• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.563-563
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• 2012

We report a one-step fabrication of single-crystal organic nanowire arrays on substrates using a new direct printing method (liquid-bridge-mediated nanotransfer moulding, LB-nTM), which can simultaneously enable the synthesis, alignment and patterning of the nanowires using molecular ink solutions. Two- or three-dimensional complex structures of various single-crystal organic nanowires were directly fabricated over a large area with a successive process. The position of the nanowires can be aligned easily on complex structures because the mold is movable on substrates before drying the polar liquid layer, which acts as an adhesive lubricant. This efficient manufacturing method can produce a wide range of optoelectronic devices and integrated circuits with single-crystal organic nanowires.

• Proceedings of the KIEE Conference
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• 2003.07d
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• pp.2190-2192
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• 2003

In this paper, a state observer based direct adaptive fuzzy controller for unknown nonlinear dynamical system is presented. The adaptive parameters of the direct adaptive fuzzy controller can be tuned by using a projection algorithm on-line based on the Lyapunov synthesis approach. A maximum control is used to guarantee the robustness of system. A stability analysis of the overall adaptive scheme is discussed based on the sense of Lyapunov. The inverted pendulum simulation example shows that proposed control algorithm can be used for the tracking problem of nonlinear system.

• The Journal of the Korea institute of electronic communication sciences
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• v.7 no.2
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• pp.333-339
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• 2012

Global flow of communication is a trend of high speed, digitalization, and high-capacity. Furthermore, spread spectrum method has been dominantly utilized to efficiently use the frequency which is the scarce resource. The PLL (Phase Lock Loop) which is a widely used frequency synthesizer in communication systems has few problems such as status interferences and hence, this study utilized the DDS (Direct Digital Synthesis) which is a digital device that can minimize the problems of PLL for the study on the performance evaluation of high speed frequency hopping system design. We designed a system that practices high speed frequency hopping and interprets improvement of error-rates and evaluated its performance.

• Journal of Korea Foundry Society
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• v.17 no.4
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• pp.371-378
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• 1997

The study for direct synthesis of TaC carbide which was a reaction product of tantalum and carbon in the cast iron was performed. Cast iron which has hypo-eutectic composition was cast bonded in the metal mold with tantalum thin sheet of thickness of $100{\mu}m$. The contents of carbon and silicon of cast iron matrix was controlled to have constant carbon equivalent of 3.6. The chracteristics of microstructure and the formation mechanism of TaC carbide in the interfacial reaction layer in the cast iron/tantalum thin sheet heat treated isothermally at $950^{\circ}C$ for various time were examined. TaC carbide reaction layer was grown to the dendritic morphology in the cast iron/tantalum thin sheet interface by the isothermal heat treatment. The composition of TaC carbide was 48.5 at.% $Ti{\sim}48.6$ at.% C-2.8 at.% Fe. The hardness of reaction layer was MHV $1100{\sim}1200$. The thickness of reaction layer linearly increased with increasing the total content of carbon in the cast iron matrix and isothermal heat treating time. The growth constant for TaC reaction layer was proportional to the log[C] of the matrix. The formation mechanism of TaC reaction layer at the interface of cast iron/tantalum thin sheet was proved to be the interfacial reaction.

• Journal of the Korean Applied Science and Technology
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• v.31 no.3
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• pp.446-452
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• 2014

Methanol was directly produced by the partial oxidation of methane with four-component mixed oxide catalysts. Four-component(Mo-Bi-Cr-Si) mixed oxide catalysts were prepared by the co-precipitation and sol-gel methods. The catalyst prepared by the sol-gel method showed about eleven times higher surface area than that prepared by the co-precipitation method. From the $O_2$-TPD experiment of the prepared catalysts, it was proven that there exists two types of oxygen species, and the oxygen species that participates in the partial oxidation reaction is the lattice oxygen desorbing around $750^{\circ}C$. The optimum reaction condition for methanol production was $420^{\circ}C$, 50 bar, flow rate of 115 mL/min, and $CH_4/O_2$ ratio of 10/1.5, providing methane conversion and methanol selectivity of 3.2 and 26.7%, respectively.

