• Bulletin of the Korean Chemical Society
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• v.15 no.12
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• pp.1098-1103
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• 1994

Atomic force microscopy (AFM) images of two conducting layered transition-metal ditellurides, $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$, were examined and their surface and bulk structural features were compared. All the measured unit cell parameters from AFM image were consistent and in complete agreement with the results of the X-ray diffraction. The microscopic structures of corrugated surface tellurium sheets were strongly affected by the modification of metal double zig-zag chains underneath Te surface. Large difference in the height amplitudes of AFM images in $TaTe_2$ and $Ta_{0.5}$$V_{0.5}$$Te_2$ phases was observed and this reflects large difference in the surface electron densities of two phases. On surface, the shorter intralayer Te…Te contacts in $TaTe_2$ induce more electron transfer from Te p-block bands to Ta d-block bands, thus electron density on surface observed in $TaTe_2$ is much lower than that of $Ta_{0.5}$$V_{0.5}$$Te_2$. However, in bulk, interlayer Te…Te contacts in V substituted phase are shorter than those in $TaTe_2$ phase, thus tellurium-to-metal electron transfer occurs more easily in $Ta_{0.5}$$V_{0.5}$$Te_2$ phase.

• Korean Journal of Microbiology
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• v.40 no.1
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• pp.54-59
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• 2004

$\beta$-Glucan has been efficiently produced with higher yield by the optimization of liquid cultivation conditions. The optimal composition of medium for batch culture was 5% (w/v) of glucose as a carbon source, 0.5% (w/v) of yeast and 0.5% (w/v) of malt extract as a nitrogen source, 0.1% (w/v) of $KH_2PO_4$ and 0.05% (w/v) $MgSO_4{\cdot}7H_2O$, which had been the base medium for determination of other conditions. The set-up conditions are pH 5.0, $28^{\circ}C$, 1 vvm for aeration and 300 rpm for agitation. In order to minimize the inhibition effect of glucose on the initial growth of mycelia and to maximize the production of extracellular $\beta$-glucan, we have reduced the initial glucose feed to 4% and added 2nd feed at the point of 70 hr from the initial feed. The 2nd feed was composed of glucose 3%, yeast extract 0.1 % and malt extract 0.1 %. It improved the $\beta$-glucan yield upto 5.2 g/L in comparison with 2.8 g/L resulted from batch cultivation. Moreover, the serial treatment of a cell wall lytic enzyme and bromelain to the mycelia was effective for extraction of the cell wall bound $\beta$-glucan. The yield of $\beta$-glucan extraction by the enzyme treatment was 3.5 g/L, which was almost 4 times higher than that by hot-water extraction.

• Membrane Journal
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• v.21 no.3
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• pp.290-298
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• 2011

The influence of co-existing gases on the hydrogen permeation was studied through a Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane. The hydrogen permeation characteristics of Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane have been investigated in the pressure range 1-3 bar under pure hydrogen and hydrogen mixture gas with carbon dioxide and carbon monoxide at $450^{\circ}C$. Preliminary hydrogen permeation experiments have been confirmed that hydrogen flux was $5.36mL/min/cm^2$ for a Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane (thick: 0.5 mm) using pure hydrogen as the feed gas. In addition, hydrogen fluxes were 4.46, 5.20, $3.91mL /min/cm^2$ for$V_{53}Ti_{26}Ni_{21}$ alloy membrane using $H_2/CO_2$, $H_2/CO$ and $H_2/CO_2/CO$ as the feed gas respectively. Therefore, the hydrogen permeation flux decreased with decrease of hydrogen partial pressure irrespective of temperature and pressure when $H_2/CO_2$, $H_2/CO$ and $H_2/CO_2/CO$ mixture applied as feed gas respectively and permeation fluxes were satisfied with Sievert's law in different feed conditions. It was found from XRD results after permeation test that the Pd-coated $V_{53}Ti_{26}Ni_{21}$ alloy membrane had good stability and durability for various mixtures feeding condition.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.8
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• pp.598-605
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• 2011

The main object of this study is to investigate the Dust Collection Characteristics of multi-layer multi-stage porous plate system with polarization charging mechanism, experimentally. The experiment is carried to analyze the characteristics of pressure drop and collection efficiency for the present system with the experimental parameters such as applied voltage, inlet velocity, inlet concentration and stage number, etc. In results, the pressure drop becomes 18 to $134mmH_2O$, with increment of stage number (1 to 5) at inlet velocity $v_{in}$ = 3.11 m/s ($v_t$ = 18 m/s) and inlet concentration 3 g/m3 for inflow current. In case of both applied voltage 0 kV and non-inflow current, the collection efficiency of 5 stage is 92.5% at $v_{in}$ = 2.58 m/s ($v_t$ = 15 m/s), while it is estimated that the collection efficiency becomes about 6% higher than that of 0 kV and non-inflow as 98.5% at $v_{in}$ = 2.58 m/s for both alternating polarization charge (applied voltage 2.5 kV) and inflow current system.

