• Journal of Sensor Science and Technology
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• v.28 no.3
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• pp.152-156
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• 2019

An ultraviolet (UV) image sensor is an extremely important optoelectronic device used in scientific and medical applications because it can detect images that cannot be obtained using visible or infrared image sensors. Because photodetectors and transistors are based on different materials, conventional UV imaging devices, which have a hybrid-type structure, require additional complex processes such as a backside etching of a GaN epi-wafer and a wafer-to-wafer bonding for the fabrication of the image sensors. In this study, we developed a monolithic GaN UV passive pixel sensor (PPS) by integrating a GaN-based Schottky-barrier type transistor and a GaN UV photodetector on a wafer. Both individual devices show good electrical and photoresponse characteristics, and the fabricated UV PPS was successfully operated under UV irradiation conditions with a high on/off extinction ratio of as high as $10^3$. This integration technique of a single pixel sensor will be a breakthrough for the development of GaN-based optoelectronic integrated circuits.

• Textile Coloration and Finishing
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• v.23 no.4
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• pp.284-289
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• 2011

Poly(phenylene sulfide)(PPS) films were photooxidized under UV/ozone irradiation. The effect of UV energy on the surface properties of the UV-irradiation PPS films were investigated by the measurement of reflectance, surface roughness, and contact angle. Reflectance decreased at the wavelength of 400nm and the surface roughness increased with increased UV energy. The improvement in hydrophilicity with increased $O_{1s}/C_{1s}$ was caused by the introduction of hydrophilic $SO_2$ bond. Surface energy increased from 46.6 to $78.3mJ/m^2$ with increased UV energy up to $21.2J/cm^2$. Also zeta potential decreased with increased UV energy. The increased dyeability to cationic dyes may be due to the photochemically introduced anionic and dipolar dyeing sites on the PPS films surfaces.he photochemically introduced anionic and dipolar dyeing sites on the PPS films surfaces.

• Textile Coloration and Finishing
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• v.24 no.4
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• pp.281-287
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• 2012

Poly(phenylene sulfide) films containing acetophenone as a photoinitiator were photocrosslinked under UV irradiation using a continuous UV irradiator. The gel fraction of the irradiated PPS in 1-Chloro naphthalene reached 94.7% with increasing UV energy and the photoinitiator concentration in the film upto $200J/cm^2$ and 12wt% respectively. Solid state $^1C$ NMR analysis suggested that the crosslinking occurred between the phenylene chains in PPS, indicating that the acetophenone may the phenylene hydrogens and subsequently adjacent polymer radicals could be recombined to form the crosslinked structure. The crosslinking improved the thermal behavior of PPS such as loss of $T_g$ and $T_c$, higher melting point and lower melting enthalphy as well as significantly higher peak pyrolysis temperature as much as $63.5^{\circ}C$. Surprisingly the tensile toughness of the most crosslinked PPS increased by 842%, resulting from the substantial enhancements in tensile modulus, strength and strain as much as 76%, 236% and 240% respectively. Also dynamic mechanical measurement indicated that the distance between crosslinks in the crosslinked PPS reached 85.3 g/mol corresponing to a crosslink density of 0.012 mol/g.

• Journal of Electrical Engineering and Technology
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• v.6 no.2
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• pp.275-279
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• 2011

Sterilization of Escherichia coli (E. coli) is examined using a unique pulsed ultra-violet (UV) elliptical reactor based on Nd:YAG laser resonator, UV radiation from a pulsed xenon flashlamp. The light from the discharge has a broadband emission spectrum extending from the UV to the infrared region with a rich UV contained. Sterilization method by using the UV light is fast, environment-friendly and it does not cause secondary pollution. A Nd:YAG laser resonator having elliptical shape has advantage of concentrating the radiation of the UV light at two foci as the quart sleeve filled with E. coli. The primary objective of this research is to determine the important parameters such as pulse per second (pps), the applied voltage for sterilizing E. coli by using an UV elliptical reactor. From the experiment result, the sterilization effect of UV elliptical reactor is better than that of UV cylindrical reactor, and it can be 99.9% of sterilization at 800V regardless of the pps within 10 minutes.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2012.03a
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• pp.52-52
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• 2012

Poly(phenylene sulfide)(PPS)는 내열성 및 내화학성이 뛰어난 고분자 소재로, 대표적인 엔지니어링 플라스틱 중 하나이다. PPS는 벤젠 링에 황원자가 파라 치환 형태로 교대로 존재하는 결정성 고분자이며, 다른 대부분의 고성능 섬유고분자가 용융되지 않는 것과는 달리 용융되는 열가소성 소재이다. PPS는 높은 내약품성과 열에 대한 장기적인 안정성을 나타내고, 방염제 첨가 없이도 방염화가 가능하며, 전기 절연성이 뛰어나고, 형태안정성도 우수하다. 또한 $200^{\circ}C$ 이하에서는 어떤 용매에도 용해되지 않으며, $200^{\circ}C$ 이상에서도 몇 가지 방향족 화합물에만 제한된 범위 내에서 용해되는 우수한 내약품성을 나타낸다. PPS의 내열성을 더욱 우수하게 하기 위해 고분자 사슬을 가교할 수 있다. 가교에는 열처리 또는 감마선, 전자선, 자외선 조사를 이용할 수 있는데 열에 의한 가교는 균일한 열전달과 고온이 필요하며 감마선 및 전자선 조사는 설비의 고비용과 방사선 노출 위험으로 인해 비친환경적이다. 반면에 자외선 조사법은 다루기 쉽고 비용이 적게 들고 친환경적인 장점을 가진다. 본 연구에서는 PPS film의 열안정성을 향상시키기 위해 자외선 조사를 이용하여 PPS film의 광가교를 수행하였다.

• Journal of the Korean Society of Safety
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• v.12 no.3
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• pp.173-178
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• 1997

The intrinsic flame retardant and heat resistant polymers such as PQXS [poly( quinoxaline )sulfide], PIQS [poly(isoquinoline)sulfide] and PQS [poly(quinoline)sulfide] were synthesized from 2, 3-dichloroquinoxaline, 1, 3-dichloroisoquinoline and 4, 7-dichloroquinoline. They were characterized by FT-IR, UV/Vis spectroscopy, DTA and elemental analysis. The melting point above $350^{\circ}C$ of the polymers show higher than that of the heat resistant PPS polymer(mp. $295^{\circ}C$), In the LOI test, the polymers exhibit an intrinsically high flame retardant property having the LOI values in the range of 41~42. The vertical burning test for the polymers also show an UL 94 V-0 performance.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.268-271
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• 1993

Discharge pumped high power excimer laser is a very useful light source of ultraviolet region. In this paper. the design and operation characteristics of UV pre-ionized discharge pumped XeCl laser are discussed. Maximum output power of 890mJ at the efficiency of 1.4% was achieved with 35kV charging voltage, 3.4atm of total pressure and 10pps of pulse repetition rate. Optimum HCl pressure is considered to be between 2.5 and 3.5torr.