• 대한산업공학회지
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• 제26권3호
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• pp.249-256
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• 2000

Bond immunization model is used to minimize interest rate risk for investing in fixed-income market, the model equalizes asset and liability values using the duration which is the sensitivity of portfolio value with respect to the interest rate. However this model might generate an error in practice because the model is based on unreal hypothesis, so called "Parallel Shift Term Structure". In this paper, we use the neural network approach to overcome the parallel shift term structure and try to employ this term structure function to the traditional immunization model. Finally, we present some computational test results that show the superiority of the partial immunization model to the traditional methods.

• 대한전자공학회논문지TC
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• 제45권8호
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• pp.41-46
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• 2008

본 논문에서는 금속 평행평판에 일반 유전체 기판인 FR4 대신 Metamaterial을 삽입할 경우에 발생할 수 있는 전자기 공진 특성과 임피던스 변화에 대하여 연구하였다. 기판을 DPS는 물론 Metamateral인 ENG, MNG, DNG 형으로 나눠, 투자율 함수를 위해 SRR 형식의 Lorentz 모델과, 유전율 함수를 위해 금속선 주기 배열 형식의 Drude 모델을 정확한 계산이 가능한 Full-wave 모드해석기법에 반영하여 평행평판이 가지는 공진모드들과 임피던스의 변화양상을 관측하였다. 관측을 통해 전자장비의 품질을 저하시키는 평행평판의 불요공진모드 억제를 위한 기판설계 가이드라인을 수립할 수 있었다.

• 정보처리학회논문지A
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• 제10A권2호
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• pp.111-122
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• 2003

군사용 워게임 시뮬레이션 모델들의 상호연동을 위해서는 국제표준연동(HLA : High Level Architecture)구조를 반드시 갖추어야하며 타 모델과 연동시 발생되는 시스템 오버헤드를 줄이기 위해서는 병렬 시뮬레이션 엔진 도입이 효과적이다. 그러나 기존 군사용 워게임 시뮬레이션 모델엔진의 이벤트 처리는 순차적 이벤트-드리븐 방식으로 처리하고 있다. 이는 병렬로 처리 시 글로벌 자료영역에 대한 동시참조등의 문제점들이 발생하기 때문이다. 아울러 기존 시뮬레이션 플랫폼으로 다중 CPU 시스템을 사용하여도 여러 개의 CPU를 다 활용하지 못하는 결과를 초래하고 있다. 따라서 이 논문에서는 군사용 워 게임 모델의 시스템 처리능력 향상과 글로벌 자료 영역에 대한 동시참조, 대외적인 시뮬레이션 시간처리, 장애 회복(Crash Recovery)시 병행 처리된 이벤트들의 순서를 보장 할 수 있는 객체모델에 기반한 병렬 시뮬레이션 엔진으로의 전환을 제안한다 이 전환된 병렬 시뮬레이션 엔진은 다중 CPU 시스템(SMP)상에서도 병렬 실행이 가능하도록 설계하고 구현하였다.

• Journal of Mechanical Science and Technology
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• 제16권6호
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• pp.799-809
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• 2002

In order to utilize a parallel mechanism as a machine tool component, it is important to estimate the errors of its end-effector due to the uncertainties in parts. This study proposes an error analysis for a new parallel device, a cubic parallel mechanism. For the parallel device, we consider two kinds of errors. One is a static error due to link stiffness and the other is a dynamic error due to clearances in the parts. In this study, we propose a stiffness model for the cubic parallel mechanism under the assumption that the link stiffness is a linear function of the link length. Also, from the fact that the errors of u-joints and spherical joints are changed with the direction of force acting on the link, they are regarded as a part of link errors, and then the error model is derived using forward kinematics. Lastly, both the error models are integrated into the total error, which is analyzed with a test example that the platform moves along a circular path. This analysis can be used in predicting the accuracy of other parallel devices.

