Jiang, Caigui
2015-10-27
We study the design and optimization of polyhedral patterns, which are patterns of planar polygonal faces on freeform surfaces. Working with polyhedral patterns is desirable in architectural geometry and industrial design. However, the classical tiling patterns on the plane must take on various shapes in order to faithfully and feasibly approximate curved surfaces. We define and analyze the deformations these tiles must undertake to account for curvature, and discover the symmetries that remain invariant under such deformations. We propose a novel method to regularize polyhedral patterns while maintaining these symmetries into a plethora of aesthetic and feasible patterns.
Boron Clusters as Highly Stable Magnesium-Battery Electrolytes**
Carter, Tyler J; Mohtadi, Rana; Arthur, Timothy S.; Mizuno, Fuminori; Zhang, Ruigang; Shirai, Soichi; Kampf, Jeff W.
2014-01-01
Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesium-battery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electro...
Simulation of swift boron clusters traversing amorphous carbon foils
Heredia Ávalos, Santiago; Abril Sánchez, Isabel; Denton Zanello, Cristian D.; García Molina, Rafael
2007-01-01
We use a simulation code to study the interaction of swift boron clusters (Bn+, n=2–6, 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interacti...
Challenges and Opportunities for the Application of Boron Clusters in Drug Design.
Leśnikowski, Zbigniew J
2016-09-08
There are two branches in boron medicinal chemistry: the first focuses on single boron atom compounds, and the second utilizes boron clusters. Boron clusters and their heteroatom counterparts belong to the family of cage compounds. A subset of this extensive class of compounds includes dicarbadodecaboranes, which have the general formula C2B10H12, and their metal biscarboranyl complexes, metallacarboranes, with the formula [M(C2B10H12)2(-2)]. The unique properties of boron clusters have resulted in their utilization in applications such as in pharmacophores, as scaffolds in molecular construction, and as modulators of bioactive compounds. This Perspective presents an overview of the properties of boron clusters that are pertinent for drug discovery, recent applications in the design of various classes of drugs, and the potential use of boron clusters in the construction of new pharmaceuticals.
Interaction of Boron Clusters with Oxygen: a DFT Study
Salavitabar, Kamron; Boggavarapu, Kiran; Kandalam, Anil
A controlled combustion involving aluminum nanoparticles has often been the focus of studies in the field of solid fuel propellants. However very little focus has been given to the study of boron nanoparticles in controlled combustion. In contrast to aluminum nanoclusters, boron nanoclusters (Bn) are known to exhibit a planar geometries even at the size of n = 19 - 20, and thus offer a greater surface area for interaction with oxygen. Earlier experimental studies have shown that boron nanoclusters exhibit different reactivity with oxygen depending on their size and charge. In this poster, we present our recent density functional theory based results, focusing on the reactivity patterns of neutral and negatively charged B5 cluster with On, where n = 1 - 5; and B6 cluster with On (n = 1 - 2). The effect of charge on the reactivity of boron cluster, variation in the stability of product clusters, i e., neutral and negatively charged B5On (n = 1 - 5) and B6On (n = 1 - 2) are also examined. Financial Support from West Chester University Foundation under FaStR grant is acknowledged.
Simulation of swift boron clusters traversing amorphous carbon foils
Heredia-Avalos, Santiago; Abril, Isabel; Denton, Cristian D.; Garcia-Molina, Rafael
2007-01-01
We use a simulation code to study the interaction of swift boron clusters ( Bn+ , n=2-6 , 14) with amorphous carbon foils. We analyze different aspects of this interaction, such as the evolution of the cluster structure inside the target, the energy and angle distributions at the detector or the stopping power ratio. Our simulation code follows in detail the motion of the cluster fragments through the target and in the vacuum until reaching a detector, taking into account the following interactions: (i) wake force, (ii) Coulomb repulsion among cluster fragments, (iii) stopping force, and (iv) elastic scattering with the target nuclei. Electron capture and loss by each fragment is also included in the code, affecting the above-mentioned interactions. The clusters size grows inside the foil due mainly to the Coulomb explosion but this increase is less pronounced in the plane transversal to the beam direction because of the alignment effect of the wake forces. We obtain an enhancement of the stopping power ratio that increases with the projectile energy and with the number of molecular constituents. Our results agree very well with the available experimental data for the thicker foils (≳10μg/cm2) and are compatible (within the experimental error bars) for the thinner foils.
Indirect photometric detection of boron cluster anions electrophoretically separated in methanol.
Vítová, Lada; Fojt, Lukáš; Vespalec, Radim
2014-04-18
3,5-Dinitrobenzoate and picrate are light absorbing anions pertinent to indirect photometric detection of boron cluster anions in buffered methanolic background electrolytes (BGEs). Tris(hydroxymethyl)aminomethane and morpholine have been used as buffering bases, which eliminated baseline steps, and minimized the baseline noise. In methanolic BGEs, mobilities of boron cluster anions depend on both ionic constituents of the BGE buffer. This dependence can be explained by ion pair interaction of detected anions with BGE cations, which are not bonded into ion pairs with the BGE anions. The former ion pair interaction decreases sensitivity of the indirect photometric detection.
Guided basin-hopping search of small boron clusters with density functional theory
Energy Technology Data Exchange (ETDEWEB)
Ng, Wei Chun; Yoon, Tiem Leong [School of Physics, Universiti Sains Malaysia, 11800 USM, Penang (Malaysia); Lim, Thong Leng [Faculty of Engineering and Technology, Multimedia University, Melacca Campus, 75450 Melaka (Malaysia)
2015-04-24
The search for the ground state structures of Boron clusters has been a difficult computational task due to the unique metalloid nature of Boron atom. Previous research works had overcome the problem in the search of the Boron ground-state structures by adding symmetry constraints prior to the process of locating the local minima in the potential energy surface (PES) of the Boron clusters. In this work, we shown that, with the deployment of a novel computational approach that incorporates density functional theory (DFT) into a guided global optimization search algorithm based on basin-hopping, it is possible to directly locate the local minima of small Boron clusters in the PES at the DFT level. The ground-state structures search algorithm as proposed in this work is initiated randomly and needs not a priori symmetry constraint artificially imposed throughout the search process. Small sized Boron clusters so obtained compare well to the results obtained by similar calculations in the literature. The electronic properties of each structures obtained are calculated within the DFT framework.
Comparative study on the spectral properties of boron clusters Bn0/-1(n = 38-40)
Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Sun, Guangyu; Qin, Shuijie
2016-04-01
The all-boron fullerenes B40-1 and B39-1 discovered in recent experiments are characterized and revealed using photoelectron spectroscopy. Except for the photoelectron spectroscopy, one may identify such boron clusters with other spectroscopic techniques, such as infrared spectra and Raman spectra. Insight into the spectral properties of boron clusters is important to understand the boron clusters and find their potential applications. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to comparatively study the vibrational frequencies, infrared spectra, Raman spectra and electronic absorption spectra of boron clusters Bn0/-1(n = 38-40). The numerical simulations show that such boron clusters have different and meaningful spectral features. These spectral features are readily compared with future spectroscopy measurements and can be used as fingerprints to distinguish the boron clusters Bn0/-1 with different structures (cage structure or quasi-planar structure) and with different sizes (n = 38-40).
Origamizing polyhedral surfaces.
Tachi, Tomohiro
2010-01-01
This paper presents the first practical method for "origamizing" or obtaining the folding pattern that folds a single sheet of material into a given polyhedral surface without any cut. The basic idea is to tuck fold a planar paper to form a three-dimensional shape. The main contribution is to solve the inverse problem; the input is an arbitrary polyhedral surface and the output is the folding pattern. Our approach is to convert this problem into a problem of laying out the polygons of the surface on a planar paper by introducing the concept of tucking molecules. We investigate the equality and inequality conditions required for constructing a valid crease pattern. We propose an algorithm based on two-step mapping and edge splitting to solve these conditions. The two-step mapping precalculates linear equalities and separates them from other conditions. This allows an interactive manipulation of the crease pattern in the system implementation. We present the first system for designing three-dimensional origami, enabling a user can interactively design complex spatial origami models that have not been realizable thus far.
Romanescu, C.; Harding, D. J.; Fielicke, A.; Wang, L. S.
2012-01-01
The structures of neutral boron clusters, B11, B16, and B17, have been investigated using vibrational spectroscopy and ab initio calculations. Infrared absorption spectra in the wavelength range of 650 to 1550 cm−1 are obtained for the three neutral boron clusters from the enhancement of their near-
Transition-Metal Planar Boron Clusters: a New Class of Aromatic Compounds with High Coordination
Wang, Lai-Sheng
2012-06-01
Photoelectron spectroscopy in combination with computational studies over the past decade has shown that boron clusters possess planar or quasi-planar structures, in contrast to that of bulk boron, which is dominated by three-dimensional cage-like building blocks. All planar or quasi-planar boron clusters are observed to consist of a monocyclic circumference with one or more interior atoms. The propensity for planarity has been found to be due to both σ and π electron delocalization throughout the molecular plane, giving rise to concepts of σ and π double aromaticity. We have found further that the central boron atoms can be substituted by transition metal atoms to form a new class of aromatic compounds, which consist of a central metal atom and a monocyclic boron ring (M B_n). Eight-, nine-, and ten-membered rings of boron have been observed, giving rise to octa-, ennea-, and deca-coordinated aromatic transition metal compounds [1-3]. References: [1] ``Aromatic Metal-Centered Monocyclic Boron Rings: Co B_9^- and Ru B_9^-" (Constantin Romanescu, Timur R. Galeev, Wei-Li Li, A. I. Boldyrev, and L. S. Wang), Angew. Chem. Int. Ed. {50}, 9334-9337 (2011). [2] ``Transition-Metal-Centered Nine-Membered Boron Rings: M B_9 and M B_9^- (M = Rh, Ir)" (Wei-Li Li, Constantin Romanescu, Timur R. Galeev, Zachary Piazza, A. I. Boldyrev, and L. S. Wang), J. Am. Chem. Soc. {134}, 165-168 (2012). [3] ``Observation of the Highest Coordination Number in Planar Species: Decacoordinated Ta B10^- and Nb B_9^- Anions" (Timur R. Galeev, Constantin Romanescu, Wei-Li Li, L. S. Wang, and A. I. Boldyrev), Angew. Chem. Int. Ed. {51}, 2101-2105 (2012).
Transformations for polyhedral process networks
Meijer, Sjoerd
2010-01-01
We use the polyhedral process network (PPN) model of computation to program and map streaming applications onto embedded Multi-Processor Systems on Chip (MPSoCs) platforms. The PPNs, which can be automatically derived from sequential program applications, do not necessarily meet the performance/res
Polyceptron: A Polyhedral Learning Algorithm
Manwani, Naresh
2011-01-01
In this paper we propose a new algorithm for learning polyhedral classifiers which we call as Polyceptron. It is a Perception like algorithm which updates the parameters only when the current classifier misclassifies any training data. We give both batch and online version of Polyceptron algorithm. Finally we give experimental results to show the effectiveness of our approach.
Space-filling polyhedral sorbents
Haaland, Peter
2016-06-21
Solid sorbents, systems, and methods for pumping, storage, and purification of gases are disclosed. They derive from the dynamics of porous and free convection for specific gas/sorbent combinations and use space filling polyhedral microliths with facial aplanarities to produce sorbent arrays with interpenetrating interstitial manifolds of voids.
Hongsheng Liu; Junfeng Gao; Jijun Zhao
2013-01-01
As attractive analogue of graphene, boron monolayers have been theoretically predicted. However, due to electron deficiency of boron atom, synthesizing boron monolayer is very challenging in experiments. Using first-principles calculations, we explore stability and growth mechanism of various boron sheets on Cu(111) substrate. The monotonic decrease of formation energy of boron cluster BN with increasing cluster size and low diffusion barrier for a single B atom on Cu(111) surface ensure cont...
B{sub 27}{sup −}: Appearance of the smallest planar boron cluster containing a hexagonal vacancy
Energy Technology Data Exchange (ETDEWEB)
Li, Wei-Li; Piazza, Zachary A.; Wang, Lai-Sheng, E-mail: xzeng1@unl.edu [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Pal, Rhitankar; Zeng, Xiao Cheng, E-mail: xzeng1@unl.edu [Department of Chemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588 (United States)
2015-05-28
Photoelectron spectroscopy and ab initio calculations have been carried out to probe the structures and chemical bonding of the B{sub 27}{sup −} cluster. Comparison between the experimental spectrum and the theoretical results reveals a two-dimensional (2D) global minimum with a triangular lattice containing a tetragonal defect (I) and two low-lying 2D isomers (II and III), each with a hexagonal vacancy. All three 2D isomers have 16 peripheral boron atoms and 11 inner boron atoms. Isomer I is shown to be mainly responsible for the observed photoelectron spectrum with isomers II and III as minor contributors. Chemical bonding analyses of these three isomers show that they all feature 16 localized peripheral B–B σ-bonds. Additionally, isomer I possesses 16 delocalized σ bonds and nine delocalized π bonds, while isomers II and III each contain 17 delocalized σ bonds and eight delocalized π bonds. It is found that the hexagonal vacancy is associated generally with an increase of delocalized σ bonds at the expense of delocalized π bonds in 2D boron clusters. The hexagonal vacancy, characteristic of borophenes, is found to be a general structural feature for mid-sized boron clusters. The current study shows that B{sub 27}{sup −} is the first boron cluster, where a hexagonal vacancy appears among the low-lying isomers accessible experimentally.
On Linear Spaces of Polyhedral Meshes.
Poranne, Roi; Chen, Renjie; Gotsman, Craig
2015-05-01
Polyhedral meshes (PM)-meshes having planar faces-have enjoyed a rise in popularity in recent years due to their importance in architectural and industrial design. However, they are also notoriously difficult to generate and manipulate. Previous methods start with a smooth surface and then apply elaborate meshing schemes to create polyhedral meshes approximating the surface. In this paper, we describe a reverse approach: given the topology of a mesh, we explore the space of possible planar meshes having that topology. Our approach is based on a complete characterization of the maximal linear spaces of polyhedral meshes contained in the curved manifold of polyhedral meshes with a given topology. We show that these linear spaces can be described as nullspaces of differential operators, much like harmonic functions are nullspaces of the Laplacian operator. An analysis of this operator provides tools for global and local design of a polyhedral mesh, which fully expose the geometric possibilities and limitations of the given topology.
Romanescu, Constantin; Harding, Dan J.; Fielicke, André; Wang, Lai-Sheng
2012-07-01
The structures of neutral boron clusters, B11, B16, and B17, have been investigated using vibrational spectroscopy and ab initio calculations. Infrared absorption spectra in the wavelength range of 650 to 1550 cm-1 are obtained for the three neutral boron clusters from the enhancement of their near-threshold ionization efficiency at a fixed UV wavelength of 157 nm (7.87 eV) after resonant absorption of the tunable infrared photons. All three clusters, B11, B16, and B17, are found to possess planar or quasi-planar structures, similar to their corresponding anionic counterparts (Bn-), whose global minima were found previously to be planar, using photoelectron spectroscopy and theoretical calculations. Only minor structural changes are observed between the neutral and the anionic species for these three boron clusters.
Carbon Nanostructures Containing Polyhedral Oligomeric Silsesquioxanes (POSS)
Potsi, Georgia; Rossos, Andreas; Kouloumpis, Antonios; Antoniou, Myrsini K.; Spyrou, Konstantinos; Karakassides, Michael A.; Gournis, Dimitrios; Rudolf, Petra
2015-01-01
This mini review describes the synthesis and properties of carbon nanostructures containing organic-inorganic cage-like polyhedral oligomeric silsesquioxane (POSS). The physical and chemical functionalization of carbon nanomaterials such as graphene, graphene oxide, carbon nanotubes, and fullerenes
Mesophase behaviour of polyhedral particles
Agarwal, Umang
2011-02-13
Translational and orientational excluded-volume fields encoded in particles with anisotropic shapes can lead to purely entropy-driven assembly of morphologies with specific order and symmetry. To elucidate this complex correlation, we carried out detailed Monte Carlo simulations of six convex space-filling polyhedrons, namely, truncated octahedrons, rhombic dodecahedrons, hexagonal prisms, cubes, gyrobifastigiums and triangular prisms. Simulations predict the formation of various new liquid-crystalline and plastic-crystalline phases at intermediate volume fractions. By correlating these findings with particle anisotropy and rotational symmetry, simple guidelines for predicting phase behaviour of polyhedral particles are proposed: high rotational symmetry is in general conducive to mesophase formation, with low anisotropy favouring plastic-solid behaviour and intermediate anisotropy (or high uniaxial anisotropy) favouring liquid-crystalline behaviour. It is also found that dynamical disorder is crucial in defining mesophase behaviour, and that the apparent kinetic barrier for the liquid-mesophase transition is much lower for liquid crystals (orientational order) than for plastic solids (translational order). © 2011 Macmillan Publishers Limited. All rights reserved.
Polyhedral (in-)stability of protein crystals
Nanev, Christo N.; Penkova, Anita N.
2002-04-01
The polyhedral (in-)stability of monoclinic hen-egg white lysozyme (HEWL) crystals, grown by means of PEG-6000, and that of orthorhombic trypsin crystals has been investigated experimentally. On the basis of a quantitative theoretical analysis, it is compared with the polyhedral (in-)stability of tetragonal HEWL and cubic ferritin crystals. The unambiguous conclusion is that the phenomenon is due to the diffusive supply of matter. This conclusion is also supported by the fact that the phenomenon has common features for both proteins and small molecular crystals.
Architecture of Platonic and Archimedean polyhedral links
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
A new methodology for understanding the construction of polyhedral links has been developed on the basis of the Platonic and Archimedean solids by using our method of the 'three-cross-curve and doubletwist-line covering'. There are five classes of polyhedral links that can be explored: the tetrahedral and truncated tetrahedral links; the hexahedral and truncated hexahedral links; the dodecahedral and truncated dodecahedral links; the truncated octahedral and icosahedral links. Our results show that the tetrahedral and truncated tetrahedral links have T symmetry; the hexahedral and truncated hexahedral links, as well as the truncated octahedral links, O symmetry; the dodecahedral and truncated dodecahedral links, as well as the truncated icosahedral links, I symmetry, respectively. This study provides further insight into the molecular design, as well as theoretical characterization, of the DNA and protein catenanes.
Architecture of Platonic and Archimedean polyhedral links
Institute of Scientific and Technical Information of China (English)
2008-01-01
A new methodology for understanding the construction of polyhedral links has been developed on the basis of the Platonic and Archimedean solids by using our method of the ‘three-cross-curve and dou- ble-twist-line covering’. There are five classes of polyhedral links that can be explored: the tetrahedral and truncated tetrahedral links; the hexahedral and truncated hexahedral links; the dodecahedral and truncated dodecahedral links; the truncated octahedral and icosahedral links. Our results show that the tetrahedral and truncated tetrahedral links have T symmetry; the hexahedral and truncated hexahedral links, as well as the truncated octahedral links, O symmetry; the dodecahedral and truncated dodeca- hedral links, as well as the truncated icosahedral links, I symmetry, respectively. This study provides further insight into the molecular design, as well as theoretical characterization, of the DNA and protein catenanes.
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
Energy Technology Data Exchange (ETDEWEB)
Palmer, T.S.; Zika, M.R.; Madsen, N.K.
2000-07-27
Unstructured mesh particle transport and diffusion methods are gaining wider acceptance as mesh generation, scientific visualization and linear solvers improve. This paper describes an algorithm that is currently being used in the KULL code at Lawrence Livermore National Laboratory to solve the radiative transfer equations. The algorithm employs a point-centered diffusion discretization on arbitrary polyhedral meshes in 3D. We present the results of a few test problems to illustrate the capabilities of the radiation diffusion module.
Laboratory Reactor for Processing Carbon-Containing Sludge
Korovin, I. O.; Medvedev, A. V.
2016-10-01
The paper describes a reactor for high-temperature pyrolysis of carbon-containing sludge with the possibility of further development of environmentally safe technology of hydrocarbon waste disposal to produce secondary products. A solution of the urgent problem has been found: prevention of environmental pollution resulting from oil pollution of soils using the pyrolysis process as a method of disposal of hydrocarbon waste to produce secondary products.
