• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.534-535
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• 2006

This study attempts to develope the micro-turbine generators which is expected to run efficiently even in very low head and small flow rate, so that the limitations on the conventional small scale hydropower could be alleviated and competition with other alternative energy sources in the changable design conditions could be attained. The micro turbine generator of a new concept was designed based on changable design conditions, hydrodynamics and theory of power transmission.

• Computers and Concrete
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• v.24 no.4
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• pp.283-293
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• 2019

The limited availability of raw materials and increasing service demands for pavements pose a unique challenge in terms of pavement design and concrete material selection. The self-compacting rubberized concrete (SCRC) can be used in pavement design. The SCRC pavement slab has advantages of excellent toughness, anti-fatigue and convenient construction. On the premise of satisfying the strength, the SCRC can increase the ductility of pavement slab. The aim of this investigation is proposing a new method to predict the crack growth and flexural capacity of large-scale SCRC slabs. The mechanical properties of SCRC are obtained from experiments on small-scale SCRC specimens. With the increasing of the specimen depth, the bearing capacity of SCRC beams decreases at the same initial crack-depth ratio. By constructing extended finite element method (XFEM) models, crack growth and flexural capacity of large-scale SCRC slabs with different fracture types and force conditions can be predicted. Considering the diversity of fracture types and force conditions of the concrete pavement slab, the corresponding test was used to verify the reliability of the prediction model. The crack growth and flexural capacity of SCRC slabs can be obtained from XFEM models. It is convenient to conduct the experiment and can save cost.

• Smart Structures and Systems
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• v.19 no.5
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• pp.499-512
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• 2017

Traditional structural dynamic analysis and Structural Health Monitoring (SHM) of large scale concrete civil structures rely on manufactured embedding transducers to obtain structural dynamic properties. However, the embedding of manufactured transducers is very expensive and low efficiency for signal acquisition. In dynamic structural analysis and SHM areas, piezoelectric transducers are more and more popular due to the advantages like quick response, low cost and adaptability to different sizes. In this paper, the applicable feasibility assessment of the designed "artificial" piezoelectric transducers called Concrete Piezoelectric Smart Module (CPSM) in dynamic structural analysis is performed via three major experiments. Experimental Modal Analysis (EMA) based on Ibrahim Time Domain (ITD) Method is applied to experimentally extract modal parameters. Numerical modal analysis by finite element method (FEM) modeling is also performed for comparison. First ten order modal parameters are identified by EMA using CPSMs, PCBs and FEM modeling. Comparisons are made between CPSMs and PCBs, between FEM and CPSMs extracted modal parameters. Results show that Power Spectral Density by CPSMs and PCBs are similar, CPSMs acquired signal amplitudes can be used to predict concrete compressive strength. Modal parameter (natural frequencies) identified from CPSMs acquired signal and PCBs acquired signal are different in a very small range (~3%), and extracted natural frequencies from CPSMs acquired signal and FEM results are in an allowable small range (~5%) as well. Therefore, CPSMs are applicable for signal acquisition of dynamic responses and can be used in dynamic modal analysis, structural health monitoring and related areas.

• Environmental Engineering Research
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• v.25 no.3
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• pp.267-273
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• 2020

This Hydrokinetic energy system is the process of extracting energy from rivers, canals and others sources to generate small scale electrical energy for decentralized usage. This study investigates the application of Soil and Water Assessment Tool (SWAT) in Geographical Information System (GIS) environment to evaluate the theoretical hydrokinetic energy potentials of selected Rivers (Asa, Awun and Oyun) all in Asa watershed, Kwara state, Nigeria. SWAT was interfaced with an open source GIS system to predict the flow and other hydrological parameters of the sub-basins. The model was calibrated and validated using observed stream flow data. Calibrated flow results were used in conjunction with other parameters to compute the theoretical hydrokinetic energy potentials of the Rivers. Results showed a good correlation between the observed flow and the simulated flow, indicated by ash Sutcliffe Efficiency (NSE) and R² of 0.76 and 0.85, respectively for calibration period, and NSE and R² of 0.70 and 0.74, respectively for the validation period. Also, it was observed that highest potential of 154.82 MW was obtained along River Awun while the lowest potential of 41.63 MW was obtained along River Asa. The energy potentials obtained could be harnessed and deployed to the communities around the watershed for their energy needs.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.78-78
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• 2023

