• Computational Structural Engineering
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• v.9 no.4
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• pp.189-198
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• 1996

The fracture behaviour of concrete gravity dam mainly due to uplift pressure acting at the crack face was studied. Triangular type and parabolic type distribution of the uplift pressure including uniform type were first considered in case of calculating stress intensity factor(SIF) by the surface integral method. Second, the directions of crack propagation according to the uplift pressure distribution were pursued by FRANC(FRacture ANalysis Code). Third, critical crack lengths according to the uplift pressure distribution under the overflow depth were calculated. The SIF values obtained from the surface integral method were compared with those by FRANC and relatively good agrements could be obtained between both of them. And it could be seen that the direction of crack propagation in case of triangular pressure distribution was a little benter to the dam base than the one by the uniform type. Maximum critical crack lengths under the overflow depth were obtained at about 2/5-1/2 of the dam height.

• The Journal of the Acoustical Society of Korea
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• v.20 no.6
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• pp.75-81
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• 2001

In this paper we analyzed the localization error of near-field detection algorithm in the sea. The near-field detection algorithms using triangulation and wavefront curvature basically assume a signal in two dimension of bearing and range. But the assumption causes localization error because there is three dimension of bearing, range, and depth in the sea. Even through three dimensional effect is considered, the localization error is occurred if multipath propagation in the sea is ignored. To analyze the localization error in the sea, we simulate the near-field localization using acoustic propagation model and focused beamforming considering wavefront curvature. The simulation results indicate that localization error always occurs in the sea and the error varied with sound velocity profile, water depth, bottom slope, source range, etc.

• Korean Journal of Remote Sensing
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• v.31 no.4
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• pp.281-291
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• 2015

Sun glint correction methods of hyperspectral data that have been developed so far have not considered the various situations and are often adequate for only certain conditions. Also there is an inaccurate assumption that the signal in NIR wavelength is zero. Therefore, this study attempts to analyze the NIR spectral properties of sun glint effect in coastal waters. For the analysis, CASI-1500 airborne hyperspectral data, bathymetry data and in-situ data obtained at coastal area near Sin-Cheon, Jeju Island, South Korea were used. The spectral characteristics of radiance and reflectance at the five NIR wavelengths (744 nm, 758 nm, 772 nm, 786 nm, and 801 nm) are analyzed by using various statistics, spatial and spectral variation of sun-glinted area under conditions of the bottom types of benthos, barren rocks and sand with similar water depth. Through the quantitative analysis, we found that the relation of water depth or bottom type with sun glint is relatively less which is a similar result with the previous studies. However the sun glint are distributed similarly with the patterns of the direction of wave propagation. It is confirmed that the areas with changed direction of wave propagation were not affected by the sun glint. The spatial and spectral variations of radiance and reflectance are mainly caused by the effect of sun glint and waves. The radiance or reflectance of more sun-glinted areas are increased approximately 1.5 times and the standard deviations are also increased three times compared to the less sun glinted areas. Through this study, the further studies of sun glint correction method in coastal water using the patterns of wave propagation and diffraction will be placed.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.175-180
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• 2003

Ultrasonic pulse velocity method is applied many times for measuring surface crack depth of concrete in case of diagnosis of concrete structures. By the way, this method has an error accompanying measured surface crack depth of concrete because there are many uncertainty factors. So, it is necessary to study for an error of this method affected by these uncertainty factors. Two error factors(uncertainty factors) are tested and analyzed in this study. One is for an error according to measuring the propagation time of ultrasonic wave and the arrangement distance of transducers. Another is for an error according to positioning the transducer as a distance to surface crack from the transducer.

• Journal of Industrial Technology
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• v.26 no.B
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• pp.101-110
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• 2006

The purpose of this study was to investigate the flexural, interfacial behavior, crack propagation, nonlinear behavior, effect repaired and rehabilitated with VES-LMC using RC beam with 4-point-loading test. The results were following: The test result showed that repair and rehabilitation effect increased as its depth increased, which was verified by the increase of flexural stiffness. More than 40% of stiffness was improved when the depth of repair was up to steel position. However, there was a little difference between 8cm and 12cm repaired beam. This means the repair depth must be considered. The interfacial behavior data showed that the repaired or rehabilitated beams had a little relative displacement. This means that two materials behave comparatively acting together. This suggested that interface treatment were one of the most important jobs in composite beams.

• The Journal of the Acoustical Society of Korea
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• v.6 no.2
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• pp.48-53
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• 1987

The depth dependent sound fields have been calculated for a single frequency source to reveal the fluctuating sound energy at both near the surface and the bottom of the water layer. Those fluctuation are mainly due to the mode function behavior along the depth where the sound-speed gradient acts like trapping lower mode sound energy in those medium.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.321-323
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• 2004

We developed the monte-carlo simulation code for analysis of the On signal in dental medium. In calculation, we obtain the two different propagation signals as a function of the probing depth. Signal 2 begins to exceed the signal 1 at a very small probing depth(=60${\mu}{\textrm}{m}$). For reduce the signal, detection area is limited to radius and detection angle. As numerical result, probing depth becomes appoximately 500${\mu}{\textrm}{m}$.

• Journal of the Korean Society of Industry Convergence
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• v.25 no.2_2
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• pp.233-238
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• 2022

This study evaluated the fatigue limit depending on microcracks using 0.57 wt.% carbon steel with different Vickers hardness. The fatigue limit was almost constant up to a certain limit regardless of the carbon content. However, the fatigue limit decreased rapidly as the size of the crack increased. As the crack aspect ratio was smaller, the fatigue limit of the depth (point A) a lot decreased. The fatigue limit ratio of the depth decreased significantly because the crack propagation in the depth direction was fast as the crack aspect ratio became smaller. On the other hand, the fatigue limit ratio of surface cracks increased as the crack aspect ratio decreased.

• Korean Journal of Optics and Photonics
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• v.11 no.6
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• pp.385-389
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• 2000

A phase-retardation function which was derived from Wigner distribution function (WDF) is used to increase a focal depth of a radially symmetric optical system. The WDF for one-dimensional signal is represented as a two-dimensional function of phasespace ($\chi,\zeta$), and a normalized irradiance is described as a form of the Strehl ratio (SR). The increase in the focal depth is accomplished by delivering a shearing tilt a that represents a characteristic of free space propagation with simple manipulation in the WDF space. In this paper we propose a method for evaluating the focal depth quantitatively by representing the phaseretardation function in terms of the focal depth term. In order to verify the validity of the proposed method, we compared the numerically analyzed result with that of J. Sochki's study. study.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.833-840
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• 2007

The experimental study was carried out to investigate propagation distance of flood wave due to levee breach in a flat inundation area without obstacle. Hitter solution was considered to formulate the experimental results and a representative form was written referring to existing researches. As a result of experiments, it was found that the propagation velocity of the wave front in inundation area was significantly influenced by the initial water level in a channel, which was similar to flow in a channel due to dam break. An empirical formula was also suggested using the experimental results. The dimensionless propagation distance L can be written as the power function of dimensionless time T Coefficients k and m were varied with the dimensionless time T whereas k and m in Ritter solution were 2 and 0, respectively. The variation of coefficients in the relationship between L and T was influenced by the water depth in the inundation area and the fact proved that the changing points of L in the slope of relationship between L and T are the same to those of relationship between the dimensionless maximum water depth in the inundation area, $h_{max}$ and L.