基于广义Pareto分布的洪水序列频率分析

广义Pareto分布是超定量洪水频率分析的常用线型,其阈值的合理选择是关键。对洪水序列超阈值分布的阈值选择和超定量样本的适用性检验两个方面深入讨论,为设计洪水提供更优的频率分析方法。基于广东省曹江流域大拜水文站1968～2013年日流量的洪水序列数据,采用不同的抽样方法,检验不同洪水超定量的泊松分布、广义极值分布和超定量样本分布的拟合优度指标。将择优的GPD、GEV和P-Ⅲ型模型推算的洪水重现水平做了对比分析。获得以下结论:大拜站洪水序列GPD模型属于重尾分布;洪水GPD阈值的选择可以参考经验平均超过函数图,而最佳阈值应采用多种指标综合确定;三种概率分布的拟合优度结果显示,构建的大拜站洪水GPD模型精度与GEV和P-Ⅲ型相比较高;GPD的参数估计方法对洪水重现水平的计算结果有较大影响。     

基于线性矩法的东江流域区域枯水频率分析

线性矩法是在概率权重法基础上发展起来的一类分布函数参数确定方法．以年最小七日平均流量作为枯水径流的统计特征量，在水文站点一致性分析、水文相似区鉴别的基础上，以常见的5种三参数分布函数：Generalized Pareto分布（GPA）、Generalized Extreme-Value分布（GEV）、Generalized Logistic分布（GLO）、LogNormal分布（LN3）和Pearson type Ⅲ（PⅢ）为研究对象进行东江流域区域枯水频率分析．分析结果表明，LN3为最适合东江流域的区域枯水分布．将实测枯水流量与采用区域化方法所得到的枯水模拟结果进行对比分析，结果表明区域化所得到的模拟精度较高，可以满足实际需要．     

天津市设计暴雨方法比较及公式修正

设计暴雨是防洪设施建设的安全标准之一,由于气候改变,水文循环过程随之改变,降雨强度及规律也相应发生改变,因此有必要对设计暴雨进行进一步研究.以天津市为研究对象,采用52年P-Ⅲ型的降雨资料作为样本;采用年最大值法、年多个样法进行选样,采用耿贝尔分布、广义极值分布、指数分布和P-Ⅲ型分布对设计暴雨进行理论频率分析,以回归分析中的决定系数作为评价指标.通过频率适线分析得出暴雨强度-历时-重现期关系曲线,并采用高斯-牛顿迭代法对暴雨强度公式进行求解,以绝对标准差及相对标准差作为暴雨强度公式评价指标.结果表明P-Ⅲ型曲线更为适用,而目前使用的设计暴雨强度小于根据52年降雨资料得出的设计暴雨强度.因此,随着数据的积累对设计暴雨进行修正是非常必要的.     

P-Ⅲ型分布与信息扩散理论的风险估算模型比较研究

在国际灾害数据库支持下,获取了中国1988—2007年发生的洪水灾害次数、人口死亡数和洪水灾害经济损失3项统计指标;利用P-Ⅲ型分布估算模型和信息扩散模型进行洪水灾害风险分析,并对二者方法进行结果对比分析.结果表明:在样本数据量较少的情况下,当风险水平在6或8时,P-Ⅲ型分布的重现期估计值变化迅速,这与实际灾害发生情况不符,不能很好地拟合洪水灾情情况;而信息扩散变幅不大,能够很好地拟合洪水灾情情况;说明信息扩散方法在小样本数据量情况下明显优于P-Ⅲ型分布估算模型,可以解决样本资料短缺的问题,是一种有效的处理小样本的方法.信息扩散理论对洪灾风险研究具有一定的理论参考价值.     

基于GAMLSS模型的小理河流域年径流研究

受气候变化和人类活动影响,小理河径流序列一致性遭到破坏,传统水文频率分析计算方法的应用受限,未来水情分析研究尤显重要.本文根据李家河站1959～2010年的水文气象资料,利用GAMLSS模型建立以时间、年降水量、年平均气温和ATD指数为协变量的不同分布模型,分析比较各分布模型的拟合效果,选择最优分布与传统的P-Ⅲ分布进行对比分析,并进行年径流量设计值计算.结果表明,在GAMLSS框架下,以年降水量和年平均气温为协变量的LOGNO分布模型拟合最优,可从物理机制阐释小理河年径流的变化,且能获得其不同设计保证率下设计年径流量区间值,为流域水资源的开发利用和规划管理提供更为科学的决策依据.     

