bluuebunny/crossref_metadata_2025 huggingface dataset:
Esporte adaptado: abordagem sobre os fatores que influenciam a prática do esporte coletivo em cadeira de rodas
Authors: Silva Anselmo de Athayde Costa e , Marques Renato Francisco Rodrigues , Pena Luis Gustavo de Souza , Molchansky Sheila , Borges Mariane , Campos Luis Felipe Castelli Correia de , Araújo Paulo Ferreira de , Borin João Paulo , Gorla José Irineu
Published: April 2013

Este ensaio suscita uma discussão acerca da complexidade do esporte adaptado, diante da forma reducionista como o fenômeno tem sido definido ao longo do tempo. Entende-se que este é um construto complexo e, portanto, a abordagem para o seu entendimento deve ser de pensamento complexo. Foram discutidos os vários aspectos relacionados à prática do esporte pelas pessoas com deficiência e como os trabalhos devem ser conduzidos neste campo. Embora o esporte adaptado tenha efeitos positivos sobre variáveis como reabilitação e inclusão social, este não pode ser definido apenas com base nestas questões e sim como um fenômeno complexo e abrangente.
Analysis of the performance of under-sleeper pads in high-speed line transition zones
Authors: Insa Ricardo , Salvador Pablo , Inarejos Javier , Medina Luis
Published: April 2013

In many high-speed railway lines, the zones between embankments and structures may present some discontinuities, in terms of track geometry and track stiffness, which may create discomfort for passengers, induce deterioration of track and vehicle materials and even raise the risk of derailment to dangerous levels. In the attempt to attenuate the consequences of such problems, some solutions pointing at progressively changing the vertical stiffness in the railway track have been tested, such as transition zones or pads placed either between the rails and the sleepers or under the sleepers. The contribution of under-sleeper pads in transition regions and their effect on the railway infrastructure is specifically analysed in the present paper. The results obtained are of interest since they provide useful information for railway managers on infrastructure design and justify the need to implement such transition zones.
Serpentinite Carbonation for CO2 Sequestration
Authors: Power Ian M. , Wilson Sasha , Dipple Gregory M.
Published: April 2013

Serpentinites offer a highly reactive feedstock for carbonation reactions and the capacity to sequester carbon dioxide (CO2) on a global scale. CO2 can be sequestered in mined serpentinite using high-temperature carbonation reactors, by carbonating alkaline mine wastes, or by subsurface reaction through CO2 injection into serpentinite-hosted aquifers and serpentinized peridotites. Natural analogues to serpentinite carbonation, such as exhumed hydrothermal systems, alkaline travertines, and hydromagnesite–magnesite playas, provide insights into geochemical controls on carbonation rates that can guide industrial CO2 sequestration. The upscaling of existing technologies that accelerate serpentinite carbonation may prove sufficient for offsetting local industrial emissions, but global-scale implementation will require considerable incentives and further research and development.
Detection of Bypassed Pay Zones and Water Production Control of Sandstone Reservoirs Using TDT and CHFR Logs
Authors: Hamada G. M.
Published: April 2013

Reservoir saturation monitoring, through cased wells, usually is the main key factor for proper reservoir management and recovery optimization in the cases of developed and mature oil fields. Thermal decay time tool (TDT) has been the main technique used for monitoring the inter wells water saturations in developed reservoir. One of the main problems that encountered while using TDT log is the reservoirs with low formation water salinity, this problem may also appear in reservoirs that are supported by water injection projects, in which the formation water is diluted by the injected water. This problem has been solved by combining TDT technique and cased hole formation resistivity tool (CHFR).

The ability to detect and evaluate bypassed hydrocarbon and monitor fluid movement in sandstone reservoir is a vital question to improve production and increase recovery. It is difficult to interpret the TDT data in reservoirs with low-salinity sandstone formation water. This problem cannot be solved because TDT measurements depend on the salt content in formation brine. Instead the cased hole formation resistivity tool (CHFR) is proposed to overcome the limitations associated with pulsed-neutron tools. This paper presents case studies of pay zones-saturation monitoring obtained from TDT and CHFR logs recorded in wells in mature sandstone reservoir which suffers from high water cut. The results are referenced to open-hole resistivity logs to monitor the vertical movement of reservoir fluids. It was found that water saturations calculated from CHFR logs are more accurate than TDT log in most cases. Water shut-off remedial action to manage water production from producing sections in the studied wells has been much more successful based on CHFR / TDT logs than the proposed remedial action based only on TDT data interpretation.
Overcoming Challenges while Acidizing Sandstone Formation Successfully in the Gulf of Cambay, Offshore India
Authors: Stolyarov Sergey , Alam Anwar
Published: April 2013

