• Proceedings of the Korean Society of Marine Engineers Conference
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• 2002.05a
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• pp.49-59
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• 2002

For the purpose of helping development of a GDI(Gasoline Direct Injection) engine, the spray behaviors and fuel distributions were investigated in a single cylinder GDI engine. The experimental engine is a swirl type GBI engine with a SCV(Swirl Control Valve). PLIF(Planar Laser Induced Fluorescence) system with KrF Excimer laser was used for the measurement of the fuel distributions. The effects of SCV opening angle and the Injector specifications, such as the spray cone angle and the offset an91e on the fuel distributions characteristics were investigated. As a result, it was found that the SCV opening angle had a great effect on the fuel distributions in the late stage of compression process by changing flow fields in the combustion chamber.

• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.59-65
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• 2019

Phosphor particles ((Sr,Mg)₂ SiO₄:Eu²⁺ were suspended in deionized water in quartz cuvette and used for measuring liquid temperature field by using two-color-ratio method. In the temperature range of 23~77℃, it showed the relative error from 2.4% to 4% and the temperature sensitivity of 0.65 %/℃ at 30℃ and 0.95 %/℃ at 77 ℃. This performance is comparable to measurement techniques using thermographic liquid crystal or laser induced fluorescence or other thermographic phosphor particle. Among investigated potential error sources, the particle number density affected the intensity ratio and the temperature, but the effect of laser fluence was not evident.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2001.05a
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• pp.75-90
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• 2001

For the purpose of helping development of a GDI(Gasoline Direct Injection) engine, the in-cylinder phenomena, such as the spray behaviors and fuel distributions, unburned fuel, and flame characteristics were investigated in a single cylinder GDI engine. The GDI engine was equipped with a swirl type electronic injector and SCV(Swirl Control Valve). PLIF(Planar Laser Induced Fluorescence) system with KrF Excimer laser was used for the measurements of the fuel distributions. The effects of the injector specifications, such as the spray cone angle and the offset angle on the fuel distributions and combustion characteristics were investigated. As a result, it was found that the injected fuel spray collided with the bottom of the bowl and moved upward along the exhaust side wall of the piston bowl. This fuel vapor played a important role in the instance of spark ignition. The injector specifications has a great influence on the flame characteristics.

• 한국가시화정보학회:학술대회논문집
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• 2002.11a
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• pp.101-104
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• 2002

Simultaneous measurement of turbulent velocity and concentration field in a stirred mixer tank is carried out by using PIV/LIF technique. Instantaneous velocity fields are measured by a $1K\times1K$ CCD camera adopting the frame straddle method while the concentration fields are obtained by measuring the fluorescence intensity of Rhodamine B tracer excited by the second pulse of Nd:Yag laser light. Image distortion due to the camera view-angle is compensated by a mapping function. It is found that the general features of the mixing pattern are quite dependent on the local flow characteristics during the rapid decay of mean concentration. However, the small scale mixing seems to be independent on the local turbulent velocity fluctuation.

• Bulletin of the Korean Chemical Society
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• v.10 no.5
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• pp.411-414
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• 1989

A new sensitive fluorimetric method for the determination of N-methylcarbamates, a class of well known insecticides, based on the derivatization with 7-chloro-4-nitrosobenz-2-oxa-1,3-diazole (NBD-Cl) has been developed. Unreacted NBD-Cl was eluted ahead of derivatized carbamates from C-18 bonded column. An argon ion laser was used as an excitation source of chromatographic eluents and its fluorescence signal was monitored with optical multichannel analyzer. The detection limits of various carbamates were about 100 pg range and the working curves were linear to $10^4-10^5$ nanogram ranges.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.3
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• pp.171-177
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• 2005

In order to investigate the effect of dimethyl ether (DME) on PAH and soot formation, the fuel has been mixed to the counter-flow diffusion flames of ethylene. Laser-induced incandescence and laser-induced fluorescence techniques were employed to measure relative concentrations of soot volume fraction and polycyclic aromatic hydrocarbon (PAH) concentration, respectively. Results showed that even though pure DME flame produces the minimal amount of PAH and soot, the mixture fuel of DME and ethylene could increase PAH and soot formation, as compared to those of pure ethylene flame. This implies that even though DME has been known to be a clean fuel for soot formation, the mixture fuel of DME and the hydrocarbon fuel could produce enhanced production of soot. Numerical simulation demonstrated that methyl (CH$_{3}$) radical generated by the initial pyrolysis of DME can be contributed to the enhancement of PAH and soot formation, through the formation of propargyl (C$_{3}$H$_{3}$) radical.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.11
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• pp.1464-1469
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• 2000

