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Synthesis And Characterization Of Co-Pb/Sba-15 Mesoporous Catalysts, Mukaddes Can, Burcu Akça, Ayşen Yilmaz, Deni̇z Üner
Synthesis And Characterization Of Co-Pb/Sba-15 Mesoporous Catalysts, Mukaddes Can, Burcu Akça, Ayşen Yilmaz, Deni̇z Üner
Turkish Journal of Physics
Pure SBA-15 and Co and/or Pb incorporated SBA-15 have been prepared by direct synthesis. The synthesized samples were characterized by powder X-ray diffraction and N_2 adsorption isotherms. It is observed that the surface area of pure SBA-15 mesoporous structure slowly decreases by the addition of metal oxides. By the loading of 5, 10, 15 wt % Pb into SBA-15, no characteristic peaks of metal oxide observed in the large angle XRD pattern. But loading of 20 wt % Pb in SBA-15 shows more appreciable characteristic peaks, indicating small quantity of crystallites of metal oxide existing on the surface of silica. …
High Conducting Nanowires Obtained From Uniform Titanium Covered Carbon Nanotubes, Sefa Dağ, Engi̇n Durgun, Sali̇m Çiraci
High Conducting Nanowires Obtained From Uniform Titanium Covered Carbon Nanotubes, Sefa Dağ, Engi̇n Durgun, Sali̇m Çiraci
Turkish Journal of Physics
We have shown that Ti atoms can form continuous coating of carbon nanotubes at different amount of coverage. The circular cross section changes to a square-like form, and the semiconducting tube becomes ferromagnetic metal with high quantum ballistic conductance. Metallicity is induced not only by the metal-metal coupling, but also by the band gap closing of SWNT at the corners of the square. The magnetic properties of Ti coated tubes depend strongly on the geometry, amount of Ti coverage and also on the elastic deformation of the tube. While the magnetic moment can be pronounced significantly by the positive axial …
Photoluminescence Characterization Of Al/Al_2o_3/Inp Mis Structures Passivated By Anodic Oxidation, Abdelhakim Mahdjoub, Hadj Bourdoucen, Abdelkader Djelloul
Photoluminescence Characterization Of Al/Al_2o_3/Inp Mis Structures Passivated By Anodic Oxidation, Abdelhakim Mahdjoub, Hadj Bourdoucen, Abdelkader Djelloul
Turkish Journal of Physics
Metal-insulator-semiconductor (MIS) structures were produced by electron beam evaporation of Al_2O_3 on InP. Polyphosphate thin films of thickness 100-150 Å were used to passivate the interface InP\Insulator. Photoluminescence spectra are reported at low temperature at various stages of the realization process of the MIS-InP structure. Photoluminescence topography at ambient temperature made it possible to characterize the surface state after each technological stage. The interface degradation under the effect of repeated annealing is insignificant up to temperatures of 350 °C. Radiative major defects detected by photoluminescence spectrum with energy 0.95-1.15 eV attributed to the complexes impurities of phosphorus vacancies are substantially …
Ultra Wide-Band : State Of The Art; Implementation Of A Performance-Controllable Low-Noise Amplifier, Serigne Dia, Balwant Godora, Frederic Alicalapa, Alain Fabre
Ultra Wide-Band : State Of The Art; Implementation Of A Performance-Controllable Low-Noise Amplifier, Serigne Dia, Balwant Godora, Frederic Alicalapa, Alain Fabre
Turkish Journal of Electrical Engineering and Computer Sciences
Ultra Wide-Band (UWB) transmissions exhibit performances vastly superior to existing wireless systems - superlative data-rate capacity, high security, low cost, low power consumption - and are emerging as the hottest topic of research for upcoming wireless generations. This communication protocol is studied in detail, with mention of the history and estimates for the near future; the present and possible applications are mentioned; the advantages and unresolved issues are detailed; a typical UWB transceiver architecture is studied; the modulation and coding schemes are enumerated; and the possibility of long-range communication is touched upon. Finally, a new performance-controllable low-noise amplifier (LNA) destined …
A New Cmos Differential Otra Design For The Low Voltage Power Supplies In The Sub-Micron Technologies, Alper Duruk, Hakan Kuntman
A New Cmos Differential Otra Design For The Low Voltage Power Supplies In The Sub-Micron Technologies, Alper Duruk, Hakan Kuntman
