• Journal of the Korean Society of Propulsion Engineers
• /
• v.15 no.5
• /
• pp.96-106
• /
• 2011

There are many advantages in applying gel propellant to a gel propulsion system. These include higher performances, the energy management of liquid propulsion system, reliable storability and low leakage characteristics. Additionally, gel propulsion system are preferable to the high density impulse of propulsion system. Also, when compared to liquid propellants, the gel propellants acquire greater heat energy. Gel propellants achieve a high specific impulse when metal particles with aluminum and boron are added. With respect to atomization, an inactive process occurs due to the variable viscosity of the metal particles and gelling agents. To improve the defect of atomization and combustion characteristics of gel propellant, a variety of issues related to spray and combustion is introduced here.

• Journal of the Korea Furniture Society
• /
• v.24 no.2
• /
• pp.156-182
• /
• 2013

In this paper, the origin, development and features of a Korean folding stool are studied. A folding stool is a piece of collapsible seating furniture with its legs crossed in the form of the letter "X" and no back attached. In China, the folding stool was introduced from the West around the second century A.D. The folding stool of Korea was influenced by that of China. It is known from the records that the king used the folding stool from the Three Kingdom period. During the Koryo period, Chosun period and the modern period, the folding stool was used to show the authority of the king and nobleman. The folding stool was also used at outside places such as a hunting ground, a ceremonial walk, a battlefield, a garden etc. due to its portableness. Buddha worship policy of Koryo period supported the usage of the folding stool for shanding (禪定) by ascetics of Buddhist temple, or aristocrats. In a contemporary period, the folding stool is continuously produced and used as one kind of a folding chair due to its functionality, movability, storability and efficient space utilization. This research will serve as a momentum to investigate the origin and development of the East Asian seating furniture culture, and contribute to the further study and manufacturing of Korean seating furniture.

• Journal of Biosystems Engineering
• /
• v.35 no.5
• /
• pp.316-322
• /
• 2010

The packaging of fruits is very important because appropriate packaging can optimize the maintenance of freshness of fruits during their distribution in low or normal temperatures until the products reach consumers. The focus of this study was on the use of functional packaging materials for the post-harvest maintenance of the freshness of fruits. Oak charcoal has excellent far infrared emission and ethylene absorption qualities, and we developed a charcoal-processing packaging linerboard to evaluate the possibility for the use of charcoal as a functional packaging material for pears. Oriental pears of the Niitaka cultivar used in this study account for about 70% of pears harvested every year, and are a very popular domestic fruit in Korea. Pears packaged in packaging materials processed with charcoal were of significantly higher quality (p<0.05) than those packaged with conventional packaging materials, suggesting that charcoal-processed packaging materials can be used as functional packaging material for extending the storability and distribution time of fruits. Charcoal-coated linerboard was shown to be the most appropriate packaging material based on its compression strength, ethylene absorption performance, and the firmness and minimal weight loss of pears.

• Journal of Aerospace System Engineering
• /
• v.10 no.1
• /
• pp.66-73
• /
• 2016

Space propulsion system produces required thrust for satellites and space launch vehicles by using chemical reactions of a liquid fuel and a liquid oxidizer typically. For example, monomethylhydrazine-dinitrogen tetroxide, liquid hydrogen-liquid oxygen and RP-1-liquid oxygen are conventional combinations of liquid propellants used for the liquid propulsion system. Among several liquid propellants, the monomethylhydrazine is expecially preferred for a satellite fuel due to its better storability in liquid phase during a relatively long mission period under a space environment. Thus, a development importance of a bipropellant system using the monomethylhydrazine fuel is recognized recently as the national space program proceeds on a large scale. The objective of the present study is to review a foreign research trend of a thermal decomposition reaction of monomethyhydrazine to understand a fundamental basis of its chemical reaction to prepare for domestic development in future.

• Horticultural Science & Technology
• /
• v.30 no.2
• /
• pp.158-161
• /
• 2012

The influence of lysophosphatidylethanolamine (LPE) on anti-senescence of melon leaves and the change in fruit quality during the storage at low temperature were studied. In most of the crops, freshness of leaves is important factor for characteristics of fruits, such as sugar contents, color, and firmness. Melon ($Cucumis$ $melo$ L. cv. Prince) plants were sprayed with LPE at 5 and 3 weeks before commercial harvest. In upper part, LPE treatment showed slight high number of fresh leaf compared to no treatment (None). However, in lower part, LPE resulted in apparent inhibition effect on senescence, showing that lower side of melon plant kept fresh upon LPE application up to about 30%. The SSC of melon treated with LPE was similar to that of fruit from None at harvest. There was no change in soluble solids content (SSC) for all treatment during the storage at $7^{\circ}C$. There were no significant differences in firmness of mesocarp from melons given different treatments at harvest. The firmness of mesocarp from melon treated with LPE was higher than none after 2 weeks storage. The electrolyte leakage means for melon treated with LPE did not differ significantly from the means at initial storage after 2 weeks storage among the treatments. None increased 57% from its initial electrolyte leakage during storage. These results suggest that the application of LPE may have potential to inhibit senescence of leaves and maintain fruit quality during the storage in melon.

