• Environmental Engineering Research
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• v.14 no.2
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• pp.134-139
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• 2009

In this study, oxidation of As (III) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (III), Mn (IV), Al (III)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (III) or As (V) was studied. As (V) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (V) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (V) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (V) although it contains 217.9 g-Fe/kg-adsorbent, Oxidation result shows that manganese coated sand (MCS) has the greatest As (III) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (III) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.

• Journal of Korean Society of Water and Wastewater
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• v.20 no.4
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• pp.559-571
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• 2006

The overall objective of this research was to find out the interrelation of coagulant and organic matter during rapid mixing process and to identify the change of organic matter by mixing condition and to evaluate the effect of coagulation pH. During the coagulation, substantial changes in dissolved organics must be occurred by coagulation due to the simultaneous formation of microflocs and NOM precipitates. Increase in the organic removal efficiency should be mainly caused by the removal of microflocs formed during coagulant injection. That is, during the mixing period, substantial amount of dissolved organics were transformed into microflocs due to the simultaneous formation of microflocs and NOM precipitates. The results also showed that 40 to 80% of dissolved organic matter was converted into particulate material after rapid mixing process of coagulation. During the rapid mixing period, for purewater, formation of dissolved Al(III) (monomer and polymer) constant by rapid mixing condition, but for raw water, the species of Al hydrolysis showed different result. During the rapid mixing period, for high coagulant dose, Al-ferron reaction increases rapidly. At A/D(Adsorption and Destabilization) and sweep condition, both $Al(OH)_3(s)$ and dissolved Al(III) (monomer and polymer) exist, concurrent reactions by both mechanism appear to cause simultaneous precipitation.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.2
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• pp.125-131
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• 2002

we analyzed acoustic emission signals obtained from three kinds of brittle materials under compression load by Vickers hardness tester. The results obtained can be summarized as follows; The signal in each material could be divided into three signal based on the properties of load. All specimens were not detected acoustic emission signals in stage II which was load constant region., and were detected in stage I and stage III. Glass was detected high amplitude signals in stage III. $Al_2O_3\;and\;Al_2O_3/Sic$ were detected high amplitude signals in stage I.

• Journal of Conservation Science
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• v.29 no.3
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• pp.279-286
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• 2013

It is characterized and classified as the type of red brown glass beads to compare the chemical composition and manufacturing technique on the 141 samples in 12 sites of the Three Kingdom Period analyzed until now. It can be divided into three types according to the chemical composition of stabilizers(CaO & $Al_2O_3$) and soda raw materials(MgO & $K_2O$) on the red brown glass beads except one sample. Type I of high alumina glass is identified as the most common types that is 78.6 % of the distribution ratio at analytical samples and is excavated the most from ruin sites. In contrast, type II, 13.6 % of distribution ratio at analytical samples, is about 5 % CaO and $Al_2O_3$, MgO and $K_2O$ at around 1.5 % is similar to the composition of plant ash glass. Type III is that the content of CaO is higher than $Al_2O_3$ and the content of MgO and $K_2O$ is below 1.5 %. It is the same as the composition of natron glass and its share is the lowest as 7.9 %. Of these, type III is divided into two types according to the content of MgO and $K_2O$. It is identified that manufacturing technique of type I and II is drawing and type III is casting method with microscopic investigations. Type II and III is estimated that raw materials is different because is confirmed in the majority of ruins in spite of the fact that distribution ratio is very low. So, red brown glass beads distributed in Korea Peninsula are divided into three types of glass culture.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.711-716
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• 1999

This research explored the feasibility of preparing and utilizing a prefonned polymeric solution of Al(III) for coagulation in water treatment. Slow base(NaOH) injection into supersaturated aluminum chloride and aluminum sulfate solutions did produce high yields of Al polymers useful to water treatment applications. The method of characterization analysis was based on timed spectrophotometer with ferron as a color developing reagent. The hydrolytic Al species were divided into $monomeric(Al_a),\;polymeric(Al_b),\;and\;precipitate(Al_c)$ from the difference in reaction kinetics. The analysis of PACl's characteristics showed that the quantity of polymeric Al produced at value of$ r(OH_{added}/AI)=2.2$ was $83\%$ of the total aluminum in solution, as showing maximum contents and precipitated Al was dramatically increased when r was increased above 2.35. In addition, the characteristics of polyaluminum sulfate (PAS) showed that polymeric Al contained at r = 0.75 was $18\%$ of the total aluminum in solution. The synthesized PACI and PAS were stable during storing period, as indicating negligible aging effect. The effect of sulfate ion on PACI was dependent on the concentration of sulfate ion. That is, polymeric species decrease and precipitate species increase as sulfate ion concentration increased. It can be concluded that the sulfate cause the formation of $Al(OH)_{3(S)}$ at low pH. However, The effect of calcium ion was negligible for distribution of Al species.

