• Geophysics and Geophysical Exploration
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• v.22 no.4
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• pp.177-185
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• 2019

Ground roll is a surface wave which is usually observed in the land seismic data. It is one of the typical coherent noise. During the reflection data processing, ground roll is removed because it is considered as noise. This removal process often causes the loss of reflection signals if the ground roll overlaps reflection signals. In this study, we look over Karhunen-Loeve Transform (KLT) and analyze its effects to suppress the ground roll appropriately while reducing the reflection loss. Numerical tests in homogeneous elastic media show that the ground roll has been properly rejected. However, the field data application reveals that there is no significant suppression of ground roll when compared to band-pass filtering. This can be considered that it is hard to calculate horizontally aligned gathers in the field data because the ground roll contains a wide range of frequency bands. On the contrary, the result of singular value decomposition (SVD) filtering shows that the ground roll has been significantly reduced. It is thought that the SVD filtering performs better in the ground roll suppression than KLT because it is easy to calculate the horizontally aligned gathers in the SVD filtering.

• Journal of the Korean GEO-environmental Society
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• v.11 no.3
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• pp.33-41
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• 2010

The rammed aggregate compaction pile method is widely used as soft ground improvement method because of the installed piles improve not only overall composite capacity but also discharge capacity. But the discharge capacity is declined when the clogging is generated due to the clay penetration into voids of rammed aggregate compaction pile with the time elapsed. The purpose of this study is to reduce the clogging problem occurred in rammed aggregate compaction pile constructed in the soft ground and to minimize voids of rammed aggregate compaction pile. The proper mixing ratio was determined which is based on the results of the large scale direct shear tests conducted to get strength and permeability as optimum mixing ratio of crushed stone and bottom ash. The test results indicated that the highest internal friction angle was obtained at 80:20 mixing ratio of crushed stone and bottom ash. The internal friction angle was declined when the mixing ratio of the bottom ash increased over 20%. The results of the clogging tests, presented that the mixture of 80:20 crushed stone and bottom ash is highest effective of clogging than ratio of pure crushed stone.

• The KIPS Transactions:PartD
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• v.18D no.5
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• pp.371-384
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• 2011

This paper considers logistics decision support system which deals with transportation mode selection considering transportation and carbon emission cost. Transportation and carbon emission costs vary with the choice of transportation modes and to become competitive companies need to find proper transportation modes for their logistics services. However, due to the restricted capacity of transportation modes, it is difficult to balance transportation and carbon emission costs when designing logistics network including transportation mode choice for each service. Therefore this paper aims to analyze the trade-off relationship between transportation and carbon emission cost in mode selection of intermodal transportation and to provide optimal green logistics strategy. In this paper, the logistics decision support system is designed based on mixed integer programming model. To understand the trade-off relationship of transportation and carbon emission cost, the system is tested with various scenarios including transportation of containers between Seoul and Busan. The analysis results show that, even though sea transportation combined with trucking is competitive in carbon emission per unit distance travelled, the total cost of carbon emission and transportation for the sea transportation may not have competitive advantage over other transportation modes including rail and truck transportation modes. The sea-based intermodal logistics service may induce detours which have negative impacts on the overall carbon emission. The proposed logistics decision support system is expected to play key role in green logistics and supply chain management.

• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.539-544
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• 2015

There is drift toward moving offshore structures operating sites to deep water that brings subsea systems and types of apparatus to meet more severe environment than onshore. At this moment, climatic condition and seabed state affect trenching efficiency so trenching process is need to make steady progress in a short time. This paper is research on estimation about construction performance of waterjet trenching machine mounted on ROV trencher. Optimal number of nozzles that can maximize trenching efficiency is selected by considering clearance and angle of nozzles through CFD. Then verified effectiveness of waterjet apparatus on the result of trenching depth and velocity by model test analogized performance for construction work of waterjet trenching machine.

• Journal of Climate Change Research
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• v.4 no.3
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• pp.291-303
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• 2013

After establishing national greenhouse gas emission reduction goals, the South Korean government has been pursuing sector- and industry-specific greenhouse gas emission reduction measures; in support of which, metropolitan city / state governing entities, such as Gyeonggi Province, etc., have been in lock steps by establishing and executing climate change measures that are appropriate for the regional characteristics. However, in the case of local governments, difficulties abound due to the fact that the per-unit greenhouse gas emission amounts and the future emission estimates for establishing reduction targets are not clear. In order to establish correct climate change measure policies, the policy directions and the assessment of verified greenhouse gas emission amounts would need to serve as the basis, and along with the national level climate change effect and vulnerability assessment, there's a need to develop methodologies that take into consideration the local characteristics and conditions. To this end, this study calculated the greenhouse gas emission amounts of the City of Siheung, a basic local government in Gyeonggi Province, by using the GEBT (Greenhouse gas Emission Business-as-usual Tool) developed by the National Institute of Environmental Research to facilitate easy calculations of BAU (business-as-usual) emission quantities by local governing entities.

