• Journal of Korean Society for Geospatial Information Science
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• v.6 no.2 s.12
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• pp.133-141
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• 1998

Terrain modelling is composed of a method using the rectangular grid and another using the triangulated irregular network. The method using the triangulated irregular network is most widely used because it can express the characteristics of the terrain well with only a small amount of information on the terrain and also reduces the rendering time. The process of extracting the surface-specific point and a triangular process is needed to construct such triangulated irregular network. This paper concentrates on the process of extracting the surface-specific point. The 8-direction neighborhood method and other transformed methods of the former method are frequently used to extract the surface-specific point. Another method which eliminates the unnecessary points using the Polygon reduction method is also suggested However, the 8-direction neighborhood method has a big fault of also drawing out some unnecessary points. To resolve such problem, we suggest a method of extracting the surface-specific point using the cross section of the terrain. This method reduces the time to extract the surface-specific point and enables a more precise extraction with less terrain information.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.6
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• pp.382-390
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• 2015

To simulate a complicated hydrodynamic phenomena in the surf zone, the SWASH model is used in Haeundae Beach. The SWASH model is well known as a model competing with the Boussinesq-type model in terms of near shore waves and wave-induced currents modelling. This study is aimed to the detailed analysis of seasonal waves and wave-induced current simulation in Haeundae Beach, where the representative seasonal wave conditions was obtained from hourly measured wave data in 2014 by Korea Hydrographic and Oceanographic Administration( KHOA). Incident wave conditions were given as irregular waves by JONSWAP spectrum. The calculated seasonal wave-induced current patterns were compared with the field observation data. In summer season, a dominant longshore current toward the east of the beach appears due to the effect of incident waves from the South and the bottom bathymetry, then some rip currents occurs at the central part of the beach. In the winter season, ESE incident waves generates a strong westward longshore currents. However, a weak eastward longshore currents appears at the restricted east side areas of the beach.

• Microbiology and Biotechnology Letters
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• v.26 no.2
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• pp.143-150
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• 1998

Many enzymes catalyze a primary reaction and/or secondary reaction. Dextransucrase usually synthesize dextran from sucrose as a primary reaction. The secondary reaction of dextransucrase is the transfer of glucose from sucrose to carbohydrate accepters. We have reacted dextransucrase from Leuconostoc mesenteroides B-742CB with sucrose and starches; granule or gelatinized starches, and Small or Potato starches. The yield of modified starch was ranged from 46% to 72%(s.d.<${pm}$5%) of theoretical depends on various reaction conditions. Modified products were more resistant against the hydrolysis of ${alpha}$-amylase, isoamylase, pullulanase and endo-dextranase than those of native starch. Based on the reactions from enzyme hydrolysis and methylation followed by acid hydrolysis modification of granule starch was more efficient than the modification of gelatinized starch. After modification of granule starch with dextransucrase, there produced a soluble modified starch. After modification the starch granules were fractionated to small size. The positions of glucose substitution of the modified products were determined by methylation followed by acid hydrolysis and analyzed by TLC. The products were modified by the addition of glucose to the position of C3, C4 and C6 free hydroxyl group of glucose residues in the starch.

• Journal of the Earthquake Engineering Society of Korea
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• v.11 no.2 s.54
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• pp.81-94
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• 2007

