bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel Examples of the Use of Surface Jet Pumps (SJPs) to Enhance Production & Processing. Case Studies & Lessons Learnt
Authors: Peeran Syed M , Beg N.. , Sarshar S.. 
Published: April 2013

Abstract
Production from many oil and gas fields is restricted as the reservoir pressure drops. This situation becomes worse when water-cut also increases. The restrictions in production also apply to satellite fields or in deep water applications where long distance transport of fluids is involved. In order to maintain production at an economical rate and also to increase total recovery from the field, a production boosting system is always required. Some production boosting solutions require major investment and major changes or upgrading of the existing production system.
Surface Jet Pumps (SJPs) are simple, low cost, passive devices which use a high pressure (HP) fluid as the motive force to boost the pressure of produced gas and liquid phases. The system enables the flowing wellhead pressure (FWHP) to be reduced in order to increase production, whilst meeting the downstream production pressure requirements. A high pressure fluid is needed as the source of energy or motive flow.
The applications of Surface Jet Pumps include revival of dead or liquid loaded oil and gas wells. The oil and gas industry has in recent years become more aware of their applications and benefits.
This paper covers their main applications including boosting production from selected oil and gas wells, boosting the pressure of low pressure gas, prevention of flaring very low pressure gas, eliminating the need for intermediate compressors, de-bottlenecking compressors, preventing HP wells backing out LP wells and revival of liquid loaded wells. In addition to referring to recent field examples, issues such as performance, ranges of operation, key features of the system and solutions for gas or oil production applications are described. The paper also addresses the economic aspects and pay-back periods. Field applications have shown that the recovery of the capital spent in installing surface jet pumps is generally achieved within a few weeks to a few months.
A Robotized Projective Interface for Human-Robot Learning Scenarios
Authors: De Tommaso Davide , Calinon Sylvain , Caldwell Darwin 
Published: April 2013

Abstract
In this work we discuss a novel robotics interface with perception and projection capabilities for facilitating the skill transfer process. The interface aims at allowing humans and robots to interact with each other in the same environment, with respect to visual feedback. During the learning process, the real workspace can be used as a graphical interface for helping the user to better understand what the robot has learned up to then, to display information about the task or to get feedback and guidance. Thus, the user can incrementally visualize and assess the learner's state and, at the same time, focus on the skill transfer without disrupting the continuity of the teaching interaction. We also propose a proof-of-concept, as a core element of the architecture, based on an experimental setting where a picoprojector and an rgb-depth sensor are mounted onto the end-effector of a 7-DOF robotic arm.
Integral Equations of the Linear Sloshing in an Infinite Chute and Their Discretization
Authors: Gavrilyuk Ivan. P. , Kulyk Anatoli B. , Makarov Vladimir L. 
Published: April 2013

AbstractA mathematical model of the linear sloshing in an infinite chute with a rectangular section filled by an inviscid incompressible liquid is considered. This model is an abstract second order differential equation in time with a singular integral operator coefficient on a free surface. In the case of a chute with a rib this operator coefficient is defined semi-explicitely through an auxiliary singular integral equation. Mathematical properties of the solution of the model are studied. The fundamental frequencies of the liquid as functions of the width and depth of the rib are investigated. The mathematical model is discretized by using the collocation quadrature method for the operator on the free surface and the Cayley transform method for the time derivative. This fully discrete model is investigated and the error estimates are obtained showing the spectral accuracy with respect to both the spatial and the time discretization parameters.
On the Representation of Functions and Finite Difference Operators on Adaptive Dyadic Grids
Authors: Hemker P.W. , Sprengel F. 
Published: April 2013

Abstract In this paper we describe methods to approximate functions and dif-
ferential operators on adaptive sparse (dyadic) grids. We distinguish between several
representations of a function on the sparse grid and we describe how finite difference
(FD) operators can be applied to these representations.
For general variable coefficient equations on sparse grids, genuine finite element (FE)
discretizations are not feasible and FD operators allow an easier operator evaluation
than the adapted FE operators. However, the structure of the FD operators is complex.
With the aim to construct an efficient multigrid procedure, we analyze the structure of
the discrete Laplacian in its hierarchical representation and show the relation between
the full and the sparse grid case. The rather complex relations, that are expressed by
scaling matrices for each separate coordinate direction, make us doubt about the pos-
sibility of constructing efficient preconditioners that show spectral equivalence. Hence,
we question the possibility of constructing a natural multigrid algorithm with optimal
O(N) efficiency.
We conjecture that for the efficient solution of a general class of adaptive grid problems
it is better to accept an additional condition for the dyadic grids (condition L) and to
apply adaptive hp-discretization.
Superconvergence Postprocessing for Eigenvalues
Authors: Racheva Milena R. , Andreev Andrey B. 
Published: April 2013

