• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.9
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• pp.868-882
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• 2009

In this paper, channel model and wireless link performance analysis for the short-range wireless communication system applications in the terahertz frequency which is currently interested in many countries will be described. In order to realize high data rates above 10 Gbps, the more wide bandwidths will be required than the currently available bandwidths of millimeter-wave frequencies, therefore, the carrier frequencies will be pushed to THz range to obtain larger bandwidths. From the THz atmospheric propagation characteristics based on ITU-R P.676-7, the available bandwidths were calculated to be 68, 48 and 45 GHz at the center frequencies of 220, 300 and 350 GHz, respectively. With these larger bandwidths, it was shown from the simulation that higher data rate above 10 Gbps can be achieved using lower order modulation schemes which have spectral efficiency of below 1. The indoor propagation delay spread characteristics were analyzed using a simplified PDP model with respect to building materials. The RMS delay spread was calculated to be 9.23 ns in a room size of $6\;m(L){\times}5\;m(W){\times}2.5\;m(H)$ for the concrete plaster with TE polarization, which is a similar result of below 10 ns from the Ray-Tracing simulation in the reference paper. The indoor wireless link performance analysis results showed that receiver sensitivity was $-56{\sim}-46\;dBm$ over bandwidth of $5{\sim}50\;GHz$ and antenna gain was calculated to be $26.6{\sim}31.6\;dBi$ at link distance of 10m under the BPSK modulation scheme. The maximum achievable data rates were estimated to be 30, 16 and 12 Gbps at the carrier frequencies of 220, 300 and 350 GHz, respectively, under the A WGN and LOS conditions, where it was assumed that the output power of the transmitter is -15 dBm and link distance of 1 m with BER of $10^{-12}$. If the output power of transmitter is increased, the more higher data rate can be achieved than the above results.

• Journal of the Korean earth science society
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• v.29 no.6
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• pp.495-505
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• 2008

The main purposes of this study are to: (1) to develop astronomy observation program based on a standardized coefficient decision program; and (2) to apply the developed program to after-school or club activities. As a first step, we analyzed activities related to astronomy in the authorized textbooks that are currently adopted in high schools. based on the analysis, we developed an astronomy observation program according to the standardized coefficient decision program, and the program was applied to students' astronomical observations as part of the club activities. Specifically, this program used a 102 mm refracting telescope and digital camera. we took into account the observation site's environment of the urban areas in which many school were located and then developed a the computer program for observation activities. The results of this study are as follows. First, the current astronomical education in schools was based off of the textbooks. Specifically, it was mostly about analyzing the materials and making simulated experiments. Second, most schools participated in this study were located in urban areas where students had more difficulty in observation than in rural areas. Third, an exemplary method was investigated in order to make an astronomical observation efficiently in urban areas with the existing devices. In addition, the standardized coefficient decision program was developed to standardize the magnitude of stars according to the observed value. Finally, based on the students' observations, we found that there was no difference between the magnitude of a star in urban sites and in rural sites. The current astronomical education in schools lacks an activity of practical experiments, and many schools have not good observational sites because they are located in urban areas. However, use of this program makes it possible to collect significant data after a series of standardized corrections. In conclusion, this program not only helps schools to create an active astronomy observation activity in fields, but also promotes students to be more interested in astronomical observation through a series of field-based activities.

• Journal of the Korean earth science society
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• v.34 no.7
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• pp.693-710
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• 2013

This study investigates the distribution of suspended particulates during the Asian dust period in Busan, Korea in the spring of 2009. Weather map and automatic weather system (AWS) data were used to analyze the synoptic weather conditions during the period. Particulate matter 10, laser particle counter data, satellite images and a backward trajectories model were used to analyze the aerosol particles distribution and their origins. In Case 1 (20 February 2009), when the $PM_{10}$ concentration increased, the aerosol volume distribution of small ($0.3-1.0{\mu}m$) particles decreased, while the concentration of large ($1.0-10.0{\mu}m$) particles increased. When the $PM_{10}$ concentration decreased, the aerosol volume distribution was observed to decrease as well. The prevailing winds changed from weak northerly winds to strong southwesterly winds when the concentration of the large particles increased. The correlation coefficient between the $PM_{10}$ concentration and aerosol volume distribution of large particles showed a high positive value of over 0.9. The results from the trajectory model show that the Asian dust originated in the Gobi desert and the Nei Mongol plateau. In Case 2 (25 April 2009), when the $PM_{10}$ concentration increased, the aerosol volume concentration of small ($0.3-0.5{\mu}m$) particles decreased, but the concentration of large ($0.5-10.0{\mu}m$) particles increased. The opposite was observed when the $PM_{10}$ concentration decreased. The prevailing winds changed from northeasterly winds to southwesterly and northeasterly winds. The correlation coefficient between the $PM_{10}$ concentration and aerosol volume distribution of large particles ($1.0-10.0{\mu}m$) showed a high positive value of about 0.9. The results from the trajectory model show that the Asian dust originated in Manchuria and the eastern coast of China.

