Geography of asbestos contamination near the World Trade Center site     

William C. Thayer  Daniel A. Griffith  Gary L. Diamond 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(5):461-471

Despite the dust cleanup and indoor air testing program led by the U.S. Environmental Protection Agency (EPA) and offered to all residents of Lower Manhattan (south of Canal Street), concern remains about local chemical residues from the collapse of the World Trade Center (WTC) buildings. Data on post-cleanup indoor airborne asbestos concentration, available from EPA Region 2, were analyzed to assess the possibility that the WTC site is the source of geographically concentrated rare post-cleanup exceedances of the health-based standard for asbestos. Recognizing that these rare exceedances may be attributable to sources other than the WTC disaster, and that these sources are very likely to exhibit geographic patterns, the data were analyzed using a spatial filter specification of the auto-Poisson probability model. Our analysis shows that ignoring geographic patterns latent in these exceedances affects the empirical probability of exceeding the health-based standards for airborne asbestos. We did not find any statistically-significant geographic pattern in the exceedance events that would indicate the WTC site as the source of the post-cleanup exceedances. Apparent geographic patterns may be due to the geographic variability in sampling intensity. Our analysis indicates the Residential Dust Cleanup Program lead by EPA Region 2 has been effective at reducing the concentration of air-borne asbestos in indoor air to below the health-based benchmark.  相似文献   

细部测量中控制点不通视的处理方法     

叶国明  周园 《现代测绘》2007,30(2):23-24

通过在使用全站仪测图的实践,总结出一些处理细部测量中控制点不通视的作业方式、操作经验、数据处理方法,很有现实操作意义.  相似文献   

Response of glacier area variation to climate change in the Kaidu-Kongque river basin,Southern Tianshan Mountains during the last 20 years     

《China Geology》2021,4(3):389-401

Glaciers are crucial water resources for arid inland rivers in Northwest China. In recent decades, glaciers are largely experiencing shrinkage under the climate-warming scenario, thereby exerting tremendous influences on regional water resources. The primary role of understudying watershed scale glacier changes under changing climatic conditions is to ensure sustainable utilization of regional water resources, to prevent and mitigate glacier-related disasters. This study maps the current (2020) distribution of glacier boundaries across the Kaidu-Kongque river basin, south slope of Tianshan Mountains, and monitors the spatial evolution of glaciers over five time periods from 2000–2020 through thresholded band ratios approach, using 25 Landsat images at 30 m resolution. In addition, this study attempts to understand the role of climate characteristics for variable response of glacier area. The results show that the total area of glaciers was 398.21 km² in 2020. The glaciers retreated by about 1.17 km²/a (0.26%/a) from 2000 to 2020. The glaciers were reducing at a significantly rapid rate between 2000 and 2005, a slow rate from 2005 to 2015, and an accelerated rate during 2015–2020. The meteorological data shows slight increasing trends of mean annual temperature (0.02°C/a) and annual precipitation (2.07 mm/a). The correlation analysis demonstrates that the role of temperature presents more significant correlation with glacier recession than precipitation. There is a temporal hysteresis in the response of glacier change to climate change. Increasing trend of temperature in summer proves to be the driving force behind the Kaidu-Kongque basin glacier recession during the recent 20 years.© 2021 China Geology Editorial Office.  相似文献   

Stability of expansive cement grout borehole seals emplaced in the vicinity of underground radioactive waste repositories   总被引：1，自引：1，他引：0  

H.?AkgünEmail author  J.?J.?K.?Daemen 《Environmental Geology》2004,45(8):1167-1171

An expansive cementitious borehole plug emplaced in an underground opening in the vicinity of an underground nuclear waste repository may generate radial stresses on the walls of the opening due to an axial stress applied to the borehole plug and due to plug swelling. As these radial stresses may lead to the tensile fracturing of the rock, minimizing or preferably eliminating tensile stresses in rock is particularly important to preserve waste containment. Presented in this paper are the theoretical radial (normal) stress distribution and tensile strength in a borehole plug–rock system due to combined axial, thermal and lateral loading, along with analyses of plug–rock mechanical interactions in regards to borehole stability against tensile fracturing.  相似文献   

Development of the hard X-ray imaging experiment timax: Laboratory images and first balloon flight     

JOÃO BRAGA  FLAVIO D'AMICO  THYRSO VILLELA 《Experimental Astronomy》1994,5(3-4):269-278

We present calibration results and laboratory images produced by the balloon-borne hard X-ray imaging telescope TIMAX. The images were produced with an²⁴¹Am radioactive source placed 45 m away from the detector plane, in the center of the field of view. It is shown that the mask 3-antimask imaging reconstruction process, when combined with flat-fielding techniques, is very effective at recovering signal-to-noise ratio lost due to systematic non-uniformity in the background measured by the 35 detectors. The experiment was launched in June 8th, 1993 from Birigüi, SP, Brazil, onboard a 186,000 m³ stratospheric balloon, and remained at an atmospheric depth of 2 g cm^–2su for 8 hours. Even though no scientific data were gathered in this first flight, we obtained valuable engineering data and could also calculate the sensitivity of the experiment based on the instrumental background spectrum at balloon altitudes. In the 60–70 keV energy band, the experiment can detect 3 sources at a level of 1.2 x 10^–4 photons cm^–2 s^–1 keV^–1 for an integration of 6 hours at 2.1 g cm^–2.  相似文献   

