Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently for their applications in fields such as nanoscience, granular and colloidal matter, and biology. In all...
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Packings of hard polyhedra have been studied for centuries due to their mathematical aesthetic and more recently for their applications in fields such as nanoscience, granular and colloidal matter, and biology. In all these fields, particle shape is important for structure and properties, especially upon crowding. Here, we explore packing as a function of shape. By combining simulations and analytic calculations, we study three two-parameter families of hard polyhedra and report an extensive and systematic analysis of the densest known packings of more than 55 000 convex shapes. The three families have the symmetries of triangle groups (icosahedral, octahedral, tetrahedral) and interpolate between various symmetric solids (Platonic, Archimedean, Catalan). We find optimal (maximum) packing-density surfaces that reveal unexpected richness and complexity, containing as many as 132 different structures within a single family. Our results demonstrate the importance of thinking about shape not as a static property of an object, in the context of packings, but rather as but one point in a higher-dimensional shape space whose neighbors in that space may have identical or markedly different packings. Finally, we present and interpret our packing results in a consistent and generally applicable way by proposing a method to distinguish regions of packings and classify types of transitions between them.
Trabecular bone is a porous nanocomposite material with a hierarchical structure. In this study, a multi-scale modeling approach, addressing scales spanning from the nanometer (collagen-mineral) to mesoscale (trabecul...
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Energy storage devices, such as lithium‐ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities ...
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Energy storage devices, such as lithium‐ion batteries and supercapacitors, are required for the modern electronics. However, the intrinsic characteristics of low power densities in batteries and low energy densities in supercapacitors have limited their applications. How to simultaneously realize high energy and power densities in one device remains a challenge. Herein a fiber‐shaped hybrid energy‐storage device (FESD) formed by twisting three carbon nanotube hybrid fibers demonstrates both high energy and power densities. For the FESD, the energy density (50 mWh cm −3 or 90 Wh kg −1 ) many times higher than for other forms of supercapacitors and approximately 3 times that of thin‐film batteries; the power density (1 W cm −3 or 5970 W kg −1 ) is approximately 140 times of thin‐film lithium‐ion battery. The FESD is flexible, weaveable and wearable, which offers promising advantages in the modern electronics.
Gas and fire barrier property enhancement of flexible polymeric films was studied experimentally in coextruded multilayer systems with alternating layers of particulate filled nanocomposites. Microlayers of alternatin...
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ISBN:
(纸本)9781605951652
Gas and fire barrier property enhancement of flexible polymeric films was studied experimentally in coextruded multilayer systems with alternating layers of particulate filled nanocomposites. Microlayers of alternating linear low density polyethylene (LLDPE)/small particulate (graphene) composites and low density polyethylene (LDPE) layers can be utilized to produce films with barrier properties expected for unprocessable high loading systems. This was possible by exploiting the moving boundary phenomenon, where a system of alternating layers of miscible polymers with highly different mobilities shows a convective flow of the more slowly diffusing molecules (LDPE) opposite to the faster molecules (LLDPE) when annealed in the melt. This study harnesses this moving boundary phenomenon to improve upon the barrier properties of these commercial polymers by creating shrunken layers of concentrated impermeable nanoparticles in the LLDPE layers. In this study, LLDPE-xGnP® graphene nanoplatelet composite morphologies and properties at multiple particle loadings and different nanoparticles were investigated and compared to the multilayer systems at various stages of interdiffusion.
Stability level of tunnels that exist in an underground mine has a great influence on the safety,production and economic performance of *** of stability for soft-rock tunnels is an important task for deep coal mines l...
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Stability level of tunnels that exist in an underground mine has a great influence on the safety,production and economic performance of *** of stability for soft-rock tunnels is an important task for deep coal mines located in high in situ stress *** the available information on stratigraphy,geological structures,in situ stress measurements and geo-mechanical properties of intact rock and discontinuity interfaces,a three-dimensional numerical model was built by using 3DEC software to simulate the stress conditions around a tunnel located under high in situ stress conditions in a coal rock mass in *** were conducted for several tunnel shapes and rock support *** obtained for the distribution of failure zones,and stress and displacement felds around the tunnel were compared to select the best tunnel shape and support pattern to achieve the optimum stability conditions.
Graphene,as a typical two-dimensional layered material,possesses extraordinary electronic and optical properties that render it for a wide range of potential applications including *** by the graphene research and dev...
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Graphene,as a typical two-dimensional layered material,possesses extraordinary electronic and optical properties that render it for a wide range of potential applications including *** by the graphene research and development,graphene-like two-dimensional materials（2DMats）also show application potentials in biomedicine due to their unique ***,environmental and biological influences of these 2DMats remain to be *** we reported the antibacterial activity of two-dimensional（2D）chemically exfoliated M0S2（ce-MoS2）*** found that the antibacterial activity of ce-MoS sheets was much more potent than that of the raw MoS powders used for the synthesis of ce-MoS sheets possibly due to the 2D planar structure（high specific surface area）and higher conductivity of the *** investigated the antibacterial mechanisms of the ce-MoS2 sheets and proposed their antibacterial *** found that the ce-MoS2 sheets could produce reactive oxygen species（ROS）,different from previous report on graphenebased ***,the oxidation capacity of the ce-MoS2 sheets toward glutathione oxidation showed a time and concentration dependent trend,which is fully consistent with the antibacterial behaviour of the ce-MoS *** results suggest that antimicrobial behaviors were attributable to both membrane and oxidation *** antibacterial pathways include MoS-bacteria contact induced membrane stress,superoxide anion（O2·）induced ROS production by the ce-MoS,and the ensuing superoxide anion-independent *** study thus indicates that the tailoring of dimension of nanomaterials and their electronic properties would manipulate antibacterial activity.
We have used specific heat and neutron diffraction measurements on single crystals of URu2−xFexSi2 for Fe concentrations x≤0.7 to establish that chemical substitution of Ru with Fe acts as “chemical pressure” Pch a...
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We have used specific heat and neutron diffraction measurements on single crystals of URu2−xFexSi2 for Fe concentrations x≤0.7 to establish that chemical substitution of Ru with Fe acts as “chemical pressure” Pch as previously proposed by Kanchanavatee et al. [Phys. Rev. B 84, 245122 (2011)] based on bulk measurements on polycrystalline samples. Notably, neutron diffraction reveals a sharp increase of the uranium magnetic moment at x=0.1, reminiscent of the behavior at the “hidden order” to large-moment-antiferromagnetic phase transition observed at a pressure Px≈0.5−0.7 GPa in URu2Si2. Using the unit-cell volume determined from our measurements and an isothermal compressibility κT=5.2×10−3 GPa−1 for URu2Si2, we determine the chemical pressure Pch in URu2−xFexSi2 as a function of x. The resulting temperature (T)–chemical pressure (Pch) phase diagram for URu2−xFexSi2 is in agreement with the established temperature (T)–external pressure (P) phase diagram of URu2Si2.
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