Flexible Polyhedral Surfaces with Two Flat Poses
Directory of Open Access Journals (Sweden)
Hellmuth Stachel
2015-05-01
Full Text Available We present three types of polyhedral surfaces, which are continuously flexible and have not only an initial pose, where all faces are coplanar, but pass during their self-motion through another pose with coplanar faces (“flat pose”. These surfaces are examples of so-called rigid origami, since we only admit exact flexions, i.e., each face remains rigid during the motion; only the dihedral angles vary. We analyze the geometry behind Miura-ori and address Kokotsakis’ example of a flexible tessellation with the particular case of a cyclic quadrangle. Finally, we recall Bricard’s octahedra of Type 3 and their relation to strophoids.
Polybenzoxazine/Polyhedral Oligomeric Silsesquioxane (POSS Nanocomposites
Directory of Open Access Journals (Sweden)
Mohamed Gamal Mohamed
2016-06-01
Full Text Available The organic/inorganic hybrid materials from polyhedral oligomeric silsesquioxane (POSS, inorganic nanoparticles and polybenzoxazine (PBZ have received much interesting recently due to their excellent thermal and mechanical properties, flame retardance, low dielectric constant, well-defined inorganic framework at nanosized scale level, and higher performance relative to those of non-hybrid PBZs. This review describes the synthesis, dielectric constants, and thermal, rheological, and mechanical properties of covalently bonded mono- and multifunctionalized benzoxazine POSS hybrids, other functionalized benzoxazine POSS derivatives, and non-covalently (hydrogen bonded benzoxazine POSS composites.
Interactive volume visualization of general polyhedral grids
Muigg, Philipp
2011-12-01
This paper presents a novel framework for visualizing volumetric data specified on complex polyhedral grids, without the need to perform any kind of a priori tetrahedralization. These grids are composed of polyhedra that often are non-convex and have an arbitrary number of faces, where the faces can be non-planar with an arbitrary number of vertices. The importance of such grids in state-of-the-art simulation packages is increasing rapidly. We propose a very compact, face-based data structure for representing such meshes for visualization, called two-sided face sequence lists (TSFSL), as well as an algorithm for direct GPU-based ray-casting using this representation. The TSFSL data structure is able to represent the entire mesh topology in a 1D TSFSL data array of face records, which facilitates the use of efficient 1D texture accesses for visualization. In order to scale to large data sizes, we employ a mesh decomposition into bricks that can be handled independently, where each brick is then composed of its own TSFSL array. This bricking enables memory savings and performance improvements for large meshes. We illustrate the feasibility of our approach with real-world application results, by visualizing highly complex polyhedral data from commercial state-of-the-art simulation packages. © 2011 IEEE.
On polyhedral approximations in an n-dimensional space
Balashov, M. V.
2016-10-01
The polyhedral approximation of a positively homogeneous (and, in general, nonconvex) function on a unit sphere is investigated. Such a function is presupporting (i.e., its convex hull is the supporting function) for a convex compact subset of R n . The considered polyhedral approximation of this function provides a polyhedral approximation of this convex compact set. The best possible estimate for the error of the considered approximation is obtained in terms of the modulus of uniform continuous subdifferentiability in the class of a priori grids of given step in the Hausdorff metric.
A polyhedral approach to computing border bases
Braun, Gábor
2009-01-01
Border bases can be considered to be the natural extension of Gr\\"obner bases that have several advantages. Unfortunately, to date the classical border basis algorithm relies on (degree-compatible) term orderings and implicitly on reduced Gr\\"obner bases. We adapt the classical border basis algorithm to allow for calculating border bases for arbitrary degree-compatible order ideals, which is \\emph{independent} from term orderings. Moreover, the algorithm also supports calculating degree-compatible order ideals with \\emph{preference} on contained elements, even though finding a preferred order ideal is NP-hard. Effectively we retain degree-compatibility only to successively extend our computation degree-by-degree. The adaptation is based on our polyhedral characterization: order ideals that support a border basis correspond one-to-one to integral points of the order ideal polytope. This establishes a crucial connection between the ideal and the combinatorial structure of the associated factor spaces.
Zero point energy of polyhedral water clusters.
Anick, David J
2005-06-30
Polyhedral water clusters (PWCs) are cage-like (H2O)n clusters where every O participates in exactly three H bonds. For a database of 83 PWCs, 8 zero point energy (ZPE) was calculated at the B3LYP/6-311++G** level. ZPE correlates negatively with electronic energy (E0): each increase of 1 kcal/mol in E0 corresponds to a decrease of about 0.11 kcal/mol in ZPE. For each n, a set of four connectivity parameters accounts for 98% or more of the variance in ZPE. Linear regression of ZPE against n and this set gives an RMS error of 0.13 kcal/mol. The contributions to ZPE from stretch modes only (ZPE(S)) and from torsional modes only (ZPE(T)) also correlate strongly with E0 and with each other.
Pham, Hung Tan; Nguyen, Minh Tho
2015-07-14
Using density functional theory with the TPSSh functional and the 6-311+G(d) basis set, we extensively searched for the global minima of two metallic atoms doped boron clusters B6M2, B7M2, B12M2 and B14M2 with transition metal element M being Co and Fe. Structural identifications reveal that B7Co2, B7Fe2 and B7CoFe clusters have global minima in a B-cyclic motif, in which a perfectly planar B7 is coordinated with two metallic atoms placed along the C7 axis. The B6 cluster is too small to form a cycle with the presence of two metals. Similarly, the B12 cluster is not large enough to stabilize the metallic dimer within a double ring 2 × B6 tube. The doped B14M2 clusters including B14Co2, B14Fe2 and B14CoFe have a double ring 2 × B7 tubular shape in which one metal atom is encapsulated by the B14 tube and the other is located at an exposed position. Dissociation energies demonstrate that while bimetallic cyclic cluster B7M2 prefers a fragmentation channel that generates the B7 global minimum plus metallic dimer, the tubular structure B14M2 tends to dissociate giving a bimetallic cyclic structure B7M2 and a B@B6 cluster. The enhanced stability of the bimetallic doped boron clusters considered can be understood from the stabilizing interactions between the anti-bonding MOs of metal-metal dimers and the levels of a disk aromatic configuration (for bimetallic cyclic structures), or the eigenstates of the B14 tubular form (in case of bimetallic tubular structure).
Robust structural identification via polyhedral template matching
Mahler Larsen, Peter; Schmidt, Søren; Schiøtz, Jakob
2016-06-01
Successful scientific applications of large-scale molecular dynamics often rely on automated methods for identifying the local crystalline structure of condensed phases. Many existing methods for structural identification, such as common neighbour analysis, rely on interatomic distances (or thresholds thereof) to classify atomic structure. As a consequence they are sensitive to strain and thermal displacements, and preprocessing such as quenching or temporal averaging of the atomic positions is necessary to provide reliable identifications. We propose a new method, polyhedral template matching (PTM), which classifies structures according to the topology of the local atomic environment, without any ambiguity in the classification, and with greater reliability than e.g. common neighbour analysis in the presence of thermal fluctuations. We demonstrate that the method can reliably be used to identify structures even in simulations near the melting point, and that it can identify the most common ordered alloy structures as well. In addition, the method makes it easy to identify the local lattice orientation in polycrystalline samples, and to calculate the local strain tensor. An implementation is made available under a Free and Open Source Software license.
Self organized locomotion via polyhedral geometry: a minimal example
Ghosh, Shankar; Bhattacharya, S; Nitsure, Nitin
2016-01-01
In this paper we establish a geometrical route to self-organisation. We show that the relevant underlying geometry of the configuration space is a curvilinear polyhedral region. The energetics over the polyhedral region localizes the available space within the close proximity of a corner of this polyhedra. This results into a stronger entrapment of the state which provides it the observed geometrical shape, functionality, and maintains its stability. These theoretical considerations are borne out in the experiments where we study the case of an uphill locomotion of a self organised dumbbell pair placed in a rotating cylinder.
Optimization of antioxidant additives in carbon-containing castables
He, Huiqing
Oxidation of carbon is a major drawback for oxide-carbon composite refractories, especially for a castable which is inherently more porous than a brick. Magnesia-based material system hold a potential to be used in slag line of steelmaking ladles due to their high corrosion resistance to basic slag and are chosen as the material of study in this thesis. Overcoming the difficulties of introducing flake graphite into such castables and of protecting it from oxidation have constituted the principal goals of this work. The results have demonstrated that important factors to minimize oxidation of carbon-containing castables are the nature of carbon source, the antioxidants and the densification of the materials. In this thesis it has been shown that: 1. The mode of incorporating flake graphite into castables plays a decisive role in developing graphite containing castables. Modified flake graphite pellets by extruding (EG) and coating (CG) efficiently reduce water addition and pore size, increasing bulk density, CMOR, thermal shock parameter and oxidation resistance of the castables. 2. Packaging natural flake graphite by incorporating antioxidants and oxide fillers into extruded graphite pellets sufficiently improve densification, pore size distribution, new compound formations and oxidation resistance of the pellets. The best EG pellets for the MgO-MA-C system contains 80% graphite, 15% Al2O3 and 5% B4C or 80% graphite, 15%Al and 5% B4C. The best EG pellets for the MgO-M2S-C system contains 80% graphite and 20% Si or 80% graphite and 20% SIC. 3. Specific antioxidants sufficiently improve oxidation resistance both locally in extruded graphite pellets and overall in the matrix of the castables. Based upon our findings it is more appropriate to use aluminium buried in EG pellets and a minimum amount into the castable matrix part. 4. The antioxidants not only protect graphite from oxidation but also improve the mechanical properties of the EG pellets and the castables
Polyhedral oligomeric silsesquioxane grafted polymer in polymeric foam
King, Bruce A.; Patankar, Kshitish A.; Costeux, Stephane; Jeon, Hyun K.
2017-01-17
A polymeric foam article with a polymer matrix defining multiple cells therein has a polymer component with a first polymer that is a polyhedral oligomeric silsesquioxane grafted polymer that has a weight-average molecular weight of two kilograms per mole or higher and 200 kilograms per mole or lower.
Polyhedrical Heuristics of Periodical Qualities in the Numerical Divisibility Variation
Directory of Open Access Journals (Sweden)
José Ricardo Díaz Caballero
2013-06-01
Full Text Available The present work demonstrate how this polyhedral heuristic is also revealed in the Set of NaturalNumbers, where it is manifested numerical regularities similar to he platonic polyhedra developmentswhich open a wide field for the study of new numerical regularities as those associated to the periodicityvariation of its divisibility.
Estimation and optimization of the performance of polyhedral process networks
Haastregt, Sven Joseph Johannes van
2013-01-01
A system-level design methodology such as Daedalus provides designers with a forward synthesis flow for automated design, programming, and implementation of multiprocessor systems-on-chip. Daedalus employs the polyhedral process network model of computation to represent applications. These networks
Effect of Carbon Containing Materials on Pure Carbon Reaction-bonded SiC
Institute of Scientific and Technical Information of China (English)
JI Xiaoli; WEI Lei; SUN Feng
2008-01-01
Petroleum coke, graphite, gas carbon and lower sulfur carbon black were used to prepare reaction-bonded silicon carbide. The influences of different carbon containing materials on properties of carbonaceous precursors, sintering process, and microstructure of the prepared SiC were researched. The results show that:(1)With the density of carbon containing materials increasing, the porosity of carbonaceous precursors decreases and the infiltrating process of liquid silicon is more difficult.(2)The reaction between carbon containing materials and liquid silicon, the volume effect is more obvious with the density of carbon containing materials increasing.(3)As the carbon containing materials density decreasing, residual carbon in reaction bonded SiC also decreases.
Clustered deep shadow maps for integrated polyhedral and volume rendering
Bornik, Alexander
2012-01-01
This paper presents a hardware-accelerated approach for shadow computation in scenes containing both complex volumetric objects and polyhedral models. Our system is the first hardware accelerated complete implementation of deep shadow maps, which unifies the computation of volumetric and geometric shadows. Up to now such unified computation was limited to software-only rendering . Previous hardware accelerated techniques can handle only geometric or only volumetric scenes - both resulting in the loss of important properties of the original concept. Our approach supports interactive rendering of polyhedrally bounded volumetric objects on the GPU based on ray casting. The ray casting can be conveniently used for both the shadow map computation and the rendering. We show how anti-aliased high-quality shadows are feasible in scenes composed of multiple overlapping translucent objects, and how sparse scenes can be handled efficiently using clustered deep shadow maps. © 2012 Springer-Verlag.
Symmetry and size of membrane protein polyhedral nanoparticles
Li, Di; Haselwandter, Christoph A
2016-01-01
In recent experiments [T. Basta et al., Proc. Natl. Acad. Sci. U.S.A. 111, 670 (2014)] lipids and membrane proteins were observed to self-assemble into membrane protein polyhedral nanoparticles (MPPNs) with a well-defined polyhedral protein arrangement and characteristic size. We develop a model of MPPN self-assembly in which the preferred symmetry and size of MPPNs emerge from the interplay of protein-induced lipid bilayer deformations, topological defects in protein packing, and thermal effects. With all model parameters determined directly from experiments, our model correctly predicts the observed symmetry and size of MPPNs. Our model suggests how key lipid and protein properties can be modified to produce a range of MPPN symmetries and sizes in experiments.
Form-finding with polyhedral meshes made simple
Tang, Chengcheng
2014-07-27
We solve the form-finding problem for polyhedral meshes in a way which combines form, function and fabrication; taking care of user-specified constraints like boundary interpolation, planarity of faces, statics, panel size and shape, enclosed volume, and last, but not least, cost. Our main application is the interactive modeling of meshes for architectural and industrial design. Our approach can be described as guided exploration of the constraint space whose algebraic structure is simplified by introducing auxiliary variables and ensuring that constraints are at most quadratic. Computationally, we perform a projection onto the constraint space which is biased towards low values of an energy which expresses desirable "soft" properties like fairness. We have created a tool which elegantly handles difficult tasks, such as taking boundary-alignment of polyhedral meshes into account, planarization, fairing under planarity side conditions, handling hybrid meshes, and extending the treatment of static equilibrium to shapes which possess overhanging parts.
Flops and mutations for crepant resolutions of polyhedral singularities
de Celis, Alvaro Nolla
2011-01-01
We prove that any crepant resolution of a polyhedral singularity C^3/G for G a subgroup of SO(3) of types Z/nZ, D_{2n} and T is isomorphic to a moduli space of representations of a quiver with relations. Moreover we classify all crepant resolutions explicitly by giving an open cover and find a one-to-one correspondence between them and mutations of the McKay quiver.
Nanoscale Continuum Modelling of Carbon Nanotubes by Polyhedral Finite Elements
Directory of Open Access Journals (Sweden)
Logah Perumal
2016-01-01
Full Text Available As the geometry of a cell of carbon nanotube is hexagonal, a new approach is presented in modelling of single-walled carbon nanotubes using polyhedral finite elements. Effect of varying length, diameter, and thickness of carbon nanotubes on Young’s modulus is studied. Both armchair and zigzag configurations are modelled and simulated in Mathematica. Results from current approach found good agreement with the other published data.
Erosion Effect of Molten Steel on Carbon Containing Refractories for Continuous Casting
Institute of Scientific and Technical Information of China (English)
LI Hongxia; YANG Bin; LIU Guoqi; CHENG Hepeng
2007-01-01
The erosion resistance of carbon containing refractories for continuous casting to molten steel was investigated by means of simulative erosion test and examining used refractories.Decolonization and reaction between molten steel and decolonization layer are main erosion process of carbon containing refractories by1 molten steel.The reactions between molten steel and oxide in refractories determine the thickness of decarbonization layer A dense layer formation on the working surface contacting with molten steel during casting will suppress decarbonization and erosion process.
When do the recession cones of a polyhedral complex form a fan?
Gil, José Ignacio Burgos
2010-01-01
We study the problem of when the collection of the recession cones of a polyhedral complex forms also a complex. We exhibit an example showing that this is no always the case. We also show that if the support of the given polyhedral complex satisfies a Minkowski-Weyl type condition, then the answer is positive. As a consequence, we obtain a classification theorem for proper toric schemes over a discrete valuation ring in terms of complete strongly convex rational polyhedral complexes.
2010-10-21
Technical Paper 3. DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Functional Perfluoroalkyl Polyhedral Oligomeric Silsesquioxane (F...long chain fluorinated alkyl groups ranging from 6-12 carbon atoms in length. Herein, a disilanol perfluoroalkyl polyhedral oligomeric...FUNCTIONAL PERFLUOROALKYL POLYHEDRAL OLIGOMERIC SILSESQUIOXANES (F-POSS): BUILDING BLOCKS FOR LOW SURFACE ENERGY MATERIA LS Sean M Rami,.e:, Yvonne Dia
On the accuracy of uniform polyhedral approximations of the copositive cone
Yıldırım, Emre Alper
2012-01-01
We consider linear optimization problems over the cone of copositive matrices. Such conic optimization problems, called copositive programs, arise from the reformulation of a wide variety of difficult optimization problems. We propose a hierarchy of increasingly better outer polyhedral approximations to the copositive cone. We establish that the sequence of approximations is exact in the limit. By combining our outer polyhedral approximations with the inner polyhedral approximations due to de...
The braid index of complicated DNA polyhedral links.
Directory of Open Access Journals (Sweden)
Xiao-Sheng Cheng
Full Text Available The goal of this paper is to determine the braid index of two types of complicated DNA polyhedral links introduced by chemists and biologists in recent years. We shall study it in a more broad context and actually consider so-called Jaeger's links (more general Traldi's links which contain, as special cases, both four types of simple polyhedral links whose braid indexes have been determined and the above two types of complicated DNA polyhedral links. Denote by b(L and c(L the braid index and crossing number of an oriented link L, respectively. Roughly speaking, in this paper, we prove that b(L = c(L/2 + 1 for any link L in a family including Jaeger's links and contained in Traldi's links, which is obtained by combining the MFW inequality and an Ohyama's result on upper bound of the braid index. Our result may be used to to characterize and analyze the structure and complexity of DNA polyhedra and entanglement in biopolymers.
Polyhedral Boranes: A Versatile Building Block for Nanoporous Materials
Clingerman, Daniel Jon
The studies described in this dissertation examine several new concepts related to polyhedral boranes and their applications towards the synthesis of novel nanoporous materials. The unique thermal and chemical robustness, rigidity, quasi-spherical geometry, and high boron content of polyhedral boranes are explored to generate materials not possible with typical organic synthons. Aside from the fundamental synthetic work, this work was also aimed at solving larger global issues such as energy storage and new routes to therapeutics. Chapter 2 highlights the discovery of the first highly porous carborane-based metal-organic framework, where the spherical nature of the carborane increases volumetric surface area without reducing pore volume. Chapter 3 examines the first tritopic carborane-based ligand and the stabilizing effect the rigid, sterically bulky carboranyl groups have on highly porous topologies not stable with typical organic ligands. Chapters 4 and 5 describe the use of polyhedral borane-based ligands as a means to influence and generate unexpected topologies. Lastly, chapter 6 explores using a simple carborane-based ligand that harnesses the power of coordination-driven assembly to rapidly generate a high boron-containing supramolecular cuboctahedron.
Physical and numerical modeling of labyrinth weirs with polyhedral bottom
Directory of Open Access Journals (Sweden)
J. San Mauro
2016-07-01
Full Text Available In order to comply with the new safety regulations a significant number of Spanish dam spillways must be upgraded. In this scenario and with the aim of increasing the discharge capacity with a reduced investment innovative designs become interesting solutions. One of these innovative designs are the labyrinth weirs. Project POLILAB is carrying out with the objective of optimize the design of labyrinth weirs, physical and numerical tests exposed in this article were developed within this framework. The most relevant results are related with the discharge capacity, the flow pattern and the structural reinforcement achieved by the implementation of a polyhedral bottom.
