• Journal of Magnetics
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• v.20 no.2
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• pp.110-113
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• 2015

Two kinds of magnetic fluids with different volume fractions are symmetrically filled into the W0.9 photonic crystal waveguide structure. The 2D plane-wave expansion method is used to investigate the slow light properties numerically. The constant group index criterion is employed to evaluate the slow light performance. The wavelength bandwidth ${\Delta}{\lambda}$ centering at ${\lambda}_0=1550nm$ varies from 32.4 to 44.2 nm when the magnetic field factor ${\alpha}_{\parallel}$ changes from 0 to 1. And the corresponding normalized delay bandwidth product can be tuned from 0.221 to 0.258. For comparison and optimization, two infiltration cases are investigated and the more advantageous infiltration scheme is found.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.6
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• pp.599-608
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• 2002

The mechanical properties of mullite $(3Al_2O_3\;2SiO_2)$ environmental barrier coatings are determined using a laser-based ultrasonic system. The waveforms generated by a laser source in mullite coatings in the $1-20{\mu}m$ thickness range are evaluated theoretically using the integral transform technique. It is shown that the laser source generated the two lowest order SAW modes in these systems. Experimental waveforms are generated using a 600ps pulsed Nd:YAG microchip laser and detected using a stabilized Michelson interferometer. The dispersion curves for the generated modes are extracted from the experimental data and the mechanical properties of the coatings are obtained by minimizing the error between the measured and calculated velocity values. The waveforms generated in mullite coatings agree well with theory and laser-based ultrasonics is shown to provide an effective tool for the nondestructive evaluation of ceramic coatings.

• Journal of the Korean Vacuum Society
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• v.10 no.2
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• pp.189-193
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• 2001

We have characterized physical and electrical properties of W-TiN stacked gate electrode structure with TiN as a diffusion barrier of fluorine. As the $N_2/Ar$ gas ratio increased during sputter deposition, TiN thin films became N-rich, and the resistivity of the films increased. However, the resistivity of W-TiN stacked gate reduced as a result of the crystallization of tungsten with the increase of $N_2/Ar$ gas ratio. On the other hand, tungsten in W-TiN stacked gate structure have the (100)-oriented crystalline structure although TiN films were subjected to annealing at high temperature (600~$800^{\circ}C$). Leakage currents of W-TiN gate MOS capacitors were less than $10^{-7}\textrm{/Acm}^2$ and also were lowered by the order of 2 compared with those of pure W gate electrode.

• Korean Journal of Optics and Photonics
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• v.16 no.6
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• pp.535-541
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• 2005

We report on the development of a passively mode-locked near-infrared femtosecond laser with Cr:YAG crystal that operates near room temperature. The laser wavelength could easily be tuned by using only the internal prism pair over 110 nm from 1400 nm to 1510 nm in cw and over about 30 nm in mode-locked operation, respectively Maximum cw output powers of 810 mW were obtained with $1.5 \%$ output coupler for absorbed pump powers of 7.6 W. For compensation of the internal group velocity dispersion, an IR graded prism pair was used. The Cr:YAG laser delivered nearly Fourier-transform limited pulses with a pulse duration as short as 64 fs at 100 MHz repetition rate. In the mode-locked regime, the laser was operating at 1510 nm with a spectral bandwidth of 44 nm. In order to avoid unstable mode-locking and power instabilities, self-built tubes were inserted into the beam path in the resonator and purged with N2 gas. Finally, output powers of the Cr:YAG laser were optimized to 250 mW fer long time stable mode-locked operation.

• Journal of Adhesion and Interface
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• v.17 no.3
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• pp.110-116
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• 2016

A decrease in the retro-reflectivity of glass-bead-covered road paint because of a rainwater film significantly reduces the visibility of drivers at night, and has been considered as a critical cause of traffic accidents. For enhanced visibility, the microencapsulation of hydrophobically modified $SrAl_2O_4:Eu^{2+}$,$Dy^{3+}$ phosphorescent phosphor was carried out via suspension polymerization of methyl methacrylate (MMA). The effects of surface modification agent and radical initiator types, loading amount of phosphorescent phosphor, and microcapsule size on the phosphor content ($W_{TGA}$) in the luminous poly(methyl methacrylate) (PMMA) microcapsules were investigated by thermogravimetric analyses (TGA). It was found that the $W_{TGA}$ value was ranged from 7 wt% to 81 wt%, which suggests suspension polymerization is suitable for the preparation of luminous microcapsules with a wide range of phosphor content. At a lower loading amount of phosphor, the $W_{TGA}$ value obviously increased as the microcapsule size decreased; however, the $W_{TGA}$ values with a higher loading amount of phosphor were less affected by the microcapsule size. The luminous microcapsules with the size range of $425{\sim}710{\mu}m$ were collected and tested as a luminous road lanes. It was found that luminance intensities of the microcapsule-coated plates remained higher than $300mcd/m^2$ for up to 100 s in darkness after 20 min of light emitting diode lamp irradiation. The results suggest that the luminous microcapsules can be a candidate for the replacement of glass beads for enhanced visibility of drivers.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.578-584
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• 2009

