• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.297-303
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• 2016

This paper introduces auxiliary power supply systems (APS) for railroad applications and proposes a new power conversion structure for highly-efficient and lightweight APS systems. The proposed structure focuses on an improvement of the power density in APS. It eliminates unnecessary power conversion stages in the conventional APS structure by modulating the dc/dc converter circuit and the structure of the system. The dc/dc converter circuit used in the proposed structure is based on a multi-level half-bridge converter, a widely used topology in railroad APS applications; a flying capacitor is newly added to the conventional circuit. The added capacitor is used not only to enhance the soft switching condition of the switches, but also so that the new pantograph will have a side voltage source of a battery charger in the APS structure. Since the battery charger uses the pantograph side voltage source in the proposed structure, rather than using the output of the main dc/dc converter in the conventional structure, the size and efficiency of the main dc/dc converter are reduced and increased, respectively. To verify the effectiveness of the proposed structure, simulation results will be presented with metropolitan transit APS specifications.

• Journal of Radiation Protection and Research
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• v.21 no.3
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• pp.147-153
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• 1996

The Korea Atomic Energy Research Institute(KAERI) conducted a intercomparison study for personnel dosimetry services in Korea to enhance the accuracy and precision of the dosimetry system. Nine types of dosimeters(6 TLD, 3 film badge) from 7 institutions took part in this intercomparison study. Each participant submitted 30 dosimeters including transit control for irradiations. Both TLDs and film badges were irradiated with Cs-137 gamma, Sr/Y-90 beta and 4 X-ray beams in ISO wide series. Four dosimeters were irradiated on phantom with same dose equivalent for each field category. The delivered dose equivalent was in the range of $0.1{\sim}10mSv$. The participants assessed the results of their dosimeter readings in terms of the ICRU operational quantities for personal monitoring, Hp(10) and Hp(0.07). Most participants except 1 dosimeter estimated the delivered dose equivalent with biases less than ${\pm}25%$ for Cs-137 and Sr/Y-90. But for X-rays, the biases exceeded ${\pm}35%$ in some cases bacause the dose evaluation algorithm was based on the ANSI N13.11 X-ray fields which are different from those given by ISO.

• Journal of Korean Society of Transportation
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• v.23 no.6 s.84
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• pp.81-89
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• 2005

Real-time bus arrival information within the Bus Information System (BIS) is an invaluable resource for users that demand accurate and up-to-date bus headway information while waiting at a bus stop. The associated benefits of such a system come in two folds, that is to 1) resolve the psychological uncertainty caused by the lack of real-time bus arrival information and 2) empower the user waiting at bus stops with the ability to reliably coordinate various tasks and errands, such as a quick trip into a convenience store or restroom without fear of missing a bus pick-up. This paper discusses the appropriate methodology with which to measure the economic value of reliable bus arrival information, with particular emphasis on the psychological uncertainty in users associated with the lack of real-time headway information at bus stops. Data regarding bus transit users' willingness to pay for such a service is obtained through questionnaire surveys, and the Contingent Valuation Method is used to analyze and derive the associated economic value. Our findings indicate the monetary value associated with a real-time bus arrival information system is approximately 132.5 won/min at the 0.3 significance level.

• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.3
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• pp.505-511
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• 2004

The effects of single cells of carrot or radish on the fecal excretion, mineral absorption rate and structure of small intestine and colon were investigated in rats fed 5% single cell diet for 4 weeks. Carrot contained 28.76% of total dietary fiber and 21.45% of insoluble dietary fiber, and radish contained 23.14% of total dietary fiber and 16.77% of insoluble dietary fiber on a dry weight basis. Total dietary fiber contents of the single cell were 44.68% for carrot, 48.0% for radish. Absorption rates of magnesium were higher in the carrot and radish single cell groups than the other groups. Cellulose significantly increased fecal weight and weight of small intestine. The consumption of cellulose and single cells decreased digestibility of lipid. The length of colon were longer in the carrot and the radish group than the other groups. Scanning electron microscopy studies showed that small intestine microvilli with leaf-shaped were seen in cellulose and single cell fed groups. These results suggest that the diet containing 5% single cells of carrot or radish increases the digestibility of dietary fiber, weight gain, and fecal output and shorten the gastrointestinal transit time.

