bluuebunny/crossref_metadata_2025 huggingface dataset:
ADI after Austenitising from Intercritical Temperature
Authors: Kowalskia A. , Kluska-Nawarecka S. , Regulski K.
Published: April 2013

ADI subjected to austenitising at intercritical temperatures contains in its matrix the precipitates of pre-eutectoid ferrite. Studies were carried out on the ductile iron of the following chemical composition: C = 3,80%, Si = 2,30%, Mn = 0,28%, P = 0,060%, S = 0,010%, Mg = 0,065%, Ni = 0,60%, Cu = 0,70%, Mo = 0,21% This cast iron was austenitised at three different temperatures, i.e. 800, 815 and 830oC and austempered at 360 and 380oC. For each variant of the cast iron heat treatment, the mechanical properties, i.e. YS, TS, EL and Hardness, were measured, and structure of the matrix was examined. Higher plastic properties were obtained owing to the presence of certain amount of pre-eutectoid ferrite. The properties were visualised using fuzzy logic model in a MATLAB. software.
Fabrication and Microstructure of Layers Containing Intermetallic Phases on Magnesium
Authors: Mola R.
Published: April 2013

Al- and Al/Zn-enriched layers containing intermetallic phases were deposited on the Mg substrate by heating the Mg specimens in contact with the powdered materials in a vacuum furnace. The Al-enriched surface layers were produced using Al powder, whereas the Al/Znenriched layers were obtained from an 80 wt.% Al + 20 wt.% Zn powder mixture. The microstructure and composition of the layers were analyzed by optical microscopy, scanning electron microscopy and X-ray diffraction. The results showed that the Al-enriched layer comprised an Mg17Al12 intermetallic phase and a solid solution of Al in Mg. The layer obtained from the Al+Zn powder mixture was composed of Mg-Al-Zn intermetalic phases and a solid solution of Al and Zn in Mg. Adding 20% of Zn into the Al powder resulted in the formation of a considerably thicker layer. Moreover, the hardness of the surface layers was much higher than that of the Mg substrate.
The Cambrian trilobites of Jordan – taxonomy, systematic and stratigraphic significance
Authors: Elicki Olaf , Geyer Gerd
Published: April 2013

Elicki, O. and Geyer, G. 2013. The Cambrian trilobites of Jordan - taxonomy, systematic and stratigraphic significance. Acta Geologica Polonica, 63(1), 1-56. Warszawa. Marine carbonates and siliciclastic rocks of the Burj Formation in Jordan include paucispecific trilobite associations of the (traditional) Lower-Middle Cambrian boundary interval. Comprehensive new material of these trilobites allows a review of their taxonomy and systematic positions as well as a refined morphological description and a reconsideration of previous interpretations of their stratigraphic position and thus the correlation of the fossiliferous beds. In addition to the classic species Kingaspis campbelli (King, 1923) and Redlichops blanckenhorni Richter and Richter, 1941, Timnaella? orientalis (Picard, 1942) and Hesa problematica Richter and Richter, 1941, the discussed trilobites include Issalia gen. nov. with Issalia scutalis gen. nov., sp. nov., Tayanaspis gen. nov. with Tayanaspis bulbosus gen. nov., sp. nov., Uhaymiria gen. nov. with Uhaymiria glabra gen. nov., sp. nov., Cambrunicornia ? jafnaensis sp. nov., Myopsolenites palmeri (Parnes, 1971), M. hyperion sp. nov., and Enixus cf. antiquus (Chernysheva, 1956). Myopsolenites boutiouiti Geyer and Landing, 2004 is now regarded as a junior synonym of Myopsolenites altus (Linan and Gozalo, 1986). A detailed discussion of the correlation with a focus on global aspects provides clues for the utility of potential index fossils for the global Cambrian Series 3 and Stage 5.
Palaeoenvironmental evolution of the Southern Alps across the Faraoni Level equivalent: new data from the Trento Plateau (Upper Hauterivian, Dolomites, N. Italy)
Authors: Lukeneder Alexander , Grunert Patrick
Published: April 2013

Lukeneder, A. and Grunert, P. 2013. Palaeoenvironmental evolution of the Southern Alps across the Faraoni Level equivalent: new data from the Trento Plateau (Upper Hauterivian, Dolomites, N. Italy). Acta Geologica Polonica, 63 (1), 89-104. Warszawa. New stratigraphic and palaeoenvironmental data are presented for the northeastern part of the Trento Plateau (Puez area, Southern Alps, Italy). The studied section corresponds to the upper Hauterivian Balearites balearis and “Pseudothurmannia ohmi” ammonite zones and normal palaeomagnetic chron upper M5. A c. 30-cm-thick bed is identified as the equivalent of the Faraoni Level, based on its position within the Pseudothurmannia mortilleti Subzone, the composition of its ammonite fauna and the peak of a minor positive trend in the δ 13 C bulk record. Microfacies and geochemical proxies compare well with those of the southeastern part of the Trento Plateau and indicate palaeoceanographic continuity along the eastern margin of the plateau. The abundances of radiolarians and nannoconids suggest a turnover in the trophic structure from eutrophic conditions around the Faraoni Level equivalent to oligotrophic conditions. Low organic matter and sulphur content and frequent bioturbation indicate a well-oxygenated environment. Ammonite diversity and life-habitat groups document the influence of sea level on the plateau: while epi- and mesopelagic ammonites occur commonly during sea-level highstands, all life-habitat groups become reduced during a sea-level lowstand in the Spathicrioceras seitzi and P. ohmi subzones. The Faraoni event is heralded by a faunal turnover expressed as the diversification of epipelagic ammonites. Palaeoenvironmental conditions along the eastern margin of the Trento Plateau during the Faraoni event contrast with those of the organic-rich black shales in the west. A re-evaluation of the depositional model based on the new results suggests a general water depth of 300-500 m for the plateau. The severe reduction of mesopelagic ammonites during the sea-level lowstand indicates a shallowing towards the epi-/mesopelagic boundary. During the Faraoni event, the eastern areas of the Trento Plateau were located at the upper limit of the oxygen-minimum layer and were thus only occasionally affected by oxygen depletion, whereas the western areas were located well within the upper part of the oxygen-depleted layer.
Calcareous plankton bio-chronostratigraphy of the Maltese Lower Globigerina Limestone member
Authors: Baldassini Niccolo’ , Mazzei Roberto , Foresi Luca Maria , Riforgiato Federica , Salvatorini Gianfranco
Published: April 2013

