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이세복,이재범,방윤수 한국물리학회 2015 Current Applied Physics Vol.15 No.11
1,2-Dihydroxyanthraquinone (alizarin) shows dual emission bands with a large Stokes shift from a “locally-excited (LE)” and “proton-transferred (PT)” tautomers in the excited state. Excited state intramolecular proton transfer (ESIPT) reaction of alizarin is tunable by changing concentration, solvent polarity, excitation wavelength, and etc. ESIPT reaction of alizarin in the excited state was investigated by steady-state absorption/emission spectroscopy and femtosecond transient absorption spectroscopy. In ethanol solution, the lifetime of PT tautomer of alizarin was measured as 87 ps, in addition to 0.35 and 8.3 ps vibrational cooling dynamics for the LE and PT tautomers of alizarin, respectively. In binary mixtures of ethanol and water, the excited state dynamics became more complicated; the LE and PT tautomers appeared to decay with 8.9 and 30.8 ps lifetimes, which is much shorter compared to the lifetime of the PT tautomer in ethanol. A long-lived nonradiative state in the excited states of alizarin was found as well, which was proposed as a “trapped” state with tightly hydrogen-bonded water molecules. The ESIPT reaction of alizarin was blocked in a 1:1 mixture of ethanol-water due to strong hydrogen bonding between water molecules and alizarin, which was further confirmed by the efficient coupling of alizarin to TiO2 nanoparticles in the 1:1 binary mixture of ethanol-water.
이세복,김경돈,정성종,Lee, Se-Bok,Kim, Gyeong-Don,Jeong, Seong-Jong 대한기계학회 2000 大韓機械學會論文集A Vol.24 No.4
The assessment of machined surface is difficult because the freeform surface must be evaluated by surface fairness as well as dimensional accuracy. In this study, the machined freeform surface is modeled by interpolating the data measured on the machine tool into the mathematical continuous surface, and then the surface model is improved with the parameterization to minimize surface fairness. The accuracy reliability of the measured data is confirmed through compensation of volumetric errors of the machine tool and of probing errors. Non-uniform B-spline surface interpolation method is adopted to guarantee the continuity of surface model. Surface fairness is evaluated with the consideration of normal curvature on the interpolated surface. The validity and usefulness of the proposed method is examined through computer simulation and experiment on the machine tool.
이세복(Seybok Lee),여태정(Taejung Yeo),하원필(Wonphil Ha) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In order to develop occupant safety system, airbag module must satisfy various performance targets. One of them is to operate very well in hot and cold temperature conditions and the other is to meet the various injury criteria. In this study, under considering various design variables, driver side airbags are estimated in various experimental conditions such as hot and cold conditions. By using simulation model and design of experiments, the optimal design combination of occupant restraint system is derived. Both drop tower and real crash test are used to make the simulation model more reliable.
이세복(Seybok Lee),이정근(Jungkeun Lee) 한국자동차공학회 2009 한국자동차공학회 학술대회 및 전시회 Vol.2009 No.11
In order to meet the customer’s needs for occupant safety in crash accidents, Many car makers and suppliers are required to develop the active safety system for advanced safety vehicle. Pre-crash system is composed of sensing device, main ECU, electronic braking device and active seatbelt(motorized seatbelt). In this paper, design methodology for active seatbelt based on occupant injuries is proposed. First of all, the occupant injuries are estimated by using computer simulation when the seatbelt slack is appeared. Second, the target performance of active seatbelt is derived by using DOE(Design Of Experiments). Finally, the motor, reduction device and electronic controller are designated and verified to meet the target.
Excited-State Dynamics of Carotenoids Studied by Femtosecond Transient Absorption Spectroscopy
이인구,이세복,방윤수 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.3
Carotenoids, natural antenna pigments in photosynthesis share a symmetric backbone of conjugated polyenes. Contrary to the symmetric and almost planar geometries of carotenoids, excited state structure and dynamics of carotenoids are exceedingly complex. In this paper, recent infrared and visible transient absorption measurements and excitation dependent dynamics of 8'-apo-β-caroten-8'-al and 7',7'-dicyano-7'-apo-β- carotene will be reviewed. The recent visible transient absorption measurements of 8'-apo-β-caroten-8'-al in polar and nonpolar solvents will also be introduced to emphasize the complex excited-state dynamics and unsolved problems in the S2 and S1 excited states.
Myungsam Jen,이세복,방윤수 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.3
Time-resolved electronic and vibrational spectroscopy has been applied to understand ultrafast excited state dynamics of all-trans-retinal. Femtosecond transient absorption spectroscopy provides an overview of the excited-state dynamics of all-trans-retinal, and femtosecond-stimulated Raman and infrared absorption measurements, which have not been reported previously, provide further details of the structural changes in the excited states. Three singlet excited states and one triplet excited state have been identified from these experimental results, which are in good agreement with many previous reports. A change in the energy order of the singlet excited state of all-trans-retinal between in polar and nonpolar solvents abruptly modifies the excited state dynamics. The intersystem crossing to the T1 state from the S1 state (nπ*) almost disappears in polar solvents, whereas the fluorescence from S3 and S2 states (ππ*) is almost absent in nonpolar solvents.