Kenan Danışman | Erciyes University (original) (raw)

Papers by Kenan Danışman

Research paper thumbnail of The Development Of The Computer Controlled Electro-Fiber Optic System For Surface Roughness Measurement Of Metals

Proceedings of SPIE, Nov 6, 1987

The measurement of the surface roughness requires the advanced measuring systems when the mirror ... more The measurement of the surface roughness requires the advanced measuring systems when the mirror finished surfaces are concerned. The use of mechanical method gives the measurement errors and damages the surface. Therefore, the alternative measurement systems must become necessary to investigate. The present study covers the design and development of the electro - fiber - optic system for the experimental purposes. It is found that electro - fiber - optic system results are in a good agreement with the mechanical measurements results.

Research paper thumbnail of Doğrusal Degişen Fark Transformatörlerinin (LVDT) Çalışma Prensipleri, Özellikleri ve Uygulamaları

DergiPark (Istanbul University), Jun 1, 1992

Research paper thumbnail of Neural predictor for temperature estimation

Research paper thumbnail of A comparative study of two different FPGA-based arrhythmia classifier architectures

Turkish Journal of Electrical Engineering and Computer Sciences, 2015

Early diagnosis of dangerous heart conditions is very important for the treatment of heart diseas... more Early diagnosis of dangerous heart conditions is very important for the treatment of heart diseases and for the prevention of sudden cardiac death. Automatic electrocardiogram (ECG) arrhythmia classifiers are essential to timely diagnosis. However, most of the medical diagnosis systems proposed in the literature are software-based. This work focused on the hardware implementation of a mobile artificial neural network (ANN)-based arrhythmia classifier that is implemented on a field programmable gate array (FPGA) as a single chip solution, as an alternative to various software models of ANNs. Due to the parallel nature of ANNs, hardware implementation of ANNs needs a large amount of chip resources. In order to create an ANN structure in an FPGA, the dimensions of the ANN structure must be reduced; therefore, a data reduction algorithm was employed in the training phase and ECG features and consequently the ANN structure size was reduced with principal component analysis. An eight-input ANN-based arrhythmia classifier that has one hidden layer with two neurons and one output layer with one neuron was implemented on a single-chip FPGA. In this work, two different classifiers were consequently implemented in both 32-bit floating and 16-bit fixed point numerical representations on the same FPGA.

Research paper thumbnail of Design of a High Precision Temperature Measurement System

Lecture Notes in Computer Science, 2006

ABSTRACT An experimental method is designed and proposed in order to estimate the non-linearity, ... more ABSTRACT An experimental method is designed and proposed in order to estimate the non-linearity, test and the calibration of a thermocouple using artificial neural network (ANN) based algorithms integrated in a virtual instrument (VI). An ANN and a data acquisition board with signal conditioning unit designed are used for data optimization and to collect experimental data respectively. In both training and testing phases of the ANN, Wavetek 9100 calibration unit is used to obtain the experimental data. After the successful training completion of the ANN, it is used as a neural linearizer to calculate the temperature from the thermocouple’s output voltage.

Research paper thumbnail of EECP Sistem Uygulamasında ST Segmentinin Yapay Sinir Ağları ile Belirlenmesi

