• Journal of Embryo Transfer
• /
• v.27 no.4
• /
• pp.259-264
• /
• 2012

Solution of glycerol, ethylene glycol, sucrose, dextrose (GESD) and cryotop methods were carried out to investigate the survivability on vitrification of embryos. Embryos cultured in vitro were vitrified by GESD of 10 or 8 step and cryotop methods of 6 step, from cryopreservation step to frozen-thawed and culture step. Survival rate and ICM, TE cells of embryos were investigated after frozen-thawed 24 h. As a results, cryotop method was significantly (p<0.05) higher ($85.76{\pm}5.3$ vs. $66.71{\pm}2.4$, $44.80{\pm}2.1%$) than GESD 10 or 8 step methods on survivability. Also, In ICM cell number, cryotop method was significantly (p<0.05) higher to $45.67{\pm}4.7$ cells than GESD 8 step method. TE cell number was significantly (p<0.05) highest to $111.00{\pm}11.0$ cells in cryotop method. On the other hand, survival rate, TE and total cell number were all the significantly (p<0.05) high, except ICM in GESD 10 step method between GESD 10 step method and GESD 8 step method. In conclusion cryotop method was to be most effective, but it is considered necessary to study vitrification method for step-by-step freezing and thawing process.

• Journal of the Korean GEO-environmental Society
• /
• v.14 no.3
• /
• pp.35-40
• /
• 2013

In most cases, Geotechnical Structures installed in freezing areas require extra countermeasures for reducing freeze damage. However, in terms of domestic tunnels, studies and case reports for geotechnical structures such as tunnels and retaining walls are not fluently carried out, causing lack of research about ways to decrease freeze damage. For these causes, domestic design criteria about structures does not specifically institutionalization for geotechnical structures. This research have done on-site investigation about tunnels, cut slopes and retaining walls. Also, this research includes the process of analyzing the histories of maintenance for class 1 and class 2 structures that happened in the past 40 years, studying characteristics of structure's maintenance and reinforcement in different areas with different climate. As the result, it was analyzed that domestic geotechnical structures showed need for longer maintenance and reinforcement that are located in Gangwon mountain area, Gangwon north region and Gyeonggi north region where the temperature is relatively low. This research can be concluded in need for revision of design criteria for structures located in freeze damage area.

• Journal of ILASS-Korea
• /
• v.8 no.2
• /
• pp.1-6
• /
• 2003

The liquid phase LPG injection (LPLI) system (the third generation technology) has been considered as one of the next generation fuel supply systems for LPG vehicles, since it has a very strong potential to accomplish the higher power, higher efficiency, and lower emission characteristics than the mixer type(the second generation technology) fuel supply system However. when a liquid LPG fuel is injected into the inlet duct of an engine, a large quantity of heat is extracted due to evaporation of fuel. This leads to freezing of the moisture in the air around the outlet of a nozzle, which is called icing phenomenon. It may cause damage to the outlet nozzle of an injector or inlet valve seat. In this work, the experimental investigation of the icing phenomenon was carried out The results showed that the icing phenomenon and process were mainly affected by humidity of inlet air instead of air temperature in the inlet duel. Also, it was observed that the total ice formed around the nozzle weighs at about $150mg{\sim}260mg$ after injection for ten minutes. And some fuel species were found in the ice attached at the front side of a nozzle, while frozen ice attached at the back of a nozzle was mostly' consisted of moisture of inlet air. Therefore, some frozen ice deposit. detached from front nozzle of an injector, may cause a problem of unfavorable air fuel ratio control in the small LPLI engine.

