计及PMU的混合非线性状态估计新方法

提出一种将同步相量测量单元（PMU）的直接电压相量量测变换为间接支路电流量测，并与监控与数据采集（SCADA）量测量一起进行混合迭代的非线性状态估计方法。对构造等效电流修正量而带来的间接量测误差进行了详细和定量的分析，并对该混合估计算法的精度进行了定性分析和定量计算。理论分析和算例表明，该方法可以获得较高的估计精度，在收敛次数和滤波效果上也有所改进。     

A New Precipitation Prediction Method Based on CEEMDAN-IWOA-BP Coupling

Water Resources Management - Precipitation is the most basic part of the water cycle process. Aiming at the problem of low prediction accuracy caused by the nonlinear and unstable characteristics...     

基于EEMD方法的区域降水事件特征分析——以京津冀地区为例

区域降水事件特征影响水循环,进而对社会经济各个方面有着深远的影响.京津冀地区是我国的政治、经济、文化中心,水旱灾害频发,亟需全面了解该地区区域降水事件特征.以京津冀地区173个气象站1989-2018年间逐日降水数据为基础,共识别出552次区域降水事件,采用集合经验模态分解(EEMD)等方法,从持续时间、覆盖范围、降水...     

A Heuristic Gap Filling Method for Daily Precipitation Series

The gap filling is common practice to complete hydrological data series without missing values for environmental simulations and water resources modeling in a changing climate. However, gap filling processes are often cumbersome because physical constraints, such as complex terrain and density of weather stations, often limit the ability to improve the performance. Although several studies of gap filling methods have been developed and improved by researchers, it is still challenging to find the best gap filling method for broad applications. This research explores a gap filling method to improve climate data estimates (e.g., daily precipitation) using gamma distribution function with statistical correlation (GSC) in conjunction with cluster analysis (CA). The daily dataset at the source stations (SSs) is utilized to estimate missing values at the target stations (TSs) in the study area. Three standard gap filling methods, including Inverse Distance Weight (IDW), Ordinary Kriging (OK), and Gauge Mean Estimator (GME) are evaluated along with cluster analysis based on statistical measures (RMSE, MAE, R) and skill scores (HSS, PSS, CSI). The result indicates that cluster analysis can improve estimation performances regardless of the gap filling methods used. However, the GSC method associated with cluster analysis, in particular, outperformed other methods when the performance comparison task was conducted under rain and no-rain conditions in the study area. The proposed method, GSC, therefore, will be used as a case toward advancing gap filling methods in the field.     

A New Estimation Method for Copula Parameters for Multivariate Hydrological Frequency Analysis With Small Sample Sizes

Water Resources Management - Multivariate hydrological frequency analysis is important when designing hydraulic and civil infrastructures. However, hydrologic data scarcity and insufficiency are...     

Regional Models for the Estimation of Streamflow Series in Ungauged Basins

The assessment of water resources in a region usually must cope with a general lack of data, both in time (short observed series) as well as in space (ungauged basins). Such a lack of data is generally overcome by combining rainfall–runoff models with regionalization techniques in order to transfer information to sites without or with short available observed series. The present paper aims to analyze applicability and limitations of two regionalization procedures for estimating the parameters of simple rainfall–runoff models respectively based on a “two-step” and on a “one-step” approach, for the estimation of monthly streamflow series in ungauged basins. In particular, an application to a Sicilian river basin of multiple regression equations according to a “two-step” and a “one-step” approaches and of a “one-step” approach based on neural networks is reported. For the investigated region, results indicate that models based on the “one-step” approach appear to be robust and adequate for estimating the streamflows in ungauged basins.     

定量遥感蒸散研究进展及关键问题

遥感技术为区域蒸散的定量提供了有效手段,在综述了国内外定量遥感蒸散研究概况的基础上,比较分析了目前较常用的几种遥感蒸散模型,并指出同类研究在地表温度与空气动力学温度差异、阻抗、平流、尺度效应及结果验证等方面存在一些问题,提出了提高定量遥感蒸散计算精度的具体措施,包括:运用高光谱提高地表温度反演精度;加强对瞬时地表蒸散转换为日总蒸散的研究;运用微波遥感解决阴雨天的地表蒸散;提高净辐射通量反演精度;借助动力学过程模型进行地表蒸散反演的研究;加强地面定标和试验遥感的研究等。     

基于测量不确定度的电力系统状态估计（二）方法研究

基于正常测点概念构造了相应测点评价函数,用于评价测点是正常测点还是异常测点;在此基础上,提出了以测点正常率最大为目标函数的状态估计新模型。为使估计结果更接近于实际运行情况,模型中可考虑潮流约束和实际物理约束。用现代内点法求解该模型,计算速度快,收敛性好。与以往方法相比,文中所述方法的状态估计结果测点正常率高,可自动辨识不良数据,估计结果不易受不良数据影响,有较强的抗差性;所求得的解为潮流解,满足各种物理约束,更加接近实际;计算中无需进行不良数据检验,无需主观设定测点权重,大幅度减少了调试和维护工作量。     

低扬程水泵选型新方法

通过理论分析和模型试验 ,研究泵与泵装置特性的关系 .进出水管道水力损失占泵站净扬程的比重越大 ,泵装置最高效率点的流量越小 ,而泵装置最高效率点的扬程与最高效率点的泵段扬程基本一致 .为保证泵装置运行在高效率点 ,所选用泵的扬程应与泵站净扬程相当 ,而流量必须加大 ,据此提出泵的等扬程加大流量选型方法     

