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Articles 1591 - 1620 of 3106
Full-Text Articles in Engineering
A New Approach For Minimizing Torque Ripple In A Bldc Motor Drive With A Front End Ido Dc-Dc Converter, Ramya Amirthalingam, Balaji Mahadevan
A New Approach For Minimizing Torque Ripple In A Bldc Motor Drive With A Front End Ido Dc-Dc Converter, Ramya Amirthalingam, Balaji Mahadevan
Turkish Journal of Electrical Engineering and Computer Sciences
This paper proposes a front end integrated dual output (IDO) dc-dc converter for commutation torque ripple reduction in a permanent magnet brushless DC (BLDC) motor drive. The current ripple owed to the inductance and resistance of the motor during commutation instant results in torque ripple. In this work the dc link voltage of the converter is varied at commutation instants to minimize current ripple and hence torque ripple. The wider output range and faster response of the IDO converter make it a suitable choice as a front end converter for minimizing torque ripple. Simulation results validate the proposed converter for …
A Spectral Element Method For The Solution Of Magnetostatic Fields, Ibrahim Mahariq, Atakan Erciyas
A Spectral Element Method For The Solution Of Magnetostatic Fields, Ibrahim Mahariq, Atakan Erciyas
Turkish Journal of Electrical Engineering and Computer Sciences
Recently, we have seen good progress in our capability to simulate complex electromagnetic systems. However, still there exist many challenges that have to be tackled in order to push limits restricting the field of computational electromagnetics upward. One of these challenges is the limitations in the available computational resources. Over several decades, the traditional computational methods, such as finite difference, finite element, and finite volume methods, have been extensively applied in the field of electromagnetics. On the other hand, the spectral element method (SEM) has been recently utilized in some branches of electromagnetics as waveguides and photonic structures for the …
Multiphase Segmentation Based On New Signed Pressure Force Functions And One Level Set Function, Haider Ali, Noor Badshah, Ke Chen, Gulzar Ali Khan, Nosheen Zikria
Multiphase Segmentation Based On New Signed Pressure Force Functions And One Level Set Function, Haider Ali, Noor Badshah, Ke Chen, Gulzar Ali Khan, Nosheen Zikria
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper we propose a new model to detect multiple objects of various intensities in images having maximum, minimum, or middle-intensity background by evolving only one level set function. In this model, a new signed pressure force function based on novel generalized averages is used for segmentation of images with maximum or minimum intensity background. For images with middle-intensity backgrounds, which are indeed challenging for 2-phase models, we propose a new product generalized signed pressure force function. Finally, to give experimental and qualitative evidence, our model is tested on both synthetic and real images with the Jaccard similarity index. …
Token-Based Authentication Method For M2m Platforms, Hüseyi̇n Polat, Saadi̇n Oyucu
Token-Based Authentication Method For M2m Platforms, Hüseyi̇n Polat, Saadi̇n Oyucu
Turkish Journal of Electrical Engineering and Computer Sciences
Nowadays the fields in which machine-to-machine (M2M) applications are used and the numbers of M2M devices and users are increasing gradually. In an M2M application, M2M platforms are used in order to follow and analyze the data presented by M2M devices. The communication of multiple users and devices via an M2M platform causes some problems in terms of security. In this study, an M2M platform has been developed by using RestFul web services and NoSQL database. On this platform a token-based authentication method was used for multiple users and devices. In this method, an authorized request approach was adopted for …
K-Nn-Based Classification Of Sleep Apnea Types Using Ecg, Oğuz Han Ti̇muş, Emi̇ne Doğru Bolat
