水库优化调度中的异轨同效问题

针对确定性水库优化调度问题,引入近似最短路径方法,寻求优化调度的近似最优解,从而证实"异轨同效"现象存在的可能性。借鉴流域水文模型的"异参同效"研究成果,视隐随机调度问题中的调度规则参数为具有概率分布特征的参数,视调度目标函数为似然函数,采用贝叶斯方法估计最优调度轨迹的区间分布,开展水库调度的最优调度轨迹的等效性研究。实例分析结果表明:进行水库优化调度的"异轨同效"研究,可以估计最优调度轨迹区间,从而将传统调度的单点决策转变为区间决策,更符合调度操作实际情况。     

水文频率计算研究面临的挑战与建议

水文频率计算是水文分析计算的主要内容之一，是各类涉水工程规划、设计确定工程规模和管理决策的主要依据。经过１４０多年的研究和实践，水文频率计算已经形成较为完整的理论体系与方法。包括:水文样本选择和数据检验、经验频率计算、频率分布函数选取、分布函数参数估计、分布模型检验、设计值计算和设计值不确定性分析。所有这些支撑了涉水工程的规划、设计和管理。根据国内外有关研究进展，总结了水文序列频率计算的前提条件、频率分布函数和参数计算方法。从水文频率分布函数选择、水文数据、分布函数参数计算、经验频率等方面分析了水文频率计算研究面临的挑战。在此基础上，提出了水文频率计算研究的一些建议，以期促进水文频率计算理论的进一步发展。     

变化环境下雅砻江流域水文极值演变及不确定性分析

为了探讨环境变化前后雅砻江流域的水文极值演变特征及不确定性,以雅砻江流域雅江水文站和洼里水文站为代表站,基于年极大值和超门限阈值样本,结合序列变异理论、多种极值统计模型(GEV、GPD、P-III)和轮廓似然函数参数估计及不确定性分析方法,分析了变化环境下雅砻江水文极值序列演变特征。结果表明:受气候变化和人类活动的影响,雅江水文站和洼里水文站环境变化前后的最优分布线型由P-III型分布转变为GEV分布。环境变化后的水文极值序列相应设计流量增大,重现期变小。设计值估算中,重现期越长,相应设计流量的不确定性也越大,其中参数的不确定性对于设计值的影响最为显著,但极值选样及分布函数的不确定性也不容忽视。轮廓似然函数法的使用可有效降低设计值不确定性,基于极值理论与轮廓似然函数估计法进行变化环境下水文极值演变分析可提高设计值的可靠性。研究成果可为雅砻江流域水库设计管理及防洪规划等提供参考。     

Excel在水文频率分析中的应用

水文频率分析是推求设计年径流、设计洪水的关键步骤。由于其大量繁琐的计算,很多水文专业人员对这部分内容掌握得不牢靠,影响了在工程实践中的实际应用。利用Excel内置的函数和工具,可以很快完成统计参数计算、配线、绘图,并可以求出最优统计参数,绘制最优理论频率曲线,提高水文工作人员使用现代工具进行水文分析计算的能力。     

球状理论变差函数模型与多时段泛克立格空间理论在插补延长水文数据中的应用

文章利用多时段泛克立格空间理论,针对扎兰屯市及周边流域水文气象站分布不均匀,水文数据在时间上缺测的特点,能够实现水文变量的最优估计和外推预测,检验统计参数全部在检验限度之内,插值结果与实测降雨量数据相比较,插值误差较小,精度较高,表明该理论可以实现流域降雨量的插补延长。     

用随机模型分析三峡年输沙量

矩法估算水文实测系列的统计参数存在抽样误差，随机模型可估算抽样误差，应用水文随机模拟方法，对三峡工程设计主要依据水文站屏山，寸滩，宜昌年输沙量进行随机模拟，估计了均值的抽样误差，并用均方误估计，累积平均和滑动平均等３种方法对随机模拟结果作了分析比较，结果表明，上述３站多年平均输沙量较稳定，以宜昌站多年平均输沙量５．３亿ｔ作为三峡工程泥沙设计的基本数值是合理的。     

东江流域气象干旱向水文干旱传递阈值研究

对不同干旱类型之间传递阈值研究可有效分析干旱传递的发生规律和机理,特别是对气象干旱向水文干旱传递阈值的研究。以东江流域为研究对象,计算月尺度的标准化降水指数SPI和标准化径流指数SRI,并基于游程理论识别干旱事件,提取干旱事件及其特征,包括干旱历时和干旱烈度。对发生时间全部或部分重叠的气象干旱事件和水文干旱事件进行匹配。对匹配后的干旱特征属性进行边缘分布拟合,验证气象干旱和水文干旱的历时或烈度之间的相关性,基于二变量Copula函数分别建立气象干旱与水文干旱特征的联合分布模型,计算不同气象干旱条件下不同等级水文干旱(中旱、重旱、极旱)发生的条件概率,取条件概率为0.95时对应的气象干旱历时或烈度值,作为气象干旱向该等级水文干旱传递的干旱历时(烈度)阈值。结果表明:东江流域气象干旱历时和烈度的最优拟合函数均为伽玛分布,水文干旱历时的最优拟合函数为伽玛分布,水文干旱烈度的边缘分布函数为广义正态分布。Gumbel-copula函数拟合干旱历时和烈度的效果较好。东江流域中旱、重旱、极旱等级的干旱历时传递阈值分别为6.9、8.3、9.4个月;干旱烈度的传递阈值分别为4.6、5.7、6.6。干旱传递阈值可以为水文干旱的预测以及防旱减灾的决策提供参考。     

