Pulse generation models for daily intermittent streamflows / Modèles de génération d’impulsions pour des débits journaliers intermittents     

《水文科学杂志》2013,58(3)

Abstract

Abstract Generating pulses and then converting them into flow are two main steps of daily streamflow generation. Three pulse generation models have been proposed on the basis of Markov chains for the purpose of generating daily intermittent streamflow time series in this study. The first one is based on two two-state Markov chains, whereas the second uses a three-state Markov chain. The third model uses harmonic analysis and fits Fourier series to the three-state Markov chain. Results for a daily intermittent streamflow data series show a good performance of the proposed models.  相似文献   

Daily variability of river concentrations and fluxes: indicators based on the segmentation of the rating curve     

Michel Meybeck  Florentina Moatar 《水文研究》2012,26(8):1188-1207

The variability of water chemistry on a daily scale is rarely addressed due to the lack of records. Appropriate tools, such as typologies and dimensionless indicators, which permit comparisons between stations and between river materials, are missing. Such tools are developed here for daily concentrations (C), specific fluxes or yields (Y) and specific river flow (q). The data set includes 128 long‐term daily records, for suspended particulate matter (SPM), total dissolved solids (TDS), dissolved and total nutrients, totalling 1236 years of records. These 86 river basins (10³–10⁶ km²) cover a wide range of environmental conditions in semi‐arid and temperate regions. The segmentation—truncation of C–q rating curves into two parts at median flows (q₅₀) generates two exponents (b_50inf and b_50sup) that are different for 66% of the analysed rating curves. After segmentation, the analysis of records results in the definition of nine major C–q types combining concentrating, diluting or stable patterns, showing inflexions, chevron and U shapes. SPM and TDS are preferentially distributed among a few types, while dissolved and total nutrients are more widely distributed. Four dimensionless indicators of daily variability combine median (C₅₀, Y₅₀), extreme (C₉₉, Y₉₉) and flow‐weighted (C*, Y*) concentrations and yields (e.g. C₉₉/C₅₀, Y*/Y₅₀). They vary over two to four orders of magnitude in the analysed records, discriminating stations and river material. A second set of four indicators of relative variability [e.g. (Y*/Y₅₀)/(q*/q₅₀)], takes into account the daily flow variability, as expressed by q*/q₅₀ and q₉₉/q₅₀, which also vary over multiple orders of magnitude. The truncated exponent b_50sup is used to describe fluxes at higher flows accounting for 75% (TDS) to 97% (SPM) of interannual fluxes. It ranges from ? 0·61 to + 1·86 in the database. It can be regarded as the key amplificator (positive b_50sup) or reductor (negative b_50sup) of concentrations or yields variability. C₅₀, Y₅₀, b_50sup can also be estimated in discrete surveys, which provides a new perspective for quantifying and mapping water quality variability at daily scale. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

焦耳效应标定高温卡尔维微量热计     

Tang Yuanjun Tan Dafang Mao Yi 《地球科学》1989,(3)

根据热流式量热计的Tian氏方程,用焦耳效应标定高温卡尔维微量热计。用偏差法得到的灵敏度值与积分法测得的值一致。用回归曲线对灵敏度实验值进行拟合,利用计算机求得灵敏度—温度回归曲线,得到了室温至700℃的全部灵敏度值,从而即可使用微量热计测量此温度范围内的未知样品热效应。  相似文献   

位场DFT算法研究   总被引：5，自引：0，他引：5       下载免费PDF全文

柴玉璞 《地球物理学报》1988,31(2):211-224

本文推广了经典的抽样定理,并据此导出了函数有限离散傅里叶变换误差方程（简称DFT误差方程,下同）。该方程把有限离散傅里叶变换中固有的离散效应和有限效应表示为确切的数学形式。离散效应被表示为一个含整参变量（参变量取0,1,…,N-1）的复无穷级数;有限效应被表示为一个含整参变量（参变量取0,1,…,N-1）的复无穷级数的DFT。 基于DFT误差方程和位函数特点,作者提出了两种位场数值傅里叶变换新算法--移样法和等效源续尾叠样法。移样法可近百倍地提高位场数值傅里叶反变换的精度,等效源续尾叠样法可数十倍地提高正变换精度。两种算法都不需要增加资料长度和取样密度,因而基本不需要增加计算机时间和内存。文中给出了算例。  相似文献   

