• Design & Manufacturing
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• v.15 no.4
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• pp.65-71
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• 2021

In the early days of laser invention, it was simply used as a measuring tool, but as lasers became more common, they became an indispensable processing tool in the industry. Short-wavelength lasers are used to make patterns on wafers used in semiconductors depending on the wavelength, such as CO2 laser, YAG laser, green laser, and UV laser. At first, the hole of the PCB board mainly used for electronic parts was not thin and the hole size was large, so a mechanical drill was used. However, in order to realize product miniaturization and high integration, small hole processing lasers have become essential, and pattern exposure for small hole sizes has become essential. This paper intends to analyze the characteristics through patterns by exposing the PCB substrate through DMD and polygon scanner, which are different optical systems. Since the optical systems are different, the size of the patterns was made the same, and exposure was performed under the optimal conditions for each system. Pattern characteristics were analyzed through a 3D profiler. As a result of the analysis, there was no significant difference in line width between the two systems. However, it was confirmed that dmd had better pattern precision and polygon scanner had better productivity.

• International Journal of Computer Science & Network Security
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• v.24 no.6
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• pp.200-206
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• 2024

Laser induced breakdown spectroscopy (LIBS) technique has been used for the elemental composition of the soils. In this technique, a high energy laser pulse is focused on a sample to produce plasma. From the spectroscopic analysis of such plasma plume, we have determined the different elements present in the soil. This technique is effective and rapid for the qualitative and quantitative analysis of all type of samples. In this work a Q-switched Nd: YAG laser operating with its fundamental mode (1064 nm laser wavelength), 5 nanosecond pulse width, and 10 Hz repetition rate was focused on soil samples using 10 cm quartz lens. The emission spectra of soil consist of Iron (Fe), Calcium (Ca), Titanium (Ti), Silicon (Si), Aluminum (Al), Magnesium (Mg), Manganese (Mn), Potassium (K), Nickel (Ni), Chromium (Cr), Copper (Cu), Mercury (Hg), Barium (Ba), Vanadium (V), Lead (Pb), Nitrogen (N), Scandium (Sc), Hydrogen (H), Strontium (Sr), and Lithium (Li) with different finger-prints of the transition lines. The maximum intensity of the transition lines was observed close to the surface of the sample and it was decreased along the axial direction of the plasma expansion due to the thermalization and the recombination process. We have also determined the plasma parameters such as electron temperature and the electron number density of the plasma using Boltzmann's plot method as well as the Stark broadening of the transition lines respectively. The electron temperature is estimated at 14611 °K, whereas the electron number density i.e. 4.1 × 10¹⁶ cm^-3 lies close to the surface.

• Journal of Chest Surgery
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• v.34 no.9
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• pp.662-671
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• 2001

Background: This study was aimed to assess improvement in myocardial perfusion after TMR by measuring regional myocardial blood flow(RMBF) in porcine model of chronic myocardial ischemia. Material and Method: Ameroid ring was placed around the proximal left circumflex coronary artery in fourteen pigs. After 4 weeks, the control group(7 pigs) underwent rethoracotomy only, and the TMR group(7 pigs) underwent Ho:YAG laser TMR at the circumflex territory. After another 4 weeks, the animals were sacrificed for the measurement of RMBF using colored microspheres. The ratio of RMBF between the circumflex territory and the interventricular septum was calculated and compared. Result: At 4 weeks after ameroid constriction, RMBF of the circumflex territory decreased to 46∼89% of RMBF of the interventricular septum. In five of six animals in the TMR group, RMBF of the circumflex territory at 8 weeks after ameroid constriction was higher compared with RMBF at 4 weeks after ameroid constriction. However, the improvement was statistically significant only in two animals. In three of the four animals in the control group, RMBF of the circumflex territory also increased at 8 weeks compared with RMBF at 4 weeks. The degree of increase in RMBF was not different between the control and the TMR groups. Conclusion: In porcine model of chronic myocardial ischemia, the degree of increase in RMBF of the ischemic area after Ho:YAG TMR was not different from the increase by development of native collateral circulation. Perfusion of ischemic myocardium after TMR is not thought to improve to the degree that can be demonstrated by currently available method of assessment such as radioisotope myocardial scintigraphy.

• Korean Journal of Materials Research
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• v.15 no.4
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• pp.257-262
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• 2005

Nano-sized ZrVFe alloy powders were prepared by the ablation of powder compact in alcobol using a Nd-YAG pulsed Laser. The $Zr_{57}V_{35.}8Fe_{7.2}$ alloy commercially designated as ST707 has long been known as the ideal solution for various vacuum applications. The target for the ablation was sintered pellets of $Zr_{57}V_{35.}8Fe_{7.2}$ alloy powder. The alloy was prepared by arc melting and Hydride-DeHydride method. The ablated powders were mostly circular having fairly large size distribution smaller than 200 nm in all cases. The X-ray diffraction study revealed that the ablated alloy retained the crystal structure of the target alloy. Nevertheless, Fe and V contents in the ablated powder were lower than those in the target alloy. This was believed to result from the high vapour pressures of Fe and V compared to that of Zr. The size of the powders ablated at high energy fluence tends to decrease due at least partly to the breakdown of previously made ones.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.306.1-306.1
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• 2016

