• Journal of Powder Materials
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• v.27 no.3
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• pp.198-202
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• 2020

The effect of sublimable vehicles on the pore structure of Cu fabricated by freeze drying is investigated. The 5 vol% CuO-dispersed slurries with camphene and various camphor-naphthalene compositions are frozen in a Teflon mold at -25℃, followed by sublimation at room temperature. After hydrogen reduction at 300℃ and sintering at 600 ℃, the green bodies of CuO are completely converted to Cu with various pore structures. The sintered samples prepared using CuO/camphene slurries show large pores that are aligned parallel to the sublimable vehicle growth direction. In addition, a dense microstructure is observed in the bottom section of the specimen where the solidification heat was released, owing to the difference in the solidification behavior of the camphene crystals. The porous Cu shows different pore structures, such as dendritic, rod-like, and plate shaped, depending on the composition of the camphornaphthalene system. The change in pore structure is explained by the crystal growth behavior of primary camphor and eutectic and primary naphthalene.

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.205-216
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• 1998

천연제올라이트를 사용한 콘크리트의 특성을검토하기 위하여 천연제올라이트의 대체율 및 입자크기에 따라 콘크리트의 압축강도, 동결융해저항성, 건조수축 및 투수성 등을 실험하였다. 이때 천연제올라이트는 입자크기(중간값)가 12.7$\mu\textrm{m}$과 10.39$\mu\textrm{m}$인 것을 사용하였으며 콘크리트실험에서 천연제올라이트의 시멘트 중량에 대한 대체율은 5%, 10%, 15% 및 20%로 하였다. 천연제올라이트의 대체율이 15%이하인 콘크리트는 동일한 물-결합재비에서 천연제올라이트를 사용하지 않은 경우와 비교하여 재령 28일 및 91일의 압축강도가 크게나타났으며 이러한 강도의 증가는 천연제올라이트의 입자크기가 작은 경우 보다 크게 나타났다. 콘크리트의 동결융해에 대한 저항성이나 건조수축에 의한 길이변화는 천연제올라이트의 대체율에 따라 명확한 차이를 보이자 않았으나 다만 천연제올라이트의 대체율이 20%인 경우는 길이변화가 크게 되는 경향을 나타냈다. 수밀성시험에서는 천연제올라트의 입자크기가 12.7$\mu\textrm{m}$인 경우 그의 사용량이 증가함에 따라 수밀성이 저하하였으며 입자크기가 10.39$\mu\textrm{m}$인경우는 천연제올라이트의 대체율이 10% 이하인 경우 수밀성이 다소 개선되는 것으로 나타났으나 그 이상의 대체율에서는 수밀성이 저하되는 경향을 나타냈다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.11a
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• pp.69-72
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• 2009

This research is focused on the applying of the foaming agent which can make the independent pore in the concrete structure in order to make a lightweight concrete structure. This lightweight foamed concrete can satisfy both the required strength and the mechanical properties as structural members. In addition, anti freezing-thawing properties also required. As a result of the unit volume-weight measurement, when the foaming agent mixed at 0.5% to 1%, the lightweight foamed concrete can be applied for the structural member. Also the density and compressive strength measurement results reveals that it will be suitable as structural member with 21MPa strength, when the density is betweenity8 to 1.9 and foaming agent quantities are 0.5% to 1%. Finally the result of freezing-thawing experiment, the effect freezing-thawing damage reduced according to adding foaming agent because those foaming agent make micro-pores in the structure which are not seen in the ordinary concrete structure.

• Journal of The Geomorphological Association of Korea
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• v.25 no.1
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• pp.47-65
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• 2018

Frost shattering has traditionally been considered as one of the most effective process in rock weathering. Each slab specimens of five or six rhyolite, basalt and tuff was prepared and put in freeze-thaw cycles and repeated 300 times in the temperature of $-25^{\circ}C$ to $+30^{\circ}C$ and their weathering patterns and products were analyzed by surface observation, particle size, XRD and thin section. As the result, some changes were observed in weathering patterns and weathering products. Rock shattering was more active in waterlogging rather than atmospheric conditions, but there are many differences depending on the type of rock. Rhyolite is hardly weathered by 300 times freeze-thaw cycles and generates the least amount of weathering products. Weathering of Basalt is limited to the surface layer where water can be absorbed, and produces a few amount of platy-shape debris. Tuff are separated by blocky structure which the particles are aggregated along their edges rather than enlarged existing cracks/joins or generated new joints.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.191-200
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• 1979

