• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.114-114
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• 2020

Water contamination in a water distribution network (WDN) is harmful since it directly induces the consumer's health problem and suspends water service in a wide area. Actions need to be taken rapidly to countermeasure a contamination event. A contaminant source ident ification (CSI) is an important initial step to mitigate the harmful event. Here, a CSI approach focused on determining the contaminant intrusion possible location and time (PLoT) is introduced. One of the methods to discover the PLoT is an inverse calculation to connect all the paths leading to the report specification of a sensor. A filtering procedure is then applied to narrow down the PLoT using the results from individual sensors. First, we spatially reduce the suspect intrusion points by locating the highly suspicious nodes that have similar intrusion time. Then, we narrow the possible intrusion time by matching the suspicious intrusion time to the reported information. Finally, a likelihood-score is estimated for each suspect. Another important aspect that needs to be considered in CSI is that there are inherent uncertainties, such as the variations in user demand and inaccuracy of sensor data. The uncertainties can lead to overlooking the real intrusion point and time. To reflect the uncertainties in the CSI process, the Monte-Carlo Simulation (MCS) is conducted to explore the ranges of PLoT. By analyzing all the accumulated scores through the random sets, a spread of contaminant intrusion PLoT can then be identified in the network.

• Journal of the Korean Mathematical Society
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• v.44 no.6
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• pp.1397-1415
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• 2007

We consider an inverse heat conduction problem(IHCP) in a quarter plane which appears in some applied subjects. We want to determine the heat flux on the surface of a body from a measured temperature history at a fixed location inside the body. This is a severely ill-posed problem in the sense that arbitrarily "small" differences in the input temperature data may lead to arbitrarily "large" differences in the surface flux. A semi-discrete central difference scheme in time is employed to deal with the ill posed problem. We obtain some error estimates which also give the information about how to choose the step length in time. Some numerical examples illustrate the effects of the proposed method.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2001.10a
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• pp.11-14
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• 2001

A systematic construction and re-use of technology related to the product development and production has been the most important for the semiconductor industry dependent on process and equipment. Therefore, numerous outputs in the form of paper has been produced in the process of information management ranging from the creation to recycling and disposal of technologies. In this research, the technology and documents necessary for the business management in the field of semiconductor manufacturing were classified in an effort to solve problems while the modeling of document management architecture at the enterprise level was performed by properly setting up the security system to prevent the unauthorized disclosure of the product development technology to the third parties. Especially, the product and process specification are designed in such a way as to ensure a real-time response in interface with the production system in order to shorten the development lead-time and improve the productivity. This paper is to discuss the modeling approach, the strategy to construct the system and its results.

• Industrial Engineering and Management Systems
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• v.8 no.3
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• pp.139-147
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• 2009

Control charts are used to distinguish between chance and assignable causes in the variability of quality characteristics. When a control chart signals that an assignable cause is present, process engineers must initiate a search for the assignable cause of the process disturbance. Identifying the time of a process change could lead to simplifying the search for the assignable cause and less process down time, as well as help to reduce the probability of incorrectly identifying the assignable cause. The change point estimation by likelihood theory and the built-in change point estimation in a control chart have been discussed until now. In this article, we discuss two kinds of process change point estimation when the CUSUM ($\bar{x}$, s) control chart for monitoring process mean and variance simultaneously is operated. Throughout some numerical experiments about the performance of the change point estimation, the change point estimation techniques in the CUSUM ($\bar{x}$, s) control chart are considered.

• Communications for Statistical Applications and Methods
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• v.10 no.3
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• pp.825-833
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• 2003

Knowing the time of the process change could lead to quicker identification of the responsible special cause and less process down time, and it could help to reduce the probability of incorrectly identifying the special cause. In this paper, we propose a maximum likelihood estimator of the process change point when a Shewhart $\bar{X}$ chart with variable sample size (VSS) scheme signals a change in the process mean. Also we build a confidence interval for the process change point by using the likelihood function.

• Proceedings of the IEEK Conference
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• 2003.11a
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• pp.331-334
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• 2003

In this paper a new OSD (On-Screen Display) development system for digital devices is presented. The proposed system is an example of the ubiquitous systems because it can be used to co-develop an OSD tn any time at any place if the web can be accessed. In UI, OSD is an important pan of digital devices. Especially, OSD implementations for multiple languages are essential to export digital devices and make them user-friendly. The proposed system consists of four components: font editor, menu editor. R/C simulator, and screen editor. It provides all the functions to develop an OSD and the result can be downloaded to a digital device. The proposed system was used to develop an OSD for 31 countries and the lead time of development was reduced from 52.7 days to 20 days.

• Journal of Korean Society of Water and Wastewater
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• v.19 no.6
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• pp.781-790
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• 2005

Granular Activated Carbon(GAC) is widely used in drinking water treatment. Many of the problems occurring in the GAC process are associated with the operation goal and performance. The purpose of this study were to evaluate the design, operation, and performance of granular activated carbon process in D water treatment plant. The optimal operation conditions of GAC process such as backwashing condition, granular activated carbon replacement time were discussed. The design, operation and performance of GAC process is influenced by their raw water characteristics and placement within the treatment process sequence. A critical analysis of plants experience and the information from the literature identifies the effectiveness of GAC process and indicates where modifications in design and operation could lead to improved performance. It would be useful to evaluate and optimize the GAC process in other treatment plant.

• Proceedings of the Korea Contents Association Conference
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• 2004.05a
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• pp.497-502
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• 2004

OCSP has specific characters which can suspend, close, and correct in real time. But, as more clients use the OCSP server verification, more updated information is needed, which can lead to jamming in the OCSP server. To apply this technique of Distributed OCSP server so as to reduce the certificate verification OCSP from jamming. Also, the Distributed OCSP server will solve the problems of the intensive central structure.

• The Magazine of Kiice
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• v.17 no.1
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• pp.57-63
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• 2016

What will the gaming industry look like in the future? Where is it heading? Most producers, developers, and gamers have been pondering such questions since the very beginning of video games. This paper asserts that the current trend in video games to emphasize rationalization will, in time, bring about an extreme polarization within the game industry. Each year the barriers to entry are becoming lower and the size of the game market is growing, which will bring about an emphasis on who has the power to be recognized in the industry. This paper argues that such trends will, in turn, lead to a power play in which the winner will always be the player with the most monetary power. In time, this prolonged power play is expected to bring about what this discussion refers to as a dystopian model within the game industry.

• Journal of Korea Water Resources Association
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• v.33 no.S1
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• pp.37-47
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• 2000

The method of delays is widely used for reconstruction chaotic attractors from experimental observations. Many studies have used a fixed delay time ${\tau}_d$ as the embedding dimension m is increased, but this is not necessarily the best choice for obtaining good convergence of the correlation dimension. Recently, some researchers have suggested that it is better to fix the delay time window ${\tau}_w$ instead. Unfortunately, ${\tau}_w$ cannot be estimated using either the autocorrelation function or the mutual information, and no standard procedure for estimating ${\tau}_w$ has yet emerged. However, a new technique, called the C-C method, can be used to estimate either ${\tau}_d\;or\;{\tau}_w$. Using this method, we show that, for small data sets, fixing ${\tau}_w$, rather than ${\tau}_d$, does indeed lead to a more rapid convergence of the correlation dimension as the embedding dimension m in increased.