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Journal of Hydrodynamics 2018年第4期30卷 549-563页

作者： Yu-Hsiang Chen Keh-Han Wang Department of civil and environmental engineering University of Houston

This paper presents a newly developed 3-D fully nonlinear wave model in a transient curvilinear coordinate system to simulate propagation of nonlinear waves and their interactions with curved boundaries and cylindrical structures. A mixed explicit and implicit finite difference scheme was utilized to solve the transformed governing equation and boundary conditions in grid systems fitting closely to the irregular boundaries and the time varying free surface. The model＇s performance was firstly tested by simulating a solitary wave propagating in a curved channel. This three-dimensional solver, after comparing the results with those obtained from the generalized Boussinesq（g B） model, is demonstrated to be able to produce stable and reliable predictions on the variations of nonlinear waves propagating in a channel with irregular boundary. The results for modeling a solitary wave encountering a vertical cylinder are also presented. It is found the computed wave elevations and hydrodynamic forces agree reasonably well with the experimental measurements and other numerical results.

关键词： Solitary wave curvilinear coordinate transformation curved channel wave scattering hydrodynamic forces

Development of an adaptive Kalman filter-based storm tide forecasting model

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Journal of Hydrodynamics 2016年第6期28卷 1029-1036页

作者：莫启明黎宇轩许嘉贤 Department of civil and environmental engineering University of Macao

Extreme storm tide usually causes flooding of low-lying land in a coastal city. Hence, developing an efficient and accurate forecasting model for issuing a timely warning is important. In this study, an adaptive Kalman filter-based storm tide forecasting model was proposed and applied to the inner Harbor of Macau. The model is a dynamic linear regression model with the harmonic tidal prediction, wind speed, wind direction and atmospheric pressure as its input parameters. With persistence forecast of weather assumed during the prediction period, the model was tested with 40 cases of storm tide induced by tropical cyclones in Macau between 2005 and 2012. Success was found for forecasts with lead times up to 3 hours. The proposed adaptive model is considered a practical tool for storm tide forecast in small coastal cities.

关键词： adaptive model flooding Kalman filter Macao storm tide

Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

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Earthquake engineering and engineering Vibration 2013年第1期12卷 143-154页

作者： Chandra Shekhar Goit Masato Saitoh Department of civil and environmental engineering Saitama University

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant *** practical pile inclinations of 5掳 and 10掳 in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are *** obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of *** impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination *** values of horizontal impedance functions are obtained for the ＇positive＇ and ＇negative＇ cycles of harmonic loadings,leading to asymmetric force-displacement relationships for the inclined *** of these experimental results is carried out through three-dimensional nonlinear finite element analyses,and the results from the numerical models are in good agreement with the experimental *** analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

关键词： inclined single piles harmonic loads horizontal impedance functions local nonlinearity finite element model

Selection of noise parameters for Kalman filter

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Earthquake engineering and engineering Vibration 2007年第1期6卷 49-56页

作者：阮家荣许嘉贤莫启明 Department of civil and environmental engineering University of Macao

The Bayesian probabilistic approach is proposed to estimate the process noise and measurement noise parameters for a Kalman filter. With state vectors and covariance matrices estimated by the Kalman filter, the likehood of the measurements can be constructed as a function of the process noise and measurement noise parameters. By maximizing the likelihood function with respect to these noise parameters, the optimal values can be obtained. Furthermore, the Bayesian probabilistic approach allows the associated uncertainty to be quantified. Examples using a single-degree-of-freedom system and a ten-story building illustrate the proposed method. The effect on the performance of the Kalman filter due to the selection of the process noise and measurement noise parameters was demonstrated. The optimal values of the noise parameters were found to be close to the actual values in the sense that the actual parameters were in the region with significant probability density. Through these examples, the Bayesian approach was shown to have the capability to provide accurate estimates of the noise parameters of the Kalman filter, and hence for state estimation.

