Exfoliated graphene nanosheets as high‑power anodes for lithium‑ion batteries

Duc‑Luong Vu,Yeon Ju Kwon,Soon Chang Lee,Jea Uk Lee,Jae‑Won Lee 한국탄소학회 2019 Carbon Letters Vol.29 No.1

High-quality and solution processable graphene sheets are produced by a simple electrochemical exfoliation method and employed as a high-power anode for lithium-ion batteries (LIBs). The electrochemically exfoliated graphene (EEG) composed of a few layers of graphene sheets, have low oxygen content and high C/O ratio (~ 14.9). The LIBs with EEG anode exhibit ultrafast lithium storage and excellent cycling stability, but low initial efficiency. The excellent rate capability and cycling stability are attributed to the favorable structural and chemical properties of the EEG, but the large irreversibility needs to be overcome for practical applications.

Microstructural Investigation of CoCrFeMnNi High Entropy Alloy Oxynitride Films Prepared by Sputtering Using an Air Gas

Duc Duy Le,Soon‑Ku Hong,Trong Si Ngo,Jeongkuk Lee,Yun Chang Park,홍순익,나영상 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.6

Microstructural properties of as-grown and annealed CoCrFeMnNi high entropy alloy (HEA) oxynitride thin films wereinvestigated. The CoCrFeMnNi HEA oxynitride thin film was grown by magnetron sputtering method using an air gas, andannealed under the argon plus air flow for 5 h at 800 °C. The as-grown film was homogeneous and uniform composed ofnanometer-sized crystalline regions mixed with amorphous-like phase. The crystalline phase in the as-grown film was facecentered cubic structure with the lattice constant of 0.4242 nm. Significant microstructural changes were observed afterthe annealing process. First, it was fully recrystallized and grain growth happened. Second, Ni-rich region was observed innanometer-scale range. Third, phase change happened and it was determined to be Fe3O4spinel structure with the latticeconstant of 0.8326 nm. Hardness and Young’s modulus of the as-grown film were 4.1 and 150.5 GPa, while those were 9.4and 156.4 GPa for the annealed film, respectively.

A Sudoku Based Wet Paper Hiding Scheme

The Duc Kieu,Chin-Chen Chang,Zhi-Hui Wang,Ming-Chu Li 보안공학연구지원센터 2009 International Journal of Smart Home Vol.3 No.2

Good image quality and high hiding capacity are two basic requirements of information hiding systems. Technically, it is very challenging to achieve these two factors simultaneously. The purpose of obtaining either high hiding capacity or good image quality are various from application to application. Inspired from the wet paper codes proposed by Fridrich et al., we propose an information hiding scheme for grayscale images. The proposed scheme first uses a secret key to randomly select a subset of pixels from a cover image as dry pixels. Next, the toral automorphism is applied to the cover image to maximize the number of dry pixel pairs. Then, each secret digit in the base-9 numeral system is embedded into one dry pixel pair. The experimental results show that the proposed scheme can achieve good image quality (i.e., PSNR > 46 dB) and flexible hiding capacity. In addition, unauthorized users without knowing the secret key and the secret parameters used for the toral automorphism can not extract the embedded message.

Gaze tracking system at a distance for controlling IPTV

Hyeon Chang Lee,Duc Thien Luong,Chul Woo Cho,Eui Chul Lee,Kang Ryoung Park IEEE 2010 IEEE transactions on consumer electronics Vol.56 No.4

<P>Gaze tracking is used for detecting the position that a user is looking at. In this research, a new gaze-tracking system and method are proposed to control a large-screen TV at a distance. This research is novel in the following four ways as compared to previous work: First, this is the first system for gaze tracking on a large-screen TV at a distance. Second, in order to increase convenience, the user's eye is captured by a remote gaze-tracking camera not requiring a user to wear any device. Third, without the complicated calibrations among the screen, the camera and the eye coordinates, the gaze position on the TV screen is obtained by using a simple 2D method based on a geometric transform with pupil center and four cornea specular reflections. Fourth, by using a near-infrared (NIR) passing filter on the camera and NIR illuminators, the pupil region becomes distinctive in the input image irrespective of the change in the environmental visible light. Experimental results showed that the proposed system could be used as a new interface for controlling a TV with a 60-inch-wide screen (16:9).</P>

