Learning efficiency in a university context is predicated on a conducive learning environment. This in turn requires settings offering thermal comfort. In this study, we experimentally explored the relationship between the thermal environment of colleges and universities in hot-summer and cold-winter regions on the thermal comfort and learning efficiency of Chinese college students. Findings are intriguing in that temperatures delivering optimal thermal comfort and optimal learning efficiency differ. Specifically: (1) Students generally feel most comfortable when the room temperature is approximately 24 °C; (2) Combined studies comparing temperature on thermal comfort and learning efficiency found that college students learn better in slightly colder environments; (3) Based on the comprehensive value of satisfying the best thermal comfort and high learning efficiency, the optimal temperature range is 20.6 °C to 22.2 °C.

Amid the global climate and energy crises, developing green buildings has become the key to the low-carbon transition of the construction industry. However, academic attention to the collaborative development of China’s green building industry (GBISD) remains relatively limited, and the exploration of its spatiotemporal heterogeneity laws and the spatiotemporal effects of core influencing factors is still insufficient. To fill this research gap, this study constructs a multi-dimensional analytical framework of “subject-factor-path-goal” based on synergy theory. Combining the AHP-CRITIC combined weighting method, composite system synergy degree model, Dagum Gini coefficient, and Spatio-temporal geographically weighted regression (GTWR) model, it conducts an empirical study on the GBISD level of 27 provinces in China from 2012 to 2022. Its core goal is to reveal the characteristics of spatio-temporal heterogeneity, spatial correlation laws, and spatio-temporal effects of influencing factors, so as to provide scientific support for industrial synergy optimization and regional green development. The findings reveal that: (1) Provincial levels of GBISD exhibit sustained growth with enhanced resilience while demonstrating emerging regional polarization and spatial diffusion effects. (2) The three major regions (Eastern, Central, and Western China) show differentiated development trajectories with significant spatial differences. (3) The overall GBISD distribution displays clustering patterns, with pronounced agglomeration effects in central and eastern China, whereas the spatial correlations remain weak in most provinces. (4) The GBISD performance in Northwest and Northeast China is suboptimal, which is related to insufficient attention to low-carbon development and restricted construction industry scale. The impacts of factors such as technological innovation, government attention to green and low-carbon development, and green finance exhibit significant spatiotemporal heterogeneity. This study enriches the theoretical system and quantitative methods of GBISD, and provides targeted practical strategies for the low-carbon transition of the construction industry and regional synergistic governance.

Hydrogen co-firing with liquid hydrocarbon fuels offers a near-term pathway toward decarbonizing aviation propulsion, yet its effects on flame organization and thermoacoustic behavior in evaporating spray flames have received limited attention. This study experimentally investigates n-decane/hydrogen dual-fuel swirling spray flames over hydrogen energy fractions of 0-30% at constant thermal power. A paired-baseline framework is adopted by comparing each dual-fuel condition with a pure n-decane reference at matched liquid-fuel flow rate. OH* chemiluminescence shows that all conditions retain a V-shaped flame structure, while stable anchoring in the dual-fuel sequence is established through upstream migration of the merged reaction zone rather than by strengthening weak dual-branch roots. In both sequences, flame height remains governed primarily by liquid-fuel loading. CH* imaging and particle image velocimetry further indicate that hydrogen shifts the high-intensity CH* chemiluminescence region from the inner root toward the merged shear-layer-supported zone, accompanied by stronger near-field shear-layer motion and a reduced inner-root CH* contribution. This redistribution coincides with a staged thermoacoustic transition: a pronounced narrowband pressure tone first appears at 10% hydrogen fraction, dominant flame-acoustic frequency locking is observed from 15% onward, and a well-defined selfexcited limit cycle develops at 30% hydrogen fraction. A qualitative OH*-based Rayleigh-type analysis indicates that, as the OH* chemiluminescence region becomes more compact, its response becomes more favorably phased with the pressure fluctuations. These results identify a stabilization-instability trade-off specific to peripheralH2/central-spray dual-fuel swirl combustion.