We investigated acid hydrolysis characteristics of yellow poplar woodmeal with concentrated sulfuric acid for high concentration of monosaccharides production. Woodmeal to 72% sulfuric acid ratio (w/w), $2^{nd}$ hydrolysis temperature and time were main variables for finding optimum reaction condition. Optimum woodmeal to 72% sulfuric acid ratio was 1 : 2.61 (w/w) and $2^{nd}$ hydrolysis temperature and time was $105^{\circ}C$ and 40 min as 44.8 g/L of glucose and 25.2 g/L of xylose in hydrolysis solution. In this acid hydrolysis solution, furfural, 5-HMF, low molecular weight phenolic compounds were identified. Furfural and 5-HMF concentration were increased as increasing $2^{nd}$ hydrolysis time. More than 40 min of $2^{nd}$ hydrolysis at $110^{\circ}C$, xylose concentration was decreased but glucose concentration was leveled out because xylose to furfural reaction was faster than xylan to xylose, but cellulose to glucose reaction was similar rate with glucose to 5-HMF at that $2^{nd}$ hydrolysis reaction condition.

• Journal of Advanced Navigation Technology
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• v.25 no.1
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• pp.68-77
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• 2021

In this paper, a GPS/MEMS IMU integrated navigation receiver module capable of operating in a high dynamic environment is designed and fabricated, and the results is confirmed. The designed module is composed of RF receiver unit, inertial measurement unit, signal processing unit, correlator, and navigation S/W. The RF receiver performs the functions of low noise amplification, frequency conversion, filtering, and automatic gain control. The inertial measurement unit collects measurement data from a MEMS class IMU applied with a 3-axis gyroscope, accelerometer, and geomagnetic sensor. In addition, it provides an interface to transmit to the navigation S/W. The signal processing unit and the correlator is implemented with FPGA logic to perform filtering and corrrelation value calculation. Navigation S/W is implemented using the internal CPU of the FPGA. The size of the manufactured module is 95.0×85.0×.12.5mm, the weight is 110g, and the navigation accuracy performance within the specification is confirmed in an environment of 1200m/s and acceleration of 10g.

• Microbiology and Biotechnology Letters
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• v.21 no.4
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• pp.373-380
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• 1993

When the cells of yeast K35 were immobilized in Ca-alginate gel, cell concentration and viability decreased as alginate concentration increased. Considering the results, 2% (w/v) Ca-alginate concentration would be suitable. Among various concentrations of additives and cross-lin-king agent, the addition of 1.67% (w/v) of bentonite together with 0.33% (v/v) of glutaraldehyde (ABG bead) resulted in the highest ethanol production of 1.8%(w/v), using YPD medium containing 2% glucose. ABG bead seemed to be more resistant to phosphate ion than Ca-alginate bead. 0.33%(w/v) of phosphate was a proper concentration for the ethanol production by ABG bead. Scanning electron microscopic observation depicted that the immobilized cells on the bead surface were coated by alginate gel and that the cells in the internal bead were cross-linked with alginate matrix. When repeated-batch culture was performed with ABG bead for 40 days in a packed-bed reactor, ethanol concentration of about 90~110 g/l-gel was maintained. Cell viability was maintained around 70%, and outgrowing cell concentration was below 6.3% of total cell concentration. Consequently, the results showed that ABG head was a potential carrier for continuous production of ethanol compared to conventional Ca-alginate bead.

• KSBB Journal
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• v.24 no.1
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• pp.59-64
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• 2009

The callus formation from inferior leaf of Aloe saponaria was induced in M & S medium supplemented with 10-30 ${\mu}M$ NAA (${\alpha}$-naphthalene acetic acid) and 3-7 ${\mu}M$ kinetin under incubation in the dark at $25^{\circ}C$ for 6 weeks. The hot water extract ($100^{\circ}C$, 24 hrs) from cultured callus was obtained and the components analysis for the extract were examined to determine the callus can synthesized the bioactive component such as Aloe polysaccharide. The freeze dried extract contained the sugar of 53.2%, protein of 7.3%, ash of 18.5% and water of 21% (w/w). Two fractions (Fr-I and Fr-II) were obtained by Sepharose CL-4B gel permeation chromatography and Fr-I, major fraction was further purified with dialysis. From sugar analysis by TLC and GC, the purified Fr-I fraction consisted of glucose (77.6%), galactose (17.7%), mannose (4.7%, w/w) and uronic acid (trace). The molecular weight of purified Fr-I fraction determined by GPC was about 110 kDa.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.19-24
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• 2003

This paper is to research the heat transfer characteristic in copper-water variable conductance heat pipes(VCHP) with a non-condensable gas and gas reservoir. The heat transfer characteristics in the VCHP have not yet been studied much researches. VCHP are used in many applications. These applications range from thermal control of components and systems on satellites, to precise temperature calibration duties, conventional electronics temperature control and thermal diodes. The practical use of VCHP is a simple way to control the temperature of satellites. As the quantity of NCG was increased, there was an increase in the saturation vapor temperatures. As the input heat has loaded from 90 W to 110 W, the difference of the evaporator surface is lower than $10^{\circ}C$.