• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.1
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• pp.83-90
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• 2009

In this paper, the problem of electromagnetic transmission through slits in two parallel conducting plates which separate two half spaces is considered. The coupled integral equations for the electric field distributions over the slits are developed for the case that the TM polarized plane wave is incident on the slit and solved by the method of moments. The transmitted power beyond the slit-perforated conducting parallel plates is computed in order to check the variations of the coupled power through slits against some parameters such as the incident angle of the TM polarized wave, slit width, lateral distance between two slits, and distance between the conducting plates. When the lateral distance between two slits approaches near the multiples of half wavelengths, the transmission resonance (maximum power transmission) is observed. If the slit width in the incident side is narrow and the distance between conducting plates is small compared to the wavelength, the maximum of transmitted power is observed to be nearly independent of the incident angle and slit width. In addition, the mechanism of the transmission resonance in the present geometry is explained using a simplified geometry and its equivalent circuit.

• Journal of the Korean Society of Radiology
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• v.14 no.6
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• pp.733-740
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• 2020

As the use of radiation for medical purposes increases, the exposure dose of medical workers is also increasing. To reduce this dose, various studies on changing the shielding material have been conducted. Recently, a new method to reduce the dose at the entrance of the radiation treatment room was proposed by using the photoelectric effect that occurs when the radiation is scattered. Because this method is particularly effective for low-energy photons, in this study, a slit-type structure was proposed as a excellent shielding structure against scattered x-ray in a general photography room, and was evaluated the shielding effect by Monte Carlo simulation. As a result of the calculation, this study found that in the case of a structure in which steel plates with a thickness of 2 mm and a width of 5 cm are stacked at 2 mm intervals, a shielding effect was approximately 99.9% or more, excluding the heights of the floor and the patient where scattering occurs directly.

• Korean Journal of Plant Taxonomy
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• v.38 no.2
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• pp.93-109
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• 2008

The morphological variation was analysed to examine previous hypotheses on the taxonomy of B. amurensis complex which includes B. amurensis Rupr. var. amurensis, B. amurensis var. quelpaertensis (Nakai) Nakai and B. amurensis var. latifolia Nakai. The results from the univariational and principal components analyses employing 22 putatively diagnostic characters indicate that B. amurensis var. quelpaertensis is distinct from var. amurensis in the length and width of leaves, angle of leaf apex, distance between spinose teeth, length of internode, number of flowers per inflorescence, whereas B. amurensis var. latifolia is different from other varieties in the angle of leaf apex and leaf length/width ratio. In principal component analysis, the characters of the leaf including leaf width and length were the main characteristics to distinguish those three taxa. The evidence both from the principal components analyses and current geographical distribution pattern suggest that retaining the varietal status for the two taxa, B. amurensis var. latifolia and B. amurensis var. quelpaertensis is reasonable.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.669-673
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• 2010

현재 EAP(Emergency Action Plan) 수립 시 가장 많이 사용되는 DAMBRK 모형은 붕괴유출수문곡선 유도 시 댐 재료 특성을 고려하지 않지만, BREACH 모형은 댐 축조재료 특성과 유사이송능력을 고려하여 붕괴유출수문곡선을 산정하기 때문에 물리적으로 BREACH 모형이 흙댐의 붕괴특성을 실제와 더욱 유사하게 추적할 수 있을 것으로 판단된다. 본 연구에서는 두 모형을 안동댐(흙댐)에 적용하여 첨두유출량, 첨두유출 발생시간, 붕괴 시작, 붕괴 완료 시간 등의 댐 붕괴시 유출특성을 비교하였다. 적용 결과 BREACH 모형은 붕괴가 매우 서서히 진행되다가 일정수위에 도달하게 되면 급격하게 붕괴유출량의 증가폭이 커지는 데 비하여 DAMBRK 모형은 붕괴 시작과 동시에 붕괴유출량이 급격하게 증가하는 경향을 보였다. 또한 최대총유출량은 BREACH 모형이 DAMBRK 모형에 비해 약 5% 작게 산정되었지만, 34시간까지의 유출 총량은 DAMBRK 모형에 비하여 BREACH 모형이 약 16% 크게 나타났다. 두 모형의 붕괴유출수문곡선 비교를 통하여 댐 제체의 재료특성이 유출특성에 미치는 영향을 파악할 수 있었지만, 더 정확한 영향성을 파악하기 위하여 지속적인 비교연구가 필요할 것으로 판단된다.

