• Journal of Korean Society of Industrial and Systems Engineering
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• v.27 no.3
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• pp.59-65
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• 2004

This paper explores an image segmentation and representation method using Vector Quantization(VQ) on color and texture for content-based image retrieval system. The basic idea is a transformation from the raw pixel data to a small set of image regions which are coherent in color and texture space. These schemes are used for object-based image retrieval. Features for image retrieval are three color features from HSV color model and five texture features from Gray-level co-occurrence matrices. Once the feature extraction scheme is performed in the image, 8-dimensional feature vectors represent each pixel in the image. VQ algorithm is used to cluster each pixel data into groups. A representative feature table based on the dominant groups is obtained and used to retrieve similar images according to object within the image. The proposed method can retrieve similar images even in the case that the objects are translated, scaled, and rotated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.3
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• pp.1131-1143
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• 2016

Differential detection schemes do not require any channel estimation, which can be employed under user mobility with low computational complexity. In this work, a soft-input soft-output (SISO) differential detection algorithm is proposed for amplify-and-forward (AF) over time-varying relaying channels based cooperative communications system. Furthermore, maximum-likelihood (ML) detector for M-ary differential Phase-shift keying (DPSK) is derived to calculate a posteriori probabilities (APP) of information bits. In addition, when the SISO is exploited in conjunction with channel decoding, iterative detection and decoding approach by exchanging extrinsic information with outer code is obtained. Finally, simulation results show that the proposed non-coherent approach improves detection performance significantly. In particular, the system can obtain greater performance gain under fast-fading channels.

• 한국데이터정보과학회:학술대회논문집
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• 2004.04a
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• pp.91-101
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• 2004

The turbulent flow is of fundamental interest because the conservation equations for thermodynamics, mass and momentum are linked together. This turbulent flow consists of some coherent time- and space-organized vortical structures. Research has already shown that some dynamic systems and experimental models still cannot provide a good nonlinear analysis of turbulent time series. In the real turbulent flow, very complicated nonlinear behaviors, which are affected by many vague factors are present. In this paper, a kernel-based machine for fuzzy nonlinear regression analysis is proposed to predict the nonlinear time series of turbulent flows. In order to show the practicality and usefulness of this model, we present an example of predicting the near-wall turbulence time series as a verifiable model and compare with fuzzy piecewise regression. The results of practical applications show that the proposed method is appropriate and appears to be useful in nonlinear analysis and in fuzzy environments to predict the turbulence time series.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04a
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• pp.660-662
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• 2000

오늘날 네트웍의 발달로 인하여 사용자가 원하는 영상매체를 실시간으로 요구하는 멀티미디어 서비스에 대한 사용자의 요구가 날로 증가하고 있다. 때문에 영상매체를 제공하는 서버는 여러 사용자들이 동시에 접속하였을 때 서비스를 제공 할 수 있는 능력을 가져야 한다. 본 논문에서는 멀티미디어 서비스를 위한 VOD(Video-On-Demand)시스템을 설계 및 구현한다. VOD 시스템은 미디어를 분석하여 BES(Back-End-Server)에 저장하는 영화 관리자(Movie Manager), 분산 저장된 데이터를 읽어 들여 사용자나 연결된 FES(Front-End Server)로 보내는 BES, 사용자에게 미디어 데이트를 전송하는 FES와 전송된 데이트를 받아서 재생하는 클라이언트(Client)를 구성된다. 또한 다수의 서버를 연결하기 위하여 SCI(Scalabel Coherent Interface)를 이용한 효율적인 메시지 전송방법을 구현한다.

