• Journal of the Korean Chemical Society
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• v.46 no.3
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• pp.229-232
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• 2002

Poly-o-toluidine (POT) was chemically and electrochemically synthesized for the study of electronic and steric effect of methyl substituents. The turn-on voltage of organic light emitting diode (OLED) was 9~14 V. ITO/POT/Al structured OLED were fabricated with various oxidation states of POT. PL, I-V characteristics and EL spectra were investigated.

• Journal of Welding and Joining
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• v.8 no.2
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• pp.58-69
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• 1990

In conventional arc welding, position error of the weld torch with respect to the weld seam and variation of groove dimension are induced by inaccurate fitup and fixturing. In this study, a vision system has been developed to recognize and compensate the position error and dimensional inaccuracy. The system uses a structured laser light illuminated on the weld groove and perceived by a C.C.D camera. A new algorithm to detect the edge of the reflected laser light is introduced for real time processing. The developed system was applied to arbitarary weld paths with various types of joint in arc welding process. The experimental results show that the proposed system can detect the weld groove parameters within good accuracy and yield good tracking performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.554-557
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• 2001

Indium Tin Oxide(ITO) thin films have been fabricated by the dc magnetron sputtering technique with a target of a mixture $In_{2}O_{3}$(90mol%) and $SnO_{2}$(10mol%). We prepared ITO thin films with substrate temperature 200 to $400^{\circ}C$ and annealing temperature 200 to $500^{\circ}C$. Good polycrystalline-structured ITO films with a low electrical resistivity of $3.4{\times}10^{-4}\Omega{\cdot}cm$ have been obtained. The visible light transmittance of all obtained films was over 80 %.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.554-557
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• 2001

Indium Tin Oxide(ITO) thin films have been fabricated by the dc magnetron sputtering technique with a target of a mixture In$_2$O$_3$(90mo1%) and SnO$_2$(10mo1%). We prepared ITO thin films with substrate temperature 200 to 400$^{\circ}C$ and annealing temperature 200 to 500$^{\circ}C$ food polycrystalline-structured ITO films with a low electrical resistivity of 3.4${\times}$10$\^$-4/ Ω$.$cm have been obtained. The visible light transmittance of all obtained films was over 80 %.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.9
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• pp.4541-4554
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• 2019

This paper proposes a planar projection DV-hop location algorithm (PTCDV-hop) based on the LED semi-angle at half power (SAHP, which accounts for LED SAHP characteristics in visible light communication (VLC)) and uses the DV-hop algorithm for range-free localization. Distances between source nodes and nodes positioned in three-dimensional indoor space are projected onto a two-dimensional plane to reduce complexity. Circles are structured by assigning source nodes (projected onto the horizontal plane of the assigned nodes) to be centers and the projection distances as radii. The proposed PTCDV-hop algorithm then determines the position of node location coordinates using the trilateral-weighted-centroid algorithm. Simulation results show localization errors of the proposed algorithm are on the order of magnitude of a millimeter when three sources are used. The PTCDV-hop algorithm has higher positioning accuracy and stronger dominance than the traditional DV-hop algorithm.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.226-226
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• 2013

Si is a dominant solar material, which is the second most abundant element in the earth giving a benefit in the aspect in cost with low toxicity. However, the inherent limit of Si has an indirect band gap of 1.1 eV resulting in the limited optical absorption. Therefore, a critical issue has been raised to increase the utilization of the incident light into the Si absorber. The enhancement of light absorption is a crucial to improve the performances and thus relieves the cost burden of Si photovoltaics. For the optical aspect, an efficient design of a front surface, where the incident light comes in, has been intensively investigated to improve the performance of photon absorption. Lambertian light trapping can be attained when the light active surface is ideally rough to increase the optical length by about 50 compared to a planar substrate. This suggests that an efficient design may reduce thickness of the Si absorber from the conventional 100~300 ${\mu}m$ to less than 3 ${\mu}m$. Theoretically, a hole-array structure satisfies an equivalent efficiency of c-Si with only one-twelfth mass and one-sixth thickness. Various approaches have been applied to improve the incident light utilization in a Si absorber using textured structures, periodic gratings, photonic crystals, and nanorod arrays. We have designed hole and pillar structured Si absorbers. Four-different Si absorbers have been simultaneously fabricated on an identical Si wafer with hole arrays or pillar arrays at a fixed depth of 2 ${\mu}m$. We have found that the significant enhanced solar cell performances both for the hole arrayed and pillar arrayed Si absorbers compared to that of a planar Si wafer resulting from the effective improvement in the quantum efficiencies.