• Korean Journal of Optics and Photonics
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• v.1 no.2
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• pp.135-141
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• 1990

Optical nonlinearity of laser heated Si with thickness of 160$\mu$m is investigated by pump-probe method. Si is heated by pdsed Nd:YAG laser of $TEM_{00}$-mode with pulse duration of 180$\mu$sec. Temperature change is monitored by observing transmittance change of probe light whose wavelength lies near band gap of Si. It is found that temperature rise is linearly proportional to incident laser intensity and the maximum temperat~re increment is measured to be $16^{\circ}C$ for the maximum incident intensity of 25KW/$\textrm{cm}^2$. From these results, the third order nonlinear susceptibility .d3) at the wavelength of 1.06$\mu$mis estimated to be $6.6\times10^{-5}$esu due to laser heating.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.459-467
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• 2008

This paper describes a proposal for average crack width and immediate deflection calculation in structural concrete members. The model is mathematically derived from actual bond stressslip relationships and tension stiffening effect between reinforcement and the surrounding concrete, and the actual strains of steel and concrete are integrated respectively along the embedded length between the adjacent cracks so as to obtain the difference in the axial elongation. With these, a model for average crack width and immediate deflection in reinforced concrete flexural members are proposed utilizing difference in the axial elongation and average steel strain and moment-curvature relationship with taking account of bond characteristics. The model is applied to the test specimens available in literatures, and the crack width and deflections predicted by the proposal equation in this study are closed to the experimentally measured data compared the current code provisions.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.407-414
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• 2012

The purpose of this study is to experimentally investigate the shear behavior of reinforced concrete beams embedded with GFRP (glass fiber reinforced polymer) plate with openings. In this study, the parameters include the shape of reinforcement, reinforcement area, and thickness and width of reinforcements. The test was performed on 9 specimens with shear spanto-depth ratio of 2.8. When the reinforcement area was varied, the GFRP plate showed 3.6 times greater shear strength than steel stirrup. The test result showed that shear strength increased as reinforcement area increased. Also, when the shape of a parallelogram GFRP plate was used, it showed higher shear strength than that with rectangular shape. Effect of thickness and width of reinforcement showed that shear capacity increased as width increased. For a comparison study, a calculation of the shear strength of reinforced beams with GFRP plate based on the ACI 318M-08 was compared with the test results. The test results were compared with the maximum shear reinforcement areas required by ACI 318M-08, CSA-04, and EC2-02 provision.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.415-422
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• 2012

This paper analyzed seventy eight previous test results to evaluate bond strength of Near Surface-Mounted (NSM) FRP and prediction formulas previously proposed by researchers. The results showed that the most reliable bond strength prediction was the one proposed by Seracino, who considered the shape coefficient (ratio of width-thickness) and stiffness of FRP. However, the equation tended to underestimate the bond strength, especially serious when FRP bond length was relatively short, because the equation did not consider the effect of bond length. Based on the analysis of previous test results, the relation between bond length and bond strength and the group effect due to close proximity of FRPs were determined. Based on the findings, the Seracino's formula was modified and it's applicability was evaluated. The result showed that the suggested formula can be used effectively to predict the bond strength of NSM FRP.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.545-552
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• 2009

An experimental study was performed on the yLRC composite column. Its external surface was manufactured with y-shape steel sheets and L-shape steel angles, and concrete was poured inside in the field. This composite column has improved the section capacity due to the composite action of steel and concrete, and provides good efficiency in reducing the terms of construction works because of its abridged formworks. The stub column specimens (three small and three large specimens) were tested through concentrical axial loading, and the effect of the width-to-thickness ratio of the steel angle on the column axial strength was examined. The axial strength and behavior of the composite columns were analyzed, and a formula for predicting the axial load capacity was proposed.

• Magazine of the Korea Concrete Institute
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• v.7 no.5
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• pp.133-144
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• 1995

This study investigated to the properties of structural behaviors through a series of experiment with the key parameter, such as diameter-to-thickness(D/t) ratio, selenderness ratio of steel t~ube and strength of concrete under loading condition simple confined concrete by steel tube as a fundmental study on adaptability with structural members in high-rise building. The obtained results are sumnarised as follow. (1) The fracture mode of confined concrete was presented digonal tension fracture in the direction of $45^{\circ}$ with compression failure at the end of specimen in stub column, but the fracture mode of long column was assumed an aspect of bending fracture transversely. (2) The deformation capacity and ductility effect was increased by confine steel tube for concrete. (3) 'The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint of concrete considered D / t ratio, selenderness ratio of steel tube anti strength of' concrete were proposed.