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Articles 31 - 60 of 212
Full-Text Articles in Physical Sciences and Mathematics
Comparing Open Book And Heegaard Decompositions Of 3-Manifolds, J. Hyam Rubinstein
Comparing Open Book And Heegaard Decompositions Of 3-Manifolds, J. Hyam Rubinstein
Turkish Journal of Mathematics
We study the maximal value of the Euler characteristic of the pages of all open book decompositions of closed orientable 3-manifolds. In particular, we describe some examples where the minimal genus Heegaard splittings of such 3-manifolds give rise to open book decompositions and other examples where the simplest open book decomposition has larger maximal Euler characteristic of pages than the smallest genus Heegaard splittings. Also, special properties of the Heegaard splitting associated to an open book decomposition are given. Techniques of minimal surface theory and hyperbolic geometry are shown to be useful for such problems.
Abelian Fibred Holomorphic Symplectic Manifolds, Justin Sawon
Abelian Fibred Holomorphic Symplectic Manifolds, Justin Sawon
Turkish Journal of Mathematics
We study holomorphic symplectic manifolds which are fibred by abelian varieties. This structure is a higher dimensional analogue of an elliptic fibration on a K3 surface. We investigate when a holomorphic symplectic manifold is fibred in this way, and are led to several natural conjectures. We then study the geometry of these fibrations. The expectation is that this point of view will prove useful in understanding holomorphic symplectic manifolds, and possibly lead to a classification.
Symplectic Surgeries From Singularities, Ivan Smith, Richard Thomas
Symplectic Surgeries From Singularities, Ivan Smith, Richard Thomas
Turkish Journal of Mathematics
We describe a variety of symplectic surgeries (not a priori compatible with Kaehler structures) which are obtained by combining local Kaehler degenerations and resolutions of singularities. The effect of the surgeries is to replace configurations of Lagrangian spheres with symplectic submanifolds. We discuss several examples in detail, relating them to existence questions for symplectic manifolds with c_1 > 0, c_1 = 0, c_1 < 0 in four and six dimensions.
Some Asymptotic Results For The Semi-Markovian Random Walk With A Special Barrier, Tahi̇r Khani̇yev
Some Asymptotic Results For The Semi-Markovian Random Walk With A Special Barrier, Tahi̇r Khani̇yev
Turkish Journal of Mathematics
In this study, the semi-Markovian random walk with a special barrier (X(t)) is considered and under some weak assumptions the ergodicity of this process is discussed. Moreover, the characteristic function of ergodic distribution of X(t) is given by using a joint distribution of random variables N and Y_{N} and some exact formulas for the first and second moments of ergodic distribution of the process X(t) are obtained. Based on these results, the asymptotic behaviours of expectation and variance of this process are investigated as S-s \to \infty . It is finally proved that the ergodic distribution of the process is …
Boundary Points Of Self-Affine Sets In R, İbrahi̇m Kirat
Boundary Points Of Self-Affine Sets In R, İbrahi̇m Kirat
Turkish Journal of Mathematics
Let A be an n \times n expanding matrix with integer entries and D = \{0, d_1, ... , d_{N-1} \} \subseteq {\Bbb{Z}}^n be a set of N distinct vectors, called an N-digit set. The unique non-empty compact set T = T(A,D) satisfying AT = T + D is called a self-affine set. If T has positive Lebesgue measure, it is called a self-affine region. In general, it is not clear how to determine a point to be on the boundary of a self-affine region. In this note, we consider one-dimensional self-affine regions T and present a simple approach to …
On Lightlike Hypersurfaces Of A Semi-Riemannian Space Form, Rifat Güneş, Bayram Şahi̇n, Erol Kiliç
On Lightlike Hypersurfaces Of A Semi-Riemannian Space Form, Rifat Güneş, Bayram Şahi̇n, Erol Kiliç
Turkish Journal of Mathematics
In this paper, we study a Lightlike hypersurface of a semi-Riemann manifold. We show that a lightlike hypersurface is totally geodesic if and only if it is locally symmetric. Also, we show that a lightlike Hypersurface of IR_{4q}^{4m}(m,q > 1) is totally geodesic under some restrictions. Finally, we give some results on Ricci curvature of a lightlike hypersurface to be symmetric.
On Pseudohyperbolical Curves In Minkowski Space-Time, Çeti̇n Camci, Kazim İlarslan, Emilija Sucurovic
On Pseudohyperbolical Curves In Minkowski Space-Time, Çeti̇n Camci, Kazim İlarslan, Emilija Sucurovic
Turkish Journal of Mathematics
In this paper, we characterize all spacelike, timelike and null curves lying on the pseudohyperbolic space H_0^3 in the Minkowski space--time E_1^4. Moreover, we prove that there are no timelike and no null curves lying on the pseudohyperbolic space H_0^3 in Minkowski space--time E_1^4.
