• Bulletin of the Society of Naval Architects of Korea
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• v.26 no.2
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• pp.25-31
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• 1989

Two-dimensional large-amplitude motions in regular harmonic wave are treated in time domain, by satisfying the exact body boundary condition and the linear free surface condition. For the present numerical calculation, the method of free-surface spectral representation with simple source distribution on the instantaneous body surface has been extended to include the effect of the incident wave. Calculations of the wave exciting force are performed for a submerged circular cylinder fixed or oscillating with large amplitude. Especially, nonlinear effects on the time-mean forces are studied in detail. It is shown that relative motion between the body and the fluid particle gives a significant effect on the lift and drift forces. Also, large-amplitude motion of a submerged circular cylinder and that of a floating Lewis-form cylinder are directly simulated in time domain. In the calculation results, some nonlinear effects are shown.

• Journal of the Korean Geotechnical Society
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• v.29 no.6
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• pp.19-31
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• 2013

In engineering practices, the superstructure was analyzed under a fixed boundary condition and the foundation was designed by considering the loading condition of superstructure. It may result in overestimation of forces, the bending moment, settlement of superstructure and foundation. In this study, an interactive analytical method is proposed for the interaction between the superstructure and the piled raft. The overall objective of this study is focused on the application of interactive analysis method for predicting behavior of entire structures. And a series of numerical analyses are performed to verify the interactive analysis routine in comparison to the unified analysis method. Through the comparative studies, it is found that the iterative and interactive analysis gave similar results of settlement and raft bending moment compared with those of finite element analysis. And it is also found that the proposed design method considering interaction between superstructure and foundation is capable of predicting reasonably well the behavior of entire structures. It can be effectively used to the design of a superstructure-piled raft foundation system.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.249-252
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• 2008

In recent large-scale structures, as mass concrete type structure is frequently applied to the building, temperature crack due to hydration heat needs to be considered. Since a volume change is internally or externally restricted in a mold after placing concrete, temperature crack of mass concrete takes place. By this reason, the reduction method to control this crack is required. In this study, low heat mixture and hydration heat difference is used to execute the analysis of hydration heat, considering the changes of heat transfer coefficient according to curing conditions and block placement of mass concrete. For the analytical modelling, original portland cement and concrete of low heat mixture are placed in the upper and lower payer, respectively. A convection boundary condition is fixed because mass concrete of block placement is characterized by the difference of mold form and curing condition. Through the analysis results considering the changes of low heat mixture, block placement, and heat transfer coefficient, we check out the temperature and stress distribution and analyze the temperature crack reduction effect.

• Phonetics and Speech Sciences
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• v.7 no.4
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• pp.139-145
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• 2015

The present study investigates the effects of syllable structure and prosodic prominence on the patterns of tonal alignment and scaling of the phrase-initial rise in Seoul Korean. Two syllable structures (Onset (/#CVC.../ as in minsa) vs. No-onset (/#VC.../ as in insa)) and two prominence conditions (Focus vs. Neutral) were considered. Results showed that the alignment of the L and the H tones in the phrase-initial rise was affected by syllable structure but not by prominence. The time of L was before the vowel onset of the first syllable in the Onset condition (i.e., within the onset consonant) and it was after the vowel onset in the No-onset condition. The difference was attributable to the fact that the initial L was anchored at a fixed distance from the phrase boundary, which was about 30ms after the onset of the syllable in both cases. The time of H was also consistently observed about 20ms after the second vowel onset (i.e., /a/ in minsa/insa). Moreover, the rise time (the duration from the L to the H tones) was longer as the local syllable duration became longer due to different syllable structure and prominence conditions. Taken together, the results provide a support for the segmental anchoring hypothesis, which claims that both the beginning and the end of F0 movement are consistently aligned with segmental 'anchor' points with relatively high stability (Ladd et al., 1999). Results also showed that the scaling of the early rise was slightly influenced by syllable structure but not by prominence. The differences between the results of the current study and a previous study (Cho, 2011) are further discussed.

