施工导流风险损失估量模型研究

施工导流作为水电工程的重要组成部分,其风险损失不仅是工程决策的依据,还是工程保险费率厘定的重要因素。在施工导流运行期,上游超标洪水导致围堰漫顶甚至基坑淹没,不仅导致经济损失,而且延误工期。为准确计算施工导流损失,根据工程施工进度和泄水条件将其分为施工导流系统损失、基坑系统损失和工期损失,并对各部分损失进行定义和量化计算,建立施工导流运行期损失模型。实例计算表明,该模型可为施工导流标准的选择和保险费率的厘定提供参考。     

上游水电站初期导流条件下下游水电站施工导流风险分析

上游水电工程初期导流围堰库容较大时,其调蓄削峰作用改变了施工洪水过程的天然属性。基于"大库-小库"梯级导流系统的独特性,建立上游水电站初期导流条件下施工导流风险数学模型。综合考虑施工洪水过程、水位库容、泄流能力不确定性,采用变倍比放大法模拟施工洪水过程,利用Monte-Carlo方法耦合各风险要素估计下游水电站施工导流风险。以西南地区某流域梯级水电工程为例,分析结果表明,风险模型及计算方法是有效的、适用的,并通过敏感性分析量化了各随机参数对导流风险的影响程度,为梯级导流方案的优化设计及风险决策提供了重要依据。     

白龙江苗家坝水电站泄洪消能设计

苗家坝水电站为二等大(2)型工程,拦河坝为混凝土面板堆石坝.工程身处深山峡谷,施工导流流量较大.在参考国内类似电站泄洪消能设计经验后,结合其水文泥沙、地形地质条件、施工导流、运行要求以及枢纽布置特点,泄洪建筑物最终采用由导流洞改建的"龙抬头"表孔溢洪洞 泄洪排沙洞组成,水工模型试验结果表明该方案是合理可行的.     

基于多重不确定性因素的施工导流风险分析

通过分析施工洪水过程中的洪峰流量、洪量和历时的不确定性．以及导流建筑物的水力参数的不确定性，确定施工洪水过程和导流建筑物泄流能力的模拟计算模型。运用Monte-Carlo方法模拟计算施工导流系统度汛各时段的状态参数，得到上游围堰堰前水位的分布函数，在此基础上确定导流系统的风险。通过实例验证比较说明，该研究方法和计算模型是可靠的、适用的。     

基于BP神经网络的施工导流风险评价

针对现阶段施工导流风险评价模型存在的不足,提出了采用BP神经网络定性与定量相结合的方法评价施工导流风险,构建了施工导流风险评价模型,并介绍了应用BP神经网络评价施工导流风险的操作步骤,以期为施工导流风险评价提供一种新途径.     

杨房沟水电站初期导流模型过流试验

杨房沟水电站工程施工导流采用围堰断流、隧洞导流方式,为进一步掌握施工初期导流阶段的水流条件,确定围堰和坝体的施工安全,进行了初期导流模型试验研究。通过模型试验,测试了导流隧洞的泄洪能力、水流流态、空化数及下游流速与河床的冲刷情况,验证导流隧洞过流安全。根据模型试验结果,进一步优化了围堰堰顶高程与导流隧洞进口的进水条件,为工程初期导流设计与施工组织提供了重要的指导作用。     

白龙江苗家坝水电站泄洪消能设计

苗家坝水电站为二等大（2）型工程，拦河坝为混凝土面板堆石坝。工程身处深山峡谷，施工导流流量较大。在参考国内类似电站泄洪消能设计经验后，结合其水文泥沙、地形地质条件、施工导流、运行要求以及枢纽布置特点，泄洪建筑物最终采用由导流洞改建的“龙抬头”表孔溢洪洞＋泄洪排沙洞组成，水工模型试验结果表明该方案是合理可行的。     

喜河水电站施工导流

汉江洪水峰高量大、陡涨陡落,年内最大洪枯比达600倍,坝址地形左陡右缓,施工导流采用分三期导流的方式,施工导流程序复杂。     

施工导流风险多目标决策的三维可视化模型

鉴于施工导流风险评价指标的权重变化会直接影响决策结果,基于导流风险多目标决策模型,集合所有可能权重组合条件下的决策排序信息,构建决策指标三维空间映射,建立施工导流风险多目标决策三维可视化模型。实例应用表明,该模型分析了导流方案评价指标权重的敏感度,可直观反映各权重组合条件下各导流方案的优劣性,为施工导流方案决策提供了辅助决策工具。     

基于概率分布优选的水电工程施工初期导流风险率估计

科学准确地评估水电工程施工初期导流风险率为施工导流方案决策提供了重要依据。以往风险模型中施工洪水洪峰的随机分布均假设服从P-Ⅲ分布,这会影响导流风险率的精度和可靠性。首先采用K-S检验法对初拟的施工洪水洪峰概率分布类型进行初选,并通过R_RMSE、M_MAE、Q_QD值的拟合优度综合评比优选最佳概率分布;然后综合考虑水文、水力随机性,构建基于概率分布优选的施工初期导流风险率计算框架,并给出采用Monte-Carlo方法求解风险率的具体流程;最后对国内两座大型水电工程实例进行应用分析。结果表明,风险率计算框架及求解流程是可行的、有效的;I-MED具有一定的拟合能力,可用于导流风险模拟;两个案例的概率分布排序不同、最佳概率分布不同,进而影响导流风险率大小。研究结果有效拓展了施工导流风险理论框架。     

Potential method in the theory of thermoviscoelastic mixtures

In this article, the linear theory of binary thermoviscoelastic mixtures is considered and the basic boundary value problems (BVPs) of steady vibrations are investigated. Namely, the fundamental solution of the system of equations of steady vibrations is constructed explicitly and its basic properties are established. Green’s second and third identities are obtained and the uniqueness theorems for classical solutions of the internal and external basic BVPs of steady vibrations are proved. The surface and volume potentials are constructed and their basic properties are given. The determinants of symbolic matrices are calculated explicitly. The BVPs are reduced to the always solvable singular integral equations for which Fredholm’s theorems are valid. Finally, the existence theorems for classical solutions of the internal and external BVPs of steady vibrations are proved by the potential method and the theory of singular integral equations.     

