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Articles 2971 - 3000 of 3096
Full-Text Articles in Physical Sciences and Mathematics
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 …
A Realization Of Sc-Cnn-Based Circuit Using Ftfn, Eni̇s Günay, Esma Uzunhi̇sarcikli, Recai̇ Kiliç, Mustafa Alçi
A Realization Of Sc-Cnn-Based Circuit Using Ftfn, Eni̇s Günay, Esma Uzunhi̇sarcikli, Recai̇ Kiliç, Mustafa Alçi
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a realization of the State Controlled Cellular Neural Network (SC-CNN)-based circuit using Four Terminal Floating Nullor (FTFN) as active element is presented. In this realization, a new version of autonomous Chua's circuit has been considered using FTFN realization of SC-CNN-based circuit. The performance of the proposed SC-CNN-based circuit is demonstrated by PSpice simulations.
Prior Knowledge Input Method In Device Modeling, Serdar Heki̇mhan, Serdar Menekay, N. Serap Şengör
Prior Knowledge Input Method In Device Modeling, Serdar Heki̇mhan, Serdar Menekay, N. Serap Şengör
Turkish Journal of Electrical Engineering and Computer Sciences
The artificial neural networks are being used in modelling electronic elements and devices especially at microwave frequencies where non-linearity and dependence on frequency cannot be neglected. In this paper, instead of using artificial neural networks as a unique modelling device prior knowledge input method based on feed-forward artificial neural network structures as multi-layer perceptrons and wavelet-based neural networks is investigated. The benefits of prior knowledge input method over plain usage of artificial neural networks in modelling BJT is explored by comparing models obtained with and without prior knowledge input. The novelty of the paper is utilizing wavelet-based neural networks as …
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 …
Transformer Protection Using The Wavelet Transform, Okan Özgönenel, Güven Önbi̇lgi̇n, Çağri Kocaman
Transformer Protection Using The Wavelet Transform, Okan Özgönenel, Güven Önbi̇lgi̇n, Çağri Kocaman
Turkish Journal of Electrical Engineering and Computer Sciences
This paper introduces a novel approach for power transformer protection algorithm. Power system signals such as current and voltage have traditionally been analysed by the Fast Fourier Transform. This paper aims to prove that the Wavelet Transform is a reliable and computationally efficient tool for distinguishing between the inrush currents and fault currents. The simulated results presented clearly show that the proposed technique for power transformer protection facilitates the accurate discrimination between magnetizing inrush and fault currents in transformer protection.
Multilayer Capacitor Model Of The Earth's Upper Crust, Berk Üstündağ, Özcan Kalenderli̇, Haluk Eyi̇doğan
Multilayer Capacitor Model Of The Earth's Upper Crust, Berk Üstündağ, Özcan Kalenderli̇, Haluk Eyi̇doğan
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, an equivalent electric circuit model of Earth's upper crust is proposed to explain the behavior of measurement patterns acquired from network of the earthquake forecast project. A multi-layer capacitor model having active components that couples with the monopolar probe close to the surface is used to determine earthquake precursory patterns due to structural changes in time. Equivalent circuit model was developed for a) dilatency process that is assumed to be a stress weakening reason and b) external force source that increases shear stress over the fault until sudden decrement before the earthquake. A data acquisition system consisting …
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 …
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.
A Robustness Analysis Procedure For Realistic Missiles, Reşat Özgür Doruk, Erol Kocaoğlan
A Robustness Analysis Procedure For Realistic Missiles, Reşat Özgür Doruk, Erol Kocaoğlan
Turkish Journal of Electrical Engineering and Computer Sciences
This paper presents a robustness analysis procedure for short range realistic missile autopilots. The sensitivity of the autopilots to the aerodynamic parameter uncertainties is investigated through the structured singular value theory where the results are verified through nonlinear simulations. Different types of perturbations are implemented in order to measure the complete performance of the missile.
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.
