Hot Regions Research Articles

Drought risk assessment based on hazard, vulnerability, and coping capacity concepts for hot and dry climate regions of Iran

Due to the complex and multi-dimensional nature of droughts, it is not possible to assess drought-induced damage and its consequences for various social, economic, and environmental aspects of societies by relying only on a univariate index such as precipitation-based drought indices. The present study aimed to develop a practical and scientific framework based on hazard, vulnerability (social, economic, and environmental), and coping capacity to generate a drought risk map for the hot and dry climate regions of Iran. Accordingly, the Drought Hazard Index (DHI), Drought Vulnerability Index (DVI), and Drought Coping Capacity Index (DCCI) were derived from “the Standardized Precipitation Evapotranspiration Index (SPEI)”, “16 social, economic and environmental variables” and “three social, economic variables”, respectively. The layers of all variables of the three indices in the GIS were provided, and they were combined in the form of an equation to produce a drought hazard map of central and southeastern Iran. The results indicate that the counties most and least vulnerable to drought were located in the southeast and west of the case study area, respectively. A number of large households, long distances from provincial centers, and soil erosion were the most important social, economic, and environmental factors making the southeast of the case study (including south of Sistan and Baluchestan and south of Kerman provinces) most vulnerable to drought. Due to their high drought coping capacity, counties located in the west of the case study (west of Kerman and south of Yazd provinces) were least vulnerable to drought. Extended support for low-income households by charitable organizations, tertiary education, and most importantly, a variety of jobs and career opportunities were the most important factors in reducing vulnerability in this part of Iran. Furthermore, our methodology by taking social, economic, and environmental dimensions into account as risk, vulnerability, and coping capacity indices can be far more efficient than the methods considering only risk and vulnerability factors.

Numerical investigation on the core thermal hydraulic behavior of pool-type sodium-cooled fast reactor (SFR)

A thorough understanding of the reactor core thermal hydraulic behavior is essential for the design and safety analysis of Sodium-cooled Fast Reactors (SFR). Due to the application of hexagonal subassembly, the core thermal hydraulic behavior is significantly affected by the flow field within the subassemblies, the inter-wrapper region and the hot pool. Analysis of the core thermal hydraulic behavior requires a model coupling the three regions mentioned above, which has been identified as one of the thermal hydraulic challenges in SFR. In the present study, a 3D model that covers the three regions was developed for the core of the China Experimental Fast Reactor (CEFR) with the Computational Fluid Dynamic (CFD) code, Fluent. The inter-wrapper region and the hot pool were modeled in detail, while the subassemblies were modeled with a special porous medium model. The core thermal hydraulics behavior under steady state was studied, more specifically, information for the flow field distribution at the core outlet, the inter-wrapper flow and the duct wall temperature distribution was obtained. Under steady state, liquid sodium in the inter-wrapper region is supplied by the inner region of the hot pool. And it enters the inter-wrapper region from the core outer region and returns back to the hot pool inner region from the core central region. The inter-wrapper flow is cooled by non-fuel subassemblies and heated up by fuel subassemblies. For non-fuel subassembly, the ratio of the total heat transfer rate between the inter-wrapper flow and the subassemblies to the heat generated within subassemblies could reaches 96%; for fuel subassemblies, the maximum ratio of the total heat transfer rate between the inter-wrapper flow and the subassemblies to the heat generated within subassemblies is 2.45%. Significant temperature gradients have been observed on the duct wall, with maximum values of 156.69 K/m in the vertical direction and 2,196.00 K/m in the circumferential direction. The largest temperature gradient appears on the duct of subassemblies adjacent to the transition region of fuel subassemblies and non-fuel subassemblies.

