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فهرست مقالات
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دسترسی آزاد مقاله
1 - Presenting a New Fault Current Limiter Structure to Reduce the Over-voltage of the DFIG DC Link in the Voltage Sag Condition
Mohsen Ghorbani Babak Mozafari Mehdi Firouzi Farzad GolshanIn this study a new type of fault current limiter is introduced. It has been named multi-functional capacitive fault current limiter (MCFCL). as a variable capacitor, its function is to control active power flow in normal conditions as well as improving the capability o چکیده کاملIn this study a new type of fault current limiter is introduced. It has been named multi-functional capacitive fault current limiter (MCFCL). as a variable capacitor, its function is to control active power flow in normal conditions as well as improving the capability of low voltage rid-through (LVRT) in fault operating conditions. The new structure has been proposed based on the capacitive bridge-type fault current limiter (BFCL) and the RL-type fault current limiter (FCL), which is modified to enhance low-voltage ride-through capability. To assess the efficacy of proposed fault current limiter, the time domain simulations were executed in PSCAD/EMTDC software and its function is compared with the RL-type SSFCLs in normal and symmetrical or asymmetrical fault conditions. Also its efficacy has been evaluated in a fixed speed based wind farm. The result of simulations showed that the MCFCL is not only able to control the power flow in normal operating condition, but also improves the LVRT performance in fault operating condition in the wind farms. پرونده مقاله -
دسترسی آزاد مقاله
2 - Small Signal Modeling of a Synchronous Isolated Cuk Converter used in Photovoltaic Systems
Atila Skandarnezhad Yaghoob Mohammadmoradi Nader JavadifarThis paper presents the small-signal modeling of a synchronous Cuk converter using state-space averaging method. In the proposed isolated converter, the conduction and switching losses reduced by replacing the traditional diode with transistor and employing an auxiliary چکیده کاملThis paper presents the small-signal modeling of a synchronous Cuk converter using state-space averaging method. In the proposed isolated converter, the conduction and switching losses reduced by replacing the traditional diode with transistor and employing an auxiliary circuit. It causes the conversion efficiency of the photovoltaic system to be increased and better matching of the supplied load. Also this circuit has significant advantage over other topologies since it enables low voltage ripple on both input/output sides of the converter and better dynamic response. The low frequency small-signal model is done using state space averaging technique and two main power-stage transfer functions are derived, which are control-to-output voltage transfer function and input-to-output voltage transfer function. Using the proposed model of the converter we can analyze and simulate the time domain transient behavior of the system accurately and intuitively. Finally, the accuracy and validity of the proposed system model is verified by simulation results. پرونده مقاله -
دسترسی آزاد مقاله
3 - Fake News Detection Using Feature Extraction, Resampling Methods, and Deep Learning
Mirmorsal Madani Homayun Motameni Hosein MohamadiThe production of fake news were practiced even before the advent of the internet. However, with the development of the internet and traditional media giving way to social media, the growing and unstoppable process of making and spreading this kind of news have become a چکیده کاملThe production of fake news were practiced even before the advent of the internet. However, with the development of the internet and traditional media giving way to social media, the growing and unstoppable process of making and spreading this kind of news have become a widespread concern. Fake news by disrupting the proper flow of information and deluding public opinion, potentially causes serious problems in society. Therefore, it is necessary to detect such news, which is associated with some challenges. These challenges may be related to various issues such as datasets, events, or audiences. Lack of sufficient information about news samples, or an imbalance are the main problems in some of these datasets, which will be addressed in this paper. In the proposed model, firstly the key features in relevant datasets will be extracted to increase information about news samples. After that, using the K-nearest neighbors, a genetic, and TomekLink algorithms as the cleaning techniques, as well as designing a Generative Adversarial network, as a technique for generating synthetic data, three novel methods in the area of hybrid resampling will be presented to balance these datasets. The presented methods cause a significant increase in the performance of the deep learning algorithms to detect fake news. پرونده مقاله -
