• Korean Journal of Remote Sensing
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• v.37 no.5_1
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• pp.989-998
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• 2021

In the utilization of optical satellite imagery, which is greatly affected by clouds, periodic composite technique is a useful method to minimize the influence of clouds. Recently, a technique for selecting the optimal pixel that is least affected by the cloud and shadow during a certain period by directly inputting cloud and cloud shadow information during period compositing has been proposed. Accurate extraction of clouds and cloud shadowsis essential in order to derive optimal composite results. Also, in the case of an surface targets where spectral information is important, such as crops, the loss of spectral information should be minimized during cloud-free compositing. In thisstudy, clouds using two spectral indicators (Haze Optimized Tranformation and MeanVis) were used to derive a detection technique with low loss ofspectral information while maintaining high detection accuracy of clouds and cloud shadowsfor cabbage fieldsin the highlands of Gangwon-do. These detection results were compared and analyzed with cloud and cloud shadow information provided by Sentinel-2A/B. As a result of analyzing data from 2019 to 2021, cloud information from Sentinel-2A/B satellites showed detection accuracy with an F1 value of 0.91, but bright artifacts were falsely detected as clouds. On the other hand, the cloud detection result obtained by applying the threshold (=0.05) to the HOT showed relatively low detection accuracy (F1=0.72), but the loss ofspectral information was minimized due to the small number of false positives. In the case of cloud shadows, only minimal shadows were detected in the Sentinel-2A/B additional layer, but when a threshold (= 0.015) was applied to MeanVis, cloud shadowsthat could be distinguished from the topographically generated shadows could be detected. By inputting spectral indicators-based cloud and shadow information,stable monthly cloud-free composited vegetation index results were obtained, and in the future, high-accuracy cloud information of Sentinel-2A/B will be input to periodic cloud-free composite for comparison.

• Korean Journal of Remote Sensing
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• v.37 no.6_1
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• pp.1657-1667
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• 2021

Anthropogenic activities and natural processes have been causes of land subsidence which is sudden sinking or gradual settlement of the earth's solid surface. Mexico City, the capital of Mexico, is one of the most severe land subsidence areas which are resulted from excessive groundwater extraction. Because groundwater is the primary water resource occupies almost 70% of total water usage in the city. Traditional terrestrial observations like the Global Navigation Satellite System (GNSS) or leveling survey have been preferred to measure land subsidence accurately. Although the GNSS observations have highly accurate information of the surfaces' displacement with a very high temporal resolution, it has often been limited due to its sparse spatial resolution and highly time-consuming and high cost. However, space-based synthetic aperture radar (SAR) interferometry has been widely used as a powerful tool to monitor surfaces' displacement with high spatial resolution and high accuracy from mm to cm-scale, regardless of day-or-night and weather conditions. In this paper, advanced interferometric approaches have been applied to get a time-series of land subsidence of Mexico City using four-year-long twenty ALOS PALSAR L-band observations acquired from Feb-11, 2007 to Feb-22, 2011. We utilized persistent scatterer interferometry (PSI) and small baseline subset (SBAS) techniques to suppress atmospheric artifacts and topography errors. The results show that the maximum subsidence rates of the PSI and SBAS method were -29.5 cm/year and -27.0 cm/year, respectively. In addition, we discuss the different subsidence rates where the study area is discriminated into three districts according to distinctive geotechnical characteristics. The significant subsidence rate occurred in the lacustrine sediments with higher compressibility than harder bedrock.

• Korean Journal of Remote Sensing
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• v.37 no.6_2
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• pp.1819-1827
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• 2021