On Prime Submodules Of Finitely Generated Free Modules, Di̇lek Pusat Yilmaz
On Prime Submodules Of Finitely Generated Free Modules, Di̇lek Pusat Yilmaz
Turkish Journal of Mathematics
The aim of this work is to investigate prime submodules of finitely generated free modules over commutative domains in some special cases.
Groups Whose Proper Subgroups Are Hypercentral Of Length At Most \Leq \Omega, Selami̇ Ercan
Groups Whose Proper Subgroups Are Hypercentral Of Length At Most \Leq \Omega, Selami̇ Ercan
Turkish Journal of Mathematics
Groups, all proper subgroups of which are hypercentral of length at most \omega and every proper subgroup of which is a B_{n}-group for a natural number n depending on the subgroup, are studied in this article.
Automorphism Groups Of (M-1)-Surfaces With The M-Property, Adnan Melekoğlu
Automorphism Groups Of (M-1)-Surfaces With The M-Property, Adnan Melekoğlu
Turkish Journal of Mathematics
A compact Riemann surface X of genus g is called an (M-1)-surface if it admits an anticonformal involution that fixes g simple closed curves, the second maximum number by Harnack's theorem. If X also admits an automorphism of order g which cyclically permutes these g curves, then we shall call X an (M-1)-surface with the M-property. In this paper we investigate the automorphism groups of (M-1)-surfaces with the M-property.
Fuzzy Ideals In Gamma-Rings, Mehmet Ali̇ Öztürk, Mustafa Uçkun, Young Bae Jun
Fuzzy Ideals In Gamma-Rings, Mehmet Ali̇ Öztürk, Mustafa Uçkun, Young Bae Jun
Turkish Journal of Mathematics
The converse of [7, Theorem 3.3] is provided. For an Artinian \Gamma-ring, a few results are investigated.
On The Weak-Integrity Of Trees, Alpay Kirlangiç
On The Weak-Integrity Of Trees, Alpay Kirlangiç
Turkish Journal of Mathematics
In this paper the concept of {\em weak-integrity} is introduced as a new measure of the stability of a graph \( G \) and it is defined as I_{w}(G)={\min_{S\subset V(G)}\{ S +m_{e}(G-S)\}}, where m_{e}(G-S) denotes the number of edges of a largest component of G-S. We investigate the weak-integrity of trees and compute the weak-integrity of a binomial tree and all the trees with at most 7 vertices. We also give some results about the weak-integrity of graphs obtained from binary operations.
On Invariant Submanifolds Of Riemannian Warped Product Manifold, Mehmet Atçeken, Bayram Şahi̇n, Erol Kiliç
On Invariant Submanifolds Of Riemannian Warped Product Manifold, Mehmet Atçeken, Bayram Şahi̇n, Erol Kiliç
Turkish Journal of Mathematics
In this paper, we generalize the geometry of the invariant submanifolds of Riemannian product manifold to the geometry of the invariant submanifolds of Riemannian warped product manifold. We investigate some properties of an invariant submanifolds of a Riemannian warped product manifold. We show that every invariant submanifold of the Riemannian warped product manifold is a Riemannian warped product manifold. Also, we give a theorem on the pseudo-umbilical invariant submanifold. Further, we obtain that integral manifolds on an invariant submanifold are curvature-invariant submanifolds. Finally, we give a necessary condititon on a totally umbilical invariant submanifold to be totally geodesic.
Uniqueness Of Primary Decompositions, Patrick F. Smith
Uniqueness Of Primary Decompositions, Patrick F. Smith
Turkish Journal of Mathematics
Uniqueness properties of primary decompositions in modules over non-commutative rings are presented.
On Intuitionistic Fuzzy Subhypernear-Rings Of Hypernear-Rings, Kyung Ho Kim
On Intuitionistic Fuzzy Subhypernear-Rings Of Hypernear-Rings, Kyung Ho Kim
Turkish Journal of Mathematics
In this paper, we introduce the concept of an intuitionistic fuzzy subhypernear-ring of a hypernear-ring and obtain some results in this connection.
Professor Masatoshi Gündüz Ikeda: A Life Devoted To Mathematics, Cemal Koç
Professor Masatoshi Gündüz Ikeda: A Life Devoted To Mathematics, Cemal Koç
Turkish Journal of Mathematics
No abstract provided.