• Bulletin of the Korean Chemical Society
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• v.25 no.2
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• pp.263-266
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• 2004

A sensitive, selective and rapid method has been developed for the determination ${\mu}$g/L level of vanadium ion based on the rapid reaction of vanadium(V) with 2-(2-quinolylazo)-5-diethylaminophenol (QADEAP) and the solid phase extraction of the colored chelate with $C_{18}$ cartridge. The QADEAP reacts with V(V) in the presence of citric acid-sodium hydroxide buffer solution (pH = 3.5) and cetyl trimethylammonium bromide (CTMAB) medium to form a violet chelate of a molar ratio 1 : 2 (V(V) to QADEAP). This chelate was enriched by solid phase extraction with $C_{18}$cartridge and the enrichment factor of 50 was obtained by elution of the chelates from the cartridge with ethanol. The molar absorptivity of the chelate is $1.28 {\times}10^5L\;mol^{-1}cm^{-1}$ at 590 nm in the measured solution. Beer's law is obeyed in the range of 0.01-0.6 ${\mu}$g/mL. The detection limit is 0.04 ${\mu}$g/L in the original samples. This method was applied to the determination of vanadium(V) in water and biological samples with good results.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.4
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• pp.223-229
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• 2022

In this paper, the ignition trans used in boilers was studied. Regardless of the change in the ignition rod length and the ignition rod gap, the output frequency was measured between 59.5 and 61.3 Hz, and it was found that the low frequency circuit operated normally. When the ignition rod gap changed by 2 to 10 mm, the ignition rod length was measured from 2.8A to 3.45A at 30cm. The ignition rod length was measured from 9.37 A to 14.5 A at 500 cm and from 13.2 A to 32.6 A at 1000 cm. As the ignition rod length and the ignition rod gap increased, the current increased. As a result of measuring the secondary coil output voltage. The ignition rod length was measured from AC 0.84 kV to AC 1.75 kV at 30 cm, AC 1.17 kV to AC 1.944 at 500 cm, and AC 1.4 kV to AC 7.18 kV at 1000 cm. As the ignition rod length and the ignition rod gap increased, the output voltage of the secondary coil also increased. As a result of measuring the output voltage of the ignition trans, the ignition rod length was measured from DC 1.11 kV to DC 1.57 kV at 30cm, DC 2.49 kV to DC 3.72 kV at 500cm, and DC 3.78 kV to DC 9.42 kV at 1000cm, and the power voltage increased as the ignition rod length and interval increased.

• Bulletin of the Korean Chemical Society
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• v.17 no.12
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• pp.1123-1127
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• 1996

Crystalline compound RbV2SeO7, a Rb analogue of KV2SeO7, was synthesized from a hydrothermal reaction of V2O5, V2O3, SeO2, and Rb2CO3 in the mole ratio 3: 1: 15: 6 (in millimoles) at 230℃. RbV2SeO7 crystallizes in an orthorhombic space group Pnma (No. 62) with a=18.444(8), b=5.415(3), c=7.070(4) Å, Z=8. The two structures of KV2SeO7 and RbV2SeO7 are almost the same except that bond lengths in the latter are slightly longer than in the former. The magnetic susceptibility measurement for RbV2SeO7 in the temperature range 4-300 K showed an antiferromagnetic ordering with TN=45 K, higher than that for KV2SeO7 of 27 K. The origin of the magnetic coupling and the different ordering temperatures in the two phases are discussed in relation to the crystal structures.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.9 no.1
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• pp.1-10
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• 1984

The time division multiplexing PCM encoder which is constructed for an airborne telemetering system is investigated. Selected by program switch, the PCM encoder has 0~64 words/framd($\pm$5V full scale) of allowable analog input channels, 0~30bits(5V$\pm$1V or 0V$\pm$1V dc) of discrete channels, 70 and 140K bits/sec of bit rate and 8~12bits/word of resolution. And filtered output PCM code is NRZ-L and Bi-S through the 5 pole Bessel LPF(f=100kHz), and the maximum accuracy of PCM encoder is $\pm$0.2% of its full scale.

• Applied Biological Chemistry
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• v.40 no.2
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• pp.107-111
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• 1997

To recover protopectinase (PPase) secreted from Bacillus subtilis IFO 12113, culture filtrate of the microorganism was treated with acetone, methanol, and ethanol, respectively. In the case of treatment with acetone at a ratio of 1: 1 (culture filtrate: acetone, v/v), PPase was purified 1.7-fold with 59.2% recovery The recovery of PPase was increased by increasing the acetone concentration. PPase was purified 4-fold with 100% recovery when the culture filtrate was precipitated with methanol at a ratio of 1 : 2 (culture filtrate: methanol, v/v). However, recovery of PPase was decreased by increasing the methanol concentration. PPase was purified 13.5-fold resulting in 68% recovery by the addition of ethanol with the final ratio 1 : 1(culture filtrate: ethanol, v/v) to the supernatant, which was obtained after precipitation of the culture filtrate with ethanol at a ratio of 1 : 0.5. These results show that methanol treatment is better than other organic solvent treatments for the simple recovery of PPase, whereas fractionated treatment of ethanol can recover PPase with higher purification fold.

• Journal of Advanced Navigation Technology
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• v.22 no.5
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• pp.436-441
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• 2018

In this paper, a design method for a compact double dipole quasi-Yagi antenna with a V-shaped ground plane operating in dual bands including 2.45 GHz and 5 GHz wireless LAN frequency bands is studied. First, a quasi-Yagi antenna operating in the 2.45 GHz band is designed, and a V-shaped ground plane is used instead of a conventional strip ground plane to reduce the length of the antenna. A second dipole is connected to the dipole driver of the quasi-Yagi antenna for 2.45 GHz band and a director is appended for 5 GHz band operation. A prototype of the proposed dual-band antenna operating at 2.45 GHz WLAN band and 4.57-7.11 GHz band is fabricated on an FR4 substrate with a dimension of 40 mm by 55 mm. Fabricated antenna shows frequency bands of 2.33-2.75 GHz and 4.38-7.5 GHz for a voltage standing wave ratio less than 2. Measured gain remains more than 4 dBi in both bands.