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ON 𝜙-EXACT SEQUENCES AND 𝜙-PROJECTIVE MODULES

  • Zhao, Wei
    • Journal of the Korean Mathematical Society
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    • v.58 no.6
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    • pp.1513-1528
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    • 2021
  • Let R be a commutative ring with prime nilradical Nil(R) and M an R-module. Define the map 𝜙 : R → RNil(R) by ${\phi}(r)=\frac{r}{1}$ for r ∈ R and 𝜓 : M → MNil(R) by ${\psi}(x)=\frac{x}{1}$ for x ∈ M. Then 𝜓(M) is a 𝜙(R)-module. An R-module P is said to be 𝜙-projective if 𝜓(P) is projective as a 𝜙(R)-module. In this paper, 𝜙-exact sequences and 𝜙-projective R-modules are introduced and the rings over which all R-modules are 𝜙-projective are investigated.

Comparison of Exergy in a Refrigerating System using R404A and R134a for a Refrigeration Truck with Operating Conditions (운전조건에 따른 R404A와 R134a를 적용한 냉동탑차용 냉장시스템의 엑서지 비교)

  • Shin, Yunchan;Kim, Taejung;Cho, Honghyun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.26 no.11
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    • pp.497-503
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    • 2014
  • The performances of refrigeration truck systems using R404A and R134a were investigated by experimental testing, and compared. The optimal COPs of the R404A and R134a systems were 2.96 and 3.42, when the refrigerant charge amount was 1.3 kg and 1.4 kg, respectively. When the indoor side air temperature increased from $5^{\circ}C$ to $9^{\circ}C$, the total exergy destruction rate of the R404A system was on average 39.1% higher than that of the R134a system. In addition, the exergy efficiency of the R404A system was 12.9% higher than that of R134a system, for various indoor air temperatures. When the outdoor side air temperature increased from $25^{\circ}C$ to $35^{\circ}C$, the total exergy destruction rate of the R404A and R134a systems decreased by 18.9% and 19.5%, respectively. In addition, the exergy efficiency of the R404A and R134a systems increased by 25.2% and 30.7%, respectively. As the compressor rotating speed increased, the COP of the R404A and R134a systems decreased by 23.6% and 18.4%. The total exergy destruction rate and exergy efficiency of the R404A system were 27.2% and 15.7% higher than those of R134a system, respectively. Compared to the R404A system, the R134a system showed a higher COP and a lower exergy destruction rate; thus it can be concluded that the R134a system has the better performance.

Research on economic analysis on Competitive R&D investments of Multinational Enterprises (다국적기업의 경쟁적 R&D 투자에 관한 경제성 분석)

  • PARK, SEOK-GANG;KIM, GIL-SUNG
    • International Area Studies Review
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    • v.13 no.3
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    • pp.439-458
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    • 2009
  • In this paper, Two countries have invested directly using the two models Multinational Enterprises, foreign companies doing R&D subsidy policy analysis in their activities to attract. Multinational Enterprises to get the spillover effect from competitors, the introduction of subsidiary R&D resources with an incentive to R&D activities. The government has established a subsidiary to bring the country to foreign Multinational Enterprises for the purpose of improving the technological capabilities of Multinational Enterprises with their parent company R&D to increase the resources by foreign companies in their R&D investment to subsidize R&D activities that have an incentive to attract. In addition, foreign companies and government cooperative R&D by two things also increase the rate of funding for activities to bring the two subsidiaries of multinational R&D has increased the amount of additional resources, the economic interests of both countries get more will increase.

The Effect of waste Oyster Shell on Anaerobic Composting of Garbage (굴 패각이 음식쓰레기의 혐기성 퇴비화에 미치는 영향)

  • Kim, Nam-Chan;Han, Se-Hyun
    • Journal of the Korea Organic Resources Recycling Association
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    • v.8 no.3
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    • pp.89-96
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    • 2000
  • Waste oyster shell was used to study the applicability on anaerobic composting of garbage. Experiment was conducted with five anaerobic reactors. After garbage and compost for inoculation were mixed, waste oyster shell was added into mixed waste in mesophillic temperature for 60 days with 30%, 60% respectively. The amount of produced methane gas, gas composition, organic removal efficiency and pH were measured. Result showed that the amounts of produced gas were 0.62 l /g-VS in R-1, 0.63 l /g-VS in R-2, 0.16 l /g-VS in R-3, 0.75 l /g-VS in R-4, 0.21 l /g-VS in R-5 and the amounts of produced methane gas were 0.32 l /g-VS in R-1, 0.37 l /g-VS in R-2, 0.04 l /g-VS in R-3, 0.42 l /g-VS in R-4, 0.05 l /g-VS in R-5. Proportion of mathane gas which determines the efficiency of anaerobic composting was over 55%. pH were 6.0~8.0 in R-2 and R-4 which contained 30% of waste oyster shell and pH were increased over 8.5 in R-3 and R-5 which contained 60% of waste oyster shell. Since pH were so high and it had a negative effect on microbial growth, anaerobic reaction were not well operated in R-3 and R-5.

