• 제어로봇시스템학회논문지
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• 제10권2호
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• pp.112-124
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• 2004

A neural network based adaptive reconfigurable flight controller is presented for a class of discrete-time nonlinear flight systems in the presence of variations of aerodynamic coefficients and control effectiveness decrease caused by control surface damage. The proposed adaptive nonlinear controller is developed making use of the backstepping technique for the angle of attack, sideslip angle, and bank angle command following without two time separation assumption. Feedforward multilayer neural networks are implemented to guarantee reconfigurability for control surface damage as well as robustness to the aerodynamic uncertainties. The main feature of the proposed controller is that the adaptive controller is developed under the assumption that all of the nonlinear functions of the discrete-time flight system are not known accurately, whereas most previous works on flight system applications even in continuous time assume that only the nonlinear functions of fast dynamics are unknown. Neural networks learn through the recursive weight update rules that are derived from the discrete-time version of Lyapunov control theory. The boundness of the error states and neural networks weight estimation errors is also investigated by the discrete-time Lyapunov derivatives analysis. To show the effectiveness of the proposed control law, the approach is i]lustrated by applying to the nonlinear dynamic model of the high performance aircraft.

• 제어로봇시스템학회논문지
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• 제9권4호
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• pp.329-339
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• 2003

A neural network based adaptive controller design method is proposed for reconfigurable flight control systems in the presence of variations in aerodynamic coefficients or control effectiveness decrease caused by control surface damage. The neural network based adaptive nonlinear controller is developed by making use of the backstepping technique for command following of the angle of attack, sideslip angle, and bank angle. On-line teaming neural networks are implemented to guarantee reconfigurability and robustness to the uncertainties caused by aerodynamic coefficients variations. The main feature of the proposed controller is that the adaptive controller is designed with assumption that not any of the nonlinear functions of the system is known accurately, whereas most of the previous works assume that only some of the nonlinear functions are unknown. Neural networks loam through the weight update rules that are derived from the Lyapunov control theory. The closed-loop stability of the error states is also investigated according to the Lyapunov theory. A nonlinear dynamic model of an F-16 aircraft is used to demonstrate the effectiveness of the proposed control law.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권4호
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• pp.878-894
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• 2013

Secure multimedia multicast applications involve group communications where group membership requires secured dynamic key generation and updating operations. Such operations usually consume high computation time and therefore designing a key distribution protocol with reduced computation time is necessary for multicast applications. In this paper, we propose a new key distribution protocol that focuses on two aspects. The first one aims at the reduction of computation complexity by performing lesser numbers of multiplication operations using a ternary-tree approach during key updating. Moreover, it aims to optimize the number of multiplication operations by using the existing Karatsuba divide and conquer approach for fast multiplication. The second aspect aims at reducing the amount of information communicated to the group members during the update operations in the key content. The proposed algorithm has been evaluated based on computation and communication complexity and a comparative performance analysis of various key distribution protocols is provided. Moreover, it has been observed that the proposed algorithm reduces the computation and communication time significantly.

• Journal of information and communication convergence engineering
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• 제12권3호
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• pp.181-185
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• 2014

The lifetime of a solid-state drive (SSD) is limited because of the number of program and erase cycles allowed on its NAND flash blocks. Data cannot be overwritten in an SSD, leading to an out-of-place update every time the data are modified. This result in two copies of the data: the original copy and a modified copy. This phenomenon is known as write amplification and adversely affects the endurance of the memory. In this study, we address the issue of reducing wear leveling through efficient handling of write requests. This results in even wearing of all the blocks, thereby increasing the endurance period. The focus of our work is to logically divert the write requests, which are concentrated to limited blocks, to the less-worn blocks and then measure the maximum number of write requests that the memory can handle. A memory without the proposed algorithm wears out prematurely as compared to that with the algorithm. The main feature of the proposed algorithm is to delay out-of-place updates till the threshold is reached, which results in a low overhead. Further, the algorithm increases endurance by a factor of the threshold level multiplied by the number of blocks in the memory.

• 한국측량학회지
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• 제17권1호
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• pp.69-78
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• 1999

최근 급속한 산업발전으로 환경오염에 대한 인식이 고조되고 있으며 오염방지에 대한 방법 및 기술 또한 다각적으로 연구되고 있다. 과거에는 환경오염에 대한 대응방향이 오염물질의 농도저감과 처리기술 개발등에 국한되어 왔으나 현재는 오염물질의 관리 및 평가와 같은 좀더 고차원적인 연구로 전환되고 있다. 본 연구에서는 환경정보 시스템구축에 대한 개념을 수립하고 그 기법을 제시하였으며 오염원과 오염부하량에 따른 환경정보의 데이터베이스 설계, 질의, 분석 그리고 출력기법을 개발하였다. 또한, LANDSAT TM 영상을 이용하여 토지이용도를 작성하였으며, PC상에서 Excel과 PC ArcView 프로그램간에 동적데이터교환을 이용하여 폐수배출시설허가관리대장 관리를 가능하게 하여 기존 GSIS용 프로그램의 문서관리에 대한 취약성을 극복할 수 있었다.

