• 한국전자파학회논문지
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• 제16권10호
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• pp.965-972
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• 2005

본 연구에서는 DTV, HDTV 서비스를 동시에 제공하는 차세대 위성 방송시스템의 표준안인 DVB-S2에서 채널 부호화 알고리즘으로 채택한 LDPC 부호의 복호 알고리즘에 대해 연구를 하였다. 샤논의 한계에 근접하기 위해서는 큰 블록 사이즈의 LDPC 부호어 길이와 많은 반복 횟수를 요구한다. 이는 많은 계산량을 요구하며, 그리고 이에 따른 전력 소비량(power consumption)을 야기시키므로 본 논문에서는 세 가지 형태의 low complexity LDPC 복호 알고리즘을 제시한다. 첫째로 큰 블록 사이즈와 많은 반복 회수는 많은 계산량과 power 소모량을 요구하므로 성능 손실 없이 반복 횟수를 줄일 수 있는 SUBSET 방법을 이용한 복호 알고리즘, 둘째로 early stop 알고리즘에 대해 연구하였고, 셋째로 비트 노드 계산과 체크 노드 계산시 일정한 신뢰도 값보다 크면 다음 반복시 계산을 하지 않는 early detection 알고리즘에 대해 연구하였다.

• 지능정보연구
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• 제5권1호
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• pp.95-101
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• 1999

In this paper, a comparison between different methods to combine predictions from neural networks will be given. These methods are bagging, bumping, and balancing. Those are based on the analysis of the ensemble generalization error into an ambiguity term and a term incorporating generalization performances of individual networks. Neural Networks and AI machine learning models are prone to overfitting. A strategy to prevent a neural network from overfitting, is to stop training in early stage of the learning process. The complete data set is spilt up into a training set and a validation set. Training is stopped when the error on the validation set starts increasing. The stability of the networks is highly dependent on the division in training and validation set, and also on the random initial weights and the chosen minimization procedure. This causes early stopped networks to be rather unstable: a small change in the data or different initial conditions can produce large changes in the prediction. Therefore, it is advisable to apply the same procedure several times starting from different initial weights. This technique is often referred to as training ensembles of neural networks. In this paper, we presented a comparison of three statistical methods to prevent overfitting of neural network.

• 한국통신학회논문지
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• 제30권6C호
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• pp.442-449
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• 2005

최근 터보 부호에 비해서 구현시 복잡하지 않고, 높은 부호화율에서 거의 샤논 이론에 접근하는 Turbo Product Code(TPC)에 대해 관심이 고조되고 있다. 본 논문에서는 초고속 통신 시스템에 적용하기 위한 고속 TPC 복호를 위한 세가지의 알고리즘을 제안하는 바이다. 첫째로, 기존의 Turbo Product code 복호기에서 row과 column을 직렬로 복호를 하지 않고 복호 구조가 병렬로 동작하는 Turbo Product code 복호기를 제안한다. 둘째로 반복 중지 알고리즘을 제안하고 마지막으로, P-Parallel 알고리즘을 통해 P rows와 P columns을 병렬로 처리하여 복호한다. 모의 실험을 한 결과 기존의 방식에 비해 복호 지연이 줄어들고 성능면에서 직렬 방식과 거의 비슷한 성능이 나타난다. 또한 고속알고리즘을 바탕으로 VHDL모델링을 하였으며, 이를 timing 시뮬레이션 하여 메모리 요구량 및 복호 속도 향상도를 분석하였다.

• 한국통신학회논문지
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• 제32권4C호
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• pp.379-388
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• 2007

In this paper, we propose an adaptive turbo decoding algorithm for high order modulation scheme combined with originally design for a standard rate-1/2 turbo decoder for B/QPSK modulation. A transformation applied to the incoming I-channel and Q-channel symbols allows the use of an off-the-shelf B/QPSK turbo decoder without any modifications. Adaptive turbo decoder process the received symbols recursively to improve the performance. As the number of iterations increase, the execution time and power consumption also increase as well. The source of the latency and power consumption reduction is from the combination of the radix-4, dual-path processing, parallel decoding, and early-stop algorithms. We implemented the proposed scheme on a field-programmable gate array (FPGA) and compared its decoding speed with that of a conventional decoder. From the result of implementation, we confirm that the decoding speed of proposed adaptive decoding is faster than conventional scheme by 6.4 times.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 춘계학술대회 논문집
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• pp.128-132
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• 1997

The conventional fire detection devices are operated after a processed fire phase, which are sensing only a high density of smoke level or high temperature heat. They are not so precision to detect a fire in the early phase to protect the facility from the fire. We need to develope a new high precision smoke detection system to keep expensive industial facilities most reliably from fire. A new optical precision smoke detection system was developed. It monitors very low level density of smoke psrticles in the air. It is operated continuously through many years without a stop or any malfunction. The developed precision smoke detection system will be installed in important industrial facilities,such as power plants, underground common tunnel,main control rooms,computer rooms etc.

