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101.
Kim Neil Irvine John J. Drake 《Journal of the American Water Resources Association》1987,23(6):1017-1025
ABSTRACT: Least squares regression and ARIMA models were developed from suspended sediment data for the Ausable River, Southern Ontario, Canada. A poor correlation between discharge and suspended sediment concentration results from the dynamics of the physical system, including seasonality, antecedent conditions, and hysteresis. Regression model results were significantly improved by the division of the data set into seasons and the addition of simple. but physically meaningful variables. Misleading improvements obtained from the regression of sediment load and discharge are discussed. ARIMA models provided accurate forecasts of sediment concentration on a real-time basis, but the rigorous data requirements limit their use in modeling suspended sediment concentrations in Canadian rivers. 相似文献
102.
根据混合气的爆炸极限与混合气各成分的体积浓度之间具有非线性关系的特点,笔者提出采用神经网络非线性方法来计算含有H2,CH4和CO的多元混合气体的爆炸极限。在模型中,H2,CH4和CO的体积浓度作为输入,爆炸上限和下限作为输出。计算结果表明,该非线性模型预测混合气爆炸下限和上限的最大相对误差为3.90%,3.57%,而模型预测值与计算值的相关系数分别为0.971,0.981;非线性模型的预测结果要好于偏最小二乘回归的预测结果。当H2,CO,CH4在混合气中的体积浓度给定时,非线性模型能够准确预测混合气的爆炸极限。 相似文献
103.
104.
Safety Instrumented Systems (SIS) constitute an indispensable element in the process of risk reduction for almost all of nowadays' industrial facilities. The main purpose of this paper is to develop a set of generalized and simplified analytical expressions for two commonly employed metrics to assess the performance of SIS in terms of safety integrity, namely: the Average Probability of Failure on Demand (PFDavg) and the Probability of Dangerous Failure per Hour (PFH). In addition to the capability to treat any K-out-of-N architecture, the proposed formulas can smoothly take into account the contributions of Partial Stroke Testing (PST) and Common Cause Failures (CCF). The validity of the suggested analytical expressions is ensured through various comparisons that are carried out at different stages of their construction. 相似文献
105.
The Ordinary Least Squares (OLS) is one of the widely used methods which is used for estimating the diffuse solar radiation. However, in order to use the OLS method in the estimation, the dataset must provide certain assumptions. In this study, alternative robust methods have been described and they were compared with the OLS method, which is used for estimating diffuse radiation frequently in an application. At the end of the analysis, the R2 value obtained by the OLS method is less than the values obtained by M regression models. In other words, the explanation of the dependent value is weak when the OLS method is used. Finally, it can be said that the most appropriate method is Andrews for estimating the diffuse solar radiation. 相似文献
106.
According to the current international standards, to perform the correct evaluation of the explosion and flammability parameters, a uniform distribution of the dust particles should be achieved inside the 20 L and/or 1 m3 standard vessels.CFD simulations have shown that in both standard test vessels (20 L and 1 m3), the dust particles are not uniformly dispersed, being mostly concentrated at the edge of the macro-vortices generated by the injection of the fluid and particle through the nozzle. In addition, only a partial fed of the particles is obtained, and dust particles sedimentation phenomena can occur.As a result, the dust participating to the reactive process may be much lower than the expected nominal concentration in the vessel due to sedimentation and incomplete feeding. Consequently, misleading values of the flammability/explosion parameters could be measured.Particle sedimentation and incomplete feeding depends both on the Stokes number and on the Reynolds number, whereas the concentration distribution depends on the turbulence level, the fluid flow maps, and the number of particles which enter into the vessel through the nozzle.The aim of this work is to evaluate the key parameters (particle size, particle density, and fluid velocity) affecting sedimentation and incomplete feeding in 20 L vessel. To this end, CFD simulations of dust dispersion are performed at varying the particle density and size. Operating maps, in terms of the key parameters and/or their dimensionless combinations, are developed and a correlation for correction of the data is proposed. 相似文献
107.
SPSS10.0是目前功能齐全、便于应用的优秀统计软件。文章介绍了该软件在环境监测数据分析和监测网设计中的应用。文中简述了该软件的功能及优点,并通过实例,展示其在环境监测数据分析和监测网设计中的应用,这对于优化监测数据分析结果和监测网的设计均有较好的借鉴作用。 相似文献
108.
Qian Li Zhaoyang Hou Xingyuan Huang Shuming Yang Jinfan Zhang Jingwei Fu Yu-You Li Rong Chen 《Frontiers of Environmental Science & Engineering》2023,17(6):68
109.
Marco Ferrante Francesco Napolitano Lucio Ubertini 《Journal of the American Water Resources Association》2000,36(5):1115-1120
ABSTRACT: In this paper a numerical model for flood propagation in urban areas is proposed. It has been applied to evaluate flooding hydraulic characteristics in terms of potential flood elevations, depths, and inundated areas. Furthermore, the algorithm efficiency and the consequent reduced computation time allow the use of the hydraulic model as a part of a more complex system for civil protection actions, planning, and management. During flood events, the transportation network plays a main role both in rescuing people when they are more vulnerable and in moving people and materials from and toward affected areas. The reduced efficiency of this transportation network is evaluated based on a least‐flood‐risk path‐finding algorithm. The results of a case study concerning the northern part of the city of Rome, show that the numerical model for unsteady flow in open channel networks achieves the proposed aims. It has proven to be able to describe the flood hydraulic characteristics and to be suitable for real‐time flood emergency management in urban areas. 相似文献
110.
探明土地利用方式与水质的关系对改善地表水环境具有重要意义.基于2021年天津市16个国家地表水水质监测站的月数据及土地利用数据,利用GIS空间分析和数理统计方法研究不同尺度缓冲区的土地利用方式对地表水水质的影响.结果表明:①研究区土地利用类型以建设用地、耕地和水域为主,对河流水质影响显著.除水温(WT)和pH外,耕地、建设用地和水域与各水质指标均呈负相关;林地和草地与溶解氧(DO)和总氮(TN)呈正相关,与其他水质指标均呈负相关.②水质指标在不同季节表现出明显的空间差异.pH、DO与TN浓度在旱季较高,而高锰酸盐指数、氨氮(NH4+-N)与总磷(TP)浓度在雨季较高.③冗余分析(RDA)结果表明,800 m缓冲区土地利用对旱季水质变化具有最大的解释能力(50.4%),而3 000 m缓冲区土地利用可以最大程度解释雨季水质变化情况(49.6%);从旱雨季的平均解释率来看,3 000 m缓冲区是天津市土地利用对水质指标的最佳影响尺度(50.0%);④偏最小二乘回归(PLSR)分析可知,3 000 m缓冲区内建设用地、耕地和水域是影响地表水水质变化最显著的地类.旱季大多数水质指标PLSR模型的预测能力比雨季强.在旱季,除WT和pH外,其余水质指标均受耕地的影响最大.在雨季,建设用地对WT和NH4+-N浓度的影响最大,其余水质指标的最重要影响因子仍是耕地.研究表明合理规划河流或湖库3 000 m内的土地利用方式有利于改善地表水水环境质量. 相似文献