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Öğe A Conformal Fractional Derivative-based Leaky Integrate-and-Fire Neuron Model(2022) Mutlu, Reşat; Devecioğlu, İsmailNeuron model have been extensively studied and different models have been proposed. Nobel laureate Hodgkin-Huxley model is physiologically relevant and can demonstrate different neural behaviors, but it is mathematically complex. For this reason, simplified neuron models such as integrate-and-fire model and its derivatives are more popular in the literature to study neural populations. Lapicque’s integrate-and-fire model is proposed in 1907 and its leaky integrate-and-fire version is very popular due to its simplicity. In order to improve this simple model and capture different aspects of neurons, a variety of it have been proposed. Fractional order derivative-based neuron models are one of those varieties, which can show adaptation without necessitating additional differential equations. However, fractional-order derivatives could be computationally costly. Recently, a conformal fractional derivative (CFD) is suggested in literature. It is easy to understand and implement compared to the other methods. In this study, a CFD-based leaky integrate-and-fire neuron model is proposed. The model captures the adaptation in firing rate under sustained current injection. Results suggest that it could be used to easily and efficiently implement network models as well as to model different sensory afferents.Öğe A methodology for memristance calculation(Tubitak Scientific & Technical Research Council Turkey, 2014) Mutlu, Reşat; Karakunal, ErtugrulA memristor is a newly found fundamental circuit element whose behavior can be predicted using either the charge-dependent function called memristance or the flux-dependent function called memductance. Therefore, it is important to find the memristance or memductance function of a memristor. To the best of our knowledge, there is no methodology describing how to obtain the memristance function or memristor characteristic in the literature for this purpose as of yet. In this work, a methodology is suggested to find the memristance or memductance functions. The methodology suggests first doing several experiments with a memristor using a square-wave signal to acquire data and then using an algorithm inspired by the experience on ionic memristors reported in the literature to obtain its memristance and memductance functions. The methodology is applied to calculate the memristance function and memristor characteristic of a memristor emulator. Justifications for this method are also given.Öğe A Microcontroller Implementation of Hindmarsh-Rose Neuron Model-Based Biological Central Pattern Generator(Institute of Electrical and Electronics Engineers Inc., 2019) Yener, Şuayb Çağrı; Mutlu, ReşatCentral Pattern Generator (CPG) has an important role in controlling the locomotion part of the animals. Bio-inspired Central Pattern Generators can find application areas in robotic and control applications. FPGA implementations of Central Pattern Generators have already been studied in literature. Not all institutes have FPGA systems. In this paper, it is shown that like STM32F103 devices which use the Cortex-M3, a Hindmarsh-Rose (HR) neuron model can be made using a cheap microcontroller board. The experimental results verify that the system is successfully able to reproduce the original Central Pattern Generator patterns. © 2019 IEEE.Öğe A microcontroller-based ECG signal generator design utilizing microcontroller PWM output and experimental ECG data(Institute of Electrical and Electronics Engineers Inc., 2018) Yener, Şuayb Çağrı; Mutlu, ReşatSignal generators are commonly used in biomedical engineering studies. Biomedical circuits must often be tested using EEG, ECG etc. signals. The circuit tests are usually done by connecting electronic circuits to humans. It is a cumbersome process. Electronic biomedical signal sources or signal generators can be used to test biomedical measurement circuits at the early stage of the design processes. Such signal generators are expensive and are not always found in laboratories. In this study, a biomedical signal generator is designed using a cheap and easy- to-use Arduino Mega 2560 R3 microcontroller. SD card connected to the microcontroller is uploaded with an experimental ECG waveform. It is shown that the circuit is able to produce the desired ECG waveforms by sending through its PWM output and low-pass filter and performs well. © 2018 IEEE.Öğe A new memristor-based low-pass filter topology and its small-signal solution using MacLaurin series(Natl Inst Optoelectronics, 2015) Yener, Şuayb Çağrı; Mutlu, Reşat; Kuntman, Hulusi HakanIn this work, a new memristor-based low-pass filter topology is suggested. Memristor-based filters are nonlinear circuits and many of them cannot be solved analytically. To find an approximate analytical solution of the filter equations, MacLaurin series is used for the first time. Time and frequency domain behavior of the filter are obtained. Also, the frequency domain gain and total harmonic distortion characteristics of the filter are given. Results obtained by the small signal model have been compared with the dynamic model results. It is shown that the small signal model is able to predict the filter behavior very well.