• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.7 s.337
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• pp.63-70
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• 2005

We investigated the phase noise of an oscillator with a extremely high-Q resonator used as the resonant element. A TE$_{011}$ mode rutile-loaded resonator with high-temperature superconductive (HTS) $YBa_2Cu_3O_{7-\delta}$(YBCO) films used as the endplates is prepared for this purpose. At 23.5 K, the unloaded Q and the loaded Q are 863000 and 180000, respectively. The phase noise of -104.8 dBc/Hz at 1 KHz offset was observed for the oscillator having a resonator with $Q_{L}$ =180000 at the $TE_{01\delta$ mode resonant frequency of 8.545 GHz at 23.5 K Such oscillators with very low phase noise are expected to be used for building up communication systems capable of efficient use of the frequency band and high-speed data transmission as well as for Doppler radars. Frequency tuning could be realized for the resonator by using a piezoactuator Applicability of the tunable rutile resonator for fabricating tunable oscillators of high performances is discussed.

• Journal of Ocean Engineering and Technology
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• v.28 no.4
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• pp.356-362
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• 2014

Wear and corrosion of the engine parts surrounded with combustion chamber is more serious compared to the other parts of the engine because temperature of the exhaust gas in a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. Therefore, an optimum repair weldment as well as an available choice of the base metal for these parts are very important to prolong their lifetime in a economical point of view. It reported that there was an experimental result for repair weldment on the forged steel which would be generally used with piston crown material, however, it is considered that there is no study for the repair weldment on the cast steel of piston crown material. In this study, four types of electrodes such as 1.25Cr-0.5Mo, 0.5Mo Inconel 625 and 718 were welded with SMAW and GTAW methods on the cast steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected zone and base metal were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% $H_2SO_4$ solution. In the cases of Inconel 625, 718, the weld metals and base metals exhibited the best and worst corrosion resistance respectively, however, 1.25Cr-0.5Mo and 0.5Mo indicated that corrosion resistance of the base metal was better than the weld metal. And the weld metal welded with electrodes of Inconel 625 revealed the best corrosion resistance among the electrodes, and Inconel 718 followed the Inconel 625. Hardness relatively also indicated higher value in the weld metal compared to heat affected zone and base metal. In particular, Inconel 718 indicated the highest value of hardness compared to other electrodes in the heat affected zone.

• Composites Research
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• v.24 no.4
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• pp.23-28
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• 2011

Recently CFRP laminate joints process by bolts and nets are developed rapidly in aircraft industries. However, there are serious drawback during jointing process. Many hole processes are needed for the manufacturing and structural applications using composite materials. Generally, very durable polycrystalline crystalline diamond (PCD) drill has been used for the CFRP hole process. However, due to the expensive price and slow process speed, chemical vapor deposition (CVD) diamond drill has been used increasingly which are relatively-low durability but easily-adjustable process speed via drill shape change and price is much lower. In this study, the comparison of hole process between PCD and CVD diamond coated drills was done. First of all, CFRP hole processbility was evaluated using the equations of hole processing conditions (feed amount per blade, feed speed). The comparison on thermal damage occurring from the CFRP specimen was also studied during drilling process. Empirical equation was made from the temperature photo profile being taken during hole process by infrared thermal camera. In addition, hole processability was compared by checking hole inside condition upon chip exhausting state for two drills. Generally, although the PCD can exhibit better hole processability, hole processing speed of CVD diamond drill exhibited faster than PCD case.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.3
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• pp.334-339
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• 1983

With the 91 lines of Italian millet collected throughout the whole country in Korea and the 238 varieties from several Asian countries, trial was carried out to elucidate its differentiation, dissemination and distribution, and the ethnobotanical relations to the adjacent area. Glutinous millets which consisted of 66% among the collected Korean lines were widely distributed throughout the whole country, but non-glutinous ones were mainly distributed in the mountainous regions and Jeju island. The variations in germinability at low temperature were recognized among lines, but seemed not to be closely related to their regional distribution. The collected lines with small grain size were distributed mainly in the mountainous regions of middle and northern part of Korea and larger ones in Jeonnam province and Jeju island. And some of them were larger in grain size as compared with that of Japanese and Republic of China varieties. Seed coat color of collected lines in Korea showed wide variations from yellow to gray, especially in Gyungbuk province. However, all lines from Chungnam, Jeonnam and Gyungnam province were yellow in seed coat color. All lines from Korean collection except two lines indicated negative(-) phenol reaction which is very similar to that of Japan and China, while these were quite different from the varieties of Republic of China, Philippines and India, of which 30-60% showed positive(+) phenol reaction. The pattern of the esterase isozyme m Korean lines was simillar to that of Japanese lines and this was quite different from that of Republic of China, Philippines and India. Variation of this trait was greater in Chinese and Korean lines.

