• 분석과학
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• 제7권3호
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• pp.387-393
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• 1994

원자 흡수 분광법과 용매추출을 이용한 크롬의 정량분석 조건을 연구하였다. tertiary amine류 중 octy기를 갖는 trioctylamine(TOA)과 quaternary ammonium salt류 중 octyl기를 갖는 trioctylmethylammonium chloride(TOMAC)가 음이온 교환기로 사용되었다. 또한 첨가되는 산의 종류와 산의 농도 변화에 따라서 원자 흡수 분광기를 이용하여 흡광도를 측정하였다. TOA 사용시 염산의 농도가 0.1M에서 0.3M 사이, TOMAC 사용시 염산의 농도가 0.03M~0.1M 사이에서 최대 흡광도를 나타내었다. 산이 첨가된 MIBK에 용해된 TOA나 TOMAC와 Cr과의 mole 농도 비율이 1:1 이상이 된 것이 최대 추출 효율을 보였다. 추출과정을 검토한 결과, 본 실험에서 사용된 방법은 비슷한 다른 방법들과 비교하여 보면 크롬이 추출 효율이 좋은 것으로 판명되었다.

• 설비공학논문집
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• 제5권4호
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• pp.257-264
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• 1993

This is the second report of a three part study on the absorption and heat transfer characteristics of absorber, the correlation of refrigerating capacity and heating capacity. The 2nd report deals with the heat transfer characteristics of a vertical falling film type absorber of inner copper tube. The solute is LiBr-Water solution(60wt%) and the solvent is water vapor. The film Reynoles numbers are varied in the range of 35~130. The states of LiBr solution at the top of absorber are supercooled liquid and superheated liquid. The results are summarized as follows ; Heat transfer results reveal that for the absorption of falling film, the state of LiBr solution appears to be influential in determining the heat transfer. Thus, for the state of supercooled liquid, heat transfer coefficient decreases with increasing the film Reynolds number, but in the condition of superheated liquid, it increases conversely. The mass transfer coefficients that were presented in the 1st.report and heat transfer coefficients of this paper are presented as the dimensionless correlation. The optimum water flowrate which brings about maximum value of heat flux in the film exists, and that increases with increasing the cooling water temperature.

• Bulletin of the Korean Chemical Society
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• 제23권9호
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• pp.1315-1327
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• 2002

The model compounds, 8-methoxypsoralen-CH2O(CH2)n-adenine (MOPCH2OCnAd, n=2, 3, 5, 6, 8, and 10) in which 5 position of 8-methoxypsoralen (8-MOP) is linked by various lengths of polymethylene bridge to N9 of adenine. UV absorption spectra are identical with the sum of MOPCH2OC3 and adenine absorption spectra. Solvent effects on the UV absorption and fluorescence emission spectra indicate that the lowest excited singlet state is the $(\pi${\rightarrow}$\pi*)$ state. The spectral characteristics of the fluorescence of MOPCH2OCnAd are strongly dependent upon the nature of the solvents. The fluorescence emission spectra in aprotic solvents are broad and structureless due to the excimer formation through the folded conformation accelerated by hydrophobic ${\pi}-{\pi}$ stacking interaction. Increasing polarity of the protic solvents leads to higher population of unfolded conformation stabilized through favorable solvation and H-bonding, and consequently to an increase in the fluorescence intensity, fluorescence lifetime, and a shift of fluorescence maximum to longer wavelengths. The decay characteristics of the fluorescence in polar protic solvents shows two exponential decays with the lifetimes of 0.6-0.8 and 1.6-1.9 ns in 5% ethanol/water, while MOPCH2OC3 shows 0.5 and 1.7 ns fluorescence lifetimes. The long-lived component of fluorescence can be attributed to the relaxed species (i.e., the species for which the solvent reorientation (or relaxation) has occurred), while the short-lived components can be associated with the unrelaxed, or only partially relaxed, species.

