• Journal of Ocean Engineering and Technology
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• v.22 no.5
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• pp.87-93
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• 2008

The objective of this paper is the investigation of the statistical properties of Vickers hardness (HV) of friction welded parts in nickel based super resisting steel, alloy 718 steel. First, we examine the statistical properties on the case of as-welded parts. Several Virkers indentations were made under same nominal conditions. This was repeated for three different applied loads, 100, 200 and 300g with a duration time, 10 second. The arithmetic mean of Vickers hardness in base metal (BM) materials is larger than that of HAZ in all applied loads. The measure of dispersion, that is, the coefficient of variation (COV) for BM and HAZ is decreased by increasing with the applied load. The distribution of Vickers hardness was not found to be symmetric type. The probability distribution of Vickers hardness was well followed Weibull distribution. The shape parameter and the scale parameter (characteristic hardness) are increased by increasing with the applied load, as both BM and HAZ.

• Journal of Environmental Science International
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• v.17 no.1
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• pp.113-118
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• 2008

[ $6{\sim}13mg/L$ ] base water concentration on monthly BOD has been kept at the Geukrak bridge point for this research target and it indicates the water quality under the existed rank. Due to this present condition of water quality, the demage of ecology from the upper stream to the lower one of the bridge could be conjectured. Moreover, nonstructural extinction of the ecology seems to have gotten worse between both the streams of Yeoungsan River. On this research, eco-corridor between the upper stream and the lower stream of the river should be ensured, the ecological demage needs to be cut off, a dispersed discharge method which the existed method of the 1st sewage plant in Gwangju was enhanced to should be inducted for the procuring of various water ecosystem, and the conditions by the scenario suggested from this research could be applied to a water quality model. then, analysis the improvement effect of the water quality adjacent the river. From the test result, Case3-Type1 scenario is thought to be the best one. From the test result with Case3-Type1 when the concentrated discharge was never done, 0.07 mg/L of BOD concentration was increased at the lower stream where Yeoungbon B point (Haksan Bridge) is but the water improvement effect of $0.24{\sim}2.87mg/L$ is thought to have been done at the area of water deterioration.

• Journal of the Korean Society for Nondestructive Testing
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• v.14 no.3
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• pp.151-156
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• 1994

Exertion has been made to develop high-temperature (about $250{\sim}650^{\circ}C$) immersion ultrasonic sensor for the visualization of objects, temperature measurement, dimensional check, or nondestructive testing of welds under liquid sodium. In this study, the feasibility of the ultrasonic sensor taking advantage of a strip waveguide was confirmed by water-experiment. The lowest order of antisymmetric Lamb wave was used in the frequency range with negligible dispersion. This plate wave was excited in the stainless steel strip waveguide of 1.0mm thickness and 13mm width by the comb-structure transducer of 2.3MHz frequency. Its attenuation coefficient was 1.2dB/m in air and 380dB/m in water. The signal to noise ratio of 25dB was obtained from a planar reflector 270mm away from the beam aperture of $13mm{\times}39mm$ size.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.142-148
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• 2013

Conventional cold isostatic pressing, slip casting, and filter pressing are not completely suitable for fabricating large plates because of disadvantages such as the high cost of equipment and formation of density gradient. These problems could be avoided by employing pressure-vacuum hybrid slip casting (PVHSC). In the PVHSC, the consolidation occurs not only by the compression of the slip in casting room, but also by vacuum sucking of the dispersion medium around the mold. We prepared the alumina bodies by the PVHSC in a static- or stepwise-pressure manner for loading up to 0.5 MPa using an aqueous slip. The green bodies were dried at $30^{\circ}C$ with 40 ~ 80% relative humidity. Under static pressure, casting induced a density gradient in the formed body, resulting in cracking and distortion after the firing. However, the stepwise pressure loading resulted in green bodies with homogeneous density, and the minimization of the appearance of those defects in final products. Desirable drying results were obtained from the cast bodies dried with 80% RH environment humidity. When sintered at $1650^{\circ}C$ for 4 h, the alumina plate made by stepwise-pressure casting reached full density (> 99.7% relative density).

• KSBB Journal
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• v.11 no.2
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• pp.218-224
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• 1996

The adsorption of cellulase on celluloses with different crystallinities was carried out In nonionic surfactant(Tween 20) solution. Highly crystallized celluloses were prepared by enzymatic prehydrolyzation. From the experiments, the Langmuir isotherm parameters, maximum adsorption amount (Amax) and adsorption equilibrium constant(Kad) for the adsorption, were obtained in the presence and absence of nonionic surfactant. It was found that the Kad values were decreased by adding Tween 20. This indicates that the adsorption affinity is reduced by nonionic surfactant, and Amax decreased with increasing crystallinity under conditions accompanying in both the presence and absence of surfactant. The thermodynamic parameters such as $\Delta$Ha, $\Delta$Ga, and $\Delta$Sa for the adsorption were calculated by using the experimental data. From these results, it was found that the adsorption processes are exothermic reactions in both the presence and absence of surfactant. The heats of adsorption in surfactant solution(-4.68∼-3.62KJmol-1) are smaller than that of the adsorption in the absence of surfactant(-15.60∼-12.10KJmol-1). These results indicated that the tightness of adsorption was reduced by the addition of surfactant. The $\Delta$Sa values were estimated to be positive. This may suggest that the water and solute are released from cellulose on adsorption. The $\Delta$Sa values in surfactant solution are larger than that of the adsorption in the absence of surfactant. This may suggest that the binding of surfactant on hydrophobic region of cellulase cause dispersion of water and solute molecule orienting around the enzyme molecule. The surfactant played an important role in the desorption of enzyme from cellulose functional groups, and enhance the saccharification of the cellulose.

