• Journal of the Korean Geosynthetics Society
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• v.9 no.3
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• pp.39-45
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• 2010

When the ground temperature drops below $0^{\circ}C$, wet soils expand due to the ice formation in their porous space. This results in frost heave which causes structural stability problems. Frost heave is attributed by several factors such as physical soil properties and heat transfer including pore water phase change. Due to the complex physical phenomena, reliable and verified multi-dimensional numerical models for frost heave problems are still in a research stage. This study presents an efficient and simple method of overcoming numerical problems associated with sudden jump of heat capacity due to the phase change from water to ice in the pore space. This paper proposes heat transfer equation and finite element method when the saturated soils or porous rocks are subjected to freezing. Numerical analyses using the proposed method agree well with the known closed form solution and the laboratory test results.

• Journal of architectural history
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• v.20 no.1
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• pp.23-39
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• 2011

The Sungnyemun roofing tiles were twice disassembled for maintenance work, in 1963 and 1997, and modern tiles were applied in 1997. However, besides differing in visual appearance, the modern tiles had distinctly different physical properties. A study has been carried out on 22 different tiles, including original Sungnyemun tiles, modern tiles applied during maintenance, traditional tiles made by tile-makers, and others, to examine their physical properties, such as bending strength, frost resistance, absorption, whole-rock magnetic susceptibility, chromaticity, differential thermal analysis, and other characteristics. Since the method of making modern tiles involves compressing clay in a vacuum, modern tiles showed relatively greater bending strength and specific gravity, while Sungnyemun tiles and those made by tile-makers, in comparison, demonstrated less bending strength and specific gravity owing to their production method of 'treading,' in which clay is mixed by having someone tread upon it repeatedly. Over time, the absorption rate of the original tile used for Sungyemun gradually decreased from 21% to 14.7%; traditional tiles from tile-makers showed absorption rates of 17%, while the absorption rate of modern tiles was just 1%, which is significantly low. As for frost resistance, Sungnyemun tiles and traditional tiles from tile-makers showed cracking and exfoliation after being subjected to testing 4 or 5 times, while slight cracking was seen on the surface for modern tiles after 1ngy, or 3 times. In other words, no significant difference from influence by frost was found. According to the results of differential thermal analysis, the plastic temperature was shown to have been no less than 1, $on^{\circ}C$ for all types of tile, and cristobalite was measuredthrough XRD analysis from a Sungnyemun female tile applied during maintenance in 1963, which appeared to have been plasticized at between $1,200^{\circ}C{\sim}1,300^{\circ}C$. Based on these research results on the physical properties of tiles from the Sungnyemun roof, a fundamental production method for tiles to be applied in the restoration of Sungnyemun has been identified.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.2
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• pp.79-86
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• 2009

The present study was investigates the effect of the parameters on the frost formation and heat transfer performance such as fin shape, air temperature and air velocity. Heat transfer rate and pressure drop by frost were experimentally investigated. Effect of the wet blub temperature and air velocity on the heat transfer performance has been also investigated. The heat transfer performance of the louver fin and tube type heat exchanger was higher by maximum of 0.85% than the corrugate fin type at the air temperature of $2.0/1.5^{\circ}C$. As the wet blub temperature of air were increased, the heat transfer rate, pressure drop and mass of frost of three test models were increased. Especially, the maximum heat transfer rate and maximum pressure drop were shown for the Type B louver fin heat exchanger. As an experimental result, the enhancement factor(EF) of louver fin and tube type heat exchanger was only $0.2{\sim}0.4$ due to the high pressure drop.

• Journal of the Korean GEO-environmental Society
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• v.11 no.12
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• pp.5-11
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• 2010

If the groundwater in rock joint is changed into ice, it induces the stress increment by volume increase. Also, if the ice is changed into groundwater again, the stress in joint decreases by volume decrease. The accumulated displacement and fatigues of joints are increased by the stress-hysterisis, induced from the continuous frost-thawing. Also the shear strength is decreased by them continuously. The stress-hysterisis is affected by the atmospheric temperature changes, whose behavior is visco-elasticity, usually. Therefore, Kelvin model could be used to analyze the frost-thawing behavior in winter. The measured data of total 5 points are examined, which are composed of 3 points of shallow joints and 2 points of deep joints. Because shallow weathered rocks have many joints, a lot of Kelvin model are connected and the behaviors are complicated. In case of deep joints, simple Kelvin model is applied and the behaviors are also simple.

• Journal of the Korean association of regional geographers
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• v.12 no.4
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• pp.437-448
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• 2006

Bare-topped thufur is called as frost scars, implying the rupturing stage of vegetated mounds, Field observations and measurements provide empirical information on the process and factors of thufur disintegration in Mt. Halla, Initial bare patches on mound apexes are scaled up by continuous removal of soil and vegetation, resulting in the formation of crater-like thufur, Frost action plays a primary role in thufur disintegration, In particular, pipkrake loosens soil particles within the bare patches and subsequently accelerates the degradation of vegetated mounds during periods with frequent diurnal freeze-thaw cycle and high soil moisture, Deflation also has an impact on thufur breakup in that the bare patches usually lack upper dark brown soil and are covered with granules, Withered shrubs such as Juniperus chinensis var. sargentii are frequently observed in frost scars and disrupted mounds, indicating that thufur disintegration has been probably influenced by global warming.

