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

A group of numerical methods suitable for describing the propagation of light in a Photonic Crystal Fiber (PCF) are discussed. PCFs can be classified according to the mechanism of light propagation. The methodology of the analysis is briefly reviewed to understand how changing the different physical parameters of the fiber and the design affects its optical properties. By analyzing the systematic studies presented, a design with the desired optical fiber properties can be realized.
PCFs can be made from just one material with two-dimensional photonic crystals or periodic arrays of air holes parallel to the fiber axis to form a shell and core shape. Several types of PCFs have been considered. The mechanism for trapping light in the fiber core is explained. The use of the wave methods for electromagnetic field analysis is discussed. The application of variation principles and weighted residual methods is shown. The advantages of the finite element method (FEM) are indicated. The vector FEM for obtaining the modes in photonic crystal fibers is considered.

A clear trend of Industry 4.0 and smart manufacturing is to promote the increased use of multi-tasking machine tools. These machines are easily integrated into digital production systems and enable real-time data acquisition, remote monitoring and adaptive cutting processing. The integration of multi-tasking machine tools and digital manufacturing systems will improve the implementation of predictive maintenance, process optimization and production efficiency. Moreover, the development of robotics and AI along with the adoption of Industry 4.0 will increase the market share of these machine tools. The market demand is expected to increase further due to the rise of Industry 4.0. The paper analyzes the main advantages of multi-tasking machining, focusing on the advanced features of multi-tasking machine tools, as well as the latest trend of integrating additive manufacturing processes with CNC machining.

Heavy metal pollution from various industries has received much attention worldwide due to their toxicity and persistence in the environment. Traditional water quality monitoring relies on sampling, preservation, transportation and subsequent laboratory analysis. All these procedures require considerable time and make it impossible to timely detect heavy metal contamination. To overcome the drawback, SMFC-based biosensors can be used for monitoring water pollution with heavy metals. The electrochemical characteristics of SMFCs are sensitive to heavy metal ions, therefore, when heavy metals enter them, the cell voltage immediately rises in proportion to their concentration. The change in voltage can be used to find the presence of heavy metals in the water and their concentration. In the present study, the possibilities for monitoring water contaminated with copper, zinc, nickel and chromium by means of SMFC-based biosensors were investigated. The constructed biosensors showed high sensitivity to the ions of the four investigated metals.

In 2022 the Erath rotation velocity reached its maximum and in 2017-2020 the Chandler wobble of the rotational axis disappeared for the second time in the history of observations. Unexplained modulations of 90 and 20-25 year periods are observed. They reflect geophysical processes in the atmosphere, ocean, and Earth’s interior and can be linked to climate. It is important to understand their causes and predict them for navigation etc. We found out, that the orientation of the lunar orbital plain and position of perigee revolves in such manner, that their mutual positions repeat with 90-year semi-periods at the minimum of the Chandler wobble. At the same time synodic period of syzygies in perigee (every 412 days) with respect to the position of the Chandler pole (433 days) rotates within ~22-23 years. We have collected arguments in favor of the hypothesis that the mass flows and redistribution within the Earth systems under the influence of apsidal-nodal effects of luni-solar tide could be responsible for the above mentioned modulations in the Earth rotation.

The aim of this research is to obtain nanodiamonds-containing collagen sponges (lyophilisates) for wound healing. The purpose is to create an antimicrobial barrier on the dressing based on active tropocollagen. The research problem in this task is the use of antibacterial properties of nanodiamonds to modify new collagen-based materials being the products of this investigations.

In this pilot study, microfluidic flow analysis and atomic force microscopy (AFM), are used, to determine microrheological properties of the blood – aggregation, and deformability of erythrocytes in women with preeclampsia (PE). The aggregation of red blood cells (RBCs) is evaluated with the microfluidic system BioFlux, by applying an experimental approach and image analysis created by the authors of this study. The elastic properties of erythrocytes are defined by Young’s modulus, using AFM. The aggregation index of erythrocytes and their elastic modulus are statistically significantly increased in patients with PE, in comparison to healthy normotensive pregnant women. In addition, it is found that the RBCs are less deformable and the interaction between them in aggregates is stronger in women with preeclampsia as compared with healthy pregnant women.