关键词： Bayesian inference Kalman filter measurement noise process noise state estimation

Thermodynamics of NaHCO_3 decomposition during Na_2CO_3-based CO_2 capture

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Journal of environmental Sciences 2019年第4期31卷 74-80页

作者： Sam Toan William O'Dell Christopher K.Russell Sun Zhao Qinghua Lai Huiping Song Ying Zhao Maohong Fan College of engineering and Applied Science University of Wyoming Chemical and environmental engineering University of California civil and environmental engineering Stanford University Institute of Resources and environmental engineering Shanxi University School of civil and environmental engineering Georgia Institute of Technology

Amine-basedcarbon-capture technologies have been shown to be energetically expensive and to cause significant environmental and epidemiological impacts due to their *** formation from carbon dioxide's reaction with water has been suggested as an effective alternative for capturing CO_2;however,the thermodynamics of this reaction are not well *** study experimentally determined the equilibrium constant of sodium bicarbonate(Na HCO_3)decomposition to sodium,water,and carbon dioxide;the study also compared the equilibrium constant to theoretical *** a combination of experimentation and thermodynamic relationships,the unitless equilibrium constants of the forward and reverse reactions were calculated accurately(errorenvironmentally friendly nextgeneration CO_2-capture technologies.

关键词： Sodium bicarbonate Sodium carbonate Gibbs free energy Enthalpy Entropy

Performance-based seismic assessment of skewed bridges with and without considering soil-foundation interaction effects for various site classes

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Earthquake engineering and engineering Vibration 2014年第3期13卷 357-373页

作者： Abdoul R.Ghotbi civil & environmental engineering Department University of California

The seismic behavior of skewed bridges has not been well studied compared to straight bridges. Skewed bridges have shown extensive damage, especially due to deck rotation, shear keys failure, abutment unseating and column- bent drift. This research, therefore, aims to study the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction （SSI） due to near-fault ground motions. Due to several sources of uncertainty associated with the ground motions, soil and structure, a probabilistic approach is needed. Thus, a probabilistic methodology similar to the one developed by the Pacific Earthquake engineering Research Center （PEER） has been utilized to assess the probability of damage due to various levels of shaking using appropriate intensity measures with minimum dispersions. The probabilistic analyses were performed for various bridge configurations and site conditions, including sand ranging from loose to dense and clay ranging from soft to stiff, in order to evaluate the effects. The results proved a considerable susceptibility of skewed bridges to deck rotation and shear keys displacement. It was also found that SSI had a decreasing effect on the damage probability for various demands compared to the fixed-base model without including SSI. However, deck rotation for all types of the soil and also abutment unseating for very loose sand and soft clay showed an increase in damage probability compared to the fixed-base model. The damage probability for various demands has also been found to decrease with an increase of soil strength for both sandy and clayey sites. With respect to the variations in the skew angle, an increase in skew angle has had an increasing effect on the amplitude of the seismic response for various demands. Deck rotation has been very sensitive to the increase in the skew angle; therefore, as the skew angle increased, the deck rotation responded accordingly. Furthermor

关键词： skewed bridges SSI demand model probabilistic assessment damage probability

Dual reciprocity boundary element based block model for discontinuous deformation analysis

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Science China(Technological Sciences) 2015年第9期58卷 1575-1586页

作者： FU GuoYang MA GuoWei QU XiaoLei School of civil Environmental and Mining Engineering University of Western Australia School of civil Environmental and Chemical Engineering RMIT University College of Architecture and civil engineering Beijing University of Technology

This paper presents a further development of the dual reciprocity boundary element method(DRBEM) with stepwise updating to pave the way for the introduction of boundary element mesh into the discontinuous deformation analysis(DDA). The advantage of the proposed method lies in its adoption of static fundamental solutions and reduction in the size of the governing equations by transforming the inertial term domain integrals to boundary integrals in the dynamic large displacement analysis. The unconditionally stable Newmark-β time integration method involving numerical damping to enhance the numerical stability is implemented for the dynamic analysis. In order to be coupled with the DDA to improve the deformability of the DDA block domains, a stepwise updating algorithm of the system variables is introduced. The stress updating in the analysis involved in the calculation of a domain integral and internal cells are used for the integration of the initial stress term. Several examples are used to verify the geometry-updated DRBEM model and satisfactory results have been obtained.

