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V. Sreekanth Meenakshi Kushwaha Padmavati Kulkarni Adithi R. Upadhya B. Spandana Vignesh Prabhu 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(7):2140-2150
Leveraging the COVID-19 India-wide lockdown situation, the present study attempts to quantify the reduction in the ambient fine particulate matter concentrations during the lockdown (compared with that of the pre-lockdown period), owing to the highly reduced specific anthropogenic activities and thereby pollutant emissions. The study was conducted over Bengaluru (India), using PM2.5 (mass concentration of particulate matter having size less than or equal to 2.5 µm) and Black Carbon mass concentration (BC) data. Open-access datasets from pollution control board (PCB) were also utilised to understand the spatial variability and region-specific reduction in PM2.5 across the city. The highest percentage reduction was observed in BCff (black carbon attributable to fossil fuel combustion), followed by total BC and PM2.5. No decrease in BCbb (black carbon attributable to wood/biomass burning) was observed, suggesting unaltered wood-based cooking activities and biomass-burning (local/regional) throughout the study period. Results support the general understanding of multi-source (natural and anthropogenic) nature of PM2.5 in contrast to limited-source (combustion based) nature of BC. The diurnal amplitudes in BC and BCff were reduced, while they remained almost the same for PM2.5 and BCbb. Analysis of PCB data reveal the highest reduction in PM2.5 in an industrial cluster area. The current lockdown situation acted as a natural model to understand the role of a few major anthropogenic activities (viz., traffic, construction, industries related to non-essential goods, etc.) in enhancing the background fine particulate matter levels. Contemporary studies reporting reduction in surface fine particulate matter and satellite retrieved columnar Aerosol Optical Depth (AOD) during COVID-19 lockdown period are discussed. 相似文献
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刘亚英 《中国空间科学技术》1997,17(4):35-40
分析研究了空间碎片数随太阳辐射流量F10.7的变化;给出预报F10.7长期变化的计算方法和预测空间碎片数的数学模型。结果显示:①强太阳活动造成空间碎片年增长率下降;②空间碎片数与太阳活动11年变化密切相关,相关数为0.9;③空间碎片增长率约为发射率的两倍;④若发射率保持不变,则到2020年,大于10cm的碎片数将达到14500;⑤若小碎片的增长为大碎片增长的两倍,则到2020年,大于1cm的碎片数可达125000。 相似文献
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该标准是采用10kHz低中频串联替代技术,以八位精密感应分压器作参考衰减器,并用特制的选放和差分电压表作接收机的衰减标准装置。它主要用于各种衰减校准装置、精密接收机、量值传递,以及各种精密衰减器、元器件损耗的检定。其频率范围为:1~1000MHz和10kHz;准确度为:0~20dB±0.001dB,20~80dB±(0.001~0.002)dB/10dB。文章详细叙述了其工作原理、主要特点、误差分析、与国家衰减基准装置的比对数据、国内外同类装置水平比较等。 相似文献
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本文叙述射频衰减计理保证方案(MAP)的数学模型及t检验和F检验方法。MAP是一种新的量值传递方法,中心实验室通过传递标准衰减器的传递,参加实验室用核查标准衰减器,使其参考标准测量过程不确定度控制在一定范围以内。 相似文献
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