• Bulletin of the Korean Chemical Society
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• 제35권8호
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• pp.2245-2250
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• 2014

A new accepter unit, 6,7-difluoro-2,3-dihexylquinoxaline, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. New series of copolymers with dioctyloxybenzodithiophene as the electron rich unit and 6,7-difluoro-2,3-dihexylquinoxaline as the electron deficient unit are synthesized. The solid films of poly[2,6-(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexylquinoxaline)] (PBQxF) and poly[2,6-(4,8-bis(2-ethylhexyloxy) benzo[1,2-b:4,5-b']dithiophene)-alt-5,8-(6,7-difluoro-2,3-dihexyl-5,8-di(thiophen-2-yl) quinoxaline)] (PBDTQxF) show absorption bands with maximum peaks at about 599 and 551 nm and the absorption onsets at 692 and 713 nm, corresponding to band gaps of 1.79 and 1.74 eV, respectively. The devices comprising PBQxF with $PC_{71}BM$ (1:2) showed open-circuit voltage ($V_{OC}$) of 0.64 V, short-circuit current density ($J_{SC}$) of $1.58mA/cm^2$, and fill factor (FF) of 0.39, giving power conversion efficiency (PCE) of 0.39%. To obtain absorption in the longer wavelength region, thiophene units without any alkyl group are incorporated as one of the monomers in PBDTQxF, which may result in low solubility of the polymers to lead lower efficiency.

• 대한치과기공학회지
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• 제33권4호
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• pp.291-297
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• 2011

Purpose: The purpose of this study was to know the availability of three photosensitizers, CQ, PD, DA, as a photosensitizer of dental resin composite. We want to know abortion band around visible light region for the using potential possibility as a photosensitizer for visible light cured dental composite resin. And I studied to know the relative photodecomposition ratio of three photosensitizers with or without photoinitiator, DAEM. Methods: The photodecomposition of three photosensitizers were studied by UV absorption spectroscopy in ethanol and determined by same instrument with irradiation time for relative photodecomposition. In order to study the effect of amine on photodecomposition was added the DAEM in the photosensitizer solution and the relative rate was measured by the same procedure with aove mentioned. Results: The all of three photosensitizers are absorbed around visible light region. The relative rate of decrease in absorbance incereased in the order: CQ < BD < PD. The effect of DAEM on the photodecomposition of the photosensitizers was appeared different results without DAEM. The photodecomposition rate of PD and DA decreased somewhat with the addition of amine, while that of CQ increased. The rtealtive photodecomposition rate increased in the oprder: BD ${\leq}$ CQ < PD with the addition of amine, but the differnce was not significant. Conclusion: PD and DA like CQ gives to the possibility of use as a photosensitizer for visible light cured dental composite resin by absorption around visible light region and photodecomposition in the maximum absorption wavelength. And it is showed that PD and DA are not effective decomposed with amine initiator, DAEM but CQ decomposed with DAEM effectively. This result may be due to a different mechanism operating for the decomposition of photosensitizers in the presence of amine.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.162-165
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• 2007

Chlorophyll concentration is an important factor for physical oceanography as well as biological oceanography. For these necessity many oceanographic researchers have been investigated it for a long time. But investigation using vessel is very inefficient, on the other hands, ocean color remote sensing is a powerful means to get fine-scale (spatial and temporal scale) measurements of chlorophyll concentration. Geostationary Ocean Color Imager (GOCI), for ocean color sensor, loaded on COMS (Communication, Ocean and Meteorological Satellite), will be launched on late 2008 in Korea. According to the necessity of algorithm for GOCI, we developed chlorophyll algorithm for GOCI in this study. There are two types of chlorophyll algorithms. One is an empirical algorithm using band ratio, and the other one is a fluorescence-based algorithms. To develop GOCI chlorophyll algorithm empirically we used bands centered at 412 nm, 443 nm and 555 nm for the DOM absorption, chlorophyll maximum absorption and for absorption of suspended solid material respectively. For the fluorescence-based algorithm we analyzed in-situ remote sensing reflectance $(R_{rs})$ data using baseline method. Fluorescence Line Height $({\Delta}Flu)$ calculated from $R_{rs}$ at bands centered on 681 nm and 688 nm, and ${\Delta}Flu_{(area)}$ are used for development of algorithm. As a result ${\Delta}Flu_{(area)}$ method leads the best fitting for squared correlation coefficient $(R^2)$.

