• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.563-569
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• 2008

In this study, fluid/structure coupled analyses have been conducted f3r 3-D stator and rotor configuration. Advanced computational analysis system based on computational fluid dynamics (CFD) and computational structural dynamics (CSD) has been developed in order to investigate fluid/structure responses of general stator-rotor configurations. To solve the fluid/structure coupled problems, fluid domains are modeled using the structural grid system with dynamic moving and local deforming techniques. Reynolds-averaged Navier-Stokes equations with Spalart-Allmaras (S-A) and SST ${\kappa}-{\omega}$ turbulence models are solved for unsteady flow problems. A fully implicit time marching scheme based on the Newmark direct integration method is used for computing the coupled aeroelastic governing equations of the 3-D turbine blades for fluid-structure interaction (FSI) problems. Detailed fluid/structure analysis responses for stator-rotor interaction flow conditions are presented to show the physical performance and flow characteristics.

• 정보화연구
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• 제10권1호
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• pp.1-11
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• 2013

Various computing systems are used in naval ships. Since each system has a single purpose and its applications are tightly coupled with the physical machine, applications cannot share physical resources with each other. It is hard to utilize resources efficiently in conventional naval shipboard computing environment. In this paper, we present an integration architecture for virtualized naval shipboard computing systems based on open architecture. Our proposed architecture integrates individual computing resources into one single integrated hardware pool so that the OS and applications are encapsulated as a VM. We consider the issue of varying needs of all applications in a naval ship that have different purposes, priorities and requirements. We also present parallel VM migration algorithm that improves the process time of resource reallocation of given architecture. The evaluation results with the prototype system show that our algorithm performs better than conventional resource reallocation algorithm in process time.

• 인터넷정보학회논문지
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• 제6권5호
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• pp.123-132
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• 2005

초고속 글로벌 이동통신을 제공하기 위해서 3세대망인 UMTS와 WLAN시의 각각의 장단점을 보완하여 통합한다. 현재 B3G 망의 구조는 크게 장기적인 관점의 tightly-coupled방식과 현재 연구의 초점이 되고 있는 loosely-coupled 방식으로 나눌 수 있다. loosely-coupled 방식은 MIP의 HA/FA를 사용하여 수직적 핸드오버를 구현하는 방식이다. Loosely-coupled 방식은 tightly-coupled 방식에 비해 독립적 확장이 가능하고 비교적 구현이 쉬우나 핸드오버의 지연으로 인한 패킷 손실과 서비스 끊김 등의 단점이 있다. 본 논문에서는 이를 개선하기 위하여 HMPv6의 MAP를 사용하여 WLAN과 UMTS의 인터워킹에 대한 수직적 핸드오버 프로시저를 제안한다. 각 단계별 총 지연시간을 통하여 블로킹 확률을 측정해 본 결과 제안된 HMIPv6를 사용한 방식이 기존의 MIP를 사용한 방식보다 성능이 우수함을 확인한다.

• Coupled systems mechanics
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• 제2권1호
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• pp.85-110
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• 2013

Generally, mass concrete structural behavior is governed by the strain components. However, relevant guidelines in dam engineering evaluate the structural behavior of concrete dams using stress-based criteria. In the present study, strain-based criteria are proposed for the first time in a professional manner and their applicability in seismic failure evaluation of an arch dam are investigated. Numerical model of the dam is provided using NSAD-DRI finite element code and the foundation is modeled to be massed using infinite elements at its far-end boundaries. The coupled dam-reservoir-foundation system is solved in Lagrangian-Eulerian domain using Newmark-${\beta}$ time integration method. Seismic performance of the dam is investigated using parameters such as the demand-capacity ratio, the cumulative inelastic duration and the extension of the overstressed/overstrained areas. Real crack profile of the dam based on the damage mechanics approach is compared with those obtained from stress-based and strain-based approaches. It is found that using stress-based criteria leads to conservative results for arch action while seismic safety evaluation using the proposed strain-based criteria leads to conservative cantilever action.

• 대한원격탐사학회지
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• 제19권1호
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• pp.91-97
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• 2003

The design of Graphic Information System(GIS) in various applications is suffering from the difficulty of data acquisition, which is labor-intensive and time consuming. In order to provide the spatial data rapidly and accurately, 4S-Van, a prototype mobile mapping system, has been developed. The 4S-Van consists of 1)Global Positioning System(GPS), Inertial Navigation System(INS) for estimating the geographic position and attitude of the moving van, i.e.,(x, y, z) and the direction of the Van, 2) Charge Coupled Device(CCD) camera and laser scanner for capturing images and for measuring depth from geographic objects, and 3) External Synchronization Device(ESD) and industrial PC for synchronizing data from GPS/INS/CCD camera and for storing the data. In this paper, we present the design and implementation of the proto-Dpe 4S-Van system for spatial data acquisition for various GIS applications.