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An Analysis on the R&D Productivity and Efficiency of Korea: Focused on Comparison with the OECD Countries (우리나라의 R&D 생산성 및 효율성 분석: OECD 국가와의 비교를 중심으로)

  • Kim, Young-H.;Kim, Sun-G.
    • Journal of Technology Innovation
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    • v.19 no.1
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    • pp.1-27
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    • 2011
  • This paper aims to measure and analyze R&D productivities and efficiencies of 17 major OECD countries including Korea over the 1984-2008 period by using the Malmquist Productivity Index and Data Envelopment Analysis, classifying R&D performance into an output and outcome aspects. It also searches the Korea's current status and characteristics in each R&D stage to enhance Total Factor Productivity (TFP) compared with other developed countries. Our major findings are the followings: (i) Korea's productivity index of R&D input vis-a-vis R&D output is very high (13.39% annual growth rate) compared with those of major advanced countries, whereas the annual average of efficiency index is very low (0.33), i.e. Korea's technical efficiency index has risen to 0.83 at the last time series started at 0.10 point and come up to the level of major advanced countries. (ii) the Korea's productivity index of R&D output vis-a-vis R&D outcome is very low (14.02% annual reduction rate) compared with those of major advanced countries, whereas the annual average of efficiency index is very high (0.22), i.e. Korea's integrated frontier technical efficiency index has dropped to 0.057 at the last time series started at 1.00 point and coming up to the level of major advanced countries. (iii) The productivity of R&D input vis-a-vis R&D outcome is positively correlated with that of R&D output vis-a-vis R&D outcome and the growth of R&D input factors. In a nutshell, it implicates that the effort to take advantage of R&D outputs, namely establishing the diffusion and commercialization system of technical knowledge to the level of developed countries, should be strengthened over that on the growth of R&D investment and output for enhancing R&D productivity and efficiency in Korea.

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The Line n-sigraph of a Symmetric n-sigraph-V

  • Reddy, P. Siva Kota;Nagaraja, K.M.;Geetha, M.C.
    • Kyungpook Mathematical Journal
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    • v.54 no.1
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    • pp.95-101
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    • 2014
  • An n-tuple ($a_1,a_2,{\ldots},a_n$) is symmetric, if $a_k$ = $a_{n-k+1}$, $1{\leq}k{\leq}n$. Let $H_n$ = {$(a_1,a_2,{\ldots},a_n)$ ; $a_k$ ${\in}$ {+,-}, $a_k$ = $a_{n-k+1}$, $1{\leq}k{\leq}n$} be the set of all symmetric n-tuples. A symmetric n-sigraph (symmetric n-marked graph) is an ordered pair $S_n$ = (G,${\sigma}$) ($S_n$ = (G,${\mu}$)), where G = (V,E) is a graph called the underlying graph of $S_n$ and ${\sigma}$:E ${\rightarrow}H_n({\mu}:V{\rightarrow}H_n)$ is a function. The restricted super line graph of index r of a graph G, denoted by $\mathcal{R}\mathcal{L}_r$(G). The vertices of $\mathcal{R}\mathcal{L}_r$(G) are the r-subsets of E(G) and two vertices P = ${p_1,p_2,{\ldots},p_r}$ and Q = ${q_1,q_2,{\ldots},q_r}$ are adjacent if there exists exactly one pair of edges, say $p_i$ and $q_j$, where $1{\leq}i$, $j{\leq}r$, that are adjacent edges in G. Analogously, one can define the restricted super line symmetric n-sigraph of index r of a symmetric n-sigraph $S_n$ = (G,${\sigma}$) as a symmetric n-sigraph $\mathcal{R}\mathcal{L}_r$($S_n$) = ($\mathcal{R}\mathcal{L}_r(G)$, ${\sigma}$'), where $\mathcal{R}\mathcal{L}_r(G)$ is the underlying graph of $\mathcal{R}\mathcal{L}_r(S_n)$, where for any edge PQ in $\mathcal{R}\mathcal{L}_r(S_n)$, ${\sigma}^{\prime}(PQ)$=${\sigma}(P){\sigma}(Q)$. It is shown that for any symmetric n-sigraph $S_n$, its $\mathcal{R}\mathcal{L}_r(S_n)$ is i-balanced and we offer a structural characterization of super line symmetric n-sigraphs of index r. Further, we characterize symmetric n-sigraphs $S_n$ for which $\mathcal{R}\mathcal{L}_r(S_n)$~$\mathcal{L}_r(S_n)$ and $$\mathcal{R}\mathcal{L}_r(S_n){\sim_=}\mathcal{L}_r(S_n)$$, where ~ and $$\sim_=$$ denotes switching equivalence and isomorphism and $\mathcal{R}\mathcal{L}_r(S_n)$ and $\mathcal{L}_r(S_n)$ are denotes the restricted super line symmetric n-sigraph of index r and super line symmetric n-sigraph of index r of $S_n$ respectively.

