• Journal of Welding and Joining
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• v.34 no.6
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• pp.20-27
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• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.5 no.3
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• pp.191-197
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• 1993

Mathematical models of nonlinear waves due to disturbances moving with the near critical velocity in a basin of variable depth are discussed. A two-dimensional model for waves of arbitrary amplitude is developed. In the case of small perturbation it is shown that nonlinear ray method can be applied to obtain the generalized forced Korteweg-de Vries equation.

• International Journal of Naval Architecture and Ocean Engineering
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• v.7 no.2
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• pp.375-389
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• 2015

An improved boundary element method is presented for numerical analysis of hydrodynamic behavior of marine structures. A new algorithm for numerical solution of the finite depth free-surface Green function in three dimensions is developed based on multiple series representations. The whole range of the key parameter R/h is divided into four regions, within which different representation is used to achieve fast convergence. The well-known epsilon algorithm is also adopted to accelerate the convergence. The critical convergence criteria for each representation are investigated and provided. The proposed method is validated by several well-documented benchmark problems.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.79-82
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• 1999

Using Small Angle Light Scattering (SALS), the effect of quench depth on the kinetics of phase separation for ternary solution blends was investigated. The system was composed of two polymers (polystyrene and polybutadiene) and a solvent (toluene). The analyses of the early stage of phase separation were based of the Cahn-Hilliard theory [1,5]. Apparent diffusion coefficients and the fastest mode of fluctuations were evaluated, when quench depth of the system were varied near the critical composition of polymer. In the late stage of phase separation, the domain growth showed a power law with the 1/3 exponent, i.e. $q_m(t)~t^{-1/3}$. For comparison between real images and scattering profiles with time, the image of phase domains with time were obtained by using Laser Confocal Scanning Microscopy (LSCM).

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1735-1737
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• 2003

To find the best intagliated shape on edgelit signboard, it was prepared wilt variations of illumination by changing the depth and angle of an engraved letter, the thickness of acrylic panel and wavelength of light source in this paper. As the result of analyzing optical design program, shallower depth and larger than critical angle on a visible side of panel, a favorable illumination characteristics was found. Also considering those factors, it was able to select the model which showed effectively engraved letter.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.1
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• pp.35-46
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• 2008

Harmonic vibration characteristics for the general rotor model having a breathing crack are analyzed. Analyses are performed at the half critical speed ranges. The vibration characteristics are explained by using the additional slope and bending moment at the crack position and the influence coefficient showing the structural dynamic characteristics of the rotor. With the low crack depth the magnitude of the additional slope is kept constant even at the speed range at which the orbit magnitude is very sensitive to the rotational speed change. At this speed range the vibration is affected by the influence coefficient only. As the dynamic bending moment exceeds the static bending moment with the increase of crack depth. the additional slope affects the vibration amplitude of cracked rotor and the crack propagation rate increases.

• Journal of The Korean Association For Science Education
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• v.27 no.8
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• pp.743-754
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• 2007

Whether This paper argues that teacher efficacy is an affective affiliate of pedagogical content knowledge (PCK) based on empirical data of a study on the nature and construct of PCK. This study was a collective case study utilizing qualitative research methods. The participants of the study were three high school science teachers in the U.S. Data was collected from multiple sources such as classroom observation, interviews, teachers' written reflection, students' work samples, and researchers' field notes. Data was analyzed using the "In-depth Analysis of Explicit PCK" developed by the author. Data analysis indicated that teacher efficacy played a critical role in developing PCK by facilitating the movement from PCK to the enactment of PCK.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.36-42
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• 2018

GGBFS(Ground Granulated Blast Furnace Slag)-replacement is very effective for improving resistance to chloride attack and this can induce a long service life for RC(Reinforced Concrete) structures exposed to chlorides. In the work, the design parameters such as cover depth, surface chloride content, critical chloride content, and replacement ratio of GGBFS are considered, and optimum replacement ratio of GGBFS are derived with intended service life. The changes of surface chloride content and cover depth show 3.16~3.38 and 3.02~3.34 times of service life variation, which are most influencing parameters. Critical chloride content shows 1.53~1.57 times of service life variation regardless of w/b(Water to Binder) ratios. In the case of surface chloride content $18.0kg/m^3$, the most severe condition, cover depth over 70 mm and GGBFS replacement ratio over 42% are required with concrete containing w/b ratio under 0.42 for 100 years of intended service life. The condition of $13.0kg/m^3$, GGBFS replacement over 35% is required. For reasonable durability design, quantitative exterior condition and critical chloride content should be determined, and the criteria in Domestic Specification is evaluated to be conservative.

• Journal of the Korean Society for Nondestructive Testing
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• v.9 no.1
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• pp.106-110
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• 1989

Bolting degradation problems in primary coolant pressure boundary applications have become a major concern in the nuclear industry. In the bolts concerned, the failure mechanism was either corrosion wastage(loss of bolt diameter) or stress-corrosion cracking.(3) Here the manual ultrasonic testing of RPV(Reactor Pressure Vessel) and RCP(Reactor Coolant Pump) stud has been performed. But it is difficult to detect indications because examiner can not exactly control the rotation angle and can not distinguish the indication from signals of bolt. In many cases, the critical sizes of damage depth are very small(1-2 mm order). At critical size, the crack tends to propagatecompletly through the bolt under stress, Resulting in total fracture.(3) Automatic stud scanner for studs(bolts) was developed because the precise measurement of bolt diameter is required in this circumstance. By use of this scanner, the rotation angle of probe was exactly controlled and the exposure time of radiations was reduced.

• Journal of Korean Academy of Nursing
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• v.35 no.8
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• pp.1461-1475
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• 2005

Purpose. The main purpose of this critical ethnography was to examines the process and discourses through which family caregivers experience while caring for their sick family member in a hospital. Methods. This was achieved by conducting in-depth interviews with 12 family caregivers, and by observing their caring activities and daily lives in natural settings. The study field was a unit for neurologic patients. Data was analyzed using taxonomy, discourse analysis, and proxemics. All research work was iteratively processed from March 2003 to December 2004. Results. Constant comparative analysis of the data yielded the process of becoming a successful family caregiver: encountering the differences and chaos as novice; constructing their world of skilled caregivers; and becoming a hospital family as experienced caregivers. During the process of becoming an experienced hospital family, the discourse of family centered idea guided their caring behaviors and daily lives. Conclusion. The paternalistic family caregivers struggled, cooperated, and harmonized with the patriarchal world of professional health care system. During this process of becoming hospital family, professional nurses must act as cultural brokers between the lay family caring system and the professional caring system.