• Proceedings of the KSME Conference
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• 2001.06d
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• pp.54-59
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• 2001

OH radical concentration have been measured in a methane-air partially premixed flames using PLIF. Excitation lines were selected $Q_{1}(6)$ branch, (1,0) band. The system is consisted of Nd:YAG laser, dye laser and frequency doubler to make pump beam for OH radical. On the direct photographs, flame height increases as fuel flow rate and equivalence ratio increase. And on the PLIF images, OH radical is distributed from premixed flame front to nonpremixed flame front through the flame structure with all equivalence ratio. OH overall concentrations increase with equivalence ratio. At the stoichiometric equivalence ratio, the peak of OH radical concentration exists strongly near the inner cone. As equivalence ratio is changed to richer, OH radical distribution goes thinly and the peak is increased as longitudinal direction. As the flow goes to the downstream, OH radical concentration decreases and broadens, because OH radical reacts with another species after OH formation at the initial oxidization. This phenomenon resembles radial distribution. At the l00cc fuel flowrate, the radial peak of OH radical exists from x/R=l.0 to 1.5.

• International Journal of Automotive Technology
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• v.2 no.4
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• pp.165-170
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• 2001

This study is focussed on the investigation of spray characteristics from the high pressure gasoline injector for the application of gasoline direct injection engine. For the analysis of spray structure of high pressure gasoline injector; the laser scattering method with a Nd-Yag laser and the Phase Doppler particle analyzer system were applied to observe the spray development and the measurement of the droplet size and velocity of the spray, respectively. Also spatial velocity distribution of the spray droplet was measured by use of the particle image velocity system. Experimental results show that high pressure gasoline injector shapes the hollow-cone spray, and produce the upward ring shaped vortex on the spray surface region. This upward ring shaped vortex promotes the secondary atomization of fuel droplets and contributes to a uniform distribution of fuel droplets. Most of fuel droplets are distributed under 31$\mu m$ of the mean droplet size (SMD) and the frequency distribution of the droplet size under 25$\mu m$ is over 95% at 7 MPa of injection pressure. According to the experimental results of PIV system, the flow patterns of the droplets velocity distribution in spray region are in good agreement with the spray macroscopic behaviors obtained from the visualization investigation.

• Journal of Photoscience
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• v.10 no.2
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• pp.203-208
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• 2003

Two coupled molecules were successfully synthesized by condensation of amine-donor-substituted barbituric acid derivativies as nonlinear optical chromophores. A flexible spacer of the alkyl chain with different lengths of carbon chains (5 and 6 carbons) was introduced between two chromophores, which prevented crystallization and aggregation of molecules. Two coupled molecules (B-Cn-B, n=5, 6) had glass-transition temperatures on a second heating around 81 and 76$^{\circ}C$ without melting points, respectively. To explore the linear optical properties, thin-films were prepared and examined by a photometry method using Nd:YVO$_4$ CW laser. Also, microscopic and macroscopic nonlinear optical properties were measured by Hyper-Rayleigh Scattering (HRS) and the Maker Fringes method using Nd:YAG ps pulse laser, respectively. In spite of the moderate hyperpolarizabilities of coupled molecules, the second order NLO coefficient (d$\_$33/) was larger than the conventional Disperse Red 1 doped PMMA polymeric system.

• Transactions of Materials Processing
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• v.20 no.2
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• pp.160-166
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• 2011

Weight reduction while maintaining functional requirements is one of the major goals in the automotive industry. The use of lightweight magnesium alloys offers great potential for reducing weight because of the low density of these alloys. However, the formability and the surface quality of the final magnesium alloy product for auto-body structures are not acceptable without a careful optimization of the design parameters. In order to overcome some of the main formability limitations in the stamping of magnesium alloys, a new approach, the so-called "hybrid technology", has been recently proposed for body-in-white structural components. Within this approach, necessary level of mechanical joining can be obtained through the use of lightweight material-steel adhesion promoters. This paper presents the development process of an automotive hybrid hood assembly using magnesium alloy sheets. In the first set of material pairs, the selected materials are magnesium alloy AZ31B alloy and steel(SGCEN) as inner and outer panels, respectively. In order to optimize the design of the inner panel, the stamping process was analyzed with the finite element method (FEM). Laser welding by CW Nd:YAG were used to join the magnesium alloy sheets. Based on the simulation results and mechanical test results of the joints, the determination of die design variables and their influence on formability were discussed. Furthermore, a prototype based on the proposed design was manufactured and the static stiffness test was carried out. The results demonstrate the feasibility of the proposed hybrid hood with a weight reduction of 25.7%.

