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2008

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Articles 421 - 450 of 585

Full-Text Articles in Mathematics

Posner´S Second Theorem And An Annihilator Condition With Generalized Derivations, Vincenzo De Filippis Jan 2008

Posner´S Second Theorem And An Annihilator Condition With Generalized Derivations, Vincenzo De Filippis

Turkish Journal of Mathematics

Let R be a prime ring of characteristic different from 2, with extended centroid C, U its two-sided Utumi quotient ring, \delta\neq 0 a non-zero generalized derivation of R, f(x_1,..,x_n) a non-central multilinear polynomial over C in n non-commuting variables, a \in R such that a[\delta(f(r_1,..,r_n)),f(r_1,..,r_n)]=0, for any r_1,..,r_n \in R. Then one of the following holds: 1. a=0; 2. there exists \lambda \in C such that \delta(x)=\lambda x, for all x \in R; 3. there exist q \in U and \lambda \in C such that \delta(x)=(q+\lambda)x+xq, for all x\in R, and f(x_1,..,x_n)^2 is central valued on R.

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Diametral Dimension And Köthe Spaces, Tosun Terzi̇oğlu Jan 2008

Diametral Dimension And Köthe Spaces, Tosun Terzi̇oğlu

Turkish Journal of Mathematics

We generalize some well-known results about the diametral dimension of classical Köthe spaces

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Metric Trees, Hyperconvex Hulls And Extensions, Asuman G. Aksoy, B. Maurizi Jan 2008

Metric Trees, Hyperconvex Hulls And Extensions, Asuman G. Aksoy, B. Maurizi

Turkish Journal of Mathematics

In this paper we examine the relationship between hyperconvex hulls and metric trees. After providing a linking construction for hyperconvex spaces, we show that the four-point property is inherited by the hyperconvex hull, which leads to the theorem that every complete metric tree is hyperconvex. We also consider some extension theorems for these spaces.

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Basic Properties And Multipliers Space On L^{1}(G)\Cap L(P,Q)(G) Spaces, İlker Eryilmaz, Cenap Duyar Jan 2008

Basic Properties And Multipliers Space On L^{1}(G)\Cap L(P,Q)(G) Spaces, İlker Eryilmaz, Cenap Duyar

Turkish Journal of Mathematics

Let G be locally compact Abelian group with Haar measure. First is discussed some properties of L^{1}(G) \cap L(p,q)(G) spaces. Then is mentioned the multipliers space on L^{1}(G) \cap L(p,q) (G) spaces.

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On The Distribution Of Random Dirichlet Series In The Whole Plane, Qiyu Jin, Daochun Sun Jan 2008

On The Distribution Of Random Dirichlet Series In The Whole Plane, Qiyu Jin, Daochun Sun

Turkish Journal of Mathematics

For some random Dirichlet series of order(R) infinite almost surely, every horizontal line is a strong Borel line of order(R) infinite and without exceptional Little functions.

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Lyapunov-Type Inequalities For Certain Nonlinear Systems On Time Scales, Mehmet Ünal, Devri̇m Çakmak Jan 2008

Lyapunov-Type Inequalities For Certain Nonlinear Systems On Time Scales, Mehmet Ünal, Devri̇m Çakmak

Turkish Journal of Mathematics

In this study, we prove Lyapunov-type inequalities for certain nonlinear systems on an arbitrary time scale T by using elementary time scale calculus. These inequalities enable us to obtain a criterion of disconjugacy for such systems. Special cases of our results contain the classical Lyapunov inequality for both differential and difference equations.

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On Some Algebraic Properties Of Semi-Discrete Hyperbolic Type Equations, İsmagi̇l Habibullin, Asli Pekcan, Natalya Zheltukhina Jan 2008

On Some Algebraic Properties Of Semi-Discrete Hyperbolic Type Equations, İsmagi̇l Habibullin, Asli Pekcan, Natalya Zheltukhina

Turkish Journal of Mathematics

Nonlinear semi-discrete equations of the form t_x(n+1) = f(t(n), t(n+1), t_x(n)) are studied. An adequate algebraic formulation of the Darboux integrability is discussed and an attempt to adopt this notion to the classification of Darboux integrable chains has been undertaken.

