• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.21-21
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• 2003

To increase the light-emission efficiency of LED, we increased the internal and external quantum efficiency by suppressing the defect formation in the quantum well and by increasing the light extraction efficiency in LED, respectively. First, the internal quantum efficiency was improved by investigating the effect of a low temperature (LT) grown p-GaN layer on the In$\sub$0.25/GaN/GaN MQW in green LED. The properties of p-GaN was optimized at a low growth temperature of 900oC. A green LED using the optimized LT p-type GaN clearly showed the elimination of blue-shift which is originated by the MQW damage due to the high temperature growth process. This result was attributed to the suppression of indium inter-diffusion in MQW layer as evidenced by XRD and HR-TEM analysis. Secondly, we improved the light-extraction efficiency of LED. In spite of high internal quantum efficiency of GaN-based LED, the external quantum efficiency is still low due to the total internal reflection of the light at the semiconductor-air interface. To improve the probability of escaping the photons outside from the LED structure, we fabricated nano-sized cavities on a p-GaN surface utilizing Pt self-assembled metal clusters as an etch mask. Electroluminescence measurement showed that the relative optical output power was increased up to 80% compared to that of LED without nano-sized cavities. I-V measurement also showed that the electrical performance was improved. The enhanced LED performance was attributed to the enhancement of light escaping probability and the decrease of resistance due to the increase in contact area.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.6 no.1
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• pp.71-98
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• 1998

The study proved the fitness between competitive strategy and service operation strategy of service companies. The competitive strategy of a corporation is a major strategy playing the role of bridge linking both corporate strategy and functional strategy. And it is a choice of method how to win competitors in given area. There have been such a specific methodologies for acquiring competitive advantage as Porters competitive strategy, Miles and Snows adaptive strategy, and Life cycle strategy. But, many scholars have pointed that its more important for high corporate performance to determine the competitive strategy of a corporation fitting the external environment and internal structure. So its needed for successful cost-leadership or differentiation strategy to differentiate organizational function, resources, and various organizational factors. But there have been no methodologies or practical guidelines fitting competitive strategy, corporate structure, and external environment in sprite do service corporations growth. So, the study proved the fitness between competitive strategy and service operation structure in Airlines after selecting service structural elements necessary for strategic management.

• Journal of Adhesion and Interface
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• v.3 no.4
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• pp.37-43
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• 2002

A number of thin-film deposition technologies have been developed. However, even a thin film whose properties are excellent may not be used as long as the adhesion strength between the thin film and the substrate is poor. For thin films, the adhesion strength is as important as the properties. In the present article, relation between interface structure and thin film adhesion, and factors affecting thin film adhesion are reviewed. Two kinds of factors, internal factors and external factors, affect thin film adhesion. Such factors as composition, structure, and reactivity of both thin film and substrate as well as surface roughness of the substrate and residual stress of the thin film belong to internal factors. And such factors as load, temperature, humidity, and corrosive environment belong to external factors. It is also reviewed that how we can control the internal factors and the external factors to enhance or keep the adhesion strength.

• Proceedings of the KWS Conference
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• 2001.05a
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• pp.165-167
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• 2001

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.691-703
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• 2022

To obtain the seismic response of lead-cored rubber, shape memory alloy (SMA)-rubber isolation Plate-shell Integrated Concrete Liquid-Storage Structure (PSICLSS), based on a PSICLSS in a water treatment plant, built a scale experimental model, and a shaking table test was conducted. Discussed the seismic responses of rubber isolation, SMA-rubber isolation PSICLSS. Combined with numerical model analysis, the vibration characteristics of rubber isolation PSICLSS are studied. The results showed that the acceleration, liquid sloshing height, hydrodynamic pressure of rubber and SMA-rubber isolation PSICLSS are amplified when the frequency of seismic excitation is close to the main frequency of the isolation PSICLSS. The earthquake causes a significant leakage of liquid, at the same time, the external liquid sloshing height is significantly higher than internal liquid sloshing height. Numerical analysis showed that the low-frequency acceleration excitation causes a more significant dynamic response of PSICLSS. The sinusoidal excitation with first-order sloshing frequency of internal liquid causes a more significant sloshing height of the internal liquid, but has little effect on the structural principal stresses. The sinusoidal excitation with first-order sloshing frequency of external liquid causes the most enormous structural principal stress, and a more significant external liquid sloshing height. In particular, the principal stress of PSICLSSS with long isolation period will be significantly enlarged. Therefore, the stiffness of the isolation layer should be properly adjusted in the design of rubber and SMA-rubber isolation PSICLSS.

