Wang, Zhiheng
2015-01-01
A simple multidomain Chebyshev pseudo-spectral method is developed for two-dimensional fluid flow and heat transfer over square cylinders. The incompressible Navier-Stokes equations with primitive variables are discretized in several subdomains of the computational domain. The velocities and pressure are discretized with the same order of Chebyshev polynomials, i.e., the PN-PN method. The Projection method is applied in coupling the pressure with the velocity. The present method is first validated by benchmark problems of natural convection in a square cavity. Then the method based on multidomains is applied to simulate fluid flow and heat transfer from square cylinders. The numerical results agree well with the existing results. © Taylor & Francis Group, LLC.
Pseudo spectral collocation with Maxwell polynomials for kinetic equations with energy diffusion
Sánchez-Vizuet, Tonatiuh; Cerfon, Antoine J.
2018-02-01
We study the approximation and stability properties of a recently popularized discretization strategy for the speed variable in kinetic equations, based on pseudo-spectral collocation on a grid defined by the zeros of a non-standard family of orthogonal polynomials called Maxwell polynomials. Taking a one-dimensional equation describing energy diffusion due to Fokker–Planck collisions with a Maxwell–Boltzmann background distribution as the test bench for the performance of the scheme, we find that Maxwell based discretizations outperform other commonly used schemes in most situations, often by orders of magnitude. This provides a strong motivation for their use in high-dimensional gyrokinetic simulations. However, we also show that Maxwell based schemes are subject to a non-modal time stepping instability in their most straightforward implementation, so that special care must be given to the discrete representation of the linear operators in order to benefit from the advantages provided by Maxwell polynomials.
Modified Chebyshev Collocation Method for Solving Differential Equations
Directory of Open Access Journals (Sweden)
M Ziaul Arif
2015-05-01
Full Text Available This paper presents derivation of alternative numerical scheme for solving differential equations, which is modified Chebyshev (Vieta-Lucas Polynomial collocation differentiation matrices. The Scheme of modified Chebyshev (Vieta-Lucas Polynomial collocation method is applied to both Ordinary Differential Equations (ODEs and Partial Differential Equations (PDEs cases. Finally, the performance of the proposed method is compared with finite difference method and the exact solution of the example. It is shown that modified Chebyshev collocation method more effective and accurate than FDM for some example given.
Dijkstra, D.
2002-01-01
In the conventional pseudo-spectral collocation method to solve an ordinary first order differential equation, the derivative is obtained from Lagrange interpolation and has degree of precision N for a grid of (N+1) points. In the present, novel method Hermite interpolation is used as point of
Li, Guo-jun; Wei, Lin-Yang
2018-01-01
Chebyshev collocation spectral method based on discrete ordinates equation is employed to solve radiative heat transfer problems in participating media with variable physical prosperities (including space-dependent or temperature-dependent refractive index, absorption coefficient and scattering coefficient). Discrete ordinates method is employed to discretize the solid angle domain. Chebyshev polynomial and collocation spectral method are adopted to express and discretize space domain, respectively. Numerical results obtained by the Chebyshev collocation spectral-discrete ordinates method (CCS-DOM) are presented in this paper and the results show the CCS-DOM has a good accuracy and efficiency for radiative heat transfer problems in participating media. At last, the effects of variable physical properties on radiative heat transfer are analyzed and it can be found that the distributions of refractive index, absorption coefficient and scattering coefficient have a significant effect on radiative transfer and energy distribution.
Mason, JC
2002-01-01
Chebyshev polynomials crop up in virtually every area of numerical analysis, and they hold particular importance in recent advances in subjects such as orthogonal polynomials, polynomial approximation, numerical integration, and spectral methods. Yet no book dedicated to Chebyshev polynomials has been published since 1990, and even that work focused primarily on the theoretical aspects. A broad, up-to-date treatment is long overdue.Providing highly readable exposition on the subject''s state of the art, Chebyshev Polynomials is just such a treatment. It includes rigorous yet down-to-earth coverage of the theory along with an in-depth look at the properties of all four kinds of Chebyshev polynomials-properties that lead to a range of results in areas such as approximation, series expansions, interpolation, quadrature, and integral equations. Problems in each chapter, ranging in difficulty from elementary to quite advanced, reinforce the concepts and methods presented.Far from being an esoteric subject, Chebysh...
DEFF Research Database (Denmark)
Tong, M.S.; Lu, Y.; Chen, Y.
2005-01-01
A planar stratified dielectric slab medium, which is an interesting problem in optics and geophysics, is studied using a pseudo-spectral time-domain (PSTD) algorithm. Time domain electric fields and frequency domain propagation characteristics of both single and periodic dielectric slab...
Zou, Peng
2017-05-10
Staggering grid is a very effective way to reduce the Nyquist errors and to suppress the non-causal ringing artefacts in the pseudo-spectral solution of first-order elastic wave equations. However, the straightforward use of a staggered-grid pseudo-spectral method is problematic for simulating wave propagation when the anisotropy level is greater than orthorhombic or when the anisotropic symmetries are not aligned with the computational grids. Inspired by the idea of rotated staggered-grid finite-difference method, we propose a modified pseudo-spectral method for wave propagation in arbitrary anisotropic media. Compared with an existing remedy of staggered-grid pseudo-spectral method based on stiffness matrix decomposition and a possible alternative using the Lebedev grids, the rotated staggered-grid-based pseudo-spectral method possesses the best balance between the mitigation of artefacts and efficiency. A 2D example on a transversely isotropic model with tilted symmetry axis verifies its effectiveness to suppress the ringing artefacts. Two 3D examples of increasing anisotropy levels demonstrate that the rotated staggered-grid-based pseudo-spectral method can successfully simulate complex wavefields in such anisotropic formations.
A Chebyshev matrix method for spatial modes of the Orr-Sommerfeld equation
Danabasoglu, G.; Biringen, S.
1989-01-01
The Chebyshev matrix collocation method is applied to obtain the spatial modes of the Orr-Sommerfeld equation for Poiseuille flow and the Blausius boundary layer. The problem is linearized by the companion matrix technique for semi-infinite domain using a mapping transformation. The method can be easily adapted to problems with different boundary conditions requiring different transformations.
A Chebyshev matrix method for the spatial modes of the Orr-Sommerfeld equation
Danabasoglu, Gokhan; Biringen, Sedat
1990-01-01
The Chebyshev matrix collocation method is applied to obtain the spatial modes of the Orr-Sommerfeld equation for Poiseuille flow and the Blasius boundary layer. The problems is linearized by the companion matrix technique for semiinfinite domain using a mapping transformation. The method can be easily adapted to problems with different boundary conditions requiring different transformations.
Rapid expansion and pseudo spectral implementation for reverse time migration in VTI media
Pestana, Reynam C
2012-04-24
In isotropic media, we use the scalar acoustic wave equation to perform reverse time migration (RTM) of the recorded pressure wavefield data. In anisotropic media, P- and SV-waves are coupled, and the elastic wave equation should be used for RTM. For computational efficiency, a pseudo-acoustic wave equation is often used. This may be solved using a coupled system of second-order partial differential equations. We solve these using a pseudo spectral method and the rapid expansion method (REM) for the explicit time marching. This method generates a degenerate SV-wave in addition to the P-wave arrivals of interest. To avoid this problem, the elastic wave equation for vertical transversely isotropic (VTI) media can be split into separate wave equations for P- and SV-waves. These separate wave equations are stable, and they can be effectively used to model and migrate seismic data in VTI media where |ε- δ| is small. The artifact for the SV-wave has also been removed. The independent pseudo-differential wave equations can be solved one for each mode using the pseudo spectral method for the spatial derivatives and the REM for the explicit time advance of the wavefield. We show numerically stable and high-resolution modeling and RTM results for the pure P-wave mode in VTI media. © 2012 Sinopec Geophysical Research Institute.
DEFF Research Database (Denmark)
Revier, Robert Lee; Henriksen, Birgit
2006-01-01
Very little pedadagoy has been made available to teachers interested in teaching collocations in foreign and/or second language classroom. This paper aims to contribute to and promote efforts in developing L2-based pedagogy for the teaching of phraseology. To this end, it presents pedagogical...... insight obtained from a cross-sectional study of Danish EFL learners' knowledge and use of collocations in their written L2 and L1 production....
Perturbed segmented domain collocation Tau-method for the ...
African Journals Online (AJOL)
This paper concerns the numerical solution of second order boundary value problems using a Perturbed segmented domain collocation-Tau method. The entire interval for which the problem is defined is partitioned into two segments and the solution technique is demonstrated on each of the segments. The Chebyshev ...
Development and Validation of A 3d Staggered Fourier Pseudo-spectral Method For Wave Modeling
Seriani, G.; Vuan, A.; Priolo, E.; Carcione, J.
We have developed and implemented an algorithm for the 3D forward modeling of seismic wave-fields in complex geological structures. The algorithm is based on the solution of the elastic full wave equation in heterogeneous media using the Fourier pseudo-spectral method. Numerical accuracy and computational efficiency have been improved using a staggered scheme and parallel implementation, respectively. The parallel code can handle both SHMEM and MPI libraries which allow to perform the computations whether using a single massive parallel computer or distributed PC- clusters. The wave equation is written in a displacement-velocity-stress formulation using the equation of conservation of momentum, and the stress-strain relations for an isotropic elastic medium undergoing infinitesimal deformation. In the time domain, the system of partial differential equations is integrated through a leap-frog finite dif- ference discrete scheme. Spatial derivatives are computed globally by using the FFT. Attenuation is accommodated at each time step by multiplying the stress and velocity field by the attenuation factor. The presence of a free surface is obtained by FFT zero- padding. Wave reflections from the model edges are removed by applying absorbing strips. A generalized moment-tensor source formulation is used to represent source mechanisms. The 3-D staggered Fourier pseudo-spectral method is validated with both analytical and numerical solutions. In particular, we have used as reference solutions the full wave-field in homogeneous and layered media computed by the Cagniard-de Hoop technique and the wave-number integration method, respectively. The compari- son showed that the time histories are in good agreement with the reference solutions. Moreover, because of the staggered approach, the three components of the wave-field are defined on dual meshes displaced by a half grid-step. Therefore three components records are recovered by a fast interpolation.
Efficient modified Chebyshev differentiation matrices for fractional differential equations
Dabiri, Arman; Butcher, Eric A.
2017-09-01
This paper compares several fractional operational matrices for solving a system of linear fractional differential equations (FDEs) of commensurate or incommensurate order. For this purpose, three fractional collocation differentiation matrices (FCDMs) based on finite differences are first proposed and compared with Podlubny's matrix previously used in the literature, after which two new efficient FCDMs based on Chebyshev collocation are proposed. It is shown via an error analysis that the use of the well-known property of fractional differentiation of polynomial bases applied to these methods results in a limitation in the size of the obtained Chebyshev-based FCDMs. To compensate for this limitation, a new fast spectrally accurate FCDM for fractional differentiation which does not require the use of the gamma function is proposed. Then, the Schur-Pade and Schur decomposition methods are implemented to enhance and improve numerical stability. Therefore, this method overcomes the previous limitation regarding the size limitation. In several illustrative examples, the convergence and computation time of the proposed FCDMs are compared and their advantages and disadvantages are outlined.
Seismic waves modeling with the Fourier pseudo-spectral method on massively parallel machines.
Klin, Peter
2015-04-01
The Fourier pseudo-spectral method (FPSM) is an approach for the 3D numerical modeling of the wave propagation, which is based on the discretization of the spatial domain in a structured grid and relies on global spatial differential operators for the solution of the wave equation. This last peculiarity is advantageous from the accuracy point of view but poses difficulties for an efficient implementation of the method to be run on parallel computers with distributed memory architecture. The 1D spatial domain decomposition approach has been so far commonly adopted in the parallel implementations of the FPSM, but it implies an intensive data exchange among all the processors involved in the computation, which can degrade the performance because of communication latencies. Moreover, the scalability of the 1D domain decomposition is limited, since the number of processors can not exceed the number of grid points along the directions in which the domain is partitioned. This limitation inhibits an efficient exploitation of the computational environments with a very large number of processors. In order to overcome the limitations of the 1D domain decomposition we implemented a parallel version of the FPSM based on a 2D domain decomposition, which allows to achieve a higher degree of parallelism and scalability on massively parallel machines with several thousands of processing elements. The parallel programming is essentially achieved using the MPI protocol but OpenMP parts are also included in order to exploit the single processor multi - threading capabilities, when available. The developed tool is aimed at the numerical simulation of the seismic waves propagation and in particular is intended for earthquake ground motion research. We show the scalability tests performed up to 16k processing elements on the IBM Blue Gene/Q computer at CINECA (Italy), as well as the application to the simulation of the earthquake ground motion in the alluvial plain of the Po river (Italy).
Sparse Pseudo Spectral Projection Methods with Directional Adaptation for Uncertainty Quantification
Winokur, J.
2015-12-19
We investigate two methods to build a polynomial approximation of a model output depending on some parameters. The two approaches are based on pseudo-spectral projection (PSP) methods on adaptively constructed sparse grids, and aim at providing a finer control of the resolution along two distinct subsets of model parameters. The control of the error along different subsets of parameters may be needed for instance in the case of a model depending on uncertain parameters and deterministic design variables. We first consider a nested approach where an independent adaptive sparse grid PSP is performed along the first set of directions only, and at each point a sparse grid is constructed adaptively in the second set of directions. We then consider the application of aPSP in the space of all parameters, and introduce directional refinement criteria to provide a tighter control of the projection error along individual dimensions. Specifically, we use a Sobol decomposition of the projection surpluses to tune the sparse grid adaptation. The behavior and performance of the two approaches are compared for a simple two-dimensional test problem and for a shock-tube ignition model involving 22 uncertain parameters and 3 design parameters. The numerical experiments indicate that whereas both methods provide effective means for tuning the quality of the representation along distinct subsets of parameters, PSP in the global parameter space generally requires fewer model evaluations than the nested approach to achieve similar projection error. In addition, the global approach is better suited for generalization to more than two subsets of directions.
Directory of Open Access Journals (Sweden)
P. Di Maida
2016-01-01
Full Text Available A pseudo-spectral approximation is presented to solve the problem of pull-in instability in a cantilever micro-switch. As well known, pull-in instability arises when the acting force reaches a critical threshold beyond which equilibrium is no longer possible. In particular, Coulomb electrostatic force is considered, although the method can be easily generalized to account for fringe as well as Casimir effects. A numerical comparison is presented between a pseudo-spectral and a Finite Element (FE approximation of the problem, both methods employing the same number of degrees of freedom. It is shown that the pseudo-spectral method appears more effective in accurately approximating the behavior of the cantilever near its tip. This fact is crucial to capturing the threshold voltage on the verge of pull-in. Conversely, the FE approximation presents rapid successions of attracting/repulsing regions along the cantilever, which are not restricted to the near pull-in regime.
Chebyshev and Fourier spectral methods
Boyd, John P
2001-01-01
Completely revised text focuses on use of spectral methods to solve boundary value, eigenvalue, and time-dependent problems, but also covers Hermite, Laguerre, rational Chebyshev, sinc, and spherical harmonic functions, as well as cardinal functions, linear eigenvalue problems, matrix-solving methods, coordinate transformations, methods for unbounded intervals, spherical and cylindrical geometry, and much more. 7 Appendices. Glossary. Bibliography. Index. Over 160 text figures.
Directory of Open Access Journals (Sweden)
A. H. Bhrawy
2013-01-01
Full Text Available We extend the application of the Galerkin method for treating the multiterm fractional differential equations (FDEs subject to initial conditions. A new shifted Legendre-Galerkin basis is constructed which satisfies exactly the homogeneous initial conditions by expanding the unknown variable using a new polynomial basis of functions which is built upon the shifted Legendre polynomials. A new spectral collocation approximation based on the Gauss-Lobatto quadrature nodes of shifted Legendre polynomials is investigated for solving the nonlinear multiterm FDEs. The main advantage of this approximation is that the solution is expanding by a truncated series of Legendre-Galerkin basis functions. Illustrative examples are presented to ensure the high accuracy and effectiveness of the proposed algorithms are discussed.
Hershkovitz, Yaron; Anker, Yaakov; Ben-Dor, Eyal; Schwartz, Guy; Gasith, Avital
2010-05-01
In-stream vegetation is a key ecosystem component in many fluvial ecosystems, having cascading effects on stream conditions and biotic structure. Traditionally, ground-level surveys (e.g. grid and transect analyses) are commonly used for estimating cover of aquatic macrophytes. Nonetheless, this methodological approach is highly time consuming and usually yields information which is practically limited to habitat and sub-reach scales. In contrast, remote-sensing techniques (e.g. satellite imagery and airborne photography), enable collection of large datasets over section, stream and basin scales, in relatively short time and reasonable cost. However, the commonly used spatial high resolution (1m) is often inadequate for examining aquatic vegetation on habitat or sub-reach scales. We examined the utility of a pseudo-spectral methodology, using RGB digital photography for estimating the cover of in-stream vegetation in a small Mediterranean-climate stream. We compared this methodology with that obtained by traditional ground-level grid methodology and with an airborne hyper-spectral remote sensing survey (AISA-ES). The study was conducted along a 2 km section of an intermittent stream (Taninim stream, Israel). When studied, the stream was dominated by patches of watercress (Nasturtium officinale) and mats of filamentous algae (Cladophora glomerata). The extent of vegetation cover at the habitat and section scales (100 and 104 m, respectively) were estimated by the pseudo-spectral methodology, using an airborne Roli camera with a Phase-One P 45 (39 MP) CCD image acquisition unit. The swaths were taken in elevation of about 460 m having a spatial resolution of about 4 cm (NADIR). For measuring vegetation cover at the section scale (104 m) we also used a 'push-broom' AISA-ES hyper-spectral swath having a sensor configuration of 182 bands (350-2500 nm) at elevation of ca. 1,200 m (i.e. spatial resolution of ca. 1 m). Simultaneously, with every swath we used an Analytical
A fast Chebyshev method for simulating flexible-wing propulsion
Moore, M. Nicholas J.
2017-09-01
We develop a highly efficient numerical method to simulate small-amplitude flapping propulsion by a flexible wing in a nearly inviscid fluid. We allow the wing's elastic modulus and mass density to vary arbitrarily, with an eye towards optimizing these distributions for propulsive performance. The method to determine the wing kinematics is based on Chebyshev collocation of the 1D beam equation as coupled to the surrounding 2D fluid flow. Through small-amplitude analysis of the Euler equations (with trailing-edge vortex shedding), the complete hydrodynamics can be represented by a nonlocal operator that acts on the 1D wing kinematics. A class of semi-analytical solutions permits fast evaluation of this operator with O (Nlog N) operations, where N is the number of collocation points on the wing. This is in contrast to the minimum O (N2) cost of a direct 2D fluid solver. The coupled wing-fluid problem is thus recast as a PDE with nonlocal operator, which we solve using a preconditioned iterative method. These techniques yield a solver of near-optimal complexity, O (Nlog N) , allowing one to rapidly search the infinite-dimensional parameter space of all possible material distributions and even perform optimization over this space.
Directory of Open Access Journals (Sweden)
Yu-Ju Wang
2016-02-01
Full Text Available Ground motions from normal-faulting earthquakes are generally considered to be smaller than those of strike-slip and thrust events. On 11 April 2011 a crustal normal-faulting earthquake [the Fukushima earthquake (Mw 6.6] occurred in Eastern Japan. The peak ground acceleration (PGA observed was considerably higher than the predictions of several ground-motion prediction equations (GMPEs, which were derived mainly from thrust or strike-slip earthquakes. In northeast Taiwan, the tectonic structure of the Ryukyu Arc and the Okinawa Trough typically entail normal-faulting earthquakes. Because of the normal-faulting earthquakes relevance to ground motions and nuclear power plant sites in northeast Taiwan, we evaluated the impact of the ground motion of normal-faulting earthquakes in offshore northeast Taiwan using a newly constructed attenuation relationship for PGA and pseudo-spectral acceleration (Sa. We collected 832 records from 13 normal-faulting earthquakes with focal depths of less than 50 km. The moment magnitude (Mw of the 13 events was between 4 - 6. The Sa and PGA of normal-faulting earthquakes offshore northeast Taiwan determined with the newly constructed attenuation relationship were higher and lower, respectively, than those obtained using attenuation equations commonly used in the Taiwan subduction zone.
Collocations in Business English
Directory of Open Access Journals (Sweden)
Matjaž Martič
2009-12-01
Full Text Available The article starts with a brief theoretical overview that defines the term ‚collocation.‛ It then presents a corpus study designed to determine the most frequent lexical collocations in Business English using the concordance program WordSmith Tools. This study is based on the assumption that English mainly consists of various (changeable phraseological units and that both free combinations as well as completely ‚frozen‛ word combinations account for only a small share of the language. English is therefore a language of collocations and one can assume that this is valid not only for general English, but also for ESP and thus for Business English as well. In addition, the study investigated whether the most frequent collocations in this corpus could be found in major dictionaries of collocations, which would then establish their suitability for Business English purposes.
Stochastic dynamic models and Chebyshev splines
Fan, Ruzong; Zhu, Bin; Wang, Yuedong
2015-01-01
In this article, we establish a connection between a stochastic dynamic model (SDM) driven by a linear stochastic differential equation (SDE) and a Chebyshev spline, which enables researchers to borrow strength across fields both theoretically and numerically. We construct a differential operator for the penalty function and develop a reproducing kernel Hilbert space (RKHS) induced by the SDM and the Chebyshev spline. The general form of the linear SDE allows us to extend the well-known connection between an integrated Brownian motion and a polynomial spline to a connection between more complex diffusion processes and Chebyshev splines. One interesting special case is connection between an integrated Ornstein–Uhlenbeck process and an exponential spline. We use two real data sets to illustrate the integrated Ornstein–Uhlenbeck process model and exponential spline model and show their estimates are almost identical. PMID:26045632
Solutions of First-Order Volterra Type Linear Integrodifferential Equations by Collocation Method
Directory of Open Access Journals (Sweden)
Olumuyiwa A. Agbolade
2017-01-01
Full Text Available The numerical solutions of linear integrodifferential equations of Volterra type have been considered. Power series is used as the basis polynomial to approximate the solution of the problem. Furthermore, standard and Chebyshev-Gauss-Lobatto collocation points were, respectively, chosen to collocate the approximate solution. Numerical experiments are performed on some sample problems already solved by homotopy analysis method and finite difference methods. Comparison of the absolute error is obtained from the present method and those from aforementioned methods. It is also observed that the absolute errors obtained are very low establishing convergence and computational efficiency.
Superiority of legendre polynomials to Chebyshev polynomial in ...
African Journals Online (AJOL)
In this paper, we proved the superiority of Legendre polynomial to Chebyshev polynomial in solving first order ordinary differential equation with rational coefficient. We generated shifted polynomial of Chebyshev, Legendre and Canonical polynomials which deal with solving differential equation by first choosing Chebyshev ...
Proxemic Mobile Collocated Interactions
DEFF Research Database (Denmark)
Porcheron, Martin; Lucero, Andrés; Quigley, Aaron
2016-01-01
Recent research on mobile collocated interactions has been looking at situations in which collocated users engage in collaborative activities using their mobile devices. However, existing practices fail to fully account for the culturally-dependent spatial relationships between people and their d......Recent research on mobile collocated interactions has been looking at situations in which collocated users engage in collaborative activities using their mobile devices. However, existing practices fail to fully account for the culturally-dependent spatial relationships between people...... would allow devices to not only react to presence and interaction, but also other indicators, such as the interpersonal distance people naturally use in everyday life. The aim of this one-day workshop is to bring together a community of researchers, designers and practitioners who are interested...
Mobile Collocated Interactions
DEFF Research Database (Denmark)
Lucero, Andrés; Clawson, James; Lyons, Kent
2015-01-01
Mobile devices such as smartphones and tablets were originally conceived and have traditionally been utilized for individual use. Research on mobile collocated interactions has been looking at situations in which collocated users engage in collaborative activities using their mobile devices, thus...... going from personal/individual toward shared/multiuser experiences and interactions. However, computers are getting smaller, more powerful, and closer to our bodies. Therefore, mobile collocated interactions research, which originally looked at smartphones and tablets, will inevitably include ever......-smaller computers, ones that can be worn on our wrists or other parts of the body. The focus of this workshop is to bring together a community of researchers, designers and practitioners to explore the potential of extending mobile collocated interactions to the use of wearable devices....
Geostationary satellites collocation
Li, Hengnian
2014-01-01
Geostationary Satellites Collocation aims to find solutions for deploying a safe and reliable collocation control. Focusing on the orbital perturbation analysis, the mathematical foundations for orbit and control of the geostationary satellite are summarized. The mathematical and physical principle of orbital maneuver and collocation strategies for multi geostationary satellites sharing with the same dead band is also stressed. Moreover, the book presents some applications using the above algorithms and mathematical models to help readers master the corrective method for planning station keeping maneuvers. Engineers and scientists in the fields of aerospace technology and space science can benefit from this book. Hengnian Li is the Deputy Director of State Key Laboratory of Astronautic Dynamics, China.
Collocations in Marine Engineering English
Directory of Open Access Journals (Sweden)
Mirjana Borucinsky
2016-05-01
Full Text Available Collocations are very frequent in the English language (Hill, 2000, and they are probably the most common and most representative of English multi-word expressions (Lewis, 2000. Furthermore, as a subset of formulaic sequences, collocations are considered to be a central aspect of communicative competence (Nation, 2001. Hence, the importance of teaching collocations in General English (GE as well as in English for Specific Purposes (ESP is undeniable. Understanding and determining the relevant collocations and their mastery are of “utmost importance to a ME instructor” (Cole et al., 2007, p. 137, and collocations are one of the most productive ways of enriching vocabulary and terminology in modern ME. Vişan & Georgescu (2011 have undertaken a relevant study on collocations and “collocational competence” on board ships, including mostly nautical terminology. However, no substantial work on collocations in Marine Engineering English as a sub-register of ME has been carried out. Hence, this paper tries to determine the most important collocations in Marine Engineering English, based on a small corpus of collected e-mails. After determining the most relevant collocations, we suggest how to implement these in the language classroom and how to improve the collocational competence of marine engineering students.
DEFF Research Database (Denmark)
Nielsen, S.A.; Hesthaven, J.S.
2002-01-01
elastodynamic formulation, giving a direct solution of the time-domain elastodynamic equations. A typical calculation is performed by decomposing the global computational domain into a number of subdomains. Every subdomain is then mapped on a unit square using transfinite blending functions and spatial...
Chebyshev collocation approach to stability of blood flows in a large ...
African Journals Online (AJOL)
In this study, treating the large artery as a rigid channel with uniform width and the blood as an incompressible Newtonian fluid with variable viscosity due to transverse variation in hematocrit ratio, the basic flow structure and its temporal stability to small disturbances were studied. A fourth-order Eigenvalues problem which ...
Mobile Collocated Interactions With Wearables
DEFF Research Database (Denmark)
Lucero, Andrés; Wilde, Danielle; Robinson, Simon
2015-01-01
Research on mobile collocated interactions has been looking at situations in which collocated users engage in collaborative activities using their mobile devices, thus going from personal/individual toward shared/multiuser experiences and interactions. However, computers are getting smaller, more...... powerful, and closer to our bodies. Therefore, mobile collocated interactions research, which originally looked at smartphones and tablets, will inevitably move towards fully integrated wearable technologies. The focus of this workshop is to bring together a community of researchers, designers...... and practitioners to explore the potential of extending mobile collocated interactions from, through and around the body using wearable technologies....
Application of spectral collocation techniques to the stability of swirling flows
Khorrami, Mehdi R.; Ash, Robert L.; Malik, Mujeeb R.
1989-01-01
The linearized stability equations in cylindrical coordinates of a Chebyshev spectral collocation method for the temporal and spatial stability of swirling flows are presently solved with the eigenvalues obtained through the use of the QZ routine. The algorithm thus created is robust and easily adaptable to a range of flow configurations encompassing internal and external flows with minor boundary condition application modifications. Accuracy and efficiency tests of the method are made for the cases of plane Poiseulle, rotating-pipe, and trailing line vortex flows.
Modelling and Simulation of a Packed Bed of Pulp Fibers Using Mixed Collocation Method
Directory of Open Access Journals (Sweden)
Ishfaq Ahmad Ganaie
2013-01-01
Full Text Available A convenient computational approach for solving mathematical model related to diffusion dispersion during flow through packed bed is presented. The algorithm is based on the mixed collocation method. The method is particularly useful for solving stiff system arising in chemical and process engineering. The convergence of the method is found to be of order 2 using the roots of shifted Chebyshev polynomial. Model is verified using the literature data. This method has provided a convenient check on the accuracy of the results for wide range of parameters, namely, Peclet numbers. Breakthrough curves are plotted to check the effect of Peclet number on average and exit solute concentrations.
Collocations and collocation types in ESP textbooks: Quantitative pedagogical analysis
Directory of Open Access Journals (Sweden)
Bogdanović Vesna Ž.
2016-01-01
Full Text Available The term collocation, even though it is rather common in the English language grammar, it is not a well known or commonly used term in the textbooks and scientific papers written in the Serbian language. Collocating is usually defined as a natural appearance of two (or more words, which are usually one next to another even though they can be separated in the text, while collocations are defined as words with natural semantic and/or syntactic relations being joined together in a sentence. Collocations are naturally used in all English written texts, including scientific texts and papers. Using two textbooks for English for Specific Purposes (ESP for intermediate students' courses, this paper presents the frequency of collocations and their typology. The paper tries to investigate the relationship between lexical and grammatical collocations written in the ESP texts and the reasons for their presence. There is an overview of the most used subtypes of lexical collocations as well. Furthermore, on applying the basic corpus analysis based on the quantitative analysis, the paper presents the number of open, restricted and bound collocations in ESP texts, trying to draw conclusions on their frequency and hence the modes for their learning. There is also a section related to the number and usage of scientific collocations, both common scientific and narrow-professional ones. The conclusion is that the number of present collocations in the selected two textbooks imposes a demand for further analysis of these lexical connections, as well as new modes for their teaching and presentations to the English learning students.
Collocation Impact on Team Effectiveness
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M Eccles
2010-11-01
Full Text Available The collocation of software development teams is common, specially in agile software development environments. However little is known about the impact of collocation on the team’s effectiveness. This paper explores the impact of collocating agile software development teams on a number of team effectiveness factors. The study focused on South African software development teams and gathered data through the use of questionnaires and interviews. The key finding was that collocation has a positive impact on a number of team effectiveness factors which can be categorised under team composition, team support, team management and structure and team communication. Some of the negative impact collocation had on team effectiveness relate to the fact that team members perceived that less emphasis was placed on roles, that morale of the group was influenced by individuals, and that collocation was invasive, reduced level of privacy and increased frequency of interruptions. Overall through it is proposed that companies should consider collocating their agile software development teams, as collocation might leverage overall team effectiveness.
Chebyshev recursion methods: Kernel polynomials and maximum entropy
Energy Technology Data Exchange (ETDEWEB)
Silver, R.N.; Roeder, H.; Voter, A.F.; Kress, J.D. [Los Alamos National Lab., NM (United States). Theoretical Div.
1995-10-01
The authors describe two Chebyshev recursion methods for calculations with very large sparse Hamiltonians, the kernel polynomial method (KPM) and the maximum entropy method (MEM). They are especially applicable to physical properties involving large numbers of eigenstates, which include densities of states, spectral functions, thermodynamics, total energies, as well as forces for molecular dynamics and Monte Carlo simulations. The authors apply Chebyshev methods to the electronic structure of Si, the thermodynamics of Heisenberg antiferromagnets, and a polaron problem.
On the Connection Coefficients of the Chebyshev-Boubaker Polynomials
Directory of Open Access Journals (Sweden)
Paul Barry
2013-01-01
Full Text Available The Chebyshev-Boubaker polynomials are the orthogonal polynomials whose coefficient arrays are defined by ordinary Riordan arrays. Examples include the Chebyshev polynomials of the second kind and the Boubaker polynomials. We study the connection coefficients of this class of orthogonal polynomials, indicating how Riordan array techniques can lead to closed-form expressions for these connection coefficients as well as recurrence relations that define them.
Rectangular spectral collocation
Driscoll, Tobin A.
2015-02-06
Boundary conditions in spectral collocation methods are typically imposed by removing some rows of the discretized differential operator and replacing them with others that enforce the required conditions at the boundary. A new approach based upon resampling differentiated polynomials into a lower-degree subspace makes differentiation matrices, and operators built from them, rectangular without any row deletions. Then, boundary and interface conditions can be adjoined to yield a square system. The resulting method is both flexible and robust, and avoids ambiguities that arise when applying the classical row deletion method outside of two-point scalar boundary-value problems. The new method is the basis for ordinary differential equation solutions in Chebfun software, and is demonstrated for a variety of boundary-value, eigenvalue and time-dependent problems.
Picard Iteration, Chebyshev Polynomials and Chebyshev-Picard Methods: Application in Astrodynamics
Junkins, John L.; Bani Younes, Ahmad; Woollands, Robyn M.; Bai, Xiaoli
2013-12-01
This paper extends previous work on parallel-structured Modified Chebyshev Picard Iteration (MCPI) Methods. The MCPI approach iteratively refines path approximation of the state trajectory for smooth nonlinear dynamical systems and this paper shows that the approach is especially suitable for initial value problems of astrodynamics. Using Chebyshev polynomials, as the orthogonal approximation basis, it is straightforward to distribute the computation of force functions needed in MCPI to generate the polynomial coefficients (approximating the path iterations) to different processors. Combining Chebyshev polynomials with Picard iteration, MCPI methods iteratively refines path estimates over large time intervals chosen to be within the domain of convergence of Picard iteration. The developed vector-matrix form makes MCPI methods computationally efficient and a more systematic approach is given, leading to a modest correction to results in the published dissertation by Bai. The power of MCPI methods for solving IVPs is clearly illustrated using a simple nonlinear differential equation with a known analytical solution. Compared with the most common integration scheme, the standard Runge-Kutta 4-5 method as implemented in MATLAB, MCPI methods generate solutions with better accuracy as well as orders of magnitude speedups, on a serial machine. MCPI performance is also compared to state of the art integrators such as the Runge-Kutta Nystrom 12(10) methods applied to the relevant orbit mechanics problems. The MCPI method is shown to be well-suited to solving these problems in serial processors with over an order of magnitude speedup relative to known methods. Furthermore, the approach is parallel-structured so that it is suited for parallel implementation and further speedups. When used in conjunction with the recently developed local gravity approximations in conjunction with parallel computation, we anticipate MCPI will enable revolutionary speedups while ensuring
"Minimum input, maximum output, indeed!" Teaching Collocations ...
African Journals Online (AJOL)
Fifty-nine EFL college students participated in the study, and they received two 75-minute instructions between pre- and post-tests: one on the definition of ... Keywords: Collocation, Collocation Dictionary, Dictionary Skills, Efl Writing, L2 Writing, Collocation Errors, L1 Interference, Collocational Competence, Learner ...
Directory of Open Access Journals (Sweden)
Xiaojia Xiang
2015-01-01
Full Text Available The collocation method is extended to the special orthogonal group SO(3 with application to optimal attitude control (OAC of a rigid body. A left-invariant rigid-body attitude dynamical model on SO(3 is established. For the left invariance of the attitude configuration equation in body-fixed frame, a geometrically exact numerical method on SO(3, referred to as the geometric collocation method, is proposed by deriving the equivalent Lie algebra equation in so(3 of the left-invariant configuration equation. When compared with the general Gauss pseudo-spectral method, the explicit RKMK, and Lie group variational integrator having the same order and stepsize in numerical tests for evolving a free-floating rigid-body attitude dynamics, the proposed method is higher in accuracy, time performance, and structural conservativeness. In addition, the numerical method is applied to solve a constrained OAC problem on SO(3. The optimal control problem is transcribed into a nonlinear programming problem, in which the equivalent Lie algebra equation is being considered as the defect constraints instead of the configuration equation. The transcription method is coordinate-free and does not need chart switching or special handling of singularities. More importantly, with the numerical advantage of the geometric collocation method, the proposed OAC method may generate satisfying convergence rate.
Translating English Idioms and Collocations
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Rochayah Machali
2004-01-01
Full Text Available Learners of English should be made aware of the nature, types, and use of English idioms. This paper disensses the nature of idioms and collocations and translation issues related to them
Directory of Open Access Journals (Sweden)
L. Wang
2015-01-01
Full Text Available Economical space transportation systems to launch small satellites into Earth’s orbits are researched in many countries. Using aerospace systems, included aircraft and air-launched launch vehicle, is one of the low cost technical solutions. The airborne launch vehicle application to launch a small satellite with the purpose of remote sensing requires high precision exit on specified sun-synchronous orbit. So a problem is stated to construct an optimal ascent trajectory and optimal control.In this paper, the mathematical motion model of the air-launched launch vehicle with the external disturbances caused by the Earth’s non-sphericity, drag and wind is put forward based on the three-stage flight program with passive intermediate section. A discrete process based on pseudo-spectral method is used to solve the problem, which allows converting the initial problem into a nonlinear programming problem with dynamic constraints and aims for the criteria of maximization of the final mass released onto the target orbit.Application of the proposed solution procedure is illustrated by calculating the optimal control and the corresponding trajectory for two-stage liquid launch vehicle, which places the small spacecraft on the orbit of sun-synchronous at the height of 512 km. The numerical simulation results have demonstrated the effectiveness of the proposed algorithm and allow us to analyze three-stage trajectory parameters with intermediate passive flight phase. It can be noted that in the resulting ascent trajectory, the intermediate passive flight part is a suborbital trajectory with low energy integral, perigee of which is under the surface of the Earth.
A Note on The Convexity of Chebyshev Sets
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Sangeeta
2009-07-01
Full Text Available Perhaps one of the major unsolved problem in Approximation Theoryis: Whether or not every Chebyshev subset of a Hilbert space must be convex. Many partial answers to this problem are available in the literature. R.R. Phelps[Proc. Amer. Math. Soc. 8 (1957, 790-797] showed that a Chebyshev set in an inner product space (or in a strictly convex normed linear space is convex if the associated metric projection is non-expansive. We extend this result to metricspaces.
Chebyshev super spectral viscosity method for water hammer analysis
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Hongyu Chen
2013-09-01
Full Text Available In this paper, a new fast and efficient algorithm, Chebyshev super spectral viscosity (SSV method, is introduced to solve the water hammer equations. Compared with standard spectral method, the method's advantage essentially consists in adding a super spectral viscosity to the equations for the high wave numbers of the numerical solution. It can stabilize the numerical oscillation (Gibbs phenomenon and improve the computational efficiency while discontinuities appear in the solution. Results obtained from the Chebyshev super spectral viscosity method exhibit greater consistency with conventional water hammer calculations. It shows that this new numerical method offers an alternative way to investigate the behavior of the water hammer in propellant pipelines.
Inelastic scattering with Chebyshev polynomials and preconditioned conjugate gradient minimization.
Temel, Burcin; Mills, Greg; Metiu, Horia
2008-03-27
We describe and test an implementation, using a basis set of Chebyshev polynomials, of a variational method for solving scattering problems in quantum mechanics. This minimum error method (MEM) determines the wave function Psi by minimizing the least-squares error in the function (H Psi - E Psi), where E is the desired scattering energy. We compare the MEM to an alternative, the Kohn variational principle (KVP), by solving the Secrest-Johnson model of two-dimensional inelastic scattering, which has been studied previously using the KVP and for which other numerical solutions are available. We use a conjugate gradient (CG) method to minimize the error, and by preconditioning the CG search, we are able to greatly reduce the number of iterations necessary; the method is thus faster and more stable than a matrix inversion, as is required in the KVP. Also, we avoid errors due to scattering off of the boundaries, which presents substantial problems for other methods, by matching the wave function in the interaction region to the correct asymptotic states at the specified energy; the use of Chebyshev polynomials allows this boundary condition to be implemented accurately. The use of Chebyshev polynomials allows for a rapid and accurate evaluation of the kinetic energy. This basis set is as efficient as plane waves but does not impose an artificial periodicity on the system. There are problems in surface science and molecular electronics which cannot be solved if periodicity is imposed, and the Chebyshev basis set is a good alternative in such situations.
Chebyshev Finite Difference Method for Fractional Boundary Value Problems
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Boundary
2015-09-01
Full Text Available This paper presents a numerical method for fractional differential equations using Chebyshev finite difference method. The fractional derivatives are described in the Caputo sense. Numerical results show that this method is of high accuracy and is more convenient and efficient for solving boundary value problems involving fractional ordinary differential equations. AMS Subject Classification: 34A08 Keywords and Phrases: Chebyshev polynomials, Gauss-Lobatto points, fractional differential equation, finite difference 1. Introduction The idea of a derivative which interpolates between the familiar integer order derivatives was introduced many years ago and has gained increasing importance only in recent years due to the development of mathematical models of a certain situations in engineering, materials science, control theory, polymer modelling etc. For example see [20, 22, 25, 26]. Most fractional order differential equations describing real life situations, in general do not have exact analytical solutions. Several numerical and approximate analytical methods for ordinary differential equation Received: December 2014; Accepted: March 2015 57 Journal of Mathematical Extension Vol. 9, No. 3, (2015, 57-71 ISSN: 1735-8299 URL: http://www.ijmex.com Chebyshev Finite Difference Method for Fractional Boundary Value Problems H. Azizi Taft Branch, Islamic Azad University Abstract. This paper presents a numerical method for fractional differential equations using Chebyshev finite difference method. The fractional derivative
Interpolation on sparse Gauss-Chebyshev grids in higher dimensions
F. Sprengel
1998-01-01
textabstractIn this paper, we give a unified approach to error estimates for interpolation on sparse Gauss--Chebyshev grids for multivariate functions from Besov--type spaces with dominating mixed smoothness properties. The error bounds obtained for this method are almost optimal for the considered
Interlanguage Development and Collocational Clash
Shahheidaripour, Gholamabbass
2000-01-01
Background: Persian English learners committed mistakes and errors which were due to insufficient knowledge of different senses of the words and collocational structures they formed. Purpose: The study reported here was conducted for a thesis submitted in partial fulfillment of the requirements for The Master of Arts degree, School of Graduate…
Energy Technology Data Exchange (ETDEWEB)
Sidler, Rolf, E-mail: rsidler@gmail.com [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland); Carcione, José M. [Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), Borgo Grotta Gigante 42c, 34010 Sgonico, Trieste (Italy); Holliger, Klaus [Center for Research of the Terrestrial Environment, University of Lausanne, CH-1015 Lausanne (Switzerland)
2013-02-15
We present a novel numerical approach for the comprehensive, flexible, and accurate simulation of poro-elastic wave propagation in 2D polar coordinates. An important application of this method and its extensions will be the modeling of complex seismic wave phenomena in fluid-filled boreholes, which represents a major, and as of yet largely unresolved, computational problem in exploration geophysics. In view of this, we consider a numerical mesh, which can be arbitrarily heterogeneous, consisting of two or more concentric rings representing the fluid in the center and the surrounding porous medium. The spatial discretization is based on a Chebyshev expansion in the radial direction and a Fourier expansion in the azimuthal direction and a Runge–Kutta integration scheme for the time evolution. A domain decomposition method is used to match the fluid–solid boundary conditions based on the method of characteristics. This multi-domain approach allows for significant reductions of the number of grid points in the azimuthal direction for the inner grid domain and thus for corresponding increases of the time step and enhancements of computational efficiency. The viability and accuracy of the proposed method has been rigorously tested and verified through comparisons with analytical solutions as well as with the results obtained with a corresponding, previously published, and independently benchmarked solution for 2D Cartesian coordinates. Finally, the proposed numerical solution also satisfies the reciprocity theorem, which indicates that the inherent singularity associated with the origin of the polar coordinate system is adequately handled.
Chebyshev super spectral viscosity method for a fluidized bed model
Sarra, S A
2003-01-01
A Chebyshev super spectral viscosity method and operator splitting are used to solve a hyperbolic system of conservation laws with a source term modeling a fluidized bed. The fluidized bed displays a slugging behavior which corresponds to shocks in the solution. A modified Gegenbauer postprocessing procedure is used to obtain a solution which is free of oscillations caused by the Gibbs-Wilbraham phenomenon in the spectral viscosity solution. Conservation is maintained by working with unphysical negative particle concentrations.
CHEBYSHEV ACCELERATION TECHNIQUE FOR SOLVING FUZZY LINEAR SYSTEM
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S.H. Nasseri
2009-10-01
Full Text Available In this paper, Chebyshev acceleration technique is used to solve the fuzzy linear system (FLS. This method is discussed in details and followed by summary of some other acceleration techniques. Moreover, we show that in some situations that the methods such as Jacobi, Gauss-Sidel, SOR and conjugate gradient is divergent, our proposed method is applicable and the acquired results are illustrated by some numerical examples.
A Stochastic Collocation Algorithm for Uncertainty Analysis
Mathelin, Lionel; Hussaini, M. Yousuff; Zang, Thomas A. (Technical Monitor)
2003-01-01
This report describes a stochastic collocation method to adequately handle a physically intrinsic uncertainty in the variables of a numerical simulation. For instance, while the standard Galerkin approach to Polynomial Chaos requires multi-dimensional summations over the stochastic basis functions, the stochastic collocation method enables to collapse those summations to a one-dimensional summation only. This report furnishes the essential algorithmic details of the new stochastic collocation method and provides as a numerical example the solution of the Riemann problem with the stochastic collocation method used for the discretization of the stochastic parameters.
Measuring receptive collocational competence across proficiency levels
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Déogratias Nizonkiza
2015-12-01
Full Text Available The present study investigates, (i English as Foreign Language (EFL learners’ receptive collocational knowledge growth in relation to their linguistic proficiency level; (ii how much receptive collocational knowledge is acquired as proficiency develops; and (iii the extent to which receptive knowledge of collocations of EFL learners varies across word frequency bands. A proficiency measure and a collocation test were administered to English majors at the University of Burundi. Results of the study suggest that receptive collocational competence develops alongside EFL learners’ linguistic proficiency; which lends empirical support to Gyllstad (2007, 2009 and Author (2011 among others, who reported similar findings. Furthermore, EFL learners’ collocations growth seems to be quantifiable wherein both linguistic proficiency level and word frequency occupy a crucial role. While more gains in terms of collocations that EFL learners could potentially add as a result of change in proficiency are found at lower levels of proficiency; collocations of words from more frequent word bands seem to be mastered first, and more gains are found at more frequent word bands. These results confirm earlier findings on the non-linearity nature of vocabulary growth (cf. Meara 1996 and the fundamental role played by frequency in word knowledge for vocabulary in general (Nation 1983, 1990, Nation and Beglar 2007, which are extended here to collocations knowledge.
Measuring receptive collocational competence across proficiency ...
African Journals Online (AJOL)
Kate H
extent to which receptive knowledge of collocations of EFL learners varies across word frequency bands. ..... language through in-class reading and conversation tasks which totalled 75 hours. The .... 4 Readers are referred to Wray (2002) and Barfield and Gyllstad (2009) for more details on how to teach collocations.
Geostationary Collocation: Case Studies for Optimal Maneuvers
2016-03-01
GEO geosynchronous earth orbit GOES Geostationary Operational Environmental Satellites ISP specific impulse ITU International Telecommunications...insertion into Geosynchronous Earth Orbit (GEO) in 1963 to the present day, the satellite population at the geostationary belt has been increasing...recently addressed the specific topic of collocation on his book, Geostationary Satellites Collocation. We also referenced Applied Orbit Perturbation and
Supporting Collocation Learning with a Digital Library
Wu, Shaoqun; Franken, Margaret; Witten, Ian H.
2010-01-01
Extensive knowledge of collocations is a key factor that distinguishes learners from fluent native speakers. Such knowledge is difficult to acquire simply because there is so much of it. This paper describes a system that exploits the facilities offered by digital libraries to provide a rich collocation-learning environment. The design is based on…
Improving academic literacy by teaching collocations | Nizonkiza ...
African Journals Online (AJOL)
This study explores the effect of teaching collocations on building academic vocabulary and hence improving academic writing abilities. A pre-/post-test experimental design was used to analyse collocations produced in two tasks completed by the study's participants, English majors at a university in Burundi. They were ...
Measuring receptive collocational competence across proficiency ...
