nonlinear water waves
Klopman, Gert; Groesen, van Brenny; Dingemans, Maarten W.
2010-01-01
In this paper we present a new method to derive Boussinesq-type equations from a variational principle. These equations are valid for nonlinear surface-water waves propagating over bathymetry. The vertical structure of the flow, required in the Hamiltonian, is approximated by a (series of) vertical
Apparatus for accurately measuring high temperatures
Smith, D.D.
The present invention is a thermometer used for measuring furnace temperatures in the range of about 1800/sup 0/ to 2700/sup 0/C. The thermometer comprises a broadband multicolor thermal radiation sensor positioned to be in optical alignment with the end of a blackbody sight tube extending into the furnace. A valve-shutter arrangement is positioned between the radiation sensor and the sight tube and a chamber for containing a charge of high pressure gas is positioned between the valve-shutter arrangement and the radiation sensor. A momentary opening of the valve shutter arrangement allows a pulse of the high gas to purge the sight tube of air-borne thermal radiation contaminants which permits the radiation sensor to accurately measure the thermal radiation emanating from the end of the sight tube.
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 emulators for large-scale computer experiments
Haaland, Ben; 10.1214/11-AOS929
2012-01-01
Large-scale computer experiments are becoming increasingly important in science. A multi-step procedure is introduced to statisticians for modeling such experiments, which builds an accurate interpolator in multiple steps. In practice, the procedure shows substantial improvements in overall accuracy, but its theoretical properties are not well established. We introduce the terms nominal and numeric error and decompose the overall error of an interpolator into nominal and numeric portions. Bounds on the numeric and nominal error are developed to show theoretically that substantial gains in overall accuracy can be attained with the multi-step approach.
A novel simple and accurate flatness measurement method
Thang, H L
2011-01-01
Flatness measurement of a surface plate is an intensive and old research topic. However ISO definition related and other measurement methods seem uneasy in measuring and/ or complicated in data analysis. Especially in reality, the mentioned methods don't take a clear and straightforward care on the inclining angle which is always included in any given flatness measurement. In this report a novel simple and accurate flatness measurement method was introduced to overcome this prevailing feature in the available methods. The mathematical modeling for this method was also presented making the underlying nature of the method transparent. The applying examples show consistent results.
Calibration Techniques for Accurate Measurements by Underwater Camera Systems
Directory of Open Access Journals (Sweden)
Mark Shortis
2015-12-01
Full Text Available 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.
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.
Automatic Construction of Accurate Models of Physical Systems
1998-07-10
order to develop an AI-adapted global optimization tool that combines qualitative reasoning and local numerical methods; see the Annals of Mathematics and...34Global Solutions for Nonlinear Systems using Qualitative Reasoning," Annals of Mathematics and Artificial Intelligence (1998) • • E. Bradley and
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....
Accurate invariant pattern recognition for perspective camera model
Serikova, Mariya G.; Pantyushina, Ekaterina N.; Zyuzin, Vadim V.; Korotaev, Valery V.; Rodrigues, Joel J. P. C.
2015-05-01
In this work we present a pattern recognition method based on geometry analysis of a flat pattern. The method provides reliable detection of the pattern in the case when significant perspective deformation is present in the image. The method is based on the fact that collinearity of the lines remains unchanged under perspective transformation. So the recognition feature is the presence of two lines, containing four points each. Eight points form two squares for convenience of applying corner detection algorithms. The method is suitable for automatic pattern detection in a dense environment of false objects. In this work we test the proposed method for statistics of detection and algorithm's performance. For estimation of pattern detection quality we performed image simulation process with random size and spatial frequency of background clutter while both translational (range varied from 200 mm to 1500 mm) and rotational (up to 60°) deformations in given pattern position were added. Simulated measuring system included a camera (4000x4000 sensor with 25 mm lens) and a flat pattern. Tests showed that the proposed method demonstrates no more than 1% recognition error when number of false targets is up to 40.
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 Critical Parameters for the Modified Lennard-Jones Model
Okamoto, Kazuma; Fuchizaki, Kazuhiro
2017-03-01
The critical parameters of the modified Lennard-Jones system were examined. The isothermal-isochoric ensemble was generated by conducting a molecular dynamics simulation for the system consisting of 6912, 8788, 10976, and 13500 particles. The equilibrium between the liquid and vapor phases was judged from the chemical potential of both phases upon establishing the coexistence envelope, from which the critical temperature and density were obtained invoking the renormalization group theory. The finite-size scaling enabled us to finally determine the critical temperature, pressure, and density as Tc = 1.0762(2), pc = 0.09394(17), and ρc = 0.331(3), respectively.
An accurate model for the thin film flow
Institute of Scientific and Technical Information of China (English)
Hamid Ait Abderahmane; Georgios H. Vatistas
2008-01-01
This paper deals with the linear stability of a liquid film flowing down an inclined plane. The Navier-Stokes equations were reduced into four evolution equations that describe the development of the film depth, the flow rate, the free surface velocity, and the wall shear stress, using the Karman-Polhausen boundary layer integral method. Thus, we were able to determine the stability threshold and approach well the critical wave number for long waves. The obtained results were found to be in good agreement with the experiments of Liu et al.
Accurate modelling of anisotropic effects in austenitic stainless steel welds
Nowers, O. D.; Duxbury, D. J.; Drinkwater, B. W.
2014-02-01
The ultrasonic inspection of austenitic steel welds is challenging due to the formation of highly anisotropic and heterogeneous structures post-welding. This is due to the intrinsic crystallographic structure of austenitic steel, driving the formation of dendritic grain structures on cooling. The anisotropy is manifested as both a `steering' of the ultrasonic beam and the back-scatter of energy due to the macroscopic granular structure of the weld. However, the quantitative effects and relative impacts of these phenomena are not well-understood. A semi-analytical simulation framework has been developed to allow the study of anisotropic effects in austenitic stainless steel welds. Frequency-dependent scatterers are allocated to a weld-region to approximate the coarse grain-structures observed within austenitic welds and imaged using a simulated array. The simulated A-scans are compared against an equivalent experimental setup demonstrating excellent agreement of the Signal to Noise (S/N) ratio. Comparison of images of the simulated and experimental data generated using the Total Focusing Method (TFM) indicate a prominent layered effect in the simulated data. A superior grain allocation routine is required to improve upon this.
