• Carbon letters
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• v.26
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• pp.88-94
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• 2018

This manuscript explains the effective determination of urea by redox cyclic voltammetric analysis, for which a modified polypyrrole-graphene oxide (PPY-GO, GO 20% w/w of PPY) nanocomposite electrode was developed. Cyclic voltammetry measurements revealed an effective electron transfer in 0.1 M KOH electrolytic solution in the potential window range of 0 to 0.6 V. This PPY-GO modified electrode exhibited a moderate electrocatalytic effect towards urea oxidation, thereby allowing its determination in an electrolytic solution. The linear dependence of the current vs. urea concentration was reached using square-wave voltammetry in the concentration range of urea between 0.5 to $3.0{\mu}M$ with a relatively low limit of detection of $0.27{\mu}M$. The scanning electron microscopy was used to characterize the morphologies and properties of the nanocomposite layer, along with Fourier transform infrared spectroscopy. The results indicated that the nanocomposite film modified electrode exhibited a synergistic effect, including high conductivity, a fast electron-transfer rate, and an inherent catalytic ability.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.10a
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• pp.11.2-11.2
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• 2011

A key technological issue related to the implementation of dye-sensitized solar cells (DSSCs) is the replacement of Pt at the counter electrodes with an inexpensive and electro-chemically stable alternative. Carbon based nanomaterials could be promising candidates, but in practice they exhibit inadequate device performance. Here, we report very thin graphene oxide (GO)/metal hybrid films as transparent counter electrodes for high-efficiency DSSCs. Transparent GO/Pt and GO/Au hybrid films showed cell efficiencies of 9.2 and 9.0%, respectively (improvements of 9.5 and 7.1% over conventional Pt counter electrodes). More interestingly, highly stable DSSCs with GO hybrid films from relatively inexpensive metals such as Cu and Ni have been demonstrated with efficiency values comparable to Pt counter electrodes. The results reported in this study should enable low-cost fabrication of DSSCs because it allows the use of relatively inexpensive metals such as Au, Cu, Ni, and Ag that could not be previously employed in DSSCs with iodide/tri-iodide electrolyte due to corrosion.

• Journal of the Korean Society of Costume
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• v.60 no.8
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• pp.86-99
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• 2010

This study considered the characteristics and use of the jokduri during the 18th century, which was shown in Ijae-nan-go written by Yoon-Seok Hwang. In Ijae-nan-go, not only the origin of the jokduri, but also its colors, materials, sizes, and construction methods are recorded, in detail. The Jokdori is assumed to have been influenced by costumes of China. The 18th century jokduri is mainly made up of black satin, and is composed of eight pieces of cloth. This looks similar to a contemporary jokduri, but the 18th century jokduri is bigger. At court during the 18th century, women decorated their hair styles higher by using the jokduri. Not only did the jokduri fix the topknot at the top of a woman's hair by wrapping the topknot, but also it raised the height of the topknot. This is different from the generally known method of wearing jokduri. Therefore, this demonstrates that there have been changes in the role and use of the jokduri over time.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.653-653
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• 2013

In this study, ITO extended gate reduced graphene oxide field effect transistor (rGO FET) was demonstrated as a transducer for a proton sensing application. In this structure, the sensing area is isolated from the active area of the device. Therefore, it is easy to deposit or modify the sensing area without affecting on the device performance. In this case, the ITO extended gate was used as a gate electrode as well as a proton sensing material. The proton sensing properties based on the rGO FET transducer were analyzed. The rGO FET device showed a high stability in the air ambient with a TTC encapsulation layer for months. The device showed an ambipolar characteristic with the Dirac point shift with varying the pH solutions. The sensing characteristics have offered the potential for the ion sensing application.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.633-639
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• 2007

This paper presents a new homing guidance law based on well-known BPN to achieve an impact time constraint as well as an impact angle constraint. The guidance commands are synthesized by introducing an additional command to control impact-time. The structure of the additional command has a BPN-based loop multiplied by time-varying gains being proportional to the time difference between the required time-to-go and the estimated time-to-go by BPN. Moreover, the proposed homing loop converges to BPN as the time-to-go error is reduced. The performance of the proposed guidance law is evaluated by the computer simulations.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2000.06a
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• pp.205-218
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• 2000

