• Proceedings of the KAIS Fall Conference
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• 2000.10a
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• pp.233-236
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• 2000

산업화에 따라 발생하는 산업폐수에는 많은 종류의 유해한 유기물들이 함유되어 있으며, 이러한 유독성 유기물을 제거하기 위하여 많은 연구가 진행되어 왔으나. 기존의 처리 방법들은 2차 환경오염을 유발한다는 문제점을 갖고 있다. 최근 폐수처리에 광촉매를 이용한 광분해 반응이 기존의 처리방법들에서 나타날 수 있는 문제점과 폐수중의 유독성 유기물을 제거할 수 있는 환경친화적 공정이라는 보고가 있은 후 광촉매에 대한 연구가 활발히 진행되고 있다. 본 연구에서는 광촉매 TiO₂의 표면특성을 XRD, SEM 및 BET를 사용하여 자세히 고찰하였다. XRD 결과 Degussa P25는 anatase 구조와 rutile 구조가 섞인 형태였으며, Aldrich Degissa TiO₂는 100% anatase 구조, KIER TiO₂는 100% rutile 구조를 가졌고 SEM 결과 Aldrich와 Degussa TiO₂의 입자형태는 작은 입자들이 뭉쳐있는 형태였으나 KIER TiO₂는 작은 입자들이 독립적으로 분리된 타원형으로 입자크기가 가장 컸다. 반면 BET 결과 Degussa TiO₂의 비표면적이 59㎡/g으로 Aldrich TiO₂(6㎡/g)나 KIER TiO₂(14 ㎡/g)에 비하여 매우 큼을 알 수 있었다.

• Journal of Animal Environmental Science
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• v.7 no.2
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• pp.111-118
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• 2001

This study was performed for measuring the emission of greenhouse gases, $CH_4,\;N_2O$, from the composting process for pig slurry. For the experiment the benchscale pilot plant was designed by 1$m^3$ volume reactor with a closed type and operated; sawdust 142kg filled before input slurry, slurry about 10~20l inputed per day (total 380l), air supplied 5l/min for 24 hours, mixing time 10 min./day and 1 time a day. From the total experiment period(30days), the amount of VS degradation and emission $CH_4$, $N_2O$ were 10.9kg-VS and 1,582.4g-$CH_4$, 68.1g-$N_2O$ respectively. Based on VS inputed the emission of $CH_4$, $N_2O$ were 15.3(g-$CH_4$/kg-V $S_{input}$), 0.7(g-$N_2O$ /kg-V $S_{input}$), and based on VS degradated were 145.2(g-$CH_4$/kg-V $S_{removed}$), 6.2(g-$N_2O$ /kg-V $S_{removed}$).

• Journal of Life Science
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• v.12 no.6
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• pp.669-675
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• 2002

Introduction of sliced raw fish meat(SRFM) to fast food business has been considered seriously. However bacteria causing food poisoning should be controlled. Organic acids such as vinegar and lactic acid used in the sauce for SRFM were evaluated for their antibacterial activities. At low concentration levels of vinegar and lactic acid exerted strong antibacterial activities toward Vibriu sp.. In contrast, in case of Salmonella typhimurium and Escherichia coli O157:H7 low anitbacterial activities were observed even at relatively high concentrations. Minimum inhibitory concentrations(MIC) of vinegar for V. vulnificus, V. cholerae non-O1, V. parahaemolyticus, V. mimicus, S. typhimurium and E. coli O157:H7 were 16, 18, 16, 12, 26, and $20{\mu}\ell /m\ell, respertively. MIC of lactic acid for V. vilnificus, V. cholerae non-O1, V. parahaemolyticus, V. mimicus, S. typhimurium and E. coli O157:H7 were 20, 25, 25, 25, 40, and $35{\mu}\ell /m\ell, respectively. In case of vinegar bactericidal concentration upon 10 second contact for V. vulnificus, V. cholerae non-O1, V. parahaenolyticus, V. mimicus and E. coli O157:H7 were 8, 14, 10, 4, and 48%, respectively; however, even at 50% colony of S. typhimurium was observed. In case of lactic acid any colony was observed for V. vulnificus, V. cholerae non-O1, V. parahaemolyticus, V. mimicus, S. typhimurium and E. coli O157:H7 at the concentration of 2, 3, 4, 3, 14, and 17%, respectively. Vinegar and lactic acid of low concentration inhibited the growth of Vibrio sp., food poisoning pathogen in SRFM; in contrast, at high concentration these organic acids inhibited Salmonella sp. and Escherichia sp., food poisoning pathogen in other than SRFM.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.1
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• pp.83-89
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• 2013

Microbiological treatment, chlorination, and ozonation are usually used for water treatment. However, there is weakness that these methods can't decompose and eliminate recalcitrant organic pollutants perfectly. It is possible to eliminate recalcitrant organic pollutants when photocatalysis of $TiO_2$ is used. In this study, the removal efficiencies of organic pollutants by using photocatalyst of $TiO_2$ in the slightly polluted golf club water hazard and a river were investigated. The amount of $TiO_2$ was divided into three categories of 1 g/L, 2 g/L and 4 g/L in order to investigate the adequate amount of $TiO_2$ and the removal efficiency. UV light was used as a light source for the reaction of photocatalyst. As a conclusion in this study, the efficiency of turbidity removal was increased in proportion to the amount of $TiO_2$ until 4 hours. After then the turbidity was gradually decreased. Finally, the optimum concentration of $TiO_2$ was 4 g/L. The efficiency of COD removal was increased in proportion to the amount of $TiO_2$ regardless of time.

