This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out...This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out of a bulk (1000 Kg) of clay obtained from Ipetumodu in Nigeria was analyzed for size range, consequent upon which the remaining bulk was sieved to 100 μm, being the average size. The bulk was there after leached under a predetermined condition (1.6 mol/dm3 of oxalic acid at 70oC for 150 min and 200 rev/min agitation speed) and cylindrical samples (5 cm diameter by 5 cm high) containing different quantities of high alumina cement (5% - 20%) and sawdust (1% - 5%) were prepared, dried at 110oC and subsequently fired at 900oC, 1100oC, 1300oC and 1500oC, at the rate of 4oC/min and soaked for 2 hrs. These samples were subjected to different refractory tests (permanent linear change, modulus of rupture, bulk density, cold crushing strength and apparent porosity). Even though samples containing more than 20% alumina crumbled at elevated temperatures, it was still observed that the bricks performed to expectations at lower alumina contents, even at 1500oC. The sample containing 3% sawdust and 10% alumina cement however, gave the desired requirement for preparing good insulating firebricks with reliable phase integrity, as revealed by scanning electron microscopy (SEM).展开更多
LONGQUAN,a historic city in east China’s Zhejiang Province,is renowned for its exquisite celadon ware,featuring fine texture and pure,jade-like glaze.The region has a potterymaking tradition that spans over 1,600 yea...LONGQUAN,a historic city in east China’s Zhejiang Province,is renowned for its exquisite celadon ware,featuring fine texture and pure,jade-like glaze.The region has a potterymaking tradition that spans over 1,600 years.Its celadon firing technique originated during the Three Kingdoms Period(220-280)and reached its peak in the Southern Song Dynasty(1127-1279).Since the Song Dynasty(960-1368),Longquan was among the main suppliers of porcelain for the imperial court.From the 12th to the 15th centuries.展开更多
The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-ves...The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-vestigate temporal response of remotely-sensed active fires to intra-annual climate change,several 1-km datasets,including the Moderate-resolution Imaging Spectroradiometer Collection 6(MODIS C6)active fires and the Cli-matologies at High Resolution for the Earth’s Land Surface Areas(CHELSA)climate variables,were gathered to examine the climatic characteristics of active fire incidences,fire-climate correlations,and the average monthly response of active fire occurrences to climate change using the Geographic Information System(GIS)Fishnet tool,Theil-Sen Median slope estimation,Mann-Kendall significance test,and Pearson’s correlation.We concluded that climate variables’trends of nearly two-decade active fires displayed varied degrees of increment in precipitation(Pre),temperature(Tas),and surface downwelling shortwave radiation(Rsds)and inconsistent decrement in near-surface relative humidity(Hurs)and near-surface wind speed(sfcWind).MODIS multi-year(2003-2018)active fires were moderately to strongly correlated negatively with Pre and Hurs at 10 km grid-resolution but positively with sfcWind and Rsds,showing marked geographical variations in correlation direction and strength.The most significant finding is the newly observed inverse relationship between active fires and precipitation on both sides of the equator.High occurrence areas of active fires regularly appear back and forth along with latitudinal changes(at one-degree intervals)in monthly minimum precipitation between the tropical Northern and Southern Hemispheres.The present study contributes to exploring the underlying mechanism of fire-climate interactions against the backdrop of climate warming.展开更多
