• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.307-312
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• 2020

Fluidized bed reactors operated in subatmospheric pressure has been focused because several industrial applications such as vacuum drying and plasma cvd requires reduced pressure fludization. However, the hydrodynamics of fluidized beds in subatmospheric pressure has not been extensively investigated. The pressure drop in the fluidized bed has been measured with variation of downstream pressures from 1.33 to 101.3 kPa in the shallow and deep fluidized beds under the sub-atmospheric pressures. The obtained minimum fluidization velocity of powders is a function of pressure due to the changes of gas density and mean free path. We can experimentally determine the critical Knudsen number and the critical pressure to define the slip regime significantly to influence the hydrodynamics of fluidized beds.

• Applied Chemistry for Engineering
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• v.10 no.5
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• pp.677-681
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• 1999

For the binary cyclohexanol-cyclohexanone system the vapor-liquid equilibrium data, which are the necessary ones for the design of the distillation columns in separation process of volatile liquid-mixtures, are measured at subatmospheric pressure of 150, 300 and 500 mmHg. An empirical relation between logarithmic values of relative volatility(log $\alpha$) and liquid phase composition(x), which predicts the vapor-liquid equilibrium data, is obtained from above measured data of 150, 300 and 500 mmHg and the published ones of 30, 100, 200, 395 and 750 mmHg. The predicted data are compared with the measured and published ones to be in good agreement.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1564-1570
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• 1998

In-situ particle monitors(ISPMs) are widely used for monitoring contaminant particles in vacuum-based semiconductor manufacturing equipment. In the present research, the performance of a Particle Measuring Systems(PMS) Vaculaz-2 ISPM at subatmospheric pressures has been studied. We created uniform upstream conditions of particle concentration and measured the detection efficiency, the lower detection limit, and the size response of the ISPM using uniform sized methylene blue aerosol particles. The effect of particle size, particle velocity, particle concentration, and system pressure on the detection efficiency was examined. Results show that the detection efficiency of the ISPM decreases with decreasing chamber pressure, and with increasing mass flow rate. The lower detection limit of the ISPM, determined at 50 % of the measured maximum detection efficiency, was found to be about $0.15{\sim}0.2{\mu}m$, which is similar to the minimum detectable size of $0.17{\mu}$ given by the manufacturer.

• Journal of the Korean Society of Industry Convergence
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• v.7 no.1
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• pp.97-105
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• 2004

The Vapor-liquid equilibrium data for the binary system of 2-methyl-2-propanol-2-butanone are measured at subatmospheric pressure of 100, 200, 300, 400, 500, 600, 700 and 760 torr. This study shows that the relations between logarithmic values of relative valatility(log ${\alpha}$)and liquid phase composition(${\chi}$) in the above binary systems are expressed as a linear function. When the linear relationships of between logarithmic values of relative volatilities and liquid phase compositions in the binary systems of various pressure intersect at a point, this empirical equation can be applied to the systems of this kind. From these relations the vapor-liquid equilibrium data are estimated and compared with the measured values to be in a good agreement with in accuracy ${\pm}0.0021$ for the various pressure.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1274-1275
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• 2005

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.05a
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• pp.383-386
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• 2006

Several HTPB/AP and HTPB/AP/HMX propellants were investigated experimentally for ignition characteristics in subatmospheric pressure. The threshold ignition pressure was 4psia for HTPB/AP composite propellant. The partial replacement of AP in HTPB/AP composite propellant by $5\sim15%$ of HMX, HNIW showed improvements in the threshold pressure was below 0.4psia. This appears to be due to the exothermic dissociation characteristics of HMX and HNIW at lower temperature $(\sim220^{\circ}C)$ than that of AP. The ignition substance B/KNO3 was coated thinly on the propellant surface for better ignition effect. As a result, ignition delay time of 15% was improved. NC is applied to $B/KNO_3$ ignition substance as a secondary binder and $NC-B/KNO-3$ suspension solution is coated to the propellant surface.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.3
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• pp.67-72
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• 2006

