A landscape pattern analysis method based on boundaries and nodes: A case study in upper Minjiang River, China

Traditionally,patch-based analysis at the landscape scale fragmentation has been used in the study of landscape ecology while the study of boundary and node has not been considered as much detail until recently.This study investigated the possibility of applying boundary-and node-based methods in landscape pattern analysis to the upper reaches of the Minjiang River in the southwestern China.Boundary-based and node-based landscape indices were selected to be used in analyzing changes in landscape patterns,and the results were compared with analysis using traditional pattern indices.We compared the responses of patch-area-based,boundary-length-based and node-number-based indices,and concluded that boundary-based and node-based indices are more sensitive to disturbance than patch-based indices with various patterns,and node-based indices are even more sensitive than boundary-based ones.Thus,the results suggest that boundary-based and node-based pattern analysis methods provide helpful supplementary information to traditional patch-based pattern analysis methods.The results about pattern dynamics of landscapes in the upper reaches of the Minjiang River based on boundaries and nodes showed that with human disturbance,the dominance of forest landscape was weakened by other landscape types; thus the landscape pattern of the study area became more homogeneous and the boundary network became more complex.These changes further augmented disturbance interfaces in the landscape and increased the possibilities of further landscape fragmentation.     

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汀溪水库三维防洪调度管理信息系统研发

水库防洪调度是一个非常复杂的过程。水库防洪调度的信息化主要是借助测量、遥测、遥感(RS)、地理信息系统(G IS)、全球定位系统(GPS)等手段采集基础数据,构建数字化水库防洪数据管理平台和水库虚拟三维环境。在该平台和环境中,以系统软件和数学模型对水库流域的水雨情及洪水的调度方案进行模拟、分析和研究,提供决策支持,从而增强防洪调度决策的科学性和预见性。实践表明,通过RS、GIS技术建立的水库三维防洪调度系统能够为水库管理者提供水库防洪调度方案制定与分析、防洪调度决策等方面的强有力的、科学的辅助支持。本文结合厦门"汀溪水库三维防洪调度系统"的实际研发,探讨了RS和GIS技术在水库防洪调度中的应用。     

一种削弱信噪混叠的EMD降噪方法

针对经验模态分解(empirical mode decomposition,EMD)降噪过程中存在信号与噪声模态混叠及直接将分界本征模态函数(intrinsic mode function,IMF)分量归入高频噪声造成真实信号被“湮没”等问题,提出一种改进的EMD降噪方法。该方法将经EMD得到的第2个IMF分量至分界IMF分量进行重构,对重构信号进行下一次EMD,获取其中的“真实”信号,多次重复此操作,最后将所有获得的低频信号累加,从而达到降噪的目的。利用2种模拟数据和1种GPS实测高程数据进行实验,模拟数据与实测数据采用不同的评价指标评价降噪效果,结果表明,改进的EMD方法较传统EMD方法降噪效果更佳,验证了该方法的可靠性。     

排序对模糊度解算中降相关性能的影响分析

针对不同排序算法对模糊度解算存在降相关性能影响的问题,从理论上分析了自然升序法、对称旋转法及扰动升序法的降相关原理,并基于模拟数据和实测数据,从降相关时间、搜索时间、总体耗时、Bootstrapping成功率及条件数5个方面对3种算法进行对比分析。结果表明,降相关效率与搜索椭球压缩程度呈负相关关系,搜索椭球压缩程度越高,降相关效率越低;对于不同的排序算法,提高降相关性能的关键在于减少降相关时间及对条件方差按一定方向排序,进而提高搜索效率。     

基于噪声谱比法的内蒙古西部地区台站场地响应研究

利用内蒙古西部12个台站的地脉动噪声数据，采用噪声谱比法研究台站的场地响应情况。分析表明，台站场地响应按曲线形态可分为3类，且可能受地形地貌、局部构造和台基状况等条件影响。对比分析噪声谱比法与Moya方法的场地响应结果发现，场地响应曲线形态基本一致，只有极少数台站存在明显差异。结果表明，内蒙古西部区域大部分台站的台基状况总体较好，场地响应曲线较为平坦，无明显频率放大点。     

郯庐断裂带苏皖段及邻区b值时空特征研究

采用郯庐断裂带苏皖段及邻区近50 a的地震数据,在定量分析区域最小完备震级Mc和推导b值计算的极大似然法基础上,重点研究G-R关系,尤其是b值时空分布演化特征,并依据b值指示意义进行5级以上地震关联性和断裂带影响区域的构造应力分布状况分析.结果显示,依据b值的时间分布特征,研究区中强地震发生时段与中短期b值下降时段关联...     

一种改进的GNSS高维模糊度快速降相关算法

为了提高GNSS高维模糊度的解算效率,提出一种改进的GNSS模糊度快速降相关算法.算法采用对称旋转排序策略和延后降相关策略对下三角Cholesky分解的整数高斯变换算法进行改进.通过模拟和实测数据进行验证,结果表明,改进算法在一定程度上减少了降相关过程中的条件方差交换次数和整数高斯变换次数,从而有效提高了解算效率,增强...     

Research progress of TiO2 photocathodic protection to metals in marine environment

Corrosion protection has become an important issue as the amount of infrastructure construction in marine environment increased.Photocathodic protection is a promising method to reduce the corrosion of metals,and titanium dioxide(TiO_2) is the most widely used photoanode.This review summarizes the progress in TiO_2 photo gene rated protection in recent years.Different types of semiconductors,including sulfides,metals,metal oxide s,polymers,and other materials,are used to design and modify TiO_2.The strategy to dramatically improve the efficiency of photoactivity is proposed,and the mechanism is investigated in detail.Characterization methods are also introduced,including morphology testing,light absorption,photoelectrochemistry,and protected metal observation.This review aims to provide a comprehensive overview of Ti02 development and guide photocathodic protection.     

The Tropical Pacific–Indian Ocean Associated Mode Simulated by LICOM2.0

Oceanic general circulation models have become an important tool for the study of marine status and change. This paper reports a numerical simulation carried out using LICOM2.0 and the forcing field from CORE. When compared with SODA reanalysis data and ERSST.v3 b data, the patterns and variability of the tropical Pacific–Indian Ocean associated mode(PIOAM) are reproduced very well in this experiment. This indicates that, when the tropical central–western Indian Ocean and central–eastern Pacific are abnormally warmer/colder, the tropical eastern Indian Ocean and western Pacific are correspondingly colder/warmer. This further confirms that the tropical PIOAM is an important mode that is not only significant in the SST anomaly field, but also more obviously in the subsurface ocean temperature anomaly field. The surface associated mode index(SAMI) and the thermocline(i.e., subsurface) associated mode index(TAMI) calculated using the model output data are both consistent with the values of these indices derived from observation and reanalysis data. However, the model SAMI and TAMI are more closely and synchronously related to each other.