Lower Surface Temperature Research Articles

Development and application of a thermoregulatory control for a thermal manikin: A comparative study of the thermal response of young and elderly individuals

Thermal manikins enable a detailed, reproducible evaluation of the human body heat exchange with clothing and the surrounding environment. Conventional control of thermal manikins limits their use to steady-state conditions, but several studies have reported successful coupling of thermal manikins and human thermoregulatory models to expand their applicability to transient conditions. This study reports on the coupling of a thermal manikin with the open-source human thermoregulatory model JOS-3. The performance of the developed control was confirmed through climate chamber measurements within a temperature range corresponding to a predicted mean vote (PMV) of ± 2. Utilizing the capability of the JOS-3 model to personalize parameters such as age and body composition, a case study emulating the thermal response of young and elderly individuals was conducted. The manikin was exposed to transient conditions with and without local heating at room temperatures of 16, 19, and 21 °C. The measurement results showed that the manikin controlled with parameters of elderly individuals were more sensitive to the ambient temperatures and showed a larger decrease in body surface temperature. At 16 °C room temperature, the predicted whole-body thermal sensation based on body surface temperature showed a substantial increase with local heating only for the young individual setting. Measurements with the elderly individual setting did not yield a noticeable increase due to the lower surface temperature of body parts not targeted by the heater. The results confirmed that the developed control can assess the thermal response of different individuals in transient conditions.

Disk resonator metasurface emitter for infrared-laser compatible stealth with dual-band thermal management

Significant advancements have been made in multiband infrared detectors, making the integration of multiband infrared compatibility with stealth capabilities essential for counteracting multiband infrared detection. This paper introduces a multiband metamaterial selective thermal emitter featuring an Ag/TiO2/Ag nanosandwich structure capable of achieving both infrared and laser-compatible stealth. Through the use of inherent absorption in lossy dielectrics, magnetic resonance properties of MIM structures, and coupling of propagating surface plasmons with Fabry-Pérot cavity resonances, the multiband infrared stealth compatibility is effectively controlled. The fabricated samples show low emissivity (ɛ 3-5 µm = 0.09, ɛ 8-14 µm = 0.54) in atmospheric windows, contributing to infrared stealth invisibility, and high emissivity (ɛ 2.5-3 µm = 0.50, ɛ 5-8 µm = 0.69) in non-atmospheric windows, facilitating radiative cooling. The sample exhibits lower surface temperatures compared to aluminum thin films, demonstrating superior thermal management. Additionally, high absorption at 1.55 µm (ɛ = 0.86) and 10.6 µm (ɛ = 0.94) is achieved due to the interference of the TiO2 layer and its inherent loss characteristics, facilitating laser camouflage. Moreover, this study centers on a multiband selective thermal emitter based on a metasurface structure, offering significant potential for multiband infrared camouflage technology.

ИЗУЧЕНИЕ КОЛЛЕКЦИИ СОРТООБРАЗЦОВ ОЗИМОЙ ПШЕНИЦЫ ЗАРУБЕЖНОЙ СЕЛЕКЦИИ В УСЛОВИЯХ ЗАПАДНОЙ СИБИРИ

The purpose of the study is to conduct a breeding assessment of variety samples and identify sources of valuable traits for winter wheat breeding. A collection of 52 varieties of winter soft wheat of different ecological and geographical origins was studied. Field and laboratory studies were carried out in 2020–2022 on the experimental field of the Omsk State Agrarian University in the conditions of the southern forest-steppe of Western Siberia. Sowing was carried out in fallows at generally accepted sowing times. The research results showed that American and Turkish varieties had the highest yield (284 and 297 g/m2), winter hardiness (6–6.5 points) and resistance to snow mold (5–5.5 points). Mexican lines had greater variability in the studied traits in comparison with other groups of variety samples and are recommended for breeding to expand the genotypic diversity of domestic varieties for drought resistance and grain quality. Bulgarian samples are unique in grain quality (on average they contain: protein – 17.1 %; gluten – 37.2; ash content – 1.81; gluten index – 95.8 % and sedimentation – 68 ml). Varieties and lines have been identified as adaptive and promising genotypes for winter wheat breeding in Western Siberia: Mv-Ispan, Mv-Bojtar, Mv-Dandar, SYWolf, KS13DH00 37-66, KS13DH00 30-32, CO13D 1299, WBLL1*2 / Tukuru // Billings. These varieties formed the highest yield (341–453 g/m2) in dry growing conditions, had higher rates and a smooth increase in biomass (NDVI = 0.37–0.68), high drought resistance (6.0–7.0 points ) and lower leaf surface temperature (≥ 35.3 °C).