Baldassini, N., Mazzei, R., Foresi L.M., Riforgiato, F. and Salvatorini, G. 2012. Calcareous plankton bio-chronostratigraphy of the Maltese Lower Globigerina Limestone member. Acta Geologica Polonica, 63 (1), 105-135. Warszawa. The planktonic foraminifera and calcareous nannofossil biostratigraphy of the Maltese Lower Globigerina Limestone member has been investigated. The member was dated to early planktonic foraminiferal P22 Zone and nannofossil NP25 Zone (upper Chattian). A climate-stratigraphic approach, based on the quantitative analyses of calcareous nannofossils, was used additionally to achieve a more precise chronology. The species Coccolithus pelagicus (diameter £11 μm) and the genus Umbilicosphaera were selected for the recognition of cold and warm surface waters intervals respectively. The ratio of their percentages enabled the construction of a Climatic Factor (CLF) curve. The CLF values were consistent with a warm climatic phase, which is probably represented by the portion of the oxygen stable isotope curve of Miller et al. above the Oi2c event and below the beginning of the cooling trend that culminates in the Mi1 event. Considering these two climatic events and the upper boundary of the NP25 Zone, it can be inferred that the deposition of the Lower Globigerina Limestone member took place between 25.1 and 24.3 Ma.
Fast convergence of the Coiflet-Galerkin method for general elliptic BVPs
Authors: Akbari Hani
Published: April 2013

We consider a general elliptic Robin boundary value problem. Using orthogonal Coifman wavelets (Coiflets) as basis functions in the Galerkin method, we prove that the rate of convergence of an approximate solution to the exact one is O(2 −nN ) in the H1 norm, where n is the level of approximation and N is the Coiflet degree. The Galerkin method needs to evaluate a lot of complicated integrals. We present a structured approach for fast and effective evaluation of these integrals via trivariate connection coefficients. Due to the fast convergence rate, very good approximations are found at low levels and with low Coiflet degrees, hence the size of corresponding linear systems is small. Numerical experiments confirm these claims.
Predictive control for trajectory tracking and decentralized navigation of multi-agent formations
Authors: Prodan Ionela , Olaru Sorin , Stoica Cristina , Niculescu Silviu-Iulian
Published: April 2013

This paper addresses a predictive control strategy for a particular class of multi-agent formations with a time-varying topology. The goal is to guarantee tracking capabilities with respect to a reference trajectory which is pre-specified for an agent designed as the leader. Then, the remaining agents, designed as followers, track the position and orientation of the leader. In real-time, a predictive control strategy enhanced with the potential field methodology is used in order to derive a feedback control action based only on local information within the group of agents. The main concern is that the interconnections between the agents are time-varying, affecting the neighborhood around each agent. The proposed method exhibits effective performance validated through some illustrative examples.
Mode set focused hybrid estimation
Authors: Rienmüller Theresa , Hofbaur Michael , Travé-Massuyès Louise , Bayoudh Mehdi
Published: April 2013

Estimating the state of a hybrid system means accounting for the mode of operation or failure and the current state of the continuously valued entities concurrently. Existing hybrid estimation schemes try to overcome the problem of an exponentially growing number of possible mode-sequence/continuous-state combinations by merging hypotheses and/or deducing likelihood measures to identify tractable sets of the most likely hypotheses. However, they still suffer from unnecessarily high computational costs as the number of possible modes increases. Hybrid diagnosis schemes, on the other hand, estimate the current mode of operation/failure only, thus leaving the continuous evolution of the system implicit. This paper proposes a novel scheme that uses a combination of both the approaches in order to define posterior transition probabilities between the specified modes of the hybrid system, hence focusing better on relevant hypotheses. In order to demonstrate the effectiveness of the proposed method, the algorithm is applied to a satellite attitude control system and compared with existing hybrid estimation/diagnosis schemes, such as the Interacting Multiple Model (IMM) algorithm, a purely parity based method (HyDiag), and an existing hybrid Mode Estimation (hME) algorithm.
An unscented Kalman filter in designing dynamic GMDH neural networks for robust fault detection
Authors: Mrugalski Marcin
Published: April 2013