Land-use/cover change caused by rapid urbanization in South Korea is one of the concerns in flood risk management because groundwater recharge by precipitation hardly occurs due to an increase in impermeable surfaces in urban areas. This study investigated the hydrologic effects of land-use/cover on groundwater recharge in the Yeonje-gu district of Busan, South Korea. A statistical time series analysis was conducted with temporal variations of precipitation and groundwater level to estimate lag-time based on correlation coefficients calculated from auto-correlation function (ACF), cross-correlation function (CCF), and moving average (MA) at five sites. Landform and land-use/cover within 250 m radius of the monitoring wells(GW01, GW02, GW03, GW04, and GW05) at five sites were identified by land cover and digital map using Arc-GIS software. Long lag-times (CCF: 42-71 days and MA: 148-161 days) were calculated at the sites covered by mainly impermeable surfaces(GW01, GW03, and GW05) while short lag-times(CCF: 4 days and MA: 67 days) were calculated at GW04 consisting of mainly permeable surfaces. The results suggest that lag-time would be one of the good indicators to evaluate the effects of land-use/cover on estimating groundwater recharge. The results of this study also provide guidance on the application of statistical time series analysis to environmentally important issues on creating an urban green space for natural groundwater recharge from precipitation in the city and developing a management plan for hydrological disaster prevention.

• Journal of Korean Society of Forest Science
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• v.107 no.4
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• pp.344-350
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• 2018

This study was carried out to improve the forest management method considering the use of high value added timber in the natural broadleaf forests. For this purpose, the criteria for evaluating the quality grade of standing trees were established and applied to the oak stand in the central region of Korea. The evaluation factors of the grade were bending of stem, branch, stem damage, and other defects. If the logs are divided into 2.1 m units and three logs up to 6.3 m are available, they are classified as Grade I (G-I). If two logs are available, they are classified as Grade II (G-II), If only one log is available, it is classified as Grade III (G-III). When any log is not available as timber, it is classified as Grade IV (G-IV). As a result of applying the grade to the oak stand, G-I was 6.7 %, G-II was 28.0 %, G-III was 38.3 %, and G-IV was 27.0 %. The ratio of standing trees by oak species of higher than G-III was 88.2 % for Quercus acutissima, 88.1 % for Q. variabilis, 83.5 % for Q. serrata, 56.3 % for Q. aliena, and 50.3 % for Q. mongolica, respectively. The G-IV ratio for Q. variabilis and Q. mongolica tended to decrease with increasing diameter at breast height. The order of major defect affecting the grading level was bending of stem > branch > stem damage > other defects. Considering the grade level and oak species distribution, it was concluded possible to produce high quality hardwood timber when we concentrate forest tending techniques on Q. acutissima and Q. variabilis stand. In order to improve the accuracy of grading, it is necessary to continuous complement through the monitoring research for evaluation factors.

• Journal of Environmental Impact Assessment
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• v.28 no.2
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• pp.113-128
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• 2019

The concentration and coating thickness of black carbon (BC) were measured along with fine dust in the fall of 2018, at the Seoul Metropolitan Area Intensive Monitoring Station (SIMS). In fall, the concentration of $PM_{10}$ and $PM_{2.5}$ was $23{\pm}12.6{\mu}g/m^3$ and $12{\pm}5.8{\mu}g/m^3$, respectively, lower than that in other seasons. The BC level, measured using an Aethalometer, was $0.73{\pm}0.43{\mu}g/m^3$, while the levels of elemental carbon (EC) and refractory-BC (rBC), measured by semi-continuous carbon analyzer (SOCEC) and single particle soot photometer (SP2), were $0.34{\pm}0.18{\mu}g/m^3$ and $0.32{\pm}0.18{\mu}g/m^3$, respectively. As such, the concentration level differed according to the measurement method, but its time-series distribution and diurnal variation showed the same trends. The BC concentration at SIMS was primarily affected by automobiles with higher levels of BC during morning and evening commuting times due to increased traffic congestion. rBC, measured by SP2, had a peak concentration and coating thickness of 84 nm and 43 nm, respectively. Notably, the coating thickness had an inverse relationship with particle size.