AbstractThe main goal of this paper is to present a new strategy of increasing
the convergence rate for the numerical solution of the linear finite element eigenvalue
problems. This is done by introducing a postprocessing technique for eigenvalues. The
postprocessing technique deals with solving a corresponding linear elliptic problem. We
prove that the proposed algorithm has the superconvergence property of the eigenvalues
and this improvement is attained at a small computational cost. Thus, good finite
element approximations for eigenvalues are obtained on the coarse mesh. The numerical
examples presented and discussed here show that the resulting postprocessing method
is computationally more efficient than the method to which it is applied.
On Multilevel Preconditioners which are Optimal with Respect to Both Problem and Discretization Parameters
Authors: Axelsson O. , Margenov S. 
Published: April 2013

Abstract Preconditioners based on various multilevel extensions of two-level piecewise linear finite element methods lead to iterative methods which have an optimal order computational complexity with respect to the size (or discretization parameter) of
the system. The methods can be in block matrix factorized form, recursively extended via certain matrix polynomial approximations of the arising Schur complement matrices or on additive, i.e., block diagonal form using stabilizations of the condition number at certain levels. The resulting spectral equivalence holds uniformly with respect to
jumps in the coefficients of the differential operator and for arbitrary triangulations. Such methods were first presented by Axelsson and Vassilevski in the late 1980s. An important part of the algorithm is the treatment of systems with a diagonal block matrix, which arises on each finer level in a recursive refinement method and corresponds
to the added degrees of freedom on that level. This block is well-conditioned for model type problems but becomes increasingly ill-conditioned when the coefficient matrix becomes more anisotropic or, equivalently, when the mesh aspect ratio increases. This paper presents some methods for approximating this matrix also leading to a preconditioner
with spectral equivalence bounds which hold uniformly with respect to both the problem and the discretization parameters. Therefore, the same holds also for the preconditioner to the global matrix.
Jacobi-Bernstein Basis Transformation
Authors: Rababah Abedallah 
Published: April 2013

Abstract In this paper we derive the matrix of transformation of the Jacobi
polynomial basis form into the Bernstein polynomial basis of the same degree n and
vice versa. This enables us to combine the superior least-squares performance of the
Jacobi polynomials with the geometrical insight of the Bernstein form. Application to
the inversion of the Bézier curves is given.
A Two Point Difference Scheme of an Arbitrary Order of Accuracy for BVPS for Systems of First Order Nonlinear Odes
Authors: Makarov V.L. , Gavrilyuk I.P. , Kutniv M.V. , Hermann M. 
Published: April 2013

AbstractWe consider two-point boundary value problems for systems of first-order
nonlinear ordinary differential equations. Under natural conditions we show that
on an arbitrary grid there exists a unique two-point exact difference scheme (EDS),
i.e., a difference scheme whose solution coincides with the projection onto the grid of
the exact solution of the corresponding system of differential equations. A constructive
algorithm is proposed in order to derive from the EDS a so-called truncated difference
scheme of an arbitrary rank. The m-TDS represents a system of nonlinear
algebraic equations with respect to the approximate values of the exact solution on
the grid. Iterative methods for its numerical solution are discussed. Analytical and
numerical examples are given which illustrate the theorems proved.
Keywords: systems of nonlinear ordinary differential equations, difference scheme,
exact difference scheme, truncated difference scheme of an arbitrary order of accuracy,
fixed point iteration.
The Influence of Higher Order FEM Discretisations on Multigrid Convergence
Authors: Köster M. , Turek S. 
Published: April 2013

AbstractQuadratic and even higher order finite elements are interesting candidates
for the numerical solution of partial differential equations (PDEs) due to their
improved approximation properties in comparison to linear approaches. The systems of
equations that arise from the discretisation of the underlying (elliptic) PDEs are often
solved by iterative solvers like preconditioned Krylow-space methods, while multigrid
solvers are still rarely used – which might be caused by the high effort that is associated
with the realisation of the necessary data structures as well as smoothing and intergrid
transfer operators.
In this note, we discuss the numerical analysis of quadratic conforming finite elements
in a multigrid solver. Using the “correct” grid transfer operators in conjunction
with a quadratic finite element approximation allows to formulate an improved approximation
property which enhances the (asymptotic) behaviour of multigrid: If m
denotes the number of smoothing steps, the convergence rates behave asymptotically
like O(1/m2) in contrast to O(1/m) for linear FEM.
On Improved Approximate Solution of the Fredholm Integral Equation
Authors: Berikelashvili G. , Karkarashvili G. 
Published: April 2013

AbstractA method of approximate solution of the linear one-dimensional Fredholm
integral equation of the second kind is constructed. With the help of the Steklov
averaging operator the integral equation is approximated by a system of linear algebraic
equations. On the basis of the approximation used an increased order convergence
solution has been obtained.
Fundamental Solutions of PDEs as Radial Basis Functions in Multivariate Interpolation
Authors: Masjukov A. 
Published: April 2013

