bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Glutathione Depletion on Nrf2/ARE Activation by Deltamethrin in PC12 Cells
Authors: Li Huangyuan , Wu Siying , Chen Junnian , Wang Bo , Shi Nian
Published: April 2013

Transcription factor NF-E2-related factor 2 (Nrf2) is important for cell protection against chemical-induced oxidative stress. Previously, we have reported that in PC12 cells, Nrf2 can be triggered by deltamethrin (DM), a commonly used pyrethroid insecticide. Molecular mechanisms behind Nrf2 activation by DM are still unclear. Here we studied the effects of cell glutathione (GSH) depletion on Nrf2 activation by DM. We found that DM enhanced Nrf2 expression at the mRNA and protein levels and increased nuclear Nrf2 levels. Activation of Nrf2 was associated with activation of its downstream targets, such as heme oxygenase-1 (HO-1) and glutamate cysteine ligase catalytic subunit (GCLC). In contrast, DL-buthionine-[S,R]- sulfoximine (BSO), a known GSH-depleting agent, did not increase Nrf2 protein expression or cause its nuclear accumulation. However, pre-treatment with BSO triggered mRNA expression of HO-1 and GCLC. Furthermore, BSO pre-treatment suppressed DM-induced Nrf2 upregulation and activation and lowered mRNA expression of HO-1 and GCLC upon DM treatment. These data demonstrate that GSH depletion is not necessary for the activation of Nrf2/ARE by DM in PC12 cells, and that GCLC and HO-1 expression can increase through other signalling pathways.
Thin Wall Ductile Iron Castings: Technological Aspects
Authors: Fraś E. , Górny M. , Kapturkiewicz W.
Published: April 2013

The paper discusses the reasons for the current trend of substituting ductile iron castings by aluminum alloys castings. However, it has been shown that ductile iron is superior to aluminum alloys in many applications. In particular it has been demonstrated that is possible to produce thin wall wheel rim made of ductile iron without the development of chills, cold laps or misruns. In addition it has been shown that thin wall wheel rim made of ductile iron can have the same weight, and better mechanical properties, than their substitutes made of aluminum alloys.
Application of Averaged Voronoi Polyhedron in the Modelling of Crystallisation of Eutectic Nodular Graphite Cast Iron
Authors: Burbelko A.A. , Początek J. , Królikowski M.
Published: April 2013

The study presents a mathematical model of the crystallisation of nodular graphite cast iron. The proposed model is based on micro- and macromodels, in which heat flow is analysed at the macro level, while micro level is used for modelling of the diffusion of elements. The use of elementary diffusion field in the shape of an averaged Voronoi polyhedron [AVP] was proposed. To determine the geometry of the averaged Voronoi polyhedron, Kolmogorov statistical theory of crystallisation was applied. The principles of a differential mathematical formulation of this problem were discussed. Application of AVP geometry allows taking into account the reduced volume fraction of the peripheral areas of equiaxial grains by random contacts between adjacent grains. As a result of the simulation, the cooling curves were plotted, and the movement of "graphite-austenite" and "austenite-liquid” phase boundaries was examined. Data on the microsegregation of carbon in the cross-section of an austenite layer in eutectic grains were obtained. Calculations were performed for different particle densities and different wall thicknesses. The calculation results were compared with experimental data.
The oldest Cambrian trilobites from the Holy Cross Mountains, Poland: taxonomic, stratigraphic and biogeographic reappraisal
Authors: Żylińska Anna
Published: April 2013

Żylińska, A. 2013. The oldest Cambrian trilobites from the Holy Cross Mountains, Poland: taxonomic, stratigraphic and biogeographic reappraisal. Acta Geologica Polonica, 63 (1), 57-87. Warszawa. Authorship issues are clarified, new photographic documentation is provided and emended systematic descriptions are presented for the oldest Cambrian trilobite taxa from the Holy Cross Mountains (Poland). Biostratigraphic analysis of the fauna allows correlation with the traditional Holmia kjerulfi-group Zone of Scandinavia, the Callavia Zone of Britain and Newfoundland, the lower and middle part of the Sectigena Zone of Morocco and the Marianian Stage of Spain. The trilobites display a strong biogeographic signal linked with West Gondwana and Avalonia and a suggestion is made that the TESZ margin of Baltica with the Małopolska Massif was liable to currents from those areas that distributed planktonic trilobite larvae.
Linear adaptive structure for control of a nonlinear MIMO dynamic plant
Authors: Bańka Stanisław , Dworak Paweł , Jaroszewski Krzysztof
Published: April 2013

In the paper an adaptive linear control system structure with modal controllers for a MIMO nonlinear dynamic process is presented and various methods for synthesis of those controllers are analyzed. The problems under study are exemplified by the synthesis of a position and yaw angle control system for a drillship described by a 3DOF nonlinear mathematical model of low-frequency motions made by the drillship over the drilling point. In the proposed control system, use is made of a set of (stable) linear modal controllers that create a linear adaptive controller with variable parameters tuned appropriately to operation conditions chosen on the basis of two measured auxiliary signals. These are the ship’s current forward speed measured in reference to the water and the systematically calculated difference between the course angle and the sea current (yaw angle). The system synthesis is carried out by means of four different methods for system pole placement after having linearized the model of low-frequency motions made by the vessel at its nominal “operating points” in steady states that are dependent on the specified yaw angle and the sea current velocity. The final part of the paper includes simulation results of system operation with an adaptive controller of (stepwise) varying parameters along with conclusions and final remarks.
Energy Balance of Hemp (Cannabis sativa L.) Grown for Energy Purposes
Authors: Kolarikova Michel , Havrland Bohumil , Ivanova Tatiana
Published: April 2013

