Reliability of digit length impression as a character of tetrapod ichnotaxobase: considerations from the Carboniferous–Permian ichnogenus Ichniotherium

Although the relative length of digit impressions is often adopted as a binding character in ichnotaxa discrimination and trackmaker identification, it cannot be considered unequivocally operative. The reliability of this character has been evaluated by means of principal component analysis on several well‐preserved footprints (both manus and pes) referred to as Ichniotherium sphaerodactylum from the Early Permian Tambach Formation (Thuringia, Germany). The analysis reveals a substantial variability of digit impression length (especially in the manus), relativizing the validity of digit IV length as a diagnostic character as practised in different ichnological studies. Regarding the use of such a character, results clearly suggest the need to preliminarily conduct explorative analysis on the whole available ichnological material in order to detect which digit is the most consistent from an ichnotaxonomical standpoint, thus avoiding an arbitrary selection. Such a preliminary analysis should provide a better control on ichnotaxonomical splitting/lumping, particularly in the case of allied footprints, and can also be considered a valuable tool, if associated to functionality analysis, in improving and refining trackmaker identification. Copyright © 2014 John Wiley & Sons, Ltd.     

结合PCA和滑动时窗的电离层异常探测方法研究

针对主成分分析（PCA）方法探测电离层异常时探测范围有限且无法区分正负扰动的问题,提出一种结合PCA和滑动时窗的探测方法,并以3次强震为例检测其异常探测能力。结果显示,PCA-滑动时窗方法同时具备了2种方法的探测优势,相较于滑动时窗法,其探测结果更加直观、简明,且不易受空间环境影响,有相对更高的异常探测置信度和可靠度;相较于PCA方法,其能更好地用于长时间时空异常探测,并准确区分出正负异常。另外,通过进一步分析2020年瓦哈卡地震后发现,电离层在震前11~13 d、9 d及4~6 d出现明显异常,且异常位于震中偏南区域。综合4次地震可知,异常主要出现在震中偏南方向,大多呈共轭结构。     

Evaluation of Linear and Non-Linear Downscaling Methods in Terms of Daily Variability and Climate Indices: Surface Temperature in Southern Ontario and Quebec,Canada

We downscaled atmospheric reanalysis data using linear regression and Bayesian neural network (BNN) ensembles to obtain daily maximum and minimum temperatures at ten weather stations in southern Quebec and Ontario, Canada. Performance of the linear and non-linear downscaling models was evaluated using four different sets of predictors, not only in terms of their ability to reproduce the magnitude of day-to-day variability (i.e., “weather,” mean absolute error between the daily values of the predictand(s) and the downscaled data) but also in terms of their ability to reproduce longer time scale variability (i.e., “climate,” indices of agreement between the predictand's observed annual climate indices and the corresponding downscaled values). The climate indices used were the 90th percentile of the daily maximum temperature, 10th percentile of the daily minimum temperature, number of frost days, heat wave duration, growing season length, and intra-annual temperature range.

Our results show that the non-linear models usually outperform their linear counterparts in the magnitude of daily variability and, to a greater extent, in annual climate variability. In particular, the best model simulating weather and climate was a BNN ensemble using stepwise selection from 20 reanalysis predictors, followed by a BNN ensemble using the three leading principal components from the aforementioned predictors. Finally, we showed that, on average, the first three indices presented higher skills than the growing season length, number of frost days, and the heat wave duration.     

黄河三角洲土壤盐渍化原因分析与生态风险评价

以黄河三角洲为研究区域,选择土壤全盐为标志,以海拔高程、地下水位、地下水矿化度、、灌溉排水状况、土壤有机质和人口密度6个土壤盐渍化主要控制性因子,采用聚类分析方法进行了土壤盐渍化原因分析;基于ArcGIS 9.3和Matlab,选择上述7个要素为评价因子,以归一化植被指数(NDVI)为生态终点,利用灰色关联度方法建立了区域土壤盐渍化的生态风险评价模型,并进行了生态风险评价。结果表明:黄河三角洲土壤盐渍化主要受自然和人为因素驱动,其中地下水位和海拔高程等自然因素是造成研究区土壤盐渍化的自然因素,土壤有机质和人口密度等是人为因素;土壤盐渍化极大和重度风险区域集中分布于黄河三角洲东南沿海区域、西北沿海、东北部的部分地区,该区域受海洋影响强烈,土壤盐渍化面积最大,占到总面积的58%以上;无风险、轻度风险和中度风险区域主要与黄河径流的距离有关,且随着距离增大而风险增加。     

