• Korean Journal of Microbiology
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• v.45 no.4
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• pp.324-331
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• 2009

MK1 strain, an obligate aerobic heterotrophic bacterium isolated from the rotten tissue of Neungee mushroom (Sarcodon aspratus), produces a copious amount of exopolysaccharide (EPS), which could evoke macrophage activation. Investigations on optimal culture conditions of MK1 and physical properties of MK1 EPS were made. Glucose, galactose, fructose, and sucrose supported well growth of MK1, but potato starch and dextrin did not. However, lactose seemed to be a less favorable carbon source. Optimal growth of MK1 was obtained at pH 7.0, $30^{\circ}C$, and 200 rpm with 2% glucose, and 0.2~0.05% $(NH_4)_2SO_4$. $EPS_{opt}$ obtained from an optimal growth condition constituted of carbon (37.1%), nitrogen (2.2%), oxygen (49.3%), and hydrogen (6.4%), but no sulfur. Paper chrogromatogram of the acid-hydrolysate of $EPS_{opt}$ suggested that MK1 EPS seemed to be hetropolysaccharide composed of a few number of monosaccharides including amino- and acidic-sugars. Its molecular mass determined by SDS-polyacrylamide gel electrophoresis varied from 14.8 to 47.9 kDa. Physical properties of $EPS_{glu}$ obtained from cell grown in glucose medium, such as relative viscosity ($_{rel}$) and crystalline morphology were rather affected by pH of the growth medium. Relative viscosity ($_{rel}$) of exopolysaccaride (0.1 g/ml) harvested from cells grown at medium pH ranging from 6.0 and 7.5 was 1.23 and 1.39, respectively. The freeze-dried exopolysaccharide obtained at low pH (6.0 and 6.5) was fine crystaloid and water-soluble, whereas those obtained at high pH (7.0 and 7.5) was rather gluey and less water-soluble.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.541-555
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• 2020

The grouting method is used for reinforcing and waterproofing the soft ground, increasing the bearing capacity of structures damaged by lowering or subsidence due to rise and vibration, and for ordering. This study attempted to develop a blast furnace slag-based cementless grout material to increase the strength and hardening time of the grout material using reinforcing fibers. In this regard, in this study, it was used in combination with calcium hydroxide, which is an alkali stimulant of the three fine powders of blast furnace slag, and the content of calcium hydroxide was used by substituting 10, 20, and 30% of the fine powder of blast furnace slag. In addition, in order to compare the strength according to the presence or absence of reinforcing fibers, an experiment was performed by adding 0.5% of each fiber. As the content of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased, and it was confirmed that the crosslinking action of the fibers in the grout material increased the uniaxial compressive strength. In addition, it was confirmed that the gel time sharply decreased as the content of the alkali stimulate increased.

• The Journal of Engineering Geology
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• v.31 no.1
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• pp.67-81
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• 2021

Grouting is used for reinforcement and waterproofing of soft ground to increase its bearing capacity, reduce the impacts of rising or lowering groundwater levels, and reduce subsidence due to vibration and general causes. This study investigated the enhancement of grout strength and hardening time by the addition of reinforcing fibers, and the development of non-cement grouting materials from blast furnace slag. An experiment was performed to measure the increase in grout strength resulting from the addition of 0.5% increments of aramid and carbon reinforcing fibers. The results show that the uniaxial compressive strength of grout increases with increasing content of reinforcing fiber. Comparison of three admixtures of finely powdered blast furnace slag and 10%, 20%, and 30% calcium hydroxide stimulating agent showed that the uniaxial compressive strength of the mixture increases with increasing content of alkaline stimulant; however, the strength was lower than for 100% pure cement. The reaction of calcium hydroxide with blast furnace slag powder, which increases the strength of the grout, is more effective if injected as a solution rather than a powder.

