• 말소리와 음성과학
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• 제6권3호
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• pp.41-48
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• 2014

This study investigated the differences between emotional parameters BDI, VHI, STAI-X-I and STAI-X-II according to the menstrual cycles of the female and the relation between changes of the depression index and voice characteristics (jitter, shimmer, CPP, HNR, $pF0{\cdot}F1{\cdot}F2{\cdot}F3$, sF0, sF4, sB1, $H1_{c/u}$, $A1_u$, $A3_c$, $H1A3_{c/u}$, $H1A1_u$). Twenty three females ($30{\pm}4.4$ years old) living in Seoul and Gyeonggi Province were participated in this study to answer the questionnaires and record their voice. The participants prolonged /a/ vowel for 5 seconds in a natural condition for their voice recording. Voice data were analyzed using the Matlab and Praat program. A t-test and a correlation analysis were conducted by using SPSS for the statistical analysis. The results are as follows. First, the BDI is significantly higher in group I (lurear phase contrast the menstrual period) and group II (follicular phase against the menstrual period) than group III (luteal phase for follicular phase) (p<.05). Second, shimmer, CPP, pF0 showed a statistically high correlation regarding the BDI in group I (lurear phase contrast the menstrual period). Voice parameters may be useful as supplement in evaluating the emotional change in the phase of menstrual cycle.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.133-136
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• 2004

Since the residential load is an AC load and the output of solar cell is a DC power, the photovoltaic system needs the DC/AC converter to utilize solar cell. In case of driving to interact with utility line, in order to operate at unity power factor, converter must provide the sinusoidal wave current and voltage with same phase of utility line. Since output of solar cell is greatly fluctuated by insolation, it is necessary that the operation of solar cell output in the range of the vicinity of maximum power point. In this paper, DC/AC converter is three phase PWM converter with smoothing reactor. And then, feedforward control used to obtain a superior characteristic for current control and digital PLL circuit used to detect the phase of utility line.

• Tribology and Lubricants
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• 제13권4호
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• pp.60-65
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• 1997

The tungsten disulfide $(WS_2)$ solid lubricant was synthesized by two different reaction processes, i.e., the reaction between $CS_2$ gas phase and solid $WO_3$powder, and the vapour phase transport method of tungsten and sulfur in a high vacuum. The chemical and physical characteristics of synthesized $WS_2$powder were analyzed in terms of the average particle size, morphology, crystalline phase etc. in comparison with those of commercial $WS_2$powder. The solid $WO_3$ powder with the average size of 0.2 ${\mu}{\textrm}{m}$ was reacted with $CS_2$gas flowed with$N_2$or 96%$N_2{\times}4%H_2$forming gas for 36 h and 24 h at 90$0^{\circ}C$ respectively. $WS_2$ crystalline phase was then formed through the intermediate phase of .$W_{20}O_{58}$ In the case of vapour phase transport method, the 3.5 wt% iodine was added as a vapour transport reagent into the composition of tungsten and sulfur powders maintaining a constant molar ratio of W:S=1:2.2. The mixture was then heat treated at 85$0^{\circ}C$ for 2 weeks in vacuum. The reaction product obtained showed the average size of 12 ${\mu}{\textrm}{m}$ and the hexagonal plate shape of typical solid lubricant with 2H-$WS_2$crystalline phase.

• 열처리공학회지
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• 제8권1호
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• pp.65-74
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• 1995

This research was performed to investigate the effect of ageing on grain refinement of 82wt%Cu-13.5wt%Al-4.5wt%Ni-0.1wt% misch metal alloy with ageing temperature and time. The results obtained in this study are as follows; The variation of transformation temperature with ageing temperature had very influence on ageing time at $300^{\circ}C$. But it had not influence on ageing time at $100^{\circ}C$. The variation of transformation temperature after second reversed transformation cycle was not occured in martensitic phase ageing, but $M_s$ point was appeared equally with third reversed transformation cycle in parent phase ageing. The variation of $M_s$ point was not nearly with ageing time at $100^{\circ}C$ ageing temperature. But it was decreasing with ageing time at $300^{\circ}C$ ageing temperature and $A_s$ point was increasing with ageing time. Structure of parent phase ageing was being M18R martensitic and N2H martensitic phase. It was found that ${\alpha}$ and ${\gamma}_2$ phase were created by ageing of long time at $300^{\circ}C$ ageing temperature.

