• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.4
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• pp.255-262
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• 2016

There has been intense research on self-diagnosis systems in railway applications, since stability and reliability have become more and more significant issues. Wired sensors have been widely used in the railway vehicles, but because of the difficulty in their maintenance and accessibility, they ar not considered for self-diagnosis systems. To have a self-monitoring system, wireless data transmission and self-powered sensors are required. For this purpose, a thermoelectric energy harvesting module that can generate electricity from temperature gradient between the bogie axle box and ambient environment was introduced in this work. The temperature gradient was measured under actual operation conditions, and the behavior of the thermoelectric module with an external load resistance and booster circuits was studied. The proposed energy harvesting system can be applied for wireless sensor nodes in railroad vehicles with optimization of thermal management.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.12
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• pp.1325-1333
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• 2011

An analytical, numerical, and experimental comparison of the hydraulic and thermal performance of new vascular channels with semicircular cross sections was conducted. The following conditions were employed in the study: Reynolds number, 30-2000; cooling channels with a volume fraction of the cooling channels, 0.04; and pressure drop, $30-10^5$ Pa. Three flow configurations were considered: first, second, and third constructal structures with diameters optimized for hydraulic operations. To validate the proposed vascular designs by an analytical approach, 3-D numerical analysis was performed. The numerical model was also validated by the experimental data, and the comparison results were in excellent agreement in all cases. The validation study against the experimental data showed that compared to traditional channels, the optimized structure of the cooling plates could significantly enhance heat transfer and decrease pumping power.

• Journal of Wetlands Research
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• v.19 no.1
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• pp.103-111
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• 2017

In this study, we estimate the NNI(Nearest Neighbor Index) which is considered altitude of rain gauge network as a method for evaluating appropriateness of spatial distribution and the current rain gauge network is evaluated. The altitude is divided by equal-area-ratio and optimal NNI within given basin condition is estimated using harmony search method for considering geographical conditions that vary from altitude to altitude. After calculating current state and optimal NNI for each altitude, the distribution of the rain gauge network is evaluated based on the difference between the two NNIs. As a result, it founds that the density of rain gauge networks is relatively thin as the altitude increases. Furthermore, it will be possible to construct an efficient rain gauge network if the characteristics of different altitudes are considered when a new rain gauge network is newly constructed.

• Korean Journal of Materials Research
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• v.17 no.3
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• pp.152-159
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• 2007

When the electronics are tested with thermal shock for Pb-free solder joint reliability, there are temperature conditions with use environment but number of cycles for test don't clearly exist. To obtain the long term reliability data, electronic companies have spent the cost and times. Therefore this studies show the test method and number of thermal shock cycles for evaluating the solder joint reliability of electronic components and also research bonding strength variation with formation and growth of intermetallic compounds (IMC). SMD (surface mount device) 3216 chip resistor and 44 pin QFP (quad flat package) was utilized for experiments and each components were soldered with Sn-40Pb and Sn-3.0 Ag-0.5 Cu solder on the FR-4 PCB(printed circuit board) using by reflow soldering process. To reliability evaluation, thermal shock test was conducted between $-40^{\circ}C\;and\;+125^{\circ}C$ for 2,000 cycles, 10 minute dwell time, respectively. Also we analyzed the IMCs of solder joint using by SEM and EDX. To compare with bonding strength, resistor and QFP were tested shear strength and $45^{\circ}$ lead pull strength, respectively. From these results, optimized number of cycles was proposed with variation of bonding strength under thermal shock.

• Mycobiology
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• v.47 no.4
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• pp.512-520
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• 2019

Statistical experimental methods were used to optimize the medium for mass production of a novel laccase3 (Lac3) by recombinant Saccharomyces cerevisiae TYEGLAC3-1. The basic medium was composed of glucose, casamino acids, yeast nitrogen base without amino acids (YNB w/o AA), tryptophan, and adenine. A one-factor-at-a-time approach followed by the fractional factorial design identified galactose, glutamic acid, and ammonium sulfate, as significant carbon, nitrogen, and mineral sources, respectively. The steepest ascent method and response surface methodology (RSM) determined that the optimal medium was (g/L): galactose, 19.16; glutamic acid, 5.0; and YNB w/o AA, 10.46. In this medium, the Lac3 activity (277.04 mU/mL) was 13.5 times higher than that of the basic medium (20.50 mU/mL). The effect of temperature, pH, agitation (rpm), and aeration (vvm) was further examined in a batch fermenter. The best Lac3 activity was 1176.04 mU/mL at 25 ℃, pH 3.5, 100 rpm, and 1 vvm in batch culture.

