bluuebunny/crossref_metadata_2025_split huggingface dataset:
Problem of the Moving Boundary in Continuous Casting Solved by The Analytic-Numerical Method
Authors: Grzymkowski R. , Hetmaniok E. , Pleszczyński M. 
Published: April 2013

Abstract
Mathematical modeling of thermal processes combined with the reversible phase transitions of type: solid phase - liquid phase leads to formulation of the parabolic or elliptic moving boundary problem. Solution of such defined problem requires, most often, to use some sophisticated numerical techniques and far advanced mathematical tools. The paper presents an analytic-numerical method, especially attractive from the engineer’s point of view, applied for finding the approximate solutions of the selected class of problems which can be reduced to the one-phase solidification problem of a plate with the unknown a priori, varying in time boundary of the region in which the solution is sought. Proposed method is based on the known formalism of initial expansion of a sought function, describing the field of temperature, into the power series, some coefficients of which are determined with the aid of boundary conditions, and on the approximation of a function defining the freezing front location with the broken line, parameters of which are determined numerically. The method represents a combination of the analytical and numerical techniques and seems to be an effective and relatively easy in using tool for solving problems of considered kind.
Investigations of Protective Coatings for Castings of High-Manganese Cast Steels
Authors: Holtzer M. , Bobrowski A. , Drożyński D. , Mocek J. 
Published: April 2013

Abstract
When cast steel castings are made in moulding sands on matrices of high-silica sand, which has a low fire resistance the problem of the so-called chemical penetration is distinctly visible. Whereas this effect appears to a small degree only when moulding sand matrices are of chromite, zircon or olivine sands. Therefore in case of making castings of high-manganese cast steel (e.g. Hadfield steel) sands not containing free silica should be applied (e.g. olivine sand) or in case of a high-silica matrix protective coatings for moulds and cores should be used. Two protective coatings, magnesite alcoholic (marked as coating 1 and coating 2) originated from different producers and intended for moulds for castings of the Hadfield steel, were selected for investigations. Examinations of the basic properties were performed for these coatings: viscosity, thermal analysis, sedimentation properties, wear resistance. In order to estimate the effectiveness of protective coatings the experimental castings were prepared. When applying coating 1, the surface quality of the casting was worse and traces of interaction between the casting material (cast steel) and the coating were seen. When protective coating 2 was used none interactions were seen and the surface quality was better.
Examples of New Models Applied in Selected Simulation Systems with Respect to Database
Authors: Ignaszak Z. , Hajkowski J. , Popielarski P. 
Published: April 2013

Abstract
The tolerance of damage rule progressively meets the approval in the design casting parts procedures. Therefore, there were appeared the new challenges and expectations for permanent development of process virtualization in the mechanical engineering industry. Virtualization is increasingly developed on the stage of product design and materials technologies optimization. Increasing expectations of design and process engineers regarding the practical effectiveness of applied simulation systems with new proposed up-grades modules is observed. The purpose is to obtain simulation tools allowing the most possible realistic prognosis of the casting structure, including indication, with the highest possible probability, places in the casting that are endangered with the possibility of shrinkage- and gas porosity formation. This 3D map of discontinuities and structure transformed in local mechanical characteristics are used to calculate the local stresses and safety factors. The needs of tolerance of damage and new approach to evaluate the quality of such prognosis must be defined. These problems of validation of new models/modules used to predict the shrinkage- and gas porosity including the chosen structure parameters in the example of AlSi7 alloy are discussed in the paper.
Fatigue Life Assessment of Selected Engineering Materials Based on Modified Low-Cycle Fatigue Test
Authors: Maj M. 
Published: April 2013

Abstract
In this study, the mechanical tests were carried out on ductile iron of EN-GJS-600-3 grade and on grey cast iron of EN-GJL-250 grade. The fatigue life was evaluated in a modified low-cycle fatigue test (MLCF), which enables the determination of parameters resulting from the Manson-Coffin-Morrow relationship. The qualitative and quantitative metallographic studies conducted by light microscopy on selected samples of ductile iron with spheroidal graphite and grey cast iron with lamellar graphite (showing only small variations in mechanical properties,) confirmed also small variations in the geometrical parameters of graphite related with its content and morphological features.
Determinants of Perceived Effectiveness of Organic Fertilizer Used by Farmers in Oyo State, Nigeria
Authors: Oluwasegun Fasina Oluwatosin 
Published: April 2013