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 and stable time stepping in ice sheet modeling
Cheng, Gong; Lötstedt, Per; von Sydow, Lina
2017-01-01
In this paper we introduce adaptive time step control for simulation of the 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 Δt is bound by stability requirements or accuracy requirements. Our method takes a shorter Δt 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 stability bounds in the experiments are explained by and agree well with the theoretical results.
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.
Fast and accurate exhaled breath ammonia measurement.
Solga, Steven F; Mudalel, Matthew L; Spacek, Lisa A; Risby, Terence H
2014-06-11
This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels. Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive. The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations.
Noninvasive hemoglobin monitoring: how accurate is enough?
Rice, Mark J; Gravenstein, Nikolaus; Morey, Timothy E
2013-10-01
Evaluating the accuracy of medical devices has traditionally been a blend of statistical analyses, at times without contextualizing the clinical application. There have been a number of recent publications on the accuracy of a continuous noninvasive hemoglobin measurement device, the Masimo Radical-7 Pulse Co-oximeter, focusing on the traditional statistical metrics of bias and precision. In this review, which contains material presented at the Innovations and Applications of Monitoring Perfusion, Oxygenation, and Ventilation (IAMPOV) Symposium at Yale University in 2012, we critically investigated these metrics as applied to the new technology, exploring what is required of a noninvasive hemoglobin monitor and whether the conventional statistics adequately answer our questions about clinical accuracy. We discuss the glucose error grid, well known in the glucose monitoring literature, and describe an analogous version for hemoglobin monitoring. This hemoglobin error grid can be used to evaluate the required clinical accuracy (±g/dL) of a hemoglobin measurement device to provide more conclusive evidence on whether to transfuse an individual patient. The important decision to transfuse a patient usually requires both an accurate hemoglobin measurement and a physiologic reason to elect transfusion. It is our opinion that the published accuracy data of the Masimo Radical-7 is not good enough to make the transfusion decision.
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...
Accurate upper body rehabilitation system using kinect.
Sinha, Sanjana; Bhowmick, Brojeshwar; Chakravarty, Kingshuk; Sinha, Aniruddha; Das, Abhijit
2016-08-01
The growing importance of Kinect as a tool for clinical assessment and rehabilitation is due to its portability, low cost and markerless system for human motion capture. However, the accuracy of Kinect in measuring three-dimensional body joint center locations often fails to meet clinical standards of accuracy when compared to marker-based motion capture systems such as Vicon. The length of the body segment connecting any two joints, measured as the distance between three-dimensional Kinect skeleton joint coordinates, has been observed to vary with time. The orientation of the line connecting adjoining Kinect skeletal coordinates has also been seen to differ from the actual orientation of the physical body segment. Hence we have proposed an optimization method that utilizes Kinect Depth and RGB information to search for the joint center location that satisfies constraints on body segment length and as well as orientation. An experimental study have been carried out on ten healthy participants performing upper body range of motion exercises. The results report 72% reduction in body segment length variance and 2° improvement in Range of Motion (ROM) angle hence enabling to more accurate measurements for upper limb exercises.
Accurate thermoplasmonic simulation of metallic nanoparticles
Yu, Da-Miao; Liu, Yan-Nan; Tian, Fa-Lin; Pan, Xiao-Min; Sheng, Xin-Qing
2017-01-01
Thermoplasmonics leads to enhanced heat generation due to the localized surface plasmon resonances. The measurement of heat generation is fundamentally a complicated task, which necessitates the development of theoretical simulation techniques. In this paper, an efficient and accurate numerical scheme is proposed for applications with complex metallic nanostructures. Light absorption and temperature increase are, respectively, obtained by solving the volume integral equation (VIE) and the steady-state heat diffusion equation through the method of moments (MoM). Previously, methods based on surface integral equations (SIEs) were utilized to obtain light absorption. However, computing light absorption from the equivalent current is as expensive as O(NsNv), where Ns and Nv, respectively, denote the number of surface and volumetric unknowns. Our approach reduces the cost to O(Nv) by using VIE. The accuracy, efficiency and capability of the proposed scheme are validated by multiple simulations. The simulations show that our proposed method is more efficient than the approach based on SIEs under comparable accuracy, especially for the case where many incidents are of interest. The simulations also indicate that the temperature profile can be tuned by several factors, such as the geometry configuration of array, beam direction, and light wavelength.
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.
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.
Optimizing cell arrays for accurate functional genomics
Directory of Open Access Journals (Sweden)
Fengler Sven
2012-07-01
Full Text Available Abstract Background Cellular responses emerge from a complex network of dynamic biochemical reactions. In order to investigate them is necessary to develop methods that allow perturbing a high number of gene products in a flexible and fast way. Cell arrays (CA enable such experiments on microscope slides via reverse transfection of cellular colonies growing on spotted genetic material. In contrast to multi-well plates, CA are susceptible to contamination among neighboring spots hindering accurate quantification in cell-based screening projects. Here we have developed a quality control protocol for quantifying and minimizing contamination in CA. Results We imaged checkered CA that express two distinct fluorescent proteins and segmented images into single cells to quantify the transfection efficiency and interspot contamination. Compared with standard procedures, we measured a 3-fold reduction of contaminants when arrays containing HeLa cells were washed shortly after cell seeding. We proved that nucleic acid uptake during cell seeding rather than migration among neighboring spots was the major source of contamination. Arrays of MCF7 cells developed without the washing step showed 7-fold lower percentage of contaminant cells, demonstrating that contamination is dependent on specific cell properties. Conclusions Previously published methodological works have focused on achieving high transfection rate in densely packed CA. Here, we focused in an equally important parameter: The interspot contamination. The presented quality control is essential for estimating the rate of contamination, a major source of false positives and negatives in current microscopy based functional genomics screenings. We have demonstrated that a washing step after seeding enhances CA quality for HeLA but is not necessary for MCF7. The described method provides a way to find optimal seeding protocols for cell lines intended to be used for the first time in CA.
