A Practical Measurement Strategy to Estimate Nonlinear Chlorinated Solvent Sorption in Low foc Sediments     

Guohui Wang  Richelle M. Allen‐King  Sungwook Choung  Stanley Feenstra  Robert Watson  Michael Kominek 《Ground Water Monitoring & Remediation》2013,33(1):87-96

In this study, we tested a practical strategy useful for accurate chlorinated volatile organic compound (cVOC) sorption prediction. Corresponding to the feature of the superposition of adsorption due to thermally altered carbonaceous matter (TACM) with organic carbon‐water partitioning, a nonlinear Freundlich sorption isotherm covering a wide range of aqueous concentrations was defined by equilibrium sorption measurement at one or a few low concentration points with extrapolation to the empirical organic carbon‐water partition coefficient (K_oc,e) near compound solubility. We applied this approach to obtain perchloroethene equilibrium sorption isotherm parameters for TACM‐containing glacial sand and gravel subsoil samples from a field site in New York. Sorption and associated K_oc,c applicable to low (5–500 µg/L) and high (>100,000 µg/L) aqueous concentrations were determined in batch experiments. (The K_oc,c is the organic carbon‐normalized sorption partition coefficient corresponding to aqueous concentration C_w.) The K_oc,c measurements at low concentration (~5 µg/L) were 6 to 34 times greater than the K_oc,e. The importance of this type of data is illustrated through presentation of its substantial impact on the site remedy. In so doing, we provide an approach that is broadly applicable to cVOC field sites with similar circumstances (low carbon content glacial sand and gravel with TACM).  相似文献   

Storm-generated,hummocky stratification on the outer-Scotian Shelf     

Carl L. Amos  M. Z. Li  K. -S. Choung 《Geo-Marine Letters》1996,16(2):85-94

Hummocky megaripples occur on Sable Island Bank, Scotian Shelf. Submersible observations show that the megaripples form during winter storms and are subsequently obliterated through bioturbation and fair-weather reworking. The megaripples of this study were underlain by a storm bed composed of: (A) a basal scoured and infilled gravel lag facies; (B) low-angle tangential crossbedding in gravel to coarse sand; (C) anisotropic hummocky stratification in medium sand; and (D) wave ripple cross-lamination in medium/fine sand. This sequence forms a tempestite bed created by a winter storm during our sampling program. Numerical simulation of bed conditions during the storm suggests that the hummocky megaripples and hummocky stratification formed together during late stages of storm decay from conditions of sheet flow. Near-bed wave motion during deposition exceeded steady currents by an order of magnitude.  相似文献   

ISEE: Internet‐based Simulation for Earthquake Engineering—Part I: Database approach     

Yuan‐Sen Yang  Shang‐Hsien Hsieh  Keh‐Chyuan Tsai  Shiang‐Jung Wang  Kung‐Juin Wang  Wei‐Choung Cheng  Chuan‐Wen Hsu 《地震工程与结构动力学》2007,36(15):2291-2306

An Internet‐based framework, named Internet‐based Simulation for Earthquake Engineering (ISEE) was developed to facilitate collaborative earthquake engineering experiments performed by multiple laboratories in a network environment. One of the approaches in the ISEE framework, named Database Approach, offers an easy way to perform multi‐site networked collaborative pseudo‐dynamic experiments. The Database Approach uses the Structured Query Language (SQL), a common and standardized computer language used in database management systems, for inter‐laboratory communications. Using the SQL protocol, it is easy to monitor the experiments' progress, access the data, as well as develop additional programs to expand the functions for a networked experiment. This approach offers consistency and durability of selected experimental data both during and after experiments. Two networked pseudo‐dynamic experiments were conducted to demonstrate the feasibility and expansibility of the Database Approach in ISEE. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Non-parametric simulations-based conditional stochastic predictions of geologic heterogeneities and leakage potentials for hypothetical CO2 sequestration sites     

