• The KIPS Transactions:PartB
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• v.8B no.3
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• pp.319-326
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• 2001

오차확산법은 중간조 처리에서 우수한 영상의 재현능력을 갖는 기법이다. 그러나 이의 기법은 경계재현 능력이 미약하며, 주기적인 패턴이 발생하여 영상의 화질을 저하시키는 단점이 있다. 본 논문에서는 경계재현의 능력을 개선하기 위한 경계강조법과 주기적인 패턴 발생을 감소시키기 위한 적응형 임계값 변조를 적용하는 방법을 제안하였다. 경계강조를 위한 임계값을 변조는 원영상의 공간적 기울기 정보를 활용하여 수행하였고, 동시에 기울기 정보를 이용하여 청색잡음 마스크를 적응적으로 적용하는 임계값 변조로 주기적인 패턴의 발생을 감소시키도록 하였다. 적응형 임계값 변조를 적용한 실험에서 영상의 주기적인 패턴이 감소된 보다 선명한 경계강조의 중간조 영상을 얻을 수 있었으며, 객관적인 특성분석을 위한 표시오차의 RAPSD, 거리에 따른 경계상관도 및 로컬 평균 일치도의 분석에서 제안한 기법이 효율적임을 확인하였다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.3
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• pp.111-120
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• 2004

This paper proposes a vector error diffusion method for smear artifact reduction in the boundary region. This artifact mainly results from a large accumulation of quantization errors. In particular, color bands with a smear artifact, the width of a few pixels appear along the edges. Accordingly, to reduce this artifact, the proposed halftoning process excludes the large accumulated Quantization error by comparing the vector norms and vector angles between the error-corrected vector and eight primary color patches. When the vector norm of the error corrected vector is larger than those of eight primary color patches, the quantization error vector is excluded from the quantization error distribution process. In addition, the quantization error is also excluded when the angle between eight primary color patches and error corrected vector is large. As a result, the proposed method enables a visually pleasing halftone pattern to be generated by all three color separations into account in a device- independent color space and reduces smear artifact in the boundary regions.

• Journal of Internet Computing and Services
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• v.13 no.3
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• pp.93-105
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• 2012

A data stream is a series of tuples which are generated in real-time, incessant, immense, and volatile manner. As new information technologies are actively emerging, stream processing methods are being needed to efficiently handle data streams. Especially, finding out an efficient evaluation for a multi-way join would make outstanding contributions toward improving the performance of a data stream management system because a join operation is one of the most resource-consuming operators for evaluating queries. In this paper, in order to evaluate efficiently a multi-way join continuous query, we propose a novel method to decrease the cost of a query by eliminating unsuccessful intermediate results. For this, we propose a matrix-based structure for monitoring data streams and estimate the number of final result tuples of the query and find out unsuccessful tuples by matrix multiplication operations. And then using these information, we process efficiently a multi-way join continuous query by filtering out the unsuccessful tuples in advance before actual evaluation of the query.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8
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• pp.2565-2574
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• 2000

The error diffusion method is good for reproducing continuous image to binary image. However the reproduction of edge characteristic is weak in power spectrum analysis of display error. In this paper. we present an edge-enhanced error-diffusion method which include pre-processing algorithm for edge characteristic enhancement. Pre-processing algorithm consists of the difference value between current pixel and local average of original image and weighting function of pre-filter. First. it is obtained the difference value between current pixel and the local average of peripheral pixels(5x5) in original image. Second, weighting function of pre-filter is composed by function including absolute value and sign of difference value. The improved Error diffusion algorithm using pre-processing algorithm, present a good result visually which edge characteristic is enhanced. The performance of the proposed algorithm is compared with that of the conventional edge-enhanced error diffusion by measuring the RAPSD of display error, the egde correlation and the local average accordance.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.6
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• pp.51-59
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• 2004

This paper proposes an improved six-color separation reducing the graininess in a middle tone region based on the standard deviation of the lightness and chrominance in S-CIELAB space. Graininess is regarded as visual perception for the fluctuation of the lightness of the light cyan and cyan or light magenta and magenta. In the conventional methods, the granularity is extremely heuristic and inaccurate due to the use of the visual examination score. Accordingly, this paper proposes a method to calculate the objective granularity for six color separation. First, we use the lightness, redness-greenness, and yellowness-blueness of the S-CIELAB space reflecting the spatial-color sensitivity of the human and normalize the sum of the three standard deviations. Finally, we apply the proposed granularity to the six color separation after assigning the granularity to the lookup table and obtain the result reducing the graininess in a middle tone region.