South Asian Summer Monsoon under stratospheric aerosol intervention

The South Asian summer monsoon (SAM) bears significant importance for agriculture, water resources, economy, and environmental aspects of the region for nearly 2 billion people. To minimize the adverse impacts of global warming, Stratospheric Aerosol Intervention (SAI) has been proposed to lower surface temperatures by reflecting a portion of solar radiation back into space. However, the effects of SAI on SAM are still very uncertain. Our study identifies the main drivers leading to a reduction in the mean and extreme summer monsoon precipitation under SAI. These include SAI-induced lower stratospheric warming and the associated weakening of the northern hemispheric subtropical jet, changes in the upper-tropospheric wave activities, geopotential height anomalies, a reduction in the strength of the Asian Summer Monsoon Anticyclone, and, to some degree, local dust changes. As the interest in SAI research grows, our results demonstrate the urgent need to further understand SAM variability under different SAI scenarios.

Observed determinants of urban outdoor thermal exposure during hot summer and snowy winter periods in a humid continental climate

Many cities in the midlatitudes experience both extreme heat and cold, and pedestrians are exposed to thermal extremes that cause bodily stress. With growing urban populations, city design that contributes to mitigating summer heat while reducing winter cold exposure is increasingly important. Pedestrian thermal exposure depends on several microclimatic factors, including shortwave and longwave radiation absorption, which can be quantified by the mean radiant temperature (Tmrt). Limited research has been conducted on the radiative components of thermal exposure in hot, humid summers and cold, snowy winters. We gathered micrometeorological data from diverse urban sites and in multiple seasons in Guelph, Canada, using a mobile human-biometeorological weather station (MaRTy cart) that applies the six-directional method to determine Tmrt. Seasonal datasets were analysed and compared to examine the drivers of thermal exposure and recommend strategies for mitigating heat and cold stress. In summer, shade is the primary factor that reduces daytime heat exposure and it slightly increases nighttime heat exposure. Enhanced pervious ground cover is a secondary factor day and night. In winter, reduced shade alleviated daytime cold exposure, while snow cover provided daytime benefits from increased solar reflections and post-sunset penalties associated with reduced longwave radiation from low snow surface temperatures.

Study on acoustic streaming characteristics around elliptical heat exchanger tubes at different angles of attack

The distribution of acoustic streaming outside the tube in a planar standing wave field is calculated by numerical simulation using an elliptical heat exchanger tube at the low-temperature heating surface of a 600 MW unit as an example. The study discusses the impact of angle of attack (AOA), Strouhal number (St0), and Reynolds number (Re0) on the external acoustic streaming characteristics of the tube from structural, intensity, and scale perspectives. The results indicate that the strong nonlinearity of the second-order acoustic streaming in the Stokes boundary layer is driven by the first-order acoustic field. As the AOA increases, the external acoustic streaming vortices exhibit a phenomenon of inner and external vortex merging. Along the direction of the inner vortex center, the acoustic streaming velocity shows peak and valley fluctuations influenced by the vortices. In the normal direction, the acoustic streaming is significantly weakened, and the velocity distribution characteristics vary at different distances s. The inner vortices i = 1 and 2 achieve maximum and minimum values around AOA = 60° and 30°, respectively. The relative Nusselt number NU and relative shear rate SH quantify heat transfer and ash removal effects, respectively. Both small St0 and large Re0 enhance the heat transfer effectiveness. The SH shows a similar variation pattern to the scale of the acoustic streaming under the corresponding cases. The conclusion aligns well with the requirements of enhanced heat transfer and ash resistance for low-temperature heating surfaces, providing important reference for the selection of AOA for elliptical heat exchange tubes.

