• 한국주조공학회지
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• 제12권2호
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• pp.131-138
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• 1992

The effects of B additions, alone or in combination with Si, on the microstructure, $DO_3{\rightleftharpoons}B2$ transition temperature($T_c$) and corrosion behavior of Fe-25at%Al alloys were investigated. The raw materials were arc-melted in vacuum and then subjected to the following heat treatments to maximize the $DO_3$ order : homogenized at $1000^{\circ}C$ for 48hrs, slowly cooled to $500^{\circ}C$, and held at that temperature for 24hours. Results showed that the B addition to Fe-25at%Al alloys does indeed refine the grain and change from intergranular to transgranular fracture mode at room temperature, indicating a strengthening of grain boundaries. The Fe-25at% Al-1at% B-3at% Si alloy showed the highest $T_c$(${\Delta}T_c=150^{\circ}C$) in this work. However, the effectiveness of Si in raising $T_c$ decreased with more than 5at% Si additions combined with B. Since the preferential corrosion occurs at the precipitates, the corrosion resistance decreased due to the increased amount of precipitates with alloying additions.

• 대한기계학회논문집A
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• 제32권6호
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• pp.481-487
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• 2008

Rapid mold heating has been recent issue to enable the injection molding of thin-walled parts or micro/nano structures. Induction heating is an efficient way to heat material by means of an electric current that is caused to flow through the material or its container by electromagnetic induction. It has various applications such as heat treatment, brazing, welding, melting, and mold heating. The present study covers an experimental investigation of induction heating in order to rapidly raise the mold temperature. It is observed that the mold surface temperature is raised up to $200^{\circ}C$ in 2 seconds. This induction heating is applied to injection molding of a flexspline for a plastic harmonic drive, which has difficulty in cavity filling because its minimum thickness is only 0.35 mm. The induction heating is then successfully implemented on this ultra-thin wall molding by raising the mold surface temperature around the glass-transition temperature of the molding material.

• 한국작물학회지
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• 제23권2호
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• pp.126-132
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• 1978

To examine the effects of P.E. film and rice straw mulching on fall grown potato(Shimabara cultivar) in the middle region of Korea, sprouted seed tuber pieces were transplanted with six kinds of mulching treatments on 24th July and harvested on 25th October. P.E. film mulching from transplanting resulted the perfect rot of transplanted seed pieces due to the excessive high soil temperature (noon soil temperature of about 4$0^{\circ}C$ continued until the middle of August). P.E. film mulching from 15th September to harvest increased the marketable tuber yields by 35% due to the raising of soil temperature by 1-3$^{\circ}C$ and maintaining of available soil moisture in dry season. Rice straw (whole or cut in 10cm length) mulching lowered the soil temperature in hot season and raised it in cool season and maintained available soil moisture in dry season. Therefore better emergence, growth and yields were induced. Effects of whole straw, whole growing season and thicker mulching were greater than cut straw, half growing season and thinner mulching. 6cm mulching of whole or cut straw during whole growing season resulted the increasing of marketable tuber yields by 56 or 48%.

• 대한화학회지
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• 제24권6호
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• pp.405-412
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• 1980

메시틸렌과 요오드 사이의 전하이동착물의 안정도에 미치는 압력과 온도의 영향을 n-헥산용액에서 자외선 분광광도법으로 연구하였다. 압력은 1에서 1600 bar, 온도는 25,40,$60^{\circ}C$ 사이에서 측정하였다. 착물의 평형상수는 압력 및 온도의 증가와 더불어 증가 및 감소하고 흡수계수는 대체로 증가함을 알았다. 이들 각 평형상수로부터 착물형성에 따른 부피, 엔탈피, 자유에너지 및 엔트로피 변화양을 구하였다. 또한 압력의 증가에 의한 red-shift, 온도의 증가에 의한 blue-shift 현상 및 압력변화에 의한 진동자 세기의 관계를 열역학적 함수와 관계지워 설명하였다.

• 대한화학회지
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• 제22권4호
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• pp.245-253
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• 1978

p-크실렌과 요오드 사이의 전하이동착물의 안정도에 미치는 압력과 온도의 영향을 n-헥산용액에서 자외선 분광광도법으로 연구하였다. 압력은 1에서 1,600bar, 온도는 25, 40, $60^{\circ}C$ 사이에서 측정하였다. 착물의 평형상수는 압력 및 온도의 증가와 더불어 증가 및 감소하고 흡수계수는 대체로 증가함을 알았다. 이들 각 평형상수로부터 착물형성에 따른 부피, 엔탈피, 자유에너지 및 엔트로피 변화 양을 구하였다. 또한 압력의 증가에 의한 red-shift, 온도의 증가에 의한 blue-shift현상 및 압력변화에 의한 진동자 세기와의 관계를 열역학적 함수와 관계지워 설명하였다.

• Macromolecular Research
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• 제17권8호
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• pp.575-579
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• 2009

Copolymerization of L-lactide and s-caprolactone initiated by tin (II) octoate (Sn(Oct)$_2$) was carried out in supercritical chlorodifluoromethane (R22) with varying reaction conditions (time and temperature) and amounts of monomer and catalyst, under a pressure of 250 bar. The optimum conditions were a reaction time of 10 h and a temperature of 130 $^{\circ}C$, which is similar to the temperature used in bulk copolymerization system. The conversion increased from 56% to 76% by increasing the reaction time from 1 to 10 h. The molecular weight also increased to 75,900 g.mol$^{-1}$ over the same period, while the increased monomer concentration resulted in a high molecular weight of 86,400 g.mol$^{-1}$ and a monomer conversion of 84%. Raising the reaction temperature from 90 to 130 $^{\circ}C$ increased the monomer conversion as well as the poly-L-lactide-co-${\varepsilon}$-caprolactone (PLCL) molecular weight. The variation on the stannous octoate catalyst suggested that less catalyst would decrease the caprolactone content of the polymer.

