• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.6
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• pp.2826-2832
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• 2012

A smart grid is an electric-power grid that employs a new information technology.This technology makes it possible to exchange real-time energy information between suppliers and consumers, finally resulting in high energy efficiency. The energy management system in smart grid provides up to date information on electricity consumption as well as dynamic electricity price to consumers of smart grid system. However, the existing energy management systems only focus on pricing system, for example, real-time electricity prices. In this paper, we try to improve the existing energy management system and propose the energy management system that mainly focuses on the efficiency of electricity consumption. In the proposed management system, PMU(Phasor Measurement Units) installed in switchboards gathers electricity data in a real time. We also propose to use data mining method, which is applied to analyzed electricity data for improving energy efficiency. Also, the proposed energy management system is designed to efficiently control the electricity between PMU and management system in case of a shortage of electricity or surplus electricity.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.193-204
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• 2011

To develop more robust oil boom which is vulnerable to various failure mode under severe weather condition, highly accurate wave model is developed using Spatially filtered Navier-Stokes Eq., LDS (Lagrangian Dynamic Smagorinsky model) for residual stresses, SPH (Smoothed Particle Hydrodynamics). To clarify the hydraulic characteristics of floating type oil boom, we numerically simulate the behavior of oil spill around oil boom under very energetic progressive waves. At the first stage, we firmly anchored the oil boom, and then, allowed the excursion of the oil boom. It turns out that oil boom with skirt of enough length (longer than 30% of depth) effectively confines the oil spill even against very energetic waves. We can also observe obliquely descending vertical eddies between y = 1~2 m as horizontal vortices shedding at the interface of oil spill and water are diffused toward the bottom, which is believed to be the birth, growing and break-down of Kelvin-Helmholz wave.

• Smart Media Journal
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• v.12 no.7
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• pp.76-83
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• 2023

This study proposes a method to assist webtoon artists in the process of webtoon creation by utilizing a pretrained Text-to-Image model to generate webtoon images from text. The proposed approach involves fine-tuning a pretrained Stable Diffusion model using a webtoon dataset transformed into the desired webtoon style. The fine-tuning process, using LoRA technique, completes in a quick training time of approximately 4.5 hours with 30,000 steps. The generated images exhibit the representation of shapes and backgrounds based on the input text, resulting in the creation of webtoon-like images. Furthermore, the quantitative evaluation using the Inception score shows that the proposed method outperforms DCGAN-based Text-to-Image models. If webtoon artists adopt the proposed Text-to-Image model for webtoon creation, it is expected to significantly reduce the time required for the creative process.

• Journal of the Korea Society of Computer and Information
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• v.29 no.7
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• pp.89-98
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• 2024

In this paper, we propose a system for recommending lecture videos at the chapter level, addressing the balance between accuracy and processing speed in chapter-level video recommendations. Specifically, it has been observed that enhancing recommendation accuracy reduces processing speed, while increasing processing speed decreases accuracy. To mitigate this trade-off, a hybrid approach is proposed, utilizing techniques such as TF-IDF, k-means++ clustering, and Graph Neural Networks (GNN). The approach involves pre-constructing clusters based on chapter similarity to reduce computational load during recommendations, thereby improving processing speed, and applying GNN to the graph of clusters as nodes to enhance recommendation accuracy. Experimental results indicate that the use of GNN resulted in an approximate 19.7% increase in recommendation accuracy, as measured by the Mean Reciprocal Rank (MRR) metric, and an approximate 27.7% increase in precision defined by similarities. These findings are expected to contribute to the development of a learning system that recommends more suitable video chapters in response to learners' queries.

• The Journal of Society for e-Business Studies
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• v.18 no.4
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• pp.315-326
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• 2013

Users in social media post various types of opinions such as product reviews and movie reviews. It is a common trend that customers get assistance from the opinions in making their decisions. However, as opinion usage grows, distorted feedbacks also have increased. For example, exaggerated positive opinions are posted for promoting target products. So are negative opinions which are far from common evaluations. Finding these biased opinions becomes important to keep social media reliable. Techniques of opinion mining (or sentiment analysis) have been developed to determine sentiment polarity of opinionated documents. These techniques can be utilized for finding the biased opinions. However, the previous techniques have some drawback. They categorize the text into only positive and negative, and they also need a large amount of training data to build the classifier. In this paper, we propose methods for discovering the biased opinions which are skewed from the overall common opinions. The methods are based on angle based outlier detection and personalized PageRank, which can be applied without training data. We analyze the performance of the proposed techniques by presenting experimental results on a movie review dataset.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.7
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• pp.1330-1338
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• 2015