This paper presents an identification method of dynamic systems based on a group method of data handling approach. In particular, a new structure of the dynamic multi-input multi-output neuron in a state-space representation is proposed. Moreover, a new training algorithm of the neural network based on the unscented Kalman filter is presented. The final part of the work contains an illustrative example regarding the application of the proposed approach to robust fault detection of a tunnel furnace.
Actuator fault diagnosis for flat systems: A constraint satisfaction approach
Authors: Seydou Ramatou , Raissi Tarek , Zolghadri Ali , Efimov Denis
Published: April 2013

This paper describes a robust set-membership-based Fault Detection and Isolation (FDI) technique for a particular class of nonlinear systems, the so-called flat systems. The proposed strategy consists in checking if the expected input value belongs to an estimated feasible set computed using the system model and the derivatives of the measured output vector. The output derivatives are computed using a numerical differentiator. The set-membership estimator design for the input vector takes into account the measurement noise thereby making the consistency test robust. The performances of the proposed strategy are illustrated through a three-tank system simulation affected by actuator faults.
Nitrogen Uptake and Free Amino-acid Accumulation in Roots of Lotus corniculatus Cultivars under Al-stress
Authors: Palove-Balang Peter , Murinova Anna , Zelinova Veronika
Published: April 2013

Nitrogen uptake and free amino acid accumulation was evaluated in two South American cultivars of Lotus corniculatus L. differing in their tolerance to Al stress. The uptake of nitrate was affected by 1 mM Al more in the sensitive cultivar INIA Draco than in a relatively tolerant UFRGS (the uptake rate was 39.1% and 52.9%, respectively, of the control value at pH=5.5), whereas the opposite was true for the uptake of ammonia (60.1% and 50.1%). Treatment with Al also decreased the free amino-acid level to similar extent in both cultivars, mostly due to the significantly decreased level of asparagine (p = 0.003 and 0.026, respectively), the dominant amino-acid in Lotus roots. On the other hand, accumulation of stress metabolite - proline was achieved that was up to 5 time higher than in control. No considerable differences in this accumulation in INIA Draco and in UFRGS were found, so it is rather unlikely that proline content could contribute to the differences in Al-tolerance between the cultivars.
Effect of Changes in Behaviour on the Heart Rate and its Diurnal Variation in a Male and a Female Eland (Taurotragus oryx)
Authors: Zizkova Katerina , Kotrba Radim , Kocisova Alica
Published: April 2013

Heart rate (HR) is related to the physiological state of most of vertebrates, e.g. the level of metabolism, motion or stress. In previous reports, the HR of eland was measured during sedation and general anaesthesia. Therefore, we wanted to evaluate HR in alert eland with emphasis on variations by different behaviours and time of the day. We measured HR by Polar S610 device in an adult male and an adult female. Behaviour during recumbent and rumination, standing and rumination, standing, standing and eating, movement, excitement during feeding, stressful event, handling in restraint box and sleep were recorded and synchronised with data from HR device. In the male, HR was lowest during recumbency and rumination. In the female, HR was lowest during sleep. The highest HR was measured during handling in a restraint box. The HR was higher during the night for most of the behaviours. Further research should focus on explaining the diurnal variation in HR as it relates to specific behaviour.
Detecting Sex-Biased Gene Flow in African-americans Through the Analysis of Intra- and Inter-Population Variation at Mitochondrial DNA and Y- Chromosome Microsatellites
Authors: Battaggia C. , Anagnostou P. , Bosch I. , Brisighelli F. , Destro-Bisol G. , Capocasa M.
Published: April 2013

This study reports on variations at the mitochondrial DNA (mtDNA) hypervariable region 1 (HVR-1) and at seven Y-chromosome microsatellites in an African-American population sample from Chicago, IL, USA. Our results support the hypothesis that the population studied had undergone a European malebiased gene flow. We show that comparisons of intraand inter-population diversity parameters between African-Americans, Europeans and Africans may help detect sex-biased gene flow, providing a complement to quantitative methods to estimate genetic admixture.
Association Between Obsessive Compulsive Disorder And Tumor Necrosis Factor-Α Gene –308 (G>A) And –850 (C>T) Polymorphisms In Turkish Children
Authors: Lüleyap H.U. , Onatoğlu D. , Tahiroğlu A.Y. , Alptekin D. , Yılmaz M.B. , Çetiner S. , Pazarbaşı A. , Ünal İ. , Avcı A.
Published: April 2013

Obsessive compulsive disorder (OCD) is a neurobiological disease characterized with obsessions and compulsions. Obsessive compulsive disorder occurs with an autoimmune mechanism after Group A β hemolytic streptococcus (GABHS) infection. Tumor necrosis factor (TNF) is an important cytokine, as well as having an important role in the apoptosis mechanism of autoimmune diseases. It is expressed by the TNF-α gene. The aim of this study was to examine the relationship between the TNF-α gene promoter region -308 (G>A) and -850 (C>T) polymorphisms and OCD. In this study, ages of the OCD patients and the control group ranged between 4 and 12 years. We studied two patient groups, one included childhood onset OCD patients (n = 49) and the control group was composed of healthy children (n = 58). Patients were diagnosed according to the Diagnostic and Statistical Manual of Mental Disorder (DSM-IV) criteria and with Kiddie Schedule for Affective Disorders and Schizophrenia-Present and Lifetime (KSAD-S-PL) version. For identifying the polyorphisms, polymerase chain reaction (PCR), restriction fragment length polymorphism (RFLP) and polyacrylamide gel electrophoresis (PAGE) methods were used.

