• Journal of Mechanical Science and Technology
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• v.16 no.8
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• pp.1127-1134
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• 2002

The effects of pressure and temperature on the autoignition of propane and n-butane blends were investigated using a rapid compression machine (RCM) , which is widely used to examine the autoignition characteristics. The RCM was designed to be capable of varying the compression ratio between 5 and 20 and minimize the vortex formation on the cylinder wall using a wedge-shaped crevice. The initial temperature and pressure of the compressed gas were varied in range of 720∼900 K and 1.6∼ 1.8 MPa, respectively, by adjusting the ratio of the specific heat of the mixture by altering the ratio of the non-reactive components (N$_2$, Ar) under a constant effective equivalence ratio (ø$\_$f/= 1.0) The gas temperature after the compression stroke could be obtained from the measured time-pressure record. The results showed a two-stage ignition delay and a Negative Temperature Coefficient (NTC) behavior which were the unique characteristic of the alkane series fuels. As the propane concentration in the blend were increased from 20% and 40% propane, the autoignition delay time increased by approximately 41 % and 55% at 750 K. Numerical reduced kinetic modeling was performed using the Shell model, which introduced some important chemical ideas, represented by the generic species. Several rate coefficients were calibrated based on the experimental results to establish an autoignition model of the propane and n-butane blends. These coefficients can be used to predict the autoignition characteristics in LPG fueled Sl engines.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.5 no.4
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• pp.374-380
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• 2000

Dissolved aliphatic hydrocarbon concentrations in the surface seawater were investigated to describe their distribution and elucidate their sources in the Cheju-Korea Straits region (33$^{\circ}$30‘-34$^{\circ}$N 125$^{\circ}$-128$^{\circ}$E). Seawater sampling was made in spring and autumn in 1998. A large temporal and spatial variability were observed in the dissolved hydrocarbon concentrations in the region. The sources of dissolved hydrocarbons in seawater were elucidated based on the molecular concentrations of n-alkanes and pristane. Dissolved hydrocarbons in the surface water appears to be largely originated from phytoplankton and petroleum in the southern Yellow Sea (125$^{\circ}$), and terrigenous and petrogenic in the Cheju-Korea Straits region in April 1998. In September 1998, dissolved hydrocarbons in the surface waters were largely derived from phytoplanktons and terrestrial material in the Cheju-Korea Soaits region.

• Ocean and Polar Research
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• v.41 no.2
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• pp.89-97
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• 2019

Long chain plant waxes (n-alkanes, n-alkanoic acids, and n-alcohols) and their carbon isotopic compositions (${\delta}^{13}C$) in geologic archives are valuable tools for paleovegetation reconstruction. However, the sensitivity of different plant wax constituents to vegetation shift is not well understood. This study explores controls on the variation in ${\delta}^{13}C$ values of long-chain n-alkanes ($C_{27}$ to $C_{33}$) and n-alkanoic acids ($C_{26}-C_{30}$) in the Gulf of Mexico core sediments (ODP 625B) near the Mississippi River delta. n-Alkanoic acids' ${\delta}^{13}C$ values were higher than those of n-alkanes by 1-2‰ on average and such a pattern is the opposite from their isotope fractionation observed in living plants: 1-2‰ smaller in n-alkanes than n-alkanoic acids. We attribute this offset to contributions from aquatic plants or microbes that produce high concentrations of $^{13}C-enriched$ long-chain n-alkanoic acids. The sensitivity of n-alkanes and n-alkanoic acids to vegetation and climate varied among chain lengths. The $n-C_{33}$ alkanes were most sensitive to $C_4$ grassland expansion among n-alkane homologues, while no specific trend was observed in n-alkanoic acids. This is due to the similarity in n-alkanoic acid concentrations between $C_3$ and $C_4$ plants by homologues and low terrestrial plant-derived n-alkanoic acid contributions to the sediments. The results of this study suggest that long chain n-alkanoic acids' ${\delta}^{13}C$ values in sediments may be influenced by contributions from different sources such as aquatic plants or microbial inputs and therefore interpretations regarding this matter should be cautiously formulated. We suggest that there is a need for further studies on characterizing long-chain n-alkanoic acids ($C_{26}-C_{34}$) in aquatic plants and microbes from various climates and environments in order to investigate their production and integration into sedimentary archives.

