bluuebunny/crossref_metadata_2025_split huggingface dataset:
Innovative Gas Lift in Heavy Oil Wells: Case Study in Block 6, Sudan
Authors: Xueqing Tang , Guocheng Li , Alawad Fahmi Abdalla , Keqiang Yu , Bo Cai , Musa Tagwa Ahmed 
Published: April 2013

Abstract
Although heavy oil producers in Block 6, Sudan have been difficult to exploit with gas lift because crude oil has 19 °API, the reservoir pressure was low, and surface dead oil viscosity ranged from 30,000 to 40,000 cp. New advances have recently been made to increase oil production. These innovative practices include: (1)Injected condensate gas into the reservoir prior to gas lift, and soaked for a time (e.g.one day) sufficient for condensate-gas to dilute the heavy oil's API gravity, reduce viscosity, and pressurized the zone near the wellbore.(2)Large tubing string was extended to near the bottom of perforations, gas lift valves were not utilized to ensure that a continuous volume of high-pressure condensate gas was injected into the annulus, could blend with heavy oil at the bottom hole and avoided multi-point injection caused by possible sanding.(3)Sand trap was installed to capture the produced sand.(4)Injection pressure and injection gas rate were optimized to produce more condensate from the gas condensate reservoir for dilution of heavy oil at the wellbore.
Field data show that these new techniques have gained excellent results, with oil gain of 6-fold compared to average oil rate by PCP.
A Sedimentlogical & Integrated Case Study Towards More Understanding Of The Depositional Regimes In Complex Structures
Authors: Essam M.. , El-Sayed A.. , Benyamin M.. , El-Batal A.. 
Published: April 2013

Abstract
This study discusses the depositional setting of the Upper Cretaceous clastic dominated Abu Roash G reservoirs of Cenomanian age which deposited during in an overall transgressive setting continued into the Turonian and reached culmination in the deposition of the overlying Abu Roash F limestone as a clear regional marker.
Abu Roash G is divided into two main units, Upper & Lower Abu Roash G separated by the transgressive surface represented by the Intra Abu Roash G limestone which is easily to be tracked allover Abu Gharadig basin. Each of the Upper or the Lower Abu Roash G units has more than one sand reservoir unit.
This study tries to construct a paleogeographic model for each of the sand units of Abu Roash G in Alam El Shawish area. The interpretation was derived from wireline logs, Image, seismic attributes, depositional regimes & the experience absorbed from the nearby areas in Abu Gharadig basin using calibrated correlation / sequence stratigraphic framework through detailed core based facies.
The sea level oscillation had a profound influence on sedimentation of Abu Roash"G" Member in Alam El Shawish area. Abu Roash "G" Sandstone reservoir provide a good case history for coastal setting & believed to be exhibit both regressive and transgressive trends. This is related in lateral changes in distribution of sandstone from tidal channel, tidal flat, and barrier bar to tidal bar cross Alam El Shawish fields & vertical change through the time.
According to the integrated vision of the geological & seismic data that always add value to any prospect, field, or basin, seismic attributes computed from the 3D seismic data set proved useful in relating different reservoir characteristics interpreted from well data. These attributes were merged into the geological models & provided a description of the porosity distribution in Bahga field.
Structure and Properties Investigation of MCMgAl12Zn1 Magnesium Alloy
Authors: Dobrzański L.A. , Król M. 
Published: April 2013

Abstract
This work presents an influence of cooling rate on crystallization process, structure and mechanical properties of MCMgAl12Zn1 cast magnesium alloy. The experiments were performed using the novel Universal Metallurgical Simulator and Analyzer Platform. The apparatus enabled recording the temperature during refrigerate magnesium alloy with three different cooling rates, i.e. 0.6, 1.2 and 2.4°C/s and calculate a first derivative. Based on first derivative results, nucleation temperature, beginning of nucleation of eutectic and solidus temperature were described. It was fund that the formation temperatures of various thermal parameters, mechanical properties (hardness and ultimate compressive strength) and grain size are shifting with an increasing cooling rate.
The Effect of Toughening Combined with Microjet Cooling During Quenching (Solution Heat Treatment) of Calcium Carbide-Modified CuAl10Fe4Ni4 Alloy on its Mechanical Properties
Authors: Górny Z. , Nawarecka S. Kluska , Saja K. 
Published: April 2013