For the -308 polymorphism, 45 of 49 OCD patients’ results were completed, and for the -850 polymorphism, 47 of 49 OCD patients’ results were completed. According to our statistical results, there is a positive relationship between OCD and the -308 polymorphism (p <0.001) but no association between OCD and the -850 polymorphism (p = 0.053). There is no positive relationship between antistreptolysin O (ASO) titers and the -308 polymorphism (p = 0.953) but there is an important significance between the -850 polymorphism and ASO (p = 0.010). There is no positive relationship between gender of patients and OCD (p = 0.180) and no positive association between ASO and gender (p = 0.467). According to our results, we hypothesize that we can propose the mutant AA genotype for the -308 polymorphism, and that the mutant CT genotype for the -850 polymorphism may be used as molecular indicators for OCD.
Towards Autonomous Robotic Valve Turning
Authors: Carrera A. , Ahmadzadeh S. R. , Ajoudani A. , Kormushev P. , Carreras M. , Caldwell D. G.
Published: April 2013

In this paper an autonomous intervention robotic task to learn the skill of grasping and turning a valve is described. To resolve this challenge a set of different techniques are proposed, each one realizing a specific task and sending information to the others in a Hardware-In-Loop (HIL) simulation. To improve the estimation of the valve position, an Extended Kalman Filter is designed. Also to learn the trajectory to follow with the robotic arm, Imitation Learning approach is used. In addition, to perform safely the task a fuzzy system is developed which generates appropriate decisions. Although the achievement of this task will be used in an Autonomous Underwater Vehicle, for the first step this idea has been tested in a laboratory environment with an available robot and a sensor.
On Global Optimization of Walking Gaits for the Compliant Humanoid Robot, COMAN Using Reinforcement Learning
Authors: Dallali Houman , Kormushev Petar , Li Zhibin , Caldwell Darwin
Published: April 2013

In ZMP trajectory generation using simple models, often a considerable amount of trials and errors are involved to obtain locally stable gaits by manually tuning the gait parameters. In this paper a 15 degrees of Freedom dynamic model of a compliant humanoid robot is used, combined with reinforcement learning to perform global search in the parameter space to produce stable gaits. It is shown that for a given speed, multiple sets of parameters, namely step sizes and lateral sways, are obtained by the learning algorithm which can lead to stable walking. The resulting set of gaits can be further studied in terms of parameter sensitivity and also to include additional optimization criteria to narrow down the chosen walking trajectories for the humanoid robot.
Structured Information Extraction from Medical Texts in Bulgarian
Authors: Boytcheva Svetla
Published: April 2013

This paper presents an approach for Information Extraction (IE) from Patient Records (PRs) in Bulgarian. The specific terminology and lack of resources in electronic format are some of the obstacles that make the task of current patient status data extraction in a structured format quite challenging. The usage of N-grams, collocations and words’ distances allows us to cope with this problem and to extract automatically the attribute-value pairs with relatively high precision.
Difference Schemes with Nonlocal Boundary Conditions
Authors: Goolin Alexei V. , Ionkin Nikolai I. , Morozova Valentina A.
Published: April 2013

The paper deals with the stability, with respect to initial data, of
difference schemes that approximate the heat-conduction equation with constant coefficients and nonlocal boundary conditions. Some difference schemes are considered
for the one-dimensional heat-conduction equation, the energy norm is constructed, and
the necessary and sufficient stability conditions in this norm are established for explicit
and weighted difference schemes.
Improved Least-squares Error Estimates for Scalar Hyperbolic Problems
Authors: Bochev P.B. , Choi J.
Published: April 2013

We consider an L_2-norm least-squares principle for a scalar hyperbolic
problem. A proper variational framework for the associated finite element method is
developed and studied. Analysis of the discretization error based on the least-squares
projection property shows a gap of one. This number cannot be improved
with a standard duality argument because the least-squares dual does not possess full
elliptic regularity. Using a perturbed dual problem we are able to show that the actual
gap of the least-squares method in the constant convection case is not worse than 2/3.
Operator-splitting Schemes for Solving Unsteady Elasticity Problems
Authors: Lisbona Francisco J. , Vabishchevich Pert N.
Published: April 2013

In this paper we consider the numerical approximation of the solution
of the 2D unsteady Lame equations on a rectangular domain. The basic problems
that appear, using both finite difference and finite element methods, are connected
with the fact that these equations are strongly coupled. Thus it is natural to design
computational algorithms in such a way that they allow one to consider boundary
value problems only for uncoupled equations. To implement this general concept, some
special (unconditionally stable) operator-splitting schemes are constructed. Its major
peculiarity is that transition to the next time level is performed by solving separate
elliptic problems for each component of the displacement vector. The previous results
make it possible to design efficient numerical algorithms for elasticity equations.
Solution of a Finite-Dimensional Problem With M-mappings and Diagonal Multivalued Operators
Authors: Laitinen E. , Lapin Alexander
Published: April 2013

