• Computers and Concrete
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• v.27 no.2
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• pp.99-109
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• 2021

Experimental and discrete element methods were used to investigate the effects of echelon non-persistent joint on the failure behaviour of joint's bridge area under uniaxial compressive test. Concrete samples with dimension of 150 mm×100 mm×50 mm were prepared. Uniaxial compressive strength and tensile strength of concrete were 14 MPa and 1MPa, respectivly. Within the specimen, three echelon non-persistent notches were provided. These joints were distributed on the three diagonal plane. the angle of diagonal plane related to horizontal axis were 15°, 30° and 45°. The angle of joints related to diagonal plane were 30°, 45°, 60°. Totally, 9 different configuration systems were prepared for non-persistent joint. In these configurations, the length of joints were taken as 2 cm. Similar to those for joints configuration systems in the experimental tests, 9 models with different echelon non-persistent joint were prepared in numerical model. The axial load was applied to the model by rate of 0.05 mm/min. the results show that the failure process was mostly governed by both of the non-persistent joint angle and diagonal plane angle. The compressive strengths of the specimens were related to the fracture pattern and failure mechanism of the discontinuities. It was shown that the shear behaviour of discontinuities is related to the number of the induced tensile cracks which are increased by increasing the joint angle. The strength of samples increase by increasing both of the joint angle and diagonal plane angle. The failure pattern and failure strength are similar in both methods i.e. the experimental testing and the numerical simulation methods.

• Journal of the korean academy of Pediatric Dentistry
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• v.7 no.1
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• pp.33-40
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• 1980

The author observed the eruption pattern of the mandibular premolars. For this study the author took 406 cases of oblique cephalographs of 6 to 12 year old children. The measurement were with regard to the vertical and horizontal dimensional changes and tooth axis changes to the occlusal plane. The following results were obtained. 1. At stage V the tooth axis of 1st premolar inclined mesially to the occlusal plane, as the tooth erupt toward vertically the angulation changed that at stage X the tooth axis almost right angle to the occlusal plane. 2. The distance from the root apex of premolars to the lower border of mandible were slightly increased to the stage VII, while after stage VII rapid increasing appeared. At stage X the distance of 1st premolar was more longer than 2nd premolar. 3. The distance from the mesial surface of 1st molar to the mesial surface of premolars were decreased slightly to the stage VII, but this distances were decreased rapidly after stage VII. 4. The distance between distal surface of 1st premolar and mesial surface of 2nd premolar was almost constant before stage VIII, at stage IX this distance was little presented because the premolars were contacted.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.741-746
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• 2012

The increase of energetic efficiency in plane bearing is getting more important in the transfer mechanism of semi-conductor and display panel manufacturing processes. To accomplish this objective, the technique of surface texturing on bearing surface has recently emerged as one of the most effective candidates. In this study, the effects of various pattern parameters on two bearing performance indices(load carrying capacity and effective friction coefficient) are investigated through a semi-analytic method, i.e., the 2-dimensional Reynolds equation incorporated into the finite difference scheme. Here, cavitation effect is also taken into account by employing an appropriate numerical scheme. In this study, the patterns in the textured surface are composed of a series of semi-spheres or semi-ellipsoids in shape. The effects of their size and number density on the performance indices are examined through the performance of various numerical experiments. Also, the effects of the anisotropy of the semi-ellipsoidal pattern on the bearing's lubrication characteristics are investigated and discussed.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.108-113
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• 2001

Recently, the mechanical structures applied to many industrial products, especially in electronic products, appear to be miniaturized and complicated. This trend makes it difficult to analyze the stress distribution of those mechanical structures and generates new challenges for precise measurement of strain. Therefore, generally most of those cases largely depend on the finite element analysis. But the development of optical metrology which has the capability of non-contact, full-field and precise measurement makes it possible to solve these measuring problems. Among the optical measurement techniques, the electronic speckle pattern interferometry (ESPI) has been developed and considered as one of the most useful tools for measuring displacement and deformation. But the shortage of recognition and difficulties of measurement have limited its industrial applications in spite of its excellent capabilities. Therefore in this study, in order to enhance the industrial application of ESPI, the measurement of in-plane displacement of mechanical structure with ESPI, which is applied to washing machine and cannot be measured by strain gauges, was performed. And the verification of validity of FEA results was also done.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.11
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• pp.69-74
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• 2004

