• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.184-187
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• 1987

The method of Conjugate Gradient(C.G.M) is applied to the solution of current distribution from body of revolution (B.O.R).Using the C.G.M it is possible to analyze electrically large arbtrarily oriented B.O.R. The fundamental differences between C.G.M and moment method are outlined. This method converges for any initial guess and this techniqe gurantees a monotonic convergence. Numerical results are presented for electromagnetic case which show good agreement with moment solution.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.347-360
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• 1989

Spinel, mullite, forsterite and cordierite composition powders were synthesized from Mg(NO3)2.6H2O, Al(NO3)3.9H2O and SiCl4-ethanol solution by spray pyrolysis method and the sinterability of these powders were investigated. The bulk density of spinel and mullite specimens sintered at 1,$700^{\circ}C$ for 1hr was 3.56g/㎤(99.5% relative density) and 3.16g/㎤(99.7% relative density), respectively. (Green compacts were made from powders prepared at 1,00$0^{\circ}C$). The bulk density of forsterite and cordierite specimens sintered at 1,480 and 1,40$0^{\circ}C$ for 2hrs were 3.217 and 2.155g/㎤, respectively. (Green compacts were made from powders prepared at 1,00$0^{\circ}C$). The constituent compositions of spinel and mullite specimens sintered at 1,$700^{\circ}C$ for 1hr were 27.5wt% MgO and 70.5wt% Al2O3, respectively. Vickers microhardness and fracture toughness of spinel sintered at the above condition were 13.7GPa and 2.6MN.m3/2, respectively, and room temperature bending strength, 425MPa, was nearly maintained even at the elevated temperature. In the case ofmullite specimens, those values were 13.5GPa, 2.2MN/m3/2 and 430MPa, respectively.

• The Korean Journal of Mycology
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• v.25 no.4 s.83
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• pp.369-376
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• 1997

These researches were carried out for improvement of medium for mycelial growth of Hericium erinaceus isolate KU-1. It grew well at pH 4 and $25^{\circ}C$. Glucose and sucrose were favorable carbon sources for mycelial growth. As nitrogen sources, ammonium acetate and arginine enhanced mycelial growth. Optimum C/N ratio was 200. Based On the results, the following recipe is suggested for synthetic medium for the mycelial growth: glucose 18.02 g, arginine 2.613 g, ammonium acetate 2.313 g, $CaCl_2\;0.33\;g$, $KH_2PO_4\;8.5\;g$, $MgSO_4{\cdot}7H_2O\;2.0\;g$, $FeSO_4{\cdot}7H_2O\;0.02\;g$, $ZnSO_4{cdot}7H_2O\;0.02\;g$, $MnSO_4{\cdot}7H_2O\;0.02\;g$, water 1 liter. This medium was superior for the mycelial growth to other conventional media such as Yeast malt extract agar (YMA), Park medium, Potato dextrose agar (PDA), Malt extract agar, Czapek-dox agar, Macaya-lizano medium and Yeast extract agar. This new synthetic medium is designated as Ko medium.

• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.220-225
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• 1998

The spinel structured $LiMn_2O_4$ was prepared from $Li_2CO_3$ and $MnO_2$ by calcination at various temperatures in the range of $750{\sim}900^{\circ}C$. It was found that the most suitable cubic structure of $LiMn_2O_4$ was obtained by heating at $850^{\circ}C$ for 12 hrs. However, in the calcination at $900^{\circ}C$, $Mn^{4+}$ of 0.06M was changed to $Mn^{+3}$ by the oxygen loss, so that it has been shown that the formula has changed to $LiMn_2O_{3.97}$. This phenomena were in agreement with the Jahn-Teller distortion by the increment of $Mn^{+3}$ ion on the octahedral sites of the spinel structured $LiMn_2O_4$. The results showed that after 15 charge/discharge cycles in the voltage range from 3.5V to 4.3V versus Li/$Li^+$ with a current density of $0.25mA/cm^2$, the spinel structured $LiMn_2O_4$ that was prepared at $900^{\circ}C$ showed a lower discharge capacity, 82~50 mAh/g, while the $LiMn_2O_4$, prepared at $850^{\circ}C$, showed the discharge capacity of 102~64 mAh/g.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.3
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• pp.219-225
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• 2000

The spinel structured $LiMn_2O_4$was obtained by two consecutive heat treatment on xerogel; the first heat treatment was at $150^{\circ}C$ and the second at $350^{\circ}C$ was obtained by sol-gel process using an aqueous solution of lithium hydroxide and manganese acetate. The synthesized $LiMn_2O_4$ by the sol-gel process showed a discharge capacity of 88~56 mAh/g after 15 cycles in Li/lM $LiClO_4$(in PC)/$LiMn_2O_4$at a current density of 0.25 mA/$\textrm{cm}^2$ and the voltage ranged 3.5 V to 4.3 V. For the second heat treatment above $350^{\circ}C$, $Mn_2O_3$was formed as a by-product during the synthesis of $LiMn_2O_4$. The heat treatment at $500^{\circ}C$, for example, showed a lower discharge capacity 81~47 mAh/g, after the 15 charge/discharge cycles. The lower capacity was due to the increment of $Mn^{3+}$ ion and this phenomenon was in agreement with the Jahn-Teller distortion.

