• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.126-129
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• 2005

Change detections is carried out under the assumption that pixel boundaries of geometrically corrected time series satellite images cover the same location. However that assumption can be wrong when shifts in the pointing direction of a satellite sensor occurs. Currently, although the influence of misregistration on landcover change detection has been investigated, there has been little research on the influence of pointing direction shifts of a satellite sensor. In this study, a simple method for reducing the effects of pointing direction shifts of a satellite sensor is proposed: the classification of two ASTER images was carried out using the linear spectral mixture analysis, the two classification results were resampled into a geometrically fixed grid, and then the change detection of the two ASTER images was carried out by comparing the resampled classification results of the two images. The proposed method showed high performance in discriminating between changed areas and unchanged areas by removing the pointing direction shifts of a satellite sensor.

• 대한원격탐사학회지
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• 제35권4호
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• pp.573-587
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• 2019

A multi-temporal approach using remotely sensed time series data obtained over multiple years is a very useful method for monitoring land covers and land-cover changes. While spectral-based methods at any particular time limits the application utility due to instability of the quality of data obtained at that time, the approach based on the temporal profile can produce more accurate results since data is analyzed from a long-term perspective rather than on one point in time. In this study, a multi-temporal approach applying a multi-periodic harmonic model is proposed for classification of remotely sensed data. A harmonic model characterizes the seasonal variation of a time series by four parameters: average level, frequency, phase, and amplitude. The availability of high-quality data is very important for multi-temporal analysis.An satellite image usually have many unobserved data and bad-quality data due to the influence of observation environment and sensing system, which impede the analysis and might possibly produce inaccurate results. Harmonic analysis is also very useful for real-time data reconstruction. Multi-periodic harmonic model is applied to the reconstructed data to classify land covers and monitor land-cover change by tracking the temporal profiles. The proposed method is tested with the MODIS and GOCI NDVI time series over the Korean Peninsula for 5 years from 2012 to 2016. The results show that the multi-periodic harmonic model has a great potential for classification of land-cover types and monitoring of land-cover changes through characterizing annual temporal dynamics.

• 유통과학연구
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• 제14권1호
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• pp.93-102
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• 2016

Purpose - The purpose of paper is studying the static and dynamic side for long-term memory storage properties, and increase the explanatory power regarding the long-term memory process by looking at the long-term storage attributes, Korea Composite Stock Price Index. The reason for the use of GPH statistic is to derive the modified statistic Korea's stock market, and to research a process of long-term memory. Research design, data, and methodology - Level shifts were subjected to be an empirical analysis by applying the GPH method. It has been modified by taking into account the daily log return of the Korea Composite Stock Price Index a. The Data, used for the stock market to analyze whether deciding the action by the long-term memory process, yield daily stock price index of the Korea Composite Stock Price Index and the rate of return a log. The studies were proceeded with long-term memory and long-term semiparametric method in deriving the long-term memory estimators. Chapter 2 examines the leading research, and Chapter 3 describes the long-term memory processes and estimation methods. GPH statistics induced modifications of statistics and discussed Whittle statistic. Chapter 4 used Korea Composite Stock Price Index to estimate the long-term memory process parameters. Chapter 6 presents the conclusions and implications. Results - If the price of the time series is generated by the abnormal process, it may be located in long-term memory by a time series. However, test results by price fixed GPH method is not followed by long-term memory process or fractional differential process. In the case of the time-series level shift, the present test method for a long-term memory processes has a considerable amount of bias, and there exists a structural change in the stock distribution market. This structural change has implications in level shift. Stratum level shift assays are not considered as shifted strata. They exist distinctly in the stock secondary market as bias, and are presented in the test statistic of non-long-term memory process. It also generates an error as a long-term memory that could lead to false results. Conclusions - Changes in long-term memory characteristics associated with level shift present the following two suggestions. One, if any impact outside is flowed for a long period of time, we can know that the long-term memory processes have characteristic of the average return gradually. When the investor makes an investment, the same reasoning applies to him in the light of the characteristics of the long-term memory. It is suggested that when investors make decisions on investment, it is necessary to consider the characters of the long-term storage in reference with causing investors to increase the uncertainty and potential. The other one is the thing which must be considered variously according to time-series. The research for price-earnings ratio and investment risk should be composed of the long-term memory characters, and it would have more predictability.