Weon Shik Han  Kue-Young Kim  Sungwook Choung  Jina Jeong  Na-Hyun Jung  Eungyu Park 《Environmental Earth Sciences》2014,71(6):2739-2752

The present study focuses on understanding the leakage potentials of the stored supercritical CO₂ plume through caprocks generated in geostatistically created heterogeneous media. For this purpose, two hypothetical cases with different geostatistical features were developed, and two conditional geostatistical simulation models (i.e., sequential indicator simulation or SISIM and generalized coupled Markov chain or GCMC) were applied for the stochastic characterizations of the heterogeneities. Then, predictive CO₂ plume migration simulations based on stochastic realizations were performed and summarized. In the geostatistical simulations, the results from the GCMC model showed better performance than those of the SISIM model for the strongly non-stationary case, while SISIM models showed reasonable performance for the weakly non-stationary case in terms of low-permeability lenses characterization. In the subsequent predictive simulations of CO₂ plume migration, the observations in the geostatistical simulations were confirmed and the GCMC-based predictions showed underestimations in CO₂ leakage in the stationary case, while the SISIM-based predictions showed considerable overestimations in the non-stationary case. The overall results suggest that: (1) proper characterization of low-permeability layering is significantly important in the prediction of CO₂ plume behavior, especially for the leakage potential of CO₂ and (2) appropriate geostatistical techniques must be selectively employed considering the degree of stationarity of the targeting fields to minimize the uncertainties in the predictions.  相似文献   

Seismic performance and probabilistic collapse resistance assessment of steel moment resisting frames with fluid viscous dampers   总被引：1，自引：0，他引：1       下载免费PDF全文

Choung‐Yeol Seo  Theodore L. Karavasilis  James M. Ricles  Richard Sause 《地震工程与结构动力学》2014,43(14):2135-2154

This paper evaluates the seismic resistance of steel moment resisting frames (MRFs) with supplemental fluid viscous dampers against collapse. A simplified design procedure is used to design four different steel MRFs with fluid viscous dampers where the strength of the steel MRF and supplemental damping are varied. The combined systems are designed to achieve performance that is similar to or higher than that of conventional steel MRFs designed according to current seismic design codes. Based on the results of nonlinear time history analyses and incremental dynamic analyses, statistics of structural and non‐structural response as well as probabilities of collapse of the steel MRFs with dampers are determined and compared with those of conventional steel MRFs. The analytical frame models used in this study are reliably capable to simulate global frame collapse by considering full geometric nonlinearities as well as the cyclic strength and stiffness deterioration in the plastic hinge regions of structural steel members. The results show that, with the aid of supplemental damping, the performance of a steel MRF with reduced design base shear can be improved and become similar to that of a conventional steel MRF with full design base shear. Incremental dynamic analyses show that supplemental damping reduces the probability of collapse of a steel MRF with a given strength. However, the paper highlights that a design base shear equal to 75% of the minimum design base shear along with supplemental damping to control story drift at 2% (i.e., design drift of a conventional steel MRF) would not guarantee a higher collapse resistance than that of a conventional MRF. At 75% design base shear, a tighter design drift (e.g., 1.5% as shown in this study) is needed to guarantee a higher collapse resistance than that of a conventional MRF. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Comparative studies of fracture models for marine structural steels     

Joonmo Choung 《Ocean Engineering》2009,36(15-16):1164-1174

Smooth and notched round specimens and smooth flat specimens are prepared from two steels, API-2W50 and DnV-DH32TM. From incremental tensile tests for smooth specimens, average true stress–logarithmic true strain curves are obtained. By using Bridgman's formula for round specimens and Choung's formula for flat specimens, average true stress is rectified. Then, tensile tests for notched specimens with various notch radiuses are carried out and damage tests are performed to identify material parameters of the damage mechanics model. Three yield models are taken into account: a shear fracture model based on a von Mises's yield function, a linear damage mechanics model based on Lemaitre's law of damage evolution, and a porous plasticity model based on Gurson's yield function. While the shear fracture model can forecast the tested plastic deformation path including final fracture for smooth specimens, it unrealistically estimates that the hydrostatic stress at the necking section largely contributes the plastic behaviors for notched specimens. The linear damage mechanics model assumes linear relationship between the damage value and plastic strain, and fails to accurately estimate the test results. The porous plasticity model presents very good agreement with experimental results regardless of the notch radiuses as long as material parameters are reasonably chosen.  相似文献   

