北斗Ⅱ载波相位差分定位法在高填方变形监测中的应用     

杜伟飞  张继文  夏娜  郑建国  于永堂  张慧海 《测绘科学技术学报》2017,34(4)

通过对北斗Ⅱ载波相位差分定位技术在高填方变形监测中的应用研究,包括实时动态差分定位(RTK)和静态相对定位,构建了完整的北斗Ⅱ高填方变形监测软硬件系统。该系统采用基于贯序极限学习机的卫星信号周跳探测与修复方法进行数据预处理,并利用基于卫星历元数的分层置信滤波算法对静态相对定位结果进行修正,提高了定位结果的准确性和可靠性。通过自制的精度测试装置,以百分表和钢尺测量的位移变化量为相对真值,完成了上述变形监测系统的精度试验。试验结果表明:该系统的RTK高程测量精度优于2 cm,静态高程测量精度优于2 mm,静态水平位移测量精度优于1.5 mm,可有效抑制卫星信号周跳和卫星历元数量较少等因素的影响。  相似文献   

A new algorithm to find raster-based least-cost paths using cut and fill operations     

Jieun Baek 《International journal of geographical information science》2017,31(11):2234-2254

We developed a least-cost path analysis algorithm that satisfies a slope threshold condition in hilly terrain. The new algorithm uses an expanding moving-window to explore a combination of cells that satisfy an elevation threshold condition and then supplements this by executing cut and fill operations when there are obstacle cells between source and destination cells. Cut and fill factors regarding the difference in the actual elevation and revised elevation are considered and a least-cost path is analyzed after calculating the accumulated travel cost to the destination point. After applying the developed algorithm to synthetic and real-world data, the least accumulated travel cost from the source point can then be calculated for all cells on the raster surface by considering various slope thresholds, moving-window sizes and raster data resolutions. This algorithm can be implemented as a useful tool in GIS software as well as engineering design software utilized in the construction and mining industries.  相似文献   

Sinusoidal variables from the Tycho Epoch Photometry Annex     

Chris Koen  Robert Schumann 《Monthly notices of the Royal Astronomical Society》1999,310(3):618-628

The Tycho Epoch Photometry Annex A, a data base of photometry of more than 34 000 bright stars, has been searched for periodic variable stars with approximately sinusoidal light curves. Advantage was taken of special properties of the observing programme (photometry in two wavebands, availability of repeated measurements) to use simple but efficient variable selection criteria. Details of 70 strong candidate variables are presented.  相似文献   

Mass estimation in the outer regions of galaxy clusters     

Antonaldo Diaferio 《Monthly notices of the Royal Astronomical Society》1999,309(3):610-622

We present a technique for estimating the mass in the outskirts of galaxy clusters where the usual assumption of dynamical equilibrium is not valid. The method assumes that clusters form through hierarchical clustering and requires only galaxy redshifts and positions on the sky. We apply the method to dissipationless cosmological N -body simulations where galaxies form and evolve according to semi-analytic modelling. The method recovers the actual cluster mass profile within a factor of 2 to several megaparsecs from the cluster centre. This error originates from projection effects, sparse sampling, and contamination by foreground and background galaxies. In the absence of velocity biases, this method can provide an estimate of the mass-to-light ratio on scales ∼1–10  h ⁻¹ Mpc where this quantity is still poorly known.  相似文献   

中国南方二叠纪层序地层时空格架及充填特征   总被引：9，自引：0，他引：9  

李祥辉  王成善 《沉积学报》1999,17(4):521-527

据华南二叠纪不同沉积盆地层序地层区域分布、纵向演化及其充填特征分析研究,初步建立了上扬子克拉通-右江盆地-钦防盆地、中扬子克拉通及全区的层序地层时空格架模型;提出层序充填可分为两个阶段:早二叠世碳酸盐缓坡-台地层序充填阶段,晚二叠世陆源碎屑为主与火山碎屑相混层序充填阶段;认为全区二叠纪四个Ⅰ型层序受控于构造隆升事件,晚二叠世层序TST普遍发育火山碎屑沉积,古陆边缘HST或少量SMT/LST大多由三角洲沉积体系进积叠加而成,上扬子克拉通及右江地区的生物礁以海侵和高位型为特色。  相似文献   

一种基于格网的快速等值线充填算法   总被引：16，自引：0，他引：16  

吴自银  高金耀 《测绘学报》1999,28(4):350-354

本文提出一种基于格网的等值线跟踪,适用于任意边界分割的快速充填算法,实现充填的 量化效果。根据边界线与非封闭等值线间的关系,建立等值线间的拓扑关系,并以树结构方式存储,以准确快速地实现边界线、非封闭等值线之间的封闭和封闭等值线间的嵌套。该算法已成功应用于海量多波束地形数据的成图,克服了常用多波束后处理成图软件栅格充与等值线之间的失配。  相似文献   

Nanpanjiang basin: A window on the tectonic development of south China during Triassic assembly of the southeastern and eastern Asia     

