• Journal of the Korean Wood Science and Technology
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• 제13권3호
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• pp.27-33
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• 1985

Air-drying tests were carried out on green taun (Pometia pinnata f glabra) for 25-mm and 50-mm thickness to elucidate drying characteristics on air-drying rate, time and defects in spring and air-drying calendar. The results of this study were as follows: 1. The air-dried lumber for 25-mm thickness from an initial average moisture content (MC) of $58.3{\pm}3.5$ percent reached 30 percent MC in 17 days, 25 percent MC in 24 days, 20 percent MC in 38 days and 15 percent MC in 84 days. 2. The air-dried lumber for 50-mm thickness from an initial average MC of $59.6{\pm}5.0$ percent reached 30 percent MC in 39 days, 25 percent MC in 55 days and 20 percent MC in 84 days. 3. Air-drying calendar that could be useful in estimating drying times for each month developed by the use of climatological data for Suwon. Total number of effective air-drying days during a year were 243.5 days and the major determinant of the effect air-drying days was temperature. 4. The air-drying rates for 25-mm and 50-mm coated lumber were slight1y slower than those of uncoated lumber. The number and total length of both end checks and surface checks for end coated lumber were less severe than those of uncoated lumber.

• 천문학회보
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• 제39권2호
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• pp.72.1-72.1
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• 2014

In the Joseon Dynasty, A day divided into 100 gak (刻, approximately a quarter) or 12 Sijin (時辰, double hours) that was composed of half-Sijin as Cho (初, beginnings of double hours) and Jeong (正, mid-points double hours). The timekeeping system was changed from 100 gak to 96 gak with using $sh{\acute{i}}xi{\grave{a}}n$ calendar (時憲曆) in 1654. And then 12 Sijin was changed to the 24-hours system in the same manner as current with the enforcement of the solar calendar (太陽曆) in 1896. We examine the record of the timekeeping system and notation of hours from the astronomical almanacs and official gazettes during 50 years after 1896. The Korean Empire Government first adopted the standard meridian of the Gyeongseong (former name of the Seoul in Korea) in 1908. However the mean solar time was applied to the almanac since 1913. After 1896, the year of enforcement of the solar calendar, the expression of times on a Korean almanac was written with O-jeon (午前, morning) and O-hu (午後, afternoon). The definition of 1day 24-hours system was first stated by the legislation in 1900. The expression of times was used 24 hours without O-jeon and O-hu in 1916. In daily life, the 24-hours system has used in parallel with 12-hours system divided into morning and afternoon even today.

• 한국시뮬레이션학회논문지
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• 제18권4호
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• pp.29-37
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• 2009

본 논문은 기존의 멀티 리스트 기반 엠리스트(MList)의 성능을 개선하기 위하여 동적 쉬프트 방식을 적용한 방법을 소개한다. 개선된 엠리스트는 일정한 수의 이벤트가 Tier 3에 쌓이게 되면 삭제 이벤트가 발생하지 않더라도 자동 쉬프트 작업을 통해 Tier 3에 저장된 이벤트들을 Tier 2의 새로운 칼렌다 큐로 이동시킨다. 즉, 기존에는 Tier 2에 하나의 칼렌다 큐가 있었으나, 개선된 방법에서는 다수의 칼렌다 큐가 동적으로 생성, 삭제된다. 이러한 동적 구조는 저장된 이벤트 수에 따라 적응력을 갖는 장점을 가져 성능측정 실험 결과 동적 쉬프트를 적용한 엠리스트는 기존의 엠리스트에 비해 20% 이상의 성능개선을 보였다.

• 응용통계연구
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• 제36권5호
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• pp.457-471
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• 2023

월별 시계열은 일별 시계열의 월별 합이지만, 일별 시계열을 대체로 관측할 수 없어서 요일구성변동, 명절·공휴일변동 등 달력변동을 가상적으로 가정한 가변수를 포함한 RegARIMIA 모형을 이용하여 추정하고 있다. 일별 시계열을 관측할 수 있다면 요일구성변동, 명절·공휴일변동 등 달력변동을 일별 시계열을 바탕으로 추정할 수 있고 이를 이용하여 월별 시계열의 계절조정을 개선할 수 있다. 이 논문에서는 일별 시계열의 달력변동 추정을 이용하여 월별 시계열의 계절조정을 개선하는 방법을 제안하고, 이 방법을 적용하여 3개의 월별 시계열을 계절조정하고 기존의 X-13ARIMA-SEATS를 이용한 계절조정과 비교하였다.

• 유통과학연구
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• 제17권3호
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• pp.69-83
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• 2019

