• Korean Journal of Remote Sensing
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• v.37 no.3
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• pp.515-530
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• 2021

This study is to estimate soil moisture (SM) using Sentinel-1A/B C-band SAR (synthetic aperture radar) images and Multiple Linear Regression Model(MLRM) in the Yongdam-Dam watershed of South Korea. Both the Sentinel-1A and -1B images (6 days interval and 10 m resolution) were collected for 5 years from 2015 to 2019. The geometric, radiometric, and noise corrections were performed using the SNAP (SentiNel Application Platform) software and converted to backscattering coefficient of VV and VH polarization. The in-situ SM data measured at 6 locations using TDR were used to validate the estimated SM results. The 5 days antecedent precipitation data were also collected to overcome the estimation difficulty for the vegetated area not reaching the ground. The MLRM modeling was performed using yearly data and seasonal data set, and correlation analysis was performed according to the number of the independent variable. The estimated SM was verified with observed SM using the coefficient of determination (R²) and the root mean square error (RMSE). As a result of SM modeling using only BSC in the grass area, R² was 0.13 and RMSE was 4.83%. When 5 days of antecedent precipitation data was used, R² was 0.37 and RMSE was 4.11%. With the use of dry days and seasonal regression equation to reflect the decrease pattern and seasonal variability of SM, the correlation increased significantly with R² of 0.69 and RMSE of 2.88%.

• Korean Journal of Ecology and Environment
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• v.45 no.2
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• pp.158-173
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• 2012

The objectives of this study were to analyze the longitudinal gradient and temporal variations of water quality in Daecheong Reservoir in relation to the major inflowing streams from the watershed, during 2001~2010. For the study, we selected 7 main-stream sites of the reservoir along the main axis of the reservoir, from the headwater to the dam and 8 tributary streams. In-reservoir nutrients of TN and TP showed longitudinal declines from the headwater to the dam, which results in a distinct zonation of the riverine ($R_z$, M1~M3), transition ($T_z$, M4~M6), and lacustrine zone ($L_z$, M7) in water quality, as shown in other foreign reservoirs. Chlorophyll-a (CHL) and BOD as an indicator of organic matter, were maximum in the $T_z$. Concentration of total phosphorus (TP) was the highest (8.52 $mg\;L^{-1}$) on March in the $R_z$, and was the highest (165 ${\mu}g\;L^{-1}$) in the $L_z$ on July. Values of TN was the maximum (377 ${\mu}g\;L^{-1}$) on August in the $R_z$, and was the highest (3.76 $mg\;L^{-1}$) in the $L_z$ on August. Ionic dilution was evident during September~October, after the monsoon rain. The mean ratios of TN : TP, as an indicator of limiting factor, were 88, which indicates that nitrogen is a surplus for phytoplankton growth in this system. Nutrient analysis of inflowing streams showed that major nutrient sources were headwater streams of T1~T2 and Ockcheon-Stream of T5, and the most influential inflowing stream to the reservoir was T5, which is located in the mid-reservoir, and is directly influenced by the waste-water treatment plants. The key parameters, influenced by the monsoon rain, were TP and suspended solids (SS). Empirical models of trophic variables indicated that variations of CHL in the $R_z$ ($R^2$=0.044, p=0.264) and $T_z$ ($R^2$=0.126, p=0.054) were not accounted by TN, but were significant (p=0.032) in the $L_z$. The variation of the log-transformed $I_r$-CHL was not accounted ($R^2$=0.258, p=0.110) by $I_w$-TN of inflowing streams, but was determined ($R^2$=0.567, p=0.005) by $I_w$-TP of inflowing streams. In other words, TP inputs from the inflowing streams were the major determinants on the in-reservoir phytoplankton growth. Regression analysis of TN : TP suggested that the ratio was determined by P, rather than N. Overall, our data suggest that TP and suspended solids, during the summer flood period, should be reduced from the eutrophication control and P-input from Ockcheon-Stream should be controlled for water quality improvement.

