A discontinuity in the late Pleistocene alluvial deposits,Hwacheon‐ri,Gyeongju, Korea: Occurrences and paleoenvironmental implication          下载免费PDF全文

Hoil Lee  In Sung Paik  Hyun Joo Kim  Hee‐Cheol Kang  Won Gyeong Seol  Jin‐Young Lee 《Island Arc》2018,27(4)

A sedimentary discontinuity is present in the late Pleistocene alluvial deposits exposed along the cliff in stream side, Gyeongju, Korea. Sedimentological study, Optically Stimulated Luminescence (OSL) age dating, and X‐ray diffraction (XRD), and X‐ray fluorescence spectrometer (XRF) analyses were conducted in order to interpret the origin of the discontinuity surface. Based on the sedimentological study, these deposits can be divided into three distinct stages, in ascending order: (Stage 1) development of a braided stream flowing from south to north and deposition by debris flows from the mountain aside the stream during and/or after deposition of the braided stream; (Stage 2) deposition by intermittent events during a state of stagnation after the abandonment or migration of the previously existed braided stream; and (Stage 3) deposition of gravels from debris flows from the mountain aside the stream. Hornfelsic gravels are common in Stage 1, whereas andesitic gravels are predominant in Stage 3, suggesting the provenance change from Stage 1 to Stage 3. The discontinuity surface is laterally extensive and marked by a distinct carbonaceous dark grey horizon between Stage 2 and Stage 3. It is characteristic that rootlets mineralized by vivianite are present, and iron‐oxide crusts are cutting across irregularly below the discontinuity surface. It is thus interpreted that the shift of depositional environment from an alluvial plain (Stage 2) (125 ka) to an alluvial fan (Stage 3) (94–55 ka) was an alluvial response to sea level change from the interglacial to the glacial. The development of iron‐oxide crusts and diagenetic vivianite in the discontinuity surface suggests humid condition persisted during the paleoclimatic shift from the last interglacial to the last glacial stages.  相似文献   

Predicting future water demand for Long Xuyen Quadrangle under the impact of climate variability     

Seung Kyu Lee  Truong An Dang 《Acta Geophysica》2018,66(5):1081-1092

Long Xuyen Quadrangle is one of the important agricultural areas of the Mekong Delta of Vietnam accounting for 25% of rice production. In recent years, the area faces drought and salinization problems, as part of climate change impact and sea level rise. These are the main causes that led to the crop water deficits for agricultural production. Therefore, this work was conducted to predict crop water requirement (CWR) based on consideration of other related meteorological factors and further redefine the crop planting calendar (CPC) for three main cropping seasons including winter–spring (WS), summer–autumn (SA) and autumn–spring (AS) using the Cropwat crop model based on the current climate conditions and future climate change scenarios. Meteorological data for the baseline period (2006–2016) and future corresponding to timescales 2020s, 2055s and 2090s of Representative Concentration Pathways (RCP)4.5 and RCP8.5 scenarios are used to predict CWR and CPC for the study area. The results showed that WS and SA crops needed more irrigation water than AS crop and the highest irrigation water requirement of the WS and SA crops occurred on developmental stage, while the AW crop appeared on growth, developmental and late stage for the baseline and timescales of RCP4.5 and RCP8.5 scenarios. Calculation results of the shift of CPC indicated that the CWR of the AW crop decreased lowest approximately 6.6–20.6% for timescales of RCP4.5 scenario and 20.6–25.5% for RCP8.5 scenario compared with the baseline.  相似文献   

Improved design of sliding mode control for civil structures with saturation problem     

Sang‐Hyun Lee  Kyung‐Won Min  Young‐Cheol Lee  Lan Chung 《地震工程与结构动力学》2004,33(11):1147-1164

A systematic and improved design procedure for sliding mode control (SMC) of seismically excited civil structures with saturation problem is provided in this paper. In order to restrict the control force to a certain level, a procedure for determining the upper limits of the control forces for single or multiple control units is proposed based on the design response spectrum of external loads. Further, an efficient procedure using the LQR method for determining sliding surfaces appropriate for different controller types is provided through the parametric evaluation of the dynamic characteristics of sliding surfaces in terms of SMC controller performance. Finally, a systematic design procedure for SMC required to achieve a given performance level is provided and its effectiveness is verified by applying it to multi‐degree‐of‐freedom (MDOF) systems. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Application of a Conceptual Ecological Model to Predict the Effects of Sand Mining around Chilsan Island Group in the West Coast of Korea     

Jae-Won Yoo  Chan-Woo Lee  Yong-Woo Lee  Chang-Soo Kim  Chang-Gun Lee  Keun-Hyung Choi  Seung Won Jung  Sung-Joo Jin  Kyu-Hee Son 《Ocean Science Journal》2018,53(3):521-534

