• Water for future
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• v.11 no.2
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• pp.62-69
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• 1978

Interstational and interseasonal analyses of the correlation and variability in the seasonal and annual precipitation for 10 basic synoptic stations in South Korea, on the basis of rainfall record of over 40 years, are carried out. It is found that the climatic regions of precipitation could be classified by means of the interstational analysis for the correlations. Corrleation coefficients in interstational relationship of precipitation are lowest in autumn which characterizeds a strong locality while the highest value shows a relatively weak locality in winter. Interseasonal relationship between summer and winter precipitation shows mostly 10 percent significant level with all positive values. The magnitude of the variation coefficients are appeared to be in the order of winter, autumn, spring and summer. It is shown that the highest which is winter ranges between 0.33 0.58, and for the lowest summer, 0.26-0.44, respectively in the areal distribution of the coefficient. The secular changes of the variation coefficient in the recent trend show increases in spring at two station; Seoul and Incheon, in summer at Busan and in autumn at two stations; Busan and Incheon while in winter show devreases at the whole stations. An annual variation seems to show generally a constant trend as whole for all the stations.

• Journal of Korean Society of Forest Science
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• v.36 no.1
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• pp.33-37
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• 1977

The secular trends and seasonal variation of the prices of imported lauan sawtimber, domestic red pine logs and sawtimber have been analyzed to find out the features and origins of price fluctuation in Korea for the period of 1961~1971. The results may be summarized as follows: 1. The relative prices of red pine logs were raised by 1.23 percent per year, and those of red pine and lauan sawtimber were decreased by 0.10 and 0.93 percent, respectively through the period. As a whole, there is a tendency in the country that timber prices were gradually decreased by lowing timber demand through savings in consumption and exploitation of alternative materials, with the increased supply through continuous log import. 2. There is also a tendency that the seasonal variation reduced in the last 15 years. In the period of 1961~1968, the seasonal price indices were peaked in spring and autumn, but thereafter peaked in spring and dropped down until winter. 3. In secular and seasonal variations of timber prices, the trend of sawtimber prices was dependent upon that of log prices but the fluctuation was larger in log prices.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.17-30
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• 2009

In this study, the existence of possible deterministic longterm trend of precipitation amount, monthly maximum precipitation, rain day, the number of rain day greater than 20mm, 30mm, and 80mm was analyzed using the Mann-Kendall rank test and the data from 62 stations between 1905 and 2004 in South Korea. Results indicate that the annual and monthly rainfall amount increases and the number of rain days which have more than 80mm rainfall a day, increases. However the number of rain days decreases. Also, monthly trend analysis of precipitation amount and monthly maximum precipitation increases in Jan., May, Jun., Jul., Aug., and Sep. and they decrease in Mar., Apr., Oct., Nov., and Dec. Monthly trend of the number of rain day greater than 20mm, 30mm, and 80mm increases in Jun., Jul., Aug., and Sep. However results of Mann-Kedall test demonstrated that the ratio of stations, which have meaningful longterm trend in the significance level of 90% and 95%, is very low. It means that the random variability of the analyzed precipitation related data is much greater than their linear increment.

• KDI Journal of Economic Policy
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• v.14 no.1
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• pp.121-145
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• 1992

This paper examines characteristics of time series data related to the construction investment(stationarity and time series components such as secular trend, cyclical fluctuation, seasonal variation, and random change) and surveys predictibility, fitness, and explicability of independent variables of various models to build a short-term construction investment forecasting model suitable for current economic circumstances. Unit root test, autocorrelation coefficient and spectral density function analysis show that related time series data do not have unit roots, fluctuate cyclically, and are largely explicated by lagged variables. Moreover it is very important for the short-term construction investment forecasting to grasp time lag relation between construction investment series and leading indicators such as building construction permits and value of construction orders received. In chapter 3, we explicate 7 forecasting models; Univariate time series model (ARIMA and multiplicative linear trend model), multivariate time series model using leading indicators (1st order autoregressive model, vector autoregressive model and error correction model) and multivariate time series model using National Accounts data (simple reduced form model disconnected from simultaneous macroeconomic model and VAR model). These models are examined by 4 statistical tools that are average absolute error, root mean square error, adjusted coefficient of determination, and Durbin-Watson statistic. This analysis proves two facts. First, multivariate models are more suitable than univariate models in the point that forecasting error of multivariate models tend to decrease in contrast to the case of latter. Second, VAR model is superior than any other multivariate models; average absolute prediction error and root mean square error of VAR model are quitely low and adjusted coefficient of determination is higher. This conclusion is reasonable when we consider current construction investment has sustained overheating growth more than secular trend.

