automatica
K. Boshnakov, Transfer of Scientific Developments for Control Systems from Laboratories to Industry. Thematic Summary Based on IFAC Industry Committee and IEEE Control Systems Society Publications

Key Words: Academic research; technology transfer; validation and technology transfer; validation steps and tools.
Abstract. This thematic summary is based on publications of the Industry Committee of the International Federation of Automatic Control (IFAC), T. Samad et al., Industry engagement with control research: Perspective and messages, Annual Reviews in Control, vol. 49, pp. 1–14, 2020 and IEEE Control Systems Society: Control for Societal-Scale Challenges: Road Map 2030, published May 2023. The main goal of both developments is to bridge the gap between academia and industry. Based on IFAC Industry Committee discussions, surveys and research, 10 messages to the research community have been formulated. The road from academic research to industrial incorporation is difficult and lengthy. It is argued that the lack of validation is a major obstacle to the transfer of technologies developed as a result of academic research, and in practice the academic community can play a crucial role in the validation process. Five steps in validation and tools for each step are identified, and recommendations are presented to advance validation and facilitate the transition to innovation and technology transfer in the short, medium and long term.

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informatics
G. Mihalev, S. Yordanov, H. Stoycheva, Application of Segmentation Algorithms in the Reconstruction of a 3D Scene from Images

Key Words: 3D reconstruction; Structure From Motion (SFM); Image segmentation; Robotics.
Abstract. The technique of 3D reconstruction of real scenes from images represents a significant advancement in visual technologies, offering the potential for the development of numerous new applications in various engineering fields. In general, 3D reconstruction from images is a computer process that utilizes a set of two-dimensional images captured from different angles and positions to create a three-dimensional model of the scene or object. By analyzing features such as key points, comparing their positions, and applying geometric principles, this process transforms the images into three-dimensional representations with spatial information. The complexity of 3D scene reconstruction from images arises from the need to detect points of interest, match and track them across different images, as well as analyze and merge multiple visual data from different perspectives. This article proposes the use of simpler image processing algorithms to obtain more points of interest, providing a more accurate 3D model without overburdening the reconstruction process with complex computational procedures. The investigated methods implement image segmentation through the first and second derivatives of the image intensity function to determine and separate edges and boundaries in the image. A practical implementation of 3D reconstruction of real scenes from images in the Matlab environment is presented. In the implementation, algorithms based on the first and second derivatives of the image intensity function are used to achieve a denser 3D model by segmenting images to detect edges and boundaries. The investigated algorithms are implemented in the stage of discovering properties in the image. Some of the most well-known algorithms have been tested and compared with the use of the standard SURF algorithm. The algorithms from this class have significantly improved results, with the density of the 3D model increased several times compared to the number of generated points, and in some cases, the execution time remains the same relative to the percentage ratio of the generated 3D points.

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education and qualification
N. Dishovski, P. Ruskov, S. Terzieva-Zhelyazkova, From Theory to Practice: Technology Transfer and Commercialization of Scientific Research at University of Chemical Technology and Metallurgy

Key Words: Education; sciences; IP; technology transfer; technology commercialization.
Abstract. The article studies a training model that includes the development, planning, organization, and implementation of training on the topic “Technology transfer and commercialization of technologies” at University of Chemical Technology and Metallurgy (UCTM). The purpose of the article is to present the process and content of the training conducted with the support of the BiOrgaMCT project. The article also includes and discusses the learning outcomes and plans for future development of technology transfer and commercialization of scientific research at UCTM. The following concepts were awarded as projects with serious opportunities for technology transfer and commercialization: Development of advanced materials and technical ceramics for special purposes, Clean technologies and utilization of waste from plant raw materials and wastewater, Development of biologically active molecules for multi-target therapies and Creation of a new, regenerative material from used textiles for cleaning up oil pollution.The lesson learned is that the course was very useful, both in relation to the realization of the project on which it was organized, and in view of the future development of the university as a research institution. That is why we believe that similar education can be successfully implemented in other higher education institutions in Bulgaria.

