Surface Temperature Difference Research Articles

Importance of temporal dimension and rural land cover when computing surface urban Heat Island intensity

Surface urban heat islands (SUHI) translate the difference in surface temperature between urban and surrounding rural regions. This study makes use of geostationary remote sensing data (Meteosat Second Generation) rather than polar orbiting satellites, taking advantage of its higher temporal resolution. Three cities were selected: Paris, Madrid and Milan. This allowed studying both the seasonal and diurnal cycles of SUHI. The SUHI is here computed with reference to the agricultural and forest rural land covers, and the two combined. We found that for a generic rural background, the SUHI maximum occurs at 12/20/12 UTC in spring/spring/summer with values of 3.1/1.6/4.0 °C for Paris/Madrid/Milan. Secondary peaks of SUHI are also sometimes found during the nighttime in the cities of Paris and Milan. Our results highlight the need for understanding the diurnal variability of SUHI throughout the year, considering the different city surroundings. It is found that for the same urban temperature, different SUHI intensities can occur when varying the rural cover reference. Also, for the same urban temperatures, neither SUHI intensity, nor its diurnal cycle is constant throughout the year, emphasizing the need for high temporal resolution datasets in SUHI studies.

A junction temperature model based on heat flow distribution in an IGBT module with solder layer voids

The presence of voids in a solder layer affects the thermal reliability of an insulated-gate bipolar transistor (IGBT). In this work, the effects of the size and fraction of solder layer voids and the power losses of chips on heat flow distribution, junction temperature and thermal resistance were investigated. It was found that it was difficult for the heat to flow through the voids due to the high thermal resistance of air. Therefore, the heat above the voids could only flow horizontally, and then avoid the voids and move downward in the solder layer and the following layers, leading to a temperature difference in the surface chip layer. An improved junction temperature model based on the heat flow distribution (HD) considering the solder layer voids was established, the horizontal thermal resistance and horizontal heat capacity are introduced to characterize the effect of the solder layer voids, and the parameter extraction method was proposed. The temperature difference on the surface of the module increased with the increase of the void fraction, and when the void fraction increased from 0 % to 40 %, the surface temperature difference increased from 9.591 °C to 109.86 °C. The results showed that the proposed model not only had a higher accuracy in the estimation of the junction temperature compared with the traditional Cauer model and the improved Cauer model, but also monitored the horizontal temperature differences in the chip layer precisely.

An Integrated Way to Monitor the Health Condition of Building Facades by Analyzing Thermal Infrared Images

Thermography is widely used for defect detection through analysing thermography. Thermography is used to record the surface temperatures with a thermal infrared camera. Visual interpretation can be employed to identify defects according to the differences in surface temperatures. Recently, image-processing techniques have provided a quantitative way to detect defects rather than visual interpretation. Robust principal component analysis (RPCA) is employed to analyze a series of thermal infrared images [1]. Traditionally, principal component analysis (PCA) is used to investigate a series of thermal infrared images by projecting the thermal data onto a low-dimension space such that a template image inherits the significant characteristics of the given thermal data. However, PCA introduces noise effects such that the template generated with PCA contains the noise effects. RPCA offers a similar way to project the given data onto a low-dimension space and a feature space and provides a robust way to depress the noise effects. With the introduction of RPCA, a template image can be selected from the low- dimension space, and image segmentation is employed to segment the template. Those segmented regions illustrated on the segmented template indicate the surface temperature differences, and those differences can be used as clues to identify the defects.