This paper presents ESPI system for the measurement of thermal expansion coefficient of STS430 up to 1,00$0^{\circ}C$ . Existing methods, strain gauge and moire have the limitation of contact to object and do not supply the coefficient up to 80$0^{\circ}C$ . There needs to measure the data up to 80$0^{\circ}C$, because heat resistant materials have high melting temperature up to 1,000'E In previous studies related to thermal strain analysis, the quantitative results have not reported by ESPI at high temperature, yet. In-plane ESPI and vacuum chamber for the reduction of air turbulence and oxidation are designed for the measurement of the coefficient up to 1,00$0^{\circ}C$ and speckle correlation fringe pattern images are processed by commercial image filtering tool-smoothing, thinning and enhancement- to obtain quantitative results, which is compared with references data. The comparison shows two data are agreed within 4.1% blow $600^{\circ}C$ however, there is some difference up to $600^{\circ}C$. Also, the incremental ratio of the coefficient is changed up to 80$0^{\circ}C$ . The reason is the phase transformation of STS430 probably begins at 80$0^{\circ}C$

• Current Optics and Photonics
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• v.2 no.6
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• pp.540-546
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• 2018

We propose an implementation scheme for an optical encryption system with hybrid-pattern random keys. In the encryption process, a pair of random phase keys composed of a white-noise phase key and a structured phase key are positioned in the input plane and Fourier-spectrum plane respectively. The output image is recoverable by digital reconstruction, using the conjugate of the encryption key in the Fourier-spectrum plane. We discuss the system encryption performance when different combinations of phase-key pairs are used. To measure the effectiveness of the proposed method, we calculate the statistical indicators between original and encrypted images. The results are compared to those generated from a classical double random phase encoding. Computer simulations are presented to show the validity of the method.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.11
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• pp.52-59
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• 1996

This paper presents a monopulse feed structure with low sidelobe monopulse pattern, which consists of a E-plane corrugated horn and a unfiorm pick-up aperture power divider. Tfhe design methods and epxerimental resutls of the E-plane corrugated feeder are described. Modified hybrid mode analysis and GSM (generalized scattering matrix) methods are introduced to design the E-plane corrugated feed horns. The 24-port corrugated feeder is designed using modified hybrid mode analysis initially and verified using GSM methods. Measurement results show that this feeder has low return loss and sidelobe level at sum and difference channel, respectively.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.1
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• pp.58-64
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• 2012

Instead of the surface pattern arranged repeatedly in two axial direction on a plane, we propose double patterns superposing two one-axial linear patterns as a reference target for surface encoding. A upper layer of the superposed pattern is the transparent glass with grooves cut in it at a fixed pitch. The position is sensed by detecting a shift of beam due to difference of a refractive index. And a lower layer is the aluminum with color-coated grooves. The amount of beam reflected on the layer varies according to its targeting position and is detected for encoding. For the above reference pattern, we can detect two-axial positions using only the single beam. Furthermore, the pattern size can be expanded with a size of the detector kept constant, meaning that the measured range can be expanded easily. In this paper, we review the existing optical encoding methods for grid pattern, and discuss the hardware implementation of the suggested surface encoding method.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.4
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• pp.219-225
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• 2000

In this paper, we report the experimental setup and characterization of experimental results for the HTS antenna. The constructions of experimental setup must be fabricated, cautiously. We constructed the cryostat made of 3 stages which consists of radome, vacuum stage and helium refrigerator for the HTS antenna. The HTS antenna was mounted to cryostat and various characteristics were measured at room temperature and liquid nitrogen temperature, 77 K. Also the results for the HTS antenna and the gold antenna were compared in terms of reflection coefficient, E-plane and H-plane radiation pattern, input impedance, SWR and efficiency. It appeared that the HTS antenna was superior to gold counterpart over the all characteristics.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2001.05a
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• pp.211-214
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• 2001

Electronic Speckle Pattern Interferometry(ESPI) is one of optical technique to measure displacement precisely, uses CCD camera to show result image in real time. General ESPI system measures in-plane or out-of-plane displacement. Shearography is one of electronic speckle pattern interferometric methods which allow full-field observation of surface displacement derivatives and it is robust in vibration. The shearography provides non-contacting technique of evaluating defects nondestructively. In this study, the shearography was used to evaluate defects in Carbon Fiber Reinforced Plastic(CFRP). Various sizes of artificial defects were embedded in various depths of woven CFRP plate. Effects due to the variation of size and depth of defects were evaluated in this study.