• The Korean Journal of Applied Statistics
• /
• v.34 no.3
• /
• pp.439-447
• /
• 2021

Due to the frequent emergence of global abnormal climates, related studies on meteorological change is being actively proceed. However, the research on trend analysis using weather data accumulated over a long period of time was insufficient. In this study, the trend of temperature time series data accumulated from automated surface observing system (ASOS) for 40 years was analyzed by using a non-parametric analysis method. As a result of the Mann-Kendall test on the annual average temperature and seasonal average temperature time series data in South Korea, it has shown that an upward trend exists. In addition, the result of calculating the Sen's slope, which can determine the degree of tendency before and after the searched change point by applying the Pettitt test, recent data after the fluctuation point confirmed that the tendency of temperature rise was even greater.

• Journal of Soil and Groundwater Environment
• /
• v.14 no.5
• /
• pp.41-50
• /
• 2009

Water levels in groundwater monitoring wells of Jeju Island were analyzed using parametric and non-parametric trend analyses. Number of used monitoring wells in the analysis are 94 among totally 106 monitoring wells and the monitoring period is greater than single year, from 2001 to 2009. For the trend analysis, both parametric (linear regression) and nonparametric (Mann-Kendall trend test and Sen's trend test) methods were adopted. Results of the linear regression analysis on daily basis indicated that about 58.5% of the monitoring wells showed a decreasing trend, and analysis using monthly median indicated that about 79.8% showed a decreasing trend. The Mann-Kendall trend test and Sen's trend test with monthly median values in confidence levels of 95% and 99% showed the same analysis results. In confidence level of 95%, 32% were decreased, 3% were increased and the remains showed no trend. However, in confidence level of 99%, 16% were decreased, 2% were increased and the remains showed no trend. The largest decline rates of water levels were detected mainly at the coast of the northwestern and southwestern parts, which is expected to closely related to the increased pumping in the urban area and tourist resort.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.1B
• /
• pp.65-77
• /
• 2008

The effects of climatic changes owing to urbanization, geographical and topographical conditions on annual and monthly FAO Penman-Monteith (FAO P-M) reference evapotranspiration, and energy and aerodynamic terms of FAO P-M reference evapotranspiration were studied. In this study, 21 climatological stations were selected. The statistical methods applied for trend analysis are Spearman rank test, Sen's test, linear regression analysis and analysis of actual variation ratio. Furthermore, the cluster analysis was applied to cluster 21 study stations by considering the geographical and topographical characteristics of study area. The study results indicate that urbanization affects the trend and amount of FAO P-M reference evapotranspiration, energy term and aerodynamic term; however, the result of Sen's test indicates that urbanization does not significantly affect the magnitude of trend (Sen's slope). The energy term increased at study stations located in coastal area; however, decreased at study stations located in inland area. The topographical slope of study area did not significantly influence on the trend of energy term. The aerodynamic term increased in both coastal area and inland area, indicating much significantly increasing trend in inland area, and it was also affected by the topographical slope of the study area.

• Environmental Engineering Research
• /
• v.21 no.1
• /
• pp.58-68
• /
• 2016

The study explored droughts using the Standardized Precipitation Index (SPI) in the northwestern region of Bangladesh, which is the drought prone area. In order to assess the trend and variability of monthly rainfall, as well as 3-month scale SPI, non-parametric Mann-Kendall (MK) tests and continuous wavelet transform were used respectively. The effect of climatic parameters on the drought in this region was also evaluated using SPI, with the Southern Oscilation Index (SOI) by means of the wavelet coherence technique, a relatively new and powerful tool for describing processes. The MK test showed no statistically significant monthly rainfall trends in the selected stations, whereas the seasonal MK test showed a declining rainfall trend in Bogra, Ishurdi, Rangpur and Sayedpur stations respectively. Sen's slope of six stations also provided a decreasing rainfall trend. The trend of the SPI, as well as Sen's slope indicated an increasing dryness trend in this area. Dominant periodicity of 3-month scale SPI at 8 to 16 months, 16 to 32 months, and 32 to 64 months were observed in the study area. The outcomes from this study contribute to hydrologists to establish strategies, priorities and proper use of water resources.