On The Extended Hecke Groups \Overline{H}(\Lambda _Q), Ni̇hal Yilmaz Özgür, Recep Şahi̇n
On The Extended Hecke Groups \Overline{H}(\Lambda _Q), Ni̇hal Yilmaz Özgür, Recep Şahi̇n
Turkish Journal of Mathematics
Hecke groups H(\lambda _q) have been studied extensively for many aspects in the literature, [5], [8]. The Hecke group H(\lambda_3), the modular group PSL(2, \Bbb{Z} ) , has especially been of great interest in many fields of mathematics, for example number theory, automorphic function theory and group theory. In this paper we consider the extended Hecke groups \overline{H}(\lambda _q) which are defined analogously with the extended modular group. We find the conjugacy classes of torsion elements in \overline{H}(\lambda _q). Using this we give some results about the normal subgroups and Fuchsian subgroups of \overline{H}(\lambda _q).
On Positive Solutions Of Boundary Value Problems For Nonlinear Second Order Difference Equations, Nüket Aykut, Gusein Sh. Guseinov
On Positive Solutions Of Boundary Value Problems For Nonlinear Second Order Difference Equations, Nüket Aykut, Gusein Sh. Guseinov
Turkish Journal of Mathematics
In this paper we study nonlinear second order difference equations subject to separated linear boundary conditions. Sign properties of the associated Green's functions are investigated and existence results for positive solutions of the nonlinear boundary value problem are established. Upper and lower bounds for these positive solutions also are given.
On General Fibonacci Sequences In Groups, Engi̇n Özkan
On General Fibonacci Sequences In Groups, Engi̇n Özkan
Turkish Journal of Mathematics
In this paper, we have constituted 3-step general Fibonacci sequences in a nilpotent group with exponent p (p is a prime number) and nilpotency class 4 and given formulas to find the \alpha term of the sequence.
Rough Oscillatory Singular Integral Operators-Ii, Ahmad Al-Salman, Ali A. Al-Jarrah
Rough Oscillatory Singular Integral Operators-Ii, Ahmad Al-Salman, Ali A. Al-Jarrah
Turkish Journal of Mathematics
In this paper, we study certain classes of oscillatory singular integral operators with kernels in Llog L(S^{n-1}) which is known to be the most desirable size condition for the L^{p} boundedness to hold. We prove that such operators are bounded on L^{p}. Our results extend and improve previously known results. Variations of our approach in this paper can be applied to handle more general oscillatory singular integral operators. This concludes by indicating a variety of results that can be obtained.
An Analytical Model For Calculating Bounds On Call Blocking Probabilities In Leo Satellite Networks, A. Hali̇m Zai̇m
An Analytical Model For Calculating Bounds On Call Blocking Probabilities In Leo Satellite Networks, A. Hali̇m Zai̇m
Turkish Journal of Electrical Engineering and Computer Sciences
We present an analytical model for calculating upper and lower bounds for call-blocking probabilities in a LEO satellite network that carries voice calls. The method is especially useful for large systems where calculation of call-blocking probabilities are too expensive. Our method calculates upper and lower bounds very easily and produces fairly accurate results.
Resonant Demagnetization Pwm Forward Converter, B. Bi̇lgi̇n, Işik Çadirci, R. Ergül, M. Ermi̇ş
Resonant Demagnetization Pwm Forward Converter, B. Bi̇lgi̇n, Işik Çadirci, R. Ergül, M. Ermi̇ş
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a new approach to demagnetization process of a PWM forward converter (FC) is proposed. According to this approach, the demagnetization winding and diode of a conventional FC are removed, and an external capacitor is added in parallel with the secondary diode. This replacement changes the linear demagnetization process of a conventional FC into a resonant demagnetization process. The theoretical performance results of the proposed resonant demagnetization forward converter (RDFC) are compared with those of a conventional FC. A side by side comparison made between the two types of demagnetization strategies has shown that RDFC has some advantages …
Music, Cbf And Differential Algebraic Constant Modulus Algorithms For Direction Of Arrival Estimation In Passive Coherent Locators, Ahmet Özçeti̇n
Music, Cbf And Differential Algebraic Constant Modulus Algorithms For Direction Of Arrival Estimation In Passive Coherent Locators, Ahmet Özçeti̇n
Turkish Journal of Electrical Engineering and Computer Sciences
In passive coherent locators (PCL) systems, noise and the precision of direction of arrival (DOA) estimation are key issues. This paper addresses the implementation of high-resolution DOA estimation methods, in particular the multiple signal classification (MUSIC) algorithm, the conventional beam forming (CBF) algorithm, and the algebraic constant modulus algorithm (ACMA). The goal is to compare the ACMA to the MUSIC and CBF algorithms for application to PCL. The results and analysis presented here support the use of constant modulus information, where available, as an important addition to DOA estimation. The ACMA offers many simple solutions to noise and separation related …
A Full Adaptive Observer For Dc Servo Motors, Ata Sevi̇nç
A Full Adaptive Observer For Dc Servo Motors, Ata Sevi̇nç
