Modification of the Bouwer and Rice Method to a Cutoff Wall with a Filter Cake     

The-Bao Nguyen  Chulho Lee  Sewon Kim  Hangseok Choi 《Ground water》2010,48(6):898-902

The Bouwer and Rice method is a line-fitting method used to estimate the hydraulic conductivity of an aquifer by means of a slug test. When considering a relatively impermeable layer, called a filter cake, which may form at the interface between a cutoff wall and the natural soil formation, the assumptions of the Bouwer and Rice method are violated. A modification of the Bouwer and Rice method is proposed that incorporates the concept of a flow net, whereby the geometry of the cutoff wall and filter cake is effectively considered in estimating the hydraulic conductivity of a vertical cutoff wall.  相似文献   

Potassium–Argon Ages of the Epithermal Gold–Silver Mineralization in the Haenam–Jindo Area,Southwestern Korea     

Chang Seong Kim  Seon‐Gyu Choi 《Resource Geology》2009,59(4):415-421

The Haenam–Jindo area, located on the southwestern margin of the Korean Peninsula, was the site of vigorous volcanic activity during the Late Cretaceous and Early Tertiary periods. Large parts of the area record strong hydrothermal alteration, and there exist many clay–alunite and gold–silver deposits. We undertook potassium–argon (K–Ar) age dating of five mineral samples (including adularia, sericite and alunite) from the Eunsan, Moisan and Gasado epithermal gold–silver deposits in this area. The purities of the samples were confirmed by X‐ray diffraction analysis. The K–Ar ages of adularia from the Eunsan deposit and adularia and sericite from the Moisan deposit (related to gold–silver mineralization) are 75.0 ± 1.6, 74.7 ± 1.6 and 75.1 ± 1.6 Ma, respectively. The similarity of these ages, combined with the close proximity and similar geochemical characteristics of the deposits, indicates that the mineralization occurred as part of a single hydrothermal system. The K–Ar ages of alunite at the surface and adularia at depth within the Gasado deposit are 82.2 ± 1.9 and 70.7 ± 1.9 Ma, respectively, revealing that the clay–alunite and gold–silver mineralization formed at different ages. K–Ar age data indicate that the gold–silver mineralization in this area occurred mainly at 75–70 Ma, resulting from hydrothermal activity in the Haenam–Jindo area (82–70 Ma). This is the first time that the mineralization of precious metals in Korea has been identified during this period.  相似文献   

Two‐dimensional waveform inversion of multi‐component data in acoustic‐elastic coupled media     

Yunseok Choi  Dong‐Joo Min  Changsoo Shin 《Geophysical Prospecting》2008,56(6):863-881

In order to account for the effects of elastic wave propagation in marine seismic data, we develop a waveform inversion algorithm for acoustic‐elastic media based on a frequency‐domain finite‐element modelling technique. In our algorithm we minimize residuals using the conjugate gradient method, which back‐propagates the errors using reverse time migration without directly computing the partial derivative wavefields. Unlike a purely acoustic or purely elastic inversion algorithm, the Green's function matrix for our acoustic‐elastic algorithm is asymmetric. We are nonetheless able to achieve computational efficiency using modern numerical methods. Numerical examples show that our coupled inversion algorithm produces better velocity models than a purely acoustic inversion algorithm in a wide variety of cases, including both single‐ and multi‐component data and low‐cut filtered data. We also show that our algorithm performs at least equally well on real field data gathered in the Korean continental shelf.  相似文献   

On the Possible Extension of the Sulu Belt Toward the East through the Korean Peninsula     

Ueechan Chwae  Sung-Ja Choi   《Gondwana Research》1999,2(4):540-542

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Behavior of marine pipelines under seismic faults     

N.Y Kershenbaum  S.A Mebarkia  H.S Choi   《Ocean Engineering》2000,27(5):132

A new study investigates an unburied offshore “snaked” pipeline behavior under various types of seismic faults. The snaking of the pipeline is caused by the thermal/pressure expansion and soil friction. The snaking takes place at a certain distance from the pipeline's unrestrained end and gradually increases towards the restraint. It is shown that longitudinal seismic faults have less effect on a straight pipeline than a snaked pipeline. The new seismic analysis demonstrates that an increase of ground displacement causes a very small change in bending and longitudinal stresses. The new approach results in a safe, subsea pipeline construction and operation with a significant cost reduction.  相似文献   

Nationwide monitoring of nonylphenolic compounds and coprostanol in sediments from Korean coastal waters     

