• Journal of radiological science and technology
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• v.44 no.3
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• pp.261-267
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• 2021

As the number of Coronavirus Disease-19 (COVID-19) patients increases in a global pandemic situation, the usefulness of mobile computed tomography (CT) is gaining attention. Currently, mobile CT follows the basic safety and essential performance evaluation criteria of whole-body or limited-view X-ray CT in order to obtain device approval and evaluation in the Republic of Korea. Unlike stationary CT, mobile CT is not operated in shielded areas but rather areas such as intensive care units, operating rooms, or isolation rooms. Therefore, it requires a different basic safety and essential performance evaluation standard than stationary CT. In this study, four derived basic safety evaluation criteria related to electrical, mechanical, and radiation safety were included (dose indication test, protection against stray radiation, safety measures against excessive X-rays, half-value layer measurement); and seven essential performance evaluation criteria were included (tube voltage accuracy, mAs accuracy, radiation dose reproducibility, CT number of water, noise, uniformity, and spatial resolution); total eleven basic safety and essential performance evaluation criteria were selected. This study aims to establish appropriate basic safety and essential performance evaluation criteria for simultaneously obtaining images with diagnostic value and reducing the exposure of nearby patients, medical staff, and radiologic technologists during the use of mobile CT.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.1
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• pp.19-27
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• 2010

Sky cover method can be used to determine sky condition by cloud amount of the Korea Meteorological Administration. And, HCI (Hourly Clearness Index) method is another method determined by measured horizontal global radiation data. The results of the HCI methods of Erbs et al. (1982), Orgill and Hollands (1977) seem to be not good enough because of the air pollution such as smog phenomenon or yellow sand phenomenon and so on. Therefore, HCI should be corrected. The aim of this study is to improve HCI. Therefore, this study is to analyze and compare on the sky conditions from Sky cover method and HCI, and then presents hourly correction factor based on Sky 채팩 method. The results of corrected HCI improved.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.27 no.4
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• pp.437-444
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• 2009

A bi-directional, multi-step numerical integrator is developed to determine the GPS (Global Positioning System) orbit based on a dynamic approach, which shows micrometer-level accuracy at GPS altitude. The acceleration due to the planets other than the Moon and the Sun is so small that it is replaced by the empirical forces in the Solar Radiation Pressure (SRP) model. The satellite orbit parameters are estimated with the least-squares adjustment method using both the integrated orbit and the published IGS (International GNSS Service) precise orbit. For this estimation procedure, the integration should be applied to the partial derivatives of the acceleration with respect to the unknown parameters as well as the acceleration itself. The accuracy of the satellite orbit is evaluated by the RMS (Root Mean Squares error) of the residuals calculated from the estimated orbit parameters. The overall RMS of orbit error during March 2009 was 5.2 mm, and there are no specific patterns in the absolute orbit error depending on the satellite types and the directions of coordinate frame. The SRP model used in this study includes only the direct and once-per-revolution terms. Therefore there is errant behavior regarding twice-per-revolution, which needs further investigation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.5 no.2
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• pp.128-137
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• 2003

Net radiation (Rn) is one of the most fundamental components in surface energy budget. For an accurate measurement of Rn, periodic and consistent calibrations of net radiometers are required. With a 4-month time interval, two field experiments were conducted to inter-compare and calibrate two types of net radiometers (the Q-7.1 and the CNR1), widely used in flux measurements. Differences between the Q-7.1 and the CNR1 net radiometers were within 7.7%, and the errors after calibration against the standard net radiometer were ＜3.2%. Radiometric responses and calibration factors appeared to have changed with sky renditions, especially temperature difference with season's progress. We concluded that the periodically calibrated Q-7.1 can replace more expensive, more accurate CNR1 net radiometer for long-term field measurements, providing that field calibrations of net radiometers are performed every 4-6 months interval.

• Atmosphere
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• v.27 no.2
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• pp.163-175
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• 2017

The global terrestrial ecosystems have shown a large spatial variability in recent decades and represented a carbon sink pattern at mid-to-high latitude in Northern Hemisphere. However, there are many uncertainties in magnitude and spatial distribution of terrestrial carbon fluxes due to the effect of climate factors. So, it needs to accurately understand the spatio-temporal variations on carbon exchange flux with climate. This study focused on the effects of climate factors, .i.e. temperature, precipitation, and solar radiation, to terrestrial biosphere carbon flux. We used the terrestrial carbon flux that is simulated by a CarbonTracker, which performs data assimilation of global atmospheric $CO_2$ mole fraction measurements. We demonstrated significant interactions between Net Ecosystem Production (NEP) and climate factors by using the partial correlation analysis. NEP showed positive correlation with temperature at mid-to-high latitude in Northern Hemisphere but showed negative correlation pattern at $0-30^{\circ}N$. Also, NEP represented mostly negative correlation with precipitation at $60^{\circ}S-30^{\circ}N$. Solar radiation affected NEP positively at all latitudes and percentage of positive correlation at tropical regions was relatively lower than other latitudes. Spring and summer warming had potentially positive effect on NEP in Northern Hemisphere. On the other hand as increasing the temperature in autumn, NEP was largely reduced in most northern terrestrial ecosystems. The NEP variability that depends on climate factors also differently represented with the type of vegetation. Especially in crop regions, land carbon sinks had positive correlation with temperature but showed negative correlation with precipitation.

