• Polymer(Korea)
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• v.35 no.1
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• pp.52-59
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• 2011

L-PLA or D-PLA was synthesized in bulk at $140^{\circ}C$ by ring opening polymerization(ROP) of L-lactide or D-lactide as a monomer using tin(II) octoate and lauryl alcohol as a catalyst and an initiator with changing the amounts of catalyst(0.25~1.0 wt%) and initiator(0.l~0.5 wt%). And stereocomplex-PLA was prepared by L-PLA/D-PLA having a wide range of molecular weight(30000~90000 g/mol) and L-PLA/D-PLA blends having different mixing ratio ($X_D$). The melting temperature. thermal degradation temperature and thermal stability of stereocomplex-PLA were higher than those of homopolymers(L-PLA, D-PLA). We supposed that these improvements arose from a strong interaction between L-PLA and D-PLA. The improved mechanical properties and changes in morphology of LPLA/D-PLA blends were compared to those of homopolymers(L-PLA, D-PLA).

• KOREAN JOURNAL OF CROP SCIENCE
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• v.58 no.1
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• pp.8-14
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• 2013

The newly developed fertilizer is the slow-releasing fertilizer which can be used as a basal fertilizer without no additional fertilization at tillering stage. It has 30-4-6% of $N-P_2O_5-K_2O$ and was coated with mixture of LDPE (Low density polyethylene), EVA (Ethylene vinyl acetate), BDP (Bio degraded polymer), TALC and nonionic surfactant for the controlled release up to 50 days after application. Coating materials were designed to be decomposed naturally. This fertilizer can be applied directly to the seedling tray mechanically just before transplanting, resulting in significant labor saving effect. The developed slow-release fertilizer, which can replace both basal fertilization and top dressing at tillering stage by single application directly to seedling tray, showed the highest release at 14~21 days after transplanting. Considering the plant growth at different growth stages and yield, the optimal application rate of developed slow-release fertilizer was 300 g per rice nursery tray and the yield of rice at this application rate was 5.25 MT/ha. Rice quality in terms of head rice grain ratio, amylose content, whiteness, and taste value decreased as fertilization rate increased from 200 g to 500 g per nursery tray. Fertilization rate based on quantity of fertilizer ingredients (N, P, K) was reduced by 49.3% compared to the standard application rate and there was 49.2% reduction in labor input for fertilization.

• Journal of the Korean Institute of Gas
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• v.18 no.5
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• pp.52-59
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• 2014

In general, sulfur containing odorants are added to fuel gases, such as LPG, and city gas, to prevent gas poisoning, ignition, explosion, or other accident caused by fuel gases, and to enable immediate and easy detection of fuel-gas leakage by emitting an offensive smell. In this study, sulfur free odorant for low sulfur fuel and prevention of metal corrosion were developed to replace current sulfur containing odorant for gas fuel. They were selected from 12 odorant containing non-sulfur organic compounds and evaluated by odor olfactory method (odor quality, odor intensity). Finally, selected mixture odorants were methyl isovalerate, methyl acrylate, 2-ethyl-3-methyl pyrazine with blending ratio of 50% : 40% : 10%. Final Sulfur free odorant was added 40 wt ppm in LPG fuels and evaluated fuel quality characteristics, metal corrosion test and long term stability of LPG fuel. It were limit in current LPG fuel standard in fuel quality characteristics. Final Sulfur free odorant also had no influence on metal corrosion and long term stability test with 60 days by adding in LPG fuels. Finally, they were shown to be warning agent candidates to reduce sulfur content and metal corrosion for LPG fuel.

• Food Engineering Progress
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• v.14 no.2
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• pp.112-117
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• 2010

Black ginger, obtained from steaming and drying process, provides the various functional properties. This study was performed to investigate the optimum processing conditions for black ginger with high content of biologically active substance such as anti-oxidations. Optimum processing conditions such as temperature and time for black ginger was determined by response surface methodology (RSM) with manufacturing process and functionality. The optimum steaming condition was determined 6 hours at 93.2$^{\circ}C$, and 82.7 mg/L DPPH scavenging activities was obtained at this condition. The black ginger drink was made with black ginger extracts, Japanese apricot, and honey. Interaction effects of these ingredients were investigated by modified distance based on design and analyzed by linear, nonlinear regression model, and RSM. The optimization of mixture ratio was made by statistical modeling using DPPH scavenging activities and sensory properties which are the important target constraints in drink. Total flavonoids showed a linear canonical form, while preference and antiradical activity showed a nonlinear canonical form indicating the higher interaction among mixtures. The response trace plot revealed that antiradical activity, sensory properties and total flavonoids were quite sensitive to the drink blending. The optimum formulation of the drink was set at 14.2% of black ginger extracts, 5% of Japanese apricot, and 10.8% honey.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.37-43
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• 2019

