Hot Area Research Articles

Research on assessing and enhancing indoor thermal and air conditions within typical elementary school classrooms in southern China

The thermal design of buildings in hot summer and cold winter regions must meet the requirements of thermal insulation in summer and heat preservation in winter. As a vital component of national compulsory education, primary schools must create a good indoor thermal environment for classrooms, which is particularly important for students. Due to the lack of construction standards and limited research on Chinese regions with hot summers and cold winters, policymakers have no comprehensive and efficient approach to creating optimal indoor thermal conditions in primary school classrooms. Therefore, based on the climate conditions of hot summer and cold winter areas, this study conducted field surveys in primary and secondary schools in hot summer and cold winter areas, summarized and analyzed the current situation of the surveyed classrooms and users' subjective evaluation of the indoor thermal environment of classrooms, and summarized the current hot summer and cold winter conditions. Problems in classrooms in primary and secondary schools in the region are clarified, and the research direction of construction strategies is clarified. The study found that most of the school hours in summer and winter were in a poor indoor thermal environment without refrigeration equipment. This study adjusted the school leaving time to 17:20 in summer and 17:00 in winter by adjusting the school leaving time to reduce the time of adverse thermal environment.

A Multicriteria Decision-Making Approach for Urban Water Features: Ecological Landscape Architecture Evaluation

In recent decades, the issues of ecology and environmental sustainability have become a global concern in contemporary urban design. Among various urban elements, water features play a significant role in improving the ecological characteristics of their surrounding environment, especially in hot and arid areas. The aim of this study is to evaluate the ecological characteristics of urban water features comprehensively and quantitatively, which has been overlooked in previous studies, taking their physical characteristics into account. To this end, a multicriteria decision-making method, an analytic network process, was proposed to quantitatively evaluate the ecological characteristics of water features. In this approach, four ecological criteria—microclimate, biodiversity, greenery, and human wellbeing—and ten physical characteristics of water features were considered. Twenty-one experts were asked to complete a questionnaire for pairwise comparisons of all ecological criteria and the influence of physical characteristics. The results showed that vegetation and scale, with the relative influencing values of 0.255 and 0.188, respectively, were identified as the most decisive features influencing ecological criteria. Conversely, texture, with a value 0.023, had the least impact. Moreover, it was shown that water features have the greatest impact on the microclimate compared with other ecological criteria. The results were used to compare water features at the Koohsangi Transregional Park, located in a hot and arid city of Iran. The results of this study lead to a framework that can help urban designers integrate ecological criteria into water feature planning to enhance urban ecology and sustainability.

The Impact of Different Types of Trees on Annual Thermal Comfort in Hot Summer and Cold Winter Areas

Trees positively improve the annual thermal comfort of the built environment in tropical areas, where climate change is slight throughout the year. However, for areas with high changes in climate all year, the current studies have only explored the summer cooling performance of trees without the impact of different types of trees on annual thermal comfort, especially in cold seasons. Therefore, to quantify the impacts and scientifically guide the optimization of green space layout in hot summer and cold winter areas, this study selected Changsha City as the study area and analyzed how the annual thermal comfort is affected by evergreen trees and deciduous trees, which are two common types of trees in hot summer and cold winter areas. The analytical results indicated that the difference in the effect of deciduous and evergreen trees on outdoor thermal comfort was insignificant in summer, where the difference in the monthly mean PET for the three summer months was slight, being 0.28 °C, 0.14 °C, and 0.29 °C, respectively. However, evergreen trees greatly exacerbated winter cold compared to deciduous trees, with a monthly mean PET decrease by nearly 1.0 °C and an hourly PET reduced by up to 3.57 °C. The difference is mainly attributed to the absorption and reflection of solar radiation by the tree canopy, as well as the cooling and humidifying effect of the tree leaf. In hot summer and cold winter areas, outdoor thermal comfort is still in the “comfortable” and “slightly warm” acceptable stage despite the warming effect of deciduous trees in the spring and autumn seasons. Planting evergreen trees is an inevitable thermal mitigation choice for tropical areas. However, for the areas with high annual climate change, such as hot summer and cold winter areas in China, a change in empirical tree planting patterns and selecting deciduous trees where appropriate will improve year-round outdoor thermal comfort.