Micromechanical damage modeling and simulation of punch test     

Joonmo Choung 《Ocean Engineering》2009,36(15-16):1158-1163

In order to verify the validity and applicability of the porous plasticity model for the simulation of non-local plastic fractures, punch tests are carried out for round steel plates of JIS G3131 SPHC. Incremental tensile coupon tests for the material are also conducted to obtain the plastic mechanical properties. Material parameters required for the porous plasticity model are identified through parametric numerical simulations of the coupon tests. It is proved that that force vs. indentation curves from punch test simulations using the porous plasticity model with the identified material parameters show good agreement with punch test results. It is also verified that simulated fracture shapes in the punch specimens are almost similar to the experimental ones in which fracture occurs along the circumferential edge of indenter where the hydrostatic stress develops highly.  相似文献   

ISEE: Internet‐based Simulation for Earthquake Engineering—Part II: The application protocol approach     

Kung‐Juin Wang  Keh‐Chyuan Tsai  Shiang‐Jung Wang  Wei‐Choung Cheng  Yuan‐Sen Yang 《地震工程与结构动力学》2007,36(15):2307-2323

This paper develops new techniques for integrating a number of different structural laboratories together through the Internet in order to jointly conduct a single structural experiment. A computer‐networking platform, called Platform for Networked Structural Experiments (PNSE), was developed to achieve this goal. PNSE runs directly on top of the Transmission Control Protocol/Internet Protocol (TCP/IP). It is a multi‐client system consisting of a number of client programs, which include one command generation program and a number of facility control programs, connected to a server program via TCP point‐to‐point connections across the Internet. An associated application protocol, called Networked Structural Experiment Protocol (NSEP), was developed to work with the PNSE. In addition to communication rules, the NSEP defines general experimental information, significant laboratory events, commands and signals, as well as obligated behaviours of all PNSE programs. Both domestic and transnational pseudo‐dynamic (PSD) tests were performed to verify the validity and efficiency of the PNSE. Test results showed that on the PNSE: signals were correctly transmitted; significant laboratory events were promptly reflected; and data transmission was remarkably efficient, with the round‐trip time (RTT) between Taiwan and the United States less than 0.1701 s. The characteristic of environment independency was also demonstrated through the successful collaboration of different facility control programs running on different operating systems. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Development of a Vector-Based Method for Coastal Bluffline Mapping Using LiDAR Data and a Comparison Study in the Area of Lake Erie     

Yunjae Choung  Rongxing Li  Myung-Hee Jo 《Marine Geodesy》2013,36(3):285-302

This paper introduces a new method for bluffline extraction based on analysis of surface normal vectors derived from a 2.5-dimensional Delaunay triangulation network generated using a set of LiDAR points. The developed method has been implemented and tested for the extraction of blufflines in a section of the Lake Erie coastline near Painesville, Ohio. Comparison of the research results with those generated by a method for bluffline extraction based on slope information along elevation profiles on transects shows an improvement in both horizontal and vertical accuracies in situations where the bluff has a relatively sharp edge formation.  相似文献   

Prediction of drift in a free surface     

Kwan Hyoung Kang  Choung Mook Lee 《Ocean Engineering》1996,23(3):243-255

An analytical model including the boundary-layer effect is developed to find the steady drift induced by the non-linear effect of the surface-wave motion. The analytical result is compared with the experimental results obtained from a wave tank. Results show a qualitative agreement. A semi-empirical formula which predicts drift velocity of a contaminant layer on the free surface is introduced and its validity is investigated.  相似文献