• 대한전자공학회논문지SD
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• 제39권10호
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• pp.35-42
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• 2002

Modulation frequency dependences of the pyroelectric properties of PLT (P $b_{1-x}$ L $a_{x}$ $Ti_{1-x}$ 4/ $O_3$) thin films with La concentrations of 5, 10 and 15㏖% have been investigated by using the dynamic method. The PLT thin film with 10㏖% of the La concentration (PLT(10) thin film) shows the most excellent pyroelectric properties among the films. For PLT(10) thin film, the pyroelectric coefficient shows the maximum value of 6.6$\times$10$^{-9}$ C/$\textrm{cm}^2$ㆍK without frequency dependence. The figure of merits for the voltage responsivity and specific detectivity are 1.03$\times$10$^{-11}$ Cㆍcm/J and 1.46$\times$10$^{-9}$ Cㆍcm/J, respectively. Voltage responsivity corresponding to the pyroelectric voltage is almost constant at low modulation frequency and decreases in proportional to frequency at high modulation frequency. Voltage responsivity is 5.15 V/W at 8Hz. Noise equivalent power (NEP) and specific detectivity ( $D^{*}$) of the PLT(10) thin film are 9.93$\times$10$^{-8}$ W/H $z^{1}$2/ and 1.81$\times$10$^{6}$ cmH $z^{1}$2/W at the frequency of 100Hz, respectively. The results indicate that PLT(10) thin film is very suitable for pyroelectric IR sensors.s.s.

• 한국건축시공학회지
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• 제14권1호
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• pp.68-75
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• 2014

In order to increase the integrity of the wellbore which is used to prevent the leakage of supercritical $CO_2$, it is necessary to develop a concrete that is strongly resistant to carbonation. In an environment where the concentration of $CO_2$ is exceptionally high, $Ca^{2+}$ ion concentration in pore solution of Portland cement concrete will drop significantly due to the rapid consumption of calcium hydroxide, which decreases the stability of the calcium silicate hydrate. In this research, calcium phosphates were used to modify Portland cement system in order to produce hydroxyapatite, a hydration product that is strongly resistant to carbonation under such an environment. According to the experimental results, calcium phosphates reacted with Portland cement to form hydroxyapatite. The formation of hydroxyapatite was verified using X-ray diffraction analyses with selective extraction techniques. When using dicalcium phosphate dihydrate and tricalcium phosphate, the 28-day compressive strength was lower than that of plain cement paste. However, the specimen with monocalcium phosphate monohydrate showed equivalent strength to that of plain cement paste.

• 한국환경보건학회지
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• 제29권1호
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• pp.74-83
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• 2003

Microcystin, stable compounds with circular heptapeptides, is presented inside cyanobacterial cell. So far, over 30 types have been known to exist and microcystin-LR, RR among them are the most potent toxin compound. By this reason, a strong oxidant, ozone was used in this study to remove the microcystins produced by cyanobacteria. Removal efficiency of microcystin at M water treatment plant was also evaluated. Microcystin concentration was determined by protein phosphatase inhibition assay. The results showed that dissolved microcystin in raw water detected in the range of 0.011-0.028 ㎍ Microcystin-RR equivalent/l. Above 98% of microcystin was removed through overall treatment system. Therefore, the water treatability of M treatment plant seemed to be excellent. Removal efficiency of microcystin according to unit process varied as characteristics of raw water such as DOC, UV/sub 254/ and turbidity. Removal efficiency of microcystin by ozonation was investigated in laboratory according to contact time and ozone dose. Dissolved microcystin was increased by twice fold according to ozone contact time, but increased by fifth fold according to ozone dose. So, changing of ozone dose more affected microcystin release than changing of ozone contact time. Behavior of microcystin by ozonation was similar to that of DOC, and residual ozone concentration gave influence to removal ratio of microcystin. In conclusion, single ozone treatment wasn't effective on microcystin removal in case of water containing a lot of cells. Therefore, it's more effective to use ozonation process after the removal of cyanobacterial cells in advance.

