• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1048-1053
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• 2009

It proposes an simple and intuitive method that calculates the equilibrium pressures of a propellant tank by appling the mass conservation principle on the helium in the liquid propellant and in an ullage volume of the propellant tank. A propellant loading analysis program is developed and validated against the existing reference data. And it has applied to the present developing program, COMS Chemical Propulsion Subsystem and the results are compared, it may use to develop a technology of the next geostationary complex satellite's propulsion system.

• Journal of Mechanical Science and Technology
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• v.20 no.2
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• pp.278-285
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• 2006

The present study has been conducted to simulate dynamics of a gas engine-driven heat pump (GHP) for design of control algorithm. The dynamics modeling of a GHP was based on conservation laws of mass and energy. For automatic control of refrigerant pressures, actuators such as engine speed, outdoor fans, coolant three-way valves and liquid injection valves were PI or P controlled. The simulation results were found to be realistic enough to apply for control algorithm design. The model can be applied to build a virtual real-time GHP system so that it interfaces with a real controller in purpose of prototyping control algorithm.

• Natural Product Sciences
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• v.27 no.4
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• pp.280-283
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• 2021

Cercidiphyllum japonicum is being used for the treatment of obesity and liver fibrosis in Korean local clinics. In the present study, we tried to develop an analytical methodology for the determination of the chemical markers of Cercidiphyllum japonicum. Four chemicals, maltol (1), chlorogenic acid (2), quercetin (3), and avicularin (4), were selected for method validation, and the analytical conditions were optimized and validated using high-performance liquid chromatography coupled with an ultraviolet detector (HPLC-UV). Additionally, the seasonal variations of four markers were monitored every month for six months. The contents of four chemicals markers were most detected in a sample collected in June.

• Journal of Applied Biological Chemistry
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• v.66
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• pp.244-249
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• 2023

Artemisia keiskeana and A. stolonifera are plants of the genus Artemisia, distributed in various regions, especially China and Korea. They are renowned as medicinal plants with biological and pharmacological activities. Fraxidin, isofraxidin, and daphnoretin are coumarins present in Artemisia spp.; however, research on them is limited. Therefore, this study was carried out to quantify the content of these compounds in the aerial parts of A. keiskeana and A. stolonifera in different regions in Korea. High-performance liquid chromatography was performed with a photodiode array detector and a reverse-phase INNO column. A. stolonifera only contained fraxidin with the highest amount found in Yongmun commune. A. keiskeana cultivation in Soyang commune gave the highest fraxidin and daphnoretin content. However, isofraxidin was not present in all samples. The findings suggest that the concentrations of the three compounds may differ depending on the growth site and provide a foundation for future studies.

• Journal of Microbiology and Biotechnology
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• v.26 no.7
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• pp.1216-1223
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• 2016

The aim of this study was to isolate antioxidant peptides from an enzymatic hydrolysate of Spirulina platensis. A novel antioxidant peptide was obtained by ultrafiltration, gel filtration chromatography, and reverse-phase high-performance liquid chromatography, with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay used to measure the antioxidant activity, and the sequence was determined to be Pro-Asn-Asn (343.15 Da) by electrospray ionization tandem mass spectrometry. This peptide was synthesized to confirm its antioxidant properties, and it exhibited 81.44 ± 0.43% DPPH scavenging activity at 100 μg/ml, which was similar to that of glutathione (82.63 ± 0.56%). Furthermore, the superoxide anion and hydroxyl free-radical scavenging activities and the SOD activity of the peptide were 47.84 ± 0.49%, 54.01 ± 0.82%, and 12.55 ± 0.75%, respectively, at 10 mg/ml. These results indicate that S. platensis is a good source of antioxidant peptides, and that its hydrolysate may have important applications in the pharmaceutical and food industries.

• Korean Journal of Plant Resources
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• v.30 no.6
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• pp.612-617
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• 2017

The preservation of pear germplasm, like that of other clonal germplasms, is difficult because it requires conservation of whole plants or their tissues. Among the currently available methods for long-term conservation of clonal germplasm, cryopreservation of shoot tips is the most reliable and cost- and space-effective option. Alginate-coated axillary shoot tips from in vitro-grown pear were conserved successfully in liquid nitrogen (LN) following dehydration. Shoot recovery from cryopreserved shoot tips was improved greatly after 8 weeks of cold acclimation, but recovery decreased slightly after then. The highest regeneration rate was observed when in vitro shoot tips were preincubated in MS (Murashige and Skoog) medium with 0.3 M sucrose for 48 h, and when alginate-coated shoot tips were precultured in MS medium with increasing sucrose concentrations (0.5 M and 0.7 M) for 8 and 16 h, respectively. When the encapsulated beads were dehydrated for up to 7 h [25% water content (fresh weight basis)] under laminar flow, the highest regeneration rate was observed in "BaeYun No. 3" (55.7%) and "Whanggeum" (43.3%) after warming from LN. This technique is useful as a practical procedure to cryopreserve plant material that is sensitive to freezing of the surrounding cryoprotectant medium. Therefore, this technique appears to be promising for the cryopreservation of shoot tips from in vitro-grown plantlets of pear germplasm.