Due to the high energy conversion efficiency and portability, diesel engines are chosen as the main power source for the basic power generation of mobile military units. However, the exhaust gas emitted will heat up the pipe and generate a large amount of thermal radiation signals, which can be captured by enemy and thereby expose the location information of the military base. To reduce the thermal radiation signals generated by the heating of the pipelines by the exhaust, this study proposes to introduce swirling cold air between the high-temperature exhaust of the diesel engine and the pipeline wall to prevent the heating of the pipeline wall by the hightemperature exhaust gas. Using the validated numerical model, studies were conducted on the local maximum temperature of the pipe wall and corresponding pressure loss under different temperatures, swirl angles, and cold flows. The analysis of the influencing mechanism was carried out through single-factor analysis and response surface analysis. The results show that the lower the temperature of the cold fluid, the stronger its cooling capacity, but the temperature that needs to be controlled for cooling is also smaller, which makes winter the key protection stage. In addition, the results also reveal the non-monotonic influence of the increase in cold flows and angles on the local maximum temperature rise of the pipe wall. For the two target values with opposite trend changes, the optimal operating conditions determined by multi-objective optimization and ideal point method are respectively optimized with average ratio of 59.67 % and 20.66 % compared to the baseline operating conditions.

As a primary economic engine and strategic region in China, the development of the green building industry in the Yangtze River Economic Belt (YREB) holds demonstrative significance for the low-carbon transition of the country’s construction sector. Utilizing panel data from 11 provinces and municipalities within the YREB during 2012–2022, this study constructs a comprehensive evaluation index system to measure the coupling coordination degree (CCD) between the green building industry and the development environment. The spatio-temporal evolution of the CCD is analyzed using methods including kernel density estimation, the Dagum Gini coefficient, spatial autocorrelation, and standard deviational ellipse. A fixed-effects model is further employed to identify its influencing factors. The results show that (1) both the green building industry and its development environment in the YREB exhibited upward trends, with the gap between them gradually narrowing. (2) The CCD across provinces and municipalities showed an overall upward trend, characterized by simultaneous “overall improvement” and “internal gradient differentiation” in spatio-temporal distribution, and displayed a spatial pattern of “higher values in the east and lower in the west.” (3) Urbanization level, government regulation, technological innovation, and consumption capacity exerted significant positive effects on the CCD, whereas the influence of education level and public environmental awareness remained insignificant. This study provides insights for formulating differentiated regional policies and optimizing the development environment for the green building industry.

Diesel engine will emit a lot of high temperature flue gas to heat the exhaust pipe, which will radiate a lot of infrared signals to the outside world. To reduce the heat signal radiated by the exhaust pipe, the cold air film insulation protection method is proposed in this study. However, for the long exhaust pipe, the longer traveling distance makes the hot smoke rise phenomenon obvious, which forms a strong heating effect on the exhaust pipe. Therefore, this study proposes to increase the swirl effect on the cold air film and rely on rotation to increase the adhesion between the film and the tube wall. In this study, a numerical simulation method was used to compare the thermal protection effect of cold fluid on smoke exhaust pipe under swirling and non-swirling conditions with the numerical model verified by experiments. The temperature distribution, velocity distribution, carbon dioxide distribution and heat transfer to the pipe wall are discussed when the mixed jet with hot flue gas reaches steady state under swirling and non-swirling conditions. The results show that the cyclone cold fluid has better thermal protection, and the maximum temperature rise of the pre-swirling cold fluid is 90.39% lower than that of the non-swirling cold fluid. With the increase of cold fluid flow, the pipe temperature rise first decreases and then increases, and there exists a wall temperature rise that shows the best performance when the cold fluid flow is not the maximum.

