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Articles 10081 - 10110 of 10317
Full-Text Articles in Physical Sciences and Mathematics
Performance Of Prefiltered Model-Based Frequency Estimators, Mustafa A. Altınkaya, Bülent Sankur, Emin Anarım
Performance Of Prefiltered Model-Based Frequency Estimators, Mustafa A. Altınkaya, Bülent Sankur, Emin Anarım
Turkish Journal of Electrical Engineering and Computer Sciences
In this work, the performance improvement due to prefiltering of inputs in model-based frequency estimators is investigated based on simulation experiments. Initial estimates on the tone frequency locations, which are obtained via DFT peak picking type preanalysis, are used to design a prefilter to remove noise and interference. The simulations indicate that prefiltering can improve the accuracy of Pisarenko and AR frequency estimators and MUSIC and KT frequency estimators with low subspace order significantly. The SNR thresholds of model-based frequency estimators are lowered by prefiltering. Additionally, interesting trade-offs between prefiltering gain and the gain due to subspace noise filtering have …
Object-Oriented Computer Simulations Of Physical Systems Using Dual Reciprocity Boundary Element Methodology, J. Friedrich
Object-Oriented Computer Simulations Of Physical Systems Using Dual Reciprocity Boundary Element Methodology, J. Friedrich
Turkish Journal of Electrical Engineering and Computer Sciences
Models of physical systems are essential in every engineering field. This work deals with computer simulations of physical systems that can be mathematically modelled by differential equations together with sufficient boundary conditions. The computer simulations are based on object-oriented technology and the dual reciprocity boundary element method which is a universal solution scheme for various types of partial differential equations (e.g. Laplace, Poisson, diffusion, convection-diffusion, and steady Navier-Stokes equation). This technique fulfills efficiency criteria like precision, robustness, versatility, programmability, user-friendliness, need of computational time and computer memory to a very high degree. This is demonstrated by three examples: Laplace's solution …
Analysis Of Nonlinear Sustained Oscillations In Discrete Systems With Backlash And Resolution By Using A Discretization-Oriented Describing Function, M. De La Sen, A. Pena, J. Esnaola
Analysis Of Nonlinear Sustained Oscillations In Discrete Systems With Backlash And Resolution By Using A Discretization-Oriented Describing Function, M. De La Sen, A. Pena, J. Esnaola
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a discretization-oriented describing function is derived for nonlinear devices combining backlash and quantization (resolution) while being subject to discretization through a sampler and zero-order hold. Such a describing function is frequency-dependent so that the overall nonlinearity, which includes both resolution and backlash, is interpreted as possessing nonlinear inertia. That nonlinear inertia is generated by the sampling process, since it does not appear if the system is continuous. The presence of nonlinear sustained oscillations (limit cycles) is investigated through simulations.
Adaptive Shape From Shading, Ati̇lla Gülteki̇n, Muhi̇tti̇n Gökmen
Adaptive Shape From Shading, Ati̇lla Gülteki̇n, Muhi̇tti̇n Gökmen
Turkish Journal of Electrical Engineering and Computer Sciences
Extracting surface orientation and surface depth from one or more images is one of the classic problems in computer vision. Shape-from-shading (SFS) deals with the recovery of 3-D shape from a single shaded image. The shape is recovered by minimizing an energy functional involving constraints such as smoothness. In this constrained problem, although the smoothness constraint helps to stabilize the minimization process, it pushes the reconstruction toward a smooth surface. In this paper, we present a new adaptive shape-from-shading method which reduces this oversmoothing by controlling the smoothness spatially over the image space. In order to improve the quality of …
A Parallel Pipelined Computer Architecture For Digital Signal Processing, Haluk Gümüşkaya, Bülent Örenci̇k
A Parallel Pipelined Computer Architecture For Digital Signal Processing, Haluk Gümüşkaya, Bülent Örenci̇k
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a parallel pipelined computer architecture and its six network configurations targeted for the implementation of a wide range of digital signal processing (DSP) algorithms described by both atomic and large grain data flow graphs. The proposed architecture is considered together with programmability, yielding a system solution that combines extensive concurrency with simple programming. It is an SSIMD (Skewed Single Instruction Multiple Data) or MIMD (Multiple Instruction Multiple Data) machine depending on the algorithms implemented and the programming methodologies. The concurrency that can be exploited by the algorithms using this Parallel pipelined architecture is both temporal and spatial …
Hierarchical Interconnection Network Architecture For Real-Time Systems, Bülent Örenci̇k
Hierarchical Interconnection Network Architecture For Real-Time Systems, Bülent Örenci̇k
Turkish Journal of Electrical Engineering and Computer Sciences
