• Journal of the Korean Society for Precision Engineering
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• v.17 no.11
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• pp.199-205
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• 2000

The vibration and noise of gears is due to the vibration exciting force caused by the tooth stiffness which changes periodically as the mesh of teeth proceeds and by the transmission error, that is, the rotation delay between driving gear and driven gear caused by manufacturing error and alignment error in assembly and so on. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification, end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the mesh analysis of gears. The constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth fillet stress, surface durability and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. And, since the aspect ratio is an important parameter of tooth modification, we investigate the relation between it and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is to be utilized to resolve the problem of vibration of helical gears.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4597-4603
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• 2010

A factorization is a very important part of multi-level logic synthesis. The number of literals in a factored form is an estimate of the complexity of a logic function, and can be translated directly into the number of transistors required for implementation. Factored forms are described as either algebraic or Boolean, according to the trade-off between run-time and optimization. A Boolean factored form contains fewer number of literals than an algebraic factored form. In this paper, we present a new method for a Boolean factorization. The key idea is to identify two-cube nonkernel Boolean pairs from given expression. Experimental results on various benchmark circuits show the improvements in literal counts over previous other factorization methods.

• Polymer(Korea)
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• v.34 no.4
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• pp.381-385
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• 2010

Aiphatic diester monomer, 3-[(benzyloxycarbonylamino)butyl]-1,4-dioxane-2,5-dione (BABD), was synthesized with the N-$\varepsilon$-benzyloxy-carbonyl-L-lysine as starting material. This monomer was synthesized to add the functionality to poly(lactic acid)s. BABD unit was successfully incorporated into the PLLA chain which was confirmed by $^1H$ NMR. The copolymer composition could be controlled by the feed ratios of monomer. The $M_n$ of this resultant polymer is expected to reach high molecular weight after the purification of monomer and optimization of polymerization time, though the polymer showed relatively low degree of polymerization ($M_n$＝3300). The copolymer is expected to possess the enhanced hydrophilicity and the possibility of chemical modification on amino group.

• Journal of Soil and Groundwater Environment
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• v.18 no.5
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• pp.39-45
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• 2013

Many researchers have studied the effectiveness of ultrasound in chemical and environmental engineering fields including material synthesis, pollutant removal, cleaning, extraction, and disinfection. Acoustic cavitation induced by ultrasound irradiation in aqueous phase can cause various sonophysical and sonochemical reactions without any chemicals. However most of the previous studies focused only on the relationships between ultrasonic conditions and the results of sonochemical reactions in lab-scale sonoreactors. As a results of this, only a few studies have been devoted to design and optimization of industrial scale sonoreactors. In this study, the effect of the distance between two opposite transducer modules on sonochemical reactions was investigated in single and dual irradiation systems (334 kHz) for four distances including 50, 100, 150, and 200 mm using KI dosimetry. It was found that the dual irradiation systems provided higher performance in terms of the zeroth reaction coefficient and the cavitation yield compared to the single irradiation systems. The sonochemiluminescence (SCL) images for the visualization of the cavitation field showed that cavitation active zone was larger and sonochemical reaction intensity was much higher in the dual irradiation system than in the single irradiation system.

• Journal of Electrochemical Science and Technology
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• v.10 no.1
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• pp.1-13
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• 2019

Na-ion batteries are being considered as promising cost-effective energy storage devices for the future compared to Li-ion batteries owing to the crustal abundance of Na-ion. However, the large radius of the Na ion result in sluggish electrode kinetics that leads to poor electrochemical performance, which prohibits the use of these batteries in real time application. Therefore, identification and optimization of the anode, cathode, and electrolyte are essential for achieving high-performance Na-ion batteries. In this context, the current review discusses the suitable high-voltage cathode materials for Na-ion batteries. According to a recent research survey, sodium vanadium fluorophosphate (NVPF) compounds have been emphasized for use as a high-voltage Na-ion cathode material. Among the fluorophosphate groups, $Na_3V_2(PO_4)_2F_3$ exhibited the high theoretical capacity ($128mAh\;g^{-1}$) and working voltage (~3.9 V vs. $Na/Na^+$) compared to the other fluorophosphates and $Na_3V_2(PO_4)_3$. Here, we have also highlighted the classification of Fluorophosphates, NVPF composite with carbonaceous materials, the appropriate synthesis methods and how these methods can enhance the electrochemical performance. Finally, the recent developments in NVPF for the application in energy storage devices and its outlook are summarized.

