• Korean Journal of Environmental Biology
• /
• v.17 no.2
• /
• pp.191-198
• /
• 1999

Enzyme-aided bleaching of softwood and hardwood kraft pulps by a xylanase preparation from an alkalophilic fungus Cephalospotium sp. RYM-202 was studied. Maximal solubilization of Pulp xylan was obtained at 5$0^{\circ}C$ in both kraft pulps. The optimum pH of the enzyme for the hydrolysis of pulp xylan was 8.0 and more than 90% of the maximal activity was detected at 9.0. The positive effects of xylanase pretreatment on bleachability of softwood and hardwood kraft pulps were observed. The kappa number of softwood and hardwood kraft pulps was decreased by 3.7 and 2.0 units, respectively. The pulp fibre integrity was not significantly affected by xylanase pretreatment when the physical properties of handsheets made from xylanase-treated pulps were compared with those of handsheets from untreated pulps. These results indicate that the alkaline xylanase of Cephalospotium sp. RYM-202 is well suitable for application in enzymatic prebleaching of softwood and hardwood kraft pulps under the alkaline conditions.

• Journal of Sensor Science and Technology
• /
• v.6 no.6
• /
• pp.451-457
• /
• 1997

The thick films of oxide semiconductors such as $WO_{3}$, $SnO_{2}$ and ZnO for the $NO_{2}$ detection of sub-ppm range have been prepared and their characteristics were investigated. It is showed that the optimum operating temperatures of the sensors are $300^{\circ}C$ and $220{\sim}260^{\circ}C$ for $WO_{3}$-based and $SnO_{2}$-based thick films, and ZnO-based thick films, respectively. Since the resistance of ZnO-based thick films are extremely high($>10^{6}{\Omega}$), the signal to noise ratio was comparatively low. In order to determine the selectivity, the films are exposed to the interfering gases such as ozone, ammonia, methane and the mixture of carbon monoxide and propane. $WO_{3}$-ZnO(3 wt.%) and $SnO_{2}-WO_{3}$(3 wt.%) thick film sensors show high sensitivity, good selectivity, excellent reproducibility and the linearity of $NO_{2}$ concentration versus sensor resistance. The preliminary results clearly demonstrated that the sensor can be successfully applied for the detection of $NO_{2}$ in sub-ppm range.

• Korean Journal of Food Science and Technology
• /
• v.35 no.5
• /
• pp.856-864
• /
• 2003

The purpose of this study was to examine the quality variations of cake and cake batter when either butter or soybean oil was added in plain sponge cake batter. Soybean oil or butter was added to the batter at ratios of 20, 40, and 60% at 20, 35, 60, and $80^{\circ}C$. The physico-chemical properties of cake batter and cake were measured to evaluate the effects of ratio and temperature of butter and soybean oil. At higher ratios of butter or soybean oil and lower temperatures, the specific gravity of the cake batter increased while the interrelations among weight, volume, and specific loaf volume decreased. L- and b- values were the same, but a-value increased remarkably with higher ratios of butter. The effect of adding butter or soybean oil on hardness was shown to be lowest at 40% and $80^{\circ}C$. Baking loss in the baking process with soybean oil decreased with increasing oil quantity and temperature. Moisture content did not change with temperature, but did decline with increasing amounts of butter or soybean oil. These results show that the optimum condition for sponge cake would be 40% soybean oil at $80^{\circ}C$.

• Korean Journal of Food Science and Technology
• /
• v.35 no.1
• /
• pp.7-14
• /
• 2003

