基于地理空间要素的雅砻江流域面雨量估算          下载免费PDF全文

袁定波  艾萍  洪敏  廖亨利  陈彬彬  岳兆新 《水科学进展》2018,29(6):779-787

反映流域整体降水情势的面雨量一直是水文模型的重要输入参数之一,在泰森多边形雨量法的基础上考虑地理空间要素对降雨空间分布的影响,采用面向对象的遥感信息聚类方法提取出雅砻江流域2项形状因子(周长、面积)和5项地形因子(平均高程、平均坡度、平均坡向、高程差周长比和高程差面积比)。降雨—径流相关性分析结果表明:地形因子雨量法在月尺度上的降雨估算精度高于年尺度,且在月尺度上能更好地反映流域不同区段的降雨空间分布特征;在月、年际降雨变化趋势分析方面,年尺度上的降雨与径流一阶差分后平均相关系数为0. 903,高于月尺度的0. 629,主要由于水电站调蓄过程对流域径流异质性的影响,且影响度随着时间尺度缩小而放大。  相似文献   

Quantitative characterization of grain shape: Implications for textural maturity analysis and discrimination between depositional environments     

《Sedimentology》2018,65(5):1761-1776

Grain shape plays an important role in textural analysis of sedimentary grains. Textural analysis helps to determine the formation, transportation and deposition processes of sedimentary rocks. However, there is a lack of standardized methodology for quantitative characterization of grain shapes. The utility of fully automated image analysis for grain shape measurement is assessed in this paper. This research aimed to identify the most useful shape parameters for textural characterization of populations of grains and determine the relative importance of the parameters. A key aspect of this study is to determine whether, in a particular sedimentary environment, textural maturity of the samples can be ranked based on their grain shape data. Furthermore, discrimination of sedimentary depositional environments is explored on the basis of grain shape. In this study, 20 loose sediment samples from four known depositional environments (beach, aeolian, glacial and fluvial) were analysed using newly implemented automatic image analysis methods. For each sample, a set of 11 shape parameters were calculated for 200 grains. The data demonstrate a progression in textural maturity in terms of roundness, angularity, irregularity, fractal dimension, convexity, solidity and rectangularity. Furthermore, statistical analysis provides strong support for significant differences between samples grouped by environment and generates a ranking consistent with trends in maturity. Based on novel application of machine learning algorithms, angularity and fractal dimension are found to be the two most important parameters in texturally classifying a grain. The results of this study indicate that textural maturity is readily categorized using automated grain shape parameter analysis. However, it is not possible to absolutely discriminate between different depositional environments on the basis of shape parameters alone. This work opens up the possibility of detailed studies of the relationship between textural maturity and sedimentary environment, which may be more complicated than previously considered.  相似文献   

中国非正规经济发展格局及与城镇化的关系——基于多指标多原因(MIMIC)模型的研究北大核心CSCDCSSCI     

邢祖哥  黄耿志  薛德升 《地理研究》2022,41(3):597-615

非正规经济是世界城市化过程的普遍现象,关于它的发展态势及与城市化的关系是学界长期关注的重要问题。本文引入多指标多原因(MIMIC)模型估算中国非正规经济规模,在分析其发展空间格局的基础上,运用计量模型揭示了非正规经济与城镇化的动态关系。研究表明,2000年以来中国非正规经济不断增长,2008年后出现较快增长态势,2017年占GDP比例达到20.55%,非正规就业人员达1.59亿人。非正规经济的空间分布呈现西北-东南高、西南-东北低的不平衡特点。模型显示,中国非正规经济与人口城镇化水平存在倒U型关系,即非正规经济占整体经济的份额随城镇化水平的提高呈现先上升、后下降的变化过程,发生这一变化的城镇化水平临界值为72.48%。由此推断中国非正规经济占比还将伴随城镇化进程而继续上升,由于城镇化发展阶段的差异,不同地区的非正规经济发展态势将不同。非正规经济还受到经济发展阶段、产业结构、流动人口、国有经济和政府管制等因素的影响。本文有助于加深认识非正规经济的发展规律,为制定基于城镇化发展阶段差异的非正规经济政策提供理论依据。  相似文献   

