We deal with the solution of the systems of linear algebraic equations arising from Symmetric Interior Penalty discontinuous Galerkin (SIPG) discretization of linear elasticity problems in primal (displacement) formulation. The main focus... more
We deal with the solution of the systems of linear algebraic equations arising from Symmetric Interior Penalty discontinuous Galerkin (SIPG) discretization of linear elasticity problems in primal (displacement) formulation. The main focus of the paper is on constructing a uniform preconditioner which is based on a natural splitting of the space of piecewise linear discontinuous functions. The presented approach has recently been introduced in [2] in the context of designing subspace correction methods for scalar elliptic partial differential equations and is extended here to linear elasticity equations, i.e., a class of vector field problems. Similar to the scalar case the solution of the linear algebraic system corresponding to the SIPG method is reduced to the solution of a problem arising from discretization by nonconforming Crouzeix-Raviart elements plus the solution of a well-conditioned problem on the complementary space.
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In this study we demonstrate how some different techniques which were introduced and studied in previous works by the authors can be integrated and extended in the construction of efficient algebraic multilevel iteration methods for more... more
In this study we demonstrate how some different techniques which were introduced and studied in previous works by the authors can be integrated and extended in the construction of efficient algebraic multilevel iteration methods for more complex problems. We devise an optimal order algorithm for solving linear systems obtained from locking-free discretization of 3D pure displacement elasticity problems. The presented
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ABSTRACT
ABSTRACT
ABSTRACT In this paper we present a new construction of generalized hierarchical bases for symmetric positive definite matrices arising from discontinuous Galerkin discretization of second‐order partial differential equations (PDE) with... more
ABSTRACT In this paper we present a new construction of generalized hierarchical bases for symmetric positive definite matrices arising from discontinuous Galerkin discretization of second‐order partial differential equations (PDE) with highly varying coefficients. In the well‐established theory of hierarchical basis multilevel methods one basic assumption is that the PDE coefficients are smooth functions on the elements of the coarsest mesh partition. It is shown numerically that the developed hierarchical bases yields a robust splitting with respect to jump discontinuities of the PDE coefficient at arbitrary element interfaces on the finest mesh.
New results about preconditioning of rotated trilinear nonconforming FEM elasticity systems in the case of mesh anisotropy are presented. The solver of the arising linear system is based on the constructed efficient preconditioner of the... more
New results about preconditioning of rotated trilinear nonconforming FEM elasticity systems in the case of mesh anisotropy are presented. The solver of the arising linear system is based on the constructed efficient preconditioner of the coupled stiffness matrix. Displacement decomposition of the stiffness matrix is used as a first step of the algorithm. At the second step, modified incomplete factorization MIC(0) with perturbation is applied to a proper auxiliary M-matrix to get an approximate factorization of the obtained block-diagonal matrix. The derived condition number estimates and the presented numerical tests well illustrate the behaviour of the theoretically studied algorithms as well as their robustness for some more realistic benchmark problems.
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Downloadable! The purpose of this paper is to show the way for increasing the local capacity for public discussion in the sphere of environmental protection in the municipalities of South East part of Bulgaria. Target groups are... more
Downloadable! The purpose of this paper is to show the way for increasing the local capacity for public discussion in the sphere of environmental protection in the municipalities of South East part of Bulgaria. Target groups are representatives of local authorities, municipal administrations ...
