Ivelina Cholakova - Academia.edu (original) (raw)
Papers by Ivelina Cholakova
2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST)
2023 46th International Spring Seminar on Electronics Technology (ISSE)
THERMOPHYSICAL BASIS OF ENERGY TECHNOLOGIES (TBET 2020)
Acoustics, Dec 31, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
2022 XXXI International Scientific Conference Electronics (ET)
2019 IEEE XXVIII International Scientific Conference Electronics (ET)
In the present publication we have investigated the temperature dependence of a resistive structu... more In the present publication we have investigated the temperature dependence of a resistive structure printed with Inkjet technology. We have also investigated the change of impedance with heating in a thermo-chamber and its change at cooling. The results obtained are described and analysed to determine the influence of temperature sintering on the properties of the printed layers as well as to find application of the structures as sensing elements.
2018 IX National Conference with International Participation (ELECTRONICA)
In the present paper, a numerical study of the acoustic characteristics of a new acoustic absorbe... more In the present paper, a numerical study of the acoustic characteristics of a new acoustic absorber construction has been conducted. The cross-section of the plastic acoustic absorber is in the form of a semi-tube. The acoustic absorber is modeled and studied with COMSOL Multyphisics®. Some of the simulation numerical results of the acoustic absorber model and the experimental verification are compared and presented.
2019 X National Conference with International Participation (ELECTRONICA)
Analyses of energy harvesting methods and devices for use in transport noise harvesting is done i... more Analyses of energy harvesting methods and devices for use in transport noise harvesting is done in this study. An overall review of most often used systems for vibration to electricity energy conversion is presented. A classification of these systems is made based on comparison of their fields of application, conversion effectiveness, advantages and disadvantages. Special attention is given on possible implementation of these systems in passive transport acoustic noise barriers aiming acoustic energy harvesting as well as active noise reduction.
2017 XXVI International Scientific Conference Electronics (ET), 2017
Capacitance measurement at different DC voltage levels, different signal amplitudes and different... more Capacitance measurement at different DC voltage levels, different signal amplitudes and different frequencies, finds extensive application to qualify semiconductor and multiple-layered structures. Generally, the cost of such type instrumentation is in range of several thousand dollars and they are not very popular in the market. In present paper an approach of combining conventional measuring instruments and high-level programming environment is suggested in order to achieve system with complete functionalities for capacitance measurements.
2018 IEEE XXVII International Scientific Conference Electronics - ET, 2018
In this paper we analyze measurements data of different 14 nm bulk FinFET structures – both n- an... more In this paper we analyze measurements data of different 14 nm bulk FinFET structures – both n- and p-type. The analysis is based on the smoothness of the experimental characteristics. Smoothness is important for the subsequent parameter extraction procedures. It is estimated by taking first derivatives of the experimental curves and comparing them to their fitted polynomial. Calculations have been performed in Matlab.
IET Digital Library, 2017
2018 41st International Spring Seminar on Electronics Technology (ISSE), 2018
Extraction procedure for 14 nm bulk FinFET devices is realized in Matlab. Parameters selected for... more Extraction procedure for 14 nm bulk FinFET devices is realized in Matlab. Parameters selected for extraction include the threshold voltage at zero bulk voltage (VT0), the output conductance parameter (λ), the parameter, which models the transition between linear and saturation regions (MEXP), the subthreshold parameter (η), and the transconductance (gch). The extraction is based on experimental measurements of 14-nm FinFETs wafers. Extracted parameters are simulated in a PTM MG SPICE model for verification.
2018 IX National Conference with International Participation (ELECTRONICA), 2018
Recently inkjet printing has emerged as an attractive technology for a variety of scientific appl... more Recently inkjet printing has emerged as an attractive technology for a variety of scientific applications due to its low-cost and simplicity. Outstanding characteristics of inks based on nanoparticles and carbon nanotubes has made this technology a good choice for various electronic applications such as sensors, transparent electrodes and flexible electronics. The incorporation of metallic, organic and oxide nanoparticles and carbon nanotubes into functional inks is used in order to obtain sensibility to different physical quantities. The present paper focuses on the systematization of commercial and custom-made inks recently developed for desktop inkjet printers.