• Bulletin of the Korean Chemical Society
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• 제6권2호
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• pp.74-79
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• 1985

The stabilities of the charge transfer complexes of pentamethyl benzene with iodine in n-hexane have been investigated by UV-spectrophotometric measurements at 25, 40 and 60$^{\circ}C$ up to 1600 bars. The equilibrium constant of the complex formation was increased with pressure while being decreased with temperature raising. Changes of volume, enthalpy, free energy and entropy for the formation of the complexes were obtained from the equilibrium constants. The red-shift at higher pressure, the blue-shift at higher temperature, and the relation between pressure and oscillator strength have been discussed by means of thermodynamic functions. In comparison with the results in the previous studies, the absolute values of ${\Delta}$V at each temperature were increased with the number of methyl groups of polymethyl benzene. However, it can be seen that both ${\Delta}$H and ${\Delta}$S show extreme behaviors in durene near atmospheric pressure but they are negatively increased with the number of methyl groups near 1600 bar. This order of the thermodynamic parameters may be a measure of the relative basicities of polymethyl benzenes toward iodine under each pressure, and these phenomena are explained in terms of a positive inductive effect and a steric hindrance effect of the polymethyl benzene molecule.

• Bulletin of the Korean Chemical Society
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• 제6권4호
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• pp.186-191
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• 1985

The effect of pressure and temperature on the stabilities of the charge transfer complexes of hexamethyl benzene with iodine in n-hexane has been investigated by UV-spectrophotometric measurements. In this experiment the absorption spectra of mixed solutions of hexamethyl benzene and iodine in n-hexane were measured at 25, 40 and $60^{\circ}C$ under 1,200, 600, 1200 and 1600 bar. The equilibrium constant of the complex formation was increased with pressure while being decreased with temperature raising. Changes of volume, enthalpy, free energy and entropy for the formation of the complexes were obtained from the equilibrium constants. The red shift at higher pressure, the blue shift at higher temperature and the relation between pressure and oscillator strength were discussed by means of thermodynamic functions. In comparison with the results in the previous studies, it can be seen that the pressure dependence of oscillator strength has a extremum behavior in durene as the variation of ${\Delta}H$ or ${\Delta}S$ with the number of methyl groups of polymethyl benzene near atmospheric pressure in the previous study. The shift or deformation of the potential in the ground state and in the excited state of the complexes formed between polymethyl benzene and iodine was considered from the correlation between the differences of the electron transfer energies and the differences of free energies of the complex formation for the pressure variation.

• Structural Monitoring and Maintenance
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• 제8권4호
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• pp.379-402
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• 2021

Traditional approaches for structural health monitoring (SHM) seldom take ambient uncertainty (temperature, humidity, ambient vibration) into consideration, while their impacts on structural responses are substantial, leading to a possibility of raising false alarms. A few predictors model-based approaches deal with these uncertainties through complex numerical models running online, rendering the SHM approach to be compute-intensive, slow, and sometimes not practical. Also, with model-based approaches, the imperative need for a precise understanding of the structure often poses a problem for not so well understood complex systems. The present study employs a data-based approach coupled with Empirical mode decomposition (EMD) to correlate recorded response time histories under varying temperature conditions to corresponding damage scenarios. EMD decomposes the response signal into a finite set of intrinsic mode functions (IMFs). A two-dimensional Convolutional Neural Network (2DCNN) is further trained to associate these IMFs to the respective damage cases. The use of IMFs in place of raw signals helps to reduce the impact of sensor noise while preserving the essential spatio-temporal information less-sensitive to thermal effects and thereby stands as a better damage-sensitive feature than the raw signal itself. The proposed algorithm is numerically tested on a single span bridge under varying temperature conditions for different damage severities. The dynamic strain is recorded as the response since they are frame-invariant and cheaper to install. The proposed algorithm has been observed to be damage sensitive as well as sufficiently robust against measurement noise.

• 생물환경조절학회지
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• 제15권2호
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• pp.149-155
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• 2006

풋고추(청양)의 육묘 온도를 주간온도는 같게 하고 야간온도를 달리하여 유묘의 화아분화와 생장 및 포장에서의 생장을 조사하였다. 육묘기간 중의 야간 온도가 높을수록 고추 묘의 엽수, 지상부 생체중 및 건물중이 증가하였고, 화아분화 및 첫 개화일은 단축되었다. 정식 후 초장, 경경, 분지장, 절간장은 저온구($28/11^{\circ}C$)에서 증가한 반면 고온구($28/21^{\circ}C$)에서 억제되었다. 측지수는 고온구에서 현저히 감소되었으나 온도 처리에 따라 주경에서 발달하는 1차분지의 수는 일정한 경향을 보이지 않았다. 고추 모종의 생장은 저온구에서 억제되었다가 하우스에 정식한 후부터 점차로 회복된 반면, 고온구는 이와 반대의 경향을 보였다.