Europan journal of science and technology, Apr 30, 2020

Öz Bu çalışmada gelişmiş harici karşı darbe (External Enhanced Counter Pulsation-EECP) cihazının ... more Öz Bu çalışmada gelişmiş harici karşı darbe (External Enhanced Counter Pulsation-EECP) cihazının işaret işleme biriminin kardiyovasküler dolaşımın diyastol faz başlangıcını hatasız biçimde tespit edebilmesini sağlamak için elektrokardiyogram (EKG) işaretinin ST parçasının segmentasyonu gerçekleştirilmiştir. EECP cihazı özellikle miyokard iskemisinin non-invazif tedavisinde kullanılmaktadır. Cihaz (EKG) işaretini analiz etmekte ve kan dolaşımının diyastol fazında hastanın alt uzuvlarına bağlı manşonları şişirerek haricen basınç uygulamaktadır. Dolaşımın sistol fazında ise manşonlar söndürülerek harici basıncın ortadan kaldırılması suretiyle sistemik vasküler rezistansın azalması sağlanmaktadır. Bu etki kalbin art yükünün (afterload) düşmesine yol açar. EKG işaretinin QRS parçası ventrikülün (karıncık) kasılmasını başlatır. Bir başka ifadeyle QRS dalgasının ortaya çıkışından hemen sonra kalp kasılması yani sistol fazı başlar. T dalgasının ortaya çıkışını takiben ventrikülün kasılması son bulur. Dolayısıyla EECP cihazının doğru zamanda devreye girmesini sağlamak için ST dalga kompleksinin tespit edilmesi bir zorunluluktur. Yapılan çalışmada ST segmentasyonu için Physio.net'in sağlamış olduğu MIT-BIH Arrhythmia Database kullanılmıştır. Sisteme yüklenen işaretler öncesinde ön işleme tabi tutularak gürültülerden ve baseline kaymalarından arındırılmıştır. Gürültü eliminasyonu ve baseline kayması düzenlenen işaretin P, Q, R, S ve T noktaları tespit edilmiştir. Tespit edilen bu noktalardan P, Q ve R noktalarıyla birlikte bu noktalarla ilişkili 7 nokta daha giriş işaretlerini oluşturarak 10 girişli ve S, T noktalarını belirleyecek şekilde 2 çıkışlı bir ara katmanlı bir yapay sinir ağı oluşturulmuştur. Oluşturulan bu yapıda k cross validation (k katlamalı çaprazlama) yöntemi kullanılmıştır. Sistem eğitiminde sabit eğitim algoritması, farklı k katsayıları, farklı nöron sayıları ve farklı transfer fonksiyonları kullanılarak en iyi yapı elde edilmeye çalışılmıştır. Sabit olarak seçilen eğitim algoritması Levenberg-Marquardt'dır. Yapılan çalışma sonucunda k katlama değeri 5 olarak belirlenmiştir. 25 nöronun kullanıldığı gizli katman için logsig tipi transfer fonksiyonu ve çıkış için poslin tipi transfer fonksiyonu kullanılarak en küçük hatayı veren yapı elde edilmiştir.

Research paper thumbnail of Comparison of PID based Control Algorithms for Daily Blood Glucose Control

World Congress on Electrical Engineering and Computer Systems and Science, 2016

Type 1 Diabetes Mellitus (T1DM) is a worldwide disease. Although a complete cure has not been fou... more Type 1 Diabetes Mellitus (T1DM) is a worldwide disease. Although a complete cure has not been found yet, an artificial pancreas (AP), also known as a closed-loop insulin therapy, is becoming more important for the treatment of this disease. Controller part of the AP can compute insulin infusion rate that will keep blood glucose concentration (BGC) in normoglycemic ranges for patients with T1DM. In this paper, three different control algorithms are proposed as a controller part of the AP. These control algorithms include genetic algorithm based proportional-integral-derivative (GA-PID) control, artificial bee colony algorithm based PID (ABC-PID) control, and particle swarm optimization algorithm based PID (PSO-PID) control. In silico control studies are implemented through a virtual diabetic patient based on the Stolwijk-Hardy's glucose-insulin regulation model. Simulations are performed to assess control function in terms of tracking BGC profile of a healthy person against to a daily food intake of three meals. In order to demonstrate robustness, sensor noise test is implemented. Simulation results are promising in terms of regulating the daily BGC.

Research paper thumbnail of GPRS Üzeri̇nden Web Tabanli Bölgesel Enerji̇ Taki̇p Si̇stemi̇

emo.org.tr

... Ahmet Turan ÖZDEMİR1 Kenan DANIŞMAN2 ... Ülkeler gelecekte enerji sıkıntıları yaşamamak için ... more ... Ahmet Turan ÖZDEMİR1 Kenan DANIŞMAN2 ... Ülkeler gelecekte enerji sıkıntıları yaşamamak için enerji planlaması yaparlar. İhtiyaç duyulan tahmini enerji ortaya konur ve bu ihtiyacı karşılamak amacı ile yeni santraller devreye alınır. ...

