• Applied Biological Chemistry
• /
• v.33 no.2
• /
• pp.129-132
• /
• 1990

The role of hydrogen peroxide which is accumulated in plants under low temperature has been studied with respect to the regulation of physiological IAA level. At 10 mM of $H_2O_2$, accelerating effects of IAA on the elongation of Avena coleoptiles and the root Initiation of pea cuttings have been greatly inhibited. These inhibitions were reversed by introduction of catalase. The reaction of free IAA with Salkowski reagent was inhibited in the presence of $H_2O_2$, but that of IAA-glutamic acid was not, suggesting the inactivation of free IAA by $H_2O_2$. The data support that increase in the content of hydrogen peroxide under low temperature partially down-regulates the available IAA through inactivation of IAA.

• Textile Coloration and Finishing
• /
• v.11 no.4
• /
• pp.1-7
• /
• 1999

Urethane-acrylate propelymers for secondary coating of optical fiber and high - performance material were prepared from the 4,4'-diphenylmethane diisocyanate(MDI), poly(tetramethylene oxide)glycol(PTMG, Mw 650 or 1000), 1,6-hexanediol(HD), 2-hydroxyethyl acrylate(HEA), and dibutyltin dilaurate as a catalyst. UV-Curable polyurethane acrylates were formulated from the urethane-acrylate prepolymers, three types of reactive diluents(DTs) having mono-, di-, and trifunctional-phenoxyethyl acrylate(PEA), hexanediol diacrylate(HDDA), and trimethylolpropane triacrylate(TMPTA), and 1-hydtoxycyclohexyl phenyl ketone(Irgacure 184) as a photoinitiator. The UV-cured films of polyurethane acrylates were obtained by curing using a medium-pressure mercury lamp(U W/cm, $\lambda_{max}=365\;nm)$. In this work, the effects of molecular weights of polyol and diol with low molecular weight into polymer chain on mechanical and dynamic mechanical properties of UV-cured polyurethane acrylates were studied. The structure and properties of the films obtained from the UV photopolymerization of urethane-acrylate prepolymer were investigated by FT-IR spectroscopy, dynamic mechanical measurement, tensile testing, and X-ray diffractometry.

• Textile Coloration and Finishing
• /
• v.3 no.1
• /
• pp.17-24
• /
• 1991

Polyesteramide(PEA) has been synthesized with different molar ratio of 6-aminocaproic acid(ACA) and oligo butylene terephthalate(OBT) prepared from Dimethyl terephthalate(DMT) and 1, 4-butanediol(BD) by the melt polymerization. Oligomer and polymer molecular structure were characterized by IR spectra, H'-NMR spectra. Also the thermal properties were examined by thermogravimetric analysis(TGA) and differential scanning calorimetry(DSC). DSC and TGA results exhibited that the$ T_m$ s were detectable in the vicinity of $170-220^{\circ}C$ and the Ta's were detectable in the vicinity of $380-390^{\circ}C$ . X-ray diffraction analysis results show that the synthesized polyesteramide has high degree of crystallinity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.05c
• /
• pp.96-100
• /
• 2001

We have measured the space charge distribution and PD patterns simultaneously in XLPE under AC voltages by modified PEA method in order to investigate the effect of space charge on PD patterns in XLPE with air-gap. From the experimental results, we found that the dynamic space charge accumulated on the surface of XLPE due to the PD dominantly affects the PD pattern in the dielectric-barrier structure and governs the voltage across the air-gap. Moreover, the space charge formed by applying DC voltage still remained after applying AC voltage, which means that the space charge formed during DC strength test is likely to be fatal to the long-time AC insulating characteristics of HV equipments. On the other hand, the PD patterns was much influenced by the pre-formed space charge by DC application. Therefore, it is possible to detect the effects of space charge by monitoring the infinitesimal change of PD patterns before and after DC strength.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1612-1614
• /
• 1997

고분자 절연재료의 결함에 의하여 발생하는 부분방전은 고분자 재료의 화학적, 전기적 열화를 가져오며 때로는 전기 트리로 성장하여 재료의 절연파괴에 이르게 하기도 한다. 따라서 부분 방전 현상의 메카니즘 뿐만 아니라 측정법에 대한 많은 연구들이 있었으나 부분방전 열화가 고분자 재료에 미치는 열화과정에 대하여서는 명확한 메카니즘이 보고되지 않았다. 본 논문에서는 부분방전에 의한 고분자 절연재료 내의 공간전하 축적 현상에 대하여 연구하였다. 고분자 재료로는 현재 전력용 케이블에 주로 사용되고 있는 가교 폴리에틸렌(XLPE)를 사용하였으며, 1kHz의 주파수로6kV, 8kV, 10kv 및 11kV로 수시간 부분방전을 발생시킨 후 펄스정전응력법(PEA)으로 공간전하를 측정하였다. 실험결과 부분방전에 의하여 고분자 재료 내에 이종공간전하의 주입이 확인되었으며 따라서 부분방전에 의하여 고분자 재료가 열화되며 이러한 열화에 의한 전자의 방출율의 변화와 같은 고분자 표면의 상태 변화에 의하여 부분방전의 패턴에 지배적인 영향을 미친다. 이러한 공간전하의 축적에 의하여 부분방전 현상에 미치는 영향은 추후 보고할 예정이다.

