• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.1C
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• pp.102-109
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• 2008

The higher data rate of mobile communications has been required for various multimedia services. In DS-CDMA system, one of the solutions to increase the throughput is to use multicode. However, multipath channel destorys the orthogonality of spreading codes, which causes the intercede interference(ICI). ICI gives severe effect on multicode DS-CDMA for BER performance. Conventionally, multicode DS-CDMA system uses the Rake receiver with turbo code, which cannot overcome error floor caused by ICI. In this paper, we propose frequency domain turbo equalization based on minimum mean squared error(FDTE-MMSE) for multicode DS-CDMA in frequency selective channel and evaluate its BER performance by computer simulation. The simulation results show that FDTE-MMSE gives much better performance in high Eb/N0 than the Rake receiver with turbo code in multipath length L>1.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.569-577
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• 2010

A multiscale particle simulation technique that can be applied to a multiphase fluid system has been developed. In the boundary region where the macroscopic- and microscopic-scale models overlap each other, three distinctive features are introduced in the simulation. First, a wall is set up between the gas and liquid phases to separate them and match the phases respectively to the macroscopic conditions stably. Secondly, the interfacial profile is obtained near the matching region and the wall translates and rotates to accommodate the change in the liquid-vapor interfacial position in the molecular model. The contact angle thus obtained can be sent to the macroscopic model. Finally, a state of mass and temperature in the region is maintained by inserting and deleting the particles. Good matching results are observed in the cases of the complete and partial wetting fluid systems.

• The KIPS Transactions:PartB
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• v.19B no.4
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• pp.209-220
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• 2012

In this paper, we propose an adaptive pavement region detection method that is robust to changes of structural patterns in a natural scene. In order to segment out a pavement reliably, we propose two step approaches. We first detect the borderline of a pavement and separate out the candidate region of a pavement using VRays. The VRays are straight lines starting from a vanishing point. They split out the candidate region that includes the pavement in a radial shape. Once the candidate region is found, we next employ the adaptive multi-seed region growing(A-MSRG) method within the candidate region. The A-MSRG method segments out the pavement region very accurately by growing seed regions. The number of seed regions are to be determined adaptively depending on the encountered situation. We prove the effectiveness of our approach by comparing its performance against the performances of seed region growing(SRG) approach and multi-seed region growing(MSRG) approach in terms of the false detection rate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1B
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• pp.120-127
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• 2000

In this paper, we propose multispectral image compression using classified interband prediction and vector quantization in wavelet domain. This method classifies each region considering reflection characteristics of each band in image data. In wavelet domain, we perform the classified intraband VQ to remove intraband redundancy for a reference band image that has the lowest spatial variance and the best correlation with other band. And in wavelet domain, we perform the classifled interband prediction to remove interband redundancy for the remaining bands. Then error wavelet coefficients between original image and predicted image are intraband vector quantized to reduce prediction error. Experiments on remotely sensed satellite image show that coding efficiency of theproposed method is better than that of the conventional method.

• Journal of KIISE:Information Networking
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• v.32 no.3
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• pp.318-326
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• 2005

This paper presents the image feature extraction method and the image classification technique to select the harmful image flowed from the Internet by grade of image contents such as harmlessness, sex-appealing, harmfulness (nude), serious harmfulness (adult) by the characteristic of the image. In this paper, we suggest skin area detection technique to recognize whether an input image is harmful or not. We also propose the ROI detection algorithm that establishes region of interest to reduce some noise and extracts harmful degree effectively and defines the characteristics in the ROI area inside. And this paper suggests the multiple-SVM training method that creates the image classification model to select as 4 types of class defined above. This paper presents the multiple-SVM classification algorithm that categorizes harmful grade of input data with suggested classification model. We suggest the skin likelihood image made of the shape information of the skin area image and the color information of the skin ratio image specially. And we propose the image feature vector to use in the characteristic category at a course of traininB resizing the skin likelihood image. Finally, this paper presents the performance evaluation of experiment result, and proves the suitability of grading image using image feature classification algorithm.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.83-88
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• 2010