Abstract
The work presents the results of the experimental research concerning the impact of a heat treatment (toughening) of aluminum bronze CuAl10Fe4Ni4 on its mechanical properties. The conditions of the experiments and selected results are described. A detailed description of the effects of individual heat treatment conditions namely low and high temperature aging is also presented in the work.
Effect of Chemical Composition on Number of Eutectic Colonies in Ni-Mn-Cu Cast Iron
Authors: Janus A. 
Published: April 2013

Abstract
Determined were direction and intensity of influence of alloying additions on the number of eutectic graphite colonies in austenitic cast iron Ni-Mn-Cu. Chemical composition of the cast iron was 1.7 to 3.3% C, 1.4 to 3.1% Si, 2.8 to 9.9% Ni, 0.4 to 7.7% Mn, 0 to 4.6% Cu, 0.14 to 0.16% P and 0.03 to 0.04% S. Analysed were structures of mottled (20 castings) and grey (20 castings) cast iron. Obtained were regression equations determining influence intensity of individual components on the number of graphite colonies per 1 cm2 (LK). It was found that, in spite of high total content of alloying elements in the examined cast iron, the element that mainly decides the LK value is carbon, like in a plain cast iron.
Virtual Factory as a Method of Foundry Design and Production Management
Authors: Stawowy A. , Wrona R. , Brzeziński M. , Ziółkowski E. 
Published: April 2013

Abstract
The paper outlines the methodology of virtual design of a foundry plant as a system. The most important stage in the procedure involves the development of a model defined as a set of data about the system. Model development involves two stages: defining the model’s architecture and specifying the model data in the form of parameters and input-output relationships. The structure is understood as configuration of machines and transport units, representing the sub-systems and system components. As the main purpose of the simulation procedure is to find the characteristics of the system’s behaviour, the merits of the iterative method involving analysis, synthesis and evaluation of results are fully explored.
The Silumin Coat Structure on Alloy Ductile Iron
Authors: Szymczak T. 
Published: April 2013

Abstract
The work presents the research results of the silumin coat structure applied on the carbidic alloy ductile iron with the metal matrix: pearlitic, bainitic and martensitic. The coats were made in the AlSi5 silumin bath at the temperature tk = 750±5°C. The holding time of cast iron element in the bath was τ = 180s. Irrespective of the kind of tested ductile iron the obtained coat consisted of three layers with a different phase composition. The first layer from the cast iron ground “g1`” is built from Fe4CSi carbide which contains selected alloy additives of the cast iron. On it the second layer “g1``” crystallizes. It consists of the AlFeSi inter-metallic phase which can appear in its pure form or contain a small quantity of the alloy additives of the cast iron. The last external part of the layer “g2” mainly consists of the hypo-eutectic phases of silumin. The AlFeSi inter-metallic phases in the form of free precipitations with a lamellar or faceted morphology can also appear there. These phases also can contain a small quantity of the alloy additives of the cast iron. More than that, in all the layers of the coat there are graphite precipitations. The phenomenon of graphite movement to the coat is caused by intensive dissolving of the cast iron element surface by the aluminum of the silumin bath.
Technology Enhanced Learning for Humanities by Active Learning − the Sinus Project Approach
Authors: Agre Gennady , Dochev Danail , Slavkova Liliana 
Published: April 2013

Abstract
The paper presents an approach to active learning facilitated by the use of semantic technologies. Some features of active learning and understanding of learning in humanities are discussed. The specifics of a well defined learning task - learner’s authoring of analytical materials, grounded by materials from a digital library - are analyzed to shape the functionality of experimental Technology Enhanced Learning (TEL) environment with a built-in domain and pedagogical knowledge. The environment structure and realization are discussed and a learning example is presented.
Pattern Synthesis Using Multiple Kernel Learning for Efficient SVM Classification
Authors: Seetha Hari , Saravanan R. , Murty M. Narasimha 
Published: April 2013

