Effect of the Three Gorges Reservoir on vertical distribution of suspended sediment concentration and estimation accuracy of depth-average concentration in downstream reaches

The sediment regime in the middle Yangtze River has been significantly changed from quasi-equilibrium to nonequilibrium since the impoundment of the Three Georges Reservoir (TGR). To understand the effects of the TGR on vertical distribution of suspended sediment concentration (SSC) and estimation accuracy of mean concentration, vertical sediment concentration and flow velocity data at the Shashi and Jianli hydrological stations in the reach before and after the impoundment were collected. Comparisons and analysis of vertical profiles of SSC before and after the TGR impoundment show that after the impoundment of the TGR, due to the coarsening of sediment particle size, the reduction in sediment load, and the significant decrease in sediment saturation, the vertical distribution of SSC in the downstream reaches became more uneven under medium and low water flows, which was reflected in the vertical gradient and the fluctuation degree of SSC significantly increased. In addition, the depth-average sediment concentrations were calculated by the selected-point method and the mean values calculated by the “multi-point method” were regarded as the “true mean” to evaluate the accuracy of the mean value calculated by the “few-point method.” It was found that the relative errors for the selected-point method were mainly positive before impoundment but mainly negative after impoundment. Additionally, the correction factors of one-point, two-point, and three-point methods and the position of the near-bed substituted point for the five-point method were given to reduce the error when the point measurements were used to calculate the depth-average sediment concentration in the downstream reaches.     

上拔荷载对斜桩水平承载性状影响的试验研究

斜桩在承受水平荷载的同时,往往会受到上拔荷载的作用。为研究上拔荷载对斜桩水平承载性状的影响,开展了10根直、斜桩的室内模型试验,研究上拔荷载对斜桩桩顶水平位移和水平承载力的影响,对比了直桩与斜桩桩身弯矩和剪力的差异,并分析了上拔荷载对正、负斜桩桩身内力及桩侧摩阻力的影响规律。模型试验结果表明:上拔荷载从直桩水平极限承载力的12.5%增大到75%时,正斜桩水平承载力比增大21%,负斜桩水平承载力比减小25%。上拔荷载的存在会使正、负斜桩桩身轴力均增大,且上拔荷载越大,桩身轴力越大。上拔荷载能减小正斜桩桩身弯矩和剪力,使其抵抗弯矩和剪力的能力得到提高,而增大负斜桩桩身弯矩和剪力,使其抵抗弯矩和剪力的能力被削弱;不论正斜桩还是负斜桩,其上部区段桩身侧表面均出现了方向向上的摩阻力,而下部区段桩身侧表面均为方向向下的摩阻力,随着上拔荷载的增大,斜桩桩身侧摩阻力逐渐增大。     

An automatic parameter calibration method for the SWAT model in runoff simulation

Runoff simulation is highly significant for hydrological monitoring, flood peak simulation, water resource management, and basin protection. Runoff simulation by distributed hydrological models, such as the soil and water assessment tool (SWAT) model which is the most widely used, is becoming a hotspot for hydrological forecasting research. However, parameter calibration is inefficient and inaccurate for the SWAT model. An automatic parameter calibration (APC) method of the SWAT model was developed by hybrid of the genetic algorithm (GA) and particle swarm optimization (PSO). Multi‐station and multi‐period runoff simulation and accuracy analysis were conducted in the basin of the Zhangjiang River on the basis of this hybrid algorithm. For example, in the Yaoxiaba Station, the calibration results produced an R² of 0.87 and Nash Sutcliffe efficiency (NSE) index of 0.85, while verification results revealed an R² of 0.83 and NSE of 0.83. Results of this study show that the proposed method can effectively improve the efficiency and simulation accuracy of the model parameters. It can be concluded that the feasibility and applicability of GA‐PSO as an APC method for the SWAT model were confirmed via case studies. The proposed method can provide theoretical guidance for many hydrological research fields, such as hydrological simulation, flood prevention, and forecasting.     

利用T-PROGS确定最优钻孔密度

为了在水文地质钻探时找到合理的钻孔密度,避免钻孔集中出现数据的冗余,造成介质类别有偏向于高密度钻孔岩性类别的趋势。本文以某实测区域为研究对象,运用GMS软件中T-PROGS模块,模拟在非均匀介质中均匀分布钻孔以确定最优钻孔密度。通过马尔可夫数学预测模型对计算机模拟数据进行甄选,得出在钻孔密度为30孔/km2,获得的水文地质资料的可信度较高,可以最大限度的节省人力物力。本文研究结果表明:结合GMS软件与马尔科夫预测模型对探明地质类型分布是可行的。     

知识创造机理:认识论-本体论的观点

知识已经成为关键的经济资源，知识创造过程日益受到重视。在对知识创造过程有关文献分析研究的基础上，对知识创造过程从认识论和本体论的角度进行了研究，最终建立了基于认识论和本体论的知识创造模型（E-O-SECI）。     

铜陵矿区生态经济建设

本文根据矿区生态经济系统协调发展和演化的原理,提出合理规划、建设铜陵生态市的建议,以实现铜陵经济、社会的可持续发展。     

遗传算法及其在客户关系管理中的应用研究

遗传算法是一种宏观意义下的仿生优化算法，它模拟生物在自然环境中的遗传和进化过程而形成的一种自适应全局优化概率搜索算法。这种算法可以用于对海量的客户信息进行搜索，提取对决策有用的信息，让企业在激烈的市场竞争中处于有利地位，最终达到最高利润。本文还通过一个简单的实例研究将该算法应用在客户关系管理中。     

地方官员与经济增长——来自中国省长、省委书记交流的证据

通常认为地方官员在我国经济发展中扮演着积极角色,近来国家也有意通过干部交流促进省区平衡发展,但国内还没有定量识别地方官员影响经济增长的文献。本文基于1978—2005年间省长(书记)交流样本构造了省长(书记)与省区相匹配的面板数据,系统地实证分析省长(书记)交流对流入省区经济增长的影响(即省长交流效应),结果发现,整体而言,省长交流能够使流入地的经济增长速度提高1个百分点左右;这种省长交流效应是通过在流入地采取大力发展二产、重视一产、忽视三产的产业发展取向实现的。本文的发现是稳健的,有助于增进对加强干部交流破解省区发展不平衡的理解。     

试论我国食品安全供应链综合管理

食品供应链综合管理的核心内容是质量认证与跟踪管理,其思想为解决我国食品供应链中的安全问题提供了基本的思路。本文在分析我国食品供应链中存在的与食品安全相关的问题基础上,对我国实践食品安全供应链综合管理进行了思考,提出了从宏观、中观、微观三个层面上进行食品安全供应链综合管理的框架,并对食品安全供应链综合管理中的信息集成与共享进行了探讨。     

从经济理性到有限理性:经济学研究理性假设的演变

"经济理性"是经济学的传统研究假设,却因背离现实而受到质疑.基于行为人稀缺的心理资源和系统固有的不确定性而产生的"有限理性"正逐步取代"经济理性"成为经济学研究的理性假设.不同的理性观点可以从决策的视角得到系统地解释和比较.并且,随着理性假设的演变,经济行为的决策标准也相应从单一静态最优向多元动态平衡转变.