• Safety and Health at Work
• /
• v.2 no.2
• /
• pp.169-175
• /
• 2011

Objectives: The questionnaire of occupational stress index (OSI) has been popular in the workplace, and it has been tailored for bus drivers in Taiwan. Nevertheless, its outcomes for participants are based on self-evaluations, thus validation by their physiological stress biomarker is warranted and this is the main goal of this study. Methods: A cross-sectional study of sixty-three city bus drivers and fifty-four supporting staffs for comparison was conducted. Questionnaire surveys, 24-hour urine cortisol testing, and blood draws for dehydroepiandrosterone-sulfate (DHEA-S) testing were performed. The measured concentrations of these biological measures were logarithmically transformed before the statistical analysis where various scores of stressor factors, moderators, and stress effects of each OSI domain were analyzed by applying multiple linear regression models. Results: For drivers, the elevated 24-hour urine cortisol level was associated with a worker's relationship with their supervisor and any life change events in the most recent 3 months. The DHEA-S level was higher in drivers of younger age as well as drivers with more concerns relating to their salary and bonuses. Non-drivers showed no association between any stressor or satisfaction and urine cortisol and blood DHEA-S levels. Conclusion: Measurements of biomarkers may offer additional stress evaluations with OSI questionnaires for bus drivers. Increased DHEA-S and cortisol levels may result from stressors like income security. Prevention efforts towards occupational stress and life events and health promotional efforts for aged driver were important anti-stress remedies.

• Journal of Korea Water Resources Association
• /
• v.35 no.3
• /
• pp.275-284
• /
• 2002

In this study, a method of random resampling of residuals from stochastic models such as the Monte-Carlo model, the lag-one autoregressive model(AR(1)) and the periodic lag-one autoregressive model(PAR(1)), has been adopted to generate a large number of long traces of annual and monthly steamflows. Main advantage of this resampling scheme called the Bootstrap method is that it does not rely on the assumption of population distribution. The Bootstrap is a method for estimating the statistical distribution by resampling the data. When the data are a random sample from a distribution, the Bootstrap method can be implemented (among other ways) by sampling the data randomly with replacement. This procedure has been applied to the Yongdam site to check the performance of Bootstrap method for the streamflow generation. and then the statistics between the historical and generated streamflows have been computed and compared. It has been shown that both the conventional and Bootstrap methods for the generation reproduce fairly well the mean, standard deviation, and serial correlation, but the Bootstrap technique reproduces the skewness better than the conventional ones. Thus, it has been noted that the Bootstrap method might be more appropriate for the preservation of skewness.

• Journal of Korean Neurosurgical Society
• /
• v.61 no.6
• /
• pp.689-699
• /
• 2018

Objective : The goal of this study was to compare several parameters, including wall shear stress (WSS) and flow pattern, between unruptured and ruptured anterior communicating artery (ACoA) aneurysms using patient-specific aneurysm geometry. Methods : In total, 18 unruptured and 24 ruptured aneurysms were analyzed using computational fluid dynamics (CFD) models. Minimal, average, and maximal wall shear stress were calculated based on CFD simulations. Aneurysm height, ostium diameter, aspect ratio, and area of aneurysm were measured. Aneurysms were classified according to flow complexity (simple or complex) and inflow jet (concentrated or diffused). Statistical analyses were performed to ascertain differences between the aneurysm groups. Results : Average wall shear stress of the ruptured group was greater than that of the unruptured group (9.42% for aneurysm and 10.38% for ostium). The average area of ruptured aneurysms was 31.22% larger than unruptured aneurysms. Simple flow was observed in 14 of 18 (78%) unruptured aneurysms, while all ruptured aneurysms had complex flow (p<0.001). Ruptured aneurysms were more likely to have a concentrated inflow jet (63%), while unruptured aneurysms predominantly had a diffused inflow jet (83%, p=0.004). Conclusion : Ruptured aneurysms tended to have a larger geometric size and greater WSS compared to unruptured aneurysms, but the difference was not statistically significant. Flow complexity and inflow jet were significantly different between unruptured and ruptured ACoA aneurysms.

• Nutrition Research and Practice
• /
• v.11 no.4
• /
• pp.334-339
• /
• 2017

BACKGROUND/OBJECTIVES: Telomere length is a useful biomarker for determining general aging status. Some studies have reported an association between alcohol consumption and telomere length in a general population; however, it is unclear whether the alcohol flush reaction, which is an alcohol-related trait predominantly due to acetaldehyde dehydrogenase deficiency, is associated with telomere length. This cross-sectional study aimed to evaluate the associations of alcohol consumption and alcohol flush reaction with leukocyte telomere length (LTL). SUBJECTS/METHODS: The study included 1,803 Korean adults. Participants provided blood specimens for LTL measurement assay and reported their alcohol drinking status and the presence of an alcohol flush reaction via a questionnaire-based interview. Relative LTL was determined by using a quantitative polymerase chain reaction. Statistical analysis used multiple linear regression models stratified by sex and age groups, and potential confounding factors were considered. RESULTS: Age-specific analyses showed that heavy alcohol consumption (> 30 g/day) was strongly associated with a reduced LTL in participants aged ${\geq}65years$ (P < 0.001) but not in younger participants. Similarly, the alcohol flush reaction was associated with a reduced LTL only in older participants who consumed > 15 g/day of alcohol (P < 0.01). No significant alcohol consumption or alcohol flush reaction associations with LTL were observed in the sex-specific analyses. CONCLUSIONS: The results suggest that older alcohol drinkers, particularly those with the alcohol flush reaction, may have an accelerated aging process.

