• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.218-225
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• 1990

Studies on the performance of a heat pump using non-azeotropic refrigerant mixtures are done. In order to estimate the thermodynamic properties for the selected non-azeotropic refrigerant mixtures including R22/R152a, R22/R142b, R22/R114 and R13B1/R152a, Peng-Robinson equation of state is adopted. The pressure-enthalpy diagram and the temperature-entropy diagram are plotted for each refrigerant mixture. Considerations on the capacity modulation for the heat pump system using refrigerant mixtures are taken into. Results show that when the heating load varies, the possibility for the capacity modulation is found in the heat pump system using a compressor with constant volume flow rate. Under a constant heating capacity condition in the heat pump system, the coefficient of performance increases when the refrigerant mixtures are used. The volume flow rate decreases as the mass fraction of lower boiler increases in this case.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.2
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• pp.142-154
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• 1990

A theoretical cycle analysis has been performed for a basic heat pump, charged with non-azeotropic refrigerant mixtures, R22/R114 and R13B1/R152a. At first, a procedure is introduced to calculate thermodynamic properties simply and correctly, and the advantages of using refrigerant mixtures are discussed through the cycle analysis. It is shown that by using refrigerant mixtures in the heat pump, several improvements can be made. In comparison with conventional pure refrigerants, the application of refrigerant mixtures results in high reliabilities caused by the extension of the application limit, energetic improvements, and a continuous capacity control. From generalizing various results, the optimum compositions in refrigerant mixtures are also determined. The 30%/70% and 40%/60% compositions are selected for R22/R114 and R13B1/R152a, respectively.

• Kyungpook Mathematical Journal
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• v.47 no.1
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• pp.127-132
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• 2007

In this paper, we show that if R is a commutative ring with identity and (S, ${\leq}$) is a strictly totally ordered monoid, then the ring [[$R^{S,{\leq}}$]] of generalized power series is a PF-ring if and only if for any two S-indexed subsets A and B of R such that $B{\subseteq}ann_R(|A)$, there exists $c{\in}ann_R(A)$ such that $bc=b$ for all $b{\in}B$, and that for a Noetherian ring R, $[[R^{S,{\leq}}$]] is a PP ring if and only if R is a PP ring.

• Archives of Pharmacal Research
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• v.23 no.2
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• pp.151-154
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• 2000

Two sesquiterpene endoperoxides, 1S, 4R, 6R-1, 4-endoperoxy-bisabola-2, 10-diene (1), 1R, 4S, 6R-1, 4-endoperoxy-bisabola-2, 10-diene (II), and a sesquiterpene hydroperoxide, 1$\beta$-hydroperoxygermacra-4 (15), 5, 10 (14)-triene (III) were isolated from the aerial parts of Artemisia stolonifera (Compositae). Their chemical structures were assigned by spectral evidences. Compounds I and II exhibited cytotoxicity against five human tumor cell lines with their $\ED_50 values ranging from 0.20 to 5.43 ${\mu}g/m\ell$ and from <0.1 to 0.87 ${\mu}g/m\ell$, respectively.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.12 no.12
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• pp.1081-1089
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• 2000

Evaporating heat transfer coefficients of R-22 and R-134a were measured in smooth horizontal copper tubes with inner diameters of 1.77, 3.36 and 5.35mm, respectively. The experiments were conducted in a closed loop, which was driven by a magnetic gear pump. Experiments were performed for the following range of variables: mass velocity (200 to 400 kg/$m^2$.s), saturation temperature($0^{circ}C,; 5^{\circ}C$) and quality(0 to 1.0). Main results obtained are as follows: evaporating heat transfer coefficients in the small diameter tubes (ID<7mm) were observed to be strongly affected by various diameters and to differ from those in the large diameter tubers. The heat transfer coefficients of the small diameter tubes were higher than those of the large diameter tubs. And it was very difficult to apply some well-known previous predictions (Shah`s, Gungor-Winterton`s and Kandlikar`s correlation) to small diameter tubes.

• Bulletin of the Korean Mathematical Society
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• v.54 no.6
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• pp.1913-1925
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• 2017

Let R be a ring with identity. An ideal N of R is called ideal-symmetric (resp., ideal-reversible) if $ABC{\subseteq}N$ implies $ACB{\subseteq}N$ (resp., $AB{\subseteq}N$ implies $BA{\subseteq}N$) for any ideals A, B, C in R. A ring R is called ideal-symmetric if zero ideal of R is ideal-symmetric. Let S(R) (called the ideal-symmetric radical of R) be the intersection of all ideal-symmetric ideals of R. In this paper, the following are investigated: (1) Some equivalent conditions on an ideal-symmetric ideal of a ring are obtained; (2) Ideal-symmetric property is Morita invariant; (3) For any ring R, we have $S(M_n(R))=M_n(S(R))$ where $M_n(R)$ is the ring of all n by n matrices over R; (4) For a quasi-Baer ring R, R is semiprime if and only if R is ideal-symmetric if and only if R is ideal-reversible.

• Korean Journal of Medicinal Crop Science
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• v.14 no.3
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• pp.178-182
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• 2006

This study was conducted to investigate the variation in sequence, the base composition and the sequence similarity of 18S rDNA (18S ribosomal RNA coding region) in the 10 Polygonatum spp. collections. The entire 18S rDNA region of 10 Polygonatum spp. collections ranged from 913 bp to 914 bp. There were 8 variable sites in the entire 18S region, and they were attributable to nucleotide substitution and deletion. $T{\rightarrow}C$ transition happened in 4 sites, and $A{\rightarrow}G$ transition happened in 1 site. $C{\rightarrow}A$ transversion happened in 1 site, and deletion happened in 2 sites. Transition rates were five times that of transversion. Base compositions of 18S rDNA were $23.09{\sim}23.33%$ in adenine, $23.33{\sim}23.52%$ in guanine, $25.60{\sim}25.85%$ in thymine and $27.38{\sim}27.79%$ in cytosine. The A + T content of 18S rDNA of 10 Polygonatum spp. collections averages 48.99%, ranging from 48.80% to 49.18%, and the G + C content averages 51.01%, ranging from 50.82% to 51.20%. Pairwise sequence comparisons indicated that 18S rDNA sequence similarity ranged from 99.7% to 100%.

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.42.6-43
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• 2008

• Proceedings of the Korean Statistical Society Conference
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• 2005.11a
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• pp.1-3
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• 2005

통계 소프트웨어 R은 여러 가지 특징을 가진 도구이다. S라는 전산언어를 기반으로 하고 이에 수학함수와 통계함수, 그리고 그래픽함수들이 결합되어 편리한 계산 작업 환경을 제공하고 있다. R이 기반으로 하고 있는 S언어에는 문법적, 의미론적 특징이 잘 어울려 있다. S언어의 주요 특징 중 하나는 객체지향성이다. 본 연구에서는 R의 특징인 객체지향성과 그 의미에 대하여 살펴보게 된다.

• Proceedings of the Materials Research Society of Korea Conference
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• 1998.08a
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• pp.99.4-99
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• 1998