• 한국정보통신설비학회:학술대회논문집
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• 한국정보통신설비학회 2009년도 정보통신설비 학술대회
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• pp.211-214
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• 2009

In this paper, we present an efficient handover method avoiding ping-pong phenomenon in Wireless LAN systems. In order to provide the seamless VoIP service for terminals with mobility in Wireless LAN systems. Since the variation range of the received signal strength of the moving terminals is large, the handover procedure can be started by an instant drop of the signal strength. Then the handover procedure is repeated, which makes ping-pong phenomenon. Since the quality of service of VoIP can be lowered by ping-pong phenomenon, in this paper, we present the necessary condition to avoid the ping-pong phenomenon. Through LAB test, we show that the proposed handover method can provide an seamless service without the ping-pong phenomenon.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.225-232
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• 2014

The traditional RAP (Redundancy Allocation Problem) of complex systems has considered only the redundancy of subsystem with homogeneous components. In this paper we extend it as a RAP of complex systems with heterogeneous components which is more flexible than the case of homogeneous components. We model this problem as a nonlinear integer programming problem, find its optimal solution by tabu search, and suggest an example of the efficient reliability design with heterogeneous components. In order to improve the quality of the solution of the tabu search, we suggest a modified tabu search to employ an adaptive procedure (1-opt or 2-opt exchange) to generate the efficient neighborhood solutions. Computational results show that our modified procedure obtains better solutions as the size of problem increases from 30 to 50, even though it requires rather more computing time. With some adjustment of the parameters of the proposed method, it can be applied to the optimal reliability designs of complex systems of ships.

• 전자공학회논문지B
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• 제32B권12호
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• pp.1581-1590
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• 1995

Recently, advanced video coding techniques using segmentation technique have been actively researched as candidates for video coding of MPEG-4 standard. The conventional segmentation techniques are unsuitable for real-time process because they have sequential structure. In this paper, we propose a new image segmentation technique using competitive learning neural network for vector quantization. The proposed segmentation procedure consist of prefiltering, primary and secondary segmentation, and a small region ellimination process. Primary segmentation segments input image in detail. Secondary segmentation merges similar region using a repetitive FSCL(Frequency sensitive competive learning) neural network. In this process, it is possible to segment an image from high resolution to low resolution by adjusting the number of repetition. Finally, small regions are merged into adjacent regions. Experimental results show that the procedure described yields reconstructed images of reasonably acceptable quality at bit rates of 0. 25 - 0.3 bit/pel.

• 한국산업융합학회 논문집
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• 제3권3호
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• pp.251-256
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• 2000

This report analyzes the Source Qualification Test which is composed of main functional and environmental tests for the localizing avionics(electronic subsystem for aircrafts and spacecraft) and high performance mechanical subsystem. Especially the detail test approaches of integrated servo actuators which is the main part to supply the power to the main and other flying control panel. Nowadays this subsystem works with mechanical and electrical engineering technique. In detail, electrical signal is used as input and transferring tool and mechanical part is the output as a power and manufacture the physical dimensions and functions. Finally in this review, the new test procedure to prove the function by the new manufacturer is established.

• Journal of applied mathematics & informatics
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• 제29권3_4호
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• pp.697-712
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• 2011

We present in this paper two versions of a general correction procedure applied to a classical linear iterative method. This gives us the possibility, under certain assumptions, to obtain an extension of it to inconsistent linear least-squares problems. We prove that some well known extended projection type algorithms from image reconstruction in computerized tomography fit into one or the other of these general versions and are derived as particular cases of them. We also present some numerical experiments on two phantoms widely used in image reconstruction literature. The experiments show the importance of these extension procedures, reflected in the quality of reconstructed images.

• 음성과학
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• 제3권
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• pp.177-186
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• 1998

This paper describes the procedure of implementing a real-time speech codec, G.723.1 which was developed by DSP Group and standardized by ITU-T, using fixed-point DSP, ADSP-2181. This codec has two bit rates associated with it, 5.3 and 6.3 kbit/s. We implemented only one bit rate, 6.3 kbit/s, of the two with fixed-point 32-bit precision. According to the result of the experiment, the amount of computational burden is about 55 MIPS and its quality is similar to the result of the PC simulation with floating-point arithmetic. In this paper, we proposed a method to use a fixed-point DSP and a procedure for developing a real-time speech codec using DSPs and finally developed a G.723.l speech codec for ADSP-2181.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집
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• pp.2038-2043
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• 2009

RAMS(Reliability, Availability, Maintainability, Safety) analyses are particularly important in the railway engineering sector and are increasingly required the specialized procedures. The RAMS analysis is performed to meet the high safety and quality standards. The RAMS standards were established in 1990s. EN 50126 of CENELEC, and IEC 62278 provide railway authorities and railway company with a procedure which will enable the implementation of a consistent approach to the management of RAMS. IEC 62278 will be often referred to in the field of railway system. This paper represents the RAMS procedure to apply to the EMU (Electrical Multiple Unit) based on the referenced RAMS standards.

• Journal of the Korean Data and Information Science Society
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• 제26권6호
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• pp.1593-1600
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• 2015

A control chart is very useful in monitoring various production process. There are many situations in which the simultaneous control of two or more related quality variables is necessary. We construct bivariate Shewhart control charts based on the trace of the product of the estimated variance-covariance matrix and the inverse of the in-control matrix and investigate the properties of bivariate Shewart control charts with VSI procedure for monitoring covariance matrix in term of ATS (Average time to signal) and ANSW (Average number of switch) and probability of switch, ASI (Average sampling interval). Numerical results show that ATS is smaller than ARL. From examining the properties of switching in changing covariances and variances in ${\Sigma}$, ANSW values show that it does not switch frequently and does not matter to use VSI procedure.

• 한국전자파학회논문지
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• 제11권5호
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• pp.830-838
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• 2000

약 2에 걸쳐서 대전지역을 대상으로 DTV 현장측정을 실시하였다. 총 33개의 측정지점을 선정하였고 각 지점에서 수신전력, 잡음전력, SER, RMS 지연확산 및 등화기의 성능을 측정하였다. 전체 측정지점 중의 약 50%가 영상과 음성의 질이 만족할 만한 수준이었고, 등화기는 고스트신호에 대하여 보상능력이 있었으며 13.7dB의 S/N개선을 얻었다. 이 결과로부터 DTV를 위한 측정결과를 확립할 수 있을 것이다.

• 한국조리학회지
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• 제4권
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• pp.295-315
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• 1998

This paper attempts to examine the degree of chef's satisfaction on food purchasing in 5-star hotel in Seoul. Nowadays, hotel industry in Korea is becoming more and more competitive and the hotel products higher education. Among a range of divisions in deluxe hotel in Seoul, in particular, a F&B division has been more profitable than the others. It is widely accepted that the proportion of revenue obtained from F&B sales is higher than that of revenue from room sales. However, under the IMF intervention, hotels in Korea trend to depend on room sales rather than F&B sales in terms of profit. In such a environment, it is essential that F&B division should carefully seek for an appropriate purchasing procedure which will affect an organizational structure and allow the company to fulfill its goals. Moreover, it is timely their performance and quality of services through ideal food purchasing procedure. In this paper, the author uses a survey technique distributed to approximately 200 chefs who work at 5-stars hotel in Seoul. The author expects that this paper will contribute to the researchers or practitioners who might need a reference on the food purchasing system.