• 산업경영시스템학회지
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• 제6권9호
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• pp.27-33
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• 1983

This Paper represents time-dependent stochastic variations of common discounted cash flow formulae with explicit consideration given to inflation. The cash flow, the ratio of discounting or compounding, and the rate of inflation are allowed to vary with time in a random fashion in equations for the compound amount of a single payment, present worth of a single payment, amount of an annuity, periodic deposits to accumulate a future amounts, present worth of an annuity and capital recovery And all formulae are derived for the case of discrete random variations.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.1397-1405
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• 2009

In recent decades, exergy analysis has been holding spotlight as a useful tool in the design, assessment, optimization, and improvement of energy system. This paper presents the results of the energy and exergy analysis of a steam turbine cogeneration system for industrial complex using two efficiency concepts of conventional one and exergetic one. In order to obtain the destroyed exergy of each component, mathematical analysis is conducted by using exergy balance and the second law of thermodynamics, according as the parameters are changed, such as the ratio of returned process steam, process steam supplied, temperature and pressure of boiler and power. The computer program developed in this study can determine the efficiencies and exergy destroyed at each component of cogeneration system. As a result of this study, a component having the largest destroyed exergy was boiler. And closed and opened feedwater heater had the lowest one. The affects to the cogeneration system due to the variation of process steam flow and return rate of condensed water is shown that the total electric power efficiency(${\eta}_E$) is decreased as increasing the return rate of condensed water under constant process steam flow. As the boiler pressure is increased for the more production of electricity, the efficiency of cogeneration system was decreased.

• 국제학술발표논문집
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• The 5th International Conference on Construction Engineering and Project Management
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• pp.602-607
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• 2013

Financial risks associated with capital investments are often measured with different feasibility indicators such as the net present value (NPV), the internal rate of return (IRR), the payback period (PBP), and the benefit-cost ratio (BCR). This paper aims at demonstrating practical applications of probabilistic feasibility analysis techniques for an integrated feasibility evaluation of the IRR and PBP. The IRR and PBP are concurrently analyzed in order to measure the profitability and liquidity, respectively, of a cash flow. The cash flow data of a real wind turbine project is used in the study. The presented approach consists of two phases. First, two newly reported analysis techniques are used to carry out a series of what-if analyses for the IRR and PBP. Second, the relationship between the IRR and PBP is identified using Monte Carlo simulation. The results demonstrate that the integrated feasibility evaluation of stochastic cash flows becomes a more viable option with the aide of newly developed probabilistic analysis techniques. It is also shown that the relationship between the IRR and PBP for the wind turbine project can be used as a predictive model for the actual IRR at the end of the service life based on the actual PBP of the project early in the service life.

• 한국콘텐츠학회논문지
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• 제9권1호
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• pp.407-416
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• 2009

경제성 분석에 의한 재무타당성 분석은 이론적으로나 실무적으로 그 타당성이 인정되고 있으나, 할인율 추정이 어려운 관계로 경제성 분석과 결과해석이 실무적으로 쉽지 않다. 따라서 본 연구는 신규호텔 건설 시 경제성 분석에 의한 재무타당성 분석의 구체적인 틀과 실무적용방법 및 기술을 제시하는데 근본적인 목적을 두고 연구하였다. 연구의 결과, 첫째, 대용베타방식에 의한 할인율(자본비용)을 실무적으로 추정하는 방식을 제시하여 경제성 분석결과에 대한 신뢰성과 타당성을 증대시킬 수 있었다. 둘째, 할인율과 현금흐름을 이용한 경제성 분석기법(순현가법, 내부수익율법, 수익성지수법 등)에 의한 재무타당성 분석의 전체적인 틀을 설명할 수 있었다. 셋째, 재무타당성 분석의 각 단계에서 요구되는 실무적인 분석기술을 제시할 수 있었다.

