• Journal of Digital Convergence
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• v.16 no.8
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• pp.169-179
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• 2018

Recently, web search query information has been applied in advanced predictive model research. Google dominates the global web search market in the Korean market; however, Naver possesses a dominant market share. Based on this characteristic, this study intends to compare the utility of the Korean web search query information of Google and Naver using predictive models. Therefore, this study develops three time-series predictive models to estimate the youth unemployment rate in Korea using the ARIMA model. Model 1 only used the youth unemployment rate in Korea, whereas Models 2 and 3 added the Korean web search query information of Naver and Google, respectively, to Model 1. Compared to the predictability of the models during the training period, Models 2 and 3 showed better fit compared with Model 1. Models 2 and 3 correlated different query information. During predictive periods 1 (continuous with the training period) and 2 (discontinuous with the training period), Model 3 showed the best performance. During predictive period 2, only Model 3 exhibited a significant prediction result. This comparative study contributes to a general understanding of the usefulness of Korean web query information using the Naver and Google search engines.

• Korean Journal of Remote Sensing
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• v.36 no.5_1
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• pp.735-747
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• 2020

Recent advanced UAV (Unmanned Aerial Vehicle) technology supply new opportunities for estimating crop condition using high resolution imagery. We analyzed the diurnal change of reflectance and NDVI (Normalized Difference Vegetation Index) in UAV imagery for crop monitoring in clear day condition. Multi-spectral images were obtained from a 5-band multi-spectral camera mounted on rotary wing UAV. Reflectance were derived by the direct method using down-welling irradiance measurement. Reflectance using UAV imagery on calibration tarp, concrete and crop experimental sites did not show stable by time and daily reproducible values. But the CV (Coefficient of Variation) of diurnal NDVI on crop experimental sites was less than 5%. As a result of comparing NDVI at the similar time for two day, the daily mean average ratio of error showed a difference of 0.62 to 3.97%. Therefore, it is considered that NDVI using UAV imagery can be used for time series crop monitoring.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.3
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• pp.229-234
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• 2002

Nowadays, the blast method is mainly operated in the fields of the rock excavation accompanied by construction site in Korea. Blast method has many merits such as improvement of workability, reducement of operation period, and etc. However, blast operation also create much loss and troubles with the neighbours for the environmental pollutions such as the noise, blast vibration, fly rocks and dusts. Thus, the non-vibration and shallow vibration methods have been used but they have also another problems in the view of the economy and the efficiency in operation. In this study, we had made laboratory tests for the breaking of the various Rock types by White Light Thermal Stress. The tests shows that one unit consuming 500kilowatts of electricity, would go 90 feet a day in tunneling if the tunnel was 16 feet by 16 feet. Also, if a faster rate of tunneling could be handled, other white light units could be added.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.6
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• pp.578-586
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• 2005

Recently, due to the launch of digital broadcasting service, the demand of Flat Panel Display (FPD) is sharply rising. Among them, the PDP is expected to be one of the most promising digital displays of next generation because of its large screen size, high resolution, thinness and board field of view. Meanwhile, the PDP uses ADS (Address Display-period Separation) scheme which divide one subfield into address and sustaining period to express the grey scale of images. Since the output of sustaining power module Is mostly used for sustaining period, the load of the sustaining power module can be considered as a pulsating load. Due to this particular load condition, if the wide ZVS range of the power switches is not guaranteed, the hard switching causes large amount of switching loss and serious thermal problem in power module. In this paper, a high efficiency power conversion circuit for 60' PDP sustaining power module which achieves wide ZVS range with the help of additional ZVS tank is proposed. According to the various gating methods, the different operations of the proposed converter are presented. And, to confirm the properties of the proposed converter, an experimental prototype of 900W power converter is constructed md tested. As a result, more than $92\%$ of high efficiency is obtained at $10\%$ load condition, and the ZVS operation is achieved from full load to $10\%$ load condition.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.207-214
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• 2002

The purpose of this study was to examine the putter head movement during the putting strokes. Highly skilled 5 golfers(less than 3 handicaps) and 5 novice golfers(having no golf experience) participated in this study. A target distance was 3 m. Movements of the putter head were recorded at 60 Hz with two video cameras(1/500 shutter speed). The results showed that the angle of the clubface of expert golfers was almost 1 degree, but the novice golfers were more than 6 degrees. Expert golfers moved their hands faster than the head movement, therefore the clubface was not opened during impact. However, the novice golfers moved their hands slower than the head movement, therefore the clubface was opened during impact. The ratio of input and output angles of total movement was 1:3-4, however, the ratio of input and output angles of impact zone was 1:2. The angle of normal vector of expert golfers was less than the angle of normal vector of novice golfers.