African Journals Online (AJOL)
The present study investigates (i) English as Foreign Language (EFL) learners' receptive collocational knowledge growth in relation to their linguistic proficiency level; (ii) how much receptive collocational knowledge is acquired as linguistic proficiency develops; and (iii) the extent to which receptive knowledge of ...
Discrete Fourier Analysis and Chebyshev Polynomials with G2 Group
Li, Huiyuan; Sun, Jiachang; Xu, Yuan
2012-10-01
The discrete Fourier analysis on the 30°-60°-90° triangle is deduced from the corresponding results on the regular hexagon by considering functions invariant under the group G2, which leads to the definition of four families generalized Chebyshev polynomials. The study of these polynomials leads to a Sturm-Liouville eigenvalue problem that contains two parameters, whose solutions are analogues of the Jacobi polynomials. Under a concept of m-degree and by introducing a new ordering among monomials, these polynomials are shown to share properties of the ordinary orthogonal polynomials. In particular, their common zeros generate cubature rules of Gauss type.
Discrete Fourier Analysis and Chebyshev Polynomials with G2 Group
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Huiyuan Li
2012-10-01
Full Text Available The discrete Fourier analysis on the 30°-60°-90° triangle is deduced from the corresponding results on the regular hexagon by considering functions invariant under the group G2, which leads to the definition of four families generalized Chebyshev polynomials. The study of these polynomials leads to a Sturm-Liouville eigenvalue problem that contains two parameters, whose solutions are analogues of the Jacobi polynomials. Under a concept of m-degree and by introducing a new ordering among monomials, these polynomials are shown to share properties of the ordinary orthogonal polynomials. In particular, their common zeros generate cubature rules of Gauss type.
Modified Chebyshev-Picard Iteration Methods for Orbit Propagation
Bai, Xiaoli; Junkins, John L.
2011-10-01
Modified Chebyshev-Picard Iteration methods are presented for solving high precision, long-term orbit propagation problems. Fusing Chebyshev polynomials with the classical Picard iteration method, the proposed methods iteratively refine an orthogonal function approximation of the entire state trajectory, in contrast to traditional, step-wise, forward integration methods. Numerical results demonstrate that for orbit propagation problems, the presented methods are comparable to or superior to a state-of-the-art 12th order Runge-Kutta-Nystrom method in a serial processor as measured by both precision and efficiency. We have found revolutionary long solution arcs with more than eleven digit path approximations over one to three lower-case Earth orbit periods, multiple solution arcs can be patched continuously together to achieve very long-term propagation, leading to more than ten digit accuracy with built-in precise interpolation. Of revolutionary practical promise to much more efficiently solving high precision, long-term orbital trajectory propagation problems is the observation that the presented methods are well suited to massive parallelization because computation of force functions along each path iteration can be rigorously distributed over many parallel cores with negligible cross communication needed.
Downward Continuation of Potential Field Data Based on Chebyshev-Padé Approximation Function
Zhou, Wenna; Li, Jiyan; Yuan, Yuan
2017-09-01
To further improve the stability and accuracy of the downward continuation, we presented a new strategy based on the Chebyshev-Padé approximation in the frequency domain. First, we compared the errors between the function exp(x) and its different approximation functions, including Taylor series, Chebyshev approximation, Padé approximation, and Chebyshev-Padé approximation. Meanwhile, the filter characteristic curves of the different functions in the frequency domain are calculated. It turned out that the Chebyshev-Padé approximation is the most precise function. Similar to the Taylor series expansion, different downward continuation methods were established based on these approximation functions in the frequency domain. We compared the accuracy of these downward continuation methods using model tests with and without noise. The results showed that the downward continuation based on Chebyshev-Padé approximation was insensitive to the noise and can obtain a more precise result. To further compare these methods and prove the superiority of Chebyshev-Padé approximation, the iteration methods of downward continuation were proposed. We can obtain an accurate result within less iterations using Chebyshev-Padé approximation. To further suppress the noise effect, we improved the iteration methods using upward continuation. Once again, the model tests showed that the Chebyshev-Padé approximation is a preferred method to implement downward continuation. Finally, the method was applied on a field gravity data and showed its superiority. It demonstrated that we can use the Chebyshev-Padé approximation to replace the classical Taylor series expansion to implement more precise and stable downward continuation.
Slovene-English Contrastive Phraseology: Lexical Collocations
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Primož Jurko
2010-05-01
Full Text Available Phraseology is seen as one of the key elements and arguably the most productive part of any language. %e paper is focused on collocations and separates them from other phraseological units, such as idioms or compounds. Highlighting the difference between a monolingual and a bilingual (i.e. contrastive approach to collocation, the article presents two distinct classes of collocations: grammatical and lexical. %e latter, treated contrastively, represent the focal point of the paper, since they are an unending source of translation errors to both students of translation and professional translators. %e author introduces a methodology of systematic classification of lexical collocations applied on the Slovene-English language pair and based on structural (lexical congruence and semantic (translational predictability criteria.
Verb-Noun Collocation Proficiency and Academic Years
Fatemeh Ebrahimi-Bazzaz; Arshad Abd Samad; Ismi Arif bin Ismail; Nooreen Noordin
2014-01-01
Generally vocabulary and collocations in particular have significant roles in language proficiency. A collocation includes two words that are frequently joined concurrently in the memory of native speakers. There have been many linguistic studies trying to define, to describe, and to categorise English collocations. It contains grammatical collocations and lexical collocations which include nouns, adjectives, verbs, and adverb. In the context of a foreign language environment such as Iran, co...
A Novel Learning Scheme for Chebyshev Functional Link Neural Networks
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Satchidananda Dehuri
2011-01-01
dimensional-space where linear separability is possible. Moreover, the proposed HCFLNN combines the best attribute of particle swarm optimization (PSO, back propagation learning (BP learning, and functional link neural networks (FLNNs. The proposed method eliminates the need of hidden layer by expanding the input patterns using Chebyshev orthogonal polynomials. We have shown its effectiveness of classifying the unknown pattern using the publicly available datasets obtained from UCI repository. The computational results are then compared with functional link neural network (FLNN with a generic basis functions, PSO-based FLNN, and EFLN. From the comparative study, we observed that the performance of the HCFLNN outperforms FLNN, PSO-based FLNN, and EFLN in terms of classification accuracy.
A Fast, Simple, and Stable Chebyshev--Legendre Transform Using an Asymptotic Formula
Hale, Nicholas
2014-02-06
A fast, simple, and numerically stable transform for converting between Legendre and Chebyshev coefficients of a degree N polynomial in O(N(log N)2/ log log N) operations is derived. The fundamental idea of the algorithm is to rewrite a well-known asymptotic formula for Legendre polynomials of large degree as a weighted linear combination of Chebyshev polynomials, which can then be evaluated by using the discrete cosine transform. Numerical results are provided to demonstrate the efficiency and numerical stability. Since the algorithm evaluates a Legendre expansion at an N +1 Chebyshev grid as an intermediate step, it also provides a fast transform between Legendre coefficients and values on a Chebyshev grid. © 2014 Society for Industrial and Applied Mathematics.
Some Identities Involving the Derivative of the First Kind Chebyshev Polynomials
Tingting Wang; Han Zhang
2015-01-01
We use the combinatorial method and algebraic manipulations to obtain several interesting identities involving the power sums of the derivative of the first kind Chebyshev polynomials. This solved an open problem proposed by Li (2015).
Some Identities Involving the Derivative of the First Kind Chebyshev Polynomials
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Tingting Wang
2015-01-01
Full Text Available We use the combinatorial method and algebraic manipulations to obtain several interesting identities involving the power sums of the derivative of the first kind Chebyshev polynomials. This solved an open problem proposed by Li (2015.
Wolter, Brent; Gyllstad, Henrik
2013-01-01
This study investigated the influence of frequency effects on the processing of congruent (i.e., having an equivalent first language [L1] construction) collocations and incongruent (i.e., not having an equivalent L1 construction) collocations in a second language (L2). An acceptability judgment task was administered to native and advanced…
A note on the rate of convergence for Chebyshev-Lobatto and Radau systems
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Berriochoa Elías
2016-01-01
Full Text Available This paper is devoted to Hermite interpolation with Chebyshev-Lobatto and Chebyshev-Radau nodal points. The aim of this piece of work is to establish the rate of convergence for some types of smooth functions. Although the rate of convergence is similar to that of Lagrange interpolation, taking into account the asymptotic constants that we obtain, the use of this method is justified and it is very suitable when we dispose of the appropriate information.
On the Relation between Composite Right-/Left-Handed Transmission Lines and Chebyshev Filters
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Changjun Liu
2009-01-01
Full Text Available Composite right-/left-handed (CRLH transmission lines have gained great interest in the microwave community. In practical applications, such CRLH sections realized by series and shunt resonators have a finite length. Starting from the observation that a high-order Chebyshev filter also exhibits a periodic central section of very similar structure, the relations between finite length CRHL transmission lines and Chebyshev filters are discussed in this paper. It is shown that a finite length CRLH transmission line in the balanced case is equivalent to the central part of a low-ripple high-order Chebyshev band-pass filter, and a dual-CRLH transmission line in the balanced case is equivalent to a low-ripple high-order Chebyshev band-stop filter. The nonperiodic end sections of a Chebyshev filter can be regarded as matching sections, thus leading to an even better amplitude and phase response. It is also shown that, equally to a CRHL transmission line, a Chebyshev filter exhibits negative phase velocity in part of its passband. As a consequence, an improved behavior of finite length CRLH transmission lines may be achieved adding matching sections based on filter theory; this is demonstrated by a simulation example.
Evaluating a new test of whole English collocations
DEFF Research Database (Denmark)
Revier, Robert Lee
2009-01-01
of L2 collocation knowledge needs to focus on the recognition and production of whole collocations. It is this set of assumptions that the new collocation test presented in this chapter is desined to probe. More specifically, the test is designed to assess L2 learners' productive knowledge of whole...... of theoretical and practical issues informing the experimental study. Once I have desribed how collocations are defined and classified, I go on to explain how collocation knowledge is conceptualized and operationalized in the present research and how the collocation test was designed and developed. In the second...
An alternative approach to robust collocation
Schaffrin, Burkhard
1989-12-01
The now classical collocation method in geodesy has been derived by H. Moritz (1970; 1973) within an appropriate Mixed Linear Model. According to B. Schaffrin (1985; 1986) even a generalized form of the collocation solution can be proved to represent a combined estimation/prediction procedure of type BLUUE (Best Linear Uniformly Unbiased Estimation) for the fixed parameters, and of type inhom BLIP (Best inhomogeneously LInear Prediction) for the random effects with not necessarily zero expectation. Moreover, " robust collocation" has been introduced by means of hom BLUP (Best homogeneously Linear weakly Unbiased Prediction) for the random effects together with a suitable LUUE for the fixed parameters. Here we present an equivalence theorem which states that the robust collocation solution in the original Mixed Linear Model can identically be derived as traditional LESS (LEast Squares Solution) in a modified Mixed Linear Model without using artifacts like "pseudo-observations". This allows us a nice interpretation of "robust collocation" as an adjustment technique in the presence of " weak prior information".
Weighted Chebyshev distance classification method for hyperspectral imaging
Demirci, S.; Erer, I.; Ersoy, O.
2015-06-01
The main objective of classification is to partition the surface materials into non-overlapping regions by using some decision rules. For supervised classification, the hyperspectral imagery (HSI) is compared with the reflectance spectra of the material containing similar spectral characteristic. As being a spectral similarity based classification method, prediction of different level of upper and lower spectral boundaries of all classes spectral signatures across spectral bands constitutes the basic principles of the Multi-Scale Vector Tunnel Algorithm (MS-VTA) classification algorithm. The vector tunnel (VT) scaling parameters obtained from means and standard deviations of the class references are used. In this study, MS-VT method is improved and a spectral similarity based technique referred to as Weighted Chebyshev Distance (WCD) method for the supervised classification of HSI is introduced. This is also shown to be equivalent to the use of the WCD in which the weights are chosen as an inverse power of the standard deviation per spectral band. The use of WCD measures in terms of the inverse power of standard deviations and optimization of power parameter constitute the most important side of the study. The algorithms are trained with the same kinds of training sets, and their performances are calculated for the power of the standard deviation. During these studies, various levels of the power parameters are evaluated based on the efficiency of the algorithms for choosing the best values of the weights.
Testing controlled productive knowledge of adverb-verb collocations ...
African Journals Online (AJOL)
The present study examines English as a Foreign Language (EFL) junior researchers' use of adverb- verb collocations of ... Key words: academic writing, adverb-verb collocations, productive knowledge of collocations, .... This is even more so for the expression to blow the gaff, which is totally opaque in meaning – to reveal ...
The relationship between productive knowledge of collocations and ...
African Journals Online (AJOL)
indicating that knowledge of collocations corresponds to students' academic literacy. The pedagogical consequences these results have for the widespread attempt to improve tertiary level students' use of collocations in writing are discussed1. Key words: productive knowledge of collocations, academic literacy, academic ...
Testing controlled productive knowledge of adverb-verb collocations ...
African Journals Online (AJOL)
Results indicate that free-productive knowledge of adverb-verb collocations is challenging for EFL users. This finding supports previous studies that focused mainly on verb-noun collocations, and that reached the conclusion that EFL students are not sensitive enough to collocations to use them in their written productions (cf ...
Relation work in collocated and distributed collaboration
DEFF Research Database (Denmark)
Christensen, Lars Rune; Jensen, Rasmus Eskild; Bjørn, Pernille
2014-01-01
, emergent in personal and often humorous situations. Relation work is intertwined with other activities such as articulation work and it is rhythmic by following the work patterns of the participants. By comparing how relation work is conducted in collocated and geographically distributed settings we...
Solution of inverse heat conduction equation with the use of Chebyshev polynomials
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Joachimiak Magda
2016-12-01
Full Text Available A direct problem and an inverse problem for the Laplace’s equation was solved in this paper. Solution to the direct problem in a rectangle was sought in a form of finite linear combinations of Chebyshev polynomials. Calculations were made for a grid consisting of Chebyshev nodes, what allows us to use orthogonal properties of Chebyshev polynomials. Temperature distributions on the boundary for the inverse problem were determined using minimization of the functional being the measure of the difference between the measured and calculated values of temperature (boundary inverse problem. For the quasi-Cauchy problem, the distance between set values of temperature and heat flux on the boundary was minimized using the least square method. Influence of the value of random disturbance to the temperature measurement, of measurement points (distance from the boundary, where the temperature is not known arrangement as well as of the thermocouple installation error on the stability of the inverse problem was analyzed.
Khanmohamadi, Omid; Xu, Daolin
2009-09-01
A system identification methodology based on Chebyshev spectral operators and an orthogonal system reduction algorithm is proposed, leading to a new approach for data-driven modeling of nonlinear spatiotemporal systems on nonperiodic domains. A continuous model structure is devised allowing for terms of arbitrary derivative order and nonlinearity degree. Chebyshev spectral operators are introduced to realm of inverse problems to discretize that continuous structure and arrive with spectral accuracy at a discrete form. Finally, least squares combined with an orthogonal system reduction algorithm are employed to solve for the parameters and eliminate the redundancies to achieve a parsimonious model. A numerical case study of identifying the Allen-Cahn metastable equation demonstrates the superior accuracy of the proposed Chebyshev spectral identification over its finite difference counterpart.
Chebyshev blossoming in Müntz spaces: Toward shaping with Young diagrams
Ait-Haddou, Rachid
2013-08-01
The notion of a blossom in extended Chebyshev spaces offers adequate generalizations and extra-utilities to the tools for free-form design schemes. Unfortunately, such advantages are often overshadowed by the complexity of the resulting algorithms. In this work, we show that for the case of Müntz spaces with integer exponents, the notion of a Chebyshev blossom leads to elegant algorithms whose complexities are embedded in the combinatorics of Schur functions. We express the blossom and the pseudo-affinity property in Müntz spaces in terms of Schur functions. We derive an explicit expression for the Chebyshev-Bernstein basis via an inductive argument on nested Müntz spaces. We also reveal a simple algorithm for dimension elevation. Free-form design schemes in Müntz spaces with Young diagrams as shape parameters are discussed. © 2013 Elsevier Ltd. All rights reserved.
The collocation approach to Moho estimate
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Riccardo Barzaghi
2014-03-01
Full Text Available In this paper, the collocation approach to Moho estimate is presented. This method is applied to the inversion of gravity data that can be complemented by Moho depth information coming from e.g. seismic information. In this context, a two layers model is considered and discussed in order to give a general theoretical framework for the inversion method. A body with two inner constant density layers and an inner separation surface between is considered and a uniqueness theorem is proved for the estimability of the separation surface given the gravity outside the body itself. Based on this result, a discussion is given on the estimation of the Moho depths based on terrestrial gravity observations. The observation equation is presented and its local planar approximation is derived. The application of the collocation method to the estimate of Moho depths is then studied and discussed in relationship to the planar observation equation. Also, numerical tests are presented. To this aim, the collocation inversion algorithm is implemented and tested on simulated data to prove its effectiveness. The results show that the proposed method is reliable provided that proper data reductions for model discrepancies are taken into account.
Collocation networks in the language of crime journalism
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David Brett
2017-12-01
Full Text Available Standard procedures for the treatment of collocates, which involve the elaboration of lists of collocates on a two-by-two basis, are far from optimum for the study of connectivity, i.e. observing whether these collocates in turn display a tendency to co-occur or not. This paper explores an alternative strategy that has garnered considerable interest in recent years: that of using Social Network Analysis procedures. Lists of collocates (concgrams were extracted from a one million word corpus of crime journalism using standard techniques. Gephi software was then used to transform the list of collocates into a network. A small number of collocate pairs were seen to be isolates, i.e. collocating only with each other, while the majority belonged to the giant component, composed of pairs in which at least one member collocates with at least one other word. Modules (clusters of highly interconnected collocates were identified; these were seen to pertain to specific subject areas. The corpus was then re-examined to see where these clusters of collocates occurred, and co-occurred, and to gauge how much this technique may tell us about the ‘aboutness’ of particular texts.
Hubbell rectangular source integral calculation using a fast Chebyshev wavelets method.
Manai, K; Belkadhi, K
2016-07-01
An integration method based on Chebyshev wavelets is presented and used to calculate the Hubbell rectangular source integral. A study of the convergence and the accuracy of the method was carried out by comparing it to previous studies. Copyright © 2016 Elsevier Ltd. All rights reserved.
Numerical solution of nonlinear Volterra-Fredholm integral equation by using Chebyshev polynomials
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R. Ezzati
2011-03-01
Full Text Available In this paper, we have used Chebyshev polynomials to solve linearand nonlinear Volterra-Fredholm integral equations, numerically.First we introduce these polynomials, then we use them to changethe Volterra-Fredholm integral equation to a linear or nonlinearsystem. Finally, the numerical examples illustrate the efficiencyof this method.
Chebyshev-based technique for automated restoration of digital copies of faded photographic prints
Uchaev, Dmitry V.; Uchaev, Denis V.; Malinnikov, Vasiliy A.
2017-01-01
We present a technique for automated restoration of digital images obtained from faded photographic prints. The proposed defading technique uses our early proposed image contrast enhancement algorithm based on a contrast measure of images in the Chebyshev moment transform domain. Obtained experimental results demonstrate some advantages of the technique as compared to other widely used image enhancement methods.
On Collocations and Their Interaction with Parsing and Translation
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Violeta Seretan
2013-10-01
Full Text Available We address the problem of automatically processing collocations—a subclass of multi-word expressions characterized by a high degree of morphosyntactic flexibility—in the context of two major applications, namely, syntactic parsing and machine translation. We show that parsing and collocation identification are processes that are interrelated and that benefit from each other, inasmuch as syntactic information is crucial for acquiring collocations from corpora and, vice versa, collocational information can be used to improve parsing performance. Similarly, we focus on the interrelation between collocations and machine translation, highlighting the use of translation information for multilingual collocation identification, as well as the use of collocational knowledge for improving translation. We give a panorama of the existing relevant work, and we parallel the literature surveys with our own experiments involving a symbolic parser and a rule-based translation system. The results show a significant improvement over approaches in which the corresponding tasks are decoupled.
Semantic Analysis of Verbal Collocations with Lexical Functions
Gelbukh, Alexander
2013-01-01
This book is written for both linguists and computer scientists working in the field of artificial intelligence as well as to anyone interested in intelligent text processing. Lexical function is a concept that formalizes semantic and syntactic relations between lexical units. Collocational relation is a type of institutionalized lexical relations which holds between the base and its partner in a collocation. Knowledge of collocation is important for natural language processing because collocation comprises the restrictions on how words can be used together. The book shows how collocations can be annotated with lexical functions in a computer readable dictionary - allowing their precise semantic analysis in texts and their effective use in natural language applications including parsers, high quality machine translation, periphrasis system and computer-aided learning of lexica. The books shows how to extract collocations from corpora and annotate them with lexical functions automatically. To train algorithms,...
The Study of the Students' Collocation Performance in Argumentative Writing
Oktavera, Haryati
2014-01-01
Collocation is used by most of the native speaker in both writing and speaking authentic English. This paper focused on knowing the students' collocation knowledge by examining their lexical and grammatical collocation performance in their argumentative writing. This research, therefore, conducted by analyzing deeply 10 argumentative writings of the third semester students of PBI STAIN JuraiSiwo Metro in academic year 2013/2014. The result of this research showed that there were 41 % errors f...
Terminological collocations in medical latin and english: a comparative study.
Bieliaieva, Olena M; Lysanets, Yuliia V; Znamenska, Ivanna V; Rozhenko, Inesa V; Nikolaieva, Nataliia M
The present paper examines the linguistic status of terminological collocations in medical Latin and English, discusses the most productive term-formation models and ways of Latin-English translation. The authors aim to provide the comparative analysis of Latin and English terminological collocations and suggest their classification in terms of the idiomaticity level and semantic valency. The research is based on the corpus of terminological collocations in Latin and English medical discourse using structural, etymological, typological, comparative methods, as well as the method of semantic analysis and conceptual metaphor theory. The research has resulted in the delineation of the following groups of terminological collocations in medical Latin and English: (1) terminological collocations with lower degree of idiomaticity - analytical units whose semantics correlates with the amount of free meanings of the components; (2) terminological collocations with semantic cohesion of the components due to metaphorical nature of the terminological element with active / passive valency; (3) clinical idioms - terminological collocations with higher degree of idiomaticity. Within the latter group, we suggest to discern eponymic, toponymic, zoomorphic, botanic and mythonimic subtypes of terminological collocations. A promising area of future research is the development of bilingual explanatory dictionaries with Latin and English equivalents of terminological collocations, as well as the information about the semantics of their components.
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Kangwen Sun
2015-01-01
Full Text Available The purpose of this paper is to study the Chebyshev polynomials for the solution of a class of variable order fractional integral-differential equation. The properties of Chebyshev polynomials together with the four kinds of operational matrixes of Chebyshev polynomials are used to reduce the problem to the solution of a system of algebraic equations. By solving the algebraic equations, the numerical solutions are acquired. Further some numerical examples are shown to illustrate the accuracy and reliability of the proposed approach and the results have been compared with the exact solution.
Verb-Noun Collocation Proficiency and Academic Years
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Fatemeh Ebrahimi-Bazzaz
2014-01-01
Full Text Available Generally vocabulary and collocations in particular have significant roles in language proficiency. A collocation includes two words that are frequently joined concurrently in the memory of native speakers. There have been many linguistic studies trying to define, to describe, and to categorise English collocations. It contains grammatical collocations and lexical collocations which include nouns, adjectives, verbs, and adverb. In the context of a foreign language environment such as Iran, collocational proficiency can be useful because it helps the students improve their language proficiency. This paper investigates the possible relationship between verb-noun collocation proficiency among students from one academic year to the next. To reach this goal, a test of verb-noun collocations was administered to Iranian learners. The participants in the study were 212 Iranian students in an Iranian university. They were selected from the second term of freshman, sophomore, junior, and senior years. The students’ age ranged from 18 to 35.The results of ANOVA showed there was variability in the verb-noun collocations proficiency within each academic year and between the four academic years. The results of a post hoc multiple comparison tests demonstrated that the means are significantly different between the first year and the third and fourth years, and between the third and the fourth academic year; however, students require at least two years to show significant development in verb-noun collocation proficiency. These findings provided a vital implication that lexical collocations are learnt and developed through four academic years of university, but requires at least two years showing significant development in the language proficiency.
Collocations and Grammatical Patterns in a Multilingual Online Term ...
African Journals Online (AJOL)
... African terminological databanks and language for special purposes (LSP) dictionaries. Various strategies for the effective semi-automatic extraction of collocational data from specialized corpora are explored. Possibilities regarding access to and presentation of collocational information to the user are briefly considered.
Collocations of High Frequency Noun Keywords in Prescribed Science Textbooks
Menon, Sujatha; Mukundan, Jayakaran
2012-01-01
This paper analyses the discourse of science through the study of collocational patterns of high frequency noun keywords in science textbooks used by upper secondary students in Malaysia. Research has shown that one of the areas of difficulty in science discourse concerns lexis, especially that of collocations. This paper describes a corpus-based…
The Effect of Grouping and Presenting Collocations on Retention
Akpinar, Kadriye Dilek; Bardakçi, Mehmet
2015-01-01
The aim of this study is two-fold. Firstly, it attempts to determine the role of presenting collocations by organizing them based on (i) the keyword, (ii) topic related and (iii) grammatical aspect on retention of collocations. Secondly, it investigates the relationship between participants' general English proficiency and the presentation types…
Collocative meaning in the Igbo language | Okeke | Southern African ...
African Journals Online (AJOL)
The corpora comprise 20 randomly selected documents from different scholars published from 2013 to 2016 in the University of Nigeria, Nsukka; and a total of 405 tokens of collocates were used. Following Berkley's and Okoro's definitions of collocation, this paper engages on two major objectives of first, analysing the ...
Gottlieb, D.; Turkel, E.
1980-01-01
New methods are introduced for the time integration of the Fourier and Chebyshev methods of solution for dynamic differential equations. These methods are unconditionally stable, even though no matrix inversions are required. Time steps are chosen by accuracy requirements alone. For the Fourier method both leapfrog and Runge-Kutta methods are considered. For the Chebyshev method only Runge-Kutta schemes are tested. Numerical calculations are presented to verify the analytic results. Applications to the shallow water equations are presented.
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Hassan A. Zedan
2017-01-01
Full Text Available Chebyshev spectral method based on operational matrix is applied to both systems of fractional integro-differential equations and Abel’s integral equations. Some test problems, for which the exact solution is known, are considered. Numerical results with comparisons are made to confirm the reliability of the method. Chebyshev spectral method may be considered as alternative and efficient technique for finding the approximation of system of fractional integro-differential equations and Abel’s integral equations.
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Carlos E. Cadenas R.
2017-09-01
Full Text Available In this work, a new family of Newton-Chebyshev type methods for solving nonlinear equations is presented. The dynamics of the Newton-Chebyshev family for the class of quadratic polynomials is analyzed and the convergence is established. We find the fixed and critical points. The stable and unstable behaviors are studied. The parameter space associated with the family is studied and finally, some dynamical planes that show different aspects of the dynamics of this family are presented.
Secure Image Transmission over DFT-precoded OFDM-VLC systems based on Chebyshev Chaos scrambling
Wang, Zhongpeng; Qiu, Weiwei
2017-08-01
This paper proposes a physical layer image secure transmission scheme for discrete Fourier transform (DFT) precoded OFDM-based visible light communication systems by using Chebyshev chaos maps. In the proposed scheme, 256 subcarriers and QPSK modulation are employed. The transmitted digital signal of the image is encrypted with a Chebyshev chaos sequence. The encrypted signal is then transformed by a DFT precoding matrix to reduce the PAPR of the OFDM signal. After that, the encrypted and DFT-precoded OFDM are transmitted over a VLC channel. The simulation results show that the proposed image security transmission scheme can not only protect the DFT-precoded OFDM-based VLC from eavesdroppers but also improve BER performance.
Operation analysis of a Chebyshev-Pantograph leg mechanism for a single DOF biped robot
Liang, Conghui; Ceccarelli, Marco; Takeda, Yukio
2012-12-01
In this paper, operation analysis of a Chebyshev-Pantograph leg mechanism is presented for a single degree of freedom (DOF) biped robot. The proposed leg mechanism is composed of a Chebyshev four-bar linkage and a pantograph mechanism. In contrast to general fully actuated anthropomorphic leg mechanisms, the proposed leg mechanism has peculiar features like compactness, low-cost, and easy-operation. Kinematic equations of the proposed leg mechanism are formulated for a computer oriented simulation. Simulation results show the operation performance of the proposed leg mechanism with suitable characteristics. A parametric study has been carried out to evaluate the operation performance as function of design parameters. A prototype of a single DOF biped robot equipped with two proposed leg mechanisms has been built at LARM (Laboratory of Robotics and Mechatronics). Experimental test shows practical feasible walking ability of the prototype, as well as drawbacks are discussed for the mechanical design.
Rational Chebyshev spectral transform for the dynamics of broad-area laser diodes
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Javaloyes, J., E-mail: julien.javaloyes@uib.es [Universitat de les Illes Balears, C/Valldemossa, km 7.5, E-07122 Palma de Mallorca (Spain); Balle, S. [Institut Mediterrani d' Estudis Avançats, CSIC-UIB, E-07071 Palma de Mallorca (Spain)
2015-10-01
This manuscript details the use of the rational Chebyshev transform for describing the transverse dynamics of broad-area laser diodes and amplifiers. This spectral method can be used in combination with the delay algebraic equations approach developed in [1], which substantially reduces the computation time. The theory is presented in such a way that it encompasses the case of the Fourier spectral transform presented in [2] as a particular case. It is also extended to the consideration of index guiding with an arbitrary transverse profile. Because their domain of definition is infinite, the convergence properties of the Chebyshev rational functions allow handling the boundary conditions with higher accuracy than with the previously studied Fourier transform method. As practical examples, we solve the beam propagation problem with and without index guiding: we obtain excellent results and an improvement of the integration time between one and two orders of magnitude as compared with a fully distributed two dimensional model.
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Jong-Seung Park
2016-11-01
Full Text Available Collocations in Japanese and Korean have been studied extensively based on statistical tools. The criteria for collocations in these languages, however, have not been fully established in the literature, and it is not obvious whether all statistically significant combinations of words could be regarded as collocations. In this article, we point out empirical problems in extracting collocations in Japanese and Korean, and provide a standard for identifying collocations (to be separated from “free combination” and “idiom” in these languages. We concentrate on the discussion of empirical aspects of collocation research, rather than the statistical analyses of collocational patterns. As a preliminary to developing a database for Japanese-Korean contrastive work on collocations, the present study focuses on ten “Chinese-words” (漢語. We show that (i the co-occurring verbs for eight Chinese-words in Korean all carry over to Japanese (but not vice versa; (ii in the other two cases, Korean exhibits co-occurring verbs not found in Japanese; (iii language-specific patterns of verb co-occurring are also observed in some instances. Overall, it is indicated that a much wider variety of co-occurring verbs are found in Japanese than in Korean.
Park, Jong-Seung; Seraku, Tohru; Kiaer, Jieun
2016-11-01
Collocations in Japanese and Korean have been studied extensively based on statistical tools. The criteria for collocations in these languages, however, have not been fully established in the literature, and it is not obvious whether all statistically significant combinations of words could be regarded as collocations. In this article, we point out empirical problems in extracting collocations in Japanese and Korean, and provide a standard for identifying collocations (to be separated from "free combination" and "idiom") in these languages. We concentrate on the discussion of empirical aspects of collocation research, rather than the statistical analyses of collocational patterns. As a preliminary to developing a database for Japanese-Korean contrastive work on collocations, the present study focuses on ten "Chinese-words" (). We show that (i) the co-occurring verbs for eight Chinese-words in Korean all carry over to Japanese (but not vice versa); (ii) in the other two cases, Korean exhibits co-occurring verbs not found in Japanese; (iii) language-specific patterns of verb co-occurring are also observed in some instances. Overall, it is indicated that a much wider variety of co-occurring verbs are found in Japanese than in Korean.
Varlamova, Elena V.; Naciscione, Anita; Tulusina, Elena A.
2016-01-01
Relevance of the issue stated in the article is determined by the fact that there is a lack of research devoted to the methods of teaching English and German collocations. The aim of our work is to determine methods of teaching English and German collocations to Russian university students studying foreign languages through experimental testing.…
Macomber, B.; Woollands, R. M.; Probe, A.; Younes, A.; Bai, X.; Junkins, J.
2013-09-01
Modified Chebyshev Picard Iteration (MCPI) is an iterative numerical method for approximating solutions of linear or non-linear Ordinary Differential Equations (ODEs) to obtain time histories of system state trajectories. Unlike other step-by-step differential equation solvers, the Runge-Kutta family of numerical integrators for example, MCPI approximates long arcs of the state trajectory with an iterative path approximation approach, and is ideally suited to parallel computation. Orthogonal Chebyshev Polynomials are used as basis functions during each path iteration; the integrations of the Picard iteration are then done analytically. Due to the orthogonality of the Chebyshev basis functions, the least square approximations are computed without matrix inversion; the coefficients are computed robustly from discrete inner products. As a consequence of discrete sampling and weighting adopted for the inner product definition, Runge phenomena errors are minimized near the ends of the approximation intervals. The MCPI algorithm utilizes a vector-matrix framework for computational efficiency. Additionally, all Chebyshev coefficients and integrand function evaluations are independent, meaning they can be simultaneously computed in parallel for further decreased computational cost. Over an order of magnitude speedup from traditional methods is achieved in serial processing, and an additional order of magnitude is achievable in parallel architectures. This paper presents a new MCPI library, a modular toolset designed to allow MCPI to be easily applied to a wide variety of ODE systems. Library users will not have to concern themselves with the underlying mathematics behind the MCPI method. Inputs are the boundary conditions of the dynamical system, the integrand function governing system behavior, and the desired time interval of integration, and the output is a time history of the system states over the interval of interest. Examples from the field of astrodynamics are
Two-dimensional Chebyshev hybrid functions and their applications to integral equations
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Zahra JafariBehbahani
2015-06-01
Full Text Available A combination of bivariate Chebyshev polynomials and two-dimensional block-pulse functions are introduced and applied for approximating the numerical solution of two-dimensional Fredholm integral equations. All calculations in this approach would be easily implemented. The method has the advantage of reducing computational burden. The convergence analysis is given. Some numerical examples are provided to illustrate the accuracy and computational efficiency of the proposed method.
An Improved Laguerre-Samuelson Inequality of Chebyshev-Markov Type
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Werner Hürlimann
2014-01-01
Full Text Available The Chebyshev-Markov extremal distributions by known moments to order four are used to improve the Laguerre-Samuelson inequality for finite real sequences. In general, the refined bound depends not only on the sample size but also on the sample skewness and kurtosis. Numerical illustrations suggest that the refined inequality can almost be attained for randomly distributed completely symmetric sequences from a Cauchy distribution.
Yıgıt, Gülsemay; Bayram, Mustafa
2017-01-01
In this study linear and nonlinear higher order singularly perturbed problems are examined by a numerical approach, the differential quadrature method. Here, the main idea is using Chebyshev polynomials to acquire the weighting coefficient matrix which is necessary to get numerical results. Following this, different class of perturbation problems are considered as test problems. Then, all results are shown in tables and also comparison between numerical and exact solution shows the accuracy a...
Hasrizam, C. M.; Fawazi, Noor
2017-11-01
Structure Health Monitoring (SHM) has been applied in various application such as aerospace, machinery and civil structures to maintain structure’s safety and integrity. Gapped smoothing method (GSM) is most popular non-destructive identification (NDI) method due to its simplicity and did not require baseline data for comparisons. However, GSM is less accurate to detect wide size of damage in structure and cause false detection. Objective of this study is to propose a method to detect damage in structure using curvature mode shape data estimated from damaged structure and did not require data from undamaged structure. Finite element analysis (FEA) on a free-free boundary condition steel beam was carried out to demonstrate the feasibility of the proposed method that estimate undamaged curvature mode shape data using cubic polynomial regression (CPR) and Chebyshev filters (CF) methods. The results shows proposed method that used Chebyshev filters has better accuracy damage detection on wide notch compared to GSM. Although application of an interpolation and Chebyshev filters showed results with a high potential for overcoming the issue of false detection due to different notch size, however the proposed method still need refinement to better detection of different damage cases.
The Fundamental Blossoming Inequality in Chebyshev Spaces—I: Applications to Schur Functions
Ait-Haddou, Rachid
2016-10-19
A classical theorem by Chebyshev says how to obtain the minimum and maximum values of a symmetric multiaffine function of n variables with a prescribed sum. We show that, given two functions in an Extended Chebyshev space good for design, a similar result can be stated for the minimum and maximum values of the blossom of the first function with a prescribed value for the blossom of the second one. We give a simple geometric condition on the control polygon of the planar parametric curve defined by the pair of functions ensuring the uniqueness of the solution to the corresponding optimization problem. This provides us with a fundamental blossoming inequality associated with each Extended Chebyshev space good for design. This inequality proves to be a very powerful tool to derive many classical or new interesting inequalities. For instance, applied to Müntz spaces and to rational Müntz spaces, it provides us with new inequalities involving Schur functions which generalize the classical MacLaurin’s and Newton’s inequalities. This work definitely demonstrates that, via blossoms, CAGD techniques can have important implications in other mathematical domains, e.g., combinatorics.
Productive knowledge of collocations may predict academic literacy
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Van Dyk, Tobie
2016-12-01
Full Text Available The present study examines the relationship between productive knowledge of collocations and academic literacy among first year students at North-West University. Participants were administered a collocation test, the items of which were selected from Nation’s (2006 word frequency bands, i.e. the 2000-word, 3000-word, 5000-word bands; and the Academic Word List (Coxhead, 2000. The scores from the collocation test were compared to those from the Test of Academic Literacy Levels (version administered in 2012. The results of this study indicate that, overall, knowledge of collocations is significantly correlated with academic literacy, which is also observed at each of the frequency bands from which the items were selected. These results support Nizonkiza’s (2014 findings that a significant correlation between mastery of collocations of words from the Academic Word List and academic literacy exists; which is extended here to words from other frequency bands. They also confirm previous findings that productive knowledge of collocations increases alongside overall proficiency (cf. Gitsaki, 1999; Bonk, 2001; Eyckmans et al., 2004; Boers et al., 2006; Nizonkiza, 2011; among others. This study therefore concludes that growth in productive knowledge of collocations may entail growth in academic literacy; suggesting that productive use of collocations is linked to academic literacy to a considerable extent. In light of these findings, teaching strategies aimed to assist first year students meet academic demands posed by higher education and avenues to explore for further research are discussed. Especially, we suggest adopting a productive oriented approach to teaching collocations, which we believe may prove useful.
Event-related temporary collocations in modern english newspaperdiscourse
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Е В Терехова
2010-06-01
Full Text Available The paper discusses collocations called by the author as «temporary collocations». The temporary collocations (TC under discussion are understood as expressions with one marked component, being peripheral to the mainstream of idioms and phrasal expressions, which enables us to treat the analyzed TC in a narrow slightly idiomatic meaning. Quite a few examples borrowed from the authentic English newspapers and magazines are used to demonstrate the relationship between the event and the emergence of the TC; also the discourse definition is provided with a focus on interdependence between the TC and the discourse.
The Learning Burden of Collocations: The Role of Interlexical and Intralexical Factors
Peters, Elke
2016-01-01
This study investigates whether congruency (+/- literal translation equivalent), collocate-node relationship (adjective-noun, verb-noun, phrasal-verb-noun collocations), and word length influence the learning burden of EFL learners' learning collocations at the initial stage of form-meaning mapping. Eighteen collocations were selected on the basis…
Corpus-Aided Business English Collocation Pedagogy: An Empirical Study in Chinese EFL Learners
Chen, Lidan
2017-01-01
This study reports an empirical study of an explicit instruction of corpus-aided Business English collocations and verifies its effectiveness in improving learners' collocation awareness and learner autonomy, as a result of which is significant improvement of learners' collocation competence. An eight-week instruction in keywords' collocations,…
Perceptions on L2 Lexical Collocation Translation with a Focus on English-Arabic
Alqaed, Mai Abdullah
2017-01-01
This paper aims to shed light on recent research concerning translating English-Arabic lexical collocations. It begins with a brief overview of English and Arabic lexical collocations with reference to specialized dictionaries. Research views on translating lexical collocations are presented, with the focus on English-Arabic collocations. These…
Orthogonal spline collocation methods for partial differential equations
Bialecki, B.; Fairweather, G.
2001-03-01
This paper provides an overview of the formulation, analysis and implementation of orthogonal spline collocation (OSC), also known as spline collocation at Gauss points, for the numerical solution of partial differential equations in two space variables. Advances in the OSC theory for elliptic boundary value problems are discussed, and direct and iterative methods for the solution of the OSC equations examined. The use of OSC methods in the solution of initial-boundary value problems for parabolic, hyperbolic and Schrödinger-type systems is described, with emphasis on alternating direction implicit methods. The OSC solution of parabolic and hyperbolic partial integro-differential equations is also mentioned. Finally, recent applications of a second spline collocation method, modified spline collocation, are outlined.
Collocability in Languages for Special Purposes (LSPs): some ...
African Journals Online (AJOL)
... not necessarily be familiar at all. Keywords: chunking; co-occurrence; cognitive entity; collocability; concept; corpora; discourse community; distribution; dyad; encyclopaedic competence; language for special purposes; lexicography; mental lexicon; multiword unit; occurrence; sociolect; statistics; terminology; term; triad ...
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M. Heydari
2013-05-01
Full Text Available A new and effective direct method to determine the numerical solution of linear and nonlinear differential-algebraic equations (DAEs is proposed. The method consists of expanding the required approximate solution as the elements of Chebyshev cardinal functions. The operational matrices for the integration and product of the Chebyshev cardinal functions are presented. A general procedure for forming these matrices is given. These matrices play an important role in modelling of problems. By using these operational matrices together, a differentialalgebraic equation can be transformed to a system of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of the technique
Chebyshev and Modified Wavelet Algorithm Based Sleep Arousals Detection Using EEG Sensor Database
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Mahalaxmi U. S. B. K.
2017-04-01
Full Text Available Electroencephalographic (EEG arousals are generally observed in EEG recordings as an awakening response of the human brain. Sleep apnea is a major sleep disorder. The patients, with Severe Sleep Apnea (SAS suffers from frequent interruptions in their sleep which brings about EEG arousals. In this paper, a new method for Segmentation and Filtering process of EEG sensor database signals for finding sleep arousals using Chebyshev and Modified Wavelet Algorithm is proposed. The Segmentation Algorithm appears as various features extracted from EEG Data’s and PSG Recordings. The Chebyshev Equiripple Filter is used in Filtering algorithm and then MSVM [M-Support Vector Machine] was utilized as Classification Tool. Algorithms are performed and different features are extracted and the ROC characteristics are performed. The extracted features are Delta, Gama, Beta, Alpha, Sigma of the EEG signal, EEG Signal Mean, EEG Signal Standard Deviation, EEG Signal Peak Signal to Noise Ratio [PSNR], and EEG Signal Normalization. MSVM tool showing EEG signals results.
A NEW TOOL FOR IMAGE ANALYSIS BASED ON CHEBYSHEV RATIONAL FUNCTIONS: CHEF FUNCTIONS
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Jimenez-Teja, Y.; Benitez, N., E-mail: yojite@iaa.es [Instituto de Astrofisica de Andalucia (CSIC), Glorieta de la Astronomia s/n, Granada E-18008 (Spain)
2012-02-01
We introduce a new approach to the modeling of the light distribution of galaxies, an orthonormal polar basis formed by a combination of Chebyshev rational functions and Fourier polynomials that we call CHEF functions, or CHEFs. We have developed an orthonormalization process to apply this basis to pixelized images, and implemented the method as a Python pipeline. The new basis displays remarkable flexibility, being able to accurately fit all kinds of galaxy shapes, including irregulars, spirals, ellipticals, highly compact, and highly elongated galaxies. It does this while using fewer components than similar methods, as shapelets, and without producing artifacts, due to the efficiency of the rational Chebyshev polynomials to fit quickly decaying functions like galaxy profiles. The method is linear and very stable, and therefore is capable of processing large numbers of galaxies in a fast and automated way. Due to the high quality of the fits in the central parts of the galaxies, and the efficiency of the CHEF basis modeling galaxy profiles up to very large distances, the method provides highly accurate estimates of total galaxy fluxes and ellipticities. Future papers will explore in more detail the application of the method to perform multiband photometry, morphological classification, and weak shear measurements.
Multi-Index Stochastic Collocation for random PDEs
Haji Ali, Abdul Lateef
2016-03-28
In this work we introduce the Multi-Index Stochastic Collocation method (MISC) for computing statistics of the solution of a PDE with random data. MISC is a combination technique based on mixed differences of spatial approximations and quadratures over the space of random data. We propose an optimization procedure to select the most effective mixed differences to include in the MISC estimator: such optimization is a crucial step and allows us to build a method that, provided with sufficient solution regularity, is potentially more effective than other multi-level collocation methods already available in literature. We then provide a complexity analysis that assumes decay rates of product type for such mixed differences, showing that in the optimal case the convergence rate of MISC is only dictated by the convergence of the deterministic solver applied to a one dimensional problem. We show the effectiveness of MISC with some computational tests, comparing it with other related methods available in the literature, such as the Multi-Index and Multilevel Monte Carlo, Multilevel Stochastic Collocation, Quasi Optimal Stochastic Collocation and Sparse Composite Collocation methods.
Collocation and Pattern Recognition Effects on System Failure Remediation
Trujillo, Anna C.; Press, Hayes N.
2007-01-01
Previous research found that operators prefer to have status, alerts, and controls located on the same screen. Unfortunately, that research was done with displays that were not designed specifically for collocation. In this experiment, twelve subjects evaluated two displays specifically designed for collocating system information against a baseline that consisted of dial status displays, a separate alert area, and a controls panel. These displays differed in the amount of collocation, pattern matching, and parameter movement compared to display size. During the data runs, subjects kept a randomly moving target centered on a display using a left-handed joystick and they scanned system displays to find a problem in order to correct it using the provided checklist. Results indicate that large parameter movement aided detection and then pattern recognition is needed for diagnosis but the collocated displays centralized all the information subjects needed, which reduced workload. Therefore, the collocated display with large parameter movement may be an acceptable display after familiarization because of the possible pattern recognition developed with training and its use.
Multi-Index Stochastic Collocation (MISC) for random elliptic PDEs
Haji Ali, Abdul Lateef
2016-01-06
In this work we introduce the Multi-Index Stochastic Collocation method (MISC) for computing statistics of the solution of a PDE with random data. MISC is a combination technique based on mixed differences of spatial approximations and quadratures over the space of random data. We propose an optimization procedure to select the most effective mixed differences to include in the MISC estimator: such optimization is a crucial step and allows us to build a method that, provided with sufficient solution regularity, is potentially more effective than other multi-level collocation methods already available in literature. We then provide a complexity analysis that assumes decay rates of product type for such mixed differences, showing that in the optimal case the convergence rate of MISC is only dictated by the convergence of the deterministic solver applied to a one dimensional problem. We show the effectiveness of MISC with some computational tests, comparing it with other related methods available in the literature, such as the Multi-Index and Multilevel Monte Carlo, Multilevel Stochastic Collocation, Quasi Optimal Stochastic Collocation and Sparse Composite Collocation methods.
de Raedt, H.A.; Michielsen, K.F L; Kole, J.S.; Figge, M.T
2003-01-01
We present a one-step algorithm that solves the Maxwell equations for systems with spatially varying permittivity and permeability by the Chebyshev method. We demonstrate that this algorithm may be orders of magnitude more efficient than current finite-difference time-domain (FDTD) algorithms.
Coghetto Roland
2016-01-01
In [21], Marco Riccardi formalized that ℝN-basis n is a basis (in the algebraic sense defined in [26]) of ℰTn${\\cal E}_T^n $ and in [20] he has formalized that ℰTn${\\cal E}_T^n $ is second-countable, we build (in the topological sense defined in [23]) a denumerable base of ℰTn${\\cal E}_T^n $.
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Coghetto Roland
2016-06-01
Full Text Available In [21], Marco Riccardi formalized that ℝN-basis n is a basis (in the algebraic sense defined in [26] of ℰTn${\\cal E}_T^n $ and in [20] he has formalized that ℰTn${\\cal E}_T^n $ is second-countable, we build (in the topological sense defined in [23] a denumerable base of ℰTn${\\cal E}_T^n $.