High-loading 316L stainless steel by integrated low-temperature surface nitriding and DLC deposition

High-loading 316L stainless steel by integrated low-temperature surface nitriding and DLC deposition

Numerical Investigation of Thermal Cooling Performance of Prismatic Lithium-Ion Battery Pack for Electric Vehicle

At present, the electric vehicles have an increasingly important role in both personal cars and public transportation because of reducing carbon dioxide emissions, that is the main reason of the global warming. The important energy source for all types of electric vehicles is battery. In this paper, the thermal cooling of lithium-ion battery pack with 4 rectangular prismatic battery cells is investigated in flow simulation. The performance of battery convection is simulated within the wind tunnel. The mass flow rate is controlled at 40, 80, and 120 g/s. The temperature distribution of the battery surface and the outlet air is analyzed from three parameters: the battery cell spacing of 5, 10, and 15 mm, the battery cells arrangement in three angles of 0, 60, and 150 from the wind direction, and the discharge rates of 0.50, 0.75, and 1.00 C. The results indicate that the battery cells have the lowest surface temperature at 15 mm of the battery cell spacing. The angle of the battery pack placement increases, resulting in the Wake Vortex Turbulence and heat dissipation from the battery cells. It is also suitable to design the battery base for installation. In addition, the mass flow rates and discharge rates are analyzed together. the results show that the surface of battery cells and the outlet air have the highest temperature at the discharge rate of 1.00 C, and the airflow rate of 40 g/s.

Spatial-Temporal Evolution and Cooling Effect of Irrigated Cropland in Inner Mongolia Region

Monitoring the dynamic distribution of irrigated cropland and assessing its cooling effects are essential for advancing sustainable agriculture amid climate change. This study presents an integrated framework for irrigated cropland monitoring and cooling effect assessment. Leveraging dense time series vegetation indices with Google Earth Engine (GEE), we evaluated multiple machine learning algorithms within to identify the most robust approach (random forest algorithm) for mapping irrigated cropland in Inner Mongolia from 2010 to 2020. Furthermore, we developed an effective method to quantify the diurnal, seasonal, and interannual cooling effects of irrigation. Our generated irrigated cropland maps demonstrate high accuracy, with overall accuracy ranging from 0.85 to 0.89. This framework effectively captures regional cropland expansion patterns, revealing a substantial increase in irrigated cropland across Inner Mongolia by 27,466.09 km2 (about +64%) between 2010 and 2020, with particularly pronounced growth occurring after 2014. Analysis reveals that irrigated cropland lowered average daily land surface temperature (LST) by 0.25 °C compared to rain-fed cropland, with the strongest cooling effect observed between July and August by approximately 0.64 °C, closely associated with increased evapotranspiration. Our work highlights the potential of satellite-based irrigation monitoring and climate impact analysis, offering a valuable tool for supporting climate-resilient agriculture practices.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Recurrent Swarms of Planktonic Shrimp Luciferidae De Haan, 1849 (Order: Decapoda) in the Neritic Waters of Tamil Nadu, Southeast Coast of India

