• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.6
• /
• pp.545-550
• /
• 2000

In order to synthesize Ba-ferrite particles by molten salt method KCl and NaCl were added to basic composition to 50% by weight. X was varied from 0.0 to 1.0 to control the magnetic properties in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ and 1 mol% of $SiO_2$was added to control the aspect ratio of hexagonal platelets. And the effects of reaction temperatures were examined by varying the temperature from 85$0^{\circ}C$ to 120$0^{\circ}C$ with 5$0^{\circ}C$ intervals. Eutectic composition of NaCl and KCl lowered the crystallizing temperature of Ba-ferrite in molten salts than using KCl and NaCl separatly. The morphology of resulting Ba-ferrite particles was clearly hexagonal-shaped plates. $H_{c}$ and $M_{r}$ were decreased when F $e^{3+}$ was substitued with $Co^{2+}$ and $Ti^{4+}$ from x=0 to x=1.0 in $BaFe_{12-2x}$/ $Co_{x}$ / $Ti_{x}$ / $O_{19}$ . Adding 1mol% $SiO_2$in molten salt method increased the size but shortened c-axis of the hexagonal ferrites and this result is an opposite phenomenon compared with the result in solid-statge reaction.n.ion.n.

• Journal of Korean Society on Water Environment
• /
• v.22 no.4
• /
• pp.711-719
• /
• 2006

The effluent from anaerobic digestion process of slurry-type piggery waste has a characteristic of very low C/N ratio. Because of high nitrogen content, it is necessary to evaluate nitrogen removal alternative rather than conventional nitrification-denitrification scheme. In this study, two parallel treatment schemes of SBR-like partial nitritation reactor coupled with anaerobic ammonium oxidation (ANAMMOX) reactor, and a nitritation reactor followed by nitrite denitrification process were evaluated with a slurry-type piggery waste. The feed to reactors adjusted with various $NH_4-N$ and organics concentration. The nitrite accumulation was successfully accomplished at the loading rate of about $1.0kgNH_4-N/m^3-day$. The $NO_2-N/NH_4-N$ ratio 1~2.6 in nitritated effluent that operated at HRT of 1 day indicated that SBR-like partial nitritation was applicable to ANAMMOX operation. Meanwhile, the nitrite accumulation of 87% was achieved at SBR operated with HRT of 3 days and $0.4mgO_2/L$ for denitritation. Experimental results further suggested that HRT (SRT) and free ammonia(FA) rather than DO are an effective control parameter for nitrite accumulation in piggery waste.

• Korean Journal of Microbiology
• /
• v.30 no.6
• /
• pp.432-437
• /
• 1992

When $H^{2}$ was provided as the electron donor, optimum $O_{2}$ levels for growth of Wolinella succinogenes ATCC 29543 were 2% and 8% on brucella agar and in brucella broth, respectively. No growth occurred under 21% $O_{2}$, and scant or no growth occurred under anaerobic condition. $O_{2}$ uptake was inhibited by cyanide and 2-heptyl-4-hydroxyquinoline N-oxide. Protons were translocated out of the cell when oxygen was used as the terminal electron accetor. The $H^{+}$/O ratio with $H_{2}$ and formate as an electron donor were 1, 97 and 1.49, respectively. Proton translocation was inhibited by the protonophore carbonylcyanide m-chlorophenylhydrazone.e.

