Search Results (254)

Detecting power transformer winding degradations at an early stage is very important for the safe operation of nuclear power plants. Most transformer failures are caused by insulation breakdown; the winding turn-to-turn short circuit fault is frequently encountered. Experience has shown that routine testing techniques, e.g., winding resistance, leakage inductance, and sweep frequency response analysis (SFRA), are not sensitive enough to identify minor turn-to-turn short defects. The SFRA technique is effective only if the fault is in such a condition that the flux distribution in the core is prominently distorted. This paper proposes the frequency domain reflectometry (FDR) technique for detecting and locating transformer winding defects. FDR measures the wave impedance and its change along the measured windings. The wire over a plane model is selected as the transmission line model for the transformer winding. The effectiveness is verified through lab experiments on a twist pair cable simulating the transformer winding and field testing on a real transformer. The FDR technique successfully identified and located the turn-to-turn short fault that was not detected by other testing techniques. Using FDR as a complementary tool for winding condition assessment will be beneficial. Full article

This research evaluates the rheological and mechanical properties of polymer- and nanomaterials-modified bitumen by incorporating nanosilica (NSA), nanoclay (NCY), and Acrylonitrile Styrene Acrylate (ASA) at 5% by weight of the bitumen. The samples were prepared at 165 °C for one hour to obtain homogeneous blends. All samples were subjected to short- and long-term aging to simulate the effects of different operating conditions. The research conducted a series of tests, including consistency, frequency sweep, and multiple creep stress and recovery (MSCR) using the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The results showed that all modified bitumen outperformed the neat bitumen. The frequency sweep showed a higher complex modulus (G*) and lower phase angle (δ), indicating enhanced viscoelastic properties and, thus, higher resistance to permanent deformation. The BBR test revealed that the bitumen modified with NCY5% has a creep stiffness of 47.13 MPa, a 51.5% improvement compared to the neat bitumen, while the NSA5% has the highest m-value, a 28.5% enhancement compared with the neat bitumen. The MSCR showed that the modified blends have better recovery properties and, therefore, better resistance to permanent deformation under repeated loadings. The aging index demonstrated that the modified bitumen is less vulnerable to aging and maintains their good flexibility and resistance to permanent deformations. Finally, these results showed that adding 5% polymer and nanomaterials improved the bitumen’s’ performance before and after aging by reducing permanent deformation and enhancing crack resistance at low temperatures, thus extending the pavement service life and making them an effective alternative for improving pavement performance in various climatic conditions and under high traffic loads. Full article

We develop a modular, wireless, solar- and battery-powered system for detecting chlorpyrifos (Lorsban^TM 2.5% DP) in water using electrochemical impedance spectroscopy (EIS). The system integrates a Raspberry Pi Zero 2W for data processing, Python-based software (version 3.12.2), and a solar charge manager to power all components via a lithium-ion battery and solar panel. A commercial EmStat Pico Module and an amperometric biosensor with acetylcholinesterase (AChE) detect chlorpyrifos. Nine water samples with varying concentrations were tested using a 20 Hz–200 kHz frequency sweep and 15 mV excitation. Bode plots and statistical analyses confirmed statistically significant impedance variation as a function of chlorpyrifos concentration, validating the system as a portable, sensitive, and effective tool for environmental monitoring. Full article

The inherent damping deficiency in metal lattice structures leads to inadequate attenuation of both resonant peaks and shock-induced vibrations, significantly limiting their effectiveness in vibration isolation and shock resistance applications. To address this limitation, we developed a novel parallel polyurea method that utilizes the viscoelastic energy dissipation mechanism of polyurea to substantially improve structural damping performance. The metal lattice–polyurea parallel vibration isolation system was designed with its theoretical model established to characterize damping properties, vibration isolation, and shock-resistant performance. An experimental setup was developed to validate theoretical predictions through controlled semi-sinusoidal shock and swept-frequency tests. Experimental results demonstrate excellent agreement with theoretical predictions. The introduction of the polyurea damping structure significantly enhances the system’s damping performance. Compared to the conventional metal lattice isolator, the proposed metal lattice–polyurea parallel composite structure shows remarkable damping improvements: under shock excitation, it achieves substantial attenuation of peak response amplitude with accelerated decay rate, while under frequency-sweep excitation, it maintains the original resonance frequency but reduces the transmissibility peak significantly. Full article

