Search Results (2,210)

Electrical and thermal transport measurements on quenched NaCl-type Ag_1/3Pb_1/3Sb_1/3Se reveal an n-type semiconductor with a Seebeck coefficient up to −140 μVK⁻¹ and a thermal conductivity as low as 0.52 WmK⁻¹. Short-range order is indicated by disorder diffuse scattering in electron diffraction patterns. In contrast, ⁴L-Ag_0.61Pb_1.79Sb_2.61Se₆ (space group Cmcm with a = 4.2129(1) Å, b = 13.852(1) Å, and c = 20.866(1) Å, Z = 4) features the first lillianite-type structure in the system Ag/Pb/Sb/Se. It consists of slab-like NaCl-type building blocks that are interconnected via trigonal [PbSe₆] prisms. As such structures typically do not form with Te as an anion, the first “sulfosalt-like” compound, Ag_0.38Pb_0.25Sb_2.38Te₄, in the system Ag/Pb/Sb/Te forms a layered tetradymite-like structure (space group R$\stackrel{-}{3}$m with a = 4.2887(1) Å, c = 41.544(1) Å, Z = 3). Its slabs, which are separated by van der Waals gaps, are built up from three layers of distorted [MTe₆] octahedra. Crystals of Ag_0.38Pb_0.25Sb_2.38Te₄ were grown by chemical transport. Full article

Hot-spot generation is critical to the performance and lifespan of photovoltaic (PV) modules; however, the underlying mechanisms of hot-spot formation have not been fully elucidated. This work conducted a localized shading test on a PV module, measured the micro-electrical characteristics and temperature distributions of both the shaded and unshaded cells, calculated the heat-source power densities, and then predicted the occurrence and locations of hot and cold spots via numerical simulations. It was found that, under an irradiance of 750 W/m², when one cell in a PV module is shaded by 1/2, the unshaded area within the shaded cell exhibited a hot spot, with the temperature reaching up to 77.66 °C, approximately 22.5 °C higher than the surrounding cells. The intrinsic mechanism for the occurrence of the hot spot is that, compared with the unshaded cells, the unshaded portion of the shaded cell can generate an extra significantly large Joule heat power density, about 1079.62 W/m². The reason for generating such a large Joule heat power density is that this portion is in a reverse-bias state with a high current density flowing through it, according to our measurements. In contrast, the shaded portion forms a cold spot, about 7.5 °C cooler than the surrounding cells. This is because the shaded portion can only generate a Joule heat power density of about 46.98 W/m² due to the small reverse-bias current density flowing through it and fails to absorb heat from solar irradiance, which is about 645 W/m². Moreover, this work demonstrates that the hot-spot temperature initially rises and then decreases with increasing shading ratio, with the highest temperatures and the most pronounced temperature changes occurring around a shading ratio of 1/2. The presented method can be also used to evaluate the performance and reliability of various other PV modules under local shading conditions. Full article

Working memory (WM) is crucial for adequate performance execution in effective decision-making, enabling individuals to identify patterns and link information by focusing on current and past situations. This work explored behavioral and electrophysiological (EEG) WM correlates through a novel decision-making task, based on real-life situations, assessing WM workload related to contextual variables. A total of 24 participants performed three task phases (encoding, retrieval, and metacognition) while their EEG activity (delta, theta, alpha, and beta frequency bands) was continuously recorded. From the three phases, three main behavioral indices were computed: Efficiency in complex Decision-making, Tolerance of Decisional Complexity, and Metacognition of Difficulties. Results showed the central role of alpha and beta bands during encoding and retrieval: decreased alpha/beta activity in temporoparietal areas during encoding might indicate activation of regions related to verbal WM performance and a load-related effect, while decreased alpha activity in the same areas and increased beta activity over posterior areas during retrieval might indicate, respectively, active information processing and focused attention. Evidence from correlational analysis between the three indices and EEG bands are also discussed. Integration of behavioral and metacognitive data gathered through this novel task and their interrelation with EEG correlates during task performance proves useful to assess WM workload during complex managerial decision-making. Full article