기후변화 위기는 유사 이래 인류가 직면한 가장 큰 도전으로 범정부적 글로벌 문제로서 이를 해결하기 위한 다양한 정책들이 범국가 차원 혹은 세계적 기업들에 의해 발표 혹은 시행되고 있다. 이러한 기후변화위기와 탄소배출 저감을 위한 대표적인 대응 방안 중 하나가 바로 재생에너지의 확대·보급 노력이다. 그러나 재생에너지는 날씨와 계절 등 자연환경의 영향을 받는 에너지원으로써 간헐성, 변동성을 가지므로, 시간대별 발전량 예측과 전력공급 안정성에 어려움이 있다. 이러한 문제를 해결하기 위하여 재생에너지 발전은 석탄화력 발전과 달리 전력의 수요와 공급의 균형을 위한 에너지저장장치(Energy Storage System, 이하 ESS)가 있어야 한다. ESS는 전력공급 안정성 향상과 전력 수급의 유연성을 제공하는 장점이 있지만, 초기 설치비용이 높은 단점이 있다. 특히, 배터리 기반 ESS의 경우 높은 구축 비용과 한정적인 충. 방전수명으로 인하여 대용량 ESS로써의 역할 수행에는 분명한 한계가 있다. 하지만 재생에너지와 연계한 ESS로 양수발전댐을 활용할 경우 장주기, 장수명, 대용량 에너지 저장에 매우 합리적인 수단으로 판단되었다. 다만, 양수발전 댐 구축에는 토목공사로 인한 환경 훼손이라는 문제점도 존재한다. 본 고에서는 지역 분산형 소규모 양수발전(Pumped Storage Hydropower, 이하 PSH)댐 구축 및 운영기술 개발을 통해 지역 전력공급과 전력 수급을 조절하면서 변동성 재생에너지를 안정적으로 사용할 수 있는 방안을 소개하고자 한다. 특히, 해당 기술은 지역별 특성에 맞춰 유연하게 설치할 수 있으며, 대규모 토목공사로 의한 환경적 부작용을 최소화할 수 있다. 또한 소규모 PSH는 지역의 저수지 및 수자원을 이용하여 에너지를 저장함으로써 변동성 큰 재생에너지의 유연화 대응과 동시에 안정적인 에너지 공급이 가능하다. 본 고에서는 재생에너지의 확대·보급에 따른 문제점과 대표적 ESS 기술들을 분석·소개한다. 지역분산형 소규모 PSH 기술개발 연구기획 내용 소개를 통하여 전력 생산 및 공급의 탈중앙화를 달성하고, 지역별 변동성 재생에너지의 안정적 활용과 지역 전력공급 특성 및 전력 수급에 대응할 수 있는 방안을 제안하고자 한다.

• Korean Journal of Ecology and Environment
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• v.51 no.4
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• pp.268-286
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• 2018

The eutrophication and algal blooms by harmful cyanobacteria (CyanoHAs) and freshwater redtide (FRT) that severely experiencing in typical regulated weir system of the Nakdong River are one of the most rapidly expanding water quality problems in Korea and worldwide. To compare with the factors of rainfall, hydrology, and dominant algae, this study explored spatiotemporal variability of the major water environmental factors by weekly intervals in eight weir pools of the Nakdong River from January 2013 to July 2017. There was a distinct difference in rainfall distribution between upstream and downstream regions. Outflow discharge using small-scale hydropower generation, overflow and fish-ways accounted for 37.4%, 60.1% and 2.5%, respectively. Excluding the flood season, the outflow was mainly due to the hydropower release through year-round. These have been associated with the drawdown of water level, water exchange rate, and the significant impact on change of dominant algae. The mean concentration (maximum value) of chlorophyll-a was $17.6mg\;m^{-3}$ ($98.2mg\;m^{-3}$) in the SAJ~GAJ and $29.6mg\;m^{-3}$ ($193.6mg\;m^{-3}$) in the DAS~HAA weir pools reaches, respectively. It has increased significantly in the downstream part where the influence of treated wastewater effluents (TWEs) is high. Indeed, very high values (>50 or $>100mg\;m^{-3}$) of chlorophyll-a concentration were observed at low flow rates and water levels. Algal assemblages that caused the blooms of CyanoHAs and FRT were the cyanobacteria Microcystis and the diatom Stephanodiscus populations, respectively. In conclusion, appropriate hydrological management practices in terms of each weir pool may need to be developed.

• Korean Journal of Construction Engineering and Management
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• v.16 no.2
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• pp.65-76
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• 2015

The Clean Development Mechanism (CDM) is the multi-lateral 'cap and trade' system endorsed by the Kyoto Protocol. CDM allows developed (Annex I) countries to buy CER credits from New and Renewable (NE) projects of non-Annex countries, to meet their carbon reduction requirements. This in effect subsidizes and promotes NE projects in developing countries, ultimately reducing global greenhouse gases (GHG). To be registered as a CDM project, the project must prove 'additionality,' which depends on numerous factors including the adopted technology, baseline methodology, emission reductions, and the project's internal rate of return. This makes it difficult to determine ex ante a project's acceptance as a CDM approved project, and entails sunk costs and even project cancellation to its project stakeholders. Focusing on hydro power projects and employing UNFCCC public data, this research developed a prediction model using logistic regression and CART to determine the likelihood of approval as a CDM project. The AUC for the logistic regression and CART model was 0.7674 and 0.7231 respectively, which proves the model's prediction accuracy. More importantly, results indicate that the emission reduction amount, MW per hour, investment/Emission as crucial variables, whereas the baseline methodology and technology types were insignificant. This demonstrates that at least for hydro power projects, the specific technology is not as important as the amount of emission reductions and relatively small scale projects and investment to carbon reduction ratios.