新冠疫情防控措施对新疆地区地球背景噪声影响分析     

邓明文  李晓东  张森  徐小明  马建 《大地测量与地球动力学》2021,41(9):985-990

2020年7月中旬至8月下旬,新疆地区采取疫情防控措施。选取2020-06~2020-09新疆台网28个宽频带数字地震计的波形数据,获取相应的PSD（功率谱密度）和PDF（概率密度函数）,统计不同频段PSD值分布情况,分析疫情期间新疆地区噪声水平变化特征。结果显示,受新冠疫情的影响,乌鲁木齐地区高频段（2~20 Hz）噪声水平下降4.5%,其他地区也出现不同程度的降低,主要影响因素为人类活动的持续减少。同时,这种噪声减弱现象也由地表传达到地下。  相似文献   

基于国产卫星 AIS数据的新冠疫情前后 南极考察活动变化研究     

陈一凡  刘建强  艾松涛  丁曦  张汝诚  曾韬 《海洋通报》2022,(3)

新冠疫情冲击下, 各国经济和安全都受到极大的考验。为了保障科考人员的安全, 许多国家缩减了南极科考的行程 和人员。本研究基于国产卫星海洋一号 、海洋二号搭载的A1s 传感器, 整理了2019 年 10 月至 2021 年 5 月南极主要科考国 家的考察船 A1s 数据, 并对比考察船轨迹变化, 分析疫情前后南极科考活动的变化情况。本研究发现了考察船前往南极通道 的新特点, 分析了各南极考察大国考察热点区域的变化, 总结了南极考察热点区域受疫情影响变化, 最后对我国南极考察提 出建议。“十四五”规划中, 深空、深地、深海和极地探测被列为科技前沿领域攻关项, 本研究通过分析各极地强国疫情前 后考察船的轨迹变化, 探索我国未来的考察发展方向, 以期助力极地事业高质量可持续发展。  相似文献   

Discovery of a large-structure emission nebula near PN G200.7+08.4 (A 19)     

C.T. Hua  J. Martinis 《Astrophysics and Space Science》2003,283(2):267-271

We report narrowband (Δλ ≤ 10Å) imaging data obtained for the planetary nebula A 19 (PN G200.7+0.84) in continuing our programme of morphological study of planetary nebulae (PNe). Our deep survey through the Hα filter reveals a new nebula – probably a huge HII region –centred at R.A.(2000) = 6h59mn, DEC.(2000) = +14^°40′.  相似文献   

The airborne contagiousness of respiratory viruses: A comparative analysis and implications for mitigation     

《地学前缘(英文版)》2022,13(6):101285

The infectious emission rate is a fundamental input parameter for airborne transmission risk assessment, but data are limited due to reliance on estimates from chance superspreading events. This study assesses the strength of a predictive estimation approach developed by the authors for SARS-CoV-2 and uses novel estimates to compare the contagiousness of respiratory pathogens. We applied the approach to SARS-CoV-1, SARS-CoV-2, MERS, measles virus, adenovirus, rhinovirus, coxsackievirus, seasonal influenza virus and Mycobacterium tuberculosis (TB) and compared quanta emission rate (ER_q) estimates to literature values. We calculated infection risk in a prototypical classroom and barracks to assess the relative ability of ventilation to mitigate airborne transmission. Our median standing and speaking ER_q estimate for SARS-CoV-2 (2.7 quanta h^?1) is similar to active, untreated TB (3.1 quanta h^?1), higher than seasonal influenza (0.17 quanta h^?1), and lower than measles virus (15 quanta h^?1). We calculated event reproduction numbers above 1 for SARS-CoV-2, measles virus, and untreated TB in both the classroom and barracks for an activity level of standing and speaking at low, medium and high ventilation rates of 2.3, 6.6 and 14 L per second per person (L s^–1 p^–1), respectively. Our predictive ER_q estimates are consistent with the range of values reported over decades of research. In congregate settings, current ventilation standards are unlikely to control the spread of viruses with upper quartile ER_q values above 10 quanta h^?1, such as SARS-CoV-2, indicating the need for additional control measures.  相似文献   

Impact of COVID-19 lockdown on the optical properties and radiative effects of urban brown carbon aerosol     

《地学前缘(英文版)》2022,13(6):101320

Intensive measurements were conducted in Xi’an, China before and during a COVID-19 lockdown period to investigate how changes in anthropogenic emissions affected the optical properties and radiative effects of brown carbon (BrC) aerosol. The contribution of BrC to total aerosol light absorption during the lockdown (13%–49%) was higher compared with the normal period (4%–29%). Mass absorption cross-sections (MACs) of specific organic aerosol (OA) factors were calculated from a ridge regression model. Of the primary OA (POA), coal combustion OA (CCOA) had the largest MACs at all tested wavelengths during both periods due to high molecular-weight BrC chromophores; that was followed by biomass burning OA (BBOA) and hydrocarbon-like OA (HOA). For secondary OA (SOA), the MACs of the less-oxidized oxygenated OA (OOA) species (LO-OOA) at λ = 370–590 nm were higher than those of more-oxidized OOA (MO-OOA) during both periods, presumably due to chromophore bleaching. The largest contributor to BrC absorption at the short wavelengths was CCOA during both periods, but BrC absorption by LO-OOA and MO-OOA became dominant at longer wavelengths during the lockdown. The estimated radiation forcing efficiency of BrC over 370–600 nm increased from 37.5 W·g^?1 during the normal period to 50.2 W·g^?1 during the lockdown, and that enhancement was mainly caused by higher MACs for both LO-OOA and MO-OOA. This study provides insights into the optical properties and radiative effects of source-specific BrC aerosol when pollution emissions are reduced.  相似文献   