Research paper thumbnail of Blood glucose control using an ABC algorithm-based fuzzy-PID controller

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2018

In this paper, a Mamdani-type fuzzy controller is proposed as the controller part of an artificia... more In this paper, a Mamdani-type fuzzy controller is proposed as the controller part of an artificial pancreas. The controller is optimized with the artificial bee colony optimization algorithm. The glucose-insulin regulatory system, based on a nonlinear differential model in the presence of delay, is used both for virtual patient and healthy person data. The main target of the controller is to mimic a blood glucose concentration profile of the healthy person with exogenous insulin infusion. Simulations are performed to assess the control function in terms of tracking the blood glucose concentration profile of the healthy person and minimizing errors. To show robustness, a group of three tests are implemented. These tests include unusual glucose intake, sensor noise, and uncertainty in the clearance rate parameter. The simulation results demonstrate that the adopted method is more effective than similar studies in the literature.

Research paper thumbnail of P a M U K K a L e Volterra-Wi̇ener Seri̇si̇ Kullanilarak Opti̇k Geri̇beslemeli̇ Yarii̇letken Lazer Di̇yodun Anali̇zi̇

ZET Bu çalışmada, lazer diyodun (LD) lineerize edilmiş tek mod oran denklemleri harici boşluklu L... more ZET Bu çalışmada, lazer diyodun (LD) lineerize edilmiş tek mod oran denklemleri harici boşluklu LD'ye göre yeniden düzenlenerek bu denklemler harmonik giriş metoduyla birlikte Volterra serileri kullanılarak çözülmüştür. Harmonik transfer fonksiyonlarının elde edilmesinde Volterra-Wiener seri yaklaşımı kullanılmıştır. Bulunan transfer fonksiyonları kullanılarak çıkıştan-girişe doğru kararlılık analizleri yapılmış olup bu analizlerde Nyquist kararlılık kriteri temel alınmştır. Bu çalışmada, açık sistem transfer fonksiyonu TF = (H1/1-G1) elde edilmiştir. TF transfer foksiyonunun Nyquist eğrisi de çizilerek LD'un akım-denetimli osilatör gibi çalıştığı da gösterilmiştir.

Research paper thumbnail of The effect of optical confinement factor and gain constant on the distortion levels in InGaAsP semiconductor laser diodes

SPIE Proceedings, 1998

The effect of optical confinement factor and gain constant (optical gain coefficient) on harmonic... more The effect of optical confinement factor and gain constant (optical gain coefficient) on harmonic distortion in 1.55 micrometers semiconductor laser diodes are investigated by using a mathematical model based on multi-mode rate equations. The model can be extended and used to simulate the output of any direct modulated Fabry-Perot semiconductor laser in long wavelength by changing some of the parameters.

Research paper thumbnail of <title>Static and dynamic behavior of the three-cavity semiconductor laser diodes and oscillation frequency shift suppression</title>

1998 International Conference on Applications of Photonic Technology III: Closing the Gap between Theory, Development, and Applications, 1998

ABSTRACT

Research paper thumbnail of The role of optical feedback for controlling chaotic cases in semiconductor laser diodes

SPIE Proceedings, 1998

In this study the effect of optical feedback in semiconductor laser diodes (LD) has been examined... more In this study the effect of optical feedback in semiconductor laser diodes (LD) has been examined using small signal analysis. The transfer function of LD is given as H (j(omega) m)D and transfer function of external cavity LD is given as TF (j(omega) m)HD respectively. The investigated parameters of these transfer functions are external cavity length (Lext), line-width enhancement factor

Research paper thumbnail of Single model proposed for the combination of narrow and wide GaAs wells for the computation of the linewidth enhancement factor

