• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.983-989
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• 2004

In this paper, a modeling method for the vibration analysis of rotating structures employing multi-reference frames is presented. The geometric stiffening effect that results from centrifugal inertia force is considered. In most previous studies single reference frame has been employed for the analysis. In the present study, a modeling method employing multi-reference frames is presented, and the effects of employing multi-reference frames on the analysis accuracy are investigated through solving numerical examples.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.103-110
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• 2006

Automatic optical alignment modules are a key technology in optical communication system. However, the optic component assembly depends highly on manual or semi-automated alignment process. In this paper, a novel alignment mechanism with minimum degree-of-freedom has been designed and theoretical models are derived from geometric optical characteristics on collimators, optical filters and optical ray alignment. The automatic alignment control algorithm has been newly developed based on the mechanism and models, and then we make fast, precise and reliable alignment through the algorithm. The reliability of developed modules has been verified with various simulations and performance evaluations.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.3
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• pp.55-61
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• 2003

The form accuracy of parts has become an important parameter. Therefore, not only dimensional tolerance but also geometric tolerances are used in the design stage to satisfy the required quality and functions of parts. But the information on the machining conditions, which can satisfy the assigned geometric tolerance in do sign, is insufficient. The objectives of this research are to study the effects of the grinding parameters such as traverse speed, work speed, depth of cut, and dwell time on the after-ground workpiece shape, and to find out the major parameters among them The results are as follows; The effects of work speed and depth of cut on the workpiece shape are negligible compared with the effect of traverse speed. These is an optimal dwell time depending on the traverse speed. The optimal dwell time is decreasing as the traverse speed is increasing.

• Steel and Composite Structures
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• v.19 no.5
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• pp.1237-1258
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• 2015

This paper proposes a simple inelastic analysis approach to efficiently map out the complete nonlinear post-collapse (strain-softening) response and the maximum load capacity of axially loaded concrete encased steel composite columns (stub and slender). The scheme simultaneously incorporates the influences of difficult instabilizing phenomena such as concrete confinement, initial geometric imperfection, geometric nonlinearity, buckling of reinforcement bars and local buckling of structural steel, on the overall behavior of the composite columns. The proposed numerical method adopts fiber element discretization and an iterative M${\ddot{u}}$ller's algorithm with an additional adaptive technique that robustly yields solution convergence. The accuracy of the proposed analysis scheme is validated through comparisons with various available experimental benchmarks. Finally, a parametric study of various key parameters on the overall behaviors of the composite columns is conducted.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.20 no.2
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• pp.155-164
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• 2002

In this study, in order to discuss the geometric correction methods of high-resolution IKONOS satellite image, the existing polynomial model and RFM which is able to rectify satellite image without auxiliary data are applied to IKONOS satellite image data. Then the accuracy of ground point versus number of GCPs and each order of RFM are assessed. A numerical instability is removed by application of Tikhonov regularization method. As the results of this study, the root mean square errors of RFM is decreased more than 2 pixels in comparison with the two dimensional polynomial model.

• Journal of the Korean Institute of Rural Architecture
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• v.2 no.3
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• pp.77-84
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• 2000

Kurye-gun, which Hwaeomsa temple is located, has huge scale's geographical characteristics, such as mountains, rivers and open fields. This is really blessing area because of Som-jin river at the bottom of Ghiri mountain and open fields, which this situation is very difficult. The location of Hwaeomsa temple is an end of The Baek-Doo Mountains and very important spot(where influences to its geometric converge) of the theory of feng-shui. On exposure logic of the Korean traditional theory of feng-shui, the organization in Ga-Ram of Hwaeomsa temple is inconsistent with representative theory and analyzing system. So, this is one of successful examples with the theory of feng-shui because exhalation from the earth and water was organized well with accuracy.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.57-59
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• 2003

Digital surface model generation from IKONOS stereo imagery is a new challenge in photogrammetric community, especially when the satellite company does not provide the raw data as well as their ancillary ephemeris data. In this paper we utilized an estimated relief displacement azimuth and the nominal collection elevation data included in the metadata file to correct the relief displacement of GCPs, together with a linear transformation for geometric modeling of IKONOS imagery. Space intersection is performed by the trigonometric intersection assuming a parallel projection of IKONOS imagery due to its small FOV and frame size. In the experiment, less than 2-meters of RMSE in orbit modeling is achieved denoting the potential positioning accuracy of the IKONOS stereo imagery.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.11
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• pp.67-75
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• 1998

Geometric and thermal errors are key contributors to the errors of a computer numerically controlled turning center. A planar error synthesis model is obtained by synthesizing 11 geometric and thermal error components of a turning center with homogeneous coordinate transformation method. This paper shows the sensitivity analysis on the temperature change, the confidence evaluation on the uncertainty Of measurement systems, and the error contribution analysis from the planar error synthesis model. Planar error in the z direction was very sensitive to the temperature change. and planar errors in the x and z directions were not affected by the uncertainty of measurement systems. The error contribution analysis ,which is applicable to designing a new turning center, was helpful to find the large error components which affect planar errors of the turning center.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.61-68
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• 1998

The form accuracy of parts has become an important parameter. Therefore, dimensional tolerance and geometric tolerance are used in the design stage to satisfy required quality and functions of parts. But the informations on the machining conditions, which can satisfy the assigned geometric tolerance in design, are insufficient. The objectives of this research are to study the effects of the grinding parameters such as traverse speed, work speed, depth of cut, and dwell time on the after-ground workpiece shape, and to find out the major parameters among them. The results are as follows, The effects of work speed and depth of cut on workpiece shape are negligible compared with the effect of traverse speed. There is an optimal dwell time depending on the traverse speed. The optimal dwell time is decreasing as the traverse speed is increased.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.115-118
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• 2005

A workpiece with a large surface area is likely to be uneven due to form error and waviness. These geometric disturbances can cause inaccurate micro shapes to be formed when micro features are micro-grooved into the surface and cause the resulting workpiece to fail to function as desired. Thus, real-time measurement and compensation is required to guarantee the form accuracy of micro features while machining a workpiece with a large surface area. In this study, a method is suggested for real-time measurement of geometric error for the micro grooving of a large flat surface using a laser displacement sensor. The measurements are demonstrated for the workpieces with large surface areas and the experimental results show that the waviness and form error are well detected.