• KSBB Journal
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• v.11 no.6
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• pp.654-662
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• 1996

Bacterial strains which degrade crude oil were isolated by liquid culture from oil-spilled soil, and four isolates were selected among them. The strain Hl7-1 was finally selected after testing emulsifying activity and oil conversion rate. The strain Hl7-1 was identified as a Nocardia sp. based on the test for morphological, biochemical and physiological characteristics. It appears to be highly specialized for growth on crude oil in minimal salts medium since it showed preference for oil or degradation products as substrates for growth. It was found that it could grow on at least fifteen different hydrocarbons. The optimum cultural and environmental conditions were seeked. Cell growth and emulsification activity as a function of time were also determined. Crude oil degradation and the reduction of product peak was identified by the analysis of remnant oil by gas chromatography after 3 days of cultivation. Approximately 83% of oil were converted into a form no longer extractable by organic solvents.

• Journal of Microbiology and Biotechnology
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• v.18 no.9
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• pp.1522-1528
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• 2008

The morphogenetic behavior of a tropical marine Yarrowia lipolytica strain on hydrophobic substrates was studied. Media containing coconut oil or palm kernel oil (rich in lauric and myristic acids) prepared in distilled water or seawater at a neutral pH supported 95% of the cells to undergo a transition from the yeast form to the mycelium form. With potassium laurate, 51 % of the cells were in the mycelium form, whereas with myristate, 32% were in the mycelium form. However, combinations of these two fatty acids in proportions that are present in coconut oil or palm kernel oil enhanced the mycelium formation to 65%. The culture also produced extracellular lipases during the morphogenetic change. The yeast cells were found to attach to the large droplets of the hydrophobic substrates during the transition, while the mycelia were associated with the aqueous phase. The alkane-grown yeast partitioned more efficiently in the hydrophobic phases when compared with the coconut oil-grown mycelia. A fatty acid analysis of the mycelial form revealed the presence of lauric acid in addition to the long-chain saturated and unsaturated fatty acids observed in the yeast form. The mycelia underwent a rapid transition to the yeast form with n-dodecane, a medium-chain aliphatic hydrocarbon. Thus, the fungus displayed a differential behavior towards the two types of saturated hydrophobic substrates.

• Journal of Environmental Science International
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• v.6 no.5
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• pp.473-480
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• 1997

Microorganisms producing bioemulslfiler were isolated from the sea water In Pusan coastal area. The isolated strain which had the highest emulsification activity and stability was identified as the genus Achetobacter from the results of morphological. cultural and biochemical tests and named Achetobacter sp. EL-C6 for convenience. The compositions of optimum medium for emulsification of crude oil by Acinetobacter sp. EL-C6 were crude oil 2.0%, NH4NO3 0.2%, $K_2HPO_4$ 0.01%, $MgSO_4$.$7H_2O$ 1.o%, $CaCl_2$.$2H_2O$ 0.1% and NaCl 3.0% at initial pH 7.5 and 3$0^{\circ}C$, respectively. The cultivation for emulsification of crude ell was carried out in 500m1 shaking flask containing 100m1 of the optimum medium at 3$0^{\circ}C$. The highest emulsification was observed after 5 days. The utilization on the various hydrocarbon of the Achetobacter sp. EL-C6 showed that utilization of n-alkane compounds were better than that of aromatic compounds. Among the petroleum compounds, crude ell was best utilized by the Achetobacter sp. EL-C6.

• Ocean and Polar Research
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• v.36 no.1
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• pp.25-37
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• 2014

To understand the degradation processes of organic matter related to sulfate reduction by Sulfate Reduction Bacteria (SRB) in the tidal flat sediments of Hwang-do and Sogeun-ri, Tae-an Peninsula in Chungnam-do, biogeochemical characteristics were analyzed and highlighted using specific microbial biomarkers. The organic geochemical parameters (TOC, ${\delta}^{13}C_{org}$, C/N ratio, long-chain-n-alkane) indicate that most of the organic matter has been derived from marine phytoplankton and bacteria in the fine-grained sediment of Sogeun-ri, although terrestrial plant components have occasionally been incorporated to a significant degree in the coarse-grained sediment of Hwang-do. The concentration of sulfate in pore water is a constant tendency with regard to depth profile, while methane concentration appears to be slightly different with regard to depth profile at the two sites. Especially, the sum of bacteria fatty acid (a-C15:0 + i-C15:0 + C16:1w5) confirms that the these concentrations in Sogeun-ri are related to the degradation of Benzene, Toluene, Ethylbenzene and Xylene (BTEX) compounds from the crude oil retained in the sediments as a result of the Hebei Spirit oil-spill accident in 2007. The methane-related microbial communities as shown by lipid biomarkers (crocetane, PMI) are larger in some sedimentary sections of Hwang-do than in the Sogeunri tidal flat. These findings suggest that methane production by microbiological processes is clearly governed by SRB activity along the vertical succession in organic-enriched tidal flats.

