Machines. Technologies. Materials.
Vol. 20 (2026), Issue 2

Table of Contents

  • MACHINES

    • Thermodynamic analysis of steam turbine and condenser from combined cycle power plant

      pg(s) 45-48

      Energy and exergy analyses results of steam turbine and steam condenser, which operate in commercial combined cycle power plant are presented in this paper. Energy analysis shows that steam turbine has high energy (isentropic) loss equal to 71.71 MW, and very low energy (isentropic) efficiency of 58.79% only. Simultaneously, steam condenser is an almost perfect component from the energy viewpoint. At the base ambient state, steam turbine has high exergy destruction of 61.80 MW and low exergy efficiency of 62.34%, so both used analyses show that steam turbine operation can and should be notably improved. Steam condenser has an exergy destruction of 17.12 MW and exergy efficiency of 55.17% at the base ambient state, what are acceptable results. Observed steam condenser is much more sensitive to the ambient temperature change than steam turbine. Increase in the ambient temperature from 5 °C to 35 °C decreases steam condenser exergy efficiency for 35.90%, while the same increase in the ambient temperature decreases steam turbine exergy efficiency for 2.39% only.

    • Bio-electrochemical system based electro-generative pipeline element

      pg(s) 49-52

      In the context of a changing climate and the pursuit of sustainable development, any technology or device that produces green energy will help reduce dependence on fossil fuels. This work presents a prototype of an electro-generative pipeline element based on a bio-electrochemical system. The element is suitable for integration into pipelines carrying various liquids. The electro-generative element has shown high efficiency in laboratory conditions, and depending on the passing liquid, it can generate energy in the range of 0.5W – 1.5W. A different number of elements can be located in the pipeline system, depending on its length. Depending on the number of elements in the chain, enough energy can be obtained to power various devices.

    • Active damping in cable-stayed-bridge structures using hydraulic actuators

      pg(s) 53-55

      Cable-Stayed-Bridges are an important part of today’s constructions in the traffic infrastructure. New materials and computational technology have led to the construction of longer and slender Cable-Stayed-Bridges are under the effect of dynamic loads as wind, traffic or earthquakes. Besides comfort restrictions, the vibrations of large amplitudes effects also the lifetime of the entire structure. Oscillations of Cable-Stayed-Bridges can be reduced significantly by active damping systems. In this paper is represented shortly an electro-hydraulic actuator concept for the active damping of Cable-Stayed-Bridges. This type of control is very efficient even in large bridges (up to 900 m span). Also, the tests on a large-scale bridge show the efficiency of active damping in Cable-Stayed-Bridges using electro-hydraulic actuators. The damping of deck and cables, has become crucial in the design of cable-supported structures. Because of the effectiveness of passive damping systems is limited, this new electro-hydraulic actuator concept is developed.

  • TECHNOLOGIES

    • Kinetic investigation of copper ions adsorption onto corn stalks

      pg(s) 56-58

      Corn stalk was used as a biosorbent for the adsorption of copper ions from synthetic solutions. To examine the mechanism of the adsorption process and identify the potential rate-determining step, the following kinetic models were used in this study: the pseudo-first order kinetic model, the pseudo-second order kinetic model, the Elovich kinetic model, and the interparticle diffusion model. Kinetic studies show that copper ions adsorption followed the pseudo-second order kinetic model. The maximum adsorption capacity was 5.5 mg g⁻¹. The results indicate that corn stalk can be successfully used as a biosorbent for the adsorption of copper ions from synthetic solutions.

