• Journal of Korean Society of Forest Science
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• v.110 no.4
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• pp.554-568
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• 2021

Forests are the largest carbon (C) sinks in terrestrial ecosystems. Recently, as enhancing forest C sequestration capacity has been proposed as a basic direction of the Republic of Korea's "2050 Carbon Neutral Strategy," accurate estimation of forest C sequestration has been emphasized. According to the Intergovernmental Panel on Climate Change guidelines, sequestration quantity is calculated from changes in C stocks in forest C pools, such as biomass, deadwood, litter and soil layer, and harvested wood products. However, in Korea, only the overstory biomass increase is now considered the amount of sequestration quantity, so there can be a significant difference from the actual forest C sequestration. In this study, we quantified forest C exchange through C flux measurement using an eddy covariance system and an automated soil chamber system in a 57-year-old Korean pine plantation located in Mt. Taehwa, Gwangju-si, Gyeonggi-do. Then, the net amount of C sequestration was compared with the amount of the overstory biomass increase. We estimated the annual C stock change in the remaining C pools by comparing the net sequestration amount from the C flux measurement with the overstory biomass increase and C stock change in the litter layer. Therefore, the net C sequestration of the Korean pine plantation estimated from the flux measurement was 5.96 MgC ha^-1, which was about 2.2 times greater than 2.77 MgC ha^-1 of the overstory biomass increase. The annual C stock increase in the litter layer was estimated to be 0.75 MgC ha^-1, resulting in a total annual C stock increase of 2.45 MgC ha^-1 in the remaining C pools. Our results indicate that the domestic forest is a larger C sink than the current methods, implying that more accurate calculations of the C sequestration capacity are necessary to quantify C stock changes in C pools along with the C flux measurement.

• Journal of the Korea Society of Computer and Information
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• v.14 no.10
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• pp.133-139
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• 2009

A P2P technology in distributed computing fields is presented various methods to share resources between network connected peers. This is very efficient that a degree of resources to good use as compared with peers by using centralized network by a few servers. However peers to compose P2P system is not always online status, therefore it is difficult to support high reliability to user. In our previous work of this paper, it is contributing to reduce the loading rates to select of new resource support peer but a selection method the peers to share works to download resources is very simple that it is just selected about peer to have lowest job. In this paper, we reduced frequency offline peers by estimate based on a average value of success rates for peers.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.481-493
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• 2023

In high-density urban areas, the urban heat island effect increases urban temperatures, leading to negative impacts such as worsened air pollution, increased cooling energy consumption, and increased greenhouse gas emissions. In urban environments where it is difficult to secure additional green spaces, rooftop greening is an efficient greenhouse gas reduction strategy. In this study, we not only analyzed the current status of the urban heat island effect but also utilized high-resolution satellite data and spatial information to estimate the available rooftop greening area within the study area. We evaluated the mitigation effect of the urban heat island phenomenon and carbon sequestration capacity through temperature predictions resulting from rooftop greening. To achieve this, we utilized WorldView-2 satellite data to classify land cover in the urban heat island areas of Busan city. We developed a prediction model for temperature changes before and after rooftop greening using machine learning techniques. To assess the degree of urban heat island mitigation due to changes in rooftop greening areas, we constructed a temperature change prediction model with temperature as the dependent variable using the random forest technique. In this process, we built a multiple regression model to derive high-resolution land surface temperatures for training data using Google Earth Engine, combining Landsat-8 and Sentinel-2 satellite data. Additionally, we evaluated carbon sequestration based on rooftop greening areas using a carbon absorption capacity per plant. The results of this study suggest that the developed satellite-based urban heat island assessment and temperature change prediction technology using Random Forest models can be applied to urban heat island-vulnerable areas with potential for expansion.

• Resources Recycling
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• v.26 no.3
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• pp.32-38
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• 2017

For the massive recycling of mine tailings, which are an inorganic by-product of mining process, in the field of civil engineering, pretreatments to extract heavy metals are required. This study focuses on the use of pre-treated tailings as substitute fillers for controlled low-strength material (CLSM). As a comparative study, untreated tailing, microwave-treated tailing and magnetic separated with microwaved tailing were used in this study. Cement contents amounting to 10%, 20% and 30% by the weight of the tailings were designed. Both compressive strength and flowability for all types of mixture were satisfied with the requirements of the American Concrete Institute (ACI) Committee 229, i.e., 0.3-8.3 MPa of compressive strength and longer than 200 mm flowability. Furthermore, all mixtures showed settlements less than 1% by volume of the mix.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.93-100
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• 2019