A System for Controlling IPTV at a Distance Using Gaze Tracking

Duc Thien Luong,Hyeon Chang Lee,Kang Ryoung Park,Hee Kyung Lee,Min Sik Park,Jihun Cha 대한전자공학회 2010 대한전자공학회 학술대회 Vol.2010 No.6

Recently, internet protocol television (IPTV) has become popular. And a lot of functionalities based on internet protocol (IP) such as web surfing, video-on-demand (VOD) and voice over IP (VoIP), etc can be added to the IPTV. That is the reason why the remote controller for IPTV requires many functional buttons. As a alternative, gaze tracking technology, which detects the position where the user looking at, can be used as a new method to control the IPTV. Although many researchers studied about gaze tracking, there was not any previous research of gaze tracking at a distance. In this paper, we propose a new gaze tracking system which can capture eye images at a distance for controlling the IPTV.

Development of a Low Pressure Auxiliary Fan for Local Large-opening Limestone Mines

Chang Woo Lee(이창우),Van Duc Nguyen(웅웬 반득) 한국암반공학회 2015 터널과지하공간 Vol.25 No.6

최근 대단면 갱도로 개발하고 있는 국내 석회석광산은 작업공간 환기를 위하여 과거 석탄광산에 광범위하게 사용되던 형태의 국부 선풍기를 주로 이용하고 있다. 대단면 갱도에서의 낮은 정압손실을 고려할 때 고풍압 선풍기는 과다 설비용량으로 인하여 비용측면에서 심각한 한계를 보이고 있다. 대단면 갱도에서의 최적 선풍기는 안전한 작업환경 유지를 위한 충분한 환기량을 공급할 수 있어야 할 뿐만 아니라 저운전비용도 보장하여야 한다. 본 연구는 대단면 갱도 내에서 높은 환기효율과 경제성을 가지는 저풍압 국부선풍기를 개발함이 목적이다. 이론적 연구와 아울러 2개소의 단면적이 다른 현장 실험 연구를 통하여 저풍압 선풍기의 환기효율을 분석하였다. 본 연구결과는 작업공간 공기질 및 작업환경 개선을 위한 국부선풍기의 경제성과 효율 제고에 적용 가능할 것으로 기대된다. At present, local limestone mines with large opening employ auxiliary fans for workplace ventilation which have been used in coal mines with much smaller airways. Considering the low static pressure loss in the large-opening mines, high pressure auxiliary fans face serious economical limitations mainly due to their excessive capacity. The optimal fan selected for the ventilation in large-opening working places should supply air quantity enough for maintaining safe environment and keep its operating cost as low as possible. This study focuses on the development of a low pressure auxiliary fan designed to have smaller range of the static head but to have more potential for higher ventilation and energy efficiency. The flow characteristics of high and low pressure auxiliary fans were theoretical as well as experimentally investigated to assess the ventilation efficiency in term of environmental and economical aspects. Moreover, the low pressure fan was tested in two limestone mine sites with small and large cross-sectional areas for evaluating its ventilation efficiency. Results from this study can be applied to improve the economy and efficiency of auxiliary fan for ensuring better air quality and work environment management.

A Study on the Optimal Installation of Ducted Fan Ventilation System in Long Mine Airways