The existence of a solution of the finite-dimensional problem with continuous M-mappings and multivalued diagonal
maximal monotone operators on an ordered interval, which is formed by the so-called subsolution,
is proved. Under several additional assumptions on the
operators the monotone dependence of a solution upon the right-hand
side is investigated. This result implies, in particular, the uniqueness of a solution
and serves as a basis for the analysis of the convergence for a multisplitting iterative
method. As an illustrative example, the finite difference scheme approximating a model
variational inequality is studied by using the general results.
Convergence Of a Finite Difference Scheme for the Third Boundary-Value Problem for an Elliptic Equation with Variable Coefficients
Authors: Jovanović Boško S. , Popović Branislav Z.
Published: April 2013

In this paper we study the convergence of a finite difference scheme that
approximates the third boundary-value problem for an elliptic equation with variable
coefficients on a unit square. An ”almost” second-order convergence rate estimate
(with additional logarithmic multiplier) is obtained.
Finite Difference Schemes for Convection-diffusion Problems with a Concentrated Source and a Discontinuous Convection Field
Authors: Linß Torsten
Published: April 2013

A singularly perturbed convection-diffusion problem with a concentrated
source is considered. The problem is solved numerically using two upwind difference
schemes on general meshes. We prove convergence, uniformly with respect to the
perturbation parameter, in the discrete maximum norm on Shishkin and Bakhvalov
meshes. Numerical experiments complement our theoretical results.
Finite Difference Schemes for Poro-elastic ProblemS
Authors: Gaspar Francisco J. , Lisbona Francisco J. , Vabishchevich Petr N.
Published: April 2013

In this paper, we present a finite difference analysis of the consolidation
problem for saturated porous media. In the classical model, the behaviour of the
porous environment – fluid system is described by a set of equations for the unknown
vector displacements of the matrix skeleton and the fluid pressure. For simplicity we
consider a model problem with constant coefficients in a rectangular domain. A priori
estimates for the difference solution of the problem are obtained and on their basis the
convergence of two-level difference schemes is investigated.
Numerical Modelling of Heat and Magnetohydrodynamic Flows in a Finite Cylinder
Authors: Buikis Andris , Kalis Harijs
Published: April 2013

The distribution of electromagnetic fields, forces and temperatures
induced by a three- phase axially-symmetric system of electric current in a conducting
cylinder of finite length has been calculated. An original method was used to calculate
the mean values of electromagnetic forces. The magnetohydrodynamic (MHD) flow
of viscous incompressible liquid and distribution of temperature are obtained by the
finite-difference method, using monotonic finite difference schemes.
Mathematical and Numerical Study of an Industrial Scheme for Two-phase Flows in Porous Media under Gravity
Authors: Enchéry G. , Masson R. , Wolf S. , Eymard R.
Published: April 2013

In this paper, we consider a dead-oil model where the capillary pressure
is neglected. In a multidimensional space and for a phase-by-phase upstream weigthing
cell-centered finite volume scheme, we prove the pressure estimates, the existence of
solutions to the discrete equations and the stability of the saturation calculation. This
is done in the explicit case as well as in the implicit case. Some numerical tests show
the convergence of the scheme.
Monotone Schemes of a Higher Order of Accuracy for Differential Problems with Boundary Conditions of the Second and Third Kind
Authors: Matus Peter
Published: April 2013

In the present paper monotone difference schemes of the second order
of approximation and accuracy for differential boundary-value problems of the second
and third kind without using the basic differential equation at the domain of the
boundary are constructed. The main idea is based on the assumption of the existence
and uniqueness of a smooth solution in some sufficiently small neighborhood of the
definition domain of the problem and the use of only half-integer nodes of the grid
(boundary points are excluded from the calculated nodes). In this case, the boundary
conditions are directly approximated with the second order on a two-point stencil. If
we assume that the equation has a meaning at the boundary nodes as well, then in this
case monotone schemes of the fourth order of accuracy have been constructed. It is
shown that in the case of Neumann problem it is necessary to construct such computational
procedures, which are monotone and satisfy the grid maximum principle with
respect to the flow (of the first derivatives with respect to space variables).
Discontinuous Galerkin Discretization with Embedded Boundary Conditions
Authors: Hemker P. W. , Hoffman W. , Van Raalte M. H.
Published: April 2013

The purpose of this paper is to introduce discretization methods of discontinuous Galerkin type for solving second-order elliptic PDEs on a structured,
regular rectangular grid, while the problem is defined on a curved boundary. The methods aim at high-order accuracy and the difficulty arises since the regular grid
cannot follow the curved boundary. Starting with the Lagrange multiplier formulation for the boundary conditions, we derive variational forms for the discretization of 2-D
elliptic problems with embedded Dirichlet boundary conditions. Within the framework of structured, regular rectangular grids, we treat curved boundaries according to the
principles that underlie the discontinuous Galerkin method. Thus, the high-order DGdiscretization is adapted in cells with embedded boundaries. We give examples of
approximation with tensor products of cubic polynomials. As an illustration, we solve a convection-dominated boundary-value problem on a complex domain. Although,
of course, it is impossible to accurately represent a boundary layer with a complex structure by means of cubic polynomials, the boundary condition treatment appears
quite effective in handling such complex situations.
A Fitted Mesh Method for a Class of Singularly Perturbed Parabolic Problems with a Boundary Turning Point
Authors: Dunne Raymond K. , O'Riordan Eugene , Shishkin Gregorii I.
Published: April 2013

