• Biotechnology and Bioprocess Engineering:BBE
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• v.5 no.5
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• pp.372-378
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• 2000

The cell culture of Angelica gigas Nakai producing decursin derivatives and immunostimulating polysaccharides was preserved in liquid nitrogen after pre-freezing in a deep freezer at -70$^{\circ}C$ for 480 min. The effects of the cryoprotectant and pretreatment before cooling were investigated to obtain the optimal procedure for cyropreservation. When compared to mannitol, sorbitol, or NaCl with a similar osmotic pressure, 0.7 M sucrose was found to be the best osmoticum for the cryopreservation of A. gigas cells. In the pre-culture medium, the cells in the exponential growth phase showed phase showed the best post-freezing survival after cryopreservation. A mixture of sucrose, glycerol, and DMSO was found to be an effective cryoprotectant and a higher concentration of the cryoprotectant provided better cell viability. When compared with the vitrification, the optimum cryopreservation method proposed in this study would seem to be more effective for the long-term storage of suspension cells. The highest relative cell viability established with the procedure was 89%.

• Journal of the Korea Safety Management & Science
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• v.19 no.3
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• pp.1-9
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• 2017

In the industrial field, various type of fuel have been used for product processing facilities. Recent for 10 years, the usage of natural gas (NG) was gradually increased. Because it has many merits; clean fuel, no transportation, storage facility and so on. There are common safety concept that strict explosion protection approaches are needed for facilities where explosive materials such as flammable liquid, vapor and gases exist. But some has an optimistic point of view that the lighter than air gases such as NG disperse rapidly, hence do not form explosion environment upon release into the atmosphere, many parts has a conventional safety point of view that those gases are also inflammable gases, hence can form explosion environment although the extent is limited and present. In this paper, the heating equipments (Hot Oil Heater) was reviewed and some risk management measures were proposed. These measures include hazardous area classification and explosion-proof provisions of electric apparatus, an early gas leak detection and isolation, ventilation system reliability, emergency response plan and training and so on. This study calculates Hazardous Area Classification using the hypothetical volume in the KS C IEC code.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.3
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• pp.63-69
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• 1998

In this paper, a new input method is proposed to improve shift-invariant property of a photorefractive correlator andwe implemented real-time optical pattern recognition system using it. In the conventional photorefractive correlator, it is vrey difficult to satisfy the Bragg condition in the pattern recognition process. So, correlation peak is decreased heavily for the shift of input image. If a liquid crystal television(LCTV) without an anlyzer is used as input device, we can get the correlation result regardless of shift of input image because beam path is not changed during storage of holographic filter and correlation process. Also recording time of a holographic matched filter in photorefractive crystal is reduced and the correlation peak is increased because incident beam on the LCTV is transmitted completely. Therefore total optical efficiency is improved. We compared and analyzed the correlation results of proposed photorefractive correlator by computer simulation and optical experiment. We used a BaTiO$_{3}$ single crystal which has high diffraction efficiency in optical experiment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.289-296
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• 2001

We propose a method to add phase-modulation to binary amplitude data pages using a twisted-nematic liquid crystal display as a dynamic phase mask. For this, the phase modulation characteristics of the display were examined both theoretically and experimentally, and an unexpected abnormal phenomenon was found experimentally in which the modulation property changed as the incident beam intensity increased. To investigate the characteristics of holographically storing the binary data images, eight pages of holograms were stored at one spot of in un-thick Dupont's photopolymer with angle multiplexing. When phase-modulation-added pages were stored at the Fourier plane, the uniformity of the signal beam at the plane was improved, and thus more holograms can be recorded with our method, compared with the conventional case of using only binary amplitude modulation under the same condition.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.573-576
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• 2010

The propulsion systems such as upper stages of launch vehicles, orbiters, spacecrafts have to operate in the zero gravity environment. Because the flight condition where the vehicle undergoes is different from the normal gravity state, many studies have been being in progress. Fluid behavior in the zero gravity condition is differently shown in the normal gravity state because the importance of the intermolecular force, such as adhesion, cohesion, and surface tension is enlarged. In this paper, we investigate the characteristic of fluid behavior and describe effects and problems on the liquid propulsion system due to these fluid behavior. We also check which studies are in progress in order to solve these problems.

