Search Results (1,447)

This study investigates the decay-like degradation mechanisms of the matrix material in composite insulators, focusing on the pronounced influence of humid environments on partial discharge (PD) characteristics and degradation pathways. A sealed chamber discharge platform was established, integrating PD signal monitoring, surface characterization, and gas chromatography-mass spectrometry (GC-MS) with molecular network analysis to examine the synergistic effects of thermal influences from PD and active atmospheric particles at humidity levels of 0% RH, 50% RH, and 100% RH. Results show that dry conditions favor high-energy, low-repetition-rate discharges, promoting cleavage and recombination of high-bond-energy bonds (e.g., benzene rings and (α)C–O), yielding primarily long-chain carboxylic acids (C9 and above). In contrast, humid conditions shift to low-energy, high-repetition-rate discharges, with water vapor decomposition generating highly oxidizing hydroxyl radicals (·OH). These facilitate selective scission of lower-bond-energy (β)C–O bonds and deep oxidation, significantly increasing short-chain dicarboxylic acids—especially oxalic acid—whose acidity and water solubility are nearly an order of magnitude higher than in dry environments, becoming the dominant acidic products. The work demonstrates that many PD-generated organic acids act as intrinsic corrosive agents in insulating systems, independent of ambient nitric acid. This elucidates, at the reaction pathway level, how high humidity modulates PD to enhance corrosive acid production, providing a microchemical basis for understanding regional decay-like failure patterns in composite insulators. Full article

Earth-based materials are promising candidates for balancing thermal performance, hygrothermal regulation, and environmental sustainability. The objective of this study is to evaluate and compare the hygrothermal behavior of two earthen materials, structural cob and lightweight insulating earth, against conventional reference concrete, taking into account not only their insulating properties but also their ability to regulate coupled heat and moisture transfers. Experimental tests show a significantly higher hygroscopic buffering capacity for earth-based materials, with an MBV of 2.23 g/(m²∙%RH) for the structural material and 1.21 g/(m²∙%RH) for the insulation material, compared to less than 0.5 g/(m²∙%RH) for concrete. The sorption isotherms confirm distinct water storage behaviors, with an average sensitivity to relative humidity of 10.47% for the insulation material, compared to 3.8% for concrete and 2.25% for the structural material, in addition to an average reduction of 26% in the adsorption capacity between 23 °C and 45 °C for both earthen materials. Coupled heat–moisture simulations in COMSOL quantitatively demonstrate the hygrothermal superiority of bio-based materials over conventional concrete, as concrete promotes interstitial moisture accumulation due to its low vapor permeability. The parametric sensitivity analysis highlights the effect of hygrothermal properties, where diffusivity controls transport kinetics and sorption governs water storage, while thermal conductivity modulates the spatial redistribution of thermo-hygric fields. The next and final step made it possible to link the phenomena observed at the material scale to the actual energy performance of the building, confirming the potential of the double-wall cob + lightweight earth system to reduce heating and cooling requirements and maintain stable indoor comfort, where the annual heating demand is reduced by approximately 24% compared to the conventional prototype. Full article

Lithium niobate on insulator (LNOI) has emerged as a promising platform for compact, low-loss phase modulators. The extant LNOI studies evaluate device performance almost exclusively through the Pockels effect, treating piezoelectric–photoelastic strain and thermo-optic drift as decoupled channels. Crucially, both mechanisms directly perturb the phase bias of a fiber-optic gyroscope (FOG), rendering them indispensable in sensing-oriented design. This work establishes a unified multiphysics model of an X-cut TFLN ridge phase modulator that self-consistently couples the electro-optic, piezoelectric–photoelastic, thermo-optic, and pyroelectric channels. The contributions of the four mechanisms are quantitatively decomposed under realistic FOG operating conditions, and the slab thickness, ridge-top width, and electrode gap are systematically optimized to balance modulation efficiency against environmental robustness. The co-optimization of the ridge geometry and electrode gap design maintains the EO overlap factor near 0.55, while reducing the half-wave voltage requirement. This results in a half-wave voltage length of V_πL = 1.65 V·cm at a 4.4 μm electrode gap. The optimized geometry and electrode gap (4.4 μm) are essentially temperature-independent: extracted from the Pockels modulation slope, V_πL remains stable at ≈1.65 V·cm (push–pull single-pass; within ~0.3%) across 25~85 °C. Furthermore, an externally imposed substrate temperature rise of 60 K (the upper end of the 25~85 °C FOG operating range) induces a mode-field-weighted thermal residual corresponding to approximately 27% of the Pockels modulation depth at an applied voltage of 5 V. The present study demonstrates that the DC-coupled operation of TFLN sensor-grade modulators is viable across the full FOG temperature range, without dedicated active temperature stabilization, and the residual thermal-bias offset is absorbed by the FOG’s standard closed-loop servo electronics. The results of the study provide quantitative design guidelines for high-performance, environmentally stable TFLN phase modulators in compact FOG systems. Full article