Abstract
Support Vector Machines (SVMs) have gained prominence because of their high generalization ability for a wide range of applications. However, the size of the training data that it requires to achieve a commendable performance becomes extremely large with increasing dimensionality using RBF and polynomial kernels. Synthesizing new training patterns curbs this effect. In this paper, we propose a novel multiple kernel learning approach to generate a synthetic training set which is larger than the original training set. This method is evaluated on seven of the benchmark datasets and experimental studies showed that SVM classifier trained with synthetic patterns has demonstrated superior performance over the traditional SVM classifier.
Multi-Criteria Models for Clusters Design
Authors: Radeva Irina 
Published: April 2013

Abstract
The paper describes economic agents’ integration in clusters on a predefined technological network. The process is divided and directed by three multi-criteria models. The first one allows selection of economic agents. The second one aims at definition of alternative cluster designs. The third model evaluates the risk of the clusters. The process and models are tested on nineteen economic agents.
Resolvent Estimates in l_p for Discrete Laplacians on Irregular Meshes and Maximum-norm Stability of Parabolic Finite Difference Schemes
Authors: Crouzeix Michel , Thomée Vidar 
Published: April 2013

AbstractIn an attempt to show maximum-norm stability and smoothing estimates for finite element discretizations of parabolic problems on nonquasi-uniform triangulations
we consider the lumped mass method with piecewise linear finite elements in one and two space dimensions. By an energy argument we derive resolvent estimate for the
associated discrete Laplacian, which is then a finite difference operator on an irregular mesh, which show that this generates an analytic semigroup in l_p for p‹∞
uniformly in the mesh, assuming in the two-dimensional case that the triangulations are of Delaunay type, and with a logarithmic bound for p=∞.
By a different argument based on a weighted norm estimate for a discrete Green's function this is improved to hold without a logarithmic factor for p=∞
in one dimension under a weak mesh-ratio condition. Our estimates are applied to show stability also for time stepping methods.
On the Strong Stability of Operator-Difference Schemes in Time-Integral Norms
Authors: Jovanović Boško S. , Matus Piotr P. 
Published: April 2013

Abstract In this paper we investigate the stability of two-level operator-difference
schemes in Hilbert spaces under perturbations of operators, the initial condition and
right hand side of the equation. A priori estimates of the error are obtained in time-
integral norms under some natural assumptions on the perturbations of the operators.
Parameter–uniform Fitted Mesh Method for Quasilinear Differential Equations with Boundary Layers
Authors: Farrell Paul A. , O’Riordan Eugene , Miller John J.H. , Shishkin Grigorii I. 
Published: April 2013

AbstractSingularly perturbed quasilinear boundary value problems exhibiting
boundary layers are considered. Special piecewise-uniform meshes are constructed
which are fitted to these boundary layers. Numerical methods composed of upwind
difference operators and these fitted meshes are shown to be parameter robust, in
the sense that the solutions satisfy an error estimate in the maximum norm which is
independent of the value of the singular perturbation parameter. Numerical results
supporting the theory are presented.
Difference Methods for Fuzzy Partial Differential Equations
Authors: Allahviranloo Tofigh 
Published: April 2013

AbstractIn this paper numerical methods for solving ’fuzzy partial differential
equations’(FPDE) is considered. Fuzzy reachable set can be approximated by proposed
methods with complete error analysis which is discussed in details. The methods are
illustrated by solving some linear and nonlinear FPDE.
Numerical Solution of a Rimming Flow Problem Using a Moving Mesh Method
Authors: Hegarty Alan F. , O'Brien Stephen B. G. , Sikwila Stephen 
Published: April 2013

AbstractWe consider the evolution of a thin film of viscous fluid on the inside surface of a cylinder with the horizontal axis, rotating with a constant angular velocity
about this axis. We use a lubrication approximation extended to the first order in the dimensionless film thickness (including the small effects of the variation of the film
pressure across its thickness and the surface tension) and numerically we compute the time evolution of the film to a steady state.
On Numerical Methods for a Boundary Layer on a Body of Revolution
Authors: Hossain Bayezid , Ansari Ali R. , Shishkin Gregorii I. 
Published: April 2013