Öğe A process control method for the electric current-activated/assisted sintering system based on the container-consumed power and temperature estimation(Springer, 2018) Yener, Şuayb Çağrı; Yener, Tuba; Mutlu, ReşatIn this paper, the current, voltage and temperature of the container of an electric current-activated/assisted sintering (ECAS) system are measured and recorded with respect to time during the sintering process. By post-processing of the recorded data, the power and thermal energy of the system container are calculated. Interpretation of the measured and post-processed data has provided a criterion: It has been found that the dissipated electrical power in quasi-steady state is almost equal to the power conducted from the container to the copper bars throughout the stiffs and the convection and radiation powers are negligible compared to the conducted power. Therefore, the container-stored thermal energy or the container surface temperature can be estimated from the dissipated electrical power with the values of the container heat capacitance and the stiff thermal resistances without the need for a temperature measurement equipment. If the thermal energy or the temperature required to make the samples has a known/required minimum value and if this amount of the thermal energy is provided to the sample, the sample production process can be stopped. In this study, for an actual implemented design, we suggest that ECAS current and voltages should be continuously measured in real time and the process is automatically terminated when the calculated steady-state container temperature becomes equal to the required container temperature. Therefore, a standard procedure for material production in ECAS system is provided to automate sample production and the performance of the produced samples is guaranteed.Öğe AC Chopper Harmonic Magnitudes in Narrowband Power Line Communication Frequencies(IEEE, 2019) Yener, Şuayb Çağrı; Mutlu, ReşatPower Line Communication is becoming more common each passing day. Narrowband Power Line Communication systems use a frequency range from 3 kHz to 500 kHz. Nonlinear loads are common in residences and unfortunately they produce harmonics. It is possible that some harmonics produced by the nonlinear loads may interact with the power line communication system. AC dimmers produce impulse noise. In this study, Fourier series of an AC chopper is computed and its current harmonics magnitudes which is in Narrowband Power Line Communication frequencies are examined with and without a smoothing inductor. Their harmonic magnitudes in the power line communication frequencies are compared. It has been found that the smoothing inductor performs well to decrease the AC chopper harmonics within the Narrowband power line frequencies.Öğe AC Power Formula for Unsaturated TiO2 Memristors with Linear Dopant Drift, Small Signal AC Power Formula for All Memristors, and Some Applications for These Formulas(Namık Kemal Üniversitesi, 2018) Mutlu, ReşatIn 1971, Chua has claimed that there should have been one more fundamental circuit element called memristor. Memristor is nonlinear charge-dependent resistor. It dissipates power. No ideal memristor has been found yet. In 2008, a TiO2 thin-film memristive system which behaves as a memristor for some part of its operation has been found by a HP research team. The new circuit component can allow new types of analog and digital applications which are not possible with other fundamental circuit elements. This has resulted an emerging interest in memristor and memristive systems. In this paper, the average power formula of TiO2 memristor with linear dopant speed under AC excitation is derived. It is shown that a similar formula is applicable to all ideal memristors excited with a small signal AC source. The formulas derived here or similar formulas can be used to size the programmable memristor and memory circuits having AC waveforms.Öğe An optoelectronic-based memristor emulator circuit with a rational memristance function(National Institute of Optoelectronics, 2021) Tulumbacı, Fatih; Mutlu, ReşatMemristor which has been claimed as the fourth fundamental circuit element in 1971 is a nonlinear circuit element having memory. Recently, an optoelectronics-based memristor emulator is reported in the literature. To the best of our knowledge, a memristor emulator with a rational memristance function has not been reported in literature yet. In this study, a memristor emulator which operates on optic principles or with optic circuit components with a rational memristance function is designed. The optoelectronic-based memristor emulator has two LEDs and an LDR. The emulator is made of off-the-shelf components and easy to build. Using simulations and experiments, it has been shown that the emulator is able to mimic memristor behavior well upto kilohertz region. © 2021, National Institute of Optoelectronics. All rights reserved.Öğe Analysis of a Capacitor Modelled with Conformable Fractional Derivative Under DC and Sinusoidal Signals(2021) Palaz, Utku; Mutlu, ReşatFractional order circuit elements are successfully used to model circuits and systems in the last few decades. There are different types of fractional derivatives. Recently, another one named “the conformable fractional derivative” (CFD) has been introduced and shown to give good results for modeling supercapacitors. It is imperative to know how circuit elements behave for different current and voltage waveforms in circuit theory so that they can be exploited at their full potential. A CFD capacitor is not a well-known element and its usage and circuit solutions are rarely addressed in literature. In this study, it is examined how a CFD capacitor would behave under DC and AC excitations when it is fed by not only a current source but also a voltage source.