• Korean Chemical Engineering Research
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• v.57 no.2
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• pp.267-273
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• 2019

Hierarchically porous $Fe_2O_3$ nanofibers with meso- and macro- pores are designed and synthesized by electrospinning and subsequent heat-treatment. The macro pores are generated by selectively decomposition of polystyrene as a dispersed phase in the as-spun fibers containing $Fe(acac)_3$/polyacrylonitrile continuous phases during heat-treatment. Additionally, meso-pores formed by evaporation of infiltrated water vapor during electrospinning process interconnected the macro-pores and results in the formation of hierarchically porous $Fe_2O_3$ nanofibers. The initial discharge capacity and Coulombic efficiency of the hierarchically porous $Fe_2O_3$ nanofibers at a current density of $1.0A\;g^{-1}$ are $1190mA\;h\;g^{-1}$ and 79.2%. Additionally, the discharge capacity of the nanofibers is $792mA\;h\;g^{-1}$ after 1,000 cycles. The high structural stability and morphological benefits of the hierarchically porous $Fe_2O_3$ nanofibers resulted in superior lithium ion storage performance.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.113-119
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• 2001

This paper presents a model for a pin-to-cylinder discharge type ozonizer, which utilizes the superposition of surface discharge and corona discharge operation. By changing the gas flow rate, the discharge power and the number of SDO units, the characteristics of ozone concentration ( $O_{3con}$), ozone generation ( $O_{3g}$) and ozone yield ( $O_{3Y}$) were investigated. Using one SDO unit the maximum values of $O_{3con}$, $O_{3g}$ and $O_{3Y}$ were found as 8100[ppm], 1623[mg/h] and 213[g/kWh] respectively. With two SDO units the corresponding values were found as 12800[ppm], 2893[mg/h] and 248[g/kWh] respectively. Hence using two SDO units the efficiency was improved by 16[%].y 16[%].

• The Journal of the Acoustical Society of Korea
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• v.21 no.2E
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• pp.91-97
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• 2002

One of the most important things in mobile phone service is Hand-Off (H/O). Meantime soft H/O and softer H/O have been used between the same generations (2G↔2G) and there is little problem. With user's needs and the development of communication technology, the system with different generation coexists and pilot beacon and time-periodic beacon are used for H/O between generations (2.5G↔2G) to start service, but it is not economic and efficient. To improve such problems, ENHHO developed in April 2001 has recently used. Unfortunately, this method also has the defect of momentary cutoff of communication information during the procedure of H/O in case of more than 5 pilot signals. Accordingly, we suggest algorithm to improve the problem of ENHHO and examines its propriety by analyzing the results of field survey using the algorithm.

• Restorative Dentistry and Endodontics
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• v.48 no.1
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• pp.3.1-3.14
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• 2023

Objectives: This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods: The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (R_ad), setting time (S_et), dimensional change (D_c), solubility (S_ol), compressive strength (C_st), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results: The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the S_et (p < 0.05) and lower values of D_c at 24 hours (p < 0.05). The C_st was higher for G4, with a significant difference for the other groups (p < 0.05). The S_ol did not present significant differences among groups (p > 0.05). Conclusions: The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1108-1112
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• 2002

pellets were fabricated as a reactor control material by the powder process. Sinterability of $Dy_2O_3+TiO_2$ mixtures and phases of solid solutions were analyzed by using TMA and XRD, respectively. The thermal conductivity of pellet was determined from the measurement data of the specific heat and the thermal diffusivity of the pellet. The sinterability and the sintered density varied as a function of Dy content in $Dy_xTi_yO_z$. The pellet of $3\;g\;Dy/cm^3\;Dy_xTi_yO_z$ melted in the sintering temperature of $1580{\circ}C$. There were two phases of $Dy_2TiO_5+Dy_2Ti_2O_7$ and a single phase of $Dy_2TiO_5$ for the pellet that has the Dy content of and , respectively. The thermal conductivity of $Dy_xTi_yO_z$ was nearly constant in the temperature range of $25~600{\circ}$. It was 1.69~1.78 W/mK for the pellet sintered in and 1.49~1.55 W/mK for the pellet sintered in $1550{\circ}$.

• KSBB Journal
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• v.13 no.2
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• pp.203-208
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• 1998

We investigated the effects of dissolved oxygen (D.O.) and fructose (C-source) on cell growth and biosynthesis of cyclosporin A (CyA) produced as a secondary metabolite by a wild-type filamentous fungus, Tolypocladium inflatum. This was performed by controlling the level of D.O. and the residual C-source, as required, through adjustment of medium flow rate, medium concentration and agitation rate in fed-batch cultures. CyA production was furned out to be maximal, when D.O. level was controlled around 10% saturated D.O. and concentration of the C-source was maintained sufficiently low (below 2 g/L) not to cause carbon catabolite repression. Under this culture condition, we obtained the highest values of CyA concentration (507.14 mg/L), Qp (2.11 mg CyA/L/hr), $Y_x/s$ (0.49 g DCW/g fructose), $Y_p/s$<(22.56 mg CyA/g fructose), and YTEX>$_p/x$ (48.31 mg CyA/g DCW), but relatively lower values of cell concentration (11.98 g DCW/L) and cell productivity (0.043 g DCW/L/hr), in comparison with other parallel fed-batch fermentation conditions. These results implied that, in the carbon-limited culture with 10% saturated D.O. level, the producer microorganism utilized the C-source more efficiently for secondary metabolism.