• Structural Engineering and Mechanics
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• 제35권6호
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• pp.659-676
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• 2010

An energy-based fatigue life prediction framework was previously developed by the authors for prediction of axial and bending fatigue life at various stress ratios. The framework for the prediction of fatigue life via energy analysis was based on a new constitutive law, which states the following: the amount of energy required to fracture a material is constant. In this study, the energy expressions that construct the new constitutive law are integrated into minimum potential energy formulation to develop new finite elements for uniaxial and bending fatigue life prediction. The comparison of finite element method (FEM) results to existing experimental fatigue data, verifies the new finite elements for fatigue life prediction. The final output of this finite element analysis is in the form of number of cycles to failure for each element in ascending or descending order. Therefore, the new finite element framework can provide the number of cycles to failure for each element in structural components. The performance of the fatigue finite elements is demonstrated by the fatigue life predictions from Al6061-T6 aluminum and Ti-6Al-4V. Results are compared with experimental results and analytical predictions.

• 한국태양에너지학회 논문집
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• 제33권5호
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• pp.41-50
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• 2013

Economic feasibility study using weighted average variable Jeju System Marginal Price, SMP, was conducted for Gasiri wind farm of Jeju Island. To predict the variable Jeju SMP, generator share ratio for SMP was calculated from the real time wind power production and the power demand data for years. Also, sensitivity analysis on Net Present Value, NPV, and Benefit/Cost Ratio, B/C ratio, were performed to clarify which factors are more important in assessing economic feasibility. The result shows that the Gasiri wind farm has a minimum of 110 billion won and a maximum of 132 billion won difference between fixed and variable SMP. Also, Capacity Factor, C.F., had the highest sensitivity for NPV, followed by SMP. Accordingly, when economic analysis for a potential wind farm site is carried out, the variable SMP as well as C.F. should be considered for more accurate assessment of the wind farm.

• Interaction and multiscale mechanics
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• 제2권4호
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• pp.413-430
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• 2009

The stator tooth is a key component of the electromechanical integrated toroidal drive system. The stator tooth is spiral in shape and the calculation of its displacements is difficult. In this paper, using the coordinate transformation method, the displacements of the stator tooth in the local coordinate system are expressed as the function of the variable in the drive coordinate system. Using the minimum potential energy principle, the equations of the displacements of the stator tooth under the loads are deduced. The displacement distributions within the stator tooth are investigated and the changes of the displacement distributions along with the main parameters are analyzed. This research can offer the basis for the strength and stiffness design of the drive system.

• Journal of Photoscience
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• 제6권4호
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• pp.157-158
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• 1999

The conformational studies of glycinemethylester have been carried out by the ab initio method. We have optimized the geometries of glycinemethylester at various levels of sophisticated for electron exchange and correlation within MP2 level. The scale factors of glycinemethylester were used to obtain the scaled ab initio force field of the minimum energy conformer of it, which was used to predict the vibrational frequencies and their potential energy distribution. The Raman spectra of the glycinemethylester were compared with the observed one and the other calculated with HF/6-3IG level.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.260-269
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• 2020

The Steam Assisted Gravity Drainage (SAGD) process is an enhanced method to extract oil from bitumen which involves surface and central process facilities. This paper describes the Central Process Facilities (CPF) of SAGD and proposes several retrofit plans to the Heat Exchanger Network (HEN). In this approach, the process integration scheme is applied to estimate the energy saving in HENs, and various cases are modeled in favor of a commercial simulator. Throughout this work, a minimum approach temperature of 10℃ is assumed. The results reveal that, due to the HEN optimization using process integration, the heating and cooling duties can be reduced to 29.68MW and 1.886MW, respectively. Compared with the Husky case, all cases considered in this study indicate a potential reduction of at least 6% in total cost, including investment and operation costs.

• 대한기계학회논문집
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• 제11권2호
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• pp.287-295
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• 1987

본 논문에서는 보강평간이론의 일반화를 위하여 해석모델을 비대칭 사교보강 평판으로 설정하였으며 응력과 변형율의 관계식을 수정도심을 이용하여 표시하였다. 힘의 평형관계로부터 직교축방향 곡률의 영향을 고려한 수정도심의 위치를 산정하였으 며 변형에너지법에 의하여 보강재교차부의 역학적 특성을 고려한 판의 처짐의 4계편미 분방정식을 유도하였다. 또한, 본 이론의 정밀성을 입증하기 위하여 진동법에 의한 실험 등가강성을 산정하고 이론치와 비교, 검토하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권12호
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• pp.5307-5327
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• 2016

Restricted by finite battery energy, traditional wireless sensor networks (WSNs) can only maintain for a limited period of time, resulting in serious performance bottleneck in long-term deployment of WSN. Fortunately, the advancement in the wireless energy transfer technology provides a potential to free WSNs from limited energy supply and remain perpetual operational. A mobile charger called wireless charging vehicle (WCV) is employed to periodically charge each sensor node and keep its energy level above the minimum threshold. Aiming at maximizing the ratio of the WCV's vocation time over the cycle time as well as guaranteeing the perpetual operation of networks, we propose a feasible and optimal solution to this issue within the context of a real-time large-scale deployed WSN. First, we develop two different types of charging cycles: initialization cycles and renewable cycles and give relevant algorithms to construct these two cycles for each sensor node. We then formulate the optimization problem into an optimal construction algorithm and prove its correctness through theoretical analysis. Finally, we conduct extensive simulations to demonstrate the effectiveness of our proposed algorithms.

