Stratum ventilation (SV) for heating can provides a comfortable indoor environment, good intake air quality, and energy efficiency when operated correctly. The studies that have been conducted have ...focused on the operations of SV that occupants’ clothing insulation was set to a fixed value (i.e., clothing insulation of cooling season and heating season is 0.5 clo and 1 clo, respectively), with little attention to different clothing insulations. This study aimed to access the optimal ventilation parameters (i.e., supply air velocity, supply vane angle, and supply air temperature) to satisfy the requirements of thermal comfort for occupants with different clothing insulations, whilst improving indoor air quality and achieving energy savings. Firstly, based on experimentally validated Computational Fluid Dynamics (CFD) simulations, the Taguchi method was used to analyze the effects of operation parameters (i.e., supply vane angle, supply air velocity, supply air temperature, and outdoor air temperature) on the thermal comfort of occupants with different clothing insulations. The results show that the operation parameters affected the thermal comfort of occupants with different clothing insulations inconsistently. Then, taking clothing insulation as one of the important influencing factors in the optimization process, the multi-objective optimization of stratum ventilation for heating conditions was performed by a sequential preference technique based on the set pair analysis method (SPA-TOPSIS) of similarity to the ideal solution. To reduce the costs of computational, response surface models (RSMs) of ventilation performance was formulated and then used to assess the ventilation performance for all operations optimized by SPA-TOPSIS. The results showed that the dynamical optimization of ventilation parameters significantly improves ventilation performance considering different clothing insulations.
•Stratum ventilation for heating considering different clothing insulations.•Effects of operation parameters on thermal comfort are studied by Taguchi method.•Operation of stratum ventilation for heating is optimized.•The proposed RSM-based SPA-TOPSIS optimization is efficient.•Thermal comfort, air quality, and energy efficiency are significantly improved.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Stratum ventilation (SV) for heating with proper operation can effectively reduce the energy consumption of the system on the premise of meeting the requirements of thermal comfort. Previous studies ...mainly focused on the influence of non-human factors on ventilation performance (i.e., thermal comfort and energy consumption), such as multiple ventilation operation parameters (i.e., supply air temperature and supply vane angle) and outdoor temperature. Existing studies show that metabolic rate also greatly influences thermal comfort. Therefore, this study carried out multi-criteria dynamic optimization for the operation of SV for heating that considers the factors of metabolic rate, air supply parameters, and outdoor temperature. Firstly, 25 specific operation cases corresponding to combinations of different levels of factors are determined via the Box–Behnken design. Then, using computational fluid dynamics to simulate the above-mentioned operation cases, so as to construct the response surface model of ventilation performance. Finally, the multi-criteria performance of heating ventilation is optimized through the technique of order preference by similarity to ideal solution based on the set pair analysis (SPA-TOPSIS) method. The results show that after the optimization of SV for heating considering different metabolic rates, the dynamic optimization effect of ventilation performance is significant. The vertical air temperature difference between head and ankle levels, the energy consumption, and the predicted percentage of dissatisfied for 21 different metabolic rates decrease by 19.112%, 3.597%, and 21.289% on average, respectively. The draft risk increases slightly, with an average increase of only 4.736%, and still satisfies the requirements of the standard ISO-7730.
•BPNN can build prediction models of great precision for ventilation performance of heating systems of stratum ventilation.•The optimization with the optimal strategy of PMV-based TOPSIS (strategy 1) ...is efficient.•The optimal strategy of PMV and DR save energy with providing proper thermal comfort requirement than the strategy 1.•Clothing insulation instead of high air supply temperature indirectly save energy.•The BPNN-based strategies can achieve dynamical energy optimization as the outdoor weather varies.