A New Method for Joint Frequency Analysis of Modified Precipitation Anomaly Percentage and Streamflow Drought Index Based on the Conditional Density of Copula Functions

In this study, a new method was proposed to model the occurrence of related variables based on the conditional density of copula functions. The proposed method was adopted to investigate the dynamics of meteorological and hydrological droughts in the Zarinehroud basin, southeast of Lake Urmia, during the period 1994–2015. For this purpose, the modified precipitation anomaly percentage and streamflow drought indices were extracted. Finally, the joint frequency analysis of duration-duration and severity-severity characteristics of meteorological and hydrological droughts was analyzed. Analysis of 7 different copulas used to create the joint distribution in the Zarinehroud basin indicated that the Frank copula had the best performance in describing the relationship between the meteorological and hydrological drought severities and durations. By examining the results of the bivariate analysis of duration-duration of meteorological and hydrological droughts at different stations, the expected meteorological and hydrological drought durations were estimated in the years ahead. For example, at Chalkhmaz station, 4- to 7-month duration for the hydrological drought and 9- to 12-month duration for the meteorological drought is expected in the years ahead. The joint frequency analysis of drought characteristics allows to determine the meteorological and hydrological drought characteristics at a single station at the same time using joint probabilities. Also, the results indicated that by knowing the conditional density, the hydrological drought characteristics can be easily estimated for the given meteorological drought characteristics. This could provide users and researchers useful information about the probabilistic behavior of drought characteristics for optimal operation of surface water.

     

对流方程的一种新数值解法

运用修正局部 Crank-Nicolson 方法解流方程, 得到了一种新的计算简单、无条件稳定的显式格式. 计算结果表明, 新格式的计算结果与精确解吻合较好, 与原 Crank-Nicolson 格式相比计算误差明显改善.     

多路换向阀流道数值模拟的一种新方法——代数应力模型

本文根据Ｎａｉｖｅｒ－Ｓｔｏｋｅｓ方程推导一种比传统数学方法更优越的代数应力模型，这种模型除了能计算出传统的速度和压力外，它还能计算出紊动能和紊动耗散率等。对多路换向阀的流道进行数值模拟的结果与实验结果相比，吻合较好，因此可以证明这是研究液压阀流道的一种很有效的数值方法。     

Development of a New Quantile-Based Method for the Assessment of Regional Water Resources in a Highly-Regulated River Basin

Water Resources Management - In this paper, we present a study of assessing regional water resources in a highly regulated river basin, the Dee river basin in the UK. The aims of this study...     

新法培育大规格鱼种试验

采用新法—昼夜按温投饵的方法来延长鱼的生长期，克服北方地区生长期短的缺点，培育出大规格的鱼种，提高经济效益。     

黄河下游平滩流量的估算方法

在以往关于平滩流量研究的基础上,建立了黄河下游沿程主要测站平滩流量的估算方法,即在已知小浪底、黑石关、小董3站设计水沙条件的情况下,首先根据设计沿程引水量得到下游沿程各站的汛期水量,然后计算沿程各站的汛期输沙量,进而利用滑动平均法或滞后响应模型计算下游沿程各站的平滩流量。该方法简单实用,计算结果与数学模型计算结果基本一致。     

A New Weighting Scheme for Diminishing the Effect of Extreme Values in Regional Drought Analysis

Water Resources Management - Climate warming has increased the risk of recurrent drought hazards. Previous research has indicated potential associations between climate warming and extreme climate...     

Precipitation Estimation Using Support Vector Machine with Discrete Wavelet Transform

Precipitation prediction is of dispensable importance in many hydrological applications. In this study, monthly precipitation data sets from Serbia for the period 1946–2012 were used to estimate precipitation. To fulfil this objective, three mathematical techniques named artificial neural network (ANN), genetic programming (GP) and support vector machine with wavelet transform algorithm (WT-SVM) were applied. The mean absolute error (MAE), mean absolute percentage error (MAPE), root mean square error (RMSE), Pearson correlation coefficient (r) and coefficient of determination (R²) were used to evaluate the performance of the WT-SVM, GP and ANN models. The achieved results demonstrate that the WT-SVM outperforms the GP and ANN models for estimating monthly precipitation.     

Long-term Precipitation Estimation Combining Time-Series Retrospective Forecasting and Downscaling-Calibration Procedure

Water Resources Management - Long-term precipitation datasets with high spatial resolution are crucial for hydrological, meteorological, and ecological research. However, due to the coarse spatial...     

以合格率最大为目标的电力系统状态估计新方法

以合格率最大为目标,考虑潮流约束和运行中上下界约束,提出一种电力系统状态估计方法。该方法可用现代内点法求解,收敛性好。与以往方法相比,文中方法得到的状态估计结果合格率高;估计结果有较强的抗差性;所求的解为潮流解,满足各种物理约束,更加接近实际;计算中无需做坏数据检验、可观性校验,无需主观设定测点权重,大幅减少了调试和维护工作量。IEEE 39节点系统、IEEE 118节点系统和某实际输电网等试验系统的测试结果验证了该方法的优越性。