• Macromolecular Research
• /
• v.12 no.4
• /
• pp.367-373
• /
• 2004

We have developed a rigorous heat treatment method to improve the biocompatibility of chitosan as a tissue-engineered scaffold. The chitosan scaffold was prepared by the controlled freezing and lyophilizing method using dilute acetic acid and then it was heat-treated at 110$^{\circ}C$ in vacuo for 1-3 days. To explore changes in the physicochemical properties of the heat-treated scaffold, we analyzed the degree of deacetylation by colloid titration with poly(vinyl potassium sulfate) and the structural changes were analyzed by scanning electron microscopy, Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffractometry (WAXD), and lysozyme susceptibility. The degree of deacetylation of chitosan scaffolds decreased significantly from 85 to 30% as the heat treatment time increased. FT-IR spectroscopic and WAXD data indicated the formation of amide bonds between the amino groups of chitosan and acetic acids carbonyl group, and of interchain hydrogen bonding between the carbonyl groups in the C-6 residues of chitosan and the N-acetyl groups. Our rigorous heat treatment method causes the scaffold to become more susceptible to lysozyme treatment. We performed further examinations of the changes in the biocompatibility of the chitosan scaffold after rigorous heat treatment by measuring the initial cell binding capacity and cell growth rate. Human dermal fibroblasts (HDFs) adhere and spread more effectively to the heat-treated chitosan than to the untreated sample. When the cell growth of the HDFs on the film or the scaffold was analyzed by an MTT assay, we found that rigorous heat treatment stimulated cell growth by 1.5∼1.95-fold relative to that of the untreated chitosan. We conclude that the rigorous dry heat treatment process increases the biocompatibility of the chitosan scaffold by decreasing the degree of deacetylation and by increasing cell attachment and growth.

• Korean Journal of Materials Research
• /
• v.23 no.1
• /
• pp.67-71
• /
• 2013

Porous $Al_2O_3$ dispersed with nano-sized Cu was fabricated by freeze-drying process and solution chemistry method using Cu-nitrate. To prepare porous $Al_2O_3$, camphene was used as the sublimable vehicle. Camphene slurries with $Al_2O_3$ content of 10 vol% were prepared by milling at $50^{\circ}C$ with a small amount of oligomeric polyester dispersant. Freezing of the slurry was done in a Teflon cylinder attached to a copper bottom plate cooled to $-25^{\circ}C$ while unidirectionally controlling the growth direction of the camphene. Pores were subsequently generated by sublimation of the camphene during drying in air for 48 h. The green body was sintered in a furnace at $1400^{\circ}C$ for 1 h. Cu particles were dispersed in porous $Al_2O_3$ by calcination and hydrogen reduction of Cu-nitrate. The sintered samples showed large pores with sizes of about $150{\mu}m$; these pores were aligned parallel to the camphene growth direction. Also, the internal walls of the large pores had relatively small pores due to the traces of camphene left between the concentrated $Al_2O_3$ particles on the internal wall. EDS analysis revealed that the Cu particles were mainly dispersed on the surfaces of the large pores. These results strongly suggest that porous $Al_2O_3$ with Cu dispersion can be successfully fabricated by freeze-drying and solution chemistry routes.

• Journal of Korea Foundry Society
• /
• v.31 no.5
• /
• pp.293-301
• /
• 2011

Representative magnesium alloys applied to the die-casting are AZ91, AM60, etc., and the application of these alloys is restricted to components operating at moderate temperatures, due to grain boundary siding of ${\beta}$-phase($Mg_{17}Al_{12}$) at temperatures above $120^{\circ}C$. Heat-resistant magnesium alloys such as AE42, AE44 have been developed, but that have been too burdensome to produce because of the expensive rare earth materials. Research work for the development of low-priced heat-resistant magnesium alloy is actively in progress and positive results are being reported. This study aims to investigate the effect of Ca additions on mechanical properties of Mg-4Al-2Sn heat resistant magnesium alloys. Mg-4Al-2Sn alloys with Ca (0wt.%, 0.3wt.%, 0.7wt.%, 1wt.%) have been produced through the die-casting process for the development of low-priced heat-resistant magnesium alloy, and high temperature tensile tests are performed using the specimens. The results showed that mechanical properties of Mg-4Al-2Sn-xCa increased with the addition of Ca up to 0.7wt.% Ca and further addition of Ca deteriorated the mechanical properties of the alloys. A significant amount of porosity was observed at the sample with 1wt%. Ca and the longer freezing range of the alloy was believed to cause the formation of porosity.

