• Bulletin of the Korean Mathematical Society
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• v.61 no.1
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• pp.1-12
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• 2024

In this paper, we introduce the notion of Gorenstein (m, n)-flat modules as an extension of (m, n)-flat left R-modules over a ring R, where m and n are two fixed positive integers. We demonstrate that the class of all Gorenstein (m, n)-flat modules forms a Kaplansky class and establish that (𝓖𝓕_m,n(R),𝓖𝓒_m,n(R)) constitutes a hereditary perfect cotorsion pair (where 𝓖𝓕_m,n(R) denotes the class of Gorenstein (m, n)-flat modules and 𝓖𝓒_m,n(R) refers to the class of Gorenstein (m, n)-cotorsion modules) over slightly (m, n)-coherent rings.

• KSBB Journal
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• v.9 no.2
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• pp.115-121
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• 1994

A Purification device with 30-channel free-flow electrophoresis was assembled to treat samples of 240m1 volume for purification of lentil lectin (LcH) from lentil seeds with no impurities in a silverstained PAGIEF gel. HEPES(50mM)-Ttis(50mM), Cycloserine(50mM)-urea(3M), Histidine(50mM)-urea(3M) were used as ampholytea among which Histidine(50mM)-urea(3M) (pI 7.65) was found best in resolution. LcH is known to be present in the form of LcH-A, LcH-B and the complex of the two. The complex, however, disappeared when urea was added in the ampholytes, which suggested that the complete purification of two isolectins is possible using the present multistep purificaton device.

• Korean Management Science Review
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• v.32 no.2
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• pp.91-109
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• 2015

The M&A of firms has been emerged as the effective means of fast diversification and growth in dynamic environment. However, the empirical research about M&A in Korea has not been implemented rich due to the difficulty of obtaining M&A data. In this research, we empirically investigate the relationships among M&A, environment and firms' performance focused on Korean manufacturing firms, understanding the current practice of M&A in Korea. We use the Manufacturing Productivity Panel Survey Data, which are collected by Korea Productivity Center in 2013. The sample size is 575 and the sample is divided into M&A group and non-M&A group. We conduct logit analysis with the independent variables of environment factors (munificence, dynamic, uncertainty), and firms' performance (sales growth, ROS, labor productivity and Inventory turnover), and dependent variable of M&A group or non M&A group. The results show that M&A is closely related to environment feature and firm performance: M&A firms are likely to be the higher munificence and dynamic and the lower sales growth and higher profitability than non-M&A group. In addition, we also examine the characteristics of firms by M&A types (competitors, customer/supplier and firms from unrelated industry). These results imply that if firms confront the pressure of uncertainty (dynamic) and the lower growth, they tend to choose M&A. Futhermore, to profoundly understand the behavior of firms about M&A, it is required to classify the M&A firms by merge types.

• Honam Mathematical Journal
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• v.39 no.2
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• pp.275-296
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• 2017

All rings considered here are commutative rings with identity and all modules considered here are unital left modules. A submodule N of an R-module M is said to be extended to M if $N=aM$ for some ideal a of R and it is said to be fully invariant if ${\varphi}(L){\subseteq}L$ for every ${\varphi}{\in}End(M)$. An R-module M is called a [resp., fully invariant] multiplication module if every [resp., fully invariant] submodule is extended to M. The class of fully invariant multiplication modules is bigger than the class of multiplication modules. We deal with prime submodules and associated prime submodules of fully invariant multiplication modules. In particular, when M is a nonzero faithful multiplication module over a Noetherian ring, we characterize the zero-divisors of M in terms of the associated prime submodules, and we show that the set Aps(M) of associated prime submodules of M determines the set $Zdv_M(M)$ of zero-dvisors of M and the support Supp(M) of M.

