• International Journal of Advanced Culture Technology
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• v.10 no.1
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• pp.284-293
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• 2022

After extracting the calcium component from the KR slag and the converter slag using ammonium chloride solution, the extract was reacted with carbon dioxide to synthesize precipitated calcium carbonate (PCC). In order to understand the effect of ultrasonic waves on calcium extraction from slags and calcium carbonate synthesis, the efficiency of calcium carbonate synthesis according to the with or without of ultrasonic waves was analyzed. The synthetic efficiency of PCC was investigated according to various experimental conditions, and the synthesized calcium carbonate was analyzed using XRD and SEM. In both slags, the amount of PCC decreased as the reaction temperature increased. The pH at the end of the experiment capable of synthesizing the maximum PCC in the carbonation reaction was 7 (irradiated with ultrasound) and 8 (irradiated without ultrasound), respectively. Because the pH of the extraction filtrate is different when irradiated with or without ultrasound, the pH was adjusted to 9 by injecting an additive (10 M NaOH) before the carbonation experiment, and then the experiment was performed. When calcium was extracted from KR slag, the crystal phase appeared as calcite regardless of the pH at the end of the experiment. However, when calcium was extracted from the converter slag and the pH was set to 7 at the end of the experiment, the crystal phase of PCC appeared as a mixture of calcite and vaterite.

• Journal of Microbiology and Biotechnology
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• v.12 no.1
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• pp.46-52
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• 2002

As a functional additive for intestinal microflora, panose ($6^2-{\alpha}$-D-glucopyranosylmaltose) was synthesized during kimchi fermentation using the glucose transferring reaction of glucansucrase from Leuconostoc mesenteroides. For the glucose transferring reaction, sucrose and maltose were added ($2\%$ each, w/v) to dongchimi-kimchi as the glucosyl donor and acceptor molecule, respectively. After five days of incubation at $10^{\circ}C$, referring to the initial phase for the production of lactic acid in kimchi, over $60\%$ (w/v) of the total sugars were converted into panose and other branched oligosaccharides. Thereafter, the kimchi was stored at $4^{\circ}C$ and the amount of panose remained at a constant level for three weeks, thereby indicating the stability of panose to microbial degradation during the period of kimchi consumption. The use of maltose as the acceptor molecule in the kimchi also facilitated a lower viscosity in the kimchi-juice by preventing the synthesis of a dextran-like polymer which caused an unfavorable taste. Accordingly, the application of this new method of simultaneous biocatalytic synthesis of oligosaccharides during lactate fermentation should facilitate the extensive development of new function-added lactate foods.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.1
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• pp.60-70
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• 1995

In the field of marine transportation the energy saving is one of the most important factors for profit. In order to reduce the fuel oil consumption the ship's propulsion efficiency must be increased as much as possible. The propulsion efficiency depends upon a combination of an engine and a propeller. The propeller has better efficiency as lower rotational speed. This situation led the engine manufacturers to design the engine that has lower speed, longer stroke and a small number of cylinders. Consequently the variation of rotational torque became larger than before because of the longer delay-time in the fuel oil injection process and an increased output per cylinder. As this new trends the conventional mechanical-hydrualic governors for engine speed control have been replaced by digital speed controllers which adopted the PID control or the optimal control algorithm. But these control algorithms have not enough robustness to suppress the variation of the delay-time and the parameter pertubation. In this paper we consider the delay-time and the perturbation of engine parameters as the modeling uncetainties. Next we design the controller which has zero offset in steady state engine speed, based on the two-degree-of-freedom control theory and $\mu$-synthesis. Thd validity of the controller is investigated through the response simulation. We use a personal computer and an analog computer as the digital controller and the engine (plant) part respectively. And, we certify that the designed controller maintains its performance even though the engine parameters may vary.

• Membrane Journal
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• v.33 no.3
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• pp.137-147
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• 2023

In this study, Br-PPO was developed by applying additive organic particles through a suspension polymerization synthesis method. The anion exchange membrane fuel cell system performance was evaluated using it to an anion exchange membrane. To improve the performance, organic ion exchange particles were prepared and added to the anion exchange membrane. Chemical structure analysis and synthesis were determined through FT-IR and NMR, and tensile strength and thermal stability were measured through TGA and UTM to determine whether it could be driven. Before the anion exchange membrane fuel cell test, the performance was evaluated by measuring the ion conductivity and ion exchange capacity. Finally, the Br-PPO-TMA-SDV (0.7%) anion exchange membrane with excellent ion conductivity and ion exchange capacity was introduced into the fuel cell system. Its performance was compared with FAA-3-50, a commercial membrane, to determine whether it could be introduced into a fuel cell system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.31 no.5
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• pp.335-340
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• 2018

Transition metal oxide materials have attracted widespread attention as Li-ion battery electrode materials owing to their high theoretical capacity and good Li storage capability, in addition to various nanostructured materials. Here, we fabricated a CoO Li-ion battery in which Co nanoparticles (NPs) are deposited into a current collector through electrophoretic deposition (EPD) without binding and conductive agents, enabling us to focus on the intrinsic electrochemical properties of CoO during the conversion reaction. Through optimized Co NP synthesis and electrophoretic deposition (EPD), CoO Li-ion battery with 630 mAh/g was fabricated with high cycle stability, which can potentially be used as a test platform for a fundamental understanding of conversion reaction.

