• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.4
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• pp.46-55
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• 2021

Concrete structures can cause various problems as the number of common years increases when exposed to external extreme climate conditions. Among these problems, freezing and thawing occur due to the action of extreme climate factors such as heavy rain and heavy snow, which have become the most problematic in recent years. In this study, we present a rapid freezing and thawing test method of concrete in the air, referring to KS F 2456, as Seoul exhibits very dry weather during the period of freezing and thawing. Concrete test specimens and RC beams were fabricated to perform rapid freezing and thawing of 0, 100, 200, and 300 cycles, and the performance evaluation confirmed the degradation of each subject in material and member units. The design strength of 24 MPa, which performs rapid freezing and thawing in the air up to 300 cycles, decreases by 5.24 MPa (21%), and as rapid freezing and thawing in the air increases the stress burden on reinforced concrete bending members, reducing the energy absorption (dissipation) ability of structures due to earthquakes.

• Korean Journal of Veterinary Research
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• v.33 no.1
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• pp.171-178
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• 1993

The present study was carried out to investigate the developmental potency to blastocyst after freezing and thawing of nuclear transplanted 2-cell embryos. The nuclei from 2-, 4- and 8-cell mouse embryos were transferred into enucleated 2-cell embryos, and the reconstituted embryos were submitted to direct current(DC) pulse at output voltage of 2.0 kV/cm for $100{\mu}$ sec to induce cell fusion. The recovery rate and developmental potency to blastocyst after freezing and thawing of nuclear transplanted 2-cell embryos was investigated. 1. The recovery rate of nuclear transplanted 2-cell embryos in normal morphology after freezing and thawing was significantly higher in rapid freezing(DMSO 4.5M) than in slow cooling(p<0.01). 2. When the recovered embryos in normal morphology were cultured in vitro, there were no significant differences in the developmental potency to blastocyst between the freezing methods and the concentrations of cryoprotectant. In summary, these experiments have proved that rapid freezing method(DMSO 4.5M) is effective in nuclear transplanted 2-cell mouse embryos. If improved micromanipulation techniques and freezing are combined, nuclear transplantation technique will contribute to the improvement of productivity in livestock animals.

• Clinical and Experimental Reproductive Medicine
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• v.26 no.2
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• pp.127-135
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• 1999

Cryopreservation is able to store the surplus pre-embryos for freezing and furthermore thawing and transfer in a subsequent cycle. Cryopreserving cells which are maintaining their viability are the very complex process. This study has been carried out in order to find the effects of cryopreservation steps, freezing media and embryonic stages on the rates of viability and development of cryopreserved mouse embryos. Female ICR mice ($6{\sim}8$ weeks old) were induced to superovulate by sequential intraperitoneal injection of 5 IU PMSG and 5 IU hCG 48h apart. Mouse embryos were collected according to its developmental stage after the injection of hCG. Embryos were cryopreserved not only by cryoprotectant step (1 step${\sim}$4 step) but also in a variety of media (HTF, IVF medium, D-PBS) and cell stage. The results were as follows: There is no clear advantage in these freezing media of rapid method, but 4 cell and 8 cell of slow method (2, 3, 4 step) have advantage in D-PBS. The development of embryos according to cell stage become greater in 8 cell stage. In the treatment steps of cryopreservation, the development of embryo to blastocyst was similar among rapid method, but the development of 4 cell and 8 cell embryos to blastocyst according to slow method was better than rapid method.

• Bulletin of the Korean Chemical Society
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• v.29 no.2
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• pp.352-356
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• 2008

An analytical method has been developed for measuring chlorostyrenes in fish tissue sample. Extraction of chlorostyrenes from fish tissue was carried out by ultrasonication using acetone/n-hexane (5:2, v/v) mixture. Most of the lipids in the extract were eliminated by freezing-lipid filtration, prior to solid-phase extraction (SPE) cleanup. During freezing-lipid filtration, about 90% of the lipids extracted from the fish samples were easily removed without any significant losses of chlorostyrenes. For purification, SPE using Florisil was used for the rapid and effective cleanup. Quantification was performed using gas chromatography-mass spectrometry in the selected ion monitoring mode. Spiking experiments were carried out to determine the recovery, precision, and limits of detection (LODs) of the method. The overall recovery was above 80% in the spiked fish tissue sample at 10 and 100 ng/g levels, respectively. The detection limits for chlorostyrenes were ranged from 0.05 to 0.1 ng/g. This developed method is demonstrated to give efficient recoveries and LODs for detecting chlorostyrenes spiked into fish tissue with high lipid content.

• Applied Microscopy
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• v.20 no.2
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• pp.1-11
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• 1990

The ultrastructure of freeze-substituted Malpighian tubule cells of German cockroach after rapid freezing was compared to that fixed with conventional chemical fixation. As results, freeze-substitution proved to be the superior technique revealing much more structural details of the tissue cells. Especially, all kinds of membrane structures including infoldings, microfilament, microtubules and ribosomes were best preserved in this material.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.294-300
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• 1999