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On Certain Type Of Modular Sequence Spaces, Manjul Gupta, Shesadev Pradhan Jan 2008

On Certain Type Of Modular Sequence Spaces, Manjul Gupta, Shesadev Pradhan

Turkish Journal of Mathematics

In this paper we consider a particular type of modular sequence spaces defined with the help of a given sequence \alpha = {\alpha_n} of strictly positive real numbers \alpha_n's and an Orlicz function M. Indeed, if we define M_n(x) = M(\alpha_nx) and \tildeM_n(x)=M(x/\alpha_n), x\in[0, \infty), we consider the modular sequence spaces l{M_n} and l{\tildeM_n}, denoted by l_M^{\alpha} and l_{\alpha}^M respectively. These are known to be BK-spaces and if M satisfies \Delta_2-condition, they are AK-spaces as well. However, if we consider the spaces l_{\alpha}^M and l_n^{\alpha} corresponding to two complementary Orlicz functions M and N satisfying \Delta_2-condition, they are perfect sequence …

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On Generalized Solution Of A Class Of Higher Order Operator-Differential Equations, Rovshan Z. Gumbataliev Jan 2008

On Generalized Solution Of A Class Of Higher Order Operator-Differential Equations, Rovshan Z. Gumbataliev

Turkish Journal of Mathematics

In this paper the sufficient conditions on the existence and uniqueness of a generalized solution on the axis are obtained for higher order operator-differential equations, the main part of which is multi characteristic.

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Killing And Geodesic Lightlike Hypersurfaces Of Indefinite Sasakian Manifolds, Fortune Massamba Jan 2008

Killing And Geodesic Lightlike Hypersurfaces Of Indefinite Sasakian Manifolds, Fortune Massamba

Turkish Journal of Mathematics

In this paper, we study a lightlike hypersurface of indefinite Sasakian manifold, tangent to the structure vector field \xi. Theorems on parallel and Killing distributions are obtained. Necessary and sufficient conditions have been given for lightlike hypersurface to be mixed totally geodesic, D-totally geodesic, D\perp-totally geodesic and D'-totally geodesic. We prove that, if the screen distribution of lightlike hypersurface M of indefinite Sasakian manifold is totally umbilical, the D\perp-geodesibility of M is equivalent to the D\perp-parallelism of the distribution T M^\perp of rank 1 (Theorem \ref{Theoscre}). Finally, we give the D\perp-version (Theorem 4.22) of the Theorem 2.2 ([11], page 88).

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A Condition For Warped Product Semi-Invariant Submanifolds To Be Riemannian Product Semi-Invariant Submanifolds In Locally Riemannian Product Manifolds, Mehmet Atçeken Jan 2008

A Condition For Warped Product Semi-Invariant Submanifolds To Be Riemannian Product Semi-Invariant Submanifolds In Locally Riemannian Product Manifolds, Mehmet Atçeken

Turkish Journal of Mathematics

In this article, we give a necessary and sufficient condition for warped product semi-invariant submanifolds to be Riemannian product semi-invariant submanifolds in a locally Riemannian product manifold whose factor manifolds are real space form.

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Rickart-Type Annihilator Conditions On Formal Power Series, Ebrahim Hashemi Jan 2008

Rickart-Type Annihilator Conditions On Formal Power Series, Ebrahim Hashemi

Turkish Journal of Mathematics

Let R be an \alpha-rigid ring and R_0[[x;\alpha]] be the nearring of a formal skew power series in which addition and substitution are used as operations. It is shown that R is Rickart and any countable family of idempotents of R has a join in I(R) if and only if R_0[[x;\alpha]]\in R_{r1} if and only if R_0[[x;\alpha]]\in R_{\ell 1} if and only if R_0[[x;\alpha]]\in qR_{r2}. An example to show that, \alpha-rigid condition on R is not superfluous, is provided.