• Journal of Mushroom
• /
• v.16 no.3
• /
• pp.140-146
• /
• 2018

Pleurotus eryngii is one of the most commercially important mushrooms cultivated in Korea. However, the shelf-life of the fruiting body is short, limiting its export. A new hybrid strain H17 of P. eryngii was developed to extend the shelf-life by mono-mono crossing between monokaryotic strains derived from DanBi and KNR2774. Although the cultivation period of H17 was slightly longer than that of the reference cultivar Kenneutari No.2, the quality did not change and remained normal after a period of 65.0 days at $4^{\circ}C$. This result was significantly different from that of the reference cultivar Kenneutari No.2. Analysis of the genetic characteristics of the new hybrid strain H17 revealed a different profile from that of the parental and reference cultivars when random amplification of polymorphic DNA (RAPD) primers was used. These results demonstrate that H17 is a new cultivar with improved storability after harvesting.

• Korean Journal of Food Science and Technology
• /
• v.22 no.5
• /
• pp.530-532
• /
• 1990

The moisture sorption behaviors of dry corn(DC). dry-corn (DCC) and soaked-rooked corn(SCC) at $25^{\circ}C$ were analyzed. The corn was soaked in water at $26^{\circ}C$ for 8hr. The cooking times for DCC and SCC were 30 and 20min. respectively, at $80^{\circ}C$. Desorption occurred for DC and DCC at RH below 23% and SCC at RH below 33% during storage. Moldiness was observed in all samples at RH 97%, after 192hr for DC and 288 hr for both DCC and SCC. At the same water activity. SCC sample had the highest moisture content, followed by DC. The SCC sample had the highest monolaver value and sorption heat. Stability isotherms indicated that DC and SCC had better storability than DCC.

• Korean Journal of Agricultural Science
• /
• v.38 no.4
• /
• pp.607-612
• /
• 2011

The occurrence of grape berry shattering and decay is influenced by the pre- and/or postharvest infection of decay organisms and pest. Postharvest infection is associated with physical damage due to rough handling. To control quality loss during storage of table grapes, the effects of slow releasing $SO^2$ pad on storability of 'Rosario Bianco' (Vitis vinifera) and 'Campbell Early' (Vitis labruscana) grapes were examined, respectively. The $SO^2$ concentration in package of tables grapes reached to at about 40 $ug{\cdot}L^{-1}$ after 40 days of treatment and remained more than 80 days above 15 $ug{\cdot}L^{-1}$. Decay was found in untreated 'Rosario Bianco' and 'Campbell Early' grapes at each for 44 and 85 days after storage, but not in $SO^2$ pad treated grapes. The storage potential of grape berries at $0^{\circ}C$ increased 2~3 times depending on cultivar by $SO^2$ pad treatment. The application of $SO^2$ pad is confirmed to be effective on the increase of market potential with minimizing quality loss such as berry shattering and decay.

• Journal of ILASS-Korea
• /
• v.16 no.3
• /
• pp.140-145
• /
• 2011

Gelled propellants are non-Newtonian fluids in which the viscosity is a function of the shear rate, and they have a high dynamic shear viscosity which depends on the amount of gelling agent contents. The present study has focused on the breakup process, wave development of ligament and liquid sheets formed by impinging jets with various gelling agent contents. The breakup process of like-on-like doublet impinging jets are experimentally characterized using non-Newtonian liquids. The spray shape with elliptical pattern is distributed in a perpendicular direction to the momentum vectors of the jets. Gelled propellant simulants with high viscosity jets are more stable and produce less pronounced surface waves than low viscosity jets. Gelled propellant simulants from like-on-like doublet impinging jets have the spray shape of closed rim patterns at low pressure. As the injection pressure increased, rimless patterns which were composed of ligament sheets and small droplets emerged due to the effect of the aerodynamic action.

• Horticultural Science & Technology
• /
• v.33 no.5
• /
• pp.633-637
• /
• 2015

Cucumber and paprika transplants were stored at 9, 12, 15, and $18^{\circ}C$ under dark conditions for 15 days and then grown in a greenhouse for 14 days after transplanting. To determine the effects of low storage temperature and long-term continuous darkness on the quality and vigour of transplants, we investigated the quality of transplants during storage and the growth of stored transplants after transplanting. In cucumber transplants, decreasing storage temperature reduced stem elongation and decrease in SPAD value. The quality of cucumber transplants stored at $9^{\circ}C$ was well preserved during storage, but they did not survive after transplanting due to chilling damage. Growth and development after transplanting were significantly greater when cucumber transplants were stored at $12^{\circ}C$. In paprika transplants, the quality of transplants did not significantly differ before and after storage. After transplanting, there was no significant difference in the survival rate and growth, but the number of flower buds was greater in the paprika transplants stored at lower temperatures (9 and $12^{\circ}C$). These results indicate that the responses of transplants to the conditions of low temperature and darkness differed between cucumber and paprika, and storage temperature in darkness must be controlled carefully considering species-specific responses to reduce quality deterioration during storage and improve the recovery of transplants after transplanting.