Ecohydrological Dynamics and Temporal Water Origin in a European Mediterranean Vineyard

ABSTRACTViticulture is an essential sector in agriculture as wine production plays a vital role in the socio‐economic life of many countries, especially in the Mediterranean area. Grapevines are a valuable, long‐lived species able to grow in hot and dry regions. We currently do not know whether rain‐fed grapevines entirely rely on deep soil water or make substantial use of shallow water from summer precipitation events. Without knowing this, we poorly understand what fraction of summer precipitation inputs contributes to grapevine transpiration. This has implications for how we quantify grapevine‐relevant precipitation budgets and for predicting the impacts of climate change on grape and wine production. We investigated grapevine water use in a vineyard in the Chianti region, central Italy. During the growing season of 2021, we monitored precipitation and soil moisture at 30‐ and 60‐cm depth. We collected over 250 samples for stable isotope analysis from rainfall, soil, and plants. Since traditional plant water sampling is problematic for grapevines, we collected samples from shoots, leaves, and condensed leaf transpiration after sealed plastic bags were wrapped around a shoot. We use these alternative plant samples to reconstruct the isotopic signal in the xylem water and infer the plant's seasonal water origin throughout the growing season. The analysis of the seasonal origin of water revealed that, throughout the growing season, soil water and plant water received disproportional contributions by rain that had fallen in the winter, even when compensating for the Mediterranean climate of the area. Only in late summer did the grapevines use substantial amounts of summer rainfall, whose contribution occasionally became dominant. These results provide a better understanding of ecohydrological interactions and uptake dynamics in valuable socio‐economic agroecosystems such as vineyards.

The impact of Pangean subducted oceans on mantle dynamics: Passive piles and the positioning of deep mantle plumes

Seismic imaging of the Earth’s interior reveals plumes originating from relatively hot regions of the lowermost mantle, surrounded by cooler material thought to be remnants of ancient subducted oceans. Currently, there is no clear consensus on the internal composition of the hot regions, with end-member conditions being that they are thermo-chemical in nature or purely thermal plume clusters. Previous modelling studies have shown a range of scenarios where deep chemical heterogenities or purely thermal anomalies are essential in developing appropriate present-day mantle dynamics. Here, we add to this discus- sion by quantifying the location of rising mantle plumes using numerical 3-D global mantle convection models constrained by 410 million years of palaeo-ocean evolution (encompassing the formation and breakup of supercontinent Pangea). Our study compares numerical simulations with purely thermal convection to those where a deep thermo-chemical anomaly is laterally mobile. The results show that models both with and without large-scale chemical heterogeneities can generate appropriate present-day plume dynamics, which illustrate the power of sinking ocean plates to stir mantle ow and control the thermal evolution of the mantle. Our models add to the discussion on bottom-up and top-down mantle dynamics, indicating the difficulty in unravelling the processes using numerical models alone.

Pulsating Heat Pipe Performance Modeling with Liquid Metal Coolants Under Hypersonic Aerothermal Heating

Hypersonic heating loads concentrate at leading-edge compression areas to create excessively high local temperatures and thermally driven stresses. The fast and reliable thermal dispersion of heat pipes with significantly high thermal conductance can alleviate these localized thermal stiffness problems. The pulsating heat pipe (PHP) holds numerous advantages when compared to capillary, constant-conductance heat pipes for hypersonic thermal management applications, primarily because they lack a wicking structure. This paper numerically investigates thermal performances of a four-turn C103 niobium alloy PHP operating with lithium, potassium, sodium, and a eutectic sodium–potassium alloy (NaK-78) when exposed to heating conditions relevant to the hypersonic environment, investigating flight Mach numbers ranging from 6 to 8 and dynamic pressures ranging from 40 to 44 kPa. The robust thermofluidic properties of liquid metals, along with the powerful fluid pulsation induced in the PHP, can provide significant thermal transport from hot stagnant regions of the leading edge to the cooler trailing surfaces. Potassium showed superior thermal performance when compared to other liquid metal coolants under the presently tested conditions, with overall PHP thermal conductance as high as 34 W/K predicted for Mach 8 flight conditions. In contrast, sodium was associated with startup difficulties in the PHP; this paper attributes this to its significantly larger thermal conductivity, which can limit the vapor pressure difference over the liquid slug lengths. These predictions indicate an overall latent heat transfer dominance of around 70–95% in liquid metal PHPs.

