• Proceedings of the Korean Statistical Society Conference
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• 2003.10a
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• pp.85-90
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• 2003

이 논문에서는 Samuel, Pignatiello와 Calvin(1998)이 제안한 ${\overline{X}}$ 관리도에서 이상원인 발생시점에 대한 최대우도추정량에 기초하여 변량표본크기(VSS) ${\overline{X}}$ 관리도를 수행하는 경우에 사용할 수 있는 최대우도추정량을 제안한다. 또한 제안된 최대우도추정량을 이용하여 이상원인 발생 시점에 대한 신뢰구간을 설정하였다.

• Journal of the Korean Data and Information Science Society
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• v.20 no.2
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• pp.435-443
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• 2009

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 the maximum likelihood estimator (MLE) for the process change point when a control chart is used in monitoring the parameters of a process in which the observations can be modeled as a IMA(1,1).

• Journal of KIISE:Information Networking
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• v.33 no.3
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• pp.201-217
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• 2006

In this paper, we collected the physical traces from high speed Internet backbone traffic and analyze the various characteristics of the underlying packet traces. Particularly, our work is focused on analyzing the characteristics of an anomalous traffic. It is found that in our data, the anomalous traffic is caused by UDP session traffic and we determined that it was one of the Denial of Service attacks. In this work, we adopted the unsupervised machine learning algorithm to classify the network flows. We apply the k-means clustering algorithm to train the learner. Via the Cramer-Yon-Misses test, we confirmed that the proposed classification method which is able to detect anomalous traffic within 1 second can accurately predict the class of a flow and can be effectively used in determining the anomalous flows.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.149-151
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• 2014

최근 진도 해역에서 발생한 세월호 침몰사고에 대한 문제를 다루었다. 공개 발표된 AIS 데이터를 이용하여 사고 발생 시점에서의 선박 조종 특성을 분석하였다. 또한 해당 선박과 유사한 선박의 선박 조종 특성과 세월호를 비교 분석하여 사고 당시 데이터가 보여주고 있는 선박 조종 특성에 대하여 검토하였다. 그 결과 사고 당시 세월호는 타에 의한 선박 회두 범위를 크게 벗어나는 선회 회두가 발생하는 것을 발견하였다. 이를 근거로 사고 발생 시점 및 사고 발생 원인에 대하여 제시하였다.

• Congress of the korean instutite of fire investigation
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• 2010.12a
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• pp.120-136
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• 2010

엔진 정지 중 발생한 자동차화재는 엔진 정지 전에 이미 화재가 발생해 있었으나 이를 모르고 엔진 정지 중에 화재가 발견되는 경우와 엔진 정지 후에 발생한 경우로 나눌 수 있다. 엔진정지 전 발생한 화재는 운행 중 화재가 발생할 수 있는 모든 원인에 의해 발생할 수 있고, 엔진정지 후 발생한 화재는 전기적인 원인에 의한 화재, 담뱃불에 의한 화재, 방화, 다른 곳에서 발화된 후 자동차로 확대된 화재 중의 하나로 압축할 수 있다. 그러므로 외부발화 또는 방화나 담뱃불에 의한 화재가 배제되는 경우는 전기적인 원인만을 생각할 수 있다. 엔진정지 전에 이미 엔진룸 등에 불이 붙어 있어도 주차 중 이를 인식하지 못하는 것은 엔진정지 시 화재의 규모가 작거나 눈에 띄는 이상징후가 나타나 있지 않고 또한 이를 관심 있게 확인하지 않기 때문이다. 엔진정지 전에 화재가 발생한 경우에는 일반적으로 주차 후 대략 10분 이내에 화재가 발견되고 있다. 따라서 주차 후 10분이 경과하지 않은 시점에 화재가 발견되었다면 엔진정지 전에 이미 화재가 발생하였을 가능성이 크다고 볼 수 있다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.1
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• pp.26-32
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• 2017

