Search Results (6,295)

The microwave sintering of various materials is a promising technology, which has received much attention for its demonstrated potential. Both the conventional (furnace) and microwave sintering rely on thermal activation for particle bonding, for which a high temperature environment is essential. In comparison, microwave treatment achieves the same degree of densification as furnace sintering in a time shorter by a factor of two or higher and at a temperature lower by 5% to 15%. However, this is a phenomenon not yet fully understood and is commonly referred to as a non-thermal effect. Its understanding is a subject of both physics and practical interest. The non-thermal effect has been studied under years of research in order to broaden the applicability of microwave sintering. Here, we first present an overview of experimentally demonstrated advantages of microwave sintering. To facilitate further studies, we then review the literature and put together four commonly recognized interpretations of the non-thermal effects: the ponderomotive force-driven mass transport, magnetism-created cohesive forces, polarization charge-enhanced wave electric field, and polarization charge-induced attractive force among the sintered particles, with an emphasis on recent development. Full article

The field of additive manufacturing increasingly demands innovative solutions to optimize material processing, improve equipment efficiency, and address maintenance challenges in high-utilization environments. This study investigates the operation and management of an FFF 3D printing production line comprising eight remotely controlled printers. The system supports custom manufacturing and educational activities, focusing on processing a range of thermoplastics and composite materials. A key contribution of this work lies in addressing the impact of frequent hardware servicing caused by shared use among users. Augmented reality (AR)-guided assembly and disassembly workflows were developed to ensure uninterrupted operations. These workflows are accessible via smart devices and provide step-by-step guidance tailored to specific material and equipment requirements. The research evaluates the effectiveness of AR-enhanced maintenance in minimizing downtime, extending equipment lifespans, and ensuring consistent material performance during manufacturing processes. Furthermore, it explores the role of AR in maintaining the mechanical, thermal, and chemical properties of processed materials, ensuring high-quality outputs across diverse applications. This paper highlights the integration of advanced material processing methodologies with emerging technologies like AR, aligning with the focus on enhancing manufacturing schemes. The findings contribute to improving process efficiency and adaptability in additive manufacturing, offering insights into scalable solutions for remote-controlled and multi-user production systems. Full article

In this study, we present an exact solution to the Lindblad master equation describing the interaction of two quantized electromagnetic fields in a decaying cavity coupled to a thermal reservoir at a finite temperature. The solution is obtained using the superoperator technique, leveraging commutation relations to factorize the exponential of the Lindblad superoperators into a product of exponentials. To demonstrate the applicability of this approach, we analyze the dynamics of the system both analytically and numerically for two initial conditions: nonentangled and entangled coherent states, exploring their temporal evolution. Additionally, we employ entropy and quantum discord analysis to characterize quantum correlations and analyze the behavior of entanglement (or lack thereof) during the evolution. This comprehensive analysis provides valuable insights into the behavior of open quantum systems and their interaction with the environment. Full article

Color stability of acrylic resins is essential for preserving the aesthetic appearance of denture bases over time. This study explores how food pigments and thermal changes affect the color stability of commonly used denture base resins. Four acrylic resins were tested: three heat-cured acrylic resins with different characteristics (Zhermack^® Villacryl H Plus V2, H Plus V4, and H Rapid FN V4) and one self-cured acrylic resin (Zhermack^® Villacryl S V4). To simulate the oral environment, the resins underwent 1000 thermal cycles between 5 °C and 55 °C, followed by a 7-day immersion period in beverages such as coffee, red wine, a caramel-colored soft drink (cola), and distilled water (control), forming sixteen group of specimens (n = 5). Color changes (∆E) were measured using the VITA Easyshade V^® spectrophotometer, following the CIEDE2000 standard. The findings revealed that thermal aging caused noticeable color changes in all resins (p < 0.001). Red wine led to the most intense discoloration, followed by coffee. The caramel-colored soft drink caused moderate staining, while distilled water had a negligible effect. The type of polymerization did not affect the degree of discoloration, as no significant differences were found between the resins after exposure to beverages (p > 0.05). Overall, this study highlights how both internal and external factors impact the appearance of acrylic resins. Thermal aging can accelerate polymer degradation, while pigments in beverages cause visible staining. Among the tested beverages, red wine proved to be the most aggressive due to its high pigment concentration and low pH. These findings emphasize the need for improved material formulations to enhance the longevity and aesthetic performance of dentures. Full article