Abstract The flow of a viscous incompressible uid past a body of revolution with aparabolic profile when the stream is parallel to its axis falls into a class of problems that exhibit boundary layers. This problem does not have solutions in closed form, and is
modeled by boundary-layer equations. Using a self-similar approach based on a Blasius series expansion (up to two terms), the boundary-layer equations can be reduced to
a Blasius-type problem consisting of a system of three 3rd order ordinary differential equations on a semi-infinite interval. Numerical methods need to be employed to
attain the solutions of these equations and their derivatives, which are required for the computation of the velocity components, on a finite domain with accuracy independent
of the viscosity v, which can take arbitrary values from the interval (0; 1]. Numerical methods for which the accuracy of the velocity components depend on the number
of mesh points N, used to solve the Blasius-type problem, and do not depend on the viscosity v, are referred to as robust methods. To construct a robust numerical method
we reduce the original problem on a semi-infinite axis to a problem on the finite interval [0;K], where K = K(N) = lnN. Employing numerical experiments, we justify that
the constructed numerical method is parameter robust.
Solution of Some Differential Equations of Quantum Physics by the Numerical Functional Integration Method
Authors: Lobanov Y. Y. , Zhidkov E. P. 
Published: April 2013

Abstract The application of the numerical functional integration method to the solution of differential equations in quantum physics is discussed. We have developed a
method of numerical evaluation of functional integrals in abstract complete separable metric spaces, which proves to have important advantages over the conventional Monte
Carlo method of path integration. One of the considered applications is the investigation of open quantum systems (OQS), i.e., systems interacting with their environment.
The density operator of OQS satisfies the known Lindblad differential equation. We have obtained the expression for matrix elements of this operator in the form of the
double conditional Wiener integral and considered its application to some problems of nuclear physics. Another application is the solution of the Scr¨odinger equation with
imaginary time and anticommuting variables for studying many-fermion systems. We have developed a numerical method based on functional integration over ordered subspaces.
The binding energies of some nuclei are computed using this method. Comparison of the results with those obtained by other authors and with experimental values
is presented.
A Priori Error Analysis for the hp-Version of the Discontinuous Galerkin Finite Element Method for the Biharmonic Equation
Authors: Mozolevski Igor , Süli Endre 
Published: April 2013

AbstractWe consider the hp-version of the discontinuous Galerkin finite element approximation of boundary value problems for the biharmonic equation. Our main concern is the a priori error analysis of the method, based on a nonsymmetric bilinear form with interior discontinuity penalization terms. We establish an a priori error bound for the method which is of optimal order with respect to the mesh size h , and nearly optimal with respect to the degree p of the polynomial approximation. For analytic solutions, the method exhibits an exponential rate of convergence under p- refinement. These results are shown in the DG-norm for a general shape regular family of partitions consisting of d-dimensional parallelepipeds. The theoretical results are confirmed by numerical experiments. The method has also been tested on several practical problems of thin-plate-bending theory and has been shown to be competitive in accuracy with existing algorithms.
Numerical Stability Analysis of Solutions of PDEs
Authors: Čiegis Raimondas , Čiegis Remigijus 
Published: April 2013

Abstract In this paper we investigate two iterative methods for solving one problem of nonlinear optics. The main goal is not only to find a stationary solution but also
to investigate its stability. It is shown that both methods have very different stability
properties and the less stable algorithm is close to the approximation of the physically
important non-stationary problem. We also propose a new iterative algorithm for solving a more complicated problem which describes the optical conjugation in stimulated
Brillouin backscattering with pump depletion. This algorithm is based on a symmetrical splitting scheme and the nonlinear interaction is approximated by using the special
mass conservation property of the discrete problem. Thus, we obtain a conservative
iterative algorithm. The results of the numerical experiments are presented and they
confirm our theoretical conclusions.
A Class of Singularly Perturbed Convection-Diffusion Problems with a Moving Interior Layer. An a Posteriori Adaptive Mesh Technique
Authors: Shishkin Grigory I. , Shishkina Lidia P. , Hemker Pieter W. 
Published: April 2013

