• Journal of the Korean Solar Energy Society
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• v.37 no.1
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• pp.47-57
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• 2017

Solar energy is one of the important renewable energy resources. It can be used for air heating, hot water supply, heat source of desiccant cooling system and so on. And many researches for enhancing efficiency have been conducted because of these various uses of solar thermal energy. This study was performed to investigate the air heating performance of hybrid solar air-water heater that can heat air and liquid respectively or simultaneously and finding method for improving thermal performance of this collector. This collector has both liquid pipe and air channel different with the traditional solar water and air heater. Fins were installed in the air channel for enhancing the air heating performance of collector. Also air inlet & outlet temperature, ambient temperature and solar collector's inner part temperature were confirmed with different air velocity on similar solar irradiance. As a result, temperature of heated air was shown about $43^{\circ}C$ to $60^{\circ}C$ on the $30^{\circ}C$ of ambient temperature and thermal efficiency of solar collector was shown 28% to 73% with respect to air velocity. Also, possibility of improvement of thermal performance of this collector could be ascertained from the heat transfer coefficient calculated from this experiment. Thus, it is considered that the research for finding optimal structure of hybrid solar air-water heater for enhancing thermal performance might be needed to conduct as further study based on the method for improving air heating performance confirmed in this study.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.653-660
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• 2007

Since the temperature of asphalt for deck plate of steel bridge during paying procedure is relatively high as $240^{\circ}C\;to\;260^{\circ}C$, the temperature of deck plate of bridge rises mere than $100^{\circ}C$ and excessive displacement and stress could occur. In order to avoid undesirable failure of base plate and determine the optimal pavement pattern, a thorough thermal analysis is needed. General structural model which is made of beam and plate element should be modified for transient heat transfer analysis; asphalt pavement material and convection effect on surface of structure need to be added. A new technique with the Equivalent Heat Source (EHS) for numerical thermal analysis for steel bridge under thermal load of Guss asphalt pavement is proposed. Since plate/beam elements which were generally used for structural analysis for bridge cannot explain convection effect easily on plate/beam surface, EHS which is determined based on calculated temperature with convection effect is used. To verify the EHS proposed in this study, numerical analyses with plate elements are performed and the results are compared with estimated temperatures. EHS might be used for other thermal analyses of steel bridge such as welding residual stress analysis and bridge fire analysis.

• Journal of Korean Society of Forest Science
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• v.106 no.4
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• pp.457-464
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• 2017

This study has utilized the stand density management diagram to devise an efficient management standard for the stand density for Pinus densiflora that secures the health of the stands and predicted the harvest goals. The appropriate stand control level was estimated by modeling the relationship of the relative yield index (Ry) to the ratio of slender trees within the stand through an exponential function; the coefficient of determination ($R^2$) was found to be 0.424 according to the estimation. The ratio of slender trees within the stand showed a tendency of rapid increase at a certain relative yield index; with this relational function, the appropriate Ry value of 0.84 was obtained. By estimating the curve of the Ry value 0.84, which was the appropriate stand density management level, as well as the height of dominant trees in the central region of Korea, the production objective for each site index was set. Assuming that the final age by the site indices ranged from 10 to 16 for the P. densiflora in central region of Korea, the number of production was estimated to be between 426 to 1,311 trees per ha. It was predicted that the production of medium-diameter logs larger than 30 cm in diameter is possible for the target DBH at a site index of more than 16; small-diameter logs larger than 20 cm in diameter for site indices 12 and 14 enabled, and small-diameter logs of less than 20 cm for site index 10.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.839-848
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• 2011

TBM (Tunnel Boring Machine) tunnel should be carry out with the adopted machine until the end of excavation because of impossibility of replacement or modification of machine. Observation of the face of the tunnel is difficult, especially in EPB(Earth Pressure Balance) shield TBM, predict changes in the ground condition with analyzing data, collected during the excavation, and it should be reflected in construction. Until recently, subjects of studies on TBM are mainly the determination of machine and the development of advance rate prediction model, according to the characteristics of ground which is the target of excavation. However, study focused on the estimation of ground conditions and the improvement in operational methods using excavation data of TBM equipment, the principal of the excavation, has been done not so much. This study examine the variances in advance rate depending on changes in operating conditions and evaluate the optimal operating conditions of adopt machine, using working data obtained from EPB shield TBM project. The result of this study is suggested as follows. First, cutter head RPM and total thrust force are biggest influences on advance rate, Second, it is recommended for proper advance rate that total thrust force is controlled while optimum cutter head RPM is kept, Third, according to the increasing trend of total thrust force, the changes in ground conditions can be predicted, the appropriate operating conditions can be determined.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.57-65
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• 2006

