Angel Kanchev University of Ruse

Problem statement Oocyte cryopreservation for non-medical reasons has been widely promoted among young women who tend to delay their reproduction. As the methodology has proved its safety and efficiency in the field of assisted reproduction technology and the embryo laboratory, the interest in oocyte cryopreservation has increased highly. However, do social freezers ever come back and use these oocytes, or they keep them as a safety boat with no real near-future plans for reproduction? Methods The following study has been performed as a retrospective analysis of 296 women who had oocyte freezing procedure for non-medical (social) reasons, medical conditions (oncological treatment) and oocyte donation from January 2013 to June 2023 at Medical Complex Ob/Gyn “Dr Shterev” – Sofia, Bulgaria. Results Throughout the observed period, 190 women with 221 procedures vitrified their oocytes for future use. Only 9.47% of them had medical conditions and 7.36% were hindered to use their reproductive gametes at the day of the oocyte retrieval (absence of spermatozoa, sickness). The average age of the women in this group was 35.59 ± 1.5 years and the mean number of cryopreserved oocytes was 5.63 ± 1.4 per women. Compared to social cryopreserves, and bound to the Bulgarian legislation, the 106 women who donated their oocytes were younger (28.86 ± 1.5 years (p < 0.05)) with 7.34 ± 1.7 (p < 0.05) cryopreserved oocytes per donor. As the clinic has well represented program for oocyte donation 82.1% of the donors were used. In result, there were 37 clinical pregnancies with 47 children born. In the same period, only 46 (24.2%) women who stored their own gametes in our cryobank came back and claimed them for assisted reproduction. Nine clinical pregnancies had been registered and 10 children were born. An intriguing fact we can point from the medical history of the clear social freezers (SF) is the record of previous procedure(s) for abortion on demand. It was reported for 12% of the women in this group. Conclusion According to the results we observed as evident that patients need more clarity towards the procedures for oocyte cryopreservation and consequent fertility treatment. We should rise more awareness to the most preferable age for cryopreservation and number of oocytes to be stored.

In modern conditions, it is important to develop alternative energy sources, but at the same time take into account the analytics of pollutant emissions into the atmosphere. Within the framework of this article, the goal is to study the volume of pollutant emissions during production in comparison with other types of fuel. It is important to demonstrate the environmental friendliness of energy production to determine a possible direction for further development. Classifiers of categories of the energy sector under two conventions, methods for calculating pollutants and greenhouse gases, sources of primary data, emission factors according to the IPCC and EMEP guidelines, methods for restoring gaps in the series of values of primary data are briefly described/ The cycles of work on the preparation of national greenhouse gas inventories, the difficulties at the beginning of work and the general approaches that are used in the calculations, as well as the innovations of each cycle are described. Changes in emissions over 30 years for 25 pollutants and 3 greenhouse gases are briefly described, and a comparison is made with similar indicators in some countries using several specific indicators, which may be useful for researchers in other countries.

The process of obtaining high quality fertilizers consists of the following stages: raw material preparation—loading—anaerobic digestion—biogas extraction—purification from impurities—methane production. The spent biomass serves as a fertilizer for agricultural crops. Solving an environmental problem. As a rule, organic waste is stored outdoors. At the same time, methane and carbon dioxide are released into the atmosphere, which are the cause of global warming. Soil pollution also occurs. It becomes unusable, and there is a threat of groundwater contamination and poisoning of people. Solving the energy problem. Methane, which is a product of a biogas plant, can serve as a fuel for an electric generator, which will make it possible to obtain electrical and thermal energy to cover the needs of the enterprise. Solution of the economic problem: 1. The generation of electrical and thermal energy allows you to significantly save money on the purchase of energy resources. In the event of a surplus, energy can be sold. 2. The sale of fertilizers brings good profits. 3. Waste disposal and storage require money, which can be saved by using a biogas plant, as the waste will be converted into fertilizer and used in agriculture. 4. Fines are imposed for pollution, which can be avoided.