Based on the geological and geothermal information of 20 wells in the deep layer of five geomorphic units of Xi'an China, the effect of local geomorphic units on the heat transfer performance of buried pipes was analyzed. Three-dimensional full-scale numerical models were established for the inner-outer heat transfer behaviors of two coaxial casing-type coupled pipes with different depths (2000 and 2500 m), and the reliability of the models was validated with the measured data of a project in operation. Results revealed that the outlet water temperature and heat transfer intensity were the highest for the well in the tertiary alluvial-proluvial fan (30.8 degrees C and 768 kW, respectively), while they were lowest for the well in the primary terrace landform unit (20 degrees C and 459 kW). Furthermore, the effect became more obvious with increase in burial pipe depth. By comparing the increase rate of heat transfer of the burial pipe at depths of 2500 m and 2000 m in the same geomorphic unit, it was found that the tertiary alluvial-proluvial fan geomorphic unit and the primary terrace geomorphic unit showed the maximum and minimum increase rates (107.80% and 28.32%, respectively). This study revealed the key influence of geological factors on geothermal development efficiency, which is of great significance to improving large-scale utilization of deep geothermal energy.

As a primary engine and strategically leading region for China’s economic development, the Yangtze River Economic Belt (YREB) has a green building industry whose growth holds demonstrative significance for the low-carbon transition of the national construction sector. Based on panel data from 11 provinces (municipalities) within the YREB from 2012 to 2022, this study constructs a comprehensive evaluation index system to measure the Coupling Coordination Degree (CCD) between the green building industry and its development environment. Employing methods such as the Dagum Gini coefficient, spatial autocorrelation, and Standard Deviation Ellipse(SDE), we analyze the spatiotemporal evolution characteristics of this CCD. Furthermore, a fixed-effects model is utilized to explore the influencing factors. The results indicate that: (1) Both the level of the green building industry and the quality of the development environment in the YREB show an upward trend, with the gap between them gradually narrowing. (2) The CCD between the green building industry and the development environment across provinces and municipalities generally increased, exhibiting a coexistence of "overall level improvement" and "internal gradient differentiation" in spatiotemporal distribution, and a spatial correlation characteristic of "high in the east and low in the west". (3) Urbanization level, government regulation, technological innovation, and consumption capacity have significant positive effects on the CCD, whereas the roles of education level and public environmental concern are not yet significant. This study can provide references for formulating differentiated regional policies and optimizing the development environment for the green building industry.

It is important to determine the ventilation required in the construction of deep and long tunnels and the variation law of tunnel temperature fields to reduce the numbers of high-temperature disasters and serious accidents. Based on a tunnel project with a high ground temperature, with the help of convection heat transfer theory and the theoretical analysis and calculation method, this paper clarifies the contribution of various heat sources to the air demand during tunnel construction, and reveals the important environmental parameters that determine the ventilation value by changing the construction conditions. The results show that increasing the fresh air temperature greatly increases the required air volume, and the closer the supply air temperature is to 28 °C, the more the air volume needs to be increased. The air temperature away from the palm face is not significantly affected by changes in the supply air temperature. Adjusting the wall temperature greatly accelerates the rate of temperature growth. The supply air temperature rose from 15 to 25 °C, while the tunnel temperature at 800 m only increased by 1.5 °C. Over a 50 m range, the wall temperature rose from 35 to 60 degrees Celsius at a rate of 0.0842 to 0.219 degrees Celsius per meter. The total air volume rises and the surface heat transfer coefficient decreases as the tunnel’s cross-section increases. For every 10 m increase in the tunnel diameter, the temperature at 800 m from the tunnel face drops by about 0.5 °C. Changing the distance between the air duct and the tunnel face has little influence on the temperature distribution law. The general trend is that the farther the air duct outlet is from the tunnel face, the higher the temperature is, and the maximum difference is within the range of 50 m~250 m from the tunnel face. The maximum difference between the air temperatures at 12 m and 27 m is 0.79 °C. The geological structure and geothermal background have the greatest influence on the temperature prediction of high geothermal tunnels. The prediction results are of great significance for guiding tunnel construction, formulating cooling measures, and ensuring construction safety.

