空间波数混合域磁异常场积分解三维数值模拟

本文提出一种空间波数混合域磁异常场三维数值模拟方法.该方法利用磁位三维空间域积分为卷积的特点,沿水平方向进行二维傅里叶变换,把空间域磁位满足的三维积分问题转化为不同波数之间相互独立的垂向一维积分问题.保留垂向为空间域,优势之一在于便于浅层单元剖分可适当加密,随着深度增加,单元剖分适当稀疏,可以准确模拟任意复杂地形和磁性体的磁异常,兼顾了计算精度与计算效率;优势之二在于一维积分垂向可离散为多个单元积分之和,每个单元采用二次形函数表征磁化强度,可得出单元积分的解析表达式,计算精度高、效率高.该方法充分利用一维形函数积分的高效和高精度、快速傅里叶变换的高效性及算法高度并行性,实现了磁异常场高效、高精度的数值模拟.设计棱柱体模型,将模型解析解与空间波数混合域法的数值解对比,结果表明该方法计算精度高、效率高.设计了组合棱柱体复杂模型,对比分析了标准FFT扩边法与Gauss-FFT法的计算精度与计算效率,总结了标准FFT的扩边系数选取策略.针对任意复杂地形条件下的磁异常模拟问题,本文提出一种适用于起伏地形条件下的磁异常场快速计算方法,并对其有效性进行了验证.     

Very high resolution Earth Observation features for testing the direct and indirect effects of landscape structure on local habitat quality

Modelling the empirical relationships between habitat quality and species distribution patterns is the first step to understanding human impacts on biodiversity. It is important to build on this understanding to develop a broader conceptual appreciation of the influence of surrounding landscape structure on local habitat quality, across multiple spatial scales. Traditional models which report that ‘habitat amount’ in the landscape is sufficient to explain patterns of biodiversity, irrespective of habitat configuration or spatial variation in habitat quality at edges, implicitly treat each unit of habitat as interchangeable and ignore the high degree of interdependence between spatial components of land-use change. Here, we test the contrasting hypothesis, that local habitat units are not interchangeable in their habitat attributes, but are instead dependent on variation in surrounding habitat structure at both patch- and landscape levels. As the statistical approaches needed to implement such hierarchical causal models are observation-intensive, we utilise very high resolution (VHR) Earth Observation (EO) images to rapidly generate fine-grained measures of habitat patch internal heterogeneities over large spatial extents. We use linear mixed-effects models to test whether these remotely-sensed proxies for habitat quality were influenced by surrounding patch or landscape structure. The results demonstrate the significant influence of surrounding patch and landscape context on local habitat quality. They further indicate that such an influence can be direct, when a landscape variable alone influences the habitat structure variable, and/or indirect when the landscape and patch attributes have a conjoined effect on the response variable. We conclude that a substantial degree of interaction among spatial configuration effects is likely to be the norm in determining the ecological consequences of habitat fragmentation, thus corroborating the notion of the spatial context dependence of habitat quality.     

Depositional evolution of a progradational to aggradational,mixed-influenced deltaic succession: Jurassic Tofte and Ile formations,southern Halten Terrace,offshore Norway

Predicting the hydrodynamics, morphology and evolution of ancient deltaic successions requires the evaluation of the three-dimensional depositional process regime based on sedimentary facies analysis. This has been applied to a core-based subsurface facies analysis of a mixed-energy, clastic coastal-deltaic succession in the Lower-to-Middle Jurassic of the Halten Terrace, offshore mid-Norway. Three genetically related successions with a total thickness of 100–300 m and a total duration of 12.5 Myr comprising eight facies associations record two initial progradational phases and a final aggradational phase. The progradational phases (I and II) consist of coarsening upward successions that pass from prodelta and offshore mudstones (FA1), through delta front and mouth bar sandstones (FA2) and into erosionally based fluvial- (FA3) and marine-influenced (FA4) channel fills. The two progradational phases are interpreted as fluvial- and wave-dominated, tide-influenced deltas. The aggradational phase (III) consists of distributary channel fills (FA3 and FA4), tide-dominated channels (FA5), intertidal to subtidal heterolithic fine-grained sandstones (FA6) and coals (FA7). The aggradational phase displays more complex facies relationships and a wider range of environments, including (1) mixed tide- and fluvial-dominated, wave-influenced deltas, (2) non-deltaic shorelines (tidal channels, tidal flats and vegetated swamps), and (3) lower shoreface deposits (FA8). The progradational to aggradational evolution of this coastal succession is represented by an overall upward decrease in grain size, decrease in fluvial influence and increase in tidal influence. This evolution is attributed to an allogenic increase in the rate of accommodation space generation relative to sediment supply due to tectonic activity of the rift basin. In addition, during progradation, there was also an autogenic increase in sediment storage on the coastal plain, resulting in a gradual autoretreat of the depositional system. This is manifested in the subsequent aggradation of the system, when coarse-grained sandstones were trapped in proximal locations, while only finer grained sediment reached the coastline, where it was readily reworked by tidal and wave processes.     

