Volume 52, Issue 1-2, 2017

20230400-01
Investigating the effects of glasses on electric field distribution from a mobile phone inside the human eye during web surfing

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This paper discusses the effects of the glasses exposed to electromagnetic radiation from mobile phones on the electric field distribution inside the human eye. The numerical analysis has been performed for the case when the mobile phone is used for web surfing at the frequency of 2.6 GHz. Obtained results are presented within different biological tissues from which the human eye model was made. Since the human body consists of various tissues and organs, each needs to be described in terms of its corresponding electromagnetic properties. A realistic 3D model of the human head has been created to obtain the most accurate results. The main aim of this investigation is to determine the electric field distribution in the human eye. For this research, besides the realistic model of a human head, it was necessary to develop a realistic eye model formed of nine different tissues and a model of glasses with a metal frame. A comparative analysis of the model behavior with and without glasses has been carried out to evaluate the effects of the glasses with metal frame. Finally, the paper presents the results of electric field distribution for a horizontal cross-section of the human head model.


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Jovanovic D., Stankovic V., Cvetkovic N., Zivaljevic D., Vuckovic D., Investigating the effects of glasses on electric field distribution from a mobile phone inside the human eye during web surfing. Electrotechnica & Electronica (Е+Е), Vol. 58 (4), 2023, pp.75-80, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20230300-04
Software-defined radio (SDR) versus Digital Signal Processor (DSP) hardware – a comparison of approaches in teaching RF communications at Sofia University
Emil E. Vladkov, Stanimir T. Kolev

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Teaching modern communication technology undoubtedly requires students to be familiar with the latest standards for digital radio frequency transmission and modulation. In times of rapid development in this field, however, this turns out to be a real challenge, as communication standards change literally in months. The introduction of new, more powerful technologies for fast transmission over radio frequency networks requires a versatile approach to familiarization with coding and modulation methods. Such an approach provides the so-called software-defined radio, which is about to replace almost completely specific hardware and software systems based on specialized radio frequency interfaces and digital signal processors. The purpose of the present study is to reveal the advantages and disadvantages of the two approaches for studying modern radio frequency communications within the framework of the respective courses offered to students at the Faculty of Physics of the Sofia University “St. Kliment Ohridski”, namely the use of Analog Devices ADALM-Pluto SDR, representative of the software-defined radio modules, and the study of RF digital transmission methods using a digital signal processor development system and purpose-built hardware, representing the older approach to teaching the subject.

 

Преподаването на съвременни комуникационни технологии несъмнено изисква студентите да са запознати с най-новите стандарти за цифрово радиочестотно предаване и модулация. Във времена на бурно развитие в тази сфера обаче това се оказва истинско предизвикателство, тъй като стандартите за комуникация се променят буквално за месеци. Въвеждането на нови, по-мощни технологии за бърз пренос на данни чрез радиочестотни мрежи изисква универсален подход за запознаване с методите на кодиране и модулация. Подобен подход осигурява така нареченото софтуерно-дефинирано радио, което е на път да замени почти напълно специфичните хардуерни и софтуерни системи, базирани на специализирани радиочестотни интерфейси и цифрови сигнални процесори. Целта на настоящото изследване е да разкрие предимствата и недостатъците на двата подхода за изучаване на съвременните радиочестотни комуникации в рамките на съответните дисциплини, предлагани на студентите от Физическия факултет на СУ “Св. Климент Охридски”, а именно: използването на ADALM-Pluto SDR-модула на Analog Devices, представител на софтуерно-дефинираните радио модули, и изучаването на радиочестотни цифрови методи за предаване с помощта на развойна система на цифров сигнален процесор и специално създаден за целта хардуер, представляващ по-стария подход към преподаването на материята.