Öğe Analysis of filter characteristics based on PWL Memristor(Istanbul Univ, Fac Engineering, 2014) Yener, Şuayb Çağrı; Mutlu, Reşat; Kuntman, Hulusi HakanMemristor is claimed as a passive two terminal fundamental circuit element in 1971 and declared to be physically fabricated in 2008. The memristor can provide new features in analog circuit design thanks to its properties which cannot be mimicked by a resistor, a capacitor and an inductor. It is believed that in future it can be used in analog applications such as programmable amplifiers, oscillators, filters and chaotic sources. In this paper, detailed simulations of a low-pass filter and a high-pass filter with memristor are done using a piece-wise linear hypothetical memristor characteristic for sinusoidal input. The memristive switching issue in these filters is analyzed. Also the total harmonic distortions of the memristor based filters are inspected as a function of charge and the input signal frequency using simulations.Öğe ANN Circuit Application of Complementary Resistive Switches(2019) Uçar, Erdem; Karakulak, Ertuğrul; Mutlu, ReşatArtificial neural networks are successfully used for classification, prediction, estimation, modeling and system control. However, artificial neural networks integrated circuits are expensive and not matured enough. Memristors or memristive systems which show a nonvolatile memory behavior has a high potential for use in artificial neural network circuit applications. Some memristive synapse or memristive neural network applications already exist in literature. The complementary memristor or resistive switch memories have been suggested as an alternative to one-cell memristor memories. Their sensing is more difficult and complex than the others. The complementary memristor memory topologies with a sensing node are also inspected in literature. To the best of our knowledge, a neural network circuit which is based on the complementary resistive switches with a sensing/writing node does not exist in literature yet. In this paper, several neural network circuits which are based on the complementary resistive switches with a sensing/writing node have been designed and examined for the first time in literature. Their analysis are given and simulations are performed to verify their operation. We expect that such a complementary resistive switch implementation may find use in artificial neural networks chips in the future.Öğe AXISYMMETRIC SPILLED POLLUTANT ANALYSIS IN STEADY-STATE USING FINITE DIFFERENCE METHOD(Parlar Scientific Publications (P S P), 2022) Ordu, Şeyma; Ordu, Ertuğrul; Mutlu, ReşatWater resources in our world are decreasing day by day. Therefore, maintaining the cleanliness of water sources is very important. Spilled pollutants or seepage from garbage may sometimes cause contamination of groundwater resources. Diffusion equation is difficult to solve. It is also hard to calculate the spilled pollutant quantity. In this study, assuming that the soil is homogenous and its temperature and permeability is constant, infiltration from a surface with cylindrical symmetry into the soil is analyzed and the Laplace equation of the pollutant concentration in steady-state is solved in the cylindrical coordinates considering the axial symmetry by the finite difference method and then the velocity of the pollutant is calculated by post-processing of the solved concentration using Darcy's law in vector form. The concentration leaking from a small pond into the ground is assumed to be constant. The normalized concentration within the ground is given with respect to soil depth. This method given here can be modified to use for the more sophisticated soil models to analyze pollutants.Öğe Blocking Filter for Power Line Communication Systems(IEEE, 2019) Yener, Şuayb Çağrı; Mutlu, ReşatPower Line Communication is becoming more common each passing day. It is important to block conducted radiations from the source to the neighbors and vice-versa. In this study, after examining the residential electrical circuit model, a blocking filter is suggested to block Power Line Communication signals in the undesired directions, parallel resistor-inductor model of the electrical loads and series resistor-inductor model of cables are used, the transfer functions are derived for the Power Line Communication System with or without the filter, the performance of the blocking filter is analyzed using simulations. It has been found that the power factor of the concerned apartment and neighbors does not affect the filter gain or the filter performance.Öğe Computer Aided Design of PID Control of Pulse DC Sintering System(Institute of Electrical and Electronics Engineers Inc., 2019) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, ReşatPulse DC sintering (PDCS) systems, an effective way of producing sintered materials, are complex systems. They need to be modelled both electrically and thermally. Such a system can be controlled manually or automatically. To the best of our knowledge, a closed loop control of the PDCS system is not available in the literature yet. In this study, simplified model of a PDCS system is performed and a PID controller is designed to control the container temperature using Simulink toolbox of Matlab. The PDCS model and the PID controller design method based on the computer aided design proposed in this study can be used by the PDCS designers as an essential part of the system level design issues. © 2019 IEEE.