Table of Contents


    • Sustainability and application of life cycle assessment in welded structures

      pg(s) 3-5

      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.

    • Conceptual model for overcoming the consequences of the pandemic

      pg(s) 6-9

      The paper presents a conceptual model for overcoming the consequences of the pandemic based on summarized results from research focused on societal challenges in Bulgaria caused by COVID-19. The study aims to submit a unified methodological framework for application by experts in researching, analyzing, and bench-marking the entrepreneurs’ activity and suggestions for applicable and reasonable measures in the field of business development during the pandemic situation caused by COVID-19. The findings of this research can assist managers in national institutions and business organizations to recognize the strengths and weaknesses of different measures which influence creativity and innovation and focus on proactive suggestions to overcome the negative consequences of the pandemic.

    • Creation of an automated tool for evaluation and selection of NoSQL databases intended for financial services based on predefined criteria

      pg(s) 10-11

      As technology advances every day of our lives and generates vast amounts of data while different systems, sensors etc. are working, it is important to meet their needs and demands. Digitalization is one of the biggest driving forces for developing of databases – relational and non-relational – in every sphere that they are used, and especially the utilization of NoSQL dBs in areas that were once unthinkable. Financial services offered by different institutions usually relied on relational databases only, but with continuously changing technologies new ways for managing data emerged. This paper presents an automated tool for evaluation and selection of NoSQL databases intended for financial services based on predefined criteria.

    • Analysis of Different Energy Efficiency Technologies Based on Cost and Return of Investment

      pg(s) 12-13

      Application of different retrofitting technologies can play a significant role in reducing energy consumption of existing buildings. This research work analyses a building in Cork (Ireland) where underfloor heating system, and natural ventilation are used to maintain comfort conditions. Underfloor heating system is the main electricity consumer of this building. Different energy efficient technologies were implemented and analyzed in terms of reducing electricity consumption through an energy software. These technologies include replacing illumination with high efficiency light; replacement of electric motos with high efficiency; introducing underfloor heating time scheduling turning on and off based on predicted weather condition; installation of presence sensors to switch ON/OFF lighting. Finally, it was decided to implement underfloor heating time scheduling as energy efficient technology to be analyzed because of limited budget available and high return on investments provided by applying this method. Result analysis shows that electricity saving on bills was about 20% on monthly basis compared to previous consumption.

    • Methods and theoretical foundations for assessing the quality of products and services of a transport firm

      pg(s) 14-17

      The study of the formation process of the operation quality of a transport firm is the most topical, since this process significantly determines the dynamics of its evolution. The paper presents the concept of the product and service quality, describes the difference between the service and the product, as well as a step-by-step scheme of quality development. The history of quality management development is also discussed on the example of three leading regions of the world: USA, Japan and Western Europe.
      Methods for assessing the quality of products and services have been established, which are somewhat different from each other and are of great importance for assessing the activities of a transport enterprise.


    • A new type of nail for wooden structures with increased resilience

      pg(s) 18-21

      In the following work, we present the results from a research of a type of nail with a new form of section, in comparison to the round section that currently used nails have. This new form is similar to an equilateral triangle, the sides of which’ are curves [Reuleaux Triangle]. The body section of this new type of nail has three curves and three edges; his surface SR is with 5.56% larger than the surface SC of a round nail with the same section area. From the experimental research that has been made so far, it was established: (i) because of the larger compaction of the wooden material in the ends of the edges, and of the larger surface, you get a bigger friction force, resulting in a pulling-out force Fto,R that is on average twice as bigger as the pulling-out force Fto,C; (ii) because that the new form of nail has edges, this leads to bigger resistance during the rotating of the joined wooden elements one against another – the moment Mr is on average 60% bigger than the one with elements, joined with a normal nail. These advantages, as well as the use of the existing technology and machines for the production of nails without having to effect any major changes, create the conditions for the application of the new type of nail in construction, furniture production and in the everyday life, for an output of products with larger resistance to external forces. This effect will be especially useful for increasing the residential buildings’ resilience during earthquakes, hurricanes and other natural disasters.

