• 설비공학논문집
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• 제10권3호
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• pp.292-302
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• 1998

In this study, 14 refrigerant mixtures composed of R32, R125, R134a, R143a, R152a, and R1270(Propylene) were tested in a breadboard heat pump in an attempt to replace R22 used in most of the residential air conditioners and heat pumps. The heat pump was of 1 ton capacity and water was employed as the secondary heat transfer fluids. All tests were conducted under ARI test A condition. Ternary mixtures composed of R32, R125, and R134a were shown to have 4∼5% higher COP and capacity than R22 and hence they seem to be very promising candidates to replace R22. On the other hand, ternary mixtures containing R125, R134a, and R152a have lower COP and capacity than R22. R32/R134a binary mixtures show a 7% increase in COP and have the similar capacity to that of R22 and hence they are also good candidates to replace R22. Special care must be exercised when a suction line heat exchanger is used with these mixtures in air conditioners. Finally, the compressor discharge temperatures of all mixtures tested were lower than those of R22 by 15.g∼34.7t, which indicates that these mixtures would offer better system reliability and longer life time than R22.

• 한국지능시스템학회논문지
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• 제21권2호
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• pp.250-253
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• 2011

본 논문에서는 일반화 된 fuzzy r-minimal 열린 집합들을 이용하여 fuzzy 약 r-M 연속함수의 특성을 조사한다.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제11권2호
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• pp.103-107
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• 2011

The concepts of fuzzy r-minimal semicompact, almost fuzzy r-minimal semicompact, and nearly fuzzy r-minimal semicompact on fuzzy r-minimal spaces arc introduced. We also investigate the relationships between fuzzy r-M-semicontinuous mappings and several types of fuzzy r-minimal semicompactness.

• 대한수학회보
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• 제20권1호
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• pp.45-49
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• 1983

If R is ring and M is a right (or left) R-module, then M is called a faithful R-module if, for some a in R, x.a=0 for all x.mem.M then a=0. In [4], R.E. Johnson defines that M is a prime module if every non-zero submodule of M is faithful. Let us define that M is of prime type provided that M is faithful if and only if every non-zero submodule is faithful. We call a right (left) ideal I of R is of prime type if R/I is of prime type as a R-module. This is equivalent to the condition that if xRy.subeq.I then either x.mem.I ro y.mem.I (see [5:3:1]). It is easy to see that in case R is a commutative ring then a right or left ideal of a prime type is just a prime ideal. We have defined in [5], that a chain of right ideals of prime type in a ring R is a finite strictly increasing sequence I$_{0}$.contnd.I$_{1}$.contnd....contnd.I$_{n}$; the length of the chain is n. By the right dimension of a ring R, which is denoted by dim, R, we mean the supremum of the length of all chains of right ideals of prime type in R. It is an integer .geq.0 or .inf.. The left dimension of R, which is denoted by dim$_{l}$ R is similarly defined. It was shown in [5], that dim$_{r}$R=0 if and only if dim$_{l}$ R=0 if and only if R modulo the prime radical is a strongly regular ring. By "a strongly regular ring", we mean that for every a in R there is x in R such that axa=a=a$^{2}$x. It was also shown that R is a simple ring if and only if every right ideal is of prime type if and only if every left ideal is of prime type. In case, R is a (right or left) primitive ring then dim$_{r}$R=n if and only if dim$_{l}$ R=n if and only if R.iden.D$_{n+1}$ , n+1 by n+1 matrix ring on a division ring D. in this paper, we establish the following results: (1) If R is prime ring and dim$_{r}$R=n then either R is a righe Ore domain such that every non-zero right ideal of a prime type contains a non-zero minimal prime ideal or the classical ring of ritght quotients is isomorphic to m*m matrix ring over a division ring where m.leq.n+1. (b) If R is prime ring and dim$_{r}$R=n then dim$_{l}$ R=n if dim$_{l}$ R=n if dim$_{l}$ R<.inf. (c) Let R be a principal right and left ideal domain. If dim$_{r}$R=1 then R is an unique factorization domain.TEX>R=1 then R is an unique factorization domain.

• 대한의용생체공학회:의공학회지
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• 제22권2호
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• pp.197-204
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• 2001

• 한국지능시스템학회:학술대회논문집
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• 한국퍼지및지능시스템학회 2007년도 춘계학술대회 학술발표 논문집 제17권 제1호
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• pp.179-182
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• 2007

In this paper, we introduce the concepts of fuzzy (r, s)-semi-preopen sets and fuzzy (r, s)-semi-precontinuous maps on intuitionistic fuzzy topological spaces in Sostak's sense. The relations among fuzzy (r, s)-semicontinuous, fuzzy (r, s)-precontinuous, and fuzzy (r, s)-semi-precontinuous maps are discussed. The concepts of fuzzy (r, s)-semi-preinterior, fuzzy (r, s)-semi-preclosure, fuzzy (r, s)-semi-preneighborhood, and fuzzy (r, s)-quasi-semi-preneighborhood are given. Using these concepts, the characterization for the fuzzy (r, s)-semi-precontinuous map is obtained. Also, we introduce the notions of fuzzy (r, s)-semi-preopen and fuzzy (r, s)-semi-preclosed maps on intuitionistic fuzzy topological spaces in Sostak's sense, and then we investigate some of their characteristic properties.

