• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.29 no.3 s.234
• /
• pp.425-431
• /
• 2005

The efficiency of complex slurry preparation route for developing the high performance SiC matrix of $RS-SiC_{f}/SiC$ composites has been investigated. The green bodies for RS-SiC materials prior to the infiltration of molten silicon were prepared with various C/SiC complex slurries, which associated with both the sizes of starting SiC particles and the blending conditions of starting SiC and C particles. The characterization of Rs-SiC materials was examined by means of SEM, EDS and three point bending test. Based on the mechanical property-microstructure correlation, the process optimization is also discussed. The flexural strength of Rs-SiC materials greatly depended on the content of residual Si. The decrease of starting SiC particle size in the C/SiC complex slurry was effective for improving the flexural strength of RS-SiC materials.

• Journal of Advanced Marine Engineering and Technology
• /
• v.3 no.1
• /
• pp.32-39
• /
• 1979

Alignment of marine engine shafting generally implies a judicious slope alignment of supporting bearings in order to achieve acceptable values of bearing reactions and shaft stresses for all deformation conditions of hull. Authors developed a computer program, which computes the bearing reaction forces, the bearing reaction influence numbers and etc, using quadruple integration method. And the results of calculation for a 26,000 DWT steam container carrier were in good agreements with those of foreign shipyard. Also they introduced the optimization technique of slope alignment combined technical economic basis, and as a result of comparing characteristics of shafting in case of straight alignment whit those in case of slope alignment, the latter was found to be much better than the former.

• Macromolecular Research
• /
• v.14 no.5
• /
• pp.510-516
• /
• 2006

Lactide was produced from oligomeric PLA by back-biting reaction of the OH end groups. For optimization of the reaction conditions, the effects of temperature, pressure, PLA molecular weight, and catalyst type on the lactide synthesis were examined. The fraction of D,L-lactide decreased with increasing temperature. Among the various Sn-based catalysts, the D,L-lactide fraction was maximized when SnO was used. A higher yield with lower racemization was observed at lower pressure. The conversion of PLA was maximized at an oligomeric PLA molecular weight of ca. 1380. The yield of lactide increased but the fraction of D,L-lactide decreased with increasing molecular weight. The highest conversion with the lowest racemization degree was obtained at a catalyst concentration of 0.1 wt%. The lactide was more sensitive to racemization because of the entropic effect.

• Archives of Pharmacal Research
• /
• v.29 no.11
• /
• pp.1061-1065
• /
• 2006

A new chiral derivatization agent with sugar moiety, 2,3,4,6-tetra-O-acetyl-${\beta}$-D-galactopyranosyl isothiocyanate (GATC) was synthesized. Several ${\beta}-blockers$ were investigated for the possible separation of the enantiomers by reversed-phase HPLC after derivatization with this new chiral derivatization agent (GATC). GATC was reacted readily with ${\beta}-blockers$ at room temperature and the reaction mixture could directly be injected into the HPLC system. The corresponding diastereomers were well resolved on an ODS column with acetonitrile-ammonium acetate buffer as a mobile phase and monitored at UV 254 nm. The optimization of the derivatization procedure (concentration of GATC, reaction temperature and time) and HPLC conditions (pH and ionic strength of mobile phase) were investigated and compared with GITC.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.40 no.10
• /
• pp.1430-1437
• /
• 2011

Synthesis conditions of cocoa butter equivalents were optimized using the response surface method (RSM) by interesterification of canola oil (Ca), palmitic ethyl ester (PEE), and stearic ethyl ester (StEE). The reaction was catalyzed by immobilized lipase (Lipozyme TLIM) from Thermomyces lanuginosa to produce structured lipids containing a composition of triacylglycerols similar to cocoa butter. Reaction conditions were optimized using D-optimal design with the three reaction factors of the substrate molar ratio of canola oil to palmitic ethyl ester and stearic ethyl ester (Ca : PEE : StEE=1:1:3, 1:1.66:5, 1:2:6, 1:2.33:7, 1:3:9, $X_1$), enzyme ratio (2~6%, $X_2$), and reaction time (30~270 min, $X_3$). The optimal conditions that minimized acyl-migration while maximizing 1-palmitoyl-2-oleoyl-3-stearoyl glycerol (POS), 1,3-distearoyl-2-oleoyl glycerol (SOS), and 1,3-dipalmitoyl-2-oleoyl glycerol (POP) were predicted, resulting in Ca : PEE : StEE=1:3:9, 6% of enzyme ratio, and 40 min of reaction time. The reaction product of structured lipids was synthesized again under the same conditions, showing 10.43 area% of acyl-migration, 25.31 area% of POS/PSO, 19.79 area% of SOS, and 11.22 area% of POP.