K-Nn-Based Classification Of Sleep Apnea Types Using Ecg, Oğuz Han Ti̇muş, Emi̇ne Doğru Bolat
Turkish Journal of Electrical Engineering and Computer Sciences
Obstructive sleep apnea syndrome (OSAS) is a common sleep disorder that yields cardiovascular diseases, excessive daytime sleepiness, and poor quality of life if not treated. Classification of OSAS from electrocardiograms (ECGs) is a noninvasive method and much more affordable than traditional methods. This study proposes a pattern recognition system for automated apnea diagnosis based on heart rate variability (HRV) and ECG-derived respiratory signals. The k-nearest neighbor (k-NN) classifier has been used to develop the models for classifying the sleep apnea types. For comparison purposes, classification models based on multilayer perceptron, support vector machines, and C4.5 decision tree (C4.5 DT) have …
Analytical Modeling Of A Coaxial Cylindrical Probe Capacitive Sensor Based On Matlab/Simulink For Conductive Liquids Level Measurements, Majid Toghyani Rizi, Mohammad Hadi Shahrokh Abadi
Analytical Modeling Of A Coaxial Cylindrical Probe Capacitive Sensor Based On Matlab/Simulink For Conductive Liquids Level Measurements, Majid Toghyani Rizi, Mohammad Hadi Shahrokh Abadi
Turkish Journal of Electrical Engineering and Computer Sciences
Measurement of liquid level is an important process variable in the operation of many process industries such as water treatment plants. There are different types of level sensors to measure this parameter, categorized into ultrasonic, capacitive, optical, microwave, magnetostrictive, resistive chain, magnetoresistive, hydrostatic pressure, air bubbler, gamma ray, etc. In this paper, a cylindrical probe capacitive sensor for measuring the level of conductive liquids has been modeled based on a step-by-step mathematical procedure, using MATLAB/Simulink. The steps take the relation between the different capacitances in the model with the height of the conductive liquid into account. The results show a …
A Bidirectional Wireless Power Transfer System For An Electric Vehicle With A Relay Circuit, Chenyang Xia, Wei Wang, Yuling Liu, Kezhang Lin, Yanhe Wang, Xiaojie Wu
A Bidirectional Wireless Power Transfer System For An Electric Vehicle With A Relay Circuit, Chenyang Xia, Wei Wang, Yuling Liu, Kezhang Lin, Yanhe Wang, Xiaojie Wu
Turkish Journal of Electrical Engineering and Computer Sciences
In order to extend the transfer distance, enhance the tolerance for coil misalignment, and improve the capability of energy feedback and power transfer efficiency of conventional wireless power transfer (WPT) systems for electric vehicles, this paper presents a bidirectional WPT topology with a relay circuit. In the proposed topology, the primary and pickup circuits are implemented with virtually identical structures, which can operate in both magnetic field excitation and magnetic field receiving modes to facilitate bidirectional power flow between the primary side and the pickup side. A relay circuit is introduced to achieve high transfer efficiency under special conditions such …
Energy And Area Spectral Efficiency Trade-Off For Mc-Cdma With Carrier Frequency Offset, Junaid Ahmed, Moazzam Islam Tiwana, Omer Ahmed, Sarmad Sohaib
Energy And Area Spectral Efficiency Trade-Off For Mc-Cdma With Carrier Frequency Offset, Junaid Ahmed, Moazzam Islam Tiwana, Omer Ahmed, Sarmad Sohaib
Turkish Journal of Electrical Engineering and Computer Sciences
Intercell interference is a major factor that limits the capacity of cellular wireless communication systems. This paper proposes an accurate statistical model that caters to interference and noise to determine the ergodic capacity. A new expression for ergodic capacity is derived that enables us to calculate area spectral efficiency (ASE) and energy efficiency (EE). This expression has been used to calculate and compare ASE and EE for low and high traffic scenarios with various signal-to-noise ratios and intercell distances.
