Search Results (159)

Rogowski coils are increasingly being used in electricity metering systems. However, owing to their operating principle, they require an additional active integrating circuit to produce an output voltage or current that is directly proportional to the input current. A signal conditioner has the most significant impact on the overall conversion accuracy of the combined transducer. In this paper, a new measurement system and testing procedure utilizing a digital power meter and arbitrary waveform generator are proposed. This approach enables the characterization of the conversion accuracy of both types of active integrators: voltage-to-voltage and voltage-to-current converters. The conversion error for distorted input voltage harmonics and additional phase shift across a range of frequencies are determined. Instead of using the actual signal from the Rogowski coil during testing —which would be challenging owing to the required high RMS value of the distorted current for its input and difficulties in accurately measuring the RMS values of harmonics and their phase angles in relation to the output voltage or current of the tested converter—an arbitrary waveform generator is used. The input voltage to the active integrating circuit replicates the output voltage of the Rogowski coil: as the harmonic order increases, its RMS voltage rises proportionally. Full article

Caffeic acid (CA) can be applied as a green corrosion inhibitor for metals and alloys. The inhibition properties of caffeic acid for Zn in 0.1 M NaCl were investigated using electrochemical methods. The changes in Zn morphology were studied via scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) techniques. Potentiodynamic polarisation (PDP) and electrochemical impedance spectroscopy (EIS) measurements proved that caffeic acid applied in the form of coatings on Zn surface was more effective than the addition of CA to NaCl. Furthermore, CA coatings revealed better corrosion protection with increasing duration of immersion. The highest inhibition efficiency was achieved for CA coating obtained from ethanol solution of CA (10 mM), and its value was almost 95%. The positive impact of CA coatings on the corrosion of Zn surface was confirmed with SEM-EDS, XRD and TOF-SIMS measurements. They proved not only the presence of CA on the Zn surface but also noticeably a lower amount of Zn corrosion products. Full article

This paper presents an analysis of the dynamic properties of the Rogowski coil, primarily by determining the dynamic errors for several selected test signals and the upper bound of the dynamic error for two quality criteria: the integral-square error and the absolute error. A procedure for filtering and reproducing these signals is also presented. The foundation of the presented research is an equivalent circuit model of the Rogowski coil, developed primarily for applications in electrical power and electromechanical systems. Two novel aspects of this work are the determination of dynamic errors for the Rogowski coil and a graphical and quantitative comparison of their values. The research results presented in this paper may serve as a foundation for enhancing the accuracy and dynamic reliability of both the Rogowski coil and other devices (e.g., transformers and current transformers) used in the power industry and mechanical engineering, particularly in the condition monitoring of a broad range of power equipment and in the experimental analysis of electromechanical systems operating under variable load conditions. The findings also highlight the importance of accurate current measurement in modern energy systems, where transient and high-frequency components increasingly affect performance and reliability. Consequently, the presented methodology provides a useful framework for guiding sensor selection and signal processing strategies in advanced monitoring and control applications. Full article

Background: Human immunodeficiency virus (HIV) remains a global health challenge despite significant advancements in antiretroviral therapy and prevention strategies. Developing a safe and effective vaccine that protects people worldwide has been a major goal, yet the genetic variability and rapid mutation rate of the virus continue to pose substantial challenges. Methods: In this review paper, we aim to provide a comprehensive review of previous vaccine candidates and the progress made in HIV vaccine clinical trials, spanning from the late 1990s to 2025. PubMed and ClinicalTrials.gov were searched for English-language Phase 1–3 HIV vaccine trials published from 1990 to March 2025. After de-duplication, titles/abstracts and then full texts were screened; trial phase, regimen, immunogenicity, efficacy, and correlates were extracted into a structured spreadsheet. Owing to platform heterogeneity, findings were synthesized narratively and arranged chronologically to trace the evolution of vaccine strategies. Results: Early vaccine trials demonstrated that a protein subunit vaccine failed to protect against infection, revealing the complexity of HIV evasion strategies and shifting the focus to a comprehensive immune response, including both antibody and T-cell responses. Trials evaluating the role of viral vectors in generating cell-mediated immunity were also insufficient, and suggested that targeting T cell response alone was not enough. In 2009, the RV144 trial made a breakthrough by showing partial protection against HIV infection and providing the first indication of efficacy. This partial success influenced subsequent trials, prompting researchers to further explore the complex immune response required for protection and consider combinations of vaccine technologies to achieve robust, long-lasting immunity. Conclusion: Despite setbacks, decades of rigorous efforts have provided significant contributions to HIV vaccine discovery and development, offering hope for preventing and protecting against HIV infection. The field remains active by continuing to advance our understanding of the virus, refining vaccine strategies, and employing novel technologies. Full article

