通过神经网络加速实现大型黏弹性计算

认识重复地震周期活动的影响,其最大的挑战之一是大尺度的黏弹性地震周期模型的计算成本。对于计算密集型黏弹性代码,须在数以千计的时间和位置点上进行评估。因此,研究趋向于采用几个固定的流变结构和模型几何结构,考查所预测的大震后短时间(小于10年)内给定深度处不同时间的形变。训练一个深层神经网络来学习黏弹性解在任意时间、位置和大范围流变结构计算效率的表示,可快速且可靠地完成计算,并具有较高时空分辨率。结果表明,该机器学习方法可以将黏弹性计算速度提高50 000%以上。这种加速量级将使得在更大的模型参数范围内、在比以前更大的时空尺度上和数千个地震周期内,模拟几何结构复杂的断层成为可能。     

"The Bush is No More": Insights on Institutional Change and Natural Resource Availability in Rural South Africa

The past decade has brought substantial transition to South Africa. The introduction of democracy in 1994 has yielded important political and socioeconomic transformations affecting millions of people. Here, we explore the impact of institutional and structural changes on the availability and management of fuelwood, a key natural resource in rural South Africa. As in other developing regions, many households depend on natural resources for both sustenance and energy needs. Drawing on qualitative data from 32 interviews, our objective is to describe, from the perspective of the respondents, (1) resource scarcity, (2) the underlying causes of resource scarcity, (3) the role of traditional authority in managing resources, and (4) strategies used by community members in the face of resource scarcity. The results have important implications for the well-being of both social and natural systems in many transitional, rural developing societies.     

源于地震沉积学的高精度层序地层学应用：以路易斯安那近海老虎滩地区50号中新统弗米利恩区块为例

介绍了应用钻井和三维地震资料来划分高精度(四级)层序和体系域的地震沉积学方法。其关键技术包括:(1)将地震数据进行90°相位调整来记录岩性,从而获得更完善的测井资料;(2)假设并解释沉积体系中连续的平面地貌特征。下面我们推荐一种新的解释方法,就是将高精度层序地层学的研究重点从解释垂直地震剖面转变为分析更加水平、分辨率更高的地震地貌信息。这方面的研究表明,有岩性限制的地震资料中,地层切片可提供通常为同沉积体系的连续地震图像。反过来,这种图像又可作为识别和划分高频体系域、层序边界以及层序地质年代范围的基础。在路易斯安那近海的中新统地层中,运用测井资料划分的四级层序或层序组,可通过地震资料来划分,地震数据体的主频为30Hz,相当于分辨率为30ft(10m)。所用的这一分辨率在井控外的地震覆盖区,对高精度层序地层格架进行精确再现非常有效。     

Multifrequency Polarization Variations in the Quasar 0917＋624

We present a detailed analysis of multi-frequency observations of linear polarization in the intraday variable quasar 0917+624 (z = 1.44). The observations were made in May 1989 at five frequencies (1.4, 2.7, 5.0, 8.3 and 15GHz) with the VLA and the Effelsberg 100 m-telescope and in December 1988 at two frequencies (2.7 and 5.0 GHz) with the latter. It is shown that the relationship between the variations of the polarized and total flux density is highly wavelength dependent, and the multi-frequency polarization behavior may be essential for investigating the mechanisms causing these variations. It is shown that the variations observed at 20 cm can be interpreted in terms of refractive interstellar scintillation. However, after subtracting the variation due to scintillation, three 'features' emerged in the light-curve of the polarized flux density, indicating an additional variable component. Interestingly, these features are shown to be correlated with the variations at 2-6 cm, thus indicating that thes     

Submarine groundwater discharge into the near-shore zone of the Great Barrier Reef, Australia

Along the tropical coastline of the Great Barrier Reef (GBR) region, little is known to date about submarine groundwater discharge (SGD) into the near-shore ocean. In an oceanographic sense, SGD consists of freshwater flow from land as well as seawater circulated through sediments. Recent radiochemical and geophysical studies, using the tracer (222)Rn and apparent ground conductivity respectively, provide evidence for SGD to occur in a variety of hydrogeological settings. In this paper, a non-quantitative overview of different settings of SGD in the region is presented: (1) recirculation of seawater through animal burrows in mangrove forests, (2) freshwater SGD from unconfined aquifers as a narrow coastal fringe of freshwater along Wet Tropics beaches, (3) SGD from coastal dune systems in form of localised freshwater springs in the intertidal zone, (4) inner-shelf SGD from confined submarine aquifer systems comprised of riverine paleochannels incised into the shelf.     

苏联经济区划理论的发展历程

由于企业自主权增加、全面经济核算的引入和经济管理问题观念的更新,经济区划应该具有比目前更加重要的意义。因而评价以往70年来苏联经济区划(包括经济地理学)理论和实践的成就和失误,已成为重要而迫切的任务之一。