白龙江中游干旱河谷水土流失与地理环境          下载免费PDF全文

魏宏庆  沈永平  魏鹂慧  张峰 《干旱区地理》2019,42(5):1023-1028

基于实地调查研究，结合现有资料和研究成果，总结分析白龙江中游地理环境结构特点，调查研究该区水土流失性质、带状分异特征以及小流域形态结构，剖析地理环境与水土流失作用关系，提出以小流域为单元，以其空间结构有序和区段功能有序特征，配置水土保持防治措施体系，为建立综合治理模式提供有效参考。  相似文献   

新型干树式半潜平台浮体结构设计研究     

李建勋  凌进  王仁军  郁芳  刘木南  唐修俊  王中念 《海洋工程》2019,37(1):12-19

为适应中国南海深水区域的油气田开发,研发出了一种具有渐变式立柱的深吃水干树式半潜钻井/生产平台(TCDDSemi)。平台的浮体采用了深吃水、变截面长立柱构型,即向底部逐渐扩大的渐变截面形式。结合干树式深吃水半潜平台的研发过程,通过采用压缩空气压载系统、全注水下浮体、压缩空气水密检测以及水密面板的三级正交加强筋设计等新兴技术,极大地提高了钢材的利用效率,达到了节省材料、减轻浮体自重的目的。对浮体的有限元(FEM)整体分析结果表明,浮体结构设计满足各工况强度要求。  相似文献   

《巴黎协定》排放情景下中亚地区降水变化响应     

王芳  张晋韬 《地理学报》2020,75(1):25-40

为了应对全球气候变化,《巴黎协定》提出各国将以“国家自主贡献”（INDC）的方式参与全球温室气体减排行动,而在“国家自主贡献”排放目标情景下区域降水变化的格局和特征尚不清楚。中亚地区位于欧亚大陆腹地,是中国“一带一路”倡议发展的关键地区。本文研究了中亚地区的降水变化对全球INDC排放的响应,基于参与国际耦合模式比较计划第五阶段（CMIP5）的33个全球气候模式的模拟。结果表明：在INDC目标情景下,到21世纪末中亚地区的平均年降水量相对现代水平（1985—2005年平均）增加10.6%（4.6%~13.3%）,其中高纬度地区的响应大于低纬度地区。进一步看,中亚地区极端强降水事件随着气候变暖而持续增加,但极端持续干期事件在不同区域呈现不同的变化趋势。考虑极端降水事件相关风险,极端强降水和持续干期事件的人口暴露度在中亚大部分区域都增加,将全球温升控制在较低水平（如2.0 ℃或1.5 ℃）可显著降低暴露度。以上结果有助于增进对未来极端气候事件风险的认识,为中亚这一生态脆弱地区的气候变化的减缓与适应政策提供参考。  相似文献   

Diatom blooms and associated vegetation shifts in a subarctic peatland: responses to distant volcanic eruptions?          下载免费PDF全文

U. Kokfelt  R. Muscheler  A. Mellström  E. Struyf  M. Rundgren  S. Wastegård  D. Hammarlund 《第四纪科学杂志》2016,31(7):723-730

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新型多功能干树储油半潜平台研发   总被引：1，自引：1，他引：0  

谢文会  谢彬  粟京  韩旭亮  李阳  赵晶瑞  冯加果 《海洋工程》2020,38(1):1-10

针对凝析油气田开发了一型适应我国南海环境条件的深水多功能干树半潜平台,平台运动性能优良,可实现干树开采、回接水下井口、油气生产处理、凝析油存储、钻修井等功能。平台由上部组块、主船体、细长柔性连接结构、垂荡板、顶张紧式立管(TTR立管)系统、系泊系统构成,结构特点为采用细长柔性连接结构连接主船体与箱型垂荡板。垂荡板采用箱型结构,承受作业吃水压力,可实现平台与箱型垂荡板的整体拖航,平台安装简易,细长柔性连接结构可在位维修或更换。平台立柱内设置储油舱存储天然气凝析油,解决凝析油存储外输问题。平台采用成熟系统系统集成,运动性能优良,海上施工风险可控,未来有望成为一种新的深水油气田开发平台型式。  相似文献   

2019年长江口南北槽水域表层沉积物特征分析     

刘启雄  陈家祺  刘海江  张东来 《海洋工程》2020,38(4):100-108

为探究长江口区域最新的泥沙运动特征,于2019年枯季(1月,21个样本)和洪季(8月,58个样本)在长江口南北槽及周边区域现场取样河床表层泥沙样本,测量了样本的中值粒径和级配分布。采用Folk-Ward公式计算了泥沙样本的粒度参数(分选系数、偏度和峰度),并分析了沙样本内磁性物质含量。基于上述泥沙物理参数,进一步对比分析洪枯季研究区域河床表层泥沙的时空分布变化特征。分析结果表明北槽内洪枯季泥沙样本中值粒径空间分布特征一致,南槽中段洪季泥沙样本中值粒径远小于枯季泥沙样本中值粒径,南槽其他区域洪枯季泥沙样本中值粒径空间分布特征一致。同一中值粒径下,不同沙样本(中值粒径大于63μm)各粒度参数之间差异显著,而泥样本(中值粒径小于63μm)粒度参数间差异相对较小。此外,磁性物质含量测量结果表明枯季沙样本磁性物质组成的空间分布存在一定的差异,而洪季沙样本磁性物质的空间分布相对均一。  相似文献   