模糊多属性决策法在海底电缆路由方案比选中的应用

海底电缆预选路由方案的比选需要参考多种指标,这些指标包含定量和定性两种,但各指标间的不可公度性,给路由方案的选择提出挑战。文章提出了一种基于离差思想和模糊向量投影的多属性决策法。首先引入三角模糊数,将定性指标合理量化,构建决策矩阵,规范化后运用离差思想求解各指标权重,然后计算各方案在正理想方案和负理想方案上的投影,最后求出相对贴近度,依据其大小比选出最佳方案。     

Cenozoic sequence stratigraphy of the Kachchh Basin,India

The Kachchh sedimentary basin in the western continental margin of India is a peri-cratonic rift basin which preserves a nearly complete rock record from Middle Jurassic to Recent, punctuated by several stratigraphic breaks. The Cenozoic sediments exposed in the western part of the Kachchh mainland extend offshore into the present-day continental shelf. The unique feature of the outcropping area is a nearly complete, richly fossiliferous and easily accessible Cenozoic succession. Detailed field mapping and litho-biostratigraphic studies have made it possible to identify the chronostratigraphic units, map them in the field and extend the correlation into the offshore, aided by the development of continuously recognizable key biostratigraphic horizons and time boundaries. Detailed field mapping of key sections integrated with the litho-biostratigraphic information has helped in working out a sequence stratigraphic framework for the Cenozoic succession in the basin. The succession comprises a first-order passive margin sequence. Excellent biostratigraphic control has enabled identification of unconformities of various magnitudes which in turn have helped in mapping 5 second-order and four third-order sequences. Each sequence is discussed with respect to its extent, nature of sequence boundaries, sedimentary fill, key sequence stratigraphic surfaces and depositional setup, to understand the Cenozoic sequence stratigraphic architecture of the basin.     

卫星数据和地面观测结合的珠三角地区颗粒物质量浓度统计估算方法

利用卫星观测的气溶胶光学厚度资料和模式模拟数据,与地面颗粒物观测资料结合,探讨近地面颗粒物质量浓度的估算方法。具体包括：利用区域气侯模式RAMS（Regional Atmospheric Modeling System）模拟的边界层高度对气溶胶光学厚度进行垂直订正,获得近地面颗粒物消光系数;利用模式模拟的相对湿度和颗粒物吸湿增长经验模型对消光系数进行湿度订正,获得近地面颗粒物干消光系数;并基于干消光系数与颗粒物质量浓度地面站点资料建立的统计关系估算获得每个像元的颗粒物质量浓度。利用地面站点观测的颗粒物浓度资料验证表明,基于卫星资料可以获得近地面颗粒物质量浓度,而且细颗粒物质量浓度具有更好的估算精度。     

混合层的建立对一次强阵风天气过程的影响

利用NCEP再分析资料和常规地面观测资料,分析混合层的建立对2012年3月23日天津地区强阵风天气过程的影响机理。结果表明：强气压梯度和强变压梯度的共同动力作用是地面强阵风形成的背景条件。强阵风出现在午后气温较高、湿度较低且地面气压较低的时段。午后深厚混合层内的干热对流使高空急流北侧下沉气流将动量下传至对流层中层后向近地面层进一步有效下传,导致地面阵风增大。深厚混合层的建立也是地面强阵风形成的一个重要原因。WRF模拟结果表明,局地混合层强度差异使高空动量下传产生局地差异,这可能是天津各地区阵风强度存在空间差异的重要原因。     

不同边界层参数化方案在暴雨数值模拟中的对比分析

本文利用非静力平衡的中尺度模式(MM5),通过对一次华南锋前暖区暴雨的数值模拟,比较了3种边界层参数化方案的作用。结果表明：从24小时累积降水的分布来看,MRF方案的预报与实况对比效果最好,其次是Blaekadar高分辨率PBL模式,最差是no PBI,方案。分析MRF方案的输出结果,发现对应每个时刻的累积雨团上空,925hPa都有较强的辐合辐散偶极子与之相配合,而在300hPa则有较强的辐散。不同边界层方案模拟的辐散场有一定的差别,导致了降水的不同预报效果。     

层滑构造煤岩体微观特征及其应力应变分析

层滑构造在煤层及其顶、底板间普遍发育,它对地质勘探、煤矿生产、矿井工程灾害防治以及煤层气的开发等方面都有着重要影响。本文以淮北煤田海孜煤矿为例,在研究宏观层滑构造带组合特征的基础上,探讨了层滑构造的微观特征和形成机理。构造煤是层滑引起的煤层流变最显著的特征之一。通过对构造煤与构造岩的微观特征测试,发现层滑运动除了产生脆性变形外,还产生较强烈的塑性变形。利用煤镜质组光率体各向异性和构造岩组构,结合层滑构造的实测数据进行了煤岩体应力、有限应变分析。结果表明:层滑构造以顺层剪切为主,煤层受力的主要方向为NW-SE向。     

Tides in the Tongan Region of the Pacific Ocean

Tidal levels and currents in the Tongan region of the Pacific were simulated using a two-dimensional frequency-domain finite element model. The eight major diurnal and semidiurnal tidal constituents were modeled successfully, using open boundary conditions taken from a global tidal model based on the Topex/Poseidon satellite altimeter. Comparison of model results with observations from the single tide gauge site in the area were later used to adjust the boundary conditions. The validity of omitting horizontal eddy viscosity from the finite element model was checked by running an equivalent finite difference model. The results show that although the submarine Tongan ridge does not appear to trap tidal energy, there are residual tidal currents and possible recirculations which are capable of influencing biological productivity around Tonga. The model results are reduced to a simple method for predicting tidal heights in outlying areas, based only on the tidal calendar for the capital, Nuku'alofa.