• Journal of the Korean Geotechnical Society
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• v.27 no.9
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• pp.87-98
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• 2011

In this study, the magnitude and phase variation of dynamic earth pressure acting on a pile in liquefiable soils were analyzed using a series of 1g shaking table tests. In the case of a pile in dry sand, the value of the dynamic earth pressure was the highest near the surface due to the inertia force of the upper load on the pile and it decreased as the depth of the pile got lower. On the other hand, for a pile in liquefiable sand, the magnitude and shape of the dynamic earth pressure were similar to those of the excess pore pressure and was largely affected by the deformation of soils. Furthermore, the inertia force of the upper load and the dynamic earth pressure acted in opposite directions in cases of dry sand and saturated sand where low excess pore pressure had developed. However, after liquefaction, those force components near surface acted unfavorably in the same direction. Finally, the Westergaard’s solution was modified and proposed as a method to evaluate the magnitude of dynamic earth pressure acting on a pile during liquefaction.

• Ocean and Polar Research
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• v.32 no.4
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• pp.337-350
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• 2010

This study conducted sedimentological and geophysical surveys for 3 years (2006-2008) in southern Gyeonggi Bay, Korea to elucidate temporal changes in subaqueous dune morphology on a sand ridge trending northeast to southwest that has been excavated by marine sand mining. The sand ridge (~20 m in height, ~2 km in width and 3~4 km in length) has a steep slope on the NW side and a gentle slope on the SE side, creating an asymmetric profile. Large (10~100 m in length) and very large (>100 m in length) dunes occurring on the SE side of the ridge show a northeastward asymmetrical shape, whereas dunes on the NW side destroyed by marine sand mining display a southwestward asymmetry. The comparison between Flemming (1988)'s correlation and the height-length correlation of this study indicates that tidal current and availability of sand sediment are major controlling factors to the development and maintenance of dunes. Depth and sedimentary characteristics (grain size) are not likely to be major controlling factors, but indirectly influence dune growth by hydrological and sedimentary processes. The length and the height of dunes decrease toward the southeastern trough away from the crest of the ridge. These features result from the decrease of tidal current and sediment availability. The length and the height of dunes on the southeast side decrease gradually over time. This is a result of the interaction between tidal current and the decrease in sediment availability due to sediment extraction by marine sand mining. Marine sand mining has destroyed the dunes directly, causing irregular shapes of shorter length and lower height. The coarse fraction of suspended sediments is transported and deposited very close to the sand pit. By contrast, relatively fine sediments are transported by the tidal current and deposited over a wide range by the settling-lag effect, resulting in a decrease of sediment grain size in the area where suspended sediments are deposited. In addition, marine sand mining, decreases the height of dunes. Therefore, morphological and sedimentological characteristics of dunes around the sand pits will be significantly changed by future sand mining activities.

• Journal of Environmental Impact Assessment
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• v.25 no.2
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• pp.141-154
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• 2016

This study was conducted laying the focus on finding the mutual action between the substantial ecological value and economic system in the national land, and calculating the environmental carrying capacity and sustainability of the national land using the emergy synthesis. Particularly, this study pays attention watchfully to the reality that the analytic framework to analyze sustainability is not arranged well, as the concept of sustainable development considering environmental carrying capacity, which becomes a widely discussed topic today, is defined differently according to the subjective views of respective researchers, and the situation which needs in-depth evaluation on the interaction between nature and economy which becomes the fundamental of sustainable development. This study also aims at groping for correct direction for the national land development by calculating the environmental carrying capacity and index value which is appropriate to the national land and providing the framework for preparing the policy to induce the sustainable use and management of the national land. The concept of emergy synthesis which is used for the evaluation of environmental carrying capacity and sustainability in the national land, as in this case, can notify the information on current situation of the national land as well as explain how the national land transforms according to time pass (the role of information synthesis), and gives knowledge if the national land policies advances toward the direction of sustainable development (the role of policy evaluation and observation). Emergy synthesis also can take role for selecting best policy on the process of decision making on the exploitation of the national land (the role on the process of decision making).