Hull forms of Jiao Yi Ship for shipping and foreign trade in Silla and Tang Dynasty were transformed and developed in accordance to their voyage and rational routes. The trade ship was a sea ship, used by Chang Po Go's, the Silla great sea merchant ship, in the marine trade with China during the 8th and 9th century. It is not easy to presume the hull type and trade formal of Chang Po Go's Jiao Yi Ship of the 8th and 9th Century. Studying on the ship type of the trade ship is the urgent problem to be solved, in the sphere of leaning about the history of communication between China and Korea. The authors take the initial prove into this subjects, by researching Chang Po Go's marine activities, and point out that the trade ship's original type should be the Sha Ship which was the sea ship sailing th sea in northern China, in the Tang Dynasty. This study aims to present materials concerning hull forms of Chang Po Go's Jian Yi Ship by analysing ancient voyage history, foreign trade history, and ship history of Silla, Tang and Japan during the 8th and 9th century.

• International Journal of Aeronautical and Space Sciences
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• v.8 no.1
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• pp.46-53
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• 2007

In this paper, a guidance law for vision-based automatic landing of unmanned aerial vehicles (UAVs) is proposed. Automatic landing is a challenging but crucial capability for UAVs to achieve a fully autonomous flight. In an autonomous landing maneuver of UAVs, the decision of where to landing and the generation of guidance command to achieve a successful landing are very significant problem. This paper is focused on the design of guidance law applicable to automatic landing problem of fixed-wing UAV and rotary-wing UAV, simultaneously. The proposed guidance law generates acceleration command as a control input which derived from a specified time-to-go ($t_go$) polynomial function. The coefficient of $t_go$-polynomial function are determined to satisfy some terminal constraints. Nonlinear simulation results using a fixed-wing and rotary-wing UAV models are presented.

• Journal of Broadcast Engineering
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• v.17 no.6
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• pp.1106-1109
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• 2012

The stability of object tracking in non-stationary camera environment, such as intelligent surveillance system using a pan/tilt camera, is less stable compared with stationary camera environment. This is due to the fact that it is difficult to model a background image in non-stationary environment. In this letter, we propose a non-stationay pan/tilt camera surveillance system which uses a stop/go procedure together with a real-time active contour. The proposed system can track the object stable even in an environment where only a few difference frames can be obtained.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.4
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• pp.363-367
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• 2015

This paper reports on thermally adjusted graphene oxide (GO) as the hole transport layer (HTL) for organic light-emitting diodes (OLEDs). GO is generally not suitable for HTL of OLEDs because of intrinsic specific resistance. In this paper, the specific resistance of GO is adjusted by the thermal annealing process. The optimum specific resistance of HTL is found to be $10^2{\Omega}{\cdot}m$, and is defined by the maximum current efficiency of OLEDs, 2 cd/A. In addition, the reasons for specific resistance change are identified by x-ray photoelectron spectroscopy (XPS). First, the XPS results show that several functional groups of GO were detached by thermal energy, and the amount of epoxide changed substantially following the temperature. Second, the full width at half maximum (FWHM) of the C-C bond decreased during the process. That means the crystallinity of the graphene improved, which is the scientific basis for the change in specific resistance.

• Journal of the Korean Society of Propulsion Engineers
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• v.14 no.1
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• pp.40-47
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• 2010

In this study, basic research on the thrust control by controling oxidizer mass flow rate of a $GO_2$/PE hybrid rocket is presented. For this purpose, hybrid rocket system including oxidizer flow control system and data acquisition system was developed. To control oxidizer mass flow rate, we used needle valve with stepping motor which was controled by LabVIEW program. During the fundamental experiments, this system managed to follow the pre-programmed (20 N - 10 N - 20 N - 0 N) thrust level.