An efficient method is used to optimize indoor air distribution in heating systems of stratum ventilation to be beneficial to develop a potential of energy-saving with providing proper thermal comfort. To save much energy with providing proper thermal comfort, asearch for good optimization methods or strategies is required to optimize indoor air distribution affected the parameters (i.e., supply air temperature, supply vane angle, clothing insulation and outdoor air temperature) in stratum ventilation systems. In this study, the air distribution of stratum ventilation for heating is optimized by using the strategy 1 (the optimal strategy of the predicted mean vote (PMV) between −0.7 and 0.7 based on a technique of order preference by similarity to ideal solution (TOPSIS)) and the strategy 2 (the optimal strategy of PMV between −0.7 and 0.7, and draft rate (DR) less than 20). Firstly, the Computational Fluid Dynamics software is used to perform ventilation operations on the parameters for stratum ventilation systems. Secondly, according to the simulation results, the parameters are set as the input variables to construct the predictive model of ventilation performance (i.e., Energy consumption, PMV and DR) by using the Back Propagation Neural Network (BPNN) method and response surface model (RSM) method, respectively. According to the accuracy analysis of models, the BPNN method is chosen to build the predictive model. Finally, the ventilation performance is output through the optimization of the proposed BPNN-based strategy 1 and strategy 2. The optimized result shows that BPNN can build prediction models of great precision for ventilation performance. The proposed strategy 2 can save more energy by providing thermal comfort than the strategy 1. And the strategies can be beneficial to save energy as the outdoor air temperature varies. Moreover, the clothing insulation instead of supply air temperature indirectly saves energy, while providing proper thermal comfort.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Unprecedented global vegetation greening during past decades is well known to affect annual and seasonal land surface temperatures (LST). However, the impact of observed vegetation cover change on ...diurnal LST across global climatic zones is not well understood. Using global climatic time-series datasets, we investigated the long-term growing season daytime and nighttime LST changes globally and explored associated dominant contributors including vegetation and climate factors including air temperature, precipitation, and solar radiation. Results revealed asymmetric growing season mean daytime and nighttime LST warming (0.16 °C/10a and 0.30 °C/10a, respectively) globally from 2003 to 2020, as a result, the diurnal LST range (DLSTR) declined at 0.14 °C/10a. The sensitivity analysis indicated the LST response to changes in LAI, precipitation, and SSRD mainly concentrated during daytime instead of nighttime, however, which showed comparable sensitivities for air temperature. Combining the sensitivities results and the observed LAI and climate trends, we found rising air temperature contributes to 0.24 ± 0.11 °C/10a global daytime LST warming and 0.16 ± 0.07 °C/10a nighttime LST warming, turns to be the dominant contributor to the LST changes. Increased LAI cooled global daytime LST (−0.068 ± 0.096 °C/10a) while warmed nighttime LST (0.064 ± 0.046 °C/10a); hence LAI dominates declines in DLSTR trends (−0.12 ± 0.08 °C/10a), despite some day-night process variations across climate zones. In Boreal regions, reduced DLSTR was due to nighttime warming from LAI increases. In other climatic zones, daytime cooling, and DLSTR decline, was induced by increased LAI. Biophysically, the pathway from air temperature heats the surface through sensible heat and increased downward longwave radiation during day and night, while the pathway from LAI cools the surface by enhancing energy redistribution into latent heat rather than sensible heat during the daytime. These empirical findings of diverse asymmetric responses could help calibrate and improve biophysical models of diurnal surface temperature feedback in response to vegetation cover changes in different climate zones.
