• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.12a
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• pp.27-32
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• 2006

In this paper, we introduced a LIF measurement method and summarized the theoretical side. When an altered wavelength of laser and electric power, lamp applied electric power, we measured the relative density of the metastable state in mercury after observing a laser induced fluorescence signal of 404.8nm and 546.2nm, and confirmed the horizontal distribution of plasma density in the discharge lamp. Due to this generation, the extinction of atoms in a metastable state occurred through collision, ionization, and excitation between plasma particles. The density and distribution of the metastable state depended on the energy and density of plasma particles, intensely. This highlights the importance of measuring density distribution in plasma electric discharge mechanism study. The results confirmed the resonance phenomenon regarding the energy level of atoms along a wavelength change, and also confirmed that the largest fluorcscent signal in 436nm, and that the density of atoms in 546.2nm ($6^3S_1{\rightarrow}6^3P_2$) were larger than 404.8nm ($6^3S_1{\rightarrow}6^3P_2$). According to the increase of lamp applied electric power, plasma density increased, too. When increased with laser electric power, the LIF signal reached a saturation state in more than 2.6mJ. When partial plasma density distribution along a horizontal axis was measured using the laser induced fluorescence method, the density decreased by recombination away from the center.

• Transactions on Electrical and Electronic Materials
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• v.3 no.3
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• pp.29-33
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• 2002

A procedure was developed for preparing bulk carbon nitride crystals from a polymeric $\alpha$ -C$_3$N$\_$4.2/ at high pressure and temperature in the presence of seeds of crystalline carbon nitride films prepared by a high voltage discharge plasma combined with pulsed laser ablation of graphite target. The samples were evaluated by x-ray photoelectron spectroscopy (XPS), infrared (IR) spectroscopy, Auger electron spectroscopy (AES), secondary-ion mass spectrometry (SIMS), scanning electron microscopy (SEM) and x-ray diffraction (XRD). Notably, XPS studies of the film composition before and after thermobaric treatments demonstrate that the nitrogen composition in $\alpha$ -C$_3$N$\_$4.2/ material initially containing more than 58% nitrogen decreases during the annealing process and reaches a common, stable composition of ~45%. The thermobaric experiments were performed at 10-77 kbar and 350-1200 $\^{C}$.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2335-2342
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• 2007

Laser stimulation has been widely studied and used in clinic. However, electrical response by laser stimulation on meridians has not been investigated. In this study, we compared electric potential of laser and acupuncture stimulation on meridians. We measured electric potential variation at acupoints(Samgan(LI3) and Hapgok(LI4)) on Large Intestine Meridian. In laser stimulation results, average peak electric potential is very low($7.53{\pm}3.44{\mu}V$) for before and after stimulation. However, acupuncture stimulation was performed in ground connection condition and resulted in huge variation of average peak electric potential($2.65{\pm}1.53mV$). That is, the intensity and pattern of electric potential were dependent on the ground connection condition and individual. Also, the electric potential pattern was very similar to the pattern of electric charge and discharge of capacitor. The acupuncture stimulation using a insulating needle resulted in lower average peak electric potential variation($0.25{\pm}0.16mV$) than that of acupuncture stimulation. It might present little electrical response of acupuncture stimulation using insulating needles. In point of electrical response, the laser stimulation was determined to be no acupuncture effect at meridian. Acupuncture stimulation seems to be most effective method to induce electrical response at meridians. The procedure and effect of acupuncture might be considered as energy consensus phenomenon by transportation of bio-ion charge between a practitioner and patient.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.176-180
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• 2002

During the last two decades the laser beam has progressed from a sophisticated laboratory apparatus to an adaptable and viable industrial tool. Especially, in its welding mode, the laser offers high travel speed, low distortion, and narrow fusion and heat-affected zones (HAZ). The principal obstacle to selection of a laser processing method in production is its relatively high equipment cost and the natural unwillingness of production supervision to try something new until it is thoroughly proven. The major objective of this work is focused on the combined features of gas tungsten arc and a low-power cold laser beam. Although high-power laser beams have been combined with the plasma from a gas tungsten arc (GTA) torch for use in welding as early as 1980, recent work at the Ohio State University has employed a low power laser beam to initiate, direct, and concentrate a gas tungsten arcs. In this work, the laser beam from a 7 watts carbon monoxide laser was combined with electrical discharges from a short-pulsed capacitive discharge GTA welding power supply. When the low power CO laser beam passes through a special composition shielding gas, the CO molecules in the gas absorbs the radiation, and ionizes through a process known as non-equilibrium, vibration-vibration pumping. The resulting laser-induced plasma (LIP) was positioned between various configurations of electrodes. The high-voltage impulse applied to the electrodes forced rapid electrical breakdown between the electrodes. Electrical discharges between tungsten electrodes and aluminum sheet specimens followed the ionized path provided by LIP. The result was well focused melted spots.

• Proceedings of the KIEE Conference
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• 1999.07e
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• pp.2434-2437
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• 1999

In order to detect the ultrasonic that is generated by the partial discharge of the heavy electric machinery, a Laser Doppler Vibrometer (LDV) was developed. A Michelson type interferometer which employed heterodyne signal process technique was built to measure the frequency and amplitude of vibration. The output signal of the fast photodetector was a frequency modulated signal centered at 40 MHz. The signal from the detector was amplified and downconverted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that was proportional to the velocity of the moving surface(PZT) was obtained using PLL. The spectrum of the FM signal was analyzed and integration method was introduced to obtain amplitude information. This LDV can be used to measure the vibration of MEMS devices, automobiles, HDD and CDP.

