• Journal of the Optical Society of Korea
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• v.17 no.4
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• pp.312-316
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• 2013

A novel fiber-optic sensor system is suggested in which fiber Bragg grating sensors are demodulated by a wavelength-sweeping fiber laser source and a spectrometer. The spectrometer consists of a diffraction grating and a 512-pixel photo-diode array. The reflected Bragg wavelength information is transformed into spatial intensity distribution on the photo-diode array. The peak locations linearly correspond to the Bragg wavelengths, regardless of the nonlinearities in the wavelength tuning mechanism of the fiber laser. The high power density of the fiber laser enables obtaining high signal-to-noise ratio outputs. The improved demodulation characteristics were experimentally demonstrated with a fiber Bragg grating sensor array with 5 gratings. The sensor outputs were in much more linear fashion compared with the conventional tunable band-pass filter demodulation. Also it showed advantages in signal processing, due to the high level of photo-diode array signals, over the broadband light source system, especially in measurement of fast varying dynamic physical quantities.

• Journal of Sensor Science and Technology
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• v.28 no.2
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• pp.113-116
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• 2019

A three-dimensional porous structure was fabricated by pattern transfer printing for applications of electrodes in gas sensors. To form replica patterns, solutions were mixed with acetone, toluene, heptane, and poly(methyl methacrylate). These replica patterns can also be formed on substrates such as polyimide, polydimethylsiloxane, and silicon. The wide range of line widths from 1 to $5{\mu}m$ was derived from the surface grating patterns of master substrates. The cross-bar pattern with 40 layers showed a thickness of 600 nm. The area of platinum transferred patterns with different line widths was enhanced to $20{\times}25mm$, which is applicable to various electrode patterns of gas sensors.

• Polymer(Korea)
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• v.39 no.1
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• pp.185-190
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• 2015

Since a transition from liquid crystal to crystal state is slow for the large photo-reactive liquid crystal molecules, it needs a long time for recrystallization of LC242 molecules when lowering the temperature of the liquid crystal. Although liquid crystals usually align along one direction, the directions of individual liquid crystal molecules are little different from one another with increasing temperature, resulting in changes of birefringence of the liquid crystal films. When the photo-reactive liquid crystals are photo-cured, faster curing kinetics and much larger curing degrees are observed for the films cured at the liquid crystal phase.

• Applied Chemistry for Engineering
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• v.20 no.6
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• pp.622-627
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• 2009

Using an alkali-solution developable photosensitive resin and a carbon black as a conductive filler, photo-patternable pastes for polymer thick film resistor were fabricated and evaluated. A photo solder resist (PSR), which is usually used as protecting layer of printed circuit board (PCB), was used as a photosensitive resin so that ultraviolet exposure and alkali-aqueous solution development of paste were possible. After fabricating the photosensitive polymer resistor paste, the electrical properties of thick film resistors were measured using PCB test boards. Sheet resistance was decreased with increasing amount of carbon black, but the developability was limited in excess loading of carbon black. The sheet resistance was also reduced by re-curing and the change rate was smaller in higher carbon black loading. Moreover, finely patterned meander-type thick film resistors were fabricated using photo-process and large resistance up to several tens of sheet resistance could be obtained in small area by this technique.

• Current Photovoltaic Research
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• v.8 no.2
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• pp.45-49
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• 2020

Molybdenum (Mo) thin films are widely used as back contact in copper indium diselenide (CISe) solar cells. However, despite this, there are only few published studies on the properties of Mo and characteristics of CISe solar cells formed on such Mo substrates. In this studies, we investigated the properties of sputter deposited Mo bilayer, and fabricated non-vacuum CISe solar cells using bilayer Mo substrates. The changes in surface morphology and electrical resistivity were traced by varying the gas pressure during deposition of the bottom Mo layer. In porous surface structure, it was confirmed that the electrical resistivity of Mo bilayer was increased as the amount of oxygen bonded to the Mo atoms increased. The resulting solar cell characteristics vary as the bottom Mo layer deposition pressure, and the maximum solar cell efficiency was achieved when the bottom layer was deposited at 7 mTorr with a thickness of 100 nm and the top layer deposited at 3 mTorr with a thickness of 400 nm.

