• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.2
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• pp.116-122
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• 2015

A simulation is applied to evaluate sea surface observations such as wave heights and surface currents by using a microwave Doppler radar. It is reported that the microwave irradiation width on the sea surface and Fourier transform time taken to sample data for frequency analysis affect Doppler spectra. To investigate the influences by these parameters, Doppler spectra are simulated with various numerical sea surface waves with currents. From the results, in the case of the microwave irradiation width is five times smaller than the wavelength of the sea surface wave, and the Fourier transform time is also five times shorter than the period of the sea surface wave, there is a possibility to measure wave heights accurately with a Doppler radar. In addition, relative surface currents can be estimated by analysis of long Fourier transform time. The simulation results showed the appropriate observing conditions with a microwave Doppler radar.

• Korean Journal of Plant Resources
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• v.32 no.5
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• pp.478-485
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• 2019

As environmentally sound agriculture emphasize gradually as well as the importance of environment, many studies on weed and soil nematode control of new concept which does not affect adversely environment are in progress. For this purpose, plant seeds which are representative weed species in field were selected and treated with microwave having generating capacity of $17.73kw/m^3$, and investigated germination rates of weed seeds and the number of soil nematode according to soil moisture contents, soil depth and irradiation times. The microwave effect on the germination rates was extremely high in soil moisture content of 40% and irradiation time over 40 seconds for irradiation time, while soil depth did not affect germination rate. In view of the results so far achieved, it seems that universal dispersed microwave system is effective for the control of weed seeds.

• Resources Recycling
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• v.15 no.5 s.73
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• pp.11-16
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• 2006

A novel microwave-induced pyrolysis was used for the recovery of valuable products from waste polystyrene in motor oil. Quartz tube was introduced as microwave reactor and silicon carbide was used as the microwave absorbent. In the experiments, different pyrolysis conditions were applied, such as time range from 30 minutes to 1 hour and microwave input power range from 180 to 250W. The distillate products from pyrolysis were analyzed with GC/MS. Styrene, 1-methyl styrene, toluene, ethyl benzene were the four main products. Styrene recovery rate from polystyrene was around 50%. Temperature for the complete pyrolysis using microwave was around $300^{\circ}C$ which is much lower than that of conventional thermal pyrolysis.

• Korean Chemical Engineering Research
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• v.46 no.6
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• pp.1063-1068
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• 2008

The photocatalytic degradation of methylene blue water solution was carried out by irradiating microwave and UV light simultaneously using $TiO_2$ photocatalyst balls prepared by Chemical Vapor Deposition method. A microwave-discharged electrodeless UV lamp was developed to use microwave and UV simultaneously for photocatalytic reactions. The results of photocatalytic degradation of methylene blue showed that the decomposition rate increased with the microwave intensity, the circulating fluid velocity and auxiliary oxidizing agents added. Especially, the rate constant of $H_2O_2$-added photocatalytic reaction increased about three times from $0.0061min^{-1}$ to $0.0197min^{-1}$ when microwave was additionally irradiated. This study demonstrates that the microwave irradiation can play a very important role in photocatalytic degradation using peroxides although it is not easy to quantitatively assess the effect of microwave on photocatalytic reactions from the experimental data of this study.

• Applied Chemistry for Engineering
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• v.31 no.2
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• pp.172-178
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• 2020

In this study, the optimization of the biodiesel production process from waste oil using microwave with response surface methodology (RSM) was conducted. The microwave irradiation time and power in addition to the alcohol/oil mole ratio were chosen as process parameters. Also the fatty acid methyl ester (FAME) content (over 96.5%) and kinematic viscosity (1.9~5.5 cSt) were selected as response values. From basic experiments, the range of quantitative factors were set as following; 4~6 min, 400~600 W, and 7~9 for the microwave irradiation time and power, and alcohol/oil molar ratio, respectively. The optimum conditions for the methanolysis were 5.0~5.1 min, 481.3~525.5 W, 7.9~8.4, and 2.0 or 3.0 mg KOH/g for the microwave irradiation time and power, methanol/oil molar ratio, and each acid value, respectively. The FAME content and kinematic viscosity were predicted as 97.49~96.34% and 4.01~4.12 cSt, respectively, under the condition above. Under the optimum experimental conditions, the results showed that the FAME content and kinematic viscosity of 97.82~96.42% and 4.07~4.16 cSt, respectively were measured and the mean error rates were 0.22% and 0.98%, respectively.

