• Journal of the Korean Society of Tobacco Science
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• v.7 no.2
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• pp.151-167
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• 1985

Generally, the same quality tobacco may give similar concentration of each chemical component. This research investigation was studied to obtain the differences in concentrations of volatile oil compounds in physically similar tobacco produced in different environment and managements-in Korea and in the United States. The flue-cured leaf tobacco produced in Korea and America was regraded to B3L and P3L by American grading system and analyzed for volatile oils relating to tobacco flavor and aroma. Sixty compounds of the more than 100 peaks distinguishable on the total neutral volatile oils were identified by G5-MS and quantified. Their concentrations are compared between B3 L and P3L produced in Korea and in the United States. The most volatile oil concentrations of B3 L and P3L grade tobacco arc higher in American than in Korean. Only a few components such as benzaldehyde, pulegonc, 4, 6, 9 - megastigmatriene - 3 - one, and coumaran are less in American.

• Korean Journal of Ecology and Environment
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• v.44 no.4
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• pp.337-346
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• 2011

We investigated nutrient loading and trophic states in a coastal estuarine system in the Asan estuary by assessing phytoplankton biomass and using the trophic index (TRIX). The monthly and yearly nutrient loading (TN, TP) from freshwater discharge from the Asan and Sapgyo reservoirs into the estuary were estimated and analyzed with related factors. Monitoring data (physio-chemical and biological variables) collected at five estuary stations were used to assess trophic states. Descriptive statistics of total phytoplankton cells, chl a concentrations and primary productivity were also used to assess seasonal trophic status. N loading from freshwater ranged $1.0{\sim}1.3{\times}10^4$ ton yearly. The yearly P loading ranged between 350 and 400 ton during 2004~2006, increasing to 570 ton in 2007. Regression results suggest that DIN and DSi were correlated with freshwater discharge at the upper region. Based on phytoplankton biomass and total cell abundance, the trophic state of the estuary was found to be eutrophic during spring due to phytoplankton bloom. Primary productivity level was remarkably high, especially in summer coinciding with high nutrient loading. Pheopigments increased during warm seasons, i.e. summer and fall. Trophic index results indicate that the trophic state varied between mesotrophic and eutrophic in the estuary water body, especially in the upper region. The results suggest that phytoplankton production was regulated by nutrient loading from freshwater whereas biomass was affected by other properties than nutrient loading in the Asan Estuary ecosystem.

• Journal of the Korean Society of Safety
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• v.33 no.6
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• pp.37-41
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• 2018

Process safety technology has developed from qualitative methods such as HAZOP (hazard and operability study) to semi-quantitative methods such as LOPA (layer of protection analysis), and quantitative methods are actively studied these days. Quantitative risk assessment (QRA) is often based on fault tree analysis (FTA). FTA is efficient, but difficult to apply when failure events are not independent of each other. This problem can be avoided using a Markov process (MP). MP requires definition of all possible states, and thus, generally, is more complicated than FTA. A method is proposed in this work that uses an MP model and a Weibull distribution model in order to construct a reliability model for multiple dependent failures. As a case study, a pressure safety valve (PSV) is considered, for which there are three kinds of failure, i.e. open failure, close failure, and gas tight failure. According to recently reported inspection results, open failure and close failure are dependent on each other. A reliability model for a PSV group is proposed in this work that is to reproduce these results. It is expected that the application of the proposed method can be expanded to QRA of various systems that have partially dependent multiple failure states.

• Journal of Photoscience
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• v.2 no.2
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• pp.83-87
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• 1995

Luminscence spectra and decay of crystalline hexahydro-1,3,5-trinitro-1,3,5-s-tetrazine (RDX) are observed at 90 K and the effects of photochemical reaction on the luminescence of RDX are investigated. The uv light from high power Hg lamp is used for the photochemical reaction of RDX. While no significant changes are observed in the luminescence spectra after the photochemical reaction, the intensity profile of the spectra changes with the progress of chemical reactions. The biexponential decay of luminescence is modified by chemical reactions. Features of the electronic states of crystalline RDX are discussed in relation to the luminescence.

• Journal of the Korean Chemical Society
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• v.49 no.3
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• pp.247-254
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• 2005

• Bulletin of the Korean Chemical Society
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• v.23 no.9
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• pp.1247-1252
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• 2002

Mass-analyzed threshold ionization (MATI) technique is optimized to generate substantial amount of state-selected molecular ions sufficient for dynamics study. The main strategy is to stabilize intermediate (n = 100- 200) Rydberg states by l,m-mix ing induced by AC field. Electrical jitter inherent in high voltage switching is utilized for this purpose. A related technique to locate the MATI onset is also described.

• Bulletin of the Korean Chemical Society
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• v.32 no.4
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• pp.1415-1418
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• 2011

• Bulletin of the Korean Chemical Society
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• v.28 no.3
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• pp.408-412
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• 2007

Combining the analytical transfer matrix method with supersymmetry algebra, a new quantization condition is suggested. To demonstrate the efficiency of the new quantization condition, the eigenenergies of the Coulomb potential are analytically derived. The scattering-led phase shifts are also determined and they are the same for all Coulomb potential states. It is found that the new quantization condition is mathematically simple and exact.

• Bulletin of the Korean Chemical Society
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• v.29 no.11
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• pp.2103-2108
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• 2008

• Bulletin of the Korean Chemical Society
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• v.27 no.12
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• pp.2045-2050
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• 2006

The interstitial hydrogen bonding in NiTi solid and its effect on the metal-to-metal bond is investigated by means of the EH tight-binding method. Electronic structures of octahedral clusters $Ti_4Ni_2$ with and without hydrogen in their centers are also calculated using the cluster model. The metal d states that interact with H 1s are mainly metal-metal bonding. The metal-metal bond strength is diminished as the new metal-hydrogen bond is formed. The causes of this bond weakening are analyzed in detail.