SPIE Proceedings, 2004

A different method and single model to determine the linewidth enhancement factor [alpha (Alpha) ... more A different method and single model to determine the linewidth enhancement factor [alpha (Alpha) parameter] for narrow and wide GaAs Quantum-wells (QWs) as a function of modal peak gain and current density is presented. Based on the Artificial Neural Network (ANN) modeling approach, different learning algorithms are trained and tested. Both the training and the test results are in very

Research paper thumbnail of Neural computation of alpha parameter with the use of differential gain, wavelength, and number of quantum wells

SPIE Proceedings, 2004

A different method to determine alpha (Alpha) parameter for different number of Quantum-wells is ... more A different method to determine alpha (Alpha) parameter for different number of Quantum-wells is presented. The Levenberg-Marquardt algorithm is used to train the Artificial Neural Networks (ANNs) which has a quadratic speed of convergence. Both the computed and the test results are in very good agreement with the experimental results reported elsewhere.

Research paper thumbnail of Different approach for distortion analysis of external-cavity laser diode using Volterra series

SPIE Proceedings, 1998

In this study, external cavity laser diode has been modeled and non-linear equations of system ar... more In this study, external cavity laser diode has been modeled and non-linear equations of system are being solved by using Volterra series. In the study, linearized laser diodes rate equations are reorganized for external cavity and these equations are solved with harmonic input method using Volterra series. The transfer functions brought about for harmonics are obtained using Volterra-Weiner series approach.

Research paper thumbnail of Determination of amplitude-phase relationship in laser diodes using linear system approximation

SPIE Proceedings, 2000

In this study, amplitude-phase relationship of laser diodes is analyzed under modulation with the... more In this study, amplitude-phase relationship of laser diodes is analyzed under modulation with the help of the transfer functions. The dynamic behavior of laser diodes is observed as functions of both damping and relaxation resonance frequencies. Within the linear system approach, the amplitude-phase relationship is harmonious up to some extent and both of them have dependence on each other. Phase changes occurring within the system are not stable and cause oscillations which prevent the system from stable working. These oscillations have some threshold value and the system may be driven in to chaos after this point.

Research paper thumbnail of Effect of nonradiative recombination coefficient and gain saturation parameter on second harmonic distortion in 1.55-μm InGaAsP semiconductor laser diodes

SPIE Proceedings, 1998

In this study, different second harmonic distortion (2HD) levels of a 1.55 micrometers , InGaAsP ... more In this study, different second harmonic distortion (2HD) levels of a 1.55 micrometers , InGaAsP ridge waveguide laser diode are investigated by using a mathematical model based on multi-mode rate equations. The rate equations with an input current i are solved numerically by using fourth order Runge-Kutta algorithm for frequencies ranging from 1 GHz to 10 GHz with 1 GHz

Research paper thumbnail of <title>A different approach for the computation of refractive index change in quantum-well diode lasers for different injection levels</title>

A model is developed for the carrier induced refractive-index change in Quantum-well (QW) lasers ... more A model is developed for the carrier induced refractive-index change in Quantum-well (QW) lasers which affects different mechanisms. The model is based on Artificial Neural Network (ANN) which provides a powerful approach for setting up a complex non-linear model. Different algorithms are tried and tested for different injection current levels. Both the training and the test results for refractive-index change

Research paper thumbnail of Closed-loop control of blood glucose level in type-1 diabetics: A simulation study

2013 8th International Conference on Electrical and Electronics Engineering (ELECO), 2013

Survey on diabetes is one of the popular fields of biomedical signal processing. In this paper, a... more Survey on diabetes is one of the popular fields of biomedical signal processing. In this paper, a closed-loop system which utilizes modified Stolwijk-Hardy glucose insulin interaction model is considered. The modified model was derived by adding an exogenous insulin infusion term. Two control algorithms are used for exogenous insulin infusion: a Mamdani type fuzzy logic controller (FLC), and a fuzzy-PID controller. Simulations are performed to assess control function in terms of keeping desired steady state plasma glucose level (0.81 mg/ml) against to exogenous glucose input. Simulation results are notable and significant in terms of controlling blood glucose level (BGL). The control algorithms that applied to the model are firstly proposed, therefore this study is made a contribution to the literature.