• Journal of the Korea Concrete Institute
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• v.21 no.1
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• pp.85-92
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• 2009

A concrete is considered unfriendly-environmental material because it uses cement which emits much $CO_2$ during producing process. However, a concrete absorbs $CO_2$ through carbonation process during service life. In this paper how much concrete absorbs $CO_2$ through carbonation was calculated using 1) concentration of carbonatable substances in concrete, 2) carbonated volume of concrete, 3) molecular weight of $CO_2$ based on references and the method was proposed. $CO_2$ emission from producing $1m^3$ concrete was calculated based on $CO_2$ emission datum of materials used in concrete. From using these methods that calculate $CO_2$ emission and absorption of concrete, assessment of $CO_2$ emission-absorption against a real apartment was conducted by subtracting absorption $CO_2$ according to service life from $CO_2$ emission in the process of making concrete. As a result, a ratio of absorption over emission of $CO_2$ through concrete carbonation according to service life 40, 60, 80 years was assessed about 3.65, 4.47, 5.18%. An objective of this study is to propose how to calculate emission - absorption of $CO_2$ from producing and using concrete. Although the result value, emission - absorption of $CO_2$, is 5.18% very low when the service life of an apartment is 80years, the value can be improved by reducing emission from using blended cement such as blast furnace slag or increasing replacement ratio of cement and increasing carbonated volume of concrete from expanding service life of a building. This study may be useful when $CO_2$ emission - absorption of concrete is evaluated in the further study.

• KDI Journal of Economic Policy
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• v.30 no.1
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• pp.1-31
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• 2008

Various opinions have been suggested to explain the slump in equipment investment, such as increased government regulations, shareholder-oriented management by expanded foreign equity investment, response against M&A threats, conservative investment trends seen after a series of bankruptcy of large conglomerates (amidst crumbling myth of "Too Big to Fail"), and financial restructuring. Some also argued that the increased uncertainty in business environment is mainly responsible for conservative management, though there are few domestic studies made regarding the situation. But, in other countries, including the U.S., studies have shown that more volatility is seen now surrounding stock prices, profitability, and sales growth rate reflecting business performance. Also, there are other studies showing such expanded volatility have led to conservative management by businesses. In this regard, this study reviews the volatility conditions of business performance of Korean companies based on profitability, and then attempts to analyze the impact on investment brought on by increased volatility. Each company's profitability volatility used here is from the standard deviation of companies for the past five years. As a profitability indicator, the ROA (= operating profit/total asset) is used. According to the analysis, profitability volatility has remarkably increased from the mid 3% in 1994 to low 5% in 2005. Profitability volatility of the Korean companies has expanded to a great extent since the financial crisis. The crisis might have served to raise the volatility in the macroeconomic conditions. If increased volatility observed during the economic crisis had gradually declined after the crisis, the situation could be interpreted as a temporary phenomenon, not to be too concerned over. But, this was not the case for Korea. The volatility level, after the crisis, has not dropped back to its pre-crisis level. Hence, in the Korea's case, high volatility cannot be explained by the impact of financial crisis. Not only that, the fact that such expansion is seen in every industrial sector indicates that this phenomenon cannot be explained by the composition change of industries alone. An undergoing study shows that with a rapid spread of globalization, industries fiercely competing with China experience more volatility. Such increased volatility tends to contract investment, and since the crisis the impact of volatility on investment has slightly increased. It is noteworthy that this study only includes a part of 'uncertainty' that could be measured statistically. For instance, the profitability volatility indicator used in this study is unable to reflect all the effects that the tacit reduction of protection by the government or regulations might have made. So, the result here also indicates that other 'uncertain' factors not mentioned in this study may have served to contract investment sentiment. It would be impossible for policies to completely remove uncertainties measured by profitability volatility, but at least it is necessary to put effort to reduce the macroeconomic volatility in the future economic management. Stabilized macroeconomic management may not be enough to diminish all volatility that occurs within each company, but it would make a meaningful contribution in encouraging investment.