自然通风技术研究方法及工具

目前自然通风主要有三种研究方法:简单的理论分析法、实验法和数值模拟法。本文概括介绍了后两种方法的研究现状,并对它们进行了分析比较,提出各种方法的适用场合。在数值模拟法中还介绍了几种可用于分析自然通风系统的通风特性和热特性的常用工具软件,对各自工作原理和应用特点进行了比较,并对使用方法和应用场合提出了建议。     

Study of contact melting inside isothermally heated vertical cylindrical capsules

Close-contact melting processes of phase change material (PCM) inside vertical cylindrical capsule are studied. PCM are heated by the capsule isothermally at the bottom and side. The theoretical formulas of the melting rate and thickness of liquid layer during the heat transfer process are obtained by analysis, which are convenient for engineering predictions. Finally, the factors that affect melting are discussed, and conclusions are drawn.     

US nuclear energy policy Provision of funds for decommissioning

The five recognized methods of decommissioning nuclear power plants are reviewed, and are linked with US nuclear regulatory policy. Although over 60 US nuclear reactors have been decommissioned since 1960, none have been large-scale commercial facilities. Costs of the decommissioning alternatives are estimated, but are acknowledged to be highly tentative and uncertain. Five methods of providing funds for decommissioning and the actual practices of US electric utilities are analysed in terms of the policy issues they present. Revenue bonding and sinking fund approaches are argued to be the soundest means to recover decomissioning uncertainties surrounding decommissioning are considered.     

质子交换膜燃料电池系统控制与应用现状

描述了质子交换膜燃料电池(PEMFC)系统的控制及其在中低功率领域中的应用现状。首先概述了过程模型和电压预测模型，对影响电堆性能的各参数进行分析。其次，从目前运用的简单控制方法、混合动力驱动、效率优化、故障容许等方面对PEMFC系统的分析与控制结构作了说明。然后介绍了PEMFC的几种具体应用。最后结合国内外的相关研究进展，提出了一些有待进一步研究的方向。     

Stochastic approach for daily solar radiation modeling

Mathematical modeling of solar radiation continues to be an important issue in renewable energy applications. In general, existing models are mostly empirical and data dependent. In this paper, a novel approach for solar radiation modeling is proposed and illustrated. The proposed application consists of hidden Markov processes, which are widely used in various signal processing topics including speech modeling with successful results. In the experimental work, mean of hourly measured ambient temperature values are considered as observations of the model, whereas mean of hourly solar radiation values are considered as the hidden events, which constitute the outcomes of the proposed mathematical model. Both solar radiations and temperatures are converted to quantized number of states. Finally, after a training stage that forms the transition probability values of the described states, the hidden Markov model parameters are obtained and tested. The tests are repeated for various numbers of states and observations are presented. Plausible modeling results with distinct properties in terms of accuracy are achieved.     

针对转速偏差调节和汽门快关控制的连续阀门控制的研究

常规的汽轮机控制器包括小拔动控制和汽门快关，产生两个相对独立的控制信号，本文提出了一种基于最优复合控制策略的连续转速控制器，由2组结构完全相同，参数增益不同的控制器组成，可以对转速偏差调节和汽门快关进行连续的控制，可以在整个控制过程中进行无扰动切4换，避免了常规的开关式汽门快关的缺点，这种控制器考虑了汽轮机的非线性，进行了线性化，采用了满足稳态和暂稳态的线性二次最优控制。仿真比较了所研究的复合控制器和常规的控制器在三相短中和故障后带本地负荷暂稳态的情况，结果表明，这种复合控制器有良好的控制特性。     

用面向对象方法开发现代制造企业的管理信息系统

现代制造企业经营管理环境及思想正发生着深刻的变化,现代软件工程思想和方法也正朝着面向对象方向发展,通过将二者融入制造企业的管理信息系统,探讨了现代制造企业管理信息系统的结构及功能,并给出了用面向对象技术分析和设计管理信息系统的方法。     

二甲醚在能源行业应用前景综述

介绍了二甲醚（DME）的特点,结合我国能源结构的实际情况,详细论述了其在能源行业的应用前景,特别是替代民用LPG燃料和车用柴油燃料的应用前景,分析了基于DME为燃料相关系统的关键技术、应用前景及主要障碍。通过与柴油、LPG、天然气的物性对比,就二甲醚的推广所要解决的技术问题进行了分析,提出相关解决方案,并对二甲醚在燃料市场的应用方向进行了阐述。     

Heat transfer performance of a double-loop separate-type heat pipe: Measurement results

An experimental study is presented for the heat transfer performance of a rectangular double-loop natural circulation system, in which the condensers are made of double tubes with water-steam as the working fluid. Detailed temperature measurements of the core fluid and the wall are made, from which overall heat transfer coefficients for the evaporator, condensers, and entire system are obtained. Parametric studies of the liquid charge level, fluid properties, and heating or cooling conditions on the heat transfer performance are presented and correlation equations are given. The results show that the overall heat transfer coefficients for the evaporator, condensers, and entire loop are all increasing with decreasing liquid charge level. Overhead phenomena at low liquid charge level and thermal oscillation at some situations are also observed and discussed.