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Articles 6541 - 6570 of 10319
Full-Text Articles in Physical Sciences and Mathematics
Continuous Invariant Averagings, Djavvat Khadjiev, Abdullah Çavuş
Continuous Invariant Averagings, Djavvat Khadjiev, Abdullah Çavuş
Turkish Journal of Mathematics
Main results: For every equicontinuous almost periodic linear representation of a group in a complete locally convex space L with the countability property, there exists the unique invariant averaging; it is continuous and is expressed by using the L-valued invariant mean of Bochner and von-Neumann. An analog of Wiener's approximation theorem for an equicontinuous almost periodic linear representation in a locally convex space with the countability property is proved.
Quasinormability And Diametral Dimension, Ahmet Tosun Terzi̇oğlu
Quasinormability And Diametral Dimension, Ahmet Tosun Terzi̇oğlu
Turkish Journal of Mathematics
Two versions of diametral dimension are shown to coincide for quasinormable Fréchet spaces. The diametral dimension is determined by a single bounded subset in certain cases.
Complete Cotorsion Pairs In The Category Of Complexes, Zhanping Wang, Zhongkui Liu
Complete Cotorsion Pairs In The Category Of Complexes, Zhanping Wang, Zhongkui Liu
Turkish Journal of Mathematics
In this paper, we study completeness of cotorsion pairs in the category of complexes of R-modules. Let (A, B) be a cotorsion pair in R-Mod. It is shown that the cotorsion pair (\widetilde{A}, dg\widetilde{B}) and (\overline{A}, \overline{A}^{\perp}) are complete if A is closed under pure submodules and cokernels of pure monomorphisms, where in Gillespie's definitions \widetilde{A} is the class of exact complexes with cycles in A and dg\widetilde{B} is the class of complexes X with components in B such that the complex Hom(A, X) is exact for every complex A \in \widetilde{A}; and \overline{A} is the class of all complexes …
Slant Submersions From Almost Product Riemannian Manifolds, Yilmaz Gündüzalp
Slant Submersions From Almost Product Riemannian Manifolds, Yilmaz Gündüzalp
Turkish Journal of Mathematics
In this paper, we define the concept of almost product Riemannian submersion between almost product Riemannian manifolds. We introduce slant submersions from almost product Riemannian manifolds onto Riemannian manifolds. We give examples and investigate the geometry of foliations that arise from the definition of a Riemannian submersion. We also find necessary and sufficient conditions for a slant submersion to be totally geodesic.
Factorization Of Composite Polynomials Over Finite Fields, Saeid Mehrabi
Factorization Of Composite Polynomials Over Finite Fields, Saeid Mehrabi
Turkish Journal of Mathematics
This paper presents the reducibility of some composite polynomials and explicitly determines the factorization over finite fields. Also families of irreducible polynomials over finite fields are introduced.
A Class Of 3-Dimensional Almost Cosymplectic Manifolds, İrem Küpeli̇ Erken, Cengi̇zhan Murathan
A Class Of 3-Dimensional Almost Cosymplectic Manifolds, İrem Küpeli̇ Erken, Cengi̇zhan Murathan
Turkish Journal of Mathematics
The main interest of the present paper is to classify the almost cosymplectic 3-manifolds that satisfy \Vert grad\lambda \Vert = const.(\neq 0) and \bigtriangledown_{\xi} h=2ah\phi.
On The Existence Of Nonzero Injective Covers And Projective Envelopes Of Modules, Xiaoxiang Zhang, Xianmei Song
On The Existence Of Nonzero Injective Covers And Projective Envelopes Of Modules, Xiaoxiang Zhang, Xianmei Song
Turkish Journal of Mathematics
In general, the injective cover (projective envelope) of a simple module can be zero. A ring R is called a weakly left V-ring (strongly left Kasch ring) if every simple left R-module has a nonzero injective cover (projective envelope). It is proven that every nonzero left R-module has a nonzero injective cover if and only if R is a left Artinian weakly left V-ring. Dually, every nonzero left R-module has a nonzero projective envelope if and only if R is a left perfect right coherent strongly left Kasch ring. Some related rings and examples are considered.