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reviews
I. Lambov, Decentralized Identity: Recent Scientific Advancements and Applications

Key Words: Reusable identity; decentralized identity; self-sovereign identity; web3 identity; zero-knowledge proofs; trust models.
Abstract. The trajectory of decentralized identity, anchored in the principles of self-sovereign identity (SSI), Decentralized Identifiers (DIDs), and verifiable credentials, holds the potential to redefine the contours of the digital landscape. This paradigm shift not only signifies a pivotal transformation but also heralds the advent of an epoch characterized by heightened trust, enhanced privacy, and fortified security. This article presents the major scientific developments and applications of 2023 in the field of Decentralized Identity. Decentralized identity (DID) continues to witness significant progress, with 2023 shaping up as a year of noteworthy scientific advancements and impactful applications. This article delves into the major developments that have propelled the field forward. Firstly, we explore the evolution of DID specifications and standards. We examine the progress of ongoing initiatives like the W3C DID Working Group and the Hyperledger Aries framework, highlighting their contributions to interoperability and secure identity management. Secondly, we review the existing publications on the subject and categorize them based on the nature and focus of the research. This classification scheme provides a framework for understanding the diverse facets of scientific research on Decentralized Identity. It highlights the multidisciplinary nature of SSI research, which spans computer science, cryptography, engineering, etc. Another approach we took in the classification of the scientific publications on SSI, especially the more technologically focused studies, was based on the working groups, operating within the DIF. Thirdly, we delve into the security and privacy advancements in 2023. This section explores novel research on zero-knowledge proofs for DID systems, privacy-preserving credential issuance, and techniques for mitigating security vulnerabilities. Furthermore, the article examines the social and economic impacts of DID implementations. We analyze case studies and emerging applications across various sectors like healthcare, supply chain management, and education, highlighting how DID is transforming trust models and empowering individuals. Finally, we discuss the challenges and future directions for the field. This section considers the need for scalability, regulatory frameworks, and broader adoption to unlock the full potential of DID. By synthesizing these key aspects, this article provides a comprehensive overview of the current state of DID, showcasing its scientific advancements and diverse applications in 2023. It aims to inform researchers, practitioners, and policymakers about the transformative potential of DID and the ongoing efforts to shape a more secure and user-centric future for digital identity management.

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modeling and control of energy systems
N. Deliiski, L. Dzurenda, D. Angelski, P. Vitchev, K. Atanasova1Computation of Energy Consumption and Efficiency of Concrete Pits during Boiling of Logs for Veneer Production

Кey Words: Concrete pits; non-frozen logs; boiling; energy consumption; energy efficiency; veneer production.

Abstract. An approach for computing the energy consumption and energy efficiency of pits during boiling of non-frozen logs intended for veneer production has been presented. The approach is based on the use of two personal mathematical models: 1D non-linear model of the unsteady distribution of the temperature along the radius in the central cross section of non-frozen logs subjected to boiling at conductive boundary conditions, and model of the thermal balance of concrete pits during boiling of wood materials in them. For numerical solving of the models and practical application of the suggested approach, a software packages were prepared in the calculation environment of Visual FORTRAN Professional and in Excel respectively. With the help of the first model, the boiling times of beech logs with a diameter of 0.4 m, initial temperature of 0, 10, and 20 °C and moisture content of 0.6 kg∙kg-1 were determined at water temperatures in the pit equal to 70, 80, and 90 °C. Using the determined logs’ boiling durations, with the help of the second model the change in energy required for the entire boiling process and that for each of the components of the thermal balance was calculated. Computer simulations were performed for a well-insulated concrete pit with working volume of 20 m3 and degree of filling it with logs 45%, 60%, and 75%. It was found that the energy consumption of the pit decreases from 159.7 to 145.3 kWh·m-3 when the initial temperature of the logs increases from 0 °C to 20 °C at temperature of the boiling water of 80 °C and maximum possible degree of feeling of 75%. In this case, the thermal efficiency of the pit decreases from 32.2% to 26.1%. It was found also that at the same degree of feeling of the pit the increase in the boiling water temperature from 70 °C to 90 °C causes an increase in the energy consumption of the pit from 135.3 to 170.9 kWh·m-3 when the initial temperature of the logs is equal to 10 °C. Under these conditions the thermal efficiency of the pit decreases from 29.9% to 28.8%. The approach can be applied to compute the energy consumption and thermal balances of concrete pits during boiling of non-frozen logs to any desired final average mass temperature required for the mechanical processing of the plasticized wood. It could be easily modified and used to calculate the energy consumption and efficiency of concrete pits of any design and construction parameters.

