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211.
1 研究背景
北京及邻区(39 °—41.5 °N,115 °—118 °E)地震活动背景活跃,政治、经济、文化高度集中,是我国经济社会发展以及减轻地震灾害的重点监视区之一(徐锡伟等,2002;陈颙等,2006).随着北京及邻区地震台网组成的不断完善和台站变更频度的加快,亟待及时动态评估地震监测能力变化,为北京及邻区日常监测预报业务提供数据支撑.国内外应用广泛的"基于概率的完整性震级"(probability-based magnitude of completeness,简称PMC)方法(Schorlemmer and Woessner,2008;Schorlemmer et al,2010),基于地震台阵/地震台网实际产出的观测资料,可实时、客观、准确地评估地震台网监测能力.采用PMC方法,对北京及邻区地震监测能力进行动态评估,以便摸清该区监测能力,进而为防震减灾部署、监测预报相关业务开展等提供重要的参考资料. 相似文献
212.
European Maritime States already have commitments to protect species and habitats and maintain quality standards in coastal and offshore waters. These are a direct response to environmental legislation in Europe and commitments made to biodiversity conservation in OSPAR and at the World Summit on Sustainable Development. An integrated approach to management requires that these are consistent with the requirements for sustainable development, and include wider social considerations and active stakeholder participation. This review describes a hierarchical framework that incorporates the marine objectives and delivery statements of ecological, social and economic sectors. The framework leads from the UK's guiding principles for sustainable development, through visionary statements and strategic goals for high level delivery, to operational objectives and statements of action which deliver management. Parts of this hierarchy can already be populated for the UK, especially those at the higher levels. At the operational level, however, there is less clarity. The review shows that, despite some gaps, existing commitments for ecological components of the ecosystem are transparent and generally conform to this framework, due largely to high profile government funding of environmental protection and science and a single national vision for the marine environment. Specific objectives for six components of the ecosystem were developed; benthic habitats, seabirds and mammals, phytoplankton and zooplankton, fish, and physical/chemical quality of the water and atmosphere. The objectives included some that avoided limits and others that aimed to achieve targets, and for management to be effective it will be important to have a common understanding of how these can together be interpreted and made operational. In a review of 13 social and economic sectors, few provided a clear breakdown of objectives leading from a high level vision or a sustainable development principle. Six sectors did not have high level government targets for production or other measures of sectoral performance. Such commercial operations generally determine their own operational delivery targets based on market forces. Recent proposals in Europe to create an integrated framework for social, economic and environmental activities will need to carefully balance the development of a strong and competitive marine economy with existing international obligations to environmental protection. 相似文献
213.
水下滑翔机其通过集成生物、化学、物理传感器可以测量如温度、盐度、溶解氧等多种海洋基础水文要素,其利用卫星定位系统获得实际出水速度和理论出水模型获得理论出水速度之差可以计算深度平均流,。本文利用海翼水下滑翔机获得温盐场及卫星定位数据评估深度平均流,结果显示利用温盐场获得深度平均地转流与水下滑翔机获得深度平均流相关系数0.95,表明其流场的一致性,同时根据船载观测ADCP误差分析法估算深度平均流误差约为0.036 m/s。借助深度平均流可以估算绝对地转流,包括正压地转流和斜压地转流。在零动力面的假设下,我们选取了海翼号水下滑翔机在南海的一组实验对流量误差进行了评估。该实验为2019年1月3日-2月16日海翼号水下滑翔机自南向北穿越西沙群岛附近一个中尺度涡观测。观测结果表明,该中尺度涡为冷涡流核,在涡心以南,绝对地转流为东向流,最大流速约为0.48 m/s;涡心以北,绝对地转流为西向流,最大流速约为0.47 m/s,稍弱于南侧。受不均匀时空观测计划影响,本文未对流量做出估计。 相似文献
214.
应用型本科院校在面对"三项试点"工程的新模式下,测绘CAD课程教学改革迫在眉睫。分析测绘CAD课程体系的现状,探讨其教学内容、教材、实训基地、师资队伍等方面的问题。提出从课程定位与培养目标、理论教学、实践教学、教学方法等几方面进一步深化教学改革,实施应用型高等学校测绘CAD课程的全方位改革,提高教学质量。 相似文献
215.
