• Journal of Veterinary Clinics
• /
• v.19 no.1
• /
• pp.80-85
• /
• 2002

This study was performed to investigate the freezomg condition especially focused on extender composition to achieve good post-thaw viability and motility of canine sperm. Semen were collected from 6 male dogs which had been proved to be fertile in the past and were treated for freezing. Equex-STM paste was contained in both the 1st(3%) and the 2nd(7%) diluent and the 2nd diluent was added to the 1st diluent following glycerol equilibration for an hour and a half. To investigate the effect of Equex-STM paste in the extender on post-thaw canine sperm characteristics, the post-thaw viability, motility, and HOS(Hypoosmotic swelling) values were evaluated according to the different composition of extender with or without Equex-STM paste, thawing conditions, and different thawing media added to thawed semen. 1. Canine sperm removed from seminal plasma and frozen )n Sweden extender containing Equex showed higher post-thaw viability, motility, and HOS values than those frozen in the extender containing Equex-STM paste with seminal plasma and those frozen in the extender without Equex and seminal plasma. 2. Canine sperm frozen in Sweden extender containing Equex-STM paste with 5% glycerol showed higher post-thaw viability, motility, and HOS values than those frozen with 3%, 8% glycerol or 5% DMSO. 3. The canine semen frozen in Sweden extender with 5% glycerol and Equex-STM paste showed higher viability, motility, and HOS values when thawed at $70^{\circ}C$ for 8 seconds than when thawed at $37.5^{\circ}C$ for 1 min and at $18-20^{\circ}C$ for 5 min. 4. TFC (tris -fructose-citrate) and PB S (phosphate buffered saline) medium added immediately to thawed canine semen brought better viability, motility, and HOS values for the sperm than those semen added with TGC(tris-glucose-citrate) and no medium. These results indicated that Equex-STM paste in Sweden extender for freezing the canine sperm which were removed from seminal plasma brought good post-thaw viability and motility of canine sperm. Also of the freezing conditions of canine sperm with the same extender containing Equex, the concentration of 5% glycerol, the thawing condition at $70^{\circ}C$ for 8 sec, and TFC and PBS medium added to the thawed semen brought better post-thaw viability and motility of canine sperm than the other conditions used in this study.

• Journal of the Korea Concrete Institute
• /
• v.20 no.1
• /
• pp.13-22
• /
• 2008

The initiation and growth processes of cyclic ice body in porous systems are affected by the thermo-physical and mass transport properties, as well as gradients of temperature and chemical potentials. Furthermore, the diffusivity of deicing chemicals shows significantly higher value under cyclic freeze-thaw conditions. Consequently, the disintegration of concrete structures is aggravated at marine environments, higher altitudes, and northern areas. However, the properties of cyclic freeze-thaw with crack growth and the deterioration by the accumulated damages are hard to identify in tests. In order to predict the accumulated damages by cyclic freeze-thaw, a regression analysis by the response surface method (RSM) is used. The important parameters for cyclic freeze-thawdeterioration of concrete structures, such as water to cement ratio, entrained air pores, and the number of cycles of freezing and thawing, are used to compose the limit state function. The regression equation fitted to the important deterioration criteria, such as accumulated plastic deformation, relative dynamic modulus, or equivalent plastic deformations, were used as the probabilistic evaluations of performance for the degraded structural resistance. The predicted results of relative dynamic modulus and residual strains after 300 cycles of freeze-thaw show very good agreements with the experimental results. The RSM result can be used to predict the probability of occurrence for designer specified critical values. Therefore, it is possible to evaluate the life cycle management of concrete structures considering the accumulated damages due to the cyclic freeze-thaw using the proposed prediction method.

