• 대한기계학회논문집B
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• 제26권8호
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• pp.1088-1094
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• 2002

A channel flow with a high Reynolds number but coarse grids is numerically studied to investigate the prediction possibility of its turbulence which is three-dimensional and time-dependent. In the present paper, a Reynolds-Averaged Navier-Stokes (RANS) model, a Large Eddy Simulation (LES) and a Navier-Stokes equation with no model are tested with a new approach of hybrid RANS/LES, which reduces to RANS model in the boundary layers and at separation, and to Smagorinsky-like LES downstream of separation, and then compared with each other. It is found that the simulations of hybrid RANS/LES method sustain turbulence like those of LES and with no model, and the results are stable and fairly accurate. This indicates strongly that gradual improvements could lead to a simple, stable, and accurate approach to predict turbulence phenomena of wall-bounded flow.

• 한국산업정보학회논문지
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• 제22권2호
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• pp.79-89
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• 2017

본 연구에서는 적응형혼합유전알고리즘(Adaptive Hybrid Genetic Algorithm: AHGA) 접근법을 이용한 폐쇄루프 공급망(Closed-Loop Supply Chain: CLSC) 모델 최적화를 다루고 있다. CLSC 모델 구축을 위해 공급업체(Part Supplier), 제품제조업체(Product Manufacturer)등으로 구성된 전방향물류(Forward Logistics)와 수집업체(Collection Center), 회복센터(Recovery Center)등으로 구성된 역물류(Reverse Logistics)를 함께 고려하고 있다. 제안된 CLSC 모델은 수리모형(Mathematical Model)으로 표현되며, AHGA접근법을 이용해 이행되어 그 최적해를 구하게 된다. 수치실험에서는 기존연구에서 제안된 몇몇 접근법과 AHGA 접근법을 함께 사용하여 그 수행도를 비교분석하였다.

• 한국지구과학회지
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• 제27권1호
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• pp.6-14
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• 2006

본 연구에서는 중학교 과학 영재아들이 가지고 있는 조석에 관한 정신모형을 탐색하기 위하여 두 가지 상황에서의 개념 유형을 분류하고, 각 유형들을 구성하는 국면들을 분석하였다. 조석 현상에 관해 두 가지 상황으로 구성된 과제 수행을 실시한 후 그 응답 결과를 분석한 결과, 상당수의 학생들이 상황에 따라 서로 다른 개념 유형을 나타내었다. 상황에 따른 개념 유형들을 구성하고 있는 국면을 분석한 결과, 내용-특정적 국면에서는 큰 차이가 없었으나 전략적 국면에서는 많은 차이를 나타내었다. 두 가지 상황에서 나타나는 개념 유형들과 이들 유형을 구성하는 국면들을 조합하여 학생들의 조석에 관한 정신모형을 분석한 결과 다음과 같은 4가지 모형으로 나눌 수 있었다: (1) Tide model (2) Force model (3) Phase model (4) Hybrid model. Tide model은 과학적으로 옳은 모형이며, Force model과 Phase model은 옳지 않은 모형으로, 상황에 따른 개념유형은 서로 일치하나 조석현상을 각각 달과 태양의 합력과 달의 위상(모양)의 관계로만 이해하고 있는 경우이다. Hybrid model 혼합 모형으로 상황에 따라 나타나는 개념 유형이 서로 부합되지 않는 모형이다. 중학교 과학 영재아들은 조석 현상에 대해 가장 많이 가지고 있는 모형은 Tide model(45.0%) 이었으며, 그 다음으로는 Hybrid model(30.0%), Force model(12.5%), Phase model(7.5%) 순으로 나타났다.

• 컴퓨터교육학회논문지
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• 제18권6호
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• pp.43-51
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• 2015

본 논문의 목적은 진로 상담 분야에서 직접 코치와 학습자가 만나서 확인하고 상담하는 면대면 코칭과 인터넷을 통해 코치와 학습자가 상담하는 E-코칭을 조합한 하이브리드 진로코칭 모형을 개발하고 대학생들의 진로 지도에 적용하고 그 효과를 분석하는데 있다. 하이브리드 진로코칭에서는 프로파일, 적성 검사 등 인터넷 상에서 원격 접속하여 수행 가능하고 데이터 저장이 필요한 것은 E-코칭으로 처리하고, 점검, 상담 및 성찰 등 학생의 상황을 파악하고 대화가 필요한 부분은 면대면으로 설계하였다. 제안한 하이브리드 진로코칭 모형은 진로코칭 안내, 자기이해, 진로의사결정, 진로실행계획 수립, 실행계획 및 실행의지 점검, 실행결과 점검 6단계로 나누어 진행하였다. 하이브리드 진로코칭 모형을 대학생에게 적용하여 진로개발을 위한 인지적, 행동적 행동변화를 촉진하고 그 효과를 분석하였다. 연구 결과 진로준비행동이 높아졌으며, 코칭을 통해 자신의 현재 상태 분석과 실행 전략이 중요성 및 학습법과 자기조절능력 등을 획득하였다고 분석되었다. 이러한 결과를 토대로 이 연구에서 개발된 하이브리드 진로코칭 모형은 진로지도가 강화되는 대학에서 교수의 진로지도를 지원할 수 있을 것이라 기대된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.500-501
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• 2013

