Evaluation of suspended load transport rate using transport formulas and artificial neural network models （Case study： Chelchay Catchment）＊

Accurate estimation of sediment load or transport rate is very important to a wide range of water resources projects. This study was undertaken to determine the most appropriate model to predict suspended load in the Chelchay Watershed, northeast of Iran. In total, 59 data series were collected from four gravel bed-rivers and a sand bed river and two depth integrating suspended load samplers to evaluate nine suspended load formulas and feed forward backpropagation Artificial Neural Network (ANN) structures. Although the Chang formula with higher correlation coefficient (r = 0.69) and lower Root Mean Square Error (RMSE = 0.013) is the best suspended load predictor among the nine studied formulas, the ANN models significantly outperform traditional suspended load formulas and show their superior performance for all statistical parameters. Among different ANN structures two models including 4 inputs, 4 hidden and one output neurons, and 4 inputs, 4 and one hidden and one output neurons provide the best simulation with the RMSE values of 0.0009 and 0.001, respectively.     

口诀法快速绘制梁的内力图

绘制梁的内力图是正确设计和校核梁的关键步骤,其绘制方法虽有多种,但如何快速和准确的绘制,尚有待进一步探索,本文用实例阐述了用口诀法快速绘制梁内力图的步骤。     

ASYMPTOTIC BEHAVIOR OF DISTRIBUTION DENSITIES IN MODELS WITH STOCHASTIC VOLATILITY. I

We study the asymptotic behavior of distribution densities arising in stock price models with stochastic volatility. The main objects of our interest in the present paper are the density of time averages of a geometric Brownian motion and the density of the stock price process in the Hull–White model. We find explicit formulas for leading terms in asymptotic expansions of these densities and give error estimates. As an application of our results, sharp asymptotic formulas for the price of an Asian option are obtained.     

煤气流量测量过程中的公式导出和仪表实现

文章通过设备的调试、单体、连接和安装,对流量量程的差压、温度压力补偿、不同状态间的转换和参数的计算求出最佳的最适合煤气运用的方案。     

Ruin probabilities and optimal capital allocation for heterogeneous life annuity portfolios

A large part of the actuarial literature is devoted to the derivation of ruin probabilities in various non-life insurance risk models. On the contrary, very few papers deal with ruin probabilities for life insurance portfolios. The difficulties arise from the dependence and non-stationarity of the annual payments made by the insurance company. This paper shows that the ruin probability in case of life annuity portfolios can be computed from algorithms derived by De Pril (1989) and Dhaene & Vandebroek (1995). Approximations for ruin probabilities are discussed. The present article complements the works of Frostig et al. (2003) who considered whole life, endowment, and temporary assurances, and of Denuit & Frostig (2008) who considered homogeneous life annuities portfolios. Here, heterogeneous portfolios (with respect to age and/or face amounts) are studied. Particular attention is paid to the capital allocation problem. The total amount of reserve is shared among the risk classes in order to minimize the ruin probability. It is then fair to charge a higher margin to the risk classes requiring more capital.     

弧形坡脚梯形渠道实用经济断面计算方法的改进

简单介绍了弧形坡脚梯形渠道实用经济断面的计算式和计算方法．详细叙述了改进计算式的推导过程及计算方法．对改进计算式的验证结果表明,改进计算式的计算简单、可行．     

硫酸盐渍土盐胀机理及处理措施浅析

本文基于硫酸盐渍土室内试验结果,分析了硫酸盐渍土盐胀率的影响因素,提出了盐胀治理措施,为进一步治理盐胀病害提供了一定的理论基础。     

Finding Bayesian Optimal Designs for Nonlinear Models: A Semidefinite Programming‐Based Approach

This paper uses semidefinite programming (SDP) to construct Bayesian optimal design for nonlinear regression models. The setup here extends the formulation of the optimal designs problem as an SDP problem from linear to nonlinear models. Gaussian quadrature formulas (GQF) are used to compute the expectation in the Bayesian design criterion, such as D‐, A‐ or E‐optimality. As an illustrative example, we demonstrate the approach using the power‐logistic model and compare results in the literature. Additionally, we investigate how the optimal design is impacted by different discretising schemes for the design space, different amounts of uncertainty in the parameter values, different choices of GQF and different prior distributions for the vector of model parameters, including normal priors with and without correlated components. Further applications to find Bayesian D‐optimal designs with two regressors for a logistic model and a two‐variable generalised linear model with a gamma distributed response are discussed, and some limitations of our approach are noted.     

逐步图解法淹没式堰流公式推流的使用范围

堰闸水文站出现淹没式堰流时可以使用逐步图解法定线推流,但小水位差时用自记水位推流,计算流量的误差可能很大。通过对淹没式堰流计算流量的不确定度的分析计算,得到水位差的百分不确定度XΔz,根据计算流量的不确定度要求,推算得到满足计算流量不确定度要求的水位差的范围:对于开宽大于2.0 m、下游水头大于0.5 m的堰闸站出现淹没式堰流时,只有水位差大于0.14 m时,才能使用自记水位推流。