比估计法在节水工程节水量计算中的应用

在大规模的节水工程中，用简单抽样方法抽取典型灌区，然后在典型灌区进行实地的精确观测和研究计算。运用统计方法中较复杂的非线性估计中的比估计，计算各个中间值并对中间值进行处理分析。通过辅助函数，寻求最优权系数，从而得到均方差最小的估计值，并求出置信区间。从而完成对整体总和的最优估计，以及量化这种估计的偏离概率。     

随机梯度法在新安江模型参数 优选中的应用

基于近似梯度法及模式搜索法,提出了复合两种方法的随机优化方法。以Nash确定性系数为目标函数,对新安江模型的参数空间随机搜索后运用梯度法进行了优化,然后采用参数空间筛选策略,以获得全局最优解集。上述方法结合导数信息和随机性质的算法,使优化方法脱离局部极小解从而达到近似全局最优解集。以杨楼单元流域为应用实例进行了研究,结果表明,随机梯度法可以成功地率定概念性水文模型参数。     

利用加权回归方程外延水文变量

以加权残差平方和为目标函数,根据最小二乘法原理给出了估计(等权)一元线性回归模型中两个参数的新的估值公式,建立了加权回归方程,并证明了这种新估值公式的无偏性。用Monte-Carlo(蒙特卡罗)方法找出了“最优权重”值,并进行了实际对比计算,说明用来外延水文变量的优越性。     

Stochastic simulation of fluid flow in porous media by the complex variable expression method

A stochastic simulation of fluid flow in porous media using a complex variable expression method (SFCM) is presented in this paper. Hydraulic conductivity is considered as a random variable and is then expressed in complex variable form, the real part of which is a deterministic value and the imaginary part is a variable value. The stochastic seepage flow is simulated with the SFCM and is compared with the results calculated with the Monte Carlo stochastic finite element method. In using the Monte Carlo method to simulate the stochastic seepage flow field, the hydraulic conductivity is assumed in three different probability distributions using random sampling method. The obtained seepage flow field is examined through skewness analysis, and the skewed distribution probability density function is given. The head mode value and the head comprehensive standard deviation are used to represent the statistics of calculation results obtained by the Monte Carlo method. The stochastic seepage flow field simulated by the SFCM is confirmed to be similar to that given by the Monte Carlo method from numerical aspects. The range of coefficient of variation of hydraulic conductivity in SFCM is larger than used previously in stochastic seepage flow field simulations, and the computation time is short. The results proved that the SFCM is a convenient calculating method for solving the complex problems.     

随机有限元与最大熵法联合求混凝土拱坝可靠度

将拱坝的主要荷载及材料参数看作随机变量，并考虑其相关性，以Ansys5．7随机有限元作为一个模块，结合某拱坝进行了蒙特卡罗随机模拟，得出拱坝各响应量(随机变量)的统计量，以及随机变量对功能函数的敏感性，再利用最大熵法得到各随机变量的概率密度函数，然后用数值积分求得拱坝可靠度指标的分布．     

A Novel Solution for Stochastic Dynamic Game of Water Allocation from a Reservoir Using Collocation Method

In this study, a continuous model of stochastic dynamic game for water allocation from a reservoir system was developed. The continuous random variable of inflow in the state transition function was replaced with a discrete approximant rather than using the mean of the random variable as is done in a continuous model of deterministic dynamic game. As a result, a new solution method was used to solve the stochastic model of game based on collocation method. The collocation method was introduced as an alternative to linear-quadratic (LQ) approximation methods to resolve a dynamic model of game. The collocation method is not limited to the first and second degree approximations, compared to LQ approximation, i.e. Ricatti equations. Furthermore, in spite of LQ related problems, consideration of the stochastic nature of game on the action variables in the collocation method would be possible. The proposed solution method was applied to the real case of reservoir operation, which typically requires considering the effect of uncertainty on decision variables. The results of the solution of the stochastic model of game are compared with the results of a deterministic solution of game, a classical stochastic dynamic programming model (e.g. Bayesian Stochastic Dynamic Programming model, BSDP), and a discrete stochastic dynamic game model (PSDNG). By comparing the results of alternative methods, it is shown that the proposed solution method of stochastic dynamic game is quite capable of providing appropriate reservoir operating policies.     