• Proceedings of the KIEE Conference
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• 2000.07c
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• pp.2195-2197
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• 2000

In order to detect the ultrasonic that is generated by the partial discharge of the heavy electric machinery a Laser Doppler Vibrometer (LDV) is developed. A Michelson type interferometer which employed heterodyne signal process technique is built to measure the frequency and amplitude of vibration. The output signal of the fast photodetector is a frequency modulated signal centered at 40 MHz. The signal from the detector is amplified and converted to intermediate frequency centered at 1 MHz after mixing process. The voltage output that is proportional to the velocity of the moving surface(PZT) is obtained using PLL. The spectrum of the FM signal is analyzed and integration method was introduced to obtain amplitude information. This LDV can be used to measure the vibration of MEMS devices, automobiles, HDD and CDP.

• Design & Manufacturing
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• v.16 no.1
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• pp.43-49
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• 2022

As technologies in various industrial fields develop, high-quality parts are required. In the past, precision parts were produced by the contact machining method, but the contact machining method has clear limitations. In order to solve this problem, research on a non-contact processing method has been conducted, and laser processing and electric discharge processing are representative. However, the non-contact method has a problem in that productivity is insufficient, and there is a problem that it takes a lot of time to continuously process microholes. Researchers have developed an electron beam drilling equipment for continuous processing of fine holes, and a vaporization amplification sheet to increase the processing efficiency of the equipment. In this study, a cylindrical vaporization amplification sheet using room temperature curing type silicon was fabricated, and the metal distribution and thickness uniformity of the produced sheet were analyzed. In order to manufacture a cylindrical vaporization amplification sheet, an equipment capable of using centrifugal force was developed, and a sample in which metal powder was evenly distributed and a constant thickness was produced.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.120-120
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• 2003

The metallic oxide nanomaterials including ZnO, Ga$_2$O$_3$, TiO$_2$, and SnO$_2$ have been synthesized by a number of methods including laser ablation, arc discharge, thermal annealing procedure, catalytic growth processes, and vapor transport. We have been interested in preparing the nanomaterials of Ga$_2$O$_3$, which is a wide band gap semiconductor (E$_{g}$ =4.9 eV) and used as insulating oxide layer for all gallium-based semiconductor. Ga$_2$O$_3$ is stable at high temperature and a transparent oxide, which has potential application in optoelectronic devices. The Ga$_2$O$_3$ nanoparticles and nanobelts were produced using GaN single crystals, which were grown by flux method inside SUS$^{TM}$ cell using a Na flux and exhibit plate-like morphologies with 4 ~ 5 mm in size. In these experiments, the conventional electric furnace was used. GaN single crystals were pulverized in form of powder for the growth of Ga$_2$O$_3$ nanomaterials. The structure, morphology and composition of the products were studied mainly by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM).).

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.393-399
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• 2018

It is well recognized that residual stresses of the rails, generated from the manufacturing process including roller straightening and heat treatment, play an important role in determining fatigue and fracture properties of the rails. Thus, it has been a challenge to measure the residual stresses accurately. In this work, contour method was employed to evaluate the residual stresses existing in interior of the rails. The cross section perpendicular to the longitudinal direction of the rail was cut at a very slow rate using electric discharge machining (EDM), after which a laser-based flexural measuring instrument enabled us to precisely measure the flection of the cross section. The measured data were converted into the residual stresses using the commercial finite element package, ABAQUS, through a user-defined element (UEL) subroutine, and the residual stresses of the new rails (50N, KR60, UIC60) with three different specifications were compared.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.81.2-81.2
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• 2012

To fabricate a metal mold for injection molding, hot-embossing and imprinting process, mechanical machining, electro discharge machining (EDM), electrochemical machining (ECM), laser process and wet etching ($FeCl_3$ process) have been widely used. However it is hard to get precise structure with these processes. Electrochemical etching has been also employed to fabricate a micro structure in metal mold. A through mask electrochemical micro machining (TMEMM) is one of the electrochemical etching processes which can obtain finely precise structure. In this process, many parameters such as current density, process time, temperature of electrolyte and distance between electrodes should be controlled. Therefore, it is difficult to predict the result because it has low reliability and reproducibility. To improve it, we investigated this process numerically and experimentally. To search the relation between processing parameters and the results, we used finite element simulation and the commercial finite element method (FEM) software ANSYS was used to analyze the electric field. In this study, it was supposed that the anodic dissolution process is predicted depending on the current density which is one of major parameters with finite element method. In experiment, we used stainless steel (SS304) substrate with various sized square and circular array patterns as an anode and copper (Cu) plate as a cathode. A mixture of $H_2SO_4$, $H_3PO_4$ and DIW was used as an electrolyte. After electrochemical etching process, we compared the results of experiment and simulation. As a result, we got the current distribution in the electrolyte and line profile of current density of the patterns from simulation. And etching profile and surface morphologies were characterized by 3D-profiler(${\mu}$-surf, Nanofocus, Germany) and FE-SEM(S-4800, Hitachi, Japan) measurement. From comparison of these data, it was confirmed that current distribution and line profile of the patterns from simulation are similar to surface morphology and etching profile of the sample from the process, respectively. Then we concluded that current density is more concentrated at the edge of pattern and the depth of etched area is proportional to current density.