• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3637-3641
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• 2014

In this study, we analyzed the toxicity of mixtures of dimethylformamide (DMF) and methyl ethyl ketone (MEK) or DMF and toluene (TOL) and predicted their toxicity using quantitative structure-activity relationships (QSAR). A QSAR model for single substances and mixtures was analyzed using multiple linear regression (MLR) by taking into account the statistical parameters between the observed and predicted $EC_{50}$. After preprocessing, the best subsets of descriptors in the learning methods were determined using a 5-fold cross-validation method. Significant differences in physico-chemical properties such as boiling point (BP), specific gravity (SG), Reid vapor pressure (rVP), flash point (FP), low explosion limit (LEL), and octanol/water partition coefficient (Pow) were observed between the single substances and the mixtures. The $EC_{50}$ of the mixture of DMF and TOL was significantly lower than that of DMF. The mixture toxicity was directly related to the mixing ratio of TOL and MEK (MLR $EC_{50}$ equation = $1.76997-1.12249{\times}TOL+1.21045{\times}MEK$), as well as to SG, VP, and LEL (MLR equation $EC_{50}=15.44388-19.84549{\times}SG+0.05091{\times}VP+1.85846{\times}LEL$). These results show that QSAR-based models can be used to quantitatively predict the toxicity of mixtures used in manufacturing industries.

• Journal of the Korean Solar Energy Society
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• v.34 no.4
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• pp.9-16
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• 2014

A proton exchange membrane is a core component in the proton exchange membrane fuel cell because the role of proton exchange membrane(PEM)is supplying proton conductivity to fuel cell, a gas separator, and insulating between an anode and cathode. Among various role of PEM, supplying proton conductivity is the most important and the proton conductivity is strongly related the structural evolution of PEM by hydration. Thus a lot of studies have done by past few decade based on small angle X-ray scattering and wide angle X-ray scattering for understanding morphological structure of the PEM. Resulting from these studies, several morphological models of hydrated PEM are proposed. Current sensing atomic force microscopy (CSAFM) can map morphology and conductance on the membrane simultaneously. It can be the best tool for studying heterogenous structured materials such as PEM. In this study, the hydration of the membrane is examined by using CSAFM. Conductance and morphological images are simultaneously mapped under different relative humidity. The conductance images, which are mapped from different relative humidity, are analyzed by statistical methode for understanding ionic channel variation in PEM.

• Korean Journal of Plant Resources
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• v.18 no.3
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• pp.367-373
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• 2005

The purposes of this dissertation were to examine relativity between growth characteristics factors and develop the model of growth characteristics. In the result of statistical summaries of the factors in growth characteristic, the highest level of correlation was in plant height, plant width, petiole and chlorophyll in the case of Artemisia iwayomogi; leaf length, in the case of A. stolonifera;, leaf width, of A. princeps var. orientalis;, diameter, of A. feddei;, leaf thickness, of A. iwayomogi, A. princeps var. orientalis, A. montana, A. stolonifera, A. sylnatica; leaf length and leaf width of the other species. In the case of correlation analysis, leaf width and diameter were most correlative in A. capillaris;, plant height and plant width, in A. montana; plant height and leaf width, in A. stolonifera; leaf length and leaf width, in other species. The results of model analysis of growth characteristics were as follows. A. capillaris proved to be about $79.4\%$ effective ; A. princeps var. orientalis, about $91.7\%$ ; A. montana, about $70.3\%$ ; A. iwayomogi, about $49.0\%$ ; A. stolonifera, about $72.5\%$; A. sylnatica, about $75.0\%$;, A. feddei about $60.4\%$ ; A. rubripes about $54.0\%$.

• Journal of Korean society of Dental Hygiene
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• v.17 no.1
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• pp.145-153
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• 2017

Objectives: This paper aimed to contribute to better oral disease prevention and practice of health behavior for immigrant women in multi-cultural families, to define missing and filled permanent teeth index of immigrant women, data from the 6th Korea National Health and Nutrition Examination Survey from the Korea Centers for Disease Control and Prevention was used. Methods: For the immigrant women to be subjects, they needed to be born overseas, had acquired Korean citizenship as a married immigrant women, and the estimate of the number of subjects was 133,093 women. For analyzing data, SPSS 21statistical program was used. We used covariance analysis (ANCOVA) andgeneral linear models for finding the relation with the missing and filled permanent teeth index. The significance level was 0.05. Results: DMFT-index of immigrant women was 7.33 points. $R^2$ was 0.416; and increased with age, and $R^2$ was 0.126 points higher (p<0.01). In household income, 'lower' was 5.933 points lower than 'upper' (p<0.05), and in toothbrushing after lunch, 'yes' was 3.598 points lower than 'no' (p<0.01). In preventive treatment, 'yes' was 4.301 points lower than 'no' (p<0.05). Conclusions: The result of this paper is as follows: for maintaining oral health of immigrant women, we think that the government needs to develop an oral health policy and a customized education system suited to immigrant women for preventive management of dental disease in immigrant women. In addition, basic data will be provided for public dental health programs based on the result of the study.

• Journal of Internet Computing and Services
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• v.15 no.6
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• pp.117-124
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• 2014

Cluttered background is a major obstacle in developing salient object detection and tracking system for mobile device captured natural scene video frames. In this paper we propose a context aware feature vector selection model to provide an efficient noise filtering by machine learning based classifiers. Since the context awareness for feature selection is achieved by searching nearest neighborhoods, known as NP hard problem, we apply a fast approximation method with complexity analysis in details. Separability enhancement in feature vector space by adding the context aware feature subsets is studied rigorously using principal component analysis (PCA). Overall performance enhancement is quantified by the statistical measures in terms of the various machine learning models including MLP, SVM, Naïve Bayesian, CART. Summary of computational costs and performance enhancement is also presented.