دسترسی آزاد مقاله
4 - A Review of Single Electron Transistors
Yaghoob Mohammadmoradi Nader Javadifar Atila SkandarnezhadThe single electron transistor (SET) is an effectual device to quantize current. It has been highly considered as the most fundamental single-electron device in the research field of nanotechnology. An electron from the single electron transistor (SET) is a pivotal elem چکیده کاملThe single electron transistor (SET) is an effectual device to quantize current. It has been highly considered as the most fundamental single-electron device in the research field of nanotechnology. An electron from the single electron transistor (SET) is a pivotal element in the research field of nanotechnology. This type of transistor with very low power consumption and high-performance speed is considered as a nano-scaled switching device that can control the motion of a single electron. The principles of SET and some of its applications are discussed in this paper. In this research paper, we also focus on some basic device characteristics like ‘Coulomb blockade’, single electron tunneling effect & ‘Coulomb staircase’ on which this Single electron transistor [SET] works and the basic comparison of SET characteristics and also its [SET] advantages as well as disadvantages to make a clear picture about the reason behind its popularity in the field of nanoelectronics. پرونده مقاله -
دسترسی آزاد مقاله
5 - Design and Analysis of a Two stage Class AB Operational Trans-conductance Amplifier in 180 –nm Technology
shahrbanoo ghorbanzadeh hadi dehbovid Alireza ghorbani Seyed Mehdi Abedi PahnekolaeiThis paper presents design concept of Operational Transconductance Amplifier (OTA). Using active loads in the first stage and improved recycling structure, the effective trans-conductance of the first stage is increased. Nonlinear current mirror boosts the current of th چکیده کاملThis paper presents design concept of Operational Transconductance Amplifier (OTA). Using active loads in the first stage and improved recycling structure, the effective trans-conductance of the first stage is increased. Nonlinear current mirror boosts the current of the second stage; Therefore, Slew Rate (SR) is increased. The class-AB technique is achieved without enhancing power dissipation and without unity-gain bandwidth (UGBW) or noise deterioration. The efficiency of the proposed OTA is evaluated by several simulations in a 0.18μm CMOS process with the 1.8 V supply voltage. This technique is very helpful for high amplification, stability, and low power applications. From the simulation results, the two stage amplifier gives better performance compared to other topologies, especially in terms of gain, output swing, slew rate and unity-gain bandwidth. The circuit is able to achieve 95 dB gain, a 3V output swing, a 169 slew rate and a unity-gain bandwidth of 344 MHZ with a power supply voltage of 1.8 V. پرونده مقاله -
دسترسی آزاد مقاله
6 - New Super-twisting Sliding Mode Control of an Upper Limb Rehabilitation Robot Based on the TLBO Algorithm
Naghmeh Mirrashid Esmaeil Alibeiki Seyed Mehdi RakhtalaRehabilitation robots are very popular because they are beneficial tools in helping stroke patients and people with physical disabilities, so controlling them to get accurate performance is necessary. This paper presents a new super-twisting controller based on the dete چکیده کاملRehabilitation robots are very popular because they are beneficial tools in helping stroke patients and people with physical disabilities, so controlling them to get accurate performance is necessary. This paper presents a new super-twisting controller based on the determined gain with the TLBO algorithm (STA-TLBO) for an upper limb rehabilitation robot for the first time. One of the most important parts of designing the super twisting algorithm (STA) controller is determining the gains, which requires accurate calculations and obtaining disturbance. In this paper, the Teaching–Learning-Based Optimization (TLBO) algorithm is used to obtain the gains of the STA controller. To illustrate the validity of the proposed controller, the results are compared to PID, STA, and PID-TLBO controllers. The results indicate that the proposed controller ensures accurate tracking, finite-time convergence, and reduced chattering. The stability and the robustness of the PID-TLBO and STA-TLBO controllers are examined by three tests, parameter uncertainties, external disturbances, and step response. The results show that the STA-TLBO controller has a better performance than the others under different conditions; that means the proposed controller has a shorter convergence time, more accurate tracking, and fewer tracking error than the other three controllers. پرونده مقاله -
دسترسی آزاد مقاله
7 - Image Hiding Using Logistic Map Chaotic Function
