• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.293-297
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• 2006

Submarine groundwater discharge (SGD) and the interface between seawater and freshwater in an unconfined coastal aquifer was evaluated by numerical modeling. A two-dimensional vertical cross section of the aquifer was constructed. Coupled flow and salinity transport modeling were peformed by using a numerical code FEFLOW In this study, we investigated the changes in groundwater flow and salinity transport in coastal aquifer with hydraulic condition such as the magnitude of recharge flux, hydraulic conductivity. Especially, transient simulation considering tidal effect and seasonal change of recharge rate was simulated to compare the difference between quasi-steady state and transient state. Results show that SGD flux is in proportion to the recharge rate and hydraulic conductivity, and the interface between the seawater and the freshwater shows somewhat retreat toward the seaside as recharge flux increases. Considered tidal effect, SGD flux and flow directions are affected by continuous change of the sea level and the interface shows more dispersed pattern affected by velocity variation. The cases which represent variable daily recharge rate instead of annual average value also shows remarkably different result from the quasi-steady case, implying the importance of transient state simulation.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.205-212
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• 2006

Atmospheric drag is the most significant factor effecting the low Earth satellites under the altitude of 800 km Although the atmospheric density of the low Earth orbit is very low compared to that of the sea level, the accumulated effect of the atmospheric drag slowly lowers the satellite velocity at the perigee. Decrease in velocity at perigee directly causes decrease in altitude at apogee which changes the eccentricity of the orbit. The orbit finally reaches a circular orbit before reentering the Earth. This paper states the methods of calculating the atmospheric drag and the lifetime of the satellite. The lifetime of the kick motor and the satellites which will be used on KSLV-L are calculated by Satellite Tool Kit.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.1
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• pp.34-42
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• 1990

The tides in the Saemanguem Area, the western coast of Korea have been examined based on simulations with barotropic depth-integrated model. As a first step tidal computations were performed with open-boundary sea level forcing from four major constitutents ($M_2$, $S_2$, $K_1$, and $O_1$). Subsequently the established model was utilized to investigate the effect of construction of tidal barriers for Saemanguem development plan on the existing tidal regime. It has been shown that tide of semi-diurnal constituents may be reduced to 2-7 cm in amplitude along the frontal area of proposed barrier. In connection with above changes the tidal current regime may be subjected to significant reduction in intensity. thus suggesting the high possibility of sedimentation along the frontal region of tidal barrier.

• Journal of the Korean Magnetic Resonance Society
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• v.6 no.2
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• pp.84-88
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• 2002

Dating and dosimetry using electron spin resonance (ESR) in 20th Century developed at both Yamaguchi University and Osaka University have been reviewed with emphasis on new prospects and strategies in 21th century. Natural radiation have been generating radicals that accumulated in archaeological and geological materials. ESR detects these radicals and the ESR signal intensity is proportional to the radiation dose and therefore the age. The assessment of the total dose of natural radiation and the annual dose rate give their ESR ages. The ESR dating of stalactites and stalagmites ant Akiyoshi cave in Yamaguchi prefecture in 1975 was extended to anthropological dating using bones and tooth enamel excavated in Greek Petralona cave. Fossils of shells and corals gave the ages of marine terraces and sea-level changes. Quartz grains gave the ages of geothermal alteration and fault movements. Future ESR dating of ices at outer planets anf their satellite are also investigated as basic studies for ices od $H_2O,\;CO_2,\;SO_2$ as well as terrestrial hydrates in laboratory. Atomic bomb radiation dosimetry at Hiroshima and Nagasaki using ESR lead to the dosimetry of personnel, Chemobyl and JCO criticality accidents. Monitoring of radiation dose with sensitive materials with tissue equivalence are being developed. finally a new scanning ESR imaging apparatus (a near field microwave microscope) developed in our laboratory gave ESR images of Radicals from fossils to Si-CVD and diamond films as summarized in my book in 2002.

• Journal of The Geomorphological Association of Korea
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• v.24 no.2
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• pp.51-64
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• 2017

The paleo-environments including changes in vegetation, climate, and sea level since the middle Holocene(6,400(?)-1,800(?) yr BP) were reconstructed with the special reference to pollen analysis from two trench samples at Yulha-dong, Kimhae-si, southern Korea. The environmental characteristics by the pollen zonation wassummarized asfollows: Pollenzone I(6,400(?)~3,940(?) yr BP)showed the dominance of Quercus species with broad-leaved trees, it was warm condition. Pollenzone II(3,940(?)~2,300(?) yr BP) was characterized to the yellow soil indicating terrestrial environment. Moreover, it showed Alnus-NAP period related to the extension of agriculture and deforestation by the rapid decrease of Quercus and increase of Gramineae. Pollenzone III(2,300(?)~1,800(?) yr BP) showed human impact from the increase of NAP and Pinus. Plenty of Quercus with deciduous broad-leaved trees also suggested warmer condition than before.

• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.95-105
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• 2021

Extensive groundwater abstraction has been recognized as one of the major challenges in management of coastal groundwater. The purpose of this study was to assess potential changes of groundwater distribution of northeastern Jeju Island over 10-year duration, where brackish water have been actively developed. To quantitatively estimate the coastal groundwater resources, numerical simulations using three-dimensional finite-difference density-dependent flow models were performed to describe spatial distribution of the groundwater in the aquifer under various pumping and recharge scenarios. The simulation results showed different spatial distribution of freshwater, brackish, and saline groundwater at varying seawater concentration from 10 to 90%. Volumetric analysis was also performed using three-dimensional concentration distribution of groundwater to calculate the volume of fresh, brackish, and saline groundwater below sea level. Based on the volumetric analysis, a quantitative analysis of future seawater intrusion vulnerability was performed using the volume-based vulnerability index adopted from the existing analytical approaches. The result showed that decrease in recharge can exacerbate vulnerability of coastal groundwater resources by inducing broader saline area as well as increasing brackish water volume of unconfined aquifers.

• Korean Journal of Exercise Nutrition
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• v.13 no.1
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• pp.45-50
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• 2009

This study evaluated the effects of D-ribose supplementation on exercise time in a hypoxic chamber. Eight healthy young males participated in experiments under all four different conditions; placebo+normoxic, placebo+hypoxic, ribose+normoxic, and ribose+hypoxic. Subjects took 1 g per 10 kg body weight of ribose dissolved in drinking water 30 minutes before and immediately before running. We observed the run-to-exhaustion time, the maximum heart rate, and the changing pattern of the heart rate during exercise. The longest running time was achieved when subjects ran under normoxic condition with ribose supplementation. The shortest running time occurred when subjects ran under hypoxic conditions without ribose supplementation. We measured MDA and GPx to determine any changes in oxidative stresses or antioxidative systems. MDA was affected by the environmental conditions and the running time. The activity of GPx showed a significant difference only with the different environmental conditions of exercise. The results of this study indicate that ribose can be considered a possible ergogenic during exercise in specific conditions, but more detailed and well-controlled studies are needed to make a definitive conclusion.

• Journal of the Mineralogical Society of Korea
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• v.28 no.1
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• pp.71-81
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• 2015

This study was carried out in order to investigate the mineralogical characteristics of the core sediments (03GHP-02 and HB13-2), obtained from the Ulleung Basin and Hupo Basin, Korea. The results on mineral compositions, clay mineral compositions, and the total contents and sequential extraction of different fractions of the phosphorus in core samples showed that those values are different in two cores and also at different depths. In both samples, mineral compositions were the same, composed mainly of quartz, microcline, albite, calcite, opal A, pyrite, and clay minerals (illite, chlorite, kaolinite, and smectite). However, the sample from Hupo Basin contains more opal A. Both samples, especially the ones from Hupo Basin contains more smectite than those reported from East Sea, indicating the influence of paleo-Hwangwei River and the Tertiary Formation of Korea Peninsula. For the samples from Uleung Basin, at 0.7-3.5 m range in depth, the low content of opal A and the low illite crystallinity index can be inferred to indicate the relatively cool climate, corresponding to the ice age. Also, the content of total phosphorus was low in those samples. It was reported that East Sea at that time was isolated from the neighboring seas due to the decrease of the sea level, and as a result, the influx of sediments was supposed to be little through the strait and rivers. For the samples from Hupo Basin, there is no significant changes in clay mineral composition and the distribution of phosphorus with increasing depth. This little change can be interpreted to indicate that the sediments comprising the core might be deposited in a relatively short period of time or deposited in sedimentary environment in which there's no significant changes in sediment supplies. The values of crystallinity index of clay minerals are high in those samples, indicating that it was relatively warm during that time. Although the increase of fluctuation pattern can be observed, showing that the climate of this period often changed, it is supposed that it was generally warm.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.23 no.1
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• pp.55-59
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• 1978

This study was carried out to investigate the sea sonal changes of the contents of inhibitors in leaves and fruits of Ginseng plant during ripening. Three kinds of inhibitors in leaves and all parts of fruit, i.e., seed, sarcocarp and endocarp were recognized at the Rf 0.1, 0.4-0.6 and 0.8-1.0 zones by the bioassay of lettuce seed germination. Among them, the level of the inhibitor at the Rf 0.4-0.6 zone in leaf and seed increased most significantly in accordance with fruit ripening. The activities of three inhibitors found in endocarp gradually decreased during ripening.

• Journal of the Korean earth science society
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• v.32 no.6
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• pp.586-594
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• 2011

Gravity Recovery and Climate Experiment (GRACE), launched in April, 2002, makes it possible to monitor Earth's mass redistribution with its time-varying gravity observation. GRACE provides monthly gravity solutions as coefficients of spherical harmonics, and thus ones need to convert the gravity spectrum to gravity grids (or mass grids) via the spherical harmonics. GRACE gravity solutions, however, include spatial alias error as well as noise, which requires to suppress in order to enhance signal to noise ratio. In this study, we present the GRACE data processing procedures and introduce some applications of time-varying gravity, which are studies of terrestrial water storage changes, Antarctic and Greenland ice melting, and sea level rise. Satellite missions such as GRACE will continue up to early 2020, and they are expected to be an essential resource to understand the global climate changes.