2020 21st International Symposium on Electrical Apparatus & Technologies (SIELA), 2020
The present article introduces a new type of piezoelectric barrier with energy harvesting element... more The present article introduces a new type of piezoelectric barrier with energy harvesting elements. After modelling the noise barriers with COMSOL and conducting experiments, the location of the piezo elements for energy harvesting was determined. The purpose of this article is to test the efficiency optimization of the energy harvesting at noise reduction. The influence of three different typical types of acoustic spectra and different sound pressure levels on the generated electric energy were determined, as well as the efficiency of the acoustic noise power generation system at three different spectra and at different acoustic noise pressure levels on the acoustic barrier
2020 XXIX International Scientific Conference Electronics (ET), 2020
The monitoring and control of soil moisture has always been the subject of attention of both deve... more The monitoring and control of soil moisture has always been the subject of attention of both developers of sensor elements and agro-engineers. New developments are available on the market, using different methods, with different functionalities, accuracy and price. This article proposes an innovative approach for non-contact measurement of soil moisture using capacitive flexible sensors. Three different forms of capacitive structures printed with Inkjet technology, silver nanoparticle ink and PET substrate were studied. The results for the change of the capacity and impedance of the structures when the soil moisture changes are presented.
2019 IEEE XXVIII International Scientific Conference Electronics (ET), 2019
In the present paper we have studied the impedance dependence of resistive and three different ca... more In the present paper we have studied the impedance dependence of resistive and three different capacitive structures printed with Inkjet technology. We have studied the impedance variation at different frequencies ranging from 100Hz to 200kHz. The results obtained are described and analysed to find application of the structures for different types of sensors.
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
This paper presents a methodology for parameters extraction of photovoltaic cell based on real me... more This paper presents a methodology for parameters extraction of photovoltaic cell based on real measurement. The modeling of equivalent schemes of solar cells is of great importance in order to be included in electric circuits for wireless sensor networks power supply. The parameters extraction of these devices is still a very difficult task, which requires experimental data, computing and modeling. In recent years different analytic, iterative, and evolutionary computational methods have been suggested in various references to extract the parameters of solar cell and modules. This paper presents an innovative approach to estimate model parameters by completely extracting them from real measured data.
2020 III International Conference on High Technology for Sustainable Development (HiTech), 2020
The presented article examines a new type of Sonic Crystal noise barrier and the possibility of c... more The presented article examines a new type of Sonic Crystal noise barrier and the possibility of collecting energy generated by noise. After COMSOL modelling and various experiments performed in our previous articles, we have determined the best location of the piezo materials used for energy harvesting. The aim of the article is to verify the designed model, to quantify the collected energy and to analyse the efficiency of energy harvesting in noise reduction
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
One of our most vital resources nowadays is fresh water. Water quality refers to the condition of... more One of our most vital resources nowadays is fresh water. Water quality refers to the condition of the water, including chemical, biological and physical characteristics with respect to its suitability for a particular purpose. The main purpose of this publication is to set up a virtual system for water analysis in order to measure particular parameters of the water before and after physicochemical treatment. The water is treated with clinoptilolite, which has recently been used for water filtration. It is suitable especially for water treatment due to its ion exchange, absorption properties and high porosity. The main geochemical and technological concerns are how the chemical behavior of natural clinoptilolite affects the quality of different types of water.
2020 43rd International Spring Seminar on Electronics Technology (ISSE), 2020
Capacitive liquid level sensors have long been known in the scientific areas. In recent years, fl... more Capacitive liquid level sensors have long been known in the scientific areas. In recent years, flexible sensor structures printed using inkjet technology have been introduced that allow the measurement of the level in vessels of different shapes without the need for immersion of the sensor in the liquid. Classical (interdigital) sensor structure is used in more publications. The purpose of this article is to investigate the influence of pattern on the capacitance and impedance of the sensor at different fluid levels. Sensors of three different shapes are printed on the Polyethylene Terephthalate PET substrate, using silver nanoparticle ink and a conventional desktop printer. The measured results are presented and analyzed.