본 연구는 유량에 의한 수면폭의 변화로 인한 하천경관의 시각적 선호도에 미치는 선호요인 파악하였다. 등간척도의 점수부가체계를 적용하여 이용자에 의한 금강경관의 시각적 선호를 평가한 후 시각적 선호와 이에 영향을 미치는 선호요인들과의 관계를 다중회귀분석방법으로 검정하였다. 수면폭 변화에 따른 금강경관의 시각적 선호요인 변수는 심미성 인자, 물리적 특성 인자, 복잡성 인자로서 3개 변수 모두 유의성이 있는 것으로 판명되었다. 모든 선호요인의 값이 증가함에 따라 시각적 선호의 값도 증가를 가져오고 그 반대의 경우도 마찬가지였다.다중회귀모형에서 다른 조건이 불변일 경우, 심미성 인자의 값이 증가할 때 전체적인 시각적 선호에 가장 크게 영향을 미치고, 다음으로 물리적 특성 인자가 두 번째로 영향을 미치는 것으로 판명되었다. 선호요인이 시각적 선호에 기여하는 상대적 중요도는 심미성 인자, 물리적 특성 인자, 복잡성 인자 순으로 나타났다. 심미성 인자는 복잡성 인자에 비해 3.2배 만큼 중요도가 크며 물리적 특성 인자는 복잡성 인자에 비해 3배의 중요도를 가지고 있는 것으로 나타났다. 따라서 심미성인자는 가장 중요한 선호요인으로 판명되었다. 수면폭 변화에 따른 금강경관의 시각적 평가에 의한 선호 요인 분석 결과는 하천의 수면폭 및 수량에 큰 영향을 미칠 것이다. 수위 변화로 인한 하천 경관의 선호 요인을 파악함으로서 금강 유지유량의 결정에 지침을 마련하고, 시각적 선호도에 따른 최적의 수면폭/하폭비 산정하였으며 본 연구 결과는 수량에 의한 수면폭/하폭 비의 변화로 인한 하천경관의 수량결정에 중요한 정보를 제공하고 이용자의 만족을 극대화할 수 있는 경관조성에 기여할 것으로 판단된다. 통하여 유기농업의 실현을 도모하여 소비자의 욕구에 맞는 작물 생산 및 농촌관광단지 조성을 통해 부가가치증대 및 소득증대를 꾀함으로 농촌문제 해결에 도움이 될 것으로 기대된다. 본 연구를 통해 GIS 와 RS의 기술이 농촌분야에 더 효율적으로 적용될 것으로 기대되며, 농업기술센터를 통한 정보제공을 함으로써 대농민 서비스 및 농업기관의 위상이 제고 될 것으로 기대된다.여 전자파의 공간적인 가시화를 수행할 수 있었다. 본 전자파 시뮬레이션 기법이 실무에 이용될 경우, 일반인이 전자파의 분포에 대한 전문지식을 습득할 필요 없이, 검색하고자 하는 지역과 송전선, 전철 등 각종 전자파의 발생 공간 객체를 선택하여 실생활과 관련된 전자파 정보에 예측할 수 있어, 대민 환경정보 서비스 질의 개선측면에서 획기적인 계기를 마련할 것으로 사료된다.acid$(C_{18:3})$가 대부분을 차지하였다. 야생 돌복숭아 과육 중의 지방산 조성은 포화지방산이 16.74%, 단불포화지방산 17.51% 및 다불포화지방산이 65.73%의 함유 비율을 보였는데, 이 중 다불포화지방산인 n-6계 linoleic acid$(C_{18:2})$와 n-3계 linolenic acid$(C_{18:3})$가 지질 구성 총 지방산의 대부분을 차지하는 함유 비율을 나타내었다.했다. 하강하는 약 4일간의 기상변화가 자발성 기흉 발생에 영향을 미친다고 추론할 수 있었다. 향후 본 연구에서 추론된 기상변화와 기흉 발생과의 인과관계를 확인하고 좀 더 구체화하기 위한 연구가 필요할 것이다.게 이루어질 수 있을 것으로 기대된다.는 초과수익률이 상승하지만, 이후로는 감소하므로, 반전

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.4
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• pp.40-51
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• 2015

This study is to estimate the viability of aerobic stabilization technology for reducing greenhouse gas (GHG) emissions from landfills in Korea. In this study, methane emissions were estimated by applying Landfill gas estimation model (LandGEM) to Y landfill in Korea. By comparison of an anaerobic condition (baseline) and an aerobic condition, the amount of $CO_2eq$ savings was calculated. The $CO_2eq$ savings take place inside the landfilled waste during aeration due to the conversion of previously anaerobic biodegradation to aerobic processes, releasing mainly $CO_2$. It was demonstrated that 86.6% of the total GHG emissions occurring under anaerobic conditions could be reduced by aerobic stabilization technology. This means the aerobic stabilization technology could reduce environmental contamination through early stabilization and GHG emissions considerably at the same time. Therefore, the aerobic stabilization technology is one of the optimal technologies that could be employed to domestic landfill sites to achieve sustainable landfill.