• 한국해양환경ㆍ에너지학회지
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• 제10권3호
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• pp.173-180
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• 2007

파력에너지 변환을 위해 설계된 착저식 진동수주형 공기실 내의 파진폭 변화를 우리나라 연안의 특징적인 파랑 조건을 적용하여 조사하였다. 진동수주형 공기실의 형상인자가 파력에너지 변환에 미치는 영향을 파력에너지의 흡수 효율 관점에서 분석하였다. 실험적 및 수치적 접근법을 함께 사용하여 그 결과들을 상호 비교하였으며, 주어진 파랑 분포 하에서 파력에너지 흡수가 최대가 되는 형상인자들의 최적화를 목적으로 연구가 수행되었다. 실험은 공기실의 이차적원 형상을 가정하여 이차원 조파수조에서 실시되었으며, 수치적 해석은 공기실 내에서는 변동하는 공기압을 고려할 수 있도록 Rankine Green 함수를 적용하고 공기실 밖에서는 Kelvin Green 함수를 적용하는 합성 적분방정식에 기초하여 수행되었다. 공기실 상부의 덕트 직경, 공기실 폭, 공기실 전면벽 및 후면벽의 깊이는 흡수되는 파력에너지의 크기와 정점 주기를 민감하게 변화시키는 주요한 형상인자들임을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제35권10호
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• pp.2963-2968
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• 2014

We report synthesis and photovoltaic properties of two new conjugated copolymers, PCPDTQxF and PDTSQxF, with 6,7-difluoro-2,3-dihexylquinoxaline unit prepared by Stille coupling reaction. The advantage of 6,7-difluoro-2,3-dihexylquinoxaline based copolymer are high PCEs due to lower HOMO energy level, long wavelength absorption and high hole mobility. The solid films of PCPDTQxF and PDTSQxF showed absorption bands with maximum peaks at about 623 and 493 nm and the absorption onsets at 711 and 635 nm, corresponding to band gaps of 1.74 and 1.95 eV, respectively. The oxidation onsets of the PCPDTQxF and PDTSQxF polymers were estimated to be 0.68 and 0.95 V, which correspond to HOMO energy levels of -5.48 and -5.75 eV, respectively. The PDTSQxF has lower HOMO energy level as compared to PCPDTQxF to lead higher $V_{OC}$ value. The device comprising PCPDTQxF:PCBM (1:2) dissolved to a concentration of 1 wt % in ODCB showed $V_{OC}$ value of 0.62 V, $J_{SC}$ value of $1.14mA/cm^2$, and FF of 0.35, which yielded PCE of 0.25%.

• 대한화학회지
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• 제36권2호
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• pp.273-281
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• 1992

원자흡수분광법을 위한 글로우방전 분광 장치를 sputtering된 시료원자가 기저상태의 원자가 최대이며 여기 상태의 원자가 최소가 되는 지역을 측정하도록 설계 개발하였다. 빠른 속도의 가스 jet는 방전의 육안 및 전기적 변화 뿐만 아니라 시료표면의 변화에서 처럼 시료가 원자화되는 양을 현저히 증가시킨다. 가스 jet는 원자흡수분광법으로 시료를 직접할 수 있는 가능성을 보여주었다. 감도와 재현성에 영향을 끼치는 여러 가지 요인들에 관하여 연구하였다.

• Journal of Ginseng Research
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• 제39권2호
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• pp.183-187
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• 2015

Background: Gut microflora play a crucial role in the biotransformation of ginsenosides to compound K (CK), which may affect the pharmacological effects of ginseng. Prebiotics, such as NUTRIOSE, could enhance the formation and consequent absorption of CK through the modulation of gut microbial metabolic activities. In this study, the effect of a prebiotic fiber (NUTRIOSE) on the pharmacokinetics of ginsenoside CK, a bioactive metabolite of ginsenosides, and its mechanism of action were investigated. Methods: Male Sprague-Dawley rats were given control or NUTRIOSE-containing diets (control diet + NUTRIOSE) for 2 wk, and ginseng extract or vehicle was then orally administered. Blood samples were collected to investigate the pharmacokinetics of CK using liquid chromatography-tandem mass spectrometry. Fecal activities that metabolize ginsenoside Rb1 to CK were assayed with fecal specimens or bacteria cultures. Results: When ginseng extract was orally administered to rats fed with 2.5%, 5%, or 10% NUTRIOSE containing diets, the maximum plasma concentration ($C_{max}$) and area under the plasma concentration-time curve values of CK significantly increased in a NUTRIOSE content-dependent manner. NUTRIOSE intake increased glycosidase activity and CK formation in rat intestinal contents. The CK-forming activities of intestinal microbiota cultured in vitro were significantly induced by NUTRIOSE. Conclusion: These results show that prebiotic diets, such as NUTRIOSE, may promote the metabolic conversion of ginsenosides to CK and the subsequent absorption of CK in the gastrointestinal tract and may potentiate the pharmacological effects of ginseng.