• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.18 no.4
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• pp.262-270
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• 2008

This study was conducted to measure concentrations of particulate matter ($PM_{10}$, $PM_{2.5}$) and endotoxin in thirty public facilities (7 elderly-care facilities, 4 hypermarkets, 4 university hospitals, 7 child-care facilities, 4 subway stations and 4 bus terminals) from September 2004 to February 2007 in Seoul and Gyeonggi-do province. $PM_{10}$ or $PM_{2.5}$ was measured with glass fiber filter and mini volume air sampler for 6 to 8 hours in indoor and outdoor of the facilities and expressed as ${\mu}g/m^3$. After weighing the filter, endotoxin was analyzed by Limulus Ameobocyte Lysate method ($EU/m^3$). $PM_{10}$ in indoor air was higher (GM and GSD was 78.00 and $1.92\;{\mu}g/m^3$, respectively) than the outdoor air (GM and GSD was 60.70 and $2.23\;{\mu}g/m^3$, respectively, I/O=1.28). All measurements was not exceeded the national maintenance standard. Elderly-care and child-care facilities showed relatively higher concentrations ($83.27\;{\mu}g/m^3$ and $81.75\;{\mu}g/m^3$; I/O=2.01 and 1.19, respectively) than hypermarkets or university hospitals. The highest PM2.5 was seen in child-care facilities ($62.15\;{\mu}g/m^3$, I/O=2.42). The I/O of the endotoxin in the PM10 and the $PM_{2.5}$ was exceeded 1.0 (1.37 and 1.57, respectively). Indoor $PM_{10}$ was affected by user/day and humidity, and endotoxin in the PM10 was affected by temperature. In conclusion, elderly- and child-care facilities are high priority facilities to be improved indoor air quality.

• Journal of Korean Society of Transportation
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• v.22 no.2 s.73
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• pp.27-39
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• 2004

The purpose of this paper presents realistic policy alternative about recent tendency to decrease of subway-users and diminution of use efficiency which are serious problems of Busan Subway. Several policy alternatives have been studied until now, such as subway transfer impedance solution plan, introduction of subway to transfer fare discounting policy, and etc.. But, those policy alternatives are difficult to carried out, because they are less effective and overburden to financial aspect. Therefore, I made use of research on subway utilization to presuppose service improvement, as an alternative, in the transfer fare discounting system between bus and subway which might be powerful influence over subway-users. To verify this proposed study, I took advantage of Stated Preference(SP) where I estimated fare revenue and effects on fluctuation of subway-users with nested logit model based on research results. Suitable alternatives are as follows: First, If municipal government carries out transfer fare discounting policy without shortening in-vehicle time and out-of-vehicle time transfer fare, it is reasonable to discount transfer fare 50% off on the assumption of financial support as much as \6.700 million annually. Secondly, in case of application of multi-factors at a time, transfer fare discounting and in & out vehicle time, it is preferred to have no charge for transfer option with financial support as much as expected income-loss \5,600 million.

• Journal of Korean Society of Transportation
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• v.33 no.2
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• pp.125-135
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• 2015

In this study our main focus is to verify the relationship between social value of transportation system and its perceived features. To achieve this objective, we investigated the value of public bike system (PBS) through willingness to pay (WTP) analysis using contingent valuation method (CVM) and the survey was conducted for 1726 respondents who live in Suwon, Korea. Moreover the determinants related to features related to bicycle use were also gathered. The estimated binary logistic regression and censored regression reveal that the value of PBS is influenced by perceived features towards bicycle use incorporating non-congestion, transportation mode like auto and bus, and high mobility system as well as other variables such as income, bicycle ownership etc. Furthermore the results show that the perceiving of positive features to bicycle use leads to higher social value of PBS. Based on the findings, we discuss the importance of pre-review for transport policy implementation, and also explore the possibilities for application to PBS.

• Journal of Korean Society of Transportation
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• v.32 no.3
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• pp.187-197
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• 2014

The objective of this study is to analyze the travel behaviors of customers accessing to three different types of shopping facilities - traditional markets(TM), hyper markets(HM), and super supermarkets(SSM) - and also to find out the most desirable location for each type of shopping facilities that encourage sustainable transportation and smart urban growth. It also demonstrates what mode has the highest percentage of modal split and what is the access distance for public transport mode by each shopping facilities (SSM: 84.5% walking and 667m, TM: 20.1% bus and 1.6km, HM : 46.2% private car and 4.2km). Among TM, HM, and SSM, statistically significant differences are found in terms of mode choices and other associated travel behaviors. The research findings are expected to contribute to finding future urban planning and transportation solutions that promote walking and public transit uses for shopping trips and thus help support green transportation and sustainable urban growth.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.399-416
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• 2004

The FIMS (Far-ultraviolet IMaging Spectrograph), the main payload onboard the first Korean science satellite STSAT-1, has performed various observations since its launch on September 2003. It has been found that the attitude informations provided by spacecraft bus system have a time offset problem, and the problem has been extensively studied. After the time offset correction, boresight offsets between FIMS fields of view, of long and short wavelength bands, respectivley, and spacecraft attitude systems, which are mainly due to alignment error between the FIMS and spacecraft mechanical systems, were calculated through the observations of well known calibration targets. Monthly status and precision of the attitude information are also described. Correction methods for spatially variable exposure, intrinsic to FIMS data, are discussed. These results are essential to the FIMS data analysis, and will be used as references for subsequent studies on more accurate attitude corrections.

