三峡水库消落区植物群落演变趋势及优势植物适应策略

三峡水库周期性蓄水显著改变了消落区植物群落组成及多样性,植物群落的演变过程能反映和影响整个消落区生态系统的变化,但目前还缺乏长期连续的观测数据记录,因而本研究基于2009—2021年6月的固定样方长时间序列监测数据和优势植物叶片功能性状数据,分析了消落区3个高程(145～155、155～165和165～175m)区域植物群落多样性和优势植物重要值的变化趋势,通过冗余分析和蒙特卡罗检验揭示了水库运行特征参数和气象因子对消落区植物特征的影响。研究发现:1)消落区3个高程区域,优势植物差异明显,145～155和155～165 m区域以狗牙根、香附子和苍耳等为主,165～175 m区域以狗牙根、野胡萝卜和鬼针草等为主。145～155 m区域植物群落Shannon-Wiener多样性指数(1.47±0.47)和Pielou均匀度指数(0.67±0.07)显著低于165～175 m区域。2)2009—2021年期间,高程145～155和155～165 m区域Shannon-Wiener多样性指数和Pielou均匀度指数呈波动下降趋势,优势植物狗牙根和香附子的重要值呈增加趋势。3) RDA分析表明,...     

一种基于16S rRNA基因检测海洋浮游细菌群落的微阵列基因芯片

A better understanding of bacterioplankton community shifts following change in marine environments is critical to predict the marine ecosystem function. In order to get a snapshot of the microbial taxonomy profiling of a wide range marine area, a quick, convenient and low cost method would be favorable. In this study, we developed a 16S rRNA gene-based microarray using ARB software, which contained 447 probes targeting 160 families of marine bacteria. The specificity, sensitivity and quantitative capability of this microarray were assessed by single cloned16S rRNA genes. The reliability of this microarray was tested by eight environmental samples. The results showed that the microarray was specific, only 1.16% false results were detected in five single-clone hybridization tests. The microarray could detect DNA samples as few as 1 ng/μL and the signal intensity could reflect the relative abundance of the bacteria in the range of 1 ng/μL to 100 ng/μL of DNA concentration. Hybridization with environmental samples showed that it can discriminate bacterioplankton communities by sites and time. High throughput sequencing results from the eight samples confirmed the hybridization results. It indicated that this developed microarray could be used as a convenient tool to monitor the bacterioplankton community in marine environment.     

Detrital zircon provenance analysis in the Zagros Orogen,SW Iran: implications for the amalgamation history of the Neo-Tethys

International Journal of Earth Sciences - The Zagros Orogen developed as a result of Arabia–Eurasia collision. New in situ detrital zircon U–Pb and Hf isotopic analyses from a Cenozoic...     

Stability evaluation method for hyperbolic coal pillars under the coupling effects of high temperature and ground stress

We studied an underground coal gasification technique using strip mining-face mining gasifier controlled retraction injection technology (SMFM). This green mining approach offers several advantages over conventional strip mining but the stress distribution and stability of SMFM operations remain largely untested. In particular, hyperbolic coking pillars are used in SMFM compared with rectangular pillars used in traditional strip mining, which can influence the ultimate bearing capacity and stability. We use numerical simulations to investigate the influence of different factors (arch height, pillar height and width, mechanical characteristics), under the coupling effect of high temperature, on the ultimate bearing capacity of hyperbolic pillars. Our results indicate that arch height has a strong influence on pillar stress, while changes in pillar width and height are less significant. A stability evaluation method is proposed and tested on a case study in Inner Mongolia. Our theoretical results have practical significance for the promotion and application of SMFM.     