关键词： boundary element method stepwise updating initial stress large displacement

Experimental verification of bridge seismic damage states quantified by calibrating analytical models with empirical field data

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Earthquake engineering and engineering Vibration 2008年第4期7卷 383-393页

作者： Swagata Banerjee Masanobu Shinozuka Department of civil and environmental engineering University of California

Bridges are one of the most vulnerable components of a highway transportation network system subjected to earthquake ground motions. Prediction of resilience and sustainability of bridge performance in a probabilistic manner provides valuable information for pre-event system upgrading and post-event functional recovery of the network. The current study integrates bridge seismic damageability information obtained through empirical, analytical and experimental procedures and quantifies threshold limits of bridge damage states consistent with the physical damage description given in HAZUS. Experimental data from a large-scale shaking table test are utilized for this purpose. This experiment was conducted at the University of Nevada, Reno, where a research team from the University of California, Irvine, participated. Observed experimental damage data are processed to identify and quantify bridge damage states in terms of rotational ductility at bridge column ends. In parallel, a mechanistic model for fragility curves is developed in such a way that the model can be calibrated against empirical fragility curves that have been constructed from damage data obtained during the 1994 Northridge earthquake. This calibration quantifies threshold values of bridge damage states and makes the analytical study consistent with damage data observed in past earthquakes. The mechanistic model is transportable and applicable to most types and sizes of bridges. Finally, calibrated damage state definitions are compared with that obtained using experimental findings. Comparison shows excellent consistency among results from analytical, empirical and experimental observations.

关键词： highway bridges nonlinear time history analysis fragility curves threshold damage limits mechanisticmodel calibration

Use of polymeric sub-micron ion-exchange resins for removal of lead,copper,zinc,and nickel from natural waters

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Journal of environmental Sciences 2019年第1期31卷 247-254页

作者： Audrey Murray Banu ?rmeci Department of civil and environmental engineering Carleton University

This research investigated the removal capacity of polymeric sub-micron ion-exchange resins(SMR) for removal of lead, copper, zinc, and nickel from natural waters in competition with natural organic matter(NOM). Polymeric SMR particles were created and tested to ensure that they were adequately dispersed in the solution. They removed little NOM(10%or less) from river water and wastewater, indicating that competition from NOM was not a major concern. SMR were able to remove 82% ± 0.2% of lead, 46% ± 0.6% of copper, 55% ±20% of zinc, and 17% ± 2% of nickel from river water spiked with 500 μg/L of each. Similarly,in wastewater, they were able to remove 86% ± 0.1% of lead, 38% ± 0.8% of copper, 28% ± 1%of zinc, and 11% ± 1% of nickel.

关键词： Water Wastewater Heavy metals Ion exchange Polymeric submicron resin Natural organic matter (NOM)

Estimation of drag forces caused by natural woody vegetation of different scales

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Journal of Hydrodynamics 2014年第4期26卷 608-623页

作者： JALONEN Johanna JRVEL Juha Department of civil and environmental engineering Aalto University

To reliably estimate water levels and velocities in vegetated rivers and floodplains, flow resistance models based on physical plant properties are advantageous. The purpose of this study is （1） to assess the suitable parameterization of woody riparian vegetation in estimating the drag forces, （2） to address the effect of plant scale on the drag estimates and reconfiguration, and （3） to evaluate the applicability of three recently developed flow resistance models. Experiments on four tree species in a towing tank together with detailed characterization of tree properties were carried out to establish a novel dataset. Despite the variability in the tree height （0.9 m-3.4 m）, the stem, leaf and total areas proved to be suitable characteristic dimensions for estimating the flow resistance at different scales. Evaluations with independent data revealed that the tested models produced reasonable results. The performance of the models was controlled by the parameter values used rather than the model structure or the plant scale.

关键词： drag force flow resistance woody vegetation modelling