Discrimination of the phenotypic sardine Sardina pilchardus stocks off the Moroccan Atlantic coast using a morphometric analysis

Morphometric variation can be very useful for discriminating ‘phenotypic stocks’ as groups with similar life-history traits. Such groups are of great importance for accurate population-dynamics modelling for purposes of fishery stock assessment and management, independent of their genetic differences or similarities. This study is a contribution to the stock identification of the sardine Sardina pilchardus off the Moroccan Atlantic coast. The objectives were to (i) assess whether specimens from stocks defined by the FAO correspond to different morphotypes, and (ii) compare the obtained results with those recently published on the genetic variability of the studied populations. Morphometric analyses, using truss variables and landmarks data from sardine sampled from four widely spaced ports of landing along the Moroccan Atlantic coast (from north to south: Larache, Safi, Tantan and Dakhla), were carried out using multivariate and geometric approaches. Principal components analysis of truss variables and cluster analysis of the average shape of the sardine revealed the existence of three distinct morphotypes: ‘Larache,’ ‘Safi–Tantan’ and ‘Dakhla.’ These correspond well with the FAO’s stock subdivision. The morphometric variation might be related to the mesoscale hydrodynamic characteristics of the study area. However, these morphometric results do not fully accord with recently published data on genetic variability of the species. Those data indicated the genetic singularity of the Safi population, which could have led to the historical collapse of that sardine stock in the 1970s. Additional work is needed to validate the obtained results by taking into account seasonal variations and transitional areas between stocks.     

潞安矿区中部煤矿充水水源水化学特征及水源识别意义

采集了潞安矿区中部煤矿5类80份已知水源水样,利用PIPER三线图对不同来源水样水文地球化学特征进行了分析;利用聚类分析方法(Ward法)对三线图上存在重叠的砂岩水、太灰水与奥灰水进行分类,显示奥灰水与太灰水明显聚类,局部存在两者混合,砂岩水则与上述两者难以区分;最后利用Bayes模型建立了不同水源判别函数(自我检验准...     

Output only modal identification and structural damage detection using time frequency ＆ wavelet techniques

The primary objective of this paper is to develop output only modal identifi cation and structural damage detection.Identif ication of multi-degree of freedom(MDOF) linear time invariant(LTI) and linear time variant(LTV—due to damage) systems based on Time-frequency(TF) techniques—such as short-time Fourier transform(STFT),empirical mode decomposition(EMD),and wavelets—is proposed.STFT,EMD,and wavelet methods developed to date are reviewed in detail.In addition a Hilbert transform(HT) approach to determine ...     

Condition assessment of structures under unknown support excitation

A new method is proposed to assess the condition of structures under unknown support excitation by simultaneously detecting local damage and identifying the support excitation from several structural dynamic responses. The support excitation acting on a structure is modeled by orthogonal polynomial approximations, and the sensitivities of structural dynamic response with respect to its physical parameters and orthogonal coeffi cients are derived. The identifi cation equation is based on Taylor’s fi rst orde...     

砂砾岩体内幕岩性识别方法初探——以东营凹陷盐家油田盐22断块砂砾岩体为例

东营坳陷盐家油田砂砾岩体为近物源、快速堆积的近岸水下扇沉积,扇体厚度大,横向变化快。巨厚砂砾岩体内部的精细地层划分对比一直是制约该区进一步勘探开发的难点。根据该区盐22断块砂砾岩体的沉积特征,首先运用测井曲线重构方法划分出砂砾岩体的砂砾岩段、泥岩段,剔去明显的非储层;其次运用聚类分析方法识别砂砾岩段的岩性构成。砂砾岩体内幕岩性划分结果与岩心资料比较吻合率为966%,与成像资料比较吻合率为962%。该方法为该区厚层砂砾岩体内部地层精细划分与对比提供了可靠的地质依据。     

旅游产业集群形成条件与识别方法

根据"产业集聚"和"产业联系"两个识别旅游集群存在的标准,结合旅游业的特点,从旅游资源空间集聚条件、旅游要素集中度和集聚效果3个方面构造区位熵指数,再根据投入产出表,用主成份分析法,确定旅游产业联系,计算产业联系密度,最后结合区位熵指数和产业联系密度,得出旅游产业集群度,同时分析旅游产业集群的形成条件,有利于制定政策引导促进旅游产业发展.     

浅析山西省数字地磁台站观测数据的预处理

文章通过实例列举了“十五”数字化后,全省地磁观测数据预处理工作中存在的三方面的问题。认为,必须重视并改正这些不正确的处理方法,才能保证观测数据反映客观真实的信息。     

ARX结构模态参数识别方法对比(Ⅱ)——基于地震观测记录的对比

结构参数识别是结构抗震安全性能鉴定和健康诊断的基础,利用地震观测记录来识别结构模态参数,是地震工程领域备受关注的研究课题之一。本文利用实际结构的地震观测记录,对一维、多维和整体ARX模型三种模态参数识别方法进行了对比分析。结果表明：整体ARX模型对多自由度结构的模态参数识别较为稳定且精度较高;实际应用中多维ARX模型有时会导致丢失模态和虚假模态现象。     

基于遗传算法的磁流变阻尼器模型参数识别

磁流变阻尼器是一种具有广阔应用前途的半主动控制装置,但其复杂的力学特性很难精确描述。非线性参数模型是一个相对简单并且能够很好地描述磁流变阻尼器力学特性的力学模型,但该模型既是非线性的、又是非解析的,参数识别十分困难。结合传统遗传算法良好的全局搜索能力和二分法可靠的收敛性,本文提出了一种改进的遗传算法——层次压缩遗传算法。对非线性参数模型的参数识别结果显示：层次压缩遗传算法简单可行,具有较高的识别精度。同时也验证了非线性参数模型描述磁流变阻尼器阻尼力特性的准确性。     

滇西某铁路拟选线路地质灾害遥感解译特征研究

以SPOT-4／5卫星影像为信息源,以ERDAS8．7软件为处理平台,运用多种图像处理方法对影像进行综合处理,在此基础上对滇西山区某铁路选线勘察进行了实例研究。根据滇西山区地质灾害的分布规律及遥感影像特征,结合地学知识对该线路部分区段的地质灾害进行遥感解译,查明了区段内滑坡、泥石流及崩塌对线路的影响,为该铁路拟选线路的建设提供了科学依据。