• Journal of Ocean Engineering and Technology
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• v.13 no.4 s.35
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• pp.1-9
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• 1999

일차원 및 이차원의 단순한 문제에 대하여 계층 요소를 사용한 혼합 차수 유한 요소해의 정확성 및 수렴성을 조사하였다. 이러한 작업은 임의의 차수를 가진 블록들을 조합하여 요소를 구성함으로서 이루어질 수 있다. 블록간의 연결성이 유지될 수 있는 블록의 구성과 요소 생성에 대하여는 코드개발과 관련하여 설명하고 있으며, 서로 다른 차수를 가진 인접 블록간의 해의 연속성에 대하여는 계층 요소의 구성과 관련하여 서술되었다. 수치적 결과는 블록의 차수를 잘 선택함으로서 유한 요소해의 수렴성과 정확성을 증가시킬 수 있음을 보여주고 있으며, 고차 요소 영역을 너무 많이 할당하여 선형 요소의 영역이 너무 적을 경우에는 경계 조건에 따라 오차가 내부로 전파됨을 보여준다. 또한 세분화된 요소에 대한 고차 보간의 경우, 해의 수렴성이 저해될 수 있음이 발견되었다.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11a
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• pp.32-35
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• 2003

최근 국내외적으로 침해 공격 사고율이 증가에 대한 방안으로 여러 보안 기술이 개발되어 왔다. 그 중 방화벽은 내부의 중요한 자원과 외부 네트워크와의 경계를 생성하고, 정책기반의 접근제어를 효과적으로 제공하고 있지만 DoS공격, 변형 프로토콜을 통한 공격에는 효과적으로 막지 못한다. 또한 침입탐지 시스템은 공격, 침입, 원하지 않는 트래픽을 구별할 수 있다는 점에서 가치가 있지만 정확한 시점에 공격을 차단하지 못하며 침입탐지 이후에 생기는 불법행동에 대한 커다란 위협이 따르며, 실질적인 방어는 관리자의 수동적인 개입을 필요로 하게 된다. 본 논문에서는 이에 대한 해결 방안으로 방화벽의 침입차단 기능과 침입탐지 시스템의 실시간 침입탐지 기능을 갖춘 리눅스 기반의 공개 보안 툴을 결합한 침입방지 시스템을 설계 및 구현한다.

• Proceedings of the KIEE Conference
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• 2006.07d
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• pp.2107-2108
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• 2006

본 논문에서는 범용 공학 소프트웨어인 셈툴과 연계한 FEM 패키지의 3D Visualization 및 Operation에 대해 기술 한다. FEM 해석을 위한 Graphical Interface로서 각종 오브젝트의 생성, 로드와 더불어 해당 오브젝트를 3D Visualization하여 각종 Manipulation을 하는 기법에 대해 서술하도록 한다. 특히, 해석에 필요한 경계 조건이나 하중을 부여하기 위해 노드를 Picking 하는 기법과, 해석 후 객체의 내부 하중 상태 등에 대한 컨투어링을 위해 객체를 분할하는 Cut Section 등에 대해서도 다루도록 한다.

• Journal of the Society of Naval Architects of Korea
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• v.37 no.1
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• pp.91-98
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• 2000

The present paper is Part 2 of three-part paper for an experimental study on breaking waves generated by a submerged cylinder. Measurements of velocity and head loss profiles at the wakes of cylinder and breaker as well as the turbulent intensities in breaking region were made to elucidate the viscous aspects of breaking waves. Their mutual correlation is also investigated. It is found that the head loss profile is an excellent indicator of the strength and extent of breaker. Very high turbulent intensities measured at and just downstream of the breaker indicate the consequence of energy transfer of wave breaking into turbulence.

• Journal of KIISE:Computer Systems and Theory
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• v.32 no.10
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• pp.520-529
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• 2005

A feature-based 3D modeling algorithm is presented in this paper. Since conventional methods use depth-based techniques, they need much time for the image matching to extract depth information. Even feature-based methods have less computation load than that of depth-based ones, the calculation of modeling error about whole pixels within a triangle is needed in feature-based algorithms. It also increase the computation time. Therefore, the proposed algorithm consists of three phases, which are an initial 3D model generation, model evaluation, and model refinement phases, in order to acquire an efficient 3D model. Intensity gradients and incremental Delaunay triangulation are used in the Initial model generation. In this phase, a morphological edge operator is adopted for a fast edge filtering, and the incremental Delaunay triangulation is modified to decrease the computation time by avoiding the calculation errors of whole pixels and selecting a vertex at the near of the centroid within the previous triangle. After the model generation, sparse vertices are matched, then the faces are evaluated with the size, approximation error, and disparity fluctuation of the face in evaluation stage. Thereafter, the faces which have a large error are selectively refined into smaller faces. Experimental results showed that the proposed algorithm could acquire an adaptive model with less modeling errors for both smooth and abrupt areas and could remarkably reduce the model acquisition time.