钻孔走向偏斜的初步探讨     

周裕经 《上海国土资源》1988,(2)

在急倾斜构造部位大力使用硬合金回转钻进时,常常会产生弯曲度很大的走向偏斜情况。这是因为不同岩层的阻力差异使钻头受到一种平行于岩层走向的偏斜力,迫使钻头向侧方研磨井壁;在不同井径变换部位所产生的偏斜效果是不同的。这样造成钻孔沿地层走向发生有规律的定向偏斜。  相似文献   

晶体点阵参数最小二乘法计算程序     

陈蓉美 《湖南地质》1990,9(1):54-59

作者以最小二乘法理法导出了晶体点阵参数计算的公式,并顾及了X射线粉晶衍射图测定所引起的系统误差修正,从而得到点阵参数的最佳估值。以导出的公式为数学模型编制了PC-1500微机的扩展BASIC语言程序,可适用于各晶系点阵参数的计算,使用方便。  相似文献   

Location　of　Tibetan　earthquakes──a　nonlinear　approach　by　a　simplex　optimized　technique   总被引：1，自引：0，他引：1  

赵珠  丁志峰  易桂喜  王建格 《地震学报(英文版)》1994,(2)

Ｌｏｃａｔｉｏｎ　ｏｆ　Ｔｉｂｅｔａｎ　ｅａｒｔｈｑｕａｋｅｓ──ａ　ｎｏｎｌｉｎｅａｒ　ａｐｐｒｏａｃｈ　ｂｙ　ａ　ｓｉｍｐｌｅｘ　ｏｐｔｉｍｉｚｅｄ　ｔｅｃｈｎｉｑｕｅ（赵珠）（丁志峰）（易桂喜／）（王建格）ＬｏｃａｔｉｏｎｏｆＴｉｂｅｔａｎｅａ...  相似文献   

折射波地震勘探中几个问题的探讨   总被引：1，自引：0，他引：1  

孟补在  黄玉国  赵国敏 《东北地震研究》1994,(4)

在多年实际工作的基础上，从理论上对工作中的观测系统、资料处理方法、断层、ｔ。闭合等四个方面论述了存在的问题及相应的解决方法。  相似文献   

近海多种卫星测高联合数据处理技术     

高永泉  章传银 《测绘科学》2002,27(2):20-25

海域海况复杂多变 ,潮汐不但受外海能量输入的控制 ,而且在复杂的海岸线、浅海海底和内陆河流运输的作用下变得异常复杂。卫星测高由于受复杂的海洋动力环境和陆地反射的影响 ,数据质量普遍较深海差。将多种卫星测高数据联合处理 ,可以大大提高近海海域平均海面高的精度与分辨率 ,增强测高卫星监测近海复杂动力现象与反演近海复杂动力机制的能力。本文讨论近海多种卫星联合数据处理的技术与方法 ,分别从提取海平面稳态和时变信息的角度较系统地研究了多种卫星测高联合数据处理方法 ,通过提取不同测高卫星海平面观测数据中与时间无关的系统偏差 ,建立多种卫星测高数据的海平面时变基准 ,从而将多种测高卫星海面监测数据融合到一个动力系统中。大大提高测高卫星海平面监测的时空分辨率 ,为联合多种卫星测高数据在大地测量与近海海洋动力学研究中的应用创造基本条件。  相似文献   

湖南土地资源可持续利用的生态安全评价   总被引：41，自引：0，他引：41  

张建新  邢旭东等 《湖南地质》2002,21(2):119-121

生态安全是土地可持续利用的基础，土地生态安全评价是土地可持续利用研究的前沿课题。以湖南省14个地州市为样本，从1999年社会经济和土地生态环境压力、土地生态环境质量、土地生态环境保护和整治能力等方面的运行数据中选取人口密度、城镇化水平、人均耕地等24个指标，采用均方差客观赋权，从各指标的统计特征值及全国的平均值出发，确定本省的生态安全评价阈值S，计算各地市多指标加权综合评价值，试图对本省土地生态安全进行客观综合评价。  相似文献