• Archives of Plastic Surgery
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• v.40 no.6
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• pp.687-696
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• 2013

Background Ischemic preconditioning has been shown to improve the outcomes of hypoxic tolerance of the heart, brain, lung, liver, jejunum, skin, and muscle tissues. However, to date, no report of ischemic preconditioning on vascularized bone grafts has been published. Methods Sixteen rabbits were divided into four groups with ischemic times of 2, 6, 14, and 18 hours. Half of the rabbits in each group underwent ischemic preconditioning. The osteomyocutaneous flaps consisted of the tibia bone, from which the overlying muscle and skin were raised. The technique of ischemic preconditioning involved applying a vascular clamp to the pedicle for 3 cycles of 10 minutes each. The rabbits then underwent serial plain radiography and computed tomography imaging on the first, second, fourth, and sixth postoperative weeks. Following this, all of the rabbits were sacrificed and histological examinations were performed. Results The results showed that for clinical analysis of the skin flaps and bone grafts, the preconditioned groups showed better survivability. In the plain radiographs, except for two non-preconditioned rabbits with intraoperative ischemic times of 6 hours, all began to show early callus formation at the fourth week. The computed tomography findings showed more callus formation in the preconditioned groups for all of the ischemic times except for the 18- hour group. The histological findings correlated with the radiological findings. There was no statistical significance in the difference between the two groups. Conclusions In conclusion, ischemic preconditioning improved the survivability of skin flaps and increased callus formation during the healing process of vascularized bone grafts.

• Journal of Korean Society of Transportation
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• v.22 no.3 s.74
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• pp.27-39
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• 2004

The previous studies on analyzing the effects of traffic safety policies are very limited. Implementing traffic safety policies in view of their own urban traffic characteristics would be fairly desirable to handle properly the traffic safety problems. The relationships between traffic accidents and traffic safety policies have been researched by classifying the eighty one cities in Korea into four groups in terms of the size of the city population. Statistical analysis have been conducted for traffic accidents data and traffic safety policies, respectively. In order to mearsure the effectiveness of the traffic policies in the real world, regression models have been developed by handling the accident data and policy data. As a result of analysing the data, the traffic policies have showed different effects according to the size of the cities. While budget investment policies had provided enormous influences to reduce traffic accidents in the big cities more than a half million polulation, traffic enforcement and traffic education have been so efficient to control traffic accident problems in the smaller cities less than a half million poluation.

• Journal of Korean Society of Transportation
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• v.33 no.1
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• pp.81-89
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• 2015

Crashes that occur at tollgates have different characteristics compared to those of the mainline on expressways in terms of crash cause, crash type, and vehicle type. Due to this fact, the safety performance function (SPF) focused on the expressway tollgates, apart from the mainline, should be developed. The aim of this study is, therefore, to identify the influential factors and develope a SPF for crashes at tollgates. Firstly, we established independent variables affecting crashes at tollgates through literature review and descriptive statistical analysis. Based on these variables, two negative binomial regression models with different form of independent variables were developed and goodness-of-fits of each model were compared. According to the results, the number of crashes increases i) as AADT, Hi-pass rate, and heavy vehicle rate increase, ii) as average lane width decreases, iii) on the mainline tollgate type. The safety performance function developed in this study could be applied to select hot-spots for expressway tollgates.

• Journal of Korean Society on Water Environment
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• v.21 no.6
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• pp.584-594
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• 2005

The spatio-temporal abundance pattern of algae in Lake Paldang from 2002 to 2004 was investigated. The concentration of chlorophyll a representing algal biomass had fluctuated intensively throughout the year. Among three years, the highest algal biomass was shown in 2002, and typical growth peak of concentration of chlorophyll a was occurred in spring and autumn. There had been frequent rainfall in spring drought period in 2003 and it resulted in the decrease of the algal biomass. The distribution pattern of four algal groups on the surface water of Lake Paldang showed different abundance by season and by water area. In particular, different algal growth characteristics by water areas were observed. Influences of various environmental parameters on algal abundance in four water areas of Lake Paldang were analyzed statistically. From the results of Peason correlation analysis, it was understood that the kinds and affects of environmental parameters were different according to water areas and seasons. Based on the factors analysis of environmental parameters on the concentration of chlorophyll a, stepwise regression models whose independent variables were the factors produced by factor analysis and dependent variable was the concentration of chlorophyll a were derived by water areas and seasons. As a whole, factors related with organics and photosynthesis were revealed to have high affects to algal abundance, whereas limiting nutrients such as phosphorus and nitrogen showed little affect in Lake Paldang.

• The Korean Journal of Applied Statistics
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• v.18 no.3
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• pp.639-654
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• 2005

The Lee and Carter method has widely used to forecast mortality because of the simple structure of model and the stable forecasting. The Lee and Carter method, however, also has limitations. The assumption of the rate of decline in mortality at each age remaining invariant over time has been violated in several decades. And, there is no way to include covariates in the model for better forecasts. Here we introduce Park, Choi and Kim method to make up for Lee and Carter's weak points by using two random processes. We discuss structural features of two methods. furthermore, for each method, we forecast life expectancy for 2005 to 2050 using South Korea data and compare the results.