• Asian Pacific Journal of Cancer Prevention
• /
• v.14 no.8
• /
• pp.4759-4763
• /
• 2013

Background: Prognostic factors of postoperative early and late recurrence in patients with hepatocellular carcinoma (HCC) undergoing curative resection remain to be clarified. The aim of this study was to identify risk factors for postoperative early (${\leq}$ 2 year) and late (> 2 year) intrahepatic recurrences in patients with single HCCs without macrovascular invasion. Methods: A total of 280 patients from December 2004 to December 2007 were retrospectively included in this study. Intrahepatic recurrence was classified into early (${\leq}$ 2 year) and late (> 2 year) and the Chi-Square test or Fisher's exact test and multivariate logistic regression analysis were performed to determine significant risk factors. Results: During the follow-up, 124 patients had intrahepatic recurrence, early and late in 82 and 42 patients, respectively. Multivariate logistic regression analysis showed that microvascular invasion (p=0.006, HR: 2.397, 95% CI: 1.290-4.451) was the only independent risk factor for early recurrence, while being female (p = 0.031, HR: 0.326, 95% CI: 0.118-0.901), and having a high degree of cirrhosis (P=0.001, HR: 2.483, 95% CI: 1.417-4.349) were independent risk factors for late recurrence. Conclusions: Early and late recurrence of HCC is linked to different risk factors in patients with single HCC without macrovascular invasion. This results suggested different emphases of strategies for prevent of recurrence after curative resection, more active intervention including adjuvant therapy, anti-cirrhosis drugs and careful follow-up being necessary for patients with relevant risk factors.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2003.04a
• /
• pp.94-96
• /
• 2003

Since 1995, MOCT(Ministry of Construction and Transportation) and KOWACO(Korea Water Resources Corporation) have established the National Groundwater Monitoring Network in South Korea and also MOE(Ministry of Environment) has operated Groundwater Quality Monitoring network. Until 2001, 202 monitoring stations by MOCT and 780 monitoring wells by MOE have been constructed, measured groundwater level and analyzed water samples. Groundwater quality analysis has been conducted two times a year during last 6 years for all monitoring wells. The quality data has about 15 components including pH, COD, Count of Coliform group, and etc.. Trend analysis has been peformed for 6 components(Coliform, pH, COD, NO$_3$-N, Cl and EC) of water quality which are analyzed more than 7 times for total monitoring wells. Two test methods have been used ; Sen's test and Mann-Kendall test. These trend tests have been done at the 0.05 significance level. By the result of Sen's test, Count of Coliform group has either upward or downward trends at 4.3 percent of the monitoring points. pH does at 5.6 percent, COD does at 8.6 percent, Nitrate-Nitrogen does at 13.2 percent, Chloride does at 13.4 percent, and. EC does at 11.6 percent of the monitoring points. The exact causes of the groundwater quality trends are difficult to specify. Notable downward trends in nitrate at many monitoring points may be the result of reduction on some contamination sources. Potential causes include diminished agricultural areas, improvements in sewage treatment and a decrease in atmospheric deposition. Increase in chloride at many monitoring points may be the result of increased non-point source pollution such as road salting and runoff from sprawling paved developments and suburbs.