• Progress in Medical Physics
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• v.14 no.1
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• pp.15-19
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• 2003

High dose rate (HDR) brachytherapy for treating a cervix carcinoma has become popular, because it eliminates many of the problems associated with conventional brachytherapy. In order to improve the clinical effectiveness with HDR brachytherapy, a dose calculation algorithm, optimization procedures, and image registrations need to be verified by comparing the dose distributions from a planning computer and those from a phantom. In this study, the phantom was fabricated in order to verify the absolute doses and the relative dose distributions. The measured doses from the phantom were then compared with the treatment planning system for the dose verification. The phantom needs to be designed such that the dose distributions can be quantitatively evaluated by utilizing the dosimeters with a high spatial resolution. Therefore, the small size of the thermoluminescent dosimeter (TLD) chips with a dimension of <1/8"and film dosimetry with a spatial resolution of <1mm used to measure the radiation dosages in the phantom. The phantom called a pelvic phantom was made from water and the tissue-equivalent acrylic plates. In order to firmly hold the HDR applicators in the water phantom, the applicators were inserted into the grooves of the applicator holder. The dose distributions around the applicators, such as Point A and B, were measured by placing a series of TLD chips (TLD-to-TLD distance: 5mm) in the three TLD holders, and placing three verification films in the orthogonal planes. This study used a Nucletron Plato treatment planning system and a Microselectron Ir-192 source unit. The results showed good agreement between the treatment plan and measurement. The comparisons of the absolute dose showed agreement within $\pm$4.0 % of the dose at point A and B, and the bladder and rectum point. In addition, the relative dose distributions by film dosimetry and those calculated by the planning computer show good agreement. This pelvic phantom could be a useful to verify the dose calculation algorithm and the accuracy of the image localization algorithm in the high dose rate (HDR) planning computer. The dose verification with film dosimetry and TLD as quality assurance (QA) tools are currently being undertaken in the Catholic University, Seoul, Korea.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.2
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• pp.60-74
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• 2017

To facilitate prevention of highly pathogenic avian influenza (HPAI), a GIS is widely used for monitoring, investigating epidemics, managing HPAI-infected farms, and eradicating the disease. After the outbreak of foot-and-mouth disease in 2010 and 2011, the government of the Republic of Korea (ROK) established the GIS-based Korean Animal Health Integrated System (KAHIS) to avert livestock epidemics, including HPAI. However, the KAHIS is not sufficient for controlling HPAI outbreaks due to lack of responsibility in fieldwork, such as sterilization of HPAI-infected poultry farms and regions, control of infected animal movement, and implementation of an eradication strategy. An outbreak prediction model to support efficient HPAI control in the ROK is proposed here, constructed via analysis of HPAI outbreak patterns in the ROK. The results show that 82% of HPAI outbreaks occurred in Jeolla and Chungcheong Provinces. The density of poultry farms in these regions were $2.2{\pm}1.1/km^2$ and $4.2{\pm}5.6/km^2$, respectively. In addition, reared animal numbers ranged between 6,537 and 24,250 individuals in poultry farms located in HPAI outbreak regions. Following identification of poultry farms in HPAI outbreak regions, an HPAI outbreak prediction model was designed using factors such as the habitat range for migratory birds(HMB), freshwater system characteristics, and local road networks. Using these factors, poultry farms which reared 6,500-25,000 individuals were filtered and compared with number of farms actually affected by HPAI outbreaks in the ROK. The HPAI prediction model shows that 90.0% of the number of poultry farms and 54.8% of the locations of poultry farms overlapped between an actual HPAI outbreak poultry farms reported in 2014 and poultry farms estimated by HPAI outbreak prediction model in the present study. These results clearly show that the HPAI outbreak prediction model is applicable for estimating HPAI outbreak regions in ROK.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.10 no.1
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• pp.92-99
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• 2005