• 인터넷정보학회논문지
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• 제5권5호
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• pp.69-77
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• 2004

인터넷이 널리 보급되면서 지능형 검색 에이전트들이 사용자의 요구를 만족시키기 위해 일반화되어 사용되고 있다. 그러나 이러한 지능형 멀티에이전트들은 서로 독립적으로 사용되어 멀티에이전트들 간의 분산된 정보를 원활하고 효율적으로 처리하기 위한 상호 협력 작용이 부족해 정보의 신뢰성이 낮고 동적으로 변화하는 분산 환경에 대처하기가 어렵다. 이런 문제를 해결하기 위해 본 논문에서는 멀티에이전트간의 효율적인 상호 협력과 빠른 정보처리를 위해 브로커 에이전트에 에이전시를 생성하고 신경망을 이용해 멀티에이전트들의 에이전시들을 분류하여 더욱 신속·정확한 정보를 사용자에게 제공하도록 한다. 또한 정보의 신뢰성을 위해서 에이전트 관리기법을 제안하여 기존의 검색 시스템이 가지고 있는 정보갱신문제를 향상시키고, 시뮬레이션을 통해 본 연구의 성능을 평가한다.

• Structural Engineering and Mechanics
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• 제56권4호
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• pp.625-648
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• 2015

Modern super-tall buildings are more sensitive to strong winds. The evaluation of wind loads for the design of these buildings is of primary importance. A direct monitoring of wind forces acting on super-tall structures is quite difficult to be realized. Indirect measurements interpreted by inverse techniques are therefore favourable since dynamic response measurements are easier to be carried out. To this end, a Kalman filtering based inverse approach is developed in this study so as to estimate the wind loads on super-tall buildings based on limited structural responses. The optimum solution of Kalman filter gain by solving the Riccati equation is used to update the identification accuracy of external loads. The feasibility of the developed estimation method is investigated through the wind tunnel test of a typical super-tall building by using a Synchronous Multi-Pressure Scanning System. The effects of crucial factors such as the type of wind-induced response, the covariance matrix of noise, errors of structural modal parameters and levels of noise involved in the measurements on the wind load estimations are examined through detailed parametric study. The effects of the number of vibration modes on the identification quality are studied and discussed in detail. The made observations indicate that the proposed inverse approach is an effective tool for predicting the wind loads on super-tall buildings.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.709-718
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• 2017

This paper proposes the guidance laws for an agile turn of air-to-air missiles during the initial boost phase. Optimal solution for the agile turn is obtained based on the optimal control theory with a simplified missile dynamic model. Angle-of-attack command generating methods for completion of agile turn are then proposed from the optimal solution. Collision triangle condition for non-maneuvering target is reviewed and implemented for update of terminal condition for the agile turn. The performance of the proposed method is compared with an existing homing guidance law and the minimum-time optimal solution through simulations under various initial engagement scenarios. Simulation results verify that transition to homing phase after boost phase with the proposed method is more effective than direct usage of the homing guidance law.

• 한국콘텐츠학회:학술대회논문집
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• 한국콘텐츠학회 2007년도 추계 종합학술대회 논문집
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• pp.846-848
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• 2007

최근 웹 2.0에 대한 관심이 높아지면서 대부분의 웹 사이트에서 RSS를 지원하고 있다. RSS 구독기는 여러 웹 사이트에서 제공되는 RSS 포맷의 콘텐츠를 한곳으로 수집하여 사용자가 해당 웹 사이트를 직접 방문하지 않고도 관심분야의 최신 정보를 얻을 수 있도록 도와주는 소프트웨어 어플리케이션이다. 본 논문에서는 RSS 구독기의 구현을 위하여 비동기 방식인 Ajax와 동적 스크립트 언어인 JSP/Servlet을 이용해서 개발하였다. RSS 포맷 1.0과 2.0대를 지원할 수 있게 하였고, 유동적인 Ajax기반 메뉴들과 카테고리 항목 및 사용자 편의를 생각한 기능들을 추가하여 개발하였다.

• 한국컴퓨터산업학회논문지
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• 제5권1호
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• pp.87-100
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• 2004

최근에 인터넷의 급속한 발전과 더불어 대량의 정보를 효과적으로 표현 및 교환할 수 있는 새로운 데이터 표준으로 XML (extensible Markup Language)이 제안되었으며, XML 문서에 대한 저장과 인덱싱에 대한 연구가 활발하게 진행되고 있다. 본 논문에서는 실시간 XML 문서 처리에 효율적인 주기억장치 기반의 XML 전용 저장 시스템을 설계하고, 사용자 질의에 포함된 엘리먼트 타입 정보를 이용하여 XML 문서트리에 대한 순회를 최소화시킬 수 있는 구조적 검색 기법을 설계한다 또한, 엘리먼트의 삭제 및 삽입 등 동적인 변경에 빠르고 유연하게 대처할 수 있는 인덱스 구조와, 링크 정보를 가지고 있는 XML 문서의 질의 처리를 위해 XLink 표준을 준수하여 테이블 형식의 링크 정보 인덱스 구조를 설계한다.