几种保存方法对中华哲水蚤和强壮箭虫体型的影响     

冯秋园  孙晓霞  任琳琳 《海洋科学》2014,38(4):20-26

选取5%的甲醛,–20℃冰冻和液氮为保存方法,以中国近海的2种优势浮游动物中华哲水蚤(Calanus sinicus)和强壮箭虫(Sagitta crassa)为研究对象,以体长、体宽和面积为体型参数,研究了上述几种保存方法在2个月的时间内对浮游动物体型的影响。研究结果显示,对于中华哲水蚤,甲醛保存2个月后,体长下降为原始体长的99.4%,体宽和面积都增加为107%;冰冻和液氮保存2个月后,体长分别增加为原始体长的101%和106.8%,体宽下降为90%和81.6%,面积下降为92.2%和88.8%。对于强壮箭虫,在甲醛、冰冻和液氮3种保存条件下,保存2个月后体长有所下降,分别为原始体长的92.8%,50.7%和48.4%。体宽和面积有所增加,体宽分别变为原始体宽的139.9%,159.4%和263.8%,面积分别变为原始面积的119%,97.8%和107%。综合分析发现,胶质类浮游动物在冰冻和液氮保存条件下,身体变形严重,因此用ZooScan测得的结果误差较大,相较而言,甲醛对胶质类浮游动物体型的影响较小;中华哲水蚤比强壮箭虫在各种保存条件下体型的变化要小;保存初期,浮游动物体型的变化幅度较大,后期趋于稳定;在3种保存条件下,中华哲水蚤和强壮箭虫体长的变化最稳定,其次是面积。对浮游动物的体型进行研究时,推荐使用甲醛保存条件下的体长或面积。  相似文献   

Application of otolith shape analysis for stock discrimination and species identification of five goby species （Perciformes： Gobiidae） in the northern Chinese coastal waters   总被引：1，自引：0，他引：1  

于鑫  曹亮  刘金虎  赵博  单秀娟  窦硕增 《中国海洋湖沼学报》2014,32(5):1060-1073

We tested the use of otolith shape analysis to discriminate between species and stocks of five goby species( Ctenotrypauchen chinensis, Odontamblyopus lacepedii, Amblychaeturichthys hexanema, Chaeturichthys stigmatias, and Acanthogobius hasta) found in northern Chinese coastal waters. The five species were well differentiated with high overall classification success using shape indices(83.7%), elliptic Fourier coefficients(98.6%), or the combination of both methods(94.9%). However, shape analysis alone was only moderately successful at discriminating among the four stocks(Liaodong Bay, LD; Bohai Bay, BH; Huanghe(Yellow) River estuary HRE, and Jiaozhou Bay, JZ stocks) of A. hasta(50%–54%) and C. stigmatias(65.7%–75.8%). For these two species, shape analysis was moderately successful at discriminating the HRE or JZ stocks from other stocks, but failed to effectively identify the LD and BH stocks. A large number of otoliths were misclassified between the HRE and JZ stocks, which are geographically well separated. The classification success for stock discrimination was higher using elliptic Fourier coefficients alone(70.2%) or in combination with shape indices(75.8%) than using only shape indices(65.7%) in C. stigmatias whereas there was little difference among the three methods for A. hasta. Our results supported the common belief that otolith shape analysis is generally more effective for interspecific identification than intraspecific discrimination. Moreover, compared with shape indices analysis, Fourier analysis improves classification success during inter- and intra-species discrimination by otolith shape analysis, although this did not necessarily always occur in all fish species.  相似文献   

Effectiveness of superelastic bars for seismic rehabilitation of clay‐unit masonry walls     

Kshitij C. Shrestha  Yoshikazu Araki  Takuya Nagae  Toshihiro Omori  Yuji Sutou  Ryosuke Kainuma  Kiyohito Ishida 《地震工程与结构动力学》2013,42(5):725-741

This paper presents the results on shaking table tests of half‐scale brick walls performed to investigate the effectiveness of newly developed Cu–Al–Mn superelastic alloy (SEA) bars in retrofitting of historical masonry constructions. Problems associated with conventional steel reinforcing bars lie in degradation of stiffness and strength, or pinching phenomena, under cyclic loading, and presence of large residual cracks in structures during and after intense earthquakes. This paper attempts to resolve the problems by applying newly developed Cu–Al–Mn SEA bars, characterized by large recovery strain, low material cost, and high machinability, as partial replacements for steel bars. Sets of unreinforced, steel reinforced, and SEA‐reinforced specimens are subjected to scaled earthquake excitations in out‐of‐plane direction. Whereas steel‐reinforced specimens showed large residual inclinations, SEA‐reinforced specimens resulted in stable rocking response with slight residual inclinations. Corresponding nonlinear finite element (FE) models are developed to simulate the experimental observations. The FE models are further used to examine the sensitivity of the response with respect to the variations in experimental conditions. Both the experimental and numerical results demonstrate the superiority of Cu–Al–Mn SEA bars to conventional steel reinforcing bars in avoiding pinching phenomena. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

