• Radiation Oncology Journal
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• v.22 no.1
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• pp.64-68
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• 2004

Purpose : To study the feasibility of verifying real-time 2-D dose distribution measurement system with the scintillation screen for the quality assurance. Materials and Methods : The water phantom consisted of a scintillation screen (LANEX fast screen, Kodak, USA) that was axially located in the middle of an acrylic cylinder with a diameter of 25 cm. The charge-coupled device (CCD) camera was attached to the phantom In order to capture the visible light from the scintillation screen. To observe the dose distribution In real time, the intensity of the light from the scintillator was converted to a dosage. The isodose contours of the calculations from RTP and those of the measurements using the scintillation screen were compared for the arc therapy and the Intensity modulated radiation therapy (IMRT). Results : The kernel, expressed as a multiplication of two error functions, was obtained in order to correct the sensitivity of the CCD of the camera and the scintillation screen. When comparing the calculated isodose and measured isodose, a discrepancy of less than 8 mm in the high dose region was observed. Conclusion : Using the 2-D dosimetry system, the relationship between the light and the dosage could be found, and real-time verification of the dose distribution was feasible.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.2
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• pp.121-128
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• 2014

In this study, The purpose of this study is to experimentally investigate the shear behavior of reinforced flat plate embedded with GFRP(glass fiber reinforced polymer) plate with openings. The GFRP shear reinforcement is manufactured into a plate shape with several openings to ensure perfect integration with concrete. The test was performed on 7 specimens. the parameters include the type of reinforcement and amount of the shear reinforcement., From the test, we analysed the crack, failure mode, Strain, load-displacement graph. a calculation of the shear strength of reinforced flat plate with GFRP plate based on the ACI 318-11 was compared with the test results. The results of the experiment indicate that GFRP plate is successfully applied as a shear reinforcement in the flat plate under punching shear.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.495-502
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• 2010

A study for the nonlinear analysis method of flexural behavior of concrete girders strengthened with unbonded prestressed CFRP plates is presented. The concrete girders strengthened with unbonded prestressed CFRP plates exhibit more complex nonlinear behavior due to the slip between the concrete girder and the CFRP plates than the case of bonded CFRP plates. The unbonded CFRP plate is modeled as an assemblage of the curved elements both ends of which are rigidly linked to the nodes of fibered frame elements. The slip effect of the unbonded CFRP plate is taken into account using the force equilibrium relationship at each node. To evaluate the validity and the capability of the proposed analysis method, the ultimate analysis results of the concrete beams strengthened with unbonded prestressed CFRP plate are compared with the experimental results obtained from other investigators. The proposed analysis method is found to predict ultimate behaviors of these beams fairly well. Additionally the time-dependent deformations of the concrete beam seems to have little influence on the ultimate behaviors of concrete beams strengthened with unbonded prestressed CFRP plate, and the cracks of the concrete beam which occurred before strengthening it with CFRP plate are found to have almost no influence on the ultimate capacity of the beam.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.969-980
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• 2003

The interactions between curved cracks are examined in an orthotropic plate and the effects of rectilinear anisotropy on the stress intensity factors are analyzed. The finite element alternating method (FEAM) is used in this study to get the stress intensity factors for the multiple curved cracks. To obtain analytical solutions, which is necessary in FEAM, the curved cracks are modeled as continuous distributions of dislocations, and integral equations are formulated for unknown dislocation density functions to satisfy the given resultant forces on the crack surfaces. Several basic problems are solved to verify the accuracy and efficiency of the proposed method and it can be found that present results show good agreements with the previously published results.

• Journal of the Korean Geotechnical Society
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• v.31 no.8
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• pp.17-28
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• 2015

The purpose of this study is to measure the volumetric water content of unsaturated soils during drying and wetting process by using volumetric pressure plate extractor (VPPE) incorporated with time domain reflectometry (TDR). The VPPE consists of a pressure cell, a pressure regulator, a burette system and a TDR probe. Two samples with different initial void ratios were prepared in the pressure cell, and the air pressure at the range of 0.1 kPa - 50 kPa was applied to adjust the matric suction by the pressure regulator. The burette system was used to measure the volumetric water content change of the sample according to the matric suction. In addition, the TDR probe, installed in the cell, was used to evaluate the dielectric constant from the reflected signal of the electromagnetic wave at the probe. The volumetric water content of specimen was estimated by the empirical equation between the volumetric water content and dielectric constant, which was calibrated with the Jumunjin sand. The test results show that the volumetric water content calculated by TDR probe is strongly correlated to the measured value by burette system. The hysteresis occurs during drying and wetting process. Furthermore, the degree of hysteresis reduces in the repeated process. This study suggests that TDR may be effectively used to evaluate the water content soil for the determination of water characteristic curve of unsaturated soils.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.34 no.3
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• pp.238-244
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• 2001

