• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2018년도 학술발표회
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• pp.146-146
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• 2018

Basin evapotranspiration is the result of water balance and energy balance, which is affected by climate and underlying surface characteristics, the process is complex, and spatial and temporal variability is large, the evapotranspiration estimation of river basin is an important but difficult problem in the field of hydrology, over the years, many scholars devoted to the basin actual evapotranspiration estimation and achieved excellent results. We discuss Budyko coupled water-energy balance theory and evaporation paradox, then use the Fu's equation to estimate actual evapotranspiration yearly in different areas with different dryness. The result shows that Fu's equation has high precision for estimating evapotranspiration yearly in our selected study area, and the estimation result has higher precision in the area with high dryness. Then, we propose an improved formula which can be used to estimate actual evapotranspiration monthly. Furthermore, we found that the parameter in the formula reflects general conditions of underlying surface and it is affected by several factors, at last, we tried to propose the calculation formula. The study indicates that Fu's equation provides a reliable method for evapotranspiration estimation in dry regions as well as semi-humid and semi-arid regions, which has great significance for forecasting river basin water resources and inquiring into ecological water requirement.

• 에너지공학
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• 제14권2호
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• pp.147-152
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• 2005

본 논문에서는 화력발전소 보일러 연료소비량을 측정에 의하지 않고 계산으로 구하는 방법을 세부 항목 별로 유도하고 그 결과를 검증하였다. 보일러 경계를 출입하는 Energy in Energy out의 정량적 관계를 분석하여 Energy in에 해당하는 투입열량과 Energy out에 해당하는 흡수열량 및 손실열량으로부터 에너지 출입의 유기적인 관계식을 수립하여 연료소비량 계산식을 유도, 정립하고 실제 운전중인 석탄 및 중 유연소 발전소에 적응하여 계산식의 정확성을 검증하였다.

• Steel and Composite Structures
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• 제42권4호
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• pp.477-487
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• 2022

The shear stiffness of headed-stud shear connectors has no unified definition due to the nonlinear characteristics of its load-slip relationship. A unified framework was firstly adopted to develop a general expression of shear load-slip equation for headed-stud shear connectors varying in a large parameter range based on both force and energy balance. The pre- and post-yield shear stiffness were then determined through bilinear idealization of proposed shear load-slip equation. An updated and carefully selected push-out test database of 157 stud shear connectors, conducting on studs 13~30mm in diameter and on concretes 30~180 MPa in cubic compressive strength, was used for model regression and sensitivity analysis of shear stiffness. An empirical calculation model was also established for the stud shear stiffness. Compared with the previous models through statistical analysis, the proposed model demonstrates a better performance to predict the shear load-slip response and stiffness of the stud shear connectors.

• 전기화학회지
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• 제22권1호
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• pp.43-52
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• 2019

리튬이차전지(Lithium Secondary Batteries)를 에너지원으로 채용하는 분야가 다양해짐에 따라, 기존 요구 특성뿐만 아니라 각 분야에 특화된 성능 평가 결과까지 요구하고 있다. 이에 대응하기 위해 각 전지 제조사는 연구 인력을 충원하고 고가의 장비를 지속적으로 도입해서 다수의 전지를 오랜 기간 평가해야 하는 어려움을 겪고 있다. 이를 해소하기 위해, 전지 모델링(Modeling)을 기반으로 한 모사(Simulation) 기법을 도입하여, 실험 횟수를 최소화하고 실험 시간도 단축하려는 시도를 지속하고 있다. 현재까지 다양한 리튬이차전지 모델링 기법이 보고되고 있으며, 목적에 따라 최적 기법이 선택 및 활용되어 왔다. 본 리뷰 논문에서는 뉴만(Newman) 모델을 기반으로 한 전기화학적 모델링(Electrochemical Modeling) 기법을 상세히 설명한다. 특히, 전극 반응속도를 나타내는 버틀러-볼머식(Butler-Volmer Equation), 각 상(Phase)에서 전자와 이온의 균형 방정식 (Material and Charge Balance Equations), 그리고 전지의 온도 변화를 설명할 수 있는 에너지 균형 방정식 (Energy Balance Equation)의 물리적 의미를 쉽게 설명하고, COMSOL Multiphysics를 이용한 간단한 해석 과정과 결과를 제시한다.

