• Transactions of the Korean Society of Mechanical Engineers
• /
• v.17 no.8
• /
• pp.2069-2078
• /
• 1993

The buoyancy-driven turbulent thermal convection is predicted using an anisotropic hybrid turbulence model, which is incorporated with a low Reynolds k-.epsilon. turbulence model and an anisotropic buoyant part of algebraic stress model(ASM). The numerical predictions are compared with the Davidson's model,(1) the full ASM and the experimental results of Cheesewright et al.(2) All the models are shown to predict good agreements with the experiments for the averaged turbulence quantities. It is found that the effect of an anisotropic part on the Reynolds stress and the turbulent heat fluxes is substantial. In this study, the present hybrid model gives a fairly reasonable prediction in terms of the computational accuracy, convergence and stability. The contribution of an anisotropic buoyant part to turbulent heat fluxes are also scrutinized over the range of Rayleigh numbers $(4.79{\times}10^{10}{\le}Ra{\le}7.46{\times}10^{10}).$

• Structural Engineering and Mechanics
• /
• v.21 no.1
• /
• pp.1-18
• /
• 2005

Foschi's connector model is used as a basic component in the development of nonlinear analysis programs for timber structures. This paper presents the extension of the model to include the effect of shaft frictional forces. The wood medium is modeled using the Foschi embedment model, while shaft friction is modeled using an elastic Coulomb-type friction model. The initial confining pressure for the case of driven fasteners is accounted for by a lateral shift of the load-embedment curve. The model is used to compute the cyclic response of both driven and inserted fasteners. The results obtained from the cases studied indicate that initial confining pressure and friction do not have a significant effect on the computed hysteretic response, however, they significantly affect the computed amount of fastener withdrawal. This model is particularly well-suited for modeling the hysteretic response of shear walls with moderate fastener withdrawal under lateral cyclic or earthquake loading.

• Speech Sciences
• /
• v.11 no.2
• /
• pp.247-257
• /
• 2004

There has been many research efforts to overcome the problems of speech recognition in the noisy conditions. Among them, the model-based compensation methods such as the parallel model combination (PMC) and vector Taylor series (VTS) have been found to perform efficiently compared with the previous speech enhancement methods or the feature-based approaches. In this paper, a data-driven model compensation approach that adapts the HMM(hidden Markv model) parameters for the noisy speech recognition is proposed. Instead of assuming some statistical approximations as in the conventional model-based methods such as the PMC, the statistics necessary for the HMM parameter adaptation is directly estimated by using the Baum-Welch algorithm. The proposed method has shown improved results compared with the PMC for the noisy speech recognition.

• Journal of the Korean Geotechnical Society
• /
• v.15 no.6
• /
• pp.167-185
• /
• 1999

A series of model tests was performed to find the characteristics of lateral behavior of single rigid pile. This paper shows the results of model tests on the lateral behavior of single rigid driven pile in non-homogeneous(two layered) Nak-Dong River sands. The purpose of this paper is to investigate the effect of the ratio of lower layer thickness to embedded pile length, the coefficient ratio of the subgrade reaction and the pile construction conditions(driven & embedded piles) on the characteristics of lateral behavior of single pile. The results of model tests show that the lateral behavior in non-homogeneous soil depends upon drop energy considerably, that is, in the case of H/L=0.75, as the drop energy increases three times the decrease percentage increases about 2.12 times. In the driven pile with non-homogeneous soil of $E_{h1}/E_{h2}=5.56$, the effect of upper layer with large stiffness on the decrease of lateral deflection is remarkably smaller than embedded pile. In non-homogeneous soil, the maximum bending moment of driven pile is in the range of 100 132% in comparison with embedded pile. The reason is that the stiffness of soil around pile increases with drop vibration and so the pile behavior is similar to the flexible pile behavior by means of the increase of relative stiffness of pile, In this paper, the experimental equations for lateral load and H/L on $y_D/y_E \; & \; MBM_D/MBM_E$ are suggested from model tests.

• Journal of the Korea Society for Simulation
• /
• v.17 no.4
• /
• pp.209-218
• /
• 2008

The Unified Modeling Language becomes popular to specify, visualize, construct, and document software-intensive systems, especially in supporting the design phase of software engineering. Most of designs in UML have focused on firm designing of software system structure. Recently, some researches have raised additional demands in many emerging complex software systems, such as aspect-oriented design. In this paper, we work on the dynamic aspect of policy-driven architecture. We present a UML-based high-level modeling of policy-driven management which is applicable in various application domains. In order to manage a number of activities of applications, dynamics and flexibility should be supported with policies consistently on different resources in the same context. Thus, a methodology of meta-modeling to represent dynamic aspects of policy-driven architecture is studied. Based on our methodology, we could achieve meta-modeling to develop a number of policy-driven management applications.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2017.07a
• /
• pp.281-284
• /
• 2017

최근 임베디드 시스템 개발이 Model Driven Engineering 방식으로 변화하면서 요구사항과 모델 간의 추적성을 보장하는 것이 매우 중요해졌다. 이 논문에서는 기존의 FDD(Feature Driven Development)와 FOSE(Feature Oriented Software Engineering) 방법론에 적용된 feature 개념을 재정의하여 이를 AUTOSAR platform에 적용하는 방법을 제시하며 요구사항부터 model, code까지 추적성을 검증한다.