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, a new CMOS differential OTRA topology is proposed. This topology can operate with a very low voltage power supply as \pm 0.6V. In this design, CMOS 0.13 \mu m STMicroelectronics technology transistor models are used for the simulations. The designed CMOS OTRA has a transresistance gain (Rm) of 7478 V/I with a 28.1 MHz bandwidth (-3 dB) and a transresistance unity-gain bandwidth of 2 GHz. To demonstrate the performance of the OTRA, designed low pass, high pass and band pass filters employing a single CMOS differential OTRA and passive elements are tested with SPICE simulation program to …
Sigma-Delta Voltage To Frequency Converter With Phase Modulation Possibility, Milan Stork
Sigma-Delta Voltage To Frequency Converter With Phase Modulation Possibility, Milan Stork
Turkish Journal of Electrical Engineering and Computer Sciences
Voltage to frequency converter (VFC) is an oscillator whose frequency is linearly proportional to control voltage. There are two common VFC architectures: the current steering multivibrator and the charge-balance VFC. For higher linearity, the charge-balancing method is preferred. The charge balanced VFC may be made in asynchronous or synchronous (clocked) forms. The synchronous charge balanced VFC or "sigma delta" (\Sigma-\Delta) VFC is used when output pulses are synchronized to a clock. The charge balance VFC is more complex, more demanding in its supply voltage and current requirements, and more accurate. It is capable of 16 to18 bit linearity. In this …
An Algorithm For Image Clustering And Compression, Meti̇n Kaya
An Algorithm For Image Clustering And Compression, Meti̇n Kaya
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a new approach to image compression based on fuzzy clustering. This new approach includes pre-filtering, and fuzzy logic image enhancing to reduce undesirable noise effects on segmentation result; separation of image into 4x4 blocks and two dimensional discrete cosine transform; obtaining of peak values of cosine membership functions by combining of performing the zig-zag method with discrete cosine transform coefficients; obtaining of membership values and cluster centroids; and finally, creation of segmented image and compression. After applying the new method on sample images at different number of clusters, better compression ratio, performing time and good validity measure …
Design, Simulation And Tests Of A Low-Cost Microstrip Patch Antenna Arrays For The Wireless Communication, Gonca Çakir, Levent Sevgi̇
Design, Simulation And Tests Of A Low-Cost Microstrip Patch Antenna Arrays For The Wireless Communication, Gonca Çakir, Levent Sevgi̇
Turkish Journal of Electrical Engineering and Computer Sciences
Typical low-cost, low-weight microstrip base station antenna arrays with beam-scanning capabilities are taken into account. In downtowns of large cities like New York, Chicago, and in historical cities like Istanbul, where high buildings are separated by narrow but densely occupied streets, antenna arrays with approximately 20°-35° beam-widths are required to complete the cellular communication coverage. To meet this requirement, new antenna arrays are designed with 35° beam-widths and 60° electronic scanning capabilities. Their characteristics are investigated both numerically and experimentally. An FDTD-based antenna simulation package (M-PATCH) is prepared, tested on canonical structures and against the literature first, for verification and …
Computation Of Association Probabilities For Single Target Tracking With The Use Of Adaptive Neuro-Fuzzy Inference System, İlke Türkmen, Keri̇m Güney
Computation Of Association Probabilities For Single Target Tracking With The Use Of Adaptive Neuro-Fuzzy Inference System, İlke Türkmen, Keri̇m Güney
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, a simple method based on the adaptive neuro-fuzzy inference system (ANFIS) is presented for computing the association probabilities. The computed association probabilities are used to track the single manoeuvring target in the cluttered environment. A hybrid learning algorithm, which combines the least square method and the backpropagation algorithm, is used to identify the parameters of ANFIS. The tracks estimated by using the method proposed in this study are in very good agreement with the true tracks. Better accuracy with respect to the well known nearest neighbour Kalman filter and probabilistic data association algorithms is obtained.