Mehdi AlirezanejadSteganography is the action of hiding a secret message within another cover message. The secret message and the cover image can be text, image, voice even signal. In this article an image is used as the secret message while the cover message is also a gray level image. چکیده کاملSteganography is the action of hiding a secret message within another cover message. The secret message and the cover image can be text, image, voice even signal. In this article an image is used as the secret message while the cover message is also a gray level image. This paper proposes a new method of steganography based on logistic chaotic maps. This function is used to determine the position of different bits of the secret image in the covering image. The main advantage of the proposed method is that the pixels of the secret image in the covering image is uniformly distributed, which increases the robustness of the proposed method to common attacks. The robustness and performance of the proposed method against common attacks in the area of steganography including corruption, clipping, and noise is tested. The high PSNR of the proposed method (about 45) expresses the high performance of the proposed method. پرونده مقاله -
دسترسی آزاد مقاله
8 - Increasing the Heat Transfer Performance of a Turbulator Equipped Concentric Gas-liquid Heat Exchanger Using Al2O3 – Water Nanofluid
seyyed rahim hosseini Seyyed Masoud Seyyedi Mehdi Hashemi TilenoeeIn this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and چکیده کاملIn this study, the turbulent fluid flow and heat transfer performance of a concentric two-tube (air-nanofluid) heat exchanger with a helical turbulator is studied using STAR-CCM+. First, the computational code is validated according to the related experimental data and its simulation results for air and water. Then, the heat transfer performance and the effect of the different pitches of the helical turbulators are analyzed by replacing nanofluid instead of water for heat removal. The results show that the turbulator and nanoparticle has a high impact on heat transfer capability of the heat exchanger. The result shows that, the heat transfer is increased using turbulators in comparison with smooth tube for pitches of 15, 30 and 45 mm, respectively. In addition, the STAR-CCM+ is a proper tool for simulation of a complex geometries in three-dimensional. It is not only the CFD solver, STAR- CCM+ is an entire engineering process for solving problems involving flow (of fluids or solids), heat transfer and stress. It provides a suite of integrated components that combine to produce a powerful package that can address a wide variety of modeling needs. These components include: • 3D-CAD Modeler • CAD Embedding • Surface Preparation Tools • Automatic Meshing Technology • Physics Models • Post-processing پرونده مقاله -
دسترسی آزاد مقاله
9 - Ab-initio Investigation of Mechanical Properties of MX2(M=Zr, Hf; X=S, Se, Te) Transition Metal Dichalcogenides Nano Tubes (TMDNTs)
Abdollah Haji Malekkheili Mojtaba Yaghoubi Alireza AmaniMiniaturization of bulk crystals in any direction down to nanometer dimensions leads to the emergence of quantum confinement phenomenon, which is technologically favorable. Transition Metal Dichalcogenides (TMDs) are important mechanical materials that have a layered st چکیده کاملMiniaturization of bulk crystals in any direction down to nanometer dimensions leads to the emergence of quantum confinement phenomenon, which is technologically favorable. Transition Metal Dichalcogenides (TMDs) are important mechanical materials that have a layered structure. In addition, ach layer consists of three atomic layers. TMD Nano Tubes (TMDNTs) can be created by rolling such a layer. This study investigates structural, mechanical, and bonding properties of TMDNTs. In particular, two important quantities, Young’s modulus and Poisson’s ratio, are calculated for 6 zigzag MX2 (M=Zr, Hf; X=S, Se, Te) nanotubes and the results are compared with those of other known nanotubes. The computed value of Young’s modulus is greater than that of blue Phosphorus and, in some cases, higher than those of WS2 nanotubes (which are experimentally synthesized). Given the increase in the bond length between M and X atoms, the ratio of Young’s modulus to Poisson’s increases as the atomic number X is reduced. However, there is no significant difference in the aforementioned quantity for ZrX2 and HfX2 nanotubes due to the close bond lengths of Zr-X and Hf-X. The band gap confirms this finding. A Mulliken charge analysis was conducted to investigate the amount of charge transfer between M and X atoms to observe the strength of bond lengths. پرونده مقاله -
دسترسی آزاد مقاله
10 - Automatic Control of Anesthesia During Surgery Using Fuzzy Controller