• Journal of Fisheries and Marine Sciences Education
• /
• v.17 no.2
• /
• pp.193-208
• /
• 2005

The object of this study is to provide a framework of increasing the effectiveness of the R&D planning of experts in fisheries and the education of students with the theoretical background and analytical skills through the adoption of technology roadmapping process in the marine production industry. The study was conducted by fact-finding surveys and the response content for surveys obtained from each expert advisor in the field of fisheries and maritime affairs such as fishery industries, some government organizations and research institutes including the Ministry of Maritime Affairs and Fisheries (MOMAF), National Fisheries Research and Development Institute (NFRDI) and fisheries-related universities was analyzed. The major implementation tasks to effectively achieve the basic goals of technology roadmap for short and middle-term research and development in the fisheries production field are as follows: 1. Research in order to achieve the realization of community-based resource management fisheries or fishermen-oriented co-management fisheries with paradigm shift in fisheries management. 2. Research in order to derive the construction of cost reducing and manpower saving systems in fishery-related science, technology and engineering. 3. Research in order to create the high value-added fisheries products with a focus on the upgrading of processing, freezing and refrigerating facilities, the reduction of logistics costs and the minimization of distribution steps. 4. Research in order to achieve the realization and development of environmental-friendly fisheries and internationally competitive fisheries through restructuring the entire fishing industries, in particular, small-scale fisheries. 5. Research in order to achieve the effective utilization of fisheries resources with a new creation of clean and living marine environment by fisherman under the balanced management and protection of marine living resources and fishing grounds.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.3
• /
• pp.700-712
• /
• 2011

Due to recently advanced electrical devices, human can access computer network regardless of working location or time restriction. However, currently widely used mouse, joystick, and trackball input system are not easy to carry and they bound user hands exclusively within working space. Those make user inconvenient in Ubiquitous environments.. In this paper, we propose multiple dimension human motion detection system based on wireless sensor networks. It is a portable input device and provides easy installation process and unbinds user hands during input processing stages. Our implemented system is comprised of three components. One is input unit that senses user motions and transmits collected data to receiver. Second is receiver that conveys the received data to application, which runs on server computer. Third is application that performs command operations according to received data. Experiments shows that proposed system accurately detect the characteristics of user arm motions and fully support corresponding input requests.

• Development and Reproduction
• /
• v.23 no.1
• /
• pp.11-19
• /
• 2019

The study was conducted to investigate the effects of alpha-linolenic acid (ALA) combined with bovine serum albumin (BSA) or methyl-beta-cyclodextrin (MBCD) on plasma and acrosomal membrane damages, mitochondrial activity, morphological abnormality, motility, and oxidative stress in frozen-thawed boar sperm. In previous our study, 3 ng/mL ALA had been shown protective effect during freezing process of boar sperm. Therefore, we used 3 ng/mL ALA in present study and ALA was combined with same molar ratio of BSA or MBCD (ALA+BSA and ALA+MBCD, respectively). To confirm the effect of two carrier proteins, same volume of BSA and MBCD without ALA were added during cryopreservation. Membrane damage, mitochondrial activity, reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were measured using flow cytometry, and movement of sperm tail as motility parameter and morphological abnormality were observed under light microscope. In results, all of sperm parameters were enhanced by ALA combined with BSA or MBCD compared to control groups (p<0.05). Mitochondrial activity, morphological abnormality, ROS and LPO levels in ALA+BSA or MBCD groups were no significant difference compared with ALA, BSA and MBCD treatment groups. On the other hand, plasma and acrosomal membrane intact, and sperm motility in ALA+MBCD group were higher than single treatment groups (p<0.05), whereas ALA+BSA did not differ. Our findings indicate that carrier proteins such as BSA and MBCD could improve the effect of ALA during cryopreservation of boar sperm, and treatment of ALA with carrier proteins enhance membrane integrity, mitochondrial activity through reduction of ROS-induced LPO.

• Journal of Sericultural and Entomological Science
• /
• v.53 no.2
• /
• pp.101-109
• /
• 2015

To extend shelf life of mulberry fruits, usually expensive freeze drying of freezing process is required. In this study an economic to multipurpose agricultural products dryers with mulberry dryer and technique was developed to reduce postharvest processing cost. Fuel and electricity consumption for drying were lowest when drying temperature was $60^{\circ}C$. And various drying conditions (fuel 3 hrs, heat 1 hr, room temperature air velocity 51 hrs) of the developed dryer were analyzed to improve drying performance. Dried mulberry fruits had dark brown color and marketable high quality explain the semi-dried characteristics.