基于改进K-SVD字典学习方法的地震数据去噪

为实现更好的地震数据去噪技术,笔者引入一种新的算法:快速迭代收缩阀值法(FISTA),通过FISTA和K-奇异值分解(K-SVD)不断迭代更新K-SVD字典,利用更新得到的K-SVD字典对地震数据进行稀疏表示,去除稀疏系数中较小的数值,使数据中的随机噪声得到压制。对层状模型合成地震记录,Marmousi模型合成地震记录以及实际地震数据进行对比实验,得出FISTA算法较OMP算法能更好地提高地震数据的信噪比,同时有效地保护了反射信号。     

Representation and participation in formulating Nepal’s REDD+ approach

ABSTRACT

REDD+ is an international policy aimed at incentivizing forest conservation and management and improving forest governance. In this article, we interrogate how newly articulated REDD+ governance processes established to guide the formulation of Nepal’s REDD+ approach address issues of participation for different social groups. Specifically, we analyse available forums of participation for different social groups, as well as the nature of their representation and degree of participation during the country’s REDD+ preparedness phase. We find that spaces for participation and decision-making in REDD+ have been to date defined and dominated by government actors and influential civil society groups, whereas the influence of other actors, particularly marginalized groups such as Dalits and women’s organizations, have remained limited. REDD+ has also resulted in a reduction of influence for some hitherto powerful actors (e.g. community forestry activists) and constrained their critical voice. These governance weaknesses related to misrepresentation and uneven power relations in Nepal cast doubt on the extent to which procedural justice has been promoted through REDD+ and imply that implementation may, as a consequence, lack the required social legitimacy and support. We discuss possible ways to address these shortcomings, such as granting greater prominence to neglected civil society forums within the REDD+ process, allowing for an increase in their influence on policy design, enhancing capacity and leadership of marginalized groups and institutionalizing participation through continued forest governance reform.

Key policy insights

• Participation is a critical asset in public policy design.

• Ensuring wide and meaningful participation can enhance policy legitimacy and thus its endorsement and potential effective implementation.

• Fostering inclusive processes through dedicated forums such as multi-stakeholder groups can help overcome power dynamics.

• While REDD+ is open to participation by different actors through a variety of formal means, many countries lack a clear framework for participation in national policy processes.

• Nepal’s experience with representation and participation of non-state actors in its REDD+ preparedness programme provides useful insights for similar social and policy contexts.

     

基于镜像图的LRC和CRC偏差结合的人脸识别

为了提高人脸识别率及更好地显示人脸特征,本文提出了一种基于镜像图的LRC和CRC偏差结合的人脸识别方法.该方法首先生成一种镜像人脸,再通过融合原始人脸和镜像人脸形成新的混合训练样本,最后利用LRC和CRC偏差结合进行人脸识别.新方法增加了训练样本的数目,克服了由于光照和姿态等外部因素带来的影响.实验结果表明,镜像图与LRC和CRC偏差结合的人脸识别方法提高了人脸识别的准确性.     

地震作用下结构时变物理参数识别

利用小波分析函数多尺度逼近方法,将剪切型结构在地震作用下时变的阻尼和刚度用尺度函数的线性组合表示,将时变参数的辨识问题转化为由已知的正交尺度函数和系统的输入输出来估计线性组合中的时不变系数问题,用最小二乘法对剪切型框架结构在地震作用下时变的刚度和阻尼进行了有效的辨识。此方法无需事先假定系统参数的时变规律,在有噪声情况下可以用Tikhonov正则化方法减小识别方程的不适定性对识别结果的影响。数值算例表明了该方法的有效性。     

Verification of significant wave representation method

The significant wave representation method is the simplest method for computing the transformation of significant wave height across-shore. However, many engineers are reluctant to use this method because many researchers have pointed out that the method possibly contains a large estimation error. Nevertheless, Rattanapitikon et al. [Rattanapitikon, W., Karunchintadit, R., Shibayama, T., 2003. Irregular wave height transformation using representative wave approach. Coastal Engineering Journal, JSCE 45(3), 489–510.] showed that the wave representation method could be used to compute the transformation of root mean square wave heights. It may also be possible to use it for computing the significant wave height transformation. Therefore, this study was carried out to examine the possibility of simulating significant wave height transformation across-shore by using the significant wave representation method. Laboratory data from small- and large-scale wave flumes were used to calibrate and examine the models. Six regular wave models were applied directly to irregular waves by using the significant wave height and spectral peak period. The examination showed that three regular wave models (with new coefficients) could be used to compute the significant wave height transformation with very good accuracy. On the strength of both accuracy and simplicity of the three models, a suitable model is recommended for computing the significant wave height transformation. The suitable model was also modified for better predictions. The modified model (with different coefficients) can be used to compute either regular wave height or significant wave height transformation across-shore.     