Analysis of carbon emission characteristics and establishment of prediction models for residential and office buildings in China

Intensifying environmental issues make carbon reduction crucial, especially in the construction industry. Embodied carbon emissions (ECE) in buildings characteristically involve concentrated, intensive emissions over a short period. Implementing energy-saving and carbon-reducing technologies has raised ECE rates. Therefore, analyzing carbon emission (CE) characteristics during the production and construction phases is necessary. Currently, essential data on ECE is lacking, the calculation methods are complex, and ECE's characteristics and influential factors in residential and office buildings remain unclear. Moreover, there is a lack of prediction models for ECE in the construction phase that apply to current construction methods and CE factors. The research on prediction models for ECE has primarily focused on the production phase but has paid little attention to the contribution of non-structural materials to embodied carbon (EC). In this study, reinforced concrete residential and office buildings in hot summer and cold winter regions (located in the southeast part of mainland China, with a subtropical monsoon climate) were considered typical types, and the CE characteristics of two main phases, the production and construction phases, were analyzed. Based on critical features, such as the number of floors and the basement, prediction models for ECE in residential and office buildings were established at the design stage. The models were validated with mean absolute percentage error (MAPE) values below 4%, and coefficient of variation (root mean square error) (CV [RMSE]) values less than 0.02. The prediction models enabled a rapid estimation of ECE, encouraging designers to consider EC in the early design stages.

Assessing the impacts of air-sealing on the sizing, operation, and economic feasibility of ground-source heat pumps for electrifying single-family houses in the US

According to recent studies and reports, in single-family houses (SFHs), air-sealing can significantly lower the thermal loads for space heating and cooling. Thus, air-sealing in SFHs could reduce the required size and cost of ground source heat pump (GSHP) systems for electrifying SFHs. This study investigated the costs and benefits of integrating air-sealing with GSHPs for retrofitting existing SFHs when compared with air-source heat pumps. A whole building energy simulation tool integrated with an advanced design tool for modeling ground heat exchangers was used to calculate changes in required GSHP capacity, total borehole length, and building energy consumption with and without air-sealing in SFHs in 16 US climatic regions. The results from this study showed that reducing outdoor air infiltration from 0.8 air changes per hour (ACH) to the minimum ventilation requirement (0.35 ACH) can significantly reduce borehole length (up to 55%), GSHP capacity (up to 48%), and total heating electricity reduction, especially in cold climates (up to 44%). The results also showed that for airtight homes (0.03 ACH infiltration) with a direct outdoor air system, the minimum required borehole length, GSHP capacity, and total heating electricity consumption can be reduced up to 70%, 68%, and 67%, respectively, when compared with SFHs with 0.8 ACH infiltration. Moreover, the life cycle cost analysis showed that air-sealing in conjunction with a GSHP is more profitable than replacing the existing system with an air-source heat pump, even without any incentives for most climatic regions in the US (except for some hot regions).

Annual emissions of N2O, NO, HONO, and NH3 from maize-wheat fields in the North China Plain

Fertilized agricultural soil is a significant source of gaseous nitrogen compounds (GNCs), including N2O, NO, HONO, and NH3. The North China Plain (NCP) is the “hot region” for the release of these GNCs due to intensive fertilization practices. However, existing research has primarily focused on N2O emissions from fertilized farmland in the NCP, lacking comprehensive observational studies on other GNCs. Therefore, a continuous cumulative sampling technique (open-top dynamic chamber system) was utilized in this study to simultaneously measure the exchange fluxes of N2O, NO, HONO, and NH3 over summer maize-winter wheat rotation fields in the NCP. Results showed that GNC emissions from the soil displayed distinct diurnal variations, with higher emissions during the day attributed to elevated soil temperature. However, N2O emissions remained consistent between day and night, potentially influenced not only by soil temperature but also by soil humidity. Annual cumulative emissions and emission factors (EFs) for four GNCs were determined, indicating that N2O, NO, and NH3 emissions during the maize season were 1.38–2.37 times higher than those during the wheat season, with 98 % of HONO emissions occurring in the maize season. Additionally, the study first presented the annual HONO EFs of 0.36 ± 0.03 % in fertilized farmland. Furthermore, a comparison revealed that the fluxes of N2O, NO, NH3, and HONO using the conventional single-point sampling method were 26.4 %, 13.9 %, and 8.10 % lower, and 7.86 % higher compared to the continuous cumulative sampling method recommended in this study. In general, this study provided precise measurements of GNC emissions from farmland, offering essential foundational data for modeling parameters and contributing to the formulation of regional air pollution prevention and control policies.

