一种基于InSAR相干系数的SAR阴影提取方法

给出了一种新的阴影提取方法,根据阴影区域在InSAR相干系数图上的特性,利用Sigma滤波和最优阈值分割算法实现阴影的自动提取。实验结果表明,本方法是一种高效的阴影提取方法。     

CRUSTAL CONFIGURATION OF NW HIMALAYA: EVIDENCES FROM THE ISOSTATIC AND FLEXURAL ANALYSIS OF GRAVITY DATA

CRUSTAL CONFIGURATION OF NW HIMALAYA: EVIDENCES FROM THE ISOSTATIC AND FLEXURAL ANALYSIS OF GRAVITY DATA     

基于相干特征的岩石薄片序列图像边缘提取及颗粒分割

针对岩石颗粒边缘模糊、结构复杂的特点,为了更有效地识别颗粒边缘,在基于特征值的C3相干算法的基础上,融合多尺度和多角度的特征表达,提出了一种改进的C3相干算法。该算法综合考虑岩石薄片图像角度域光学特征、空间尺度信息和各向异性信息,能更有效地表征颗粒边缘特征,表现出对复杂矿物结构的适应能力。在采集的岩石薄片正交偏光图像上验证提出的算法,实验结果表明,与原生C3相干算法相比,改进后的C3相干算法在全局图像上的方差和灰度差分乘积分别提升了68.41%和22.91%,信息熵下降了21.61%。     

Alignment between nationally determined contributions and the sustainable development goals for West Africa

The UN Sustainable Development Goals (SDGs) and the 2015 Paris Agreement are two of the most important policy frameworks of the twenty-first century. However, the alignment of national commitments linked to them has not yet been analysed for West African states. Such analyses are vital to avoid perverse outcomes if states assess targets and develop SDG implementation plans, and Nationally Determined Contributions (NDC) under the Paris Agreement, without integrated planning and cross-sectoral alignment. This article provides a situation analysis guided by the following questions: (a) Which priority sectors are mentioned in relation to adaptation and mitigation in West African NDCs? (b) Are the NDCs of West African states well aligned with the SDGs? (c) What are the co-benefits of NDCs in contributing towards the SDGs? and (d) How are West African states planning to finance actions in their NDCs? The study uses iterative content analysis to explore key themes for adaptation and mitigation within NDCs of 11 West African states and their alignment to selected SDGs. A national multi-stakeholder workshop was held in Ghana to examine the co-benefits of the NDCs in contributing towards the SDGs and their implementation challenges. Results show that agriculture and energy are priority sectors where NDCs have pledged significant commitments. The analysis displays good alignment between mitigation and adaptation actions proposed in NDCs and the SDGs. These represent opportunities that can be harnessed through integration into national sectoral policies. However, cross-sectoral discussions in Ghana identify significant challenges relating to institutional capacity, a lack of coordination among institutions and agencies, and insufficient resources in moving towards integrated implementation of national planning priorities to address successfully both NDC priorities and the SDGs.

Key policy insights

• Positive alignments between West African NDCs and SDGs present opportunities for mutual benefits that can advance national development via a more climate resilient pathway.

• NDCs of West African states can provide mutual benefits across the water–energy–food nexus, such as through climate-smart agriculture and low carbon energy technologies.

• Ghanaian multi-sectoral insights show the need to empower national coordinating bodies to overcome misalignments across different sectors.

     

InSAR干涉图滤波方法对比

针对不同滤波算法在InSAR数据处理中去噪效果的差异,该文从滤波理论出发,采用模拟和真实干涉数据进行实验。在各种滤波算法中,均值滤波(多视处理)、Goldstein滤波及其变种滤波应用广泛,本文对4种滤波方法进行了系统分析,深入探讨了经典InSAR滤波和国内外学者算法的优缺点。实验表明:4种滤波均能有效抑制噪声,提升干涉图质量。其中,Goldstein滤波以及两种改进的滤波效果要明显优于均值滤波,且具有更好的自适应性或条纹保持能力,较经典Goldstein滤波而言,变种滤波方法不仅保持了Goldstein滤波的优点,在边缘信息和细节保持能力方面优势更加显著。     

球面散射屏远场散斑的若干统计特征

本文采用标量衍射理论导出球面屏衍射的瑞利-索末菲公式及其远场近似。并据此导出球面散射屏远场散斑的若干统计特征。     

Closing the governance gaps in the water-energy-food nexus: Insights from integrative governance

