• Analytical Science and Technology
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• v.15 no.4
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• pp.373-380
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• 2002

Humic and fulvic acids present in soil of different depth were extracted and their characteristics were analyzed as a basic study to evaluate the effect of humic substances on the behaviour of radioactive elements deposited on soil. Molecular size distribution of the humic and fulvic acids was measured by stirred cell ultrafiltration technique and the structural informations were obtained from their UV-Vis., IR and synchronous fluorescence (SyF) spectral analysis. Main molecular size ranges of the soil 1) humic and fulvic acids were 30~100 kDa (46~56%) and 10~30 kDa (33~43%) respectively, and their overall molecular sizes were found to became smaller with increasing the soil depth. Absorptivities measured at 280 nm in the UV-Visible spectra of humic acids were 1.4~1.5 times higher than those of fulvic acids, and increased with increasing the soil depth. SyF spectral data showed two distinct peak components having maximum peak positions of 428 nm (type I) and 498 nm (type II) for the soil humic and fulvic acids. From the analysis of the peak components, it was found that humic molecules are mainly made up of aromatic compounds corresponding to longer wavelength (type II), and the molecular components increased with increasing the soil depth. Analysis of IR spectral data indicated that the humic molecules contain a higher relative concentration of carboxylic groups than those of fulvic molecules, and the carboxylic group contents are seen to increase as the soil depth increase.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.122-129
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• 2003

In the case of a AIGalnP/GaP system rectangular parallelepiped high brightness LED which has side walls etched to be slanted off the vertical direction, we have studied the effects of lossy electrodes and material absorption and etching depth and angle of side walls on its light extraction efficiency. If LEDs have no electrodes, in order to obtain an 80％ light extraction efficiency of a TIP (truncated inverted pyramid) LED, the side-etched LEDs should have an etching angle of 22$^{\circ}$~45$^{\circ}$ and an etching depth of 8~17% of a dice height and an absorption coefficient less than 1 $cm^{-1}$ / In case of etching depth of 16~39% of a dice height, we can obtain a 90% light extraction efficiency of a TIP LED. But when LEDs have two electrodes and no absorption loss, in order to obtain an 80％ light extraction efficiency of a TIP LEBs, the side-etched LEDs should have an etching angle of 25$^{\circ}$-45$^{\circ}$ and an etching depth of 30～36% of a dice height. In case of etching depth of 57~71％ of a dice height, we can obtain a 90％ light extraction efficiency of a TIP LED.

• The Journal of the Acoustical Society of Korea
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• v.10 no.3
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• pp.13-18
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• 1991

In this study, the analysis technique of fracture stress using the reflection coefficient of SAW reflected from a brittle solid with surface crack has been studied. Fracture stress of brittle solid with surface crack has been obtained by the function of the critical stress intensity factor and the maximum normalized stress intensity factor of the crack in the body. And the maximum normalized stress intensity factor of a surface crack can be inferred from a measurement of reflection coefficient of SAW. In experiment, the surface cracks ranging from 0.5mm to 0.9mm in crack depth has been made at the center of each Pyrex disc, and the SAW wedge transducer has been set up for the pitch-catch mode. It has been compared the theoretical values of the fracture stress calculated from the reflection coefficient of SAW with the values of the fracture stress measured from UTM.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.4
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• pp.883-891
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• 1990

본 연구에서는 항공기 구조용 재료로서 널리 사용되고 고장력 7075-T73 알루 미늄합금을 준비하고, 균열깊이 a/W변화에 따른 단일과대하중후의 지연현상을 기준응 력확대계수범위 .DELTA.K$_{b}$ 및 과대하중비 %O.L. 과 함께 검토하였다.

• Journal of Korea Soil Environment Society
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• v.1 no.2
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• pp.73-81
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• 1996

The self-diffusion coefficients of chloride and tritiated water ranged from 4.8 $\times$ 10-7 to 7.2 $\times$ 10-7 cm2/sec and 5.5 $\times$ 10-5 to 1.6 $\times$ 10-4 cm2/sec for three different depths of soil constituents at about 50% water content by volume, respectively Mobility of solute and water was conducted under steady-state flow conditions in a field soil consisting of 70 cm of clay to silty clay over a medium sand. A steady-state water flow conditions was maintained by applying irrigation water at a constant flux of 2cm per day. The water labeled with chloride and tritium was leached into the plot during the steady-state condition for 87 days. The positions of tritium and chloride as a function of soil depth and the time was measured by extracting samples of the soil solution with suction probes. Extremes in solute displacement occurred at equal and different depths within the plot. An analysis of these measurements indicated the observations of the pore-water velocity and the apparent diffusion coefficient were log normally disturbed. Twenty-four soil suction probes, used to identify the rate at which a solute was displaced in the soil, will yield an estimate of the mean pore-water velocity of this soils within a range of approximately 5% of its true value providing the effects of potential solute-soil interaction are taken into account.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.2
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• pp.8-15
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• 2021