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Dual Quaternions In Spatial Kinematics In An Algebraic Sense, Bedi̇a Akyar Jan 2008

Dual Quaternions In Spatial Kinematics In An Algebraic Sense, Bedi̇a Akyar

Turkish Journal of Mathematics

This paper presents the finite spatial displacements and spatial screw motions by using dual quaternions and Hamilton operators. The representations are considered as 4 \times 4 matrices and the relative motion for three dual spheres is considered in terms of Hamilton operators for a dual quaternion. The relation between Hamilton operators and the transformation matrix has been given in a different way. By considering operations on screw motions, representation of spatial displacements is also given.

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Certain Rings Whose Simple Singular Modules Are Nil-Injective, Junchao Wei Jan 2008

Certain Rings Whose Simple Singular Modules Are Nil-Injective, Junchao Wei

Turkish Journal of Mathematics

In this paper, we first study some characterizations of left min-abel ring, strongly left min-abel ring and left MC2 ring. Next, we discuss and generalize some well known results for a ring whose simple singular left modules are nil- injective. Finally, as a byproduct of these results we are able to show that if R is a left GMC2 left Goldie ring whose every simple singular left R - module is YJ- injective, then R is a finite product of simple left Goldie ring.

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A Numerical Solution Of Wave Equation Arising In Non-Homogeneous Cylindrical Shells, Allaberen Ashyralyev, Mehmet Emi̇r Köksal Jan 2008

A Numerical Solution Of Wave Equation Arising In Non-Homogeneous Cylindrical Shells, Allaberen Ashyralyev, Mehmet Emi̇r Köksal

Turkish Journal of Mathematics

A numerical solution of wave equation arising in non-homogeneous cylindrical shells\ is considered. Stable numerical schemes are developed. The stability estimates for the solution of these difference schemes and first and second order difference derivatives are presented. Applying the difference schemes, the numerical methods are proposed for solving the the given initial-boundary value problem.

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Sufficient Conditions For The Lp-Equivalence Between Two Nonlinear Impulse Differential Equations, A. Georgieva, S. Kostadinov Jan 2008

Sufficient Conditions For The Lp-Equivalence Between Two Nonlinear Impulse Differential Equations, A. Georgieva, S. Kostadinov

Turkish Journal of Mathematics

Sufficient conditions for the Lp-equivalence between two nonlinear impulse differential equations with unbounded linear parts and possibly unbounded nonlinearity parts are given. An example of two nonlinear impulse differential parabolic equations is considered.

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On Pseudo-Inverses Of Fredholm Operators, Christoph Schmoeger Jan 2008

On Pseudo-Inverses Of Fredholm Operators, Christoph Schmoeger

Turkish Journal of Mathematics

Suppose that A is a Fredholm operator on a Banach space. We prove that A has index =0 (resp. >= 0, resp. Keywords: Fredholm operator, pseudo-inverse

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Essential Spectra Of Composition Operators On The Space Of Bounded Analytic Functions, Uğur Gül Jan 2008

Essential Spectra Of Composition Operators On The Space Of Bounded Analytic Functions, Uğur Gül

Turkish Journal of Mathematics

In this small note we characterize the essential spectra of a class of composition operators on H^{\infty}(H) of the upper half-plane H and on H^{\infty}(D) of the unit disc D. These composition operators are induced by perturbations of translations

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Length Bias In The Measurements Of Carbon Nanotubes, Paul H. Kvam Jan 2008

Length Bias In The Measurements Of Carbon Nanotubes, Paul H. Kvam

Department of Math & Statistics Faculty Publications

To measure carbon nanotube lengths, atomic force microscopy and special software are used to identify and measure nanotubes on a square grid. Current practice does not include nanotubes that cross the grid, and, as a result, the sample is length-biased. The selection bias model can be demonstrated through Buffon’s needle problem, extended to general curves that more realistically represent the shape of nanotubes observed on a grid. In this article, the nonparametric maximum likelihood estimator is constructed for the length distribution of the nanotubes, and the consequences of the length bias are examined. Probability plots reveal that the corrected length …