Form-finding with polyhedral meshes made simple
Tang, Chengcheng
2015-08-09
We solve the form-finding problem for polyhedral meshes in a way which combines form, function and fabrication; taking care of user-specified constraints like boundary interpolation, planarity of faces, statics, panel size and shape, enclosed volume, and cost. Our main application is the interactive modeling of meshes for architectural and industrial design. Our approach can be described as guided exploration of the constraint space whose algebraic structure is simplified by introducing auxiliary variables and ensuring that constraints are at most quadratic.
Temperature dependence of polyhedral cage volumes in clathrate hydrates
Chakoumakos, B.C.; Rawn, C.J.; Rondinone, A.J.; Stern, L.A.; Circone, S.; Kirby, S.H.; Ishii, Y.; Jones, C.Y.; Toby, B.H.
2003-01-01
The polyhedral cage volumes of structure I (sI) (carbon dioxide, methane, trimethylene oxide) and structure II (sII) (methane-ethane, propane, tetrahydrofuran, trimethylene oxide) hydrates are computed from atomic positions determined from neutron powder-diffraction data. The ideal structural formulas for sI and sII are, respectively, S2L6 ?? 46H2O and S16L???8 ?? 136H2O, where S denotes a polyhedral cage with 20 vertices, L a 24-cage, and L??? a 28-cage. The space-filling polyhedral cages are defined by the oxygen atoms of the hydrogen-bonded network of water molecules. Collectively, the mean cage volume ratio is 1.91 : 1.43 : 1 for the 28-cage : 24-cage : 20-cage, which correspond to equivalent sphere radii of 4.18, 3.79, and 3.37 A??, respectively. At 100 K, mean polyhedral volumes are 303.8, 227.8, and 158.8 A??3 for the 28-cage, 24-cage, and 20-cage, respectively. In general, the 20-cage volume for a sII is larger than that of a sI, although trimethylene oxide is an exception. The temperature dependence of the cage volumes reveals differences between apparently similar cages with similar occupants. In the case of trimethylene oxide hydrate, which forms both sI and sII, the 20-cages common to both structures contract quite differently. From 220 K, the sII 20-cage exhibits a smooth monotonic reduction in size, whereas the sI 20-cage initially expands upon cooling to 160 K, then contracts more rapidly to 10 K, and overall the sI 20-cage is larger than the sII 20-cage. The volumes of the large cages in both structures contract monotonically with decreasing temperature. These differences reflect reoriented motion of the trimethyelene oxide molecule in the 24-cage of sI, consistent with previous spectroscopic and calorimetric studies. For the 20-cages in methane hydrate (sI) and a mixed methane-ethane hydrate (sII), both containing methane as the guest molecule, the temperature dependence of the 20-cage volume in sII is much less than that in sI, but sII is overall
Al4C3 Hydration Thermochemical Analysis for Burned Carbon-containing Refractories with Al
Institute of Scientific and Technical Information of China (English)
YANG Ding'ao; YU Zhiming; FAN Liuwu
2003-01-01
In this paper, X-ray diffractogram analysis and SEM observation of Al4 C3 formed at high temperature from carbon-containing refractories with Al have been carried out.Aluminum added to carbon-containing refractories reacts with C(s)to form Al4 C3(s) gradually during heating from 600 ℃ to 1200℃.It is considered that the interlocked structure of Al4 C3 plate crystals promotes the outstanding increase of hot modulus of rupture of carbon-containing refractories with Al. The HMOR of carbon-containing refractories added with Al additive from 0 to 5wt％ increases by 2.8 times being from 6.5MPa to 18.2MPa.After a thermochemical calculation for hydration reaction processes of Al4 C3 and H2O(g), the equilibrium partial pressure chart of H2O(g)in H2O-Al4C3-Al(OH)3 system vs various temperatures has been attained . The H2O (g) partial pressure in the air needed for the Al4 C3 hydration reaction is no more than 10～18 atm at the temperature below 120℃.It is considered that the burned carbon-containing refractories with Al is extremely easy to hydrate and the cracking of burned carbon-containing refractories is generated because that the hydration expansion is 2.11 times during transforming from Al4 C3 to Al(OH)3.The fundamental measure against hydration of the refractories is to insulate the refractories from H2O(g)by various means such as pitch impregnation or other sealing materials.
Gauss images of hyperbolic cusps with convex polyhedral boundary
Fillastre, François
2009-01-01
We prove that a 3--dimensional hyperbolic cusp with convex polyhedral boundary is uniquely determined by its Gauss image. Furthermore, any spherical metric on the torus with cone singularities of negative curvature and all closed contractible geodesics of length greater than $2\\pi$ is the metric of the Gauss image of some convex polyhedral cusp. This result is an analog of the Rivin-Hodgson theorem characterizing compact convex hyperbolic polyhedra in terms of their Gauss images. The proof uses a variational method. Namely, a cusp with a given Gauss image is identified with a critical point of a functional on the space of cusps with cone-type singularities along a family of half-lines. The functional is shown to be concave and to attain maximum at an interior point of its domain. As a byproduct, we prove rigidity statements with respect to the Gauss image for cusps with or without cone-type singularities. In a special case, our theorem is equivalent to existence of a circle pattern on the torus, with prescrib...
Green Nanocomposites from Renewable Plant Oils and Polyhedral Oligomeric Silsesquioxanes
Directory of Open Access Journals (Sweden)
Takashi Tsujimoto
2015-06-01
Full Text Available Green nanocomposites based on renewable plant oils and polyhedral oligomeric silsesquioxanes (POSS have been developed. An acid-catalyzed curing of epoxidized plant oils with oxirane-containing POSS derivatives produced transparent nanocomposite coatings with high gloss surface, in which the organic and inorganic components were linked via covalent bonds. The hardness and mechanical strength were improved by the incorporation of the POSS unit into the organic polymer matrix. Nanostructural analyses of the nanocomposites showed the formation of homogeneous structures at the micrometer scale. On the other hand, such improvements of the coating and mechanical properties were not observed in the composite without covalent bonds between the plant oil-based polymer and POSS unit. The study demonstrates the correlation between the nanostructure of composites and macroscopic properties.
Ricci Curvature on Polyhedral Surfaces via Optimal Transportation
Directory of Open Access Journals (Sweden)
Benoît Loisel
2014-03-01
Full Text Available The problem of correctly defining geometric objects, such as the curvature, is a hard one in discrete geometry. In 2009, Ollivier defined a notion of curvature applicable to a wide category of measured metric spaces, in particular to graphs. He named it coarse Ricci curvature because it coincides, up to some given factor, with the classical Ricci curvature, when the space is a smooth manifold. Lin, Lu and Yau and Jost and Liu have used and extended this notion for graphs, giving estimates for the curvature and, hence, the diameter, in terms of the combinatorics. In this paper, we describe a method for computing the coarse Ricci curvature and give sharper results, in the specific, but crucial case of polyhedral surfaces.
Electrorheology of polystyrene filler/polyhedral silsesquioxane suspensions.
McIntyre, Ernest C; Yang, Hengxi; Green, Peter F
2012-04-01
An important challenge in the field of electrorheology is identifying low-viscosity fluids that would exhibit significant changes in viscosity, or a yield stress, upon the application of an external electric field. Our recent research showed that optimal compositions of mixtures, 10 wt % sulfonated polyhedral oligomeric silsesquioxanes (s-POSS) mixed with polydimethyl siloxane (PDMS), exhibited significant electrorheological activity. Here we show that s-POSS/PDMS mixtures containing polystyrene (PS) fillers, of micrometer-sized dimensions, containing as little as ~1 wt % s-POSS, exhibited an increase in ER activity by an order of magnitude, beyond that of s-POSS/PDMS mixtures. The dynamic yield stress was found to scale with the particle diameter, a, as τ(y) is proportional to a(0.5) and with the electric field as τ(y) is proportional to E(1.5-2.5); this behavior is reasonably well understood within the context of dielectric electrorheological theory.
Materials and Concepts for Full Ceramic SOFCs with Focus on Carbon Containing Fuels
DEFF Research Database (Denmark)
Holtappels, Peter; Sudireddy, Bhaskar Reddy; Veltzé, Sune
Todays' solid oxide fuels cells based on composite Ni-cermet anodes have been developed op to reasonable levels of performance and durability. However, especially for small combined heat and power supply systems, known failure mechanisms e.g. re-oxidation, sulfur tolerance and coking have...... stimulated the development for full ceramic anodes based on strontium titanates. Furthermore, the Ni-cermet is primarily a hydrogen oxidation electrode and efficiency losses might occur when operating on carbon containing fuels. In a recent European project full ceramic cells comprising CGO/Ni infiltrated Nb......, stability, and S- tolerance has been investigated. These results and an assessment on a 1 kW system level using CPOX reformed natural gas will be reviewed and further perspectives of the cell concept discussed, especially with respect to efficient operation on high carbon containing fuels....
Facile synthesis of Ag2S nanoparticles functionalized by carbon-containing citrate shell
Sadovnikov, S. I.; Gusev, A. I.; Gerasimov, E. Yu.; Rempel, A. A.
2015-12-01
Silver sulfide nanoparticles with non-toxic citrate shell are synthesized by chemical bath deposition from aqueous mixtures of silver nitrate and sodium sulfide in the presence of sodium citrate used as a complexing and stabilizing agent. The prepared nanoparticles have Ag2S core with monoclinic crystal structure functionalized by a carbon-containing citrate shell. By varying the concentrations of reagents it was possible to prepare core-shell nanoparticles with pre-assigned size of Ag2S core from 10 and 50 nm and pre-assigned thickness from 1.5 to 10 nm of citrate shell. A probable mechanism of formation of carbon-containing citrate shell on Ag2S core has been proposed.
Directory of Open Access Journals (Sweden)
G. Zhang
2012-12-01
Full Text Available Growing evidence suggests that size-resolved mixing state of carbon-containing particles is very critical in determining their optical properties, atmospheric lifetime, and impact on the environment. However, still little is known about the mixing state of particles in urban area of Pearl River Delta (PRD region, China. To investigate the mixing state of submicron carbon-containing particles, measurements were carried out during spring and fall periods of 2010 using a single particle aerosol mass spectrometer (SPAMS. Approximate 700 000 particles for each period were detected. This is the first report on the size-resolved mixing state of carbon-containing particles by direct observations in PRD region. Cluster analysis of single particle mass spectra was applied to identify carbon-containing particle classes. These classes represented ~80% and ~90% of all the detected particles for spring and fall periods, respectively. Carbon-containing particle classes mainly consisted of biomass/biofuel burning particles (Biomass, organic carbon (OC, fresh elemental carbon (EC-fresh, internally mixed OC and EC (ECOC, internally mixed EC with sulfate (EC-Sulfate, vanadium-containing ECOC (V-ECOC, and amines-containing particles (Amine. In spring, the top three ranked carbon-containing particle classes were ECOC (26.1%, Biomass (23.6% and OC (10%, respectively. However, the fraction of Biomass particles increased remarkably and predominated (61.0%, while the fraction of ECOC (3.0% and V-ECOC (0.1% significantly decreased in fall. To highlight the influence of monsoon on the properties of carbon-containing particles in urban Guangzhou, their size distribution, mixing state, and aerosol acidity were compared between spring and fall seasons. In addition, a case study was also performed to investigate how the formation of fog and haze influenced the mixing state of carbon-containing particles. These results are of importance in understanding atmospheric chemistry
Energy Technology Data Exchange (ETDEWEB)
Pham Minh, Doan, E-mail: doan.phamminh@mines-albi.fr [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Tran, Ngoc Dung; Nzihou, Ange [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Sharrock, Patrick [Université de Toulouse, SIMAD, IUT Paul Sabatier, Avenue Georges Pompidou, 81104 Castres (France)
2013-07-01
The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 °C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG–MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 °C to 80 °C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG–MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 °C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials. Highlights: • The synthesis of carbonate-containing apatites from CaCO{sub 3} and H{sub 3}PO{sub 4} was studied. • The decomposition of CaCO{sub 3} particles was complete at 80 °C, 13.2 bar for 48 h. • The transformation of CaCO{sub 3} and H{sub 3}PO{sub 4} into apatitic products was also complete. • Pure carbonate-containing apatite was directly obtained without water-rising step.
Institute of Scientific and Technical Information of China (English)
Zhuang Yahui; Zhang Hongxun; Wang Xiaoke; Li Changsheng
2004-01-01
The report summarizes surveys on carbon inventories and initiatives on sustainable carbon cycling taken by the Research Center for EcoEnvironmental Sciences, where the authors work/worked. The first part of the report, which appeared in the preceding issue of this journal, deals with the concept of sustainable carbon cycling, the historic evolution of carbon cycling processes in China, carbon pool enhancement, value addition,carbon sequestration and carbon balance. This very paper, as the second part of the report, covers the results of carbon dynamics modeling, emission inventories of various carbon-containing greenhouse gases and their potential abatement measures.
Methods of pretreating comminuted cellulosic material with carbonate-containing solutions
Francis, Raymond
2012-11-06
Methods of pretreating comminuted cellulosic material with an acidic solution and then a carbonate-containing solution to produce a pretreated cellulosic material are provided. The pretreated material may then be further treated in a pulping process, for example, a soda-anthraquinone pulping process, to produce a cellulose pulp. The pretreatment solutions may be extracted from the pretreated cellulose material and selectively re-used, for example, with acid or alkali addition, for the pretreatment solutions. The resulting cellulose pulp is characterized by having reduced lignin content and increased yield compared to prior art treatment processes.
Polyhedral Oligomeric Silsesquioxane Functionalized Carbon Dots for Cell Imaging.
Wang, Wen-Jing; Hai, Xin; Mao, Quan-Xing; Chen, Ming-Li; Wang, Jian-Hua
2015-08-05
In the present study, octa-aminopropyl polyhedral oligomeric silsesquioxane hydrochloride salt (OA-POSS) functionalized carbon dots (CDs/POSS) are prepared by a one-pot approach with glycerol as carbon source and solvent medium. OA-POSS serves as a passivation agent, and it is obtained via hydrolytic condensation of 3-aminopropyltriethoxysilane (APTES). During the functionalization process, the amino groups on OA-POSS combine with carboxylic groups on the bare CDs via formation of amide bond to construct organic-inorganic hybrid carbon dots. The obtained CDs/POSS are well dispersed in aqueous medium with a diameter of ca. 3.6 nm. It is demonstrated that CDs/POSS provide favorable photoluminescent property with a quantum yield of 24.0%. They also exhibit resistance to photobleaching and excellent photoluminescence stability in the presence of biological sample matrix (characterized by heavy metals and organic molecules), which facilitate cell imaging in biological systems. Both the photoluminescent emission wavelength and the fluorescence intensity depend closely on the excitation wavelength, and thus, it provides a potential for multicolor imaging as demonstrated with HeLa cells and MCF-7 cells.
Ribulose 1,5-bisphosphate carboxylase and polyhedral bodies of Chlorogloeopsis fritschii.
Lanaras, T; Codd, G A
1981-11-01
Ribulose 1,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) activity was approximately equally distributed between supernatant and pellet fractions produced by differential centrifugation of disrupted cells of Chlorogloeopsis fritschii. Low ionic strength buffer favoured the recovery of particulate RuBP carboxylase. Density gradient centrifugation of resuspended cell-free particulate material produced a single band of RuBP carboxylase activity, which was associated with the polyhedral body fraction, rather than with the thylakoids or other observable particles. Isolated polyhedral body stability was improved by density gradient centrifugation through gradients of Percoll plus sucrose in buffer, which yielded apparently intact polyhedral bodies. These were 100 to 150 nm in diameter and contained ring-shaped, 12 nm diameter particles. It is inferred that the C. fritschii polyhedral bodies are carboxysomes. Sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis of SDS-dissociated polyhedral bodies revealed 8 major polypeptides. The most abundant, with molecular weights of 52,000 and 13,000, correspond with the large and small subunits, respectively, of RuBP carboxylase.
Liu, Hongyu; Petrini, Michele; Rondi, Luca; Xiao, Jingni
2017-02-01
The aim of the paper is to establish optimal stability estimates for the determination of sound-hard polyhedral scatterers in RN, N ≥ 2, by a minimal number of far-field measurements. This work is a significant and highly nontrivial extension of the stability estimates for the determination of sound-soft polyhedral scatterers by far-field measurements, proved by one of the authors, to the much more challenging sound-hard case. The admissible polyhedral scatterers satisfy minimal a priori assumptions of Lipschitz type and may include at the same time solid obstacles and screen-type components. In this case we obtain a stability estimate with N far-field measurements. Important features of such an estimate are that we have an explicit dependence on the parameter h representing the minimal size of the cells forming the boundaries of the admissible polyhedral scatterers, and that the modulus of continuity, provided the error is small enough with respect to h, does not depend on h. If we restrict to N = 2 , 3 and to polyhedral obstacles, that is to polyhedra, then we obtain stability estimates with fewer measurements, namely first with N - 1 measurements and then with a single measurement. In this case the dependence on h is not explicit anymore and the modulus of continuity depends on h as well.
Hydrogen storage properties of carbon nanomaterials and carbon containing metal hydrides
Energy Technology Data Exchange (ETDEWEB)
Maehlen, Jan Petter
2003-07-01
The topic of this thesis is structural investigations of carbon containing materials in respect to their hydrogen storage properties. This work was initially triggered by reports of extremely high hydrogen storage capacities of specific carbon nanostructures. It was decided to try to verify and understand the mechanisms in play in case of the existence of such high hydrogen densities in carbon. Two different routes towards the goal were employed; by studying selected hydrides with carbon as one of its constituents (mainly employing powder diffraction techniques in combination with hydrogen absorption and desorption measurements) and by carefully conducting hydrogen sorption experiments on what was believed to be the most ''promising'' carbon nanomaterial sample. In the latter case, a lot of effort was attributed to characterisations of different carbon nanomaterial containing samples with the aid of electron microscopy. Three different carbon-containing metal hydride systems, Y2C-H, YCoC-H and Y5SiC0.2-H, were examined. A relation between hydrogen occupation and the local arrangement of metal and carbon atoms surrounding the hydrogen sites was established. Several characteristic features of the compounds were noted in addition to solving the structure of the former unknown deuterideY5Si3C0.2D2.0 by the use of direct methods. Several carbon-nanomaterial containing samples were studied by means of transmission electron microscopy and powder diffraction, thus gaining knowledge concerning the structural aspects of nanomaterials. Based on these investigations, a specific sample containing a large amount of open-ended single-wall carbon nanotubes was chosen for subsequent hydrogen storage experiments. The latter experiments revealed moderate hydrogen storage capacities of the nanotubes not exceeding the values obtained for more conventional forms of carbon. These two different routes in investigating the hydrogen storage properties of carbon and
Probing Black Carbon-containing Particle Microphysics with the Single-Particle Soot Photometer (SP2)
Sedlacek, A. J.; Lewis, E. R.; Onasch, T. B.; Lambe, A. T.; Davidovits, P.; Kleinman, L. I.
2012-12-01
Knowledge of the structure and mixing state of black-carbon containing particles is important for calculating their radiative forcing and provides insight into their source and life cycle. Recently analysis of black carbon-containing particles has demonstrated that for a fraction of such particles, the black carbon may reside on or near the surface of the particle as opposed to the traditional core-shell configuration typically assumed in which the black carbon core is surrounded by a shell of non-refractory material. During the DOE-sponsored Aerosol Lifecycle field campaign held in summer, 2011 at Brookhaven National Laboratory on Long Island, NY, episodes were encountered in which a high fraction of particles containing black carbon had such configurations, and these episodes corresponded to air masses that contained biomass burning plumes (Sedlacek et al., 2012). Subsequent analysis found other episodes in field campaigns in Colorado and California in which high fractions this configuration corresponded to biomass burning plumes. In an effort to evaluate this interpretation and explore formation mechanisms, a series of laboratory-based experiments examining the coagulation of regal black (surrogate for collapsed soot) with model non-refractory coatings [dioctyl sebacate (surrogate for organic aerosols with liquid-like character) and deliquesced ammonium sulfate (solid)] were carried out. The results of these experiments and their potential implications on black carbon radiative forcing will be discussed. Sedlacek, III, Arthur, E. R. Lewis, L. I. Kleinman, J. Xu and Q. Zhang (2012), Determination of and Evidence for Non-core-shell structure of particles containing black carbon using the single particle soot photometer (SP2). Geophys. Res. Lett., 39 L06802, doi:10.1029/2012GL050905
Rohr, Annette; McDonald, Jacob
2016-02-01
Air pollution is a complex mixture of gas-, vapor-, and particulate-phase materials comprised of inorganic and organic species. Many of these components have been associated with adverse health effects in epidemiological and toxicological studies, including a broad spectrum of carbonaceous atmospheric components. This paper reviews recent literature on the health impacts of organic aerosols, with a focus on specific sources of organic material; it is not intended to be a comprehensive review of all the available literature. Specific emission sources reviewed include engine emissions, wood/biomass combustion emissions, biogenic emissions and secondary organic aerosol (SOA), resuspended road dust, tire and brake wear, and cooking emissions. In addition, recent findings from large toxicological and epidemiological research programs are reviewed in the context of organic PM, including SPHERES, NPACT, NERC, ACES, and TERESA. A review of the extant literature suggests that there are clear health impacts from emissions containing carbon-containing PM, but difficulty remains in apportioning responses to certain groupings of carbonaceous materials, such as organic and elemental carbon, condensed and gas phases, and primary and secondary material. More focused epidemiological and toxicological studies, including increased characterization of organic materials, would increase understanding of this issue.