The following study investigated the melting behavior of coconut oil as a phase-change material in shell-and-tube and shell-and-coil thermal energy storage systems. The primary objective was to deepen the understanding of PCM melting dynamics under varying boundary conditions, aiming to optimize TES designs for renewable energy applications. This research addresses a gap in understanding how different heat-transfer configurations and boundary conditions affect melting efficiency. Experimental setups included two distinct heat-transfer surfaces in a cylindrical shell—a copper tube and a copper coil—tested under constant wall temperatures (34 °C for the tube, 33 °C for the coil) and constant heat flux (597 W/m² for the coil). Findings reveal that melting under constant heat flux takes approximately twice as long as under constant wall temperatures, underscoring the critical role of heat-transfer conditions in TES performance. The liquid fraction was estimated using two approaches: image-based analysis and the volume-averaged temperature method. The former proved less reliable due to geometric limitations, particularly when the heat-transfer surface was distant from the shell wall. Conversely, the latter yielded higher accuracy, especially in the shell-and-tube setup. Due to the scarcity of correlations for constant heat-flux conditions, the novel contribution of this work is the development of a modified semi-empirical correlation for the shell-and-coil TES system. For this purpose, an existing model, which demonstrated strong alignment with experimental data, was adapted. The findings suggest that slower melting under constant heat flux could benefit applications needing sustained heat release, like solar energy systems. Future work could investigate additional PCMs or novel geometries to further improve TES efficiency and scalability. Full article

This study investigates the aerodynamic performance of a symmetric NACA 0018 airfoil under harmonic pitching motions at low Reynolds numbers, a regime characterized by the presence of laminar separation bubbles and their impact on aerodynamic forces. The analysis encompasses oscillation frequencies of 1 Hz, 2 Hz, and 13.3 Hz, with amplitudes of 4° and 8°, along with steady-state simulations conducted for angles of attack up to 20° to validate the numerical model. The results reveal that the γ-Re_θ turbulence model provides improved predictions of aerodynamic forces at higher Reynolds numbers but struggles at lower Reynolds numbers, where laminar flow effects dominate. The inclusion of the 13.3 Hz frequency, relevant to Darrieus vertical-axis wind turbines, demonstrates the effectiveness of the model in capturing dynamic hysteresis loops and reduced oscillations, in contrast to the k-ω SST model. Comparisons with XFOIL further highlight the challenges in accurately modeling laminar-to-turbulent transitions and dynamic flow phenomena. These findings offer valuable insights into the aerodynamic behavior of thick airfoils under low Reynolds number conditions and contribute to the advancement of turbulence modeling, particularly in applications involving vertical-axis wind turbines. Full article

Background: The number of senior chronic kidney disease (CKD) patients is steadily increasing worldwide. Falls are more frequent in this group than in the general population, and they are associated with a variety of complications ranging from minor (bruises) to severe (fracture, brain injury, or death). The significant burden of comorbidities, particularly cardiovascular disorders, impacts coordination. The aim of the study was to assess coordination disorders in CKD patients in the context of cardiovascular complications and vascular status. Methods: In this prospective study, 132 patients with CKD 2–5, including 40 (30%) hemodialysis patients, were enrolled. The short form physiological profile assessment (S-PPA) was used to assess coordination. Results: During a 2-year follow-up period, 49 individuals experienced 84 falls. The median S-PPA score (Z score) was 3.36. Based on this, we divided our cohort into two groups: a Z score of <3.36 and a Z score of ≥3.36. The groups with high scores (≥3.36) characterized by higher parameters of vessel stiffness, including AIx@75, augmentation pressure, and PWV, experienced considerably greater numbers of falls (41 vs. 8, p < 0.001), CV events (10 vs. 2, p < 0.05), and deaths (14 vs. 0, p < 0.001). Conclusions: Coordination impairments and the associated risk of falls in CKD patients are directly related to cardiovascular diseases and vascular conditions. Lower arterial compliance has been linked with the largest coordination disorder. Visual impairments, especially contrast sensitivity, are an independent risk factor for falls. Full article

