• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.45.3-46
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• 2016

Solar activity shows a self-similarity as it has many periods of activity cycle in the time series of long-term observation, such as 13.5, 51, 150, 300 days, and 11, 88 years and so on. Since fractal dimension is a quantitative parameter for this kind of an irregular time series, we applied this method to long-term observations including sunspot number, total solar irradiance, and 3.75 GHz solar radio flux to predict the start and maximum times as well as expected maximum sunspot number for the next solar cycle. As a result, we found that the radio flux data tend to have lower fractal dimensions than the sunspot number data, which means that the radio emission from the sun is more regular than the solar activity expressed by sunspot number. Based on the relation between radio flux of 3.75 GHz and sunspot number, we could calculate the expected maximum sunspot number of solar cycle 24 as 156, while the observed value is 146. For the maximum time, estimated mean values from 7 different observations are January 2013 and this is quite different to observed value of February 2014. We speculate this is from extraordinary extended properties of solar cycle 24. As the cycle length of solar cycle 24, 10.1 to 12.8 years are expected, and the mean value is 11.0. This implies that the next solar cycle will be started at December 2019.

• Journal of Korean Society for Atmospheric Environment
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• v.4 no.2
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• pp.67-71
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• 1988

To estimate the probability of short term concentration of air pollution using long term arithmetic average concentration, the procedure was developed and added to Texas Climatological Model version 2. In the procedure, such statistical characteristics that frequency distribution of short term concentration may be approximated by a lognormal distribution, were applied. This procedure is capable of estimating not only highest concentration for a variety of averaging times but also concentrations for arbitrary occurrence frequency. Evaluation of the procedure with the results of short term concentrations calculated by Texas Episodic Model version 8 using the meteorological data and emission data in Seoul shows that the procedure estimates concentrations fairly well for wide range of percentiles.

• Journal of Environmental Science International
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• v.25 no.1
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• pp.107-125
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• 2016

Long-term variations of $PM_{10}$ and the characteristics of local meteorology related to its concentration changes were analyzed at 4 air quality sites (Ido-dong, Yeon-dong, Donghong-dong, and Gosan) in Jeju during two different periods, such as PI (2001-2006) and PII (2007-2013), over a 13-year period. Overall, the long-term trend of $PM_{10}$ was very slightly downward during the whole study period, while the high $PM_{10}$ concentrations in PII were observed more frequently than those in PI. The concentration variations of $PM_{10}$ during the study period was clarified in correlation between $PM_{10}$ and meteorological variables, e.g. the low (high) $PM_{10}$ concentration with large (small) precipitation or high (low) radiation and in part high $PM_{10}$ concentrations (especially, Donghong-dong and Gosan) with strong wind speed and the westerly/northwesterly winds. This was likely to be caused by the transport effect (from the polluted regions of China) rather than the contribution of local emission sources. The $PM_{10}$ concentrations in "Asian dust" and "Haze" weather types were higher, whereas those in "Precipitation", "Fog", and "Thunder and Lighting" weather types were lower. The contribution of long-range transport to the observed $PM_{10}$ levels in the urban center (Ido-dong, Yeon-dong, and Donghong-dong), if estimated by comparison to the data of the background site (Gosan), was found to explain about 80% (on average) of its input.

• Journal of Soil and Groundwater Environment
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• v.17 no.3
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• pp.21-31
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• 2012

This paper presents the short-term and long-term measures to determine the fugitive dust concentration in a contaminated site, which is a crucial step for the determination of particulate emission factor (PEF) for risk assessment. As a long-term measure, USEPA method employing Q/C value (inverse of the ratio of the geometric mean air concentration to the emission flux at center of a 0.5-acre square source) seems to be suitable as it reflects regional-specific meteorological conditions. However, it requires nation-wide database collection and interpretation. Use of ASTM method is an alternative as a short-term measure. The method is readily field-applicable as PEF calculation equation is simple and input parameters can be easily derived at the site of interest as well without the nation-wide efforts. Using ASTM method, PEF at the Former Janghang Smelter Site was determined. According to various mode of aggregate size distribution and fractions of vegetative cover, which are the most important factors in PEF calculation, PEF values at the Former Janghang Smelter Site varied greatly. When the mode of aggregate size distribution was set at 0.25 mm, PEF values at the Former Janghang Smelter Site was 5~20 times higher than the default PEF value (i.e., 35 ${\mu}g/m^3$) shown in the current Korean Soil Contamination Risk Assessment Guidance. On contrast, when the mode was set at 2 mm, PEF values at the Former Janghang Smelter Site was 160~640 times lower than the default PEF value in the Korean Guidance.

