• 한국항공우주학회지
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• 제34권7호
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• pp.1-11
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• 2006

본 논문에서는 불연속면이 포함된 다차원 유동에서 흔히 발생하는 수치적 진동현상을 막기 위해 기존의 TVD 제한자를 분석함으로써 새로운 형태의 다차원 제한 함수를 유도하였다. MLP 기법은 유도된 다차원 제한 함수를 기반으로 하며, 다차원 불연속면에서의 수치 진동을 효과적으로 제거하고 동시에 3차 이상의 공간 정확도 내삽기법과 함께 사용할 수 있다는 장점을 갖는다. 또한, 정상 유동의 경우 수치 진동이 제거됨으로써 수렴성이 향상됨을 확인할 수 있었고, 실제 코드에 적용하는 방법도 간단하다. MLP 기법을 적용함으로써 불연속 유동 뿐 만 아니라 연속 유동에서도 정확성, 효율성, 강건성 면에서 향상된 결과를 얻을 수 있음을 여러 가지 수치 실험을 통하여 확인하였다.

• 대한기계학회논문집
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• 제9권6호
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• pp.691-698
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• 1985

본 논문에서는 종래의 FRF법을 이용하였을때의 문제점을 보완하고 계의 정확 한 진동원을 파악하기 위하여 진동원 간에 강한 상관관계가 존재하는 경우에 사용되는 다차원 스펙트럼해석(Multi-Dimensional Spectral Analysis` MDSA)법을 가솔린엔진에 적용 검토하였다.

• Journal of Information Technology Applications and Management
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• 제17권3호
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• pp.135-150
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• 2010

Interactivity has been referred to as an important element promoting students' active participation in virtual classes. Assuming that interactivity cannot be defined by a single dimension, this study proposes multi-dimensional interactivity. Multi-dimensional interactivity includes all types of interactivity in e-learning. This study explored multi-dimensional interactivity which affects learners' satisfaction with e-learning. Data were collected from 132 students who had attended e-learning courses and the relationship between multi-dimensional interactivity and learners' satisfaction levels were tested through regression analysis. The result of this study showed that mechanical, reactive, and creative interactivity were positively related to learners' satisfaction. However, social interactivity seemed not to be related to learners' satisfaction. This study provides new insights on interactivity and verifies the importance of the multi-dimensional interactivity. The result of this study is expected to provide practical implications for interactivity strategies in e-learning.

• Nuclear Engineering and Technology
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• 제41권10호
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• pp.1347-1360
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• 2009

A multi-dimensional component for the thermal-hydraulic system analysis code, MARS, was developed for a more realistic three-dimensional analysis of nuclear systems. A three-dimensional and two-fluid model for a two-phase flow in Cartesian and cylindrical coordinates was employed. The governing equations and physical constitutive relationships were extended from those of a one-dimensional version. The numerical solution method adopted a semi-implicit and finite-difference method based on a staggered-grid mesh and a donor-cell scheme. The relevant length scale was very coarse compared to commercial computational fluid dynamics tools. Thus a simple Prandtl's mixing length turbulence model was applied to interpret the turbulent induced momentum and energy diffusivity. Non drag interfacial forces were not considered as in the general nuclear system codes. Several conceptual cases with analytic solutions were chosen and analyzed to assess the fundamental terms. RPI air-water and UPTF 7 tests were simulated and compared to the experimental data. The simulation results for the RPI air-water two-phase flow experiment showed good agreement with the measured void fraction. The simulation results for the UPTF downcomer test 7 were compared to the experiment data and the results from other multi-dimensional system codes for the ECC delivery flow.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1651-1664
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• 2023

It is very difficult to capture the multi-dimensional phenomena such as asymmetric flow and temperature distributions with the one-dimensional (1D) model, obviously, due to its inherent limitation. In order to overcome such a limitation of the 1D representation, many state-of-the-art system codes have equipped a three-dimensional (3D) component for multi-dimensional analysis capability. In this study, a standard multi-dimensional analysis model of APR1400 (Advanced Power Reactor 1400) has been developed using TRACE (TRAC/RELAP Advanced Computational Engine). The entire reactor pressure vessel (RPV) of APR1400 has been modeled using a single 3D component. The fuels in the reactor core have been described with detailed and coarse representations, respectively, to figure out the impact of the fuel description. Using both 3D RPV models, a comparative analysis has been performed postulating a double-ended guillotine break at a cold leg. Based on the results of comparative analysis, it is revealed that both models show no significant difference in general plant behavior and the model with coarse fuel model could be used for faster transient analysis without reactor kinetics coupling. The analysis indicates that the asymmetric temperature and flow distributions are captured during the transient, and such nonuniform distributions contribute to asymmetric quenching behaviors during blowdown and reflood phases. Such asymmetries are directly connected to the figure of merits in the LBLOCA analysis. Therefore, it is recommended to employ a multi-dimensional RPV model with a detailed fuel description for a realistic safety analysis with the consideration of the spatial configuration of the reactor core.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.378-385
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• 2008

The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.378-385
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• 2008

The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

• 한국소음진동공학회논문집
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• 제20권10호
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• pp.940-945
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• 2010

Noise reduction of vacuum cleaner is important, according as get into standard that estimate quality of product. To reduce noise of vacuum cleaner, we need analysis of correct noise source and contribution grasping about Identified noise sources' output noise. Because noise sources' correlation exists in vacuum cleaner that is small and complicated system, analysis is not easy. In this case, we need to apply Multi-dimensional spectral analysis(MDSA) method that can remove correlation between noise sources and grasp pure contribution degree of noise sources. In this study, we take transfer path analysis between output noise and noise that measured in inside/outside of vacuum cleaner.

• 대한기계학회논문집
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• 제10권4호
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• pp.442-449
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• 1986

본 연구에서는 소음원 및 진동원을 규명하기 위하여 사용되어 온 종래의 주파 수응답함수(Frequency Response Function`FRF)법과 소음원 및 진동원 간에 강한 상관 관계가 존재한 경우에 사용되는 기여도함수(coherence function)법을 이용한 다차원 스텍트럼해석(Multi-Dimensional Spectral Analysis`MDSA)법에 의하여 가속도응답 및 방사음과의 기여관계를 규명하였다.

• 한국컴퓨터산업학회논문지
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• 제3권8호
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• pp.1007-1018
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• 2002

평가결과에 대한 과학적이고 다차원적인 분석은 학습자, 교수자에게 중요한 정보를 제공해 주는 역할을 한다. 기존의 평가관련 연구들이 평가도구 개발에 치우친 경향이 있고, 평가결과에 대한 분석은 단편적이고 일차원적인 분석이 대부분이었다. 본 연구에서는 평가결과를 다차원적으로 분석함으로써, 질 높은 교수학습이 이루어질 수 있도록 학습자 및 교수자에게 다양한 정보를 제공해 주는 데 목적을 두고 개발되었다. 차원은 기간, 학생, 평가영역, 난이도, 점수의 5차원으로 분류하였다. 분석결과는 Dcube. 그래프, 스프레드시트 등의 다양한 형태로 제공된다.