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

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1996.06a
• /
• pp.422-448
• /
• 1996

Low-temperature epitaxial growth of Si and SiGe layers of Si is one of the important processes for the fabrication of the high-speed Si-based heterostructure devices such as heterojunction bipolar transistors. Low-temperature growth ensures the abrupt compositional and doping concentration profiles for future novel devices. Especially in SiGe epitaxy, low-temperature growth is a prerequisite for two-dimensional growth mode for the growth of thin, uniform layers. UHV-ECRCVD is a new growth technique for Si and SiGe epilayers and it is possible to grow epilayers at even lower temperatures than conventional CVD's. SiH and GeH and dopant gases are dissociated by an ECR plasma in an ultrahigh vacuum growth chamber. In situ hydrogen plasma cleaning of the Si native oxide before the epitaxial growth is successfully developed in UHV-ECRCVD. Structural quality of the epilayers are examined by reflection high energy electron diffraction, transmission electron microscopy, Nomarski microscope and atomic force microscope. Device-quality Si and SiGe epilayers are successfully grown at temperatures lower than 600℃ after proper optimization of process parameters such as temperature, total pressure, partial pressures of input gases, plasma power, and substrate dc bias. Dopant incorporation and activation for B in Si and SiGe are studied by secondary ion mass spectrometry and spreading resistance profilometry. Silicon p-n homojunction diodes are fabricated from in situ doped Si layers. I-V characteristics of the diodes shows that the ideality factor is 1.2, implying that the low-temperature silicon epilayers grown by UHV-ECRCVD is truly of device-quality.

• Proceedings of the Korea Association of Crystal Growth Conference
• /
• 1996.06a
• /
• pp.508-508
• /
• 1996

;The growth of films have considerable interest in the field of superlattice structured multi-layer epitaxy led to realization of new devices concepts. Molecular beam epitaxy (MBE) with in situ observation by reflection high-energy electron diffraction (RHEED) is a key technology for controlled layered growth on the atomic scale in oxide crystal thin films. Also, the combination of radical oxygen source and MBE will certainly accelerate the progress of applications of oxides. In this study, the growth process of single crystal films using by MBE method is discussed taking the oxide materials of Bi-Sr-Ca-Cu family. Oxidation was provided by a flux density of activated oxygen (oxygen radicals) from an rf-excited discharge. Generation of oxygen radicals is obtained in a specially designed radical sources with different types (coil and electrode types). Molecular oxygen was introduced into a quartz tube through a variable leak valve with mass flowmeter. Corresponding to the oxygen flow rate, the pressure of the system ranged from $1{\;}{\times}{\;}10^{-6}{\;}Torr{\;}to{\;}5{\;}{\times}{\;}10^{-5}$ Torr. The base pressure was $1{\;}{\times}{\;}10^{-10}$ Torr. The growth of Bi-oxides was achieved by coevaporation of metal elements and oxygen. In this way a Bi-oxide multilayer structure was prepared on a basal-plane MgO or $SrTiO_3$ substrate. The grown films compiled using RHEED patterns during and after the growth. Futher, the exact observation of oxygen radicals with MBE is an important technology for a approach of growth conditions on stoichiometry and perfection on the atomic scale in oxide. The oxidization degree, which is determined and controlled by the number of activated oxygen when using radical sources of two types, are utilized by voltage locked loop (VLL) method. Coil type is suitable for oxygen radical source than electrode type. The relationship between the flux of oxygen radical and the rf power or oxygen partial pressure estimated. The flux of radicals increases as the rf power increases, and indicates to the frequency change having the the value of about $2{\times}10^{14}{\;}atoms{\;}{\cdots}{\;}cm^{-2}{\;}{\cdots}{\;}S^{-I}$ when the oxygen flow rate of 2.0 seem and rf power 150 W.150 W.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.13 no.3
• /
• pp.185-192
• /
• 1993

