• Korean Journal of Materials Research
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• v.5 no.2
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• pp.197-202
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• 1995

The surface morphology and grain growth of amophous silicon (a-Si) films deposited by low pressure chemical vapor deposition (LPCVD) have been investigated as a function of deposition and in sltu annealing condition. The film deposited at the amorphous to polycrystalline transition temperature has an extra-rough, rugged surface with (311) t.exture. At the same deposition temperature, the grain structure tends to shirr. from the polycrystalline to the amorphous phase with increasing the film thickness. It is found that nucleation of a-Si during in situ annealing at the transition temperature without breaking the vacuum starts to occur from surface Si atom migration in contrast to a heterogeneous nucleation during film deposition.

• Electrical & Electronic Materials
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• v.5 no.2
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• pp.189-197
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• 1992

고온 초전도체 $Y_{1}$Ba$_{2}$Cu$_{3}$O$_{7-y}$에서 Y를 Sm으로 치환시켰을 때의 자기 임계 전류밀도와 저항은 각각 30K와 80-160K의 온도에서 측정되었다. 그리고 X-선 회절분석 및 적외선 투과율 측정은 실온에서 수행되었으며 시료들은 고상 반응법에 의해서 제조되었다. 93K근에의 값을 갖는 초전도 전이온도 T$_{c}$는 치환양에 따라 거의 변하지 않았다. 시료들의 결정구조는 X-선 회절무늬로 부터 모두 직방정계임이 판명되었다. 적외선 투과율 측정에서 날카로운 peak들은 472.78-618.53$cm^{-1}$ /범위에 있었다. 이것은 특이할 정도로의 low-lying plasmalike edge와 낮은 에너지의 전자적인 여기가 존재함을 나타내는 것이다. 자기 임계 전류밀도는 $10^{3}$~$10^{4}$A/$cm^{2}$범위에 있었다. 전이온도 T$_{c}$에 상자성 불순물의 영향이 거의 없는 것으로 보아 123phase에서 Y가 고온 초전도성에 주된 역할을 하지 않음을 알수 있었다.다.

• Proceedings of the Korean Magnestics Society Conference
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• 2010.06a
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• pp.135-135
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• 2010

• Journal of the Korean Magnetics Society
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• v.15 no.3
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• pp.167-171
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• 2005

Detailed aspects of the charge disproportionation (CD) transition for a polycrystalline $La_{1/3}Sr_{2/3}FeO_{2.96}$ were studied with the X-ray diffraction, $M\ddot{o}ssbauer$ spectroscopy, and SQUID magnetometer. The crystal structure was found to be rhombohedral with a space group R/3c. The lattice parameters were $a_R=5.4874\;\AA,\;and\;a_R=60.07^{\circ}$, respectively. $M\ddot{o}ssbauer$ spectra were taken within a wide range of temperature from 4.2 K up to room temperature. In the low temperature region, the spectra were comprised of two superimposed sextets which originated from $Fe^{3+}\;and\;Fe^{5+}$, respectively. This was the antiferromagnetic mixed valence state produced by the charges disproportionated into two different species. In the high temperature region, however, only a singlet from $Fe^{3.6+}$ was observed, indicating that it was a paramagnetic averaged valence state. The CD transition occurred in the temperature range from 175 K to 200 K, in which the two phases coexisted. The origin for the CD transition was explained by the thermally generated fast hopping of electrons. Hysteresis loop showed that there existed a strong antiferromagnetic interaction among magnetic ions. As the temperature increased thru the CD transition temperature, it was very likely that the interaction between $Fe^{3+}\;and\;Fe^{5+}$ was replaced by a more stronger one.