• Korean Journal of Veterinary Research
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• v.32 no.3
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• pp.421-427
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• 1992

The study was basically carried out to establish the appropriate condition for applying the Westergren method for erythrocyte sedimentation rate(W-ESR) in Throughbred racehorses at recess. To do this, we examined the correlationship among some factors including the kind of anticoagulants, optimal ambient temperature and reading time for W-ESR in healthy racehorses. The difference between the blood samples treated with only 3.8% solution of sodium citrate(SC) and both EDTA and SC as a coagulant, there was not recognized any significant difference(p<0.05) in the levels of W-ESR irrespective of the ambient temperature of $20^{\circ}C$ or $30^{\circ}C$. The best optimal ambient temperature for W-ESR in horses was proved at $30^{\circ}C$ resulting from the tendency of the most reduced dispersion in mean values analyaed from repeatly 4 times to the same blood samles compared with those of $10^{\circ}C$ and $20^{\circ}C$. The optimal reading time was determined as 60 minutes(Y=237.2~4.1X, $r^2=0.998$) and 70 minutes(Y=247.8~4.2X, $r^2=0.999$) under the same temperature of $30^{\circ}C$; the latter showed the better result on the basis of the correlation of packed cell volume(PCV) and ESR values. About 13 healthy racehorses, we compared the real values of W-ESR respectively obtained at 60 minutes and 70 minutes at $30^{\circ}C$ with the anticipated values of PCV by means of the analysis of linear regression equitation. As the result of this, the strong correlation between both of them was confirmed. For practical use of W-ESR in Thoroughbred racehorese, we can recommend the condition of 60 or 70 minutes for the optimal reading time as well as $30^{\circ}C$ for the best ambient temperature.

• Journal of Navigation and Port Research
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• v.37 no.3
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• pp.269-273
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• 2013

Underwater acoustic channels are generally recognized as one of the most difficult communication media because of the multipath propagation, dispersion, and so on. MIMO (Multiple-input multiple-output) techniques have been actively pursued in underwater acoustic communications recently to increase the data rate over the bandwidth-limited channels. The transmit diversity techniques can be applied in this case, and one of them is Alamouti's scheme. In this paper the performances of the transmit diversity technique are evaluated via experiment. Two transmitters and two receivers were used in experiment, and the experiment was performed in indoor water tank. The error rate 5~8% was confirmed in experimental results, and these are the improved values than the error rate 14.8% for SISO(Single-input single-output) channel under same data rate condition.

• Journal of the Korean Institute of Gas
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• v.21 no.5
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• pp.45-55
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• 2017

Release and fire/explosion tests of flammable gas are extremely dangerous. Furthermore, it is difficult to select the site where the experiment can be performed. In these reasons, gas flow analysis(CFD) has been used as much as possible. However, with the opening of the Energy Safety Empirical Research Center in Yeongwol-gun, Gangwon-do in October 2016, it was possible to conduct releases and detection tests of small scale combustible gas as well as large scale / high pressure / ultra low temperature experiments. In this study, LPG leaked after the calibration and placement of the sensor, the sensor detected LPG and the data were visualized as a contour map. And the differences between the actual release(28s, max 3.7[m]) and the analysis were analyzed compared to the FLACS analyzed under the same conditions.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.17 no.3
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• pp.148-154
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• 2018

When shooting small arms, the inner surface temperature is heated up to about $700{\sim}1,000^{\circ}C$ by the friction of the bullet and the inner wall of the barrel and the combustion of propellant. High-temperature propellant gas and high-speed movement of the bullet cause corrosion of the inner wall, which is noticeable immediately in front of the chamber. In this study, the mechanical properties of Cr-Mo-V steel, which is the base material, were tested using Taguchi experimental design to find the best nitriding treatment conditions. For the nitriding process, the working time, salt bath temperature, and salt concentration were combined as three conditions and placed in the $L_9(3^4)$, orthogonal array table. The thicknesses of the white layer and the nitrogen diffusion layer were measured after nitriding under each condition in a salt bath furnace. Durability was evaluated by measuring the degree of dispersion through actual shooting because it was difficult to evaluate the mechanical properties of the cylinder inner structure. As a result, it was confirmed that the durability was optimal at $565^{\circ}C$, 1 hour, 0.5%. These optimal conditions were selected by the statistical analysis of the Minitab program(ver.17).

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.44 no.5
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• pp.8-13
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• 2012

The flexography ink has disadvantage in a deinking process because it tends to form too fine particles in alkali condition to be removed in flotation deinking. The influence of pH conditions on the particle size of phthalocyanine cyan ink used for flexo-printing was investigated to see the effect of pH conditions on flexography ink dispersion. Flexography ink particles prepared by grinding dried ink films were used in this experiment. Greater reduction of the ink particle size was noticed under alkaline pH condition, which was attributed to dissolution of resin component of the ink. Adsorption behavior of flexography ink onto pigment particles was examined using clay and talc as substrate pigments. Pretreatment of inorganic pigments with a cationic poly-DADMAC increased the surface adsorption of flexography ink particles, which improved the removal of the inks by centrifugal sedimentation of inorganic pigments. Most efficient removal of the ink particles was achieved when an optimal addition level of the cationic polymer was used for pretreatment of inorganic pigments, and this optimal addition level corresponds to the surface saturation point of the polyelectrolyte. Adsorption of flexography ink particles onto inorganic pigments improved the ink removal in flotation deinking since the pigment particles has the optimal particle size for flotation deinking.