Microstructure and hot deformation behavior of Cu–Ti–Zr(-Mg) alloys

In this study, the thermal deformation behavior of Cu–Ti–Zr(-Mg) alloys were investigated by Gleeble-1500D. The two alloys were deformed at 700–900 °C with 0.003–10 s−1 strain rate. The intrinsic equations of the two alloys were constructed and calculated thermal activation energies, which indicates that it is improved from 325.67 kJ/mol to 344.03 kJ/mol after Mg addition. The result showed that the hot working area of Cu–Ti–Zr alloy is greatly extended after Mg addition, and rheological instability area is reduced. The morphology of the alloys was observed to analyze thermal behavior. It revealed that Mg elements inhibited the occurrence of dynamic recrystallization and shifted the texture types in the alloys by characterization of EBSD. TEM results showed that the phases during hot deformation in Cu–Ti–Zr–Mg are Cu4Ti and Cu10Zr7, which are in a semi-coherent relationship with the Cu matrix.

Performance of Windcatchers in Improving Indoor Air Quality, Thermal Comfort, and Energy Efficiency: A Review

The growing concerns over climate change and energy scarcity have highlighted the need for building energy conservation. Windcatchers, renowned for their effective ventilation capabilities, have emerged as a pivotal solution for saving energy and improving indoor thermal comfort. Serving as rooftop installations, windcatchers harness high-altitude airflow to provide fresh indoor air while expelling stale air. This comprehensive review encompasses over 96 studies published between 2000 and 2024, examining the performance of various types of windcatchers. The review reviews previous articles and concludes that using different types of wind catchers in hot and arid areas can increase indoor air velocity by about 10–50%, reduce building energy consumption by about 20–50%, and increase thermal comfort duration by about 25–50%. The article combines the perspectives of multiple disciplines such as architecture, environmental engineering, and sustainable design, providing a new perspective for the study of windcatchers. The article not only summarizes the design and performance of existing wind catchers, but also provides 13 suggestions for the design of wind capture towers, while also identifying areas for future research, such as combining wind capture machines with other passive cooling technologies and evaluating their performance under different climate and urban conditions.

Research on Summer Environmental Thermal Comfort Model of Buildings in Hot Summer and Cold Winter Area

Research on Summer Environmental Thermal Comfort Model of Buildings in Hot Summer and Cold Winter Area

Biosynthesis of calcium oxide nanoparticles by employing Mulberry (Morus nigra) leaf extract as an efficient source for Rhodamine B remediation

Green processes for synthesizing nanocomposites are a hot area of research today as traditional processes are expensive, inefficient, harmful for synthesizing organic and inorganic molecules, and unsuitable for large-scale operations. The present study investigates the capacity of green synthesized Calcium oxide nanoparticles (CaO NPs) for efficiently removing Rhodamine B. Chemical reduction was replaced with Mulberry (Morus nigera) leaf extract as an environmentally friendly reaction mechanism. CaO NPs are characterized by various analytical techniques including EDX, BET, SEM, FTIR, TGA, Zeta Potential, Point of Zero Charge (PZC), and XRD. Maximum adsorption of Rhodamine B by CaO NPs is revealed at an initial concentration of Rhodamine B of 80 ppm, a temperature of 343 K, and contact time of 60 min, 0.4 g of adsorbent at a pH value of 7. Maximum removal of Rhodamine B by CaO NPs was found to be 98.2% which is promising with this small amount of adsorbent (0.4 g). Diverse Kinetic and adsorption isotherms are employed in this study to determine the requirement and significance of the adsorption process. Various adsorption isotherms such as Freundlich, Temkin, Dubinin–Radushkevich (D–R), and Langmuir models have been employed. Among the kinetic adsorption isotherms Elovich, Intraparticle kinetic model, pseudo 1st order, and pseudo 2nd order models were applied. The current study investigates the thorough understanding of the Rhodamine B adsorption process including the mechanism of adsorption using condition optimization, characterization, and model applications. The proposed adsorbent can be employed for the green removal of Rhodamine B from wastewater of industry with maximum efficiency and favorable regeneration properties.

