• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.592-602
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• 2014

In the Integrated Gasification Combined Cycle (IGCC), the stability of the gasifier has strong influences on the rest of the plant as it supplies the feed to the rest of the power generation system. In order to ensure a safe and stable operation of the entrained-flow gasifier and for protection of the gasifier wall from the high internal temperature, the solid slag layer thickness should be regulated tightly but its control is hampered by the lack of on-line measurement for it. In this study, a previously published dynamic simulation model of a Shell-type gasifier is reproduced and two different linear model predictive control strategies are simulated and compared for multivariable control of the entrained-flow gasifier. The first approach is to control a measured secondary variable as a surrogate to the unmeasured slag thickness. The control results of this approach depended strongly on the unmeasured disturbance type. In other words, the slag thickness could not be controlled tightly for a certain type of unmeasured disturbance. The second approach is to estimate the unmeasured slag thickness through the Kalman filter and to use the estimate to predict and control the slag thickness directly. Using the second approach, the slag thickness could be controlled well regardless of the type of unmeasured disturbances.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1233-1236
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• 1996

Attitude Control System for a Hydrofoil type catamaran in wave is designed using a Decentralized Adaptive Control technique which is announced already by authors. This automatic attitude control system is designed for its good seaworthiness and for robustness on the variation of center of gravity. The performance is compared with a PID controller and the results show that the Decentralized Adaptive controller has better stability on the variation of the center of gravity.

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.127-128
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• 2018

본 논문에서는 채널추정에러가 존재하는 셀룰라시스템 환경에서 D2D 통신을 위한 전력제어 알고리즘 운용방안을 제안한다. 전력제어의 목적은 요구하는 SIR 값을 유지하는 것이다. 하지만, 채널 추정에러 환경에서의 SIR 성능은 확률적 분포를 가지게 된다. 이러한 확률적 SIR 성능 분포를 고려하여, 채널추정에러를 보상하는 가변적인 SIR 적용과 재전송 기법을 복합하여 D2D 통신을 위한 전력제어 기법을 제안하도록 한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.05a
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• pp.545-546
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• 2012

일반적으로 회전력이 발생하는 제어시스템에 있어서 발생되는 외란과 시스템의 동특성에 의해 발생되는 리플 등을 보정하기 위해 다양한 제어기법들이 연구되고 있다. 특히, 제어시스템에 존재하는 미지의 외란을 제거하기 위하여 AFC(Adaptive Feedforward Cancellation) 제어이론을 적용하여 미지의 외란에 대한 시스템의 안정성을 확보하려고 노력하고 있다. 그러나 기존의 AFC의 구현을 위하여 연속 시간제어시스템의 전달함수인 IMP(Internal Model Principle)를 이용하여 특정 주파수 영역에 대한 외란을 제거하고 있지만 보다 광범위한 영역에 대해서는 제어 성능은 아직 부족한 편이다. 본 논문에서는 기존의 PID 제어기를 이용한 위치제어에 있어서 발생할 수 있는 외란을 제거하기 위해 AFC 제어이론인 IMP 전달함수와 인공지능 기법인 Fuzzy 제어기를 추가로 설계하여 모터의 위치제어에 대한 성능과 외란 제어에 대한 성능을 제시하고자 한다.

• The KIPS Transactions:PartA
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• v.11A no.5
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• pp.383-390
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• 2004

This paper propose a method that controls facial expression of 3D avatar by having the user select a sequence of facial expressions in the space of facial expressions. And we setup its system. The space of expression is created from about 2400 frames consist of motion captured data of facial expressions. To represent the state of each expression, we use the distance matrix that represents the distances between pairs of feature points on the face. The set of distance matrices is used as the space of expressions. But this space is not such a space where one state can go to another state via the straight trajectory between them. We derive trajectories between two states from the captured set of expressions in an approximate manner. First, two states are regarded adjacent if the distance between their distance matrices is below a given threshold. Any two states are considered to have a trajectory between them If there is a sequence of adjacent states between them. It is assumed . that one states goes to another state via the shortest trajectory between them. The shortest trajectories are found by dynamic programming. The space of facial expressions, as the set of distance matrices, is multidimensional. Facial expression of 3D avatar Is controled in real time as the user navigates the space. To help this process, we visualized the space of expressions in 2D space by using the multidimensional scaling(MDS). To see how effective this system is, we had users control facial expressions of 3D avatar by using the system. As a result of that, users estimate that system is very useful to control facial expression of 3D avatar in real-time.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.3
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• pp.285-289
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• 2004