A hierarchical network suitable for interconnection of real-time client processes in a distributed multiprocessor environment is presented in this paper. A multi-layer {\it Communication Unit} (CU) prototype is developed for this purpose. This unit offers the client processes communication services for real-time operation. These services are structured in such a way that they do not depend on the characteristics of the communication medium. The basic hardware of the CU consists of a PC compatible card connected to the VME Bus. Client processes run on target cards (Motorola MVME-162) which are attached to the same bus. Target cards together with a …
State Of Art In Realistic Head Modeling For Electro-Magnetic Source Imaging Of The Human Brain, Nevzat G. Gençer, İ. Oğuz Tanzer, M. Kemal Özdemi̇r, Can E. Acar, Mert Sungur
State Of Art In Realistic Head Modeling For Electro-Magnetic Source Imaging Of The Human Brain, Nevzat G. Gençer, İ. Oğuz Tanzer, M. Kemal Özdemi̇r, Can E. Acar, Mert Sungur
Turkish Journal of Electrical Engineering and Computer Sciences
Electric currents produced by the neural activity in the brain create electric potentials on the scalp and magnetic field distribution outside the scalp. Measuring electric and magnetic fields provides a means to understand the spatio-temporal distribution of the neural activity. The representations of the intracellular electric current of active cell populations based on bimodal data are called electro-magnetic source image (EMSI). With the recent development of large arrays of magnetic sensors, and systems for measuring scalp voltages at more than 100 locations, it is now feasible to implement computational methods that employ numerical models which incorporate the correct geometry and …
Fdtd Evaluation Of The Sar Distribution In A Human Head Near A Mobile Cellular Phone, Selçuk Paker, Levent Sevgi̇
Fdtd Evaluation Of The Sar Distribution In A Human Head Near A Mobile Cellular Phone, Selçuk Paker, Levent Sevgi̇
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, Finite-Difference Time-Domain (FDTD) method is used to calculate the Specific Absorbtion Rate (SAR; defined as the power absorbed by unit mass of the tissue) distribution in a human head near a hand-held cellular phone. A three dimensional FDTD algorithm is built in cartesian coordinates. A discrete human head model, derived from a Nuclear Magnetic Resonance (NMR) image by semi-automatic algorithm, is located within FDTD volume together with a discrete hand-held receiver model. FDTD simulations are carried out for both european GSM (operating at 900MHz) and DECT (operating at 1.8GHz) systems with a quarter-wavelength antenna, mounted on top …
Cardiac Passive Acoustic Localization: Cardiopal, Yildirim Bahadirlar, Hali̇l Özcan Gülçür
Cardiac Passive Acoustic Localization: Cardiopal, Yildirim Bahadirlar, Hali̇l Özcan Gülçür
Turkish Journal of Electrical Engineering and Computer Sciences
A novel non-invasive system is proposed as an adjunct diagnostic tool for cardiac disorders, which is based on processing of the heart sounds acquired using a specially designed 2-D passive acoustic array. In addition to the acoustic array, the system consists of a personal computer, specially developed instrumentation and interface hardware and an adaptive array processing scheme. A signal model is constructed in accordance with the basic assumptions made for very near-field low frequency sources. The multiple signal characterization (MUSIC) method together with the model is used for the localization of assumed point sources in the heart. Locations of the …
Functional Radionuclide Imaging Algorithm Based On The Appended Curve Deconvolution Technique And Its Use In The Diagnosis Of Renovascular Hypertension, İrfan Karagöz, Hi̇kmet Bayhan
Functional Radionuclide Imaging Algorithm Based On The Appended Curve Deconvolution Technique And Its Use In The Diagnosis Of Renovascular Hypertension, İrfan Karagöz, Hi̇kmet Bayhan
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, a new method called the pixel basis functional radionuclide imaging (PBFRI) algorithm based on the appended curve deconvolution technique, in order to be able to increase the medical diagnostic capability of a conventional gamma camera, is presented together with the clinical results. In the PBFRI method, retention function of each pixel is obtained from the renograms and cardiac curves generated by processing the filtered segments of the kidney and heart, using a special deconvolution method. The deconvolution operation is done by using the Fourier transform technique. High frequency artifacts presented by the Fourier transform are removed by …
Carbon Monoxide Hydrogenation Over Ru-Mn-K/Al_2o_3 Catalysts, S. Tajammul Hussain, M. Ashraf Atta
Carbon Monoxide Hydrogenation Over Ru-Mn-K/Al_2o_3 Catalysts, S. Tajammul Hussain, M. Ashraf Atta
Turkish Journal of Chemistry
The catalytic behavior of a series Ru/Al_2O_3 catalysts promoted with various levels of Mn and K prepared by coimpregnation were investigated in the CO-hydrogenation reaction. Catalytic studies showed that the addition of Mn enhances the production of Fischer Tropsch products and K promotion in particular enhances the production of unsaturated hydrocarbons while inhibiting the methanation reaction. The influence of K and Mn on the Fischer Tropsch product selectivity in CO-hydrogenation studies is discussed in terms of ensemble and electronic effects, and the production of a new surface site Ru:Mn:K.
