• Industrial Engineering and Management Systems
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• 제12권3호
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• pp.244-253
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• 2013

In industries, shipping is an important issue in improving the forecasting accuracy of sales. This paper introduces a hybrid method and plural methods are compared. Focusing the equation of exponential smoothing method (ESM) that is equivalent to (1, 1) order autoregressive-moving-average (ARMA) model equation, a new method of estimating the smoothing constant in ESM had been proposed previously by us which satisfies minimum variance of forecasting error. Generally, the smoothing constant is selected arbitrarily. However, this paper utilizes the above stated theoretical solution. Firstly, we make estimation of ARMA model parameter and then estimate the smoothing constant. Thus, theoretical solution is derived in a simple way and it may be utilized in various fields. Furthermore, combining the trend removing method with this method, we aim to improve forecasting accuracy. This method is executed in the following method. Trend removing by the combination of linear and 2nd order nonlinear function and 3rd order nonlinear function is executed to the original production data of two kinds of bread. Genetic algorithm is utilized to search the optimal weight for the weighting parameters of linear and nonlinear function. For comparison, the monthly trend is removed after that. Theoretical solution of smoothing constant of ESM is calculated for both of the monthly trend removing data and the non-monthly trend removing data. Then forecasting is executed on these data. The new method shows that it is useful for the time series that has various trend characteristics and has rather strong seasonal trend. The effectiveness of this method should be examined in various cases.

• 국제지역연구
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• 제21권4호
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• pp.159-172
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• 2017

비관측요인(unobserved-component)모형을 이용한 GDP의 추세-순환요인 분해에서, 통상적으로 추세는 확률보행 과정을 갖는 것으로 가정된다. 본 연구는 추세를 ARIMA 과정으로 표현하는 경우, GDP 변동에서 갖는 추세요인의 의미가 어떻게 달라지는가를 살펴보고, GDP에 대한 예측력이 개선될 수 있는가의 여부를 미국의 데이터를 이용하여 실증적으로 분석하였다. 모형은 GDP만의 단일변수모형과 물가를 포함하는 2변수모형의 두 가지를 고려하여 설정하였으며, 모형 추정은 비관측요인모형을 상태-공간모형으로 전환한 후 칼만 필터(Kalman filter)를 이용한 최대우도추정법을 사용하였다. GDP에 대한 예측은 축차적 추정(recursive estimation)을 이용한 동적 표본외예측(dynamic out-of-sample) 방식을 사용하였으며, 예측력 비교결과에 대한 검정은 Diebold-Mariano 검정을 이용하였다. 분석 결과는 첫째, 모형의 추정결과에서 ARIMA 추세의 계수가 통계적으로 유의적인 값을 가지며, 둘째, ARIMA 추세 모형이 확률보행 추세 모형보다 GDP 변동의 분산 및 자기 상관성(autocorrelation)을 보다 잘 설명하며, 셋째, 예측력에서 단일변수보다는 2변수모형의 예측력이 그리고 확률보행 추세보다는 ARIMA 추세를 갖는 모형의 예측력이 통계적으로 유의하게 높은 것으로 나타났다. 이러한 결과들은 GDP 추세-순환 요인 분해에서 추세를 ARIMA 과정으로 표현하는 것이 보다 타당하다는 것을 시사하고 있다.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권2호
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• pp.121-130
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• 2009

The power law process model the Rate of occurrence of failures(ROCOF) with monotonic trend during the operating time. However, the power law process is inappropriate when a non-monotonic trend in the failure data is observed. In this paper we deals with the reliability modeling of the failure process of large and complex repairable system whose rate of occurrence of failures shows the non-monotonic trend. We suggest a sectional model and a change-point test based on the Schwarz information criterion(SIC) to describe the non-monotonic trend. Maximum likelihood is also suggested to estimate parameters of sectional model. The suggested methods are applied to field data from an repairable system.

• 산업경영시스템학회지
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• 제32권1호
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• pp.11-19
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• 2009

A number of trend test methods, i.e., Military Handbook test and Laplace test etc., have been applied to investigate recurrent failures trend in repairable systems. Existing methods provide information about only existence of trend in the system. In this paper, we propose a new change-point test based on the Schwarz Information Criterion(SIC). The change-point approach is more informative than other trend test methods in that it provides the number of change-points and the location of change-points if it exists, as well as the existence of change-point for recurrent failures. The change-point test is applied to nine 300MW generating units operated in East China. We confirm that the change-point test has a potential for establishing optimal preventive maintenance policy by detecting change-point of failure rate.

• 한국정보전자통신기술학회논문지
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• 제15권5호
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• pp.423-432
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• 2022

본 논문은 학술연구자들이 COVID-19 관련 논문의 전체적인 연구 동향을 파악할 수 있도록 한다. KCI 사이트에서 수집한 2020년 1월부터 2022년 7월까지 총 10,599편의 COVID-19 관련 논문 정보를 LDA 토픽 모델링으로 분석한 결과를 제시한다. 또한 학술연구자들이 자신의 관심 연구분야의 토픽을 쉽게 파악할 수 있도록 LDA 토픽 모델링의 결과를 주요 연구 카테고리별로 분석하고, 토픽별로 연구가 많이 이루어지는 세부 연구 카테고리 정보를 분석한다. 학술연구자들이 시간의 흐름에 따른 연구 토픽의 추세(trend)를 파악하는 것은 연구 동향을 파악하는데 매우 중요하다. 따라서 이를 위해 본 논문에서는 시계열 분해를 사용하여 토픽들의 추세(trend)를 분석하여 제시한다.

