• 한국산업보건학회지
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• 제8권1호
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• pp.146-154
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• 1998

This study was designed to investigate the workers' exposure level to electromagnetic field(EMF) in accordance with the VDT arrangement in the work place and distance from VDT. Author compared the exposure strength of EMF in line group(workers exposed to EMF from both front and back side) and in shielding group(workers exposed to EMF exclusively from front side). The levels of EMF at 30cm and 50cm from front side and at 30cm from back side of VDT were also measured. The result were as follows: 1. Mean distance between a monitor and a worker in shielding group ($47.7{\pm}8.7cm$) significantly longer than that in line group($44.3{\pm}7.2cm$). Strength of EMF in shielding group [$1.3{\pm}0.7V/m$ (electric field) and $18.2{\pm}11.5mA/m$ (magnetic field) were lower than in line group [$1.4{\pm}0.6V/m$ and $26.6{\pm}11.6mA/m$, respectively] at the workers' position. 2. The strength of EMF was decreased with the distance from VDT. The strength at 70cm from VDT was nearly the same as the background strength in the ordinary office rooms. 3. Working distance from 9 inch monitor was significantly shorter than that from 14 inch and wider sized monitors. 4. The strength of EMF in extremely low frequency spectrum of color monitors was higher then that of black and white monitor. 5. Metal coated filters significantly decreased the electric field strength of EMF when earth line was connected. Metallic shield was effectively decreased the EMF strength from VDT, but wooden shield was not. From the above results, line type arrangement of VDT in the work place using metallic shield at the back side of VDT, and metal coated filter to monitor with application of earth line were recommended. It is also recommended to maintain workers position to be 60cm or more distance from monitor and 140cm or more between VDTs for minimizing workers' exposure to EMF.

• Journal of Welding and Joining
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• 제30권5호
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• pp.46-50
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• 2012

This study was carried out to investigate the effect of welding parameters such as shielding gas compositions welding voltage and welding current on the pore formation in the weld beads of galvanized steel pipes produced with gas metal arc welding. The porosity was evaluated and rated by metallography and radiographic test in terms of weight percentage, number and distribution of pores in weld beads. The porosity increased with increasing welding voltage and current, in which Ar gas produced the most porosity while $Ar+5%O_2$ generated the least porosity. It was found that the porosity could be reduced by selection of the proper gas mixture composition such as $Ar+5%O_2$ and $Ar+10%CO_2$ and by using current (130~150A) and voltage(16~20V).

• Journal of Welding and Joining
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• 제16권1호
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• pp.77-87
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• 1998

This paper deals with the effect of laser welding parameters on the weld formation. Thin steels for automotive application were prepared so as to be welded with high power carbon dioxide laser system. Major process parameters were position of focus and travel speed. The effect of shielding gas was also discussed by employing the high speed photometry. Test results showed that the optimal position of focus varied in accordance with the joint configuration; bead-on-plate, butt or lap welding. It was recommended that the position of focus for the lap welding be located at slightly inner part of the material to be welded. In this case, however, it was noticeable that the weld penetration ratio, d/t$_{0}$ dropped drastically at the critical region. Results also demonstrated that both the bead width and penetration reduced as the travel speed increased. The penetration ratio showed two distinct regions; stabilized zone at the lower range of the travel spped and sudden drop zone at the higher range of travel speed. Lower limit of the penetration for acceptable weld was proved to be about 90% of the parent metal thickness based on the physical properties of the weld. Mixed gas application for both the shielding of molten metal and laser induced plasma control was recommended as far as the penetration was concerned.d.

• 예술인문사회 융합 멀티미디어 논문지
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• 제9권6호
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• pp.711-718
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• 2019

전자파 측정기와 스펙트럼 분석기를 통하여 가정에서 사용되고 있는 여러 종류의 가전제품에서 발생하는 전자파 발생 거동을 조사하였다. 전자레인지 동작 중에 30cm 떨어진 지점에서 측정된 전자파 전력은 8~11mW/㎡ 범위로 측정되었고 저주파 자기장의 강도는 60~80mG, 전기장 강도는 150~160V/m로 측정되었다. 스마트폰 무선 충전 패드의 경우 10cm 떨어진 지점에서 전자파 전력 0.4mW/㎡, 전기장 160V/m, 자기장 1mG로 측정되었다. 전자레인지 및 무선 충전 패드의 경우 10cm 이내로 근접하여 사용할 경우 전기장 크기가 인체 보호 기준을 초과하는 큰 값으로 측정되었으며 인체 유해성이 우려된다. 한편 TV, 헤어드라이어, 냉장고 등의 가전제품은 전자파, 전기장, 자기장 모두 매우 낮은 수준으로 나타났으며 인체 유해성은 없는 것으로 보인다. 전자파 차폐재의 경우 금속 재질의 Cu 패브릭과 메탈 포일은 높은 수준의 전자파 차단 성능을 나타내었으나, 폴리머 필름의 경우는 전자파 차단 특성이 낮은 수준으로 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1120-1125
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• 2004

Welding characteristics of STS304 stainless steel and Inconel 600 using a continuous wave Nd:YAG laser are experimentally investigated. Alloy 600 being used in steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion environment, stress corrosion cracking can occur on this material. Presented here are the results from a series of experiments in which dissimilar metal welds were made using the gas tungsten arc welding process with pure argon shielding gas. But It is well known that solidification cracking susceptibility of austenitic alloys depends on the solidification temperature range and amount/distribution of solute rich liquid that exists at the terminal stages of solidification. An experimental study was conducted to determine effects of welding parameters and to optimize those parameters that have the most influence on eliminating or reducing the extent welding zone formation at dissimilar metal welds.

