• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.237-257
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• 2020

The role of nano bio-composites precursor to chitosan are innumerable and are known for having different applications in various branches of physical sciences. The application to the sensor development is relatively new, where only few literature works are available to address the specific and critical analysis of nanocomposites in the subject area. The bio-composites are potential and having greater affinity towards the heavy metals and several micro-pollutants hence, perhaps are having wider implications in the low or even trace level detection of the pollutants. The nano-composites could show good selectivity and suitability for the detection of the pollutants as they are found in the complex matrix. However, the greater challenges are associated using the bio-composites, since the biomaterials are prone to be oxidized or reduced at an applied potential and found to be a hinderance for the detection of target pollutants. In addition, the materials could proceed with a series of electrochemical reactions, which could produce different by-products in analytical applications, resulting in several complex phenomena in electrochemical processes. Therefore, this review addresses critically various aspects of an evaluation of nano bio-composite materials in the electrochemical detection of heavy metals and micro-pollutants from aqueous solutions.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.737-741
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• 2019

A low-cost and flexible potassium ion (K⁺) sensor was fabricated through a screen-printed process. Uniform and conformal coating of conductive inks was verified by scanning electron microscopy and optical microscopy measurements. The K⁺-sensors showed a high sensitivity, fast response time, and low detection limit. The sensitivity of K⁺-sensor was similar to that of both mechanically normal and bent states. The K⁺-sensor exhibited a good reproducibility with no hysteresis effect and excellent long term stability. In addition, the K⁺-sensor showed an excellent selectivity for K⁺ concentrations in the presence of other interfering cation ions. Successful measurements of K⁺ concentrations in sports drink samples were demonstrated by comparing K⁺ concentration values from K⁺-sensor to those of using a commercial K⁺-meter.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.89-92
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• 2007

Partail oxidation(POX) of n-butane was investigated in this research by employing ceria-promoted Ni/calcium hydroxyapatite catalysts ($Ce_xNi_{2.5}Ca_{10}(OH)_2(PO_4)_6$ ; x = $0.1{\sim}0.3$) which had recently been reported to exhibit good catalytic performance in POX of methane and propane. The experiments were carried out with changing ceria content, $O_2/n-C_4H_{10}$ ratio and temperature. As the $O_2/n-C_4H_{10}$ feed ratio increased up to 2.75, n-$C_4H_{10}$ conversion and $H_2$ yield increased and the selectivity of methane and other hydrocarbons decreased. But with $O_2/n-C_4H_{10}$ = 3.0, $n-C_4H_{10}$ conversion and $H_2$ yield decreased. This is considered due to that too much oxygen may inhibit the reduction of Ni or induce the oxidation of Ni, which results in poor catalytic activity. The optimum $O_2/n-C_4H_{10}$ ratio lay between 2.50 and 2.75. $Ce_{0.1}Ni_{2.5}Ca_{10}(OH)_2(PO_4)_6$ showed the highest $n-C_4H_{10}$ conversion and $H-2$ yield on the whole. In durability tests, higher hydrogen yield and better catalyst stability were obtained with the $O_2/n-C_4H_{10}$ ratio of 2.75 than with the ratio of 2.5.

• Korean Journal of Weed Science
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• v.32 no.2
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• pp.133-138
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• 2012

This study was conducted to investigate the herbicidal activity against resistant biotype on sulfonylurea (SU) herbicides such as Scirpus juncoides and Monochoria vaginalis at the glasshouse and paddy rice cultivation area. In order to investigate resistance breakability against SU-resistanted annual weeds, new rice herbicides containing tefuryltrione [p-hydrophenyl pyruvate dioxygenase (HPPD) inhibitor] were tested. In both lab test and field experiment, tefuryltrione mixture, 4-HPPD inhibitor had shown excellent efficacy with a bleaching on the leaves of resistant annual weeds at early time after treatment and showed excellent persistance. Especially, tefuryltrione mixture had shown excellent controlling effect on annual and perennial SU-resistant S. juncoides in the regional field experiment. In phytotoxicity test, this tefuryltrione mixture had shown good selectivity to common rice species.

• Journal of Electrochemical Science and Technology
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• v.9 no.3
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• pp.229-237
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• 2018

The electrochemical sensing performance of metal-graphene hybrid based sensor may be significantly decreased due to the dissolution and aggregation of metal catalyst during operation. For the first time, we developed a novel large-area high quality three dimensional graphene foam-incorporated gold nanoparticles (3D-GF@Au) via chemical vapor deposition method and employed as free-standing electrocatalysis for non-enzymatic electrochemical glucose detection. 3D-GF@Au based sensor is capable to detect glucose with a wide linear detection range of $2.5{\mu}M$ to 11.6 mM, remarkable low detection limit of $1{\mu}M$, high selectivity, and good stability. This was resulted from enhanced electrochemical active sites and charge transfer possibility due to the stable and uniform distribution of Au NPs along with the enhanced interactions between Au and GF. The obtained results indicated that 3D-GF@Au hybrid can be expected as a high quality candidate for non-enzymatic glucose sensor application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.5
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• pp.312-316
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• 2016