A numerical model has been used for the prediction of wave agitations in a harbor which are induced by the intrusion and transformation of incident waves. Based on linear wave theory a mild-slope equation has been used. A partial absorbing boundary condition has been used on solid boundary. Functional has been derived following Chen and Mei(l974)'s technique based on Hybrid Element Method which uses finite discretisation in the inner region and analytical solution of Helmholtz equation in the outer region. Final simultaneous equation has been solved using the Gaussian Elimination Method. Helmholtz natural period and second peak period of seiche in Donghae Harbor coincide very well with the results from numerical calculation. Computed amplification factors show good agreement, especially when the reflection coefficient on solid boundary is 0.99, with those of measurements.

• Journal of Ocean Engineering and Technology
• /
• v.30 no.6
• /
• pp.505-519
• /
• 2016

If the seabed is exposed to high waves for a long period, the pore water pressure may be excessive, making the seabed subject to liquefaction. As the water pressure change due to wave action is transmitted to the pore water pressure of the seabed, a phase difference will occur because of the fluid resistance from water permeability. Thus, the effective stress of the seabed will be decreased. If a composite breakwater or other structure with large wave reflection is installed over the seabed, a partial standing wave field is formed, and thus larger wave loading is directly transmitted to the seabed, which considerably influences its stability. To analyze the 3-D dynamic response characteristics of the seabed around a composite breakwater, this study performed a numerical simulation by applying LES-WASS-3D to directly analyze the wave-structure-soil interaction. First, the waveform around the composite breakwater and the pore water pressure in the seabed and rubble mound were compared and verified using the results of existing experiments. In addition, the characteristics of the wave field were analyzed around the composite breakwater, where there was an opening under different incident wave conditions. To analyze the effect of the changed wave field on the 3-D dynamic response of the seabed, the correlation between the wave height distribution and pore water pressure distribution of the seabed was investigated. Finally, the numerical results for the perpendicular phase difference of the pore water pressure were aggregated to understand the characteristics of the 3-D dynamic response of the seabed around the composite breakwater in relation to the water-structure-soil interaction.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.12C
• /
• pp.1193-1200
• /
• 2005

In this paper, we proposed an image hiding method which decreases the amount of calculation encrypting partial data rather than the whole image data using a discrete wavelet transform and a linear scalar quantization which have been adopted as the main technique in JPEG2000 standard and then implemented the proposed algorithm to hardware. A chaotic system was used instead of encryption algorithms to reduce further amount of calculation. It uses a method of random changing method using the chaotic system of the data in a selected subband. For ciphering the quantization index it uses a novel image encryption algorithm of cyclical shifting to the right or left direction and encrypts two quantization assignment method (Top-down coding and Reflection coding), made change of data less. The experiments have been performed with the proposed methods implemented in software for about 500 images. The hardware encryption system was synthesized to find the gate-level circuit with the Samsung $0.35{\mu}m$ Phantom-cell library and timing simulation was performed, which resulted in the stable operation in the frequency above 100MHz.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.6 no.2
• /
• pp.139-149
• /
• 1994

In this paper, a finite element technique is applied to the prediction of the wave resonance phenomena in harbors. The mild-slope equation is used with a partial reflection boundary condition introduced to model the energy dissipating effects on the solid boundary. For an efficient modeling of the radiation condition at infinity, a new infinite element is developed. The shape function of the infinite element is derived from the asymptotic behavior of the first kind of the Hankel's function in the analytical boundary series solutions. For the computational efficiency, the system matrices of the element are constructed by performing the relevant integrations in the infinite direction analytically. Comparisons with the results from experiments and other solution methods show that the present model gives fairly good results. Numerical experiments are also carried out to determine the proper distance to the infinite elements from the mouth of the halter, which directly affect the accuracy and efficiency of the solution.