• 대한가정학회지
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• 제30권2호
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• pp.35-43
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• 1992

This study is to investigate the problems of pollution caused by drycleaning solvents. From the problem of each solvents, safety count-step have to set up. It is following. 1) Solvent: Smong phenomenon of optical chemistry. It has to develop safety tumbler that is attached retrievable device. 2) Perchloroethylene: Pollution of underground water and cause of cancer. Considering the influence on environment and human bing, it has to set up more strong safty plan than now. 3) Chlorofluorocabon : Destory of ozon layer and green house effect on earth. It is being to stop the production until the early part of the year 2000. So it is developing a substitute for chlorofluorocarbon. 4) 1,1,1-trichloroethane : Pollution of underground water and destroy of ozon layzer. At the end of the year 2004, there will be end production of it.

• 한국통신학회논문지
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• 제30권6C호
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• pp.450-456
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• 2005

In this paper, we propose a high-speed turbo decoding algorithm and present results of its implementation. The latency caused by (de)interleaving and iterative decoding in conventional MAP turbo decoder can be dramatically reduced with the proposed scheme. The main cause of the time reduction is to use radix-4, center to top, and parallel decoding algorithm. The reduced latency makes it possible to use turbo decoder as a FEC scheme in the real-time wireless communication services. However the proposed scheme costs slight degradation in BER performance because the effective interleaver size in radix-4 is reduced to an half of that in conventional method. To ensure the time reduction, we implemented the proposed scheme on a FPGA chip and compared with conventional one in terms of decoding speed. The decoding speed of the proposed scheme is faster than conventional one at least by 5 times for a single iteration of turbo decoding.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1996년도 추계학술대회
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• pp.353-356
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• 1996

Early this year the construction of new high voltage power lines have been forced to stop due to the demonstration of residents in Kwa-chun. According to mutual agreement between the residents and Korea Electric Power Corporation, electromagnetic field(EMF) from present power lines was measured and EMF after completion of new power lines was estimated. The results show that EMF near power lines Is relatively low, and EMFnear electric substation is quite high due to the short distance between the power lines and ground. For 4 conduction 345kV line, magnetic field decreases to 3mG at the distance of 50m from the power line.

• Journal of Chest Surgery
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• 제18권4호
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• pp.812-816
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• 1985

In the past several years the popularity of the motor cycle has produced an increasing incidence of the injuries to the larynx and trachea. Most of all on accidents come to death and survivors to the hospital are rare. Early diagnosis and to keep air way are necessary to initiate proper treatment in injury of upper air way. Meticulous apposition of mucous membrane and reconstitution of laryngeal skeleton are important. We experienced a rare case of 26 year old men with cricothyroidal transection after trauma. On Oct. 17, 1985, the patient struck his neck on baggage frame of truck when dropping from his motor cycle on sudden stop. Emergency tracheal intubation on distal segment of trachea was accomplished by otolaryngologist in a local clinic. He was transferred to our hospital. Exploration 2 hours later revealed complete separation of cricoid cartilage from thyroid cartilage. The recurrent laryngeal nerve could not be identified. Anastomosis of thyroid and cricoid was accomplished and Portex endotracheal tube was inserted as splint for 10 days. No stenosis developed. The air way appeared adequate for moderate physical activity though paramedian fixation of vocal cord paralysis. Postoperative follow-up course has been good after he discharged on POD 14 days.

• ETRI Journal
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• 제43권6호
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• pp.1004-1012
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• 2021

The collaboration productively interacting between multi-agents has become an emerging issue in real-world applications. In reinforcement learning, multi-agent environments present challenges beyond tractable issues in single-agent settings. This collaborative environment has the following highly complex attributes: sparse rewards for task completion, limited communications between each other, and only partial observations. In particular, adjustments in an agent's action policy result in a nonstationary environment from the other agent's perspective, which causes high variance in the learned policies and prevents the direct use of reinforcement learning approaches. Unexpected social loafing caused by high dispersion makes it difficult for all agents to succeed in collaborative tasks. Therefore, we address a paradox caused by the social loafing to significantly reduce total returns after a certain timestep of multi-agent reinforcement learning. We further demonstrate that the collaborative paradox in multi-agent environments can be avoided by our proposed effective early stop method leveraging a metric for social loafing.