基于 PSTA2003状态监测系统的水布垭电厂机组运行状况分析

基于PSTA2003状态监测及趋势分析系统和水布垭电厂机组运行积累的数据,通过对比、平滑拟合和作各种曲线图形等分析方法,分析不同机组在各种条件下运行工况的表现,并重点对不同水头下机组的运行状况进行了分析,有利于指导电厂的机组运行、维护检修和保障机组的安全经济运行。     

场地受限条件下大跨度门式 启闭机安装实例

通过对特定的门式启闭机安装场地条件进行实地考查,列出了场地条件对其安装作业存在的不利因素。在分析研究了由于场地存在的不利因素对门式启闭机安装造成的难题后,有针对性地制定了安装技术措施,从而保证了安装作业过程安全、实施顺利。本文可供类似场地条件的门式启闭机安装施工作业参考。     

黄河下游河道冲淤平衡临界水流能量损失研究

从河流能量损失的角度入手,采用理论研究和资料分析相结合的手段,研究了黄河下游河道(花园口-利津)河流能量损失与河道冲淤的相关关系,研究结果表明:河流一般能量损失(如机械能损失、动能损失、势能损失)和动量损失与黄河下游河道年冲淤量之间不存在相关关系;而河流有用功损失、推移功损失与河道年冲淤量之间相关性不明显,但河流悬浮功损失与黄河下游河道年冲淤量之间存在较为明显的相关关系;维持黄河下游河道(花园口-利津)冲淤平衡的能量损失临界条件是水文年内河流悬浮功损失0.75亿J.当悬浮功损失大于此临界值,下游河道将发生淤积;小于此临界值,下游河道将发生冲刷.     

保水剂对草坪土壤持水特性影响研究

为了探明保水剂对草地种植条件下土壤水分特征曲线的影响,基于王全九等开发的入渗特性法进行了土壤水平入渗试验,得出了在草坪土壤中施用不同浓度保水剂的Brooks-Corey土壤水分特征曲线。结果表明：在低吸力段,相同水势下土壤含水量随保水剂施用浓度增大而增大,在高吸力段,相同水势下土壤含水量随保水剂施用浓度增大而减小;在0~1 bar范围内,施用保水剂处理的土壤水分特征曲线均匀降低,表明施用保水剂能够稳定而有效地供给植物所需水分。本研究可以为制定城市绿地草坪合理的灌溉制度和在草坪种植中合理推广使用保水剂提供理论依据。     

调水工程输水渠道堰闸流量计算方法探讨

调水工程输水渠道堰闸流量计算方法的准确性是运行调度数字化、信息化的关键水力条件。传统的堰闸流量计算方法是先进行孔流、堰流判别,再根据相应的经验公式进行计算,其孔、堰流判断条件为闸门的相对开度e/H。经试验研究及理论分析论证认为:传统计算公式中以e/H=0.65作为宽顶堰孔流与堰流的判断条件,仅适用于自由出流状态。调水工程输水渠道堰闸工程正常运行条件一般为大淹没孔流,传统方法计算流量误差较大。通过系列模型试验数据的拟合,提出了特定条件下调水工程堰闸流量计算方法。     

Numerical implementation of the asymptotic boundary conditions for steadily propagating 2D solitons of Boussinesq type equations

In the present paper, a difference scheme on a non-uniform grid is constructed for the stationary propagating localized waves of the 2D Boussinesq equation in an infinite region. Using an argument stemming form a perturbation expansion for small wave phase speeds, the asymptotic decay of the wave profile is identified as second-order algebraic. For algebraically decaying solution a new kind of nonlocal boundary condition is derived, which allows to rigorously project the asymptotic boundary condition at the boundary of a finite-size computational box. The difference approximation of this condition together with the bifurcation condition complete the algorithm. Numerous numerical validations are performed and it is shown that the results comply with the second-order estimate for the truncation error even at the boundary lines of the grid. Results are obtained for different values of the so-called ‘rotational inertia’ and for different subcritical phase speeds. It is found that the limits of existence of the 2D solution roughly correspond to the similar limits on the phase speed that ensure the existence of subcritical 1D stationary propagating waves of the Boussinesq equation.     

