• The Journal of Engineering Geology
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• v.19 no.1
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• pp.81-88
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• 2009

Two dimensional Monte-Carlo simulations of a non-reactive solute plume in isotropic porous media which are physically and chemically heterogeneous are conducted to determine the variations of moment. Retardation factors of 1, 2 and 5 are given to ascertain how the second moments are changed as adsorption increased. Retarded longitudinal second spatial moment, ${Z_{11}}^{'R}(t',l')$, increased during the transport process and as the dimensionless lengths of line plume source, $l_2'$, increased. ${Z_{11}}^{'R}(t',l')$ decreased as the retardation factors increased, and the simulated moments fit well to the first-order analytical results. Retarded longitudinal plume centroid variance, ${Z_{11}}^{'R}(t',l')$, decreased as the dimensionless lengths of line plume source, $l_2'$, increased and as the retardation factor increased. The result indicates that the uncertainty about the plume center decreased, and the ergodic condition for the second spatial moments is far from reaching. Simulated longitudinal one particle displacement covariance, ${Z_{11}}^{'R}(t')$, well consistent with the first-order analytical results for the three degrees of retardation factors of 1, 2 and 5 respectively. It is, consequently, concluded that the retarded longitudinal second moments could be produced by stochastic simulation, and that the first-order analytical results definitely provides very close values of the longitudinal retarded moments.

• Journal of The Korean Association For Science Education
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• v.11 no.1
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• pp.1-14
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• 1991

The objectives of the study is to examine students concepts changes using a longitudinal study. The study compared two data sets collected in 1989 and in 1990 using the same instrument and subjects. The first data set was collected by Ahn(Ahn, 1989). In the study, students' patterns of misconceptions were examined in the following aspects : 1) Comparison of the students' misconception before observation of actual phenomenon in the first data between the two data sets. 2) The analysis of the patterns of students misconceptions of the second data set In terms of students' patterns of conceptual change before and after observation in the first data set. In the study, overall patterns of students' misconceptions appeared in the second data set were similar to those of the first data set ; however, about 40% of individual student's patterns of misconceptions were changed. Even the students who changed their opinion from misconception to scientific by observing the give phenomenon in the previous study(the first data set) returned to their original misconception after one year. The researcher interpreted this phenomenon in terms of the characteristics of the three kinds of cognitive conflict suggested by Kwon(Kwon, 1989).

• Journal of Families and Better Life
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• v.35 no.1
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• pp.125-137
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• 2017

The purpose of this study was to investigate the longitudinal relationship between Korean youth's social withdrawal, depression and community sense mediated by achievement values. For this purpose, we analyzed three years of the longitudinal panel data (2011-2013) of the Korean Children and Youth Panel Survey (KCYPS). Data were collected from 2,351 first year middle school students using the latent growth model using SPSS 18.0 and AMOS 22.0. The main analysis results were as follows. First, social withdrawal and depression decreased and community sense increased as time passed. These results supported the linear change model. Second, the initial status of social withdrawal and depression had effects on the initial status and change rates of community sense. Achievement values, the partial mediator, had a positive influence on initial community sense but had a negative influence on change rates of community sense. We discussed how to improve Korean youth's community sense based on these results.

• Journal of Family Resource Management and Policy Review
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• v.18 no.4
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• pp.1-26
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• 2014

This study analyzes the effects of the three types of flexible work arrangements (part-time, flexitime, and reduced working hours for childcare) available in Korea on work-family conflict, facilitation, and job satisfaction for married working women ages 15-49. The study employs a panel analysis based on the first to the fourth data from the Korean Longitudinal Survey of Women & Families (KLoWF). The major results are as follows. First, the availability of part-time jobs and reduced working hours to facilitate childcare is significantly related to work-family conflict for married women. If a married woman is employed in a part-time position or if reduced working hours for childcare are available, the conflict within the family caused by the job is reduced. Second, none of the three types of flexible work arrangements have a statistically significant influence on work-family facilitation for married women. Third, the availability of reduced working hours for childcare has a positive effect on the job satisfaction of married women. In conclusion, flexible working hours for women who are raising children are the main factor in reducing the negative effect of a job on a woman's family life as they contribute to work and family compatibility.