Abstract The study examined the determinants of the perceived effectiveness of an organic fertilizer used by farmers in Oyo state, Nigeria. A stratified and purposive sampling technique was used to select 110 respondents from three major vegetation zones of the study area. Descriptive statistics were used to present the findings of the study while the Chi-square analysis was used to test the study hypotheses. Data revealed that 77.3% were aware of the organic fertilizer while only 60.0% of those aware made use of the fertilizer. Among the users, 37.3% applied 25 g of the organic fertilizer per crop stand which was largely on maize (92.16%). Average rate of application was 0.40 tons per hectare. Application method was mainly through side dressing (58.82%) and ‘dig and cover’ (29.41%). Time of application varied from the time of sowing to 4 weeks after planting with the majority of farmers (64.71%) applying at 2 weeks after planting. Interest in the continuous use of the fertilizer was high (62.75%) and the majority of users (52.95%) perceived that the organic fertilizer was effective. Chi-square analysis revealed that the rate and method of application were significantly related to the effectiveness of the fertilizer (χ2 = 15.66, P < 0.05 and χ2 = 8.79, P < 0.05, respectively). Rate and method of application are thus significant determinants to fertilizer effectiveness. Extension activity should therefore focus on farmer education to ensure proper use of the organic fertilizer for maximum productivity
The Impact of the D727e Polymorphism has no Significant Role in Multi Nodular Goiter
Authors: Tug E. , Sengül N. , Aydin H. , Yilmaz E.E. 
Published: April 2013

ABSTRACT Interactions between individual genetic and environ- mental factors determine the onset of the multi nodular goiter (MNG). The thyroid-stimulating hormone receptor (TSHR) gene is a convincing candidate gene in the pathogenesis of certain thyroid diseases including MNG. We investigated the codon 727 polymorphism (p.Asp727Glu, p.D727E) of the human TSHR gene using the polymerase chain reaction-restriction fragment length polymorphim (PCR-RFLP) methods in 31 Turkish patients with MNG and in 30 control subjects, aiming to evaluate the relationship between this polymorphism and MNG. After genomic DNA isolation, PCR amplification was performed using a pair of primers in exon 10 of the TSHR gene that contains the p.D727E polymorphism and digested by the NlaIII (Hin1II) restriction enzyme. We found the CC and CG genotype incidence for the patient group to be 0.71 and 0.29, respectively, and for the control group to be 0.8 and 0.2, respectively. No statistically significant difference was found between the genotype and allele distribution of both groups (p = 0.417 and p = 0.449, respectively). However, the polymorphism is significantly correlated with the low serum level of the TSH (p = 0.047). These results suggest that the p.D727E polymorphism of the TSHR gene may not contribute to the pathogenesis of nontoxic MNG diseases.
16P Subtelomeric Duplication With Vascular Anomalies: An Albanian Case Report And Literature Review
Authors: Babameto-Laku A. , Mokini V. , Kuneshka N. , Sallabanda S. , Ylli Z. 
Published: April 2013

ABSTRACT
A patient with karyotype 46,XY,der(4) was recognized by standard cytogenetic techniques, and presented with facial features, neurological impairment and pulmonary hypertension. Multiplex ligation-dependent probe amplification (MLPA) demonstrated duplication of the subtelomeric region of chromosome 16p and deletion of the subtelomeric region of chromosome 4q, suggesting a translocation between 4q and 16p. The karyotype of his parents was normal and their MLPA analysis also indicated a de novo imbalance. He had microcephaly, high frontal hairline, thin blond hair, bilateral blepharophimosis and palpebral ptosis, short nose, everted upper lip, cleft palate, micrognathia, cupped anteverted ears, hypoplastic distal phalanges and bilateral inguinal hernia. He also had pulmonary hypertension with tricuspidal regurgitation; cavernous liver hemangioma anomalies have been previously described in association with dup16p. We concluded that pulmonary and other vascular anomalies can be a feature of dup16p. We believe this is the first confirmed case of a 16p subtelomeric duplication with vascular anomalies identified in Albania.
High-order Time-accurate Schemes for Singularly Perturbed Parabolic Convection-diffusion Problems with Robin Boundary Conditions
Authors: Hemker Pieter W. , Shishkin Grigorii I. , Shishkina Lidia P. 
Published: April 2013

