• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.835-844
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• 2002

The number of channels available to a video server is limited since the number of channels a video server can support is determined by its communication bandwidth. Several approaches such as batching, piggybacking and patching have been proposed to reduce I/O demand on the video server by sharing multicast data. Patching has been shown to be efficient in the matter of the cost for VOD systems. Unlike conventional multicast techniques, patching is a dynamic multicast scheme which enables a new request to join an ongoing multicast. In addition, true VOD can be achieved since a new request can be served immediately without having to wait for the next multicast. In this paper. we propose two types of channel reservation patching algorithm : a fixed channel reservation patching and a variable channel reservation patching. To immediately schedule the requests for popular videos, these algorithms reserve the channels of video server for the fixed number of popular videos or for the variable number of popular videos which is determined dynamically according to the load of video server. The performance of the proposed algorithms is evaluated through simulations, and compared with that of simple patching. Our performance measures are average defection rate, average latency, service fairness and the amount of buffered data according to video server loads. Simulation results show that the proposed channel reservation patching algorithms provide better performance compared to simple patching algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.244-246
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• 2000

유전자 프로그래밍은 고정적인 구조가 아닌 가변 길이의 트리 구조를 가지고 있어서 여러 세대를 통하여 다양한 개체들을 만들어 낸다. 이러한 특징은 위원회 머신(committee machines)을 구축하는데 있어서 자연스럽고 또한 효과적인 알고리즘일 수 있다.하지만 해결해야 할 요소 중 하나는 다수의 개체들에서 결합할 개체의 선택과 개체의 수를 결정하기 위한 방법이다. 본 논문에서는 효과적인 개체들의 결합이 되기 위한 새로운 탐색방법을 소개한다. 이 방법은 확률적인 진화 탐색을 바탕으로 하고 있다. 제안된 방법을 여러 가지 분류 문제에 적용하였으며 실험을 통하여 탐색의 특성과 일반화 성능을 분석하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.184-186
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• 2004

검사점 작성을 이용하는 실시간 태스크의 스케줄링 가능성을 알기 위한 선행 조건으로 최악 수행시간을 분석하고 이를 최소로 하는 효율적인 검사점 작성의 위치를 결정하는 방법을 제시한다. 여기서 사용하는 조건은 k 개의 연속적인 결함을 허용하고 태스크의 검사점 작성 비용이 고정적인 경우와 가변적인 경우를 가정한다. 이러한 각 조건에서 최악 수행 시간을 최소로 하는 검사점 작성 알고리즘을 제시한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.54-58
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• 2002

PID Controller is widely used as automatic equipment for industry. However, when a system has various characters, parameter decision and tuning for accurate control is a hard task. In this paper, expert auto-tuning PID controller using PLC is presented as away of solving this problem. Expert auto tuning algorithm is based on Ziegler-Nichols step response and expert knowledge. The test of control performance is carried out in practical speed control of Induction Motor in variable load, the experimental results suggest its superior performance.

• The Journal of the Korea Contents Association
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• v.11 no.2
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• pp.31-39
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• 2011

The facial recognition algorithms using Gabor wavelet based face graph produce very good performance while they have some weakness such as a large amount of computation and an irregular result depend on initial location. We proposed a fully automatic facial recognition algorithm using a Gabor feature based geometric deformable face graph matching. The initial location and size of a face graph can be selected using Adaboost detection results for speed-up. To find the best face graph with the face model graph by updating the size and location of the graph, the geometric transformable parameters are defined. The best parameters for an optimal face graph are derived using an optimization technique. The simulation results show that the proposed algorithm can produce very good performance with recognition rate 96.7% and recognition speed 0.26 sec for FERET database.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.5
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• pp.806-811
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• 2006

In RFID system, when multiple tags respond simultaneously, a collision can occur. A method that solves this collision is referred to as anti-collision algorithm. Among the existing anti-collision algorithms, SFSA, though simple, has a disadvantage that when the number of tags is variable, the system performance degrades because of the fixed frame size. This paper proposes a new anti-collision algorithm called DFSA which determines the optimal frame size using the number of collided slots at every frame. According to the simulation results, the tag identification time of the proposed algorithm is faster than that of SFSA.

• Journal of the Korean Institute of Telematics and Electronics C
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• v.35C no.6
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• pp.67-75
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• 1998

Although the nCE(n-th order cross-entropy) error function resolves the incorrect saturation problem of conventional EBP(error back-propagation) algorithm, the performance of MLP's (multilayer perceptrons) trained using the nCE function depends heavily on the order of the nCE function. In this paper, we propose an adaptive learning rate to make the performance of MLP's insensitive to the order of the nCE error. Additionally, we propose a limited error signal of output node to prevent unstable learning due to the adaptive learning rate. The effectiveness of the proposed method is demonstrated in simulations of handwritten digit recognition and thyroid diagnosis tasks.

• Journal of Korea Multimedia Society
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• v.4 no.3
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• pp.230-237
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• 2001

Adaptive filters are widely used for acoustic echo canceler, adaptive equalizer and adaptive noise canceler. Coefficients of adaptive filters are updated by NLMS algorithm. However, Coefficients are misaligned by ambient noises when they are adapted by NLMS algorithm. In this Paper, a method determined the adaptation constant by low-pass filtered instantaneous gradient vector of LMS algorithm using orthognality principles of optimal filter is proposed. At initial states, instantaneous gradient vector, that is the cross-correlation of input signals and estimation error signals, has large value because input signals are remained in estimation error signals. When an adaptive filter is conversed, the cross-correlation will be close to zero. It isn's affected by ambient noises because ambient noises are uncorrelated with input signals. Determining adaptation constant with the cross-correlation, adaptive filters can be robust to ambient noises and the convergence rate doesn't slower As results of computer simulations, it is shown that the performance of proposed algorithm is betted than that of conventional algorithms.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.11 s.353
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• pp.192-199
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• 2006

Establishment of bandwidth and effective traffic processing are required to treat various traffics according to a rapid increase in Internet traffic. A path setup algorithm was introduced to support backbone franc processing but the failure probability is increasing according to fixed operation in nodes. In other words, fixed maximum permitted time can be raised failure probability. So as to solve this problem, this paper introduces variable path setup time algorithm which support channel service of excessive traffic that is generated from not allowed channel. We proposed GLSP(Generalized Label Switch Path) setup algorithm that use variable path setup time parameters. This algorithm can improve path setup probabilities of backbone network that is composed of fixed way.

• KIISE Transactions on Computing Practices
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• v.22 no.9
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• pp.405-418
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• 2016

Recently, many researchers have studied the VSL decision method using traffic information in multiple detector zones. However, this method selects incorrect VSL starting points, leading to the selection of the wrong speed control zone and calculation of the wrong VSL, causing traffic congestion. Eventually, the Unstable VSL system causes more congestion on the freeway. This paper proposes an improved VSL algorithm stably operated in multiple detector zones on the Korea highway. The proposed algorithm selects a preliminary VSL start station (VSS) expected to end the congestion using the acceleration of stations. It also determines the VSS at each congestion area. Finally, it calculates the VSL relative to the determined VSS and controls the vehicles that enters the traffic congestion zone. The developed strategy is compared with Real-time Variable Speed Limits for Urban Freeway (RVSL) to test the stability and efficiency of the proposed algorithm. The results show that the proposed algorithm resolves the problems of the existing algorithm, demonstrated by the correct VSS decision and the reduction of total travel time by 1-2 minutes.