• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.8A
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• pp.1247-1253
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• 2000

To fully utilize the capabilities of a SONET/ADM network, traffic grooming is needed to multiplex a number of lower-rate traffic streams into a higher-rate stream, and vice versa. Although the capacity of a SONET ring network can be upgraded by operating it over multiple wavelengths, the corresponding network design may be costly if it employs a large number of ADMs. A cost-effective design attempts to minimize the total number of ADMs used in the network while carrying the offered traffic. We introduce and evaluate the performance characteristics of a new traffic-grooming approach for WDM ring networks, called multihop. The multihop implementation places an ADM at each node based on the requested traffic in the traffic-demand matrix then, it tries to groom the wavelengths which can be groomed. We select one of the nodes to be the "hub" node which has an ADM for each wavelength. The hub node, therefore, can "bridge" traffic between all of the wavelengths. The algorithm is specified and illustrated by a simple example. Our results demonstrate that it is beneficial to use a single-hop approach, but for a large grooming ratio and node number, we advocate the use of the multihop approach.e multihop approach.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.155-158
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• 2005

본 논문에서는 MPEG 의 멀티미디어 응용 표준인 MAF(Multimedia Application Format)를 기반으로, 효율적인 비디오 콘텐츠의 검색 및 활용을 위한 통합 미디어 구조, 즉 비디오 MAF 를 제안한다. 제안하는 비디오 MAF 는 ISO 미디어 포맷을 기반으로 하고 단일의 비주얼 스트림과 다중 음성을 지원하기 위한 다수의 오디오 스트림, 내용기반의 정보를 포함하는 메타데이터, 그리고 비디오 콘텐츠의 대표 이미지를 동시에 포함하는 구조이다. 제안하는 파일포맷의 유용성을 검증하기 위해 비디오 MAF 로 생성 및 해석할 수 있는 부호기(encoder)와 복호기(decoder)를 설계하고 구현하여, 통합 미디어에 내재된 메타데이터를 이용한 효율적인 검색과 멀티트랙의 오디오 스트림을 활용한 다중 음성에 대한 지원이 가능함을 확인하였다. 또한 내재된 대표이미지는 비디오 콘텐츠에 대한 브라우징이 효과적으로 활용됨을 확인하였다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.671-680
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• 2020

This paper describes an improved beam analysis for compound rotorcraft fuselage design. The present beam approach is capable of analyzing fuselage composed of stiffeners using equivalent layer methodology. Thickness of the skin and laminated layer approach are suggested based on the unified beam formulation. The analysis which considers an equivalent stiffener layer is performed for a fuselage with stiffeners and preliminary study about the specification of stiffeners is conducted and compared by the results using the existing software.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.6
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• pp.16-22
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• 2012

Performance of a liquid rocket thrust chamber with regenerative cooling scheme has been numerically analyzed using in-house CFD code which can predict combustion/cooling performance and provide nozzle design parameters. This paper investigates trade-offs between combustion and cooling performance with varying amount of fuel directly injected into the chamber wall to form cooling films and mixture ratios for the peripheral injectors. Further efforts to verify/improve the simulation methodology including comparison with the firing test results are planned to make it a reliable tool to optimize the film cooling and other major design parameters.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2012.05a
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• pp.35-41
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• 2012

Performance of a liquid rocket thrust chamber with regenerative cooling scheme has been numerically analyzed using in-house CFD code which can predict combustion/cooling performance and provide nozzle design parameters. This paper investigates trade-offs between combustion and cooling performance with varying amount of fuel directly injected into the chamber wall to form cooling films. Also is analyzed the effect of varying mixture ratios for the peripheral injectors on combustion performance enhancement. Further efforts to verify/improve the simulation methodology including comparison with the firing test results are planned to make it a reliable tool to optimize the film cooling and other major design parameters.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.661-664
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• 2007