Research paper thumbnail of The Development Of The Computer Controlled Electro-Fiber Optic System For Surface Roughness Measurement Of Metals

Proceedings of SPIE, Nov 6, 1987

The measurement of the surface roughness requires the advanced measuring systems when the mirror ... more The measurement of the surface roughness requires the advanced measuring systems when the mirror finished surfaces are concerned. The use of mechanical method gives the measurement errors and damages the surface. Therefore, the alternative measurement systems must become necessary to investigate. The present study covers the design and development of the electro - fiber - optic system for the experimental purposes. It is found that electro - fiber - optic system results are in a good agreement with the mechanical measurements results.

Research paper thumbnail of Doğrusal Degişen Fark Transformatörlerinin (LVDT) Çalışma Prensipleri, Özellikleri ve Uygulamaları

DergiPark (Istanbul University), Jun 1, 1992

Research paper thumbnail of Neural predictor for temperature estimation

Research paper thumbnail of A comparative study of two different FPGA-based arrhythmia classifier architectures

Turkish Journal of Electrical Engineering and Computer Sciences, 2015

Early diagnosis of dangerous heart conditions is very important for the treatment of heart diseas... more Early diagnosis of dangerous heart conditions is very important for the treatment of heart diseases and for the prevention of sudden cardiac death. Automatic electrocardiogram (ECG) arrhythmia classifiers are essential to timely diagnosis. However, most of the medical diagnosis systems proposed in the literature are software-based. This work focused on the hardware implementation of a mobile artificial neural network (ANN)-based arrhythmia classifier that is implemented on a field programmable gate array (FPGA) as a single chip solution, as an alternative to various software models of ANNs. Due to the parallel nature of ANNs, hardware implementation of ANNs needs a large amount of chip resources. In order to create an ANN structure in an FPGA, the dimensions of the ANN structure must be reduced; therefore, a data reduction algorithm was employed in the training phase and ECG features and consequently the ANN structure size was reduced with principal component analysis. An eight-input ANN-based arrhythmia classifier that has one hidden layer with two neurons and one output layer with one neuron was implemented on a single-chip FPGA. In this work, two different classifiers were consequently implemented in both 32-bit floating and 16-bit fixed point numerical representations on the same FPGA.

Research paper thumbnail of Design of a High Precision Temperature Measurement System

Lecture Notes in Computer Science, 2006

ABSTRACT An experimental method is designed and proposed in order to estimate the non-linearity, ... more ABSTRACT An experimental method is designed and proposed in order to estimate the non-linearity, test and the calibration of a thermocouple using artificial neural network (ANN) based algorithms integrated in a virtual instrument (VI). An ANN and a data acquisition board with signal conditioning unit designed are used for data optimization and to collect experimental data respectively. In both training and testing phases of the ANN, Wavetek 9100 calibration unit is used to obtain the experimental data. After the successful training completion of the ANN, it is used as a neural linearizer to calculate the temperature from the thermocouple’s output voltage.

Research paper thumbnail of EECP Sistem Uygulamasında ST Segmentinin Yapay Sinir Ağları ile Belirlenmesi

