• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.292.2-292.2
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• 2013

Graphene, a two-dimensional graphite material consisting of sp2-hybridized carbons. The properties of graphene such as extremely high carrier mobility, high thermal conductivity, low resistivity, large specific make it a promising materail of divices and material. Typically, poly (methyl methacrylate) (PMMA) is used when graphene transfer to other substrates. To remove PMMA on graphene, people used to dip the graphene into the acetone. However, it is known that the remove of PMMA on the graphene is difficult to completely using the acetone. Therefore, to remove the PMMA on the graphene surface, many research groups have employed various methods such as the thermal treatment, photothermal method, and other solvent. Nevertheless, a part of PMMA still remain on graphene surface. Usually, to observe the residual PMMA on graphene surface, topography of graphene surface scanned by atomic force microscopy is used. However, in that case, we can not distinguish PMMA and other particles. In this study, to confirm the residual PMMA on graphene surface, we employed novel measurement technique which is available to distinguish PMMA and other particles by means of photothermal effect.

• Mycobiology
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• v.36 no.3
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• pp.173-177
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• 2008

The crude ethanol extracts (stem and fruits), their fractions and two triterpenes, $\beta$-Amyrin and 12-Oleanene 3$\beta$, 21$\beta$-diol, isolated as a mixture from the chloroform soluble fraction of an ethanolic extract of Duranta repens stem, were evaluated for antibacterial, antifungal activities by the disc diffusion method and cytotoxicity by brine shrimp lethality bioassay. The structures of the two compounds were confirmed by IR, $^1H$-NMR, $^{13}C$-NMR and LC-MS spectral data. The chloroform soluble fraction of stem and ethanol extract of fruits possess potent antishigellosis activity and also exhibited moderate activity against some pathogenic bacteria and fungi but the isolated compound 1 (mixture of $\beta$-Amyrin and 12-Oleanene 3$\beta$, 21$\beta$-diol) showed mild to moderate inhibitory activity to microbial growth. The minimum inhibitory concentrations (MICs) of the extracts (stem and fruits), their fractions and compound 1 were found to be in the range of 32$\sim$128 ${\mu}g/ml$. The chloroform soluble fractions of stem and ethanol extract of fruit showed significant cytotoxicity with $LC_{50}$ value of 0.94 ${\mu}g/ml$ and 0.49 ${\mu}g/ml$, respectively against brine shrimp larvae.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.754-758
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• 2005

Optimization of process variables such as arc current, welding voltage and welding speed in terms of the weld characteristics desired is the key step in achieving high quality and improving performance characteristics without increasing the cost. Consequently, incorrect settings of those process variables give rise to deviations in the welding characteristics from the desired bead geometry. Therefore, trainee welders are referred to the tabulated information relating different metal types and thickness as to recommend the desired values of process variables. Basically, the bead geometry plays an important role in determining the mechanical properties of the weld. So that it is very important to select the process variables for obtaining optimal bead geometry. However, it is difficult for the traditional identification methods to provide an accurate model because the optimized welding process is non-linear and time-dependent. In this paper, the possibilities of the Infra-red sensor in sensing and control of the bead geometry in the automated welding process are presented. Infra-red sensor is a well-known method to deal with the problems with a high degree of fuzziness so that the sensor is employed to build the relationship between process variables and the quality characteristic the proposed above respectively. Based on several neural networks, the mathematical models are derived from extensive experiments with different welding parameters and complex geometrical features. The developed system enables to select the optimal welding parameters and control the desired weld dimensions during arc welding process.

• The Korean Journal of Nuclear Medicine
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• v.24 no.1
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• pp.101-107
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• 1990