    • Fiberglass casing string cementation operations in wellbore

      pg(s) 59-62

      Casing string is critical component in wellbore construction, defining wellbore diameter and providing structural integrity throughout drilling and production operations. Traditionally, steel casings are generally used due to their mechanical strength; however, problems connected with corrosion, particularly in environments containing hydrogen sulfide or saline formation water, presents significant operational and financial challenges. This paper explores the use of fiber-reinforced plastic (FRP) casing as a corrosion-resistant alternative, focusing on glass fiber-reinforced epoxy composites, especially concerning cementing operation. FRP casing properties depend on the fiber–matrix composition, fiber type, and manufacturing quality, which affect tensile and compressive strength, thermal stability, and resistance to environmental degradation. Laboratory and field studies, including pilot projects in Argentina, Oman, Brunei, and Kuwait, evaluated casing handling, rig down speed, anchoring, and cement bonding. Special attention was given to cementation procedures, fluid formulations for mud cake removal, and ultrasonic methods for assessing casing-to-cement bonding, adapted for the acoustic characteristics of FRP materials. Results indicate that while steel casings exhibit superior cement bonding, FRP casings can achieve adequate structural performance when mechanical stresses during handling and installation are carefully controlled and proper chemical compatibility between fluids and cement is ensured. Field data show that FRP casings can be deployed with only minor reductions in installation speed for smaller diameters and that optimized handling and cementation practices are crucial for operational success. These data demonstrate that FRP casings offer a technically feasible and economically advantageous alternative for wells in highly corrosive environments. However, their successful implementation requires tailored operational procedures, including modified handling equipment, optimized fluid systems, and specialized evaluation methods. Further field studies are needed to develop comprehensive guidelines for widespread adoption.

    • Rolling element bearing fault detection using accelerometer and laser displacement measurements

      pg(s) 65-68

      Rolling element bearing fault detection is of significant importance due to the widespread use of bearings across numerous industrial applications. In this study, vibration measurements using an accelerometer and a laser displacement sensor are carried out on a laboratory bearing test rig under different operating conditions, including a healthy state and bearings with localized inner- and outer-ring faults. Measurements are conducted at a constant rotational speed of 1700 rpm and the acquired signals are analysed to extract characteristic features associated with potential bearing faults. The results demonstrate that the applied methodology enables indicative bearing fault detection using both measurement approaches.

  • MATERIALS

    • Development of an All-Optical Platform for Real-Time Monitoring of Hypoxia Dynamics

      pg(s) 69-72

      Oxygen levels in the cellular microenvironment, particularly under hypoxic conditions, play an active regulatory role in modulating cellular function, signaling pathways, and metabolic networks. A radically new concept for sensing the oxygen concentration at the extracellular liquid microenvironment was developed, based on nanoconfined upconversion optical sensors. The experimental achievements in developing technologically applicable strategies for minimally invasive monitoring of the oxygen concentration in cell microenvironment will be presented and discussed.

    • Comparative Analysis of Natural Ruby and Synthetic Corundum Ceramics by UV–Vis and Raman Spectroscopy

      pg(s) 73-76

      This study presents a comparative spectroscopic investigation of natural Cr³⁺-bearing ruby and multiphase Al₂O₃-based ceramics derived from industrial waste. The natural corundum shows characteristic Cr³⁺ crystal-field absorption bands at ~405 and ~550 nm and sharp R-line emission near 693 nm, confirming a structurally ordered α-Al₂O₃ lattice. In contrast, the waste-derived ceramics exhibit charge-transfer-dominated absorption associated mainly with V⁵⁺ and Fe³⁺ under oxidizing firing conditions. Strong UV absorption (220–300 nm) and the absence of vanadium crystal-field transitions indicate predominant V⁵⁺ stabilization, consistent with chemical and phase analysis. The ceramics display high lightness (L* ≈ 93) and a yellow hue (b* = 10–23) governed by ligand-to-metal charge-transfer processes. The results demonstrate the effectiveness of combined UV–Vis and Raman spectroscopy for distinguishing crystal-field and charge-transfer mechanisms and for resolving dopant-related colour formation in alumina systems.

    • Effect of non-metallic inclusions on the grain structure of low-carbon steels under severe plastic deformation

      pg(s) 77-80

      The features of localization of severe plastic deformation in a steel matrix near non-metallic inclusions are studied. In the steel matrix, near inclusions and at the inclusion-matrix interphase boundaries, the nature of the stressed and deformed states changes, the strain increment is determined by the rotation angle of the inclusion during its movement in the plastic region. Processes of local structural transformations near non-metallic inclusions in steels exposing to intensive plastic deformation were investigated. The influence of non-metallic inclusions on the local refinement of the steel microstructure is an important effect during severe plastic deformation, which makes it possible to obtain additional nanostructural strengthening near the inclusions during the general refinement of grains to a submicrocrystalline state. It was shown the influence of non-metallic inclusions on mechanical properties of these steels.