• Coupled systems mechanics
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• 제1권4호
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• pp.361-379
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• 2012

This paper presents a fully coupled three-dimensional solver for the analysis of interaction between pulsatile flow and large deformation structure. A partitioned time marching algorithm is employed for the solution of the time dependent coupled discretised problem, enabling the use of highly developed, robust and well-tested solvers for each field. Conservative transfer of information at the fluid-structure interface is combined with an effective multi-predict-correct iterative scheme to enable implicit coupling of the interacting fields at each time increment. The three-dimensional unsteady incompressible fluid is solved using a powerful implicit time stepping technique and an ALE formulation for moving boundaries with second-order time accurate is used. A full spectrum of total variational diminishing (TVD) schemes in unstructured grids is allowed implementation for the advection terms and finite element shape functions are used to evaluate the solution and its variation within mesh elements. A finite element dynamic analysis of the highly deformable structure is carried out with a numerical strategy combining the implicit Newmark time integration algorithm with a Newton-Raphson second-order optimisation method. The proposed model is used to predict the wave flow fields of a particular flow-induced vibrational phenomenon, and comparison of the numerical results with available experimental data validates the methodology and assesses its accuracy. Another test case about three-dimensional biomedical model with pulsatile inflow is presented to benchmark the algorithm and to demonstrate the potential applications of this method.

• 대한기계학회논문집
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• 제14권6호
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• pp.1408-1416
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• 1990

본 연구에서는 과도 연성 열탄성문제의 해를 구할때 사용되는 직접시간적분방 법과 Laplace 변환방법은 상호 장 단점을 가지고 있다. 각 방법들의 장단점은 서로 배타적이므로 서로의 장점을 살리는 수치방법이 필요하다. 그런데, 대부분의 과도 열탄성문제는 급격한 온도변화로 인한 물체의 변형에 관심이 있기때문에 이 형태의 문 제를 효율적으로 다루는 데 주안점을 두고 본 연구를 수행하였다. 유도된 유한요소 방정식은 결국 열탄성 지배 방정식 중 열전달방정식인 에너지보존식은 Gurtin의 범함 수로부터 유도된 원래의 형태를 사용하나 수치적 안정성(numerical stability)을 보장 하기 위하여 운동방정식은 시간에 대한 2차미분 형태로 수정하였다. 에너지보존식은 시간에 대한 합성적분(convolution)형태로 표현되므로 온도의 시간미분항이 소거되므 로 경계에서의 급격한 온도변화로 인한 수치 해석적 문제점은 간단히 해결된다. 그 러므로, 제안된 수치해법은 직접시간적분방법의 일종이나 결과식인 유한요소방정식은 기존의 문헌들과 상당한 차이가 있다. 과도 연성 열탄성해석을 위한 새로운 근사수 치해법의 장점을 이론적으로 설명하기보다 수치계산면에서의 안전성, 정확성 및 효율 성이 있음을 증명하기 위하여 이미 발표된 문헌들에서 다룬 예제를 선정하여 해석결과 를 비교하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.355-355
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• 2007

• 한국분말재료학회지
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• 제4권2호
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• pp.83-89
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• 1997

A finite element analysis to solve the coupled thermomechanical problem in the plane strain upsetting of the porous metals was performed. The analysis was formulated using the yield function advanced by Lee and kim and developed using the thermo-elasto-plastic time integration procedure. The density and temperature dependent thermal and mechanical properties of porous metals were considered. The internal heat generation by the plastic deformation and the changing thermal boundary conditions corresponding to the geometry were incorporated in the program. The distributions of the stress, strain, pressure, density and temperature were predicted during the free resting period, deformation period and dwelling period of the forging process.

• 전자공학회논문지SC
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• 제46권3호
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• pp.22-30
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• 2009

GPS 와 INS 통합시스템은 저가 MEMS 기술의 결과에 따라 대중적으로 널리 사용되기에 이르렀다. 그러나 저가센서에 의한 현재의 성과는 관성센서의 큰 에러 때문에 여전히 낮은 실정이다. 이것은 제한된 도시환경 안에서의 비행범위 때문에 더욱 관련이 있다. 이러한 관성센서 에러를 줄이면서 동시에 위성의 활용성을 높이기 위하여 GPS 와 저가 INS 는 연성으로 결합되어 Kalman Filter 설계를 응용하여 상호 통합되어진다. 본 논문에서는 연성으로 결합된 Kalman Filter를 이용한 GPS/INS 센서 통합을 제공한다. 우리는 또한 경로의 기하학에 의해 또는 그 목적시간 위치 따라 수학적으로 설명하는 ZH45C 궤도장치에 의한 산출된 기준 Wander Azimuth Strapdown Mechanization의 시뮬레이터 결과를 비교하여 검증하다.