南黄海CSDP-2井晚泥盆世早期真蕨类Shougangia的形态观察     

白姣  徐洪河  郭兴伟  卢辉楠 《吉林大学学报(地球科学版)》2019,49(1):65-73

南黄海CSDP-2钻井上泥盆统五通组擂鼓台段2 068.00~2 069.02 m段岩心识别出了早期真蕨类植物。该植物具有至少三次羽状复叶，末二次羽片互生，小羽片扁平，呈扇状、楔状或舌状，基部收缩，至少一次深裂，裂片边缘钝圆，二分叉的叶脉明显。据此，可鉴定为优美守刚蕨（比较种）（Shougangia cf.S.bella）。本研究为南黄海地区上泥盆统五通组增加了古植物学新资料。  相似文献   

极端条件下心墙泥浆料的渗透反滤试验研究     

左永振  赵娜 《岩土力学》2020,41(2):520-526

高土石心墙坝的渗透稳定性在很大程度上依赖于反滤层对心墙料的反滤保护作用。心墙在大坝蓄水和长期运行的条件下，要经历复杂的填筑加载、浸水饱和与水荷载的作用，在差异沉降、复杂结构应力作用、水力劈裂和渗透水流作用下，心墙一旦出现裂缝，其渗透稳定性及反滤层的保护作用就将面临严峻的考验。针对这一问题，设计了专门非常规的抛填土料反滤试验和泥浆渗透反滤试验，模拟心墙裂缝条件下其颗粒被冲刷起动后，被反滤料阻挡和淤积过程。试验结果表明，心墙料和反滤料满足反滤准则条件下，心墙颗粒被拦截和淤积在反滤层上游表面，反滤料能有效防止心墙颗粒的流失，反滤层在极端条件下对心墙料仍能起到有效的反滤保护作用。  相似文献   

国内外绳索取心钻具研发应用概况及特深孔钻进问题分析   总被引：1，自引：1，他引：0       下载免费PDF全文

李鑫淼  李宽  孙建华  梁健  尹浩 《探矿工程》2020,47(4):15-23，39

随着钻孔深度的不断增加，对绳索取心钻具的使用性能提出了更高要求。在分析了国内外绳索取心钻具研发现状、结构设计特点及特深孔应用情况的基础上，整理了特深孔钻进绳索取心钻具使用存在的技术问题，定位机构打捞可靠性、到位报信提示可靠性、堵心报信机构工作稳定性、单动机构使用寿命均有待提高，并相应地分析了原因，为5000 m特深孔绳索取心钻具优化设计打好基础。  相似文献   

Post-earthquake economic resilience and recovery efficiency in the border areas of the Tibetan Plateau: A case study of areas affected by the Wenchuan Ms 8.0 Earthquake in Sichuan,China in 2008     

Zhou  Kan  Liu  Baoyin  Fan  Jie 《地理学报(英文版)》2020,30(8):1363-1381

Journal of Geographical Sciences - The border areas of the Tibetan Plateau and the neighboring mountainous areas have a high incidence of earthquakes with a magnitude greater than Ms 5.0, as well...  相似文献   

灾区恢复重建后效评估研究进展          下载免费PDF全文

赵亮  何凡能  杨帆 《干旱区地理》2020,43(5):1337-1347

随着全球变化加剧，世界各地自然灾害的频发，国际社会为应对自然灾害进行了不懈努 力，历届世界减灾大会不断强调对应急管理全流程的研究，恢复重建作为应急管理的重要环节而 得到广泛重视。积极开展灾区恢复重建后效评估有利于保障灾区恢复重建实施与区域可持续发 展。灾区恢复重建后效评估研究时间较短，首先比较分析了国内外恢复重建的内涵，明确了恢复 重建后效评估的基本概念，并梳理了灾区恢复重建后效评估的在中国的发展演变。由于灾区恢复 重建内容复杂多样，本文结合灾区恢复重建后效评估的发展历程、研究范围与关注时段，分别从项 目、要素与可持续性三个关键视角对后效评估的理论方法等展开评述，结果表明：（1）项目后效评 估在灾区恢复重建后效评估中起步较早，现有评估多集中于居民住房、基础设施、公共设施等工程 质量的评估，但缺乏对项目设计过程中社会居民参与度、公众满意度以及社会经济效益等的评 估。（2）要素后效评估在灾区恢复重建后效评估中涉及范围最广，具体包括社会、经济与环境等要 素，这些要素的评估受政策绩效影响较大，后期需要构建综合的评估体系以开展科学评估。（3）可 持续性后效评估以联合国可持续发展目标与地方国民经济与社会发展计划为基础构建评估框架， 有利于促进灾区的可持续发展。通过综合分析《仙台减轻灾害风险框架》中“重建的更好”(BBB)理 念，联合国可持续发展目标（SDGs）以及《巴黎协定》适应全球变化等诉求，结合当前灾区恢复重建 后效评估现状进行展望，以期为灾区恢复重建与可持续发展提供一个更为系统、综合的技术参考。  相似文献   

纳滤分离铝锂过程研究          下载免费PDF全文

高琳  王怀有  赵有璟  王敏 《盐湖研究》2020,28(2)

