• 산업기술연구
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• 제22권B호
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• pp.231-240
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• 2002

The rational method of estimating peak flow is used largely for the simplicity. But the accuracy of rational method is not easy to estimate, because the rational method is analyzed by the deterministic point or view and the runoff coefficients of the rational method are proposed from other countries. In this study the rational method is analyzed by the probabilistic way to be a more reliable method. The runoff coefficient is regarded to parameter that changes the probabilistic rainfall to the peak flow. The runoff coeffient for each return period is analyzed to be a reliable index which is used to estimate the peak flow of ungauged natural catchments.

• 한국농공학회논문집
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• 제49권1호
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• pp.17-22
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• 2007

The heat flow characteristics of the Gudle (traditional Ondol) used a lot at farm houses have been performed with variations of Bunengki (Fireridge) by numerical analysis and field experiment. The Doedon-Gorae (Return-Firetunnel) Gudle is analyzed among the structure of Gudle. The distribution of heat flow in Gorse (Firetunnel) and the temperature distribution in floor of 3 Buneomgi (Fire ridge) was more uniform than that of 1 Buneomgi. The heat efficiency of 3 Buneomgi was higher than that of 1 Bunengki. That is, the 3 Bunengk is more efficient and more uniform temperature.

• 산업경영시스템학회지
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• 제40권1호
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• pp.50-56
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• 2017

The IRR (internal rate of return) is often used by investors for the evaluation of engineering projects. Unfortunately, it is widely known that it has serial flaws. Also, External rate of returns (ERRs) such as ARR (Average Rate of Return) or MIRR (MIRR, Modified Internal Rate of Return) do not differentiate between the real investment and the expenditure. The PRR (Productive rate of return) is faithful to the conception of the return on investment. The PRR uses the effective investment instead of the initial investment. In this paper, we examined two cases of the engineering project. the one is a traditional engineering project with financing activity, another is the project with R&D. Although the IRR has only one value, it overestimates or underestimate profitabilities of Engineering Projects. The ARR and the MARR assume that a returned cash reinvest other projects or assets instead of the project currently executing. Thus they are only one value of a project's profitability, unlike the IRR. But the ARR does not classify into the effective investment and non-investment expenditure. It only accepts an initial expenditure as for an investment. The MIRR also fails to classify into the investment and the expenditure. It has an error of making a loss down as the investment. The IRR works as efficiently as a NPW (Net Present Worth). It clearly expresses a rate of return in respect of an investment in an engineering project with a loan. And it shows its ability in an engineering project with a R&D investment.

• 디지털융복합연구
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• 제12권6호
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• pp.115-123
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• 2014

본 연구는 중소기업을 대상으로 첫째, 매출액순이익률, 총자산회전율 및 부채비율이 주주의 자본수익성지표인 자기자본순이익률에 어떤 영향을 미치는지, 둘째, 총자산순이익률이 자기자본순이익률에 미치는 영향관계를 부채비율이 조절하는지, 마지막으로 수정된 부채비율과 자기자본순이익률과의 영향관계를 실증적으로 분석하였다. 분석결과, 부채사용은 자기자본순이익률에 전반적으로 긍정적인 측면이 있는 것으로 나타났다. 그러나 수정된 부채비율의 2차함수 곡선모형에서 볼 수 있듯이 부채사용은 레버리지효과를 통해 자기자본순이익률의 증 감폭을 크게 확대하고 있음을 알 수 있다. 결국, 부채사용은 동전의 양면과 같이 긍정적인 측면뿐만이 아니라 부정적인 측면을 가지고 있다 할 것이다. 그래서 부채의 사용은 기존의 핵심 사업으로부터 창출되는 영업현금흐름(혹은 총자산영업이익률)으로 이자(혹은 이자율)를 커버할 수 있는 범위 내로 제한되어야 한다는 시사점을 제공하고 있다.

• 산업경영시스템학회지
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• 제25권5호
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• pp.9-14
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• 2002

A capital investment problem is essentially one of determining whether the anticipated cash inflows from a proposed project are sufficiently attractive to invest funds in the project. The net present value(NPV) criterion and internal rate of return(IRR) criterion are widely used as means of making investment decisions. A positive NPV means the equivalent worth of the inflows is greater than the equivalent worth of outflows, so, the project makes profit. Business people are familiar with rates of return because they all borrow money to finance ventures, even if the money they borrow is their own. Thus they are apt to use the IRR in preference to the NPV. The IRR can be defined as the discount rate that causes the net present value of a cash flow to equal zero. Why the project are accepted if the project's IRR is greater than the investor's minimum attractive rate of return\ulcorner Against the NPV, the definition cannot distinctly explain the concept of the IRR as decision criterion. We present a new definition of the IRR as the ratio of profit on the invested capital.