This article discusses the energy balance of the hemp biomass from the autumn and spring harvest which was used for the production of briquettes. The hemp plant (Cannabis sativa L.) used in this work is the variety Bialobrzeskie that was harvested on a trial plot in Prague-Suchdol in 2009 - 2010. Moisture content (MC), gross calorific value (GCV) and other technical parameters were evaluated for samples from the harvest of both periods. The autumn harvest results led to the assumption that the gross energy yield of the culture per superficies was 186.3 GJ ha-1. As compared to the previous results the spring harvest gave a gross energetic output of 161.4 GJ ha-1. The autumn harvest required more energy inputs compared to the spring harvest with values of 22.2 GJ ha-1 and 16.9 GJ ha-1 respectively. The most energy-consuming aspects of the biomass production were fuels (autumn) and the energy linked to the chemicals used (spring). Regardless of the higher net energy yield in autumn it was found that a spring harvest should be preferred because of its Energy Return on Energy Invested (EROEI) is 8.6. This is higher than for the autumn harvest (7.4).
Response of Poultry Agribusiness Risk to Financial Fragility and Macroeconomic Shocks in Nigeria (2004-2009)
Authors: Odemero Achoja Felix , Okereke Chukwuji Christopher
Published: April 2013

Financial Fragility and Macroeconomic shocks make poultry agribusiness vulnerable to risk (unsteady profit). This tends to dampen investment drive and inhabits aggregate growth in the poultry sub-sector in Nigeria. To address this problem, time series data of 6 years (2004-2009) were collected from 200 randomly selected poultry farms. Multiple regression and t-test were used to analyse the collected data. T-test of return on investment shows that poultry agribusiness has low financial fragility and could be resilient enough to withstand macro-economic shocks. Co-integration results indicate that poultry agribusiness risks moves together with inflation rate, interest rates and real exchange rate. According to the results of vector autoregressive (VAR) test, it is shown that poultry agri-business risk is sensitive to macroeconomic shocks. But with sound financial structure, poultry agribusiness will be able to withstand financial fragility. The impacts-response analysis shows that increase in macroeconomic distortions leads to increase in poultry agribusiness risk in Nigeria. The results of study provided information on how macro economic shocks and fragile financial structure can trigger risk in poultry agribusiness sector. This information is very crucial to effective policy making and economic planning that will bring development to the poultry sector and the Nigerian economy. Factor analysis confirmed that inflation rate (0.0039) and interest rates (0.1218) are the significant distortion factors (P < 0.01) that exert more impact on poultry agribusiness risk. Regulated interest and inflation rates would stabilize earnings and lead to growth in poultry agribusiness in Nigeria.
Clinical Impact of Proximal Autosomal Imbalances
Authors: Hamid A.B. , Weise A. , Voigt M. , Bucksch M. , Kosyakova N. , Liehr T. , Klein E.
Published: April 2013

Centromere-near gain of copy number can be induced by intra- or inter-chromosomal rearrangements or by the presence of a small supernumerary marker chromosome (sSMC). Interestingly, partial trisomy to hexasomy of euchromatic material may be present in clinically healthy or affected individuals, depending on origin and size of chromosomal material involved. Here we report the known minimal sizes of all centromere-near, i.e., proximal auto-somal regions in humans, which are tolerated; over 100 Mb of coding DNA are comprised in these regions. Additionally, we have summarized the typical symptoms for nine proximal autosomal regions including genes obviously sensitive to copy numbers. Overall, studying the carriers of specific chromosomal imbalances using genomics-based medicine, combined with single cell analysis can provide the genotype-phenotype correlations and can also give hints where copy-numbersensitive genes are located in the human genome.
Chromosomal Polymorphisms Involved in Reproductive Failure in the Romanian Population
Authors: Mierla D. , Stoian V.
Published: April 2013

Cytogenetic heteromorphisms are described as variations at specific chromosomal regions with no impact on phenotype. The purpose of this study was to investigate the effects of these chromosomal polymorphisms involved in reproductive failure in the Romanian population.

One thousand eight hundred and nine infertile patients, who were referred to Life Memorial Hospital, Bucharest, Romania, between January 2008 and April 2011, were investigated in this retrospective study. The frequency of chromosomal polymorphic variations was calculated for these patients. The control group is represented by 1116 fetuses investigated by amniocentesis between January 2009 and April 2011.

In this study 122 (6.74%) infertile patients and 63 fetuses (5.65%) showed chromosomal polymorphic variations. The differences between the two groups was not statistically significant (p <0.242) but there was statistical significance for some specific chromosomal polymor- phisms [inv(9),1qh+, 9qh+, fra(17)].