The problem of early crack formation caused by temperature stresses in hardening concrete is very relevant for massive monolithic reinforced concrete structures. The aim of the work is to develop a method for thermal cracking risk prediction during the construction of massive monolithic reinforced concrete structures. The innovation of the research consists in taking into account the dependence of the concrete elastic modulus and strength on the time and temperature of hardening. The significance of the study lies in analysis of methods for reducing the risk of early cracking using the example of a real structure. The object of the study is a fragment of a massive monolithic dock wall. The analysis is performed by the finite element method using a program developed by the authors in the MATLAB environment. Verification of the developed software was performed by comparison with the solution in ANSYS using a linear elastic model without time dependence of the elastic modulus. Next, various options were used to set the dependence of the mechanical characteristics of concrete on the time and temperature of hardening. An analysis was conducted of the possibility of reducing the risk of early cracking by reducing the length of the concrete block, correcting the heat exchange conditions of the surfaces, and reducing the heat generation of concrete. Full article

As people spend the majority of their time indoors, maintaining a comfortable and suitable thermal environment within buildings is essential for improving quality of life. Previous studies in Japan have investigated the wet-bulb globe temperature (WBGT) in indoor environments; however, studies primarily focused on residential buildings are lacking. Therefore, a field survey of 17 Japanese dwellings was carried out during the summer, for which a total of 1166 thermal sensation votes (TSVs) were collected from 23 respondents. The results show that the average indoor air temperature is 26.4 °C, which is 1.6 °C lower than the recommendation for summer temperature by the Japanese government. The variation in globe temperature and WBGT indicates that there are significant differences in cooling usage behavior, with a strong correlation between WBGT and indoor globe temperature. The acceptable indoor globe temperature exhibits a wider range in free-running (FR) mode than in cooling (CL) mode. The mean comfort temperature was 26.9 °C in FR mode, while it was 27.0 °C in CL mode. These findings indicate that the occupants felt comfortable at the high indoor temperature, suggesting there is a possibility to reduce the energy used for cooling. Full article

Aiming at the problem that asphalt pavement materials in plateau areas are vulnerable to freeze-thaw damage, research was carried out on asphalt pavements of representative road sections, and the temperature within the pavement structure was monitored using buried sensors. Based on this, an indoor test method for high-frequency freeze-thaw was established, and UV, thermo-oxygen-aging and high-frequency freeze-thaw tests were combined. The effects of aging and maximum aggregate particle size on the resistance of asphalt mixtures to high-frequency freeze-thaw were investigated using the splitting strength ratio, mass-loss rate and void-ratio changes by employing the newly made RS-type modified asphalt in the laboratory. At the same time, the high-frequency freeze-thaw resistance of the asphalt mixture was compared with that of the SS/SMA-13 asphalt mixture on the top layer of a representative road section. The results show that UV aging at 180 h followed by thermal-oxygen aging at 120 h has the greatest impact on the asphalt mixture; in this condition, the high-frequency freeze-thaw-cycle asphalt mixture with freeze-thaw damage is affected by the rule of change of the third-degree polynomial. In the plateau environment conditions, compared with the original pavement material (SS-type modified asphalt), the RS-type modified asphalt has better anti-aging properties, adhesion properties and elasticity performance. Full article

Urban heat islands (UHIs) increase urban warming and reduce outdoor thermal comfort due to changing surface characteristics and climate change. This study investigates the role of green walls (GWs) in mitigating UHI, improving outdoor thermal comfort, and reducing carbon emissions under current and future (2050) scenarios. Focusing on Via della Consolata, Turin, Italy, the study combines remote sensing for UHI detection and numerical simulations for thermal analysis during seasonal extremes. The results show that GWs slightly reduce air temperatures, with a maximum decrease of 1.6 °C in winter (2050), and have cooling effects on mean radiant temperature (up to 2.27 °C) during peak summer solar radiation. GWs also improve outdoor comfort, reducing the Universal Thermal Climate Index by 0.55 °C in the summer of 2050. The energy analysis shows that summer carbon emission intensity is reduced by 31%, despite winter heating demand increasing emissions by 45%. The study highlights the potential of GWs in urban climate adaptation, particularly in dense urban environments with low sky view factors. Seasonal optimization is crucial to balance cooling and heating energy demand. As cities face rising temperatures and heat waves, the integration of GWs offers a sustainable strategy to improve microclimate, reduce carbon emissions, and mitigate the effects of UHI. Full article

