• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.11a
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• pp.23-26
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• 2007

A preliminary， study of low temperature condition was performed to simulate high altitude condition. The mixed air temperature were investigated at various condition by experiments using cryogenic air by heat exchanger and normal temperature air. An experimental setup was constructed to simulate low temperature condition with liquid nitrogen. To control mass flow rate, orifice and pressure regulators were used. The experimental results show that the mixed air temperature increases linearly with mass flow rate of normal temperature air. Therefore it can be help to simulate a low temperature condition of high altitude.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.61 no.3
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• pp.163-170
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• 2016

Heading time is important element for yield and quality in crops. Among day length and temperature which influence on heading, temperature effect has not been investigated well. To investigate temperature effect on heading, heading date and plant growth characters were checked under the low and high temperature conditions in short day length. Analyzing heading date of six Korean varieties under the high and low temperature condition, heading date of varieties were delayed under low temperature. In the low temperature condition, dry weight and area of leaf were reduced. Varieties showing more delay of heading under low temperature also showed more reduction in leaf area. After selecting three varieties showing significant difference in leaf growth and heading date under different temperature conditions, nutrient contents of plant were analyzed. Nitrogen content was reduced in leaf and shoot under the low temperature condition. OsNRT2.3, nitrate transporter, was significantly down regulated in varieties showing more heading delay. Available phosphate content was decreased in leaf, but increased in shoot due to reduction of phosphate mobility. OsPT1, phosphate transporter regulating phosphate uptake, was more down regulated in varieties showing more heading delay. OsPT6, phosphate transporter regulating phosphate transport in plant, was also significantly down regulated in those varieties. With these data, we expected that active nitrogen and available phosphate uptake and transport in plant would increase leaf growth then might reduce heading delay under the low temperature condition.

• Tunnel and Underground Space
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• v.7 no.2
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• pp.91-99
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• 1997

To stabilize the energy price, the more storage facilities of energy are required and among the storage methods of LPG and LNG, the method of storage at low temperature under normal confining pressure is considered. It is needed to understand the mechanical and thermal characteristics of rock under temperature variation so that the behaviors of rock can be predicted. In this paper, the variation of the rock charateristics of the Hwangdeung granite and the Boryung sandstone is studied at low temperature. The mechanical characteristics of rock under low temperatures are that as temperature decreased, unaxial compression strength and Young's modulus increased for Hwangdeung granite; strength and Young's modulus in wet condition were greater than those in dry condition. In the case of Boryung sandstone, as temperature decreases unaxial compression strength and Young's modulus increase but decrease below -10$0^{\circ}C$ in dry condition and below -16$0^{\circ}C$ in wet condtion. The mechanical characteristics of rock after cooling to previous temperature and thawing are that uniaxial compression strength and Young's modulus decrease as temperature decreases. Uniaxial compression strength and Young's modulus in wet conditon decrease more than those in dry condition. Brazilian tension strength decreases as temperature decreases.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.24 no.2
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• pp.35-41
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• 1979

To observe the effects of temperature and photoperiod on the growth and yield of winter wheat (Triticum aestivum, L) eight varieties including Chang Kwang were tested at various treatments like longday-high temperature (24hrs-20\circ), shortdayhigh temperature (12hrs-20\circ), longday-low temperature (24hrs-14\circ) and shortday-low temperature (12hrs-14\circ). Among the traits measured, days to heading, plant height, spike length, number of spikes per hill and grain yield per hill were generally decreased at high temperature and long day treatment and increased at low temperature and shortday condition. Number of grains per spike was decreased at low temperature and short day condition while increased at longday and high temperature conditions. Grain weight was decreased significantly at high temperature and shortday while increased at low temperature and longday treatment.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.337-342
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• 1999

The Purpose of this study is to evaluate the strength characteristics of polyurethane(PUR) mortar cured under low temperature condition. PUR mortars are prepared with various catalyst content, methylene chloride(MC) content as a viscosity reducing agent, and curing age at low temperature condition of $0^{\circ}C$, -5$^{\circ}C$ and -1$0^{\circ}C$, tested for working life, compressive and flexural strengths. From the test results, the catalyst and MC contents affect the degree of hardening and blowing of PUR mortar. Strengths increase with an increasing catalyst content at low temperature. Flexural and compressive strength of PUR mortar are about 177kgf/$\textrm{cm}^2$ and 490kgf/$\textrm{cm}^2$ respectively at curing temperature of -1$0^{\circ}C$ with catalyst content of 0.4%. Therefore, it is apparent that this PUR mortars have a sufficient strengths for repair of concrete structures.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.2
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• pp.86-97
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• 2018

