• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.395-397
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• 2013

항로표지는 해상에서 선박의 안전한 항행에 필수적인 요소이며, 현재는 LED를 광원으로 사용하는 등명기를 개발 및 사용하고 있다. LED 멀티롤 랜턴을 개발하여 항로표지의 표체조명, 교량표지, 방파제 표시등 등으로 개발하고하는 연구가 진행되고 있다. 이를 위하여 LED 멀티롤 랜턴의 내부 LED 배치에 따른 배광특성을 분석하였다. 본 논문에서 멀티롤 랜턴은 아크릴 환봉과 설치를 위한 금속재로 구성하였으며, 내부에 LED를 2열로 배치하였다. 최적의 설계를 위하여 아크릴 환봉을 투명한 것과 유백색인 것으로 구분하고 2열의 LED 모듈에 집광렌즈($45^{\circ}$, $60^{\circ}$, 미설치)에 따른 배광특성을 분석하였다. $60^{\circ}$ 집광렌즈를 사용한 경우의 시인효과가 우수하여 이를 바탕으로 LED 멀티롤 랜턴을 최종적으로 설계하였다. 투명 아크릴 환봉에 2열의 LED를 배치하고, $60^{\circ}$ 집광렌즈를 사용한 평판형 및 v형의 2종과 집광렌즈를 사용하지 않은 v형 1종으로 선정하고, 녹색과 홍색으로 제작하여 LED의 배열에 따른 배광특성을 본석하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.4
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• pp.819-827
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• 1992

Investigations of the fatigue damage of roughing mill roll and experimentally. By the computer simulation for analysing the stresses on the roll surface and experimental hot rolling, the following results were drawn : The crakcs observed on the roll surface were initiated thermally in the initial stage of the rolling and propagated by repeated thermal and bending stresses. The size of the roll surface cracks smaller than 4.87mm could avoid the occurrence of tiny scab, surface defect of hot steel strip. Since the size of surface cracks observed on the roughing mill roll was very small, the fatigue damage of roll surface was found not to be the major factor for the formation of the scab.

• Journal of the Korea Society of Computer and Information
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• v.12 no.1 s.45
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• pp.51-56
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• 2007

Feature functions were used for the classification of music. The spectral roll-off, variance, average peak level, and class were chosen to make up a feature function vector. Among these, it is the spectral roll-off function that has a low-frequency to high-frequency ratio. To find the optimal roll-off point, the roll-off points from 0.05 to 0.95 were swept. The classification success rate was monitored as the roll-off point was being changed. The data that were used for the experiments were taken from the sounds made by a modern violin and a baroque one. Their shapes and sounds are similar, but they differ slightly in sound texture. As such, the data obtained from the sounds of these two kinds of violin can be useful in finding an adequate roll-off point. The optimal roll-off point, as determined through the experiment, was 0.85. At this point, the classification success rate was 85%, which was the highest.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.10
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• pp.912-918
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• 2011

The purpose of this research is to determine the dynamic roll-damping data of a spinning projectile in wind-tunnel testing. In the present work, the high-speed wind-tunnel tests for the roll-damping measurements were conducted on a spin-stabilized projectile model in the Agency for Defense Development's Tri-Sonic Wind Tunnel at spin rates about 12,000 rpm. The test Mach numbers ranged from 0.7 to 1.05, and the angles of attack ranged from -4 to +10 deg. The validity of the wind-tunnel measurement techniques was evaluated by comparing them with the previous test results on the same configuration.

• Asia-Pacific Journal of Business Venturing and Entrepreneurship
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• v.18 no.2
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• pp.53-66
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• 2023

Role models are also known to influence an individual's job or career choice. The positive effect of role models on entrepreneurship has already been revealed through many precious researches. It is said that people choose not only family members who are related by blood, such as parents, siblings, and relatives, but also acquaintances whom they have met through social relationships as role models. In this study, we divided into entrepreneurs with no role models other than themselves and entrepreneurs with role models. In addition, we classified parental siblings and relative role models as role models with strong ties, and acquaintance role models as role models with weak ties. We analyzed the differences in personal attributes, entrepreneurial orientation factors, and learning orientation between the entrepreneurs with role models and those without role models. Also, the differences in personal attributes, innovativeness, proactiveness, risk-taking propensity, and learning orientation between the entrepreneurs with strong ties role models and those with weak ties role models were examined. The empirical analysis results are as follows. First, it was found that the proportion of women entrepreneurs without role models is higher. Second, the entrepreneurs with role models with weak ties tend to run larger scale start-ups. Third, it was found that the entrepreneurs with role models of weak ties tend to have higher learning orientation. Fourth, gender shows the greatest influence on th absence or presence of role models. Fifth, it was found that learning orientation and startup size have the greatest influence on the decision of the role model with weak ties or that with strong ties.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.10
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• pp.894-900
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• 2012