• Geophysics and Geophysical Exploration
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• v.15 no.2
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• pp.92-101
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• 2012

Three-dimensional finite-difference simulation in a small-scale half-sphere basin with planar free-surface is performed for an arbitrary shear-dislocation point source. A new scheme to deal with free-surface boundary condition is presented. Then basin parameters are examined to understand main characteristics on ground-motion response in the basin. To analyze the frequency content of ground motion in the basin, spectral amplitudes are compared with each other for four sites inside and outside the basin. Also particle motions for those sites are examined to find which kind of wave plays a dominant role in ground-motion response. The results show that seismic energy is concentrated on a marginal area of the basin far from the source. This focusing effect is mainly due to constructive interference of the direct Swave with basin-edge induced surface waves. Also, ground-motion amplification over the deepest part of the basin is relatively lower than that above shallow basin edge. In the small-scale basin with relatively simple bedrock interface, therefore, the ground-motion amplification may be more related to the source azimuth or direction of the incident waves into the basin rather than depth of it.

• Korean Journal of Optics and Photonics
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• v.18 no.6
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• pp.441-446
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• 2007

Outcoupling efficiency of the OLED device is improved by incorporating both a microlens array and a diffractive grating pattern. The microlens array improves the light transmission at the interface of glass and air, and the diffractive grating outcouples the guided mode propagating at the waveguide, which consists of ITO and organic layers. By using the PDMS soft mold imprinting method, the microlens array is fabricated on the glass substrate. The diffractive grating pattern is directly fabricated on the ITO surface by using laser interferometry. A microlens array with a diameter of $10{\mu}m$ improves the light coupling efficiency by 22%. The diffractive grating made of TSMR photoresist enhances the luminance power efficiency by 41% at a current density of $20mA/cm^2$.

• Journal of Korean Society of Forest Science
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• v.102 no.1
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• pp.113-121
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• 2013

It has been known that edges of forest fire areas play significant roles in post-fire change of forest ecosystem and recovery process. The purpose of this study was to analyze the relationships between edge formation of burned forests and landscape characteristics with consideration on spatial autocorrelation. Samcheok fire site burned in 2000 was selected as the study area. Seven hundred fifty three of 500 $m^2$ grid cells were generated for measuring landscape characteristics. This study used the topographic variables including slop, elevation, topographic wetness index, solar radiation index and proportions of fuel and land use types. In delineating landscape characteristics correlation analysis with modified t-test were performed for exploring the relationships between edge formation and landscape characteristics. The results indicated that edge formation of burned forests was positively correlated with most variables including TWI, SRI, water, paddy, developed, farm, grass, bare soil, and negatively related with elevation, slope and all fuel types. Especially TWI (r=0.437) showed a strong positive correlation with edge formation. According to the results, edge of burned forests were likely formed when proportions of heterogeneous land use types were high with mild slope and low elevation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.4
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• pp.427-436
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• 2014

The goal of this paper is to estimate proper hardfacing material and thickness of STD61 hot-working tool steel through three-dimensional heat transfer and thermal stress analyses. Stellite6, Stellite21 and 19-9DL superalloys are chosen as alternative hardfacing materials. The influence of hardfacing materials and thicknesses on temperature, thermal stress and thermal strain distributions of the hardfaced part are investigated using the results of the analyses. From the results of the investigation, it has been noted that a hardfacing material with a high conductivity and a thinner hardfaced layer are desired to create an effective hardfacing layer in terms of heat transfer characteristics. In addition, it has been revealed that the deviation of effective stress and principal strain in the vicinity of the joined region are minimized when the Stellite21 hardfaced layer with the thickness of 2 mm is created on the STD61. Based on the above results, a proper hardfacing material and thickness for STD61 tool steel have been estimated.

• The Journal of the Petrological Society of Korea
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• v.18 no.2
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• pp.153-169
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• 2009

Hornblende gabbro-lamprophyre-diorite Complex in Guwoonri, Hwacheon distributes in a zonal pattern, where the diorite distributed along the margin of the Complex encompasses the hornblende gabbro body in the central part of the Complex, and lamprophyre intruded in vein along the boundary between diorite and hornblende gabbro. The hornblende gabbro in the central part of the Complex also shows a zonal distribution pattern, where hornblende gabbro containing subspherical amphibole phenocrysts as a major mafic mineral(Sag) surrounds hornblende gabbro with prismatic amphiboles as a principal mafic mineral(Pag). The zonal distributions observed in hornblende gabbro-lamprophyre-diorite Complex in Guwoonri resulted from two different geological processes. The zonal distribution among diorite, lamprophyre, and hornblende gabbro was due to intrusions of three distinct magmas derived from different degree of partial melting of a common source rock, whereas the zonal distribution shown within the hornblende gabbro body occupying the central part of the Complex resulted from an inward fractional crystallization of a single magma. Geochemical characteristics and mineral mode of hornblende gabbro, lamprophyre, and diorite indicate that these rocks formed from hydrous mafic to intermediate magma derived from partial melting of enriched mantle, which has been caused by infiltration of volatiles including water into mantle in plate margin.