• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.08a
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• pp.217-225
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• 2004

Introduction of wave model, considered the effect of shoaling, refraction, diffraction, partial reflection, bottom friction, breaking at the coastal waters of complex bathymetry, is a very important factor for most coastal engineering design and disaster prevention problems. As waves move from deeper waters to shallow coastal waters, the fundamental wave parameters will change and the wave energy is redistributed along wave crests due to the depth variation, the presence of islands, coastal protection structures, irregularities of the enclosing shore boundaries, and other geological features. Moreover, waves undergo severe change inside the surf zone where wave breaking occurs and in the regions where reflected waves from coastline and structural boundaries interact with the incident waves. Therefore, the application of mild-slope equation model in this field would help for understanding of wave transformation mechanism where many other models could not deal with up to now. The purpose of this study is to form a extended mild-slope equation wave model and make comparison and analysis on variation of harbor responses in the vicinities of Ulsan Harbor and Ulsan New Port, etc. due to construction of New Port in Ulsan Bay. This type of trial might be a milestone for port development in macro scale, where the induced impact analysis in the existing port due to the development could be easily neglected.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1447-1454
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• 2013

In this study, we developed the equation of ship wave crests in intermediate as well as deep waters by extending Kelvin's (1887) theory using the recursive relation for the dispersion relation. The present equation can be applied for varying water depth as well as constant water depth. Using FLOW-3D we conducted numerical experiments to verify analytical prediction. The ship wave crest patterns became asymmetric on a plane slope when the ship propagates alongshore direction. That is, in shallower side, wave crests tend to be parallel to the coastline due to refraction and, in deeper side, wave crests tend to be orthogonal due to reverse refraction.

• Geophysics and Geophysical Exploration
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• v.5 no.3
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• pp.178-184
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• 2002

For economy and convenience, seismic refraction survey is widely used in surveying for large civil engineering work. The purpose of this study is to obtain the numerical responses of various models using Kirchhoff migration, and to analyze its application to the real data processing. Synthetic traveltime curve was calculated by vidale's algorithm, and various models such as 2 or 3 layer model and irregular topography model are tested to simulate the response of real structure. In order to compare the effect of initial velocity model, true velocity models, inversion results by tomography, smooth velocity models are used as an initial guess. The responses of model data show that the algorithm of this study is more sensitive to initial velocity model than the reflection survey, so choosing a suitable initial velocity model will be the most important thing in real data processing.

• Journal of the Korean Society of Clothing and Textiles
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• v.9 no.2
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• pp.75-84
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• 1985

In order to improve dyeing and finishing technology of thin cloth of microfiber(super-fine fiber), the degrees of deep dyeing method, the light fastness, and the washing fastness were investiagted. 1. The thin cloth made of microfiber, $0.15^d\~0.2^d$, was conjugated type and the dyeing degree was lower at 5 to $10\%$ than that of cloth made of common fiber. The cloth of excellent dyeing fastness, light fastness, was developed by increasing the concentration of dye of high quality up to $5\~10\%$. 2. Because refractory rate of microfiber of $0.2^d$ was lower than that of $0.01^d$, the surface refractory rate of $0.2^d$ was lower than that of $0.01^d$ fiber. Therefore the surface of micro-fiber, $0.2^d$, was more rougher than that of $0.01^d$ and it belongs to separate type. 3. The higher degree of dyeing was increased by using dye of microparticle. Also the degree of textile printing was increased by adding urea solution ($20\%$) and glycerine diethylene glycol. 4. Light fastness was very excellent, marked 5 grade. However, washing fastness was 2$\~$3 grade. After dyeing, we could improve to 4 grade, through hot water washing including some organic chlorine solvent. 5. Super microfiber of $0.01^d$ will not be dyed by present dye and dyeing equipment, because right reflection light rate(white light) of fiber surface was too high and the more refraction rate higher the more surface refraction rate will be increased.

• Journal of Korean Clinical Health Science
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• v.2 no.4
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• pp.239-246
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• 2014

Purpose. to describe the prevalence of refractive error according to aging in young children in South Korea. Methods : From July 2013 to June 2014, five hundred subjects( 250 male subjects, 250 female subjects; aged between 7 and 12 years) were performed in refraction test using the Auto-Refraction. Myopia, hyperopia, astigmatism, and anisometropia were defined as spherical equivalent(SE)${\leq}-0.50$ diopters, SE ${\geq}+2.00$ D, cylinder error ${\geq}0.75$ D and SE difference${\geq}1.00$ D between binocular eyes, respectively. Results. The refractive error by spherical equivalent among all subjects was myopia 80.41%, astigmatism 44.89%, emmetropia 18.27%, anisometropia 16.92%, and hyperopia 1.32%. The prevalence of myopia increased with age. but hyperopia was decrease. Myopia and astigmatism were much more common in male than females although the difference was not statically significant. Emmetropia and hyperopia were much more common in female than males although the difference was not statically significant. The prevalence of spherical equivalent was much common from -1.00 diopter to 0.99 diopter. On the other hand, the prevalence of myopia was much more than hyperopia. There was a statistical significance between 9 year and 10 year of female in the spherical equivalent power(p>0.05). In all another group of age, there was not a statistical significance as aging in spherical equivalent power(p>0.5). However, there was a statistical significance between male and female as age in the spherical equivalent power(P>0.01). Conclusions: Myopia was the most common refractive error in Korea young children, while hyperopia was decreased after 7 years. There was a statistical significance as age between male and female at spherical equivalent power(P> 0.01). these results suggested that the analysis of the refractive error as age at young children can give the useful diagnosis data for the correction of visual function.

