• Journal of the Korean Mathematical Society
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• v.49 no.1
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• pp.49-67
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• 2012

In this paper we give asymptotic formulas for the number of ${\ell}$-cyclic extensions of the rational function field $k=\mathbb{F}_q(T)$ with prescribe ${\ell}$-class numbers inside some cyclotomic function fields, and density results for ${\ell}$-cyclic extensions of k with certain properties on the ideal class groups.

• Bulletin of the Korean Mathematical Society
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• v.36 no.4
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• pp.629-636
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• 1999

We introduce Lipschitz algebras of differentiable functions of a perfect compact plane set X and extend the definition to Lipschitz algebras of infinitely differentiable functions of X. Then we define the subalgebras generated by polynomials, rational functions, and analytic functions in some neighbourhood of X, and determine the maximal ideal spaces of some of these algebras. We investigate the polynomial and rational approximation problems on certain compact sets X.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.6
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• pp.1273-1278
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• 1997

Pseudonoise sequences of period 2$^{m}$ -1 with idel autocorrelation have been researched such as m-sequences, GMW sequences, Legendre sequences, and extended sequences. The m-sequences, the GMW sequences, the Legendre sequences, and the extended sequences are best described in terms of the trace function by previous works. Besides, there are Hall's sextic residue sequences and miscellaneous sequences with ideal autocorrelation, whose general constructions are not known so far. However, are are no explicit descripton of the Hall's sextic residue sequences and the miscellaneous sequences in terms of the trace function. In this paper, the Hall's sextic residue sequences and the miscellaneous sequences of period 2$^{m}$ -1 are expressed as a sum of trace functions. The miscellaneous sequences with ideal autocorrelation, which are newly found by computer search, are also expressed as a sum of trace functions.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.1
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• pp.35-42
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• 2009

In Taguchi's quadratic expected loss function used as robustness metric of performance characteristics, the mean and variance contributions are confounded. The consolidation of the mean and variance in the expected loss function may not always be the ideal approach. This paper presents a procedure for multi-attributes design optimization, where the mean and variance of performance characteristics are considered as separate attributes having designer's relative preferences for them and Technique for Order Preference by Similarity to Ideal Solution(TOPSIS) is introduced to attain robust optimal design. The effectiveness of proposed approach is shown with an example of a weld line minimization problem in the injection molding process.

• Journal of applied mathematics & informatics
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• v.23 no.1_2
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• pp.517-523
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• 2007

Let R/I be an Artinian algebra of codimension 3 with Hilbert function H such that $h_{d-1}>h_d=h_{d+1}$. Ahn and Shin showed that A cannot be level if ${\beta}_{1,d+2}(Gin(I))={\beta}_{2,d+2}(Gin(I))$ where Gin(I) is a generic initial ideal of I. We prove that some certain graded Artinian algebra R/I cannot be level if either ${\beta}_{1,d}(I^{lex})={\beta}_{2,d}(I^{lex})+1\;or\;{\beta}_{1,d+1}(I^{lex})={\beta}_{2,d+1}(I^{lex})\;where\;I^{lex}$ is a lex-segment ideal associated to I.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.40 no.12
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• pp.1230-1241
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• 1991

Asymmetrical pulse width modulated(APWM) control technique for AC chopper is proposed which can improve the input power factor. The ideal switching function for the proposed technique is derived and its optimal slope to maintain the input power factor to unity is calculated. By digital simulation several characteristics are investigated theoretically and then compared with those of the conventional PWM and the phase angle control technique. In order to maintain the input power factor to unity the optimal slope and the average value of the ideal switching function are calculated. The experimental results show a good agreement with the calculated ones, which proves the feasibility of the proposed technique.

• Kyungpook Mathematical Journal
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• v.49 no.1
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• pp.183-193
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• 2009

Pseudo-rank functions on Rickart *-rings are introduced and their properties are studied.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.28 no.6
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• pp.440-455
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• 2002

The final goal for an orthognathic surgery is a functional and esthetic achievement based on occlusion theory. All the dental treatment should be done with the occlusion in mind, though, they tend to be ignored with no good reason. We cannot think of occlusion without temporomandibular joint because it is the first clue to define an occlusion. As normal occlusion comes from the central tendency of distribution of population, we can get it by examining the population that closely meet the criteria of ideal occlusion. To perform proper occlusal function and to maintain the stability after treatment, the case must be finished in normal occlusion closer to ideal one. Our aim is to achieve the ideal occlusal scheme like the mutually protected occlusion with the best masticatory efficiency and the stability. The facial esthetics are influened by culture, race and the time in which human live. While the occlusal function rarely changes as time goes by, esthetics tend to do from one country to another. Orthodontists and maxillofacial surgeons should have solid sets of treatment goals to achieve the best facial esthetics and the ideal occlusion dictated by the joint. Doing orthognathic surgery, two factors aforementioned should be taken into account to establish the Surgical Treatment Objectives(STO). The doctors who are planning orthognathic surgery need to have a very logical and systematic thought process to make STO. The author examined 28 selected beautiful Korean female adults with normal skeleton with normal occlusion and analyzed the hard and the soft tissue relationship into five parts : dentomaxillary relationship, intermaxillary relationship, posture to hard tissue relationship, facial balance, and posture to soft tissue relationship. This study presents a sequential flow of diagnosis and treatment planning especially for surgical patients and it also can be applied to the nonsurgical patients.

• Honam Mathematical Journal
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• v.28 no.2
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• pp.185-196
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• 2006

A scheme based on the cryptography for enforcing multilevel security in a system where hierarchy is represented by a partially ordered set was first introduced by Akl et al. But the key generation algorithm of Akl et al. is infeasible when there is a large number of users. In 1985, MacKinnon et al. proposed a paper containing a condition which prevents cooperative attacks and optimizes the assignment in order to overcome this shortage. In 2005, Kim et al. proposed key management systems for multilevel security using one-way hash function, RSA algorithm, Poset dimension and Clifford semigroup in the context of modern cryptography. In particular, the key management system using Clifford semigroup of imaginary quadratic non-maximal orders is based on the fact that the computation of a key ideal $K_0$ from an ideal $EK_0$ seems to be difficult unless E is equivalent to O. We, in this paper, show that computing preimages under the bonding homomorphism is not difficult, and that the multilevel cryptosystem based on the Clifford semigroup is insecure and improper to the key management system.

• Journal of the Chungcheong Mathematical Society
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• v.23 no.1
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• pp.169-176
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• 2010

Let $k={\mathbb{F}}_q(T)$ and ${\mathbb{A}}={\mathbb{F}}_q[T]$. In this paper, we obtain the the criterion for the parity of the ideal class number h(${\mathcal{O}}_K$) of the real biquadratic function field $K=k(\sqrt{P_1},\;\sqrt{P_2})$, where $P_1$, $P_2{\in}{\mathbb{A}}$ be two distinct monic primes of even degree.