To discriminate the provenance of shelf sediments in the East China Sea, textural and elemental compositions along with strontium isotopic ratio ($^{87}Sr/^{86}Sr$) were analyzed and compared with the sediments originated from Chinese rivers. The sediments in the study area are composed of fine-grained mud with a mean grain size of $47\;{\phi}$ and their $CaCO_3$, contents range from 3.9 to 11.5% (average 7.6%). In the study area, the content of most metallic elements are strongly constrained by sediment grain size (quartz dilution effect) and that of biogenic material and, thereby, their spatial distribution seems not enough for understanding sediment provenance in the study area. The muddy sediments of the Yangtze river have much lower $^{87}Sr/^{86}Sr$ ratio ($0.71197{\sim}0.71720$) than the Yellow Sea shelf muddy sediments which are supposed to be originated from the Huanghe river ($0.72126{\sim}0.72498$), suggesting the distribution pattern of $^{87}Sr/^{86}Sr$ ratios as a new tracer to discriminate the provenance of shelf sediments in the study area. Different source rock compositions and weathering processes between both drainage basins may account for the differences in $^{87}Sr/^{86}Sr$ ratio. Although the ratios show wide range, from 0.71445 to 0.72184 with an average 0.71747 in the study area, they are close to the values of the Yangtze river sediments, suggesting that the sediments were mainly originated from the Yangtze river. The previous studies on the dispersal pattern of modern sediments and the physico-chemical properties of seawater in the Yellow and East China seas support the possibility that the fine-grained Yangtze river sediments can reach to the East China Sea shelf as well as to the southeastern Yellow Sea.

• Korean Journal of Ecology and Environment
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• v.46 no.4
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• pp.488-498
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• 2013

A three-dimensional hydrodynamic model was applied to the Lake Euiam. The lake has three inflows, of which Gongji Stream has the smallest flow rate and poorest water. The dam-storage volume, watershed area, lake shape and discharge type of the Chuncheon Dam and the Soyang Dam are different. Therefore, it is difficult to analyze the water plume and mixing pattern due to the difference of the two dams regarding the amount of outflow and water temperature. In this study, we analyzed the effects of different characteristics on temperature and conductivity using the model appropriate for the Lake Euiam. We selected an integrated system supporting 3-D time varying modeling (GEMSS) to represent large temporal and spatial variations in hydrodynamics and transport of the Lake Euiam. The model represents the water temperature and hydrodynamics in the lake reasonably well. We examined residence time and spreading patterns of the incoming flows in the lake based on the results of the validated model. The results of the water temperature and conductivity distribution indicated that characteristics of upstream dams greatly influence Lake Euiam. In this study, the three-dimensional time variable water quality model successfully simulated the temporal and spatial variations of the hydrodynamics in the Lake Euiam. The model may be used for efficient water quality management.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.31-39
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• 2009

This study has found that there is a reverse phase with interdecadal variation in temporal variations of tropical cyclone (TC) genesis frequency (TCGF) between Northwest sector and Southeast sector, based on climatological mean tropical cyclone genesis location over the western North Pacific. The TCGF in the Northwest sector has been increased since the mid 1980s (1986-2005), while TCGF in the Southeast sector was higher until the early 1970s (1951-1970). The analysis of a difference between 1986-2005 and 1951-1970 showed results as follows: i) Through the analysis of vertical wind shear (VWS) and sea surface temperature (SST), less VWS and higher SST in the former (latter) period was located in the Northwest (Southeast) sector. ii) In the analysis of TC passage frequency (TCPF), TCs occurred in the Northwest sector frequently passed from east sea of the Philippines, through East China Sea, to Korea and Japan in the latter period, while TCs in the former period frequently has a lot of influences on South China Sea (SCS). In the case of TCs occurred in the Southeast sector, TCs in the west (east), based on $150^{\circ}E$ had a high passage frequency in the latter (former) period. In particular, TCs during the latter period frequently moved toward from the east sea of the Philippines to SCS and southern China. iii) This difference of TCPF between the two periods was characterized by 500 hPa anomalous pressure pattern. Particularly, anomalous cyclonic circulation strengthened over the East Asian continent caused anomalous southerlies along the East Asian coast line from the east sea of the Philippines to be predominate. These anomalous winds served as steering flows that TC can easily move toward same regions.

