• Journal of the Korean Magnetics Society
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• v.7 no.5
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• pp.250-257
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• 1997

The microstructure and magnetic properties of Fe-Nb-B-N thin film alloys, which produced by rf magnetron sputtering method in $Ar+N_2$ mixed gas atmosphere, were investigated. The $Fe_{70}Nb_{14}B_{11}N_5$ films, annealed at 59$0^{\circ}C$, exhibit soft magnetic properties: $4{\pi}M_s=16.5kG$ , $H_c=0.13Oe$ and ${\mu}_{eff}$ (1~10 MHz)=5, 000. The frequency stability of the Fe-Nb-B-N films has also been found to be good up to 10 MHz. The Fe-Nb-B-N thin film alloys annealed at 59$0^{\circ}C$ consist of three phase; fine crystalline $\alpha$-Fe phase with grain size of about 5~10 nm, Nb-B rich amorphous phase and Nb-nitride precipitates with the size of less than 3 nm. Annealed Fe-Nb-B films have two phases; $\alpha$-Fe grains with the size of about 10 nm and Nb-B rich amorphous phase. The addition of N decreased $\alpha$-Fe grain size due to the precipitation of NbN. The good magnetic properties of the Fe-Nb-B-N film alloys are due to fine $\alpha$-Fe grains resulting from the precipitation of NbN.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.6
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• pp.875-882
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• 2021

To minimize occupational noise induced hearing loss, it is recommended that workers should not be exposed to noise levels exceeding 85 dBA for over 8 h. In the present study, noise exposure levels were measured for seven workers based on their tasks on a training ship. The A-weighted noise exposure level (L_ex,24h) was measured by taking into account the A-weighted equivalent continuous sound level (L_Aeq,i), duration (h) and noise contribution (L_ex,24h,i) from the workers' locations. Results are thus obtained for different job categories as follows: officer group L_ex,24h=56.1 dB, navigation crew L_ex,24h=58.9 dB, navigation cadet L_ex,24h=62.0 dB, ship's cook L_ex,24h=64.3 dB, engine cadet L_ex,24h=91.1 dB, engineer L_ex,24h=91.1 dB, and engine crew L_ex,24h=95.1 dB. It was determined that the engineers, engine crews, and engine cadets in charge of machinery must wear hearing protection devices. By wearing hearing protection devices when working in highly noisy engine rooms, it is estimated that the noise expose levels could be reduced by the following amounts: engineer L_ex,24h=23.1 dB, engine Crew L_ex,24h=24.4 dB, and engine cadet L_ex,24h=21.5 dB. Moreover, if the no. 2 lecture room and mess room bottom plates in the cadets accommodations were improved to the 64 mm A-60-class floating plates, then further reductions are possible as follows: navigation cadet L_ex,24h=4.3 dB and engine cadet L_ex,24h=1.8 dB.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.80-89
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• 2008

Patch antennas with an array of pins interconnecting the patch and the ground (Pin array patch antennas) are fabricated and their characteristics are measured. The radiation characteristics of pin array patch antennas are compared to those of conventional patch antennas. The suppressions of the radiation in horizontal directions in E-plane and H-plane are more than 10 dB and 4 dB, respectively. The forward radiation is increased, while the backward radiation is decreased. The directivity is improved because the half-power beamwidth of radiation patterns in both E-plane and H-plane is reduced. The resonance frequency of a pin array patch antenna increases as the pin radius of a pin amy patch antenna increases. An optimum pin radius of a pin array patch antenna exists for the maximum suppression of the radiation in horizontal directions.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.576-578
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• 2000

This paper address the prediction method of a soil thermal property depending on soil moisture contents and suggests the guideline to determine the soil thermal resistivity for the calculation of the cuurent carrying capacity of underground power cables in Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.5
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• pp.433-437
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• 2004

The MmSH is a process of injecting ABS to produce innovated physical properties compared to the conventional injection process. Physical properties such as thickness and adhesion strength of Ni plate electrolessly coated on a conventional and a MmSH injected ABS have been studied in the pH range 4~8. Thickness of the plate on the MmSH and the conventionally injected ABS appeared to be directly proportional to pH. The ABS processed by the conventional injection showed adhesion strength corresponded to ASTM 4B above pH 5. On the other hand, the ABS processed by the MmSH injection showed a superior adhesion strength corresponded to ASTM 5B above pH 6. It was calculated the shielding effectiveness of above 50 dB in all conditions.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1484-1485
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• 2006