• Progress in Superconductivity and Cryogenics
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• v.20 no.3
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• pp.21-27
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• 2018

It is difficult to fabricate and maintain moving parts of expander at cryogenic temperature. This paper describes numerical analysis and experimental investigation on a cryogenic reciprocating expander without moving piston. An intake valve which takes high-pressure gas, and an exhaust valve which discharges low-pressure gas, are connected to a tube. The inside pressure of the tube is pulsated for work production. This geometric configuration is similar to that of pulse tube refrigerator but without regenerator. An orifice valve and a reservoir are installed to control the phase of the mass flow and the pressure. At the warm end, a heat exchanger rejects the heat which is converted from the produced work of the expanded gas. For the numerical analysis, mass conservation, energy conservation, and local mass function for valves are used as the governing equations. Before performing cryogenic experiments, we carried out the expander test at room temperature and compared the performance results with the numerical results. For cryogenic experiments, the gas is pre-cooled by liquid nitrogen, and then it enters the pulse tube expander. The experiments are controlled by the opening of the orifice valve. Numerical analysis also found the expander conditions that optimize the expander performance by changing the intake pressure and valve timing as well as the opening of the orifice valve. This paper discusses the experimental data and the numerical analysis results to understand the fundamental behavior of such a newly developed non-mechanical expander and elucidate its potential feature for cryogenic application.

• Korean Journal of Plant Resources
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• v.17 no.2
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• pp.75-81
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• 2004

This study was conducted to investigate effects of cryopreservation by vitrification on the seed germination rate and growth and physiological properties of seedlings of Maackia amurensis. Cryopreservation significantly decreased the germination rate of seeds of M. amurensis, but the reduction of germination rate was mitigated by the treatment of cryoprotectant (plant vitrification solution, PVS2) before plugging into liquid nitrogen and fast thawing rate after cryopreservation. Long-term PVS2 exposure decreased seed germination rate, whereas cryopreservation time didn't have influence on seed germination rate. In addition, growth and physiological properties of seedlings were not affected by PVS2 exposing time and cryopreservation time. Therefore cryopreservation could be widely used as a technique of long-term ex situ conservation without any damage and deterioration of cells or tissues of the forest seeds. However, in order to increase the effect of cryopreservation, we have to develope the lower toxic cryoprotectant and suitable techniques to the structural or chemical properties of a variety of seeds.

• Journal of Conservation Science
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• v.26 no.4
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• pp.407-416
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• 2010

Bacteria with ability for iron reduction in the soil can use corrosion products of iron remains as energy source. The activities of this bacteria cause the change of corrosion products. As a result, it can be difficult to identify corrosion products promoting corrosion of iron remains. The purpose of this study, is to investigate the change in corrosion products that bacteria causes and to improve understanding about the corrosion of iron remains. To simulate corroded condition of excavated iron remains, carbon steel corroded by solution of NaCl and $Na_2SO_4$ was prepared. Then the prepared carbon steel was immersed in a liquid medium with bacteria. The incubation period was 42days. After experiment, the carbon steel was analyzed by SEM-EDS, X-ray diffraction method. The result is that the carbon was changed to green because of activity of bacteria and that the plate crystal and lozenge crystal were generated on the corrosion specimen. Also, we confirmed that the activities of bacteria differenciated colors and forms of corrosion products.

• Journal of Korean Society of Forest Science
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• v.90 no.3
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• pp.277-294
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• 2001

This study is aimed to analyze and to evaluate the technology development for sanddune fixation and sandy land conservation in China, resulting from the project of "Studies on the desertification combating and sand industry development". There are various types of sanddunes, including shrub-bunch type, dendritic, honey combed lattice, crescentic, parabolic, pyramid, complex and irregular types, domed, and so on. The height distribution ratios of these sanddunes are 13% of less than 5m, 17% of 6~10m, 18% of 11~25m, 14% of 26~50m, 28% of 51~100m, 10% of more than 100m, and so on. In dry land of China, shifting direction of the sanddune is mainly varying with main direction of wind, but types of shifting sanddunes have many differences in accordance with region, topography, size and shape of sanddunes. The main sanddune fixation technologies could be divided into the bio-ecological measures, physical measures and chemical measures. The bio-ecological measures include such vegetation measures as shrub-grasses measures, sandbreaks between sand dunes, sand fixation shelterblets and establishment of farmland shelterbelts, etc. The physical measures include establishment of high-sanddune stabilization walls and low-sanddune stabilization walls, sanddune fixation levees and coverage method with sediment clay, etc. The chemical measures include fixation-materials spraying and synthetical liquid spraying methods, etc. Besides, irrigation and sand settlement measures, shifting sand trapping channel, ditchsand fixation measures, etc. have been effectively applied.