• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.502-507
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• 2009

We present a real-time photomosaics method for small image set optimized by feature selection method. Photomosaics is an image that is divided into cells (usually rectangular grids), each of which is replaced with another image of appropriate color, shape and texture pattern. This method needs large set of tile images which have various types of image pattern. But large amount of photo images requires high cost for pattern searching and large space for saving the images. These requirements can cause problems in the application to a real-time domain or mobile devices with limited resources. Our approach is a genetic feature selection method for building an optimized image set to accelerate pattern searching speed and minimize the memory cost.

• Journal of Korea Game Society
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• v.5 no.1
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• pp.53-60
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• 2005

To produce deep, entertaining mobile content, a large number of images must be included. But because of the limits on runtime memory for mobile phones, images cannot be used as easily in a mobile environment as they are in a computer. Therefore in this paper, I propose several different methods for efficiently using images in a mobile environment. The various methods I propose for using images are: Creating images using compression/decompression and rotation/symmetry Creating images of several different colors by changing the palette index of a bitmap Creating images through image combination Creating background images by using tile maps Creating new images through effects.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.1
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• pp.44-51
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• 2004

Fractal-space multiplexing using a moving window(MW) can multiplex holograms by moving a window left and right. and up and down. But, crosstalk occurs by two neighboring moving windows in the vertical direction of the holographic memory system and limits high-density information recording. Accordingly, we analyzed the crosstalk with the focal length of lens, the distance of MW, and the number of multiplexed hologram to record high-density infromation and presented the optical experimental results of fractal-space multiplexing using volumetric photorefractive crystal and disc type photopolymer.

• The KIPS Transactions:PartD
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• v.11D no.1
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• pp.211-218
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• 2004

Compared with the desktop, the MIDP on J2ME has many limitations on memory capacity, screen size, networking ability and processing speed. In addition, screens vary with device providers in size, and service platforms vary with mobile service providers. These factors require additional functions to server and cause overheads of the server. On this paper, we propose the wav to reduce overheads of the server and to overcome disadvantages of the J2ME clients, with the server that provides the service of data in XML document type and the client on MIDP that is developed including the kXML parser.

• The Journal of the Korea Contents Association
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• v.9 no.1
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• pp.147-158
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• 2009

Recently, the data model in stream data environment has massive, continuous, and infinity properties. However the stream data processing like query process or data analysis is conducted using a limited capacity of disk or memory. In these environment, the traditional frequent pattern discovery on transaction database can be performed because it is difficult to manage the information continuously whether a continuous stream data is the frequent item or not. In this paper, we propose the method which we are able to predict the frequent items using the regression model on continuous stream data environment. We can use as a prediction model on indefinite items by constructing the regression model on stream data. We will show that the proposed method is able to be efficiently used on stream data environment through a variety of experiments.

• Proceedings of the Korean Information Science Society Conference
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• 2010.06a
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• pp.166-170
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• 2010

센서네트워크는 유비쿼터스 환경을 실현할 수 있는 기술로서, 최근 무인 경비 시스템이나 에너지 관리, 환경 모니터링, 홈 자동화, 헬스케어 응용 등과 같은 다양한 응용 분야에 활용되고 있다. 하지만 자신의 정보가 무선통신상에 쉽게 노출됨으로써 도청과 전송 메시지에 대한 위변조, 서비스 거부 공격을 받을 위험이 있다. 더욱이 센서네트워크의 자원 제약성(적은 메모리, 컴퓨팅 성능의 제약)과 키분배 관리의 어려움으로 인해 기존의 공개키, 대칭키 기반의 면안프로토콜을 대체할 수 있는 프로토콜이 필요하다. 그러므로 키분배 관리에 장 접을 가지는 Bilinear map 기반 프로토콜은 적합한 대안이다. 하지만 프로토콜에 사용되는 Pairing연산은 높은 컴퓨팅 성능이 요구된다. 따라서 제한된 성능을 가진 센서상의 구현을 위해서는 Computation Cost를 줄이고 연산 수행 속도를 가속화 할 필요성이 있다. 본 논문에서는 프로토콜 구현에 필요한 Pairing의 핵심 연산인 Multiplication을 대표적인 센서노드 프로세서인 MSP430상에서 최적화 구현함으로써 성능을 개선한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.1C
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• pp.14-19
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• 2006

