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Origin of Anomalous Water Permeation through Graphene Oxide Membrane
Boukhvalov, Danil W.,Katsnelson, Mikhail I.,Son, Young-Woo American Chemical Society 2013 Nano letters Vol.13 No.8
<P>Water inside the low-dimensional carbon structures has been considered seriously owing to fundamental interest in its flow and structures as well as its practical impact. Recently, the anomalous perfect penetration of water through graphene oxide membrane was demonstrated although the membrane was impenetrable for other liquids and even gases. The unusual auxetic behavior of graphene oxide in the presence of water was also reported. Here, on the basis of first-principles calculations, we establish atomistic models for hybrid systems composed of water and graphene oxides revealing the anomalous water behavior inside the stacked graphene oxides. We show that formation of hexagonal ice bilayer in between the flakes as well as melting transition of ice at the edges of flakes are crucial to realize the perfect water permeation across the whole stacked structures. The distance between adjacent layers that can be controlled either by oxygen reduction process or pressure is shown to determine the water flow thus highlighting a unique water dynamics in randomly connected two-dimensional spaces.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2013/nalefd.2013.13.issue-8/nl4020292/production/images/medium/nl-2013-020292_0005.gif'></P>
sp-Electron Magnetic Clusters with a Large Spin in Graphene
Boukhvalov, Danil W.,Katsnelson, Mikhail I. American Chemical Society 2011 ACS NANO Vol.5 No.4
<P>Motivated by recent experimental data (Sepioni, M.; <I>et al. Phys. Rev. Lett</I>. <B>2010</B>, <I>105</I>, 207−205), we have studied the possibility of forming magnetic clusters with spin <I>S</I> > <SUP>1</SUP>/<SUB>2</SUB> on graphene by adsorption of hydrogen atoms or hydroxyl groups. Migration of hydrogen atoms and hydroxyl groups on the surface of graphene during the delamination of HOPG led to the formation of seven atom or seven OH-group clusters with <I>S</I> = <SUP>5</SUP>/<SUB>2</SUB> that were of a special interest. The coincidence of symmetry of the clusters with the graphene lattice strengthens the stability of the cluster. For (OH)<SUB>7</SUB> clusters that were situated greater than 3 nm from one another, the reconstruction barrier to a nonmagnetic configuration was approximately 0.4 eV, whereas for H<SUB>7</SUB> clusters, there was no barrier and the high-spin state was unstable. Stability of the high-spin clusters increased if they were formed on top of ripples. Exchange interactions between the clusters were studied and we have shown that the ferromagnetic state is improbable. The role of the chemical composition of the solvent used for the delamination of graphite is discussed.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2011/ancac3.2011.5.issue-4/nn103510c/production/images/medium/nn-2010-03510c_0001.gif'></P>
Oxygen reduction reactions on pure and nitrogen-doped graphene: a first-principles modeling
Boukhvalov, Danil W.,Son, Young-Woo The Royal Society of Chemistry 2012 Nanoscale Vol.4 No.2
<P>Based on first principles density functional theory calculations we explored energetics of oxygen reduction reaction over pristine and nitrogen-doped graphene with different amounts of nitrogen doping. The process of oxygen reduction requires one more step than the same reaction catalyzed by metals. Results of calculations evidence that for the case of light doped graphene (about 4% of nitrogen) the energy barrier for each step is lower than for the same process on a Pt surface. In contrast to the catalysis on a metal surface the maximal coverage of doped graphene is lower and depends on the corrugation of graphene. Changes of the energy barriers caused by oxygen load and corrugation are also discussed.</P>
설명 문장 생성을 통한 해석 가능한 시각적 질의응답 모델 분석
김단일(Danil Kim),한보형(Bohyung Han) 한국컴퓨터정보학회 2020 한국컴퓨터정보학회 학술발표논문집 Vol.28 No.2
본 연구에서는 설명 문장 생성을 통한 해석 가능한 시각적 질의응답 모델을 설계하고 학습 방법을 제시한다. 설명 문장은 시각적 질의응답 모델이 응답을 예측하는 데에 필요한 이미지 및 질문 정보와 적절한 논리적인 정보의 조합 및 정답 추론 과정이 함의되어 있을 것으로 기대한다. 설명 문장 생성 과정이 포함된 시각적 질의응답의 기본적인 모델을 기반으로 여러 가지 학습방법을 통해 설명 문장 생성 과정과 응답 예측 과정간의 상호관계를 분석한다. 이러한 상호작용을 적극적으로 활용할 수 있는 보다 개선 시각적 질의응답 모델을 제안한다. 또한 학습한 결과를 바탕으로 설명 문장의 특성을 활용하여 시각적 질의응답 추론 과정을 개선함으로써 시각적 질의응답 모델의 발전 방향을 논의한다. 본 실험을 통해서 응답 예측에 적절한 설명 문장을 제시하는 해석 가능한 시각적 질의응답 모델을 제공한다.
Performance Evaluation of ISA100.11a Superframe Using Deadline Monotonic Scheduling
Oka Danil Saputra,Soo Young Shin(신수용) 한국통신학회 2014 韓國通信學會論文誌 Vol.39 No.12(융합기술)
최근 무선 기술은 저가, 유연성, 쉬운 설치, 그리고 무엇보다 중요하게도 라우팅 문제를 해결할 수 있다는 측면에서 산업용 네트워크 분야에서 주목을 받고 있다. 그 중 ISA100.11a는 산업용 무선 환경에서 촉망 받는 표준들중의 하나이다. 산업 환경에서의 데이터 트래픽은 일반적으로 주기성을 가지며, 데드라인이라는 실시간성을 만족해야 하는 요구사항을 갖는다. 본 논문은 ISA100.11a의 주기적 태스크들의 처리를 위해 deadline monotonic scheduling 을 적용하는 것을 제안하고 이러한 제안된 알고리즘을 기반으로 ISA 100.11의 성능을 schedulability 및 beacon 오버헤드 관점에서 평가한다. 모의실험 결과 제안된 알고리즘은 기존 결과 대비 schedulability를 유지하면서도 스케줄링 오버헤드를 감소시킬 수 있다는 것을 보인다. 추가로, 이러한 네트워크 오버헤드의 감소를 통해, 제안된 알고리즘은 무선 산업용 네트워크의 성능 저하 없이 더 많은 데이터 전송이 가능할 것으로 기대된다. Recently, wireless technology gains attention for industrial networks due to low cost, flexibility, relatively easy installation and most importantly, solving the rouring issue. ISA100.11a is one of promising standard for wireless industrial networks (WINs). Data traffic in industrial networks are known to be periodic and must satisfy the real-time property namely deadline. Therefore, in this paper, we proposed to apply deadline monotonic scheduling to periodic tasks in ISA100.11a networks and to evaluate the performance of ISA100.11a by checking the schedulability and beacon frame overhead. Simulation results showns, that our proposed scheme can reduces the network overhead while maintaining schedulability as compared to the previous algorithm. In addition, by reducing the network overhead, our proposed scheme can send more data without degrading the overall performance of WINs.