• Journal of the Korea Organic Resources Recycling Association
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• v.25 no.1
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• pp.23-33
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• 2017

In this study, water and organic treatment efficiency and operating characteristics (temperature, salinity effect) were evaluated when food waste with high water content was treated by Bio-dying method. In addition, the optimum conditions for producing pellets for evaluating the decomposition products as SRF(Solid Refuse Fuel) after Bio-drying and evaluating the use value of SRF as a solid fuel were analyzed. As a result, the temperature, $CO_2$ concentration, organic matter removal rate and weight reduction rate according to the daily dose were about 86% and 68% at the input of 2.4 kg/day. The optimal food waste input was estimated to be 2.4 kg/day. As a result of the pellet molding and produce, Pellets can be produced within 10~25% of raw material water content. It was judged that the water content of 25%, which showed the best quality results in terms of external shape maintenance and strength. The high calorific value of SRF of decomposition products after Bio-drying was more than 3,500 kcal/kg.

• Korean Journal of Remote Sensing
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• v.34 no.3
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• pp.481-494
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• 2018

The accurate radiative transfer model simulation is essential for an accurate ozone profile retrieval using optimal estimation from backscattered ultraviolet (BUV) measurement. The input parameters of the radiative transfer model are the main factors that determine the model accuracy. In particular, meteorological parameters such as temperature and surface pressure have a direct effect on simulating radiation spectrum as a component for calculating ozone absorption cross section and Rayleigh scattering. Hence, a sensitivity of UV ozone profile retrievals to these parameters has been investigated using radiative transfer model. The surface pressure shows an average error within 100 hPa in the daily / monthly climatological data based on the numerical weather prediction model, and the calculated ozone retrieval error is less than 0.2 DU for each layer. On the other hand, the temperature shows an error of 1-7K depending on the observation station and altitude for the same daily / monthly climatological data, and the calculated ozone retrieval error is about 4 DU for each layer. These results can help to understand the obtained vertical ozone information from satellite. In addition, they are expected to be used effectively in selecting the meteorological input data and establishing the system design direction in the process of applying the algorithm to satellite operation.

• Korean Journal of Agricultural and Forest Meteorology
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• v.17 no.4
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• pp.333-339
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• 2015

A thermal time-based phenology model of Kimchi cabbage was developed by using the field observed growth and temperature data for the purpose of accurately predicting heading and harvest dates among diverse cropping systems. In this model the lifecycle of Kimchi cabbage was separated into the growth stage and the heading stage, while the growth amount of each stage was calculated by optimal mathematical functions describing the response curves for different temperature regimes. The parameter for individual functions were derived from the 2012-2014 crop status report collected from seven farms with different cropping systems located in major Kimchi cabbage production area of South Korea (i.e., alpine Gangwon Province for the summer cultivation and coastal plains in Jeonnam Province for the autumn cultivation). For the model validation, we used an independent data set consisting of local temperature data restored by a geospatial correction scheme and observed harvest dates from 17 farms. The results showed that the root mean square error averaged across the location and time period (2012-2014) was 5.3 days for the harvest date. This model is expected to enhance the utilization of the Korea Meteorological Administration's daily temperature data in issuing agrometeorological forecasts for developmental stages of Kimchi cabbage grown widely in South Korea.

• The Journal of Engineering Geology
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• v.18 no.1
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• pp.17-26
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• 2008

In this study, the design method of slope reinforced by the earth retention systems were systematically developed, and the flow chart of design procedure fur each system were constructed to design the slope rationally. The proposed design method is composed of 5 steps such as field condition investigation step, slope design step, landslide occurrence prediction step, slope failure scale estimation step and reinforcement countermeasure selection step. The quantitative standard of slope failure scale was established based on the arrangement of various overseas standards which is estimating the slope failure, and the analysis of slope failure scale which is occurred in the country. The slope failure scale is classified into three categories the small scale of slope failure is less than $150m^3$ of slope failure volume, the middle scale of slope failure is from $150m^3$ to $900m^3$ and the large scale of slope failure is more than $900m^3$. The earth retention system could be selected by the proposed slope failure scale based on the slope failure volume. Meanwhile, the design methods of earth retention system such as piles, soil nails and anchors were developed. The optimal countermeasure for slope stability could be proposed using above design methods.