• Applied Chemistry for Engineering
• /
• v.22 no.6
• /
• pp.685-690
• /
• 2011

In this study, a solvothermal reaction to prepare nanocrystalline titania was carried out using $TiCl_4$ and mixed solvents of alcohol and water. The effects of the type and the composition of alcohol on the crystal structure and agglomeration of final $TiO_2$ products were investigated. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM). In the solvothermal reaction using the n-butanol solutions with different volume ratios of n-butanol/water (100/0, 75/25, 50/50, 25/75, 0/100), the extent of agglomeration of obtained rutile $TiO_2$ was found to change with the volume ratio of n-butanol/water, and the n-butanol/water ratio of 75/25 revealed the best result for the preparation of well-dispersed nanocrystalline $TiO_2$ powders. The crystal phase of $TiO_2$ prepared through the solvothermal reaction changed with the type of alcohol in solvent (alcohol/water = 75/25). $TiO_2$ products obtained with the aqueous solutions of methanol, ethanol and isopropanol have an anatase phase, while that with n-butanol has a rutile phase. The results showed that, in the solvothermal reaction using both $TiCl_4$ as a starting material and the alcohol-water mixed solvents without any other additive, the enhancement of dispersion and control of crystal structure of $TiO_2$ products can be feasible by simply varying the composition and type of alcohol in the mixed solvents.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.580-584
• /
• 2008

Second-order rate constants (kN) have been measured spectrophotometrically for reactions of Y-substituted phenyl benzoates (1a-h) with azide ion (N3) in 80 mol % H2O/20 mol % DMSO at 25.0 0.1 oC. The Brnsted-type plot for the azidolysis exhibits a downward curvature, i.e., the slope (b lg) changes from 0.97 to 0.20 as the basicity of the leaving group decreases. The pKao (defined as the pKa at the center of the Brnsted curvature) is 4.8, which is practically identical to the pKa of the conjugate acid of N3 ion (4.73). Hammett plots correlated with s o and s constants exhibit highly scattered points for the azidolysis. On the contrary, the corresponding Yukawa-Tsuno plot results in an excellent linear correlation with r = 2.45 and r = 0.40, indicating that the leaving group departs in the rate-determining step. The curved Brnsted-type plot has been interpreted as a change in the rate-determining step in a stepwise mechanism. The microscopic rate constants (k1 and k2/k1 ratio) have been calculated for the azidolysis and found to be consistent with the proposed mechanism.

• Mycobiology
• /
• v.39 no.2
• /
• pp.92-95
• /
• 2011

Lignosus rhinocerus is a macrofungus that belongs to Polyporaceae and is native to tropical regions. This highly priced mushroom has been used as folk medicine to treat diseases by indigenous people. As a preliminary study to develop a culture method for edible mushrooms, the cultural characteristics of L. rhinocerus were investigated in a range of culture media under different environmental conditions. Mycelial growth of this mushroom was compared on culture media composed of various carbon and nitrogen sources in addition to C/N ratios. The optimal conditions for mycelial growth were $30^{\circ}C$ at pH 6 and 7. Rapid mycelial growth of L. rhinocerus was observed on glucose-peptone and yeast extract peptone dextrose media. Carbon and nitrogen sources promoting mycelial growth of L. rhinocerus were glucose and potassium nitrate, respectively. The optimum C/N ratio was approximately 10 : 1 using 2% glucose supplemented as a carbon source in the basal media.

• Journal of Power Electronics
• /
• v.17 no.4
• /
• pp.849-859
• /
• 2017

This paper illustrates the analysis and design of a multi-resonant converter applied to an electric vehicle (EV) charger. Thanks to the notch resonant characteristic, the multi-resonant converter achieve soft switching and operate with a narrowed switching frequency range even with a wide output voltage range. These advantages make it suitable for battery charging applications. With two more resonant elements, the design of the chosen converter is more complex than the conventional LLC resonant converter. However, there is not a distinct design outline for the multi-resonant converters in existing articles. According to the analysis in this paper, the normalized notch frequency $f_{r2n}$ and the second series resonant frequency $f_{r3n}$ are more sensitive to the notch capacitor ratio q than the notch inductor ratio k. Then resonant capacitors should be well-designed before the other resonant elements. The peak gain of the converter depends mainly on the magnetizing inductor ratio $L_n$ and the normalized load Q. And it requires a smaller $L_n$ and Q to provide a sufficient voltage gain $M_{max}$ at ($V_{o\_max}$, $P_{o\_max}$). However, the primary current increases with $(L_nQ)^{-1}$, and results in a low efficiency. Then a detailed design procedure for the multi-resonant converter has been provided. A 3.3kW prototype with an output voltage range of 50V to 500V dc and a peak efficiency of 97.3 % is built to verify the design and effectiveness of the converter.