• Journal of Welding and Joining
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• 제5권3호
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• pp.38-45
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• 1987

An investigation was conducted to find out the factors influencing on the impact toughness of austenitic-and duplex stainless steel weld metal. Various welding process with commerically available consumables was adopted to get weld doposited metal. The oxygen content of each weld metal was very sensitiive to welding process, involving flux composition, shielding gas and structural features. The results of this study show tat the content of oxygen as an oxide inclusion significantly affects impact toughness, and .delta.-ferrite distribution is also correlated with resultant toughness value.

• 한국정밀공학회지
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• 제21권11호
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• pp.53-60
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• 2004

Laser welding techniques have been characterised for various materials. In this paper, the laser weldability of STS304 stainless steel and Inconel 600 at dissimilar metal welds using a continuous wave Nd:YAG laser are experimentally investigated. Inconel 600 is being used in a steam generator tubing of pressurized water reactor(PWR) exposed to some corrosion. Stress corrosion cracking can occur on this material. An experimental study was conducted to determine effects of welding parameters, on eliminating or reducing the extent welding zone formation at dissimilar metal welds and to optimize those parameters that have the most influence parameters such as focus length, power, beam speed, shielding gas, and wave length of laser were tested.

• 한국방사선학회논문지
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• 제13권7호
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• pp.1015-1024
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• 2019

최근 의료분야에서 X선은 질병의 진단 및 치료영역에서 필수적으로 요구되며, 영상의학 기술의 발전과 더불어 X선의 이용은 지속적으로 증가하는 추세지만, X선은 방사선 피폭의 단점을 가지고 있다. 방사선피폭을 방어하기 위해 임상에서는 납 방호도구를 사용하지만 납은 중금속으로 분류되어 납중독 등 인체에 유해한 반응을 일으킬 수 있다. 따라서 본 연구는 FDM(Fused Deposition Modeling)방식의 3차원 프린터의 재료를 이용하여 제작한 차폐체의 유용성을 알아보고자 한다. 필라멘트의 선감약계수를 확인하기 위해 PLA, XT-CF20, Wood, Glow, Brass를 이용해 팬텀을 제작 하고, CT scan을 하였다. 그리고 100 × 100 × 2 mm 크기의 차폐 시트를 모델링하고, 진단용 X선발생장치와 조사선량계를 이용하여 선량 및 차폐율을 측정하였으며, 납 방호도구와의 차폐율을 비교하였다. 실험결과 Brass의 CT number가 가장 높게 측정되어 Brass를 이용하여 차폐시트를 제작하였으며, 진단용 X선발생장치로 확인한 결과 100 kV, 40 mAs 조건으로 X선 조사 시 6 mm 두께의 차폐시트에서 차폐율이 90 % 이상으로 측정되어 apron 0.25 mmPb보다 차폐율이 높은 것을 확인하였다. 본 연구의 결과 3차원 프린팅 기술로 제작한 차폐체가 진단용 X선 영역에서 높은 차폐율을 보이는 것을 확인하였으며, 납 방호도구와의 비교를 통하여 납을 대체하여 방사선 방호도구로서의 가능성을 알 수 있었다.

• Corrosion Science and Technology
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• 제16권6호
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• pp.278-284
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• 2017

The effects of TIG welding and post-treatment procedures on the microstructure and the pitting corrosion resistance of welded lean duplex stainless steel S82441 were investigated. Autogenous TIG welding was used with different amounts of heat input and shielding gases such as Ar, and mixtures of $Ar-N_2$ and Ar-He. The addition of 5% to 15% of nitrogen to argon practically did not affect the level of the pitting corrosion resistance. However, the application of gas mixtures (50% Ar + 50% He) resulted in a significant decrease in pitting corrosion resistance. We found that increased current (200 A and 250 A) led to lower values of CPT of welds compared with welds obtained with 50 A, 100 A and 150 A. In addition, the removal of the weld surface layer (0.2 ~ 0.3 mm thickness) in most cases not only resulted in a significant increase in resistance to the pitting corrosion but also post-treatment of weld, implying that corrosion resistance depended on factors such as surface roughness or the presence of undesirable oxides.

• 한국해양공학회지
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• 제5권1호
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• pp.81-87
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• 1991

In this paper, an attempt has been taken for improving the weldability of wer welds of TMCP steel plate by shielding around weld arc surroundings. The principal results of this experimental investigation can be summarized as follows: 1) The cooling rates resulting from wet wlds with the developed electrode on TMCP steel plate could be lower than that of the non-shieled wet welds. 2) The metallurgical characteristics in umderwater wet welds of TMCP steel plate and the developed electrode could be improved by shielding around weld arc surroundings.