Since the Industrial Revolution,humanity’s extensive burning of fossil fuels(coal,oil,and natural gas)has led to a continuous rise in the concentration of greenhouse gases,such as carbon dioxide(CO_(2)),in the atmosp...Since the Industrial Revolution,humanity’s extensive burning of fossil fuels(coal,oil,and natural gas)has led to a continuous rise in the concentration of greenhouse gases,such as carbon dioxide(CO_(2)),in the atmosphere.According to data from the World Meteorological Organization(WMO),the global average CO_(2) concentration in 2023 exceeded 420×10^(−6),reaching the highest level in the past 800000 years.This has led to the increasing frequency of extreme climate events-such as glacier melting,sea-level rise,heatwaves,droughts,floods,and hurricanes-posing a severe threat to ecosystems and human society.展开更多
To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fire...To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.展开更多
森林火点检测在林火应急救援中起着至关重要的作用.鉴于现有模型在样本质量、多尺度检测以及多视角图像泛化能力方面存在不足,以YOLOv7为基础,提出一种森林火点目标检测方法FFD-YOLO(forest fire detection based on YOLO).首先,构建多...森林火点检测在林火应急救援中起着至关重要的作用.鉴于现有模型在样本质量、多尺度检测以及多视角图像泛化能力方面存在不足,以YOLOv7为基础,提出一种森林火点目标检测方法FFD-YOLO(forest fire detection based on YOLO).首先,构建多视角可见光图像森林火灾高点检测数据集FFHPV(forest fire of high point view),旨在增强模型对多视角火点知识的学习能力;其次,引入全维动态卷积,构建空间金字塔池化层(OD-SPP),以此提升模型针对多视角数据的火点特征提取能力;最后,引入具有动态非单调聚焦机制的边界框定位损失函数Wise-IoU(wise intersection over union),降低低质量数据对模型精度的影响,提高小目标火点的检测能力.实验结果表明:所提出的FFD-YOLO方法相较于YOLOv7,精度提高3.9%,召回率提高3.7%,均值平均精度提高4.0%,F1分数提高0.038;同时,在与YOLOv5、YOLOv8、DDQ(dense distinct query)、DINO(detection transformer with improved denoising anchor boxes)、Faster R-CNN、Sparse R-CNN、Mask R-CNN、FCOS和YOLOX的对比实验中,FFD-YOLO具有最高的精度75.3%、召回率73.8%、均值平均精度77.6%和F1分数0.745,验证了该方法的可行性与有效性.展开更多
文摘This work studied the effects of firing temperatures on the refractory properties of insulating firebricks produced from a blend of hydrometallurgically purified clay, high alumina cement and sawdust. Twenty grams out of a bulk (1000 Kg) of clay obtained from Ipetumodu in Nigeria was analyzed for size range, consequent upon which the remaining bulk was sieved to 100 μm, being the average size. The bulk was there after leached under a predetermined condition (1.6 mol/dm3 of oxalic acid at 70oC for 150 min and 200 rev/min agitation speed) and cylindrical samples (5 cm diameter by 5 cm high) containing different quantities of high alumina cement (5% - 20%) and sawdust (1% - 5%) were prepared, dried at 110oC and subsequently fired at 900oC, 1100oC, 1300oC and 1500oC, at the rate of 4oC/min and soaked for 2 hrs. These samples were subjected to different refractory tests (permanent linear change, modulus of rupture, bulk density, cold crushing strength and apparent porosity). Even though samples containing more than 20% alumina crumbled at elevated temperatures, it was still observed that the bricks performed to expectations at lower alumina contents, even at 1500oC. The sample containing 3% sawdust and 10% alumina cement however, gave the desired requirement for preparing good insulating firebricks with reliable phase integrity, as revealed by scanning electron microscopy (SEM).
文摘LONGQUAN,a historic city in east China’s Zhejiang Province,is renowned for its exquisite celadon ware,featuring fine texture and pure,jade-like glaze.The region has a potterymaking tradition that spans over 1,600 years.Its celadon firing technique originated during the Three Kingdoms Period(220-280)and reached its peak in the Southern Song Dynasty(1127-1279).Since the Song Dynasty(960-1368),Longquan was among the main suppliers of porcelain for the imperial court.From the 12th to the 15th centuries.