•Vegetation is the dominant driver to asymmetric diurnal surface temperature changes.•Rising air temperature determined the surface temperature warming day and night.•LST-related biophysical mechanisms varied across climate zones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Numerous studies have documented the effects of irrigation on local, regional, and global climate. However, most studies focused on the cooling effect of irrigated dryland in semiarid or arid ...regions. In our study, we focused on irrigated paddy fields in humid regions at mid to high latitudes and estimated the effects of paddy field expansion from rain-fed farmland on local temperatures based on remote sensing and observational data. Our results revealed much significant near-surface cooling in spring (May and June) rather than summer (July and August) and autumn (September), which was −2.03 K to 0.73 K and −1.08 K respectively. Non-radiative mechanisms dominated the local temperature response to paddy field expansion from rain-fed farmland in the Sanjiang Plain. The contributions from the changes to the combined effects of the non-radiative process were 123.6%, 95.5%, and 66.9% for spring (May and June), summer (July and August), and autumn (September), respectively. Due to the seasonal changes of the biogeophysical properties for rain-fed farmland and paddy fields during the growing season, the local surface temperature responses, as well as their contributions, showed great seasonal variability. Our results showed that the cooling effect was particularly obvious during the dry spring instead of the warm, wet summer, and indicated that more attention should be paid to the seasonal differences of these effects, especially in a region with a relatively humid climate and distinct seasonal variations.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Global warming has contributed to the extension of the growing season in North Hemisphere. In this paper, we investigated the spatial characteristics of the date of the start of the season (SOS), the ...date of the end of the season (EOS) and the length of the season (LOS) and their change trends from 1982 to 2015 in Northeast China. Our results showed that there was a significant advance of SOS and a significant delay of EOS, especially in the north part of Northeast China. For the average change slope of EOS in the study area, the delay trend was 0.25 d/y, which was more obvious than the advance trend of -0.13 d/y from the SOS. In particular, the LOS of deciduous needleleaf forest (DNF) and grassland increased with a trend of 0.63 d/y and 0.66 d/y from 1982 to 2015, indicating the growth season increased 21.42 and 22.44 days in a 34-year period, respectively. However, few negative signals were detected nearby Hulun Lake, suggesting that the continuous climate warming in the future may bring no longer growing periods for the grass in the semiarid areas as the drought caused by climate warming may limit the vegetation growth.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
•Crop greening slightly decreased regional soil moisture but showed spatial variations.•Landscape pattern can affect how rainfall and soil moisture responds to crop greening.•Background precipitation ...increase masked the moisture deficit caused by crop greening.
The discrepancy between water resource availability and agricultural production has become a dominant constraint on the sustainable development of agriculture. Recent satellite records have documented increasing vegetation growth since the 21st century, and this so-called “vegetation greening” has been unprecedented in the agricultural region of Northeast China. However, the influence of increased crop growth on regional water resources through the alteration of hydrological cycling remains unclear. This study investigated the impact of crop greening on the regional water balance in Northeast China using time-series satellite and observational records, machine learning, and numerical scenario simulations from WRF. Our results indicate that the enhanced water cycling during 2001–2020 in this region was characterized by a significant increasing trend in evapotranspiration, precipitation, and soil moisture. We found a complex sensitivity to the leaf area index (LAI) across Northeast China, with positive sensitivity in the southwestern regions and negative sensitivity in the typical black soil zones. The downwind precipitation induced by crop greening suggests that at the regional scale, the landscape pattern may play a more significant role in determining the water cycling response to crop greening. Our data-driven and model-driven results indicate that the background precipitation increase was the dominant contributor to the soil moisture increase, which masked the water deficit caused by crop greening. We also found that the continuous precipitation increasing trend projected by CMIP6 could further relieve conflicts between agriculture and water resources. In summary, our study provides insights into the impact of crop greening on the regional water balance in Northeast China and highlights the importance of considering both landscape patterns and background precipitation changes in understanding the water cycling response to crop greening.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Heilong-Amur River Basin (HARB) in Northeast Asia has experienced distinct land surface changes during the past 40 years due to extensive ecological restoration programs, agricultural management, ...and grassland grazing in different ecosystems. However, the regional climate impact caused by the long-term spatially heterogeneous land surface changes in this mid-high latitude region is not well documented. Therefore, this study used multi-source satellite measurements records and a high-resolution land-atmosphere coupled regional climate model (WRF) to investigate the land surface changes and their associated thermal and moisture impacts across three main ecosystems over the Heilong-Amur River basin from 1982 to 2018. Firstly, satellite observations indicated an overall greening in HARB, with variations across ecosystems. The significant summer farmland greening is the most representative, with the farmland green vegetation fraction (GVF) remarkably increasing by 7.78% in summer. The forest greening magnitude is stronger in spring (3.42%) than in summer (2.85%), while the grassland vegetation showed some local browning signals in summer. Secondly, our simulated results showed the summer farmland greening accelerated evapotranspiration (ET) by 0.161 mm/d and significantly cools the surface temperature by 0.508 °C averaged at the ecosystem scale, which was highly correlated with the satellite observations but with lower cooling magnitude. The forest greening brought less surface cooling in spring than summer due to the stronger albedo feedback, despite with greater increase in GVF and ET. While with the opposite process, the local grassland browning leads to consistent warming effects, which can be detected from both satellite observations and our simulation results. Finally, our results also found that rainfall increasing averagely at the ecosystem scale can't fully compensate the water emission from enhanced ET due to the surface greening, contributing to soil moisture decline in both farmland and relative dry forests.
