• KIEAE Journal
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• v.2 no.3
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• pp.33-38
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• 2002

The intermediate range of temperatures($100{\sim}300^{\circ}C$) which can be achieved with CPCs(Compound Parabolic Concentrators) without tracking device provides both economic and thermal advantages for solar collector design. The present paper summarizes critical design considerations for CPC with cylindrical absorber and its optical performance using ray tracing program. Concentration ratios vary as acceptance half angle, ratio of reflector height to aperture width and ratio of reflector area to aperture area. This effects showed that the concentration ratio was increased as acceptance angle but optimum ratio of reflector height to aperture width existed at critical value. As a result of ray tracing, solar ray losses was maximized at acceptance half angle and this problem was solved by increasing absorber tube diameter. The concentrating flux distribution on the absorber surface was uniform but peak flux existed.

• Environmental Engineering Research
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• v.23 no.3
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• pp.309-315
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• 2018

Chlortetracycline (CTC) is one of the most important compounds in antibiotic production, and its distribution has been widely investigated due to health and ecological concerns. This study presents systematic approach to optimize the high-performance liquid chromatography-tandem mass spectrometry for analyzing CTC in a multiple reaction monitoring mode ($479{\rightarrow}462m/z$). One-factor-at-a-time (OFAT) test with response surface analysis (RSA) was used as optimization strategy. In OFAT tests, the fragmentor voltage, collision energy, and ratio of acetonitrile in the mobile phase were selected as major factors for RSA. The experimental conditions were determined using a composite in cube design (CCD) to maximize the peak area. As a result, the partial cubic model precisely predicted the peak area response with high statistical significance. In the model, the (solvent composition) and (collision $energy^2$) terms were statistically significant at the 0.1 ${\alpha}$-level, while the two-way interactions of the independent variables were negligible. By analyzing the model equation, the optimum conditions were derived as 114.9 V, 15.7 eV, and 70.9% for the fragmentor voltage, collision energy, and solvent composition, respectively. The RSA, coupled with the CCD, offered a comprehensive understanding of the peak area that responds to changes in experimental conditions.

• Journal of Welding and Joining
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• v.18 no.2
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• pp.232-232
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• 2000

The hydrogen attack characteristics of 3Cr-1Mo-V steel as simulated weld heat affected state were studied in this paper. The hydrogen attack susceptibility was evaluated by the ratios of Charpy impact absorbed energy at 0℃($vE_{0HA}$/$vE_{0}$) and reduction of area by tensile test ($RA_{HA}$/RA) before and after exposure to hydrogen at 600℃ under 450kgf/㎠ for 300hr. The values of $vE_{0HA}$/$vE_{0}$ and $RA_{HA}$/RA were aggravated as the peak temperature of the simulated heat affected zone(HAZ) raised. These results were due to the increase of the possession of bubbles along the grain boundaries, which were resulted in the reduction of grain boundary area to be precipitated carbides due to grain coarsening and the carbon dissolved in the martensite-austenite constituent near by the prior austenite grain boundary. The possession ratio of methane bubbles formed along prior austenite grain boundaries were increased with raising the peak temperature. (Received February 22, 2000)

• Journal of Welding and Joining
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• v.18 no.2
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• pp.105-111
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• 2000

The hydrogen attack characteristics of 3Cr-1Mo-V steel as simulated weld heat affected state were studied in this paper. The hydrogen attack susceptibility was evaluated by the ratios of Charpy impact absorbed energy at 0℃({TEX}$vE_{0} {HA}_/vE_{0}${/TEX}) and reduction of area by tensile test({TEX}$RA_{HA}/RA${/TEX}) before and after exposure to hydrogen at 600℃ under 450kgf/㎠ for 300hr. The values of {TEX}$vE_{0} {HA}_/vE_{0}${/TEX} and {TEX}$RA_{HA}/RA${/TEX} were aggravated as the peak temperature of the simulated heat affected zone(HAZ) raised. These results were due to the increase of the possession of bubbles along the grain boundaries, which were resulted in the reduction of grain boundary area to be precipitated carbides due to grain coarsening and the carbon dissolved in the martensite-austenite constituent near by the prior austenite grain boundary. The possession ratio of methane bubbles formed along prior austenite grain boundaries were increased with raising the peak temperature.