• 대한교통학회지
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• 제26권5호
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• pp.81-90
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• 2008

버스노선개편 및 환승요금무료와 같은 대중교통체계개편을 실시함에 따라 시내버스 이용자들이 개편된 노선에 익숙히 대처하기 위해서는 일정기간이 소요된다. 따라서 본 연구는 시내버스 승객수요의 월별 특성에 대해 분석하고, 시계열분석을 실시함으로써 버스노선개편 이후에 변화하는 시내버스 승객수요가 다시 안정된 월별특성을 나타내기까지의 기간에 관하여 연구하고자 한다. 먼저 여러 도시들의 시내버스 승객수요가 공통된 월별 특성을 나타내는지 분석하기 위해 켄달의 일치계수검정을 실시하였다. 또한 노선개편으로 인해 변화된 승객수요가 일정한 패턴을 보이는 기간을 분석하기 위해 시계열분석으로 예측된 2006년의 시내버스 월별 승객수와 실제 집계된 시내버스 월별 승객수를 비교하였다. 이에 따라 각 도시들은 공통된 월별 특성을 보이는 것으로 분석되었고, 대구광역시는 약 6개월 뒤에 예측값과 실제값이 같은 패턴으로 변화하는 것으로 분석되었다. 본 연구는 타도시에서도 적용이 가능하며 시내버스 승객수요의 미시적인 예측과 평가에 활용될 것으로 기대된다.

• 복식
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• 제11권
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• pp.31-43
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• 1987

The present research is to study a variation of skirt length in the time series, from 1955 to 1986. The results are summarized as follows; 1. The most important event is the acceptance of Mini skirts during this period. This phenomenon will play an important role in later skirt length. 2. The year of the shortest skirt length is 1972, while the year of the longest skirt length is 1983. 3. Based upon the year of the shortest skirt length, the periods of the same skirt length are as follows; 1956-1975. 1964-1978. 1959, 1960-1980, 1981. 1961-1982. This phenomenon is irregularly appeared in this study, but shows the change of recurring skirt length. 4. The skirt length has been changed slowly and continuously during the long period of time. In particular, to reach the shortest skirt length takes longer time than that of the longest skirt length. 5. It has taken 6-8 years to reach the top period of Mini skirts (1971-1973) since shorts are introduced. Comparing this phenomenon in Korea with that in Japan, the time difference is about two years. 6. The periods of various skirts length are the year of 1970-1971 and the year of 1972-1973; This result is assumed that individual persons accept sooner or later the changed skirt length. 7. It is belived that Mini skirts are appeared and popularized by external factors. Once Mini skirts are accepted, we can expect that they will be continuosly changed in the course of recurring skirt length.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2018년도 추계학술대회
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• pp.360-363
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• 2018

인간의 활동은 척추 옆굽음증, 골반 뒤틀림과 같은 개개인의 신체적 특징부터 기쁨, 분노, 슬픔 등의 감정들까지 다양한 요인들에 영향을 받는다. 하지만 이러한 동작의 특성은 오랜 시간에 걸쳐서 변화하며, 단기적으로 행동의 특성은 크게 변하지 않는다. 사람의 활동 데이터는 시간 흐름에 따라서 변화하는 시계열 적 특징과 각 행동별로 일정한 규칙성을 갖는다. 본 연구에서는 시계열 적 특징을 다루기 위한 순환신경망의 한 종류인 LSTM을 활동유형을 인식하는 기술에 적용하였으며, 측정시간과 LSTM 모델의 구성요소들에대한 파라미터 최적화로 활동유형의 인식률을 개선하였다.

• 천문학논총
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• 제30권2호
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• pp.605-607
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• 2015

The development of time-frequency analysis techniques allow astronomers to successfully deal with the non-stationary time series that originate from unstable physical mechanisms. We applied a recently developed time-frequency analysis method, the Hilbert-Huang transform (HHT), to two non-stationary phenomena: the superorbital modulation in the high-mass X-ray binary SMC X-1 and the quasi-periodic oscillation (QPO) of the AGN RE J1034+396. From the analysis of SMC X-1, we obtained a Hilbert spectrum that shows more detailed information in both the time and frequency domains. Then, a phase-resolved analysis of both the spectra and the orbital profiles was presented. From the spectral analysis, we noticed that the iron line production is dominated by different regions of this binary system in different superorbital phases. Furthermore, a pre-eclipse dip lying at orbital phase ~0:6-0:85 was discovered during the superorbital transition state. We further applied the HHT to analyze the QPO of RE J1034+396. From the Hilbert spectrum and the O-C analysis results, we suggest that it is better to divide the evolution of the QPO into three epochs according to their different periodicities. The correlations between the QPO periods and corresponding fluxes were also different in these three epochs. The change in periodicity and the relationships could be interpreted as the change in oscillation mode based on the diskoseismology model.

