• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.45-53
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• 2009

This study concerned remediation of heavy metal contaminated farmland soils near abandoned mine, using stabilization method, with particular emphasis on the remediating the soils contaminated with multi-elements. In this study, stabilizing heavy metals based on 'In-situ chemical fixation' has been applied to the soil collected from an abandoned mine in Korea, using column test, with various stabilizing agents, including $FeSO_4$, $KMnO_4$, sludge (collected from coal mine drainage treatment pond), zero-valent iron (ZVI), zeolite and $CaCO_3$. Sixty five-days operation of the flow-through columns yield $FeSO_4\;+\;KMnO_4$ and zeolite are efficient on reducing As leaching from the soil. ZVI and sludge are reducing the leaching of Cu. Although $FeSO_4\;+\;KMnO_4$ seem to be efficient for most heavy metals, high pH in the initial stage of test enabled high leaching of the heavy metals, whereas fixation of the heavy metals maintain throughout the rest of the test period, with increasing pH up to around 6. Addition of some alkaline agent may inhibit the low pH during the application. The column test was also run as two set: one set incubated with deionized water for 72 hours prior to starting the test, and the other without incubation. The incubated set demonstrated better stabilizing efficiency, indicating the potential optimized operation method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.5
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• pp.557-565
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• 2021

Path-following control is considered as one of the most fundamental skills to realize autonomous navigation of marine vessels in the ocean. This study addresses with the path-following control for a ship in which there are environmental disturbances in the directions of the surge, sway, and yaw motions. The guiding principle and back-stepping method was utilized to solve the ship's tracking problem on the reference path generated by a virtual ship. For path-following control, error dynamics is one of the most important skills, and it extends to the research fields of automatic collision avoidance and automatic berthing control. The algorithms for the guiding principles and error variables have been verified by numerical simulation. As a result, most error variables converged to zero values with the controller except for the yaw angle error. One of the most interesting results is that the tracking errors of path-following control between two ships are smaller than the existing safe passing distances considering interaction forces from near passing ships. Moreover, a trade-off between tracking performance and the ship's safety should be considered for determining the proper control parameters to prevent the destructive failure of actuators such as propellers, fins, and rudders during the path-following of marine vessels.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1317-1328
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• 2021

This study aims to provide a predictive model based on climate models for simulating continuous daily rainfall sequences by combining bias-correction and spatio-temporal downscaling approaches. For these purposes, this study proposes a combined modeling system by applying conditional Copula and Multisite Non-stationary Hidden Markov Model (MNHMM). The GloSea5 system releases the monthly rainfall prediction on the same day every week, however, there are noticeable differences in the updated prediction. It was confirmed that the monthly rainfall forecasts are effectively updated with the use of the Copula-based bias-correction approach. More specifically, the proposed bias-correction approach was validated for the period from 1991 to 2010 under the LOOCV scheme. Several rainfall statistics, such as rainfall amounts, consecutive rainfall frequency, consecutive zero rainfall frequency, and wet days, are well reproduced, which is expected to be highly effective as input data of the hydrological model. The difference in spatial coherence between the observed and simulated rainfall sequences over the entire weather stations was estimated in the range of -0.02~0.10, and the interdependence between rainfall stations in the watershed was effectively reproduced. Therefore, it is expected that the hydrological response of the watershed will be more realistically simulated when used as input data for the hydrological model.

• The Journal of the Korea Contents Association
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• v.21 no.11
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• pp.320-332
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• 2021

This paper investigates the influence of stock-level left-tail risk, which is defined using Value-at-Risk(VaR) estimates of past one-year daily stock returns, in the expected stock returns in the Korean stock market. Our results are summarized as follows: First, monthly-constructed zero-cost portfolios that buy (shortsell) the highest (lowest) left-tail risk decile in the previous month exhibit an average monthly return (called left-tail risk premium) of -2.29%. Second, Fama-MacBeth cross-sectional regressions suggest that left-tail risk in the previous month shows significant and negative explanatory power over return in this month, after controlling for various firm characteristics such as firm size, B/M, market beta, liquidity, maximum daily return, idiosyncratic volatility, and skewness. Third, the stocks with larger recent month loss have lower returns in the next month. Fourth, the magnitude of left-tail risk premium is negatively related with lagged market-level volatility. These results support the hypothesis from a perspective of behavioral finance that the overpricing of stocks with left-tail risk is attributed to the investors' underreaction to it.

