• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.131-138
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• 2010

This research intends to analyze the basic characteristics of cements(hereinafter "CC") with affordable price and particle distribution effective as hydration heat face which are discharged at the outlet of smashing process of ordinary portland cement(hereinafter "OPC") manufacturing process such as fluidity, rigidity, temporary insulation temperature increase amount etc to review the potential of developing "CC" to 3 ingredients low heat cement that substitutes fly ash and blast furnace slag(hereinafter "BS"). As a result of experiment, fluidity tended to decrease with increase in CC substitution rate, and increase with increase in FA+BS substitution rate. Air amount tended to slightly decrease with increase in CC substitution rate, and decrease with increase in FA+BS substitution rate. Condensation characteristics were such that condensation time was delayed with increase in CC and FA+BS substitution rate. As for the temperature rising amount by temporary insulation, peak temperature decreased with increase in CC substitution rate and increase in FA+BS substitution rate in general, and thereafter, temperature tended to decrease slowly. Compressive strength decreased with increase in CC and FA+BS substitution rate, and as aging goes on, long term strength was equivalent to plain or higher. By and large, when FA+BS was substituted to CC, fluidity and air amount tended to decrease, but hydration heat face showed good reduction effects, suggesting possibility of development to 3 ingredients low heat cement.

• Journal of Energy Engineering
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• v.24 no.1
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• pp.104-113
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• 2015

This study tried to conduct a comparative analysis on the yearly economic effects of petroleum products sector. Inter-industry tables published 1990~2012 are used in this study. Especially petroleum products sector is specified as exogenous to identify the economic effects on own and other sectors. Production-inducing effect, value-added creation effect, and employment-inducing effect are quantified based on demand-driven model. The results of the analysis, the case of annual production inducing-effect, show the downward trend from 1993 to 2008. and It seemed to be constant from 2009 to 2012. The value-added inducing-effect, from 1990 to 1998, shows a rising trend. the since 1998, it was found to decline steadily. Employment-inducing effect is shown a steadily decreasing trend from 1990 to 2008, and has been kept constant from 2010 at the level under 1.300(person/one billion won). These results of in comparison with the past are significant in that it can be objectively evaluate the domestic oil industry at the present time. and it can be usefully utilized to predict the economic effect of future oil industry.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.4
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• pp.165-173
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• 2005

Field observations have been conducted to investigate the physical environment around oyster farms in Gamak Bay. Tidal waves near the two channels at the northeast and south of the bay had almost the same amplitudes and phases. Water temperature responded sensibly to the tides, rising at high water and falling at low water, except for the northwest region. The currents more regularly varied in accordance with a tidal period as long as they are at the faster-flowing region. A considerable flow has been found near the seabed of the northwest of the bay, normally known to be a stagnant area, and also the flow was opposite to the surface flow. Average moving speeds and directions of the flow at each station coincided well with patterns of the residual currents computed by Lee ef al. [2004], except for the northwest region. The discrepancy for the northwest region is not clear but it may have resulted from the facts that the computed flow pattern represents only the case of spring tide and in addition, a northwesterly wind prevailed all the observation time.

• Cross-Cultural Studies
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• v.44
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• pp.373-391
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• 2016