Purpose - This paper investigates the long term impact of RFID investment on firm value in Korea. We wand to find out why the long term performance of some firm's RFID investment is better than others. To understand the dynamics of the long term returns from RFID investment announcements, we divide our events into groups for each of the independent firm characteristic variable such as investment time period, kind of markets, industries, solvency and growth potential. We composed portfolios based on the RFID investment announcement date for each group and evaluate the monthly abnormal excess returns. Research design, data, and methodology - Based on these calendar-time portfolios, we measure the long term returns from 86 RFID investment announcements of 46 firms from 2003 to 2017. We construct the calendar-time portfolio for 3, 6, 9, 12 months of holding periods. Using the weighted least squares method, we regress the raw monthly returns of the portfolios on the Fama-French model and Carhart(1997) model. As a result, we can get the estimated risk adjusted mean monthly abnormal excess return α_P for each of the calendar-time portfolio. Results - We found that early adopters, large firms, non-manufacturing firms have very significant excess returns. We also found modestly significant excess returns for financially stable firms and slow growing firms. Put together, top managers of the firms which plan to invest RFID should understand the strategic role of RFID adoption and the generalized business process of distribution information technology investment in Korea. Moreover, the findings of this paper provide useful trading strategies to the managers of large funds who are considering on investing in RFID adopting firms. Conclusions - Put together, the results of this paper give us a new insight into how the RFID and IT technology in general and other characteristic factors' interactions affect the long term performance of firms. Using the unbiased estimates of long term returns of the calendar-time portfolios, this paper extends the understandings on short term impact of RFID adoption of existing studies. This paper also extends the current understandings of firm characteristics that affect the long term performance of RFID adopting firms.

• 공업화학
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• 제35권1호
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• pp.48-53
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• 2024

전기화학 기반의 SEI 성장 모델을 이용하여 리튬이온 배터리의 캘린더 노화 및 장기 수명을 예측하였다. 네 가지 유형의 장기 SEI 성장 모델(용매 확산 제한 모델, 전자 이동 제한 모델, 리튬-간극 확산 제한 모델, 반응 제한 모델)을 적용하여 수치해석이 이루어졌고, 캘린더 에이징 동안의 용량 감소와 리튬 재고 손실을 계산하였다. 수치해석 결과, 전자 이동 제한 모델과 리튬-간극 확산 제한 모델이 낮은 용량 감소를 보였으며, 용매 확산 제한 모델과 반응 제한 모델은 10년이내에 80%의 용량 감소를 보였다. 캘린더 노화 중 저온 보관 시 SEI의 성장을 저하시켜 용량 감소가 적었다. 사이클링 중 C-rate가 증가할수록 SEI 두께 증가로 수명 하락이 크게 나타났으나 그 차이는 크지 않았다.

• Journal of the Korean Data and Information Science Society
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• 제14권4호
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• pp.805-815
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• 2003

This study examines two hypothesis regarding return generating process of corporate bonds: the trading day hypothesis and calendar day hypothesis. To differentiate two hypothesis ANOVA(analysis of variance) and regression analysis were used. If the statistical result can not reject calendar day hypothesis, it implies that there is weekend effect. The statistical result didn't support any particular hypothesis for the period of September 7th, 1999 through December 31, 2002. However, corporate bonds were supporting calendar day hypothesis for the period of October 9, 2000 through December 31, 2002. The result indicates that the Korean corporate bond market got through the impact of IMF.

• 정보학연구
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• 제9권3호
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• pp.77-89
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• 2006

The event study analyzes returns around event date at a time. Event study provides estimation periods and cumulative returns. Stock split announcements are generally associated with positive abnormal returns. It is important to investigate the responses of stocks to new information contained in the announcements of stock splits. So It is important to study the long term performance in the case of Stock Split. This Study forced to two approach method in evaluating the performance, the event time portfolio approach and calendar time portfolio approach. The event time portfolio approach exists the CAR model, BHAR model and WR model. And the calendar time portfolio approach has the 3 factor model, 4 factor model, CTAR model, and RATS model.

• 천문학논총
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• 제32권2호
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• pp.367-380
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• 2017

The life and astronomical activity of Lee Deok-Seong (李德星, 1720-1794) was studied using various historical sources, including the astronomical almanac, Seungjeongwon-Ilgi (Daily records of Royal Secretariat of Joseon dynasty), and the Gwansang-Gam's logbooks during Joseon dynasty (A.D. 1392-1910). We present the results of the study including the following main findings. First, from the investigation of Lee's family tree, we find that a number of his relatives were also astronomers, notably Samryeok-Gwan (三曆官, the post of calendrical calculation). Second, we find that he took part in the compilation of an annual astronomical almanac over a period of at least 16 years. His major achievements in the astronomy of the Joseon dynasty were to establish a new method of calendar-making calculation and to bring astronomical materials to the Joseon court through a visit to China. The Joseon dynasty enforced the Shixianli (時憲曆, a Chinese calendar made by Adam Shall) in 1654 without fully understanding the calendar. So an astronomer and an envoy were dispatched to China in order to master the intricacies of the calendar and to learn as much of Western science as was available in that time and place. Lee Deok-Seong worked at the Gwansang-Gam (觀象監, Royal Astronomical Bureau) during the reigns of King Yeongjo (英祖) and Jeongjo (正祖). As best as we can ascertain in relation with the calculations in the Shixian calendar, Lee visited China four times. During his trips and interactions, he learned a new method for calendar-making calculations, and introduced many Western-Chinese astronomical books to Joseon academia. Lee greatly improved the accuracy of calendrical calculations, even while simplifying the calculation process. With these achievements, he finally was promoted to the title of Sungrok-Daebu (崇祿大夫), the third highest grade of royal official. In conclusion, history demonstrates that Lee Deok-Seong was one of the most outstanding astronomers in the late-Joseon dynasty.

• 천문학회지
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• 제7권1호
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• pp.19-23
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• 1974

The interpolation formula Chao-ch'a-shn devised for the Chinese calendar, Shou-shih-li, has been shown as the one of the 3rd order polynomial. Its 3 coefficients have been determined from the table of the Sun in Shou-shih-li. Its applications to the moon and planets are also briefly mentioned.