• The Journal of Korean Academy of Prosthodontics
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• v.39 no.5
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• pp.556-575
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• 2001

For the improvement of denture fitness of changed residual ridge, denture liner can be used. Denture liner should be very stable physically in various environments of the mouth as well as be bonded strongly with denture resin. In this study. the specimens bonded with four kinds of soft denture liner and three kinds of hard denture liner were used to test the physical properties of the liners. All experimental groups were stored in $37{\pm}1^{\circ}C$ distilled water for 24hours, followed by thermocycling between $15^{\circ}C$ and $45^{\circ}C$ with 15 second dwell time. 1000, 2000, 3000 cycles of thermocycling were excuted and physical properties were measured by Instron Universal Testing Machine. The obtained results were as follows : 1. In tensile bond test of sea liners, it was shown that both of $Molloplast-B^{(R)}$ specimens before and after thermocycling had the highest tensile strength, and in case of hard liners, Dura-Liner $II^{(R)}$ specimen had the highest tensile strength before and after thermocycling. Depending on thermocycling, $Soft-Relining^{(R)}$, $Denture-Relining^{(R)}$, $Molloplast-B^{(R)}$, $Coe-Soft^{(R)}$ and $Kooliner^{(R)}$ specimen showed significant difference(p<0.05). 2. In strain test of soft liners, it was shown that $Molloplast-B^{(R)}$ specimen before thermocycling and the $Coe-Soft^{(R)}$ after thermocycling showed highest results, and in case of hard liners, the Dura-Liner $II^{(R)}$ specimen before and after thermocycling had the highest result. Depending on thormocycling, $Denture-Relining^{(R)}$, $Molloplast-B^{(R)}$ and Dura-Liner $II^{(R)}$ specimen showed significant difference(p<0.05). 3. In maximum distance test of soft liners. the $Molloplast-B^{(R)}$ specimen before thermocycling and the $Coe-Soft^{(R)}$ after thermocycling showed highest results. and in case of hard liners, the Dura-Liner $II^{(R)}$ specimen before and after thermocycling showed highest result. Depending on thermocycling, $Denture-Relining^{(R)}$, $Molloplast-B^{(R)}$ specimens showed significant difference(p<0.05). 4. In elasticity test of soft liners, the $Molloplast-B^{(R)}$ specimen before and after thermocycling showed highest result. and in case of hard liners, the Dura-Liner $II^{(R)}$ specimen before thermocycling and the $Tokuso-Rebase^{(R)}$ after thermocycling showed highest results. Depending on thermocycling, $Soft-Relining^{(R)}$ $Molloplast-B^{(R)}$ specimens showed significant difference (p<0.05).

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.53-64
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• 2017

Ultra-high performance fiber-reinforced concrete (UHPFRC) is characterized by a post-cracking residual tensile strength with a large tensile strain as well as a high compressive strength. To determine a material tensile strength of UHPFRC, three-point loading test on notched prism and direct tensile test on doubly notched plate were compared and then the design tensile strength is decided. Shear tests on nine I-shaped beams with varied types of fiber volume ratio, shear span ratio and size effect were conducted to investigate shear behavior in web. From the test results, the stress redistribution ability represented as diagonal cracked zone was quantified by inclination of principal stress in web. The test results shows that the specimens were capable of resistance to shear loading without stirrup in a range of large deformation and the strength increase with post-cracking behavior is stable. However at the ultimate state all test specimens failed as a crack localization in the damaged zone and the shear strength of specimens is affected by shear span ratio and effective depth. Strength predictions show that the existing recommendations should be modified considering shear span ratio and effective depth as design parameters.

• International Journal of High-Rise Buildings
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• v.10 no.4
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• pp.335-344
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• 2021

In structural engineering practice, understanding the performance of composite columns under extreme loading conditions such as high-rise bulding, long span and heavy loads is essential to accuratly predicting of material responses under severe loads such as fires or earthquakes. Hitherto, the combined effect of partial axial loads and subsequent elevated temperatures on the performance of hollow steel column filled fly ash concrete have not been widely investigated. Comprehensive test was carried out to investigate the effect of elevated temperatures on partial axially loaded square hollow steel column filled fly ash concrete as reported in this paper. Four batches of hollow steel column filled fly ash concrete ( 30 percent replacement of fly ash), (HySC) and normal concrete (CFHS) were subjected to four different load levels, n_f of 20%, 30%, 40% and 50% based on ultimate column strength. Subsequently, all batches of the partially damage composite columns were exposed to transient elevated temperature up to 250℃, 450℃ and 650℃ for one hour. The overall stress - strain relationship for both types of composited columns with different concrete fillers were presented for each different partial load levels and elevated temperature exposure. Results show that CFHS column has better performance than HySC at ambient temperature with 1.03 relative difference. However, the residual ultimate compressive strength of HySC subjected to partial axial load and elevated temperature exposure present an improvement compared to CFHS column with percentage difference in range 1.9% to 18.3%. Most of HySC and CFHS column specimens failed due to local buckling at the top and middle section of the column caused by concrete crushing. The columns failed due to global buckling after prolong compression load. After the compression load was lengthened, the columns were found to fail due to global buckling except for HySC02.