In wireless communication network, the amount of packet data for the video streaming in the playout buffer of the receiver is changed with time according to network condition. If the amount of packet data is less than a specific buffer amount, the buffer underflow problem is generated. On the contrary, if the amount of packet data is more than a given buffer amount, the buffer overflow problem is occurred. When the playout of the video streaming is processed, these buffer underflow and overflow problems cause stop and skip phenomenons and then provide the discontinuity of playout. Therefore, to solve the buffer underflow and overflow problems of the video streaming in wireless communication network, This paper analyzes the combined effect of Token Bucket scheme, which controls the bursty traffic, and AMP(Adaptive Media Playout) scheme, which adaptively changes the playout speed of receiver. Through simulation, we found that the combination of Token Bucket and AMP schemes provides the superiority in terms of the occurrence number of buffer underflow and overflow, the stop duration time and the number of removed frames generated by underflow and overflow, and PSNR.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.168-178
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• 2006

In recent years, an ingress of mass jellyfish into cooling water intake system causes interruption of electric power production at the Uljin nuclear power plant. Therefore, monitering and forecast on the mass ingress of marine organisms are demanded as one of the early preventing measurements. Sea water movement is a major factor on the ingress of marine organisms like Moon jellyfish which has weak self-mobile ability. When sea surface flow direction adjacent to the Uljin is the northwest, the jellyfish on the Tsushima warm currents move to the Uljin power plant. To detect the direction of sea surface warm flows, the spatial range with $25km{\times}25km$ is set up and NOAA sea surface temperature(SST) data are collected in this area. For the statistical analysis, the SST data are made as GIS point data and geostatistical analysis of ArcGIS is used. Analyzing directional semivariogram, the anisotropy of the SST point data are calculated and warm flow direction is detected. This experimental results are expected to use as an element technology for the early warning system development of mass jellyfish ingress in power plant.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5B
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• pp.547-558
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• 2008

With the advent of super cargo ship due to the explosive increase in the amount of cargo shipped via seas, some mega ports are under construction in South Korea, to accommodate the super cargo ship, and some of them already enter their final phase. To sustain the harbor tranquility, mega ports usually comprise huge vertical type breakwaters which are intrinsically vulnerable to the attack of long waves. In this rationale, we present the chamber type breakwater with a circular curtain wall - Eco-breaker 2, to alleviate the reflection of long waves and numerically investigate the hydraulic characteristics of Eco-breaker 2. As a wave driver, we use the Navier-Stokes eq., the most robust wave driver, using SPH (Smoothed Particle Hydrodynamics) and LES (Large Eddy Simulation). For the verification of numerical results, we also carried out hydraulic model test. It is shown that Eco-breaker 2 can effectively alleviate the reflection of long waves with its inherited large organized eddies encompassing the water chamber and some region off the curtain wall of varying size. It is also shown that the scope and strength of large organized eddies strongly depends on the incident wave period, and the reflection coefficient can be lowered to 0.18 by tuning the size of water chamber such that resident time at the chamber is just short of the half period of incident waves. Based on these results, we present the specification of Eco-breaker 2 to boost its use on the development of water environment friendly harbor worldwide.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1774-1778
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• 2008