Robust Sensorless Predictive Control Of Induction Motors With Sliding Mode Voltage Model Observer, Seyed Alireza Davari, Davood Arab Khaburi, Fengxiang Wang, Ralph Kennel
Robust Sensorless Predictive Control Of Induction Motors With Sliding Mode Voltage Model Observer, Seyed Alireza Davari, Davood Arab Khaburi, Fengxiang Wang, Ralph Kennel
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a robust sliding mode prediction model is combined with a sliding mode voltage model observer to achieve a sensorless predictive torque control method. In order to compensate the uncertainties of the stator and rotor resistances and the offset of measured current, sliding mode feedbacks were added to the voltage model observer. To reduce the effect of the errors that are injected from the observer to the prediction model in the sensorless application, the prediction model was also reinforced by a sliding mode feedback. The feedback gains for the prediction and observer models are assigned by a robustness …
Artificial Immunity-Based Induction Motor Bearing Fault Diagnosis, Hakan Çaliş, Abdülkadi̇r Çakir, Emre Dandil
Artificial Immunity-Based Induction Motor Bearing Fault Diagnosis, Hakan Çaliş, Abdülkadi̇r Çakir, Emre Dandil
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, the artificial immunity of the negative selection algorithm is used for bearing fault detection. It is implemented in MATLAB-based graphical user interface software. The developed software uses amplitudes of the vibration signal in the time and frequency domains. Outer, inner, and ball defects in the bearings of the induction motor are detected by anomaly monitoring. The time instants of the fault occurrence and fault level are determined according to the number of activated detectors. Anomaly detection in the frequency domain is implemented by monitoring the fault indicator bearing frequencies and harmonics, calculated using the bearing dimensions and …
The Vortex Effect Of Francis Turbine In Electric Power Generation, Veli̇ Türkmenoğlu
The Vortex Effect Of Francis Turbine In Electric Power Generation, Veli̇ Türkmenoğlu
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, the vibration effects of a vortex that occurred in high-head Francis turbines and an alternator are examined. The vortex effect, which directly affects the efficiency and the quality of the energy, was tested at the DarÔøΩca-1 hydroelectric power plant (HPP) located in Ordu Province, Turkey. Formed by undissolved oxygen in the water, the vortex effect, which is parallel to the alternator load, causes tremendous vibration within the alternator and Francis turbine bearings. This problem, which has a direct negative effect on the alternator capacity, was solved by adding an air-admission system. In doing so, power production was …
A Practical Disturbance Generator To Test Performances Of Various Power Quality Mitigation Devices, Ahmet Teke, Mehmet Emi̇n Meral, Mehmet Tümay, Mehmet Uğraş Cuma
A Practical Disturbance Generator To Test Performances Of Various Power Quality Mitigation Devices, Ahmet Teke, Mehmet Emi̇n Meral, Mehmet Tümay, Mehmet Uğraş Cuma
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a practical thyristor-based 3-phase sag/swell/outage generator (disturbance generator) is designed to test various power quality mitigation devices (PQMDs), such as solid state transfer switch (SSTS), static voltage compensator (SVC), and uninterruptible power supply. The latest technological disturbance generators (DGs) and the proposed DG are comprehensively discussed and compared with focus on usefulness, economic aspects, and simplicity. The proposed DG is used for experimentally generating different fault conditions and testing a SSTS. The comparisons and analyses show that the proposed DG is an optimum and simple solution to generate sag, swell, unbalance, overvoltage, undervoltage, and outage to test …