Development of a doubly-fed compound control for hybrid ground source heat pump systems in hot summer and cold winter areas

In hot summer and cold winter areas, the impact of soil thermal accumulation is significant even for hybrid ground source heat pump systems (HGSHPs), especially after a long-term operation. To alleviate the energy performance degradation caused by soil temperature rise, a detailed temperature field heat transfer model of ground heat exchangers (GHXs) has been established and a doubly-fed compound control for HGSHPs is developed and integrated into a central controller module. The central controller can automatically control the loop flow distribution of units and achieve group activation of GHXs based on the load sequences forecasting feedforward and system variables feedback processes. Five control modes are included in the central controller, and the energy performances and soil temperature rise distribution of the HGSHPs with different control modes for fifteen years are compared. The results indicated that the HGSHPs performs best in terms of energy performance and soil thermal alleviation with Control Unit 13. Compared to the Normal control mode, the mean water temperature of GHXs, energy consumption of the chiller and heat pump decreased by 1.6 °C, 5.9 %, and 15.5 %, respectively, and the units COP increased by 11.3 %.

Seismic behavior and failure analysis of prefabricated foamed concrete composite walls for passive houses

In view of the lack of research on the failure mode and seismic behavior of high-performance insulation walls utilizing lightweight concrete as the structural material, this study presents experimental findings from a seismic behavior investigation of prefabricate foamed concrete composite walls (PFCCWs) for passive house in China. The PFCCWs incorporate low thermal conductivity and high-strength foamed concrete, polyurethane, decorative magnesium straw slabs to provide excellent thermal and mechanical properties for prefabricated passive houses in hot summer and cold winter area. The seismic behavior of PFCCWs under different influence factors were elaborated using quasi-static test data and observation of external damage. The lightweight and porous nature of foamed concrete leads to significant crack formation during failure. The findings suggest that the skin effect of magnesium straw slabs and polyurethane impedes crack development and improve the load-bearing capacity with ductility enhancement. Additionally, reducing the aspect ratio and substituting post-cast column concrete with common concrete are effective to improve the seismic behavior. The window opening changes the worst damage area of the wall and notably weakens the seismic behavior. The enhanced integrity of cast-in-place wall leads to the difference in the failure mechanism and increases in load-bearing and deformation capacities. Meanwhile, design suggestions for the foamed concrete insulation walls are also proposed by comparing the failure mode and hysteretic response of various wall types.

Effects of water cooling of friction stir welding of magnesium alloy stiffness joint

This study presents a comparative analysis of friction stir welding (FSW) and underwater friction stir welding (UFSW) of AZ31 magnesium alloy in T-configuration, emphasizing the effects on heat distribution, material properties, and mechanical performance. Simulation results revealed a more uniform heat distribution in both welding techniques, with the hottest area on the advancing side. The maximum temperatures recorded at the shoulder-workpiece contact were 404 °C for FSW and 349 °C for UFSW, a 13.6 % reduction in UFSW. Material velocity at the trailing edge was 63 mm/s for FSW and 42 mm/s for UFSW, showing a 34 % decrease due to lower heat generation in UFSW. Strain rates were 450 s⁻¹ for FSW and 420 s⁻¹ for UFSW. Grain size in the stir zone was 26 micrometers for FSW and 21 micrometers for UFSW, a 19 % reduction. Ultimate tensile strength (UTS) increased by 6 % in the skin direction and 12.8 % in the flange direction for UFSW compared to FSW. SEM analysis indicated enhanced ductility in UFSW fractures. These results demonstrate UFSW's superiority in improving thermal management, microstructural properties, and mechanical performance of welded joints.

An adaptive learning based aberrance repressed multi-feature integrated correlation filter for Visual Object Tracking (VOT)

Target tracking via Correlation Filter (CF) is a hot research area of computer vision domain, and offers various credible benefits. Existing CF algorithms face challenges when there are target appearance variations due to background noise, scale and illumination changes, occlusion, and fast motion, which severely degrades the overall tracker performance. To get maximum benefits, an object tracker should perform well with the less computational burden in the presence of real time challenging situations. To address this issue, a novel visual object trackeris proposed based on multi feature fusion and adaptive learning technique with aberrance suppression. At first, multiple features i.e., Histogram of gradient (HOG), Color Naming (CN), saliency, and gray level intensities are combined using feature fusion technique. Further, based on the evaluation of final fused response map using Peak-to-Sidelobe Ratio (PSR), an adaptive learning strategy is integrated to improve the learning phase of tracker. Tracking results show that the proposed strategy beats the other modern CF trackers with Distance Precision (DP) scores of 88.2%, 85.9%, and 74.1% and 64.7% over OTB2013, OTB2015, and TempleColor128 and UAV123 datasets respectively.

