• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.77-78
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• 2016

최근 신재생에너지 발전시스템 등 분산전원 시스템을 활용하는 경우가 증가함에 따라 마이크로그리드의 효율적인 제어와 안정성에 대한 연구가 활발히 이루어지고 있다. 분산전원 발전설비를 마이크로그리드에 연계하기 위해서는 계통연계 인버터가 필수적으로 요구된다. 계통연계 인버터를 구성하기 위해서는 계통전압과 인버터 출력 전류 등을 측정하기 위한 센서가 요구되며 이는 계통연계 인버터의 생산비용을 상승시키는 원인이 된다. 본 논문에서는 계통연계 인버터의 경제성을 향상시키기 위해 전압센서를 사용하지 않는 새로운 인버터의 제어기법을 제안한다. 제안된 기법은 전압센서를 사용하지 않고 인버터 출력전류 정보와 외란관측기를 이용해 계통전압을 추정한다. 하지만 외란관측기로 계통전압을 추정하는 경우 관측기의 한정된 대역폭으로 인해 추정 계통 전압에는 위상 지연이 발생하며 이는 제어 성능 저하의 원인이 된다. 이러한 문제를 해결하기 위해 추정 계통 전압의 위상지연을 보상하기 위한 위상 보상기법이 설계된다. 제안된 기법의 안정성과 성능이 시뮬레이션 및 실험을 통해 입증된다.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1569-1573
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• 2004

Two ring-type conductance meters were manufactured to measure void fraction and its propagation speed in slug flow. The signal of conductance meter with two rings depends on liquid temperature. Therefore a conductance meter with separated probe designed by Coney (1973), which is independent of liquid temperature, was used and experimentally proved. The manufactured conductance meters showed a good repeatability and agreement with the analytical solution by Coney (1973). From time lag between two conductance meter, we could calculate the propagation speed of void fraction.

• Journal of Food Hygiene and Safety
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• v.12 no.4
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• pp.277-280
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• 1997

The effects of acetic acid (AA) on aerobic plate counts (APC), gram-negative bacterial counts (GNC), and generation time (GT) in chicken wings stored at 4* were assessed. Chicken wings were treated with 0.5-1.5% (v/v) AA at exposure times of 5 min. Treatments of AA for 5 min significantly (P<0.05) reduced aerobic plate counts (APC) and gram-negative bacterial counts (GNC) on the surface of chicken wings for 8 days, respectively. After 4 days of storage, treatments of 1.0% AA and 1.5% AA for 5 min completely (P<0.05) inhibited APC and GNC compared to initial controls. Based on these results, treatments of 1.0% AA and 1.5% AA for 5 min prolonged the microbiological shelf-life for 8 days compared to those of 0.5% AA and the controls. All treatments of AA increased the lag phase and GT of aerobic microorganisma.

• 한국해양학회지
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• v.11 no.1
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• pp.18-24
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• 1976

The distribution of tidal currents in Asan Bay was simulated by a numerical experiment. A homogeneous and single layer model with bottom stress taken into account was used. Although the effective configuration of the bay differs significantly between the high tide and the low tkde, its form is assumed to be fixed as a first approximation. The advective term is particularly large because the tidal range of 810cm is large compared to the depth and the changes of velocities occur abruptly. The results of calculations agree fairly well with the observations. For example, the tidal range at Manhoriis amplified 15cm higher and the phase lag is five minutes later than at the mouth of the bay. It also can generally be said that, with the semidiurnal tide at the mouth of the bay, the tidal range is increased toward the inner corner and that tidal currents are found to be large at the deeper part of the bay.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.10a
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• pp.31-35
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• 2001

Three dimensional dynamic cutting can be postulated as an equivalent orthogonal dynamic cutting through the plane containing both the cutting vector and the chip flow velocity vector in cutting process. An analytical expression of dynamic cutting force is obtained from the cutting parameters determined by the static three dimensional cutting experiments. Particular attention is paid to the energy supplied to the vibration of the tool behind the vertical vibration and the direction. The phase lag of the horizontal vibration of the tool behind the vertical vibration and the direction angel of the fluctuating cutting force must be regarded in point of stability limits. Chatter vibration can effectively be suppressed by enlarging the dynamic rigidity of the cutting system in the vertical cutting force direction. A good agreement is found between the stability limits predicted by theory and the critical width of cut determined by experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.505-507
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• 2004

