BLU Estimators and Compositional Data

One of the principal objections to the logratio approach for the statistical analysis of compositional data has been the absence of unbiasedness and minimum variance properties of some estimators: they seem not to be BLU estimator. Using a geometric approach, we introduce the concept of metric variance and of a compositional unbiased estimator, and we show that the closed geometric mean is a c-BLU estimator (compositional best linear unbiased estimator with respect to the geometry of the simplex) of the center of the distribution of a random composition. Thus, it satisfies analogous properties to the arithmetic mean as a BLU estimator of the expected value in real space. The geometric approach used gives real meaning to the concepts of measure of central tendency and measure of dispersion and opens up a new way of understanding the statistical analysis of compositional data.     

On changes in porosity and volume during burial of argillaceous sediments

The porosity and hence volume of argillaceous sediments is determined by: (1) the magnitude of the effective stress acting within the sediment; (2) the previous stress history of the sediment; and (3) at shallow depths of burial, by features such as the mineralogy and the nature of the depositional environment. Stress paths and the critical state diagrams for a number of clays are used to investigate the range of porosities possible in argillaceous sediments as the effective stresses increase. It is found that all porosity/effective stress curves converge at large stresses. The change in porosity is strongly dependent on the mean effective stress but largely independent of the deviatoric stress, and thus is largely independent of the nature of the stress field acting on the basin (compressional, extensional etc.). Because of the dependence of porosity on the mean effective stress, no simple relationship exists between porosity and depth of burial but in the absence of overpressured pore fluids and assuming the sediment is not overconsolidated, it is possible to contour the porosity/effective stress diagram in terms of burial depths. These data should assist in recalculating stratigraphic thicknesses for basin reconstruction and stratigraphic correlation studies.     

尕斯库勒盐湖卤水模拟自然蒸发试验研究

尕斯库勒湖是柴达木盆地众盐湖中较为典型的硫酸镁亚型盐湖。利用相图规律对该盐湖卤水自然蒸发的结晶路线进行了分析,并通过室内模拟自然蒸发试验进行了验证,最终获得了在自然条件下蒸发卤水分步结晶不同盐类的工艺路线,可为该盐湖资源综合利用提供依据。     

阿克苏断层氢气浓度动态特征及其映震效能

首先对阿克苏断层氢气浓度观测资料的周期成分进行了时频分析,然后分别利用线性回归和互相关方法分析了气温、气压与氢气浓度年周期成分的关系,并利用Molchan图表法对阿克苏断层氢气的映震效能进行了定量检验。结果显示:① 阿克苏断层氢气浓度具有清晰的年周期和半日周期成分;② 阿克苏断层氢气浓度的年周期动态变化与气温具有显著的正相关性,与气压的相关性一般,表明其年周期变化主要受气温影响;③ 阿克苏断层氢气浓度异常对观测点周边中强以上地震的反应较灵敏,映震效果较好。      

星座图贴近度方法在广西北海近海水质监测优化布点上的应用

本文将星座图聚类、欧几里得距离贴近度、中国近海水质评价及t检验方法结合起来,对广西北海近海水质监测点进行分类、择优布点及检验。结果表明,这是一种实用的优化布点方法。     

Voronoi图在地图制图中的应用

在搜集整理Voronoi相关文献与资料的基础上,首先简要介绍了Voronoi图及其应用领域,然后着重从地图信息识别与提取、地图综合和自动注记等方面总结了它在地图制图学中的应用情况,最后分析并探讨了应用中遇到的问题和今后的发展方向。指出Voronoi图在地图制图中的应用是由其特殊的几何与拓扑性质决定的,加权Voronoi图、广义Voronoi图及3DVoronoi图的引入使得其应用有着更远大的前景。     

台湾近海的温、盐垂直结构与t－S图解类型

本文根据我国台湾海洋工作者的调查分析资料，对台湾近海的温、盐垂直分布及ｔ－Ｓ图解特征进行分析，按其相似性特点进行归类和分型，并探讨它们的特点和异同之处。主要结果如下：１．冬、夏季台湾近海的温、盐垂直分布类型有５种，ｔ－Ｓ图解类型为９种。２．冬季台湾近海的水温垂直分布存在着一层、二层、三层结构，夏季多为三层结构；冬、夏季的盐度垂直分布为二层和三层结构。３．台湾西南、南和东北近海，ｔ－Ｓ图解类型复杂，出现多种类型交错。４．夏季台湾南端的猫鼻头、鹅銮鼻沿岸附近，其温、盐垂直分布皆出现上均匀层，此现象实属少见。     

靖海湾表层沉积物粒度特征及沉积动力环境分区

随着人类开发活动的加剧,靖海湾沉积动力环境受到显著影响。靖海湾57个站位的表层沉积物调查资料的分析结果表明,靖海湾表层沉积物以砂质粉砂和粉砂为主,含有少量泥,沉积物粒径偏小;随着水动力条件的增强,表层沉积物平均粒径增大,分选系数呈增大趋势,正偏更显著;以此为依据,利用Pejrup三角图式把靖海湾划分出4个沉积动力环境单元,结合粒度概率图,认为靖海湾沉积物搬运方式以悬浮为主,跃移次之,并有少量以推移方式搬运,随着水动力条件的增强,悬浮组分减少,跃移组分和推移组分增加。     

Liquid moment amplitude assessment in sloshing type problems with smooth particle hydrodynamics

Sloshing moment amplitudes in a rectangular tank for a wide range of rolling frequencies are investigated both experimentally and numerically. In a previous paper, Souto et al. [2004. Simulation of anti-roll tanks and sloshing type problems with smoothed particle hydrodynamics. Ocean Eng. 31 (8–9), 1169–1192] numerical results obtained with a 3-D Smooth Particle Hydrodynamics (SPH) formulation were presented. These only corresponded to the phase lag between the tank motion and the liquid response moment. This paper is aimed at improving those results by obtaining accurate values for the moment amplitudes. We present the corrections with respect to the aforementioned implementation that focus on the time integration scheme and on the treatment of the boundary conditions. In addition better quality experimental results are presented.     

中国森林乡村的多尺度分异特征与分区优化

国家森林乡村建设是实施乡村振兴战略和改善农村人居环境的重要措施,但森林乡村在不同尺度的分异特征及优化方向尚不明晰。本文综合运用探索性空间数据分析、耦合度模型和Voronoi图分析等研究方法,从全国、区域和行政尺度分析了国家森林乡村空间格局、数量规模和内部分异特征,并基于森林乡村与人口耦合关系及乡村可达类型识别,分析了全国森林乡村的分区格局及其优化方向。结果表明：全国森林乡村密度具有明显的东高西低分异特征,长江三角洲地区是森林乡村高密度集中分布最大的连片区。基于县域单元的省域森林乡村泰尔指数差异较大,东南区域森林乡村分布相对均衡,西南和东北区域内部差异显著。森林乡村空间可达性呈现自东向西的梯度递减,森林乡村与人口密度的耦合类型分布具有较强的内部分异性。文章基于森林乡村可达类型与耦合分区的组合分析,将全国划分为重点发展区、特色挖掘区、集聚提升区、适度引导区和功能转型区五类,明确了不同类型区森林乡村建设的重点方向,将为面向乡村振兴的全国森林乡村建设与分区优化提供决策依据。