基金funded by National Natural Science Foundation of China(Grants No.42371282 and 42130508)the Second Ti-betan Plateau Scientific Expedition and Research Program(Grant No.2019QZKK1006)Youth Innovation Promotion Association of the Chinese Academy of Sciences(Grant No.2020055)。
文摘The interactions between fire,ecosystems,and climate are complex.Tropical ecosystems have dominated global active fires nowadays,yet its causes,mechanisms,and consequences remain relatively poorly understood.To in-vestigate temporal response of remotely-sensed active fires to intra-annual climate change,several 1-km datasets,including the Moderate-resolution Imaging Spectroradiometer Collection 6(MODIS C6)active fires and the Cli-matologies at High Resolution for the Earth’s Land Surface Areas(CHELSA)climate variables,were gathered to examine the climatic characteristics of active fire incidences,fire-climate correlations,and the average monthly response of active fire occurrences to climate change using the Geographic Information System(GIS)Fishnet tool,Theil-Sen Median slope estimation,Mann-Kendall significance test,and Pearson’s correlation.We concluded that climate variables’trends of nearly two-decade active fires displayed varied degrees of increment in precipitation(Pre),temperature(Tas),and surface downwelling shortwave radiation(Rsds)and inconsistent decrement in near-surface relative humidity(Hurs)and near-surface wind speed(sfcWind).MODIS multi-year(2003-2018)active fires were moderately to strongly correlated negatively with Pre and Hurs at 10 km grid-resolution but positively with sfcWind and Rsds,showing marked geographical variations in correlation direction and strength.The most significant finding is the newly observed inverse relationship between active fires and precipitation on both sides of the equator.High occurrence areas of active fires regularly appear back and forth along with latitudinal changes(at one-degree intervals)in monthly minimum precipitation between the tropical Northern and Southern Hemispheres.The present study contributes to exploring the underlying mechanism of fire-climate interactions against the backdrop of climate warming.
文摘Since the Industrial Revolution,humanity’s extensive burning of fossil fuels(coal,oil,and natural gas)has led to a continuous rise in the concentration of greenhouse gases,such as carbon dioxide(CO_(2)),in the atmosphere.According to data from the World Meteorological Organization(WMO),the global average CO_(2) concentration in 2023 exceeded 420×10^(−6),reaching the highest level in the past 800000 years.This has led to the increasing frequency of extreme climate events-such as glacier melting,sea-level rise,heatwaves,droughts,floods,and hurricanes-posing a severe threat to ecosystems and human society.
文摘To reduce greenhouse gases emission and increase the renewable energy uti</span><span style="font-family:Verdana;">lization portion in the world, the biomass gasification coupled with a coal-fired </span><span style="font-family:Verdana;">boiler power generation system is studied. It is a challenge to achieve optimum performance for the coupled system. The models of biomass gasification coupled with co-firing of coal in a boiler have been established. A comparative study of three kinds of biomass (Food Rubbish, Straw and Wood Pellets) has </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">been </span></span></span><span><span><span><span style="font-family:Verdana;">done. The syngas produced in a 10 t/h gasifier is fed to a 330 MWe coal-fired boiler for co-combustion, and the co-firing performances have been compared with pure coal combustion case under the conditions of constant boiler load. Results show that co-firing decreases the furnace combustion temperature and raises the flue gas temperature for Food Rubbish and Straw, while, flue gases temperature decrease in case of Wood Pellets. At the same time NO<sub>x</sub> and SO<sub>x</sub> emissions have reduced. The system efficiencies at constant load for Food Rubbish, Straw and Wood Pellets are 83.25%, </span><span style="font-family:Verdana;">83.88% and 82.56% when the optimum conditions of gasification and co-firing </span><span style="font-family:Verdana;">process are guaranteed.
文摘森林火点检测在林火应急救援中起着至关重要的作用.鉴于现有模型在样本质量、多尺度检测以及多视角图像泛化能力方面存在不足,以YOLOv7为基础,提出一种森林火点目标检测方法FFD-YOLO(forest fire detection based on YOLO).首先,构建多视角可见光图像森林火灾高点检测数据集FFHPV(forest fire of high point view),旨在增强模型对多视角火点知识的学习能力;其次,引入全维动态卷积,构建空间金字塔池化层(OD-SPP),以此提升模型针对多视角数据的火点特征提取能力;最后,引入具有动态非单调聚焦机制的边界框定位损失函数Wise-IoU(wise intersection over union),降低低质量数据对模型精度的影响,提高小目标火点的检测能力.实验结果表明:所提出的FFD-YOLO方法相较于YOLOv7,精度提高3.9%,召回率提高3.7%,均值平均精度提高4.0%,F1分数提高0.038;同时,在与YOLOv5、YOLOv8、DDQ(dense distinct query)、DINO(detection transformer with improved denoising anchor boxes)、Faster R-CNN、Sparse R-CNN、Mask R-CNN、FCOS和YOLOX的对比实验中,FFD-YOLO具有最高的精度75.3%、召回率73.8%、均值平均精度77.6%和F1分数0.745,验证了该方法的可行性与有效性.
