Search Results (145)

The photon spin Hall effect (PSHE) arises from the spin–orbit interaction of light. Metasurfaces enable precise control over the PSHE through their influence. Using electromagnetic simulations as its foundation, this work engineers a metal–insulator–metal (MIM) metasurface for generating vortex beams in the near-infrared band, targeting enhanced modulation of the PSHE. Electromagnetic simulations embed vanadium dioxide (VO₂)—a thermally responsive phase-change material—within the MIM metasurface architecture. Numerical evidence confirms that harnessing VO₂’s insulator–metal-transition-mediated optical switching dynamically tailors spin-dependent splitting in the illuminated MIM-VO₂ hybrid, thereby achieving a significant amplification of the PSHE displacement. Electromagnetic simulations determine the reflection coefficients for both VO₂ phase states in the MIM-VO₂ structure. Computed spin displacements under vortex beam incidence reveal that VO₂’s phase transition couples to the MIM’s top metal and dielectric layers, modifying reflection coefficients and producing phase-dependent PSHE displacements. The simulation results show that the displacement change of the PSHE before and after the phase transition of VO₂ reaches 954.7 µm, achieving a significant improvement compared with the traditional layered structure. The dynamic modulation mechanism of the PSHE based on the thermal–optical effect has been successfully verified. Full article

Advancements in thermoregulating textiles have been propelled by innovations in nanotechnology, composite materials, and smart fiber engineering. This article reviews recent scholarly papers on experimental passive and active thermoregulating textiles to present the latest advancements in these fabrics, their mechanisms of thermoregulation, and their feasibility for use. The review underscores that phase-change materials enhanced with graphene, boron nitride, and carbon nanofibers offer superior thermal conductivity, phase stability, and flexibility, making them ideal for wearable applications. Shape-stabilized phase-change materials and aerogel-infused fibers have shown promising results in outdoor, industrial, and emergency settings due to their durability and high insulation efficiency. Radiative cooling textiles, engineered with hierarchical nanostructures and Janus wettability, demonstrate passive temperature regulation through selective solar reflection and infrared emission, achieving substantial cooling effects without external energy input. Thermo-responsive, shape-memory materials, and moisture-sensitive polymers enable dynamic insulation and actuation. Liquid-cooling garments and thermoelectric hybrids deliver precise temperature control but face challenges in portability and power consumption. While thermoregulating textiles show promise, the main challenges include achieving scalable manufacturing, ensuring material flexibility, and integrating multiple functions without sacrificing comfort. Future research should focus on hybrid systems combining passive and active mechanisms, user-centric wearability studies, and cost-effective fabrication methods. These innovations hold significant potential for applications in extreme environments, athletic wear, military uniforms, and smart clothing, contributing to energy efficiency, health, and comfort in a warming climate. Full article

The development of sustainable insulation materials plays a crucial role in creating energy-efficient and environmentally responsible buildings. This study investigates eco-friendly composite materials based on plaster and wood shavings for insulation purposes. Incorporating wood shavings into plaster improves thermal insulation and mechanical behavior by enhancing porosity, reducing density, and improving bonding. As the wood shaving content increases from 5% to 15%, the thermal conductivity decreases from 0.252 W/mK to 0.099 W/mK, reflecting superior insulating performance. Concurrently, thermal resistance rises, showcasing enhanced insulation. The material also demonstrates increased flexibility, with the Young’s modulus decreasing at higher wood shaving proportions. Numerical simulations confirm these observations, indicating a 12 K temperature drop for composites with 15% wood shavings compared to a 6 K drop for pure plaster. This study suggests that an insulation thickness of 6–7 cm for the 15% composite strikes the optimal balance between performance and cost-efficiency. The findings underscore the potential of wood shavings to significantly enhance the thermal efficiency and mechanical adaptability of plaster composites, promoting sustainable and effective building insulation solutions. Full article

