• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.209-212
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• 1987

This paper presents a control scheme to stabilize a two-axes microwave antenna system which is located on a ship and is subject to roll, pitch and yaw(RPY) motions. The scheme first computes the compensated angular positions of the antenna for RPY disturbances through coordinate transformations, and then use a servo con roller of PID type for each axis to track the compensated position command with a good transient behavior.

• Proceedings of the Korean Society of Rheology Conference
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• 2006.06a
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• pp.153-156
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• 2006

• Elastomers and Composites
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• v.33 no.4
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• pp.255-266
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• 1998

One-step continuous reactive blend with EPDM is investigated using a modular intermeshing corotating twin screw extruder This was performed via anionic polymerization mechanism. Mechanical properties were characterized and compared with mechanical blends.

• Journal of Korean Society of Steel Construction
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• v.26 no.6
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• pp.581-594
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• 2014

In this paper, flexural resistance of hybrid girder under uniform bending moment was evaluated, which is composed of HSB800 and HSB600 steel for the flange and web, respectively. Doubly-symmetric and monosymmetric sections with noncompact or compact flange and slender, noncompact or compact web were considered. Nonlinear analyses with 3-dim. shell element model were performed to determine the 'flexural resistance of section' and the 'lateral torsional buckling strength' by taking initial imperfection and residual stress into account. The numerical results were compared with the AASHTO LRFD and Eurocode 3 specifications and also the applicability of AASHTO LRFD appendix A6 was examined for the sections with noncompact and compact web.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.2
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• pp.373-380
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• 2020

A valve product can be over-designed or too heavy. Finite element analysis was performed using ANSYS for two and three-dimensional ball valve models, and the ball weight was reduced by optimization within the allowable design criteria. The ball is structurally safe according to the computed stress values, which are within the material's admissible stress. The weight was reduced by about 22%, and the structural safety factor was 1.25. The structural safety of the seat insert and ring, which are used to prevent leakage, was confirmed through finite element analysis. It is shown that the two-dimensional analysis can result in similar values to the three-dimensional analysis for the axisymmetric structure. The redesign of the valve is not included in the results since such changes require a whole new design process, including all valve components.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.547-557
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• 2013

The mode II fracture toughness and strength due to shear stress are important parameters in the stability of caprock and injection zone with application to geological sequestration of carbon dioxide. In this research, a short beam compression test has been used to determine the shear strength and the mode II fracture toughness for Coconino sandstone. The average value of the shear strength and mode II fracture toughness are estimated to be 23.53 MPa and 1.58 MPa${\surd}$m respectively. The stress intensity factor is suggested by finite element analysis using the displacement extrapolation method. The effect of biaxial stress and water saturation on the fracture toughness has also been investigated. The fracture toughness increases with confining stresses, but decreases by 11.4% in fully saturated condition.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.1
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• pp.62-69
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• 2016

Current guidance considers that uniaxially loaded specimen with a deep crack is used for the determination of the ductile-to-brittle transition temperature. However, reactor pressure vessel is under biaxial loading in real and the existence of deep crack is not probable through periodic in-service-inspection. The elastic stress intensity factor and the elastic-plastic J-integral which were used for crack-tip stress field and fracture mechanics assessment parameters. The difference of the loading condition and crack geometry can significantly influence on these parameters. Thus, a constraint effect caused by differences between standard specimens and a real structure can over/underestimate the fracture toughness, and it affects the results of the structural integrity assessment, consequentially. The present paper investigates the constraint effects by evaluating the master curve $T_0$ reference temperature of PCVN (Pre-cracked Charpy V-Notch) and small scale cruciform specimens which was designed to simulate biaxial loading condition with shallow crack through the fracture toughness tests and 3-dimensional elastic-plastic finite element analyses. Based on the finite element analysis results, the fracture toughness values of a small scale cruciform specimen were estimated, and the geometry-dependent factors of the cruciform specimen considered in the present study were determined. Finally, the transferability of the test results of these specimens was discussed.

• Tunnel and Underground Space
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• v.12 no.4
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• pp.237-247
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• 2002

A total of 18 stress measurements were performed in the rock and rock-like blocks in the laboratory to estimate the influence of anisotropy in rock. Full scale overcoring equipment, which consists of a coring machine and a biaxial loading system by flat jacks, was developed to simulate the in-situ rock stress condition in the laboratory By comparing the isotropic analysis with the anisotropic analysis in measuring the stress, conclusions have been drawn as to the influence of anisotropy. The maximum difference between the isotropic and the anisotropic analysis was 34% and it was shown that the stress measurement considering the anisotropy was needed. To confirm the validity of the observed data, a diagnostic analysis of stress relief curve by overcoring was conducted using the three dimensional finite difference program, FLAC 3D.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.3
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• pp.21-32
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• 1999

A ground motion resulting from the destructive earthquakes can subject reinforced concrete members to very large forces. The reinforced concrete shear walls are designed as earthquake-resistant members of building structure in order to prevent severe damage due to the ground motions. The current research activities on seismic behavior of reinforced concrete member under ground motions have been limited to the shaking table test or equivalent static cyclic test and the obtained results have been summarized and proposed for the seismic design retrofit of structural columns or shear walls. The present study predicted the seismic response and failure behavior of reinforced concrete shear wall subjected to base acceleration using the finite element method. A decrease in strength and stiffness, yielding of reinforcing bar, and repetition of crack closing and opening due to seismic load with cyclic nature are accompanied by the crack which is necessarily expected to take place in concrete member. In this study the nonlinear material models for concrete and reinforcing bar based on biaxial stress field and algorithm of dynamic analysis were combined to construct the analytical program using the finite element method. The analytical seismic response and failure behaviors of reinforced concrete shear wall subjected to several base accelerations were compared with reliable experimental result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.11
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• pp.5930-5938
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• 2013

The sigmoid functionally graded mateiral(S-FGM) theory is reformulated using the nonlocal elatictiry of Erigen. The equation of equilibrium of the nonlocal elasticity are derived. This theory has ability to capture the both small scale effects and sigmoid function in terms of the volume fraction of the constituents for material properties through the plate thickness. Navier's method has been used to solve the governing equations for all edges simply supported boundary conditions. Numerical solutions of biaxial buckling of nano-scale plates are presented using this theory to illustrate the effects of nonlocal theory and power law index of sigmoid function on buckling load. The relations between nonlocal and local theories are discussed by numerical results. Further, effects of (i) power law index, (ii) length, (iii) nonlocal parameter, (iv) aspect ratio and (v) mode number on nondimensional biaxial buckling load are studied. To validate the present solutions, the reference solutions are discussed.