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Degradation Models, Suk Joo Bae, Paul H. Kvam Jan 2008

Degradation Models, Suk Joo Bae, Paul H. Kvam

Department of Math & Statistics Faculty Publications

Reliability testing typically generates product lifetime data, but for some tests, covariate information about the wear and tear on the product during the life test can provide additional insight into the product’s lifetime distribution. This usage, or degradation, can be the physical parameters of the product (e.g., corrosion thickness on a metal plate) or merely indicated through product performance (e.g., the luminosity of a light emitting diode). The measurements made across the product’s lifetime are degradation data, and degradation analysis is the statistical tool for providing inference about the lifetime distribution from the degradation data.

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Load Sharing Models, Paul H. Kvam, Jye-Chyi Lu Jan 2008

Load Sharing Models, Paul H. Kvam, Jye-Chyi Lu

Department of Math & Statistics Faculty Publications

Consider a system of components whose lifetimes are governed by a probability distribution. Load sharing refers to a model of stochastic interdependency between components that operate within a system. If components are set up in a parallel system (see Parallel, Series, and Series–Parallel Systems) for example, the system survives as long as at least one component is operating. In a typical load-sharing system, once a component fails, the remaining components suffer an increase in failure rate due to the extra “load” they must encumber due to the failed component.

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Indestructible Blaschke Products, William T. Ross Jan 2008

Indestructible Blaschke Products, William T. Ross

Department of Math & Statistics Faculty Publications

No abstract provided.

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Algorithm-Independent Optimal Input Fluxes For Boundary Identification In Thermal Imaging, Kurt Bryan, Lester Caudill Jan 2008

Algorithm-Independent Optimal Input Fluxes For Boundary Identification In Thermal Imaging, Kurt Bryan, Lester Caudill

Department of Math & Statistics Faculty Publications

An inverse boundary determination problem for a parabolic model, arising in thermal imaging, is considered. The focus is on intelligently choosing an effective input heat flux, so as to maximize the practical effectiveness of an inversion algorithm. Three different methods, based on different interpretations of the term “effective", are presented and analyzed, then demonstrated through numerical examples. It is noteworthy that each of these flux-selection methods is independent of the particular inversion algorithm to be used.

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The Bar-Natan Skein Module Of The Solid Torus And The Homology Of (N,N) Springer Varieties, Heather M. Russell Jan 2008

The Bar-Natan Skein Module Of The Solid Torus And The Homology Of (N,N) Springer Varieties, Heather M. Russell

Department of Math & Statistics Faculty Publications

This paper establishes an isomorphism between the Bar-Natan skein module of the solid torus with a particular boundary curve system and the homology of the (n, n) Springer variety. The results build on Khovanov's work with crossingless matchings and the cohomology of the (n, n) Springer variety. We also give a formula for comultiplication in the Bar-Natan skein module for this specific three-manifold and boundary curve system.

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Empirical Bayes And Hierarchical Bayes Estimation Of Skew Normal Populations, Naveen K. Bansal, Mehdi Maadooliat, Xiaowei Wang Jan 2008

Empirical Bayes And Hierarchical Bayes Estimation Of Skew Normal Populations, Naveen K. Bansal, Mehdi Maadooliat, Xiaowei Wang

Mathematics, Statistics and Computer Science Faculty Research and Publications

We develop empirical and hierarchical Bayesian methodologies for the skew normal populations through the EM algorithm and the Gibbs sampler. A general concept of skewness to the normal distribution is considered throughout. Motivations are given for considering the skew normal population in applications, and an example is presented to demonstrate why the skew normal distribution is more applicable than the normal distribution for certain applications.

