Head/Tail Breaks: A New Classification Scheme for Data with a Heavy-Tailed Distribution

This article introduces a new classification scheme—head/tail breaks—to find groupings or hierarchy for data with a heavy-tailed distribution. The heavy-tailed distributions are heavily right skewed, with a minority of large values in the head and a majority of small values in the tail, commonly characterized by a power law, a lognormal, or an exponential function. For example, a country's population is often distributed in such a heavy-tailed manner, with a minority of people (e.g., 20 percent) in the countryside and the vast majority (e.g., 80 percent) in urban areas. This new classification scheme partitions all of the data values around the mean into two parts and continues the process iteratively for the values (above the mean) in the head until the head part values are no longer heavy-tailed distributed. Thus, the number of classes and the class intervals are both naturally determined. I therefore claim that the new classification scheme is more natural than the natural breaks in finding the groupings or hierarchy for data with a heavy-tailed distribution. I demonstrate the advantages of the head/tail breaks method over Jenks's natural breaks in capturing the underlying hierarchy of the data.     

Evolution of sedimentary environments of the middle Jiangsu coast, South Yellow Sea since late MIS 3

An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 （late MIS 3, i.e., ca. 39 cal ka BP） along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea （SYS）, and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments （Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel）. This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial （Para-Sq2）, including the highstand and forced regressive wedge system tracts （HST and FRWST）, and the parasequence of the postglacial period （Para-Sql）, including the transgressive and highstand system tracts （TST and HST）. The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.     

伽马拟声波分频重构反演在储层预测中的应用

在地质和地震资料研究基础上,通过岩心、录井和测井分析,探索不同频率尺度测井曲线的储层意义,优选研究区内钻穿古近系底砂岩段砂泥薄互层储层5口探井的储层敏感曲线.在曲线预处理、标准化和敏感性分析的前提下,利用曲线分频拟合,对储层敏感曲线和声波曲线做小波多尺度分解,提取反映薄互层储层岩性变化的中频中尺度伽马曲线和反映地层速度的低频大尺度声波曲线.利用统计模型信息融合构建具有声波量纲的拟声波曲线.在地质研究和沉积演化模式的指导下,运用井约束反演的方法补充地震资料的高频和低频信息,提高地震资料的质量,预测有利储层分布.研究表明,伽马拟声波分频重构反演能有效的提高地震资料的纵向和横向分辨率,刻画复杂地质条件下的薄层储层分布.     

近45年全球海域波浪能资源研究及等级区划

基于来自ECMWF的资料将1957年09月---2002年08月风浪、涌浪分离的ERA-40 wave reanalysis,对全球海域的波浪能资源进行重新审视．充分依据涌浪具有能量大、稳定性好等优点,利于波浪能的采集与转换,从提高波浪能资源有效利用率的角度出发,综合考虑能流密度的大小、能级频率、能流密度的稳定性和长期变化趋势等,对全球海域的波浪能资源进行系统性研究,并构建一套波浪能资源评估系统,对全球海域的波浪能资源进行功能区划,为海浪发电、海水淡化等波浪能资源开发工作提供科学依据．     

灯塔5．1级地震的烈度与震害

2013年1月23日辽宁省灯塔市柳条寨镇发生M5．1级地震,震中烈度达到Ⅵ度。本文阐述了这次地震的地震参数,烈度划分标志,烈度分布及震害特点等内容。     

基于房屋普查数据的房屋增长规律研究

以辽宁省县级以上城镇房屋普查数据、辽宁农村民居房屋普查数据、统计年鉴及抽样调查等房屋数据为基础,对房屋普查数据统计单元进行重新划分及统计计算,实现了房屋普查数据与应急基础数据库房屋数据单元的统一。通过对统计单元各种房屋结构增长率的计算,结合统计分析方法,给出了辽宁省1134个乡镇级统计单元的房屋增长率分类情况。     

民采空区危险性两级模糊综合评判——以招远市北截村为例

在充分搜集资料的基础上,对招远市北截村民采空区进行实地勘查,从地质条件、灾害发育程度及采空区特征3个影响因素入手,选取了9个评判因子进行两级模糊综合评判,采取最大隶属度原则确定采空区危险性等级,并进行了评估分区。评判结果能较准确地反应实际情况,为该区地质灾害防治工作及开发建设规划提供了依据。     

内蒙古西部银额盆地及邻区二叠系隆林阶—冷坞阶层序地层格架

依据露头层序地层学原理,对银额盆地及邻区二叠系隆林阶—冷坞阶露头剖面进行层序界面的识别和层序划分,共划分为2个Ⅲ级层序。在对东西、南北向层序地层对比的基础上,初步建立了研究区的层序地层格架。隆林期—罗甸期全区发生大范围的海侵接受海相沉积,以滨海—浅海陆棚相为主,局部发育碳酸盐岩台地相,盆地边缘发育过渡相沉积,有2个沉积中心,黑鹰山-额济纳旗坳陷带的沉积中心在碧云泉南-芦草井地区,柳园-巴丹吉林坳陷带的沉积中心在卡路山-杭乌拉一带。祥播期-冷坞期继承了前期的沉积格局,只是沉积范围向北西缩小,黑鹰山-额济纳旗坳陷带的沉积中心在芦草井地区,柳园-巴丹吉林坳陷带水体变浅,沉积中心在古硐井地区。     

济阳坳陷惠民凹陷临盘地区始新统孔店组一段—沙河街组四段红层划分和对比

受气候控制的洪水事件沉积因其短暂性、广布性和周期性等特征,具有相对的等时效应,可以作为地层划分和对比的标志层。通过分析不同规模周期下的事件沉积和正常沉积特征,并结合基准面旋回理论,识别出济阳坳陷惠民凹陷临盘地区始新统孔店组一段—沙河街组四段下亚段红层短期、中期和长期三个级次的基准面旋回特征,短期旋回以洪水期和间洪水期内发育的不同类型沉积微相组合为特征,中期旋回以发育一套完整的洪水期—间洪水期沉积为标志,长期旋回则以多个中期旋回组成的地层叠加为特征;以此为依据将惠民凹陷临盘地区孔店组一段—沙河街组四段下亚段划分为5个长期旋回、16个中期旋回及若干个短期旋回层序,并对第一个长期旋回进行了精细层序地层对比,在此基础上建立了干旱气候控制下的红层层序的划分和对比模式。     

基于气候变化特征的红层划分对比——以东营凹陷南坡为例

首次利用气候变化特征,对由于缺少特征古生物化石资料而长期难以进行地层划分的东营凹陷南坡始新统沙河街组四段下亚段——孔店组一段的红层进行了有效划分。采用基于孢粉化石Ephedripites相对含量约束下的测井数据法恢复相对古气候变化,首先根据Ephedripites相对含量的变化确定气候变化拐点(最干旱点)的位置段,再根据能谱测井数据或常规测井数据计算出的连续粘土矿物组成确定气候拐点的具体点,即为层位界线。根据标准井测井数据建立的数学模型,可以对该井附近新钻探井的红层进行划分对比,其科学性、合理性已被之后的勘探成果所证实。该方法为缺少古生物化石数据的"哑地层"划分提供了一种新思路。