To develop $^{131}I-labelled$ m-iodobeneylguanidine $(^{131}I-MIBG)$, various experiments such as synthesis of MIBG, establishment of labelling conditions, determination of radiochemical purity, and examination of stability were carried out. 1) m-Iodobenzylguanidine (MIBG) sulfate was synthesized with a total yield of 62.4% by the condensation of m-iodobenzylamine hydrochloride with cyanamide via MIBG bicarbonate. Its physical properties, IR, $^1H-NMR$, and elemental analysis data were nearly identical to those of literature. 2) Freeze-dried or vacuum-dried kit vials were prepared from the mixture so as to contain MIBG (2 mg), ascorbic acid (10 mg), copper (II) sulfate (0.14 mg), and tin (II) sulfate (0.5 mg) per vial. Copper ( I ) catalyzed radioiodination of MIBG was carried out using kit vials and 0.01 M $H_2SO_4$ as solvent at $100^{\circ}C$ for 30 min under nitrogen atmosphere (optimal conditions). Labelling yield was 98% and radiochemical purity was 99.5%, respectively. 3) Solid-phase radioiodination of MIBG was carried out at $155^{\circ}C$ for 30 min using the prepared vials to contain MIBG (2 mg) and ammonium sulfate (10 mg). Duplicate reactions under the same conditions showed labelling yield of 95% and radiochemical purity of 99.5%. 4) $^{131}I-MIBG$ prepared either by catalytic or by solid-phase exchange method showed radio-chemical purity of 99% even after 3 days storing at room temperature.

• Journal of the Korean Chemical Society
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• v.38 no.2
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• pp.160-168
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• 1994

Pentadentate Schiff base molybdenum(Ⅴ) complexes such as [Mo(Ⅴ)O(Sal-DET)(NCS)] and [Mo(Ⅴ)O(Sal-DPT)(NCS)] were synthesized by Sabat method. The structure of these complexes were identified by elemental analysis, spectroscopy, and thermogravimetric analysis(T.G.A.). It was found that the mole ratio of Schiff base ligand to the complexes was found to be 1 : 1. The redox processes of the complexes were investigated by cyclic voltammetric and differential pulse polarographic technique in nonaqueous solvent containing 0. 1 M tetraethyl ammonium perchlorate(TEAP) as supporting electrolyte at glassy carbon electrode. It was found that diffusion controlled reduction processes of four steps with one electron were 2Mo(Ⅴ)$\rightleftarrow^{e-}$ Mo(Ⅴ)Mo(Ⅳ) $\longrightarrow^{e-}$ 2Mo(Ⅳ), Mo(Ⅳ) $\longrightarrow^{e-}$ Mo(Ⅲ) $\longrightarrow^{e-}$ Mo(Ⅱ)

• Advances in nano research
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• v.5 no.2
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• pp.127-140
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• 2017

Metal nanoparticles have been intensively studied within the past decade. Nano-sized materials have been an important subject in basic and applied sciences. Zinc oxide nanoparticles have received considerable attention due to their unique antibacterial, antifungal, and UV filtering properties, high catalytic and photochemical activity. In this study, microbiological aspects of scale formation in PVC pipelines bacteria and fungi were isolated. In the emerging issue of increased multi-resistant properties in water borne pathogens, zinc oxide (ZnO) nanoparticle are being used increasingly as antimicrobial agents. Thus, the minimum bactericidal concentration (MBC) and minimum fungal concentration of ZnO nanoparticles towards pathogens microbe were examined in this study. The results obtained suggested that ZnO nanoparticles exhibit a good anti fungal activity than bactericidal effect towards all pathogens tested in in-vitro disc diffusion method (170 ppm, 100 ppm and 30 ppm). ZnO nanoparticles can be a potential antimicrobial agent due to its low cost of production and high effectiveness in antimicrobial properties, which may find wide applications in various industries to address safety issues. Stable ZnO nanoparticles were prepared and their shape and size distribution characterized by Dynamic light scattering (35.7 nm) and transmission electron microscopic TEM study for morphology identification (20 nm), UV-visible spectroscopy (230 nm), X-ray diffraction (FWHM of more intense peak corresponding to 101 planes located at $36.33^{\circ}$ using Scherrer's formula), FT-IR (Amines, Alcohols, Carbonyl and Nitrate ions), Zeta potential (-28.8). The antimicrobial activity of ZnO nanoparticles was investigated against Bacteria and Fungi present in drinking water PVC pipelines biofilm. In these tests, Muller Hinton agar plates were used and ZnO nanoparticles of various concentrations were supplemented in solid medium.