    • Feasibility of food processing treatment using plasma-based ion implantation method

      pg(s) 22-25

      Plasma-based ion implantation (PBII) is a surface modification method, which applies a negative high-voltage pulse to a sample in plasma. Ions are implanted uniformly by reducing the width of the ion sheath formed near the sample and by aligning the sheath shape more with the sample for complexly shaped samples. This method is considered a potentially effective surface treatment method for various shapes of objects. This study investigated the PBII method to explore its potential use as a food processing device. The research samples were pork belly and cabbage. The investigation results showed decreased bacteria viability, although the sample temperature at the treatment time was less than 40 °C. Additionally, the plasma treatment could not decrease the vitamin C content. Furthermore, fine holes could be created on the sample surface. These results indicate that PBII treatment is usable in food processing to improve the permeability of seasoning solutions while ensuring food safety and nutrient stability.

    • Drilling mud properties with added egg shell

      pg(s) 26-29

      The use of biodegradable waste is interesting for many companies from different industries, and in the last few years, more detailed research about its usefulness in the oil and gas industry, specifically as potential additives for the preparation of water-based drilling mud, has begun. Given that this type of research is globally important, there are data on the use of different types of food waste for this purpose, and scientists have mainly researched the biodegradable waste that is generated in larger quantities in a certain part of the world. Among the different types of waste whose effect has been investigated through laboratory measurements of various properties essential for drilling mud, there is also some data on egg shell. In this article, detalied set of data shows how egg shell affects the filtration properties of the drilling mud, the rheological properties, as well as the swelling reduction of the clay component of the rock when it is in contact with drilling mud with added egg shell in its composition.

    • Investigation of the influence of the convergent part of the FSAE vehicle restrictor on the airflow using CFD

      pg(s) 30-33

      The Formula Student competition is the most challenging, complex, and attractive student engineering competition in the world. Students from universities around the world compete to build better vehicles. The competition consists of several different disciplines, which are divided into two groups. The first group consists of static disciplines, where students who are members of the team defend the vehicle project in front of eminent experts from the world of the automotive industry and auto-moto sports. The second group is the group of dynamic disciplines, which is made up of several disciplines related to the analysis of vehicle behavior in real conditions. One of the main challenges facing the team members is designing the vehicle’s propulsion system. At competitions in the IC engine class, power units from a certain class of motorcycles are most often used. The main limitation related to the power unit is that all intake air must pass through a 20 mm diameter. One of the solutions to the mentioned problem is the use of a convergent-divergent nozzle with a throat diameter of 20 mm. In this paper, the influence of the convergent part of the nozzle on the airflow through the nozzle itself was examined. Models were created for several restrictors and they were tested by CFD simulation in ANSYS Fluent software

    • Results from the plastic pressing of experimental ceramic pavers of “yellow” paving stone type

      pg(s) 34-36

      The results of the plastic forming of ceramic pavers with a large volume and size are observed to produce better compaction of the raw material. The used ceramic mixture is based on a sedimentary rock with relatively high moisture content and firing shrinkage which gives the common yellow colour after a high-temperature liquid phase synthesis. The results of one-fold pressing revealed the occurrence of deformation processes in the drying stage and during the temperature regime. As a consequence, the pressing pressure should be increased and the residual water amount needs to be reduced to an optimal content.

    • Theoretical study of β-cyclodextrin inclusion complexes with vitamin K

      pg(s) 37-40

      One of the main problems in modern society is related to improper and insufficient nutrition, as a result of which various diseases develop, the treatment of which requires additional intake of vitamins in the form of nutritional supplements. Fat-soluble vitamins have important biological activities, but their application is limited due to their low solubility and stability. One way to improve their properties is to incorporate them into complexes with host molecules, such as cyclodextrins, the most commonly used host molecules in the pharmaceutical industry. The theoretical study presented here aims at delianating the interactions of vitamin K3 and its analog phthiocol with β-CD drug delivery system. To achieve this goal, 1:1 complexes of different forms of vitamin K with β-CD were modeled. The influence of various factors on the thermodynamics of interactions of the guest molecules with the macrocycle (host molecule) was evaluated.