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Vladkov E.E., Kolev S.T., Software-defined radio (SDR) versus Digital Signal Processor (DSP) hardware – a comparison of approaches in teaching RF communications at Sofia University. Electrotechnica & Electronica (Е+Е), Vol. 58 (3), 2023, pp.58-65, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20240100-full
Issue 1, 2024

ELECTROTECHNICA & ELECTRONICA E+E

Vol. 59. No 1/2024
Monthly scientific and technical journal
Published by:
The Union of Electronics, Electrical Engineering and Telecommunications /CEEC/, BULGARIA

20240100-full

C O N T E N T S

Georgi Petrov, Velimir Vasilev
Blockchain integration in measurement systems: enhancing industrial data login systems 1

Emil E. Vladkov
The 6G future: a survey of technological promises and challenges 9

Strahil Е. Sabev, Nikolay D. Madjarov, Dobroslav D. Dankov
Overview of modern methods for state-of-health and state-of-charge electric vehicles applications 17

Kjani Guri 
Correlation between degree of polymerization and data from transformer oil analysis 24

20240100-04
Correlation between degree of polymerization and data from transformer oil analysis
Kjani Guri

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The aging of transformers increases the possibility of failures in the insulation system and structural parts. In this case, the insulation system is the most attacked, because the main component is cellulose. The condition of the insulating paper can be identified based on the degree of polymerization (DP) measurement. In some cases, when the degree of polymerization measurement is difficult, the degree of polymerization estimation can be done by collecting information on some of the test parameters, such as oil acidity, moisture content, and furan concentration in the specific 2-furfuraldehyde. In this paper, to build a mathematical model and correlation between oil analysis, the multiple linear regression method was used, where 50 samples of transformers were taken in the study, to create a relationship that connects the degree of polymerization with by-products during the paper degradation process. The empirical formula for calculating the degree of polymerization based on the concentration of 2-furaldehyde was developed and gave promising results to calculate the degree of polymerization and the correlations that exist between these two components. The results show an estimation error of less than 4.06 % for the proposed logarithmic equation with a high correlation coefficient of 0.9995 and an estimation error of 7.21 % for the proposed polynomial equation, against the measured DP with a coefficient excellent correlation of 0.983, excluding oil, acidity, and moisture content.

 


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Guri K., Correlation between degree of polymerization and data from transformer oil analysis. Electrotechnica & Electronica (Е+Е), Vol. 59 (1), 2024, pp.24-32, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20240100-03
Overview of modern methods for state-of-health and state-of-charge electric vehicles applications
Strahil Е. Sabev, Nikolay D. Madjarov, Dobroslav D. Dankov

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Energy storage systems (ESS) play a crucial role in various applications, including electric vehicles, renewable energy integration, and grid stabilization. Assessing the state-of-health (SOH) and state-of-charge (SOC) of these systems is paramount for ensuring their reliable performance and longevity. This article presents a comprehensive review of recent advances in methods for SOH and SOC evaluation in ESS. Firstly, the article discusses traditional techniques such as coulomb counting, voltage-based estimation, and impedance spectroscopy. While these methods are widely used, they often lack accuracy and robustness, especially under dynamic operating conditions. Secondly, emerging approaches utilizing machine learning (ML) and artificial intelligence (AI) techniques for SOH and SOC estimation are explored. ML algorithms, including support vector machines (SVM), neural networks, demonstrate promising capabilities in modeling complex ESS behaviors and improving accuracy in predicting SOH and SOC. In conclusion, this article presents a comprehensive overview of the current landscape of methods for SOH and SOC evaluation in ESS, highlighting the recent advancements and future directions in this rapidly evolving field. Accurate and reliable assessment of SOH and SOC is essential for optimizing the performance, reliability, and longevity of energy storage systems in various applications.

