• 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.

  • 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.

  • 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

  • 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.

  • 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.

  • 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.

  • Use of oriented strandboard in construction industry

    pg(s) 93-96

    In recent years, 3D printing has gradually appeared in people’s field of vision. The addition of wood in thermoplastics improve their some mechanical properties such as tensile and bending modulus without affecting its biodegradability. The decrease in the cost of filaments may enlarge the utilization of biodegradable filaments after the disposal in near future. Small-scale elements used in furniture production, such as connector fittings or fasteners for shelves, may give functional and structural properties without significant investment. 3D-printed connections are suitable when the the production complex shaped connectors and quick disassembly are required, to reduce the product’s weight and price

  • Studing the temperature microclimate in beehives made out of defferent materials

    pg(s) 91-92

    The use of clay as a structural material has been known for centuries. The authors set the task of studying the applicability of clay as a constructive material in the production of beehives. The study aims to make a comparative analysis of temperature conditions in different types and identical in construction beehives by comparing the indicator for ceramic and wooden hives. For the purpose were used three 10-frame hives type “Dadan-Blat” – two ceramic (one made entirely of marl clay, and the other – with increased kaolin content, both ceramic tiles are with high cavity) and one wooden (pine). Measurements of the air temperature and the temperature inside the hives were made for one month. From the obtained results it is established that for the studied beehives, the ceramic hive with high kaolin content has the best thermal insulation properties.

  • Application of submodeling in strength analysis of horizontal tank for storage of petroleum products

    pg(s) 87-90

    This paper shows the approach of submodeling in finite element analysis in process of designing the horizontal tank for storing petroleum products. Those kinds of tanks are made at exact standards or slightly altered by customers’ demands. Before the numerical analysis of the tank, the tank standards are described as well as numerical analysis. In the paper, the methods which will be used in obtaining solutions by finite element method were described. 3D finite elements have been used for numerical analysis. After getting the results of full tank model meshed with 3D tetrahedral final elements, the technique of submodeling has been used to achieve more accurate results in critical locations of the tank. In the final aspect, result analysis was conducted, where the results were confirmed so that the tank complies with the standard and meets all the criteria given to the designer.

  • Comparison of different position controllers implemented with a Beckhoff controller and TwinCAT 3 software

    pg(s) 83-86

    Achieving the required dynamics and accuracy of movement of electromechanical linear axes is one of the basic tasks in the field of modern production machines and devices. In addition to a sufficiently powerful electric motor, e.g. electric servomotor, the appropriate controller and control concept also play a key role. As the top performance of the electromechanical axle controller is still a key feature of efficient and quality production, this topic is discussed in this paper.
    At the forefront of the paper are the development and implementation of various position controllers developed in the Beckhoff TwinCAT 3 environment. In addition to the classic PID controller already available in the Beckhoff software, a special PID controller has been developed in the Matlab / Simulink environment, as well as a Fuzzy controller and a Feedforward control strategy. For all mentioned types of controllers, the basic characteristics, design approach and parameterization of the controllers are presented. The efficiency of individual position controllers on an industrial-type electromechanical linear axis, driven by an electric servomotor, was tested experimentally and the results are compared.
    The efficiency of these closed loop controllers was also tested in terms of robustness and ability to adapt to changes in the control loop, where a different load of moving mass was used as a characteristic change in the control loop.

  • Innovative method for repair of reinforced concrete water facilities by “wet” shotcreting

    pg(s) 79-82

    The report presents the different stages of development and implementation of two similar innovative technical solutions for repair and restoration of defected reinforced-concrete constructions of existing swimming pool and artificial lake using the methods of “wet” shotcreting. In the first case, the object of renovation is a seriously defected outdoor mineral pool of a prestigious hotel in the town of Hissarya. Given the significant leaks of water from the pool in the surrounding area over the years, a specialized technical inspection was initially conducted to determine the causes of defects in the main load-bearing monolithic steel-reinforced concrete construction – walls and bottom slab. An innovative technical solution has been proposed to restore the operational suitability of the pool, based on the possibility of using the existing load-bearing structure as external formwork for a new built-in load-bearing structure of the facility. The proposed solution envisages jointless thickening of the existing walls through additional reinforcement and concrete laying of new high-tech sprayed concrete. The bottom of the pool is being renovated by additional new layer of a hybrid fiber-reinforced jointless concrete slab and machine powerfloated of the finishing surface. A composition of high-tech concrete with the participation of an internal crystallization chemical admixture and shrinkage-compensating one is proposed. A similar solution has been applied for the repair and restoration of the walls and bottom of an artificial lake in West Park, Sofia. Implementation of the project creates a unique art vision of the lake, the rock garden and the surrounding park space. This pilot implementation creates objective preconditions for expanding the range of innovative concrete structural systems, which, in addition to specific functions, are also applicable as opportunities for aestheticizing the urban and park environment.

  • Friction stir welding of dissimilar materials based on aluminum alloys

    pg(s) 76-78

    The paper focuses on the application of friction stir welding (FSW) technology for welding of unequal materials based on aluminum alloys. Joints were made from AW 5083 and AW 6082 materials using FSW technology at different weld speed values. The joints were analyzed metallographically, the hardness of the materials was tested across the cross section of the joint and the strength of the joint was tested by destructive static tensile test. At the lowest weld speed, the materials were not perfectly mixed, there was a macroscopically visible gap at the joint location, which was reflected in the lack of joint strength. At the medium and highest weld speed values, a joint with mechanical properties comparable to those of the base material was formed. Metallographically, the bond between the materials was free of any internal defects.