Energy Optimized Scheduling For Non-Preemptive Real-Time Systems, Vasanthamani Kannaian, Visalakshi Palanisamy
Energy Optimized Scheduling For Non-Preemptive Real-Time Systems, Vasanthamani Kannaian, Visalakshi Palanisamy
Turkish Journal of Electrical Engineering and Computer Sciences
Embedded systems have geared up their applications in the field of smart phones, mobile devices, automobiles, and medical instrumentation. Along with the growth of technology, the functional requirements of the systems have also grown multifold. To accommodate these ever increasing functional requirements, the hardware should be designed to include the maximum capability, which in turn increases power consumption. Thus this has to be dynamically managed using software techniques. The dynamic voltage and frequency scaling (DVFS) feature provided in most of the recent processors has enabled power optimization through software. With this feature the processor operating frequency can be reduced on …
An Intelligent Pso-Based Energy Efficient Load Balancing Multipath Technique In Wireless Sensor Networks, Sukhchandan Randhawa, Sushma Jain
An Intelligent Pso-Based Energy Efficient Load Balancing Multipath Technique In Wireless Sensor Networks, Sukhchandan Randhawa, Sushma Jain
Turkish Journal of Electrical Engineering and Computer Sciences
To provide a reliable and efficient service, load balancing plays an important role in wireless sensor networks (WSNs). There is a need to maximize the network lifetime for WSNs applications with periodic generation of data. Due to the relationship between energy consumption and network sensor node lifetime, energy consumption in a network should be minimized and balanced in order to increase network lifetime. Energy-efficient load-balancing techniques are needed to solve this problem. In this paper, a particle swarm optimization (PSO)-based energy-efficient load-balancing technique is proposed, in which the required number of routing paths and energy consumption of different nodes and …
Minimizing Reverse Current Flow Due To Distributed Generation Via Optimal Network Reconfiguration, Jasrul Jamani Jamian, Muhammad Mohsin Aman, Muhammad Ariff Baharuddin, Ahmad Safawi Mokhtar, Mohd Noor Abdullah
Minimizing Reverse Current Flow Due To Distributed Generation Via Optimal Network Reconfiguration, Jasrul Jamani Jamian, Muhammad Mohsin Aman, Muhammad Ariff Baharuddin, Ahmad Safawi Mokhtar, Mohd Noor Abdullah
Turkish Journal of Electrical Engineering and Computer Sciences
Distributed generation (DG) is widely used to minimize total power losses in distribution networks. However, one of the problems of DG in a grid system is reverse current flow (RCF), which is when the DG output becomes greater than the connected load. Therefore, this paper proposes a multiobjective artificial bee colony (MOABC) algorithm to determine the optimal network reconfiguration for reducing total RCF in DG. The proposed algorithm is tested on 33-bus radial distribution systems in two different scenarios, i.e. base case and with 50% load. The proposed technique can reduce reverse current by up to 93%; however, the total …
Robust Local Parameter Estimator Based On Least Absolute Value Estimator, Volkan Özdemi̇r, Murat Göl
Robust Local Parameter Estimator Based On Least Absolute Value Estimator, Volkan Özdemi̇r, Murat Göl
Turkish Journal of Electrical Engineering and Computer Sciences
Changes in weather conditions such as temperature and humidity, miscommunication between the control center and circuit breaker transducers and tap changers, and inaccurate manufacturing data may cause parameter errors. Because of incorrect parameters, the state estimator may provide biased state estimates, which may lead to many serious economic and operational results. In order to prevent that, one must identify and correct those parameter errors. This work proposes a local parameter estimator based on the least absolute value (LAV) estimator, which is known to be robust against bad measurements, i.e. measurements with gross error. Considering the increasing number of phasor measurement …
Constrained Control Allocation For Nonlinear Systems With Actuator Failures Or Faults, Saman Ebrahimi Boukani, Mohammad Javad Khosrowjerdi, Roya Amjadifard
Constrained Control Allocation For Nonlinear Systems With Actuator Failures Or Faults, Saman Ebrahimi Boukani, Mohammad Javad Khosrowjerdi, Roya Amjadifard