Endogenous ethanol- and thermo-tolerant strain from Malaysia pineapple peel: Screening and molecular characterisation

The current study aims to identify an endogenous acetic acid bacterial strain isolated from a Malaysian pineapple capable of tolerating high ethanol and temperatures. A total of 23 strains of presumed acetic acid bacteria were isolated from the pineapple peel waste. Subsequently, three isolates with the highest acid yield were subjected to 16S rDNA sequencing; Acetobacter tropicalis (A. tropicalis), Staphylococcus haemolyticus, and Staphylococcus ureilyticus. Tolerance evaluations against pH, temperature, ethanol, sugar, and acetic acid demonstrated that all three strains tolerated significant temperatures, ethanol, and sugar levels. Based on the results, A. tropicalis possesses the potential to reduce cooling system load during acetic acid manufacture in hot climate regions with a notable acetic acid yield.

Superconductivity and Mott Physics in Organic Charge Transfer Materials.

The phase diagrams of quasi two-dimensional organic superconductors display a plethora of fundamental phenomena associated with strong electron correlations, such as unconventional superconductivity, metal-insulator transitions, frustrated magnetism and spin liquid behavior. We analyze a minimal model for these compounds, the Hubbard model on an anisotropic triangular lattice, using cutting-edge quantum embedding methods respecting the lattice symmetry. We demonstrate the existence of unconventional superconductivity by directly entering the symmetry-broken phase. We show that the crossover from the Fermi liquid metal to the Mott insulator is associated with the formation of a pseudogap. The predicted momentum-selective destruction of the Fermi surface into hot and cold regions provides motivation for further spectroscopic studies. Our theoretical results agree with experimental phase diagrams of κ-BEDT organics.

The effect of cavity shape on critical high-temperature regions formation pattern and structural evolution difference in explosive particle bed

The occurrence of critical high-temperature regions within explosives is a crucial factor in initiating combustion and explosion. The primary causes of hot regions in cavity-containing explosives are dissipative processes occurring inside the explosive or at its interface, such as shear, friction, viscosity, plasticity, and heat transfer. Currently, there is limited research on the generation and dissipation mechanisms of critical high-temperature regions in cavity-containing explosives during impacts, based on the mesoscale analysis that describes particle motion. In this study, a model based on the discrete element method is employed allowing for an accurate analysis of the dynamic and thermodynamic processes among particles, which systematically considers the shear history between particles, elastoplastic collisions, and heat transfer between particles. The temporal evolution of particle temperature and dissipated work contours during the impact process of explosives with different cavity shapes is analyzed. Explosives with cavities undergo three stages during the impact process: the formation of the trapezoidal high-temperature region, cavity collapse, and dispersion of the particle bed, ultimately leading to the formation of two main critical high-temperature regions: near the cavity and near the wall. The temperature rise of hot particles near the wall can be roughly divided into two stages, and the temperature rise mechanisms are different. Initially, the temperature rise is primarily attributed to plastic dissipation of hot particles, and the same initial impact velocity results in the same temperature rise. During the cavity collapsing, continuous momentum transfer occurs between the hot particles near the wall and the particles in the high-temperature shear bands, deeply influencing the development of the high-temperature shear bands through the movement of the hot particles near the cavity. Therefore, the different collapse modes of hot particles near cavities of different shapes lead to differences in the later temperature evolution of the hot particles near the wall. The unique aggregation processes of hot particles near cavities of various shapes result in distinct high-temperature region morphologies: circular cavity exhibits approximate “——” shape, triangular cavity displays arch shape, and inverted triangular cavity presents “M” shape. Significantly, a new mechanism resulting from the interaction of two opposing “jet “flows for the formation of higher-temperature hot regions near the circular cavity has been discovered.

