Industry 4.0
Vol. 10 (2025), Issue 3

Table of Contents

  • TECHNOLOGICAL BASIS OF “INDUSTRY 4.0”

    • Multiple access interference protection in multichannel data transmission systems

      pg(s) 91-94

      The article is a continuation of previous studies and deals with the results of research on the protection of multichannel data transmission systems with channel division by the signal code from unauthorized access. It is proposed to use derivatives of Walsh functions (with different generating functions) as spreading codes for the formation of noise-like signals in multichannel communication systems. The analysis showed that the correlation properties of the derivatives of Walsh functions used as spreading codes have significantly better correlation characteristics than the original ones. An analysis of various types of Walsh functions used as spreading codes for signals transmitted in multi-channel systems was carried out. As a result, there were defined the types of pseudo-random sequences for Walsh generating functions, in which
      multiple access interference is absent. It was justified the advantage of using these signals in the development of CDMA systems in order to protect against interference from multiple and unauthorized access.

    • Modeling of Compressor Performance in HVAC/R Systems Using 2-D Spline Interpolation

      pg(s) 95-98

      This paper presents a method for predicting the performance of compressors in HVAC/R systems using 2-D quadratic spline interpolation. Compared to traditional third-order polynomial interpolation, the spline model provides smoother and more accurate approximations, especially useful when limited manufacturer data is available. Using real-world compressor data, we constructed mathematical models and evaluated their performance through key statistical indicators. Results indicate that the spline-based model yields lower RMSE values with reduced model order, improving its integration in system simulations. This study also provides a comparative analysis against a polynomial-based model developed in earlier research.

  • DOMINANT TECHNOLOGIES IN “INDUSTRY 4.0”

    • Thermodynamic evaluation of a 250 MW three-cylinder steam turbine from ccpp

      pg(s) 99-102

      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.

    • Preparation, phase and optical characterization of Sm2O3-ZrO2 coatings on glasses obtained by sol-gel technology using the Dip Coating method

      pg(s) 103-106

      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.

    • Effect of thermal insulation on comfort and energy savings in buildings

      pg(s) 107-110

      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.

    • Statistical analysis of modification of joints of metals and composites by thermal drilling

      pg(s) 111-114

      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.

    • Correlation-Based Sensor Pruning and Malfunction Detection in Multi-Sensor Condition Monitoring

      pg(s) 115-118

      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.

  • SOCIETY & ”INDUSTRY 4.0”

    • Regarding cybersecurity in Bulgarian educational institutions at the K–12 level

      pg(s) 119-121

      Cybersecurity studies increasingly prioritize empirical methodologies to understand and alleviate security risks arising from human behavior, organizational practices, and the advancement of technologies used to perform cyberattacks. This research paper explores how the school management and key educators in Bulgarian K-12 schools comprehend cybersecurity within the academic framework of the Bulgarian education system. Our survey of 927 Bulgarian K–12 educational institutions revealed that a very small number of them assess their level of cybersecurity as extremely low. Respondents see cybersecurity training as essential for ensuring information security within their institutions. Our findings indicate that only 25% of K-12 employees are able to incorporate this training into their qualification programs.