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The use of polymer materials in various fields has increased significantly due to their ease of thermoforming and relatively low production costs. The production volume of these materials is extremely high, and according to forecasts from global statistical centers, it is expected to continue rising in the future. However, the extensive use and easy availability of polymeric materials have caused significant ecological problems. The world faces large amounts of polymer waste and environmental pollution. Plastic recycling remains challenging due to issues related to sorting polymer waste and separating it according to polymer types. Recycling certain plastics requires only a quarter of the energy needed to produce new plastic. To address this, circular economy principles should be applied to 3D printing products made from polymeric materials. A particularly wide application of these technologies is found when polymeric materials are used due to their low cost, low melting temperatures, and other advantageous properties. This paper investigates the impact of plastic recycling on the quality of 3D-printed products. During the research, samples were 3D printed and tested using both virgin and recycled PLA, ABS, and PET-G materials. The samples underwent static and dynamic tests to determine their mechanical properties, such as tensile strength, elongation, and impact resistance. The research results showed that the properties of recycled polymer materials deteriorate, with relative elongation of recycled and 3D-printed materials decreased by 16–45%. Despite this, recycled polymer materials can still be used, but it is necessary to account for the reduction in plasticity when creating products that will be exposed to dynamic loads. The impact strength is reduced by 6% for PLA, 54% for ABS, and 58% for PET-G. Additionally, the research included tests on samples printed with 3D printing technology that were exposed to UV irradiation. The results indicated similar dependences, as UV exposure also affects the reduction of material plasticity. After 66 Wh/m2 of UV radiation, the tensile strength of PET-G and PLA decreased by 17%, while ABS showed a reduction of about 5%. [ABSTRACT FROM AUTHOR]

Composite materials based on paper honeycomb structure do have a potential in today's fast changing markets and within the present context as sustainable products the demand for more economical and environmentally friendly products is highly increasing and stands out for environmental issues but must outstand the strength properties as the alternative products used in packaging industry. Strength properties of composite materials made of paper honeycomb were investigated experimentally. Static compression tests were made using testing machines "Zwick/Roell". Composite materials were made with different honeycomb properties: cell high, cell size, various grammage of laminate layer. Honeycombs were dried and soaked before testing their strength properties. It was confirmed and determined that moisture is important factor for paper honeycombs. It was determined that strength properties are quite different for dried honeycombs and depend signific on the drying time which was adjusted for the specimens. Dried honeycombs hade higher resistance to compression up to 70% and depended on the increased drying time and other honeycomb structure aspects as the cell height and the laminated layer in the composite structure. Strength of all investigated composite materials was higher using honeycombs with smaller size cells (with same cell high). Sandwich panels with bigger laminated layer grammage had higher strength characteristics especially panels with smaller cell high honeycombs. [ABSTRACT FROM AUTHOR]

The operational problem of container unloading from the ship is analyzed in this paper. Dynamic “crane-cargo-ship” system was investigated, and a mathematical model was created. In the model, the gap between the container and the ship’s cargo hold, the mass of the cargo, the container’s center of the mass, and the frictional forces that may occur during lifting from the cargo hold were estimated. Numerical analysis of the system was performed. Results of numerical analysis were compared with experimental measurements of containers unloading process in port. Requirement of lifting power was modelled depending on mass of cargo. Additional power needs in case of contact forces between container and wall of the ship’s cargo hold were calculated. Rational lifting conditions could be deduced using a created mathematical model and the reliability of the container and cargo during lifting could be deduced. [ABSTRACT FROM AUTHOR]

In order to protect the world from the invasive species of organisms the cleaning ballast water is required, in other words, discharged water must meet requirements posted by the International Maritime Organization (IMO). The paper provides a comparative analysis of ballast water treatment equipment and its technical parameters. The research has been performed to analyse and assess the effect of the introduced equipment on ship stability, including the effect of its weight, dimensions, performance, price and the efficacy of choice. [ABSTRACT FROM AUTHOR]

The hydrodynamic and thermodynamic processes of geothermal well extraction are investigated and presented in this paper. The paper presents mathematical models for a multi-level centrifugal pump and pipeline system. The mathematical models were used to evaluate gas (nitrogen) emission in water and its effects on hydrodynamic processes. Experimental studies and mathematical modelling showed that the gas content of the fluid increases the pressure and flow pulsations within a centrifugal pump. The variation in the height of the liquid column in extraction has an influence on characteristics of the multistage centrifugal pump used in wells. [ABSTRACT FROM AUTHOR]

The energy costs of oil transportation by pipeline are one of the most important questions for oil companies. Large amounts of energy are used in the oil pumping process. One of the ways to reduce energy costs is to use additives, which can change the rheological characteristics of oil. Anti-turbulent polymer additives reduce the hydraulic resistance and allow a significant reduction in pumping costs. The hydrodynamic processes in the pipeline and efficiency of oil transportation costs, dependent on the concentration of anti-turbulent additives, are investigated in this paper. The pressure and velocity of the flow in each point of the pipeline are obtained by solving a system of nonlinear algebraic equations, which were solved utilizing the Newton-Raphson method. The dependencies of the efficiency coefficient in the oil pumping process were deduced, depending on the concentration of the additives. [ABSTRACT FROM AUTHOR]