• Structural Engineering and Mechanics
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• v.14 no.4
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• pp.491-504
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• 2002

A state-space method is proposed to analyze the aerodynamically coupled flutter problems of long-span bridges based on the modal coordinates of structure. The theory about complex modes is applied in this paper. The general governing equation of the system is converted into a complex standard characteristic equation in a state space format, which contains only two variables. The proposed method is a single-parameter searching method about reduced velocity, and it need not choose the participating modes beforehand and has no requirement for the form of structure damping matrix. The information about variations of system characteristics with reduced velocity and wind velocity can be provided. The method is able to find automatically the lowest critical flutter velocity and give relative amplitudes, phases and energy ratios of the participating modes in the flutter motion. Moreover, the flutter analysis of Jiangyin Yangtse suspension bridge with 1385 m main span is performed. The proposed method has proved reliable in its methodology and efficient in its use.

• Progress in Medical Physics
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• v.15 no.2
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• pp.63-69
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• 2004

HDR brachytherapy administers a large dose of radiation in a short time compare with LDR, and its optimization for treatment is related to several complex factors, such as physical, radiation and optimization algorithms, so there is a need for these to be verified for accurate dose delivery. In our approach, a previous study concerning the phantom for dose verification has been modified, and a new pelvic phantom fabricated for the purpose of localization, including a structure enabling the use of a CT or MRI system. In addition, a comparison study was performed to verify an orthogonal method that is commonly used for brachytherapy localization by comparing target coordinates from a CT system. Since the developed phantom was designed to simulate the clinical setups of cervix cancer, it included an air-filled bladder and a rectum structure shaped sphere and cylinder An N-shaped localizer was used to obtain precision coordinates from both CT and films. Moreover, the IDL 5.5 software program for Windows was used to perform coordinates analysis based on an orthogonal algorithm. The film results showed differences within 1.0 mm of the selected target points compare with the CT coordinates. For these results, a Plato planning system (Nucletron, Netherlands) could be independently verified using this phantom and software. Furthermore, the new phantom and software will be efficient and powerful qualify assurance (QA) tools in the field of brachytherapy QA.

• Journal of Mechanical Science and Technology
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• v.15 no.11
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• pp.1507-1516
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• 2001

An analytical method is presented for evaluation of the steady state periodic behavior of nonlinear structural systems. This method is based on the substructure synthesis formulation and a harmonic balance procedure, which is applied to the analysis of nonlinear responses. A complex nonlinear system is divided into substructures, of which equations are approximately transformed to modal coordinates including nonlinear term under the reasonable procedure. Then, the equations are synthesized into the overall system and the nonlinear solution for the system is obtained. Based on the harmonic balance method, the proposed procedure reduces the size of large degrees-of-freedom problem in the solving nonlinear equations. Feasibility and advantages of the proposed method are illustrated using the study of the nonlinear rotating machine system as a large mechanical structure system. Results obtained are reported to be an efficient approach with respect to nonlinear response prediction when compared with other conventional methods.

• Korean Journal of Geomatics
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• v.4 no.1
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• pp.9-16
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• 2004

An object-oriented design was carried out for the digital photogrammetric processes. Classes were identified and implemented to develop an integrated digital photogrammetry system using a 3 dimensional self-calibration model for CCD cameras. This integrated system is deemed to be a significant progress from the conventional photogrammetric system which is a series of discrete processes. Object oriented methodology was selected for the implementation of the integrated photogrammetric system because it would be a very complex task to get the same result using a procedural programming language. Besides the simplification of development effort, object oriented methodology has further benefits of better management of program in case when updates to parts of the program are necessary. Using the classes designed in this study, a 3 dimensional self-calibration model was developed for a CCD camera. Classes for data input and image handling as well as classes for bundle adjustment were implemented. The bundle adjustment system was further enhanced with member functions to handle additional parameters for principal point coordinates and focal length, thereby, enabling the application to non-metric CCD cameras.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.838-843
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• 2001

Internal damping plays an important role in some rotor dynamic systems with the use of various materials for shafts, for example, composite material. However, although the effects of internal damping have been investigated for a couple of decades, there are several different internal damping models in use, none of which are accepted as the most reliable model. The purpose of this paper is to compare the results of dynamic analysis of rotor systems with several different internal damping models. The exact dynamic element method is used to formulate and analyze the problem. The simulation results provided in this paper may be useful for the dynamic analysis of high rotor systems subject to significant internal damping.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.174-180
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• 1998

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates are used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady state and incompressible. This numerical work is performed with commercial CFD-ACE code developed by CFD Research Corporation, and the results are compared wi th the experimental data

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.7
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• pp.916-923
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• 2000

Numerical study of three-dimensional turbulent flow in a forward curved centrifugal fan is presented. Standard $k-{\varepsilon}$ turbulence model and non-orthogonal curvilinear coordinates arc used to consider the turbulent flow field and complex geometry. Finite Volume approach is adopted for discretization scheme and structured grid system is used to help convergence. Multiblock grid system is used for flow field and divided into five domains that are inlet, outlet, impeller, tip clearance and scroll. It is assumed that the flow field is steady and incompressible. These numerical results are compared with the experimental data inside a rotor and at the fan outlet. Most important flow features are captured through this numerical approach. Finally details of flow field inside a fan are described and analyzed.

• Bulletin of the Korean Chemical Society
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• v.32 no.1
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• pp.49-52
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• 2011

A dinuclear copper(II) complex of [$Cu_2(aceace)_4$(dipyph)] [aceace = acetylacetone, dipyph = 1,4-di(4-pyridylethene-2-yl-)benzene] has been synthesized and characterized by elemental analysis, IR and X-ray single crystal diffraction. It crystallizes in the monoclinic system, space group P21/c, with lattice parameters a = 7.9584(16) $\AA$, b = 18.594(4) $\AA$, c = 15.063(4) $\AA$ $\beta=120.97(2)^o$ and $M_r$ = 807.85 ($C_{40}H_{44}Cu_2N_2O_8$), Z = 2. Each of the $Cu^{2+}$ ion adopts a square pyramid geometry and coordinates with four oxygen atoms from two aceace ligands and one nitrogen atom from dipyph bidentate ligand. Magnetic measurement shows that the Weiss constant and Curie constant for the title compound are -0.22 K and 0.1154 emu K/mol, respectively. Thermal stability data indicate that the title complex undergoes two steps decomposition and the residue is $Cu_2O_4$. In the potential range of -1.5 ~ 0.8 V, the title complex represents an irreversible electrochemical process.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.1-6
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• 2015

To improve the efficiency of a reverse engineering process, many researches have recently tried to develop efficient, automatic 3D scanning devices. A new automatic 3D scanning device using a spherical coordinate system mechanism is introduced in this study. This device incorporates a guide motion along the spherical coordinate to compound each 3D data point automatically. The experiments correlating the system assembling tolerance with the form accuracy were conducted to verify the efficiency of the system for the scanning of an object, including complex shapes and manifold sections. In addition, the required time and system accuracy, taken during the scanning process of complicated artifact models, were investigated. Further, based on these empirical results, it was ascertained that the superior productivity of this new device offers a more precise and efficient scan when compared to conventional methodologies.