• Food Science and Preservation
• /
• v.1 no.2
• /
• pp.117-124
• /
• 1994

To investigate characterization of the ${\alpha}$-amylase inhibitors from cereals and legumes produced in Korea, inhibitory activities against ${\alpha}$-amylase with the inhibitor from barley(Hordeum vulgare), wheat(Triticum aestivun), black bean(Glycine max), bean(Cajanus cajon) and pea(Pisum sativum) were measured. Among the samples tested, inhibitors from naked barley and black bean(sabong) which showed the highest inhibitor activities of cereals and legumes, respectively, were characterized according to treatment condition. The results obtained were summarized as follows. During the germination of naked barley and black bean, ${\alpha}$-amylase activities were gradually increased but inhibitory activities against ${\alpha}$-amylases were decreased. Both activities were gradually decreased when naked barley and black bean were stored. More than 50% of activities of the inhibitors from naked barley and black bean were remained at 100$^{\circ}C$ for 15 min and 20 min, respectively, indicating that the inhibitor from black bean was more stable to heat than that of barley.

• Fisheries and Aquatic Sciences
• /
• v.1 no.2
• /
• pp.250-254
• /
• 1998

Harmful micro algae isolated from Korean coastal waters, were tested with FITC-conjugated lectins and observed by epifluorescent microscopy to distinguish each other. Strain-specific sugar composition at the cell surface was suggested by the affinity of lectins to different microalgae. The micro algae Cochlodinium polykrikoides (CP-1) and Gymnodinium $A_3\;(GA_{3-1}\;1)$, are morphologically similar, but exhibited different binding activity with the lectins ECA, HPA and WGA. In Peridiniales, the micro alga Alexandrium tamarense (AT) bound HPA and WGA, but Scrippsiella trochoidea (ST-1) did not bind those lectins. Three species of Prorocentrum also exhibited different binding specificity with HPA, PHA and SBA. A non­toxic Korean isolate of Heterosigma akashiwo (HA-2) bound ConA, PEA and UEA. These results suggest that lectins are useful in discriminating morphologically similar species, as well as different species or strains within the same genus.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.06a
• /
• pp.377-378
• /
• 2008

Space charge formation in various glass materials under electron beam irradiation was investigated. Charging of spacecraft occurs in plasma and radiation environment. Especially, we focused on an accident caused by internal charging in a glass material that was used as the cover plate of solar panel array, and tried to measure the charge distribution in glass materials under electron beam irradiation by using a PEA (Pulsed Electro-Acoustic method) system. In the case of a quartz glass (pure $SiO_2$), no charge accumulation was observed either during or after the electron beam irradiation. On the contrary, positive charge accumulation was observed in glass samples containing metal-oxide components. It is found that the polarity of the observed charges depends on the contents of the impurities. To identify which impurity dominates the polarity of the accumulated charge, we measured charge distributions in several glass materials containing various metal-oxide components and calculated the trap energy depths from the charge decay characteristics of all glass samples. Furthermore, the dependence of the polarity of accumulated charges on the component of glass materials is discussed by using the models of energy bands.

• Advances in materials Research
• /
• v.1 no.1
• /
• pp.93-107
• /
• 2012

Epoxy resin is widely used in high voltage apparatus as insulation. Fillers are often added to epoxy resin to enhance its mechanical, thermal and chemical properties. The addition of fillers can deteriorate electrical performance. With the new development in nanotechnology, it has been widely anticipated that the combination of nanoparticles with traditional resin systems may create nanocomposite materials with enhanced electrical, thermal and mechanical properties. In the present paper we have carried out a comparative study on dielectric properties, space charge and dielectric breakdown behavior of epoxy resin/nanocomposites with nano-fillers of $SiO_2$ and $Al_2O_3$. The epoxy resin (LY556), commonly used in power apparatus was used to investigate the dielectric behavior of epoxy resin/nanocomposites with different filler concentrations. The epoxy resin/nanocomposite thin film samples were prepared and tests were carried out to measure their dielectric permittivity and tan delta value in a frequency range of 1 Hz - 1 MHz. The space charge behaviors were also observed by using the pulse electroacoustic (PEA) technique. In addition, traditional epoxy resin/microcomposites were also prepared and tested and the test results were compared with those obtained from epoxy resin/nanocomposites.

• Journal of Plant Biology
• /
• v.33 no.3
• /
• pp.203-210
• /
• 1990

Effects of blue and red light on photorespiration in the leaf disks of pea were studied. The rate of total 14CO2 fixation was more or less higher under red light than blue light irradiation of the same quantum (94.8 $\mu$Em-2.S-1/mV). The release of 14CO2 by photorespiration was more stimulated under blue than red light. Among the photorespiratory intermediates, 14C was more incorporated ito serine under blue light than red light. However, 14C was more incorporated into glycine under red light than blue light. The incorporation of 14C into glycolate was very low under both light qualities, but higher under red light than blue light. Among the enzymes related to photorespiration, only glycolate oxidase was activated and/or synthesized by blue light irradiation. Moreover, more 14C2 was released from glycoate-1-14C under blue light than red light irradiation, but 14C2 release from glyoxylate-1-14C and glycine-1-14C showed no difference by the either light qualities. These results suggest that blue light is more effective in the photorespiratory CO2 evolution than red light. The reason is considered that glycolate is easily metabolized under blue light due to the stimulation of the glycolate oxidase activity.