A method of estimating the fluid drag of a fishing gear and otter board spread in a midwater trawl on full scale was described by implementing a three-dimensional semi-analytic treatment of the towing cable (warp) of a trawl system with the field experiments obtained with the SCANMAR system. The shape of hand rope, bridle and float(or ground) rope attached behind otter boards in a horizontal plane was assumed to be of form $y_r=Ax_r^B$. The distance between otter boards (otter board spread) obtained by the three dimensional analysis of a towing cable must be equal to that obtained by the functional equation of the shape of ropes behind otter boards, The angle of attack of ropes which can be obtained from the functional equation enables one to estimate the fluid drag of trawl net (net drag) by subtracting the fluid drag of the hand rope and bridles from the drag component of the tension of hand rope attached just behind the otter boards.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.73-76
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• 2008

Bipolar Plates for PEMFC have been a key component of fuel cells with MEA, thus in this research they have been fabricated by a compression molding technique after mixing graphite powder with phenol resin. The results have shown the prominent properties compared with those by foreign advanced company with respect to the electrical conductivity and flexural strength. In addition, it has been carried out that the Voltage-Current characteristics comparison according to the unit cell experiments of bipolar plates. As a result, we have obtained good performances and we are going to research the molding feasibility of bipolar plate's flow channel.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.126-129
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• 2008

최근 들어 기존 조명기구를 대신하여 LED 조명기구가 크게 각광을 받고 있다. 이는 LED의 장점인 낮은 소비전력과 긴 수명 때문인 것으로 생각된다. 하지만, 빛을 확산시켜야 하는 조명관점에서 본다면 LED 조명기구에도 개선해야 할 부분도 많아지는 것도 사실이다. 본 논문에서는 LED 조명기구에서 빛의 확산을 위해 사용되어지는 고가의 반사판에 대해 실제 개발된 조명기구의 배광곡선 분석과 시뮬레이션을 통해 확산효과를 면밀히 분석함으로써 향후 LED 조명기구의 설계에 있어서 기술 및 경제적 관점에서 도움을 주고자 한다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.17 no.2
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• pp.119-129
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• 2004

A three dimensional (3D) method of analysis is presented for determining the free vibration frequencies and mode shapes of thick, circular and annular plates with nonlinear thickness variation along the radial direction. Unlike conventional plate theories, which are mathematically two dimensional (2D), the present method is based upon the 3D dynamic equations of elasticity. Displacement components u/sub s/, u/sub z/, and u/sub θ/ in the radial, thickness, and circumferential directions, respectively, are taken to be sinusoidal in time, periodic in θ, and algebraic polynomials in the s and z directions. Potential (strain) and kinetic energies of the plates are formulated, and the Ritz method is used to solve the eigenvalue problem thus yielding upper bound values of the frequencies by minimizing the frequencies. As the degree of the polynomials is increased, frequencies converge to the exact values. Convergence to four digit exactitude is demonstrated for the first five frequencies of the plates. Numerical results we presented for completely free, annular and circular plates with uniform linear, and quadratic variations in thickness. Comparisons are also made between results obtained from the present 3D and previously published thin plate (2D) data.

• Journal of Korea Multimedia Society
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• v.12 no.2
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• pp.281-289
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• 2009

In this paper, a new interaction technique with the virtual single or dual acoustic reflection tablet is proposed to support the perception of depth cue and implement the effective spatial input systems of reducing the depth errors in general spatial sketching tasks. And several experiments show that the virtual wall with acoustic reflections can be thought of as a meaningful feedback for the plausible virtual conceptual design. By using the proposed idea, the degree of agreement to the target model is increased by 35% due to the single acoustic reflection tablet in the constant depth plane. In the slanted plane, the degree of agreement is increased by 8% due to the dual acoustic reflection compared to the single acoustic reflection and the degree of agreement is increased by 15% on the curved vase.