In recent years, the building insulation layer peeling caused by quality problems has brought about safety hazards to human life. Existing means of non-destructive testing of building insulation layers, including laser scanning, infrared thermal imaging, ultrasonic testing, acoustic emission, ground-penetrating radar, etc., are unable to simultaneously guarantee the detection depth and resolution of the insulation layer defects, not to mention high-precision imaging of the insulation layer structure. A new type of high-precision imaging radar is specifically designed for the quantitative quality inspection of external building insulation layers in this paper. The center frequency of the radar is 8800 MHz and the −10 dB bandwidth is 3100 MHz, which means it can penetrate the insulated panel not less than 48.4 mm thick and catch the reflected wave from the upper surface of the bonding mortar. When the bonding mortar is 120 mm away from the radar, the radar can achieve a lateral resolution of about 45 mm (capable of distinguishing two parties of bonding mortar with a 45 mm gap). Furthermore, an ultra-wideband high-bunching antenna is designed in this paper combining the lens and the sinusoidal antenna, taking into account the advantages of high directivity and ultra-wideband. Finally, the high-precision imaging of data collected from multiple survey lines can visually reveal the distribution of bonded mortar and the bonding area. This helps determine whether the bonding area meets construction standards and provides data support for evaluating the quality of the insulation layer. Full article

Vanadium dioxide (VO₂) is a well-known phase-change material that exhibits a thermally driven insulator-to-metal transition (IMT) near 68 °C, leading to significant changes in its electrical and optical properties. This transition is governed by structural modifications in the VO₂ crystal lattice, enabling dynamic control over absorption, reflection, and transmission. Despite its promising tunability, VO₂-based optical absorbers face challenges such as a narrow IMT temperature window, intrinsic optical losses, and fabrication complexities associated with multilayer designs. In this work, we propose and numerically investigate a single-layer VO₂-based optical absorber for the visible spectrum using full-wave electromagnetic simulations. The proposed absorber achieves nearly 95% absorption at 25 °C (insulating phase), which drops below 5% at 80 °C (metallic phase), demonstrating exceptional optical tunability. This behavior is attributed to VO₂’s high refractive index in the insulating state, which enhances resonant light trapping. Unlike conventional multilayer absorbers, our single-layer VO₂ design eliminates structural complexity, simplifying fabrication and reducing material costs. These findings highlight the potential of VO₂-based crystalline materials for tunable and energy-efficient optical absorption, making them suitable for adaptive optics, smart windows, and optical switching applications. The numerical results presented in this study contribute to the ongoing development of crystal-based phase-transition materials for next-generation reconfigurable photonic and optoelectronic devices. Full article

Moisture ingress in power distribution cable bodies can lead to insulation degradation, jeopardizing the operational safety of power grids. However, current cable maintenance technologies lack effective diagnostic methods for identifying moisture defects in cable bodies. To address this gap, this paper proposes a dynamic frequency domain reflectometry (D-FDR) method for moisture localization and diagnosis in power distribution cables. Leveraging the temperature-sensitive nature of moisture defects—in contrast to the temperature-insensitive characteristics of other defects—the method involves the application of thermal excitation to induce differential dynamic changes in the distributed capacitance of moisture-affected cable segments compared to normal segments, enabling the precise identification and diagnosis of moisture ingress. Simulations and experiments confirm that moisture ingress in cable bodies increases the distributed capacitance, generating reflection peaks at corresponding distances on frequency domain localization plots. Under thermal excitation, the reflection peak amplitude of moisture defects exhibits a temperature-dependent decrease, distinct from the behavior of intact cables (amplitude increase) and copper shielding layer damage (negligible variation). By utilizing the dynamic characteristics of reflection peak amplitudes as diagnostic criteria, this method is able to accurately localize and diagnose moisture defects in cable bodies. Full article