This paper attempts to compensate the nonlinearity between the input voltage and the output displacement of the piezoelectric stack in dynamic actuation by the following two ways. Firstly, the charge steering by circuit configuration reduces the hysteresis of piezoelectric actuator remarkably. However, it makes the ripple in positioning due to the phase lag and noise induced from the elements of the long closed loop. Secondly, the feedforward control by neural network compensates the hysteresis of the piezoelectric actuators effectively with the appropriate selection of the input variables for the training. The improvement of the dynamic performance of the piezoelectric actuators by the developed linearization technique is verified by experiments.

• Korean Journal of Microbiology
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• v.29 no.2
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• pp.123-129
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• 1991

In order to develop the protoplast fusion method of the strains of Fusarium, the interspecific protoplast fusion was attempted between Fusarium poae and F. sporotrichioides. Various auxotrophic mutants were isolated by the treatment of N-Methyl-N'-Nitro-N-Nitrosoguanidine. The optimal conditions for the formation and regeneration of protoplasts were examined and the characteristics of a fusant were studied. As a results, protoplasts were readily obtained from 18 hours cultured mycelia by the treatment of driselase for 3 hours and 0.6 M KCl as a best osmotic stabilizer at pH 6.0 for the formation of protoplast. Sucrose was the most suitable for the regeneration. Polyetylene glycol (M.W. 8,000) in $CaCl_{2}$-glycine solution was used to induce the protoplast fusion. The interspecific fusion frequency between protoplasts among the auxotrophic mutants of the two strains ranged from $2.7*10^{-2}$ to $5.7*10^{-3}$ . DNA content and cellulase activity were rather increased in the interspecific fusant. The lag phase of growth curve was slightly elongated in the fusant.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.188-190
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• 1987

In this paper the real-time analysis of vibration objects using projection moir\ulcorner method is realized. By measuring the vibration of two different speakers using three grationgs with different pitch. it is possible to analyze the vibrating speakers, so the fundamental frequency mode of speakers is obserbed at 550Hz and 105Hz respectively and phase lag is shown nonlinear characteristics. Also it is possible to measure the vibration as to nonperiodic signals as well as peoriodic signals.

• Journal of Microbiology and Biotechnology
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• v.16 no.12
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• pp.1977-1983
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• 2006

Kaempferol was isolated and identified from the methanol extract of the flowers of Impatiens balsamina. Kaempferol showed inhibitory activity against mushroom tyrosinase with an $ID_{50}$ of 0.042 mM. Inhibition kinetics, as determined using a Lineweaver-Burk plot, showed kaempferol to be a competitive inhibitor of mushroom tyrosinase with a $K_i$ value of 0.011 mM. The lag phase of tyrosine hydroxylation catalyzed by mushroom tyrosinase clearly increased on increasing the concentration of kaempferol. In addition to its tyrosinase inhibiting activity, kaempferol strongly inhibited melanin production by Streptomyces bikiniensis, in a dose-dependent manner, without inhibiting cell growth. For comparative purposes, the tyrosinase inhibitory activity of kaempferol was also assayed versus quercetin, a positive standard.

• Journal of Applied Biological Chemistry
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• v.48 no.4
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• pp.167-169
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• 2005

Crude extract of bioconverted linoleic acid using Pseudomonas aeruginosa PR3 was evaluated for its antibacterial activity against food-borne pathogenic bacteria. Crude extract showed antibacterial activity against four Gram-positive bacteria, Staphylococcus aureus (ATCC 6538), S. aureus (KCTC 1916), Listeria monocytogenes (ATCC 19166), and Bacillus subtilis (ATCC 6633), and one Gramnegative bacterium, Pseudomonas aeruginosa (KCTC 2004), with minimum inhibitory concentrations ranging from 750 to $1,500\;{\mu}g{\cdot}ml^{-1}$. S. aureus and B. subtilis were selected for growth inhibition assays with bioconverted linoleic acid. Major antibacterial effects occurred at lag phase.