• Korean Journal of Microbiology
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• v.50 no.1
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• pp.84-86
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• 2014

Mass production of biocontrol agent is an essential step for its commercial use. Media composition and culture conditions for production of Bacillus amyloliquefaciens SKU-78, a potential biocontrol agent against bacterial wilts, were optimized by a flask culture. Low cost media combining nitrogen and carbon sources were tested. Maximum cell growth (> $2{\times}10^9$ CFU/ml) was obtained in a medium of 5% soy flour combined with 3% corn starch after 24 h cultivation. The optimum initial pH, temperature and shaking speed was 5.5, $30^{\circ}C$ and 150-250 rpm, respectively. Fermentation of SKU-78 was scaled up in 30 L fermenter and the profiles of cell density, pH, dissolved oxygen and spore formation were recorded. After 8 h lag phase, exponential growth occurred and reached at maximum viable cell number ($1.2{\times}10^{11}$ CFU/ml) after 20 h. The SKU-78 strain grown in a low cost medium exhibited the high suppression of bacterial wilts. The results indicate that SKU-78 strain can be produced in a low cost medium and provide a basis for scaling up to industrial level.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.293-300
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• 2020

Eucheuma spinosum, red macro-algae, contains carrageenan as the major polysaccharide and is commercially produced in Indonesia, Malaysia, Philippines, China and Tanzania. In this study, E. spinosum was converted to sugar and platform chemicals (5-HMF, levulinic acid, formic acid) via FeCl₃-catalytic hydrothermal reaction. In addition, statistical methodology (3-level 3-factor Box-Behnken design) was applied to optimize and evaluate the effects of reaction factors (reaction temperature, catalyst concentration and reaction time). As a result of optimization, the concentration of 5-HMF was obtained to be 2.96 g/L at 160 ℃, 0.4 M FeCl₃ and 10 min. Optimal conditions of levulinic and formic acids were determined at 200 ℃, 0.6 M FeCl₃ and 30 min, and the concentrations were obtained to be 4.26 g/L and 3.77 g/L, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.5A
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• pp.554-565
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• 2004

In this paper, we implement single cycle and multi cycle adders. We can compare area and time by using the implemented adders. The size of adders is 64, 128, 256-bits. The architecture of hybrid adders is that the carry-out of small adder groups can be interconnected by utilizing n carry propagate unit. The size of small adder groups is selected in three formats - 4, 8, 16-bits. These adders were implemented with Verilog HDL with top-down methodology, and they were verified by behavioral model. The verified models were synthesized with a Samsung 0,35(um), 3.3(V) CMOS standard cell library while a using Synopsys Design Compiler. All adders were synthesized with group or ungroup. The optimized adder for a Crypto-processor included Smart Card IC is that a 64-bit RCA based on 16-bit CLA. All small adder groups in this optimized adder were synthesized with group. This adder can operate at a clock speed of 198 MHz and has about 961 gates. All adders can execute operations in this won case conditions of 2.7 V, 85 $^{\circ}C$.

• Preventive Nutrition and Food Science
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• v.21 no.2
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• pp.138-146
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• 2016

In this study, we report the optimal extraction conditions for obtaining organosulfur compounds, such as cycloalliin, from garlic by using principal component analysis (PCA). Extraction variables including temperature ($40{\sim}80^{\circ}C$), time (0.5~12 h), and pH (4~12) were investigated for the highest cycloalliin yields. The cycloalliin yield (5.5 mmol/mL) at pH 10 was enhanced by ~40% relative to those (~3.9 mmol/mL) at pH 4 and pH 6. The cycloalliin level at $80^{\circ}C$ showed the highest yield among the tested temperatures (5.05 mmol/mL). Prolonged extraction times also increased cycloalliin yield; the yield after 12 h was enhanced ~2-fold (4 mmol/mL) compared to the control. Isoalliin and cycloalliin levels were inversely correlated, whereas a direct correlation between polyphenol and cycloalliin levels was observed. In storage for 30 days, garlic stored at $60^{\circ}C$ (11 mmol/mL) showed higher levels of cycloalliin and polyphenols than those at $40^{\circ}C$, with the maximum cycloalliin level (13 mmol/mL) on day 15. Based on the PCA analysis, the isoalliin level depended on the extraction time, while cycloalliin amounts were influenced not only by extraction time, but also by pH and temperature. Taken together, extraction of garlic at $80^{\circ}C$, with an incubation time of 12 h, at pH 10 afforded the maximum yield of cycloalliin.

• KSBB Journal
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• v.19 no.3
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• pp.200-205
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• 2004

For decolorization of various reactive dyes, 13 species of microbes were isolated from dyeing wastewater collected from Banweol industrial complex, Korea. Two strains among them showed good ability for removing celerity during the decolorization test with 5 different reactive dyes. And the optimal growth conditions were pH 7, 35$^{\circ}C$, yeast extract as nitrogen source, glucose as carbon source, and facultative anaerobic condition. As results, when Reactive Red 180 was used, 89 and 87% of decolorization efficiency were able to be obtained by using Bacillus anthracis and Bacillus cereus, respectively. Especially, Bacillus cereus showed good ability for decolorization of Reactive Blue 21, and the ratio was 76% Finally, it was considered that these two strains isolated in this study will be showed high decolorization ability to treat dyeing wastewater.