This study is going to suggest the technology to recognize a starfish by judging various starfish images. In case of recognition of single objects of the asterias amurensis, a starfish can be judged by using concave features and short line features but in case of multiple objects, it is impossible to extract the features of a starfish using concave features or short line so that it can't be recognized as a starfish. Accordingly, it is going to suggest the recognition technology using the features such as numbers of standard deviation, relative degree standard deviation and valid deviation of a long line by using the region central moment and a long line of multiple objects. As a result of experiments of the suggested technology, there were cases that recognition failed because the conditions of the standard deviation of a long line or the numbers of valid deviation of the relative degree couldn't satisfy the conditions but around 95% of a high recognition rate was shown.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.12a
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• pp.483-488
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• 2003

XKASS(XML Key Agreement Specification)는 사용자를 통해 XKMS와 연동하여 인증서 기반으로 클라이언트를 확인하고 키 동의를 하는 프로토콜이다. 기존 XKASS 에서는 공개키 암호화 기법을 사용해 키 교환을 하는 방식과 전자서명 기법을 사용해 키 교환을 하는 방식을 사용한다 기존 XKASS의 전자서명과 공개키 방식의 암호화 해독화 방법은 인증서를 그냥 전달함으로써 사용자의 신원이 노출되는 문제점이 있고, 계산 비용이 많이 든다. 본 논문에서는 기존의 XKASS 프로토콜에서 인증서 기반 공개키 암호화 방식을 사용한 키 교환 프로토콜을 사용하지 않고 키 교환 프로토콜을 수행하여 공격자에게 사용자의 신원보호를 제공하고 계산 비용을 줄인 확장된 XKASS 방식을 제안한다. 사용자에게 제한된 priority를 주는 것으로 DoS(Denial of Service) 공격을 예방한 기존의 XKASS를 확장하여 다중 영역에 사용할 수 있도록 제안하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.211-213
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• 2010

본 논문에서는 직교 주파수 다중화 (OFDM) 신호의 새로운 peak to average power ratio (PAPR) 감쇄 기법을 제안한다. 제안 기법은 시간영역에서 OFDM 심볼의 동상 (in-phase) 성분 및 직교 (quadrature) 성분을 회전시키고 재조합한다. 제안 기법은 기존의 partial transmit sequence (PTS) 기법과 비교하여 계산량을 현저히 줄일 수 있는 장점이 있었음에도 모의 실험을 통해 얻어진 PAPR의 complementary cumulative distribution function (CCDF)는 PTS와 비교할 때 거의 같은 성능을 보였다. 더욱이 제안된 기법은 additive white Gaussian (AWGN) 채널 및 다중 경로 페이딩 채널 (multi-path fading channel)에서 일반적인 OFDM 신호를 전송할 때와 거의 같은 BER (bit error rate) 성능을 보였다.

• Journal of Broadcast Engineering
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• v.15 no.2
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• pp.217-223
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• 2010

In this paper, an interchannel interference (ICI) cancellation method is proposed for multiple frequency offsets in orthogonal frequency division multiplexing (OFDM) systems. When several same signals are received from different transmitters simultaneously, multiple frequency offsets may occur at the receiver because of the frequency difference of the oscillators of the two transmitters and the receiver. This causes degradation of system performance because OFDM systems are very sensitive to the frequency offsets. In this paper, we propose a method to eliminate the effect of the multiple frequency offsets for OFDM systems. The method is accomplished in two steps: compensation of the frequency offset in the time domain and subsequent cancellation of the ICI in the frequency domain. Through computer simulations, we verify the effectiveness of the proposed ICI cancellation method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.8B
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• pp.1085-1091
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• 2001

이 논문에서는 주기적인 특성을 가진 펄스 열들이 서로 다른 초기 위상을 가지고 수신기에 입력되었을 때 도래시간 차이를 이용하여 펄스 열을 분리하는 방법을 제시하고자 한다. 주기적인 펄스 열을 주파수 관점에서 고찰해 보면 하나의 펄스 열 주파수 값으로 특성 지울 수 있으며 이러한 성질은 다중의 펄스 열이 포함된 신호 환경 하에서도 동일하게 나타난다. 제안된 기법은 기존의 스펙트럼 영역에서 사용된 신호 도래 시간의 지수함수로의 매핑을 대신하여 신호 도래 시간 차이를 이용하였으며 실제 다중 환경에서 나타날 수 있는 신호 성분들의 펄스 열 주파수 추정을 위하여 기존의 방법과 비교함으로써 제시한 방법의 타당성을 검증하였다.