• Journal of Korea Multimedia Society
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• v.8 no.7
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• pp.1012-1021
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• 2005

This paper describes the design and implementation of an efficient multi-point multimedia conference system using IP grouping. Existing multi-point multimedia conference systems are difficult for multi-user to perform efficient cooperation due to bandwidth limitation for data transmission of video, audio and documentation. In the case that multi-user uses limited bandwidth, smooth cooperation does not accomplish due to transmission delay for the real-time transmission of image and speech data. A hybrid transfer method which is mixed with distributed and centralized methods is used for smooth cooperation, and the network bandwidth is reduced by forming multi-user conference systems of IP grouping in this paper. Also, adaptive image frame variations are used to solve bottleneck effect according to the number of users. An efficient multi-user conference system is designed to support audio quality.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.142-145
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• 2005

Since the successful launch of FORMOSAT -2 satellite by National Space Organization of Taiwan in May 2004, the Remote Sensing Instrument (RSI) on- board the FORMOSAT -2 has continuously acquired images at one panchromatic and four multi-spectral bands (http://www.nspo.org.tw). In general, the RSI performs well and receives high quality images which proved to be very useful for various applications. However, some RSI panchromatic products exhibit obvious trembling artifact that must be removed. Preliminary study reveals that the trembling artifact is caused by the instability of the spacecraft attitude. Though the magnitude of this artifact is actually less than half of a pixel, it affects the applicability of panchromatic products. A procedure removing this artifact is therefore needed for providing image products of consistent quality. Due to the nature of trembling artifact, it is impossible to describe the trembling amount by employing an analytic model. Relied only on image itself, an algorithm determining trembling amount and removing accordingly the trembling artifact is proposed. The algorithm consists of 3 stages. First, a cross-correlation based scheme is used to measure the relative shift between adjacent scan lines. Follows, the trembling amount is estimated from the measured value. For this purpose, the Fourier transform is utilized to characterize random shifts in frequency domain. An adaptive estimation method is then applied to deduce the approximate trembling amount. In the subsequent stage, image re-sampling operation is applied to restore the trembling-free product. Experimental results show that by applying the proposed algorithm, the unpleasant trembling artifact is no longer evident.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.596-600
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• 2009

As the amount of available information increases rapidly, sometimes the efficient search method alone is not enough to obtain necessary information in timely manner. Therefore additional support is needed to share the burden of searching for and filtering information. In the area of ubiquitous computing, computer systems existing everywhere should be able to proactively provide information just in time. Resource matching is essential in order to develop a system searching and recommending information required for a user in a specific context. This paper describes the infrastructure and methodology of information providing including systematical organization representation, ontological resource demarcation, and resource matching in the environment of a research institute. A specific application was developed to illustrate the proposed approach.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.2072-2072
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• 2009

최근 연구들에서, 증강 현실(Augmented Reality; AR) 환경에서의 촉각 상호작용에 대한 가능성이 논의되었다. 비젼 기반의 트래킹을 기초로 한 증강 현실 기술은 미리 정의된 2차원 마커(marker)를 이용하여, 카메라로부터 획득된 실시간 영상 위에 가상 물체를 증강한다. 그러나, 카메라로부터 획득된 데이터는 몇몇 오차 요인들, 예를 들어 마커의 위치를 인식하는데 나타나는 오차, 카메라 안에 존재하는 센서 잡음 등으로 인해서 마커 잡음(마커를 인식하면서 나타나는 잡음)이 불가결하게 발생하게 된다. 이러한 이유로 인해서, 사용자가 한 손에는 마커를, 다른 한 손으로는 촉감 장치를 이용하여, 마커에 증강된 물체를 만질 때, 마커 잡음은 힘의 떨림(force trembling)을 발생시킨다. 심지어, 이러한 현상은 정지된 마커에 증강된, 마커가 움직이지 않는 상황에서도 발생한다. 게다가, 마커 위에 증강된 물체가 약간 빠른 속도로 이동하게 될 경우, 측정된 이동 거리는 연속적인 프레임(frame)들 간의 불연속적일 수 있다. 만약 사용자가, 대략 30Hz로 위치와 방향이 갱신되는 가상물체를 촉각적으로 상호작용하려 한다면, 계산되는 반력은 급작스런 힘의 변화를 생성하게 될 수도 있다. 이러한 현상을 극복하기 위해서, 마커 잡음을 최소화하기 위해서 정적 임계값(constant threshold)을 이용할 뿐만 아니라, 보간법을 같이 사용한 방법이 있었다. 하지만, 이러한 방법은 정적 임계값을 이용하고, 영상 프레임 갱신 속도와(video frame rate)와 촉각 프레임 갱신 속도가 일정하다는 가정을 사용하였기 때문에, 여전히 힘의 불연속적인 발생이 나타난다. 따라서, 이 논문에서는 두 가지 방법을 이용하여 증강 현실 내에서, 발생할 수 있는 힘의 불연속적인 변화를 보정하는 두 가지 방법, 잡음 제거를 위한 확장된 칼만 필터(Extend Kalman Filter)와 영상과 촉각 갱신 속도 차이에 따른 갑작스런 힘의 변화를 제거하기 위한 적응적 외삽법(Adaptive Extrapolation method)을 제안한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1378-1383
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• 1999