A Multivariate Model and Correlation Study on the Impact of Typical Residential Spatial Forms in the Middle Reaches of the Hanjiang River on the Thermal Environment and Thermal Comfort

Different spatial forms affect the indoor thermal environment and human thermal comfort. A good living environment largely depends on the flexibility of spatial forms, and spatial scale and proportion are the key factors affecting these forms. We selected typical residential houses in the middle reaches of the Hanjiang River in the hot summer and cold winter climate area as an example. Through on-site measurements and questionnaire surveys, we studied the impact of residential form indicators on the thermal environment and thermal comfort. We also established a multivariate model to explore the correlation among various parameters. The results showed that the spatial-real ratio of the residential spatial form index in the middle reaches of Hanjiang River was 5–58%. The height from the ground was 2.23–6.92 m. The open-space ratio was 0.04–4.55. The explanatory power of the spatial form index to indoor air temperature was 57.5%, with a strong correlation (R2 = 0.675). The explanatory power for humidity was 38.2%, with a weak correlation (R2 = 0.525). The explanatory power of SET was 30.6–50.1%, with a weak correlation (R2 = 0.466). The explanatory power of PMV was 6.5–31.7%, and PMV1.0 was weakly correlated (R2 = 0.474). The explanatory power for PPD was 15.5%, where PPD 1.0 was close to a weak correlation (R2 = 0.508). The results of this study provide reference values for the design methods of and decision-making process for green and energy-saving regional buildings.

The meteoritic record of Arabia

Meteorites provide a wealth of information about the origin of the Earth and the solar system. Systematic searches have proved successful in cold and hot desert areas. Meteorite finds are favoured in areas with light-coloured surfaces that have been stable over tens of thousands of years and in hyper-arid climates. The deserts of Arabia are well suited for the search for meteorites. Following the first finds by explorers in the 1930s, and during oil exploration in the 1950s, a significant number of finds have been recorded in Oman since 1999, with more than 4000 meteorites currently recorded. Exploratory searches in Saudi Arabia have also shown a significant potential for meteorite discoveries. A collaborative Omani-Swiss search project was initiated in 2001 and 23 search campaigns since then have yielded more than 7300 samples, including meteorites from the Moon and Mars and, 37 strewn fields. Arabia has the potential to become one of the key regions for meteorite recovery and future research. Only three confirmed (Wabar, Saqqar and Jebel Waqf as Suwwan), several suspected and some dubious impact structures have been reported. The Wabar impact locality in Saudi Arabia features impact craters in dune sands, shocked and melted sand, and finds of several large meteorites.

Design of high performances electronically reconfigurable antenna arrays by means of parasitic structures and RF-MEMS switches

AbstractThis work explores the development of smart array antennas, able to electronically change their beam patterns through reconfigurable linear, planar, or conformal parasitic structures controlled by mean of a set of electronic switches namely the radio frequency micro-electromechanical switches (RF-MEMS). The motivation of this study is to extend and make competitive the use of reconfigurable antenna arrays in areas such as the Internet of Things (IoT) and wireless sensor networks. These hot research areas require a capillary distribution of sensors characterized by compact dimensions and limited cost. The radiating systems play a key role in such applications since the improvement of the radiating properties can dramatically reduce the power consumption of such sensors and extend their operative range. Standard smart antenna arrays such as phased, or fully adaptive arrays are extremely expensive, expensive and difficult to control. In this work, the use of smart reconfigurable antenna arrays that do not require expensive digital variable phase shifters and attenuators has been considered. The proposed antenna structures are based on reconfigurable parasitic structures, that thanks to suitable RF-MEMs switches are able to obtain a desired beam pattern, by steering the main beam in a given direction, removing eventually interfering signals and maximizing the signal-to-noise ratio SNR. The versatility, simplicity, and low cost of such antennas make them particularly suitable for the emergent wireless sensor networks and IoT applications. Theoretical background, design guidelines, and suggestions for their fabrication are detailed in this work. Some antenna models for different practical applications are designed, optimized, numerically assessed with commercial electromagnetic simulators, and commented to provide a valid alternative to researchers involved in antenna design for IoT applications.

