• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.9
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• pp.1003-1012
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• 1992

This paper presents and analysis method for designing a squirrel cage induction motor, which is aimed at analyzing the dynamic characteristics of magnetic field. This scheme is capable of estimating the effects of slot harmonics due to the rotation of rotor by utilizing Macro-airgap element combination, Voltage source treatment and Time difference algorithm. Furthermore, this strategy presents and approach which effectively compensates for end-ring of rotor. And direct convergence method is applied for considering a magnetic nonlinearity in core. In addition to the precision and the convergence study of algorithm, comparisons with experimental values prove the accuracy of this analysis method.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.17.2-17.2
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• 2010

Printed electronics is an emerging technology to realize various microelectronic devices via a cost-effective method. Here we demonstrated a high performance of p-channel and n-channel top-gate/bottom contact polymer field-effect transistors (FETs), and applications to elementary organic complementary inverter and ring oscillator circuits by inkjet processing. We could obtained high field-effect mobility more than $0.4\;cm^2/Vs$ for both of p-channel and n-channel FETs, and successfully measured inkjet-printed polymer inverters. The performance of devices highly depends on the selection of dielectrics, printing condition and device architecture. Optimized CMOS ring oscillators with p-type and n-type polymer transistors showed as high as 50 kHz operation frequency. This research was financially supported by development of next generation RFID technology for item level applications (2008-F052-01) funded by the ministry of knowledge economy (MKE).

• Honam Mathematical Journal
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• v.31 no.4
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• pp.515-527
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• 2009

Let R be a commutative ring with identity. Then we prove $M_n(R)=GL_n(R)$ ${\cup}${$A{\in}M_n(R)\;{\mid}\;detA{\neq}0$ and det $A{\neq}U(R)$}${\cup}Z(M-n(R))$ where U(R) denotes the set of all units of R. In particular, it will be proved that the full matrix ring $M_n(F)$ over a field F is the disjoint union of the general linear group $GL_n(F)$ of degree n over the field F and the set $Z(M_n(F))$ of all zero-divisors of $M_n(F)$. Using the result and universal mapping property we prove that $M_n(F)$ is its total ring of fractions.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.34-36
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• 1998

In these days the hybrid interrupters are widely used for medium voltage class circuit breakers. In the design of the hybrid interrupter, the shape of the short-circuit ring is one of the most important design parameters. Recently the investigation into the phase difference between arc current and magnetic field due to the shape variation of the short circuit ring has been conducted. In this paper, the results of eddy current analyses in the hybrid interrupter and test result are presented.

• Communications of the Korean Mathematical Society
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• v.12 no.4
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• pp.855-864
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• 1997

Let K be a algebraically closed field of characteristic 0 and G a cyclic group of order n. We find the units and idempotent elements of the group ring KG by using the basic group table matrix of G.

• 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.

• Journal of the Korean Mathematical Society
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• v.34 no.1
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• pp.135-147
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• 1997

Let k be an infinite field and let $X = {P_1, \cdots, P_s}$ be a set of s-distinct points in $P^n$. We denote by $I(X)$ the defining ideal of $X$ in the polynomial ring $R = k[x_0, \cdots, x_n]$ and by A the homogeneous coordinate ring of $X, A = \sum_{t = 0}^{\infty} A_t$.

• Journal of the Korean Mathematical Society
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• v.47 no.5
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• pp.1097-1106
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• 2010

Let R be a commutative ring with identity, X the set of all nonzero, nonunits of R and G the group of all units of R. We will investigate some ring theoretic properties of R by considering $\Gamma$(R), the zero-divisor graph of R, under the regular action on X by G as follows: (1) If R is a ring such that X is a union of a finite number of orbits under the regular action on X by G, then there is a vertex of $\Gamma$(R) which is adjacent to every other vertex in $\Gamma$(R) if and only if R is a local ring or $R\;{\simeq}\;\mathbb{Z}_2\;{\times}\;F$ where F is a field; (2) If R is a local ring such that X is a union of n distinct orbits under the regular action of G on X, then all ideals of R consist of {{0}, J, $J^2$, $\ldots$, $J^n$, R} where J is the Jacobson radical of R; (3) If R is a ring such that X is a union of a finite number of orbits under the regular action on X by G, then the number of all ideals is finite and is greater than equal to the number of orbits.

• Progress in Superconductivity and Cryogenics
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• v.13 no.1
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• pp.46-50
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• 2011

The electrical insulation design of high voltage superconducting fault current limiters (SFCLs) should be confirmed to be applied for the stabilization of the power grid. This paper describes numerical analysis and AC dielectric experiments for developing high voltage SFCLs. The electric field distributions between applied high voltage part and ground were calculated by finite element method (FEM) simulation tool and AC criterion of liquid nitrogen at 200 kPa was calculated from correlation between the field utilization factor and FEM simulation results. This paper deals with ceonceptual insulation design of a 154 kV class single-phase no-inductively wound solenoid type SFCL which was focused on gap distance between the cryostat and superconducting coils. Furthermore, the shield ring effect was confirmed to reduce maximum electric field at applied high voltage part.

• Molecular & Cellular Toxicology
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• v.3 no.2
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• pp.145-149
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• 2007

Studies of relationship between structure and toxicity of azo dyes have been performed with comparative molecular field analysis (CoMFA) techniques. 3D QSTR analyses indicate that the steric and electrostatic interactions are important. The steric field based model gives strong correlation ($q^2$=0.57, $r^2$= 0.92). The steric field in conjunction with electrostatic field give more strong correlation ($q^2$=0.57, $r^2$=0.95). All study indicates that a bulky and electronegative group at benzene ring and a small group at position 3 of aniline ring might be significant to reduce the mutagenicity.