• Nuclear Engineering and Technology
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• 제54권12호
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• pp.4441-4448
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• 2022

The electrochemical oxidation process has been widely studied in the field of wastewater treatment for the decomposition of organic materials through oxidation using ·OH generated on the anode. Pt anode electrodes with high durability and long-term operability have a low oxygen evolution potential, making them unsuitable for electrochemical oxidation processes. Therefore, to apply Pt electrodes that are suitable for long-term operation and large-scale processes, it is necessary to develop a new method for improving the decomposition rate of organic materials. This study introduces a method to improve the decomposition rate of organic materials when using a Pt anode electrode in the electrochemical oxidation process for the treatment of organic decontamination liquid waste. Electrochemical decomposition tests were performed using sodium dodecylbenzenesulfonate (SDBS) as a representative organic material and a Pt mesh as the anode electrode. Y₂O₃ particles were introduced into the electrolytic cell to improve the decomposition rate. The decomposition rate significantly improved from 21% to 99%, and the current efficiency also improved. These results can be applied to the electrochemical oxidation process without additional system modification to enhance the decomposition rate and current efficiency.

• 한국연소학회지
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• 제22권4호
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• pp.51-56
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• 2017

The decomposition of tetrafluoromethane has been investigated with the reaction mechanism proposed for freely propagating $CH_4/CF_4/O_2/N_2$ premixed flames on the oxygen enrichment. The factors affecting on the removal efficiency of tetrafluoromethane were analyzed. The increase in flame temperature due to oxygen enrichment has a great influence on the removal efficiency of tetrafluoromethane. At the same oxygen enrichment condition, the removal efficiency in the rich flame is higher than one in the lean flame. The increase of the F/H ratio leads to decrease the flame temperature and the removal efficiency of tetrafluoromethan is decreased at the flame temperature of 2600 K or lower, The elementary reactions that dominate the consumption of tetrafluoromethane are (R1) $CF_4+M=CF_3+F+M$ and (R2) $CF_4+H=CF_3+HF$. (R1) has the greatest effect on the consumption of tetrafluoromethane under the oxygen enhanced flames.

• International Journal of Contents
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• 제4권3호
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• pp.1-9
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• 2008

The Korean life insurance industry has undergone profound changes, such as the beginning of the variable insurance in July 2001 and the bancassurance enforcement in August 2003. However, little empirical research has analyzed data that includes the bancassurance of life insurance companies operating in Korea. In response to this lack of research, this paper applies DEA (data envelopment analysis) models to measure and decompose their efficiency. We discovered that life insurance companies operating in Korea are a little different in their composition ratio of inputs and outputs, due to the increased variety of distribution channels and new products. We provided efficiency scores, return to scale, and reference frequencies. We also decomposed CCR, BCC, and SBM efficiency into scale efficiency and MIX efficiency. So, we try to investigate whether the sources of inefficiency were caused by the inefficient operation of DMU, disadvantageous conditions, the difference of the composition ratio in inputs and outputs with reference sets, or any combination of the above. Most companies in the sample display had either constant or decreasing returns to scale. The efficiency rankings were less consistent among models and efficient DMUs. In response to this problem, we used the super-efficiency model to rank them and then compared the rankings of the DMUs among the various models. It was also concluded that the availability of panel data, rather than cross-sectional data, would greatly improve the validity of the efficiency estimates.

• 자원ㆍ환경경제연구
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• 제17권2호
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• pp.255-286
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• 2008

에너지 요인분석의 한계와 확장을 위하여 요인분석과 계량모형의 결합을 시도하였다. 에너지 원단위 효과의 변화 결정 요인을 계량적 방법으로 추정하고, 에너지 원단위 효과와 계량모형의 에너지 효율 변화를 비교하였다. 에너지 원단위 효과를 이용한 확장모형에서 에너지 가격이 오르면 에너지 원단위 효과가 개선되는 것으로 나타나고 있다. 그리고 계량모형에서 에너지 효율 변수의 대변수인 시간추세의 준탄력성을 살펴보면, 단기에서는 -0.02로 장기에서는 -0.04로 서서히 완만한 에너지 효율 개선을 보이고 있다. 마지막으로 요인분해 결과와 계량모형의 결과를 비교하면, 전체 제조업과 8개 제조업 업종 중 4개 업종의 경우 에너지 효율의 개선 방향이 일치하는 결과를 보이고 있다. 요인분해의 결과와 계량모형의 결과 비교에서 나타나듯이, 두 방법이 서로 교류할 수 없는 방법이 아니라는 점을 확인하였다. 향후 학문적 정책적 노력에 따라 최소한 서로 보완할 수 있는 여지가 충분히 있음을 보였다. 따라서 이러한 연구가 지속될 수 있는 학문적 정책적 노력이 필요하다고 할 수 있다.

