• 한국대기환경학회지
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• 제27권5호
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• pp.494-503
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• 2011

Fine particles ($PM_{2.5}$) were collected and analyzed from December 2005 through December 2009 in Chuncheon, Korea to investigate the long-term trend of $PM_{2.5}$ concentrations. Also $PM_{10}$ concentrations were collected from Environmental Monitoring System operated by Ministry of Environment. Average concentrations of $PM_{2.5}$ and $PM_{10}$ were 30.5 and 58.2 ${\mu}g/m^3$, respectively. Both $PM_{2.5}$ and $PM_{10}$ were significantly affected by meteorological factors including wind speed, wind direction and precipitation. They generally decreased as wind speed increased (p=0.000), and increased when there was a prevailing westerly wind. Low concentrations of $PM_{2.5}$ were observed during rainy days while high concentrations were shown when fog, mist and/or haze occurred.

• East Asian mathematical journal
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• 제34권3호
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• pp.317-330
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• 2018

We develop a mathematical model for the obesity dynamics to investigate the long term obesity trend with the consideration of psychological and social factors due to the increasing prevalence of obesity around the world. Many mathematical models for obesity dynamics adopted the modeling idea of infectious disease and treated overweight and obese people infectious and spreading obesity to normal weight. However, this modeling idea is not proper in obesity modeling because obesity is not an infectious disease. In fact, weight gain and loss are related to social interactions among different weight groups not only in the direction from overweight/obese to normal weight but also the other way around. Thus, we consider these aspects in our model and implement personal weight gain feature, a psychological factor such as body image dissatisfaction, and social interactions such as positive support on weight loss and negative criticism on weight status from various weight groups. We show that the equilibrium point with no normal weight population will be unstable and that an equilibrium point with positive normal weight population should have all other components positive. We conduct computer simulations on Korean demography data with our model and demonstrate the long term obesity trend of Korean male as an example of the use of our model.

• Journal of Information Processing Systems
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• 제15권3호
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• pp.694-706
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• 2019

In this study, we applied the long short-term memory (LSTM) model to classify the cryptocurrency price time series. We collected historic cryptocurrency price time series data and preprocessed them in order to make them clean for use as train and target data. After such preprocessing, the price time series data were systematically encoded into the three-dimensional price tensor representing the past price changes of cryptocurrencies. We also presented our LSTM model structure as well as how to use such price tensor as input data of the LSTM model. In particular, a grid search-based k-fold cross-validation technique was applied to find the most suitable LSTM model parameters. Lastly, through the comparison of the f1-score values, our study showed that the LSTM model outperforms the gradient boosting model, a general machine learning model known to have relatively good prediction performance, for the time series classification of the cryptocurrency price trend. With the LSTM model, we got a performance improvement of about 7% compared to using the GB model.

• 대기
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• 제24권3호
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• pp.379-390
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• 2014

This study explores the long-term trends of surface air temperatures in 11 KMA stations over the period of 1960~2012. Both linear and nonlinear trends are examined for the $95^{th}$, $50^{th}$, and $5^{th}$ percentiles of daily maximum ($T_{max}$) and minimum temperatures ($T_{min}$) by using quantile regression method. It is found that in most stations linear trends of $T_{max}$ and $T_{min}$ are generally stronger in winter than in summer, and warming trend of the $5^{th}$ percentile temperature (cold extreme) is stronger than that of the $95^{th}$ percentile temperature (warm extreme) in both seasons. The nonlinear trends, which are evaluated by the second order polynomial fitting, show a strong nonlinearity in winter. Specifically, winter temperatures have increased until 2000s but slightly decreased afterward in all percentiles. This contrasts with the $95^{th}$ and $50^{th}$ percentiles of summer $T_{min}$ that show a decreasing trend until 1980s then an increasing trend. While this result is consistent with a seasonal dependence of the recent global warming hiatus, most of the nonlinear trends are statistically insignificant, making a quantitative attribution of nonlinear temperature trends challenging.

• 생태와환경
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• 제50권1호
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• pp.169-185
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• 2017

Physicochemical properties of water quality were analyzed to understand the long-term variations in Lake Youngrang from 1998 to 2015. Nonparametric statistical methods were applied to deduct correlation among water quality parameters and water quality trend. In total observations(N=64), the Secchi depth (SD) transparency showed significant positive correlation with salinity (r=0.458) and highly significant negative correlation with chlorophyll-a (r= -0.649) for p<0.0001 in two-tailed test of Spearman's rank correlation. Significant negative correlations of SD were observed with chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN). These correlation patterns were very similar in rainy (N=25) and non-rainy (N=39) periods too. Chlorophyll-a (Chl-a) had significant correlation with COD. Sen's slope test was performed along with Mann-Kendall trend test (significance ${\alpha}=0.05$, two-tailed) to find water quality trend. Positive trends were observed for SD and salinity with Sen's slopes 0.012 and 0.385, respectively (p<0.0001). Negative significant trends were observed for total nitrogen (TN) and Chl-a with Sen's slopes -0.02 (p<0.0001) and -0.346 (p=0.0010), respectively. Temperature, COD and phosphorus components had no trends. Carlson's trophic state index (TSI) for SD, TP and Chl-a were obtained in the ranges of 46~80, 37~82 and 39~82, respectively. Trophic index values suggest that Lake Youngrang was mesoeutrophic to eutrophic and there could be possibility of anoxia during the summer and dominance of blue-green algae. Excess nutrient inputs from external and internal sources were the causes of eutrophication in this lake. The findings of this study would be helpful to recognize water quality variables to manage the water body.