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The dynamics of cluster growth in a two-lane driven diffusive system is analyzed by extensive Monte Carlo simulations. We observe good dynamical scaling for small values of a particle-particle exchange probability γ on relatively small... more
The dynamics of cluster growth in a two-lane driven diffusive system is analyzed by extensive Monte Carlo simulations. We observe good dynamical scaling for small values of a particle-particle exchange probability γ on relatively small lattices. As γ increases, the (effective) scaling exponents develop a dependence on γ, suggesting that the observed coarsening does not result in a genuine ordered
We deal with the solution of the systems of linear algebraic equations arising from Symmetric Interior Penalty discontinuous Galerkin (SIPG) discretization of linear elasticity problems in primal (displacement) formulation. The main focus... more
We deal with the solution of the systems of linear algebraic equations arising from Symmetric Interior Penalty discontinuous Galerkin (SIPG) discretization of linear elasticity problems in primal (displacement) formulation. The main focus of the paper is on constructing a uniform preconditioner which is based on a natural splitting of the space of piecewise linear discontinuous functions. The presented approach has recently been introduced in [2] in the context of designing subspace correction methods for scalar elliptic partial differential equations and is extended here to linear elasticity equations, i.e., a class of vector field problems. Similar to the scalar case the solution of the linear algebraic system corresponding to the SIPG method is reduced to the solution of a problem arising from discretization by nonconforming Crouzeix-Raviart elements plus the solution of a well-conditioned problem on the complementary space.
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Grigorova, N., Zh. Ivanova, E. Dichlianova, T. Georgieva, T. Slavov, E. Vachkova & I. Penchev Georgiev, 2015. The effect of antioxidant treatment on blood lactate and pyruvate concentrations in a rabbit model of obesity. Bulg. J. Vet.... more
Grigorova, N., Zh. Ivanova, E. Dichlianova, T. Georgieva, T. Slavov, E. Vachkova & I. Penchev Georgiev, 2015. The effect of antioxidant treatment on blood lactate and pyruvate concentrations in a rabbit model of obesity. Bulg. J. Vet. Med. (online first). In the current study, the impact of dietary antioxidant supplementation on fasting blood lactate and pyruvate concentrations in a rabbit model of obesity was investigated. A total of 26 rabbits were randomly divided into 3 groups: castrated and obese animals (CO, n=7); castrated, obese and treated with antioxidants (Immunoprotect, n=7, CIm) and non-castrated, non-treated controls (NC, n=12). At the end of the 2-month treatment period blood lactate concentration, lactate to pyruvate and lactate to glucose ratio in CIm were significantly (P<0.05) lower than in NC and tended to be lower than in CO. No group differences in pyruvate and glucose concentrations were found. There was a significant negative (r =–0.53; P<0.05) correlat...
ABSTRACT The structure of the honeycomb-like three-dimensional networks formed on self-assembly of the tetradentate ligand 1,2-bis(5′-dipyrimidyl)ethyne with copper (I) iodide and copper (I) bromide are presented.
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... Rannacher-Turek FE Problems; Additive and Multiplicative Methods Ivan Georgiev1, Johannes Kraus2, and Svetozar Margenov3 1 Institute of Mathematics and Informatics and Institute for Parallel Processing, Bulgarian Academy of Sciences,... more
... Rannacher-Turek FE Problems; Additive and Multiplicative Methods Ivan Georgiev1, Johannes Kraus2, and Svetozar Margenov3 1 Institute of Mathematics and Informatics and Institute for Parallel Processing, Bulgarian Academy of Sciences, Acad. G. Bonchev Bl. ...
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The cytokine macrophage migration inhibitory factor (MIF) plays a critical role in inflammatory diseases and atherogenesis. We identify the chemokine receptors CXCR2 and CXCR4 as functional receptors for MIF. MIF triggered G(alphai)- and... more
The cytokine macrophage migration inhibitory factor (MIF) plays a critical role in inflammatory diseases and atherogenesis. We identify the chemokine receptors CXCR2 and CXCR4 as functional receptors for MIF. MIF triggered G(alphai)- and integrin-dependent arrest and chemotaxis of monocytes and T cells, rapid integrin activation and calcium influx through CXCR2 or CXCR4. MIF competed with cognate ligands for CXCR4 and CXCR2 binding, and directly bound to CXCR2. CXCR2 and CD74 formed a receptor complex, and monocyte arrest elicited by MIF in inflamed or atherosclerotic arteries involved both CXCR2 and CD74. In vivo, Mif deficiency impaired monocyte adhesion to the arterial wall in atherosclerosis-prone mice, and MIF-induced leukocyte recruitment required Il8rb (which encodes Cxcr2). Blockade of Mif but not of canonical ligands of Cxcr2 or Cxcr4 in mice with advanced atherosclerosis led to plaque regression and reduced monocyte and T-cell content in plaques. By activating both CXCR2 a...