• Journal of IKEEE
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• v.25 no.2
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• pp.322-329
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• 2021

In this study, a method for improving the light extraction efficiency of organic light emitting diodes was presented using the polymer Poly(vinylidenefluoride-co-trifluoroethylene) [P(VDF-TrFE)] having an island surface structure after annealing. Polydimethylsiloxane (PDMS) imprinted on the island-structured P(VDF-TrFE) surface has a spike structure, which improves the external light extraction efficiency aroud 20%. It was confirmed that the produced film showed a low haze characteristic of 8.2, and the Current and external quantum efficiency could be improved without pixel blur due to the excellent transmittance of 93.4%.

• Journal of the Korean Chemical Society
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• v.45 no.2
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• pp.156-161
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• 2001

Various oxidation states of Polyaniline(PANI) were chemically synthesized, and characterized by FT-IR, UV-Vis, GPC, TG-DTA, Single layer light emitting diodes(LED) were perpared by spin coating of LEB-PANI solutions which have various oxidation states onto an ITO substrate and subsequent vacuum deposition of aluminum top electrode and then current-voltage characteristics. EL spectrum was investigated It was found that ${\pi}$-${\pi}$* transition were shifled to longer wavelength and molecular excition transition were decreased in the UV-Vis spectra and the intensity of EL and PL were increased as the contents of fully reduced form LEB increased. The turn-on voltage of ITO/LEB/AI structured LED was 5 V. It was found that the white light was emitted only from the phase with reduced epeat unit.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.172-179
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• 2021

A near-normal-incidence ellipsometer (NNIE) is suggested as an optical critical dimension (OCD) measurement system that is highly sensitive to the bottom defect of a sample with high-aspect-ratio structured patterns. Incident light passes through a polarizer and a phase retarder in sequence, and the reflected light from the sample also passes through them, but in reverse order. The operating principle of this NNIE, where a single polarizer and a single phase retarder are shared by the incident and reflected light, is studied, and a method to determine the ellipsometric constants from the measured intensities at proper combinations of the azimuthal angles of polarizer and retarder is presented.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.487-492
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• 2009

A large-scaled research project titled "Intelligent Excavating System (IES)" sponsored by Korean government has launched in 2006. An issue of real-time 3D terrain modeling has become a crucial point for successful implementation of IES due to many application limitations of state-of-the-art techniques developed in various high-technology fields. Many feasible technologies such as laser scanning, structured lighting and so on were widely reviewed by professionals and researchers for one year. Various efforts such as literature reviews, interviews, and indoor experiments make us select a structural light technique and stereo vision technique as appropriate techniques for accomplishment of real-time 3D terrain modeling. It, however, revealed that off-the-shelf products of structural light and stereo-vision technique had many technical problems which should be resolved for practical applications in IES. This study introduces diverse methods modifying off-the-shelf package of the structural light method, one of feasible techniques and eventually allowing this technique to be successfully utilized for achieving fundamental research goals. This study also presents many efforts to resolve practical difficulties of this technique considering basic characteristics of excavating operations and particular environment of construction sites. Findings showed in this study would be beneficial for other researchers to conduct new researches for application of vision techniques to construction fields by provision of detail issues about practical application and diverse practical methods as solutions overcoming these issues.