• Journal of Satellite, Information and Communications
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• v.10 no.4
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• pp.95-100
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• 2015

These days, satellite core technologies are being developed as a way to provide various information by considering simultaneously sending, wide area covering, highly precide, and anti-disaster technologies. Not only global positioning, and image but also space launcher, satellite bus, satellite payload, earth station are being convergently developed in a different technological field. Especially, it is required a lot of initial investing expenditure to provide the Earth observational information service based on the space technologies. Such a trend and change of satellite technologies Korea has realized the necessity for the domestic independent development of next generation earth observation satellites, and are preparing the profound items such as a detailed implementation plan for the efficient development project. Like the satellite advanced countries, it should be transparently carried out that an efficient implementation of the developing target related to the geostationary earth observation satellite development, establishment of technological auditing function and quality assurance system, implementation plan, progressing courses and results of the satellite development program by way of planning, evaluation and management. For these things cited above, it is necessary to operate systematically and continuously the professional structural system by the governmental department in order to control the geostationary earth observation satellite development project. Therefore, this study proposes a development project management improvement method of the Korea next generation geostationary earth observation satellite based on the development project management system of the domestic geostationary satellite system.

• Journal of the Korean Institute of Gas
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• v.13 no.2
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• pp.41-48
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• 2009

I collected the cases of CNG vehicle accidents which had happened for 30 years and analyzed the causes of the accidents according to each type of cylinders. There are about six accidents including three cylinder explosion accidents due to bad heat treatment, one composite damage, one CNG vehicle fire, and one fuel piping accident owing to the poor maintenance. When looking into the cylinder types involved in the accidents and the causes, 29% of the cylinder accidents are Type I and 24% Type IV, 16% Type II, and 14% Type III. 37% of the accidents are caused by the defects of the raw materials and the errors of a manufacturing process, 16% by the stress corrosion cracking as a result of the repetitive use, 15% by the cylinder's explosion on account of the malfunction of PRD(Pressure Relief Device) and the overpressure. The remainders of the causes are fire and unknown causes. Therefore, cylinder manufacturers have to strengthen quality management of raw materials and manufacturing process and painting regardless of each type of cylinder. Also bus operators need to make an effort to keep safety condition through every day check.

• The Journal of the Korea Contents Association
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• v.17 no.2
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• pp.637-645
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• 2017

This study researched the toothbrushing behavior and perception of oral health condition in accordance with the use of cafeteria, 280 Students of 28 high schools in Daegu and Gyeongbuk to identify the relationship between cafeteria use and oral health. and then obtained statistically significant results like below. Toothbrushing after meals and snacks was high with female students and Grade3. Rinsing mouth for ten times or more after toothbrushing was high with female students and private car while the use of oral care products was high with female students, Grade3, and private car. The whole average frequency of using cafeteria was 2.26 while the perception of oral health condition was 3.44. The frequency of using cafeteria was high with Grade2, before time for school, and lots of allowance. The perception of oral health condition was high with male students, school bus, and lots of allowance. The frequency of using cafeteria in accordance with toothbrushing behavior was high with toothbrushing for longer than three minutes(2.45) while the perception of oral health condition was high in case when using oral care products(3.32). In the results of multiple regression analysis to understand the influence of perception of oral health condition, general characteristics, and toothbrushing behavior on the frequency of using cafeteria, it was analyzed like Y(frequency of using cafeteria)=-952+.393(perception of oral health condition)- 1.721(time for school)+ .991(allowance)+ 1.124(duration of toothbrushing). Based on the results above, it would be necessary to establish the educational system to continuously practice the correct oral health care education in school.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.67-74
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• 2002

Optical observations of Geostationary and Molynia orbit spin-stabilized satellites over the Korean peninsula have been carried out at the Kyung Hee University Observatory with a 30 inch telescope. We have observed 5 spin-stabilized satellites, and obtained 0spin periods, which can be used for deducing a design for each bus model. Verifications of spin periods of 3 known satellites from manufacturer, and observations of 2 unknown satellites were made. The difference between known spin periods and observed spin periods is 0.06sec on the average and the difference of those spin rates is 3.3rpm on the average. Those results indicate that spin periods and spin rates of observed geostationary spin-stabilized satellites are within operating limits. Spin rates of unknown satellites, Fengyun 2B and Molynia 1-87 are 89.3rpm, 78.4rpm earh. It is suggested that the research of spin stabilized satellites can be used for the determinations of standard light sources for short period celestial objects and helpful for the constructions of satellite databases with photometric and/or spectroscopic satellite observations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.817-825
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• 2017

The AC-common bus microgrid system can overcome several weaknesses of the DC microgrid system by interconnecting the DC/AC inverters used for renewable energy with an AC network. Nevertheless, the unbalanced loads inherent in the electric power systems of island and small communities can deteriorate the performance of the AC microgrid system. This is because of the limited voltage regulation capability and mixed power flow in the voltage source inverter. In order to overcome the unbalanced load condition, this paper proposes a voltage and current control algorithm for the 4-leg inverter based on the single phase d-q control method, as well as the modeling of the voltage controller using Matlab/Simulink S/W. From the S/W simulation and experiment of the 250KW proto-type inverter, it is confirmed that the proposed algorithm is a useful tool for the design and operation of the AC microgrid system.