A class of singularly perturbed time-dependent convection-diffusion problems with a boundary turning point is examined on a rectangular domain. The
solution of problems from this class possesses a parabolic boundary layer in the neighborhood of one of the sides of the domain. Classical numerical methods on uniform
meshes are known to be inadequate for problems with boundary layers. A numerical method consisting of a standard upwind finite difference operator on a fitted mesh is
constructed. It is proved that the numerical approximations generated by this method converge uniformly with respect to the singular perturbation parameter. Numerical
results are presented that verify computationally the theoretical result.
An Improved Error Estimate for a Numerical Method for a System of Coupled Singularly Perturbed Reaction-diffusion Equations
Authors: Linss Torsten , Madden Niall
Published: April 2013

We consider a central difference scheme for the numerical solution of a system of coupled reaction-diffusion equations. We show that the scheme is almost
second-order convergent, uniformly in the perturbation parameter. We present the results of numerical experiments to confirm our theoretical
results.
Singularly Perturbed Problems Modeling Reaction-convection-diffusion Processes
Authors: O' Riordan Eugene , Pickett Maria L. , Shishkin Georgii I.
Published: April 2013

In this paper, parameter - uniform numerical methods for singularly perturbed ordinary differential equations containing two small parameters are studied.Parameter-explicit theoretical bounds on the derivatives of the solutions are derived. A numerical algorithm based on an upwind finite difference operator and an appropriate piecewise uniform mesh is constructed. Parameter-uniform error bounds for the
numerical approximations are established. Numerical results are given to illustrate the parameter-uniform convergence of numerical approximations.
Parametrized Newton’s Iteration for Computing an Eigenpair of a Real Symmetric Matrix in an Interval
Authors: Datta Karabi , Hong Yoopyo , Lee Ran Baik
Published: April 2013

A parameterized Newton’s method to guarantee convergence to an eigenpair of a real symmetric matrix in a designated interval has been developed. The method is parametric in nature and with appropriate choices of parameters, the classical methods such as Newton’s method and the Rayleigh quotient method can easily be recovered.
Difference Schemes for Elliptic Equations with Mixed Derivatives
Authors: Matus Piotr , Rybak Irina
Published: April 2013

In this paper, the a priori estimates of stability in the energy and
the uniform norms are proved for the monotone and conservative difference schemes
approximating elliptic equations with mixed derivatives. The estimates are obtained
without any assumption about the symmetry of the coe±cient matrix of the initial
differential equation.
One-leg Integration of Ordinary Differential Equations with Global Error Control
Authors: Kulikov Gennady Yu. , Shindin Sergey K.
Published: April 2013

In this paper we study the family of one-leg two-step second-order methods developed by Dahlquist et al., which possess the A-stability and G-stability
properties on any grid. These methods are implemented with the local-global step size control derived by Kulikov and Shindin with the aim to obtain automatically the
numerical solution with any reasonable accuracy set by the user. We show that the error control is more complicated in one-leg methods, especially when applied to stiffproblems. Thus, we adapt our local-global step size control for the methods indicated
above and test these adaptive algorithms in practice.
Finite-difference Approximation of Mathematical Physics Problems on Irregular Grids
Authors: Vabishchevich P. N.
Published: April 2013

Mathematical physics problems are often formulated by means of the
vector analysis differential operators: divergence, gradient and rotor. For approximate
solutions of such problems it is natural to use the corresponding operator statements
for the grid problems, i.e., to use the so-called VAGO (Vector Analys Grid Operators)
method. In this paper, we discuss the possibilities of such an approach in using gen-
eral irregular grids. The vector analysis di®erence operators are constructed using
the Delaunay triangulation and the Voronoi diagrams. The truncation error and the
consistency property of the di®erence operators constructed on two types of grids are
investigated. Construction and analysis of the di®erence schemes of the VAGO method
for applied problems are illustrated by the examples of stationary and non-stationary
convection-diffusion problems. The other examples concerned the solution of the non-
stationary vector problems described by the second-order equations or the systems of
first-order equations.
Three Matlab Implementations of the Lowest-order Raviart-Thomas Mfem with a Posteriori Error Control
Authors: Bahriawati C. , Carstensen C.
Published: April 2013

The numerical approximation of the Laplace equation with inhomogeneous mixed boundary conditions in 2D with lowest-order
Raviart-Thomas mixed finite elements is realized in three flexible and short MATLAB programs. It is the aim of this paper to derive, document, illustrate, and validate the three MATLAB implementations EBmfem, LMmfem, and CRmfem for further use and modification in education and research. A posteriori error control with a reliable and efficient averaging technique is included to monitor the discretization error. Therein, emphasis is on the correct treatment of mixed boundary conditions. Numerical examples illustrate some applications of the provided software and the quality of the error estimation.
Functional-discrete Method (FD-method) for Matrix Sturm-Liouville Problems
Authors: Bandyrskiĭ B. Ĭ. , Gavrilyuk I. P. , Lazurchak I. I. , Makarov V. L.
Published: April 2013