AbstractThe boundary-value problem for a singularly perturbed parabolic PDE
with convection is considered on an interval in the case of the singularly perturbed
Robin boundary condition; the highest space derivatives in the equation and in the
boundary condition are multiplied by the perturbation parameter ε. The order of convergence
for the known ε-uniformly convergent schemes does not exceed 1. In this paper, using
a defect correction technique, we construct ε-uniformly convergent schemes of highorder
time-accuracy. The efficiency of the new defect-correction schemes is confirmed
by numerical experiments. A new original technigue for experimental studying of
convergence orders is developed for the cases where the orders of convergence in the
x-direction and in the t-direction can be substantially different.
Singular Function Mortar Finite Element Methods
Authors: Sarkis Marcus , Tu Xuemin 
Published: April 2013

AbstractWe consider the Poisson equation with Dirichlet boundary conditions on a polygonal domain with one reentrant corner. We introduce new nonconforming finite
element discretizations based on mortar techniques and singular functions. The main idea introduced in this paper is the replacement of cut-off functions by mortar element
techniques on the boundary of the domain. As advantages, the new discretizations do not require costly numerical integrations and have smaller a priori error estimates
and condition numbers. Based on such an approach, we prove optimal accuracy error bounds for the discrete solution. Based
on such techniques, we also derive new extraction formulas for the stress intensive factor. We establish optimal accuracy for the computed stress intensive factor.
Numerical examples are presented to support our theory.
Transformation of Chebyshev–Bernstein Polynomial Basis
Authors: Rababah Abedallah 
Published: April 2013

AbstractIn this paper, we derive a matrix of transformation of Chebyshev polynomials of the first kind into Bernstein polynomials and vice versa. We also study the stability of these
linear maps and show that the Chebyshev–Bernstein basis conversion is remarkably well-conditioned, allowing one to combine the superior least-squares performance of
Chebyshev polynomials with the geometrical insight of the Bernstein form. We also compare it to other basis transformations such as Bernstein-Hermite, power-Hermite,
and Bernstein–Legendre basis transformations.
Approximation Schemes for Singular Integrals and Their Application to Some Boundary Problems
Authors: Sanikidze Jemal , Mirianashvili Manana 
Published: April 2013

Abstract Certain schemes for approximate calculation of singular integrals with a
Cauchy kernel and their application to the numerical solution of the modified Dirichlet
problem are offered. Questions of justifying the corresponding computational schemes
for domains with Lyapunov boundaries are investigated.
On Modeling and Simulation of Different Regimes for Liquid Polymer Moulding
Authors: Čiegis Raimondas , Iliev Oleg , Rief Stefan , Steiner Konrad 
Published: April 2013

AbstractIn this paper we consider numerical algorithms for solving the system
of nonlinear PDEs, arising in modeling of liquid polymer injection. We investigate the
particular case where a porous preform is located within the mould, so that the liquid
polymer is flowing through a porous medium during the filling stage. The nonlinearity
of the governing system of PDEs is due to the non-Newtonian behavior of the polymer,
as well as to the moving free boundary. The latter is related to the penetration
front, and a Stefan type problem is formulated to take into account. A finite-volume
method is used to approximate the given differential problem. Results from numerical
experiments are presented.
We also solve an inverse problem and present algorithms for determination of the absolute preform permeability
coefficient for the case where the velocity of the penetration
front is known from the measurements.
In both considered cases (direct and inverse problems), we focus on the specificity
related to the non-Newtonian behavior of the polymer. For completeness, we also
discuss the Newtonian case. Results of some experimental measurements are presented
and discussed.
Symmetrizable Difference Dchemes
Authors: Gulin Alexei A. 
Published: April 2013

