• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.6
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• pp.108-113
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• 1996

Periodic gratings for 1.55$\mu$m distributed feedback laser diode (DFB LD) have been fabricated by a holographic interference exposure system using an etalon stabilized Ar ion laser. We obtain a good development condition at developer concentration of 65% and obtain etching rate of 1000$\AA$/min at 20.deg. C by the mixed solution HBr:HNO$_{3}$:H$_{2}$O(1:1:10 in volume ratio). We obtain good first order grating with period of 2400${\AA}[\pm}2{\AA}$ at etching time of 45 sec from grating period and diffraction efficiency measurement, and SEM observation of grating fabricated on InP substrate.

• 한국가시화정보학회:학술대회논문집
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• 2001.12a
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• pp.6-13
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• 2001

A new GA-3D-PTV technique has been constructed to measure an impinging jet. The measurement system consists of three CCD cameras, Ar-ion laser, an image grabber and a host computer. GA (Genetic Algorithm) was used based on one-to-one correspondences in order to take advantage of the combinatorial optimization in tracking the pairs of the whole particles of the two images having a time interval. Two fitness functions were introduced in order to enhance the correspondences of the particles. One was based on a concept of the continuum theory and the other one was based on a minimum distance error. The constructed GA-3D-PTV system was applied in success to the measurement of flow characteristics of the impinging jet.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.8
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• pp.1211-1224
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• 2004

Two round jets. impinged and pulsed. were measured with high-resolution 3D-PTV technique. The measurement system consists of three CCD cameras, Ar-ion laser, an image grabber and a host computer. Two fitness functions were introduced in a genetic algorithm in order to enhance the correspondences of the particles. One was based on a concept of the continuum theory and the other one was based on a minimum distance error. The velocity profiles of the impinged jet obtained by the constructed 3D-PTV system were compared with those of LDV measurements made in this study. The head vortex of the jet was visualized by LIF and was reconstructed by the constructed high-resolution 3D-PTV system for comparisons.

• Journal of ILASS-Korea
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• v.9 no.1
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• pp.1-7
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• 2004

This paper describes the characteristics of injection rate and macroscopic behavior of fuel spray injected from common-rail type diesel injectors with different nozzle geometries. The injection rates according to the nozzle geometries were measured at different energizing duration of the injector solenoid and injection pressure by using the Bosch's injection rate meter based on the pressure variation in the tube. The spray behaviors injected from the different nozzles were visualized using the spray visualization system composed of an Ar-ion laser, an ICCD camera, and a synchronization system at various injection and ambient pressures. It is revealed that VCO nozzle has higher spray tip velocity at the early stage of injection duration and wider spray cone angle than the mini-sac nozzles. Also the spray cone angle is increased with the increase of nozzle diameter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.3
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• pp.246-250
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• 2001

ZnO thin films for light emission device have been deposited on sapphire and silicon substrates by pulsed laser deposition technique(PLD). A Nd:YAG laser was used with the wavelength of355 nm. In order to investigate the emission properties of ZnO thin films, Pl measurements with an Ar ion laser a light source using an excitation wavelength of 351 nm and a power of 100 mW are used. All spectra were taken at room temperature by using a grating spectrometer and a photomultiplier detector. ZnO exhibited Pl bands centers around 390, 510 and 640 nm, labeled near ultra-violet(UV), green and orange bands. Structural properties of ZnO thin films are analyzed with X-ray diffraction(XRD).

• 한국연소학회:학술대회논문집
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• 2006.04a
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• pp.157-163
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• 2006

A new technique utilizing LII signal for the measurement of flow velocities of laminar diffusion flames has been investigated. Soot particles in ethylene diffusion flames are heated by a modulated Ar-ion laser beam. LII signals and their phase angles are measured using a lock-in amplifier at the different flame heights and the axial flow velocity are obtained from the measured phase angle delay. The measured velocities are similar to those from LDV measurements under the same operating conditions. The effects of laser power, LII signal wavelength, and modulation frequency are not sensitive to the velocity measurement. However, the choice of an optical chopper blade type could affect the measurement result. The use of a 6/5 chopper blade showed the better result that is possibly due to the square shape of modulated laser beam. This study successfully demonstrated that axial flow velocities of laminar diffusion flames can be measured by a new technique utilizing LII signal, which does not need particle seeding unlikely to LDV or PIV techniques.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.47-50
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• 1990

Deafs cannot speak straight voice as normal people in lack of feedback of their pronunciation, therefore speech training is required. In this study, fundamental frequency, intensity, formant frequencies, vocal tract graphic and vocal tract area function, extracted from speech signal, are used as feature parameter. AR model, whose coefficients are extracted using inverse filtering. is used as speech generation model. In connect ion between vocal tract graphic and speech parameter, articulation distances and articulation distance functions in selected 15-intervals are determined by extracted vocal tract areas and formant frequencies.

• Progress in Superconductivity
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• v.3 no.1
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• pp.60-64
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• 2001

We have studied properties of step-edge Junction prepared with crystal orientation of sapphire substrate. The Step on sapphire substrates fabricated by conventional photolithography method and Ar ion milling method. $CeO_2$ buffer layer and in-situ YBCO thin film were deposited on the stepped sapphire substrates by a pulsed laser deposition method with the predetermined optimized condition. The step angle was centre fled low angle of about $25^{\circ}$. The YBCO film thickness was varied to obtain various thickness ratios of the film to the step height in a range from 0.7 to 1.2. I-V curves of junction were showed RSJ-behavior, double junction structure, and hysteresis due to the crystal orientation of substrate.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.27-34
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• 2001

A new functionally gradient metal coating method using an atomic mixing technique was developed. In this work the effect of silver atomic mixing on the tribological characteristics of silver$.$ films. has been investigated experimentally. Atomic mixing was implemented by using the, bombardment .of accelerated Ar ions during the thermal evaporation coating process of silver films. Experiments were performed in dry conditions using a ball-on-disk test rig at a load range of 19.6 mN - 17.64 N and a sliding velocity of 20 mm/sec. Results showed that the life of functionally gradient silver coating was enhanced about 100 times more than that of thermally evaporated silver coating and 2 times more than that of IBAD silver coating. The functionally gradient. film also showed low friction and wear compared to those of the evaporated silver and

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.178-181
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• 2005

Quaternary Ti-Si-C-N coatings were deposited on WC-Co substrates by a hybrid coating system of arc ion plating (AIP) and sputtering techniques using Ti and Si targets, in an $Ar/N_2/CH_4$ gaseous mixture. The crystallinity, bending status, and microstructure of the Ti-Si-C-N coatings were measured by X-ray diffractometer (XRD) and X-ray photoelectron spectroscope (XPS), The micro-hardness of Ti(C,N) and Ti-Si-N coatings were about 30 and 40 GPa, respectively. As the Si was incorporated into Ti(C,N) coatings, the Ti-Si-C-N coatings having Si content of $8.9\;at.\%$ showed the maximum hardness value of about 55 GPa. In this work, the microstructure and mechanical properties of Ti-Si-C-N coatings were systematically investigated.