Turkish Journal of Electrical Engineering and Computer Sciences
An adaptive observer estimating all parameters and load torque is proposed for DC servo motors. The observer uses no direct feedback but the adaptation schemes use current and speed measurements. Both the observer and adaptations are simple to implement for real-time applications. Simulation results are satisfactory for the full adaptive observer. If the observer works in parallel with only load torque and armature resistance adaptations, the results are very good even if very low-quality sensors are used. In this simulation, only a single hall sensor is used as a rotational transducer, which produces a single pulse per revolution, and very …
Design Of A Tem-Cell With Increased Usable Test Area, Kresimir Malaric, Juraj Bartolic
Design Of A Tem-Cell With Increased Usable Test Area, Kresimir Malaric, Juraj Bartolic
Turkish Journal of Electrical Engineering and Computer Sciences
Transversal electromagnetic mode cells (TEM-cells) are used for electromagnetic compatibility measurements (emission and immunity), and for biomedical applications. Over the years, higher and higher frequencies are being used, which demands smaller transmission structures in order to obtain the homogeneous field distribution due to resonance. Such resonance destroys the TEM field, introducing higher order modes. The goal was to design the TEM-cell for GSM frequencies that will have a larger area with a homogeneous field used for testing, while still obtaining the characteristic impedance. Commercial TEM-cells used for frequencies of 900 MHz have only 2 cm in height available for testing, …
A Digitally Controlled Drive System For Travelling-Wave Ultrasonic Motor, Güngör Bal
A Digitally Controlled Drive System For Travelling-Wave Ultrasonic Motor, Güngör Bal
Turkish Journal of Electrical Engineering and Computer Sciences
A digitally controlled drive system was implemented in this study to control the speed and direction of a travelling-wave ultrasonic motor. The drive system, based on a 2-phase voltage-fed high-frequency serial-resonant inverter, uses the mechanical resonant frequency of an ultrasonic motor. A TMS320F243 digital signal processor was used to control an ultrasonic motor drive system. The speed control of the ultrasonic motor was achieved with a driving frequency in the 41.3-43.3 kHz frequency range. The feasible evaluations of the proposed drive and control system were tested by experiments. Experimental results demonstrated that the proposed drive and control system is flexible …
Initiatory Electrons In Compressed Gases In Positive Polarity, Mohammed Messaad, Mustapha Tioursi
Initiatory Electrons In Compressed Gases In Positive Polarity, Mohammed Messaad, Mustapha Tioursi
Turkish Journal of Electrical Engineering and Computer Sciences
This paper deals with the nature of seed electron sources in compressed N_2 for positive polarity. We present an experimental procedure that provides evidence of the fact that collisional detachment from negative ions plays the most important role in the supply of seed electrons. Conditioning phenomena in compressed SF_6, N_2 and air have been simulated under positive lightning impulses for point-plane geometry.
A New Simulator For Hvdc/Ac Systems-Part I, Baktiar Zangeneh, Abbas Shoulaie
A New Simulator For Hvdc/Ac Systems-Part I, Baktiar Zangeneh, Abbas Shoulaie
Turkish Journal of Electrical Engineering and Computer Sciences
A simulator with optimal step time (SOST) has been designed to investigate Large HVdc/ac systems. The adequacy and robustness of the simulator will be demonstrated by showing some important applications relevant to operation, operational planning and medium-term planing. Some of the features of our SOST simulator are optimal step time algorithm, interpolation, chatter removal, MATLAB interface, unlimited size of ac system, and Farsi command that help model complex power electronic circuits, provide fast and accurate results. On account of its reduced calculation effort and deterministic execution time, optimal-step simulation is a prerequisite for real-time performance. However, when simulating electromagnetic-transients behavior, …
Synthesis Of Some New Benzimidazole Carbamate Derivatives For Evaluation Of Antifungal Activity, Canan Kuş, Nurten Altanlar
Synthesis Of Some New Benzimidazole Carbamate Derivatives For Evaluation Of Antifungal Activity, Canan Kuş, Nurten Altanlar
Turkish Journal of Chemistry
The synthesis and structure elucidation of methyl 5(6)-fluoro-6(5)-substituted-1H-benzimidazole carbamate derivatives are performed and their antifungal activities evaluated against Candida albicans.
Timelike And Spacelike Ricci Collineation Vectors In String Fluid, Hüsnü Baysal, İhsan Yilmaz
Timelike And Spacelike Ricci Collineation Vectors In String Fluid, Hüsnü Baysal, İhsan Yilmaz
Turkish Journal of Physics
We study the consequences of the existence of timelike and spacelike Ricci collineation vectors (RCVs) for string fluid in the context of general relativity. Necessary and sufficient conditions are derived for a space-time with string fluid to admit a timelike RCV, parallel to u^a, and a spacelike RCV, parallel to n^a. In these cases, some results obtained are discussed.