• Special Issue of the Society of Naval Architects of Korea
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• 2005.06a
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• pp.84-89
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• 2005

The double hull VLCC(Very Large Crude Oil Tanker) have been designed to have each four(4) longitudinal bulkheads and transverse bulkheads in general. Actually, the inside longitudinal bulkheads among four(4) longitudinal bulkheads, which are extended up to the end of the aft cargo hold for continuity of the members, have been designed with knuckled type inboard due to the narrowed hull shape at bottom region, but sometimes the straight type of longitudinal bulkheads were adopted based on the degree of the hull lines shape. However, regardless the type of longitudinal bulkheads, inside and outside longitudinal bulkheads conflict each other in aft cargo hold region This makes the structure more complex thus giving difficulties to structural design and production. Recently, a vessel of straight type was reported to have cracks on bracket end and tripping bracket toe in aft cargo hold region. As a solution to this problem, in designing the first 60m Beam VLCC, DSME developed a new cargo hold structure which is good in production and structural point of view by structural strength and fatigue analysis of fore and aft cargo hold.

• Journal of Welding and Joining
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• v.21 no.5
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• pp.561-567
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• 2003

For construction of I-beam steel structures, a fillet welding is one of the main manufacturing process. However, this welding process cause some problems associated with welding residual stress and welding deformation that are harmful to the safety of structures. Accordingly, this study clarified the creation mechanism of the welding deformation on I-beam steel structure from the experimental results given by the FEM method. To prevent or minimize the longitudinal bending deformation, first of all, a field supervision is necessary to observe the optimal groove design. Secondly, the welding order for cooling weld zone is needed.

• East Asian mathematical journal
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• v.37 no.5
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• pp.619-626
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• 2021

In [1, 2], we studied the string-like system with time-varying delay. Unlike the string system, the plate system must consider both longitudinal and transverse strains. First, we consider the physical phenomenon of an axially moving plate concerning kinetic energy, potential energy, and work dones. By the energy conservation law in physics, we have a nonlinear plate-like system with internal time delay.

• The Journal of Engineering Geology
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• v.26 no.3
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• pp.393-401
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• 2016

In the present study, fault attitudes and the locations of appearance of faults in tunnel faces were predicted by analyzing the trajectory of the maximum longitudinal displacement immediately before the appearance of faults through three-dimensional finite element analysis. A total of 28 fault attitude models were used in the analysis. Those faults that have drives with dip appear first in the upper part of tunnel faces as tunnel excavation progresses and their maximum longitudinal displacement shows a tendency to move from the middle part to the upper part of tunnel faces. Those faults that have drives against dip appear first in the lower part of tunnel faces as tunnel excavation progresses and their maximum longitudinal displacement shows a tendency to move from the middle part or middle upper part to the lower part of tunnel faces. In addition, when the dip of faults is larger the maximum longitudinal displacement moves from the left upper part toward the wall part in the case of drive with dip models and from the left lower part toward the wall part in the case of drives against dip models. Therefore, it was indicated that the attitudes of faults distributed ahead of tunnel faces and the locations where faults appear in tunnel faces can be predicted by analyzing the longitudinal displacement trajectory of tunnel faces following excavation.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.886-891
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• 2003

This paper deals with designing a ground-based longitudinal landing controller which is robust to datalink time delays. Time delays occur because forward velocity measurements are downlinked and the controller output commands are uplinked. An $H_{\infty}$ controller was designed by using the input/output decomposition where time delay is modeled as a first-order system with Pade approximation. Linear simulations show that the system tracks well the predefined path and is robust to the variation of time delay.

• Journal of the Korea Furniture Society
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• v.19 no.2
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• pp.124-129
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• 2008

Moisture content of Larix kapempferi was maintained at 28% after air drying. 5% CCFZ solution penetration depth was observed through longitudinal tracheid and axial resin canal. Penetration depth was increased significantly from heartwood to sapwood and the penetration depth was found 1.3 times higher for sapwood measured at 15.0 second of penetration. On the other hand, liquid flow in sapwood and heartwood involved most liquid first entering the resin canals. Overall resin canal conducted 1.4 times more than tracheid. Latewood was found more permeable than in earlywood. At the beginning of penetration, the speed was high and then decreased in the course of time.