본 논문은 화학분리공정 중의 하나인 회분식 흡착공정의 시뮬레이션 방법에 관한 것으로, 편미분방정식을 이용한 회분식 흡착공정 시뮬레이션 방법에 있어서, 편미분방정식 해석기법인 CE/SE 방법(Conservation element and Solution element method)을 사용하여 흡착공정의 모델식을 수치해석하고, 이를 그래픽 사용자 인터페이스(Graphical User Interface) 방식에 의한 사용자편이성이 구현된 회분식 흡착공정 시뮬레이터의 설계와 구현에 관한 것이다. 본 연구를 통하여 공정모델선택 과정에서부터 시뮬레이션 결과의 시각화를 포함하는 결과 처리 과정까지의 작업을 사용자가 독립된 하나의 통합된 환경에서 회분식 흡착공정을 편리하게 시뮬레이션 할 수 있으며, 빠른 시간 안에 정확한 수치해를 구할 수 있게 되었다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.4
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• pp.369-376
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• 2016

In this study, a numerical analysis framework for investigating the nonlinear behavior of structures under fire conditions is presented. In particular, analysis procedure combining fire-driven flow simulation and thermo-mechanical analysis is discussed to investigate the mechanical behavior of fire-exposed representative volume structures made of steel and concrete, respectively. First of all, fire-driven flow analysis is conducted using Fire Dynamics Simulator(FDS) in a rectangular parallelepiped domain containing the structure. The FDS simulation yields the time history of temperature on the surface of the structure under fire conditions. Second, mechanical responses of the fire-exposed structure with respect to prescribed uniformly distributed loads are calculated by a coupled thermo-mechanical analysis using the time-varying surface temperature as boundary conditions. Material nonlinearities of steel and concrete have been considered in the thermo-mechanical analysis. A series of numerical results are presented to demonstrate the feasibility of the multiphysics structural fire analysis for investigating the structural behavior under fire conditions.

• Composites Research
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• v.30 no.1
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• pp.52-58
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• 2017

This paper presents the optimum design methodology for composite wing structure which automatically calculates the safety margin using optimization framework integrating failure modes. Particularly, its framework is possible to optimize sizing procedure to prevent failure mode which has the greatest effect on reducing the sizing time of composite structure. The main failure mode was set as the first ply failure, buckling failure mode, and bolted joint stress field, and the margin was calculated to minimize the weight. The design variable is a laminate sequence database and the responses are strain, buckling, bolted joint stress field. The objective function is the mass of the wing structure. The results of buckling analysis were compared using the finite element model to verify the robustness and reliability of Composite Optimizer.

• Convergence Security Journal
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• v.18 no.1
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• pp.33-42
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• 2018

CFD analysis is an analytical technique that applies a computer to the design and development of products across the entire industry for heat or fluid flow. This technology is used to shorten the development period and reduce costs through computerized simulation. However, the software used for CFD analysis is now required to use expensive foreign software. The Opensource CFD analysis software used in the proposed system has reliability of commercial CFD analysis software and has various user groups. However, for users who have expert knowledge, Opensource CFD software which supports only text interface environment, We have developed an environment that enables the construction of a CFD analysis environment for beginners as well as professionals. In addition, the proposed system supports the pre-processing (design and meshing) environment for CFD analysis and the environment for post-processing (result analysis & visualization), enabling the integrated CFD analysis process in one platform.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.2 s.72
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• pp.161-169
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• 2006

The study proposes component models in developing an efficient platform for internet-based structural analysis. Since a structural analysis requires an operation of complicated algorithms, a client-side computation using X-Internet is preferred to a server-side computation to provide a flexible service for multi-users. To compete with the user-friendly interfaces of available commercial analysis programs, a window-based interface using Smart Client was applied. Also, component-based programming was performed with the considerations on reusability and expandability so that active Preparation for future change or modification could be feasible. The components describe the whole system by subdivision and simplification. In the relationship between upper-and lower-level components and also in the relationship between components and objects, a unified interface was used to clearly classify the connection between the libraries. By performing data communication between different types of platforms using XML WebService, a conner-stone of data transfer is proposed for the future integrated CAE. The efficiency of the developed platform has been examined through a sample structural analysis and design on planar truss structures.