• Journal of the Korean GEO-environmental Society
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• v.24 no.1
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• pp.15-23
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• 2023

The grouting method is a method of construction for the purpose of waterproofing and reinforcing soft ground. When grout is injected into the ground, there are various types of penetration and diffusion of grout depending on the shape of the ground, the size of soil, the porosity, and the presence or absence of groundwater. the current situation. Therefore, in this study, to investigate the penetration performance of the grouting to conductive material, laboratory tests were performed on the addition of the conductive material. In the injection test, 0%, 3%, and 5% of the mixed water were added as conductive materials to the grout, and the original ground condition was composed of various types of ground composed of gravel and silica sand. Conductive grout is injected by pressure into the model ground using a dedicated injection device, and the injection time (t), pressure (p), flow rate (v) and injection amount (q) are measured, and the hardened body injected in the model ground is collected. Penetration performance was evaluated. In the results of the grout injection experiment, the amount of conductive material used and the grout injection rate showed an inverse relationship, and it was confirmed that the penetration pattern was changed according to the size of the soil particles in the model ground. The grout containing the conductive material has relatively good penetration into the ground and excellent strength and durability of the hardened body, so it was judged that it could be used as an additive for measuring the penetration range of the grout.

• Journal of Biosystems Engineering
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• v.34 no.6
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• pp.446-453
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• 2009

This study was conducted to find condition of improving the quality of peach by using surfacing washing system. The rate of weight loss of A,B groups were showed slower decreasing trend than CT group and the value of soluble solid degree was not different significantly among all groups from the results of stored peach treat with surface washing system of peach in the first experiment. The colory value of surface were increased with increasing storage period in all treatments. Browning pace of A,B groups were slower than control. Emission of carbon dioxide was increased from the results of respiration rate, 6-10 mL/kg/hr $(10^{\circ}C)$ and 32-41 mL/kg/hr $(25^{\circ}C)$. In second experiment with surface washing system of peach, the value of soluble solid was showed with similar value from 10 $Brix^{\circ}$ to 13 $Brix^{\circ}$. The pace of soft rot of EW groups were lower than CT groups from the results of hardness during storage period. The results of colory value was not showed with significant difference in $15^{\circ}C$ and $20^{\circ}C$ storage temperature but changed to browning in EW groups. The moisture contents was from 85% to 90% in all groups. And the count of total microorganism of EW groups were lower than control. Also total coliform of EW groups were negative. In sensory evaluation, washing peach was showed higher value with significant difference in all acceptability.

• Journal of the Korean Society for Nondestructive Testing
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• v.28 no.1
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• pp.25-32
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• 2008

[ $^{169}Yb$ ] industrial NDT sealed sources were developed by using $Yb_2O_3$ pellets as the target and demonstrated for their performance. To produce the pellets, optimal compacting and sintering conditions were determined experimentally. Source holders for $^{169}Yb$ were designed and fabricated. After assembling an active source produced from HANARO with the developed source holder, a demonstration experiment was performed to compare the quality of the radiographs from $^{192}Ir$ and soft X-rays. This demonstration study showed that the developed $^{169}Yb$ produced better radiographs than $^{192}Ir$ for a carbon steel with less than a 4 mm thickness.

• Journal of the Korean Geotechnical Society
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• v.21 no.6
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• pp.117-126
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• 2005

The chemical property analysis on the deposited clay using scanning electron microscope and energy dispersive x-ray spectrometer were performed. Also, the triaxial compression tests and consolidation tests using NaCl aqueous solution and leachate as substitute pore (or saturated) water in samples were carried out to find out the behaviour characteristics of strength and deformation of contaminated deposited clay. from the chemical composition analysis results of clay samples, the magnitudes of composition ratio were revealed in the order of O, C, Si, Al, and Fe. Of these, why the ratio of carbon appeared to be large is estimated as due to the increase of the phyto-planktons after the construction of tide embankment. In the triaxial compression test and consolidation test results, the shear strength and compression properties have increased with the increase in concentration of contaminant (NaCl). This phenomenon is considered as to be caused by the changes of soil structure to flocculent structure owing to the decrease in the thickness of diffuse double layer in proportion to increase in the concentration of electrolyte.

