• Journal of health informatics and statistics
• /
• v.41 no.3
• /
• pp.318-323
• /
• 2016

Objectives: Except the known risk factors for stroke, few studies have identified novel metabolic markers that could effectively detect stroke at an early stage. In this study, we explored the dose-response relationship between serum metabolites and the incidence of stroke. Methods: We studied 213 adults in the Korean Cancer Prevention Study-II (KCPS-II) biobank and estimated dose-response relationship between serum metabolites and stroke (42 cases and 171 controls). Three serum metabolites (Acetylcholine, HexadecylAcetylGlycerol, and 1-acetyl-2-formyl-sn-glycero-3-phosphocholine) were used in this study. The analysis included (1) exploratory nonlinear analysis, (2) estimation of flexion points and slopes at below and above the points. In the model to estimate risk of incidence of stroke, we controlled for conventional risk factors such as age, sex, systolic blood pressure, type 2 diabetes, triglyceride, and smoking status. Results: The relationship between incidence of stroke and log-transformed 1-acetyl-2-formyl-sn-glycero-3-phosphocholine was non-linear with flexion point around intensity score of 8.8, whereas other metabolites, log-transformed Acetylcholine and HexadecylAcetylGlycerol, showed negative linear patterns. Conclusions: The study suggests that metabolic markers are associated with incidence of stroke, particularly, at or above the flexion point. The study result may contribute to developing a novel system for precise stroke prediction.

• Korean Journal of Remote Sensing
• /
• v.23 no.5
• /
• pp.455-464
• /
• 2007

Lee(2007) suggested the Point-Jacobian iteration MAP estimation(PJIMAP) for noise removal of the images that are corrupted by multiplicative speckle noise. It is to find a MAP estimation of noisy-free imagery based on a Bayesian model using the lognormal distribution for image intensity and an MRF for image texture. When the image intensity is logarithmically transformed, the speckle noise is approximately Gaussian additive noise, and it tends to a normal probability much faster than the intensity distribution. The MRF is incorporated into digital image analysis by viewing pixel types as states of molecules in a lattice-like physical system. In this study, the MAP estimation is computed by the Point-Jacobian iteration using adaptive parameters. At each iteration, the parameters related to the Bayesian model are adaptively estimated using the updated information. The results of the proposed scheme were compared to them of PJIMAP with SAR simulation data generated by the Monte Carlo method. The experiments demonstrated an improvement in relaxing speckle noise and estimating noise-free intensity by using the adaptive parameters for the Ponit-Jacobian iteration.

• Korean Journal of Environment and Ecology
• /
• v.33 no.5
• /
• pp.605-619
• /
• 2019

The objective of this study was to analyze eutrophication characteristics, empirical model analysis, and variation of water quality according to monsoon intensity in Hapcheon Reservoir for 16 years from 2002 to 2017. Long-term annual water quality analysis showed that Hapcheon Reservoir was in a meso-nutrition to eutrophic condition, and the eutrophic state intensified after the summer monsoon. Annual rainfall volume (high vs. low rainfall) and the seasonal intensity in each year were the key factors that regulate the long-term water quality variation provided that there is no significant change of the point- and non-point source in the watershed. Dry years and wet years showed significant differences in the concentrations of TP, TN, BOD, and conductivity, indicating that precipitation had the most direct influence on nutrients and organic matter dynamics. Nutrient indicators (TP, TN), organic pollution indicators (BOD, COD), total suspended solids, and chlorophyll-a (Chl-a), which was an estimator of primary productivity, had significant positive relations (p<0.05) with precipitation. The Chl-a concentration, which is an indicator of green algae, was highly correlated with TP, TN, and BOD, which differed from other lakes that showed the lower Chl-a concentration when nutrients increased excessively. Empirical model analysis of log-transformed TN, TP, and Chl-a indicated that the Chl-a concentration was linearly regulated by phosphorus concentration, but not by nitrogen concentration. Spatial regression analysis of the riverine, transition, and lacustrine zones of $log_{10}TN$, $log_{10}TP$, and $log_{10}CHL$ showed that TN and Chl-a had significant relations (p<0.005) while TN and Chl-a had p > 0.05, indicating that phosphorus had a key role in the algal growth. Moreover, the higher correlation of both $log_{10}TP$ and $log_{10}TN$ to $log_{10}CHL$ in the riverine zone than the lacustrine zone indicated that there was little impact of inorganic suspended solids on the light limitation in the riverine zone.