• 대한약학회:학술대회논문집
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• 대한약학회 2000년도 춘계총회 및 학술대회
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• pp.124.1-124.1
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• 2000

• 한국결정학회지
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• 제13권1호
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• pp.36-40
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• 2002

중성자회절법을 이용하여 여러 다른 조건으로 열처리한 (Fe/sub 0.61/Ni/sub 0.39/)₃V 합금 분말시료의 장거리 규칙도를 측정하여 규칙-불규칙 상전이의 정도를 조사하였다. 조사 결과 680℃-94 h 열처리 시료는 완전 불규칙 상태로 상전이가 발생하지 않았으며 면심입방구조를 보였다. T < 640℃의 조건에서 열처리한 시료들은 모두 장거리 규칙도 0 < S < 1으로 면심입방구조의 일부가 단순입방구조로 상전이 함을 보여주었다. 또한 Cowley의 S-T/T/sub c/ 관계식으로부터 465℃-144 h 으로 열처리한 시료가 열평형상태에 가장 근접하였음을 확인하였다

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2021년도 봄 학술논문 발표대회
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• pp.144-145
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• 2021

Calcium silicate hydrate(C-S-H) is the principal binding phase that controls the strength and thermal stability of concrete. However, the effects of high temperature on the lattice structure and interatomic structure of C-S-H remains poorly understood due to its nanocrystallinity. This study aims to elucidate the change in interatomic distance of synthetic C-S-H with different Ca/Si molar ratios after exposure to high temperature via high energy X-ray scattering experiment which is a powerful analytical tool for amorphous materials.

• 소성∙가공
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• 제16권6호
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• pp.473-478
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• 2007

In this study, a deformation mechanism map of metallic nanocrystalline materials(NCMs) using the phase mixture model is proposed. It is based on recent modeling that appears to provide a conclusive description of the phenomenology and the mechanisms underlying the mechanical properties of NCMs. The proposed models adopted the concept of a 'phase mixture' in which the grain interior and the grain boundaries are treated as separate phases. The volume fraction of this grain boundary 'phase' may be quite appreciable in a NCM. Based on the theoretical model that provides an adequate description of the grain size dependence of plasticity covering all grain size range from coarse down to the nanoscale, the tensile deformation response of NCMs, especially focusing on the deformation mechanisms was investigated. The deformation mechanism map is newly proposed with axes of strain rate, grain size and temperature.

• 센서학회지
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• 제27권4호
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• pp.249-253
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• 2018

Infrared transparent ZnS ceramics were synthesized through hydrothermal synthesis ($180^{\circ}C$, 70 h) and sintered using a hot press process at $750^{\circ}C-1000^{\circ}C$. We carried out x-ray diffraction, scanning electron microscopy, and Fourier transform-infrared spectroscopy to confirm the optical properties of the ZnS ceramics after sintering at various temperatures. The phase of ZnS nanopowders was a single phase (cubic) without the hexagonal phase. However, as sintering temperature increased, the formation and increment of hexagonal structures was confirmed. The ZnS ceramic sintered at a temperature of $750^{\circ}C$ showed poor transmittance because it was not completely sintered and because of the pore effect. The ZnS ceramic with the highest transmittance (approximately 69%) was sintered at $800^{\circ}C$. As sintering temperature increased, transmittance gradually decreased owing to the increase in the formation of the hexagonal phase.

