• Journal of Microbiology and Biotechnology
• /
• v.8 no.6
• /
• pp.601-605
• /
• 1998

For the resolution of L-carnitine from DL-carnitine, resting cells of Enterobacter sp. NH-104, which had a higher capacity of D-carnitine decomposition, were harvested at maximal specific activity of D-carnitine decomposition of 47.05 unit/mg cell. The cells were frozen at $-80^{\circ}C$ to assess functions as enzyme sources. Optimal concentration of cells and DL-carnitine were 17 g/$\ell \; and \; 20 g/\ell$, respectively, and reaction buffer was best at 75 mM of Tris. HCl. Optimal temperature and pH were $36^{\circ}C$ and 8.2, respectively. When the reaction at optimal conditions was carried out for 14 h, the optical purity was 98.21 %, and the quantity and yield of remaining L-carnitine were 4.432 g/$\ell$ and 44.32%, respectively.

• 한국전산유체공학회:학술대회논문집
• /
• 2006.10a
• /
• pp.101-105
• /
• 2006

The computational fluid dynamic analysis has been conducted for the thermo-chemical flow field in an arcjet thruster with mono-propellant Hydrazine (N2H4) as a working fluid. The Reynolds Averaged Navier-Stokes (RANS) equations are modified to analyze compressible flows with the thermal radiation and electric field. The Maxwell equation, which is loosely coupled with the fluid dynamic equations through the Ohm heating and Lorentz forces, is adopted to analyze the electric field induced by the electric arc. The chemical reactions of Hydrazine were assumed to be infinitely fast due to the high temperature field inside the arcjet thruster. The chemical and the thermal radiation models for the nitrogen-hydrogen mixture and optically thick media respectively, were incorporated with the fluid dynamic equations. The results show that performance indices of the arcjet thruster with 1kW arc heating are improved by amount of 180% in thrust and 200% in specific impulse more than frozen flow. In addition to thermo-physical process inside the arcjet thruster is understood from the flow field results.

• Korean Journal of Agricultural Science
• /
• v.31 no.1
• /
• pp.9-14
• /
• 2004

This study was carried out for deresinning the larch boards dried in a conventional kiln. Prior to heat treatment they were steamed in an autoclave for 5 hours or frozen for 24 hours at a temperature of $-35^{\circ}C$. The velocities of ultrasound transmitted through the specimens were measured to examine the correlation with their resin contents. It was found that the specimens heated at $100^{\circ}C$ for 5 hours contained less resin that those heated at $200^{\circ}C$ for an hour. Both treatments of steaming and freezing were effective for deresinning and the former was better than the latter. The ultrasonic velocities measured before the heat treatment showed a negative correlation to the resin contents of the specimens, but those measured after the heat treatment a positive correlation. This difference may be attributed to the viscosity of resin.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.614-617
• /
• 2009

Elastomeric Flexible Cellular Insulation is widely used in construction fields to prevent condensation and frozen pipes, reduce energy, and improve insulation. However, when Elastomeric Flexible Cellular Insulation has been installed in buildings in Korea, there was no standardization, which resulted in heat loss Therefore, insulation design standards need to be developed and from these standards, pipe insulation should be improved to increase its efficiency. This study estimates temperature and surface-emissivity according to the thickness of insulation to evaluate thermal performance.

• Journal of the Korean Society of Food Culture
• /
• v.13 no.1
• /
• pp.27-35
• /
• 1998

Consumption of edible oil at food service institutions in Inchon was surveyed to provide basic data for continuous education of dietitians. Manufacturing industry was the major food service institution(78.8%) in Inchon followed by schools, hospitals and social welfare service centers. Most dietitians were at the age of twenties and college graduates with professional careers of 1-5 years. Oil was purchased on the basis of its quality within 1-3% of total food costs four times a month. Proper frying temperature was determined by dropping salt or food coating materials into the oil. Soybean oil was the most frequently used and commercial frying mix powder and flour and eggs in water were the most common food coating materials. Fish and commercial frozen foods were the most frequently used materials for frying. Fried foods were stored with covers in a basket and consumed within 30 minutes after cooking. Frying oils were used one more time after filtering and color was the index for determination of re-use.