• Journal of Welding and Joining
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• v.24 no.5
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• pp.22-28
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• 2006

A spacer grid assembly, which is an interconnected array of slotted grid straps and is welded at the intersections to form an egg crate structure, is one of the main structural components of the nuclear fuel assembly for Pressurized Water Reactors (PWRs). The weld quality of spacer grids in PWRs fuel is extremely important for the fuel assembly performance in the nuclear renter. The spacer grid welds are currently evaluated mainly by the metallographic examination although it reveals only cross-points which are welded by the laser beam. This experiment is also to compare the weldability of Zircaloy-4 spacer grids using by the GTA and LB. The effect of node geometries of spacer grids for the GTAW and LBW has been studied and optimum conditions of spacer grid welding have been found. Microstructures and micro-hardness of the GTA and LB welded zones have been also compared.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.112-114
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• 1999

Superconducting multiplexer consisting of hairpin type filters has been designed for the reduction of the physical size of the device. Pulsed laser deposition with a Nd:YAG laser has been used to grow high quality YBCO superconducting films on MgO substrates. Multiplexer has been designed to have the center frequencies at 13.6 CHz and 13.9 GHz on MgO substrate with the size of 20 ${\times}$ 20 ${\times}$ 0.5mm$^3$. It is possible to implement superconducting multiplexer having two passbands on the limited 20 ${\times}$ 20 ${\times}$ 0.5mm$^3$ MgO substrate by adopting hairpin type filters. This type of superconducting device will be useful for the integration of microwave subsystem.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.598-602
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• 2004

Organic light entitling diode panel was fabricated using pulsed laser deposition (PLD) method Nd-YAG laser with Q-Switched and 355 nm pulse was used for the PLD. While TPD(N,N'-Di-[naphthaleny]-N, N'-diphenyl-benzidine) was used as a HTL(Hole transport layer), $Alq_3$(8-Hydroxyquinoline, Aluminum Salt) was used as EML/ETL(Emitting Layer/Electron Transport Layer) Organic pellet was fabricated and employed for the PLD method. The absorbances of the organic films were investigated and the measured absorbance values of TPD and $Alq_3$ films was 362 nm and 399 nm, respectively. The turn-on voltage of the OLED panel was 7.5 V and its luminance was $90\;cd/m^2$

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1033-1036
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• 2004

Si nanocrystallites thin films on p-type (100) Si substrate have been fabricated by pulsed laser deposition using a Nd:YAG laser. After deposition, samples were annealed at the temperatures of 400 to $800^{\circ}C$. Hydrogen passivation was then performed in the forming gas (95% $N_2$ + 5% $H_2$) for 1 hr. Strong violet-indigo photoluminescence has been observed at room temperature from nitrogen ambient-annealed Si nanocrystallites. The variation of photoluminescence (PL) Properties of Si nanocrystallites thin films has been investigated depending on annealing temperatures with hydrogen passivation. From the results of PL, Fourier transform infrared (FTIR), and high-resolution transmission electron microscopy (HRTEM) measurements, it is observed that the origin of violet-indigo PL from the nanocrystalline silicon in the silicon oxide film is related to the quantum size effect of Si nanocrystallites and oxygen vacancies in the SiOx(x : 1.6-1.8) matrix affects the emission intensity.

• Korean Journal of Bronchoesophagology
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• v.15 no.2
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• pp.81-86
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• 2009

A 57 year old human immune virus(HIV)-positive male presented with a progressive dyspnea for 6 months. Chest CT showed multiple polypoid masses arising from upper tracheal wall. Bronchoscopic examination revealed that multiple large cauliflower-like polypoid tumors was obstructing tracheal lumen. They were diagnosed as multiple squamous papillomas and were removed by Nd:YAG laser photocoagulation and rigid bronchoscopic treatment. The tumors were histologically diagnosed as squamous papilloma infected with human papilloma virus(HPV) type 6 and 11 in in-situ hybridization. Rigid bronchoscopy might be safer and more efficient than flexible bronchoscopy for the treatment of multiple tracheal papillomatosis obstructing tracheal lumen because of easy establishment of airway patency and direct use of rigid bronchoscope itself for tumor resection.

• Korean Journal of Optics and Photonics
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• v.15 no.6
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• pp.575-582
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• 2004

We analyse the beam characteristics of the thermal-birefringence compensated symmetric resonator which consists of two laser rods with rod-end curvatures. The numerical results show that the stability and the beam quality can be improved in high power operation region when the rod-ends are made in the form of a negative lens. The thermal birefringence of the symmetric two-rods resonator is shown to be well compensated when the two rods closely contact each other.