Enlargement and speed-up of a ship and diversification of ship's type have served to greatly increase the importance of marine transport means. It's reported that accident occurrence frequency of collision is high next to engine damage among the ship accident types, and that the accident ratio according to human factors is also high. In addition, ship accidents come to occur caused by complex cause factors rather than a sole cause factor, it is necessary to investigate the cause factors through the written verdict. This study proposed the cause factors of collision ship accident on the basis of human factors in collision ship accident among the written verdicts provided by the Korean Maritime Safety Tribunal, and inquired into the cause factor and effect through the correlation analysis of accident occurrence factors. Also, this study predicted the collision accident through analyzed the major cause factor of the occurrence at the zero minute when collision on the basis of the time taken from the time point of detecting collision of ships to the time point of collision occurrence. This study used commercial software-Statistical Package for Social Sciences (SPSS Ver21.0) to do correlation analysis. For time analysis, this study analyzed the cause factor and time by analyzing the time taken from the time point of detected ships to the time point of collision occurrence on the basis of the written verdicts. The study analysis showed that there were many cases of collision ship accidents occurrence caused by more than two sorts of cause factors, and that the case (zero minute) where there is no time to spare for collision avoidance accounted for 36.1 %, and negligence in guard or surveillance of the other ship, and sailing while drowsy, or drinking was a contributor to an accident. Poor watch keeping is very strong relationship with pool ready for sail.

• The Korean Journal of Applied Statistics
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• v.21 no.2
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• pp.247-264
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• 2008

This paper considers the integrated process control procedure for detecting special causes in an ARIMA(0,1,1) process that is being adjusted automatically after each observation using a minimum mean squared error adjustment policy. It is assumed that a special cause can change the process mean and the process variance. We derive expressions for the process deviation from target for a variety of different process parameter changes, and introduce a control chart, based on the generalized likelihood ratio, for detecting special causes. We also propose the integrated process control scheme bases on the future loss. The future loss denotes the cost that will be incurred in a process remaining interval from a true out-of-control signal.

• Journal of IKEEE
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• v.25 no.4
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• pp.710-715
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• 2021

Power line signal can show disturbances due to various causes. Typical anomalies are temporary sag/swell of the amplitude, flat topped signal, and harmonic distortions. The disturbances need to be detected and treated properly for the quality of the power signal. In this study, the power disturbances are detected using the inflection points (IP). The inflection points are defined as points where local maxima/minima or the slope changes occur. The power line signal has a fixed IP pattern since it is basically sinusoidal, and it may have additional inflection points if there is any disturbance. The disturbance is detected by comparing the IP patterns between the normal signal and distorted signal. In addition, by defining a cost function, the time instant where the disturbance happens can be decided. The computer simulation shows that the proposed method is useful for the detection of various disturbances. The simple sag or swell signal only shows the amplitude changes at the detected inflection points. However, the flat top signal and harmonically distorted signal produce additional inflection points and large values in the cost function. These results can be exploited for the further processing of disturbance classification.

• Korean Journal of Construction Engineering and Management
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• v.7 no.3 s.31
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• pp.159-168
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• 2006

In order to respond to interest and regulations in sustainable environment which is increasing, construction industry needs to establish a sustainable production system. When generation of wastes can be diminished and recycling of them raised in the construction site as a part of a sustainable production system, it might contribute to not only establishing a sustainable production system but also gaining economical profit. This study is a preliminary research for establishing a sustainable production system, which aims to identify construction waste generation patterns and factors causing construction waste generation. Case studies were implemented to investigate these patterns and factors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10B
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• pp.936-944
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• 2006

In order to enhance their own customer satisfaction index that is one of the top level managerial performance indices, Internet communication service providers endeavor onto establishing a total quality management system. Specifically, it is under discussion that some critical Internet communication network quality characteristics closely related to customer satisfaction index should be controlled aiming to this managerial goal. This paper presents an application scheme of I-MR control charts for monitoring Internet communication network quality characteristics. This statistical quality control scheme generates a signal to practitioners when it detects the network quality characteristics out-of control. It is designed based on; 1) individual measurements; and 2) moving ranges between two consecutive individual measurements collected with a constant time interval. Empirical analyses are illustrated to estimate the expected quality improvement ratios that can be realized with the application scheme proposed in this paper. Assuming that the assignable causes can be revealed and eradicated, regarding two Internet communication services A, B, seven network quality characteristics for each service, eleven distinct measuring spots for each network quality characteristic, the expected quality improvement ratios are calculated with which the effect of the application scheme is evaluated. Results show the ranges of the expected quality improvement ratios; 1) Service A, (1) mean (0.31%-11.44%), (2) standard deviation (9.82%-71.10%): 2) Service B, (1) mean (0.29%-17.64%), (2) standard deviation (8.05%-60.59%). Hence, It is anticipated that the I-MR control charts based application scheme can be effective not only to improving the mean and dispersion of the network quality characteristics concerned but also to maintaining the network quality characteristics in-control consequently.