• Journal of the Korean Society of Food Culture
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• v.10 no.1
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• pp.19-28
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• 1995

The relationship of obesity and related behaviors was analyzed among 361 primary school children, 4th and 5th grade, in one of private school in Seoul in July 1994. Compared to 1985 Korean Children's Growth Standard, the surveyed children have shown remarkable growth, which is the secular trend in growth of Korean children accompanied with rapid economic growth. But the relative incremental weight was far larger than that of height and this trend was more evident among children over 50th percentile, which shows a wide prevalence of obesity of the surveyed children. By WLI index, 15% of the children was overweight and 13% was obese. The higher the WLI, the more frequent and stronger stress they had. The nutrition knowledge score of obese children was higher compared to others. They were especially sensitive to their physical fitness but many normal or underweight-children also experienced stress due to their body weight and have tried to lose weight by incorrect methods. On the other hand many obese children thought they were optimal or underweight. These results reasserts the importance of nutrition education focused on children aheading puberty. They need to know the correct degree of obesity and to get appropriate education through teachers, dietitians, parents and doctors. The findings of this study could be applied to a nutrition implementation policy to ensure better physical fitness of children aheading puberty in the future.

• Clinical and Experimental Pediatrics
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• v.49 no.6
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• pp.610-616
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• 2006

Purpose : The purpose of this study was to evaluate the timing of sexual maturation and secular trends of menarchial age in Korean adolescents. Methods : Nine hundred eighty two school students and 119 university female students were included. Tanner's pubertal assessment method was applied using a self-assessment sheet with pictures for their developmental stages. A medical checkup database from 1,156,022 women was also used to analyze the age of menarche from the year 1900 to 1980. Results : Onset of puberty was at $11.3{\pm}1.3$ years(y) in girls and $12.1{\pm}1.5$ y in boys and total pubertal duration was 3.6 y in girls and 3.3 y in boys. Height at the onset of puberty was $146.1{\pm}7.9cm$ in girls and $152.7{\pm}9.8cm$ in boys. Weight at the onset of puberty was $39.3{\pm}6.9kg$ in girls and $47.7{\pm}14.4kg$ in boys. The mean age of menarche was $12.0{\pm}1.0y$ and mean age at nocturnal emission was $12.3{\pm}1.8y$. By age ten, 3.0 percent of girls experienced menarche, which increased to 41.1 percent by age 12, and 98.0 percent by age over 15. By SMR 2 breast stage, 18.2 percent of girls experienced menarche, which increased to 66.1 percent and 91.7 percent by SMR stages 3 and 4, respectively. By SMR 2 pubic hair stage, 52.0 percent and by SMR 3, 93.8 percent of girls experienced menarche. While the menarchial age of women born around 1980 was $12.4{\pm}1.1y$, the menarchial age of women born around 1990 was $12.0{\pm}1.1y$. Age at menarche has been advanced approximately by 2 years between 1900 and 1980 birth cohorts. Conclusion : There was a downward secular trend in pubertal timing. Age at menarche has been advanced by 2 years during the last 80 years. Further large scale, prospective studies, including inspection by specialists, are needed to provide reference data for pubertal timing in Korean adolescents.