• Journal of the Korean Institute of Landscape Architecture
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• v.47 no.6
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• pp.12-23
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• 2019

The purpose of this study was to develop and study an experiential natural education program that could emphasize the importance of the natural environment by providing natural experience opportunities using the natural resources of the urban forest parks using Youngheung Park in Suwon, Gyeonggi Province as a target site. The research target was limited to Suwon Yeongheung Park, which had the potential to become a place for education, where urban forest conservation and sustainable use already coexist. The natural education resources derived by surveying and analyzing the basic environment and the ecology of plants and animals in Suwon Yeongheung Park were organized to establish program goals, directions, and themes. Suwon Yeongheung Park is a water-rich forest that forms an ecological system of wetlands, including rice paddies, muknon wetlands, and dungbun, near a valley area. The U-shaped walkway was smoothly formed along the ridge and includes Doran-gil, which is among the Palochrome Road, designated by the city of Suwon. The soil is acidic, with a pH 4.40, due to urban pollution and acid rain, and is not good for plant growth. Most of the artificial forests, natural forests, and arable land were found using land use and extant life surveys. Old trees were distributed in artificial forests, the oak clusters in natural forests, and the fields and darrinones were distributed in the arable areas. As the forest vegetation declined, the cedar forest was underway, and the cedar trees and red bean pear trees were cultivated due to their adaptability to the urban environment. There are 13 large of 180 sacks, one being 109 centimeters in diameter, the largest silvery tree, and 105 oak trees, provide food and shelter for animals. Six species of waterfowl that used the 22 kinds of forest wetlands, while four species of amphibians and two species of reptiles reside in the wetlands. Natural Monument No. 327, Mauryuk, Class II Endangered Wildlife, was also observed in the wetlands. Eight other species of surface dragonflies and three species of butterflies were observed. By systemizing the resources, members, and characteristics of the forest ecosystems in Suwon Yeongheung Park based on five criteria, the program for a hands-on natural education was presented with the aim of understanding the urban forest ecosystem in Suwon Yeongheung Park, having an affinity with the city, and recognizing its relationship with the community and society. However, further research is needed as there are limitations of research on programs characterized by different ages and classes.

• The Korean Journal of Ecology
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• v.25 no.3 s.107
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• pp.189-195
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• 2002

In order to elucidate the budget and cycling of Nitrogen and Sulfur, essential elements and principal constituents of acid rain, their input through precipitation, and their output by streamflow were quantified in coniferous and deciduous forested watersheds, using combination of nutrient concentration and hydrological analysis, in Kwangnung Experimental Forest from July 1991 to December 1993. Amount of annual mean precipitation was $12,916\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$, annual mean runoff $5,094\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$(39%), $7,467\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$(59%) in coniferous and deciduous forest watersheds, respectively. Amounts of annual input of $N({NO_3}^-+{NH_4}^+)$ and ${SO_4}^{2-}$ through preciptation were 12.5, $81.72\;kg{\cdot}ha^{-1}{\cdot}yr^{-1}$, repectively. Annual output via runoff of $N({NO_3}^-+{NH_4}^+)$ and ${SO_4}^{2-}$ were 0.06, $39.23\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$ in the coniferous forest watershed ecosystem, and 0.15, $55.46\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$ in the deciduous one, respectively. On the basis of annual nutrient input and output, the annual budget of $N({NO_3}^-+{NH_4}^+)$ and ${SO_4}^{2-}$ were +12.46, $+42.49\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$ in the coniferous forest watershed, and +11.35, $+26.26\;ton{\cdot}ha^{-1}{\cdot}yr^{-1}$ in the deciduous one. Thus $N({NO_3}^-+{NH_4}^+)$ and ${SO_4}^{2-}$ were accumulated in both forested watershed ecosystems.