The objective of this study was to determine the effects of low temperature on starch accumulation in rice grains. We used four major Japonica-type Korean rice cultivars as materials: Jinbu (JB), Junamjosaeng (JJ), Geumyoung (GY), and Hwawang (HW). Rice plants were moved into two phytotrons the day after heading. Temperatures in the two phytotrons were maintained at $19/29^{\circ}C$ (night/day) as the control, and $13/23^{\circ}C$ as the low temperature condition, both under natural daylight with a relative humidity of 65%. The ripening rates of JB and JJ showed no significant difference between the low temperature and control conditions at 45 days after heading (DAH). In contrast, the ripening rates of GY and HW were 86% and 57% lower than those of JB and JJ under the low temperature condition at 45 DAH, respectively. However, the ripening rates of these four varieties at 61 DAH (when accumulated temperature reached $1,100^{\circ}C$) under the low temperature condition were similar to those at 45 DAH under the control condition (JB, 94%; JJ, 97%; GY, 97%; HW, 88%). The total starch contents showed no significant difference between the control and low temperature conditions. However, the amylose contents in the cultivars were higher under the low temperature than under the control condition. The enzyme activities of starch biosynthesis were about 5-10 days slower in cultivars under the low temperature than under the control. The grain-filling rate showed significant correlations with the enzyme activities of SuSase ($r^2=0.70^{***}$), AGPase ($r^2=0.63^{***}$), UDPase ($r^2=0.36^{***}$), StSase ($r^2=0.51^{***}$), and SBE ($r^2=0.59^{***}$). In conclusion, although StSase activity was increased at $13/23^{\circ}C$ up to 20 DAH, there might not be enough time for SBE to synthesize amylopectin, thus affecting the amylose content of HW, which had the slowest grain filling rate. Notably, the decreased activity of SuSase and SBE and late increase in AGPase activity under the low temperature during the ripening stage are considered to be disadvantageous, as they delay ripening and increase the amylose content.

• Composites Research
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• v.30 no.1
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• pp.7-14
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• 2017

In this paper, the inter-lamina shear strength (ILSS) of multi-wall carbon nanotube (MWNT) reinforced carbon fiber reinforced plastics (CFRP) and thin-ply composites were verified under low earth orbit (LEO) space environment. CFRP, MWNT reinforced CFRP, thin-ply CFRP and MWNT reinforced thin-ply CFRP were tested after aging by using accelerated ground simulation equipment. The used ground simulation equipment can simulate high vacuum ($2.5{\times}10^{-6}torr$), atomic oxygen (AO, $9.15{\times}10^{14}atoms/cm^2{\cdot}s$), ultraviolet light (UV, 200 nm wave length) and thermal cycling ($-70{\sim}100^{\circ}C$) simultaneously. The duration of aging experiment was twenty hours, which is an equivalent duration to that of STS-4 space shuttle condition. After the aging experiment, ILSS were measured at room temperature ($27^{\circ}C$), high temperature ($100^{\circ}C$) and low temperature ($-100^{\circ}C$) to verify the effect of operation temperature. The MWNT and thin-ply shows good improvement of ILSS at ground condition especially with the thin-ply. And after LEO exposure large degradation of ILSS was observed at MWNT added composite due to the thermal cycle. And the degradation rate was much higher under the high temperature condition. But, at the low temperature condition, the ILSS was largely recovered due to the matrix toughening effect.

• Food Science and Preservation
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• v.5 no.2
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• pp.105-110
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• 1998

To find out suitable storage and marketing condition, northern type 'seosan' garlic was stored for 3 months at controlled atmosphere(CA), modified atmosphere(MA), low(0~1$^{\circ}C$) and room temperature(20$\pm$5$^{\circ}C$), and then marketed at low(2~3$^{\circ}C$) and room temperature (20$\pm$5$^{\circ}C$)after storage. The physiological properties of garlic were investigated among treatments. The garlic respiration increased after 2 months at room temperature storage, which seem to be dormancy break time. During storage of garlic by CA, MA condition, sprouting and weight loss were prevented effectively by suppress of respiration, and hardness was maintained higher then those of the others. Decay rate occurred 8.1% at room temperature storage, 2% at MA storage but didn't occurred at CA and low temperature storages. When marketed at room and low temperature after storage, increment of respiration and sprouting were delayed, and changes of weight and hardness were low in garlics stored at CA and MA. Decay rate occurred high in garlics stored at MA and room temperature.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.05a
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• pp.234-235
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• 2014

Recently, waterproof construction used to self adhesive waterproofing sheet in the actual field in winter for reduce cost and term. However self adhesive waterproofing sheet's quality is declined in low temperature condition. So, this study was to confirm on the low temperature condition of concrete substrate effecting the adhesion of self adhesion waterproofing sheet using interface leakage test. As a result of this study, self adhesion waterproofing sheet must not be used at temperature below 5℃. Also, adhesion between waterproofing sheet and concrete is declined in low temperature.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.553-556
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• 2009

In this study, ignition tests of a gas turbine combustor were performed to evaluate an ignition loop at low temperature condition. An experimental setup was constructed to simulate low temperature condition with a heat exchanger using dry ice as a coolant. Various low temperature conditions could be created by controlling the amount of air though the heat exchanger. The results showed that ignition limit decreased with air temperature.