• Transactions of Materials Processing
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• v.26 no.6
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.

• Transactions of Materials Processing
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• v.29 no.5
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• pp.282-289
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• 2020

Flexible roll forming is an advanced sheet-metal-forming process that allows the production of parts with various cross-sections. During the flexible process, material is subjected to three-dimensional deformation such as transverse bending, inhomogeneous elongations, or contraction. Because of the effects of process variables on the quality of the roll-formed products, the approaches used to investigate the roll-forming process have been largely dependent on experience and trial- and-error methods. Web-warping is one of the major shape defects encountered in flexible roll forming. In this study, an SVR model was developed to predict the web-warping during the flexible roll forming process. In the development of the SVR model, three process parameters, namely the forming-roll speed condition, leveling-roll height, and bend angle were considered as the model inputs, and the web-warping height was used as the response variable for three blank shapes; rectangular, concave, and convex shape. MATLAB software was used to train the SVR model and optimize three hyperparameters (λ, ε, and γ). To evaluate the SVR model performance, the statistical analysis was carried out based on the three indicators: the root-mean-square error, mean absolute error, and relative root-mean-square error.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.2
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• pp.107-113
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• 2006

The torsion beam axle type is widely used in the rear suspension for small passenger cars due to low cost, good performance, etc. To develop the torsion beam axle, it is necessary to estimate the characteristics of rear suspension from the design process. The characteristics estimation of the torsion beam axle is performed using FEM, dynamic simulation and is verified the real test. In this study, the natural frequency and roll stiffness of the torsion beam axle were measured by FEM, and the reliability of the FE model was evaluated according to the comparison of test data. This study presents a unique method for the finite element modeling and analysis of the torsion beam axle. The results of the FEA were verified using test data.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.250-253
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• 2007

In hot strip rolling, the work roll profile is one of the main factors in predicting and correcting the strip profile. Various studies concerning the wear profile and the thermal crown of work roll have been performed, and the results of these studies have shown that the work roll profile must be predicted accurately so as to efficiently control the strip qualities such as thickness, crown, flatness, and camber. Therefore, a precise prediction model of roll profile is called for in a perfect shape control system. In this paper, a genetic algorithm was applied to improve on the roll profile prediction model in hot strip rolling. In this approach, the optimal design problem is formulated on the basis of a numerical model so as to cover the diverse design variables and objective functions. A genetic algorithm was adopted for conducting design iteration for optimization to determine the coefficient of the numerical model for minimization of errors in the result of the calculated value and the measured data. A comparative analysis showed a satisfactory conformity between them.

• Aerospace Engineering and Technology
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• v.5 no.2
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• pp.240-247
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• 2006

Tilt rotor aircraft is a multi-configuration airplane which has three independent flight modes; helicopter, conversion, and aiplane. The control surface mixer resign is reqctired to generate and distribute efficient control forces and moments in each flight mode. In the conversion mode, the thrust vector is changed from helicopter mode to airplane, therefore the thrust vector makes undesired forces and moments which affect on pitch, roll and yaw dynamics. This paper describes the design results of control surface mixer design which minimize the undesired forces and moments due to nacelles tilting angle change for 4O% scaled model.

• 한국벤처창업학회:학술대회논문집
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• 2022.11a
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• pp.89-93
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• 2022

정보통신기술(ICT - Information and Communications Technology)의 발달, 정부와 민간의 스타트업 발굴 및 투자 규모의 확대로 인해 혁신적인 아이디어를 기반으로 우수한 성과를 창출하는 스타트업들이 증가하고 있다. 이를 롤모델로 삼고 창업을 준비하는 예비 창업자들도 지속적으로 증가하고 있으나, 성공을 경험으로 연쇄창업을 도전하는 창업자와 달리 초기 스타트업들은 팀원 채용, 기술 개발, 자금 유치 등 다양한 문제에 직면하게 된다. 엑셀러레이터는 스타트업들이 직면하게 되는 다양한 문제 해결을 돕기 위해 교육, 멘토링, 컨설팅, 네트워크 연계, 초기 투자 등의 활동을 통해 스타트업이 성장할 수 있도록 멘토와 투자자의 역할을 동시에 수행한다. 본 연구의 목적은 스타트업의 특성과 창업성과과 어떠한 상관관계를 가지고 있는가를 조사하고, 엑셀러레이터의 역할이 스타트업의 창업성과에 매개역할을 하는지 분석 하는데 있다. 최근 국내에서는 다시 벤처 붐이 일어나고 있으며, 유니콘 기업의 양적 질적 증가, 정부 지원을 통한 초기 스타트업의 성과 등 창업생태계에서 의미 있는 지표들을 볼 수 있다. 스타트업의 성과와 관련된 지표들은 직/간접적으로 엑셀러레이터와 관련이 있으나, 그동안 국내에서 창업성과에 영향을 미치는 요인을 스타트업의 창업가의 기업가정신이나 창업가의 역량을 기반으로 주로 연구하였다. 따라서 본 연구에서는 스타트업의 특성으로 대표되는 독립변수 혁신성, 조직 문화, 재무적 특성, 네트워크 지향성과 학습지향성이 종속변수인 창업성과에 영향을 미칠 것이라는 가설을 검증하며 매개변수인 엑셀러레이터의 역할의 효과를 확인하고자 한다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.223-224
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• 2022

