• Bulletin of the Korean Chemical Society
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• v.15 no.8
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• pp.658-662
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• 1994

Ab initio and extended Huckel calculations have been applied to discuss the electronic structure, ring inversion barrier, and geometry of the $Cp_2TiS_3$ compound. The deformation of four membered ring in the planar geometry is originated from a second-order Jahn-Teller distortion due to the small energy gap between HOMO and LUMO on the basis of extended Huckel calculations. The puckered $C_s$ geometry is stabilized by the interaction of the $x^2-y^2$ metal orbital with the hybrid orbital in sulfur. Ab initio calculations have been carried out to explore the ring inversion process for the model $Cl_2TiS_3$ compound. We have optimized $C_s$ and $C_{2v}$ structures of the model compound at the RHF level. The energy barriers for the ring inversion are sensitive to the used basis set. With 4-31$G^*$ for the Cl and S ligands, the barriers are computed to be 8.41 kcal/mol at MP2 and 8.02 kcal/mol at MP4 level.

• Structural Engineering and Mechanics
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• v.88 no.2
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• pp.109-115
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• 2023

In this paper, frequencies of zigzag structure of carbon nanotubes isinvestigated based on Donnell shell theory. These tubes are wrapped with the ring supports in the axial direction. The fundamental frequency curves displayed in article show the dependence of vibrations attributes to zigzag single walled carbon nanotubes. Various zigzag indices are introduced against the variation of length to predict the vibration. Also, the influence of ring supports is sketched with proposed structure for frequency analysis. The frequencies of zigzag tube decreases as the length increases. It is observed that the frequencies decreases with ring support and have higher frequencies without ring. The problem is formulated using Partial Differential Equation. Three expressions of modal deformation displacement functions is used for the elimination of temporal variation to form the solution in the eigen from. For the stability of present study the results are compared with experimentally and numerically in the open text.

• Journal of Aerospace System Engineering
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• v.11 no.1
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• pp.28-34
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• 2017

Elastomeric o-ring performance and structure when subjected to a foreign object is studied using finite element analysis (FEA). Elastomeric o-rings have been studied using 2D analysis for a long time. Contact pressure is an important factor in o-ring design. When contact pressure is lower than applied pressure, leaking, vibration, and noise can occur; resulting in decreased output. In this study, we compared 2D and 3D analyses of elastomeric o-rings. Similar results were shown for 2D and 3D contact pressure. However, when an o-ring encounters foreign object matter, 3D analysis is required because contact pressure in every direction needs to be considered. We determined the influence of foreign matter on o-ring performance and structure by analyzing 10 cases with different clearances in a 3D model. Therefore, an o-ring encountering foreign object matter must be analyzed in 3D with the result included in the o-ring design.

• Korean Journal of Mathematics
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• v.22 no.2
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• pp.279-288
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• 2014

The studies of reversible and 2-primal rings have done important roles in noncommutative ring theory. We in this note introduce the concept of quasi-reversible-over-prime-radical (simply, QRPR) as a generalization of the 2-primal ring property. A ring is called QRPR if ab = 0 for $a,b{\in}R$ implies that ab is contained in the prime radical. In this note we study the structure of QRPR rings and examine the QRPR property of several kinds of ring extensions which have roles in noncommutative ring theory.

• Kyungpook Mathematical Journal
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• v.61 no.1
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• pp.11-21
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• 2021

We study the structure of rings whose factor rings modulo nonzero proper ideals are right duo; such rings are called right FD. We first see that this new ring property is not left-right symmetric. We prove for a non-prime right FD ring R that R is a subdirect product of subdirectly irreducible right FD rings; and that R/N∗(R) is a subdirect product of right duo domains, and R/J(R) is a subdirect product of division rings, where N∗(R) (J(R)) is the prime (Jacobson) radical of R. We study the relation among right FD rings, division rings, commutative rings, right duo rings and simple rings, in relation to matrix rings, polynomial rings and direct products. We prove that if a ring R is right FD and 0 ≠ e2 = e ∈ R then eRe is also right FD, examining that the class of right FD rings is not closed under subrings.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.8
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• pp.1719-1724
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• 2004

In this paper, we have proposed a new structure of LDMOST, which has been expected as a next generation RF power device, to improve the BV(Breakdown Voltage) characteristics. The proposed structure, named external field ring, is formed around a drift region by the three dimensional structure. The external field ring relieves the electric field in the drift region and improves the BV characteristics. By the three dimensional TCAD simulations, it was found that the BV of LDMOST was increased by the increase of the junction depth and doping concentration of the external field ring. Therefore, the BV characteristics of the LDMOST can be remarkably improved by addition of external field ring using an existing p+ sinker process.

• East Asian mathematical journal
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• v.30 no.5
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• pp.617-623
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• 2014

Due to Bell, a ring R is usually said to be IFP if ab = 0 implies aRb = 0 for $a,b{\in}R$. It is shown that if f(x)g(x) = 0 for $f(x)=a_0+a_1x$ and $g(x)=b_0+{\cdots}+b_nx^n$ in R[x], then $(f(x)R[x])^{2n+2}g(x)=0$. Motivated by this results, we study the structure of the IFP when proper ideals are taken in place of R, introducing the concept of insertion-of-ideal-factors-property (simply, IIFP) as a generalization of the IFP. A ring R will be called an IIFP ring if ab = 0 (for $a,b{\in}R$) implies aIb = 0 for some proper nonzero ideal I of R, where R is assumed to be non-simple. We in this note study the basic structure of IIFP rings.

• Korean Journal of Mathematics
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• v.18 no.1
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• pp.97-103
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• 2010

It is well known that the group ring K[G] has the nontrivial Jacobson radical if K is a field of characteristic p and G is a finite group of which order is divided by a prime p. This paper is concerned with the structure of the Jacobson radical of such a group ring.

• Honam Mathematical Journal
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• v.37 no.4
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• pp.377-386
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• 2015

The symmetric ring property was due to Lambek and provided many useful results in relation with noncommutative ring theory. In this note we consider this property over centers, introducing symmetric-over-center. It is shown that symmetric and symmetric-over-center are independent of each other. The structure of symmetric-over-center ring is studied in relation to various radicals of polynomial rings.

• Bulletin of the Korean Mathematical Society
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• v.44 no.2
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• pp.215-223
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• 2007

We in this note introduce the concept of NCI rings which is a generalization of NI rings. We study the basic structure of NCI rings, concentrating rings of bounded index of nilpotency and von Neumann regular rings. We also construct suitable examples to the situations raised naturally in the process.