A comfortable outdoor environment, like its indoor counterpart, can significantly enhance the quality of life and improve the physical and mental health of elderly populations. Urban spatial morphology is one of the key factors influencing outdoor environmental performance. To explore the interactions between urban spatial morphology and the outdoor environment for the elderly, this study utilized parametric tools to establish a performance-driven workflow based on a “morphology generation–performance evaluation–morphology optimization” framework. Using survey data from 340 elderly neighborhoods in Beijing, a parametric urban morphology generation model was constructed. The following three optimization objectives were set: maximizing the winter pedestrian Universal Thermal Climate Index (UTCI), minimizing the summer pedestrian UTCI, and maximizing sunlight hours. Multi-objective optimization was conducted using a genetic algorithm, generating a “morphology–performance” dataset. Subsequently, the XGBoost (eXtreme Gradient Boosting) and SHAP (Shapley Additive Explanations) explainable machine learning algorithms were applied to uncover the nonlinear relationships among variables. The results indicate that optimizing spatial morphology significantly enhances environmental performance. For the summer elderly UTCI, the contributing morphological indicators include the Shape Coefficient (SC), Standard Deviation of Building Area (SA), and Deviation of Building Volume (SV), while the inhibitory indicators include the average building height (AH), Average Building Volume (AV), Mean Building Area (MA), and floor–area ratio (FAR). For the winter elderly UTCI, the contributing indicators include the AH, Volume–Area Ratio (VAR), and FAR, while the inhibitory indicators include the SC and porosity (PO). The morphological indicators contributing to sunlight hours are not clearly identified in the model, but the inhibitory indicators for sunlight hours include the AH, MA, and FAR. This study identifies the morphological indicators influencing environmental performance and provides early-stage design strategies for age-friendly neighborhood layouts, reducing the cost of later-stage environmental performance optimization. Full article

This paper describes the development of an ice creation model to be used within the framework of a model-based systems engineering approach to predict the amount of ice growing on aircraft wings during flight. This model supports the preliminary design of the ice protection system, as well as the implementation of a control system, in real-time. When the aircraft meets a high concentration of super-cooled water in the atmosphere and a low temperature, the risk of ice formation on its external surfaces is significant. This causes a decrease in aerodynamic performance, with potential loss of control of the aircraft. To mitigate this effect, ice prevention and protection systems are crucial. The characteristics of the icing phenomena are first defined, then their effects on aircraft behavior during operation are evaluated. This allows us to develop a highly parametric predictive model of the actual icing conditions experienced by the aircraft during a given flight mission. To precisely predict the ice accretion and to design an ice protection system, estimating heat fluxes involving the aircraft’s wing surfaces and the external environment is required. To allow for this, this study also develops a thermal model that is specifically applied to the above-mentioned analysis. This model includes many factors characterizing the atmospheric conditions responsible for ice creation upon the aerodynamic surfaces, and it enables an accurate estimation and quantification of all the parameters necessary to design an appropriate ice protection system. Full article

International efforts are being made to reduce environmental pollution caused by microplastics (MPs). Microplastics are released into the environment through sewage treatment sludge, and the use of sludge as a soil improvement agent is increasing rapidly, emphasising the importance of controlling microplastics in sewage treatment facilities. The release of microplastics into the environment is an increasingly significant concern, with sources including sewage treatment sludge. This study focuses on the analysis of microplastics in sewage sludge using optical (Fourier-transform infrared spectroscopy, FTIR) and thermal (Thermo Extraction Desorption–Gas Chromatograph–Mass Spectroscopy, TED-GC-MS) processing-based analytical equipment. The average amount of MPs in the sewage sludge analysed using FTIR was 228.5 microplastics/g of sludge (MPs/g), primarily of the polypropylene type. Approximately 75% of the MPs were 0.1 mm in size or smaller. However, the average amount of MPs in the sewage sludge determined using TED-GC-MS was 95.79 µg-MPs/g. For the systematic management of microplastics, it is important to estimate the amount of microplastics generated by sewage treatment plants. Therefore, a microplastic generation calculation formula was proposed and used to estimate the potential microplastic generation in sewage treatment plants. The total amount of MPs generated from sewage treatment plants in South Korea, calculated using the equation, was approximately 364 ton/yr; we further divided the total amount by administrative regions. The findings of this study can be applied to assess global trends in MP research. Full article

The concept of synthetic aperture radar (SAR) has the advantage of being able to obtain high-quality images even when the target area is at night or covered with obstacles such as clouds or fog. These imaging capabilities have led to a rapid increase in demand for space SAR imagery across a variety of sectors, including government, military, and commercial sectors. The SAR-based deployable reflector antenna was developed in this series of paper. The satellite performance is influenced by the aperture size of an antenna. To improve the image acquisition performance, the SAR antenna has the configuration of several foldable CFRP reflectors. In this paper, the experimental investigation of the Structural-thermal model deployable reflector antenna is performed. During the launch condition, the satellite and payload are subjected to the dynamic load. In the STM phase, the acoustic test was conducted to evaluate the structural stability of the deployable reflector antenna within the acoustic environment. The sinusoidal vibration test was implemented to investigate the fundamental frequency for inplane/normal directions and evaluate the structural stability of reflector antenna. By using experimental data obtained from the thermal-balance test, the well-correlated thermal analysis model was established to execute the orbital thermal analysis. The experimental results of the environmental test in STM phase show that the deployable reflector antenna has structural stability for the structural/thermal environments. The configuration of the deployable reflector antenna determined in STM phase can be applied to the qualification model. Full article