This research studied production of lightweight filling production for sink hole restoration utilizing various industrial by-products(2kinds of fly ash, petro-cokes CFBC ash, blast furnace slag fine particle). For this purpose, the mixed raw material properties(compressive strength) behaviors according to the blending ratio of industrial by-products were examined by applying the experimental design method and statistical analysis was performed using the commercial program MINITAB. Compressive strengths of industrial by-products were strongly dependent on blast furnace slag powder. Compressive strength(3days aging) was 3~11MPa depending on the amount of blast furnace slag powder used. The use of CFBC fly ash was evaluated to have the least effect on compressive strength. In addition, the compressive strength and the coefficient of permeability were measured by preparing foamed concrete for the experimental batch 1 condition in the mixture experimental design. In this case, the bulk density is 0.9 to 1.0, the apparent porosity is 30 to 50%, the compressive strength(3days old) is 1 to 2MPa, and the permeability coefficient is $10^{-2}$ to $10^{-3}cm/sec$.

• Proceedings of the Korean Society of Crop Science Conference
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• 2022.10a
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• pp.296-296
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• 2022

This study was investigated to compare the milling and physicochemical characteristics of six Korean wheat cultivars (Keumkang, KK; Jokyung, JK; Goso, GS; Joongmo2008, JM; Baekkang, BK; Saekeumkang, SKK) and five foreign wheat classes (Australian standard white wheat, ASW; Australian hard, AH; US northern spring, NS; US hard red winter, HRW; Soft wheat, SW). Korea and foreign wheat grains were milled using a Buhler MLU-202. Flour moisture, ash, protein, gluten, sedimentation, particle size, solvent retention capacity (SRC) and dough properties of flour were analyzed. Results showed that the hard wheats had a greater total flour yield and reduction fraction yield than the soft wheats regardless of the country. However, there were in the milling characteristics between the US and Korean soft wheats. GS, a soft wheat in Korea, had the lowest flour yield (59.6%) and the highest bran fraction yield (21.4%). The particle sizes of flour by milling fraction were B1>B2>B3 for the largest, and the R1〈R2〈R3 for the smallest. Particle size, ash, protein contents and the values of lactic acid SRC showed highly correlated with flour yield. The gluten-performance-index (GPI) is the ratio of the lactic acid SRC value to the sum of sodium carbonate and sucrose SRC values, and it has been used as a quality indicator for overall performance potential of flour. GPI values differed depending on the wheat variety or class, JM (0.82) was the highest value, and SKK (0.56) and SW (0.59) were low. The curve pattern of the Mixolab result also gives a quality indication of the flour sample. JM and NS flour had similar pattern at water absorption and gluten strength parameters and BK and HRW had similar viscosity patterns. These results will enable further study for blending Korean wheat cultivar to improve the flour quality.

• Composites Research
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• v.36 no.5
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• pp.349-354
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• 2023

Poly(3-hexylthiophene) (P3HT) is a conjugated polymer that is highly soluble in organic solvents and is readily available. However, its electrical properties as an active channel in electronic devices are not enough for practical applications, necessitating further improvement in the properties. In this study, we demonstrate that the blending of two P3HT polymers (i.e., regio-regular (RR) P3HT and regio-random (RRa) P3HT) with different regioregularities can significantly improve charge transport characteristics of the blend films. The morphological and electrical properties of the blend films were systematically investigated by varying the ratio between two P3HT polymers. Atomic force microscopy (AFM), X-ray diffraction (XRD), and UV-visible absorption spectroscopy (UV-vis) were employed to evaluate the morphological and optoelectronic properties of the blend films. The crystallinity of the blend films increased with increasing the content of RRa-P3HT to 20 wt% and gradually decreased as the content increased to 80%. Consistently, the highest charge carrier mobility was obtained from the blend films containing 20 wt% RRa-P3HT, which value was measured to be 0.029 cm²/V·s. The values gradually decreased to 0.0007 cm²/V·s with increasing the content of RRa-P3HT to 80 wt%.