• 한국대기환경학회지
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• 제17권1호
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• pp.97-104
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• 2001

Decomposition of trichloroethlyene(TCE) in electron beam irradiation was examined on order to obtain information on the treatment of VOC in air. Air containing vaporized TCE has been studied in a flow reactor with different reaction environments, at various initial TCE concentration and in the presence and absence of water vapor. Maximum decomposition was observed in oxygen reaction environment and the degree of decomposition was about 99% at 20kGy for 2,000ppm initial TCE. The concentration of TCE exponentially decreased with dose in air and pure oxygen. The effect of water vapor on TCE decomposition efficiency was examined. The decomposition rate of TCE in the presence of water vapor (5,600 ppm) was approximately 10% higher than that in the absence of water vapor. Dichloroacetic acid, dichloroacethyl chloride and dichloroethyl ester acid were identified as primary products of this reaction adn were decomposed and oxidized to yield CO and $CO_2$. Perchloroethylene, hexachloroethane, chloroform and carbon tetrachloride were also observed as highly chlorinat-ed by products.

• 한국안전학회지
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• 제23권5호
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• pp.54-60
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• 2008

The objective of this study is to obtain the optimal process condition and the maximum decomposition efficiency by measuring the decomposition efficiency, electricity consumption, and voltage in accordance with the change of the process variables such as the frequency, maintaining time period, concentration, electrode material, thickness of the electrode, the number of windings of the electrode, and added materials etc. of the harmful atmospheric contamination gases such as NO, $NO_2$, and $SO_2$ etc. with the plasma which is generated by the discharging of the specially designed and manufactured $TiO_2$ catalysis reactor and SPCP reactor. The decomposition efficiency of the NO, the standard samples, is obtained with the plasma which is being generated by the discharge of the combination effect of the $TiO_2$ catalysis reactor and SPCP reactor with the variation of those process variables such as the frequency of the high voltage generator($5{\sim}50kHz$), maintaining time of the harmful gases($1{\sim}10.5sec$), initial concentration($100{\sim}1,000ppm$), the material of the electrode(W, Cu, Al), the thickness of the electrode(1, 2, 3mm), the number of the windings of the electrode(7, 9, 11turns), basic gases($N_2$, $O_2$, air), and the simulated gas($CO_2$) and the resulting substances are analyzed by utilizing FT-IR & GC.

• 한국환경과학회지
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• 제21권11호
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• pp.1321-1331
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• 2012

To date, carbon and nitrogen co-doped photocatalysts (CN-$TiO_2$) for environmental application focused mainly on the aqueous phase to investigate the decomposition of water pollutants. Accordingly, the present study explored the photocatalytic performance of CN-$TiO_2$ photocatalysts for the purification of indoor-level gas-phase aromatic species under different operational conditions. The characteristics of prepared photocatalysts were investigated using X-ray diffraction, scanning emission microscope, diffuse reflectance UV-VIS-NIR analysis, and Fourier transform infrared (FTIR) analysis. In most cases, the decomposition efficiency for the target compounds exhibited a decreasing trend as input concentration (IC) increased. Specifically, the average decomposition efficiencies for benzene, toluene, ethyl benzene, and xylene (BTEX) over a 3-h process decreased from 29% to close to zero, 80 to 5%, 95 to 19%, and 99 to 32%, respectively, as the IC increased from 0.1 to 2.0 ppm. The decomposition efficiencies obtained from the CN-$TiO_2$ photocatalytic system were higher than those of the $TiO_2$ system. As relative humidity (RH) increased from 20 to 95%, the decomposition efficiencies for BTEX decreased from 39 to 5%, 97 to 59%, 100 to 87%, and 100 to 92%, respectively. In addition, as the stream flow rates (SFRs) decreased from 3.0 to 1.0 L $min^{-1}$, the average efficiencies for BTEX increased from 0 to 58%, 63 to 100%, 69 to 100%, and 68 to 100%, respectively. Taken together, these findings suggest that three (IC, RH, and SFR) should be considered for better BTEX decomposition efficiencies when applying CN-$TiO_2$ photocatalytic technology to purification of indoor air BTEX.