Determination of outdoor thermal comfort thresholds for hot and semi-arid climates: A field study of residential neighbourhoods in Jaipur city

Outdoor thermal comfort (OTC) plays a vital role in enhancing the livability and well-being of urban residents, making it an essential area of research, particularly in the context of climate change. However, few studies have specifically focused on hot and semi-arid regions, especially within residential environments. This study seeks to address this gap by assessing OTC in various residential areas classified as Local Climate Zones (LCZs), ensuring a diverse range of survey locations to evaluate people's comfort and stress levels. Using the Thermal Sensation Vote (TSV) index, the study calibrated the Physiologically Equivalent Temperature (PET) scale for hot and semi-arid climates. In Jaipur, micrometeorological data was monitored alongside thermal perceptions, resulting in 2,428 valid responses gathered during both summer and winter seasons, between 09:00 and 21:00 h, when outdoor activity is common. The analysis revealed that microclimate parameters significantly influence thermal sensations in outdoor environments. Respondents showed high tolerance levels during summer, with variations in thermoneutrality, acceptability, preferences, and comfort across different built typologies. The threshold values identified in this study offer valuable insights for urban planners and designers, enabling them to enhance outdoor thermal comfort during the planning stages, ultimately creating more comfortable and livable urban spaces for residents.

Vector Borne Disease Ecology and Environment: Remote Sensing and GIS for Control and Management: A Systematic Review

The prevalence of vector borne disease epidemics are influenced by the thickness of the vectors persistent to climate, landscape, and environment. Historically evidenced of triggering epidemics in both vertical magnitude and horizontal spread (spatial diffusion) of increasing vector borne diseases, such as; malaria, dengue, chikungunya, Japanese encephalitis, filariasis, leishmaniases, scrub typhus, Kyasanur forest disease (KFD), West Nile virus, Lyme disease, Zika virus, and Rift valley fever in the tropical and subtropical regions, particularly, in the third world countries for the past several decades. The geographical analysis of each one VBD epidemics has a unique vector ecology and environment. The prevalence of epidemic distribution patterns and seasonal variations, and associated vector ecology were analyzed throughout the world for the past periods, in order to assess the probability of potential risk and delineate the hotspot regions susceptible to the VBD outbreaks in the country, using Remote Sensing and GIS mapping analysis. It offers a quick and efficient approach to mapping of land uses/land cover patterns and its changes over space and time, and the information on these changes linking with vector profusion and disease ecology. Vector-borne disease epidemics across the country have been evidently associated with climate factors, landscape changes, potential breeding sources; such as, water bodies, rivers, streams, and mega water resource irrigation projects, dams / reservoirs, water pools, lakes, urban agglomerations, Urban sprawl, urban dynamics, industrial developments and growths, floating population, urban migration, land use / land cover changes, wet irrigation agriculture practices, seasonal migrations on occupation, cargo shipping movements, trade and commerce, etc., and have been acted upon changing the aboriginal territories by extent of epidemic scenarios into the non-endemic regions. The integrated Earth Observation Resource Satellite data integrated with GIS has effectiveness upon proved to disease mapping, ecological niche modeling, risk assessment, spatial prediction, and offering answers to both the public health programmers and research scientists concerned on vector fecundity, and vector borne disease ecology, and thus, the geographical, ecological and environmental determinants of its range is considered to be essential for sustainable public health planning. Accordingly, prevention measures and appropriate control strategy may possibly be applied during the sporadic outbreaks situations in the new epidemic regions as well in the hot spot endemic regions regularly, so as to control the erratic transmission and prevent acceleration of epidemics early in advance successfully.