• Environmental Mutagens and Carcinogens
• /
• v.22 no.4
• /
• pp.303-311
• /
• 2002

This study evaluated the concentrations of urinary metabolites of polycyclic aromatic hydrocarbons (PAHs) in industrial waste incineration workers. The effect of genetic polymorphisms of xenobiotic metabolism enzymes on urinary concentration of PAH metabolites was assessed. And, aromatic DNA adduct levels were also determined in total white blood cells. Fifty employees were recruited from a company handling industrial wastes located in Ansan, Korea: non-exposed group (n=21), exposed group (n=29). Sixteen ambient PAHs were determined by GC/MSD (NIOSH method) from personal breathing zone samples of nine subjects near incinerators. Urinary 1-hydroxypyrene glucuronide (1-OHPG), a major pyrene metabolite, was assayed by synchronous fluorescence spectroscopy after immunoaffinity purification using monoclonal antibody 8E11 (SFS/IAC). Multiplex PCR was used for genotyping for GSTMI/TI and PCR-RFLP for genotyping of CYP1A1 (MspI and Ile/Val). PAH-DNA adducts in peripheral blood WBC were measured by the nuclease P1-enhanced postlabeling assay. Smoking habit, demographic and occupational information were collected by self-administered questionnaire. The range of total ambient PAH levels were 0.00-7.00 mg/㎥ (mean 3.31). Urinary 1-OHPG levels were significantly higher in workers handling industrial wastes than in those with presumed lower exposure to PAHs (p=0.006, by Kruskal-Wallis test). There was a statistically significant dose-response increase in 1-OHPG levels with the number of cigarettes consumed per day (Pearson correlation coefficient=0.686, p<0.001). Urinary 1-OHPG levels in occupationally exposed smoking workers were highest compared with non-occupationally exposed smokers (p=0.053, by Kruskal-Wallis test). Smoking and GSTMI genotype were significant predictors for log-transformed 1-OHPG by multiple regression analysis (overall model R²=0.565, p<0.001), whereas smoking was the only significant predictor for log-transformed aromatic DNA adducts (overall model R²=0.249, p=0.201). Aromatic DNA adducts was also a significantly correlation between log transferred urinary 1-OHPG levels (pearson's correlation coefficient=0.307, p=0.04). However, the partial correlation coefficient adjusting for Age, Sex, and cigarette consumption was not significant (r=0.154, p=0.169). The significant association exists only in individuals with the GSTMI null genotype (pearsons correlation coefficient=0.516, p=0.010; partial correlation coefficient adjusting for age, sex, and cigarette consumption, r=0.363, p=0.038). Our results suggest that the significant increase in urinary 1-OHPG in the exposed workers is due to higher prevalence of smokers among them, and that the association between urinary PAH metabolites and aromatic DNA adducts in workers of industrial waste handling may be modulated by GSTMI genotype. There results remain to be confirmed in future larger studies.

• Journal of the Korean Institute of Intelligent Systems
• /
• v.17 no.4
• /
• pp.435-442
• /
• 2007

To reduce damage from high concentration ozone in the air, we have researched how to predict high concentration ozone before it occurs. High concentration ozone is a rare event and its reaction mechanism has nonlinearities and complexities. In this paper, we have tried to apply and consider as many methods as we could. We clustered the data using the fuzzy c-mean method and took a rejection sampling to fill in the missing and abnormal data. Next, correlations of the input component and output ozone concentration were calculated to transform more correlated components by modified log transformation. Then, we made the prediction models using Dynamic Polynomial Neural Networks. To select the optimal model, we adopted a minimum bias criterion. Finally, to evaluate suggested models, we compared the two models. One model was trained and tested by the transformed data and the other was not. We concluded that the modified transformation effected good to ideal performance In some evaluations. In particular, the data were related to seasonal characteristics or its variation trends.

• The Korean Journal of Applied Statistics
• /
• v.15 no.2
• /
• pp.281-296
• /
• 2002

On the new medical system separating the prescription and dispensing of the drug, the qualification of pharmacist in substitution of prescribed medicine was restricted, except bioequivalence-certified drugs. Also, Korean Food and Drug Association(KFDA) revised the bioequivalence regulation on August, 2001 Among many changes from old guideline, impressive one is the statistical consideration. Specially, to estimate and analyze bioequivalence measures, AUC and $C_{max}$, the log-transformed model is recommended and the equivalence interval is modified from $\pm$20 rule to [In(0.8),In(1.25)] one. This meaningful act is very hope-for because it is statistically reasonable and is agreed with worldwide bioequivalence guideline, including USA, EU, Japan and Canada. In this paper, we introduce the new regulation of assessing bioequivalence, announced at August, 2001, mainly on statistical view points. Key points for the new regulation are discussed and the minimum sample size based on simulation studies are proposed.