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.
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.
Accurate mass measurements on neutron-deficient krypton isotopes
Energy Technology Data Exchange (ETDEWEB)
Rodriguez, D. [GSI, Planckstrasse 1, 64291 Darmstadt (Germany)]. E-mail: rodriguez@lpccaen.in2p3.fr; Audi, G. [CSNSM-IN2P3-CNRS, 91405 Orsay-Campus(France); Aystoe, J. [University of Jyvaeskylae, Department of Physics, P.O. Box 35, 40351 Jyvaeskylae (Finland); Beck, D. [GSI, Planckstrasse 1, 64291 Darmstadt (Germany); Blaum, K. [GSI, Planckstrasse 1, 64291 Darmstadt (Germany); Institute of Physics, University of Mainz, Staudingerweg 7, 55128 Mainz (Germany); Bollen, G. [NSCL, Michigan State University, East Lansing, MI 48824-1321 (United States); Herfurth, F. [GSI, Planckstrasse 1, 64291 Darmstadt (Germany); Jokinen, A. [University of Jyvaeskylae, Department of Physics, P.O. Box 35, 40351 Jyvaeskylae (Finland); Kellerbauer, A. [CERN, Division EP, 1211 Geneva 23 (Switzerland); Kluge, H.-J. [GSI, Planckstrasse 1, 64291 Darmstadt (Germany); University of Heidelberg, 69120 Heidelberg (Germany); Kolhinen, V.S. [University of Jyvaeskylae, Department of Physics, P.O. Box 35, 40351 Jyvaeskylae (Finland); Oinonen, M. [Helsinki Institute of Physics, P.O. Box 64, 00014 University of Helsinki (Finland); Sauvan, E. [Institute of Physics, University of Mainz, Staudingerweg 7, 55128 Mainz (Germany); Schwarz, S. [NSCL, Michigan State University, East Lansing, MI 48824-1321 (United States)
2006-04-17
The masses of {sup 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 {sup 72-75}Kr outweighed 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.
HIPPI: highly accurate protein family classification with ensembles of HMMs
Directory of Open Access Journals (Sweden)
Nam-phuong Nguyen
2016-11-01
Full Text Available Abstract Background Given a new biological sequence, detecting membership in a known family is a basic step in many bioinformatics analyses, with applications to protein structure and function prediction and metagenomic taxon identification and abundance profiling, among others. Yet family identification of sequences that are distantly related to sequences in public databases or that are fragmentary remains one of the more difficult analytical problems in bioinformatics. Results We present a new technique for family identification called HIPPI (Hierarchical Profile Hidden Markov Models for Protein family Identification. HIPPI uses a novel technique to represent a multiple sequence alignment for a given protein family or superfamily by an ensemble of profile hidden Markov models computed using HMMER. An evaluation of HIPPI on the Pfam database shows that HIPPI has better overall precision and recall than blastp, HMMER, and pipelines based on HHsearch, and maintains good accuracy even for fragmentary query sequences and for protein families with low average pairwise sequence identity, both conditions where other methods degrade in accuracy. Conclusion HIPPI provides accurate protein family identification and is robust to difficult model conditions. Our results, combined with observations from previous studies, show that ensembles of profile Hidden Markov models can better represent multiple sequence alignments than a single profile Hidden Markov model, and thus can improve downstream analyses for various bioinformatic tasks. Further research is needed to determine the best practices for building the ensemble of profile Hidden Markov models. HIPPI is available on GitHub at https://github.com/smirarab/sepp .
Accurate skin dose measurements using radiochromic film in clinical applications.
Devic, S; Seuntjens, J; Abdel-Rahman, W; Evans, M; Olivares, M; Podgorsak, E B; Vuong, Té; Soares, Christopher G
2006-04-01
Megavoltage x-ray beams exhibit the well-known phenomena of dose buildup within the first few millimeters of the incident phantom surface, or the skin. Results of the surface dose measurements, however, depend vastly on the measurement technique employed. Our goal in this study was to determine a correction procedure in order to obtain an accurate skin dose estimate at the clinically relevant depth based on radiochromic film measurements. To illustrate this correction, we have used as a reference point a depth of 70 micron. We used the new GAFCHROMIC dosimetry films (HS, XR-T, and EBT) that have effective points of measurement at depths slightly larger than 70 micron. In addition to films, we also used an Attix parallel-plate chamber and a home-built extrapolation chamber to cover tissue-equivalent depths in the range from 4 micron to 1 mm of water-equivalent depth. Our measurements suggest that within the first millimeter of the skin region, the PDD for a 6 MV photon beam and field size of 10 x 10 cm2 increases from 14% to 43%. For the three GAFCHROMIC dosimetry film models, the 6 MV beam entrance skin dose measurement corrections due to their effective point of measurement are as follows: 15% for the EBT, 15% for the HS, and 16% for the XR-T model GAFCHROMIC films. The correction factors for the exit skin dose due to the build-down region are negligible. There is a small field size dependence for the entrance skin dose correction factor when using the EBT GAFCHROMIC film model. Finally, a procedure that uses EBT model GAFCHROMIC film for an accurate measurement of the skin dose in a parallel-opposed pair 6 MV photon beam arrangement is described.
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.
Learning fast accurate movements requires intact frontostriatal circuits
Directory of Open Access Journals (Sweden)
Britne eShabbott
2013-11-01
Full Text Available The basal ganglia are known to play a crucial role in movement execution, but their importance for motor skill learning remains unclear. Obstacles to our understanding include the lack of a universally accepted definition of motor skill learning (definition confound, and difficulties in distinguishing learning deficits from execution impairments (performance confound. We studied how healthy subjects and subjects with a basal ganglia disorder learn fast accurate reaching movements, and we addressed the definition and performance confounds by: 1 focusing on an operationally defined core element of motor skill learning (speed-accuracy learning, and 2 using normal variation in initial performance to separate movement execution impairment from motor learning abnormalities. We measured motor skill learning learning as performance improvement in a reaching task with a speed-accuracy trade-off. We compared the performance of subjects with Huntington’s disease (HD, a neurodegenerative basal ganglia disorder, to that of premanifest carriers of the HD mutation and of control subjects. The initial movements of HD subjects were less skilled (slower and/or less accurate than those of control subjects. To factor out these differences in initial execution, we modeled the relationship between learning and baseline performance in control subjects. Subjects with HD exhibited a clear learning impairment that was not explained by differences in initial performance. These results support a role for the basal ganglia in both movement execution and motor skill learning.