• 한국해양학회지
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• v.25 no.2
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• pp.49-61
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• 1990

The family Corycaeidae in the neighbouring seas of Korea was taxonomically studied based on the zooplankton samples collected in August, 1986. In this study, nine species belonging to two genera and three subgenera of the Corycaeidae were identified and described with illustrations; Corycaeus (Corycaeus) speciosus, G.(C.) crassiusculus, C. (Ditrichocorycaeus) affinis, C.(D.) andrewsi, C.(D.) erythraeus, C.(Onychocorycaeus) pacificus, c.(O.) catus, C.(O.) agilis, and Farranula gibbula. The distribution patterns of these species showed that C.(D.) affinis appeared to be and indicator species of the coastal waters, and C.(C.) speciosus, C.(C.) crassiusculus, c.(O.) catus, C.(D.) andrewsi, and Farranula gibbula appeared to be indicator species of the warm-oceanic waters.

• Journal of the Korean institute of surface engineering
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• v.32 no.6
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• pp.647-657
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• 1999

Due to the inherently poor adhesion strength of Cu-based leadframe/EMC (Epoxy Molding Compound) interface, popcorn cracking of thin plastic packages frequently occurs during the solder reflow process. In the present work, in order to enhance the adhesion strength of Cu-based leadframe/EMC interface, black-oxide layer was formed on the leadframe surface by chemical oxidation of leadframe, and then oxidized leadframe sheets were molded with EMC and machined to form SDCB (Sandwiched Double-Cantilever Beam) and SBN (Sandwiched Brazil-Nut) specimens. SDCB and SBN specimens were designed to measure the adhesion strength between leadframe and EMC in terms of critical energy-release rate under quasi-Mode I ($G_{IC}$ ) and mixed Mode loading ($G_{C}$ /) conditions, respectively. Results showed that black-oxide treatment of Cu-based leadframe initially introduced pebble-like X$C_2$O crystals with smooth facets on its surface, and after the full growth of $Cu_2$O layer, acicular CuO crystals were formed atop of the $Cu_2$O layer. According to the result of SDCB test, $Cu_2$O crystals on the leadframe surface did not increase ($G_{IC}$), however, acicular CuO crystals on the $Cu_2$O layer enhanced $G_{IC}$ considerably. The main reason for the adhesion improvement seems to be associated with the adhesion of CuO to EMC by mechanical interlocking mechanism. On the other hand, as the Mode II component increased, $G_{C}$ was increased, and when the phase angle was -34$^{\circ}$, crack Kinking into EMC was occured.d.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.267-271
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• 1974

The tetradentate schiff base, N,N'-bis(salicylaldehyde)-ethylene diimine has been reacted with a series of Mo(IV), Mo(V), Mo(IV), and Mo(III) oxidation states to form new Complexes; $[MoO_2(C_{16}H_{14}O_2N_2)], (MoO(C_{16}H_{14}O_2N_2)]_2O, (Mo(SCN)(C_{16}H_{14}O_2N_2)]_2O, and (Mo(H_2O)(C_{16}H_{14}O_2N_2)]_2O.$ These complexes have hexa coordinated configurations and the mole ratio of these ions to the ligand was 1:1. These complexes have been identified by visible spectra, infrared specra, T.G.A., D.T.A., and elemental analysis.

• Journal of Sensor Science and Technology
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• v.21 no.6
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• pp.451-455
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• 2012

Dense Cr-precursor nano-hexaprisms were prepared by heating the Cr-nitrate aqueous solution containing Hexamethylenetetramine and polyvinylpyrrolidone, which were converted into porous $Cr_2O_3$ nano-hexaprisms containing nanoparticles by heat treatment of Cr-precursors at $600^{\circ}C$ for 2 h in air atmosphere. At the sensor temperature of $300^{\circ}C$, porous $Cr_2O_3$ nano-hexaprism showed the high response ($R_g/R_a$, $R_g$: resistance in gas, $R_a$: resistance in air) to 100 ppm $C_2H_5OH$ ($R_g/R_a=69.8$) with negligible cross-responses to 100 ppm CO and 5 ppm $C_6H_6$. The sensitive and selective detection of $C_2H_5OH$ in porous $Cr_2O_3$ nano-hexaprism were discussed in relation to the morphology of nanostructures.

• Journal of the Korean Society of Food Science and Nutrition
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• v.29 no.1
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• pp.49-56
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• 2000

The 2-O-$\alpha$-D-glucopyranosyl L-ascorbic acid (AA-2G) which was enzymatically glucosylated with the cyclodextrin glucanotransferase (CGTase) [EC 2.4.1.19] from Bacillus sp. JK-43 has been reported previously. The presnet experiments examined the optimal conditons for the productio of AA-2G from AA and soluble starch, and characterized the properties of the CGTase from Bacillus sp. JK-43. The reaction mixture for the maximal production of AA-2G was followings; 12% total substrate concentration, 1,400 usits/mL of CGTase and a mixing ratio of 2 : 3(g or AA : g of soluble starch). Under this condition, 1.76mM of AA-2G, which corresponded to 2.53% yield based on AA, was produced after incubation for 24hrs at 45$^{\circ}C$ (pH 5.5). The optimum pH and temperature for the CGTase activity were 6.0 and 45$^{\circ}C$, respectively. The enzyme was stable at pH 5.5 to 9.5, and at temperature up to 5$0^{\circ}C$. The thermostability of the enzyme could be enhanced up to 6$0^{\circ}C$ by the addition of 30mM CaCl2.