Critical Point Theory In Mathematics And In Mathematical Physics, Raoul Bott
Critical Point Theory In Mathematics And In Mathematical Physics, Raoul Bott
Turkish Journal of Mathematics
No abstract provided.
Exotic Structures And Adjunction Inequality, Selman Akbulut, Rostislav Matveyev
Exotic Structures And Adjunction Inequality, Selman Akbulut, Rostislav Matveyev
Turkish Journal of Mathematics
No abstract provided.
Seiberg-Witten Equations On R^8, Ayşe Hümeyra Bi̇lge, Tekin Dereli̇, Şahin Koçak
Seiberg-Witten Equations On R^8, Ayşe Hümeyra Bi̇lge, Tekin Dereli̇, Şahin Koçak
Turkish Journal of Mathematics
We show that there are no nontrivial solutions of the Seiberg-Witten equations on R^8 with constant standard {spin}^c structure.
Nv-P-Groups With Nilpotent Centralizers, Ali Osman Asar, Aynur Yalincaklioğlu
Nv-P-Groups With Nilpotent Centralizers, Ali Osman Asar, Aynur Yalincaklioğlu
Turkish Journal of Mathematics
In this work a sufficient condition is given for an NC-p-group to have an epimorphic image which is an NF-p-group.
On One Sided (\Sigma, \Tau)-Lie Ideals In Prime Rings, Neşet Aydin
On One Sided (\Sigma, \Tau)-Lie Ideals In Prime Rings, Neşet Aydin
Turkish Journal of Mathematics
In this paper, we proved some results for one-sided (\sigma, \tau)-Lie ideals in prime rings.
On The Theory Of A Certain Class Of Quadratic Pencils Of Matrices And Its Applications, G.Sh. Guseinov, G. Oturanç
On The Theory Of A Certain Class Of Quadratic Pencils Of Matrices And Its Applications, G.Sh. Guseinov, G. Oturanç
Turkish Journal of Mathematics
This paper is devoted to the study of the properties of eigenvalues and eigenvectors of quadratic pencil \lambda^2C - \lambdaR - J , where C is a positive diagonal matrix, R is an arbitrary real diagonal matrix, J is a ,, tridiagonal" real symmetric and positive matrix. The obtained results are then used to solve the corresponding system of differential equations with boundary and initial conditions. Kev Words: Quadratic pencijs, eigenvalues, eigenvectors.
The Paper On The Matrix Valued Time Series, M. Tuncay Gençoğlu
The Paper On The Matrix Valued Time Series, M. Tuncay Gençoğlu
Turkish Journal of Mathematics
In this paper, random series oscillatory were examine in matrix valued time series. This series' calculated correlation coefficient between elements. Positive serial correlation coefficient between terms examined relation.
Seiberg-Witten \`{A} La Furuta And Genus Bounds For Classes With Divisibility, Jim Bryan
Seiberg-Witten \`{A} La Furuta And Genus Bounds For Classes With Divisibility, Jim Bryan
Turkish Journal of Mathematics
No abstract provided.
Algorithms To Disprove The Poincare Conjecture, Colin Rourke
Algorithms To Disprove The Poincare Conjecture, Colin Rourke
Turkish Journal of Mathematics
No abstract provided.
Nc-P-Groups Satisfying The Normalizer Condition, Ali Osman Asar
Nc-P-Groups Satisfying The Normalizer Condition, Ali Osman Asar
Turkish Journal of Mathematics
Let G be a perfect locally nilpotent p-group in which every proper subgroup is nilpotent-by-Chernikov. It is shown that in G/Z(G) every proper subgroup is a Chernikov extension of a nilpotent subgroup Of finite exponent (Theorem 1). This resut is then used to give a characterization of G if, in addition, it satisfies the normalizer condition (Theorem 2).