• Agricultural and Biosystems Engineering
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• 제1권1호
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• pp.30-37
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• 2000

Wet porous media representing agronomic soil that contains variable water content with variable electrolyte concentration was measured to study the shape of the curves of the electric double layer capacitance versus frequency (from 10 KHz to 10 MHz. This was done in an attempt to find the lowest practical operating frequency for developing low cost dielectric constant soil moisture probes. Cellulose sponge was used as the porous media. A high frequency electronic bridge circuit was developed for measuring the equivalent network parallel resistance and capacitance of porous media. It appears that the effects of the electric double layer component of the total parallel network capacitance essentially disappear at operating frequencies greater than approximately 25 MHz at low electrolyte concentrations but are still important at 50 MHz at higher concentrations. At these frequencies, the double layer capacitance masks the diffusion region capacitance where true water content capacitance values reside. The general shape of the curve of volumetric water content versus porous media dielectric constant is presented, with an empirical equation representing data for this type of curve. It was concluded that the lowest frequency where dielectric constant values which represent true water content information will most likely be found is between 30 and 50 MHz at low electrolyte concentrations but may be above 50 MHz when the total electrolyte concentration is near the upper level required for most mesophyte plant nutrition.

• 한국환경보건학회지
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• 제26권3호
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• pp.43-49
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• 2000

A laboratory experiments were performed to investigate the effects of several factors on the phosphorus removal by waste oyster shells. The waste oyster shells used in this experiments were crushed particle, calcined particle and extracted solution. A higher efficiencies of phosphorus removal were observed, when a particle size of crushed and calcined particle were smaller. The effluent concentration of phosphorus was around 1.6mg/ι in continuous column experiment which packed with crushed particle of waste oyster shell at the influent concentration of PO4-P of 10 mg/ι. But the clogging of column occurred with increasing of throughput volume of influent. The efficiency of phosphorus removal increased with increasing of dosage amount of crushed, calcined particle and extracted solution. When the calcined particle which contained only about 1/10~1/100 of crushed particle was used, the efficiency of phosphorus removal was correspondingly equivalent to the removal efficiency obtained from crushed particle. The efficiency of phosphorus removal by calcined particle after 9 runs repeated use was decreased about 21.5% as that of the first run. The removal efficiency of 100% could have been achieved at the HRT of 18 hours during the continuous treatment of phosphorus by the solution extracted from calcined particle.

• 자원리싸이클링
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• 제17권2호
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• pp.70-75
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• 2008

폐전자스크랩, 함주석 폐액 등에서 주석 성분을 회수하기 위한 기초 연구로 주석이 함유된 염산용액에서 알루미늄 분말을 이용한 치환반응에 대한 연구를 실시하였다. 주석이온의 치환 반응에 미칠 수 있는 용액의 pH, 알루미늄 분말 첨가량, 반응온도, 반응시간, 염소이온($Cl^-$) 농도, 불순물 농도 둥에 대해 고찰하였다. 치환실험 결과 알루미늄 분말의 첨가량. 반응온도, pH 및 염소이온 농도가 증가함에 따라 주석이거 치환속도가 증가함을 알 수 있었다. 이들 결과로부터 알루미늄 금속분말을 이용한 금속 주석의 치환 및 회수에 관한 최적 조건을 제시하였다.

• Environmental Engineering Research
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• 제23권2호
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• pp.195-204
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• 2018

A pilot scale study was conducted on a down-flow hanging sponge (DHS) reactor installed at a sewage treatment plant in Banda Aceh, Indonesia for treatment of desludging septic tank wastewater. Raw wastewater with an average biochemical oxygen demand (BOD) and total suspended solids of 139 mg/L and 191 mg/L, respectively, was pumped into the reactor. Two different hydraulic retention times (HRTs, 3 h and 4 h) were investigated, equivalent to organic loadings of 1.11 and $0.78kg\;BOD/m^3/d$, respectively. The average BOD concentration in the final effluent was 46 and 26 mg/L at HRTs of 3 and 4 h, respectively. The concentration of retained sludge along the reactor height was 10.2-18.7 g VSS/L-sponge, and the sludge activities were 0.24-0.32 and 0.04-0.40 mg/g VSS/h for heterotrophs and nitrification, respectively. Values of water hold-up volume, dispersion coefficient, and number of tank in-series found from tracer studies of clean sponge and biomass-loaded sponge confirmed that growth of retained sludge on the sponge module improved hydraulic performance of the reactor. Adoption of the DHS reactor by this Indonesian sewage treatment plant would enhance the role of the current desludging septic tank wastewater treatment system.