Directory of Open Access Journals (Sweden)
Der-Shan Sun
2016-12-01
Full Text Available The bactericidal activity of conventional titanium dioxide (TiO2 photocatalyst is effective only on irradiation by ultraviolet light, which restricts the applications of TiO2 for use in living environments. Recently, carbon-containing TiO2 nanoparticles [TiO2(C NP] were found to be a visible-light-responsive photocatalyst (VLRP, which displayed significantly enhanced antibacterial properties under visible light illumination. However, whether TiO2(C NPs exert antibacterial properties against Bacillus anthracis remains elusive. Here, we evaluated these VLRP NPs in the reduction of anthrax-induced pathogenesis. Bacteria-killing experiments indicated that a significantly higher proportion (40%–60% of all tested Bacillus species, including B. subtilis, B. cereus, B. thuringiensis, and B. anthracis, were considerably eliminated by TiO2(C NPs. Toxin inactivation analysis further suggested that the TiO2(C NPs efficiently detoxify approximately 90% of tested anthrax lethal toxin, a major virulence factor of anthrax. Notably, macrophage clearance experiments further suggested that, even under suboptimal conditions without considerable bacterial killing, the TiO2(C NP-mediated photocatalysis still exhibited antibacterial properties through the reduction of bacterial resistance against macrophage killing. Our results collectively suggested that TiO2(C NP is a conceptually feasible anti-anthrax material, and the relevant technologies described herein may be useful in the development of new strategies against anthrax.
Energy Technology Data Exchange (ETDEWEB)
Naga, Kazuhisa; Nakajima, Tsuyoshi; Aimura, Shinya; Ohzawa, Yoshimi [Department of Applied Chemistry, Aichi Institute of Technology, Yakusa, Toyota 470-0392 (Japan); Zemva, Boris; Mazej, Zoran [Jozef Stefan Institute, Jamova 39, 1000 Ljubljana (Slovenia); Groult, Henri [Universite Pierre et Marie Curie, LI2C Laboratoire Electrochimie, 4 Place Jussieu 75252 Paris 05 (France); Yoshida, Akira [Faculty of Engineering, Musashi Institute of Technology, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan)
2007-05-01
Surface modification of petroleum coke (PC) and those heat-treated at 1860, 2300 and 2800 C (PC1860, PC2300 and PC2800) has been performed by F{sub 2}, ClF{sub 3} and NF{sub 3} to improve their charge/discharge characteristics in propylene carbonate containing solvents. Surface fluorination by F{sub 2} increased surface disorder of PC1860, PC2300 and PC2800, leading to increase in their first coulombic efficiencies in 1 mol dm{sup -3} LiClO{sub 4}-ethylene carbonate (EC)/diethyl carbonate (DEC)/propylene carbonate (PPC) (1:1:1 in volume) solution. First coulombic efficiencies were the largest in fluorinated PC1860 with the highest surface disorder. However, surface modification by ClF{sub 3} and NF{sub 3} did not increase surface disorder of petroleum cokes, being not as effective as the fluorination with F{sub 2} to increase first coulombic efficiencies of petroleum cokes. The reactions of ClF{sub 3} and NF{sub 3} with carbon materials are radical reactions while the reaction with F{sub 2} is an electrophilic reaction yielding fluorinated layers with high disorder. Surface modification using F{sub 2}, ClF{sub 3} and NF{sub 3} also increased first charge capacities of PC and PC1860. (author)
Chemical Hydrogen Storage Using Polyhedral Borane Anions and Aluminum-Ammonia-Borane Complexes
Energy Technology Data Exchange (ETDEWEB)
Hawthorne, M. Frederick; Jalisatgi, Satish S.; Safronov, Alexander V.; Lee, Han Beak; Wu, Jianguo
2010-10-01
Phase 1. Hydrolysis of borohydride compounds offer the potential for significant hydrogen storage capacity, but most work to date has focused on one particular anion, BH4-, which requires high pH for stability. Other borohydride compounds, in particular polyhedral borane anions offer comparable hydrogen storage capacity without requiring high pH media and their long term thermal and hydrolytic stability coupled with non-toxic nature make them a very attractive alternative to NaBH4. The University of Missouri project provided the overall program focal point for the investigation of catalytic hydrolysis of polyhedral borane anions for hydrogen release. Due to their inherent stability, a transition metal catalyst was necessary for the hydrolysis of polyhedral borane anions. Transition metal ions such as cobalt, nickel, palladium and rhodium were investigated for their catalytic activity in the hydrolysis of nido-KB11H14, closo-K2B10H10, and closo-K2B12H12. The rate of hydrolysis follows first-order kinetics with respect to the concentration of the polyhedral borane anion and surface area of the rhodium catalyst. The rate of hydrolysis depends upon a) choice of polyhedral borane anion, c) concentration of polyhedral borane anion, d) surface area of the rhodium catalyst and e) temperature of the reaction. In all cases the yield of hydrogen was 100% which corresponds to ~7 wt% of hydrogen (based on material wt%). Phase 2. The phase 2 of program at the University of Missouri was focused upon developing aluminum ammonia-boranes (Al-AB) as chemical hydrogen storage materials, specifically their synthesis and studies of their dehydrogenation. The ammonia borane molecule (AB) is a demonstrated source of chemically stored hydrogen (19.6 wt%) which meets DOE performance parameters except for its regeneration from spent AB and elemental hydrogen. The presence of an aluminum center bonded to multiple AB residues might combine the efficiency of AB dehydrogenation with an aluminum
Gravity Anomalies of Arbitrary 3D Polyhedral Bodies with Horizontal and Vertical Mass Contrasts
Ren, Zhengyong; Chen, Chaojian; Pan, Kejia; Kalscheuer, Thomas; Maurer, Hansruedi; Tang, Jingtian
2017-03-01
During the last 15 years, more attention has been paid to derive analytic formulae for the gravitational potential and field of polyhedral mass bodies with complicated polynomial density contrasts, because such formulae can be more suitable to approximate the true mass density variations of the earth (e.g., sedimentary basins and bedrock topography) than methods that use finer volume discretization and constant density contrasts. In this study, we derive analytic formulae for gravity anomalies of arbitrary polyhedral bodies with complicated polynomial density contrasts in 3D space. The anomalous mass density is allowed to vary in both horizontal and vertical directions in a polynomial form of λ =ax^m+by^n+cz^t, where m, n, t are nonnegative integers and a, b, c are coefficients of mass density. First, the singular volume integrals of the gravity anomalies are transformed to regular or weakly singular surface integrals over each polygon of the polyhedral body. Then, in terms of the derived singularity-free analytic formulae of these surface integrals, singularity-free analytic formulae for gravity anomalies of arbitrary polyhedral bodies with horizontal and vertical polynomial density contrasts are obtained. For an arbitrary polyhedron, we successfully derived analytic formulae of the gravity potential and the gravity field in the case of m≤ 1, n≤ 1, t≤ 1, and an analytic formula of the gravity potential in the case of m=n=t=2. For a rectangular prism, we derive an analytic formula of the gravity potential for m≤ 3, n≤ 3 and t≤ 3 and closed forms of the gravity field are presented for m≤ 1, n≤ 1 and t≤ 4. Besides generalizing previously published closed-form solutions for cases of constant and linear mass density contrasts to higher polynomial order, to our best knowledge, this is the first time that closed-form solutions are presented for the gravitational potential of a general polyhedral body with quadratic density contrast in all spatial
Directory of Open Access Journals (Sweden)
Wangatia Lodrick Makokha
2015-03-01
Full Text Available Aggregation-induced quenching is particularly detrimental in perylene diimides, which are characterized by a near-unity fluorescence quantum yield in solution but are far less emissive in the solid state. Previously, perylene diimide has been improved by linking it to the inorganic cage of polyhedral oligomeric silsesquioxanes. As a further study on perylene diimidepolyhedral oligomeric silsesquioxanes, we report on a double functionalized molecular structure, which can be used for substitution at the bay area and as a side group in other materials. Typical solution absorption and emission features of the perylene diimide fragment have been observed in this new reactive perylene diimide-polyhedral oligomeric silsesquioxane. Moreover, reduced stacking during aggregation and spherical particles exhibiting solid fluorescence have been obtained. Organic semiconducting material with enhanced solid state photophysical properties, like solid fluorescence is a subject of great interest owing to its possible high-tech applications in optoelectronic devices.
Controlled Synthesis and Magnetic Properties of Uniform Hierarchical Polyhedral α-Fe2O3 Particles
Long, Nguyen Viet; Yang, Yong; Thi, Cao Minh; Phuc, Le Hong; Nogami, Masayuki
2017-02-01
The controlled synthesis of uniform hierarchical polyhedral iron (Fe) micro-/nanoscale oxide particles with the α-Fe2O3 structure is presented. The hierarchical polyhedral iron oxide particles were synthesized by modified polyol methods with sodium borohydride as a powerful and efficient reducing agent. A critical heat treatment process used during the synthesis allowed for the interesting formation of α-Fe2O3 hematite with a micro-/nanoscale structure. The structure and weak ferromagnetism of the α-Fe2O3 particles were investigated by x-ray diffraction with whole pattern fitting and Rietveld refinement, scanning electron microscopy, and by vibrating sample magnetometry. The as-prepared α-Fe2O3 particles and the three dimensional models presented have promising practical applications for energy storage and conversion in batteries, capacitors, and fuel cells, and related spintronic devices and technologies.
Stress analysis of 3D complex geometries using the scaled boundary polyhedral finite elements
Talebi, Hossein; Saputra, Albert; Song, Chongmin
2016-10-01
While dominating the numerical stress analysis of solids, the finite element method requires a mesh to conform to the surface of the geometry. Thus the mesh generation of three dimensional complex structures often require tedious human interventions. In this paper, we present a formulation for arbitrary polyhedral elements based on the scaled boundary finite element method, which reduces the difficulties in automatic mesh generation. We also propose a simple method to generate polyhedral meshes with local refinements. The mesh generation method is based on combining an octree mesh with surfaces defined using signed distance functions. Through several numerical examples, we verify the results, study the convergence behaviour and depict the many advantages and capabilities of the presented method. This contribution is intended to assist us to eventually frame a set of numerical methods and associated tools for the full automation of the engineering analysis where minimal human interaction is needed.
Institute of Scientific and Technical Information of China (English)
Hong Yao XU; Xiao Yan GAO; Shan Yi GUANG; Feng Zhi CHANG
2005-01-01
Hybrid polymers, poly(vinyl pyrrolidone-co-isobutyl styryl polyhedral oligomeric silsesquioxanes)s (PVP-POSS) were synthesized by one step polymerization and characterized using GPC and DSC. Addition of POSS significantly increases the Tg of polyvinylpyrrolidone at a fair high POSS content and obtained high molecular weight polymers with very narrow molecular distribution. The POSS content in the resulted hybrids can be controlled by varying the POSS feed ratio.
Energy Technology Data Exchange (ETDEWEB)
Henzie, Joel [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Grünwald, Michael [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Widmer-Cooper, Asaph [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division; Univ. of Sydney, NSW (Australia). School of Chemistry; Geissler, Phillip L. [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division; Yang, Peidong [Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Materials Science Division; Univ. of California, Berkeley, CA (United States). Dept. of Materials Science and Engineering
2011-11-20
Understanding how polyhedra pack into extended arrangements is integral to the design and discovery of crystalline materials at all length scales. Much progress has been made in enumerating and characterizing the packing of polyhedral shapes, and the self-assembly of polyhedral nanocrystals into ordered superstructures. However, directing the self-assembly of polyhedral nanocrystals into densest packings requires precise control of particle shape, polydispersity,interactions and driving forces. Here we show with experiment and computer simulation that a range of nanoscale Ag polyhedra can self-assemble into their conjectured densest packings. When passivated with adsorbing polymer, the polyhedra behave as quasi-hard particles and assemble into millimetre-sized three-dimensional supercrystals by sedimentation.We also show, by inducing depletion attraction through excess polymer in solution, that octahedra form an exotic superstructure with complex helical motifs rather than the densest Minkowski lattice. Such large-scale Ag supercrystals may facilitate the design of scalable three-dimensional plasmonic metamaterials for sensing, nanophotonics, and photocatalysis.
Institute of Scientific and Technical Information of China (English)
刘俊亮; 颜雷鸣; 陈秀雷; 王绳芸; 张明; 田长安
2015-01-01
Novel mono-dispersed hollow polyhedral ceria nano powders with the average particle size of 250 nm were directly syn-thesized via a simple template-free mixed solvothermal method by using water-ethanol as the solvent. The formation of such hollow structure with the regular polyhedral particle shape was based on a solvent-controlled Ostwald ripening coupled self-templating proc-ess. The mixed solvent promoted the formation of the regular solid particles at the beginning of solvothermal reaction and drove the Ostwald ripening as the reaction went on. Owing to the Ostwald ripening and self-assembly of nano crystallites, ceria nano particles converted into the hollow structures with regular polyhedral shape during the solvothermal process just by increasing solvothermal reaction time. The as-synthesized hollow ceria nano powders exhibited strong absorptions in the UV-vis spectrum and the evaluated energy band gaps increased according to the shape evolution and size decrease of the nano particles, which demonstrated obvious blue shift effects.
Polyhedral representation of invariant manifolds applied to orbit transfers in the Earth-Moon system
Pontani, Mauro; Teofilatto, Paolo
2016-02-01
Recently, manifold dynamics has assumed an increasing relevance for analysis and design of low-energy missions, both in the Earth-Moon system and in alternative multibody environments. This work proposes and describes an intuitive polyhedral interpolative approach for each state component associated with manifold trajectories, both in two and in three dimensions. An adequate grid of data, coming from the numerical propagation of a finite number of manifold trajectories, is employed. Accuracy of this representation is evaluated with reference to the invariant manifolds associated with a two-dimensional Lyapunov orbit and a three-dimensional Halo orbit, and is proven to be satisfactory, with the exclusion of limited regions of the manifolds. As a first, preliminary application, the polyhedral interpolation technique allows identifying the orbits in the proximity of the interior collinear libration point as either asymptotic, transit, or bouncing trajectories. Then, two applications to orbital maneuvering are addressed. First, the globally optimal two-impulse transfer between a specified low Earth orbit and a Lyapunov orbit (through its stable manifold) is determined. Second, the minimum-time low-thrust transfer from the same terminal orbits is found using again the stable manifold. These applications prove the effectiveness of the polyhedral interpolative technique and represent the premise for its application also to different problems involving invariant manifold dynamics.
Formation of polyhedral vesicles and polygonal membrane tubes induced by banana-shaped proteins
Noguchi, Hiroshi
2015-12-01
The shape transformations of fluid membranes induced by curved protein rods are studied using meshless membrane simulations. The rod assembly at low rod density induces a flat membrane tube and oblate vesicle. It is found that the polyhedral shapes are stabilized at high rod densities. The discrete shape transition between triangular and buckled discoidal tubes is obtained and their curvature energies are analyzed by a simple geometric model. For vesicles, triangular hosohedron and elliptic-disk shapes are formed in equilibrium, whereas tetrahedral and triangular prism shapes are obtained as metastable states.
DEFF Research Database (Denmark)
Aili, David; Allward, Todd; Alfaro, Silvia Martinez
2014-01-01
Composite membranes based on poly(2,2′(m-phenylene)-5,5́bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes...... humidified conditions in the 120-180°C temperature range. The conductivity improvements were also confirmed by in situ fuel cell tests at 160°C and further supported by the electrochemical impedance spectroscopy data based on the operating membrane electrode assemblies, demonstrating the technical...... feasibility of the novel electrolyte materials....
Blanco, Ignazio; Bottino, Francesco A.; Cicala, Gianluca; Cozzo, Giulia; Latteri, Alberta; Recca, Antonino
2014-05-01
The thermal and mechanical properties of a monochlorophenyl, hepta isobutyl Polyhedral Oligomeric Silsesquioxane/Polystyrene (ph,hib-POSS/PS) composite were studied and compared with those of pristine polymer. ph,hib-POSS/PS system was prepared by solubilization and precipitation of Polystyrene (PS) in the presence of POSS. Scanning Electron Microscopy (SEM) was performed to check the distribution of the filler in the polymer matrix. Dynamic Mechanical Analysis (DMA) was carried out to measure viscoelastic properties of solid samples. Degradations were carried out into a thermobalance and the obtained thermogravimetric (TG) and differential thermogravimetric (DTG) curves were discussed and interpreted.
Energy Technology Data Exchange (ETDEWEB)
Blanco, Ignazio, E-mail: iblanco@dii.unict.it; Bottino, Francesco A., E-mail: iblanco@dii.unict.it; Cicala, Gianluca, E-mail: iblanco@dii.unict.it; Cozzo, Giulia, E-mail: iblanco@dii.unict.it; Latteri, Alberta, E-mail: iblanco@dii.unict.it; Recca, Antonino, E-mail: iblanco@dii.unict.it [Department of Industrial Engineering, University of Catania, Viale A. Doria 6, 95125 Catania (Italy)
2014-05-15
The thermal and mechanical properties of a monochlorophenyl, hepta isobutyl Polyhedral Oligomeric Silsesquioxane/Polystyrene (ph,hib-POSS/PS) composite were studied and compared with those of pristine polymer. ph,hib-POSS/PS system was prepared by solubilization and precipitation of Polystyrene (PS) in the presence of POSS. Scanning Electron Microscopy (SEM) was performed to check the distribution of the filler in the polymer matrix. Dynamic Mechanical Analysis (DMA) was carried out to measure viscoelastic properties of solid samples. Degradations were carried out into a thermobalance and the obtained thermogravimetric (TG) and differential thermogravimetric (DTG) curves were discussed and interpreted.
Directory of Open Access Journals (Sweden)
Yuno Natsume
Full Text Available Giant vesicles (GVs encapsulating colloidal particles by a specific volume fraction show a characteristic configuration under a hypertonic condition. Several flat faces were formed in GV membrane with orderly array of inner particles. GV shape changed from the spherical to the asymmetrical polyhedral configuration. This shape deformation was derived by entropic interaction between inner particles and GV membrane. Because a part of inner particles became to form an ordered phase in the region neighboring the GV membrane, free volume for the other part of particles increased. Giant vesicles encapsulating colloidal particles were useful for the model of "crowding effect" which is the entropic interaction in the cell.
Natsume, Yuno; Toyota, Taro
2016-01-01
Giant vesicles (GVs) encapsulating colloidal particles by a specific volume fraction show a characteristic configuration under a hypertonic condition. Several flat faces were formed in GV membrane with orderly array of inner particles. GV shape changed from the spherical to the asymmetrical polyhedral configuration. This shape deformation was derived by entropic interaction between inner particles and GV membrane. Because a part of inner particles became to form an ordered phase in the region neighboring the GV membrane, free volume for the other part of particles increased. Giant vesicles encapsulating colloidal particles were useful for the model of "crowding effect" which is the entropic interaction in the cell.