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a combination of dynamic constrained control allocation with terminal sliding mode control is proposed for a general class of overactuated nonlinear systems with actuator faults/failures. First, the terminal sliding mode control is designed to converge the system tracking error to zero in a finite-time. Then a control allocation strategy is developed and will be solved by a Lyapunov method, which leads to a dynamic update law with finite-time convergence. This strategy satisfies input limits and when faults/failures occur in some of the actuators, the control signals are automatically redistributed among the healthy actuators. Simulation results on a …
Multiclass Semantic Segmentation Of Faces Using Crfs, Khalil Khan, Nasir Ahmad, Khalil Ullah, Irfanud Din
Multiclass Semantic Segmentation Of Faces Using Crfs, Khalil Khan, Nasir Ahmad, Khalil Ullah, Irfanud Din
Turkish Journal of Electrical Engineering and Computer Sciences
Multiclass semantic image segmentation is widely used in a variety of computer vision tasks, such as object segmentation and complex scene understanding. As it decomposes an image into semantically relevant regions, it can be applied in segmentation of face images. In this paper, an algorithm based on multiclass semantic segmentation of faces is proposed using conditional random fields. In the proposed model, each node corresponds to a superpixel, while the neighboring superpixels are connected to nodes through edges. Unlike previous approaches, which rely on three or four classes, the label set is extended here to six classes, i.e. hair, eyes, …
Dynamic Security Enhancement Of Power Systems Using Mean-Variance Mapping Optimization, Cavi̇t Fati̇h Küçüktezcan, Veysel Murat İstemi̇han Genç
Dynamic Security Enhancement Of Power Systems Using Mean-Variance Mapping Optimization, Cavi̇t Fati̇h Küçüktezcan, Veysel Murat İstemi̇han Genç
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a preventive control action that involves both generation rescheduling and load curtailment is proposed for enhancing the dynamic security of large interconnected power systems. The control action is formulated as a security-constrained optimization problem that is solved by mean-variance mapping optimization (MVMO) integrated with a self-adaptive penalization technique and artificial neural networks to develop a fast and effective methodology. The proposed methodology is applied to a 16-generator 68-bus test system to solve the security-constrained optimization problem with both continuous and discrete decision variables. To find a proper and cost-effective solution for the control actions within an acceptable …
Assessment Of Disordered Voices Based On An Optimized Glottal Source Model, Mounir Boudjerda, Abdellah Kacha
Assessment Of Disordered Voices Based On An Optimized Glottal Source Model, Mounir Boudjerda, Abdellah Kacha
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, a method for the assessment of disordered voices is proposed. A feature named mean opening quotient (MOQ) obtained from the glottal source estimation is used as an acoustic cue to summarize the degree of severity of the voice disorder. The analysis method uses the empirical mode decomposition algorithm to estimate the glottal source excitation signal from the speech signal. The logarithm of the magnitude spectrum of the speech signal is decomposed into oscillatory modes, called intrinsic mode functions, that are clustered into two classes, the spectral envelope and the harmonic component. The exploitation of the phase information …
A New Segmentation Method Of Cerebral Mri Images Based On The Fuzzy C-Means Algorithm, Mohamed Zaki Abderrezak, Mouatez Billah Chibane, Karim Mansour
A New Segmentation Method Of Cerebral Mri Images Based On The Fuzzy C-Means Algorithm, Mohamed Zaki Abderrezak, Mouatez Billah Chibane, Karim Mansour
Turkish Journal of Electrical Engineering and Computer Sciences
The aim of this work is to present a new method for cerebral MRI image segmentation based on modification of the fuzzy c-means (FCM) algorithm. We used local and nonlocal information distance in the initial function of the robust FCM model. The obtained results of the classification of MRI images showed the effectiveness of the suggested model. Calculation of the similarity index confirms that our method is well adapted to MRI images even in the presence of noise.
