• Analytical Science and Technology
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• v.23 no.6
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• pp.511-517
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• 2010

Dissolution procedure of vanadium pentoxide, which is widely used as a catalyst for production of sulfuric acid or an oxide reaction of the numerous organic compounds, was investigated. Reagent of vanadium pentoxide was completely dissolved in aqua regia-$H_2O_2$-HF solution, but plate type of vanadium pentoxide sample was not clearly dissolved with mixed acids. Thus, in order to establish the dissolution procedure for plate type of vanadium pentoxide, the solubility of vanadium pentoxide was investigated through comparison of acid treatment-fusion and microwave digestion methods. The optimized acid for dissolution of vanadium compound was found to be mixing acids of aqua regia, $H_2O_2$ and HF. Acid-fusion and microwave digestion methods have a similar property in the solubility of vanadium compound, but the latter was more quick and convenient procedure. The content of vanadium pentoxide was found to be $97.9{\pm}0.9%$ using an inductively coupled plasma atomic emission spectrometer after dissolution of a sample with the microwave digestion system.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.581-587
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• 2005

In order to obtain a highly purified p-dioxanone (PDX) as monomer of biodegradable polymer, suitable solvent must be selected. The selection was based on the solubility of impurities, and partial layer melt crystallization were carried out under the presence of solvent. The solubility of PDX in various solvents such as ethyl acetate, tetrahydrofuran, acetone, alcohols (methanol, ethanol, 1-propanol, 1-butanol and 1-pentanol) were measured over the temperature range of $-10{\sim}15^{\circ}C$. As solubility parameters, the mixing and dissolution enthalpy between the PDX and the solvents was studied based on empirical equations and the regular solution theory. The solubility and the temperature dependency of the solubility with the solvents of acetone, ethylacetate, and tetrahydrofuran of PDX were shown to have relatively high values compared to the alcohol type solvents. Also, in same alcohols, the smaller molecules and higher polarity gave higher solvency. In partial layer melt crystallization, small amount of ethylacetate selectively dissolved impurities and gave highly purified p-dioxanone, over 99.9% purity.

• Journal of Aquaculture
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• v.20 no.1
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• pp.1-6
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• 2007

Two feeding experiments were conducted to investigate the effects of fermented cactus fruit (Opuntia ficusindica) fluid (FCFF) as a feed additive to a commercial diet on the growth of red sea bream, Pagrus major, and to determine an effective dose. FCFF was prepared by mixing crushed cactus fruit with a starch solution and commercially available microorganisms for 2 weeks at room temperature. Three triplicate groups of red sea bream had initial mean weights of 84.1 g (Exp-1) and 5.1 g (Exp-2) and were fed experimental diets containing 0%, 1%, and 5% FCFF for 2 months (Exp-1) and 0%, 0.2%, 0.5%, and 1% FCFF for 3 months (Exp-2), respectively. In experiment 1, the mean body weight of fish fed the diet containing 1% FCFF was significantly higher (P<0.05) than that of fish fed the diet without FCFF. The survival rate was highest in fish fed the diet containing 1% FCFF, although the difference was not statistically significant. The feed gain ratio (FGR), specific growth rate (SGR), and condition factor (CF) values of fish fed the diet containing 1% FCFF were higher than those of fish in the other dietary groups that received lower levels of FCFF. The daily feeding rate (DFR) of fish fed the diet containing 1% FCFF was slightly lower but not statistically different than the DFR values of fish in the other dietary groups. In experiment 2, the final mean body weight of fish fed the diet containing 1% FCFF was significantly (P<0.05) higher than the mean weight of fish in the control group. The FGR, SGR, and CF values of fish fed the diet containing 1% FCFF were better than the values from fish in the other dietary groups that received lower levels of FCFF, although the differences were not statistically significant. However, the DFR of fish fed the diet containing 1% FCFF was lower than those of fish in the other groups. These results suggest that FCFF could be used as a feed additive in commercial fish food and a preferable level of supplementation is at least 1.0% in fingerling and young red sea bream.

• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.704-709
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• 2002

To improve the mechanical properties of $Al_2$O$_3$/ZrO$_2$composites, the homogeneous dispersion of ultra low size ZrO$_2$ particles in $Al_2$O$_3$ceramics have been controlled by coprecipitation method. In case of mechanical mixing of ZrO$_2$ powders with $Al_2$O$_3$, homogeneous dispersion and controlling the ZrO$_2$ size were relatively difficult due to high sintering temperature. So nanosized Zr hydroxide was coprecipitated from ZrOCl$_2$/Y(NO$_3$)$_3$ solution with commercial sub-micron sized $\alpha$-alumina (Sumitomo : AES-11(0.4 ${\mu}{\textrm}{m}$)) and high purity ultra low sized $\alpha$-alumina (Taimei Chemical (0.22 ${\mu}{\textrm}{m}$)) for low temperature sintering. By this partial coprecipitation method, relatively low sized ZrO$_2$ dispersion in $Al_2$O$_3$/ZrO$_2$ composites was achieved at 150$0^{\circ}C$-1$600^{\circ}C$ of sintering temperature range and their mechanical properties were measured.

• Polymer(Korea)
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• v.35 no.1
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• pp.52-59
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• 2011

L-PLA or D-PLA was synthesized in bulk at $140^{\circ}C$ by ring opening polymerization(ROP) of L-lactide or D-lactide as a monomer using tin(II) octoate and lauryl alcohol as a catalyst and an initiator with changing the amounts of catalyst(0.25~1.0 wt%) and initiator(0.l~0.5 wt%). And stereocomplex-PLA was prepared by L-PLA/D-PLA having a wide range of molecular weight(30000~90000 g/mol) and L-PLA/D-PLA blends having different mixing ratio ($X_D$). The melting temperature. thermal degradation temperature and thermal stability of stereocomplex-PLA were higher than those of homopolymers(L-PLA, D-PLA). We supposed that these improvements arose from a strong interaction between L-PLA and D-PLA. The improved mechanical properties and changes in morphology of LPLA/D-PLA blends were compared to those of homopolymers(L-PLA, D-PLA).

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.345-353
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• 2003

When designing network processors or implementing network equipments such as routers are implemented, IP lookup operations cause the major impact on their performance. As the organization of the IP address becomes simpler, the speed of the IP lookup operations can go faster. However, since the efficient management of IP address is inevitable due to the increasing number of network users, the address organization should become more complex. Therefore, for both IPv4(IP version 4) and IPv6(IP version 6), it is the essential fact that IP lookup operations are difficult and tedious. Lots of researcher for improving the performance of IP lookups have been presented, but the good solution has not been came out. Software approach alleviates the memory usage, but at the same time it si slow in terms of searching speed when performing an IP lookup. Hardware approach, on the other hand, is fast, however, it has disadvantages of producing hardware overheads and high memory usage. In this paper, conventional researches on IP lookups are shown and their advantages and disadvantages are explained. In addition, by mixing two representative structures, a new hybrid parallel architecture for fast IP lookups is proposed. The performance evaluation result shows that the proposed architecture provides better performance and lesser memory usage.

• Resources Recycling
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• v.22 no.5
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• pp.13-19
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• 2013

The effect of pH on the citrate leaching behavior of heavy metal ion was investigated to develop an eco-friendly process for removing heavy metals from soil contaminated with copper, zinc, and lead. The leaching tests were performed using citrate solution with pH adjusted by mixing citric acid and sodium citrate under the following leaching conditions: particle size, under $75{\mu}m$; temperature, $50^{\circ}C$; citrate concentration, $1kmol/m^3$; pulp density, 5%; shaking speed, 100 rpm; leaching time, 1 hour. The difference of pH before and after the leaching test was not observed, and this result indicates the direct effect of hydrogen ion concentration on the leaching of metals was insignificant. The removal ratios of copper, zinc, and lead from the contaminated soil decreased with increasing pH. The thermodynamic calculation suggests that the leaching behaviors of metal ions were determined by two reactions; one is the reaction to form complex ions between heavy metal ions and citrate ion species, and the other is the reaction to form metal hydroxide between heavy metal ions and hydroxide ion.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.6
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• pp.274-278
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• 2012