• Journal of the Korean Chemical Society
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• v.35 no.3
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• pp.211-218
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• 1991

A series of samples in the $Nd_{-x}Sr_{x}CoO_{3-y}$ system (x = 0.00, 0.25, 0.50, 0.75 and 1.00) have been produced by heating the reactants at 1200${\circ}$C under atmospheric pressure. The solid solutions were analysed by X-ray diffraction spectra, thermal analysis, and SEM micrographs. X-ray powder diffraction assigns the compositions of x = 0.00, 0.25, 0.50 and 0.75 to the cubic system and the composition of x = 1.00 to the orthorhombic system. The reduced lattice volume is increased with increasing x values in the system. The mole ratio of $Co^{4+}$ or ${\tau}$ values are determined by the Iodometric titration method and are maximum at the composition of x = 0.50. The magnetic measurement shows that a ferromagnetism is appeared in the compositions of x = 0.00, 0.25, 0.50 and 0.75 and then an antiferromagnetism in the composition of x = 1.00. The measurement of the electrical conductivity shows that the semiconductivity is appeared in the composition of x = 0.00, 0.25 and 1.00 and the metallic conductivity in the composition of x = 0.50 and 0.75. The magnetic and electrical properties of the samples are discussed with the nonstoichiometric chemical formulas.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.21-30
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• 2008

The fuel cell generation convert fuel source, and gas directly to electricity in an electro-chemical process. Unlike traditional and conventional turbine engines, the process of fuel cell generation do not burn the fuel and run pistons or shafts, and it has not revolutionary machine, so have fewer efficiency losses, low emissions and no noisy moving parts. A high power density allows fuel cells to be relatively compact source of electric power, beneficial in application with space constraints. In this system, the fuel cell itself is nearly small-sized by other components of the system such as the fuel reformer and power inverter. So, the fuel cell energy's stationary fuel cells produce reliable electrical power for commercial and industrial companies as well as utilities. In this paper, a fuel cell system has been modeled using PSCAD/EMTDC to analyze its electric signals and characteristics. Also the power quality of the fuel cell system has been evaluated and the problems which can be occurred during its operation have been studied by modeling it more detailed. Particularly, we have placed great importance on its power quality and signal characteristics when it is connected with a power grid.

• Korean Journal of Remote Sensing
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• v.11 no.3
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• pp.83-100
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• 1995

The land-use has changed rapidly during the last two decades in accordance with urbanization in the Seoul Metropolitan Region. As a result of these changes, the local climate has undergone changes as well. This study intends to define the land-use changes, and then to show how they have brought in significant changes in the local climates. Land-use changes in the study area so repidly that up-to date maps and documents are not available at present. Therefore, Landsat data for land-use classification and NOAA AVHRR thermal data for the temperature fields were analyzed. Additionary, to visualize the effect of the land-use on the local climate, computer-enhanced brightness temperatures, Green Belt and city boundaries were overlaid on land-use patterns obtained from satellite images using GIS techniques. The results of analysis demonstrate that Green Space in the Seoul Metropolitan Region decreased from 94% to 62% while urban land-use increased ten times, from 4% to 39% for the period of 1972-1992. The resulting disappearance of biomass caused by land-use changes may have implications for the local-and micro-climate. The results show that the local climate of the study area became drier and warmer. This study also suggests a need for further studies of man's effects on local climate to minimize adverse influences and hazardous pollution and efficacious ways for urban planning.