Distinct Degradation Processes In Zno Varistors: Reliability Analysis And Modeling With Accelerated Ac Tests, Hadi Yadavari, Mustafa Altun
Distinct Degradation Processes In Zno Varistors: Reliability Analysis And Modeling With Accelerated Ac Tests, Hadi Yadavari, Mustafa Altun
Turkish Journal of Electrical Engineering and Computer Sciences
In this study, we investigate different degradation mechanisms of zinc oxide (ZnO) varistors. We propose a model that shows how Vv (defined as DC varistor voltage when a 1-mA DC current is applied) changes with time for different stress levels. For this purpose, accelerated degradation tests are applied for different AC current levels and voltage values are then measured. Different from the common practice in the literature that considers degradation with only decreasing Vv values, we demonstrate either an increasing or a decreasing trend in the Vv parameter. The tests show a decreasing trend in Vv for current levels above …
A Particle Swarm Optimization And Block-Svd-Based Watermarking For Digital Images, Falgun Thakkar, Vinay Kumar Srivastava
A Particle Swarm Optimization And Block-Svd-Based Watermarking For Digital Images, Falgun Thakkar, Vinay Kumar Srivastava
Turkish Journal of Electrical Engineering and Computer Sciences
The major issues in most watermarking schemes are security, reliability, and robustness against attacks. To achieve these objectives in a watermarking algorithm, the selection of a scale factor to embed the watermark into the host image is a challenging problem. In this paper, a block singular value decomposition (SVD)-based reliable, robust, secure, and fast watermarking scheme is proposed that uses particle swarm optimization (PSO) in the selection of the scale factor. SVD is applied here on the nonoverlapping blocks of LL wavelet subbands. Selected singular values of these blocks are modified with the pixel values of the watermark image. Selected …
Optimal Fusion Of Multiple Gnss Signals Against Spoofing Sources, Selçuk Şahi̇n, Abedallatif Baba, Tolga Sönmez
Optimal Fusion Of Multiple Gnss Signals Against Spoofing Sources, Selçuk Şahi̇n, Abedallatif Baba, Tolga Sönmez
Turkish Journal of Electrical Engineering and Computer Sciences
Electronic attacks such as spoofing are becoming an increasing threat for satellite-based navigation receivers. The aim of this paper is to develop a preventive method against such electronic attacks. In our scheme, the localization system uses four different Global Navigation Satellite Systems (GNSSs): GPS, Galileo, GLONASS, and Compass. The signals received from these satellite systems will be fused inferentially and will be tracked according to a linear model. The linear model that we developed is solved with a Kalman filter and simulated under different scenarios. When a discrepancy is detected in the output of one of the GNSS receivers due …
Fpga-Based Soc For Hardware Implementation Of A Local Histogram-Based Video Shot Detector, Abdessalem Ben Abdelali, Mohamed Nidhal Krifa, Abdellatif Mtibaa
Fpga-Based Soc For Hardware Implementation Of A Local Histogram-Based Video Shot Detector, Abdessalem Ben Abdelali, Mohamed Nidhal Krifa, Abdellatif Mtibaa
Turkish Journal of Electrical Engineering and Computer Sciences
In this paper, we present a video application example and its implementation in a reconfigurable system-on-chip (SOC) platform. The proposed platform employs the benefits of field programmable gate array (FPGA) technology. A prototype based on a Xilinx Virtex-5 FPGA is developed. The application includes a video shot boundary detection module based on the local histogram (LH) technique. Diverse hardware module versions corresponding to different quantization levels and architectural solutions for an LH-based shot detection system are presented. The developed modules have different hardware resource occupations and can be used in a dynamic way to allow flexible management of the target …
Disk Scheduling With Shortest Cumulative Access Time First Algorithms, Nai̇l Akar, Çağlar Tunç, Mark Gaertner, Fati̇h Erden
Disk Scheduling With Shortest Cumulative Access Time First Algorithms, Nai̇l Akar, Çağlar Tunç, Mark Gaertner, Fati̇h Erden
Turkish Journal of Electrical Engineering and Computer Sciences
A new class of scheduling algorithms is proposed for disk drive scheduling. As opposed to choosing the request with the shortest access time in conventional shortest access time first (SATF) algorithms, we choose an ordered sequence of pending I/O requests at the scheduling instant with the shortest cumulative access time. Additionally, we introduce flexibility for forthcoming requests to alter the chosen sequence. Simulation results are provided to validate the effectiveness of the proposed disk scheduler. Throughput gains of 3% and above are shown to be attainable, although this occurs at the expense of increased computational complexity.