Physico-chemical and sensory characteristics of six dongchimi cultivars were evaluated. Moisture and sugar contents were 94.2% and $4.30^{\circ}Brix$ for three spring radish cultivars, while 92.9% and $7.30^{\circ}Brix$ for three autumn ones. pH $(5.7{\sim}6.1)$ and acidity $(0.09{\sim}0.12%)$ did not show significant differences among cultivars. pH decreased steadily up to 21 days to reach optimum pH of 4.0. The maximum number of total lactic acid bacteria, $10^8{\sim}10^9\;CFU/mL$, was reached at pH 4.0. The final acidity of spring radishes was lower than that of autumn ones, and was proportional to the sugar content of the radishes. The firmness of spring radish decreased rapidly compared to the autumn ones. Cheongbok was found suitable for dongchimi, because its firmness level was maintained around $165.0{\times}10^3\;N/m^2$ at 35 days. Sensory evaluation revealed 96371 among spring radishes and cheongbok among autumn radishes scored high in firmness, chewiness, flavor, and overall acceptance. These results suggest that autumn radishes are suitable for dongchimi fermentation with cheongbok being the best among the cultivars.

• Korean Journal of Food Science and Technology
• /
• v.21 no.1
• /
• pp.149-153
• /
• 1989

Polygalacturonase(PG) and pectinesterase(PE) were extracted from Chinese cabbage and physicochemical properties of the enzymes were characterized. The preheating conditions for maximum retention of Kimchi texture were also studied. The activity of PE was highest at $50^{\circ}C$ and at 0.02M $CaCl_2$ but decreased in 0.2M $CaCl_2$, PG exhibited maximum activity at $65^{\circ}C$ with 0.3mM $CaCl_2$ but was inhibited by $CaCl_2$ at 0.5mM. Both of the enzymes, however, exhibited the maximum activity with 0.25M NaCl. Optimum preheating treatment was determined for minimum PG activity and maximum PE activity. Thus a maximum crispness and firmness was obtained with preheating in 0.05M $CaCl_2$ solution at $50^{\circ}C$ for 1.5hr results indicated that PE activity and calcium ion were very effective in preserving firmness.

• Journal of Korean Society for Geospatial Information Science
• /
• v.17 no.3
• /
• pp.3-12
• /
• 2009

Soil is one of the Earth's most important resources. There are many differences among the soils of plains.like and hilly terrains, and therefore, accurate and comprehensive information on soil is essential for optimum and sustainable soil utilization. However, information on the soil of the hilly terrains of the Eastern Ghats of Tamil Nadu, India, is limited or absent. In the present study, Kolli hill, one among the hills of the Eastern Ghats, was soil.inventoried and mapped using a ground survey and remote sensing. Soil samples were collected and their physico.chemical properties analyzed according to the United States Department of Agriculture (USDA) standards. The soils were classified up to the family level. As a result of this study, 30 soil series belonging to ten sub.groups of five great groups and three sub.orders and orders each, were identified (classified to the family level) and mapped. Entisols, Inseptisols and Alfisols were the three orders, among which Entisols was the major one, occupying 75% of the area. Among the five great groups, Ustorthents occupied majority of the area (73%). Lithic Ustorthents and Typic Ustorthents were the two major sub.groups, occupying 40% and 26% of the total area, respectively. The present soil resource mapping of the Eastern Ghats of Tamil Nadu is a pioneer study, which yielded valuable information on the soil in this region.

• Journal of the Korean GEO-environmental Society
• /
• v.10 no.6
• /
• pp.19-25
• /
• 2009

The current study developed light-weighted mixed soil that can solve problems related with soft soil such as ground subsidence, sliding and lateral displacement of ground. By reducing weight of reclaimed soil through mixing phosphogypsum and recycled EPS beads with the weathered granite soil. A series of geotechnical laboratory tests including physical index test, compaction test, CBR test, and direct shear test were performed and engineering properties were reviewed in order to assess applicability of the light-weighted mixed soil for roads and abutment and various back-filling materials at the reclamation area. Based on the laboratory test results, it was found that the maximum dry unit weight of the light-weighted soil ranges $14.32{\sim}15.79kN/m^3$ and the optimum water content ranges 21.91~24.23%, which means there is 11~19.3% weight decrease effect when comparing with general weathered granite soil. Also it was found that the corrected CBR value ranges 10.4~18.4% satisfying the domestic regulations on road subgrade and back-filling material. In addition, as for shear strength parameter, cohesion ranges 10.79~18.64 kPa and internal frictional angle ranges $35.4{\sim}37.2^{\circ}$, which are similar with those of general construction soil and back-filling material used in Korea. So it can be concluded that light-weighted mixed soil with phosphogypsum can be used effectively for soft reclamation ground as actual filling material and back-filling material. From the current study, it was found that light-weighted mixed soil with phosphogypsum has not only weight reduction effect, but also has no special problems in shear strength and bearing capacity. Therefore, it is expected that phosphogypsum can be recycled in bulk as road subgrade and back-filling material at the reclamation area.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.29 no.2
• /
• pp.180-188
• /
• 2002

