Elevation trends and shrink–swell response of wetland soils to flooding and drying

Given the potential for a projected acceleration in sea-level rise to impact wetland sustainability over the next century, a better understanding is needed of climate-related drivers that influence the processes controlling wetland elevation. Changes in local hydrology and groundwater conditions can cause short-term perturbations to marsh elevation trends through shrink–swell of marsh soils. To better understand the magnitude of these perturbations and their impacts on marsh elevation trends, we measured vertical accretion and elevation dynamics in microtidal marshes in Texas and Louisiana during and after the extreme drought conditions that existed there from 1998 to 2000. In a Louisiana marsh, elevation was controlled by subsurface hydrologic fluxes occurring below the root zone but above the 4 m depth (i.e., the base of the surface elevation table benchmark) that were related to regional drought and local meteorological conditions, with marsh elevation tracking water level variations closely. In Texas, a rapid decline in marsh elevation was related to severe drought conditions, which lowered local groundwater levels. Unfragmented marshes experienced smaller water level drawdowns and more rapid marsh elevation recovery than fragmented marshes. It appears that extended drawdowns lead to increased substrate consolidation making it less resilient to respond to future favorable conditions. Overall, changes in water storage lead to rapid and large short-term impacts on marsh elevation that are as much as five times greater than the long-term elevation trend, indicating the importance of long-term, high-resolution elevation data sets to understand the prolonged effects of water deficits on marsh elevation change.     

ASO-S卫星基于太阳导行镜的高精度高稳定度姿态控制系统

先进天基太阳天文台(Advanced Space-based Solar Observatory, ASO-S)卫星姿控分系统的主要任务是实现高精度、高稳定度对日指向控制. ASO-S卫星的科学载荷中,白光望远镜(White-light Solar Telescope, WST)前端配置了太阳导行镜(Guide Telescope, GT)稳像系统,利用正交分布光电二极管组成的边缘探测器测量导行镜光轴与太阳中心的偏差角.提出了一种将GT测量值引入姿态控制闭环的控制方法:利用星敏陀螺定姿算法获得卫星-太阳方向姿态偏差, GT测量值确定非卫星-太阳方向姿态偏差;以4斜装反作用轮组为执行机构,进行三轴零动量稳定姿态控制.通过数学仿真验证,基于GT测量值的姿态控制器在非卫星-太阳方向的绝对指向精度优于2′′、相对姿态稳定度优于1′′/60 s,满足ASO-S卫星高精度高稳定度的对日指向要求.     

Analysis of spectral characteristics among different sensors by use of simulated RS images

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红树林遥感动态监测研究进展

红树林动态是地理学、生态学和湿地学等学科关注的热点之一。遥感技术具有宏观性、高效性和经济性等特点,在红树林动态监测中发挥日益重要的作用。本文通过关键词对Web of Science和中国知网2个数据库自2000年以来发表的文章进行梳理和归纳,从研究区域分布、文献数量、遥感监测数据源与方法、全球红树林动态以及全国红树林动态变化分析5个方面总结了近20年来国内外对于红树林遥感动态监测研究进展。研究结果表明,多传感器高时空分辨率数据将成为红树林遥感动态监测的重要数据源。将雷达数据和光学遥感数据进行融合,有助于进一步提升红树林卫星遥感监测能力。无人机平台搭载多种类型的传感器（如多光谱、高光谱或激光雷达传感器）,可以从不同方面获取红树林生态系统参数,结合遥感智能分析算法,有助于推动红树林遥感研究向纵深方向发展。红树林遥感动态监测相关研究表明,全球红树林总面积范围大致在1.1×10⁸ ~2.4×10⁸ hm²,总体仍呈减少趋势,而在区域上中国红树林面积则有所恢复。本文最后对红树林遥感动态监测的发展趋势进行了展望。     

填土压实质量检测及机载压实集成系统分析

对既有及正在开发中的填土压实检测技术的原理及实测方法进行了系统的介绍、分析及论证。在此基础上,阐述了开发填土压实检测与压实机械集成系统的必要性、研制机载集成系统时所依据的力学模型、实现途径及国内外关于压实机械集成系统研究、开发的最新进展,介绍了压实机械集成系统的工作原理及工作特性,同时指出了为适应当前及未来土建工程对填土压实质量（特别是沉降量及沉降速率等方面）的基本要求,应以填土压实层的力学强度（K30、动刚度系数等）作为开发压实机械集成系统时的参考对比指标。     