A Survey On The H.264/Avc Standard, Nükhet Özbek, Turhan Tunali
A Survey On The H.264/Avc Standard, Nükhet Özbek, Turhan Tunali
Turkish Journal of Electrical Engineering and Computer Sciences
H.264/AVC is a recently completed video compression standard jointly developed by ITU-T VCEG and ISO/IEC MPEG standards committees. The standard is becoming more popular as it promises much higher compression than that possible with earlier standards. The standard provides flexibilities in coding and organization of data which enable efficient error resilience. The increased coding efficiency offers new application areas and business opportunities. As might be expected, the increases in compression efficiency and flexibility come at the expense of increase in complexity, which is a fact that must be overcome. This paper provides an overview of the technical features of H.264 …
Control Charts Approach For Scenario Recognition In Video Sequences, Ersi̇n Elbaşi, Long Zuo, Kishan Mehrotra, Chilukuri Mohan, Pramod Varshney
Control Charts Approach For Scenario Recognition In Video Sequences, Ersi̇n Elbaşi, Long Zuo, Kishan Mehrotra, Chilukuri Mohan, Pramod Varshney
Turkish Journal of Electrical Engineering and Computer Sciences
A new approach, based on control charts, is presented for the task of recognition of events and scenarios in video image sequences. For each image in the sequence, low level image processing and feature extraction steps result in feature descriptors for objects of interest detected in the images. Control charts analysis is then explored to classify the nature of the activity depicted by the temporal changes in these features over the image sequence. Scenario recognition with higher accuracy is achieved using this simple approach.
A Model For User Profiling Systems With Interacting Agents, Sanem Sariel, Tevfi̇k Akgün
A Model For User Profiling Systems With Interacting Agents, Sanem Sariel, Tevfi̇k Akgün
Turkish Journal of Electrical Engineering and Computer Sciences
Service systems according to users' personal demands and preferences are on their way to provide required services in many application domains. Emulation of interactive model of human societies produces valuable outcomes for such systems. In this work, a system model with interactive agents for multi user service systems is proposed. A novel social interactive agent model using different interaction forms is also included in this proposal. In this model, agents decide how to serve to their users by considering their users' profiles and information from other agents. User clusters are formed by clustering techniques. The Q-learning algorithm is used for …
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 …
Neural Analysis Of Top Shielded Multilayered Coplanar Waveguides, Mustafa Türkmen, Celal Yildiz, Şeref Sağiroğlu
Neural Analysis Of Top Shielded Multilayered Coplanar Waveguides, Mustafa Türkmen, Celal Yildiz, Şeref Sağiroğlu
Turkish Journal of Electrical Engineering and Computer Sciences
Artificial neural networks (ANNs) have been promising tools for many applications. In recent years, a computer-aided design approach based on (ANNs) has been introduced to microwave modelling, simulation and optimization. In this work, the characteristic parameters of top shielded multilayered coplanar waveguides (CPWs) have been determined with the use of ANN models. These neural models were trained with Levenberg-Marquardt, resilient propagation, Bayesian regulation, quasi-Newton, and backpropagation learning algorithms. Better performance and learning speed with a simpler structure were achieved from these models. The results have shown that the estimated characteristic parameters are in very good agreement with the computed results …
A Simple And Global Optimization Algorithm For Engineering Problems: Differential Evolution Algorithm, Dervi̇ş Karaboğa, Selçuk Ökdem
A Simple And Global Optimization Algorithm For Engineering Problems: Differential Evolution Algorithm, Dervi̇ş Karaboğa, Selçuk Ökdem
Turkish Journal of Electrical Engineering and Computer Sciences
Differential Evolution (DE) algorithm is a new heuristic approach mainly having three advantages; finding the true global minimum regardless of the initial parameter values, fast convergence, and using few control parameters. DE algorithm is a population based algorithm like genetic algorithms using similar operators; crossover, mutation and selection. In this work, we have compared the performance of DE algorithm to that of some other well known versions of genetic algorithms: PGA, Grefensstette, Eshelman. In simulation studies, De Jong's test functions have been used. From the simulation results, it was observed that the convergence speed of DE is significantly better than …
The 7 C'S For Creating Living Software: A Research Perspective For Quality-Oriented Software Engineering, Mehmet Akşi̇t
The 7 C'S For Creating Living Software: A Research Perspective For Quality-Oriented Software Engineering, Mehmet Akşi̇t
Turkish Journal of Electrical Engineering and Computer Sciences
This article proposes the 7 C's for realizing quality-oriented software engineering practices. All the desired qualities of this approach are expressed in short by the term living software. The 7 C's are: Concern-oriented processes, Canonical models, Composable models, Certifiable models, Constructible models, Closure property of models and Controllable models. Each C is explained by the help of a set of definitions, a short overview of the background work and the problems that software engineers may experience in realizing the corresponding C. Further, throughout the article, a software development example is presented for illustrating the realization of the 7 C's. Finally, …
An Information System For Streamlining Software Development Process, Serkan Nalbant
An Information System For Streamlining Software Development Process, Serkan Nalbant
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper an information system to be employed by software development organizations is proposed, which automates software development process. The proposed system aims to lower cost, improve schedule performance and enhance quality of the software projects by the means of automation and unifying of operational information. The characteristics of the proposed system are described. Furthermore, its use is illustrated via the explanation of an exemplary software system called PACE that serves as an information system for planning, controlling, measuring and improving software development process and projects. The relationship of PACE with Software Capability Maturity Model (CMM) is also provided.