城镇化与地方性中的水资源：可持续视角的水环境保护利用与水空间规划设计   总被引：1，自引：0，他引：1  

汪芳  王舜奕  PROMINSKI Martin 《地理研究》2018,37(12):2576-2584

近年来,由于水资源不合理利用引发的水资源污染、短缺以及自然灾害的加剧,制约着城镇、区域和国家的社会经济发展,对生态环境安全及人类的可持续发展造成威胁。如何保证在环境演变、城镇发展的过程中,水资源得到可持续开发利用,水文化的地方性得以保持和丰富,成为当下生态环境保护、城市规划设计的一大挑战。2018年9月25-29日在北京召开的中德双边研讨会聚焦环境变化,以“可持续视角的水环境保护利用与水空间规划设计”为主题,在规划、地理、景观、建筑、旅游、生态、水利、历史等多学科领域,就中德双方在不同的城镇化发展阶段面临的水资源保护与可持续开发问题及其相关经验和解决对策。中德两国的29位专家学者,就城镇化过程中水环境保护与利用的挑战、水资源的可持续利用、水空间的规划设计策略等三个主题展开交流与讨论,并就双边学术研究、人才培养和成果交流方面的合作渠道和模式进行探讨。  相似文献   

科学数据共享实践：以国家地球系统科学数据中心为例   总被引：2，自引：0，他引：2  

杨雅萍  姜侯  孙九林 《地球信息科学学报》2020,22(6):1358-1369

地球系统科学是一门综合性交叉学科,起源于全球变化研究,受益于遥感技术进步,现已进入大数据时代,人工智能技术成为解决地球系统科学前沿问题的新手段。科学数据共享是推动科学发展、提升数据价值的关键,经过长期的探索和实践,全球已形成完善的数据资源管理政策与机制、持续的数据共享服务体系、多元化的科学数据整合模式,并且新的理念不断推动数据共享创新发展,其中“可发现、可访问、可互操作和可重用”原则和数据出版备受推崇。我国颁布了国家层面的政策法规,着重推动国家级科学数据中心建设、科技项目数据资源汇交及数据出版。借鉴国外数据共享经验,结合国内实际发展情况,我国探索出具有中国特色的地球系统科学数据资源分类体系,在元数据、分布式互操作、大数据分析和共享服务等关键技术方面都取得了重大突破。本文以国家地球系统科学数据中心为例,系统梳理了国内地球系统科学领域的数据共享实践进展,详细介绍了国家在地球系统科学领域的数据共享实践及其成效。国家地球系统科学数据共享工作已探索形成成熟稳定的运行服务机制、研制出适用于多源分散地球系统科学数据的标准体系、 建成多学科多时空尺度的地球系统科学数据库群、自主研发海量异构数据共享网络技术体系与服务系统,促进了地球系统科学的科学发展,同时也推动了数据共享理念的传播与推广。然而,数据孤岛现象、共享服务系统标准化程度低、系统技术标准未对接国际规范等问题仍然较为突出,阻碍了地球系统科学数据开放与共享。未来,随着共享个性化需求被激活,定制化的“数据+知识”服务有望成为主流趋势,将给数据共享带来新的机遇和挑战。  相似文献   

Rill hydraulics on a semiarid hillslope,southern Arizona     

Athol D. Abrahams  Gang Li  Anthony J. Parsons 《地球表面变化过程与地形》1996,21(1):35-47

Seventy field experiments were conducted in seven rills located on a semiarid rangeland hillslope underlain by gravelly soils at Walnut Gulch, Arizona. The rills, which are characterized by wide, shallow cross-sections and gravel-covered beds, have mean at-a-station hydraulic geometry exponents of b = 0·33, f = 0·34 and m = 0·33. Although the differences between these values and typical values of b = 0·30, f = 0·40 and m = 0·30 for cropland rills are not statistically significant, they are thought to be real, as cropland rills often have more rectangular cross-sections and steeper sides than the rangeland rills under study. For rills formed in silty loamy soils, Govers developed an empirical relation between mean flow velocity and discharge. Emphasizing the generality of this relation, he suggested that it may be used as a simple means of routing runoff through rills. He also noted that this relation appeared to be unaffected by either slope or soil materials. The present data represent rills underlain by coarser and somewhat more varied gravel-rich soils. These data do not conform to Govers' relation, and a multiple regression analysis reveals that slope and soil materials, either directly or indirectly through bed roughness, exert almost as much influence on flow velocity as does discharge. Three alternative methods are developed for predicting flow velocity in the rills under study. All three methods give good results with the largest root mean square deviation being 3·115 cm s⁻¹.  相似文献   

箱型钢结构应力场的模糊模式识别   总被引：3，自引：0，他引：3  

瞿伟廉  汪菁  郑瑾  李功标  滕军 《地震工程与工程振动》2006,26(5):177-182

本文依据模糊模式识别理论,以深圳市民中心屋顶网架结构的智能健康监测系统为背景,系统地介绍了屋顶网架结构支承箱型钢牛腿应力场的模糊模式识别方法。文中,在说明了方法的基本思路的基础上,详细介绍了方法的基本原理和仿真分析的步骤。并通过对深圳市民中心25号钢牛腿应力场识别的仿真,验证了方法的效果和可靠性。  相似文献   

国家地震速报灾备中心技术系统介绍     

洪玉清  梁明  欧阳龙斌  苏柱金  沈玉松  田平  钱银苹  汤曜玮  朱腾 《中国地震》2024,40(1):97-109

灾备中心作为我国地震速报业务功能备份中心,主要承担我国地震速报业务的功能备份和全国测震数据实时转发服务。本文介绍了国家地震速报灾备中心平台的技术构成、业务数据库系统、承载业务功能及流程等情况,对平台的技术特点和功能特性进行总结,通过对平台应用成效的初步统计分析,提出了平台的下一步完善计划。  相似文献