• Resources Recycling
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• v.33 no.1
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• pp.22-30
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• 2024

To synthesize the Ti₃AlC₂ MAX phase, a crucial precursor for generating the two-dimensional material MXene, the use of Ti scrap as an initial material is an economically feasible approach. This study aims to optimize the synthesis conditions for the phase fraction of the Ti₃AlC₂ MAX phase utilizing Ti scrap as the Ti source. The deoxidation of Ti powders, prepared through the hydrogenation-dehydrogenation process from Ti scrap, was effectively accomplished using the deoxidation in solid-state (DOSS) process. The optimal synthesis conditions were established by blending DOSS-Ti, Al, and graphite powders with particle sizes ranging from 25 ~ 32 ㎛ in a molar ratio of 3:1.1:2. The resulting phase fractions were as follows: Ti₃AlC₂ at 97.25 wt.%, TiC at 0.93 wt.%, and Al₃Ti at 1.82 wt.%. Furthermore, the oxygen content of the Ti₃AlC₂ MAX powder, spanning from 25 ~ 45 ㎛, was measured at 4,210 ppm.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.5
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• pp.707-714
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• 2005

Ingredient ratio for making nabak kimchi and the manufacturing method were standardized from the available literatures. Fermentation properties and $CO_2$ production of the nabak kimchi were investigated during the fermentation at $5^{\circ}C,\;10^{\circ}C,\;and\;20^{\circ}C$. Standardized ingredients ratio of nabak kimchi that added 100 mL of water was as follows: 45.0 g baechu cabbage, 26.9 g radish, 1.9 g green onion, 1.0 g red pepper, 1.2 g crushed garlic, 0.9 g crushed ginger, 0.7 g red pepper powder. The standardized manufacturing method of nabak kimchi was as follows: washing ingredients, cutting radish and baechu cabbage $(2.5\times2.5\times0.5\;cm)$, salting for 20 min, washing and draining, pretreatment of ingredients, dissolving red pepper powder in water, blending, mixing, and adding the water to the mixed ingredients. Fermentations at $5^{\circ}C$ for 8 days, at $10^{\circ}C$ for 3 days, and at $20^{\circ}C$ for 1 day led to the acidity levels of $0.21\%,\;0.20\%,\;and\;0.31\%$, respectively. From the relationships between optimally ripened pH and acidity, nabak kimchi showed lower acidity of $0.20\~0.25\%$ with pH $4.2\~4.5.$ Like other kinds of kimchi, the Levels of Leuconostoc sp. were high specially at later stage of fermentation at low temperature $(5^{\circ}C)$. However, the levels of Lactobacillus sp. were low at $5^{\circ}C$. Nabak kimchi produced high levels of $CO_2$ in the initial fermentation period and followed by rapid decrease of $CO_2$ production with the fermentation. From the relationships between pH and $CO_2$ content, the highest $CO_2$ contents were found pH $4.0\~4.4$, 3.8 and 3.4 at $5^{\circ}C,\;10^{\circ}C$, and $20^{\circ}C$, respectively. This fact indicated that fermentation at $5^{\circ}C$ has the highest $CO_2$ content at optimally ripened pH of 4.3 and the fermentation at lower temperature such as $5^{\circ}C$ could extend the eatable time of nabak kimchi.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.5
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• pp.104-111
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• 2015

This study shows the mechanical properties of alkali-activated slag cement (AASC) synthesized using sulfate with NaOH solution. The used sulfates were calcium sulfate ($CaSO_4$, denoted CS) and sodium sulfate ($Na_2SO_4$, denoted SS). The replacement ratio of sulfates was 2.5, 5.0, 7.5 and 10.0% by weight of slag. NaOH solution of 2M and 4M concentration was used. A sample was activated with sulfate and activated with blended activator (blending NaOH solution with sulfate) respectively. 24 mix ratios were used and the water-binder weight ratio for the test was set 0.5. This research carried out the compressive strength, flexural strength, ultrasonic pulse velocity (UPV), absorption and X-ray diffraction (XRD). In the case of samples with CS, sample with 7.5% CS, sample with 2M NaOH+5.0% CS and sample with 4M NaOH+5.0% CS showed the good performance in the strength development. In the case of samples with SS, sample with 10.0% SS, sample with 2M NaOH+7.5% SS and sample with 4M NaOH+2.5% SS obtained good performance in strength. The results of UPV and water absorption showed a similar tendency to the strength properties. The XRD analysis of samples indicated that the hydration products formed in samples were ettringite, CSH and silicate phases. In this study, it is indicated that when compared to the use of sulfate only, the use of both sulfate and NaOH solution makes mechanical properties of AASC better.