Europan journal of science and technology, Apr 30, 2020

Öz Bu çalışmada gelişmiş harici karşı darbe (External Enhanced Counter Pulsation-EECP) cihazının ... more Öz Bu çalışmada gelişmiş harici karşı darbe (External Enhanced Counter Pulsation-EECP) cihazının işaret işleme biriminin kardiyovasküler dolaşımın diyastol faz başlangıcını hatasız biçimde tespit edebilmesini sağlamak için elektrokardiyogram (EKG) işaretinin ST parçasının segmentasyonu gerçekleştirilmiştir. EECP cihazı özellikle miyokard iskemisinin non-invazif tedavisinde kullanılmaktadır. Cihaz (EKG) işaretini analiz etmekte ve kan dolaşımının diyastol fazında hastanın alt uzuvlarına bağlı manşonları şişirerek haricen basınç uygulamaktadır. Dolaşımın sistol fazında ise manşonlar söndürülerek harici basıncın ortadan kaldırılması suretiyle sistemik vasküler rezistansın azalması sağlanmaktadır. Bu etki kalbin art yükünün (afterload) düşmesine yol açar. EKG işaretinin QRS parçası ventrikülün (karıncık) kasılmasını başlatır. Bir başka ifadeyle QRS dalgasının ortaya çıkışından hemen sonra kalp kasılması yani sistol fazı başlar. T dalgasının ortaya çıkışını takiben ventrikülün kasılması son bulur. Dolayısıyla EECP cihazının doğru zamanda devreye girmesini sağlamak için ST dalga kompleksinin tespit edilmesi bir zorunluluktur. Yapılan çalışmada ST segmentasyonu için Physio.net'in sağlamış olduğu MIT-BIH Arrhythmia Database kullanılmıştır. Sisteme yüklenen işaretler öncesinde ön işleme tabi tutularak gürültülerden ve baseline kaymalarından arındırılmıştır. Gürültü eliminasyonu ve baseline kayması düzenlenen işaretin P, Q, R, S ve T noktaları tespit edilmiştir. Tespit edilen bu noktalardan P, Q ve R noktalarıyla birlikte bu noktalarla ilişkili 7 nokta daha giriş işaretlerini oluşturarak 10 girişli ve S, T noktalarını belirleyecek şekilde 2 çıkışlı bir ara katmanlı bir yapay sinir ağı oluşturulmuştur. Oluşturulan bu yapıda k cross validation (k katlamalı çaprazlama) yöntemi kullanılmıştır. Sistem eğitiminde sabit eğitim algoritması, farklı k katsayıları, farklı nöron sayıları ve farklı transfer fonksiyonları kullanılarak en iyi yapı elde edilmeye çalışılmıştır. Sabit olarak seçilen eğitim algoritması Levenberg-Marquardt'dır. Yapılan çalışma sonucunda k katlama değeri 5 olarak belirlenmiştir. 25 nöronun kullanıldığı gizli katman için logsig tipi transfer fonksiyonu ve çıkış için poslin tipi transfer fonksiyonu kullanılarak en küçük hatayı veren yapı elde edilmiştir.

Research paper thumbnail of Comparison of PID based Control Algorithms for Daily Blood Glucose Control

World Congress on Electrical Engineering and Computer Systems and Science, 2016

Type 1 Diabetes Mellitus (T1DM) is a worldwide disease. Although a complete cure has not been fou... more Type 1 Diabetes Mellitus (T1DM) is a worldwide disease. Although a complete cure has not been found yet, an artificial pancreas (AP), also known as a closed-loop insulin therapy, is becoming more important for the treatment of this disease. Controller part of the AP can compute insulin infusion rate that will keep blood glucose concentration (BGC) in normoglycemic ranges for patients with T1DM. In this paper, three different control algorithms are proposed as a controller part of the AP. These control algorithms include genetic algorithm based proportional-integral-derivative (GA-PID) control, artificial bee colony algorithm based PID (ABC-PID) control, and particle swarm optimization algorithm based PID (PSO-PID) control. In silico control studies are implemented through a virtual diabetic patient based on the Stolwijk-Hardy's glucose-insulin regulation model. Simulations are performed to assess control function in terms of tracking BGC profile of a healthy person against to a daily food intake of three meals. In order to demonstrate robustness, sensor noise test is implemented. Simulation results are promising in terms of regulating the daily BGC.

Research paper thumbnail of GPRS Üzeri̇nden Web Tabanli Bölgesel Enerji̇ Taki̇p Si̇stemi̇

emo.org.tr

... Ahmet Turan ÖZDEMİR1 Kenan DANIŞMAN2 ... Ülkeler gelecekte enerji sıkıntıları yaşamamak için ... more ... Ahmet Turan ÖZDEMİR1 Kenan DANIŞMAN2 ... Ülkeler gelecekte enerji sıkıntıları yaşamamak için enerji planlaması yaparlar. İhtiyaç duyulan tahmini enerji ortaya konur ve bu ihtiyacı karşılamak amacı ile yeni santraller devreye alınır. ...

