• Composites Research
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• 제24권4호
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• pp.29-35
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• 2011

전통적인 특성길이 방법을 이용하여 원공이 있는 복합재 적층판의 강도를 예측하기 위해서는 원공이 있는 적층뿐만 아니라 원공이 없는 적층판에 대한 시험 결과와 유한요소해석이 필요하였다. 본 논문에서는 응력집중계수와 재료상수를 이용하여 유한요소해석 없이 복합재 적층판 원공 주위의 응력분포 및 인장특성길이를 추정하고, 이를 바탕으로 원공이 있는 복합재 적층판의 인장강도를 예측할 수 있는 방법을 제안하였다. 또한 새로운 방법에서는 재료의 효과가 변수로 고려되므로 다양한 재료에 대한 적용이 가능하며 원공이 있는 복합재 적층판에 대한 시험도 생략할 수 있다. 적층판 주위의 응력분포는 유한요소해석과의 비교를 통해 검증하였고, 최종적으로는 USN125 탄소/에폭시 적층판을 제작하여 파손하중 예측 결과와 시험 결과를 비교하였다. 원공이 있는 다양한 형상의 복합재 적층판의 파손강도 예측 결과는 최대 8% 이내의 오차로 시험 결과와 잘 일치함을 확인하였다.

• 분석과학
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• 제12권2호
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• pp.99-104
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• 1999

자외선검출법과 이온크로마토그래피를 이용하여 소금물 중에 함유하는 몇 가지 음이온의 분리정량에 대하여 검토하였다. 분리관은 음이온교환수지(Dionex, AS7)를 사용하였고 용리액으로서는 sodium chloride/sodium phosphate 완충용액을 사용하였다. 단계적용리법을 적용하므로서 최적분리가 가능하였으며 8가지 음이온(iodate, bromate, nitrite, bromide, nitrate, chromate, iodide와 thiocyanate)이 40분내에 분리되었다. 여러 가지 농도의 NaCl용액(0.0 M-1.0 M)속에 존재하는 음이온들의 거동을 살펴보았다. NaCl의 농도가 진할수록 bromate, nitrite, bromide와 nitrate의 피크의 모양이 점점 넓어졌으나 chromate, iodide와 thiocyanate는 1.0 M NaCl 용액의 농도까지 피크모양이 거의 변하지 않았다. 또한 여러 가지 농도의 NaCl용액에서 음이온들의 검량곡선은 좋은 직선성을 보여주었으며, $50{\mu}L$ 시료용액에서 검출한계는 $10-720{\mu}g/L$ 이었다. 바닷물중의 bromide, nitrate와 iodide의 측정에 이방법을 적용하였다.

• 감성과학
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• 제16권3호
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• pp.409-416
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• 2013

집중은 관련된 사건을 선택적으로 주의하고, 관련 없는 사건을 무시하는 인간의 중요한 인지 기능중의 하나이다. 인간의 집중 능력을 관리 이용하는 컴퓨터 기반 장치에 있어서 집중과 비집중 상태를 구분하는 것은 필수적으로 요구되는 조건이다. 본 논문에서는, 뇌파신호로부터 분류기의 입력으로 사용되는 특징을 효율적으로 추출하기 위하여 비선형 반복 패턴 분석기법과 스펙트럼 분석 기법을 새로이 결합하였고(13개 특징 추출), 서포트벡터머신, 역전파 알고리즘, 선형분리, 로지스틱 회귀 분류 기반 분류기들을 포함하는 집중-비집중 분류기들의 성능을 분석하였다. 그중에서 81 %의 정확도를 보이는 서포트벡터머신 분류기가 가장 좋은 성능을 보였다. 또한 스펙트럼 분석으로 추출한 특징만을 사용하였을 경우(76 % 정확도)가 비선형 분석 방법으로 추출한 특징만을 사용했을 경우(67 % 정확도)보다 좀 더 우수한 성능을 보였다. 비선형-스펙트럼 분석법을 복합 적용한 서포트벡터머신 분류기가 추후 집중 관련 장비 설계에 있어서 효율적으로 적용될 수 있을 것이다.

• 신재생에너지
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• 제16권1호
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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.

• 생약학회지
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• 제41권4호
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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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• 제14권3호
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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.

• 생약학회지
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• 제45권4호
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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 $339.24{\mu}g/mL$.

• 한국환경과학회지
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• 제7권4호
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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.

• 대한기계학회논문집B
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• 제41권5호
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• pp.347-352
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• 2017

두 용액의 농도 차이를 이용하여 전기에너지를 생성하는 역전기투석 장치는 파리기후협약으로 인한 신재생에너지기술의 관심 증가와 높은 잠재적에너지량으로 인하여 활발한 연구가 진행되고 있는 분야이다. 상용화 관점에서 볼 때 역전기투석 장치의 출력 밀도를 최대화하는 것은 중요하며, 따라서 출력 밀도의 개선을 위한 다양한 방안이 논의되고 있다. 본 논문에서는 역전기투석 장치의 출력 개선 방법 중 유로 형상 변화에 초점을 맞췄다. 유로 형상 변수로서 종횡비, 개방비, 분배 및 배출 유로의 개수를 사용하였다. 결론적으로 유로의 종횡비는 감소하고 개방비와 분배 및 배출 유로의 개수가 증가할 때, 역전기투석 장치의 출력 밀도가 개선되는 것을 발견하였다.

• Natural Product Sciences
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• 제22권4호
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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.