ABSTRACTLuciferidae (Decapoda) are an important component of mesozooplankton in pelagic food webs. This study investigated the spatiotemporal distribution and frequency of Luciferidae swarms along the Tamil Nadu coast, as observed during coastal monitoring cruises conducted between 2019 and 2022. Data were collected on various hydrobiological factors, including surface water temperature, salinity, chlorophyll a, zooplankton biomass, and the abundance of other mesozooplankton (such as copepods, cladocerans, and others) across eight locations in the coastal waters of Tamil Nadu, India. Salinity values were generally low (< 30 PSU) throughout the study period, except in September 2019. Microscopic analysis identified Belzebub hanseni Nobili, 1905, as the only organism responsible for swarm formation, with its occurrence peaking in January 2022. During this period, B. hanseni reached a maximum abundance of 3294 ind. m−3 for adults and 4056 ind. m−3 for larvae, together contributing approximately 27% of the total zooplankton abundance. Swarms of B. hanseni were observed a total of seven times over the course of the study, correlating with periods of low sea surface temperature and high food availability. Pearson's correlation analysis revealed a significant relationship between the abundance of copepods and B. hanseni (r = 0.84; p < 0.001), suggesting that both groups may be influenced by similar environmental factors, such as physical transport, food availability, and favorable conditions. This study indicates that the frequent swarming of B. hanseni in the nearshore waters of the Tamil Nadu coast is largely driven by food availability and optimal environmental conditions, including water temperature and monsoonal influences. The findings also suggest that geographical features, such as mangrove habitats, may contribute to the occurrence of B. hanseni swarms in this region.

Analyzing surface temperature on street median parks in Malang’s hot-humid climate

In hot humid cities, the local microclimate can be moderated by the green open spaces. Differences in the characteristics of its hardscape and softscape elements can result in different thermal environmental conditions. As one of the green open spaces, the street median park can provide vegetation to reduce the air temperature of the region's microclimate. This paper analyzes the thermal characteristics of three street median parks in Malang, which are represent the green street medians in hot humid country of Indonesia. A thermal imaging camera was used to compare the hardscape and softscape surface temperature difference of the three parks. The thermal image results show that stone and paving materials have the highest surface temperatures. Stone as the higher surface temperature is shown in three green streets median. Coral stone has the highest surface temperature at 43.6 °C in Ijen and 42.03 °C in Veteran. Paving also has the highest surface temperature at 43.17 °C in Kunang-kunang. Grass or earth with trees has the lowest surface temperature at 28.53°C in Ijen, 27.93 °C in Kunang-kunang, and 29.17°C in Veteran Street median park. The difference in daytime surface temperature between hardscape and softscape reaches 12.86 °C in Veteran, 15.07 °C in Ijen, 15.24 °C in Kunang-kunang.

Developing energy-efficient cool roof coatings using microencapsulated eutectic phase-change material and poly(methyl methacrylate-co-methacrylic acid) copolymer shell emulsion

ABSTRACT The rise in the construction of modern structures of buildings has increased the demand for energy sources to cool indoor and outdoor temperatures. Cool coating is a highly effective roofing technology for absorbing less heat and reflecting more sunlight than conventional coating. These coatings are made from a special type of material with high solar reflectance, allowing them to reflect more sunlight. The cool coating is applied over the building roofs, which gives an efficient way to cool the building inside passively and the surrounding environment. In this context, incorporating phase-change material (PCM) into cool coating enhances its capacity for regulating temperature by storing and releasing heat as required. Combining these two would improve the coating’s overall cooling capabilities, increasing its efficacy in maintaining a lower surface temperature and lowering the cooling energy consumption in buildings. There is a lack of research studies incorporating PCM into a cool roof coating. The present work fills this gap. In this study, we have developed an easy-to-maintain thermal storage cool roof coating using microencapsulated phase-change material (MPCM) latex and white cement. This coating integrates a cooling effect, making it ideal for building applications. Lauric acid (LA), palmitic acid (PA), and stearic acid (SA) eutectic PCM as core were microencapsulated with polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) shell using oil-in-water emulsion polymerization. The microcapsule was prepared by altering the core-to-shell ratio. The microcapsules were characterized using various techniques such as thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The melting temperature of LA-PA-SA eutectic PCM, MPCM 1, and MPCM 2 was 32.66°C, 31.47°C, and 32.73°C, respectively. The TGA analysis indicates that the prepared microcapsules have good thermal stability and degrade in two steps. Microcapsules’ average particle size diameter was observed in the 3–9 µm range. The cool roof coating was fabricated by partially replacing the acrylic copolymer latex with prepared MPCM 1 latex. This study evaluates the influence of MPCM 1 latex loading on the coating’s mechanical and thermal properties. The temperature changes from the building’s exterior to the interior have been recorded using thermal energy transfer analysis. General coating properties such as water resistance, stain resistance, alkali resistance, and gloss were investigated. DSC result shows that the thermal storage enthalpy of the coating has been improved from 17.85 J/g to 37.45 J/g by partially replacing MPCM 1 latex with acrylic copolymer from 50 to 70 wt.%. Coating with 70 wt.% MPCM 1 latex reduced the rise in the room’s temperature, showing it to be a promising candidate for utilizing thermal energy within building technologies.

