• Journal of the Korean Physical Society
• /
• v.73 no.9
• /
• pp.1303-1309
• /
• 2018

In the present paper, we study the entropy analysis of boundary layer flow over a slender stretching sheet under the action of a non uniform magnetic field that is acting perpendicular to the flow direction. The effects of viscous dissipation and Joule heating are included in the energy equation. Using similarity transformation technique the momentum and thermal boundary layer equations to a system of nonlinear differential equations. Numerical solutions are obtained using the shooting and fourth-order Runge-Kutta method. The expressions for the entropy generation number and Bejan number are also obtained using a suggested similarity transformation. The main objective of this article is to investigate the effects of different governing parameters such as the magnetic parameter ($M^2$), Prandtl number (Pr), Eckert number (Ec), velocity index parameter (m), wall thickness parameter (${\alpha}$), temperature difference parameter (${\Omega}$), entropy generation number (Ns) and Bejan number (Be). All these effects are portrayed graphically and discussed in detail. The analysis reveals that entropy generation reduces with decreasing wall thickness parameter and increasing temperature difference between the stretching sheet and the fluid outside the boundary layer. The viscous and magnetic irreversibilities are dominant in the vicinity of the stretching surface.

• Journal of the Korean Institute of Rural Architecture
• /
• v.23 no.4
• /
• pp.63-71
• /
• 2021

The purpose of this study was to investigate whether the standard models for rural housing and wooden housing model have performance for hygrothermal and to propose a way of improvement relevant to hygrothermal performance for those models. All of the models to be analyzed were found to have some parts that were absent of stability in terms of performance for hygrothermal. In the process of analyzing the causes and proposing improvement measures, the following conclusions were derived. Fist, The exterior surface of the structure should be composed of a structure with good moisture permeability, and for the interior surface, a variable vapor retarder paper should be applied in consideration of the reverse condensation phenomenon in summer. Second, in terms of performance for hygrothermal, applications of external insulation plaster finish to the exterior wall or of ventilation method using a rafter vent on the roof should be avoided. Third, a rain screen method with a ventilation layer should be applied to the exterior wall, and a method of constructing ventilation layer separated from the insulation layer with a vapor retarder paper should be applied to the roof. Fourth, the application of insulation materials having capillary action, such as wood fiber insulation board or cellulose insulation board, contributes to more stable performance for hygrothermal.

• Journal of Ocean Engineering and Technology
• /
• v.25 no.3
• /
• pp.66-72
• /
• 2011

This is the fourth of a series of companion papers dealing with the mechanical property reductions of various marine structural steels. Even though a reduction of the elastic modulus according to temperature increases has not been obtained from experiments, high temperature experiments from room temperature to $900^{\circ}C$ revealed that initial the yield strength and tensile strength are both seriously degraded. The mechanical properties obtained from high temperature experiments are compared with those from EC3 (Eurocode 3). It is found that the high temperature test results generally comply with the prediction values by EC3. Based on the prediction of EC3, time domain nonlinear finite element analyses were carried out for a blast wall installed on a real FPSO. After applying the reduced mechanical properties, corresponding to $600^{\circ}C$ to the FE model of the blast wall, more than three times the deflections were observed and it was observed that most structural parts experience plastic deformations exceeding the reduced yield strength at the high temperature. It is noted that a protection facility such as PFP (passive fire protection) should be required for structures likely to be directly exposed to fire and explosion accident.

• Journal of Periodontal and Implant Science
• /
• v.40 no.4
• /
• pp.172-179
• /
• 2010

Purpose: Accurate and exact measurement is an important factor for generating meaningful results in any properly designed study. If all the participating examiners are able to yield similar results, it will be possible to evaluate the objective results of the study more easily and quickly. The purpose of this study was to evaluate the intra- and inter-examiner reproducibility of histometric measurements in the intrabony periodontal defect model. Methods: One wall intrabony defects were surgically created at the distal aspect of the second and the medial aspect of the fourth mandibular premolars in the right and left jaw quadrants in twenty beagle dogs and the defect sites received the following ${\beta}$-tri calcium phosphate, growth differentiation factor-0, growth differentiation factor-100 and sham surgery. Histometric analysis was performed after 8 weeks. Histometric parameters were recorded and repeated at three months interval by three examiners. Intra- and inter-examiner reproducibility was assessed. Results: Most parameters of all the groups showed high intra- and inter-examiner reproducibility. Parameters including defect height, bone regeneration height, cementum regeneration height, and formation of junctional epithelium yielded interexaminer correlation ${\geq}0.9$. The intra-examiner reproducibility showed a high result, over 0.9. Conclusions: Histometric evaluation of the one-wall intra-alveolar periodontal defect model showed high reproducibility not only for a single given examiner but also among the three examiners.

• Korean Institute of Interior Design Journal
• /
• v.26 no.6
• /
• pp.97-105
• /
• 2017

Korea is promoted STEAM education since 2011. Furthermore, in high school education, based on the in-depth elective course's teaching and learning contents of science. The STEAM program can improve students' competence because it encourages to self-directed learning through the vocational project performance. Therefore, in this study, we researched a design education program for the experience of fusion and complex design based on STEAM education concept. We developed an education program to design insulation wall systems using up-cycling concepts to increase energy efficiency. As a result, the characteristics of the fusion education and the theoretical study about the learner-centered education curriculum, the analysis of the high school curriculum, the STEAM elements, The program was revised and supplemented through consultation with STEAM experts. In addition, the developed program was applied to high school students, and each step were analyzed based on the educational method theory. The following results were obtained. First, this study presented a program to cope with the needs of high school intensive education. Second, it provided learning motivation by combining flipped-learning as a way to train STEAM education contents. Third, it is required to develop differentiated and continuous program development and data sharing Fourth, in order to operate and promote the future environment design STEAM school, it is necessary to expand educational programs for high school students in the region through linkage with various universities.