• 조명전기설비학회논문지
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• 제22권12호
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• pp.142-149
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• 2008

본 논문은 비열평형 플라즈마와 촉매를 이용하여 트리클로로에틸렌의 효과적인 분해방법을 제안하였다. 이를 위하여 이산화망간과 알루미나 펠렛을 플라즈마 리액터 내부에 충진한 리액터를 설계하였다. 이산화망간 충진 리백터를 이용할 경우에는 산소를 포함한 가스중의 방전에 의해 발생된 오존이 촉매 표면에서 분해되는 동안에 발생된 산소원자 라디칼에 의하여 TCE의 분해율이 향상됨을 알 수 있었다. 그리고 알루미나를 충진한 경우에는 TCE DCAC로 산화되었으며, COx 및 $Cl_2$와 같은 저분자상으로 많이 분해되지 않았다. 그러나 알루미나 충진 리액터에 의한 플라즈마 처리된 가스를 리액터 후단에 설치한 이산화망간 촉매를 통과시킴에 의하여 분해율이 매우 향상됨을 알 수 있었다. 따라서, 플라즈마 프로세스에 이산화망간을 응용함에 의하여 오존 분해에 따른 촉매 표면의 산소원자 라디칼에 의하여 TCE 및 분해 생성물(DCAC)를 효율적으로 분해하는 것이 가능하다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.1678-1683
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• 2003

DBD(Dielectric Barrier Discharge) plasma in air is well established for the production of large quantities of ozone and is more recently being applied to aftertreatment processes for HAPs(Hazardous Air Pollutants). Although DBD high electron density and energy, its potential use as nano and sub-micron sized particle charging are not well known. Aim of this work is to determine design and operating parameters of a two-stage ESP with DBD. DBD and ESP are used as particle charger and precipitator, respectively. We measured particle precipitation efficiency of two-stage ESP and estimated ozone decomposition of both pelletized $MnO_2$ catalyst and pelletized activated carbon. To examine the particle precipitation efficiency, nano and sub-micron sized particles were generated by a tube furnace and an atomizer. AC voltage of $7{\sim}10$ kV(rms) and 60 Hz is used as DBD plasma source. DC -8 kV is applied to the ESP for particle precipitation. The overall particle collection efficiency for the two-stage ESP with DBD is over 85 % under 0.64 m/s face velocity. Ozone decomposition efficiency with pelletized $MnO_2$ catalyst or pelletized activated carbon packed bed is over 90 % when the face velocity is under 0.4 m/s in dry air.

• 한국안전학회지
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• 제14권1호
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• pp.101-107
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• 1999

$TiO_2$ and $xTiO_2-ySiO_2$ system photocatalysts were developed by sol-gel method based on the change of production parameters, and their structure of crystallization and the specific surface area was measured. Considering the efficiency of the ethanol decomposition using the catalyst, the conclusion was made as follows: 1) By means of X-ray analysis of $TiO_2$ powder that is obtained from water and Titanium alkoxide with various molar ratios, it is shown that structure of crystallization is a dominating structure and, on the other hand, the crystallization of rutile also partly exists. The specific surface area is at its maximum value at R=6, which is the molar ratio of water vs. alkoxide, whereas its value goes down as the molar ratio increases. In the reaction of using $TiO_2$ catalyst, the ethanol is decomposed into the extent of 15 ~30% in an hour and three hours are necessitated for 70% decomposition. 2) $TiO_2/SiO_2$ powder is developed from Titanium and Silicon alkoxide by a hetero-condensation process. The increase of SiO$_2$ contents causes the decrease of the degree of crystallization of the gel, whereas the specific surface area preferentially increases. In the decomposition reaction of the ethanol, the decomposition efficiency represents 25~60% in an hour. It is, however, examined that the efficiency inactively increases corresponding to the duration of reaction time. It is shown that more than 90% of ethanol is decomposed when reaction time is about three hours and the efficiency illustrates the maximum value for 60-$TiO_2/4O-SiO_2$ catalyst.