The purpose of this research is to investigate the dynamic roll-damping characteristics of a spin-stabilized projectile in wind-tunnel testing. In the present work, the high-speed wind-tunnel tests for the roll-damping measurements were conducted on a finned spin-stabilized projectile model in the Agency for Defense Development's Trisonic Wind Tunnel at spin rates about 8,000 rpm. The test Mach numbers ranged from 0.6 to 0.9, and the angles of attack ranged from 0 to +15 deg. The evaluation of the bearing friction parameter was also conducted to eliminate the tare damping moment from the aerodynamic damping moment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.869-876
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• 2011

It is important to analyze the dynamic behavior of counter-rotating rigid/deformable rolls in the roll-coating process, because the stability of the process is affected by the dynamic characteristics. In the present study, the effects of material property, angular velocity, and gap size on the contact pressure and contact shape of the deformable roll are numerically investigated. The behavior of two rolls with a negative gap was analyzed using the finite element method, and the material property of the deformable roll was applied with the Mooney-Rivlin coefficients of the hyper-elastic model. The contact shape is affected by the gap size, and the contact pressure mainly depends on the stiffness of the deformable roll and the gap size. To maintain a negative gap between two rolls, controls such as load and displacement controls must be used. The results indicate that displacement control can reduce the instability.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.53.1-53.1
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• 2010

비대칭압연의 일종인 이주속압연은 기존의 압연에서 도입되는 대칭적 변형과 매우 다른 변형을 도입할 수 있으므로 새로운 금속 소재의 제조 공정 프로세스로 많은 주목을 받고 있다. 이주속압연을 행하게 되면 중립점(neutral point)이 상부롤과 하부롤에서 다른 위치에 놓이게 되며, 이로 인해 일반 동속 압연과 달리 두께 표면부위에서만 도입되는 전단 변형을 내부까지 도입시킬 수 있으므로 두께 방향으로 균일한 변형을 부가할 수 있을 뿐 아니라, 재료 전체에 큰 상당 변형량을 도입할 수 있으므로 균일한 석출상의 생성을 가능하게 한다. 본 연구팀은 지난 연구에서 무산소동에 이주속압연을 실시하여 균일변형을 위한 최적 이주속압연조건을 확립하였으며, 연구결과를 토대로 새롭게 합금 설계한 Cu-Fe-P 동합금에 이주속 압연을 실시하여 압연조건에 따른 미세조직 및 기계적 특성 변화를 조사하였다. 그 결과 이주속압연이 동속압연에 비해 세 종류의 동합금 모두에서 두께 방향으로 균일한 전단변형을 도입할 수 있었으며, macrostructure면에서 두께 방향으로 불균일성은 그다지 크게 나타나지 않았다. 또한 인장특성은 이주속압연과 동속압연재 사이에 큰 차이가 없었으나 동속압연재와 달리 이주속압연재의 집합조직은 상부롤, 중심부, 하부롤 모두에서 압연집합조직이 발달하였다. 본 연구에서는 지난 연구결과를 토대로 이주속압연된 동합급에 $100^{\circ}C-800^{\circ}C$까지 여러 온도에서 30분간 Annealing을 실시하여 미세조직 및 기계적 특성을 조사 하였다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.829-837
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• 1992

This paper presents a new approach for the analysis of hot strip rolling processes. The approach is based on the finite element method and capable of predicting velocity field in the strip, temperature field in the strip, temperature field in the roll, and roll pressure. Basic finite element formulations for heat transfer analysis are described with emphasis on the treatment of numerical instability resulting from a standard Galerkin formulation. Comparison with the theoretical solutions found in the literature is made for the evaluation of the accuracy of the temperature solutions. An iterative scheme is developed for dealing with strong correlations between the metal flow characteristics and the thermal behavior of the roll-strip system. A series of process simulations are carried out to investigate the effect of various process parameters including interface friction, interface heat transfer coefficient, roll speed, reduction in thickness, and spray zone. The results are shown and discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.11
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• pp.1623-1630
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• 2010

In this study, effective forming methods for reducing the roll-over of a sector tooth, which is a main component of an automotive seat recliner, are proposed. Due to the large amount of roll-over, accurate contact between the inner gear of a sector tooth and the outer gear of a pawl tooth cannot be normally achieved; thus sensitivity and safety for the passengers decrease. To overcome the aforementioned drawback, we investigated the effect of flowcontrol forming methods involving local embossing die, coining punch, and VIC (Variable Inverse Clearance) on the roll-over depth by FE-analysis and an experiment. The results of a fine-blanking experiment for verifying the proposed methods showed that VIC type is decidedly superior from the aspects of reduction of roll-over and tool strength of the sector tooth.