• 품질경영학회지
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• 제48권1호
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• pp.201-214
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• 2020

Purpose: The purpose of this paper is to determine an optimal number of cycle times for the replacement under the circumstance where the system is replaced at the periodic time and the multiple number of working cycles whichever occurs first and the system is minimally repaired between the replacements if it fails. Methods: The system is replaced at periodic time () or cycle time, whichever occurs first, and is repaired minimally when it fails between successive replacements. To determine the optimal number of cycle times, the expected total cost rate is optimized with respect to the number of cycle times, where the expected total cost rate is defined as the ratio of the expected total cost between replacements to the expected time between replacements. Results: In this paper, we conduct a sensitivity analysis to find the following results. First, when the expected number of failures per unit time increases, the optimal number of cycle times decreases. Second, when the periodic time for replacement becomes longer, the optimal number of cycle times decreases. Third, when the expected value for exponential distribution of the cycle time increases, the optimal number of cycle times increases. Conclusion: A mathematical model is suggested to find the optimal number of cycle times and numerical examples are provided through the sensitivity analysis on the model parameters to see the patterns for changes of the optimal number of cycle times.

• 한국태양에너지학회 논문집
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• 제27권4호
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• pp.19-26
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• 2007

This paper concerns the study of absorption refrigeration and heat pump cycle to use sewage. Simulation analysis on the double-effect absorption refrigeration cycle with parallel and two-stage heat pump cycle has been performed. The working fluid is Lithium Bromide and water solution. The absorption refrigeration cycle use sewage as a cooling water for the absorber and condenser, and absorption refrigeration cycle does that as a chilled water for the evaporator of the first stage cycle. And the two-stage cycle consists of coupling double-effect with parallel and single effect cycle so that the first stage absorber and condenser produces heating water to evaporate refrigerant in the evaporator of the second stage. The effects of operating variables such as a absorber temperature on the coefficient of performance have been studied for absorption refrigeration and heat pump cycle.

• 대한지구과학교육학회지
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• 제9권1호
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• pp.54-64
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• 2016

The purpose of this study was to see the influences of science class applying learning cycle emphasized exploration on science learning motivation and scientific attitude of elementary students. The results drawn from this analysis were as below. Firstly, positive relationship was found between science learning motivation and science class applying learning cycle emphasized exploration among the research group. This shows that science learning motivation was improved by science class applying learning cycle emphasized exploration. It indicates that science class applying learning cycle emphasized exploration is effective in improving science learning motivations. Secondly, positive relationship was found between scientific attitude and science class applying learning cycle emphasized exploration among the research group and this means that science class applying learning cycle that emphasizes exploration stimulates intellectual curiosity of elementary school students and improves their scientific attitude. Thirdly, students thought that science class applying learning cycle emphasized exploration was very effective to improve their satisfaction, interest, participation in their science classes. Above results show that science class applying learning cycle emphasized exploration is highly effective for elementary students. Thus, it is needed to utilize science class applying learning cycle emphasized exploration to current science class as it can promote wider scientific activities among elementary school students.

• 상하수도학회지
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• 제29권1호
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• pp.11-21
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• 2015

When designing Water Distribution System (WDS), determination of life cycle for WDS needs to be preceded. And designer should conduct comprehensive design including maintenance and management strategies based on the determined life cycle. However, there are only a few studies carried out until now, and criteria to determine life cycle of WDS are insufficient. Therefore, methodology to determine life cycle of WDS is introduced in this study by using Life Cycle Energy Analysis (LCEA). LCEA adapts energy as an environmental impact criterion and calculates all required energy through the whole life cycle. The model is build up based on the LCEA methodology and model itself can simulate the aging and breakage of pipes through the target life cycle. In addition the hydraulic analysis program EPANET2.0 is linked to developed model to analyze hydraulic factors. Developed model is applied to two WDSs which are A WDS and B WDS. Model runs for 1yr to maximum 100yr target life cycle for both WDSs to check the energy tendency as well as to determine optimal life cycle. Results show that 40yr and 54yr as optimal life cycle for each WDS, and tendency shows the effective energy is keep changing according to the target life cycle. Introduced methodology is expected to use as an alternative option for determining life cycle of WDS.

• 한국데이타베이스학회:학술대회논문집
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• 한국데이타베이스학회 1999년도 춘계공동학술대회: 지식경영과 지식공학
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• pp.75-84
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• 1999

본 논문에서는 지식에 대한 개념을 정의하기 보다 지식의 life-cycle을 통한 지식의 생성과 소멸을 모델화함으로 지식을 설명하려 한다. 본 논문은 노나카의 지식 창조 모델을 기반으로 하고 기존의 KMS들을 분석하여 일반적인 지식 life-cycle 모델을 도출하였으며, 기존 모델의 문제점을 보완하여 새로운 지식 life-cycle 모델을 만들었다. 이 모델과 앞으로의 지식관리 시스템 발전 방향을 고려하여 지식 관리 시스템 아키텍쳐를 제시하였다. 본 논문에서는 이 아키텍쳐를 근거로 지식 관리 시스템을 구현하기 위한 6개의 컴포넌트를 도출하였다 6개의 컴포넌트는 지식 생성, 지식 분배, 지식 측정, 지식연결, 지식 검색, 지식 저장이다. 이 컴포넌트들로 지식 관리 시스템의 prototype을 구현해 본 결과 지식life-cycle을 단계적, 부분적으로 지원하지만 부족한 부분이 있는 것을 발견하였다. 향후에는 지식 생성과 지식 연결 컴포넌트를 강화하여 전체적인 지식 life-cycle을 지원할 예정이다.