Chilsan Island Group, located on the west coast of South Korea, has been recognized as a critical breeding and nursery ground for endangered seabirds because food is abundant and human activity is low. Chilsan Island Group has been under protection as a Natural Monument (Article no. 389) since 1997, but attempts were made in 2004 to exploit the coastal sands around the islands. A conceptual ecological model (CEM) was employed with energy flow diagram (EFD) to predict the effects of sand mining on the islands’ ecosystem. The results showed that sand mining activities caused long-term damage to benthic ecosystems and threatened seabird communities by reducing fish populations throughout the food web. The changes in energy flow in the ecosystem due to sand mining operations predict that reduction in secondary production of benthic animal communities might reduce energy transfer to humans and seabirds by 30%. Different ranges of uncertainty provided by the Monte Carlo simulation lead to the conclusion that sand mining could bring about undesirable consequences. One concern is that such negative consequences would have a much more severe impact on seabirds than humans because seabirds cannot compete effectively against humans for the limited food sources. In this study, the complex interrelationships between ecosystem members were simplified and a CEM was established to clearly identify which elements would be affected. The CEM with EFD was found to be helpful in promoting communication between stakeholders, and it is expected to be widely used as a decisionmaking tool by public officials.  相似文献   

Evaluation of the compression index of soils using an artificial neural network   总被引：1，自引：0，他引：1  

Hyun Il Park  Seung Rae Lee 《Computers and Geotechnics》2011

The compression index is a one of the important soil parameters that is essential to geotechnical designs. As the determination of the compression index from consolidation tests is relatively time-consuming, empirical formulas based on soil parameters can be useful. Over the decades, a number of empirical formulas have been proposed to relate the compressibility to other soil parameters, such as the natural water content, liquid limit, plasticity index, specific gravity, and others. Each of the existing empirical formulas yields good results for a particular test set, but cannot accurately or reliably predict the compression index from various test sets. In this study, an alternative approach, an artificial neural network (ANN) model, is proposed to estimate the compression index with numerous consolidation test sets. The compression index was modeled as a function of seven variables including the natural water content, liquid limit, plastic index, specific gravity, and soil types. Nine hundred and forty-seven consolidation tests for soils sampled at 67 construction sites in the Republic of Korea were used for the training and testing of the ANN model. The predicted results showed that the neural network could provide a better performance than the empirical formulas.  相似文献   

Mechanism of tremolite carbonation     

Kyoung Won RyuMyung Gyu Lee  Young Nam Jang 《Applied Geochemistry》2011,26(7):1215-1221

The direct aqueous carbonation of fibrous tremolite was investigated by TEM, powder XRD, and FT-IR to elucidate the transformation mechanism of tremolite into calcite. The TEM study revealed that tremolite dissolves along the weak cleavage on (1 0 0) and (1 1 0) and the cleavage fragment fibers. The preferential release of Ca, relative to Si or Mg, into the solution resulted in the crystallization of compositionally homogeneous calcite and in the concurrent formation of proto-saponite. X-ray diffraction analysis revealed that the amount of product calcite increased rapidly within 15 min. Subsequently, after a 5 h carbonation period, it increased slowly to about 60%. The product calcite is euhedral. In contrast, the unreacted tremolite grains retain the original crystal structure even after prolonged carbonation. The morphological modification of tremolite from fibrous to round may have important implications for the elimination of its toxicity.  相似文献   

Mineral Chemistry and Age Dating of W-skarn Deposit at Weondong mine,Taebak in Korea     

Chang-Yoon PARK  Yungoo SONG  Il-Mo KANG  Donghoon JUNG  Khulganakhuu CHULUUNBAATAR 《《地质学报》英文版》2013,87(Z1):676-677

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Uncertainties Monitoring Groundwater Levels in Exploratory Wells     

J. David Rogers  Jae‐Won Chung 《Ground water》2013,51(1):2-4

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A comparative study on a simple two-parameter monthly water balance model and the Kajiyama formula for monthly runoff estimation     

Soojun Kim  Seung Jin Hong  Narae Kang  Hui Seong Noh  Hung Soo Kim 《水文科学杂志》2013,58(7):1244-1252

ABSTRACT

A two-parameter monthly water balance model to simulate runoff can be used for a water resources planning programme and climate impact studies. However, the model estimates two parameters of transformation of time scale (c) and of the field capacity (SC) by a trial-and-error method. This study suggests a modified methodology to estimate the parameters c and SC using the meteorological and geological conditions. The modified model is compared with the Kajiyama formula to simulate the runoff in the Han River and International Hydrological Programme representative basins in South Korea. We show that the estimated c and SC can be used as the initial or optimal values for the monthly runoff simulation study in the model.