• 한국항공우주학회지
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• 제31권1호
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• pp.73-84
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• 2003

항공기내 연료온도의 변화가 유한차분식에 의하여 해석되었다. 항공기의 여러 임무 가운데 근접항공지원 임무가 20% hot day 외부대기 조건과 함께 이음속 영역에서 고려되었다. 수정 Dufort-Frankel기법의 explicit방법에 의해 수치계산이 수행되었다. 항공기는 난류유동장내에 있는 것으로 가정되었다. 추가 연료공급-회송 개념을 갖는 항공기 연료시스템 모델이 고려되었다. 본 해석의 결과로써, 추가연료 공급이 증가함에 따라 연료탱크의 온도는 상승함을 보인 반면, 엔진 입구에서의 연료온도는 몇몇 비행단계 및 엔진 연료요구량이 많은 구간을 제외하고는 감소함을 보였다. 본 해석으로부터, 추가 연료공급-회송개념을 사용한 연료시스템이 엔진입구 연료온도를 낮추기 위한 효과적인 방법임을 나타났다. 또한, 연료/오일 열교환기로 흐르는 연료유동량이 연료온도 변화에 중요한 인자임이 밝혀졌다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.771-776
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• 2000

Fine grid calculations are reported for the developing turbulent flow in a straight duct and a curved duct of square cross-section with a radius of curvature to hydraulic diameter ratio ${\delta}=R_c/H_H=3.357$ and a bend angle of 180 deg. A sequence of modeling refinements is introduced; the replacement of wall function by a fine mesh across the sublayer and a low Reynolds number second moment closure up to the near wall sublayer in which the non-linear return to isotropy model and the cubic-quasi-isotropy model for the pressure strain are adopted; and the introduction of a multiple source model for the exact dissipation rate equation. Each refinement is shown to lead to an appreciable improvement in the agreement between measurement and computation.

• 설비공학논문집
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• 제22권7호
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• pp.460-467
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• 2010

In housing units constructed recently in Korea, the length of ondol coil is different in each room, so the flow rate of hot water is adjusted by setting valve opening. If the flow rate is not appropriate for heating load, the room temperature seriously deviates from the set temperature range for comfort. In particular, too small valve opening can induce a noise by cavitation. In order to adjust the valve opening, two methods by zone area and a new method by return temperature rise were modelled and simulated using TRNSYS and EES. As a result, heating energy consumption during one week was the same on three methods, but the room temperature of the new method minimally deviated from the range of set temperature with a low possibility of noise.

• 산업경영시스템학회지
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• 제31권4호
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• pp.177-187
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• 2008

It is very important to select optimal investment alternative. The common method of economic evaluation is to compare of NPV, FW, AE by MARR, or the rate of return for the cash flow of alternatives. This method is undergoing by assumption that cash flow can be always evaluated by MARR, but the cash flow is not always increased or discounted like MARR. So this paper suggests a model on an economic analysis and evaluation regarding to various cash pattern, that is helpful for the person in the field to use easily.

• Membrane and Water Treatment
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• 제3권2호
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• pp.113-121
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• 2012

Up-flow multi-layer bioreactor (UMBR) is a hybrid system using dual sludge that consists of an up-flow multi-layer bioreactor as anaerobic/anoxic suspended growth microorganisms followed by an aeration tank. The UMBR acts as a primary settling tank, anaerobic/anoxic reactor, thickener which requires low energy due to mixing by up-flow stream. This study focused on using a pilot UMBR plant with capacity of 20-30 $m^3$/day for domestic wastewater in HCMC. HRTs of UMBR and aeration tank were 4.8 h and 7.2 h, respectively. The average MLSS of UMBR ranged from 10,000-13,600 mg/l SS. Internal recycle rate and sludge return were 200-300% and 150-200%, respectively. The results obtained from this study at flow rate of 20 $m^3$/day showed that removal of COD, SS, TKN, N-$NH_4$, T-N, and color were 91%, 87%, 86%, 80%, 91% and 91%, respectively.

• KDI Journal of Economic Policy
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• 제39권2호
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• pp.75-98
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• 2017

This paper aims to estimate the social discount rate (SDR) rather than dig into its theoretical foundation. As SDRs can be derived by investigating both the rate of return on investment and the social time preference rate, we estimate the marginal productivity of both private and public capital and the time preference rate based on the Euler equation. In order to provide a single representative SDR, the weighted averages of the marginal productivity and time preference rate, whose weights are determined by the flow of funds data reflecting the social demand of funds, are presented. Based on the empirical results, we argue that the marginal productivity of private capital stands in the middle of the 3% range while that of public capital varies from 4.5% to 8.6%, with the time preference rate showing a decreasing trend from 3.2% in the early 2000s to 1.2% by around 2030. The single representative SDR or the weighted SDR is estimated to be approximately 3.0~4.5% and expected to continue its downward trend for the foreseeable future.