• New & Renewable Energy
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• v.16 no.4
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• pp.9-22
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• 2020

This study analyzed the short- and long-term effects of nuclear and renewable energy generation on CO2 emissions in Korea, Japan, and Germany from 1987 to 2016 by using the unit root test, Johansen cointegration test, and ARDL model. The unit root test was performed, and the Johansen cointegration test showed cointegration relationships among variables. In the long run, in Germany, the generation of both nuclear and renewable energy was found to affect CO2 emission reduction, while South Korea's renewable energy generation, including hydropower, increased the emissions. Japan only showed significance in fossil fuels. In the short run, in the three countries, the generation of nuclear and renewable energy, excluding hydropower, affected CO2 emission. However, in Korea and Germany, nuclear and renewable energy generation, respectively, affected CO2 emission reduction. Although the rest are significant, the results showed that they increased CO2 emissions.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2000.04a
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• pp.51-56
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• 2000

Demand for new nondestructive evaluations is growing to detect tensile crack growth behavior to predict long term performance of materials and structure in aggressive environments, especially when they are in non-visible area. Acoustic emission technique is well suited to these problems and has drawn a keen interests because of its dynamic detection ability, extreme sensitivity and location of growing defects. In this study, we analysed acoustic emission signals obtained in tensile test of high strength fire resistance steel for frame structure with time frequency analysis methods. The results obtained are summaries as follows ; In the T and TN specimen consisting of ferrite and pearlite grains, most of acoustic emission events were produced near yield point, mainly due to the dislocation activities during the deformation. However, B specimen under $600^{\circ}C$ - 10min had a two peak which was attribute to the presence of martensite phase. The first peak is before yield point the second is after yield point. The sources of second acoustic emission peak were the debonding of martensite-martensite interface and the micro-cracking of brittle martensite phase. In $600^{\circ}C$-30min to $700^{\circ}C$-60min specimens, many signals were observed from area before yield point and counts were decreased after yield point.

• Journal of Astronomy and Space Sciences
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• v.33 no.3
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• pp.177-183
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• 2016

Active galactic nuclei (AGN) are too compact to be resolved by any existing optical telescope facility, making it difficult to understand their structure and the emission processes responsible for their huge energy output. However, variability, one of their characteristic properties, provides a tool to probe the inner regions of AGN. Blazars are the best candidates for such a study, and hence a considerable amount of effort is being made to investigate variability in these sources across the electromagnetic spectrum. Here, using the Mt. Abu infrared observatory (MIRO) blazar monitoring program, we present intra-night, inter-night, and long term aspects of the variability in S5 0716+71, 3C66A, and OJ 287. These stars show significant variability on short (a few tens of mins, to a few hours, to a few days) to long term (months to years) timescales. Based on the light travel time argument, the shortest variability timescales (micro-variability) provide upper limits to the size of the emission region. While S5 0716 shows a very high duty cycle of variability (> 80 %), 3C66A shows a much lower intra day variability (IDV) duty cycle (< 20 %). All three show rapid variations within 2.5 to 3.5 hr, which, perhaps, are generated near the vicinity of black holes. Assuming this, estimates of the masses of the black holes are made at ~10⁹, 8×10⁸, and 2.7×10⁹ M_⨀ for S5 0716+71, 3C66A, and OJ 287, respectively. Multi-wavelength light-curves for the blazar PKS 1510-089 are discussed to infer the emission processes responsible for the recent flaring episodes in this source.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.312-316
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• 2014

Photoemission is a process in which photons are converted into free electrons. Photocathodes are the typical materials for the process. They emit electrons when a light is irradiated upon. The traditional method of manufacturing photocathodes is complicated, requires specialized equipment, and is limited very small sized samples. $Cs_3Sb$ photocathode was formed on a substrate in $N_2$ atmospheric conditions. The photocathode formation was a gas phase reaction with the substrate. Vacuum devices were made to test electron emission characteristics of the formed photocathode. Visible light of wavelength 475 nm was used for the primary light source. The results showed high current density and long term stability of the photoelectron emission.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.534-541
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• 2012

This paper tries to elicit an optimal generation mix of Korea. Two approaches, using the screening curve method and taking advantage of a generation expansion planning tool, WASP-IV, are applied in getting the mix. The data used in this study is based on the 5th basic plan for long-term electricity supply and demand. The Load Duration Curve, that is needed for applying Screening Curve Method(SCM), is made based on the load profile in 2010. In our using SCM, the nuclear plant's operation characteristic, carbon emission cost and spinning reserve are considered. In using WASP-IV to get the adequate generation mix, the base and target demand forecasts in the 5th basic plan are used and the carbon emission cost is also considered. In this paper, It introduces the domestic adequacy generation mix in 2024 though SCM and WASP-IV.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2010.04a
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• pp.41-44
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• 2010

Hazardous air pollutants such as benzo[a]pyrene (BaP), benzene, formaldehyde have been concerned about the adverse health effect of long-term exposure. Contour map is useful for finding high-concentration region, emission source, and distributions of HAPs in the ambient air. To make a contour map, we have developed simple analytical method for selected HAPs; polycyclic aromatic hydrocarbons such as BaP, benzene and its derivatives such as toluene and xylene, and aldehydes and ketones. We have applied these methods to investigate air pollution by HAPs in some cities in Japan. The results show that these methods reveal actual emission sources if the PRTR emission report was not submitted.