In this study, we fabricated $NO_x$ gas sensor by using multi-walled carbon nanotubes(MWCNT)/zinc oxide(ZnO) composite film. Carbon nanotubes (CNTs) have good electronic, chemical-stability, and sensitivity characteristics. And zinc oxide (ZnO) is a wide band gap and large exciton binding energy semiconductor. In particular, gas sensors require characteristics such as high speed, sensitivity, and selectivity. The fabricated gas sensor was used to detect $NO_x$ gas for different values of the $NO_x$ gas concentrations. The gas sensor that absorbed$NO_x$ gas molecules showed a increasing in resistance. The sensitivity of the gas sensor was increased by increasing the gas concentrations. Additionally, while changing the temperature inside the chamber for the MWCNT/ZnO composite film gas sensor, we obtained the sensitivity. And the comparison analysis to ZnO film gas sensor for detecting $NO_x$ gas. From the experiment result, we confirmed improvement of $NO_x$ gas detection characteristics using the MWCNT/ZnO composite film.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.10a
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• pp.398-402
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• 2003

In this paper, a VCDRO(Voltage Control Dielectric Resonator Oscillator) applied to FMCW(Frequency Modulated Continuous Wave)Radar as stable source is implemented and constructed with a MESFET for low noise, a dielectric resonator of high frequency selectivity, and high Q varator diode to obtain a good phase noise performance and stable sweep characteristics. The designed circuits is simulated thrash harmonic balance simulation technique to provide the optimum performance. The measured result of a fabricated VCDRO shows that output is 2.22dBm at 12.05GHz, harmonic suppression -30dBc, phase noise -130dBc at 100kHz offset, and sweep range of varator diode $\pm$18.7MHz, respectively. This oscillator will be available to FMCW Radar.

• Membrane Journal
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• v.21 no.3
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• pp.247-255
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• 2011

In this study, to obtain good dispersity of graphene which has excellent conductivity and mechanical strength, the graphene was modified by two different methods. Then the SPAES/graphene hybrid membranes were fabricated from different graphene contents. We compared performance of composite membrane with different preparing method of graphene and content of modified graphene. The morphology of the composite membranes has been investigated using SEM. Chemical structure of modified graphene was analyzed using by FT-IR and EDX. The proton conductivity and methanol permeability of the hybrid membranes were studied with changing graphene content from 0.5 to 3.0 wt.%. The SPAES/modified graphene composite membranes showed high proton conductivity (0.21 S/cm) compared with the SPAES membrane (0.09 S/cm) at $80^{\circ}C$ and 100% relative humidity condition. And the methanol permeability was decreased linearly as the content of modified graphene increased from 0 to 1.5 wt%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.68-69
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• 2005

BTO ($BaTiO_3$) thin film is one of the high dielectric materials for high-density dynamic random access memories (DRAMs) due to its relatively high dielectric constant. It is generally known that BTO film is difficult to be etched by plasma etching, but high etch rate with good selectivity to pattern mask was required. The problem of sidewall angle also still remained to be solved in plasma etching of BTO thin film. In this study, we first examined the patterning possibility of BTO film by chemical mechanical polishing (CMP) process instead of plasma etching. The sputtered BTO film on TEOS film as a stopper layer was polished by CMP process with the self-developed $BaTiO_3$- and $TiO_2$-mixed abrasives slurries (MAS), respectively. The removal rate of BTO thin film using the$ BaTiO_3$-mixed abrasive slurry ($BaTiO_3$-MAS) was higher than that using the $TiO_2$-mixed abrasive slurry ($TiO_2$-MAS) in the same concentrations. The maximum removal rate of BTO thin film was 848 nm/min with an addition of $BaTiO_3$ abrasive at the concentration of 3 wt%. The sufficient within-wafer non-uniformity (WIWNU%)below 5% was obtained in each abrasive at all concentrations. The surface morphology of polished BTO thin film was investigated by atomic force microscopy (AFM).

• Journal of the Korean Chemical Society
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• v.43 no.5
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• pp.517-521
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• 1999

Gas chromatography using sulfur chemiluminescence detection (GC-SCD) which exhibits very good selectivity, linearity, and sensitivity was applied to the analysis of suIfur compounds in gaseous fuel. The expectmental method used in this study was to resolve the problems of repeatability and reproducibility by means of the adsorption of sulfur compounds, which is different from the existing analysis method of these compounds by GC-SCD. The calibration curves of the standard gases including dimethyl sulfide, t-butylmercaptan and ethyl methyl sulfide exhibited an excellent linearity. As the result of precision tests for the above three compounds, the high reproducibility for tests showed while repeating three times during four days, respectively. In addition, the coefficient of variation was less than 3%. In consequence, the expectmental method of this study is very effective not only with low uncertainty but also with better accuracy, which can quickly determine the concentration of gas odorants in LPG (Liquefied Petroleum Gas) from oil reservoirs and filling stations.