• Communications of the Korean Mathematical Society
• /
• v.33 no.1
• /
• pp.73-83
• /
• 2018

Let R be an associative ring with involution * and ${\alpha},{\beta}:R{\rightarrow}R$ ring homomorphisms. An additive mapping $d:R{\rightarrow}R$ is called an $({\alpha},{\beta})^*$-derivation of R if $d(xy)=d(x){\alpha}(y^*)+{\beta}(x)d(y)$ is fulfilled for any $x,y{\in}R$, and an additive mapping $F:R{\rightarrow}R$ is called a generalized $({\alpha},{\beta})^*$-derivation of R associated with an $({\alpha},{\beta})^*$-derivation d if $F(xy)=F(x){\alpha}(y^*)+{\beta}(x)d(y)$ is fulfilled for all $x,y{\in}R$. In this note, we intend to generalize a theorem of Vukman [12], and a theorem of Daif and El-Sayiad [6], moreover, we generalize a theorem of Ali et al. [4] and a theorem of Huang and Koc [9] related to generalized Jordan triple $({\alpha},{\beta})^*$-derivations.

• Journal of Information Technology Services
• /
• v.7 no.4
• /
• pp.221-230
• /
• 2008

Green's relations are five equivalence relations that characterize the elements of a semigroup in terms of the principal ideals. The J relation is one of Green's relations. Although there are known algorithms that can compute Green relations, they are not useful for finding all J relations in the semigroup of all $n{\times}n$ Boolean matrices. Its computation requires multiplication of three Boolean matrices for each of all possible triples of $n{\times}n$ Boolean matrices. The size of the semigroup of all $n{\times}n$ Boolean matrices grows exponentially as n increases. It is easy to see that it involves exponential time complexity. The computation of J relations over the $5{\times}5$ Boolean matrix is left an unsolved problem. The paper shows theorems that can reduce the computation time, discusses an algorithm for efficient J relation computation whose design reflects those theorems and gives its execution results.

• Journal of Korean Classical Literature and Education
• /
• no.15
• /
• pp.245-264
• /
• 2008

This study considers Huewa悔窩 Anjung-gwan安重觀's self-consciousness and the recognition of the world. Anjung-gwan resents that fact that Qing淸 rules over China. He insists that Chosun朝鮮 must remain faithful to Ming明. But Chosun served Qing in those days. He holds strongly to his belief until his death. So he chooses living in retirement in his life. In Anjung-gwan's poems, we can see that a certain circle of Chosun Confucianists believe in Sojunghwa小中華, which is small-Sinocentrism. In the first half of the eighteenth-century, some Chosun Confucianists feel sad about the situation that stops them from realizing their ideals. But they take pride in natural beauty and configuration of Chosun. And they pay attention to the life of Chosun masses. They recognize Chosun, which is Hwa華, has to keep self-respect to the last.

• Journal of the Chungcheong Mathematical Society
• /
• v.24 no.4
• /
• pp.807-824
• /
• 2011

It has been proved that if $\mathbb{X}^{(s,s)}$ is the union of two linear star-configurations in $\mathbb{P}^2$ of type $s{\times}s$, then $(I_{\mathbb{X}^{(s,s)}})_s{\neq}\{0\}$ for s = 3, 4, 5, and $(I_{\mathbb{X}^{(s,s)}})_s=\{0\}$ for $s{\geq}6$. We extend $\mathbb{P}^2$ to $\mathbb{P}^n$ and show that if $\mathbb{X}^{(s,s)}$ is the union of two linear star-configurations in $\mathbb{P}^n$, then $(I_{\mathbb{X}^{(s,s)}})_s=\{0\}$ for $n{\geq}3$ and $s{\geq}3$. Using this generalization, we also prove that the secant variety $Sec_1(Split_s(\mathbb{P}^n))$ has the expected dimension 2ns + 1 for $n{\geq}3$ and $s{\geq}3$.

• Communications of the Korean Mathematical Society
• /
• v.34 no.1
• /
• pp.43-54
• /
• 2019

Let R be a ring with identity and J(R) denote the Jacobson radical of R, i.e., the intersection of all maximal left ideals of R. A ring R is called J-symmetric if for any $a,b,c{\in}R$, abc = 0 implies $bac{\in}J(R)$. We prove that some results of symmetric rings can be extended to the J-symmetric rings for this general setting. We give many characterizations of such rings. We show that the class of J-symmetric rings lies strictly between the class of symmetric rings and the class of directly finite rings.

