• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 동계학술발표대회 논문집
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• pp.186-191
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• 2008

In this study, a room temperature AMRR (Active magnetic regenerative refrigerator) was fabricated, and experimentally investigated. Gadolinium (Gd) was selected as a magnetic refrigerant with Curie temperature of 293 K. Permanent magnet was utilized to magnetize and demagnetize the AMR. To produce large magnetic field above 1 T in the magnetic refrigeration space, a special arrangement of permanent magnets, so called Halbach array, is employed. Sixteen segments of the permanent magnets magnetized different direction, constitute a hollow cylindrical shaped permanent magnet. The AMR is reciprocated along the bore of the magnet array and produces cooling power. Helium is selected as the working fluid and a helium compressor is utilized to supply helium flow to the regenerator. The fabricated AMRR has different structure and compared to a convectional AMRR since it has an additional volume after the regenerator. Therefore, the cooling ability is generated not only by magnetocaloric effect of magnetic refrigerant but also by the pulse tube effect. It is verified that the cooling ability of AMR is increased due to the magnetocalric effect by the fact that the temperature span becomes $16^{\circ}C$ while the temperature span is only $8^{\circ}C$ when the magnetic field is not applied to the regenerator.

• 한국자원식물학회지
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• 제19권6호
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• pp.700-705
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• 2006

Present studies were performed to determine the physiology of seed germination in Viola species native to Korea. Twelve species, 1 variety and 1 form were collected, classified and used as materials: V. collina, V. blandaefomis, V. rosii, V. chaerophylloides, V. phalacrocarpa, V. patrinii, V. mandshurica, V. mandshurica for. albescence, V. seoulensis, V. yedoensis, V. keiskei, V. variegata, V. variegata var. chinensis, and V. verecunda. V. tricolor 'Helen Mount' was also used to compare wild with cultivated species. In order to investigate the effect of temperature on seed germination, seeds stored at $4{\pm}2^{\circ}C$ for 10 months or 4 years were incubated at 10, 15, 20, $25^{\circ}C$ under 16h illumination with 4 replicates per treatment. Seeds which had not germinated at $10^{\circ}C$ were transferred to $30^{\circ}C$ to assess the effect of temperature change in germination. Germination percent and the days of first, 40% and 80% germination were assessed. Capability of seed germination varied with taxon; Species belonging to subsection Patellares had high ability of germination, compared to species in the other subsections, and series Chinensis was the best among subsection Patellares. Species capable of high germination germinated in all temperatures with reasonably high germination rate, but the other species responded sensitively to temperature with different germination patterns. Higher the temperature, shorter the incubation time required for first, 40% and 80% of germination. Therefore, high temperature was effective in almost all species, not only for inducing high rate of germination but also the uniformity of germination. Temperature change from $10^{\circ}C\;to\;30^{\circ}C$ had a positive effect on seed germination.

• 한국분무공학회지
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• 제24권2호
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• pp.66-72
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• 2019

Diesel vehicles suffer from poor starting and running problems at cold temperatures. Diesel vehicles have the characteristic that CO and PM are reduced or similarly discharged when going from low temperature to high temperature. In this study, a bypass type piezo injector for electronic control based common rail injection system was used. Numerical analysis using injector drive analysis model was performed to analyze injector drive and internal fuel flow characteristics according to fuel temperature change. The results show that the rate of density change due to the fuel temperature is proportional, and that the effect of the kinematic viscosity is relatively large between $-20^{\circ}C$ and $0^{\circ}C$. Comparing the results of temperature condition at $0^{\circ}C$ and $20^{\circ}C$, it is considered that the viscosity is more correlated with the needle displacement than the pressure chamber of the delivery chamber.

