• Journal of Korean Society of Transportation
• /
• v.32 no.2
• /
• pp.83-92
• /
• 2014

Weather condition is one of the crucial factors affecting travelers' mode choice. Nevertheless, there are numerous indefinite traffic phenomena under various weather conditions. This study was conducted to verify the hypothesis that transit riderships decrease as precipitation increases. To clarify the relationship between precipitation and transit ridership, a seemingly unrelated regression model was employed with data such as daily precipitation and daily transit riderships of 3 transit modes (bus, metro, and shuttle bus) collected in Busan for recent 24 months. The estimation results show that transit riderships decreased as the daily precipitation increased when the daily precipitation is greater or equal to 10mm/day (0.169%, 0.101%, and 0.172% reduction in bus, metro, and shuttle bus riderships, respectively, when the daily precipitation increased by 1mm). When comparing the impact of precipitation on transit riderships by modes using a cross-equation parameter restriction test, the decrease in metro ridership is relatively insensitive to the change in precipitation. However, the negative coefficient of precipitation in the metro ridership estimation model indicates that the transit users in Busan may alter their mode to taxi or automobile and/or may give up the trip itself in bad weather condition.

• Environmental Analysis Health and Toxicology
• /
• v.20 no.4 s.51
• /
• pp.311-325
• /
• 2005

A chemical ranking and scoring system, CRS - Korea, has recently been developed and proposed to use to prioritize on a screening level the toxic chemicals for monitoring and risk assessment. As CRS-Korea requires rigorous assessments prior to its wide application, an assessment was conducted in this study by examining the contribution of individual parameter score to the final chemical score or ranking. The sensitivity of the system to the default values for various parameters of missing data was also tested. The chemical ranking/score was round to depend primarily on the score of a single parameter, i. e., the chemical release, while toxicity scores show little correlation with the priority Further analysis indicated that the dominating effect of the chemical release results from i) its multiplicative relationship with the other two exposure parameters (biodegradation and persistent) and ii) the fact that a maximum score of 10 was assigned to the chemical release parameter while 5 was assigned for all others. AE the fraction of the data that are missing exceeded $70\%$ for various toxicity parameters at compared to less than $10\%$ for exposure parameters, the sensitivity of the ranking to the default value was not significant (rank correlation coefficient = 0.98) for toxicity parameters. Bated on this assessment, an improved CRS system (CRS - Korea II) was proposed in which the impact of the chemical release was properly adjusted by changing the multiplicative relationship to additive one and the maximum score to 5. Chemical priority was derived for each of 16 provinces by using CRS-Korea II. The chemical priority was found to significantly vary among the provinces. It was concluded that not only the national chemical priority but the local chemical priority should be taken into account in setting the nationwide chemical monitoring and risk assessment strategy.

• The Journal of Engineering Geology
• /
• v.20 no.4
• /
• pp.401-407
• /
• 2010

This study was carried out to produce the characteristics of pollutant loads caused by a cherry tree plot as a nonpoint sources(NPS) unit in agricultural areas. The relationship between rainfall and runoff didn't show a good coefficient with 0.5. Despite precipitation amount was less than 20 mm, runoff occurred with $0.5\;m^3$ because of high rainfall intensity of 8.8 mm/hr. In contrast, runoff was not occurred when precipitation amount was 47.4 mm in one case. In that case the primal effect on runoff was not precipitation amount. Correlation between load of pollutants such as BOD, COD, TN and TP and runoff' volumes showed significantly positive values which were more than r = 0.92 for all pollutants except SS(r = 0.71). SS could be a proper factor for estimating pollutant loads of BOD, COD, TN and TP because of a high correlation more than r = 0.73 between SS load and pollutant loads of BOD, COD, TN and TP. Both Organics and nutrient pollutants could be reduced if we control SS in runoff. The highest concentration of TN was detected in the event which was affected by fertilization activities directly. Therefore fertilization must be considered as a function of impact parameters on TN load in agricultural areas.