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modeling and control of energy systems
T. Radeva, Use of Photovoltaic Energy for Own Needs for an Educational Center for Out-Of-Class Activities and Culture

Key Words: Photovoltaic systems; solar power generation; educational institutions; design engineering; energy management.

Abstract. The solar modules that are produced have a rather fragile structure and must therefore be mechanically protected on both sides. For this purpose, a so-called sandwich structure is used, in which the photovoltaics are placed on a solid base and covered with a transparent upper protective layer. The coefficient of thermal expansion of the materials of the upper and lower protective layers must be the same and, moreover, comparable to that of the photovoltaic cell and the bonding resin used. Currently, the most widely used materials are glass and plastic. Photocells sealed under glass have the advantage that they do not change their optical, mechanical and electrical properties during prolonged outdoor operation. Polymers cannot prevent the penetration of moisture, so they are only suitable when the photovoltaics and metal contacts are protected by an anti-corrosion coating. Plastics are lighter than glass, but they have the effect of aging with prolonged exposure to atmospheric conditions, which strongly affects their qualities. The upper transparent protective layer allows easy cleaning of the solar cells, but during their installation, they must be placed in such a way as to avoid their heavy contamination and the retention of snow on them. This is practically achieved by the southern orientation of the panels and their placement at an angle corresponding to the latitude of the site, as well as taking into account the season of operation. Some panels are oriented to the southwest so that they can produce the necessary energy for the afternoon maximum. For most locations, a slope angle close to horizontal will provide the most energy year-round. The cells used today have an efficiency of 3-20% in converting solar energy into electricity. A photovoltaic generator is a set of modules that convert solar energy into direct current (DC) electricity. It consists of a module formed by several photovoltaic cells, connecting several such modules form a panel, and several panels connected together form an array. Connecting several arrays electrically in parallel forms a photovoltaic generator or photovoltaic park. By connecting a certain number of photovoltaic cells in parallel and in series, any desired power can be obtained. The main element of the photovoltaic generator is the photovoltaic cell, where the conversion of solar radiation into flowing electric current takes place. The present work presents a practical task of a photovoltaic energy system for a public educational building. The purpose of the case study is to provide technical measures to improve the energy efficiency of the building, according to the technical specification and the current regulations. Public school buildings are mainly used during the daylight hours, where solar energy will be used for self-consumption.

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education and qualification
M. Hadjiski, R. Kaltenborn, Personalized Learning Based on Artificial Intelligence as a Challenge for Modern Education Systems

Key Words: Personalized learning in education; evolution of modern personalized education; potential possibilities of personalized learning systems; possible ways to implement effective personalized training; artificial intelligence.

Abstract. The article provides a critical analysis of the achievements and insufficiently convincing results of the multi-year attempts to introduce personalized education in educational structures of different types. The evolution of personalized learning systems with varying degrees of student involvement in the functioning of the system is discussed. The great potential possibilities of personalized learning systems emphasizing the active role of students are discussed. Two variants of metastructures have been developed for the implementation of personalized training – component and functional. The main dimensions within which personalized learning systems can be treated with a view to determining their weights in multifactor optimization are derived. Possible ways to implement effective personalized training are analyzed. The notion that personalized learning can meet the challenges of the time is substantiated if it is treated as a holistic problem with a large dimension, with student-centered functioning, with finding an optimal combination of algorithms, applications and procedures in technological implementation, with a new level of competence of teachers and students in the field of artificial intelligence, with direct corporate interest for a long time horizon.

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informatics
P. Blagov, P. Ruskov. EBSI (European Blockchain Services Infrastructure) Development and EBSI Production Nodes

Key Words: EBSI; Node Expansion.