Retrofitting existing buildings has become a critical strategy for reducing energy consumption, improving thermal comfort, and achieving carbon reduction targets in the built environment. Among retrofit measures, wall insulation plays a pivotal role in minimizing heat loss and enhancing building energy efficiency. Conventional insulation materials, although effective, are often associated with high embodied energy, limited recyclability, and environmental concerns. Consequently, bio-based composite materials derived from natural fibers, agricultural residues, and renewable binders have emerged as promising sustainable alternatives. However, the moisture sensitivity of lignocellulosic materials remains a major challenge that can compromise thermal performance, durability, and long-term service life. This review provides a comprehensive and critical assessment of bio-based hydrophobic composite panels for wall insulation in retrofit applications. Unlike previous reviews that have primarily examined bio-based insulation materials, natural-fiber composites, or hydrophobic modifications separately, this study integrates these interconnected research domains within a unified framework. The review systematically examines raw material selection, composite panel manufacturing processes, hydrophobic surface-engineering strategies, thermal and moisture-related performance, durability characteristics, retrofit implementation approaches, and sustainability considerations. The analysis demonstrates that hydrophobic modification significantly reduces moisture uptake, enhances dimensional stability, and preserves thermal-insulation performance under varying environmental conditions. Natural-fiber-based composites, including hemp, flax, jute, bamboo, coconut fiber, and agricultural residues, exhibit competitive thermal conductivity (λ) values while offering reduced environmental impacts compared with conventional insulation materials. Furthermore, the integration of advanced hydrophobic treatments improves resistance to water penetration, biological degradation, and freeze–thaw damage, thereby increasing the long-term reliability of retrofit insulation systems. Full article

Sustainable lightweight materials based on renewable resources have attracted increasing attention as alternatives to synthetic materials. However, developing nanocellulose cryogels with adequate structural integrity and efficient retention of phenolic compounds remains challenging, often requiring furanic and dialdehyde-based additives associated with environmental and health concerns. In this context, tannin-containing nanocellulose cryogels were produced using vanillin and hydrogen peroxide as sustainable modification agents. The effects of the additives on the structural, morphological, colorimetric, mechanical, thermal, and leaching properties of the cryogels were investigated. FTIR and colorimetric analyses revealed the presence of phenolics and the effect of hydrogen peroxide. SEM analysis showed that tannin promoted structural densification, whereas peroxide induced fragmentation of the cryogel network and pore reorganization. These changes influenced density and mechanical performance, with nanocellulose-tannin exhibiting the highest compressive strength and elastic modulus. Thermal conductivity values remained within the range reported for highly porous lignocellulosic materials (38.93–43.79 (mW/m·K)). Tannin leaching demonstrated that peroxide significantly improved tannin retention, especially in the system including vanillin which exhibited only 13,61% tannin release. Overall, vanillin and hydrogen peroxide modified the supramolecular organization and functional properties of the cryogels, highlighting their potential as additives in porous materials for thermal insulation and adsorption applications. Full article