对流参数主分量旋转法在西昌地区雷暴预报中的应用

为研究对流参数主分量旋转方案对西昌地区雷暴预报的影响,利用2006~2008年雨季(6~9月)T213模式输出产品,采用F-分值法和主分量旋转法,分别初选和精选因子,并结合二元Logistic回归分析,建立了西昌北郊某站的雷暴释用预报的模型,并对该站2010年雨季雷暴进行预报试验。试验结果表明:精选因子的KMO检验值在0.65~0.85,且Bartlett球形度检验显著,说明该站的雷暴对流参数适用于因子分析;极大方差旋转能够较好地分离因子载荷,对雷暴信息的提取能力较强;试报的TS评分在0.3左右,24小时预报的Hedike评分可达0.337,模型的预报准确率较高,持续性较好。综上所述,采用主分量旋转法对雷暴的MOS预报有一定的改善效果。     

基于主成分和BP神经网络的智利竹筴鱼渔场预报模型研究

东南太平洋智利竹筴鱼Trachurus murphyi是我国大型拖网渔船队的重要捕捞对象。准确预报中心渔场是提高渔业生产能力的重要工作。本文根据2003—2009年我国船队在东南太平洋海域捕捞智利竹筴鱼的渔捞日志数据,结合海洋遥感获得的海表温度(SST)和海面高度(SSH)等海洋环境因子,利用主成分和BP神经网络方法对智利竹筴鱼中心渔场预报模型进行了研究。研究利用主成分分析法(PCA)得到累计贡献率在90%以上样本的主成分,综合考虑模型测试的精度与速度,基于原始样本和经PCA处理后的主成分分别建立了BP模型,其最优BP模型结构分别为5∶10∶1和3∶7∶1。研究结果表明,经PCA处理后的主成分所建立的BP神经网络模型在训练结果和测试结果上均要优于用原始样本建立的BP神经网络模型,两者的预报准确率分别为67%和60%。     

人工触发闪电连续电流过程与M分量特征

在广州野外雷电试验基地,对2008年和2011年夏季人工触发闪电回击之后的14个连续电流过程和43个M分量的通道底部电流、电场变化和通道亮度进行了同步测量和分析。结果表明:M分量的电流、快慢电场变化和亮度变化波形均近似对称;触发闪电连续电流过程的持续时间、转移电荷量、电流平均值的几何平均值分别为22 ms,6.0 C和273 A;M分量的幅度、转移电荷量、半峰值宽度、上升时间、持续时间的几何平均值分别为409 A,205 mC,520 μs,305 μs和1.6 ms;连续电流持续时间与M分量的个数、相邻M分量之间的时间间隔均存在显著的正相关关系。     

SAR change detection based on intensity and texture changes

In this paper, a novel change detection approach is proposed for multitemporal synthetic aperture radar (SAR) images. The approach is based on two difference images, which are constructed through intensity and texture information, respectively. In the extraction of the texture differences, robust principal component analysis technique is used to separate irrelevant and noisy elements from Gabor responses. Then graph cuts are improved by a novel energy function based on multivariate generalized Gaussian model for more accurately fitting. The effectiveness of the proposed method is proved by the experiment results obtained on several real SAR images data sets.     

基于主成分分析的赣江流域水资源承载力评价

沿海的产业梯度的转移,带来了赣江流域产业的迅速崛起,同时水资源问题也日显突出。水资源承载力评价是实现水资源可持续发展的重要手段,本文以主成分分析法为基础,在赣江流域内按上、中、下流域段分别选取赣州市、吉安市和南昌市3个主要城市作为水资源承载力评价对象,得出赣江流域上中游的水资源承载力明显高于下游,上中游的水资源开发潜力还很大,而下游的水资源利用应在可持续发展的原则下采取保护措施。     

柴达木盆地盐湖资源管理信息系统的设计与实现

建立基于GIS技术的柴达木盆地盐湖资源管理信息系统,可以为盐湖资源开发管理与高效利用提供信息化的决策咨询平台。文章在分析盐湖资源循环利用管理需求的基础上,讨论了柴达木盐湖资源管理软件系统的构架和功能目标,分析了系统设计流程和实现技术。通过运用C#语言和ArcGIS Engine组件技术,基于.NET框架的Microsoft Visual Studio 2008集成开发环境,实现了柴达木盆地盐湖资源分布的三维场景浏览、盐湖企业及其生产经营状况的查询分析和盐湖资源开发的动态管理,为循环经济区盐湖资源的可持续利用提供了技术支持。