Evolution of the Dok Do seamounts,Ulleung Basin,East Sea: constraints based on the reconstruction of virtual geomagnetic poles using paleomagnetic data     

Chang Hwan Kim  Chan Hong Park  Eui Young Jeong  Jong Sun Hwang  Young Tak Ko 《Geo-Marine Letters》2009,29(3):161-169

In the Ulleung Basin, East Sea, the Dok Do seamount group comprises Dok Do (Dok Island), consisting of very small islets/rocks and a large submerged volcanic edifice, and two voluminous tablemounts, Simheungtaek and Isabu. We attempted to reconstruct the evolution of these seamounts, using virtual geomagnetic poles (VGPs) determined by the least-squares and the seminorm magnetization methods, with 1,500 m upward continued magnetic anomalies. The VGPs of Dok Do with normal dipole anomaly, and of Simheungtaek with normal dipole anomaly are located near the present magnetic pole. The VGP of Isabu with normal dipole anomaly is located at low latitude, presumably due to overprints of reversals in the Tertiary, and the distortion of magnetization and structures associated with volcanism after its formation. In contrast to the tablemounts, magnetic anomalies over Dok Do are a combination of both normal polarity and reversed polarity dipoles in the northern hemisphere, indicating that Dok Do has had at least two major eruptions, one during normal and another during reversed polarity intervals. From these results, and information on the ages of the seamounts (either published radiometric ages of subaerial volcanic rocks, or ages reconstructed in terms of reported elastic thickness incorporated into an existing cooling plate model), we tentatively propose that (1) Isabu formed first, during a normal polarity interval after the opening of the East Sea had ceased; (2) this was followed by an initial and subsequent large eruption of Dok Do during a normal polarity and a reversed polarity interval after about 5 Ma; and (3) the formation of Simheungtaek occurred in between that of Isabu and Dok Do in a normal polarity interval. The pattern of normal/reversed magnetization is not inconsistent with the geomagnetic polarity timescale for at least the last 5 Ma. Nevertheless, precise ages of formation would need verification by additional geophysical/geochemical constraints. Evaluating various possible models explaining the successive formation of the Dok Do seamounts, we currently favor fracturing and volcanism related to compression-induced weakening of the extensional field from the late Miocene to Pliocene after the opening of the East Sea.  相似文献   

Antioxidant efficacy of extracts from a variety of seaweeds in a cellular system     

You Ah Kim  Chang Suk Kong  Young Ran Um  Jung Im Lee  Taek Jeong Nam  Youngwan Seo 《Ocean Science Journal》2008,43(1):31-37

As a part of an ongoing search for antioxidants frodm marine sources, antioxidant activities of 24 kinds of seaweeds (4 green algae, 8 brown algae, and 12 red algae) were investigated. The seaweeds were extracted by acetone/ dichloromethane and methanol, respectively. The antioxidant properties of both extracts were evaluated using four different activity tests, including degree of occurrence of intracellular reactive oxygen species (ROS), NO, lipid peroxidation, and GSH (glutathione) in mouse macrophage Raw 264.7 cells. The levels of intracellular reactive oxygen species (ROS) and GSH were measured using 2’,7’-dichlorofluorescin diacetate (DCF-DA) and monobromobimane as fluorescence probe, respectively. Moreover, the generation of NO and lipid peroxidation products were determined by each method based on the Griess reaction and TBARS assay. Solvent extracts from seaweeds such asScytosiphon lomentaria, Prionitis cornea, Laruencia okamurae,Callophyllis japonica, Sargassum horneri, Dictyopteris divaricat a,Lomentaria catenata, Corallina confuse, Ishige okamurae, andAhnfeltiopsis flabelliformi exhibited high antioxidant activities in cellular oxidizing systems.  相似文献   

Study of the State and Variability of Marine Environment in the Japan/East Sea in Cruise 58 of the R/V Akademik Oparin     

Lobanov  V. B.  Sergeev  A. F.  Kim  G.  Nam  S.  Maryina  E. N.  Han  H.  Popov  O. S.  Tishchenko  P. P.  Vlasova  G. A.  Zverev  S. A.  Choi  S. J.  Jeong  H.  Kim  B.  Kim  Y.  Kim  S. Y.  Lee  I.  Lee  H.  Lee  H.  Leusov  A. E.  Mariaysh  A. A.  Prushkovskaya  I. A.  Rudykh  Y. N.  Ryu  Y.  Ryumina  A. A.  Sagalaev  S. G.  Semkin  P. Y.  Seo  H.  Shkirnikova  E. M.  Shlyk  N. V.  Shvetsova  M. G.  Tsoi  V.  Ulanova  O. A. 《Oceanology》2021,61(4):586-588

