• Composites Research
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• v.24 no.4
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• pp.29-35
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• 2011

The characteristic length method used to determine a laminate's strength generally requires the test for un-notched and notched laminates and finite element analysis together. In this paper, the methods used to predict the stress distribution and tensile characteristic length of open-hole laminates using the stress concentration factor and equivalent material properties are proposed. These methods do not require data on the failure load of open-hole laminates or finite element analysis. Once the stress and characteristic length have been determined, the failure load of the open-hole laminate can be calculated. The proposed method considers the effect of the material properties as a parameter and therefore can be applied to a variety of materials. The stress distribution is verified by comparing with a finite element analysis and test results. The predicted failure load shows a maximum deviation of 8% from the test results.

• Analytical Science and Technology
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• v.12 no.2
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• pp.99-104
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• 1999

A stepwise gradient elution with two wavelengths detection was performed for the separation and determination of some anions in saline water. The eight anions such as iodate, bromate, nitrite, bromide, nitrate, chromate, iodide and thiocyanate were successfully separated using AS-7 column and sodium chloride/sodium phosphate buffer solution as an eluant within 40 min. The separation behaviors of anions were studied at various sodium chloride concentrations. The peak shapes of anions of bromate, nitrite, bromide and nitrate gradually broadened as the concentration of sodium chloride increased until 1.0 M in the sample solutions. However, no effect was observed in the peak shapes of chromate, iodide and thiocynate. A good linearity was obtained at the range of ppm(mg/L). The detection limit was proved to be $10-720{\mu}g/L$ for the eight anions with $50{\mu}L$ injection volume. This method was applied to the determination of $Br^-$, ${NO_3}^-$ and $I^-$ in sea water.

• Science of Emotion and Sensibility
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• v.16 no.3
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• pp.409-416
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• 2013

Attention is one of important cognitive functions in human affecting on the selectional concentration of relevant events and ignorance of irrelevant events. The discrimination of attentional and inattentional status is the first step to manage human's attentional capability using computer assisted device. In this paper, we newly combine the non-linear recurrence pattern analysis and spectrum analysis to effectively extract features(total number of 13) from the electroencephalographic signal used in the input to classifiers. The performance of diverse types of attention-inattention classifiers, including supporting vector machine, back-propagation algorithm, linear discrimination, gradient decent, and logistic regression classifiers were evaluated. Among them, the support vector machine classifier shows the best performance with the classification accuracy of 81 %. The use of spectral band feature set alone(accuracy of 76 %) shows better performance than that of non-linear recurrence pattern feature set alone(accuracy of 67 %). The support vector machine classifier with hybrid combination of non-linear and spectral analysis can be used in later designing attention-related devices.

• New & Renewable Energy
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• v.16 no.1
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• pp.58-67
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• 2020

Microbial electrosynthesis has recently been considered a potentially sustainable biotechnology for converting carbon dioxide (CO₂) into valuable biochemicals. In this study, bioelectrochemical acetate production from CO₂ was studied in an H-type two-chambered reactor system with an anaerobic microbial consortium. Metal-rich mud flat was used as the inoculum and incubated electrochemically for 90 days under a cathode potential of -1.1 V (vs. Ag/AgCl). Four consecutive batch cultivations resulted in a high acetate concentration and productivity of 93 mmol/L and 7.35 mmol/L/day, respectively. The maximal coulombic efficiency (rate of recovered acetate from supplied electrons) was estimated to be 64%. Cyclic voltammetry showed a characteristic reduction peak at -0.2~-0.4 V, implying reductive acetate generation on the cathode electrode. Furthermore, several electroactive acetate-producing microorganisms were identified based on denaturing- gradient-gel-electrophoresis (DGGE) and 16S rRNA sequence analyses. These results suggest that the mud flat can be used effectively as a microbial source for bioelectrochemical CO₂ conversion.