The r-step Fibonacci-Hurwitz sequences in the binary polyhedral group
Deveci, Ömür; Ćiçekci, Deniz
2016-04-01
In [1], Deveci et al. defined the r-step Fibonacci-Hurwitz sequences from the Hurwitz matrices obtained from the characteristic polynomial of the k-step Fibonacci sequence. Also, they extended the r-step Fibonacci-Hurwitz sequences to groups. In this work, we obtain the periods of the r-step Fibonacci-Hurwitz sequences in the binary polyhedral group for generating triple {x, y, z} and generating pair {y, z} by the aid of the periods of the r-step Fibonacci-Hurwitz sequences according to modulo m.
A Featureless Approach to 3D Polyhedral Building Modeling from Aerial Images
Directory of Open Access Journals (Sweden)
Karim Hammoudi
2010-12-01
Full Text Available This paper presents a model-based approach for reconstructing 3D polyhedral building models from aerial images. The proposed approach exploits some geometric and photometric properties resulting from the perspective projection of planar structures. Data are provided by calibrated aerial images. The novelty of the approach lies in its featurelessness and in its use of direct optimization based on image rawbrightness. The proposed framework avoids feature extraction and matching. The 3D polyhedral model is directly estimated by optimizing an objective function that combines an image-based dissimilarity measure and a gradient score over several aerial images. The optimization process is carried out by the Differential Evolution algorithm. The proposed approach is intended to provide more accurate 3D reconstruction than feature-based approaches. Fast 3D model rectification and updating can take advantage of the proposed method. Several results and evaluations of performance from real and synthetic images show the feasibility and robustness of the proposed approach.
Lee, Yongwon; Lee, Jaegi; Kim, Hyungsub; Kang, Kisuk; Choi, Nam-Soon
2016-07-01
Employing linear carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) as electrolyte solvents provides an opportunity to design appropriate electrolyte systems for high-performance sodium-ion batteries (SIBs). However, in practice, the use of linear carbonate-containing electrolytes is quite challenging because linear carbonates readily decompose at Na metal electrodes or sodiated anodes. One of the promising approaches is using an electrolyte additive to resolve the critical problems related to linear carbonates. Our investigation reveals that remarkable enhancement in electrochemical performance of Na4Fe3(PO4)2(P2O7) cathodes with linear carbonate-containing electrolytes is achieved by using a fluoroethylene carbonate (FEC) additive. Importantly, the initial Coulombic efficiency of the Na deposition/stripping on a stainless steel (SS) electrode is drastically improved from 16% to 90% by introducing the FEC additive into ethylene carbonate (EC)/propylene carbonate (PC)/DEC (5/3/2, v/v/v)/0.5 M NaClO4. The underlying mechanism of FEC at the electrode-electrolyte interface is clearly demonstrated by 13C nuclear magnetic resonance (NMR). In addition, the Na4Fe3(PO4)2(P2O7) cathode in EC/PC/DEC (5/3/2, v/v/v)/0.5 M sodium perchlorate (NaClO4) with FEC delivers a discharge capacity of 90.5 mAh g-1 at a current rate of C/2 and exhibits excellent capacity retention of 97.5% with high Coulombic efficiency of 99.6% after 300 cycles at 30 °C.
Directory of Open Access Journals (Sweden)
G. Zhang
2013-05-01
Full Text Available Growing evidence suggests that the size-resolved mixing state of carbon-containing particles is very critical in determining their optical properties, atmospheric lifetime, and impact on the environment. However, still little is known about the mixing state of particles in the urban area of the Pearl River Delta (PRD region, China. To investigate the mixing state of submicron carbon-containing particles, measurements were carried out during spring and fall periods of 2010 using a single-particle aerosol mass spectrometer (SPAMS. Approximately 700 000 particles for each period were detected. This is the first report on the size-resolved mixing state of carbon-containing particles by direct observations in the PRD region. Cluster analysis of single-particle mass spectra was applied to identify carbon-containing particle classes. These classes represented ~80% and ~90% of all the detected particles for spring and fall periods, respectively. Carbon-containing particle classes mainly consisted of biomass/biofuel burning particles (Biomass, organic carbon (OC, fresh elemental carbon (EC-fresh, internally mixed OC and EC (ECOC, internally mixed EC with sulfate (EC-Sulfate, vanadium-containing ECOC (V-ECOC, and amines-containing particles (Amine. In spring, the top three ranked carbon-containing particle classes were ECOC (26.1%, Biomass (23.6% and OC (10%, respectively. However, the fraction of Biomass particles increased remarkably and predominated (61.0%, while the fraction of ECOC (3.0% and V-ECOC (0.1% significantly decreased in fall. To highlight the influence of monsoon on the properties of carbon-containing particles in urban Guangzhou, their size distributions, mixing state, and aerosol acidity were compared between spring and fall seasons. In addition, a case study was also performed to investigate how the formation of fog and haze influenced the mixing state of carbon-containing particles. These results could improve our understanding of the
Institute of Scientific and Technical Information of China (English)
Yan
2010-01-01
A novel polyhedral oligomeric silsesquioxane (POSS)-based organic-inorganic hybrid nanocomposite (EF-POSS) was prepared by Pt-catalyzed hydrosilylation reaction of octahydridosilsesquioxane (T8H8, POSS) with a luminescent substituted acetylene (2-ethynyl-7-(4-(4-methylstyryl)styryl)-9,9-dioctyl-9H-fluorene (EF)) in high yield. The hybrid nanocomposite was soluble in common solvents such as CH2Cl2, CHCl3, THF and 1,4-dioxane. Its structure and property were characterized by FTIR, NMR, TGA, UV and PL, respectively. The results show that the hybrid nanocomposite with high thermal stability emits stable blue light as a result of photo excitation and possesses high photoluminescence quantum efficiency (φfL).
Campbell, Sandi G.; Lee, Andre
2005-01-01
The field of hybrid organic-inorganic materials has grown drastically over the last several years. This interest stems from our ever-increasing ability to custom-build and control molecular structure at several length scales. This ability to control both the composition and structure of hybrid materials is sometimes broadly referred to as nanocomposite systems. One class of hybrid (organic-inorganic) nanostructured material is polyhedral oligomeric silsesquioxane (POSS), shown in the preceding diagram. The hybrid composition gives POSS materials dramatically enhanced properties relative to traditional hydrocarbons and inorganics. An important benefit of this technology is that it makes possible the formulations of nanostructured chemicals with excellent thermal and oxidative stability. This is largely due to the inorganic component.
Energy Technology Data Exchange (ETDEWEB)
Bailey, T.S.; Adams, M.L. [Texas A M Univ., Dept. of Nuclear Engineering, College Station, TX (United States); Yang, B.; Zika, M.R. [Lawrence Livermore National Lab., Livermore, CA (United States)
2005-07-01
We develop a piecewise linear (PWL) Galerkin finite element spatial discretization for the multi-dimensional radiation diffusion equation. It uses piecewise linear weight and basis functions in the finite element approximation, and it can be applied on arbitrary polygonal (2-dimensional) or polyhedral (3-dimensional) grids. We show that this new PWL method gives solutions comparable to those from Palmer's finite-volume method. However, since the PWL method produces a symmetric positive definite coefficient matrix, it should be substantially more computationally efficient than Palmer's method, which produces an asymmetric matrix. We conclude that the Galerkin PWL method is an attractive option for solving diffusion equations on unstructured grids. (authors)
Energy Technology Data Exchange (ETDEWEB)
Bailey, T S; Adams, M L; Yang, B; Zika, M R
2005-07-15
We develop a piecewise linear (PWL) Galerkin finite element spatial discretization for the multi-dimensional radiation diffusion equation. It uses piecewise linear weight and basis functions in the finite element approximation, and it can be applied on arbitrary polygonal (2D) or polyhedral (3D) grids. We show that this new PWL method gives solutions comparable to those from Palmer's finite-volume method. However, since the PWL method produces a symmetric positive definite coefficient matrix, it should be substantially more computationally efficient than Palmer's method, which produces an asymmetric matrix. We conclude that the Galerkin PWL method is an attractive option for solving diffusion equations on unstructured grids.
Robust Hinf control of uncertain switched systems defined on polyhedral sets with Filippov solutions
DEFF Research Database (Denmark)
Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal
2012-01-01
This paper considers the control problem of a class of uncertain switched systems defined on polyhedral sets known as piecewise linear systems where, instead of the conventional Carathe ́odory solutions, Filippov solutions are studied. In other words, in contrast to the previous studies, solutions...... with infinite switching in finite time along the facets and on faces of arbitrary dimensions are also taken into account. Firstly, established upon previous studies, a set of linear matrix inequalities are brought forward which determines the asymptotic stability of piecewise linear systems with Filippov...... solutions. Subsequently, bilinear matrix inequality conditions for synthesizing a robust controller with a guaranteed Hinf performance are presented. Furthermore, these results has been generalized to the case of piecewise affine systems. Finally, a V–K iteration algorithm is proposed to deal...
Deshmukh, Amol; Chiu, Cheng-Chau; Chen, Yun-Wen; Kuo, Jer-Lai
2016-09-28
We study the hydrogen adsorption in porous frameworks composed of silsesquioxane cages linked via boron substituted aromatic structures by first-principles modeling. Such polyhedral oligomeric silsesquioxane (POSS) frameworks can be further modified by decorating them with metal atoms binding to the ring structures of the linkers. We have considered Sc- and Ti-doped frameworks which bind H2 via so-called Kubas interaction between hydrogen molecules and transition metal atoms. It will be demonstrated that the maximum H2 gravimetric capacity can be improved to more than 7.5 wt % by using longer linkers with more ring structures. However, the maximum H2 volumetric capacity can be tuned to more than 70 g/L by varying the size of silsesquioxane cages. We are optimistic that by varying the building blocks, POSS frameworks can be modified to meet the targets for the gravimetric and volumetric capacities set by the U.S. Department of Energy.
Yang, Xiaohui
2010-08-24
The synthesis, photophysical, and electrochemical characterization of macromolecules, consisting of an emissive platinum complex and carbazole moieties covalently attached to a polyhedral oligomeric silsesquioxane (POSS) core, is reported. Organic light-emitting devices based on these POSS materials exhibit a peak external quantum efficiency of ca. 8%, which is significantly higher than that of the analogous devices with a physical blend of the platinum complexes and a polymer matrix, and they represent noticeable improvement in the device efficiency of solution-processable phosphorescent excimer devices. Furthermore, the ratio of monomer and excimer/aggregate electroluminescent emission intensity, as well as the device efficiency, increases as the platinum complex moiety presence on the POSS macromolecules decreases. © 2010 American Chemical Society.
Development of highly open polyhedral networks from vitreous carbon for orthopaedic applications
Güiza-Argüello, V.; Bayona-Becerra, M.; Cruz-Orellana, S.; Córdoba-Tuta, E.
2017-01-01
Highly open polyhedral networks were fabricated using an economical and environmentally friendly template route. Recycled cellulose foams were impregnated with a sucrose resin and then pyrolyzed in order to produce reticulated vitreous carbon foams with morphological features that closely resemble trabecular bone. Also, cell sizes ~1mm were achieved, a trait that will allow the mechanical reinforcement of such scaffolds using a biomaterial coating without compromising the pore size that favors osteoblast cell infiltration and growth (200-500µm). Moreover, initial studies showed that carbonization conditions have an effect on the mechanical properties of the synthesized foams and, therefore, such process parameters could be further evaluated towards the enhancement of the mechanical resistance of the scaffolds. The materials developed here are visualized as the porous component of a synthetic bone graft with features that could help overcome the current limitations associated with the medical treatments used for bone defect repair.
Efficiency of the estimate refinement method for polyhedral approximation of multidimensional balls
Kamenev, G. K.
2016-05-01
The estimate refinement method for the polyhedral approximation of convex compact bodies is analyzed. When applied to convex bodies with a smooth boundary, this method is known to generate polytopes with an optimal order of growth of the number of vertices and facets depending on the approximation error. In previous studies, for the approximation of a multidimensional ball, the convergence rates of the method were estimated in terms of the number of faces of all dimensions and the cardinality of the facial structure (the norm of the f-vector) of the constructed polytope was shown to have an optimal rate of growth. In this paper, the asymptotic convergence rate of the method with respect to faces of all dimensions is compared with the convergence rate of best approximation polytopes. Explicit expressions are obtained for the asymptotic efficiency, including the case of low dimensions. Theoretical estimates are compared with numerical results.
Ye, Yi; Tian, Ming; Zhang, Chen; Du, Zhongjie; Mi, Jianguo
2016-01-12
Fluorinated polyhedral oligomeric silsesquioxane (F-POSS) nanoparticles have been widely used to enhance the hydrophobicity or oleophobicity of polymer films via constructing the specific micro/nanoscale roughness. In this work, we study the oleophobicity of pure and F-POSS-decorated poly(vinylidene fluoride) (PVDF) and poly(methyl methacrylate) (PMMA) films using a dynamic density functional theory approach. The role of nanoparticle size and coverage and the chemical features of F-POSS and the polymer film in the wetting behavior of diiodomethane droplets has been integrated to the remaining ratio of surface potential to quantitatively characterize the corner effect. It is shown that, on the basis of universal force field parameters, the theoretically predicted contact angles are in general agreement with the available experimental data.
DEFF Research Database (Denmark)
Johansen, Peter M.; Breinbjerg, Olav
1995-01-01
An exact line integral representation of the electric physical optics scattered field is presented. This representation applies to scattering configurations with perfectly electrically conducting polyhedral structures illuminated by a finite number of electric Hertzian dipoles. The positions...
Eed, H.; Hassouneh, O.; Ramadin, Y.; Zihlif, A.; Ragosta, G.; Elimat, Z. M.
2013-01-01
An epoxy network structure made of diglycidylether of bisphenol-A and diamino diphenylsulfone was modified by adding various amounts of an epoxy functionalized polyhedral oligomeric silsesquioxane. The obtained nanocomposites were characterized in terms of optical and dielectric properties. The UV-absorption spectra were collected in the wavelength range of 400-800 nm. The optical data were analyzed in terms of absorption formula for non-crystalline materials. The optical energy gap and other basic constants, such as energy tails, dielectric constants, refractive index and optical conductivity, were determined and showed a clear dependence on the POSS concentration. It was found that the optical energy gap for the neat epoxy resin is less than for nanocomposites, and it decreases with increase in the POSS content. The refractive index of nanocomposites was determined from the calculated values of absorption and reflectance. It was found that the refractive index and the dielectric constants increased with increase in the POSS concentration. The optical conductivity, which is a measure of the optical absorption, increased with the POSS content. Furthermore, it was found that the glass transition temperature and the optical energy gap correlate well with the POSS filler concentration.
Yue, Kan; Yu, Xinfei; Liu, Chang; Zhang, Wen-Bin; Cheng, Stephen
2013-03-01
Recently, our group has focus on the synthesis and characterization of novel giant molecular shape amphiphiles (GMSAs) based on functionalized molecular nanoparticles (MNPs), such as polyhedral oligomeric silsesquioxane (POSS), tethered with polymeric tails. A general synthetic method via the combination of sequential ?click? reactions has been developed and several model GMSAs with various tail lengths and distinct molecular topologies, which can be referred as the ?giant surfactants?, ?giant lipids?, ?giant gemini surfactants?, and ?giant bolaform surfactants? etc., have been demonstrated. Studies on their self-assembly behaviors in the bulk have revealed the formation of different ordered mesophase structures with feature sizes around 10 nanometers, which have been investigated in detail by small angle X-ray scattering (SAXS) technique and transmission electron microscopy (TEM). These findings have general implications on understanding the underlying principles of self-assembly behaviors of GMSAs, and might have potential applications in nano-patterning technology. This work is supported by NSF (DMR-0906898) and the Joint-Hope Foundation.
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Chin-Wei Chiou
2014-03-01
Full Text Available In this study we used anionic living polymerization to prepare two different homopolymers: a poly(methyl methacrylate (PMMA and a PMMA derivative presenting polyhedral oligomeric silsesquioxane (PMA-POSS units as its side chains. We then employed differential scanning calorimetry (DSC, Fourier transform infrared (FTIR spectroscopy, and wide-angle X-ray diffraction (WAXD to investigate the miscibility and specific interactions of PMMA and PMA-POSS with three hydrogen bonding donor compounds: poly(vinyl phenol (PVPh, phenolic resin, and bisphenol A (BPA. DSC revealed that all of the PVPh/PMMA, phenolic/PMMA, and BPA/PMMA blends exhibited a single glass transition temperature, characteristic of miscible systems; FTIR spectroscopic analyses revealed that such miscibility resulted from hydrogen bonding interactions between the C=O groups of PMMA and the OH groups of these three hydrogen bonding donor compounds. In contrast, all of the PVPh/PMA-POSS, phenolic/PMA-POSS, and BPA/PMA-POSS blends were immiscible: DSC revealed two glass transition temperatures arising from strong screening effects (FTIR spectroscopy and high degrees of aggregation (WAXD of the POSS nanoparticles. We propose that the value of the intramolecular screening effect (γ should be very close to 1 for all PMA-POSS blend systems when POSS nanoparticles appear as the side chains of PMMA, such that the OH groups of the hydrogen bonding donor compounds cannot interact with the C=O groups of PMA-POSS.
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J. J. Schwab
2012-07-01
Full Text Available The polyhedral oligomeric silsesquioxane (POSS additivated polystyrene (PS based nanocomposites were prepared by melt processing and the structure-properties relationships of the POSS-PS systems were compared to those of the neat PS. In order to investigate the effect of these structural parameters on the final properties of the polymer nanocomposites, five different kinds of POSS samples were used, in particular, POSS with different inorganic cage and with different organic pendent groups. The rheological investigation suggests clearly that the POSS acts as a plasticizer and that the processability of the PS was positively modified. The affinity between the POSS samples and the PS matrix was estimated by the calculated theoretical solubility parameters, considering the Hoy’s method and by morphology analysis. Minor difference between the solubility parameter of POSS and the matrix means better compatibility and no aggregation tendency. Furthermore, the POSS loading leads to a decrease of the rigidity, of the glass transition temperature and of the damping factor of the nanocomposite systems. The loading of different POSS molecules with open cage leads to a more pronounced effect on all the investigated properties that the loading of the POSS molecules with closed cage. Moreover, the melt properties are significantly influenced by the type of inorganic framework, by the type of the pendent organic groups and by the interaction between the POSS organic groups and the host matrix, while, the solid state properties appears to be influenced more by the kind of cage.
Zhao, Qing-Li; Zhou, Jin; Zhang, Li-Shun; Huang, Yan-Ping; Liu, Zhao-Sheng
2016-05-15
Polyhedral oligomeric silsesquioxane (POSS) was successfully applied, for the first time, to prepare imprinted monolithic coating for capillary electrochromatography. The imprinted monolithic coating was synthesized with a mixture of PSS-(1-Propylmethacrylate)-heptaisobutyl substituted (MA 0702), S-amlodipine (template), methacrylic acid (functional monomer), and 2-methacrylamidopropyl methacrylate (crosslinker), in a porogenic mixture of toluene-isooctane. The influence of synthesis parameters on the imprinting effect and separation performance, including the amount of MA 0702, the ratio of template to monomer, and the ratio of monomer to crosslinker, was investigated. The greatest resolution for enantiomers separation on the imprinted monolithic column prepared with MA 0702 was up to 22.3, about 2 times higher than that prepared in absence of the POSS. Column efficiency on the POSS-based MIP coatings was beyond 30,000 plate m(-1). The comparisons between MIP coating synthesized with the POSS and without the POSS were made in terms of selectivity, column efficiency, and resolution. POSS-based MIP capillaries with naproxen or zopiclone was also prepared and separation of enantiomers can be achieved.