• The Journal of Korean Association of Computer Education
• /
• v.22 no.6
• /
• pp.43-55
• /
• 2019

In the Fourth Industrial Revolution, a super-intelligent and super-connected society has arrived. Software is an important part of the core technologies of the Fourth Industrial Revolution. The ability to solve problems through software requires software education in that it is a core competency that everyone should have. Software education aims to improve Computational Thinking, which is the ability to solve problems through programming. Until now, most problem-solving programming learning models follow the traditional method of development: Waterfall model (Analysis-Design-Development-Test). In this model, if there is a problem in the preceding step, That could be found in the test phase. This takes a considerable amount of time and effort to find a solution to the problem and can be a burden on the programming learning. In this study, we proposed a Test-Driven Problem-Solving learning model using TDD (Test Driven Development) as Agile development method, and reviewed the appropriateness of the model through experts review. The verification results of the model showed positive evaluation results. In particular, the learning phase configuration of the model, helping in programming learning, helping of Computational Thinking improvement showed high rating, it is determined that there will be positive effects on Computational Thinking improvement through problem-solving programming learning when applying future learning.

• Annual Conference of KIPS
• /
• 2005.11a
• /
• pp.857-860
• /
• 2005

웹 기술 기반의 컨텐츠 개발 및 운영으로 다른 환경에서의 컨텐츠 활용을 토대로 교육자원의 정보들을 통합 운영할 수 있는 관리 중심체인 e-learning 시스템의 중요성과 필요성이 대두되고 있으며, 교육용 어플리케이션은 현재 표준화되지 않은 개발 프로세스를 기반하여 개발하고 있는 실정이다. 따라서, 교육 컨텐츠의 재사용을 높이기 위해 국제적 학습 표준인 SCORM (Sharable Content Object Reference Model)을 기반으로 하나의 플랫폼에 있어서 시스템 개발 중 다른 플랫폼으로의 재사용이 가능한 핵심자산을 이용하여 조립, 생산할 수 있는 방안으로 체계적인 교육자원을 개발하고 지원하기 위한 교수-학습지원 시스템 개발에 초점을 둔 연구가 요구된다. 따라서, 본 논문에서의 교육적 도메인으로 접근하여 MDA(Model Driven Architecture)상의 교수-학습지원 시스템을 정의한다. 또한 학습컨텐츠 표준 메타데이터를 이용하여 컨텐츠저장소에 관한 분석 및 설계를 하고 MDA 자동화 툴을 이용한 핵심자산을 통해 실제 교수자가 필요로하는 컨텐츠를 제공할 수 있는 교수-학습지원 시스템을 개발하고자 한다.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.41 no.3
• /
• pp.90-96
• /
• 2018

This paper proposed data driven techniques to forecast the time point of water management of the water reservoir without measuring manganese concentration with the empirical data as Juam Dam of years of 2015 and 2016. When the manganese concentration near the surface of water goes over the criteria of 0.3mg/l, the water management should be taken. But, it is economically inefficient to measure manganese concentration frequently and regularly. The water turnover by the difference of water temperature make manganese on the floor of water reservoir rise up to surface and increase the manganese concentration near the surface. Manganese concentration and water temperature from the surface to depth of 20m by 5m have been time plotted and exploratory analyzed to show that the water turnover could be used instead of measuring manganese concentration to know the time point of water management. Two models for forecasting the time point of water turnover were proposed and compared as follow: The regression model of CR20, the consistency ratio of water temperature, between the surface and the depth of 20m on the lagged variables of CR20 and the first lag variable of max temperature. And, the Box-Jenkins model of CR20 as ARIMA (2, 1, 2).

• Interaction and multiscale mechanics
• /
• v.1 no.3
• /
• pp.369-379
• /
• 2008

A combined stochastic diffusion and mean-field model is developed for a systematic study of the grain growth in a pure single-phase polycrystalline material. A corresponding Fokker-Planck continuity equation is formulated, and the interplay/competition of stochastic and curvature-driven mechanisms is investigated. Finite difference results show that the stochastic diffusion coefficient has a strong effect on the growth of small grains in the early stage in both two-dimensional columnar and three-dimensional grain systems, and the corresponding growth exponents are ~0.33 and ~0.25, respectively. With the increase in grain size, the deterministic curvature-driven mechanism becomes dominant and the growth exponent is close to 0.5. The transition ranges between these two mechanisms are about 2-26 and 2-15 nm with boundary energy of 0.01-1 J $m^{-2}$ in two- and three-dimensional systems, respectively. The grain size distribution of a three-dimensional system changes dramatically with increasing time, while it changes a little in a two-dimensional system. The grain size distribution from the combined model is consistent with experimental data available.