On local convergence of a Newton-type method in Banach space

In this study we are concerned with the local convergence of a Newton-type method introduced by us [I.K. Argyros and D. Chen, On the midpoint iterative method for solving nonlinear equations in Banach spaces, Appl. Math. Lett. 5 (1992), pp. 7–9.] for approximating a solution of a nonlinear equation in a Banach space setting. This method has also been studied by Homeier [H.H.H. Homeier, A modified Newton method for rootfinding with cubic convergence, J. Comput. Appl. Math. 157 (2003), pp. 227–230.] and Özban [A.Y. Özban, Some new variants of Newton's method, Appl. Math. Lett. 17 (2004), pp. 677–682.] in real or complex space. The benefits of using this method over other methods using the same information have been explained in [I.K. Argyros, Computational theory of iterative methods, in Studies in Computational Mathematics, Vol. 15, C.K. Chui and L. Wuytack, eds., Elsevier Science Inc., New York, USA, 2007.; I.K. Argyros and D. Chen, On the midpoint iterative method for solving nonlinear equations in Banach spaces, Appl. Math. Lett. 5 (1992), pp. 7–9.; H.H.H. Homeier, A modified Newton method for rootfinding with cubic convergence, J. Comput. Appl. Math. 157 (2003), pp. 227–230.; A.Y. Özban, Some new variants of Newton's method, Appl. Math. Lett. 17 (2004), pp. 677–682.]. Here, we give the convergence radii for this method under a type of weak Lipschitz conditions proven to be fruitful by Wang in the case of Newton's method [X. Wang, Convergence of Newton's method and inverse function in Banach space, Math. Comput. 68 (1999), pp. 169–186 and X. Wang, Convergence of Newton's method and uniqueness of the solution of equations in Banach space, IMA J. Numer. Anal. 20 (2000), pp. 123–134.]. Numerical examples are also provided.     

Parallel iteratively regularized Gauss–Newton method for systems of nonlinear ill-posed equations

We propose a parallel version of the iteratively regularized Gauss–Newton method for solving a system of ill-posed equations. Under certain widely used assumptions, the convergence rate of the parallel method is established. Numerical experiments show that the parallel iteratively regularized Gauss–Newton method is computationally convenient for dealing with underdetermined systems of nonlinear equations on parallel computers, especially when the number of unknowns is much larger than that of equations.     

Coefficient regularized regression with non-iid sampling

In this paper, we study a more general kernel regression learning with coefficient regularization. A non-iid setting is considered, where the sequence of probability measures for sampling is not identical but the sequence of marginal distributions for sampling converges exponentially fast in the dual of a Holder space; the sampling z _i , i ≥ 1 are weakly dependent, which satisfy a strongly mixing condition. Satisfactory capacity independently error bounds and learning rates are derived by the techniques of integral operator for this learning algorithm.     

The improved split-step backward Euler method for stochastic differential delay equations

A new, improved split-step backward Euler method is introduced and analysed for stochastic differential delay equations (SDDEs) with generic variable delay. The method is proved to be convergent in the mean-square sense under conditions (Assumption 3.1) that the diffusion coefficient g(x, y) is globally Lipschitz in both x and y, but the drift coefficient f(x, y) satisfies the one-sided Lipschitz condition in x and globally Lipschitz in y. Further, the exponential mean-square stability of the proposed method is investigated for SDDEs that have a negative one-sided Lipschitz constant. Our results show that the method has the unconditional stability property, in the sense, that it can well reproduce stability of the underlying system, without any restrictions on stepsize h. Numerical experiments and comparisons with existing methods for SDDEs illustrate the computational efficiency of our method.