Accurate measurement of streamwise vortices using dual-plane PIV
Waldman, Rye M.; Breuer, Kenneth S.
2012-11-01
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.
Shishvan, Masoud Soleymani; Sattarvand, Javad
2012-12-01
In this paper a new method of modeling variable slope angles has been presented based on the spline interpolation method. Slope angle modeling and defining precedency of the blocks are the vital parts of almost any open pit optimization algorithm. Traditionally heuristic patterns such as 1:5 or 1:9 have been used to generate slope angles. Cone template based models were later employed in developing variable slope angles. They normally use a linear interpolation process for determination of slope angles between the given directions which leads to sharp and non-realistic pits. The other elliptical alternatives suffer from having limitations in defining slope angles in non-geographical directions. The method is capable to consider any number of slope angles in any desired direction as well as creating quite accurate and realistic pit shapes. Three major types of the spline interpolation including cubic, quadratic and cardinal are tested, however, the cubic form is preferred due to more realistic outcomes. Main steps of the method are described through a numerical case study.
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...
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...
Accurate complex scaling of three dimensional numerical potentials.
Cerioni, Alessandro; Genovese, Luigi; Duchemin, Ivan; Deutsch, Thierry
2013-05-28
The complex scaling method, which consists in continuing spatial coordinates into the complex plane, is a well-established method that allows to compute resonant eigenfunctions of the time-independent Schrödinger operator. Whenever it is desirable to apply the complex scaling to investigate resonances in physical systems defined on numerical discrete grids, the most direct approach relies on the application of a similarity transformation to the original, unscaled Hamiltonian. We show that such an approach can be conveniently implemented in the Daubechies wavelet basis set, featuring a very promising level of generality, high accuracy, and no need for artificial convergence parameters. Complex scaling of three dimensional numerical potentials can be efficiently and accurately performed. By carrying out an illustrative resonant state computation in the case of a one-dimensional model potential, we then show that our wavelet-based approach may disclose new exciting opportunities in the field of computational non-Hermitian quantum mechanics.
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.
Accurate atom-mapping computation for biochemical reactions.
Latendresse, Mario; Malerich, Jeremiah P; Travers, Mike; Karp, Peter D
2012-11-26
The complete atom mapping of a chemical reaction is a bijection of the reactant atoms to the product atoms that specifies the terminus of each reactant atom. Atom mapping of biochemical reactions is useful for many applications of systems biology, in particular for metabolic engineering where synthesizing new biochemical pathways has to take into account for the number of carbon atoms from a source compound that are conserved in the synthesis of a target compound. Rapid, accurate computation of the atom mapping(s) of a biochemical reaction remains elusive despite significant work on this topic. In particular, past researchers did not validate the accuracy of mapping algorithms. We introduce a new method for computing atom mappings called the minimum weighted edit-distance (MWED) metric. The metric is based on bond propensity to react and computes biochemically valid atom mappings for a large percentage of biochemical reactions. MWED models can be formulated efficiently as Mixed-Integer Linear Programs (MILPs). We have demonstrated this approach on 7501 reactions of the MetaCyc database for which 87% of the models could be solved in less than 10 s. For 2.1% of the reactions, we found multiple optimal atom mappings. We show that the error rate is 0.9% (22 reactions) by comparing these atom mappings to 2446 atom mappings of the manually curated Kyoto Encyclopedia of Genes and Genomes (KEGG) RPAIR database. To our knowledge, our computational atom-mapping approach is the most accurate and among the fastest published to date. The atom-mapping data will be available in the MetaCyc database later in 2012; the atom-mapping software will be available within the Pathway Tools software later in 2012.
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.
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
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.
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.
Liquid propellant rocket engine combustion simulation with a time-accurate CFD method
Chen, Y. S.; Shang, H. M.; Liaw, Paul; Hutt, J.
1993-01-01
Time-accurate computational fluid dynamics (CFD) algorithms are among the basic requirements as an engineering or research tool for realistic simulations of transient combustion phenomena, such as combustion instability, transient start-up, etc., inside the rocket engine combustion chamber. A time-accurate pressure based method is employed in the FDNS code for combustion model development. This is in connection with other program development activities such as spray combustion model development and efficient finite-rate chemistry solution method implementation. In the present study, a second-order time-accurate time-marching scheme is employed. For better spatial resolutions near discontinuities (e.g., shocks, contact discontinuities), a 3rd-order accurate TVD scheme for modeling the convection terms is implemented in the FDNS code. Necessary modification to the predictor/multi-corrector solution algorithm in order to maintain time-accurate wave propagation is also investigated. Benchmark 1-D and multidimensional test cases, which include the classical shock tube wave propagation problems, resonant pipe test case, unsteady flow development of a blast tube test case, and H2/O2 rocket engine chamber combustion start-up transient simulation, etc., are investigated to validate and demonstrate the accuracy and robustness of the present numerical scheme and solution algorithm.
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)
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
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.
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 method for tube's endpoints based on machine vision
Liu, Shaoli; Jin, Peng; Liu, Jianhua; Wang, Xiao; Sun, Peng
2017-01-01
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.
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.
Data fusion for accurate microscopic rough surface metrology.