In this paper, an effective variable-block-based image compression technique using wavelet transform is proposed. Since the statistical property of each wavelet subband is different, we apply the adaptive quantization to each wavelet subband. In the proposed algorithm, each subband is divided into non-overlapping variable-sized blocks based on directional properties. In addition, we remove wavelet coefficients which are below a certain threshold value for coding efficiency. To compress the transformed data, the proposed algorithm quantizes the wavelet coefficients using scalar quantizer in LL subband and vector quantizers for other subbands to increase compression ratio. The proposed algorithm shows improvements in compression ratio as well as PSNR compared with the existing block-based compression algorithms. In addition, it does not cause any blocking artifacts in very low bit rates even though it is also a block-based method. The proposed algorithm also has advantage in computational complexity over the existing wavelet-based compression algorithms since it is a block-based algorithm.

• Journal of Korea Multimedia Society
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• v.11 no.3
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• pp.281-291
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• 2008

In this paper, we propose a new double talk detection algorithm which detects near end signals with less degradation, tracking echo path variation of echo canceler simultaneously. Our method makes use of a cross-correlation between channel input signals and estimated error signals and a normalized cross-correlation between microphone input signals and estimated error signals. By combing thresholds for these cross-correlations pertinently, this algorithm discriminates between variation of echo path and occurrence of double talk. These two cross-correlation are used to detect double talk periods, tracking echo path variation. During the detection period, adjustive adaptive filter is ceased to prevent the echo canceler from being disturbed by near end signals. Also, the echo canceler will still be kept on for tracking any variation in echo path. Through computer simulation results, it was confirmed that the proposed algorithm shows better performance, tracking echo path variation and detecting the double talk periods, than the Ye et. al's and the NLMS algorithms from ERLE viewpoint.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.7 no.6
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• pp.27-33
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• 1993

In order to improve complicated construction and complex control which are didvantage of optimal PWM technique aimed at harmonic elimination method, this paper presented MRA(Mode1 Reference Adaptive) PWM technique that gating signal of inverter is generated by comparing the reference signal with the induced feedback signal at the reference model of load. Design of controller is composed of microprocessor and analog circuit. MRA PWM technique used in the paper is able to compensate the degradation of voltage efficiency to be generated by the ratio of the output voltage to the DC supply voltage being low for using conventional sinusoidal PWM technique. When the trapezoidal signal is employed as the reference signal. the low order harmonics of line current can be reduced and the switching pattern is made by on-line computation using comparatively simple numerical analysis.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.137-145
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• 2004

In this paper, a new algorithm for the segmentation of the multi moving objects at the 3 dimension space and the method of measuring the distance from the camera to the moving object by using stereo video monitoring system is proposed. It get the input image of left and right from the stereo video monitoring system, and the area of the multi moving objects segmented by using adaptive threshold and PRA(pixel recursive algorithm). Each of the object segmented by window mask, then each coordinate value and stereo disparity of the multi moving objects obtained from the window masks. The distance of the multi moving objects can be calculated by this disparity, the feature of the stereo vision system and the trigonometric function. From the experimental results, the error rate of a distance measurement be existed within 7.28％, therefore, in case of implementation the proposed algorithm, the stereo security system, the automatic moving robot system and the stereo remote control system will be applied practical application.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.8
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• pp.1478-1489
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• 2006

This paper describes system to extract ISO codes in container image. A container ISO code recognition system for real-time processing is made of 5 core parts which are container ISO code detection and image acquisition, ISO code region extraction, individual character extraction, character recognition and database. Among them, the accuracy of ISO code extraction can affect significantly the accuracy of system recognition rate, and also the more exact extraction of ISO code is required in various weather and environment conditions. The proposed system produces binary of the ISO code's template lesions using an adaptive thresholding, extracts candidate regions containing distribution of ISO code, and recognizes ISO codes as detecting a final region through the verifications by using character distribution characteristics of ISO code among the extracted candidates. Experimental results reveal that ISO codes can be efficiently extracted by the proposed method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.132-137
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• 2003

This performance is motivated to develop a tracking antenna system for receive the satellite broadcasting signal in the coast sailing ship. Therefore, this system is made to small size, light weight and simple operation which is must to low cost system for popularization of small size ship and adaptive possibilities with useful on a ship in the coast using 1 axis Az-mount. The antenna mount structure is a compact size and easy operation to the Az-axis type which is operated by step motor. The antenna unit is a domestic made plate type of patch array and ship's moving detection is using the gyro sensor for ship's moving control. We are designed to algorithm, which walking is abreast for step track and ship's moving compensation. Ship's moving compensation is adapted to the closed loop control method by detection from gyro sensor. This system is consisted of micro processor, ADC, comparative amplifier, step motor driver, mount mechanism and algorithm. We have analysised the tracking performance of prototype on sailing ship board.