• Journal of the Korean Chemical Society
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• v.36 no.5
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• pp.744-752
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• 1992

Polymer bonded metalloporphyrins are synthesized by reaction between Fe(III) protoporphyrin or Mn(II) tetrakis(4-N-carboxyphenyl)porphyrin with polystyrene divinylbenzene copolymer. The spectroscopic properties of synthetic polymer bonded metalloporphyrins are investigated by using resonance Raman spectrometer. By synthetic polymer bonded metalloporphyrins as catalyst, which are model of cytochrome P-450 and peroxidases, epoxidation of olefins and oxidation of alkanes are achieved with H2O2 as oxidant. The catalytic efficiencies with polymer bonded metalloporphyrins are improved on that with corresponding nonpolymer bonded metalloporphyrins. Especially those can be reused because of stability against oxidant. Electron donating imidazole derivatives, which are attached in 5th position of central metal of metalloporphyrins, enhance the catalytic efficiencies.

• Korean Journal of Microbiology
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• v.21 no.4
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• pp.191-196
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• 1983

A Corynebacterium sp. capable of utilizing diaminododecane (DAD) were isolated from the soil by enrichment culture. Among 9 different kinds of substituted alkanes containing CN, $NH_2$, Cl, and SH groups (monoterminally or diterminally substituted) tested as carbon source, the isolate, designated as DAD 2-3, utilized DAD, putrescine dihydrochloride, dodecane and laurylamine. Dodecanethiol, thioanisole, decanedithiol, dicyanooctane, laurylcyanide,and dichlorodecane were not utilized. When emulgen 950 was added to the medium, the growth of DAD 2-3 was slightly accelerated. Isolate DAD 2-3 grown in the medium with DAD as carbon source formed .alpha.-ketoglutaric acid. Metabolic product of DAD 2-3 grown in a medium without nitrogen source was different from that of grown in a medium with $NH_4NO_3$. When glucose, putrescine, n-dodecane and other alkane derivatives were tested in place of DAD, isolate DAD 2-3 yielded products different from those they formed with DAD suggesting specificity of DAD as a carbon source.

• Analytical Science and Technology
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• v.5 no.4
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• pp.389-399
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• 1992

Liquid Chromatographic behavior of Pd(II) in Isonitrosoethylacetoacetate lmine, $Pd(IEAA-NR)_2$ (R=H, $CH_3$, $C_2H_5$, $n-C_3H_7$, $C_6H_5-CH_2$, $n-C_4H_9$) chelates were investigated by reversed-phase HPLC on Micropak MCH-5 column using methanol/water as mobile phase. The optimum conditions for the separation of $Pd(IEAA-NR)_2$ chelates were examined with respect to the effect of the flow rate, sample solvent, mobile phase strength and column temperature. It wass found that metal chelates were properly eluted in an acceptable range of capacity factor value($0{\leq}log\;k^{\prime}{\leq}1$). The dependence of the logarithm of capacity factor(k') on the volume fraction of water in the binary mobile phase was examined. Also, the dependence of k' on the liquid-liquid extration distribution ratio($D_c$) in methanol-water/n-alkane extration system was investigated. Both kinds of dependence are linear, which susggests that the retention of the electroneutral metal chelate is largely due to the solvophobic effect. Standard adsorption enthalpy changes (${\Delta}H^{\circ}$) and standard adsorption entropy changes (${\Delta}S^{\circ}$) of Pd(II) Isonitrosoethylacetoacetate imine chelates on Micropak MCH-5 column were calculated by measuring capacity factor with changing temperature of the column.