$TiO_2$ can be used optically and is applied on many areas such as gas sensor, solar cell and photocatalysis. Electrospun nanofibers have received great interest for development and utilization in some novel applications, such as chemical sensors, dye-sensitized solar cell and photo catalysis. In this study, pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers synthesized by a modified electrospinning method. The Ga doped $TiO_2$ solution is prepared by mixing poly vinyl pyrrolidone, ethyl alcohol, and titanium (IV) isopropoxide. By electrospinning these sols, nanofibers were fabricated. These fibers are heat-treated at $800^{\circ}C$ in air. The prepared pure $TiO_2$ and Ga-doped $TiO_2$ nanofibers samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy.

• Journal of Periodontal and Implant Science
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• v.37 no.4
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• pp.871-879
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• 2007

Purpose: The purpose of this study was to evaluate the bone regeneration of novel biodegradable amorphous calcium phosphate. Materials and Method: An 8-mm, calvarial, critical-size osteotomy defect was created in each of 20 male Sprague-Dawley rats(weight $250{\sim}300g$). The animals were divided into two groups of 10 animals each and allowed to heal for 2 weeks(10 rats). The first group was the control group and the other group was the experimental group which received the novel biodegradable calcium phosphate. Results: The healing of the calvarium in the control group was uneventful. The histologic results showed little bone formation in the control group. The experimental group which received the novel biodegradable calcium phosphate showed a normal wound healing. There were a lot of new bone formation around the biomaterial in 2 weeks. The bone formation increased in 8 weeks when compared to 2 weeks and there was a significant bone increase as well(P<0.01). The nobel biodegradable calcium phosphate showed statistical significance when compared to the control group (P<0.05). The novel biodegradable calcium phosphate in 8 weeks showed a significant increase in bone formation when compared to 2 weeks $(40.4{\pm}1.6)$(%). The biodegradable calcium phosphate which is made from mixing calcium phosphate glass(CPG), NaCO and NaOH solution, is biocompatible, osteoconductive and has a high potency of bone formation. Conclusion: We can conclude that the novel biodegradable calcium phosphate can be used as an efficient bone graft material for its biodegradability and osteoconductivity.

• Korean Journal of Plant Resources
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• v.24 no.4
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• pp.445-455
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• 2011

This study was performed to develop a natural preservative which had the most successful effect on prolonging the vase life of cut flowers Rosa hybrida 'Enjoy'. To determine the effect of sucrose on vase life of cut roses, R. hybrida 'Enjoy', 0, 1, 3 or 5% of sucrose was mixed with Hypnum jutlandicum extract. The result showed that in the case of adding sucrose to extracts from H. jutlandicum, vase life of cut flowers was shortened, along with the cut flowers losing chlorophyll, becoming decolorized and finally showing wilting phenomenon. However, using hydroxy quinoline sulfate (HQS) and extracts from H. jutlandicum together exhibited an improved effect of prolonging vase life, especially when adding 100 $mg{\cdot}L^{-1}$ HQS, which had the effect of prolonging the vase life of R. hybrida 'Enjoy' the most. Regarding pH of extracts, 2 $mg{\cdot}L^{-1}$ of extracts from H. jutlandicum show originally pH 3.8. This was compared with adjusted extract solutions as pH 3.0, 4.0 or 5.0. The results showed that the solution of pH 3.8 had the most successful effect on prolonging the vase life of R. hybrida 'Enjoy'. Given all the results, H. jutlandicum extract (2 $mg{\cdot}L^{-1}$) and HQS (100 $mg{\cdot}L^{-1}$) was the most effective in prolonging the vase life of cut R. hybrida 'Enjoy'. Moss is expected to be worth developing as a natural preservative since it is easy to get and causes no damage to the environment.