Abstract. The article examines the current state and the EC project for building EBSI (European Blockchain Services Infrastructure) production nodes. The main characteristics and architecture of the EBSI platform are presented. The EBSI – NE – Node Expansion project involving the authors to maintain and develop the nodes is described. The EBSI – NE – Node Expansion, Deployment of EBSI production nodes, and provision of support services to the EBSI network at the European level project will further develop the blockchain nodes in the EU and help build capacity for using the technology. The objective of the EBSI-NE consortium is to support the development and adoption of the EBSI network at the European level by increasing the number of validator nodes in the production network and the provision of support services for all relevant EBSI stakeholders. These actions will increase the robustness and maturity of the production network of EBSI, enabling the development of the prioritized EBSI cross-border use cases. The consortium is made of 24 organizations from 14 European countries including government agencies, public institutions, and academia which have extensive experience related to Distributed Ledger Technologies and past EBSI ecosystem initiatives, including the deployment of pre-production nodes. It is within the program DIGITAL-2022-DEPLOY-02, Project ID: 101102570. The tasks and expected results of the project are also presented.

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intelligent systems
R. Hrischev, N. Shakev. Embedded AI Apps in the Intelligent Cloud ERP Systems

Key Words: ERP system; SAP Business Technology Platform; Cloud Oracle Infrastructure; AI services.

Abstract. SAP Business Technology Platform (BTP) and Cloud Oracle Infrastructure (OCI) are the pioneers of the modern cloud intelligent ERP systems. This article presents investigation of the
embedded services with Artificial Intelligence (AI) in both ERP systems. The main functionalities with built-in AI are presented.

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ecological systems
L. Jusufi (LJ), S. Xhafa (SXH). Smart Water Infrastructure Technologies for Implementation of the Smart City Project in Pristina

Key Words: Smart City; Smart Water System (SWS); Smart Water Infrastructure Technologies (SWIT); GIS; DMA; NRW.

Abstract. Over the next decade, urban populations and the need for clean water will continue to grow. Cities are forced to find intelligent solutions for the rational use of clean water using Smart Water Infrastructure Technologies (SWIT). The Smart Water System is an important component, along with other components, with the particular importance to complete the implementation of the Smart
City concept. Most of the Smart City projects have a relatively short history and often the level of their impact is not clear. Cities are getting smarter every day, using information and communication technologies to enrich and enhance city life. Some cities in the Western Balkans have started implementing Smart City, some are in the feasibility study phase and some are in the planning phase of starting implementation. Before implementing a Smart City project, it is necessary to understand not only the potential impact of the project but also the priorities and the specific problems that are trying to be solved. For this reason, this paper will provide information about the level of Smart Water Infrastructure Technologies that are installed in Pristina Water Company to implement a Smart City Project in Pristina. The objective of this paper is to present an assessment of the current situation in the application of Smart Water Infrastructure Technologies in the Pristina Region and to provide a summary of potential key recommendations for the integration of such technologies the Smart Water System control for Smart Cities.

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ecological systems
Z. Radeva. Analysis of Plant Species Data in Development of an Ontology for an Intelligent System for Bulgarian Wild, Cultivated and Protected Flora

Key Words:Development of Ontology; Semantic WEB; WEB Protégé; Plant Ontology; Bulgarian flora; Biodiversity; Botany; Flora-oriented plant ontology.

Abstract. On the territory of the Republic of Bulgaria there are many plants, which are known as Bulgarian flora. The diverse vascular plants in Bulgaria with estimated enourmous number of no less than 3700 species. Bulgarian flora including a wide variety of plant species and their natural habitats. The existing information about them is collected in various sources with a rather heterogeneous structure for representing information about terms or specific terminology. In order to facilitate the integration and analysis of the information contained in the various sources describing the plant flora in our country, in this paper we presents our methodology for describing , gathering and development of a model of ontology, useful for context of semantic web tehnologies. The ontology in specific domain area, as is in area of different types of species in Bulgarian flora give us opportunity to represent plant species through building an intelligent system for Bulgarian wild, cultivated and protected flora. The work presents the analysis of plant species data in development of an ontology for an intelligent system for Bulgarian wild, cultivated and protected flora. Domain ontologies express conceptualization that is specific for particular area and presented by greatly useful in knowledge acquisition, sharing and analysis, ecspecially on the web discover knowledge for plant across all disciplines of botany. A mixed method was applied in organizing of the specification of conceptualizations on flora of Bulgaria using the domain analytic approach in order for developing an ontology. The model of ontology has been constructed by using ontology editor in open-source software Protégé. In this paper, we propose a prototype of model of ontology and describe the research methods including domain analysis for knowledge organization and ontology development, as results of classification of Bulgarian flora based on specialized literature and encyclopedia of plants in Bulgaria, floral characteristics and area of their distribution which are divided into different concepts of plant information. There are included block diagrams for the stages involved in the construction of an ontology for an intelligent system for Bulgarian flora are presented some conceptual terms of botany aspects of the Bulgarian plant species. The paper presents the first results of data analysis of building an intelligent system by ontology for wild, cultivated and protected flora.