This study investigates an integrated ecological strategy to reduce electricity consumption in semi-collective housing located in the hot–arid climate of Biskra, Algeria, a region with high solar potential. The research combines photovoltaic (PV) electricity generation with passive thermal insulation using a locally sourced bio-based material derived from date palm fibers. The case study includes 104 dwellings within a residential complex of 350 units. Results show that monocrystalline PV panels (350 W) can produce approximately 479 kWh/panel/year. To meet the total annual electricity demand (504,712 kWh), around 1052 panels are required, corresponding to 1714 m² (13.8%) of the available building envelope. This installation area demonstrates the significant photovoltaic potential of the residential complex under hot–arid climatic conditions. Thermal analysis indicates that integrating a 5 cm palm fiber insulation layer increases thermal resistance from 2.06 to 2.62 m²·°C/W and reduces heat flux from 2.18 to 1.72 W/m². This improvement decreases conductive heat transfer through the envelope by approximately 21%, while numerical simulations indicate indoor temperature reductions of 4–8°C during summer conditions. These findings demonstrate that combining PV systems with bio-based insulation significantly enhances energy efficiency and thermal comfort in residential buildings under desert climatic conditions. Full article

While double-layer insulation structures are widely adopted, their thermal performance is critically dependent on the thermophysical behavior of the interstitial air cavity, a variable often oversimplified in current design practices. This article moves beyond generic material descriptions to investigate the specific mechanism of heat transfer transition within sealed air gaps sandwiched between graphite polystyrene boards. The innovation of this experiment lies in the rigorous isolation of air gap thickness as the primary independent variable within a 1 × 1 × 1 m closed building model, instrumented with high-precision GPRS temperature and humidity sensors to capture real-time thermal gradients under the authentic climate conditions of Anyang, Henan. The results demonstrate a non-monotonic relationship between gap thickness and effective thermal resistance, governed by the competition between molecular conduction and buoyancy-driven natural convection. Specifically, the data validates that a 20 mm air gap represents the statistically significant optimum, thereby maximizing insulation efficiency while minimizing radiative heat loss. Using this optimized structure reduces steady-state heat flux compared to monolithic equivalents and aligns with the energy conservation target. Unlike previous studies limited by simulation assumptions or short-term testing, this research provides empirically verified, long-term field data that bridges the gap between theoretical fluid dynamics and practical building envelope engineering. These findings offer a robust, physics-based reference for optimizing double-layer insulation systems in the Central Plains, directly supporting the low-carbon retrofitting of existing building stocks. Full article

Reliable temperature monitoring is essential for the thermal management and safe operation of modern telecommunication equipment. However, conventional temperature sensors are often relatively large and rigid, which limits their applicability for localized temperature measurement on compact electronic components. In this study, a flexible thin-film thermocouple based on NiCr–NiSi thermoelectric materials was developed for temperature monitoring of telecommunication equipment. The sensor adopts a multilayer structure consisting of a polyimide (PI) flexible substrate, an Al₂O₃ insulating layer, NiCr and NiSi thermoelectric films, and a SiO protective layer and was fabricated using magnetron sputtering. Static calibration experiments show that the fabricated sensor exhibits a thermoelectric sensitivity of approximately 40.45 µV/°C, which is close to the reference value of conventional K-type thermocouples, with a relative error of about 1.34%. Repeated heating–cooling cycles demonstrate good repeatability and stable thermoelectric characteristics. Dynamic tests under representative transient thermal conditions showed that the sensor could continuously capture temperature variations without signal interruption or abnormal fluctuations. To further quantify its dynamic behavior, a numerical step-response simulation was performed for the PI/Al₂O₃/NiCr–NiSi/SiO multilayer structure. The simulated thermal time constant and curve-extracted 90% response time were 0.0343 s and 0.0803 s, respectively, under the specified boundary conditions. Owing to its small thickness, low thermal mass, and good mechanical flexibility, the proposed thin-film thermocouple can be conformally attached to compact and curved electronic surfaces, indicating promising potential for real-time localized temperature monitoring of telecommunication equipment and other compact electronic systems. Full article