• Polymer(Korea)
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• v.33 no.2
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• pp.144-152
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• 2009

The thermal and optical properties of poly {1-(cholesteryloxycarbonylalkanoyloxy) ethylene}s (PCALEn, n=2$\sim$8,10, the number of methylene units in the spacer) were investigated. All of the homologues formed monotropic cholesteric phases with left-handed helical structures. PCALEn with n=2 or 10, in constrast with PCALEn with $3{\leq}n{\leq}8$, did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the polyethylene chain. The glass transition temperatures decreased with increasing n. The isotropic-cholesteric phase transition temperatures decreased with increasing n up to 7 and showed an odd-even effect. However it became almost constant when n is more than 7. This behavior is rationalized in terms of the change in the average shape of the side chain on varing the parity of the spacer. This rationalization also accounts for the observed variation of the entropy gain for the clearing transition. The thermal stability and degree of order in the mesophase and the temperature dependence of the optical pitch observed for PCALEn were significantly different from those reported for cellulose tri(cholesteryloxycarbonyl)alkanoates. The results were discussed in terms of the differences in the chemical structure and flexibility of main chain and the number of the mesogenic units per repeating unit.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.12-13
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• 2002

원자력 산업용 중성자 흡수체 제조에 사용되는 Gd 금속증기 발생기에 설치할 목적으로 394.55 nm 전이선의 전이확률을 측정한 결과를 보고한다. 증기 증발률을 장시간 동안 일정한 양으로 유지하기 위해서는 증기밀도가 실시간으로 측정되어야 하고, 이를 위해 반도체 레이저를 광원으로 사용하는 원자흡수 분광계를 제작하고 있다. 전자빔 가열로 발생된 원자빔은 가속된 전자빔과의 충돌에 의하여 가열표면의 온도를 알면 설명할 수 있는 일반적인 원자빔 성질과는 매우 다른 특성을 가지고 있다. (중략)

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.149-149
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• 2011

아르곤 기체의 방사세기 또는 그 세기 비는 플라즈마 공정 진단에서 일반적으로 사용된다. 본 실험에서는 100 mTorr 압력 조건하의 유도결합 플라즈마(13.56 MHz)에서 E-H 모드 전이 영역, rf 바이어스(12.5 MHz) 전력 인가 및 N2 혼합 시 단순화한 충돌-방사 모델에 기초한 광방사 세기비 방법을 적용하여 플라즈마 변수를 진단하였다. 개발 프로그램 기반의 분광기를 사용하여 아르곤 기체의 특정 파장(750.4, 751.5 그리고 811.5 nm)들을 관측하였고, 동일한 조건하에서 정전 탐침법으을 이용하여 전자 에너지 분포함수의 변화도 측정 하였다. 맥스웰 전자 에너지 분포를 가정하는 일반적인 경우와 비교하여 볼 때 실제적인 전자 에너지 분포함수의 측정은 전자의 가열 메커니즘에 대한 상세한 정보를 제공함과 동시에 플라즈마 재흡수에 대한 보정을 가능하게 해준다. 광방사 세기비법에 의해 측정된 결과에 의하면, 750.4 nm/751.5 nm는 높은 에너지(>13.08 eV)의 전자들의 유효 전자온도에 대한 정보를 나타내는 반면 811.5 nm/750.4 nm는 아르곤 준안정 준위 밀도(1s5)에 대한 정보를 제공하게 된다. 수행된 실험 조건하에서, 측정된 준안정 준위 밀도는 E-H 모드 전이 영역에서 최대값을 나타내었고 바이어스 전압 및 N2 기체 혼합 비율이 증가함에 따라 감소하는 결과를 얻었다. 유효 전자온도의 경우 광방사 세기비법과 정전 탐침법 모두 같은 결과를 보여 주었는데, E-H 모드 전이 영역에서는 전자온도는 거의 일정하였고 바이어스 전압 및 N2 기체 혼합 비율이 증가함에 따라 전자온도는 증가하였다. 이러한 실험 결과는 방전 모드 전이, 바이어스 인가 그리고 혼합 기체 사용하는 공정 플라즈마를 이해하는데 있어 이들 변수의 진단이 중요한 요소임을 보여준다.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.5
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• pp.429-444
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• 1991

