International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Globalization in the modern world covers all areas of life, economy and modern technology, politics and culture. The rapid development of information and communication technologies makes it possible to provide competitive advantages to business organizations. In recent decades, information systems have led to a dramatic increase in the productivity of large and small businesses. This enables an accelerated transition to climate neutrality and digital transformation of the economy, society and industry and requires new technologies, investments and innovations to ensure the sustainable development and competitiveness of every business and a resource-efficient and competitive economy as a whole. The integration of digital technologies in production processes plays an increasingly important role in shaping the competitiveness of enterprises and their sustainable development in the modern world.

There are many different models and types of heat exchangers depending on the area of use. The type of fluids involved in heat transfer and their temperature play a critical role in selecting the appropriate model. Common heat exchangers include plate exchangers, tube-type exchangers, air-cooled exchangers, and graphite exchangers. In this study, a sustainable and original heat exchanger system was designed to increase energy efficiency and reduce natural gas consumption by utilizing the waste heat from natural gas. The design prioritizes ease of maintenance and cleaning. Detailed engineering analyses were conducted, and critical engineering errors identified in previous heat exchanger designs were resolved. The developed designs were validated through test studies and experiments, leading to the final design after an optimization process.
As a result of the study, a high-capacity, energy-efficient, and sustainable heat exchanger integrated with modern technology was developed.

The growing environmental concern about plastic waste has prompted research into sustainable recycling of polymer, particularly for widely used polymers such as polyethylene from the spools used in the textile industry in the second half of the 20th century. This study investigates the feasibility and optimization of recycling Polypropylene to make filaments suited for 3D printing applications, notably Fused Deposition Modelling (FDM). The study is divided into three phases: collecting and preparing post-consumer Polypropylene spools, extruding recycled Polypropylene into filaments, and optimizing the filament for 3d printing using FDM Technology.
Polyethylene spools are cleaned, shredded, and treated to ensure consistent feedstock quality. The extrusion process entailed controlling factors like temperature, screw speed, and cooling rate to produce filaments with constant diameter with less distortion. Following material characterisation, the printability of recycled Polypropylene filaments was evaluated using an FDM 3D printer. The Taguchi method is used to carefully study the influence of printing parameters such as nozzle temperature, bed temperature, print speed, and layer height to determine optimal parameters. The printed examples showed reasonable dimensional accuracy and layer adhesion, with surface roughness values within acceptable limits for practical applications.
This thorough study plan focuses on recycled Polypropylene as a feasible and sustainable material for FDM 3D printing. The findings indicate that with proper optimization, recycled Polypropylene can match the performance requirements of a variety of applications, helping to reduce waste and promote the circular economy in additive manufacturing. Long-term performance testing and the development of recycling processes will be the primary focus of future research to improve the material’s characteristics and broaden its application range.

This paper evaluates the potential of waste-to-energy (WtE) solutions in managing industrial and municipal waste in Bulgaria. It provides an overview of current WtE technologies, including thermal, biochemical, and innovative processes, and assesses their applicability within the Bulgarian context. The study highlights environmental and economic benefits such as reduced landfill use, decreased greenhouse gas emissions, and energy recovery. By examining successful implementations in Bulgaria and other EU countries, the paper identifies key challenges and opportunities for scaling WtE solutions. The findings suggest that with the right policy support and investment, WtE can significantly contribute to sustainable waste management in Bulgaria.

This paper evaluates the potential of waste-to-energy (WtE) solutions in managing industrial and municipal waste in Bulgaria. It provides an overview of current WtE technologies, including thermal, biochemical, and innovative processes, and assesses their applicability within the Bulgarian context. The study highlights environmental and economic benefits such as reduced landfill use, decreased greenhouse gas emissions, and energy recovery. By examining successful implementations in Bulgaria and other EU countries, the paper identifies key challenges and opportunities for scaling WtE solutions. The findings suggest that with the right policy support and investment, WtE can significantly contribute to sustainable waste management in Bulgaria

Regional rail transport is a key part of the transport process, and its importance is growing every year. Suburban rail forms the backbone of the regional transport system and is widely regarded as a sustainable form of mobility with societal benefits. On the other hand, the costs associated with operating rail transport are significant and it is essential to design cost-effective and efficient transport solutions. This paper takes a closer look at the prediction of passenger volumes and the associated options for effective management of regional rail transport when travel demand is known. A practical application is developed in the conditions of suburban rail transport in the vicinity of Ostrava in the Czech Republic. It analyses the available data on transport supply and travel demand of which passengers can be assigned to specific directions and time slots in relation to daily and weekly variations of travel demand. Based on the data provided, a model for assigning passengers with respect to public transport supply was proposed. The prediction is harmonised with local specific conditions. The results obtained were used to design a new operational concept for the suburban railway in the assessed area. On the basis of the data obtained, a modelled composition of vehicle units and frequency of services on individual sections was proposed. An appropriately set capacity of the vehicle units enables a significant reduction of operating costs and leads to an economical and efficient transport solution.