Evolution of Industrial Quality Parameters of Wheat during Storage in White and Colored Silo Bags: A Field-Scale Study

Over the past two decades, the silo bag system has gained popularity for storing grains and by-products under hermetic conditions. However, the impact of higher temperatures in the outer grain layer on key industrial parameters, such as wheat baking quality, remains insufficiently understood. Traditional silo bags are black on the inside and white on the outside to reflect sunlight, but colored bags, recently introduced to the market, absorb more heat, potentially warming the grain and causing damage. This study aimed to assess the effect of grain strata and bag color on grain temperature and quality under field conditions. Results showed a significant surface temperature increase in colored bags compared to white ones, approximately 3 °C, which affected the temperature of the peripheral grain layer. Moisture content slightly increased (0.2 percentage points) in the outer grain layer. However, many industrial quality parameters (protein content, P/L, W, and loaf volume) and the germination test for wheat, showed no significant differences between colored and white bags or between different strata after 120 days of storage, although the falling number increased and wet gluten decreased. These findings suggest that, despite surface temperature differences, the overall industrial quality of wheat remains unaffected by external bag coloration. The influence of ambient temperature on the peripheral layer was estimated to affect approximately 5–10% of the grain mass, indicating that adverse impacts on grain quality may go unnoticed without implementing stratified sampling techniques.

Intrinsic and extrinsic factors associated with the spatio-temporal distribution of infectious agents in early marine Chinook and coho salmon

Understanding the factors driving the spatial distribution of infectious agents in populations is key to predicting infectious agent distributions under future ecological and anthropogenic scenarios. We applied a geostatistical analysis to a data set of 59 infectious agents assayed in thousands of Chinook and coho salmon in their first marine year to identify intrinsic and extrinsic factors associated with the probability and density (infectious agent load) of infection. Meta-analysis of the pathogen-specific geostatistical models indicated that sea surface salinity was the extrinsic factor most frequently associated with infection probability and density for a majority of infectious agents. In addition, agents that were categorized as having a moderate risk of transmission from aquaculture to wild salmon were more likely to occur, and at higher infection densities, in fish collected closer to active aquaculture facilities. Although hypotheses pertaining to other intrinsic and extrinsic factors, including age at ocean entry, known hatchery origin, and sea surface temperature deviation, were not supported by the meta-analysis results, some individual agents demonstrated strong associations with these factors. Our results suggest that climate-change-driven shifts in coastal seawater salinity (and to a lesser extent, temperature) may result in changes to the infection dynamics of several infectious agents. In addition, our results contribute to existing evidence characterizing the risk of infectious agent transmission from netpen aquaculture to free-ranging salmon.

Changes in blue whale survival and abundance in the Gulf of California

AbstractUnderstanding the drivers of population abundance and distribution is fundamental to ecology and key to informing conservation actions, particularly in endangered species like blue whales (Balaenoptera musculus). Historically, some Eastern North Pacific blue whales have aggregated in the Gulf of California (GoC) each winter. Using photo‐identification data collected around Loreto Bay from 1984 to 2020, we analyzed 453 sightings histories using mark‐recapture models. Estimated apparent survival (including permanent emigration) decreased from 0.991, 95% CI [0.977, 0.997] in 1985 to 0.889, 95% CI [0.807, 0.939] in 2019. The estimated number of whales using the study area declined from 96 whales, 95% CI [50, 254] in 2012 to 13 whales, 95% CIs [12, 23 and 12, 28] in 2018 and 2019. Abundance of the whole Eastern North Pacific population is slowly increasing, so our results likely reflect declining usage of the GoC. Linear models found a relationship between the number of whales in the GoC and the difference in sea surface temperature between the study area and the Costa Rica Dome wintering area, suggesting that environmental variation could explain variation in blue whale numbers in the GoC. These results highlight the importance of tracking population dynamics as changing environmental conditions affect the range and distribution of populations.