• Journal of Pharmaceutical Investigation
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• v.40 no.3
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• pp.193-200
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• 2010

The objective of this study was to investigate the effects of sample preparation, HPLC conditions and peak measurement methods upon determining progesterone content of poly-d,l-lactide-co-glycolide microspheres. A series of the microspheres with different formulations was first prepared. To determine their actual drug contents, the microspheres were dissolved in tetrahydrofuran and diluted with various amounts of methanol to precipitate the polymer. After removal of polymeric precipitates, the filtrates were subject to HPLC analysis under versatile experimental conditions. Interestingly, the composition of a sample solution (e.g., the ratio of methanol to tetrahydrofuran) affected the magnitudes of both peak fronting and peak broadening of progesterone. Its peak became broader and more asymmetrical at lower methanol:tetrahydrofuran ratios. Furthermore, its peak height was influenced by the proportion of tetrahydrofuran in a sample solution. Such problems encountered with tetrahydrofuran were exacerbated when a larger volume of the sample solution was injected onto an analytical column. Under our experimental conditions a peak area measurement provided more accurate and reliable determination of progesterone content in various microspheres than a peak height determination. Optimizing the composition of a sample solution, HPLC chromatographic conditions and peak analysis methods was a prerequisite to an accurate determination of progesterone encapsulated within microspheres.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.12
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• pp.5931-5936
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• 2012

This study was to evaluate the clinical usefulness of the PRESS technique based on the correlation between PRESS technique and biopsy results by applying 3.0T high magnetic field MRS technique for evaluation of non-alcoholic fatty liver disease patients. This experiment were carried out using a 3.0T magnetic resonance imaging equipment. The part data of each spectrum is taken by peak area integration. The part data of resonance peak was used to calculate relative ratio. MR spectral peak in patients with non-alcoholic fatty liver disease is from 0.9 to 1.6 ppm. According to MRS method study result, Patients with NAFLD were obtained with 94% sensitivity and 80% specificity(p=0.000). When compared to normal based on MRS and Biopsy results was valid correlation(r=0.79, p=0.04). Results for NAFLD(r=0.89, p=0.002) also showed a correlation. Therefore, PRESS technique to evaluate patients with non-alcoholic fatty liver disease, the distribution difference between normal liver and fatty liver part is significantly distinguished. Biopsy and MRS fatty liver peak ratio(%) proves high lipid over grade(r = 0.7).

• Korean Journal of Food Science and Technology
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• v.33 no.1
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• pp.153-156
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• 2001

Traditional static headspace and headspace solid-phase microextraction(SPME) techniques were compared for their effectiveness in the extraction of volatile flavor compounds from the headspace of persimmon vinegar. The adsorption condition of SPME fiber for equilibrated headspace vapor was selected as $80^{\circ}C$ and 20 min. Total FID response for volatiles of persimmon vinegar was exactly higher such as total peak area $18.18{\times}10^6$ in SPMEGC technique than total peak area $1.35{\times}10^6$ in static headspace-GC. The major volatiles in persimmon vinegar were acetic acid, ethyl acetate, 3-hydroxy-2-butanone, ethanol, phenethyl alcohol. From static headspace-GC technique, 3 acids, 3 aldehydes, 5 alcohols, 9 esters and 1 ketone were identified. From SPME-GC technique, total 34 compounds including 6 acids, 7 aldehydes, 6 alcohols, 9 esters, 2 hydrocarbones, 1 ketone, 3 others were detected. Also the ratio for benzaldehyde, phenethylacetate and phenethylalcohol were higher in SPME-GC.

• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.40-47
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• 1999

A numerical study on gaseous explosion was carried out to predict the transient pressure behavior with the partial rupture in confined vessels. Equations, assumptions and solutions for central ignition of premixed gases in closed spherical vessels are proposed with various equivalence ratios of gas fuel, as $CH_4$ and $C_3H_8$, vent areas and vent opening pressures. Given vent opening pressure in a vessel, the magnitude of second peak pressure results from the vent areas and burning velocity, varied by equivalence ratio of gas fuel. In a living room of an apartment, the higher second peak pressure than the vent pressure is not appeared due to its large window areas. As vent opening pressure is higher, the larger damage by gaseous explosion is expected and the larger vent area is necessary for relieving the damage. In the same concentration, the gaseous explosion by propane rather than methane shows the larger damage due to its higher adiabatic flame temperature and equivalence ratio.

• Korean Journal of Food Science and Technology
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• v.24 no.1
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• pp.25-28
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• 1992

The changes of amount in flavor components of chewing gum during storage of various relative humidity were studied by GC/MS. The volatile components in chewing gum were extracted by sample preperation and 15 volatile components were identified by NIST/NBS library searching. According to the period of storage, quantities of major volatile components extracted by tetrahydrofuran-methanol solutions were determined by using tetradecane as internal standard. Until 4 weeks, comparing with starting peak area ratio, the decrease of chewing gum flavor components were rapid at 33, 75 than 53 R.H(%). And after 16 weeks, amount of chewing gum flavor at all storage conditions similarly decreased to $45{\sim}49%$ of the initial amount.

• Korean Journal of Environment and Ecology
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• v.9 no.2
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• pp.182-186
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• 1996

The annual increasing rate of visitors was 9.5% in Odaesan National Park from 1989 to 1995. Ninety three percent of total visitor of Odaesan National Park has visited Woljongsa and Sogumgang area in which a motorcar access is convenient. Climbing rate of Pirobong(peak) were less seven percent of total cisitors at Woljongsa in summer and less twelve point six percent in autumn. Visiting pattern showed difference by area, seasons and a day of the week. Using rate of motorcars was higher in summer than in autumn