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Computational Approach for an improved finite element domain decomposition method
JunYoung Kwak,TaeYoung Chun,SangJoon Shin,Olivier A. Bauchau 한국산업응용수학회 2011 한국산업응용수학회 학술대회 논문집 Vol.6 No.2
This paper presents the development of an improved computational algorithm based on finite element domain decomposition technique for a large scale static and dynamic structural analysis. The proposed algorithm is compared with the well-known FETI approach with regards to convergence and efficiency characteristics. The proposed approach uses both local and global Lagrange multipliers together with an augmented Lagrangian formulation to achieve computational robustness and efficiency. We additionally developed the transient time computational algorithm by extending the proposed FETI method. Numerical predictions are compared with those obtained by the original and dual-primal FETI methods to demonstrate the improvements by the proposed approach. The present algorithm is relatively simple and leads to improved convergence and efficiency characteristics.
Development of a Finite Element Domain Decomposition Analysis with Improved Characteristics
JunYoung Kwak(곽준영),TaeYoung Chun(전태영),SangJoon Shin(신상준),Olivier A. Bauchau 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
This paper describes development of an improved computational algorithm based on finite element domain decomposition technique for a large scale structural analysis. We compared computational algorithms corresponding to the original FETI method and the presently improved FETI approach with regard to convergence. In the original FETI method, Lagrange multipliers were introduced to enforce compatibility at the interface DOF’s. The improved FETI algorithm uses local Lagrange multipliers with an augmented Lagrangian formulation (ALF) as penalty formulation of the problem for computational robustness and efficiency. The present mathematical algorithm is relatively simple and leads to improved convergence of numerical computation. Thus, this algorithm will be attractive for FETI domain decomposition method. For validation of the present approach, we compared its numerical results with those obtained by the original FETI method.
ADVANCED DOMAIN DECOMPOSITION METHOD BY LOCAL AND MIXED LAGRANGE MULTIPLIERS
JUNYOUNG KWAK,TAEYOUNG CHUN,HAESEONG CHO,SANGJOON SHIN,OLIVIER A. BAUCHAU 한국산업응용수학회 2014 Journal of the Korean Society for Industrial and A Vol.18 No.1
This paper presents development of an improved domain decomposition method for large scale structural problem that aims to provide high computational efficiency. In the previous researches, we developed the domain decomposition algorithm based on augmented Lagrangian formulation and proved numerical efficiency under both serial and parallel computing environment. In this paper, new computational analysis by the proposed domain decomposition method is performed. For this purpose, reduction in computational time achieved by the proposed algorithm is compared with that obtained by the dual-primal FETI method under serial computing condition. It is found that the proposed methods significantly accelerate the computational speed for a linear structural problem.
Autonomous UAV Target Tracking and Safe Landing on a Leveling Mobile Platform
Junyoung Kwak,Sangwoong Lee,Junsoo Baek,Baeksuk Chu 한국정밀공학회 2022 International Journal of Precision Engineering and Vol.23 No.3
The demand for quadcopters capable of stably taking off from and landing on a mobile surface is rising in view of the increasing use of these aircrafts in the military and marine fi elds. Accordingly, a novel leveling mobile platform with a twodegree-of-freedom gimbal structure for landing a quadcopter safely on a moving target is designed in this work. The basis tracking and landing operation with a quadcopter and the leveling mobile platform are performed on global positioning system (GPS) and vision system. The combined system can track a moving target as well as control altitude and attitude using various sensors, such as GPS, inertial measurement unit (IMU) and LiDAR, mounted on the quadcopter. By utilizing vision sensors, a more precise landing control is achieved. The leveling platform was designed to maintain a level landing surface and assist in the stable landing of the quadcopter. This platform was fabricated because landing may be unsafe if the landing target is moving on an uneven surface. To verify the effectiveness of the above system, experiments were conducted to land a quadcopter on a target moving on level ground and sloping surfaces. When the leveling function was not implemented, the quadcopter frequently overturned while attempting to land. In contrast, when the leveling function was used, all landing attempts were successful.