The use of renewables in heat production requires methods to overcome the issue of asynchronous heat load and energy production. The most effective method for analyzing the intricate thermal dynamics of an existing building is through transient simulation, utilizing real-world weather data. This approach offers a far more nuanced understanding than static calculations, which often fail to capture the dynamic interplay of environmental factors and building performance. Transient simulations, by their nature, model the building’s thermal behavior over time, reflecting the continuous fluctuations in temperature, solar radiation, and wind speed. Leveraging actual meteorological data enables the simulation model to faithfully capture system dynamics under realistic operational scenarios. This is crucial for evaluating the effectiveness of heating, ventilation, and air conditioning (HVAC) systems, identifying potential energy inefficiencies, and assessing the impact of various energy-saving measures. The simulation can reveal how the building’s thermal mass absorbs and releases heat, how solar gains influence indoor temperatures, and how ventilation patterns affect heat losses. In this paper, a household heating system consisting of an air source heat pump, PV, and buffer tank is simulated and analyzed. The 3D model accurately represents the building’s geometry and thermal properties. This virtual representation serves as the basis for calculating heat losses and gains, considering factors such as insulation levels, window characteristics, and building orientation. The approach is based on the calculation of building heat load based on a 3D model and EN ISO 52016-1 standard. The heat load is modeled based on air temperature and sun irradiance. The heating system is modeled in EBSILON professional 16.00 software for the calculation of transient 10 min time step heat production during the heating season. The results prove that a buffer tank with the right heat production control system can efficiently increase the auto consumption of self-produced PV electric energy, leading to a reduction in environmental effects and higher economic profitability. Full article

A biopolymer was synthesized using starch, cashew nutshell liquid (CNSL), and the commercial fertilizer diammonium phosphate (DAP). The biopolymer and its constituents were characterized using SEM, infrared spectroscopy, X-ray diffraction (XRD), ultraviolet–visible diffuse reflectance spectroscopy (UV-Vis DRS), and thermal analysis by TGA and DSC. The results showed that fertilizer particles could be encapsulated by the starch and CNSL matrix. Functional groups and ions in the biopolymer showed characteristic bands associated with starch, CNSL, and DAP fertilizer. Moreover, the biopolymer diffraction peaks contained XRD peaks of starch and DAP. The crystallinity of the biopolymer decreased. Starch, CNSL, and DAP electronic transitions appeared in the biopolymer, with possible signal overlapping. The bandgap of starch and biopolymer did not differ significantly (6.19 and 6.16 eV, respectively). Both materials acted as insulators. Differential scanning calorimetry/thermogravimetric evidenced the materials’ thermal behavior, where water elimination, degradation, oxidation, and gas formation were registered. Full article

This study establishes a numerical simulation model based on heat and mass transfer theory to reflect the variations in temperature and humidity conditions within a tunnel. It analyzes the impact of high-temperature fissure water, humid porous media, and drainage methods on the temperature and humidity distribution in a tunnel. The results indicate the following: (1) When the area of the humid porous media increases from 150 m² to 300 m², the relative humidity (RH) of the air in the tunnel rises from 52.7% to 55.8%, but the impact on air temperature (T_a) is minimal. (2) The heating and humidification effects of hot water in a drainage ditch on the airflow cannot be overlooked. Meanwhile, the hot water transfers heat to the surrounding rock, with heat transfer predominantly driven by the surrounding rock convection. Compared to a drainage pipe, the heat transfer amount increases by 44.9%, and RH rises by 9.3%. (3) For every increase of 5 °C in water temperature (water volume of 90 m³/h), the ventilation outlet T_a linearly increases by 0.15 °C, and the rate of increase in RH accelerates with rising water temperature. (4) Covering a drainage ditch with a cover plate can reduce RH by 12.3%, while spraying a 10 cm insulation layer on the tunnel walls can significantly lower T_a by 0.66 °C. These findings provide a potential solution for the application of insulation materials in reducing the thermal hazards of deep high temperatures. Full article