Circulating Current Analysis Between Strands In Armature Winding Of A Turbo-Generator Using Analytical Model, Karim Abbaszadeh, Farhad Rezaee Alam
Circulating Current Analysis Between Strands In Armature Winding Of A Turbo-Generator Using Analytical Model, Karim Abbaszadeh, Farhad Rezaee Alam
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, the circulating current analysis between strands is studied while considering the different transpositions in the active part and without considering the transposition in the end winding region. First, this analysis is done while only considering the slot region, and then the end winding region is added to the model. The model used for this analysis is a circuit model, including the resistance and inductance of the strands and their induced back-electromotive force (EMF). The back-EMF sources and inductances are calculated through a 2D finite element analysis (FEA) of the active part and a 3D FEA for the …
Composite Power System Adequacy Assessment Based On Postoptimal Analysis, Amir Safdarian, Mahmood Fotuhi-Firuzabad, Farrokh Aminifar
Composite Power System Adequacy Assessment Based On Postoptimal Analysis, Amir Safdarian, Mahmood Fotuhi-Firuzabad, Farrokh Aminifar
Turkish Journal of Electrical Engineering and Computer Sciences
The modeling and evaluation of enormous numbers of contingencies are the most challenging impediments associated with composite power system adequacy assessment, particularly for large-scale power systems. Optimal power flow (OPF) solution, as a widely common approach, is normally employed to model and analyze each individual contingency as an independent problem. However, mathematical representations associated with diverse states are slightly different in one or a few generating units, line outages, or trivial load variations. This inherent attribute brings a promising idea to speed up the contingency evaluation procedure. In this paper, postoptimal analysis (POA), as a well-recognized technique to attack a …
A Novel Multirobot Map Fusion Strategy For Occupancy Grid Maps, Sebahatti̇n Topal, İsmet Erkmen, Aydan Müşerref Erkmen
A Novel Multirobot Map Fusion Strategy For Occupancy Grid Maps, Sebahatti̇n Topal, İsmet Erkmen, Aydan Müşerref Erkmen
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, we consider the problem of merging partial occupancy grid environment maps, which are extracted independently by individual robot units during search and rescue (SAR) operations in icomplex disaster environments. Moreover, these maps are combined using intensity-based and area-based features without knowing the initial position and orientation of the robots. Our proposed approach handles the limitation of existing studies in the literature; for example, the limited overlapped area between partial maps of robots is enough for good merging performance and unstructured and complex partial environment maps can be merged efficiently. These abilities allow multirobot teams to efficiently generate …
Solution To The Unit Commitment Problem Using An Artificial Neural Network, Mehdi Zareian Jahromi, Mohammad Mehdi Hosseini Bioki, Masoud Rashidi Nejad, Roohollah Fadaeinedjad
Solution To The Unit Commitment Problem Using An Artificial Neural Network, Mehdi Zareian Jahromi, Mohammad Mehdi Hosseini Bioki, Masoud Rashidi Nejad, Roohollah Fadaeinedjad
Turkish Journal of Electrical Engineering and Computer Sciences
This paper proposes a real-time solution to the unit commitment problem by considering different constraints like ramp-up rate, unit operation emissions, next hours load, and minimum down time. In this method, an optimized trade-off between cost and emission has been taken into consideration. The effectiveness of the proposed method was verified by the significant outcomes demonstrated.