Some chromosomal polymorphic variations appear to be associated with reproductive failure. The statistically significantly higher incidence of heterochromatic variations found in infertile individuals emphasizes the need to assess their role in infertility and subfertility.
Ring Autosomes: Some Unexpected Findings
Authors: Caba L. , Rusu C. , Plăiaşu V. , Gug G. , Grămescu M. , Bujoran C. , Ochiană D. , Voloşciuc M. , Popescu R. , Braha E. , Pânzaru M. , Butnariu L. , Sireteanu A. , Covic M. , Gorduza E.V.
Published: April 2013

Ring chromosomes are rare entities, usually associated with phenotypic abnormalities in correlation with the loss of genetic material. There are various breakpoints and sometimes there is a dynamic mosaicism that is reflected in clinical features. Most of the ring chromosomes are de novo occurrences. Our study reflects the experience of three Romanian cytogenetic laboratories in the field of ring chromosomes. We present six cases with ring chromosomes involving chromosomes 5, 13, 18, and 21. All ring chromosomes were identified after birth in children with plurimalformative syndromes. The ring chromosome was present in mosaic form in three cases, and this feature reflects the ring’s instability. In case of ring chromosome 5, we report a possible association with oculo-auriculo-vertebral spectrum.
Mitochondrial DNA Mutations in two Bulgarian Children with Autistic Spectrum Disorders
Authors: Avdjieva-Tzavella D. , Mihailova S. , Lukanov C. , Naumova E. , Simeonov E. , Tincheva R. , Toncheva D.
Published: April 2013

Autism is a neurodevelopmental disorder of unknown origin that manifests in early childhood. Autism spectrum disorders (ASDs) refer to a broader group of neurobiological conditions, pervasive developmental disorders. Despite several arguments for a strong genetic contribution, the molecular basis in most cases remains unexplained. Several studies have reported an association between ASDs and mutations in the mitochondrial DNA (mtDNA) molecule. In order to confirm these causative relationship, we screened 21 individuals with idiopathic ASDs for a number of the most common mtDNA mutations. We identified two patients with candidate mutations: m.6852G>A that produces an amino acid change of glycine to serine in the MT-CO1 gene and m.8033A>G (Ile→Val) in the MT-CO2 gene. Overall, these findings support the notion that mitochondrial mutations are associated with ASDs. Additional studies are needed to further define the role of mitochondrial defects in the pathogenesis of autism.
Human Leukocyte Antigen-B27 and Disease Susceptibility in Vojvodina, Serbia
Authors: Vojvodić S. , Ademović-Sazdanić D. , Busarčević I.
Published: April 2013

There are numerous studies showing the role of human leukocyte antigens (HLAs) related with susceptibility or resistance to certain diseases. The aim of this study was to determine the association of HLA-B27 with ankylosing spondylitis (AS), polyarthralgia, lumboishialgia, acute anterior uveitis (AAU), psoriatic arthritis (PA), synovitis coxae and rheumatoid arthritis (RA) in patients from Vojvodina, Serbia. An HLA I class typing was performed by the serological immunomagnetic two-color fluorescence method using peripheral blood T lymphocytes in 97 patients and 224 healthy controls from the population of Vojvodina, Serbia.We calculated HLA-B27 frequencies, relative risk (RR), ethiologic fraction (EF), e.g., population attributive risk, when RR was greater than 1, while, preventive fraction (PF) was calculated when RR was lower than 1. This study revealed the strongest association of AS with HLAB27 antigen: RR = 25.0, while the EF was greater than 0.15, respectively. The χ2 test showed the significant difference (p <0.05) in HLA-B27 in patients with AS in comparison to controls (χ2 = 52.5). It was concluded that there is a positive association of HLA-B27 with AS and that HLA-B27 can serve as a marker for predisposition to diseases.
Learning to Generalize from Demonstrations
Authors: Browne Katie , Nicolescu Monica
Published: April 2013

Learning by demonstration is a natural approach that can be used to build a robot’s task repertoire. In this paper we propose an algorithm that enables a learner to generalize a task representation from a small number of demonstrations of the same task. The algorithm can generalize a wide range of situations that typically occur in daily tasks. The paper also describes the supporting representation that we use in order to encode the generalized representation. The approach is validated with experimental results on a broad range of generalizations.
New Applications of “Ontology-to-Text Relation” Strategy for Bulgarian Language
Authors: Staykova Kamenka , Osenova Petya , Simov Kiril
Published: April 2013

The paper presents new applications of the Ontology-to-Text Relation Strategy to Bulgarian Iconographic Domain. First the strategy itself is discussed within the triple ontology-terminological lexicon-annotation grammars, then - the related works. Also, the specifics of the semantic annotation and evaluation over iconographic data are presented. A family of domain ontologies over the iconographic domain are created and used. The evaluation against a gold standard shows that this strategy is good enough for more precise, but shallow results, and can be supported further by deep parsing techniques.
Image Processing for Technological Diagnostics of Metallurgical Facilities
Authors: Doukovska Lyubka , Petkov Venko , Mihailov Emil , Vassileva Svetla
Published: April 2013