AbstractA review of the stability theory of symmetrizable time-dependent difference schemes is represented. The notion of the operator-difference scheme is introduced
and general ideas about stability in the sense of the initial data and in the sense of the right hand side are formulated. Further, the so-called symmetrizable difference
schemes are considered in detail for which we manage to formulate the unimprovable necessary and su±cient conditions of stability in the sense of the initial data. The
schemes with variable weight multipliers are a typical representative of symmetrizable difference schemes. For such schemes a numerical algorithm is proposed and realized
for constructing stability boundaries.
Stability of Implicit Difference Equations Generated by Parabolic Functional Differential Problems
Authors: Kropielnicka K. 
Published: April 2013

AbstractA general class of implicit difference methods for nonlinear parabolic
functional differential equations with initial boundary conditions of the Neumann type
is constructed. Convergence results are proved by means of consistency and stability
arguments. It is assumed that given functions satisfy nonlinear estimates of Perron type
with respect to functional variables. Differential equations with deviated variables and
differential integral problems can be obtained from a general model by specializing
given operators. The results are illustrated by numerical examples.
A Refined Mixed Finite Element Method for Stationary Navier—Stokes Equations with Mixed Boundary Conditions Using Lagrange Multipliers
Authors: Nicaise S. , Paquet L. ,   Rafilipojaona
Published: April 2013

Abstract This paper is concerned with a dual mixed formulation of the Navier —
Stokes system in a polygonal domain of the plane with mixed boundary conditions
and its numerical approximation. The Neumann boundary condition is imposed using
a Lagrange multiplier corresponding to the velocity field. Moreover, the strain tensor
and the antisymmetric gradient tensor (vorticity), quantities of practical interest, are
introduced as new unknowns. The problem is then approximated by a mixed finite element
method. Quasi-optimal error estimates are finally obtained using refined meshes
near singular corners.
Exact Difference Schemes for Multidimensional Heat Conduction Equations
Authors: Lapinska-Chrzczonowicz M. 
Published: April 2013

AbstractThe initial boundary-value problem for the two-dimensional quasi-linear heat conduction equation
is considered. A new difference scheme approximating the equation is constructed.
The main difference between the method proposed in the present paper and the other
difference schemes is that for the traveling wave solutions the constructed scheme is exact if
the grid steps satisfy certain conditions. The iteration method is used to solve
a nonlinear difference equation.
Fully and Semi-discrete Fourth-order Schemes for Hyperbolic Conservation Laws
Authors: Zahran Y.H. 
Published: April 2013

AbstractA new fourth order accurate centered finite difference scheme for the
solution of hyperbolic conservation laws is presented. A technique of making the fourth
order scheme TVD is presented. The resulting scheme can avoid spurious oscillations
and preserve fourth order accuracy in smooth parts. We discuss the extension of
the TVD scheme to the nonlinear scalar hyperbolic conservation laws. For nonlinear
systems, the TVD constraint is applied by solving shallow water equations. Then, we
propose to use this fourth order flux as a building block in spatially fifth order weighted
essentially non-oscillatory (WENO) schemes. The numerical solution is advanced in
time by the third order TVD Runge — Kutta method. The performance of the scheme
is assessed by solving test problems. The numerical results are presented and compared
to the exact solutions and other methods.
Efficient And Precise Computation Of Convolutions: Applying Fft To Heavy Tailed Distributions
Authors: SCHALLER P. , TEMNOV G. 
Published: April 2013

AbstractIn this paper we estimate and analyze the errors associated with the use of the discrete (fast) Fourier transformation for the numerical calculation of convo-lutions. We suggest and compare methods to reduce these errors without loosing the computational efficiency of the calculation scheme. A typical field of application of our findings is the calculation of aggregate loss distributions for, e.g., losses from insurance cases or operational risk losses in the finance industry.
Method of Lines Approximations to Cauchy Problems for Elliptic Equations in Two Dimensions
Authors: Charton M. , Reinhardt H.J. 
Published: April 2013