• Korean journal of food and cookery science
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• v.18 no.5
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• pp.534-542
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• 2002

This study was carried out to determine the effects of various starches (mungbean starch, cowpea starch and corn starch) on the quality characteristics of Omija jelly made of Omija extract. The viscosity of starch suspended in Omija extract and distilled water was measured by using a RVA(Rapid Visco Analyzer), and, color value, syneresis, texture(rupture test and TPA test) and sensory properties of Omija jelly and pure starch jelly were measured. Gelatinization temperature of each starch suspended in Omija extract was higher than that suspended in distilled water, whereas final viscosity of Omija jelly was decreased. Omija extract appeared to retard the gelatinization of starch and recrystallization of gelatinized starch. The viscosity of com starch was lowest among the three types of starch, suggesting thai higher concentration is needed in the use of com starch. The lightness(L) of corn starch gel was the highest among the gels. The syneresis of Omija jelly was lower than that of starch jelly, therefore, Omija extract seemed to be helpful on the stability of starch gel. Rupture properties of Omija jelly was lower than that of starch jelly, whereas the adhesiveness of omija jelly was greater. Omija jelly made of corn starch was less cohesive and more sticky than other gels, and its acceptability was very low. Sensory characteristics of the gel were relatively well correlated with the mechanical characteristics. Overall acceptability of Omija jelly was high in the concentration of 7, 8% of mungbean starch and 8, 9% of cowpea starch. Thus, the optimum concentration of starch for making Omija jelly using mungbean starch was 7, 8% and that using corn starch was 8, 9%.

• Korean Journal of Food Science and Technology
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• v.25 no.2
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• pp.191-195
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• 1993

The intestinal microflora of humans is an extraordinarily complex mixture of microorganisms, the majority of which are anaerobic bacteria. Amongst them, most prevalent bacteria are Bacteroides, Eubacterium, Peptococcus, Bifidobacteria. We isolated a Bacteroides fragilis strain from a Korean adult and examined various glycosidase activities of this strain. The activities of $N-acetyl-{\beta}-glucosaminidase,\;{\alpha}-fucosidase$, ${\beta}-glucuronidase$, chitobiase and PNPCase were stronger in Bacteroides fragilis Roid 8 than in other intestinal anaerobic bacteria. $N-acetyl-{\beta}-glucosaminidase$ was strongest, followed by ${\alpha}-fucosidase$, ${\beta}-glucuronidase$ and PNPCase. The activities of ${\beta}-galactosidase$, ${\beta}-xylosidase,\;{\alpha}-arabinofuranosidase$ were not present or very low. The activities of ${\alpha}-glucosidase$, ${\beta}-glucosidase$ and ${\alpha}-galactosidase$ were present but at a lower level than in Bifidobacterium. The effect of the carbon sources on the production of $N-acetyl-{\beta}-glucosaminidase$, ${\alpha}-fucosidase$, ${\beta}-glucuronidase$ and PNPCase of Bacteroides fragilis Roid 8 was investigated. :.actose and glucose lowered the production of the varous glycosidase enzymes studied in this work. In addition, we investigated the optimum temperature and pH of each glycosidase from Bacteroides fragilis Roid-8 using crude enzyme preparations.

• Microbiology and Biotechnology Letters
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• v.26 no.4
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• pp.297-302
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• 1998

$\beta$-Xylosidase B was produced by Escherichia coli HB101/pKMG12 carrying the xylB gene of Bacillus stearothermophilus No.236 on its recombinant plasmid. The $\beta$-xylosidase B produced was purified by ammonium sulfate fractionation, DEAE-Sepharose CL-6B, Sephacryl S-200 and Superdex 200 HR gel filtration. The purified enzyme showed the highest activity at pH 6.5 and 5$0^{\circ}C$. But, the enzyme was observed to be very sensitive to the pH and temperature of the reaction mixture. The enzyme was activated about 35% of its original activity in the presence of 1 mM of $Mn^{2+}$ but it was completely inhibited by $Ag^{+}$, $Cu^{2+}$and $Hg^{2+}$ions. In contrast with the $\beta$-xylosidase A, the B enzyme was found to have $\alpha$-arabinofuranosidase activity though the activity was fairly low compared with the $\alpha$-arabinofuranosidase produced from the arfI gene of the same Bacillus stearothermophilus. Therefore, $\beta$-xylosidase B is considered to be more suitable than $\beta$-xylosidase A at least for the biodegradation of arabinoxylan. The $K_{m}$ and V$_{max}$ values of the $\beta$-xylosidase B for o-nitrophenyl-$\alpha$-D-xylopyranoside were 6.43 mM and 1.45 $\mu$mole/min, respectively. Molecular mass of the enzyme was determind to be about 54 kDa by SDS-PAGE and 160 kDa by Superdex 200HR gel filtration, indicating that the functional $\beta$-xylosidase B was composed of three identical subunits.s.

