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

Nowadays, renewable bioenergy is considered as one of the ways to provide energy at the expense of fossil fuels. The possibility of obtaining energy from organic materials through bio-electrochemical systems attracts considerable interest. Green waste is organic plantbased materials generated from grass clippings, broken branches, fallen trees and others, the utilization of which is currently not very effective. In the present study, we constructed a composter based on bio-electrochemical systems for the utilization of green waste with cogeneration of energy. The composter showed good performance in terms of both the decomposition of organics and the generated energy.

This study presents a correlation-based approach for both detecting sensor malfunctions and identifying redundant sensors in a multi-sensor condition monitoring system. Sensor malfunctions were detected using a threshold-based method that flagged correlation drops, with persistence criteria applied to eliminate false positives. While no persistent malfunctions were observed during the study, the developed algorithm remains suitable for real-time deployment. Correlation analysis also revealed that the 3axis_Y signal exhibited the highest average correlation with others, indicating redundancy. Five machine learning models were trained and evaluated with the Leave-
One-Run-Out strategy to guarantee generalization across acquisition sessions. The findings demonstrated that correlation-driven sensor selection and anomaly detection are effective tools for optimizing predictive maintenance systems, improving model generalization, and simplifying sensor networks without sacrificing reliability.

The paper presents an innovative method for joining Al alloy sheets and polymer fibre-reinforced composites by thermal drilling. A proposal for modifying the joint geometry by reverse drilling with a larger diameter tool is presented. The proposed modification demonstrated a statistically significant increase in the failure energy of the resulting joints.

Albania’s construction sector has seen rapid growth with the introduction of diverse materials and advanced building techniques. However, the key challenge remains in effectively applying these innovations to maximize indoor comfort and energy efficiency at the lowest cost. Comfort plays a crucial role in occupant well-being and productivity, yet it is often overshadowed by concerns over upfront construction costs, overlooking long-term benefits such as improved health and reduced operational expenses.
Measurements across different seasons have shown that thermal insulation significantly enhances indoor thermal comfort. Data from the Electricity Distribution Operator also confirm that insulation can reduce electricity consumption by 15–28%, especially during peak usage periods. Supporting insulation in new buildings and encouraging retrofits in existing structures through coordinated local policies and utility programs could lead to substantial energy savings and improved living conditions nationwide.

Obtained experimental self-cleaning coatings (based on compositions with the participation of Sm2O3), applied by the sol-gel method on glass slides. This study attempts to improve the overall efficiency of a photovoltaic solar panel by using a Sm2O3 doped ZrO2 (SDZ)-based coating. The optical characterization and phase composition of the obtained experimental samples were investigated using UVVIS- NIR, XRD and XRF methods. The coatings are nanocrystalline according to XRD and XRF analyzes and show transmittance close to that of pure glass when tested with a UV–VIS–NIR spectrophotometer The experimental results represent a prerequisite for the development of a series of additional compositions and a detailed technological regime for obtaining various modifications of resistant, long-lasting selfcleaning coatings, potentially applicable to photovoltaic panels.

In this paper are presented isentropic analysis results of a steam turbine, their cylinders and cylinder parts which nominal power is equal to 250 MW. The analyzed steam turbine is a complex three-cylinder turbine which operates in a CCPP (Combined Cycle Power Plant). Considering all cylinders, the dominant mechanical power producer in the observed turbine is LPC (Low Pressure Cylinder) which produces 111.80 MW of mechanical power in real (polytropic) steam expansion process (almost half of the real mechanical power produced in the whole turbine). Developed mechanical power in turbine cylinders and isentropic losses are directly proportional – higher produced mechanical power will result in higher isentropic losses and vice versa. Whole analyzed steam turbine, their cylinders and cylinder parts how very good isentropic performance and high isentropic efficiencies of around 90%. The isentropic performance of the whole analyzed steam turbine, their cylinders and cylinder parts is in the range of the steam turbines (and their cylinders) from supercritical and ultrasupercritical power plants which are proven to be the best steam turbines from isentropic point of view.

