• 수산해양기술연구
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• 제32권2호
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• pp.191-204
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• 1996

The dynamic response characteristics with flexibility variations are examined for presenting the basic data for design of Tension Leg Platforms(TLPs)in waves. A numerical approach is based on the dynamic response analysis theory, in which the superstructure of TLPs is assumed flexible instead of the rigid body assumption used in two-step analysis method. The hydrodynamic interactions among TLP members, such as columns and pontoons are not included in the motion and structural analyse. The equations of motion of a whole structure are formulated using element-fixed coordinate systems which have the origin at the node of the each hull element.

• International Journal of Internet, Broadcasting and Communication
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• 제14권2호
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• pp.40-46
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• 2022

Recently, as the need for data access by integrating information in a distributed cloud environment increases in enterprise-wide enterprises, interoperability for collaboration between existing legacy systems is emphasized. In order to interconnect independent legacy systems, it is necessary to overcome platform heterogeneity and semantic heterogeneity. To solve this problem, middleware was built using EMRA (Extended MetaData Registry Access) based on ISO/IEC 11179. However, the designed middleware cannot guarantee the efficiency of information utilization because it does not have an adjustment function for each node's resource status and work status. Therefore, it is necessary to manage and adjust the legacy system. In this paper, we coordinate the correct data access between the information requesting agent and the information providing agent, and integrate it by designing a cooperative agent responsible for information monitoring and task distribution of each legacy system and resource management of local nodes. to make efficient use of the available information.

• Structural Engineering and Mechanics
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• 제83권6호
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• pp.825-834
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• 2022

The effectiveness and accuracy of the strain-based approach applied for analysis of two kinds of heterogeneous hollow cylinders subjected to thermal and mechanical loads are examined in this study. One is a multilayer cylinder in which the material in each layer is assumed to be linearly elastic, homogeneous and isotropic. Another is a hollow cylinder made of functionally graded materials with arbitrary gradient. The steady state condition without heat generation is considered. A sector in-plane finite element in the polar coordinate system based on strain approach is used. This element has only three degrees of freedom at each corner node. Analytical solutions available in the literature are presented to illustrate the accuracy of the sector element used. The obtained results for displacements and stresses are shown to be in good agreement with the analytical solutions.

• 한국ITS학회 논문지
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• 제14권4호
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• pp.1-9
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• 2015

도로상에 다양한 ITS 장비들의 제어기 함체를 하나의 함체로 물리적 기능적으로 통합하고자 개발중인 통합표준제어기의 설치위치에 대한 논리적인 근거나 도출방법이 마련되어 있지 못하여 현장적용에 어려움이 발생하고 있다. 특히, 노드부와 링크부 등 거리상 여러 곳에 분산 설치된 개별 제어기들을 통합하기 위한 최적의 위치를 도출하는 표준화된 방법론의 정립이 필요하다. 따라서 본 연구는 새로이 개발되는 통합표준제어기의 보다 합리적이며 효율적인 위치결정방법론을 제시하는 것을 목적으로 한다. 이를 위해 여기에서는 도시계획에서 시설입지결정에 활용하는 센트로이드를 활용하여 해결방안을 모색하였다. 분석결과 센트로이드 중에서 모든 장비에 균등한 연계가 가능한 중앙점(central point)의 적용이 가장 합리적인 것으로 나타났으며, 좌표계 설정을 통해 도로상에 정확한 좌표와 존을 설치위치로 제시하고 있다. 본 연구에서 제시한 방법론은 통합표준제어기의 시장 확대에 따른 현장적용에 활용도가 높을 것으로 보인다.

• Geomechanics and Engineering
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• 제36권2호
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• pp.183-204
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• 2024

In current investigation, a novel beam finite element model is formulated to analyze the buckling and free vibration responses of functionally graded porous beams resting on Winkler-Pasternak elastic foundations. The novelty lies in the formulation of a simplified finite element model with only three degrees of freedom per node, integrating both C⁰ and C¹ continuity requirements according to Lagrange and Hermite interpolations, respectively, in isoparametric coordinate while emphasizing the impact of z-coordinate-dependent porosity on vibration and buckling responses. The proposed model has been validated and demonstrating high accuracy when compared to previously published solutions. A detailed parametric examination is performed, highlighting the influence of porosity distribution, foundation parameters, slenderness ratio, and boundary conditions. Unlike existing numerical techniques, the proposed element achieves a high rate of convergence with reduced computational complexity. Additionally, the model's adaptability to various mechanical problems and structural geometries is showcased through the numerical evaluation of elastic foundations, with results in strong agreement with the theoretical formulation. In light of the findings, porosity significantly affects the mechanical integrity of FGP beams on elastic foundations, with the advanced beam element offering a stable, efficient model for future research and this in-depth investigation enriches porous structure simulations in a field with limited current research, necessitating additional exploration and investigation.

• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.41-50
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• 2014

The Earth is not perfectly spherical and its rotational axis is not fixed in space, and these geophysical and kinematic irregularities work as dominant perturbations in satellite orbit propagation. The International Earth Rotation Service (IERS) provides the Conventions as guidelines for using the Earth's model and the reference time and coordinate systems defined by the International Astronomical Union (IAU). These guidelines are directly applied to model orbital dynamics of Earth satellites. In the present work, the effects of the latest conventions released in 2010 on orbit propagation are investigated by comparison with cases of applying the previous guidelines, IERS Conventions (2003). All seven major updates are tested, i.e., for the models of the precession/nutation, the geopotential, the ocean tides, the ocean pole tides, the free core nutation, the polar motion, and the solar system ephemeris. The resultant position differences for one week of orbit propagation range from tens of meters for the geopotential model change from EGM96 to EGM2008 to a few mm for the precession/nutation model change from IAU2000 to IAU2006. The along-track differences vary secularly while the cross-track components show periodic variation. However, the radial-track position differences are very small compared with the other components in all cases. These phenomena reflect the variation of the ascending node and the argument of latitude. The reason is that the changed models tested in the current study can be regarded as small fluctuations of the geopotential model from the point of view of orbital dynamics. The ascending node and the argument of latitude are more sensitive to the geopotential than the other elements. This study contributes to understanding of the relation between the Earth's geophysical properties and orbital motion of satellites as well as satellite-based observations.

• 한국통신학회논문지
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• 제30권10B호
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• pp.630-638
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• 2005

네트워크 및 종단 노드의 시스템에 걸친 제한된 자원을 활용하여 실현되는 영상/음성 전달 서비스를 위한 멀티미디어 응용 프로그램의 품질을 보장하기 위해서는 지연, 지터, 손실과 같은 전송 상태와 CPU, 메모리의 사용량과 같은 시스템의 상태를 동시에 관찰하는 것이 필요하다. 본 논문에서는 액세스그리드 (Access Grid) 경우와 같이 IP 멀티캐스트 상에 동작하는 RTP/RTCP에 기반한 실시간 미디어 응용 프로그램을 대상으로 동적/정적 모니터링 방식을 혼용하여 멀티캐스트 상태와 시스템 상태를 측정하는 혼성 모니터링 방식을 제안한다. 또한 종단간 전송 품질이 저하된 경우 제안한 모니터링 방식에서 측정된 결과를 비교/분석하여 품질 저하의 원인을 판단하고 원인에 적합한 대응방안을 연계하고i라 한다. 이 결과를 바탕으로 네트워크/시스템의 상태 변화에 적응적인 영상/음성 전송 서비스의 가능성을 타진하고 종단간 전송 품질 저하 방지를 위한 효과를 예상한다.

• 한국지능시스템학회논문지
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• 제15권4호
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• pp.425-430
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• 2005

많은 문제가 그래프로 모델링될 수 있고, 그래프 이론에 기반한 방법에 의해서 해결될 수 있다. 이 논문에서는 분산되고 중첩된 대사경로 네트워크들에 대해서 경로를 찾는 방법에 대해서 다룬다. 제안한 방법은 분산된 그래프를 통합하지 않은 채, 다중 에이전트의 협동작업을 통해서 경로를 찾는 방법이다. 각 그래프에는 해당 그래프를 책임지고 있는 에이전트가 하나씩 있어서, 해당 그래프에서 시작되는 경로검색을 주도하고, 다른 에이전트로부터 경로에 대한 정보 요청에 응답하도록 한다. 제안한 방법에서는 우선 전체 분산된 그래프에 대해서 뷰그래프라고 하는 추상화된 그래프를 형성하고, 이를 이용하여 경로를 찾기 위해 에이전트간에 어떤 방법으로 협력을 할지 알 수 있게 한다. 각 에이전트는 해당 그래프에 대한 최단경로 정보를 관리하고 있다. 어떤 에이전트가 해당 그래프의 어떤 노드에서 시작하는 경로를 찾으라는 요구를 받게 되면, 다른 에이전트로부터 정보를 받아서 목적지까지는 가는 경로를 찾게 된다.

• 대한원격탐사학회지
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• 제3권1호
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• pp.41-54
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• 1987

극궤도 기상위성 NOAA-9호의 AVHRR Channel 4 영상 data로부터 해수면온도(SST)를 산출하는 과정을 기상연구소의 위성수신 시스템에 맞도록 개발하였다. 위성의 Ascending node를 기준으로 영상좌표와 SST용 Mercator 지도 좌표변환용 Table 을 만 들고 10 km $\times$ 10 km의 Sample로 SST용 영상을 제작하였다. 또, 위성측기의 복사보 정 (Radiometric Calibration) 과정과 적외선 CH 4 인 10.5 ~ 11.5 $\mu\textrm{m}$의 복사를 온도로 변환 (Radiance-To-Temperature Conversion)하는 LUT(Look Up Table)의 작성 및 SST 출력과정을 제작하였다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.383-386
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• 2006

In this study, we propose a new fast algorithm for calculating short range forces in molecular dynamics, This algorithm uses a new hierarchical tree data structure which has a high adaptiveness to the particle distribution. It can divide a parent cell into k daughter cells and the tree structure is independent of the coordinate system and particle distribution. We investigated the characteristics and the performance of the tree structure according to k. For parallel computation, we used orthogonal recursive bisection method for domain decomposition to distribute particles to each processor, and the numerical experiments were performed on a 32-node Linux cluster. We compared the performance of the oct-tree and developed new algorithm according to the particle distributions, problem sizes and the number of processors. The comparison was performed sing tree-independent method and the results are independent of computing platform, parallelization, or programming language. It was found that the new algorithm can reduce computing cost for a large problem which has a short search range compared to the computational domain. But there are only small differences in wall-clock time because the proposed algorithm requires much time to construct tree structure than the oct-tree and he performance gain is small compared to the time for single time step calculation.