• Journal of Bio-Environment Control
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• v.9 no.2
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• pp.107-114
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• 2000

We constructed climagraphs for 16 regions of Korea by using the average monthly minimum air temperature, maximum air temperature and global radiation. We characterized the outside climate requirements corresponding to the climate requirements of crops in greenhouses. The climagraphs allow to decide the appropriate climate periods for greenhouse cultivation without heating and cooling equipment. These graphs may be used for analyzing climatic characteristic of a given area, selecting the suitable region and greenhouse and making a rational plan for greenhouse cropping in Korea. We found difficulty in deciding the beginning and end of greenhouse heating and cooling period due to insufficient references.

• Journal of Radiation Protection and Research
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• v.33 no.1
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• pp.1-12
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• 2008

International Standardization in all technical area is gaining its momentum as its impact and implication over global trade is directly linked. The worldwide competition to secure a dominant position in the standardization process is ever growing over the years. In 2005, the International Technical Committee on Nuclear Instrumentation, which is a subunit of International Electro-technical Commission (IEC), was held in Korea under the auspices of MOST (Ministry of Science and Technology). Korea has adopted its Rule and Regulation as the National Standard. As a part of a link to National Mid-and Long-term Atomic Energy R&D Program of MOST, the technical development of a performance test for the radiation monitors was carried out under mechanical environment and electromagnetic immunity conditions. The characteristics of the radiation fields were also evaluated under the conditions and introduced to a techniques of performance test for the radiation protection instrumentation adopted IEC61526 standards and it's results was analyzed. We would like to share the experience gained in these efforts, failure as well as success, and to discuss the problems encountered and serious consideration to be taken into account in the future endeavor.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.275-278
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• 2006

Systematic experiments in $CH_4/Air$ counterflow diffusion flames diluted with He have been undertaken to study the oscillatory instability in which lateral heat loss could be remarkable at low global strain rate. The oscillatory instability arises for Lewis numbers greater than unity and occurs near extinction condition. The dynamic behaviors of extinction in this configuration can be classified into three modes; growing, harmonic and decaying oscillation mode near extinction. As the global strain rate decreases, the amplitude of the oscillation becomes larger. This is caused by the increase of lateral heat loss which ran be confirmed by the reduction of lateral flame size. Oscillatory edge flame instabilities at low global strain rate are shown to be closely associated with not only Lewis number but also heat loss (radiation and lateral heat loss).

• Journal of Radiation Protection and Research
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• v.35 no.3
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• pp.111-116
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• 2010

Ionizing radiation is most widely used for X-Ray examination among all artificial radiation exposure, it takes up the largest proportion. Even in Korea, the medical exposure by diagnostic X-Ray examination takes up 17.4% of all radiation exposure. It takes up 92% even in artificial radiation exposure. There were 111,567 cases X-Ray radiography for skull diagnosis in 2007, which is 3% annual increase since 2004. Thus, It is need to establish the diagnostic reference level and the medical facilities as a diagnostic reference level to optimize radiation protection of the patients and to reduce the doses of X-ray. In this paper, we survey patient dose on skull radiography - collected from 114 medical facilities nationwide by using human phantom and glass dosimeter. When the patient dose for the skull radiography was measured and evaluated to establish the diagnostic reference level, 2.23 mGy was established for posterior-anterior imaging and 1.87 mGy for lateral imaging was established. The posterior-anterior skull radiography entrance surface dose of 2.23 is less than the guidance level of 5 mGy from the global organizations such as World Health Organization (WHO) and International Atomic Energy Agency (IAEA), and 1.87 mGy for the lateral skull imaging is less than the guidance level of 3 mGy, which is guided by the global organizations such as World Health Organization (WHO) and International Atomic Energy Agency (IAEA).

• Korean Journal of Agricultural and Forest Meteorology
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• v.13 no.2
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• pp.48-55
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• 2011

Solar radiation components reflected by the sea surface ($R_{ss}\uparrow$) are additional energy sources comprising the solar radiation regime. Previous studies, based on observational approaches, indicated that $R_{ss}\uparrow$ is an available climatological resource. However, an estimation process for $R_{ss}\uparrow$ has not been established. In this case study over Jeju Island in South Korea, we applied a new estimation process to solar radiation modeling and discussed the spatial distribution of $R_{ss}\uparrow$ and its seasonal variation. Our results showed that the illuminated area and the intensity of $R_{ss}\uparrow$ became greatest at the winter solstice and least at the summer solstice. We estimated the illuminated area of $R_{ss}\uparrow$ as it expanded over the southern slope of Jeju Island. At the winter solstice, on a daily basis, the area and intensity of illumination by $R_{ss}\uparrow$ were $182.3km^2$ and $0.41\;MJ\;m^{-2}\;day\;{-1}$, respectively. Comparing the daily accumulative and instantaneous values of $R_{ss}\uparrow$ intensity, the difference was about 20 times greater in daily cases than in instantaneous cases. On the other hand, for instantaneous values, the $R_{ss}\uparrow$ intensity accounted for up to 33% of the three components, i.e., direct, diffuse and reflected radiation in winter solstice. In addition, it was estimated that the sea surface reflectance depended on the wind speed. Therefore, in a practical use of this revised model, wind conditions should be considered as a critical factor in estimating $R_{ss}\uparrow$.