A possible way to solve the problem of energy saving in construction is to introduce energy-efficient buildings at the design stage and, in particular, during retrofit. Therefore, the purpose of this study is to conduct a theoretical analysis of thermal resistance and energy loads on a building in cold climatic conditions. The study of these values was carried out in the ANSYS software package and the Maple computer algebra system, respectively. This study examines four types of structures: the existing facade of a building constructed in 1966, a traditional ventilated facade, and two designs featuring alternating insulation layers with enclosed air channels and with or without heat-reflecting screens in the insulation layer. The results of this study show that the new design incorporating heat-reflecting screens in the insulation layer is 1.15 times more energy-efficient in terms of thermal resistance than the proposed design without such screens. The effectiveness of the proposed new design with heat-reflecting screens in the insulation layer is also confirmed through an analysis of the thermal protection of the building, where the auxiliary indicators, specific characteristics, and complex values of energy efficiency and energy load of the building show greater efficiencies of 1.6, 1.03, and 1.05 times, respectively, compared to the other studied structures. The comprehensive research results presented in this study indicate that the use of energy-efficient wall structures for the retrofit of external enclosures can significantly improve the thermal performance of buildings. It was also determined that the use of such wall structures can significantly enhance the building’s overall energy efficiency rating. The findings of this study highlight that the proposed solutions can contribute to significant energy savings in buildings, while the newly developed structures can serve as valuable additions to the existing catalog of energy-efficient external wall designs. Full article

This study proposes a method for estimating the junction temperature of power semiconductors, particularly IGBTs (Insulated Gate Bipolar Transistors) and diodes. Traditional temperature measurement methods using NTC (Negative Temperature Coefficient) sensors have limitations in reflecting dynamic conditions in real time, as temperature changes take time to reach the sensors. To address this, this study proposes a junction temperature estimation method using RC curve fitting and a thermal impedance model. This model represents the thermal behavior of IGBTs and diodes using a Foster thermal network that considers the resistance and capacitance of the heat transfer path. In particular, transient temperature estimation considering thermal coupling enables the prediction of temperature changes in IGBTs and diodes. To verify the proposed temperature estimation method, experiments were conducted to build the model based on data measured with an infrared thermal camera and NTC sensors. The model’s estimated results were compared with actual values across 25 operating regions, achieving a maximum MAE (Mean Absolute Error) of 2.26 °C. A comparative analysis of first-, second-, third-, and fourth-order Foster networks revealed that, while higher orders improve accuracy, gains beyond the second order are minimal relative to computational demands. This study contributes to enhancing not only the reliability of power semiconductor modules but also minimizing the temperature margin for inverters by estimating the junction temperature with better dynamic performance than that achieved by NTC sensors. Full article

Due to massive urbanization and industrialization, modern constructions tend to be designed as technique-dependent, at the cost of high consumption and emissions for indoor environment control such as heating ventilation and air conditioning. Space heating accounts for about 40% of total building energy usage in northern China in winter. This calls for self-reflection and tracing of local traditional architectural wisdom. In this paper, Sibe Traditional Houses were chosen as a typical illustrative example to reveal the building mechanisms behind such local-adaptive traditional constructions. Based on the field investigation in Shifosi Village, a traditional Sibe settlement in Shenyang City, northern China, thermal modeling and indoor heating effects are studied in Sibe Traditional Houses with unique building spatial patterns. The indoor thermal environment is comparatively analyzed for both passive envelope insulation and active heating considerations. Preliminary results indicate that enhancing roof thermal insulation enhancement is the key passive strategy for improving indoor thermal comfort in winter. It also suggests that a space-heating configuration that combines the traditional “kang” with the architectural layout has a more significant effect on the enhancement of indoor thermal comfort in Sibe dwellings. This paper can provide methodological support and an application reference for the improvement of indoor thermal environment of traditional village dwellings. Full article

