• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.1
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• pp.37-43
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• 2023

Compressed still image or video bitstreams require protection from channel errors in a wireless channel. Embedded Zerotree Coding(EZW), SPIHT could have provided unprecedented high performance in image compression with low complexity. If bit error is generated by dint of wireless channel transmission problem, the loss of synchronization on between encoder and decoder causes serious performance degradation. But wavelet zerotree coding algorithms are producing variable-length codewords, extremely sensitive to bit errors. The idea is to partition the lifting coefficients. A many partition of lifting transform coefficients distributes channel error from wireless channel to each partition. Therefore synchronization problem that caused quality deterioration in still image and video stream was improved.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10b
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• pp.454-456
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• 2001

본 논문에서는 비디오 영상열 내에 컴퓨터가 생성한 가상의 3D 영상을 이음새 없이 추가하기 위한 문제에 초점을 맞추고 있다. 2단계의 견고한 통계적인 메소드는 추적된 커브들의 모델-영상 대응점으로부터 보다 정확한 자세를 평가하기 위하여 자세 계산을 위해 사용되었다. 또한, 관점의 정확성 향상을 위하여 두 개의 연속하는 영상들간에 매치될 수 있는 핵심점을 카메라 움직임에 대한 상관관계 함수로 사용하여 매칭 에러와 reprojection 에러를 포함한 비용함수를 최소화함에 의해 관점을 향상시킨다. 비디오 영상내 객체 영상과 가상의 3D 영상간에 발생하는 폐색 공간문제를 해결하기 위하여 반 자동 알고리즘을 제안하였다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.989-996
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• 2011

An understanding of the concentrated solar flux is critical for the analysis and design of solar-energy-utilization systems. The current work focuses on the development of an algorithm that uses the Monte Carlo ray-tracing method with excellent flexibility and expandability; this method considers both solar limb darkening and the surface slope error of reflectors, thereby analyzing the solar flux. A comparison of the modeling results with measurements at the solar furnace in Korea Institute of Energy Research (KIER) show good agreement within a measurement uncertainty of 10%. The model evaluates the concentration performance of the KIER solar furnace with a tracking accuracy of 2 mrad and a maximum attainable concentration ratio of 4400 sun. Flux variations according to measurement position and flux distributions depending on acceptance angles provide detailed information for the design of chemical reactors or secondary concentrators.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.2
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• pp.88-93
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• 2017

Due to the requirement of the development of the precision manufacturing industry, the accuracy of machine tools has become a key issue in this field. A critical factor that affects the accuracy of machine tools is the feed system, which is generally driven by a ball screw. Basically, to improve the performance of the feed drive system, which will be thermally extended lengthwise by continuous usage, a thermal error compensation system that is highly dependent on the feedback temperature or positioning data is employed in the machine tool system. Due to the overdependence on measuring technology, the cost of the compensation system and low productivity level are inevitable problems in the machine tool industry. This paper presents a novel feed drive thermal error compensation system method that could compensate for thermal error without positioning or temperature feedback. Regarding this thermal error compensation system, the heat generation of components, principal of compensation, thermal model, mathematic model, and calculation method are discussed. As a result, the test data confirm the correctness of the developed feed drive thermal error compensation system very well.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.1
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• pp.94-101
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• 2007

Streaming video is expected to become a key service in the developing heterogeneous wireless network. However, sufficient quality of service is not offered to video applications because of bursty packet losses. An effective solution for packet loss in wireless network is to perform a proper concealment at the receiver. However, most concealment methods can not conceal effectively the consecutively damaged macro blocks, since the neighboring blocks are lost. In the previous work, bidirectional motion vector tracking (BMVT) method has been proposed which uses the moving trajectory feature of the damaged macro blocks. In this paper, a channel-adaptive redundancy coding method for the better BMVT error concealment is presented. The proposed method provides enhanced video quality at the cost of a little bit overhead in the wireless error-prone network.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.72-76
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• 2006