Recently, due to the high development of the internet, needs for multimedia streams such as digital audio and video is increasing much more. In case of transmitting multimedia streams using the User Datagram Protocol (UDP), it may cause starvation of TCP traffic on the same transmission path, thus resulting in congestion collapse and enormous delay because UDP does not perform TCP-like congestion control. Because of this problem, diverse researches are being conducted on new transmission schemes and protocols intended to efficiently reduce the transmission delay of real-time multimedia streams and perform congestion control. The TCP-friendly congestion control schemes can be classified into the window-based congestion control, which uses the general congestion window management function, and the rate-based congestion control, which dynamically adjusts transmission rate by using TCP modeling equations and the like. In this paper, we suggest the square-root congestion avoidance algorithm with the hybrid TCP-friendly congestion control scheme which the window-based and rate-based congestion controls are dealt with in a combined way. We apply the proposed algorithm to the existing TEAR. We simulate the performance of the proposed TEAR by using NS, and the result shows that it gives better improvement in the stability needed for providing congestion control than the existing TEAR.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.467-472
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• 2006

This study has been done to design a precise system and develop position control algorithm to control a Composite Smoke Bomb Azimuth driving apparatus of a BLDC servo motor. Having to Blind the sight of opposite tank. the Smoke Bomb Rotational driving system needs instant response that is able to detect opponent appearance and blast the bomb at a short time. So a design that shows fast current response capability or $300[Hz]\sim500[Hz]$ is proposed. in the MIN-MAX PWM technology is used to increase the operational speed. in order to control the blasting position, a precision position control algorithm that utilizes the integral value of speed trajectory is suggested. Also these characteristics are monitored and assessed by the PC based monitoring program which shows the graphs of current, voltage, position, and speed parameters. The main controller is based on a TMS320VC33 high performance floating-point DSP(Digital Signal Process) and the PWM generator utilizes EPM7128 CPLD.

• The Journal of Korean Association of Computer Education
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• v.11 no.4
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• pp.71-83
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• 2008

The recent advances of the information technology have motivated lots of research efforts to develop new computer-aided teaching and learning methodologies on various computer science topics, such as data structures, operating system, computer networks, and computer architecture. However, there have been only few studies to educate the database subject although it is one of the most important topics in the computer science. Specifically, among the various issues in the database subject, a learner often suffers to understand the mechanism of the concurrency control and recovery of database transaction in the database because it highly interacts with other functions in the database. Obviously, an intelligent visualization tool can help a learner to understand the process of the concurrency control and the recovery of database transaction. The purpose of this study is to develop an efficient visualization tool which can help users understand the two phase locking protocol (2PLP)-based concurrency control. Specifically, this visualization tool is designed to encourage a users' participation and raise their interest by visualizing the process of transactions and allowing users to specify and manipulate their own transactions.

• Journal of KIISE:Information Networking
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• v.27 no.3
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• pp.247-255
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• 2000

최근 이동통신 서비스의 보급이 날로 증가됨에 따라 무선 접속 인터넷 서비스이 사용에 대한 요구가 급증하고 있다. 그러나 인터넷에서 사용되는 TCP 프로토콜은 에러 발생율이 낮은 유선망을 고려하여 설계되었기 때문에 망에서 발생되는 패킷 손실을 망내의 폭주로 인한 것으로 가정하고 폭죽제어 알고리즘을 동작시켜 윈도우 크기를 줄인다. 그러나 무선통신망과 같이 에러 발생율이 높은 환경에서는 패킷 손실이 주로 엘 발생에 기인하는데, 이 경우 기존의 TCP 프로토콜을 사용하면 폭주제어 알고리즘이 동작되어 TCP의 성능을 저하시키는 문제점이 발생된다. 따라서 본 논문에서는 유무선 복합망에서 TCP 프로토콜의 성능을 개선하기 위한 Split ACKs 기법을 제안하였다. 이 기법은 기지국에서 무선링크의 패킷 손실 이후에 수신된 ACK 패킷을 여러 개로 쪼개서 TCP 송신측으로 전달한다. 따라서 여러 개의 ACK 패킷을 수신한 TCP 송신측은 폭죽제어 알고리즘이 동작되어 감소시킨 윈도우 크기를 빠르게 복귀시켜 주기 때문에, 저하된 TCP 프로토콜의 성능을 신속히 향상시킬 수 있다. 아울러 제안된 기법은 기존 TCP 프로토콜을 그대로 사용할 수 있으며, TCP의 End-to-end Semantics가 유지되는 장점이 있다. 시뮬레이션을 통한 성능분석 결과 이 기법은 기존의 TCP 프로토콜에 비해 약 20%의 성능향상을 보였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.3
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• pp.361-369
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• 2001

This paper deals with numerical efficiency of nonlinear solution technique for space trusses. It will propose the combined Arc-length method to trace structural behavior after reaching buckling load as opposed to the current Arch-length method. The combined Arc-length method uses the current stiffness parameter as a control variable. It uses Secant-Newton method in stable path and applies Arc-length method in unstable path. To evaluate efficiency of solution technique, the accuracy of solution, convergence, and computing time concerning illustrative numerical examples are compared with the current Arc-length method. It show that the combined Arc-length method, as proposed in this paper, is superior to the current Arc-length method in numerical nonlinear analysis.