An electromechanical actuator system was used on a general aviation aircraft to automatically execute programmed test inputs for system identification and parameter estimation. The flight test campaign consisted of approximately 10 flight hours with over 250 carefully designed dynamic test inputs, including multisteps, frequency sweeps, phase-optimized orthogonal multisines, and the optimal inputs for parameter estimation. This paper describes the actuator system retrofitted to the REMOS GX aircraft and the software developed for automatic maneuver injection. The design of the flight test maneuvers is discussed while considering the characteristics and the limits of the onboard actuator system. The initial parameter estimation results are used to evaluate the effectiveness of the applied methods, which is a first for a light sport aircraft. The lessons learned and the advantages of such a system with respect to manual (piloted) flight testing will be described, as will recommendations for future applications of electromechanical actuators to aircraft of this weight class. Full article

This study explores the rheological performance of bitumen modified with a synthetic polymer (styrene–butadiene–styrene, SBS) and two environmentally sustainable additives—animal bone ash (AB) and waste cooking oil (WCO)—to enhance durability and deformation resistance under dynamic loading. Frequency sweep and linear amplitude sweep (LAS) tests were conducted to evaluate viscoelastic and fatigue behavior. SBS at 5% showed the highest elasticity and fatigue life, making it optimal for heavily trafficked pavements. Among bio-waste additives, 6% AB provided the highest stiffness and rutting resistance in laboratory tests; however, 5% AB offered a better balance between structural integrity and cracking resistance, making it more suitable for general pavement applications. WCO-modified binders demonstrated improved flexibility, with 4% WCO achieving the best balance between elasticity and softening, ideal for low-load or temperate environments. These results highlight the potential of combining synthetic and bio-based waste materials to tailor bitumen properties for sustainable and climate-responsive pavement design. Full article

In this study, we discussed how the increasing demand for electrical energy results in higher loads on transformers, creating the need for more effective testing and maintenance methods. Accurate fault classification is essential for the reliable operation of transformers. In this context, Sweep Frequency Response Analysis (SFRA) has emerged as an effective method for detecting potential faults at an early stage by examining the frequency responses of transformers. In this study, we used artificial intelligence (AI) and machine learning (ML) techniques to analyze the data generated by SFRA tests. These tests typically produce large datasets, making manual analysis challenging and prone to human error. AI algorithms offer a solution to this issue by enabling fast and accurate data analysis. In this study, three different transformer conditions were analyzed: a healthy transformer, a transformer with core failure, and a transformer with winding slippage. Six different machine learning algorithms were applied to detect these conditions. Among them, the Gradient Boost Classifier showed the best performance in classifying faults. This algorithm accurately predicted the health status of transformers by learning from large datasets. One of the most important contributions of this study is the use of gradient boosting algorithms for the first time to analyze SFRA test results and facilitate preventive maintenance through the early detection of transformer failures. In conclusion, this study presents an innovative approach. The interpretation of offline SFRA results through various artificial intelligence-based analysis methods will contribute to achieving the ultimate goal of reliable online SFRA applications. Full article

Background: Zinc oxide paste is traditionally compounded and applied in the therapy of various skin conditions. However, prolonged use of talc, usually present in zinc oxide pastes, may pose health risks due to potential contamination with asbestos and quartz, highlighting the need for alternative excipients. This study aimed to examine the effects of starches from various botanical sources and their particle size on the rheological and absorption properties of zinc oxide paste. Methods: Eight zinc oxide paste formulations were prepared, containing 25% zinc oxide and 25% indifferent excipient (talc, tapioca, rice, or maize starch) in two particle sizes. Rheological properties were assessed using amplitude and frequency sweep tests, and water- and oil-absorption capacities were determined using a centrifugation-based method. Results: Amplitude sweep tests confirmed the predominant solid-like nature of zinc oxide pastes, with the elastic modulus (G′) exceeding the viscous modulus (G″) in all formulations. Tapioca starch-based pastes exhibited the highest G′ and G″ values, while talc-based pastes exhibited the lowest. Frequency sweep tests showed that pastes were resistant to structural changes under stress, with G′ consistently dominating over G″ across the entire frequency range. Tapioca starch-based formulations exhibited the highest water-absorption capacity, while the talc-based formulations had the highest oil-absorption capacity. Reducing particle size improved both water- and oil-absorption capacities. Conclusions: Starches may be considered as alternatives to talc in zinc oxide pastes, due to their ability to modify the absorption and rheological properties of pastes. Future studies should assess the impact of starch substitution on sensory characteristics, shelf-life stability, and patient satisfaction. Full article