A Stable Marriage-Based Request Routing Framework For Interconnection Cdns, Bo Huang, Lijian Zou, Xiaowen Tong, Xiaoqun Yuan
A Stable Marriage-Based Request Routing Framework For Interconnection Cdns, Bo Huang, Lijian Zou, Xiaowen Tong, Xiaoqun Yuan
Turkish Journal of Electrical Engineering and Computer Sciences
Content delivery network (CDN) interconnection is a promising solution to addressing the limited service scale of CDNs. It scales the CDN's service footprint through the cooperation of CDNs without significantly changing the existing network architecture. However, in a CDN interconnection system, CDNs are independent of each other and each pursues its own goals, which means that cooperation is hard to establish and easy to break. In our paper, we propose a stable marriage-based routing framework to establish a strong cooperation service for CDNs and to select the `optimal' server for each request among the cooperative CDNs. To this end, we …
Mri Image Enhancement Using Biot-Savart Law At 3 Tesla, Yunus Emre Esi̇n, Ferda Nur Alpaslan
Mri Image Enhancement Using Biot-Savart Law At 3 Tesla, Yunus Emre Esi̇n, Ferda Nur Alpaslan
Turkish Journal of Electrical Engineering and Computer Sciences
Coil sensitivity is considered as the most valuable data in the parallel reconstruction of magnetic resonance imaging (MRI). In this study, a novel coil sensitivity map extraction method is introduced for spatially fixed phased array coils. The proposed technique uses the Biot--Savart law with coil internal shape information and low-resolution phase image data to form sensitivity maps. The performance of this method is tested in a parallel image reconstruction task, using the sensitivity-encoding (SENSE) technique. Under the quasi-static assumption and using the duality principle, we computed the sensitivity maps of a phased-array head coil and reconstructed full FOV images. The …
A Fast Feature Selection Approach Based On Extreme Learning Machine And Coefficient Of Variation, Ömer Faruk Ertuğrul, Mehmet Emi̇n Tağluk
A Fast Feature Selection Approach Based On Extreme Learning Machine And Coefficient Of Variation, Ömer Faruk Ertuğrul, Mehmet Emi̇n Tağluk
Turkish Journal of Electrical Engineering and Computer Sciences
Feature selection is the method of reducing the size of data without degrading their accuracy. In this study, we propose a novel feature selection approach, based on extreme learning machines (ELMs) and the coefficient of variation (CV). In the proposed approach, the most relevant features are identified by ranking each feature with the coefficient obtained through ELM divided by CV. The achieved accuracies and computational costs, obtained with the use of features selected via the proposed approach in 9 classification and 26 regression benchmark data sets, were compared to those obtained with all features, as well as those obtained with …
Horizontal Directional Drilling Pilot Bore Simulation, Paulius Tervydis, Ruta Jankuniene
Horizontal Directional Drilling Pilot Bore Simulation, Paulius Tervydis, Ruta Jankuniene
Turkish Journal of Electrical Engineering and Computer Sciences
Various underground communications (water or gas supply systems, sewage, power lines) have been installed in recent years using trenchless technologies, i.e. horizontal directional drilling (HDD). This technique by its nature does not disturb the traffic and is environmentally friendly. One must be aware that, with HDD, pipeline building time is shortened. With respect to the above, HDD is especially effective in highly populated or industrial areas. However, it is necessary to ensure that HDD works, in order to prevent damage to installed underground facilities. The aim of this work is to propose a user-friendly and inexpensive simulation tool with required …
Axial Flux Pm Bldc Motor Design Methodology And Comparison With A Radial Flux Pm Bldc Motor, Ertuğrul Yeşi̇lbağ, Yasemi̇n Ertuğrul, Lale Ergene
Axial Flux Pm Bldc Motor Design Methodology And Comparison With A Radial Flux Pm Bldc Motor, Ertuğrul Yeşi̇lbağ, Yasemi̇n Ertuğrul, Lale Ergene
