• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.195-198
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• 2002

Two types of conformal load-bearing antenna structure (CLAS) were designed with microwave composite laminates and Nomex honeycomb cores, to give both structural rigidity and good electrical performance. One is 4$\times$8 array for Synthetic Aperture Radar(SAR) system and the other is $5\times2$ array for wireless LAN system. Design was based on wide bandwidth, high polarization purity, low loss and good structural rigidity. We studied the design, fabrication and structural/electrical performances of the antenna structures. The flexural behavior was observed under a 3-point bending test, an impact test, and a buckling test. Electrical measurements were in good agreement with simulation results and these complex antenna structures have good flexural characteristics. The design of this antenna structure is extended to give a useful guide for sandwich panel manufacturers as well as antenna designers.

• Journal of the Korean Ceramic Society
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• v.29 no.12
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• pp.963-969
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• 1992

This paper describes the feasibility for a direct production of zinc oxalate powders from zinc-loaded D2EHPA solutions combining the purification and the precipitation in one operation unit. This process has the potential as an alternative to conventional method for the synthesis of zinc oxide precursor particles from the hydrometal-lurgical processes. Zinc was extracted into D2EHPA in kerosene and then zinc-loaded D2EHPA solution was emulsified with oxalic acid-HCl solution to precipitate zinc oxalate powder, which was readily calcined to zinc oxide. The precipitation kinetics and yield were sensitive to experimental conditions. The morphology, size and size distribution of the zinc oxalate powders varied with zinc/oxalate ion riatio, temperature, and the presence of SPAN 60, which affected nucleation, growth, and the emulsion characteristics.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.631-636
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• 1989

Submicron high-purity mullite powder was prepared by a colloidal sol-gel route. Boehmite and silica were the starting materials. 2wt% $\alpha$-Al2O3 or ZrO2 was used as a seeding material. The gelled powder was calcined at 130$0^{\circ}C$ for 100min and attrition milled for 3hrs. The mullite powder obtained was composed of submicrometer and uniform particles with a narrow size distribution. It was hot-pressed at 1$600^{\circ}C$ for 1hr under 10MPa or was sintered at 1$650^{\circ}C$ for 4hrs. The bulk densities of the products made by both processes were 3.14 and 3.12g/㎤. the mechanical, thermal and electrical properties of the sintered mullite were characterized by bending strength, thermal expansion coefficient, thermal conductivity, dielectric constant and dielectric loss, etc.

• Journal of the Korean Ceramic Society
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• v.26 no.5
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• pp.682-690
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• 1989

Fine mullite powder was prepared by colloidal sol-gel route. Boehmite as a starting material of Al2O3 and silica sol or fumed silica as a starting material of SiO2 were used. $\alpha$-Al2O3, TiO2 and ZrO2 were used as seeding materials. The combination of boehmite and silica was found to be the stoichiometric mullite powder. Techniques for drying used were spray drying, freeze drying, reduced pressure evaporation and drying in a oven. The gelled powder was heated at 130$0^{\circ}C$ for 100min and was attrition-milled for 1~3hrs. The mullite powder obtained was composed of submicrometer, uniform and spherical particles with a narrow size distribution. The mullite powder was characterized by BET, SEM, XRD and IR spectroscopy.

• Journal of Life Science
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• v.12 no.6
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• pp.765-768
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• 2002

Enantioselective hydrolysis of racemic styrene oxide by Rhodotorula sp. CL-82 was investigated. Reaction conditions including pH, temperature, and volume ratio of organic cosolvent were optimized using response surface methodology, and the optimal conditions of pH, temperature, and the volume ratio of cosolvent were determined to be 7.64, $33.26^{\circ}C$, and 3.09 %(v/v), respectively. Chiral (S)-phenyl oxirane could be obtained with high enantiomeric purity (ee ＞ 99%) and 20% yield (theoretical yield ＝ 50%) at the optimal rendition.