The high encoding complexity of LDPC codes can be solved by designing structured parity-check matrix. If the parity-check matrix of LDPC codes is composed of same type of blocks, decoder implementation can be simple, this structure allow structured decoding and required memory for storing the parity-check matrix can be reduced largely. In this parer, we propose a construction algorithm for short block length structured LDPC codes based on girth condition, PEG algorithm and variable node connectivity. The code designed by this algorithm shows similar performance to other codes without structured constraint in low SNR and better performance in high SNR than those by simulation

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.10B
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• pp.1382-1389
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• 2001

움직임 보상-이산 코사인 변환 (motion compensation-discrete cosine transform : MC-DCT) 기반의 동영상 부호화 기법이 부호화 효율성 및 구현의 단순성으로 인해 널리 사용되고 있으나, 에러 환경에서 구조적으로 취약한 면이 있다. 본 논문에서는 다중 메모리 움직임 보상 예측 (long-term memory motion compensated prediction : LTMP) 기반의 다중 레프런스 프레임을 사용하여 에러에 강인한 동영상 부호화 기법을 제안한다. 또한 제안하는 알고리듬에 기반한 에러 은닉 기법 (error concealment : EC)을 구현한다. 즉, R-D (rate-distortion) 최적화에 프레임간 움직임 벡터 (temporal motion vectors)의 확산 인자를 추가하여 에러에 대한 강인성 및 에러 은닉 기법의 효율성을 증가시켰다. 또한, 제안하는 알고리듬은 시간축상의 에러 전파를 피드백 정보 (negative acknowledgement : NAK)를 사용하여 억제한다. 즉, NAK는 채널 에러에 의해 손실된 영역과 에러가 전파된 영역을 추정하여 움직임 보상 영역에서 제외되도록 하는데 이용된다. 따라서, 제안하는 알고리듬은 PSNR 측면에서 FIU (forced intra update)에 근사하는 성능을 보이나, FIU와는 달리 비트율의 증가를 피할 수 있어 제한된 대역폭의 네트웍을 효율적으로 사용할 수 있다. 컴퓨터 모의 실험을 통해 제안하는 알고리듬이 기존의 H.263 및 LTMP 기반의 부호기에 비해 에러 환경에서 주관적 및 객관적 화질 측면에서 성능이 우수함을 보인다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.12
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• pp.1124-1132
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• 2011

This paper deals with smooth path generation using B-spline for fixed-wing unmanned aerial vehicles manuevering in 2D environment. Hexagonal cell representation is employed to model the 2D environment, which features increased connectivity among cells over square cell representation. Subsequently, hexagonal cell representation enables smoother path generation based on a discrete sequence of path from the path planner. In addition, we present an on-line path smoothing algorithm incorporating B-spline path templates. The path templates are computed off-line by taking into account all possible path sequences within finite horizon. During on-line implementation, the B-spline curves from the templates are stitched together repeatedly to come up with a reference trajectory for UAVs. This method is an effective way of generating smooth path with reduced on-line computation requirement, hence it can be implemented on a small low-cost autopilot that has limited computational resources.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5C
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• pp.627-631
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• 2004

An efficient algorithm for clustering of GPDFs(Gaussian Probability Density Functions) in a speech recognition model is proposed in this paper. The proposed algorithm is based on CNN with the divergence as its distance measure and is applied to a speech recognition. The algorithm is compared with conventional Dk-means(Divergence-based k-means) algorithm in CDHMM(Continuous Density Hidden Markov Model). The results show that it can reduce about 31.3％ of GPDFs over Dk-means algorithm without suffering any recognition performance. When compared with the case that no clustering is employed and full GPDFs are used, the proposed algorithm can save about 61.8％ of GPDFs while preserving the recognition performance.