汉江洪水频率计算不确定性分析(Ⅱ):统计过程不确定性

使用NUSAP方法对洪水频率分析中的两种流量序列选取方法进行不确定性评价,然后对于选用的4种分布函数,分别使用矩法和极大似然法进行参数估计,针对不同的参数估计方法以及分布函数,应用NUSAP方法结合曲线拟合误差综合评价其中的不确定性.结果表明,超阈值方法是一种较为科学的时间序列选取方法,广义柏拉图分布和PⅢ分布对流量序列的拟合结果较好.NUSAP方法对上述分布函数和各种参数估计方法的评价结果更直观、更合理,是其在洪水频率分析领域应用的一个良好开端.     

淮河流域枯水流量演变特征、成因与影响研究

基于1956—2016年淮河流域9个水文站的日径流量系列数据,采用M-K非参数检验法、小波分析等方法,研究淮河流域连续最小1、7、15、30d平均流量(枯水流量)时空演变规律.研究发现:1)淮河流域枯水流量Cv值为0.23~1.34,年最小枯水流量为0.002~24.5m~3·s~(-1),枯水流量年际变化剧烈.息县、王家坝、蒋家集和横排头站在4种序列中的变异点多发生于2001年;阜阳和鲁台子站在4种序列中的变异点均出现在1964年.各站点变异时间多发生在20世纪60年代初及21世纪初.2)息县、潢川、班台和王家坝站在Q1、Q7、Q15中的变化趋势基本一致,整体呈震荡上升趋势.阜阳站和蚌埠站变化恰好相反.空间分布上,上游枯水流量呈增加趋势,而中游则呈下降趋势.3)息县、班台、阜阳、蚌埠和鲁台子这5个站点均在1960—1977年存在显著周期,潢川、班台、王家坝、蒋家集、横排头和蚌埠站在1997—2012年的时间段内存在2.0~4.6a的显著周期变化.     

基于贝叶斯理论的水文频率参数估计不确定性分析——以P-Ⅲ型分布为例

水文序列受到多重不确定性因素的影响,直接关系到水文频率参数估计结果的精度及可靠性.本文将贝叶斯方法与适线法耦合起来,用于分析水文频率参数估计结果的不确定性,采用基于自适应采样算法的马尔科夫链蒙特卡洛方法(AM-MCMC)求解贝叶斯公式,以P-Ⅲ型分布为例,通过实测序列加以验证,从不确定性角度定量分析了序列长度和历史洪水信息对参数估计结果的影响.将贝叶斯方法估计结果与几种常用方法所得结果进行了对比,相比于传统的确定性方法,贝叶斯方法不仅能应用于P-Ⅲ型分布的参数估计而且可对结果进行不确定性分析,从而可进一步提高水文分析计算的可靠性.     

基于激光自混合散斑干涉的微小流量检测

为实现对激光自混合散斑干涉的微小流量的检测,提出了一种基于激光自混合散斑干涉检测方法。 通过检测得到自混合散斑干涉信号,并对信号进行频谱分析得到流体的平均频率,利用平均频率与流速的拟合 直线进一步获得流量与平均频率的关系,从而精确求解流体微小流量。理论分析和实验表明,该方法可以简单 高效测量微小流量,测量相对误差小于1． 13%。     

基于新安江水文模型的东江流域枯水径流模拟

为了探讨新安江流域水文模型模拟流域枯水径流的可行性及精度,采用该模型对东江流域中的4个子流域进行日径流过程模拟.在采用常规的评价指标对模拟结果进行初步分析的基础上,以描述枯水径流特点的枯水特征值,例如连续多日最小平均流量、基流分割结果、枯水期模拟结果和流量历时曲线等为研究对象,探讨该模型模拟枯水径流的能力.4个子流域的研究结果表明,不论对于常规的评价指标,还是枯水特征值,用新安江流域水文模型来模拟枯水期的流量均能达到较高的精度,因此可采用该模型进行东江流域枯水径流的预测.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of