• Korean Journal of Food Science and Technology
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• v.10 no.4
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• pp.423-430
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• 1978

Since 1950 there has been a dramatic progress in rationalization of the production of sweet potato and potato starch in Japan. This enabled dextrose industry by enzymatic process to develop rapidly due to the success of enzymatic liquefaction and saccharification. Isomerization of glucose to fructose has been studied, and the immobilization of isomerases prompted its products on industrial scale in 1970. Another advance is the development of effective methods of producing high purity maltose. A malto-hexaose forming amylase was discovered in 1971 and attempts are being made for its pharmaceutical utilization. Saccharification of cellulose by cellulase has been studied. Conversion of starch to other polysaccharides is another example for the numerous Japanese activities.

• Journal of Microbiology and Biotechnology
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• v.10 no.6
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• pp.753-758
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• 2000

Human leptin is identified as a 16kDa (146 amino acids) protein secreted from adipocytes which influences body weight homeostasis. In order to produce active leptin, the human obese gene coding for leptin was expressed in Bacillus subtilis WB600 strain which is deficient in six extracellular proteases. The recombinant leptin was produced in a culture supernatant, and in a culture supernatant, it was contained as high as 48% for total proteins. After simple purification steps, which consisted of ammonium sulfate precipitation and anion-exchange column chromatography, 2.3 mg of leptin with a purity greater than 95% was obtained from the 0.51 culture with the recovery yield of 38.3%. The purified leptin showed the correct folding structure with one disulfied bond.

• Journal of environmental and Sanitary engineering
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• v.11 no.1
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• pp.63-70
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• 1996

The synthesis of high purity and ultra-fine $BaTiO_3$ by precipitation with gaseous $NH_3$ as precipitator was investigated to find an alternative process to solve various problems of recent wet methods. A synthesis process for $BaTiO_3$ powder using $NH_3$ gas as a precipitator in a bubble column reactor was experimentally successful in developing the production process of piezoelectric ceramic $BaTiO_3$ powder. And a 2.33m1/sec is approprite for the feed flow rate, $BaTiO_3$ powder produced under above the condition is spherical type, its particle size was about $0.2{\mu}m$.

• Journal of Welding and Joining
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• v.14 no.6
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• pp.48-57
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• 1996

The weldability of high purity aluminum-lithium binary alloys has been investigated using the Varestraint test. Autogenous GTAW (gas-tungsten-arc-welds) were run along specimens of different lithium concentration using three sets of welding parameters. Welding voltage was held constant at 10 volts. Welding current (70∼100 amps) and travel speed (23∼33 cm/min) were the parameter varied. Hot-tearing susceptibility varied with lithium content and exhibited a steep peak at 2.6 weight percent lithium. Depth of penetration increased with increasing heat input and lithium concentration. The susceptibility is influenced by the wettability of dendrites by the interdendritic eutectic liquid as well as the time available for back-Siting by eutectic liquid. The welding condition of welding current 70A and travel speed 23 cm/min was showed good resistance to cracking in aluminum-lithium alloys. Suggestions for improving weld cracking resistance are also provided.

• Korean Journal of Veterinary Research
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• v.32 no.3
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• pp.413-419
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• 1992

Deoxynivalenol producing isolates of Fusarium Graminearum R 6576 was grown on rice for 25 days at 19,25 and $28^{\circ}C$. Maximum production of deoxynivalenol(DON) by Fusarium graminearum R 6575 occurred at $28^{\circ}C$ and 20 days. Maximum concentration of 940 ppm DON were obtained after 20 days at an initial moisture content of 40%. A DON derivative, 15-acetyl-DON (15-ADON), was also found at concentrations of 150~300ppm after 5~10 days. Crude culture extracts were purified by water-saturated silica gel column chromatography which selectivity extracted DON when methylene chloride was as the mobile phase. Purity of crystallized DON was verified by thin layer and high performance liquid chromatography. Also this method was advantage method or production of DON and require little organic sorbent than the other methods.