• 한국지능정보시스템학회:학술대회논문집
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• 한국지능정보시스템학회 1999년도 춘계공동학술대회-지식경영과 지식공학
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• pp.75-84
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• 1999

본 논문에서는 지식에 대한 개념을 정의하기 보다 지식의 life-cycle을 통한 지식의 생성과 소멸을 모델화함으로 시식을 설명하려 한다. 본 논문은 노나카의 지식 창조 모델을 기반으로 하고 기존의 KMS들을 분석하여 일반적인 지식 life-cycle 모델을 도출하였으며, 기존 모델의 문제점을 보완하여 새로운 지식 life-cycle 모델을 만들었다. 이 모델과 앞으로의 지식관리 시스템 발전 방향을 고려하여 지식 관리 시스템 아키텍쳐를 제시하였다. 본 논문에서는 이 아키텍쳐를 근거로 지식 관리 시스템을 구현하기 위한 6개의 컴포넌트를 도출하였다. 6개의 컴포넌트는 지식 생성, 지식 분배, 지식 측정, 지식 연결, 지식 검색, 지식 저장이다. 이 컴포넌트들로 지식 관리 시스템의 prototype을 구현해 본 결과 지식 life-cycle을 단계적, 부분적으로 지원하지만 부족한 부분이 있는 것을 발견하였다. 향후에는 지식 생성과 지식 연결 컴포넌트를 강화하여 전체적인 지식 life-cycle을 지원할 예정이다.

• 한국수소및신에너지학회논문집
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• 제29권5호
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• pp.490-496
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• 2018

Recently, the power and refrigeration cogeneration based on Kalina cycle has attracted much attention for more efficient utilization of low-grade energy. This study presents a thermodynamic performance analysis of a cogeneration cycle of power and absorption refrigeration based on Kalina cycle. The cycle combines Kalina cycle (KCS-11) and absorption cycles by adding a condenser and an evaporator between turbine and absorber. The effects of ammonia mass fraction and separation pressure were investigated on the system performance of the system. Results showed that the energy utilization of the system could be greatly improved compared to the basic Kalina cycle.

• 한국수소및신에너지학회논문집
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• 제33권3호
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• pp.261-265
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• 2022

In this paper, comparative studies between Linde, Claude and advanced cycle for the liquefaction of nitrogen have been completed. PRO/II with PROVISION release 2021. 1 from AVEVA company (Cambridge, UK) was used, and Peng-Robinson equation of the state model with Twu's alpha function was selected for the modeling of the condensation of nitrogen. When using Claude liquefaction, we can reduce the total compression power by 49.25% for the comparison of Linde cycle. And finally, we could conclude that 90.41% of total compression power was saved when using an advanced cycle being compared to Linde liquefaction cycle.

• 미생물과산업
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• 제19권2호
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• pp.2-10
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• 1993

이 총론에서는 cell cycle의 조절에 관계하는 p34cdc kinase의 특성과 기질 그리고 cell cycle에서의 역할을 살펴보고, 또 cell cycle에서와 여러가지 세포내의 현상에 중요한 역할을 하는 것으로 알려진 casein kinase II의 특성과 기질 그리고 cell cycle에서의 역할을 살펴보고자 한다. 그리고 이런 효소들을 연구하는 데 필수적인 방법이나 시약들로 소개하고자 한다.

• International Journal of Air-Conditioning and Refrigeration
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• 제15권1호
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• pp.34-45
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• 2007

In order to reduce the compression power and to use the overall energy contained in LNG effectively, a combined cycle is devised and simulated. The combined cycle is composed of two cycles; one is an open cycle of liquid/solid carbon dioxide production cycle utilizing LNG cold energy in $CO_2$ condenser and the other is a closed cycle gas turbine which supplies power to the $CO_2$ cycle, utilizes LNG cold energy for lowering the compressor inlet temperature, and uses the heating value of LNG at the burner. The power consumed for the $CO_2$ cycle is investigated in terms of a solid $CO_2$ production ratio. The present study shows that much reduction in both $CO_2$ compression power (only 35% of the power used in conventional dry ice production cycle) and $CO_2$ condenser pressure could be achieved by utilizing LNG cold energy and that high cycle efficiency (55.3% at maximum power condition) in the gas turbine could be accomplished with the adoption of compressor inlet cooling and regenerator. Exergy analysis shows that irreversibility in the combined cycle increases linearly as a solid $CO_2$ production ratio increases and most of the irreversibility occurs in the condenser and the heat exchanger for compressor inlet cooling. Hence, incoming LNG cold energy to the above components should be used more effectively.