A Comparative Study In Power Oscillation Damping By Statcom And Sssc Based On The Multiobjective Pso Algorithm, Ali Ajami, Mehdi Armaghan
A Comparative Study In Power Oscillation Damping By Statcom And Sssc Based On The Multiobjective Pso Algorithm, Ali Ajami, Mehdi Armaghan
Turkish Journal of Electrical Engineering and Computer Sciences
To improve the damping of power system oscillations by supplementary controller design for the static synchronous series compensator (SSSC) and static synchronous compensator (STATCOM), a multiobjective function based on the particle swarm optimization (PSO) algorithm for solving this optimization problem is introduced. The presented objective function includes the damping factor and the damping ratio of the lightly damped and undamped electromechanical modes. These controllers are adjusted to concurrently transfer the lightly damped and undamped electromechanical modes to a recommended region in the s-plane. For this purpose, the reduced linearized Phillips-Heffron model of the power system with a single machine and …
Control In Networked Systems With Fuzzy Logic, Akhan Akbulut, Oğuzhan Öztaş
Control In Networked Systems With Fuzzy Logic, Akhan Akbulut, Oğuzhan Öztaş
Turkish Journal of Electrical Engineering and Computer Sciences
Recently, the development of control systems based on network-based architecture is getting very high attention. Because of its fast data communication, network-based control is in high demand. However, there are some disadvantages, such as delays, data packet dropouts, and communication constraints. Network-based control systems are getting attention in the development of this architecture because of these disadvantages. Optimization of the system is supplied to improve the existing structure. The optimization is categorized into 2 main structures: software optimization and hardware optimization. The structure of the overall system is designed with these optimization strategies. A hierarchical and communicational structure has emerged …
Optimal Release Policies For A Software System With Warranty Cost And Change-Point Phenomenon, D.R. Prince Williams
Optimal Release Policies For A Software System With Warranty Cost And Change-Point Phenomenon, D.R. Prince Williams
Turkish Journal of Electrical Engineering and Computer Sciences
Determining the software quality and release time of the software is an important role of software reliability. Software reliability growth models (SRGMs) are applications of software reliability. The change-point is defined as the prominent change in the software testing time, in connection with the quality of a software error occurrence or error-detection phenomenon. As a result, the software reliability growth process, based on the change-point, affects the precision of the software reliability prediction, based on the SRGMs. To find the accurate total expected delivery cost with a suitable warranty period of the software system, a new cost model for the …
System Designs To Perform Bioinformatics Sequence Alignment, Çağlar Yilmaz, Mustafa Gök
System Designs To Perform Bioinformatics Sequence Alignment, Çağlar Yilmaz, Mustafa Gök
Turkish Journal of Electrical Engineering and Computer Sciences
The emerging field of bioinformatics uses computing as a tool to understand biology. Biological data of organisms (nucleotide and amino acid sequences) are stored in databases that contain billions of records. In order to process the vast amount of data in a reasonable time, high-performance analysis systems are developed. The main operation shared by the analysis tools is the search for matching patterns between sequences of data (sequence alignment). In this paper, we present 2 systems that can perform pairwise and multiple sequence alignment operations. Through the optimized design methods, proposed systems achieve up to 3.6 times more performance compared …
A Bacterial Foraging Optimization Approach For Tuning Type-2 Fuzzy Logic Controller, Mohammad Kiani, Seyed Mohammad Ali Mohammadi, Ali Akbar Gharaveisi
A Bacterial Foraging Optimization Approach For Tuning Type-2 Fuzzy Logic Controller, Mohammad Kiani, Seyed Mohammad Ali Mohammadi, Ali Akbar Gharaveisi
Turkish Journal of Electrical Engineering and Computer Sciences
The type-1 fuzzy sets theory was proposed to handle uncertainty in control systems, but some cases showed some liabilities of type-1 fuzzy sets when faced with unpredictable disturbance and uncertainties. Therefore, type-2 fuzzy sets were introduced and extended while providing more degrees of freedom in designing criteria. The most important specification of type-2 fuzzy sets is the interval between a superior membership function and an inferior membership function, which is called the footprint of uncertainty. This paper presents a bacterial foraging optimization approach for optimizing the parameterized membership function. The above criterion is applied to an automatic voltage regulator system …