Numerical investigation of slippage characteristics of normal and reverse faults under fluid injection and production

Nowadays, a great deal of petroleum geology and engineering projects associated with underground fluid injection and production (FIP) are widely conducted around the world. The FIP engineering may cause complex stress perturbation and trigger seismicity, which have been extensively reported and studied. In this paper, we investigated the fault slippage characteristics influenced by FIP. It reveals that for a fault (normal or reverse) that penetrating through the reservoir into the caprock and underburden, the footwall reservoir is the relatively stable one for fluid injection in a fluid FIP engineering. No matter it is a normal or a reverse fault, injecting fluid into footwall reservoir and producing fluid from the hanging wall reservoir can induce smaller fault slippage. After having determined the better fluid injection–production pattern, we studied the influence of three key factors of fault, i.e., dip, offset and depth, on fault stability. We found that, in our range of study, the influence of single action of fault dip, offset or depth on fault slippage in a FIP engineering was small. However, the influence of the combined effects of the factors may be large. Finally, we studied the effect of different pressure management scenarios on fault responses based on the specific fluid injection–production pattern. The results revealed that appropriate pressure management could effectively reduce fault slippage in a FIP engineering. However, inappropriate pressure management may cause much larger fault slippage. Given these concerns, it is therefore vital that the effect of pressure management scenario to be modeled prior to FIP.     

一种基于智能手机成像的立体量测方法

在分析智能手机相机成像参数稳定性的基础上,介绍了一种手机成像的立体量测方法。根据大角度、大重叠度且无控制点的情况,使用相对定向的直接解法来确定手机像对的相对位置关系,通过空间前方交会解算出待定点的物方空间坐标,并利用光束法平差来优化立体量测结果;同时,利用室内检校场控制点的坐标真值,验证了手机的测量精度,表明了智能手机相机可以用于近景摄影测量工作。     

库车-喀什北缘山前带构造特征及成因分析

通过地震非地震联合解释及多年的勘探研究,认为受基底结构、构造演化、逆冲及走滑断裂等影响,库车-喀什北缘山前冲断带具有东西分段、南北分带的构造特征。自西向东分为喀什北缘、柯坪断隆和库车坳陷三大段,受近南北向逆冲挤压作用,每段均发育多排北东-南西向展布的逆冲褶皱带,其中库车坳陷主要由克拉苏、依奇克里克、秋里塔格构造带及乌什、拜城、阳霞凹陷等呈斜列式展布的次级构造单元组成。普遍发育的膏盐岩塑性层在一系列逆冲和走滑断裂的作用下,使得山前带构造样式更为复杂,发育断层转折褶皱、断层传播褶皱、滑脱褶皱和盐底辟(刺穿)构造等四种基本构造样式及多种组合样式。     

南京地区新近纪砂砾层的沉积环境演变

南京地区分布着一套新近纪的松散砂砾沉积,曾被统称为雨花台砾石层。依据岩性、层序、沉积构造等特征,我们解译了4个地点砂砾层的沉积环境。研究发现,洞玄观组的沉积环境类似于曲流河沉积,六合组类似于砂质辫状河沉积,雨花台组则属于砾质辫状河沉积。沉积环境的不同印证了前人的观点,即这些砂砾层是不同时期形成。古流向显示,从中新世到更新世早期本区的流域格局与目前的大体一致。而河流沉积环境的演化,却指示河道的坡降具有不断增大的趋势。我们认为这可能是全球海平面不断下降导致侵蚀基准面降低所引起的,而差异性的构造运动似乎不是主要的驱动因素。     

单元畸变对动力有限元方法计算精度的影响

在有限元分析中,由于求解区域或边界的不规则,有限单元的划分会产生畸变单元。本文通过数值试验分析了有限单元畸变对动力有限元计算精度的影响,结果表明:长宽比畸变对动力有限元计算精度没有影响;当斜交角不小于30°时,斜交角对动力有限元计算精度的影响可忽略;锥度对动力有限元计算精度有影响,锥度越大,锥度对动力有限元计算精度的影响越大。     

基于WorldView卫星影像的海岛测图精度控制分析

根据WorldView卫星影像的特点,分析其原始定位精度,并结合海岛测区的地形地貌特点,应用稀少控制卫星影像航天摄影测量平差方法,合理地进行控制点布设,同时有效控制外推岛屿的定位精度。对于独立海岛进行无控自由网平差,并量测一定数量的海岸水位点作为高程点,进行模型置平作业。通过比对实测瞬时水涯线,检查、检测其海岸线高程精度。最终保证数字空中三角测量的成果满足海岛(礁)测图卫星影像成图区的成果精度要求。