• Journal of the Korea Organic Resources Recycling Association
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• v.27 no.1
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• pp.65-75
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• 2019

The government is promoting recycling of waste resources through the enactment of Fundamental Law on Resource Circulation, the revision of the Wastes Control Act and zero-landfilling of untreated waste through improved processes such as recycling and diversification. As of 2015, the total amount of landfilled waste is 38,308 ton/day in Korea. The amount of landfilled waste from industrial sectors is 23,577 ton/day, accounting for 62 % of total landfilled waste. In the study, we investigated the characteristics of the thermal treatment residue among inorganic wastes and estimated the landfill reduction potential according to the relevant recycling criteria, which can go through recycling paths. As a result, it is estimated that about 5~42 % of the landfilled waste can be reduced in case mandatory recycling and landfill suppression policies such as recycling criteria for thermal processing residues and expansion of recycling obligation targets should be implemented. In order to minimize landfill disposal, it is necessary to expand the diversity of waste recycling type and the usage of recycled products.

• Korean Journal of Remote Sensing
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• v.34 no.6_3
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• pp.1427-1443
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• 2018

Object-based image analysis (OBIA) allows higher computation efficiency and usability of information inherent in the image, as it reduces the complexity of the image while maintaining the image properties. Superpixel methods oversegment the image with a smaller image unit than an ordinary object segment and well preserve the edges of the image. SLIC (Simple linear iterative clustering) is known for outperforming the previous superpixel methods with high image segmentation quality. Although the input parameter for SLIC, number of superpixels has considerable influence on image segmentation results, impact analysis for SLIC parameter has not been investigated enough. In this study, we performed optimal parameter analysis and evaluation of change detection for SLIC-based superpixel techniques using KOMPSAT data. Forsuperpixel generation, three superpixel methods (SLIC; SLIC0, zero parameter version of SLIC; SNIC, simple non-iterative clustering) were used with superpixel sizes in ranges of $5{\times}5$ (pixels) to $50{\times}50$ (pixels). Then, the image segmentation results were analyzed for how well they preserve the edges of the change detection reference data. Based on the optimal parameter analysis, image segmentation boundaries were obtained from difference image of the bi-temporal images. Then, DBSCAN (Density-based spatial clustering of applications with noise) was applied to cluster the superpixels to a certain size of objects for change detection. The changes of features were detected for each superpixel and compared with reference data for evaluation. From the change detection results, it proved that better change detection can be achieved even with bigger superpixel size if the superpixels were generated with high regularity of size and shape.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.6
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• pp.169-180
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• 2018

White light-emitting diodes (LEDs) are more economical than fluorescent lights, and provide high brightness, a high lifetime expectancy, and greater durability. As LEDs are closely connected with people's daily lives, dimming control of LED is an important component in providing energy savings and improving quality of life. In visible light communications systems using these LEDs, multiple input multiple output (MIMO) technology has attracted a lot of attention, in that it can attain the channel capacity in proportion to the number of antennas. This paper analyzes the power performance of three kinds of modulation in visible light communications (VLC) systems applied space-time block code (STBC) techniques. The modulation schemes are return-to-zero on-off keying (RZ-OOK), variable pulse position modulation (VPPM), and overlapping pulse position modulation (OPPM), and dimming control was applied. The power requirements and power consumption were used as metrics to compare the power efficiency in $2{\times}2$ STBC-VLC environments under the three kinds of modulation. We confirm that dimming control affects the communications performance of each modulation scheme. VPPM showed greater consumption among the three modulations, and OPPM showed energy savings comparable to VPPM.

• Clean Technology
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• v.24 no.4
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• pp.307-314
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• 2018

In this study, NMO (Natural Manganese Ore), $MnO_2$, and $Mn_2O_3$ catalysts were used in the selective catalytic reduction process to remove nitrogen oxides (NOx) using $NH_3$ as a reducing agent at low temperatures in the presence of oxygen. In the case of the NMO (Natural Manganese Ore), it was confirmed that the conversion of nitrogen oxides in the stability test did not change even after 100 hours at 423 K. The Kinetics experiments were carried out within the range where heat and mass transfer were not factors. From a steady-state Kinetics study, it was found that the low-temperature SCR reaction was zero order with the respect to $NH_3$ and 0.41 ~ 0.57 order with the respect to NO and 0.13 ~ 0.26 order with the respect to $O_2$. As temperature increases, the reaction order decreases as a result of $NH_3$ and oxygen concentration. It was confirmed that the reaction between the $NH_3$ dissociated and adsorbedon the catalyst surface and the gaseous nitrogen monoxide (E-R model) and the reaction with the adsorbed nitrogen monoxide (L-H model) occur.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.339-346
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• 2019