Soft Computing Methods In Microwave Active Device Modeling, Yavuz Cengi̇z, Fi̇li̇z Güneş, Mehmet Fati̇h Çağlar
Soft Computing Methods In Microwave Active Device Modeling, Yavuz Cengi̇z, Fi̇li̇z Güneş, Mehmet Fati̇h Çağlar
Turkish Journal of Electrical Engineering and Computer Sciences
In this work, the signal and noise behaviors of a microwave transistor within its operation domain (CT,V_{DS}, I_{DS}, f) are modeled by the Artificial Neural Network (ANN) and Fuzzy Logic System (FLS) without using any information on the microwave circuit theory . A worked example is presented where the same data is employed for both models selected from the manufacturer's data sheets. Performances of the FLS and ANN models are compared and conclusions are drawn.
Impacts Of Distributed Generators On The Oscillatory Stability Of Interconnected Power Systems, İstemi̇han Genç, Ömer Usta
Impacts Of Distributed Generators On The Oscillatory Stability Of Interconnected Power Systems, İstemi̇han Genç, Ömer Usta
Turkish Journal of Electrical Engineering and Computer Sciences
Integration of distributed generation is continually and gradually affecting the stability of interconnected power systems. In this paper, the impacts of distributed synchronous generators on oscillatory stability are studied. In various parameter sub-spaces of interest, feasibility regions can be calculated to determine the conditions to sustain the stable operation of an interconnected power system. Through computations of the feasibility boundaries corresponding to Hopf bifurcations of electromechanical oscillatory modes, we determine the operating limits for a stable operation of the system under small and continual disturbances such as predictable changes in loading conditions of generators. Thus, with the case studies given …
Fault Tolerant Control With Re-Configuring Sliding-Mode Schemes, Ufuk Demi̇rci̇, Feza Kerestecioğlu
Fault Tolerant Control With Re-Configuring Sliding-Mode Schemes, Ufuk Demi̇rci̇, Feza Kerestecioğlu
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a controller design method for linear MIMO systems is presented which a sliding mode controller is reconfigured in case of system faults. Faults are detected with the residual vector generated from a standard linear observer. Once a fault has been detected the fault distribution matrix can be obtained and used to update the corrective or equivalent control parts of the sliding mode controller. As a result, fault tolerant adaptive controllers keep the system performance within acceptable limits or at least avoids the system to wind-up.
Cover And Contents
Turkish Journal of Electrical Engineering and Computer Sciences
No abstract provided.
Turbo Codes: The Issue Of Average Union Upper Bound Under Imperfect Channel State Information In Rayleigh Fading Channels, Erhan A. İnce, Syed Amjad Ali
Turbo Codes: The Issue Of Average Union Upper Bound Under Imperfect Channel State Information In Rayleigh Fading Channels, Erhan A. İnce, Syed Amjad Ali
Turkish Journal of Electrical Engineering and Computer Sciences
The potential of turbo codes to demonstrate excellent performance in the region of low signal to noise ratio is now a familiar fact. The idea of turbo codes was first introduced by Berrou and was based on the clever utilization of the existing decoding mechanism of BCJR with a change in the encoder by introducing feedback and an interleaver in the overall scheme. Since then, these powerful forward error correcting codes have attained a significant attention and have either replaced or have become a sturdy candidate for many applications in this era of modern communication systems. So far, a lot …
Silhouette Based Human Motion Detection And Analysis For Real-Time Automated Video Surveillance, Murat Eki̇nci̇, Eyüp Gedi̇kli̇
Silhouette Based Human Motion Detection And Analysis For Real-Time Automated Video Surveillance, Murat Eki̇nci̇, Eyüp Gedi̇kli̇