A Two‐Column Model Parameterization for Subgrid Surface Heterogeneity Driven Circulations

AbstractEarth system models currently struggle to account for the complex effects that land surface heterogeneity can have on land‐atmosphere interactions. There have been attempts to include the impact of this heterogeneity on the atmosphere, but they ignore the development of coherent circulations that can be driven by spatial differential surface heating. A wealth of literature, particularly large‐eddy simulation (LES) based studies, shows that these circulations have significant impacts on the development and organization of clouds. In this work, we describe a two‐column model with a parameterized circulation driven by atmospheric virtual potential temperature profiles, differences in near surface temperature between the two columns, patterns of surface heterogeneity, and the mean background wind. Key aspects of the proposed model structure are compared with LES output, and the model is then implemented between two otherwise independent single column models. While some avenues for improvement exist, when the circulations are parameterized, we see increased cloud development and realistic changes to the mean profiles of temperature and moisture. The proposed model qualitatively matches expectations from the literature and LES, and points to the potential success of its future implementation in coarse grid models.

Slab Ocean Component of the Energy Exascale Earth System Model (E3SM): Development, Evaluation, and Application to Understanding Earth System Sensitivity

AbstractThis work describes the implementation and evaluation of the Slab Ocean Model component of the Energy Exascale Earth System Model version 2 (E3SMv2‐SOM) and its application to understanding the climate sensitivity to ocean heat transports (OHTs) and CO2 forcing. E3SMv2‐SOM reproduces the baseline climate and Equilibrium Climate Sensitivity (ECS) of the fully coupled E3SMv2 experiments reasonably well, with a pattern correlation close to 1 and a global mean bias of less than 1% of the fully coupled surface temperature and precipitation. Sea ice extent and volume are also well reproduced in the SOM. Consistent with general model behavior, the ECS estimated from the SOM (4.5 K) exceeds the effective climate sensitivity obtained from extrapolation to equilibrium in the fully coupled model (4.0 K). The E3SMv2 baseline climate also shows a large sensitivity to OHT strengths, with a global surface temperature difference of about 4.0°C between high‐/low‐OHT experiments with prescribed forcings derived from fully coupled experiments with realistic/weak ocean circulation strengths. Similar to their forcing pattern, the surface temperature response occurs mainly over the subpolar regions in both hemispheres. However, the Southern Ocean shows more surface temperature sensitivity to high/low‐OHT forcing due to a positive/negative shortwave cloud radiative effect caused by decreases/increases in mid‐latitude marine low‐level clouds. This large temperature sensitivity also causes an overcompensation between the prescribed OHTs and atmosphere heat transports. The SOM's ECS estimate is also sensitive to the prescribed OHT and the associated baseline climate it is initialized from; the high‐OHT ECS is 0.5 K lower than the low‐OHT ECS.

Effects of Different Land Use Types on Surface Temperature in the Northwest Arid Zone

This study analyzed the spatial and temporal characteristics of surface temperature in Uttarakhand Banner, and explored the correlation between land use types and surface temperature. The results show that the surface temperature of Urumqi Banner is greatly influenced by the change of land use types, and the difference of surface temperature between different land use types is obvious; the spatial and temporal trend of surface temperature in Urumqi Banner is different from the trend of gradual warming of the global climate change, which is mainly due to the change of the land use types by human activities.

Convective heat transfer into moving fluid from a heated prolate spheroid

A common assumption in heat transfer models that involve fluid-solid interactions is that solid particles have a spherical shape. However, in numerous engineering applications, it is crucial to gain insights into the heat transfer mechanisms involving non-spherical particles and flowing fluids. These processes often employ particles with altered shapes, such as elongated geometries resembling prolate spheroids.A numerical study of airflow past a stationary constrained prolate spheroid under forced convective heat transfer is performed. A large temperature difference of the spheroid's surface was maintained relative to free stream temperature. Navier-Stokes and energy equations were solved to investigate the impact of Reynolds number (Re) and aspect ratio (AR) on convective heat transfer rate and Nusselt number (Nu). We focus on a wide range of spheroids' surface temperatures up to 1500 K in our study, which has never been studied in depth before. The simulations show that the mean Nu has a positive dependence on Ts, AR, and Re.A new correlation has been introduced that calculates the average Nusselt number (Nu) for spheroidal particles without assuming an isothermal condition (where the surface temperature Ts is roughly equal to the ambient temperature T∞). The suggested correlation incorporates the influence of AR, surface temperature, and Re.