The effects of SiCl$_4$addition on flame structures have been studied in flame hydrolysis deposition (FHD) processes using Coherent anti-Stokes Raman spectroscopy (CARS) and planar laser induced fluorescence (PLIF) to measure temperatures and OH concentrations, respectively. The results demonstrate that even a small amount of SiCl$_4$ addition can change thermal and chemical structures of H$_2$/O$_2$ diffusion flames. When SiCl$_4$ is added to a flame temperature decreases in non-reacting zone due to the increases in both specific heat and density of the gas mixture, while flame temperature increase in particle formation zone due to the heat release through hydrolysis and oxidation reactions of SiCl$_4$. It is also found that OH concentration decreases dramatically in particle formation zone where temperatures increase. This can be attributed to consumption of oxidative species and generation of HCl during silica formation.

• Biomedical Science Letters
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• v.15 no.2
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• pp.153-160
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• 2009

Photodynamic therapy(PDT) is a treatment utilizing the generation of singlet oxygen and other reactive oxygen species(ROS), which selectively accumulate in target cells. The aim of present work is to investigate the photodynamic therapy mechanism of 9-HpbD-a-mediated PDT in HeLa cell lines. We studied the general reactive oxygen species(G-ROS) activation after 9-HpbD-a PDT using fluorescence stain with $H_2DCF-DA$. G-ROS activation observed after 9-HpbD-a PDT and higher activation condition was 1 hour after PDT at 0.5 ${\mu}g/ml$ 9-HpbD-a concentration. Sodium azide and reduced glutathione(the singlet oxygen quencher) could protect HeLa cells from cell death induced by 9-HpbD-a PDT. But D-mannitol(the hydroxyl radical scavenger) could not protect cell death. Singlet oxygen played a decisive role in 9-HpbD-a PDT induced HeLa cell death. Type II reaction was the main type of ROS formation at 9-HpbD-a PDT.

• Bulletin of the Korean Chemical Society
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• v.19 no.3
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• pp.319-323
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• 1998

The phodissociation dynamics of t-butyl hydroperoxide at 280-285 nm has been investigated by measuring laser induced fluorescence spectra of the fragment OH. Measured fractions of the available energy distributed among the fragments are ft=0.56, fr(OH)=0.044, fint(t-BuO)=0.40, and negligible populations of OH are found in vibrationally excited states. By analyzing the Doppler profiles of the spectra of OH, the positive ν-J vector correlation has been obtained. From the measured ν-J correlation and A" propensity in the two Λ-doublets of OH, it is concluded that the dissociation takes place directly from the repulsive surface induced by the σ* ← n transition with the fragment OH rotating in the plane perpendicular to the dissociating O-O bond axis.

• Bulletin of the Korean Chemical Society
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• v.23 no.2
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• pp.184-188
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• 2002

Unsaturated $Cr(CO)_x(1{\leq}x{\leq}5)$molecules were generated in the gas phase from photolysis of $Cr(CO)_6$vapor in He using an unfocussed weak UV laser pulse and their reactions with $O_2$ and $N_2O$ have been studied. The formation and disappearance of the ground state CrO molecules were identified by monitoring laser-induced fluorescence(LIF) intensities vs delay time between the photolysis and probe pulses. The photolysis laser power dependence as well as the delay time dependence of LIF intensities from the CrO orange system showed different behavior as those from ground state Cr atoms, suggesting that the ground state CrO molecules were generated from the reaction between $O_2/N_2O$ and photo-fragments of $Cr(CO)_6$ by one photon absorption. The depletion rate constants for the ground state CrO by $O_2$ and $N_2O$ are $5.4{\pm}0.2{\times}10^{-11}$ and $6.5{\pm}0.4{\times}10^{-12}cm^3molecule^{-1}s^{-1}$, respectively.