• The Journal of the Petrological Society of Korea
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• v.24 no.1
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• pp.25-54
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• 2015

Syenite is not a common rock, unlike granitic rocks formed the major component of the continental crust. The aim of this study is to decipher the occurrences and detailed descriptive characteristics of the syenite distributed in Sancheong area, and to investigate the petrogenesis of the syenitic magma based on geochemical study. The dominant minerals in syenite are alkali feldspar (usually orthoclase and rarely microcline), plagioclase, amphibole, biotite, and quartz. Syenites are found in a wide variety of colors. The anhedral hornblende and biotite filling the boundary of feldspar and quartz indicate that the hydrous minerals were crystallized lately, and that water was insufficient at the beginning of crystallization in magma. According to the analysis of mineral composition, amphibole in syenite is mostly ferro-edenite, and the pressure is calculated as 3.3~4.9 kb with 11.9~17.3 km of emplacement depth. Biotite and pyroxene are plotted in the region of annite and hedenbergite, respectively. Based on petrochemical studies of major elements, syenite belongs to alkaline series, metaluminous, and I-type. On the other hand, the variation patterns of trace and rare earth elements of syenite differ from the patterns of diorite and granite. In the geochemical characteristics, syenite is different from gabbro-diorite spatially adjacent to syenite, as well as granite. These results suggest that each rock has been generated from the different sources of magma. Additionally, based on the experimental data, the syenitic magma can be formed (1) by the partial melting at a high pressure and dry system, (2) when the initial crystallization minerals to be residue with migration of the residual melts separated from the ascending cotectic magma (3) when fluorine compositions to be plentiful in the protolith and/or at depth of the magma. Based on the petrographic characteristics of the syenite, Sancheong syenitic magma may have been formed by partial melting in a dry system.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.199-207
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• 2016

This study was conducted to develop a forest fire occurrence model using meteorological characteristics for practical forecasting of forest fire danger rate by reflecting the climate change for the time period of 2000yrs. Forest fire in South Korea is highly influenced by humidity, wind speed, temperature, and precipitation. To effectively forecast forest fire occurrence, we developed a forest fire danger rating model using weather factors associated with forest fire in 2000yrs. Forest fire occurrence patterns were investigated statistically to develop a forest fire danger rating index using times series weather data sets collected from 76 meteorological observation centers. The data sets were used for 11 years from 2000 to 2010. Development of the national forest fire occurrence probability model used a logistic regression analysis with forest fire occurrence data and meteorological variables. Nine probability models for individual nine provinces including Jeju Island have been developed. The results of the statistical analysis show that the logistic models (p<0.05) strongly depends on the effective and relative humidity, temperature, wind speed, and rainfall. The results of verification showed that the probability of randomly selected fires ranges from 0.687 to 0.981, which represent a relatively high accuracy of the developed model. These findings may be beneficial to the policy makers in South Korea for the prevention of forest fires.

• Korean Journal of Remote Sensing
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• v.37 no.2
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• pp.321-335
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• 2021

Particulate matter (PM10 and PM2.5 with a diameter less than 10 and 2.5 ㎛, respectively) can be absorbed by the human body and adversely affect human health. Although most of the PM monitoring are based on ground-based observations, they are limited to point-based measurement sites, which leads to uncertainty in PM estimation for regions without observation sites. It is possible to overcome their spatial limitation by using satellite data. In this study, we developed machine learning-based retrieval algorithm for ground-level PM10 and PM2.5 concentrations using aerosol parameters from Geostationary Ocean Color Imager (GOCI) satellite and various meteorological parameters from a numerical weather prediction model during January to December of 2019. Gradient Boosted Regression Trees (GBRT) and Light Gradient Boosting Machine (LightGBM) were used to estimate PM concentrations. The model performances were examined for two types of feature sets-all input parameters (Feature set 1) and a subset of input parameters without meteorological and land-cover parameters (Feature set 2). Both models showed higher accuracy (about 10 % higher in R2) by using the Feature set 1 than the Feature set 2. The GBRT model using Feature set 1 was chosen as the final model for further analysis(PM10: R2 = 0.82, nRMSE = 34.9 %, PM2.5: R2 = 0.75, nRMSE = 35.6 %). The spatial distribution of the seasonal and annual-averaged PM concentrations was similar with in-situ observations, except for the northeastern part of China with bright surface reflectance. Their spatial distribution and seasonal changes were well matched with in-situ measurements.