• Journal of The Korean Society of Agricultural Engineers
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• v.52 no.6
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• pp.19-26
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• 2010

Batch experiments were conducted to investigate growth and nutrient removal performance of microalgae Chlorella vulgaris by using piggery wastewater in different concentration of pollutants and the common growth models (logistic, Gompertz and Richards) were applied to compare microalgal growth parameters. Removal of nitrogen (N) and phosphorus (P) by Chlorella vulgaris showed correlation with biomass increase, implying nutrient uptake coupled with microalgae growth. The higher the levels of suspended solids (SS), COD and ammonia nitrogen were in the wastewater, the worse growth of Chlorella vulgaris was observed, showing the occurrence of growth inhibition in higher concentration of those pollutants. The growth parameters were estimated by non-linear regression of three growth curves for comparative analyses. Determination of growth parameters were more accurate with population as a variable than the logarithm of population in terms of R square. Richards model represented better fit comparing with logistic and Gompertz model. However, Richards model showed some complexity and sensitivity in calculation. In the cases tested, both logistic and Gompertz equation were proper to describe the growth of microalgae on piggery wastewater as well as easy to application.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1045-1050
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• 2003

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests are conducted on 2124-T851 aluminum alloy specimens. Three test spectra are generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results are compared with the data obtained from the flight-simulation loading. The experimental results show that omission of the load ranges below 5% of the maximum load does not significantly affect crack growth behavior, because these are below the initial stress intensity factor range. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decrease, and therefore crack growth curve deviates from the crack growth data under the flight-simulation loading. To optimize the load range that can be omitted, crack growth curves are simulated by the stochastic crack growth model. The prediction shows that the omission level can be extended to 8% of the maximum load and test time can be reduced by 59%.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.11
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• pp.1245-1256
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• 2014

The physical nature of fatigue shows the considerable amount of scatter from intrinsic and extrinsic factors. In this study, some degradation models, such as the gamma process model, were reviewed in terms of uncertainties associated with the continuous, gradual, and monotonic nature of fatigue crack growth. Statistically varying fatigue crack growth data obtained from Lu and Meeker were used as an example to demonstrate the use of the gamma process model. This model can describe the condition and lifetime as statistical distribution curves whose shapes vary with cycles. From the skewness of the statistical distribution curves, it was confirmed that the median is suitable for being considered as the expected life. The use of the gamma process model enables the optimum replacement period and percentile life to be employed as criteria for preventive maintenance policy.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.96-98
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• 2013

Through reviewing the characteristics of digital TVs, which have emerged in CES since 2005, in the view of technology growth and substitution curves, this paper is to provide a prediction on the next generation's multi-media on smart environment. As a result, digital TV has been developed on the flow of its technology growth curve from the early version in 2005 to smart digital TV in 2013, which emphasizes the key word "connected", and it has already come to the market puberty. Also, as it has the characteristics such as supporting multi functional and multi media environments and introducing curved or flexible display, the digital TV in CES 2013 has reached in introductory stage on the technology substitution curve.

• Journal of Korean Academy of Oral Health
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• v.42 no.4
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• pp.210-215
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• 2018

Objectives: The main objectives of this study were to verify the antibacterial activity of two essential oils, lavender and peppermint, against dental caries and to review their synergistic effect when used in combination. Our results provide basic data for the evaluation of the use of these two substances towards the prevention and cure of dental caries. Methods: The sample solutions of lavender and peppermint oils were prepared in three different concentrations (30%, 50%, and 70% (v/v)) by diluting them with third-distilled water and Tween 20. Streptococcus mutans was selected as the bacterial species for testing. The disk diffusion method was used to measure the antibacterial activity of the sample solutions. For generating growth curves and measuring the number of clusters of the bacterial, the liquid medium-dilution method was used; the absorbance of the medium was measured at 600 nm after 3, 6, 12 and 24 hours. Results: When the antibacterial activity of the oils was tested via the disk diffusion method, the activity improved with increasing concentrations of all the sample solutions of peppermint, lavender, and the blend, but there was no significant difference between them with respect to the type of oil. In the growth curves of S. mutans, growth inhibition was observed after 12 hours. The inhibitory effect of 30% lavender oil on growth was 64.9% and 80.1% after 12 and 24 hours of treatment, respectively whereas that of peppermint oil was 71.3% and 80.1% after 12 and 24 hours of treatment, respectively. The inhibitory effect of the blended oil was 71.9% and 81.0% after 12 and 24 hours of treatment, respectively. Conclusions: Further research is still required in order to determine the efficacy of lavender and peppermint oils, as well as other essential oils, for wider use in preventing dental caries.