• 태양에너지
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• 제13권2_3호
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• pp.65-78
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• 1993

자연적인 기후조건하에서 농산물을 생산하는 재래식 농업으로부터 계절을 초월하는 시설 농업이 파생 발전함에 따라 태양에너지이외의 화석에너지 사용이 급증하고 있으며, 이로 인한 농산물 가격상승과 품질저 하는 물론이고, 농촌환경을 오염시키고 있다. 이와 같은 문제를 근원적으로 해결하기 위해서는 태양에너지 농업이용을 극대화 하여야 하며, 이를 실현하기 위해서는 동적이며, 순간적 공급의 특성을 갖는 태양에너지를 정적이며, 조절이용이 가능한 에너지로 전환하여야 한다. 이런 필요성에 부응하여 본 연구에서는 태양에너지를 저장할 수 있는 상변화 잠열재를 선택하였으며, 축열특성을 분석하므로서 다음과 같은 결과를 얻을 수 있었다. 유기 잠열재, $C_{28}H_{58}$은 안정된 물성을 가지고 있기 때문에 400 사이클의 상변화 후에도 열특성 변화가 없었으나, 무기 잠열재($CH_3COONa{\cdot}3H_2O,\;Na_2SO_4{\cdot}10H_2O$)는 불안정한 물성을 가지고 있기 때문에 조핵제와 농화제를 사용하여 $400{\sim}600$ 사이클의 상변화 후에 나타나는 열특성 변화를 최소화 하였다. 잠열량이 최대가 되는 결정핵의 임계반경을 수식으로 정리하므로서 잠열량 감소현상을 억제할 수 있는 방법을 찾는데 도움을 줄 수 있었다. 유기 잠열재, $C_{28}H_{58}$의 상변화 온도는 $62^{\circ}C$였으며, 잠열량은 $50{\sim}52$ kcal/kg이었고, 고상비열, $C_{ps}$는 $0.572{\sim}0.750kcal/kg^{\circ}C$였으며, 액상비열, $C_{pL}$은 $0.540{\sim}0.690kcal/kg^{\circ}C$였다. 무기 잠열재, $CH_3COONa{\cdot}3H_2O$의 상변화 온도는 $61{\sim}62^{\circ}C$였으며, 잠열량은 $64.9{\sim}65.8$ kcal/kg이었고, 고상 비열, $C_{ps}$는 $0.510{\sim}0.520kcal/kg^{\circ}C$였으며, 액상비열, $C_{pL}$은 $0.83kcal/kg^{\circ}C$였다. 무기 잠열재, $Na_2SO_4{\cdot}10H_2O$는 물성안정제를 가한 상태의 시약수준에서는 상변화 온도가 $29.72^{\circ}C$였고, 잠열량은 53.0 kcal/kg이었으며, 고상비열, Cps는 $0.742kcal/kg^{\circ}C$이었고, 액상비열, $C_{pL}$은 $1.002kcal/kg^{\circ}C$였다. 공업용 수준에서는 상변화 온도가 시약수준의 경우보다 약간 높은 $30{\sim}30.9^{\circ}C$였으며, 비열은 고상에서 $0.50{\sim}0.7kcal/kg^{\circ}C$였고, 액상에서 $0.78{\sim}0.89kcal/kg^{\circ}C$였다. SSD($Na_2SO_4{\cdot}10H_2O$)에 urea를 첨가함으로서 상변화 온도와 잠열량이 변하였으며, urea 함량을 $0{\sim}7.5wt%$로 변화시킴에 따라 상변화 온도는 $29.72^{\circ}C$에서 $25.18^{\circ}C$로 낮아졌으며, 잠열량은 53.0 kcal/kg에서 38.5 kcal/kg으로 감소하였다. Greenhouse 보온용으로 urea를 21.85% 첨가하고, 상변화를 $0{\sim}600$ 사이클까지 반복한 경우 상변화 온도는 $16.7^{\circ}C$에서 $16.0^{\circ}C$로 낮아졌고, S.V를 첨가하지 않은 경우 잠열량은 46.22 kcal/kg에서 36.30 kcal/kg으로 감소하였으나, 비열은 큰 변화가 없었다. 상변화 사이클의 증가에 의한 열특성의 감쇠현상을 줄이기 위하여 S.V를 $0{\sim}1.5wt%$ 첨가한 결과 S.V 0.5wt% 이하에서는 약간의 효과가 있었으나, 그 이상에서는 효과적인 증후가 없었다.