Identification of Anthropogenic Impact and Indicators of Landscape Transformation in the Fatala River Basin (Republic of Guinea)

The aim of this study is to identify the main factors of anthropogenic impact and indicators of landscape transformation in the Fatala River Basin in the Republic of Guinea. Our fieldwork in the Boke and Kindia regions was the main source of materials and data. The landscape and ecological situation of nine key study plots were characterized. These key plots make up a representative series of transformed and natural landscapes. We complemented our fieldwork with Landsat satellite image analysis. We learned that the main factors of anthropogenic impact in the Fatala River Basin are the systematic burning of vegetation, mechanical disturbances of soil and vegetation cover, the depletion of fertile topsoil, grazing, and the littering of the landscape with household waste. The indicators of landscape transformation are deforestation, changes in the natural vegetation cover, and mechanically disturbed lands. We identified five main stages of agro-landscape development, starting from the clearing of a plot by burning vegetation (stage I) and ending with the completion of the agricultural activity in the plot and its abandonment to restore the topsoil (stage V). The limiting factors of nature management are elevation differences, the rapid restoration of vegetation cover, and rocky/gravelly substrate. It is possible to identify transformed landscapes in large or hard-to-reach regions using satellite images. Thus, natural or quasi-natural landscapes can be identified based on the lower surface temperature relative to the surrounding lands. The normalized difference vegetation index (NDVI) and normalized difference moisture index (NDMI) could be useful for identifying agricultural pasture plots within a tropical forest using long-term satellite data series. We revealed a tendency for landscape deterioration in the middle and upper parts of the Fatala River Basin, while vegetation cover is being restored in the lower part of the basin. Finally, we propose some measures to rehabilitate transformed landscapes and increase the efficiency of agricultural production in the study region.

Combining pin-fins and superhydrophobic surfaces to enhance the performance of microchannel heat sinks

Electronics cooling and thermal management presents an immense challenge to the electrification of society. From mobile devices to stationary systems, power densification of electronics platforms is putting pressureon thermal systems. This research uniquely combines superhydrophobic surfaces with pin-fin structures to investigate their combined effects on thermal performance and fluid dynamics. We examine the impact of superhydrophobic surfaces on different internal walls for both finned and non-finned microchannels. Three-dimensional finite volume method simulations are used to analyze fluid flow and heat transfer, with surface wettability modeled using a custom user-defined function. The results of the simulations were first validated against experimental data. Thermal-hydraulic performance for finned and non-finned microchannels was studied for both conventional and superhydrophobic surfaces. Superhydrophobic properties on different internal surfaces of the microchannel yielded different outcomes for finned versus non-finned designs. We show that superhydrophobic surfaces are effective in enhancing the performance of finned channels at high Reynolds number (Re). At Re = 500, finned microchannels with superhydrophobic side walls have the same performance factor (η) as a conventional microchannel without fins with a 9.4 °C lower average base surface temperature. Additionally, superhydrophobic side walls increase the pressure drop and Nusselt number by 8.9 % and 6.6 %, respectively, compared to conventional non-superhydrophobic finned surfaces. Conversely, superhydrophobic top and bottom surfaces reduce the pressure drop and Nusselt number by 13 % and 18.5 %, respectively. Our findings reveal that the location and intensity of vortices, influenced by fins, vary with different superhydrophobic surface configurations.