Exploring the body surface temperature of the lumbosacral region and relevant back-shu points in patients with lumbar disc herniation induced low back pain based on infrared thermography.

To observe the body surface temperature of the lumbosacral region and relevant back-shu points in patients with lumbar disc herniation (LDH) induced low back pain utilizing infrared thermography, and to explore the functional attribute changes of acupoints under pathological conditions. A total of 50 patients with LDH induced low back pain were included as the observation group, and 45 healthy subjects were included as the control group. Using infrared thermography, the body surface temperature of the lumbosacral region and bilateral Sanjiaoshu (BL 22), Shenshu (BL 23), Qihaishu (BL 24), Dachangshu (BL 25), Guanyuanshu (BL 26), Xiaochangshu (BL 27), and Pangguangshu (BL 28) was measured in both groups. The temperature difference values between the bilateral lumbosacral regions and back-shu points of the two groups were calculated. Additionally, the body surface temperature of the affected and healthy sides of the lumbosacral region and relevant back-shu points was compared in the observation group. Compared with the control group, the body surface temperature of the lumbosacral region and the bilateral temperature difference values of the lumbosacral regions were increased in the observation group (P<0.001). The body surface temperature difference values of bilateral Shenshu (BL 23), Qihaishu (BL 24), Dachangshu (BL 25), Guanyuanshu (BL 26) and Xiaochangshu (BL 27) in the observation group were higher than those in the control group (P<0.05, P<0.01, P<0.001). In the observation group, the body surface temperature of the affected side of the lumbosacral region as well as Shenshu (BL 23) and Dachangshu (BL 25) was elevated compared with that of healthy side (P<0.001). The patients with LDH induced low back pain have imbalanced and asymmetrical distribution of body surface temperature in the lumbosacral region and related back-shu points, Shenshu (BL 23) and Dachangshu (BL 25) have the relative specificity.

Large spread in marine heatwave assessments for Asia and the Indo-Pacific between sea-surface-temperature products

Prolonged extremely warm ocean temperatures have great impacts on both natural ecosystems and human communities. These phenomena (i.e., marine heatwaves) could be easily monitored globally by satellite-based sea surface temperatures; however, the choice of datasets may lead to potential uncertainties in the marine heatwave assessment. Here we compared the marine heatwaves using three commonly used satellite products to illustrate the uncertainties over Asia and the Indo-Pacific. Distinct differences were found in the occurrence, duration, and long-term trend of marine heatwaves over both coastal and open oceans, while some discrepancies could become comparable with the obtained metrics themselves. Although differences in mean sea surface temperatures or their variances among datasets could not explain the abovementioned discrepancies, different sensors, procedures, and sea ice treatments in each dataset may contribute partially. Overall, our study suggests that the use of multiple datasets is crucial for evaluations of extreme events.

Temperature Dependence of the Dielectric Constant on the Lunar Surface Based on Mini-RF and Diviner Observations

Radar observation is an effective way to understand subsurface structures in terms of the dielectric constant, whose controlling factors include chemical composition, packing density, and water/ice content. Recently, laboratory measurements have shown that the dielectric constant of lunar regolith simulants also depends on the temperature, which has never been evaluated from remote sensing data. In this study, we estimated the dielectric constant from the Miniature Radio Frequency (Mini-RF) data on a lunar crater floor in the north polar region at two different local times (i.e., different surface temperatures). We calculated the dielectric constant using the inversion method and obtained the bolometric surface temperature from the Diviner Lunar Radiometer Experiment (Diviner) data. The histograms of the estimated dielectric constant values are different between the two local times. This could be interpreted as a result of the temperature dependence of the dielectric constant, while further evaluation of the influence of topography on the incidence angle and small surface roughness is needed. Nevertheless, our result suggests that the temperature dependence of the dielectric constant should be considered when interpreting S-band radar observations of the Moon and other celestial bodies with large surface temperature differences.