Since the 2000's, interest toward Africa in Korea has increased rapidly. Korea's interest in Africa began in the second half of the 1960's. However, this interest in the 1960's was motivated by political and diplomatic necessity at the time rather than the needs of indigenous groups in Africa. Korea had to oppose North Korea's diplomatic expansion in Africa to gain the support of international organizations like the United Nations. This interest in Africa motivated by diplomatic needs vanished quickly after the end of the cold war in the 1990's. Authentic Korean interest in Africa began to emerge in the 2000's. Korea's rising international status based on economic development led to a natural interest in Africa, which was the last frontier on earth. As a result, African studies in Korea increased significantly after 2010. The increase in the number of theses, articles and books was remarkable from 2010-2016, in comparison with 1957-2010. In spite of the increase in the quantity of thesis, articles, and books, the problem with Korea's African studies is above all, its preponderance. Over 75% of thesis and 70% of articles are concentrated in the domain of politics and economics. This reflects the fact that Korea's interest in Africa is based on short term political and economic interest, indicating that Korea's African studies did not deviate from the rudimentary phase in its quantity and quality. Another problem with Korea's African studies is the lack of integration of different types of research. African studies in Korea has three components, government funded research centers, university laboratories and individual researchers. The government funded research centers focus on the overview of African nations and their political and economic information. University laboratories mainly perform research on the theoretical aspects of politics, economics, human sciences and culture in Africa. Individual researchers are concerned with various categories. However, these three groups have failed to achieve a synergic effect on African studies in Korea and most of the research on Africa does not extend beyond each academic area. To overcome this problem, first of all, a live exchange may be necessary between domestic researchers.

• Journal of Convergence for Information Technology
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• v.9 no.12
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• pp.141-146
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• 2019

Economic analysis predicts that the drone market will grow, and the growth of the toy and hobby drone market is expected to gradually expand. Drone expectations are rising due to the net economic function of drone market growth, but accidents due to improper management and operations are also increasing. The difference in toy drone performance is incomparably small compared to industrial drone performance, but the ordinary buyer can not know whether the difference can cause an accident during use. The toy drones used in this study were obtained from KC and CE certification, and 20 kinds of drones were used. The flight time ranged from a minimum of 3 minutes to a maximum of 12 minutes, and the control distance ranged from a minimum of 20m to a maximum of 380m. Therefore, it is necessary to secure product safety through sampling inspection of the radio wave output of toy drones, and it is also necessary to mount an algorithm that automatically lowers the altitude or hover when exceeding the limit flight distance. For future research, we will build data to establish toy drone safety standards through a altitude testing and impact testing of toy drone.

• Journal of Korea Water Resources Association
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• v.54 no.12
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• pp.1205-1214
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• 2021

Precipitation is one of a major causes of landslides by rising of pore water pressure, which leads to fluctuations of soil strength and stress. For this reason, precipitation is the most frequently used to determine the landslide thresholds. However, using only precipitation has limitations in predicting and estimating slope stability quantitatively for reducing false alarm events. On the other hand, Soil Moisture (SM) has been used for calculating slope stability in many studies since it is directly related to pore water pressure than precipitation. Therefore, this study attempted to evaluate the appropriateness of applying soil moisture in determining the landslide threshold. First, the reactivity of soil saturation level to precipitation was identified through time-series analysis. The precipitation threshold was calculated using daily precipitation (P_daily) and the Antecedent Precipitation Index (API), and the hydrological threshold was calculated using daily precipitation and soil saturation level. Using a contingency table, these two thresholds were assessed qualitatively. In results, compared to P_daily only threshold, Goesan showed an improvement of 75% (P_daily + API) and 42% (P_daily + SM) and Changsu showed an improvement of 33% (P_daily + API) and 44% (P_daily + SM), respectively. Both API and SM effectively enhanced the Critical Success Index (CSI) and reduced the False Alarm Rate (FAR). In the future, studies such as calculating rainfall intensity required to cause/trigger landslides through soil saturation level or estimating rainfall resistance according to the soil saturation level are expected to contribute to improving landslide prediction accuracy.

• Korean Journal of Heritage: History & Science
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• v.39
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• pp.131-163
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• 2006