 

Системите за съхранение на енергия (ССЕ) играят ключова роля в различни приложения, включително електрически превозни средства, интегриране на възобновяема енергия и стабилизиране на мрежата. Оценката на състоянието на изправност (СИ) и състоянието на заряда (СЗ) на тези системи е от първостепенно значение за осигуряване на тяхната надеждна работа и дълготрайност. Тази статия представя цялостен преглед на последните постижения в методите за оценка на СИ и СЗ в ССЕ. В статията са разгледани последователно традиционните техники, базиращи се на оценка на базата на напрежение, импеданс и спектроскопия. Въпреки, че тези методи се използват широко, те често не са достатъчно точни и надеждни, особено при динамични условия на работа. Затова са разгледани и нови подходи, използващи техники за машинно обучение и изкуствен интелект за оценка на СИ и СЗ. Алгоритмите на машинното обучение, включително машини с поддържащи вектори и невронни мрежи, демонстрират обещаващи възможности за моделиране на сложното поведение на ССЕ и подобряване на точността при прогнозиране на СИ и СЗ. В заключение, тази статия представя цялостен преглед на настоящите методи за оценка на СИ и СЗ в ССЕ, като подчертава последните постижения и бъдещите насоки в тази бързо развиваща се област. Точната и надеждна оценка на СИ и СЗ е от съществено значение за оптимизиране на работата, надеждността и дълготрайността на системите за съхранение на енергия в различни приложения.


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Sabev S., Madjarov N., Dankov D., Overview of modern methods for state-of-health and state-of-charge electric vehicles applications. Electrotechnica & Electronica (Е+Е), Vol. 59 (1), 2024, pp.17-23, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20240100-02
The 6G future: a survey of technological promises and challenges
Emil E. Vladkov

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Unlike previous developments in the field of communication technology, the sixth generation of communication networks makes a request to penetrate all spheres of life, transforming them radically. Unprecedented data rates, extremely low latency and high reliability as well as global scalability and massive machine type communications deployment opportunities, even precise localization, sensing and THz-imaging will definitely lead to a completely new type of services. However, for all this to happen and to make the Ubiquitous Wireless Intelligence Paradigm possible, it is necessary to address many essential problems concerning the THz-frequency range used, the availability of adequate devicetechnology and modulation techniques, the energy efficiency and the security of 6G communication channels. All these issues are considered in this survey.

 

За разлика от предишните разработки в областта на комуникационните технологии, шестото поколение комуникационни мрежи дава заявка да проникне във всички сфери на живота, като ги трансформира радикално. Безпрецедентните скорости на обмен на данни, изключително ниската латентност и високата надеждност, както и глобална мащабируемост с възможности за масово прилагане на устройства на база интерфейс машина-машина, дори точното определяне на местоположението, детектирането на присъствие и получаването на THz-изображения определено ще доведат до напълно нов тип услуги. За да се случи обаче всичко това и да стане възможна концепцията за повсеместния безжичен интелект е необходимо да се решат много съществени проблеми, засягащи използвания THz-честотен обхват, наличието на адекватна технология за 6G устройствата и на подходящи модулационни техники, енергийната ефективност и сигурността на 6G комуникационните канали. Всички тези въпроси са разгледани в това проучване.


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Vladkov E., The 6G future: a survey of technological promises and challenges. Electrotechnica & Electronica (Е+Е), Vol. 59 (1), 2024, pp.9-16, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20240100-01
Blockchain integration in measurement systems: enhancing industrial data login systems
Georgi Petrov, Velimir Vasilev

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This paper investigates the transformative potential of integrating blockchain technology into measurement systems. By leveraging blockchain’s immutable ledger and smart contracts, the integration aims to enhance trust and transparency in diverse industrial sectors. Case studies highlight its practical applications, showcasing how blockchain fortifies data integrity and enables transparent, auditable measurements in experimental system for monitoring operating parameters of high-speed radial axial fans. The study advocates for widespread adoption, emphasizing blockchain’s role in fostering reliability and transparency in decision-making processes.