Chen, Yuhang
2016-06-01
Data fusion for rough surface measurement and evaluation was analyzed on simulated datasets, one with higher density (HD) but lower accuracy and the other with lower density (LD) but higher accuracy. Experimental verifications were then performed on laser scanning microscopy (LSM) and atomic force microscopy (AFM) characterizations of surface areal roughness artifacts. The results demonstrated that the fusion based on Gaussian process models is effective and robust under different measurement biases and noise strengths. All the amplitude, height distribution, and spatial characteristics of the original sample structure can be precisely recovered, with better metrological performance than any individual measurements. As for the influencing factors, the HD noise has a relatively weaker effect as compared with the LD noise. Furthermore, to enable an accurate fusion, the ratio of LD sampling interval to surface autocorrelation length should be smaller than a critical threshold. In general, data fusion is capable of enhancing the nanometrology of rough surfaces by combining efficient LSM measurement and down-sampled fast AFM scan. The accuracy, resolution, spatial coverage and efficiency can all be significantly improved. It is thus expected to have potential applications in development of hybrid microscopy and in surface metrology.
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.
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.
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.
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.
Manescu, Petru; Jong Lee, Young; Camp, Charles; Cicerone, Marcus; Brady, Mary; Bajcsy, Peter
2017-04-01
This paper addresses the problem of classifying materials from microspectroscopy at a pixel level. The challenges lie in identifying discriminatory spectral features and obtaining accurate and interpretable models relating spectra and class labels. We approach the problem by designing a supervised classifier from a tandem of Artificial Neural Network (ANN) models that identify relevant features in raw spectra and achieve high classification accuracy. The tandem of ANN models is meshed with classification rule extraction methods to lower the model complexity and to achieve interpretability of the resulting model. The contribution of the work is in designing each ANN model based on the microspectroscopy hypothesis about a discriminatory feature of a certain target class being composed of a linear combination of spectra. The novelty lies in meshing ANN and decision rule models into a tandem configuration to achieve accurate and interpretable classification results. The proposed method was evaluated using a set of broadband coherent anti-Stokes Raman scattering (BCARS) microscopy cell images (600 000 pixel-level spectra) and a reference four-class rule-based model previously created by biochemical experts. The generated classification rule-based model was on average 85% accurate measured by the DICE pixel label similarity metric, and on average 96% similar to the reference rules measured by the vector cosine metric.
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...
Defining Allowable Physical Property Variations for High Accurate Measurements on Polymer Parts
DEFF Research Database (Denmark)
Mohammadi, Ali; Sonne, Mads Rostgaard; Madruga, Daniel González;
2015-01-01
cooling down after injection molding. In order to obtain accurate simulations, accurate inputs to the model are crucial. In reality however, the material and physical properties will have some variations. Although these variations may be small, they can act as a source of uncertainty for the measurement...... high accurate measurements in non-controlled ambient. Most of polymer parts are manufactured by injection moulding and their inspection is carried out after stabilization, around 200 hours. The overall goal of this work is to reach ±5μm in uncertainty measurements a polymer products which...... is a challenge in today‘s production and metrology environments. The residual deformations in polymer products at room temperature after injection molding are important when micrometer accuracy needs to be achieved. Numerical modelling can give a valuable insight to what is happening in the polymer during...
Interaction potentials for water from accurate cluster calculations
Energy Technology Data Exchange (ETDEWEB)
Xantheas, Sotiris S.
2006-03-15
simulations such as the first computer simulation of liquid water by Barker and Watts and Rahman and Stillinger, the first parametrization of a pair potential for water from ab-initio calculations by Clementi and co-workers and the first simulation of liquid water from first principles by Parrinello and Carr. Many of the empirical pair potentials for water that are used widely even nowadays were developed in the early 1980's. These early models were mainly parameterized in order to reproduce measured thermodynamic bulk properties due to the fact that molecular level information for small water clusters was limited or even nonexisting at that time. Subsequent attempts have focused in introducing self-consistent polarization as a means of explicitly accounting for the magnitude of the non-additive many-body effects via an induction scheme. Again the lack of accurate experimental or theoretical water cluster energetic information has prevented the assessment of the accuracy of those models.
Robust, accurate and fast automatic segmentation of the spinal cord.
De Leener, Benjamin; Kadoury, Samuel; Cohen-Adad, Julien
2014-09-01
Spinal cord segmentation provides measures of atrophy and facilitates group analysis via inter-subject correspondence. Automatizing this procedure enables studies with large throughput and minimizes user bias. Although several automatic segmentation methods exist, they are often restricted in terms of image contrast and field-of-view. This paper presents a new automatic segmentation method (PropSeg) optimized for robustness, accuracy and speed. The algorithm is based on the propagation of a deformable model and is divided into three parts: firstly, an initialization step detects the spinal cord position and orientation using a circular Hough transform on multiple axial slices rostral and caudal to the starting plane and builds an initial elliptical tubular mesh. Secondly, a low-resolution deformable model is propagated along the spinal cord. To deal with highly variable contrast levels between the spinal cord and the cerebrospinal fluid, the deformation is coupled with a local contrast-to-noise adaptation at each iteration. Thirdly, a refinement process and a global deformation are applied on the propagated mesh to provide an accurate segmentation of the spinal cord. Validation was performed in 15 healthy subjects and two patients with spinal cord injury, using T1- and T2-weighted images of the entire spinal cord and on multiecho T2*-weighted images. Our method was compared against manual segmentation and against an active surface method. Results show high precision for all the MR sequences. Dice coefficients were 0.9 for the T1- and T2-weighted cohorts and 0.86 for the T2*-weighted images. The proposed method runs in less than 1min on a normal computer and can be used to quantify morphological features such as cross-sectional area along the whole spinal cord.
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.
Accurate estimation of the boundaries of a structured light pattern.
Lee, Sukhan; Bui, Lam Quang
2011-06-01
Depth recovery based on structured light using stripe patterns, especially for a region-based codec, demands accurate estimation of the true boundary of a light pattern captured on a camera image. This is because the accuracy of the estimated boundary has a direct impact on the accuracy of the depth recovery. However, recovering the true boundary of a light pattern is considered difficult due to the deformation incurred primarily by the texture-induced variation of the light reflectance at surface locales. Especially for heavily textured surfaces, the deformation of pattern boundaries becomes rather severe. We present here a novel (to the best of our knowledge) method to estimate the true boundaries of a light pattern that are severely deformed due to the heavy textures involved. First, a general formula that models the deformation of the projected light pattern at the imaging end is presented, taking into account not only the light reflectance variation but also the blurring along the optical passages. The local reflectance indices are then estimated by applying the model to two specially chosen reference projections, all-bright and all-dark. The estimated reflectance indices are to transform the edge-deformed, captured pattern signal into the edge-corrected, canonical pattern signal. A canonical pattern implies the virtual pattern that would have resulted if there were neither the reflectance variation nor the blurring in imaging optics. Finally, we estimate the boundaries of a light pattern by intersecting the canonical form of a light pattern with that of its inverse pattern. The experimental results show that the proposed method results in significant improvements in the accuracy of the estimated boundaries under various adverse conditions.