Fire protection remains one of the key challenges in the field of architectural heritage conservation, particularly for heritage buildings dominated by timber structures, which face greater difficulties in fire prevention and risk assessment. To systematically evaluate the fire safety performance of high-rise timber heritage buildings, this study takes the Shengjin Pagoda, a typical brick–timber pavilion-style ancient tower in Jiangxi Province, China, as the research object. A three-dimensional performance-based fire assessment framework was developed using Fire Dynamics Simulator (FDS) and PyroSim. Based on field survey data and historical documentation, the geometric characteristics, material properties, and vertical circulation system of the pagoda were reconstructed. Three representative fire scenarios, including bottom-floor ignition, simultaneous multi-level ignition, and wind-driven top-floor ignition, were established to investigate smoke propagation, thermal insulation degradation, and the thermal response of critical timber components under different fire conditions. The results show that brick walls provide effective thermal insulation during the early stages of fire, with efficiency exceeding 90%, but this decreases to approximately 55% in upper regions due to chimney-effect-driven smoke accumulation. Under wind-driven top-floor ignition, exposed dougong components can reach temperatures of 782 °C, resulting in a progressive “top-down and outside-in” failure mechanism. The study reveals the dominant smoke-driven heat transfer pathways and the failure sequence of critical load-bearing elements. Based on these findings, a performance-based fire protection strategy incorporating vertical virtual smoke control zoning and fire-resistance enhancement of key structural components is proposed to support the sustainable conservation of historic high-rise timber structures. Full article

Fenestration systems play a critical role in building thermal performance, particularly in cooling-dominated climates where envelope inefficiencies directly amplify electricity demand. In Saudi Arabia and other Gulf Cooperation Council (GCC) countries, cooling accounts for the majority of building energy consumption. Nevertheless, the facade and insulated glass industries are experiencing rapid market expansion. Despite this technological evolution, prevailing regulatory frameworks, including the Saudi Building Code Energy Conservation Requirements (SBC 601), ASHRAE 90.1, and the International Energy Conservation Code (IECC), primarily rely on area-weighted U-values and solar heat gain coefficients (SHGCs) without explicitly integrating multidimensional thermal bridge effects such as linear thermal transmittance (ψ). This paper examines the omission of ψ from current energy compliance systems, evaluates its implications in cooling-dominated climates, and proposes a phased regulatory integration pathway aligned with sustainability objectives under Vision 2030. Literature reports indicate that thermal bridges may increase cooling loads by up to 25% and total building energy use by 5–30%, depending on climate severity and façade configuration. The findings highlight the need to transition from simplified prescriptive compliance toward a physics-informed governance capable of addressing evolving facade complexity in hot-arid environments. The proposed framework offers a systematic pathway for integrating linear thermal transmittance requirements while supporting regional sustainability goals and advancing high-performance building technologies. Full article

The increasing power density of modern electronic systems intensifies challenges related to heat dissipation and long-term reliability. Insulated metal substrates (IMS), particularly three-dimensional (3D), are increasingly used as integrated thermal–mechanical solutions in high-power electronics. However, their complex geometry and material interfaces introduce new reliability concerns, especially at solder joints. This study investigates the evolution of intermetallic compounds (IMCs) in solder joints formed on 3D aluminum IMSs with ENIG metallization, focusing on SAC305 and Sn42Bi57Ag1 solder alloys. Solder joints were subjected to environmental aging under high-temperature, high-humidity, and thermal-shock conditions to simulate realistic service environments. Microstructural and compositional analyses of the interfacial IMC layers were performed, together with measurements of IMC thickness evolution. The results show that aging significantly modifies the chemical composition and morphology of IMC layers in both solder systems. In SAC305 joints, progressive development of (Cu,Ni)₆Sn₅ phases with increasing Cu participation was observed. In Sn42Bi57Ag1 joints, Bi affected reaction kinetics but did not alter the diffusion-controlled nature of IMC growth. Thickness measurements indicate higher sensitivity of SAC305 joints to environment-assisted interfacial degradation, while Sn42Bi57Ag1 joints exhibit greater susceptibility to stress-assisted IMC growth during severe thermal cycling. These findings highlight the distinct reliability behaviors of tested solders on 3D IMSs and provide insight into their suitability for high-power electronic applications. Full article

Various forms of Bacopa monnieri (BM), including original powder (Mp), tea form (Mo), and post-extraction residues (Mf), were used as natural bio-based additives in rigid polyurethane–polyisocyanurate (RPU/PIR) foams. The study investigated the influence of BM form and content on the physical, mechanical, thermal, and flammability properties of the foams. The results demonstrated that both the type and concentration of BM significantly affected foam performance. Foams containing Mf exhibited the lowest apparent density and reduced brittleness, whereas foams modified with Mp showed the highest compressive strength. The incorporation of BM also contributed to reduced flammability and enhanced thermal resistance of the foams. Thermal analysis indicated that BM additives modified the degradation behavior of RPU/PIR foams by promoting char formation and improving thermal stability at elevated temperatures. In particular, samples containing tea and post-extraction residues showed increased stability of the carbonized residue during the final degradation stage. The most favorable overall properties were obtained for BM contents between 3 and 7 wt%, while higher filler concentrations negatively affected the structural integrity of the foam matrix. The results confirm that the performance of RPU/PIR foams strongly depends on the balance between matrix continuity and biofiller functionality. The obtained materials show potential for application in floristry products and lightweight insulating systems where low density, dimensional stability, and enhanced thermal resistance are required. Full article

