• Title/Summary/Keyword: CNF

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Optimized Encoding of Sudoku Puzzle for SAT Solvers (SAT 처리기를 위한 수도쿠 퍼즐의 최적화된 인코딩)

  • Kwon, Gi-Hwon
    • Journal of KIISE:Software and Applications
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    • v.34 no.7
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    • pp.616-624
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    • 2007
  • Sudoku can be regarded as a SAT problem. Various encodings are known for encoding Sudoku as a Conjunctive Normal Form (CNF) formula, which is the standard input for most SAT solvers. Using these encodings for large Sudoku, however, generates too many clauses, which impede the performance of state-of-the-art SAT solvers. This paper presents an optimized CNF encodings of Sudoku to deal with large instances of the puzzle. We use fixed cells in Sudoku to remove redundant clauses during the encoding phase. This results in reducing the number of clauses and a significant speedup in the SAT solving time.

Effect of Nanocellulose on the Mechanical and Self-shrinkage Properties of Cement Composites (나노셀룰로오스가 시멘트복합체의 역학적 특성 및 자기수축 특성에 미치는 영향)

  • Kim, Sun-Woo;Yoon, Byung-Tae
    • Applied Chemistry for Engineering
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    • v.27 no.4
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    • pp.380-385
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    • 2016
  • Nanocelluloses, mainly cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC, i.e., defect-free, rod-like crystalline residues after acid hydrolysis of fibers), have been the subject of recent interest. Due to the presence of hydroxyl groups on the surface of nanocelluloses, their surfaces are reactive, making them suitable candidates for reinforcing materials for manufacturing polymer composites. In this study, CNF was used as a reinforcing material for manufacturing cement composites. CNF was prepared by TEMPO (2,2,6,6,-tetramethyl piperidine-1-oxyl radical) oxidation procedure combined with extensive homogenization and ultrasonication. Transmission electron microscopy (TEM) analysis of the suspension showed the width of CNF between 10 and 15 nm. The compressive strength of cement composites containing 0.5% CNF was comparable to that of conventional cement composites. On the other hand, the tensile and flexural strength were improved by 49.7% and 38.8%, respectively, compared to those of conventional cement composites. Also, at an ambient condition, the degree of self-shrinkage reduction reached to 18.9% in one day, followed by 5.9% in 28 days after molding.

CNT and CNF reinforced carbon fiber hybrid composites by electrophoresis deposition (전기영동법에 의한 탄소나노튜브 및 탄소나노섬유 강화 탄소섬유 하이브리드 복합재료)

  • Choi, O-Young;Lee, Won-Oh;Lee, Sang-Bok;Yi, Jin-Woo;Kim, Jin-Bong;Choe, Hyeon-Seong;Byun, Joon-Hyung
    • Composites Research
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    • v.23 no.3
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    • pp.7-12
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    • 2010
  • In order to increase the electrical conductivity and the mechanical properties of carbon fabric composites, multi-walled carbon nanotubes (MWCNTs) and carbon nanofibers (CNFs) were deposited on carbon fabrics by anodic and cathodic electrophoretic deposition (EPD) processes. In the cathodic EPD, carbon nano-particles and nano-sized Cu particles were simultaneously deposited on the carbon fabric, which gave a synergetic effect on the enhancement of properties as well as the degree of deposition. The hybridization of carbon nano-particles and micron-sized carbon fiber significantly improved the through-the-thickness electrical conductivity. In addition, both MWCNTs and CNFs were deposited onto the carbon fabric for multi-scale hybrid composites. Multi-scale deposition improved the through-the-thickness electrical conductivity, compared to the deposition of either MWCNTs or CNFs.

Nano-structured Carbon Support for Pt/C Anode Catalyst in Direct Methanol Fuel Cell

  • Choi Jae-Sik;Kwon Heock-Hoi;Chung Won Seob;Lee Ho-In
    • Journal of Powder Materials
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    • v.12 no.2 s.49
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    • pp.117-121
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    • 2005
  • Platinum catalysts for the DMFC (Direct Methanol Fuel Cell) were impregnated on several carbon supports and their catalytic activities were evaluated with cyclic voltammograms of methanol electro-oxidation. To increase the activities of the Pt/C catalyst, carbon supports with high electric conductivity such as mesoporous carbon, carbon nanofiber, and carbon nanotube were employed. The Pt/e-CNF (etched carbon nanofiber) catalyst showed higher maximum current density of $70 mA cm^{-2}$ and lower on-set voltage of 0.54 V vs. NHE than the Pt/Vulcan XC-72 in methanol oxidation. Although the carbon named by CNT (carbon nanotube) series turned out to have larger BET surface area than the carbon named by CNF (carbon nanofiber) series, the Pt catalysts supported on the CNT series were less active than those on the CNF series due to their lower electric conductivity and lower availability of pores for Pt loading. Considering that the BET surface area and electric conductivity of the e-CNF were similar to those of the Vulcan XC-72, smaller Pt particle size of the Pt/e-CNF catalyst and stronger metal-support interaction were believed to be the main reason for its higher catalytic activity.

