• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.742-748
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• 2019

Influence of several experimental parameters (e.g., initial dye concentration, pH, distance between electrodes, applied voltage, electrical conductivity, current density, and reaction time) on the performance of electrocoagulation (EC) process for the removal of acid blue 25 (AB25) was studied. A bipolar batch reactor was used to test the impact of the parameters. The removal efficiency (RE) of AB25 dye was promoted by increasing the contact time, voltage, electrical conductivity, and applied current density. In contrast, RE of AB25 decreased with higher level of AB25 and the longer distance between electrodes. The removal efficiency increased consistently until pH 7, but decreased above pH 7. The maximum efficiency of AB25 removal above 90% was obtained at a voltage of 60 V, reaction time of 90 min, distance between electrodes of 0.5 cm, initial concentration of 25 mg/L, conductivity of 3,000 μS/cm and pH of 7. These results imply that the high RE of AB25 dye from the aqueous solution can be achieved by EC process.

• Journal of the Korean Data and Information Science Society
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• v.25 no.1
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• pp.255-261
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• 2014

Many studies have estimated a mixture of binomial distributions. This paper considers an extension, a mixture of shifted binomial distributions, and the estimation of the distribution. The range of each component binomial distribution is rst evaluated and then for each possible value of shifted parameters, the EM algorithm is employed to estimate those parameters. From a set of possible value of shifted parameters and corresponding estimated parameters of the distribution, the likelihood of given data is determined. The simulation results verify the performance of the proposed method.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.8
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• pp.1046-1052
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• 2001

This study has been performed experimentally to measure the frost properties over a cold flat plate in order to obtain the correlations of the frost properties with various environmental parameters. Correlations of the frost surface temperature, thickness, density, and thermal conductivity are presented along with the experimental results as a function of environmental parameters, distance from the leading edge of test plate, and time. These correlations can be used to predict the frost properties with a maximum error of 8% in the following ranges : air temperature 15∼25$\^{C}$, relative humidity 60∼80%, air velocity 1∼3m/s and cooling plate temperature -15∼-25$\^{C}$.

• Journal of the Korean Society for Heat Treatment
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• v.35 no.5
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• pp.239-245
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• 2022

The purpose of this study is to evaluate the degree of microstructural change of materials using ultrasonic nonlinear parameters. For microstructure change, isothermal heat-treated ferritic 2.25Cr steel and low-cycle fatigue-damage copper alloy were prepared. The variation in ultrasonic nonlinearity was analyzed and evaluated through changes in hardness, ductile-brittle transition temperature, electron microscopy, and X-ray diffraction tests. Ultrasonic nonlinearity of 2.25Cr steel increased rapidly during the first 1,000 hours of deterioration and then gradually increased thereafter. The variation in non-linear parameters was shown to be coarsening of carbides and an increase in the volume fraction of stable M6C carbides during heat treatment. Due to the low-cycle fatigue deformation of oxygen-free copper, the dislocation that causes lattice deformation developed in the material, distorting the propagating ultrasonic waves, and causing an increase in the ultrasonic nonlinear parameters.

• Journal of fish pathology
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• v.34 no.2
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• pp.213-224
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• 2021

Experiments were performed to investigate changes in metabolic rate (MO₂), critical oxygen saturation (S_crit) and hematological parameters of black rockfish, Sebastes schlegeli exposed to hypoxia at 15, 20 and 25℃. The MO₂ was measured at an interval of 10 min using intermittent-flow respirometry. The normoxic standard metabolic rate (SMR) was 116.5±5.5, 188.6±4.2 and 237.4±6.8 mg O₂/kg/hr, and S_crit was 22.1±1.2, 30.6±1.5 and 41.9±1.4% air saturation at 15, 20 and 25℃, respectively. Q₁₀ values were 2.62 between 15 and 20℃, 1.58 between 20 and 25℃, and 2.04 over the full temperature range. In the investigation of blood (hematocrit and hemoglobin) and biochemical parameters (plasma cortisol, glucose, electrolyte and osmolality), the rockfish were subjected to S_crit for each temperature during 4 hr. All of hematological parameters of the rockfish exposed to hypoxic water were significantly higher than those of normoxic control. Moreover, blood and biochemical parameters of the rockfish maintained to normoxic water showed the tendency of increase with temperature, and were significantly higher at 25C. As a result of this experiment, it was found that physiological stress due to hypoxia increased at high temperature.

• Journal of Welding and Joining
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• v.25 no.5
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• pp.64-71
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• 2007

The aim of this paper is to investigate the effects of welding parameters on the weld shape in seal-welding of STS304L capsule for manufacturing a radioisotope source which is widely used in nondestructive testing of metal structures using gamma ray. Pulsed gas tungsten arc (Pulsed GTA) welding is performed for thin cross sectional area of the capsule. Seven welding parameters including current waveform parameters and arc length etc. are selected as main process parameters using design of experiment. The weld shape such as bead width, penetration depth, weld area, aspect ratio and area rate is investigated to assess the effects of welding parameters. As results, the combination of pulse duty/welding speed largely affects on bead width, penetration depth, area and aspect ratio. Finally, it is concluded that the key parameters are the combination of pulse duty/welding speed, base current and arc length, and their optimal conditions are 50%/1.77mm/s, 6.4A and 1 mm.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.3
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• pp.227-234
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• 2020

This paper presents the methods for the modeling and parameter optimization of the electric vehicle battery. The state variables of the battery are defined, and the test methods for battery parameters are presented. The state-space equation, which consists of four state variables, and the output equation, which is a combination of to-be-determined parameters, are shown. The parameter optimization method is the key point of this study. The least square of the modeling error can be used as an initial value of the multivariable function. It is equivalent to find the minimum value of the error function to obtain optimal parameters from multivariable function. The SIMULINK model is presented, and the 10-hour full operational range test results are shown to verify the performance of the model. The modeling error for 25 degrees is approximately 1% for full operational ranges. The comments to enhance modeling accuracy are shown in the conclusion.

• Textile Coloration and Finishing
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• v.25 no.3
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• pp.232-239
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• 2013

In this study, 25gsm melt-blown polypropylene nonwoven for dust-proof/medical masks was finished by the corona discharging treatment. The influence of corona discharging parameters on the filtration efficiency was investigated. Several parameters such as discharging voltage, discharging speed, distance to discharging wire and configuration of discharging system had an effect on filtration efficiency, while the parameters had no effect on breathing resistance. Optimum corona discharging conditions are as follows: Wires were installed on the upper part of the nonwoven and paper pipe was installed on the lower part of the nonwoven having a distance of 5cm. The sequence of wire voltages was +60 kV, +60 kV, 0, -60 kV, and -60 kV. The discharging voltage and speed were 60 kV and 30m/min respectively. The nonwoven treated by corona discharging at the optimum condition showed a filtration efficiency of 80% or more, which is suitable for dust-proof/medical masks.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.3
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• pp.272-278
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• 2015

This paper studied various parameter extraction methods using pitch information of speech for the development of the emotion recognition system. For this purpose, pitch parameters were extracted from korean speech database containing various emotions using stochastical information and numerical analysis techniques. GMM based emotion recognition system were used to compare the performance of pitch parameters. Sequential feature selection method were used to select the parameters showing the best emotion recognition performance. Experimental results of recognizing four emotions showed 63.5% recognition rate using the combination of 15 parameters out of 56 pitch parameters. Experimental results of detecting the presence of emotion showed 80.3% recognition rate using the combination of 14 parameters.

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.10a
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• pp.25-25
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• 1997