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41.
42.
Eric Berberich Efi Fogel Dan Halperin Michael Kerber Ophir Setter 《Mathematics in Computer Science》2010,4(1):67-91
We describe the algorithms and implementation details involved in the concretizations of a generic framework that enables
exact construction, maintenance, and manipulation of arrangements embedded on certain two-dimensional orientable parametric
surfaces in three-dimensional space. The fundamentals of the framework are described in a companion paper. Our work covers
arrangements embedded on elliptic quadrics and cyclides induced by intersections with other algebraic surfaces, and a specialized
case of arrangements induced by arcs of great circles embedded on the sphere. We also demonstrate how such arrangements can
be used to accomplish various geometric tasks efficiently, such as computing the Minkowski sums of polytopes, the envelope
of surfaces, and Voronoi diagrams embedded on parametric surfaces. We do not assume general position. Namely, we handle degenerate
input, and produce exact results in all cases. Our implementation is realized using Cgal and, in particular, the package that provides the underlying framework. We have conducted experiments on various data sets,
and documented the practical efficiency of our approach. 相似文献
43.
44.
Dan Ralescu 《Fuzzy Sets and Systems》1978,1(3):193-202
In this paper we shall define the concept of a fuzzy subobject of an object in arbitrary categories. This concept is generated by the representation theorem of fuzzy sets. By using fuzzy subobjects one can include most of the fuzzy concepts defined in the literature, such as: fuzzy groups, fuzzy relations and fuzzy convex sets. In the second part of the paper we shall define a new concept; that of a -set. This concept will generalize that of a fuzzy set and we shall also prove that -sets can be represented by some sets of functors. More precisely, -sets form a category which can be represented by a category of functors. The utility of -sets resides in the fact that one can replace “ordering” by the more general concept of a morphism in category. The new representation of -sets is weaker than that of fuzzy sets. 相似文献
45.
We review recent structural studies that we have undertaken aimed at elucidating the fundamental properties of metal-organic
framework materials and their interactions with hydrogen. We have shown that exposing coordinatively unsaturated metal centers
can greatly enhance the hydrogen binding energy and that they result in a significant increase of the surface packing density
of adsorbed hydrogen molecules on materials’ surface. We will review some of the structural aspects of these materials, especially
the adsorbed hydrogen molecule surface packing density in one type of metal-organic framework, MOF-74, which can be packed
even denser than that in solid hydrogen.
相似文献
46.
Chen Yang Ying Chen Dan Liu Jinfeng Wang Cheng Chen Jiemin Wang Ye Fan Shaoming Huang Weiwei Lei 《Frontiers of Physics》2018,13(4):138101
Vertically aligned γ-AlOOH nanosheets (NSs) have been successfully fabricated on flexible Al foils via a solvothermal route without morphology-directing agents. Three different reaction temperature (25, 80, and 120 ?C) and time (30 min, 45 min, and 24 h) are discussed for the growth period, which efficiently tune the density and size of the γ-AlOOH NSs. Meanwhile, the growth speed of the nanosheets confirms that dominant growth stage is seen in the initial 45 min. Furthermore, the interlayer of the γ-AlOOH NSs displays an average height of 140 nm and superhydrophilicity. By dynamic adsorption, the assynthesized γ-AlOOH NSs exhibit an outstanding NH3 adsorption capacity of up to 146 mg/g and stably excellent regeneration for 5 cycles. The mechanism of NH3 adsorption on the in-plane of the γ-AlOOH NSs is explained by the Lewis acid/base theory. The H-bond interactions among the NH3 molecules and the edge groups (-OH) further improve the capture ability of the nanosheets. 相似文献
47.