E-CARGO-based dynamic weight offload strategy with resource contention mitigation for edge networks

With the widespread use of Mobile Edge Computing (MEC) in smart manufacturing systems in Industrial Internet of Things (IIoT) and 5G networks, determining how to efficiently offload computing tasks has become a hot research area. The Role-Based Collaboration (RBC) Environments-Classes, Agents, Roles, Groups, and Objects (E-CARGO) model is introduced to comprehensively manage MEC servers and user computation tasks in edge network environments, thereby improving the effectiveness and performance of task offloading in smart manufacturing systems. To begin with, latency and energy consumption are important indicators for evaluating the offloading effect. A pre-allocation algorithm based on user latency tolerance is proposed to dynamically adjust the latency-energy consumption weighting factor to optimize system resource allocation for real-time adjustment of offloading decisions. Second, the Group Role Assignment of Agent Role Conflicts (GRACAR) model based on E-CARGO is extended, along with a dynamic weighting of the GRACAR (GRACAR-DW) model and formal modeling. By introducing resource contention constraints, the resource contention caused by excessive task data offloading to the same MEC server is proactively mitigated. Finally, a Gurobi solution based on Mixed-Integer Linear Programming (MILP) is developed to help validate and synthesize the proposed model. Simulation results show that the strategy considerably enhances the MEC system's overall performance in terms of latency and energy consumption while also providing new ideas and technological support for offloading decisions in edge networks.

Pore-scale flame oscillations and patterns of upstream combustion wave propagation in a one-layer porous burner

Upstream propagation of filtration combustion wave in a one-layer porous burner is studied experimentally using thermal imaging and high-speed filming. The burner is the one-layer packed bed of spheres modeling porous media and providing optical access to the flame. This design allowed us to study macroscopic propagation of the combustion wave as well as non-stationary flame behavior at the pore scale. Experimental results demonstrate that upstream propagating combustion wave forms non-uniform porous medium temperature distribution in transverse direction which consists of hot areas separated by low-temperature regions. Macroscopic flame propagation can be accompanied by oscillations of some flame fragments at the pore scale. The mechanism of these pulsations is identical to the flames with repetitive extinction and ignition in narrow channels with external heating. Experimental results suggest that large scale evolution of the thermal wave affects the non-stationary behavior of the flame fragments at the pore scale and vice versa. The interplay between pore-scale and macro-scale processes manifests itself in the multiple repetitions of some patterns of the combustion wave propagation. Two most typical and common patterns are described and discussed. These patterns are step-wise transition of the flame fragment into the upstream pore and transition through the series of flame oscillations with repetitive extinction and ignition. It is shown that highly simplified one-dimensional model describes flame propagation in externally heated variable cross-section channel with heat conducting walls is capable to describe main features of these two patterns. Parametric study allows to predict the effect of problem parameters on the regions of existing of one or another pattern of upstream flame propagation.Novelty and Significance StatementThis paper presents new experimental data on temperature characteristics of upstream propagating filtration combustion wave in a one-layer porous burner. For the first time the patterns of combustion wave propagation uniting macro-scale processes of the thermal wave propagation and oscillations of the flame fragments at the pore scale are described on the basis of experimental data and numerical modeling. Results obtained for the one-layer burner can apparently be generalized to the case of combustion in three-dimensional porous media and packed beds. These results are significant because extend fundamental knowledge on porous media combustion by information on pore- and macro- scale flame dynamics as well as on the interplay of these scales. Experimental results can also be useful for validation of pore-resolved numerical simulations actively developed in the last decade.

Weight Impact on Comparative Evaluation of Topographic Data

The paper addresses the problem of weighting in an analysis that supports the selection of a categorical data set according to user needs. Using the Relative Change (RC) of the Compound Correspondence Index (CCI), it is shown that weights have a significant impact on user choice – reaching extreme values in both urbanized and forested areas. Decreasing the weights from 0.25 to 0.17 in forested and built-up areas resulted in the maximum variations that were seen in the hot spot maps, with cold areas generally corresponding to builtup regions and hot areas to forested areas. The analysis covers seven counties that are located in different regions of Poland: Pomerania, Podlasie, Mazovia, Greater Poland and the Beskidy Mountains.