• 한국세라믹학회지
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• 제53권1호
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• pp.43-49
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• 2016

This analyzed a Young's modulus (E), a thermal expansion coefficient (TEC, ${\beta}$) and a thermal conductivity (${\kappa}$) of the material with simple cubic particulate inclusion using two model structures: a parallel structure and a series structure of laminated layers. The derived ${\beta}$ equations were applied to calculate the ${\beta}$ value of the W-MgO system. The accuracy was higher for the series model structure than for the parallel model structure. Young's moduli ($E_c$) of sintered porous alumina compacts were theoretically related to the development of neck growth of grain boundary between sintered two particles and expressed as a function of porosity. The series structure model with cubic pores explained well the increased tendency of $E_c$ with neck growth rather than the parallel structure model. The thermal conductivity of the three phase system of alumina-mullite-pore was calculated by a theoretical equation developed in this research group, and compared with the experimental results. The pores in the sintered composite were treated as one phase. The measured thermal conductivity of the composite with 0.5-25% porosity (open and closed pores) was in accordance with the theoretical prediction based on the parallel structure model.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 A
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• pp.72-74
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• 2000

This paper presents the linear model of the measurement system with Phasor Measurement Units (PMU's) and the parallel processing technique to determinate state vectors of a power system. The conventional model of the PMU measurement system is in a dilemma that it is not applicable to optimal PMU placements and it needs more PMU to apply this model. In order to improve this defect, in this paper, the extended linear model which adaptable to optimal PMU placements considering the feature of zero injection bus is proposed. Because the proposed model is expressed as over-determined measurement equation, the efficient algorithm is needed. This paper proposed the partitioning scheme and the process algorithm for parallel determinating state vectors of a power system efficiently. The performance of the proposed linear model and the parallel processing algorithm is evaluated with IEEE sample systems.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1186-1191
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• 2003

The 40% of wall criterion, which is generally used for the plugging of steam generator tubes, may be applied only to a single crack. In the previous study, a total of 9 failure models were introduced to estimate the local failure of the ligament between cracks and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however, known that parallel axial cracks are more frequently detected during an in-service inspection than collinear axial cracks. The objective of this study is to determine the plastic collapse model which can be applied to the steam generator tube containing two parallel axial through-wall cracks. Nine previously proposed local failure models were selected as the candidates. Subsequently interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed for the determination of the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a plastic zone contact model was selected as an optimum model.

• Nuclear Engineering and Technology
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• 제36권4호
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• pp.316-326
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• 2004

The $40\%$ of wall criterion, which is generally used for the plugging of steam generator tubes, is applied only to a single crack. In a previous study, a total number of 9 failure models were proposed to estimate the local failure of the ligament between cracks, and the optimum coalescence model of multiple collinear cracks was determined among these models. It is, however known that parallel axial cracks are more frequently detected than collinear axial cracks during an in-service inspection. The objective of this study is to determine the plastic collapse model that can be applied to steam generator tubes containing two parallel axial through-wall cracks. Three previously proposed local failure models were selected as the candidates. Subsequently, the interaction effects between two adjacent cracks were evaluated to screen them. Plastic collapse tests for the plate with two parallel through-wall cracks and finite element analyses were performed to determine the optimum plastic collapse model. By comparing the test results with the prediction results obtained from the candidate models, a COD base model was selected as an optimum model.

• 대기
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• 제22권1호
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• pp.109-115
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• 2012

We parallelized the CFD_NIMR model, which is a numerical meteorological model, for best performance on both of distributed and shared memory parallel computers. This hybrid parallelization uses MPI (Message Passing Interface) to apply horizontal 2-dimensional sub-domain out of the 3-dimensional computing domain for distributed memory system, as well as uses OpenMP (Open Multi-Processing) to apply vertical 1-dimensional sub-domain for utilizing advantage of shared memory structure. We validated the parallel model with the original sequential model, and the parallel CFD_NIMR model shows efficient speedup on the distributed and shared memory system.

• International Journal of Control, Automation, and Systems
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• 제3권3호
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• pp.453-460
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• 2005

In this paper, a prototype Cartesian Parallel Manipulator (CPM) is demonstrated, in which a moving platform is connected to a fixed frame by three PRRR limbs. Due to the orthogonal arrangement of the three prismatic joints, it behaves like a conventional X-Y-Z Cartesian robot. However, because all the linear actuators are mounted at the fixed frame, the manipulator may be suitable for applications requiring high speed and accuracy. Using a geometric method and the practical assumption that three revolute joint axes in each limb are parallel to one another, a simple forward kinematics for an actual model is derived, which is expressed in terms of a set of linear equations. Based on the error model, two calibration methods using full position and length measurements are developed. It is shown that for a full position measurement, the solution for the calibration can be obtained analytically. However, since a ball-bar is less expensive and sufficiently accurate for calibration, the kinematic calibration experiment on the prototype machine is performed by using a ball-bar. The effectiveness of the kinematic calibration method with a ball-bar is verified through the well­known circular test.