有限水深中零航速浮体波浪力计算奇点积分的数值处理方法

使用三维源汇分布法Ⅲ计算有限水深中零航速浮体所受到的波浪力,对两种不同形式的格林函数中所共同存在的奇点问题分别进行了处理。公式推导表明,使用级数形式的格林函数可以使计算更加快捷。最后,对不同尺度的圆柱体进行了验算,在对计算结果与解析解进行了比较之后,工程计算也证明选择格林函数级数计算公式是更令人满意的方案。     

Variable-discharge-river macroforms in the Sunnyside Delta Interval of the Eocene Green River Formation,Uinta Basin,USA

An outcrop dataset from the early Eocene Sunnyside Delta Interval of the Green River Formation in the Uinta Basin, Utah, USA, documents alluvial channel lithosomes. The abundance of Froude supercritical-flow sedimentary structures, together with an abundance of high-deposition-rate sedimentary structures, in-channel bioturbation and pedogenic modification, in-channel muds and thick soft-clast conglomerates, identify these lithosomes as deposits of variable-discharge rivers. These recognition criteria are part of an emerging facies model for variable-discharge rivers. This facies model, however, yet lacks robust recognition criteria for macro-scale or bar-scale stratal patterns of variable-discharge rivers. This study presents a dataset that corroborates some known stratal patterns and provides examples of hitherto unknown bar-scale stratal patterns of variable-discharge rivers, including: (i) low-angle downstream-accretion sets that may form as washed-out sheets in high sediment supply conditions or downstream of hydraulic jumps; (ii) high-angle upstream-accretion sets that imply deposition from systematically upstream-migrating channel-scale hydraulic jumps (cyclic steps); (iii) concave-up, upward-flattening high-angle downstream-accretion sets that are consistent with aggradation in channel-scale hydraulic-jump scours; (iv) upstream-accretion and lateral-accretion sets that may be linked to high-magnitude flood reworking of point bars; and (v) aggradation or vertical-accretion sets of ambiguous origin. These unconventional stratal patterns are compared to the established bar strata, such as those formed by point bars and braid bars and a discussion is provided on formative conditions for the here documented unconventional strata. This work highlights a need for further studies on the effect of discharge variability on bar formation and on the link between river morphology and bar types.     

基于吸收衰减补偿的多分量高斯束逆时偏移

高斯束逆时偏移结合了射线类偏移的高计算效率和波动方程逆时偏移的高精度,能很好地处理焦散点、大倾角成像问题,并且具有面向目标成像的能力.多分量地震资料的偏移技术可以对地下复杂构造进行更准确的成像,由于实际地下介质具有黏滞性,研究黏弹性叠前逆时偏移具有一定的现实意义.本文采用高斯束逆时偏移方法对多分量地震数据进行吸收衰减补偿,首先分别给出纵波和转换波共炮域高斯束叠前逆时偏移方法原理,在此基础上推导补偿吸收衰减的表达式,校正Q引起的振幅衰减和相位畸变,实现基于吸收衰减补偿的多分量高斯束叠前逆时偏移.数值模型的测试结果显示,在考虑地下介质的黏滞性时,本文方法具有更高的成像分辨率.     

Detecting urban ecological land-cover structure using remotely sensed imagery: A multi-area study focusing on metropolitan inner cities

With increasing attention being paid to sustainable urban development and human habitation improvement, urban ecological land cover (UELC), i.e., surface water and green space, has played an important role of the highly compact inner urban regions. In this study, we developed an efficient approach for UELC mapping by coupling Sentinel-2 multi-spectral imagery and Google Earth high-resolution imagery. In contrast with the conventional single-source and multi-source imagery-based classification methods, the proposed method respectively achieved the highest overall accuracies of 91.50% and 94.05% in the UELC mapping for two test sites (i.e. Shanghai and Seoul). The proposed method is used for urban surface mapping among six world-class cities. For an in-depth analysis of the landscape structures for inner urban regions, seven landscape metrics are introduced for the quantification of the UELC structure based on the obtained high-precision UELC maps. The result shows that London appears to have the best UELC-induced ecological quality, that is, with high percentage of landscape, area-weighted mean fractal dimension, edge density, Shannon’s evenness index values and a low contagion index value, while Tokyo is exactly the opposite. Several common characteristics found through the statistical analysis are: 1) all the inner-city regions have small UELC coverage (< 50%) and low shape complexity; 2) green space generally contributes more to urban eco-environment than the urban surface water; and 3) all cities show high landscape consistency in the inner urban region.     

A new ordinary differential equation for the evaluation of the frequency-domain Green function

Clément (2013) derived a second order ordinary differential equation (ODE) satisfied by the free-surface Green function in the frequency domain. Since then, similar ODEs for the gradient of the Green function have been developed. Unfortunately, all these ODEs degenerate at zero frequency. Therefore, it is not possible to initialize the numerical solution of these ODEs from this zero frequency. Alternative methods based on the shifting of the initial condition to frequencies strictly greater than zero have then been developed.The present paper describes an alternative approach to address this issue. It involves a new function which is the solution of a modified ODE which can be solved from the zero frequency.Finally, comparisons with evaluations of the Green function using the classical direct integration method are provided. They show that the new ODE can provide accurate estimates of the Green function.     