AIRS-CloudSat cloud mask and radar reflectivities collocation indexes V3.1
National Aeronautics and Space Administration — This is AIRS-AMSU-CloudSat collocation indexes, in ASCII format. These data map CloudSat profile indexes to the collocated AMSU field of views, and AIRS IR...
A Simulation Study of the Overdetermined Geodetic Boundary Value Problem Using Collocation
1989-03-01
VALUE PROBLEM 2.1 Fundamental principles of collocation The method of collocation was introduced in geodesy through Moritz ’ work of gravity anomaly...set of given linear functionals ( Moritz , 1980, p. 85). This definition is consistent with two aspects of collocation : the prediction aspect where...is given by Moritz (1980). For the sake of completeness the general least- squares collocation model with parameters is briefly described here in
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Etemad Roghayeh
2017-01-01
Full Text Available This paper is concerned with two variants of the reverse selective center location problems on tree graphs under the Hamming and Chebyshev cost norms in which the customers are existing on a selective subset of the vertices of the underlying tree. The first model aims to modify the edge lengths within a given modification budget until a prespecified facility location becomes as close as possible to the customer points. However, the other model wishes to change the edge lengths at the minimum total cost so that the distances between the prespecified facility and the customers satisfy a given upper bound. We develop novel combinatorial algorithms with polynomial time complexities for deriving the optimal solutions of the problems under investigation.
Presenting collocates in a dictionary of computing and the Internet according to user needs
DEFF Research Database (Denmark)
Leroyer, Patrick; L'Homme, Marie-Claude; Jousse, Anne-Laure
2011-01-01
This paper presents a novel method for organizing and presenting collocations in a specialized dictionary of computing and the Internet. This work is undertaken in order to meet a specific user need, i.e. that of searching for a collocate (or a short list of collocates) that expresses a specific...
Collocational Strategies of Arab Learners of English: A Study in Lexical Semantics.
Muhammad, Raji Zughoul; Abdul-Fattah, Hussein S.
Arab learners of English encounter a serious problem with collocational sequences. The present study purports to determine the extent to which university English language majors can use English collocations properly. A two-form translation test of 16 Arabic collocations was administered to both graduate and undergraduate students of English. The…
Gablasova, Dana; Brezina, Vaclav; McEnery, Tony
2017-01-01
This article focuses on the use of collocations in language learning research (LLR). Collocations, as units of formulaic language, are becoming prominent in our understanding of language learning and use; however, while the number of corpus-based LLR studies of collocations is growing, there is still a need for a deeper understanding of factors…
Examining Second Language Receptive Knowledge of Collocation and Factors That Affect Learning
Nguyen, Thi My Hang; Webb, Stuart
2017-01-01
This study investigated Vietnamese EFL learners' knowledge of verb-noun and adjective-noun collocations at the first three 1,000 word frequency levels, and the extent to which five factors (node word frequency, collocation frequency, mutual information score, congruency, and part of speech) predicted receptive knowledge of collocation. Knowledge…
guessing verb-adverb collocations: arab efl learners' use of ...
African Journals Online (AJOL)
user
tate dictionary users' correct use of collocations. Whereas knowledge of the meaning of the stimuli was found to be a significant contributing ...... i.e. the type Sinclair (1987) called random 'co-occurrences' (see also Siyanova and Schmitt 2008). Heidler (2011) found that international undergraduates' use of adverbs was ...
Genre-related temporary collocations in english discourse
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Е В Терехова
2009-09-01
Full Text Available The paper discusses genre-related temporary collocations (TC. It also provides genre definition, analyzes different genre-related TC which are used in TV speeches, diplomatic texts, and English media texts. TC implementing in genre-related texts, preferential reinterpretation criteria which characterize terminology formation, their interpretation, and their translation from English into Russian is considered.
Meshfree Local Radial Basis Function Collocation Method with Image Nodes
Energy Technology Data Exchange (ETDEWEB)
Baek, Seung Ki; Kim, Minjae [Pukyong National University, Busan (Korea, Republic of)
2017-07-15
We numerically solve two-dimensional heat diffusion problems by using a simple variant of the meshfree local radial-basis function (RBF) collocation method. The main idea is to include an additional set of sample nodes outside the problem domain, similarly to the method of images in electrostatics, to perform collocation on the domain boundaries. We can thereby take into account the temperature profile as well as its gradients specified by boundary conditions at the same time, which holds true even for a node where two or more boundaries meet with different boundary conditions. We argue that the image method is computationally efficient when combined with the local RBF collocation method, whereas the addition of image nodes becomes very costly in case of the global collocation. We apply our modified method to a benchmark test of a boundary value problem, and find that this simple modification reduces the maximum error from the analytic solution significantly. The reduction is small for an initial value problem with simpler boundary conditions. We observe increased numerical instability, which has to be compensated for by a sufficient number of sample nodes and/or more careful parameter choices for time integration.
A Line-Tau Collocation Method for Partial Differential Equations ...
African Journals Online (AJOL)
This paper deals with the numerical solution of second order linear partial differential equations with the use of the method of lines coupled with the tau collocation method. The method of lines is used to convert the partial differential equation (PDE) to a sequence of ordinary differential equations (ODEs) which is then ...
Teachability of collocations: The role of word frequency counts ...
African Journals Online (AJOL)
However, in both collocations types, only upper-intermediate and low-advanced students mastered the 2 000-word band. We therefore ... students and only exceed the 2 000-word band from the upper-intermediate learning stage onwards, a suggestion in line with Nation's (2006) discussion on how to teach vocabulary.
First-year university students' productive knowledge of collocations
African Journals Online (AJOL)
though collocations are not the only aspect of productive vocabulary, researchers agree that they constitute an important part .... the ability to use a word when compelled to do so by a teacher or researcher, whether in an unconstrained .... Keeping in mind Nation's (1990) view that students need at least a productive size of ...
Lexical richness and collocational competence in second-language writing
Vedder, I.; Benigno, V.
2016-01-01
In this article we report on an experiment set up to investigate lexical richness and collocational competence in the written production of 39 low-intermediate and intermediate learners of Italian L2. Lexical richness was assessed by means of a lexical profiling method inspired by Laufer and Nation
Visualisation of collocational preferences for near-synonym ...
African Journals Online (AJOL)
An advantage of the graphs is that they allow lexicographers to spot similarities and dif-ferences in collocational preference of several words in a single diagram. ... form of data presentation to avoid information overload which arises when lexicographers prepare synonym essays for productively-oriented dictionaries.
Collocation analysis for UMLS knowledge-based word sense disambiguation.
Jimeno-Yepes, Antonio; McInnes, Bridget T; Aronson, Alan R
2011-06-09
The effectiveness of knowledge-based word sense disambiguation (WSD) approaches depends in part on the information available in the reference knowledge resource. Off the shelf, these resources are not optimized for WSD and might lack terms to model the context properly. In addition, they might include noisy terms which contribute to false positives in the disambiguation results. We analyzed some collocation types which could improve the performance of knowledge-based disambiguation methods. Collocations are obtained by extracting candidate collocations from MEDLINE and then assigning them to one of the senses of an ambiguous word. We performed this assignment either using semantic group profiles or a knowledge-based disambiguation method. In addition to collocations, we used second-order features from a previously implemented approach.Specifically, we measured the effect of these collocations in two knowledge-based WSD methods. The first method, AEC, uses the knowledge from the UMLS to collect examples from MEDLINE which are used to train a Naïve Bayes approach. The second method, MRD, builds a profile for each candidate sense based on the UMLS and compares the profile to the context of the ambiguous word.We have used two WSD test sets which contain disambiguation cases which are mapped to UMLS concepts. The first one, the NLM WSD set, was developed manually by several domain experts and contains words with high frequency occurrence in MEDLINE. The second one, the MSH WSD set, was developed automatically using the MeSH indexing in MEDLINE. It contains a larger set of words and covers a larger number of UMLS semantic types. The results indicate an improvement after the use of collocations, although the approaches have different performance depending on the data set. In the NLM WSD set, the improvement is larger for the MRD disambiguation method using second-order features. Assignment of collocations to a candidate sense based on UMLS semantic group profiles is more
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endang lestariana
2017-07-01
Full Text Available Present-day, an attractive issue related to language producing phenomenon from source language into target language was frequently happened. Translating collocation in undergraduate thesis abstract often faced the problems. Consequently, the first language acquisition influenced the students’ translating production. The students could not achieve the same competence of second language acquisition. Therefore, the present study tried to investigate the students’ translating collocation problem. The primary aim of this research was to describe the output of translating collocation on undergraduate thesis abstract of the English Education Study Program of STAIN Jurai Siwo Metro Lampung. This research applied qualitative research in the form of embedded research. In collecting the data applied documentation and interview. Purposive sampling was used as the technique for choosing the participant. The participants of this research were ten students who had written undergraduate thesis abstract of the English Education Study Program of STAIN Jurai Siwo Metro Lampung in the academic year of 2013/2014 M. The research findings showed that the Indonesian collocation was translated into English collocation on undergraduate thesis abstract consisted of the incorrect collocation 74,45% and correct collocation 25,55%. There were two types of incorrect collocation namely lexical collocation 89,01% and grammatical collocation 10,99%. Moreover, problems that were faced by the student in translating collocation were caused by approximation, ignorance of the rule restriction, overgeneralization, interlingual transfer, false concept of hypothesized, the use of synonym, word coinage and the meaning of lexical item. The solutions of this problem were the usage of appropriate Collocation Dictionary and learned deeply about collocation. Therefore, the students should be more active to increase their English proficiency and the lecturers
Leonardi, Magda
1977-01-01
Discusses the importance of two Firthian themes for language teaching. The first theme, "Restricted Languages," concerns the "microlanguages" of every language (e.g., literary language, scientific, etc.). The second theme, "Collocation," shows that equivalent words in two languages rarely have the same position in…
Kaustubh Gaikwad; Mahesh Chavan
2016-01-01
ASIC Chips and Digital Signal Processors are generally used for implementing digital filters. Now days the advanced technologies lead to use of field programmable Gate Array (FPGA) for the implementation of Digital Filters.The present paper deals with Design and Implementation of Digital IIR Chebyshev type II filter using Xilinx System Generator. The Quantization and Overflow are main crucial parameters while designing the filter on FPGA and that need to be consider for getting th...
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Chih-Hong Lin
2016-06-01
Full Text Available A permanent magnet (PM synchronous generator system driven by wind turbine (WT, connected with smart grid via AC-DC converter and DC-AC converter, are controlled by the novel recurrent Chebyshev neural network (NN and amended particle swarm optimization (PSO to regulate output power and output voltage in two power converters in this study. Because a PM synchronous generator system driven by WT is an unknown non-linear and time-varying dynamic system, the on-line training novel recurrent Chebyshev NN control system is developed to regulate DC voltage of the AC-DC converter and AC voltage of the DC-AC converter connected with smart grid. Furthermore, the variable learning rate of the novel recurrent Chebyshev NN is regulated according to discrete-type Lyapunov function for improving the control performance and enhancing convergent speed. Finally, some experimental results are shown to verify the effectiveness of the proposed control method for a WT driving a PM synchronous generator system in smart grid.
RBF Multiscale Collocation for Second Order Elliptic Boundary Value Problems
Farrell, Patricio
2013-01-01
In this paper, we discuss multiscale radial basis function collocation methods for solving elliptic partial differential equations on bounded domains. The approximate solution is constructed in a multilevel fashion, each level using compactly supported radial basis functions of smaller scale on an increasingly fine mesh. On each level, standard symmetric collocation is employed. A convergence theory is given, which builds on recent theoretical advances for multiscale approximation using compactly supported radial basis functions. We are able to show that the convergence is linear in the number of levels. We also discuss the condition numbers of the arising systems and the effect of simple, diagonal preconditioners, now proving rigorously previous numerical observations. © 2013 Society for Industrial and Applied Mathematics.
Variational collocation for systems of coupled anharmonic oscillators
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal DIaz del Castillo 340, Colima (Mexico); Fernandez, Francisco M [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Diag. 113 y 64 (S/N), Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2010-04-15
By means of a collocation approach based on little sinc functions (LSF), we obtain accurate eigenvalues and eigenfunctions of the stationary Schroedinger equation for systems of coupled oscillators. Adjustable parameters introduced by means of scaling and rotation of the coordinates improve the rate of convergence of the approach. A careful comparison with the results published earlier by other authors shows the advantages of the present approach.
A variational sinc collocation method for strong-coupling problems
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal Diaz del Castillo 340, Colima (Mexico)
2006-06-02
We have devised a variational sinc collocation method (VSCM) which can be used to obtain accurate numerical solutions to many strong-coupling problems. Sinc functions with an optimal grid spacing are used to solve the linear and nonlinear Schroedinger equations and a lattice {phi}{sup 4} model in (1 + 1). Our results indicate that errors decrease exponentially with the number of grid points and that a limited numerical effort is needed to reach high precision. (letter to the editor)
Numerical simulation of GEW equation using RBF collocation method
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Hamid Panahipour
2012-08-01
Full Text Available The generalized equal width (GEW equation is solved numerically by a meshless method based on a global collocation with standard types of radial basis functions (RBFs. Test problems including propagation of single solitons, interaction of two and three solitons, development of the Maxwellian initial condition pulses, wave undulation and wave generation are used to indicate the efficiency and accuracy of the method. Comparisons are made between the results of the proposed method and some other published numerical methods.
Friedmann's equations in all dimensions and Chebyshev's theorem
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Chen, Shouxin [Institute of Contemporary Mathematics, School of Mathematics and Statistics, Henan University, Kaifeng, Henan 475004 (China); Gibbons, Gary W. [D.A.M.T.P., University of Cambridge, Cambridge CB3 0WA (United Kingdom); Li, Yijun [School of Mathematics and Statistics, Henan University, Kaifeng, Henan 475004 (China); Yang, Yisong, E-mail: chensx@henu.edu.cn, E-mail: gwg1@damtp.cam.ac.uk, E-mail: liyijun@henu.edu.cn, E-mail: yisongyang@nyu.edu [Department of Mathematics, Polytechnic School, New York University, Brooklyn, New York 11201, U.S.A (United States)
2014-12-01
This short but systematic work demonstrates a link between Chebyshev's theorem and the explicit integration in cosmological time t and conformal time η of the Friedmann equations in all dimensions and with an arbitrary cosmological constant Λ. More precisely, it is shown that for spatially flat universes an explicit integration in t may always be carried out, and that, in the non-flat situation and when Λ is zero and the ratio w of the pressure and energy density in the barotropic equation of state of the perfect-fluid universe is rational, an explicit integration may be carried out if and only if the dimension n of space and w obey some specific relations among an infinite family. The situation for explicit integration in η is complementary to that in t. More precisely, it is shown in the flat-universe case with Λ ≠ 0 that an explicit integration in η can be carried out if and only if w and n obey similar relations among a well-defined family which we specify, and that, when Λ = 0, an explicit integration can always be carried out whether the space is flat, closed, or open. We also show that our method may be used to study more realistic cosmological situations when the equation of state is nonlinear.
Kopeliovich, V. B.
2017-01-01
The angular dependence of the cumulative particles production off nuclei near the kinematical boundary for multistep process is defined by characteristic polynomials in angular variables, describing spatial momenta of the particles in intermediate states. Physical argumentation, exploring the small phase space method, leads to the appearance of equations for the polynomials in cos(θ/N), where θ is the polar angle defining the momentum of final (cumulative) particle, the integer N being the number of interactions. The recurrent relations between polynomials with different N and their factorization properties are derived, the connection of these polynomials with known in mathematics Chebyshev polynomials of 2-d kind is established. As a result, differential cross section of the cumulative particle production has characteristic behaviour dσ ∼ 1/\\sqrt {π - θ } near the strictly backward direction (θ ∼ π, the backward focusing effect). Such behaviour takes place for any multiplicity of the interaction, beginning with n = 3, elastic or inelastic (with resonance excitations in intermediate states) and can be called the nuclear glory phenomenon.
Energy Technology Data Exchange (ETDEWEB)
Spata, Michael [Old Dominion Univ., Norfolk, VA (United States)
2012-08-01
An experiment was conducted at Jefferson Lab's Continuous Electron Beam Accelerator Facility to develop a beam-based technique for characterizing the extent of the nonlinearity of the magnetic fields of a beam transport system. Horizontally and vertically oriented pairs of air-core kicker magnets were simultaneously driven at two different frequencies to provide a time-dependent transverse modulation of the beam orbit relative to the unperturbed reference orbit. Fourier decomposition of the position data at eight different points along the beamline was then used to measure the amplitude of these frequencies. For a purely linear transport system one expects to find solely the frequencies that were applied to the kickers with amplitudes that depend on the phase advance of the lattice. In the presence of nonlinear fields one expects to also find harmonics of the driving frequencies that depend on the order of the nonlinearity. Chebyshev polynomials and their unique properties allow one to directly quantify the magnitude of the nonlinearity with the minimum error. A calibration standard was developed using one of the sextupole magnets in a CEBAF beamline. The technique was then applied to a pair of Arc 1 dipoles and then to the magnets in the Transport Recombiner beamline to measure their multipole content as a function of transverse position within the magnets.
Zou, An-Min; Dev Kumar, Krishna; Hou, Zeng-Guang
2010-09-01
This paper investigates the problem of output feedback attitude control of an uncertain spacecraft. Two robust adaptive output feedback controllers based on Chebyshev neural networks (CNN) termed adaptive neural networks (NN) controller-I and adaptive NN controller-II are proposed for the attitude tracking control of spacecraft. The four-parameter representations (quaternion) are employed to describe the spacecraft attitude for global representation without singularities. The nonlinear reduced-order observer is used to estimate the derivative of the spacecraft output, and the CNN is introduced to further improve the control performance through approximating the spacecraft attitude motion. The implementation of the basis functions of the CNN used in the proposed controllers depends only on the desired signals, and the smooth robust compensator using the hyperbolic tangent function is employed to counteract the CNN approximation errors and external disturbances. The adaptive NN controller-II can efficiently avoid the over-estimation problem (i.e., the bound of the CNNs output is much larger than that of the approximated unknown function, and hence, the control input may be very large) existing in the adaptive NN controller-I. Both adaptive output feedback controllers using CNN can guarantee that all signals in the resulting closed-loop system are uniformly ultimately bounded. For performance comparisons, the standard adaptive controller using the linear parameterization of spacecraft attitude motion is also developed. Simulation studies are presented to show the advantages of the proposed CNN-based output feedback approach over the standard adaptive output feedback approach.
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Azizov Taljat
2017-01-01
Full Text Available The article shows the influence of torsional rigidity of reinforced concrete elements on the spatial work of bridges, overlappings, building frames and other complex statically indeterminate systems. It is shown that the determination of torsional stiffnesses by the existing methods assumes the obligatory presence of spatial spiral cracks, and torsional stiffness in the presence of normal cracks is not investigated. A method for determining the torsional rigidity of reinforced concrete elements is described in the presence of normal cracks in them. It is shown that this approach allows calculating the torsion of reinforced concrete elements of any cross-section and taking into account the nonlinear properties of concrete. The article also describes the use of approximation methods, in particular, the apparatus of the best Chebyshev approximation. In Table 2, the displacements obtained as a result of the approximation with the displacements obtained directly from the calculations using the Lira software using volumetric finite elements are compared. In column 6 of the table, the displacement values obtained by software package (Lira software and in column 7, the displacements obtained on the basis of approximation in the Matlab environment are given.
Chebyshev Bandpass Filter Using Resonator of Tunable Active Capacitor and Inductor
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Yu Wang
2017-01-01
Full Text Available A classic second-order coupled-capacitor Chebyshev bandpass filter using resonator of tunable active capacitor and inductor is presented. The low cost and small size of CMOS active components make the bandpass filter (BPF attractive in fully integrated CMOS applications. The tunable active capacitor is designed to compensate active inductor’s resistance for resistive match in the resonator. In many design cases, more than 95% resistive loss is cancelled. Meanwhile, adjusting design parameter of the active component provides BPF tunability in center frequency, pass band, and pass band gain. Designed in 1.8 V 180 nanometer CMOS process, the BPF has a tuning frequency range of 758–864 MHz, a controllable pass band of 7.1–65.9 MHz, a quality factor Q of 12–107, a pass band gain of 6.5–18.1 dB, and a stopband rejection of 38–50 dB.
Vyas, Bhargav Y; Das, Biswarup; Maheshwari, Rudra Prakash
2016-08-01
This paper presents the Chebyshev neural network (ChNN) as an improved artificial intelligence technique for power system protection studies and examines the performances of two ChNN learning algorithms for fault classification of series compensated transmission line. The training algorithms are least-square Levenberg-Marquardt (LSLM) and recursive least-square algorithm with forgetting factor (RLSFF). The performances of these algorithms are assessed based on their generalization capability in relating the fault current parameters with an event of fault in the transmission line. The proposed algorithm is fast in response as it utilizes postfault samples of three phase currents measured at the relaying end corresponding to half-cycle duration only. After being trained with only a small part of the generated fault data, the algorithms have been tested over a large number of fault cases with wide variation of system and fault parameters. Based on the studies carried out in this paper, it has been found that although the RLSFF algorithm is faster for training the ChNN in the fault classification application for series compensated transmission lines, the LSLM algorithm has the best accuracy in testing. The results prove that the proposed ChNN-based method is accurate, fast, easy to design, and immune to the level of compensations. Thus, it is suitable for digital relaying applications.
Wei, Yunxia; Chen, Yanping; Shi, Xiulian; Zhang, Yuanyuan
2016-01-01
We present in this paper the convergence properties of Jacobi spectral collocation method when used to approximate the solution of multidimensional nonlinear Volterra integral equation. The solution is sufficiently smooth while the source function and the kernel function are smooth. We choose the Jacobi-Gauss points associated with the multidimensional Jacobi weight function [Formula: see text] (d denotes the space dimensions) as the collocation points. The error analysis in [Formula: see text]-norm and [Formula: see text]-norm theoretically justifies the exponential convergence of spectral collocation method in multidimensional space. We give two numerical examples in order to illustrate the validity of the proposed Jacobi spectral collocation method.
Fully Consistent SIMPLE-Like Algorithms on Collocated Grids
DEFF Research Database (Denmark)
Kolmogorov, Dmitry; Shen, Wen Zhong; Sørensen, Niels N.
2015-01-01
To increase the convergence rate of SIMPLE-like algorithms on collocated grids, a compatibility condition between mass flux interpolation methods and SIMPLE-like algorithms is presented. Results of unsteady flow computations show that the SIMPLEC algorithm, when obeying the compatibility condition......, may obtain up to 35% higher convergence rate as compared to the standard SIMPLEC algorithm. Two new interpolation methods, fully compatible with the SIMPLEC algorithm, are presented and compared with some existing interpolation methods, including the standard methods of Choi [9] and Shen et al. [8...
Benchmarking the Collocation Stand-Alone Library and Toolkit (CSALT)
Hughes, Steven; Knittel, Jeremy; Shoan, Wendy; Kim, Youngkwang; Conway, Claire; Conway, Darrel J.
2017-01-01
This paper describes the processes and results of Verification and Validation (VV) efforts for the Collocation Stand Alone Library and Toolkit (CSALT). We describe the test program and environments, the tools used for independent test data, and comparison results. The VV effort employs classical problems with known analytic solutions, solutions from other available software tools, and comparisons to benchmarking data available in the public literature. Presenting all test results are beyond the scope of a single paper. Here we present high-level test results for a broad range of problems, and detailed comparisons for selected problems.
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Somayeh Nemati
2016-11-01
Full Text Available In this paper, we consider the second-kind Chebyshev polynomials (SKCPs for the numerical solution of the fractional optimal control problems (FOCPs. Firstly, an introduction of the fractional calculus and properties of the shifted SKCPs are given and then operational matrix of fractional integration is introduced. Next, these properties are used together with the Legendre-Gauss quadrature formula to reduce the fractional optimal control problem to solving a system of nonlinear algebraic equations that greatly simplifies the problem. Finally, some examples are included to confirm the efficiency and accuracy of the proposed method.
Gimme Context – towards New Domain-Specific Collocational Dictionaries
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Sylvana Krausse
2011-04-01
Full Text Available The days of traditional drudgery-filled lexicography are long gone. Fortunately today, computers help in the enormous task of storing and analysing language in order to condense and store the found information in the form of dictionaries. In this paper, the way from a corpus to a small domain-specific collocational dictionary will be described and thus exemplified based on the example of the domain-specific language of mining reclamation, which can be duplicated for other specific languages too. So far, domain-specific dictionaries are mostly rare as their creation is very labour- and thus cost-effective and all too often they are just a collection of terms plus translation without any information on how to use them in speech. Particular small domains which do not involve a lot of users have been disregarded by lexicographers as there is also always the question of how well it sells afterwards. Following this, I will describe the creation of a small collocational dictionary on mining reclamation language which is based on the consequent use of corpus information. It is relatively quick to realize in the design phase and is thought to provide the sort of linguistic information engineering experts need when they communicate in English or read specialist texts in the specific domain.
Lashmet, P. K.; Woodrow, P. T.
1975-01-01
Numerical instabilities often arise in the use of high-ordered collocation approximations for numerically solving parabolic partial differential equations. These problems may be reduced by formulations involving evaluation of collocation polynomials rather than combination of the polynomials into a power series. As an illustration, two formulations using shifted Legendre polynomials of order 26 and less are compared.
Towards a Learner Need-Oriented Second Language Collocation Writing Assistant
Ramos, Margarita Alonso; Carlini, Roberto; Codina-Filbà, Joan; Orol, Ana; Vincze, Orsolya; Wanner, Leo
2015-01-01
The importance of collocations, i.e. idiosyncratic binary word co-occurrences in the context of second language learning has been repeatedly emphasized by scholars working in the field. Some went even so far as to argue that "vocabulary learning is collocation learning" (Hausmann, 1984, p. 395). Empirical studies confirm this…
On the Effect of Gender and Years of Instruction on Iranian EFL Learners' Collocational Competence
Ganji, Mansoor
2012-01-01
This study investigates the Iranian EFL learners' Knowledge of Lexical Collocation at three academic levels: freshmen, sophomores, and juniors. The participants were forty three English majors doing their B.A. in English Translation studies in Chabahar Maritime University. They took a 50-item fill-in-the-blank test of lexical collocations. The…
A Newton-Picard collocation method for periodic solutions of delay differential equations
Verheyden, Koen; Lust, Kurt
This paper presents a collocation method with an iterative linear system solver to compute periodic solutions of a system of autonomous delay differential equations (DDEs). We exploit the equivalence of the linearized collocation system and the discretization of the linearized periodic boundary
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A.K. Parida
2016-09-01
Full Text Available In this paper Chebyshev polynomial functions based locally recurrent neuro-fuzzy information system is presented for the prediction and analysis of financial and electrical energy market data. The normally used TSK-type feedforward fuzzy neural network is unable to take the full advantage of the use of the linear fuzzy rule base in accurate input–output mapping and hence the consequent part of the rule base is made nonlinear using polynomial or arithmetic basis functions. Further the Chebyshev polynomial functions provide an expanded nonlinear transformation to the input space thereby increasing its dimension for capturing the nonlinearities and chaotic variations in financial or energy market data streams. Also the locally recurrent neuro-fuzzy information system (LRNFIS includes feedback loops both at the firing strength layer and the output layer to allow signal flow both in forward and backward directions, thereby making the LRNFIS mimic a dynamic system that provides fast convergence and accuracy in predicting time series fluctuations. Instead of using forward and backward least mean square (FBLMS learning algorithm, an improved Firefly-Harmony search (IFFHS learning algorithm is used to estimate the parameters of the consequent part and feedback loop parameters for better stability and convergence. Several real world financial and energy market time series databases are used for performance validation of the proposed LRNFIS model.
Verb-Noun Collocations in Written Discourse of Iranian EFL Learners
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Fatemeh Ebrahimi-Bazzaz
2015-07-01
Full Text Available When native speakers of English write, they employ both grammatical rules and collocations. Collocations are words that are present in the memory of native speakers as ready-made prefabricated chunks. Non-native speakers who wish to acquire native-like fluency should give appropriate attention to collocations in writing in order not to produce sentences that native speakers may consider odd. The present study tries to explore the use of verb-noun collocations in written discourse of English as foreign language (EFL among Iranian EFL learners from one academic year to the next in Iran. To measure the use of verb-noun collocations in written discourse, there was a 60-minute task of writing story based on a series of six pictures whereby for each picture, three verb-noun collocations were measured, and nouns were provided to limit the choice of collocations. The results of the statistical analysis of ANOVA for the research question indicated that there was a significant difference in the use of lexical verb-noun collocations in written discourse both between and within the four academic years. The results of a post hoc multiple comparison tests confirmed that the means are significantly different between the first year and the third and fourth years, between the second and the fourth, and between the third and the fourth academic year which indicate substantial development in verb-noun collocation proficiency. The vital implication is that the learners could use verb-noun collocations in productive skill of writing.
DEFF Research Database (Denmark)
Henriksen, Birgit; Westbrook, Pete
2017-01-01
and classifying collocations used by L2 speakers in advanced, domain-specific oral academic discourse. The main findings seem to suggest that to map an informant’s complete collocational use and to get an understanding of disciplinary differences, we need to not only take account of general, academic and domain......This study describes the English collocational use of non-native university teachers from two different disciplines lecturing in an English- medium instruction context at the University of Copenhagen (UCPH). The primary focus is on how we addressed the research challenges involved in identifying...
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Maryani Maryani
2012-01-01
Full Text Available Abstract: Frequent content words in a mini-corpus of 131 Indonesian children’s storybooks, which resulted in a corpus of 134, 320 words, were investigated. The result was used to identify what English collocations to teach first to Indonesian preschool children. The data were run through a collocation menu in MonoConc Pro, a corpus program. To identify the frequent collocations in the corpus, the preceding and following words from each frequent lemma were analyzed. All the data were calculated in terms of the whole corpus and normalized per 100,000 occurrences. The result showed that the children were already exposed to various collocations; however, it turned out that several English and Indonesian collocations were not similar in terms of syntax and morphology. Teachers cannot literally introduce those collocations to children. Key words: corpus, frequent collocation, content words
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Irena SRDANOVIĆ
2011-05-01
Full Text Available In this paper, we explore presence of collocational relations in the computer-assisted language learning systems and other language resources for the Japanese language, on one side, and, in the Japanese language learning textbooks and wordlists, on the other side. After introducing how important it is to learn collocational relations in a foreign language, we examine their coverage in the various learners’ resources for the Japanese language. We particularly concentrate on a few collocations at the beginner’s level, where we demonstrate their treatment across various resources. A special attention is paid to what is referred to as unpredictable collocations, which have a bigger foreign language learning-burden than the predictable ones.
Eren, K.
1980-01-01
The mathematical background in spectral analysis as applied to geodetic applications is summarized. The resolution (cut-off frequency) of the GEOS 3 altimeter data is examined by determining the shortest wavelength (corresponding to the cut-off frequency) recoverable. The data from some 18 profiles are used. The total power (variance) in the sea surface topography with respect to the reference ellipsoid as well as with respect to the GEM-9 surface is computed. A fast inversion algorithm for matrices of simple and block Toeplitz matrices and its application to least squares collocation is explained. This algorithm yields a considerable gain in computer time and storage in comparison with conventional least squares collocation. Frequency domain least squares collocation techniques are also introduced and applied to estimating gravity anomalies from GEOS 3 altimeter data. These techniques substantially reduce the computer time and requirements in storage associated with the conventional least squares collocation. Numerical examples given demonstrate the efficiency and speed of these techniques.
High-frequency collocations of nouns in research articles across eight disciplines
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Matthew Peacock
2012-04-01
Full Text Available This paper describes a corpus-based analysis of the distribution of the high-frequency collocates of abstract nouns in 320 research articles across eight disciplines: Chemistry, Computer Science, Materials Science, Neuroscience, Economics, Language and Linguistics, Management, and Psychology. Disciplinary variation was also examined – very little previous research seems to have investigated this. The corpus was analysed using WordSmith Tools. The 16 highest-frequency nouns across all eight disciplines were identified, followed by the highest-frequency collocates for each noun. Five disciplines showed over 50% variance from the overall results. Conclusions are that the differing patterns revealed are disciplinary norms and represent standard terminology within the disciplines arising from the topics discussed, research methods, and content of discussions. It is also concluded that the collocations are an important part of the meanings and functions of the nouns, and that this evidence of sharp discipline differences underlines the importance of discipline-specific collocation research.
An efficient spectral collocation algorithm for nonlinear Phi-four equations
National Research Council Canada - National Science Library
Bhrawy, Ali H; Assas, Laila M; Alghamdi, Mohammed A
2013-01-01
A Jacobi-Gauss-Lobatto collocation method is developed in this work to obtain spectral solutions for different versions of nonlinear time-dependent Phi-four equations subject to nonhomogeneous initial...
Communication Collocations of the Lexeme Geld in General and Business German
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Mirna Hocenski-Dreiseidl
2010-07-01
Full Text Available The authors aim to analyse and compare the lexeme Geld and its collocations on the grammatical and semantic levels in general and in business German. A special emphasis will be put on the importance of the communicative function that this lexeme and its collocations have in the language of banking. The paper also has a practical purpose. Its applicability in teaching is envisaged to improve the communicative competence of students of economics.
The Effects of Feedback Types on Learners’ Recognition of Lexical Collocations
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Abbas Ali Zarei
2016-03-01
Full Text Available This study investigated the effects of three types of feedback on Iranian EFL learners’ recognition of lexical collocations. 78 pre-intermediate students from among 90 were selected to participate in this study. A KET (Key English Test was used in order to homogenize them. A teacher-made pre-test including all 150 target lexical collocations was used to make sure that the students did not know the target lexical collocations beforehand. Then the participants were divided into three experimental groups. All groups received the same instruction during 10 sessions of treatment. However, they received different types of feedback. Each session, the teacher gave a handout including 15 English sentences to each student. There was one lexical collocation in each sentence which was written in parentheses. Students were asked to write 15 collocations within twenty minutes and then submit the paper to the teacher. Then the teacher underlined the errors and gave them back to the students. Students in group A received direct feedback from the teacher. Students in group B received indirect feedback and the last group received peer feedback on their collocational errors. At the end of the treatment, 30 multiple-choice items were used to test students’ recognition of lexical collocations. The result of One-Way ANOVA procedure revealed that the group that received indirect feedback had the best performance, followed closely by the group that received peer feedback. Students in direct feedback group had the lowest performance. The findings suggest that different types of feedback have different effects on EFL learners’ recognition of lexical collocations.
Carpenter, Mark H.; Fisher, Travis C.; Nielsen, Eric J.; Frankel, Steven H.
2013-01-01
Nonlinear entropy stability and a summation-by-parts framework are used to derive provably stable, polynomial-based spectral collocation methods of arbitrary order. The new methods are closely related to discontinuous Galerkin spectral collocation methods commonly known as DGFEM, but exhibit a more general entropy stability property. Although the new schemes are applicable to a broad class of linear and nonlinear conservation laws, emphasis herein is placed on the entropy stability of the compressible Navier-Stokes equations.
Translating Legal Collocations in Contract Agreements by Iraqi EFL Students-Translators
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Muntaha A. Abdulwahid
2017-01-01
Full Text Available Legal translation of contract agreements is a challenge to translators as it involves combining the literary translation with the technical terminological precision. In translating legal contract agreements, a legal translator must utilize the lexical or syntactic precision and, more importantly, the pragmatic awareness of the context. This will guarantee an overall communicative process and avoid inconsistency in legal translation. However, the inability of the translator to meet these two functions in translating the contract item not only affects the contractors’ comprehension of the contract item but also affects the parties’ contractual obligations. In light of this, the purpose of this study was to find out how legal collocations used in contract agreements are translated from Arabic into English by student-translators in terms of (1 purely technical, (2 semi-technical, and (3 everyday vocabulary collocations. For the data collection, a multiple-choice collocation test was used to be answered by 35 EFL Iraqi undergraduate translator-students to decide on the aspects of weaknesses and strengths of their translation, thus decide on the aspects of correction. The findings showed that these students had serious problems in translating legal collocations as they lack the linguistic knowledge and pragmatic awareness needed to achieve the legal meaning and effect. They were also unable to make a difference among the three categories of legal collocations, purely technical, semi-technical, and everyday vocabulary collocations. These students should be exposed to more legal translation practices to obtain the required experience needed for their future career.
Age of Acquisition Effects in Chinese EFL learners’ Delexicalized Verb and Collocation Acquisition
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Miao Haiyan
2015-05-01
Full Text Available This paper investigates age of acquisition (AoA effects and the acquisition of delexicalized verbs and collocations in Chinese EFL learners, and explores the underlying reasons from the connectionist model for these learners’ acquisition characteristics. The data were collected through a translation test consisted of delexialized verb information section and English-Chinese and Chinese-English collocation parts, aiming to focus on Chinese EFL learners’ receptive and productive abilities respectively. As Chinese EFL is a nationally classroom-based practice beginning from early primary school, the pedagogical value and different phases of acquisition are thus taken into consideration in designing the translation test. Research results show that the effects of AoA are significant not only in the learners’ acquisition of individual delexicalized verbs but also in delexicalized collocations. Although learners have long begun to learn delexicalized verbs, their production indicates that early learning does not guarantee total acquisition, because their grasp of delexicalized verbs still stay at the senior middle school level. AoA effects significantly affect the recognition but not the production of collocations. Furthermore, a plateau effect occurs in learners’ acquisition of college-level delexicalized collocations, as their recognition and production have no processing advantages over earlier learned collocations.
On the foundation of collocation in physical geodesy
Bjerhammar, Arne
1982-12-01
The boundary value problem in physical geodesy is nowadays mostly presented with the use of an advanced stochastic model by Krarup-Moritz. This model includes a primary Gauss-Markov model and an adjoining Wiener-Hopf model. Degenerations of the Wiener-Hopf section are found in the singular auto-covariance matrix of the residuals. The non-singular inverse of the auto-covariance matrix of the signal is proved to be a generalized inverse of the singular auto-covariance matrix of the residuals. The joint model is given a non-stochastic evaluation for a case with spherical external surface (using a non-singular inverse). These findings will not prevent a successful application of the model, which has important merits, specially when using suitable a priori values for the stochastic parameters in the covariance functions. A method for quadratic unbiased estimation of a priori variances is presented in an introductory section. It is meant to be of value when using a solution of the boundary value problem with the collocation technique based on the classical Gauss-Markov solution. ( Bjerhammar (1963).)
Evaluating the performance of collocated optical disdrometers: LPM and PARSIVEL
Angulo-Martinez, Marta; Begueria, Santiago; Latorre, Borja
2017-04-01
Optical disdrometers are present weather sensors with the ability of providing integrate information of precipitation like intensity and reflectivity together with discrete information of drop sizes and velocities distribution (DSVD) of the hydrometeors crossing the laser beam sampling area. These sensors constitute a step forward in comparison with pluviometers towards a more complete characterisation of precipitation. Their use is spreading in many research fields for several applications. Understanding the differences from one another helps in the election of the sensor and point out limitations to be fixed in future versions. Four collocated optical disdrometers, two Laser Precipitation Monitors (LPM-Thies Clima) and two PARSIVEL, 1-minute measurements of 800 natural rainfall events were compared. Results showed a general agreement in integrated variables, like intensity or liquid water content. Nevertheless, comparing raw data, as the number of particles and DSVD, great differences were found. LPM generally measures more and smaller drops than PARSIVEL and this difference increases with rainfall intensity. These results may affect especially the reflectivity value every disdrometer provide. A complete description of the measurements obtained, quantifiying the differences is provided, indicating their possible sources.
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Saudin Saudin
2017-05-01
Full Text Available The important role of collocation in learners’ language proficiency has been acknowledged widely. In Systemic Functional Linguistics (SFL, collocation is known as one prominent member of the super-ordinate lexical cohesion, which contributes significantly to the textual coherence, together with grammatical cohesion and structural cohesion (Halliday & Hasan, 1985. Collocation is also viewed as the hallmark of truly advanced English learners since the higher the learners’ proficiency is, the more they tend to use collocation (Bazzaz & Samad, 2011; Hsu, 2007; Zhang, 1993. Further, knowledge of collocation is regarded as part of the native speakers’ communicative competence (Bazzaz & Samad, 2011; and lack of the knowledge is the most important sign of foreignness among foreign language learners (McArthur, 1992; McCarthy, 1990. Taking the importance of collocation into account, this study is aimed to shed light on Indonesian EFL learners’ levels of collocational competence. In the study, the collocational competence is restricted to v+n and adj+n of collocation but broken down into productive and receptive competence, about which little work has been done (Henriksen, 2013. For this purpose, 49 second-year students of an English department in a state polytechnic were chosen as the subjects. Two sets of tests (filling in the blanks and multiple-choice were administered to obtain the data of the subjects’ levels of productive and receptive competence and to gain information of which type was more problematic for the learners. The test instruments were designed by referring to Brashi’s (2006 test model, and Koya’s (2003. In the analysis of the data, interpretive-qualitative method was used primarily to obtain broad explanatory information. The data analysis showed that the scores of productive competence were lower than those of receptive competence in both v+n and adj+n collocation. The analysis also revealed that the scores of productive
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Maryani
2012-01-01
Full Text Available Frequent content words in a mini-corpus of 131 Indonesian children’s storybooks, which resulted in a corpus of 134, 320 words, were investigated. The result was used to identify what English collocations to teach first to Indonesian preschool children. The data were run through a collocation menu in MonoConc Pro, a corpus program. To identify the frequent collocations in the corpus, the preceding and following words from each frequent lemma were analyzed. All the data were calculated in terms of the whole corpus and normalized per 100,000 occurrences. The result showed that the children were already exposed to various collocations; however, it turned out that several English and Indonesian collocations were not similar in terms of syntax and morphology. Teachers cannot literally introduce those collocations to children.
Selvi, M Salai Mathi; Hariharan, G; Kannan, K
2017-12-01
A mathematical model of a reaction-diffusion within an entrapped-cell photobioreactor packed with gel granules containing immobilized photosynthetic bacterial cells is discussed. A theoretical model is based on a system of coupled nonlinear reaction-diffusion equations. In this research work, we have developed an efficient wavelet-based spectral approach for solving the proposed model. Analytical expressions for the concentration of substrate and product are established for all values of reaction-diffusion parameters using second kind Chebyshev wavelet method. The analytical results were also compared with Homotopy perturbation method (HPM) and Adomian decomposition method (ADM). Satisfactory agreement with ADM and HPM solutions is observed. Moreover, the use of Chebyshev wavelets is found to be simple, reliable, efficient, and computationally attractive.
Maryani Maryani
2012-01-01
Abstract: Frequent content words in a mini-corpus of 131 Indonesian children’s storybooks, which resulted in a corpus of 134, 320 words, were investigated. The result was used to identify what English collocations to teach first to Indonesian preschool children. The data were run through a collocation menu in MonoConc Pro, a corpus program. To identify the frequent collocations in the corpus, the preceding and following words from each frequent lemma were analyzed. All the data were calculate...
National Research Council Canada - National Science Library
Bhrawy, A. H; Assas, L. M; Alghamdi, M. A
2013-01-01
Since the collocation method approximates ordinary differential equations, partial differential equations, and integral equations in physical space, it is very easy to implement and adapt to various...
Impact of WhatsApp on Learning and Retention of Collocation Knowledge among Iranian EFL Learners
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Zahra Ashiyan
2016-10-01
Full Text Available During the recent technological years, language learning has been attempted to transform its path from the conventional methods to instrumental applications. Mobile phone provides people to reach and exchange information through chats (WhatsApp. It is a tool or mode that means the facilities are used for main purposes. The unique features of the application are its compatibility to exchange information, enhance communication and relationship. A mobile phone provides to download, upload and store learning materials and information files. The purpose of the current study was to investigate the use and effect of mobile applications such as WhatsApp on school work and out of school work. In this way, Oxford Placement Test (OPT was conducted among 80 learners in order to select intermediate EFL learners. In total, 60 participants whose scores were 70 or higher were elected as the intermediate level and were divided into experimental and control groups. In order to control the reliability of the collocation pretest, the test was pilot studied on 15 learners. Then, the pretest was conducted to measure the learner’s collocation knowledge in both of the groups. The experimental group frequently installed WhatsApp application in order to learning and practicing new collocations in order to learning and practicing new collocations, while the control group did not use any tool for learning them. An immediate posttest after the treatment was administered. The results in each group were statistically evaluated and the findings manifested that the experimental group who used WhatsApp application in learning collocation significantly outperformed the control group in posttest. Thus usage of WhatsApp application to acquire collocations can reinforce and enhance the process of collocations acquisition and it can guarantee retention of collocations. This study also prepares pedagogical implications for utilizing mobile application as an influential instrument
English collocations: A novel approach to teaching the language's last bastion
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Rafe S. Zaabalawi
2017-01-01
Full Text Available Collocations are a class of idiomatic expressions comprised of a sequence of words which, for mostly arbitrary reasons, occur together in a prescribed order. Collocations are not necessarily grammatical and/or cannot be generated through knowledge of rules or formulae. Therefore, they are often not easily mastered by EFL learners and typically only dealt with during the latter phase of second language apprenticeship. Literature has mostly examined the phenomenon of collocations from one of two perspectives. First, there are studies focusing on error analysis and contingent pedagogical advice. Second, there is research concerned with theory development; a genre associated with a specific methodological limitations. This study reports on data pertaining to a novel approach to learning collocations; one based on a learner's incidental discovery of such structures in written texts. Our research question is: will students who have been introduced to and practiced specific collocations in reading texts be inclined to naturally use such exemplars appropriately in novel/unfamiliar subsequent contexts? Findings have implications for EFL teachers and those concerned with curriculum development.
A two-level stochastic collocation method for semilinear elliptic equations with random coefficients
Energy Technology Data Exchange (ETDEWEB)
Chen, Luoping; Zheng, Bin; Lin, Guang; Voulgarakis, Nikolaos
2017-05-01
In this work, we propose a novel two-level discretization for solving semilinear elliptic equations with random coefficients. Motivated by the two-grid method for deterministic partial differential equations (PDEs) introduced by Xu, our two-level stochastic collocation method utilizes a two-grid finite element discretization in the physical space and a two-level collocation method in the random domain. In particular, we solve semilinear equations on a coarse mesh $\\mathcal{T}_H$ with a low level stochastic collocation (corresponding to the polynomial space $\\mathcal{P}_{P}$) and solve linearized equations on a fine mesh $\\mathcal{T}_h$ using high level stochastic collocation (corresponding to the polynomial space $\\mathcal{P}_p$). We prove that the approximated solution obtained from this method achieves the same order of accuracy as that from solving the original semilinear problem directly by stochastic collocation method with $\\mathcal{T}_h$ and $\\mathcal{P}_p$. The two-level method is computationally more efficient, especially for nonlinear problems with high random dimensions. Numerical experiments are also provided to verify the theoretical results.
Hyslop, Nicole P.; White, Warren H.
The Interagency Monitoring of Protected Visual Environments (IMPROVE) program is a cooperative measurement effort in the United States designed to characterize current visibility and aerosol conditions in scenic areas (primarily National Parks and Forests) and to identify chemical species and emission sources responsible for existing man-made visibility impairment. In 2003 and 2004, the IMPROVE network began operating collocated samplers at several sites to evaluate the precision of its aerosol measurements. This paper presents the precisions calculated from the collocated data according to the United States Environmental Protection Agency's guidelines Code of Federal Regulations [CFR, 1997. Revised requirements for designation of reference and equivalent methods for PM 2.5 and ambient air quality surveillance for particulate matter: final rule, 1997. Code of Federal Regulations. Part IV: Environmental Protection Agency, vol. 40 CFR Parts 53 and 58, pp. 71-72. Available from pdf>]. These values range from 4% for sulfate to 115% for the third elemental carbon fraction. Collocated precision tends to improve with increasing detection rates, is typically better when the analysis is performed on the whole filter instead of just a fraction of the filter, and is better for species that are predominantly in the smaller size fractions. The collocated precisions are also used to evaluate the accuracy of the uncertainty estimates that are routinely reported with the concentrations. For most species, the collocated precisions are worse than the precisions predicted by the reported uncertainties. These discrepancies suggest that some sources of uncertainty are not accounted for or have been underestimated.