• Archives of Hand and Microsurgery
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• v.23 no.4
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• pp.230-238
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• 2018

Purpose: Metacarpal fractures are common injuries of the hand. They are treated using closed reduction (CR) or open reduction (OR) techniques. The management strategy depends on fracture site characteristic and fixation methods. In this study, we evaluated pre- and postoperative fracture angulation, when metacarpal fractures bad been treated using two different techniques: CR with parallel transverse pinning and OR with plate fixation. Methods: Forty-six patients undergoing anatomic reduction to treat extra-articular metacarpal fractures were recruited. They were included in one of two therapeutic groups: Group 1, CR with parallel transverse pinning (n=21); Group 2, OR with plate fixation (n=25). Fracture angulation values have been measured on pre- and postoperative radiologic images. Values were compared between pre- and postoperative states, and between corresponding measurements of each group. Results: All extra-articular metacarpal fractures were successfully treated without wound related complications or the limit of joint motion. Both groups demonstrated adequate reduction at immediate postoperative period (postoperative angulation of group 1, $20^{\circ}{\pm}7^{\circ}$; group 2, $19^{\circ}{\pm}5^{\circ}$). During the observation at follow-up period, Group 1 exhibited slight recurrence (follow-up angulation of group 1, $24^{\circ}{\pm}10^{\circ}$). Nonetheless, Group 2 showed adequate reduction state in both immediate postoperative and long-term follow-up periods (follow-up angulation of group 2, $18^{\circ}{\pm}6^{\circ}$). Conclusion: Extra-articular metacarpal fractures were successfully restored without functional complications. CR with parallel transverse pinning method exhibited recurrence after pin removal, which necessitates cautious postoperative exercise and monitoring.

• Journal of Intelligence and Information Systems
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• v.25 no.1
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• pp.127-137
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• 2019

Recidivism prediction has been a subject of constant research by experts since the early 1970s. But it has become more important as committed crimes by recidivist steadily increase. Especially, in the 1990s, after the US and Canada adopted the 'Recidivism Risk Assessment Report' as a decisive criterion during trial and parole screening, research on recidivism prediction became more active. And in the same period, empirical studies on 'Recidivism Factors' were started even at Korea. Even though most recidivism prediction studies have so far focused on factors of recidivism or the accuracy of recidivism prediction, it is important to minimize the prediction misclassification cost, because recidivism prediction has an asymmetric error cost structure. In general, the cost of misrecognizing people who do not cause recidivism to cause recidivism is lower than the cost of incorrectly classifying people who would cause recidivism. Because the former increases only the additional monitoring costs, while the latter increases the amount of social, and economic costs. Therefore, in this paper, we propose an XGBoost(eXtream Gradient Boosting; XGB) based recidivism prediction model considering asymmetric error cost. In the first step of the model, XGB, being recognized as high performance ensemble method in the field of data mining, was applied. And the results of XGB were compared with various prediction models such as LOGIT(logistic regression analysis), DT(decision trees), ANN(artificial neural networks), and SVM(support vector machines). In the next step, the threshold is optimized to minimize the total misclassification cost, which is the weighted average of FNE(False Negative Error) and FPE(False Positive Error). To verify the usefulness of the model, the model was applied to a real recidivism prediction dataset. As a result, it was confirmed that the XGB model not only showed better prediction accuracy than other prediction models but also reduced the cost of misclassification most effectively.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.1
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• pp.1-28
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• 2019

This study analyzed the density and mortality rate of Korean fir at 9 sites where individuals of Korean firs were marked into the live and dead trees with coordinates on orthorectified aerial images by digital photogrammetric system. As a result of the analysis, Korean fir in each site showed considerable heterogeneity in density and mortality rate depending on the location within site. This make it possible to assume that death of Korean fir can occur by specific factors that vary depending on the location. Based on the analyzed densities and mortality rates of Korea fir, we investigated the correlation between topographic factors such as altitude, terrain slope, drainage network, solar radiation, aspect and the death of Korean fir. The density of Korean fir increases with altitude, and the mortality rate also increases. A negative correlation is found between the terrain slope and the mortality rate, and the mortality rate is higher in the gentle slope where the drainage network is less developed. In addition, it is recognized that depending on the aspect, the mortality rate varies greatly, and the mean solar radiation is higher in live Korean fir-dominant area than in dead Korean fir-dominant area. Overall, the mortality rate of Korean fir in Mt. Halla area is relatively higher in areas with relatively low terrain slope and low solar radiation. Considering the results of previous studies that the terrain slope has a strong negative correlation with soil moisture and the relationship between solar radiation and evaporation, these results lead us to infer that excess soil moisture is the cause of Korean fir mortality. These inferences are supported by a series of climate change phenomena such as precipitation increase, evaporation decrease, and reduced sunshine duration in the Korean peninsula including Jeju Island, increase in mortality rate along with increased precipitation according to the elevation of Mt. Halla and the vegetation change in the mountain. It is expected that the spatial patterns in the density and mortality rate of Korean fir, which are controlled by topography such as altitude, slope, aspect, solar radiation, drainage network, can be used as spatial variables in future numerical modeling studies on the death or decline of Korean fir. In addition, the method of forest distribution survey using the orthorectified aerial images can be widely used as a numerical monitoring technique in long - term vegetation change research.