• 설비공학논문집
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• 제22권12호
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• pp.837-844
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• 2010

In this study, performance of R1234yf and R1234yf/R134a mixture is measured on a heat pump bench tester in an attempt to substitute R134a used widely in mobile air conditioners (MACs). The bench tester is equipped with a open type compressor providing a nominal capacity of 3.5 kW. All tests are conducted under the summer cooling and winter heating conditions of 7/4 $5^{\circ}C$ and $-7/41^{\circ}C$ in the evaporator and condenser, respectively. For R1234yf/R134a mixture, measurements are made at 5%, 10%, and 15% of R134a by mass. Test results show that the coefficient of performance (COP) and capacity of R1234yf are up to 2.7% and 4.0% lower than those of R134a, respectively. For R1234yf/R134a mixture, the COP and capacity are up to 3.9% lower and 3.6% higher than those of R134a. For R1234yf and R1234yf/R134a mixture, the compressor discharge temperature is $4.1{\sim}6.7^{\circ}C$ lower than that of R134a while the amount of charge is reduced up to 11% as compared to R134a. 90%R1234yf/10%R134a is a better refrigerant than pure R1234yf in that it is less flammable and more compatible with existing R134a system. Based upon the results, it is concluded that R1234yf and R1234yf/R134a mixture are long term environmentally friendly solutions to mobile air-conditioners due to their excellent environmental properties with acceptable performance.

• 한국철도학회논문집
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• 제13권5호
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• pp.528-534
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• 2010

신성장이론에서 R&D Stock은 노동과 자본 외에 제3의 생산요소이다. 이 관점에서 R&D Stock은 기존의 자본처럼 비용이 투입되어야만 축적이 가능한 자본의 위치를 차지하게 되며 이것을 지식자본이라고 한다. 이러한 지식자본을 향상시키기 위한 노력이 R&D투자이며 이의 축적이 R&D Stock이다. R&D Stock과 총요소생산 성과의 관계를 추정함으로써 경제성장의 기여도, R&D 투자의 수익률 등을 분석한다. 본 논문에서는 철도 R&D 투자에 대한 R&D Stock을 분석하고 기술수준과 비교 한 결과 R&D Stock이 증가하면 기술수준도 비례적으로 증가되었다. 그리고 GDP에 대한 철도산업의 비중과 전 부문에 대한 철도 R&D Stock 비중을 비교한 결과 철도산업의 비중에 비해 철도 R&D Stock 비중이 상대적으로 작아 지속적인 철도 R&D 투자가 필요함을 알 수 있다.

• 대한수학회보
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• 제41권3호
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• pp.507-519
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• 2004

For a ring endomorphism $\sigma$ of a ring R, J. Krempa called $\sigma$ a rigid endomorphism if a$\sigma$(a)＝0 implies a＝0 for a ${\in}$R. A ring R is called rigid if there exists a rigid endomorphism of R. In this paper, we extend the (J'-rigid property of a ring R to the upper nilradical $N_{r}$(R) of R. For an endomorphism R and the upper nilradical $N_{r}$(R) of a ring R, we introduce the condition (*): $N_{r}$(R) is a $\sigma$-ideal of R and a$\sigma$(a) ${\in}$ $N_{r}$(R) implies a ${\in}$ $N_{r}$(R) for a ${\in}$ R. We study characterizations of a ring R with an endomorphism $\sigma$ satisfying the condition (*), and we investigate their related properties. The connections between the upper nilradical of R and the upper nilradical of the skew power series ring R[[$\chi$;$\sigma$]] of R are also investigated.ated.

• 서비스연구
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• 제13권1호
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• pp.144-158
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• 2023

기업과 정부의 연구개발(R&D: Research and Development) 투자는 지속적으로 증가해, 2021년 공공과 민간의 전체 연구개발비는 102조 1,352억 원으로 100조원을 돌파하였고, GDP 대비 R&D 투자 비중이 4.96%로 이스라엘에 이어 전 세계 2위 수준으로 나타났다. 본 연구는 100조원을 돌파한 국내 연구개발 투자의 R&D 생산성 제고 측면에서 국내 연구 서비스산업 현황과 연구개발(R&D) 혁신 생태계를 통계청의 기업활동조사 데이터를 바탕으로 분석하고 글로벌 연구 서비스산업과 기업 현황과 연구(R&D) 서비스 산업 지원을 위한 정부 정책을 조사 및 분석하였다. 특히, 본 연구에서는 기업활동조사 데이터를 바탕으로 업종별 연구개발(R&D) 서비스 외부 위탁에 대한 분석과 연도별 연구개발(R&D) 서비스 외부 위탁에 대한 조사를 통해 국내 연구(R&D) 서비스산업 현황에 대해 조사 분석하였다. 이를 통해 업종별 국내 연구(R&D) 서비스 산업 수요에 대한 주요 변화 추이를 제조업과 서비스업 관점에서 도출하였다. 분석 결과 국내 R&D 생태계는 전통적인 제조기업의 R&D 아웃소싱 수요가 정체된 것에 비해 서비스기업의 R&D 아웃소싱 수요가 급속도로 증가하고 있는 것으로 나타났다. 특히 국외 위탁기업이 지속적으로 확대되는 반면에 국내 연구개발 위탁 기업은 비중이 감소 추세를 보이고 있는 상태이다. 또한 서비스 업종별로 차별적인 특징을 보여주었다. 본 연구에서는 글로벌 연구 서비스 기업에 대한 조사와 연구(R&D) 서비스산업 지원 정책에 대한 분석을 바탕으로, 이러한 변화하는 기술 혁신과 연구(R&D) 서비스 수요에 대응하기 위해 제조기업과 서비스기업 R&D 아웃소싱 균형지원, 국내 연구개발 외부위탁 확대, 서비스업종 특화 R&D 아웃소싱 전략수립, 개방형 R&D 생태계 구축, 소재·부품·장비 전략과의 연계 혁신 방안을 제시하였다.