• Membrane and Water Treatment
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• 제6권6호
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• pp.451-476
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• 2015

Membrane distillation (MD), which can utilize low-grade thermal energy, has been extensively studied for desalination. By incorporating solar thermal energy, the solar membrane distillation desalination system (SMDDS) is a potential technology for resolving the energy and water resource problems. Small-scale SMDDS (s-SMDDS) is an attractive and viable option for the production of fresh water for small communities in remote arid areas. The minimum-cost design and operation of s-SMDDS are determined by a systematic method, which involves a pseudo steady state approach for equipment sizing and the dynamic optimization using overall system mathematical models. The s-SMDDS employing three MD configurations, including the air gap (AGMD), direct contact (DCMD) and vacuum (VMD) types, are optimized. The membrane area of each system is $11.5m^2$. The AGMD system operated for 500 kg/day water production rate gives the lowest unit cost of $5.92/m^3$. The performance ratio and recovery ratio are 0.85 and 4.07%, respectively. For the commercial membrane employed in this study, the increase of membrane mass transfer coefficient up to two times is beneficial for cost reduction and the reduction of membrane heat transfer coefficient only affects the cost of the DCMD system.

• Korean Chemical Engineering Research
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• 제55권3호
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• pp.332-340
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• 2017

본 연구에서는 다목적 최적화 기법을 이용하여 다양한 신재생에너지 자원 기반 통합 에너지 공급 시스템을 설계 및 평가 한다. 본 연구에서는 에너지 공급 시스템의 주요 구성요소로써 태양광 모듈, 풍력터빈 및 화석연료 기반 발전장치 등 에너지 생산 기술을 비롯하여 배터리와 인버터 등의 전력 에너지 저장 및 변환 장치 등도 포함한다. 특히, 6개의 한국 대표 지역을 선별하여 각 지역의 에너지 요구량 및 실제 신재생 에너지 자원 데이터를 기반으로 최적의 독립 통합 에너지 공급 시스템을 설계하였으며, 총 소요비용, 단위에너지비용 및 생애주기 이산화탄소 배출 분석 등, 다양한 지표를 이용하여 시스템의 경제성 및 환경성을 분석한다. 특히 다목적최적화 기법을 이용하여 최소 비용과 최소 이산화탄소 배출 등 두 목적함수를 동시에 만족하는 파레토 솔루션을 규명함으로써 신재생 자원 기반 독립 에너지 공급 시스템 설계의 가능성 및 효과를 정량적으로 분석하였다. 분석 결과, 신재생에너지 자원이 좋은 지역일수록 시스템 구축 비용 증가에 따른 이산화탄소 절감 효과가 높은 것으로 나타났다. 또한, 신재생에너지 자원 기반 에너지 공급 시스템의 전력 단가는 현재 기존 단가보다 평균 0.35~0.46 $/kWh높게 나타났으며, 이산화탄소 배출량의 경우 기존 배출량보다 470~490 g$CO_2$/kWh정도의 저감효과를 보임을 분석하였다.

• 한국세라믹학회지
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• 제39권11호
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• pp.1042-1047
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• 2002

$Al_2O_3-SiO_2$계 세라믹 화이버를 주원료로 하는 세라믹섬유지를 제조하기 위하여 스러리 점도변화에 따른 세라믹화이버의 침강특성과 pH 변화에 따른 제타전위의 변화와 세라믹화이버 분산특성과의 관계를 분석하였다. 슬러리에서 세라믹화이버의 해섬 및 분산을 위한 슬러리 적정 점도는 28~31 cps이었고, pH 변화에 따라 제타전위는 민감하게 변화하여 pH 7.5~9.5에서 -35~-36 mV로 최대치를 나타내었으며, 이때 세라믹화이버의 침강량도 가장 적게 나타나 슬러리의 제타전위가 증가함에 따라 세라믹화이버의 분산도 잘 이루어짐을 알 수 있었다. 습식초지공정 중 흡입탈수는 함수율 83 wt% 이상으로 유지시켜야 바인더 손실을 막을 수 있었으며, 압축탈수 후 함수율이 62wt% 미만이 되어야 습식회수가 가능하였다. 제조된 세라믹섬유지는 인장강도 $102 kgf/cm^2$, 평량 $98 g/m^2$를 나타내었다.