The effect of hygroscopic liquids on the spatial controlling of condensation on low-temperature surfaces

Condensation is a ubiquitous natural phenomenon with both detrimental and beneficial implications. The key point to minimize its harmful effects while harnessing its potential for various applications is the spatial controlling of condensation. In recent years, using hygroscopic liquids for spatially controlling condensation has gradually emerged as a promising strategy. However, the underlying mechanisms and influencing parameters of controlling condensation with hygroscopic liquids remain insufficiently understood. In this paper, the effect of hygroscopic droplets in suppressing condensation on low-temperature surfaces, specifically -15 ℃ to 15 ℃, under different conditions, including substrate temperature, cooling time, droplet volume are studied. A typical hygroscopic liquid, dipropylene glycol, was employed to illustrate this issue. The results indicated that distinct ring-shaped dry zone forms around dipropylene glycol droplets on low-temperature surfaces, evidencing their efficacy in inhibiting condensation. Experiments and theoretical analysis reveal that the ratio of the dry-zone radius to the droplet radius is a function of substrate surface temperature, scaling as 1/(Tdew-Tc). The results also show that cooling time has a negligible effect on this ratio over short periods. Furthermore, the ratio slightly decreases with increasing droplet volume at higher substrate temperatures, while remaining nearly constant at lower temperatures. These findings may enhance our understanding of the condensation inhibition effect of hygroscopic droplets and also provide valuable insights for potential applications in condensation control.

Integrating Phase Change Materials Into Cotton Ring Spun Yarn Structure for Thermoregulating Function

ABSTRACTPhase change materials (PCMs) have been incorporated into textiles to provide thermoregulation and temperature buffering effects on the human body. From this point of view, the aim of this study was to develop the phase change material (PCM) incorporated into the yarns for the production of textiles with a thermo‐regulating function. In the study, two types of capsules poly(methyl methacrylate‐co‐methacrylic acid) (P(MMA‐co‐MAA)) walled and 1‐tetradecanol core, and gelatin‐gum Arabic walled and n‐octadecane core were synthesized and applied to cotton textile fibers using an alternative application method developed by the authors. PCM dispersion with 6% concentration was incorporated into cotton ring spun yarns at 62.5 and 80 mL/h feeding rates. Morphological and thermal properties of the capsules and spun yarns were investigated. Thermoregulation properties of fabricated yarns were detailed evaluated by segmenting thermal history (T‐history) curves into four phases and logarithmic and linear trendlines were applied to the temperature change data for unloaded and PCM incorporated yarns. Data including temperature range (°C), R2 (coefficient of determination or regression factor), rate coefficient (a) and duration of phase (s) were analyzed for both capsule types and feeding rate values. The results indicated that PCM capsules with ideal spherical morphology and enough energy storage capacity were successfully applied into the cotton fibers. All cotton yarns with PCM additives exhibited lower surface temperature values greater than 2°C which is considered sufficient for the thermoregulation effect although with some distinct variations in their temperature profiles and rate coefficients. Compared to untreated cotton ring spun yarn, the temperature difference for 1‐tetradecanol core@P(MMA‐co‐MAA) walled capsules was found to be around 4.29°C–4.56°C, whereas it was around 8.2°C–9°C for n‐octadecane core@gelatin‐gum Arabic walled capsules. With respect to all the results, obtained novel heat storage cotton yarn is a promising material for thermal energy storage and desirable thermal comfort applications.

Application of surface and subsurface anomaly linkage in geothermal resource evaluation: A case study of the Corbetti geothermal prospect, main Ethiopian rift

