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Kim, Jaewon,Lee, Kyung Eun,Kim, Kyung Hwan,Wi, Sungun,Lee, Sangheon,Nam, Seunghoon,Kim, Chunjoong,Kim, Sang Ouk,Park, Byungwoo Elsevier 2017 Carbon Vol.114 No.-
<P>Graphene has been intensively adopted into boosting the electrochemical performances of battery electrode materials due to its superior nature. In the case of Li4Ti5O12 (LTO), the application of graphene has been specifically focused on ameliorating the low electronic conductivity of LTO. So far, these attempts aiming to increase the composite's electronic conductivity involved thick graphene layers, which inevitably hindered Li-ion diffusion and eventually harmed the electrochemical kinetics in LTO's surface. In this work, high quality minimum-impurity graphene oxide was prepared by means of thorough cleaning and dialysis, which enabled each single-layered graphene to successfully wrap individual LTO particles. The resulting single-layer graphene-wrapped LTO exhibits an excellent specific capacity of 130 mAh g(-1) even at a lithiation/delithiation of 30 degrees C. Such a high rate capability is one of the highest values among the reported LTO with comparable sizes (similar to 200 nm). To uncover the reasons for such high performance, electrochemical properties from varied graphene contents were juxtaposed for comparison, and as a result, number of graphene layers and the corresponding kinetic parameters were found correlated. With adequate validity, single graphene layer was revealed to be the uttermost optimum for both Li+ diffusion and electronic conduction. (C) 2016 Elsevier Ltd. All rights reserved.</P>
Interactive Documentary on Perspective of New Media
Nayun Kim,Sangheon Kim 보안공학연구지원센터 2014 International Journal of Multimedia and Ubiquitous Vol.9 No.12
An Interactive Documentary is web and multimedia documentary with interactivity and user participatory that present non-linear narratives. These features come from that of new media including hypertext, remediation, modulation and interactivity which is combination of cinema and digital technologies. Focused features of new media and interactive documentary are presented and compared. Variant modes of interactive documentary compared to traditional documentary or media are presented. Interactive Documentary is a New media, mostly affected by user related interactions.
Kim, Taewoo,Jeon, Sangheon,Lone, Saifullah,Doh, Song Jun,Shin, Dong-Myeong,Kim, Hyung Kook,Hwang, Yoon-Hwae,Hong, Suck Won Elsevier 2018 Nano energy Vol.54 No.-
<P><B>Abstract</B></P> <P>The ongoing expedition to harvest ambient renewable energies from the environment by wearable fabric-based nanogenerators is a promising route to sustainably drive the small electronics with unprecedented opportunities in next-generation self-powered devices. Here, we report a simple method to fabricate a washable, breathable and wearable triboelectric nanogenerator that harvests the energy of triboelectricity through an enhanced friction surface area made of the gold nanodot-pattern crafted by electron-beam sputtering on an inexpensive polyurethane surface. The gold deposition which crops-up as regular small islands, under oxygen plasma is subsequently, etched into nanodot-pattern on a polyurethane surface to convert mechanical energy into an electrical signal via in-plane sliding mode with a maximum output of ~2 μW. The nanodot engineering plays an important role to improve the active sliding frictional area, as well as the corresponding output-performance of the triboelectric nanogenerator. To demonstrate the potential applications of our approach, we designed a self-powered wearable device integrated with clothes to harvest different kinds of mechanical energies from the human motion. To elevate the power output-performance, we fabricated waterproof fiber with flutter membrane and quantified triboelectric charge against airflow speed. At mild wind speed, the fabricated triboelectric nanogenerator shows a maximum output of 70 µW. Besides, as an example of practical application, the nanogenerator constructed can produce an improved capacitor charge voltage to drive dozens of light-emitting diodes and apply them to low power consumption devices. This technology is produced in a simple and cost-effective manner and reports an easy way to produce an energy harvesting system based on triboelectric effects using a sustainable and renewable energy source of body motions and air flows. This system is expected to be one of the best green energy sources for portable and wearable electronic devices in the near future.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The harvest of the triboelectric energy is accomplished by increasing the surface area through nanodot-patterned arrays formed on a woven fabric surface. </LI> <LI> Wearable triboelectric nanogenerators for a self-powered energy-supply by attaching it onto sportswear to harvest the energy, collected from the motion of the human body. </LI> <LI> Adapting a textile-based fluttering membrane to synergistically combine aerodynamic movement enables dramatic improvements in the electrical output of the triboelectric nanogenerator. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Design of Intelligent Home Media Server
Sangheon Lee,Myoungkyu Sohn,Chiho Park,Byungmin Kim,Chulho Won,Dongwook Kim,Junghyun Lee 한국멀티미디어학회 2009 한국멀티미디어학회 국제학술대회 Vol.2009 No.-
Home TV systems were developed from black and white to color, and have also changed from a cathode-ray tube to LCD. Today, Internet IPTV connected to the network is being developed. In this paper, we discuss the current state of Internet IPTV and how it could develop in the future. If TV connected to the Internet is possible, bidirectional communications will support various additional services, and the set-top box of the TV will be a media box that can be developed to a higher value in homes. Consequently, the user will have the opportunity to acquire more intelligent service because of the increase in memory and an operation process for processors. We will also design an intelligent service for a future environment in the home which is based on t IPTV and explain the service scenario.
VoIP Capacity Analysis in Full Duplex WLANs
Kim, Wonjung,Song, Taewon,Kim, Taeyoon,Park, Hyunhee,Pack, Sangheon IEEE 2017 IEEE Transactions on Vehicular Technology VT Vol.66 No.12
<P>With the increase of the popularity of voice over wireless local area networks (VoWLANs), how to improve the capacity of VoWLANs is being actively investigated. A recent technology to allow simultaneous transmission and reception, i.e., full duplex (FD) communications, can be a promising candidate for improving the capacity of VoWLANs. In this paper, we develop an analytical model of an FD medium access control protocol for VoWLANs, and study its capacity. Extensive simulation results are given to show the effects of FD communications, different voice over IP (VoIP) codecs, and data connections on the VoIP capacity.</P>
Sangheon Han,Hyoungtae Kim,Sungwoo Lee,Wook Kim 대한전기학회 2016 Journal of Electrical Engineering & Technology Vol.11 No.2
In order for the optimal solution of generators’ annual maintenance scheduling to be applicable to the actual power system it is crucial to incorporate the constraints related to the equivalent operation hours (EOHs) in the optimization model. However, most of the existing researches on the optimal maintenance scheduling are based on the assumption that the maintenances are to be performed periodically regardless of the operation hours. It is mainly because the computation time to calculate EOHs increases exponentially as the number of generators becomes larger. In this paper an efficient algorithm based on demand grouping method is proposed to calculate the approximate EOHs in an acceptable computation time. The method to calculate the approximate EOHs is incorporated into the optimization model for the maintenance scheduling with consideration on the EOHs of generators. The proposed method is successfully applied to the actual Korean power system and shows significant improvement when compared to the result of the maintenance scheduling algorithm without consideration on EOHs.