2023 58th International Scientific Conference on Information, Communication and Energy Systems and Technologies (ICEST)
2023 46th International Spring Seminar on Electronics Technology (ISSE)
THERMOPHYSICAL BASIS OF ENERGY TECHNOLOGIES (TBET 2020)
Acoustics, Dec 31, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
2022 XXXI International Scientific Conference Electronics (ET)
2019 IEEE XXVIII International Scientific Conference Electronics (ET)
In the present publication we have investigated the temperature dependence of a resistive structu... more In the present publication we have investigated the temperature dependence of a resistive structure printed with Inkjet technology. We have also investigated the change of impedance with heating in a thermo-chamber and its change at cooling. The results obtained are described and analysed to determine the influence of temperature sintering on the properties of the printed layers as well as to find application of the structures as sensing elements.
2018 IX National Conference with International Participation (ELECTRONICA)
In the present paper, a numerical study of the acoustic characteristics of a new acoustic absorbe... more In the present paper, a numerical study of the acoustic characteristics of a new acoustic absorber construction has been conducted. The cross-section of the plastic acoustic absorber is in the form of a semi-tube. The acoustic absorber is modeled and studied with COMSOL Multyphisics®. Some of the simulation numerical results of the acoustic absorber model and the experimental verification are compared and presented.
2019 X National Conference with International Participation (ELECTRONICA)
Analyses of energy harvesting methods and devices for use in transport noise harvesting is done i... more Analyses of energy harvesting methods and devices for use in transport noise harvesting is done in this study. An overall review of most often used systems for vibration to electricity energy conversion is presented. A classification of these systems is made based on comparison of their fields of application, conversion effectiveness, advantages and disadvantages. Special attention is given on possible implementation of these systems in passive transport acoustic noise barriers aiming acoustic energy harvesting as well as active noise reduction.
2017 XXVI International Scientific Conference Electronics (ET), 2017
Capacitance measurement at different DC voltage levels, different signal amplitudes and different... more Capacitance measurement at different DC voltage levels, different signal amplitudes and different frequencies, finds extensive application to qualify semiconductor and multiple-layered structures. Generally, the cost of such type instrumentation is in range of several thousand dollars and they are not very popular in the market. In present paper an approach of combining conventional measuring instruments and high-level programming environment is suggested in order to achieve system with complete functionalities for capacitance measurements.
2018 IEEE XXVII International Scientific Conference Electronics - ET, 2018
In this paper we analyze measurements data of different 14 nm bulk FinFET structures – both n- an... more In this paper we analyze measurements data of different 14 nm bulk FinFET structures – both n- and p-type. The analysis is based on the smoothness of the experimental characteristics. Smoothness is important for the subsequent parameter extraction procedures. It is estimated by taking first derivatives of the experimental curves and comparing them to their fitted polynomial. Calculations have been performed in Matlab.
IET Digital Library, 2017
2018 41st International Spring Seminar on Electronics Technology (ISSE), 2018
Extraction procedure for 14 nm bulk FinFET devices is realized in Matlab. Parameters selected for... more Extraction procedure for 14 nm bulk FinFET devices is realized in Matlab. Parameters selected for extraction include the threshold voltage at zero bulk voltage (VT0), the output conductance parameter (λ), the parameter, which models the transition between linear and saturation regions (MEXP), the subthreshold parameter (η), and the transconductance (gch). The extraction is based on experimental measurements of 14-nm FinFETs wafers. Extracted parameters are simulated in a PTM MG SPICE model for verification.
2018 IX National Conference with International Participation (ELECTRONICA), 2018
Recently inkjet printing has emerged as an attractive technology for a variety of scientific appl... more Recently inkjet printing has emerged as an attractive technology for a variety of scientific applications due to its low-cost and simplicity. Outstanding characteristics of inks based on nanoparticles and carbon nanotubes has made this technology a good choice for various electronic applications such as sensors, transparent electrodes and flexible electronics. The incorporation of metallic, organic and oxide nanoparticles and carbon nanotubes into functional inks is used in order to obtain sensibility to different physical quantities. The present paper focuses on the systematization of commercial and custom-made inks recently developed for desktop inkjet printers.