• Korean Journal of Materials Research
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• v.10 no.3
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• pp.223-226
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• 2000

The oxygen deficient ferrites $(Ni_x,\; Zn_{1-x})Fe_2O_{4-{\delta}}$ can decompose $CO_2$ as C and $O_2$ at a low temperature of about $300^{\circ}C$. Ultra powders of $(Ni_x,\; Zn_{1-x})Fe_2O_4$ for the $CO_2$ decomposition were prepared by the hydrothermal methods. The XRD result of synthesized ferries showed the spinel structure of ferrites and ICP-AES and EDS quantitative analyses showed the composition similar with the starting molar ratios of the mixed solution prior to reaction. The BET surface area of the synthesized(Ni, Zn)-ferrites was above $110\textrm{m}^2/g$ and its particle size was very as small as about 5~10 nm. The $CO_2$ decomposition efficiency of the oxygen deficient ferrites($(Ni_x,\;Zn_{1-x})Fe_2O_{4-{\delta}}$) was almost independent with composition and the $CO_2$ decomposition efficiency of ternary (Ni, Zn)-ferrites was better than of binary Ni-ferrites.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.179-191
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• 2016

In addition to the measurement of the concentration of soil contaminants, the new idea of indicative parameters was proposed to validate the remedial works through the monitoring for the changes of soil characteristics after applying the clean up technologies. The parameters like CFU (colony forming unit), pH and soil texture were recommended as indicative parameters for land farming. In case of soil washing, water content and the particle size distribution of the sludge were recommended as indicative parameters. The sludge is produced through the particle separation process in soil washing and it is usually treated as a waste. The parameters like water content, organic matter content, CEC (cation exchange capacity) and CFU were recommended as indicative parameters for the low temperature thermal desorption method. Besides the indicative parameter, sampling methods in stock pile and the optimal minimum amount of composite soil sample were proposed. The rates of sampling error in regular grid, zigzag, four bearing, random grid methods were 17.3%, 17.6%, 17.2% and 16.5% respectively. The random grid method showed the minimum sampling error among the 4 kinds of sampling methods although the differences in sampling errors were very little. Therefore the random grid method was recommended as an appropriate sampling method in stock pile. It was not possible to propose a value of optimal minimum amount of composite soil sample based on the real analytical data due to the dynamic variation of $CV_{fund{\cdot}error}$. Instead of this, 355 g of soil was recommended for the optimal minimum amount of composite soil sample under the assumption of ISO 10381-8.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.39 no.2
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• pp.146-157
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• 1994

Wasong(Orostachys japonicus A. Berger) has been used as anti-cancer medicinal plants from ancient time. This experiment was conducted to obtain some fundamental informations concerning anatomical study, germination test, soil analysis of indigenious districks, adaptaion of soil for wasong. The leaf of wasong was xerotype with spine, mesophyl chloroplast is dense surrounded vascular bundle, with a many large water storage tissue without chloroplast, and was bifacial stomata leaf type. The stem of wasong was amphicribral vascular bundle, central cylinder was cylinder type and protostele. Root was polarch type, potoxylem of it's was arranged in ring shape of annulation and metaxylem. The structure of flower was cymose, was caylyx of 5 sepals, corolla of 5 petals, roecium of 10 stames, ovules of five, placentation parietal, ovary superior, axile placenta. The optimum temperature for seed germination was $25^{\circ}C$ under light and germination percentage was 22.5%. Dormancy breaking was effective for 6-8 days at 5$^{\circ}C$ and at 100 ppm level of $GA_3$ The soil analysis of wasong local districks, content of available $P_2O_5$, Ca were higer than optimal level of upland and C.E.C., exchangeable k was not significantly different of that, but exchangeable magnesium was very low. The growth of wasong was affected draining regardless soil combination treatment.