《Gondwana Research》2020

As the largest siliciclastic sink in the South China block, the Triassic Nanpanjiang basin is generally thought of as a foreland basin related to Indosinian collision between the South China and Indochina blocks. Our basin analysis, spanning an eight years period, provides details of Lopingian to Middle Triassic stratigraphic fill and tectonic subsidence of the basin. Field observation and sedimentological analyses reveal that the basin was not filled by a monotonous turbidite system and suggest instead the development of five primary depositional units constituted by deep-water turbidite systems, mass-transport deposits, condensed drapes, shallow-water isolated carbonate platforms, and volcano-volcaniclastic rocks. The stratigraphic completeness of the basin, the coexistence of widespread but localized carbonate platforms within axially filled deep-water basin, tectonically generated cyclothems of transverse mass-transport deposits along intrabasinal faults and basin fill of extrusive rocks of bimodal composition together apparently call in question the claim that crustal shortening prevailed during the Late Permian to pre-Norian Triassic. Patterns of basin fill, differential tectonic subsidence and very high subsidence rate of the region adjacent to master fault are more closely match the pattern expected for extensional to transtensional basin in a back-arc setting. The crustal extension in the southwestern South China was not consistent with hypothesized Indosinian collision between South China and Indochina blocks, but more likely developed in response to northwestward subduction of the paleo-Pacific plate. Our results, combined with regional considerations, lead to a new model for the Triassic tectonic evolution of South China during Triassic assembly of the southeastern and eastern Asia.  相似文献   

26Al and 10Be dating of late pleistocene and holocene fill terraces: a record of fluvial deposition and incision,Colorado front range     

Taylor Schildgen  David P. Dethier  Paul Bierman  Marc Caffee 《地球表面变化过程与地形》2002,27(7):773-787

Cosmogenic ²⁶Al, ¹⁰Be, and ¹⁴C dating of fluvial fill terraces in steep canyons of the Colorado Front Range provides a temporal framework for analysing episodic aggradation and incision. Results from Boulder Canyon show that terrace heights above the modern channel (grade) can be divided into: (1) Bull Lake (≳100 ka; 20–15 m above grade); (2) Pinedale (32–10 ka; 15–4 m above grade); and (3) Holocene age (<4 m above grade). No pre‐Bull Lake deposits are preserved along Boulder Canyon, and only three small remnants >15 m above grade record Bull Lake deposition. Well‐preserved terraces of Pinedale age suggest that the range of terrace height above grade reflects short‐term fluctuations in the river profile during periods of rapidly changing stream load and power. Net river incision apparently occurred during transitions to interglacial periods. Soil development and stratigraphic position, along with limited cosmogenic and ¹⁴C dating, suggest that ∼130 ka terraces in Boulder Canyon correlate with the Louviers Alluvium, and that 32 to 10 ka fills in the canyon correlate with the Broadway Alluvium on the adjacent High Plains. Late Pleistocene incision rates (∼0·15 m ka⁻¹) along Boulder Canyon exceed pre‐late Pleistocene incision rates, and are higher than middle to late Pleistocene incision rates (∼0·04 m ka⁻¹) on the High Plains. This study provides an example of how modern geochronologic techniques allow us to understand better rivers that drain glaciated catchments. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

斜轴式望远镜动力学建模与鲁棒控制          下载免费PDF全文

梁静思  王海仁  左营喜  张明珠  高婧婧  程文胜  王博铖  张天哲 《天文学报》2023,64(6):62

斜轴式望远镜是一种新颖的望远镜结构, 其独特的结构设计更适合南极等极端气候环境, 但目前国内外缺乏针对斜轴式望远镜详细的动力学建模与控制研究. 提出一套斜轴式望远镜动力学建模与鲁棒控制方法, 首先, 对斜轴式望远镜进行了动力学分析, 采用拉格朗日法建立望远镜2自由度刚体模型; 接着, 结合望远镜驱动系统的柔性和所受干扰, 完成了斜轴式望远镜的干扰情况下刚柔耦合系统数学模型的推导; 然后, 针对抗干扰问题, 根据所建数学模型, 设计了基于干扰观测器的滑模控制器, 对于所受干扰进行抑制, 实现了斜轴式望远镜的鲁棒控制; 最后, 仿真结果显示, 在考虑模型的非线性外部干扰的情况下, 相比于传统的比例-积分-微分控制器, 基于干扰观测器的滑模控制器使得系统具有更好的动态性能和抗干扰特性.  相似文献   

考虑二期荷载的高填明洞加筋减载土压力计算     

李盛  马莉  王起才  李建新  李善珍  张延杰 《岩土力学》2015,36(11):3229-3234

随着城市建设的迅速发展,既有高填明洞填土顶面将不可避免地出现新增结构物等二期荷载的情况。为了明确明洞回填完成后新增二期荷载对其顶部垂直土压力的影响,在已有明洞减载结构土压力计算公式的基础上,利用土体沉降弹性理论计算公式建立了土工格栅变形与土体沉降变形的关系,并考虑二期荷载作用,进一步完善了高填明洞减载前后的洞顶垂直土压力计算公式。建立数值分析模型,将数值分析结果与文中公式计算结果进行了对比。结果表明：公式计算与数值分析结果较为接近,表现出相同的规律性;有无减载措施对明洞回填土压力影响较大,填土越高,减载越显著,实际作用在明洞顶土压力越小。新增二期荷载作用下的明洞顶垂直土压力计算,应考虑其对土体沉降变形的影响,而非简单叠加。  相似文献