• Food Science and Preservation
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• v.21 no.6
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• pp.892-902
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• 2014

The quality characteristics of Takju were investigated according to the different rice varieties and mixing ratio of Nuruk for the advanced quality of Takju. The yeast was selected by alcohol-producing ability. Then a liquid starter was prepared using brewing fungi (Aspergillus luchuensis 34-1 and Lichtheimia ramosa CN042), and rice Nuruk was manufactured with two rice types (Chucheong and Hanareum). The quality characteristics of Takju were investigated based on the rice type and the mixing ratio of A. luchuensis 34-1 and Lich. ramosa CN042 (1:0, 0:1, 1:1, 1:3). S. cerevisiae Y268 showed an alcohol yield of $9.3{\pm}0.33%$ at a 0.3% concentration in the YPD broth medium, and the rice Nuruk with A. luchuensis 34-1, regardless of rice type, was confirmed to have a higher enzyme activity and physiochemical property than Lich. ramosa CN042. According to the quality analysis of Takju, the physiochemical property was increased for the fermentation period, and the acidity differed by type of fungi and rice. The quality of Takju was changed with the composition differences of organic acid and free amino acid by rice type and mixing ratio. As a result of the sensory evaluation of Takju, the preference for it was increased with the Hanareum and A. luchuensis 34-1, respectively. Thus, this study shows the possibilities for activating the industry of traditional liquor by improving the Nuruk and Takju manufacturing technique.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.157-157
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• 2010

RDF는 장기저장이 가능한 것이 특징 중의 하나이지만, 우리나라보다 앞서 대량저장을 시작한 일본의 RDF 저장 사일로에서 폭발사고가 발생한 사례가 있어, RDF를 실제로 저장하여 RDF 온도 및 가연성가스 발생상황 등을 장기간 감시 측정하여 사일로 안전관리지표를 도출하였다. 실험에 사용한 RDF 저장조는 직경 3.1m, 높이 11.4m의 사일로방식으로 제작하였다. RDF 저장량은 $70m^3$이었으며, 저장기간은 475일이었다. 사일로에는 15개의 열전대를 설치하여 사일로 표면, 직경방향 1.2m 지점 및 기온을 측정하여 수직방향 및 수평방향의 온도변화를 분석하였다. 가스 샘플링포트는 온도측정지점과 동일한 위치 설치하여 진공펌프로 흡인하여 테트라 백에 포집하여 GC로 분석하였으며, 가스샘플링은 17회 실시하였다. 비교적 대형 저장설비이고 RDF가 열전도성이 낮은 물질임에도 불구하고 사일로 내부온도는 기온보다는 높았지만, 기온의 영향을 많이 받아 7월에 정점, 1월에 하점을 나타내는 사인곡선과 같은 패턴을 보였다. 측정지점별 온도차는 수평방향 보다 수직방향에서 높게 나타났으며, RDF층으로 전열 및 축열이 진행되고 생화학반응을 촉진시키는 상승작용의 결과로 월평균온도가 $49^{\circ}C$를 나타내는 지점도 있었다. 실제 사일로는 RDF의 투입과 배출이 연속적으로 진행되어 방열이 이루어지므로 하계에 대량저장을 실시하지 않는 한 RDF층 내부에서 생화학적 반응열이 생성되더라도 $40^{\circ}C$를 상회할 가능성은 매우 희박할 것으로 판단된다. RDF 저장시 발생하는 가스는 대부분 $CO_2$였으며, 미량이지만 $H_2$, CO, $CH_4$도 검출되었다. 가연성 가스는 저장 후 2개월 동안은 발생하지 않았으며, 하계에는 타 계절에 비해 상대적으로 고농도로 검출되었다. 발생가스와 온도 및 $CO_2$와 $H_2$농도의 상관성은 높게 나타나지 않았지만, 정의 상관관계를 나타내었다. 저장한 RDF의 성상(수분, 발열량, 분화물)은 실험개시 전의 RDF분석결과와 실험종료 후 분석결과에서는 큰 차이가 나타나지 않았다. 따라서 RDF의 안전 저장을 위해서는 (1) 반입되는 RDF성상관리, (2) RDF가 2개월 이상 장기간 체류하는 데드스페이스가 발생하지 않고 선입선출이 확보되는 저장조 설계, (3) 사일로 내부에 최소 3개 이상의 지점에서 온도를 측정하여 상시감시하고 $40^{\circ}C$이하로 관리, (4) 발생가스는 CO, $CO_2$, $H_2$, $CH_4$ 등의 가연성가스를 모두 측정 감시하는 것이 바람직하지만, 최소 $CO_2$와 $H_2$는 상시감시하고 각각 1%와 100ppm 미만으로 관리, (5) 배풍기 등을 이용한 상시 환기실시, (6) 하계에는 대량저장이 이루어지지 않도록 저장조 운용계획 수립 등을 실시해야 한다.