In this study, the mechanical properties of early-age concrete were evaluated by mixing the electric arc furnace oxidizing slag fine aggregate with 30% and 50% replacement ratio. Slump test, air content test and unit volume weight test were performed for fresh concrete, and compressive strength test and chloride penetration experiments were carried out in hardened concrete. The compressive strength increased up to 7 days of curing age with increasing replacement ratio of the electric furnace oxidizing slag, but the strength decreased to 90% level of OPC concrete at 28 days of age. Regarding the result of chloride penetration test, no significant differences from OPC concrete were evaluated, which shows a feasibility of application to concrete aggregate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.1-7
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• 2017

Concrete behavior in early-age is changing due to hydration reaction with time, and a resistance to chloride attack and strength development are different characterized. In the present work, changing strength and resistance to chloride attack are evaluated with ages from 28 days to 6 months. For the purpose, strength, diffusion coefficient, and passed charge are evaluated for normal concrete with 3 different mix proportions considering 28-day and 6-month curing conditions. With increasing concrete age, the changing ratio of strength falls on the level of 135.3~138.3%, while diffusion coefficient and passed charge shows 41.8%~51.1% and 53.6%~70.0%, respectively. The results of chloride diffusion coefficient and passed charge show relatively similar changing ratios since they are much dependent on the chloride migration velocity in electrical field. The changing ratios in chloride behaviors are evaluated to be much larger than those in compressive strength since the ion transport mechanism is proportional to not porosity but square of porosity.

• Journal of the Korean Wood Science and Technology
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• v.32 no.2
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• pp.65-72
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• 2004

A melamine-urea-formaldehyde (MUF) resin, based on 5 percent melamine addition of the resin solids weight, was synthesized in the laboratory for particleboard (PB) manufacture. Laboratory PBs were made with the MUF resin at three press times (3, 4, 5 min) and two resin application rates (6, 8 percent). Enclosed caul system was used for collecting the exhaust gases materials generated during the hot-pressing of PBs. Exhaust gases materials generated inside the enclosed caul during the hot-pressing of PBs were collected in a controlled air stream. Formaldehyde from the exhaust gases collected was determined per a chromotropic method of the National Institute of Occupational Safety and Health Method 3500. The measurement results showed that formaldehyde emissions during the hot-pressing of PB significantly increased with increasing press time, and MUF resin application rates. PB' performance test results showed that internal bond (IB) of PB made with 3-minute press time exceeded the minimum requirement for KS F 3104 PB type 8.0.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.140-145
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• 2015

This study focused on the development of a fundamental technology for coating of concrete surface using slime produced from bacteria. To assign self-purification ability and improve durability performance of concrete, Rhodobater capsulatus that generates slime were selected and absorption technology for the selected bacteria was then examined. From the production of slime and growth activity of the bacteria, the optimum medium for Rhodobater capsulatus can be recommended as maltose. Furthermore, image analysis showed that high porous resin powder is more effective for absorption of the Rhodobater capsulatus than the other materials tested.

• Proceedings of the Korean Society of Organic Agriculture Conference
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• 2009.12a
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• pp.304-305
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• 2009

시설재배지의 토양화학성 변화는 작물재배 기간 시비한 화학비료에서 유래된 무기성분 뿐만아니라, 가축분퇴비의 질소성분의 토양잔류량이 요소비료 보다 9.4배 많아 염류집적 주 요인이라는 보고('05 경기도)가 시사하는 봐와 같이 유기자원으로 시용하는 가축분 등의 부산물비료의 무기화에서 유래된 비료성분이 토양염류집적 및 토양환경악화에 더 큰 영향을 미칠 수 있다. 시설재배지의 유기물자원 시용기준이 토양의 특성에 관계 없이 작물에 따라 양적인 시험성적이 주로되어 있으며, 토양검정에 의한 시용기준도 유기물함량에 따라 볏짚, 우분, 돈분 및 계분으로 돠어 있다. 일반노지와 달리 시설재배지에서는 유기물함량이 토양의 비옥도 및 작물생육에 영향을 미치는 것 보다는 토양의 전기전도도(EC)가 더 중요한 작물생육 조건이 될 수 있다. 따라서 토양의 특성에 따라 물질순환에 의한 유기자원 시용기준으로 개선할 필요성이 있다. 시설재배지의 장기적인 토양관리를 위하여 유기물자원에 의한 토양환경 개선 효과를 구명하고자. 무처리, 가축분부산 물비료 관행 시용 기준 대비 볏짚 등 5개의 유기자원을 토양의 무기태질소 함량 대비 유기자원의 탄소함량을 C/N율 10 조절량을 시용하여 시험하였고, 또한 토양의 전기전도도(EC)가 상이한 3개( <2.0 dS/m, 2.0~6.0 dS/m, 6.0 dS/m<)토양에 유기물자원(우드칩)을 C/N율 10, 20, 30 조절하여 수박을 시험작물로 비닐하우스에서 재배하여 수행하였다. 시험 후 토양의 전기전도도(EC)는 시험 전에 비하여 시험 후 토양에서 가축분부산물비료는7% 증가되었으나 유기물자원 처리는 26~33% 경감되는 효과가 있었다. 수박의 과중은 무처리를 제외하고 처리간에 차이가 없었다. 유기물자원 C/N율 조절간에는 시험전 토양의 EC에 따라 차이가 있어 C/N 10 조절에서는 26~44%, C/N 20 조절에서는 30~51%, C/N 30 조절에서는 27~48% 경감효과가 있었으며, 3토양의 평균 토양EC 경감율은 C/N 10, 20, 30 조절에서 각각 34, 39 및 38 % 이었다. 수박의 생육 및 과중은 토양의 C/N율 조절간에는 차이가 없었으나, 토양의 EC 간에는 토양의 EC가 6.0dS/m 이상 토양에서 가장 낮았다. 따라서 탄소원의 유기자원을 C/N율 조절에 의한 시용기준 개선으로 토양의 무기태질소와 토양의 전기전도도(EC)를 경감시켜 친환경적 토양관리와 수박의 수량과 품질을 향상시킬 수 있을 것으로 평가되었다.

