• The Transactions of the Korea Information Processing Society
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• v.4 no.6
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• pp.1615-1624
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• 1997

In this paper, we propose and analyze various repair methods for a disk subsystem using mirroring. We also study the effects of the repair process that is invoked on disk faults on the mean response time of user disk requests. Finally, we analyze the effects of two different access patterns (uniform and non-uniform) on the repair process and performance. According to the results, average response times for non-uniform access pattern compared with uniform access pattern become shorter as the system load increases. Our simulation results show that the proposed repair algorithm with a short delay gives a better performance than the previous algorithms.

• Korean Journal of Remote Sensing
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• v.33 no.1
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• pp.61-67
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• 2017

The detection of oil spills using radar image has been studied extensively. However, most of the proposed techniques have been focused on improving detection accuracy through the advancement of algorithms. In this study, research has been conducted to improve the accuracy of oil spill detection by improving the quality of radar images, which are used as input data to detect oil spills. Thresholding algorithms were used to measure the image improvement both before and after processing. The overall accuracy increased by approximately 16%, the producer accuracy increased by 40%, and the user accuracy increased by 1.5%. The kappa coefficient also increased significantly, from 0.48 to 0.92.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.1954-1971
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• 2017

In this work, first, a multiuser detection (MUD) algorithm based on component-level soft interference cancellation and linear minimum mean square error (CLSIC-LMMSE) is proposed, which can enhance the bit error ratio (BER) performance of the traditional SIC-LMMSE-based MUD by mitigating error propagation. Second, for non-binary low density parity check (NB-LDPC) coded high-order modulation systems, when the proposed algorithm is integrated with partial mapping, the receiver with iterative detection and decoding (IDD) achieves not only better BER performance but also significantly computational complexity reduction over the traditional SIC-LMMSE-based IDD scheme. Extrinsic information transfer chart (EXIT) analysis and numerical simulations are both used to support the conclusions.

• The Journal of the Acoustical Society of Korea
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• v.16 no.1E
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• pp.9-14
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• 1997

Check valves used in industrial and Nuclear Power Plant safety systems are susceptible to failure modes generally associated with wear of internal parts. Specifically, hinge pins, disc studs, pistons, and other mechanical parts may degrade over time, and in some cases, may which might produce a disabling event leading to plant or process shutdown. The primary diagnostic technique in the past has been to disassemble the valves. This procedure is costly, time consuming, and in the nuclear industry, it can lead to radiation exposure in some situations. Additionally repair and reassembly of a valve does not ensure proper operation. Non-intrusive diagnostic technologies including acoustics and magnetics with a digital signal analysis allow to evaluate check valve performance without a disassembly and is able to help the user detect degraded valve conditions.

• Korean Journal of Computational Design and Engineering
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• v.4 no.1
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• pp.19-31
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• 1999

One of the non-photorealistic rendering method, a drawing technique which uses only fine curves and dashed line, is widely employed in an knots and post stamps printing. Engraving of the curves and lines are traditionally performed by human engravers which leads to low productivity in printing preparation. As an effort to improve productivity and quality, a drawing automation method which can easily produce a portrait composed of vector data for laser or chemical engraving is proposed. The method shows that it is possible to draw a portrait by controling the width and length of predefined fine lines according to the gray scales a the end points of each fine lines. A gradually controled weighting factor method is proposed in addition to the author previous works to prevent undesirable boundaries in an identical texture region. User interface functions of a commercial CAD system are heavily employed to exploit the presented method.

• Journal of Korean Institute of Industrial Engineers
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• v.26 no.2
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• pp.146-154
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• 2000

This study showed a way to develop web site of shopping mall through systematic identification of the interface elements affecting user's performance and subjective sensibility for Internet shopping mall. To quantify the effects of factors, simulators were designed and used in experiments. It was shown that location of 'Table of Contents'(left > right = up = down) and 'Menu' type(non_Drop down and page Movement = Drop down and page Movement > Drop down and non_age Movement) were the significant factors. However, whether 'Frame' was used or not, there was no significant difference. Also, in the evaluation of subjective sensibility, 'Background color' was a significant factor. And for 'Header & Scanning Column color', yellow color had a tendency to enhance satisfaction for 'simplicity', while green or blue color strengthened 'balance' feeling. But 'text style' was not significant.

• International Commerce and Information Review
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• v.10 no.4
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• pp.23-45
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• 2008

As Knowledge Management (KM) has taken an essential position of managing businesses in the knowledge-oriented society, many companies have adopted Knowledge Management System (KMS) into their organization. Many have questioned, however, in the result and the effectiveness in KMS. The purpose of this study is to explore ways to improve the current KMS by analyzing and identifying the causes that affect effectiveness of KMS. Blog which is an effective tool for communication could be used for KMS in order to make KMS more user friendly and more effective. This research is intended to conduct an empirical study on the differences between Blog-based KMS and Non-Blog-based KMS and suggest resolutions to potential issues of KMS. Blog-based KMS users show higher degree of satisfaction and usage toward their system. The result of this study suggests that the differences between two groups are primarily on system quality and knowledge quality, and many of these differences come from functions and characteristics of Blog.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.12
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• pp.601-608
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• 2001

The ever increasing density of adjustable speed drives(ASD) device with non-linear operating characteristics has been to put tremendous harmonic stress on end user's electrical application. All ASD controllers which employ solid state power devices cause harmonic currents in the source side line. This paper describes harmonic problems for use of ASD. In order to investigate the effect of harmonics caused by using of nonlinear load at the low voltage system, we fixed up simple load model and measured the voltage and current waveforms. Measurement results show that additional operation of linear load at the parallel bus with nonlinear load such as ASD is helpful to the reduction of harmonic influence.

• Journal of Communications and Networks
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• v.18 no.6
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• pp.873-883
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• 2016

In this paper, we focus on maximizing weighted sum energy efficiency (EE) for a multi-cell multi-user channel. In order to solve this non-convex problem, we first decompose the original problem into a sequence of parallel subproblems which can optimized separately. For each subproblem, a base station employs dirty paper coding to maximize the EE for users within a cell while regulating interference induced to other cells. Since each subproblem can be transformed to a convex multiple-access channel problem, the proposed method provides a closed-form solution for power allocation. Then, based on the derived optimal covariance matrix for each subproblem, a local optimal solution is obtained to maximize the sum EE. Finally, simulation results show that our algorithm based on non-linear precoding achieves about 20 percent performance gains over the conventional linear precoding method.

• The Korean Journal of Applied Statistics
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• v.15 no.1
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• pp.107-117
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• 2002

In this paper we present the optimal replacement policies following the expiration of combination warranty. We consider two types of combination warranty policies: renewing warranty and non-renewing warranty. The criterion used to determine the optimal replacement period is the expected cost rate per unit time from the user'perspective. The optimal maintenance period following the expiration of combination warranty is obtained. Some numerical examples are presented for illustrative purpose.