This study presents post-installed anchors whose heads and extension sleeves are improved. The optimal lengths of the extension sleeves and headers were analytically determined by simulations. As a result of analysis using Finite element method (FEM), 9.0mm and 3.0mm were determined as the optimal lengths of sleeves and headers respectively. In pull-out tests using the improved post-installed anchors, all specimens satisfied the coefficient of variation of 15%. Comparing the pull-out strengths of existing anchors and the improved anchors, it was increased by 1.25 times for anchors embedded with a depth of 50mm, and 1.54 times for 70mm. In the cases of high-strength concrete, the strengths were increased by 1.28 and 1.55 times for 50mm and 70mm respectively. Moreover, as a result of shear tests, the improved anchors perform the greater strength of 1.38 times than the existing anchors.

• Economic and Environmental Geology
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• v.28 no.6
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• pp.553-558
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• 1995

The purpose of this paper is recovery of the profiles of the wave speed and density from the reflection coefficients of the continuously layered acoustic medium with depth dependent density and wave speed at various angles of incidence. A downward continuation or layer stripping algorithm, which recursively reconstructs the medium in increasing depth and then strips away the effects of the reconstructed portion of the medium, is the method with fewer computations than integral equation procedures. This paper implements an improved downward continuation algorithm that uses reflection data at several angles of incidence and performs a least-squares fitting at each depth. The result is a considerable improvement in performance over the usual downward continuation algorithm.

• Tunnel and Underground Space
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• v.13 no.1
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• pp.20-32
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• 2003

To understand the behavior of migration of contaminants in a fractured porous medium is a key to assure the overall safety of a potential radwaste repository. The feasible retention mechanism of contaminant transport in a tinctured medium are sorption of contaminants on solid surface and matrix diffusion of contaminants from a fracture into an adjacent porous medium. The acceleration mechanisms are the migration of contaminants in the form of pseudo-colloids and the limit of a volume f3r matrix diffusion. In this paper, the effects of these two acceleration mechanisms are studied mathematically, then semi-analytically computed by the application of the Talbot theorem and verified. Results indicate that the acceleration processes cannot be neglected in the modeling of contaminant transport in a fractured porous medium.

• Journal of the Korean Geotechnical Society
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• v.33 no.12
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• pp.21-33
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• 2017

This paper presents the analysis of plugging effect especially when the large diameter steel pipe pile was installed by considering driveability (BPM, blow per meter). The Coupled Eulerian-Lagrangian (CEL) technique was used to simulate the driving of open-ended piles into soil. To consider the driveability, the applied driving energy for each pile was obtained from the analysis results by using the wave equation. The parametric studies were performed for different pile diameters, penetration depths of pile, soil elastic modulus and BPM. It was found that the SPI is almost constant with increasing both the pile diameter and the required driving energy. It is also found that the plugging effect increases with increasing the pile length, resulting in the increase of lateral earth pressure. Based on this study the apparent magnitude and distribution of the lateral earth pressure is proposed for inside portion mobilizing soil plug.

• Journal of the Korean Geotechnical Society
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• v.20 no.1
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• pp.21-27
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• 2004

In this test, there was two-dimensional model loading test implemented for analysis with respect to the problem of evaluating bearing capacity and the application range on the dredged and reclaimed ground, so it was possible to get the following result by comparing a result of loading test and an equation proposed previously. When the difference between average undrained shea. strength by (equation omitted)B of loading board width and the strength under. (equation omitted)B is mere than $\pm50%$, the applicability of Nc(coefficient of bearing capacity where $\phi=0$ analysis is considered in the single layer) was declined. As well, using Nc=5.7, 5.14(coeffcient of bearing capacity where $\phi=0$ analysis is applicable to saturated clay without special limit) for evaluating bearing capacity on the dredged and reclaimed ground causes poor applicability, therefore that seem to be applicable when water content is less than about 75% which makes the unconfined compression test possible.