• Physical Therapy Korea
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• v.4 no.2
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• pp.18-35
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• 1997

The purpose of this study were to determine causes of low back pain in bus drivers who usually work in prolonged sitting position and to find the relationship of back pain with general characteristics and work environmental characteristics, stress symptoms, to com맹re lordosis angle of habitual driving posture and resting posture in low back pain group and non-low back pain group, and to use this result as a basis for improvement of work environment and comprehensive rehabilitative management of low back pain. Ninety-eight bus drivers were selected from the membership of an urban transit union in Seoul. These informations were collected from May 1, 1997 to May 25, 1997 by means of structured questionnaires and X-ray findings. These data were analyzed by $x^2$ test, t-test, logistic regression using SAS. The major results were as follows: 1. Of the respondents, 66.3% of bus drivers were found to be experiencing back pain. 2. Of the respondents of low back pain groups, 78.5% reported that major cause of low back pain was due to prolonged sitting. 3. The group with experiences of frequent or continuous vibration had more low back pain (p<0.05). There were no significant differences among other work environmental factors. 4. Average stress score was significantly higher in the group with low back pain than in the group without low back pain (p<0.05). 5. The results of the logistic regression analyses were statistically significant vibration from seat and stress score among the risk factors (p<0.05). 6. Averaged lordosis angle of habitual driving posture was $7.6{\pm}14.9$ degrees in low back pain group, $16.5{\pm}8.7$ degrees in non-low back pain and averaged lordosis angle of resting sitting posture was $10.8{\pm}13.7$ degrees in low back pain, $18.9{\pm}9.6$ degrees in non-low back pain group but the difference in mean lordosis angles of two groups was not statistically significant. The results of this study indicate that professional drivers developed chronicity of low back pain due to unfit seat, poor habitual posture and stress from vibration or other risk factors. Therefore, there is need to improve work environment, i.e. enough resting, to set a seat to support lumbar spine properly and to provide comprehensive rehabilitation program including early diagnosis, proper treatment and education for self help management.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.369-377
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• 2017

The city of Busan implemented the 'Bus Quasi-Public Operating System' as a part of the Public Transit Activation Policy. Although the reorganization of routes and fares had temporarily increased the number of passengers, it is facing a downtrend currently. This implies the limited capability of increasing the use of the city buses only by adjusting the systematic components of the system. Thus, the research aims to analyse the effect of improving the 'kindness service' as an alternative way to vitalize the use of city buses. The analysis uses the survey encompassing sixteen 'kindness service' factors that was collected from the passengers and the drivers of the city buses in Busan, and some of the notable findings are followed. According to the analysis of determining the level of importance on the 'kindness service' factors, four major categories were derived; a category to maintain/reinforce the kindness service, a category to make incremental improvement, a category to encourage improvement, and a category to make focusing improvement. Using the categories, the study then performed the cluster analysis on 33 city bus companies in Busan to determine the differences between the companies. Consequently, the companies were grouped into four; two groups (14 companies) showing more importance on the kindness service while the other two groups (19 companies) showing less. In addition, multivariate an analysis of variance (MANOVA) identified the significant differences of the four categories among the groups of companies, and the findings were taken into consideration on further improvement plans of kindness service in the city buses of Busan.

• Progress in Medical Physics
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• v.18 no.3
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• pp.149-160
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• 2007

Recent advent of 64-multidetctor (MD) CT enables more coverage of Z-axis in the perfusion imaging. The purpose of this study was to evaluate the clinical usefulness of perfusion CT by using 64-MD CT in detecting the lesion in patients with acute stroke. The perfusion CT was performed by using 64-MD CT in 62 consecutive patients who were initially suspected to have subacute ischemic stroke symptoms during the period of recent 9 months. These patients had subacute stroke (n=62). CT scanning was conducted with Jog Mode which provided 16 imaging slices with 5 mm of slice thickness, and 8 cm of coverage in Z-axis. Scan interval was 1 seconds for each imaging slice and total 15 scans were repeated. After CT scanning, perfusion maps (CBV, CBF, MTT and TTP) were created at Extended Brilliance Workstation. The CBV and CBF maps showed that lesions were smaller images. While on the MTT and TTP map lesions were seen to be larger fifty-one were large than they appeared on these images. Two slices of perfusion maps obtained at the level of the basal ganglia were chosen to simulate conventional older perfusion CT with 8 cm of coverage in Z-axis. TTP and MTT maps may be clinically useful for evaluation of the penumbral zone in cases of aubacute cerebral ischemic stroke. The perfusion CT is useful in the assessment of acute stroke as an initial imaging modality.