• 기술혁신연구
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• 제15권2호
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• pp.83-102
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• 2007

This study extends the existing method of Technology Forecasting with Data Envelopment Analysis (TFDEA) by incorporating a ranking method into the model so that we can reduce the required number of DMUs (Decision Making Units). TFDEA estimates technological rate of change with the set of observations identified by DEA(Data Envelopment Analysis) model. It uses an excessive number of efficient DMUs(Decision Making Units), when the number of inputs and outputs is large compare to the number of observations. Hence, we investigated the possibility of incorporating CCCA(Constrained Canonical Correlation Analysis) into TFDEA so that the ranking of DMUs can be made. Using the ranks developed by CCCA(Constrained Canonical Correlation Analysis), we could limit the number of efficient DMUs that are to be used in the technology forecasting process. The proposed hybrid model could establish technology frontiers with the efficient DMUs for each generation of technology with the help of CCCA that uses the common weights. We applied our hybrid model to forecast the technological progress of main battle tank in order to demonstrate its forecasting capability with practical application. It was found that our hybrid model generated statistically more reliable forecasting results than both TFDEA and the regression model.

• Smart Structures and Systems
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• 제14권6호
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• pp.1081-1103
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• 2014

Real-time hybrid simulation (RTHS) has emerged as an important tool for testing large and complex structures with a focus on rate-dependent specimen behavior. Due to the real-time constraints, accurate dynamic control of servo-hydraulic actuators is required. These actuators are necessary to realize the desired displacements of the specimen, however they introduce unwanted dynamics into the RTHS loop. Model-based actuator control strategies are based on linearized models of the servo-hydraulic system, where the controller is taken as the model inverse to effectively cancel out the servo-hydraulic dynamics (i.e., model-based feedforward control). An accurate model of a servo-hydraulic system generally contains more poles than zeros, leading to an improper inverse (i.e., more zeros than poles). Rather than introduce additional poles to create a proper inverse controller, the higher order derivatives necessary for implementing the improper inverse can be calculated from available information. The backward-difference method is proposed as an alternative to discretize an improper continuous time model for use as a feedforward controller in RTHS. This method is flexible in that derivatives of any order can be explicitly calculated such that controllers can be developed for models of any order. Using model-based feedforward control with the backward-difference method, accurate actuator control and stable RTHS are demonstrated using a nine-story steel building model implemented with an MR damper.

• 반도체디스플레이기술학회지
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• 제20권4호
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• pp.10-15
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• 2021

Cache bypassing schemes have been studied to remove unnecessary updating the data in cache blocks. Among them, a statistics-based cache bypassing method for asymmetric-access caches is one of the most efficient approach for non-voliatile memories and shows the lowest cache access latency. However, it is proposed under the condition of the normal cache system, so further study is required for the hybrid cache architecture. This paper proposes a novel cache bypassing scheme, called hybrid bypassing block selector. In the proposal, the new model is established considering the SRAM region and the non-volatile memory region separately. Based on the model, hybrid bypassing decision block is implemented. Experiments show that the hybrid bypassing decision block saves overall energy consumption by 21.5%.

• Carbon letters
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• 제14권2호
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• pp.105-109
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• 2013

Effects of the amount of nickel powder (Ni) in Ni-carbon fiber (CF) hybrid filler systems on the conductivity(or resistivity) and thermal coefficient of resistance (TCR) of filled high density polyethylene were studied. Increases of the resistivity and TCR with increasing Ni concentration at a given hybrid filler content were observed. Using the fiber contact model, we showed that the main role of Ni in the hybrid filler system is to decrease the interfiber contact resistance when Ni concentration is less than the threshold point. The formation of structural defects leading to reduced reinforcing effect resulted in both a reduction of strength and an increase of the coefficient of thermal expansion in the composite film; these changes are responsible for the increases of both resistivity and TCR with increasing Ni concentration in the hybrid filler system.

• 한국소음진동공학회논문집
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• 제13권7호
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• pp.524-531
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• 2003

This paper presents an active vibration control of a flexible beam structure using a hybrid mount which consists of elastic rubber and Piezoelectric material. After identifying stiffness and damping properties of the rubber and piezoelectric elements, a mechanical model of the hybrid mount is established. The mount model is then Incorporated into the beam structure, and the governing equation of motion is obtained in a state space. A sliding mode controller is designed in order to actively attenuate the vibration of the beam structure subjected to high frequency and small magnitude excitations. The controller is experimentally realized and control responses such as acceleration of the beam structure and force transmission through the hybrid mount are evaluated. In addition. a comparative work is done between the passive and hybrid mount systems.