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321.
闽台两岸区域地震监测台网及地震监测能力比较 总被引:2,自引:0,他引:2
介绍了闽台两岸地震台网的历史与现状,现今地震观测台网布局及监测及台站使用仪器类型的历史沿革。同时,使用1993 ̄1994年两岸分别出版的地震观测报告,系统分析了同一地震中两岸台网分别测定的地震参数的差异,探讨了引起这种差异的可能原因,提出了今后联合进行台湾海峡地震监测预报与地球结构研究的必要性和可行性。 相似文献
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最佳地电台台址条件与环境条件的讨论 总被引:3,自引:0,他引:3
地电台观测地电阻率及其变化以研究地震活动规律,首要的问题是如何选择或评估其台址的优劣,选取最佳地电台台址。文中讨论了地电台台址的地质构造条件、测区地下介质结构条件、介质水文条件、地形地貌条件、电磁干扰等对地电台站观测效能的影响,为选建和评估地电台台址提供较全面、系统的依据。 相似文献
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采用结合匹配法和经验正交函数法的射线声层析反演方法,针对流场水平分布不均匀特点,使用距离等效分段方法对反演算法进行改进,利用三个断面声层析数据,对胶州湾口潮流场的垂直和水平分布进行反演。与传统方法比较,大大降低与实测流速垂直分布间的偏差,平均偏差小于0.02 m/s,流场垂直分布间的相关系数提高到0.85以上。分析了声传播断面上不同的流场结构,以及涨潮期间在胶州湾团岛附近出现的涡流现象,并计算得到湾口海水流量变化。结果表明,改进的射线声层析反演方法可有效地用于水平分布不均匀流场监测,仅采用少量声学观测站位,即可获得大范围的复杂流场三维信息,有利于近海海洋资源开发、海洋环境保护和船舶航行安全。 相似文献
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Murali Krishna Gumma Prasad S. Thenkabail Pardharsadhi Teluguntla Mahesh N. Rao Irshad A. Mohammed Anthony M. Whitbread 《International Journal of Digital Earth》2016,9(10):981-1003
The goal of this study was to map rainfed and irrigated rice-fallow cropland areas across South Asia, using MODIS 250?m time-series data and identify where the farming system may be intensified by the inclusion of a short-season crop during the fallow period. Rice-fallow cropland areas are those areas where rice is grown during the kharif growing season (June–October), followed by a fallow during the rabi season (November–February). These cropland areas are not suitable for growing rabi-season rice due to their high water needs, but are suitable for a short -season (≤3 months), low water-consuming grain legumes such as chickpea (Cicer arietinum L.), black gram, green gram, and lentils. Intensification (double-cropping) in this manner can improve smallholder farmer’s incomes and soil health via rich nitrogen-fixation legume crops as well as address food security challenges of ballooning populations without having to expand croplands. Several grain legumes, primarily chickpea, are increasingly grown across Asia as a source of income for smallholder farmers and at the same time providing rich and cheap source of protein that can improve the nutritional quality of diets in the region. The suitability of rainfed and irrigated rice-fallow croplands for grain legume cultivation across South Asia were defined by these identifiers: (a) rice crop is grown during the primary (kharif) crop growing season or during the north-west monsoon season (June–October); (b) same croplands are left fallow during the second (rabi) season or during the south-east monsoon season (November–February); and (c) ability to support low water-consuming, short-growing season (≤3 months) grain legumes (chickpea, black gram, green gram, and lentils) during rabi season. Existing irrigated or rainfed crops such as rice or wheat that were grown during kharif were not considered suitable for growing during the rabi season, because the moisture/water demand of these crops is too high. The study established cropland classes based on the every 16-day 250?m normalized difference vegetation index (NDVI) time series for one year (June 2010–May 2011) of Moderate Resolution Imaging Spectroradiometer (MODIS) data, using spectral matching techniques (SMTs), and extensive field knowledge. Map accuracy was evaluated based on independent ground survey data as well as compared with available sub-national level statistics. The producers’ and users’ accuracies of the cropland fallow classes were between 75% and 82%. The overall accuracy and the kappa coefficient estimated for rice classes were 82% and 0.79, respectively. The analysis estimated approximately 22.3?Mha of suitable rice-fallow areas in South Asia, with 88.3% in India, 0.5% in Pakistan, 1.1% in Sri Lanka, 8.7% in Bangladesh, 1.4% in Nepal, and 0.02% in Bhutan. Decision-makers can target these areas for sustainable intensification of short-duration grain legumes. 相似文献
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全景图在虚拟环境、街景地图等应用中发挥的作用日益重要,成为地理信息表达的一种重要方式。本文通过介绍全景图生成的关键技术,重点利用目前主流的三款全景图生成软件Photo Stitch、Panorama Maker、Pix Maker,分别对室内图像及室外图像进行全景图的拼接实验,并对三款软件的拼接结果及图像融合效果进行对比分析,从而为用户选择及使用软件提供指导。 相似文献
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地磁导航是一种根据地磁场磁要素信息进行匹配制导的重要导航方式,由于地磁场信息丰富、敏感,利于匹配,且没有累积误差等优势,目前,地磁导航正受到越来越多的关注。本文简要介绍了地磁导航的基本原理,结合国内外导航研究现状,重点介绍了地磁导航的多项关键技术研究进展情况,最后对地磁导航在未来国防建设发展中的应用进行了展望。 相似文献