• Applied Chemistry for Engineering
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• v.29 no.6
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• pp.746-752
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• 2018

In this study, an optimized process for the waste cooking oil based biodiesel production using microwave energy was designed by using Box-Behnken design model. The process variables were chosen as a mole ratio of the methanol to oil, microwave power, and reaction time. Fatty acid methyl ester (FAME) content was then measured. Through the results of basic experiments, the range of optimum operation variables for the Box-Behnken design model, such as the methanol/oil mole ratio and reaction time, were set as between 8 to 10 and between 4 to 6 min, respectively. Ranges of the microwave power were set as from 8 to 12 W/g for 1.30 mg of KOH/g, acid value, while from 10 to 14 W/g for 2.00 mg of KOH/g, acid value. The optimum methanol/oil mole ratio, microwave power, and reaction time were reduced to 7.58, 10.26 W/g, and 5.1 min, respectively, for 1.30 mg KOH/g of acid value. Also, the optimum methanol/oil mole ratio, microwave power, and reaction time were 7.78, 12.18 W/g, and 5.1 min, respectively, for 2.00 mg KOH/g of acid value. Predicted FAME contents were 98.4% and 96.3%, with error rates of less than 0.3%. Therefore, when the optimized process of biodiesel production using microwave energy was applied to the Box-Behnken design model, the low error rate could be obtained.

• Journal of the Korean Society of Food Science and Nutrition
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• v.41 no.7
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• pp.936-942
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• 2012

In the present study, the effects of green tea catechin on microsomal phospholipase $A_2$ ($PLA_2$) activity and the arachidonic acid (AA) cascade in the lungs of microwave exposed rats were investigated. One Sprague-Dawley male rats weighting $100{\pm}10$ g was randomly assigned to the normal group and three were assigned to the microwave exposed groups. The microwave exposed groups were subdivided into three groups according to the levels of dietary catechin supplementation: catechin free diet (MW) group, 0.25% catechin (MW-0.25C) group and 0.5% catechin (MW-0.5C) group. Rats were sacrificed on the 6th day after microwave irradiation (2.45 GHz, 15 min). The lung microsomal $PLA_2$ activity in the MW and MW-0.25C groups was 30% and 15% greater than that of the normal group, respectively, whereas no significant difference between the normal group and MW-0.5C group was observed. The percentage of phosphatidylethanolamine (PE) hydrolyzed in the lung microsome in the MW, MW-0.25C and MW-0.5C group increased by 47%, 18% and 20%, respectively, due to microwave irradiation. The formation of thromboxane $A_2$ ($TXA_2$) in the lung microsome was 50% greater in the MW group than in the normal group. However, the levels of $TXA_2$ in the MW-0.25C and MW-0.5C group were normal. The formation of prostacyclin ($PGI_2$) in the lung microsome was 31% lower in the MW group than in the normal group, while the levels of $PGI_2$ in the MW-0.25C and MW-0.5C group were similar to the normal group. The lung microsomal thiobarbituric acid reactive substances (TBARS) concentration, which can be used as an index of lipid peroxide was 34% greater in the MW group, when compared with the normal group. However, there was no difference between the MW-0.25C, MW-0.5C and normal groups. In conclusion, lung function appeared to be improved by green tea catechin supplementation due to its antithrombus action, which in turn controls the AA cascade system.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.80.2-80.2
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• 2012