• Korean Journal of Culture and Social Issue
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• v.18 no.2
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• pp.235-260
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• 2012

This study was aimed at looking into and understanding child-rearing experience of mothers from multicultural families based on the grounded theory, one of the qualitative research methods. For this, twelve mothers from multicultural families were selected and data were collected through in-depth interviews with them and then analyzed through the open coding, axial coding and selective coding. The analysis suggested that main phenomena mothers from multicultural families experienced are the conflict of child-rearing and educational crisis, and the confused identity of parenting. These main phenomena had much to do with contextual factors such as economic hardship, lower level of the Korean language, cultural differences, prejudices and ignorance. The severeness of conflict and crisis of child-rearing and the intensity of identity confusion for parenting depended on arbitral conditions such as family bonds, positive expectation for the future of their children, and the help of supportive systems. Mothers were dealing with difficulties of child-rearing through action and interaction of resignation and denial, introspection and the intention to overcome difficulties, and the capacity building. As a result, mothers from multicultural families acknowledged that there is a limit to their position and roles they can play and tried to change in order to resolve problems related to their children, positioning themselves for more active lives in Korean society. Through discussion based on the findings of the study, this study can help better understand child-rearing experience of mothers from multicultural families and suggest several directions for future researches on multicultural families.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.5
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• pp.506-515
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• 2024

Owing to the interaction between a ship and the river bed, several phenomena resulting in increased resistance may have occurred. This increase in resistance is primarily due to the wave-making performance. Thus, this study aims to reduce the wave-making resistance by optimizing the performance of an electric canal cruise through changing the longitudinal center of gravity (LCG). Numerical simulations are performed to obtain the lowest resistance by optimizing the LCG position; subsequently, the ef ect of water depth is included as the next variable. Results show that LCG variations of 37.5%-52.5% Lpp can result in a wide range of total resistance. In deep water, a 72.67% resistance gap is achieved by comparing the highest and lowest resistances, whereas a slightly lower gap of up to 62.97% is achieved in shallow water. Additionally, smaller water depths correspond to higher resistance. The resistance increased by a maximum of 67.68% in shallow water measuring 1.5 m, as compared with the case of deep water. This increase in resistance is primarily due to wave-making resistance, which constitutes 84.99% of the total resistance.

• Journal of the Korean Geotechnical Society
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• v.31 no.1
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• pp.5-14
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• 2015

Seabed may undergo large excess pore water pressure in the case of long duration of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. Thus, it is necessary to develop a numerical technique which can precisely evaluate the dynamic response of seabed due to wave action. In this study, a new numerical technique named mixed model (2D NIT & FLIP models) was proposed. The dynamic wave pressure and water flow velocity acting on the boundary between seabed and the wave field was estimated using 2D-NIT model. This result was used as input data in FLIP program for investigation of dynamic response of seabed. To secure the reliability of the mixed model, the numerical analysis results of the mixed model were compared with Yamamoto's solution and Chang's experiment results. The comparison results indicated that there were some differences between them, but the general trend of the effective stress increment and the excess pore water pressure along the depth of seabed was similar to each other. Thus, this study clearly supports the plausibility of the numerical analysis of the mixed model.

• Journal of Broadcast Engineering
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• v.25 no.2
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• pp.218-232
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• 2020

Data home shopping is a kind of T-commerce service with traditional TV home shopping, product DB of data broadcasting, and advantages of catalog shopping based on data broadcasting technology. Since the data home shopping service was partially started in 2012, there were no in-depth researches regarding the perception of data home shopping. Therefore in this paper, the traditional TV home shopping and data home shopping is analyzed how the perception is in terms of platform quality, service quality and content quality and what the difference in perception is. To verify this, a questionnaire survey was conducted on TV home shopping and data home shopping 140 workers who have good understanding of data home shopping. The results showed that the difference of platform quality, service quality and content quality between TV home shopping and data home shopping was significant and TV home shopping had better quality. In terms of platform quality, TV home shopping was 3.75 on a five-point scale and data home shopping was 2.93. Service quality was significantly different between TV home shopping (3.60) and data home shopping (3.25). For the quality of contents, TV home shopping had better quality as 3.21 while data home shopping was 2.82. There was no interaction effect in gender, age, position, and work field except between the age and platform quality.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.26 no.3
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• pp.265-274
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• 1990