Rectangular bismuth oxychloride with high mid-wave infrared reflectance to strengthen radiative cooling performance

Abstract Radiative cooling materials (RCMs) based on polymers, that reflect solar irradiance (0.24–2.5 µm) strongly and emit radiation within atmospheric window (8–13 µm) intensively, have yielded obviously cooling performance. However, RCMs reported failed to realize high mid-wave infrared (2.5–8 µm) reflectance (i.e., spectral selectivity), which play an importance role in reject the radiation from ambient especially in high relative humidity. Thus, enhancing the reflectance of RCMs in mid-wave infrared can further strengthen the cooling effect in the environment of high relative humidity. Additive of fillers with high reflectance in mid-wave infrared is effective, low cost and convenient to modified the cooling performance polymeric RCMs. In this paper, micron rectangular bismuth oxychloride (BiOCl) powders were proposed and synthesized by hydrothermal method. And, rectangular BiOCl boasts excellent mid-wave infrared reflective capacity (85%). Then, rectangular BiOCl was added into the top-layer of flexible hierarchically porous complex membrane, and improved the reflectance of porous membrane within 2.5–8 µm from 48.3% to 58.1%. While the emittance of the obtained bilayer membrane within atmospheric window was hardly affected. The membrane with BiOCl exhibited better cooling performance in humid ambient (70%), demonstrating the importance of spectral selectivity experimentally. This work proposed an effective strategy to modify spectral selectivity of RCMs and it could expand the application of radiative cooling materials in hot and humid areas.

A dataset of soil organic carbon density of typical ecosystems in the arid areas of Northwest China from 2005 to 2020

The soil organic carbon pool is the largest and most active part of the terrestrial ecosystem carbon pool, and plays an important role in the global carbon cycle and global climate change. The arid region of northwest China is located in the hinterland of Eurasia, with extremely fragile ecosystems and extremely sensitive responses to climate change. It is a hot area that many scholars have paid attention to in recent years, and the estimation and spatial distribution characteristics of soil organic carbon storage have increasingly become one of the research focuses in this region. However, insufficient data sharing and the relative lack of measured data are important factors causing the uncertainty of the research results. Based on the long-term soil observation data collected from the ecological field stations of China Ecosystem Research Network (CERN) located in five provinces and regions of northwest China, the soil organic carbon density dataset of typical ecosystems in the arid region of Northwest China was calculated by organic carbon estimation model. This dataset contains the soil organic carbon density data of topsoil (0-20 cm) and soil profile of various long-term observation plots at 11 ecological field stations from 2005 to 2020, in order to provide valuable measured data for the estimation of soil carbon storage and the study of carbon cycle process in the arid area of northwest China.

A Miniature PMUT Array for Medical Applications

Abstract Wearable continuous monitoring technology and internal and cerebrovascular imaging are the frontier hot area of current scientific research, which are of great significance to improving human life and health. Ultrasonic imaging can obtain information such as deep tissue structure by transmitting ultrasonic waves into the tissue and detecting echo signals, and ultrasonic imaging technology has the advantages of high imaging depth, high resolution, high safety, fast and convenient, etc. It is one of the important technologies in the medical field such as wearable continuous monitoring technology and internal cardiovascular and cerebrovascular imaging. But miniaturization and low power consumption are necessary conditions for the success of such medical applications. Therefore, the ultrasonic imaging technology using a miniature ultrasonic probe is one of the most promising imaging technologies for this type of medical application. Aiming at the common technical problems of traditional ultrasonic transducers such as large volume, narrow bandwidth, high power consumption, difficulty in preparing two-dimensional arrays, and difficulty in integrating with ICs. In this paper, the electromechanical-acoustic multi-field coupling mechanism and array structure design technology of MEMS high-performance PMUT ultrasonic transducer elements are first studied, and a CMOS-compatible miniature PMUT high-performance array ultrasonic device suitable for this type of medical application is developed. The simulation results of the transducer are given. The measurement of various physical parameters of the transducer sample and the results of its application in the ultrasonic imaging system show that the miniature PMUT linear array ultrasonic sensor we designed is a kind of high performance ultrasonic array sensors that can be widely used in wearable continuous monitoring technology and internal cardiovascular and cerebrovascular imaging.