AbstractWe study numerical approximations for a class of singularly perturbed
convection-diffusion type problems with a moving interior layer. In a domain (segment)
with a moving interface between two subdomains, we consider an initial boundary value
problem for a singularly perturbed parabolic convection-diffusion equation. Convection
ﬂuxes on the subdomains are directed towards the interface. The solution of this
problem has a moving transition layer in the neighbourhood of the interface. Unlike
problems with a stationary layer, the solution exhibits singular behaviour also with
respect to the time variable. Well-known upwind ﬁnite difference schemes for such
problems do not converge ε-uniformly in the uniform norm. In the case of rectangular meshes
which are (a priori or a posteriori ) locally condensed in the transition layer. However, the condition for convergence can be considerably weakened
if we take the geometry of the layer into account, i.e., if we introduce a new coordinate
system which captures the interface. For the problem in such a coordinate system,
one can use either an a priori, or an a posteriori adaptive mesh technique. Here we
construct a scheme on a posteriori adaptive meshes (based on the solution gradient),
whose solution converges ‘almost ε-uniformly’.
Iterative Solutions of a Mixed Hybrid Finite Element Scheme for the Signorini Problem
Authors: Ignatieva Marina A. , Lapin Alexander V. 
Published: April 2013

AbstractA mixed hybrid ﬁnite element method of the lowest order is studied
for the Signorini problem. An iterative method with a preconditioner being a classical
ﬁnite element approximation of the Laplace operator is constructed. A multistage
iterative procedure for the mixed hybrid ﬁnite element scheme is constructed, the rate
of convergence and the complexity of this method are analysed.
On the Generation of a Hexagonal Collision Model for the Boltzmann equation
Authors: Andallan Laek S. 
Published: April 2013

AbstractIn this article we prove the existence of two different classes of regular
hexagons in the hexagonal grid. We develop a generalized layer-wise construction of a hexagonal
discrete velocity model and derive general
formulae to identify all regular hexagons belonging to the grid. We also present some
numerical results based on the hexagonal grid.
Solution of a Wave Equation by a Mixed Finite Element - Fictitious Domain Method
Authors: Glowinski Roland , Lapin Serguei 
Published: April 2013

AbstractThe main goal of this article is to investigate the capability of fictitious
domain methods to simulate the scattering of linear waves by an obstacle whose shape
does not fit the mesh. The space-time discretization relies on a combination of a mixed
finite element method µa la Raviart-Thomas with a fairly standard finite difference
scheme for the time discretization. The numerical results described in the article point
to a good performance of the numerical method investigated here.
Space Mapping and Defect Correction
Authors: Echeverrĭa D. , Hemker P. W. 
Published: April 2013

Abstract In this paper we show that space-mapping optimization can be understood in the framework of defect correction. Then, space-mapping algorithms can be seen as special cases of defect correction iteration. In order to analyze the properties of space mapping and the space-mapping function, we introduce the new concept of flexibility of the underlying models. The best space-mapping results are obtained for so-called equally flexible models. By introducing an a±ne operator as a left preconditioner, two models can be made equally flexible, at least in the neighborhood of a solution. This motivates an improved space-mapping (or manifold-mapping) algorithm. The left preconditioner complements traditional space mapping where only a right preconditioner is used. In the last section a few simple examples illustrate some of the phenomena analyzed in this paper.
Incompressible Fluid Flow Computation in an Arbitrary Two-dimensional Region on Nonstaggered Grids
Authors: Chuiko Mikhail , Lapanik Andrei , Nochetto Ricardo H. 
Published: April 2013

Abstract A numerical algorithm for solving the Navier-Stokes equations for incom-
pressible viscous fluid in an arbitrary two-dimensional region on nonstaggered grids is
presented. The idea of the transition to a general curvilinear coordinate system, trans-
forming the physical region into a parametrical square is used. For the discrete solution
an unconditional a priory estimate has been obtained. The results of the benchmark
computations for a driven skewed cavity flow and the results of the fluid flow modeling
in a cavity of an arbitrary shape are given.