• Journal of Korean Ophthalmic Optics Society
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• v.10 no.1
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• pp.47-52
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• 2005

The purpose of this study was to provide the accurate information on improvement of visual life by examining old age's eye refraction state and investigating distribution of ametropia in old age. The test was performed the visual acuity test by object and subject methods to over 60 years of age. The results were as follows: 1. As the result to investigate the inconvenience degree of visual life, the subjects appealed 81% for very inconvenience and 14% for a little inconvenience. 5% of them didn't feel any inconvenience in visual life. 2. The eye types were 1.7% for emmetropia, 10% for myopia, 74.7% for hyperopia, and 13.6% mixed astigmatism, respectively. 3. The axis of astigmatisms were 65% positive for indirect astigmatism, 8% for direct astigmatism, and 27% for oblique astigmatism, respectively.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.281-281
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• 2010

Very low refractive index (<1.4) materials have been proved to be the key factor improving the performance of various optical components, such as reflectors, filters, photonic crystals, LEDs, and solar cell. Highly porous SiO2 are logically designed for ultralow refractive index materials because of the direct relation between porosity and index of refraction. Among them, ordered macroporous SiO2 is of potential material since their theoretically low refractive index ~1.10. However, in the conventional synthesis of ordered macroporous SiO2, the time required for the crystallization of organic nanoparticles, such as polystyrene (PS), from colloidal solution into well ordered template is typical long (several days for 1 cm substrate) due to the low interaction between particles and particle - substrate. In this study, polystyrene - polyacrylic acid (PS-AA) nanoparticles synthesized by miniemulsion polymerization method have hydrophilic polyacrylic acid tails on the surface of particles which increase the interaction between particle and with substrate giving rise to the formation of PS-AA film by simply spin - coating method. Less ordered with controlled thickness films of PS-AA on silicon wafer were successfully fabricated by changing the spinning speed or concentration of colloidal solution, as confirmed by FE-SEM. Based on these template films, a series of macroporous SiO2 films whose thicknesses varied from 300nm to ~1000nm were fabricated either by conventional sol - gel infiltration or gas phase deposition followed by thermal removal of organic template. Formations of SiO2 films consist of interconnected air balls with size ~100 nm were confirmed by FE-SEM and TEM. These highly porous SiO2 show very low refractive indices (<1.18) over a wide range of wavelength (from 200 to 1000nm) as shown by SE measurement. Refraction indices of SiO2 films at 633nm reported here are of ~1.10 which, to our best knowledge, are among the lowest values having been announced.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.10-15
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• 2012

Wave characteristics in the presence of energy damping are investigated using the linear shallow water equations. To get the phase and energy velocities, geometric optics approach is used and then these values are validated through numerical experiments. Energy damping affects wave height, phase and energy velocities which result in wave transformation. When the complex wavenumber is used by the Eulerian approach, it is found that the phase velocity decreases as the damping increases while the energy velocity increases showing higher values than the phase velocity. When the complex angular frequency is used by the Lagrangian approach, the energy-damping wave group is found to propagate in the energy velocity. The energy velocity is found to affect shoaling and refraction coefficient which is verified through numerical experiments for waves on a plane slope.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.19 no.6
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• pp.565-573
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• 2007

The effect of wave and current interactions on irregular wave transformation over a submerged elliptic shoal is investigated based on numerical simulations of the Vincent and Briggs experiment [Vincent, C.L., Briggs, M.J., 1989. Refraction-diffraction of irregular waves over a mound. Journal of Waterway, Port, Coastal and Ocean Engineering, 115(2), pp. 269-284]. The numerical simulations are conducted by a combination of REF/DIF S(a wave model) and SHORECIRC(a current model) and a time dependent phase-resolving wavecurrent model, FUNWAVE. In the simulations, the breaking-induced currents defocus waves behind the shoal and bring on a wave shadow zone that shows relatively low wave height distributions. The computed results of the combined model system agree better with the measurements than the computed results obtained by neglecting wave-current interaction do. In addition, the results of FUNWAVE show a good agreement with the measurements. The agreement indicates that it is necessary to take into account the effect of breaking-induced current on wave refraction when wave-breaking occurs over a submerged shoal.

• Economic and Environmental Geology
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• v.36 no.6
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• pp.501-510
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• 2003

Several geophysical surveys(electrical resistivity, electromagnetic, seismic refraction, CPR) were conducted to primarily investigate the gallery and the geomembrane at an abandoned mine(Imcheon mine). The subsurface structure mapped from seismic refraction survey mainly consists of three velocity layers(>1000 m/s, 1000∼2000 m/s,＜2000 m/s). Top of the bedrock, whose velocities exceed 2000 m/s, appears to be at depth of 7.5∼10m. Higher resistivities (of ten thousands-hundred of thousands ohm-m) are interpreted to be associated with a open(cavities) gallery. The events at depth of approximately 0.5∼0.7m in GPR sections are probably caused by high-density-poly-ethylene geomembrane. Taking into consideration of the differences in the spatial resolution between georadar and electrical surveys, the events of geomembrane correspond to the top of the high resistivities at depth of about 2m. The segments, characterized with the higher conductivities in the electromagnetic data and the lower resistivities in the electrical resistivity data, are probably associated with surface water or tear zone of geomembrane.