• Journal of Welding and Joining
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• v.17 no.6
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• pp.38-45
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• 1999

Shielding gas has significant effects on arc stability, metal transfer and weld quality in the gas metal arc welding (GMAW) process. The double gas-shielded MAG(DMAG) and auxiliary gas-shielded MAG (AMAG) torches are investigated for their capability to provide argon-rich gas mixture using small amount of argon gas through the inner and auxiliary nozzles, respectively. Argon composition with the DMAG torch is calculated numerically, and compared with the measured data using the gas chromatogrphy. Gas flow pattern of the DMAG torch is calculated to change from the laminar to turbulent flow when total gas flow rate becomes larger than 4.5 liter/min at room temperature. While argon-rich shielding gas was obtained using both the AMAG and DMAG torches, the AMAG torch provides higher argon composition than the DMAG torch, which demonstrates that argon gas can be utilized more efficiently with the AMAG torch.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1172-1174
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• 1998

Spatial(radial and height) distributions of excited argon species are measured for an inductively coupled plasma under five operating conditions: 1) no carrier gas, 2) carrier gas without aerosol, 3) carrier gas with desolvated aerosol, 4) carrier gas with aerosol, 5) carrier gas with aerosol and excess lithium. A complete RF power mapping of argon excited states is obtained. The excited states of argon for a typical analytical torch rapidly diffuse towards the center in the higher region of the plasma. The presence of excess lithium makes no significant change in the excited states of argon. The increase in the RF power increases the intensity of argon excited states uniformly across the radial coordinate.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.7
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• pp.76-84
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• 2005

For flight loads analysis of Smart UAV, applicable regulations and loads conditions should be prepared in advance, and modeling for aerodynamics, weight, and structure should be performed. Panel method is usually adopted for aircraft loads analysis to obtain aerodynamic loads. In this study, ARGON which is a multidisciplinary fixed wing aircraft design software co-developed by KARI and TsAGI was used for loads analysis. ARGON can be utilized for flutter and stress analysis as well as for flight and ground loads analysis. In this paper, flight loads analysis of Smart UAV which is a FAR 23 category airplane was performed with ARGON and the results were presented.

• Journal of Welding and Joining
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• v.17 no.6
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• pp.46-52
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• 1999

The auxiliary gas-shielded MAG (AMAG) process, which was devised to provide an argon-rich shielding environment using small amount of argon gas, was investigated experimentally to figure out its effects on metal transfer and weld quality. Proper conditions for the AMAG process including the argon gas ratio, position and direction of the auxiliary nozzle were determined experimentally. Performance of the AMAG process was compared with that of the double gas-shielded MAG(DMAG) and MAG processes by monitoring the bead profile, current and voltage waveforms. The AMAG process was found to provide better bead profile, more stable arc and wider operating range of spray transfer mode compared with the DMAG process. In general, performance of the AMAG process using the argon ratio of 30% was comparable to that of the MAG process using 80% argon and 20% CO₂ gas.

• Proceedings of the Korean Vacuum Society Conference
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• 1999.07a
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• pp.63-63
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• 1999

The stability of hydrogenated amorphous silicon (a-Si:H) films under the light soaking are very important since the applications of a-Si:H films are solar cells, color sensors, photosensors, and thin film transistors(TFTs). We found the changes of the electric conductivity and the conductivity activation energy (Ea) of a-Si:H films by argon radical annealing. The deposition rate of a-Si:H films depends on the argon radical annealing time. The optical band gap and the hydrogen contents in the a-Si:H films are changes along the argon radical annealing time. We will discuss the microscopic processes of argon radical annealing in a-si:H films.

• Journal of the korean academy of Pediatric Dentistry
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• v.25 no.2
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• pp.368-382
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• 1998