The implementation of energy-saving measures has a substantial and beneficial impact on the preservation of energy resources as well as the reduction of carbon dioxide emissions. This study focuses on the design and experimental analysis of a water-to-air heat recovery system aimed at capturing waste heat from wastewater and transferring it to a fresh cold air stream using heat pipe technology. The research problem addressed in this study is the efficient recovery of low-grade thermal energy from wastewater, which is often underutilized. The prototype heat recovery unit was designed, manufactured, and tested in the laboratory to assess its performance across various operating conditions. The experimental setup included a system where the primary agent, hot water, was heated to 60 °C and circulated through the evaporator section of the heat recovery unit, while the secondary agent, fresh air, was forced through the condenser section. The system’s performance was evaluated under different air velocities, ranging from 3.5 m/s to 4.5 m/s, corresponding to airflow rates of 207.1 m³/h and 268.6 m³/h, respectively. The study employed analytical methods alongside empirical testing to determine the effectiveness of the heat recovery system, with the global heat transfer coefficient calculated for different scenarios. The efficiency of the system varied between 25% and 51.6%, depending on the temperature and speed of the fresh air stream. The most significant temperature difference observed between the inflow and outflow of the fresh air stream was 16.8 °C, resulting in a thermal output of 1553 W. Additionally, the average (mean) overall heat transfer coefficient of the unit was calculated to be 49 W/m² K, which aligns with values reported in the literature for similar systems. The results demonstrate the potential of the designed system for practical applications in energy conservation and carbon emission reduction. Full article

Anthropogenic heat emissions, which are quantified as anthropogenic heat flux (AHF), have attracted significant attention due to their pronounced impacts on urban thermal environments and local climates. However, there remains a notable gap in research regarding the distinctions in the distribution of anthropogenic heat emissions (AHEs) along urban–rural gradients. To address this gap, the present study introduces a new concept—the anthropogenic urban heat island (ArUHI)—where the AHF within urban areas is higher than that in background areas. To quantitatively describe the magnitude and spatial extent of the ArUHI effect, two metrics—namely, ArUHI intensity (ArUHII) and ArUHI footprint (ArUHIFP)—are introduced. We conducted a comprehensive study across 208 cities in China to investigate the spatiotemporal patterns of AHF variations along urban–rural gradients during the period of 2000–2016. In addition, we explored how the complex interactions between land cover and building form components affect changes in the AHF along urban–rural gradients. Additionally, we analyzed how economic zones and city sizes alter the ArUHI intensity and ArUHI footprint. The results showed that 97% (201/208) of Chinese cities exhibited a significant ArUHI effect from 2000 to 2016. The modeled ArUHI intensity value exhibited a substantial increase of nearly fivefold, increasing from 5.55 ± 0.19 W/m² to 26.84 ± 0.99 W/m² over time. Regarding the spatial distribution of the ArUHI footprint, the analysis revealed that, for the majority of cities (86% or 179 out of 208), the ArUHI footprint ranged from 1.5 to 5.5 times that in urban areas. City sizes and economic zones yielded significant influences on the ArUHI intensity and ArUHI footprint values. Building forms were significantly positively correlated with AHF, with R² values higher than 0.94. This study contributes to the understanding of ArUHI effects and their driving factors in China, providing valuable insights for urban climate studies and enhancing our understanding of surface urban heat island mechanisms. Full article