Various studies have been conducted to evaluate the probabilistic fatigue life of steel railway bridges, but many of them are based on a relatively simple model of crack propagation. The model assumes zero minimum stress and constant loading amplitude, which is not appropriate for the fatigue life evaluation of railway bridges. Thus, this study proposes a new probabilistic method employing an advanced crack propagation model that considers the live-dead load ratio for the fatigue life evaluation of steel railway bridges. In addition, by using the rainflow cycle counting algorithm, it can handle variable-amplitude loading, which is the most common loading pattern for railway bridges. To demonstrate the proposed method, it was applied to a numerical example of a steel railway bridge, and the fatigue lives of the major components and structural system were estimated. Furthermore, the effects of various ratios of live-dead loads on bridge fatigue life were examined through a parametric study. As a result, with the increasing live-dead stress ratio from 0 to 5/6, the fatigue lives can be reduced by approximately 30 years at both the component and system levels.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2019.06a
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• pp.212-215
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• 2019

지난 4월4일 고성 산불로 사망자 2명과 부상자 1명, 가옥 500여 채, 삼림 1757ha가 불에 탔다. 강원 산불에 이어 영덕지진 등에서 늑장대응을 보여준 재난방송시스템에는 많은 국민들에게 실망감을 안겨주었다. 재난방송 주관방송사인 KBS는 물론, MBC, SBS의 경우도 재난방송시스템에 관련 된 측면에서 본다면 아직 이웃나라 인 일본에 비해서는 매우 열악한 형편이다. 그럼에도 불구하고 점점 대형화, 다발화 하는 재난발생에 대응하기 위해서는 국가적인 차원에서도 특단의 조치가 필요하다. 미국의 경우는 차세대 재난정보 전달체계인 IPAWS(Integrated Public Alert and Warning System)를 개발해 지상파뿐만 아니라, 케이블TV, SNS 등 다양한 매체를 통해 재난정보를 신속하게 전달하고 있다. 일본도 이와 유사한 재난경보전달시스템인 J-Alert를 개발해 2020년까지는 '재난 약자 제로(Zero)시대'를 목표로 구현하고 있다. 우리나라는 지난 아현동 KT 화재사건에서도 경험했듯이 통신이 먹통이 되는 통신블랙아웃도 경험했다. 따라서 대형재난발생 시는 신속한 재난경보전달시스템이 재난피해를 줄일 수 있는 가장 중요한 생명줄이 될 수 있다. 미국이나 일본의 경우는 재난방송전달시스템을 관련법령으로 제도화 하고 있다. 특히, 일본에는 재난에 관한 모법이라고 할 수 있는 (1)"재해대책기본법"이 있는데, 이는 재해로부터 국토, 국민의 생명과 재산을 보호하기 위한 기본법으로 규정되어 있다. 그 밖에도 (2)방송법 (3)대규모지진대책특별 조치법 (4)국민보호법 (5)소방조직법 (6)수해방지법 등으로 규정하고 있다. 과거 일본도 우리나라와 같이 대형 산불이 잦았으나 요즘은 소형 산불만 발생하는 추세다. 이는 NHK가 보유한 700여 대의 로봇카메라와 전 국토를 샅샅이 감시하는 CCTV 덕택이다. 또한, NHK 보도국의 '기상 재해센터'는 재난에 대비해 40여 명의 전문 인력이 24시간 대응체제를 갖추고 있다. 나아가 NHK는 전국 12개의 거점지역에 헬리콥터 15대를 배치하여 신속하게 취재하고 있다. 이 뿐만 아니라, 46개의 지역방송국을 7개의 거점방송국으로 분할하여, 거점방송국마다 40여명의 카메라맨을 상주시켜 언제든지 재난을 취재할 수 있도록 하고 있다. 세계 각국에서 사용하고 있는 방송 주파수는 공공재(公共材)다. 국제전기통신연합(ITU : International Telecommunication Union)으로부터 주파수를 할당받아 사용하고 있기 때문에 주파수에 관한 사용 권한은 각국의 국민 모두에게 있다. 그러나 효과적인 주파수 활용을 전제로 정부가 일정한 자격을 갖춘 방송사업자에게 일시적으로 주파수 사용권을 위임하고 있다. 따라서 일본 정부도 국가적인 위기나 대형 재난발생으로 국민들의 생명과 재산이 위협받고 있을 때에는 공공재인 주파수를 즉시 재난방송으로 사용할 수 있도록 <재해대책기본법 제6조>와 방송법 제108조에 규정하고 있다.