• Journal of Electrochemical Science and Technology
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• v.2 no.2
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• pp.110-115
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• 2011

The effect of $TiO_2$ nanotube (TNT) and nanoparticle (TNP) composite photoelectrode and the role of TNT to enhance the photo conversion efficiency in dye-sensitized solar cell (DSSC) have investigated in this study. Results demonstrated that the increase of the TNT content (1-15 %) into the electron collecting TNP film increases the open-circuit potential ($V_{oc}$) and short circuit current density ($J_{sc}$). Based on the impedance analysis, the increased $V_{oc}$ was attributed to the suppressed recombination between electrode and electrolyte or dye. Photochemical analysis revealed that the increased Jsc with the increased TNT content was due to the scattering effect and the reduced electron diffusion path of TNT. The highest $J_{sc}$ (12.6 mA/$cm^2$), Voc (711 mV) and conversion efficiency (5.9%) were obtained in the composite photoelectrode with 15% TNT. However, $J_{sc}$ and $V_{oc}$ was decreased for the case of 20% TNT, which results from the significant reduction of adsorbed dye amount and the poor attachment of the film on the fluorine-doped tin oxide (FTO). Therefore, application of this composite photoelectrode is expected to be a promising approach to improve the energy conversion efficiency of DSSC.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.12
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• pp.806-811
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• 2017

An all-transparent ultraviolet (UV) photodetector was fabricated by structuring $p-NiO/n-SnO_2/ITO$ on a glass substrate. $SnO_2$ is an important semiconductor material because of its large bandgap, high electron mobility, high transmittance (as high as 80% in the visible range), and high stability under UV light. For these reasons, $SnO_2$ is suitable for a range of applications that involve UV light. In order to form a highly transparent p-n junction for UV detection, $SnO_2$ was deposited onto a device containing NiO as a high-transparent metal conductive oxide for UV detection. We demonstrated that all-transparent UV photodetectors based on $SnO_2$ could provide a definitive photocurrent density of $4nA\;cm^{-2}$ at 0 V under UV light (365 nm) and a low saturation current density of $2.02nA{\times}cm^{-2}$. The device under UV light displayed fast photoresponse with times of 31.69 ms (rise-time) and 35.12 ms (fall-time) and a remarkable photoresponse ratio of 69.37. We analyzed the optical and electrical properties of the $NiO/SnO_2$ device. We demonstrated that the excellent properties of $SnO_2$ are valuable in transparent photoelectric device applications, which can suggest various routes for improving the performance of such devices.

• Journal of Information Technology and Architecture
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• v.10 no.2
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• pp.273-281
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• 2013

Smart work can classify three types. First, mobile office equipped with a portable computer and connect to the company servers and Intranet via mobile phones. Second, home working using video conference system. Third, smart work center. Smart work has enabled us to work efficiently, to work anytime and to work anywhere, beyond conventional office working. This paper presents development processes of a smart work for After Service Business, especially, for the elevator industry. we called implemented mobile office system "A/S work". A/S work using mobile devices has some advantages as compared with previous system. 1) Before/After photo management function 2) Assessment process of customer satisfaction 3) The work history management app. 4) The inquiry and confirmation function to current status of all workers 5) The group SMS function sending selected workers. 'M' elevator company has used A/S work as efficient smart work system.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.386.2-386.2
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• 2014