• Polymer(Korea)
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• v.36 no.2
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• pp.145-148
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• 2012

The effects of the linearly polarized UV (LPUV) irradiation and thermal treatment of a photo-degradable polyimide (CBDA-ODA) alignment layer (AL) on its AL properties, liquid crystal (LC) alignment, and LCD characteristics have been investigated. The best quality of LC photo-alignment have been induced by the LPUV-irradiation with much (about 5~10 times) less dosage than that generating the maximum anisotropy of the AL. A thermal treatment of the LPUV-irradiated AL has effectively removed the undesirable, low-M.W. fragments of the AL generated during the photo-decomposition and increased the stability of the AL, which has resulted in improvement of the LC alignment and the LCD property.

• Textile Coloration and Finishing
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• v.25 no.3
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• pp.172-180
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• 2013

Aramid fibers are being used increasingly in a wide range of application due to low density, high specific strength, high modulus, and high thermal resistance. But owing to its special physical and chemical structures, it is sensitive to absorb the ultraviolet light which will degrade the fiber's useful mechanical properties and structure. In this paper, the sol-gel technique was used to improve the photo-stability of p-aramid fibers. $TiO_2$, modified $SiO_2$/$TiO_2$ sol were used as coating solutions. The influence of the such coatings on the photo-stability of p-aramid fiber was investigated by an accelerated photo-ageing method using xenon lamp. The photo-stability of p-aramid fiber showed obvious improvement after the modified silica binding coating. But the amorphous $TiO_2$ sol coatings showed a negative effect. After 144h light exposure, the modified silane binder-coated fibers showed less degradation in mechanical properties with the retained tensile strength greater than about 70% of the original value.

• Nuclear Engineering and Technology
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• v.31 no.5
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• pp.506-511
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• 1999

The pilot system for radioactive liquid laundry waste was developed with treatment capacity, 1ton/hr and set up in the Yong Kwang unit #4. The system is composed of tank module, RO systems and a UV/$H_2O$$_2$photo-oxidation unit. The RO system consists of the BW unit (low-pressure RO for brackish water desalination) and the SW unit (high-pressure RO for seawater desalination). The BW unit possesses 4 RO membranes and it can reduce the feed water volume down to 1/10. This concentrated feed water can be reduced again up to 1/10 in its volume in the SW unit composed of 4 RO membranes. The UV/$H_2O$$_2$ photo-oxidation process unit was used for the detergent degradation. The operation of the pilot system was carried out and verified in its capability through the continuous operation and concentration operation using the actual liquid waste from the power plant. The design criteria and data for industrialization were yielded. The efficiency of the UV/$H_2O$$_2$ photo-oxidation process and the optimum operational procedure were evaluated. The decontamination factors for radioactive cobalt and cesium were measured. This on-site test showed the experimental result in the DF$\geq$300 and volume reduction factor$\geq$100.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.4
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• pp.133-137
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• 2001

In this research, we synthesized various photo-crosslinkable polyimide based polymers. The control of pretilt angles for a nematic liquid crystal (NLC) using the photodimerization method on the photopolymers was studied. A good thermal stability of the photopolymers was measured by thermogravimetric analysis (TGA) measurement until 450C. High pretilt angles of the NLC were otained by polarized UV exposure on the photopolymers containing biphenyl (BP), decyl (de), and cholesteryl (chal) groups, respectively. However, low pretilt angles of the NLC were measured by polarized UV exposure on the photopolymers containing fluorine and chalcone groups. The high NLC pretilt angles generated are attributable to the biphenyl and alkyl moieties, and the photodimerized chalocone group of the photopolymers. Additionally, good voltage-transmittance and response time characteristics were observed by UV exposure on the photopolymers.

• Bulletin of the Korean Chemical Society
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• v.35 no.5
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• pp.1269-1274
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• 2014

Monoamine oxidases catalyze the oxidative deamination of dietary amines and amine neurotransmitters, and assist in maintaining the homeostasis of the amine neurotransmitters in the brain. Dysfunctions of these enzymes can cause neurological and behavioral disorders including Parkinson's and Alzheimer's diseases. To understand their physiological roles, efficient assay methods for monoamine oxidases are essential. Reviewed in this Perspective are the recent progress in the development of fluorescent probes for monoamine oxidases and their applications to enzyme assays in cells and tissues. It is evident that still there is strong need for a fluorescent probe with desirable substrate selectivity and photophysical properties to challenge the much unsolved issues associated with the enzymes and the diseases.