• 대한화학회지
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• 제29권1호
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• pp.23-30
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• 1985

${\pi}^{\ast}$-${\pi}^{\ast}$ 궤도간 상호작용에 관한 섭동식을 유도하였다. 섭동식으로부터 예측되는 ${\pi}$-${\pi}$와 ${\pi}^{\ast}$-${\pi}^{\ast}$ 상호작용간의 중요한 두가지 차이점은 : (ⅰ)에너지분리정도가 ${\pi}$-${\pi}$ 상호작용의 경우보다 ${\pi}^{\ast}$-${\pi}^{\ast}$의 경우가 더 컸으며, ( ii ) 상호작용에 의한 에너지 변화량은 ${\pi}$-${\pi}$ 상호작용의 경우보다 ${\pi}^{\ast}$-${\pi}^{\ast}$의 경우가 더 불안정화 되었다. 이러한 예측들은 실험결과들과 MO이론적 계산에 의하여 잘 밝혀졌다. 한편 STO-3G 및 INDO-LCBO 계산방법은 ${\pi}^{\ast}$-${\pi}^{\ast}$ 상호작용을 과소평가하고 있음을 알았으며 MO이론적 계산을 이용하여 이러한 ${\pi}^{\ast}$-${\pi}^{\ast}$상호작용을 적절히 표현하는 데는 split valence 기초함수를 사용하여야 함을 밝혔다.

• Bulletin of the Korean Chemical Society
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• 제30권1호
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• pp.205-213
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• 2009

This study reports on the geometry optimizations and electronic structure calculations for methyl pyropheophorbide (MPPa), tropolonyl methyl pyropheophorbides (TMPPa, ITMPPa), and cationic tropolonyl methyl pyropheophorbides ($TMPPa^+{{\cdot}BF_4}^-,\;ITMPPa^+{{\cdot}BF_4}^-,\;TMPPa^+,\;and\;ITMPPa^+$) using Local Spin Density Approximation (LSDA/ 6-31G*) and the Restricted Hatree-Fock (RHF/6-31G*) level theory. From the calculated results, we found that substituted cationic tropolonyl groups have larger structural effects than those of substituted neutral tropolonyl groups. The order of structural change effects is $ITMPPa^+ > ITMPPa^+{{\cdot}BF_4}^-$ > ITMPPa, as a result of the isopropyl group. Because it is an electron-releasing group, the substituted isopropyl group electronic effect on a 3-position tropolone increases the Highest Occupied Molecular Orbital and Lowest Unoccupied Molecular Orbital (HOMO-LUMO) energy gap. It was constituted that the larger the cationic characters of these photosensitizers, the smaller the HOMOLUMO band gaps are. The orbital energies of the cationic systems and the ions are stronger than those of a neutral system because of a strong electrostatic interaction. However, this stabilization of orbital energies are counteracted by the distortion of chlorin macrocycle, which results in a large destabilization of chlorin-based compound HOMOs and smaller destabilization of LUMOs as shown in TMPPa (ITMPPa), $TMPPa^+{{\cdot}BF_4}^- (ITMPPa^+{{\cdot}BF_4}^-),\;and\;TMPPa^+\;(ITMPPa^+)$ of Figure 6 and Table 6-7. These results are in reasonable agreement with normal-coordinate structural decomposition (NSD) results. The HOMO-LUMO gap is an important factor to consider in the development of photodynamic therapy (PDT).

• 항공우주시스템공학회지
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• 제16권6호
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• pp.90-98
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• 2022

EO/IR 위성에 탑재된 적외선 센서(IR Sensor)는 궤도환경에서 임무기간 동안 복사 에너지에 대한 센서 출력의 변화가 발생한다. 고품질 영상을 획득하기 위해 출력을 교정할 수 있는 주기적인 교정이 필요하며, 센서의 주기적이고 정밀한 교정을 위해 탑재체 내부에 흑체 시스템이 적용하였다. 우주 환경에서 사용되는 모든 시스템은 궤도환경에서의 목표 성능을 검증하기 위해 지상에서의 성능시험이 요구되고 있다. 흑체 시스템은 운용환경에서 목표 온도 범위에서 대표추정온도 오차와 흑체 표면온도균일도 성능의 시험적 검증이 요구되고 있다. 본 연구에서는, 궤도환경으로 우주배경복사 냉각이 모사된 열진공 시험을 통해 제안된 흑체 시스템의 대표추정온도 오차 교정 및 성능 검증을 진행하였다.

• Bulletin of the Korean Chemical Society
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• 제26권11호
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• pp.1706-1710
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• 2005

The excited-state intramolecular proton transfer (ESIPT) fluorescence in the 2-(2'-hydroxyphenyl)benzoxazole (HBO) derivatives with different electron donor and acceptor substituents was studied by spectroscopic and theoretical methods. Changes in the electronic transition, energy levels, and orbital diagrams of HBO analogues were investigated by the semi-empirical molecular orbital calculation and were correlated with the experimental spectral position of ESIPT keto emission. It was found that the presence of substituents, regardless of their nature, resulted in the red-shifted absorption relative to HBO. However, the spectral change of the ESIPT fluorescence was differently affected by the nature of substituent: hypsochromic shift with electron donor and bathochromic shift with electron acceptor.