• Journal of the Korean Institute of Landscape Architecture
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• v.46 no.6
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• pp.111-119
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• 2018

This study was carried out to investigate the growth characteristics and propagation methods of the Korean native Amelanchier asiatica, A. arborea, and A. alnifolia as fruit trees for gardens. Due to the lack of recent research on Amelanchier spp., their superficial classification is still unclear and the names are being used interchangeably. The results are obtained as follows : A. arborea and A. alnifolia were globular type multi-stemmed shrubs. A 20-year-old tree of A. asiatica was 7.8m in height, with a 5.2m crown width, with one trunk. As for the morphological characteristics, leaves of A. asiatica were oblong, with an acuminate of, 6.1cm and 3.6cm width, but A. arborea and A. alnifolia had acute obovate leaves. The leaf size of A. alnifolia was the largest among the three species. The flower size of A. asiatica was bigger than that of A. arborea and A. alnifolia. In addition, its petals and flower clusters were also the largest among the three species. The flowering of A. asiatica initiated on April 21 and then bloomed for a duration of 24 days in Osan, while that of A. arborea and A. alnifolia initiated flowering on April 12 and then bloomed for a duration of 22 days in the same location. The fruit of A. arborea and A. alnifolia were green on May 10~12, it changed into purplish red on May 24~26, and its matured on June 1~3. The duration of fruit persistence of A. arborea and A. alnifolia were 48~50 days. On the other hand, A. asiatica showed greenish fruit on May 20, it became red on September 4, and had fallen by October 3. The fruit size was the largest at 1.03cm of height and 1.12cm of diameter in the A. arborea, followed by the big berry of A. alnifolia and the smallest fruit in the native, A. asiatica. It was difficult to root due to the hardwood cutting of A. arborea at a 40% rate of rooting. In the softwood cutting, the rooting rate of A. arborea was increased by the treatment with concentrated IBA, especially at 5,000 and 7,000ppm. The optimum date for cutting was on June 27, when the rooting rate was more than 80%. The most effective method for rooting of A. arborea was rootone or 7,000 ppm IBA treatment on June 27 softwood cuttings, which showed a rooting rate of over 80%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.558-569
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• 2020

This study examined the frequency of a broiler's stay in each area as stock density using an ICT-based image analysis technique from the perspective of precision livestock farming (PLF) according to the increase in the domestic broiler farms to understand the normal behavior patterns of broilers by age. The broiler was used in the experimental box (3.3×2.7 m) in a poultry house in Gyeonggi province. The stock densities were 9.5 birds/㎡ (n=85) and 19 birds/㎡ (n=170), respectively, and the frequency of stay by feeding, water, and rest area was monitored using a top-view camera. The image data of three-colored-specific broilers identified as the stock density were acquired by age (12, 16, 22, 27, and 29 days) for six hours. In the collected image data, the object tracking technique was used to record the cumulative movement path by connecting approximately 640,000 frames at 30 fps to quantify the frequency of stay in each area. In each stock density, it was significant in the order of the rest area, feeding, and water area (p<0.001). In 9.5 birds/㎡, it was at 57.9, 24.2, and 17.9 %, and 73.2, 16.8, and 10 % in 19 birds/㎡. The frequency of a broiler's stay could be evaluated in each area as the stock density using an ICT-based image analysis technique that minimizes stress. This method is expected to be used to provide basic material for developing an ICT-based management system through real-time monitoring.