• Communications of the Korean Mathematical Society
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• v.33 no.2
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• pp.581-590
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• 2018

In this paper, we consider surfaces in the 3-dimensional Euclidean space $\mathbb{E}^3$ which are of finite III-type, that is, they are of finite type, in the sense of B.-Y. Chen, corresponding to the third fundamental form. We present an important family of surfaces, namely, tubes in $\mathbb{E}^3$. We show that tubes are of infinite III-type.

• Advances in nano research
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• v.3 no.1
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• pp.13-27
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• 2015

Size dependent emission properties and the interband optical transition energies in group-III nitride based quantum dots are investigated taking into account the geometrical confinement. Exciton binding energy and the optical transition energy in $Ga_{0.9}In_{0.1}N$/GaN and $Al_{0.395}In_{0.605}N$/AlN quantum dots are studied. The largest intersubband transition energies of electron and heavy hole with the consideration of geometrical confinement are brought out. The interband optical transition energies in the quantum dots are studied. The exciton oscillator strength as a function of dot radius in the quantum dots is computed. The interband optical absorption coefficients in GaInN/GaN and AlInN/AlN quantum dots, for the constant radius, are investigated. The result shows that the largest intersubband energy of 41% (10%) enhancement has been observed when the size of the dot radius is reduced from $50{\AA}$ to $25{\AA}$ of $Ga_{0.9}In_{0.1}N$/GaN ($Al_{0.395}In_{0.605}N$/AlN) quantum dot.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1994.11a
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• pp.50-53
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• 1994

In this study. we report the properties of optically pumped stimulated emission at room temperature (RT) from column-III nitride semiconductors of GaN, GaInN, AlGaN/GaN double hetero-structure (DH) and AlGaN/GaInN DH which grown by low pressure metal-organic vapor phase epitaxy on sapphire substrate using an AIN buffer-layer. The peak wavelength of the stimulated emission at RT from AlGaN/GaN DH is 370nm and the threshold of excitation pumping power density (P$\_$th/) is about 89㎾/$\textrm{cm}^2$, and they from AlGaN/GaInN DH are 403nm and 130㎾/$\textrm{cm}^2$, respectively. The P$\_$th/ of AlGaN/GaN and AlGaN/GaInN DHs are lower than the bulk materials due to optical confinement within the active layers of GaN and GaInN. The optical gain and the polarization of stimulated emission characteristics are presented in this article.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.3
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• pp.149-154
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• 2012

According to the coagulation tests for PACs with various basicities, the PACB with lower basicity showed higher coagulation efficiencies of organics and phosphorus than the PAC with higher basicity. The PACB contained higher amount of monomeric Al (III) hydrolytic species comparing with PAC. In case of the coagulation for the sewage treated water, the coagulation efficiency by the charge neutralization and sweep floc formation was higher with PACB than with PAC. Accordingly, when $Al_2O_3$ concentration was similar in the coagulant, PACB showed higher removal efficiencies of turbidity, $COD_{Mn}$, TP, and $PO_4$-P comparing with PAC, especially in the lower range of coagulant dose.

• Journal of the Korean Ceramic Society
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• v.27 no.1
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• pp.55-61
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• 1990

Effect of Al2O3 addition on the mechanical properties and microstructure of Ce-TZP were studied. 12, 14, 16Ce-TZP containing 0-40wt% Al2O3 were prepared by sintering at 155$0^{\circ}C$ for 2h. in air. Density, linear shrinkage, bending strength, Vickers hardness, microstructuer and the amount of stress induced phase transformation were examined. Vickers hardness increased linearly with increasing amounts of Al2O3. The amount of transformation and fracture toughness decreased linearly with increasing amount of Al2O3. Linear shrinkage and relative density decreased with increasing Al2O3 content in all composition of Ce-TZP. Grain growth of Ce-TZP was inhibited by Al2O3 dispersion and fracture mode of Ce-TZP/Al2O3 composites transformed from intergranular to transgranular fracture as the amount of Al2O3 increased. TEM observation revealed that Al2O3 particles were located mainly at grain boundaries of ZrO2.