In most experimental researches on the liquefaction phenomenon, an earthquake as a random vibration has been regraded as a sinusoidal wave or a triangular wave with an equivalent amplitude. Together with the development in the part of signal control and data acquisition, dynamic experimental equipments in the soil dynamics have also developed rapidly and further more, several real earthquakes have been simulated in the large model test such as shaking table tests and centrifuge tests. In Korea, several elementary laboratory tests to simulate the real earthquake load were performed. From these test results, it was reported that the sinusoidal wave cannot reliably reflect the soil dynamic behavior under the real earthquake motion. In this study, 4 types of dynamic motions such as the sinusoidal wave, the triangular wave, the incremental triangular wave and several real earthquake motions which were classified with shock-type and vibration-type were loaded to find something new to explain the change of the excess pore water pressure under the real earthquake load. Through the detailed investigation and comparison on all test results, it is found that the dynamic flow is generated by the soil plastic deformation and the velocity head of dynamic flow is changed the pressure head in the un-drained condition. It can be concluded that the change of the excess pore water pressure is related to the pressure head of dynamic flow. Lastly, a new hypothesis to explain such a liquefaction initiation phenomenon under the real earthquake load is also proposed and verified.

• Composites Research
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• v.26 no.4
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• pp.223-229
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• 2013

Hybrid composite strut tower was designed to prevent permanent deformation of upper mount by the impact from the uneven road. When exceeding energy absorption capacity of tire and suspension systems, residual impact is delivered to upper mount. Especially, in case of using high-rigidity suspension system for high driving performance, the conventional strut tower can be easily deformed due to reduction of energy absorption capacity of suspension systems. In this study, optimal design of hybrid composite strut tower which made of back-up metal and carbon fiber reinforced composite was suggested by using finite element analysis, and low velocity impact test was performed to investigate their dynamic characteristics. Also, 3D measuring and ultra c-scanning methods were carried out to diagnose damages in the strut towers.

• Journal of Ocean Engineering and Technology
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• v.3 no.2
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• pp.45-50
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• 1989

원유의 발견과 함께 북극의 개발이 활발해저왔고, 지역의 특수한 환경적인 요건으로 인해 시설물의 개발, 설치, 이동, 운용에 많은 어려움을 갖고 있다. 특히 빙산에 의한 극지 해안가의 해저면은 파이고, 손상되고, 변형된다. 북 알라스카의 해저면을 고르지 못하고, 불규칙하게 파이고, 손상된 형태를 보여주고, 특히 빙산의 활동이 활발한 지역과 시기에는 그 손상이 더욱 심하고, 자주 일어난다. 빙산에 의한 해저면의 홈은 빙산 해저 끝이 해저면에 접촉하여 해저 바닥을 파 나갈때 일어나는 현상이다. 빙산의 운동에너지는 해저면을 파 나가는 에너지로 변형되고, 그 힘이 평형하게 될 때까지 빙산의 운동은 계속된다. 빙산에 의한 해저면 손상은 극지 해안가의 해저시설물의 설계, 설치, 운용에 중대한 영향을 끼친다. 그러므로, 해저면 손상의 데이타 분석은 해안의 개발과 시설물의 설치에 큰 도움이 된다. 이 논문에서는 8년간에 걸친 약 십만개가 넘는 데이타를 토대로 알라스카 뷰오포트 해안가의 빙산에 의한 해저면 손상의 통계학적인 연구결과를 보여준다. 또한 각 변수의 최대치와 수심에 따른 변수의 최대 경계선을 추정하였고, 변수들의 상호관계를 연구하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.3 s.246
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• pp.260-268
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• 2006

The micromechanical approach was used to investigate the interfacial strain distributions of a unidirectional composite under transverse loading in which fibers were usually found to be randomly packed. Representative volume elements (RVE) for the analysis were composed of both regular fiber arrays such as a square array and a hexagonal array, and a random fiber array. The finite element analysis was performed to analyze the normal, tangential and shear strains at the interface. Due to the periodic characteristics of the strain distributions at the interface, the Fourier series approximation with proper coefficients was utilized to evaluate the strain distributions at the interface for the regular and random fiber arrays with respect to fiber volume fractions. From the analysis, it was found that the random arrangement of fibers had a significant influence on the strain distribution at the interface, and the strain distribution in the regular fiber arrays was one of special cases of that in the random fiber array.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.3 no.3
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• pp.163-169
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• 1991