• Korean Journal of Environmental Agriculture
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• v.34 no.3
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• pp.210-216
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• 2015

BACKGROUND: In korea, sweet persimmon(Diospyros kaki) cultivation is front to abiotic stresses such as frost damage at fruit maturing stage. The cold and rapid freezing stresses are most damaging to fruit production which is most actively progressed in late fall. This study was performed to evaluate the validity of chlorophyll fluorescence imaging(CFI) technology to determine the degree of frost damage in sweet persimmon fruits. METHODS AND RESULTS: The sweet persimmon fruits were measured separately for each treatment(15, 30, 60 minutes) at 24 hours after treatment(HAT) rapid freezing. A CFI FluorCam (FC 1000-H, PSI, Czech Republic) was used to measure the fluorescence images of the fruits. In rapid freezing for 15 minutes, photochemical parameters were not changed. However, in rapid freezing for 30 and 60 minutes, photochemical parameters were lowered. Especially, $F_m$, $F_v$, $F_v/F_m$ and ${\Phi}PSII$ values were declined under rapid freezing. CONCLUSION: In our study, it was clearly indicated that the rapid freezing could be a stress in sweet persimmon fruits. The CFI analysis and its related parameters are applicable as a rapid assessing technique for the determination of frost damage.

• Korean Journal of Agricultural and Forest Meteorology
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• v.4 no.3
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• pp.133-140
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• 2002

Site-specific minimum temperature forecasts are critical in a short-term decision making procedure for preventive measures as well as a long-term strategy such as site selection in fruits industry. Nocturnal cold air pools frequently termed in mountainous areas under anticyclonic systems are very dangerous to the flowering buds in spring over Korea, but the spatial resolution to detect them exceeds the current weather forecast scale. To supplement the insufficient spatial resolution of official forecasts, we developed a GIS - assisted frost risk assesment scheme for using in mountainous areas. Daily minimum temperature data were obtained from 6 sites located in a 2.1 by 2.1 km area with complex topography near the southern edge of Sobaek mountains during radiative cooling nights in spring 2001. A digital elevation model with a 10 m spatial resolution was prepared for the entire study area and the cold air inflow was simulated for each grid cell by counting the number of surrounding cells coming into the processing cell. Primitive temperature surfaces were prepared for the corresponding dates by interpolating the Korea Meteorological Administration's automated observational data with the lapse rate correction. The cell temperature values corresponding to the 6 observation sites were extracted from the primitive temperature surface, and subtracted from the observed values to obtain the estimation error. The errors were regressed to the flow accumulation at the corresponding cells, delineating a statistically significant relationship. When we applied this relationship to the primitive temperature surfaces of frost nights during April 2002, there was a good agreement with the observations, showing a feasibility of site-specific frost warning system development in mountainous areas.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.386-394
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• 2022

In this study, the mechanical properties and frost resistance of concrete with steel and nylon fibers were experimentally investigated. Both of OPC concrete with 100 % ordinary portland cement and SGC concrete replaced with 50 % GGBFS were manufactured to evaluate effects of fibers to the performance of concrete. Compressive and split tensile strength, ultrasonic pulse velocity and surface electric resistivity measurements of concrete were carried out at a predetermined interval. In addition, the freezing & thawing resistance of concrete in accordance with ASTM C666 standard was also examined. As a result, it is seemed that the effect of fibers was remarkable to improve the mechanical properties and frost resistance of concrete, especially for the concrete incorporating steel fiber.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.5
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• pp.399-405
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• 2010

The accumulated displacements and fatigues of rock are increased by the stress-hysteresis, induced from repeated frost-thawing. Also the shear strength is decreased by them continuously. The stress-hysteresis is affected by the atmospheric temperature changes, whose behavior is visco-elasticity, usually. Therefore, to do ideal body analysis, Kelvin model could be used to analyze the frost-thawing behavior in winter. In general, rock slope failure occurs by the deterioration of rocks, which is caused by the repetition of freezing-thawing process. In order to keep the safety of such rock mass structures the deterioration process of rock needs to be described quantitatively using some meaningful parameters. In this work, the deterioration process in freezing-thawing cycle of tuff, which is a famous soft porous rock, is investigated through laboratory tests and successfully described as a differential equation for the change of porosity. And then, the deterioration of the mechanical properties of rock, such as Young's modulus and uniaxial compressive strength, are quantitatively described as a function of the porosity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1D
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• pp.55-61
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• 2009

In this research freezing depth analyses were performed for the recent 9 project field sites using FrostAM which is a freezing analysis model developed recently within the country and a model based on regional environmental factors and physical properties of pavement materials. The environmental factors needed for freezing depth analysis were obtained from the meteorological agency website. And there were laboratory tests and analyses using a measuring device for properties of unsaturated soil for the field site samples across country to obtain hydrographical properties among physical properties. The freezing depths analyzed by FrostAM were deeper in the range of 14cm~44cm than those based on freezing index. It is considered that the freezing depths based on freezing index were overestimated. And there are considerable differences among the freezing depths based on freezing index which were designed by different designers.