基于时间序列叶面积指数稀疏表示的作物种植区域提取

以华北平原黄河以北地区为研究区域,以时间序列叶面积指数LAI(Leaf Area Index)傅里叶变换的谐波特征作为不同作物识别的数据源,利用稀疏表示的分类方法识别2007年—2016年冬小麦、春玉米、夏玉米等主要农作物种植区域。首先利用上包络线Savitzky-Golay滤波分别对2007年—2016年的时间序列MODIS LAI曲线进行重构,进而对重构的年时间序列LAI进行傅里叶变换,以0—5级谐波振幅、1—5级谐波相位作为作物识别的依据,基于各类地物的训练样本,通过在线字典学习算法构建稀疏表示方法的判别字典,对每个待测样本利用正交匹配追踪算法求解稀疏系数,从而计算对应于各类地物的重构误差,根据最小重构误差判定待测样本的作物类型,并对作物识别结果的位置精度进行验证。结果表明,2007年—2016年作物识别的总体精度为77.97%,Kappa系数为0.74,表明本文提出的方法可以用于研究区域主要作物种植区域的提取。     

一种改进的基于转角函数法的面状居民地Morphing变换方法

提出了一种顾及位置偏差与凹部同异性的面状居民地Morphing变换转向角函数方法.该方法通过构造大比例尺居民地的凸包作为中间图形,辅助与小比例尺居民地进行特征顶点匹配,避免因位置偏差造成的特征点误匹配;针对大比例尺居民地的凹部,依据凹部的模式类型,判定凹部边的同异性;最后构建插值模型,得到中间任意尺度下的面状居民地要素...     

A multi-scale 3-D crust velocity model in the Hefei-Chao Lake area around the southern segment of Tanlu Fault Zone

Regional high-precision velocity models of the crust are an important foundation for examining seismic activity, seismogenic environments, and disaster distribution characteristics. The Hefei-Chao Lake area contains the main geological units of Hefei Basin, with thick sediments and the Chao Lake depression. Several major concealed faults of the southern NNE-trending Tanlu Fault Zone cross this area. To further explore the underground distribution characteristics of the faults and their tectonic evolutionary relationship with adjacent tectonic units, this study used ambient noise data recorded by a seismic array deployed in Hefei City and Chao Lake, constructing a 3-D velocity model at the depth of 1–8 km. Then a multi-scale high-resolution 3-D velocity model of this area was constructed by this new upper crustal velocity model with the previous middle and lower crustal model. The new model reveals that a high-velocity belt is highly consistent with the strike of the Tanlu Fault Zone, and a low-velocity sedimentary characteristic is consistent with the Hefei Basin and Chao Lake depression. The distribution morphology of high and low velocity bodies shows that the sedimentary pattern of Hefei-Chao Lake area is closely related to the tectonic evolution of the Tanlu Fault Zone since the Mesozoic. This study also identifies multiple low-velocity anomalies in the southeastern Hefei City. We speculate that strong ground motion during the 2009 Feidong earthquake (magnitude of 3.5) was related to amplification by the thick sediments in the Hefei Basin. We also discuss further applications of multi-scale high-resolution models of the shallow layer to strong ground motion simulations in cities and for earthquake disaster assessments.     

1980—2018年黄河上游气候变化及其对生态植被和径流量的影响

黄河上游是黄河流域最重要的水源涵养地和产流区,对黄河流域的水资源安全、生态环境和粮食安全有决定性的意义。近年来在西北地区气候暖湿化的背景下,黄河上游气候生态水文等问题受到了各方的高度关注。本文利用卫星遥感数据、格点融合数据和水文监测数据,分析了黄河上游气候的多尺度变化特征及其对植被和径流量的影响。结果表明：1）1980-2018年黄河上游暖湿化趋势呈现全区域较一致的气候特征,温度增加率为0.023℃/a,降水增加率为1.09 mm/a,但同时又存在明显的区域差异性,湟水流域至甘肃中部降水增加最显著,宁蒙荒漠地带增温趋势最明显,2000年以来整个黄河上游降水明显增加。2000年后汇流区与流径区的蒸散发明显增加,但源头区南部波动减少。2）当前的暖湿化有利于黄河上游植被生长,1999年以来汇流区和源头区部分区域的植被增加率达到0.04/（10 a）;从长期趋势看,源头区、汇流区植被指数与上年降水呈显著正相关关系,而流径区植被指数与当年降水相关性显著;降水对黄河上游流域植被具有明显的改善作用,而温度对其影响较复杂,各区域不同的植被类型是导致降水、温度、蒸散影响存在差异的可能原因。3）1980-2018年唐乃亥站和兰州站的年径流量均呈减少趋势,但1998年以来两站的年径流量明显增加,兰州站年径流量的增加率是唐乃亥站的近3倍。长期趋势表明,唐乃亥站年径流量与当年降水呈显著正相关关系,兰州站年径流量与当年降水、蒸散的相关系数均明显低于唐乃亥站;从年际波动看,降水是决定年径流量的最主要影响因子,而生态植被、冻土退化、水储量变化及社会活动等因素对径流量的影响也不容忽视。该研究为科学应对黄河上游生态保护及实现黄河流域高质量发展提供了参考依据。