• Journal of Astronomy and Space Sciences
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• 제6권2호
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• pp.109-117
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• 1989

A total of 266 photoelectric observations(91 in V, 93 in B, and 82 in U) for an eclipsing binary, ZZ Cnc, has been secured by using the 61-cm reflector and an uncooled iP21 photomultiplier phototube of Yonsei University Observatory during 4 years from March 1984 to May 1988. One time of minimum light, JD 2446887.534 is obtained. Although Kim et al.(1988) suggested the possibility of the period change, the present study shows that the orbital period of ZZ Cnc should be constant. According in a reasonable interpretation of the eclipse light curves. Min I = JD Hel 2446887.574+25d.5944E $pm$2 $pm$2 may be useflul as new light elements for future observations.

• Journal of Welding and Joining
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• 제27권1호
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• pp.71-78
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• 2009

In the circumferential welding of pipe, welding phenomenon changes with the position of pipe. Especially in the overhead position, back bead of vertical-up position would be sunk. To investigate the size of back bead and keyhole with the change of the flow rate of pilot and shield gas at each position, bead-on plate welds were conducted on 6mm thickness SS400 with inclined-up position. When the rest of welding conditions remained constant, the width of back bead was increased as the flow rate of pilot gas was increased. And back bead tended to convex as the flow rate of shield gas was increased.

• 천문학회보
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• 제42권1호
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• pp.59.1-59.1
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• 2017

Massive Population III black hole binary systems are one of the suggested candidate sources of the recently detected gravitational wave radiation (GWR). GWR detection from a black hole binary system requires a sufficiently short orbital separation at the time of their formation, such that they would undergo coalescence within the Hubble time. This condition cannot be simply fulfilled by a short initial period, because binary interactions such as mass transfer and common envelope evolution can largely change the orbital parameters and the masses of stellar components. Here, we discuss the possibility of black hole binary mergers from massive Pop III binary systems, using a new grid of Pop III binary evolutionary models with various initial primary masses ($20M_{\odot}{\leq}M{\leq}100M_{\odot}$) and initial separations, for different initial mass ratios (q = 0.5 - 0.9).

• 한국자기학회지
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• 제20권2호
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• pp.68-74
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• 2010

핵자기공명은 물질 내부의 국소적인 스핀 환경에 대한 정보를 제공하기 때문에 자성체 연구에 대단히 유용하다. 자성체 내 이온의 원자가 혹은 자기모멘트, 스핀들의 기울어짐각, 오비탈 상태 등을 직접 측정할 수 있게 해주며 자성이온들의 위치나 자구와 자구벽의 변화 등에 대한 정보를 제공한다. 이렇게 정보를 제공할 수 있는 단순화된 원리를 적용사례를 들어 설명한다.

• Journal of Astronomy and Space Sciences
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• 제10권1호
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• pp.17-27
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• 1993

The orbit characteristics and perturbation effects of an artificial satellite with critical inclination have been studied. The critical inclination problem in artificial satellite theory is treated as Ideal Resonance Problem(IRP). The KITSAT-1 satellite launched by Arian 42P at Guiana in August 11, 1992 has orbital inclination close to the critical value cos-1(1/√5). In that case, there is a singularity in some perturbation terms and perigee of the orbit is fixed because d$\omega$/dt is theoretically equal to zero. But actually the long periodic behaviour in argument of perigee, $\omega$ shows a small oscillation. The causes of the oscillation and the relativistic effect in IRP have been studied and applied to the KITSAT-1. The geo-potential perturbation terms which are seperated inclination terms have been obtained using Algebraic manipulation. Also luni-solar disturbing funtion based on the relative position of the sun, moon, and satellite has been obtained. Phase portraits are used to depict the change of eccentricity and grgument of perigee. The variations of each orbital elements have been obtained in case of the KITSAT-1.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.415-420
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• 2013

Effect of chemical substitution at the para-position of the thiophenoxyl radical has been theoretically investigated in terms of energetics, structures, charge densities and orbital shapes for the ground and first electronically excited states. It is found that the adiabatic energy gap increases when $CH_3$ or F is substituted at the para-position. This change is attributed to the stabilization of the ground state of thiophenoxyl radical through the electron-donating effect of F or $CH_3$ group as the charge or spin of the singly-occupied molecular orbital is delocalized over the entire molecule especially in the ground state whereas in the excited state it is rather localized on sulfur and little affected by chemical substitutions. Quantitative comparison of predictions based on four different quantum-mechanical calculation methods is presented.