• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.1
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• pp.30-42
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• 1986

In order to find out the best media, explants and environmental conditions for induction of calluses and organogeneses of Pinellia ternata (Thunb.) Breit in vitro, various parts of adult have been cultured on Murashige & Skoog's medium containing various levels of 2,4-dichlorophenoxy acetic acid(2,4-D) and kinetin. The results obtained were as follows: Calluses were induced from the surface of apical meristem and leaf tissue. Formation and growth of calluses in petiole ex plants were best on the MS medium complemented with 2,4-D 2.0 mg/l and kinetin 0.2mg/l. But callus formation in stem ex plants of the nearest tuber was not induced at all kinds of media. Plantlets occured at all treatment except absence of growth regulator. Their numbers, size, leaf and fresh weight were promoted by 2,4-D 2.0mg/l and kinetin 0.2mg/l. Root growth was increased on the medium containing higher 2,4-D concentrations. Size and fresh weight of callus were increased at 25$^{\circ}C$ compared with 10, 20 and 30$^{\circ}C$, respectively. Optimal pH value was at 6.0 for growth of callus. Morphological aberrations were observed in plantlets, especially in regenerated leaves. The separation of the broad leaved plantlets and albino were observed in some cultures. Growth of plantlets after transplantation was best in pots with the sterilized vermiculte. But abnormal variants withered up.

• Journal of Plant Biotechnology
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• v.29 no.1
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• pp.19-23
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• 2002

This experiment was conducted to micropropagate bulblets via shoot cluster formation and massproduce normal bulblets from the sections of proliferated shoot clusters in Lilium asiatic hybrid 'Hae Hwa'. The induction of shoot clusters from the culture of bulblet sections was more effective than that of bulb scales on MS medium with 1.0 mg/L BA and 0.5 mg/L IAA. Proliferation of shoot clusters from the formed shoot cluster sections was the most favorable on medium containing 5.0 mg/L BA and 0.5 mg/L IAA. The formation and the growth of bulblets from shoot cluster sections were achieved effectively on medium with 60∼90 g/L sucrose. The leaves derived from shoot clusters grew vigorously but the bulblets from shoot clusters grew very poor in 5L air-lift bioreactor culture. By the addition of 30 mL fresh liquid medium containing doulble strength MS salts, 250 g/L sucrose and 5 g/L activated charcoal after 8 weeks in the shoot cluster culture on MS medium with 5.0 mg/L BA and 0.5 mg/L IAA, the number of bulblets was increased in light condition, but the growth of bulblets was not affected by light. Bulblet production was possible with the bulblet product at 53 to 68 mg in fresh weight by liquid medium addition after the proliferation of shoot cluster.

• Journal of the Korean Magnetics Society
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• v.5 no.3
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• pp.179-184
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• 1995

The ac magnetic susceptibility of {100} iron whiskers as a function of currents is studied with and without external field. The ac susceptibility depends on the magnitude and the direction of the applied dc current when a small external field is applied along the magnetization of the central domain of the whisker. Variation of the central domain size accounts for the current-dependent response. The measured magnetic responses are explained, using a micromagnetic calculation based on a simple model, as a function of applied currents over a wide range except critical values.

• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.165-169
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• 1996

The relationship between grain size and number of magnetic domain walls for tertiary recrystallized ultra thin 3 % Si-Fe strips was investigated. It was found that the strips with different grain size can be produced by controlling the inserting speed of sample in annealing furnace. Though grain size of the stirip became smaller than 1mm, $B_{8}$ of high value above 1.95T was obtained. But $H_{c}$ increased with decaying the grain size. The magnetic domains and losses of the ultra thin grain oriented silicon steel with smaller grian size were observed. The eddy current losses of the strips were decreased with decreasing the grain size in high frequency range because strips with smaller grain have narrower magnetic domain wall spacings. But Hysteresis losses of the strips with smaller grain have high value in low frequency range. Therefore the iron loss of ultra thin grain oriented silicon steel could be controlled by the grain size. It was clarified that the minumum tatal loses depended on the exciting frequency and grain size.

• Korean Journal of Plant Resources
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• v.19 no.1
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• pp.50-53
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• 2006

Nerine was originated from South Africa and around 30 kinds of species are distributed in worldwide. In present study we have characterized the condition of storage and growing conditions on the bulb propagation of Nerine by the tissue culture. Result indicated that the percentage of decrement, decay and sprouting of bulblets in the tissue culture was high at the higher temperature compare to lower temperature. The optimum conditions for storage and time were 12 weeks at $15^{\circ}C$ which were having 86.4% sprouting rate. The sprouting rate at different temperature and acclimation time, using bulblets in the tissue culture, were optimum at early June when temperature is relatively higher($22^{\circ}C$) that facilitate to breaking the dormancy. Growth characteristics and capacity of photosynthesis of Nerine were better at red and blue mixed lightness.