In the early days of the oilfield, matrix acidizing was considered useful only for stimulating carbonate formations. However it has been known for many years that with proper job design, acid and additive choices, and in-depth study of potential formation damage sources, matrix acidizing can safely and successfully stimulate production in sandstone formations. By incorporating carefully designed tubing pickle, pre-flush, main acid system and post-flush (including optimum doses of corrosion inhibitors, mutual solvents, iron control agents, clay control additives, surfactants, etc.), matrix acidizing can provide excellent productivity improvements even in sandstone formations with complex mineralogy.

This paper describes a matrix acidizing campaign executed successfully in the Gulf of Cambay (Khambhat) on the west coast of India. In initial laboratory tests and during simulation runs, it was aimed to design a pre-flush, acid system and post-flush to best suit the challenging reservoir conditions while also considering offshore logistics. Further as the formation had iron-rich minerals like chlorite clay, siderite, etc., a chemically modified organic sandstone acid system was selected as opposed to conventional hydrofluoric acid system. Moreover a spacer system was designed and pumped to push any iron precipitation far away from the near-wellbore area and to clean the area for the organic acid system.

After pumping the system in one well, the system design, pumping procedures and volumes were modified to further improve results in the next well. Fines-stabilizing agents were introduced to avoid clay migration or swelling that may otherwise jeopardize a successful treatment. The paper will explain the basis for modifying the design and pumping procedure, based on lessons learned from the prior operation.
Case Study on Handling Paraffinic and Viscous Crude of Mangala Oil Field of Rajasthan-India
Authors: Zalawadia Hardik , Pawde Chaitanya
Published: April 2013

The Mangala oil field, discovered in 2004 is one of the largest onshore oilfields in India. The field is divided into five reservoir units and contains approximately 1.3 billion barrels of STOOIP. The field currently produces around 175,000 BOPD. The oil is highly viscous, with high paraffinic content, a high pour point, high Wax Appearance Temperature (WAT), as well as high wax dissolution temperature. In addition, high CO2 content, sand production and a high water cut are some of the other notable problems. Keeping this in mind, a combination of innovative technologies had been envisaged right from the development and appraisal stage of the field. The technologies used have been reviewed from a flow-assurance point of view and possible reasons for the selection of these techniques over other methods are also investigated and presented.

The waterfloods, EOR pilots, artificial lift systems as well as surface facilities have been designed and implemented keeping in mind the nature of the crude. From a flow assurance point of view, techniques such as hot water injection, coiled tubing heater string, jet pumps etc. have been used extensively. A 670 km long pipeline has been laid from the field to Bhogat in Gujarat for transporting the crude. This pipeline is the world's longest independent heated section pipeline and makes use of another innovation called Skin Effect Heat Management System (SEHMS). A careful examination of these techniques can help us gauge whether they can be put to use to handle similar crudes in other parts of the world.

This being a review paper, the working methodologies of flow assurance techniques used for the Mangala crude and the reasons for their success are studied.
Application of TRIZ Methodology in Research and Development of Oilfield Technologies
Authors: Dass Chanchal , Gandhi Kanan
Published: April 2013