Interest in Korean cultural properties has rising in recent years, not only on the part of existing researcher and scholars but also among the general public. The scope of interest has expand also, no longer being confined to Korea, and has given rise to movements for redemption of cultural properties preserved overseas and plans on how to make use of information about them. Aside from the basic idea that all cultural properties overseas are subjects for redemption, this paper argues that it is time to seek ways to actively make use of information on those cultural properties, and that this must be preceded by dear understanding of the current status through systematic on-site research and investigation of the channels through which they left the country. In addition, it is necessary to look at the issue with a broader perspective. The cultural properties in question must be regarded not as the sole property of Korea, the country that produced them, but as artworks of the world with outstanding universal value, to be protected and utilized by all human beings. From this point of view, this paper organize studies the kinds of Korean cultural properties kept at three major museums in the United Stated, including the Museum of Fine Arts, Roston, and traces the routes and methods by which they were taken out of Korea. Based on the perception of Korean artworks overseas as explained above, the purpose of this paper is to examine materials those cultural properties not only for academic research, but also todistinguish between those properties that should be redeemed and those that should be publicized overseas by clarifying how they were taken overseas, and thus provide basic materials for policy purposes.

• Journal of Korean Society of Forest Science
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• v.110 no.1
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• pp.13-21
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• 2021

In this research, monoterpene emissions were investigated from pine trees(Pinus densiflora) and in the forest air in Simwon village at the Jiri Mountain. Air samples from an enclosed chamber and pine forest air were collected using a Tenax TA Tube five times a day(at 09:00, 11:00, 13:00, 15:00, and 17:00) on 1 day per month from March to November 2014. Selected needles and branches from individual pine trees were enclosed for the measurement of their monoterpene emissions. The concentration and composition of emitted monoterpenes were analyzed in a time series. The major components of monoterpenes emitted from pine trees were α-pinene, β-myrcene, β-phellandrene, and β-pinene. Seasonal data showed that the concentration of monoterpenes emitted from pine trees began increasing in June and reached its peak in August, decreasing thereafter. In addition, seasonal emissions of monoterpenes were dependent on environmental factors such as temperature. The major species of monoterpenes in forest air were α-pinene, β-pinene, and camphene. The concentration of monoterpenes in forest air began rising from March to April and reached its peak in May; multiple peaks subsequently formed in July and November. Diurnal variation in monoterpenes decreased from 09:00-10:00, reaching a low and high at 13:00-14:00 and 17:00-18:00, respectively.

• Journal of the Korean Association of Geographic Information Studies
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• v.25 no.1
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• pp.16-27
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• 2022

Due to climate change, temperature is rising worldwide. Since rapid growth has been achieved focused on cities, South Korea is experiencing serious environmental problems such as heat island and air pollution in urban areas. To solve this problem, the central and each local government are actively promoting tree planting campaigns. This study quantitatively calculated changes in green areas and vegetation of Gumi by the tree planting campaign, and analyzed the temperature changes accordingly. For the target area, the green area, vegetation index, and ground temperature were calculated for 4 different time periods using the given Landsat satellite images. As a result of the study, the green area of was increased by 7.24km² and 4.93km² for two regions, respectively. Accordingly, the vegetation index increased by 0.14 to 0.16, and the temperature decreased by 0.8 to 1.2℃. The Tree planting campaign not only plays a role in lowering the temperature of the city but also does various roles such as air purification, carbon absorption, and providing green rest areas to citizens. Therefore the campaign should be carried out continuously.

• The Journal of Engineering Geology
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• v.31 no.1
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• pp.67-81
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• 2021

Grouting is used for reinforcement and waterproofing of soft ground to increase its bearing capacity, reduce the impacts of rising or lowering groundwater levels, and reduce subsidence due to vibration and general causes. This study investigated the enhancement of grout strength and hardening time by the addition of reinforcing fibers, and the development of non-cement grouting materials from blast furnace slag. An experiment was performed to measure the increase in grout strength resulting from the addition of 0.5% increments of aramid and carbon reinforcing fibers. The results show that the uniaxial compressive strength of grout increases with increasing content of reinforcing fiber. Comparison of three admixtures of finely powdered blast furnace slag and 10%, 20%, and 30% calcium hydroxide stimulating agent showed that the uniaxial compressive strength of the mixture increases with increasing content of alkaline stimulant; however, the strength was lower than for 100% pure cement. The reaction of calcium hydroxide with blast furnace slag powder, which increases the strength of the grout, is more effective if injected as a solution rather than a powder.