For the use of antarctic krill as a fond protein source its compositional characteristics were investigated as the first part of the work includes other subjects such as processing of drill paste, concentrates, and fermented or seasoned product. In general composition of fresh frozen and preboiled frozen krill on board, the contents of crude fat and free amino nitrogen were higher in the former than in the latter which contained a high amount of ash. VBN was rather high as much as 37.6 and $26.4\;mg\%$ in both fresh frozen and preboiled krill. The pH of drill homogenates was 7.1 to 7.2 in both cases. Such a low pH might be attributed to a long term storage and temperature fluctuations during frequent transshipping. The amino acid competition of fresh frozen krill meat showed relatively high amount of glutamic acid, aspartic acid, lysine, proline, and leucine while methionine, histidine, serine, tyrosine, and phenylalanine were lower. Among the essential amino acids lysine and leucine were higher and methionine was lower. In tile composition of free amino acid proline, lysing, arginine, and alanine were higher comparatively to the contents of histidine, aspartic acid, serine, and threonine. It is noteworthy for nutritional qualification that tile essential amino acids particularly as lysine were abundant similarly to that of fishes. Heavy metal contents of krill meat 0.039 to 0.048 ppm as Hg, 0.06 to 0.11 ppm as Pb, less than 0.32 ppm as Zn, 0.008 to 0.012 ppm as Cd, 0.61 to 0.68 ppm as Fe, 0.87 to 1.37 ppm as Cu, and nondetective as Cr. A high Cu content seems to be resulted by tile blood pigment of crustacea. The ratio,1 of edible portion to non-edible portion were 37:63 in fresh frozen and 42:58 in preboiled frozen krill respectively. Release of drip after thawing was more in fresh frozen than in preboiled frozen drill marking $36\%$ and $24\%$ of both respectively.

• Journal of Embryo Transfer
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• v.16 no.2
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• pp.117-125
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• 2001

Vitrification of oocytes has been applied recently fur pigs, but remains elusive. The purpose of this study is to investigate the effects of vitrification in open pulled straws (OPS) on in vitro survival of porcine oocytes. When immature follicular oocytes frozen-thawed were cultured for in vitro maturation, maturation rates to metaphase-II stage were higher in oocytes with (25%) than without (15%) cumulus cells. After In vitro fertilization of oocytes frozen-thawed, the maturation rates were also significantly (P<0.05) higher in oocytes with (41%) that than without (17%) cumulus cells. However, the penetration rates were higher in oocytes without (19%) that than with (9%) cumulus. In another experiment, porcine oocytes matured in vitro were frozen and thawed for in vitro fertilization. The penetration rates were higher than in oocytes without (35%) that than with (26%) cumulus cells. However, the proportions of oocytes dead after in vitro fertilization were significantly (P<0.05) higher in oocytes with that than without cumulus cells. On the other hand, the rates of penetration and dead oocytes at 6 h after in vitro fertilization were not significant differences between oocytes with and without cumulus cells. However, the proportions of dead oocytes with (18%) and without (16%) cumulus cells were higher than in oocytes of control group (0%). These finding indicated the possible broader application for OPS, as they demonstrated that the maturation and fertilization in vitro by frozen-thawed oocytes may be accompained by cumulus cells and culture periods according to the requirements of the survival ability after freezing of mature and immature oocytes in pigs.

• Korean Journal of Food Science and Technology
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• v.34 no.4
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• pp.617-624
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• 2002

Health drinks were prepared with freeze dried powder of 60% ethanol extract (60% EFDP), 60% ethanol extract after hydrolysis with amyloglucosidase (60% AEFDP) and 80% ethanol extract (80% EFDP) from roasted safflower seed. Quality characteristics and antioxidative properties were investigated. Yield of freeze dried powders were ranged in $4.67%{\sim}5.62%$. Brix, pH and titratable acidity of safflower drinks were ranged in $11.4{\sim}14.2%$, $2.83{\sim}3.34$ and $0.09{\sim}0.91%$, respectively. Content of total phenolic compounds was much more in 80% EFDP (117 mg/g) and safflower drink-I (SD-I, 440 ppm) than others. Content of total flavonoid was observed in higher level in 60% EFDP (49 mg/g) and safflower drink-V (SD-V, 138 ppm) than others. Antioxidant compounds such as N-[2-(5-hydroxy-1H-indol-3-yl)ethyl]ferulamide(serotonin-I) and N-[2-(5-hydroxy-1H-indol-3yl)ethyl]-p-coumaramide(serotonin-II) exhibited higher contents of 21.09 ppm, 33.56 ppm in 60% EFDP and of 3.83 ppm, 5.81 ppm in safflower drink-II (SD-II) than others. Content of acacetin was much more in 80% EFDP (13.53 ppm) and safflower drink-IV (SD-IV, 1.14 ppm) than others. From the DPPH test to measure antioxidant activity, it was shown that 80% EFDP and SD-I have stronger scavenging activities of 94.58% and 94.88%, respectively, while BHA standard solution does 93.88%. Among drinks, SD-II was revealed to have highest level on overall acceptance, color and flavor through sensory evaluation. These results induced that safflower seed can be used as natural antioxidant and functional food material.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.241-244
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• 1999

This study is represented the strength and freeing-thawing properties of recycled aggregate concrete mixed fly ash by experiment. The experimental variables are the substitution ratio of recycled aggregate and the mixing ratio of fly-ash. For each specimens, there were tested compressive strength and freeze-thaw resistance. It is able to find from the experimental result that the recycled aggregate concrete has good properties as general concrete on the compressive strength and the durability.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
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• 1997.06a
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• pp.106-106
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• 1997

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.625-630
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• 2002

The availability of natural aggregates has decreased in recent years due to depleting reserves. From the viewpoint of energy and resources saving, it may be advantageous to use the waste concrete as construction aggregates. The purpose of this study is to analyze petrographic and chemical properties of recycled aggregate, and to investigate the resistance of concrete to rapid freezing and thawing by using replacement ratios (0, 10, 20, 30, 40, 50, 60, 70, 100% ) of recycled aggregate.