• The KIPS Transactions:PartD
• /
• v.17D no.6
• /
• pp.471-480
• /
• 2010

The purpose of this study is to explore determinants which affect the significant increase in the user acceptance of smart phone. This study also analyzes the effect of each variable on the actual acceptance by empirical methods. In this study, first, the system quality and the service quality are defined as independent variables based on developed IS success model of DeLone & McLean(2003). Second, we proposed the research model by providing trust and perceptual immersion as intermediate variables, and user satisfaction and actual use as dependent variables by the proceeding research for accepting information technology and new service. Third, the statistical analysis is conducted by surveying to 200 smart phone users for verifying a validity of research models and hypotheses. As a result, almost hypotheses are accepted in confidence interval except for the hypothesis between security and trust variable.

• The KIPS Transactions:PartC
• /
• v.11C no.5
• /
• pp.621-632
• /
• 2004

Recent measurement studies of real teletraffic data in modern telecommunication networks have shown that self-similar (or fractal) processes may provide better models of teletraffic in modern telecommunication networks than Poisson processes. If this is not taken into account, it can lead to inaccurate conclusions about performance of telecommunication networks. Thus, an important requirement for conducting simulation studies of telecommunication networks is the ability to generate long synthetic stochastic self-similar sequences. A new generator of pseu-do-random self-similar sequences, based on the fractional Gaussian nois and a wavelet transform, is proposed and analysed in this paper. Specifically, this generator uses Daubechies wavelets. The motivation behind this selection of wavelets is that Daubechies wavelets lead to more accurate results by better matching the self-similar structure of long range dependent processes, than other types of wavelets. The statistical accuracy and time required to produce sequences of a given (long) length are experimentally studied. This generator shows a high level of accuracy of the output data (in the sense of the Hurst parameter) and is fast. Its theoretical algorithmic complexity is 0(n).

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.9
• /
• pp.1682-1688
• /
• 2008

The Counterpropagation algorithm(CP) is a combination of Kohonen competition network as a hidden layer and the outstar structure of Grossberg as an output layer. CP has been used in many real applications for pattern matching, classification, data compression and statistical analysis since its learning speed is faster than other network models. However, due to the Kohonen layer's winner-takes-all strategy, it often causes instable learning and/or incorrect pattern classification when patterns are relatively diverse. Also, it is often criticized by the sensitivity of performance on the learning rate. In this paper, we propose an enhanced CP that has multiple Kohonen layers and dynamic controlling facility of learning rate using the frequency of winner neurons and the difference between input vector and the representative of winner neurons for stable learning and momentum learning for controlling weights of output links. A real world application experiment - pattern recognition from passport information - is designed for the performance evaluation of this enhanced CP and it shows that our proposed algorithm improves the conventional CP in learning and recognition performance.

• Journal of the Korea Society for Simulation
• /
• v.25 no.4
• /
• pp.109-115
• /
• 2016

This study intended to testify the causality among three variables such as accident, depression and cognitive failure of the train drivers. For this purpose, two research models were suggested. Model 1 hypothesized the causality among three variables as 'depression ${\rightarrow}$ cognitive failure ${\rightarrow}$ accident'. On the other hand, model 2 hypothesized the causality among three variables as 'accident ${\rightarrow}$ depression ${\rightarrow}$ cognitive failure'. Results based on AMOS using 416 train drivers' questionnaire showed that model 2 is more valid than model 1. The statistical result of model 1 showed that depression has a positive effect on cognitive failure, however no significant relationship between depression and accident as well as between cognitive failure and accident. In model 2, the result showed that the accident has a positive effect on cognitive failure mediated by depression. This result suggests the necessity for establishment of countermeasures to mitigate mistake and cognitive failure caused by train drivers in a wider context, considering the causality between accident and depression.

• Journal of the Society of Naval Architects of Korea
• /
• v.31 no.1
• /
• pp.50-62
• /
• 1994

This paper presents the results of a comparative analysis of the model test results to investigate the effect of bulbous bow installed on a large full form ship to the ship resistance performance. Seven parameters related to the shape of bulbous bow were selected and varied systematically to inquire their effects experimentally. A total number of twenty-three ship models with different bulbous bow were manufactured, and resistance tests. flow visualization test, and wave profile measurement were carried out for each model. For the comparative analysis between the various bulb forms and their model test results, bulbous bow forms are classified into nine groups according to their form characteristics. From the analysis of the trend of the resistance components, it was verified that form resistance has dominant effect on the total resistance of a slow full form ship. The model test and its statistical analysis showed that the direction of streamlines around bulbous bow has close relationship with resistance components. especially with form resistance

• The Korean Journal of Applied Statistics
• /
• v.34 no.6
• /
• pp.945-956
• /
• 2021

In this study, we considered the algorithm of Legendre and Legendre (2012), which derives canonical correspondence analysis from weighted principal component analysis. And, it was proved that the canonical correspondence analysis based on the weighted principal component analysis is exactly the same as Ter Braak's (1986) canonical correspondence analysis based on the Gaussian response model. Ter Braak (1986)'s canonical correspondence analysis derived from a Gaussian response curve that can explain the abundance of species in ecology well uses the basic assumption of the species packing model and then conducts generalized linear model and canonical correlation analysis. It is derived by way of binding. However, the algorithm of Legendre and Legendre (2012) is calculated in a method quite similar to Benzecri's correspondence analysis without such assumptions. Therefore, if canonical correspondence analysis based on weighted principal component analysis is used, it is possible to have some flexibility in using the results. In conclusion, this study shows that the two methods starting from different models have the same site scores, species scores, and species-environment correlations.