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Jang, Hochang,Lee, Wonsuk,Lee, Jeonghwan Elsevier 2018 Colloids and surfaces. A, Physicochemical and engi Vol.554 No.-
<P><B>Abstract</B></P> <P>The main challenge of nanotechnologies for enhanced oil recovery (EOR) in carbonate reservoirs is to maintain the colloidal stability of nanoparticle dispersion (nanofluid) under the reservoir conditions with high salinity and high temperature. This study presents a nanofluid as an injection fluid for EOR under the extreme condition. The nanofluid was composed of surface-modified silica nanoparticles by a silane coupling agent (GPTMS, (3-Glycidoxypropyl)trimethoxysilane). The particle size distribution and particle aggregation were measured and observed to evaluate colloidal stability of the nanofluid by the light scattering and electron microscopy methods. As a result, the colloidal stability of the nanofluid was achieved at the salinity up to 20 wt% of base fluid at 90 °C, when the amount of GPTMS was 1 mmol/g. The wettability alteration test of carbonate rocks was carried out to validate the applicability of the nanofluid in the reservoir conditions. The results showed that the rock wettability of dolomite and limestone was effectively altered to neutral-wet and water-wet from strongly oil-wet, respectively, by the nanofluid with a small portion of particle concentration. Therefore, it is believed that the nanofluid can be an effective EOR agent in carbonate reservoirs.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Buffer Sizing and Polarity Assignment in Clock Tree Synthesis for Power/Ground Noise Minimization
Hochang Jang,Deokjin Joo,Taewhan Kim IEEE 2011 IEEE transactions on computer-aided design of inte Vol.30 No.1
<P>In synchronous systems, clock tree causes high peak current at clock edges, increasing power/ground noise significantly, if the clock tree is not carefully designed. This paper addresses the problem of minimizing power/ground noise in the clock tree synthesis. Contrary to the previous approaches which only make use of assigning polarities to clock buffers to reduce power/ground noise, our approach solves a new problem of simultaneous consideration of assigning polarities to clock buffers and determining buffer sizes to fully exploit the effects of buffer sizing together with polarity assignment on the minimization of power/ground noise while satisfying the clock skew constraint. Specifically, the contributions of this paper are: 1) precisely estimating peak currents by clock buffers and reflecting them on the power/ground noise minimization; 2) proposing a pseudo-polynomial time optimal algorithm based on dynamic programming for solving the integrated problem, together with the proof of intractability of the problem; 3) devising a systematic design flow framework for reducing the power/ground noise over the entire chip; and 4) considering the effect of thermal variation on the clock skew bound and the noise minimization.</P>
Fog Rendering Using Distance-Altitude Scattering Model on 2D Images
Hochang Lee,JaeNi Jang,KyungHyun Yoon 한국멀티미디어학회 2011 한국멀티미디어학회 국제학술대회 Vol.2011 No.-
We present a fog generation algorithm in 2D images. The proposed algorithm provides a scattering model for the approximated calculation of fog density. The scattering model needs parameters of distance and altitude information. However, 2D images do not include those information, so that we calculate them from the depth information generated in an interactive manner, and estimate the scattering factor by using the scattering model. Then we generate fog effect on an input image using the scattering factor by distance-oriented selection blur and color blending. With the algorithm, we can easily create the fog-effected images and fog generated animation from 2D images.
이호창(HoChang Lee),한명훈(MyungHoon Han),장재니(JaeNi Jang),윤경현(KyungHyun Yoon) 한국멀티미디어학회 2009 한국멀티미디어학회 학술발표논문집 Vol.2009 No.1
회화적 렌더링에서 스트로크의 방향은 객체의 형태를 나타내는데 중요한 요소가 된다. 본 연구에서는 스트로크의 방향을 결정하기 위해 사용할 모션 정보 추출방법을 제안하고자 한다. 우리는 동영상 이미지로부터 모션의 방향, 크기 정보를 추출하고 이것을 기존의 그래디어트 정보와 통합한다. 통합된 최종 모션 정보는 객체의 사실적인 흐름을 표현가능하며 보는 사람에게 대상의 움직임을 효과적으로 인지할 수 있도록 하는 장점을 가진다.