ZnO semiconductor material has been widely utilized in various applications in semiconductor device technology owing to its unique electrical and optical features. It is a promising as solar cell material, because of its low cost, n-type conductivity and wide direct band gap. In this work ZnO/Si heterojunctions were fabricated by using pulsed laser deposition. Vacuum chamber was evacuated to a base pressure of approximately $2{\times}10^{-6}Torr$. ZnO thin films were grown on p-Si (100) substrate at oxygen partial pressure from 5mTorr to 40mTorr. Growth temperature of ZnO thin films was set to 773K. A pulsed (10 Hz) Nd:YAG laser operating at a wavelength of 266 nm was used to produce a plasma plume from an ablated a ZnO target, whose density of laser energy was $10J/cm^2$. Thickness of all the thin films of ZnO was about 300nm. The optical property was characterized by photoluminescence and crystallinity of ZnO was analyzed by X-ray diffraction. For fabrication ZnO/Si heterojunction diodes, indium metal and Al grid patterns were deposited on back and front side of the solar cells by using thermal evaporator, respectively. Finally, current-voltage characteristics of the ZnO/Si structure were studied by using Keithly 2600. Under Air Mass 1.5 Global solar simulator with an irradiation intensity of $100mW/cm^2$, the electrical properties of ZnO/Si heterojunction photovoltaic devices were analyzed.

• International Union of Geodesy and Geophysics Korean Journal of Geophysical Research
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• v.26 no.1
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• pp.43-58
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• 1998

The Kwinana Shoreline Fumigation Experiment (KSFE) took place at Fremantle, WA, Australia between January 23 and February 8, 1995. The CSIRO DAR LIDAR measured plume sections from near the Kwinana Power Station (KPS) stacks to up to about 5 km downstream. It also measured boundary layer aerosols and the structure of the boundary layer on some occasions. Both stages A and C of KPS were used as tracers at different times. The heart of the LIDAR system is a Neodymium-doped Yttrium-aluminum-garnet (Nd:YAG) laser operating at a fundamental wavelength of 1064 nm, with harmonics of 532 nm and 355 nm. For these experiments the third harmonic was used because the UV wavelength at 355 nm is eye safe beyond about 50 m. The laser fires a pulse of light 6 ns in duration (about 1.8 m long) and with an energy (at the third harmonic) of about 70 mJ. This pulse subsequently scattered and absorbed by both air molecules and particles in the atmosphere. A small fraction of the laser beam is scattered back to the LIDAR, collected by a telescope and detected by a photo-multiplier tube. The intensity of the signal as a function of time is a measure of the particle concentration as a function of distance along the line of the laser shot. The smoke plume was clearly identifiable in the scans both before and after fumigation in the thermal internal boundary layer (TIBL). Both power station plumes were detected. Over the 9 days of operation, 1,568 plumes scans (214 series) were performed. Essentially all of these will provide instantaneous plume heights and widths, and there are many periods of continuous operation over several hours when it should be possible to compile hourly average plume statistics as well. The results of four days LIDAR observations of the dispersion of smoke plume in the TIBL at a coastal site are presented for the case of stages A and C.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2015.05a
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• pp.24-24
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• 2015

최근 생체재료의 개발이 눈부시게 발전되고 생체적합성이 우수한 표면을 요구함에 따라 생체재료의 표면처리에 대한 연구가 활발히 진행되고 있다. Laser Deposition법은 항공기 부품제조 분야에 주로 사용되고 있으며 최근에 오하이오 주립대 타이타늄합금연구센터를 중심으로 표면처리에 관한 연구가 주로 이루어졌다. 특히 이를 이용하여 치과재료의 표면처리에 응용을 시도하였다. 치과에서 응용될 수 있는 경우는 주로 임플란트는 부분 또는 완전 무치악 환자의 보철수복에 사용되는 보철물의 제작등에 사용될 수 있으며 이중에서도 특히 생체용 임플란트의 표면처리응용으로 임플란트와 조직간의 접합성을 개선하는 표면처리법으로 연구되었다. 임플란트의 성공과 실패는 물성적인 측면에서 임플란트의 형태, 표면거칠기 및 표면처리방법, 초기하중 등에 의하여 좌우되며 임플란트 재료에 작용하는 응력차폐는 생체적합성을 좌우하는 큰 요인이 되고 있다. 이를 위하여 저 탄성계수합금을 설계하지만 하중을 버티는 강도가 낮아지는 단점이 있어 레이저증착법을 이용하여 임플란트재료인 Ti6Al4V합금에 탄성계수가 낮은 Ta, Nb등을 코팅하는 방법을 통하여 이를 해결하고자하는 시도가 이루어지고 있다. 이 방법은 최근의 3D 프린팅의 원리가 되고 있다. 따라서 발표에서는 Laser Deposition방법을 이용하여 치의학분야에서 응용되고 있는 예를 강연하고 응용 가능 분야에 대하여 토론 하고자한다. 또한 펨토레이저를 이용하여 생체합금의 표면처리는 생체활성화를 더욱 증진시키며 이를 위하여 많은 연구 수행되고 있다. 본 발표에서는 매식용 합금 표면에 펨토레이저를 이용하여 텍스춰링하여 세포가 잘 성장 할 수 있는 크기의 조절함으로써 기존의 표면처리와는 다른 효과를 얻을 수 있는 장점을 알아본다. 펨토레이저를 이용하면 여러 가지 형태의 텍스춰링이 가능하며 원형, 사각형등등 자유자제로 형태의 묘사가 가능하고 깊이 또한 쉽게 조절할 수 있는 장점이 있다. 지금까지는 표면 개질에 사용되는 레이저는 주로 Nd:YAG 레이저의 파장을 반으로 줄인 녹색레이저 (${\lambda}=532nm$)를 사용하거나, 자외선파장영역의 레이저를 사용하는 경우가 일반적으로 가장 보편화되었다. 이를 이용하여 제조된 Ti합금에 펨토 초(10-15 second) 펄스폭 대역을 갖는 레이저를 이용하여 나노크기의 미세 요철을 표면에 형성한 후, 나노튜브를 형성하여 그 표면특성의 변화를 알아보고 펨토레이저가 의료분야에 적용되고 있는 예를 살펴보고자 한다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.631-634
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• 2004

