• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.31-34
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• 2002

최근 많은 웹 기반 서비스나 애플리케이션들이 XML 형태로 지원되면서 XML 데이터의 보안에 대해서 많은 연구가 이루어지고 있다. 기존의 XML 보안은 암호, 서명, 접근제어의 형태로 이루어지고 있으며 그 중에서 접근제어는 DTD기반과 문서기반으로 분류되어 임의적 접근제어 모델을 적용한 연구가 진행되어 왔다. 그러나 DTD의 대안으로서 객체지향개념을 수용하는 XML 스키마의 사용이 증가되고 있어 이를 위한 보안요구사항과 접근제어정책이 추가로 필요하게 되었다. XML문서의 데이터보호를 위해서 기존의 DTD기반과 문서기반 접근제어정책을 수용하면서 스키마 기반의 접근제어정책을 지원하기 위해서 이 논문에서는 역할기반접근제어 모델을 적용한 XML 스키마 기반의 접근제어 모델을 제안한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.5
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• pp.125-133
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• 2006

This paper presents comparison results of Step Response Model of Dynamic Matrix Control(DMC) for a drum-type boiler-turbine system of a fossil power plant. Two possible kinds of step response models are investigated in designing the DMC, one is developed with the linearization of theoretical model and the other is developed with the process step-test data. Then, the control performances of each model-based DMC are simulated and evaluated. It is observed that the simulation results with the step-response model based on the test data show satisfactory results, while the linearized model is not suitable for the control of boiler-turbine system.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.1-10
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• 2008

The problem of controlling asynchronous sequential machines is addressed in this paper. Corrective control means to make behavior of an asynchronous sequential machine equal to that of a given model. The main objective is to develope a corrective controller, especially when a model is given as nondeterministic, or a set of reference models. The structure of corrective control system for asynchronous sequential machines is addressed first, followed by description of nondeterministic models. Then, we propose a method for analyzing reachability of asynchronous machines and nondeterministic models. Proposed methods are demonstrated in an example.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.127-132
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• 2003

This paper presents a new model that can precisely simulate the attenuation characteristics of the voltage-controlled PIN diode attenuators. After carefully investigating the problems in the conventional PIN diode models, a new PIN diode model was proposed and verified with experimental data. The proposed model is well operated when it is used in the voltage-controlled mode as well as current-controlled mode, and is simple and straightforward model, since the PN junction diode of this model has the same curve as that of the PIN diode. This model is very effective to design voltage-controlled attenuator and its implementation in commercial simulators is simple and accurate. This model will allow RF and Microwave designers to better use the PIN diodes in various circuits.

• Journal of the Institute of Convergence Signal Processing
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• v.5 no.2
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• pp.138-142
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• 2004

This paper proposes the design of the model following control system using the PID control structure. PID control system became model following control by inserting new pre-compensator in order to improve control performance in discrete-time region. Gain of the PID controller needs to be readjusted when response of system changes due to disturbance or load fluctuation. Performance of control system improves by joining neural network to PID control system because performance of control system depends largely on each PID gain in PID control system. And the games of the PID controller in the proposed control system are automatically adjusted by back-propagation algorithm of the neural network. Angular position of DC servo motor is selected as a plant in order to verify control performance in model following control. After it is applied to the position control system, it's performance is verified through computer experiment.

• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.88-88
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• 2003

로켓 엔진 시스템에는 가압가스로 추진제를 엔진으로 공급하는 가압 시스템과 터보펌프를 이용해 엔진으로 고압의 추진제를 공급하는 터보펌프 시스템으로 나눌 수 있으며 터보펌프 시스템은 다시 Gas Generator를 이용하는 개방형 엔진과 Prebumer를 이용한 폐쇄형 엔진인 다단 엔진으로 구분할 수 있다. 로켓의 엔진 시스템은 Turbine, Turbopump, Gas Generator, Thrust Chamber, Tube, Valve, Propellant Tank 등 각 구성품 간에 서로 상호간섭이 매우 심한 공정이다 로켓 엔진 시스템은 이와 같은 상호간섭에 의해 추력 제어 및 혼합비 제어, 추진제 소진 제어 적용 시 정확하고 강인한 제어를 수행하여야 한다. 이를 위해 정확한 동특성 모델을 구축하는 것이 중요하며 모델을 통해 적절한 제어 시스템을 선택하여야 한다. 그러나 현재 국내에는 이에 대한 연구가 미미하며 해외의 경우 로켓은 특수 분야에 속함으로 공개되어 있지 않다. 로켓에 대한 개발 연구에 있어서는 위와 같은 작업이 선행되어야 하며 이에 대한 선행 연구로 한국항공우주연구원에서 Gas Generator를 이용한 개방형 터보펌프 엔진 시스템에 대한 연구를 진행하고 있다. 본 논문에서는 Gas Generator를 이용한 개방형 터보펌프 엔진시스템에 대한 동특성 모델을 구성하였다. 배관부, 터빈, 펌프, 밸브, Gas Generator, 재생냉각, 추력연소실 등 엔진 시스템을 구성하는 구성품에 대한 동특성 모델을 구성하였으며 이를 matlab의 simulink를 통해 각 구성품을 연결하여 최종 엔진시스템의 동특성 모델을 구성하였다. 구성된 동특성 모델을 통해 각종 변화(추진제 밀도 변화, 추력 변화, 혼합비 변화 등)에 대한 엔진 시스템 변화를 예측하여 정확한 엔진 시스템에 대한 이해를 넓혔으며 추력 제어 및 혼합비, 추진제 소진 제어를 최적으로 할 수 있는 제어 시스템 구축을 위한 기초 자료로 이용할 수 있을 것이다.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.1
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• pp.28-36
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• 2016

Theoretical model of a variable thrust solid rocket motor with a pintle nozzle was derived. For the chamber pressure control, classical model linearization and proportional-intergral controller was used. And then two types of gain scheduling controller were suggested to imporve controller performance for the non-linear propulsion model. Considering characteristics of systems, control gains were scheduled by chamber pressure or free volume. Step responses of each controllers were compared. As a result, the proper control algorithm about characteristics of variable thrust rocket motor was suggested.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.177-182
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• 2004

Delegation is one of important security policies in the access control area. We propose a management model of delegation integrated with ARBAC model for environment of distributed access control. We Integrate PBDM delegation model with ARBAC97 model, and suggest integrity rules of delegation for preventing security threats in new model. Our model supports both free delegation for users without intervention of administrators, and controlling delegation for security administrators.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.219-225
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• 2005

In this paper, a new discrete-time small signal model of an average current mode control is proposed to predict the inductor current responses. Compared to the peak current mode control, the analysis of the average current mode control is difficult because of its presence of an compensation network. By utilizing sampler model, a new discrete-time small signal model is derived and used to predict the behaviors of an inductor current of average current mode control employing generalized compensation networks. In order to show the usefulness of the proposed model, prediction results of the proposed model are compared to those of the circuit level simulator, PSIM and experiment.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.95-100
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• 2021

This paper introduces model-based meta reinforcement learning as a control for the manipulator of an underwater construction robot. Model-based meta reinforcement learning updates the model fast using recent experience in a real application and transfers the model to model predictive control which computes control inputs of the manipulator to reach the target position. The simulation environment for model-based meta reinforcement learning is established using MuJoCo and Gazebo. The real environment of manipulator control for underwater construction robot is set to deal with model uncertainties.