• 한국유체기계학회 논문집
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• 제10권4호
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• pp.29-38
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• 2007

In this study, flow structure in a two-stage centrifugal compressor for a turbo-chiller with the refrigerant, R134a, was numerically investigated at the design point of the compressor using a commercial code. Flow characteristics in the passages of impeller, diffuser and return channel were analyzed in detail including velocity vector, secondary flow, Mach number and pressure contours in blade spanwise and meridional plane for each stage. The estimation on the one-dimensional output from the preliminary design and three-dimensional shape of the impeller blade and the meridional shape of the return channel were performed through the flow analysis, while some numerical schemes and techniques including Multiple Frames of Reference technique, real gas property data and inlet boundary condition changes, which were used in CFD, were compared with their features. The results will be used as reference data for a new design of 3-D impeller shape to improve R134a compressor performance.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.2039-2043
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• 2007

Like other major river basin systems in the West of the United States the Platte River Basin are faced with the challenges of allocating more water for plant and animal species. A part of the Central Platte River was designated as critical habitat for the whooping crane in 1978. The water allocation system in the Platte River Basin is dominated by the Prior Appropriation Doctrine, which allocates water according to the priorities based on the date of water use. The Platte River Basin segregated into five subregions for purpose of analysis. 24 years of historic records of monthly flow and all the demands were complied. The simulation of river basin modeling includes physical operation of the system including water allocation by water rights and interstate compact agreements, reservoir operations, and diversion with consumptive use and return flow. MODSIM, a generalized river basin network model, was used for estimating the timing and magnitude of impacts on river flows and diversions associated with water transfers from each region. A total of 20 alternatives were considered, covering transfers from each of the five regions of basin with several options. The result shows that the timing and availability of augmented water at the critical habitat is not only a function of use by junior appropriators, but also of river losses, and timing of return flows.

• 드라이브 ㆍ 컨트롤
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• 제9권2호
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• pp.8-14
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• 2012

Electro-hydraulic spring return actuator(ESRA) is utilized for air conditioning facilities in a nuclear power plant. It features self-contained, hydraulic power that is integrally coupled to a single acting hydraulic cylinder and provides efficient and precise linear control of valves as well as return of the actuator to the de-energized position upon loss of power. In this paper, the algebraic equations of ESRA at steady-state have been developed for the analysis of static characteristics that includes control pressure and valve displacement of pressure reducing valve, flow force on flapper as well as its displacement over the entire operating range. Also, the effect of external load on piston deviation is investigated in terms of linear system analysis. The results of static characteristics show the unique feature of force balance mechanism and can be applied to the stable self-controlled mechanical system design of ESAR.

• 한국분말재료학회지
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• 제29권4호
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• pp.303-308
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• 2022

The plastic deformation behavior of additively manufactured anisotropic structures are analyzed using the finite element method (FEM). Hill's quadratic anisotropic yield function is used, and a modified return-mapping method based on dual potential is presented. The plane stress biaxial loading condition is considered to investigate the number of iterations required for the convergence of the Newton-Raphson method during plastic deformation analysis. In this study, incompressible plastic deformation is considered, and the associated flow rule is assumed. The modified return-mapping method is implemented using the ABAQUS UMAT subroutine and effective in reducing the number of iterations in the Newton-Raphson method. The anisotropic tensile behavior is computed using the 3-dimensional FEM for two tensile specimens manufactured along orthogonal additive directions.

• Ecology and Resilient Infrastructure
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• 제1권1호
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• pp.8-18
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• 2014

본 연구에서는 수공구조물 하류에서의 하천흐름 특성을 3차원 수치모형인 Delft3D 모형을 이용하여 분석하고, 하천흐름 특성을 분석한 결과를 기반으로 홍수시에 어류의 피난처를 예측하였다. 수공구조물은 통수단면적을 변화시키고 유속과 수심을 변화시켜서 어류활동에 영향을 준다. 대상유역인 구미보 직하류에서는 흐름의 중심이 되는 저수로가 좌안으로 집중되면서 우안에서 수심이 낮고, 유속이 느리게 나타나서 어류의 피난처 형성은 우안을 중심으로 발생하였다. 어류의 활동범위를 분석하기 위해 수직방향 유속을 비교한 결과, 30년 빈도와 50년 빈도 경우 우안에서 최대 0.0043 m/s, 0.0052 m/s로 나타났고, 80년 빈도와 100년 빈도는 좌안에서 최대 0.0046 m/s, 0.0039 m/s로 나타났다. 또한 유량이 증가함에 따라 수심이 깊어지고 난류에너지가 상승하여 어류의 피난처가 감소되었다. 30년 빈도 홍수량와 100년 빈도 홍수량에 대하여 어류의 피난처를 비교하면 우안에 형성되는 어류의 피난처 예상 면적이 61.5%에서 39.0%으로 감소하였다.