• Korean Journal of Materials Research
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• v.8 no.6
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• pp.571-576
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• 1998

This study was carried out for investigating the corrosion behaviors, corrosion mechanisms, and behaviors of elements on a separator for a molten carbonate fuel cell under both the electrolyte and anode side environment. A 310S austenitic stainless steel was used as the separator material. Corrosion proceeded via three steps; the formation step of corrosion product in which rapid corrosion takes place until stable corrosion product is formed after the beginning of corrosion, the protection step against corrosion until breakaway occurs after the formation step of stable corrosion product and the advancing step of corrosion after the breakaway. From the standpoint of the behavior of the elements in the specimen, Fe and Cr, Ni were enriched in the region of corrosion product, in the region of corrosion protection, and at the Cr-deplete zone, respectively. With respect to corrosion mechanism, ionization of electrolyte at the anode side was the main corrosion mechanism, and the final corrosion products were $LiFeO_2$ and $LiCrO_2$ at the anode side.

• Proceedings of the KWS Conference
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• 2005.06a
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• pp.223-225
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• 2005

In order to demonstrate the friction stir weldability of the Al 6061 T-6 unequal thickness joint and determine optimum welding parameters, the relations between welding parameters and properties of the joints have been studied in this paper. The experimental results showed that the tensile properties of the joints are affected by the welding heat inputs and tool shape. In this study, the maximum ultimate strength of the as-welded joint is equivalent to 78% and 18hour aged joint is equivalent to 93% that of the base metal. Though the voids-free joints are fractured at the thermally affected zone on the advancing side, the fracture occurs at the weld center when the void defects exist in the joints.

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.75-81
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• 2011

Dissimilar joining of aluminum 6061-T6 alloy to aluminum 5083-O alloy was performed using friction-stir welding technique. The mechanical properties, hardness, macro- and micro-structure on dissimilar friction-stir-weld aluminium alloy were investigated. Mechanical properties of the weld mainly depend on which Al alloy is placed at the retreating sides of the rotating tool respectively during dissimilar friction-stir weld because the microstructure of stir zone was mainly composed of welded Al alloys of the retreating side. Onion ring pattern was observed like lamella structure stacked by each Al alloy in turn. It apparently results in defect-free weld zone that traverse speed was changed to 124 mm/min under conditions of tool rotation speed like 1250 rpm with 5 mm of tool's prove diameter, 4.5 mm of prove length, 20 mm of shoulder diameter, and $2^{\circ}$ of tilting angle. The 231 MPa of ultimate stress and the 121 MPa of yield point are obtained about the friction-stir-welded Al 6061-T6(AS) to Al 5083-O(RS).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.5
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• pp.364-370
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• 2019

In this paper, an individual blade control (IBC) methodology is applied to find the best input scenario for vibratory hub loads reduction of XH-59A co-axial rotorcraft in high speed flight. A comprehensive aeromechanics analysis code CAMRAD II is employed to analyze the aircraft. A parametric study is conducted for optimum IBC inputs leading to the maximum vibration reduction. Numerical results demonstrate that up to 50% reduction in the hub vibration index is obtained for an IBC input at 3/rev frequency with the amplitude and phase angle of 0.5 deg. and 300 deg., respectively. The upper rotor exhibits as much as 6% more vibration reduction as compared to that of the lower rotor due to a clean inflow characteristic of the rotor. It is found that further vibration reduction gain is reached for IBC inputs with advancing-side only control. The hub vibration becomes reduced by up to 17% in reference to that with full rotor disk control. It is noted that the additional gain is obtained with significantly less power input with the advancing-side only control.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.249-259
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• 1991

The purpose of this study was to evaluate the incidence and radiographic features of 677 cases of hypercementosis by means of the analysis of full mouth periapical radiograms in 4,236 persons visited the Department of Oral Radiology, School of Dentistry, Kyung Hee University during January 1984 to December 1989. The obtained results were as follows: 1. The incidence of hypercementosis was revealed to be 8.2% in total examined persons, and there was a higher incidence in females (9.4%) than in males (7.1%). 2. The hypercementosis was most frequently occurred in the 6th decades (29.2%), and the incidence was increased by advancing age until 6th decades. 3. There was a higher incidence in the maxilla (59.5%) than in the mandible (40.5%), and maxillary second premolar (18.5%) was the most frequently involved tooth. The maxillary first premolar (11.7%) was next in order to frequency followed by maxillary canine (10.0%) and mandibular first and second premolars (9.6%). 4. In the etiologic factors, 35.0% were inflammation, 31.2% were elongation, 6.2% were trauma from occlusion, 0.1 % were uneruption, and 27.5% were unknown. 5. In the degree of cementum apposition, 35.3% were Type Ⅰ, 29.5% were Type Ⅱ, and 35.2% were Type Ⅲ. 6. In the status of cementum apposition, 3.2% were mesial side, 8.9% were distal side, and 87.9% were mesial & distal side. 7. In the identification of radiographic density between normal cementum and excessive cementum, 12.7% could be identified, and 87.3% could be unidentified.

