• 한국해양공학회지
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• 제18권2호
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• pp.46-51
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• 2004

Natural frequencies of the transverse vibration of beams with step change in cross-section are obtained by using the asymptotic closed form solution. This closed form solution is found by using WKB method under the assumption of slowly varying properties, such as mass, cross-section, tension etc., along the beam length. However, this solution is found to be still very accurate even in the case of large variation in cross-section and tension. Therefore, this result can be easily applied to many engineering problems.

• Smart Structures and Systems
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• 제15권6호
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• pp.1583-1600
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• 2015

When natural disasters occur, including earthquakes, tsunamis, and debris flows, they are often accompanied by various types of damages such as the collapse of buildings, broken bridges and roads, and the destruction of natural scenery. Natural disaster detection and warning is an important issue which could help to reduce the incidence of serious damage to life and property as well as provide information for search and rescue afterwards. In this study, we propose a novel computer vision technique for debris flow detection which is feature-based that can be used to construct a debris flow event warning system. The landscape is composed of various elements, including trees, rocks, and buildings which are characterized by their features, shapes, positions, and colors. Unlike the traditional methods, our analysis relies on changes in the natural scenery which influence changes to the features. The "background module" and "monitoring module" procedures are designed and used to detect debris flows and construct an event warning system. The multi-criteria decision-making method used to construct an event warring system includes gradient information and the percentage of variation of the features. To prove the feasibility of the proposed method for detecting debris flows, some real cases of debris flows are analyzed. The natural environment is simulated and an event warning system is constructed to warn of debris flows. Debris flows are successfully detected using these two procedures, by analyzing the variation in the detected features and the matched feature. The feasibility of the event warning system is proven using the simulation method. Therefore, the feature based method is found to be useful for detecting debris flows and the event warning system is triggered when debris flows occur.

• 한국환경성돌연변이발암원학회:학술대회논문집
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• 한국환경성돌연변이발암원학회 2004년도 KSOT/KEMS Fall Annual Meeting
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• pp.131-131
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• 2004

• 한국양식학회지
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• 제16권2호
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• pp.69-75
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• 2003

Genetic variability and population structure of 11 natural ayu, Plecoglossus altivelis populations and one hatchery stock were assessed by starch gel electrophoretic analysis with 10 enzyme coding loci. Three loci were polymorphic (lower than 0.95 in major allele frequency) in natural populations,2 loci in hatchery stock. The average number of alleles per locus was 1.38. Observed heterozygosities ranged from 0.0235 to 0.088 (0.055 on the average) in natural population while 0.0925 in hatchery stock. The genetic distance among natural populations measured 0.000047-0.005407 and no significant differentiation was observed among them. On the other hand, a signifcant genetic distance was found between natural populations and the hatchery stock with measuring 0.002032-0.O08605. The results in this study suggest that the hatchery stock has diverged from natural populations, and also that careful to maintain sustainable and effective population size (parents number) should be made.

• 한국생명과학회:학술대회논문집
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• 한국생명과학회 2003년도 제40회 국제학술심포지움
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• pp.81-81
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• 2003

• 대한기계학회논문집A
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• 제38권3호
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• pp.337-344
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• 2014

한국 전통 악기인 편경을 체계적으로 설계하기 위한 최적 형상 설계 알고리즘을 제안한다. 편경은 16 개의 서로 다른 크기의 경편으로 구성되어 있다. 각 경편의 첫 번째 진동 고유 주파수는 전통 소리 튜닝 방법에 의해 결정되는 특정 주파수에 일치하여야 하고, 두 번째와 세 번째 진동 고유 주파수들은 첫 번째 진동 고유 주파수와 단 3 화음 관계(1:1.498:2.378)를 가져야 한다. 제안한 설계 알고리즘의 핵심은 경편의 각 변의 길이 변화에 따른 고유 주파수의 민감도를 구하고, 이를 이용하여 위 두 가지 설계 목적에 부합하는 경편의 치수를 결정하는 것이다. 제안하는 방법으로 5 개의 서로 다른 경편의 형상 치수를 결정하였다. 그리고, 제작 과정에서 발생할 수 있는 오차를 보상하기 위해, 경편의 국부적인 두께 변화에 따른 진동 고유 주파수의 변화에 대해서도 살펴보았다.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.123-131
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• 1999

Natural gas is one of the most promising alternative fuels for automotive vehicles. However, natural gas varies in compositional between the originating fields and may be further modified due to processing and additional mixing. These variations are known to affect engine performance and emissions through changes in fuel metering and combustion characteristics. In the present study, the effect of gas compositions on vehicle performance such as fuel economy, driveability and exhaust emissions was examined. Analysis are made of using 3 types of NGVs which were made by automakers and 6 different fuels which are selected in consideration of the variation in fuel composition on the worldwide market. The results may be utilized to develop natural gas natural gas engine in automaekrs and/or to establish the fuel standard in the refueling stations.