Research paper thumbnail of Blood glucose control using an ABC algorithm-based fuzzy-PID controller

TURKISH JOURNAL OF ELECTRICAL ENGINEERING & COMPUTER SCIENCES, 2018

In this paper, a Mamdani-type fuzzy controller is proposed as the controller part of an artificia... more In this paper, a Mamdani-type fuzzy controller is proposed as the controller part of an artificial pancreas. The controller is optimized with the artificial bee colony optimization algorithm. The glucose-insulin regulatory system, based on a nonlinear differential model in the presence of delay, is used both for virtual patient and healthy person data. The main target of the controller is to mimic a blood glucose concentration profile of the healthy person with exogenous insulin infusion. Simulations are performed to assess the control function in terms of tracking the blood glucose concentration profile of the healthy person and minimizing errors. To show robustness, a group of three tests are implemented. These tests include unusual glucose intake, sensor noise, and uncertainty in the clearance rate parameter. The simulation results demonstrate that the adopted method is more effective than similar studies in the literature.

Research paper thumbnail of P a M U K K a L e Volterra-Wi̇ener Seri̇si̇ Kullanilarak Opti̇k Geri̇beslemeli̇ Yarii̇letken Lazer Di̇yodun Anali̇zi̇

ZET Bu çalışmada, lazer diyodun (LD) lineerize edilmiş tek mod oran denklemleri harici boşluklu L... more ZET Bu çalışmada, lazer diyodun (LD) lineerize edilmiş tek mod oran denklemleri harici boşluklu LD'ye göre yeniden düzenlenerek bu denklemler harmonik giriş metoduyla birlikte Volterra serileri kullanılarak çözülmüştür. Harmonik transfer fonksiyonlarının elde edilmesinde Volterra-Wiener seri yaklaşımı kullanılmıştır. Bulunan transfer fonksiyonları kullanılarak çıkıştan-girişe doğru kararlılık analizleri yapılmış olup bu analizlerde Nyquist kararlılık kriteri temel alınmştır. Bu çalışmada, açık sistem transfer fonksiyonu TF = (H1/1-G1) elde edilmiştir. TF transfer foksiyonunun Nyquist eğrisi de çizilerek LD'un akım-denetimli osilatör gibi çalıştığı da gösterilmiştir.

Research paper thumbnail of The effect of optical confinement factor and gain constant on the distortion levels in InGaAsP semiconductor laser diodes

SPIE Proceedings, 1998

The effect of optical confinement factor and gain constant (optical gain coefficient) on harmonic... more The effect of optical confinement factor and gain constant (optical gain coefficient) on harmonic distortion in 1.55 micrometers semiconductor laser diodes are investigated by using a mathematical model based on multi-mode rate equations. The model can be extended and used to simulate the output of any direct modulated Fabry-Perot semiconductor laser in long wavelength by changing some of the parameters.

Research paper thumbnail of <title>Static and dynamic behavior of the three-cavity semiconductor laser diodes and oscillation frequency shift suppression</title>

1998 International Conference on Applications of Photonic Technology III: Closing the Gap between Theory, Development, and Applications, 1998

ABSTRACT

Research paper thumbnail of The role of optical feedback for controlling chaotic cases in semiconductor laser diodes

SPIE Proceedings, 1998

In this study the effect of optical feedback in semiconductor laser diodes (LD) has been examined... more In this study the effect of optical feedback in semiconductor laser diodes (LD) has been examined using small signal analysis. The transfer function of LD is given as H (j(omega) m)D and transfer function of external cavity LD is given as TF (j(omega) m)HD respectively. The investigated parameters of these transfer functions are external cavity length (Lext), line-width enhancement factor

Research paper thumbnail of Single model proposed for the combination of narrow and wide GaAs wells for the computation of the linewidth enhancement factor