• Journal of architectural history
• /
• v.23 no.1
• /
• pp.7-19
• /
• 2014

This study considers the proper repair techniques by examining the most representative repair cases of the Korean arch bridges and proposes the constructional manual which can apply similar occasions. The cases are Seonamsa Seungseongyo and Songgwangsa Geukrockgyo where this researcher had taken part in the repair works. This Study proposes the maintenance construction manual about the performance degradation drew by performance degradation of the both Korean arch bridges in the maintenance process. First, arch bridge maintenance should be carried out in the dry season, when water is impermeable in the bottom surface of the bridge. Moreover, risk factors of the maintenance should be excluded to secure the water vally flow, the bypass and the temporary bridge. Second, prior to repair, it has to precede (1)3D shooting (2)formal examination (3)structure safety test (4)geological and lithic surveys (5)arch curvature establishment and makeshift frame settlement before transformation (6)relationship expert comments. Third, if the baduk and the foundation stones are inevitable to replace due to performance degradation on the foundation, it should use the high quality stones and secure greater stress by extending the standard range. The foundation on irregular rock needs to be flattened and underside on the replaced materials require Grengyijil to deliver the equal loads. Fourth, In the process of dismantling the stones of the arched bridge, it could make heavy weathering degree and not reuse the materials. Charge should converge the expert advices to choose the reuseable, the conservate and the alternative materials, and increase the reutilization of the raw materials by preservation and reinforcement treatments. Fifth, the side wall should be repaired by the rubble work technique which is not able to pile compost satiety, so it must use long depth of masonary stones for reinforcement. It is considered to reinforce the stone wall in shore as much as possible and protect the abutment and the side wall on the upstream for the arch bridge maintenance works.

• Journal of Periodontal and Implant Science
• /
• v.42 no.2
• /
• pp.50-58
• /
• 2012

Purpose: This study evaluated histologically the tissue responses to and the effects of a customized nano-hydroxyapatite (n-HA) block bone graft on periodontal regeneration in a one-wall periodontal-defect model. Methods: A customized block bone for filling in the standardized periodontal defect was fabricated from prefabricated n-HA powders and a polymeric sponge. Bilateral $4{\times}{\times}4{\times}5$ mm (buccolingual width${\times}$mesiodistal width${\times}$depth), one-wall, critical-size intrabony periodontal defects were surgically created at the mandibular second and fourth premolars of five Beagle dogs. In each dog, one defect was filled with block-type HA and the other served as a sham-surgery control. The animals were sacrificed following an 8-week healing interval for clinical and histological evaluations. Results: Although the sites that received an n-HA block showed minimal bone formation, the n-HA block was maintained within the defect with its original hexahedral shape. In addition, only a limited inflammatory reaction was observed at sites that received an n-HA block, which might have been due to the high stability of the customized block bone. Conclusions: In the limitation of this study, customized n-HA block could provide a space for periodontal tissue engineering, with minimal inflammation.

• Journal of Mechanical Science and Technology
• /
• v.14 no.9
• /
• pp.997-1004
• /
• 2000

The experiments were conducted by using water and paraffin slurry to investigate the effect of a chip spacing in the multichip module on the cooling characteristics from an in-line $4{\times}3$ array of discrete heat sources which were flush mounted on the top wall of a channel. The experimental parameters were chip spacing in a multichip module, heat flux of simulated VLSI chip, mass fraction of paraffin slurry, and channel Reynolds number. The removable heat flux at the same chip surface temperature decreased as the chip spacing decreased at the first and fourth rows. The local heat transfer coefficients for the paraffin slurry were larger than those for water, and the chip spacing on the local heat transfer coefficients for paraffin slurry influenced less than that for water. The enhancement factor for paraffin slurry showed the largest value at a mass fraction of 5% regardless of the chip spacing, and the enhancement factors increased as the chip spacing decreased. This means that the paraffin slurry is more effective than water for cooling of the highly integrated multichip module.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.5 no.4
• /
• pp.350-356
• /
• 1993

We carry out a numerical calculation to understand the nonlinear wave deformation around breakwaters using the Boussinesq equation, which is weakly nonlinear and weakly dispersive shallow water equation. A numerical method based on a finite element scheme and fourth order Runge-Kutta algorithm is employed to investigate the diffraction of incident waves by the breakwater. As a computational model, two-dimensional wave flume is treated. The breakwaters is perpendicular to the side wall of a channel. From the numerical results, the wave deformations according to the change of the length and the thickness of breakwaters are investigated. We also investigate the effect of the nonlinearity by comparing the results with the linear solutions.

• Archives of Plastic Surgery
• /
• v.32 no.6
• /
• pp.706-709
• /
• 2005

The absence of the nipple-areolar complex(NAC) in men are seldom stated, as a result of trauma, burn, mastectomy, or after the correction of extreme bilateral gynecomastia. A total of 50 healthy men aged 21 to 27 years were examined. We recorded the configuration (dimensions and shape) and the location of the NAC with respect to fixed skeletal anatomic landmarks. Of the 50 subjects examined, 44 had oval and 6 had a round NAC. The mean diameter for a round NAC was 24.3 mm. The center of the NAC was in the fourth intercostal space in 41 volunteers and in the fifth intercostal space in 9 of the subjects. To localize the NAC on the chest wall, at least three reproducible measurements proved to be necessary, composed of a horizontal line(distance from the midsternal line to the nipple, A), a medial oblique line(distance from the sternal notch to the nipple, B) and a lateral oblique line(distance from the acromioclavicular joint to the nipple, C). Using these three parameters, we recommend that the appropriate location can be calculated derived from the circumference of the chest.