• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1C
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• pp.53-62
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• 2008

A constitutive model, which can simulate the effect of principal stress rotation associated with direct simple shear test, is proposed in this study. The model is based on two mobilized planes. The plastic strains occur from the two mobilized planes, and depend on stress state, and they are added. The first plane is a plane of maximum shear stress, which rotates about the horizontal axis, and the second plane is a horizontal plane which is spatially fixed. The second plane is used to consider the effect of principal stress rotation on simple shear tests under different stress states. The soil skeleton behavior observed in drained simple shear tests is captured in the model. This constitutive model is incorporated into the dynamic coupled stress-flow finite difference program FLAC. The model is first calibrated with drained simple shear tests on loose Fraser River sand. The measured shear stress and volume change are partially induced by principal stress rotation and compared with model calculations. The model is verified by comparing predicted and measured settlements due to rigid footing resting on loose sands. Settlements predicted by the proposed model were very similar to measured settlements. Mohr-Coulomb model can not consider the effect of principal stress rotation and its prediction was only 20% of measured settlements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4D
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• pp.635-647
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• 2006

Korean construction companies first advanced to the international markets in 1960's and so far have brought more than 4,900 projects which account for 193 billion dollars approximately. With the large increase of national employment and income being followed by the achievement, Korea's construction industry has made an enormous contribution to the improvement of domestic economy for the last 40 years. However, recently the increased risk in international markets as well as the sharpening competition with foreign companies promising in terms of advanced technologies and low labor cost have been driving Korean construction away from the market shares. According to ENR (Engineering News Record, 1994~2003), it is revealed that 15.1% of top 225 global contractors are suffering from loss in international construction markets. This phenomenon is largely due to the highly uncertain characteristics of international projects, which are inherently exposed to various and complicated risky situations. Furthermore, especially for Korean construction companies, it is often the case that the failure in an international construction project cannot be offset by even a sufficient number of successful domestic achievements. Therefore, not only the selective screening among the nominated projects which have strong possibility of collapse but the systematic strategies for controlling potential risk factors are also considered indispensable in international construction portfolio management. The purpose of this study is to first analyze the causal relationships of the profit-influencing variables and the project success, and develop the profitability forecasting model in international construction projects.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.699-707
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• 2008

For most structural evaluation of bridge integrity, it is very important to measure the geometric profile, which is a major factor representing the global behavior of civil structures, especially bridges. In the past, because of the lack of appropriate methods to measure the deflection profile of bridges on site, the measurement of deflection has been restricted to just a few discrete points along the bridge, and the measuring points have been limited to the locations installed with displacement transducers. Thus, some methods for predicting the static deflection by using fiber optic strain sensors has been applied to simply supported bridges. In this study, a method of estimating the static deflection profile by using strains measured from suspension bridges was proposed. Based on the classical deflection theory of suspension bridges, an equation of deflection profile was derived and applied to obtain the actual deflection profile on Namhae suspension bridge. Field load tests were carried out to measure strains from FBG strain sensors attached inside the stiffening girder of the bridge. The predicted deflection profiles were compared with both precise surveying data and numerical analysis results. Thus, it is found that the equation of predicting the deflection profiles proposed in this study could be applicable to suspension bridges and the FBG strain sensors could be reliable on acquiring the strain data from bridges on site.

• Journal of Navigation and Port Research
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• v.47 no.3
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• pp.167-173
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• 2023

The manufacturing industry is the backbone of the Korean economy. Among them, the petrochemical industry is a strategic growth industry, which makes a profit through reexports based on eminent technology in South Korea which imports all of its crude oil. South Korea imports whole amount of crude oil, which is the raw material for many manufacturing industries, by sea transportation. Therefore, it must respond swiftly to a highly volatile tanker freight market. This study aimed to make an early warning model of crude oil shipping market using a signal approach. The crisis of crude oil shipping market is defined by BDTI. The overall leading index is made of 38 factors from macro economy, financial data, and shipping market data. Only leading correlation factors were chosen to be used for the overall leading index. The overall leading index had the highest correlation coefficient factor of 0.499 two months ago. It showed a significant correlation coefficient five months ago. The QPS value was 0.13, which was found to have high accuracy for crisis prediction. Furthermore, unlike other previous time series forecasting model studies, this study quantitatively approached the time lag between economic crisis and the crisis of the tanker ship market, providing workers and policy makers in the shipping industry with an framework for strategies that could effectively deal with the crisis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.61-67
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• 2006

Various methods have been applied for the research to model the relationship between rainfall-runoff, which shows a strong nonlinearity. In particular, most researches to model the relationship between rainfall-runoff using artificial neural networks have used back propagation algorithm (BPA), Levenberg Marquardt (LV) and radial basis function (RBF). and They have been proved to be superior in representing the relationship between input and output showing strong nonlinearity and to be highly adaptable to rapid or significant changes in data. The theory of artificial neural networks is utilized not only for prediction but also for classifying the patterns of data and analyzing the characteristics of the patterns. Thus, the present study applied self?organizing map (SOM) based on Kohonen's network theory in order to classify the patterns of rainfall-runoff process and analyze the patterns. The results from the method proposed in the present study revealed that the method could classify the patterns of rainfall in consideration of irregular changes of temporal and spatial distribution of rainfall. In addition, according to the results from the analysis the patterns between rainfall-runoff, seven patterns of rainfall-runoff relationship with strong nonlinearity were identified by SOM.