This study examines the effects of thermal (1000 °C), hydrothermal (100 °C), mechanochemical (ambient T), and microwave (~100 °C) treatments on three types of Chinese vermiculites, one with lower potassium content than the others. The goal was to obtain materials with enhanced properties related to specific surface areas. The response of the vermiculites to treatments and their physicochemical properties were analyzed using X-ray diffraction (XRD), thermal analysis (TG and DTG), and textural characterization via the BET method. XRD analyses showed similar mineral composition in treated and untreated samples, but the treatments affected the intensity and width of phase reflections, altering crystallinity and structural order, as well as the proportions of vermiculite, hydrobiotite, and phlogopite. Thermogravimetric analysis revealed two mass loss stages: water desorption (from 25 °C to about 250 °C) and recrystallization or dehydroxylation (above 800 °C). The isotherms indicated mesoporous characteristics, with hydrothermally CO₂-treated samples having the highest specific surface area and adsorption capacity. The samples with vermiculite, hydrobiotite, and phlogopite generally showed moderate to high specific surface area (S_BET) values, and mechanochemical treatments significantly increase S_BET and pore volume (V_p) in the vermiculite and hydrobiotite samples. Crystallinity affects S_BET, average V_p, and average pore size, and its monitoring is crucial to achieve the desired material characteristics, as higher crystallinity can reduce S_BET but improve mechanical strength and thermal stability. This study highlights the influence of different treatments on vermiculite properties, providing valuable insights into their potential applications in various fields (such as thermal insulation in vehicles and aircraft, and the selective adsorption of gases and liquids in industrial processes, improving the strength and durability of building materials like cement and bricks). Full article

This manuscript presents a theoretical study of a newly developed energy-efficient external wall structure in comparison with a traditional ventilated facade. To conduct numerical studies based on mathematical models of the heat transfer of water vapor filtration through a multilayer filler structure with ventilated and non-ventilated air gaps, a calculation method was developed that additionally considers the presence of heat-reflecting screens and different variations in the geometric parameters of air gaps and thermal insulation layers. The study results demonstrated that the new energy-efficient multilayer wall structure was 6.1–7.2% more efficient in terms of heat transfer resistance than the traditional one, and due to the presence of heat-reflecting screens, the efficiency increased to 15.2–16.3% depending on the geometric parameters of the air and thermal insulation layers of the wall structure. In addition, in all the considered variants of the filler structure geometry (i.e., with closed and ventilated air gaps), there were water vapor condensation zones, but it was established that according to the value of the inadmissibility of moisture accumulation in multilayer wall structures, over the annual period of operation, the structures complied with the standard climatic conditions of Shymkent. The results of this study thus positively complement the existing catalog of energy-efficient wall structures, and the new wall structure can be used while considering the necessary geometric parameters of air and heat-insulating layers when designing buildings in the corresponding climatic conditions. Full article

The increased concerns about climate change, diminishing natural resources, and environmental degradation call for deep research into new environmentally friendly building systems that use natural or recycled materials. The article presents an assessment of the environmental and climatic benefits associated with the construction of a tiny house made of quincha, a building system based on a wooden structure filled with locally sourced earth and straw. The tiny house is located in the Elqui Valley, in the Chilean region of Coquimbo, and it is designed to be compact, functional, comfortable, and efficient. The study uses a life cycle approach to assess the environmental impacts of building construction, maintenance, and end-of-life treatment, comparing the adopted quincha solution with four hypothetical scenarios using industrial, prefabricated, and/or synthetic construction materials currently adopted in the region. The thermal performance of all the analyzed solutions is also included in order to provide insights into the impact of the operational phase. This paper demonstrates that the quincha solution, in the face of lower thermal insulation compared to the other prefabricated solutions (the U-value of the quincha wall is 0.79 W/m²K while the U-value of the best prefabricated wall is 0.26 W/m²K), has higher thermal inertia (time lag (TL) and decrement factor (DF) are, respectively, 6.97 h and 0.60, while other systems have a TL below 4 h and DF higher than 0.81). For a quantitative environmental evaluation, the carbon footprint (global warming potential), water footprint, and embodied energy indicators are assessed through LCA, which takes into account the mass of the materials and their emission factors. The effectiveness of the quincha solution is also reflected in environmental terms; in fact, it is found to have the lowest carbon footprint (2635.47 kgCO₂eq) and embodied energy (42.7 GJ) and the second-lowest water footprint (2303.7 m³). Moreover, carbon sequestration values, which are assessed by estimating the carbon contained in building systems using wood and straw, demonstrate that the quincha tiny house is the only solution that can theoretically reach carbon neutrality (with its carbon storage value at −5670.21 kgCO₂eq). Full article