The paper presents an overview of the image-processing techniques. The set of basic theoretical instruments includes methods of mathematical analysis, linear algebra, probability theory and mathematical statistics, theory of digital processing of one-dimensional and multidimensional signals, wavelet-transforms and theory of information. This paper describes a methodology that aims to detect and diagnose faults, using thermographs approaches for the digital image processing technique.
Escape-on-Sight: An Efficient and Scalable Mechanism for Escaping DDoS Attacks in Cloud Computing Environment
Authors: Jeyanthi N. , Iyengar N. Ch. S. N.
Published: April 2013

Availability is one of the primary security issues in Cloud computing environment. The existing solutions that address the availability related issues can be applied in cloud computing environment, but because of their unique characteristics, such as on-demand self service, rapid elasticity, etc., there is a need to develop a detection mechanism that must satisfy the characteristics and an optimal profit for the Cloud Service Provider (CSP). A solution named Escape-on- Sight (EoS) algorithm is proposed in this paper that helps in detecting the attacker’s characteristics by analyzing traffic conditions stage by stage and protects the Data Center (DC) from malicious traffic. The profit analysis shows that the proposed approach has a reasonable chance of deploying EoS mechanism at DCs that are prone to DDoS attacks.
Shadow Detection and Removal from a Single Image Using LAB Color Space
Authors: Murali Saritha , Govindan V. K.
Published: April 2013

A shadow appears on an area when the light from a source cannot reach the area due to obstruction by an object. The shadows are sometimes helpful for providing useful information about objects. However, they cause problems in computer vision applications, such as segmentation, object detection and object counting. Thus shadow detection and removal is a pre-processing task in many computer vision applications. This paper proposes a simple method to detect and remove shadows from a single RGB image. A shadow detection method is selected on the basis of the mean value of RGB image in A and B planes of LAB equivalent of the image. The shadow removal is done by multiplying the shadow region by a constant. Shadow edge correction is done to reduce the errors due to diffusion in the shadow boundary.
Solution of Time-dependent Advection-Diffusion Problems with the Sparse-grid Combination Technique and a Rosenbrock Solver
Authors: Lastdrager Boris , Koren Barry , Verwer Jan
Published: April 2013

In the current paper the efficiency of the sparse-grid combination tech-
nique applied to time-dependent advection-diffusion problems is investigated. For the
time-integration we employ a third-order Rosenbrock scheme implemented with adap-
tive step-size control and approximate matrix factorization. Two model problems are
considered, a scalar 2D linear, constant-coe±cient problem and a system of 2D non-
linear Burgers' equations. In short, the combination technique proved more efficient
than a single grid approach for the simpler linear problem. For the Burgers' equations
this gain in efficiency was only observed if one of the two solution components was set
to zero, which makes the problem more grid-aligned.
Three-Level Difference Schemes on Non-Uniform in Time Grids
Authors: Matus Piotr , Zyuzina Elena
Published: April 2013

In this work, a stability of three-level operator-difference schemes on
nonuniform in time grids in Hilbert spaces is studied. A priori estimates of a long
time stability (for t → ∞) in the sense of the initial data and the right-hand side
are obtained in different energy norms without demanding the quasiuniformity of the
grid. New difference schemes of the second order of local approximation on nonuniform
grids both in time and space on standard stencils for parabolic and wave equations are
adduced.
Approximation of Singularly Perturbed Parabolic Reaction-Diffusion Equations with Nonsmooth Data
Authors: Shishkin Grigorii
Published: April 2013

In this paper we consider the Dirichlet problem on a rectangle for
singularly perturbed parabolic equations of reaction-diffusion type. The reduced (for
ε = 0) equation is an ordinary differential equation with respect to the time variable;
the singular perturbation parameter ε may take arbitrary values from the half-interval
(0,1]. Assume that sufficiently weak conditions are imposed upon the coefficients and
the right-hand side of the equation, and also the boundary function. More precisely,
the data satisfy the Hölder continuity condition with a small exponent α and α/2 with
respect to the space and time variables. To solve the problem, we use the known
ε-uniform numerical method which was developed previously for
problems with sufficiently smooth and compatible data. It is shown that the numerical
solution converges ε-uniformly. We discuss also the behavior of local accuracy of the scheme in
the case where the data of the boundary-value problem are smoother on a part of the
domain of definition.
Exponentially Convergent Parallel Discretization Methods for the First Order Evolution Equations
Authors: Gavrilyuk Ivan , Makarov Vladimir L.
Published: April 2013

We propose a new discretization of an initial value problem for differen-
tial equations of the first order in a Banach space with a strongly P-positive operator
coefficient. Using the strong positiveness, we represent the solution as a Dunford-
Cauchy integral along a parabola in the right half of the complex plane, then transform
it into real integrals over (−∞,∞), and finally apply an exponentially convergent Sinc
quadrature formula to this integral. The integrand values are the solutions of a finite
set of elliptic problems with complex coefficients, which are independent and may be
solved in parallel.
A High-Order Difference Scheme for a Nonlocal Boundary-Value Problem for the Heat Equation
Authors: Sun Zhi-Zhong
Published: April 2013