Global Stability Analysis Of An End-To-End Congestion Control Scheme For General Topology Networks With Delay, Tansu Alpcan, Tamer Başar
Global Stability Analysis Of An End-To-End Congestion Control Scheme For General Topology Networks With Delay, Tansu Alpcan, Tamer Başar
Turkish Journal of Electrical Engineering and Computer Sciences
We analyze the stability properties of an end-to-end congestion control scheme under fixed heterogeneous delays, and for general network topologies. The scheme analyzed is based on the congestion control game of [1], with the starting point being the unique Nash equilibrium of that game. We prove global stability of this solution (and hence of the congestion control algorithm) under a mild symmetricity condition. We further demonstrate the stability of the algorithm numerically for various delays, user numbers, and topologies
An Implicit Surface Modeling Technique Based On A Modular Neural Network Architecture, Manuel Carcenac
An Implicit Surface Modeling Technique Based On A Modular Neural Network Architecture, Manuel Carcenac
Turkish Journal of Electrical Engineering and Computer Sciences
Independently from artificial intelligence applications, an artificial neural network can be viewed as a powerful tool for function reconstruction. Previous papers used this property to model an implicit surface out of some control points by reconstructing its underlying scalar field. Such an approach requests the neural network to memorize the control points, which has turned problematic for complex surfaces. In our paper, we show that this problem can be efficiently tackled by adapting the architecture of the neural network to the features compounding the surface: by learning first these features independently and then blending them gradually together, our modular architecture …
Mining Classification Rules By Using Genetic Algorithms With Non-Random Initial Population And Uniform Operator, Korkut Koray Gündoğan, Bi̇lal Alataş, Ali̇ Karci
Mining Classification Rules By Using Genetic Algorithms With Non-Random Initial Population And Uniform Operator, Korkut Koray Gündoğan, Bi̇lal Alataş, Ali̇ Karci
Turkish Journal of Electrical Engineering and Computer Sciences
Classification is a supervised learning method that induces a classification model from a database and is one of the most commonly applied data mining task. The frequently employed techniques are decision tree or neural network-based classification algorithms. This work presents an efficient genetic algorithm (GA) for classification rule mining technique that discovers comprehensible IF-THEN rules using a generalized uniform population method and a uniform operator inspired from the uniform population method. Initial population is generated by methodically eliminating the randomness by generalized uniform population method. In the subsequence generations, genetic diversity is ensured and premature convergence is prevented by the …
Real-Time Classification Algorithm For Recognition Of Machine Operating Modes By Use Of Self-Organizing Maps, Gancho Vachkov, Yuhiko Kiyota, Koji Komatsu, Satoshi Fujii
Real-Time Classification Algorithm For Recognition Of Machine Operating Modes By Use Of Self-Organizing Maps, Gancho Vachkov, Yuhiko Kiyota, Koji Komatsu, Satoshi Fujii
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper a new algorithm for classification and real-time recognition of different a-priorily assumed operating modes for construction machines is proposed. This algorithm utilizes the effectiveness of the Self-Organizing Maps (SOM) for creating the so called Separation Models, that are able to distinguish each operating mode separately. After training, these models are used in a real-time procedure, which calculates at each sampling time the minimal Euclidean distances from the current data point to a certain node of each SOM. Then the separation model (represented by a respective SOM) that has the least minimal distance to this data point defines …
A Platform For Software Engineering Course Projects, Bi̇rol Aygün
A Platform For Software Engineering Course Projects, Bi̇rol Aygün
Turkish Journal of Electrical Engineering and Computer Sciences