• Environmental Engineering Research
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• 제18권3호
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• pp.145-150
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• 2013

Optimal preparation guidelines of a cathode catalyst layer by non-precious metal catalysts were evaluated based on electrochemical performance in single-chamber microbial fuel cells (MFCs). Experiments for catalyst loading rate revealed that iron(II) phthalocyanine (FePc) can be a promising alternative, comparable to platinum (Pt) and cobalt tetramethoxyphenylporphyrin (CoTMPP), including effects of substrate concentration. Results showed that using an optimal FePc loading of $1mg/cm^2$ was equivalent to a Pt loading of $0.35mg/cm^2$ on the basis of maximum power density. Given higher loading rates or substrate concentrations, FePc proved to be a better alternative for Pt than CoTMPP. Under the optimal loading rate, it was further revealed that 40 wt% of FePc to carbon support allowed for the best power generation. These results suggest that proper control of the non-precious metal catalyst layer and substrate concentration are highly interrelated, and reveal how those combinations promote the economic power generation of single-chamber MFCs.

• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.133-140
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• 2016

Backgrounds: The accident at Fukushima Daiichi Nuclear Power Plant (NPP), March 2011, caused serious radioactive contamination over wide area in east Japan. Therefore, it is important to know the effect of the accident and the status of NPP. Materials and Methods: This paper provides a review on the status of radiation dose and radioactive contamination caused by the accident on the basis of publicized information. Results and Discussion: Monitoring of radiation dose and exposure dose of residents has been conducted extensively by the governments and various organizations. The effective dose of general residents due to the accident proved to be less than a mSv both for external and internal dose. The equivalent committed dose of thyroid was evaluated to be a few mSv in mean value and less than 50 mSv even for children. Monitoring of radioactivity concentration has been carried out on food ingredients, milk and tap water, and actual meal. These studies indicated the percentage of foods above the regulation standard was over 10% in 2011 but decreasing steadily with time. The internal dose due to foods proved to be tens of ${\mu}Sv$ and much less than that due to natural $^{40}K$ even in the Fukushima area and decreasing steadily, although high level concentration is still observed in wild plants, wild mushrooms, animals and some kind of fishes. Conclusion: According to extensive studies, not only the effect of the accident but also the pathway and countermeasures against radioactive contamination have been revealed, and they are applied very effectively for restoration of environment and reconstruction of the area.

• 한국지하수토양환경학회:학술대회논문집
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• 한국지하수토양환경학회 2004년도 임시총회 및 추계학술발표회
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• pp.450-452
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• 2004

Using factor analysis and bivariate comparisons of major components in ground water, three geochemical processes were identified as controlling factors of ground water chemistry; 1) natural mineralization by water rock interactions, 2) effect of seawater which includes salinization by seawater near seashores and deposition of sea salt, and 3) nitrate contamination by N fertilization. Contribution of rainfall was also estimated from the measured composition of wet deposition. The geochemical processes were separated using total alkalinity as an indicator for natural mineralization, Cl for effect of seawater, and nitrate for N fertilization. Relatively high correlation of major components with nitrate suggests that nitrification of nitrogenous fertilizers significantly affects ground water chemistry. Total cations derived from nitrate sources have good linearity for nitrate in equivalent basis with a slope of 1.8, which is a mean of proton production coefficients in nitrification of two major compounds in nitrogenous fertilizers, ammonium and urea. Contribution of nitrate sources to base cations, Cl, and SO$_4$ in ground water was determined considering maximum contribution of natural mineralization to estimate a threshold of the effect of N fertilization for ground water chemistry, which shows W fertilization has a greatest effect than any other processes in ground water with nitrate concentration greater than 50 mg/L for Ca, Mg, Na and with concentration greater than 30 mg/L for Cl and SO$_4$.