This paper is concerned with a high order difference scheme for a non-
local boundary-value problem of parabolic equation. The integrals in the boundary
equations are approximated by the composite Simpson rule. The unconditional solv-
ability and L_∞ convergence of the difference scheme is proved by the energy method.
The convergence rate of the difference scheme is second order in time and fourth order
in space. Some numerical examples are provided to illustrate the convergence.
Iterative Methods for Solving Convection-diffusion Problem
Authors: Vabishchevich Petr N.
Published: April 2013

To obtain an approximate solution of the steady-state convectiondiffusion
problem, it is necessary to solve the corresponding system of linear algebraic
equations. The basic peculiarity of these LA systems is connected with the fact that
they have non-symmetric matrices. We discuss the questions of approximate solution
of 2D convection-diffusion problems on the basis of two- and three-level iterative methods.
The general theory of iterative methods of solving grid equations is used to present
the material of the paper. The basic problems of constructing grid approximations for
steady-state convection-diffusion problems are considered. We start with the consideration
of the Dirichlet problem for the differential equation with a convective term in
the divergent, nondivergent, and skew-symmetric forms. Next, the corresponding grid
problems are constructed. And, finally, iterative methods are used to solve approximately
the above grid problems. Primary consideration is given to the study of the
dependence of the number of iteration on the Peclet number, which is the ratio of the
convective transport to the diffusive one.
Convergence of Finite Fifference Method for Parabolic Problem
Authors: Bojović Dejan
Published: April 2013

In this paper we consider the first initial boundary-value problem for the
heat equation with variable coefficients in a domain (0; 1)x(0; 1)x(0; T]. We assume that the
solution of the problem and the coefficients of the equation belong to the corresponding
anisotropic Sobolev spaces. Convergence rate estimate which is consistent with the
smoothness of the data is obtained.
A Schwarz Preconditioner for a Hybridized Mixed Method
Authors: Gopalakrishnan Jayadeep
Published: April 2013

In this paper, we provide a Schwarz preconditioner for the hybridized versions of the Raviart-Thomas and Brezzi-Douglas-Marini mixed methods. The preconditioner
is for the linear equation for Lagrange multipliers arrived at by eliminating the flux as well as the primal variable. We also prove a condition number estimate
for this equation when no preconditioner is used. Although preconditioners for the lowest-order case of the Raviart-Thomas method have been constructed previously by
exploiting its connection with a nonconforming method, our approach is different in that we use a new variational characterization of the Lagrange multiplier equation.
This allows us to precondition even the higher-order cases of these methods.
On the Rate of Convergence of Difference Schemes for the Poisson Equation with Dynamic Interface Conditions
Authors: Jovanovič Boško , Vulkov Lubin G.
Published: April 2013

The convergence of difference schemes for the two–dimensional weakly
parabolic equation (elliptic equation with a dynamic interface condition) is studied.
Estimates for the rate of convergence “almost” (except for the logarithmic factor)
compatible with the smoothness of the differential problem solution in special discrete
Sobolev norms are obtained.
Stability of Difference Schemes for Nonlinear Time-dependent Problems
Authors: Matus Piter
Published: April 2013

In the present paper, a priori estimates of the stability in the sense of the initial data of the difference schemes approximating quasilinear parabolic equations and
nonlinear transfer equation have been obtained. The basic point is connected with the necessity of estimating all derivatives entering into the nonlinear part of the difference
equations. These estimates have been proved without any assumptions about the properties of the differential equations and depend only on the behavior of the initial
and boundary conditions. As distinct from linear problems, the obtained estimates of stability in the general case exist only for the finite instant of time t 6 t0 connected with
the fact that the solution of the Riccati equation becomes infinite.
is already associated with the behavior of the second derivative of the initial function and coincides with the time of the exact solution destruction (heat localization in
the peaking regime). A close relation between the stability and convergence of the difference scheme solution is given. Thus, not only a priori estimates for stability
have been established, but it is also shown that the obtained conditions permit exact determination of the time of destruction of the solution of the initial boundary value
problem for the original nonlinear differential equation in partial derivatives. In the present paper, concrete examples confirming the theoretical conclusions are given.
The Sdfem for a Convection-diffusion Problem with Two Small Parameters
Authors: Roos Hans-Görg , Uzelac Zorica
Published: April 2013

A singularly perturbed convection-diffusion problem with two small parameters is considered. The problem is solved using the streamline-diffusion finite element method on a Shishkin mesh. We prove that the method is convergent independently of the perturbation parameters. Numerical experiments support these theoretical results.
On Fast Domain Decomposition Solving Procedures for hp-Discretizations of 3-D Elliptic Problems
Authors: Korneev V. , Langer U. , Xanthis L. S.
Published: April 2013

A DD (domain decomposition) preconditioner of almost optimal in p arithmetical complexity is presented for the hierarchical hp discretizations of 3-d second
order elliptic equations. We adapt the wire basket substructuring technique to the hierarchical hp discretization, obtain a fast preconditioner-solver for faces by Kinterpolation
technique and show that a secondary iterative process may be efficiently used for prolongations from faces. The fast solver for local Dirichlet problems on subdomains
of decomposition is based on our earlier derived finite-difference like preconditioner for the internal stiffness matrices of p-finite elements and fast solution procedures
for systems with this preconditioner, which appeared recently.
A Numerical Model for the Radial Flow Through Porous and Deformable Shells
Authors: Gaspar Francisco J. , Lisbona Francisco J. , Vabishchevich Petr N.
Published: April 2013

