Binary coefficients: A theoretical and empirical study   总被引：1，自引：0，他引：1  

Michael Ed. Hohn 《Mathematical Geology》1976,8(2):137-150

Binary coefficients can be assigned to several categories on the basis of algebraic and conceptual properties. The phi coefficient of association is related algebraically to the chi-square statistic for 2-by-2 contingency tables, and use of this coefficient in cluster analysis permits the objective, nonarbitrary partitioning of objects among groups on the basis of previously selected levels of significant, positive association. Similarity, matching, and distance coefficients possess neither conceptual nor operational statistical meaning for many geological data sets. The weighted pair group method and flexible clustering strategy may give an overly conservative partitioning of objects among groups. Clustering by the unweighted pair group method, using the phi coefficient, is recommended for the analysis of biostratigraphic and paleoecologic presence—absence data.  相似文献   

星系团的分层效应     

赵君亮 《天文学进展》2007,25(3):206-214

对星系团各类分层效应的有关问题做了概要的评述,包括成员星系在位置空间和(或)速度空间中的形态分层、光度(质量)分层和元素丰度分层的表现形式和探测途径,分层效应可能的形成机制及其对星系和星系团的结构和演化的影响。  相似文献   

Variability of sediment diatom assemblages in an upland,wind-stressed lake (Loch Fleet,Galloway, S.W. Scotland)     

N. J. Anderson 《Journal of Paleolimnology》1990,4(1):43-59

The variability of diatom distribution in an acidified, upland wind-stressed lake (Loch Fleet, Galloway, S. W. Scotland) was assessed by analysis of 28 surface sediment samples and 11 cores. Correspondence analysis (CA) and cluster analysis were used to illustrate the variability of the surface sediment and core samples. There was reasonable uniformity of taxa in most of the surface sediment samples, although 7 samples, as indicated by both CA and cluster analyses were atypical. Most cores recorded clearly the acidification of the lake, although percentages of individual taxa varied up to 20% between cores. Two cores had old, preacidification diatom assemblages (of indeterminate age) close to the sediment surface. These old sediments were probably the source of the re-worked diatoms found in the atypical surface sediment assemblages. Diatom trends, as CA ordinations and pH profiles, were less variable than the surface sediment assemblages. It is argued that non-uniform sediment accumulation rates and diatom deposition cause variability in surface sediment diatom samples. This variability may be reduced in core profiles by homogenization during further resuspension/deposition cycles and burial. Cores, and the associated time component they offer, may be useful in assessing the variability of surface sediment assemblages.  相似文献   

一致性哈希算法在数据库集群上的拓展应用   总被引：2，自引：0，他引：2  

赵飞  苏忠 《成都信息工程学院学报》2015,30(1):52-58

在数据库集群的研究中,可扩展性是一个重要的性能指标。为实现在数据高速增长或部分集群服务器故障情况下,数据依然能够快速、可靠、安全的分布到新的集群服务器节点上的目的,就必须合理设置数据划分的策略。将Key-Value存储技术中使用的一致性哈希算法思想借鉴运用到并行分析型数据库集群中,提出针对大规模结构化类特殊数据的一致性哈希划分方法,并在MapReduce框架下设计具体的数据划分方案。最后,以TPC-DS作为测试基准,与同类系统进行性能对比测试,实验结果表明方案不仅有良好的划分性能,且扩展性也较好。  相似文献   

一致性哈希算法在数据库集群上的拓展应用     

赵飞  苏忠 《成都信息工程学院学报》2015,30(2)

在数据库集群的研究中,可扩展性是一个重要的性能指标.为实现在数据高速增长或部分集群服务器故障情况下,数据依然能够快速、可靠、安全的分布到新的集群服务器节点上的目的,就必须合理设置数据划分的策略.将Key-Value存储技术中使用的一致性哈希算法思想借鉴运用到并行分析型数据库集群中,提出针对大规模结构化类特殊数据的一致性哈希划分方法,并在MapReduce框架下设计具体的数据划分方案.最后,以TPC-DS作为测试基准,与同类系统进行性能对比测试,实验结果表明方案不仅有良好的划分性能,且扩展性也较好.  相似文献   

城市创伤中心空间选址的层次分析模型     

朱一姝  杜清运  梁实  石光辉  林德南 《地理信息世界》2015,(3):1-7

针对城市创伤中心空间选址问题,建立包含四大类、八小类影响因素的层次分析模型,邀请不同领域的专家对构造出的判断矩阵综合打分,得出各因素的相应权重后运用到深圳市创伤中心空间选址的实例研究上。模型中所涉及的空间数据均基于网络分析,更贴合实际情况。同时,考虑到深圳市创伤中心的依托医院相对集中这一特殊情况,通过聚类分析划分区域后再使用层次分析模型选址。优化后的结果将改善深圳市创伤医疗救治资源配置、提高创伤救治效率,为创伤救治机构规划部门提供参考意见。  相似文献   