Non-stoichiometric permingeatites Cu_3+mSbSe₄ (−0.04 ≤ m ≤ −0.02) were synthesized, and their thermoelectric properties were examined depending on the Cu deficiency. Phase analysis by X-ray diffraction revealed no detection of secondary phases. Due to Cu deficiency, the lattice parameters of tetragonal permingeatite decreased compared to the stoichiometric permingeatite, resulting in a = 0.5654–0.5654 nm and c = 1.1253–1.1254 nm, with a decrease in the c/a ratio in the range of 1.9901–1.9903. Electrical conductivity exhibited typical semiconductor behavior of increasing conductivity with temperature, and above 423 K, the electrical conductivity of all samples exceeded that of stoichiometric permingeatite; Cu_2.96SbSe₄ exhibited a maximum of 9.8 × 10³ Sm⁻¹ at 623 K. The Seebeck coefficient decreased due to Cu deficiency, showing p-type semiconductor behavior similar to stoichiometric permingeatite, with majority carriers being holes. Thermal conductivity showed negative temperature dependence, and both electronic and lattice thermal conductivities increased due to Cu deficiency. Despite the decrease in the Seebeck coefficient due to Cu deficiency, the electrical conductivity increased, resulting in an increase in the power factor (especially a great increase at high temperatures), with Cu_2.97SbSe₄ exhibiting the highest value of 0.72 mWm⁻¹K⁻² at 573 K. As the carrier concentration increased due to Cu deficiency, the thermal conductivity increased, but the increase in power factor was significant, with Cu_2.98SbSe₄ recording a maximum dimensionless figure-of-merit of 0.50 at 523 K. This value was approximately 28% higher than that (0.39) of stoichiometric Cu₃SbSe₄. Full article

The scalable production of high-quality perovskite thin films is pivotal for the industrialization of perovskite thin film solar cells. Consequently, the solvent system employed for the fabrication of large-area perovskite films via coating processes has attracted significant attention. In this study, a solvent system utilizing a volatile solvent as the primary reagent has been developed to facilitate the rapid nucleation of volatile compounds. While adding the liquid Lewis base dimethylformamide (DMF) can help to improve the microstructure of perovskite films, its slow volatilization renders the crystal growth process uncontrollable. Based on the solvent system containing DMF and ethanol (EtOH), introducing a small amount of NH₄Cl increases the proportion of the intermediate phase in the precursor films. This not only results in a controllable growth process for the perovskite crystals but also contributes to the improvement of the film microstructure. Under the simulated illumination (AM1.5, 1000 W/m²), the photoelectric conversion efficiency (PCE) of the inverted solar cells has been improved to 20.12%. Furthermore, after 500 hours of continuous illumination, the photovoltaic device can retain 95.6 % of the initial, indicating that the solvent system is suitable for the scalable fabrication of high-quality FAPbI₃ thin films. Full article

Background: Idiopathic intracranial hypertension (IIH) is typically characterized by headaches and vision loss. However, neurocognitive deficits are also described. Our study aimed to test the influence of therapeutic lumbar puncture on the latter. Methods: A total of 15 patients with IIH were tested with a battery of neurocognitive tests at baseline and after therapeutic lumbar drainage. Hereby, Logical Memory of the Wechsler Memory Scale—Revised Edition (WMS-R), the California Verbal Learning Test Short Version (CVLT), alertness, selective attention, and word fluency were used. Changes in cognitive functioning in the course of CSF pressure lowering were analysed and compared with age, sex, and education-matched healthy controls. Results: Before intervention, scores of Logical Memory, the RWT, and the HADS-D were significantly lower in IIH patients compared to matched controls. After short-term normalization of CSF pressure, the RWT improved significantly. Additionally, significant positive correlations were found between headache intensity and subjective impairment, as well as between BMI and CSF opening pressure. Conclusions: Our findings confirm lower performance in terms of long-term verbal memory and word fluency compared to controls, as well as depressive symptoms in IIH patients. Significant improvement after short-term normalization of intracranial pressure by means of CSF drainage was seen only for word fluency. This indicates that short-term normalization of CSF pressure is not sufficient to normalize observed neurocognitive deficits. Full article