본 연구에서는 웨이브릿과 신경망을 결합하여 플라즈마 고장을 감시하기 위한 시계열 모델을 개발하였다. 본 기법은 플라즈마 증착장비에 의해 수집된 18 개의 센서정보에 적용하여 평가하였다. 이산치 웨이브릿(Discrete Wavelet Transformation)은 장비에서 수집된 센서정보의 전 처리를 위해 이용되었다. 시계열 모델의 성능은 과거와 미래정보의 함수로 평가하였다. 수집된 18 개의 센서정보에 대한 모델성능 비교를 위해 표준화된 성능평가지표가 적용되었다. 평가결과, 본 기법에 의해 개발된 시계열 모델은 대략 4% 정도의 예측에러를 보였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.04d
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• pp.145-147
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• 2003

인터넷상에서의 패킷손실은 멀티미디어의 수신 품질을 크게 저하시킨다 따라서 멀티미디어 데이터의 실시간성을 유지하면서 손실된 패킷을 복구할 수 있는 에러 제어 기법이 필요하다. 이를 위해 본 논문에서는 어플리케이션 수준에서 패킷단위의 에러제어를 수행하는 RSE 기반 FEC 기법을 사용한다. 또한 FEC 기법의 단점인 부가정보의 양을 네트웍의 상황에 따라 적응적으로 조절하기 위친 본 논문에서는 네트웍의 상태정보(RTP/RTCP)에 따라 부가정보의 양을 조절하는 기법을 제안한다. 그리고 제안한 기법을 실제 어플리케이션에서 쉽게 활용할 수 있게 라이브러리로 구현하였다. 실험에서는 이 라이브러리를 바탕으로 동영상을 전송하는 프로그램을 구현하여 패킷로스에 따른 패킷 복구율과 부가점보의 양을 측정하여, RSE만을 사용하였을 경우와 비교하여 보았다.

• Journal of the Korea Society of Computer and Information
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• v.25 no.9
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• pp.143-150
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• 2020

The purpose of this study is to investigate the human error of bodyguards caused in the process of performing access control activities between security missions, focusing on multiple risk cases, and to suggest countermeasures accordingly. To verify this, after arranging the sequence of events in a time series, the VTA technique and Why-Why analysis technique that can easily identify the problem centered on the variable node were used. In addition, environmental factors and personal factors that cause human errors were extracted through M-SHEL Metrix. As a result of analyzing multiple risk cases through such a method, the security environment factors that cause access control accidents include lack of time (impatience), prejudice against visitors, intensive work methods, lack of security management, unattended travel, and familiar atmosphere. (Relaxation), formal work activities, convenience provision, and underestimation were surveyed. In addition, human errors caused by personal security guards were investigated as low alertness, formal work, negligence of inspection, and comfortable coping.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.5
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• pp.447-455
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• 2014

In this paper, we consider a representative integral imaging method in glasses-free 3D image processing and propose a prioritized transmission scheme for guaranteeing a received video quality in error-prone environments. According to the correlation of pixels consisting of each voxel of integral image, we set the priority differently and apply the modulation level according to this priority value. That is to say, the corresponding pixels with small variance are set to a high priority and transmitted by using a low level modulation that is robust under transmission errors, but the corresponding pixels with greater variance are set to a lower priority and transmitted by using a high level modulation that has a high bit error rate but fast transmission rate. Result shows that the proposed scheme that applies the error-robust modulation level to the important image bit stream with the high priority improves the peak to sidelobe ratio (PSR) of the received 3D image, compared with a typical method that use the same modulation level without distinction of priorities.

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.4
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• pp.79-86
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• 2019

This paper describes a time-series data prediction based on artificial neural networks (ANN). In this study, a batch based ANN model and a stochastic ANN model have been implemented using TensorFlow libraries. Each model are evaluated by comparing training and testing errors that are measured through experiment. To train and test each model, tax dataset was used that are collected from the government website of indiana state budget agency in USA from 2001 to 2018. The dataset includes tax incomes of individual, product sales, company, and total tax incomes. The experimental results show that batch model reveals better performance than stochastic model. Using the batch scheme, we have conducted a prediction experiment. In the experiment, total taxes are predicted during next seven months, and compared with actual collected total taxes. The results shows that predicted data are almost same with the actual data.