• Wind and Structures
• /
• v.23 no.6
• /
• pp.559-575
• /
• 2016

In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

• Environmental Analysis Health and Toxicology
• /
• v.30
• /
• pp.11.1-11.19
• /
• 2015

Objectives The objective of this study was to conduct a systematic review to provide summarized evidence on the association between maternal exposure to particulate air pollution and birth weight (BW) and preterm birth (PTB) after taking into consideration the potential confounding effect of maternal smoking. Methods We systematically searched all published cohort and case-control studies examining BW and PTB association with particulate matter (PM, less than or equal to $2.5{\mu}m$ and $10.0{\mu}m$ in diameter, $PM_{2.5}$ and $PM_{10}$, respectively) from PubMed and Web of Science, from January 1980 to April 2015. We extracted coefficients for continuous BW and odds ratio (OR) for PTB from each individual study, and meta-analysis was used to combine the coefficient and OR of individual studies. The methodological quality of individual study was assessed using a standard protocol proposed by Downs and Black. Forty-four studies met the inclusion criteria. Results In random effects meta-analyses, BW as a continuous outcome was negatively associated with $10{\mu}g/m^3$ increase in $PM_{10}$ (-10.31 g; 95% confidence interval [CI], -13.57 to -3.13 g; I-squared=0%, p=0.947) and $PM_{2.5}$ (-22.17 g; 95% CI, -37.93 to -6.41 g; Isquared=92.3%, p<0.001) exposure during entire pregnancy, adjusted for maternal smoking. A significantly increased risk of PTB per $10{\mu}g/m^3$ increase in $PM_{10}$ (OR, 1.23; 95% CI, 1.04 to 1.41; I-squared=0%, p=0.977) and $PM_{2.5}$ (OR, 1.14; 95% CI, 1.06 to 1.22; I-squared=92.5%, p<0.001) exposure during entire pregnancy was observed. Effect size of change in BW per $10{\mu}g/m^3$ increase in PM tended to report stronger associations after adjustment for maternal smoking. Conclusions While this systematic review supports an adverse impact of maternal exposure to particulate air pollution on birth outcomes, variation in effects by exposure period and sources of heterogeneity between studies should be further explored.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.9
• /
• pp.907-912
• /
• 2008

In order to reduce the availability of dissolved inorganic phosphorus in surface water, lakes, and estuaries, black shale and zero valent iron can be used as reacitve materials. Sorption of phosphate to sampled sediment, black shale, and zero valent iron was quantitatively evaluated in this research. Effect of coexistence of calcium was also tested, since coexisting ions can enhance the precipitation of phosphate. An empirical kinetic model with fast sorption(k$_t$), slow sorption(k$_s$), and precipitation(k$_p$) was well fitted to experiment data from this research. Langmuir and Freundlich sorption isotherms were also used to evaluated phosphate maximum sorption capacity. Calcium ions at 0, 1 and 5 mM affected the precipitation kinetic coefficient in empirical kinetic model but did not have impact on the maximum sorbed concentration.

• The Journal of the Korea Contents Association
• /
• v.16 no.6
• /
• pp.627-635
• /
• 2016

The purpose of this study was to investigate the communication skill of a dental hygienist for the elderly. The self-administered questionnaire selected by convenience sampling method from January 2 to February 14, 2015, Seoul, Kyungki, Incheon regions final analysis section 233 to target dental hygienist working under a dentist institutions. This study analyzed collected data by t-test, ANOVA, pearson correlation coefficient, and multiple regression. According to multiple regression analysis results can be number of worker, the main task, living experience feelings adjusted variable, as a result work in the dental hospital(B=.292 SE=.074), more like the elderly preference(B=.282, SE=.141), the behavior of the elderly(B=-.223, SE=.043) found that the more positive the impact. Therefore, the more exposure for your understanding and the elderly relationships for the the elderly appeared to affect the communication skill necessary to develop training programs that can improve the communication skill of a dental hygienist and apply to be prepared for the coming aging society.