노후주거시설의 개보수의 필요성이 대두 되고 있으나 관련법규의 제약에 의해 내 외부 미관수선 정도에 그치고 있는 것이 현실이다. 그래 조금 나은 동선과 공간으로 수선시 법을 위반하여 불법 건축물로 낙인되어 지는 것이다. 경제적인 여유가 없는 노령층등 사회적 약자가 거주하는 공간은 더욱 더 열약하여 화장실, 주방, 수평이동 통로, 승강기등의 편의시설과 붕괴, 침하, 화재, 폭발, 오염등의 안전을 위협하는 위험요소의 제거등이 당장 필요하여도 미봉에 그치는 경우가 다반사이다. 또 이러한 노후 건물의 개보수는 신, 개축 보다 어렵고 비용도 많이 들면서 그 효과도 미미한 것이 사실이나 당장 신, 개축하기에는 관련 법규에 저촉되거나 주변 여건에 부합하지 않아 실시 할 수 없는 경우가 많아 이를 개선하고 합리적인 롤 모델을 만들고 필요하다면 관련법령도 정비할 필요가 있는 것이다. 노후되지 않아도 현시점에서 생활의 불편함을 느껴 개선할 필요가 있는 경우도 관련 법규의 유연함이 필요할 것이다. 본 연구는 이러한 노후 주거 시설 및 현실 여건에 맞지않는 주거 시설을 보다 쉽고 합리적으로 개 보수할 수 있는 여건이 조성되도록 관련 건축법령의 개선, 또 경제적 여유가 없는 저소득층의 개보수여건을 개선할 수 있는 정부지원방안, 이러한 노후 주거시설의 개보수가 부동산 시장에 어떠한 영향을 초래할 수 있는지를 기존 연구들과 비교하여 합리적인 방안을 도출하고저 함.

• Journal of Korea Game Society
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• v.16 no.2
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• pp.75-86
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• 2016

Game studies of theatrical approach explained interactive property of game in humanistic background. Those studies analyze the game, and based on Aristoteles Poetic Attribute. But theatrical approach has a problem by user's unpredictable intervention in narrative (Active narrative). This paper intended to see in the glance of any impact on the Aristotelian model by active narrative. As a result of the active narrative remake the causality between materials of drama. Also, it can be seen to define a kind of the "Improvisation" in theatrical view. But it exposed a essential difference in the form an expression by substance and material of media. It was defined forms of improvisation in the gaming environment which are 'Self-generated Individuality', 'Self-definition Faction', 'Eccentric Behavior Contending', 'Trolling' and 'Bug Play'. Finally this paper proposes the characteristics of the improvisation of the game and the direction to be improved game analysis model in humanities through forms of improvisation in game environment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.10
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• pp.1443-1453
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• 2010

We simulated the roughing train of the rod mill of SEAH BESTEEL Inc. using finite element method to inhibit surface cracks initiation on workpiece. We designed 2nd pass (square roll) and applied to this roll in the roughing train of the rod mill. Also, we proposed new pass schedule, which changed roll gap of 3rd and 4th groove by using finite element method. We used shear damage model, which is dependent on shear stress ratio and compared the number of damaged elements on workpiece. A damaged element means surface crack. Consequently, after 2nd pass (square roll) is changed, the error rate decreased by 1.43% when compare to that of the old groove. And the number of damaged elements in the new pass schedule decreased by 37.6%, which is less than present pass schedule.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.11
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• pp.1463-1471
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• 2012

In this study, a 3-axis camera system design is proposed for application to an existing 2-axis surveillance robot. A camera-image-based target-tracking algorithm for this robot has also been proposed. The algorithm has been validated using a virtual simulation. In the algorithm, the heading direction vector of the camera system in the mobile surveillance robot is obtained by the position error between the center of the view finder and the center of the object in the camera image. By using the heading direction vector of the camera system, the desired pan and tilt angles for target-tracking and the desired roll angle for the stabilization of the camera image are obtained through inverse kinematics. The algorithm has been validated using a virtual simulation model based on MATLAB and ADAMS by checking the corresponding movement of the robot to the target motion and the virtual image error of the view finder.