음악교수법연구 : 피아노 교육수요 변화와 성인 피아노 학습 활성 방안
곽준영 ( Junyoung Kwak ),정완규 ( Wankyu Chung ) 한국피아노교수법학회 2014 음악교수법연구 Vol.14 No.-
본 연구는 21세기에 들어 점점 가속화되고 있는 피아노 학습자 수요 감소의 문제점을 분석하고, 피아노 학습에서 새로운 소비층으로 떠오르고 있는 성인 학습자를 학습계층으로 유도하기 위한 방법과 방향을 피아노 교육 활성화 대안으로 제시하고 있다. 성인 피아노 학습자가 활성화 되어 있는 선진국들의 경우 경제수준의 향상과 성인들의 문화 활동 증가가 비례하고 있는 것으로 나타나고 있어 한국에서도 성인 학습자의 증가를 전망할 수 있다. 그러나 어린 아동의 학습과 전문 연주자 양성을 주목표로 발전해온 대한민국 피아노 교육은, 선진국과 달리 취미생활과 여가선용을 위하여 성인 학습자를 수용하고 그들의 다양한 목표를 충족하기에 취약한 실정이다. 그러므로 새로운 교육 수요층으로 주목받고 있는 성인 학습자를 활성화하기 위해서는 성인 학습자의 특성을 이해하고, 이를 고려한 다양한 지도방법, 다양한 문화체험의 활용, 그리고 새로운 성인 교재의 연구 개발 및 전문 교사의 양성이 필요할 것으로 예상한다. The purpose of this study is to investigate the value of adult piano learners as a solution to revitalization of the piano education market in Korea. As the 21st Century dawns, the sudden contraction of the markets for piano education caused the imbalance between supply and demand. Generally, a rise of income is directly proportional to a rise of adult``s cultural activity in many developed countries, such as Japan, United Kingdom, and United States, and a lot of adults want to learn a piano for entertainment. Therefore, promotion of adult piano learning can be one of the best solutions to our current situation in the piano education marketplace. However, most of teachers and pedagogues in Korea have little recognition the implicit value of adults piano learners because they concentrate on cultivating people of musical talent for being a professional performer. To invigorate a adult piano learner will be required to understand characters of adult piano leaner, to study the new piano teaching methods for a adult learner. Also teachers will provide a adult learner to a variety of cultural events through piano learning, and new teaching material.
Junyoung Song,Inhwa Jung,Minyoung Song,Young-Ho Kwak,Sewook Hwang,Chulwoo Kim IEEE 2013 IEEE transactions on circuits and systems. a publi Vol.60 No.2
<P>This paper proposes a 2.7 Gb/s referenceless transceiver with weighted PFD for frequency detection of random signals. A single loop referenceless CDR is also proposed to overcome the disadvantages of a dual loop CDR. The ANSI 8b/10b encoder & decoder with the scrambler, the serializer & de-serializer, and the output driver with pre-emphasis are included in the proposed transceiver architecture for DisplayPort v1.1a. The jitter of the generated clock at the Tx PLL is 3.28 ps<SUB>rms</SUB> at 2.7 Gb/s with 1.2 V supply. The eye opening of the transmitter output with 3 m cable is 0.54 UI. The measured jitter of the recovered clock at the CDR is 1.57 ps<SUB>rms</SUB>, and BER is less than 10<SUP>-12</SUP>. The receiver consumes 23 mW at 2.7 Gb/s with 1.2 V supply. The CDR core and transceiver occupy 0.07 mm<SUP>2</SUP> and 0.94 mm<SUP>2</SUP>, respectively, in a 0.13 μm 1P8M CMOS process.</P>
Bag-of-Feature 특징과 랜덤 포리스트를 이용한 의료영상 검색 기법
손정은 ( Jungeun Son ),곽준영 ( Junyoung Kwak ),고병철 ( Byoungchul Ko ),남재열 ( Jaeyeal Nam ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.2
본 논문에서는 의료영상의 특성을 반영하여 영상의 그래디언트 방향 값을 특징으로 하는 Oriented Center Symmetric Local Binary Patterns (OCS-LBP) 특징을 개발하고 추출된 특징 값에 대해 차원을 줄이고 의미 있는 특징 단위로 재 생성하기 위해 Bag-of-Feature (BoF)를 적용하였다. 검색을 위해서는 기존의 영상 검색 방법과는 다르게, 학습 영상을 이용하여 랜덤 포리스트 (Random Forest)를 사전에 학습시켜 데이터베이스 영상을 N 개의 클래스로 자동 분류 시키고, 질의로 입력된 영상을 같은 방법으로 랜덤 포리스트에 적용하여 상위 확률 값을 갖는 2 개의 클래스에서만 K-nearestneighbor 방법으로 유사 영상을 검색결과로 제시하는 새로운 영상검색 방법을 제시하였다. 실험결과에서 본 논문의 우수성을 증명하기 위해 일반적인 유사성 측정 방법과 랜덤 포리스트를 이용한 방법의 검색 성능 및 시간을 비교하였고, 검색 성능과 시간 면에서 상대적으로 매우 우수한 성능을 보여줌을 증명하였다.