그라핀(graphene)은 탄소 원자의 2차원 육각형 $sp^2$ 결합체로서 탄소 나노구조체가 가지는 여러 가지 우수한 특성을 보유하면서 대면적 기판 위에서 소자구현 및 투명전극 등으로의 우수한 응용성 때문에 고품질 그라핀 제조와 물리적 특성, 소자응용에 관한 연구가 활발히 진행되고 있다. 최근 그라핀 제조를 위한 여러 가지 방법이 개발되고 있으나 화학적 박리법이 저비용으로 대량생산을 위해 가장 유리한 방법으로 주목을 받고 있다. 화학적 박리법은 벌크 그라파이트를 강한 산을 이용하여 산화시켜 형성된 산화 그라파이트(graphite oxide)을 열적으로 팽창시켜 박리하고 환원하여 그라핀으로 제조하는 것이다. 보통 열적팽창을 위해서 열처리 로를 사용하게 되는데, 본 연구에서는 박리를 보다 효율적으로 진행시키고 고품질의 그라핀을 얻기 위해 마이크로웨이브를 이용한 박리법을 적용하였다. 마이크로웨이브는 설비가 간단하고 매우 균일하게 열팽창을 시킬 수 있을 뿐만 아니라 대량생산에서도 유리할 것으로 기대하였다. 천연 그라파이트(99.9%, 평균입도 $200{\mu}m$)를 Hummer 방법에 따라 $H_2SO_4$와 $KMnO_4$를 사용하여 산화시키고 필터링 후 마이크로웨이브를 조사하였다. 이후 환원 처리를 거쳐 그라핀을 제조하였다. 라만스펙트럼 및 투과전자현미경으로 분석한 결과 우수한 품질의 그라핀이 형성되었음을 알 수 있었다. 그라핀의 두께 및 품질은 마이크로웨이브의 인가시간 및 반복 횟수가 증가함에 따라 크게 영향받는 것을 확인하였다. 본 발표에서는 마이크로웨이브를 사용한 산화 그라파이트 박리 및 그라핀 제조라는 새로운 시도와 주요변수에 따른 그라핀 특성에 관한 결과를 논의할 것이다.

• Economic and Environmental Geology
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• v.53 no.2
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• pp.159-166
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• 2020

In this research, we investigate the effect of microwave pretreatment on the recovery of gold from the gold concentrates by thiourea leaching. The changes in mineral phases by decomposition of pyrites in the gold concentrates using microwave were observed, and the result of microwave irradiation showed that the temperature of the irradiated sample increases with increasing irradiation time. With the reaction of temperature increases, Sulfur (S) in pyrites was converted to sulfur dioxide (SO₂), and then the content of S in the sample was reduced. The analytical results of XRD and SEM-EDS showed that pyrites are converted to magnetite and hematite, and its surfaces are changed to a porous shape where micro-cracks are developed. The Au leaching efficiency from the irradiated gold concentrates using thiourea-mixed solvent increased with the increases of irradiation time and solvent concentration. The experimental results considering leaching parameters indicate that the mechanism of microwave irradiation increases the maximum leaching efficiency and leaching rate of the gold concentrates, and the solvent does a role for the increasing of leaching rate constant.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.64 no.4
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• pp.366-372
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• 2019

The use of flour milled from the Ofree wheat cultivar for baking attenuates allergies because some of the genes related to the allergic reaction have been knocked because some of its genes related to allergic reactions have been knocked down or knocked out through genetic mutation. However, the utilization of this flour is limited because the Ofree grain contains high content of total protein and gluten. Microwave irradiation has been used for changing the protein and gluten characteristics of wheat flour. Thus, this study investigated appropriate conditions of microwave irradiation to enhance the utilization of Ofree flour. As a result, when the flour was microwave-treated for 2 min, although the total protein and gluten contents were not changed, some qualities of the baked sugar-snap cookies, such as spread factor (diameter and thickness) and appearance (crack), were ameliorated. However, excessive heat treatment of the flour for over 3 min led to protein denaturation, which negatively affected the quality of the products. These results indicate that 2 min of microwave irradiation of flour that has high content of total protein and gluten can be used for the enhancement of cookie quality. Therefore, these results are expected to increase the utilization of Ofree wheat flour.