Nondestructive detection of fruit fly (Bactrocera dorsalis) infestation in Alphonso and Totapuri varieties of mango fruits by thermal imaging technique

AbstractThermal imaging is a noncontact and nondestructive sensing technique that provides thermal signatures of objects by detecting the infrared radiations emitted by them above 1 K. The nondestructive detection of internal defects and infestations has vast applications in the Food Industry. In the present experiment, a C3 thermal camera (FLIR systems) having a thermal sensitivity of &lt;0.10°C was used for the detection of fruit fly infestation in mango fruits. The healthy mango fruits of both varieties had a uniform surface temperature with a variation of only ±0.1°C. The maximum temperature difference between the healthy and fruit fly infested regions in fruit fly infested Totapuri mango was found to be 4.56°C in the heated and dark conditions. The maximum difference in the surface temperature of 4.3°C was observed between the healthy and infested regions of the infested Alphonso mango under heated and dark conditions. The difference in temperature between the healthy and infested regions of mangoes can be attributed to the changes in the internal structure, thermal properties, and biochemical properties of the healthy and infested regions of the infested mango fruits. The statistical analysis showed a significant difference (p &lt; 0.05) in surface temperature between the infested and healthy regions of fruit fly infested Alphonso and Totapuri mango fruits. This envisages that nondestructive fruit fly infestation in Alphonso and Totapuri varieties of mango fruits can be detected under active thermography.Practical ApplicationsThe quality of mango fruit can be described in terms of external and internal quality. The external quality parameters such as color, size, and weight are usually considered during the sorting of mangoes. The internal defects such as diseases, physiological disorders, and damage due to pests are also significant in mango processing. The visual inspection methods for detecting pest infestation in fruits are nonreliable, time‐consuming, and subjective. Therefore, there is a need for efficient, reliable, and accurate methods to detect fruit fly infestation in mango fruits. A nondestructive method for the detection of fruit fly infestation has the potential to increase fruit quality and acceptability, thereby benefiting processors, traders, and consumers. Thermal imaging has a distinct advantage over other nondestructive quality assessment techniques as it is noncontact, practically feasible, and economically viable.

Validation of Thermal Imaging and the ALT-70 Prediction Model to Differentiate Cellulitis From Pseudocellulitis

Cellulitis is misdiagnosed in up to 30% of cases due to mimic conditions termed pseudocellulitis. The resulting overuse of antibiotics is a threat to patient safety and public health. Surface thermal imaging and the ALT-70 (asymmetry, leukocytosis, tachycardia, and age ≥70 years) prediction model have been proposed as tools to help differentiate cellulitis from pseudocellulitis. To validate differences in skin surface temperatures between patients with cellulitis and patients with pseudocellulitis, assess the optimal temperature measure and cut point for differentiating cellulitis from pseudocellulitis, and compare the performance of skin surface temperature and the ALT-70 prediction model in differentiating cellulitis from pseudocellulitis. This prospective diagnostic validation study was conducted among patients who presented to the emergency department with acute dermatologic lower extremity symptoms from October 11, 2018, through March 11, 2020. Statistical analysis was performed from July 2020 to March 2021 with additional work conducted in September 2023. Temperature measures for affected and unaffected skin were obtained. Cellulitis vs pseudocellulitis was assessed by a 6-physician, independent consensus review. Differences in temperature measures were compared using the t test. Logistic regression was used to identify the temperature measure and associated cut point with the optimal performance for discriminating between cellulitis and pseudocellulitis. Diagnostic performance characteristics for the ALT-70 prediction model, surface skin temperature, and both combined were also assessed. The final sample included 204 participants (mean [SD] age, 56.6 [16.5] years; 121 men [59.3%]), 92 (45.1%) of whom had a consensus diagnosis of cellulitis. There were statistically significant differences in all skin surface temperature measures (mean temperature, maximum temperature, and gradients) between cellulitis and pseudocellulitis. The maximum temperature of the affected limb for patients with cellulitis was 33.2 °C compared with 31.2 °C for those with pseudocellulitis (difference, 2.0 °C [95% CI, 1.3-2.7 °C]; P < .001). The maximum temperature was the optimal temperature measure with a cut point of 31.2 °C in the affected skin, yielding a mean (SD) negative predictive value of 93.5% (4.7%) and a sensitivity of 96.8% (2.3%). The sensitivity of all 3 measures remained above 90%, while specificity varied considerably (ALT-70, 22.0% [95% CI, 15.8%-28.1%]; maximum temperature of the affected limb, 38.4% [95% CI, 31.7%-45.1%]; combination measure, 53.9% [95% CI, 46.5%-61.2%]). In this large diagnostic validation study, significant differences in skin surface temperature measures were observed between cases of cellulitis and cases of pseudocellulitis. Thermal imaging and the ALT-70 both demonstrated high sensitivity, but specificity was improved by combining the 2 measures. These findings support the potential of thermal imaging, alone or in combination with the ALT-70 prediction model, as a diagnostic adjunct that may reduce overdiagnosis of cellulitis.