The company Tehnoplast profili d.o.o. from Zagreb, in cooperation with the Faculty of Civil Engineering University of Rijeka and the company Palijan d.o.o. from Zagreb, is conducting a scientific research project dealing with buildings of near-zero energy produced in an industrial way. The construction system of these buildings consists of ceiling and wall panels, which are integrated into the building’s construction system. The structural wall/ceiling panels consist of external gypsum-fibreboard, thin-walled steel structure in the panel core and polymer foam in between. To enable the practical application of the innovative wall/ceiling panel system as a load-bearing structural element, the design model based on the comprehensive experimental and numerical investigation must be defined. In the research presented in this paper the performance of the composite wall/ceiling panels and the steel core wall/ceiling structure during out-of-plane to failure tests is shown.

This paper presents the results of an investigation aimed at evaluating the geometric and material characteristics of welds, such as dimensions, shape, pores, cracks and other imperfections. An automated weld inspection workstation has been designed which includes suitable sensors, equipment and software solutions for data acquisition and processing. Tests were performed on selected welds to determine the material superheat and weld quality.

The paper presents the results of research focused on the application of innovative procedures for surface topography modification. The experimental work was aimed at adjusting the microgeometry and surface topography of new and renovated shaped parts of molds for casting aluminium alloys under high pressure. In the phase of experimental verification of suitable surface topography, a group of samples from Dievar material was prepared. A multilayer nanostructured PVD coating of the 4th generation duplex nACRo4 was deposited on part of the experimental samples. The surface of the samples was ground and polished. The microgeometry of the surface of the samples was modified by low-energy laser radiation – microtexturing. The maximum interval was chosen to create a stochastic texture, also called a random texture crater distance up to 200 μm. The aim of this surface treatment was to analyze the adhesion effect of commercially used ones of lubricants in the technology of treatment of shaped parts of molds when casting aluminium alloys under high pressure on machines with a cold filling chamber. In the run-in of the mold, after the first cycles of spraying with a separating agent, a compact layer was created to increase the technological life of the shaped parts of the molds.

The paper focuses on the evaluation of the quality of joints of thin-walled dissimilar overlapped materials, formed by thermal drilling without a screw. The shaped interference fit joint is formed by simultaneously forming both overlapped materials, preheated by the friction of a flowdrill tool, and forming a pair of embedded concentric bushings. The joints were made on a CNC milling centre, at constant speed, with tool feed being the only variable. Three tool movement strategies – three movement schemes – were tested. By evaluating the quality of the joints using metallographic sections, the optimum tool movement strategy was selected.

We achieved a CT(ozone concentration(ppm) X exposure time(min) )value of 60, which can inactivate coronavirus from 1/10 to 1/100 by operating for 24 h at an appropriate ozone concentration (less than 0.1 ppm) using feedback control in the previous report. In this system, the only way to reduce the ozone concentration is the decomposition reaction of ozone in the natural world, and it was not possible to cope with the rapid increase in ozone. In this study, we investigated the reduction of ozone concentration using hydrogen. As a result, it was clarified that the concentration of ozone rapidly decreased even with about 1/100 of hydrogen’s explosion limit (about 4%).

Formula Student is a student engineering competition. Students all over the world compete to build a racing vehicle. One of the main elements of this vehicle is the vehicle chassis. The chassis is one of the most important elements from the aspect of driver safety. There are different chassis design concepts. The two most common are the monocoque chassis and the tubular chassis. In this paper, a detailed structural analysis of the tubular chassis of the Formula Student vehicle was performed using the software. The chassis model was created in the CATIA software, and then the structural analysis was done in the ANSYS software. By applying modern software, it is possible to better understand the problems during construction, and significant financial and time savings can be made. ANSYS software can also be of great help in chassis optimization.