Energy estimates and convergence analysis of finite difference methods
for Biot's consolidation model are presented for several types of radial
ow. The model
is written by a system of partial differential equations which depend on an integer
parameter (n = 0; 1; 2) corresponding to the one-dimensional
ow through a deformable
slab and the radial
ow through an elastic cylindrical or spherical shell respectively.
The finite difference discretization is performed on staggered grids using separated
points for the approximation of pressure and displacements. Numerical results are
given to illustrate the obtained theoretical results.
A Discreate Calculus with Applications of High-Order Discretizations to Boundary-Value Problems
Authors: Steinberg Stanly
Published: April 2013

We develop a discrete analog of the differential calculus and use this
to develop arbitrarily high-order approximations to Sturm–Liouville boundary-value
problems with general mixed boundary conditions. An important feature of the method
is that we obtain a discrete exact analog of the energy inequality for the continuum
boundary-value problem. As a consequence, the discrete and continuum problems
have exactly the same solvability conditions. We call such discretizations mimetic.
Numerical test conﬁrm the accuracy of the discretization.
We prove the solvability and convergence for the discrete boundary-value problem
modulo the invertibility of a matrix that appears in the discretization being positive
deﬁnite. Numerical experiments indicate that the spectrum of this matrix is real,
greater than one, and bounded above by a number smaller than three.
An Almost Sixth-Order Finite-Difference Method for Semilinear Singular Perturbation Problems
Authors: Vulanović Relja
Published: April 2013

The discretization meshes of the Shishkin type are more suitable for high-
order finite-difference schemes than Bakhvalov-type meshes. This point is illustrated
by the construction of a hybrid scheme for a class of semilinear singularly perturbed
reaction-diffusion problems. A sixth-order five-point equidistant scheme is used at most
of the mesh points inside the boundary layers, whereas lower-order three-point schemes
are used elsewhere. It is proved under certain conditions that this combined scheme is
almost sixth-order accurate and that its error does not increase when the perturbation
parameter tends to zero.
Unsteady Flow of a Two-Layer Blood Stream Past a Tapered Flexible Artery under Stenotic Conditions
Authors: Chakravarty Santabrata ,   Sarifuddin, Mandal Prashanta Kumar
Published: April 2013

The mechanics of the blood flow in a flexible tapered artery with stenosis
is studied from the viewpoint of a mathematical model. The flowing blood is represented
by a two-fluid model, consisting of a core region of suspension of all erythrocytes
assumed to be characterized by a Casson fluid and a peripheral plasma layer free from
cells of any kind as a Newtonian fluid. The moving wall of the artery is treated as an
anisotropic, linear viscoelastic incompressible circular cylindrical membrane cell. The
effect of the surrounding connective tissues on the motion of the artery wall is also
given due attention. The unsteady flow mechanism, subjected to a pulsatile pressure
gradient has been solved using the finite difference scheme by exploiting the appropriate
physically realistic prescribed conditions. The present model is also employed
to study the effect of taper angle, the wall deformation, the severity of the stenonis,
the viscosity of the peripheral layer, and the non-Newtonian rheology of streaming
blood on the dynamic flow field. Finally, the numerical illustration presented at the
end of the paper provides an effective quantitative measure of the flux, the resistive
impedance and the wall shear stress through their graphical representations and also
a few comparisons with the existing results have been made in order to validate the
applicability of the present model.
Numerical Blow-up for the p-Aplacian Equation with a Source
Authors: Ferreira Raŭl , De Pablo Arturo
Published: April 2013

We study numerical approximations of nonnegative solutions of the
p-Laplacian equation with a nonlinear source. We describe when solutions of a semidiscretization in space exist globally in time and when they blow up in a finite time. We also find the blow-up rates and the blow-up sets by means of the discrete self-similar profiles.
Explicit FV Scheme for the Perona-Malik Equation
Authors: Krivă Zuzana
Published: April 2013

The Perona|Malik equation for nonlinear di®usion is the well-known equation widely used in image processing. This equation can be applied with great success for selective smoothing of images, where the noise is represented by small gradients and the spurious edges are represented by the large ones. For a numerical solution of this equation we use the ¯nite volume method. We analyze convergence of a corresponding explicit finite volume scheme to its weak solution and show some numerical experiments. We suggest also some modi¯cations of this scheme to obtain better CPU time performance of the algorithm.
Exact Difference Schemes for Time-dependent Problems
Authors: Matus P , Irkhin U. , Lapinska-Chrzczonowicz M.
Published: April 2013