Urban heritage areas are characterized by unique architectural and cultural elements, often coupled with specific challenges such as vulnerability to climate change and urban heat islands (UHIs). Investigating thermal performance at the neighborhood scale is crucial for preserving these areas while enhancing thermal comfort and sustainability. The aim of this research is to prove that the application of passive cooling techniques and urban green spaces can reduce the urban temperature and upgrade the conditions of thermal comfort, even in densely populated areas with small urban void spaces. ENVI-Met, a microclimate modeling software for evaluating the thermal performance of heritage urban neighborhoods, is applied in order to assess current thermal conditions, identify hotspots, perform simulations, and propose mitigation strategies to improve thermal comfort while preserving the architectural and cultural integrity of these areas. The test bed of this study is a historical urban area in central Athens, “Academia Platonos”. The methodology is mainly based on the design of different parametric scenarios for the study area, by integrating specific parameters that characterize the area of Academia Platonos (elevation distribution, materials, vegetation, etc.) and the microclimatic simulations of the area, designed in the digital environment of ENVI-Met. Five scenarios are implemented and studied in the study area, four of which are based on the existing situation of the study area, either by changing the construction materials of the built environment (passive cooling through cool material techniques) or by enhancing the area with vegetation. One of the most important findings of this study is that the use of plants with a high foliage density is more effective in reducing air temperature than the selection of species with sparse foliage. Full article

Perpendicular-orbit circular scanning satellites overcome the conflict between ground resolution and width observed in traditional optical satellites by using a perpendicular-orbit circular scanning imaging method and splicing along the orbit, achieving a balance between an ultra-large width and a high resolution. However, laboratory calibrations of perpendicular-orbit circular scanning satellites exhibit large errors due to the influence of factors such as the thermal and mechanical environment of space during the launch and operation of satellites, and thus, they cannot be applied. In this paper, we start by analysing the in-camera azimuth element errors of perpendicular-orbit circular scanning satellites, then derive a probe element pointing angle calibration model from the physical in-camera calibration model and carry out in-camera parameter calibration based on simulated image data from an ultra-wide perpendicular-orbit circular scanning satellite. Edge and centre strips were selected for the experiment, and a certain number of control points were placed uniformly near the middle column (perpendicular orbit) of the image in each strip and covering all row directions (along orbit). Checkpoints were uniformly selected across a range of widths. The results show that in-orbit geometric calibration can significantly improve the direct-to-ground positioning accuracy of perpendicular-orbit circular scanning satellites, with the positioning accuracy error shown to be better than 30 m within a width of 300 km, 30 m within a width of 1000 km, and 50 m within a width of 2000 km. Full article

The rapid urbanization of Jaipur has profoundly altered its urban climate, driven by anthropogenic heat flux (A_F) and shifts in surface energy dynamics. This study leverages remote sensing techniques, utilizing Landsat data, to quantify A_F and assess its influence on the city’s climate. The findings reveal a striking paradox; despite a significant rise in A_F from 127.31 W/m² in 1993 to 201.82 W/m² in 2020, Jaipur exhibits an anomalous urban cool island (UCI) effect during the daytime. In this phenomenon, surrounding fallow lands experience higher land surface temperatures (LSTs) than the urban core, defying the typical urban heat island (UHI) effect observed in most cities worldwide. This paradox is especially pronounced in semi-arid urban environments, where factors such as limited vegetation, arid conditions, and water scarcity intricately shape peculiar thermal behaviour. This study further highlights the role of urban expansion, with built-up areas growing from 11.95% in 1993 to 19% in 2020, intensifying A_F. Notably, the latent heat flux was highest in vegetated areas, significantly reducing LSTs by facilitating evapotranspiration. Daytime surface temperatures have surged significantly, with temperatures ranging from 26–46.9 °C in 1993 to 31–56.5 °C in 2020, indicating an overall increase in surface heat intensity. Despite these increases, the UCI effect remains observable, further illustrating the cooling potential of urban vegetation. This study offers novel insights into the intricate dynamics of urban heat in semi-arid cities, providing refined perspectives on urban heat mitigation strategies and climate adaptation, with implications for future sustainable urban planning and environmental management. Full article