Energy Technology Data Exchange (ETDEWEB)
Mutz, M. [University of Tennessee, Department of Chemistry (United States); Eastwood, Eric [Honeywell Kansas City Plant (United States); Lee, Mark E. [University of Missouri (United States); Bowen, Daniel E. [Honeywell Kansas City Plant (United States); Dadmun, M. D., E-mail: dad@utk.edu [University of Tennessee, Department of Chemistry (United States)
2012-11-15
The solubility of boron containing nanoparticles in a variety of solvents is quantified using static light scattering in conjunction with refractometry. Four polyhedral boranes were tested in this work, using refractometry to obtain dn/dc, while static light scattering quantifies A{sub 2}. A{sub 2} obtained from these measurements was then used to calculate {chi}, the solute-solvent interaction parameter, and the Hildebrand solubility parameter, {delta}, which provides a quantifiable method to identify good solvents. Of the nanoparticles studied, 1,3-di-o-carboranylpropane is thermodynamically stable in toluene, with a {chi} less than 0.5, a solubility limit of 2.47 mg/mL, and all solutions remaining clear with no visible particle settling. For all of the particles tested, there was good correlation between the physical observations of the solutions, {chi}, and {delta}. For instance, lower values of {chi} correspond to a smaller radius of gyration (R{sub g}). A list of suitable solvents based on {delta} is also presented.
Energy Technology Data Exchange (ETDEWEB)
Mutz, M [The University of Tennessee; Eastwood, Eric Allen [ORNL; LeeJr, Mark E [University of Missouri; BowenIII, Daniel E [Honeywell, Inc.; Dadmun, Mark D [ORNL
2012-01-01
The solubility of boron containing nanoparticles in a variety of solvents is quantified using static light scattering in conjunction with refractometry. Four polyhedral boranes were tested in this work, using refractometry to obtain dn/dc, while static light scattering quantifies A2. A2 obtained from these measurements was then used to calculate v, the solute solvent interaction parameter, and the ildebrand solubility parameter, d, which provides a quantifiable method to identify good solvents. Of the nanoparticles studied, 1,3-di-o-carboranylpropane is thermodynamically stable in toluene, with a v less than 0.5, a solubility limit of 2.47 mg/mL, and all solutions remaining clear with no visible particle settling. For all of the particles tested, there was good correlation between the physical observations of the solutions, v, and d. For instance, lower values of v correspond to a smaller radius of gyration (Rg). A list of suitable solvents based on d is also presented.
Detection of long and short DNA using nanopores with graphitic polyhedral edges.
Freedman, Kevin J; Ahn, Chi Won; Kim, Min Jun
2013-06-25
Graphene is a unique material with a thickness as low as a single atom, high in-plane conductivity and a robust lattice that is self-supporting over large length scales. Schematically, graphene is an ideal solid-state material for tuning the properties of a nanopore because self-supported sheets, ranging from single to multiple atomic layers, can create pores with near-arbitrary dimensions which can provide exquisite control of the electric field drop within the pore. In this study, we characterize the drilling kinetics of nanopores using a thermionic electron source and various electron beam fluxes to minimize secondary hole formation. Once established, we investigated the use of multilayer graphene to create highly tailored nanostructures including nanopores with graphite polyhedral crystals formed around the nanopore edge. Finally, we report on the translocation of double stranded and single stranded DNA through such graphene pores and show that the single stranded DNA translocates much slower allowing detection of extremely short fragments (25 nucleotides in length). Our findings suggest that the kinetic and controllable properties of graphene nanopores under sculpting conditions can be used to further enhance the detection of DNA analytes.
Yang, Shubin; Bachman, Robert E; Feng, Xinliang; Müllen, Klaus
2013-01-15
The development of high-performance electrochemical energy storage and conversion devices, including supercapacitors, lithium-ion batteries, and fuel cells, is an important step on the road to alternative energy technologies. Carbon-containing nanomaterials (CCNMs), defined here as pure carbon materials and carbon/metal (oxide, hydroxide) hybrids with structural features on the nanometer scale, show potential application in such devices. Because of their pronounced electrochemical activity, high chemical and thermal stability and low cost, researchers are interested in CCNMs to serve as electrodes in energy-related devices. Various all-carbon materials are candidates for electrochemical energy storage and conversion devices. Furthermore, carbon-based hybrid materials, which consist of a carbon component with metal oxide- or metal hydroxide-based nanostructures, offer the opportunity to combine the attractive properties of these two components and tune the behavior of the resulting materials. As such, the design and synthesis of CCNMs provide an attractive route for the construction of high-performance electrode materials. Studies in these areas have revealed that both the composition and the fabrication protocol employed in preparing CCNMs influence the morphology and microstructure of the resulting material and its electrochemical performance. Consequently, researchers have developed several synthesis strategies, including hard-templated, soft-templated, and template-free synthesis of CCNMs. In this Account, we focus on recent advances in the controlled synthesis of such CCNMs and the potential of the resulting materials for energy storage or conversion applications. The Account is divided into four major categories based on the carbon precursor employed in the synthesis: low molecular weight organic or organometallic molecules, hyperbranched or cross-linked polymers consisting of aromatic subunits, self-assembling discotic molecules, and graphenes. In each case
Ge, Xiaoqian; Dong, Liang; Sun, Lining; Song, Zhengmei; Wei, Ruoyan; Shi, Liyi; Chen, Haige
2015-04-01
A new and facile method was used to transfer upconversion luminescent nanoparticles from hydrophobic to hydrophilic using polyhedral oligomeric silsesquioxane (POSS) linking on the surface of upconversion nanoparticles. In comparison with the unmodified upconversion nanoparticles, the POSS modified upconversion nanoplatforms [POSS-UCNPs(Er), POSS-UCNPs(Tm)] displayed good monodispersion in water and exhibited good water-solubility, while their particle size did not change substantially. Due to the low cytotoxicity and good biocompatibility as determined by methyl thiazolyl tetrazolium (MTT) assay and histology and hematology analysis, the POSS modified upconversion nanoplatforms were successfully applied to upconversion luminescence imaging of living cells in vitro and nude mouse in vivo (upon excitation at 980 nm). In addition, the doped Gd3+ ion endows the POSS-UCNPs with effective T1 signal enhancement and the POSS-UCNPs were successfully applied to in vivo magnetic resonance imaging (MRI) for a Kunming mouse, which makes them potential MRI positive-contrast agents. More importantly, the corner organic groups of POSS can be easily modified, resulting in kinds of POSS-UCNPs with many potential applications. Therefore, the method and results may provide more exciting opportunities for multimodal bioimaging and multifunctional applications.A new and facile method was used to transfer upconversion luminescent nanoparticles from hydrophobic to hydrophilic using polyhedral oligomeric silsesquioxane (POSS) linking on the surface of upconversion nanoparticles. In comparison with the unmodified upconversion nanoparticles, the POSS modified upconversion nanoplatforms [POSS-UCNPs(Er), POSS-UCNPs(Tm)] displayed good monodispersion in water and exhibited good water-solubility, while their particle size did not change substantially. Due to the low cytotoxicity and good biocompatibility as determined by methyl thiazolyl tetrazolium (MTT) assay and histology and hematology
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Wang WG
2014-02-01
Full Text Available Weiguo Wang,1,* Xiang Sun,1,* Li Huang,2,* Yu Gao,1 Jinghao Ban,1 Lijuan Shen,1 Jihua Chen1 1Department of Prosthodontics, 2Department of General Dentistry and Emergency, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China*These authors contributed equally to this workAbstract: Organic-inorganic hybrid materials, such as polyhedral oligomeric silsesquioxanes (POSS, have the potential to improve the mechanical properties of the methacrylate-based composites and resins used in dentistry. In this article, nanocomposites of methacryl isobutyl POSS (MI-POSS [bears only one methacrylate functional group] and methacryl POSS (MA-POSS [bears eight methacrylate functional groups] were investigated to determine the effect of structures on the properties of dental resin. The structures of the POSS-containing networks were determined by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Monofunctional POSS showed a strong tendency toward aggregation and crystallization, while multifunctional POSS showed higher miscibility with the dimethacrylate monomer. The mechanical properties and wear resistance decreased with increasing amounts of MI-POSS, indicating that the MI-POSS agglomerates act as the mechanical weak point in the dental resins. The addition of small amounts of MA-POSS improved the mechanical and shrinkage properties. However, samples with a higher MA-POSS concentration showed lower flexural strength and flexural modulus, indicating that there is a limited range in which the reinforcement properties of MA-POSS can operate. This concentration dependence is attributed to phase separation at higher concentrations of POSS, which affects the structural integrity, and thus, the mechanical and shrinkage properties of the dental resin. Our results show that resin with 3% MA-POSS is a potential candidate for resin-based dental materials
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Luciano Ribeiro CORREA NETTO
2015-10-01
Full Text Available Marginal integrity is one of the most crucial aspects involved in the clinical longevity of resin composite restorations.Objective To analyze the marginal integrity of restorations produced with a model composite based on polyhedral oligomeric silsesquioxane (POSS.Material and Methods A base composite (B was produced with an organic matrix with UDMA/TEGDMA and 70 wt.% of barium borosilicate glass particles. To produce the model composite, 25 wt.% of UDMA were replaced by POSS (P25. The composites P90 and TPH3 (TP3 were used as positive and negative controls, respectively. Marginal integrity (%MI was analyzed in bonded class I cavities. The volumetric polymerization shrinkage (%VS and the polymerization shrinkage stress (Pss - MPa were also evaluated.Results The values for %MI were as follows: P90 (100% = TP3 (98.3% = B (96.9% > P25 (93.2%, (p<0.05. The %VS ranged from 1.4% (P90 to 4.9% (P25, while Pss ranged from 2.3 MPa (P90 to 3.9 MPa (B. For both properties, the composite P25 presented the worst results (4.9% and 3.6 MPa. Linear regression analysis showed a strong positive correlation between %VS and Pss (r=0.97, whereas the correlation between Pss and %MI was found to be moderate (r=0.76.Conclusions The addition of 25 wt.% of POSS in methacrylate organic matrix did not improve the marginal integrity of class I restorations. Filtek P90 showed lower polymerization shrinkage and shrinkage stress when compared to the experimental and commercial methacrylate composite.
Investigation of Crack Propagation in Rock using Discrete Sphero-Polyhedral Element Method
Behraftar, S.; Galindo-torres, S. A.; Scheuermann, A.; Li, L.; Williams, D.
2014-12-01
In this study a micro-mechanical model is developed to study the fracture propagation process in rocks. The model is represented by an array of bonded particles simulated by the Discrete Sphero-Polyhedral Element Model (DSEM), which was introduced by the authors previously and has been shown to be a suitable technique to model rock [1]. It allows the modelling of particles of general shape, with no internal porosity. The motivation behind using this technique is the desire to microscopically investigate the fracture propagation process and study the relationship between the microscopic and macroscopic behaviour of rock. The DSEM method is used to model the Crack Chevron Notch Brazilian Disc (CCNBD) test suggested by the International Society of Rock Mechanics (ISRM) for determining the fracture toughness of rock specimens. CCNBD samples with different crack inclination angles, are modelled to investigate their fracture mode. The Crack Mouth Opening Displacement (CMOD) is simulated and the results are validated using experimental results obtained from a previous study [2]. Fig. 1 shows the simulated and experimental results of crack propagation for different inclination angles of CCNBD specimens. The DSEM method can be used to predict crack trajectory and quantify crack propagation during loading. References: 1. Galindo-Torres, S. A., et al. "Breaking processes in three-dimensional bonded granular materials with general shapes." Computer Physics Communications 183.2 (2012): 266-277. 2. Erarslan, N., and D. J. Williams. "Mixed-mode fracturing of rocks under static and cyclic loading." Rock mechanics and rock engineering 46.5 (2013): 1035-1052.
Son, Seunghwan; Won, Jongok; Kim, Jeong-Jin; Jang, Yun Deuk; Kang, Yong Soo; Kim, Sa Dug
2009-02-01
Alkoxysilane solutions based on tetraethoxysilane (TEOS) have been widely used for the consolidation of decaying heritage stone surfaces. TEOS-based products polymerize within the porous structure of the decaying stone, significantly increasing the cohesion of the grains of stone components. However, they suffer from practical drawbacks, such as crack formation of the gel during the drying phase due to the developing capillary force and dense gel fractures left inside of the stone. In this study, a TEOS-based stone consolidant containing functional (3-glycidoxypropyl)trimethoxysilane (GPTMS) and polyhedral oligomeric silsesquioxane (POSS) has been prepared in order to reduce gel crack formation during the drying phase. The addition of nanometer-sized POSS and/or GPTMS having a flexible segment reduces the capillary force developed during solvent evaporation. The properties of the TEOS/GPTMS/POSS composite solutions were compared with those of commercial products (Wacker OH and Unil sandsteinfestiger OH 1:1). The gelation time was similar to that of commercial consolidants, and the TEOS/GPTMS/POSS solution was stable over a period of up to 6 months. The addition of POSS and GPTMS provided a crack-free gel, while the gel from the commercial consolidants exhibited cracks after drying. The surface hydrophobicity of the treated decayed granite increased with the addition of POSS and GPTMS, and it was higher than that of the commercial product, implying the possibility of POSS and GPTMS as barriers to the penetration of water. This result implies that the TEOS/GPTMS/POSS solution showed a high suitability for the consolidation of granite heritage.
Kou, Xiaonan
Carbon nanotube (CNT) polymer nanocomposites are promising advanced materials. These materials exhibit the advantages of traditional polymeric materials, such as being light weight and easy to process, combined with the potential to exhibit enhanced mechanical, thermal and electrical properties compared to pure polymers. To achieve substantial improvement of composite properties at low CNT loading, uniform dispersion of CNTs in the polymer matrix and strong CNT-polymer interfacial interaction are needed. However, it is difficult to achieve adequate dispersion and interfacial interactions due to the inert nature of CNTs. In this project, polyhedral oligomeric silsequioxane (POSS) will be used as a dispersing agent for multi-walled carbon nanotubes (MWNTs) in polyurethane (PU) matrices. This dissertation consists of six chapters. Chapter I provides a detailed introduction of the fundamental knowledge of CNTs, PU, and POSS. At the end of this chapter, the motivation and rationale of this research are given. Chapter II establishes the overall goal and specific objectives of this research. Chapter III describes the synthesis and characterization of three POSS modified CNTs and one organosilane modified CNT. Grafting efficiency of the different grafted molecules are calculated and compared. Chapter IV discusses the dispersion behavior of four covalently modified CNTs in both solvents and PU matrices. Differences in dispersion behaviors of the modified CNTs are correlated to the solubility parameters of the grafting molecules and the surface structures of modified CNTs. Chapter V provides further discussion of the dispersion of POSS and silane modified CNTs by reviewing the assessment of the physical properties of PU composites containing the modified CNTs. Morphological, thermal, mechanical and electrical properties are used to estimate the interactions of the modified CNTs with the PU matrix. Chapter VI explores the function of the trisilanolphenyl POSS lithium salt
Subianto, Surya; Mistry, Mayur K; Choudhury, Namita Roy; Dutta, Naba K; Knott, Robert
2009-06-01
A new type of supported liquid membrane was made by combining an ionic liquid (IL) with a Nafion membrane reinforced with multifunctional polyhedral oligomeric silsesquioxanes (POSSs) using a layer-by-layer strategy for anhydrous proton-exchange membrane (PEM) application. The POSS was functionalized by direct sulfonation, and the sulfonated POSS (S-POSS) was incorporated into Nafion 117 membranes by the infiltration method. The resultant hybrid membrane shows strong ionic interaction between the Nafion matrix and the multifunctional POSS, resulting in increased glass transition temperature and thermal stability at very low loadings of S-POSS (1%). The presence of S-POSS has also improved the proton conductivity especially at low humidities, where it shows a marked increase due to its confinement in the ionic domains and promotes water uptake by capillary condensation. In order to achieve anhydrous conductivity, the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMI-BTSI) was incorporated into these membranes to provide proton conduction in the absence of water. Although the incorporation of an IL shows a plasticizing effect on the Nafion membrane, the S-POSS composite membrane with an IL shows a higher modulus at high temperatures compared to Nafion 117 and a Nafion-IL membrane, with significantly higher proton conductivity (5 mS/cm at 150 degrees C with 20% IL). This shows the ability of the multifunctional POSS and IL to work symbiotically to achieve the desirable proton conductivity and mechanical properties of such membranes by enhancing the ionic interaction within the material.
Energy Technology Data Exchange (ETDEWEB)
Yahyaei, Hossein [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Mohseni, Mohsen, E-mail: mmohseni@aut.ac.ir [Department of Polymer Engineering and Color Technology, Amirkabir University of Technology, P.O. Box 15875-4413, Tehran (Iran, Islamic Republic of); Ghanbari, Hossein [Department of Medical Nanotechnology, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences (TUMS), Tehran (Iran, Islamic Republic of); Messori, Massimo [Dipartimento di Ingegneria ‘Enzo Ferrari’, Università di Modena e Reggio Emilia, Modena (Italy)
2016-04-01
Organic–inorganic hybrid materials have shown improved properties to be used as biocompatible coating in biomedical applications. Polyhedral oligomeric silsesquioxane (POSS) containing coatings are among hybrid materials showing promising properties for these applications. In this work an open cage POSS has been reacted with a titanium alkoxide to end cap the POSS molecule with titanium atom to obtain a so called polyhedral oligomeric metalized silsesquioxane (POMS). The synthesized POMS was characterized by FTIR, RAMAN and UV–visible spectroscopy as well as {sup 29}Si NMR and matrix assisted laser desorption/ionization time-of-flight (MALDI-TOF) techniques. Appearance of peaks at 920 cm{sup −1} in FTIR and 491 cm{sup −1} and 1083 cm{sup −1} in Raman spectra confirmed Si–O–Ti linkage formation. It was also demonstrated that POMS was in a monomeric form. To evaluate the biocompatibility of hybrids films, pristine POSS and synthesized POMS were used in synthesis of a polycarbonate urethane polymer. Results revealed that POMS containing hybrid, not only had notable thermal and mechanical stability compared to POSS containing one, as demonstrated by DSC and DMTA analysis, they also showed controlled surface properties in such a manner that hydrophobicity and biocompatibility were both reachable to give rise to improved cell viability in presence of human umbilical vein endothelial cells (HUVEC) and MRC-5 cells. - Highlight: • Polyhedral Oligomeric Metalized Silsesquioxane (POMS) based on titanium was synthesized. • POMS can improve mechanical properties of polyurethane. • POMS increases hydrophobicity of polyurethane. • POMS is a unique nanocage to enhance biocompatibility of polyurethane.
Xu, Zixuan; Yu, Tianzhi; Zhao, Yuling; Zhang, Hui; Zhao, Guoyun; Li, Jianfeng; Chai, Lanqin
2016-01-01
A new inorganic–organic hybrid material based on polyhedral oligomeric silsesquioxane (POSS) capped with carbazolyl substituents, octakis[3-(carbazol-9-yl)propyldimethylsiloxy]-silsesquioxane (POSS-8Cz), was successfully synthesized and characterized. The X-ray crystal structure of POSS-8Cz were described. The photophysical properties of POSS-8Cz were investigated by using UV–vis,photoluminescence spectroscopic analysis. The hybrid material exhibits blue emission in the solution and the solid film.The morphology and thermal stablity properties were measured by X-ray diffraction (XRD) and TG-DTA analysis.
Divya; Prasad, R; Deepak
2016-01-01
The coordination polyhedra around the cations are the building blocks of ionic solids. In context of amorphous InGaZn oxide (a-IGZO), even though the coordination polyhedra are irregularly arranged, it will be beneficial to identify them. In this work, we address the questions, (a) is it possible to classify all the polyhedra that occur in a-IGZO into only a few distinct groups? and (b) are these the same polyhedral motifs as those observed in the crystalline indium gallium zinc oxide (c-IGZO...
Kim, Ho-Joong; Kwon, Younghwan; Kim, Chang Kee
2014-08-01
Mechanical properties and thermal stability of polyurethane composites were investigated with a combination of polyhedral oligomeric silsesquioxane (POSS) molecules and inorganic barium sulfate. These hybrid composites were prepared using one-step method through the incorporation of flexible hydroxyl-terminated polybutadiene prepolymer, reactive POSS nanoparticles, and barium sulfate under isophorone diisocyanate curative system. In polyurethane composites, POSS and inorganic barium sulfate were utilized for mechanical reinforcement and flame retardant filler, respectively. The decomposition of POSS molecules during oxyacetylene torch exposure resulted in the formation of silica-based nanosized droplets, contributing on ablation behavior.