 

Тази статия разглежда потенциал на интегрирането на блокчейн технологията в индустриалните измервателни системи. Чрез използването на блокчейн и интелигентните договори, интеграцията има за цел да повиши доверието и прозрачността в различни индустриални сектори. Посочени са практическите приложения, демонстрирайки как блокчейнът укрепва целостта на данните и позволява прозрачни, подлежащи на одит измервания в експериментална система за наблюдение на работните параметри на радиални аксиални вентилатори. Проучването се застъпва за широкото приемане на технологията, като подчертава ролята на блокчейна за подобряване на надеждността и прозрачността в процесите на вземане на решения.


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Petrov G., Vasilev V., Blockchain integration in measurement systems: enhancing industrial data login systems. Electrotechnica & Electronica (Е+Е), Vol. 59 (1), 2024, pp.1-8, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20230400-full
Issue 4, 2023

ELECTROTECHNICA & ELECTRONICA E+E

Vol. 58. No 4/2023
Monthly scientific and technical journal
Published by:
The Union of Electronics, Electrical Engineering and Telecommunications /CEEC/, BULGARIA

20230400-full

C O N T E N T S

Dejan Jovanovic, Vladimir Stankovic, Nenad Cvetkovic, Dragana Zivaljevic, Dragan Vuckovic
Investigating the effects of glasses on electric field distribution from a mobile phone inside the human eye during web surfing 75

Jelena Đorđević Kozarov, Platon Sovilj, Milan Simić, Marjan Urekar, Milica Stojanović, Dragan Živanović
Further experimental research of interval overlapping method for biomedical signal measurement 81

Natalija V. Ivković, Ana N. Vučković, Mirjana T. Perić, Dušan M. Vučković
Machine learning application in cylindrical permanent magnet force calculation 88

Saša S. Nikolić, Dragan S. Antić, Nikola B. Danković, Miroslav B. Milovanović, Darko B. Mitić, Petar S. Đekić, Igor B. Kocić, Marko Ž. Živković
Application of orthogonal controllers in control of the nonlinear industrial dynamical systems 93

Aleksandar Ivanov
A review of brain-computer interfaces and their applications 100

20230400-05
A review of brain-computer interfaces and their applications

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Brain-Computer Interfaces (BCIs) have emerged as a transformative technology at the intersection of neuroscience, engineering, and computer science. This paper provides a concise overview of the recent achievements and ongoing challenges in the field of BCIs. With the ability to decode neural activity and translate it into meaningful commands, BCIs hold promise for revolutionizing diverse domains, such as medical rehabilitation, communication, prosthetics, forensics and entertainment. The paper reviews the advancements in BCI technologies, including invasive and non-invasive techniques, elucidating the contributions of machine learning and artificial intelligence algorithms to signal processing.


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Ivanov A., A review of brain-computer interfaces and their applications. Electrotechnica & Electronica (Е+Е), Vol. 58 (4), 2023, pp.100-105, ISSN: 0861-4717 (Print), 2603-5421 (Online)

20230400-04
Application of orthogonal controllers in control of the nonlinear industrial dynamical systems

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In this study, we introduce a novel application of orthogonal controllers within control systems theory. Specifically, we propose a novel approach for utilizing generalized orthogonal Malmquist polynomials, also known as Müntz polynomials, to control complex nonlinear industrial systems. These polynomials are employed in the final stage of our hybrid-fuzzy orthogonal controllers. To validate the effectiveness of our approach, we implement and experiment with the proposed hybridfuzzy Takagi-Sugeno orthogonal controllers on a tower crane system, confirming significant enhancements in control efficiency.


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Nikolić S.S., Antić D.S., Danković N.B., Milovanović M.B., Mitić D.B., Đekić P.S., Kocić I.B., Živković M.Z., Application of orthogonal controllers in control of the nonlinear industrial dynamical systems. Electrotechnica & Electronica (Е+Е), Vol. 58 (4), 2023, pp.93-99, ISSN: 0861-4717 (Print), 2603-5421 (Online)