After researching the physical properties of the concrete included Rice Husk Ash(RHA concrete) and workability of fresh concrete admixed RHA, we have tested durability of RHA-concrete against freeaing and thawing in the winter using rapid freezing and thawing test method(KS F 2456) . There aretwo hypotheses to explain the failure mechanism of a freezing and thawing action. First, the hydraulic pressure in the pores of freezing concrete make an internal stress of concrete structures outbreaking micro crack in the face of concrete, Second, Frost action causing damage to cement paste repeatedly come from soil frost action, freezing water in the capillaries. Initial Relative Dynamic Modulus of Elasticity (DME) was biggest in cae of unit binder weight 600kgf/㎥ and relative dynamic modulus of elasticity increased until 300cycles. In general , initial relative DME was proportional to unit binder weight . Relative DME was decreased in proportion to unit binder weight in the case of 300, 400, 500kgf/㎥ , but relative DME fo the others remained more than 90% until 300 cycles. It was not good effect of intermixed RHA to concrete in case of below unit binder weight 300kgf/㎥ and the resistance of freezing and thawing was not good either.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.5
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• pp.401-412
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• 2016

It is extremely difficult to apply conventional grouting methods to subsea tunnelling construction in the high water pressure condition. In such a condition, the rapid artificial freezing method can be an alternative to grouting to form a watertight zone around freezing pipes. For a proper design of the artificial freezing method, the influence of salinity on the freezing process has to be considered. However, there are few domestic tunnel construction that adopted the artificial freezing method, and influential factors on the freezing of the soil are not clearly identified. In this paper, a series of laboratory experiments were performed to identify the physical characteristics of frozen soil. Thermal conductivity of the frozen and unfrozen soil samples was measured through the thermal sensor adopting transient hot-wire method. Moreover, a lab-scale freezing chamber was devised to simulate freezing process of silica sand with consideration of the salinity of pore-water. The temperature in the silica sand sample was measured during the freezing process to evaluate the effect of pore-water salinity on the frozen rate that is one of the key parameters in designing the artificial freezing method in subsea tunnelling. In case of unfrozen soil, the soil samples saturated with fresh water (salinity of 0%) and brine water (salinity of 3.5%) showed a similar value of thermal conductivity. However, the frozen soil sample saturated with brine water led to the thermal conductivity notably higher than that of fresh water, which corresponds to the fact that the freezing rate of brine water was greater than that of fresh water in the freezing chamber test.

• Food Science of Animal Resources
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• v.36 no.5
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• pp.650-655
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• 2016

This study investigated the effects of artificial supercooling followed by still air freezing (SSF) on the qualities of pork loin. The qualities of pork frozen by SSF were compared with the fresh control (CT, stored at 4℃ for 24 h), slow freezing (SAF, still air freezing) and rapid freezing (EIF, ethanol immersion freezing) treatments. Compared with no supercooling phenomena of SAF and EIF, the extent of supercooling obtained by SSF treatment was 1.4℃. Despite that SSF was conducted with the same method with SAF, application of artificial supercooling accelerated the phase transition (traverse from -0.6℃ to -5℃) from 3.07 h (SAF) to 2.23 h (SSF). The observation of a microstructure indicated that the SSF prevented tissue damage caused by ice crystallization and maintained the structural integrity. The estimated quality parameters reflected that SSF exhibited superior meat quality compared with slow freezing (SAF). SSF showed better water-holding capacity (lower thawing loss, cooking loss and expressible moisture) and tenderness than SAF, and these quality parameters of SSF were not significantly different with ultra-fast freezing treatment (EIF). Consequently, the results demonstrated that the generation of supercooling followed by conventional freezing potentially had the advantage of minimizing the quality deterioration caused by the slow freezing of meat.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.48-53
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• 2003

The steel slag, a by-product which is produced on the process of manufacturing steel by refining pig iron is mainly used as road materials after aging it. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the volume expanded. Due to this reason it prevents steel slag from being used as aggregate of concrete. But steel slag used in this study is controled by a air-jet method which rapidly cools substance melted at a high temperature. Rapid cooling prevents from generating of free-CaO in steel slag. In this study, it was investigated that steel slag manufactured by air-jet method affects on concrete in the freezing and thawing. As results of this study, concrete mixed with steel slag was worse in the freezing and thawing than concrete mixed with sand in spite of using air entraining agent. To obtain durability of concrete in the freezing and thawing, it is desirable to mix 50% of steel slag in concrete per unit weight of volume.

• Clinical and Experimental Reproductive Medicine
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• v.25 no.2
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• pp.129-134
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• 1998

The objective of this study was to test whether the developmental capacity of human multi-pronuclear (PN) zygotes after ultra-rapid freezing using EM grid can be maintained. For this experiment, multi-PN zygotes which produced in human IVF program were used as an alternatives of normal 2PN zygotes, and they were separated into 3PN or $\geq4PN$ zygotes to compare their in vitro development and cryoinjury according to PN number. As freezing solution, EFS30 which consisted of 30% ethylene glycol, 18% bcoll, 0.5 M sucrose and 10% FBS added D-PBS was used. The result obtained in this experiment was summarized as follows; When the multi..PN zygotes were ultrarapidly frozen and thawed, the high mean percentages (85.5%) were survived. Also when the cleavage rates between control and freezing group were compared with PN number, there were not significantly different in each group (3PN; 81.3% & 85.4% and $\geq4PN$; 90.0% & 95.7%). When the in vitro development rates after thawing were examined, freezing 3PN group (22.0%) was not differed to control 3PN group (38.5%), although the development result of freezing $\geq4PN$ group (45%) was significantly lower than that of control $\geq4PN$ group (44.4%) (p<0.05). These results demonstrate that developmental capacity of human zygote can be obtained by ultra-rapid freezing method using EM grid and EFS30.