A technological revolution is going on in almost every sphere of modern life which is being possible due to regular and systematic innovations. In spite of this fact, there are few areas where there is no innovation or improvement in the system. Multiple zone well completion technology is one of such area. Over 100 years back, professionals started to develop an effective and efficient multiple zone well completion technology. But the dream of producing multiple zones encountered in a well, simultaneously, without causing inter well cross flow, remained a distant reality. This has not only resulted in poor productivity per well but has also created a bottleneck in the application of advanced technologies for secondary and tertiary recovery methods. Author has developed a technology for the production of all oil and gas bearing zones encountered in a well through a single completion without allowing any inter layer cross flow. Author is extensively using TRIZ methodologies and highly benefitted with the application of TRIZ-a systematic approach for solving problems which was developed in Russia during 1946. In multiple tubing, simultaneous and segregated production is possible but the total system becomes complex. In commingle production, system is simple but interlayer cross flow is a problem. Moving from conventional to unconventional thinking, a hybrid completion system has been developed which retains the advantages of multiple tubing completions and commingle production and eliminating the disadvantages of both the systems. In this paper author has tried to explain how TRIZ methodologies have helped him to develop an effective multiple zone well completion technology which will help other petroleum engineers to develop different innovative oilfield technologies using advanced innovative inventive tool like TRIZ.
A New Strategy to Explore Tight Oil/Gas Reservoirs "Fit for Purpose Acid Fracturing"
Authors: Hegazy G. M. , Salem Adel M. , Shedid Shedid A. , Shalaby Shouhdi E. , Abbott J..
Published: April 2013

Oil and gas exploration in carbonate reservoirs typically utilize conventional techniques in perforation, matrix acidizing stimulation and well testing. Currently, oil companies have moved to more marginal reservoir targets. Application of these techniques has often yielded disappointing results and tighter zones are often abandoned for more promising target intervals.

With increases in oil and gas production targets, operators are being forced to investigate more marginal reservoir layers for reserves and production potential. The real challenge facing oil industry today is that successful exploration requires a change in drilling, completion and stimulation techniques currently utilized by operators.

Marginal reservoirs can have lots of resource potential and reserves, but may require horizontal well drilling, and/or multiple stage hydraulic fracturing to achieve economic production targets. This type of strategy is more expensive than conventional method(s) and is proven in some circles as potentially risky and many of these risks must be addressed and mitigated. In an effort to reduce risks and costs associated with the exploration process, a new stimulation strategy has been adopted for tight intervals to explore and appraise these intervals using vertical wells prior to going to horizontal wells.

This paper presents and analyzes oil exploration well case study in which a new strategy has been applied and evaluated. The study also demonstrates that this approach can lead to new resource discoveries, better reservoir understanding and improved well and completion design for future appraisal wells. Moreover, the paper highlights some of the additional challenges that this strategy may evoke and shows how these challenges may be overcome in the future.
Numerical Analysis of Influence of the Mold Material on the Distribution of Shrinkage Cavities
Authors: Dyja R.
Published: April 2013

Production of castings, like any other field of technology is aimed at providing high-quality product, free from defects. One of the main causes of defects in castings is the phenomenon of shrinkage of the casting. This phenomenon causes the formation of shrinkage cavities and porosity in the casting. The major preventive measure is supplementing a shortage of liquid metal. For supplement to be effective, it is necessary to use risers in proper shapes. Usually, the risers are selected on the basis of determination the place of formation of hot-spots in the castings. Although in these places the shrinkage defects are most likely to occur, shape and size of these defects are also affected by other factors. The article describes the original program setting out the shape and location of possible cavities in the casting. In the program is also taken into account the effect of temperature on the change in volume of liquid metal and the resultant differences in the shape and size of formed shrinkage cavities. The aim of the article is to describe the influence that have material properties of the mold on the simulation results.
Problem of the Moving Boundary in Continuous Casting Solved by The Analytic-Numerical Method
Authors: Grzymkowski R. , Hetmaniok E. , Pleszczyński M.
Published: April 2013

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

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

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

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.
Evaluation of Quantitative and Qualitative Traits of Wild Ecotypes of Forage Grasses
Authors: Kizeková Miriam , Martincová Janka , Jančová Ľubica
Published: April 2013

Wild ecotypes of Festuca rubra L. (four accessions), Poa pratensis L. (three accessions ) and Phleum pratense L. (three accessions) originating from Central Slovakia were investigated. Dry matter production, qualitative traits as well as mineral content were studied under identical soilclimatic conditions in a three-cut system. Yield potential of wild ecotypes of Festuca rubra L. coming from mountain regions was significantly lower (P < 0.01) when compared to Festuca rubra L. cultivar Levočská. In contrast, as a consequence of low variability, the dry matter yield of Phleum pratense L. wild ecotypes originating from higher altitudes was comparable to the dry matter yields of Festuca rubra L. cultivar Levočská. There were not noted any considerable differences found in the content of crude protein, fibre or mineral substances between the wild ecotypes and the cultivars. All accessions showed consistent patterns in seasonal distribution with the highest dry matter yield at the first cut and with the lowest one at the third cut. In general, concentration of crude protein and fibre did not vary considerably among cultivars and wild ecotypes at all species under uniform growing conditions.
Attainability analysis in the problem of stochastic equilibria synthesis for nonlinear discrete systems
Authors: Bashkirtseva Irina , Ryashko Lev
Published: April 2013