The purpose of this study is to evaluate and compare the results of argon laser for 5 seconds, argon laser for 10 seconds, and visible light for 40 seconds photo-polymerization in compressive strength, microhardness, curing depth, temperature rising during polymerization, and polymerization shrinkage. Hybrid type composite resin(Z-100) and compomer(Dyract) were used to be compared. The compressive strength was measured by an Instron(1mm/min cross head speed) in 60 specimens and the microhardness of the surface was expressed by Vickers Hardness Number(VHN) in 30 specimens. The curing depth was evaluated comparing the different values of upper and lower VHN according to irradiation time and thickness for the light source polymerization in 60 specimens. The temperature rising during photopolymerization was observed by the temperature change with thermocouple sensitizer beneath 40 specimens at the argon laser for 10 seconds and visible light 40 seconds irradiation. The polymerization shinkage was evaluated by calculating the decrease of % volume by using a dilatometer in 30 specimens. The results were as follows ; 1. In the case of compressive strength, the argon laser polymerization groups were higher than visible light group in Z-100 (p<0.05). In Dyract, the argon laser 5 seconds group did not show a significant difference with the visible light 40 seconds group. The argon laser 10 seconds group showed the markedly low value when compared with other groups (p<0.05) 2. In microhardness, Z-100 was better than Dyract when comparing by VHNs (p<0.05); however, there was not a significant difference between two materials in the visible light 40 seconds group and the argon laser 10 seconds group. 3. In the study of curing depth, Z-100 showed the consistent polymerization in argon laser irradiation because there was no difference in the VHN decrease according to the thickness change. Over the thickness control, the results did not show a significant difference between visible light and argon laser group in Z-100; however, in the case of Dyract, the visible light 40 seconds group was better than the argon laser groups(p<0.05). 4. There was a significant difference between the two materials in temperature rising during polymerization (p<0.05), but not a significant difference between irradiation times, 5. There was not a significant difference between the two materials in polymerization shrink age. The argon laser 5 seconds group was smaller than the other groups (p<0.05). It could be concluded that Z-100 polymerization was recommended to use the argon laser for reduction of the irradiation time while Dyract was recommended to use the visible light polymerization.

• Proceedings of the Materials Research Society of Korea Conference
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• 2002.05a
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• pp.132-132
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• 2002

Diamond is well known as the hardest material in nature. It also has other unique bulk physical and mechanical properties, such as very high thermal conductivity and broad optical transparency, which enable a number of new applications now that large areas of diamond can be fabricated by the new diamond plasma chemical vapor deposition (CVD) technologies. A study on the effects of growth kinetics and properties of diamond films obtained by addition of argon (~7 vol. %) into the methane/hydrogen mixture is carried out using HFCVD system. A negative bias was used as a nucleation enhancement method in addition to the argon dilution. The scanning electron microscopy (SEM) image of surface morphology shows well faceted crystallites with a predominance of angular shapes corresponding to <100> and <110> crystalline surfaces. The nucleation density and growth rate with argon dilution is two orders of magnitude higher than without argon deposition. The Raman spectra show a good quality film whereas XPS spectra show existence of only diamond phase.

• Progress in Superconductivity and Cryogenics
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• v.10 no.4
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• pp.38-42
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• 2008

Miniature J-T cryocooler using nitrogen or argon has been widely adopted in cooling infrared sensor for space/military application and cryosurgery. Argon or nitrogen, however, has relatively low specific cooling power compared to nitrous oxide, but the ultimate operating temperature is much lower than nitrous oxide. On the other hand, nitrous oxide has large specific cooling power, but the operating temperature is limited to its boiling point (>183K). To compromise the different characteristics of these gases, the performance of miniature J-T cryocooler using argon and nitrous oxide mixture is investigated in this paper. Three different compositions of mixture (25/75, 50/50, and 75/25 molar fraction) are blended and tested. The results are compared with the experiments of pure argon and pure nitrous oxide. The experimental results show some encouraging potentiality of mixed refrigerant J-T cryocooler. The critical clogging problem, however, was observed with argon and nitrous oxide mixture, and the lowest achievable temperature with this mixture was limited to the freezing point of nitrous oxide. The paper discusses detailed clogging process of the mixture and suggests an alternative.

• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.1-8
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• 2005

Civil aviation regulation such as FAR and loads analysis procedure based on this was explained, and loads analysis procedure and results for Smart UAV was presented for application case. For loads analysis, applicable regulations and loads conditions should be prepared in advance, and modeling for aerodynamics, weight, and structure should be performed. Panel method is usually adopted for aircraft loads analysis to obtain aerodynamic loads. In this study, ARGON which is multidisciplinary fixed wing aircraft design software co-developed by KARI and TsAGI was used for loads analysis. ARGON can be utilized for flutter and stress analysis as well as for flight and ground loads analysis. In this paper, flight loads analysis of 4-seater canard airplane was performed with ARGON and that results were presented.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.309-312
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• 1999

Fiber Bragg gratings have many applications such as fiber sensors, band-stop filters, add-drop filters, and mode convertors. In this paper, we present the fabrication method of various fiber Bragg gratings by using continuous wave UV-Argon(frequency-doubled Argon) laser. In our experiments, hydrogenation of fibers was used to enhance photosensitivity of fiber. And we fabricated fiber gratings by the phase mask method.