• The Korean Journal of Financial Management
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• v.9 no.2
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• pp.77-100
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• 1992

경영성과(經營成果)의 평가지표(評價指漂)는 개별조직의 목표와 제약환경, 즉 이용가능한 자원량과 개별적 특수요인 등을 고려하여 설정하여야 하며, 산업내의 특성과 동질적 비교집단을 이해함으로써 조직의 성과와 직접적으로 연결될 수 있어야 한다. 또한 조직의 평가는 부분적(部分的)인 효율성(效率性)에 편중되지 않고 투입과 산출간의 유기적인 관계를 총체적인 관점에서 분석함으로써 종합적(綜合的) 효율성(效率性)에 그 촛점이 두어져야 한다. 이러한 문제의 인식에 바탕을 두어 본 연구에서는 Charnes, Cooper와 Rhodes(1978)에 의해 처음 개발되어 주로 비영리기관의 경영성과의 평가에 많이 사용하여 온 DEA(Data Envelopment Analysis)기법을 이용하여 금융기관(金融機關)의 효율성(效率性)을 평가(評價)한다. 금융기관은 다양한 투입요소를 사용하여 다양한 서비스 상품을 제공하는 조직이기 때문에, 또 재무비율을 이용한 기존의 평가나 통계적 생산함수의 추정에 의한 평가방법은 단순히 과거의 실적을 평가하는 데 그치게 되고 객관성이 결여되기 쉽기 때문에 조직의 미래운영방향의 설정에 도움이 되지 못한다는 단점을 가지고 있다. 그러나, DEA은 다수의 투입과 산출요소를 요구하는 경우에 적합하게 설계된 분석방법이므로 금융기관의 성과분석에 적절하게 이용될 수 있다. 본 연구에서는 먼저 금융기관(金融機關)의 효율성(效率性)을 평가(評價)하는 기존의 방법을 간략하게 검토한 다음, DEA에 관한 이론적 기초와 그 특성을 검토한다. 실증분석에서는 여 수신업무(與 受信業務)를 수행하고 있는 국내금융기관들 중에서 자료의 동질성과 표본대상 기업의 수를 고려하여 은행업(銀行業)과 투자금융업(投資金融業)을 선정하고 이들 업종에 속한 37개 회사들에 대한 운영효율성(運營效率性)을 측정한다. 투입요소로 직원의 수와 영업비용을, 그리고 산출요소로 영업수익과 경상이 익을 선정하고, 3년간의 자료를 사용하여 실증분석을 한다. 분석의 결과에 의하면, 18개 전체 은행의 평균적인 효율성의 정도는 가장 효율적인 은행을 기준으로 할 때, 약 85% 수준에 그치고 있어서, 나머지 대부분의 은행들 특히 대규모 시중은행들의 경영상의 개선의 여지가 매우 크다고 할 수 있다. 5대 시중은행들간에는 효율성의 차이가 거의 없는 반면, 지방은행들간에는 매우 큰 차이가 있는 것으로 나타난다. 이는 영업지역의 제한으로 인하여 지역경제 규모가 은행의 수지상황에 결정적인 영향을 미치고 있다는 것을 반영하고 있다. 29개 단자회사를 대상으로 한 투자금융업의 경우에도 은행업의 경우와 동일하게 낮은 효율성과 지역간 격차현상이 나타나고 있다.