Maryam Goodarzian Mohammad Reza Yousefi Neda BehzadfarCreating the desired depth of anesthesia is done by controlling the amount of anesthetic drug applied to the patient. Applying an excessive amount of anesthetic causes the patient to regain consciousness, and on the other hand, using an amount less than necessary causes چکیده کاملCreating the desired depth of anesthesia is done by controlling the amount of anesthetic drug applied to the patient. Applying an excessive amount of anesthetic causes the patient to regain consciousness, and on the other hand, using an amount less than necessary causes the patient to perceive the painful stimuli caused by the surgery. In this article, using the lowest amount of drug as a control input, the desired depth of anesthesia (the desired value of 50%) is created as the output of the model in the patient. The aim of designing an improved control method to adjust the drug dose is to use the second type of fuzzy logic, which is more advanced and has higher accuracy and flexibility than the first type of fuzzy logic. In order to analyze the results of this research, the system has been simulated using MATLAB software, and the effects of disturbance and noise have been considered in the output of the model. The results show that the proposed control structure controls the model well. Based on the simulation done in MATLAB software, the use of type two fuzzy control structure can reduce the amount of fluctuations in disturbance and measurement noise by 25% compared to type one fuzzy method, and in the conditions Without disturbance and noise, the proposed method does not have any subjugation and at the same time, the amount of time to achieve the desired value is improved by 87% compared to the type one fuzzy method. پرونده مقاله -
دسترسی آزاد مقاله
11 - Design and Simulation of Torque Controller for Two-Mass Mechanical System Using Eigenvalue Analysis
Mansoor Zeinali Somaye YaghoubiMechanical system in motor drive in industry can be modeled by multi-mass system. In this paper, the equations of the two-mass system are first stated in the state space and the two-mass mechanical system model is determined using the transfer functions. In torque contr چکیده کاملMechanical system in motor drive in industry can be modeled by multi-mass system. In this paper, the equations of the two-mass system are first stated in the state space and the two-mass mechanical system model is determined using the transfer functions. In torque control of this system, in order to have mechanical oscillation, PID controller is often used as a simple control method. Using the torque controller coefficients diagram method, it is designed and the behavior of the system is investigated and simulated using the analysis of eigenvalues. From the prominence of this study, we can mention the expression of electric torque changes in the two-mass system based on the inputs and their relationship with each other. The simulation results show that designing the parameters using the coefficient diagram method can reduce the fluctuations of the electric torque in the two-mass system. In this design, the eigenvalues of the system are placed on the left side of the imaginary axis. پرونده مقاله -
دسترسی آزاد مقاله
12 - Study and Simulation of No-Load Synchronous Generator Equipped with Static Excitation System
Fariborz Haghighatdar-Fesharaki Majid Dehghani Mehdi RiahinasabSynchronous machine is a two-excitation machine and is widely used in energy conversion systems such as wind energy conversion system and hydropower plants. Providing and regulating the direct current of the excitation coil of the synchronous machine is the main task of چکیده کاملSynchronous machine is a two-excitation machine and is widely used in energy conversion systems such as wind energy conversion system and hydropower plants. Providing and regulating the direct current of the excitation coil of the synchronous machine is the main task of the excitation system. The excitation system in the synchronous machine must have a high voltage limit. For high reliability, each generator has its own exciter. The excitation system by controlling the excitation voltage can control the voltage and reactive transmission power and strengthen the stability of the system and cause the proper operation of a power system. In the dynamic analysis of the power system, to check the stability of the synchronous generator, it is enough to consider the excitation system and its primary drive controls can be ignored. In this article, the aim is to study and simulate the behavior of a no-load synchronous generator equipped with a static excitation system. Changes in the output voltage of the excitation system due to changes in the parameters of the excitation gain reduction (TGR) and the excitation system stabilizer (ESS) have been investigated. The simulation results show the effect of TGR and ESS on damping the oscillatory response and reducing the settling time of the response. پرونده مقاله
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