• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1511-1515
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• 2014

The multiconfiguration second-order perturbation theory (CASPT2) and complete active space self-consistent field (CASSCF) methods were employed to calculate the geometries and energy levels for the low-lying electronic states of 1,3,5-$C_6H_3Cl{_3}^+$ ion. The CASPT2 values for the 1,3,5-$C_6H_3Cl{_3}^+$ ion were in reasonable agreement with the available experimental values. The current calculations augmented previous theoretical investigations on the ground state and assigned the low-lying excited electronic states of the 1,3,5-$C_6H_3Cl{_3}^+$ ion. The Jahn-Teller distortion in the excited electronic state for the 1,3,5-$C_6H_3Cl{_3}^+$ ion were reported for the first time.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.303-308
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• 1990

The stand alone induction generator has been excited by capacitor bank or voltage source inverters. The conventional excitation methods offer several restrictions on the operation of the induction generator in various operating conditions. To overcome the restrictions, this paper presents the induction generator system excited by the current controlled inverter which operates on the principle of vector control. The proposed control scheme is based on the rotor flux oriented indirect vector control. The steady state characteristics are investigated to yield control ranges under various operating conditions. Through the simulation, it is confirmed that the system has good dynamic characteristics wi thin the controllable ranges given by the steady state analysis.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.27-28
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• 2003

Synthesis and properties of novel excited-state intramolecular proton transfer (ESIPT) materials recently developed in our group are described. Highly efficient ESIPT in polymeric system has been investigated theoretically and experimentally with a semi-rigid polyquinoline (PQH, PQDH) possessing an intramolecular tautomerizable hydrogen bond. Poly(aryl ether) dendrimers of three different generations that are cored with photo-tautomerizable quinoline (QGn, n=1,2,3) were also synthesized and characterized to investigate the effect of dendritic architecture on the ESIPT activity. Stimulated emission and amplified spontaneous emission in these organic materials system are discussed in terms of ESIPT activity.

• Journal of Photoscience
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• v.1 no.1
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• pp.67-68
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• 1994

INTRODUCTION : The photochemistry of nitro chromophore has been the subject of intense study only in recent years. Unlike the carbonyl functional group, of which the photochemistry has been quite extensively studied and fairly well understood, as a result of excellent work done by numerous physical and organic photochemists alike, the nature of photochemistry of nitro group has only recently been systematically explored. The photochemistry of nitro group exhibits general features of the photochemistry of the carbonyl groups such as hydrogen abstraction by the diradical species generated from the n-$\pi$$^*$ excited state of the nitro group. Other photochemical pathways common to the carbonyl group such as the biradical intermidiate formation, photocycloelimination, and cydoaddition reactions are also open for the nitro group. Of all the photochemical reactions of the nitro group mentioned above, hydrogen abstraction by the n-$\pi$$^*$ excited state of the nitro group has drawn much attention by synthetic organic chemists and polymer chemists. In the field of organic synthesis, above mintioned photochemical reaction has been utilized in the photoprotection-deprotection chemistry.

• Journal of Photoscience
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• v.9 no.1
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• pp.29-32
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• 2002

The solvent effect in a series of polar and non-polar solvents of varying dielectric constants and refractive indices has been investigated by studying electronic spectra (S$_1$band) of a series of exalite laser dyes at room temperature (25$\pm$1$\^{C}$). These data are used to determine the magnitude ($\mu$$\_$e/) and direction ($\theta$) of the electric dipole moments in the first electronically excited state. The results indicate that the observed band systems in these compounds may be attributed to ←$\pi$ transition.

• Rapid Communication in Photoscience
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• v.4 no.3
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• pp.59-62
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• 2015

We investigated photo-induced electron transfer (PET) in a dye-labeled peptide, fluorophore-Ala-Gly-Gln-Tyr, employing time-resolved fluorescence. As an effort to develop new functional dyes, we studied an acriflavine derivative for the electron-acceptor in the excited state from tyrosine, an electrondonor in the ground-state. The pH dependence of the fluorescence lifetime of the model peptide indicates that electron transfer between the excited dye and tyrosine occurs when the tyrosine is deprotonated. The proton-coupled electron transfer appears to be sequential rather than concerted. We also report direct time measurements on the end-to-end loop formation processes of the peptide in water.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.52-55
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• 2009

A red phosphor, $(Sr,Ca)_2P_2O_7:Eu^{2+},Mn^{2+}$, for UV-LED was synthesized under a reducing atmosphere, and its luminescent properties were investigated. The phosphor absorbs ultraviolet light at around 400 nm and efficiently emits red light at approximately 610 nm through an energy transfer from $Eu^{2+}$ to $Mn^{2+}$. Using the varied input current test for the phosphor-loaded LED lamps, it was found that the luminescent efficiency of the phosphor decreased with increasing light flux. This might be due to an increased probability of excited-state absorption and the consequent non-radiative relaxation in $Mn^{2+}$ ions in the condition of high photon influx.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.663-669
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• 1999

This paper presents new self excited DC-DC converters such as Buck-boost type, Buck type and also non-inverting Buck-boost type. The proposed converters has the following advantages: simple topology, small number of circuit components, easy control method. Therefore, these converters are suitable for the portable appliances with battery source. It is especially suited for low power DC-DC conversion applications where non isolation output power is usually required. The steady state characteristics of proposed self exciting Buck-boost DC-DC converter are analysis and the result shows good agreement with experimental value. Furthermore the experimental results for 50W class self oscillating Buck-boost DC-DC converter have been obtained, which demonstrate the high efficiency and good performance.

• Proceedings of the KIEE Conference
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• 2000.07b
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• pp.867-869
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• 2000

This paper describes the steady state performance of a self-excited wound type induction generator with stator and rotor windings connected in series along with excitation capacitors. For this purpose a mathematical model is developed by means of the well known generalized machine theory utilizing d-q axis orthogonal transformation. This model can be used to analyze short shunt and long shunt generators as well as shunt generator and the algorithm for this analysis is persented. The characteristics of generators are compared one another by using parameters which are validated by Mostafa et al.

• Wind and Structures
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• v.10 no.3
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• pp.215-232
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• 2007

This paper presents an aeroelastic analysis procedure to highlight the influence of wind velocity on the structural damping and frequency of a long span cable-stayed bridge. Frequency dependent self-excited forces in terms of flutter derivatives are expressed as continuous functions using rational function approximation technique. The aeroelastically modified structural equation of motion is expressed in terms of frequency independent modal state-space parameters. The modal logarithmic dampings and frequencies corresponding to a particular wind speed are then determined from the eigen solution of the state matrix.