• Bulletin of the Korean Chemical Society
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• 제9권3호
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• pp.153-156
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• 1988

Ab initio calculations are performed for $ArCO_2^+$ and $ArCO_2$. Between the two configurations of $ArCO_2^+$ the orbital interactions and the higher order correlation calculations favor the T-shape, and their interaction energies are calculated to be approximately half the experimental values using 6-31G$^{\ast}$ basis set. In $ArCO_2$, the calculations qualitatively favor the T-structure, which is compatible with the experiment. However, the true interaction energy is obscured since it is within the BSSE limit at this basis set size and the correlation level. Addition of sp type diffuse functions increase the interaction energies by a considerable amount, but the BSSE estimated by CP method are responsible for the significant portion of the difference. The possible equilibrium structure of the $Ar^+-CO_2$ complex, where the charge is localized on Ar, is suggested as having a linear structure. The potential energy surface and the amount of charge transfer are shown to be sensitive to the type and balancing of basis set.

• 한국수산과학회지
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• 제12권2호
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• pp.95-102
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• 1979

glutamin산 발효용 균 Brevibacterium flavum을 phenol유도체인 guaiacol, o-vanillin의 처리 및 존재하에서 발효를 행한 결과를 요악하면 다음과 같다. 1) glutamin산 축적량은 guaiacol 및 o-vanillin을 처리하였을 때에는 각각 12.5g/l와 14.2g/l이 었으며 비 처리균에서는 7.0g/l이었다. 2) 발효중 세균의 단위량의 호흡계수(r)는 guaiacol 처리균, o-vanillin 처리균의 순서로 각각 2.1, 1.7mol/UOD.hr 이었으며, 비 처리균에서는 1.6mol/UOD.hr였다. 3. 발효중 산소의 용량계수는 guaiacol 처리균이 0.28/hr, o-vanillin 처리균이 0.40/hr였으며 비 처리균에서는 0.20/hr로서 o-vanillin 처리때가 가장 컸다. 4) Brevibacterium flavum의 개스교환배율은 guaiacol 300ppm의 존재시 0.85, o-vanillin 20ppm의 존재시에는 1.0이 되어 비 처리균의 0.75보다 큼으로서 phenol 유도체의 존재에 의해 RQ가 증가하였다. 5) $5%$의 포도당을 기질로 하여 발효를 행하였을 때 glutamin산의 최고농도에 달하는 시간은 guaiacol 처리 및 o-vanillin 처리때는 각각 52시간과 48시간이었으며 비 처리때에는 56시간이었다. 6) glutamin산 최고농도에 달했을 때의 세균농도는 guaiacol 처리균, o-vanillin 처리균, 비 처리균의 순서로 8.91, 9.41 UOD/ml 및 8.82 UOD/ml이었다. 7) $5\%$의 포도당은 기질로 했을 때 축적되는 glutamin산의 포도당에 대한 전이비율을 guaiacol 처리균에서는 $25\%$, o-vanillin 처리균에서는 $28.5\%$, 비 처리균에서는 $14.0\%$의 전이율을 나타내었다. 8) phenol유도체 처리로 발효능이 증가되는 현상이 phenol 유도체가 산소와 전자이동착체를 형성하여 원골한 산소공급을 배양계에 해주는 때문이라 생각된다.

• Bulletin of the Korean Chemical Society
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• 제31권6호
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• pp.1615-1620
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• 2010

Bis-[dipyrido[3,2-$\alpha$:2',3'-c]phenazine)$_2$(1,10-phenanthroline)$_2Ru_2$]$^{2+}$ complexes (bis-Ru(II) complexes) tethered by linkers of various lengths were synthesized and their binding properties to DNA investigated by normal absorption and linear dichroism spectra, and fluorescence techniques in this study. Upon binding to DNA, the bis-Ru(II) complex with the longest linker (1,3-bis-(4-pyridyl)-propane), exhibited a negative $LD^r$ signal whose intensity was as large as that in the DNA absorption region, followed by a complicate $LD^r$ signal in the metal-to-ligand charge transfer region. The luminescence intensity of this bis-Ru(II) complex was enhanced. The observed $LD^r$ and luminescence results resembled that of the [Ru(1,10-phenanthroline)$_2$ dipyrido[3,2-$\alpha$:2',3'-c]phenazine]$^{2+}$ complex, whose dipyrido[3,2-$\alpha$:2',3'-c]phenazine (dppz) ligand has been known to intercalate between DNA bases. Hence, it is conclusive that both dppz ligands of the bis-Ru(II) complex intercalate. The binding stoichiometry, however, was a single intercalated dppz per ~ 2.3 bases, which violates the "nearest binding site exclusion" model for intercalation. The length between the two Ru(II) complexes may be barely long enough to accommodate one DNA base between the two dppz ligands, but not for two DNA bases. When the linker was shorter (4,4'-bipyridine or 1,2-bis-(4-pyridyl)-ethane), the magnitude of the LD in the dppz absorption region, as well as the luminescence intensity of both bis-Ru(II) complexes, was half that of the bis-Ru(II) complex bearing a long linker. This observation can be elucidated by a model whereby one of the dppz ligands intercalates while the other is exposed to the aqueous environment.