Hu, Shou-Cun; Ji, Jiang-Hui
2017-12-01
In asteroid rendezvous missions, the dynamical environment near an asteroid’s surface should be made clear prior to launch of the mission. However, most asteroids have irregular shapes, which lower the efficiency of calculating their gravitational field by adopting the traditional polyhedral method. In this work, we propose a method to partition the space near an asteroid adaptively along three spherical coordinates and use Chebyshev polynomial interpolation to represent the gravitational acceleration in each cell. Moreover, we compare four different interpolation schemes to obtain the best precision with identical initial parameters. An error-adaptive octree division is combined to improve the interpolation precision near the surface. As an example, we take the typical irregularly-shaped near-Earth asteroid 4179 Toutatis to demonstrate the advantage of this method; as a result, we show that the efficiency can be increased by hundreds to thousands of times with our method. Our results indicate that this method can be applicable to other irregularly-shaped asteroids and can greatly improve the evaluation efficiency.
Chen, Weitian; Sica, Christopher T; Meyer, Craig H
2008-11-01
Off-resonance effects can cause image blurring in spiral scanning and various forms of image degradation in other MRI methods. Off-resonance effects can be caused by both B0 inhomogeneity and concomitant gradient fields. Previously developed off-resonance correction methods focus on the correction of a single source of off-resonance. This work introduces a computationally efficient method of correcting for B0 inhomogeneity and concomitant gradients simultaneously. The method is a fast alternative to conjugate phase reconstruction, with the off-resonance phase term approximated by Chebyshev polynomials. The proposed algorithm is well suited for semiautomatic off-resonance correction, which works well even with an inaccurate or low-resolution field map. The proposed algorithm is demonstrated using phantom and in vivo data sets acquired by spiral scanning. Semiautomatic off-resonance correction alone is shown to provide a moderate amount of correction for concomitant gradient field effects, in addition to B0 imhomogeneity effects. However, better correction is provided by the proposed combined method. The best results were produced using the semiautomatic version of the proposed combined method.
THE CASE FOR VERB-ADJECTIVE COLLOCATIONS: CORPUS-BASED ANALYSIS AND LEXICOGRAPHICAL TREATMENT
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Moisés Almela
2011-10-01
Full Text Available This article explores a type of co-occurrence pattern which cannot be adequately described by existing models of collocation, and for which combinatory dictionaries have yet failed to provide sufficient information. The phenomenon of “oblique inter-collocation”, as I propose to call it, is characterised by a concatenation of syntagmatic preferences which partially contravenes the habitual grammatical order of semantic selection. In particular, I will examine some of the effects which the verb cause exerts on the distribution of attributive adjectives in the context of specific noun classes. The procedure for detecting and describing patterns of oblique inter-collocation is illustrated by means of SketchEngine corpus query tools. Based on the data extracted from a large-scale corpus, this paper carries out a critical analysis of the micro-structure in Oxford Collocations Dictionary.
Shifted Jacobi spectral collocation method for solving two-sided fractional water wave models
Abdelkawy, M. A.; Alqahtani, Rubayyi T.
2017-01-01
This paper presents the spectral collocation technique to solve the two-sided fractional water wave models (TSF-WWMs). The shifted Jacobi-Gauss-Lobatto collocation (SJ-GL-C) and shifted Jacobi-Gauss-Radau collocation (SJ-GR-C) methods are developed to approximate the TSF-WWMs. The main idea in the novel algorithm is to reduce the TSF-WWM to a systems of algebraic equations. The applicability and accuracy of the present technique have been examined by the given numerical examples in this paper. By means of these numerical examples, we ensure that the present technique is a simple and very accurate numerical scheme for solving TSF-WWMs.
Testing knowledge of whole English collocations available for use in written production
DEFF Research Database (Denmark)
Revier, Robert Lee
2014-01-01
in the design of foreign language instruction and the development of teaching material. For these reasons, CONTRIX-2 was administered to a relatively large body of intermediate and advanced Danish learners of English, representing three levels of formal education. With respect to instrument validation...... collocation is in part a function of its semantic composition. One of the main objectives of the present research was to empirically investigate the validity of these assumptions. Thus, the CONTRIX test was developed with the objective of exploring first-hand whether it was at all possible to operationalize...... the development of Danish EFL learners’ productive knowledge of whole English collocations. Five empirical studies were designed to generate information that would shed light on the reliability and validity of the CONTRIX as a measure of collocation knowledge available for use in written production. Study 1...
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A. H. Bhrawy
2014-01-01
Full Text Available The shifted Jacobi-Gauss collocation (SJGC scheme is proposed and implemented to solve the fractional neutral functional-differential equations with proportional delays. The technique we have proposed is based upon shifted Jacobi polynomials with the Gauss quadrature integration technique. The main advantage of the shifted Jacobi-Gauss scheme is to reduce solving the generalized fractional neutral functional-differential equations to a system of algebraic equations in the unknown expansion. Reasonable numerical results are achieved by choosing few shifted Jacobi-Gauss collocation nodes. Numerical results demonstrate the accuracy, and versatility of the proposed algorithm.
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Winfried Auzinger
2006-01-01
Full Text Available We demonstrate that eigenvalue problems for ordinary differential equations can be recast in a formulation suitable for the solution by polynomial collocation. It is shown that the well-posedness of the two formulations is equivalent in the regular as well as in the singular case. Thus, a collocation code equipped with asymptotically correct error estimation and adaptive mesh selection can be successfully applied to compute the eigenvalues and eigenfunctions efficiently and with reliable control of the accuracy. Numerical examples illustrate this claim.
Preconditioning cubic spline collocation method by FEM and FDM for elliptic equations
Energy Technology Data Exchange (ETDEWEB)
Kim, Sang Dong [KyungPook National Univ., Taegu (Korea, Republic of)
1996-12-31
In this talk we discuss the finite element and finite difference technique for the cubic spline collocation method. For this purpose, we consider the uniformly elliptic operator A defined by Au := -{Delta}u + a{sub 1}u{sub x} + a{sub 2}u{sub y} + a{sub 0}u in {Omega} (the unit square) with Dirichlet or Neumann boundary conditions and its discretization based on Hermite cubic spline spaces and collocation at the Gauss points. Using an interpolatory basis with support on the Gauss points one obtains the matrix A{sub N} (h = 1/N).
Pereira, Lis; Manguilimotan, Erlyn; Matsumoto, Yuji
2016-01-01
One of the challenges of learning Japanese as a Second Language (JSL) is finding the appropriate word for a particular usage. To address this challenge, we developed a collocational aid designed to suggest more appropriate collocations in Japanese. In particular, we address the problem of generating and ranking noun and verb candidates for…
Chang, Yu-Chia; Chang, Jason S.; Chen, Hao-Jan; Liou, Hsien-Chin
2008-01-01
Previous work in the literature reveals that EFL learners were deficient in collocations that are a hallmark of near native fluency in learner's writing. Among different types of collocations, the verb-noun (V-N) one was found to be particularly difficult to master, and learners' first language was also found to heavily influence their collocation…
Developments in the implementation and use of least-squares collocation
DEFF Research Database (Denmark)
Tscherning, Carl Christian
2015-01-01
The method of Least-Squares Collocation (LSC) was developed in the 1960s based on theoretical advances by T. Krarup and H. Moritz. The method may be used for the determination of approximations to the anomalous gravity potential (T) and associated parameters like biases or tilts. All gravity field...
Spectral Collocation and FDTD Approaches for the Design of Focusung Grating Couplers
DEFF Research Database (Denmark)
Dridi, Kim; Dinesen, P.G.
1999-01-01
Theoretical and numerical investigations on sub-wavelength waveguide focusing grating couplers are presented. The analyses are based on two approaches, the spectral collocation method and the finite-difference time-domain method. The methods solve the full-vectorial time-domain Maxwell equations....
The Effect of Corpus-Based Activities on Verb-Noun Collocations in EFL Classes
Ucar, Serpil; Yükselir, Ceyhun
2015-01-01
This current study sought to reveal the impacts of corpus-based activities on verb-noun collocation learning in EFL classes. This study was carried out on two groups--experimental and control groups- each of which consists of 15 students. The students were preparatory class students at School of Foreign Languages, Osmaniye Korkut Ata University.…
Processing and Learning of Enhanced English Collocations: An Eye Movement Study
Choi, Sungmook
2017-01-01
Research to date suggests that textual enhancement may positively affect the learning of multiword combinations known as collocations, but may impair recall of unenhanced text. However, the attentional mechanisms underlying such effects remain unclear. In this study, 38 undergraduate students were divided into two groups: one read a text…
Estimation of amplitude of pulse signals by means of collocation in terms of Krakovian calculus
Fertner, Antoni
1982-10-01
A special type of digital filtering technique (i.e. least-squares collocation) as can be applied to nuclear radiation spectrometry is discussed. It extends the filtration process to noises with non-zero autocorrelation functions. Special properties of Krakovian calculus are used to contruct the algorithm for the determination of impulse amplitude.
A Stochastic Collocation Method for Elliptic Partial Differential Equations with Random Input Data
Babuška, Ivo
2010-01-01
This work proposes and analyzes a stochastic collocation method for solving elliptic partial differential equations with random coefficients and forcing terms. These input data are assumed to depend on a finite number of random variables. The method consists of a Galerkin approximation in space and a collocation in the zeros of suitable tensor product orthogonal polynomials (Gauss points) in the probability space, and naturally leads to the solution of uncoupled deterministic problems as in the Monte Carlo approach. It treats easily a wide range of situations, such as input data that depend nonlinearly on the random variables, diffusivity coefficients with unbounded second moments, and random variables that are correlated or even unbounded. We provide a rigorous convergence analysis and demonstrate exponential convergence of the “probability error” with respect to the number of Gauss points in each direction of the probability space, under some regularity assumptions on the random input data. Numerical examples show the effectiveness of the method. Finally, we include a section with developments posterior to the original publication of this work. There we review sparse grid stochastic collocation methods, which are effective collocation strategies for problems that depend on a moderately large number of random variables.
A stochastic collocation method for the second order wave equation with a discontinuous random speed
Motamed, Mohammad
2012-08-31
In this paper we propose and analyze a stochastic collocation method for solving the second order wave equation with a random wave speed and subjected to deterministic boundary and initial conditions. The speed is piecewise smooth in the physical space and depends on a finite number of random variables. The numerical scheme consists of a finite difference or finite element method in the physical space and a collocation in the zeros of suitable tensor product orthogonal polynomials (Gauss points) in the probability space. This approach leads to the solution of uncoupled deterministic problems as in the Monte Carlo method. We consider both full and sparse tensor product spaces of orthogonal polynomials. We provide a rigorous convergence analysis and demonstrate different types of convergence of the probability error with respect to the number of collocation points for full and sparse tensor product spaces and under some regularity assumptions on the data. In particular, we show that, unlike in elliptic and parabolic problems, the solution to hyperbolic problems is not in general analytic with respect to the random variables. Therefore, the rate of convergence may only be algebraic. An exponential/fast rate of convergence is still possible for some quantities of interest and for the wave solution with particular types of data. We present numerical examples, which confirm the analysis and show that the collocation method is a valid alternative to the more traditional Monte Carlo method for this class of problems. © 2012 Springer-Verlag.
A sparse collocation method for solving time-dependent HJB equations using multivariate B-splines
Govindarajan, N.; De Visser, C.C.; Krishnakumar, K.
2014-01-01
This paper presents a sparse collocation method for solving the time-dependent Hamilton–Jacobi–Bellman (HJB) equation associated with the continuous-time optimal control problem on a fixed, finite timehorizon with integral cost functional. Through casting the problem in a recursive framework using
DEFF Research Database (Denmark)
Henriksen, Birgit; Westbrook, Pete
2017-01-01
This study describes the English collocational use of non-native university teachers from two different disciplines lecturing in an English- medium instruction context at the University of Copenhagen (UCPH). The primary focus is on how we addressed the research challenges involved in identifying...
Usta, Fuat
2017-04-01
In conjunction with the development of fractional calculus, conformable derivatives and integrals has been widely used a number of scientific areas. In this talk, we provide a numerical scheme to solve Katugampola conformable fractional differential equations via radial basis function (RBF) collocation technique. In order to confirm our numerical scheme, we present some numerical experiments results.
The Role of Language for Thinking and Task Selection in EFL Learners' Oral Collocational Production
Wang, Hung-Chun; Shih, Su-Chin
2011-01-01
This study investigated how English as a foreign language (EFL) learners' types of language for thinking and types of oral elicitation tasks influence their lexical collocational errors in speech. Data were collected from 42 English majors in Taiwan using two instruments: (1) 3 oral elicitation tasks and (2) an inner speech questionnaire. The…
Reynolds, Barry Lee
2016-01-01
Lack of knowledge in the conventional usage of collocations in one's respective field of expertise cause Taiwanese students to produce academic writing that is markedly different than more competent writing. This is because Taiwanese students are first and foremost English as a Foreign language (EFL) readers and may have difficulties picking up on…
2010-10-01
... the standard number of new equipment cabinets for the technology involved, not to exceed four, or more... 47 Telecommunication 1 2010-10-01 2010-10-01 false Nationwide Programmatic Agreement for the Collocation of Wireless Antennas B Appendix B to Part 1 Telecommunication FEDERAL COMMUNICATIONS COMMISSION...
CSIR Research Space (South Africa)
Napier, JAL
2002-09-01
Full Text Available intensity factors to be solved directly at the crack edges. This is achieved by employing an enhanced edge collocation procedure. The limiting interpretation of the governing integral equations is discussed and two simple examples are presented to illustrate...
Strategies in Translating Collocations in Religious Texts from Arabic into English
Dweik, Bader S.; Shakra, Mariam M. Abu
2010-01-01
The present study investigated the strategies adopted by students in translating specific lexical and semantic collocations in three religious texts namely, the Holy Quran, the Hadith and the Bible. For this purpose, the researchers selected a purposive sample of 35 MA translation students enrolled in three different public and private Jordanian…
Investigation of Native Speaker and Second Language Learner Intuition of Collocation Frequency
Siyanova-Chanturia, Anna; Spina, Stefania
2015-01-01
Research into frequency intuition has focused primarily on native (L1) and, to a lesser degree, nonnative (L2) speaker intuitions about single word frequency. What remains a largely unexplored area is L1 and L2 intuitions about collocation (i.e., phrasal) frequency. To bridge this gap, the present study aimed to answer the following question: How…
Bates, Kevin R.; Daniels, Andrew D.; Scuseria, Gustavo E.
1998-01-01
We report a comparison of two linear-scaling methods which avoid the diagonalization bottleneck of traditional electronic structure algorithms. The Chebyshev expansion method (CEM) is implemented for carbon tight-binding calculations of large systems and its memory and timing requirements compared to those of our previously implemented conjugate gradient density matrix search (CG-DMS). Benchmark calculations are carried out on icosahedral fullerenes from C60 to C8640 and the linear scaling memory and CPU requirements of the CEM demonstrated. We show that the CPU requisites of the CEM and CG-DMS are similar for calculations with comparable accuracy.
Sokolova, L V; Cherkasova, A S
2015-01-01
Texts or words/pseudowords are often used as stimuli for human verbal activity research. Our study pays attention to decoding processes of grammatical constructions consisted of two-three words--collocations. Russian and English collocation sets without any narrative were presented to Russian-speaking students with different English language skill. Stimulus material had two types of collocations: paradigmatic and syntagmatic. 30 students (average age--20.4 ± 0.22) took part in the study, they were divided into two equal groups depending on their English language skill (linguists/nonlinguists). During reading brain bioelectrical activity of cortex has been registered from 12 electrodes in alfa-, beta-, theta-bands. Coherent function reflecting cooperation of different cortical areas during reading collocations has been analyzed. Increase of interhemispheric and diagonal connections while reading collocations in different languages in the group of students with low knowledge of foreign language testifies of importance of functional cooperation between the hemispheres. It has been found out that brain bioelectrical activity of students with good foreign language knowledge during reading of all collocation types in Russian and English is characterized by economization of nervous substrate resources compared to nonlinguists. Selective activation of certain cortical areas has also been observed (depending on the grammatical construction type) in nonlinguists group that is probably related to special decoding system which processes presented stimuli. Reading Russian paradigmatic constructions by nonlinguists entailed increase between left cortical areas, reading of English syntagmatic collocations--between right ones.
Wodraszka, Robert; Carrington, Tucker
2018-01-28
We present a new collocation-based multi-configuration time-dependent Hartree (MCTDH) approach for solving the Schrödinger equation required to compute (ro-)vibrational spectra, photodissociation cross sections, reaction rate constants, etc., that can be used with general potential energy surfaces. Collocation obviates the need for quadrature and facilitates using complicated kinetic energy operators. When the basis is good, the accuracy of collocation solutions to the Schrödinger equation is not sensitive to the choice of the collocation points. We test the collocation MCTDH equations we derive by showing that they can be used to compute accurate vibrational energy levels of CH 3 . It is possible to choose (imaginary) time-independent collocation points with which collocation-based MCTDH energies are accurate. It is therefore not necessary to calculate potential values many times during the propagation.
Energy Technology Data Exchange (ETDEWEB)
Mahmood, Asad, E-mail: asadmahmood_86@yahoo.com [Department of Mathematics and Statistics, International Islamic University, Islamabad 44000 (Pakistan); Chen, Bin [School of Environment, Beijing Normal University, Beijing 100875 (China); Ghaffari, Abuzar [Department of Mathematics and Statistics, International Islamic University, Islamabad 44000 (Pakistan)
2016-10-15
Hydromagnetic stagnation point flow and heat transfer over a nonlinearly stretching/shrinking surface of micropolar fluid is investigated. The numerical simulation is carried out through Chebyshev Spectral Newton Iterative Scheme, after transforming the governing equations into dimensionless boundary layer form. The dual solutions are reported for different values of magnetic and material parameters against the limited range of stretching/shrinking parameter. It is also noted that second solution only occurs for the negative values of stretching/shrinking parameter, whereas for the positive values unique solution exists. The effects of dimensionless parameters are described through graphs. It is seen that the flow and heat transfer rates can be controlled through the material parameter and magnetic force. - Highlights: • Constitutive equations of micropolar fluid and heat transfer are employed. • Magnetic effect on velocity and temperature profile of micropolar fluid is observed. • Dual solution is reported in the region of stagnation point flow. • A numerical technique i.e. Chebyshev Spectral Newton Iterative Scheme is applied to obtain the desire results.
Global collocation methods for approximation and the solution of partial differential equations
Solomonoff, A.; Turkel, E.
1986-01-01
Polynomial interpolation methods are applied both to the approximation of functions and to the numerical solutions of hyperbolic and elliptic partial differential equations. The derivative matrix for a general sequence of the collocation points is constructed. The approximate derivative is then found by a matrix times vector multiply. The effects of several factors on the performance of these methods including the effect of different collocation points are then explored. The resolution of the schemes for both smooth functions and functions with steep gradients or discontinuities in some derivative are also studied. The accuracy when the gradients occur both near the center of the region and in the vicinity of the boundary is investigated. The importance of the aliasing limit on the resolution of the approximation is investigated in detail. Also examined is the effect of boundary treatment on the stability and accuracy of the scheme.
Parallel algorithm of trigonometric collocation method in nonlinear dynamics of rotors
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Musil T.
2007-11-01
Full Text Available A parallel algorithm of a numeric procedure based on a method of trigonometric collocation is presented for investigating an unbalance response of a rotor supported by journal bearings. After a condensation process the trigonometric collocation method results in a set of nonlinear algebraic equations which is solved by the Newton-Raphson method. The order of the set is proportional to the number of nonlinear bearing coordinates and terms of the finite Fourier series. The algorithm, realized in the MATLAB parallel computing environment (DCT/DCE, uses message passing technique for interacting among processes on nodes of a parallel computer. This technique enables portability of the source code both on parallel computers with distributed and shared memory. Tests, made on a Beowulf cluster and a symmetric multiprocessor, have revealed very good speed-up and scalability of this algorithm.
A Sparse Stochastic Collocation Technique for High-Frequency Wave Propagation with Uncertainty
Malenova, G.
2016-09-08
We consider the wave equation with highly oscillatory initial data, where there is uncertainty in the wave speed, initial phase, and/or initial amplitude. To estimate quantities of interest related to the solution and their statistics, we combine a high-frequency method based on Gaussian beams with sparse stochastic collocation. Although the wave solution, uϵ, is highly oscillatory in both physical and stochastic spaces, we provide theoretical arguments for simplified problems and numerical evidence that quantities of interest based on local averages of |uϵ|2 are smooth, with derivatives in the stochastic space uniformly bounded in ϵ, where ϵ denotes the short wavelength. This observable related regularity makes the sparse stochastic collocation approach more efficient than Monte Carlo methods. We present numerical tests that demonstrate this advantage.
A space-time spectral collocation algorithm for the variable order fractional wave equation.
Bhrawy, A H; Doha, E H; Alzaidy, J F; Abdelkawy, M A
2016-01-01
The variable order wave equation plays a major role in acoustics, electromagnetics, and fluid dynamics. In this paper, we consider the space-time variable order fractional wave equation with variable coefficients. We propose an effective numerical method for solving the aforementioned problem in a bounded domain. The shifted Jacobi polynomials are used as basis functions, and the variable-order fractional derivative is described in the Caputo sense. The proposed method is a combination of shifted Jacobi-Gauss-Lobatto collocation scheme for the spatial discretization and the shifted Jacobi-Gauss-Radau collocation scheme for temporal discretization. The aforementioned problem is then reduced to a problem consists of a system of easily solvable algebraic equations. Finally, numerical examples are presented to show the effectiveness of the proposed numerical method.
The convergence problem of collocation solutions in the framework of the stochastic interpretation
Sansò, F.; Venuti, G.
2011-01-01
The problem of the convergence of the collocation solution to the true gravity field was defined long ago (Tscherning in Boll Geod Sci Affini 39:221-252, 1978) and some results were derived, in particular by Krarup (Boll Geod Sci Affini 40:225-240, 1981). The problem is taken up again in the context of the stochastic interpretation of collocation theory and some new results are derived, showing that, when the potential T can be really continued down to a Bjerhammar sphere, we have a quite general convergence property in the noiseless case. When noise is present in data, still reasonable convergence results hold true. "Democrito che 'l mondo a caso pone" "Democritus who made the world stochastic" Dante Alighieri, La Divina Commedia, Inferno, IV - 136
Spectral Shifted Jacobi Tau and Collocation Methods for Solving Fifth-Order Boundary Value Problems
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A. H. Bhrawy
2011-01-01
Full Text Available We have presented an efficient spectral algorithm based on shifted Jacobi tau method of linear fifth-order two-point boundary value problems (BVPs. An approach that is implementing the shifted Jacobi tau method in combination with the shifted Jacobi collocation technique is introduced for the numerical solution of fifth-order differential equations with variable coefficients. The main characteristic behind this approach is that it reduces such problems to those of solving a system of algebraic equations which greatly simplify the problem. Shifted Jacobi collocation method is developed for solving nonlinear fifth-order BVPs. Numerical examples are performed to show the validity and applicability of the techniques. A comparison has been made with the existing results. The method is easy to implement and gives very accurate results.
Numerical treatment of Hunter Saxton equation using cubic trigonometric B-spline collocation method
Hashmi, M. S.; Awais, Muhammad; Waheed, Ammarah; Ali, Qutab
2017-09-01
In this article, authors proposed a computational model based on cubic trigonometric B-spline collocation method to solve Hunter Saxton equation. The nonlinear second order partial differential equation arises in modeling of nematic liquid crystals and describes some aspects of orientation wave. The problem is decomposed into system of linear equations using cubic trigonometric B-spline collocation method with quasilinearization. To show the efficiency of the proposed method, two numerical examples have been tested for different values of t. The results are described using error tables and graphs and compared with the results existed in literature. It is evident that results are in good agreement with analytical solution and better than Arbabi, Nazari, and Davishi, Optik 127, 5255-5258 (2016). In current problem, it is also observed that the cubic trigonometric B-spline gives better results as compared to cubic B-spline.
Computing vibrational energy levels of CH4 with a Smolyak collocation method
Avila, Gustavo; Carrington, Tucker
2017-10-01
In this paper, we demonstrate that it is possible to apply collocation to compute vibrational energy levels of a five-atom molecule using an exact kinetic energy operator (with cross terms and coordinate-dependent coefficients). This is made possible by using (1) a pruned basis of products of univariate functions; (2) a Smolyak grid made from nested sequences of grids for each coordinate; (3) a collocation method that obviates the need to solve a generalized eigenvalue problem; (4) an efficient sequential transformation between the (nondirect product) grid and the (nondirect product) basis representations; and (5) hierarchical univariate functions that make it possible to avoid storing large intermediate vectors. The accuracy of the method is confirmed by computing 500 vibrational energy levels of methane.
The report develops working equations for carrying out the combination of gravimetric and satellite data starting from the equations of Moritz , and...using the principles of the usual least squares adjustment and the least squares collocation . Of the two methods of combining data considered, one...coefficients, and second whether the usual least squares or collocation adjustment scheme is used for the estimation of the potential coefficients. To
Analysis of Laminated Shells by Murakami’s Zig-Zag Theory and Radial Basis Functions Collocation
Directory of Open Access Journals (Sweden)
D. A. Maturi
2013-01-01
Full Text Available The static and free vibration analysis of laminated shells is performed by radial basis functions collocation, according to Murakami’s zig-zag (ZZ function (MZZF theory . The MZZF theory accounts for through-the-thickness deformation, by considering a ZZ evolution of the transverse displacement with the thickness coordinate. The equations of motion and the boundary conditions are obtained by Carrera’s Unified Formulation and further interpolated by collocation with radial basis functions.
On Using Collocation in Three Dimensions and Solving a Model Semiconductor Problem
Marchiando, J. F.
1995-01-01
A research code has been written to solve an elliptic system of coupled nonlinear partial differential equations of conservation form on a rectangularly shaped three-dimensional domain. The code uses the method of collocation of Gauss points with tricubic Hermite piecewise continuous polynomial basis functions. The system of equations is solved by iteration. The system of nonlinear equations is linearized, and the system of linear equations is solved by iterative methods. When the matrix of t...
Shiralashetti, S. C.; Deshi, A. B.
Wavelet analysis is a recently developed mathematical tool for many problems. One of its main attractive features is the ability to accurately represent general functions with small number of adaptively chosen wavelet coefficients. In this paper, the Legendre wavelet collocation method (LWCM) for the numerical solution of differential equations is presented. The proposed method gives better results than the existing ones. Some of the illustrative examples are included to observe the performance of the proposed scheme.
The collocation method for first-kind boundary integral equations on polygonal regions
Yan, Yi
1990-01-01
In this paper the collocation method for first-kind boundary integral equations, by using piecewise constant trial functions with uniform mesh, is shown to be equivalent to a projection method for second-kind Fredholm equations. In a certain sense this projection is an interpolation projection. By introducing this technique of analysis, we particularly consider the case of polygonal boundaries. We give asymptotic error estimates in {L_2} norm on the boundaries, and some superconvergence results for the single layer potential.
Energy Technology Data Exchange (ETDEWEB)
Verdu, G. [Departamento de Ingenieria Quimica Y Nuclear, Universitat Politecnica de Valencia, Cami de Vera, 14, 46022. Valencia (Spain); Capilla, M.; Talavera, C. F.; Ginestar, D. [Dept. of Nuclear Engineering, Departamento de Matematica Aplicada, Universitat Politecnica de Valencia, Cami de Vera, 14, 46022. Valencia (Spain)
2012-07-01
PL equations are classical high order approximations to the transport equations which are based on the expansion of the angular dependence of the angular neutron flux and the nuclear cross sections in terms of spherical harmonics. A nodal collocation method is used to discretize the PL equations associated with a neutron source transport problem. The performance of the method is tested solving two 1D problems with analytical solution for the transport equation and a classical 2D problem. (authors)
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Salih Yalcinbas
2016-01-01
Full Text Available In this paper, a new collocation method based on the Fibonacci polynomials is introduced to solve the high-order linear Volterra integro-differential equations under the conditions. Numerical examples are included to demonstrate the applicability and validity of the proposed method and comparisons are made with the existing results. In addition, an error estimation based on the residual functions is presented for this method. The approximate solutions are improved by using this error estimation.
Numerical solutions of the Kawahara equation by the septic B-spline collocation method
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Battal Gazi Karakoc
2014-08-01
Full Text Available In this article, a numerical solution of the Kawahara equation is presented by septic B-spline collocation method. Applying the Von-Neumann stability analysis, the present method is shown to be unconditionally stable. The accuracy of the proposed method is checked by two test problems. L2 and L1 error norms and conserved quantities are given at selected times. The obtained results are found in good agreement with the some recent results.
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Elaheh Hamed Mahvelati
2012-11-01
Full Text Available Many researchers stress the importance of lexical coherence and emphasize the need for teaching collocations at all levels of language proficiency. Thus, this study was conducted to measure the relative effectiveness of explicit (consciousness-raising approach versus implicit (input flood collocation instruction with regard to learners’ knowledge of both lexical and grammatical collocations. Ninety-five upper-intermediate learners, who were randomly assigned to the control and experimental groups, served as the participants of this study. While one of the experimental groups was provided with input flood treatment, the other group received explicit collocation instruction. In contrast, the participants in the control group did not receive any instruction on learning collocations. The results of the study, which were collected through pre-test, immediate post-test and delayed post-test, revealed that although both methods of teaching collocations proved effective, the explicit method of consciousness-raising approach was significantly superior to the implicit method of input flood treatment.
Energy Technology Data Exchange (ETDEWEB)
Yankov, A.; Downar, T. [University of Michigan, 2355 Bonisteel Blvd, Ann Arbor, MI 48109 (United States)
2013-07-01
Recent efforts in the application of uncertainty quantification to nuclear systems have utilized methods based on generalized perturbation theory and stochastic sampling. While these methods have proven to be effective they both have major drawbacks that may impede further progress. A relatively new approach based on spectral elements for uncertainty quantification is applied in this paper to several problems in reactor simulation. Spectral methods based on collocation attempt to couple the approximation free nature of stochastic sampling methods with the determinism of generalized perturbation theory. The specific spectral method used in this paper employs both the Smolyak algorithm and adaptivity by using Newton-Cotes collocation points along with linear hat basis functions. Using this approach, a surrogate model for the outputs of a computer code is constructed hierarchically by adaptively refining the collocation grid until the interpolant is converged to a user-defined threshold. The method inherently fits into the framework of parallel computing and allows for the extraction of meaningful statistics and data that are not within reach of stochastic sampling and generalized perturbation theory. This paper aims to demonstrate the advantages of spectral methods-especially when compared to current methods used in reactor physics for uncertainty quantification-and to illustrate their full potential. (authors)
Adaptive-Anisotropic Wavelet Collocation Method on general curvilinear coordinate systems
Brown-Dymkoski, Eric; Vasilyev, Oleg V.
2017-03-01
A new general framework for an Adaptive-Anisotropic Wavelet Collocation Method (A-AWCM) for the solution of partial differential equations is developed. This proposed framework addresses two major shortcomings of existing wavelet-based adaptive numerical methodologies, namely the reliance on a rectangular domain and the ;curse of anisotropy;, i.e. drastic over-resolution of sheet- and filament-like features arising from the inability of the wavelet refinement mechanism to distinguish highly correlated directional information in the solution. The A-AWCM addresses both of these challenges by incorporating coordinate transforms into the Adaptive Wavelet Collocation Method for the solution of PDEs. The resulting integrated framework leverages the advantages of both the curvilinear anisotropic meshes and wavelet-based adaptive refinement in a complimentary fashion, resulting in greatly reduced cost of resolution for anisotropic features. The proposed Adaptive-Anisotropic Wavelet Collocation Method retains the a priori error control of the solution and fully automated mesh refinement, while offering new abilities through the flexible mesh geometry, including body-fitting. The new A-AWCM is demonstrated for a variety of cases, including parabolic diffusion, acoustic scattering, and unsteady external flow.
Extraction of V-N-Collocations from Text Corpora A Feasibility Study for German
Breidt, E
1996-01-01
The usefulness of a statistical approach suggested by Church et al. (1991) is evaluated for the extraction of verb-noun (V-N) collocations from German text corpora. Some problematic issues of that method arising from properties of the German language are discussed and various modifications of the method are considered that might improve extraction results for German. The precision and recall of all variant methods is evaluated for V-N collocations containing support verbs, and the consequences for further work on the extraction of collocations from German corpora are discussed. With a sufficiently large corpus (>= 6 mio. word-tokens), the average error rate of wrong extractions can be reduced to 2.2% (97.8% precision) with the most restrictive method, however with a loss in data of almost 50% compared to a less restrictive method with still 87.6% precision. Depending on the goal to be achieved, emphasis can be put on a high recall for lexicographic purposes or on high precision for automatic lexical acquisiti...
An adaptive multi-element probabilistic collocation method for statistical EMC/EMI characterization
Yücel, Abdulkadir C.
2013-12-01
An adaptive multi-element probabilistic collocation (ME-PC) method for quantifying uncertainties in electromagnetic compatibility and interference phenomena involving electrically large, multi-scale, and complex platforms is presented. The method permits the efficient and accurate statistical characterization of observables (i.e., quantities of interest such as coupled voltages) that potentially vary rapidly and/or are discontinuous in the random variables (i.e., parameters that characterize uncertainty in a system\\'s geometry, configuration, or excitation). The method achieves its efficiency and accuracy by recursively and adaptively dividing the domain of the random variables into subdomains using as a guide the decay rate of relative error in a polynomial chaos expansion of the observables. While constructing local polynomial expansions on each subdomain, a fast integral-equation-based deterministic field-cable-circuit simulator is used to compute the observable values at the collocation/integration points determined by the adaptive ME-PC scheme. The adaptive ME-PC scheme requires far fewer (computationally costly) deterministic simulations than traditional polynomial chaos collocation and Monte Carlo methods for computing averages, standard deviations, and probability density functions of rapidly varying observables. The efficiency and accuracy of the method are demonstrated via its applications to the statistical characterization of voltages in shielded/unshielded microwave amplifiers and magnetic fields induced on car tire pressure sensors. © 2013 IEEE.
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Postolea Sorina
2016-12-01
Full Text Available The research devoted to special languages as well as the activities carried out in specialized translation classes tend to focus primarily on one-word or multi-word terminological units. However, a very important part in the making of specialist registers and texts is played by specialised collocations, i.e. relatively stable word combinations that do not designate concepts but are nevertheless of frequent use in a given field of activity. This is why helping students acquire competences relative to the identification and processing of collocations should become an important objective in specialised translation classes. An easily accessible and dependable resource that may be successfully used to this purpose is represented by corpora and corpus analysis tools, whose usefulness in translator training has been highlighted by numerous studies. This article proposes a series of practical, task-based activities-developed with the help of a small-size parallel corpus of specialised texts-that aim to raise the translation trainees′ awareness of the collocations present in specialised texts and to provide suggestions about their processing in translation.
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Mohsen Shahrokhi
2014-05-01
Full Text Available The present study investigates the extent to which lexical and grammatical collocations are used in Iranian high school English textbooks, compared with the American English File books. To achieve the purposes of this study, this study had to be carried out in two phases. In the first phase, the content of the instructional textbooks, that is, American English File book series, Book 2 and Iranian high school English Book 3, were analyzed to find the frequencies and proportions of the collocations used in the textbooks. Since the instructional textbooks used in the two teaching environments (i.e., Iranian high schools and language institutes were not equal with regard to the density of texts, from each textbook just the first 6000 words, content words as well as function words, were considered. Then, the frequencies of the collocations among the first 6000 words in high school English Book 3 and American English File Book 2 were determined.The results of the statistical analyses revealed that the two text book series differ marginally in terms of frequency and type of collocations. Major difference existed between them when it came to lexical collocations in American English File book 2.
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Likun Wang
2016-01-01
Full Text Available Given the fact that Cross-track Infrared Sounder (CrIS and the Visible Infrared Imaging Radiometer Suite (VIIRS are currently onboard the Suomi National Polar-orbiting Partnership (Suomi NPP satellite and will continue to be carried on the same platform as future Joint Polar Satellite System (JPSS satellites for the next decade, it is desirable to develop a fast and accurate collocation scheme to collocate VIIRS products and measurements with CrIS for applications that rely on combining measurements from two sensors such as inter-calibration, geolocation assessment, and cloud detection. In this study, an accurate and fast collocation method to collocate VIIRS measurements within CrIS instantaneous field of view (IFOV directly based on line-of-sight (LOS pointing vectors is developed and discussed in detail. We demonstrate that this method is not only accurate and precise from a mathematical perspective, but also easy to implement computationally. More importantly, with optimization, this method is very fast and efficient and thus can meet operational requirements. Finally, this collocation method can be extended to a wide variety of sensors on different satellite platforms.
Spectral optical layer properties of cirrus from collocated airborne measurements and simulations
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F. Finger
2016-06-01
Full Text Available Spectral upward and downward solar irradiances from vertically collocated measurements above and below a cirrus layer are used to derive cirrus optical layer properties such as spectral transmissivity, absorptivity, reflectivity, and cloud top albedo. The radiation measurements are complemented by in situ cirrus crystal size distribution measurements and radiative transfer simulations based on the microphysical data. The close collocation of the radiative and microphysical measurements, above, beneath, and inside the cirrus, is accomplished by using a research aircraft (Learjet 35A in tandem with the towed sensor platform AIRTOSS (AIRcraft TOwed Sensor Shuttle. AIRTOSS can be released from and retracted back to the research aircraft by means of a cable up to a distance of 4 km. Data were collected from two field campaigns over the North Sea and the Baltic Sea in spring and late summer 2013. One measurement flight over the North Sea proved to be exemplary, and as such the results are used to illustrate the benefits of collocated sampling. The radiative transfer simulations were applied to quantify the impact of cloud particle properties such as crystal shape, effective radius reff, and optical thickness τ on cirrus spectral optical layer properties. Furthermore, the radiative effects of low-level, liquid water (warm clouds as frequently observed beneath the cirrus are evaluated. They may cause changes in the radiative forcing of the cirrus by a factor of 2. When low-level clouds below the cirrus are not taken into account, the radiative cooling effect (caused by reflection of solar radiation due to the cirrus in the solar (shortwave spectral range is significantly overestimated.
Lin, Yi-Chung; Pandy, Marcus G
2017-07-05
The aim of this study was to perform full-body three-dimensional (3D) dynamic optimization simulations of human locomotion by driving a neuromusculoskeletal model toward in vivo measurements of body-segmental kinematics and ground reaction forces. Gait data were recorded from 5 healthy participants who walked at their preferred speeds and ran at 2m/s. Participant-specific data-tracking dynamic optimization solutions were generated for one stride cycle using direct collocation in tandem with an OpenSim-MATLAB interface. The body was represented as a 12-segment, 21-degree-of-freedom skeleton actuated by 66 muscle-tendon units. Foot-ground interaction was simulated using six contact spheres under each foot. The dynamic optimization problem was to find the set of muscle excitations needed to reproduce 3D measurements of body-segmental motions and ground reaction forces while minimizing the time integral of muscle activations squared. Direct collocation took on average 2.7±1.0h and 2.2±1.6h of CPU time, respectively, to solve the optimization problems for walking and running. Model-computed kinematics and foot-ground forces were in good agreement with corresponding experimental data while the calculated muscle excitation patterns were consistent with measured EMG activity. The results demonstrate the feasibility of implementing direct collocation on a detailed neuromusculoskeletal model with foot-ground contact to accurately and efficiently generate 3D data-tracking dynamic optimization simulations of human locomotion. The proposed method offers a viable tool for creating feasible initial guesses needed to perform predictive simulations of movement using dynamic optimization theory. The source code for implementing the model and computational algorithm may be downloaded at http://simtk.org/home/datatracking. Copyright © 2017 Elsevier Ltd. All rights reserved.
Energy Technology Data Exchange (ETDEWEB)
Webster, Clayton G [ORNL; Zhang, Guannan [ORNL; Gunzburger, Max D [ORNL
2012-10-01
Accurate predictive simulations of complex real world applications require numerical approximations to first, oppose the curse of dimensionality and second, converge quickly in the presence of steep gradients, sharp transitions, bifurcations or finite discontinuities in high-dimensional parameter spaces. In this paper we present a novel multi-dimensional multi-resolution adaptive (MdMrA) sparse grid stochastic collocation method, that utilizes hierarchical multiscale piecewise Riesz basis functions constructed from interpolating wavelets. The basis for our non-intrusive method forms a stable multiscale splitting and thus, optimal adaptation is achieved. Error estimates and numerical examples will used to compare the efficiency of the method with several other techniques.
Application of Collocated GPS and Seismic Sensors to Earthquake Monitoring and Early Warning
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Bofeng Guo
2013-10-01
Full Text Available We explore the use of collocated GPS and seismic sensors for earthquake monitoring and early warning. The GPS and seismic data collected during the 2011 Tohoku-Oki (Japan and the 2010 El Mayor-Cucapah (Mexico earthquakes are analyzed by using a tightly-coupled integration. The performance of the integrated results is validated by both time and frequency domain analysis. We detect the P-wave arrival and observe small-scale features of the movement from the integrated results and locate the epicenter. Meanwhile, permanent offsets are extracted from the integrated displacements highly accurately and used for reliable fault slip inversion and magnitude estimation.
Application of collocated GPS and seismic sensors to earthquake monitoring and early warning.
Li, Xingxing; Zhang, Xiaohong; Guo, Bofeng
2013-10-24
We explore the use of collocated GPS and seismic sensors for earthquake monitoring and early warning. The GPS and seismic data collected during the 2011 Tohoku-Oki (Japan) and the 2010 El Mayor-Cucapah (Mexico) earthquakes are analyzed by using a tightly-coupled integration. The performance of the integrated results is validated by both time and frequency domain analysis. We detect the P-wave arrival and observe small-scale features of the movement from the integrated results and locate the epicenter. Meanwhile, permanent offsets are extracted from the integrated displacements highly accurately and used for reliable fault slip inversion and magnitude estimation.
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Elçin Gökmen
2015-03-01
Full Text Available In this paper, a numerical method is presented to obtain approximate solutions for the system of nonlinear delay integro-differential equations derived from considering biological species living together. This method is essentially based on the truncated Taylor series and its matrix representations with collocation points. Also, to illustrate the pertinent features of the method examples are presented and results are compared to the Adomian decomposition method, the variational iteration method, pseudospectral Legendre method. All numerical computations have been performed on the computer algebraic system Maple 15.
A Semi-Implicit Free Surface Formulation for the Semi-Collocated Grid Diecast Ocean Model
1998-04-15
free-surface formulation for the DieCAST Ocean model that retains the accurate, low dissipation numerics of its latest and best semi collocated rigid...lid DieCAST version (reflecting the fact that the rigid lid barotropic mode numerics are also a sigma-like approach,) and requires less than 50 percent...more computing. Thus, the numerics used by both rigid lid and free-surface DieCAST versions combines the best of z-level and sigma coordinate numerics, as well as, the best of ’a’ and ’c’ grid numerics.
Implementation of optimal Galerkin and Collocation approximations of PDEs with Random Coefficients
Beck, Joakim
2011-12-22
In this work we first focus on the Stochastic Galerkin approximation of the solution u of an elliptic stochastic PDE. We rely on sharp estimates for the decay of the coefficients of the spectral expansion of u on orthogonal polynomials to build a sequence of polynomial subspaces that features better convergence properties compared to standard polynomial subspaces such as Total Degree or Tensor Product. We consider then the Stochastic Collocation method, and use the previous estimates to introduce a new effective class of Sparse Grids, based on the idea of selecting a priori the most profitable hierarchical surpluses, that, again, features better convergence properties compared to standard Smolyak or tensor product grids.
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R. C. Mittal
2014-01-01
Full Text Available We present a technique based on collocation of cubic B-spline basis functions to solve second order one-dimensional hyperbolic telegraph equation with Neumann boundary conditions. The use of cubic B-spline basis functions for spatial variable and its derivatives reduces the problem into system of first order ordinary differential equations. The resulting system subsequently has been solved by SSP-RK54 scheme. The accuracy of the proposed approach has been confirmed with numerical experiments, which shows that the results obtained are acceptable and in good agreement with the exact solution.
NURBS-Based Collocation Methods for the Structural Analysis of Shells of Revolution
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Maria Laura De Bellis
2016-03-01
Full Text Available In this work we present a collocation method for the structural analysis of shells of revolution based on Non-Uniform Rational B-Spline (NURBS interpolation. The method is based on the strong formulation of the equilibrium equations according to Reissner-Mindlin theory, with Fourier series expansion of dependent variables, which makes the problem 1D. Several numerical tests validate convergence, accuracy, and robustness of the proposed methodology, and its feasibility as a tool for the analysis and design of complex shell structures.
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Pentti Järvi
2004-10-01
Full Text Available This study addresses analysing quarterly reports from a brandtheoretical viewpoint. The study addresses the issue through a method which introduces both a quantitative tool based on linguistic theory and qualitative decisions of the researchers. The research objects of this study are two quarterly reports each of three telecommunications companies: Ericsson, Motorola and Nokia. The method used is a collocational network. The analyses show that there are differences in communication and message strategies among investigated companies and also changes during a quite short period in each company
DEFF Research Database (Denmark)
E. Fischer, Joel; Porcheron, Martin; Lucero, Andrés
2016-01-01
In the 25 years since Ellis, Gibbs, and Rein proposed the time-space taxonomy, research in the ‘same time, same place’ quadrant has diversified, perhaps even fragmented. This one-day workshop will bring together researchers with diverse, yet convergent interests in tabletop, surface, mobile, and ...
An h-adaptive stochastic collocation method for stochastic EMC/EMI analysis
Yücel, Abdulkadir C.
2010-07-01
The analysis of electromagnetic compatibility and interference (EMC/EMI) phenomena is often fraught by randomness in a system\\'s excitation (e.g., the amplitude, phase, and location of internal noise sources) or configuration (e.g., the routing of cables, the placement of electronic systems, component specifications, etc.). To bound the probability of system malfunction, fast and accurate techniques to quantify the uncertainty in system observables (e.g., voltages across mission-critical circuit elements) are called for. Recently proposed stochastic frameworks [1-2] combine deterministic electromagnetic (EM) simulators with stochastic collocation (SC) methods that approximate system observables using generalized polynomial chaos expansion (gPC) [3] (viz. orthogonal polynomials spanning the entire random domain) to estimate their statistical moments and probability density functions (pdfs). When constructing gPC expansions, the EM simulator is used solely to evaluate system observables at collocation points prescribed by the SC-gPC scheme. The frameworks in [1-2] therefore are non-intrusive and straightforward to implement. That said, they become inefficient and inaccurate for system observables that vary rapidly or are discontinuous in the random variables (as their representations may require very high-order polynomials). © 2010 IEEE.
Orthogonal grid generation of an irregular region using a local polynomial collocation method
Wu, Nan-Jing; Tsay, Ting-Kuei; Yang, Tun-Chi; Chang, Hung-Yuan
2013-06-01
In this study, a 2-D orthogonal grid generation model is developed by solving the governing equations of coordinate transformation with a local polynomial collocation method accompanied with the moving least squares (MLS) approach. This method was developed in a way that on the boundaries both the governing equation and boundary condition are satisfied, so it is more robust and accurate than conventional collocation methods. Though the method used to solve the coordinate transforming equations is meshless, it does not deteriorate the value of present work, because most numerical models in modern use are grid-dependent, and grid generation of service to these models is still strongly desired, particularly for finite difference models in irregular domains. Before applying to grid generation problems, the performance of present method is tested by a bench mark potential flow problem. Additional to two basic grid generation problems, a bottleneck problem of previous works, which contains zero-degree corners in the domain, is carried out. Finally, the model is applied to the orthogonal grid generation in a multi-connected domain. The correctness is testified by checking the orthogonality of the generated results.