• Development and Reproduction
• /
• v.2 no.1
• /
• pp.63-68
• /
• 1998

This study was done to find optimal cryopreservation medium and method to improve the post-thaw motility of human sperm. Thirty three semaen samples were included in the study. Of these, nineteen Samples showing normal semen profile were frozen using three cryprotectants (TYB, TYB+DTT and KS II)to compare post-thaw motility. Fourteen samples were frozen with vapor freezing and programmable freezing methods to compare post-thaw motility in correlation with freezing method. After 24 hrs of cryostorage , the vials were thawed and the post-thaw sperm motility was assessed by two kinds of computer-aededsperm analysis (CASA; SAIS and Hamilton Thorn). As a result, the post-thaw motility of the KS II group was higher than the TYB or TYB+DTT group in normal semen(34.8%, 28.3% and 23.0%, respectively). In the asthenospermia group, a significantly hither post-thaw motility was observed in the KS II (18.5%) compared to those of TYB or TYB+DTT group (13.6%, 10.0%, respectively). No difference was observed between vapor freezing group and computerized freezing group in normal semen (27.8%, 33.2%, respectively) and semen group showing asthenospermia (12.8%, 12.9%, respectively). In conclusion, our results indicate that KS II medium is reliable for cryopreservation of human sperm and vapor freezing and programmable freezing were equally effective in terms of the recovery of motile spermatozoa.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.1
• /
• pp.49-58
• /
• 2017

The phenomena that we experience in everyday life such as snow, rain, wind, and temperature are referred to as weather, and the average state of atmospheric phenomena that occur over a long period of time in a specific region is referred to as climate. In addition, significant variation of climate compared to the average state is referred to as climate change. Concrete structures can have various problems when exposed to elements. Among the problems, the freeze-thaw problem due to extreme climatic factors such as heavy rain and snowfall has become a particularly significant issue recently. The concrete that has been subjected to repeated freeze-thaw rather than too high or low temperature shows serious degradation of durability, and the performance of structures with degraded performance is difficult to recover. Therefore, in this study, concrete durability performance with respect to freeze-thaw from curing conditions change due to wind speed and sunshine exposure time. Concrete freeze-thaw experiment are performed. using wind speed and sunlight exposure time. Also, performance based evaluation through the satisfaction curve based on the freeze-thaw test results are performed.

• Journal of The Geomorphological Association of Korea
• /
• v.19 no.3
• /
• pp.109-121
• /
• 2012

Rock-surface temperatures were observed at a trachytic lava dome, called as Baeknokdam Northwest Face, in the summit area of Mt. Halla, Jeju Island, to examine the frequency and occurrence season of freeze-thaw cycles and the rate of temperature changes during a freezing period. Long-term measurements were recorded over 18 months from November 2006 to April 2008, at a 1-hour logging interval and rock depth of 1.5 cm. Both diurnal freeze-thaw cycles and effective freeze-thaw cycles appear in larger numbers on a south-facing rock face than a north-facing rock face. The diurnal cycles were dominantly observed on February and March for the south face and on November and April for the north face, respectively. The annual freeze-thaw cycles were confirmed in terms of the presence of seasonal freezing periods lasting from mid-November to mid-April for the south face and from early-November to late-April for the north face, respectively. The rate of decreasing temperatures during the seasonal freezing periods is larger on the north face than the south face. Notwithstanding the lower numbers of freeze-thaw events, the north face experiences a higher frost intensity since the number of hours below $-3^{\circ}C$ is larger on the north face than the south face. The number of freeze-thaw events and the duration of days with continuous sub-zero rock temperatures largely depend on the solar radiation controlled by the aspect of the monitored rock surfaces, and thus the high-frequency short-term frost cycle dominantly appears on the south face and the annual frost cycle on the north face, respectively.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.6
• /
• pp.148-156
• /
• 2022

Although most domestic concrete structures are simultaneously exposed to freeze-thaw and chloride environments, concrete durability in the field is evaluated by each single action, and the evaluation of chloride-caused damage of concrete requires additional indoor experimental analysis of chloride contents by coring samples from structures in the field. However, in Korea, policies to strengthen facility maintenance, such as 「Special Act on the Safety Control and Maintenance of Establishments」 and 「Framework Act on Sustainable Infrastructure Management」, have been established and implemented since 2018 and facilities subject to safety inspection management by the government and local governments increases, the effective simplification technology for the inspection and diagnosis of concrete structure is needed. Therefore, this study attempted to evaluate the possibility of determining the acceleration chloride penetration of freeze-thaw damaged concrete by using the surface rebound value. For this purpose, concrete specimens already having freeze-thaw damage by exposure to the freeze-thaw acceleration environment were immersed in chloride water. After that, the acceleration relationship of chloride penetration according to freeze-thaw damage was analyzed using the amount of chloride contents in concrete.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.12 no.5
• /
• pp.161-168
• /
• 2008