A new algorithm for Sturm|Liouville problems with matrix coefficients is proposed which possesses the convergence rate of a geometric progression with a denominator depending inversely proportional on the order number of eigenvalues. The
asymptotic behavior of the distance between neighboring eigenvalues if the order number tends to infinity is investigated too. Numerical examples confirming the theoretical results are given.
Error Analysis for a Galerkin Finite Element Method Applied to a Coupled Nonlinear Degenerate System of Advection-diffusion Equations
Authors: Fadimba Koffi B.
Published: April 2013

We consider a standard Galerkin Method applied to both the pressure
equation and the saturation equation of a coupled nonlinear system of degenerate
advection-diffusion equations modeling a two-phase immiscible flow through porous
media. After regularizing the problem and establishing some regularity results, we
derive error estimates for a semi-discretized Galerkin Method. A decoupled nonlinear
scheme is then proposed for a fully discretized (backward in time) Galerkin Method,
and error estimates are derived for that method. We also prove the existence and
uniqueness for the nonlinear operator intervening in the backward time discretization.
Bounds of Information Expenses in Constructing Projection Methods for Solving Ill-posed Problems
Authors: Solodky Sergei G. , Lebedeva Evgeniya V.
Published: April 2013

An approach to constructing regularized projection methods to solve illposed
problems is proposed. This approach is based on a modification of the Galerkin
discretization scheme. It has been established that such a modification leads to a
significant reduction of information expenses compared to other known methods.
Transport-stabilized Semidiscretizations of the Incompressible Navier—Stokes Equations
Authors: Angermann L.
Published: April 2013

Within the framework of finite element methods, the paper investigates a
general approximation technique for the nonlinear convective term of Navier — Stokes
equations. The approach is based on an upwind method of the finite volume type. It
has been proved that the discrete convective term satisfies the well-known collection
of sufficient conditions for convergence of the finite element solution. For a particular
nonconforming scheme, the assumptions have been verified in detail and the estimate
of the semidiscrete velocity error has been proved.
Stability of Solutions of Differential-operator and Operator-difference Equations in the Sense of Perturbation of Operators
Authors: Jovanović B. S. , Lemeshevsky S. V. , Matus P. P. , Vabishchevich P. N.
Published: April 2013

Estimates of stability in the sense perturbation of the operator for
solving first- and second-order differential-operator equations have been obtained. For
two- and three-level operator-difference schemes with weights similar estimates hold.
Using the results obtained, we construct estimates of the coefficient stability for onedimensional
parabolic and hyperbolic equations as well as for the difference schemes
approximating the corresponding differential problems.
A Simple Equilibrium Finite Element over Quadrilaterals
Authors: Agouzal A.
Published: April 2013

In this paper a simple equilibrium finite element on quadrilaterals is
introduced and analysed. An optimal a priori error estimate has been obtained for
arbitrary regular quadrilaterals.
Stability of the Difference Schemes for the Equations of Weakly Compressible Liquid
Authors: Matus P. , Korolyova O. , Chuiko M.
Published: April 2013

A priory estimates of the stability in the sense of the initial data
of the difference scheme approximating weakly compressible liquid equations in the
Riemann invariants have been obtained. These estimates have been proved without
any assumptions about the properties of the solution of the differential problem and
depend only on the behavior of the initial conditions. As distinct from linear problems,
the obtained estimates of stability in the general case exist only for a finite instant of
time t≤t_0. In particular, this is confirmed by the fact, that nonfulfilment of these
stability conditions lead to the appearance of supersonic flows or domains with large
gradients. The questions of uniqueness and convergence of the difference solution are
considered also. The results of the computating experiment confirming the theoretical
conclusions are given.
Regularization Extragradient Method for a System of Equilibrium Problems
Authors: Buong NG.
Published: April 2013

The aim of the present paper is to investigate the regularization extragradient
method for solving a system of ill-posed equilibrium problems in Hilbert
spaces. An application to the mathematical programming with coupled constraints is
also given.
Numerical Enclosures for Variational Inequalities
Authors: Plum M. , Wieners Ch.
Published: April 2013

We present a new method for proving the existence of a unique solution
of variational inequalities within guaranteed close error bounds to a numerical
approximation. The method is derived for a specific model problem featuring most
of the difficulties of perfect plasticity. We introduce a finite element method for the
computation of admissible primal and dual solutions which a posteriori guarantees the
existence of a unique solution (by the verification of the safe load condition) and which
allows determination of a guaranteed error bound. Finally, we present explicit existence
results and error bounds in some significant specific configurations.
Nonlinear Stability Of The Difference Schemes For Equations Of Isentropic Gas Dynamics
Authors: MATUS P. , KOLODYNSKA A.
Published: April 2013

For the difference scheme approximating the gas dynamics problem in Riemann invariants a priory estimates with respect
to the initial data have been obtained. These estimates are proved without any assumptions about the solution of the
differential problem using only limitations for the initial and boundary conditions. Estimates of stability in the general
case have been obtained only for the finite instant of time. The uniqueness and convergence
of the difference solution are also considered. The results of the numerical experiment confirming theoretical results are given.
Tomographic Approach For Tropospheric Water Vapor Detection
Authors: MIIDLA P. , RANNAT K. , UBA P.
Published: April 2013