For one-dimensional and multidimensional semilinear transport equations of quite a general form with given initial data and boundary
conditions the exact difference schemes (EDSs) are constructed. In the case of constant coe±cients, such numerical methods can be created on rectangular grids, while in the
case of variable coefficients - on moving grids only. The questions of developing difference schemes of arbitrary order for quasi-linear transport equations with a nonlinear
right-hand side are discussed. In this paper, the EDSs are constructed also for certain classes of linear and quasilinear parabolic equations, for convection-diffusion problems with a small parameter,
as well as inhomogeneous wave equations with constant coe±cients.
Degenerate Time-dependent Variational Inequalities with Applications to Traffic Equilibrium Problems
Authors: Barbagallo A.
Published: April 2013

The aim of this paper is to study the continuity of the solutions to
degenerate time-dependent variational inequalities. In order to obtain the continuity
of the solution, a previous continuity result for strongly monotone variational
inequalities and an appropriate use of the convergence set in Mosco’s sense play an
important role. The continuity result allows us to provide a discretization procedure
for the calculation of the solution to the variational inequality which expresses the
time-dependent traffic network equilibrium problem.
Domain Decomposition Approach for Automatic Parallel Generation of Tetrahedral Grids
Authors: Ivanov E.G. , Andrä H. , Kudryavtsev A.N.
Published: April 2013

The desire to simulate even more geometrical and physical features of
technical structures and the availability of parallel computers and parallel numerical
solvers which can exploit the power of these machines have led to a steady increase
in the number of the grid elements used. Memory requirements and computational
time are too large for usual serial PCs. An a priori partitioning algorithm for the
parallel generation of 3D non-overlapping compatible unstructured meshes based on a
CAD surface description is presented in this paper. Emphasis is placed on practical
issues and implementation rather than on theoretical complexity. In order to achieve
robustness of the algorithm with respect to the geometrical shape of the structure, the
authors propose that there should be several or many but relatively simple algorithmic
steps. The geometrical domain decomposition approach has been applied. It allows
us to use standard 2D and 3D high-quality Delaunay mesh generators for independent
and simultaneous volume meshing. Different aspects of load balancing methods are
also explored in the paper. The MPI library and SPMD model are used for parallel
grid generator implementation. Several 3D examples are given.
Structured Rank-(r1, . . . , rd) Decomposition of Function-related Tensors in R_D
Authors: Khoromskij B.N.
Published: April 2013

The structured tensor-product approximation of multidimensional nonlocal
operators by a two-level rank-(r1, . . . , rd) decomposition of related higher-order
tensors is proposed and analysed. In this approach, the construction of the desired
approximant to a target tensor is a reminiscence of the Tucker-type model, where the
canonical components are represented in a fixed (uniform) basis, while the core tensor
is given in the canonical format. As an alternative, the multilevel nested canonical
decomposition is presented. The complexity analysis of the corresponding multilinear
algebra shows an almost linear cost in the one-dimensional problem size. The existence
of a low Kronecker rank two-level representation is proven for a class of function-related
tensors.
Numerical Algorithms of Optimal Complexity for Weakly Singular Volterra Integral Equations
Authors: Tynda A.N.
Published: April 2013

In this paper we construct complexity order optimal numerical methods
for Volterra integral equations with different types of weakly singular kernels. We
show that for Volterra equations (in contrast to Fredholm integral equations) using the
”block-by-block” technique it is not necessary to employ the additional iterations to
construct complexity optimal methods.
ANALYTIC ITERATIVE PROCESSES AND NUMERICAL ALGORITHMS FOR STIFF PROBLEMS
Authors: FALEICHIK B.V.
Published: April 2013

The goal of the research is to construct practicable numerical algorithms for stiff systems of ordinary differential equations which let you increase the accuracy of the approximate solution without decreasing the length of the time interval. To achieve this goal, we have constructed a family of new iterative analytic processes generalising the Picard process. For a basic representative of this family, we demon-strate its better convergence properties on a scalar linear problem in comparison with the classical Picard process. For the general form of such iterative processes, we discuss their connection with existing methods for operator equations and propose a method for choosing their parameters. The efficiency of this parameter determination method is justified with a numerical experiment. In conclusion we propose a general approach to the construction of numerical algorithms which is based on the discretisation of the constructed iterative analytic processes.
On The Analog Of The Monotone Error Rule For Parameter Choice In The (Iterated) Lavrentiev Regularization
Authors: HAMARIK U , PALM R. , RAUS T.
Published: April 2013

We consider linear ill-posed problems in Hilbert spaces with a noisy right hand side and a given noise level. To solve non-self-adjoint problems by the (it-erated) Tikhonov method, one effective rule for choosing the regularization parameter is the monotone error rule (Tautenhahn and Hamarik, Inverse Problems, 1999, 15, 1487– 1505). In this paper we consider the solution of self-adjoint problems by the (iterated) Lavrentiev method and propose for parameter choice an analog of the monotone error rule. We prove under certain mild assumptions the quasi-optimality of the proposed rule guaranteeing convergence and order optimal error estimates. Numerical examples show for the proposed rule and its modifications much better performance than for the modified discrepancy principle.
Dual Regularized Total Least Squares And Multi-Parameter Regularization
Authors: LU S. , PEREVERZEV S.V. , TAUTENHAHN U.
Published: April 2013

