• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.143-151
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• 2010

In this paper, a novel rectangular patch antenna is proposed to have Zeroth Order Resonance(ZOR) generated based on the Metamaterial Complosite Right- and Left-Handed(CRLH) structure. Making the in-phase electric field over the entire antenna other than a half-wavelength as the fundamental resonance mode of a standard microstrip patch or its positive multiple, the metallic patch is suggested to be capacitively coupled with only one surrounding rectangular ring, different from the previous 1D ZOR antennas commonly having several metal cells in line. The performance of the proposed antenna is simulated by a 3D field solver that inputs the sizes of the physical structure corresponding to the equivalent circuit designed to have ZOR at 2.4 GHz. Consequently, the resonance frequency, the gain and the antenna efficiency are observed 2.4 GHz, 5 dB and 98%, respectively. Besides, the important property of the proposed antenna is addressed as the combination of the low profile as an advantage of microstrip patch antennas, and the omni-directional field pattern typical of monopole antennas.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07a
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• pp.396-399
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• 2003

4H-SiC un diodes with field limiting rings(FLRs) were fabricated and characterized. The dependences of reverse breakdown voltage on the number of FLRs, the distance between p-base main junction and first FLR, and activation temperatures, were investigated. Al and B ions were implanted and activated at high temperature to form p-base region and p+ region in the n-epilayer. We have obtained up to 1782V of reverse breakdown voltage in the un diode with two FLRs on loom thick epilayer. The differential on-resistances of the fabricated diode are $5.3m{\Omega}cm^2$ at $100A/cm^2$ and $2.7m{\Omega}cm^2$ at $1kA/cm^2$, respectively. All pn diodes with FLRs have higher avalanche breakdown voltages than that of diode without an FLR. Regardless of the activation temperature, the un diode with a FLR located 5um apart from main junction has the highest mean breakdown voltage around 1600V among the diodes with one ring. On the other hand, the pn diode with two rings showed different behavior with activation temperature. It reveals that high voltage SiC pn diodes with low on-resistance can be fabricated by using the FLR edge termination.

• Bulletin of the Korean Chemical Society
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• v.26 no.12
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• pp.1941-1945
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• 2005

To raises the possibility of designing effective inhibitors, 3D-QSAR for the inhibition of calcineurin-NFAT signaling by new N-(4-oxo-1(4H)-naphthalenylidene benzenesulfonamide derivatives as inhibitors of intracellular protein-protein interactions were studied using CoMFA and CoMSIA methodology. The three templates, N-(4-oxo-1(4H)-naphthalenylidene)benzenesulfonamide (A), benzenesulfonamide (B) and 4-oxo-1(4H)-naphthalenylidene (C) were selected to improve the statistic of the present 3D-QSAR models. The best models with combination of standard field in CoMFA, and steric field and electrostatic field in CoMSIA derived from the template, B and C, because most of the compounds tend not to be aligned in template A. From the based on the CoMFA and CoMSIA contour maps, the $R_1$ and $R_2$ groups on 4-oxo-1(4H) naphthalenylidene ring are steric favor. The ortho position on the benzenesulfonyl ring is steric disfavor and the meta position is steric favor. In addition, the oxygene atom of carbonyl group will have better inhibition activities as it has a negative charge favor. From these findings, we can conclude that the analyses of the contour maps provided insight into possible modification of molecules for effective inhibitiors.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.2
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• pp.54-59
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• 2014

The electric power can be converted into the mechanical power by a corona discharge system. This way has not stronger force than a electric motor. But it has been applied in various industrial fields because of many advantages, no moving parts, smaller noise, simpler structure, minimizing et al. In this paper, corona discharge system with multiple corona electrode installed in form of the ring, has been studied by focusing on the electrical and mechanical characteristics. Intensity of the corona discharge depends on applied electric field, and electric field is related to the applied voltage, discharge gap spacing(s), distance between each corona electrodes(d). As a result, in the case d/s=0.9, most intensive discharge occurred in this experiments. In the region of d/s<0.9, ionic wind velocity has saturation value in spite of decreasing corona current, because each ion velocities increase by the increasing electric field.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.8
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• pp.28-34
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• 2008

A magnetic field detector as a potential MRI receiver is proposed. The proposed device is composed of SRR(split ring resonator) which is a kind of LC resonator first introduced as a negative permeability material and a simple loop antenna. The proposed device showed similar degree of performance to commercial one with a simpler circuit.

• Proceedings of the KIEE Conference
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• 2003.10a
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• pp.312-315
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• 2003

In recent, there have been several developments in lamp technology that promise savings in electrical power consumption and improved quality of the lighting space. Above all, the advantage of ring-shaped electrodeless fluorescent lamp is the removal of internal electrodes and heating filaments that are a light-limiting factor of conventional fluorescent lamps. The ring-shaped electrodeless lamp is intended as a high efficacy replacement for the incandescent reflector lamp in many applications. Therefore, the life time of ring-shaped electrodeless fluorescent lamps is substantially higher than that of conventional fluorescent lamps and last up to 60,000 hours. In this paper, maxwell 3D finite element analysis program (Ansoft) was used to obtain electromagnetic properties associated with the coil and nearby structures. The electromagnetic emitting properties were presented by 3D simulation software operated at 250[kHz] and some specific conditions.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.5
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• pp.869-875
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• 2007