Quantifying the Impacts of Courtyard Vegetation on Thermal and Energy Performance of University Buildings in Hot Arid Regions

Quantifying the Impacts of Courtyard Vegetation on Thermal and Energy Performance of University Buildings in Hot Arid Regions

Reinterpretation of Passive Cooling Strategies in Hot And Dry Climate Traditional Architecture: Vents in The Building

The building sector is among the most critical factors affecting environmental sustainability due to its impacts, such as energy consumption and greenhouse gas production. The reasons for energy consumption and greenhouse gas production in the building sector may vary according to climatic characteristics. In hot and arid climate regions, a significant portion of energy consumption is caused by indoor cooling, especially since the focus is on reducing the indoor temperature. In the periods when traditional architecture was developed, the lack of technological products that would increase energy consumption was effective in providing indoor air conditioning with passive design strategies. This study aims to identify the building openings for natural ventilation and cooling used in the traditional architecture of hot and dry climates and to analyze and evaluate their modern interpretations. A total of 235 award-winning projects were analyzed, and 21 were included in the study. In this context, it was determined that 16 different strategies used in traditional architecture were re-interpretation, and their modern interpretations were analyzed through award-winning projects. The traditional passive design strategies identified in this context have been adapted to modern architecture in 18 types. Wind orientators come to the forefront. In addition, it was determined that the strategies adapted to modern architecture are generally integrated. This study guides modern interpretations of traditional passive design strategies for sustainable building design.

Optimization of Ground Source Heat Pump System Based on TRNSYS in Hot Summer and Cold Winter Region

A cooling tower-assisted ground source heat pump system is proposed to solve the problem of soil heat accumulation in areas with hot summers and mild winters. TRNSYS is used to establish the simulation model of the ground source heat pump system. Taking the ground source heat pump demonstration project in Nanchang City as the research object, the operation effect of the ground source heat pump is simulated and analyzed. The key parameters of the optimization system are proposed, and the operation time of the cooling tower is controlled. The optimization results show that the cooling tower can not only improve the system performance in a short time but also enable long-term stable and efficient operation of the refrigeration system, the compound ground source heat pump system optimized by the cooling tower has almost no soil heat accumulation, and the system performance has been improved. The optimal running time of the cooling tower is 3216~4344 h and 5424~6696 h, and the system running effect is the best at this time. The research results can provide a theoretical basis for the optimal design of the cooling tower auxiliary ground source heat pump system.

A Study on Outdoor Thermal Comfort of College Students in the Outdoor Corridors of Teaching Buildings in Hot and Humid Regions

It is important to create a favorable environment for various student activities and interactions by improving the thermal comfort of semi-outdoor spaces in teaching buildings. However, there has been limited research focusing on the thermal comfort levels of college students in these areas, such as corridors (access ways connecting different buildings outdoors). This study aims to assess the thermal comfort levels of college students in the corridors of teaching buildings in hot and humid regions. Based on field measurements and questionnaire surveys, the study evaluated the thermal comfort levels of male and female college students. The findings indicate the following: (1) air temperature and air velocity are the primary thermal environmental parameters affecting college students in corridor spaces, regardless of gender; (2) physiological equivalent temperature (PET) and Universal Thermal Climate Index (UTCI) were used as indices to evaluate the thermal environment of outdoor corridor spaces. Males and females perceive the outdoor environment as hot when PET (UTCI) values reach 33.5 (34.5) °C and 33.3 (33.5) °C, respectively. When the PET (UTCI) values reach 39.0 °C (37.5 °C) for males and 37.7 °C (38.3 °C) for females, individuals in corridor spaces will face extreme heat stress; (3) females find it more challenging than males to tolerate hot outdoor environments. The unacceptable temperatures for males and females are 31.1 °C and 31.8 °C, respectively; and (4) in hot outdoor environments, females are more susceptible than males to experiencing fatigue and negative emotions. The results of this study provide valuable insights for the future design and renovation of teaching buildings on university campuses.