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In this paper algebraic two-level and multilevel preconditioning algorithms for second order elliptic boundary value problems are constructed, where the discretization is done using Rannacher-Turek non-conforming rotated trilinear finite... more
In this paper algebraic two-level and multilevel preconditioning algorithms for second order elliptic boundary value problems are constructed, where the discretization is done using Rannacher-Turek non-conforming rotated trilinear finite elements. An important point to make is that in this case the finite element spaces corresponding to two successive levels of mesh refinement are not nested in general. To handle this,
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We study the behavior of the CBS constant as a quality measure for hierarchical two-level splittings of quadratic FEM stiffness matrices. The article is written in the spirit of [3] where the focus is on the robustness with respect to... more
We study the behavior of the CBS constant as a quality measure for hierarchical two-level splittings of quadratic FEM stiffness matrices. The article is written in the spirit of [3] where the focus is on the robustness with respect to mesh and coefficient anisotropy. The considered splittings are: Differences and Aggregates (DA); First Reduce (FR); and hierarchical P-decomposition (P). The presented results show sufficient conditions for the existence of optimal order Algebraic MultiLevel Iteration (AMLI) preconditioners.
Downloadable! The purpose of this paper is to show the way for increasing the local capacity for public discussion in the sphere of environmental protection in the municipalities of South East part of Bulgaria. Target groups are... more
Downloadable! The purpose of this paper is to show the way for increasing the local capacity for public discussion in the sphere of environmental protection in the municipalities of South East part of Bulgaria. Target groups are representatives of local authorities, municipal administrations ...
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In this study we demonstrate how some different techniques which were introduced and studied in previous works by the authors can be integrated and extended in the construction of efficient algebraic multilevel iteration methods for more... more
In this study we demonstrate how some different techniques which were introduced and studied in previous works by the authors can be integrated and extended in the construction of efficient algebraic multilevel iteration methods for more complex problems. We devise an optimal order algorithm for solving linear systems obtained from locking-free discretization of 3D pure displacement elasticity problems. The presented
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This paper estimates the effect of diversification on farm effectiveness through modelling using data from the National Statistical Institute of Bulgaria. The estimation of the role of diversification in agriculture is similar to this in... more
This paper estimates the effect of diversification on farm effectiveness through modelling using data from the National Statistical Institute of Bulgaria. The estimation of the role of diversification in agriculture is similar to this in corporate firms. The results show ...
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ABSTRACT New results on preconditioning of the rotated multilinear non-conforming finite element method (FEM) applied to elliptic systems in the case of mesh anisotropy are presented. The stiffness matrix is first approximated by a proper... more
ABSTRACT New results on preconditioning of the rotated multilinear non-conforming finite element method (FEM) applied to elliptic systems in the case of mesh anisotropy are presented. The stiffness matrix is first approximated by a proper auxiliary M-matrix, and then modified incomplete factorization MIC(0) with perturbation is applied. The derived condition number estimates and the presented numerical tests illustrate well the dependency of the preconditioned conjugate gradient iterations on the anisotropy ratio.
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Chapter 6 Role of colostrum and milk components in the development of the intestine structure and function in calves 1 1 Studies have been supported by the Swiss National Science Foundation, CH-Berne (Grants No. 32.30188.90, 32.36140.92, 32–49729.96, 32.051012.97, 32–56823.99 and 32–59311.99), th...more
The ability to digest colostrum and milk requires specific structures and functions of the gastrointestinal tract (GIT). Colostrum composition exhibits major changes after the onset of lactation. Nutrient and non-nutrient substances can... more
The ability to digest colostrum and milk requires specific structures and functions of the gastrointestinal tract (GIT). Colostrum composition exhibits major changes after the onset of lactation. Nutrient and non-nutrient substances can modify gastrointestinal development and function. The chapter summarizes recent data on colostrum feeding, colostrum extracts, and insulin-like growth factor-I (IGF1) on the small intestine and colon in neonatal calves during the first week of life. The small and large intestine is characterized by several layers of cells with different functions and interactions. The epithelial cell layer in the small intestine consists of a single layer of cells that lines the crypts and covers the villi. Ingestion of colostrum modifies GIT development and function, affects digestive enzyme activities and GI hormone systems, and absorptive capacity. Colostrum contains non-nutrient factors that counteract the influence of dexamethasone on the intestinal epithelial cells. Growth promoting peptides such as IGF-I retain their structure and function in the intestine because both the acid production and proteolytic activity in the neonatal abomasum are low and because factors are present in the colostrum that inhibits proteolysis.