Fortier, Marie-Odile P; Sturm, Belinda S M
2012-10-16
Resource demand analyses indicate that algal biodiesel production would require unsustainable amounts of freshwater and fertilizer supplies. Alternatively, municipal wastewater effluent can be used, but this restricts production of algae to areas near wastewater treatment plants (WWTPs), and to date, there has been no geospatial analysis of the feasibility of collocating large algal ponds with WWTPs. The goals of this analysis were to determine the available areas by land cover type within radial extents (REs) up to 1.5 miles from WWTPs; to determine the limiting factor for algal production using wastewater; and to investigate the potential algal biomass production at urban, near-urban, and rural WWTPs in Kansas. Over 50% and 87% of the land around urban and rural WWTPs, respectively, was found to be potentially available for algal production. The analysis highlights a trade-off between urban WWTPs, which are generally land-limited but have excess wastewater effluent, and rural WWTPs, which are generally water-limited but have 96% of the total available land. Overall, commercial-scale algae production collocated with WWTPs is feasible; 29% of the Kansas liquid fuel demand could be met with implementation of ponds within 1 mile of all WWTPs and supplementation of water and nutrients when these are limited.
Carpenter, Mark H.; Parsani, Matteo; Fisher, Travis C.; Nielsen, Eric J.
2015-01-01
Staggered grid, entropy stable discontinuous spectral collocation operators of any order are developed for Burgers' and the compressible Navier-Stokes equations on unstructured hexahedral elements. This generalization of previous entropy stable spectral collocation work [1, 2], extends the applicable set of points from tensor product, Legendre-Gauss-Lobatto (LGL) to a combination of tensor product Legendre-Gauss (LG) and LGL points. The new semi-discrete operators discretely conserve mass, momentum, energy and satisfy a mathematical entropy inequality for both Burgers' and the compressible Navier-Stokes equations in three spatial dimensions. They are valid for smooth as well as discontinuous flows. The staggered LG and conventional LGL point formulations are compared on several challenging test problems. The staggered LG operators are significantly more accurate, although more costly to implement. The LG and LGL operators exhibit similar robustness, as is demonstrated using test problems known to be problematic for operators that lack a nonlinearly stability proof for the compressible Navier-Stokes equations (e.g., discontinuous Galerkin, spectral difference, or flux reconstruction operators).
Structural and statistical properties of the collocation technique for error characterization
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S. Zwieback
2012-02-01
Full Text Available The validation of geophysical data sets (e.g. derived from models, exploration techniques or remote sensing presents a formidable challenge as all products are inherently different and subject to errors. The collocation technique permits the retrieval of the error variances of different data sources without the need to specify one data set as a reference. In addition calibration constants can be determined to account for biases and different dynamic ranges. The method is frequently applied to the study and comparison of remote sensing, in-situ and modelled data, particularly in hydrology and oceanography. Previous studies have almost exclusively focussed on the validation of three data sources; in this paper it is shown how the technique generalizes to an arbitrary number of data sets. It turns out that only parts of the covariance structure can be resolved by the collocation technique, thus emphasizing the necessity of expert knowledge for the correct validation of geophysical products. Furthermore the bias and error variance of the estimators are derived with particular emphasis on the assumptions necessary for establishing those characteristics. Important properties of the method, such as the structural deficiencies, dependence of the accuracy on the number of measurements and the impact of violated assumptions, are illustrated by application to simulated data.
Corpus-Based Websites to Promote Learner Autonomy in Correcting Writing Collocation Errors
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Pham Thuy Dung
2016-12-01
Full Text Available The recent yet powerful emergence of E-learning and using online resources in learning EFL (English as a Foreign Language has helped promote learner autonomy in language acquisition including self-correcting their mistakes. This pilot study despite conducted on a modest sample of 25 second year students majoring in Business English at Hanoi Foreign Trade University is an initial attempt to investigate the feasibility of using corpus-based websites to promote learner autonomy in correcting collocation errors in EFL writing. The data is collected using a pre-questionnaire and a post-interview aiming to find out the participants’ change in belief and attitude toward learner autonomy in collocation errors in writing, the extent of their success in using the corpus-based websites to self-correct the errors and the change in their confidence in self-correcting the errors using the websites. The findings show that a significant majority of students have shifted their belief and attitude toward a more autonomous mode of learning, enjoyed a fair success of using the websites to self-correct the errors and become more confident. The study also yields an implication that a face-to-face training of how to use these online tools is vital to the later confidence and success of the learners
ANALYSIS OF SPECIALISED COLLOCATIONS IN THE AREA OF REMOTE SENSING IN THE PERSPECTIVE OF PHRASEOLOGY
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Diva Cardoso de CAMARGO
2013-12-01
Full Text Available The aim of this research is to build and analyze a parallel corpus in the field of remote sensing in order to identify, according to its frequency, specialized collocations in English and then search for their equivalents in Portuguese. The research is based on the interdisciplinary approach of Corpus-Based Translation Studies (BAKER, 1995; CAMARGO, 2007, Corpus Linguistics (BERBER SARDINHA, 2004; TOGNINI-BONELLI, 2001, Phraseology (ORENHA-OTTAIANO, 2009; PAVEL, 1993, and some principles of Terminology (BARROS, 2004. For manipulating the corpora, the program WordSmith Tools (SCOTT, 2012 version 6.0 is used. To support this study, two comparable corpora in English and Portuguese were also built from articles published in both national and international journals in remote sensing. The results show that the collocations in Portuguese seem to be still in the process of conventionalization, as the translators made use of greater variation in their translational options, which can be a way to make the text clearer for the reader.
Interpolation of Superconducting Gravity Observations Using Least-Squares Collocation Method
Habel, Branislav; Janak, Juraj
2014-05-01
A pre-processing of the gravity data measured by superconducting gravimeter involves removing of spikes, offsets and gaps. Their presence in observations can limit the data analysis and degrades the quality of obtained results. Short data gaps are filling by theoretical signal in order to get continuous records of gravity. It requires the accurate tidal model and eventually atmospheric pressure at the observed site. The poster presents a design of algorithm for interpolation of gravity observations with a sampling rate of 1 min. Novel approach is based on least-squares collocation which combines adjustment of trend parameters, filtering of noise and prediction. It allows the interpolation of missing data up to a few hours without necessity of any other information. Appropriate parameters for covariance function are found using a Bayes' theorem by modified optimization process. Accuracy of method is improved by the rejection of outliers before interpolation. For filling of longer gaps the collocation model is combined with theoretical tidal signal for the rigid Earth. Finally, the proposed method was tested on the superconducting gravity observations at several selected stations of Global Geodynamics Project. Testing demonstrates its reliability and offers results comparable with the standard approach implemented in ETERNA software package without necessity of an accurate tidal model.
Olikara, Zubin P.
Many astrodynamical systems exhibit both ordered and chaotic motion. The invariant manifold structure organizes these behaviors and is a valuable tool for the design of spacecraft trajectories. The study of a system's dynamics often begins with the computation of its invariant tori (equilibrium points, periodic orbits, quasi-periodic orbits) and associated stable and unstable manifolds. Periodic orbits, in particular, have been used effectively for the design of low-energy transfers in the circular restricted 3-body problem (CR3BP). Quasi-periodic orbits offer similar benefits and are often more prevalent in the phase space, but additional complexities are involved in their computation. The foundation of this work is the development of a numerical method for computing two-dimensional quasi-periodic tori. The approach is applicable to a general class of Hamiltonian systems. Using a Fourier discretization and Gauss-Legendre collocation, a continuous representation of the torus is obtained. Included in the scheme is the computation of the torus's stable and unstable manifolds. These manifolds can then be used for the design of natural transfers. Two methods are presented for locating and continuing families of heteroclinic connections between quasi-periodic orbits in the CR3BP. A collocation-based approach for transitioning trajectories to a higher-fidelity ephemeris model is also included.
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Man, Jun; Li, Weixuan; Zeng, Lingzao; Wu, Laosheng
2016-06-01
The ensemble Kalman filter (EnKF) has gained popularity in hydrological data assimilation problems. As a Monte Carlo based method, a relatively large ensemble size is usually required to guarantee the accuracy. As an alternative approach, the probabilistic collocation based Kalman filter (PCKF) employs the polynomial chaos to approximate the original system. In this way, the sampling error can be reduced. However, PCKF suffers from the so-called "curse of dimensionality". When the system nonlinearity is strong and number of parameters is large, PCKF could be even more computationally expensive than EnKF. Motivated by most recent developments in uncertainty quantification, we propose a restart adaptive probabilistic collocation based Kalman filter (RAPCKF) for data assimilation in unsaturated flow problems. During the implementation of RAPCKF, the important parameters are identified and active PCE basis functions are adaptively selected. The "restart" technology is used to eliminate the inconsistency between model parameters and states. The performance of RAPCKF is tested with numerical cases of unsaturated flow models. It is shown that RAPCKF is more efficient than EnKF with the same computational cost. Compared with the traditional PCKF, the RAPCKF is more applicable in strongly nonlinear and high dimensional problems.
Zhang, Jian; Sun, Haimeng; Wang, Wengang; Hu, Zhen; Yin, Xiaole; Ngo, Huu Hao; Guo, Wenshan; Fan, Jinlin
2017-01-01
In the present study, a novel seasonal plant collocation system (SPCS), specifically the Potamogeton crispus and Phragmites australis series system, was investigated to enhance the performance of surface flow constructed wetlands (SFCWs) at low temperature. Results of a year-round experiment showed that SPCS conquered the adverse effect of low temperature and achieved sustainable nutrients removal. In addition, during winter, removal efficiencies of NH4-N, TP, COD, and TN in SPCS were 18.1%, 17.6%, 10.1% and 5.2% higher than that in the control, respectively. P. crispus and P. australis complemented each other in terms of plant growth and plant uptake during the experiment period. Furthermore, it emerged that P. crispus could increase the quantity of ammonia oxidizing bacteria by 10.2%, due to its high oxygen enrichment ability. It is suggested that seasonal plant collocation has a promising future in SFCWs of areas being affected by climate change, e.g. northern China. Copyright © 2016 Elsevier Ltd. All rights reserved.
DEFF Research Database (Denmark)
Westbrook, Pete
might exist between overall language proficiency, collocational competence and spoken fluency in non-native English-speaking university lecturers. The data came from 15 20-minute mini-lectures recorded between 2009 and 2011 for an English oral proficiency test for lecturers employed at the University......Despite the large body of research into formulaic language and fluency, there seems to be a lack of empirical evidence for how collocations, often considered a subset of formulaic language, might impact on fluency. To address this problem, this dissertation examined to what extent correlations...
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Christina Dechamps
2017-09-01
Full Text Available Cet article se propose d’étudier la question du type de dictionnaire le mieux approprié dans le cadre de l’enseignement/apprentissage des collocations et de présenter un projet de dictionnaire d’apprentissage français-portugais. Ce dernier décrira en particulier les collocations de la langue juridiques, sur la base de l’analyse de la combinatoire verbale réalisée à partir d’un corpus comparable bilingue de textes juridiques appartenant au discours scientifique pédagogique.
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Ali H. Bhrawy
2014-01-01
Full Text Available The modified generalized Laguerre-Gauss collocation (MGLC method is applied to obtain an approximate solution of fractional neutral functional-differential equations with proportional delays on the half-line. The proposed technique is based on modified generalized Laguerre polynomials and Gauss quadrature integration of such polynomials. The main advantage of the present method is to reduce the solution of fractional neutral functional-differential equations into a system of algebraic equations. Reasonable numerical results are achieved by choosing few modified generalized Laguerre-Gauss collocation points. Numerical results demonstrate the accuracy, efficiency, and versatility of the proposed method on the half-line.
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George OGUNTALA
2017-08-01
Full Text Available In this study, the thermal performance analysis of porous fin with temperature-dependent thermal conductivity and internal heat generation is carried out using Haar wavelet collocation method. The effects of various parameters on the thermal characteristics of the porous fin are investigated. It is found that as the porosity increases, the rate of heat transfer from the fin increases and the thermal performance of the porous fin increases. The numerical solutions by the Haar wavelet collocation method are in good agreement with the standard numerical solutions.
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M.M. Khader
2014-10-01
Full Text Available In this article, we present a new numerical method to solve the integro-differential equations (IDEs. The proposed method uses the Legendre cardinal functions to express the approximate solution as a finite series. In our method the operational matrix of derivatives is used to reduce IDEs to a system of algebraic equations. To demonstrate the validity and applicability of the proposed method, we present some numerical examples. We compare the obtained numerical results from the proposed method with some other methods. The results show that the proposed algorithm is of high accuracy, more simple and effective.
A data parallel pseudo-spectral semi-implicit magnetohydrodynamics code
Keppens, R.; Poedts, S.; Meijer, P. M.; Goedbloed, J. P.; Hertzberger, B.; Sloot, P.
1997-01-01
The set of eight nonlinear partial differential equations of magnetohydrodynamics (MHD) is used for time dependent simulations of three-dimensional (3D) fluid flow in a magnetic field. A data parallel code is presented, which integrates the MHD equations in cylindrical geometry, combining a
A Study of Learners' Usage of a Mobile Learning Application for Learning Idioms and Collocations
Amer, Mahmoud
2014-01-01
This study explored how four groups of language learners used a mobile software application developed by the researcher for learning idiomatic expressions and collocations. A total of 45 participants in the study used the application for a period of one week. Data for this study was collected from the application, a questionnaire, and follow-up…
Alqarni, Ibrahim R.
2017-01-01
This study investigates the impact that study in Australia has on the lexical knowledge of Saudi Arabian students. It focuses on: 1) the effects that the length of study in Australia has on the acquisition of lexical collocations, as reflected by lexical knowledge tests, and 2) whether there is a significant gender difference in the acquisition of…
Amer, Mahmoud Atiah
2010-01-01
This study explored how four groups of English learners used a mobile software application developed by the researcher for learning idiomatic expressions and collocations. A total of 45 learners in the study used the application for a period of one week. Data for this study was collected from a questionnaire, the application, and follow-up…
Ördem, Eser; Paker, Turan
2016-01-01
The purpose of this study was to investigate whether teaching vocabulary via collocations would contribute to retention and use of foreign language, English. A quasi-experimental design was formed to see whether there would be a significant difference between the treatment and control groups. Three instruments developed were conducted to 60…
DEFF Research Database (Denmark)
Troldborg, Niels; Sørensen, Niels N.; Réthoré, Pierre-Elouan
2015-01-01
This paper describes a consistent algorithm for eliminating the numerical wiggles appearing when solving the finite volume discretized Navier-Stokes equations with discrete body forces in a collocated grid arrangement. The proposed method is a modification of the Rhie-Chow algorithm where the for...
Improvement of neutron kinetics module in TRAC-BF1code: one-dimensional nodal collocation method
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Jambrina, Ana; Barrachina, Teresa; Miro, Rafael; Verdu, Gumersindo, E-mail: ajambrina@iqn.upv.es, E-mail: tbarrachina@iqn.upv.es, E-mail: rmiro@iqn.upv.es, E-mail: gverdu@iqn.upv.es [Universidade Politecnica de Valencia (UPV), Valencia (Spain); Soler, Amparo, E-mail: asoler@iberdrola.es [SEA Propulsion S.L., Madrid (Spain); Concejal, Alberto, E-mail: acbe@iberdrola.es [Iberdrola Ingenieria y Construcion S.A.U., Madrid (Spain)
2013-07-01
The TRAC-BF1 one-dimensional kinetic model is a formulation of the neutron diffusion equation in the two energy groups' approximation, based on the analytical nodal method (ANM). The advantage compared with a zero-dimensional kinetic model is that the axial power profile may vary with time due to thermal-hydraulic parameter changes and/or actions of the control systems but at has the disadvantages that in unusual situations it fails to converge. The nodal collocation method developed for the neutron diffusion equation and applied to the kinetics resolution of TRAC-BF1 thermal-hydraulics, is an adaptation of the traditional collocation methods for the discretization of partial differential equations, based on the development of the solution as a linear combination of analytical functions. It has chosen to use a nodal collocation method based on a development of Legendre polynomials of neutron fluxes in each cell. The qualification is carried out by the analysis of the turbine trip transient from the NEA benchmark in Peach Bottom NPP using both the original 1D kinetics implemented in TRAC-BF1 and the 1D nodal collocation method. (author)
DEFF Research Database (Denmark)
Tscherning, Carl Christian
2015-01-01
The method of Least-Squares Collocation (LSC) may be used for the modeling of the anomalous gravity potential (T) and for the computation (prediction) of quantities related to T by a linear functional. Errors may also be estimated. However, when using an isotropic covariance function or equivalen...
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Nawal Gholami
2017-03-01
Full Text Available Few studies have investigated the effects of input-based and output-based instructions on collocational knowledge of EFL learners. Therefore, this study aimed to examine the effects of these instructional approaches on Iranian EFL learners’ productive knowledge of collocations. To this end, 80 senior high school students from three intact classes at Tali-e High School in Ahvaz, Iran, were selected. Each class was assigned to a control group (n = 28 and two experimental groups including the input group (n = 27 and the output group (n = 25. Twenty collocations were selected as the target collocations. Then, a pretest was administered to all groups. Two days after the last treatment session, an immediate posttest was given to the participants. A delayed posttest was also administered two weeks later. The results of Mixed-ANOVA, one-way ANOVA, and Tukey post hoc tests revealed that both input and output groups outperformed the control group on the immediate and delayed posttests. However, there were no significant differences between the input and output groups on the posttests. The implications and suggestions for future research are also presented.
Loeven, G.J.A.; Bijl, H.
2009-01-01
In this paper a Two-Step approach is presented for uncertainty quantification for expensive problems with multiple uncertain parameters. Both steps are performed using the Probabilistic Collocation method. The first step consists of a sensitivity analysis to identify the most important parameters of
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Dutta Sujesh
2016-01-01
Full Text Available This paper describes the development of 4-Pole Chebyshev and Quasi-Elliptic Ka Band Dielectric Resonator Filter using Higher Order Mode TE01δ+1. A microwave filter is a two port network used to control the frequency response at a certain point in a microwave system by providing transmission at frequencies within the passband of the filter and attenuation in the stop-band of the filter. The satellite communication industry created demand for low-mass narrow-band low-loss filters with severe specification on amplitude selectivity and phase linearity. The microwave region of the electromagnetic spectrum has certain unique properties. This enable microwave signals to propagate over long distances through the atmosphere under all the most severe weather conditions. These have both military and civilian applications, including Radar, Navigation and Wireless Communication. Microwave Filters are vital components in a huge variety of electronic systems, including cellular radio, satellite communications and radar. The design of filters uses network synthesis, with which it is possible to apply systematic procedures to work forward from specification to a final theoretical design.
On the a priori estimation of collocation error covariance functions: a feasibility study
DEFF Research Database (Denmark)
Arabelos, D.N.; Forsberg, René; Tscherning, C.C.
2007-01-01
and the associated error covariance functions were conducted in the Arctic region north of 64 degrees latitude. The correlation between the known features of the data and the parameters variance and correlation length of the computed error covariance functions was estimated using multiple regression analysis......Error covariance estimates are necessary information for the combination of solutions resulting from different kinds of data or methods, or for the assimilation of new results in already existing solutions. Such a combination or assimilation process demands proper weighting of the data, in order...... for the combination to be optimal and the error estimates of the results realistic. One flexible method for the gravity field approximation is least-squares collocation leading to optimal solutions for the predicted quantities and their error covariance estimates. The drawback of this method is related to the current...
Farrell, Patricio
2015-04-30
© 2015John Wiley & Sons, Ltd. Symmetric collocation methods with RBFs allow approximation of the solution of a partial differential equation, even if the right-hand side is only known at scattered data points, without needing to generate a grid. However, the benefit of a guaranteed symmetric positive definite block system comes at a high computational cost. This cost can be alleviated somewhat by considering compactly supported RBFs and a multiscale technique. But the condition number and sparsity will still deteriorate with the number of data points. Therefore, we study certain block diagonal and triangular preconditioners. We investigate ideal preconditioners and determine the spectra of the preconditioned matrices before proposing more practical preconditioners based on a restricted additive Schwarz method with coarse grid correction. Numerical results verify the effectiveness of the preconditioners.
Between initial familiarity and future use – a case of Collocated Collaborative Writing
DEFF Research Database (Denmark)
Bødker, Susanne; Polli, Anna Maria
2014-01-01
with them that may affect early use and further development of use. We base our analyses on interviews in the art gallery and on socio-cultural theories of artefactmediated learning and collaboration. The analyses help identify three forms of collaborative writing, which are placed in the space between......This paper reports on a design experiment in an art gallery, where we explored visitor practices of commenting on art, and how they were shaped in interaction with a newly designed collocated, collaborative writing technology. In particular we investigate what potentials previous practices carry...... future use possibilities and initial familiarity based on everyday practices. These forms met and at times collided in a space where the actual use was shaped. We furthermore look back on initial assumptions made in design regarding a productive collaborative writing style, and confront...
Collocated electrodynamic FDTD schemes using overlapping Yee grids and higher-order Hodge duals
Deimert, C.; Potter, M. E.; Okoniewski, M.
2016-12-01
The collocated Lebedev grid has previously been proposed as an alternative to the Yee grid for electromagnetic finite-difference time-domain (FDTD) simulations. While it performs better in anisotropic media, it performs poorly in isotropic media because it is equivalent to four overlapping, uncoupled Yee grids. We propose to couple the four Yee grids and fix the Lebedev method using discrete exterior calculus (DEC) with higher-order Hodge duals. We find that higher-order Hodge duals do improve the performance of the Lebedev grid, but they also improve the Yee grid by a similar amount. The effectiveness of coupling overlapping Yee grids with a higher-order Hodge dual is thus questionable. However, the theoretical foundations developed to derive these methods may be of interest in other problems.
Directory of Open Access Journals (Sweden)
Tempone R.
2011-12-01
Full Text Available In this work we first focus on the Stochastic Galerkin approximation of the solution u of an elliptic stochastic PDE. We rely on sharp estimates for the decay of the coefficients of the spectral expansion of u on orthogonal polynomials to build a sequence of polynomial subspaces that features better convergence properties compared to standard polynomial subspaces such as Total Degree or Tensor Product. We consider then the Stochastic Collocation method, and use the previous estimates to introduce a new effective class of Sparse Grids, based on the idea of selecting a priori the most profitable hierarchical surpluses, that, again, features better convergence properties compared to standard Smolyak or tensor product grids.
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Timothy J. Dickey
2008-03-01
Full Text Available The Functional Requirements for Bibliographic Records (FRBR’s hierarchical system defines families of bibliographic relationship between records and collocates them better than most extant bibliographic systems. Certain library materials (especially audio-visual formats pose notable challenges to search and retrieval; the first benefits of a FRBRized system would be felt in music libraries, but research already has proven its advantages for fine arts, theology, and literature—the bulk of the non-science, technology, and mathematics collections. This report will summarize the benefits of FRBR to nextgeneration library catalogs and OPACs, and will review the handful of ILS and catalog systems currently operating with its theoretical structure.
Trajectory planning based on collocation methods for multiple aerial and ground autonomous vehicles
Vera Rendón, Santiago
2015-01-01
Esta tesis doctorar presenta una serie de contribuciones en los métodos de coordinación y generación de trayectorias de grupos de vehículos, concretamente de vehículos autónomos. Los métodos de colocación, más conocidos por su nombre en inglés “Collocation methods”, han despertado un creciente interés en los últimos años, entre los distintos métodos numéricos para resolver cualquier tipo de problema dentro del campo de la ingeniería. Esta tesis en concreto, presenta un nuevo punto de vista de...
Chanthrasuwan, Maveeka; Asri, Nur Asreenawaty Mohd; Hamid, Nur Nadiah Abd; Majid, Ahmad Abd.; Azmi, Amirah
2017-08-01
The cubic B-spline and cubic trigonometric B-spline functions are used to set up the collocation in finding solutions for the Buckmaster equation. These splines are applied as interpolating functions in the spatial dimension while the finite difference method (FDM) is used to discretize the time derivative. The Buckmaster equation is linearized using Taylor's expansion and solved using two schemes, namely Crank-Nicolson and fully implicit. The von Neumann stability analysis is carried out on the two schemes and they are shown to be conditionally stable. In order to demonstrate the capability of the schemes, some problems are solved and compared with analytical and FDM solutions. The proposed methods are found to generate more accurate results than the FDM.
Solving Dym equation using quartic B-spline and quartic trigonometric B-spline collocation methods
Anuar, Hanis Safirah Saiful; Mafazi, Nur Hidayah; Hamid, Nur Nadiah Abd; Majid, Ahmad Abd.; Azmi, Amirah
2017-08-01
The nonlinear Dym equation is solved numerically using the quartic B-spline (QuBS) and quartic trigonometric B-spline (QuTBS) collocation methods. The QuBS and QuTBS are utilized as interpolating functions in the spatial dimension while the finite difference method (FDM) is applied to discretize the temporal space with the help of theta-weighted method. The nonlinear term in the Dym equation is linearized using Taylor's expansion. Two schemes are performed on both methods which are Crank-Nicolson and fully implicit. Applying the Von-Neumann stability analysis, these schemes are found to be conditionally stable. Several numerical examples of different forms are discussed and compared in term of errors with exact solutions and results from the FDM.
Costabel, M.; Ervin, V. J.; Stephan, E. P.
1990-07-01
Previously Costabel and Stephan proved the convergence of the collocation method for boundary integral equations on polygonal domains for piecewise linear trial functions which are constant on subintervals next to corners. The convergence and associated error estimates were given in suitable Sobolev spaces with appropriately weighted norms. In this paper we present, for Laplace's equation, the implementation of their method and a slightly modified version. In the latter we use piecewise linear trial functions which are discontinuous at the corners. Of particular note is that the computed experimental convergence rates are in complete agreement with the predicted theoretical rates. In particular, our numerical results underline clearly how the order of convergence depends on the graded mesh.
Numerical Study of Separated Flows in Backward Facing Step by Using Collocated Grid Arrangement
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Ahmed Mustafa
2013-05-01
Full Text Available The effects of Reynolds number and the inlet height ratio on separated flow over backward facing step are investigated. The flow field is studied numerically with different inlet height ratio. The laminar flow field is analyzed numerically by solving the steady, two-dimensional incompressible Navier-Stokes equations. A collocated (non-staggered grid is used in the momentum equations, which discretized by finite volume method, SIMPLE algorithm is used to adjust the velocity field to satisfy the conservation of mass. The range of Reynolds number is (Re = 100 - 800. The results show that at low height ratio (h/H = 0.25 and high Reynolds number the flow separated along the top wall of the channel. Good agreement with the experimental data is obtained.
An iterative finite-element collocation method for parabolic problems using domain decomposition
Energy Technology Data Exchange (ETDEWEB)
Curran, M.C.
1992-11-01
Advection-dominated flows occur widely in the transport of groundwater contaminants, the movements of fluids in enhanced oil recovery projects, and many other contexts. In numerical models of such flows, adaptive local grid refinement is a conceptually attractive approach for resolving the sharp fronts or layers that tend to characterize the solutions. However, this approach can be difficult to implement in practice. A domain decomposition method developed by Bramble, Ewing, Pasciak, and Schatz, known as the BEPS method, overcomes many of the difficulties. We demonstrate the applicability of the iterative BEPS ideas to finite-element collocation on trial spaces of piecewise Hermite bicubics. The resulting scheme allows one to refine selected parts of a spatial grid without destroying algebraic efficiencies associated with the original coarse grid. We apply the method to two dimensional time-dependent advection-diffusion problems.
An iterative finite-element collocation method for parabolic problems using domain decomposition
Energy Technology Data Exchange (ETDEWEB)
Curran, M.C.
1992-01-01
Advection-dominated flows occur widely in the transport of groundwater contaminants, the movements of fluids in enhanced oil recovery projects, and many other contexts. In numerical models of such flows, adaptive local grid refinement is a conceptually attractive approach for resolving the sharp fronts or layers that tend to characterize the solutions. However, this approach can be difficult to implement in practice. A domain decomposition method developed by Bramble, Ewing, Pasciak, and Schatz, known as the BEPS method, overcomes many of the difficulties. We demonstrate the applicability of the iterative BEPS ideas to finite-element collocation on trial spaces of piecewise Hermite bicubics. The resulting scheme allows one to refine selected parts of a spatial grid without destroying algebraic efficiencies associated with the original coarse grid. We apply the method to two dimensional time-dependent advection-diffusion problems.
Analytic regularity and collocation approximation for elliptic PDEs with random domain deformations
Castrillon, Julio
2016-03-02
In this work we consider the problem of approximating the statistics of a given Quantity of Interest (QoI) that depends on the solution of a linear elliptic PDE defined over a random domain parameterized by N random variables. The elliptic problem is remapped onto a corresponding PDE with a fixed deterministic domain. We show that the solution can be analytically extended to a well defined region in CN with respect to the random variables. A sparse grid stochastic collocation method is then used to compute the mean and variance of the QoI. Finally, convergence rates for the mean and variance of the QoI are derived and compared to those obtained in numerical experiments.
Bäck, Joakim
2010-09-17
Much attention has recently been devoted to the development of Stochastic Galerkin (SG) and Stochastic Collocation (SC) methods for uncertainty quantification. An open and relevant research topic is the comparison of these two methods. By introducing a suitable generalization of the classical sparse grid SC method, we are able to compare SG and SC on the same underlying multivariate polynomial space in terms of accuracy vs. computational work. The approximation spaces considered here include isotropic and anisotropic versions of Tensor Product (TP), Total Degree (TD), Hyperbolic Cross (HC) and Smolyak (SM) polynomials. Numerical results for linear elliptic SPDEs indicate a slight computational work advantage of isotropic SC over SG, with SC-SM and SG-TD being the best choices of approximation spaces for each method. Finally, numerical results corroborate the optimality of the theoretical estimate of anisotropy ratios introduced by the authors in a previous work for the construction of anisotropic approximation spaces. © 2011 Springer.
Alemohammad, S. H.; McColl, K. A.; Konings, A. G.; Entekhabi, D.; Stoffelen, A.
2015-08-01
Validation of precipitation estimates from various products is a challenging problem, since the true precipitation is unknown. However, with the increased availability of precipitation estimates from a wide range of instruments (satellite, ground-based radar, and gauge), it is now possible to apply the triple collocation (TC) technique to characterize the uncertainties in each of the products. Classical TC takes advantage of three collocated data products of the same variable and estimates the mean squared error of each, without requiring knowledge of the truth. In this study, triplets among NEXRAD-IV, TRMM 3B42RT, GPCP 1DD, and GPI products are used to quantify the associated spatial error characteristics across a central part of the continental US. Data are aggregated to biweekly accumulations from January 2002 through April 2014 across a 2° × 2° spatial grid. This is the first study of its kind to explore precipitation estimation errors using TC across the US. A multiplicative (logarithmic) error model is incorporated in the original TC formulation to relate the precipitation estimates to the unknown truth. For precipitation application, this is more realistic than the additive error model used in the original TC derivations, which is generally appropriate for existing applications such as in the case of wind vector components and soil moisture comparisons. This study provides error estimates of the precipitation products that can be incorporated into hydrological and meteorological models, especially those used in data assimilation. Physical interpretations of the error fields (related to topography, climate, etc.) are explored. The methodology presented in this study could be used to quantify the uncertainties associated with precipitation estimates from each of the constellations of GPM satellites. Such quantification is prerequisite to optimally merging these estimates.
Zyta Hakuba, Maria; Folini, Doris; Wild, Martin; Sanchez-Lorenzo, Arturo
2013-04-01
Anthropogenic climate change is physically speaking a perturbation of the atmospheric energy budget through the insertion of constituents such as greenhouse gases or aerosols. Changes in the atmospheric energy budget largely affect the global climate and hydrological cycle, but the quantification of the different energy balance components is still afflicted with large uncertainties. The overall aim of the present study is the assessment of the mean state and the spatio-temporal variations in the solar energy disposition, in which we focus on obtaining an accurate partitioning of absorbed solar radiation between the surface and the atmosphere. Surface based measurements of solar radiation (GEBA, BSRN) are combined with collocated satellite-retrieved surface albedo (MODIS, CERES FSW, or CM SAF GAC-SAL) and top-of-atmosphere net incoming solar radiation (CERES EBAF) to quantify the absorbed solar radiation (ASR) at the surface and within the atmosphere over Europe for the period 2001-2005. In a first step, we examine the quality and temporal homogeneity of the monthly time series beyond 2000 provided by GEBA in order to identify a subset of sufficient quality. We find the vast majority of monthly time series to be suitable for our purposes. Using the satellite-derived CM SAF surface solar radiation product at 0.03° spatial resolution, we assess the spatial representativeness of the GEBA and BSRN sites for their collocated 1° grid cells as we intend to combine the point measurements with the coarser resolved CERES EBAF products (1° resolution), and we find spatial sampling errors of on average 3 Wm-2 or 2% (normalized by point values). Based on the combination of 134 GEBA surface solar radiation (SSR) time series with MODIS white-sky albedo and CERES EBAF top-of-atmosphere net radiation (TOAnet), we obtain a European mean partitioning (2001-2005) of absorbed solar radiation (relative to total incoming radiation) of: ASRsurf= 41% and ASRatm= 25%, together equaling
Zyta Hakuba, Maria; Folini, Doris; Wild, Martin; Schaepmann-Strub, Gabriela
2014-05-01
Solar radiation is the primary source of energy for the Earth's climate system. While the incoming and outgoing solar fluxes at the top-of-atmosphere can be quantified with high accuracy, large uncertainties still exist in the partitioning of solar absorption between surface and atmosphere. To compute best estimates of absorbed solar radiation at the surface and within the atmosphere representative for Europe during 2000-2010, we combine ground-based observations of surface downwelling solar radiation (GEBA, BSRN) with collocated satellite-retrieved surface albedo (MODIS) and top-of-atmosphere net irradiance (CERES EBAF, 1° resolution). The combination of these datasets over European land yields best estimates of annual mean surface and atmospheric absorption of 117 ±6 Wm¯² (42 ±2 % of TOA incident irradiance) and 65 ±3 Wm¯² (23 ±1 %). The fractional atmospheric absorption of 23% represents a robust estimate largely unaffected by variations in latitude and season, thus, making it a potentially useful quantity for first order validation of regional climate models. These estimates are based on quality assessed surface data. First of all, we examine the temporal homogeneity of the monthly GEBA time series beyond 2000 and find the vast majority to be suitable for our purposes. The spatial representativeness of the GEBA and BSRN sites for their collocated 1° CERES EBAF grid cells we assess by using a satellite-derived surface solar radiation product (CM SAF) at 0.03° spatial resolution. We find representation errors of on average 3 Wm¯² or 2% (normalized by point values). Care is taken to identify and quantify uncertainties, which arise mostly from the measurements themselves, in particular surface albedo and ground-based solar radiation data. Other sources of uncertainty, like the spatial coverage by surface sites, the multiplicative combination of spatially averaged surface solar radiation and surface albedo, and the spatial representativeness of the
Directory of Open Access Journals (Sweden)
A. H. Bhrawy
2013-01-01
Full Text Available Since the collocation method approximates ordinary differential equations, partial differential equations, and integral equations in physical space, it is very easy to implement and adapt to various problems, including variable coefficient and nonlinear differential equations. In this paper, we derive a Jacobi-Gauss-Lobatto collocation method (J-GL-C to solve numerically nonlinear time-delayed Burgers-type equations. The proposed technique is implemented in two successive steps. In the first one, we apply nodes of the Jacobi-Gauss-Lobatto quadrature which depend upon the two general parameters , and the resulting equations together with the two-point boundary conditions constitute a system of ordinary differential equations (ODEs in time. In the second step, the implicit Runge-Kutta method of fourth order is applied to solve a system of ODEs of second order in time. We present numerical results which illustrate the accuracy and flexibility of these algorithms.
Energy Technology Data Exchange (ETDEWEB)
Webster, Clayton; Tempone, Raul (Florida State University, Tallahassee, FL); Nobile, Fabio (Politecnico di Milano, Italy)
2007-12-01
This work describes the convergence analysis of a Smolyak-type sparse grid stochastic collocation method for the approximation of statistical quantities related to the solution of partial differential equations with random coefficients and forcing terms (input data of the model). To compute solution statistics, the sparse grid stochastic collocation method uses approximate solutions, produced here by finite elements, corresponding to a deterministic set of points in the random input space. This naturally requires solving uncoupled deterministic problems and, as such, the derived strong error estimates for the fully discrete solution are used to compare the computational efficiency of the proposed method with the Monte Carlo method. Numerical examples illustrate the theoretical results and are used to compare this approach with several others, including the standard Monte Carlo.
Clemente, P. C. M.; de Oliveira, H. P.
2017-07-01
We present a single-domain Galerkin-collocation method to calculate puncture initial data sets for single and binary black holes, either in the trumpet or wormhole geometries. The combination of aspects belonging to the Galerkin and the collocation methods together with the adoption of spherical coordinates in all cases are shown to be very effective. We propose a unified expression for the conformal factor to describe trumpet and spinning black holes. In particular, for the spinning trumpet black holes, we exhibit the deformation of the limit surface due to the spin from a sphere to an oblate spheroid. We also revisit the energy content in the trumpet and wormhole puncture data sets. The algorithm can be extended to describe binary black holes.
Egli, R.; Geiger, A.; Wiget, A.; Kahle, H.-G
2017-01-01
The calculation of recent crustal movements and the associated crustal deformation rely on a suitable interpolation of geodetic measurements with repetition cycles of years or decades and modern GPS permanent networks. A common interpolation methods is the least-square collocation (LSC). LSC requires some a priori assumptions about the characteristics of the velocity field, that is, stocasticity in Moritz's definition of LSC. We present a novel approach, called adaptative LSC (ALSC) to the in...
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Z. Mosayebi
2014-07-01
Full Text Available In this paper a numerical technique is presented for the solution of fuzzy linear Volterra-Fredholm-Hammerstein integral equations. This method is a combination of collocation method and radial basis functions(RBFs.We first solve the actual set are equivalent to the fuzzy set, then answer 1-cut into the equation. Also high convergence rates and good accuracy are obtain with the propose method using relativeiy low numbers of data points.
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo; Rodriguez, Martin [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M, E-mail: paolo.amore@gmail.com, E-mail: martinalexander.rv@gmail.com, E-mail: fernande@quimica.unlp.edu.ar [INIFTA (UNLP, CCT La Plata-CONICET), Division Quimica Teorica, Blvd 113 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2011-04-15
We show that some of the conclusions drawn recently about the performance and convergence of the little sinc functions collocation method are misleading. To this end, we prove the convergence of the method and recalculate the ground-state energy for the Pullen-Edmonds Hamiltonian. In addition, we show the results for another nonseparable Hamiltonian operator with a somewhat more complicated potential-energy function. (comment)
Ocko, Ilissa B.; Ginoux, Paul A.
2017-04-01
Anthropogenic aerosols are a key factor governing Earth's climate and play a central role in human-caused climate change. However, because of aerosols' complex physical, optical, and dynamical properties, aerosols are one of the most uncertain aspects of climate modeling. Fortunately, aerosol measurement networks over the past few decades have led to the establishment of long-term observations for numerous locations worldwide. Further, the availability of datasets from several different measurement techniques (such as ground-based and satellite instruments) can help scientists increasingly improve modeling efforts. This study explores the value of evaluating several model-simulated aerosol properties with data from spatially collocated instruments. We compare aerosol optical depth (AOD; total, scattering, and absorption), single-scattering albedo (SSA), Ångström exponent (α), and extinction vertical profiles in two prominent global climate models (Geophysical Fluid Dynamics Laboratory, GFDL, CM2.1 and CM3) to seasonal observations from collocated instruments (AErosol RObotic NETwork, AERONET, and Cloud-Aerosol Lidar with Orthogonal Polarization, CALIOP) at seven polluted and biomass burning regions worldwide. We find that a multi-parameter evaluation provides key insights on model biases, data from collocated instruments can reveal underlying aerosol-governing physics, column properties wash out important vertical distinctions, and improved models does not mean all aspects are improved. We conclude that it is important to make use of all available data (parameters and instruments) when evaluating aerosol properties derived by models.
Weber, F.; Distl, H.
2015-11-01
This paper derives an approximate collocated control solution for the mitigation of multi-mode cable vibration by semi-active damping with negative stiffness based on the control force characteristics of clipped linear quadratic regulator (LQR). The control parameters are derived from optimal modal viscous damping and corrected in order to guarantee that both the equivalent viscous damping coefficient and the equivalent stiffness coefficient of the semi-active cable damper force are equal to their desired counterparts. The collocated control solution with corrected control parameters is numerically validated by free decay tests of the first four cable modes and combinations of these modes. The results of the single-harmonic tests demonstrate that the novel approach yields 1.86 times more cable damping than optimal modal viscous damping and 1.87 to 2.33 times more damping compared to a passive oil damper whose viscous damper coefficient is optimally tuned to the targeted mode range of the first four modes. The improvement in case of the multi-harmonic vibration tests, i.e. when modes 1 and 3 and modes 2 and 4 are vibrating at the same time, is between 1.55 and 3.81. The results also show that these improvements are obtained almost independent of the cable anti-node amplitude. Thus, the proposed approximate real-time applicable collocated semi-active control solution which can be realized by magnetorheological dampers represents a promising tool for the efficient mitigation of stay cable vibrations.
Li, Shengquan; Li, Juan; Mo, Yueping; Zhao, Rong
2014-01-01
A novel active method for multi-mode vibration control of an all-clamped stiffened plate (ACSP) is proposed in this paper, using the extended-state-observer (ESO) approach based on non-collocated acceleration sensors and piezoelectric actuators. Considering the estimated capacity of ESO for system state variables, output superposition and control coupling of other modes, external excitation, and model uncertainties simultaneously, a composite control method, i.e., the ESO based vibration control scheme, is employed to ensure the lumped disturbances and uncertainty rejection of the closed-loop system. The phenomenon of phase hysteresis and time delay, caused by non-collocated sensor/actuator pairs, degrades the performance of the control system, even inducing instability. To solve this problem, a simple proportional differential (PD) controller and acceleration feed-forward with an output predictor design produce the control law for each vibration mode. The modal frequencies, phase hysteresis loops and phase lag values due to non-collocated placement of the acceleration sensor and piezoelectric patch actuator are experimentally obtained, and the phase lag is compensated by using the Smith Predictor technology. In order to improve the vibration control performance, the chaos optimization method based on logistic mapping is employed to auto-tune the parameters of the feedback channel. The experimental control system for the ACSP is tested using the dSPACE real-time simulation platform. Experimental results demonstrate that the proposed composite active control algorithm is an effective approach for suppressing multi-modal vibrations.
Parametric study on a collocated PZT beam vibration absorber and power harvester
Energy Technology Data Exchange (ETDEWEB)
Huang, Shyh Chin [Mechanical Engineering, Ming Chi University of Technology, New Taipei (China); Tsai, Chao Yang [Mechanical Engineering Army Academy, R.O.C., Taoyuan (China); Liao, Hsiao Hui [LNG Construction and Project Division, CPC Corp., Taipei (China)
2016-11-15
The parametric effects of a PZT beam that is simultaneously used as a vibration absorber and a power harvester were investigated in this study. A cantilever beam paved with PZT layers and with added tip mass has been widely used as a harvester or sometimes as a Dynamic vibration absorber (DVA). However, the beam is rarely considered a collocated device. In this study, the first step was theoretical derivation of a distributed beam covered with bimorph PZT layers. Then, the beam was attached to a 1DOF vibratory main system. Two indicators for vibration absorption and power harvesting were defined. Numerical results demonstrated that the lumped mass ratio favored both of the abilities, but that the DVA mass ratio influenced these two abilities in exactly the opposite way. The conjunction of a harvester circuit into a DVA shifted its resonance frequency up to 5 % (an extreme case of open circuit R→∞). Simultaneous power harvesting diminished the absorption capability up to 35 % for each set of mass ratios. To achieve the maximum degree of power harvesting, a corresponding load resistance that somewhat increases with the lumped mass ratio is applied. Experimental results verified the existence of the best load resistance, but the measured harvested curve was lower than the theoretical calculation because of structure damping and deviations of PZT material properties.
Visual Typo Correction by Collocative Optimization: A Case Study on Merchandize Images.
Wei, Xiao-Yong; Yang, Zhen-Qun; Ngo, Chong-Wah; Zhang, Wei
2014-02-01
Near-duplicate retrieval (NDR) in merchandize images is of great importance to a lot of online applications on e-Commerce websites. In those applications where the requirement of response time is critical, however, the conventional techniques developed for a general purpose NDR are limited, because expensive post-processing like spatial verification or hashing is usually employed to compromise the quantization errors among the visual words used for the images. In this paper, we argue that most of the errors are introduced because of the quantization process where the visual words are considered individually, which has ignored the contextual relations among words. We propose a "spelling or phrase correction" like process for NDR, which extends the concept of collocations to visual domain for modeling the contextual relations. Binary quadratic programming is used to enforce the contextual consistency of words selected for an image, so that the errors (typos) are eliminated and the quality of the quantization process is improved. The experimental results show that the proposed method can improve the efficiency of NDR by reducing vocabulary size by 1000% times, and under the scenario of merchandize image NDR, the expensive local interest point feature used in conventional approaches can be replaced by color-moment feature, which reduces the time cost by 9202% while maintaining comparable performance to the state-of-the-art methods.
Molinaro, Nicola; Carreiras, Manuel
2010-03-01
Despite the potentially infinite creativity of language, many words are patterned in ordered strings called collocations. Final words of these clusters are highly predictable; in addition, their overall meaning can vary on the literality dimension, ranging from (figurative) idiomatic strings to literal strings. These structures thus offer a natural linguistic scenario to contrast ERP correlates of contextual expectation and semantic integration processes during comprehension. In this study, expected endings elicited a positive peak around 300ms compared to less expected synonyms, suggesting that the earlier recognition of the string leads to the specific pre-activation of the lexical items that conclude the expression. On the other hand, meaning variations of these fixed strings (either a literal or a figurative whole meaning) affected ERPs only around 400ms, i.e. in the frontal portion of the N400. These findings are discussed within a more general cognitive framework as outlined in Kok's (2001) dual categorization model. Copyright 2009 Elsevier B.V. All rights reserved.
Huang, Jingfeng; Hsu, N. Christina; Tsay, Si-Chee; Holben, Brent N.; Welton, Ellsworth J.; Smirnov, Alexander; Jeong, Myeong-Jae; Hansell, Richard A.; Berkoff, Timothy A.
2012-01-01
Cirrus clouds, particularly sub visual high thin cirrus with low optical thickness, are difficult to be screened in operational aerosol retrieval algorithms. Collocated aerosol and cirrus observations from ground measurements, such as the Aerosol Robotic Network (AERONET) and the Micro-Pulse Lidar Network (MPLNET), provide us with an unprecedented opportunity to examine the susceptibility of operational aerosol products to thin cirrus contamination. Quality assured aerosol optical thickness (AOT) measurements were also tested against the CALIPSO vertical feature mask (VFM) and the MODIS-derived thin cirrus screening parameters for the purpose of evaluating thin cirrus contamination. Key results of this study include: (1) Quantitative evaluations of data uncertainties in AERONET AOT retrievals are conducted. Although AERONET cirrus screening schemes are successful in removing most cirrus contamination, strong residuals displaying strong spatial and seasonal variability still exist, particularly over thin cirrus prevalent regions during cirrus peak seasons, (2) Challenges in matching up different data for analysis are highlighted and corresponding solutions proposed, and (3) Estimation of the relative contributions from cirrus contamination to aerosol retrievals are discussed. The results are valuable for better understanding and further improving ground aerosol measurements that are critical for aerosol-related climate research.
On the optimal polynomial approximation of stochastic PDEs by galerkin and collocation methods
Beck, Joakim
2012-09-01
In this work we focus on the numerical approximation of the solution u of a linear elliptic PDE with stochastic coefficients. The problem is rewritten as a parametric PDE and the functional dependence of the solution on the parameters is approximated by multivariate polynomials. We first consider the stochastic Galerkin method, and rely on sharp estimates for the decay of the Fourier coefficients of the spectral expansion of u on an orthogonal polynomial basis to build a sequence of polynomial subspaces that features better convergence properties, in terms of error versus number of degrees of freedom, than standard choices such as Total Degree or Tensor Product subspaces. We consider then the Stochastic Collocation method, and use the previous estimates to introduce a new class of Sparse Grids, based on the idea of selecting a priori the most profitable hierarchical surpluses, that, again, features better convergence properties compared to standard Smolyak or tensor product grids. Numerical results show the effectiveness of the newly introduced polynomial spaces and sparse grids. © 2012 World Scientific Publishing Company.
Directory of Open Access Journals (Sweden)
Sepahvand K.