• 대한화학회지
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• 제23권5호
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• pp.314-319
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• 1979

바닥 말무리 dinoflagellate의 광합성 에너지 수용 색소인 peridinin의 전자 흡수스펙트럼을 PPP SCF MO 계산결과와 형광 편광 실험결과에 견주어 분석하였다. 청색광 부위의 흡수띠 (470 nm)는 $B{\leftarrow}A$ 천이에 대응하여 분자의 장축과 거의 평행 방향으로 편광되어 있음이 예측된다. 소위 "cis peak" 영역의 근자외선 흡수띠는 두개의 비교적 약한 ${\pi}{\rightarrow}{\pi}^*$천이 $(C{\leftarrow}A$와 $D{\leftarrow}A)$에 기인하며 그 편광축은 $^1B{\leftarrow}A$편광축 방향과 근접되어 있음이 MO 계산과 편광 측정에 의해 추정되었다. 그리고 락톤 카르보닐 원자단의 전자구조는 $^1B$ 상태에서도$^1A$ 상태 (ground state)에 비해서 과히 변화함이 없으나, allene기는 charge transfer적 성격을 농후하게 띠고 있어서 들뜬상태에서는 allene기가 전자결핍상태가 되는 것이 예측된다.

• 에너지공학
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• 제22권4호
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• pp.399-405
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• 2013

엔진 실린더 내부의 난류유동 특성은 내연기관의 열효율을 결정하는 매우 중요한 역할을 한다. 실린더 내 난류유동은 복잡한 3차원 유동으로 유동특성에 대한 자세한 정보는 엔진설계의 최적화를 위해 필수적이다. 균일 예혼합 압축착화(HCCI) 엔진은 가솔린과 디젤엔진 사이의 하이브리드 연소개념이다. 실린더 내 기체의 난류유동은 운동량과 열의 혼합 및 전달률을 증가시키므로 벽면에서의 열전달에 관여하여 HCCI 연소 과정에 중요한 영향을 미치게 된다. 본 연구에서는 연소실 형상에 따른 연소실 내의 기체 난류유동을 LES 모델을 사용한 전산수치해석을 통해 분석하여 HCCI 엔진 연소과정에 미치는 영향을 확인하였고 연구결과는 HCCI 엔진에서 연소실 형상에 따른 연소 특성과 엔진 성능을 개선하기 위한 기본적인 지침에 활용될 수 있다.

• 공업화학
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• 제9권6호
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• pp.811-816
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• 1998

염분을 함유한 시멘트 모르터 내의 철근의 부식현상을 교류 임피던스법에 의해 고찰하였다. 부식 가속화 장치를 이용하여 단기간 내에 부식현상을 예측하였으며, 측정된 임피던스 값은 제안된 전기화학적 등가회로 및 모델에 적용할 수 있었으며, CNLS(complex nonlinear least squares) fitting법에 의하여 계산된 값과 실험에서 얻은 값이 잘 일치함을 알 수 있었다. 주어진 모델로부터 구한 전하이동저항 (charge transfer resistance, $R_2$)은 염분 농도와 시간에 따른 철근의 무게 감소량의 예측을 가능하게 하였으며, 이는 실제 철근의 무게 감소치에 근접함을 알 수 있었다.

• Bulletin of the Korean Chemical Society
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• 제27권12호
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• pp.2002-2010
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• 2006

This study examined the quenching of ofloxacin (OFL) and flumequine (FLU) fluorescence by $Cuj^{2+}$, $Ni^{2+}$, $Co^{2+}$ and $Mn^{2+}$ in an aqueous solution. The change in the fluorescence intensity and lifetime was measured at various temperatures as a function of the quencher concentration. According to the Stern-Volmer plots, the fluorescence emission was quenched by both collisions (dynamic quenching) and complex formation (static quenching) with the same quencher but the effect of static quenching was larger than that of dynamic quenching. Large static and dynamic quenching constants for both OFL and FLU support significant ion-dipole and orbital-orbital interactions between fluorophore and quencher. For both molecules, the static and dynamic quenching constants by $Cu^{2+}$ were the largest among all the metal quenchers examined in this study. In addition, both the static and dynamic quenching mechanisms by $Cu^{2+}$ were somewhat different from the quenching caused by other metals. Between $Ni^{2+}$ and FLU, a different form of chemical interaction was observed compared with the interaction by other metals. The change in the absorption spectra as a result of the addition of a quencher provided information on static quenching. With all these metals, the static quenching constant of FLU was larger than those of OFL. The fluorescence of OFL was quite insensitive to both the dynamic and static quenching compared with FLU. This property of OFL can be explained by the twisted intramolecular charge transfer in the excited state.