• Korean Journal of Metals and Materials
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• v.50 no.3
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• pp.201-205
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• 2012

The effects of various manganese precursors for the low-temperature selective catalytic reduction (SCR) of $NO_x$ were investigated in terms of structural, morphological, and physico-chemical analyses. $MnO_x/TiO_2$ catalysts were prepared from three different precursors, manganese nitrate, manganese acetate(II), and manganese acetate(III), by the sol-gel method. The manganese acetate(III)-$MnO_x/TiO_2$ catalyst tended to suppress the phase transition from the anatase structure to the rutile or the brookite after calcination at $500^{\circ}C$ for 2 h. It also had a high specific surface area, which was caused by a smaller particle size and more uniform distribution than the others. The change of catalytic acid sites was confirmed by Raman and FT-IR spectroscopy and the manganese acetate(III)-$MnO_x/TiO_2$ had the strongest Lewis acid sites among them. The highest de-NOx efficiency and structural stability were achieved by using the manganese cetate(III) as a precursor, because of its high specific surface area, a large amount of anatase $TiO_2$, and the strong catalytic acidity.

• Korean Journal of Remote Sensing
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• v.20 no.5
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• pp.337-351
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• 2004

Our laboratory originally developed the compact, multi-spectral, automatic aerial photographic system PKNU3 to allow greater flexibility in geological and environmental data collection. We are currently developing the PKNU3 system, which consists of a color-infrared spectral camera capable of simultaneous photography in the visible and near-infrared bands; a thermal infrared camera; two computers, each with an 80-gigabyte memory capacity for storing images; an MPEG board that can compress and transfer data to the computers in real-time; and the capability of using a helicopter platform. Before actual aerial photographic testing of the PKNU3, we experimented with each sensor. We analyzed the lens distortion, the sensitivity of the CCD in each band, and the thermal response of the thermal infrared sensor before the aerial photographing. As of September 2004, the PKNU3 development schedule has reached the second phase of testing. As the result of two aerial photographic tests, R, G, B and IR images were taken simultaneously; and images with an overlap rate of 70% using the automatic 1-s interval data recording time could be obtained by PKNU3. Further study is warranted to enhance the system with the addition of gyroscopic and IMU units. We evaluated the PKNU 3 system as a method of environmental remote sensing by comparing each chlorophyll image derived from PKNU 3 photographs. This appraisement was backed up with existing study that resulted in a modest improvement in the linear fit between the measures of chlorophyll and the RVI, NDVI and SAVI images stem from photographs taken by Duncantech MS 3100 which has same spectral configuration with MS 4000 used in PKNU3 system.

• Bulletin of the Korean Chemical Society
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• v.21 no.7
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• pp.720-726
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• 2000

The analytic gradient method for the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) energy has been extended to employ a reduced molecular orbital (MO) space. Not only the innermost core MOs but also some of the outermost virtua l MOs can be dropped in the reduced MO space, and a substantial amount of computation time can be reduced without deteriorating the results. In order to study the magnitudes and trends of the effects of the dropped MOs, the geometries and vibrational properties of the ground and excited states of BF, CO, CN, N2, AlCl, SiS, P2, BCl, AIF, CS, SiO, PN and GeSe are calculated with different sizes of molecular orbital space. The 6-31 G* and the aug-cc-pVTZ basis sets are employed for all molecules except GeSc for which the 6-311 G* and the TZV+f basis sets are used. It is shown that the magnitudes of the drop-MO effects are about $0.005\AA$ in bond lengths and about 1% on harmonic frequencies and IR intensities provided that the dropped MOs correspond to (1s), (1s,2s,2p), an (1s,2s,2p,3s,3p) atomic orbitals of the first, the second, and the third row atoms, respectively. The geometries and vibrational properties of the first and the second excited states of HCN and HNC are calculated by using a drastically reduced virtual MO space as well as with the well defined frozen core MO space. The results suggest the possibility of using a very smalI MO space for qualitative study of valence excited states.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.5
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• pp.27-35
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• 2019

Stealth technology is a technique to avoid detection from detectors such as radar and infrared seekers. In particular, detection by infrared signature is more threatening because infrared missiles detect heat from the aircraft itself. Therefore, infrared stealth technology is essential for ensuring the survival of aircraft and unmanned combat aerial vehicles (UCAV). In this study, we analyzed aerodynamic and infrared stealth performance in relation to UCAV nozzle design. Based on simulation results, a double serpentine nozzle was effective in reducing the infrared signature because it could shield high-temperature components in the engine. In addition, we observed that the infrared signature was reduced at the turning position of the duct located at the rear part of the double serpentine nozzle.