본 연구에서는 바이오 센서 응용을 위해 그래핀을 전극으로 제작하여 그래핀 표면 결함준위에 따른 센서의 민감도를 전기화학 실험을 통해 관찰하였다. 그래핀은 니켈/구리촉매를 이용한 저 진공 화학 기상 증착 장비(Low-Pressure Chemical Vapor Deposition; LP-CVD)와 Photo-lithography로 제작한 것과 탄소 산화물을 환원시켜 만든 환원-그래핀, 두 가지를 사용하였다. 전기화학 실험에서 그래핀 전극 및 Silver/Silver chloride (Ag/AgCl), Fluorine doped Tin Oxide (FTO)은 작업 전극 및 기준 전극, 상대 전극으로 각각 사용하였고, 반응용액은 potassium hexacyanoferrate (III)를 농도를 다르게 하여 사용하였다. 그래핀의 표면 상태, 층수, 결함 정도 등 구조적인 특성은 원자력현미경(Atomic Force Microscopy; AFM), 주사 전자 현미경(Secondary Electron Microscopy; SEM)과 Raman spectroscopy를 각각 이용하여 확인하였고, 그래핀의 결함준위에 따른 반응면적 및 센서 감도 의존성을 전류모드-원자력현미경(Current-Atomic Force Microscopy; I-AFM)과 전기화학 임피던스 분광법(Electrochemical Impedance Spectroscopy; EIS)를 통해 그래핀 전극의 성능을 분석하고, 그래핀 결함 준위에 따른 센서 감도 의존성은 순환전위 분광법 (Cyclic Voltammetry; CV)를 이용하여 관찰하였다. 또한 농도가 다른 반응용액은 센서의 민감도를 관찰하는데 사용하였다. 결과적으로 LP-CVD로 성장한 그래핀과 환원-그래핀의 결함준위에 따른 센서의 성능을 비교 분석한 결과와 반응용액 농도에 따른 센서의 민감도 결과는 그래핀 바이오센서에 대한 응용 및 상용화를 앞당기는데 기여할 것으로 예상한다.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.9
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• pp.1112-1124
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• 2011

The development of computer graphics and Internet technology has created a 3D Web-based virtual world that has transformed the global fashion industry environment. In this study, the application cases of 3D virtual fashion education were analyzed to discuss the necessity and application of a 3D apparel CAD curriculum as part of a special education for global fashion talent at Korean fashion-related colleges. Prior studies, literature, photo data and Internet data (in and out of Korea) were used for this study. The demonstration case studies were conducted for the virtual fashion education 'SLCC 2007' of Buffalo State College (U.S.), 'Ratava's Line (2004)' of SFU/FIT Collaborative Design Project (Canada and U.S.) and '2011 Graduation Fashion Show' of Ueda Fashion College (Japan). The results of the study show that the 3D apparel CAD system (as a core technology of the IT fashion industry) would allow the current mass production concept to change to a new paradigm of 'mass customization' along with new fashion business types that include global fashion companies and Web-based Internet, mobile and virtual-world shopping malls. In addition, it appears that the system should be included in the curriculum of fashion-related colleges and institutes to educate technical designers for the global fashion industry and global fashion talent with comprehensive system operation and management ability, and to promote single proprietor companies.

• Journal of Sensor Science and Technology
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• v.10 no.2
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• pp.91-100
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• 2001

A $8{\times}8$ foveated (log-polar) retina chip for edge detection has been designed and fabricated using CMOS technology. Retina chip performs photo-input sensing, edge extraction and motion detection and we focused edge extraction. The pixel distribution follows the log-polar transform having more resolution in the center than in the periphery and can reduce image information selectively. This kind of structure has been already employed in simple image sensors for normal cameras, but never in edge detection retina chip. A scaling mechanism is needed due to the different pixel size from circumference to circumference. A mechanism for current scaling in this research is channel width scaling of MOS transistor. The designed chip has been fabricated using standard $1.5{\mu}m$ single-poly double-metal CMOS technology.

• Journal of Sensor Science and Technology
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• v.4 no.1
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• pp.3-8
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• 1995

n-ITO/p-PSL heterojunction photodetector have been fabricated on the Si wafer by using ITO(indium tin oxide) and PSL(porous silicon layer). They were anodized selectively by using silicon nitride and Ni-Cr/Au and were passivated by using ITO as well as being isolated by using mesa structure. With white light from 0 to 3000 Lux, the photocurrent varied linearly with incident light intensity. The reverse characteristics of fabricated devices were very stable up to a bias voltage of -40V and dark current density was about $40nA/mm^{2}$. When the device was exposed by Xe lamp whose wavelength range from 400nm to 1100nm, the maximum photo responsivity was about 0.6A/W between 600 and 700nm. Variation of the characteristics of fabricated devices after 5 weeks was negligible.