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automatica
M. Hadjiski, N. Deliiski, P. Vitchev, D. Angelski, N. Tumbarkova. Computation of Average Moisture Content in Batches of Wood Materials during Thermal Treatment

Key Words: Wood materials; average moisture content; autoclave steaming; 2D mathematical models; Table Curve 2D; veneer production.

Abstract. A method and an algorithm for computing the average moisture content of the whole quantity of wood materials in given batch subjected to thermal treatment has been suggested. This value of the average wood moisture content is needed for calculation and automatic realization of optimal energy saving regimes for such treatment of the materials. The method is based on the use of two own mathematical models: one of the 2D temperature distributions in non-frozen prismatic wood materials during their thermal treatment and another – of the heat balance of steaming autoclaves. For numerical solving of the models and practical application of the suggested method, a software program was prepared in the calculation environment of Visual FORTRAN Professional developed by Microsoft and operating under Windows. Using this program computation of the non-stationary change in the processing medium temperature in an autoclave during steaming in it of non-frozen beech prisms with different moisture content aimed at their plasticizing before cutting them into veneer have been carried out. The variables used during the simulations were equal, as follows: an initial wood temperature of 0 °C, moisture content u from 0.4 to 0.8 kg·kg−1 with an interval of 0.05 kg·kg−1, and cross-section dimensions of prisms 0.4 × 0.4 m; steaming autoclave with inner diameter of 2.4 m, length of its cylindrical part of 9.0 m, and loading level with prisms of 50%; limited heat power of 500 kW of the generator, which feeds the autoclave with saturated water steam. The calculated by the models increase of the steaming medium temperature in the beginning stage of basic regime at u = 0.6 kg·kg−1 is compared with the real increase of that temperature at different values of u, which is periodically measured with a sensor in the automatic control system. After proper processing of the obtained differences between measured and calculated temperatures with the software package Table Curve 2D, an equation for calculating the average moisture content of the wood materials in the whole batch loaded in an autoclave is derived. The good accuracy of the suggested method is proved for the cases of autoclave steaming of non-frozen beech prisms intended for production of veneer.

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automatica
N. Petkov. How Process Control Systems Development Supports Digital Transformation

Key Words: Digital transformation; digitalization; process industries; process automation; simulation.

Abstract. The remarkable evolution of technologies in the last decade enables producers of automaton products, software, and systems to goes further in their solutions. At the same time process industries are challenged by the continuously changing competitive environment, keeping new health and safety regulations, and developing environmental-friendly products. New business models are created, and producers need to fit to be successful in their markets. Digital transformation (DT) is the way how process industries could go further. Process automation systems takes significant part in that transformation using the latest developed technologies. Different studies and research in the automation control theory, especially in the last decades, provides us the available knowledge base for further technology improvement. Normally there is a timeline gap between the theory and the practice due to the complex mathematical models and algorithms which were difficult and expensive to be executed in a real production process. With the development of the new automation hardware, software technologies and edge devices, driven by Industry 4.0, the implementation of theory is more applicable, and the return of investment is more visible. Nowadays, the development of science and production processes go more and more hand in hand from the stage of conceptual design the products production. The leading role has the rapid development of artificial intelligence, supported by the availability of new computer technologies, computational algorithms, and programming languages. The aim of this paper is to show a difference in digital transformation of discrete and process industries. The focus is the DT of process automation using parallel examples from the automation control theory and currently available software and hardware solutions.

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modeling and control of energy systems
V. Boishina. Applying Machine Learning to Energy Objects Control

Key Words: SISO; power plant; Machine Learning; PID control; error assessments.