A Temporal Xml Data Model In Anaesthesia Information Systems, Oya Ünlü Duygulu, Taflan İmre Gündem
A Temporal Xml Data Model In Anaesthesia Information Systems, Oya Ünlü Duygulu, Taflan İmre Gündem
Turkish Journal of Electrical Engineering and Computer Sciences
Time information is an important aspect of a health information system. Health information cannot be represented and queried correctly without time in medical research, auditing, and medicolegal cases. Extensible Markup Language (XML) is being used in health information systems and has been formerly proposed as a data model for anaesthesia information systems. In this paper, we propose incorporating time into an XML model for anaesthesia information systems. A new storage structure and a temporal index structure are proposed in order to store temporal XML data and process time queries efficiently. In our proposed model, time has 4 dimensions: valid time, …
A New Technique For Rare-Event Simulation Based On Partition Of The Region, Amir Jalaly Bidgoly, Mohammad Abdollahi Azgomi
A New Technique For Rare-Event Simulation Based On Partition Of The Region, Amir Jalaly Bidgoly, Mohammad Abdollahi Azgomi
Turkish Journal of Electrical Engineering and Computer Sciences
Rare events are an important limitation of discrete-event simulation in some areas of applications. The existing rare-event simulation (RES) techniques, such as importance sampling (IS), splitting, and RESTART, have been used for RES so far. However, these techniques not only have some limitations, but also are not general or easy to use. In this paper, the partition of the region (PoR) method is used as a variance reduction technique in a new RES technique for usage with a wide range of modeling and simulation languages. Three variants of the proposed technique will be introduced: simple PoR, recursive PoR, and advanced …
Characterization Of Internal Disturbances And External Faults In Transformers Using An S-Transform--Based Algorithm, Abdolaziz Ashrafian, Mehrdad Rostami, Gevorg .B Gharehpetian
Characterization Of Internal Disturbances And External Faults In Transformers Using An S-Transform--Based Algorithm, Abdolaziz Ashrafian, Mehrdad Rostami, Gevorg .B Gharehpetian
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, the S-transform is used to discriminate between the internal disturbances and external faults of transformers. The proposed algorithm consists of 2 stages. The internal disturbances and the external faults are distinguished in the first stage. Next, the S-transform is applied to differential currents of faulty phases and the absolute deviation of the S-matrix is calculated. The relay scheme issues a trip signal in the case of an internal fault, according to the absolute deviation of the S-matrix. The scheme is implemented in a MATLAB environment and the inputs are differential currents, derived from EMTP software. In order …
Solution Of Transient Stability-Constrained Optimal Power Flow Using Artificial Bee Colony Algorithm, Kürşat Ayan, Ulaş Kiliç
Solution Of Transient Stability-Constrained Optimal Power Flow Using Artificial Bee Colony Algorithm, Kürşat Ayan, Ulaş Kiliç
Turkish Journal of Electrical Engineering and Computer Sciences
The transient stability constraint should be taken into consideration for the solution of the optimization problems in power systems. This paper presents a solution for the transient stability-constrained optimal power flow (TSCOPF) by a novel approach based on the artificial bee colony algorithm. The formulas of TSCOPF are derived through the addition of rotor angle inequality constraints into optimal power flow relationships. In this nonlinear optimization problem, the objective function is taken into consideration as the fuel cost of the system. The proposed approach is tested on both a WSCC 3-generator, 9-bus system and a IEEE 30-bus system, and the …
Stability Analysis Of Time-Delayed Dc Motor Speed Control System, Saffet Ayasun
Stability Analysis Of Time-Delayed Dc Motor Speed Control System, Saffet Ayasun
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, the stability of time-delayed DC motor speed control systems is analyzed. The measurement devices and communication links used by networked control systems, cause a significant amount of time delays. The stability boundary of the system in terms of the time delay is theoretically determined and an expression is obtained to compute the delay margin in terms of system parameters. The delay margin is defined as the maximum amount of time delay for which the DC motor speed control system is marginally stable. The results indicate that the system becomes unstable if the time delay exceeds the delay …