• 시큐리티연구
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• 제4호
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• pp.169-187
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• 2001

NGOs occupy so high international position that it is said the age of NGOs or Renaissance of NGOs has came. Recently, they continuously succeeded in hindering and blocking large-scale international events through their violent struggles. This paper studied the concept of NGO, examples of NGO struggles during recent international events and stated anticipated struggles during ASEM III and their trend. Thereafter, with future prospect of NGO activities, some measures for successful 2002 World Cup and 2005 APEC were provided in this paper. The contents of this paper is as follows ; Chapter I : Introduction Chapter II : The concept of NGO and aspects of their struggles during recent international events Chapter III : Struggles during the 3rd ASEM, Seoul and their trend Chapter IV : Future prospect of NGO activities Chapter V : Conclusion

• 대한조선학회 특별논문집
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• 대한조선학회 2005년도 특별논문집
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• pp.165-170
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• 2005

The weight of a ship depends on the size of the ship. Normal lightweight of a ship is over 10,000 tons. So it is inevitable to divide a ship into about more than hundreds of lumps. Each of lumps is called as a block in shipbuilding. The sizes of blocks are decided by a yard's facilities. Among them lifting cranes are most decisive facilities. By block's size the productivity of a yard is decided very much. So it is very important to have a proper block division during shipbuilding. This paper refers to the recent trend of block division among yards. This paper would give an idea how to decide boundaries of blocks. Block division also decides both quality of a ship and work volume of it. These days the block erection method is changed dramatically due to use sea barge mounted crane for erection of a grand ring block. This paper explains the new trend of block division in shipbuilding.

• Communications for Statistical Applications and Methods
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• 제29권3호
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• pp.353-371
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• 2022

This paper analyzes death counts after World War II of several countries to identify and to compare their stochastic structures. The stochastic structures that this paper entertains are three structural time series models, a local level with a random walk model, a fixed local linear trend model and a local linear trend model. The structural time series models assume that a time series can be formulated directly with the unobserved components such as trend, slope, seasonal, cycle and daily effect. Random effect of each unobserved component is characterized by its own stochastic structure and a distribution of its irregular component. The structural time series models use the Kalman filter to estimate unknown parameters of a stochastic model, to predict future data, and to do filtering data. This paper identifies the best-fitted stochastic model for three types of death counts (Female, Male and Total) of each country. Two diagnostic procedures are used to check the validity of fitted models. Three criteria, AIC, BIC and SSPE are used to select the best-fitted valid stochastic model for each type of death counts of each country.

• 한국정보통신학회논문지
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• 제19권5호
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• pp.1110-1116
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• 2015

본 논문에서는 정보보안에 대한 글로벌 연구 트렌드에 대한 분석을 다룬다. 정보를 이용하는 모든 분야에서 보안을 필요로 하기 때문에, 새롭게 생성되거나 급격하게 발전하는 분야를 발굴하는 것이 정보보안의 방향을 설정하는 것이 될 수 있다. 이에 본 연구의 목적은 정보보안과 관련한 기술들을 파악하고, 이들을 트렌드 관점에서 해석함으로써 향후를 전망해보고자 한다. 현재의 수준은 거시적 관점에서의 분석을 위한 초기 연구로써, 기술들 사이의 연도별 공기정보를 이용하여 2001년부터 2014년까지의 연관성을 측정하고, 상위 연관 기술 자체의 트렌드와 상호 비교하여 그 의미를 분석하였다. 결론적으로는 안드로이드 플랫폼, 빅데이터, 사물인터넷, 모바일 분야, 클라우드 컴퓨팅이 정보보안에 유망한 기술 분야라 할 수 있다.

• 패션비즈니스
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• 제15권5호
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• pp.161-177
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• 2011

The purpose of this research is to analyze the effect of the traditional color sentiment on the contemporary clothing color by researching the street fashion of 2010 Winter season of Dalian in China, in view of the clothing color of women in their 20-30 years of age, along with traditional Chinese color. This is the 2nd paper following the paper no. 1, focusing on 2010 Summer season, so the research method is same as the paper no. 1. As a result, Black and deep tone PB color most frequently appeared. The vivid and strong tone of R, YR, Y color showed high frequency of clothing colors. This results illustrate that the clothing color choices of Chinese women was affected by Chinese traditional color sentiment rather than the international color trend. Characteristically, in winter season, frequency of R and Y color categories were higher than in summer season, specially in the top and accessories color, those colors showed higher frequency than the other colors. These were the important points in dealing with winter color trend, so that the fashion company and brands should take it an important points when they are planning winter clothing colors. The achromatic colors show the high frequency in both seasons. The bottom color shows high incidence of Black and deep tone of PB color categories as in the previous researches. That means consistent color trend existed in Dalian city, however it does not seem to have its origin from traditional Chinese color preferences. This kinds of regional and seasonal research might contribute to finding the basic informations about the design and marketing strategies to launch into the Chinese fashion market.