Turkish Journal of Electrical Engineering and Computer Sciences
The aim of this paper is to develop a methodology to design an axial flux permanent magnet brushless direct current (AFPM) motor for a washing machine and compare the results with a conventional radial flux permanent magnet brushless direct current (RFPM) motor with the same power ratings. The AFPM motor is designed based on the maximum power density for an optimum inner-to-outer diameter ratio by using the reference RFPM motor constraints, such as the same rated torque at the rated speed. Both motors use the same materials in terms of lamination, permanent magnet, and conductor. They both use ferrite magnets; …
Relaxation Rate And Polarization Charge Density Model For Aln/Al$_{X}$Ga$_{1 - X}$N/Aln Heterostructures, Nagarajan Sivarajan, Reeba Korah, Mariya Kalavathy Ganamani
Relaxation Rate And Polarization Charge Density Model For Aln/Al$_{X}$Ga$_{1 - X}$N/Aln Heterostructures, Nagarajan Sivarajan, Reeba Korah, Mariya Kalavathy Ganamani
Turkish Journal of Electrical Engineering and Computer Sciences
This work describes the strain-relaxation--dependent carrier concentration ($n_{s})$ profile model using spontaneous and piezoelectric polarization for AlN/Al$_{x}$Ga$_{1 - x}$N/AlN HEMTs in all mole fraction ($x)$ interpolations. As $x$ varies, the Aluminum Gallium Nitride (AlGaN) channel shows strain relaxation with the Aluminum Nitride (AlN) barrier. The degree of relaxation is modeled from AlN to GaN regions in the channel. It shows that the AlN barrier and buffer relaxation and strain recovery occurs due to the gradual crystal quality degradation from barrier/buffer to the channel interface. These combination devices show less drain current degradation with temperature variation from 300 K to 573 …
Numerical Study Of Ac Loss Of Two-Layer Hts Power Transmission Cables Composed Of Coated Conductors With A Ferromagnetic Substrate, Şükrü Yildiz, Fedai̇ İnanir, Ahmet Çi̇çek, Fedor Gömöry
Numerical Study Of Ac Loss Of Two-Layer Hts Power Transmission Cables Composed Of Coated Conductors With A Ferromagnetic Substrate, Şükrü Yildiz, Fedai̇ İnanir, Ahmet Çi̇çek, Fedor Gömöry
Turkish Journal of Electrical Engineering and Computer Sciences
This work includes the simulation of hysteretic AC losses in two-layer HTS power transmission cables made of second-generation high-temperature superconducting tapes with a ferromagnetic substrate subject to an oscillating AC transport current, calling upon the COMSOL Multiphysics finite-element software program and exploiting an AC/DC module. How the AC transport loss is influenced by the arrangement of tapes, as well as the optimized design of superconducting power cables based on YBCO-coated conductors, are investigated. According to the radial arrangement of the tapes, four different orientations of ferromagnetic substrate are considered: 1) out-in (substrate of inner/outer layer facing outward/inward), 2) in-out (substrate …
Calculation Of Creepage Discharge Safety Factors Against The Tangential Component Of Electric Fields In The Insulation Structure Of Power Transformers, Arsalan Hekmati
Calculation Of Creepage Discharge Safety Factors Against The Tangential Component Of Electric Fields In The Insulation Structure Of Power Transformers, Arsalan Hekmati
Turkish Journal of Electrical Engineering and Computer Sciences
Creepage discharges are a main cause of insulation damage in power transformers during repeated tests or during operation. In this paper, a hazardous region in the insulation structure of power transformers (the interface between solid and liquid insulation at the top edge of a high-voltage electrode) is considered, and the impact of a very important factor of the surface discharge initiation and propagation (the tangential component of the electric field) on the strength of the insulation structure is investigated in power transformers. Insulation system reliability against this tangential component is presented as a safety factor. Two methods based on cumulative …