Background: This study aimed to examine how concurrent working memory (WM) loads affect selective attention, and to explore developmental differences between young adults and children/adolescents aged 10 to 14 years. Methods: We employed a modified Stroop task with verbal or spatial WM loads to assess their impact on attention. Results: In adults, we found increased Stroop effects when WM load overlapped with target processing and decreased Stroop effects when WM load overlapped with distractor processing. Conversely, in children/adolescents, WM loads did not significantly impact target or distractor processing, indicating no change in Stroop effects under dual-task conditions. Interestingly, results from the correlational analyses revealed that as participants’ ages increase, the interference effect under the WM load that shares resources with distractor processing in the attention task decreases. Conclusions: Our findings suggest that the interaction between attention and WM differs across developmental stages. While adults showed distinctive effects of concurrent WM loads on attention processing depending on the cognitive resources utilized, children/adolescents failed to show the interaction between the two cognitive systems. Furthermore, a significant relationship between age and the effects of WM load on attention was observed, providing insights into the development of the interaction between WM and attention. Full article

This manuscript highlights the mechanical, economical, ecological, and thermal investigations performed on paving quality geopolymer concrete (PQGC) incorporating processed steel slag (PSS) as a substitute for river sand (RSa). The replacement of RSa with PSS ranged from 0 to 100% in the PQGC mix. The mix with 100% PSS content exhibited enhanced geopolymerization, resulting in a denser and more amorphous matrix. This improved the mechanical properties, increasing compressive strength by 10.9%, flexural strength by 23.5%, and splitting tensile strength by 8.3%. The replacement of RSa with PSS in PQGC led to a marginal reduction in (embodied energy) EE and CO₂ emissions. However, compared to conventional Pavement Quality Concrete (PQC) and Fly Ash PQC (FPQC), the reduction in EE for PQGC was 44% and 34%, while the CO₂ emissions of PQGC were reduced by 1.22 and 1.49 times. Despite these benefits, PQGC with 100% PSS was 19% and 30% more expensive than PQC and FPQC, respectively. The Global Warming Potential (GWP) of PQGC was approximately one-third that of PQC and FPQC at all levels of replacement of RSa in PQGC when compared to PQC and FPQC. Additionally, thermal conductivity decreased from k = 0.67 W/m °C to k = 0.51 W/m °C with 100% replacement of RSa, keeping the concrete cooler. Therefore, PQGC with 100% PSS, when practically implemented, may help reduce surrounding temperatures. This study concludes that PSS is a feasible and reliable alternative to RSa, enhancing the sustainability of PQGC. Full article

Triply periodic minimal surfaces (TPMSs) show potential as porous materials in different engineering applications. Amongst them, heat sink is the subject of this paper. The advantage of such a structure is the ability to design it based on the intended applications. In the present paper, an attempt is made to experiment with a better understanding of the performance of TPMSs in heat sink applications. The experiment was conducted for different flow rates, and two heat sink materials, aluminum and silver, were used. In addition, two fluids were used experimentally: The first was water, and the second was a mixture of water containing 0.6% aluminum nanoparticles and identified as a nanofluid. The applied heat flux was maintained constant at 30,800 W/m². The results reveal experimentally and confirm numerically that the TPMS structure secures a uniform heat extraction in the system. The development of the boundary layer in the porous structure is reduced due to the current structure design. A higher Nusselt number is obtained when the nanofluid is used as the circulating fluid. The performance evaluation criteria in the presence of the nanofluid exceed 100. Full article

Over the last two decades, animal models have been used to evaluate the physiological and cognitive effects of mobile phone exposure. Here, we used a head-only exposure system in rats to determine whether exposure to 900 MHz GSM electromagnetic fields (EMFs) induces regional changes in neuronal activation as revealed by c-Fos imaging. In a first study, rats were exposed for 2 h to brain average specific absorption rates (BASARs) ranging from 0.5 to 6 W/kg. Changes in neuronal activation were found to be dose-dependent, with significant increases in c-Fos expression occurring at BASAR of 1 W/kg in prelimbic, infralimbic, frontal, and cingulate cortices. In a second study, rats were submitted to either a spatial working memory (WM) task in a radial maze or a spatial reference memory (RM) task in an open field arena. Exposures (45 min) were conducted before each daily training session (BASARs of 1 and 3.5 W/kg). Control groups included sham-exposed and control cage animals. In both tasks, behavioral performance evolved similarly in the four groups over testing days. However, c-Fos staining was significantly reduced in cortical areas (prelimbic, infralimbic, frontal, cingulate, and visual cortices) and in the hippocampus of animals engaged in the WM task (BASARs of 1 and 3.5 W/kg). In the RM task, EMF exposure-induced decreases were limited to temporal and visual cortices (BASAR of 1 W/kg). These results demonstrate that both acute and subchronic exposures to 900 MHz EMFs can produce region-specific changes in brain activity patterns, which are, however, insufficient to induce detectable cognitive deficits in the behavioral paradigms used here. Full article