AbstractFor bivariate and trivariate interpolation we propose in this paper a
set of integrable radial basis functions (RBFs). These RBFs are found as fundamental
solutions of appropriate PDEs and they are optimal in a special sense. The condition
number of the interpolation matrices as well as the order of convergence of the inter-
polation are estimated. Moreover, the proposed RBFs provide smooth approximations
and approximate fulfillment of the interpolation conditions. This property allows us
to avoid the undecidable problem of choosing the right scale parameter for the RBFs.
Instead we propose an iterative procedure in which a sequence of improving approx-
imations is obtained by means of a decreasing sequence of scale parameters in an a
priori given range. The paper provides a few clear examples of the advantage of the
proposed interpolation method.
On The Parallel Multiblock Geometric Multigrid Algorithm
Authors: CIEGIS R. , GASPAR F. , RODRIGO C. 
Published: April 2013

Abstract The application of a parallel multiblock geometric multigrid is consid-ered. It is applied to solve a two-dimensional poroelastic model. This system of PDEs is approximated by a special stabilized monotone finite-difference scheme. The obtained system of linear algebraic equations is solved by a multigrid method, when a domain is partitioned into structured blocks. A new strategy for the solution of the discrete problem on the coarsest grid is proposed and the efficiency of the obtained algorithm is investigated. The geometrical structure of the sequential multigrid method is used to develop a parallel version of the multigrid algorithm. The convergence properties of several smoothers are investigated and some computational results are presented.
Convergence Rates For Lavrentiev-Type Regularization In Hilbert Scales
Authors: NAIR M.T. , TAUTENHAHN U. 
Published: April 2013

AbstractFor solving linear ill-posed problems with noisy data regularization methods are required. We analyze a simplified regularization scheme in Hilbert scales for operator equations with nonnegative self-adjoint operators. By exploiting the op-erator monotonicity of certain functions, order-optimal error bounds are derived that characterize the accuracy of the regularized approximations. These error bounds have been obtained under general smoothness conditions.
Bifurcation Analysis Of Nonlinear Parameterized Two-Point Bvps With Liapunov — Schmidt Reduced Functions
Authors: HERMANN M. , MILDE T.H. 
Published: April 2013

Abstract In this paper, we study nonlinear two-point boundary value problems (BVPs) which depend on an external control parameter. In order to determine numeri-cally the singular points (turning or bifurcation points) of such a problem with so-called extended systems and to realize branch switching, some information on the type of the singularity is required. In this paper, we propose a strategy to gain numerically this information. It is based on strongly equivalent approximations of the corresponding Liapunov — Schmidt reduced function which are generated by a simplified Newton method. The graph of the reduced function makes it possible to determine the type of singularity. The efficiency of our numerical-graphical technique is demonstrated for two BVPs.
Image Edge Respecting Denoising with Edge Denoising by a Designer Nonisotropic Structure Tensor Method
Authors: Santitissadeekorn N. , Bollt E.M. 
Published: April 2013

AbstractWe consider image denoising as the problem of removing spurious
oscillations due to noise while preserving edges in the images. We will suggest here
how to directly make infinitesimal adjustment to standard variational methods of
image denoising, to enhance desirable target assumption of the noiseless image. The
standard regularization method is used to define a suitable energy functional to
penalize the data fidelity and the smoothness of the solution. This energy functional
is tailored so that the region with small gradient is isotropically smoothed whereas in
a neighborhood of an edge presented by a large gradient smoothing is allowed only
along the edge contour. The regularized solution that arises in this fashion is then the
solution of a variational principle.
To this end the associated Euler — Lagrange equation needs to be solved numerically
and the half-quadratic minimization is generally used to linearize the equation and to
derive an iterative scheme. We describe here a method to modify Euler — Largrange
equation from commonly used energy functionals, in a way to enhance certain desirable
preconceived assumptions of the image, such as edge preservation. From an algorithmic
point of view, we may deem this algorithm as a smoothing by a local average with an
adaptive gradient-based weight. However, this algorithm may result in noisy edges
although the edge is preserved and noise is suppressed in the low-gradient regions of
the image. The main focus here is to present an edge-preserving regularization in the
aforementioned view point, and to provide an alternative and simple way to modify the
existing algorithm to mitigate the phenomena of noisy edges without explicitly defining
step where we specify an energy functional to be minimized.
A Problem-Independent Slope Limiting Algorithm for the Runge-Kutta Discontinuous Galerkin Method
Authors: Tokareva S.A. 
Published: April 2013