饱和软黏土中不同形状深水防沉板基础承载特性研究   总被引：4，自引：0，他引：4  

刘润  刘孟孟  杨树耕 《海洋学报》2016,38(3):131-144

防沉板基础是水下井口、管汇节点与管汇终端等的永久支撑结构,其承受的荷载具有明显的复杂性、非线性和不确定性,给防沉板基础的稳定性研究带来了巨大挑战。本文研究了在剪切强度随深度线性增长的不排水饱和软黏土中,相同用钢量条件下矩形、方形、六边形和圆形防沉板基础的承载特性。采用数值模拟方法确定了竖向荷载V、水平向荷载H(H_x、H_y)、弯矩荷载M(M_x、M_y)和扭矩荷载T联合作用下,防沉板基础在V-H、V-M、V-T、H_x-H_y、M_x-M_y、T-H和T-M荷载空间的地基承载力包络线,并建立了相应的拟合公式。研究表明,不同的基础形状对其承载力影响显著,当V较大时,适宜选用圆形基础;当H较为显著时,应选用矩形或方形基础;圆形、方形和矩形基础的抗弯特性分别适用于不同条件下M为主控荷载的情况;当T的影响不可忽视时,矩形或方形基础为首选形式,六边形和圆形基础次之。  相似文献   

Characterization of lunar dust and a synopsis of available lunar simulants     

Yang Liu  Lawrence A. Taylor 《Planetary and Space Science》2011,59(14):1769-1783

Understanding the formation and evolution of the soil and dust of the Moon addresses the fundamental question of the interactions of space with the surface of an airless body. The physical and chemical properties of the lunar dust, the <20 μm portion of lunar soil, are key properties necessary for studies of the toxicity and the electrostatic charging of the dust. These properties have been largely overlooked until recent years. Although chemical and physical studies of the <20 μm portion of lunar soil have been the topic of several studies, there is still need for further studies, primarily of the <1 μm particles. This paper presents a review of the studies of lunar dust that have been conducted to date. As many preparations for future exploration or science activities on the Moon require testing using lunar soil/dust simulants, we also include a brief review of past and current simulants.  相似文献   

基于3D MAX的矿体三维立体形态研究   总被引：2，自引：0，他引：2  

张锋  梁一鸿  陈国华  焦森 《吉林大学学报(地球科学版)》2007,37(1):48-53

以小西南岔铜金矿北山矿段Ⅰ-Ⅱ号脉系金、铜矿体为例,提出按品位分级的研究方法,探讨其形态特征和空间赋存规律,进而将矿体细分为矿饼微元,由此建立北山矿段金、铜矿体的三维立体形态模型。从而得出如下结论：（1）使用3D MAX软件将矿体形态可视化,方法简单易行,便于指导矿山管理、设计和生产;（2）提出品位分级形态的概念,有利于人们更好地认识矿体在空间的展布形态和分布规律,为解决矿体随时间等因素变化提出了一种新的研究思路;（3）对分段富集规律有了新的认识,将其应用范围从平面域扩展到空间领域,进而更好地预测隐伏矿体。  相似文献   

广义非线性强度理论形状参数研究     

罗汀  赵翔 《岩土力学》2007,28(3):555-559

姚仰平等提出的广义非线性强度理论,将各种摩擦材料的非线性强度理论统一起来,使统一后的非线性强度理论能够合理地反映各类摩擦材料的强度特性。在广义非线性强度理论体系中,形状参数?是影响在?平面上破坏曲线形状的重要因素之一,因此,需要对形状参数进行如下研究：（1）将广义非线性理论应用于各类砂土中,根据其在?平面上破坏曲线特性,在判断该破坏曲线凹凸的基础上,得到砂土形状参数?临界值与破坏应力比参数Mf之间的关系;（2）通过对几个经典砂土真三轴试验结果的整理,验证广义非线性强度理论对砂土破坏特性的预测能力,并在此基础上建立该理论中形状参数?和破坏应力比参数Mf的线性关系。因此,在实际应用时,仅通过三轴压缩试验即可得到三维应力条件下的强度包线。  相似文献