Tephrostratigraphy and paleoenvironmental variation in late Quaternary core sediments of the southwestern Ulleung Basin, East Sea (Sea of Japan)     

Il-Soo  Kim  Myong-Ho  Park  Byong-Jae  Ryu Kang-Min  Yu 《Island Arc》2006,15(1):178-186

Abstract   Data on the late Quaternary tephra layers, tephrostratigraphy, geochemistry and environment were determined in two sediment cores from the southwestern part of Ulleung Basin (East Sea/Sea of Japan), representing marine-oxygen isotope stages 1–3. The cores consist mainly of muddy sediments that are partly interbedded with silty sands, lapilli tephra and ash layers. The lapilli tephra layers (Ulleung-Oki tephra, 9.3 ka) originating from Ulleung Island consist mainly of massive-type glass shards, whereas the ash layers (Aira-Tanzawa ash, 22.0–24.7 ka) derived from southern Kyushu Island are mainly composed of typical plane-type and bubble-wall glasses that are higher in SiO₂ and lower in Na₂O + K₂O than the lapilli tephra layers. Except for the tephra layers, fine-grained sediments throughout the core sections are mostly of marine origin based on geochemical data (C/N ratios, hydrogen index, S2 peak) and Tmax. In particular, organic carbon contents increased during Termination I, probably as a result of an influx of the deglacial Tsushima Current through the Korea Strait.  相似文献   

Seasonally Varying Reference Atmospheres for East Asia     

Byung-Ju SOHN  Geun-Hyeok RYU 《大气科学进展》2007,24(2):181-190

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Removal of lead(II) from aqueous stream by hydrophilic modified kapok fiber using the Fenton reaction     

Dongfang Wang  Daeik Kim  Chul-Ho Shin  Yufeng Zhao  Joon-Seok Park  Moonhee Ryu 《Environmental Earth Sciences》2018,77(18):653

A hydrophilic kapok fiber was prepared by a chemical process of the Fenton reaction and used as an adsorbent to remove Pb(II) from aqueous solution. The effects of experimental parameters including pH, contact time, Pb(II) concentration, and coexisting heavy metals were estimated as well as evaluated. The optimum concentrations of FeSO₄ and H₂O₂ for the Fenton reaction-modified kapok fiber (FRKF) were 0.5 mol L^?1 and 1 mol L^?1, respectively. The adsorption kinetic models and isotherm equations of Langmuir and Freundlich were conducted to identify the most optimum adsorption rate and adsorption capacity of Pb(II) on FRKF. The FRKF displayed an excellent adsorption rate for Pb(II) in single metal solution with the maximum adsorption capacity of 94.41?±?7.56 mg g^?1 at pH 6.0. Moreover, the FRKE still maintained its adsorption advantage of Pb(II) in the mixed metal solution. The FRKF exhibited a considerable potential in removal of metal content in wastewater streams.  相似文献   

A numerical study of the interactions of urban breeze circulation with mountain slope winds     

Gantuya Ganbat  Jong-Jin Baik  Young-Hee Ryu 《Theoretical and Applied Climatology》2015,120(1-2):123-135

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Geological and Geotechnical Characteristics of Marine Clays at the Busan New Port   总被引：1，自引：0，他引：1  

S. G. Chung  C. K. Ryu  K. Y. Jo  D. Y. Huh 《Marine Georesources & Geotechnology》2005,23(3):235-251

Despite a number of geotechnical investigations that have been carried out in the Busan new port area of South Korea, the local practicing engineers have been unable to deduce successfully the geotechnical properties of the clays due to their spatial variation. In the area, clay deposits, so-called Pusan clays, are unusually thick, varying from 20 m to 70 m in thickness. For this study, comprehensive geological and geotechnical investigations were carried out with sophisticated sampling techniques, in situ and laboratory tests as well as geological analyses at an additional three locations. As a result of the investigations, it was found that depositional environments are closely related to the relative changes in sea level and have different features depending on location and depth. The clays consist of soft and stiff clays in the upper and the lower layers, respectively, which are classified as normally consolidated and cemented clay. Moreover, most of the geotechnical properties undergo small changes due to their depositional environment. Information about these effects would be quite helpful to understand the spatial variation of geotechnical properties as well as the effect of sample disturbance. Some correlations which reflect the geological history of the deposts were conducted for physical indexes and mechanical properties.  相似文献   

Applying a coupled hydrometeorological simulation system to flash flood forecasting over the Korean Peninsula     

Young Ryu  Yoon-Jin Lim  Hee-Sook Ji  Hyun-Hee Park  Eun-Chul Chang  Baek-Jo Kim 《Asia-Pacific Journal of Atmospheric Sciences》2017,53(4):421-430

In flash flood forecasting, it is necessary to consider not only traditional meteorological variables such as precipitation, evapotranspiration, and soil moisture, but also hydrological components such as streamflow. To address this challenge, the application of high resolution coupled atmospheric-hydrological models is emerging as a promising alternative. This study demonstrates the feasibility of linking a coupled atmospheric-hydrological model (WRF/WRFHydro) with 150-m horizontal grid spacing for flash flood forecasting in Korea. The study area is the Namgang Dam basin in Southern Korea, a mountainous area located downstream of Jiri Mountain (1915 m in height). Under flash flood conditions, the simulated precipitation over the entire basin is comparable to the domain-averaged precipitation, but discharge data from WRF-Hydro shows some differences in the total available water and the temporal distribution of streamflow (given by the timing of the streamflow peak following precipitation), compared to observations. On the basis of sensitivity tests, the parameters controlling the infiltration of excess precipitation and channel roughness depending on stream order are refined and their influence on temporal distribution of streamflow is addressed with intent to apply WRF-Hydro to flash flood forecasting in the Namgang Dam basin. The simulation results from the WRF-Hydro model with optimized parameters demonstrate the potential utility of a coupled atmospheric-hydrological model for forecasting heavy rain-induced flash flooding over the Korean Peninsula.  相似文献   