气测录井在南方页岩气黔绥地1井中的应用

南方页岩气黔绥地1井为全井取心钻进,通过加工模拟绞车实现了绞车传感器的安装、安装开关代替了悬重传感器的安装、将泵冲传感器安装到皮带轮保护罩上等解决方法,使得气测录井在黔绥地1井中顺利进行。影响黔绥地1井气测录井结果的主要因素有储集层、钻井液、钻井工程以及脱气器,这些影响因素的存在给黔绥地1井气测录井资料解释带来了很大的困扰。为了减少对气测录井资料解释的困扰,必须加强对现场工作人员的录井培训,使录井人员在工作当中能够有效地消除可控因素对气测录井的影响,在一定程度上提高地质钻探气测录井的准确度,为南方页岩气地层划分提供有力的数据支撑。     

岩石变形破裂过程中电荷感应信号的检测

设计了采用非接触方式、高放大倍数、高效率的电荷传感器,并给出了电荷传感器的设计原理和技术指标。利用研制的电荷传感器对岩石变形破裂过程中产生的电荷感应信号进行了检测试验。结果表明,岩石在变形破裂过程中会产生电荷感应信号,并能够被研制的电荷传感器检测到;电荷感应信号是瞬时脉冲的;随着加载应力水平的增加,电荷感应信号强度增强,在峰值应力前,电荷感应信号强度达到最大值;在破裂面接收到的电荷感应信号较强,主破裂面接收到的信号最强,因而电荷的产生和岩石的破裂有很大的关系。作为正在探索的检测岩石破坏过程的手段之一,电荷感应方法应是一种很具潜力的方法,值得深入研究。     

Distributed fiber optic monitoring and stability analysis of a model slope under surcharge loading

In the discipline of geotechnical engineering, fiber optic sensor based distributed monitoring has played an increasingly important role over the past few decades. Compared with conventional sensors, fiber optic sensors have a variety of exclusive advantages, such as smaller size, higher precision, and better corrosion resistance. These innovative monitoring technologies have been successfully applied for performance monitoring of geo-structures and early warning of potential geo- hazards around the world. In order to investigate their ability to monitor slope stability problems, a medium-sized model of soil nailed slope has been constructed in laboratory. The fully distributed Brillouin optical time-domain analysis （BOTDA） sensing technology was employed to measure the horizontal strain distributions inside the model slope. During model construction, a specially designed strain sensing fiber was buried in the soil mass. Afterward, the surcharge loading was applied on the slope crest in stages using hydraulic jacks and a reaction frame. During testing, an NBX-6o5o BOTDA sensing interrogator was used to collect the fiber optic sensing data. The test results have been analyzed in detail, which shows that the fiber optic sensors can capture the progressive deformation and failure pattern of the model slope. The limit equilibrium analyses were also conducted to obtain the factors ofsafety of the slope under different surface loadings. It is found that the characteristic maximum strains can reflect the stability of the model slope and an empirical relationship was obtained, This study verified the effectiveness of the distributed BOTDA sensing technology in performance monitoring of slope.     

MUSIC算法在矢量水听器阵中的应用研究

文中推导了阵元为矢量水听器时的MU S IC算法。对直线阵情况进行了计算机仿真,结果表明,矢量阵MU-S IC算法与声压阵相比具有更高的方位分辨力。     

存储式高温高压钻孔测温仪的研制与应用

为解决大于200 ℃高温环境下的测温难题,为高温地热和干热岩资源勘查提供技术支撑,利用铂电阻测温技术和真空绝热保温技术研发了存储式高温高压钻孔测温仪。该仪器设计适用工作环境温度为300 ℃,耐水压100 MPa,主要用于高温高压环境下的钻孔测温。在广东惠州惠热1井和青海共和GH-01井进行了实测应用,满足目前钻遇到的孔底温度的测温要求。