Newly developed curing units(plasma arc curing units) operate at relatively high intensity and are claimed to result in optimum properties of composite resin in a short curing time. The purpose of this study was to evaluate the microhardness and microleakage at the resin-tooth interface of two types of composite resins polymerized with visible light and plasma arc curing units. The results from the present study can be summarized as follows 1. Microhardness in each depth was shown to be higher in group AHL than AP3 & AP6. Group ZHL was lower than AP6 at surface(p<0.05) and had no statistically significant difference at 1mm and 2mm(p>0.05). In other depths, group ZHL was higher than ZP3 and ZP6(p<0.05). 2. The incremental reduction in microhardness with depth was shown to be in all group except in surface-1mm of group AHL and $1{\sim}2mm$ of group ZHL(p<0.05). 3. Degree of microleakage in all oops were shown to be higher in gingival margin than occlusal margin but no statistically significant difference(p>0.05). 4. Differences between curing methods in microleakage were shown to be no statistically significant difference(p>0.05). 5. Differences between composite resins in microleakage were shown to be no statistically significant differ once(p>0.05).

• Korean Chemical Engineering Research
• /
• v.48 no.6
• /
• pp.704-711
• /
• 2010

Lignocellulose ($2^{nd}$ generation) is difficult to hydrolyze due to the presence of lignin and the technology developed for cellulose fermentation to ethanol is not yet economically viable. However, recent advances in the extremely new field of biotechnology for the ethanol production are making it possible to use of agriculture residuals and nonedible crops biomass, e.q., rice straw and miscanthus sinensis, because of their several superior aspects as agriculture residual and nonedible crops biomass; low lignin, high contents of carbohydrates. In this article, as the basic study of AP(Ammonia Percolation), the properties and the optium conditions of process were established, and then the overall efficiency of AP was investigated. The important independent variables for AP process were selected as ammonia concentration, reaction temperature, and reaction time. The percolation condition for maximizing the content of cellulose, the enzymatic digestibility, and the lignin removal was optimized using RSM(Response Surface Methodology). The determined optimum condition is ammonia concentration; 11.27%, reaction temperature; $157.75^{\circ}C$, and reaction time; 10.01 min. The satisfying results were obtained under this optimized condition, that is, the results are as follows: cellulose content(relative); 39.98%, lignin content(relative); 8.01%, and enzymatic digestibility; 85.89%.

• Journal of the Korean Electrochemical Society
• /
• v.2 no.1
• /
• pp.5-12
• /
• 1999

By the PVA-precursor method, polycrystalline powder of $Li_xNi_{1-y}Co_yO_2$, cathode material for lithium battery, was synthesized. Using the powder as the cathode material, lithium ion batteries were fabricated, whose electrochemical properties were measured. The effect of changing synthetic conditions, such as PvA/metal mole ratio, concentration of PVA, degree of polymerization of PVA, pyrolysis condition, and metal stoichiometry, on the battery performance was investigated. Considering the initial performance of the cell, the optimum stoichiometry of the $Li_xNi_{1-y}Co_yO_2$, synthesized by the PVA-precursor method was observed to be x: 1.0 and y=0.26. A minor phase of $Li_2CO_3$, which was generated by the residual carbon in the powder precursor, deteriorated the performance of the cell. In order to eliminate the minor phase, the precursor had to be pyrolyzed under the flow of dry air. Annealing the powder at $500^{\circ}C$ under the flow of dry air also eliminated the minor phase, and the performance of the cell was largely improved by the treatment.