Optimum configuration of internal walls in intermittently conditioned rooms with different ventilation-behavior during off-periods and air conditioner operation durations

Investigations focus on optimizing insulation placement and thickness within internal walls of rooms equipped with intermittently operated air conditioners (AC), specifically targeting buildings located in China's Hot Summer and Cold Winter region. To achieve this objective, cooling and heating transmission loads for internal walls with varying insulation thicknesses, both internally and externally insulated, are calculated using EnergyPlus. Calculations are repeated across different air change rate (ACH) during AC off-periods and for varying AC operation durations. Subsequently, these transmission loads facilitate the determination of the optimal insulation position and thickness. The findings demonstrate that the internal walls with inside insulation (Wall-2) achieves an energy-saving rate of approximately 16–20 % during the cooling season and 30–60 % throughout the heating season when compared to that with outside insulation (Wall-1). Moreover, Wall-2's energy-saving advantage over Wall-1 is further accentuated with heightened ACH during off-periods and reduced durations of AC operation. Additionally, the optimal insulation thickness for Wall-2 was determined to be 0.06 m, 0.08 m, and 0.098 m for AC operation durations of 4 h, 7 h, and 10 h, respectively, with ACH having no impact on this optimal thickness. Life cycle savings varied between 254.56 and 552.31 ¥/m2/year, while payback periods varied between 1.76 and 2.33 years. These two indexes are both influenced by AC operation durations and ACH. Finally, the total energy consumption for cooling and heating is reduced by 40–50 %, when the internal wall is insulated to the optimal thickness internally.

Environmental simulation and refrigeration demand analysis for shield tunnel construction in hot summer and cold winter regions

The thermal hazards generated during the tunnel boring machine construction process significantly impact the physical and mental health of personnel. A field test was conducted on the tunnel of Metro Line 1 in Changsha, China, where the average temperature in the work zone reached up to 33.16 °C, and the air velocity was generally below 0.2 m/s. These conditions were unfavorable for ventilation and heat dissipation. In this paper, a full-scale CFD simulation model was established to simulate the construction environment and analyze the cooling demand. The results indicated that increasing the fresh air velocity could lower the temperature in the work zone; however, this effect was limited. When the fresh air temperature exceeded a certain threshold, it actually raised the average temperature of the work zone. Consequently, there is a need for supplementary cooling of the fresh air during the hot summer months. At a fresh air velocity of 15 m/s, the maximum temperature in the work zone was recorded at 27.8 °C when the fresh air was cooled down to 22.5 °C through auxiliary cooling measures. This approach effectively controlled the temperature in the work zone, reduced flow dead zones, and significantly improved air distribution and heat dissipation. Additionally, it ensured the physical and mental well-being of the construction workers and the safe operation of the equipment. This study provides valuable guidance for managing thermal environments in underground tunnel construction.

Green-synthesized Ag hierarchical assemblies for SERS detection of rhodamine dye

This study presents a simple benchtop synthetic protocol for the fabrication of silver (Ag) hierarchical structures in aqueous media using environmentally friendly and inexpensive reagents under mild experimental conditions. Natural organic acids that are known to be present in plants were employed as reducing and morphology-directing reagents. SEM and TEM imaging revealed that the products are three-dimensional hierarchical structures that were formed from self-assembly of smaller nanoparticles. They are generally spherical in shape, measure around 1.5 to 5 μm in size, and possess highly roughened surfaces due to the interstitial gaps between their nanoparticle subunits. Their hierarchical architecture allows for strong absorption of light in a broad range of wavelengths that extends to the near-infrared region. In addition, their surface morphology has an abundance of hot spot regions, which are capable of inducing strong SERS enhancement effects. The green-synthesized Ag nanostructures showed remarkable SERS activity when used as substrates for the detection of rhodamine 6G dye, a highly toxic water contaminant, even at a concentration as low as 10–8 M. Overall, this study does not only provide a greener approach to Ag hierarchical structures, but also demonstrates the immense potential of these nano-assembled architectures in the sensitive detection of organic dye pollutants.