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a real-time background modeling and maintenance based human motion detection and analysis in an indoor and an outdoor environments for visual surveillance system is described. The system operates on monocular gray scale video imagery from a static CCD camera. In order to detect foreground objects, first, background scene model is statistically learned using the redundancy of the pixel intensities in a training stage, even the background is not completely stationary. This redundancy information of the each pixel is separately stored in an history map shows how the pixel intensity values changes till now. Then the highest ratio …
Two-Variable Scattering Formulas To Describe Some Classes Of Lossles Two-Ports With Mixed, Lumped Elements And Commensurate Stubs, Ahmet Sertbaş
Two-Variable Scattering Formulas To Describe Some Classes Of Lossles Two-Ports With Mixed, Lumped Elements And Commensurate Stubs, Ahmet Sertbaş
Turkish Journal of Electrical Engineering and Computer Sciences
Using the semi-analytic method based on the construction of two-variable scattering functions, which describe lossless two-ports with two kinds of elements, for some classes of ladder networks formed with lumped elements and commensurate stubs, the explicit descriptive formulas are produced up to six mixed-elements. To exhibit the efficiency of the explicit descriptive equations in the design of the broadband microwave circuits, a single matching design problem (UHF antenna matching) is solved by using the obtained two-variable scattering formulas.
Performance Analysis Of A Fuzzy Logic Based Rotor Resistance Estimator Of An Indirect Vector Controlled Induction Motor Drive, Y. Miloud, Azeddine Draou
Performance Analysis Of A Fuzzy Logic Based Rotor Resistance Estimator Of An Indirect Vector Controlled Induction Motor Drive, Y. Miloud, Azeddine Draou
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a simple method for estimating rotor resistance in an indirect vector-controlled induction motor drive. This is important in vector control, if high-performance torque control is needed. For this purpose, a rotor resistance estimator using fuzzy logic technique is used and analysis, design, and digital simulations are carried out to demonstrate the effectiveness of the proposed estimator.
Cover And Contents
Turkish Journal of Electrical Engineering and Computer Sciences
No abstract provided.
A Content-Based Fuzzy Image Database Based On The Fuzzy Artmap Architecture, M. Uysal, Fatoş Tünay Yarman Vural
A Content-Based Fuzzy Image Database Based On The Fuzzy Artmap Architecture, M. Uysal, Fatoş Tünay Yarman Vural
Turkish Journal of Electrical Engineering and Computer Sciences
A major design issue in content-based image retrieval system is the selection of the feature set. This study attacks the problem of finding a discriminative feature for each class, which is optimal in some sense. Fuzzy ARTMAP architecture is used to find this discriminative feature set. For this purpose, initially, a large variety of features are extracted from the regions of the pre-segmented images. Then, the feature set of each object class is learned using the Fuzzy Art Map Architecture, by identifying the weights of each feature for each object class. In the querying phase, trained set of feature weights …
Color Image Profiling Using Fuzzy Sets, Amine Ait Younes, Isis Truck, Herman Akdag
Color Image Profiling Using Fuzzy Sets, Amine Ait Younes, Isis Truck, Herman Akdag
Turkish Journal of Electrical Engineering and Computer Sciences
In this article, a software for image indexing and retrieval is presented. The classification proposed here is based on the dominant color(s) of the images. The process consists in assigning a colorimetric profile to the image in HLS space (Hue, Lightness, Saturation). First, the definition of hue is done thanks to a fuzzy representation to take into account the non-uniformity of colors distribution. And then, lightness and saturation are represented through linguistic qualifiers also defined in a fuzzy way. Finally, the profile is built through fuzzy functions representing the membership degree of the image to different classes. In order to …