• Journal of Korean Society of Water and Wastewater
• /
• v.29 no.2
• /
• pp.183-192
• /
• 2015

Response surface methodology (RSM) based on a Box-Behnken Design (BBD) was applied to optimize the thermal-alkaline pre-treatment operating conditions for anaerobic digestion of flotation scum in food waste leachate. Three independent variables such as thermal temperature, NaOH concentration and reaction time were evaluated. The maximum methane production of 369.2 mL $CH_4/g$ VS was estimated under the optimum conditions at $62.0^{\circ}C$, 10.1% NaOH and 35.4 min reaction time. A confirmation test of the predicted optimum conditions verified the validity of the BBD with RSM. The analysis of variance indicated that methane production was more sensitive to both NaOH concentration and thermal temperature than reaction time. Thermal-alkaline pretreatment enhanced the improvement of 40% in methane production compared to the control experiment due to the effective hydrolysis and/or solubilization of organic matters. The fractions with molecular weight cut-off of scum in food waste leachate were conducted before and after pre-treatment to estimate the behaviors of organic matters. The experiment results found that thermal-alkaline pre-treatment could reduce the organic matters more than 10kD with increase the organic matters less than 1kD.

• BMB Reports
• /
• v.28 no.4
• /
• pp.359-362
• /
• 1995

The highly polymorphic variable number of tandem repeat (VNTR) loci in the human genome are informative markers for the genetic characterization of individuals in the paternity test and forensic science as well as for the study of human disease. In this study, VNTR loci D1S80 and D2S123 have been amplified by PCR and the amplified length polymorphic alleles were detected with a discontinuous vertical PAGE system and silver staining. For explicit DNA typing, PCR optimization, in which amplification efficiencies are similar over a wide range of allele sizes, non-specific amplifications are minimal, and new longer alleles have high amplification efficiency, has been performed by changing the PCR reaction buffer composition and thermal cycling conditions. It turned out that adding an appropriate amount of Tween 20 and NP40 to the PCR reaction buffer and raising the annealing temperature to $68^{\circ}C$ in thermal cycling made it possible for optimal VNTR loci amplification. A modified PAGE system for VNTR separation was established. Under these conditions, new longer alleles in the 01580 locus were discovered and 025123 pattern changes in colorectal tumors were observed. These technical tips are valuable for detecting various amplified fragment length polymorphisms.

• Journal of Radiation Protection and Research
• /
• v.23 no.4
• /
• pp.243-249
• /
• 1998

The methodology for justification and optimization of the countermeasures related with contamination management of milk was designed based on the cost and benefit analysis. The application results were discussed for the deposition on August 15, when pasture is fully developed in Korean agricultural conditions. A dynamic food chain model DYNACON was used to estimate the time-dependent radioactivity of milk after the deposition. The considered countermeasures are (1) the ban of milk consumption (2) the substitution of clean fodder, which are effective in reducing the ingestion dose as well as simple and easy to carry out in the first year after the deposition. The total costs of the countermeasures were quantitatively estimated in terms of cost equivalent of doses and monetary costs. It is obvious that a fast reaction after the deposition is an important factor in cost effectiveness of the countermeasures. In most cases, the substitution of clean fodder was more effective countermeasure than the ban of consumption. A fast reaction after the deposition made longer justifiable/optimal duration of the countermeasure.

• Journal of Hydrogen and New Energy
• /
• v.27 no.6
• /
• pp.621-627
• /
• 2016

Low-priced hydrogen is required in petrochemical industry for producing low-sulfur oil, and upgrading low-grade crude oil since environmental regulations have been reinforced. Steel industry can produce hydrogen from by-product gases such as Blast Furnace Gas (BFG), Coke Oven Gas (COG), and Linze Donawitz Gas (LDG) with water gas shift (WGS) reaction by catalysis. In this study, we optimized conditions for WGS reaction with commercial catalysts by BFG and LDG. In particular, the influence on activity of gas-hourly-space-velocity, and $H_2O/CO$ ratios at different temperatures were investigated. As a result, 99.9%, and 97% CO conversion were showed with BFG, and LDG respectively under $350^{\circ}C$ High Temperature Shift (HTS), $200^{\circ}C$ Low Temperature Shift (LTS), 3.0 of $H_2O/CO$, and $1500h^{-1}$ of GHSV. Furthermore, 99.9% CO conversion lasted for 250 hours with BFG as feed gas.

• Journal of Life Science
• /
• v.13 no.6
• /
• pp.794-798
• /
• 2003

Batch production of (S)-phenyl oxirane was investigated using epoxide hydrolase activity of Rhodosporidium toruloides SJ-4. Effect of reaction condition of asymmetric biohydrolysis of racemic phenyl oxirane was analyzed and optimized by response surface methodology. The optimal conditions of pH, temperature and DMSO cosolvent ratio were 7.4, $34^P\circ}C$, and 2.3%(v/v), respectively. The final yield was enhanced up to 67%, and reaction times required to reach 99% ee (enatiomeric excess) decreased down to 50% by response surface methodology Enantiopure (S)-phenyl oxirane with 100% enantiopurity and 24% yield (theoretical yield = 50%) was obtained from racemic substrate.