双决策变量法在水电站优化调度中的应用

对调度模型以隐随机优化为基本途径求解，采用两个决策变量，用传统最小二乘法及水能计算方法，寻求合理、有效的水电站优化调度规则。通过实例计算表明：双决策调度实际应用所得的经济效益明显优于常规调度。     

随机波浪力连续场的降维模拟

根据水质点的水平速度和加速度过程的功率谱密度,利用线性化的Morison方程,从平稳随机过程自相关函数的角度推导了随机波浪力的功率谱密度函数。在平稳随机过程的源谱表达基础上,通过将标准正交随机变量集定义为仅含1个基本随机变量的正交函数形式,实现了随机波浪力连续场的降维模拟。同时,结合快速傅里叶变换（FFT）技术,给出了随机波浪力连续场降维模拟的快速算法。应用该方法对某一单个小尺度直立圆柱桩所受的随机波浪力进行模拟,给出了随机波浪力过程的均值、标准差、自相关函数及互相关函数等数值特征,并与Monte Carlo方法的结果进行对比分析。研究表明,降维模拟方法具有较高的模拟精度与效率。     

Stochastic back analysis of permeability coefficient using generalized Bayesian method

Owing to the fact that the conventional deterministic back analysis of the permeability coefficient cannot reflect the uncertainties of parameters, including the hydraulic head at the boundary, the permeability coefficient and measured hydraulic head, a stochastic back analysis taking consideration of uncertainties of parameters was performed using the generalized Bayesian method. Based on the stochastic finite element method （SFEM） for a seepage field, the variable metric algorithm and the generalized Bayesian method, formulas for stochastic back analysis of the permeability coefficient were derived. A case study of seepage analysis of a sluice foundation was performed to illustrate the proposed method. The results indicate that, with the generalized Bayesian method that considers the uncertainties of measured hydraulic head, the permeability coefficient and the hydraulic head at the boundary, both the mean and standard deviation of the permeability coefficient can be obtained and the standard deviation is less than that obtained by the conventional Bayesian method. Therefore, the present method is valid and applicable.     

广义Bayes法在裂隙岩体渗透系数随机反演中的应用

工程中由于存在各种随机因素,采用确定性的渗流分析方法进行渗透系数的反演必然会导致结果的不确定性.本文基于渗流场的随机有限元分析方法,结合变尺度优化算法和广义Bayes法,建立了一种渗透系数的随机反演方法,推导了详细的计算公式.该方法不仅考虑量测水头、渗透系数的随机性,还考虑了边界水头的随机性,不仅可以获得渗透系数的均值反演结果,还可以得到标准差的反演结果.最后将该法应用于重力坝坝基渗流算例分析中,以渗流有限元正分析计算结果作为"假想"的实测点水头值,通过随机反演,同时获得渗透系数均值与标准差的反演结果,将输入信息与反演结果对比分析,验证了渗透系数和标准差反演结果的正确性.     

用任意加密有限元剖分的方法研究拱坝强度裂缝的产状

本文建立了强度裂缝产状和应力状态的解析关系。建立了面相关单元、线(棱)相关单元和单元细分的相关级差的概念，利用两种任意结点数的三维等参单元和两种任意结点数的二维等参单元的研究结果，在相关级差等于1的约束下，建立了任意加密有限元剖分网格的三维随机有限元自适应算法。应用上述研究结果，解决了拱坝强度裂缝产状的精细算法。本文最后给出了一个算例，讨论了研究成果在控制拱坝强度裂缝发展和拱坝诱导缝的理性设置方面的应用。     

水环境风险评价的随机模拟与三角模糊数耦合模型

探讨了将三角模糊数理论用于描述和处理水环境风险评价系统中的随机性、模糊性,以及资料信息的不完整、不精确性等不确定性特征的具体实现途径。采用Monte Carlo方法模拟三角模糊数,把三角模糊数及其函数之间的运算转化为普通的实数之间的运算,建立了水环境风险评价的随机模拟与三角模糊数耦合模型(SS-TFN)。应用结果表明:SS-TFN通过Monte Carlo方法可得到水环境系统的质量状态变量的大量模拟序列,其计算结果比三角模糊数的截集技术的计算结果更简便、全面和合理;用SS-TFN通过调整水环境系统的质量状态变量的控制参数,可方便地获得水环境风险管理的对策方案。     

A Modified Constrained State Formulation of Stochastic Soil Moisture for Crop Water Allocation

In response to uncertainty in crop water allocation, several methodologies have been proposed in the literature, most of them considering rainfall as a stochastic variable affecting soil moisture. A methodology considering uncertainties both in irrigation depth and soil moisture is more realistic for irrigated crops as developed here using an explicit stochastic optimization model. This new work is based on an earlier constrained state formulation which did not consider the irrigation depth as stochastic. In constrained state formulation methods, the first and second moments of state variables are developed considering the uncertainties which are then used as constraints in an optimization model. In contrast to alternative methods that are dynamic programming-based, the proposed optimization method can be solved using standard nonlinear optimization tools. Performance of the proposed model is evaluated for the case of two different crops, winter wheat and barley. Model verification is performed by comparing the results with simulation results. The model is quite acceptable and shows considerable improvement over analogous models.