• 한국방사성폐기물학회:학술대회논문집
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• 한국방사성폐기물학회 2018년도 춘계학술논문요약집
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• pp.94-95
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• 2018

• 한국경영과학회지
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• 제17권1호
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• pp.67-75
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• 1992

In this paper, by using perturbation analysis method, We find the sensitivity of the mean busy cycle with respect to means interrival time in M/M/1 Queue. We show that the Perturbation analysis estimate can be expressed as a sum of the infinitesimal perturbation analysis (IPA) estimate and the effect caused by changes in transition probabilities, thus explaining why IPA estimates are not consistent in general.

• 설비공학논문집
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• 제24권1호
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• pp.51-60
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• 2012

Optimization procedures of performance analysis for ORC(Organic Rankine Cycle) system are established to the characteristics of low temperature heat sources such as open-type and closed-type. Effective heat recovery and heat extraction related to maximum power of the cycle as well as heat quality and thermal efficiency must be considered in the case of the open-type low temperature heat source. On the other hand, in the case of the closed-type low temperature heat source, only thermal efficiency is important due to constant heat input. In this study, thermal efficiency and exergy efficiency representing a level of close to Carnot cycle are studied, as useful index for the optimization of the ORC system. To validate the results of cycle analysis, those are compared with appropriate experimental data of ORC system as a thermal efficiency point of view.

• 한국수소및신에너지학회논문집
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• 제29권2호
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• pp.148-154
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• 2018

This paper presents a comparative analysis of thermodynamic performance of ammonia-water Rankine cycles with and without regeneration and Kalina cycle for recovery of low-temperature heat source. Special attention is paid to the effect of system parameters such as ammonia mass fraction and turbine inlet pressure on the characteristics of the system. Results show that maximum net power can be obtained in the regenerative Rankine cycle for high turbine inlet pressures. However, Kalina cycle shows better net power and thermal efficiency for low turbine inlet pressures, and the optimum ammonia mass fractions of Kalina cycle are lower than Rankine cycles.

• 설비공학논문집
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• 제25권10호
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• pp.548-554
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• 2013

A thermodynamic analysis of the R404A refrigeration system with an internal heat exchanger using R744 as a secondary refrigerant is presented in this paper to optimize the design for operating parameters of the system. The main results are summarized as follows: The COP increases with increasing subcooling and superheating degree of R404A, internal heat exchanger and compression efficiency of the R404A cycle and evaporating temperature of the R744 cycle and decreasing temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle. The mass flow ratio decreases with increasing evaporating temperature of the R744 cycle and internal heat exchanger efficiency of the R404A cycle and decreasing subcooling and superheating degree of the R744 cycle, temperature difference of the cascade heat exchanger and condensing temperature of the R404A cycle.

• 한국안전학회지
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• 제29권6호
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• pp.94-98
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• 2014

본 연구는 구조물의 최적안전수준과 수명기간동안 투자되는 총비용과의 상관관계를 연구하였다. 설계, 건설 및 공용 중 투자되는 총비용을 최소화하면서 최적의 안전수준을 결정하기 위하여 신뢰성해석을 수행하였다. 신뢰성해석에는 설계인자들의 불확실성과 설계 및 공사, 유지관리를 수행하는 인간의 오류 등 인적 불확실성을 확률변수로 고려하였다. 이러한 확률해석을 통한 안전지수와 생애주기비용의 상관관계를 연구하고, 생애주기비용의 분산도에 따른 안전지수의 민감도해석을 통하여 최적의 안전수준을 결정하였다. 해석결과는 이러한 평가방법이 교통시설물에 투자되는 비용을 최소화하면서 최적의 안전수준을 결정할 수 있는 정확하고 유용한 방법임을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집B
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• pp.252-257
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• 2000

An efficient method is developed for mold thermal cycle analysis in repeated forming process, which is well suited to the analysis in TV glass production. plunger, which is a mold to press-form the glass, undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state in the end. If analyzed straightforwardly of this problem, it leads to more than 80 cycles to get reasonable solution, and it is yet hard to setup stopping creteria due to extremely slow convergence. An exponential fitting method is proposed to solve the problem, where an exponential function is found to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the function value at infinite time. From numerical implementation, it is found that the method reduces the number of cycles dramatically to only $6{\sim}15$ cycles to reach accurate solution within $1^{\circ}$ error. A system for the analysis is contructed, in which the thermal analysis is performed by commercial software ANSYS, and the fitting of the result is done by IMSL library.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집B
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• pp.192-198
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• 2000

Three dimensional thermal cycle analysis of the plunger is carried out in repeated forming process of the TV glass, which is continued work of two dimensional analysis where an efficient method has been proposed. The plunger undergoes temperature fluctuation during a cycle due to the repeated contact and separation from the glass, which attains a cyclic steady state having same temperature history at every cycle. Straightforward analysis of this problem brings about more than 90 cycles to get reasonable solution. An exponential function fitting method is proposed, which finds exponential function to best approximate temperature values of 3 consecutive cycles, and new cycle is restarted with the fitted value at infinite time. Number of cases are analyzed using the proposed method and compared to the result of straightforward repetition, from which one finds that the method always reaches nearly convergent solution within $9{\sim}12$ cycles, but turns around afterwards without further convergence. Two step use is found most efficient, in which the exponential fitting is carried out fer the first 12 cycles, followed by simple repetition, which shows fast convergence expending only 6 additional cycles to get the accuracy within 2 error. This reduces the computation cycle remarkably from 90 to 18, which is 80% reduction. From the parametric studies, one reveals that the overall thermal behavior of the plunger in terms of cooling parameters and time is similar to that of 2 dimensional analysis.

• 가정과삶의질연구
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• 제13권4호
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• pp.165-180
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• 1995

The purpose of this study was to investigate the influences of family life cycle stages and perceived time pressure on strategies for coping with time constraints in housewife-teachers. The subjects of this study were 570 married women teachers who live with their husebands and children in junior and senior high schools in Taegu, A questionaire was used as survey method. Factor analysis and MANOVA were employed for data analysis and Scheffe test forpost-hoc analysis. The main findings were : First the effect of family life cycle stages on the use of personal time reducing strategies was different according to perceived time pressure. Second the effect of perceived time pressure on the use of personal time reducing strategies differed according to family life cycle stages. Third the use of strategies for coping with time contratins was found to be significantly different according to family life cycle stages, Forth there were significant differences in the use of strategies for coping with time constrainsts according to perceived time pressure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.2169-2170
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• 2011

This paper presents about the analysis on cost factor reduction using the life cycle cost model for motor block in the KTX-1. Until now, most life cycle cost of the system as a whole that has been studied. but in case of railway industry part, LCC studies are needed on the subsystem like a propulsion control system because subsystems are developed continuously localization. Therefore, In this paper presents cost breakdown structure for life cycle cost (LCC) estimation for localization development of propulsion control system (Motor Block) in high speed railway vehicle (KTX-1). Also to analysis LCC on motor block, it was analyzed physical breakdown structure (PBS) and preventive cost on propulsion control system in view of maintenance cost. Based on this, we describe life cycle cost on motor block of KTX-1.