2016-01-01
Full Text Available Stochastic analysis of structures having nonlinearity by means of sampling methods leads to expensive cost in term of computational time. In contrast, non-sampling methods based on the spectral representation of uncertainty are very efficient with comparable accurate results. In this pa- per, the application of spectral methods to nonlinear dynamics of structures with random parameters is investigated. The impact of the parameter randomness on structural responses has been consid- ered. To this end, uncertain parameters and the structure responses are represented using the gPC expansions with unknown deterministic coefficients and random orthogonal polynomial basis. The deterministic finite element model of the structure is used as black-box and it is executed on a set of random collocation points. As the sample structure responses are estimated, a nonlinear optimization process is employed to calculate the unknown coefficients. The method has this main advantage that can be used for complicated nonlinear structural dynamic problems for which the deterministic FEM model has been already developed. Furthermore, it is very time efficient in comparison with sampling methods, as MC simulations. The application of the method is applied to the nonlinear transient analysis of composite beam structures including uncertain quadratic random damping. The results show that the proposed method can capture the large range of uncertainty in input parameters as well as in structural dynamic responses while it is too time-efficient.
Ozer, Ekin; Feng, Dongming; Feng, Maria Q.
2017-10-01
State-of-the-art multisensory technologies and heterogeneous sensor networks propose a wide range of response measurement opportunities for structural health monitoring (SHM). Measuring and fusing different physical quantities in terms of structural vibrations can provide alternative acquisition methods and improve the quality of the modal testing results. In this study, a recently introduced SHM concept, SHM with smartphones, is focused to utilize multisensory smartphone features for a hybridized structural vibration response measurement framework. Based on vibration testing of a small-scale multistory laboratory model, displacement and acceleration responses are monitored using two different smartphone sensors, an embedded camera and accelerometer, respectively. Double-integration or differentiation among different measurement types is performed to combine multisensory measurements on a comparative basis. In addition, distributed sensor signals from collocated devices are processed for modal identification, and performance of smartphone-based sensing platforms are tested under different configuration scenarios and heterogeneity levels. The results of these tests show a novel and successful implementation of a hybrid motion sensing platform through multiple sensor type and device integration. Despite the heterogeneity of motion data obtained from different smartphone devices and technologies, it is shown that multisensory response measurements can be blended for experimental modal analysis. Getting benefit from the accessibility of smartphone technology, similar smartphone-based dynamic testing methodologies can provide innovative SHM solutions with mobile, programmable, and cost-free interfaces.
Accuracy Analysis of Hrsi-Based Geopositioning Using Least Squares Collocation
Shen, Y.; Li, C.; Qiao, G.; Liu, S.
2012-07-01
Rational function model with bias compensation has been widely used in geopositioning of High Resolution Satellite Imagery (HRSI). We studied the geopositioning issue using a pair of QuickBird imagery in the Shanghai urban area with 126 Control Points (CPs) measured by GPS RTK. We proposed in this paper a stochastic model of HRSI geopositioning in which we modeled the random observed error and signal parts, then the Least Squares Collocation (LSC) is suggested to process the geopositioning with such kind of stochastic model. In order to correctly determine the variance components of the observed random error and signal parts, the variance components estimation of MINQUE is applied to compute the variance components for the LSC approach. And the cofactor matrix of signals is computed according to a prior given function. Then the same pair of QuickBird imagery is processed by using LSC approach with the stochastic model of this paper. In the experiments parts of the CPs are used as Ground Control Points (GCPs) to compute the bias-corrected parameters and parts of them are used as check points to calculate the root mean square errors for different schemes. Experimental results show that the proposed LSC approach for affine transformation model could improve geopositioning accuracy significantly, about 15 cm numerically (15% on average), even better than secondorder bias-corrected model with the same GCPs.
A probabilistic collocation based iterative Kalman filter for landfill data assimilation
Zheng, Qiang; Xu, Wenjie; Man, Jun; Zeng, Lingzao; Wu, Laosheng
2017-11-01
Accurate forecast of landfill gas (LFG) transport has remained as an active research area, due to the safety and environmental concerns, as well as the green energy potential. The iterative ensemble Kalman filter (IEnKF) has been used to characterize the heterogeneous permeability field of landfills. As a Monte Carlo-based method, IEnKF requires a sufficiently large ensemble size to guarantee its accuracy, which may result in a huge computational cost, especially for large-scale problems. In this study, an efficient probabilistic collocation based iterative Kalman filter (PCIKF) is developed. The polynomial chaos expansion (PCE) is employed to represent and propagate the uncertainties, and an iterative form of Kalman filter is used to assimilate the measurements. To further reduce the computational cost, only the zeroth and first-order ANOVA (analysis of variance) components are kept in the PCE approximation. As demonstrated by two numerical case studies, PCIKF shows significant superiority over IEnKF in terms of accuracy and efficiency. The developed method has the potential to reliably predict and develop best management practices for landfill gas production.
ANOVA-based transformed probabilistic collocation method for Bayesian data-worth analysis
Man, Jun; Liao, Qinzhuo; Zeng, Lingzao; Wu, Laosheng
2017-12-01
Bayesian theory provides a coherent framework in quantifying the data worth of measurements and estimating unknown parameters. Nevertheless, one common problem in Bayesian methods is the considerably high computational cost since a large number of model evaluations is required in the likelihood evaluation. To address this issue, a new surrogate modeling method, i.e., ANOVA (analysis of variance)-based transformed probabilistic collocation method (ATPCM), is developed in this work. To cope with the strong nonlinearity, the model responses are transformed to the arrival times, which are then approximated with a set of low-order ANOVA components. The validity of the proposed method is demonstrated by synthetic numerical cases involving water and heat transport in the vadose zone. It is shown that, the ATPCM is more efficient than the existing surrogate modeling methods (e.g., PCM, ANOVA-based PCM and TPCM). At a very low computational cost, the ATPCM-based Bayesian data-worth analysis provides a quantitative metric in comparing different monitoring plans, and helps to improve the parameter estimation. Although the flow and heat transport in vadose zone is considered in this work, the proposed method can be equally applied in any other hydrologic problems.
Trajectory Planning of Satellite Formation Flying using Nonlinear Programming and Collocation
Lim, Hyung-Chu; Bang, Hyochoong
2008-12-01
Recently, satellite formation flying has been a topic of significant research interest in aerospace society because it provides potential benefits compared to a large spacecraft. Some techniques have been proposed to design optimal formation trajectories minimizing fuel consumption in the process of formation configuration or reconfiguration. In this study, a method is introduced to build fuel-optimal trajectories minimizing a cost function that combines the total fuel consumption of all satellites and assignment of fuel consumption rate for each satellite. This approach is based on collocation and nonlinear programming to solve constraints for collision avoidance and the final configuration. New constraints of nonlinear equality or inequality are derived for final configuration, and nonlinear inequality constraints are established for collision avoidance. The final configuration constraints are that three or more satellites should form a projected circular orbit and make an equilateral polygon in the horizontal plane. Example scenarios, including these constraints and the cost function, are simulated by the method to generate optimal trajectories for the formation configuration and reconfiguration of multiple satellites.
Trajectory Planning of Satellite Formation Flying using Nonlinear Programming and Collocation
Directory of Open Access Journals (Sweden)
Hyung-Chu Lim
2008-12-01
Full Text Available Recently, satellite formation flying has been a topic of significant research interest in aerospace society because it provides potential benefits compared to a large spacecraft. Some techniques have been proposed to design optimal formation trajectories minimizing fuel consumption in the process of formation configuration or reconfiguration. In this study, a method is introduced to build fuel-optimal trajectories minimizing a cost function that combines the total fuel consumption of all satellites and assignment of fuel consumption rate for each satellite. This approach is based on collocation and nonlinear programming to solve constraints for collision avoidance and the final configuration. New constraints of nonlinear equality or inequality are derived for final configuration, and nonlinear inequality constraints are established for collision avoidance. The final configuration constraints are that three or more satellites should form a projected circular orbit and make an equilateral polygon in the horizontal plane. Example scenarios, including these constraints and the cost function, are simulated by the method to generate optimal trajectories for the formation configuration and reconfiguration of multiple satellites.
Solar absorption estimated from surface radiation measurements and collocated satellite products
Hakuba, M. Z.; Wild, M.; Folini, D.; Sanchez-Lorenzo, A.; Schaepman-Strub, G.
2012-04-01
The Earth's climate and life-relevant processes are governed by the incoming solar radiation as part of the global energy balance. Changes in the atmospheric energy budget largely affect the global climate and hydrological cycle, but the quantification of the different energy balance components is still afflicted with large uncertainties. The overall aim of the research presented here is an improved understanding of the mean state and spatio-temporal variations of the global energy balance through reducing the uncertainties in one of its components, i.e., the absorption of solar radiation within the climate system. To quantify the solar absorption at the surface and within the atmospheric column, we combine the worldwide surface radiation measurements of the Global Energy Balance archive (GEBA) and Baseline Surface Radiation Network (BSRN) with collocated satellite-inferred surface albedo and top-of-atmosphere (TOA) radiation data (MODIS, CERES). Our analysis of the present mean state, temporal and spatial variability during the last decade (2000-2010) focuses on Europe and Asia, and will expand worldwide in a later step. We examined the quality and homogeneity of station records beyond 2000 provided by GEBA to identify a subset of station records of sufficient quality. We find the vast majority of monthly records to be suitable for our purposes. The considered GEBA sites indicate overall positive trends in Europe, and mostly negative trends over Asia during the last decade (2000-2010). To derive the surface solar absorption at the measurement sites, we intend to combine the shortwave fluxes with the collocated surface albedo from MODIS. The MODIS products include the so-called black-sky albedo (under the assumption of direct radiation only) and white-sky albedo (under diffuse isotropic conditions). The majority of GEBA sites comprises only global radiation data, which do not differentiate between direct and diffuse components. To determine solar absorption from
Zhang, D.; Liao, Q.
2016-12-01
The Bayesian inference provides a convenient framework to solve statistical inverse problems. In this method, the parameters to be identified are treated as random variables. The prior knowledge, the system nonlinearity, and the measurement errors can be directly incorporated in the posterior probability density function (PDF) of the parameters. The Markov chain Monte Carlo (MCMC) method is a powerful tool to generate samples from the posterior PDF. However, since the MCMC usually requires thousands or even millions of forward simulations, it can be a computationally intensive endeavor, particularly when faced with large-scale flow and transport models. To address this issue, we construct a surrogate system for the model responses in the form of polynomials by the stochastic collocation method. In addition, we employ interpolation based on the nested sparse grids and takes into account the different importance of the parameters, under the condition of high random dimensions in the stochastic space. Furthermore, in case of low regularity such as discontinuous or unsmooth relation between the input parameters and the output responses, we introduce an additional transform process to improve the accuracy of the surrogate model. Once we build the surrogate system, we may evaluate the likelihood with very little computational cost. We analyzed the convergence rate of the forward solution and the surrogate posterior by Kullback-Leibler divergence, which quantifies the difference between probability distributions. The fast convergence of the forward solution implies fast convergence of the surrogate posterior to the true posterior. We also tested the proposed algorithm on water-flooding two-phase flow reservoir examples. The posterior PDF calculated from a very long chain with direct forward simulation is assumed to be accurate. The posterior PDF calculated using the surrogate model is in reasonable agreement with the reference, revealing a great improvement in terms of
Energy Technology Data Exchange (ETDEWEB)
Castillo, Victor Manuel [Univ. of California, Davis, CA (United States)
1999-01-01
A collocation method using cubic splines is developed and applied to simulate steady and time-dependent, including turbulent, thermally convecting flows for two-dimensional compressible fluids. The state variables and the fluxes of the conserved quantities are approximated by cubic splines in both space direction. This method is shown to be numerically conservative and to have a local truncation error proportional to the fourth power of the grid spacing. A ''dual-staggered'' Cartesian grid, where energy and momentum are updated on one grid and mass density on the other, is used to discretize the flux form of the compressible Navier-Stokes equations. Each grid-line is staggered so that the fluxes, in each direction, are calculated at the grid midpoints. This numerical method is validated by simulating thermally convecting flows, from steady to turbulent, reproducing known results. Once validated, the method is used to investigate many aspects of thermal convection with high numerical accuracy. Simulations demonstrate that multiple steady solutions can coexist at the same Rayleigh number for compressible convection. As a system is driven further from equilibrium, a drop in the time-averaged dimensionless heat flux (and the dimensionless internal entropy production rate) occurs at the transition from laminar-periodic to chaotic flow. This observation is consistent with experiments of real convecting fluids. Near this transition, both harmonic and chaotic solutions may exist for the same Rayleigh number. The chaotic flow loses phase-space information at a greater rate, while the periodic flow transports heat (produces entropy) more effectively. A linear sum of the dimensionless forms of these rates connects the two flow morphologies over the entire range for which they coexist. For simulations of systems with higher Rayleigh numbers, a scaling relation exists relating the dimensionless heat flux to the two-seventh's power of the Rayleigh number
Multi-index Stochastic Collocation Convergence Rates for Random PDEs with Parametric Regularity
Haji Ali, Abdul Lateef
2016-08-26
We analyze the recent Multi-index Stochastic Collocation (MISC) method for computing statistics of the solution of a partial differential equation (PDE) with random data, where the random coefficient is parametrized by means of a countable sequence of terms in a suitable expansion. MISC is a combination technique based on mixed differences of spatial approximations and quadratures over the space of random data, and naturally, the error analysis uses the joint regularity of the solution with respect to both the variables in the physical domain and parametric variables. In MISC, the number of problem solutions performed at each discretization level is not determined by balancing the spatial and stochastic components of the error, but rather by suitably extending the knapsack-problem approach employed in the construction of the quasi-optimal sparse-grids and Multi-index Monte Carlo methods, i.e., we use a greedy optimization procedure to select the most effective mixed differences to include in the MISC estimator. We apply our theoretical estimates to a linear elliptic PDE in which the log-diffusion coefficient is modeled as a random field, with a covariance similar to a Matérn model, whose realizations have spatial regularity determined by a scalar parameter. We conduct a complexity analysis based on a summability argument showing algebraic rates of convergence with respect to the overall computational work. The rate of convergence depends on the smoothness parameter, the physical dimensionality and the efficiency of the linear solver. Numerical experiments show the effectiveness of MISC in this infinite dimensional setting compared with the Multi-index Monte Carlo method and compare the convergence rate against the rates predicted in our theoretical analysis. © 2016 SFoCM
Collocation methods for uncertainty quanti cation in PDE models with random data
Nobile, Fabio
2014-01-06
In this talk we consider Partial Differential Equations (PDEs) whose input data are modeled as random fields to account for their intrinsic variability or our lack of knowledge. After parametrizing the input random fields by finitely many independent random variables, we exploit the high regularity of the solution of the PDE as a function of the input random variables and consider sparse polynomial approximations in probability (Polynomial Chaos expansion) by collocation methods. We first address interpolatory approximations where the PDE is solved on a sparse grid of Gauss points in the probability space and the solutions thus obtained interpolated by multivariate polynomials. We present recent results on optimized sparse grids in which the selection of points is based on a knapsack approach and relies on sharp estimates of the decay of the coefficients of the polynomial chaos expansion of the solution. Secondly, we consider regression approaches where the PDE is evaluated on randomly chosen points in the probability space and a polynomial approximation constructed by the least square method. We present recent theoretical results on the stability and optimality of the approximation under suitable conditions between the number of sampling points and the dimension of the polynomial space. In particular, we show that for uniform random variables, the number of sampling point has to scale quadratically with the dimension of the polynomial space to maintain the stability and optimality of the approximation. Numerical results show that such condition is sharp in the monovariate case but seems to be over-constraining in higher dimensions. The regression technique seems therefore to be attractive in higher dimensions.
Multi-Index Monte Carlo and stochastic collocation methods for random PDEs
Nobile, Fabio
2016-01-09
In this talk we consider the problem of computing statistics of the solution of a partial differential equation with random data, where the random coefficient is parametrized by means of a finite or countable sequence of terms in a suitable expansion. We describe and analyze a Multi-Index Monte Carlo (MIMC) and a Multi-Index Stochastic Collocation method (MISC). the former is both a stochastic version of the combination technique introduced by Zenger, Griebel and collaborators and an extension of the Multilevel Monte Carlo (MLMC) method first described by Heinrich and Giles. Instead of using firstorder differences as in MLMC, MIMC uses mixed differences to reduce the variance of the hierarchical differences dramatically. This in turn yields new and improved complexity results, which are natural generalizations of Giles s MLMC analysis, and which increase the domain of problem parameters for which we achieve the optimal convergence, O(TOL-2). On the same vein, MISC is a deterministic combination technique based on mixed differences of spatial approximations and quadratures over the space of random data. Provided enough mixed regularity, MISC can achieve better complexity than MIMC. Moreover, we show that in the optimal case the convergence rate of MISC is only dictated by the convergence of the deterministic solver applied to a one-dimensional spatial problem. We propose optimization procedures to select the most effective mixed differences to include in MIMC and MISC. Such optimization is a crucial step that allows us to make MIMC and MISC computationally effective. We finally show the effectiveness of MIMC and MISC with some computational tests, including tests with a infinite countable number of random parameters.
Wu, Y. J.; Williams, E.; Chang, S. C.; Chou, J. K.; Hsu, R. R.; Friedrich, M.; Kuo, C. L.; Chen, A. B.; Peng, K. M.; Su, H. T.; Frey, H. U.; Mende, S. B.; Takahashi, Y.; Lee, L. C.
2017-05-01
The elve is the dominant type of transient luminous event (TLE) at the base of the E region ionosphere. The hydroxyl nightglow (OH* nightglow hereafter) has been reported at a similar altitude. Statistical studies show that the mean heights of elve and OH* nightglow are 87 km and 87.5 km, respectively, and that 91% of the 291 limb elves are located within ±5 km of the altitude of the brightest OH* nightglow emission and both elves and OH* nightglow show the semiannual oscillation (SAO) at low latitude. The physical reasons for the collocation of elves and OH* nightglow are the main focus of attention. A model for elve emission with the environmental-adapted electron density profile is tested with three density profiles of atomic oxygen (O): the original profile from the NRLMSISE-00 model and two other profiles which are shifted 5 km upward/downward from the original. For higher altitudes of the given O density profile, the peak altitudes of the elve emission layers are also increased. This result reveals the leading role of atomic oxygen in the collocation. Furthermore, the altitude variation of elves is compared with the VLF reflection height observed by DEMETER. The latter height not only shows the SAO similarity to the elve/OH* heights but also exhibits a difference between land and ocean. The possible relationship between VLF reflection height and elve/OH* height is also discussed.Plain Language SummaryThe collocation of elves and OH Meinel band nightglow implies that OH* nightglow is the visible upper boundary of the VLF waveguide.
The Chebyshev Hyperplane Optimization Problem
Still, Georg J.; Streng, Martin; Streng, M.
1997-01-01
We consider the following problem. Given a finite set of pointsyj inR n we want to determine a hyperplane H such that the maximum Euclidean distance betweenH and the pointsyj is minimized. This problem(CHOP) is a non-convex optimization problem with a special structure. Forexample, all local minima
Chebyshev splines and Kolmogorov inequalities
National Research Council Canada - National Science Library
Bagdasarov, Sergey
1998-01-01
.... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.1.2 Cases of the complete solution of the Kolmogorov problem... 0.2 Kolmogorov - Landau problem in the Sobolev class W~+l(I) ... 0.2.1 Inequalities...
Xiaokui Yue; Xuechuan Wang; Honghua Dai
2014-01-01
A numerical approach for obtaining periodic orbits of satellite relative motion is proposed, based on using the time domain collocation (TDC) method to search for the periodic solutions of an exact J2 nonlinear relative model. The initial conditions for periodic relative orbits of the Clohessy-Wiltshire (C-W) equations or Tschauner-Hempel (T-H) equations can be refined with this approach to generate nearly bounded orbits. With these orbits, a method based on the least-squares principle is the...
Gaudreau, Philippe; Safouhi, Hassan
2017-10-01
We show that the double exponential sinc-collocation method provides an efficient uniformly accurate solution to the one-dimensional time independent Schrödinger equation for a general class of rational potentials of the form V (x) = p(x)/q(x). The derived algorithm is based on the discretization of the Hamiltonian of the Schrödinger equation using sinc expansions. This discretization results in a generalized eigenvalue problem, the eigenvalues of which correspond to approximations of the energy values of the starting Hamiltonian. A systematic numerical study is conducted, beginning with test potentials with known eigenvalues and moving to rational potentials of increasing degree.
An efficient approach to numerical study of the coupled-BBM system with B-spline collocation method
Directory of Open Access Journals (Sweden)
khalid ali
2016-11-01
Full Text Available In the present paper, a numerical method is proposed for the numerical solution of a coupled-BBM system with appropriate initial and boundary conditions by using collocation method with cubic trigonometric B-spline on the uniform mesh points. The method is shown to be unconditionally stable using von-Neumann technique. To test accuracy the error norms2L, ?L are computed. Furthermore, interaction of two and three solitary waves are used to discuss the effect of the behavior of the solitary waves after the interaction. These results show that the technique introduced here is easy to apply. We make linearization for the nonlinear term.
A tandem approach for collocated measurements of microphysical and radiative cirrus properties
Klingebiel, Marcus; Ehrlich, André; Finger, Fanny; Röschenthaler, Timo; Jakirlić, Suad; Voigt, Matthias; Müller, Stefan; Maser, Rolf; Wendisch, Manfred; Hoor, Peter; Spichtinger, Peter; Borrmann, Stephan
2017-09-01
altitudes or by making use of the collocated irradiance measurements at different altitudes of the tandem platform. Due to unavoidable biases of the measurements between the individual flight legs, the single-platform approach failed to provide a realistic solar heating rate profile, while the uncertainties of the tandem approach are reduced. Here, the solar heating rates range up to 6 K day-1 at top of the cirrus layer.
Parsani, Matteo
2016-10-04
Staggered grid, entropy stable discontinuous spectral collocation operators of any order are developed for the compressible Euler and Navier--Stokes equations on unstructured hexahedral elements. This generalization of previous entropy stable spectral collocation work [M. H. Carpenter, T. C. Fisher, E. J. Nielsen, and S. H. Frankel, SIAM J. Sci. Comput., 36 (2014), pp. B835--B867, M. Parsani, M. H. Carpenter, and E. J. Nielsen, J. Comput. Phys., 292 (2015), pp. 88--113], extends the applicable set of points from tensor product, Legendre--Gauss--Lobatto (LGL), to a combination of tensor product Legendre--Gauss (LG) and LGL points. The new semidiscrete operators discretely conserve mass, momentum, energy, and satisfy a mathematical entropy inequality for the compressible Navier--Stokes equations in three spatial dimensions. They are valid for smooth as well as discontinuous flows. The staggered LG and conventional LGL point formulations are compared on several challenging test problems. The staggered LG operators are significantly more accurate, although more costly from a theoretical point of view. The LG and LGL operators exhibit similar robustness, as is demonstrated using test problems known to be problematic for operators that lack a nonlinear stability proof for the compressible Navier--Stokes equations (e.g., discontinuous Galerkin, spectral difference, or flux reconstruction operators).
Directory of Open Access Journals (Sweden)
M. Rahimi-Gorji
2015-06-01
Full Text Available An analytical investigation is applied for unsteady motion of a rigid spherical particle in a quiescent shear-thinning power-law fluid. The results were compared with those obtained from Collocation Method (CM and the established Numerical Method (Fourth order Runge–Kutta scheme. It was shown that CM gave accurate results. Collocation Method (CM and Numerical Method are used to solve the present problem. We obtained that the CM which was used to solve such nonlinear differential equation with fractional power is simpler and more accurate than series method such as HPM which was used in some previous works by others but the new method named Akbari-Ganji’s Method (AGM is an accurate and simple method which is slower than CM for solving such problems. The terminal settling velocity—that is the velocity at which the net forces on a falling particle eliminate—for three different spherical particles (made of plastic, glass and steel and three flow behavior index n, in three sets of power-law non-Newtonian fluids was investigated, based on polynomial solution (CM. Analytical results obtained indicated that the time of reaching the terminal velocity in a falling procedure is significantly increased with growing of the particle size that validated with Numerical Method. Further, with approaching flow behavior to Newtonian behavior from shear-thinning properties of flow (n → 1, the transient time to achieving the terminal settling velocity is decreased.
Ibdah, H.; Khuri, S. A.; Sayfy, A.
2014-09-01
The ultimate purpose of this article is to introduce and describe a combined approach, based on asymptotic boundary conditions (ABCs) and a fourth order cubic B-spline collocation, for the numerical solution of a general class of two-point linear boundary-value problems (BVPs) over a semi-infinite interval that arises in various engineering applications. The scheme will be extended and then implemented to handle a system of BVPs. The idea of the proposed strategy is to first reduce the condition at infinity to an asymptotic boundary condition that approaches the specified value at infinity over a large finite interval. Then, the problem complimented with the resulting ABC is solved using a fourth-order spline collocation approach constructed over uniform meshes. The scheme is numerically verified to have a fourth order rate of convergence. The work is illustrated by considering a number of test examples that confirm the accuracy, efficient treatment of the boundary condition at infinity, and applicability of the approach. The computational results show that the scheme is reliable, converges fast, and compares very well with the existing analytic solutions.
Directory of Open Access Journals (Sweden)
Pedro Patiño García
2013-04-01
Full Text Available This paper describes the Corpus of Free Trade Agreements (henceforth FTA, a specialized parallel corpus in English and Spanish from Europe and America and a smaller subcorpus in English-Norwegian and Spanish-Norwegian that was prepared and then aligned with Translation Corpus Aligner 2 (Hofland & Johansson, 1998. The data was taken from Free Trade Agreements. These agreements are specialized texts officially signed and ratified by several countries and blocks of countries in the last twenty years. Thus, FTAs are a rich repository for terminology and phraseology that is used in different fields of business activity throughout the world. The corpus contains around 1.37 million words in the English section and 1.48 million words in its Spanish counterpart, plus 60,000 words each in the Spanish-Norwegian and English-Norwegian subcorpus. The corpus is being used primarily to study the terms and specialized collocations that include these terms in this kind of specialized texts.Keywords: specialized collocation, specialized parallel corpus, corpus linguistics, Free Trade Agreement
Wu, Yi-ju
2016-01-01
Data-Driven Learning (DDL), in which learners "confront [themselves] directly with the corpus data" (Johns, 2002, p. 108), has shown to be effective in collocation learning in L2 writing. Nevertheless, there have been only few research studies of this type examining the relationship between English proficiency and corpus consultation.…
Simurda, Matej; Duggen, Lars; Basse, Nils T; Lassen, Benny
2018-02-01
A numerical model for transit-time ultrasonic flowmeters operating under multiphase flow conditions previously presented by us is extended by mesh refinement and grid point redistribution. The method solves modified first-order stress-velocity equations of elastodynamics with additional terms to account for the effect of the background flow. Spatial derivatives are calculated by a Fourier collocation scheme allowing the use of the fast Fourier transform, while the time integration is realized by the explicit third-order Runge-Kutta finite-difference scheme. The method is compared against analytical solutions and experimental measurements to verify the benefit of using mapped grids. Additionally, a study of clamp-on and in-line ultrasonic flowmeters operating under multiphase flow conditions is carried out.
Directory of Open Access Journals (Sweden)
Xiaokui Yue
2014-01-01
Full Text Available A numerical approach for obtaining periodic orbits of satellite relative motion is proposed, based on using the time domain collocation (TDC method to search for the periodic solutions of an exact J2 nonlinear relative model. The initial conditions for periodic relative orbits of the Clohessy-Wiltshire (C-W equations or Tschauner-Hempel (T-H equations can be refined with this approach to generate nearly bounded orbits. With these orbits, a method based on the least-squares principle is then proposed to generate projected closed orbit (PCO, which is a reference for the relative motion control. Numerical simulations reveal that the presented TDC searching scheme is effective and simple, and the projected closed orbit is very fuel saving.
Energy Technology Data Exchange (ETDEWEB)
Jiaxing, Cheng; Dongfa, Sheng [Southwest Forestry University, Yunnan (China)
2017-05-15
As an important supplement and development to crystallography, the applications about quasicrystal materials have played a core role in many fields, such as manufacturing and the space industry. Due to the sensitivity of quasicrystals to defects, the research on the fracture problem of quasicrystals has attracted a great deal of attention. We present a boundary collocation method to research fracture problems for a finite dimension rectangular one-dimensional hexagonal quasicrystal plate. Because mode I and mode II problems for one- dimensional hexagonal quasicrystals are like that for the classical elastic materials, only the anti-plane problem is discussed in this paper. The correctness of the present numerical method is verified through a comparison of the present results and the existing results. And then, the size effects on stress field, stress intensity factor and energy release rate are discussed in detail. The obtained results can provide valuable references for the fracture behavior of quasicrystals.
Ruppert, Michael G.; Yong, Yuen K.
2017-08-01
The quality (Q) factor is an important parameter of the resonance of the microcantilever as it determines both imaging bandwidth and force sensitivity. The ability to control the Q factor of multiple modes is believed to be of great benefit for atomic force microscopy techniques involving multiple eigenmodes. In this paper, we propose a novel cantilever design employing multiple piezoelectric transducers which are used for separated actuation and sensing, leading to guaranteed collocation of the first eight eigenmodes up to 3 MHz. The design minimizes the feedthrough usually observed with these systems by incorporating a guard trace on the cantilever chip. As a result, a multimode Q controller is demonstrated to be able to modify the quality factor of the first two eigenmodes over up to four orders of magnitude without sacrificing robust stability.
Bahşı, Ayşe Kurt; Yalçınbaş, Salih
2016-01-01
In this study, the Fibonacci collocation method based on the Fibonacci polynomials are presented to solve for the fractional diffusion equations with variable coefficients. The fractional derivatives are described in the Caputo sense. This method is derived by expanding the approximate solution with Fibonacci polynomials. Using this method of the fractional derivative this equation can be reduced to a set of linear algebraic equations. Also, an error estimation algorithm which is based on the residual functions is presented for this method. The approximate solutions are improved by using this error estimation algorithm. If the exact solution of the problem is not known, the absolute error function of the problems can be approximately computed by using the Fibonacci polynomial solution. By using this error estimation function, we can find improved solutions which are more efficient than direct numerical solutions. Numerical examples, figures, tables are comparisons have been presented to show efficiency and usable of proposed method.
Rahan, Nur Nadiah Mohd; Ishak, Siti Noor Shahira; Hamid, Nur Nadiah Abd; Majid, Ahmad Abd.; Azmi, Amirah
2017-04-01
In this research, the nonlinear Benjamin-Bona-Mahony (BBM) equation is solved numerically using the cubic B-spline (CuBS) and cubic trigonometric B-spline (CuTBS) collocation methods. The CuBS and CuTBS are utilized as interpolating functions in the spatial dimension while the standard finite difference method (FDM) is applied to discretize the temporal space. In order to solve the nonlinear problem, the BBM equation is linearized using Taylor's expansion. Applying the von-Neumann stability analysis, the proposed techniques are shown to be unconditionally stable under the Crank-Nicolson scheme. Several numerical examples are discussed and compared with exact solutions and results from the FDM.
DEFF Research Database (Denmark)
Dankowicz, Harry; Schilder, Frank
This paper presents a collocation toolbox for multi-point, boundary-value problems. This toolbox has been recently developed by the authors to support general-purpose parameter continuation of sets of constrained orbit segments, such as i) segmented trajectories in hybrid dynamical systems......, for example, mechanical systems with impacts, friction, and switching control, ii) homoclinic orbits represented by an equilibrium point and a finite-time trajectory that starts and ends near this equilibrium point, and iii) collections of trajectories that represent quasi-periodic invariant tori...... the continuation of families of periodic orbits in a hybrid dynamical system with impacts and friction as well as detection and constrained continuation of selected degeneracies characteristic of such systems, such as grazing and switching-sliding bifurcations....
Directory of Open Access Journals (Sweden)
E.C. Biscaia Junior
2001-06-01
Full Text Available A dynamic kinetic-diffusive model for the extraction of metallic ions from aqueous liquors using liquid surfactant membranes is proposed. The model incorporates undesirable intrinsic phenomena such as swelling and breakage of the emulsion globules that have to be controlled during process operation. These phenomena change the spatial location of the chemical reaction during the course of extraction, resulting in a transient moving boundary problem. The orthogonal collocation method was used to transform the partial differential equations into an ordinary differential equation set that was solved by an implicit numerical routine. The model was found to be numerically stable and reliable in predicting the behaviour of zinc extraction with acidic extractant for long residence times.
Scaling of a Fast Fourier Transform and a pseudo-spectral fluid solver up to 196608 cores
Chatterjee, Anando G.
2017-11-04
In this paper we present scaling results of a FFT library, FFTK, and a pseudospectral code, Tarang, on grid resolutions up to 81923 grid using 65536 cores of Blue Gene/P and 196608 cores of Cray XC40 supercomputers. We observe that communication dominates computation, more so on the Cray XC40. The computation time scales as Tcomp∼p−1, and the communication time as Tcomm∼n−γ2 with γ2 ranging from 0.7 to 0.9 for Blue Gene/P, and from 0.43 to 0.73 for Cray XC40. FFTK, and the fluid and convection solvers of Tarang exhibit weak as well as strong scaling nearly up to 196608 cores of Cray XC40. We perform a comparative study of the performance on the Blue Gene/P and Cray XC40 clusters.
Gottschalk, I.; Hermans, T.; Caers, J.; Cameron, D. A.; Knight, R. J.; Regnery, J.; McCray, J. E.
2016-12-01
Aquifer recharge and recovery (ARR) is the process of enhancing natural groundwater resources and recovering water for later use by constructing engineered conveyances. Insufficient understanding of lithological heterogeneity at ARR sites often hinders attempts to predict where and how quickly infiltrating water will flow in the subsurface, which can adversely affect the quality and quantity of available water in the ARR site. In this study, we explored the use of electrical resistivity tomography (ERT) to assist in characterizing lithological heterogeneity at an ARR site, so as to incorporate it into a flow and contaminant transport model. In this case, we had non-collocated well core log data and ERT data from a full-scale ARR basin. We compared three independent methods for producing conditional lithology-resistivity probability distributions: 1) a search template to relate the nearest logged well lithologies with ERT resistivity panels, given search criteria; 2) a maximum likelihood estimation (MLE) to match bimodal normal distributions to the histogram of each ERT line; and 3) variogram-based lithology indicator simulations constrained to well data. Each approach leverages Bayes' Rule to estimate lithology probability given electrical resistivity. The simplest approach (method 1) yields an erroneous conditional probability function where sand dominates the conditional probability at nearly all resistivities, due in part to the strong presence of sand in the wells nearest the ERT lines. The approaches using MLE and lithology simulations (methods 2 and 3) produce similar, more realistic lithofacies probability functions. The range of resistivities where clay and sand overlap differs between methods 2 and 3: ranging between 100 and 200 ohm-m for method 2, and between 30 and 50 ohm-m for the method 3. These differences affect the posterior lithology distributions in multiple point geostatistical (MPS) simulations, and in turn, predictions of flow from models which
Tirani, M. D.; Maleki, M.; Kajani, M. T.
2014-11-01
A numerical method for solving the Lane-Emden equations of the polytropic index α when 4.75 ≤ α ≤ 5 is introduced. The method is based upon nonclassical Gauss-Radau collocation points and Freud type weights. Nonclassical orthogonal polynomials, nonclassical Radau points and weighted interpolation are introduced and are utilized in the interval [0,1]. A smooth, strictly monotonic transformation is used to map the infinite domain x ∈ [0,∞) onto a half-open interval t ∈ [0,1). The resulting problem on the finite interval is then transcribed to a system of nonlinear algebraic equations using collocation. The method is easy to implement and yields very accurate results.
DEFF Research Database (Denmark)
Sadiq, Muhammad; Tscherning, Carl C.; Ahmad, Zulfiqar
2009-01-01
This paper deals with the analysis of gravity anomaly and precise levelling in conjunction with GPS-Levelling data for the computation of a gravimetric geoid and an estimate of the height system bias parameter N-o for the vertical datum in Pakistan by means of least squares collocation technique...... covariance parameters has facilitated to achieve gravimetric height anomalies in a global geocentric datum. Residual terrain modeling (RTM) technique has been used in combination with the EGM96 for the reduction and smoothing of the gravity data. A value for the bias parameter N-o has been estimated...... with reference to the local GPS-Levelling datum that appears to be 0.705 m with 0.07 m mean square error. The gravimetric height anomalies were compared with height anomalies obtained from GPS-Levelling stations using least square collocation with and without bias adjustment. The bias adjustment minimizes...
2011-10-14
multispectral SeaPRISM system (CIMEL ELECTRONIQUE , France) which is now part of the AERONET Ocean Color Network [13,15,20], with a collocated hyperspectral... structure itself or its shadow [15]. The SeaPRISM system configuration of LISCO performs ocean color measurements at the 413, 442, 491, 551, 668...quality. Second, the sun glint removal step has been shown to generally overcorrect the SeaPRISM data, and thereby skew the wave structure statistics
Directory of Open Access Journals (Sweden)
Arne Van Londersele
2017-01-01
Full Text Available Graphene-based electrical components are inherently multiscale, which poses a real challenge for finite-difference time-domain (FDTD solvers due to the stringent time step upper bound. Here, a unidirectionally collocated hybrid implicit-explicit (UCHIE FDTD method is put forward that exploits the planar structure of graphene to increase the time step by implicitizing the critical dimension. The method replaces the traditional Yee discretization by a partially collocated scheme that allows a more accurate numerical description of the material boundaries. Moreover, the UCHIE-FDTD method preserves second-order accuracy even for nonuniform discretization in the direction of collocation. The auxiliary differential equation (ADE approach is used to implement the graphene sheet as a dispersive Drude medium. The finite grid is terminated by a uniaxial perfectly matched layer (UPML to permit open-space simulations. Special care is taken to elaborate on the efficient implementation of the implicit update equations. The UCHIE-FDTD method is validated by computing the shielding effectiveness of a typical graphene sheet.
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Petrus Chandra
2014-11-01
Full Text Available This research was to give insight to English teachers and practitioners who had the same problem faced by the writer and his students especially dealing with the lack of collocation. Moreover, this research inspired particularly those who involved in teaching practices for how to improve their professionalism by implementing Lexical-Based Approach in class activities and to find the solution and hindrances for a better teaching technique in the future. For students who had problems in collocation, this Lexical-Based Approach as used in Made Frida Yulia’s Vocabulary: Lexically-Based Second Thousand Words of General Service List book might improve the awareness toward lexical phrases, chunks and collocations. For teachers and practitioners who want to use this Lexical-Based Approach in the future could use bilingual explanation that is needed for Indonesian students rather than monolingual explanation in English, try to create a good note taking habit for lexical phrases as soon as possible, and use vivid pictures or audio visuals to kill the boredom of the students
Krypiak-Gregorczyk, Anna; Wielgosz, Paweł; Jarmołowski, Wojciech
2017-04-01
The ionosphere plays a crucial role in space weather that affects satellite navigation as the ionospheric delay is one of the major errors in GNSS. On the other hand, GNSS observations are widely used to determine the amount of ionospheric total electron content (TEC). An important aspect in the electron content estimation at regional and global scale is adopting the appropriate interpolation strategy. In this paper we propose and validate a new method for regional TEC modeling based on least squares collocation (LSC) with noise variance estimation. This method allows for providing accurate TEC maps with high spatial and temporal resolution. Such maps may be used to support precise GNSS positioning and navigation, e.g. in RTK mode and also in the ionosphere studies. To test applicability of new TEC maps to positioning, double-difference ionospheric corrections were derived from the maps and their accuracy was analyzed. In addition, the corrections were applied to GNSS positioning and validated in ambiguity resolution domain. The tests were carried out during a strong ionospheric storm when the ionosphere is particularly difficult to model. The performance of the new approach was compared to IGS and UPC global, and CODE regional TEC maps. The results showed an advantage of our solution with resulting accuracy of the relative ionospheric corrections usually better than 10 cm, even during the ionospheric disturbances. This proves suitability of our regional TEC maps for, e.g. supporting fast ambiguity resolution in kinematic GNSS positioning.
Jarmołowski, Wojciech
2017-07-01
Maximum likelihood (ML) and restricted maximum likelihood (REML) are nowadays very popular in geophysics, geodesy and many other fields. There is also a growing number of investigations into how to calculate covariance parameters by ML/REML accurately and fast, and assure the convergence of the iteration steps in derivative-based approaches. The latter condition is not satisfied in many solutions, as it requires composed procedures or takes an unacceptable amount of time. The article implements efficient Fisher scoring (FS) to covariance parameter estimation in least-squares collocation (LSC). FS is optimized through Levenberg-Marquardt (LM) optimization, which provides stability in convergence when estimating two covariance parameters necessary for LSC. The motivation for this work was a very large number of non-optimized FS in the literature, as well as a deficiency of its scientific and engineering applications. The example work adds some usefulness to maximum likelihood estimation (ML) and FS and shows a new application—an alternative approach to LSC—a parametrization with no empirical covariance estimation. The results of LM damping applied to FS (FSLM) require some additional research related with optimal LM parameter. However, the method appears to be a milestone in relation to non-optimized FS, in terms of convergence. The FS with LM provides a reliable convergence, whose speed can be adjusted by manipulating the LM parameter.
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Philippa Maurer-Stroh
2005-06-01
Full Text Available Everybody is talking about collocational analyses these days… Despite recent advances in the monolingual sector, the bilingual environment has not yet come under close scrutiny. It is especially the adjective-noun combinations that have become the focus of attention when it comes to contrastive phraseological studies. Adjectives in particular are subject to semantic tailoring and it is important to bear in mind that (predictable interlingual lexical one-to-one occurrence, such as the English starless night and the German sternlose Nacht, is a mere exception rather than the rule in the bilingual adjective-noun state of affairs. Factors that have to be considered are (non- compositionality in contrastive multiword units, like barefaced lie – faustdicke Luge (‘a lie as thick as a man’s fist’, and metaphorical extensions, like haushoher Favorit – hot favourite (*house-high favourite as well as structural differences in the two languages in question, like (at short notice – kurzfristig.
Hu, Zhang-Mao; Tian, Hong; Li, Ben-Wen; Zhang, Wei; Yin, Yan-Shan; Ruan, Min; Chen, Dong-Lin
2017-10-01
The ray-effect is a major discretization error in the approximate solution method for the radiative transfer equation (RTE). To overcome this problem, the incident energy transfer equation (IETE) is proposed. The incident energy, instead of radiation intensity, is obtained by directly solving this new equation. Good numerical properties are found for the incident energy transfer equation. To show the properties of numerical solution, the collocation spectral method (CSM) is employed to solve the incident energy transfer equation. Three test cases are taken into account to verify the performance of the incident energy transfer equation. The result shows that the radiative heat flux obtained based on IETE is much more accurate than that based on RTE, which means that the IETE is very effective in eliminating the impacts of ray-effect on the heat flux. However, on the contrary, the radiative intensity obtained based on IETE is less accurate than that based on RTE due to the ray-effect. So, this equation is more suitable for those radiative heat transfer problems, in which the radiation heat flux and incident energy are needed rather than the radiation intensity.
Belyaev, V. A.; Shapeev, V. P.
2017-10-01
New versions of the collocations and least squares method of high-order accuracy are proposed and implemented for the numerical solution of the boundary value problems for the biharmonic equation in non-canonical domains. The solution of the biharmonic equation is used for simulating the stress-strain state of an isotropic plate under the action of transverse load. The differential problem is projected into a space of fourth-degree polynomials by the CLS method. The boundary conditions for the approximate solution are put down exactly on the boundary of the computational domain. The versions of the CLS method are implemented on the grids which are constructed in two different ways. It is shown that the approximate solution of problems converges with high order. Thus it matches with high accuracy with the analytical solution of the test problems in the case of known solution in the numerical experiments on the convergence of the solution of various problems on a sequence of grids.
Wei, Linyang; Qi, Hong; Sun, Jianping; Ren, Yatao; Ruan, Liming
2017-05-01
The spectral collocation method (SCM) is employed to solve the radiative transfer in multi-layer semitransparent medium with graded index. A new flexible angular discretization scheme is employed to discretize the solid angle domain freely to overcome the limit of the number of discrete radiative direction when adopting traditional SN discrete ordinate scheme. Three radial basis function interpolation approaches, named as multi-quadric (MQ), inverse multi-quadric (IMQ) and inverse quadratic (IQ) interpolation, are employed to couple the radiative intensity at the interface between two adjacent layers and numerical experiments show that MQ interpolation has the highest accuracy and best stability. Variable radiative transfer problems in double-layer semitransparent media with different thermophysical properties are investigated and the influence of these thermophysical properties on the radiative transfer procedure in double-layer semitransparent media is also analyzed. All the simulated results show that the present SCM with the new angular discretization scheme can predict the radiative transfer in multi-layer semitransparent medium with graded index efficiently and accurately.
Ophaug, Vegard; Gerlach, Christian
2017-11-01
This work is an investigation of three methods for regional geoid computation: Stokes's formula, least-squares collocation (LSC), and spherical radial base functions (RBFs) using the spline kernel (SK). It is a first attempt to compare the three methods theoretically and numerically in a unified framework. While Stokes integration and LSC may be regarded as classic methods for regional geoid computation, RBFs may still be regarded as a modern approach. All methods are theoretically equal when applied globally, and we therefore expect them to give comparable results in regional applications. However, it has been shown by de Min (Bull Géod 69:223-232, 1995. doi: 10.1007/BF00806734) that the equivalence of Stokes's formula and LSC does not hold in regional applications without modifying the cross-covariance function. In order to make all methods comparable in regional applications, the corresponding modification has been introduced also in the SK. Ultimately, we present numerical examples comparing Stokes's formula, LSC, and SKs in a closed-loop environment using synthetic noise-free data, to verify their equivalence. All agree on the millimeter level.
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Mina E. Ossiander
2014-01-01
Full Text Available We derive a new method of conditional Karhunen-Loève (KL expansions for stochastic coefficients in models of flow and transport in the subsurface, and in particular for the heterogeneous random permeability field. Exact values of this field are never known, and thus one must evaluate uncertainty of solutions to the flow and transport models. This is typically done by constructing independent realizations of the permeability field followed by numerical simulations of flow and transport for each realization and assembling statistical estimates of moments of desired quantities of interest. We follow the well-known framework of KL expansions and derive a new method that incorporates known values of the permeability at given locations so that the realizations of the permeability field honor this data exactly. Our method relies on projections to an appropriate subspace of random weights applied to the eigenfunctions of the covariance operator. We use the permeability realizations constructed with our stochastic simulation method in simulations of flow and transport and compare the results to those obtained when realizations are constructed with sequential Gaussian simulation (SGS. We also compare efficiency and stochastic convergence with that of stochastic collocation.
Ross, Alexa; Holz, Robert E.; Ackerman, Steven A.
2017-08-01
In April 2006, the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) launched aboard the CALIPSO satellite and into the A-Train constellation of satellites with its transmitter pointed near nadir. This proved problematic due to specular reflection from horizontally oriented ice crystals occurring more frequently than expected. Because the specular backscatter from oriented ice crystals has large attenuated backscatter and almost no depolarization, the standard lidar inversions cannot be applied. To mitigate this issue, the CALIOP transmitter was moved to 3° off nadir in November 2007. Though problematic for global CALIOP retrievals, the sensitivity to oriented ice during the first year of observations provides a unique data set to investigate scenes of this ice crystal signature. This study focuses on the CALIOP-oriented signature that occurs in midlatitude ocean regions whose cloud tops are relatively warm and low, existing below 6 km. A significant seasonal dependence is found in the Northern Hemisphere with up to 19% of clouds below 6 km yielding specular reflection by CALIOP during the colder months. In contrast, the Southern Hemisphere lacks such seasonal dependence and sees fewer oriented ice crystals. Using collocated CloudSat observations with both CALIOP and Moderate Resolution Imaging Spectroradiometer (MODIS), we investigate the correlations of the oriented signature with MODIS cloud properties. Comparing with CloudSat precipitation retrievals, we find that the oriented signature is strongly correlated with surface precipitation with 64% of CALIOP-oriented ice crystal cases precipitating compared to 40% for nonoriented cases.