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.
Realization of Quadrature Signal Generator Using Accurate Magnitude Integrator
DEFF Research Database (Denmark)
Xin, Zhen; Yoon, Changwoo; Zhao, Rende
2016-01-01
-signal parameters, espically when a fast resonse is required for usages such as grid synchronization. As a result, the parameters design of the SOGI-QSG becomes complicated. Theoretical analysis shows that it is caused by the inaccurate magnitude-integration characteristic of the SOGI-QSG. To solve this problem......, an Accurate-Magnitude-Integrator based QSG (AMI-QSG) is proposed. The AMI has an accurate magnitude-integration characteristic for the sinusoidal signal, which makes the AMI-QSG possess an accurate First-Order-System (FOS) characteristic in terms of magnitude than the SOGI-QSG. The parameter design process...
Fabricating an Accurate Implant Master Cast: A Technique Report.
Balshi, Thomas J; Wolfinger, Glenn J; Alfano, Stephen G; Cacovean, Jeannine N; Balshi, Stephen F
2015-12-01
The technique for fabricating an accurate implant master cast following the 12-week healing period after Teeth in a Day® dental implant surgery is detailed. The clinical, functional, and esthetic details captured during the final master impression are vital to creating an accurate master cast. This technique uses the properties of the all-acrylic resin interim prosthesis to capture these details. This impression captures the relationship between the remodeled soft tissue and the interim prosthesis. This provides the laboratory technician with an accurate orientation of the implant replicas in the master cast with which a passive fitting restoration can be fabricated.
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.
DEFF Research Database (Denmark)
Hermannsson, Pétur Gordon; Vannahme, Christoph; Smith, Cameron L. C.
2014-01-01
and superstrate materials. The importance of accounting for material dispersion in order to obtain accurate simulation results is highlighted, and a method for doing so using an iterative approach is demonstrated. Furthermore, an application for the model is demonstrated, in which the material dispersion...... of a liquid is extracted from measured resonance wavelengths....
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...
Accurate determination of process variables in a solid-state fermentation system
Smits, J.P.; Rinzema, A.; Tramper, J.; Schlösser, E.E.; Knol, W.
1996-01-01
The solid-state fermentation (SSF) method described enabled accurate determination of variables related to biological activity. Growth, respiratory activity and production of carboxymethyl-cellulose-hydrolysing enzyme (CMC-ase) activity by Trichoderma reesei QM9414 on wheat bran was used as a model
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 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.
Multi-objective optimization of inverse planning for accurate radiotherapy
Institute of Scientific and Technical Information of China (English)
曹瑞芬; 吴宜灿; 裴曦; 景佳; 李国丽; 程梦云; 李贵; 胡丽琴
2011-01-01
The multi-objective optimization of inverse planning based on the Pareto solution set, according to the multi-objective character of inverse planning in accurate radiotherapy, was studied in this paper. Firstly, the clinical requirements of a treatment pl
Controlling Hay Fever Symptoms with Accurate Pollen Counts
... counts Share | Controlling Hay Fever Symptoms with Accurate Pollen Counts This article has been reviewed by Thanai ... rhinitis known as hay fever is caused by pollen carried in the air during different times of ...
Digital system accurately controls velocity of electromechanical drive
Nichols, G. B.
1965-01-01
Digital circuit accurately regulates electromechanical drive mechanism velocity. The gain and phase characteristics of digital circuits are relatively unimportant. Control accuracy depends only on the stability of the input signal frequency.
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.
Mass spectrometry based protein identification with accurate statistical significance assignment
Alves, Gelio; Yu, Yi-Kuo
2014-01-01
Motivation: Assigning statistical significance accurately has become increasingly important as meta data of many types, often assembled in hierarchies, are constructed and combined for further biological analyses. Statistical inaccuracy of meta data at any level may propagate to downstream analyses, undermining the validity of scientific conclusions thus drawn. From the perspective of mass spectrometry based proteomics, even though accurate statistics for peptide identification can now be ach...
High-Accurate, Physics-Based Wake Simulation Techniques
2015-01-27
physically accurate problem as well as to show that the sensor can account for artificial viscosity where needed but not overload the problem and ”wash out...code) 1/27/2015 Final Technical Report 02/25/10 - 08/31/14 High-Accurate, Physics -Based Wake Simulation Techniques N00014-10-C-0190 Andrew Shelton...code was developed that utilizes the discontinuous Galerkin method to solve the Euler equations while utilizing a modal artificial viscosity sensor
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.
An Accurate Approach to Large-Scale IP Traffic Matrix Estimation
Jiang, Dingde; Hu, Guangmin
This letter proposes a novel method of large-scale IP traffic matrix (TM) estimation, called algebraic reconstruction technique inference (ARTI), which is based on the partial flow measurement and Fratar model. In contrast to previous methods, ARTI can accurately capture the spatio-temporal correlations of TM. Moreover, ARTI is computationally simple since it uses the algebraic reconstruction technique. We use the real data from the Abilene network to validate ARTI. Simulation results show that ARTI can accurately estimate large-scale IP TM and track its dynamics.
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
Guidelines for accurate EC50/IC50 estimation.