• Journal of The Geomorphological Association of Korea
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• v.18 no.1
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• pp.41-56
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• 2011

This study analyzes the change in land-cover based on satellite imagery to draw up land-cover map in the future, and estimates the change in land category using statistical data of the land category. To estimate land category, this study applied the double exponentially smoothing method. The result of the land cover classification according to year using satellite imagery showed that the type with the largest increase in area of land cover change in the cities of Cheonan and Asan was artificial structure, followed by water, grass field and bare land. However forest, paddy, marsh and dry field were reduced. Further, the result of the time-series analysis of the land category was found to be similar to the result of the land cover classification using satellite imagery. Especially, the result of the estimation of the land category change using the double exponentially smoothing method showed that paddy, dry field, forest and marsh are anticipated to consistently decrease in area from 2010 to 2100, whereas artificial structure, water, bare land and grass field are anticipated to consistently increase. Such results can be utilized as basic data to estimate the change in land cover according to climate change in order to prepare climate change response strategies.

• Journal of Korea Port Economic Association
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• v.39 no.2
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• pp.1-13
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• 2023

This study forecasted the manpower demand of eco-friendly smart shipbuilding, whose importance and weight are increasing according to the environmental regulations of the IMO and the spread of the 4th industrial revolution technology. It predicted the shipbuilding industry manpower by applying various models of trend analysis and time series analysis based on data from 2000 to 2020 of Statistics Korea. It was found that the prediction applying geometric mean had the smallest gap among the trend and time series analysis methods in comparing between forecast results and actual data for the past 5 years. Therefore, the demand for manpower in the shipbuilding industry was predicted by using the geometric mean method. In addition, the manpower demand of smart eco-friendly ships wast forecasted by using the 2018 and 2020 manpower survey results of the Ministry of Trade, Industry and Energy and reflecting the trend of manpower increase in the shipbuilding industry. The result of forecasting showed that 62,001 person in 2025 and 85,035 people in 2030. This study is expected to contribute to the adjustment of manpower supply and demand and the training professional manpower in the future by increasing the accuracy of forecasting for high value-added eco-friendly smart ships.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.1-8
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• 2023

If there is a defect in the wheel bearing, which is a major part of the car, it can cause problems such as traffic accidents. In order to solve this problem, big data is collected and monitoring is conducted to provide early information on the presence or absence of wheel bearing failure and type of failure through predictive diagnosis and management technology. System development is needed. In this paper, to implement such an intelligent wheel hub bearing maintenance system, we develop an embedded system equipped with sensors for monitoring reliability and soundness and algorithms for predictive diagnosis. The algorithm used acquires vibration signals from acceleration sensors installed in wheel bearings and can predict and diagnose failures through big data technology through signal processing techniques, fault frequency analysis, and health characteristic parameter definition. The implemented algorithm applies a stable signal extraction algorithm that can minimize vibration frequency components and maximize vibration components occurring in wheel bearings. In noise removal using a filter, an artificial intelligence-based soundness extraction algorithm is applied, and FFT is applied. The fault frequency was analyzed and the fault was diagnosed by extracting fault characteristic factors. The performance target of this system was over 12,800 ODR, and the target was met through test results.

• Journal of Environmental Impact Assessment
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• v.32 no.6
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• pp.545-555
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• 2023

This study aimed to predict the distribution density and potential habitat of domestic cats (Felis catus) in order to identify core distribution areas. It also aimed to overlay protected areas to identify priority areas for cat management. Kernel density estimation was used to determine the distribution density, and areas with high density were classified in Greater Seoul, Chungnam, Daejeon, and Daegu. Elevation, distance from the used area and roughness were identified as important variables in predicting potential habitat using the MaxEnt model. In addition, the classification of suitable and unsuitable areas based on thresholds showed that the predicted presence of habitat was more extensive in Seoul, Sejong, Daejeon, Chungnam, and Daegu. Core distribution areas were selected by overlapping high-density areas with suitable areas. Priority management areas were identified by overlaying core distribution areas with designated wildlife sanctuaries. As a result, Gyeonggi, and Chungnam have the largest areas. In addition, buffer zones will be implemented to effectively manage the core distribution area and minimize the potential for additional introductions in areas of high management priority, such as protected areas. These results can be used as a basis for investigating the status of the cat's habitat and developing more effective management strategies.

• Korean Journal of Culture and Social Issue
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• v.13 no.4
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• pp.113-134
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• 2007

This study investigated body-related values, body-esteem, and the relationship between them based on the survey data drawn from female college students in three East Asian countries(Korea, Japan, and China). 168 Korean, 108 Chinese, and 152 Japanese female college students responded to questions designed to measure four sorts of body values (operability, inclination, locus of evaluation, and social utility) and four dimensions of body esteem (appearance, weight, health, overall). The results showed that body-related values and body-esteem differ among three countries. Japanese showed the highest acceptance level for the voluntary body alteration(operability), while chinese scored the lowest. Inclination to body appearance over health was higher in Korean than in Japanese and in Chinese. Korean also evaluated the importance of body appearance and its social utility the highest, followed by Japanese and Chinese. There were dramatic differences in body esteem between Korean and Japanese. Regarding body-esteem, Korean showed the highest appearance-esteem, but the health-esteem was the lowest. On the contrary, Japanese showed the highest health-esteem, but the appearance-esteem was lowest. Chinese showed the highest weight-esteem. Four sorts of body values showed significant correlations with appearance-esteem and weight-esteem, respectively but not with health-esteem. Overall, the result supported the prediction that different political, social, and economic backdrops in three countries would be related with different body-related values and body esteem in the female college students.