Abstract. The research is focused on possibility of applying the Machine Learning (ML) approach, which is using previous data knowledge for the energy system and monitored process values for control behaviour. The main focus of the research is to make assessments for the quality of the control process by comparing the classical PID Control algorithm and Machine Learning Control (ML) one. The investigation is based on possibility to apply supervisor Machine Learning Control to Single Input Single Output (SISO) Power Plant. In the current research the previous information about the system data (manipulated, control, output variables and system states) are used for forming the training sets which is used for performing the Machine Learning Control. Some simulation results illustrating the behaviour of the power system, which is controlled via ML and PID have been presented. The research gives some assessments about the quality of the control by assumption for presence of low and big system disturbances and uncertainties, which may occur in energy system. In current paper applying the supervisor ML algorithm is only under consideration. The steady describes the basic architecture of developed software system implementing the SISO Plant Control. The research gives assessments for four cases – PID and ML control with low disturbances, PID and ML control with big disturbances. Some assessments about system behavior have been made with possibility to overfeed the training set applying big uncorrelated data. The software system is released with java and weka ML library. Realization of system program modules and architecture of the system has been presented.

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modeling and control of energy systems
T. Radeva. Stages and Measures in Preparing an Energy Efficiency Report of an Educational Center

Key Words: Energy efficiency; survey; costs.

Abstract. The object of the study is treated as an integrated system, consisting of a building, systems for ensuring the microclimate, inhabitants and modes of habitation, climatic eff ects of the environment. The source information required for the analysis was gathered from existing documentation and surveying. In solving the task, the following methods and procedures were used and applied: interviews with owners; inspections; modeling and simulation of energy transfer processes; calculations. The source information required for the analysis was collected from: existing documentation; recordings. Solving the task is implemented in the following sequence of actions: analysis of the existing situation; formation of the necessary database for modeling and simulation of energy transfer processes; creating models of real energy consumption; establishment of the main energy characteristics under normal mode of exploitation; simulating the energy transfer processes and revealing the potential possibilities for energy saving; generation of energy-saving measures and technical solutions for their implementation; technical-economic evaluation of prospective measures and their combinations; assessment of saved carbon dioxide emissions as a result of the implementation of measures to increase energy effi ciency. The presented material refl ects only the obtained results without going into detail the implementation of the individual stages.

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intelligent systems
A. V. Atanassov, D. Pilev, F. Tomova. Improving the Accuracy of Facial Emotion Recognition through Deep Neural Networks for Facial Emotions and Weather Conditions Recognition

Key Words: Deep Neural Networks; Facial Emotions Recognition; Weather Condition Recognition; Python.

Abstract. Emotions are one of the main ways to communicate between people and to express their attitude towards objects, products, services, etc. Emotions are divided into two classes – verbal and non-verbal. Human speech and intonation belong to the first class, and to the second class are facial and body emotions, also known as body language. The subject of this paper is facial emotions and their relationship to the scene in which they occur. A number of studies have established that there is a strong relationship between a person’s emotions and their surroundings. The latter includes meteorological conditions (weather) and other objects, such as other people, landscape, etc. Facial emotions range (FER) from seven basic emotions (joy, anger, surprise, fear, sadness, neutral and disgust and neutral) categorized by P. Ekman through his Facial Action Coding System to 26 emotions represented by Russell through his 3D Valence Arousal Dominance model. Most of the existing deep neural networks for Facial Emotions Recognition recognize mentioned seven emotions. In our previous research, we presented a pre-trained FER model with 69.85% accuracy. Weather conditions are closely related to geographic regions and vary in some cases from sunny to cloudy, or in other cases include some subset of sunny, foggy, snowy, rainy, hot, etc. In this research, we analyze deep learning neural networks, for weather conditions recognition and selected appropriate model. We combined our FER DNN with the selected weather recognition DNN and build a bimodal system, which improves facial emotion recognition to 80-83% especially in the cases when FER model provides contradictory results.

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ecological systems
G. Mihalev, S. Yordanov, H. Stoycheva. Beehive Condition Monitoring System Intended for Application in Beekeeping

Key Words: Beehive monitoring system; precision beekeeping.

