• ETRI Journal
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• v.34 no.1
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• pp.118-121
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• 2012

In this letter, a miniaturized log-periodic dipole array (LPDA) antenna operating from 1 GHz to 6 GHz is proposed for portable direction finding applications. To reduce the lateral size of an LPDA antenna, bow-tie elements and a top-loading technique are utilized and spacing factor is decreased to reduce the spacing between the LPDA elements. The proposed miniaturized LPDA antenna has the measured gain and front-to-back ratio ranging from 1.2 dBi to 3 dBi and from 7 dB to 22 dB, respectively.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.182-187
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• 2000

The application of fracture mechanics have traditionally concentrated on cracks leaded by tensile stresses, and growing under an opening or mode I mechanism. However, many cases of failures occur from growth of cracks subjected to mixed mode loading. Several criteria have been proposed regarding the crack growth direction under mixed mode loadings. This paper is aimed at prediction of fatigue crack growth behaviour under mixed mode(I+II) in two dimensional branched type precrack. In this paper, the maximum tangential stress(MTS) criterion was used to predict crack growth direction. Not only experiment but also finite element analysis(FEA) was carried out. The theoretical predictions were compared with experimental results in this paper

• Fashion & Textile Research Journal
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• v.12 no.1
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• pp.1-9
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• 2010

A purpose of this study was to find out how the casual and formal style clothes of stripe pattern giving variety by pattern direction, pattern width, and contrast coloration have an effect on image of wearers. 432 stimuli were made and 2,800 testee evaluated them using semantic differential scale. As a result, five image dimensions were drawn as a factor of attractiveness, activeness, gracefulness, visibility, and tenderness. In consequence of analysing the image difference by stripe pattern and clothing style, the stripe pattern and clothing style affect image presentation as a significant clue. And besides, as a result of positioning stimuli by image, pattern direction, coloration, and tone combination were important clues that decide image. Consequently, clothing style, stripe pattern, and contrast coloration were made clear as an efficient parameter in image presentation of clothing wearers.

• Journal of information and communication convergence engineering
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• v.15 no.3
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• pp.137-142
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• 2017

A general linearly constrained narrowband adaptive array is examined in the eigenvector space. The optimum weight vector in the eigenvector space is shown to have the same performance as in the standard coordinate system, except that the input signal correlation matrix and look direction steering vector are replaced with the eigenvalue matrix and transformed steering vector. It is observed that the variation in gain factor results in the variation in the distance between the constraint plane and the origin in the translated weight vector space such that the increase in gain factor decreased the distance from the constraint plane to the origin, thus affecting the nulling performance. Simulation results showed that the general linearly constrained adaptive array performed better at an optimal gain factor compared with the conventional linearly constrained adaptive array in a coherent signal environment and the former showed similar performance as the latter in a noncoherent signal environment.

• Aerospace Engineering and Technology
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• v.8 no.2
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• pp.13-18
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• 2009

In this study, an equivalent unit load methodology has been presented to simplify the fatigue analysis procedure. And fuselage structure fatigue life has been evaluated based on equivalent unit load. Finite element analysis has been carried out to analyze the stress intensity factor and geometrical correction factor that is needed for crack growth analysis. And strain energy density factor is used to predict the initial direction of crack propagation.

• The Journal of Information Systems
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• v.12 no.2
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• pp.109-128
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• 2003

This study is intended to suggest an ideal direction of the information systems policy for the local small business firms. In an effort to accomplish this objective, this paper tried to identify the current states of the information systems and measure the level of the information systems of local small business firms based on the maturity stage and the development level. The study then explored the evidence how the maturity stage and the development level affect the business performance of the local small business firms. The research found out that the organizational factor such as the support of CEO and the financial factor such as IS investment took major roles to improve the business performance. Based on the research findings of this study, the paper suggested the desirable solution of the information system policy to deal with the problems the local small business firms need to overcome.

• Journal of Mechanical Science and Technology
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• v.15 no.9
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• pp.1217-1225
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• 2001

The governing equations are derived for the analysis of a stepped labyrinth gas seal generally used in high performance compressors, gas turbines, and steam turbines. The bulk-flow is assumed for a single cavity control volume set up in a stepped labyrinth cavity and the flow is assumed to be completely turbulent in the circumferential direction. The Moodys wall-friction-factor model is used for the calculation of wall shear stresses in the single cavity control volume. For the reaction force developed by the stepped labyrinth gas seal, linearized zeroth-order and first-order perturbation equations are developed for small motion about a centered position. Integration of the resultant first-order pressure distribution along and around the seal defines the rotordynamic coefficients of the stepped labyrinth gas seal. The resulting leakage and rotordynamic characteristics of the stepped labyrinth gas seal are presented and compared with Scharrers theoretical analysis using Blasius wall-friction-factor model. The present analysis shows a good qualitative agreement of leakage characteristics with Scharrers analysis, but underpredicts by about 20%. For the rotordynamic coefficients, the present analysis generally yields smaller predictied values compared with Scharrers analysis.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.379-384
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• 2000

High-Tc superconducting current leads with multi-step and continually varied cross-sectional area are studied to reduce heat leak into cryostat and material use. Assuming conduction-cooled lead the cross-sectional area is reduced along the heat flow direction according to the increase of critical current density which increases with decreasing temperature. In this study, we also analyze the multi-step cross-sectional area High-Tc current leads. The multi-st데 current leads changes the cross-sectional area to have constant safety-factor at changed section. The heat leak into cryostat, total voume, safety-factor and the temperature profiles are compared to those of the constant safety-factor current leads. The developed methods are applied to the Bi-2223 superconductor sheathed with Ag-Au alloy.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.12
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• pp.654-659
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• 2013

This paper presents a numerical optimization of louvered fins to enhance the JF factor in terms of the design parameters, including the fin pitch, the number of louvers, the louver angle, the fin thickness, and the re-direction louver length. We carried out a parametric study to select the three most important parameters affecting the JF factor, which were the fin pitch, number of louvers, and the louver angle. We optimally designed the louvered fin by using 3rd-order full factorial design, the kriging method, and a micro genetic algorithm. Consequently, the JF factor of the optimum model increased by 16% compared to that of the base model. Moreover, the optimum model reduced the pressure drop by 17% with a comparable heat transfer rate.

• Journal of the Ergonomics Society of Korea
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• v.27 no.3
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• pp.53-60
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• 2008

The work-related musculoskeletal disorders have constantly increased since it became an issue in 1996. In 2002, the Government established the risk factors analysis system in order to prevent musculoskeletal disorders. The proclamation by the Ministry of Labor defined eleven spheres of work associated with musculoskeletal disorders. As a result, business proprietors, who have workers engaged in tasks associated with musculoskeletal disorders, are required to conduct the risk factor analysis on a regular basis every three years. However, numerous issues have been raised while carrying out the risk factor analysis in various industries. One of the issues is that even though work sampling is an ideal method in risk factor analysis, most cases have selected extreme task postures, which is judged by an expert, due to limited time. This study will propose the desired direction of the risk factor analysis by comparing task assessment results between work sampling scenes and extreme task scenes.