• Communications of the Korean Mathematical Society
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• v.9 no.2
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• pp.355-359
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• 1994

It would be interesting to know if energy minimizing harmonic maps between manifolds have symmetric properties when the manifolds under consideration have some. In this paper, we consider among others radial symmetry. A radially symmetric manifold M of dimension m is the one with a point, called a pole, and an O(m) action as an isometric rotation with respect to the pole, or more precisely a radially symmetric manifold M has a coordinate on which the metric is of the form $ds_{M}$$^2$ = d$r^2$ + m(r)$^2$d$\theta^2$ for some function m(r) depending only on r. Of course m(0) = 0, m'(0) = 1, and when m(r) = r, (M, $ds_{ M}$/$^2$) is the Euclidean space $R^2$.(omitted)

• Bulletin of the Korean Mathematical Society
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• v.56 no.2
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• pp.505-514
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• 2019

Let R be a commutative ring with identity and M be a unitary R-module. A submodule N of M is called a dense submodule if $Hom_R(M/N,\;E_R(M))=0$, where $E_R(M)$ is the injective hull of M. The R-module M is said to be monoform if any nonzero submodule of M is a dense submodule. In this paper, among the other results, it is shown that any kind of the following module is monoform. (1) The prime R-module M such that for any nonzero submodule N of M, $Ann_R(M/N){\neq}Ann_R(M)$. (2) Strongly prime R-module. (3) Faithful multiplication module over an integral domain.

• Bulletin of the Korean Mathematical Society
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• v.61 no.3
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• pp.717-734
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• 2024

Let R be a commutative ring with identity and m, n be positive integers. In this paper, we introduce the class of weakly (m, n)-prime ideals generalizing (m, n)-prime and weakly (m, n)-closed ideals. A proper ideal I of R is called weakly (m, n)-prime if for a, b ∈ R, 0 ≠ a^mb ∈ I implies either aⁿ ∈ I or b ∈ I. We justify several properties and characterizations of weakly (m, n)-prime ideals with many supporting examples. Furthermore, we investigate weakly (m, n)-prime ideals under various contexts of constructions such as direct products, localizations and homomorphic images. Finally, we discuss the behaviour of this class of ideals in idealization and amalgamated rings.

• Journal of the Chungcheong Mathematical Society
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• v.26 no.4
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• pp.799-809
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• 2013

An ideal I of a local ring (R, m, k) is said to be m-full if there exists an element $x{\in}m$ such that Im : x = I. An ideal I of a local ring R is said to have the Rees property if ${\mu}$(I) > ${\mu}$(J) for any ideal J containing I. We study properties of m-full ideals and we characterize m-primary m-full ideals in terms of the minimal number of generators of the ideals. In particular, for a m-primary ideal I of a 2-dimensional regular local ring (R, m, k), we will show that the following conditions are equivalent. 1. I is m-full 2. I has the Rees property 3. ${\mu}$(I)=o(I)+1 In this paper, let (R, m, k) be a commutative Noetherian local ring with infinite residue field k = R/m.

• Bulletin of the Korean Mathematical Society
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• v.47 no.3
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• pp.645-651
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• 2010

In this note we study positive solutions of the mth order rational difference equation $x_n=(a_0+\sum{{m\atop{i=1}}a_ix_{n-i}/(b_0+\sum{{m\atop{i=1}}b_ix_{n-i}$, where n = m,m+1,m+2, $\ldots$ and $x_0,\ldots,x_{m-1}$ > 0. We describe a sufficient condition on nonnegative real numbers $a_0,a_1,\ldots,a_m,b_0,b_1,\ldots,b_m$ under which every solution $x_n$ of the above equation tends to the limit $(A-b_0+\sqrt{(A-b_0)^2+4_{a_0}B}$/2B as $n{\rightarrow}{\infty}$, where $A=\sum{{m\atop{i=1}}\;a_i$ and $B=\sum{{m\atop{i=1}}\;b_i$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.12
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• pp.2127-2137
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• 2016

In this paper, characteristic tests for current transformers with maximum mA secondary current of 250 mA is performed. The purpose of this paper is not only to test the mA current transformers by following the IEEE Draft Standard for Current Transformers with Maximum mA Secondary Current of 250mA, but also to take into consideration certain applications in the use of the mA CTs for billing purposes.