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The somatotropic axis and insulin are involved in pre- and postnatal development. In pre- and full-term calves (GrPo and GrNo; born after 277 and 290 d of pregnancy, respectively) and in preterm calves on d 8 of life after being fed for 7... more
The somatotropic axis and insulin are involved in pre- and postnatal development. In pre- and full-term calves (GrPo and GrNo; born after 277 and 290 d of pregnancy, respectively) and in preterm calves on d 8 of life after being fed for 7 d (GrP8), we studied whether there are differences in the abundance of mes- senger RNA (mRNA) of
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Research Interests: Engineering, Game Theory, Population Dynamics, Predator-prey interaction, Stochastic processes, and 17 moreHumans, Computer Simulation, Mathematical Sciences, Lattice Beam Model, Animals, Lotka Volterra, Physical sciences, Nearest Neighbor, Ecosystem, Population Cycles, Survival Rate, Spatial structure, Biological clocks, Stochastic Model, Predatory Behavior, Food Chain, and Mean Field Theory
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ABSTRACT
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Changes in the serum creatine kinase (CK) activity were studied in 12 Black and White breed cows following single intramuscular (i.m.) injection of Tylovet-200 and Bromhexotylosin-2 (BHT-2) at a dose rate of 0.5 ml/kg. Individual blood... more
Changes in the serum creatine kinase (CK) activity were studied in 12 Black and White breed cows following single intramuscular (i.m.) injection of Tylovet-200 and Bromhexotylosin-2 (BHT-2) at a dose rate of 0.5 ml/kg. Individual blood samples were collected from the jugular vein at 0 (pre- dose) and 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 24, and 48 h after dosing. It was established a time dependent moderate elevation of the serum CK activity after treatment with both tylosin products, reaching peak values at 12 h post-dose. The i.m. injection of BHT-2 caused a more intensive increase of serum CK levels, but it was not statistically significant compared to the effect of Tylovet-200.
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Research Interests: Monte Carlo Simulation, Statistical Physics, Numerical Simulation, Mathematical Sciences, Lotka Volterra, and 10 morePhysical sciences, Population Density, Phase transition, Oscillations, Population Cycles, Initial Condition, Mean Field Theory, Population dynamic, Degree of Freedom, and PACS numbers
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ABSTRACT The article concerns subrecursive computability of real numbers. Certain significant real numbers are shown to be M2-computable, and the set of the M2-computable real numbers is shown to be closed under the elementary functions... more
ABSTRACT The article concerns subrecursive computability of real numbers. Certain significant real numbers are shown to be M2-computable, and the set of the M2-computable real numbers is shown to be closed under the elementary functions of calculus.
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... For the stronger hydrogen bondthedistanceN(2) O(4)andN(2) H(40)are 2.628 and 1.519 ˚A respectively with a bond an-gleN(2) H(40) O(4)of171.45 ◦ . ... 11. Barbour, L.; Atwood, JA Cryst. Growth Design 2003, 3, 3. 12. Farrugia, LJ J.... more
... For the stronger hydrogen bondthedistanceN(2) O(4)andN(2) H(40)are 2.628 and 1.519 ˚A respectively with a bond an-gleN(2) H(40) O(4)of171.45 ◦ . ... 11. Barbour, L.; Atwood, JA Cryst. Growth Design 2003, 3, 3. 12. Farrugia, LJ J. Appl. Crystallogr. 1997, 30, 565.