• Journal of Korean Society of Transportation
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• v.29 no.2
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• pp.7-14
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• 2011

This paper discusses operational technique and effectiveness of Variable Speed Limits system that is implemented to control the traffic-flow on the Naebu Expressway. As the first step of the analysis, traffic data collected from vehicle detectors are corrected and smoothed. Applying a pattern analysis technique to the traffic data, the weekday traffic is classified into four different groups, and median of each group is calculated. Using three state variables, i.e., diverted traffic volume, average density and average speed, the conditions of roadway segments are determined. Computational outputs resulted from the application of the proposed model to the scenarios show that implementation of Variable Speed Limits system improved both safety and efficiency of the expressway. For the operational strategy, this paper also presents the change rate of the speed limit, and the effective duration of the speed limit according to the entering traffic volume.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.75.2-75.2
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• 2011

고온고압에서 운전되는 IGCC용 분류층 석탄가스화기는 석탄에 포함된 회 성분을 대부분 용융 슬래그 형태로 가스화기 벽을 타고 흘러내리게 하여 가스화기 하부로 배출시킨다. 이러한 용융 슬래그를 원활하게 배출시키는 것은 가스화기의 안정적인 운전에 있어서 매우 중요하다. 본 연구에서는 슬래그 층 내의 물질수지, 운동량 및 에너지 보존을 고려하여 석탄가스화기내의 슬래그 거동을 해석할 수 있는 모델 식을 유도하였다. 유도된 슬래그 거동 모델 식들을 적용하고 가스화기의 형상을 고려하여 가스화기 내부에서의 슬래그 거동을 해석하였다. 또한 슬래그 물성치들인 슬래그 점도, 슬래그 비열, 슬래그 밀도, 슬래그 열전달 계수 등을 슬래그의 조성 변화에 따라 별도로 산정하여 슬래그 해석의 입력 데이터로 사용하였다. 슬래그에 첨가되는 석회석의 비율을 해석의 주요 변수로 사용하여 가스화기 하부에서 용융 슬래그 및 고체 슬래그 두께, 용융 슬래그 층 내부에서의 슬래그 점도분포 및 슬래그 속도분포 등 슬래그 거동의 주요 특성들을 예측하였다. 해석결과로 석탄에 석회석의 첨가량을 증가시키면 슬래그의 임계점도온도(temperature of critical viscosity)와 점도가 낮아지므로 가스화기 벽면에서의 용융 슬래그의 유동속도는 빨라지며, 고체 슬래그와 용융 슬래그의 두께가 감소하는 것을 정량적으로 확인할 수 있었다.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.1
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• pp.29-34
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• 2018

The systems associated with the ESS never stop. It runs 24 hours everyday. The system must be managed to run. The ESS system should perform normally even if the power IT equipment fails or communication failure occurs. Therefore, there is a need for a system that actively addresses, manages and controls the high precision power data of the ESS, even if a variety of failures occur. I would like to propose a power management communication unit to cope with the occurrence of communication failure. This paper also includes an integrated management system that can perform micro grid site management, maintenance and monitoring for the ESS system connected with the solar power generation facility.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.123-130
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• 1988

Two kinds of 16bit-personal computer-based fatigue testing automation and monitoring system were constructed; one is Single-System utilizing a personal computer, the other si Dual-System consisting of two personal computers. The system developed in this study permits to perform multi-step programmed loading and pseudo-random loading fatigue tests, three parameters such as load, total displacement and subtracted displacement can be measured simultaneously. For improvements in measurements of fatigue behavior, two kinds of signal noise reduction software was developed. In addition, a software was also designed to automatically measure the crack opening point and crack length using the unloading elastic compliance technique.

• Journal of Information Technology Applications and Management
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• v.20 no.2
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• pp.127-146
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• 2013

The online social networking services (SNS) have been growing as the means of communication. In this study, we investigated word-of-mouth (WOM) effect under the SNS environment and evaluated the impact of message sender's influence on the WOM effect. Especially, this study focused on the betweenness centrality calculated through the social network analysis (SNA) of SNS network information, and proposed it as the measure of WOM message sender's influence, SNA may provide more accurate and objective measures than subjective self-reporting survey method. Fifty-one Facebook users responded to each of their four Facebook friends, who had been selected based on their betweenness centrality, Statistical analyses were performed using the responses and the betweenness centralities of the Facebook friends. The results showed that the direction (positive vs, negative) of a WOM message in SNS had an impact on the attitude of the message receiver toward the product. Moreover, the betweenness centrality of the message sender as well as his/her opinion leadership had a moderating effect on the WOM effect. Opinion leadership is a measure that has been frequently used for indicating the influence of WOM message sender in the previous studies. Considering the result that the betweenness centrality of the message sender was Significantly correlated to his/her opinion leadership, the betweenness centrality can be used for indicating the influence of WOM message sender.