• Korean Journal of Agricultural Science
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• v.25 no.1
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• pp.97-106
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• 1998

This study was carried out to investigate the problem of analysis method of circular sliding, which uses a high rate to work out a countermeasure for landslides. The results of this study were summarized as follows : 1. As a result of the analysis of sliding surface along the soil layers in forty model slopes, the boundary layer in weathered soil and weathered rock indicated a very high possibility of sliding than in other places. 2. Because most landslides in Korea occur along the discontinuity face at the boundary of soil layers, below 2m. from land surface, it is a good method for safe design to work the countermeasure for these kinds of landslides in cutting slopes. 3. When the inclination of slopes is fixed and the length of slopes is changed, the cercular sliding slopes were more safe as the soil layers are more shallow and the length of slopes are shorter, but the safety ratio of infinite sliding slopes was same as the other even though their length of slopes was different. 4. As a result of the analysis by cercular sliding analysis method and infinite sliding analysis method with some condition that the inclination of slopes was $30^{\circ}$ degree, because most landslides in Korea occur at this condition, these methods indicated different results to each other as well as cercular sliding analysis method showed too much safety ratio than infinite sliding analysis method.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.131-138
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• 1997

Silicon carbide films were chemically vapor deposited onto graphite substrates using MTS(Ch3SiCl3) as a source and Ar or H2 as a diluent gas. The experiments were performed at a fixed condition such as a de-position temperature of 130$0^{\circ}C$, a total pressure of 10 torr, and a flow rate of 100 sccm for each MTS and carrier gas. The purpose of this study is to consider the variation of the growth behavior with the addition of each diluent gas. It is shown that the deposition rate leads to maximum value at 200 sccm addition ir-respective of diluent gases and the deposition rate of Ar addition is faster than that of H2 one. It seems that these characteristics of deposition rate are due to varying interrelationship between boundary layer thick-ness and the concentration of a source with each diluent gas addition, when overall deposition rate is con-trolled by mass transport kinetics. The preferred orientation of (220) plane was maintained for the whole range of Ar addition. However, above 200 sccm addition, especially that of (111) plane was more increased in proportion to H2 addition. Surface morphologies of SiC films were the facet structures under Ar addition, but those were gradually changed from facet to smooth structures with H2 addition. Surface roughness be-came higher in Ar, but it became lower in H2 with increasing the amount of diluent gas.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.1
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• pp.73-79
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• 2009

In this paper, the structural analysis and optimization of the door supporting rail structure in the header box located at the top of the aluminum passenger safety door(PSD) at the subway station, which opens and closes regularly, is performed. In case the simple fixed boundary condition is used for the bolt fixture on the supporting rail where the glass door is moving, excessive stresses are obtained. Therefore, more realistic finite element modeling of the bolts is used at the bolt fixture in the whole structure in order to obtain the more physically acceptable FEM results. As a result, fatigue life of twenty years of the structure is obtained to satisfy the design object. Also the optimal design of cross section of the rail part is performed using the response surface method and 15% of weight of the supporting rail part on the door is reduced.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.3
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• pp.225-240
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• 2006

In order to calculate bending moments of rectangular plates with three edges clamped the other free subjected to both a uniform load and a triangular load, a finite difference equation for the non-dimensional governing equation are presented and numerical solutions with different aspect ratios and/or number of grid points are analyzed. The finite difference solutions are obtained by use of grid points up to 11,520 and the optimum grid points according to aspect ratios of the plate are presented as well. The obtained numerical solutions are shown to satisfy the given x moment boundary condition at the free edge, which can not be satisfied in Levy's analytical solutions and peculiar behaviour of the calculated moments is observed around the corners between the free edge and fixed ones. The numerical solutions of bending moments subjected to both a uniform load and a triangular load are compared with the corresponding analytical solutions which are shown in very good agreement on the solution domain except the neighborhood of the free edge.

• Journal of the Korean Society of Propulsion Engineers
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• v.7 no.1
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• pp.1-9
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• 2003

The rectangular profile annular fin with fixed volume is optimized using 2-dimensional analytic method. For a base boundary condition, convection from fluid within the pipe to the inside wall of the pipe and conduction from the inside wall of the pipe to the fin base are considered. Heat loss from the fin tip radius is not ignored. The maximum heat loss, the optimum fin tip radius and the optimum fin half thickness corresponding to the maximum heat loss are presented as a function of fin base radius, Biot number over the fin surface and Biot number within the pipe. Results show 1) the maximum heat loss increases as both Biot number over the fin surface and Biot number within the pipe increase and as fin base radius decreases 2) the optimum fin thickness increases as Biot number within the pipe decreases or as fin base radius and Biot number over the fin surface increase.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.127-138
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• 1999

In this study steady state solutions of cavity flows driven by two moving walls are studied. The north and east walls of the cavity are movable where as the remaining two walls are fixed in space. Numerical experiments for three different driving schemes for moving walls are done at two different Reynolds numbers of Re=40 and 400. The first scheme is to accelerate north and east walls simultaneously. In the second one, the north wall is started first and the east wall is accelerated later. In the third one the east wall starts first. It is usually expected that all these three cases yield the same steady state solution after sufficiently long time. However, present numerical experiments show that such a usual belief is valid only when the Reynolds number is low enough (Re=40). At higher Reynolds number (Re=400), the flow develops to three different steady states depending on the history of the boundary condition change.