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Pathos: Pervasive At Home Sleep Monitoring, Ian Obermiller, Sheikh Iqbal Ahamed Jan 2008

Pathos: Pervasive At Home Sleep Monitoring, Ian Obermiller, Sheikh Iqbal Ahamed

Mathematics, Statistics and Computer Science Faculty Research and Publications

Sleeping disorders affect a large percentage of the population, and many of them go undiagnosed each year because the method of diagnosis is to stay overnight at a sleep center. Because pervasive technologies have become so prevalent and affordable, sleep monitoring is no longer confined to a permanent installation, and can therefore be brought directly into the user home. We present a unique solution to the problem of home sleep monitoring that has the possibility to take the place of and expand on the data from a sleep center. PATHOS focuses not only on analyzing patterns during the night, but …

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Characterization Of Digraphs With Equal Domination Graphs And Underlying Graphs, Kim A. S. Factor, Larry J. Langley Jan 2008

Characterization Of Digraphs With Equal Domination Graphs And Underlying Graphs, Kim A. S. Factor, Larry J. Langley

Mathematics, Statistics and Computer Science Faculty Research and Publications

A domination graph of a digraph D , dom(D)dom(D), is created using the vertex set of D and edge {u,v}∈E[dom(D)]{u,v}∈E[dom(D)] whenever (u,z)∈A(D)(u,z)∈A(D) or (v,z)∈A(D)(v,z)∈A(D) for every other vertex z∈V(D)z∈V(D). The underlying graph of a digraph DD, UG(D)UG(D), is the graph for which D is a biorientation. We completely characterize digraphs whose underlying graphs are identical to their domination graphs, UG(D)=dom(D)UG(D)=dom(D). The maximum and minimum number of single arcs in these digraphs, and their characteristics, is given.

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Order Restricted Inference For Comparing The Cumulative Incidence Of A Competing Risk Over Several Populations, Hammou El Barmi, Subhash C. Kochar, Hari Mukerjee Jan 2008

Order Restricted Inference For Comparing The Cumulative Incidence Of A Competing Risk Over Several Populations, Hammou El Barmi, Subhash C. Kochar, Hari Mukerjee

Mathematics and Statistics Faculty Publications and Presentations

There is a substantial literature on testing for the equality of the cumulative incidence functions associated with one specific cause in a competing risks setting across several populations against specific or all alternatives. In this paper we propose an asymptotically distribution-free test when the alternative is that the incidence functions are linearly ordered, but not equal. The motivation stems from the fact that in many examples such a linear ordering seems reasonable intuitively and is borne out generally from empirical observations. These tests are more powerful when the ordering is justified. We also provide estimators of the incidence functions under …

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Polynomial Extension Operators. Part I, Leszek Demkowicz, Jay Gopalakrishnan, Joachim Schöberl Jan 2008

Polynomial Extension Operators. Part I, Leszek Demkowicz, Jay Gopalakrishnan, Joachim Schöberl

Mathematics and Statistics Faculty Publications and Presentations

In this series of papers, we construct operators that extend certain given functions on the boundary of a tetrahedron into the interior of the tetrahedron, with continuity properties in appropriate Sobolev norms. These extensions are novel in that they have certain polynomial preservation properties important in the analysis of high order finite elements. This part of the series is devoted to introducing our new technique for constructing the extensions, and its application to the case of polynomial extensions from H½(∂K) into H¹(K), for any tetrahedron K.

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A Mixed Method For Axisymmetric Div-Curl Systems, Dylan M. Copeland, Jay Gopalakrishnan, Joseph E. Pasciak Jan 2008

A Mixed Method For Axisymmetric Div-Curl Systems, Dylan M. Copeland, Jay Gopalakrishnan, Joseph E. Pasciak

Mathematics and Statistics Faculty Publications and Presentations

We present a mixed method for a three-dimensional axisymmetric div-curl system reduced to a two-dimensional computational domain via cylindrical coordinates. We show that when the meridian axisymmetric Maxwell problem is approximated by a mixed method using the lowest order Nédélec elements (for the vector variable) and linear elements (for the Lagrange multiplier), one obtains optimal error estimates in certain weighted Sobolev norms. The main ingredient of the analysis is a sequence of projectors in the weighted norms satisfying some commutativity properties.

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