Several propellants were investigated experimentally for ignition characteristics in subatmospheric pressure. The threshold ignition pressure was 4 psia for HTPB/AP composite propellant. The partial replacement of AP in HTPB/AP propellant by $5{\sim}l5%$ of HMX, HNIW showed that the improvements in ignition delay was over 50% and the threshold pressure was below 0.4 psia. This appears to be due to the characteristics of HMX and HNIW exothermic dissociated at the temperature(${\sim}220^{\circ}C$) love. than that of AP. The ignition substance $B/KNO_3$ was coated thinly on the propellant surface for better ignition performance. As a result, ignition delay time of 15% was improved. NC is applied to $B/KNO_3$ ignition substance as a secondary binder and $NC-B/KNO_3$ suspension solution is coated to the propellant surface.

• Applied Biological Chemistry
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• v.28 no.3
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• pp.174-181
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• 1985

Ultrastructural changes in the chloroplast of apple fruits was examined with Malus Pumila Mill var. Fugi harvested during preclimacteric stage the subatmospheric pressure storage condition at 380mmHg, $20^{\circ}C$. Electron micrographs obtained from the fruits stored at 760mmHg, $20^{\circ}C$ indicated that the initiation of ultrastructural changes is in parallel with the onset of respiratory climacteric. Chloroplast of the apple fruits stored for 25 days is vacuolated and the lamellar system are a little disorganized. Chloroplast of the apple fruits stored for 50 days is showing extensive vacuolation, the lamellar system are completely disorganized and the plasma membrane has pulled away from the cell wall. In the case of subatmospheric presssure storage caused to delay the onset of ultrastructural changes in chloroplast such as vacuolation, disorganization of lamellar system and dispersal of stroma lamella about 2 months. These results suggested that ripening of apple fruits is correlated not only to the activity of respiration but to the involvement of ultrastructural changes in fruit cells. The evidences obtained here led to the conclusion that subatmospheric pressure treatment extends storage life of apple fruits by inhibiting ultrastructural changes of cell organelles in concomitance with respiratory activity.

• Journal of Ginseng Research
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• v.5 no.2
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• pp.99-107
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• 1981

Physical, chemical and microbiological changes were periodically studied during six-month storage of fresh ginseng under N2, CO2 gas or subatmospheric pressure condition. The results were summarized as follows. 1. The moisture contents of fresh ginseng gradually decreased during the first 2-month storage and thereafter generally reached at equillibrium. 2. There was no significant change in the reducing sugar content in 1-month storage, followed by$.$a decrease in between 2-and 3-month storage. Thereafter, the reducing sugar content increased at the end of 4-month storage. 3. The total sugar content increased significantly during the first 3-month storage. Under CO2 and Nr gas storage, the total sugar content gradually decreased after 3-month storage, while no significant change was observed in the samples stored under subatmospheric Pressure. Amylase activity gradually decreased as storage period increased 4. The content of saponin decreased as storage period increased, but ginsengoide Rf, Rd, Rc and Rb2 increased significantly in 1-month storage. 5. Regardless of storage methods, sprouting of ginseng and growth of microorganisms were inhibited in all samples during the first 4-month storage. However, growth of microorganisms was observed in the rhizome and injured areas of ginseng after 5-month storage in the N2 and CO2 gas atmosphere.

• Applied Biological Chemistry
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• v.31 no.3
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• pp.298-307
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• 1988

The kinds of volatiles in tomato fruits during storage were increased with the period of climacteric rise. The increasing and decreasing rate of their contents were slower under subatmospheric pressure-low temperature (SAP-L) than under normal atmospheric pressure-normal temperature (NAP-N). High contents of 2-hexanone, n-pentanol, and ethanol were decreased at the early period of storage and then increased. The content of n-octanol and furfural were increased, while that of n-butanol, cyclohexanone, and phenylacetaldehyde was decreased during storage. On the other hand, the content of trans, trans-2,4-decadienol, benzyl alcohol, and 2-heptanone was not changed during storage.