• Journal of Microbiology and Biotechnology
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• v.29 no.7
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• pp.1043-1052
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• 2019

Active lipase-producing bacterium Burkholderia gladioli Bps-1 was rapidly isolated using a modified trypan blue and tetracycline, ampicillin plate. The electro-phoretically pure enzyme was obtained by purification using ethanol precipitation, ion-exchange chromatography, and gel filtration chromatography. The molecular weight was 34.6 kDa and the specific activity was determined to be 443.9 U/mg. The purified lipase showed the highest activity after hydrolysis with $p-NPC_{16}$ at a pH of 8.5 and $50^{\circ}C$, and the $K_m$, $k_{cat}$, and $k_{cat}/K_m$ values were 1.05 mM, $292.95s^{-1}$ and $279s^{-1}mM^{-1}$, respectively. The lipase was highly stable at $7.5{\leq}pH{\leq}10.0$. $K^+$ and $Na^+$ exerted activation effects on the lipase which had favorable tolerance to short-chain alcohols with its residual enzyme activity being 110% after being maintained in 30% ethanol for 1 h. The results demonstrated that the lipase produced by the strain B. gladioli Bps-1 has high enzyme activity and is an alkaline lipase. The lipase has promising chemical properties for a range of applications in the food-processing and detergent industries, and has particularly high potential for use in the manufacture of biodiesel.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.485-496
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• 2013

In recent years, frequent terror or military attacks by explosion or impact accidents have occurred. Examplary case of these attacks were World Trade Center collapse and US Department of Defense Pentagon attack on Sept. 11 of 2001. These attacks of the civil infrastructure have induced numerous casualties and property damage, which raised public concerns and anxiety of potential terrorist attacks. However, a existing design procedure for civil infrastructures do not consider a protective design for extreme loading scenario. Also, the extreme loading researches of prestressed concrete (PSC) member, which widely used for nuclear containment vessel, gas tank, bridges, and tunnel, are insufficient due to experimental limitations of loading characteristics. To protect concrete structures against extreme loading such as explosion and impact with high strain rate, understanding of the effect, characteristic, and propagation mechanism of extreme loadings on structures is needed. Therefore, in this paper, to evaluate the impact resistance capacity and its protective performance of bi-directional unbonded prestressed concrete member, impact tests were carried out on $1400mm{\times}1000mm{\times}300mm$ for reinforced concrete (RC), prestressed concrete without rebar (PS), prestressed concrete with rebar (PSR, general PSC) specimens. According to test site conditions, impact tests were performed with 14 kN impactor with drop height of 10 m, 5 m, 4 m for preliminary tests and 3.5 m for main tests. Also, in this study, the procedure, layout, and measurement system of impact tests were established. The impact resistance capacity was measured using crack patterns, damage rates, measuring value such as displacement, acceleration, and residual structural strength. The results can be used as basic research references for related research areas, which include protective design and impact numerical simulation under impact loading.

• Journal of Life Science
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• v.18 no.6
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• pp.789-795
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• 2008

To study the possible use of probiotics in fish farming, we evaluated antagonism of antibacterial strain Bacillus amyloliquefaciens H41 against the fish pathogenic bacterium Vibrio anguillarum NCMB1. The purification of growth inhibition factor produced by B. amyloliquefaciens H41 was achieved by obtaining supernatant of this bacterium. The growth inhibition factor was purified to homogeneity by 70% ammonium sulfate precipitation, DEAE-sephadex A-50 ion exchange chromatography, sephadex G-200 gel filtration column chromatography, and sephadex G-50 gel filtration column chromatography with 40.8 fold of purification and 2.9% yield. The molecular weight of the purified growth inhibition factor was 48 kDa as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The optimum pH and temperature for the growth inhibition factor were pH 7.5 and $30^{\circ}C$, respectively. The activity of growth inhibition factor was enhanced slightly by some metal ions, such as $Mg^{+2}$, $Mn^{+2}$, but was inhibited by the addition of $Co^{+2}$, $Hg^{+2}$, $Zn^{+2}$ and $Ag^{+2}$. NaCl stability of the growth inhibition factor was observed with 50% residual activity at 3% NaCl concentration. Toxicity test showed that the purified B. amyloliquefaciens H41 growth inhibition factor did not affect the live of Japanese flounder (Paralichthys olivaceus) and the effectiveness was 78% of residual lethality compared to commercial antibacterial agents.