Strategic Integration of a Vegetative Component on a Metal Roof Base: An Evaluation of Its Impacts on Thermal and Acoustic Performance in the Tropics

This paper attempts to ascertain the thermal and acoustic impacts of introducing a vegetative roof layer on insulated and uninsulated metal roofs for tropical climates, through field measurements in Skudai, Johor, Malaysia, that were conducted for both dry and wet days. Four small-scale roof modules were tested, namely an uninsulated metal roof (uiMDR), an insulated metal roof (iMDR), and two identical corresponding modules with an additional vegetative component (uiGR and iGR, respectively). Outdoor ambient temperature (Tamb) was the most influential correlated variable affecting the roof outer surface temperature (RTOS) in 50% of the assessed scenarios. On the selected dry day, the inter-quartile ranges (IQR) of iGR, iMDR, uiGR, and uiMDR were 6.21 °C, 8.32 °C, 6.69 °C, and 1.66 °C, respectively; the IQRs were 1.6 °C, 4.11 °C, 2.59 °C, and 1.78 °C, respectively, on the selected wet day. Based on design U-value calculations, iGR was better than iMDR and uiMDR for both dry and wet days. The U-value of uiGR was also better than iMDR under dry-day conditions. The Wilcoxon signed-rank test also indicated a statistically significant difference in the roof inner surface temperature (RTIS) measurements (p-value = 0.00) during Malaysian daylight hours, between 8.00 a.m. and 6.00 p.m., regardless of the weather. In terms of sound level reduction under dry-day conditions, the Kruskal–Wallis and Wilcoxon signed-rank tests showed statistically significant differences in sound level reductions, with iGR and uiGR performing better than iMDR and uiMDR (p-values = 0.00). The sound level reductions for iGR, iMDR, and uiGR were 51%, 32%, and 31%, respectively, while uiMDR experienced sound level amplifications by 6%, possibly due to the acoustic resonance effect. This proof of concept may encourage a broader application of extensive GRs in Malaysia using metal roofs, beyond the conventional RC base construction method.

Design and Simulation of High-Temperature Micro-Hotplate for Synthesis of Graphene Using uCVD Method.