Synthesis of Fe3C-Embedded Nitrogen Doped Carbon for Oxygen Reduction Reaction (산소환원반응을 위한 탄화철이 내재된 질소 도핑된 탄소의 제조)

  • Lee, Young-Geun;An, Geon-Hyoung;Ahn, Hyo-Jin
    • Korean Journal of Materials Research
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    • v.28 no.11
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    • pp.640-645
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    • 2018
  • The design of non-precious electrocatalysts with low-cost, good stability, and an improved oxygen reduction reaction(ORR) to replace the platinium-based electrocatalyst is significant for application of fuel cells and metal-air batteries with high energy density. In this study, we synthesize iron-carbide($Fe_3C$) embedded nitrogen(N) doped carbon nanofiber(CNF) as electrocatalysts for ORRs using electrospinning, precursor deposition, and carbonization. To optimize electrochemical performance, we study the three stages according to different amounts of iron precursor. Among them, $Fe_3C$-embedded N doped CNF-1 exhibits the most improved electrochemical performance with a high onset potential of -0.18 V, a high $E_{1/2}$ of -0.29 V, and a nearly four-electron pathway (n = 3.77). In addition, $Fe_3C$-embedded N doped CNF-1 displays exellent long-term stabillity with the lowest ${\Delta}E_{1/2}=8mV$ compared to the other electrocatalysts. The improved electrochemical properties are attributed to synergestic effect of N-doping and well-dispersed iron carbide embedded in CNF. Consequently, $Fe_3C$-embedded N doped CNF is a promising candidate for non-precious electrocatalysts for high-performance ORRs.

Bacterial Cellulose Membrane for Wastewater Treatment: A Review (폐수 처리를 위한 박테리아 셀룰로오스 막: 리뷰)

  • Jang, Eun Jo;Patel, Rajkumar
    • Membrane Journal
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    • v.31 no.6
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    • pp.384-392
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    • 2021
  • Growing pollution due to industrialization leads to difficulties in survival of mankind. Generation of clean water from wastewater by membrane separation process is emerging cost efficient technology. Membrane prepared from renewable resources are in lots of demand to reduce burden on synthetic polymers which is one of the source of environmental pollution. Bacterial cellulose (BC) is very pure and distinct form of cellulose nanofibrils (CNF). Nanopapers prepared from CNF are used ad ultrafiltration (UF) and nanofiltration (NF) membrane for different applications. High crystallinity of BC gives rise to excellent mechanical property, an essential criterion for wastewater treatment membrane. In this review, BC based membrane for application in dye, oil, heavy metal and chemical removal from wastewater is discussed.

Capacitance Property for a Carbon-nanofiber/Cobalt Oxide Composite Electrode (탄소나노섬유/코발트산화물 복합전극의 케폐시턴스 특성)

  • Yoon, Yu-Il;Ko, Jang-Myoun
    • Journal of the Korean Ceramic Society
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    • v.45 no.8
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    • pp.482-485
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    • 2008
  • Composite electrode consisting of carbon nanofiber (CNF) and cobalt oxide was prepared for supercapacitor electrode, and its electrochemical property was investigated by means of cyclic voltammetry. Cyclic voltammetric results for the composite electrode showed it had specific capacitance value of 420 F/g at 5 mV/s, which was higher than capacitance value of 180 F/g for the bare CNF. It is concluded that the capacitive property of CNF can be improved by coating cobalt oxide on it to increase the surface area of cobalt oxide.

Carbon Nanofibers with Controlled Size and Morphology Synthesized with a Ni-MgO Catalyst Treated by Mechnochemical Process

  • Fangli, Yuan;Ryu, Ho Jin
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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    • 2003.12a
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    • pp.94-98
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    • 2003
  • Carbon nanofibers (CNF) with uniform diameter and controlled size could be prepared from catalytic decomposition of $C_2H_2$ with the catalyst treated by mechnochemical(MC) process. The distribution and size of Ni catalyst can be governed by tuning grinding time using MC process. As a result, size and structure of CNF can be controlled. The effect of grinding time to the as-grown CNF was checked. CNFs with diameter from 10-70nm can be synthesized. CNFs with bundle formation sharing one tip were found for MC treated catalyst.

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Mechanical Properties of Carbon Fiber Nano Composites for Nano-fiber Additives and Fabric Orientation (나노섬유 분산과 섬유 배향성에 따른 탄소섬유 나노 복합재료의 기계적 특성)

  • Song, Jun Hee;Choi, Jun Yong;Kim, Yonjig
    • Korean Journal of Metals and Materials
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    • v.50 no.2
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    • pp.93-99
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    • 2012
  • The mechanical properties of nano composites were evaluated for structural performance in order to enhance their applicability to the car and machine industrial fields. Carbon fiber reinforced plastics (CFRP) and GFRP were manufactured by vacuum-assisted resin transfer molding (VARTM) process with good mechanical properties. Tensile test was conducted to obtain the process factor of each composite. Also, carbon nano fiber (CNF) was dispersed in the composites and the relationship between the mechanical property and the CNF fraction was compared. The tensile strength and stiffness of 0/90 laminated CFRP were the best. CFRP/CNF (0.5 wt.%) was confirmed to be an excellent material for its elasticity and tensile strength.

A Case Study on Satisfiability : Rubik's Cube (SAT 사례 연구: 루빅 큐브)

  • Lim, Hyoung-Joo;Kwon, Gi-Hwon
    • Proceedings of the Korea Information Processing Society Conference
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    • 2008.05a
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    • pp.378-381
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    • 2008
  • 최근 정형 검증 분야에서 만족가능성 처리기를 사용한 연구가 많아지면서 이를 적용한 사례들이 많이 나타나고 있다. 만족가능성 처리기를 사용하기 위해서는 검증 되어야 할 시스템을 CNF식으로 변환해야 한다. 우리는 루빅 큐브를 만족가능성 처리기를 통해 풀어보기 위해 이를 CNF식으로 변환해 보았다. 루빅 큐브는 정육면체로 이루어진 퍼즐의 일종으로 모든 면이 각각 한가지 색으로만 채워져야 하는 문제이다. 우리는 본 논문에서 만족가능성 처리기를 사용한 사례 중에 아직 적용한적이 없는 루빅 큐브를 CNF식으로 변환해 풀었음을 보여준다.