安徽铜陵凤凰山夕卡岩型铜矿床中辉钼矿Re-Os同位素年龄及其地质意义   总被引：5，自引：2，他引：3  

瞿泓滢  裴荣富  王永磊  李进文 《岩石学报》2010,26(3):785-796

铜陵矿集区是我国长江中下游Cu-Au-Fe-Mo成矿带中最重要的有色金属基地之一,凤凰山矿床是铜陵矿集区的重要组成部分,为一个典型的夕卡岩型铜矿床。本文利用Re-Os同位素定年方法对凤凰山铜矿床进行了成矿时代测定,获得了辉钼矿的Re-Os同位素模式年龄范围为139.1±2.4～142.0±2.2Ma,等时线年龄为141.1±1.4Ma,与矿区内石英二长闪长岩和花岗闪长岩SHRIMP锆石U-Pb年龄(144.2±2.3Ma)相吻合,也与铜陵地区其他矿田的成矿时代基本一致,可能为岩石圈减薄事件的成矿响应。  相似文献   

武汉市不同站域建成环境与轨道交通站点客流特征关系分析     

李清嘉  彭建东  杨红 《地球信息科学学报》2021,23(7):1246-1258

中国已经成为全世界城市轨道交通建设里程最长、建设速度最快的国家,合理识别城市轨道站点类别与影响不同类别站点客流特征的建成环境因素对轨道交通的建设具有十分重要的作用。因此,本文以武汉市为例,通过轨道交通刷卡数据,运用引入客流特征的EM聚类方法,将轨道交通站点分为职住错位型、居住导向型、就业导向型、居住综合型、就业综合型、综合型6类。并在此基础上,建立无序多分类logistic回归模型,定量分析站点客流吸引范围内建成环境因素对不同类型站点轨道交通客流特征的影响。结果表明：以综合型站点为对照组,路网密度和交叉口密度对所有类型站点的客流特征有显著影响,低路网密度高交叉口密度更有利于职住平衡;公交车站密度与就业导向型站点的客流特征存在负相关;商务用地占比对职住错位型、居住导向型、居住综合型站点有负向关系;服务业设施用地占比与职住错位型、居住导向型和就业综合型站点的客流特征负相关;科研教育用地占比与居住导向型和就业导向型站点客流特征负相关;土地利用混合度与居住导向型和就业综合型站点的客流特征负相关。研究结论将对武汉市轨道交通建设、轨道交通和土地利用协调发展等具有重要意义。  相似文献   

Relationship between surface pollen assemblages and vegetation in Luonan Basin,Eastern Qinling Mountains,Central China     

ZHANG Wenchao  LI Chunhai  LU Huayu  TIAN Xianhua  ZHANG Hongyan  LEI Fang  TANG Lingyu 《地理学报》2014,24(3):427-445

The catchment of South Luohe River in Central China is an important region for investigating modern pollen-environment relationship, because it is located in the transitional zone between south and north China, an environment which is sensitive to climate changes. In this study, 40 surface samples under ten vegetation types were collected to reveal the relationship between pollen assemblages and vegetation. The results show that the surface pollen assemblages reflect the vegetation quite well. In forest topsoils, the average of arboreal pollen content is greater than 40%, and the Selaginella sinensis spore is high. As to sparse forest grassland and shrub community, the average arboreal pollen is 13.2% and 16.6% respectively, and the shrub pollen is relatively higher than that of grassland samples. The grassland and farmland are characterized by low percentage of tree and shrub pollen (<10% and <1%), and high percentage of herbs (>80%). Pinus, Quercus and some other arboreal pollen can indicate the regional vegetation because of their dispersal ability. Quercus pollen is under-representative and so is Pinus. Artemisia pollen is significantly over-represented, has poor correlation with the plant coverage, and may reflect human disturbance. Gramineae can indicate plant quite well, but with low representation. High content of Chenopodiaceae probably suggests human impact. Predominant Selaginella sinensis can be used as an indicator of forest environment. Cluster analysis and principal components analysis of pollen assemblages can distinguish forest and non-forest vegetation well. The former method is better at separating pine and mixed forests, while the latter is more stable and could better differentiate farmland and other non-forest area. The first axis of PCA mainly reflects the humidity.  相似文献   

Using a Bayesian estimator to combine information from a cluster analysis and remote sensing data to estimate high-resolution data for agricultural production in Germany     

Alexander Gocht  Norbert Röder 《International journal of geographical information science》2014,28(9):1744-1764

In Germany, a county-resolution data set that consists of 35 land-use and animal-stock categories has been used extensively to assess the impact of agriculture on the environment. However, because such environmental effects as emission or nutrient surplus depend on the location, even a county resolution might produce misleading results. The aim of this article is to propose a Bayesian approach which combines two sorts of information, with one being treated as defining the prior and the other the data to form a posterior, used to estimate a data set at a municipality resolution. We define the joint prior density function based on (i) remote sensing data, thus accounting for differences in county data and missing data at the municipality level, and (ii) the results of a cluster analysis that was previously applied to the micro-census, whereas the data are defined by official statistics at the county level. This approach results in a fairly accurate data set at the municipality level. The results, using the proposed method, are validated by the national research data centre by comparing the estimates to actual observations. The test statistics presented here demonstrate that the proposed approach adequately estimates the production activities.  相似文献