SPIE Proceedings, 2004

A different method and single model to determine the linewidth enhancement factor [alpha (Alpha) ... more A different method and single model to determine the linewidth enhancement factor [alpha (Alpha) parameter] for narrow and wide GaAs Quantum-wells (QWs) as a function of modal peak gain and current density is presented. Based on the Artificial Neural Network (ANN) modeling approach, different learning algorithms are trained and tested. Both the training and the test results are in very

Research paper thumbnail of Neural computation of alpha parameter with the use of differential gain, wavelength, and number of quantum wells

SPIE Proceedings, 2004

A different method to determine alpha (Alpha) parameter for different number of Quantum-wells is ... more A different method to determine alpha (Alpha) parameter for different number of Quantum-wells is presented. The Levenberg-Marquardt algorithm is used to train the Artificial Neural Networks (ANNs) which has a quadratic speed of convergence. Both the computed and the test results are in very good agreement with the experimental results reported elsewhere.

Research paper thumbnail of Different approach for distortion analysis of external-cavity laser diode using Volterra series

SPIE Proceedings, 1998

In this study, external cavity laser diode has been modeled and non-linear equations of system ar... more In this study, external cavity laser diode has been modeled and non-linear equations of system are being solved by using Volterra series. In the study, linearized laser diodes rate equations are reorganized for external cavity and these equations are solved with harmonic input method using Volterra series. The transfer functions brought about for harmonics are obtained using Volterra-Weiner series approach.

Research paper thumbnail of Determination of amplitude-phase relationship in laser diodes using linear system approximation

SPIE Proceedings, 2000

In this study, amplitude-phase relationship of laser diodes is analyzed under modulation with the... more In this study, amplitude-phase relationship of laser diodes is analyzed under modulation with the help of the transfer functions. The dynamic behavior of laser diodes is observed as functions of both damping and relaxation resonance frequencies. Within the linear system approach, the amplitude-phase relationship is harmonious up to some extent and both of them have dependence on each other. Phase changes occurring within the system are not stable and cause oscillations which prevent the system from stable working. These oscillations have some threshold value and the system may be driven in to chaos after this point.

Research paper thumbnail of Effect of nonradiative recombination coefficient and gain saturation parameter on second harmonic distortion in 1.55-μm InGaAsP semiconductor laser diodes

SPIE Proceedings, 1998

In this study, different second harmonic distortion (2HD) levels of a 1.55 micrometers , InGaAsP ... more In this study, different second harmonic distortion (2HD) levels of a 1.55 micrometers , InGaAsP ridge waveguide laser diode are investigated by using a mathematical model based on multi-mode rate equations. The rate equations with an input current i are solved numerically by using fourth order Runge-Kutta algorithm for frequencies ranging from 1 GHz to 10 GHz with 1 GHz

Research paper thumbnail of <title>A different approach for the computation of refractive index change in quantum-well diode lasers for different injection levels</title>

A model is developed for the carrier induced refractive-index change in Quantum-well (QW) lasers ... more A model is developed for the carrier induced refractive-index change in Quantum-well (QW) lasers which affects different mechanisms. The model is based on Artificial Neural Network (ANN) which provides a powerful approach for setting up a complex non-linear model. Different algorithms are tried and tested for different injection current levels. Both the training and the test results for refractive-index change

Research paper thumbnail of Closed-loop control of blood glucose level in type-1 diabetics: A simulation study

2013 8th International Conference on Electrical and Electronics Engineering (ELECO), 2013

Survey on diabetes is one of the popular fields of biomedical signal processing. In this paper, a... more Survey on diabetes is one of the popular fields of biomedical signal processing. In this paper, a closed-loop system which utilizes modified Stolwijk-Hardy glucose insulin interaction model is considered. The modified model was derived by adding an exogenous insulin infusion term. Two control algorithms are used for exogenous insulin infusion: a Mamdani type fuzzy logic controller (FLC), and a fuzzy-PID controller. Simulations are performed to assess control function in terms of keeping desired steady state plasma glucose level (0.81 mg/ml) against to exogenous glucose input. Simulation results are notable and significant in terms of controlling blood glucose level (BGL). The control algorithms that applied to the model are firstly proposed, therefore this study is made a contribution to the literature.