• International Journal of Reliability and Applications
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• v.9 no.1
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• pp.95-112
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• 2008

This paper gives the reliability equivalence factors of a parallel system with n independent and non-identical components. It is assumed here that, the failure rates of the system's components are constants. We used three different methods to improve the system given. Two reliability characteristics (the mean time to failure and the reliability function) are used to perform the system improvement. For this purpose, the reliability functions and the mean times to failures of the original and improved systems are obtained. The results given in this paper generalize the results given in the literatures by setting n = 1, 2. An illustrative numerical example is presented to compare the different reliability factors obtained.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.18 no.34
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• pp.51-60
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• 1995

The key competition factor of manufacturing industries has progressively changed from cost to quality and time. Recently, the manufacturing environments more rapidly change than before. So, many companies want to introduce a advanced manufacturing system like CIMS to meet various user's needs and short delivery. But there is a considerable gap between the decision to invest and the achievement of promised benefits. Managers, generally, cannot afford CIM invesment unless they can determine beforehand that CIM will work in thier company and that will provide a coherent strategy and satisfactory return on investment In many cases, it is impossible to justify CIM investment by only economical analysis. Decision making problems like CIM investment are of a multiple objective nature. So, decision making process and multiattribute utility function are very useful methods to evaluate CIM justification In this paper, we described the key functions of CIM justification evaluation using IDEF methodology and developed the applicattion procedure of DMP and MUF method for CIM justification.

• Journal of the Korean Institute of Telematics and Electronics
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• v.16 no.5
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• pp.12-17
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• 1979

This paper presents the investigation of the theoretical symbol error performances of an M-ary differential phase-shift-keyed(DPSK) system in an interference environment. A simple method is transmitted over a nondistroting channel, but additively corrupted by Gaussian noise and cochannel interference. Computed DPSK symbol error performance results for M=2, 4, and 8 are compared with the corresponding curves for coherent phase-shift-Keyed(CPSK) system as a function of carrier-to-noise power ratio(CNR) with carrier-to-interferer power ratio(CIR) as a parameter. Comparisons between DPSK systems reveal, as we might expect, that DPSK system suffers more degradation.

• Journal of the military operations research society of Korea
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• v.16 no.2
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• pp.118-134
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• 1990

This paper considers the mutual interference problem of several users employing the same FH systems in selected multiple user environments. The environment consists of a desired transmitter-receiver pair located in an area where there are M interfering users distributed in accordance with a specified probability density function. Both coherent Phase-Shift-Keyed and incoherent Frequencey-Shift-Keyed modulations are considered. The general formulas of the average bit error probability are derived. The calculation results are summarized and analyzed. The average bit error probability is highly dependent on the relative location of interferences to the desired link, the time duty factor of the hopping and the number of available channels.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.972-983
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• 1996

This paper proposes a new technique for frequency offset correction for OFDM systems on a frequency selective fading channel. Frequency offset in OFDM introduces interchannel interference among the multiple subcarriers of OFDM signal. To compensate the interference, this paper describes an algorithm with two stages:acquisition and tracking. At both stages, the proposed algorithm oversamples the received OFDM signal to obtain a couple of demodulated symbol sets. At acquisition stage the frequency offset is reduced to half or less of the intercarrier spacings by matching the sign pattern of each element of the sets. Next, at tracking stage the frequency offset is corrected with a frequency detector which is controlled by the correlation of the two sets. It is shown that the proposed algorithm can correct the frequency offset in the event of uncertainty in the initial offset that exceeds one half of the intercarrier spacing. In addition, the proposed algorithm is robust to transmitted symbols and channel characteristics by using oversampled symbol sets.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.6
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• pp.1043-1048
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• 2011

In this paper, a newsynchronization technique applied to burst-mode communication is proposed. A synchronization technique is to estimate carrier frequency and phase offsets in a noisy channel environment. A fundamental problem for estimating the parameters(carrier phase and frequency offsets) in burst-mode transmission is that the ways of pursuing estimation accuracy and transmission efficiency are always trade-off. To solve this problem, a new carrier recovery technique is proposed to improve the transmission efficiency with reliable performance especially at low S/N. In the proposed technique, the synchronization parameters are first estimated based on a data-aided feed-forward estimation scheme. Then, a phase tracker using decision-directed DPLL estimates the phase offset for the data portion of the burst data. From simulation results, it shows fast synchronization with shorter preamble maintaining reasonable BER performance at low S/N.