本文探讨了纳滤分离Al~(3+)和Li~+的可行性,研究了含盐量和铝锂比对分离效率的影响,提出了从锂云母浸出液中分离回收锂的新方法。实验结果表明,纳滤膜对Al~(3+)和Li~+的截留率随含盐量的升高而降低,其中Li~+始终呈现负浓度梯度扩散的趋势,而Al~(3+)的截留率始终稳定在99%以上。当含盐量为45 g/L时,铝锂分离因子最高可达248.33,膜面相应Zeta电位的绝对值达到最大。随着溶液中铝锂比的变化,Al~(3+)和Li~+的截留率分别在不同铝锂比的条件下出现拐点,溶液的pH呈现先下降后上升最后下降的复杂趋势。本实验研究发现,DK膜能够在酸性环境下实现高效的铝锂分离和锂的浓缩,从而为锂云母浸出液中锂的提取提供新的思路。  相似文献   

水源钻机在超深土层绳索取心钻进中的应用          下载免费PDF全文

杨联锋  段云星 《探矿工程》2020,47(11):44-50

山西省清徐县区域地质调查项目设计800、2000、3000 m科学钻探孔，以调查填补新生界底板埋深控制空白区，各孔钻入基岩30 m完钻。要求全孔取心，岩心采取率≮85%，岩心直径≮60 mm，采用塑料保护管采取原状岩样。针对超深软土层、各组地层特性及厚度未知、钻遇基岩完钻深度未知、大直径高保真全孔取心、项目价格远低于目前市场成本等难题，经过“水源钻机+大提钻取心+长裸眼孔段”实施800 m孔、“岩心钻机+绳索取心+套管固井”实施640 m参数对比孔，创新性使用“水源钻机+绳索取心+长裸眼孔段”工艺完成了2000 m孔的施工。该工艺岩心采取率达到93%，孔径和孔斜符合地质要求，为3000 m孔顺利施工打下了坚实的基础，为同类型项目提供了经验和借鉴。  相似文献   

基于HYCOM再分析数据研究琉球海流的形成与起源     

汪敏  刘昭君  朱小华  闫晓梅  张钟哲  赵瑞祥 《海洋学报(英文版)》2019,38(11):1-10

The origin of the Ryukyu Current(RC) and the formation of its subsurface velocity core were investigated using a 23-year(1993–2015) global Hybrid Coordinate Ocean Model(HYCOM) dataset. The volume transport of the RC comes from the Kuroshio eastward branch(KEB) east of Taiwan and part of the North Pacific Subtropical Gyre(pNPSG). From the surface to 2 000 m depth, the KEB(p-NPSG) transport contributes 41.5%(58.5%) to the mean total RC transport. The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge(sill depth: 700 m). Above 700 m, the Kuroshio can enter the East China Sea(ECS) over the Ilan Ridge, meanwhile, the blocked Kuroshio below 700 m turns to the right and flows along the Ryukyu Islands. With the RC flowing northeastward, the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge. In the surface layer, the pNPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps(with net volume transport into ECS) between the Ryukyu Islands.  相似文献   

Stormflow threshold behaviour in a subtropical mountainous headwater catchment during forest recovery period     

Lezhang Wei  Zhijun Qiu  Guangyi Zhou  Tsuyoshi Kinouchi  Yu Liu 《水文研究》2020,34(8):1728-1740

Forest ecohydrological feedbacks complicate the threshold behaviour of stormflow response to precipitation or wetting conditions on a long-term scale (e.g. several years). In this study, the threshold behaviours in an evergreen-deciduous mixed forested headwater catchment in southern China were examined during 2009–2015, when damaged vegetation was recovering after the great 2008 Chinese ice and snowstorm. The non-uniqueness of the thresholds and the slow and rapid responses of stormflow at the outlet of the catchment in different hydro-climate datasets with different maximum values of gross precipitation (P) and sums of precipitation and antecedent soil moisture index (P + ASI) were assessed. The thresholds of P and P + ASI required to trigger stormflows (i.e. ‘generation thresholds’) and the transition from slow to rapid responses of stormflow (i.e. ‘rise thresholds’) were compared both seasonally and annually. The results indicated significant differences in the analysed datasets, highlighting the need to compare thresholds with care to avoid misinterpretation. Seasonal variations in threshold behaviours in the catchment suggested that vegetation canopy interception contributed to higher rise thresholds, and wetter conditions resulted in higher runoff sensitivity to precipitation during the growing and rainy seasons. Furthermore, the generation thresholds were higher in the dormant season, possibly due to drier soil moisture conditions in the near-channel areas. During the vegetation recovery period, the annual generation thresholds increased, however the rise thresholds did not exhibit a similar trend. The rapid stormflow response above the threshold decreased, possibly due to transpiration and interception of the recovered vegetation. However, the slow stormflow response to small rainfall events below the thresholds was higher in wetter years but lower in drier years, suggesting that the total water input dominated the stormflow response during small rainfall events. In conclusion, the seasonal and annual variations in threshold behaviours highlight that vegetation recovery and hydro-climatic conditions had a notable impact on the stormflow response.  相似文献   

The 1‐million‐year‐old quartz assemblage from Pont‐de‐Lavaud (Centre,France) in the European context          下载免费PDF全文

Jackie Despriée  Marie‐Hélène Moncel  Marta Arzarello  Gilles Courcimault  Pierre Voinchet  Jean‐Jacques Bahain  Christophe Falguères 《第四纪科学杂志》2018,33(6):639-661

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