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Suleiman Banihani
2013-01-01
Full Text Available The point collocation method of finite spheres (PCMFS is used to model the hyperelastic response of soft biological tissue in real time within the framework of virtual surgery simulation. The proper orthogonal decomposition (POD model order reduction (MOR technique was used to achieve reduced-order model of the problem, minimizing computational cost. The PCMFS is a physics-based meshfree numerical technique for real-time simulation of surgical procedures where the approximation functions are applied directly on the strong form of the boundary value problem without the need for integration, increasing computational efficiency. Since computational speed has a significant role in simulation of surgical procedures, the proposed technique was able to model realistic nonlinear behavior of organs in real time. Numerical results are shown to demonstrate the effectiveness of the new methodology through a comparison between full and reduced analyses for several nonlinear problems. It is shown that the proposed technique was able to achieve good agreement with the full model; moreover, the computational and data storage costs were significantly reduced.
Farrell, M. E.; Russo, R. M.
2013-12-01
The installation of Earthscope Transportable Array-style geophysical observatories in Chile expands open data seismic recording capabilities in the southern hemisphere by nearly 30%, and has nearly tripled the number of seismic stations providing freely-available data in southern South America. Through the use of collocated seismic and atmospheric sensors at these stations we are able to analyze how local atmospheric conditions generate seismic noise, which can degrade data in seismic frequency bands at stations in the ';roaring forties' (S latitudes). Seismic vaults that are climate-controlled and insulated from the local environment are now employed throughout the world in an attempt to isolate seismometers from as many noise sources as possible. However, this is an expensive solution that is neither practical nor possible for all seismic deployments; and also, the increasing number and scope of temporary seismic deployments has resulted in the collection and archiving of terabytes of seismic data that is affected to some degree by natural seismic noise sources such as wind and atmospheric pressure changes. Changing air pressure can result in a depression and subsequent rebound of Earth's surface - which generates low frequency noise in seismic frequency bands - and even moderate winds can apply enough force to ground-coupled structures or to the surface above the seismometers themselves, resulting in significant noise. The 10 stations of the permanent Geophysical Reporting Observatories (GRO Chile), jointly installed during 2011-12 by IRIS and the Chilean Servicio Sismológico, include instrumentation in addition to the standard three seismic components. These stations, spaced approximately 300 km apart along the length of the country, continuously record a variety of atmospheric data including infrasound, air pressure, wind speed, and wind direction. The collocated seismic and atmospheric sensors at each station allow us to analyze both datasets together, to
Joiner, J.; Lee, H.-T.; Strow, L. L.; Bhartia, P. K.; Hannon, S.; Miller, A. J.; Rokke, L.
1998-08-01
We have carried out a detailed analysis of radiative transfer and observational errors for the high-resolution infrared radiation sounder 2 (HIRS2)channel 9 centered in the 9.6 μm ozone absorption band. Several previous studies have shown significant differences between the total column ozone derived from HIRS2 and the ultraviolet (UV) radiometers. Here we use collocated ozone profiles derived from the solar backscatter ultraviolet (SBUV) spectrometer to isolate errors in HIRS2 channel 9. Radiative transfer in the 9.6 μm band is complicated because it is affected by atmospheric ozone, temperature, humidity, and the surface skin temperature and emissivity. We examine the accuracy of three fast radiative transfer algorithms. We validate current models for weak water vapor continuum absorption at 9.6 μm. In addition, we develop a method to correct for errors in older continuum models, in ozone transmittances, and in the channel 9 spectral response function. We also identify errors resulting from the spectral dependence of the surface emissivity and propose a correction method. Using UV-derived reflectivity, we have detected instances where IR cloud-detection and cloud-clearing algorithms have apparently failed. Our results show that if appropriate corrections and quality control are applied, it is possible to compute HIRS2 channel 9 brightness temperatures with an root-mean-square (RMS) accuracy of better than ˜0.6 K and a bias less than 0.1 K in clear skies and RMS of better than ˜0.9 K and a bias less than 0.1 K in partially cloudy skies. We plan to use the methods described here to improve IR ozone retrieval algorithms.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Guannan [ORNL; Webster, Clayton G [ORNL; Gunzburger, Max D [ORNL
2012-09-01
Although Bayesian analysis has become vital to the quantification of prediction uncertainty in groundwater modeling, its application has been hindered due to the computational cost associated with numerous model executions needed for exploring the posterior probability density function (PPDF) of model parameters. This is particularly the case when the PPDF is estimated using Markov Chain Monte Carlo (MCMC) sampling. In this study, we develop a new approach that improves computational efficiency of Bayesian inference by constructing a surrogate system based on an adaptive sparse-grid high-order stochastic collocation (aSG-hSC) method. Unlike previous works using first-order hierarchical basis, we utilize a compactly supported higher-order hierar- chical basis to construct the surrogate system, resulting in a significant reduction in the number of computational simulations required. In addition, we use hierarchical surplus as an error indi- cator to determine adaptive sparse grids. This allows local refinement in the uncertain domain and/or anisotropic detection with respect to the random model parameters, which further improves computational efficiency. Finally, we incorporate a global optimization technique and propose an iterative algorithm for building the surrogate system for the PPDF with multiple significant modes. Once the surrogate system is determined, the PPDF can be evaluated by sampling the surrogate system directly with very little computational cost. The developed method is evaluated first using a simple analytical density function with multiple modes and then using two synthetic groundwater reactive transport models. The groundwater models represent different levels of complexity; the first example involves coupled linear reactions and the second example simulates nonlinear ura- nium surface complexation. The results show that the aSG-hSC is an effective and efficient tool for Bayesian inference in groundwater modeling in comparison with conventional
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T. M. Agbaje
2015-06-01
Full Text Available In this study, the spectral perturbation method (SPM is utilized to solve the momentum, heat and mass transfer equations describing the unsteady MHD mixed convection flow over an impulsively stretched vertical surface in the presence of chemical reaction effect. The governing partial differential equations are reduced into a set of coupled non similar equations and then solved numerically using the SPM. The SPM combines the standard perturbation method idea with the Chebyshev pseudo-spectral collocation method. In order to demonstrate the accuracy and efficiency of the proposed method, the spectral perturbation (SPM numerical results are compared with numerical results generated using the spectral relaxation method (SRM and a good agreement between the two methods is observed up to a minimum of eight decimal digits. Several simulation are conducted to ascertain the accuracy of the SPM and the SRM. The computational speed of the SPM is demonstrated by comparing the SPM computational time with the SRM computational time. A residual error analysis is also conducted for the SPM and the SRM in order to further assess the accuracy of the SPM. The study shows that the spectral perturbation method (SPM is more efficient in terms of computational speed when compared with the SRM. The study also shows that the SPM can be used as an efficient and reliable tool for solving strongly nonlinear boundary value partial differential equation problems that are defined under the Williams and Rhyne [3] transformation. In addition, the study shows that accurate results can be obtained using the perturbation method and thus, the conclusions earlier drawn by researchers regarding the accuracy of perturbation methods is corrected.
Wu, Y. J.; Williams, E. R.; Chang, S. C.; Chou, J. K.; Friedrich, M.; Peng, K. M.; Hsu, R. R.; Chen, A. B. C.; Su, H. T.; Frey, H. U.; Takahashi, Y.; Lee, L. C.
2016-12-01
The elve is the dominant type of Transient Luminous Event (TLE) at the base of the E-region ionosphere and the OH* Meinel band nightglow (OH* nightglow hereafter) has been reported at a similar altitude. However, a physical basis for this collocation has long been doubted because the OH* nightglow is the result of photochemical reactions, while for elves an electromagnetic process is involved. By virtue of the time resolution on the order of 29 millisecond and the specific filter of the imager for the 1PN2 and the OH* Meinel (8,3) and (9,3) in the wavelength range 620 nm to 750 nm, the Imager of Sprite and Upper Atmospheric Lightning (ISUAL) onboard Formosat 2 is the only space-borne instrument equipped for simultaneous observation of elves and OH* nightglow. Major ISUAL re-calibration of both OH* nightglow and elve imaging with star-finding methods has led to major improvements in the height accuracy in limb viewing. The most frequent height is 87 km with a HMFW of 7 km based on a total 130,000 sample images. 90% of the 168 limb elves at the center of the image are located within +/- 4 km of the altitude of the brightest OH* nightglow emission. Both elves and OH* nightglow show the semiannual oscillation (SAO) at low latitude. An environment-based and sounding-verified electron density profile is used as an input to the conventional elve model to know the brightest height. The inputs are the neutral gas profiles from the MSISE-90 model, the meteoric dust particle profile in Plane et al. (2015), as well as the loss of Lyman-α by O2 above the target height. Atomic oxygen, product of uv dissociation, is a necessary reactant to produce ozone, then go on to achieve the key reaction of OH* nightglow and the quenching process [Xu et al., 2010]. Both models show that the brightest layer is higher when the ledge of the atomic oxygen profile is higher, and vice versa. Finally, the incident lightning radiation electric field at VLF decreases exponentially by the height
Zulueta, R. C.; Metzger, S.; Ayres, E.; Luo, H.; Meier, C. L.; Barnett, D.; Sanclements, M.; Elmendorf, S.
2013-12-01
provides an evidence-based and repeatable method for combining sensor-based measurements and field sampling and observations at predefined levels of disturbance and spatial representativeness. The developed approach represents a general framework which is applicable to other environmental research sites where similar collocation is desired.
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo; Saenz, Ricardo A; Salvo, Koen [Facultad de Ciencias, CUICBAS, Universidad de Colima, Bernal DIaz del Castillo 340 Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (UNLP, CCT La Plata-Conicet), Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)], E-mail: paolo.amore@gmail.com, E-mail: fernande@quimica.unlp.edu.ar, E-mail: rasaenz@ucol.mx, E-mail: koen.salvo@gmail.com
2009-03-20
In this paper we derive four sets of sinc-like functions, defined on a finite interval and obeying different boundary conditions. The functions in each set are orthogonal and their nodes are uniformly distributed on the interval. We have applied each set to solve a large class of eigenvalue equations, with different boundary conditions, both on finite intervals and on the real line, showing that precise numerical results can be obtained efficiently and rapidly. A comparison with results available in the literature is also performed.
Phillips, J. R.
1996-01-01
In this paper we derive error bounds for a collocation-grid-projection scheme tuned for use in multilevel methods for solving boundary-element discretizations of potential integral equations. The grid-projection scheme is then combined with a precorrected FFT style multilevel method for solving potential integral equations with 1/r and e(sup ikr)/r kernels. A complexity analysis of this combined method is given to show that for homogeneous problems, the method is order n natural log n nearly independent of the kernel. In addition, it is shown analytically and experimentally that for an inhomogeneity generated by a very finely discretized surface, the combined method slows to order n(sup 4/3). Finally, examples are given to show that the collocation-based grid-projection plus precorrected-FFT scheme is competitive with fast-multipole algorithms when considering realistic problems and 1/r kernels, but can be used over a range of spatial frequencies with only a small performance penalty.
Martin, R. M.; Nicolas, A. N.
2003-04-01
A modeling approach of gas solid flow, taking into account different physical phenomena such as gas turbulence and inter-particle interactions is presented. Moment transport equations are derived for the second order fluctuating velocity tensor which allow to involve practical closures based on single phase turbulence modeling on one hand and kinetic theory of granular media on the other hand. The model is applied to fluid catalytic cracking processes and explosive volcanism. In the industry as well as in the geophysical community, multiphase flows are modeled using a finite volume approach and a multicorrector algorithm in time in order to determine implicitly the pressures, velocities and volume fractions for each phase. Pressures, and velocities are generally determined at mid-half mesh step from each other following the staggered grid approach. This ensures stability and prevents oscillations in pressure. It allows to treat almost all the Reynolds number ranges for all speeds and viscosities. The disadvantages appear when we want to treat more complex geometries or if a generalized curvilinear formulation of the conservation equations is considered. Too many interpolations have to be done and accuracy is then lost. In order to overcome these problems, we use here a similar algorithm in time and a Rhie and Chow interpolation (1983) of the collocated variables and essentially the velocities at the interface. The Rhie and Chow interpolation of the velocities at the finite volume interfaces allows to have no oscillations of the pressure without checkerboard effects and to stabilize all the algorithm. In a first predictor step, fluxes at the interfaces of the finite volumes are then computed using 2nd and 3rd order shock capturing schemes of MUSCL/TVD or Van Leer type, and the orthogonal stress components are treated implicitly while cross viscous/diffusion terms are treated explicitly. Pentadiagonal linear systems are solved in each geometrical direction (the so
National Aeronautics and Space Administration — This is a CloudSat-collocated subset of the original product OMSO2, for the purposes of the A-Train mission. The goal of the subset is to select and return OMI data...
National Aeronautics and Space Administration — This is a CloudSat-collocated subset of the original product OMTO3, for the purposes of the A-Train mission. The goal of the subset is to select and return OMI data...
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Ruili Wen
2016-08-01
Full Text Available We consider an open-loop system of a fourth order Schrodinger equation with variable coefficients and Neumann boundary control and collocated observation. Using the multiplier method on Riemannian manifold we show that that the system is well-posed in the sense of Salamon. This implies that the exponential stability of the closed-loop system under the direct proportional output feedback control and the exact controllability of open-loop system are equivalent. So in order to conclude feedback stabilization from well-posedness, we study the exact controllability under a uniqueness assumption by presenting the observability inequality for the dual system. In addition, we show that the system is regular in the sense of Weiss, and that the feedthrough operator is zero.
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Jonas Asprion
2014-01-01
Full Text Available The numerical solution of optimal control problems by direct collocation is a widely used approach. Quasi-Newton approximations of the Hessian of the Lagrangian of the resulting nonlinear program are also common practice. We illustrate that the transcribed problem is separable with respect to the primal variables and propose the application of dense quasi-Newton updates to the small diagonal blocks of the Hessian. This approach resolves memory limitations, preserves the correct sparsity pattern, and generates more accurate curvature information. The effectiveness of this improvement when applied to engineering problems is demonstrated. As an example, the fuel-optimal and emission-constrained control of a turbocharged diesel engine is considered. First results indicate a significantly faster convergence of the nonlinear program solver when the method proposed is used instead of the standard quasi-Newton approximation.
Odum, Jack K.; Stephenson, William J.; Williams, Robert A.; von Hillebrandt-Andrade, Christa
2013-01-01
Shear‐wave velocity (VS) and time‐averaged shear‐wave velocity to 30 m depth (VS30) are the key parameters used in seismic site response modeling and earthquake engineering design. Where VS data are limited, available data are often used to develop and refine map‐based proxy models of VS30 for predicting ground‐motion intensities. In this paper, we present shallow VS data from 27 sites in Puerto Rico. These data were acquired using a multimethod acquisition approach consisting of noninvasive, collocated, active‐source body‐wave (refraction/reflection), active‐source surface wave at nine sites, and passive‐source surface‐wave refraction microtremor (ReMi) techniques. VS‐versus‐depth models are constructed and used to calculate spectral response plots for each site. Factors affecting method reliability are analyzed with respect to site‐specific differences in bedrock VS and spectral response. At many but not all sites, body‐ and surface‐wave methods generally determine similar depths to bedrock, and it is the difference in bedrock VS that influences site amplification. The predicted resonant frequencies for the majority of the sites are observed to be within a relatively narrow bandwidth of 1–3.5 Hz. For a first‐order comparison of peak frequency position, predictive spectral response plots from eight sites are plotted along with seismograph instrument spectra derived from the time series of the 16 May 2010 Puerto Rico earthquake. We show how a multimethod acquisition approach using collocated arrays compliments and corroborates VS results, thus adding confidence that reliable site characterization information has been obtained.
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Tony Berber Sardinha
2006-01-01
Full Text Available This paper reports a study on the use of collocation lists as instruments for detecting metaphors in corpora. A collocation list contains the collocations for selected words in corpora together with concordances for those words. As corpora become more available to metaphor researchers, there is a growing need for developing ways to gain access to as much data as the corpus can offer. The research described here has hopefully come some way toward meeting the challenges of developing tools for metaphor corpus research. Results suggest that the collocation lists seem to be a good pre-processing instrument for corpus research of metaphor, despite accuracy problems.Este trabalho apresenta uma pesquisa sobre o uso de listas de colocações como instrumentos para detecção de metáforas em corpora. Uma lista de colocação contém as colocações de palavras selecionadas de corpora juntamente com as concordâncias dessas palavras. Na medida que os corpora se tornam mais acessíveis aos pesquisadores de metáfora, começa a surgir uma necessidade de desenvolver maneiras de acessar a maior quantidade possível de dados que um corpus oferece. A pesquisa descrita aqui tentou enfrentar esse desafio, criando e testando ferramentas para pesquisa de metáfora baseada em corpus. Os resultados sugerem que as listas de colocações podem ser um instrumento eficaz de pré-processamento de corpus com vistas à análise humana de metáforas, a despeito de alguns problemas de precisão.
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Anna Nikolaevna Panamaryova
2013-10-01
Full Text Available The aim of this research is to find out conceptual characteristics of English, German, French, Italian languages world image. The subject of this paper is English collocations with the verbs “to be”, “to have” and “to take” and their equivalents in German, French and Italian languages. The task of this paper is to compare English collocations of the verbs “to be”, “to have” and “to take” and their equivalents in German, French and Italian languages in linguistic–cultural aspect. In Russian language studies such word groups are called “synlexis”. This term was coined by G. I. Klimovskaya, the professor ofTomskStateUniversity. The main method of the research is a comparative study of linguistic units. The conclusions made in the research are essential in the further study of European linguistic world image and can be used in textbooks on Cultural Linguistics.The practical result of the research can be a cross-cultural collocation dictionary of some languages. Such a dictionary is important for linguists, translators and people studying foreign languages.DOI: http://dx.doi.org/10.12731/2218-7405-2013-8-32
Barber, Jared; Tanase, Roxana; Yotov, Ivan
2016-06-01
Several Kalman filter algorithms are presented for data assimilation and parameter estimation for a nonlinear diffusion model of epithelial cell migration. These include the ensemble Kalman filter with Monte Carlo sampling and a stochastic collocation (SC) Kalman filter with structured sampling. Further, two types of noise are considered -uncorrelated noise resulting in one stochastic dimension for each element of the spatial grid and correlated noise parameterized by the Karhunen-Loeve (KL) expansion resulting in one stochastic dimension for each KL term. The efficiency and accuracy of the four methods are investigated for two cases with synthetic data with and without noise, as well as data from a laboratory experiment. While it is observed that all algorithms perform reasonably well in matching the target solution and estimating the diffusion coefficient and the growth rate, it is illustrated that the algorithms that employ SC and KL expansion are computationally more efficient, as they require fewer ensemble members for comparable accuracy. In the case of SC methods, this is due to improved approximation in stochastic space compared to Monte Carlo sampling. In the case of KL methods, the parameterization of the noise results in a stochastic space of smaller dimension. The most efficient method is the one combining SC and KL expansion. Copyright © 2016 Elsevier Inc. All rights reserved.
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Messaouda MEKHILEF
2016-12-01
Full Text Available Our study envisages, through a contrastive linguistic perspective, to shed light on the linguistic reality of what we call the set phrases. In fact, a student of the French language or any other language (not French faces serious difficulties that are mostly recurrent in verbal exchanges and in the identification of the meaning insinuated. Indeed, they even find difficulties in finding appropriate equivalent for such expressions in their national or mother tongue .The expected tendency in all this is to come to a compromise for the exact meaning of the set phrase. Firstly and for an efficiency in such an approach ,we thought to sort out the difference in characteristics between the concepts locutions, collocations, idiomatic or set phrases .Hence ,our work will be analytical and descriptive that help us define these operational notions in the study of this language fact. In sum, our distinctions are classified into four fundamental distinctions-a set phrases andcollocations ; b expressions or/locutions ; c verbal locutions and proverbs lastly d set phrases, idiomatic or phraseo logic.
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...
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Ana-Marina Tomescu
2015-11-01
Full Text Available Dans le présent article nous allons examiner plusieurs logiciels disponibles en ligne mais rarement utilisés par les professeurs roumains, même s’ils représentent des ressources intéressantes pour un enseignant de français langue étrangère (désormais FLE pour aborder le domaine de la phraséologie et notamment des collocations
Gilardoni, M.; Reguzzoni, M.; Sampietro, D.
2012-04-01
Neighbouring countries often have national geoids that do not fit to each other, typically showing a discontinuity along the border. This discontinuity is mainly due to the different height datum used, producing biased local geoids which can also have different accuracies and spatial resolutions. In addition, each local geoid has its own border effects giving rise to unwanted features. In some applications, for instance in case of international civil engineering works, a merging between two neighbouring geoids is necessary. Obviously this procedure cannot be done by simply averaging overlapping areas, completely disregarding biases. To solve this problem the availability of a global geoid coming from satellite data, such as one of the GOCE models or a GOCE-GRACE combined model, can be of great importance. These models in fact are not affected by local biases (local reference systems) since they do not make use of any ground gravity data or levelling. Basically this means that these models can provide the long wavelengths of the resulting merged geoid, in this way removing national biases or other systematic effects. On the other hand, the short wavelengths will directly come from a combination of the available local geoids. This merging strategy is implemented by a unique collocation procedure, also taking into account the estimation error covariance matrix of the global model spherical harmonic coefficients. In this paper the solution to the problem is first described from the methodological point of view and then applied to the merging of the Italian and Swiss geoids. Particular attention is dedicated to the estimate of the signal covariance function, which is adapted to the Alpine area characteristics and is derived by a proper variogram to be independent from local geoid biases.
Qu, Wei; Lu, Zhong; Zhang, Ming; Zhang, Qin; Wang, Qingliang; Zhu, Wu; Qu, Feifei
2017-05-01
The Ordos Block and its surrounding areas play a special role in the kinetic pattern of current tectonic deformation in mainland China (East Asia). In order to better understand the recent crustal deformation and geodynamics of this region, we use GPS velocities and employ the least-squares collocation (LSC) technique to estimate the distribution of the crustal strain rate fields. We calculate the principal components of strains, such as the maximum shear strains, the plane strain gradients and the principal axes of strains. The strain fields obtained in this paper can well portray crustal deformation in the region. Our results show that the relatively higher maximum shearing strain rates are mainly distributed over region surrounding the Ordos Block, indicating these periphery areas have intense crustal activities. Indeed, these periphery areas encompass major active tectonic belts (e.g., the western edge of the Qilian Fold System, the northeastern margin of the Tibetan Plateau and the Taihang Mountain) and active grabens (e.g., Yinchuan, Hetao, Shanxi and Weihe Grabens). Significant plane strain gradients concentrated over the periphery areas of the Ordos Block, indicating that these areas have more intense crustal activity and are more prone to earthquakes. The principle strain rates also show the strain rates for the periphery of the Ordos Block are higher than other regions. The highest strain rates are along the southwestern side of the Ordos Block, indicating that the eastward extrusion dynamics from the Tibetan Plateau may still be the main cause of tectonic deformation in this region. The extensional strains are present in most parts of the Yinchuan, Hetao and Shanxi Grabens. Finally, the characteristics of the strain fields predicted by the LSC technique are discussed, and some interesting tectonic deformation information can be found through further comparison with the strain results predicted by other methods The detailed results and findings obtained
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J. Messerschmidt
2012-08-01
Full Text Available The in situ boundary layer measurement site in Białystok (Poland has been upgraded with a fully automated observatory for total greenhouse gas column measurements. The automated Fourier Transform Spectrometer (FTS complements the on-site in situ facilities and FTS solar absorption measurements have been recorded nearly continuously in clear and partially cloudy conditions since March 2009. Here, the FTS measurements are compared with the collocated tall tower data. Additionally, simulations of the Jena CO_{2} inversion model are evaluated with the Białystok measurement facilities. The simulated seasonal CO_{2} cycle is slightly overestimated by a mean difference of 1.2 ppm ± 0.9 ppm (1σ in comparison with the FTS measurements. CO_{2} concentrations at the surface, measured at the tall tower (5 m, 90 m, 300 m, are slightly underestimated by −1.5 ppm, −1.6 ppm, and −0.7 ppm respectively during the day and by −9.1 ppm, −5.9 ppm, and −1.3 ppm during the night. The comparison of the simulated CO_{2} profiles with low aircraft profiles shows a slight overestimation of the lower troposphere (by up to 1 ppm and an underestimation in near-surface heights until 800 m (by up to 2.5 ppm. In an appendix the automated FTS observatory, including the hardware components and the automation software, is described in its basics.
Ubiquitous media for collocated interaction
DEFF Research Database (Denmark)
Morrison, Ann; Jacucci, Giulio; Peltonen, Peter
2010-01-01
Has ubiquitous computing entered our lives as anticipated in the early 90s or at the turn of the millennium? In this last decade, the processing of media combined with sensing and communication capabilities has been slowly entering our lives through powerful smartphones, multimodal game consoles,...
Variational collocation on finite intervals
Energy Technology Data Exchange (ETDEWEB)
Amore, Paolo [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Cervantes, Mayra [Facultad de Ciencias, Universidad de Colima, Bernal DIaz del Castillo 340, Colima, Colima (Mexico); Fernandez, Francisco M [INIFTA (Conicet, UNLP), Diag. 113 y 64 S/N, Sucursal 4, Casilla de Correo 16, 1900 La Plata (Argentina)
2007-10-26
In this paper, we study a set of functions, defined on an interval of finite width, which are orthogonal and which reduce to the sinc functions when the appropriate limit is taken. We show that these functions can be used within a variational approach to obtain accurate results for a variety of problems. We have applied them to the interpolation of functions on finite domains and to the solution of the Schroedinger equation, and we have compared the performance of the present approach with others.
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Isabel Cristina Tedesco Selistre
2010-07-01
Full Text Available O objetivo deste trabalho é evidenciar a necessidade de se incluir as colocações de forma sistemática nos dicionários escolares inglês/português – português/inglês, especialmente na seção português/inglês. Para tanto, apresentamos, brevemente, asprincipais abordagens que tratam das colocações, buscamos a caracterização desse fenômeno, tratamos da questão da transferência linguística em relação a esse aspecto, distinguimos os dicionários passivos e os dicionários ativos e, por fim, com base nos resultados de um estudo comparativo entre sete dicionários escolares bilíngues, fazemos algumas considerações sobre a apresentação de colocações nesse tipo de obra.This article aims to make evident the need to include collocations in english/portuguese – portuguese/english school dictionaries, especially in the portuguese/english direction, in a systematic way. Therefore, we briefly present the main approaches that deal with collocations, outline the characteristics of this linguistic phenomenon, discuss the issue of language transfer (mainly the collocational errors caused by L1 transfer and lastly, based on the results of a comparative study with seven bilingual school dictionaries, we provide some comments on the presentation of collocations in this type of dictionary.
Spectral methods for partial differential equations
Hussaini, M. Y.; Streett, C. L.; Zang, T. A.
1984-01-01
Origins of spectral methods, especially their relation to the Method of Weighted Residuals, are surveyed. Basic Fourier, Chebyshev, and Legendre spectral concepts are reviewed, and demonstrated through application to simple model problems. Both collocation and tau methods are considered. These techniques are then applied to a number of difficult, nonlinear problems of hyperbolic, parabolic, elliptic, and mixed type. Fluid-dynamical applications are emphasized.
An efficient algorithm for solving nonlinear system of differential equations and applications
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Mustafa GÜLSU
2015-10-01
Full Text Available In this article, we apply Chebyshev collocation method to obtain the numerical solutions of nonlinear systems of differential equations. This method transforms the nonlinear systems of differential equation to nonlinear systems of algebraic equations. The convergence of the numerical method are given and their applicability is illustrated with some examples.
Euler-Chebyshev methods for integro-differential equations
P.J. van der Houwen; B.P. Sommeijer (Ben)
1996-01-01
textabstractWe construct and analyse explicit methods for solving initial value problems for systems of differential equations with expensive righthand side functions whose Jacobian has its stiff eigenvalues along the negative axis. Such equations arise after spatial discretization of parabolic
UNCOUPLING LAMINAR CONJUGATE HEAT TRANSFER THROUGH CHEBYSHEV POLYNOMIAL
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ANTONIO J. BULA
2010-01-01
verificados con la solución obtenida por medio de software CFD comercial, FIDAP ®. La solución ncluyo el cálculo del coeficiente de transferencia de calor, el número de Nusselt, el número de Biot, todos tanto local como promedio. La distribución de temperatura en la interface también fue obtenida.
The paradigm of complex probability and Chebyshev's inequality
National Research Council Canada - National Science Library
Abou Jaoude, Abdo
2016-01-01
... an additional three axioms. Therefore, we create the complex probability set , which is the sum of the real set with its corresponding real probability, and the imaginary set with its corresponding imaginary probability...
Chebyshev method to solve the time-dependent Maxwell equations
Raedt, H. De; Michielsen, K.; Kole, J.S.; Figge, M.T.; Landau, DP; Lewis, SP; Schuttler, HB
2003-01-01
We present a one-step algorithm to solve the time-dependent Maxwell equations for systems with spatially varying permittivity and permeability. We compare the results of this algorithm with those obtained from unconditionally stable algorithms and demonstrate that for a range of applications the
Energy Technology Data Exchange (ETDEWEB)
Chedin, A.; Serrar, S.; Hollingsworth, A.; Armante, R.; Scott, N.A
2003-03-15
The NOAA polar meteorological satellites have embarked the TIROS-N operational vertical sounder (TOVS) since 1979. Using radiosondes and NOAA-10 TOVS measurements which are collocated within a narrow space and time window, we have studied the differences between the TOVS measurements and simulated measurements from a new fast, Rapid Radiance Reconstruction Network (3R-N), non-linear radiative transfer model with up to date spectroscopy. Simulations use radiosonde temperature and humidity measurements as the prime input. The radiative transfer model also uses fixed greenhouse gas absorber amounts (CO{sub 2},CO,N{sub 2}O) and reasonable estimates of O{sub 3} and of surface temperature. The 3R-N model is first presented and validated. Then, a study of the differences between the simulated and measured radiances shows annual trends and seasonal variations consistent with independent measurements of variations in CO{sub 2} and other greenhouse gases atmospheric concentrations. The improved accuracy of 3R-N and a better handling of its deviations with respect to observations allow most of difficulties met in a previous study (J. Climate 15 (2002) 95) to be resolved.
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Adriane Orenha-Ottaiano
2012-07-01
Full Text Available Taking into consideration the relevance of foreign language teaching and the learning of collocations (ALTENBERG; EEG-OLOFSSON, 1990; FONTENELLE, 1994; MEUNIER; GRANGER, 2008, this paper aims at showing results of an investigation on whether the teaching of collocations should be implicit or explicit to the Brazilian university students. Furthermore, the research has the purpose of presenting some collocational aspects from a corpus of the written language learners made up of intermediate, upper intermediate and advanced university students’ argumentative essays at a public university in Brazil. With the help of WordSmith Tools (SCOTT, 2007, it was possible to raise students’ most frequent collocational choices and patterns, the most/least used type of collocations, the influence of the mother tongue on their choices, among other aspects. With the purpose of motivating and involving students in classroom research, it was also introduced The Corpus of Contemporary American English (COCA, created by Mark Davies. By doing so, students could compare their collocational choices with the patterns found in the online corpus, extract more collocational patterns and, consequently, be aware of the potential of corpora for the foreign learning process, specifically for raising language awareness, with focus on prefabricated chunks.Considerando a relevância das colocações para o ensino-aprendizagem de língua estrangeira (ALTENBERG; EEG-OLOFSSON, 1990; FONTENELLE, 1994; MEUNIER; GRANGER, 2008, este artigo tem como propósito mostrar os resultados de uma investigação a respeito do ensino implícito ou explícito de colocações para alunos universitários brasileiros. Além disso, a pesquisa visa apresentar alguns aspectos colocacionais, levantados a partir de um corpus de aprendizes de língua escrita, composto por textos argumentativos de alunos de nível intermediário, intermediário avançado e avançado, de uma universidade pública, no Brasil
Isogeometric Collocation for Elastostatics and Explicit Dynamics
2012-01-25
of stresses at quadrature points. In this case, storage and compute cost are directly pro- portional to the number of quadrature points. Typical...that is, the one-point Gauss rule. This minimizes storage of stresses and the number of constitutive evaluations and results in an efficient...We confirm the higher-order con- vergence rates of the explicit multi-corrector method on a one-dimensional example and a two dimensional plane strain
Improving academic literacy by teaching collocations
African Journals Online (AJOL)
Kate H
... key elements for defining academic literacy/literacies. This study adheres to the dimensional approach to academic literacy outlined in Van Dyk and Van de Poel's (2013) definition, which distinguishes between “three different dimensions: a social (exchange information), cognitive (understand, organise and reason about.
Adult Learners' Retention of Collocations from Exposure
Durrant, Philip; Schmitt, Norbert
2010-01-01
Formulaic language is widely recognized to be of central importance to fluent and idiomatic language use. However, the mechanics of how formulaic language is acquired are not well understood. Some researchers (e.g. Nick Ellis) believe that the chunking inherent in formulaic language drives the language learning process. Others (e.g. Wray) claim…
Does collocation inform the impact of collaboration?
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Kyungjoon Lee
Full Text Available BACKGROUND: It has been shown that large interdisciplinary teams working across geography are more likely to be impactful. We asked whether the physical proximity of collaborators remained a strong predictor of the scientific impact of their research as measured by citations of the resulting publications. METHODOLOGY/PRINCIPAL FINDINGS: Articles published by Harvard investigators from 1993 to 2003 with at least two authors were identified in the domain of biomedical science. Each collaboration was geocoded to the precise three-dimensional location of its authors. Physical distances between any two coauthors were calculated and associated with corresponding citations. Relationship between distance of coauthors and citations for four author relationships (first-last, first-middle, last-middle, and middle-middle were investigated at different spatial scales. At all sizes of collaborations (from two authors to dozens of authors, geographical proximity between first and last author is highly informative of impact at the microscale (i.e. within building and beyond. The mean citation for first-last author relationship decreased as the distance between them increased in less than one km range as well as in the three categorized ranges (in the same building, same city, or different city. Such a trend was not seen in other three author relationships. CONCLUSIONS/SIGNIFICANCE: Despite the positive impact of emerging communication technologies on scientific research, our results provide striking evidence for the role of physical proximity as a predictor of the impact of collaborations.
A novel class of highly efficient and accurate time-integrators in nonlinear computational mechanics
Wang, Xuechuan; Atluri, Satya N.
2017-05-01
A new class of time-integrators is presented for strongly nonlinear dynamical systems. These algorithms are far superior to the currently common time integrators in computational efficiency and accuracy. These three algorithms are based on a local variational iteration method applied over a finite interval of time. By using Chebyshev polynomials as trial functions and Dirac-Delta functions as the test functions over the finite time interval, the three algorithms are developed into three different discrete time-integrators through the collocation method. These time integrators are labeled as Chebyshev local iterative collocation methods. Through examples of the forced Duffing oscillator, the Lorenz system, and the multiple coupled Duffing equations (which arise as semi-discrete equations for beams, plates and shells undergoing large deformations), it is shown that the new algorithms are far superior to the 4th order Runge-Kutta and ODE45 of MATLAB, in predicting the chaotic responses of strongly nonlinear dynamical systems.
An efficient numerical method for solving nonlinear foam drainage equation
Parand, Kourosh; Delkhosh, Mehdi
2018-02-01
In this paper, the nonlinear foam drainage equation, which is a famous nonlinear partial differential equation, is solved by using a hybrid numerical method based on the quasilinearization method and the bivariate generalized fractional order of the Chebyshev functions (B-GFCF) collocation method. First, using the quasilinearization method, the equation is converted into a sequence of linear partial differential equations (LPD), and then these LPDs are solved using the B-GFCF collocation method. A very good approximation of solutions is obtained, and comparisons show that the obtained results are more accurate than the results of other researchers.
Martin, R.; Gonzalez Ortiz, A.
In the industry as well as in the geophysical community, multiphase flows are mod- elled using a finite volume approach and a multicorrector algorithm in time in order to determine implicitly the pressures, velocities and volume fractions for each phase. Pressures, and velocities are generally determined at mid-half mesh step from each other following the staggered grid approach. This ensures stability and prevents os- cillations in pressure. It allows to treat almost all the Reynolds number ranges for all speeds and viscosities. The disadvantages appear when we want to treat more complex geometries or if a generalized curvilinear formulation of the conservation equations is considered. Too many interpolations have to be done and accuracy is then lost. In order to overcome these problems, we use here a similar algorithm in time and a Rhie and Chow interpolation (1983) of the collocated variables and essentially the velocities at the interface. The Rhie and Chow interpolation of the velocities at the finite volume interfaces allows to have no oscillatons of the pressure without checkerboard effects and to stabilize all the algorithm. In a first predictor step, fluxes at the interfaces of the finite volumes are then computed using 2nd and 3rd order shock capturing schemes of MUSCL/TVD or Van Leer type, and the orthogonal stress components are treated implicitly while cross viscous/diffusion terms are treated explicitly. A pentadiagonal system in 2D or a septadiagonal in 3D must be solve but here we have chosen to solve 3 tridiagonal linear systems (the so called Alternate Direction Implicit algorithm), one in each spatial direction, to reduce the cost of computation. Then a multi-correction of interpolated velocities, pressures and volumic fractions of each phase are done in the cartesian frame or the deformed local curvilinear coordinate system till convergence and mass conservation. At the end the energy conservation equations are solved. In all this process the
Spectral methods for time dependent partial differential equations
Gottlieb, D.; Turkel, E.
1983-01-01
The theory of spectral methods for time dependent partial differential equations is reviewed. When the domain is periodic Fourier methods are presented while for nonperiodic problems both Chebyshev and Legendre methods are discussed. The theory is presented for both hyperbolic and parabolic systems using both Galerkin and collocation procedures. While most of the review considers problems with constant coefficients the extension to nonlinear problems is also discussed. Some results for problems with shocks are presented.
47 CFR 51.323 - Standards for physical collocation and virtual collocation.
2010-10-01
... within the same time periods and with failure rates that are no greater than those that apply to the... be available in the same time frame as, or a shorter time frame than, non-separated space; (iv) The cost of the separated space to the requesting carrier will not be materially higher than the cost of...
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Tazegül DEMİR
2012-06-01
Full Text Available The present study aims to identify the collocational patterns of the value elements in eight grade Turkish course books of MNE publications in light of textual context. According to the results of the study which employed document analysis, the texts in the course book have a rich collocational word pattern in terms of value transfer. Since national values can be directly or indirectly transferred in stories, the collocation pattern towards value transfer was found to support this condition and both values transfer and collocational dimensions were found to be at a good level Bu çalışmada, MEB yayınlarına ait ilköğretim ikinci kademe sekizinci sınıf Türkçe ders kitaplarında yer alan değer unsurlarının, metin bağlamından hareketle eşdizimsel örüntüsü ortaya çıkarılmaya çalışılmıştır. Doküman incelemesi yöntemine göre yapılan çalışmanın sonuçlarına göre ders kitabında yer alan metinlerin değer aktarımı oluşturmada zengin bir eşdizimli sözcük örüntüsüne sahip olduğu tespit edilmiştir. Hikâye metinlerinde ulusa ait değerler açık ve dolaysız olarak aktarılabildiğinden ders kitabında yer alan değer aktarımına yönelik eşdizimsel örüntünün de bu durumu desteklediği ve hem değer aktarımı hem de eşdizim boyutlarında iyi bir düzeyde olduğu belirlenmiştir.
A comparison of numerical methods for the Rayleigh equation in unbounded domains
Liou, W. W.; Morris, P. J.
1991-01-01
A second-order finite difference and two spectral methods, including a Chebyshev tau and a Chebyshev collocation method were implemented to determine the linear hydrodynamic stability of an unbounded shear flow. The velocity profile of the basic flow in the stability analysis mimicks that of a one-stream free mixing layer. Local and global eigenvalue solution methods are used to determine individual eigenvalues and the eigenvalue spectrum, respectively. The calculated eigenvalue spectrum includes a discrete mode, a continuous spectrum associated with the equation singularity and a continuous spectrum associated with the domain unboundedness. The efficiency and the accuracy of these discretization methods in the prediction of the eigensolutions of the discrete mode were evaluated by comparison with a conventional shooting procedure. Their capabilities in mapping out the continuous eigenvalue spectra are also discussed.
Systems of nonlinear Volterra integro-differential equations of arbitrary order
Directory of Open Access Journals (Sweden)
Kourosh Parand
2018-10-01
Full Text Available In this paper, a new approximate method for solving of systems of nonlinear Volterra integro-differential equations of arbitrary (integer and fractional order is introduced. For this purpose, the generalized fractional order of the Chebyshev orthogonal functions (GFCFs based on the classical Chebyshev polynomials of the first kind has been introduced that can be used to obtain the solution of the integro-differential equations (IDEs. Also, we construct the fractional derivative operational matrix of order $\\alpha$ in the Caputo's definition for GFCFs. This method reduced a system of IDEs by collocation method into a system of algebraic equations. Some examples to illustrate the simplicity and the effectiveness of the propose method have been presented.
The application of the Chebyshev-spectral method in transport phenomena
Guo, Weidong; Narayanan, Ranga
2012-01-01
Transport phenomena problems that occur in engineering and physics are often multi-dimensional and multi-phase in character. When taking recourse to numerical methods the spectral method is particularly useful and efficient. The book is meant principally to train students and non-specialists to use the spectral method for solving problems that model fluid flow in closed geometries with heat or mass transfer. To this aim the reader should bring a working knowledge of fluid mechanics and heat transfer and should be readily conversant with simple concepts of linear algebra including spectral decomposition of matrices as well as solvability conditions for inhomogeneous problems. The book is neither meant to supply a ready-to-use program that is all-purpose nor to go through all manners of mathematical proofs. The focus in this tutorial is on the use of the spectral methods for space discretization, because this is where most of the difficulty lies. While time dependent problems are also of great interes...
Covaci, L.; Peeters, F. M.; Berciu, M.
2010-10-01
We propose a highly efficient numerical method to describe inhomogeneous superconductivity by using the kernel polynomial method in order to calculate the Green’s functions of a superconductor. Broken translational invariance of any type (impurities, surfaces, or magnetic fields) can be easily incorporated. We show that limitations due to system size can be easily circumvented and therefore this method opens the way for the study of scenarios and/or geometries that were unaccessible before. The proposed method is highly efficient and amenable to large scale parallel computation. Although we only use it in the context of superconductivity, it is applicable to other inhomogeneous mean-field theories.
National Research Council Canada - National Science Library
K. Issa; F. Salehi
2017-01-01
In this work, we obtain the approximate solution for the integrodifferential equations by adding perturbation terms to the right hand side of integrodifferential equation and then solve the resulting...
Fast and High-Quality Bilateral Filtering Using Gauss-Chebyshev Approximation
Ghosh, Sanjay; Chaudhury, Kunal N.
2016-01-01
The bilateral filter is an edge-preserving smoother that has diverse applications in image processing, computer vision, computer graphics, and computational photography. The filter uses a spatial kernel along with a range kernel to perform edge-preserving smoothing. In this paper, we consider the Gaussian bilateral filter where both the kernels are Gaussian. A direct implementation of the Gaussian bilateral filter requires $O(\\sigma_s^2)$ operations per pixel, where $\\sigma_s$ is the standard...
A review of collocated multi-user TV
McGill, Mark; Williamson, John H.; Brewster, Stephen A.
2015-01-01
The TV plays a central role in our homes, bringing friends and family together by providing a common reference point for live, on-demand and interactive media. However, the capabilities of the modern day TV poorly reflect this social, multi-user context. The TV is in the process of being supplemented, and in some cases replaced, by other devices and displays (e.g. phones, tablets) in what is termed “multi-screening”. This allows users to engage in separate and private activities alongside TV ...
Peculiarity in the Coinages, Collocations and Allusions in Wole ...
African Journals Online (AJOL)
Soyinka has often been labelled as an 'obscure' and 'difficult' writer. One text which helps in giving him this reputation is The Interpreters which has not enjoyed as wide a readership as other texts published at the same period. This paper is an attempt to delineate the peculiarities in the way Soyinka uses familiar literary ...
First-year University Students' Productive Knowledge of Collocations ...
African Journals Online (AJOL)
Only the 2000-word band is mastered by most of these first year student participants, with some of them not entirely mastering this band. On the basis of these results, pedagogical consequences are discussed in terms of how to help students reach the minimum threshold of productive knowledge that is needed to cope with ...
Collocations in popular religious literature: an analysis in corpus ...
African Journals Online (AJOL)
This register is, broadly speaking, language for special purposes (LSP) and, more particularly, popular religious literature as an instance of LSP. The analysis therefore aims to describe the features unique to the language of popular religious texts, against the background of descriptive translation studies and, more ...
On a Misconception Involving Point Collocation and the Rayleigh Hypothesis
DEFF Research Database (Denmark)
Christiansen, Søren; Kleinman, Ralph E.
1996-01-01
It is shown that the Rayleigh hypothesis does notgovern convergence of the simple point collocationapproach to the numerical solutions of scatteringby a sinusoidal grating. A recently developed numerical technique, interval arithmetic, is employed to perform some decisive numerical experiments...
Magnetic cubes-collocated coils as sensors for displacement positioning
Directory of Open Access Journals (Sweden)
Jovičić Nenad S.
2015-01-01
Full Text Available We describe design and verification of a novel autonomous sensor system (Magnetic Cubes for evaluating the distance between two points as well as the rotation matrix between the coordinate systems attached to the sensors. The system is based on two sensors, each comprising three orthogonal coils wound on foam cubes, and near-field coupling between the sensors, which operate the medium frequency band. Testing and verification of the designed system was done by performing various 2D and 3D movements, and comparing positions and orientations estimated by Magnetic Cubes with those measured by an optical motion capture system. In all cases, good agreement is obtained: the RMS error for the estimation of the distances between the cubes is less than 10 mm (less than 2%, while the RMS errors for the estimation of the Cartesian coordinates are less than 7%. The discrepancies between the results obtained from the two systems were also assessed by the Pearson correlation coefficient (greater than 0.9 for the Cartesian coordinates and greater than 0.99 for the distances between the cubes.
A note on the convergence of the direct collocation boundary
DEFF Research Database (Denmark)
Juhl, Peter Møller
1998-01-01
An overview of the literature dealing with convergence of boundary element formulations is presented, and an intuitive account of the results is given. The convergence of an axisymmetric boundary element formulation is studied using linear, quadratic or superparametric elements. It is demonstrate...
In "Other" Words: Some Thoughts on the Transferability of Collocations
Odlin, Terence
2011-01-01
In discussions of cross-linguistic influence (also known as language transfer), the focus is usually on the influence of a particular structure in a particular instance of language contact, for instance, the negative transfer of serial verbs by Vietnamese learners of English: "She has managed to rise the kite fly over the tallest…
A new derivation of continuous collocation multistep methods using ...
African Journals Online (AJOL)
Journal of the Nigerian Association of Mathematical Physics. Journal Home · ABOUT THIS JOURNAL · Advanced Search · Current Issue · Archives · Journal Home > Vol 14 (2009) >. Log in or Register to get access to full text downloads.
Granularity collocation of single coal on comprehensive combustion of blends
Directory of Open Access Journals (Sweden)
X. T. Zhao
2018-01-01
Full Text Available The combustion of anthracite and bituminite blends with different bituminite particle size was investigated with thermogravimetric analysis (TGA. It is indicated in the results that the increase of bituminite particle size may influence the pyrolysis of blends and consequently the decomposition of blends moved to higher temperature zones with the increase of bituminite particle size. However, the negative influence of specific area is not that significant to some bituminite and anthracite mixtures, the comprehensive combustion behavior of blends was stable when particle size of some bituminie PC was increased from 0,074 mm to 0,150 mm.
Collocations and grammatical patterns in a Multilingual Online Term ...
African Journals Online (AJOL)
user
African terminological databanks and language for special purposes (LSP) dictionaries. Various strategies for the ... tiary education system where the language of teaching and learning is not the strongest language, i.e. the .... pletely opaque idioms to combinations which are subject to arbitrary lexical restrictions, e.g. take ...
Thesaurus of Educational Technology Terms and Their Collocations.
Serdiukov, Peter, Comp.
This paper presents several samples from a Thesaurus of educational technology (ET) terms that is based on the analysis of recent publications (journal articles, conference papers, and books), various related texts, and Internet databases. The Thesaurus pulls together all the knowledge acquired in the development of ET from 1990 through 1999, to…
Airfoil Analysis with Uncertain Geometry using the Probabilistic Collocation method
Loeven, G.J.A.; Bijl, H.