Institute of Scientific and Technical Information of China (English)
Bing Tao Wang; Yan Zhang; Ping Zhang; Zheng Ping Fang
2012-01-01
One novel difunctionalized polyhedral oligomeric silsesquioxanes (POSS) derivative was designed and synthesized by a convenient method with high yield.1H NMR and FT-IR characterizations suggested that Michael addition reaction successfully took place between 2-hydroxyethyl acrylate (HEA) and aminopropylisobutyl POSS (POSS-NH2) under mild conditions,which finally formed bi(hydroxyethyl) ester-functionalized POSS derivatives (BH-POSS).Due to the similar functional groups and high reactivity,BH-POSS could be easily incorporated into the main-chain of biodegradable aliphatic-aromatic copolyesters PBTL via in situ melt polycondensation to prepare corresponding degradable nanohybrids with high mechanical properties.
Misra, Rahul
Control of dispersion and segregation states of nanostructured additives is one of the biggest challenges in realizing the optimum potential of high performance hybrid polymer nanocomposites. Polyhedral oligomeric silsesquioxane (POSS) nanostructured chemicals, with their hybrid organic-inorganic nature and flexible functionalization with a variety of organic substituents, yield possibilities to control dispersion and tune compatibility in a wide range of polymer systems. The overall goal of this research is to investigate the fundamental parameters that influence the dispersion and segregation states of POSS nanostructured chemicals, and to understand chain dynamics and conformations in physically blended POSS hybrid polymer nanocomposites (HPNC's). Multiple structural and mechanical factors influencing macro to nano scale surface and bulk properties were successfully investigated and correlated. A strategy based on thermodynamic principles for selective control of POSS dispersion states in a given polymer matrix is developed and discussed. This dissertation consists of eight chapters. Chapter 1 provides a detailed introduction about the development and current research interest in POSS/polymer nanocomposites. This chapter also discusses limitations of current advanced nanoprobe techniques. Chapter 2 establishes the overall goal of this research and specific research ii objectives. Chapter 3 establishes the preferential surface migration behavior of physically dispersed, non-reactive, closed cage octaisobutyl POSS (Oib-POSS) in a non-polar polypropylene matrix. Furthermore, influence of POSS surface segregation on the surface properties, especially nano-tribomechanical behavior is also discussed. Chapter 4 expands the studies by melt blending two different types of POSS molecules, a non-reactive, closed cage Oib-POSS and an open cage trisilanolphenyl POSS (Tsp-POSS), in a nylon 6 matrix. This chapter discusses the morphology, nano-dispersion and macro- to
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S. Auezkhanova
2012-12-01
Full Text Available Polymer-copper catalysts supported on a carbon-containing sorbent(CS, obtained by rice husk pyrolysis have been studied in the reactions of hydrogen peroxide decomposition and cyclohexane oxidation by hydrogen peroxide at 40°C and atmospheric pressure. The effect of the polymer nature on the activity of the developed catalysts have been shown. Polyhexamethyleneguanidine (PHMG was an optimal modifier for the developed catalysts. The calculated number of catalytic cycles (TON for 7% Cu-PGMG/CS was 450.
Koo, Ja-Ho; Walker, Kaley A.; Jones, Ashley; Sheese, Patrick E.; Boone, Chris D.; Bernath, Peter F.; Manney, Gloria L.
2017-01-01
In this paper, we present a new climatology based on the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) version 3.5 data set from February 2004 to February 2013. This extends the ACE-FTS climatology to include profile information in the mesosphere and carbon-containing species in the upper troposphere and lower stratosphere. Climatologies of 21 species, based on nine years of observations, are calculated, providing the most comprehensive and self-consistent climatology available from limb-viewing satellite measurements. Pressure levels from the upper troposphere to the mesosphere and lower thermosphere are included with 3 to 4 km vertical resolution up to 10-4 hPa ( 105 km). Volume mixing ratio values are filtered prior to the climatology estimation using the ACE-FTS data quality recommendations. The multi-year mean climatology contains zonal mean profiles for monthly and three-monthly (DJF, MAM, JJA, and SON) periods. These are provided with 5-degree spacing in either latitude or equivalent latitude. Also, the local daytime and nighttime distributions are provided separately for nitrogen-containing species, enabling diurnal differences to be investigated. Based on this climatology, examples of typical spatiotemporal patterns for trace gases in the mesosphere and for carbon-containing gases in the upper troposphere and lower stratosphere are discussed.
Indian Academy of Sciences (India)
Zhecun Wang; Chengdong Xiong; Qing Li
2015-10-01
In this study, biodegradable poly(p-dioxanone) (PPDO)/octamethyl-polyhedral oligomeric silsesquioxanes (ome-POSS) nanocomposites were fabricated by the simple solution casting method with various ome-POSS loadings. Scanning electron microscopic observations indicate that ome-POSS is well dispersed in the PPDO matrix. Effect of ome-POSS on the isothermal melt crystallization and dynamic mechanical properties of PPDO in the nanocomposites were studied in detail. It shows that the overall crystallization rates are faster in the nanocomposites than in neat PPDO and increase with the increase in ome-POSS loadings; however, X-ray diffraction patterns, POM and the Avrami exponent suggest that the crystal structure and the crystallization mechanism do not change despite the presence of ome-POSS. The mechanical property of PPDO/ome-POSS nanocomposites was enhanced with respect to neat PPDO.
Han, Zhongyou; Xi, Yukun; Kwon, Younghwan
2016-02-01
Series of polydimethylsiloxane (PDMS)-based polyurethane (PU)/polyhedral oligomeric silsesquioxane (POSS) composites are prepared using ether or polyether modified diol/polyol PDMS prepolymers, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS. The effect of POSS incorporated chemically or physically, number of ethylene oxide units and crosslinking on PDMS based PU is investigated in terms of thermal stability and ablation properties. The ablation property is measured using an oxyacetylene torch test, and the ablation rate is evaluated. The results show that POSS molecules make a considerable influence on the ablative resistance, because they act as protective silica forming precursors under oxyacetylene condition. POSS molecules, especially methyl POSS, in PU matrix leads to the formation of densely accumulated spherical silica layers on the top of the ablated surface, resulting in improved ablation resistance.
Zhao, Xiao-Li; Zhang, Lin-Ping; Mak, Thomas C W
2006-07-01
Reactions of the pyridine N-oxide ligands L, L2 and L3 with the silver acetylenediide-containing system under hydrothermal conditions gave rise to four silver-acetylenediide complexes bearing interesting C2@Agn motifs: (Ag2C2)2(AgCF3CO2)8(L1)3.5 (1), (Ag2C2)2(AgCF3CO2)8(L2)2 (2), (Ag2C2)(AgCF3CO2)4(L3) (3) and [(Ag7(C2)(CF3SO3)3(L3)2(H2O)2] x 2CF3SO3 (4) (L = nicotinic acid N-oxide, L(1) = pyridine N-oxide, L2 = 1,2-bis(4-pyridyl)ethane N,N'-dioxide, L3 = 1,3-bis(4-pyridyl)propane N,N'-dioxide), which exhibit new distorted polyhedral C2@Agn cage motifs. Complex 1 has a pair of acetylenediide dianions encapsulated in a Ag(14) aggregate composed of three polyhedral parts, whereas 2 contains an irregular (C2)2@Ag13 double cage. In 3, the basic building unit is a centrosymmetric (C2)2@Ag12 double cage with each component single cage taking the shape of a highly distorted triangulated dodecahedron with one missing vertex. As to complex 4, the core is a C2@Ag7 single cage in the form of a slightly distorted monocapped trigonal prism with four cleaved edges that include all three vertical sides. Furthermore, in the silver-rich environment, the pyO-type ligands are induced to exhibit unprecedented coordination modes, such as the mu(5)-O,O,O,O',O' ligation mode of L2 in 2 and the mu4-O,O,O',O' mode of L3 in 3 and 4.
Chen, Sicong
2014-02-01
This paper investigated the individual effects of reverse salt flux and permeate flux on fouling behaviors of as-spun and annealed polybenzimidazole (PBI)-polyhedral oligomeric silsesquioxane (POSS)/polyacrylonitrile (PAN) hollow fiber membranes under forward osmosis (FO) and pressure retarded osmosis (PRO) processes. Two types of membrane fouling had been studied; namely, inorganic fouling (CaSO4·2H2O gypsum scaling) during FO operations and organic fouling (sodium alginate fouling) during PRO operations. It is found that gypsum scaling on the membrane surface may be inhibited and even eliminated with an increase in reverse MgCl2 flux due to competitive formations of MgSO4° and CaSO4·2H2O. In contrast, the increase of reverse NaCl flux exhibits a slight enhancement on alginate fouling in both FO and PRO processes. Comparing to the reverse salt flux, the permeate flux always plays a dominant role in fouling. Therefore, lesser fouling has been observed on the membrane surface under the pressurized PRO process than FO process because the reduced initial flux mitigates the fouling phenomena more significantly than the enhancement caused by an increase in reverse NaCl flux. © 2013 Elsevier B.V.
Energy Technology Data Exchange (ETDEWEB)
Long, Nguyen Viet, E-mail: nguyenviet_long@yahoo.com [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Posts and Telecommunications Institute of Technology, Nguyen Trai, Hanoi (Viet Nam); Asaka, Toru; Matsubara, Takashi [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Nogami, Masayuki, E-mail: nogami@nitech.ac.jp [Department of Materials Science and Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan)
2011-04-15
Pt-Pd core-shell nanoparticles were synthesized by a simple synthetic method. First, Pt nanoparticles were synthesized in a controlled manner via the reduction of chloroplantinic acid hexahydrate in ethylene glycol (EG) at 160 deg. C in the presence of silver nitrate and the stabilization of polyvinylpyrrolidon. AgNO{sub 3} used acts as a structure-modifying agent to the morphology of the Pt nanoparticles. These Pt nanoparticles function as the seeds for the successive reduction of sodium tetrachloropalladate (II) hydrate in EG under stirring for 15 min at 160 deg. C in order to synthesize Pt-Pd core-shell nanoparticles. To characterize the as-prepared Pt-Pd nanoparticles, transmission electron microscopy (TEM) and high-resolution TEM are used. The high-resolution elemental mappings were carried out using the combination of scanning TEM and X-ray energy-dispersive spectroscopy. The results also demonstrate the homogeneous nucleation and growth of the Pd metal shell on the definite Pt core. The synthesized Pt-Pd core-shell nanoparticles exhibit a sharp and polyhedral morphology. The epitaxial growth of the controlled Pd shells on the Pt cores via a polyol method was observed. It is suggested that Frank-van der Merwe and Stranski-Krastanov growth modes coexisted in the nucleation and growth of Pt-Pd core-shell nanoparticles.
Sudarmadji, N; Tan, J Y; Leong, K F; Chua, C K; Loh, Y T
2011-02-01
An important requirement for a bone tissue engineering scaffold is a stiffness gradient that mimics that of native bone. Such scaffolds can be achieved by controlling their structure and porosity and are termed functionally graded scaffolds (FGS). Currently, the main challenges in FGS fabrication include the iterative and tedious design process as well as a heavy reliance on the user's CAD/CAM skills. This work aims to bring automated FGS production a step closer by providing a database that correlates scaffold porosity values and the corresponding compressive stiffness and integrating it into the design process. To achieve this goal, scaffolds with different structural configurations were designed using CASTS (Computer Aided System for Tissue Scaffolds), an in-house developed library system consisting of 13 different polyhedral units that can be assembled into scaffold structures. Polycaprolactone (PCL) was chosen as the scaffold material, while selective laser sintering, a powder-based rapid prototyping or additive manufacturing system was employed to fabricate the scaffolds. Mathematical relations correlating scaffold porosity and compressive stiffness readings were formulated and compiled. In addition, cytotoxicity assessment was conducted to evaluate the toxicity of the fabricated PCL scaffolds. Lastly, a brief demonstration of how the formulated relations are used in the FGS design process is presented.
Directory of Open Access Journals (Sweden)
Mohamed Gamal Mohamed
2017-03-01
Full Text Available In this study, we synthesized an unusual 2-aminobutyl maleimide isobutyl polyhedral oligomeric silsesquioxane (MIPOSS-NHBu monomer lacking conventional fluorescent groups. We then prepared poly(styrene-alt-2-aminobutyl maleimide isobutyl POSS [poly(S-alt-MIPOSS-NHBu] and poly(4-acetoxystyrene-alt-2-aminobutyl maleimide isobutyl POSS [poly(AS-alt-MIPOSS-NHBu] copolymers through facile free radical copolymerizations using azobisisobutyronitrile as the initiator and tetrahydrofuran as the solvent. A poly(4-hydroxystyrene-alt-2-aminobutyl maleimide isobutyl POSS [poly(HS-alt-MIPOSS-NHBu] copolymer was prepared through acetoxyl hydrazinolysis of poly(AS-alt-MIPOSS-NHBu. We employed 1H, 13C, and 29Si nuclear magnetic resonance spectroscopy; Fourier transform infrared spectroscopy; differential scanning calorimetry; and photoluminescence spectroscopy to investigate the structures and the thermal and optical properties of the monomers and novel POSS-containing alternating copolymers. Intramolecular hydrogen bonding between the amino and dihydrofuran-2,5-dione group and clustering of the locked C=O groups from the POSS nanoparticles in the MIPOSS-NHBu units restricted the intramolecular motion of the polymer chain, causing it to exhibit strong light emission. As a result, the MIPOSS-NHBu monomer and the poly(AS-alt-MIPOSS-NHBu copolymer both have potential applicability in the detection of metal ions with good selectivity.
Directory of Open Access Journals (Sweden)
A. Miguel Iznaga Benítez
2000-10-01
Full Text Available El conocimiento de la estructura de datos de los modelos geométricos ha posibilitado el desarrollo de algoritmos parasolucionar problemas complejos. Estos algoritmos han facilitado a su vez, la automatización en las oficinas de diseño através de los medios computacionales.Por tal motivo, se presenta el desarrollo de un algoritmo para la obtención de cortes y secciones en cuerpos geométricospoliédricos, se plantean las etapas fundamentales del algoritmo y a través de un ejercicio se ejemplifica el mismo.Este algoritmo puede ser utilizado en la creación de software que ayuden al proceso docente.Palabras claves: enseñanza, gráfica, separación de sólidos, geometría, dibujo, algoritmo, CAD._________________________________________________________________________Abstract:The knowledge of data structure in geometric models has facilitated the development of algorithms to solve complexproblems. These algorithms have facilitated in turn, the automation in the design by computational means. For such reason,is presented the development of an algorithm for the obtaining of sections in polyhedral geometric bodies, the fundamentalstages of the algorithm are stated and illustrated using an example.This algorithm can be use in the software creation that will help to the educational processKey words: section, separation of solids, algorithm, geometric modeling, graphic, CAD. teaching.
Wadhwani, Sweety A; Shedbalkar, Utkarsha U; Singh, Richa; Karve, Meena S; Chopade, Balu A
2014-10-01
Gold nanoparticles have enormous applications in cancer treatment, drug delivery and nanobiosensor due to their biocompatibility. Biological route of synthesis of metal nanoparticles are cost effective and eco-friendly. Acinetobacter sp. SW 30 isolated from activated sewage sludge produced cell bound as well as intracellular gold nanoparticles when challenged with HAuCl4 salt solution. We first time report the optimization of various physiological parameters such as age of culture, cell density and physicochemical parameters viz HAuCl4 concentration, temperature and pH which influence the synthesis of gold nanoparticles. Gold nanoparticles thus produced were characterized by various analytical techniques viz. UV-Visible spectroscopy, X-ray diffraction, cyclic voltammetry, transmission electron microscopy, selected area electron diffraction, high resolution transmission electron microscopy, environmental scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy and dynamic light scattering. Polyhedral gold nanoparticles of size 20 ± 10 nm were synthesized by 24 h grown culture of cell density 2.4 × 10(9) cfu/ml at 50 °C and pH 9 in 0.5 mM HAuCl4. It was found that most of the gold nanoparticles were released into solution from bacterial cell surface of Acinetobacter sp. at pH 9 and 50 °C.
Directory of Open Access Journals (Sweden)
Varvara V. Avdeeva
2016-05-01
Full Text Available Synthesis and structure of silver and copper salts and complexes with polyhedral boron hydride anions, including closo-decaborate [B10H10]2−, closo-dodecaborate [B12H12]2−, 1-carba-closo- decaborate [1-CB9H10]−, carba-closo-dodecaborate [CB11H12]−, and cobalt bis(dicarbollide [3,3′-Co(1,2-C2B9H112]− anions and their derivatives, are reviewed. The complexes demonstrate a wide variety of structural types, relating to both the metal coordination environment and coordination modes of boron hydride anions. The latter can range from strong coordination via the polyhedron triangular face including formation of 3c-2e MHB bonds in the case of the [B10H10]2− dianion, the structure of which contains two four-coordinated boron atoms, to very weak M…H interactions with the hydride atoms in the case of bulky [3,3′-Co(1,2-C2B9H112]− monoanion.
Li, Yizhuo; Guan, Yanqing; Liu, Yang; Yin, Jianbo; Zhao, Xiaopeng
2016-05-01
Graphene oxide (GO) shows potential as an anisotropic nanofiller or a dispersed phase of electro-responsive electrorheological (ER) nanofluid due to its small size and high aspect ratio. But it is difficult to disperse GO in non-polar oil due to the hydrophilic nature of GO and thus the resulting fluid is often subject to dispersion instability and low ER effect. These disadvantages largely limit the real application of GO-based ER nanofluid. In this paper, we develop the polyhedral oligomeric silsesquioxane (POSS)-decorated GO (POSS-GO) nanosheets and demonstrate that decorating with POSS overcomes the dispersion instability of GO in silicone oil and enhances the ER effect. The morphology and structure of samples are characterized by atomic force microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and x-ray photoelectronic spectroscopy. The results show that the POSS-GO nanosheets are ultrathin with ∼3 nm thickness and have good compatibility with silicone oil and, as a result, the nanofluid of POSS-GO nanosheets in silicone oil shows high dispersion stability. After standing for one year at room temperature, no sedimentation occurs. Under an external electric field, the ER efficiency of the POSS-GO nanofluid is ten times as high as that of the pure GO fluid. This enhanced electro-responsive behavior is related to the fact that decorating with POSS partly reduces the GO and compresses the dielectrophoretic effect of the negatively charged pure GO fluid.
Duo, Shuwang; Song, Mimi; Liu, Tingzhi; Hu, Changyuan; Li, Meishuan
2013-02-01
A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) had been prepared by copolymerization of trisilanolphenyl-POSS, 4,4'-oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The AO resistance of these PI/POSS hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces were characterized by SEM and X-ray photoelectron spectroscopy. SEM images showed that the surface of the 20 wt% PI/POSS became much less rough than that of the pristine polyimide. Mass measurements of the samples showed that the erosion yield of the PI/POSS (20 wt.%) hybrid film was 1.2 x 10(-25) cm3/atom, and reduced to 4% of the polyimide film. The XPS data indicated that the carbon content of the near-surface region was decreased from 60.1 to 13.2 at% after AO exposure. The oxygen and silicon concentrations in the near-surface region increased to 1.96 after AO exposure. The nanometer-sized structure of POSS, with its large surface area, had led AO-irradiated samples to form a SiO2 passivation layer, which protected the underlying polymer from further AO attack. The incorporation of POSS into the polyimide could dramatically improve the AO resistance of polyimide films in low earth orbit environment.
Li, Jin-Cheng; Zhao, Shi-Yong; Hou, Peng-Xiang; Fang, Ruo-Pian; Liu, Chang; Liang, Ji; Luan, Jian; Shan, Xu-Yi; Cheng, Hui-Ming
2015-12-01
A nitrogen-doped mesoporous carbon containing a network of carbon nanotubes (CNTs) was produced for use as a catalyst for the oxygen reduction reaction (ORR). SiO2 nanoparticles were decorated with clusters of Fe atoms to act as catalyst seeds for CNT growth, after which the material was impregnated with aniline. After polymerization of the aniline, the material was pyrolysed and the SiO2 was removed by acid treatment. The resulting carbon-based hybrid also contained some Fe from the CNT growth catalyst and was doped with N from the aniline. The Fe-N species act as active catalytic sites and the CNT network enables efficient electron transport in the material. Mesopores left by the removal of the SiO2 template provide short transport pathways and easy access to ions. As a result, the catalyst showed not only excellent ORR activity, with 59 mV more positive onset potential and 30 mV more positive half-wave potential than a Pt/C catalyst, but also much longer durability and stronger tolerance to methanol crossover than a Pt/C catalyst.