Sixty seven regular wave tests were performed in a wave-current flume to investigate proper-ties of waves breaking on irregular slope profiles. In these tests, 1/10, 1/20 beach slopes were made using angles and plywoods. A little differences were found in such properties as breaker depth and height indices. runup for plane slopes comparing with other laboratory experiments. however. for smaller deepwater wave steepness, measured breaker height and depth data values were smaller than other formulas. On wave runup agreement was good between experiments and Hunt formula. however. measured data values were influenced by number of breaking. Significant differences were found in breaker depth index for plane and barred slopes. Wave height decay after breaking was found to be smaller than Dally et al.'s formula (1984).

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.299-300
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• 2022

구조물의 내진보강방법 중에서 가장 널리 이용되는 방법인 강재 이력형 감쇠장치는 수평하중에 대한 응력-변위 곡선을 이용하여 지진 에너지를 소산시키는 방법인데, 이 경우 편심하중 등에 의해서 부재가 면 외 방향으로 거동하여 응력-변위곡선이 불규칙하여 그 결과의 신뢰성이 떨어지는 경우가 있다. 이러한 형상을 방지하기 위해서는 별도의 채널(Channel)을 시공하는 불편함을 감수해야 하며, 또한 수평력이 반복적으로 작용할 때 그 효과를 장담할 수 없는 문제점이 있다. 본 연구에서는 강재 스트립과 스프링을 결합한 댐퍼를 고안하여 스프링은 탄성변형을, 강재 스트립은 소성변형을 받게 하는 혼합형 댐퍼를 개발하고자한다. 여기서, 스프링은 복원력으로 작용하여 반복하중에 대한 저항성을 키우고 강재 스트립의 하중변위 곡선을 규칙적으로 하는 역할을 수행하게 되며 에너지 소산량을 계산할 때 편리함과 정확도를 높이고자 한다. 강재 스트립의 폭과 길이는 일정하지만 두께를 변화시켜서 5종류를 선택하였으며, 댐퍼 1개당 3개의 스트립을 정삼각형 형태로 배치하고 그 중심에 상당한 강성을 갖는 스프링을 갖는 형태로 제작하였다. 댐퍼 시험체는 5개를 제작한 후, 이 댐퍼를 구조물에 배치하였을 때의 지진에 대한 에너지 소산량과 부재력을 검토하여 댐퍼의 안전성(Safety)를 검증하고자 한다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.26 no.3
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• pp.174-183
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• 2014

Seabed beneath and near coastal structures may undergo large excess pore water pressure composed of oscillatory and residual components in the case of long durations of high wave loading. This excess pore water pressure may reduce effective stress and, consequently, the seabed may liquefy. If liquefaction occurs in the seabed, the structure may sink, overturn, and eventually increase the failure potential. In this study, to evaluate the liquefaction potential on the seabed, numerical analysis was conducted using the expanded 2-dimensional numerical wave tank to account for an irregular wave field. In the condition of an irregular wave field, the dynamic wave pressure and water flow velocity acting on the seabed and the surface boundary of the composite breakwater structure were estimated. Simulation results were used as input data in a finite element computer program for elastoplastic seabed response. Simulations evaluated the time and spatial variations in excess pore water pressure, effective stress, and liquefaction potential in the seabed. Additionally, the deformation of the seabed and the displacement of the structure as a function of time were quantitatively evaluated. From the results of the analysis, the liquefaction potential at the seabed in front and rear of the composite breakwater was identified. Since the liquefied seabed particles have no resistance to force, scour potential could increase on the seabed. In addition, the strength decrease of the seabed due to the liquefaction can increase the structural motion and significantly influence the stability of the composite breakwater. Due to limitations of allowable paper length, the studied results were divided into two portions; (I) focusing on the dynamic response of structure, acceleration, deformation of seabed, and (II) focusing on the time variation in excess pore water pressure, liquefaction, effective stress path in the seabed. This paper corresponds to (II).