• Journal of Aquaculture
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• v.21 no.1
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• pp.54-59
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• 2008

The present study aimed to find the best diluent and cryoprotectant for sperm cryopreservation of filefish Thamnaconus modestus. Two kinds of artificial seminal plasma(ASP1, ASP2), 0.3 M glucose and marine fish Ringer's solution(MFRS) were employed as diluent. Dimethyl sulfoxide(DMSO) and methanol as cryoprotectant were selected for sperm cryopreservation. Sperm was diluted at the ratio of 1:3 with diluents containing cryoprotectants and adjusted for final concentration at 5%, 10%, 15% and 20%. Mixed milt was frozen at liquid nitrogen vapor after equilibration for 5 min. The highest motility($40.5{\pm}2.8%$) and swimming speed($81.5{\pm}4.1{\mu}m/s$) of frozen/thawed sperm were observed in ASP1 diluent containing 10% DMSO and in ASP2 containing 15% DMSO, respectively. Results showed that cryopreservation with ASP as diluent and DMSO as cryoprotectant could be adopted for long term storage of filefish sperm.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2017.05a
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• pp.160-162
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• 2017

When rubber elastomer has contact with fuel, since the component and additive having low molecular weight can flow out, the physical properties of both elastomer and fuel could be hindered. In order to predict the life of the rubber elastomer, this study is to determine the change of weight, thickness, hardness, strain, and compression set as mechanical properties of the sealant rubber O-ring, which was dependent on volume, temperature, and storage time of the contacted fuel. We also determined purity of fuel via GC analysis and measured gross heat of combution. The results could be used as a reference to evaluate the life of the rubber elastomer.

• Structural Engineering and Mechanics
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• v.31 no.4
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• pp.371-382
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• 2009

The concrete plates are most widely used structural elements in the hulls of floating concrete structures such as concrete barges and pontoons, bridge decks, basement floors and liquid storage tanks. The study on the behavior of high-strength fiber reinforced concrete (HSFRC) plates was carried out to evaluate the performance of plates under in-plane and transverse loads. The plates were tested in simply supported along all the four edges and subjected to in-plane and traverse loads. In this experimental program, twenty four 150 mm diameter cylinders and twelve plate elements of size $600{\times}600{\times}30$ mm were prepared and tested. Water-to-cementitious materials ratios of 0.3 and 0.4 with 10% and 15% silica fume replacements were used in the concrete mixes. The fiber volume fractions, $V_f$ = 0%, 1% and 1.5% with an aspect ratio of 80 were used in this study. The HSFRC mixes had the concrete compressive strengths in the range of 52.5 to 70 MPa, flexural strengths ranging from 6.21 to 11.08 MPa and static modulus of elasticity ranging from 29.68 to 36.79 GPa. In this study, the behavior of HSFRC plate elements subjected to combined uniaxial in-plane and transverse loads was investigated.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.279-284
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• 2021

The high theoretical specific capacity of lithium-sulfur (Li-S) batteries makes them a more promising energy storage system than conventional lithium-ion batteries (LIBs). However, the slow kinetics of the electrochemical conversion reaction seriously hinders the utilization of Li-S as an active battery material and has prevented the successful application of Li-S cells. Therefore, exploration of alternatives that can overcome the sluggish electrochemical reaction is necessary to increase the performance of Li-S batteries. In this work, an ionic liquid (IL) is proposed as a functional additive to promote the electrochemical reactivity of the Li-S cell. The sluggish electrochemical reaction is mainly caused by precipitation of low-order polysulfide (l-PS) onto the positive electrode, so the IL is adopted as a solubilizer to remove the precipitated l-PS from the positive electrode to promote additional electron transfer reactions. The ILs effectively dissolve l-PS and greatly improve the electrochemical performance by allowing greater utilization of l-PS, which results in a higher initial specific capacity, together with a moderate retention rate. The results presented here confirmed that the use of an IL as an additive is quite effective at enhancing the overall performance of the Li-S cell and this understanding will enable the construction of highly efficient Li-S batteries.

• Atmosphere
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• v.28 no.4
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• pp.393-402
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• 2018

This study investigated future changes in the Arctic permafrost features and related biogeochemical alterations under global warming. The Community Land Model (CLM) with biogeochemistry (BGC) was run for the period 2005 to 2099 with projected future climate based on the Special Report on Emissions Scenarios (SRES) A2 scenario. Under global warming, over the Arctic land except for the permafrost region, the rise in soil temperature led to an increase in soil liquid and decrease in soil ice. Also, the Arctic ground obtained carbon dioxide from the atmosphere due to the increase in photosynthesis of vegetation. On the other hand, over the permafrost region, the microbial respiration was increased due to thawing permafrost, resulting in increased carbon dioxide emissions. Methane emissions associated with total water storage have increased over most of Arctic land, especially in the permafrost region. Methane releases were predicted to be greatly increased especially near the rivers and lakes associated with an increased chance of flooding. In conclusion, at the end of $21^{st}$ century, except for permafrost region, the Arctic ground is projected to be the sink of carbon dioxide, and only permafrost region the source of carbon dioxide. This study suggests that thawing permafrost can further to accelerate global warming significantly.