• The Journal of the Korean life insurance medical association
• /
• v.3 no.1
• /
• pp.103-141
• /
• 1986

The present study was undertaken to establish the decision standard of builds for the insured by using the ratio of weight-for-height as build index. Materials being examined were the ratio of weight-for-height being calculated from the actually measured heights and weights of a total of 15,838 insured persons who were examined medically at Honam Medical Department of Dong Bang Life Insurance Company, Ltd. from June, 1979 to September, 1985. The ratio of weight-for-height is calculated by the following formula. The ratio of weight-for-height(%)=$\frac{weight(kg){\times}100}{\{height(cm)-100\}{\times}0.9(kg)$ The results were as follows: 1. The distribution of the ratio of weight. for-height of the 15,838 insureds follows Log normal distribution being skewed to the left(the direction of underweight). 2. The ratio of weight-for-height were Log transformed to lead to a sym metrical pattern of distribution in which statistical rules are known to be applied more exactly. Thereafter, the establishment of dicision standard of builds was undertaken by using the log of the ratio of weight-for-height as build index. Through all ages in male, the ratio of weight-for-height indicating the range of standard lives including slight overweighted and underweighted lives besides normal lives is 80-130%, and corresponds to $"M-2{\delta}"-"M+1.5{\delta}"$ and to $M{\pm}20%$ ; in female, 85-135%, and corresponds to $"M-2{\delta}"-"M+1.5{\delta}"$ and to $M{\pm}20%$. Through all ages in male, the ratio of weight-for-height indicating the initial level of super-overweighted and super-underweighted lives is 130-150% and 75-80%,and corresponds to $M+3{\delta}\;and\;M-3{\delta}$ and to M+40% and M-25% respectively;in female, 140-160% and 75-80%, and corresponds to $M+3{\delta}\;and\;M-3{\delta}$ and to M+40%-+50% and M-25% respectively. 3. Author's rating table model for builds(a table of weight per height) is proposed. On the table, the ratings for builds, i. e. standard, super-weighted and super-underweighted lives, are listed.

• Journal of the Korean Statistical Society
• /
• v.28 no.4
• /
• pp.415-433
• /
• 1999

This paper considers the design of step-stress accelerated life tests for the Weibull distribution with a nonconstant shape parameter under Type I censoring. It is assumed that scale and shape parameters are log-linear functions of (possibly transformed) stress and that a cumulative exposure model holds for the effect of changing stress. The asymptotic variance of the maximum likelihood estimator of a stated quantile at design stress is used as an optimality criterion. The optimum three step-stress plans are presented for selected values of design parameters and the effects of errors in pre- estimates of the design parameters are investigated.

• Journal of the Korean Data and Information Science Society
• /
• v.21 no.4
• /
• pp.813-818
• /
• 2010

The least squares estimation method for model parameters under failure step-stress accelerated life tests is studied and a numerical example will be given to illustrate the proposed inferential procedures under the compound linear plans proposed as an alternative to the optimal quadratic plan, assuming that the exponential distribution with a quadratic relationship between stress and log-mean lifetime. The proposed compound linear plan for constant stress accelerated life tests and 4:2:1 plan are compared for various situations. Even though the compound linear plan was proposed under constant stress accelerated life tests, we found that this plan did well relatively in failure step-stress accelerated life tests.

• The Korean Journal of Ecology
• /
• v.26 no.4
• /
• pp.199-202
• /
• 2003

According to the energy hypothesis, the energy input per unit area primarily determines species richness in regions of roughly equal area. Some energy-related ecological research included identification of major climatic variables to determine regional species richness. In this study, the local butterfly species richness was examined to find out whether weather variables affected the local distribution or abundance of butterfly populations. Butterfly monitoring data from May 2001 to April 2002 taken at Mt. Yudal, Mokpo, in the southwestern part of Korea, and six weather variables (monthly mean values of temperature, precipitation, evaporation, wind speed, air pressure, and sunlight) were analyzed. Multiple regression analysis showed that only temperature explained 80% and 70% of the variability of log-transformed number of species and individuals, respectively, indicating that temperature played an important role in local species richness. Furthermore, global warming could affect the abundance and distribution of butterflies regionally as well as locally.