2008-01-01
Due to manufacturing tolerances, the airfoil of a wing after production is never exactly the same as the designed airfoil. Also during operation the geometry may change due to aerodynamic loading, icing or wear of the construction. The geometry can, therefore, be treated as uncertain. Uncertainties
Collocation for diffeomorphic deformations in medical image registration
DEFF Research Database (Denmark)
Darkner, Sune; Pai, Akshay Sadananda Uppinakudru; Liptrot, Matthew George
2018-01-01
Diffeomorphic deformation is a popular choice in medical image registration. A fundamental property of diffeomorphisms is in vertibility, implying that once the relation between two points A to B is found, then the relation B to A is given per definition. Consistency is a measure of a numerical...
Collocability in Languages for Special Purposes (LSPs): Some ...
African Journals Online (AJOL)
Aantal inleidende aspekte. Hierdie artikel handel oor die taal wat professionele gespreks- gemeenskappe gebruik vir interne kommunikasie. Die kenmerke van hierdie tale vir ...... luation of the crown 3,134 in .tea4¥ tra4i"g. The gold index added 24 or 3 per c in the morning session on techllical tra4i"g related to the hands in ...
A meshless point collocation treatment of transient bioheat problems.
Bourantas, G C; Loukopoulos, V C; Burganos, V N; Nikiforidis, G C
2014-05-01
A meshless numerical method is proposed for the solution of the transient bioheat equation in two and three dimensions. The Pennes bioheat equation is extended in order to incorporate water evaporation, tissue damage, and temperature-dependent tissue properties during tumor ablation. The conductivity of the tissue is not assumed constant but is treated as a local function to simulate local variability due to the existence of usually unclear interfacing of healthy and pathological segments. In this way, one avoids the need for accurate identification of the boundaries between pathological and healthy regions, which is a typical problem in medical practice, and sidesteps, evidently, the corresponding mathematical treatment of such boundaries, which is usually a tedious procedure with some inevitable degree of approximation. The numerical results of the new method for test applications of the bioheat transfer equation are validated against analytical predictions and predictions of other numerical methods. 3D simulations are presented that involve the modeling of tumor ablation and account for metabolic heat generation, blood perfusion, and heat ablation using realistic values for the various parameters. An evaluation of the effective medium approximation to homogenize conductivity fields for use with the bioheat equation is also provided. Copyright © 2014 John Wiley & Sons, Ltd.
Directory of Open Access Journals (Sweden)
N. V. Kantartzis
2012-10-01
Full Text Available A generalized conformal time-domain method with adjustable spectral accuracy is introduced in this paper for the consistent analysis of large-scale electromagnetic compatibility problems. The novel 3-D hybrid schemes blend a stencil-optimized finite-volume time-domain and a multimodal Fourier-Chebyshev pseudo-spectral time-domain algorithm that split the overall space into smaller and flexible areas. A key asset is that both techniques are updated independently and interconnected by robust boundary conditions. Also, combining a family of spatial derivative approximators with controllable precision in general curvilinear coordinates, the proposed method launches a conformal field flux formulation to derive electromagnetic quantities in regions with fine details. For advanced grid reliability at dissimilar media interfaces, dispersion-reduced adaptive operators, which assign the proper weights to each spatial increment, are developed. So, the resulting discretization yields highly rigorous and computationally affordable simulations, devoid of lattice errors. Numerical results, addressing detailed comparisons of various realistic applications with reference or measurement data verify our methodology and reveal its significant applicability.
Heat transfer in rotor/stator cavity
Tuliszka-Sznitko, Ewa; Majchrowski, Wojciech; Kiełczewski, Kamil
2011-12-01
In the paper we analyze the results of DNS/LES of the flow with heat transfer in the rotor/stator cavity. The rotor and the outer cylinder are heated. Computations have been performed for wide range of Reynolds numbers and aspect ratios. Computations are based on the efficient pseudo-spectral Chebyshev-Fourier method. In LES we used a Lagrangian dynamic subgrid-scale model of turbulence. Analysis allowed to check the influence of the aspect ratio and Reynolds number on the statistics and the structure of the flow. We analyzed all six Reynolds stress tensor components, turbulent fluctuations, three turbulent heat fluxes and different structural parameters which can be useful for modeling purposes. The distributions of Nusselt numbers obtained for different Re and aspect rations along disks are given. We also investigated influence of thermal Rosssby number as well as distributions of temperature along heated disk on statistics. Computations have shown that turbulence is mostly concentrated in the stator boundary layer with a maximum at the junction between the stator and the outer cylinder. The results are compared to the experimental and numerical data taken from literature.
A phase-field method to analyze the dynamics of immiscible fluids in porous media
de Paoli, Marco; Roccon, Alessio; Zonta, Francesco; Soldati, Alfredo
2017-11-01
Liquid carbon dioxide (CO2) injected into geological formations (filled with brine) is not completely soluble in the surrounding fluid. For this reason, complex transport phenomena may occur across the interface that separates the two phases (CO2+brine and brine). Inspired by this geophysical instance, we used a Phase-Field Method (PFM) to describe the dynamics of two immiscible fluids in satured porous media. The basic idea of the PFM is to introduce an order parameter (ϕ) that varies continuously across the interfacial layer between the phases and is uniform in the bulk. The equation that describes the distribution of ϕ is the Cahn-Hilliard (CH) equation, which is coupled with the Darcy equation (to evaluate fluid velocity) through the buoyancy and Korteweg stress terms. The governing equations are solved through a pseudo-spectral technique (Fourier-Chebyshev). Our results show that the value of the surface tension between the two phases strongly influences the initial and the long term dynamics of the system. We believe that the proposed numerical approach, which grants an accurate evaluation of the interfacial fluxes of momentum/energy/species, is attractive to describe the transfer mechanism and the overall dynamics of immiscible and partially miscible phases.
Energy Technology Data Exchange (ETDEWEB)
Lombard, V.
2008-12-15
Exact self-similar solutions of gas dynamics equations with nonlinear heat conduction for semi-infinite slabs of perfect gases are used for studying the stability of ablative flows in inertial confinement fusion, when a shock wave propagates in front of a thermal front. Both the similarity solutions and their linear perturbations are numerically computed with a dynamical multi-domain Chebyshev pseudo-spectral method. Laser-imprint results, showing that maximum amplification occurs for a laser-intensity modulation of zero transverse wavenumber have thus been obtained (Abeguile et al. (2006); Clarisse et al. (2008)). Here we pursue this approach by proceeding for the first time to an analysis of perturbations in terms of Kovasznay modes. Based on the analysis of two compressible and incompressible flows, evolution equations of vorticity, acoustic and entropy modes are proposed for each flow region and mode couplings are assessed. For short times, perturbations are transferred from the external surface to the ablation front by diffusion and propagate as acoustic waves up to the shock wave. For long times, the shock region is governed by the free propagation of acoustic waves. A study of perturbations and associated sources allows us to identify strong mode couplings in the conduction and ablation regions. Moreover, the maximum instability depends on compressibility. Finally, a comparison with experiments of flows subjected to initial surface defects is initiated. (author)
CSIR Research Space (South Africa)
Sokoya, O
2008-05-01
Full Text Available error probability (PEP) and the average bit error probability (BEP) in slow (quasi-static) fading channel of the HR-STTCM using the orthogonal transmission matrix shown in (1). In [4], performance criteria for space–time codes were derived based... estimate for the BEP can be computed, taking into account the dominant error events. A closed form expression for the exact PEP for space–time trellis code was derived in [9] based on the residual method using characteristic function [11], which has...
Stability of stratified two-phase flows in horizontal channels
Barmak, Ilya; Ullmann, Amos; Brauner, Neima; Vitoshkin, Helen
2016-01-01
Linear stability of stratified two-phase flows in horizontal channels to arbitrary wavenumber disturbances is studied. The problem is reduced to Orr-Sommerfeld equations for the stream function disturbances, defined in each sublayer and coupled via boundary conditions that account also for possible interface deformation and capillary forces. Applying the Chebyshev collocation method, the equations and interface boundary conditions are reduced to the generalized eigenvalue problems solved by standard means of numerical linear algebra for the entire spectrum of eigenvalues and the associated eigenvectors. Some additional conclusions concerning the instability nature are derived from the most unstable perturbation patterns. The results are summarized in the form of stability maps showing the operational conditions at which a stratified-smooth flow pattern is stable. It is found that for gas-liquid and liquid-liquid systems the stratified flow with smooth interface is stable only in confined zone of relatively lo...
Study on dynamic behavior analysis of towed line array sensor
Directory of Open Access Journals (Sweden)
Hyun Kyoung Shin
2012-03-01
Full Text Available A set of equations of motion is derived for vibratory motions of an underwater cable connected to a moving vehicle at one end and with drogues at the other end. From the static analysis, cable configurations are obtained for different vehicle speeds and towing pretensions are determined by fluid resistance of drogues. Also the dynamic analysis is required to predict its vibratory motion. Nonlinear fluid drag forces greatly influence the dynamic tension. In this study, a numerical analysis program was developed to find out the characteristic of cable behaviour. The motion is described in terms of space and time coordinates based on Chebyshev polynomial expansions. For the spatial integration the collocation method is employed and the Newmark method is applied for the time integration. Dynamic tensions, displacements, velocities, accelerations were predicted in the time domain while natural frequencies and transfer functions were obtained in the frequency domain.
Hydromagnetic Stagnation-Point Flow towards a Radially Stretching Convectively Heated Disk
Directory of Open Access Journals (Sweden)
S. Shateyi
2013-01-01
Full Text Available The steady stagnation-point flow and heat transfer of an electrically conducted incompressible viscous fluid are extended to the case where the disk surface is convectively heated and radially stretching. The fluid is subjected to an external uniform magnetic field perpendicular to the plane of the disk. The governing momentum and energy balance equations give rise to nonlinear boundary value problem. Using a spectral relaxation method with a Chebyshev spectral collocation method, the numerical solutions are obtained over the entire range of the physical parameters. Emphasis has been laid to study the effects of viscous dissipation and Joule heating on the thermal boundary layer. Pertinent results on the effects of various thermophysical parameters on the velocity and temperature fields as well as local skin friction and local Nusselt number are discussed in detail and shown graphically and/or in tabular form.
Directory of Open Access Journals (Sweden)
A.P Gupta
2010-09-01
Full Text Available Two-dimensional boundary characteristic orthonormal polynomials are used in Rayleigh-Ritz method to study the title problem. In general, it is found that this method gives better results than the other traditional method such as boundary integral equation methods, Spline methods, Chebyshev collocation method, Frobenius method etc. The thickness is taken to be linearly varying in two orthogonal directions. Comparisons in particular cases have been made with the existing results in the literature. Convergence of frequencies of at least up to five significant figures is obtained. Results showing the variation in frequencies with taper parameters and aspect ratios are presented in tabular form. Mode shapes are shown using three-dimensional graphs of plates in displaced configurations.
Entropy Generation on MHD Casson Nanofluid Flow over a Porous Stretching/Shrinking Surface
Directory of Open Access Journals (Sweden)
Jia Qing
2016-04-01
Full Text Available In this article, entropy generation on MHD Casson nanofluid over a porous Stretching/Shrinking surface has been investigated. The influences of nonlinear thermal radiation and chemical reaction have also taken into account. The governing Casson nanofluid flow problem consists of momentum equation, energy equation and nanoparticle concentration. Similarity transformation variables have been used to transform the governing coupled partial differential equations into ordinary differential equations. The resulting highly nonlinear coupled ordinary differential equations have been solved numerically with the help of Successive linearization method (SLM and Chebyshev spectral collocation method. The impacts of various pertinent parameters of interest are discussed for velocity profile, temperature profile, concentration profile and entropy profile. The expression for local Nusselt number and local Sherwood number are also analyzed and discussed with the help of tables. Furthermore, comparison with the existing is also made as a special case of our study.
Directory of Open Access Journals (Sweden)
Muhammad Mubashir Bhatti
2017-01-01
Full Text Available In this article, entropy generation on non-Newtonian Eyring-Powell nanofluid has been analysed through a permeable stretching sheet. The governing flow problem is based on linear momentum, thermal energy, and nanoparticle concentration equation which are simplified with the help of similarity transformation variables. The resulting coupled nonlinear ordinary differential equations are solved numerically with the help of Successive Linearization method (SLM and Chebyshev Spectral collocation method. The novel characteristics of all the physical parameters are discussed with the help of graphs and tables. The expression for local Nusselt number and local Sherwood number is also taken into account. It is observed that velocity profile increases due to the greater influence of suction parameter. Moreover, Brownian motion and thermophoresis parameter significantly enhance the temperature profile, however Brownian motion parameter shows converse behaviour on nanoparticle concentration profile. Entropy profile acts as an increasing function of all the pertinent parameters.
Directory of Open Access Journals (Sweden)
S. S. Motsa
2012-01-01
Full Text Available The problem of magnetomicropolar fluid flow, heat, and mass transfer with suction through a porous medium is numerically analyzed. The problem was studied under the effects of chemical reaction, Hall, ion-slip currents, and variable thermal diffusivity. The governing fundamental conservation equations of mass, momentum, angular momentum, energy, and concentration are converted into a system of nonlinear ordinary differential equations by means of similarity transformation. The resulting system of coupled nonlinear ordinary differential equations is the then solved using a fairly new technique known as the successive linearization method together with the Chebyshev collocation method. A parametric study illustrating the influence of the magnetic strength, Hall and ion-slip currents, Eckert number, chemical reaction and permeability on the Nusselt and Sherwood numbers, skin friction coefficients, velocities, temperature, and concentration was carried out.
Directory of Open Access Journals (Sweden)
Muhammad Mubashir Bhatti
2016-05-01
Full Text Available In this article, entropy generation with radiation on non-Newtonian Carreau nanofluid towards a shrinking sheet is investigated numerically. The effects of magnetohydrodynamics (MHD are also taken into account. Firstly, the governing flow problem is simplified into ordinary differential equations from partial differential equations with the help of similarity variables. The solution of the resulting nonlinear differential equations is solved numerically with the help of the successive linearization method and Chebyshev spectral collocation method. The influence of all the emerging parameters is discussed with the help of graphs and tables. It is observed that the influence of magnetic field and fluid parameters oppose the flow. It is also analyzed that thermal radiation effects and the Prandtl number show opposite behavior on temperature profile. Furthermore, it is also observed that entropy profile increases for all the physical parameters.
Surface strain gradient effects in the torsion of a circular bar with radial cracks
Xu, Yang; Wang, Xu
2016-12-01
We study the contribution of surface strain gradient elasticity to the Saint-Venant torsion problem of a circular cylinder containing a radial crack. The surface strain gradient elasticity is incorporated by using an enriched version of the continuum-based surface/interface model of Gurtin and Murdoch. By using Green's function method, the original boundary value problem is reduced to a Cauchy singular integro-differential equation which can be numerically solved by using the Gauss-Chebyshev integration formula, the Chebyshev polynomials and the collocation method. Due to the presence of surface strain gradient elasticity on the crack faces, the stresses are bounded at the crack tips. The torsion problem of a circular cylinder containing two symmetric collinear radial cracks of equal length with surface strain gradient elasticity is also solved by using a similar method. Numerical results indicate that the surface strain gradient effect exerts a significant influence on the torsional rigidity and the jump in warping function. In particular, the jump in warping function forms a cusp shape with zero enclosed angle at the crack tips.
DEFF Research Database (Denmark)
Simurda, Matej; Lassen, Benny; Duggen, Lars
2017-01-01
A numerical model for a clamp-on transit-time ultrasonic flowmeter (TTUF) under multi-phase flow conditions is presented. The method solves equations of linear elasticity for isotropic heterogeneous materials with background flow where acoustic media are modeled by setting shear modulus to zero...... is then employed to model a complete TTUF measurement setup to simulate the effect of a flow profile on the flowmeter accuracy and a study of an impact of inclusions in flowing media on received signals is carried out....
Investigating Copyright Terminology and Collocations in Polish, English, Japanese and German
Directory of Open Access Journals (Sweden)
Trzaskawka Paula
2017-03-01
Full Text Available The article deals with the comparison of key terminology in the field of copyright in the Polish, English, Japanese and German languages. The research material consists of copyright acts binding in Poland, Great Britain, the United States of America, Japan and Germany. The terminology has been compared in order to reveal similarities and differences in the meaning. Firstly, statutory terms from the Polish, English (British and American, German and Japanese acts will be presented and discussed. Also, a list of functional equivalents (Polish, English, German and Japanese will be presented. The task was to search for functional equivalents, and if there is partial equivalence or no equivalence, an equivalent was provided according to techniques of providing equivalents for non-equivalent terms (c.f. Kłos, Matulewska, Nowak-Korcz 2007. They were made in such a way that equivalents will correspond with the reality of the laws in the above mentioned languages. The terms have been extracted with the usage of AntConc (corpus linguistics software. The method of analysis of comparable texts has been applied as well as the one based on three categories of equivalence by Šarčević (1997: “near equivalence”, “partial equivalence” and “non-equivalence”. Special attention has been paid to system-bound terminology existing in those five legal systems. To sum up, it should be borne in mind that the copyright law has been unified almost world-wide. As a result many countries have adopted similar or almost identical principles in this respect. Therefore, there is a significant convergence of meanings of analysed copyright terms with only slight differences resulting from deeply ingrained local and national legal traditions.
Advanced Techniques for Non-Collocated Fault Detetion of Satellite Formations Project
National Aeronautics and Space Administration — This proposal is for the development of a dynamic fault detection filter for a formation of satellites operating in a highly nonlinear dynamic environment but...
Multi-fidelity stochastic collocation method for computation of statistical moments
Energy Technology Data Exchange (ETDEWEB)
Zhu, Xueyu, E-mail: xueyu-zhu@uiowa.edu [Department of Mathematics, University of Iowa, Iowa City, IA 52242 (United States); Linebarger, Erin M., E-mail: aerinline@sci.utah.edu [Department of Mathematics, University of Utah, Salt Lake City, UT 84112 (United States); Xiu, Dongbin, E-mail: xiu.16@osu.edu [Department of Mathematics, The Ohio State University, Columbus, OH 43210 (United States)
2017-07-15
We present an efficient numerical algorithm to approximate the statistical moments of stochastic problems, in the presence of models with different fidelities. The method extends the multi-fidelity approximation method developed in . By combining the efficiency of low-fidelity models and the accuracy of high-fidelity models, our method exhibits fast convergence with a limited number of high-fidelity simulations. We establish an error bound of the method and present several numerical examples to demonstrate the efficiency and applicability of the multi-fidelity algorithm.
2013-02-06
function Ni,0 (ξ) = 1, if ξi ≤ ξ ≤ ξi+1 0, otherwise (1) For p > 0, the basis function is defined using the Cox-de Boor recursion formula Ni,p (ξ...1992. [107] J. Peters and U. Reif. Subdivision surfaces. Springer, 2008. [108] M. Sabin . Analysis and Design of Univariate Subdivision Schemes
A Collocation Method by Moving Least Squares Applicable to European Option Pricing
Directory of Open Access Journals (Sweden)
M. Amirfakhrian
2016-05-01
Full Text Available The subject matter of the present inquiry is the pricing of European options in the actual form of numbers. To assess the numerical prices of European options, a scheme independent of any kind of mesh but rather powered by moving least squares (MLS estimation is made. In practical terms, first the discretion of time variable is implemented and then, an MLS-powered method is applied for spatial approximation. As, unlike other methods, these courses of action mentioned here don't rely on a mesh, one can firmly claim they are to be categorized under mesh-less methods. And, of course, at the end of the paper, various experiments are offered to prove how efficient and how powerful the introduced approach is.
A collocation method for surface tension calculations with the density gradient theory
DEFF Research Database (Denmark)
Larsen, Peter Mahler; Maribo-Mogensen, Bjørn; Kontogeorgis, Georgios M.
2016-01-01
Surface tension calculations are important in many industrial applications and over a wide range of temperatures, pressures and compositions. Empirical parachor methods are not suitable over a wide condition range and the combined use of density gradient theory with equations of state has been...... proposed in literature. Often, many millions of calculations are required in the gradient theory methods, which is computationally very intensive. In this work, we have developed an algorithm to calculate surface tensions an order of magnitude faster than the existing methods, with no loss of accuracy...
DEFF Research Database (Denmark)
Kolmogorov, Dmitry
Direct numerical solutions of the Navier-Stokes equations using Computational Fluid Dynamics methods are recognized as some the most advanced and accurate methods for prediction of flows around wind turbines. The ability of these methods to capture the dynamics of the complex flow properties...... is typical for some commonly used mass flux interpolations, is estimated, and a new interpolation technique, which eliminates these errors, is developed together with fully consistent SIMPLE-like algorithms. For the algorithms, both the accuracy and the convergence rate are shown to be higher than standard...... versions of the SIMPLE algorithm. The new technique is implemented in an existing conservative 2nd order finite-volume scheme flow solver (EllipSys), which is extended to cope with grids with nonconformal interfaces. The behavior of the discrete Navier-Stokes equations is discussed in detail...
Interval Shannon Wavelet Collocation Method for Fractional Fokker-Planck Equation
Directory of Open Access Journals (Sweden)
Shu-Li Mei
2013-01-01
Full Text Available Metzler et al. introduced a fractional Fokker-Planck equation (FFPE describing a subdiffusive behavior of a particle under the combined influence of external nonlinear force field and a Boltzmann thermal heat bath. In this paper, we present an interval Shannon wavelet numerical method for the FFPE. In this method, a new concept named “dynamic interval wavelet” is proposed to solve the problem that the numerical solution of the fractional PDE is usually sensitive to boundary conditions. Comparing with the traditional wavelet defined in the interval, the Newton interpolator is employed instead of the Lagrange interpolation operator, so, the extrapolation points in the interval wavelet can be chosen dynamically to restrict the boundary effect without increase of the calculation amount. In order to avoid unlimited increasing of the extrapolation points, both the error tolerance and the condition number are taken as indicators for the dynamic choice of the extrapolation points. Then, combining with the finite difference technology, a new numerical method for the time fractional partial differential equation is constructed. A simple Fokker-Planck equation is taken as an example to illustrate the effectiveness by comparing with the Grunwald-Letnikov central difference approximation (GL-CDA.
The Present of the English Future: Grammatical Variation and Collocations in Discourse
Cacoullos, Rena Torres; Walker, James A.
2009-01-01
We use the variationist method to elucidate the expression of future time in English, examining multiple grammaticalization in the same domain ("will" and "going to"). Usage patterns show that the choice of form is not determined by invariant semantic readings such as proximity, certainty, willingness, or intention. Rather, particular instances of…
GPM Level 1C R Common Calibrated Brightness Temperatures Collocated VV03B
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
Lexical complexity: Metaphors and collocations in native, non-native and bilingual speech
Gouteraux, Pascale
2017-01-01
International audience; This paper reports on a study of metaphorical speech produced by forty native, non-native and bilingual students from University Paris-Diderot expressing themselves in English and in French. A corpus of spontaneous reactions to works of art was collected within the framework of Emphiline, an interdisciplinary project exploring the expression of surprise and associated emotions. Recent studies have bridged the gap between the Cognitive Linguistics definition of conceptu...
The contribution of collocations to L1 and L2 fluency
Sprenger, Simone; Bergmann, Christopher; Schmid, Monika
2016-01-01
In their seminal paper, Pawley and Syder (1983) argued that fluent and idiomatic control of a language is largely the result of what they described as access to "lexicalized sentence stems". Such word sequences are familiar to both speaker and hearer and presumably can be retrieved from the mental
Energy Technology Data Exchange (ETDEWEB)
Hamm, L.L.; Van Brunt, V.
1982-08-01
The Christiansen and Fredenslund programs for calculating vapor-liquid equilibria have been modified by replacing the Soave-Redlich-Kwong equation of state with the newly developed Peng-Robinson equation of state. This modification was shown to be a decided improvement for high pressure systems, especially in the critical and upper retrograde regions. Thermodynamic consistency tests were developed and used to evaluate and compare calculated values from both the modified and unmodified programs with reported experimental data for several vapor-liquid systems.
Responses to tasks involving make/do collocations by Turkic beginning learners of English
Shibliyev, Javanshir
1993-01-01
Ankara : Faculty of Humanities and Letters and the Institute of Economics and Social Sciences of Bilkent University, 1993. Thesis (Master's) -- Bilkent University, 1993. Includes bibliographical refences. Although vocabulary acquisition plays an irreplaceable role among the aspects of the language teaching and learning process, it is a relatively neglected area of second language. Such an unjustifiable lack of attention on vocabulary acquisition is especially noticeable in the teachi...
Translating Legal Collocations in Contract Agreements by Iraqi EFL Students-Translators
Abdulwahid, Muntaha A.; Hamzah, Zaitul Azma Binti Zainon; Hajimaming, Pabiyah; Alkhawaja, Hussein W.
2017-01-01
Legal translation of contract agreements is a challenge to translators as it involves combining the literary translation with the technical terminological precision. In translating legal contract agreements, a legal translator must utilize the lexical or syntactic precision and, more importantly, the pragmatic awareness of the context. This will…
DEFF Research Database (Denmark)
Hyvönen, Niina; Kaarnioja, V.; Mustonen, L.
2017-01-01
tomography, a real-world measurement configuration includes other unknown parameters as well: The information on the contact resistances, electrode positions, and body shape is almost always incomplete. In this work, the dependence of the electrode measurements on all aforementioned model properties......The objective of electrical impedance tomography is to reconstruct the internal conductivity of a physical body based on measurements of current and potential at a finite number of electrodes attached to its boundary. Although the conductivity is the quantity of main interest in impedance...
Schmitt, Norbert
1999-01-01
One way of determining construct validity of vocabulary items in language tests is to interview subjects directly after taking the items to ascertain what is known about the target words in question. This approach was combined within the framework of lexical competency in a study of the behavior of lexical items on the Test of English as a Foreign…
The Structure of an Afrikaans Collocation and Phrase Dictionary·
African Journals Online (AJOL)
speakers (primary target group) as well as advanced learners (secondary target group) is dis- cussed. The position ... The advantages and/or disadvantages of these approaches are considered. Three types of words and their .... the compiler's own database containing data (mainly from Afrikaans maga- zines) as well as the ...
2009-02-20
the Navy, SECNAVINST 1300.12C, December 28, 2005), 4. 12 Susan Dominus. “The War’s Deadliest Day for Women,” Glamour , May 1, 2006. http...January 4, 2009). Dominus, Susan. “The War’s Deadliest Day for Women,” Glamour , May 1, 2006. http://www.leatherneck.com/forums/ showthread.php?t
On the collocation between dayside auroral activity and coherent HF radar backscatter
Directory of Open Access Journals (Sweden)
J. Moen
Full Text Available The 2D morphology of coherent HF radar and optical cusp aurora has been studied for conditions of predominantly southward IMF conditions, which favours low-latitude boundary layer reconnection. Despite the variability in shape of radar cusp Doppler spectra, the spectral width criterion of > 220 m s^{–1} proves to be a robust cusp discriminator. For extended periods of well-developed radar backscatter echoes, the equatorward boundary of the > 220 m s^{–1} spectral width enhancement lines up remarkably well with the equatorward boundary of the optical cusp aurora. The spectral width boundary is however poorly determined during development and fading of radar cusp backscatter. Closer inspection of radar Doppler profile characteristics suggests that a combination of spectral width and shape may advance boundary layer identification by HF radar. For the two December days studied the onset of radar cusp backscatter occurred within pre-existing 630.0 nm cusp auroral activity and appear to be initiated by sunrise, i.e. favourable radio wave propagation conditions had to develop. Better methods are put forward for analysing optical data, and for physical interpretation of HF radar data, and for combining these data, as applied to detection, tracking, and better understanding of dayside aurora. The broader motivation of this work is to develop wider use by the scientific community, of results of these techniques, to accelerate understanding of dynamic high-latitude boundary-processes. The contributions in this work are: (1 improved techniques of analysis of observational data, yielding meaningfully enhanced accuracy for deduced cusp locations; (2 a correspondingly more pronounced validation of correlation of boundary locations derived from the observational data set; and (3 a firmer physical rationale as to why the good correlation observed should theoretically be expected.
Key words: Ionosphere (ionospheric irregularities; polar ionosphere
GPM GMI Level 1C Common Calibrated Brightness Temperatures Collocated VV03A
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
GPM Level 1C R Common Calibrated Brightness Temperatures Collocated V03
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
Haines, B. J.; Christensen, E. J.; Norman, R. A.; Parke, M. E.; Born, G. H.; Gill, S. K.
1996-01-01
Prior to the launch of TOPEX/ Poseidon in August 1992, NASA established its primary in situ verification site on the Harvest oil platform located in the Pacific Ocean off the coast of central California. Data from a suite of geodetic and oceanographic instruments attached to the platform have been combined to yield a precise record of absolute sea level simce the beginning of the mission. Critical to the computation of this geocentric sea level record is the precise determination of the platform geodetic height and the vertical velocity in the global terrestrial reference frame.We compare estimates of the platform height and vertical velocity from global positioning system (GPS) data alone and from a combination of GPS and satellite laser ranging (SLR) information. Current estimates suggest the platform is subsiding at a rate of about 8 mm per year. This height information is combined with in situ tide gauge measurements of sea level relative to a platform reference mark in order to produce a continuous record of the local geocentric sea height.
Mass-corrections for the conservative coupling of flow and transport on collocated meshes
Energy Technology Data Exchange (ETDEWEB)
Waluga, Christian, E-mail: waluga@ma.tum.de [Institute for Numerical Mathematics (M2), Technische Universität München, Boltzmannstraße 3, D-85748 Garching bei München (Germany); Wohlmuth, Barbara [Institute for Numerical Mathematics (M2), Technische Universität München, Boltzmannstraße 3, D-85748 Garching bei München (Germany); Rüde, Ulrich [Department of Computer Science 10, University Erlangen–Nuremberg, Cauerstr. 11, D-91058 Erlangen (Germany)
2016-01-15
Buoyancy-driven flow models demand a careful treatment of the mass-balance equation to avoid spurious source and sink terms in the non-linear coupling between flow and transport. In the context of finite-elements, it is therefore commonly proposed to employ sufficiently rich pressure spaces, containing piecewise constant shape functions to obtain local or even strong mass-conservation. In three-dimensional computations, this usually requires nonconforming approaches, special meshes or higher order velocities, which make these schemes prohibitively expensive for some applications and complicate the implementation into legacy code. In this paper, we therefore propose a lean and conservatively coupled scheme based on standard stabilized linear equal-order finite elements for the Stokes part and vertex-centered finite volumes for the energy equation. We show that in a weak mass-balance it is possible to recover exact conservation properties by a local flux-correction which can be computed efficiently on the control volume boundaries of the transport mesh. We discuss implementation aspects and demonstrate the effectiveness of the flux-correction by different two- and three-dimensional examples which are motivated by geophysical applications.
GPM GMI Level 1C Common Calibrated Brightness Temperatures Collocated V03
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
GPM GMI Level 1C Common Calibrated Brightness Temperatures Collocated VV03B
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
GPM Level 1C R Common Calibrated Brightness Temperatures Collocated VV03A
National Aeronautics and Space Administration — All 1C products have a common L1C data structure, simple and generic. Each L1C swath includes scan time, latitude and longitude, scan status, quality, incidence...
Studying the influence of a secondary variable in Collocated Cokriging estimates
Directory of Open Access Journals (Sweden)
Marcelo M. Rocha
Full Text Available Neste artigo examina-se a influência da variável secundária como função da correlação com a variável primária na cokrigagem colocalizada. Para este estudo cinco bases de dados completas foram geradas no computador a partir das quais amostras com 60 e 104 pontos de dados foram retirados através do método de amostragem aleatória estratificada. Estas bases de dados completas foram geradas partindo-se de um par de variáveis, primária e secundária, que apresentam boa correlação. Então sucessivos conjuntos foram gerados adicionando-se uma quantidade de ruído branco de modo que a correlação se tornasse menor. Utilizando-se estas amostras foi possível encontrar o quanto as informações primária e secundária são utilizadas na estimativa de um ponto não amostrado conforme o nível de correlação.
AMBIGUITY OF THE COLLOCATION “STATE SUBJECT TO THE RULE OF LAW”
Directory of Open Access Journals (Sweden)
IULIAN NEDELCU
2013-05-01
Full Text Available This work has as purpose the analysis of the notion of “State Subject to the Rule of Law”, considered within the doctrine as being ambiguous due to the fact that there are several methods to understand the base of state being subject to the rule of law, on one hand and on the other hand because, similarly to the concept of democracy, the abusive use of the concept to describe political and legal regimes which are completely different from one another voids it of any meaning. The concept of state subject to the rule of law is a doctrinary creation. Although normativised by many current constitutions, its contents mostly remains uncertain, precisely due to its origin which makes it an incessant debate theme, a theme upon which a generalised agreement has not been possible up to presently. The analysis of this notion shall approach the visions upon the state subject to the rule of law expressed within the doctrine: formalist, functionalist and material which provide three different types of organisation of the state subject to the rule of law which are complementary instead, not antagonistic ones.
Schmale, J.; Henning, S.; Henzing, B.; Keskinen, H.; Sellegri, K.; Ovadnevaite, J.; Bougiatioti, A.; Kalivitis, N.; Stavroulas, I.; Jefferson, A.; Park, M.; Schlag, P.; Kristensson, A.; Iwamoto, Y.; Pringle, K.; Reddington, C.; Aalto, P.; Äijälä, M.; Baltensperger, U.; Bialek, J.; Birmili, W.; Bukowiecki, N.; Ehn, M.; Fjæraa, A.M.; Fiebig, M.; Frank, G.; Fröhlich, R.; Frumau, A.; Furuya, M.; Hammer, E.; Heikkinen, L.; Herrmann, E.; Holzinger, R.; Hyono, H.; Kanakidou, M.; Kiendler-Scharr, A.; Kinouchi, K.; Kos, G.; Kulmala, M.; Mihalopoulos, N.; Motos, G.; Nenes, A.; O'Dowd, C.; Paramonov, M.; Petäjä, T.; Picard, D.; Poulain, L.; Prévôt, A.S.H.; Slowik, J.; Sonntag, A.; Swietlicki, E.; Svenningsson, B.; Tsurumaru, H.; Wiedensohler, A.; Wittbom, C.; Ogren, J.A.; Matsuki, A.; Yum, S.S.; Myhre, C.L.; Carslaw, K.; Stratmann, F.; Gysel, M.
2017-01-01
Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other
Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O'Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, Martin
2017-03-01
Cloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.
Impact of WhatsAPP on Learning and Retention of Collocation Knowledge among Iranian EFL Learners
Ashiyan, Zahra; Salehi, Hadi
2016-01-01
During the recent technological years, language learning has been attempted to transform its path from the conventional methods to instrumental applications. Mobile phone provides people to reach and exchange information through chats (WhatsApp). It is a tool or mode that means the facilities are used for main purposes. The unique features of the…
2002-05-01
are given by xj = x+ hξj. (1.3) For the example given in Figure 1.1, the upper limit of j is n = 6. In a terminology consistent with Henrici [3...University of Cincinnati, 1996. [3] P. Henrici . Discrete variable methods in ordinary differential equations. John Wiley & Sons Inc., New York, 1962. [4] D
Surrogate models and optimal design of experiments for chemical kinetics applications
Bisetti, Fabrizio
2015-01-07
Kinetic models for reactive flow applications comprise hundreds of reactions describing the complex interaction among many chemical species. The detailed knowledge of the reaction parameters is a key component of the design cycle of next-generation combustion devices, which aim at improving conversion efficiency and reducing pollutant emissions. Shock tubes are a laboratory scale experimental configuration, which is widely used for the study of reaction rate parameters. Important uncertainties exist in the values of the thousands of parameters included in the most advanced kinetic models. This talk discusses the application of uncertainty quantification (UQ) methods to the analysis of shock tube data as well as the design of shock tube experiments. Attention is focused on a spectral framework in which uncertain inputs are parameterized in terms of canonical random variables, and quantities of interest (QoIs) are expressed in terms of a mean-square convergent series of orthogonal polynomials acting on these variables. We outline the implementation of a recent spectral collocation approach for determining the unknown coefficients of the expansion, namely using a sparse, adaptive pseudo-spectral construction that enables us to obtain surrogates for the QoIs accurately and efficiently. We first discuss the utility of the resulting expressions in quantifying the sensitivity of QoIs to uncertain inputs, and in the Bayesian inference key physical parameters from experimental measurements. We then discuss the application of these techniques to the analysis of shock-tube data and the optimal design of shock-tube experiments for two key reactions in combustion kinetics: the chain-brancing reaction H + O2 ←→ OH + O and the reaction of Furans with the hydroxyl radical OH.
Trajectory Optimization: OTIS 4
Riehl, John P.; Sjauw, Waldy K.; Falck, Robert D.; Paris, Stephen W.
2010-01-01
The latest release of the Optimal Trajectories by Implicit Simulation (OTIS4) allows users to simulate and optimize aerospace vehicle trajectories. With OTIS4, one can seamlessly generate optimal trajectories and parametric vehicle designs simultaneously. New features also allow OTIS4 to solve non-aerospace continuous time optimal control problems. The inputs and outputs of OTIS4 have been updated extensively from previous versions. Inputs now make use of objectoriented constructs, including one called a metastring. Metastrings use a greatly improved calculator and common nomenclature to reduce the user s workload. They allow for more flexibility in specifying vehicle physical models, boundary conditions, and path constraints. The OTIS4 calculator supports common mathematical functions, Boolean operations, and conditional statements. This allows users to define their own variables for use as outputs, constraints, or objective functions. The user-defined outputs can directly interface with other programs, such as spreadsheets, plotting packages, and visualization programs. Internally, OTIS4 has more explicit and implicit integration procedures, including high-order collocation methods, the pseudo-spectral method, and several variations of multiple shooting. Users may switch easily between the various methods. Several unique numerical techniques such as automated variable scaling and implicit integration grid refinement, support the integration methods. OTIS4 is also significantly more user friendly than previous versions. The installation process is nearly identical on various platforms, including Microsoft Windows, Apple OS X, and Linux operating systems. Cross-platform scripts also help make the execution of OTIS and post-processing of data easier. OTIS4 is supplied free by NASA and is subject to ITAR (International Traffic in Arms Regulations) restrictions. Users must have a Fortran compiler, and a Python interpreter is highly recommended.
International Journal of Natural and Applied Sciences - Vol 3, No 4 ...
African Journals Online (AJOL)
Free radical scavenging activity, flavonoid and phenolic contents of selected ... Comparison of the pseudo-spectral and galerkin methods in solving a ... Mathematical modeling of profit-maximization · EMAIL FULL TEXT EMAIL FULL TEXT
Energy Technology Data Exchange (ETDEWEB)
Hoffmann, P.; Serafimovich, A.; Peters, D.; Latteck, R. [Leibniz-Inst. fuer Atmosphaerenphysik, Kuehlungsborn (Germany); Dalin, P. [Swedish Inst. of Space Physics, Kiruna (Sweden); Goldberg, R. [NASA/Goddard Space Flight Center, Greenbelt, MD (United States)
2006-07-01
During the MaCWAVE campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andoeya rocket range (ARR) near Andenes and the Swedish rocket range (ESRANGE) near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHP radar in the upper troposphere/ lower stratosphere at Andenes (69.3 N, 16.0 E) and the ESRAD VHP radar near Kiruna (67.9 N, 21.9 E). Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24-26 January 2003 with dominant vertical wavelengths of about 4-5 km as well as with dominant observed periods of about 13-14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of {proportional_to}200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of {proportional_to}5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains. (orig.)
Hoffmann, P.; Serafimovich, A.; Peters, D.; Dalin, P.; Goldberg, R.; Latteck, R.
2006-11-01
During the {MaCWAVE} campaign, combined rocket, radiosonde and ground-based measurements have been performed at the Norwegian Andøya Rocket Range (ARR) near Andenes and the Swedish Rocket Range (ESRANGE) near Kiruna in January 2003 to study gravity waves in the vicinity of the Scandinavian mountain ridge. The investigations presented here are mainly based on the evaluation of continuous radar measurements with the ALWIN VHF radar in the upper troposphere/ lower stratosphere at Andenes (69.3° N, 16.0° E) and the ESRAD VHF radar near Kiruna (67.9° N, 21.9° E). Both radars are separated by about 260 km. Based on wavelet transformations of both data sets, the strongest activity of inertia gravity waves in the upper troposphere has been detected during the first period from 24-26 January 2003 with dominant vertical wavelengths of about 4-5 km as well as with dominant observed periods of about 13-14 h for the altitude range between 5 and 8 km under the additional influence of mountain waves. The results show the appearance of dominating inertia gravity waves with characteristic horizontal wavelengths of 200 km moving in the opposite direction than the mean background wind. The results show the appearance of dominating inertia gravity waves with intrinsic periods in the order of 5 h and with horizontal wavelengths of 200 km, moving in the opposite direction than the mean background wind. From the derived downward energy propagation it is supposed, that these waves are likely generated by a jet streak in the upper troposphere. The parameters of the jet-induced gravity waves have been estimated at both sites separately. The identified gravity waves are coherent at both locations and show higher amplitudes on the east-side of the Scandinavian mountain ridge, as expected by the influence of mountains.
Directory of Open Access Journals (Sweden)
Farshid Mirzaee
2014-06-01
Full Text Available In this paper, we present a numerical method for solving two-dimensional Fredholm–Volterra integral equations (F-VIE. The method reduces the solution of these integral equations to the solution of a linear system of algebraic equations. The existence and uniqueness of the solution and error analysis of proposed method are discussed. The method is computationally very simple and attractive. Finally, numerical examples illustrate the efficiency and accuracy of the method.
Andjelić-Nikolendžić, Vesna
2010-01-01
The paper focuses on the problem of false pairs in English and Serbian languages, and the issues stemming from and related to this phenomenon. Special attention was given to false pairs in occupational registers, and particularly to the register of medical profession. The author gives a number of examples showing that translators often fail to perceive the differences in semantic fields covered by the pairs observed in the two languages, which may cause serious misunderstanding. While in everyday life such a misunderstanding can be a source of amusement or embarrassment, in scientific or academic registers it could have more serious consequences.
Walker, Crayton
2011-01-01
In this paper I use two case studies to show how corpus linguistics can be used to help in the teaching of business English. Senior managers in global companies often find themselves having to do their job in a foreign language. Given that language is one of the key tools of management, the senior managers are normally very keen to develop a…
Terry, Kristen M. Kennedy
2017-01-01
This study uses a mixed-effects model to examine the acquisition of targetlike patterns of phonological variation by 17 English-speaking learners of French during study abroad in France. Naturalistic speech data provide evidence for the incipient acquisition of a phonological variable showing sociostylistic variation in native speaker speech: the…
Mahvelati, Elaheh Hamed; Mukundan, Jayakaran
2012-01-01
The differences in cognitive style between individuals and the effect these differences can have on second language learning have long been recognized by educators and researchers. Hence, this issue is the focal center of the present study. More precisely, the purpose of this study was to investigate the role of participants' cognitive style…
AMSR-E Rainfall Subset, collocated with the CloudSat track, in HDF-EOS format V002
National Aeronautics and Space Administration — This is a subset of AMSR-E rain rat eproduct along CloudSat field of view track. The goal of the subset is to select and return AMSR-E data that are within +-100 km...
Numerical modeling of bubble dynamics in viscoelastic media with relaxation
Warnez, M. T.; Johnsen, E.
2015-01-01
Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller–Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin–Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time. PMID:26130967
Linear stability analysis of thin films in wall bounded shear flow
Kaffel, Ahmed; Riaz, Amir
2013-11-01
In this study we examine the stability of core annular flow of two fluids with large density and viscosity ratios to investigate the physical mechanisms associated to thin liquid films flow in microgap channels. Emphasis will be placed on predicting and controlling the growth of interfacial instabilities which can lead to the rupture of the thin liquid films encountered in annular flows. A multi-domain Chebyshev collocation spectral method along with QZ eigenvalue solver are used to solve the Orr-Sommerfeld stability equations in both layers. The algorithm is computationally efficient and accurate in reproducing the whole spectrum of the eigenvalues and associated eigenfunctions. The derivation of the asymptotics of these modes shows that the numerical eigenvalues are in agreement with the analytic formula obtained previously by Yih (1967), Orszag (1971), Higgins et al. (1988), Dongarra (1996) and Sahu et al. (2007). The numerical simulations and experiments are carried out to quantify unstable wave patterns with respect to the underlying fluid dynamic mechanism for various flows rates. We consider the case of isothermal, non-adiabatic, parallel flow of liquid and vapor phases. A parametric study is analyzed and the numerical stability results are presented and will be used later as a tool to validate the direct numerical solver and to identify the physical mechanisms in two-phase liquid vapor flows.
Relative Effects of Asymmetry and Wall Slip on the Stability of Plane Channel Flow
Directory of Open Access Journals (Sweden)
Sukhendu Ghosh
2017-12-01
Full Text Available The effect of wall velocity slip on the stability of a pressure-driven two-dimensional asymmetric channel flow is examined by considering Navier slip condition on the channel walls. The two-parameter families of mean velocity profiles are considered to approximate the underlying asymmetric basic flow. Competing effects of skewness and maximum velocity on the stability of the flow are explored for a range of model parameters. The Orr–Sommerfeld system of the asymmetric flow is solved using a Chebyshev spectral collocation method for both symmetric and non-symmetric type slip boundary conditions. Numerical results indicate that moderate asymmetry in the basic flow has a significant role on the stability of the Poiseuille-kind parallel/nearly parallel flows. Wall slip shows a passive control on the instability of the asymmetric flow by increasing or decreasing the critical Reynolds number and the set of unstable wave numbers. The stabilizing/destabilizing effect of slip velocity on the flow instability is weak or strong depending on the presence of velocity slip at the upper or lower wall. Velocity slip has a profound grip on the flow behaviour by changing the shear rate inside the perturbed flow.
Numerical modeling of bubble dynamics in viscoelastic media with relaxation
Warnez, M. T.; Johnsen, E.
2015-06-01
Cavitation occurs in a variety of non-Newtonian fluids and viscoelastic materials. The large-amplitude volumetric oscillations of cavitation bubbles give rise to high temperatures and pressures at collapse, as well as induce large and rapid deformation of the surroundings. In this work, we develop a comprehensive numerical framework for spherical bubble dynamics in isotropic media obeying a wide range of viscoelastic constitutive relationships. Our numerical approach solves the compressible Keller-Miksis equation with full thermal effects (inside and outside the bubble) when coupled to a highly generalized constitutive relationship (which allows Newtonian, Kelvin-Voigt, Zener, linear Maxwell, upper-convected Maxwell, Jeffreys, Oldroyd-B, Giesekus, and Phan-Thien-Tanner models). For the latter two models, partial differential equations (PDEs) must be solved in the surrounding medium; for the remaining models, we show that the PDEs can be reduced to ordinary differential equations. To solve the general constitutive PDEs, we present a Chebyshev spectral collocation method, which is robust even for violent collapse. Combining this numerical approach with theoretical analysis, we simulate bubble dynamics in various viscoelastic media to determine the impact of relaxation time, a constitutive parameter, on the associated physics. Relaxation time is found to increase bubble growth and permit rebounds driven purely by residual stresses in the surroundings. Different regimes of oscillations occur depending on the relaxation time.
Directory of Open Access Journals (Sweden)
T.M. Agbaje
2017-03-01
Full Text Available In this paper we investigate the unsteady boundary-layer flow of an incompressible Powell-Eyring nanofluid over a shrinking surface. The effects of heat generation and thermal radiation on the fluid flow are taken into account. Numerical solutions of the nonlinear differential equations that describe the transport processes are obtained using a multi-domain bivariate spectral quasilinearization method. This innovative technique involves coupling bivariate Lagrange interpolation with quasilinearization. The solutions of the resulting system of equations are then obtained in a piecewise manner in a sequence of multiple intervals using the Chebyshev spectral collocation method. A parametric study shows how various parameters influence the flow and heat transfer processes. The validation of the results, and the method used here, has been achieved through a comparison of the current results with previously published results for selected parameter values. In general, an excellent agreement is observed. The results from this study show that the fluid parameters ε and δ reduce the flow velocity and the momentum boundary-layer thickness. The heat generation and thermal radiation parameters are found to enhance both the temperature and thermal boundary-layer thicknesses.