A literature review has been conducted, helping outline some of the main peculiarities that exists within the 3D object file format domain. The difficulties that are present when working with different file formats in various fields have been noted-incompatibility issues, data loss, conversion difficulties, software wrappers, manufacturing industry standards and more. The problem of file format comparison has been defined-workflows are bogged down by the different output software tools use, expertise in different fields is a requirement, difficulties with conversion, complexity of file formats themselves and proprietary solutions, all lead to tremendous amount of manual work and technical knowledge required to keep track of differences between 3D file formats. As web sources for file format information can often become unreliable with time, new sources become available and analysis are constantly made, an argument has been made to try and use LLMs to alleviate some or most of the workload in file comparison. Such research necessitates a researcher to manually check all the output data of a model, in order to verify the correctness and accuracy of the used model. A methodology for the research process has been developed and implemented. Its main points include the definition of criteria for comparison, using manufacturing industry expert opinion to further verify the validity of the researcher and LLMs statements and the criteria itself, creation of comparison tables based on the criteria for all the chosen formats, short descriptions of the file formats themselves by the researcher and by the LLM and their comparison, as well as an analysis of file formats searchability on google trends. A comparison of binary data for some file formats is shown and described for further understanding of the issues with metadata and understanding proprietary 3D file formats. ISO standards for STEP ISO 10303-242:2022 and IGES, as well as their effects on the industry are briefly discussed. File formats that are discussed and compared: OBJ (Waveform obj, .obj); FBX (Filmbox, .

Education for sustainable development in universities is shaping the agenda in this area, demanding continuous improvement in quality. There is a trend towards integrating sustainability issues and the implementation of sustainable development goals into higher education. Universities responsible for educating SD professionals must teach knowledge and develop skills in line with the SDGs. However, there is insufficient attention to this in educational programs; more often it is implemented through disparate initiatives. The article presents research conducted in universities in the countries of Central Asia (Kazakhstan, Kyrgyzstan, Tajikistan, Uzbekistan), South Caucasus (Georgia, Armenia) and the European Union (Italy, Bulgaria, Poland). The awareness of students and teachers about the SDGs, the problems of implementing SD were assessed, and ways to solve these problems were analyzed. Countries were divided into clusters for comparative analysis. The results show that students generally have limited knowledge about the global sustainable development goals, while teachers have a higher level of awareness. The article examines the contribution of education to raising students' awareness in the countries studied and their attitudes towards integrating sustainability into the curriculum. The questionnaire showed that the educational intervention significantly influences students’ intention to engage in sustainability. Overall, students demonstrate positive attitudes towards incorporating sustainability issues into their education. The results of a study conducted in higher education institutions in Central Asia, South Caucasus and the European Union showed that students are generally unaware of the sustainable development goals, their information received through the Internet, media and university studies is insignificant, while teachers are better informed. Students and teachers expressed the greatest concern about environmental, social and economic problems. At the same time, students of engineering, technical and medical fields are more informed about the SDGs compared to pedagogical and socio-humanitarian fields. To increase awareness, universities are encouraged to integrate sustainability education into various disciplines, conduct seminars, round tables, promote student participation in projects and research, and promote international cooperation and knowledge sharing.

This article explores and optimizes network technologies for wind energy systems, focusing on the RS-485 interface to ensure reliable data transmission in extreme conditions. The study aims to address the impact of various distortions on data quality and wind turbine management. A system was proposed with two wind turbines, each equipped with a Raspberry Pi 4, connected to sensors measuring temperature, vibration, and wind speed. The research examined how data transmission rates affect signal shape, calculating the distortion coefficient. At 460,800 baud, the signal was almost completely distorted, with significant amplitude loss. The distortion coefficients were 1.84 for logic ‘1’ and 1.92 for logic ‘0’. The optimal speed to minimize distortions was found to be 19,200 baud, providing the most stable signal. Additionally, temperature significantly impacted transmission quality, highlighting the need to consider climatic conditions in system design. The findings and methods can help improve existing data transmission systems and enhance wind turbine performance.

As a result of the thermo-mechanical impact during welding, distortions are generated in welded structures. These distortions significantly influence the geometric and dimensional accuracy of welded structures, in many cases lowering their working characteristics and reliability. An optimal design for welded structures is a prerequisite for increased reliability and reduction in manufacturing cost, and such an optimal design can be achieved knowing the distortions in weldments. Despite the fact that pulsed metal inert gas welding and metal active gas welding have been broadly applied in the last few decades, nowadays, few manufacturers, for instance, Fronius, EWM, Redco, and Perfect Power Welders, offer such an option for manual arc welding. This work aims to determine the influence of the parameters of pulsed welding modes on distortions that are generated during manual arc welding. Two different inverter welding power sources were used, and the welding distortions were measured by 3D scanning. The results showed that the pulsed mode during manual arc welding led to a reduction in distortions compared to the conventional welding mode. The crucial part of the manual welding system proved to be the qualification and performance of the welder.

