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Lee, Seunghyeon,Lee, Jaemin,Hwang, Hayoung,Yeo, Taehan,Lee, Howon,Choi, Wonjoon Elsevier 2018 Carbon Vol.140 No.-
<P><B>Abstract</B></P> <P>Biporous structures at the nano–microscale are promising candidates for controlling phase change heat transfer, through their enhanced capillary wicking and fluid transportation. However, existing methods for fabricating biporous structures involve complex process which is not suitable for small-scale thermal devices such as heat pipes, owing to their confined and non-flat inner structures. Herein, we report the biporous structures inside copper-sintered heat pipes, enabled by layer-by-layer (LbL) assembled multi-walled carbon nanotube (MWCNT)-polyethyleneimine (PEI) coating for enhanced thermal performance. The repetitive filling and removing of the oppositely charged solutions with MWCNT-PEI and carboxylic-functionalized MWCNTs assembled the nanoporous MWCNT-PEI coatings (10, 20, and 40 bilayers) on the microporous copper-sintered inner surfaces. The fiber-like MWCNT networks structurally manipulated morphology and thickness of biporous structures, while the hydrophilic PEI shells chemically optimized wettability. A reduced thermal resistance (∼14.3%) was observed for MWCNT-PEI coating in 10 bilayers, due to the enhanced capillary wicking, interfacial contact areas, and bubble dynamics, whereas the 40 bilayers did not exhibit improved thermal performance owing to the redundant nanoporous layers causing reduced volume of microporous structures and increased thermal resistance. The LbL-assembled MWCNT-PEI coatings would act as functional layers to improve the performance of miniaturized and thin-film-based thermal devices.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Unanticipated Difficult Intubation in Patient with Undiagnosed Posterior Glottic Stenosis
Seunghyeon Lee,Misoon Lee,Bon Sung Koo,Yang Hoon Chung 순천향대학교 순천향의학연구소 2019 Journal of Soonchunhyang Medical Science Vol.25 No.1
Posterior glottic stenosis (PGS) is frequently caused by prolonged intubation complications, which may limit the movement of the vocal cords and obstruct airway obstruction. Despite of a life-threatening condition, it might be overlooked in asymptomatic individual. A 63-year-old female was scheduled for arthroscopic rotator cuff repair. The patient had experienced 2 times of intubation and organophosphate poisoning for suicide. Both of 7.0- and 6.5-mm inner diameter endotracheal tubes could not be passed vocal cords. After two failed attempts at intubation, adhesion of posterior part of vocal cord was revealed. We stopped the tracheal intubation and called the otolaryngologist, and adhesiolysis was performed under direct laryngosope. Thereafter, endotracheal intubation was performed successfully with 6.5-mm endotracheal tube.
Duo: Software Defined Intrusion Tolerant System Using Dual Cluster
Lee, Yongjae,Lee, Seunghyeon,Seo, Hyunmin,Yoon, Changhoon,Shin, Seungwon,Yoon, Hyunsoo Hindawi Limited 2018 Security and communication networks Vol.2018 No.-
<P>An intrusion tolerant system (ITS) is a network security system that is composed of redundant virtual servers that are online only in a short time window, called exposure time. The servers are periodically recovered to their clean state, and any infected servers are refreshed again, so attackers have insufficient time to succeed in breaking into the servers. However, there is a conflicting interest in determining exposure time, short for security and long for performance. In other words, the short exposure time can increase security but requires more servers to run in order to process requests in a timely manner. In this paper, we propose Duo, an ITS incorporated in SDN, which can reduce exposure time without consuming computing resources. In Duo, there are two types of servers: some servers with long exposure time (White server) and others with short exposure time (Gray server). Then, Duo classifies traffic into benign and suspicious with the help of SDN/NFV technology that also allows dynamically forwarding the classified traffic to White and Gray servers, respectively, based on the classification result. By reducing exposure time of a set of servers, Duo can decrease exposure time on average. We have implemented the prototype of Duo and evaluated its performance in a realistic environment.</P>
A Study on Virtual Studio Application using Microsoft Hololens
Lee, Jaehyun,Kim, Seunghyeon,Kim, Lyounghui,Kang, Jinwook,Lee, Seunghyun,Kwon, Soonchul The Institute of Internet 2017 International journal of advanced smart convergenc Vol.6 No.4
Mixed Reality (MR) shows a composite image of a virtual object in the real world. It has been applied to various fields by the introduction of head mounted display (HMD) such as Microsoft's Hololens [1-3]. The virtual studio in broadcasting combines the contents created by computer graphics with the actual set to reproduce the 3D image screen. This requires physical space such as a set of chroma keys. It also requires professional knowledge and manpower and costly equipment to post-process the graphics and information for long periods of time. Therefore, in this paper, we aim to study the implementation of virtual studio based on Mixed Reality using Microsoft Hololens. Through the implementation of 'Holo-studio' application, realistic and virtual objects of broadcasting camera viewpoint were acquired at the same time. Using Microsoft's spectator view library, the frame rate is degraded in objects with high polygons (100,000 polygons). The proposed method maintains 60 fps image transmission in high polygon objects. The results of this paper show the possibility of using virtual studio at low cost which does not need separate physical space.
High Performance of NanoCellulose/Nanochitin Coating Polypropylene Film for Food Packaging Materials
Seunghyeon LEE,Dongsoo HWANG 한국생물공학회 2021 한국생물공학회 학술대회 Vol.2021 No.10
In food packaging industry, it is important to possess barrier properties which prevent oxygen gas and water vapor. In general, aluminum coated polypropylene films are used because aluminum has a good gas barrier ability. However, this film is difficult to reuse and generate harmful particle when finally incinerated. In this study, we made a renewable food packaging film using the two most abundant biorenewable resources, cellulose and chitin. The structure of this film is simply made by stacking TEMPO cellulose nanofibers and Chitin nanowhiskers on polypropylene, and coating layers can sufficiently prevent oxygen gas and water vapor permeation. Compared with pristine pp, oxygen gas and water vapor permeability were significantly reduced from 1118 to 13.10㏄ m-2day-1 and from 2.43 to 2.13g m-2day-1, respectively. Furthermore, it has high transparency and antibacterial effect, so it can be expected as a new renewable food packaging material.