• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.273-283
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• 1999

When microorganism is injected into porous medium such as soils, biomass is retained in the pore. Soil pore size and shape are varied from the initial condition as a result of biofilm formation which makes hydraulic conductivity reduced and friction rate between soil aggregates increased. In this research, hydraulic conductivity reduction was measured after microorganism are inoculated and cultured with synthetic substrate and nutrient. In addition, this research evaluated the applicability of biomass-soil mixture to the field condition as an alternative cover material in landfill by measuring hydraulic conductivity change after repetitive freeze-thaw cycles. Hydraulic conductivity of silty soil decreased by approximately 1/50 after biomass inoculation and cultivation. Biofilm attached on soil aggregates is resistant to acidic or basic condition. After repetitive freeze-thaw cycles, however, hydraulic conductivity increase implies that biomass clogging can be impaired.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.21-22
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• 2009

This paper presents the results of an experimental study on flexural behavior and cracking process of concrete beams subjected to cycles of freezing and thawing after patch-repaired with strain-hardening cement composites (SHCCs). The SHCCs were reinforced with hybrid 0.75% PVA and 0.75% PE fibers. Experimental testing of concrete beams patch-repaired with SHCCs revealed that the SHCC patch-repair system without freeze thaw (FT) exposure showed average 3.31 times increased load carrying capacity and for beams exposed to 300 FT cycles, load carrying capacity increased up to 2.42 times. Cracking damage of SHCC patch-repaired beams mitigated compared to plain concrete beams but this trend decreased under FT exposure.

• The Korean Journal of Ecology
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• v.22 no.5
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• pp.305-309
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• 1999

The occurrence of tetQ and aacC2 genes encoding tetracycline and gentamicin resistance determinant, respectively, was assessed in total bacterial community DNA isolated from Dongchon stream of Sunchon area. To examine the resistance potential of bacteria that were not cultured, total DNA from 1 liter of stream water was extracted by freeze-thaw method. The PCR technique was employed to determine the abundance of the target genes. The highest frequency of tetQ gene was obtained from site 1, located near the animal farms area, whereas the incidence of aacC2 was highest in site 5, the downstream area. These results showed that the occurrence of antibiotic resistance gene may be used as a convenient marker of water quality related to source.

• Korean Journal of Animal Reproduction
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• v.7 no.2
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• pp.57-71
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• 1983

1. Diluted chicken semen can be preserved at 2 to 5$^{\circ}C$ for 24 to 48 hr with resultant fertility of greater than 90% of that of fresh semen. Turkey semen can be preserved at 10 to 15$^{\circ}C$ for 6 to 24 hr and provide economical fertility. 2. Frozen chicken semen has given variable results; a 21 to 93% fertility ranges as compared to 92 to 94% expected with fresh semen. Highest fertility levels obtained with frozen turkey semen intravaginally inseminated have been 61 and 63% using DMSO and glycerol, respectively, as cryoprotectants. 3. The use of glycerol as a cryoprotectant reauires that its concentration in semen be reduced to less than 2% either by dialysis or centrifugation after thawing and before intravaginal insemination if optimal fertility is to be obtained. 4. The temperature at which cryoprotectants are added to semen and the time allowed for equilibration are important for subsequent fertility pre- and post-freezing. 5. The type of container used for packaging the semen, freeze or cooling rates, thaw rates and level of cryoprotectant all interact in affecting cell survival. 6. Plastic freeze straws as a packaging device for semen offers the following advantages: easy to handle, require minimal storage space, offer a wide range of freeze and thaw rates, and insemination can be made directly from them upon thawing. 7. Controlled slow cooling rates of 1 to 8$^{\circ}C$/min have thus far provided the best results for cooling chicken semen throught the transition phase change (liquid to solid) or critical temperature range of ＋5 to -20 or -35$^{\circ}C$. 8. Highest fertilities have been achieved with frozen chicken semen where a slow thaw rate (2。 to 5$^{\circ}C$) has been used regardless of the freeze rate. 9. To maintain a constant high level of fertility throughout a breeding season with frozen semen, a higher absolute number of spermatozoa must be inseminated (2 to 3 times as many) as compared to fresh semen since a, pp.oximately 50% are destroyed during processing and freezing. 10. The quality of semen may vary with season and age of the male. Such changes in sperm quality could be accentuated by storage effects. Thus, the correct number of spermatozoa may very well vary during the course of a breeding period. 11. As to time of insemination, it is best to avoid inseminating chicken hens within 1-2 hr after or 3-5 hr before oviposition; and turkey hens during or 7-10 hr before oviposition. 12. The physiological receptiveness of the oviduct at the time of insemination is a very important biological factor influencing fertility levels throughout the breeding season.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.38 no.5 s.118
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• pp.54-59
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• 2006