• Proceedings of the Korean Institute of Interior Design Conference
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• 2008.05a
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• pp.128-133
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• 2008

As societal development improves the quality of life and changes the structure of society, the needs of the residents have been varied. As a result, the spaces in Korean houses have also been varied. This phenomenon can be found in both external and internal spaces; a transitional space, which connects the outside space and the inside space, is formed as transition occurs at each phase of movement. As the importance of external and internal spaces is emphasized, and as internal spaces are extended to the exterior, various forms of transitional space are needed. In this study, the boundary types of internal/external spaces are analyzed through transitional spaces that are formed in relation with internal and external spaces. Based on the analysis, transitional spaces in modem Korean houses are classified into the addition type, the cutting type, and the connection type. The results of the study show that transitional spaces in detached houses tend to be placed closely to rooms and a public space, and in terms of material use, the externalization of internal spaces is occurring.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.3
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• pp.44-50
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• 2012

The noise reduction is important one of considerations in the process of a civil aircraft development program. External noise sources are classified into an air-born source and a structure-born source. Among these noise sources, the most affected noise source into a cabin is the air-born noise source from an engine or propeller. The external noise is transmitted into the cabin through the fuselage structure of airplane which are composed of an fuselage structure, an interior trim panel and an acoustic insulation layer between an fuselage structure and an interior trim panel. Therefore, appropriate fuselage structure and acoustic insulation layer is very important to reduce the internal noise level. In this paper, the vibro-acoustic coupled analysis of the cabin noise of the 80~90 seats regional turboprop aircraft is carried out to validate the acoustic analysis method using Direct BEM and FEM. The sound pressure level onto the fuselage skin is acquired by fan-source noise analysis using BEM, and which sound pressure is used as acoustic noise source in vibro-acoustic noise analysis for cabin noise analysis using FEM.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.7
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• pp.22-28
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• 1997

In this paper, We have studied internal quality incluiding chemical compositions, microscopic structure and nonmetalic inclusion of test material. We have analyzed dynamic characteristics of cutting resistence and compared chip treatment of the test material. In analyzing internal quality, all of the test material have typical ferrite+pearlite structure. But, nonmetallic inclusion has oxide and sulfide inclusion has oxide and sulfide inclusion in medium carbon steel, mainly sulfide inclusion is existed in S-free cutting steel. In Ca+S-free cutting steel, calcium aluminate and sulfide complex inclusion, had low-melting point, as deformation of sulfide and oxide inclusion is existed. Machining characteristics, cutting resistence is maximum in medium carbon steel. Chip treatement are excellent in S-free cutting steel, similar to the Ca+S free cutting steel and medium carbon steel.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.1
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• pp.101-108
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• 2012

The purpose of this study is to establish a design method of tower service lift for offshore wind power system, as well as to conduct structure analysis of the service lift system. The service lift system will be built in the internal area of tower of the offshore wind power system. Design and structure analysis for the tower service lift system are conducted to clarify the stability and reliability of the system. Main objective of the design is to secure sufficient capability of transportation of workers and equipment with satisfactory performance within the designed tolerance limit. Total deformation and equivalent stress of the lift system by external load are examined using the results of structure analysis.

• Asia-Pacific Journal of Business
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• v.14 no.1
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• pp.215-229
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• 2023

Purpose - Based on the funding-horizon theory, this study aims to test the effects of cash needs and the persistence of external funding needs on firms' external financing. Design/methodology/approach - Financial data of Korean listed companies were collected from DataGuide. Immediate and near-term cash shortfalls are defined using the methodology of Haung and Ritter (2021). We estimate multinomial logit regressions for the financing choice. Findings - First, all three cash depletion variables used in our study increase the likelihood of external financing. Second, firms prefer to issue debt to meet immediate spending and equity to meet long-lived cash needs. Third, this effect is more pronounced for high R&D firms. Fourth, chaebol firms with internal capital markets defer raising external capital for immediate and near-term cash needs. Research implications or Originality - This paper provide empirical evidence that immediate and near-term cash needs induce external financing, and the persistence of cash needs affects the choice between debt and equity, the finding which is consistent with the funding-horizon theory of financing decisions. Being the first paper to test the funding-horizon theory using Korean data, this paper contributes to the literature on the capital structure of Korean firms.