Sustainability is topic of great concern since the last decade and still today does not lose of its popularity. Reason for that is that the contemporary way of living is causing great damages to the environment. Designers have been talking about changing the ways in which the products are designed in order to have sustainable product. But, for achieving sustainability many aspects need to be addressed, such as: cultural, social, economical and technological. Nowadays, we believe that these aspects are on higher level and we can talk about sustainable design.
Every product development process starts with the design phase and this is why we believe that it is most important for making improvements of the products. In this paper we have the premise that good and appropriate design can have positive influence on the sustainability. In order to check the validity of the premise we are reviewing paper dealing with sustainability, eco design, and engineering materials.

As global environmental impacts have increased, modern societies have expressed a strong interest in implementing sustainable solutions to reduce emissions and use operational energy and natural resources. The construction industry is a leading promoter of significant environmental impacts because it consumes a significant amount of water, energy, and materials. Steel and welding are critical in all three major sectors of the industry: construction, infrastructure, and industry. This paper discusses the significance of meeting sustainable development goals in welded structures and identifies ways that this industry can help to reduce environmental impact and improve employment conditions while achieving economic growth, saving time, and maintaining structural quality. The paper discusses how to optimize various aspects ranging from raw material extraction to construction waste disposal using the life cycle assessment (LCA) methodology. It provides a starting point and demonstrates how these tools can contribute to more sustainable welded structures.

Direct At the Technical University of Liberec, Faculty of Textiles, there was a cooperation between this state university and a small private company. The cooperation was created for the development of sustainable aids for menstrual periods. All development took place at the university, including the search for local production partners, and the private company financed the development. The output is a utility model owned by the university and the private company, and in addition the private company pays the license fee. Th e article describes in more detail this cooperation, as well as the development and the developed product, up to its actual commercialization.

The paradigm of Industry 4.0 pushes additive manufacturing (AM) from rapid prototyping towards the position of series production. Especially in metal 3D printing, increased attention is being paid to the topics of sustainability and resource efficiency. Energy demand during production and the calculation of building times play a decisive role here. Science has developed models for calculating energy consumption based on analytical and empirical approaches. Building time calculators have been introduced using a wide variety of analytical, analogical and parametric approaches. The present review summarizes the results and the state of the art, illustrates the results graphically and thus paves the way for further research approaches. The specific energy consumption per kilogram of processed material has risen over the last decades, which can be explained by higher technical requirements for production machines. Building time calculations continue to be subject to errors, depending on the type of calculation. The introduction of machine learning approaches has the potential to reduce this discrepancy.

Mankind faces a number of challenges in the 21st century. Many of them are related to the achievement of the goals and ideas set in the concept of sustainable development of modern UN society. The bio-sector, which is developing within the borders of the Bulgarian economy, has undergone rapid development in the last few years. Many factors have influenced this process, the most sign ificant of which are: increased demand for organic products in international markets, high levels of public support for this type of production and the availability of favorable climatic conditions for their development. Innovation is the main tool for achieving competitiveness and economic growth at all levels – enterprise, industry, region or country. They are the fundamental means of improving people’s quality of life. The purpose of this report is to present the results of a survey conducted among bio-enterprises in the regions of Bulgaria and to show that the green innovation in the bio-sectors is the foundation for regional economic, social and environmental prosperity. The results of the study summarize the main directions for achieving regionally balanced sustainable development.

Cities today are highly endangered by the global urbanization trends and the sustainability issues that they may bring. With the increasing environmental awareness and the development of technology, there is an urgent need to rethink how we plan and manage our cities. With the advancements in technology, we are entering the era of smart cities where information and communication technologies are used to collect large amount of data to transform city economies, social cohesion and city governance. This paper explains the concept of the smart city and its characteristics which can be used to solve the sustainability problems that the city may face. Following the introduction, the paper continues by presenting six main characteristics of smart cities and their role in sustainability. The chapter then proceeds to a description of a smart sustainable city model that derives from merging three main city models related to sustainability and smartness, namely the eco-city, compact city and data driven city. Finally, the application of smart city technologies that are being used to achieve sustainability in some randomly chosen cities is presented and discussed.