• Analytical Science and Technology
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• v.11 no.3
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• pp.194-201
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• 1998

The formaldehyde vapor produced from wood and steel furniture was absorbed in distilled water and derivatized with acetylacetone and determined by UV-visible spectrophotometry. Variation in HCHO emission with time was monitored at room temperature. The emission of volatile compounds from wood, wood-based and steel-based materials was investigated in a 50 mL glass vial. The concentration of the gases emitted in a glass vial was determined by ion-trap GC-MS.

• Journal of Korea Foundry Society
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• v.12 no.1
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• pp.62-73
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• 1992

상변환시 수반되는 경계면에서의 잠열의 방출(또는 흡수)의 정확한 해석은 용접, 주조, 결정 생성, 일기 예보 등의 응용에 필수적인 것이다. 특히 주조의 경우 캐스팅 온도와 고체 용적분율의 관계를 앎으로서 잠열 방출의 해석이 가능하다. 본 연구는 상변환시 수반되는 잠열의 방출 형태를 4개의 다른 모델을 사용하여 비정상 온도분포, 용융형태, 자연대류가 미치는 영향을 수치적으로 구하였다. 2개의 서로 다른 물성치를 가진 합금을 선택하였는데 하나는 넓은 mushy 영역을 가진 알루미늄 합금이고 다른 하나는 좁은 mushy 영역을 가진 철금속계 합금이다. 알루미늄 합금의 경우 온도 분포와 시간에 따른 온도의 변화가 모델에 따라 상당한 차이가 있는 반면 철금속계 합금의 경우 상이한 모델일지라도 거의 차이가 없음을 알 수 있었다. 결론으로 용융시 정확한 온도 분포와 상변화 형태를 예측하기 위해서는, 알루미늄 합금(넓은 mushy 영역)의 경우 적절한 잠열 방출 모델의 채택이 필요 불가급한 것으로 사료된다.

• Journal of Hydrogen and New Energy
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• v.16 no.1
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• pp.25-30
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• 2005

수소 분위기에서 10wt.%MnO와 기계적인 분쇄(반응성 기계적 분쇄)에 의해 Mg의 수소 저장 성질을 향상시켰다. 회전 속도는 250 rpm, 밀링시간은 2 h, 그리고 시료 대 볼 중량비는 1/45이었다. 준비한 Mg-10wt.%MnO 시료는 활성화를 위한 수소화물 형성 분해 싸이클링이 필요없었으며, 첫 번째 싸이클 593k 12 bar $H_2$에서, 10분 동안에 3.12wt.%, 60분 동안에 3.95wt.%의 수소를 흡수하였다. 또한 Mg-10wt.%MnO는 593k 0.8 bar $H_2$에서 60분 동안에 2.12wt.%의 수소를 방출하였다. MnO와 Mg의 방응성 분쇄는, 핵생성을 용이케하고 (Mg 입자의 표면에 결함 형성과 첨가물에 의해), Mg 입자의 표면에 crack을 만들어 Mg의 입자 크기를 줄여 그 결과 수소 원자의 확산 거리를 작게 함으로써 수소 흡수 방출 속도를 증가시킨다. 수소화물 형성 분해 싸이클링은 Mg 입자의 표면에 crack을 만들고 Mg의 입자 크기를 줄여 수소 흡수 방출 속도를 증가시킨다.

• Journal of Hydrogen and New Energy
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• v.10 no.4
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• pp.191-196
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• 1999

4-probe resistivity measurement technique was used to study hydrogen A-D(Absorption-Desorption)kinetics on Pd films(18 to 67nm thick) from 25 to $50^{\circ}C$, from 0 to 5 torr hydrogen pressure. Pd films were made on sapphire substrate by thermal evaporation technique under high vacuum at room temperature. Upto about 100 hydrogen A-D cyclings, no pulverization was observed, but film was detached partially from substrate. Forward reaction and backward reaction rate were analyzed separately. The activation energies of hydrogen A-D processes were obtained from the Arrhenius plot of the reaction rates. The activation energies of Pd films are not strongly dependent on the thickness of the film. But the activation energy of very thin film( l8nm thick) was smaller than the others.

• Journal of Hydrogen and New Energy
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• v.9 no.3
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• pp.127-133
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• 1998

This study was conducted to know to the effect of Pd film($180{\AA}$ thick) evaporation condition on the kinetics of hydrogen absorption-desorption. The activation energy of the forward reaction, the activation energy of the backward reaction, and the enthalpy were calculated by hydrogen absorption-desorption in ${\alpha}$-phase.($25{\sim}50^{\circ}C$ temperature) The activation energy of the forward reaction of Pd film, which is made at room temperature, is $6.4{\pm}0.4$ kcal/mol H and of the backward reaction $8.4{\pm}1.5$ kcal/mol H, which yields the reaction enthalpy -2kcal/mol H. The activation energy of forward reaction of Pd film, which is made at $300^{\circ}C$, is $-0.18{\pm}0.61$ kcal/mol H and of the backward reaction $-0.17{\pm}2.3$ kcal/mol H. The sample of $300^{\circ}C$ is more stable than the sample of room temperature in its struciural compactness and resistance value but standard error of result of $300^{\circ}C$ sample is higher than sample of room temperature do.