Lightning strikes are a leading cause of outages on overhead transmission lines, significantly compromising power system reliability. Consequently, monitoring lightning activity is critical to mitigate its impact on lines with high outage rates. This study presents an autonomous lightning strike counter system utilizing a split-core Rogowski coil for non-invasive current measurement on transmission towers. The system combines the Rogowski coil with an active integrator circuit to reconstruct the incident current waveform from the coil voltage signal. A microcontroller-based processing unit records strike occurrences and classifies them by amplitude using predefined thresholds. Laboratory tests were carried out to evaluate the performance of the Rogowski coil and integrator circuit, validating the system accuracy in detecting current pulses associated with lightning strikes. Underway field tests will assess the sensor’s reliability during long-term autonomous operation on 345-kV transmission towers. The results demonstrate that the proposed system represents a practical and cost-effective solution for lightning monitoring in remote areas, contributing to enhanced data collection for engineering studies and improved reliability of electrical infrastructure. Full article

Tuberculosis (TB) remains a leading cause of mortality, with drug resistance highlighting the need for new vaccine targets. Peptidyl-prolyl isomerase A (PpiA), a conserved Mycobacterium tuberculosis (Mtb) protein, plays a role in bacterial stress adaptation and immune evasion, making it a potential target for immunotherapy. This study uses computational methods to assess PpiA’s antigenicity, structural integrity, and immunogenic potential. The PpiA sequence was retrieved from NCBI and analyzed for antigenicity and allergenicity using VaxiJen, AllerTOP, and AllergenFP. Physicochemical properties were evaluated using ProtParam, and structural models were generated through PSIPRED and SWISS-MODEL. Structural validation was performed with MolProbity, QMEANDisCo, and ProSA-Web. B-cell epitopes were predicted using BepiPred 2.0 and IEDB, while T-cell epitopes were mapped via IEDB’s MHC-I and MHC-II tools. Epitope conservation across Mtb strains was confirmed using ConSurf. Results indicate PpiA is highly antigenic, non-allergenic, and stable, with several immunogenic epitopes identified for both B- and T-cells. This study supports PpiA as a promising immunogenic target for TB vaccine development. Full article

Recently, there has been a growing interest in issues related to mining equipment maintenance, with particular focus on pumping systems’ continuous operation. However, despite wide applications of pump system maintenance in a wide range of industries, such as water and wastewater, aviation, petrochemical, building (HVAC system), and nuclear power plant industries, the literature on maintenance of pump systems operating in the mining industry still needs development. This study aims to review the existing literature to present an up-to-date analysis of maintenance strategies for mining pumps, with a particular focus on proactive maintenance approaches. Key aspects considered include predictive diagnostics and prognosis, health status monitoring, maintenance management, and the integration of intelligent mining systems to enhance operational reliability and efficiency in harsh mining environments. The proposed methodology includes a systematic literature review with the use of the Primo multi-search tool, adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The selection criteria focused on English studies published between 2005 and 2024, resulting in 88 highly relevant papers. These papers were categorized into six groups: (a) condition/health status monitoring, (b) dewatering system operation and maintenance, (c) health diagnosis and prognosis, (d) intelligent mining (modern technologies), (e) maintenance management, and (f) operational efficiency and reliability optimization. A notable strength of this study is its use of diverse scientific databases facilitated by the multi-search tool. Additionally, a bibliometric analysis was performed, showcasing the evolution of research on pump maintenance in the mining sector over the past decade and identifying key areas such as predictive diagnostics, dewatering system optimization, and intelligent maintenance management. This study highlights the varied levels of research and practical implementation across industries, emphasizing the mining sector’s unique challenges and opportunities. Significant research gaps were identified, including the need for tailored diagnostic tools, real-time monitoring systems, and cost-effective maintenance strategies specific to harsh mining environments. Future research directions are proposed, focusing on advancing predictive maintenance technologies, integrating intelligent systems, and enhancing operational efficiency and reliability. The study concludes with a detailed discussion of the findings and their implications, offering a roadmap for innovations in pump maintenance within the mining industry. Full article