AbstractThis paper deals with the new algorithm of slope limiting in the Runge-
Kutta discontinuous Galerkin (RKDG) method. The slope limiting is applied at each
intermediate step of the Runge-Kutta process to guarantee the monotonicity of the
resulting RKDG scheme. The standard formulation of the RKDG method assumes a
manual prescription of the special parameter used in the limiting procedure. Such definition
of the limiter makes the method problem-dependent, which is disadvantageous
for practical computations. A new problem-independent way of estimating the limiting
parameter is proposed and its performance in the second- and third-order RKDG
methods is studied in this paper.
Computational Analysis of Displacement of Particles with Given Size on the Nonstationary Bulging Membrane as a Theoretical Model of Membrane Fouling
Authors: Gac Jakub M. , Gradoń Leon 
Published: April 2013

Abstract
A simple model of behaviour of a single particle on the bulging membrane was presented. As a result of numerical solution of a motion equation the influence of the amplitude and frequency of bulging as well as the particle size on particle behaviour, especially its downstream velocity was investigated. It was found that the bulging of a membrane may increase the mean velocity of a particle or reinforce its diffusive behaviour, dependeing on the permeation velocity. The obtained results may help to design new production methods of highly fouling-resistant membranes.
Shades of Freire: Exorcising the spectre haunting pedagogy
Authors: Wilkins Andrew 
Published: April 2013

Abstract
In the second part of this special issue on neoliberalism, pedagogy and curriculum, I explore the contributions of each author to confronting neo-liberal reforms of education, notably the spectre of neo-liberalism haunting aspects of pedagogy, teaching and curriculum. Exemplary of the scholarly work produced by many critical educators, the contributing authors share an understanding of the oppressive function of educational apparatuses and their complicity with the reproduction of dominant epistemes of knowledge/power. In this case, neo-liberalism is defined as a canonical narrative through which existing education relations, practices and discourses are structured and mediated. Against this neo-liberal imaginary, the authors argue in favour of models of knowing, learning and teaching that work to sustain practices of critical inquiry and self-discovery among learners as active, reflexive and engaged subjects. The result is a timely collection of papers critiquing the nuances pertaining to the global transmission of neo-liberal education and a much- -needed reinvigoration of the Freirean demand for a liberating and critical pedagogy.
Preliminary Study on the Use of Ozonation for the Degradation of Dithiocarbamate Residues in the Fruit Drying Process: Mancozeb Residue in Blackcurrant is the Example Used
Authors: Antos Piotr , Kurdziel Anna , Sadło Stanisław , Balawejder Maciej 
Published: April 2013

Abstract
In order to reduce the level of dithiocarbamate fungicide mancozeb residues in blackcurrants, two different ozone treatment procedures were evaluated. The first one entailed washing the plant material with an aqueous solution of ozone. This ozone enriched water solution allowed for a 59% reduction of mancozeb residues, compared with the initial concentration. The latter method was based on the utilization of ozone in a gaseous phase combined with a drying process. In that procedure, samples of blackcurrant fruit were exposed to a 19 ppm ozone concentration, and then the blackcurrants were dried. The utilization of ozone in a gaseous phase permitted a 38% reduction of mancozeb residues, in comparison with the initial concentration. As a result of the combination of both processes; ozonation and drying, a 58% reduction of mancozeb residues was achieved.
Full Dynamic Reactions in the Basic Shaft Bearings of Big Band Saw Machines
Authors: Marinov Boycho 
Published: April 2013

Abstract
The band saws machines are a certain class woodworking machines for longitudinal or transversal cutting as well as for curvilinear wood cutting. These machines saw the wood through a band-saw blade and two feeding wheels. These wheels usually are very large and they are produced with inaccuracies. The centre of mass of the disc is displaced from the axis of rotation of the distance e (eccentricity) and the axis of the disk makes an angle with the axis of rotation. In this paper, the dy- namic reactions in the bearings of the basic shaft, which drives the band saw machines, are analyzed. These reactions are caused by the external loading and the kinematics and the mass characteristics of the rotating disk. The expressions for the full dynamic reactions are obtained. These expressions allow the parameters of the machines to be chosen in such a way that the loading in the shaft and the bearings to be minimal.
Diagnosis of Type, Location and Size of Cracks by Using Generalized Differential Quadrature and Rayleigh Quotient Methods
Authors: Akbarzadeh Khorshidi Majid , Soltani Delara 
Published: April 2013

Abstract
In this paper, an appropriate and accurate algorithm is pro- posed to diagnosis of lateral or vertical cracks on beam, based on beam natural frequencies. Clamped-free boundary conditions are assumed for the beam. The crack in beam is modelled by without mass torsion spring. Then, the relationship between the beam natural frequencies, location and stiffness of the crack is presented by using the Rayleigh quotient and the governing equation is solved by using generalized differential quadrature method (GDQM). If there is only one crack in the beam, then three natural frequencies are used as inputs to the algorithm and mode shapes corresponding to each the natural frequencies are calculated. Finally, type, location and severity of cracks in beam, are diagnosed.