Stratigraphy Of The Volcanic Products Around Nemrut Caldera: Implications For Reconstruction Of The Caldera Formation, Özgür Karaoğlu, Yavuz Özdemi̇r, A. Ümi̇t Tolluoğlu, Mustafa Karabiyikoğlu, Onur Köse, Jean-Luc Froger
Stratigraphy Of The Volcanic Products Around Nemrut Caldera: Implications For Reconstruction Of The Caldera Formation, Özgür Karaoğlu, Yavuz Özdemi̇r, A. Ümi̇t Tolluoğlu, Mustafa Karabiyikoğlu, Onur Köse, Jean-Luc Froger
Turkish Journal of Earth Sciences
The volcanological development of the Nemrut stratovolcano, located near the southwestern tip of Lake Van in eastern Turkey, is subdivided into three stages: pre-caldera, post-caldera and late stages. Two ignimbrite flows have been recognized in the pre-caldera stage. The earlier of the two occurred after basaltic lavas formed along extensional fissures. The latter, which forms the main subject of this paper, was a major flow associated with the development of the Nemrut caldera. The pyroclastic deposits of the Nemrut volcano in the pre-caldera stage are divided into three phases on the basis of palaeosols that separate them. The first phase …
Alpine Metamorphism And Granitoid Magmatism In The Strandja Zone: New Data From The Sakar Unit, Se Bulgaria, Ianko Gerdjikov
Alpine Metamorphism And Granitoid Magmatism In The Strandja Zone: New Data From The Sakar Unit, Se Bulgaria, Ianko Gerdjikov
Turkish Journal of Earth Sciences
The Strandja Zone is a pre-Cenomanian orogen consisting of three tectonic units: the Veleka, Strandja and Sakar units. The first two units display very low-grade Alpine metamorphism, whereas in the Sakar unit the Triassic sediments are metamorphosed to the amphibolite facies. For years this high-grade metamorphism was enigmatic and most of the metamorphic rocks were interpreted as a reworked Precambrian crust of the Rhodope. This contribution begins with a review of the recent data about the structure and evolution of the Sakar unit. Probably the most important recent finding was the demonstration of the lack of a structural break between …
On Banach Lattice Algebras, Ayşe Uyar
On Banach Lattice Algebras, Ayşe Uyar
Turkish Journal of Mathematics
In this study, without using the assumption a^{-1} > 0, it is shown that E is lattice - and algebra - isometric isomorphic to the reals R whenever E is a Banach lattice f-algebra with unit e, e = 1, in which for every a > 0 the inverse a^{-1} exists. Subsequently, an alternative proof to a result of Huijsmans is given for Banach lattice algebras.
Petrography And Petrology Of The Calc-Alkaline Sarıhan Granitoid (Ne Turkey): An Example Of Magma Mingling And Mixing, Zafer Arslan
Petrography And Petrology Of The Calc-Alkaline Sarıhan Granitoid (Ne Turkey): An Example Of Magma Mingling And Mixing, Zafer Arslan
Turkish Journal of Earth Sciences
There are many acidic intrusions of varying age in the northern and southern zones of the eastern Pontides, NE Turkey, and the Sarıhan Granitoid is one of these. The Maastrichtian Sarıhan Granitoid was emplaced into the pre-Permo-Carboniferous Pulur Massif, generally comprising medium-grade metamorphic rocks; the Liassic Hamurkesen Formation, that begins with the Dikmetaş conglomerate and continues upward into volcano-sedimentary rocks; and the Malm-Lower Cretaceous Hozbirikyayla Formation, comprising limestone and sandy limestones. The Sarıhan Granitoid crops out in an area of approximately 40 km2, has an ellipsoidal shape, and comprises mainly quartz monzodiorite, granodiorite and lesser quartz diorite. The pluton contains …
Investigation Of Safe And Sustainable Yields For The Sandy Complex Aquifer System In The Ergene River Basin, Thrace Region, Turkey, Şebnem Ökten, Hasan Yazicigi̇l
Investigation Of Safe And Sustainable Yields For The Sandy Complex Aquifer System In The Ergene River Basin, Thrace Region, Turkey, Şebnem Ökten, Hasan Yazicigi̇l
Turkish Journal of Earth Sciences