AbstractIn this paper, the method of lines approximation for a rather general
elliptic equation containing a diffusion coefficient is considered. Our main results are
the regularization of the ill-posed Cauchy problem and the proof of error estimates
leading to convergence results for the method of lines. These results are based on the
conditional stability of the continuous Cauchy problem and the approximation by appropriately
chosen finite-dimensional spaces, onto which the possibly perturbed Cauchy
data are projected. At the end of this paper, we present and discuss results of some of
our numerical computations. There are multiple applications in material sciences, thermodynamics,
medicine etc.; related problems are shape optimization problems which
are important, e.g. for nondestructive testing, crack location, thermal tomography,
and other applications.
Error Estimates on Arbitrary Grids for a 2nd-order Mimetic Discretization of Boundary-value Problems for Linear Odes
Authors: Zingano J.P. , Steinberg S.L. 
Published: April 2013

AbstractWe obtain sharp pointwise 2nd-order estimates for both solution and
derivative errors on arbitrary grids for a mimetic finite-difference approximation to
solutions of one-dimensional linear boundary-value problems with separated boundary
conditions. Although the scheme considered is formally inconsistent with the differential
equation, it turns out to possess nice convergence properties which make it a good
alternative to more standard, consistent discretizations of similar arithmetic complexity,
particularly with respect to derivative errors.
Multi-scale Method for the Crack Problem in Microstructural Materials
Authors: Hoppe R. H. W. , Petrova S.I. 
Published: April 2013

AbstractThe paper deals with the numerical computation of a crack problem
posed on microstructural heterogeneous materials containing multiple phases in the
microstructure. The failure of such materials is a natural multi-scale effect since cracks
typically nucleate in regions of defects on the microscopic scale. The modeling strategy
for solving the crack problem concerns simultaneously the macroscopic and microscopic
models. Our approach is based on an efficient combination of the homogenization technique
and the mesh superposition method (s-version of the finite element method). The
homogenized model relies on a double-scale asymptotic expansion of the displacement
field. The mesh superposition method uses two independent (global and local) finite
element meshes and the concept of superposing the local mesh arbitrarily on the global
continuous mesh. The crack is treated by the local mesh and the homogenized material
model is considered on the global mesh. Numerical experiments for problems on
biomorphic microcellular ceramic templates with porous microstructures of different
materials constituents are presented.
Potentialities of the Robust Multigrid Technique
Authors: Martynenko S.I. 
Published: April 2013

AbstractThe present paper discusses the parallelization of the robust multigrid
technique (RMT) and the possible way of applying this to unstructured grids. As opposed
to the classical multigrid methods, the RMT is a trivial method of parallelization
on coarse grids independent of the smoothing iterations. Estimates of the minimum
speed-up and parallelism efficiency are given. An almost perfect load balance is demonstrated
in a 3D illustrative test. To overcome the geometric nature of the technique, the
RMT is used as a preconditioner in solving PDEs on unstructured grids. The procedure
of auxiliary structured grids generation is considered in details.
On Positivity and Maximum-Norm Contractivity in Time Stepping Methods for Parabolic Equations
Authors: Schatz A.H. , Thomèe V. , Wahlbin L.B. 
Published: April 2013

Abstract
In an earlier paper the last two authors studied spatially semidiscrete
piecewise linear finite element approximations of the heat equation and showed that,
in the case of the standard Galerkin method, the solution operator of the initial-value
problem is neither positive nor contractive in the maximum-norm for small time, but
that for the lumped mass method these properties hold, if the triangulations are essentially
of Delaunay type. In this paper we continue the study by considering fully
discrete analogues obtained by discretization also in time. The above properties then
carry over to the backward Euler time stepping method, but for other methods the
results are more restrictive. We discuss in particular the θ-method and the (0; 2) Padé
approximation in one space dimension.
A numerical-analytic method for solving the Cauchy problem for ordinary differential equations
Authors: Makarov Volodymyr , Dragunov Denys 
Published: April 2013

AbstractA functional-discrete method for solving the Cauchy problem for first-order ordinary
differential equations (ODEs) is proposed. Generally speaking, this method (FD-method) is
similar to the Adomian Decomposition Method (ADM). However, we have shown that for some
problems the FD-method is convergent whereas the ADM is divergent. The results presented
in this paper can easily be generalized to the case of systems of ODEs.