On Irreducible Simply-Connected 4-Manifolds, Zoltan Szabo
On Irreducible Simply-Connected 4-Manifolds, Zoltan Szabo
Turkish Journal of Mathematics
No abstract provided.
Seiberg-Witten Invariants When Reversing Orientation, Tedi Draghici
Seiberg-Witten Invariants When Reversing Orientation, Tedi Draghici
Turkish Journal of Mathematics
In this paper, the very first step is taken towards solving the recently proposed conjecture by Kronheimer and Mrowka [KM2] concerning the Casson's invariant of an oriented homology 3-sphere and its Seiberg-Witten Floer homology.
Complex Conjugation Equivariant Topology Of Complex Surfaces, Sergey Finashin
Complex Conjugation Equivariant Topology Of Complex Surfaces, Sergey Finashin
Turkish Journal of Mathematics
Suppose X is a non-singular complex surface defined over \R, which is a complete intersection constructed by the method of a small perturbation, and Y=X/\conj is its quotient by the complex conjugation \conj\: X\to X. Assume that \conj has a fixed point. Then Y is completely decomposable, i.e., splits into a connected sum \#_n \Cp^2\#_m\barCP^2 or \#_n(S^2\!\times\! S^2).
A (--86)-Sphere In The K3 Surface, Sergey Finashin, Grigory Mikhalkin
A (--86)-Sphere In The K3 Surface, Sergey Finashin, Grigory Mikhalkin
Turkish Journal of Mathematics
Consider the self-intersection number [\Sigma].[\Sigma] of a 2-dimensional sphere \Sigma embedded into a K3 surface. Since a K3 surface is spin, [\Sigma].[\Sigma] is even and by Gauge theoretical arguments [\Sigma].[\Sigma]\le 0. No other restriction on [\Sigma].[\Sigma] is known. It is a problem 4.105(D) from the Kirby list \cite{K} to determine the possible values of [\Sigma].[\Sigma]. This paper shows that the even numbers between 0 and -86 do appear as [\Sigma].[\Sigma].
Fibonacci Sequences In Finite Nilpotent Groups, Ramazan Di̇ki̇ci̇, Geoff C. Smith
Fibonacci Sequences In Finite Nilpotent Groups, Ramazan Di̇ki̇ci̇, Geoff C. Smith
Turkish Journal of Mathematics
We have proved that, for the 3-step Fibonacci recurrence and any finite p-group of exponent p and nilpotency class 3, the length of a fundamental period of any loop satisfying the recurrence must divide the period of the ordinary 3-step Fibonacci sequence in the field GF(p).
About Some Normal Subgroups Of Hecke Groups, İsmail Naci Cangül
About Some Normal Subgroups Of Hecke Groups, İsmail Naci Cangül
Turkish Journal of Mathematics
In this work we study the suucture of some special normal subgroups of Hecke groups. Particwarly those of genus O and 1 are studied by means of the regwar map theory which has been a growing subject in recent years. As a nice application, we calcwate the total number of genus 1 normal subgroups for a given index.
The Hardy -Littlewood-Sobolev Inequality For Non-Isotropic Riesz Potentials, İnan Çinar
The Hardy -Littlewood-Sobolev Inequality For Non-Isotropic Riesz Potentials, İnan Çinar
Turkish Journal of Mathematics
In this study the inequality of Hardy-Littlewood-Sobolev type are established for non-isotropic generalized Riesz potential depending on \lambda -distance. In this paper we establish analogues of the well known Hardy-Littlewood-Sobolev inequality (see[3]) for Riesz potentials with non-isotropic kernel depended on \lambda distance. Note that different problems for convolution type integrals with kernels, depending on \lambda-distance were considered in [1] and [2].
Near Ultrafilters And Compactification Of Topological Groups, Mahmut Koçak, Zekeriya Arvasi̇
Near Ultrafilters And Compactification Of Topological Groups, Mahmut Koçak, Zekeriya Arvasi̇
Turkish Journal of Mathematics
No abstract provided.
Locally Topological Groupoids, Osman Mucuk
Locally Topological Groupoids, Osman Mucuk
Turkish Journal of Mathematics
The notion of Iocally topological groupoid was introduced by Aof and Brown in [2]. On the other hand in [6] by Mackenzie a topological groupoid MG, called monodromy groupoid, is constructed. In this paper we prove that this groupoid MG gives a Iocally topological groupoid.