Chang Woo Lee(이창우),Van Duc Nguyen(응우엔반득) 한국암반공학회 2017 터널과지하공간 Vol.27 No.1

국내 석회석광산은 주로 자연통기에 의존하고 있으나 자본 및 운전비용이 과다하게 소요되는 광산 전체통기방법보다 풍관과 선풍기를 이용한 국부통기방법이 바람직한 방법으로 평가된다. 국내 대단면 장대 광산갱도에 풍관이 접속된 국부선풍기를 직렬로 연결 설치하는 경우에 통기시스템의 경제성과 효율의 최적화가 반드시 요구된다. 최적화를 위한 가장 중요한 두가지의 설계변수는 벽면 이격거리와 풍관 간의 이격거리이다. 본 연구에서는 경제적 및 환경적으로 최적화된, 즉 풍관간의 이격 공간을 통한 압력손실, 누기 그리고 오염된 공기의 재유입을 최소화할 수 있는 두 설계변수 값을 도출하기 위하여 광범위한 CFD분석을 시행하였다. 기존 연구결과와 권고기준들을 고려하여 이들 변수의 연구대상 범위를 선정하였다. 본 연구의 궁극적 목표는 국내 장대 광산갱도내 설치되는 풍관 접속 선풍기의 직렬연결 국부통기시스템의 최적화를 통하여 깨끗하고 안전한 작업장 환경을 제공하기 위함이다. In local underground mines heavily depending on the natural ventilation, ducted fan auxiliary ventilation system is strongly recommended instead of the total mine ventilation system requiring large capital and operating costs. Optimizing the installation of ducted fans in series in long large-opening mines is required to assure the economy and efficiency of the ventilation system. The two most critical design parameters for optimization are the wall separation distance and gap length between adjoining ducts. This study aims at deriving the optimal values for those two parameters concerning the economic and environmental aspects through the extensive CFD analysis, which minimizes pressure loss, leakage and entrainment of the contaminated air in the gap space. The ranges of the wall separation distance and gap length for study are selected by taking into consideration the existing recommendations and guidelines. The ultimate goal is to optimize the auxiliary ventilation system using ducted fans in series to provide a reliable and efficient solution to maintain clean and safe workplace environment in local long underground mines.

Computational Approach to Estimate Functional Significance of Stenotic Lesion of Coronary Artery

Duc Minh Tran(쩐득민),Minh Tuan Nguyen(웬민투안),Hyoung Gwon Choi(최형권),Hyuk-Jae Chang(장혁재),Sang-Wook Lee(이상욱) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

Computed tomographic (CT) angiography often overestimates the significance of stenotic lesion of coronary and it leads to a need for functional diagnostic measurements. Currently, invasive pressure-wire-based fractional flow reserve (FFR) is becoming the standard of reference for assessing the physiological significance of coronary stenoses in clinical decisions regarding revascularization and exhibits favorable outcomes in identifying the ischemia-causing stenosis. A noninvasive approach for FFR prediction based on computational fluid dynamics with CT angiography was developed. Since the hemodynamic conditions in distal vascular beds highly affects the coronary flow structures, it is necessary to incorporate zero-dimensional (0D) lumped parameter network (LPN) model for coronary microvascular flow by coupling with 3D CFD simulation. This demonstrated high diagnostic and prognostic accuracy with a reduction of adverse events. MPI parallel algorithm based on domain decomposition method was applied for the 3D-0D coupled model of coronary flow dynamics simulations in a monolithic approach. In this paper, we introduce the development of clinically practical computational tool to estimate physiological significance of stenotic lesion of coronary with aims of accelerating clinical outcomes, basically by bench to bedside approach.

Nanomechanical Mass Detection Using Nonlinear Oscillation

Mai Duc Dai,Kilho Eom(엄길호),Chang-Wan Kim(김창완) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Nanomechanical resonators have allowed the in vitro molecular recognition. Most of detection is implemented in harmonic oscillation regime, albeit nanomechanical resonators can easily reach the nonlinear oscillation regime. In this work, we have studied the nanomechanical mass detection using nonlinear oscillators based on continuum elastic model. It is shown that nonlinear oscillation leads to the unique resonant frequency shift due to mass adsorption, quite different from that in harmonic oscillation. This study highlights the nonlinear oscillation for label-free detection.

Two new species of harpacticoid copepods from anchialine caves in karst area of North Vietnam

Tran, Duc Luong,Chang, Cheon-Young The Korean Society for Integrative Biology 2012 Animal cells and systems Vol.16 No.1

Two new harpacticoid species belonging to the genera $Microarthridion$ Lang, 1944 (Tachidiidae) and $Nitocra$ Boeck, 1864 (Ameiridae) are recorded from underground caves in the karst area of Ninh Binh Province, North Vietnam. $Microarthridion$ $thanhi$ n. sp. is distinguished from congeneric species by the number of setae on the antennary exopod, the structure of leg 5 in both sexes, and the finger-like process modified from an outer distal pinnate seta of the third endopodal segment of leg 2 in the male. $Nitocra$ $vietnamensis$ n. sp. has the character combination of six setae on the ellipsoidal exopod of leg 5 in both sexes, the first endopodal segment of leg 1 shorter than the whole exopod, the seta/spine armature of an inner seta of P2-P4 enp-1 and four elements on P2 enp-3, and the reduction of the proximal endite to a seta on the maxillary syncoxa.