• Proceedings of the Korean Society for Food Science of Animal Resources Conference
• /
• 2004.10a
• /
• pp.407-411
• /
• 2004

Ohmic heating occurs when an electric current is passes through food, resulting in a temperature rise in the product due to the conversion of the electric energy into heat. The time spent in the thawing is critical for product sterility and quality. The objective of this study is to conduct numerical modelling between the effect of ohmic thawing intensity on PTT(phase transition time) at constant concentration and the effect of matrix concentrations on PTT at constant voltage condition. the stronger ohmic thawing intensity resulted in decreasing the PTT. High ohmic intensity causes short PTT. And the higher gelatin concentration, the faster increment of PTT. A numerical modeling was executed to predict the PTT influenced by the power intensity using exponential regression and the PTT influenced by gelatin concentration using logarithmic regression. Therefore, from this numerical model of gelatin matrix, it is possible to estimate exact values extensively.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2000.02a
• /
• pp.35-38
• /
• 2000

A preliminary design of gas-gp thermal switch is presented to reduce the cooldown time of superconducting system conduction-cooled by a two-stage refrigerator without liquid cryogens. The switch connects thermally the first and the second stages (ON) to take advantage of the larger refrigeration capacity at the first stage during the beginning period. After the cryogenic temperature is reached, the switch should isolate thermally the two stages (OFF) in order to reduce the heat leak to the cold end. In this paper, a new concept for the performance index is introduced to evaluate the reduction of the cooldown time and the increase of the cooling load at the same time. In addition, the design of a gas-gap switch is discussed as a closed container of several staggered concentric tubes filled with gas, which is frozen at low temperatures for the shut-off of heat without any mechanical actuation. Some of the detailed features in the design is quantitative investigated by the gas convection model in the continuum or the rarefied gas region.

• Biotechnology and Bioprocess Engineering:BBE
• /
• v.5 no.3
• /
• pp.202-206
• /
• 2000

The genetically-engineered Escherichia coli strain, DPD2540, which contains a fabA:::luxCDAbefusion gene, gives a bioluminescent output when membrane fatty acid synthesis is needed. For more pactical application of this strain in the filed as biosensor, freezedrying was adopted. A 12% surcrose solution with Luria-Bertani (LB) broth, as determined by the viability after freeze-drying, was found to be most most effective composition for lyophilization solution among various compositions testitons tested. Rapid freezing with liquid nitrogen also gave the best viability after freeze-drying as compared to samples frozen at-7$0^{\circ}C$ and -2$0^{\circ}C$. The biosensing activities of the cells showed a greater sensitivity when the cells from the expontial phase were freeze-dried. Finally, the optimum temperature for use of the freeze-dried cells in the biodencor field was determined.

• Parasites, Hosts and Diseases
• /
• v.31 no.2
• /
• pp.91-98
• /
• 1993

To determine the infectivlty and maturity of nletacercanae of Parqgonimur westermani after keeping at low temperature for a long period, 45 mice and 45 rats were each infected with 20 metacercariae which were kept at $4^{\circ}C$ for 8 to 234 days. The worm recovery in mice increased with age of worm and reached a peak of 32% at 41-50 days and then decreased with age. The rate In rats first decreased to a lowest point of 6% at 71-100 days and then Increased with age. In 42 infected mice and 41 infected rats, 187 immature worms (183 tiny and 4 Juvenile ones) and 190 worms (164 tiny, 19 Juvenile and 7 mature ones) were recovered respectively. Two wormcysts with eggs only and 8 empty wormcysts were also found In the rats. In addition, the frozen metacercanae can still develop to mature worms in SD rats.

• Journal of the Korean Society for Precision Engineering
• /
• v.25 no.4
• /
• pp.47-52
• /
• 2008

Recently, the study for filling imbalance in thermoplastic polymer has gradually been increased. However, it is hard to find the researches for filling imbalance of thermoplastic elastomer(TPE). The experiment of filling imbalance was conducted for the three kinds of thermoplastic vulcanizes(TPVs) and PP polymer in the mold with geometrically balanced runner system(Unary Branch Type Runner System). In this experiment, the effects of the melt temperature, injection pressure and injection speed on the filling imbalance were investigated. There was also the imbalance in TPV injection molding process as well as in conventional injection molding with plastics. The tendency of filling imbalance in TPV injection molding specially decreased by taking place the hesitation of TPV melt.