The temperature inversions were studied on the basis of Digital Memory Bathythermography(DBT) data collected by training ship, Pusan 402, of the National Fisheries University of Pusan in August 23~25, 1986 and Fisheries Reserach and Development Agency of Korea in August, 1986, The results were as follows; Among the 67 stations of studied area, occurrence frequency of temperature inversion was 58.20%, And the frequency of onefold occurrence of temperature inversion at its profile of each station was 13.42%. of twofold occurrence was 20.80%, and of threefold occurrence was 23.88%. In the studied area, the temperature inversion usually occurred below the 40m depth and its layers also located below the thermocline. The temperature range of its inversion was from 14$^{\circ}C$ to 16$^{\circ}C$. The temperature inversion in the study area was oaused by the interaction between Tsushima Warm Current and Korea Coastal Waters.

• Journal of the Korean Home Economics Association
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• v.43 no.5 s.207
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• pp.131-147
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• 2005

The purpose of this study was to provide a better understanding of foreign-born Korean children's early school adjustment in the U.S. The interaction between the foreign-born Korean children in the U.S. and several of the children's microsystems, including family, school, and peer was assessed to meet this purpose. The study subjects were 43 foreign-bom Korean children who were sampled from Korean Sunday Language schools and who attended local schools in the Boston area, MA, USA. Quantitative analysis was conducted to identify which variables of interest predicted the early adjustment of this group of children. Furthermore, in-depth interviews were conducted with mothers of the children from the top and bottom groups 1) the most successful (in the top quartile) and 2) the least successful adjustment groups (in the bottom quartile) sorted by scores on the Peabody Picture Vocabulary Test-Revised (PPVT-R). The interview results were analyzed to elicit maternal perceptions/beliefs on education, in general, and those of home-school relationships, in specific. Several conclusions can be drawn from both the quantitative and qualitative analyses. The results of multiple regression and path analysis showed that the children's language development predicted their adjustment, but the effects of the other two variables, peer relationships and school experiences, on the adjustment of children, were mediated through the children's language. Moreover, common themes and patterns in the responses to a series of open-ended questions emerged from the interviews with the two groups of mothers. The two mothers of the least successful group were concerned about their children's future and school success, but thev did not show anv responsive attitudes toward achieving this goal. By contrast, the mothers from the most successful group were self-determined with regard to their children's education and had strong beliefs and values on how to raise their children in the new culture. The implications were discussed.

• Journal of the Korean Magnetics Society
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• v.11 no.6
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• pp.272-277
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• 2001

A spin valve structure of Ta/NiFe/CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta which has a synthetic antiferromagnet (CoFe/Ru/CoFe), was fabricated by using a magnetron sputtering system. The thickness and composition of magnetic free and pinned layers affect the magnetic properties such as exchange interaction strength of each layer and so on. Even though Rutherford Backscattering Spectrometry (RBS) has advantages of quantitative and non-destructive analysis, it is almost impossible to determine the thickness and composition of magnetic thin films using lBS because of its poor mass resolution for a higher atom number (Z>20). In this study, quantitative analysis of the element composition and thickness for the spin valve sample was performed by combining both Proton Induced X-ray Emission Spectrometry (PIXE), which is one of element specific analysis techniques, and grazing-exit RBS with a highly improved depth resolution and absolute quantitative analysis. For the quantitative analysis, standardization of PIXE was carried out with NiFe, CoFe, and FeMn layers, which are one of constituent layers of spin valve films. Through PIXE standardization and the aid of PHE experimental results of the spin valve sample, ire overlapped signal in a grazing-exit RBS spectrum were successfully resolved and the thickness of the Ru layer was determined with a resolution of ∼1 .