Heavy rainfall, a natural phenomenon reinforced by climate change and global warming, can cause severe social, economic, and safety impacts. Due to the impact of climate change and global warming, heavy rainfall events have become more frequent and intense in recent years, underscoring the urgent need to develop robust stormwater management systems that can prevent related social, economic, and safety issues. This is of greater importance in developing countries. The present study identified areas in Urmia City, Iran, that require stormwater management to develop a comprehensive understanding of the hydrological processes within the study area and to prevent the subsequent effects of heavy rainfall. For this purpose, a combination of the watershed modeling system (WMS) and stormwater management model (SWMM) was employed. Also, three possible scenarios that could be implemented to address the issue of water flow in the medium were proposed. Results indicated that the scenario involving the application of a vegetative swale was the most promising solution. Overall, the results of the present study offer a valuable framework for decision-makers in regions facing heavy rainfalls to effectively manage and minimize the adverse impacts of such events. Full article

Heat dissipation has emerged as a critical challenge in server cooling due to the escalating number of servers within data centers. The potential of immersion jet technology to be applied in large-scale data center server operations remains unexplored. This paper introduces an innovative immersion jet liquid cooling system. The primary objective is to investigate the synergistic integration of immersion liquid cooling and jet cooling to enhance the heat dissipation capacity of server liquid cooling systems. By constructing a single-server liquid cooling test bench, this study compares the heat dissipation efficiencies of pure immersion and immersion jet liquid cooling systems and examines the impact of inlet water temperature, jet distance, and inlet water flow rate on system performance. The experimental outcomes show that the steady-state surface heat transfer coefficient of the immersion jet liquid cooling system is 2.6 times that of the pure immersion system, with increases of approximately 475.9 W/(m²·K) and 1745.0 W/(m²·K) upon adjustment of the jet distance and flow rate, respectively. Furthermore, the system model is streamlined through dimensional analysis, yielding a dimensionless relationship that encompasses parameters such as inlet water temperature, jet distance, and inlet water velocity. The correlation error is maintained below 18%, thereby enhancing the comprehension of the immersion jet cooling mechanism. Full article

Accurate land-use and land-cover (LULC) mapping is crucial for effective watershed management and hydrological modeling in arid regions. This study examines the use of high-resolution PlanetScope imagery for LULC mapping, change detection, and hydrological modeling in the Wadi Ham watershed, Fujairah, UAE. The authors compared LULC maps derived from Sentinel-2 and PlanetScope imagery using maximum likelihood (ML) and random forest (RF) classifiers. Results indicated that the RF classifier applied to PlanetScope 8-band imagery achieved the highest overall accuracy of 97.27%. Change detection analysis from 2017 to 2022 revealed significant transformations, including a decrease in vegetation from 3.371 km² to 1.557 km² and an increase in built-up areas from 3.634 km² to 6.227 km². Hydrological modeling using the WMS-GSSHA model demonstrated the impact of LULC map accuracy on simulated runoff responses, with the most accurate LULC dataset showing a peak discharge of 1160 CMS at 930 min. In contrast, less accurate maps showed variations in peak discharge timings and magnitudes. The 2022 simulations, reflecting urbanization, exhibited increased runoff and earlier peak flow compared to 2017. These findings emphasize the importance of high-resolution, accurate LULC data for reliable hydrological modeling and effective watershed management. The study supports UAE’s 2030 vision for resilient communities and aligns with UN Sustainability Goals 11 (Sustainable Cities and Communities) and 13 (Climate Action), highlighting its broader relevance and impact. Full article