The safe disposal of sharps, particularly acupuncture and dry needling needles, remains a challenge in clinical and therapeutic environments, where inadequate management increases the risk of occupational injuries and infections. Commercial needle disposal devices are often costly, non-portable, and closed-source, limiting their adoption in small clinics and low-resource contexts. This work presents the design, construction, and validation of an open-source electric needle incinerator developed as a low-cost, safe, and reproducible alternative for biomedical waste management. The device was designed using accessible materials, 3D-printed components, and standard electronic parts, ensuring ease of replication. Detailed build and operating instructions are provided, to facilitate reproduction and future development of the system. Validation tests confirmed that the prototype incinerates individual needles in 3–5 s, processing typical sessions of 5–20 needles without performance degradation. Safety was ensured through thermal insulation, protective casing, and compliance with international standards. The fabrication cost of approximately 199 USD represents a reduction of over 65% compared to commercial devices priced at 600–1500 USD. By openly releasing the design, this contribution supports the hardware community with a replicable solution that enhances occupational safety, reduces costs, and fosters innovation in therapeutic and educational contexts. Full article

In industrial applications such as in situ leaching and uranium mining, permanent magnet synchronous motors (PMSMs) for submersible pumps are frequently connected to frequency converters via long cables. During this long-distance transmission, traveling wave reflections induced by high-frequency pulse width modulation (PWM) generate severe transient overvoltages that threaten motor insulation. Because installation space at deep-well motor terminals is severely restricted, overvoltage suppression must be implemented at the inverter output. Here, the parameter design and optimization of a passive LC filter specifically developed for 250 Hz high-frequency PMSMs are presented. The optimal inductance and capacitance parameters were determined by balancing multiple operational constraints, including fundamental voltage drop, high-frequency harmonic attenuation, and the avoidance of low-order harmonic resonance. Furthermore, the anti-saturation performance of the magnetic core material, evaluated thermal characteristics through electromagnetic-thermal co-simulation, and analyzed the risk of self-excited oscillation between the filter capacitors and the motor was analyzed. Finally, hardware experiments conducted on a 20 m cable test bench validate that the designed LC filter effectively mitigates terminal overvoltage. The peak terminal voltage was reduced from 900 V to 505 V, and total harmonic distortion (THD) was limited to below 5%. This design provides a highly reliable, space-efficient solution for overvoltage suppression in high-speed, long-cable motor drive systems. Full article

With the rapid construction of new power systems characterized by high renewable energy penetration, high power electronics integration, and high voltage levels, the insulation reliability of critical power equipment—including cable accessories, gas-insulated switchgear (GIS), and power electronic modules—faces unprecedented challenges. Field grading materials (FGM), as core functional media for adaptive electric field homogenization and insulation failure prevention, have emerged as a research hotspot spanning materials science, electrical engineering, and polymer engineering. Starting from the current research status of FGM, this review systematically summarizes filler optimization strategies, covering single fillers, hybrid fillers, trace co-fillers, and structural modification approaches. The applications of FGM in transmission cables, GIS, high-voltage electrical machines, and wide-bandgap power electronic modules are then elaborated in detail. Emphasis is placed on performance enhancement routes of FGM, particularly thermal conductivity improvement via constructing three-dimensional thermally conductive networks and intelligent early warning based on thermochromic materials. Finally, the existing bottlenecks of FGM are analyzed in terms of material stability, multi-physical field coupling adaptation, and engineering industrialization. Future development trends are prospected toward high-performance, multifunctional, intelligent, and engineering-oriented FGM. This review aims to provide theoretical references and technical support for the design and application of advanced FGM in new power systems. Full article