2020 21st International Symposium on Electrical Apparatus & Technologies (SIELA), 2020
The present article introduces a new type of piezoelectric barrier with energy harvesting element... more The present article introduces a new type of piezoelectric barrier with energy harvesting elements. After modelling the noise barriers with COMSOL and conducting experiments, the location of the piezo elements for energy harvesting was determined. The purpose of this article is to test the efficiency optimization of the energy harvesting at noise reduction. The influence of three different typical types of acoustic spectra and different sound pressure levels on the generated electric energy were determined, as well as the efficiency of the acoustic noise power generation system at three different spectra and at different acoustic noise pressure levels on the acoustic barrier
2020 XXIX International Scientific Conference Electronics (ET), 2020
The monitoring and control of soil moisture has always been the subject of attention of both deve... more The monitoring and control of soil moisture has always been the subject of attention of both developers of sensor elements and agro-engineers. New developments are available on the market, using different methods, with different functionalities, accuracy and price. This article proposes an innovative approach for non-contact measurement of soil moisture using capacitive flexible sensors. Three different forms of capacitive structures printed with Inkjet technology, silver nanoparticle ink and PET substrate were studied. The results for the change of the capacity and impedance of the structures when the soil moisture changes are presented.
2019 IEEE XXVIII International Scientific Conference Electronics (ET), 2019
In the present paper we have studied the impedance dependence of resistive and three different ca... more In the present paper we have studied the impedance dependence of resistive and three different capacitive structures printed with Inkjet technology. We have studied the impedance variation at different frequencies ranging from 100Hz to 200kHz. The results obtained are described and analysed to find application of the structures for different types of sensors.
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
This paper presents a methodology for parameters extraction of photovoltaic cell based on real me... more This paper presents a methodology for parameters extraction of photovoltaic cell based on real measurement. The modeling of equivalent schemes of solar cells is of great importance in order to be included in electric circuits for wireless sensor networks power supply. The parameters extraction of these devices is still a very difficult task, which requires experimental data, computing and modeling. In recent years different analytic, iterative, and evolutionary computational methods have been suggested in various references to extract the parameters of solar cell and modules. This paper presents an innovative approach to estimate model parameters by completely extracting them from real measured data.
2020 III International Conference on High Technology for Sustainable Development (HiTech), 2020
The presented article examines a new type of Sonic Crystal noise barrier and the possibility of c... more The presented article examines a new type of Sonic Crystal noise barrier and the possibility of collecting energy generated by noise. After COMSOL modelling and various experiments performed in our previous articles, we have determined the best location of the piezo materials used for energy harvesting. The aim of the article is to verify the designed model, to quantify the collected energy and to analyse the efficiency of energy harvesting in noise reduction
2017 40th International Spring Seminar on Electronics Technology (ISSE), 2017
One of our most vital resources nowadays is fresh water. Water quality refers to the condition of... more One of our most vital resources nowadays is fresh water. Water quality refers to the condition of the water, including chemical, biological and physical characteristics with respect to its suitability for a particular purpose. The main purpose of this publication is to set up a virtual system for water analysis in order to measure particular parameters of the water before and after physicochemical treatment. The water is treated with clinoptilolite, which has recently been used for water filtration. It is suitable especially for water treatment due to its ion exchange, absorption properties and high porosity. The main geochemical and technological concerns are how the chemical behavior of natural clinoptilolite affects the quality of different types of water.
2020 43rd International Spring Seminar on Electronics Technology (ISSE), 2020
Capacitive liquid level sensors have long been known in the scientific areas. In recent years, fl... more Capacitive liquid level sensors have long been known in the scientific areas. In recent years, flexible sensor structures printed using inkjet technology have been introduced that allow the measurement of the level in vessels of different shapes without the need for immersion of the sensor in the liquid. Classical (interdigital) sensor structure is used in more publications. The purpose of this article is to investigate the influence of pattern on the capacitance and impedance of the sensor at different fluid levels. Sensors of three different shapes are printed on the Polyethylene Terephthalate PET substrate, using silver nanoparticle ink and a conventional desktop printer. The measured results are presented and analyzed.