This study provides a comprehensive analysis of indoor air pollutant control technologies and reports on the current status of indoor air pollution and its hazards to human health in China. This research also emphasizes the biological mechanisms through which indoor air pollutants affect human health at the cellular and molecular levels. The study explores the mechanisms, kinetics, thermodynamics, and material design and performance optimization of various control methods, including physical adsorption, chemical decomposition, and biological purification. A detailed discussion is included on how indoor air pollutants interact with biological systems, focusing on mechanistic pathways such as oxidative stress, inflammatory responses, and cellular signaling alterations induced by exposure to pollutants. Data analysis reveals the removal efficiencies and application effects of different technologies, highlighting the biological impacts of these pollutants on human health. It was concluded that in the future, emphasis should be placed on the research and development of efficient and low-cost adsorbent materials, the optimization of the chemical decomposition method in order to reduce energy consumption and extend the catalyst life, the in-depth study of biological purification methods in order to screen highly efficient degrading microorganisms. Additionally, a combined approach utilizing various technologies is recommended to achieve comprehensive treatment of indoor air pollutants, thereby mitigating their harmful effects on biological systems.

One notable characteristic of the working process of proton exchange membrane fuel cells (PEMFCs) is that their output power and temperature are significantly influenced by factors such as operating conditions and the flow field at the anode and cathode. In this work, numerical simulations were conducted to study the operational performance and thermal management of a hydrogen-oxygen PEMFC stack. The study utilizes the method of controlling variables to investigate the impact of pressure and humidity on the performance and thermal management of fuel cells. The results indicate that within a specified range, an increase in humidity leads to a decrease in current densities while promoting a more uniform temperature distribution. As the pressure increases, both the average, maximum, and minimum temperatures across each proton exchange membrane also rise, while the current density shows a decreasing trend.

This paper examined the influence of adjacent nozzles on the flow and fuel atomization characteristics of the central nozzle in a triple-nozzle model combustor. High-frequency particle imaging velocimetry testing for airflow and phase Doppler particle analyzer testing for fuel particles were employed. Under the central nozzle air intake mode, the momentum exchange between the swirling flow and the surrounding stationary air leads to a seemingly shrinking flow field. While under the triple nozzles air intake mode, the low static pressure at the geometric center between adjacent nozzles attracts the swirling flows to converge, resulting in a larger expansion angle. Confinement has a complex impact on swirling flow. When the angle of the swirling airflow is small, it guides the flow to expand. However, when the angle becomes too large, it restricts further expansion. Observed Sauter mean diameter (SMD) peaks for the tested cases lie within a similar range, suggesting comparable spray angles. Nevertheless, the triple-nozzle air intake mode exhibits consistently higher SMD values and significantly greater spray core penetration depth. Instantaneous flow characteristics deepen the understanding of these differences in atomization results. The large range of airflow oscillation under the central nozzle air intake mode allows the airflow to directly interact with the droplets. While under the triple-nozzle air intake mode, the air flow path is too far away from the spray, resulting in that most droplets do not receive sufficient aerodynamic forces for atomization.

The operation of a diesel engine leads to the emission of a substantial amount of waste heat flue gas, resulting in a continuous increase in the wall temperature of the exhaust system. To mitigate this continuous rise in temperature, a pre-swirling device has been developed to enhance the heat exchange between cold air and the wall, thus averting heating wall by the hot air. In this study, an experimental system was devised and implemented to analyze the dynamic behavior of the wall temperature in an air duct. The system considered both with and without the pre-swirling device, incorporating different cold air temperatures and flow rates to examine its impact on the increase in wall temperature. The results revealed a gradual rise in wall temperature after reaching a steady state, particularly demonstrating lower wall temperatures at 19 measurement points in the presence of pre-swirl compared to without swirl. Notably, the maximum temperature rise in the air duct wall was reduced by 55.7 %, from 7.9 °C without pre-swirl to 3.5 °C with the inclusion of the pre-swirling device, highlighting the significant thermal protection it provides and suggesting potential applications in exhaust thermal protection engineering. Moreover, the experimental findings consistently indicate that the incorporation of a pre-swirling device effectively diminishes the increase in wall temperature across different cold air flow rates and temperatures.