• Journal of the Korean Magnetics Society
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• v.14 no.6
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• pp.224-227
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• 2004

We have studied local magnetization reversal by laser annealing in exchange biased NiFe/FeMn bilayer. Local magnetization reversal was performed by using the DPSS laser under external magnetic field of 600G. When the laser illuminated the patterned film with the power of above 300 mW during 15 min, a magnetoresistance (MR) curve with symmetric peaks at the opposite field was obtained due to the local reversal of exchange biasing. The direction of exchange anisotropy in the locally reversed region can be restored by local laser annealing under alternating magnetic field, even if its MR peak was reduced by the damage and interdiffusion. The magnetic domain structure of the locally reversed region was measured by MFM. The new domains were generated by laser annealing near the exposed area.

• Horticultural Science & Technology
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• v.16 no.2
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• pp.242-243
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• 1998

This research was conducted to find the most effective and economical artificial propagation method of Lycoris squamigera among chipping, half-chipping, twin-scaling, coring, scooping and notching, in order to investigate the number of bulblets obtained from one bulb and the number of bulbs treated by a man in a day for artificial propagation. We got 42.2 bulblets from one bulb by twin-scaling, 23.2 bulblets by half-chipping, 18.2 bulblets by chipping, 14.3 bulblets by notching, 1 bulblet by coring and also 1 bulblet by scooping. Although we got the most bulblets by twin-scaling, it took the most time to treat the bulbs for artificial propagation (200 bulbs per day) and the bulblets formed were very small. But 400 bulbs were treated in a day by chipping and the bulblets formed were comparatively large. In addition, machines could be used for chipping, so chipping was considered to be the most effective and economical artificial propagation method.

• Electrical & Electronic Materials
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• v.3 no.1
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• pp.36-44
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• 1990

본 연구는 34wt%(5Ce-Didymium)-Fe-1wt%B 합금의 분말입도, 성형압력 및 소결온도 에 따른 자기적 성질에 관하여 연구하였다. 그리고 각각의 자기적 성질에 영향을 주는 인자를 알아내기 위하여 밀도측정, 미세조직 및 자구를 관찰하였다. 미세조직은 금속현미경을 이용하여 관찰하였으며 자구는 Bitter법으로 관찰하였다. 결과는 아래와 같다. (1)분말의 입도와 결정립 크기가 작아질수록 경질자기 특성은 증가하였으며 소결온도가 증가할수록 경질자기 특성도 증가하였다. 그러자 압력은 1000kg/$cm^{2}$일때 가장 좋은 경질자기 특성이 얻어졌다. (2)결정립이 클수록 자구의 구조는 복잡했으며 미세한 결정립일수록 큰 결정립에 비해 큰 보자력을 갖는다. 포화된 후에는 거의 모든 결정립이 단자구였으며 열적으로 탈자되었을 경우에는 모두가 multi-domain였다. (3)가장 우수한 경질자기 특성은 3-5.mu.m의 분말을 사용하여 1080.deg.C에서 소결한 후 590.deg.C에서 열처리한 시편에서 얻어졌으며 (BH)$_{max}$는 214.6kJ.m$_{-3}$이다.

• Journal of the Korean Magnetics Society
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• v.20 no.2
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• pp.68-74
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• 2010

Nuclear Magnetic Resonance (NMR) is a very useful tool for magnet study because it provides information on local spin environment. The valence of magnetic ions, spin canting angle, orbital state can be measured by NMR and the information on the position of the ions and the change of domains and domain walls can be obtained. The principle of operation is discussed with corresponding application examples.

• Journal of the Korean Magnetics Society
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• v.20 no.1
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• pp.1-7
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• 2010

We investigate the spin dynamics of the magnetic domain wall using the magnetic noise in the magnetic nanowire structure by employing micromagnetic simulations. Magnetic noise due to the thermal fluctuations in ferromagnetic materials is related to magnetic susceptibility and resonance frequency, which are important physical quantities in the study of the spin dynamics. In this study, we present the magnetic noise of the single domain without magnetic domain wall, and with the magnetic domain wall between two magnetic domains in ferromagnetic nanowires. It is confirmed that the Kittel equation with simple ellipsoid model with demagnetizing factor well describe the resonance frequency due to magnetic noise of the single domain. Besides, we find that there is a distinguishable additional resonance frequency, when a magnetic domain wall exists. It is verified that the additional resonance frequency is originated from the magnetic domain wall, and it is lower than one of the single domain. It implies that the spins inside the domain wall have a different effective field.