• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.3
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• pp.162-168
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• 2006

Speckle interferometry with phase-shifting method has been applied to measurement of micro-scale displacement through optical signal processing. Four-step phase-shifting method by PZT is used to measure out-of-plane displacement in spot-welded cantilever and results of optical experiments are comparable to those of FEM. Phase-shifting method using Fourier transform by PZT is applied to measurement of in-plane displacement on rectangular steel plate with a circular hole. The results of optical experiment agree well with theoretical calculation. New phase-shifting method in speckle interferometry has been implemented with a quarter wave plate. In-plane displacement of specimen is measured by the new phase-shifting method. Results of optical experiment show that the quarter wave plate can be used for phase-shifting method that is cheap and easy to use in speckle interferometry.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.3
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• pp.38-43
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• 2004

This paper describes the construction of a circular polariscope. Generally, a circular polariscope contains four optical elements and a light source. The first element following the light source is called the linear polarizer. It converts the ordinary light into plane-polarized light. The second element is a quarter wave plate which converts the plane-polarized light into circularly polarized light. Following the quarter wave plate, a specimen made of transparent photoelastic material is located in a loading device. The second quarter wave plate is set and the last element is the analyzer. These polarizing elements, two quarter wave plates and two linear polarizing filters, were purchased from the USA. Frames and other structures for holding polarizing filters were machined and assembled to be rotated. Light box, which includes four incandescent lamps and two sodium-vapor lamps, was made. In order to proof the function of the newly built polariscope, Tardy compensation test was applied to a rectangular shaped specimen made of poly-carbonate material (PSM 1). The error of the fringe constant, which was measured by the newly built polariscope, was within 4.4 percent compared to the standard value of this material. It is possible to make a good quality of polariscope if accurate polarizing filters will be used.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.437-441
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• 2001

This paper describes the construction of a circular polariscope. Generally, a circular polariscope contains four optical elements and a light source. The first element following the light source is called the polarizer. It converts the ordinary light into plane-polarized light. The second element is a quarter wave plate which converts the plane-polarized light into circularly polarized light. Following the quarter wave plate, a specimen made of transparent photoelastic material is located in a loading device. The second quarter wave plate is set and the last element is the analyzer. These polarizing elements, two quarter wave plates and two polarizing filters, were purchased from the USA. Frames and other structures for holding polarizing filters were machined and assembled to be rotated. Light box, which include four incandescent lamps and two sodium-vapor lamps, was made. In order to proof the function of the newly built polariscope, Tardy compensation test was applied to a rectangular shaped specimen made of poly-carbonate material (PSM1). The error of the fringe constant, which was measured by the newly built polariscope, was within 4.4 percent compared to the standard value of this material. It is possible to make a good quality of polariscope if accurate polarizing filters will be used.

• Structural Engineering and Mechanics
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• v.48 no.2
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• pp.241-255
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• 2013

The receding contact problem for two elastic layers whose elastic constants and heights are different supported by two elastic quarter planes is considered. The lower layer is supported by two elastic quarter planes and the upper elastic layer is subjected to symmetrical distributed load whose heights are 2a on its top surface. It is assumed that the contact between all surfaces is frictionless and the effect of gravity force is neglected. The problem is formulated and solved by using Theory of Elasticity and Integral Transform Technique. The problem is reduced to a system of singular integral equations in which contact pressures are the unknown functions by using integral transform technique and boundary conditions of the problem. Stresses and displacements are expressed depending on the contact pressures using Fourier and Mellin formula technique. The singular integral equation is solved numerically by using Gauss-Jacobi integration formulation. Numerical results are obtained for various dimensionless quantities for the contact pressures and the contact areas are presented in graphics and tables.