This paper investigates the mechanical behaviour of SnSb11Cu6 Babbitt alloys solidified under pressure and under atmospheric conditions. Quasi-static tests were performed at three different constant strain rates: 0.001 s⁻ ¹, 0.003 s⁻ ¹, and 0.01 s⁻ ¹, while dynamic tests were conducted at strain rates corresponding to impact speeds of 10 m/s and 20 m/s. The results indicate that alloys solidified under atmospheric conditions exhibit higher compressive strength in the quasi-static regime than those solidified under pressure. However, as the impact speed increases to 1400 s-1 the compressive strength of both materials converges. Beyond this rate (up to 2800 s⁻ ¹), the alloy solidified under pressure shows a slight performance shift, suggesting better property stability at higher loading rates. Overall, the alloy solidified under atmospheric conditions offers superior performance for low-strain applications, whereas the alloy solidified under pressure demonstrates more stable properties under high-strain loadings. These findings offer valuable insights for the selection and design of materials in tribological systems, particularly where performance varies under different loading conditions.

In this paper are presented isentropic analysis results of a steam turbine and each of its cylinders which operate in Municipal Solid Waste (MSW) power plant. Low Pressure Cylinder (LPC) which produces the highest real mechanical power has the lowest isentropic loss of all cylinders equal to 4344.75 kW, while High Pressure Cylinder (HPC) which produces the lowest real mechanical power has the highest isentropic loss of all cylinders equal to 5204.54 kW. Isentropic losses and isentropic efficiencies are reverse proportional, because the cylinder with the lowest isentropic loss (LPC) has the highest isentropic efficiency equal to 88.92%, while the cylinder with the highest isentropic loss (HPC) has the lowest isentropic efficiency equal to 84.58%. Surprisingly, isentropic efficiency of the Intermediate Pressure Cylinder (IPC) is equal to 86.80% only, which is higher in comparison to HPC but notably lower than LPC. The observed turbine strongly differs from other comparable steam turbines from the literature where IPC has notably higher isentropic efficiencies than both HPC and LPC. Whole observed steam turbine produces real mechanical power equal to 97513 kW, while its isentropic efficiency is equal to 86.87%.

Traditionally, solar flare detection has been achieved through methods that rely on the presence of expensive satellites. We propose an alternative method that produces reliable detection of solar flares in a cheap and conveniently earth-based way. This paper discusses the design, practical implementation, demonstration of functionality and usefulness of a reception and monitoring system for VLF (Very Low Frequency, 3 kHz–30 kHz) radio signals, transmitted by stations located thousands of kilometers from the reception point, that can be used to accurately detect solar flares. We chose this frequency range because VLF radio waves are efficiently reflected by the lower layers of the ionosphere, and diurnal or sudden changes in these layers cause corresponding variations in the received signal level over long distances (over 1000 km).

In this paper, a two-dimensional (2D) material graphene with exceptional electronic and mechanical properties is discussed as a promising candidate for chemiresistive sensor applications. High surface area and superior charge carrier mobility of graphene enable rapid and sensitive detection of gaseous analytes, making it an attractive alternative to conventional metal oxide semiconductor (MOS) sensors. The review of recent advancements in graphene-based chemiresistive gas sensors is done, highlighting their operational principles, fabrication techniques, and performance enhancements through material modifications such as reduced graphene oxide (rGO). Additionally, we examine the application of graphene sensors in environmental monitoring, where their ability to detect pollutants like NO₂ , NH₃ , and CO₂ with high sensitivity and low power consumption provides a significant advantage over traditional sensing technologies. Despite these advancements, challenges such as selectivity, standardization, and sensor stability remain critical areas for future research.

In this article, the maximum tensile strength and hardness of 3D printed samples of Nylon CF15 Carbon were investigated. 20 test specimens were produced with dimensions according to the ASTM D 638 standard for tensile strength and 3 specimens for Shore D hardness testing. The experimental results were processed statistically.

This paper presents a study on the current state of research and use of dichalcogenides of transition metals, particularly WS2. The properties of WS2 in the context of its application in sensor technology and highlight the anticipated advantages of nanostructured disulfides are discussed.