The Corbetti geothermal prospect (CGP) represents a rapidly uplifting, dynamically deforming volcanic region and a seismically active zone within the central Main Ethiopian Rift. Beyond its fundamental role in understanding rift evolution, the Corbetti caldera complex hosts multiple active volcanoes that serve as potential heat sources for generating geothermal energy. While the influence of tectonic and volcanological structures on the occurrence of these geothermal resources is well known, understanding how subsurface heterogeneous structures govern the availability of geothermal fluid reservoirs remains a challenge An integrated analysis of thermal infrared remote sensing data and gravity and magnetic within the CGP was used to identify anomalous temperature areas, delineate subsurface geological structures, and investigate their connection with geothermal resources. The highest concentrations of high surface temperature regions were observed at the Shala volcanic complex and north of the Corbetti caldera complex, while the lowest surface temperatures were identified in the southern and southeastern parts of the Wondo Genet. The analysis of the gravity and magnetic anomaly maps, along with 2D gravity/magnetic models and a 3D conceptual model, provided insights into subsurface magma plumbing systems and to the presence of deep-seated geothermal heat sources within the CGP. The groundwater outflow from Lake Awasa towards Lake Shala interacts with the intrusive heat under the Corbetti caldera complex at the middle of the two lakes which enhances the occurrence of geothermal resources. The existence of faults and fractures determined from geological mapping and gravity and magnetic derivative analyzes likely facilitate the migration of melt from deep intrusions to shallow magma reservoirs, acting as conduits for groundwater and ultimately manifesting as thermal anomalies at the surface beneath the Corbetti caldera and southern shore of Lake Shala.

Response of laser power bed fusion manufactured austenitic stainless steel towards combined heat treatment and low-temperature thermochemical surface strengthening

In this work, a combination of heat treatment (HT) and surface strengthening is explored to adjust the residual stress distribution in 316L stainless steel manufactured by laser powder bed fusion (L-PBF). Different HT in the range 750 °C to 950 °C were applied to relieve the overall residual stress, followed by low-temperature gaseous carburization (LTGC) to introduce compressive residual stress in the surface region. The results indicate that the hierarchical microstructure in as built 316L gradually disappeared during HT, accompanied by the relaxation of thermal residual stresses, a reduction in hardness, yield strength and ultimate tensile strength and an improvement of the elongation. HT at 900 °C for 1 h is sufficient to completely relax residual stresses in the built. At elevated temperatures, low angle grain boundaries (LAGBs) vanish, leading to a rapid change in mechanical properties. Based on these findings, the impact of different microstructures in HT specimens on the application of LTGC was investigated. It reveals that all HT specimens exhibited the formation of a uniform, approx. 30 μm thick, case after LTGC. This case possesses high hardness (∼ 12 GPa) and a carbon content at the surface of ∼ 3 wt.%. Although interdependencies occur between composition, residual stress and hardness profiles over the thickness of the expanded austenite zone, the differences in hardness and composition profiles for different conditions are minor, albeit measurable. In contrast, the residual stress profiles over the expanded austenite zone are notably affected by the initial residual stress present in the starting material and the yield stress associated with the cellular structure.

Experimental investigation of the impact and freezing processes of supercooled water droplet on different cold curved surfaces

The impact of supercooled water droplets (SCWD) on aircraft cold surfaces constitutes a major cause of aircraft icing, posing a considerable threat to flight safety. Developing a safe, efficient, and energy-efficient anti-icing method necessitates an in-depth investigation of the icing mechanism of SCWD impacting cold curved surfaces. This study experimentally investigates the freezing behavior of SCWD on cold surfaces with diverse curvatures. The results show that the water droplet spreading factor (WDSF) significantly increases as surface curvature ranges from 0 to 125 while simultaneously decreasing the freezing time. Furthermore, the ice ring morphology from droplet freezing transitions from a raised crown shape to a concave cake shape at the center. Changing the impact position of droplet resulted in a marked increase in WDSF, a substantially reduced freezing time, and the emergence of strip icicles at the lower part. Additionally, this study examines the effects of Weber number (We = 459–650) and impact surface temperature (Tw = −30 °C–0 °C) on the impact freezing process. An increase in We leads to a higher WDSF and reduced freezing times, while lower surface temperatures decelerate droplet retraction, thereby shortening freezing time. At surface temperatures below −25 °C, Tw results in droplets splashing upon impact and rapidly freezing during the spreading stage. The findings of this research provide experimental insights crucial for developing aircraft anti-icing technology.