• Journal of Wetlands Research
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• v.21 no.4
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• pp.257-266
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• 2019

In this study, we selected 6 vegetation sites (reed community) and 6 non-vegetation sites (tidal flat) in the Muan tidal flat of Hampyeong Bay, and observed seasonal changes in carbon dioxide concentration, flux and soil temperature at low tide conditions. The study was conducted to identify the characteristics of seasonal changes in vegetation and non-vegetation areas through the data observed in May 30, August 8, 2012 and January 31, 2013. The average carbon dioxide concentration in the vegetation area was the highest in winter, followed by spring and summer, and the non-vegetation area showed the same concentration change as the vegetation area. The carbon dioxide flux in the vegetation area showed a positive (+) value in both spring and summer, but it was negative (-) in the winter. The average value of carbon dioxide flux was the highest in spring, but it was almost similar to summer, and winter was the lowest negative value. Non-vegetation areas showed positive emission in spring, and negative uptake in summer and winter; mean values were the highest in spring, and the difference between summer and winter was small. In summary of seasonal change characteristics of the research area, the emission of carbon dioxide was dominant in both areas in spring. In summer, carbon dioxide emission was dominant in the vegetation area, and the non-vegetation area was observed to uptake by photosynthesis of phytoplankton, but it was very small. In winter, changes in flux in both areas were very slight.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 1999.11a
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• pp.13-24
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• 1999

식물이 생장하고 발육하며 자신의 생명을 유지해 나가기 위해서는 끊임없이 에너지를 공급받아야 하는데, 이 에너지의 공급원은 태양으로부터 오는 광에너지이다. 이러한 광에너지는 엽록소(chlorophyll)를 함유한 녹색식물의 잎이나 줄기 등에서 기공(stomata)을 통하여 흡수되는 이산화탄소($CO_2$)와 뿌리에서 주로 흡수되는 물($H_2O$)로부터 당류ㆍ전분과 같은 탄수화물을 합성하고 산소를 방출하는데 이러한 광에너지가 화학에너지로 변환되는 과정을 광합성(photosynthesis) 또는 탄소동화작용(carbon assimilation)이라고 한다. (중략)

• Analytical Science and Technology
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• v.12 no.4
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• pp.299-305
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• 1999

The electrolyte cathode atomic glow discharge (ELCAD) is a new plasma source for direct determination of trace heavy metals in drinking and waste water. ELCAD has been successfully developed for on-line monitoring of heavy metals, however, shows difficulty to measure mercury. In this study, ELCAD has been modified to apply the atomic absorption spectrometry (AAS) for the direct determination of trace elements of mercury in flowing water.The fundamental characteristics of this new types of plasma source have been investigated and found that the pH of the solution, discharge voltage, and current are most important factors.The absorbance of 1.0 ppm Hg standard solution increases as pH of the solution increases from pH 1.0 to 3.0.However, % RSD of the absorbance also increases as the pH of solution increasesdue to plasma unstability.The detection limits of the standard solution of pH 1.5 and pH 3.0 are about 40 ppb and 10 ppb level, respectively.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.252-253
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• 2000

본 실험에서는 수 MW/$ extrm{cm}^2$ 의 매우 낮은 영역의 세기에서 순수한 GaAs의 bulk에 대하여 실험한 결과 비선형 흡수가 나타남을 관찰 하였으며, 더불어 자유전하 흡수 계수를 여러 가지 세기의 빛에서 측정한 결과 자유전하 흡수 단면적이 빛의 세기에 따라 변화하는 것을 관찰하였다.$^{(1)}$ GaAs의 굴절률이 3.6으로 매우 커서 Fabry-Perot 효과가 나타나므로 시료의 한쪽 면을 SiN로 무반사 코팅을 하여 실험 하였다. GaAs의 표면은 쉽게 레이저 빛에 의해 손상을 입는 것을 고려하여 같은 자리에서 여러 번의 실험을 하여 같은 결과가 나오는 것을 확인하여 실험 결과를 얻었다. 사용된 레이저는 Nd:YAG 레이저로서 1.064 $mu extrm{m}$의 파장에서 7 나노초의 펄스를 방출한다. 빛의 세기는 편광기와 half wave plate를 이용하여 변화 시켰다. (중략)

• Analytical Science and Technology
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• v.24 no.4
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• pp.282-289
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• 2011

Rapid screening method for the determination of the emissions of pollutants from vehicle interior parts and materials have been developed as ISO 12219-2 which is using bag and based on a static condition. The method was not controlled humidity in the test bag, so it is not suitable test method for formaldehyde emission test which is highly related to humidity condition. In this study, possibility of control humidity in the static test bag by adding extra water and the effect of humidity condition for formaldehyde emissions have been investigated. The relative humidity in the test bag was affected not only amount of water added also material of test bag and test specimen. The emission intensity of formaldehyde was increased according to increasing relative humidity in test bag. But excessively supplied water was condensed on the inner surface of test bag and surface of sample specimen that were sorption formaldehyde and were reduced its emission intensity.