Asphalt pavements are prone to various distresses under complex environmental influences during service, which significantly affects their fatigue life. This study conducted complex environmental simulation tests, including pressure aging, ultraviolet (UV) aging, and coupling effects with salt solutions at different concentrations. A dynamic shear rheometer (DSR) was employed to perform frequency sweep tests, linear amplitude sweep (LAS) tests, and fatigue–healing–fatigue tests. The fatigue self-healing properties of fast-melting SBS (SBS-T)-modified asphalt were evaluated based on the viscoelastic continuous damage theory. The results indicate that coupled aging effects significantly increase the viscoelastic characteristic parameters of SBS-T-modified asphalt, with more elastic components transforming into viscous components. Compared to other aging effects, the coupled pressure-UV-salt solution condition induces the most severe degradation in the fatigue durability of SBS-T-modified asphalt. Simultaneously, the self-healing capability of aged asphalt is also reduced. Specifically, with increasing strain, more complex aging conditions lead to the faster deterioration of asphalt fatigue life and lower self-healing capacity. While asphalt demonstrates measurable fatigue life restoration through self-healing, the synergistic coupling of salt solution exposure and multi-factor aging significantly compromises both the absolute fatigue resistance and the relative recovery efficiency. Full article

Background/Objectives: Recent studies highlight the excellent wound-healing properties of collagen and chitosan materials. Combining these polymers with a bioactive compound could enhance their effectiveness as next-generation wound dressings. Hydroxytyrosol (HT), an antioxidant derived from olive oil, may aid wound healing due to its anti-inflammatory, antimicrobial, and angiogenesis-stimulating properties, making it a beneficial addition to collagen–chitosan dressings. It could be a beneficial addition to collagen–chitosan dressings, thus improving their therapeutic effects. This study screens the potential of collagen–chitosan composites with HT for wound-healing applications and assesses the influence of the compound’s incorporation on the materials’ properties. Methods: The material production involved incorporating chitosan and HT into a marine collagen extract. The resulting collagen–chitosan–HT material was obtained through freeze-drying. Prototype dressing characterization included morphology by scanning electron microscopy, solid and hydrated state by textural and rheological studies, and in vitro HT release studies. The materials’ cytocompatibility screening was assessed using a mouse fibroblast cell line, and the antibacterial activity was evaluated against microorganisms commonly implicated in wound infections. Results: Burst strength, viscosity, frequency sweep test, tackiness, and adhesion results indicate that chitosan contributes to the material’s mechanical robustness by maintaining a high viscosity and preserving the material’s gel structure. The in vitro release studies suggest an HT-controlled release profile with a maximum release (70%) achieved after 10 h. Biological experiments confirmed the materials’ cytocompatibility with skin cells and very promising antibacterial efficacy against Staphylococcus aureus and Pseudomonas aeruginosa. Conclusions: In conclusion, HT was successfully incorporated into a collagen–chitosan matrix, enhancing the therapeutic prospect of the resultant material. The collagen–chitosan–HT composite presents a promising potential as an advanced wound-healing material. Full article

Airway mucus plays a critical role in respiratory health, with diseases such as cystic fibrosis (CF) being characterized by mucus that exhibits increased viscosity and altered viscoelasticity. In vitro models that emulate these properties are essential for understanding the impact of CF mucus on airway function and for the development of therapeutic strategies. This study characterizes a mucus mimic composed of xanthan gum and locust bean gum, which is designed to exhibit the rheological properties of CF mucus. Mucus concentrations ranging from 0.07% to 0.3% w/v were tested to simulate different states of bacterial infection in CF. Key rheological parameters, including yield stress, storage modulus, loss modulus, and viscosity, were measured using an HR2 rheometer with strain sweep, oscillation frequency, and flow ramp tests. The results show that increasing the concentration enhanced the mimic’s elasticity and yield stress, with values aligning with those reported for CF mucus in pathological states. These findings provide a quantitative framework for tuning the rheological properties of mucus in vitro, allowing for the simulation of CF mucus across a range of concentrations. This mucus mimic is cost-effective, readily cross-linked, and provides a foundation for future studies examining the mechanobiological effects of mucus yield stress on epithelial cell layers, particularly in the context of bacterial infections and airway disease modeling. Full article