The main factor affecting the laser damage resistance of optical components is the damage precursor introduced in the manufacturing process. Some studies have shown that the ideal intrinsic matrix of fused quartz has a laser radiation damage threshold of up to 100J/cm2, but the manufactured optical components are far below this index. Therefore, effectively inhibiting or even eliminating the damage precursor is the key to improve the anti-laser damage performance of optical components. Abrasive Water Jet Polishing (AWJP) technology mainly removes materials through the collision and shear between abrasive particles and the workpiece surface, which has the characteristics of non-damage and non-contact processing. However, due to the small size of Tool Influence Function (TIF) and low efficiency, it is still challenging to achieve widespread application. In this paper, we analyzed the flow field characteristics near the workpiece surface when different nozzle tilt angles were used for processing under two different machining methods: maintaining the jet length unchanged and maintaining the standoff distance unchanged and corrected the pressure distribution. It was found that the changes in pressure distribution and shear stress distribution in the impact zone under different nozzle tilt angle conditions will result in a change in the width of the Gaussian-shaped TIF obtained after nozzle rotation machining. In addition, under the condition of the same nozzle tilt angle, the TIF of Gaussian shape with larger size can be obtained by using the processing method that keeps the standoff distance constant.

The continuous deterioration of global climate is escalating the disaster risk for cities in the Chengdu-Chongqing urban agglomeration, and studying urban resilience is crucial for regional cities to prevent urban climate disasters and ensure sustainable urban development. However, few scholars discuss the mutual effects of urban social, economic and ecological resilience from the internal perspective of urban system. Therefore, this study puts forward the concept of urban resilience system, aims to measure the interaction effect between the rsubsystems' resilience of cities in the Chengdu-Chongqing urban agglomeration by coupling degree, and to measure the coordinated development effect between the rsubsystems' resilience of cities in the region by coordinating degree. Based on CRITIC–TOPSIS weighted evaluation model and revised coupling coordination method, the results suggest that (1) most cities have a low coupling degree of urban resilience system and are in the “Running-in stage”; (2) most cities have a low coordination degree of urban resilience system and are in the “Bare coordination” stage; (3) the coupling degree and coordination degree of urban resilience system are increasing in all cities with the development; (4) cities in the east and west of the region have better coupling degree and coordination degree than cities in the north and south; (5) the development of economic resilience and social resilience lags behind ecological resilience in most cities. The results could provide theoretical references for the practice of resilient city construction and urban resilience research.

In order to support the green and low-carbon transformation of China’s construction industry and accomplish the dual carbon objective, it is vital to accelerate green technology innovation. Therefore, this paper takes the Chengdu–Chongqing urban agglomeration of China as the study area, using the super-efficiency slacks-based measure (SBM)model and the gravity model to assess the efficiency of green technology innovation in the construction industry, utilizing geographical detectors to investigate the drivers of green technology innovation in the construction industry further. Additionally, we consider each influencing factor’s level of impact on the efficiency of green technology innovation in the construction sector both under the single factor and double factor scenarios. The findings indicate that there is a considerable difference in the efficiency of green technology innovation in the Chengdu–Chongqing metropolitan agglomeration’s construction industry, and the trend is upward. In addition, the research area exhibited spatially heterogeneous characteristics in terms of the efficiency of green technology innovation in the construction industry, and the spatial spillover effect was significantly limited by distance. Further research revealed that environmental legislation, economic development, public environmental concern, urbanization level, and foreign direct investment were the primary driving factors of green technology innovation efficiency in the construction sector, and industrial size was the potential driving factor. The spatial and temporal differentiation of the green technology innovation efficiency in the construction industry was also more affected by the interaction between the dominating factor and the prospective factor than by either factor acting alone. The research’s findings are useful in advancing the green and low-carbon transformation of the construction sector in the Chengdu–Chongqing metropolitan agglomeration by offering theoretical support and decision-making reference.

