• 대한수학회지
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• 제48권3호
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• pp.627-639
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• 2011

Hopf corings are dened in this work as coring objects in the category of algebras over a commutative ring R. Using the Dieudonn$\'{e}$ equivalences from [7] and [19], one can associate coring structures built from the Hopf algebra $F_p[x_0,x_1,{\ldots}]$, p a prime, with Hopf ring structures with same underlying connected Hopf algebra. We have that $F_p[x_0,x_1,{\ldots}]$ coring structures classify thus Hopf ring structures for a given Hopf algebra. These methods are applied to dene new ring products in the Hopf algebras underlying known Hopf rings that come from connective Morava ${\kappa}$-theory.

• 대한수학회논문집
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• 제33권1호
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• pp.325-335
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• 2018

We prove every oriented compact cyclic 3-orbifold has a contact structure. There is another proof in the web by Daniel Herr in his uploaded thesis which depends on open book decompositions, ours is independent of that. We define overtwisted contact structures, tight contact structures and Lutz twist on oriented compact cyclic 3-orbifolds. We show that every contact structure in an oriented compact cyclic 3-orbifold contactified by our method is homotopic to an overtwisted structure with the overtwisted disc intersecting the singular locus of the orbifolds. In course of proving the above results we prove a classification result for compact oriented cyclic-3 orbifolds which has not been seen by us in literature before.

• 대한수학교육학회지:학교수학
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• 제18권3호
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• pp.571-587
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• 2016

남진영(2008a)은 학생의 수학적 구조의 학습을 돕기 위한 교사의 역할을 암묵적 지식의 현시자라고 제안하였다. 그러나 아직 암묵적 지식의 현시의 의미를 구체화한 연구는 부족하다. 이에 본 연구에서는 Watson & Mason(2015)의 제안한 예 구성 활동이 그 목표, 내용, 방법 면에서 암묵적 지식을 현시하는 한 가지 방식임을 보임으로써, 암묵적 지식의 현시의 의미를 구체화하고자 하였다. 첫째, 예 구성 활동을 통한 암묵적 지식의 현시는 암묵적 영역에 있는 수학적 구조의 학습을 목표로 한다. 둘째, 예 구성 활동을 통한 암묵적 지식의 현시는 예를 통해 변이 속에서 불변적인 요소를 인식함으로써 암묵적 영역에 있는 수학적 구조를 교육하고자 한다. 셋째, 예 구성 활동을 통한 암묵적 지식의 현시는 명시적 지식을 창의적으로 구성해보는 활동, 활동에 대한 반성 과정, 사회적 상호작용을 통해 암묵적 영역에 있는 수학적 구조를 교육하고자 한다. 따라서 예 구성 활동은 그 목표, 내용, 방법 면에서 암묵적 지식을 현시하는 구체적인 한 수업 방식으로 볼 수 있다.

• Structural Engineering and Mechanics
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• 제84권2호
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• pp.285-293
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• 2022

Lumped damage mechanics (LDM) is a recent nonlinear theory with several applications to civil engineering structures, such as reinforced concrete and steel buildings. LDM apply key concepts of classic fracture and damage mechanics on plastic hinges. Therefore, the lumped damage models are quite successful in reproduce actual structural behaviour using concepts well-known by engineers in practice, such as ultimate moment and first cracking moment of reinforced concrete elements. So far, lumped damage models are based in the strain energy equivalence hypothesis, which is one of the fictitious states where the intact material behaviour depends on a damage variable. However, there are other possibilities, such as the energy equivalence hypothesis. Such possibilities should be explored, in order to pursue unique advantages as well as extend the LDM framework. Therewith, a lumped damage model based on the energy equivalence hypothesis is proposed in this paper. The proposed model was idealised for reinforced concrete structures, where a damage variable accounts for concrete cracking and the plastic rotation represents reinforcement yielding. The obtained results show that the proposed model is quite accurate compared to experimental responses.

• 대한수학회보
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• 제58권6호
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• pp.1507-1520
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• 2021

Let R be a commutative ring with 1 ≠ 0, n be a positive integer and M be an R-module. In this paper, we introduce the concept of weakly quasi n-absorbing submodule which is a proper generalization of quasi n-absorbing submodule. We define a proper submodule N of M to be a weakly quasi n-absorbing submodule if whenever a ∈ R and x ∈ M with 0 ≠ aⁿ x ∈ N, then aⁿ ∈ (N :_R M) or a^n-1 x ∈ N. We study the basic properties of this notion and establish several characterizations.

• 대한수학회논문집
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• 제37권1호
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• pp.45-56
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• 2022

In this paper, we introduce and study the class of rings in which every ideal consisting entirely of zero divisors is a d-ideal, considered as a generalization of strongly duo rings. Some results including the characterization of AA-rings are given in the first section. Further, we examine the stability of these rings in localization and study the possible transfer to direct product and trivial ring extension. In addition, we define the class of d_E-ideals which allows us to characterize von Neumann regular rings.

• 대한수학회논문집
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• 제38권1호
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• pp.121-122
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• 2023

In this erratum, we correct a mistake in the proof of Proposition 2.7. In fact the equivalence (3) ⇐ (4) "R is a quasi-regular ring if and only if R is a reduced ring and every principal ideal contained in Z(R) is a 0-ideal" does not hold as we only have Rx ⊆ O(S).

• 대한수학회논문집
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• 제38권3호
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• pp.705-714
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• 2023

Bennis and El Hajoui have defined a (commutative unital) ring R to be S-coherent if each finitely generated ideal of R is a S-finitely presented R-module. Any coherent ring is an S-coherent ring. Several examples of S-coherent rings that are not coherent rings are obtained as byproducts of our study of the transfer of the S-coherent property to trivial ring extensions and amalgamated duplications.

• 대한수학회논문집
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• 제39권2호
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• pp.363-372
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• 2024

In this paper, we introduce a weak version of coherent that we call regular coherent property. A ring is called regular coherent, if every finitely generated regular ideal is finitely presented. We investigate the stability of this property under localization and homomorphic image, and its transfer to various contexts of constructions such as trivial ring extensions, pullbacks and amalgamated. Our results generate examples which enrich the current literature with new and original families of rings that satisfy this property.

• 대한수학회지
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• 제37권2호
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• pp.177-191
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• 2000

All scalar CR invariants of weight $\leq$ 6 are explicitly given for 3-dimensional strictly pseudoconvex CR structures, as an application of Fefferman's ambient metric construction and its generalization by he author.