• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.13 no.10
• /
• pp.4411-4417
• /
• 2012

The present study proposes the optimization of wing structure base on reduced model which assures the solution accuracy and computational efficiency. Well-constructed reduced model assures the accurate result in the eigenvalue problem, dynamic analysis or sensitivity of design optimization. Reduced system is classified into the reduce-order model based on structural modes and the reduced system based on degrees of freedom. Because this study uses the reduced system based on degrees of freedom, it is important to select the dominant degrees of freedom properly. For this work, robust selection method, two-level selection scheme, is employed and IRS(Improved Reduced System) is applied to construct the final reduced system. In the optimization process based on the reduced system, all of the equivalent stress, eigenvalue and design sensitivities are calculated from the reduced system. Through a numerical example, it is shown that the present optimization methodology based on the reduction method can provide an optimal results for objective function satisfying constraint condition.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.20 no.3
• /
• pp.265-272
• /
• 2007

The finite element linear buckling analysis of folded plate structures using adaptive h-refinement methods is presented in this paper. The variable-node flat shell element used in this study possesses the drilling D.O.F. which, in addition to improvement of the element behavior, permits an easy connection to other elements with six degrees of freedom per node. The Box-typed structures can be analyzed using these developed flat shell elements. By introducing the variable-node elements some difficulties associated with connecting the different layer patterns, which are common in the adaptive h-refinement on quadrilateral mesh, can be overcome. To obtain better stress field for the error estimation, the super-convergent patch recovery is used. The convergent buckling modes and the critical loads associated with these modes can be obtained.

• The Journal of the Korea Contents Association
• /
• v.9 no.12
• /
• pp.836-842
• /
• 2009

On April 14, 2008, National Human Rights Commission of Korea's recommendation led to severe argument that hiring qualification of religious school. it shall not be an unlawful employment practice for a school, college, university, or other educational institution or institution of learning to hire and employ employees of a particular religion if such organizations is, in whole or in substantial part, owned, supported, controlled, or managed by a particular religion or by a particular religious corporation, association, or society, or if the curriculum of such organizations is directed toward the propagation of a particular religion. An employer is a "religious organization" entitled to the exemption. So If the employer is a school, its history and mission, the religion of the faculty and students, and the religious focus of the curriculum must be examined. Consequently it is possible for religious educational institution to reject specific religionist.

• Bulletin of the Society of Naval Architects of Korea
• /
• v.26 no.2
• /
• pp.25-31
• /
• 1989

Two-dimensional large-amplitude motions in regular harmonic wave are treated in time domain, by satisfying the exact body boundary condition and the linear free surface condition. For the present numerical calculation, the method of free-surface spectral representation with simple source distribution on the instantaneous body surface has been extended to include the effect of the incident wave. Calculations of the wave exciting force are performed for a submerged circular cylinder fixed or oscillating with large amplitude. Especially, nonlinear effects on the time-mean forces are studied in detail. It is shown that relative motion between the body and the fluid particle gives a significant effect on the lift and drift forces. Also, large-amplitude motion of a submerged circular cylinder and that of a floating Lewis-form cylinder are directly simulated in time domain. In the calculation results, some nonlinear effects are shown.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.10
• /
• pp.859-867
• /
• 2007

The objective of this study is to develop and validate a numerical method which can handle the multi-rotor aerodynamic characteristics. For the purpose of power estimation, table look-up method is implemented to the existing unsteady panel code that is coupled with a time-marching free wake model. Also, the Reynolds number scaling is implemented for the application to various regions of Reynolds number. The computed results are validated against the available experimental data for coaxial and tandem rotors. In the validation case for the coaxial rotor, more accurate result is acquired when the thickness effect is considered. The wake instability problem occurs at a particular separation distance between the rotors for tandem rotors. The wake instability is avoided by setting the single-rotor wake geometry as the initial wake geometry for the multi-rotor analysis. The estimated result for rotor separation effect is compared with the result of the momentum theory.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.6
• /
• pp.683-693
• /
• 2010

In this paper, we propose a new parallel mechanism for the legs of biped robots and the control of the robot's locomotion. A leg consists of two 3-DOF parallel platforms linked serially: one is an orientation platform for a thigh and the other is the 3-DOF asymmetric parallel platform for the shank. The desired locomotion trajectory is generated on the basis of the Gravity-Compensated Inverted Pendulum Mode (GCIPM) in the sagittal direction and the Linear Inverted Pendulum Mode (LIPM) in the lateral direction, respectively. In order to simulate the ground reaction force, a 6-DOF elastic pad model is used underneath each of the soles. The performance and effectiveness of the proposed parallel mechanism and locomotion control are shown by the results of computer simulations of a 12-DOF parallel biped robot using $SimMechanics^{(R)}$.

