• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.439-444
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• 2006

Korea Peninsula consists of approximately 70% of mountainous terrain of total area, in addition, annual average rainfall is plentiful, especially during rainy season of summer, and it is often accompanied with typhoon and heavy rain, which results in frequent landslides. Since there are limitations with existing methods to analyze extensive disasters, it is necessary to develop new remote sensing technology using an artificial satellite to study on landslides closely. This paper is written in order to establish the database with map information on various landslides using GIS, furthermore, to analyze precariousness of the areas, which are susceptible to landslide, and risks of potential areas in consideration of heavy rain, based on land-cover classification derived from images from satellite.

• Smart Structures and Systems
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• v.18 no.3
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• pp.485-500
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• 2016

Stay cables in some cable-stayed bridges suffer large amplitude vibrations under the simultaneous occurrence of rain and wind. This phenomenon is called rain-wind-induced vibration (RWIV). The upper rivulet oscillating circumferentially on the inclined cable surface plays an important role in this phenomenon. However, its small size and high sensitivity to wind flow make measuring rivulet size and its movement challenging. Moreover, the distribution of the rivulet along the entire cable has not been measured. This paper applies the videogrammetric technique to measure the movement and geometry dimension of the upper rivulet along the entire cable during RWIV. A cable model is tested in an open-jet wind tunnel with artificial rain. RWIV is successfully reproduced. Only one digital video camera is employed and installed on the cable during the experiment. The camera records video clips of the upper rivulet and cable movements. The video clips are then transferred into a series of images, from which the positions of the cable and the upper rivulet at each time instant are identified by image processing. The thickness of the upper rivulet is also estimated. The oscillation amplitude, equilibrium position, and dominant frequency of the rivulet are presented. The relationship between cable and rivulet variations is also investigated. Results demonstrate that this non-contact, non-intrusive measurement method has good resolution and is cost effective.

• Journal of Environmental Science International
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• v.30 no.12
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• pp.1101-1111
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• 2021

In this study, among the W-S-R(Wiper-Signal-Rainfall) relationship methods used to produce sensor-based rain information in real time, we sought to produce actual rainfall information by applying machine learning techniques to account for the effects of wiper operation. To this end, we used the gradient descent and threshold map methods for pre-processing the cumulative value of the difference before and after wiper operation by utilizing four sensitive channels for optical sensors which collected rain sensor data produced by five rain conditions in indoor artificial rainfall experiments. These methods produced rainfall information by calculating the average value of the threshold according to the rainfall conditions and channels, creating a threshold map corresponding to the 4 (channel) × 5 (considering rainfall information) grid and applying Optima Rainfall Intensity among the big data processing techniques. To verify these proposed results, the application was evaluated by comparing rainfall observations.

• Journal of Korea Soil Environment Society
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• v.2 no.1
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• pp.35-44
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• 1997

A column study using artificial acid rain was conducted to evaluate the buffering capacities in soil layer and host rock. In an effort to compare the effect of composition of host root two valleys of which compositions of host rock are different were chosen within the study area and the pHs of the water flowing in the valleys were measured from May, 1996 to October, 1996. The pHs of the artificial acid rain prepared by adding appropriate amounts of both sulfuric and nitric acids to distilled water were 3, 4, and 5, and the column effluents were analyzed for major cations and anions. The cation exchange capacities(CECs) of A Horizon and the B Horizon were 9.68 and 6.16 meq/100g, respectively, Compared to the B Horizon, the pH in the column effluent of A Horizon with larger CEC was higher. The sums of $Ca^{2+}$, $Mg^{2+}$, $Na^{+}$in the column effluents gradually decreased, indicating the loss of CEC by acid rain. The field study showed that pHs of the surface water in the valleys increased as the water flows downwards. The magnitude of this buffering capacity was greater for the valley in which smectite in addition to kaolinite and illite was a weathered product of host rocks. This also indicates that host rock as well as soil layer retains the buffering capacity.

• Journal of Korea Water Resources Association
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• v.56 no.11
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• pp.751-764
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• 2023

Gangwon State is centered on the Taebaek Mountains with very different climate characteristics depending on the region, and localized heavy rainfall is a frequent occurrence. Heavy rain disasters have a short duration and high spatial and temporal variability, causing many casualties and property damage. In the last 10 years (2012~2021), the number of heavy rain disasters in Gangwon State was 28, with an average cost of 45.6 billion won. To reduce heavy rain disasters, it is necessary to establish a disaster management plan at the local level. In particular, the current criteria for heavy rain warnings are uniform and do not consider local characteristics. Therefore, this study aims to propose a heavy rainfall warning criteria that considers the threshold rainfall for the advisory areas located in Gangwon State. As a result of analyzing the representative value of threshold rainfall by advisory area, the Mean value was similar to the criteria for issuing a heavy rain warning, and it was selected as the criteria for a heavy rain warning in this study. The rainfall events of Typhoon Mitag in 2019, Typhoons Maysak and Haishen in 2020, and Typhoon Khanun in 2023 were applied as rainfall events to review the criteria for heavy rainfall warnings, as a result of Hit Rate accuracy verification, this study reflects the actual warning well with 72% in Gangneung Plain and 98% in Wonju. The criteria for heavy rain warnings in this study are the same as the crisis warning stages (Attention, Caution, Alert, and Danger), which are considered to be possible for preemptive rain disaster response. The results of this study are expected to complement the uniform decision-making system for responding to heavy rain disasters in the future and can be used as a basis for heavy rain warnings that consider disaster risk by region.