• Asian Pacific Journal of Cancer Prevention
• /
• v.14 no.3
• /
• pp.1787-1790
• /
• 2013

This study evaluated the effects of ZD1839, an orally active, selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor, on nasopharyngeal carcinoma (NPC) both in vitro and in vivo. Influence of ZD1839 alone or combined with cisplatin on the NPC cell line CNE2 was detected by MTT assay with flow cytometry assessment of cell cycle distribution and apoptosis rates. Nude mice NPC xenografts were also used to evaluate the effects of ZD1839 alone or combined with cisplatin. The Student's t test evaluated statistical significance. ZD1839 alone or combined with cisplatin inhibited CNE2 cell line proliferation. ZD1839 induced CNE2 cell cycle arrest in the G1 phase, and higher concentrations induced apoptosis. Xenograft tumors were significantly smaller when treated with 200 mg/kg ZD1839, cisplatin, or cisplatin combined with 100 mg/kg ZD1839 than untreated controls. ZD1839 (200 mg/kg) alone showed good tumor inhibition effects, reduction of tumor weights, and smaller tumor volume without loss of body weight. ZD1839 (200 mg/kg) might provide a good and effective therapeutic reagent for NPC.

• Korean Journal of Ecology and Environment
• /
• v.50 no.1
• /
• pp.169-185
• /
• 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.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.141-141
• /
• 2020

강원도는 산림 비중이 크고 급경사지가 많은 지형적 특성과 여름철 비교적 선선하고 강우량이 많은 기후적 특성 때문에 고랭지 농업이 활발히 이루어지고 있다. 하지만, 많은 부분을 차지하는 고랭지밭 면적 탓에 강우시에 토양침식과 비점오염물이 하천으로 유입되고 있다. 강원도 송천 상류에 위치한 도암호는 장기간 탁수를 저류하고 방류로 인한 해체 논란까지 일으키기도 했다. 이에 정부는 흙탕물 저감과 비점오염원 관리를 위한 국고보조사업과 다양한 환경 정책들을 시행중이다. 효율적이고 효과적인 수질 정책을 시행하고 분석하기 위해서는 장기간의 모니터링 자료를 이용한 통계적 분석을 활용하는 것이 중요하다. 수질 자료는 변동이 심하고, 비정규분포를 이루며 결측치와 검출한계 이하의 값들이 많아 비모수 통계 방법을 널리 사용되어 왔다. 그중에서도 계절적 특성을 갖는 수질자료의 장기경향분석에 적합한 Seasonal Mann-Kendall Test을 사용하여 남한강상류 유역의 수질 경향성을 분석하였으며, Sen's Slope를 구하여 수질 자료의 경향 크기를 구하였다. 하지만, Seasonal Mann-Kendall Test는 연구 기간동안의 경향성을 반영할 수 없다는 단점이 있기 때문에 LOWESS Test를 통해 장기간 수질 자료 사이의 경향성을 분석하였다. 이러한 수질자료의 경향 분석 결과는 유역 내 취약 지점을 확인할 수 있으며, 환경 정책의 효과를 평가하고 보완할 수 있는 자료로 이용될 수 있을 것이다.

• Journal of Korean Society on Water Environment
• /
• v.39 no.5
• /
• pp.377-389
• /
• 2023

Chungcheongnam-do has been measuring the flow rate and water quality of streams in the province once a month since 2011 in order to water environment policies. Based on the results, after evaluating the coefficient of variation and the tendency of the water quality trend by using the Mann-Kendall test and Sen's Slope for each stream, the streams subject to priority introduction of Total Pollution Load Management at Tributaries were selected through the Stream Grouping Method. The water quality trend analysis results for 125 streams using the Mann-Kendall test and Sen's Slope were evaluated as streams showing a tendency of deteriorating water quality Biochemical oxygen demand (BOD): 13 streams, Total Phosphorus (T-P): 16 streams). Streams with deteriorating water quality were classified into A-D groups using the Stream Grouping Method. Group A, which has a high flow rate and high water quality, is a stream that requires priority management, and was selected as a stream for introduction of Total Pollution Load Management at Tributaries. There are 7 streams that need to be introduced into the BOD category, and there are 7 streams that need to be introduced into the T-P category. In this study, based on flow and water quality monitoring data accumulated over a long period of time (2011-2022), statistical techniques are used to select watersheds in which water quality is deteriorating. Accordingly, it is expected that it will be useful in establishing a water quality improvement plan in the future.