• Communications of the Korean Mathematical Society
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• v.23 no.2
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• pp.191-199
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• 2008

We investigate the relation between the vector variable bi-additive functional equation $f(\sum\limits^n_{i=1} xi,\;\sum\limits^n_{i=1} yj)={\sum\limits^n_{i=1}\sum\limits^n_ {j=1}f(x_i,y_j)$ and the multi-variable quadratic functional equation $$g(\sum\limits^n_{i=1}xi)\;+\;\sum\limits_{1{\leq}i<j{\leq}n}\;g(x_i-x_j)=n\sum\limits^n_{i=1}\;g(x_i)$$. Furthermore, we find out the general solution of the above two functional equations.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2299-2301
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• 1999

In this work, experimental investigation was carried out for the breakdown characteristics of $SF_6$, $N_2$ and their mixtures under the uniform and non-uniform electric field, by use of HVAC and standard impulse testing voltages, as a function of different gas pressures from 1 atm to 5 atm. The results show that the dielectric strength of the $SF_6$ mixed in $N_2$ was significantly increased at its portion of 10%, which might imply that the optimum mixture of $SF_6$ for the HV switch gear could be proposed to be 10%.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1998.09a
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• pp.47-51
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• 1998

The GaN thick films were deposited on sapphire substrates by the chloride vapor phase epitaxy (CVPE) technique suing the GaCl3-NH3-N2 chemistry. Thermodynamic simulations were carried out to predict the optimum process windows, and the results were compared with the experiments. A large difference in the growth temperature was observed between the calculation an the experiment, and it indicated that the growth of GaN by the CVPE technique is kinetically limited.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.283-289
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• 2014

This paper carries out a series of analysis of power system using Gallium Nitride (GaN) FET which has wide band gap (WBG) characteristics comparing to conventional Si MOSFET-used power system. At first, for comparison of each semiconductor device, the switching-transient parameter is quantitatively extracted from released information of GaN FET. And GaN FET model which reflect this dynamic property is configured. By using this model, the performance of GaN FET is analyzed comparing to Si MOSFET. Also, in order to enable a representative assessment on the power system level, Si MOSFET and GaN FET are applied to the most common structure of power system, full-bridge, and each power systems are compared based on various criteria, such as performance, efficiency and power density. The entire process is verified with the aid of mathematical analysis and simulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.233-233
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• 2010

It is important to form the n+ emitter layer for generating electric potential collecting EHP(Electron-Hole Pair). In this paper the formation on the n+ emitter layer of silicon wafer has been made with respect to uniformity of shallow diffusion from a liquid source. The starting material was crystalline silicon wafers of resistivity $0.5{\sim}3\{Omega}{\cdot}cm$, p-type, thickness $200{\mu}m$, direction[100]. The formation of n+ emitter layer from the liquid $POCl_3$ source was carried out for $890^{\circ}C$ in an ambient of $N_2:O_2$::10:1 by volume. And than each conditions are pre-deposition and drive-in time. It has been made uniformity of at least. so, the average of sheet resistance was about 0.12%. In this study, sheet resistance was measured by 4-point prove.

• Journal of Powder Materials
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• v.20 no.4
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• pp.285-290
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• 2013

$Ti_2AlN$ composites are a laminated compounds that posses unique combination of typical ceramic properties and typical metallic(Ti alloy) properties. In this paper, the powder synthesis, SPS sintering, composite characteristics and machinability evaluation were systematically conducted. The random orientation characteristics and good crystallization of the $Ti_2AlN$ phase are observed. The electrical and thermal conductivity of $Ti_2AlN$ is higher than that of Ti6242 alloy. A machining test was carried out to compare the effect of material properties on micro electrical discharge drilling for $Ti_2AlN$ composite and Ti6242 alloy. Also, mixture table as a kind of tables of orthogonal arrays was used to know how parameter is main effective at experimental design. Consequently, hybrid $Ti_2AlN$ ceramic composites showed good machining time and electrode wear shape under micro ED-drilling process. This conclusion proves the feasibility in the industrial applications.

• Journal of Microbiology and Biotechnology
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• v.13 no.6
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• pp.998-1000
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• 2003

This study was carried out to elucidate the mode of bacteriostatic property of xanthostatin (XS), a novel depsipeptide antibiotic with an N-acetylglycine side chain and selective antimicrobial activity against Xanthomonas spp. Two biotransformed XSs were isolated by the treatment of XS with the cell lysate of Xanthomonas campestris pv. citri, a solvent partition, preparative TLC, and HPLC. Structure determination of those two biotransformed XSs demonstrated deletion of the N-acetylglycine side chain. Noteworthily, they showed no antimicrobial activity against Xanthomonas spp. This result suggests that the N-acetylglycine side chain plays a critical role in the antimicrobial activity of XS, and that the bacteriostatic property of XS is due to susceptibility of the ester bond between the hexadepsipeptide nucleus and the N-acetylglycine side chain to hydrolytic enzyme(s) produced by Xanthomonas spp.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.113-120
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• 2002

The effect of out-of-plane loads on the fatigue strength of welded steel structures is examined through fatigue tests with weldment of two fillet weld joint types. The results of the fatigue tests are compared with those under axial loads, on the basis of the hot spot stress range at the weld toe. From the result of the comparison, a method on how to incorporate the effect of the out-of-plane bending stress is proposed using design S-N curves derived from fatigue tests under the axial load. The proposed method is useful for rational assessment of the fatigue strength of fillet-welded structures, where combined stresses of the in-plane axial stress and the out-of-plane bending stress are induced simultaneously due to the complexity of applied loads and structural geometry.

• Korean Journal of Plant Resources
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• v.10 no.2
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• pp.145-150
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• 1997

To find out the optimum fertilizer level for onion, early maturing cultivar Fechongjoseng, experiment with four fertilizer levels was conducted of the field of the paddy and upland in Muan and Changyeong from Sep.1993 to Feb.1995. The yield character of onion was higher and rate of the rottenness was lowest under the treatment of $N-P_2O_5-K_2O$=28-9.5-23Kg/10a in the soil of paddy and upland field of Muan area. But the onion yield was excellent and rate of the rottenness was lowest under the treatments, $N-P_2O_5-K_2O$=21-19-17.3Kg/10a, in the soil of paddy field and $N-P_2O_5-K_2O$=28-9.5-23Kg/10a, in the soil of upland field of Changyeong area.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1208-1211
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• 2003

High quality $Bi_2Sr_2Ca_nCu_{n+1}O_x$ superconducting thin films fabricated by using the evaporation method at various substrate temperatures, $T_{sub}$, and ozone gas pressures, $pO_3$. The correlation diagrams of the $Bi_2Sr_2Ca_nCu_{n+1}O_x$ phases with $T_{sub}$ and $pO_3$ are established in the 2212 and 2223 compositional films. In spite of 2212 compositional sputtering, Bi2201 and Bi2223 as well as Bi2212 phases come out as stable phases depending on $T_{sub}$ and $pO_3$. From these results, the thermodynamic evaluation of ${\Delta}H$ and ${\Delta}S$, which are related with Gibbs' free energy change for single Bi2212 or Bi2223 phase, was performed.