Oceanology - Multiyear monitoring of the marine environment of the Japan/East Sea was continued by the joint Korean–Russian expedition of the R/V Akademik Oparin (cruise 58) in...  相似文献   

Finite element method for strong reflection of water waves     

Yong-Sik Cho  Woo-Chang Jeong  Seung-Buhm Woo   《Ocean Engineering》2004,31(5-6):653-667

In this study, the propagation of monochromatic water waves over an arbitrarily varying topography is numerically investigated. A finite element model is developed by formulating the diffraction of waves caused by depth changes. Not only the propagating mode but also the evanescent modes are included in the model. The model developed is applied to the study of strong reflection of monochromatic waves over a sinusoidally varying topography. Predicted reflection coefficients are compared with those of available laboratory experiments and the eigenfunction expansion method. A very good agreement is observed.  相似文献   

Toxicological impact assessment of heavy metal contamination on macrobenthic communities in southern coastal sediments of Korea     

Dhong-il Lim  Jin-Woo Choi  Hyeon Ho Shin  Do Hyun Jeong  Hoi Soo Jung 《Marine pollution bulletin》2013

In the heavily industrialized Masan Bay of southern coast, Korea, the potential harmful effects of heavy metals (Cd, Co, Cu, Ni, Pb, Sn, Zn, and Hg) were evaluated in terms of the pollution load index (PLI) and ecological risk assessment index (ERI) methods, and the results obtained were considered alongside the health of the macrobenthic fauna communities. The results revealed that the bay sediments, especially in the inner bay and the outfall area of a sewage treatment plant, are exposed to moderate to serious levels of metal pollution. Hg and Cd contributed the most to the potential toxicity response indices in sediments recently deposited in the bay. The potential ecological risk assessment of heavy metals in the bay was highlighted by the use of the benthic biological pollution index (BPI), suggesting that the ERI is a useful toxicity response index, which can quantify the overall ecological risk level to a target environment.  相似文献   

Evolution and Sedimentation Mechanisms of Estuarine Beach in the Nakdong River Estuary,Korea: Natural and Human Impact     

Jeong  Joo Bong  Jung  Hoi-Soo  Lee  Jun-Ho  Park  Kyung Kyu  Kim  Seok Yun  Woo  Han Jun 《Ocean Science Journal》2022,57(3):451-466

Ocean Science Journal - Dadae Beach located in the Nakdong River estuary has been continuously evolving as the result of natural and anthropogenetic activities. Due to the geographic...  相似文献   

Characteristics of landslides induced by a debris flow at different geology with emphasis on clay mineralogy in South Korea     

Gyo-Cheol Jeong  Kyeong-Su Kim  Chang-Oh Choo  Jong-Tae Kim  Man-Il Kim 《Natural Hazards》2011,59(1):347-365

Landslides induced by debris flow have been discussed in relation to the geotechnical properties of soil developed on bedrock, together with an emphasis on the importance of mineralogy comprising precursor soils. Three areas composed of different types of geology were compared to relate landslide with soil compositions: Precambrian gneiss (Jangheung area), Jurassic granite (Sangju area), and Tertiary sedimentary rocks composed of shale and mudstone (Pohang area) in Korea. X-ray diffraction for mineral identification and quantitative analysis, Scanning Electron Microscope for observation of microtexture, and laser size analysis for very fine particles ranging from micrometer were performed, with conventional measurements of particle size, porosity, density, permeability, and consistency for the soils. Soils at landslide sites containing a large amount of finer particles have higher uniformity and gradation coefficients, but lower consistency than those at non-landslide sites. Landslide areas are characterized by higher porosity and lower density. Soil from the gneiss area shows a high plasticity index while that of mudstone has high water content. Main clay minerals contained in soils of the sites where landslides took place are illite, chlorite, kaolinite, and montmorillonite. Mineralogical information on the constituents and microtexture of soils aids in better understanding the causes and patterns of landslide, together with mechanical properties of soils.  相似文献   