Cold stress influence plant growth through a wide range of growth characters. Adverse effects of low temperature to plant growth come from results of colligative and complex physiological responses to cold stress. To evaluate more exactly cold tolerance of crop plant, it is needed to observe physiological changes induced by cold stress and to analyze relationships between intraspecific variations in physiological factors related to cold tolerance and the extent of cold tolerance in the field. Therefore, the composition and unsaturation ratio of fatty acids in phospholipid, a constituent of membrane, the transition-temperature in respiratory activity of mitochodria, the chlorophyll fluorescence as a factor related to photosynthesis were investigated in rice plant and data on these factors were compared with the degree of cold tolerance obtained in the field experiment. Also, effects of hardening and Mn++ treatment were evaluated as a method to reduce chilling injuries. The unsaturation ratio of fatty acids, whether rice plants were grown in a natural condition or under the chilling stress, was higher in the cold- tolerant varieties and was significantly correlated with the degree of cold tolerance (1-9) observed in the field experiment. And it was also increased by chilling treatment or hardening treatment, due to a reduction in palmitic acid content and an increase in linolenic acid content. The transition-temperature of respiratory activity of mitochodria isolated from etiolated rice seedlings ($25^{\circ}C$, two week-grown in the dark), was correlated with the degree of cold tolerance in the field, cold -tolerant varieties showing a lower transition-temperature. It was not influenced by growth stages. The intensity of chlorophyll fluorescence was highly correlated with the degree of cold tolerance, cold-tolerant varieties having a higher fluorescence intensity. By foliar application of Mn, the transition-temperature of respiratory activity was lowered as much as 0-2$^{\circ}C$ in all tested varieties. Soil application of Mn induced more significant effect in cold-susceptible varieties with a possibility of reducing chilling injuries. On the whole, there were high correlationships among the degree of cold tolerance, the unsaturation ratio of fatty acids in phospholipid, the transition- temperature of respiratory activity and chlorophyll fluorescence except for a few varieties. The transition- temperature of respiratory activity appeared to be negatively correlated with the unsaturation ratio of fatty acids. and the chlorophyll fluorescence to be positively correlated with the unsaturation ratio. This implies that these physical and physiological factors were very closely related to cold tolerance and can be used as an effective index of the evaluation of cold tolerance of crop plant. But other factors as well as three factors discussed above are needed to be considered colligatively and altogether with a systematic analysis for the more exact evaluation of cold tolerance. in rice cultivars. in rice cultivars.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.195-195
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• 2003

PDP, FED 등의 디스플레이와 각종 IC 칩부품에 적용 가능한 저융점 유리 프릿 중에서 환경규제가 이루어지고 있는 납성분이 포함되어 있지 않은, Bi계 유리 프릿의 열적 거동 연구를 행하였다. 열처리 온도에 따른 열거동에 따라 프릿의 소성온도 및 미세구조가 결정되므로, 열처리 온도에 따른 유리 프릿의 젖음각을 측정하였고, DTA와 TMA를 통해 유리전이온도, 연화점, 열팽창계수 변화 경향성을 관찰하였다. 본 연구에서 제조된 유리는 조성에 따라 전이온도가 390-50$0^{\circ}C$, 연화점이 400-55$0^{\circ}C$, 열팽창계수가 65-120$\times$10-7/$^{\circ}C$ 범위를 나타내었으며, 고온현미경 측정 결과 Pb-계 유리와 비교시 유사한 열거동을 나타내었다.

• Fire Science and Engineering
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• v.24 no.6
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• pp.1-6
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• 2010

A smoldering ground fire can be a probable cause of reignition of surface fire when transmitted from Fermentation layer to Humus layer with temperature higher than that of ignition. Purpose of this paper is to identify experimental methodology on the potential risk of a smoldering ground fire, which is similar to the real surface fuel bed, and its combustion characteristics. The fuel model designed in this study is composed of 3 layers such as Litter layer, Fermentation layer and Humus layer and 8 Thermocouples are set through 3 layer at each boundary and in between to detect the temperature change and duration of smoldering and propagation velocity. As a result, it was observed that ignition conditions in the boundary between L layer and F layer determined transmission and non-transmisstion to F-H layer. In addition, range of critical humidity at which a smoldering ground fire was transmitted in a material layer was 33~44% and when temperature exceeds $350^{\circ}C$, likelihood of transmission of a smoldering ground fire was high. In the research, the experimental model for multi-layer smoldering ground fire is suggested and information about propagation of smoldering fire, possibility of reignition according to moisture content, propagation velocity and temperature change are obtained, Also, the built-up methods were established to help analyze basic characteristics of smoldering ground fire.