The rheological properties of fiber-reinforced binders are remarkable. The research on acetate fibers as reinforcing agents is scant. Acetate fibers exhibit more environmental benefits than lignocellulose and other fibers. In this study, acetate fibers were pretreated with anhydrous ethanol as the extractant to disperse the fibers uniformly in the bitumen and the high/medium-temperature fatigue properties of waste acetate fibers blended with binders were investigated. Infrared spectroscopy (FT-IR) tests showed that pretreatment was effective in removing plasticizers from CBs so that the fibers could be more uniformly dispersed in the binders. The roadworthiness and fatigue performance of the adhesives were tested based on frequency sweep (FS), multiple stress creep recovery (MSCR), and linear amplitude sweep (LAS) tests with different CB (cigarette butt) doping levels. Ultimately, CBs were added to effectively improve all aspects of bitumen performance, but this phenomenon was not enhanced with an increase in the amount of admixture—optimal covariance was 0.25%. Moreover, a further correlation analysis was performed for the three traditional predicted fatigue failure points. The best correlation was R² = 0.98 for a 50% decrease in dynamic shear modulus, followed by R² = 0.96 for peak stress–strain, and R² = 0.88 for fatigue factor. Full article

The harsh environments in saline–alkaline areas and high-altitude regions with intense ultraviolet radiation pose great challenges to the durability of asphalt pavements. The fatigue performance of asphalt binder significantly determines the actual service life of asphalt pavements. Existing studies have predominantly focused on the impact of individual environmental factors (e.g., aging and saline–alkaline erosion) on asphalt performance, yet there remains a notable research gap in the systematic analysis of asphalt’s fatigue and self-healing behavior under coupled multi-factor interactions, particularly regarding the synergistic effects of UV aging and saline–alkaline conditions. Therefore, it is of great importance to understand the influence rules of the coupling effect of aging and salt–alkaline characteristics on the properties of asphalt materials. In this study, 70# base asphalt and GO-modified asphalt were taken as the research objects. Frequency sweep tests, linear amplitude sweep (LAS) tests, and LAS-based healing tests were conducted using a dynamic shear rheometer. The fatigue and self-healing properties of the two asphalt materials under different aging conditions and aging and salt–alkali coupling effects were analyzed based on the viscoelastic continuum damage theory. The results showed that the degree of aging can increase the stress peak of asphalt materials under small strains and also increase their stress attenuation rate. Except for short-term aging and salt–alkali effects, the aging and salt–alkali coupling effects generally further reduce the stress peaks of asphalt materials. Aging can increase the fatigue life of asphalt and increase the fatigue life attenuation rate of asphalt. The aging and salt–alkali coupling effects will reduce the fatigue life of asphalt and increase the decline rate of the asphalt fatigue life. The self-healing efficiency of asphalt is affected by the degree of aging, and the aging and salt–alkali coupling effects further reduce the self-healing efficiency of asphalt materials. This paper elucidates the influence mechanisms of intense UV irradiation and saline–alkaline environments on GO-modified asphalt, providing theoretical and practical references for its future engineering applications in harsh environmental conditions. Full article

Fiber-optic Fabry–Pérot (F–P) sensors offer significant potential for non-invasive hemodynamic monitoring, but existing sensing systems face limitations in multi-channel measurement capabilities and dynamic demodulation accuracy. This study introduces a sparse-frequency-scanning white-light interferometry (SFS-WLI) system with an adaptive mode-locked cross-correlation (MLCC) algorithm to address these challenges. The system leverages telecom-grade semiconductor lasers (191.2–196.15 THz sweep range, 50 GHz step) and a Fibonacci-optimized MLCC algorithm to achieve real-time cavity length demodulation at 5 kHz. Compared to normal MLCC algorithm, the Fibonacci-optimized algorithm reduces the number of computational iterations by 57 times while maintaining sub-nanometer resolution under dynamic perturbations. Experimental validation demonstrated a carotid–radial pulse wave velocity of 5.12 m/s in a healthy male volunteer. This work provides a scalable and cost-effective solution for cardiovascular monitoring with potential applications in point-of-care testing (POCT) and telemedicine. Full article

With the increasing requirement for asphalt modification, a new environmentally friendly asphalt modifier is needed. In this study, three varieties of biomass, cotton seed (CO), camelia seed shell (CA), and coffee ground (CG), were chosen for biochar preparation and asphalt modification to find an environmentally friendly asphalt modifier. A segregation test was applied to evaluate the storage stability of the modified asphalt. A dynamic shear rheometer (DSR) temperature sweep and frequency sweep were used to characterize the high-temperature performance. The low-temperature performance was evaluated by the bending beam rheometer (BBR) test. The DSR results indicate that the rutting factor increase for modified asphalt at high temperatures is CO ≈ CG > CA, and a high temperature could reflect the biochar’s properties better in modified asphalt. Furthermore, the low-temperature deterioration is well controlled in CO and CA biochar-modified asphalt. Finally, the volatile organic compound (VOC) emission behavior was evaluated using gas chromatography–mass spectrometry (GC-MS). Full article