A nonlinear discrete-time control system forced by stochastic disturbances is considered. We study the problem of synthesis of the regulator which stabilizes an equilibrium of the deterministic system and provides required scattering of random states near this equilibrium for the corresponding stochastic system. Our approach is based on the stochastic sensitivity functions technique. The necessary and important part of the examined control problem is an analysis of attainability. For 2D systems, a detailed investigation of attainability domains is given. A parametrical description of the attainability domains for various types of control inputs in a stochastic Henon model is presented. Application of this technique for suppression of noise-induced chaos is demonstrated.
Scheduling problems with a common due window assignment: A survey
Authors: Janiak Adam , Kwiatkowski Tomasz , Lichtenstein Maciej
Published: April 2013

In this article a survey of studies on scheduling problems with a common due window assignment and earliness/tardiness penalty functions is presented. A due window is a generalization of the classical due date and describes a time interval in which a job should be finished. If a job is completed before or after the due window, it incurs an earliness or a tardiness penalty, respectively. In this survey we separately analyse the classical models with job-independent and job-dependent earliness/tardiness penalty functions and some other more complicated models. We describe the computational complexity of the problems and the main features of the approaches developed to solve them. Particular attention is paid to practical applications of the analysed models. As turns out, some complicated models combining classical scheduling problems with, e.g., learning and aging effects have no reasonable practical justification in the literature.
Determinants of Perceived Effectiveness of Organic Fertilizer Used by Farmers in Oyo State, Nigeria
Authors: Oluwasegun Fasina Oluwatosin
Published: April 2013

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

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

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

The 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

We 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

In 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

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

In 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.
Global and Asymptotic Stability of Operator-Difference Schemes
Authors: Jovanović Boško S
Published: April 2013

The stability of linear two- and three-level operator difference schemes
in a Hilbert space has been investigated. A few a priori estimates of the global and
asymptotic stability in various energy norms have been obtained.
Symmetrizable Difference Dchemes
Authors: Gulin Alexei A.
Published: April 2013

A 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.
Splitting of the +' Space into a Union of Banach Spaces through Laguerre Expansions
Authors: Stojanović M.
Published: April 2013

We split the space of tempered distributions into a union of Banach
spaces with respect to the scale of spaces, which allows us to give the approximation of the generalization of function therein.
Stability of Implicit Difference Equations Generated by Parabolic Functional Differential Problems
Authors: Kropielnicka K.
Published: April 2013

A 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

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

The 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

A 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

In 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

In 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

We 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

The 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

The 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.
A Regularizing Parameter for Some Fredholm Integral Equations
Authors: Fermo L.
Published: April 2013

The regularizing parameter appearing in some Fredholm integral equations
of the second kind is discussed. Theoretical estimates and the results of numerical
tests confirming the theoretical expectations are given.
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

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

A 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.
Experiments On Additive Desulphurisation By Sodium Bicarbonate In Coal-Fuel Boilers
Authors: Kolat Pavel , Čech Bohumír , Vrtek Mojmír , Tomášek David
Published: April 2013

This paper describes experiments on the application of sodium bicarbonate desulphurisation in the coal-fuel boiler. The boiler has been in operation for several years now and it has refiably fulfilled the original assignment to reduce SO2 emissions from the value of 1200 - 1500 mg/Nm3 to 400 mg/Nm3. Higher desulphurisation efficiency is determined only by the ratio of Na/S sorbent dosage. The resulting product of desulphurisation is stored together with fly ash in underground mines, and has no influence on the groundwater. Positive experience of the tests and boiler operation lies in higher reactivity of sodium and sulphur as compared with conventional methods based on limestone. Within the scope of the secondary measures of elimination of sulphur oxides in combustion products, an experimental dry-method desulphurisation of combustion products was performed by blasting an agent containing sodium bicarbonate NaHCO3 (99.6 %) into the flue ways before the electrostatic precipitator in a coal-fuel furnace with the steam output of 220 t/h.
Optimisation of Operating Conditions in Fed-Batch Baker’s Yeast Fermentation
Authors: Atasoy Ilknur , Yuceer Mehmet , Berber Ridvan
Published: April 2013