• International Journal of Automotive Technology
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• 제1권2호
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• pp.71-77
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• 2000

High temperature materials in service are subjected to mechanical damage due to operating load and metallurgical damage due to operating temperature. Therefore, when designing or assessing life of high temperature components, both factors must be considered. In this paper, the effect of tensile hold time on high temperature fatigue crack growth and long term prior thermal aging heat treatment on creep rupture behavior were investigated using STS 316L and STS 316 austenitic stainless steels, which are widely used for high temperature components like in automotive exhaust and piping systems. In high temperature fatigue crack growth tests using STS 316L, as tensile hold time increased, crack growth rate decreased in relatively short tensile hold time region. In long term aged specimens, cavity type microcracks have been observed at the interface of grain boundary and coarsened carbide.

• 한국응용과학기술학회지
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• 제27권4호
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• pp.552-558
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• 2010

Zinc soap and Zn/Ba mixed metal soap were synthesized and PVC plastisol with mixed metal soap and various costabilizers were also synthesized with good structures and characterized by IR and $^1H$-NMR. The IR spectrums and $^1H$-NMR spectrums of the synthesized soaps were in very good accordance with the structures proposed by earlier workers. In using phosphite as a costabilizer, TIDP phosphite was shown to be the excellent thermal stabilization effect at the low temperature and TNPP phosphite was shown to be the excellent thermal stabilization effect at the high temperature. In case of antioxidant, it was revealed that antioxidant was not effective in the low temperature thermal stabilization effect while highly effective in the high temperature thermal stability. $NaClO_4$ solution with sorbitol solvent had the best thermal stabilization effect among $NaClO_4$ solution series at low and high temperature.

• Interaction and multiscale mechanics
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• 제6권2호
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• pp.127-136
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• 2013

In this study, atomistic simulations are performed to study the effect of Al solute on the behaviour of edge dislocation in Mg alloys. After the dissociation of an Mg basal edge dislocation into two Shockley partials using molecular mechanics, the interaction between the dislocation and Al solute at different temperatures is studied using molecular dynamics. It appears from the simulations that the critical shear stress increases with the Al solute concentration. Comparing with the solute effect at T = 0 K, however, the critical shear stress at a finite temperature is lower since the kinetic energy of the atoms can help the dislocation conquer the energy barriers created by the Al atoms. The velocity of the edge dislocation decreases as the Al concentration increases when the external shear stress is relatively small regardless of temperature. The Al concentration effect on the dislocation velocity is not significant at very high shear stress level when the solute concentration is below 4.0 at%. Drag coefficient B increases with the Al concentration when the stress to temperature ratio is below 0.3 MPa/K, although the effect is more significant at low temperatures.

• Current Optics and Photonics
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• 제1권4호
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• pp.263-270
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• 2017

Solar radiation data measured by pyranometers is of fundamental use in various fields. In the field of atmospheric optics, the measurement of solar energy must be precise, and the equipment needs to be maintained frequently. However, there seem to be many errors with the existing type of pyranometer, which is an element of the solar-energy observation apparatus. In particular, the error caused by the thermal dome effect occurs because of the thermal offset generated from a temperature difference between outer dome and inner casing. To resolve the thermal dome effect, intensive observation was conducted using the method and instrument designed by Ji and Tsay. The characteristics of the observed global solar radiation were analyzed by classifying the observation period into clear, cloudy, and rainy cases. For the clear-weather case, the temperature difference between the pyranometer's case and dome was highest, and the thermal dome effect was $0.88MJ\;m^{-2}\;day^{-1}$. Meanwhile, the thermal dome effect in the cloudy case was $0.69MJ\;m^{-2}\;day^{-1}$, because the reduced global solar radiation thus reduced the temperature difference between case and dome. In addition, the rainy case had the smallest temperature difference of $0.21MJ\;m^{-2}\;day^{-1}$. The quantification of this thermal dome effect with respect to the daily accumulated global solar radiation gives calculated errors in the cloudy, rainy, and clear cases of 6.53%, 6.38%, and 5.41% respectively.