• 한국수소및신에너지학회논문집
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• 제30권5호
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• pp.385-394
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• 2019

The analysis of temperature behavior of a hydrogen tank during refueling is of significance to clarify the safety of the compressed hydrogen storage in vehicles since the temperature at a tank rises with inflow of hydrogen. A mass balance and an energy balance were combined to obtain analytical model for temperature change during the hydrogen refueling. The equation was coupled to Peng-Robinson-Gasem (PRG) equation of state (EOS) for hydrogen. The PRG EOS was adopted after comparison with other four different cubic EOSs. A parameter of the model was determined to fit data from experiments of various inlet flow rates and temperatures. The temperature and pressure change with refueling time were obtained by the developed model. The calculation results revealed that the extent of precooling was more effective than the flow rate control.

• 설비공학논문집
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• 제15권5호
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• pp.360-371
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• 2003

The calculation of each unit cost of productions is very important for evaluating the economical efficiency and deciding the reasonable sale price. In the present, two methods of exergy costing on multiple energy systems are suggested to reduce the complexities of conventional SPECO method and MOPSA method and to improve the calculation efficiency of exergoeconomics. The suggested methods were applied to a gas-turbine cogeneration and the unit costs of the power and the steam energy were calculated as an example. The main points of our methods are the following three. First, one exergetic cost is applied to one cycle or system. Second, the suggested equations are the internal cost balance equation and the production cost balance equation. Third, necessary states in a system are only inlet and exit states of 1ha components producing energy.

• 한방비만학회지
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• 제3권1호
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• pp.95-105
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• 2003

The obesity is the matter of the energy balance in essential. The energy balance in human body is energy expenditure subtracted from energy intake. The energy intake is mainly supplied by carbohydrates, proteins and lipids in food, and the energy expenditure is composed of basal metabolic rate or resting energy expenditure, physical activity and thermogenesis including diet-induced thermogenesis. The resting energy expenditure is measured by direct calorimetry and indirect calorimetry. Generally we can simply use predictive equation with the variables of weight, height, age and fat-free mass to yield metabolic rate. But there is discrepancy between the estimate and real metabolic rate because the equations can not reflect individuality and environments. The resting energy expenditure is influenced by many factors but the fundamental factor is fat-free mass. We briefly reviewed the concept and evaluation of the energy balance, intake and expenditure, which are important parts in the study of obesity. Finally, we surveyed the correlation between metabolic rate and obesity and suggested applicable herb medication to increase metabolic rate.

• 대한전기학회논문지
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• 제36권9호
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• pp.655-659
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• 1987

This study presents a model of the electrical characteristics of the high-pressure mercury vapour arc discharge. Energy balance equation per unit volume of the arc tube is converted into the one per unit length by assuming the parabolic radial temperature distribution and integrating over the cross-section of the tube. Using this energy balance equation, together with the circuit equation and Ohm's law, the arc voltage and current variation for 1 cycle is numerically calculated and a good result is obtained. A simple method to calculate the axis temperature of the arc tube and the radiation output is also presented.

• 한국진공학회지
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• 제10권4호
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• pp.424-430
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• 2001

RF나 마이크로웨이브의 전기장이 작용될 때 플라즈마 방전에서의 전자에너지분포함수를 계산하기 위하여 전자 볼츠만 방정식을 수치적으로 푼다. 2차미분 방정식인 로렌츠근사를 사용하는 동차 전자 볼츠만 방정식과 적분-미분방정식인 입자균형방정식을 동시에 풀어 자체모순이 없게 방전 전기장의 크기를 결정한다. 이 수치코드를 이용하여 아르곤 방전에 대하여 전자에너지 분포함수를 RF와 마이크로파영역에 걸쳐 계산한다. 이로부터 전자에너지 분포함수와 이온화율에 대한 고주파 전기장의 주파수 변화에 따른 영향을 조사한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.108-113
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• 1996

Several analytical models for the departure from nucleate boiling (DNB) phenomenon have been developed during the last decade. Among these, Chang & Lee's model based on a bubble crowding mechanism is remarkable in the fundamental features characterized as the formulation of mass, energy, and momentum balance equation at thermal-hydraulic conditions leading to the DNB. However, Bricard and Souyri remarked that the assumption of stagnant bubbly layer at the DNB condition is questionable and the signs on the axial projections of the momentum fluxes at the core/bubbly layer interface in the momentum balance equations are erroneous. From this remark, Chang & Lee's model has been re-examined and modified by correcting the erroneous treatments in the momentum balance equations and removing the spurious assumptions. The revised model predicts well the extensive DNB data of water in uniformly heated tubes at low qualities and shows more accurate prediction compared with the original model.