• Korean Journal of Soil Science and Fertilizer
• /
• v.8 no.4
• /
• pp.199-217
• /
• 1975

For the establishment of efficient method of potassium topdressing on rice the optimum time and amount were investigated and discussed on the basis of available data from nutriophysiological studies, soil characteristics and fertilizer trials in fields. The followings were pointed out. 1. According to yield rice plants require more potassium around heading under water culture. 2. Potassium involves in harvest index, filled grain ratio, grain weight and number of spikelets per panicle. 3. Potassium is lost after heading in most fields in spite of highest requirement during this period. 4. The higher $K_2O/N$ ratio in straw at harvest is, the higher the yield. 5. Relatively low efficiency of potassium fertilizer under the field condition may be due to improper application method rather than natural supply from soil and irrigation water. 6. Appropriate topdressing time appears at in effective tillering stage for the prevention of nitrogen excess and at 15 to 20 days after transplanting, ear formation stage and 5 days after heading for the prevention of soil reduction damage. Two times of topdressing for clayey soil and three times for sandy soil seems reasonable in practice together with nitrogen topdressing, 7. The reasonable ratio basal to topdressing of potassium fertlizer seems to be 2/3 and $N/K_2O$ ratio of fertilization for ear formation stage appeared also as 2/3.

• Journal of Korean Society of Environmental Engineers
• /
• v.30 no.8
• /
• pp.831-838
• /
• 2008

This study investigated the characteristics of nitrogen removal and microbial community in a lab-scale A$_2$O activated sludge process filled with the fluidized media at an aerebic basin. The change of microbial community was monitored based on quinone profiles of activated sludge according to feeding sewage with/without external carbon source. Low C/N ratio(COD$_{Cr}$/T-N of 1.24) sewage was fed. The obtained results from this study were as follows; Ubiquinone(UQ) in the influent was in the descending order of UQ-8, UQ-10 and UQ-9. Menaquinone(MK) was simpler and much less than UQ. The ratio of UQ/MK was less than 0.41 and the dissimilarity was below 0.26. Without an external carbon source, MK-8 was the dominant species and there were 3 kinds of quinone species and low DQ and EQ values in an anaerobic basin. The ratio of UQ/MK increased to 2.3 in an anoxic basin. In an oxic basin, UQ-7 and UQ-8 were the dominant species. UQ-7 was dominating in suspended microorganisms, while UQ-8 was in attached microorganisms. With an external carbon source addition, MK-8 decreased but UQ-8 increased in an anaerobic basin. So did quinone species, DQ and EQ values. There was also a change in an anoxic basin with the improvement of denitrification. UQ-8 decreased instead, MK-7 and MK-8 increased. UQ/MK ratio decreased 2.3 to 1.4. It means that the dominant species change from Pseudomonas sp. to Bacillus and Micrococcus species. etc. In an oxic basin, UQ-8 replaced UQ-7 in suspended microorganisms and UQ-10 replaced UQ-8 in attached microbials. This seemed related with the growth of Nitrosomonas and Nitrobactor species.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.1C
• /
• pp.17-25
• /
• 2012

CLSM (Controlled Low Strength Material) using coal ash, which has the advantages of self-leveling, self-compacting, flowability, easy re-excavation, has been developed. In this study, CLSM additionally mixed with foaming agent for structural backfill material, aimed at lightness of materials, was developed called light-weight foamed CLSM. As the basic study of this material, to determine the optimum final mixing time and dilution ratio of existing light-weight foamed CLSM, flow, slurry unit weight and unconfined compressive strength test according to each impact factor were performed at the standard mix proportion. As the results of tests, CASE N (Final mixing time 4 min, dilution ratio 2%), CASE O (Final mixing time 3 min, foam agents ratio 3%, dilution ratio 2%) were satisfied with the standard of flow test (above 20cm), slurry unit weight test (12~15 $kN/m^3$) and unconfined compressive strength test (800 kPa~1200 kPa). These results will indicate the standard optimum final mixing time and dilution ratio of light-weight foamed CLSM for structural backfill.