• Journal of Platform Technology
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• 제11권4호
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• pp.62-70
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• 2023

이 논문은 농수산물 생산자가 도매시장에 상품을 출하하는 시기와 양을 결정하는 것을 돕기 위한 시스템을 구축하기 위한 일련의 과정 중 일부이다. 기존 농수산물 출하모델에서 사용하지 않은 품질변화효과를 모델링하고, 그 통계적 유의성을 확인한 후, 시스템에 도입하는 것이 이 연구의 목적이다. 이를 위해 연구자는 품질변화효과를 측정할 수 있는 네 가지 모델을 개발하였다. 시간이 지남에 따라 1) 품질이 일정하게 떨어지는 경우, 2) 품질이 처음에 급속히 떨어지다가 나중에는 천천히 떨어지는 경우, 3) 품질이 처음에 천천히 떨어지다가 나중에는 급속히 떨어지는 경우, 4) 품질이 낮았다가 시간이 흐른 후 높아지다가 다시 감소하는 경우를 모델링하였다. 각 모델의 품질변화효과가 출하량에 미지는 영향을 2014-2021년 사이에 가락도매시장에서 거래된 사과를 대상으로 실증분석 해 본 결과에 따르면 네 모델 모두 품질변화효과에 유의성을 발견하였다. 그리고 네 모델 간 설명력에 유의한 차이는 없었다. 따라서 네 개 모델 중 어느 하나를 선택해서 사과에 대한 출하시기의사결정시스템에 적용시킬 수 있는 것으로 나타났다.

• 수산경영론집
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• 제29권2호
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• pp.77-96
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• 1998

Fisheries products in Korea generally go through three markets, namely the wholesale market at production site (Market A), the wholesale market at consumption site (Market B), and the retail market (Market C), from producers to end consumers. As the products move from Market A through Market B to Market C, the marginal gap of prices asked in these markets demonstrates an apparent relationship. The producers, middlemen, consumers, and governmental departments concerned may influence the marketing prices of fisheries products. This study employing the cointegration theory tries to investigate whether causality of the price-setting among these markets exists and, if any, what it is. The authors have focused their attention on fisheries markets in Pusan, analyzing the long-run equilibrium relationship and causality between the prices of hairtail and squid among markets at different levels. Data used in this study cover the period f개m August 1984 to December 1997 fer hairtail, and the period from May 1989 to December 1997 for squid. The main findings of the study may be summarized as follows: First, regardless of the price time-series of hairtail and squid in individual market, the first difference is necessary fur satisfying the stationary conditions since each time-series is a first integration. This means homogeneous integration of time-series, which is a requirement of the long-run equilibrium of prices at different markets, is satisfied. Second, the study of the long-run equilibrium relationship between the prices at Market A and Market B shows that a long-run equilibrium relationship does exist for selling prices of the two species at Market A and Market B. Third, the ECM (error correction model ) used here to describe the long- and short-run dynamics of price change demonstrates that, in the case of squid, the price change in Market A will lead to a corresponding price change in Market B in the long-run period. In the short-run, however, the price at Market H is not only influenced by the price change in Market A but influence the price at Market A as well, that is, the Prices between Market A and Market B have a feedback effect. It should be stressed that the limitation in data collection, which cover only two species of hairtail and squid, is likely to cause a sampling bias. Nonetheless, we may conclude that a dynamic relation in the formation of prices does exist in view of the transaction amount of species at different markets. It is believed that the conclusion drawn from this study would not only contribute to a long-lasted debate on the direction of causality of price-setting among academic circle and fishing community, but would provide a useful standard for the policy makers in charge of the price-setting of fisheries products as well.

• 대한교통학회지
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• 제30권1호
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• pp.103-112
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• 2012

우리 시간의 흐름에 따라 사회 경제 구조, 생활양식 등 여러 요소가 변하면서 사람들의 통행목적과 통행행태도 변하게 된다. 하지만 기존의 통행발생모형은 장래 수요예측 시 기준연도에 추정된 parameter 값이 장래에도 동일하기 때문에 시간과 통행행태의 변화를 반영할 수 없는 문제점을 안고 있다. 이러한 문제를 개선하기 위하여 시간변화를 반영한 통행발생모형을 개발하였다. 가구통행실태조사는 특정 시점의 통행특성을 조사한 횡단면 자료이지만 그동안의 3번의 조사를 통해 시계열적 측면이 보완되었고, 조사자료를 기초로 하여 행정동을 기준으로 OD를 구축하기 때문에 이를 하나의 패널로 설정하여 패널분석을 수행할 수 있다. 따라서 본 연구에서는 1996년부터 2006년까지 조사된 가구통행실태조사자료 및 전수화 OD, 각 기준연도의 사회경제지표를 이용하여 패널분석을 통해 통행발생모형을 개발하였다. 분석 결과 시간이 지나면서 유의한 시간효과가 나타났다. 학원통행의 경우에는 시간이 지날수록 인구당 통행발생량이 증가하는 시간효과의 패턴이 나타났고, 쇼핑통행의 경우에는 감소하는 시간효과의 패턴이 나타났다.