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•We observed significant summer greening for farmland instead of forests.•Summer farmland greening accelerated ET and brought significant cooling effects.•Forest greening brought less cooling in spring than summer due to albedo feedback.•Surface greening may lead to SMOIS decline in farmland and relative dry forests.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A cation with long alkane chains has a low thermal stability and generate large amounts of heat during combustion.•The thermal stability of ionic liquids is also affected by the anion with an order ...of NTF2− >PF6− >Br−.•Ionic liquids with a single atom Br− generates higher heat than those with the compounded anion NTF2− and PF6−.•The ionic liquids released large amounts of hazardous gaseous products, such as fluoroalkanes, bromoalkanes, olefins, etc.
With the development of potential large-scale industrial application of quaternary ammonium ionic liquids in the fields of gas separation, high-temperature lubricants and even rocket propellants, deep investigations are required to reveal the possible hazards of thermal decomposition, the flammability and the hazardous gaseous products. In this study, the thermal stability of five typical quaternary ammonium ionic liquids, N2222NTF2, N2222PF6, N2222Br, N4444Br and N4444PF6, were studied using thermogravimetric analyser (TGA). The results show that the thermal stability of ionic liquids follows an order of N2222NTF2 > N2222PF6 > N4444PF6 > N2222Br > N4444Br, indicating that the thermal stability is obviously affected by the anion, with an order of NTF2− > PF6− > Br−. Besides, increasing the alkyl chain length in the cation will reduce the thermal stability. In addition, Fire Testing Technology (FTT) cone calorimeter was used to investigate the flammability and found that the longer alkyl chains of quaternary ammonium ionic liquids make great contribution on larger the total heat release, the peak value of heat releasing rate and shorter ignition time. Moreover, with the same cation, N2222Br and N4444Br were shortened the ignition time and produced larger amount of heat than N2222PF6 and N4444PF6, respectively. It clearly shows that the risk of fire is also affected by the anion, with an order of Br− > PF6− > NTF2−. Finally, the decomposition products were measured by thermogravimetry coupled with Fourier-transform infrared spectroscopy (TG-FTIR), and it is deduced that the nucleophilic Br− from NmmmmBr (m = 2,4) and F− from the NTF2− and PF6− during decomposition will attack the alkyl chain of the cation, which generated gaseous products such as fluoroalkanes, bromoalkanes, olefins, etc.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Traditional energy from fossil fuels like petroleum and coal is limited and contributes to global environmental pollution and climate change. Developing sustainable and eco-friendly energy is crucial ...for addressing significant challenges such as climate change, energy dilemma and achieving the long-term development of human society. Biomass hydrogels, which are easily synthesized and modified, have diverse sources and can be designed for different applications. They are being extensively researched for their applications in artificial intelligence, flexible sensing, biomedicine, and food packaging. The article summarizes recent advances in the preparation and applications of biomass-based photothermal conversion hydrogels, discussing the light source, photothermal agents, matrix, and preparation methods in detail. It also explores the use of these hydrogels in seawater desalination, photothermal therapy, antibacterial agents, and light-activated materials, offering new ideas for developing sustainable, efficient, and advanced photothermal conversion biomass hydrogel materials. The article concludes with suggestions for future research, highlighting the challenges and prospects in this field and paving the way for developing of long-lasting, efficient energy materials.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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