Sebaugh, J L
2011-01-01
This article provides minimum requirements for having confidence in the accuracy of EC50/IC50 estimates. Two definitions of EC50/IC50s are considered: relative and absolute. The relative EC50/IC50 is the parameter c in the 4-parameter logistic model and is the concentration corresponding to a response midway between the estimates of the lower and upper plateaus. The absolute EC50/IC50 is the response corresponding to the 50% control (the mean of the 0% and 100% assay controls). The guidelines first describe how to decide whether to use the relative EC50/IC50 or the absolute EC50/IC50. Assays for which there is no stable 100% control must use the relative EC50/IC50. Assays having a stable 100% control but for which there may be more than 5% error in the estimate of the 50% control mean should use the relative EC50/IC50. Assays that can be demonstrated to produce an accurate and stable 100% control and less than 5% error in the estimate of the 50% control mean may gain efficiency as well as accuracy by using the absolute EC50/IC50. Next, the guidelines provide rules for deciding when the EC50/IC50 estimates are reportable. The relative EC50/IC50 should only be used if there are at least two assay concentrations beyond the lower and upper bend points. The absolute EC50/IC50 should only be used if there are at least two assay concentrations whose predicted response is less than 50% and two whose predicted response is greater than 50%. A wide range of typical assay conditions are considered in the development of the guidelines.
SNPdetector: a software tool for sensitive and accurate SNP detection.
Directory of Open Access Journals (Sweden)
Jinghui Zhang
2005-10-01
Full Text Available Identification of single nucleotide polymorphisms (SNPs and mutations is important for the discovery of genetic predisposition to complex diseases. PCR resequencing is the method of choice for de novo SNP discovery. However, manual curation of putative SNPs has been a major bottleneck in the application of this method to high-throughput screening. Therefore it is critical to develop a more sensitive and accurate computational method for automated SNP detection. We developed a software tool, SNPdetector, for automated identification of SNPs and mutations in fluorescence-based resequencing reads. SNPdetector was designed to model the process of human visual inspection and has a very low false positive and false negative rate. We demonstrate the superior performance of SNPdetector in SNP and mutation analysis by comparing its results with those derived by human inspection, PolyPhred (a popular SNP detection tool, and independent genotype assays in three large-scale investigations. The first study identified and validated inter- and intra-subspecies variations in 4,650 traces of 25 inbred mouse strains that belong to either the Mus musculus species or the M. spretus species. Unexpected heterozygosity in CAST/Ei strain was observed in two out of 1,167 mouse SNPs. The second study identified 11,241 candidate SNPs in five ENCODE regions of the human genome covering 2.5 Mb of genomic sequence. Approximately 50% of the candidate SNPs were selected for experimental genotyping; the validation rate exceeded 95%. The third study detected ENU-induced mutations (at 0.04% allele frequency in 64,896 traces of 1,236 zebra fish. Our analysis of three large and diverse test datasets demonstrated that SNPdetector is an effective tool for genome-scale research and for large-sample clinical studies. SNPdetector runs on Unix/Linux platform and is available publicly (http://lpg.nci.nih.gov.
SNPdetector: A Software Tool for Sensitive and Accurate SNP Detection.
Directory of Open Access Journals (Sweden)
2005-10-01
Full Text Available Identification of single nucleotide polymorphisms (SNPs and mutations is important for the discovery of genetic predisposition to complex diseases. PCR resequencing is the method of choice for de novo SNP discovery. However, manual curation of putative SNPs has been a major bottleneck in the application of this method to high-throughput screening. Therefore it is critical to develop a more sensitive and accurate computational method for automated SNP detection. We developed a software tool, SNPdetector, for automated identification of SNPs and mutations in fluorescence-based resequencing reads. SNPdetector was designed to model the process of human visual inspection and has a very low false positive and false negative rate. We demonstrate the superior performance of SNPdetector in SNP and mutation analysis by comparing its results with those derived by human inspection, PolyPhred (a popular SNP detection tool, and independent genotype assays in three large-scale investigations. The first study identified and validated inter- and intra-subspecies variations in 4,650 traces of 25 inbred mouse strains that belong to either the Mus musculus species or the M. spretus species. Unexpected heterozgyosity in CAST/Ei strain was observed in two out of 1,167 mouse SNPs. The second study identified 11,241 candidate SNPs in five ENCODE regions of the human genome covering 2.5 Mb of genomic sequence. Approximately 50% of the candidate SNPs were selected for experimental genotyping; the validation rate exceeded 95%. The third study detected ENU-induced mutations (at 0.04% allele frequency in 64,896 traces of 1,236 zebra fish. Our analysis of three large and diverse test datasets demonstrated that SNPdetector is an effective tool for genome-scale research and for large-sample clinical studies. SNPdetector runs on Unix/Linux platform and is available publicly (http://lpg.nci.nih.gov.
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.
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.
Towards accurate and precise estimates of lion density.
Elliot, Nicholas B; Gopalaswamy, Arjun M
2016-12-13
Reliable estimates of animal density are fundamental to our understanding of ecological processes and population dynamics. Furthermore, their accuracy is vital to conservation biology since wildlife authorities rely on these figures to make decisions. However, it is notoriously difficult to accurately estimate density for wide-ranging species such as carnivores that occur at low densities. In recent years, significant progress has been made in density estimation of Asian carnivores, but the methods have not been widely adapted to African carnivores. African lions (Panthera leo) provide an excellent example as although abundance indices have been shown to produce poor inferences, they continue to be used to estimate lion density and inform management and policy. In this study we adapt a Bayesian spatially explicit capture-recapture model to estimate lion density in the Maasai Mara National Reserve (MMNR) and surrounding conservancies in Kenya. We utilize sightings data from a three-month survey period to produce statistically rigorous spatial density estimates. Overall posterior mean lion density was estimated to be 16.85 (posterior standard deviation = 1.30) lions over one year of age per 100km(2) with a sex ratio of 2.2♀:1♂. We argue that such methods should be developed, improved and favored over less reliable methods such as track and call-up surveys. We caution against trend analyses based on surveys of differing reliability and call for a unified framework to assess lion numbers across their range in order for better informed management and policy decisions to be made. This article is protected by copyright. All rights reserved.