• Journal of Distribution Science
• /
• v.17 no.2
• /
• pp.77-89
• /
• 2019

Purpose - This study presents the relationships between parent brand-self image congruence, parent brand -functional congruity, perceived fit between parent brand and extension product, and consumer's attitude toward extension product using the structural equation model. As for preceding concepts having a direct effect on consumer's attitude toward brand extension, the study focuses on parent brand-self image congruence and parent brand-functional congruity. It also looks at the effect of parent brand-self image congruence and parent brand-functional congruity on the consumer's attitude toward extension product and identifies if the perceived fit between parent brand and extension product is a concept playing a mediating role between parent brand-self image congruence or parent brand-functional congruity and consumer's attitude toward brand extension product. Research design, data, and Methodology - SPSS for Windows 18.0 and AMOS 18.0 were used for data analysis. Then, the Cronbach's α coefficient was obtained using SPSS for Windows 18.0 to measure reliability. In addition, the convergence and discriminative measures of the measured items were statistically verified using AMOS 18.0. Finally, we have validated a path model and a parameter model in which brand personality-self-matched attitude toward brand extension. Results - Studies have shown that the impact of parent brand-self image consistency and parent brand-functional consistency on the attitude of extended products was positive. Perceived fit between parent brand and extension products has been shown to play a role of intermediary between parent brand-self image congruence and consumer attitudes to extended products. However, perceived fit between parent brand and extension products did not play a role as intermediary between the parent brand-functional congruity and the attitude toward the extended product. Finally, in relation to the causal relationship between parent brand-congruity (self image/functionality) and attitudes to extended products. The effect of parent brand-functional coherency on attitudes toward extended products was found to be greater in groups with higher involvement than in those with lower involvement. Conclusions - Although few studies have been done on what variables mediated when parent brand-self image consistency and parent brand-functional coherency affect consumer attitude, this paper is significant in finding whether perceived fitness between the parent brand-congruity and the extension product is mediated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.9
• /
• pp.5585-5593
• /
• 2014

This study tested the hypothesis that the significance of the heterogeneous dispersion parameter in safety performance function (SPF) used to estimate the expected crashes is affected by the endogenous heterogeneous prior distributions, and analyzed the impacts of the mis-specified dispersion parameter on the evaluation results for traffic safety countermeasures. In particular, this study simulated the Poisson means based on the heterogeneous dispersion parameters and estimated the SPFs using both the negative binomial (NB) model and the heterogeneous negative binomial (HNB) model for analyzing the impacts of the model mis-specification on the mean and dispersion functions in SPF. In addition, this study analyzed the characteristics of errors in the crash reduction factors (CRFs) obtained when the two models are used to estimate the posterior means and variances, which are essentially estimated through the estimated hyper-parameters in the heterogeneous prior distributions. The simulation study results showed that a mis-estimation on the heterogeneous dispersion parameters through the NB model does not affect the coefficient of the mean functions, but the variances of the prior distribution are seriously mis-estimated when the NB model is used to develop SPFs without considering the heterogeneity in dispersion. Consequently, when the NB model is used erroneously to estimate the prior distributions with heterogeneous dispersion parameters, the mis-estimated posterior mean can produce large errors in CRFs up to 120%.

• Journal of Korean Society for Atmospheric Environment
• /
• v.33 no.5
• /
• pp.497-514
• /
• 2017

This study quantitatively analyzes the effects of emission inventory choices on the simulated particulate matter (PM) concentrations and the domestic/foreign contributions in the Seoul Metropolitan Area (SMA) with an air quality forecasting system. The forecasting system is composed of Weather Research and Forecasting (WRF)-Sparse Matrix Operator Kernel Emissions (SMOKE)-Community Multi-Scale Air Quality (CMAQ). Different domestic and foreign emission inventories were selectively adopted to set up four sets of emissions inputs for air quality simulations in this study. All modeling cases showed that model performance statistics satisfied the criteria levels (correlation coefficient >0.7, fractional error <50%) suggested by previous studies. Notwithstanding the apparently good model performance of total PM concentrations by all emission cases, annual average concentrations of simulated total PM concentrations varied up to $20{\mu}g/m^3$ (160%) depending on the combination of emission inventories. In detail, the difference in simulated annual average concentrations of the primary PM coarse (PMC) was up to $25.2{\mu}g/m^3$ (6.5 times) compared with other cases. Furthermore, model performance analyses on PM species showed that the difference in the simulated primary PMC led to gross model overestimation in general, which indicates that the primary PMC emissions need to be improved. The contribution analysis using model direct outputs indicated that the domestic contributions to the annual average PM concentrations in the SMA vary from 44% to 67%. To account for the uncertainty of the simulated concentration, the contribution correction factor method proposed by Bae et al. (2017) was applied, which resulted in converged contributions(from 48% to 57%). We believe this study shows that it is necessary to improve the simulated concentrations of PM components in order to enhance the accuracy of the forecasting model. It is deemed that these improvements will provide more accurate contribution results.