• 한국수소및신에너지학회논문집
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• 제24권1호
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• pp.61-69
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• 2013

Polymer exchange membrane (PEM) fuel cells have multifunctional properties, and bipolar plates are one of the key components in these fuel cells. Generally, a bipolar plate has a gas flow path for hydrogen and oxygen liberated at the anode and cathode, respectively. In this study, the influence of iodine applied to a bipolar plate was investigated. Accordingly, we compared bipolar plates with and without iodine coating, and the performances of these plates were evaluated under operating conditions of $75^{\circ}C$ and 100% relative humidity. The membrane and platinum-carbon layer were affected by the iodine-coated bipolar plate. Bipolar plates coated with iodine and a membrane-electrode assembly (MEA) were investigated by electron probe microanalyzer (EPMA) and energy-dispersive x-ray spectroscopy (EDS) analysis. Polarization curves showed that the performance of a coated bipolar plate is approximately 19% higher than that of a plate without coating. Moreover, electrochemical impedance spectroscopy (EIS) analysis revealed that charge transfer resistance and membrane resistance decreased with the influence of the iodine charge transfer complex for fuel cells on the performance.

• 폴리머
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• 제32권6호
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• pp.580-586
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• 2008

4,4'-(Hexafluoroisopropylidene) diphthalic anhydride (6FDA) 와 1,3-bis (3-aminophenoxy) benzene(BAPB)의 조성에 2,2-bis [4-(4-aminophenoxy)phenyl] hexafluoropropane (BAPP)를 다양한 몰 비에 따른 폴리이미드(PI) 공중합체를 합성하였다. PI 공중합체 필름들은 여러 열처리 과정을 통하여 용액 캐스팅 (solution casting)된 폴리아믹산(PAA)으로부터 얻었다. 퓨리에 변환 적외선 분광기(FT-IR), 넓은 각 X-선 회절(XRD), 전계 방사형 주사 전자 현미경(FE-SEM) 시차 주사 열량계(DSC)와 열 중량 분석기(TGA), 만능 인장 시험기 (UTM) 그리고 자외선-가시광선 흡광도기 (UV-Vis. spectrometer) 등을 사용하여 PI 공중합체 필름의 열적 기계적 성질, 모폴로지 및 광학 투명도를 측정하였다. PI 공중합체 필름의 유리전이온도 및 최종 강도와 초기 탄성률은 BAPP의 몰 비가 증가할수록 증가하였으나, 초기분해온도는 BAPP의 몰 비 증가에 무관하게 일정하였다. BAPP가 charge transfer complex를 형성하는 이유로 BAPP 농도가 증가함에 따라 PI 공중합체 필름의 투명도는 약간씩 감소하였다.

• Bulletin of the Korean Chemical Society
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• 제19권9호
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• pp.897-906
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• 1998

A new synthesis has been developed for 1-thia-4,7-diazacyclononane and the complexation behavior of a particular derivative has been explored. The pentadentate ligand 4,7-bis(2-pyridylmethyl)-l-thia-4,7-diazacyclononane ([9]$N_2SPY_2$) and its iron(Ⅱ) and manganese(Ⅱ) complexes were prepared and characterized. Magnetic moments of 5.17 and 5.90 μB respectively, indicate that the iron(Ⅱ) and manganese(Ⅱ) complexes are high spin. Charge transfer transitions (d-π*) occur for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$at 27027, 25000, and 24390 cm-1 for X=$H_2O$, Cl-, and OH-, respectively. In acetonitrile solution, the cyclic voltammogram of the manganese(Ⅱ) complex exhibits a redox couple at 0.92 V vs. NHE while the redox potentials for [Fe(Il)([9]$N_2SPY_2)(X)]^{n+}$ are 0.70, 0.66, and 0.37 V vs. NHE for X=$H_2O$, Cl-, and OH-, respectively. The d-π* charge transfer energy and Fe(Ⅱ)/Fe(Ⅲ) redox potential for [Fe(Ⅱ)([9]$N_2SPY_2)(X)]^{n+}$ increase in the same order: $H_2O>Cl^- >OH^-$. The crystal structures of the iron(Ⅱ) and manganese(Ⅱ) complexes reveal that the metal ions are sixcoordinate, binding to four nitrogen atoms and a sulfur atom from the pentadentate ligand, as well as a chloride anion, with the chloride and sulfur atoms in cis positions. The two metals have similar coordination geometries, which are closer to trigonal prismatic than octahedral. In both iron and manganese complexes, the M-N($sp_3$) trans to Cl- is 0.07 Å longer than the one cis to Cl- , and M-N($sp^2$) trans to S is 0.05 longer than the one cis to S atom.