Comparison of the miR-23b and miR-203 Expressions in Endometrial Cancer (자궁내막암종에서 miR-23b와 miR-203 발현 비교)

  • Lee, Kyung Eun
    • Korean Journal of Clinical Laboratory Science
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    • v.49 no.4
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    • pp.455-459
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    • 2017
  • MicroRNAs (miRNAs/miRs) are a group of small noncoding RNAs that modulate gene expression. Many studies, demonstrating altered expressions of specific miRNAs in diverse types of human neoplasia, suggested that they may play a key role in tumorigenesis. Recently, miRNA genes were found to be abnormally expressed in several types of cancer, including endometrial cancer. However, miR-23b and miR-203 expression in endometrial cancer has yet to be studied in Korea. As such, the purpose of this study was to analyze miR-23b and miR-203 expressions in endometrial cancer and to evaluate the relationship between miR-23b and miR-203 expressions. A retrospective study was carried out on the formalin-fixed, paraffin-embedded tissues of 42 endometrial cancer tissues using quantitative real-time PCR. In endometrial cancer tissues, miR-23b expression levels ($2.70{\pm}4.45$) were higher than miR-203 expression levels ($-2.34{\pm}4.08$). Endometrial cancer tissues showed an overexpression of miR-23b in 30 (71.4%) of the 42 endometrial cancer cases, whereas miR-203 was underexpressed in 29 (69.0%) of the 42 cases. There was a significant association between miR-23b and miR-203 expressions in endometrial cancer tissues (p=0.0005). These findings suggest that miR-23b and miR-203 expressions may be involved in endometrial carcinogenesis. More studies are needed to further define the relationship between miR-23b and miR-203 expressions and tissue-specific protein expression.

ON THE PRIME SPECTRUM OF A RING (환의 PRIME SPECTRUM에 관하여)

  • Kim Eung Tai
    • The Mathematical Education
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    • v.12 no.2
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    • pp.5-12
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    • 1974
  • 단위원을 가지는 하환환에 있어서의 Prime Spectrum에 관하여 다음 세가지 사실을 증명하였다. 1. X를 환 R의 prime spectrum, C(X)를 X에서 정의되는 실연적함수의 환, X를 C(X)의 maximal spectrum이라 하면 X는 C(X)의 prime spectrum의 부분공간으로서의 한 T-space로 된다. N을 환 R의 nilradical이라 하면, R/N이 regula 이면 X와 X는 위상동형이다. 2. f: R$\longrightarrow$R'을 ring homomorphism, P를 R의 한 Prime ideal, $R_{p}$, R'$_{p}$를 각각 S=R-P 및 f(S)에 관한 분수환(ring of fraction)이라 하고, k(P)를 local ring $R_{p}$의 residue' field라 할 때, R'의 prime spectrum의 부분공간인 $f^{*-1}$(P)는 k(P)(equation omitted)$_{R}$R'의 prime spectrum과 위상동형이다. 단 f*는 f*(Q)=$f^{-1}$(Q)로서 정의되는 함수 s*:Spec(R')$\longrightarrow$Spec(R)이다. 3. X를 환 S의 prime spectrum, N을 R의 nilradical이라 할 때, 다음 네가지 사실은 동치이다. (1) R/N 은 regular 이다. (2) X는 Zarski topology에 관하여 Hausdorff 공간이다. (3) X에서의 Zarski topology와 constructible topology와는 일치한다. (4) R의 임의의 원소 f에 대하여 f를 포함하지 않는 R의 prime ideal 전체의 집합 $X_{f}$는 Zarski topology에 관하여 개집합인 동시에 폐집합이다.폐집합이다....

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