The increasing demand for critical metals has intensified efforts to recover valuable metals from various sources, including secondary waste. Zn-Pb tailings contain both major and trace metals with economic and environmental significance. This study examined the extraction of transition metals from Zn-Pb tailings using inductively coupled plasma mass spectrometry (ICP-MS) at a constant time of 30 min. Metal extraction efficiencies were evaluated using N-Methyl-N,N,N-trioctylammonium chloride (Aliquat 336), methyl salicylate (MS), di(2-ethylhexyl) phosphoric acid (D2EHPA), tributyl phosphate (TBP),2,4,6-tris(allyloxy)-1,3,5-triazine (TAOT), and triethyl phosphate (TEP). Increasing mixing rates improved mass transfer, enhancing recoveries, with Hf⁴⁺, Ti⁴⁺, and Fe³⁺ reaching 88, 56, and 50%, respectively, at 1000 rpm (mixing rate; rotation per minute) using D2EHPA. At a mixing rate of 1000 rpm, 10% TEP recovered 25% of Cu²⁺ and 34% of Mn²⁺, while 150 g/L extracted 48% of Hf⁴⁺ and 46% of V⁴⁺. Additionally, 10% TBP extracted 33% of Mn²⁺ and 35% of V⁴⁺, 10% MS recovered 41% of Mn²⁺ and 39% of V⁴⁺, while TAOT extracted 35% of V⁴⁺. At room temperature (22.5 °C) and 1400 rpm, 10% of D2EHPA recovered 80% of Hf⁴⁺, 73% of Ti⁴⁺, and 61% of Fe²⁺. However, 10% TAOT selectively recovered 50% of V⁴⁺, while 10% MS, under the same conditions, recovered 50% of V⁴⁺ with co-extraction of Mn²⁺ and Cu²⁺ (<10%). A total of 150 g/L Aliquat 336 effectively extracted Hf⁴⁺ (66%), Zn²⁺ (19%), and V⁴⁺ (56%). A total of 10% TBP recovered 53% and 47% of Mn²⁺ and V⁴⁺, respectively. A total of 10% TEP recovered Cu²⁺ (45%), Mn²⁺ (55%), Zn²⁺ (29%), V (40%), and 26% of Ni²⁺. At room temperature (22.5 °C) and 1400 rpm, pH changes significantly affected extraction, with D2EHPA (10%) demonstrating 89% efficiency for Hf⁴⁺ at pH 1.3, while other metals showed lower recoveries. TEP (10%) increased Cu²⁺ and Hf⁴⁺ recovery to 52% and 80%, respectively, at pH 1.3, while 150 g/L Aliquat 336 favored Cu²⁺ (58%), with co-extraction of 16% of Zn²⁺ at pH 1.3. TBP (10%) extracted 60% and 61% of Cu²⁺ and Fe, respectively, at pH 1.3, while 10% of MS recovered 55% and 50% of V, respectively. A concentration of 10% D2EHPA favored the recovery of 90% of Hf⁴⁺ at pH 1.3, with less than 35% co-extraction of Cu²⁺, Mn²⁺, Zn²⁺, and Fe²⁺. At 1400 rpm, temperature also influenced extraction, with D2EHPA recovering 84% of Hf⁴⁺ at 35 °C, 77% of Ti (55 °C), and 79% of Fe (55 °C) and TBP extracting 73% of Cu²⁺, 67% of Mn²⁺, 68% of Zn, 60% of V⁴⁺, and 47% of Ni²⁺ at 55 °C. A concentration of 10% MS extracted 61% of V⁴⁺and 54% of Fe²⁺, while 150 g/L recovered 61% of V⁴⁺ at 55 °C. TAOT extracted 46% of Mn and 41% of V⁴⁺, while 10% TEP recovered 60% of Mn and 32% of V⁴⁺ at 55 °C. These outcomes contribute to an improved understanding of the solvent extraction mechanisms of different ligands. Full article