One of the main reasons why people do not buy electric vehicles (EVs) is the worry that they will not have anywhere to charge them. A sustainable solution can be to put more fast chargers in more places such as the parking spots and mounting photovoltaic (PV) solar panels, which convert the sunlight into energy, on top of battery banks and charging multiple electric cars at the same time. Moreover, the main power grids, which can charge the electric cars when the light from the sun is not strong or at night, are found next to the roads. For residential application, the PV solar panels can be mounted on the roof, while the entire system is grid-connected. This paper deals with modeling and simulation of three-phase grid-connected EVs charging stations with PV solar panels. The EVs charging station with PV solar panels model charging of three EV batteries from a dc fast charger unit. The model is presented in detail and validated by simulation in the Matlab/Simulink environment. Finally, simulation examples display the results for three-phase supply voltage and line current, dc bus voltage and current, battery terminal voltage and output charging current, battery state of charge, charging status, and others versus time. This work is useful for power electronics specialists who need an easy and right method to design and simulate three-phase grid-connected EVs charging stations with PV solar panels.

In this manuscript, we consider a fourth-order three-point boundary value problem. Although the corresponding Green’s function changes its sign on the square of its definition, we obtain the existence of positive and decreasing solutions under some suitable conditions. The arguments are based on the classical Krasosel’skii’s fixed point theorem in cones. Then using Avery–Henderson two fixed point theorem, we obtain multiplicity results. In the end, we establish some conditions under which the solutions of the considered problem are generalized Ulam–Hyers stable. Some examples are given to illustrate our main results.

Coronary artery disease (CAD) presents a significant risk for patients with systemic vasculitides, a group of disorders characterized by the inflammation of blood vessels. In this review, we focus on the pathophysiological mechanisms, complications, and management strategies for CAD in systemic vasculitides. We highlight how the inflammatory processes inherent in vasculitis contribute to accelerated atherosclerosis and myocardial ischemia. Key strategies in managing CAD in this patient population include using medicine treatments to mitigate vascular inflammation while balancing the risk of promoting cardiovascular events and lifestyle modifications. Understanding the nuanced relationship between systemic vasculitides and CAD is crucial for improving patient outcomes and guiding therapeutic approaches.

As high-strength and ultra-high-strength steels are widely used in all kinds of modern welded constructions, a lot of research is carried out to investigate the mechanical properties of the weldments of these steels, but there is little information on such important characteristics as their corrosion behaviour. This research focuses on the corrosion behaviour of the weld metal of the weldments of S906QL and S700MC steels. The weld metal was tested electrochemically in a 3.5% NaCl aqueous solution via a potentiodynamic scan to determine the corrosion rate and its dependence on the welding gap. No influence of the welding gap on the corrosion rate was found, but the experimental results suggested that the corrosion rate depended on the chemical composition of the filler material and the microstructure of the weld metal.

The paper aims to explore the benefits and challenges that artificial intelligence (AI) brings to business. The performed tasks are related to: (1) an a priori study of literary sources focused on the positive and negative impact of AI for business organizations; (2) an empirical study to establish the attitudes among business representatives in Bulgaria towards the application of artificial intelligence (AI). The results, from an empirical pilot study, show that the Bulgarian business representatives see the positives of AI, related to reducing time and money by automating routine processes and tasks, as well as in marketing customer data mining activities and in analysing the big data of the market. AI concerns focus on the need for: deep technical knowledge, upgrading existing software, continuous training, and reskilling of the workforce. There is no preponderance of fears or positive expectations.

This paper analyzes the current situation of interval train control systems (railway interlocking) on the railway network of Kazakhstan, geared towards enhancing the effectiveness of railway transportation, the objective is to augment the capacity of rail lines, diminish operational expenses, minimize energy consumption, and mitigate wear on both tracks and rolling stock. To evaluate the data transmission channel of the TETRA standard, a test model with a long ping and a load test has been developed, and a two–stage test methodology has been proposed for the Zhetygen – Altynkol section. According to the results of the conducted experiments, it is proved that if the connection is lost for more than 60 seconds, the train automatically stops with an emergency braking command and, subject to the restoration of data transmission between the OBU (onboard unit) and the modem, the radio-blocking system works normally for cases with loss of communication and the board permits to move. For evaluating the influence of deploying radio communication on radio-blocking and signal strength, the Hata model within the COST231 framework was chosen. This model incorporates diverse factors contingent upon the environment, such as urban or suburban settings. The model of path loss «Loss of suburban macro-path» was chosen as a model.