Paperboards used for linerboard of corrugated fiberboard box were coated with different concentrations of polylactic acid (PLA) solution and the effects of harsh environmental conditions such as high humidity and temperature (96% RH at $30^{\circ}C$ for up to 5 days), and freeze-thaw ($-20^{\circ}C$ for a day and then thaw at room temperature for 30 min) conditions on the ring crush (RC) strength of the boards were investigated. One to five percent PLA solutions were coated onto SC manila linerboard ($20{\times}27cm$) using a No. 20 wire bar coater and the ring crush strength was measured using a computer-controlled Advanced Universal Testing System in accordance with TAPPI Test Method T 822 om-93. The RC strength increased significantly when the concentration of coating solution increased and appreciable changes were found when the concentration increased from 0 to 2% (P<0.05). Similar pattern of results was found after 5-day storage at $30^{\circ}C$ and 96% RH. Although such highly humid condition increased moisture content in the samples up to 3.95 from 0.97 times, the RC strength decreased in the range from 29.9 to 48.5%. The freeze-thaw treatment increased the moisture content only up to 1.27% and the reduction in the RC strength ranged from 21.1 to 28.1 %. The results were promising: the samples coated with 5% PLA solution showed 29.9% reduction in the RC strength while that of control was 48.5% during highly humid condition stated above.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.483-486
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• 2005

This study investigates the effect of air contents on concrete properties, compressive strength, chloride migration coefficient and freeze-thaw resistance. Chloride migration and freeze-thawing test conducted in accordance with NT-BUILD 492 and pr-EN 12390-9, respectively. As a result, compressive strength reduced with air contents increase, but chloride migration coefficient more influenced by the water-binder ratios than air contents. Air contents of hardened concrete measured half times that of fresh concrete after mixing. Also, concrete scaling decreased with air contents increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.149-150
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• 2020

Granting self-sensing performance in a building is an important performance to ensure the degree of damage and safety of the building. Since the current research is being conducted in the state before deterioration loss occurs, it is necessary to confirm whether the self-sensing performance is maintained even in the damaged conductive cement composite. As part of the study, electrical resistance characteristics were analyzed in conductive cement composites in which freeze-thawing and chemical corrosion occurred. As a result, it was found that the change in electrical resistance value due to freeze-thawing was not as large as 1%, and chemical corrosion occurred. It was found that the change in electrical resistance value of the tested specimen increased by about 10%.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.2
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• pp.68-75
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• 2015

This study established key factors causing deck slab deterioration based on GPR database of 747 highway bridges, and predicted deck slab damage rates with respect to bridge service life. To minimize the influence of bridge service life on deck slab deterioration, the deck slab damage rate database was corrected based on a linear regression model of bridge service life vs. deck slab damage rate. The corrected deck slab damage rates were analyzed to determine correlation considering the number of snowy days, the amount of snowfalls, the number of freeze-thaw days, average winter temperature, altitude, the amount of deicing chemicals and equivalent traffic volume, and then both the number of freeze-thaw days and the amount of deicing chemicals were determined to be key factors causing deck slab deterioration. The complex deterioration considering both key factors was represented deck slab damage rate charts, and the average deck slab life was derived. The results of this study will be used as a guideline for highway bridge maintenance to identify the progress of deck slab deterioration for a given bridge and predict the time required deck slab rehabilitation.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.79-87
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• 2011

Concrete incorporating high volume blast-furnace slag placed in cold weather regions might be in danger of initial frost damage because dependently on the mix proportions, the setting and the hardening would be remarkably delayed. Therefore, this study investigated to effect of the degree of frost on the strength development and the resistance to freezing and thawing of the concrete incorporating blast-furnace slag when being subjected to freeze at early age. As the experimental results, the concrete incorporating blast-furnace slag attacked by initial frost damage showed the remarkable reduction of both the compressive strength development and the resistance to freezing and thawing. Especially, the resistance to freezing-thawing of the concrete incorporating high volume blast-furnace slag became much lower than that of the normal concrete.

• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.13-21
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• 2011

In seasonal frozen areas with climatic features, which have a temperature difference in the winter and thawing season, changes of mechanical properties of the soil in the zone could be seen between the freezing and thawing surface. In particular, in soil with many fine particles, a softening of the roadbed usually occurs from frost and thawing actions. The lower bearing capacity is a rapidly progressive the softening of roadbed, and occurred a mud-pumping by repeated loading. In this study, the three kind of sandy soil with contents of fine particles were conducted by directly shear box test with the number of cyclic in freeze-thawing and the water content of soil. Subsequently, the relationship between the shear strength and freeze-thaw cycling time was obtained. The shear strength was decreased with the increase of the freeze-thaw cycling time. A shear stress deterioration of the soil with power function modal is proposal.