山东省绿色发展效率时空演化及影响因素分析

运用基于非期望产出的SBM模型,对2007—2017年山东省17地市绿色发展效率进行测度,分析其时空演化特征,进一步构建Tobit模型探究其影响因素。研究表明:2007—2017年山东省各地市间绿色发展效率变化趋势呈现地域差异,东部地区效率提升快于中西部地区,且存在个别地市绿色发展效率下降与个别地市绿色发展效率上升并存的趋势特征。山东省绿色发展效率存在明显的空间分异性,且存在高效率区向东发展,低效率区转向中西部的演化特征。山东省绿色发展效率与经济发展水平之间存在U型曲线关系,且现阶段经济发展水平及城镇化水平对绿色发展具有显著的负向影响,产业结构、对外开放程度及科技创新对绿色发展效率具有显著的正向驱动作用。推动产业结构优化升级,以创新驱动发展,推动更高层次的对外开放是山东省绿色发展提升的重要途径。     

Green infrastructure,green space,and sustainable urbanism: geography’s important role

ABSTRACT

This paper is a broad review of green infrastructure theory and practice relative to urban sustainability and the space for geographers in these discussions. We use examples from various urban sustainability plans to highlight ways in which green infrastructure is being conceptualized and implemented. We explore how geography contributes research on green infrastructure as well as the emerging practices as seen within sustainability plans. We identify four areas in which geographers can influence both green infrastructure theory and practice: 1) scale; 2) mapping distribution; 3) sensitivity to place and locale; and 4) equity and access. We conclude that in these areas geographers have tremendous opportunity contribute more deliberately to sustainable urbanism.     

Stratigraphic complexity in fluvial fans: Lower Eocene Green River Formation,Uinta Basin,USA

In this study, measured outcrop sections and geolocated photomosaics are integrated with areal mapping of channel dimensions, degree of amalgamation, calculations of channel‐to‐floodplain ratios and sedimentary facies variability to study and quantify the channel and floodplain deposits in the Sunnyside Delta Interval of the Lower Eocene Green River Formation in the Uinta Basin, Utah. Vertically, sand content and bed thickness increases, due to an increase in the channel‐to‐floodplain ratio, channel size and the degree of channel amalgamation. Laterally, the channel‐to‐floodplain ratio, channel size, the degree of channel amalgamation and the sand content in channel facies decreases in the paleo‐downstream direction. Such vertical and lateral transitions identify the Sunnyside Delta Interval as a fluvial fan (or distributive fluvial system). However, the vertical and lateral transitions occur at multiple spatial scales, demonstrating considerable stratigraphic complexity as compared to the existing facies and architectural models suggested for fluvial megafans and distributive fluvial systems. The smallest‐scale transitions are identified as avulsion‐related packages that form the building blocks of the stratigraphy, whereas the intermediate‐ and largest‐scale transitions are suggested to be related to lobe and whole fan progradation respectively. This documented complexity indicates the significance of self‐organization in building fluvial fan stratigraphy, and demonstrates that changes in the degree of channel amalgamation or in channel‐to‐floodplain ratio are not linked to accommodation changes. On facies scale, an abundance of Froude supercritical‐flow and high‐deposition‐rate facies, in‐channel mud deposits, and in‐channel bioturbation and desiccation indicate deposition in rivers with highly variable discharge. Such discharge conditions suggest seasonally and inter‐annually variable precipitation conditions in the US Western Interior in the Early Eocene.     

Towards sustainable fisheries subsidies: Entering a new round of reform under the Common Fisheries Policy

On 22 April 2009 the European Commission published its ‘Green Paper on the Reform of the Common Fisheries Policy’. The Green Paper points out a contradiction in policy, noting on one hand that public financial support to the Community's fisheries sector is substantial, but on the other hand such support is often incompatible with other Common Fisheries Policy (CFP) objectives, particularly the need to reduce overcapacities. Providing an analytical framework to better understand the effects of subsidies as well as an overview of existing funding schemes under the CFP, this article aims at answering some of the questions posed by the European Commission within its Green Paper. Answers are based on two ideas: the exploitation of marine capture resources ultimately depends on the level of available fish stocks and that a large share of subsidies fuels the race to fish by inducing investment incentives for the fisheries sector. Policies that have ignored this tend to encourage inefficient and unsustainable fishing as well as the misallocation of public funds. Although support schemes under the CFP have changed in recent years, some problematic support schemes persist. A future reform will have to continue the course taken towards sustainable and efficient approaches to supporting the fisheries industry.     

二维弹性多波时空域高斯束偏移方法

随着我国勘探开发难度逐步增大,勘探目标开始向裂缝油气藏、岩性油气藏等复杂探区转移,研究高精度、适应性强的多波多分量深度偏移算法在后续的地震解释、属性分析及储层预测中具有重要意义.针对多波多分量地震数据,本文提出了一种二维弹性波时空域高斯束偏移方法.时空域高斯束沿中心射线传播时能够面向成像目标描述局部波场,且对振幅和频率可调制的Gabor基函数有天然的适应性,因而将基于Gabor分解的子波重构方法应用于震源波场构建,从而得到任意点源函数产生的时空域高斯束波场.该方法由于直接在时间域进行计算,可以避开频率域中出现的假频和边缘截断效应等问题.基于各向同性弹性波动方程的Kirchhoff-Helmholtz积分解,利用矢量时空域高斯束传播算子构建格林函数和格林位移张量,并结合上行射线追踪策略,实现了检波点波场的反向延拓.针对矢量波成像问题,本文借鉴弹性波逆时偏移方法从矢量延拓波场中分离出纯纵波分量和纯横波分量,进而采用修改后的内积成像条件产生具有明确物理意义的PP、PS成像结果,避免了转换波成像的极性反转问题.最后利用简单两层模型和不含盐体构造的部分Sigsbee2a模型的成像结果,并将其与应用近似纵横波成像条件、标量和矢量势成像条件的偏移剖面进行对比,验证了本文方法的正确性和有效性.