• 한국의류학회지
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• 제3권1호
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• pp.49-56
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• 1979

To investigate detergency of various woven fabrics in relation to the detergents and washing temperature. cotton, polyester/cotton (p/c), nylon, acetate, and polyester were soiled in aqueous artificial ($carbon-CCl_4$) soil. Each fabric was washed with soap, alkaline and neutral synthetic detergents at $30^{\circ}C$, $40^{\circ}C$ and $60^{\circ}C$ respectively. The results obtained may be summerized as follows; 1. In soap, ascension of temperature had the most important effect upon washing efficiency and the higher the temperature was, the higher the washing efficiency was showed in all fabrics. And in case of alkaline synthetic detergent, nylon and p/c fabrics were much more difficult to clean at higher temperature and also acetate and polyester had the best efficiency at $40^{\circ}C$. Detergency of neutral detergent was good but the effect of temperature in neutral detergent was less than in soap. 2. Washing efficiency of cotton was less than that of others. 3. The higher the temperature was, the higher the washing efficiency of cotton in all detergents, and the best was in soap. In p/c, detergency of neutral detergent was good but effect of ascension of temperature was lower than in soap. In nylon, washing efficiencies of alkaline synthetic detergent and neutral detergent were excellent at 30°C but detergency of soap at $60^{\circ}C$ was best. In case of acetate, detergency of all detergents was about the same at $30^{\circ}C$ but that of soap at $60^{\circ}C$ was best. In polyester at $30^{\circ}C$, efficiency of neutral detergent was excellent but that of soap was more excellent at higher temperature and the best detergency of alkaline synthetic detergent showed at $40^{\circ}C$. In general. the higher the temperature is, the higher the washing efficiency of soap is. But when synthetic fibers of nylon and polyester are washed with synthetic detergents, washing at lower temperature is advisable.

• 한국대기환경학회지
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• 제23권3호
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• pp.353-363
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• 2007

To differentiate temperature effect from the light intensity effect on the formation of secondary products during the photooxidation of toluene-$NO_x$-air mixtures, steady-state air temperature was changed from $20^{\circ}C\;to\;33^{\circ}C$ at the same light intensity of $0.39min^{-1}$ in an indoor smog chamber. Smog chamber consisted of 64 blacklights and a $5.8m^3$ reaction bag made of Teflon film. Air temperature was controlled by an air-conditioning system. The starting time for rapid conversion of NO to $NO_2$ was slightly delayed with decreasing air temperature. In contrast to light intensity effect, the ozone formation time and the ozone production rate were insensitive to air temperature. Although the formation time for secondary organic aerosols was not changed, the particle number concentration increased with temperature. However, the newly formed secondary organic aerosol mass at lower temperature was higher than that at higher temperature. Since light intensity significantly affected the starting time and quantity of ozone and aerosol formation, it is considered that the temperature could contribute partly the quantity of aerosol formation during the photooxidation of toluene-$NO_x$-air mixtures.

• 설비공학논문집
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• 제11권2호
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• pp.205-214
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• 1999

The objective of this paper is to investigate the thermal properties of TMA clathrate compound applicable to cold storage system for building air-conditioning. Especially, the test tube experiments are performed by comparing and analyzing the temperature of phase change, specific heat and subcooling characteristic according to the variation of density, temperature of heat source and charging quantity in TMA clathrate compound. The results are summarized as follows:1) $-15^{\circ}C$ is not proper as the temperature of heat source because the temperature of subcooling is above $8.3^{\circ}C$ 2) temperature of phase change is dropped as the temperature of heat source is lower, 3) the effect of subcooling suppression with about 8$^{\circ}C$ is confirmed when the temperature of heat source is $-10^{\circ}C$ in case of 26, 27, and 30wt%, while the temperature of subcooling is about $0^{\circ}C$ when the temperature of heat source is $-15^{\circ}C$ in case of 25, 26 and 30wt%. Thus, the effect of subcooling suppression is greater as the temperature of heat source is lower. Additionally, the concentrative study is needed on mass concentration causing the phase change without subcooling phenomenon when the temperature of heat source is $-15^{\circ}C$. Thus, it is concluded that TMA clathrate compound has enough thermal properties as the cold storage medium for building air-conditioning.