• Journal of Ocean Engineering and Technology
• /
• v.19 no.1 s.62
• /
• pp.39-43
• /
• 2005

The study investigated the nondestructive characteristics of damage, caused by law-velocity impact, on symmetric cross-ply laminates, composed of [0o/90o]16s, 24s, 32s, 48s. The thickness of the laminates was 2, 3, 4 and 6 mm, respectively. The impact machine used, Model 8250 Dynatup Instron, was a drop-weight type that employed gravity. The impact velocities used in this experiment were 0.75, 0.90, 1.05, 1.20 and 1.35 m/sec, respectively. Both the load and the deformation increased when the impact velocity was increased. Further, when the load increased with the laminate thickness in the same impact velocity, the deformation still decreased. The extensional velocity was quick, as the laminate thickness increased in the same impact velocity and the impact velocity increased in the same laminate thickness. In the ultrasonic scans, the damaged area represented a dimmed zone. This is due to the fact that the wave, after the partial reflection by the deflects, does not have enough energy to touch the opposite side or to come back from it. The damaged laminate areas differed, according to the laminate thickness and the impact velocity. The extensional velocities are lower in the 0o direction and higher in the 90o direction, when the size of the defect increases. However, it was difficult to draw any conclusion for the extensional velocities in the 45o direction.

• Smart Structures and Systems
• /
• v.12 no.3_4
• /
• pp.251-269
• /
• 2013

Measurement of deflections of certain bridges is usually hampered by corruption of the GPS signal by multipath associated with passing vehicles, resulting to unrealistically large apparent displacements. Field data from the Gorgopotamos train bridge in Greece and systematic experiments revealed that such bias is due to superimposition of two major effects, (i) changes in the geometry of satellites because of partial masking of certain satellites by the passing vehicles (this effect can be faced with solutions excluding satellites that get temporarily blocked by passing vehicles) and (ii) dynamic multipath caused from reflection of satellite signals on the passing trains, a high frequency multipath effect, different from the static multipath. Dynamic multipath seems to have rather irregular amplitude, depending on the geometry of measured satellites, but a typical pattern, mainly consisting of a baseline offset, wide base peaks correlating with the sequence of main reflective surfaces of the vehicles passing next to the antenna. In cases of limited corruption of GPS signal by dynamic multipath, corresponding to scale distortion of the short-period component of the GPS waveforms, we propose an algorithm which permits to reconstruct the waveform of bridge deflections using a weak fusion of GPS and RTS data, based on the complementary characteristics of the two instruments. By application of the proposed algorithm we managed to extract semi-static and dynamic displacements and oscillation frequencies of a historical railway bridge under train loading by using noisy GPS and RTS recordings. The combination of GPS and RTS is possible because these two sensors can be fully collocated and have complementary characteristics, with RTS and GPS focusing on the long- and short-period characteristics of the displacement, respectively.

• Korean Journal of Agricultural Science
• /
• v.47 no.4
• /
• pp.995-1010
• /
• 2020

In this study, a multivariate analysis model of partial least square regression (PLSR) was developed to predict the moisture content of green peppers using hyperspectral imaging (HSI). In HSI, illumination is essential for high-quality image acquisition and directly affects the analytical performance of the visible near-infrared hyperspectral imaging (VIS/NIR-HSI) system. When green pepper images were acquired using a direct lighting system, the specular reflection from the surface of the objects and their intensities fluctuated with time. The images include artifacts on the surface of the materials, thereby increasing the variability of data and affecting the obtained accuracy by generating false-positive results. Therefore, images without glare on the surface of the green peppers were created using a polarization filter at the front of the camera lens and by exposing the polarizer sheet at the front of the lighting systems simultaneously. The results obtained from the PLSR analysis yielded a high determination coefficient of 0.89 value. The regression coefficients yielded by the best PLSR model were further developed for moisture content mapping in green peppers based on the selected wavelengths. Accordingly, the polarization filter helped achieve an uniform illumination and the removal of gloss and artifact glare from the green pepper images. These results demonstrate that the HSI technique with a polarized lighting system combined with chemometrics can be effectively used for high-throughput prediction of moisture content and image-based visualization.