• Korean Chemical Engineering Research
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• v.45 no.6
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• pp.554-559
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• 2007

In order to improve the reactivity for the direct synthesis of dimethyl carbonate (DMC) using methanol and carbon dioxide, the various additives were used in the DMC synthesis using $Ce_{0.8}Zr_{0.2}O_2$ catalyst, and then effect of the additives was investigated. The various additives were molecular sieves 3A and the compounds having the various functional groups such as sulfate, carbonate, nitrate and phosphate. As a result, the compound such as $K_2SO_4$ and $Na_2SO_4$ having sulfate group were the most effective additive among the various additives. When $K_2SO_4$ was used as an additive in the direct synthesis of DMC, the amount of DMC was about 0.91 mmol, which was the highest mount of DMC among using only-$Ce_{0.8}Zr_{0.2}O_2$ catalyst and the various additives.

• Polymer(Korea)
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• v.35 no.2
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• pp.166-170
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• 2011

This study reported the synthesis of perfluoropolyether intermediate (TP-$COOCF_3$) having a $CF_3$ functional group via electrophilic fluorine substituting direct fluorination from PFPE intermediate (TP-$COOCH_3$) having a $CH_3$ functional group, which was synthesized by the ring opening polymerization and methyl esterification of HFPO. The effects of reaction conditions such as the amount of solvent, fluorine partial pressure, reaction time, were investigated. The results showed that the yield of fluorination reaction became the highest when the reaction was carried out in a mild condition for a long reaction time, which also minimized side reactions. The sample was characterized by FTIR and NMR, which confirmed the synthesis of the final product, TP-$COOCF_3$, via direct fluorination converting $CH_3$ of TP-$COOCH_3$ to $CF_3$ of TP-$COOCF_3$ with 95.4% yield.

• Transactions of the Korean hydrogen and new energy society
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• v.15 no.2
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• pp.119-128
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• 2004

DME(Dimethyl Ether) was directly produced from the synthesis gas using the slurry phase reactor. The catalyst for DME production prepared two types (A type; Cu:Zn:Al=57:33:10, B type; Cu:Zn:Al=40:45:15, molar ratio). It was evaluated for the effect of the reaction medium oil using the small size slurry phase reactor. DME production yield and the methanol selectivity decreased in the order: n-hexadecane oil> mineral oil> therminol oil. The long-term test of DME production was carried out using A and B type catalyst, and n-hexadecane oil and mineral oil, respectively. It was confirmed that the use of A type for the catalyst and n-hexadecane for the reaction medium oil was very useful for the viewpoint of the DME production form the synthesis gas.

• Applied Science and Convergence Technology
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• v.26 no.6
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• pp.164-173
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• 2017

Across the most industry, the demand for nanoparticles is increasing. Therefore, many studies have been carried out to synthesize nanoparticles using various methods. The aim of this paper is to introduce an industry-applicable as well as financially and environmentally effective solution plasma process. The solution plasma process involves fewer chemicals than the traditional kit, and can be used to replace many of the chemical agents employed in previous synthesis of nanoparticles into plasma. In this study, this process is compared to the wet-reaction process that has thus far been widely used in the most industry. Furthermore, the solution plasma process has been classified into four different types (in-solution, out of solution, direct type, and remote type), according to its plasma occurrence position and plasma types. Thus, the source of radicals, nanoparticle synthesis, and modification methods are explained for each design. Lastly, unlike nanoparticles with hydrophilic functional groups that are made inside the solution, a nanoparticle synthesis and modification method to create a hydrophobic functional group is also proposed.

• Korean Journal of Materials Research
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• v.33 no.5
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• pp.222-228
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• 2023

Transition metal oxides formed by a single or heterogeneous combination of transition metal ions and oxygen ions have various types of crystal structures, which can be classified as layered structures and non-layered structures. With non-layered structures, it is difficult to realize a two-dimensional structure using conventional synthesis methods. In this study, we report the synthesis of cobalt oxide into wafer-scale nanosheets using a surfactant-assisted method. A monolayer of ionized surfactant at the water-air interface acts as a flexible template for direct cobalt oxide crystallization below. The nanosheets synthesized on the water surface can be easily transferred to an arbitrary substrate. In addition, the synthesizing morphological and crystal structures of the nanosheets were analyzed according to the reaction temperatures. The electrochemical properties of the synthesized nanosheets were also measured at each temperature. The nanosheets synthesized at 70 ℃ exhibited higher catalytic properties for the oxygen evolution reaction than those synthesized at other temperatures. This work suggests the possibility of changing material performance by adjusting synthesis temperature when synthesizing 2D nanomaterials using a wide range of functional oxides, resulting in improved physical properties.