Minkyu Choi  Hyo-Bang Moon  Sang-Soo Kim  Hee-Gu Choi 《Marine pollution bulletin》2009,58(7):1086-1092

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Genesis and Mineralogy of Serpentinite Deposits,West of South Korea     

Song Suckhwan  Choi Seon Gyu  Lee Hyun Koo 《中国地质大学学报(英文版)》2000,11(2)

The serpentinite deposits derived from ultramafic rockswithin the South Korea mainly occur in the west ofChungcheongnam - Do,the south of South Korea,Ulsan andAndong area,and in the middle of South Korea,Gapyeongarea. The present study is on the genesis and m ineral compo-sitions of the serpentinite deposits consisting of abouteighteenmasses in the west of Chungcheongnam- Do. The ultramaficrocks mainly occur as discontinuously isolated lenticular or el-liptical bodies and extend to NNE d…  相似文献   

Laboratory experiment to measure 5-MHz volume backscattering strengths from Red-tide causing microalgae Chattonella antiqua     

Junghun Kim  Jee Woong Choi  Donhyug Kang 《Ocean Science Journal》2012,47(3):173-179

An acoustic laboratory experiment using 5-MHz signals was conducted to measure the volume backscattering strengths of red-tide causing microalgae, Chattonella antiqua, which is one of the species of harmful algal blooms in the coastal waters of Korea and Japan. The measured backscattering strengths increased with cell abundance, with a slope of approximately 10 dB per decade increase in cell numbers. The density and sound speed ratios of the Chattonella cell to the water medium were estimated via the density gradient centrifugation method and the time-travel difference method, respectively. Finally, the measured backscattering strengths were compared to those predicted by a fluid-sphere scattering model, in which the estimated sound speed and density contrasts were used as input parameters.  相似文献   

Characterizing the effect of heavy metal contamination on marine mussels using metabolomics   总被引：1，自引：0，他引：1  

YK Kwon  YS Jung  JC Park  J Seo  MS Choi  GS Hwang 《Marine pollution bulletin》2012,64(9):1874-1879

Marine mussels (Mytilus) are widely used as bioindicators to measure pollution in marine environments. In this study, (1)H NMR spectroscopy and multivariate statistical analyses were used to differentiate mussel groups from a heavy metal-polluted area (Onsan Bay) and a clean area (Dokdo area). Principal component analysis and orthogonal projection to latent structure-discriminant analysis revealed significant separation between extracts of mussels from Onsan Bay and from the Dokdo area. Organic osmolytes (betaine and taurine) and free amino acids (alanine, arginine, glutamine, phenylalanine, and threonine) were more highly accumulated in Onsan Bay mussels compared with Dokdo mussels. These results demonstrate that NMR-based metabolomics can be used as an efficient method for characterizing heavy metal contamination derived from polluted area compared to clean area and to identify metabolites related to environments that are contaminated with heavy metals.  相似文献   

Copepod feeding in a coastal area of active tidal mixing: diel and monthly variations of grazing impacts on phytoplankton biomass   总被引：1，自引：0，他引：1  

Doo B. Lee  Hye Y. Song  Chul Park  Keun H. Choi 《Marine Ecology》2012,33(1):88-105

This study examined monthly feeding rates and grazing impact on phytoplankton biomass, as well as diel feeding rhythms of four key copepod species in a tidally well mixed estuary (Asan Bay, Korean Peninsula). Monthly ingestion rates estimated based on gut pigment analysis were closely associated with their peak densities, but not with phytoplankton biomass, implying high ingestion may be related to reproductive output for population growth. The three smaller copepods, Acartia hongi, Acartia pacifica and Paracalanus parvus, showed feeding preference for smaller phytoplankton (<20 μm) with higher clearance rates, whereas the larger Calanus sinicus preferred larger phytoplankton. Acartia pacifica and P. parvus showed distinct increased nocturnal feeding rates as measured with gut fluorescence, whereas A. hongi showed no significant day–night differences. Copepod diel feeding patterns were not associated with food quantity, and endogenous physiological rhythm might be hypothesized as responsible for the observed diel feeding patterns. Grazing impact on phytoplankton biomass by the four copepods in the estuary was on average 8% (range 0.2–29.8%) of the phytoplankton standing stock, similar to values reported in other coastal waters. Very high copepod abundances but low daily carbon ration (<20% for all copepods) provided by feeding on phytoplankton indicate that copepods also grazed on other non‐phytoplankton foods in Asan Bay.  相似文献