• The Journal of the Korea Contents Association
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• v.15 no.12
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• pp.24-34
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• 2015

With the development of the semantic web, a large amount of data being produced nowadays is in RDF format. RDF is represented by a triple. An RDF database consisting of triples requires the high cost of join query processing. Materialized view is known as a scheme to reduce the query processing cost by accessing materialized views without accessing the database. It is physically stored the results or the intermediate results of the query processing in a storage area. In this paper, we propose a materialized view selection scheme by using decision tree to solve such a problem. The decision tree considers the size and maintenance costs of the materialized view as well as the profit of query response times. It is shown through performance evaluation that the proposed scheme increases the number of materialized views in the limited storage space and decreases the update rates of the materialized views.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.10 no.1
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• pp.89-97
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• 2000

공개키 암호 시스템 중에서 가장 널리 사용되는 RSA 암호 시스템은 키의 분배와 권리가 용이하고, 디지털 서명이 가능한 장점이 있으나, 암호화와 복호화 과정에서 512 비트 이상의 큰 수에 대한 멱승과 모듈라 감소 연산이 요구되기 때문에 처리 속도의 지연이 큰 문제가 되므로 모듈라 멱승 연산의 고속 처리가 필수적이다. 따라서 본 논문에서는 몫을 추정하여 중간 곱의 크기를 제한하는 interleaved 모듈라 곱셈 기법을 이용하여 모듈라 멱승 연산을 수행하는 고속 RSA 암호 칩을 VHDL을 이용하여 모델링하고 Faraday FG7000A 라이브러리를 이용하여 합성하고 타이밍 검증하여 단일 칩 IC로 구현하였다. 구현된 암호 칩은 75,000 게이트 수준으로 합성되었으며, 동작 주파수는 50MHz이고 1회의 RSA 연산을 수행하는데 소요되는 전체 클럭 사이클은 0.25M이며 512비트 당 처리 속도는 102.4Kbit/s였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.811-815
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• 2005

최근 선진 각국에서는 시각장애인을 위한 인공 망막 모델구현을 위한 연구가 매우 활발히 진행 중이다. 인공 망막의 여러 기법중 시각피질자극에 의한 방법은 망막손상과 시신경 손상 환자에게 적용할 수 있도록 시피질을 자극한다. 그러나 이 방법은 시각자극전달의 중간단계를 생략하고 직접 뇌세포를 자극하는 것이다. 따라서 본 논문에서는 시각피질자극방법에 기반하여 인간시각처리와 유사하게 영상의 압축방법을 부과함으로써 세포의 특성을 고려한 모델을 나타낸다. 실험 데이터로는 자동차 번호판 숫자들이며, 인식기는 SOM을 사용하였다. 실험결과, 제안된 인식모델과 일반적 인식모델과의 차이가 없음을 알 수 있었다.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.41 no.5
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• pp.77-85
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• 2004

This paper proposes a multi-level vector error diffusion method using 64 primary colors to improve color impulse artifact in bright region. Vector error diffusion method causes color impulse artifact in bright region because we only use the Euclidean distance measure in quantization process. In order to reduce this artifact, the proposed method divides input color into chromatic color and achromatic color according to chroma value. In the case of chromatic color, input color is classified into bright region, middle bright region, and dark region according to lightness value. N candidate primary color is organized using lightness difference between input vector and 60 chromatic primary color vector in the case of bright region. Then, primary color with minimum vector norm between input vector and N candidate primary color in addition to 4 achromatic primary colors is selected as output color. As a result of experiments, the proposed method showed visually pleasing halftone output.

• The KIPS Transactions:PartD
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• v.9D no.5
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• pp.755-768
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• 2002

We investigate the effect of the data skew of join attributes on the performance of a pipelined multi-way hash join method, and propose two new hash join methods with load balancing capabilities. The first proposed method allocates buckets statically by round-robin fashion, and the second one allocates buckets adaptively via a frequency distribution. Using hash-based joins, multiple joins can be pipelined so that the early results from a join, before the whole join is completed, are sent to the next join processing without staying on disks. Unless the pipelining execution of multiple hash joins includes some load balancing mechanisms, the skew effect can severely deteriorate system performance. In this paper, we derive an execution model of the pipeline segment and a cost model, and develop a simulator for the study. As shown by our simulation with a wide range of parameters, join selectivities and sizes of relations deteriorate the system performance as the degree of data skew is larger. But the proposed method using a large number of buckets and a tuning technique can offer substantial robustness against a wide range of skew conditions.