• Carbon letters
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• v.12 no.4
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• pp.218-222
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• 2011

Well-aligned multi-walled carbon nanotubes (MWCNTs) were successfully synthesized by catalytic chemical vapor deposition using a hydrogen sulfide ($H_2S$) additive onto Al/Fe thin film deposited on Si wafers. Transmission electron microscopy images indicated that the as-grown carbon products were thin MWCNTs with small outer diameters of less than 10 nm. $H_2S$ plays a key role in synthesizing thin MWCNTs with a large inside hollow core. The well-aligned thin MWCNTs showed a low turn-on voltage of about 1.1 V/${\mu}m$ at a current density of 0.1 ${\mu}A/cm^2$ and a high emission current of about 1.0 mA/$cm^2$ at a bias field of 2.3 V/${\mu}m$. We suggest a possible growth mechanism for the well-aligned thin MWCNTs with a large inside hollow core.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.446-449
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• 2003

In recent years, the research of an efficient transmission method is going to meet a demand for high speed and large capacity radio communication. These systems make use of ultra-short duration pulses which yield UWB(Ultra Wide Band) signals characterized by low power spectral densities. The wavelet synthesis wave is able to set up the scale freely. So it is possible to use as the transmission wave of UWB by compressing time. In this paper, we present a general analytical expression for the average BER(Bit Error Rate) performance of UWB data transmission using wavelet system as a function of the cross-correlation between the users' signatures in an additive white Gaussian noise(AWGN) channel.

• Journal of the Korean Applied Science and Technology
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• v.27 no.2
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• pp.216-221
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• 2010

Polyvinyl acetate (PVAc) prepared by emulsion polymerization has broad applications for additive such as paint binder, adhesive for wood and paper due to its low glass transition temperature which help to plasticize substrate resins. Since emulsion polymerization has a disadvantage that surfactant and ionic initiator degrade properties of the product polymer, poly (vinyl acetate-eo-ethyl acrylate) (VAc-EA) was synthesized using potassium persulfate as catalyst and polyvinylalcohol (PVA) as protective colloid to prevent the degradation. The copolymer latex product was internally plasticized and has enhanced adhesion, water resistance during VAc-EA emulsion polymerization. No coagulation and complete conversion occur with the reactant mixture of 10 mmol/L potassium persulfate, 10 mmol/L poly ( vinyl alcohol) (PVA 17). As the concentrations of PVA increase, the viscosity becomes increase.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.06a
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• pp.149-155
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• 2001

New semi-fluorinated polyol esters were synthesized by condensation reaction of polyols (NPG and TMP) and carboxylic acids such as 2-ethylhexanoic acid, stearic acid and perfluorooctanoic acid. The structures of polyol esters were confirmed by FT-IR and H-NMR etc. And, the fluorinated polyol esters were insoluble in several oils, however, the semi-fluorinated polyol esters were soluble in several oils depended on the structure of polyol esters. The physical properties such as 4-ball wear property and extreme-pressure (EP) properties were characterized by measuring wear scar diameter through ASTM D2266 and by determining the load-carrying through ASTM D2783 method, respectively. As the results, wear scar diameters of oils in which the semi-fluorinated polyol esters were added were not changed compared to those of not added oils. While extreme-pressure properties remarkably Increased with fluorine contents of the esters depended on the structure of acid moiety and polyol moiety. Also, the extreme-pressure property of semi-fluorinated NPG polyol ester in gasoline engine oil was better than that of commercial Teflon coating additive.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.255-256
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• 2022

We synthesized catechol-conjugated chitosan (CCC) to study its usefulness as a construction material additive in cement mortar. The degree of catechol conju-gation (DOC_cat) of the synthesized CCC was determined to be approximately14% by UV-vis and ¹H NMR spectroscopy. Furthermore, the hydroxyl and amine groups in CCC could play a crucial role in hydrogen bonding, metal coordination, and cross-linking processes via interaction with adducts from cement mortar. In this study, we observedanimprovement in the compressive strength and absorption rate, suggesting that CCC is a promising candidateforhigh-performance cement mortar.