Global acquisition of infrared spectra and high-resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context. Mare Serpentis, a low albedo region located northwest of Hellas Basin, is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material. Most martian surfaces are dominated by fine-grained particulate materials that bear an uncertain compositional and spatial relationship to their source. Thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials. Using spectral, thermophysical and morphologic information, we assess the local and regional stratigraphy of the Mare Serpentis surface in an effort to reconstruct the geologic history of the region. The martian highlands in Mare Serpentis are dominated by two interspersed surface units, which have distinct compositional and thermophysical properties: (1) rock-dominated surfaces relatively enriched in olivine and pyroxene, and depleted in high-silica phases, and (2) sediment or indurated material depleted in olivine and pyroxene, with relatively higher abundance of high-silica phases. This is a major, previously unrecognized trend which appears to be pervasive in the Mare Serpentis region and possibly in other highland areas. The detailed observations have led us to form two hypotheses for the relationship between these two units: either (1) they are related through a widespread mechanical and/or chemical alteration process, where less-mafic plains materials are derived from the mafic bedrock, but have been compositionally altered in the process of regolith formation, or (2) they are stratigraphically distinct units representing separate episodes of upper crust formation. Existing observations suggest that the second scenario is more likely. In this scenario, plains materials represent older, degraded, and possibly altered, “basement” rock, whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin. These hypotheses should be further testable with decimeter-resolution imagery and meter-resolution short wavelength infrared spectra. 相似文献
216.
Data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) and the Mars Odyssey Thermal Emission Imaging System (THEMIS) instruments are used to assess the mineralogic and dust cover characteristics of landing regions proposed for the Mars Science Laboratory (MSL) mission. Candidate regions examined in this study are Eberswalde crater, Gale crater, Holden crater, Mawrth Vallis, Miyamoto crater, Nili Fossae Trough, and south Meridiani Planum. Compositional units identified in each region from TES and THEMIS data are distinguished by variations in hematite, olivine, pyroxene and high-silica phase abundance, whereas no units are distinguished by elevated phyllosilicate or sulfate abundance. Though phyllosilicate minerals have been identified in all sites using near-infrared observations, these minerals are not unambiguously detected using either TES spectral index or deconvolution analysis methods. For some of the sites, small phyllosilicate outcrop sizes relative to the TES field of view likely hinder phyllosilicate mineral detection. Porous texture and/or small particle size (<∼60 μm) associated with the phyllosilicate-bearing surfaces may also contribute to non-detections in the thermal infrared data sets, in some areas. However, in Mawrth Vallis and Nili Fossae, low phyllosilicate abundance (<10-20 areal %, depending on the phyllosilicate composition) is the most likely explanation for non-detection. TES data over Mawrth Vallis indicate that phyllosilicate-bearing surfaces also contain significant concentrations (>15%, possibly up to ∼40%) of a high-silica phase such as amorphous silica or zeolite. High-silica phase abundance over phyllosilicate-bearing surfaces in Mawrth Vallis is higher than that of surrounding surfaces by 10-15%. With the exception of these high-silica surfaces in Mawrth Vallis, regions examined in this study exhibit similar bulk mineralogical compositions to that of most low-albedo regions on Mars; the MSL scientific payload will thus be able to provide important information on surface materials typical of low-albedo regions in addition to investigating the origin of phyllosilicate and/or sulfate deposits. With the exception of Gale crater, all of the landing sites have relatively low dust cover compared to classic high-albedo regions (Tharsis, Arabia and Elysium) and to previous landing sites in Gusev Crater, Utopia Planitia, and Chryse Planitia. 相似文献
217.
We report very high temporal and spectral resolution interferometric observations of some unusual solar radio bursts near
1420 MHz. These bursts were observed on 13 September 2005, 22 minutes after the peak of a GOES class X flare from the NOAA
region 10808. Our observations show 11 episodes of narrow-band intermittent emission within a span of ≈ 8 s. Each episode
shows a heavily frequency-modulated band of emission with a spectral slope of about −245.5 MHz s−1, comprising up to 8 individual blobs of emission and lasts for 10 – 15 ms. The blobs themselves have a spectral slope of
≈ 0 MHz s−1, are ≈ 200 – 250 kHz wide, appear every ≈ 400 kHz and last for ≈ 4 – 5 ms. These bursts show brightness temperatures in the
range 1012 K, which suggests a coherent emission mechanism. We believe these are the first high temporal and spectral resolution interferometric
observations of such rapid and narrow-bandwidth solar bursts close to 1420 MHz and present an analysis of their temporal and
spectral characteristics. 相似文献
218.
The NCEP/NCAR II daily mean reanalysis data and observed precipitation data are employed to
investigate the westward extension of the western Pacific subtropical high (WPSH) during the heavy rain
period over the southern China in June 2005. Results show that there may exist a relationship between the
east-west shift of the WPSH and the process of a southern China heavy rain. The analysis indicates that the
vertical motion in the WPSH area is mainly caused by the latent heat release of monsoon rain belts on its
northern and southern sides. The vertical motion could cause the accumulation of air mass in the center
and west of the WPSH, which leads to its strengthening. The appearance of the northern and southern
monsoon rain belts could not only enhance the WPSH by strengthening the descending draft, but also
excite the development of positive vorticity and restrict the WPSH’s movement in the north–south
direction. Moreover, the Indian monsoon rainfall to the west of the WPSH may excite the development of
anticyclonic vorticity on its eastern side, which leads to the westward extension of the WPSH. 相似文献
219.
220.