The method that exists in Photodynamic Therapy uses Photosensibility drug strongly Influencing tumour accumulation together with photochemical laser effect and makes the structure of tumour be localized and become extinct. The intracavity transformation of the Nd :YAP main radiation 1079 nm was Raman converted in barium nitrate crystal and the Stokes frequency (1216 nm) was doubled using KTP or RTA crystals. The LiF or Cr:YAG crystals are used for the Q-switch. The radiation Parameters were obtained at 100 Hz pump repetition frequency. The average power at 608 nm radiation with LiF and KTP was 700 mW at multi-mode generation. The 3-6 single 10-15 ns pulses were generated during one cycle of pumping. The doubling efficiency with RTA was two times more than with KTP. The cells of Ehrlich adenocarcinoma (0.1 ml) were i.m. implanted in hind thighs of ICR white non-imbred mice. The cells were preliminarily diluted in medium 199 in the ratio of 1 to 5. HpD was intravenous administered in a dose of 10 mg/kg. The left clean-shaven hind leg was irradiated with laser light 21-27 hours after the administration of the preparation. The right non-Irradiated leg of each animal served as a control. The animals with the transplanted tumor that were not injected with HpD sewed as a control to estimate the complex effect (HpD+ irradiation). Before the administration of HpD and on 3 and 4 days after irradiation the tumor size was measured and the percent of the tumor growth inhibition was calculated. The results of animal treatments has shown high efficiency of PDT method for cancer treatment by means 0.608 m high power pulse solid state laser.

• Journal of Yeungnam Medical Science
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• v.12 no.2
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• pp.331-338
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• 1995

Laserthermia is a new method of local hyperthermia using fiber optic guided probe with computer controlled Nd-YAG laser system. We used a synthetic sapphire probe and allowed irradiation with contolled low power laser energy (less than 5W), in different thermal condition (temprature: 38.5~50 degrees C) for 10 minutes, in the normal brain tissue of 18 rabbits. In results, the histological changes of brain tissue was variable (myelin condensation, chromatin condensation, nuclear waving and palisading, RBC discoloration, cell necrosis) in microscopic findings after laser irradiation, but changing area was not occured proportionally in thermal condition level. Cell necrosis appears to over 44.5 degrees C and the distance was about 1.25 mm. This study, using computer controlled laserthermia system for interstitial local hyperthermia, may offer many advantages in the experimental treatment and clinical management of tumor. Minimizing normal tissue damage is now being developed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.1-8
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• 1999

In recent years, concern has been raised about the technique of controlling electrical breakdown by using laser in many fields. Especially, laser has attracted much attention in the Electro-Discharge Machining(EDM) because of its many rrents. 1berefore, this research has been perfonred to obtain fundarrental data for the discharge guide technology by a pulsed Nd:YAG laser which can be awJied to discharge processing machining. 1be experilnnts of laser-guided de discharge have been carried out at low air pressure ranging from 0.2 to 20 torr. The minimum laser-guided de discharge voltage $V_{G.min}$ at the given pressures P and distances d between an anode and a cathode was rreasured It is found that $V_{G.min}$ is much lower than the natural discharge voltage $V_{ND}$, and the values of VGrrin and $V_{ND}$ as a function of P.d has a similar tendency. The laser output energy $E_{out}$ decreases with input pulse duration $t_p$ increasing, and the rrore the value of $t_p$ increases, the higher that of V$V_{G.min}$ is obtained because the number of photons N decreases with $t_p$ increasing. In addition, the laser-guided de discharge range and the discharge guide characteristics as laser outpIt $E_{out}$ was investigated.igated.