유량 환산에 이용되는 수위-유량 관계곡선식은 하천의 흐름을 정상 등류상태로 가정하고 유속계를 하천에 투입하여 년간 정해진 횟수의 유량측정을 실시하여 이로부터 갱신하여 작성하고 있다. 평수기에는 이렇게 기기를 이용하여 유량측정이 가능하지만 홍수기나 갈수기에는 접촉식 유속계를 이용한 하천유량 측정이 불가능한 실정이다. 홍수기에는 기기 손상과 관측자의 안전이 위협받는 실정이고, 갈수기에는 유속이 너무 느려서 (0.1 m/s 이하) 프로펠러 유속계의 경우 유속의 정확한 관측이 힘들다. 또한 전지구적 빈번한 이상기후의 현실정에서 가장 중요한 기초 수문자료인 홍수량의 정확한 측정 자료는 많지 않다. 홍수유량을 측정하기 위해서 현재에도 기존의 봉부자를 이용하거나 유비쿼터스 센서를 장착한 봉부자를 이용하는 유량측정 기법이 향해지고 계속적으로 소개되고 있는 실정이지만 봉부자의 특성상 정확한 유량을 계산하기에는 어려움이 많다. 현재 선진국에서는 흐름과 비접촉식 방법을 이용한 하천유량측정 방법이 지난 10 여년간 꾸준이 연구되어 왔다. 그중 대표전인 것이 전자파를 이용한 방법과 영상해석에 의한 방법이다. 전자의 경우 국내에서는 수자원공사에서 10년 이상 연구 개발하여 상품화 시킨바 현업에서 이를 이용하여 홍수유량측정을 실시하고 있다. 후자의 방법은 유체역학 분야에서 흐름해석에 주로 이용되어지던 PIV(particle image velocimetry) 기법을 하천과 같이 대규모의 흐름영역에 적용가능하도록 개발된 기술로 LSPIV (large-casle particle image velocimetry)라 불리우는 기술이다. 본 연구에서는 미국 Iowa 대학에서 개발한 LSPIV를 이용하여 홍수파의 진행시 수위와 유량의 두 변수 사이에 나타나는 Loop rating curve의 이론적인 관계를 하천현장에서 일정시간 간격으로 실측을 통하여 파악하고자 하였다. 현장실험을 위한 대상지점으로 미국 Iowa주 Coralville 시내 Clear Creek의 USGS (US Geologival Survey) 수위관측소 지점을 선택하여 본 연구에서 실시한 유량측정 결과의 비교가 가능토록 하였다. LSPIV는 그 특성상 야간에는 적용하는데 어려움이 있어 아침시간부터 해가 지기 직전까지의 자연채광 조건의 영상취득이 가능한 시간대에서 표면유속을 측정하였고 이에 수심평균유속환산계수를 적용하여 유량을 계산하였다. 강우의 발생으로 인한 홍수파의 진행시 총 43회의 유량을 측정하였는바 이를 이용하여 이 지점의 수위-유량 관계식과 비교한 결과 거의 일치하는 결과를 나타냈다. 특히 홍수파의 진행시 고수위 영역에서의 측정한 결과는 수위의 상승기에는 최고로 7.5% 까지 측정유량이 수위-유량관계식에서 계산한 유량보다 컸으며, 수위의 하강기에는 반대로 최고 5.4% 정도까지 측정유량이 수위-유량관계식에서 계산한 유량보다 작게 나타났다. 또한 최대유량의 발생시기는 최고수위 발생직전의 수위라는 것이 파악되었다. 이러한 경향은 수위-유량 관계곡선의 이론과 잘 일치하는 것이다.

• Economic and Environmental Geology
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• v.38 no.4 s.173
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• pp.435-450
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• 2005

The purpose of the study is to analyze the hydrogeochemical characteristics by multivariate statistical method, to interpret the hydrogeochemical processes for the new variables calculated from principal components analysis (PCA), and to infer the groundwater flow and circulation mechanism by applying the geostatistical methods for each element and principal component. Chloride and nitrate are the most influencing components for groundwater quality, and the contents of $NO_3$ increased by the input of agricultural activities show the largest variation. The results of PCA, a multivariate statistical method, show that the first three principal components explain $73.9\%$ of the total variance. PC1 indicates the increase of dissolved ions, PC2 is related with the dissolution of carbonate minerals and nitrate contamination, and PC3 shows the effect of cation exchange process and silicate mineral dissolution. From the results of experimental semivariogram, the components of groundwater are divided into two groups: one group includes electrical conductivity (EC), Cl, Na, and $NO_3$, and the other includes $HCO_3,\;SiO_2,$ Ca, and Sr. The results for spatial distribution of groundwater components showed that EC, Cl, and Na increased with approaching the coastal line and nitrate has close relationship with the presence of agricultural land. These components are also correlated with the topographic features reflecting the groundwater recharge effect. The kriging analysis by using principal components shows that PC 1 has the different spatial distribution of Cl, Na, and EC, possibly due to the influence of pH, Ca, Sr, and $HCO_3$ for PC1. It was considered that the linear anomaly zone of PC2 in western area was caused by the dissolution of carbonate mineral. Consequently, the application of multivariate and geostatistical methods for groundwater in the study area is very useful for determining the quantitative analysis of water quality data and the characteristics of spatial distribution.