Magnetic properties of electrical steel are, in general. measured by using Epstein frame or single sheet tester (SST). These methods, however, require very strict regulation of a specimen in its size and shape. thus, can not be easily applied to various types of specimen. On the other hand, a ring-test method, which measures only the isotropic properties, can be easily applied to most cases because it requires a toroidal-type specimen of arbitrary size. This method, especially, is considered as an unique available method for a bulk-type specimen. In this paper, a ring-test method is developed, and applied to the measurement of magnetic properties of a bulk-type electrical steel with a toroidal-type specimen. In the measurement, the magnetic properties and iron losses are measured and compared with each other at the both sinusoidal magnetic flux density and sinusoidal magnetic field intensity conditions under 0.2Hz and 60Hz alternating magnetic fields excitation. Through experimental measurements, a sinusoidal magnetic flux density condition is proven appropriate for the measurement of magnetic properties, including iron loss characteristics, of electrical steels.

• Journal of the Korean Mathematical Society
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• v.45 no.6
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• pp.1647-1659
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• 2008

Let R be a ring with identity, X the set of all nonzero, nonunits of R and G the group of all units of R. First, we investigate some connected conditions of the zero-divisor graph $\Gamma(R)$ of a noncommutative ring R as follows: (1) if $\Gamma(R)$ has no sources and no sinks, then $\Gamma(R)$ is connected and diameter of $\Gamma(R)$, denoted by diam($\Gamma(R)$) (resp. girth of $\Gamma(R)$, denoted by g($\Gamma(R)$)) is equal to or less than 3; (2) if X is a union of finite number of orbits under the left (resp. right) regular action on X by G, then $\Gamma(R)$ is connected and diam($\Gamma(R)$) (resp. g($\Gamma(R)$)) is equal to or less than 3, in addition, if R is local, then there is a vertex of $\Gamma(R)$ which is adjacent to every other vertices in $\Gamma(R)$; (3) if R is unit-regular, then $\Gamma(R)$ is connected and diam($\Gamma(R)$) (resp. g($\Gamma(R)$)) is equal to or less than 3. Next, we investigate the graph automorphisms group of $\Gamma(Mat_2(\mathbb{Z}_p))$ where $Mat_2(\mathbb{Z}_p)$ is the ring of 2 by 2 matrices over the galois field $\mathbb{Z}_p$ (p is any prime).

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.2089-2094
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• 2003

The flow around a circular cylinder was controlled by attaching O-rings to reduce drag force acting on the cylinder. Four experimental models were tested in this study; one smooth cylinder of diameter D (D=60mm) and three cylinders fitted with O-rings of diameters d=0.0167D, 0.05D and 0.067D with pitches of PPD=1D, 0.5D and 0.25D. The drag force, mean velocity and turbulent intensity profiles in the near wake behind the cylinders were measured for Reynolds numbers based on the cylinder diameter in the range of $Re_D=7.8{\times}10^3{\sim}1.2{\times}10^5$. At $Re_D=1.2{\times}10^5$, the cylinder fitted with O-rings of d=0.0167D in a pitch interval of 0.25D shows the maximum drag reduction of about 5.4%, compared with the smooth cylinder. The drag reduction effect of O-rings of d=0.067D is not so high. For O-ring circulars, as the Reynolds number increases, the peak location of turbulence intensity shifts downstream and the peak magnitude is decreased. Flow field around the cylinders was visualized using a smoke-wire technique to see the flow structure qualitatively. The size of vortices and vortex formation region formed behind the O-ring cylinders are smaller, compared with the smooth cylinder.

• The Mathematical Education
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• v.12 no.2
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• pp.5-12
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• 1974

단위원을 가지는 하환환에 있어서의 Prime Spectrum에 관하여 다음 세가지 사실을 증명하였다. 1. X를 환 R의 prime spectrum, C(X)를 X에서 정의되는 실연적함수의 환, X를 C(X)의 maximal spectrum이라 하면 X는 C(X)의 prime spectrum의 부분공간으로서의 한 T-space로 된다. N을 환 R의 nilradical이라 하면, R/N이 regula 이면 X와 X는 위상동형이다. 2. f: R$\longrightarrow$R'을 ring homomorphism, P를 R의 한 Prime ideal, $R_{p}$, R'$_{p}$를 각각 S=R-P 및 f(S)에 관한 분수환(ring of fraction)이라 하고, k(P)를 local ring $R_{p}$의 residue' field라 할 때, R'의 prime spectrum의 부분공간인 $f^{*-1}$(P)는 k(P)(equation omitted)$_{R}$R'의 prime spectrum과 위상동형이다. 단 f*는 f*(Q)=$f^{-1}$(Q)로서 정의되는 함수 s*:Spec(R')$\longrightarrow$Spec(R)이다. 3. X를 환 S의 prime spectrum, N을 R의 nilradical이라 할 때, 다음 네가지 사실은 동치이다. (1) R/N 은 regular 이다. (2) X는 Zarski topology에 관하여 Hausdorff 공간이다. (3) X에서의 Zarski topology와 constructible topology와는 일치한다. (4) R의 임의의 원소 f에 대하여 f를 포함하지 않는 R의 prime ideal 전체의 집합 $X_{f}$는 Zarski topology에 관하여 개집합인 동시에 폐집합이다.폐집합이다....