• 한국농공학회논문집
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• 제49권6호
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• pp.77-84
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• 2007

This study aims to analyze temporal variation of rural tourist potential in village level. In order to analyze the temporal variation, this study applied a green-tourism potential evaluation model(GPEM) to a study area, Namilmyun with 18 villages, which located on county of Kumsan, province of Chungnam. GPEM consists of two factors about human resources, which is quantified by resident population of the village who will be participated in village management for green-tourism, and amenity resources, which is calculated by an evaluation table with 31 criteria and their weighting values. Data surveying for the study area was performed at August 2003 and 2006, respectively, in order to quantity the 31 evaluation criteria of GPEM. From the analysis results, the amenity resources with three sub-classes of industrial, natural, and social resources showed that the evaluation values of 2006 were increased in more than those of 2003, displaying the increase rate of ranging from 108% to 112% in the three sub-classes, except of one village in social resources and three village in natural resources with reduction. In human resources, the evaluation values of 2006 were highly increased more than those of 2003, showing the rate of 556% in the gradient of linear regression line. In green tourism potential in each village, the evaluation results for two time series showed that the potential is increased by time, which the increase rate of the potential is 114%. Ultimately, the results of this study enable us to realize that the green-tourism potential in each village over time is increased, for example, due to developing new facilities in the village by investment of government and participating in rural tourism by resident people over time. From the analysis and results, the methodology of this study can be applied to analyze the temporal variation of the potential for villages having investment from government.

• 한국산림과학회지
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• 제94권6호
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• pp.397-401
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• 2005

개비자나무로부터 추출한 HHT(homoharringonine)는 현재 가능성 있는 암화학요법제로 주목받고 있다. 국내 개비자나무 8개 천연집단의 HHT 함량 변이는 HPLC(high performance liquid chromatography)를 이용하여 조사하였고, 집단간 변이와 개체내의 부위별(잎, 줄기, 뿌리 및 종자) 변이 및 수령과 생장특성에 따른 함량 변이를 비교 분석하였다. 개비자나무의 집단간 HHT 함량 변이는 집단간에 통계적으로 유의한 차이가 인정되었으며, 거창의 남덕 유산 집단이 $1,048{\mu}g/g$으로 가장 높았고 완도의 오봉산 집단이 가장 낮았다. 개체내 부위별 함량은 잎에서 $874{\mu}g/g$으로 가장 높았으며, 다음으로 뿌리, 줄기, 종자 순으로 나타났다. 개비자나무의 HHT 함량은 수령이 증가하고 생장이 왕성해 질수록 대략 30% 정도 감소하는 것으로 나타났다.

• 설비공학논문집
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• 제15권12호
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• pp.1078-1087
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• 2003

Kimchi refrigerator is a household electric appliance developed with the wholly domestic technology for maturing and keeping kimchi. However, the principle of keeping is not yet revealed obviously. This numerical study has been conducted to investigate the flow and heat transfer characteristics in a kimchi refrigerator. The effects of arrangement variation of a evaporation tube are examined. Also, the heat transfer characteristics through the insulation material are discussed in detail. The flow and temperature field was simulated using the commercial code of CFX-5.3. A natural convection flow is formed through about 5/6 region from the bottom within the keeping space and accordingly, the 90% region of kimchi containers satisfies the temperature requirement with 0$\pm$0.5$^{\circ}C$. The stagnant flow exists in the upper 1/6 region of the keeping space and accordingly, the stratified high temperature distributions appear in the upper region of kimchi containers. The upward shift of the start location of a evaporation tube improves the temperature concentration toward $0^{\circ}C$ but the pitch variation is of no effect. The heat fluxes on the insulation surfaces show two-dimensional distributions with being higher toward the center. Through the variation of insulation thickness, 3.5% saving of insulation material is obtained under the same heat transfer rate.