Abstract. Honey bees are one of the most important insects for human existence. They have a main role in the production of various agricultural crops, as well as in the development of nature itself. Currently, bee colonies are facing many problems related to climate change, diseases, chemical pollution and most of all human activity regarding the development, production and sustainability of the bee colony. The aim of the present development is to provide a solution or at least to partially suppress certain problems of bee families during their development in their active period, with a minimum expenditure of resources. These problems can be summarized as problems related to the health of the hive, problems related to reproduction and problems related to the production of certain bee products (honey, pollen and wax). A system for monitoring of some bee colonies parameters in real time is proposed, based on cloud services and a microprocessor system with a set of sensors. The obtained information can help the beekeeper take timely action with minimal stress to the bees in the colony. The developed system is based on an ESP32 microcontroller and measures basic parameters, such as internal and external temperature, humidity and weight of the beehive. The data is stored in a cloud structure with a good graphical presentation environment for the purpose of subsequent analysis. Attention is paid to energy saving and communication in difficult to reach places and regions. The architecture of the system and its implementation are described in details. The developed system can be used to monitor the production of honey, prevent the process of swarming, as well as to maintain a high health status of the bee colonies. Results of actual data obtained for the observed values during the active period of development of a beehive are presented. Through the technical and economic analysis, information is given about the achieved socio-economic results.

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automatica
M. Hadjiski. 30th Anniversary Symposium on Control of Energy, Industrial and Environmental Systems

Key Words: Control praxis; ecology; energy; engineering; industrial automation; innovation.

Abstract. The presented overview represents a general view of the successfully held 30th edition of the International Symposium on Control of Energy, Industrial and Environmental Systems. This was not a narrowly specialized forum, it was a search for a possible way to build a bridge between theoretical achievements and their practical implementation in industrial automation. The main automation engineering companies and the relevant organizational structures in industry and business in Bulgaria have invariably been active participants and sponsors of the symposium. The total number of reports and company presentations published in the pro- ceedings of the symposium exceeded 500. During the three decades of its existence the symposium was constantly evolving following the rapid progress of theoretical achievements, new technical devices and advanced software, emerging innovative technologies based on Big Data and Artificial Intelligence. The symposium was a place for productive discussions, exchange of experience and mutual enrichment of specialists with different profiles. It was a suitable environment for creating new contacts, which in many cases grew into long-term business cooperation. The symposium was a forum for popularizing the scientific and practical achievements of industrial automation in Bulgaria. It was often a place for first appearance and publication of young specialists from scientific circles and industry.

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modeling of energy systems
I. Simeonov, N. Pan, H. Wang, Y. Tian, E. Chorukova, N. Christov. Energy Yields Comparative Study for One-Stage and Two-Stage Anaerobic Digestion Processes

Key Words: Anaerobic digestion; one-stage anaerobic digestion processes; two-stage anaerobic digestion processes; mathematical modeling; static characteristics; biogas yields; energy yield.

Abstract. Compared to traditional one-stage anaerobic digestion processes (OSAD) with biomethane production, this paper focuses on the study of energy yield of the two-stage anaerobic digestion processes (TSAD), which are able to produce simultaneously biohydrogen and biomethane. In TSAD, relatively fast growing acidogens and H 2-producing bacteria are developed in the first-stage hydrogenic bioreactor and are involved in the production of volatile fatty acides (VFA) and H2. On the other hand, the slow growing acetogens and methanogens are developed in the second-stage methanogenic bioreactor, in which the produced VFA are further converted to CH4 and CO2. This separation allows to optimize physico-chemical parameters for both groups of microorganisms which are not the same. Using mathematical models (mass balance type) developed by our team, theoretical comparative analysis of the energy yield from one-stage and two-stage anaerobic digestion systems is performed. Transforming the differential equations of these balance models, some algebraic equations called static characteristics for both bioreactors were obtained. They represent dependencies of the main process variables from the control variable (dilution rate). On the basis of theese results, the theoretical maximal values of the corresponding enery carriers (hydrogen and methane) yields can be found for different values of the inlet organics (perturbation). The possible maximal biohydrogen and biomethane yields and the overall energy production are calculated by the static characteristics and extremum points of both systems. From the performed analytical and simulation studies, it can be seen that the energy obtained with TSAD is from 32% to 48% greater compared to OSAD under similar conditions (depending on the concentration of the incoming organics).

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