• Transactions of Materials Processing
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• v.13 no.3
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• pp.290-295
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• 2004

Mircolens and microlens V-groove are realized using a novel fabrication technology based on the exposure of a resist, usually PMMA, to deep X-rays and subsequent thermal treatment and inclined deep X-ray lithography, respectively. The fabrication technology is very simple and produces microlenses and microlens V-groove with good surface roughness of several nm. The molecular weight and glass transition temperature of PMMA is reduced when it is irradiated with deep X-rays. The microlenses were produced through the effects of volume change, surface tension, and reflow during thermal treatment of irradiated PMMA. Microlenses were produced with diameters ranging from 30 to $1500\mu\textrm{m}$. The surface X-ray mask is also fabricated to realize microlens arrays on PMMA sheet with a large area. The size of the micro V-groove is fabricated in the range of 12~$60\mu\textrm{m}$.

• Journal of radiological science and technology
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• v.12 no.1
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• pp.17-23
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• 1989

We have developed of the exposure technique for the chest radiography to get different contrast in left and right lung fields simultaneously for the effective diagnosis, I.E., get high contrast to detect tuberculosis, dispersal shadow or exudative lesions of early tuberculosis and get better sharpness and wider latitude to detect growing lesions of lung cancer or lesions overlapped with bones. As a result, by using an additional filter Cu 1.2mm with BX-III screen side and sheet of yellow cellophane on BF-III screen side at the conventional KV ($80KV{\sim}100KV$) for the chest X-ray, we can get similar densities in both left and right lung fields and, thus, this method is considered to be very effective for the quality diagnosis for the routine chest radiography.

• Transactions of Materials Processing
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• v.15 no.1 s.82
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• pp.34-41
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• 2006

Microlens arrays were fabricated by a modified LIGA process composed of the exposure of a PMMA (Polymethylmethacrylate) sheet to deep x-rays and subsequent thermal treatment. A successful modeling and analyses for microlens formation were presented according to the experimental procedure. A nickel mold insert was fabricated by the nickel electroforming process on the PMMA microlens arrays fabricated by the modified LIGA process. For the replication of microlens arrays having various diameters with different foci on the same substrate, both hot embossing and microinjection molding processes have been successfully utilized with the fabricated mold insert. Replicated microlenses showed very good surface roughness with the order of 1 nm. The focal lengths of the injection molded microlenses were successfully estimated theoretically and also measured experimentally.

• Proceedings of the KIEE Conference
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• 2009.04a
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• pp.360-361
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• 2009

1970년대부터 극저주파전자계가 인체건강에 유해한지에 대한 궁금증이 증가하고 있는 실정이다. 또한 그 시기로부터 중요한 이슈에 대한 해결방안과 향후 연구방향에 대한 지표설정을 위해 많은 연구가 행해져 왔다. 본 고에서는 세계보건기구(WHO)가 2007년 극저주파전자계와 인체건강의 관계 검토를 마무리한 공식보고서(Fact sheet No.322) 결과를 고찰해 보고자 한다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.12
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• pp.2662-2669
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• 2002

Recently structural applications of adhesive bonding method have been increased extensively in automobile industry. Adhesively-bonded joints which are used in automobile field are exposed to various environmental conditions. In this study, several environmental factors were concerned to evaluate their effects on the adhesive strength such as air temperature, water temperature, exposed time in water. The specimens are exposed for 1, 10 and 100 hours at various air temperatures to evaluate the effects of the air and water temperature on the adhesive strength. It is proved that the adhesive strength decrease with rising the air and water temperature, and the adhesive strength decrease steeply at the higher temperature with increasing the exposure time in water.

• Korean Journal of Optics and Photonics
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• v.20 no.2
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• pp.118-122
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• 2009

An optical sheet with microlens array (MLA) is designed and fabricated as a substitute for the prism sheets of LCD backlight. Using photoresist thermal reflow, MLAs were fabricated on PET film with thickness of $100{\mu}m$, and we measured the change of MLA profile in terms of exposure time, reflow temperature and reflow time.

• Journal of the Korean institute of surface engineering
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• v.50 no.6
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• pp.455-459
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• 2017

The development of flexible transparent electrode has been paid attention for flexible electronics. In this study, we have developed transparent electrode based on silver nanowires with improved electrical property and stability through ion-beam treatment. The energetic particles of ion-beam could sinter junctions of each silver nanowires and etch out polyvinylpyrollidone(PVP) coated on silver nanowires. The sheet resistance of silver nanowire transparent electrode was reduced by 74%, and the resistance uniformity was increased about 3 times after exposure of ion beam. Moreover, the stability at $85^{\circ}C$ of temperature and 85% of relative humidity could be also improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.284-287
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• 2004

Micro-structures fabricated by X-ray lithography are largely affected by doses, development conditions and other factors. For these reasons, PMMA development rates and its surface profiles under various development conditions were obseued. Development rates were measured in the rage from 1 to 6 $kJ/cm^3$ using the 9C1 white beamline of Pohang light source(PLS). In this experiment, we observed that development rates of stacked PMMA sheet using Si filter were relatively higher than that of not using Si filter. Furthermore, development rates in condition with the acoustic agitation(1 MHz, 3.67 $W/cm^3$) were twice than that in dipping condition with $35^{\circ}C$ developer considering the PMMA sheets-substrate bond strength

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.09a
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• pp.23-28
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• 2005

Microlens arrays were fabricated using a modified LIGA process based on the exposure of a PMMA (Polymethylmethacrylate) sheet to deep x-rays and subsequent thermal treatment. A successful modeling and analyses for microlens formation were presented according to the experimental procedure. A nickel mold insert was fabricated by the nickel electroforming process on the PMMA microlens arrays fabricated by the modified LIGA process. For the replication of microlens arrays having various diameters with different foci on the same substrate, the hot embossing and the microinjection molding processes have been successfully utilized with the fabricated mold insert. Fabricated microlenses showed good surface roughness than the mold insert. The focal lengths of the injection molded microlenses were successfully measured experimentally and also estimated theoretically.

• Journal of Magnetics
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• v.20 no.2
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• pp.103-109
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• 2015

In this study, the authors attempted to produce a medical radiation shielding fiber that can be produced at a nanosize scale and that is, unlike lead, harmless to the human body. The performance of the proposed medical radiation shielding fiber was then evaluated. First, diamagnetic bismuth oxide, an element which, among elements that have a high atomic number and density, is harmless to the human body, was selected as the shielding material. Next, 10-100 nm sized nanoparticles in powder form were prepared by ball milling the bismuth oxide ($Bi_2O_3$), the average particle size of which is $1-500{\mu}m$, for approximately 10 minutes. The manufactured bismuth oxide was formed into a colloidal solution, and the radiation shielding fabric was fabricated by curing after coating the solution on one side or both sides of the fabric. The thicknesses of the shielding sheets prepared with bismuth oxide were 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.0 mm. An experimental method was used to measure the absorbed dose and irradiation dose by using the lead equivalent test method of X-ray protection goods presented by Korean Industrial Standards; the resultant shielding rate was then calculated. From the results of this study, the X-ray shielding effect of the shielding sheet with 0.1 mm thickness was about 55.37% against 50 keV X-ray, and the X-ray shielding effect in the case of 1.0 mm thickness showed shielding characteristics of about 99.36% against 50 keV X-ray. In conclusion, it is considered that nanosized-bismuth radiation shielding fiber developed in this research will contribute to reducing the effects of primary X-ray and secondary X-ray such as when using a scattering beam at a low level exposure.