• Journal of Biosystems Engineering
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• v.36 no.2
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• pp.130-139
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• 2011

Three modes of VIS/NIR spectroscopic measurement (interactance and two modes of transmission) were compared for their ability to estimate soluble solids content (SSC) of 'Shingo' pear non-destructively. The two transmission modes are named as full- and semi-transmission, where full-transmission stands for passing of light through abdomen of pear and semi-transmission is for transit of light mainly through flesh of pear. For comparison of the modes, prediction models developed from the collected spectroscopic data by the three modes were developed and tested for comparison of their performance. Partial least square regression (PSLR) was used to develop the models and various pre-processing methods were applied to develop models of high accuracy. The experiment was repeated three times with pears produced in different regions. The experiments resulted that selection of pre-processing is very important to attain accurate models, and multiplicative scatter correction (MSC) was selected as a pre-processor of high accuracy for the three modes of spectroscopic measurement in every experiment. Except for MSC, different group of pre-processing methods were selected for the three modes of measurement in every experiment without any tendency to the tested modes of measurement and pears of different produced region. Root-mean-square error of prediction (RMSEP) of prediction models of the three modes of measurement using prepreocessor of MSC were compared for their ability to estimate SSC. The models resulted in ranges of $0.37{\sim}0.57^{\circ}Brix$, $0.65{\sim}0.72^{\circ}Brix$, $0.39{\sim}0.51^{\circ}Brix$ for interactance, full- and semi-transmission, respectively. As shown, modes of semi-transmission and interactance resulted about the same level of prediction accuracy and were noted as modes of high performance to predict SSC.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.5
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• pp.533-542
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• 2010

The $PM_{10}$ concentrations in the underground should be monitored for the health of commuters on the underground subway system. Seoul Metro and Seoul Metropolitan Rapid Transit Corporation are measuring several air pollutants regularly. As for the measurement of $PM_{10}$ concentrations, instruments based on $\beta$-ray absorption method and gravimetric methods are being used. But the instruments using gravimetric method give us 20-hour-average data and the $\beta$-ray instruments can measure the $PM_{10}$ concentration every one hour. In order to keep the $PM_{10}$ concentrations under a healthy condition, the air quality of the underground platform and tunnels should be monitored and controlled continuously. The $PM_{10}$ instruments using light scattering method can measure the $PM_{10}$ concentrations every less than one minute. However, the reliability of the instruments using light scattering method is still not proved. The purpose of this work is to study the reliability of the instruments using light scattering method to measure the $PM_{10}$ concentrations continuously in the underground platforms. One instrument using $\beta$-ray absorption method and two different instruments using light scattering method (LSM1, LSM2) were placed at the platform of the Jegi station of Seoul metro line Number 1 for 10 days. The correlation between the $\beta$-ray instrument and the LSM2 ($r^2$=0.732) was higher than that between the $\beta$-ray instrument and the LSM1 ($r^2$=0.393). Thus the LSM2 was chosen for further analysis. Three different regression analysis methods were tested: Linear regression analysis, Nonlinear regression analysis and Orthogonal regression analysis. When the instruments using light scattering method were used, the data measured these instruments have to be converted to actual $PM_{10}$ concentrations using some factors. With these analyses, the factors could be calculated successfully as linear and nonlinear forms with respect to the data. And the orthogonal regression analysis was performed better than the ordinary least squares method by 28.45% reduction of RMSE. These findings propose that the instruments using light scattering method light scattering method can be used to measure and control the $PM_{10}$ concentrations of the underground subway stations.

• Journal of Korean Society of Transportation
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• v.32 no.4
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• pp.327-335
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• 2014

The Korean government, as of last year, is attempting to introduce a competitive system in the rail-market. However there are some pertinent issues which need to be addressed in order to select the best possible organization for optimum railway traffic control. As there are no standard guidelines in selecting an agency, objective evaluation factors need to be properly applied to ensure the best possible decision is made. Through literature review and various interviews with experts, appropriate criteria were selected to evaluate the suitability of each potential operator. As generally mentioned, both safety and efficiency play vital roles in the selection process but in addition, there are other factors such as security and fairness, which also need to be considered. The individual weight of these factors were calculated by the AHP, in which three groups of experts were interviewed to acquire their expertise. According to the results, as a potential operator, the score of a railway operating company and the management cooperation of railway is 2.75 and 3.85, respectively. In the future, in preparation towards becoming a competitive rail-market, this research is expected to assist in choosing the best party to control the rail traffic system.