The technical successes in radio navigation and the availability of nu-merical algorithms have promoted the implementation of GPS-technology to atmo-spheric sciences. The tomographical contribution of Global Satellite Navigation Sys-tems (GNSS) is possible due to the methods of high precision detection of tropospheric delays of navigation signals from satellites to receivers. The principal specific char-acter in initial constraints, data collection and assimilation methods, the obtaining of final numerical results and their interpretation make the continuation of the success story for GPS-tomography very challenging. The authors use numerical simulation as the most time- and cost-efficient way to study different processes related to tro-pospheric water vapor tomography. This paper tends to give a short overview about some known methods in GPS-tomography for detection, monitoring and modeling of the tropospheric water vapor. The possible mathematical approach to the construc-tion of virtual network of ground-based sensors (GPS-receivers) for a real geographical location and discretization of the troposphere, also some aspects of raw data filtering and analysis are described. Output of tomographical modelling of the troposphere can be used to improve the results of large-scale numerical weather prediction models and also real-time navigation. The questions of voxel geometry and methods of data processing are supposed to be the key questions in constructing an effective network of GPS-receivers for water vapor tomography.
A Defect Correction Method for the Evolutionary Convection — Diffusion Problem with Increased Time Accuracy
Authors: LABOVSKY A.
Published: April 2013

This work presents a defect correction
method with increased time accuracy. The desired time accuracy is attained with
no extra computational cost. The method is applied to the evolutionary transport
problem, and is proven to be unconditionally stable. In the defect step, the artificial
viscosity parameter is added to the Peclet number as a stability factor, and the system is
antidiffused in the correction step. The time accuracy is also increased in the correction
step by modifying the right hand side.Computational results verifying the claimed space
and time accuracy of the approximate solution are presented.
Numerical Solution of Systems of Singularly Perturbed Differential Equations
Authors: Linss T. , Stynes M.
Published: April 2013

A survey is given of current research into the numerical solution of timeindependent
systems of second-order differential equations whose diffusion coefficients
are small parameters. Such problems are in general singularly perturbed. The equations
in these systems may be coupled through their reaction and/or convection terms.
Only numerical methods whose accuracy is guaranteed for all values of the diffusion
parameters are considered here. Some new unifying results are also presented.
Ultraspherical Differentiation Method for Solving System of Initial Value Differential Algebraic Equations
Authors: El-kady M. , Ibrahim M.A.
Published: April 2013

In this paper, we introduce a new spectral method based on ultraspherical
polynomials for solving systems of initial value differential algebraic equations.
Moreover, the suggested method is applicable for a wide range of differential equations.
The method is based on a new investigation of the ultraspherical spectral differentiation
matrix to approximate the differential expressions in equations. The produced
equations lead to algebraic systems and are converted to nonlinear programming. Numerical
examples illustrate the robustness, accuracy, and efficiency of the proposed
method.
A Macro-kinetic Hybrid Model for Traffic Flow on Road Networks
Authors: Herty M. , Moutari S.
Published: April 2013

We have developed a new hybrid model for an heterogeneous traffic
flow, based on a coupling of the Lighthill — Whitham and Richards (LWR)
macroscopic model and the kinetic model. On the highways of a road
network, we consider the macroscopic description of the traffic flow and switch to the
kinetic model to compute the mass flux through a junction. This new model reproduces
the capacity drop phenomenon at a merge junction, for instance, without imposing any
priority rule. We present some numerical simulations in which we compare the results
of the hybrid model with those given by the fully macroscopic model. Furthermore, we
illustrate the consequences of the velocity distribution on the flow through a merging
junction.
Stability and Monotonicity of Difference Schemes for Nonlinear Scalar Conservation Laws and Multidimensional Quasi-linear Parabolic Equations
Authors: Matus P. , Lemeshevsky S.
Published: April 2013

We have proved the difference analogue of a Bihari-type inequality.
Using this inequality, we study the stability in C and monotonicity of the difference
schemes approximating initial-boundary value problems for nonlinear conservation laws
and multi-dimensional parabolic equations. It has been shown that in the nonlinear
case the stability and monotonicity are determined not only by the behavior of the
approximate solution but also by its difference derivatives appearing in the nonlinear
terms of the equation. The stability estimates are obtained without any assumptions
about the properties of the solution and nonlinear coefficients of the differential problem.
Here we use restrictions only on input data (initial and boundary conditions and
the right-hand side).
The sufficient conditions of the shock wave generation is formulated for input data.
For the Riemann problem two exact and stable difference schemes are analyzed.
Numerical Treatments for Volterra Delay Integro-differential Equations
Authors: Rihan F. A. , Doha E. H. , Hassan M. I. , Kamel N. M.
Published: April 2013

This paper presents a new technique for numerical treatments of Volterra
delay integro-differential equations that have many applications in biological and physical
sciences. The technique is based on the mono-implicit Runge — Kutta method for treating the differential part and the collocation method (using
Boole’s quadrature rule) for treating the integral part. The efficiency and stability
properties of this technique have been studied. Numerical results are presented to
demonstrate the effectiveness of the methodology.
Numerical Solution of a Nonlocal Problem Modelling Ohmic Heating of Foods
Authors: Nikolopoulos C. V.
Published: April 2013

An upwind and a Lax-Wendroff scheme are introduced for the solution
of a one-dimensional non-local problem modelling ohmic heating of foods. The schemes
are studied regarding their consistency, stability, and the rate of convergence for the
cases that the problem attains a global solution in time. A high resolution scheme is
also introduced and it is shown that it is total-variation-stable. Finally some numerical
experiments are presented in support of the theoretical results.