• Journal of Korean Society of Forest Science
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• v.77 no.3
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• pp.259-268
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• 1988

For the purpose of examining the effects of simulated acid rain on nutrient contents of plant tissues in Pintos densiflora seedlings and Forsythia koreana rooted cuttings, the experimental design of randomized block arrangement with three replications was implemented in the experimental field of Yesan National Agricultural Junior College. One-year-old Pinus densiflora seedlings and Forsythia koreana cuttings were planted in the pots filled the mixed soils(nursery soil : forest soil of siliceous sandy loam=1 : 1 v/v) in the early spring of 1986. The regime of artificial acid rain, in terms of spray frequency per month and spray amount at single treatment per plot, was simulated on the basis of climatological data averaged from 30 years records. Simulated acid rain(pH 2.0, pH 4.0, and pH 5.5 as control) containing sulfuric and nutric acid in the ratio of 3 : 2(chemical equivalant basis) diluted with ground water were treated on the experimental plants under condition of cutting off the natural precipitation with vinyl tunnel, during the growing season(May 1 to August 31) in 1986. The results obtained in this study were as follow : (1) As for the nitrogen contents in plant tissues, P. densiflora increased significantly in one-year-old stembranch and root tissues, and F. koreana increased significantly in leaf and root tissues, as the pH levels of acid rain decreased. (2) The available phosphate contents in root tissues of P. densiflora, and in leaf and root tissues of F. koreana were significantly decreased, as the pH levels of acid rain decreased. (3) $K_2O$, CaO and MgO contents in plant tissues were significantly decreased in the both species as the pH levels decreased. And the effects of acid rain on F. koreana were higher than those of P. densiflora. (4) Sulfur contents of plant tissues in the both species were increased at pH 2.0 treatment. There were significant differences among three acid rain treatments in leaf and root tissues of P. densiflora, and in all parts of F. koreana. (5) In the effects of simulated acid rain on the both species and the tested soils, in general, F. koreana revealed higher sensitiveness than P. densiflora, and the lower pH levels of simulated acid rain were treated, the more sharp reaction was showed.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.171-176
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• 2004

Electro chemical corrosion tests were conducted on two structural steels, SS400 and SM490A, in various solutions with different pH values, All materials showed typical active corrosion behaviors in the solutions, and corrosion potential and current density were measured from the slopes obtained from the Tafel curves using linear polarization method. Corrosion potential increased in the acidic region and then decreased depending on the pH values of the solutions. All materials showed the fast corrosion rate in artificial acid rain(pH=4.7), but the slower corrosion rate was observed in NaOH solution(pH=12.0) for SS400 and in distilled water(pH=7.0) for SM490A, respectively, which is thought to come from the difference in chemical composition of two alloys. Generally homogeneous corrosion occurred in acid rain condition, and almost no corrosion was observed in distilled water in both alloys. NaOH solution produced more corrosion than distilled water, and more corrosion had progressed in SS400 than in SM490A in $3.5\%$ NaCl solution.

• Journal of Korea Water Resources Association
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• v.47 no.2
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• pp.207-221
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• 2014

Recently, due to global warming, climate change has affected short time concentrated local rain and unexpected heavy rain which is increasingly causing life and property damage. Therefore, this paper studies the characteristic of localized heavy rain and flash flood in Nakdong basin study area by applying Data Mining method to predict flood and constructing water level predicting model. For the verification neural network from Data Mining method and hydraulic flood routing was used for flood from July 1989 to September 1999 in Nakdong point and Iseon point was used to compare flood level change between observed water level and SAM (Slope Area Method). In this research, the study area was divided into three cases in which each point's flood discharge, water level was considered to construct the model for hydraulic flood routing and neural network based on artificial intelligence which can be made from simple input data used for comparison analysis and comparison evaluation according to actual water level and from the model.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.101-109
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• 2021

Wave observations using a marine X-band radar are conducted by analyzing the backscattered radar signal from sea surfaces. Wave parameters are extracted using Modulation Transfer Function obtained from 3D wave number and frequency spectra which are calculated by 3D FFT of time series of sea surface images (42 images per minute). The accuracy of estimation of the significant wave height is, therefore, critically dependent on the quality of radar images. Wave observations during Typhoon Maysak and Haishen in the summer of 2020 show large errors in the estimation of the significant wave heights. It is because of the deteriorated radar images due to raindrops falling on the sea surface. This paper presents the algorithm developed to increase the accuracy of wave heights estimation from radar images by adopting convolution neural network(CNN) which automatically classify radar images into rain and non-rain cases. Then, an algorithm for deriving the Hs is proposed by creating different ANN models and selectively applying them according to the rain or non-rain cases. The developed algorithm applied to heavy rain cases during typhoons and showed critically improved results.

• Research in Plant Disease
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• v.21 no.3
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• pp.231-234
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• 2015

Elsinoe fawcettii and E. australis are two currently recognized scab pathogens of citrus. E. fawcettii has at least six pathotypes while E. australis has at least two pathotypes. Colonies of E. fawcettii and E. australis do not sporulate in artificial media including potato dextrose agar (PDA). Whiteside's method has been widely used for preparing conidial inoculum in vitro. This study was carried out to develop efficient method for conidia production from artificial media. We developed a shaking method which included the following steps: 1) Colony grown on PDA was mashed with a steel spatula; 2) Mycelia fragments were cultured in 50 ml sterilized rain water in a rotary shaker-incubator (180 rpm) at $25^{\circ}C$ for 24 h: 3) The conidia suspension was filtered through two layers of cheesecloth. Average conidia production of all isolates tested using this shaking method was approximately 13.1 times higher than that from Whiteside's method in this study.