• Korean Journal of Pharmacognosy
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• v.41 no.4
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• pp.323-327
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• 2010

A high performance liquid chromatographic (HPLC) method for the simultaneous determination of dictamine, obacunone and fraxinellone was established for the quality control of traditional herb Dictamnus dasycarpus cortex. Separation and quantification were successfully achieved with a Shiseido C18 column ($5\;{\mu}m$, 4.6 mm I.D. ${\times}$ 250 mm) by gradient elution of a mixture of methanol and water at a flow rate of 1.0 ml/min. The diode-array UV/Vis detector (DAD) was used for the detection and the wavelength for quantification was set at 236 nm. The presence of dictamine, obacunone and fraxinellone in this extract was ascertained by retention time, spiking with each authentic standard and UV spectrum. All three compounds showed good linearity ($r^2$ > 0.999) in relatively wide concentration ranges. The R.S.D. recovery of each compound was 101.0~103.7% with R.S.D. values less than 1.0%. This method was successfully applied to the determination of contents of dictamine, obacunone and fraxitnellone in three commercial products of D. dasycarpus cortex. These results suggest that the developed HPLC method is simple, effective and could be readily utilized as a quality control method for commercial products.

• Natural Product Sciences
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• v.14 no.3
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• pp.147-151
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• 2008

A high performance liquid chromatographic (HPLC) method for the simultaneous determination of marker constituents, baicalin and glycyrrhizin was established for the quality control of traditional herbal medicinal preparation, Eul-Ja-Tang (EJT). Separation and quantification were successfully achieved with a Waters XTerra RP18 column ($5{\mu}m$, 4.6 mm I.D. ${\times}$ 150 mm) by gradient elution of a mixture of acetonitrile and water containing 0.03% phosphoric acid (pH 2.03) at a flow rate of 1.0 mL/min. The diode-array UV/VIS detector (DAD) was used for the detection and the wavelength for quantification was set at 250 nm. The presence of baicalin and glycyrrhizin in this decoction was ascertained by retention time, spiking with each authentic standard and UV spectrum. Both baicalin and glycyrrhizin showed good linearity ($r^2$ > 0.999) in a relatively wide concentration ranges. The R.S.D. for intra-day and inter-day precision was less than 5% and the limits of detection (LOD) were about 30 ng. The mean recovery of each compound was 99.5 - 101.2% with R.S.D. values less than 4.0%. This method was successfully applied to the determination of contents of baicalin and glycyrrhizin in three commercial products of EJT, which resulted in the difference in the contents of these compounds. These results suggest that the developed HPLC method is simple, effective and could be readily utilized as a quality control method for commercial EJT products.

• Korean Journal of Pharmacognosy
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• v.45 no.4
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• pp.300-314
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• 2014

An ultra-performance liquid chromatography-electrospray ionization-mass spectrometer (UPLC-ESI-MS) method was established for the simultaneous quantification of eighteen marker compounds in traditional Korean formula, Cheonwangbosimdan (CWBSD). In addition, we evaluated the antioxidant effects of CWBSD. Eighteen marker components were separated on a UPLC BEH $C_{18}$ analytical column ($2.1{\times}100mm$, $1.7{\mu}m$) and kept at $45^{\circ}C$ by gradient elution with 0.1% (v/v) formic acid in water and acetonitrile as mobile phase. The flow rate was 0.3 mL/min and the injection volume was $2.0{\mu}L$. The antioxidant activities of CWBSD were assessed by measuring free radical scavenging activities on 2,2'-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) and 1-1-diphenyl-2-picrylhydrazyl (DPPH). The calibration curves of all analytes showed good linearity (correlation coefficient ${\geq}0.9937$) within the test ranges. The limits of detection and quantification for the 18 marker compounds were 0.01-4.71 ng/mL and 0.03-14.13 ng/mL, respectively. The contents of the 18 compounds in CWBSD extract ranged from none to $1701.00{\mu}g/g$. The CWBSD showed the radical scavenging activity in a dose-dependent manner. The concentration required for 50% reduction ($RC_{50}$) against ABTS and DPPH radicals were $149.42{\mu}g/mL$ and $339.24{\mu}g/mL$.

