• Journal of the Korean Crystal Growth and Crystal Technology
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• v.22 no.3
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• pp.134-138
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• 2012

Recently the preparation magnetic nanoparticles by a pulsed laser ablation in liquid has gained much attention because it is easy to control experimental parameters. Iron oxide magnetic nanoparticles have been prepared by a pulsed laser ablation of ${\alpha}-Fe_2O_3$ target in ethanol at different magnitude of laser energy of 1, 20, 40 and 80 mJ/pulse. It revealed that particle size increases with increasing laser energy. It could be concluded that 40 mJ/pulse is an optimum laser energy for the preparation of iron oxide nanoparticles with uniform size distribution. The nanoparticles are homogeneously dispersed in ethanol and their stability maintained for several months.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.454-456
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• 2009

N-Type $SbI_3$ doped $95%Bi_2Te_3+5%\;Bi_2Se_3$ compounds were newly fabricated by the combination of gas atomization process and Magnetic Pulsed Compaction process. The thermoelectric properties of the MPCed bulks according to consolidation temperatures were investigated by a combination of microscopy, XRD and thermoelectric property testing. The microstructure of MPCed bulk shows homogeneous and fine distribution through consolidated bulks due to the high solidification of compound powders. The research presented the challenges toward the successful consolidation of thermoelectric powder using magnetic pulsed compaction (MPC) and analysis of thermoelectric properties of the consolidated bulks.

• The Journal of Korean Academy of Prosthodontics
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• v.34 no.3
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• pp.489-500
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• 1996

Pulsed Nd : YAG LASER has been applied to various fields in clinical dentistry including the treatment of peri-implantitis. However, LASER can affect properties of matter of dental implants which are important to maintaining the health of peri-implant tissue and can raise its temperature during lasing. So there have been warings of using LASER to treat peri-implantitis. But, the effects of laser on dental implants itself are not certain yet. So we measured the temperature rising, examined matter of properties by SEM and EDX before and after pulsed Nd : YAG lasing various intensity. 7 TPS implants and 7 HPS implants were used and pulsed Nd : YAG LASER was used in 0.3W, 1.0W, and 2.0W. 1. 2.0W LASER made polished neck portion of HPS implants reach $39.2^{\circ}C$ after 5 seconds lasing. 2. LASER made crater-like defects on plasma sprayed surface and surfaces were melted and divided by fragments after lasing. 3. There was no specific evidence of element change after lasing.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.525-527
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• 2008

N-Type $SbI_3$-doped $95%{Bi_2}{Te_3}-5%{Bi_2}{Se_3}$ compounds were prepared by a gas atomization and Magnetic Pulsed Compaction process. The dynamic recrystallization and thermoelectric properties of the MPCed bulks with consolidation temperatures and times were investigated by a combination of microscopy, XRD and thermoelectric property testing. The microstructure of MPCed bulk shows homogeneous and fine distribution through consolidated bulks due to dynamic recrystallization during hot MPC. This research presented the challenges toward the successful consolidation of thermoelectric powder using magnetic pulsed compaction (MPC).

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.59.2-59.2
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• 2015

Modification of film structure and properties in inductively-coupled plasma (ICP) assisted dc and pulsed dc sputtering has been reported by Oya and Kusano [1] and by Sakamoto, Kusano, and Matsuda [2], showing drastic changes in films structure and properties by the ICP assistance in particular to the pulsed dc discharge. Although mechanisms involved in the modification has been reported to be the increase in energy transferred to the substrate, details of effects of low-energy ion bombardment on the modification and origin of an anomalous increase in the ion quantity by the ICP assistance to the pulsed dc discharge have not been discussed. In this presentation, mechanisms involved in film structure and property modification in ICP assisted dc and pulsed dc sputtering, in which a number of low-energy ions are formed, will be discussed based on ion energy distribution as well as effectiveness of energy transfer to the substrate by low energy particles [3]. The results discussed in this presentation will emphasize the fact that the energetic particles playing an important role in the film structure modification are those to be deposited, but not those of inert gas, when their energies range in less than 100 eV in the pressure range of magnetron sputtering.