• 대한예방의학회:학술대회논문집
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• 1995.10a
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• pp.345-346
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• 1995

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.319-327
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• 2016

The objective of this study is to identify the secular trend in age at menarche and to investigate the factors influence the early menarche(<12 years old) among Korean middle and high school girls. We analyzed data from the Korean Youth Risk Behavior Web-based Survey(KYRBWS) 2006-2014. This study was a descriptive study of 216,917 Korean middle and high school girls born between 1988 and 2002. Linear trends test performed to assess the trend age at menarche and percentage of early menarche. Multiple logistic regression analysis was to assess the risk factors influence the early menarche. Mean age at menarche decreased from $12.61{\pm}1.32$ years for middle and high school girls born 1988 to $11.88{\pm}0.75$ years for those born 2002(p for trends<.001). Percentage of early menarche increased from 19.7% to 25.2% between 1988 and 2002(p for trends<.001). Living in city, higher stress level, short sleep duration, and higher body mass index were associated with an early menarche among middle and high school girls(all p<.001). We found that age at menarche is still falling in the Korean adolescents, and it need intervention strategies to control the early menarche.

• Journal of Preventive Medicine and Public Health
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• v.14 no.1
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• pp.43-51
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• 1981

The objective of the study is to measure the changes in measles infection and measles vaccination rates for the past 10 years in a rural area, Kang Wha. The study population were the entire children who were born between 1971 and 1950 in three townships (Sunwon, Naegae, Buleun) in Kangwha County. Two interview surveys were carried out during the 10 years of period, one in 1977 and the other in 1981. The data were collected by Family Health Workers through interview with structured questionnaires. The diagnosis of measles was mainly based on histories, symptoms and sighs of the disease. If a mother had reported measles history of her child, a public physician reviewed and decided the final diagnosis of the reported case. A retrospective cohort observation was done in order to see the trends of measles infections and measles vaccinations. The major findings were as follows; 1. The 5 year prevalence rate of measles vaccinations was 51.3% between 1971 and 1975 and 71.9% between 1976 and 1980 respectively. The difference between two periods was statistically significant (P<0.05). The secular trend of measles vaccinations showed increasing tendency from 1971 to 1978 and since then kept maintained. 2. In the birth cohort analysis of measles vaccinations, the vaccination rates, in general, were higher in the later cohort groups than that of earlier cohort groups. 9. The 5-year experience rates for measles infections were 24.3% between 1971 and 1975 and 17.2% between 1976 and 1980 respectively. This difference was statistically significant(P<0.05). The secular trend of experience rates for measles infections showed decreasing tendency from 1971 to 1980 except an outbreak in 1976. 4. The birth cohort analysis of experience rates for measles infections showed that the rate was higher in the later cohort groups than that of the earlier cohort groups. This decreasing tendency was prominent between $1973{\sim}1974$ and $1976{\sim}1977$. 5. The distribution of age specific incidence rates for measles infections showed unimodal curve with the peak at the age of 12 to 18 months. This findings were same in both two surveys. 6. Seasonal variations of the measles infections showed two peaks, one major peak in March through May and the another minor peak in September through December. 7. The 5-year reduction rate for measles infections among those vaccinated was 90.4% between 1971 and 1975 and 88% between 1976 and 1980.

• Journal of Korean Society of Forest Science
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• v.73 no.1
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• pp.70-75
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• 1986

The secular trend and seasonal variation of chestnut prices have been analyzed, and the production and price for the next two decades (1985-2004) have been forecasted by the derived equation model. The results of the study can be summarized as follows; 1) The chestnut prices went up at the rate of 10.95% per annum during 1965-1972, but, due to excessive supply of chestnuts, went down at the rate of 7.25% during 1973-1984. 2) In a year, the prices were lowest at the harvesting season, especially on October, and highest on July. Such a seasonal fluctuations of chestnut prices tend to be even with the passage of time, but the range of fluctuation is still wide. 3) It was forecasted under certain premises that the annual chestnut production will be increased by 99,000 tons in 1992, but the amount will fall rapidly to about 23,000 tons in 2004. The prices will be similar to the present level or have slightly upward Tendency until 1992, but this will be rapidly raised thereafter.