Jin Zhang Weiwei Lei Jurg Schutz Dan Liu Bin Tang Chun H. Wang Xungai Wang 《Journal of Polymer Science.Polymer Physics》2019,57(7):406-414
New multifunctional materials with both high structural and gas barrier performances are important for a range of applications. Herein we present a one‐step mechanochemical process to prepare molybdenum disulfide (MoS2) nanosheets with hydroxy functional groups that can simultaneously improve mechanical strength, thermal conductivity, and gas permittivity of a polymer composite. By homogeneously incorporating these functionalized MoS2 nanosheets at low loading of less than 1 vol %, a poly(vinyl alcohol) (PVA) polymer exhibits elongation at break of 154%, toughness of 82 MJ/m3, and in‐plane thermal conductivity of 2.31 W/m K. Furthermore, this composite exhibits significant gas barrier performance, reducing the permeability of helium by 95%. Under fire condition, the MoS2 nanosheets form thermally stable char, thus enhancing the material's resistance to fire. Hydrogen bonding has been identified as the main interaction mechanism between the nanofillers and the polymer matrix. The present results suggest that the PVA composite reinforced with 2D layered nanomaterial offers great potentials in packaging and fire retardant applications. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 406–414 相似文献
48.
Absolute one-handed chiral quinoline tetramers andoctamers containing different oxazolylanilines at the C-terminus have been synthesized.The absolute one-handed sense and diastereomeric excess values were valued by^1H NMR.X-ray crystal diffractionand CD studies reveal that the S-oxazolylaniline always induces a P-handed helicity and the absolute helicity is driven by the stable three-center hydrogen bonding between protons in the amide and N atoms in oxazolylaniline and adjacent quinoline ring.CPL investigations demonstrated that S-CQn-a-d are CPL active and its g(lum)values are dependent on its length.Interestingly,the sizes of the substituents in the chiral centers are different,howeve r,they exert no effect on the dissymmetric factors g(abs)and g(lum)of quinoline oligoamide foldamers. 相似文献
49.
Nogueira Petrnio A. S. Cavalieri Andr V. G. Hanifi Ardeshir Henningson Dan S. 《Theoretical and Computational Fluid Dynamics》2020,34(1):163-176
Theoretical and Computational Fluid Dynamics - The problem of finding optimal forcing and response for unbounded base flows, exemplified by the Blasius boundary layer, is assessed by means of a... 相似文献
50.
Dan Xie Huan-Huan Li Yan-Hong Shi Wan-Yue Diao Ru Jiang Prof. Hai-Zhu Sun Prof. Xing-Long Wu Dr. Wenliang Li Dr. Chao-Ying Fan Prof. Jing-Ping Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(4):853-862
The Fe-based transition metal oxides are promising anode candidates for lithium storage considering their high specific capacity, low cost, and environmental compatibility. However, the poor electron/ion conductivity and significant volume stress limit their cycle and rate performances. Furthermore, the phenomena of capacity rise and sudden decay for α-Fe2O3 have appeared in most reports. Here, a uniform micro/nano α-Fe2O3 nanoaggregate conformably enclosed in an ultrathin N-doped carbon network (denoted as M/N-α-Fe2O3@NC) is designed. The M/N porous balls combine the merits of secondary nanoparticles to shorten the Li+ transportation pathways as well as alleviating volume expansion, and primary microballs to stabilize the electrode/electrolyte interface. Furthermore, the ultrathin carbon shell favors fast electron transfer and protects the electrode from electrolyte corrosion. Therefore, the M/N-α-Fe2O3@NC electrode delivers an excellent reversible capacity of 901 mA h g−1 with capacity retention up to 94.0 % after 200 cycles at 0.2 A g−1. Notably, the capacity rise does not happen during cycling. Moreover, the lithium storage mechanism is elucidated by ex situ XRD and HRTEM experiments. It is verified that the reversible phase transformation of α↔γ occurs during the first cycle, whereas only the α-Fe2O3 phase is reversibly transformed during subsequent cycles. This study offers a simple and scalable strategy for the practical application of high-performance Fe2O3 electrodes. 相似文献