• Journal of Korea Water Resources Association
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• v.52 no.4
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• pp.235-243
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• 2019

Recently, urban inundation was frequently occurred due to the intensive rainfall exceeding marginal capacity of the flood control facility. Furthermore, needs for the underground storage facilities to mitigate urban flood are increasing according to rapidly accelerating urbanization. Thus, in this study, drainage efficiency in drain tunnel connecting to underground storage was investigated from the air-core measurements in the drop shaft against two types of inlet structure. In case of the spiral inlet, the multi-stage structure is introduced at the bottom of the inlet to improve the vortex induction effect at low inflow discharge (multi-stage spiral inlet). The average cross-sectional area of the air-core in the multi-stage spiral inlet is 10% larger than the tangential inlet, and show the highly air emission effect and the highly inflow efficiency at the high inflow discharge. In case of the tangential inlets, the air emission effect decreased after exceeding the maximum inflow discharge, which is required to maintain the inherent performance of the tangential inlet. From the measurements, the empirical formula for the cross-sectional area of the air-core according to locations inside the drop shaft was proposed in order to provide the experimental data available for the inlet model used in experiments.

• The Journal of the Korea Contents Association
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• v.21 no.6
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• pp.248-260
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• 2021

This study assumes that the smooth school life of adolescents from multicultural families is recognized as an important part of multicultural support policies and practices as a basis for realizing an integrated society, and system elements that are meaningful for their flexibility to adapt to school (individuals, families, schools) By empirically analyzing the effect of, we tried to bring out highly effective implications for the composition of a multidimensional practice system. Therefore, this study is a causal model in which self-identity (individual factor) and parental parenting attitude (family factor), which are important variables for each system level, are set as independent variables, and school support (school factor) consisting of teacher support and companion support is set as control variables. After collecting data through a questionnaire survey by interviews with 162 middle and high school students in Gyeonggi and Gangwon regions, the effect was analyzed through multiple regression analysis. As a result of the analysis, it was confirmed that school support has a very important static moderating effect in the positive (+) effect of adolescents' self-identity and parenting attitude on school adaptability. It was confirmed that the modulating effect is relatively more important.

• Journal of the Korean Regional Science Association
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• v.38 no.1
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• pp.45-56
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• 2022

The purpose of this study is to examine the differences among the income level groups of young single-person households and newlywed households in factors affecting the choice of residential location in the Seoul metropolitan region. To summarize the results of the analysis, first, there were differences in the factors affecting the choice of residential location by income level in both single-person young households and newlyweds. Second, among young households, the low-income group showed a behavior of choosing a residential location based on bounded rationality considering the economic condition of the household. Third, even though the income level is similar, the difference in the factors for choosing a residential location between single-person young households and newlywed households was confirmed, which is results of the life-cycle changes. These results imply that it is necessary to prepare appropriate housing policies that can supplement the economic conditions of young households living in the Seoul metropolitan region, and to review customized housing policies that reflect changes in life-cycle stages as well as age or income level.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.9-15
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• 2022

In order to verify the durability of the high-pressure hydrogen tank in the operating pressure range, a hydraulic rupture test should be performed. However, if the bubbles generated by the initial injection process of water are attached to the inner wall of the tank and remain, a sudden pressure change of the bubbles during the rupture of the pressurized tank may cause shock and noise. Therefore, in this study, the flow velocity required to remove the bubbles remaining on the inner wall of the tank was predicted through simplified formulas, and the shape of the injection nozzle to maintain the flow velocity was determined based on the shape of the hydrogen tank for the hydrogen bus. In addition, a numerical model was developed to predict the change in flow velocity according to the inlet pressure, and an experiment was performed through a model tank to prove the validity of the prediction result. As a result of the experiment, the flow velocity near the tank wall was similar to the predicted value of the analysis model, and when the inlet pressure was 1.5 to 5.5 bar, the minimum size of the removable bubble was predicted to be about 2.2 to 4.6 mm.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.146-164
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• 2022

Recently, the Korean government promoted the construction of metropolitan express subway to connect major transportation hub in the metropolitan area within 30 minutes. Most stations of the metropolitan express subway are connected to existing subway stations, so the importance of transfer increased. Although many studies have been conducted on the effect of transfer penalty on route choice, there are few studies on the transfer behavior of the metropolitan express subway. Therefore, in this study, a transfer behavior analysis was conducted on the Shinbundang Line, a representative metropolitan express subway. To analyze the transfer behavior according to the degree of traffic congestion and the presence of fare payment, route choice models were made using transport card data divided according to week, time, and user characteristics. As a result of the analysis, users of the metropolitan express subway had greater disutility to the transfer waiting time compared to the transfer moving time. Furthermore, especially during the peak time, EIVM(Equivalent in-vehicle minutes) of the transfer waiting time was 3.51. In this study, EIVM for metropolitan express subway users were analyzed to be 2.6 minutes, which is significantly lower than the results of previous studies on subways. This suggests that there is a difference in the transfer penalty between subways and metropolitan express subway, and that it is necessary to apply the transfer penalty between subways and express subway differently when forecasting subway traffic demand.