Changes in spatial variations of sap flow in Korean pine trees due to environmental factors and their effects on estimates of stand transpiration     

Minkyu Moon  Taekyu Kim  Juhan Park  Sungsik Cho  Daun Ryu  Sanguk Suh  Hyun Seok Kim 《山地科学学报》2016,13(6):1024-1034

It is difficult to scale up measurements of the sap flux density (Js) for the characterization of tree or stand transpiration (E) due to spatial variations in JS and their temporal changes. To assess spatial variations in the sap flux density of Korean pine (Pinus koraiensis) and their effects on E estimates, we measured the Js using Granier-type sensors. Within trees, the Js decreased exponentially with the radial depth, and the Js of the east aspects were higher than those of the west aspects. Among trees, there was a positive relationship between Js and the tree diameter at breast height, and this positive relationship became stronger as the transpiration demand increased. The spatial variations that caused large errors in E estimates (i.e., up to 110.8 % when radial variation was ignored) had varied systematically with environmental factors systematic characteristics in relation to environmental factors. However, changes in these variations did not generate substantial errors in the E estimates. For our study periods, the differences in the daily E (E _D) calculated by ignoring radial, azimuthal and tree-to-tree variations and the measured E _D were fairly constant, especially when the daily vapor pressure deficit (D__D) was higher than 0.6 kPa. These results imply that the effect of spatial variations changes on sap flow can be a minor source of error compared with spatial variations (radial, azimuthal and tree-to-tree variations) when considering E estimates.  相似文献   

Experimental investigation of dry density effects on dielectric properties of soil–water mixtures with different specific surface areas     

Orangi  A.  Narsilio  G. A.  Wang  Y. H.  Ryu  D. 《Acta Geotechnica》2020,15(5):1153-1172

The dielectric constant of soil is used to estimate its water content in a range of applications. Unlike the widely known effect of water content on the soil dielectric constant (consistent direct proportionality), only a limited number of studies have reported the effects of soil dry density, however, with equivocal results. This paper, therefore, investigates the effects of dry density or degree of compaction on the dielectric constant of five different soil types. The results of the experimental work for the soils ranging from sand to Bentonite clay with distinct specific surface areas were evaluated based on the use of two simple mixture models (De Loor and Birchak). The effects of dry density on the soil dielectric constant were found to be soil type dependent. This is demonstrated by the experimental data and further proven by the modified De Loor model. The behavior is shown to be defined by the changes in the free water, bound water, and solid particle volume fractions, ultimately controlled by the soil specific surface area. The dielectric constant changes from being directly proportional to dry density to inversely proportional at a threshold specific surface area of between 122 and 147 m²/g. Supported by the experimental observations, parametric analysis has revealed that the range for the dielectric constant of bound water was found to be 9–37, while the geometrical parameter α in the Birchak model was found to be 0.4–0.8.

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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   

Landslide susceptibility mapping using certainty factor, index of entropy and logistic regression models in GIS and their comparison at Mugling�CNarayanghat road section in Nepal Himalaya     

Krishna Chandra Devkota  Amar Deep Regmi  Hamid Reza Pourghasemi  Kohki Yoshida  Biswajeet Pradhan  In Chang Ryu  Megh Raj Dhital  Omar F. Althuwaynee 《Natural Hazards》2013,65(1):135-165

Landslide susceptibility maps are vital for disaster management and for planning development activities in the mountainous country like Nepal. In the present study, landslide susceptibility assessment of Mugling?CNarayanghat road and its surrounding area is made using bivariate (certainty factor and index of entropy) and multivariate (logistic regression) models. At first, a landslide inventory map was prepared using earlier reports and aerial photographs as well as by carrying out field survey. As a result, 321 landslides were mapped and out of which 241 (75?%) were randomly selected for building landslide susceptibility models, while the remaining 80 (25?%) were used for validating the models. The effectiveness of landslide susceptibility assessment using GIS and statistics is based on appropriate selection of the factors which play a dominant role in slope stability. In this case study, the following landslide conditioning factors were evaluated: slope gradient; slope aspect; altitude; plan curvature; lithology; land use; distance from faults, rivers and roads; topographic wetness index; stream power index; and sediment transport index. These factors were prepared from topographic map, drainage map, road map, and the geological map. Finally, the validation of landslide susceptibility map was carried out using receiver operating characteristic (ROC) curves. The ROC plot estimation results showed that the susceptibility map using index of entropy model with AUC value of 0.9016 has highest prediction accuracy of 90.16?%. Similarly, the susceptibility maps produced using logistic regression model and certainty factor model showed 86.29 and 83.57?% of prediction accuracy, respectively. Furthermore, the ROC plot showed that the success rate of all the three models performed more than 80?% accuracy (i.e. 89.15?% for IOE model, 89.10?% for LR model and 87.21?% for CF model). Hence, it is concluded that all the models employed in this study showed reasonably good accuracy in predicting the landslide susceptibility of Mugling?CNarayanghat road section. These landslide susceptibility maps can be used for preliminary land use planning and hazard mitigation purpose.  相似文献