The uCVD (microchemical vapor deposition) graphene growth system is an improved CVD system that is suitable for scientific research and experimental needs, and it is characterized by its rapid, convenient, compact, and low-cost features. The micro-hotplate based on an SOI wafer is the core component of this system. To meet the requirements of the uCVD system for the micro-hotplate, we propose a suspended multi-cantilever heating platform composed of a heating chip, cantilevers, and bracket. In this article, using heat transfer theory and thermoelectric simulation, we demonstrate that the silicon resistivity, current input cross-sectional size, and the convective heat transfer coefficient have a huge impact on the performance of the micro-heating platform. Therefore, in the proposed solution, we adopt a selective doping process to achieve a differentiated configuration of silicon resistivity in the cantilevers and heating chip, ensuring that the heating chip meets the requirements for graphene synthesis while allowing the cantilevers to withstand high currents without damage. Additionally, by adding brackets, the surfaces of the micro-hotplate have the same convective heat transfer environment, reducing the surface temperature difference, and improving the cooling rate. The simulation results indicate that the temperature on the micro-hotplate surface can reach 1050.8 °C, and the maximum temperature difference at different points on the surface is less than 2 °C, which effectively meets the requirements for the CVD growth of graphene using Cu as the catalyst.

The intrinsic relationship of the thermal stress intensity factor and the temperature difference at the crack surface

The intrinsic relationship of the thermal stress intensity factor and temperature difference between the upper and lower surface of the crack have been studied in this paper. The results show the thermal stress intensity factor is always proportional to the temperature difference between the upper and lower crack surface, and the ratio depends only on material parameters and crack length, but is independent of loading condition. For a finite medium problem, the above conclusion is still valid by simply adding a size related correction factor. When the size of medium is 10 times larger than the crack size, the size related correction factor is less than 1.019, that is, the error is less than 2%. Our conclusion provides a theoretical basis to estimate the localization thermal stress intensity factor simply by measuring the temperature difference of the crack surface.

Numerical investigation of parameter distributions in high-temperature PEMFCs under various cooling surface temperature gradients

Non-uniform current density distribution can lead to localized hotspots, resulting in shortened lifespans of fuel cells. The temperature distributions on the bipolar plate cooling surface significantly influence various parameters within a fuel cell. This study develops a mathematical model for a high-temperature proton exchange membrane fuel cell (HT-PEMFC) to simulate its operation in four different directions of temperature gradient on the cooling surface. The distributions of membrane temperature, proton conductivity, oxygen concentration, activation loss, and current density were obtained to clarify the interaction mechanism between cooling surface temperature and these parameters in fuel cell. The results show that the membrane temperature and proton conductivity increase and the oxygen concentrations decrease with increasing cooling surface temperature. A lower temperature in the catalyst layer regions leads to a decrease in the current density. In particular, when the cooling surface temperature distribution is characterized by a temperature decrease in the upstream area with a high reactant concentration and an increase in the downstream area with a low reactant concentration, the fuel cell has an excellent current density uniformity, which reaches 92.61 % at a voltage of 0.6 V and a cooling surface temperature difference of 10 K.

Development and performance verification of a water-retaining semi-flexible pavement material based on alkali-activated slag system incorporating superabsorbent polymers

Water-retaining semi-flexible pavement (WRSFP) can effectively mitigate the urban heat island (UHI) effect by reducing the pavement temperature through water evaporation. To reduce environmental impacts and enhance the water retaining capacity and mechanical properties of WRSFP, this paper investigated the effect of proportion of water-retaining grout (WRG) on workability of fresh WRG, compressive strength, flexural strength, and water absorption of hardened WRG based on alkali-activated slag (AAS) system. The optimal proportion of WRG was recommended. The microstructure of the hardened WRG was observed with a scanning electron microscope (SEM), which allowed for a better characterization and understanding of the degree of hydration and mechanical properties of WRG. The WRSFP specimens (WRSFP-20%, WRSFP-25% and WRSFP-30%) with different porosities of porous asphalt mixture (PAM) were tested for moisture susceptibility, rutting resistance and low-temperature cracking resistance. WRSFP-25% had the best moisture resistance and rutting resistance, and the worst low-temperature cracking resistance. The maximum difference of upper surface temperature between WRSFP and stone mastic asphalt (SMA), which is commonly used in pavement, was 13.3 °C. The time to reach 60 °C on the upper surface of WRSFP was 3.4 times longer than that of SMA, which showed an excellent cooling effect of WRSFP.