Saccharamyces cerevisia known as baker’s yeast is a product used in various food industries. Worldwide economic competition makes it a necessity that industrial processes be operated in optimum conditions, thus maximisation of biomass in production of saccharamyces cerevisia in fedbatch reactors has gained importance. The facts that the dynamic fermentation model must be considered as a constraint in the optimisation problem, and dynamics involved are complicated, make optimisation of fed-batch processes more difficult. In this work, the amount of biomass in the production of baker’s yeast in fed-batch fermenters was intended to be maximised while minimising unwanted alcohol formation, by regulating substrate and air feed rates. This multiobjective problem has been tackled earlier only from the point of view of finding optimum substrate rate, but no account of air feed rate profiles has been provided. Control vector parameterisation approach was applied the original dynamic optimisation problem which was converted into a NLP problem. Then SQP was used for solving the dynamic optimisation problem. The results demonstrate that optimum substrate and air feeding profiles can be obtained by the proposed optimisation algorithm to achieve the two conflicting goals of maximising biomass and minimising alcohol formation.
Temporal Activity in Particular Segments and Transitions in The Olympic Triathlon
Authors: Cejuela Roberto , Cala Antonio , Pérez-Turpin José A. , Villa José G. , Cortell Juan M. , Chinchilla Juan J.
Published: April 2013

The Olympic Triathlon is a combined endurance sport. It includes back-to-back swimming, cycling, running and the transition between events (T1 & T2). The aim of the current study was to analyse the possible relationship between the Lost Time T1 & T2 and overall performance. The results showed that the percentages of total time corresponding to each part of the race were: 16.2% for swimming, 0.74% for the swimming-cycling transition (T1), 53.07% for cycling, 0.47% for the cycling-running transition (T2) and 29.5% for running. The correlations between each part of the race and the final placing were: r=0.36 for swimming, r=0.25 for T1, r=0.62 for the cycling, r=0.33 for T2, and r=0.83 for the running. Also, values of r=0.34 & r=0.43 were obtained for Lost Time T1 and Lost Time T2, respectively. In conclusion, losing less time during T2 has been demonstrated to be related to obtaining a better final result.
Ligand-Binding Activity and Immunoreactivity of Insulin-Like growth Factor Binding Proteins in Patients with Colorectal Carcinoma And Postoperative Sepsis
Authors: Nedić Olgica , Malenković Vesna , Đukancvić Blagoje , Baričević Ivona
Published: April 2013

Background: Postoperative sepsis alters the growth hormone (GH)/insulin-like growth factor (IGF) axis leading to reduction in IGF-I and IGF-binding protein (IGFBP) 3 and elevation of GH-independent IGFBPs. The aim of this work was to investigate the differences in ligand binding and immunoreactivity of the circulating IGFBPs between surviving and nonsurviving septic patients that underwent colorectal surgery.

Methods: Ligand binding was detected only for IGFBP-3 and IGFBP-2 and, consecutively, immunoreactivity was assayed for these IGFBPs.

Results: In survivors both ligand- and immunoblotting re - vea led two IGFBP-3 isoforms (40 and 45 kDa). In non-survivors ligand-blotting hardly detected the IGFBP-3 doublet, intact immunoreactive IGFBP-3 was not detected and the major species was the 29 kDa fragment. Immunoblotting with an anti-IGFBP-2 antibody indicated an increase in the amount of intact and fragmented IGFBP-2 along the progression of illness in the non-survivors. The amount of intact IGFBP-2 in the survivors did not differ during the treatment. The amount of immunoreactive IGFBP-2 corresponded to its ligand-binding activity.

Conclusions: According to the results reported here, ligandreactivity and immunoreactivity of IGFBP-3 should be taken into account as variables that affect the GH/IGF axis in critically ill patients. The degree of their variation is not directly correlated to the total amount of IGFBP-3 determined by the immunoassay, but they may be related to patients’ meta bolic potential to combat a disease.