• Structural Engineering and Mechanics
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• v.91 no.5
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• pp.459-468
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• 2024

This study presents a frictionless receding contact problem for an orthotropic elastic layer. It is assumed that the layer is supported by two rigid quarter planes and the material of the layer is orthotropic. The layer of thickness h is indented by a rigid cylindrical punch of radius R. The problem is modeled by using the singular integral equation method with the help of the Fourier transform technique. Applying the boundary conditions of the problem the system of singular integral equations is obtained. In this system, the unknowns are the contact stresses and contact widths under the punch and between the layer and rigid quarter planes. The Gauss-Chebyshev integration method is applied to the obtained system of singular integral equations of Cauchy type. Five different orthotropic materials are considered during the analysis. Numerical results are presented to interpret the effect of the material property and the other parameters on the contact stress and the contact width.

• Structural Engineering and Mechanics
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• v.54 no.1
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• pp.69-85
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• 2015

In this paper, a receding contact problem for an elastic layer resting on two quarter planes is considered. The layer is pressed by a stamp and distributed loads. It is assumed that the contact surfaces are frictionless and only compressive traction can be transmitted through the contact surfaces. In addition the effect of body forces are neglected. Firstly, the problem is solved analytically based on theory of elasticity. In this solution, the problem is reduced into a system of singular integral equations in which contact areas and contact stresses are unknowns using boundary conditions and integral transform techniques. This system is solved numerically using Gauss-Jacobi integral formulation. Secondly, two dimensional finite element analysis of the problem is carried out using ANSYS. The dimensionless quantities for the contact areas and the contact pressures are calculated under various distributed load conditions using both solutions. It is concluded that the position and the magnitude of the distributed load have an important role on the contact area and contact pressure distribution between layer and quarter plane contact surface. The analytic results are verified by comparison with finite element results.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.13 no.4
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• pp.237-245
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• 2009

A numerical solution is provided for a jet produced by a flow emerging from a slit at the bottom corner of a quarter plane. The flow is characterized by the Froude number F, based on the net volume flux and the width of the slit. We perform the free-surface flow for various values of F and another parameter corresponding to the position of the vertical wall. A jet with back-flow near the edge of the vertical wall is obtained, and the limiting case is a jet with a stagnation point.

• The Journal of the Acoustical Society of Korea
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• v.18 no.4
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• pp.11-16
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• 1999

In this paper, we designed and fabricated QMSA(Quarter-Wavelength Microstrip Antenna) for 850MHz band on the CGP-500 PTFE substrate(by CHUKOH company) with ε/sub r/=2.6, H=1.6mm(±0.08), where width of the radiation patch is .identical with that of the ground plane. A well matched feed point was obtained by experiments and this QMSA was fed by using prove feed method. The resonant frequencies and the return losses were mcasured by cutting the gap L₃ between the radiation patch and the ground plane, with a 5mm cutting length, step by step. As a result, we found that the measured return losses were decreased and the resonant frequencies were increased when the gap L₃ was shorter, especially under 10mm, unlike we had expected.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.1
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• pp.16-26
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• 1998

This paper presents a design methodology for magnetically tunable X-band E-plane type waveguide filters. The proposed design is based on using of quarter wavelength transmission line for compensating the negative length transmission line of end K-inverters of E-plane type waveguide filters. The derived formulae are applied for initial design and the correction method is also provided for final design by considering the frequency dependent characteristic of K-inverters. The analysis results of E-plane pype waveguide structure loaded with ferrite slab are obtained using the edge based finite element method including higher order mode effecets. It is shown that the unilateral finline E-plane type waveguide filter as well as the bilateral finline E-plane type waveguide filter achieves the the manetically tunable characteristic. The X-band experimantal results for bilateral and unilateral finline E-plane type waveguide filters agree well with the simulated data.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.128-133
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• 2005

An iris-coupled partial H-plane filter as a new type of partial H-plane filter is proposed. The proposed filter can be compared with conventional H-plane filter and uses an iris-type evanescent waveguide as a coupling structure. Filter design technique based on numerical simulation is developed to design and compare the proposed filter and H-plane filter. Designed iris-coupled partial H-plane filter has the same frequency response as that of the conventional H-plane filter while its cross section is one quarter. A good agreement between measurements and theoretical prediction is achieved.