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961.
PPP/INS组合导航系统中,接收机载波相位观测值由于接收机高动态、卫星低仰角、信号被遮挡等原因,往往发生周跳。周跳不仅会影响PPP定位精度,而且可能会导致模糊度参数重新初始化以致数十分钟才能重新收敛。针对以上问题,本文提出利用惯性导航系统(INS)辅助PPP宽巷周跳探测的新策略,通过具有短时高精度的INS信息,消除宽巷组合中的站星几何位置,克服传统MW方法中码伪距噪声及多路径误差的影响。试验表明,INS辅助的宽巷周跳探测方法能够精确识别各种宽巷小周跳。将该方法与无几何距离(GF)组合方法相结合,可以实现对双频等周周跳和特殊周跳(5/4、9/7等)的探测,具有较高探测精度,并可应用于实时周跳探测。 相似文献
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A computational formulation of discrete simulations of damage and failure in brittle rocks using mathematical programming methods is proposed. The variational formulations are developed in two and three dimensions. These formulations naturally lead to second-order cone programs and can conveniently be solved using off-the-shelf mathematical programming solvers. Pure static formulations are derived so that no artificial damping parameters are required. The rock is represented by rigid blocks, with interfaces between blocks modelled by zero-thickness springs based on the rigid-body–spring network method. A modified Mohr–Coulomb failure criterion is proposed to model the failure of the interfaces. When the interface’ strength limits are reached, a microscopic crack forms and its strength is irreversibly lost. The microscopic elastic properties of the springs are related to the observed elastic behaviour of rocks with the developed empirical equations. The program is first validated with three simple tests. Then, numerical uniaxial and biaxial compression tests and the Brazilian tests are conducted. Furthermore, the proposed approach is employed to study the rock crack propagation and coalescence using cracked Brazilian disc test. The results are in good agreements with reported experimental data, which shows its potential in modelling mechanical behaviour of brittle rocks. 相似文献
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966.
Hao Yan Jixiong Zhang Nan Zhou Sheng Zhang Xiangjian Dong 《Environmental Earth Sciences》2018,77(12):458
Solid backfill coal mining is a mainstream method in green coal mining, which has gradually become a key technology to control shaft deformation when recovering industrial square pillars during mining of ultra-contiguous coal seams. On the basis of the engineering background of Nantun Coal Mine, this paper combined physical simulation, numerical simulation, and theoretical analysis for studying shaft deformation, failure characteristics, and stress variation rules during the mining of ultra-contiguous coal seams. The results revealed that shaft deformation and failure were the results of the movement of strata caused by coal mining; in addition, the backfill body compression ratios in two adjacent coal seams were the key factors in shaft deformation control during the mining of ultra-contiguous coal seams. Moreover, the effects of the backfill body compression ratios on shaft deformation in ultra-contiguous coal seam mining were simulated by ABAQUS, and the optimal compression ratios of backfill body in two coal seams were determined. Finally, based on the probability-integral method, the vertical compressive deformation and the inclined deformation of shaft were estimated and the results showed that the shaft safety and stability at ultra-contiguous coal seam mining can be provided when the backfill body compression ratios of 3upper and 3lower coal seams were set at 85%. 相似文献
967.
通过对现有AutoCAD图案填充重生成边界方法总结,提出了一种兼顾ArcGIS图形显示的AutoCAD图案填充重生成边界法,其主要包括3个步骤:1提取边界环并做循环访问;2对组成每个边界环的曲线集合按照起点和终点坐标进行排序;3对排序后的曲线集合进行连接。 相似文献
968.
黄土丘陵区地质灾害规模参数幂律相依性研究 总被引:2,自引:0,他引:2
对滑坡、崩塌和不稳定斜坡等地质灾害规模参数幂律相依性进行定量研究,拓展了规模参数之间幂律相依性的研究范围。研究结果发现:1地质灾害规模参数的幂律相依性不仅存在于体积与面积之间,而且存在于面积与长、面积与宽等参数之间;2幂指数可以作为间接反映区域地质灾害或者不同类型地质灾害的宏观特征表征谱;3体积与面积关系式的幂指数分布为不稳定斜坡滑坡崩塌;面积与长关系式的幂指数分布为崩塌滑坡不稳定斜坡。面积与宽关系式的幂指数的分布为滑坡崩塌不稳定斜坡。 相似文献
969.
Based on the daily precipitation from a 0.5°×0.5° gridded dataset and meteorological stations during 1961–2011 released by National Meteorological Information Center, the reliability of this gridded precipitation dataset in South China was evaluated. Five precipitation indices recommended by the World Meteorological Organization(WMO) were selected to investigate the changes in precipitation extremes of South China. The results indicated that the bias between gridded data interpolated to given stations and the corresponding observed data is limited, and the proportion of the number of stations with bias between –10% and 0 is 50.64%. The correlation coefficients between gridded data and observed data are generally above 0.80 in most parts. The average of precipitation indices shows a significant spatial difference with drier northwest section and wetter southeast section. The trend magnitudes of the maximum 5-day precipitation(RX5day), very wet day precipitation(R95), very heavy precipitation days(R20mm) and simple daily intensity index(SDII) are 0.17 mm·a–1, 1.14 mm·a–1, 0.02 d·a–1 and 0.01 mm·d–1·a–1, respectively, while consecutive wet days(CWD) decrease by –0.05 d·a–1 during 1961–2011. There is spatial disparity in trend magnitudes of precipitation indices, and approximate 60.85%, 75.32% and 75.74% of the grid boxes show increasing trends for RX5 day, SDII and R95, respectively. There are high correlations between precipitation indices and total precipitation, which is statistically significant at the 0.01 level. 相似文献
970.
基于2016年以来雷州半岛-海南岛陆地区(以下简称雷琼地区)的流动重力资料,对2017年下半年前后的联测资料采用不同的平差方法进行处理。将湛江和琼中2个绝对重力点作为雷琼测网基准,研究2016年以来雷琼地区重力场动态变化特征。重点研究2018-03-20广东阳江4.2级地震、2019-03-05广东雷州4.1级地震、2019-08-20海南三亚4.2级地震和2019-10-12广西北流5.2级地震震前区域重力场差分和累积动态变化。研究结果表明,除广东雷州4.1级地震外,其他3个地震震前在震中附近地区均存在重力场变化异常,表明在测网网格距和数据处理方法合理的情况下,对于4~5级地震,区域重力场在震前可能存在一定异常反应。 相似文献