DEM matching for bias compensation of rigorous pushbroom sensor models   总被引：1，自引：0，他引：1  

Taejung Kim  Jaehoon Jeong 《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(5):692-699

DEM matching is a technique to match two surfaces or two DEMs, at different reference frames. It was originally proposed to replace the need of ground control points for absolute orientation of perspective images. This paper examines DEM matching for precise mapping of pushbroom images without ground control points. We proved that DEM matching based on 3D similarity transformation can be used when model errors are only on the platform’s position and attitude biases. We also proposed how to estimate bias errors and how to update rigorous pushbroom sensor models from DEM matching results. We used a SPOT-5 stereo pair at ground sampling distance of 2.5 m and a reference DEM dataset at grid spacing of 30 m and showed that rigorous pushbroom models with accuracy better than twice of the ground sampling distance both in image and object space have been achieved through DEM matching. We showed further that DEM matching based on 3D similarity transformation may not work for pushbroom images with drift or drift rate errors. We discussed the effects of DEM outliers on DEM matching and automated removal of outliers. The major contribution of this paper is that we validate DEM matching, theoretically and experimentally, for estimating position and attitude biases and for establishing rigorous sensor models for pushbroom images.  相似文献   

Determinants of CO2 emission for post-Soviet Union independent countries     

Jeong Hwan Bae  Dmitriy D. Li  Meenakshi Rishi 《Climate Policy》2013,13(5):591-615

This article analyses the determinants of CO₂ emission for 15 post-Soviet Union independent (PSI) countries given their recent transition to market-based economies and their relatively high levels of corruption. The direct and indirect effects of economic growth on CO₂ emission for the PSI countries are derived using a multiple-equation generalized method of moment (GMM) approach to account for simultaneity among corruption, growth and CO₂ emission. A linear relationship between gross domestic product (GDP) and CO₂ emission was observed from the analysis. Furthermore, GDP influences CO₂ emission directly, but also indirectly through its impact on corruption. Similarly, corruption affects CO₂ emission directly, as well as indirectly through its impact on GDP. Political democracy and economic freedom increase CO₂ emission indirectly through their impact on economic growth. Improved energy efficiency and the EU climate policy reduce CO₂ emission, while inflows of foreign direct investment tend to increase CO₂ emission.

Policy relevance

First, PSI countries need to invest more in efficient energy technologies to mitigate CO₂ emission levels significantly. Second, PSI policies aimed at reducing deforestation (thereby increasing population density) may help mitigate carbon emission. Third, PSI countries would be well served to recognize the detrimental effects of foreign direct investment before embarking on a misguided policy path that attracts such inflows at any cost.  相似文献   

Trace metals (Co,Ni, Cu,Cd, and Pb) in the southern East/Japan Sea     

Jeongwon Kang  Man-Sik Choi  Kap-Sik Jeong  Chang-Bok Lee 《Ocean Science Journal》2014,49(1):47-65

Total dissolvable metals (Co, Ni, Cu, Cd, and Pb) in both surface waters and the water columns were acquired in the southern East/Japan Sea during a cruise around the Ulleung Basin in June 2001 to understand the spatial distributions of the metals. Concentrations in offshore surface waters were found to be Co 60 ± 12 pM, Ni 2.16 ± 0.25 nM, Cu 1.85 ± 0.55 nM, Cd 0.134 ± 0.018 nM, and Pb 155 ± 40 pM. Spatial distributions in surface waters showed that metal levels were generally enhanced at coastal sites in both Korea and Japan, where the metal distributions indicated complex patterns due to inputs, biogeochemical processes, and physical factors including upwelling. The Co distributions in the water columns seemed to be influenced predominantly by surface and bottom inputs, scavenged rather than regenerated at depth. For Cd, there was generally good agreement between the Cd and PO₄ depth distributions, in agreement with the literature. The Cd/PO₄ ratio from the water columns was found to be 0.133–0.203, lower than that in other marginal seas (e.g. the East/South China Seas and the Philippine Sea) of the western Pacific Ocean; this might be a result of the fast ventilation rate in this sea. The vertical Pb profile showed typical scavenged-type behavior with a surface maximum and deep minimum. From a comparison of inputs from the atmosphere and the Tsushima Warm Current, atmospheric deposition is substantial enough that it cannot be ignored, and its role in metal cycling is more significant in the offshore zone.  相似文献