This study aims to determine the safe and sustainable yields for the Sandy Complex aquifer system in Ergene River basin in northwestern Turkey. A numerical ground-water flow model was developed for the Sandy Complex aquifer, which is the most productive and the most widespread aquifer in the basin. The finite difference ground-water model was used to simulate steady and unsteady flow in the aquifer. The model was calibrated in two steps: a steady-state calibration, by using the observed ground-water levels of January 1970; then a transient calibration, by using the observed ground-water levels for the period of January 1970 and …
Unsteady Flow Of A Dusty Conducting Fluid Between Parallel Porous Plates With Temperature Dependent Viscosity, Hazem Ali Attia
Unsteady Flow Of A Dusty Conducting Fluid Between Parallel Porous Plates With Temperature Dependent Viscosity, Hazem Ali Attia
Turkish Journal of Physics
This paper studies unsteady laminar flow of dusty conducting fluid between parallel porous plates with temperature dependent viscosity. The fluid is acted upon by a constant pressure gradient and an external uniform magnetic field is applied perpendicular to the plates. The parallel plates are assumed to be porous and subjected to a uniform suction from above and injection from below. The viscosity of the fluid is assumed to vary exponentially with temperature. The governing nonlinear partial differential equations are solved numerically and some important effects for the variable viscosity and the uniform magnetic field on the transient flow and heat …
Magic Gold Nanotubes, R. Tuğrul Senger, Sefa Dağ, Sali̇m Çiraci
Magic Gold Nanotubes, R. Tuğrul Senger, Sefa Dağ, Sali̇m Çiraci
Turkish Journal of Physics
In recent ultra-high-vacuum transmission-electron-microscopy experiments evidence is found for the formation of suspended gold single-wall nanotubes (SWNTs) composed of five helical strands. Similar to carbon nanotubes, the (n,m) notation defines the structure of the gold SWNTs. Experimentally, only the (5,3) tube has been observed to form among several other possible alternatives. Using first-principles calculations we demonstrate that gold atoms can form both freestanding and tip-suspended, chiral, single-wall nanotubes. Although freestanding, infinite (5,5) tube is found to be energetically the most favorable, the experimentally observed (5,3) tube, suspended between two tips, corresponds to a local minimum in the variation of string-tension …
A Theoretical Study On Silicon And Iii-V Compound Nanotubes, Engi̇n Durgun, Sali̇m Çiraci
A Theoretical Study On Silicon And Iii-V Compound Nanotubes, Engi̇n Durgun, Sali̇m Çiraci
Turkish Journal of Physics
In this paper we present a theoretical study on single-wall silicon and III-V compound nanotubes. First principles plane wave calculations within density functional theory are used to predict energetics and electronic structures of armchair and zigzag nanotubes. The stability of tubular structures is further investigated at finite temperature by ab initio molecular dynamics calculations. Our results indicate that (n,0) zigzag and (n,n) armchair single-wall Si nanotubes are stable for n >= 6. Mechanically, the Si nanotubes are radially soft, however they are strong against axial deformations. Electronic analysis showed that zigzag nanotubes are metallic for n Keywords: silicon, nanotube, first …
Electrical Properites Of Superconducting Cross - (Nano) Whiskers Junction, Serdar Altin, Eyüphan Yakinci, Yakup Balci, M. Ali̇ Aksan
Electrical Properites Of Superconducting Cross - (Nano) Whiskers Junction, Serdar Altin, Eyüphan Yakinci, Yakup Balci, M. Ali̇ Aksan
Turkish Journal of Physics
Bi-2212 superconducting single crystal (nano) whiskers have been fabricated by annealing a melt-quenched (glass) Bi_3Sr_2Ca_2Cu_3O_x precursor. A couple of (nano) Whiskers obtained were placed crosswise on a YSZ single crystal substrate and then heat treated at 830 C for 25 minute to form nano-scale junction. The T_c of each nano-whisker was found to be 85 K and the critical current density, J_c, of the whiskers was calculated to be 1177 Acm^{-2} at zero field. The I-V characteristics of the nano-junction at 30 K were found to show a multiple-branch structure, which is the main behavior of the Josephson junction.