Radiant syngas cooler (RSC) is a crucial heat recovery equipment for entrained-flow coal gasification. Ash depositions in the industrial RSC endanger its operation efficiency and operation safety. In this work, the critical viscosity model and the ash shedding model are coupled to explore the ash deposition behavior in the industrial RSC for a 2000 t/d entrained-flow coal gasifier. Simulation results are in good agreement with the industrial conditions. The results show that ash depositions in RSC are mainly distributed in the upper part and the bottom cone, and the maximum ash thickness are 9.67 mm and 36.71 mm respectively. Due to ash depositions, the outlet temperature of RSC increases by 19.76%, the total heat transfer rate decreases by 21.88%, and the steam yield decreases by 22.41%. Employing low-ash coal as gasification raw coal is a good suggestion to enhance the operation performance of the industrial RSC. Moreover, when the industrial RSC is fully loaded, an appropriate increase in syngas mass flow rate can also contribute to a better operation performance.

The radiant syngas cooler (RSC) is a crucial equipment for recovering the sensible heat of high-temperature syngas produced by coal gasification. Most of the previous studies on RSC focused on the flow field and heat transfer, ignoring the chemical reactions in RSC. In this work, a three-dimensional RSC model is established to investigate the effects of homogeneous reactions on the composition distributions of syngas in RSC. The simu-lation results show that the composition distributions of syngas are similar to the temperature distribution of RSC. From the inlet to the outlet of RSC, the mole fraction of CO decreases by 2.81%, and the mole fraction of H-2, CO2 and CH4 increases by 3.44%, 8.08% and 182.09%, respectively. The relationship between temperature and the mole fraction of CH4 is concluded, which can be used as an indirect method to predict the temperature of RSC. The homogeneous reaction in RSC is dominated by water-gas shift reaction (WGSR). There are backward WGSR and forward methane-steam reforming reaction (MSR) in the inlet area, which is contrary to the situation in the outlet area. Moreover, the composition distributions of syngas present a polarized distribution under the influence of operating pressure or operating load, because the homogeneous reactions in the inlet and outlet area of RSC are affected by syngas velocity and temperature, respectively.

The present work investigated the flow and spray fields in a realistic concentric staged high-temperature-rise (HTR) combustor in isothermal conditions using high-speed (10 kHz) particle image velocimetry (PIV) and 10 Hz kerosene planar laser-induced fluorescence (kerosene-PLIF). The two stages of the combustor, including a pilot stage and a main stage, were operated both individually and jointly to investigate their corresponding flow fields and the interactions between the flow from the two stages. From the time-averaged flow field results, strong coupling between the pilot and main swirling flows has been identified, leading to the formation of a primary recirculation zone (PRZ) and a lip recirculation zone (LRZ). From the instantaneous flow fields, the presence of a precessing vortex core (PVC) was observed when the two stages were flowing jointly, and the dominant PVC unsteady motions located in the inner shear layer of the pilot swirling was identified using snapshot proper orthogonal decomposition (snapshot POD) with dominant frequencies at 1400 and 1515.4 Hz. Comparing the flow field with the spray field indicates that the unsteady flow motion, in addition to the mean bulk flow, plays a key role in the understanding of the spray distribution. Noticeably, it is shown in present study that the dominant unsteady flow motions properly captured from the POD analyses show good agreement with some primary features of the spray distribution, which can be valuable to unraveling the complex flow-spray coupling in the HTR combustor operated under realistic conditions.