• Journal of Microbiology and Biotechnology
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• v.29 no.5
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• pp.758-764
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• 2019

${\beta}$-Glucan is a chief structural polymer in the cell wall of yeast. ${\beta}$-Glucan has attracted intensive attention because of its wide applications in health protection and cosmetic areas. In the present study, the ${\beta}$-glucan biosynthesis pathway in S. Cerevisiae was engineered to enhance ${\beta}$-glucan accumulation. A newly identified bacterial ${\beta}-1$, 6-glucan synthase GsmA from Mycoplasma agalactiae was expressed, and increased ${\beta}$-glucan content by 43%. In addition, other pathway enzymes were investigated to direct more metabolic flux towards the building of ${\beta}$-glucan chains. We found that overexpression of Pgm2 (phosphoglucomutase) and Rho1 (a GTPase for activating glucan synthesis) significantly increased ${\beta}$-glucan accumulation. After further optimization of culture conditions, the ${\beta}$-glucan content was increased by 53.1%. This study provides a new approach to enhance ${\beta}$-glucan biosynthesis in Saccharomyces cerevisiae.

• Journal of Powder Materials
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• v.30 no.4
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• pp.310-317
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• 2023

Small-film-type ion sensors are garnering considerable interest in the fields of wearable healthcare and home-based monitoring systems. The performance of these sensors primarily relies on electrode capacitance, often employing nanocomposite materials composed of nano- and sub-micrometer particles. Traditional techniques for enhancing capacitance involve the creation of nanoparticles on film electrodes, which require cost-intensive and complex chemical synthesis processes, followed by additional coating optimization. In this study, we introduce a simple one-step electrochemical method for fabricating gold nanoparticles on a carbon nanotube (Au NP-CNT) electrode surface through cyclic voltammetry deposition. Furthermore, we assess the improvement in capacitance by distinguishing between the electrical double-layer capacitance and diffusion-controlled capacitance, thereby clarifying the principles underpinning the material design. The Au NP-CNT electrode maintains its stability and sensitivity for up to 50 d, signifying its potential for advanced ion sensing. Additionally, integration with a mobile wireless data system highlights the versatility of the sensor for health applications.

• Progress in Superconductivity and Cryogenics
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• v.9 no.1
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• pp.1-4
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• 2007

The total Fluorine content in the precursor solution for MOD processing of YBCO coated conductors can be significantly reduced by synthesizing precursor solution with F-free Y & Cu precursor and Barium trifluoroacetate(TFA). It was shown that crack-free and uniform precursor films were formed after calcinations in humidified oxygen atmosphere. Less than 2 hours are required to finish the calcinations process and XRD measurement shows that $BaF_2,\;CuO,\;Y_2O_3$ are major constituent of calcined precursor films. Film thickness after calcinations was improved to be 2.8um by applying slot-die coating method. In particular, addition of Samarium shows critical current of $I_c=273A/cm-w(J_c=3.8MA/cm^2)$. It is shown that uniform and fast processing route to YBCO coated conductor with high Ic can be provided by employing F-free Y & Cu precursor solution in MOD process.

• Korean Journal of Food Science and Technology
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• v.24 no.3
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• pp.240-246
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• 1992

Preparation of soybean oil fatty acid methyl esters (soybean oil FAME) through the transesterification of soybean oil with alkaline catalyst was optimized in terms of contents of residual free fatty acids (FFA) in soybean oil FAME and yield of soybean oil FAME due to the inhibitory effect of FFA on sucrose polyesters synthesis. Soybean oil FAME and residual FFA were analyzed quantitatively by simultaneous gas chromatography on a fused silica capillary column after converting the FFA in soybean oil FAME to tert.-butyldimethylsilyl (TBDMS) derivatives. Transesterification of soybean oil was successfully performed with alkaline catalyst (NaOH, 95%), which resulted in 99.1% yield of soybean oil FAME and less than 0.1% residual FFA contents under the conditions such as $30^{\circ}C$, 20min. and 6:1 molar ratio of anhydrous methanol to soybean oil.

• Korean Journal of Food Science and Technology
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• v.36 no.4
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• pp.531-536
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• 2004

Synthesis conditions were optimized using response surface methodology for producing structured lipids (SL) by interesterification of DHA-enriched algae oil derived from microalgae, Schizochytrium sp. and corn oil. Reaction was performed fer 24 hr at $55^{\circ}C$ catalyzed by immobilized lipase from Rhizomucor miehei (RM IM) in shaking water bath. Major fatty acids of SL were palmitic (21.70 mol%), oleic (20.20 mol%), and linoleic (27.34 mol%) acids, and DHA (15.06 mol%). To separate newly synthesized SL-triglycerides (TG) species, HPLC with evaporative light scatting detector (ELSD) was used. Production conditions were optimized using central composite design with reaction temperature $(35-75^{\circ}C,\;X_1)$, reaction time $(2-42\;hr,\;X_2)$, and enzyme concentration $(2-14%,\;X_3)$ as variables. When variables were $70.28^{\circ}C\;(X_1),\;28.74\;hr\;(X_2),\;and\;11.30%\;(X_3)$, maximum content of selected three peaks of synthesized SL-TG species was predicted as 6.97 area%.