• 한국습지학회지
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• 제20권3호
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• pp.201-209
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• 2018

본 연구에서는 낙동강 주요 지류지천의 수질 모니터링 자료를 이용하여 수질지수를 산정하고 우선 관리가 필요한 지류지천을 파악하기 위해 장기 경향성 분석을 수행하였다. 환경부에서 시행하고 있는 실시간수질지수 방법을 적용하여 수질지수를 산정하고 모수 통계기법인 선형회귀와 비모수 통계기법인 Mann-Kendall Test와 Sen Slope Test를 적용하여 경향성을 분석하였다. 미전천2, 서교천2 지점을 제외한 주요 지류지천의 수질지수는 Fair 등급 이하의 범위에 있으며 북안천, 천내천, 호계천, 용덕천을 제외한 나머지 지점에 대해서는 유의성을 가진 경향이 나타나지 않았다. 따라서 본류에 대한 수질개선을 위해서는 지류에 대한 관리가 선행되어야 할 것으로 검토되었다.

• Membrane and Water Treatment
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• 제10권5호
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• pp.339-352
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• 2019

Long term water quality change was analyzed to evaluate the effect of the Total Maximum Daily Load (TMDL) policy. A trend analysis was performed for biochemical oxygen demand (BOD) and total phosphorus (TP) concentrations data monitored at the outlets of the total 41 TMDL unit watersheds of the Nakdong River in the Republic of Korea. Because water quality data do not usually follow a normal distribution, a nonparametric statistical trend analysis method was used. The monthly mean values of BOD and TP for the period between 2004 and 2015 were analyzed by the seasonal Mann-Kendall test and the locally weighted scatterplot smoother (LOWESS). The TMDL policy effect on the water quality change of each unit watershed was analyzed together with the results of the trend analysis. From the seasonal Mann-Kendall test results, it was found that for BOD, 7.8 % of the 41 points showed downward trends, 26.8 % and the rest 65.9% showed upward and no trends. For TP, 51.2% showed no trends and the rest 48.8% showed downward trends. From the LOWESS analysis results, TP began to decrease in most of the unit watersheds from mid-2010s when intensive chemical treatment processes were introduced to existing wastewater treatment plants. Overall, for BOD, relatively more points were improved in the main stream compared to the points of the tributaries although overall trends were mostly no trend or upward. For TP, about half of the points were improved and the rest showed no trends.

• 정보학연구
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• 제12권4호
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• pp.19-24
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• 2009

Recently, for the efforts of low-carbon deduction and to solve the problems of global warming, many industrial nations in world have been strengthening positively their competitive power into the research, development and industrialization of new renewable sources of energy and clean energy. In the most promising source of photovoltaic, it is essential that the government take an initiative role to develop and industrialize the materials, ingot or wafer, solar cell, power conditioning system and photovoltaic system, and need to establish both short-term and long-term technical development of goal setting and forward plan in the direction of the technical development strategy and forward industrialization for the strengthening of world market. This paper analyze new technology, policies and the market trend of photovoltaic field which are currently strategically and actively enhancing the research, development and practical-industralization by Korea and other nations.

• International Journal of Industrial Entomology and Biomaterials
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• 제9권1호
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• pp.79-87
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• 2004

The silkworm rearing and growth parameters of 63 multivoltine silkworm accessions under extended period of egg preservation at 5$^{\circ}C$ from 30 days to 45 days were studied. The results indicate that, nine accessions did not respond to extended period of egg preservation at low temperature and the remaining 54 accessions responded to the treatment and three rearings were conducted for comparision with the control; to estimate the effect of prolonged egg preservation at low temperature. The non-parametric tests statistics (Wilcoxon tests) was adopted for comparing the mean performance of treated batches (45 days) over the control (30 days). Highly significant variability was found among the accessions for all the parameters under study. The genetically controlled morphological characters were not altered in the treated batches, which were found to be on par with that of control. However, the total larval duration varied significantly over the control in 51 accessions. Similarly, the fifth age larval duration of 27 accessions showed decreasing trend compared to control. Altogether 41 accessions were found to be tolerant to long-term cold preservation upto 45 days, without showing any significant variation for morphological as well as essential quantitative traits. These accessions may be recommended for long-term egg preservation schedule up to 45 days, which will reduce the cost of conservation of these silkworm germplasm.

• 한국도로학회논문집
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• 제7권2호
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• pp.77-86
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• 2005

국내 고속도로 장기공용성 조사구간의 파손자료와 기후자료 및 포장물성 자료를 이용하여 줄눈 콘크리트 포장의 스폴링 모형이 개발되었다. 줄눈 콘크리트 포장 장기공용성 조사구간 22개소의 스폴링 파손 상태가 1999년과 2004년에 각각 조사되어 총44개의 스폴링 파손 자료가 수집되었으며 각 위치에서의 기후자료 및 포장의 형태 및 물성 자료 또한 수집되었다. 수집된 자료들의 민감도 분석을 통하여 스폴링 발생에 영향이 큰 인자들을 찾아내었으며, 그 인자들을 다중 회귀분석하여 스폴링 파손 모형이 개발되었다. 개발된 스폴링 모형은 외국의 모형과 비교할 때 합리적인 스폴링 발생 추이를 보였다.