• Journal of the Korean earth science society
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• v.26 no.1
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• pp.93-105
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• 2005

Climatological characteristics in the variation of soil temperatures in Korea were investigated using Korea Meterological Administration's observation data. And the impacts of soil moisture on the variation of soil temperature were examined using observed precipitation data. The climatological averages of soil temperatures are ranged from 14.4 to $15.0^{\circ}C$ regardless of depths. And they showed an latitudinal gradient with a warm temperature at the southern region and 'U' shape as in the air temperature with a high value along the coastal region. The relatively higher heat capacity and low conductivity of soil compared to those of the air resulted in the significant delay of the maximum and minimum date with depth. As a results, soil acts as a heat source during winter while a heat sink during summer. Global warming and urban heat island have increased the soil temperatures with an average rate $0.3\~0.5^{\circ}C/10-year$ as in the air temperature during last 30 years $(1973\~2002)$. However, the warming rate is maximized during spring contrary to the winter in the air temperature. The temporal variation of soil temperatures is strongly affected by that of soil moisture through an modification of the heat capacity and heat convection. In general, the increased soil moisture clearly decreased the temporal variations and increased the deep layer soil temperatures during cold season.

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.469-479
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• 2001

This study investigated the trends in the number of applicants and mean score and applicants’ responses on the test items of Earth Science in the College Scholastic Ability Test (CSAT) implemented for 3 years (1999-2001). The percentage of applicants of science track were 43.14% in 1995, but reduced through 29.5% in 2001 to 26.92% in 2002 CSAT For elective subject, about 22% of science track students applied to Earth Science II which ranked third to Biology II and Chemistry II. In 1999, test items were developed to have the expected difficulty 40 ${\sim}$ 59% (6 items) to 60 ${\sim}$ 79% (10 items). But in 2001 every 16 items were developed to have difficulty 60 ${\sim}$ 79%, which was caused by the policy of so called ‘easy CSAT’. Thus the mean score of ‘Earth Science II’ was increased from 50.26 in 1999 through 64.47 in 2000, to 67.58 in 2001. Applicants were generally very good at solving test items focusing on process skills only and familar items but poor at solving test items related to the motion of the earth and planets and sea wave, especially items calling two or more concepts. Thus special measures to cope with the decrease in applicants of science track should be provided. And it is recommended to develop test items with wider range of difficulty and to reduce test items calling process skills only. And special consideration should be given to teaching the content area with poor achievement and high actual difficulty compared to the expected.

• Journal of the Korean earth science society
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• v.21 no.2
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• pp.137-158
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• 2000

The correlation and Empirical Orthogonal Function (EOF) analyses over the globe have been applied to intercompare lower-stratospheric (${\sim}$70hPa) temperature obtained from satellite data and two model reanalyses. The data is the19 years (1980-98) Microwave Sounding Unit (MSU) channel 4 (Ch4) brightness temperature, and the reanalyses are GCM (NCEP, 1980-97; GEOS, 1981-94) outputs. In MSU monthly climatological anomaly, the temperature substantially decreases by ${\sim}$21k in winter over southern polar regions, and its annual cycle over tropics is weak. In October the temperature and total ozone over the area south of Australia remarkably increase together. High correlations (r${\ge}$0.95) between MSU and reanalyses occur in most global areas, but they are lower (r${\sim}$O.75) over the 20-3ON latitudes, northern America and southern Andes mountains. The first mode of MSU and reanalyses for monthly-mean Ch4 temperature shows annual cycle, and the lower-stratospheric warming due to volcanic eruptions. The analyses near the Korean peninsula show that lower-stratospheric temperature, out of phase with that for troposphere, increases in winter and decreases in summer. In the first mode for anomaly over the tropical Pacific, MSU and reanalyses indicate lower-stratospheric warming due to volcanic eruptions. In the second mode MSU and GEOS present Quasi-Biennial Oscillation (QBO) while NCEP, El Ni${\tilde{n}}$o. Volcanic eruption and QBO have more impact on lower-stratospheric thermal state than El Ni${\tilde{n}}$o. The EOF over the tropical Atlantic is similar to that over the Pacific, except a negligible effect of El Ni${\tilde{n}}$o. This study suggests that intercomparison of satellite data with model reanalyses may estimate relative accuracy of both data.