An Improved Hybrid Approach For The Plc-Based Implementation Of Reduced Rw Supervisors, Murat Uzam, Gökhan Gelen
An Improved Hybrid Approach For The Plc-Based Implementation Of Reduced Rw Supervisors, Murat Uzam, Gökhan Gelen
Turkish Journal of Electrical Engineering and Computer Sciences
A successful application of a hybrid (mixed Petri net/automaton) approach for the real-time supervisory control of an experimental manufacturing system was reported recently. The hybrid approach includes a Ramadge--Wonham (RW) supervisor in the form of an automaton. The reduced RW supervisor offers fewer states for the programmable logic controller (PLC) implementation of the hybrid controller with less memory requirements, but due to a problem called the avalanche effect, the PLC implementation of the hybrid controller with the reduced RW supervisor was not possible. This paper proposes a method to both detect and eliminate the avalanche effect problem for a RW …
A Method For Ontology-Based Semantic Relatedness Measurement, Görkem Gi̇ray, Murat Osman Ünalir
A Method For Ontology-Based Semantic Relatedness Measurement, Görkem Gi̇ray, Murat Osman Ünalir
Turkish Journal of Electrical Engineering and Computer Sciences
There are many methods having different approaches for assessing similarity and relatedness and they are used in many application areas, including web service discovery, invocation and composition, word sense disambiguation, information retrieval, ontology alignment and merging, document clustering, and short answer grading. These methods can be categorized as path-based, information content-based, feature-based, geometric model-based, and hybrid approaches. These approaches use resources such as concept hierarchy, conceptual graph, and corpus for computing similarity and relatedness. With the rise of the semantic web, ontologies have attracted the attention of several researchers. Ontologies represented in the Web Ontology Language (OWL) are also valuable …
An Automotive Vehicle Dynamics Prototyping Platform Based On A Remote Control Model Car, Seli̇m Solmaz, Türker Coşkun
An Automotive Vehicle Dynamics Prototyping Platform Based On A Remote Control Model Car, Seli̇m Solmaz, Türker Coşkun
Turkish Journal of Electrical Engineering and Computer Sciences
The use of a modified remote control (RC) model car as a vehicle dynamics testing and development platform is detailed. Vehicle dynamics testing is an important aspect of automotive engineering and it plays a key role during the design and tuning of active safety control systems. Considering the fact that such tests are conductedi at great expense, scaled model cars can potentially be used to help with the process to reduce the costs. With this view, we instrument and develop a standard electric RC model car into a vehicle dynamics testing platform. We then implement 2 representative active safety control …
Design Of Adaptive Compensators For The Control Of Robot Manipulators Robust To Unknown Structured And Unstructured Parameters, Recep Burkan
Design Of Adaptive Compensators For The Control Of Robot Manipulators Robust To Unknown Structured And Unstructured Parameters, Recep Burkan
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a new adaptive-robust control approach for robot manipulators is developed. The adaptive-robust control law is not only robust to unknown structured parameters but also robust to unknown unstructured parameters such as unstructured joint friction and disturbances. The bounded disturbances and unstructured model are taken into account in a dynamic model and it is assumed that the structured and unstructured parameters are unknown. The structured and unstructured parameters are distinguished between parameters and these parameters are treated separately. Next, new parameter estimation functions are developed for each of the 2 uncertainty groups. After that, the developed dynamic adaptive …
Design And Evaluation Of Schemes For Computing Sum Of Squares In Fixed Point, Meti̇n Mete Özbi̇len, Milos D. Ercegovac
Design And Evaluation Of Schemes For Computing Sum Of Squares In Fixed Point, Meti̇n Mete Özbi̇len, Milos D. Ercegovac
Turkish Journal of Electrical Engineering and Computer Sciences
Several schemes for computing the sum of squares for fixed point numbers are designed, synthesized, and evaluated in this study. The schemes use radix-2 folding, radix-4 folding, and radix-4 dual recoding approaches for squaring. The schemes have been modeled in hardware description language, simulated, and synthesized using Cadence SOC81 in 45 nm and 90 nm libraries and with Mentor Graphics Leonardo Spectrum for 180 nm. We show delay and area for 16-, 24-, and 32-bit operands. After hard-wire and software optimizations, it is seen that schemes with radix-4 give better results, especially in area.