• Korean Journal of Agricultural Science
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• v.14 no.1
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• pp.98-133
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• 1987

The mechanical and rheological properties of agricultural materials are important for engineering design and analysis of their mechanical harvesting, handling, transporting and processing systems. Agricultural materials, which composed of structural members and fluids do not react in a purely elastic manner, and their response when subjected to stress and strain is a combination of elastic and viscous behavior so called viscoelastic behavior. Many researchers have conducted studies on the mechanical and rheological properties of the various agricultural products, but a few researcher has studied those properties of rice plant, and also those data are available only for foreign varieties of rice plant. This study are conducted to experimentally determine the mechanical and the rheological properties such as axial compressive strength, tensile strength, bending and shear strength, stress relaxation and creep behavior of rice stems, and grain detachment strength. The rheological models for the rice stem were developed from the test data. The shearing characteristics were examined at some different levels of portion, cross-sectional area, moisture content of rice stem and shearing angle. The results obtained from this study were summarized as follows 1. The mechanical properties of the stems of the J aponica types were greater than those of the Indica ${\times}$ Japonica hybrid in compression, tension, bendingand shearing. 2. The mean value of the compressive force was 80.5 N in the Japonica types and 55.5 N in the Indica ${\times}$ Japonica hybrid which was about 70 percent to that of the Japonica types, and then the value increased progressively at the lower portion of the stems generally. 3. The average tensile force was about 226.6 N in the Japonica types and 123.6 N in the Indica ${\times}$ Japonica hybrid which was about 55 percent to that of the Japonica types. 4. The bending moment was $0.19N{\cdot}m$ in the Japonica types and $0.13N{\cdot}m$ in the Indica ${\times}$ Japonica hybrid which was 68 percent to that of the Japonica types and the bending strength was 7.7 MPa in the Japonica types and 6.5 MPa in the Indica ${\times}$ Japonica hybrid respectively. 5. The shearing force was 141.1 N in Jinju, the Japonica type and 101.4 N in Taebaeg, the Indica ${\times}$ Japonica hybrid which was 72 percent to that of Jinju, and the shearing strength of Taebaeg was 63 percent to that of Jinju. 6. The shearing force and the shearing energy along the stem portion in Jinju increased progressively together at the lower portions, meanwhile in Taebaeg the shearing force showed the maximum value at the intermediate portion and the shearing energy was the greatest at the portion of 21 cm from the ground level, and also the shearing strength and the shearing energy per unit cross-sectional area of the stem were the greater values at the intermediate portion than at any other portions. 7. The shearing force and the shearing energy increased with increase of the cross-sectional area of the rice stem and with decrease of the shearing angie from $90^{\circ}$ to $50^{\circ}$. 8. The shearing forces showed the minimum values of 110 N at Jinju and of 60 N at Taebaeg, the shearing energy at the moisture content decreased about 15 percent point from initial moisture content showed value of 50 mJ in Jinju and of 30 mJ in Taebaeg, respectively. 9. The stress relaxation behavior could be described by the generalized Maxwell model and also the compression creep behavior by Burger's model, respectively in the rice stem. 10. With increase of loading rate, the stress relaxation intensity increased, meanwhile the relaxation time and residual stress decreased. 11. In the compression creep test, the logarithmic creep occured at the stress less than 2.0 MPa and the steady-state creep at the stress larger than 2.0 MPa. 12. The stress level had not a significant effect on the relaxation time, while the relaxation intensity and residual stress increased with increase of the stress level. 13. In the compression creep test of the rice stem, the instantaneous elastic modulus of Burger's model showed the range of 60 to 80 MPa and the viscosities of the free dashpot were very large numerical value which was well explained that the rice stem was viscoelastic material. 14. The tensile detachment forces were about 1.7 to 2.3 N in the Japonica types while about 1.0 to 1.3 N in Indica ${\times}$ Japonica hybrid corresponding to 58 percent of Japonica types, and the bending detachment forces were about 0.6 to 1.1 N corresponding to 30 to 50 percent of the tensile detachment forces, and the bending detachment of the Indica ${\times}$ Japonica hybrid was 0.1 to 0.3 N which was 7 to 21 percent of Japonica types. 15. The detachment force of the lower portion was little bigger than that of the upper portion in a penicle and was not significantly affected by the harvesting period from September 28 to October 20. 16. The tensile and bending detachment forces decreased with decrease of the moisture content from 23 to 13 percent (w.b.) by the natural drying, and the decreasing rate of detachment forces along the moisture content was the greater in the bending detachment force than the tensile detachment force.