• Bulletin of the Korean Mathematical Society
• /
• v.56 no.2
• /
• pp.373-382
• /
• 2019

In this note, we mainly discuss strongly Gorenstein hereditary rings. We prove that for any ring, the class of SG-projective modules and the class of G-projective modules coincide if and only if the class of SG-projective modules is closed under extension. From this we get that a ring is an SG-hereditary ring if and only if every ideal is G-projective and the class of SG-projective modules is closed under extension. We also give some examples of domains whose ideals are SG-projective.

• Journal of Contemporary Eastern Asia
• /
• v.18 no.1
• /
• pp.70-93
• /
• 2019

The contemporary educational system in South Korea is built on high-stakes standardised tests, a manifestation of the national project of social reconstruction and reform. One recent outcome is the emergence of an unfamiliar yet ubiquitous phenomenon: the "pig mum"; a Korean parent who is fully involved in organising, scheduling and managing the educational process from primary to secondary school for a group of children in a neighbourhood. Based on a quasimixed method utilizing a survey of a group of students and parents, this pilot study explores the "pig mum" phenomenon and its linkage to education policy. The authors conclude that the current educational policy fails to achieve the ideals it professes to value. This creates deep and negative societal norms that endanger a growing generation of students by creating a parallel private education market environment where "pig mums" thrive.

• Kyungpook Mathematical Journal
• /
• v.59 no.1
• /
• pp.35-45
• /
• 2019

The ${\Gamma}$-semihyperring is a generalization of the concepts of a semiring, a semihyperring and a ${\Gamma}$-semiring. Here, the notions of (strongly) regular ${\Gamma}$-semihyperring, idempotent ${\Gamma}$-semihyperring; invertible set, invertible element in a ${\Gamma}$-semihyperring are introduced, and several examples given. It is proved that if all subsets of ${\Gamma}$-semihyperring are strongly regular then for every ${\Delta}{\subseteq}{\Gamma}$, there is a ${\Delta}$-idempotent subset of R. Regularity conditions of ${\Gamma}$-semihyperrings in terms of ideals of ${\Gamma}$-semihyperrings are also characterized.

• Bulletin of the Korean Mathematical Society
• /
• v.56 no.3
• /
• pp.563-568
• /
• 2019

This study is concerned with the approximation properties of pairs. For ${\lambda}{\geq}1$, we prove that given a Banach space X and a closed subspace $Z_0$, if the pair ($X,Z_0$) has the ${\lambda}$-bounded approximation property (${\lambda}$-BAP), then for every ideal Z containing $Z_0$, the pair ($Z,Z_0$) has the ${\lambda}$-BAP; further, if Z is a closed subspace of X and the pair (X, Z) has the ${\lambda}$-BAP, then for every separable subspace $Y_0$ of X, there exists a separable closed subspace Y containing $Y_0$ such that the pair ($Y,Y{\cap}Z$) has the ${\lambda}$-BAP. We also prove that if Z is a separable closed subspace of X, then the pair (X, Z) has the ${\lambda}$-BAP if and only if for every separable subspace $Y_0$ of X, there exists a separable closed subspace Y containing $Y_0{\cup}Z$ such that the pair (Y, Z) has the ${\lambda}$-BAP.

• Communications of the Korean Mathematical Society
• /
• v.34 no.2
• /
• pp.361-374
• /
• 2019

Let R be a ring, ($S,{\leq}$) a strictly ordered monoid, and ${\omega}:S{\rightarrow}End(R)$ a monoid homomorphism. In [18], Mazurek, and Ziembowski investigated when the skew generalized power series ring $R[[S,{\omega}]]$ is a domain satisfying the ascending chain condition on principal left (resp. right) ideals. Following [18], we obtain necessary and sufficient conditions on R, S and ${\omega}$ such that the skew generalized power series ring $R[[S,{\omega}]]$ is a right or left Archimedean domain. As particular cases of our general results we obtain new theorems on the ring of arithmetical functions and the ring of generalized power series. Our results extend and unify many existing results.