The importance of projects in software engineering courses is well known. Both synthetic and real-life projects have various advantages and disadvantages. Our aim was to create a framework where students can develop projects which reflect some of the complexities of real-life, involving many concurrent, interacting, asynchronous processes, each in a different stage of development, with wide temporal differences among them - some occurring within millisconds of each other and others executing sporadically over much longer periods. In this project, which was carried out in different arrangements in several software engineering courses in three universities, the students developed both the sub- …
A Pattern Based Approach To Web Design Formalization, Ahmet Sikici, Yasemi̇n Topaloğlu
A Pattern Based Approach To Web Design Formalization, Ahmet Sikici, Yasemi̇n Topaloğlu
Turkish Journal of Electrical Engineering and Computer Sciences
World Wide Web is a global information network that affects many fields of our lives. The distributed, interlinked, visual and heterogeneous structure of the web makes it an irregular development environment. In this paper we propose a pattern based approach for increasing the effectiveness of development for the Web environment. This approach is based on the representation of the core meaning of each design as a set of patterns and requires the formulation of abstract solutions in a mathematical precision. This way not only reusable design experience will be codified unambiguously, but a smooth transition between the design and implementation …
An Agile Information Systems Development Method In Use, Mehmet Nafi̇z Aydin, Frank Harmsen, Kees Van Slooten, Robert Stegwee
An Agile Information Systems Development Method In Use, Mehmet Nafi̇z Aydin, Frank Harmsen, Kees Van Slooten, Robert Stegwee
Turkish Journal of Electrical Engineering and Computer Sciences
Recently, agile information systems development methods, agile methods in short, have got considerable attention from practitioners. One of the reasons seems that agile methods, to some degree, can be adaptable to different project situations. However, little empirical research has been conducted on this subject. The major goal of this research is to identify which aspects of agile methods are perceived as most critical and difficult to realize and how such aspects are adapted in practice. To reach this goal we studied the working practices concerning the adaptation of an agile method in the IT department of one of the leading …
Flow Controller Design And Performance Analysis For Self-Similar Network Traffic, Peng Yan
Flow Controller Design And Performance Analysis For Self-Similar Network Traffic, Peng Yan
Turkish Journal of Electrical Engineering and Computer Sciences
Recent studies of high-resolution traffic measurement discovered the self-similarity in both LAN and WAN traffic. In this paper, we introduce a two-degree of freedom rate based flow controller, which includes a robust H^{\infity} control block and an LMMSE based capacity predictor. The former part can guarantee the robust stability against time-varying time delay uncertainties and the latter improves the transient response by predicting the self-similar cross-traffic. Implementation issues are discussed and performance analysis is provided to validate our design. We also investigate the prediction and control in larger time scale which is more applicable for the real network environment
Optimum And Suboptimum Blind Channel And Symbol Estimation For Siso Channels, T. Engi̇n Tuncer
Optimum And Suboptimum Blind Channel And Symbol Estimation For Siso Channels, T. Engi̇n Tuncer
Turkish Journal of Electrical Engineering and Computer Sciences
We present three methods for blind channel and symbol identification from a single or multi-block observation. These methods are deterministic approaches suitable for the identification of quickly changing wireless channels. The first method uses the finite alphabet property and it has good performance even for noisy observations. It requires only a single data frame, which is a unique feature of the method. This method can also be used to identify the channel order. For multi-block observations, we present the maximal ratio combining cross relation (MRCCR) method. It is an optimum approach in terms of instantaneous SNR and is based on …