• Food Science and Preservation
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• v.15 no.3
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• pp.469-476
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• 2008

Lactic acid fermentation of peach juice was carried out by using Lactobacillus plantarum KLAB21, a strain with a high level of antimutagenic activity, When the fermentation was carried out at 25, 30, 37 and $40^{\circ}C$, the highest level in the viable counts and acid production was obtained at $37^{\circ}C$. The sterilized peach juice showed a higher level of viable counts and acid production than the non-sterilized juice. And more viable counts and acid production were observed in the juice fermented by L. plantarum KLAB21 only than that obtained by a mixed culture of L. plantarum KLAB21 and Leuconostoc mesenteroides cells. When the lactic acid fermentation was performed for 5 days, the first 3 days of fermentation resulted in an increase of the viable counts from 8.2 to of 9.2 of log cfu/mL which is the highest level, as well as a decrease of the residual reducing sugar content from 5.6 to 0.1 % Decrease in the viable counts and m significant changes in the residual reducing sugar content were observed for further fermentation up to 5 days. However, the titratable acid content increased and the pH value decreased during the fermentation for 5 days to reach the highest titratable acid content (1,98%) and the lowest pH value (3.14) after 5 days of fermentation. HPLC analysis of the organic acids showed 1,236 mg% of lactic acid and 841 mg% of galacturonic acid contents in the fermented juice which were not detected in the fresh juice before fermentation. Antimutagenic effects of $100\;{\mu}L$ of the fermented peach juice supernatant were shown to be 97.7% against MNNG(N-methyl-N'-nitro-N-nitrosoguanidine), and 58.3% against NPD(4-nitro-O-phenylenediamine) in Salmonella enterica serovar Typhimurium TA100.

• Korean Journal of Agricultural Science
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• v.5 no.1
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• pp.35-41
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• 1978

Extensive selection works on wild yeasts of fruits were carried cut to obtain strains which are applicable to apple wine making. Among the total number of 1,358 yeast strains which were isolated from various fruit samples collected from the vicinity of Daejeon and other regions cf Korea, the strains SH-49, SH-129 and SH-338 were found to be useful. Then experiments on their morphological and physiological characteristics, and on the aspects of practical use in apple wine making were proceeded. The results obtained were as follows: 1. The strains SH-49 and SH-129, particularly SH-49, were appeared to have good fermentation ability, tolerance to sulfur dioxide and to produce fine quality of apple wine. 2. Apple wines made by using the strain, SH-49 and SH-129 contained less amount of total acids than those by other strains. 3. Apple wines of SH-49 and SH-129 were clarified rapidly during the primary fermentation period, and their absorbancy at 430 nm after 45 days of storage were approximately half of others. 4. Apple wine of SH-338 contained higher amount of residual sugar and its quality was superior to others. It is considered that this strain could be used in the production of apple wine of a characteristic quality. 5. The strains SH-49 and SH-338 were identified as a Saccharomyces cerevisiae according to Taxanomic Study of Yeasts by Lodder, however, classification of SH-129 was suspended for further study.

• Korean Journal of Microbiology
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• v.45 no.4
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• pp.411-415
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• 2009

Some microorganisms are capable of leaching Mn(II) from nonsulfidic manganese ores indirectly via nonenzymatic processes. Such reductive dissolution requires organic substrates, such as glucose, sucrose, or galactose, as a source of carbon and energy for microbial growth. This study investigated characteristics of Mn(II) leaching from manganese nodules by using heterotrophic Bacillus sp. strain MR2 provided with corn starch as a less-expensive substrate. Leaching of Mn(II) at 25.6 g Mn(II) $kg^{-1}$ nodule $day^{-1}$ was accompanied with cell growth, but part of the produced Mn(II) re-adsorbed onto residual $MnO_2$ particles after 24 h. Direct contact of cells to manganese nodule was not necessary as a separation between them with a dialysis tube produced similar amount [24.6 g Mn(II) $kg^{-1}$ nodule $day^{-1}$]. These results indicated an involvement of extracellular diffusible compound(s) during Mn(II) leaching by strain MR2. In order to optimize a leaching process we tested factors that influence the reaction, and the most efficient conditions were $25\sim35^{\circ}C$, pH 5~7, inoculum density of 1.5~2.5% (v/v), pulp density of 2~3 g/L, and particle size <75 ${\mu}m$. Although Mn(II) leaching was enhanced as particle size decrease, we suggest <212 ${\mu}m$ as a proper size range since more grinding means more energy consumption The results would help for the improvement of bioleaching of manganese nodule as a less expensive, energy-efficient, and environment-friendly technology as compared to the existing physicochemical metal recovery technologies.