Öğe Cyber security in material manufacturing(TUBITAK, 2020) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, ReşatIndustry 4.0, a new industry revolution, is happening now and several developed countries are leading the path. Internet of things (IoT) is also encompassed by Industry 4.0. In the future, more devices in factories are to be connected to Ethernet or Internet. However, this makes the companies, devices and researchers vulnerable to cyber-attacks. Recently, some cyber-attacks which have happened to some companies or countries verify the danger. Sintering systems and furnaces are used for research by universities and for series manufacturing by factories. Arc furnaces and induction furnaces are also commonly used devices in metal factories. A sintering system, an arc furnace or an induction furnace which is connected to Internet or Ethernet may also be under cyber-attack threat. The danger may be prevented by taking necessary precautions. In this study, these threeproduction systems are first briefly introduced and then inspected assuming that they have been connected to internet and examined with considering cyber-attack point of view. Some basic solutions against cyber-attacks to the aforementioned devices are suggested. © 2020, TUBITAK. All rights reserved.Öğe Energy Consideration of a Capacitor Modelled Using Conformal Fractional-Order Derivative .(2022) Palaz, Utku; Mutlu, ReşatFractional order circuit elements have become important parts of electronic circuits to model systems including supercapacitors, filters, and many more. The conformal fractional derivative (CFD), which is a new basic fractional derivative, has been recently used to model supercapacitors successfully. It is essential to know how electronic components behave under excitation with different types of voltage and current sources. A CFD capacitor is not a well-known element and its usage in circuits is barely examined in the literature. In this research, it is examined how to calculate the stored energy of a CFD capacitor with a series resistor supplied from a DC voltage source. The solutions given in this study may be used in circuits where supercapacitors are used.Öğe Examination of a Memristor-Based Low-Pass Filter Topology(IEEE, 2017) Yener, Şuayb Çağrı; Mutlu, Reşat; Kuntman, Hulusi HakanIn this work, a memristor based low-pass filter topology in which a memristor is placed as the input element and a capacitor is placed as the negative feedback element to an inverting op-amp is examined. The memristor provides adjustable gain characteristic to the filter. Analytical solution of the filter is obtained its output voltage, the memristor current, and the capacitor voltage are found as a function of time. To obtain the filter small-signal model and examine its frequency behavior, Maclaurin series expansion for the output voltage is performed. Time and frequency domain simulations of the filter are done using both small signal and dynamic models of the filter. The frequency domain gain and THD characteristic of the filter are also obtained using both of the models. Simulation results of both of the models are compared. It is shown that the small signal model is able to predict the filter behavior accurately for small signals. It has been also found that, for this topology at low frequencies, the input signal magnitude should be limited for a low distortion.Öğe Finite Difference Analysis of a Resistive Sintering System Container(Amer Scientific Publishers, 2019) Yener, Tuba; Yener, Şuayb Çağrı; Mutlu, ReşatResistive sintering is a new method which enables the production of different material types by using mechanical load and electric current. For the required process performance, it is necessary to set the parameters such as current, voltage, dissipated power, electric energy, and production time correctly. The container is an important component of the resistive sintering system. Container electrical resistance is a value that is difficult to calculate in terms of the geometry of the build and to measure due to the smallness of the value. In this study, assuming that the container temperature is constant, the Laplace equation of the electric potential is solved in the cylindrical coordinates considering the axial symmetry by the finite difference method and then the electrical current and resistance of the sintering container was calculated by post-processing of the solved electric potential using Ohm's law in vector form. The volumetric power density is used to calculate the dissipated power in the container and the container current is calculated on the stiff area. It is seen that the current density is almost doubled at the stiff-container edges and the power density at these points reaches its maximum. At points distant from the stiffs, the electrical potential is almost constant and the potential difference is negligible. The main source of heating is shown to be the resistance of the stiffs. The resistance of the structure is found to be about 70 mu Omega. This method given here can be used in more sophisticated models to size an ECAS system.Öğe Frequency and Time Domain Characteristics of Memristor-Based Filters(IEEE, 2014) Yener, Şuayb Çağrı; Mutlu, Reşat; Kuntman, Hulusi HakanMemristor, regarded as the new fourth fundamental circuit element by many, is also being considered for analog applications. It is expected that analog filters with memristors will provide some characteristics which cannot be mimicked by resistors. In this study, memristor-based low-pass and high-pass filters are analyzed and their performance demonstrated with simulations in time and frequency domains. Saturation of the memristor in the memristor-based filters at low frequencies and distortion resulting from it are observed. Also gain and total harmonic distortion of the filters as a function of frequency are given. The results obtained in this work can be used to design, memristor-based low-pass and high-pass filters.
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