• Proceedings of the KWS Conference
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• 1997.05a
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• pp.65-68
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• 1997

Fracture behavior of ex-serviced 1Cr-0.5Mo steel was measured at room(24$^{\circ}C$) and elevated(538$^{\circ}C$) temperature and compared with that measured with virgin 1Cr-0.5Mo steel. Compact C(T) specimens were machined from the base and welded test materials. In case of the C(T) specimens of the weld, fatigue precrack was introduced along the fusion line so that a crack growth should occur along the region of heat affected zone. It was observed that the J-R curve of the serviced material was significantly lower than that of the virgin material at room temperature. Brittle fracture was observed in the serviced material. On the other hand at elevated temperature no noticeable difference was found between the J-R curves of the virgin and the serviced material. The measured J-R curves were also compared with those of the 1.25Cr-0.5Mo steel from other literatures. Optical microscopy and SEM examination of the serviced material reveal the carbide in/along the grain boundary which shows material degradation due to long-term usage.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.151-162
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• 1997

The suitability of pivalic acid was confirmed as a secondary temperature standard material. Triple-point cells of pivalic acid were obtained by using combined process of vacuum distillation with zone refining. A detailed description of the purification process was given. The melting curves were used as criteria for determination of purities of pivalic acid. Triple points of these cells with purity of 99.9997% were measured to be $35.956\pm 0.003^{\circ}C$ by using the melting plateau curves. Thus the triple point cells of pivalic acid appear to be able to use for the calibration of thermistor thermometers with moderate precision.

• Asian Journal of Atmospheric Environment
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• v.3 no.1
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• pp.19-26
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• 2009

The environmental Kuznets curve hypothesis assumes an inverted U-shaped relationship between environmental damage and income, and such curves have been used to study how economic growth affects the environment. In this study, we analyzed data for gross domestic product (GDP) per capita and for sulfur emissions in the industrialized countries of the United Kingdom, United States of America, and Japan, as well as data for the developing country of China, to determine the relationship between emissions and income in these countries. Attempts by these countries' governments to incorporate environmental policy considerations into the income-environment relationship were also examined. The potential role of the environmental Kuznets curve as a policy tool was investigated. We determined that, at least in the case of sulfur emissions, policies and institutions significantly reduced environmental degradation in the industrialized countries studied. Furthermore, the environmental Kuznets curve can reliably predict the future relationship between environmental impact and GDP for developing countries.

• Korean journal of food and cookery science
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• v.26 no.6
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• pp.848-852
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• 2010

This study investigated the antibacterial activities of extracts and fractions of Sasa borealis against eight bacteria (Bacillus cereus, Bacillus subtilis, Listeria monocytogenes, Staphylococcus aureus, Psedomonas aerginosa, Salmonella choleraesuis, Serratia marcescens and Vibrio vulnificus) by broth dilution assay. Using survival curves, the kinetics of bacterial inactivation upon exposure to the extracts and fractions were followed for 24 h. In this same manner, MIC (minimum inhibitory concentration) values were determined by broth microdilution assay and then confirmed to be the extract concentrations that inhibited bacterial growth. Sasa borealis extracts showed antibacterial activities against all tested bacteria. In particular, all tested fractions of Sasa borealis had stronger activities than 70% ethanol extract. MIC of Sasa borealis extract was determined to be 5 mg/mL against Salmonella choleraesuis. All fractions of Sasa borealis extract had extremely strong antibacterial activities. MIC of fractions were determined to be 0.03~2.5 mg/mL. These results suggest that the extracts and fractions of Sasa borealis effectively inhibited bacterial growth and thus are useful as natural antibacterial agents.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.116-119
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• 2003

[ $Hg_{1-x}Cd_xTe$ ] (MCT) was grown by hot wall epitaxy method. Prior to the MCT growth, the CdTe (111) buffer layer was grown on the GaAs substrate at the temperature of 590 C for 15 min. When the thickness of the CdTe buffer layer was 5 m or thicker, the full width at half maximum values obtained from the x-ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe (111) /GaAs substrate at various temperature in situ. The crystal quality for those epilayers was investigated by means of the x-ray rocking curves and the photocurrent experiment. The photoconductor characterization for the epilayers was also measured. The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were turned out.