• Journal of the Korean Society of Food Culture
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• v.26 no.3
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• pp.199-210
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• 2011

In this study, we compared the differences and similarities between the Korean food culture and the Vietnamese food culture by surveying food resources and researching the process of Korean food being accepted into Vietnam. We suggest countermeasures for advancing Korean food into Vietnam. We conducted in-depth interviews regarding Korean food with Vietnamese food specialists who ate Korean food. As a result, Vietnamese foodies eagerly recognized that the most representative thing about Korean food was the special properties of its various and affluent side dishes. They were also aware of kimchi, made of various vegetables and condiments, as an excellent side dish compared to the Vietnamese who's staple is boiled rice. Furthermore, the flavor of Korean food was preferred by the Vietnamese who were familiar with foods such as Neue-ok-mom or fermented seafood. It was thought that the new food could be eaten with many vegetables. The specialists replied that the most typical functional property of Korean food was health. The acceptance process of Korean food into Vietnam was based on the acculturation theory. That made the Vietnamese easily experienced strange culture in the case of propagation by whom have already experienced, through the selective filter steps by various images of Korea, and made them accept the Korean food through temporary choose and acceptance step such as recommendations by friends. Globalization strategies for Korean food proposed by the Vietnamese foodies were public relations marketing in voluntary contact environments, distinguishing traditional Korean foods through research and development, and globalization by diversifying the Korean restaurant concept.

• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.11a
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• pp.217-221
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• 2008

The goal of this research is to analyze interrelationship for layout of dwelling house and variation of its side plane by introducing concept of space in order to address as to how Korean traditional houses had been formed and varied in the middle of advancing modern city. In addition, this paper also has its meaning in a way that it identified how Korean traditional houses have been changed, and thus make residents more comfortable to live there by reviving their past characteristics, and make users have traditional food culture. Targeted area for this paper is limited to south-eastern area of Daegu such as Namsanjung, Myeongchijung, Sijangjung, Shinjung and Dalsungjng which was group dwelling houses of people of Chosun Dynasty during Japanese colonial rule' era ($1910{\sim}1945$). Among those places, the paper has chosen a place where Korea traditional houses were well preserved, variation of road and fields was less 1930s, and residential type is easy to effectively compared. As the result of this research, time when traditional cities were changed into new type of city residential area is believed to be around 1930s, and traditional residential area, through its transitional process, is believed to be changed to modern residential area. It also indicates that change of organizational road and fields directly had influence on change of houses.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.5
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• pp.623-628
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• 2006

Laser material processing is a very fast advancing technology for various industrial applications. because of many advantages. Its major advantage of less and controlled heat input has been exploited successfully for the very critical application of aluminium alloy welding. This study suggested the occurrence source of weld-defects and its solution methods in a welding of lithium ion battery by pulsed Nd:YAG laser. In experiment. battery case has changed over joint geometry from welding of side position to flat one. In the case of a electrolyte injection hole in order to seal it. welding is carried out after pressing Al ball. At this time. an eccentric degree. contact length and gap are worked as a major parameters. As improving the method of Al ball pressing. it was able to reduce an eccentricity. increase the contact length and decrease gap. As a results of a experiment. a sound weld bead shape and crack-free weld bead can be obtained.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.206-206
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• 2021

The necessity for appropriate management of water resources infrastructures such as reservoirs, levees, and dikes is increasing due to unexpected hydro-climate irregularities and rising water demands. To meet this need, past studies have focused on advancing theoretical optimization algorithms such as nonlinear programming, dynamic programming (DP), and genetic programming. Yet, the optimally derived theoretical solutions are limited to be directly implemented in making release decisions in the real-world systems for a variety of reasons. This study first aims to comparatively analyze the two prominent optimization methods, DP and evolutionary multi-objective direct policy search (EMODPS), under historical inflow series using K-fold cross validation. A total of six optimization models are formed each with a specific formulation. Then, one of the optimization models was coupled with the actual zone-based hedging rule that has been adopted in practice. The proposed methodology was applied to Boryeong Dam located in South Korea with conflicting objectives between supply and demand. As a result, the EMODPS models demonstrated a better performance than the DP models in terms of proximity to the ideal. Moreover, the incorporation of the real-world policy with the optimal solutions improved in all indices in terms of the supply side, while widening the range of the trade-off between frequency and magnitude measured in the sides of demand. The results from this study once again highlight the necessity of closing the gap between the theoretical solutions with the real-world implementable policies.

• Transactions of the Korean Society of Automotive Engineers
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• v.24 no.4
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• pp.425-431
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• 2016

The usage of Friction Stir Welding(FSW) technology has been increasing in order to reduce the weight in automobile industries. Previous studies that investigated on the FSW have focused on the aluminum alloy. In this study, Al6061-T6 alloy plates having 5 mm of thickness were welded under nine different conditions from three tool rotation speeds: 900, 1000 and 1100 rpm, and three feed rates: 270, 300 and 330 mm/min. Specimen size of Micro Shear Punch(MSP) test was $10{\times}10{\times}0.5mm$. The mechanical properties were evaluated by MSP test and Analysis of Variance (ANOVA). The specimens were classified by advancing side(AS), retreating side(RS), and center(C) of width of tool shoulder. The optimal welding condition of FSW based on micro strengh was obtained when the tool rotation speed was 1100 rpm and the feed rate was 300 mm/min. The maximum load measured AS, RS, and C in the weldment was measured 554.7 N, 642.9 N, and 579.2 N, respectively.