三门峡地区黄土状粉质黏土非饱和性质试验研究     

黄志全  陈宇  宋日英  宋丽娟 《岩土力学》2010,31(6):1759-1762

以三门峡地区黄土状粉质黏土为研究对象,通过控制重塑土样的干密度及含水率制备不同状态下的试样,在改进的三轴仪上采用不排水试验法,分别对试样进行非饱和土三轴试验。试验结果表明,黄土状粉质黏土的基质吸力变化规律与土的基本状态有着密切关系,尤其是在相同含水率、相同围压、不同干密度的状态下基质吸力会随着饱和度的增加,出现先增后减的变化规律。通过单元土体中土颗粒组成的结构体参数,分析了这种变化规律。  相似文献   

高含水率淤泥生石灰材料化土击实方法初探   总被引：3，自引：0，他引：3  

桂跃  杜国庆  张勤羽  宋文智  蔡超 《岩土力学》2010,31(Z1):127-137

为了击实高含水率淤泥生石灰材料化土,通过改进标准击实仪,设计了4种不同击实冲量的击实情形,对不同掺灰比的材料化土在不同闷料期进行击实试验,分析了击实冲量及击实功与淤泥生石灰材料化土干密度的关系,提出了材料化土的击实方法及击实评价方法。建议根据材料化土的含水比 选择击实冲量适宜的击实方法,通过土的干密度随击次变化规律判断材料化土是否击实。特别从工程角度出发,测试了击实材料化土不同龄期的无侧限抗压强度,初步探讨了高含水率疏浚淤泥生石灰材料化土作为工程填料的可行性。  相似文献   

Aeolian dust transportation and deposition by near-surface winds in arid and semiarid China     

JinChang Li  ZhiBao Dong  GuangQiang Qian  WanYin Luo 《寒旱区科学》2010,2(2):0137-0142

Dustfall collections were carried out in April and May 2001 and in March 2002 at six sites in northern China.Our results showed that the total deposition of dust fractions 250 μm in diameter and the deposition of Fe both decreased exponentially with increasing distances from the source areas,and that the half-attenuation distance (HAD) for dust deposition was about 229 km in this re-gion.The HAD was closely related to the grain-size distribution of the dust,and the 15 to 20 μm fractions had the longest HAD.However,the fractions 15 μm in diameter can be easily adsorbed to coarse particles and deposited after only short distances,and the HAD for the fractions 15 to 100 μm in diameter showed a power relationship with the grain-size distribution.The HAD for Fe deposition was 233 km,which was a little longer than that of total dust deposition,which suggests that the Fe content is higher in fine particles than in coarse particles,as previous studies have suggested.In addition,our analysis showed that under the control of current climatic conditions,the coarse fractions in dust derived from northwestern China cannot be transported over long distances,instead,it is transported primarily by near-surface winds (3 km above the ground).The Fe in aeolian dust generated from arid and semiarid regions of China and deposited in the North Pacific region is usually transported by the upper westerlies.  相似文献   

Rates,distributions and mechanisms of change in meander morphology over decadal timescales,River Dane,UK     

J. M. Hooke  L. Yorke 《地球表面变化过程与地形》2010,35(13):1601-1614

This paper analyses types and rates of change in river meander morphology and the links between mechanisms of change and emergent behaviour of planform morphology. It uses evidence of four dates of aerial photography combined with annual field mapping and ground photography to examine the morphological changes and mechanisms of change in a series of bends on an active meandering river, the River Dane in NW England, over a 25 year period. This unique data set allows insight into the spatial and temporal variability of bank line movement and component processes. Bank lines were mapped photogrametrically from air photos of 1984, 1996, 2001 and 2007 and the digitised courses compared in ArcGIS to produce calculations of erosional and depositional areas and rates. Most bends exhibit morphological change that largely follows the autogenic sequence, identified in qualitative models of meander development, from low sinuosity curves through simple symmetric and asymmetric bends to compound forms with lobe development in the apex region. Rates of erosion and bankline movement increase through this sequence until the compound phase. Relationships of amounts of movement to various curvature measures of bend morphology are complex. Several new loops, distinct from compound bend behaviour, have developed during the study period in formerly straight sections. Mechanisms of morphological change are illustrated for four types of bends: new, rapid growth bend; sharp‐angled bend with mid‐channel bar development; symmetric migrating bend; and simple to compound bend development. The changes take place in phases that are not simply related to discharge but to inherent sequences and feedbacks in development of bars and bend morphology and timescales for these are identified. Overall, emergent behaviour of systematic planform change, moderated by channel confinement and boundary features, is produced from spatially and temporally varied channel processes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献