The increasing demand for critical metals essential for renewable energy technologies necessitates efficient and environmentally sustainable extraction methods. Ilmenite (FeTiO₃) and similar ore deposits serve as abundant sources of primary elements while also incorporating a suite of strategically significant trace elements, including REEs and Hf, among others. Mixer–settler units are extensively utilized in metal purification processes. It is important to develop approaches for tracking the metal’s extraction process online and optimizing flow dynamics. One widely adopted technique for evaluating the flow dynamics of the various components is the residence time distribution (RTD) measurement, which provides insights into the hydrodynamic behavior of process reactors. This study explored the application of radiotracer techniques for online monitoring of solvent extraction processes in hydrometallurgy, focusing on Hf recovery. A mixer–settler system was employed using di(2-ethylhexyl) phosphoric acid (D2EHPA) as the extractant and the 1M HNO₃ aqueous phase of Ti ore. The radiotracer ¹⁸¹Hf was synthesized via neutron activation and introduced into the system to track phase distribution and RTD. Real-time monitoring revealed over 95% extraction efficiency within 133 min (8000 s). The RTD studies validated system performance using perfect mixers in series and axial dispersion models. The calculated mean residence time of 100 min (6000 s) closely aligned with the theoretical 104 min (6240 s), confirming the model accuracy. The findings demonstrate the viability of radiotracers in monitoring solvent extraction, offering real-time insights into flow dynamics and extraction efficiency. Full article

Nuclear power plants have the lowest life-cycle greenhouse gas emissions intensity and produce more electricity with less land use compared to any other low-carbon-emission-based energy source. There is growing global interest in Generation IV reactors and, at the same time, there is great interest in using small modular reactors. However, the development of new reactors introduces new engineering and chemical challenges critical to advancing nuclear energy safety, efficiency, and sustainability. For Generation III+ reactors, water chemistry control is essential to mitigate corrosion processes and manage radiolysis in the reactor’s primary circuit. Generation IV reactors, such as molten salt reactors (MSRs), face the challenge of handling and processing chemically aggressive coolants. Small modular reactor (SMR) technologies will have to address several drawbacks before the technology can reach technology readiness level 9 (TRL9). Issues related to the management of irradiated graphite from high-temperature reactors (HTR) must be addressed. Additionally, spent fuel processing, along with the disposal and storage of radioactive waste, should be integral to the development of new reactors. This paper presents the key chemical and engineering aspects related to the development of next-generation nuclear reactors and SMRs along with the challenges associated with them. Full article

This study investigates the aerodynamic performance and flow dynamics of an H-type Darrieus vertical axis wind turbine (VAWT) using combined numerical and experimental methods. The analysis examines the effects of operational parameters, such as rotor solidity and pitch angle, on aerodynamic loads and flow characteristics, using a 2-D URANS simulation with the Transition SST model to capture transient effects. Validation was conducted in a low-turbulence wind tunnel to observe the impact of variable flow conditions. The LineAverage method for determining the angle of attack demonstrated strong correlations between rotor configuration and load variations, particularly highlighting the influence of blade number and pitch angle on aerodynamic efficiency. This research supports optimization strategies for Darrieus VAWTs in urban environments, where turbulent, low-speed conditions challenge conventional wind turbine designs. Full article

Objective: The aim of this study was to evaluate the impact of coronary bypass surgery (CABG) on long-term mortality, comparing survival rates to those of the general population in Poland. Methods: The study was based on the Polish National Register of Cardiothoracic Surgical Procedures (KROK). Between January 2009 and December 2019, 133,973 patients underwent CABG. The study included all patients who underwent primary CABG. After excluding reoperations and patients with missing key data, there were 132,760 remaining patients who participated in the study. In order to compare patients who underwent CABG with the general population, data from Polish life expectancy tables from the Central Statistical Office (CSO) were used. Results: In the general population (GP), there is a consistent decrease in survival for both women and men throughout the entire observation period. The decline in survivability is more pronounced in the male group. Unlike the CABG group, which is at risk of perioperative mortality, there is no initial drop in survivability in the GP. The early mortality rate in CABG group within 30 days was significantly higher in the group of women than in men (3.51% compared to 2.19%, p < 0.001). The annual mortality rate was higher in the group of women (6.7% vs. 5.14%), and survival time was shorter (345.5 ± 0.4 vs. 351.2 ± 0.2 days, p < 0.001). However, the total mortality over a 13-year period of observation did not differ significantly between the groups (30.17% for women vs. 29.6% for men, p = 0.996) with survival time 10.08 ± 0.02 years in men vs. 10.06 ± 0.03 in women, p = 0.996. Conclusions: CABG surgery equalizes the probability of survival between genders. In long-term observation men have a greater survival benefit than women if compared to the predicted survival of the general population. These observations may provide a new perspective on the choice of revascularization strategy in relation to gender. Full article