• Journal of Information Technology Applications and Management
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• v.20 no.2
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• pp.109-125
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• 2013

As the number of SNS users is increasing, it has been very important how companies use SNS strategically. As a result, studies have been performed for the utilization of SNS. Most of the studies, however, focused on the overall characteristics of SNS and did not consider the characteristics of individual SNS. This study classified the main purpose of SNS use as relation-oriented purpose and information-oriented purpose, and identified the types of SNS from two viewpoints : service type and openness. Based on the classification, this study identified the characteristics of Cyworld, Facebook, and Twitter respectively, and analyzed the difference of the purpose of SNS users according to the characteristics of each service. The results showed that more users had the information-oriented purpose in the order of Twitter, Facebook, and Cyworld. There was no difference in the relation-oriented purpose among the three services. The analyses of the motive to join a group or a party made similar results. The results of additional analyses showed that the ratio of users with many acquaintances was high in the order of Facebook, Twitter, and Cyworld. In addition, more users checked their timeline or news feed more frequently in the order of Facebook, Twitter, and Cyworld.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.3C
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• pp.336-342
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• 2003

Noise predictive maximum likelihood(NPML) detector embeds noise prediction/whitening process in branch metric calculation of Viterbi detector and improves the reliability of branch metric computation. Therefore, PRML detector with a noise predictor achieves some performance improvement and has an advantage of low complexity. This thesis random sequences are applied to linear channel. In perpendicular magnetic recording density KP=2.5, NP(121)ML and NP(1221)ML detection system which is based on a noise predictive PR-equalized signal are evaluated by the Performance through a computing simulation. Therefore, NPML systems are implemented and are verified by VHDL.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2008.06a
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• pp.465-470
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• 2008

우리나라는 산림은 단순림이 많고 밀도가 높기 때문에 산불이 한번 발생하면 대형 산불로 확산될 우려가 크다. 이 때문에 산불 발생을 미리 예측하여 대응할 필요가 있다. 산불 발생예측을 위해서는 산불 발생에 영향을 미치는 인자와 산불 발생의 관계를 파악하는 것이 중요하다. 본 연구는 1997년부터 2006년까지 발생한 전국에서 발생한 산불의 point data를 이용하였다. 산불 발생 지점의 지형인자와 지리인자, 그리고 산불 발생 당시의 기상인자로 DB를 구축하고 산불 발생과의 관계를 구명하였다. 지형인자 분석은 고도, 방위, 경사에 따른 산불 발생 빈도를 분석하였고, 그 상관관계를 분석하였다. 지리인자 분석에서는 인구밀도, 산불 발생지역의 접근성(도로에 따른 접근성, 대도시와의 거리에 따른 접근성)에 대한 산불 발생의 상관관계를 분석하였다. 기상인자와 산불 발생의 관계는 전국 76개소에서 관측된 온습도 데이터를 보간한 자료와 산불 발생과의 관계를 분석하였다. 기상인자 분석은 산불이 가장 빈번하게 발생하는 3월 하순, 4월 초순, 4월 중순 자료를 평균하여 산불 발생 빈도와의 상관관계를 분석하고 산불 발생 위험지역을 도출하였다. 본 연구를 통해서 각 인자와 산불 발생의 관계를 분석해보았다. 하지만 각 인자간의 관계를 분석하지 못한 것이 한계점이라고 할 수 있다. 차후 연구에서는 각 인자간의 관련성을 분석하고 산불 발생의 원인과 인자간의 구체적인 인과관계를 밝히는 것도 필요할 것으로 보인다.

• Food Science and Preservation
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• v.7 no.4
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• pp.357-361
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• 2000

Watercore influences storage and distribution industry of fruit. Therefore, the technique for nondestructive discrimination of watercore fruit is needed. This work reports about the possibility of watercore discrimination of ante using transmitted light, and the effects of various factors. CCD camera was used to capone images of each apple fruit. An excess watercore apples were higher light transmission score than little watercore apples. The accuracy fur discrimination of watercore apple was about 70% using transmitted light. Peel thickness, anthocyanin layer thickness and density of apple affected the light transmission. Apples having thin peel, thin pigment layer and low density tended to high transmitted light score. Apples of good color degree were more probability of existence watercore than ones of bad color degree. But color distribution of apple peel was not correlated with watercore.

• The Journal of the Acoustical Society of Korea
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• v.35 no.2
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• pp.149-157
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• 2016

In this paper, we propose a new clutter reduction algorithm, which rejects heavy clutter density in shallow water environments, based on a clustering method. At first, it applies the density-based clustering to active sonar measurements by considering speed of targets, pulse repetition intervals, etc. We assume clustered measurements as target candidates and remove noise, which is a set of unclustered measurements. After clustering, we classify target and clutter measurements by the validation check method. We evaluate the performance of the proposed algorithm on synthetic data and sea-trial data. The results demonstrate that the proposed algorithm provides significantly better performances to reduce clutter than the conventional algorithm.