• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.2
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• pp.363-373
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• 1995

In this study, a FE model tuning method using experimental modal data was suggested after examining all the published conventional methods. The idea of this method is introducing scale factors to maintain both the structural connectivity and the consistency in the corrected stiffness matrix which makes it always possible to interpret the stiffness elements with the corresponding physical configuration of the targeting structure. The scale factors are determined to minimize the objective function of eigen-properties. The proposed method was tested to determine the joint stiffness of a T shaped beam. The test results were also compared with the tuned stiffness obtained from a probed commercial package (SYSTUNE) and found that this method is very accurate and compatible.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.282-287
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• 2009

In this paper, 3-stage centrifugal turbo compressor was measured and analyzed numerical simulation for find noise source and was reduced noise with changing designs. For this purpose, it was measured noise level and was analyzed noise frequency at each stage. In order to Find where is noise source, the study was investigated about structure borne noise by using modal analysis and also was checked sound radiation and leakage of noise at inlet and outlet by result of sound intensity. In order to reduce of noise, sound insulation rings were maded and were adhered at joint and noise reduction effects were verified by measurement and numerical simulation. From the analysis results of leakage of noise, this study presented new joint designs, also it was verified by result of numerical simulation.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.261-267
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• 2004

In undeniable digital signature scheme, the signature can not be verified without the signer's cooperation. The undeniable signature scheme can be used to computerize many applications which can not be done by a conventional digital signature scheme. In this study, we propose the undeniable digital multi-signature scheme which requires many signers and designated verifier. The multi-signature can be verified only in cooperation with all signers. The proposed scheme satisfies undeniable property and it is secure against active attacks such as modification and denial of the multi-signature by signers. We also discuss practical applications such as joint copyright protection on digital contents.

• 한국지구물리탐사학회:학술대회논문집
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• 2007.06a
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• pp.58-63
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• 2007

We developed a new algorithm for jointly inverting dc resistivity and seismic travel time tomography data based on the multiple constraints: (1) structural similarity based on cross-gradient, (2) correlation between two different material properties, and (3) a priori information on the material property distribution. Through the numerical experiments of surface dc resistivity and seismic refraction surveys, the performance of the proposed algorithm was demonstrated and the effects of different regularizations were analyzed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.403-410
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• 1999

General1y, H-section is used for columns and beams in the middle and low steel building, But it has a strong and weak axis. Thus if H-section is used for columns, the structure needs reinforcement on the weak axis. Therefore recently, square holler section(S.H.S) is used for columns because it is able to coiler the vulnerability of H-section. Structural analysis is usually executed under the assumption that connections are either ideally pinned joint or fully rigid joint. Actually all connections are semi-rigid which possess a rotational stiffness. Therefore it can be designed economically as using the property of connections which has a rotational stiffness. This paper presents a prediction model curve which is fitted Kishi-Chen power Model about the behavior of connection between H-beam and S.H.S column. Non-linear analysis program was considered the non-linearity of semi-rigid connection and the geometrical non-linearity under the effect of axial force. It was programed by FORTRAN90 and Visual Basic.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.111-118
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• 1997

Generally, H-section is used for columns and beams in the middle and low building steel structure, But it has a axis and a weak axis. Thus if H-section is used for columns, the structure needs reinforcement on the weak axis. Therefore recently, square hollow section(S.H.S) is used for columns because it is able to cover the vulnerability of H-section. Structural analysis is usually executed under the assumption that connections are either ideally pinned joint or fully joint. Actually all connections are semi-rigid which possess a rotational stiffness. Therefore it can be designed economically as using the property of connections which has a rotational stiffness. This paper presents a prediction model curve which is fitted with Kishi-Chen Power Model about the behavior of connection between H-beam and S.H.S column in the previous experimental paper. It also suggests the new analysis algorithm considering the non-linear of semi-rigid connection and the geometrical non-linear under the effect of axial force.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.1-5
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• 2003

By using an approach developed to determine the torque-tension relationship for bolted joints, frictional properties of several typical bolted joints were studied experimentally. The specific property by bolted joints certify that the most significant influence of materials and bearing surface condition. Experiments on thread friction shows that prevailing torque nuts with distorted threads provide benefit for preventing self-loosening of the nut. Repeated tightening-loosening generally increases frictions in a bolted joint. It was noted that the data scatter of the experimental results of frictions in a belted joint may overshadow the influence of size. speed, and contact positions. The results from the experimental investigation will help to better design bolted joints.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.283-286
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• 2005

Because CV Joint which is one of the component of automobile power train system communicates high power and performs power steering function, it requires high qualities such as high strength, high toughness and high fatigue resistance. This component undergoes a series of production processes such as forging, machining and heat treatment and required properties for this component depends on plastic deformation and heat treatment heavily. Therefore in this study, in order to these effects on mechanical properties due to plastic deformation and heat treatment we performed heat treatment following plastic deformation and then tensile test.

• Journal of Aerospace System Engineering
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• v.3 no.4
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• pp.27-34
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• 2009

This paper deals with the lifetime prediction of Aircraft Flaperon Joint made of AISI 4130 steel. Reviews are performed on the published damage models at first. And three different damage models are used for predicting the fatigue life of the structure subjected to variable amplitude fatigue loading. These models require no increase in complexity of use, nor do they require additional material property or mission loading information to achieve the improved accuracy. Finally a comparison among the fatigue results is performed. It is observed that the Miner's rule could predict longer life than other cumulative damage models which take into account loads below the endurance limit.

• Progress in Superconductivity and Cryogenics
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• v.9 no.4
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• pp.11-15
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• 2007

In practical applications of HTS tapes for electric devices such as coils and power cables, the jointing of HTS tapes is inevitable even though long length tapes have recently been achieved. The critical current, $I_c$, degradation behaviors with tensile and bending deformations were investigated in commercially available YBCO coated conductor tapes. When the V-I relationship was measured at the jointed section of the lap-jointed YBCO CC tapes, the resistance at the joint decreased with increasing joint length. The critical load for 95% $I_c$ retention were determined for the IBAD and RABiTS YBCO tapes and they were 175 and 355N, respectively. Fracture occurred at the unjointed part which represents strong copper lamination and solder jointing. The electro-mechanical properties of lap-jointed CC tapes depended on the properties of single tapes. The V-I behavior under bending strain was similar with the tensile case.