• Mycobiology
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• v.36 no.4
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• pp.249-254
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• 2008

Minimal growth inhibitory concentrations (MICs) of chitosan acetate (M.W. 60 kDa) on heterotrophic bacteria (strains MK1, S, and R) isolated from the soft-rotten tissues of Neungee mushroom (Sarcodon aspratus) were measured. The slimy substance produced by the MK1 strain was responsible for the diseased mushroom’s appearance. The S and R strains were members of the Burkholderia cepacia complex. These strains showed different levels of susceptibility toward chitosan acetate. The MIC of chitosan acetate against the MK1 and S strains was 0.06%. The MIC against the R strain was greater than 0.10%. Survival fractions of the MK1 and S strains at the MIC were $3\;{\times}\;10^{-4}$ and $1.4\;{\times}\;10^{-3}$ after 24 h, and $2\;{\times}\;10^{-4}$ and $7\;{\times}\;10^{-4}$ after 48 h, respectively. Survival fractions of the R strain after 24 and 48 hr at 0.1% chitosan acetate were $1\;{\times}\;10^{-2}$ and $6.9\;{\times}\;10^{-3}$, respectively. Compared to the MK1 and S strains, the low susceptibility of the R stain towards chitosan acetate could be due to the ability of the R strain to utilize chitosan as a carbon source. Thirty-eight percent of Neungee pieces treated in a 0.06% chitosan acetate solution for $2{\sim}3$ second did not show any bacterial growth at 4 days, whereas bacterial growth around untreated mushroom pieces occurred within 2 days. These data suggest that chitosan acetate is highly effective in controlling growth of indigenous microorganisms on Neungee. The scanning electron micrographs of the MK1 strain treated with chitosan revealed a higher degree of disintegrated and distorted cellular structures.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.448-448
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• 2010

Magnetic random access memory (MRAM) has made a prominent progress in memory performance and has brought a bright prospect for the next generation nonvolatile memory technologies due to its excellent advantages. Dry etching process of magnetic thin films is one of the important issues for the magnetic devices such as magnetic tunneling junctions (MTJs) based MRAM. CoFeB is a well-known soft ferromagnetic material, of particular interest for magnetic tunnel junctions (MTJs) and other devices based on tunneling magneto-resistance (TMR), such as spin-transfer-torque MRAM. One particular example is the CoFeB - MgO - CoFeB system, which has already been integrated in MRAM. In all of these applications, knowledge of control over the etching properties of CoFeB is crucial. Recently, transferring the pattern by using milling is a commonly used, although the redeposition of back-sputtered etch products on the sidewalls and the low etch rate of this method are main disadvantages. So the other method which has reported about much higher etch rates of >$50{\AA}/s$ for magnetic multi-layer structures using $Cl_2$/Ar plasmas is proposed. However, the chlorinated etch residues on the sidewalls of the etched features tend to severely corrode the magnetic material. Besides avoiding corrosion, during etching facets format the sidewalls of the mask due to physical sputtering of the mask material. Therefore, in this work, magnetic material such as CoFeB was etched in an ICP etching system using the gases which can be expected to form volatile metallo-organic compounds. As the gases, carbon monoxide (CO) and ammonia ($NH_3$) were used as etching gases to form carbonyl volatiles, and the etched features of CoFeB thin films under by Ta masking material were observed with electron microscopy to confirm etched resolution. And the etch conditions such as bias power, gas combination flow, process pressure, and source power were varied to find out and control the properties of magnetic layer during the process.

• Journal of Sensor Science and Technology
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• v.32 no.1
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• pp.44-50
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• 2023

In this study, a polydimethylsiloxane (PDMS)-based drag force-type flowmeter was fabricated using a graphite-carbon nanotube (CNT) composite as a piezoresistive material and evaluated. The device was in the form of a cantilever, which was composed of the soft material, PDMS, and fabricated using a mold manufactured by a three-dimensional printer. The cost-effective graphite was mixed with CNTs to serve as a piezoresistive material. The optimal mixing ratio was investigated, and the piezoresistive material formed using a graphite:PDMS:CNT ratio of 1.5:1:0.01 was adopted, which showed a stable output and a high sensitivity. Various forward and backward air flows in the range of 0-10 m/s were measured using the fabricated flowmeter, and both tensile and compression characteristics were evaluated. The measured results showed a stable output, with the resistance change gradually increasing with the air flow rate. Repeatability characteristics were also tested at a repeated air flow of 10 m/s, and the flowmeter responded to the applied air flow well. Consequently, the fabricated device has a high sensitivity and can be used as a flowmeter.