• Journal of Korea Port Economic Association
• /
• v.17 no.2
• /
• pp.183-204
• /
• 2001

This study is intended for the development of urgent facing strategies for the designation of a CFZ(Customs Free Zone) in Incheon city. First, it analyzes the current status of the Incheon CFZ. Next, it suggests several strategies for successfully growing the CFZ of Incheon City. Finally, it develops and proposes a method for establishing an integrated management system for the effective management of the CFZ. The key findings of this study are as follows: First, the CFZ should provide state-of-the-art movement of port logistics, create new added value caused by the movement of logistics, and provide other public support. The Incheon CFZ should be developed in three stages: an inducement stage in 2002-2005, a growth stage in 2005-2008, and an implementation stage in 2008-2011. Second, The parties responsible for the management of the CFZ would be as follows: for the port area, the Ministry of Maritime and Fisheries; for the back space of CFZ, Incheon City; and for port management, port management companies. However, a committee for CFZ management is strongly suggested for the improved efficiency and effectiveness of CFZ management. Furthermore, additional regulations ensuring the role of local government will likely be necessary for the sucessful designation and sustainable management of the CFZ. Third, For the creation of additional revenue, reformation of the current laws of the CFZ are recommended in the area of business administration. Fourth, A strategic marketing plan that supports the successful management of the companies of the CFZ will be a key component in the success of the CFZ. Thus, the new marketing plan should be developed in the near future based on case studies of other CFZs. Fifth A method for an integrated CFZ management system was developed and suggested for the comprehensive and transparent management of port logistics.

• Korean Journal of Optics and Photonics
• /
• v.28 no.6
• /
• pp.295-303
• /
• 2017

In this paper, we have studied a method of forming a line beam using a UV LED. The existing linear-type UV LED curing optical system is composed of several cylindrical lenses, but problems such as optical system alignment, enlargement of the module, efficiency, etc. may arise in the future. As an alternative to these problems, a bar-type TIR lens having a freeform surface only in the y-axis direction is designed, to verify that it shows advantages in maximum illuminance, uniformity of illuminance, and flux efficiency.

• Explosives and Blasting
• /
• v.24 no.1
• /
• pp.9-19
• /
• 2006

The objective of this study is to propose curve fitted equations that can facilitate calculations and improve a practical applicability when the seismic performance of buried pipelines needs to be evaluated. The curve fitted equations are derived based on the evaluation of the dynamic responses of concrete pipe with a boundary condition of fixed-free ends. To study the dynamic response of underground pipe, the numerical analysis program developed in the previous research has been used. The location of maximum strain has been determined through dynamic analyses for a boundary condition of fixed-free ends. Then $wavelength{\lambda}$ of 5-1000(m) and propagation velocity(Vs) of 100-2000(m/s) have been applied at the location of maximum strain and the unit srain curve with the changes of the $wavelength{\lambda}$ and propagation velocity(Vs) has been obtaind. Non-linear least-square regression has been used to develop highly applicable curve fitted equations and various types of exponential regression equations have been checked out. Thus curve fitted equations and necessary coefficients with best results are suggested.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.9
• /
• pp.1615-1626
• /
• 1992

In this study, vibrations and resulting acoustic radiations from an elastic beam impacted by a steel ball were studied theoretically and experimentally. First the transverse vibrations of free-free elastic beams are analysed with modal analysis technique. The impact forces are modeled with the Hertz's theory and the contanct duration is compared with the measured values. Also the calculated beam vibrations are verified with the experimental results. Then the acoustic radiations due to the beam vibration are studied numberically and experimentally. The acousticpressure is calculated assuming the beam has an elliptical cross-section. The predicted acoustic pressure is compared with the measured value. It was found that both the predicted beamvibrations using the Hertz's theory and the estimated acoustic pressure under the assumption of an elliptical cross- section are in very good agreements with the measured values.