• Journal of Oral Medicine and Pain
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• v.23 no.1
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• pp.1-9
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• 1998

The aim of the study was to evaluate the anesthetic Effecs of pulsed Nd:YAG laser irradiation to the oral mucosa and the teeth. Twenty subjects who didn't have a history of significant systemic or current oral disease were included in this study. All the subjects were divided randomly into the experimental group and the control group with 10 for each group. Pain thresholds were measured with Weighted Needle Pinprick Sensory Threshold Test for the mucosal surface of lower lip and with electric pulp test for the upper right central incisor respectively, before and immediately after pulsed Nd:YAG laser irradiation in the condition of 2 watt, 20pps for 2 minute at 10mm distance. The experiment was double-blinded clinical trial. The results were as follows : 1. The mean pain threshold of the mucosal surface of lower lip for Weighted Needle Pinprick Sensory Threshold Test was 2.94(1.00g for the contral group respectively, and there was no statistical difference between two groups. 2. The mean pain threshold of the mucosal surface of lower lip was significantly increased immediately after pulsed Nd:YAG laser irradiation. 3. The mean pain threshold of the upper right central incisor for eledtric pulp test was 34.50(4.97V in the experimental group and 34.00(13.08V in the control group respectively, and there was no statistical difference between two groups. 4. The mean pain threshold of the upper right central incisor was significantly increased immediately after pulsed Nd:YAG laser irradiation.

• Journal of Electrical Engineering and Technology
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• v.8 no.5
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• pp.1157-1162
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• 2013

We proposed AlGaN/GaN high-electron-mobility transistors (HEMTs) using thermal oxidation for NiOx passivation. Auger electron spectroscopy, secondary ion mass spectroscopy, and pulsed I-V were used to study oxidation features. The oxidation process diffused Ni and O into the AlGaN barrier and formed NiOx on the surface. The breakdown voltage of the proposed device was 1520 V while that of the conventional device was 300 V. The gate leakage current of the proposed device was 3.5 ${\mu}A/mm$ and that of the conventional device was 1116.7 ${\mu}A/mm$. The conventional device exhibited similar current in the gate-and-drain-pulsed I-V and its drain-pulsed counterpart. The gate-and-drain-pulsed current of the proposed device was about 56 % of the drain-pulsed current. This indicated that the oxidation process may form deep states having a low emission current, which then suppresses the leakage current. Our results suggest that the proposed process is suitable for achieving high breakdown voltages in the GaN-based devices.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.390-395
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• 2013

Nanocrystalline CrN films were deposited on Si (100) substrates by means of asymmetric pulsed DC reactive magnetron sputtering. We investigated the growth behavior, corrosion resistance and mechanical properties of CrN films with a change in the duty cycle and pulse frequency. The grain size of the CrN films decreased from 25.4 nm to 11.2 nm upon a decrease in the duty cycle. The corrosion potentials for the CrN films by DC sputtering was approximately - 0.6 V, and it increased to - 0.3 V in the CrN films which underwent pulsed sputtering. The nanoindentation hardness of the CrN films also increased with a decrease in the duty cycle. This enhancement of the corrosion resistance and mechanical properties of pulsed sputtered CrN films could be attributed to the densification and surface smoothness of the microstructure of the films.

• KIEE International Transactions on Electrophysics and Applications
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• v.4C no.3
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• pp.91-95
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• 2004

The pulsed power system is widely available for use in pulse generator applications. Generally, the pulse generator is required for very short pulse width and high peak value. We have designed and fabricated our own pulsed type power system and through its use, we investigated microbe removal characteristics. This paper introduces a simple pulsed power system for removing various microbes caused by dirty water. This system includes a 2 times power supply circuit, IR2110 operated by using a fixed voltage regulator 7812 and 7805, and the switching MOSFET (Metal Oxide Semiconductor Field Effect Transistor). We can also control this process by using a PIC one chip microprocessor. As a result, we can obtain good removing characteristics of various microbes by adjusting the charging voltage, the pulse repetition rate and the electrical field inducing time.

• Journal of the Korean institute of surface engineering
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• v.52 no.4
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• pp.211-226
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• 2019

Optical thin films were deposited by using a reactive pulsed DC magnetron sputtering method with a high density plasma(HDP). In this study, the effect of sputtering process conditions on the microstructure and optical properties of $SiO_2$, $TiO_2$, $Nb_2O_5$ thin films was clarified. These thin films had flat and dense microstructure, stable stoichiometric composition at the optimal conditions of low working pressure, high pulsed DC power and RF power(HDP). Also, the refractive index of the $SiO_2$ thin films was almost constant, but the refractive indices of $TiO_2$ and $Nb_2O_5$ thin films were changed depending on the microstructure of these films. Antireflection films of $Air/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/SiO_2/Nb_2O_5/Glass$ structure designed by Macleod program were manufactured by our developed sputtering system. Transmittance and reflectance of the manufactured multilayer films showed outstanding value with the level of 95% and 0.3%, respectively, and also had excellent durability.