Alumina 첨가량의 변화에 따라 국산 경년품 애자와 신품 애자의 특성을 분석하고, 외국산 신품애자와 비교분석하였다. 그 결과 알루미나가 17% 첨가된 2001년도 자기애자가 알루미나 첨가량이 m%된 2004년 신품애자에 비하여 기계적 특성이 10%정도 낮았다. 또한, 2001년도에 제조한 애자의 자기 상대밀도는 이론밀도의 96%에 도달하였으나 2004년도에 제조한 애자의 상대 밀도는 이론 밀도의 98%에 도달하였으며, 애자의 균일성을 나타내는 Qs 값은 5.01로 높게 나타났다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.751-759
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• 2015

In this study, we investigate the Characteristics of the flowfields of a circular cylinder having a small triangular prism at the upstream side. We measure the fluid force on the circular cylinder and obtain a visualization of the flow fields using particle image velocimetry (PIV). The experimental parameters employed were the width ratios (H/B = 0.2~0.6) of the triangular prisms to the circular cylinder's diameter, and the gap ratios (G/B = 0~3) between the circular cylinder and the triangular prism. We observed that the drag reduction rate and Strouhal number of the circular cylinder increased and then decreased with G/B in the case of the same H/B. The drag reduction rate increased with H/B in the case of the same G/B. In the case where the circular cylinder had a small triangular prism, the stagnation regions were represented in the upstream and downstream sides of the circular cylinder.

• Microbiology and Biotechnology Letters
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• v.23 no.5
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• pp.602-608
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• 1995

The aim of the present research program was to construct an optimum fermentation system and to characterize the properties of cathepsin B inhibitor from Streptomyces chromofuscus SMF28. Glucose and casitone were proved to be good carbon source and nitrogen source, respectively. The production of inhibitor was high at lower concentration than 10 mM of inorganic phosphate. The optimum temperature and pH for the production of inhibitor were 30$\circ$C and pH 7, respectively. The production of inhibitor was related to mycelial growth and was affected by medium composition. The inhibitor in culture filtrate of S. chromofuscus SMF28 was purified by butanol extraction, silica gel chromatography, Amberlite IRC-50 (H$^{+}$ form) chromatography, preparative TLC, and preparative HPLC. From amino acid analysis and UV, IR, $^{1}$H-NMR spectroscopic analysis, the inhibitor was identified as a peptide containing valine and phenylalanine derivative.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.5
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• pp.752-757
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• 1995

The effect of fermentation temperature on the changes of pH, acidity, salt content, color and vitamin C of mustard leaf kimchi during various storage days was investigated. The conditions of fermentation temperature were set at $4^{\circ}C$ (sample A) and $20^{\circ}C$ (sample B), and $4^{\circ}C$ after keeping at $20^{\circ}C$ for 12 hours(sample C) and $20^{\circ}C$ for 36 hours(sample D). As the fermentation proceeded, pH of sample stored at low temperature(sample A) was drop ped gradually from initial pH of 5.24 but there was great pH drop in the sample stored at high temperature(sample B, D). The salt content of the sample B at high temperature increased remarkably, and then the values showed D > A > C. The Humter values of L and a increased at the optimum ripening period, the higher the initial fermentation temperature(B) and the later the initial fermentation time at $20^{\circ}C$ those values, then decreased. The Hunter value of b constantly increased until day of 108. As fermentation time passed, the content of total vitamin C decreased to the range of 9.0mg% to 14.0mg% up to 24 days of fermentation, and at the optimum ripening period, it increased to the range of 14.0mg% to 22.0mg%, and at the fermentation period(until day 108), it decreased gradually.

• Microbiology and Biotechnology Letters
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• v.29 no.1
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• pp.50-55
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• 2001

A new bacteriocin produced by Bacillus subtilis cx1, was partially purified and characterized. The bactericoin from B. subtilis cx1 was stable in the range of pH 2.5-9.5. B. subtilis csx1 retained its antimicrobial activity to long-term exposure at $-20^{\circ}C$ and $-70^{\circ}C$. However, B. subtilis cx1 was inactivated completely within 15 min over $60^{\circ}C$ and lost 50% of its antimicrobial activity within 15 min at $50^{\circ}C$, B. subtilis cx1 was inactivated by protease, trypsin, proteinase K and carboxypeptidase, which indi-cates its protein nature. Direct detection of the antimicrobial activity on Tricine -SDS-PAGE suggested an apparent molecular mass of about 9,500 dalton.