In this paper we continue our study of solving ill-posed problems with a noisy right-hand side and a noisy operator. Regularized approximations are obtained by Tikhonov regularization with differential operators and by dual regularized total least squares (dual RTLS) which can be characterized as a special multi-parameter regularization method where one of the two regularization parameters is negative. We report on order optimality results for both regularized approximations, discuss compu-tational aspects, provide special algorithms and show by experiments that dual RTLS is competitive to Tikhonov regularization with differential operators.
Performance Of H-Lu Preconditioning For Sparse Matrices
Authors: GRASEDYCK L. , HACKBUSCH W. , KRIEMANN R.
Published: April 2013

In this paper we review the technique of hierarchical matrices and put it into the context of black-box solvers for large linear systems. Numerical examples for several classes of problems from medium- to large-scale illustrate the applicability and efficiency of this technique. We compare the results with those of several direct solvers (which typically scale quadratically in the matrix size) as well as an iterative solver (algebraic multigrid) which scales linearly (if it converges in O(1) steps).
On The Stability Of Finite-Difference Schemes For Parabolic Equations Subject To Integral Conditions With Applications To Thermoelasticity
Authors: SAPAGOVAS M , JESEVICIUTE Z.
Published: April 2013

The stability of implicit difference scheme for parabolic equations subject to integral conditions, which correspond to the quasi-static flexure of a thermoelastic rod is considered. The stability analysis is based on the spectral structure of matrix of the difference scheme. The stability conditions obtained here differ from those presented in the articles of other authors..
Two-Sided Approximations For Nonlinear Operator Equations
Authors: LAZURCHAK I.I. , MAKAROV V.L. , SYTNYK D.
Published: April 2013

We propose an analytical-numerical method for nonlinear operator equations which converges exponentially and provides two-sided approximations. A numerical example confirms the theoretical results
Domain Decomposition Methods With Overlapping Subdomains For The Time-Dependent Problems Of Mathematical Physics
Authors: VABISHCHEVICH P.N.
Published: April 2013

At the present time, the domain decomposition methods are considered as the most promising ones for parallel computer systems.
Nowadays success is attained mainly in solving approximately the classical boundary value problems for second-order elliptic equations.
As for the time-dependent problems of mathematical physics, there are, in common use, approaches based on ordinary implicit schemes and
implemented via iterative methods of the domain decomposition. An alternative technique is based on the non-iterative schemes
(region-additive schemes). On the basis of the general theory of additive schemes a wide class of difference schemes
(alternative directions, locally one-dimensional, factorized schemes, summarized approximation schemes, vec-tor additive schemes, etc.)
as applied to the domain decomposition technique for time-dependent problems with synchronous and asynchronous implementations has been
investigated. For nonstationary problems with self-adjoint operators, we have considered three dif-ferent types of decomposition operators
corresponding to the Dirichlet and Neumann conditions on the subdomain boundaries. General stability conditions have been obtained for the
region-additive schemes. We focused on the accuracy of domain decom-position schemes. In particular, the dependence of the convergence rate
on the width of subdomain overlapping has been investigated as the primary property. In the present paper, new classes of domain decomposition
schemes for nonstationary problems, based on the subdomain overlaping and minimal data exchange in solving problems in subdomains, have been
constructed.
Mixed Hybrid Finite Element Method for a Variational Inequality with a Quasi-linear Operator
Authors: Lapin A.
Published: April 2013

A mixed hybrid finite element method has been applied to a variational inequality with a potential second-order quasi-linear differential operator. The
Lagrange multiplier method for a dual problem has been used to construct this finite
element scheme. The existence and uniqueness of a solution for the resulting finite-
dimensional problem has been proved, the solution iterative methods are discussed.
The non-overlapping domain decomposition method combined with the mixed hybrid
finite element approximation is analyzed.
Some Remarks on Residual-based Stabilisation of Inf-sup Stable Discretisations of the Generalised Oseen Problem
Authors: Matthies G. , Ionkin Nikolai I. , Lube G. , Röhe L.
Published: April 2013

We consider residual-based stabilised finite element methods for the generalised
Oseen problem. The unique solvability based on a modified stability condition
and an error estimate are proved for inf-sup stable discretisations of velocity and pressure.
The analysis highlights the role of an additional stabilisation of the incompressibility
constraint. It turns out that the stabilisation terms of the streamline-diffusion
(SUPG) type play a less important role. In particular, there exists a conditional stability
problem of the SUPG stabilisation if two relevant problem parameters tend to zero.
The analysis extends a recent result to general shape-regular meshes and to discontinuous
pressure interpolation. Some numerical observations support the theoretical
results.
A Fourier Pseudospectral Method for Solving Coupled Viscous Burgers Equations
Authors: Rashid Abdur , Ismail Ahmad Izani Bin Md.
Published: April 2013

The Fourier pseudo-spectral method has been studied for a one-
dimensional coupled system of viscous Burgers equations. Two test problems with
known exact solutions have been selected for this study. In this paper, the rate of con-
vergence in time and error analysis of the solution of the first problem has been studied,
while the numerical results of the second problem obtained by the present method are
compared to those obtained by using the Chebyshev spectral collocation method. The
numerical results show that the proposed method outperforms the conventional one in
terms of accuracy and convergence rate.