面向单幅遥感图像的生成对抗网络超分辨率重建     

韩志晟  孙丕川  唐超 《测绘通报》2021,(8):106-110

利用低分辨率图像生成高分辨率图像的过程称为图像超分辨率,目的是得到一张清晰的影像。随着人工智能的蓬勃发展,在遥感、辅助文本识别等诸多领域,图像超分辨率的应用愈加广泛。本文利用生成对抗网络的深度学习模型进行单图像超分重建,SRGAN模型相较于传统方法,提出了新的感知损失函数,由对抗损失和内容损失组成。对抗损失通过训练判别器网络结构区分生成图像和实际高分辨率图像,而内容损失则利用预训练的VGG19网络模型计算图像特征的感知相似度,而不是在像素空间上的相似度。试验证明,利用SRGAN获得的高分辨率图片,MOS指标高于传统方法。本文围绕SRGAN的原理、效果、应用等进行了阐述。  相似文献   

Spatial-temporal modeling of initial COVID-19 diffusion: The cases of the Chinese Mainland and Conterminous United States     

Daniel Griffith  Bin Li 《地球空间信息科学学报》2021,24(3):340-362

COVID-19 outbreaks in China in late December 2019, then in the United States (US) in early 2020. In the initial wave of diffusion, the virus respectively took 14 and 33 days to spread across the provinces/states in the Chinese mainland and the coterminous US, during which there are 43％ and 70％ zero entries in the space-time series for China and US respectively, indicating a zero-inflated count process. A logistic growth curve as a function of the number of days since the first case appeared in each of these countries accurately portrays the national aggregate per capita rates of infection for both. This paper presents two space-time model specifications, one based upon the generalized linear mixed model, and the other upon Moran eigenvector space-time filtering, to describe the spread of COVID-19 in the initial 19 and 58 days across the Chinese mainland and the coterminous US, respectively. Results from these case studies show both models shed new light on the role of spatial structures in COVID-19 diffusion, models that can forecast new cases in subsequent days. A principal finding is that describing the spatio- temporal diffusion of COVID-19 benefits from including a hierarchical structural component to supplement the commonly employed contagion component.  相似文献   

基于阶段式传播模型COVID-19防控措施的量化评估分析     

朱连华  谭岩  肖惠文  王露薇  李安琪  何陈涛 《南京气象学院学报》2020,12(3):364-372

基于病毒动力学传染机制,构建了考虑不同时期防控措施影响下的新型冠状病毒肺炎（COVID-19）阶段式传播模型.依据空间上的严重性将全国划分为三类疫情区,对各疫情区传染人数进行了阶段式模拟.结合上述模拟结果,进一步量化评估了各疫情区所采取的如武汉交通管制、对口支援湖北和小区封闭式管理等措施对抑制病毒传播的影响.结果表明,阶段式传播模型能够较好地模拟出各疫情区不同时期传染人数的变化特征,政府采取的交通管制和小区封闭式管理等防控措施大幅减少了传染人数,感染人数呈现出大幅下降的趋势,有效抑制了COVID-19的大规模扩散.  相似文献   

Aberrant Cities: Urban Population Loss in the United States, 1820-1930     

《Urban geography》2013,34(8):672-690

Our understanding of population loss from U.S. cities draws primarily from the fate of industrial centers in the decades following World War II. Quite numerous, those cities cast off residents at unprecedented and sustained rates. Prior to this time, few large cities had ended a decade smaller in population size than they began. In order to broaden and deepen our knowledge of why some cities and not others lose population, this paper analyzes cities that shed population in the 19th century. Using Census data and capsule stories developed from city biographies, the paper explores both contextuating and precipitating factors. These findings subsequently become the basis for reflecting anew on urban decline since the mid-20th century.  相似文献   

Retail Enterprise on the U.S. Urban Periphery: The Role of Immigrant Ethnic Groups in the Late-19th Century     

《Urban geography》2013,34(7):682-701

This research adds to knowledge about ethnic entrepreneurship in U.S. cities by testing the hypothesis that, in the late-19th century, levels of retail enterprise of entrepreneurial ethnic groups (e.g., Russian and Polish Jews) were highest in the most remote locations of the nation's urban-regional hierarchy. This hypothesis is based on the proposition that (1) "gateway cities" in the hinterlands of a society are bustling centers of commerce that offer unusually good prospects for retail enterprise, and (2) ethnic groups that are richly endowed with entrepreneurial resources can most fully exploit the advantages of such locations. An analysis of census data, guided by the "interactionist approach" to the study of entrepreneurship, supports this hypothesis and advances the literature on the ethnic economy by suggesting that a city's position in an urban-regional hierarchy (i.e., core vs. peripheral location) is a key element of the opportunity structure for ethnic entrepreneurship in that city.  相似文献