• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.607-612
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• 1998

In this study, the behavior of R/C beam strengthened with carbon fiber laminate(C.F.L) is analyzed from the test results. Test parameters are the width, the thickness and the length of C.F.L. and method of construction. The failure mode and ultimate load are analyzed from these measured data. Test results shows that the peak moment of specimens strengthened with C.F.L is increased to 1.43~1.90 times of that of non-rehabilitation specimen. The wider lap width, larger amount of rehabilitation materials, the larger strength is obtained.

• 유체기계공업학회:학술대회논문집
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• 2002.12a
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• pp.331-336
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• 2002

Recently the critical nozzles with small diameter are being extensively used to measure mass flow in a variety of industrial fields and these have different configurations depending on operation condition and working gas. The curvature radius of the critical nozzle throat is one of the most important configuration factors promising a high reliability of the critical nozzle. In the present study, computations using the axisymmetric, compressible, Navier-Stokes equations are carried out to investigate the effect of the nozzle curvature on critical flows. The diameter of the critical nozzle employed is D=0.3mm and the radius of curvature of the critical nozzle throat is varied in the range from 1D to 3D. It is found that the discharge coefficient is very sensitive to the curvature radius(R) of critical nozzle, leading to the peak discharge coefficient at R = 2.0D and 2.5D, and that the critical pressure ratio increases with the curvature radius.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.46-46
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• 2008

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.237-240
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• 2002

In the present study, we perform LES of turbulent flow and temperature fields in a circular impinging jet at Re=5000 for two cases of H/D=2 and 6 (H denotes the distance between the jet exit and flat plate, and D does the diameter of the jet exit). In the case of H/D=2, the regular vortical structures observed in free jet do not exist because of the smaller distance than the potential core. The Nusselt number on the wall is largest at $r/D{\cong}10.67$ where vortex rings Impinge. At $r/D{\cong}1.5{\~}2.0$, the vortex rings induce the secondary vortices, resulting in a secondary peak in the Nusselt number there. In the case of H/D=6, the vortex rings change into three-dimensional vortical structures and the small-scale vortices impinge on the flat plate. The increase of turbulent intensity due to small-scale vortices results in the largest Nusselt number at the stagnation point.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.4
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• pp.362-367
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• 1981

Two categories in the design of thick cylinders are suggested and their computer programs are developed; the one termed processing design to ensure the precise inner radius of the cylinder and the other, termd stress compensation design to reduce peak stresses in the cylinder wall. The processing design seeks suitable interference by the method of linear iteration to determine either the radius of the mandrel R or the inner radius ofthe chlinder R$\sub$1/. On the other hand, the stress compensation design seeks first the suitable m and which satisfies the design criteria .sigma.$\sub$actual/ < .sigma.$\sub$allowable/ and then tries to find the suitable interference for given m and .zeta. The design program developed here may be used either in the office at the planning stage of thick chlinders as machine elements of on the processing line to get precise final dimension of inner radius.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.715-720
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• 1997

In this study, the behavior of R/C beam strengthened with carbon fiber laminate(C.F.L) is analyzed from the test results. Test parameters ar the width and the thickness of C.F.L. The failure mode and ultimate load are analyzed from these measured data. Test results shows that the peak load of specimens strengthened with C.F.L. is increased to 1.27~2.04 times of that of non-rehabilitation specimen. The wider lap width, large amount of rehabilitation materials, the larger strength is obtained.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.4
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• pp.255-261
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• 2000

Experiments were carried out to measure the corrosion potential and current density variations in the polarization curves of polypropylene. In particular, the results were examined to identify those influences affecting the corrosion potential, such as temperature, pH, salt, and oxygen. The Tafel slope for the anodic dissolution was determined based on the polarization effect under various conditions. Furthermore, the optimum conditions for the most rapid transformation were establish based on a variety of conditions, including temperature, pH, corrosion rate, and resistance of corrosion potential. The second anodic current density peak and maximum passive current density were designated as the critical corrosion sensitivity(I(sub)r/I(sub)f). This I(sub)r/I(sub)f value was then used to measure the critical corrosion sensitivity of polypropylene. The potentiodynamic parameters of corrosion were obtained using a Tafel plot.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.05a
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• pp.305-308
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• 2008

This paper presents characteristics of soil ionization when high currents such as lightning and switching surge currents are injected into a grounding rod. Soil ionization phenomena are investigated by using both voltage and current signals recorded by oscilloscope. As a result, a critical electric field intensity($E_C$) for ionization is decreased with reduction of grain size. The pre-ionization resistance($R_1$) and post-ionization resistance($R_2$) at the sand with fine grain size are getting lower with increasing current magnitude. Finally, the time to ionization($t_1$) and ionization current peak($t_2$) of fine grain size are significantly shorter than those of medium grain size.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.52 no.9
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• pp.547-553
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• 2003

In this paper, we designed the PC-based analyzer of the power spectral density that could estimate the heart rate variability from time series data of R-R interval. The power spectral density estimated that it applied the autoregressive model to the measured electrocardiogram during a short period. Also, the characteristics of the designed analyzer are that it could process of the signal filtering, the generation and recomposition of time series and the feature extraction at the same time. Especially the analyzer reconstructed which applied the lowpass filter of the time series composed by the linear interpolation so as to enhance the signal-to-noise feature. We could estimate the power spectral density that confirmed a variety of power peak with low frequency range and high frequency rang of autonomic nerve by the heart rate variability.

• The Korean Journal of Ecology
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• v.10 no.1
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• pp.43-51
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• 1987

The forest vegetation of Jongyeoul hill, Seoul, was classified into six secondary forests and two plantations by ZM method; Pinus densiflora, Quercus acutissima, Pinus rigida, Robinia pseudoacacia and Alnus hirsuta-Quercus mongolica community, and Castanea crenata and Pinus koraiensis plantation. In the herb layer the species richness and total coverage of deciduous broad leaf forests showed higher values than those of evergreen needle leaf forests. The peak in July at Q. acutissima forest and in the middle of June at R. pseudoacacia forest. Simpson's diversity index(Ds) in different stands are as follows: Ds>0.6 in R. pseudoacacia forest, Ds=0.3~0.6 in Q. acutissima forest and Ds<0.3 in P. densiflora and P. rigida forest. It is found that, although dominance rank and importance value were originated from different school each other, two measures can be used exchangablym showing almost linear positive correlation between them in this study.