• Macromolecular Research
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• v.17 no.7
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• pp.491-498
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• 2009

New $\pi$-conjugated multi-branched molecules were synthesized through the Homer-Emmons reaction using alkyl-substituted, 3,4-ethylenedioxythiophene-based, thiophenyl aldehydes and octaethyl benzene-l,2,4,5-tetrayltetrakis(methylene) tetraphosphonate as the core unit; these molecules have all been fully characterized. The two multi-branched conjugated molecules exhibited excellent solubility in common organic solvents and good self-film forming properties. The semiconducting properties of these multi-branched molecules were also evaluated in organic field-effect transistors (OFET). With octyltrichlorosilane (OTS) treatment of the surface of the $SiO_2$ gate insulator, two of the crystalline conjugated molecules, 7 and 8, exhibited carrier mobilities as high as $2.4({\pm}0.5){\times}10^{-3}$ and $1.3({\pm}0.5){\times}10^{-3}cm^2V^{-1}s^{-1}$, respectively. The mobility enhancement of OFET by light irradiation ($\lambda$ = 436 nm) supported the promising photo-controlled switching behavior for the drain current of the device.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.658-658
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• 2013

Graphene is an attractive material for various device applications due to great electrical properties and chemical properties. However, lack of band gap is significant hurdle of graphene for future electrical device applications. In the past few years, several methods have been attempted to open and tune a band gap of graphene. For example, researchers try to fabricate graphene nanoribbon (GNR) using various templates or unzip the carbon nanotubes itself. However, these methods generate small driving currents or transconductances because of the large amount of scattering source at edge of GNRs. At 2009, Bai et al. introduced graphene nanomesh (GNM) structures which can open the band gap of large area graphene at room temperature with high current. However, this method is complex and only small area is possible. For practical applications, it needs more simple and large scale process. Herein, we introduce a photosensitive graphene device fabrication using CdSe QD coated nano-porous graphene (NPG). In our experiment, NPG was fabricated by thin film anodic aluminum oxide (AAO) film as an etching mask. First of all, we transfer the AAO on the graphene. And then, we etch the graphene using O2 reactive ion etching (RIE). Finally, we fabricate graphene device thorough photolithography process. We can control the length of NPG neckwidth from AAO pore widening time and RIE etching time. And we can increase size of NPG as large as 2 $cm^2$. Thin CdSe QD layer was deposited by spin coatingprocess. We carried out NPG structure by using field emission scanning electron microscopy (FE-SEM). And device measurements were done by Keithley 4200 SCS with 532 nm laser beam (5 mW) irradiation.

• Journal of Environmental Science International
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• v.16 no.7
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• pp.785-791
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• 2007

The current study evaluated the technical feasibility of the application of titanium dioxide ($TiO_{2}$) photo-catalytic air cleaners for the disinfection of bioaerosols present in indoor air. The evaluation included both laboratory and field tests and the tests of hydraulic diameter (HD) and lamp type (LT). Disinfection efficiency of photocatalytic oxidation (PCO) technique was estimated by survival ratio of bacteria or fungi calculated from the number of viable cells which form colonies on the nutrient agar plates. It was suggested that the reactor coating with $TiO_{2}$ did not enhance the adsorption of bioaerosols, and that the UV irradiation has certain extent of disinfection efficiency. The disinfection efficiency increased as HD decreased, most likely due to the decrease in the light intensity since the distance of the catalyst from the light source increased when increasing the HD. It was further suggested that the mass transfer effects were not as important as the light intensity effects on the PCO disinfection efficiency of bioaerosols. Germicidal lamp was superior to the black lamp for the disinfection of airborne bacteria and fungi, which is supported by the finding that the disinfection efficiencies were higher when the germicidal lamp was used compared to the black lamp in the laboratory test. These findings, combined with operational attributes such as a low pressure drop across the reactor and ambient temperature operation, can make the PCO reactor a possible tool in the effort to improve indoor bioaerosol levels.