The water-energy-food nexus has become a popular concept in environmental change research and policy debates. Proponents suggest that a nexus approach promotes policy coherence through identifying optimal policy mixes and governance arrangements across the water, energy and food sectors. Although the nexus literature identifies some barriers to achieving coherence it does not clearly explain why the barriers are present, what influences them, and how they can be acted upon. These gaps disconnect the nexus literature from the governance processes it ultimately seeks to influence. This paper examines how the integrative environmental governance literature can help to close these gaps. It extracts insights from seven streams of research literature and discusses their relevance for the nexus literature. We argue that connecting the nexus to decision-making processes requires: i) rethinking the boundaries of nexus analysis vis-à-vis other sectors and levels; ii) elaboration of shared principles that can guide decision-making towards policy coherence − or an appropriate form of fragmentation − in different contexts; iii) viewing policy coherence as a continuous process of changing values and perception rather than as an outcome.     

Analysis of single and tandem cylinder data using an orthogonal Volterra model approach

The development of a definitive predictive model that accurately accounts for the nonlinear hydrodynamics and structural response behavior observed in arrays of closely spaced risers on deep water structures will require a more detailed understanding of this fluid–structure interaction. Through the analysis and interpretation of data from model basin tests on single and paired tandem cylinder configurations this study is directed at uncovering the nature of some aspects of this nonlinear response behavior using an orthogonal third-order Volterra technique that can delineate between linear, quadratic and cubic nonlinear frequency dependent behavior. As part of the analysis procedure the data was organized in input–output pairs that would provide logical groupings of the measured quantities. The data pairs presented in this study include wave excitation and inline cylinder displacement, wave excitation and transverse cylinder displacement, wave excitation and inline reaction force, and, upstream cylinder and downstream cylinder response. This information is presented in terms of spectral and coherence plots. The single cylinder data is presented as a means to contrast the behavior of the tandem cylinders. Both configurations were analyzed at two different pretensions adding another dimension to this investigation. It is shown that although a primary variable such as displacement may be more easily measured, pretension and force measurements provide an important key to our understanding of this difficult problem.     

Extraction method of component waves in full waveform acoustic data and its application

In conventional slowness-time coherence(STC)method,slowness and time need to be searched at the same time,which limits the precision and lowers the efficiency.The dichotomy method combined with slowness-time coherence algorithm aims to enhance the efficiency of data processing and to improve the precision.The algorithm changes the searching pattern of conventional slowness-time coherence method to acquire the slowness of component waves in array acoustic logging data.Based on energy ratio of short time window versus long time window and slowness-time coherence method,the algorithm first acquires the arrivals of the component waves using energy ratio of short time window versus long time window method.It then uses the calculated results as the arrivals in conventional slowness-time coherence method,so the slowness-time two-dimensional searching process is simplified to slowness searching process.Based on dichotomy method,the searching pattern is further optimized in replace of the ergodic searching pattern in conventional slowness-time coherence method,which means that as the iteration proceeds,the current searching interval is reduced to half of the former,so the number of searching times is decreased.The dichotomy method combined with slowness-time coherence algorithm is applied to well L in the data processing.Compared with conventional slowness-time coherence method,for compressional wave,the searching efficiency of the algorithm is 4.53 times better,while for Stoneley wave,the searching efficiency is 1.85 times better.Compared with conventional logging data,the average absolute error of the results of the dichotomy method combined with slowness-time coherence algorithm is 1.14μs/ft smaller than that of the conventional method,while the average relative error is 1.2 percent lower.The dichotomy method combined with slowness-time coherence algorithm shows good results in its application,which can enhance the processing efficiency remarkably while getting reliable results at the same time.     

珠江口磨刀门水道盐度变化对水文气象要素的频率响应特征

以2010年11月-2011年3月磨刀门水道挂定角、联石湾、竹排沙、平岗和竹银5个测站的盐度、马口水文站流量、三灶站潮位和竹银站的主流向风速为基本数据,应用偏相干谱估计方法分析了各测站盐度变化对潮汐、流量和风的频率响应。经验诊断分析结果表明:1)马口站入海径流存在准1日、半日、1/4日和1/3日等显著的潮致振荡周期;2)各测站盐度变化与潮汐主要振荡周期并不一致,沿磨刀门水道向上游,潮汐对盐度变化的影响递减,竹银站盐度可作为潮汐直接作用下咸潮上溯的平均上限位置;3)消除潮汐和径流的影响后风对盐度变化的作用明显加强;4)各测站盐度变化对潮汐、流量与风的响应过程存在时间超前或滞后但无特定规律,说明磨刀门水道盐度变化过程十分复杂。