• Journal of Energy Engineering
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• v.19 no.3
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• pp.151-155
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• 2010

Adequate visibility through a vehicle windshield and frost melting period are critical aspects of major design parameters. To make progress in this area, a good understanding of the flow behavior and heat transfer characteristics produced by the HVAC module is required. The computational study was used to perform the parametric investigation into the defroster nozzle's performance with a full-scale model. The study highlights the drawbacks of current designs and points the way to improve passive defrosting mechanism. The results show that the current design of the defroster nozzles deliver the maximum airflow in the vicinity of the lower part of the windshield, which yields unsatisfactory visibility. Defrosting performance was excellent when the injection angle of the defrost nozzle was 45 degree. The numerical analysis satisfies the criteria provided by NHTSA.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.spc1
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• pp.224-228
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• 2006

The characteristics associated with the Alisma plantago quality and the factors as the proper harvesting time and drying temperature of Alisma plantago were examined from 2004 to 2006 at Sunchon, Southern region. The Alisma plantago cultivars tested were Sunwol and Yongjun. The highest yields of root and good quality, color and luster were obtained when harvested 22 days after first frost date and dried with $35-40^{\circ}C$ of a weeks at the drying oven for Sunwol and Yongjin cultivars. Considering from our results, optimum harvesting time were most likely to be harvesting time of 22 days after first frost date and drying temperature of $35-40^{\circ}C$ of a weeks at the drying oven.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.4
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• pp.206-214
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• 2001

Cooling rate shows the highest as about 0.7$^{\circ}C$/hr on spring season and the lowest as about 0.3$^{\circ}C$/hr on september at plain place. The correlation coefficient between net radiation and cooling rate from sunrise to sunset was 0.63$^{**}$, It became higher to 0.90$^{**}$ when the wind speed decreased lower than 0.5 m/sec, and it decreased as the wind speed increased. On a clear and calm day, cooling rates were observed as 1.4$^{\circ}C$/hr on the plain (site 1, 2, 3), 1.2$^{\circ}C$/hr on the slope (site 4, 5) and 0.6$^{\circ}C$/hr on the top of mountain (site 6). In condition of the wind speed is 1.2~2 m/sec on a clear and calm day and the temperature on the top of mountain is lower than that of slope and plain, the temperature on the slope (site 4,5) was increased unlike our expectation.ion.

• Journal of ILASS-Korea
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• v.14 no.4
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• pp.147-152
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• 2009

Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

• Journal of the Korean association of regional geographers
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• v.21 no.2
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• pp.394-410
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• 2015

This study aims to classify climate zones for extreme climate indices over the Republic of Korea. First, frequencies and magitudes of extreme high temperature, spatial distributions for extreme low temperature, and extreme precipitation are analysed. Frequencies of summer days in inland region show more than coastal region. In frequencies of frost days, the characteristics of altitude and longitude are appeared. Heavy precipitation days show many frequencies in the southern coastal region and Jeju island, but little in Gyeongsangbuk-do region. The classification of climate zone for extreme climate indices by principal component analysis and cluster analysis is conducted for the first half, second half of study period, and climatology period for 1981-2010. Summer days are classified according to latitude. In case of frost days, the eastern and the southern coastal region and Jeju island are classified as same region. Heavy precipitation days are classified according to longitude in south region of Gyeonggi-do and Gangwon-do. This study will help to prepare adaptation and mitigation system for climate change in wide range of fields.

• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.227-232
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• 2008

The present study was investigated the local heat transfer characteristics and temperature distribution on the louver fin by using the expansion model. Heat transfer rate, frost mass and temperature distribution of the louver fin under frosting condition were experimentally investigated. Local heat transfer rate and heat flux on the louver were analyzed by the conduction heat transfer between top and lower part of the louver. The experimental key parameter was brine inlet temperature(-5, -10, $-15^{\circ}C$). The heat transfer performance and frost mass at brine temperature of $-15^{\circ}C$ were increased by maximum 3 time than the brine temperature of $-5^{\circ}C$. At all experimental case, local heat transfer rate and heat flux of the louver were almost symmetry at the louver number of 6. Especially, local heat transfer rate and heat flux were maximum increased on the louver number of 4 and 8.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.75-86
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• 2012

This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.1
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• pp.29-38
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• 2001

In this paper, the defrosting characteristics of a PTC heating sheet is investigated by means of a defrosting heat source for the fin-tube heat exchanger in a refrigerator The defrosting characteristics of the PTC heating sheet are examined and compared with those of a conventional electric heater experimentally. It is found that the characteristics of the water draining rate with the defrosting time show a smoothly oscillating pattern when the PTC heating sheet Is used, and the drained water is completely melted. The defrosting efficiency of the PTC heating sheet is found to be about 75%, which is about 25% higher than that of the electric heater. Also, the reduction of the defrosting time and the increment of the defrosting efficiency may be obtained by improving the arrangement of the heating elements of the healing sheet. It is shown that the defrosting time of the PTC heating sheet increases linearly with the amount of frost, whereas the defrosting efficiency is nearly constant. When applying the PTC heating sheet to the refrigerating system, one should notice the fact that the defrosting performance of the PTC heating sheet may be degraded due to the repetitive operations.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.449-454
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• 1999

Pavement concrete subjected to severe environmental condition may be vulnerable to frost attack practically where de-icing chemicals are used. This study focused on the investigation of durability characteristics of pavement concrete incorporation polypropylene fibers and application feasibility of these into the pavements of local roads and highway. A series of labortory tests were performed with main experimental variable such as fiber types, fiber contents. and type of concrete mix. The test of compressive strength was executed as primary tests, before the durability tests such as a scaling resistance were performed. De-icing salt resistance test was progressed by recycling freeze and thaw in the presence of a 4% calcium chloride solution. The deteriorated surfaces were rated by visual inspection and the loss weight were measured at every 5 cycles.

• Proceedings of the KSRS Conference
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• 2008.10a
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• pp.185-187
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• 2008

Speckle noise is primarily due to the phase fluctuations of the electromagnetic return signals. Since inherent spatial-correlation characteristics of speckle in SAR images are not exploited in existing multiplicative models for speckle noise. In this paper, we investigate the efficiency of the filters: Kuan, Gamma, Enhanced Lee, and Enhanced Frost filters in reduction of speckle noise in forestry area. Selection of the suitable filter can be played an important role in applications such as estimation of biomass in forestry areas. We employ ALOSPALSAR image use L-band frequency for this investigation. The filters test on different sites in PALSAR image of the northern forests part of Iran.