2014-10-08
models to compute accurately the molecular interactions between a mobile or stationary phase and a target substrate or analyte , which are fundamental...mobile or stationary phase and a target substrate or analyte , which are fundamental to diverse technologies, e.g., sensor or separation design. With...D. G., New Orleans, LA, April 9, 2013. 223rd Electrochemical Society Meeting, Continuum Solvation Models for Computational Electrochemistry
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.
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.
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].
Nonexposure Accurate Location K-Anonymity Algorithm in LBS
Directory of Open Access Journals (Sweden)
Jinying Jia
2014-01-01
Full Text Available This paper tackles location privacy protection in current location-based services (LBS where mobile users have to report their exact location information to an LBS provider in order to obtain their desired services. Location cloaking has been proposed and well studied to protect user privacy. It blurs the user’s accurate coordinate and replaces it with a well-shaped cloaked region. However, to obtain such an anonymous spatial region (ASR, nearly all existent cloaking algorithms require knowing the accurate locations of all users. Therefore, location cloaking without exposing the user’s accurate location to any party is urgently needed. In this paper, we present such two nonexposure accurate location cloaking algorithms. They are designed for K-anonymity, and cloaking is performed based on the identifications (IDs of the grid areas which were reported by all the users, instead of directly on their accurate coordinates. Experimental results show that our algorithms are more secure than the existent cloaking algorithms, need not have all the users reporting their locations all the time, and can generate smaller ASR.
Nonexposure accurate location K-anonymity algorithm in LBS.
Jia, Jinying; Zhang, Fengli
2014-01-01
This paper tackles location privacy protection in current location-based services (LBS) where mobile users have to report their exact location information to an LBS provider in order to obtain their desired services. Location cloaking has been proposed and well studied to protect user privacy. It blurs the user's accurate coordinate and replaces it with a well-shaped cloaked region. However, to obtain such an anonymous spatial region (ASR), nearly all existent cloaking algorithms require knowing the accurate locations of all users. Therefore, location cloaking without exposing the user's accurate location to any party is urgently needed. In this paper, we present such two nonexposure accurate location cloaking algorithms. They are designed for K-anonymity, and cloaking is performed based on the identifications (IDs) of the grid areas which were reported by all the users, instead of directly on their accurate coordinates. Experimental results show that our algorithms are more secure than the existent cloaking algorithms, need not have all the users reporting their locations all the time, and can generate smaller ASR.
Accurate MTF measurement in digital radiography using noise response
Energy Technology Data Exchange (ETDEWEB)
Kuhls-Gilcrist, Andrew; Jain, Amit; Bednarek, Daniel R.; Hoffmann, Kenneth R.; Rudin, Stephen [Toshiba Stroke Research Center, University at Buffalo, State University of New York, Biomedical Research Building, Room 445, 3435 Main Street, Buffalo, New York 14214 (United States)
2010-02-15
Purpose: The authors describe a new technique to determine the system presampled modulation transfer function (MTF) in digital radiography using only the detector noise response. Methods: A cascaded-linear systems analysis was used to develop an exact relationship between the two-dimensional noise power spectrum (NPS) and the presampled MTF for a generalized detector system. This relationship was then utilized to determine the two-dimensional presampled MTF. For simplicity, aliasing of the correlated noise component of the NPS was assumed to be negligible. Accuracy of this method was investigated using simulated images from a simple detector model in which the ''true'' MTF was known exactly. Measurements were also performed on three detector technologies (an x-ray image intensifier, an indirect flat panel detector, and a solid state x-ray image intensifier), and the results were compared using the standard edge-response method. Flat-field and edge images were acquired and analyzed according to guidelines set forth by the International Electrotechnical Commission, using the RQA 5 spectrum. Results: The presampled MTF determined using the noise-response method for the simulated detector system was in close agreement with the true MTF with an averaged percent difference of 0.3% and a maximum difference of 1.1% observed at the Nyquist frequency (f{sub N}). The edge-response method of the simulated detector system also showed very good agreement at lower spatial frequencies (less than 0.5 f{sub N}) with an averaged percent difference of 1.6% but showed significant discrepancies at higher spatial frequencies (greater than 0.5 f{sub N}) with an averaged percent difference of 17%. Discrepancies were in part a result of noise in the edge image and phasing errors. For all three detector systems, the MTFs obtained using the two methods were found to be in good agreement at spatial frequencies less than 0.5 f{sub N} with an averaged percent difference of 3
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...
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.
Accurate nuclear radii and binding energies from a chiral interaction
Ekstrom, A; Wendt, K A; Hagen, G; Papenbrock, T; Carlsson, B D; Forssen, C; Hjorth-Jensen, M; Navratil, P; Nazarewicz, W
2015-01-01
The accurate reproduction of nuclear radii and binding energies is a long-standing challenge in nuclear theory. To address this problem two-nucleon and three-nucleon forces from chiral effective field theory are optimized simultaneously to low-energy nucleon-nucleon scattering data, as well as binding energies and radii of few-nucleon systems and selected isotopes of carbon and oxygen. Coupled-cluster calculations based on this interaction, named NNLOsat, yield accurate binding energies and radii of nuclei up to 40Ca, and are consistent with the empirical saturation point of symmetric nuclear matter. In addition, the low-lying collective 3- states in 16O and 40Ca are described accurately, while spectra for selected p- and sd-shell nuclei are in reasonable agreement with experiment.
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.
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
Accurate torque-speed performance prediction for brushless dc motors
Gipper, Patrick D.
Desirable characteristics of the brushless dc motor (BLDCM) have resulted in their application for electrohydrostatic (EH) and electromechanical (EM) actuation systems. But to effectively apply the BLDCM requires accurate prediction of performance. The minimum necessary performance characteristics are motor torque versus speed, peak and average supply current and efficiency. BLDCM nonlinear simulation software specifically adapted for torque-speed prediction is presented. The capability of the software to quickly and accurately predict performance has been verified on fractional to integral HP motor sizes, and is presented. Additionally, the capability of torque-speed prediction with commutation angle advance is demonstrated.
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.
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 variation of permittivity due to small thicknesses. Even if complex, such strategy gives accurate results and we believe that, after more refinement, can be used to completely calculate a complex metallic structure placed on a substrate in a far faster manner than full simulations programs do....
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.