The freeze-thaw deterioration and chloride attack, which are the typical degradation factors for durability of marine concrete, are significantly affected by pore structures in terms of penetration and diffusion. These pore structures of concrete are closely related to the types and amount of AE agent, used to guarantee the resistance of freeze-thaw deterioration, and the elapsed time before concrete pouring. This paper evaluates the durability of concrete based on the results of tests on cylinder specimens and core specimens from mock-up members with different air content of 4~6% and 8~10%, respectively. According to the test results, the air content of hardened concrete is 2.5~5.2% at 7 days and 2.4~5.1% at 28 days. These air contents are about half of the initial values just after the concrete mixing. Judging from the amount of scale after the freeze-thaw test completed, air content of 8~10% is slightly more beneficial against the deterioration of concrete than air content of 4~6%. Meanwhile, the core specimens from mock-up members exhibit somewhat unfavorable freeze-thaw deterioration and chloride migration characteristic compared with the cylinder specimens tested in the laboratory under the same mixing condition, as to show 106% in freeze-thaw test and 160% in chloride diffusion coefficient test, respectively.

• Food Science and Biotechnology
• /
• v.15 no.5
• /
• pp.805-813
• /
• 2006

The quality of frozen bread dough made with the milk proteins casein (C), whey (W), and the gums sodium alginate (A) and ${\kappa}$-carrageenan (K), was investigated to develop methods to suppress the deterioration of the frozen dough quality. The control had a lower dough volume than dough with additives during freeze-thaw cycles. In bread stored at $5^{\circ}C$, the moisture content of bread prepared with whey plus sodium alginate (WA) decreased less than that of the control. The control also had a lower specific loaf volume than breads made with added milk proteins and gums. The hardness of the control bread and bread made with casein plus sodium alginate (CA) and whey plus ${\kappa}$-carrageenan (WK) increased during freeze-thaw cycles, although that of the control increased more than the others. There was no significant difference in sensory preference among breads with and without milk proteins and gums. Addition of CA and WA improved the baking quality by reducing the deterioration of frozen dough and retarding the staling of bread.

• Clinical and Experimental Reproductive Medicine
• /
• v.17 no.1
• /
• pp.81-85
• /
• 1990

We cryopreserved mouse morulae by a simple ultra-rapid method of freezing embryos directly in $LN_2$ after holding 2min in a $LN_2$ vapor, and thawed them in $37^{\circ}C$ water bath. The time requirements for permeation and dehydration by 2.0 M glycerol and 0.2 M sucrose before freezing were studied. When the embryos were equilibrated for 10 min, the optimun post-thaw survival was obtained. Embryos those developed normally to blastocyst after in vitro culture for over 24hrs were regarded as survival ones. Two experiments to assess post-thaw survival following predehydration in various mixtures of glycerol and sucrose were also accomplished. When sucrose was held constant (0.2 M) and glycerol concentration varied (1.5-3.5 M), post-thaw survival was best (78.0%) in 3.0 M glycerol. When glycerol was held constant (3.0M) and sucrose concentration varied (0.0-1.0M), optimun post-thaw survival (78.0%) was found in 0.2 M sucrose.

• Advances in concrete construction
• /
• v.6 no.2
• /
• pp.159-175
• /
• 2018

The main aim of this study is to investigate the possible effects of metakaolin on strength and durability properties of concrete. For this purpose, concrete mixtures are produced by substituting cement with metakaolin 0, 5, 10 and 20% by weight. The amount of binder for the concrete mixtures are 300 and $400kg/m^3$ with a constant water to cement ratio of 0.6. Compressive and bending strengths, freeze-thaw and high-temperature resistances, capillary coefficients and rapid chloride permeability properties were determined and compared each other. Because of all the experiments conducted, it has been found that the use of metakaolin as a pozzolanic additive in concrete have positive effects especially on compressive and bending strengths, capillary, rapid chloride permeability, freeze-thaw resistance, and high temperatures, up to $800^{\circ}C$. The results indicated that the performance of concrete can be enhanced by metakaolin. Particularly, compressive strength and durability properties have found to be improved with increasing metakaolin content which is attributed to pozzolanic activity and filler effect. Furthermore, metakaolin has relatively positive impacts under elevated temperatures and freeze-thaw effects. However, almost all the strengths of entire concrete specimens are lost at $800^{\circ}C$. Consequently, the optimum metakaolin substitution ratio can be suggested to be 20% as per this study.