• Journal of Environmental Science International
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• v.7 no.4
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• pp.425-432
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• 1998

The purpose of the present study is to estimate the release of dissolved Inorganic nitrogen and photophorous from sediments of Deukryang Bay. One method used In this study is to calculate nutrients released from a concentration gradient between sediment porewaters and the overlying water based on periments. The calculated and measured ammonium released from the sediments were 8.93mg-atN/$m^2$ hr and 60.4mg/atN/$m^2$ hr, respectively In July. 8.57mg-atN/$m^2$. hr and 32.9mg/atN/$m^2$ hr, respectively in October. The ammonium was released more highly in truly than in October, and the measured ammonium flux was higher than the calculated one. The calculated nitrate plus nitrite released from the sediments were 0.31mg/atN/$m^2$. hr in July and 0.84mg/atN/$m^2$. hr in October. The measured nitrate plus nitrite released from the sediments was 282mg/atN/$m^2$. hr in October. The calcuated was lower than the measured because the content of the nutrients in the sediments was always much more than in the overlying waters, and it has shown a differently seasonal pattern compared to the ammonium flux. The calculated phosphorous released from the sediments were 0.97mP/atN/$m^2$ hr and measured negative fluxed -6.50mP/atN/$m^3$ hr In truly, and alculated 0.18mg/atP/$m^2$. hr and measured 24.6mg/atP/$m^2$. hr, respectively in October.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.5
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• pp.347-352
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• 2017

Reverse electrodialysis (RED), which generates electrical energy from the difference in concentration of two solutions, has been actively studied owing to its high potential and the increased interest in renewable energy resulting from the Paris Agreement on climate change. For RED commercialization, its power density needs to be maximized, and therefore various methods have been discussed. In this paper, the power density was measured using various flow shapes based on the aspect ratio, opening ratio, and number of distribution channels. We found that the power density is enhanced with a decrease in the aspect ratio and an increase in the opening ratio and number of distribution channels.

• Natural Product Sciences
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• v.22 no.4
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• pp.299-306
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• 2016

This study aimed to establish the quantitative method to analyze the content of peroxynitrite-scavengers belonging to polyphenols in six Korean Quercus species (Quercus mongolica, Q. dentata, Q. acutissima, Q. alienta, Q. serrata, and Q. variabilis) by HPLC. The twelve peroxynitrite-scavengers, flavanols (catechins: (+)-catechin, (-)-epicatechin, and (-)-epigallocatechin), flavonols (kaempferol and quercetin), flavonol glycosides (astragalin, quercitrin, and isoquercitrin), flavonol acylated glycosides (astragalin 6''-gallate and isoquercitrin 6''-gallate), gallic acid and its dimer (ellagic acid) were analyzed by HPLC. Further, anti-Alzheimer's activity was assayed in a passive avoidance testusing mice by measuring the retention latency (sec), the concentration of acetylcholine (ACh), and acetylcholinesterase (AChE) activity. Simultaneous analysis of the extracts of the six Quercus leaves was achieved on a Capcell C18 column ($5{\mu}m$, $250mm{\times}4.6mm\;i.d.$) with a gradient elution of 0.05% HAc and 0.05% HAc in $CH_3CN$. In the extract of Q. mongolica leaves, the content of gallic acid (32.53 mg/g), (+)-catechin (28.78 mg/g), (-)-epicatehin (22.03 mg/g), astragalin 6''-gallate (20.94 mg/g), and isoquercitrin 6''-gallate (44.11 mg/g) and peroxynitrite-scavenging activity ($IC_{50}$, $0.831{\mu}g/ml$) were high. This extract delayed the retention latency and inhibited acetylcholinesterase activity in scopolamine-induced memory impairment of mice, suggesting that it has anti-Alzheimer's activity.