A novel synthesis of LiFePO4/C from Fe2O3 without extra carbon or carbon-containing reductant
Institute of Scientific and Technical Information of China (English)
肖政伟; 胡国荣
2014-01-01
A novel synthesis of LiFePO4/C from Fe2O3 with no extra carbon or carbon-containing reductant was introduced: Fe2O3 (+NH4H2PO4)→Fe2P2O7(+Li2CO3+glucose)→LiFePO4/C. X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were utilized to characterize relevant products obtained in the synthetic procedure. The reaction of Fe2P2O7 and Li2CO3 was investigated by thermo-gravimetric and differential thermal analysis (TGA-DTA). Fe2O3 is completely reduced to Fe2P2O7 by NH4H2PO4 at 700 °C and Fe2P2O7 fully reacts with Li2CO3 to form LiFePO4 in the temperature range of 663.4-890 °C. The primary particles of LiFePO4/C samples prepared at 670, 700 and 750 °C respectively exhibit uniform morphology and narrow size distribution, 0.5-3 μm for those obtained at 670 and 700 °C and 0.5-5 μm for those obtained at 750 °C. LiFePO4/C (carbon content of 5.49%, mass fraction) made at 670 °C shows an appreciable average capacity of 153.2 mA·h/g at 0.1C in the first 50 cycles.
Guo, Zhikui; Chen, Chao; Tao, Chunhui
2016-04-01
Since 2007, there are four China Da yang cruises (CDCs), which have been carried out to investigate polymetallic sulfides in the southwest Indian ridge (SWIR) and have acquired both gravity data and bathymetry data on the corresponding survey lines(Tao et al., 2014). Sandwell et al. (2014) published a new global marine gravity model including the free air gravity data and its first order vertical gradient (Vzz). Gravity data and its gradient can be used to extract unknown density structure information(e.g. crust thickness) under surface of the earth, but they contain all the mass effect under the observation point. Therefore, how to get accurate gravity and its gradient effect of the existing density structure (e.g. terrain) has been a key issue. Using the bathymetry data or ETOPO1 (http://www.ngdc.noaa.gov/mgg/global/global.html) model at a full resolution to calculate the terrain effect could spend too much computation time. We expect to develop an effective method that takes less time but can still yield the desired accuracy. In this study, a constant-density polyhedral model is used to calculate the gravity field and its vertical gradient, which is based on the work of Tsoulis (2012). According to gravity field attenuation with distance and variance of bathymetry, we present an adaptive mesh refinement and coarsening strategies to merge both global topography data and multi-beam bathymetry data. The local coarsening or size of mesh depends on user-defined accuracy and terrain variation (Davis et al., 2011). To depict terrain better, triangular surface element and rectangular surface element are used in fine and coarse mesh respectively. This strategy can also be applied to spherical coordinate in large region and global scale. Finally, we applied this method to calculate Bouguer gravity anomaly (BGA), mantle Bouguer anomaly(MBA) and their vertical gradient in SWIR. Further, we compared the result with previous results in the literature. Both synthetic model
Xu, Lei
2007-02-01
According to the proof by Liu, Chiu, and Xu (2004) on the so-called one-bit-matching conjecture (Xu, Cheung, and Amari, 1998a), all the sources can be separated as long as there is an one-to-one same-sign correspondence between the kurtosis signs of all source probability density functions (pdf's) and the kurtosis signs of all model pdf's, which is widely believed and implicitly supported by many empirical studies. However, this proof is made only in a weak sense that the conjecture is true when the global optimal solution of an independent component analysis criterion is reached. Thus, it cannot support the successes of many existing iterative algorithms that usually converge at one of the local optimal solutions. This article presents a new mathematical proof that is obtained in a strong sense that the conjecture is also true when any one of local optimal solutions is reached in helping to investigating convex-concave programming on a polyhedral set. Theorems are also provided not only on partial separation of sources when there is a partial matching between the kurtosis signs, but also on an interesting duality of maximization and minimization on source separation. Moreover, corollaries are obtained on an interesting duality, with supergaussian sources separated by maximization and subgaussian sources separated by minimization. Also, a corollary is obtained to confirm the symmetric orthogonalization implementation of the kurtosis extreme approach for separating multiple sources in parallel, which works empirically but lacks mathematical proof. Furthermore, a linkage has been set up to combinatorial optimization from a distribution approximation perspective and a Stiefel manifold perspective, with algorithms that guarantee convergence as well as satisfaction of constraints.
Blanco, Ignazio; Bottino, Francesco Agatino
2012-07-01
The thermal degradation of various Polyhedral Oligomeric Silsesquioxane/Polystyrene (POSS/PS) nanocomposites of formula R7 R'1 (SiO1.5)8/PS (where R- and R'- were a cyclopentyl and a substituted phenyl group), at various (3%, 5% and 10%) POSS concentration, was studied in both inert (flowing nitrogen) and oxidative (static air) atmospheres. Nanocomposites were prepared by the polymerization of styrene in the presence of POSS. Degradations were carried out into a thermobalance at various heating rates, and the obtained thermogravimetric (TG) and differential thermogravimetric (DTG) curves were discussed and interpreted.
Nanev, Chr. N.; Rashkov, R. St.
1992-06-01
Loss of the polyhedral stability as a result of emerging depressions on crystal faces has been observed during both vapour and solution growth under diffusion control, as well as by electrocrystallization at high current densities. A difference was found only when a quantitative comparison of the stability of the crystal shapes with the existing theoretical predictions was attempted. With the growth of zinc and cadmium single crystals from the vapour phase this phenomenon appears earlier, i.e. at smaller sizes than the expected figures, while the silver single crystals are more steady — they withstand one order of magnitude higher of current densities than the calculated values before the appearance of the depressions, in spite of the fact that the presence of an (inhomogeneous) electrical field in the second case has to decrease the polyhedral stability. One possible explanation of this fact is that the electrocrystallization of silver proceeds in highly concentrated solutions, for which Seeger's equation, laying in the base of the quantitative elucidations in this case, does not hold true. Correspondingly, here (part I of the paper) we are trying a more general approach, while part II represents a new, alternative way for explaining the higher stability of the faceted forms of the silver single crystals.
Institute of Scientific and Technical Information of China (English)
肖荣冬; 翁国星
2015-01-01
BACKGROUND:Althoughpolyurethane possesses excelent biocompatibility, its inherent inertness leads to its weak interactions with cels. So, its modification is necessary. OBJECTIVE:To prepare the polyurethane/polyhedral oligomeric silsesquioxane nanocomposite fibers with controlable morphology. METHODS:The polyhedral oligomeric silsesquioxane was dispersed in a certain concentration of polyurethane solution to prepare the polyurethane/polyhedral oligomeric silsesquioxane nanocomposite fibers using electrospinning method. Meanwhile, the effects of mass of polyurethane and oligomeric silsesquioxane, spinning voltage and spinning advance velocity on composite fiber morphology were analyzed. The optimum preparing conditions were filtrated. The stability of oligomeric silsesquioxane in polyurethane was determined. The morphology and composition of fibers were analyzed by scanning electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy. RESULTS AND CONCLUSION: Oligomeric silsesquioxane stably existed in polyurethane. Polyurethane/polyhedral oligomeric silsesquioxane nanocomposite fibers were the most uniform when the mass fraction of polyurethane in composite fibers accounted for 20%, the mass ratio of polyurethane and oligomeric silsesquioxane was 10: 1, spinning voltage was 15 kV and spinning advance velocity was 0.5 mL/h. Compared with the pure polyurethane, the O/C ratio of polyurethane/polyhedral oligomeric silsesquioxane nanocomposites increased significantly.%背景：聚氨酯具有良好的生物相容性，然而其固有的惰性导致其与细胞之间的相互作用较弱，因此需要对其改性。目的：制备形貌可控的聚氨酯/低聚倍半硅氧烷纳米复合纤维。方法：将多面体低聚倍半硅氧烷分散到一定浓度的聚氨酯溶液中，通过静电纺丝制备聚氨酯/低聚倍半硅氧烷纳米复合纤维，同时分析聚氨酯质量、低聚倍半硅氧烷质量、纺丝电
Energy Technology Data Exchange (ETDEWEB)
Xiong, Shanxin [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); Ma, Jan; Lu, Xuehong [Temasek Laboratories, Nanyang Technological University, 50 Nanyang Drive, Singapore 637553 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
2009-12-15
A high-contrast complementary electrochromic device based on polyaniline (PANI) tethered polyhedral oligomeric silsesquioxane (POSS) (POSS-PANI) and poly(3,4-ethylenedioxythiophene)/poly(4-styrene sulfonic acid) (PEDOT:PSS) is assembled. The electrochromic properties, cyclic voltammetry behavior and coloration efficiency of the device are studied. Due to the loosely packed structure, POSS-PANI gives rise to a significantly higher electrochromic contrast, coloration efficiency and faster switching speed than PANI. Despite its high contrast, the combination of POSS-PANI with PEDOT:PSS still shows synergy in terms of contrast enhancement, which can be attributed to the additional driving force for the diffusion of dopants into PEDOT:PSS provided by the dedoping of POSS-PANI. (author)
Zhang, R. L.; Wang, C. G.; Liu, L.; Cui, H. Z.; Gao, B.
2015-10-01
A novel hierarchical reinforcing carbon fiber through co-grafting carbon nanotube (CNTs) and polyhedral oligomeric silsesquioxanes (POSS) was prepared in this paper. The structure and surface characteristics of the grafted carbon fiber were investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), thermogravimetry (TG) and scanning electron microscope (SEM), respectively. The surface energy and the functional groups of the carbon fiber surface were increased obviously after modification. The ILSS results showed that there was a remarkable improvement in the interfacial properties of the new hybrid CF-CNTs-POSS composites. The investigation can prove an effective way to increase the interfacial adhesion and improve the mechanical performance of the fiber/resin composites on the desired application.
Energy Technology Data Exchange (ETDEWEB)
Shu, Jinxia [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Wang, Zhonghua, E-mail: zhwangs@163.com [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Huang, Yijiang; Huang, Ni [Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002 (China); Ren, Chunguang [Graduate School of Materials Science, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192 (Japan); Zhang, Wei [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China)
2015-06-05
Highlights: • Polyhedral Cu{sub 2}O NPs with rough surfaces were prepared by a one-pot sonochemical precipitation method. • The Cu{sub 2}O NPs show unprecedented adsorption capability toward Congo red. • CR adsorption onto Cu{sub 2}O is a spontaneous, endothermic and chemisorption process. • The Cu{sub 2}O adsorbent can be photocatalytically regenerated by visible light irradiation. - Abstract: Polyhedral cuprous oxide nanoparticles (Cu{sub 2}O NPs) with rough surfaces were prepared by a one-pot sonochemical precipitation method. The products were characterized by SEM, XRD, EDS, XPS, and UV–Vis DRS, respectively. The adsorption behavior of Congo red (CR) from aqueous solution onto the as-prepared Cu{sub 2}O NPs was systematically investigated. The equilibrium and kinetic studies suggested that the adsorption process followed Freundlich isotherm and pseudo-second order model, respectively. The as-prepared Cu{sub 2}O NPs exhibited remarkable adsorption properties toward CR. The maximum adsorption capacity at 20 °C was 3904 mg g{sup −1}, which was the highest reported value so far in adsorption removal of CR. Together with the evaluation of the thermodynamic parameters such as Gibbs free energy, enthalpy and entropy change, our results show that the adsorption of CR onto Cu{sub 2}O is a spontaneous, endothermic and chemisorption process. A putative interaction model between CR and Cu{sub 2}O NPs was proposed. Moreover, the Cu{sub 2}O adsorbent could be photocatalytically regenerated and reused without significant loss of its adsorption capability.
高温氧化物晶体界面非稳定性研究%Polyhedral Instability of High-temperature Oxide Crystal
Institute of Scientific and Technical Information of China (English)
金蔚青; 蔡丽霞; 潘志雷; 苗宇
2000-01-01
设计了一套模拟实验, 以获得关于晶体形态和界面非稳定性的差异的可靠数据，如高温溶液生长的骸晶和枝蔓晶. 这些实验是在高温实时观察装置(HITISOT)内进行的. 高温溶液晶体生长实验是在环形铂金丝炉圈内进行的. 炉圈直径为2mm. 铂金丝既起加热又起支撑熔体的作用. 选用KNbO3和Li2B4O7?的混合物进行晶体生长实验. 在只存在扩散机制的快速生长过程中，会形成不同的晶体不完整性，如晶面凹坑、骸晶和枝蔓晶. 采用淬火实验以分辨不同的KNbO3晶体形态，并用扫描电镜研究Li2B4O7溶体中KNbO3?晶体生长的形貌. 在一般情况下，当晶体在气液界面附近液相区成核时，会产?生晶体界面非稳定性. 导致晶体形状不稳定的溶液层的厚度为60. 通过扫描电镜观察，发现晶体在这一溶液层中由多面体晶变为枝蔓晶. 骸晶和枝蔓?晶的各向异性反映了KNbO3的立方特性，也反映了界面非稳定性是沿［110］晶?棱扩大的. ［110］晶棱方向的分支证实了晶体生长形状的各向异性. 形成界面非?稳定性的临界尺寸为10. 与此相反，保持稳定的晶面形状是通过60厚度以下的溶液内的晶体生长来实现的. 晶体生长过程是由高温实时观察装置进行实时观察和记录的，并能观察到晶体固液界面处的热溶质对流(如微对流).%Model experiments were designed in order to obtain more reliable data on the diversity of some crystal forms and polyhedral instability-skeletal and dendritic growth in high 妕emperature solution growth. These experiments were performed by High Temperature In Situ Observation Technique. Most of our investigations on high temperature solution growth were performed in a loop-shaped Pt wire heater, having a diameter about 2mm. The Pt wire (0.2mm) was used to heat and suspend the solution. A mixture of KNbO3 (20wt%) and Li2B4O7 was chosen for growth. Rapid growth
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M. A. Quintela
2001-12-01
Full Text Available Face à complexidade, ao custo e à duração dos testes cíclicos para avaliação da resistência ao choque térmico, os refratários contendo carbono têm sido tipicamente selecionados com base na sua superior condutividade térmica. Por essa razão, é importante uma avaliação das principais propriedades dos refratários, visando não apenas estabelecer critérios de seleção, mas, também, permitir à engenharia de projetos efetuar modificações na sua microestrutura, possibilitando assim superior desempenho do revestimento. Este trabalho apresenta os principais aspectos teóricos e a técnica adotada na Usiminas para avaliação da resistência ao choque térmico de materiais contendo carbono. A metodologia contempla a medida da energia de fratura utilizando a técnica de CMOD (crack mouth opening displacement e a determinação dos parâmetros de resistência ao dano por choque térmico, R'''' e Rst.Due to complexity, cost and time involved in evaluating the thermal shock resistance, carbon-containing refractories are usually selected based only on the thermal conductivity. It is therefore necessary to evaluate the physical properties that affect the thermal shock behavior of refractories and to generate suitable criteria for selection and development of microstructure aiming to increase the lining life. The present paper presents the methodology used at Usiminas for the determination of the thermal shock damage resistance of carbon-containing refractories for casting ladles. The test method adopted involves measurements of the fracture energy using CMOD (crack mouth opening displacement and the determination of the thermal shock parameters (R'''' e Rst.
Cao, Xuan Thang; Showkat, Ali Md; Bach, Long Giang; Jeong, Yeon Tae; Kim, Jong Soo; Lim, Kwon Taek; Gal, Yeong-Soon
2015-01-01
Photoluminescent hybrids of poly( ɛ-caprolactone) (PCL), polyhedral oligosilsesquioxane (POSS) and terbium ions (Tb3+) were synthesized by using a combination of ring-opening polymerization (ROP), click chemistry and coordination chemistry. Initially, acetylene functionalized PCL (alkyne-PCL-COOH) was prepared by using ROP of ɛ-caprolactone with propargyl alcohol, and azide-substituted POSS (POSS-N3) was prepared by using the reaction of chloropropyl-heptaisobutyl-substituted POSS with NaN3. The click reaction between alkyne-PCL-COOH and POSS-N3 afforded POSS-g-PCL, which was subsequently coordinated with Tb3+ ions in the presence of 1,10-phenanthroline to produce POSS-g-PCL-Tb3+-Phen. The structures and compositions of the hybrids were investigated by using 1H nuclear magnetic resonance (NMR), Fourier-transform infrared spectroscopy (FT-IR), Field emission scanning electron microscope (FE-SEM), Transmission electron microscopy (TEM), and Thermogravimetric analysis (TGA). The optical properties of POSS-g-PCL-Tb3+-Phen complexes were characterized by using photoluminescence spectroscopy, which showed four high emission bands centered at 489, 545, 584, and 620 nm with excitation at 330 nm. The emission spectra of the europium-ion-coordinated hybrids, POSS-g-PCL-Eu3+-Phen, had four high-intensity peaks, 594, 617, 652 and 686 nm, for an excitation wavelength of 352 nm.
Wei, Kun; Li, Lei; Zheng, Sixun; Wang, Ge; Liang, Qi
2014-01-14
In this contribution, we report the synthesis of organic-inorganic random polymers from methacrylate-terminated poly(ethylene oxide) (MAPEO) (Mn = 950) and 3-methacryloxypropylheptaphenyl polyhedral oligomeric silsesquioxane (MAPOSS) macromers via reversible addition-fragmentation chain transfer (RAFT) polymerization with 4-cyano-4-(thiobenzoylthio) valeric acid (CTBTVA) as the chain transfer agent. The organic-inorganic random copolymers were characterized by means of (1)H NMR spectroscopy, gel permeation chromatography (GPC) and differential scanning calorimetry (DSC). The results of GPC indicate that the polymerizations were carried out in a controlled fashion. Transmission electron microscopy (TEM) showed that the organic-inorganic random copolymers in bulk were microphase-separated and the POSS microdomains were formed via POSS-POSS interactions. In aqueous solutions the organic-inorganic random copolymers were capable of self-assembling into spherical nanoobjects as evidenced by transmission electron microscopy (TEM) and dynamic laser scattering (DLS). The self-assembly behavior of the organic-inorganic random copolymers was also found to occur in the mixtures with the precursors of epoxy. The nanostructures were further fixed via subsequent curing reaction and thus the organic-inorganic nanocomposites were obtained. The formation of nanophases in epoxy thermosets was confirmed by transmission electron microscopy (TEM) and dynamic mechanical thermal analysis (DMTA). The organic-inorganic nanocomposites displayed the enhanced surface hydrophobicity as evidenced by surface contact angle measurements.
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I. Blanco
2012-12-01
Full Text Available Some new Polystyrene (PS nanocomposites were prepared by using two Polyhedral Oligomeric Silsesquioxanes (POSSs, namely RR’7(SiO1.58 (where R = 4-methoxyphenyl or 2,4-difluorophenyl and R’ = cyclopentyl, as fillers, and their degradation was studied to investigate the effect of the electron-donor or electron-withdrawing character of the phenyl group substituents on thermal stability. Nanocomposites were synthesized by in situ polymerization of styrene in the presence of various concentrations of POSS. Proton nuclear magnetic resonance (1H NMR spectra indicated that the POSS content in the obtained nanocomposites was higher than that in reactant mixtures. Inherent viscosity (ηinh and glass transition temperature (Tg determinations indicated that the average molar mass of polymer in 4-methoxynanocomposites was the same than neat PS, while it was much lower in 2,4-difluoro derivatives. Degradations were carried out in both flowing nitrogen and static air atmospheres, in the scanning mode, at various heating rates, and temperature at 5% mass loss (T5% and the activation energy (Ea of degradation of various nanocomposites were determined. The values obtained for 4-methoxyderivatives were higher than unfilled PS thus indicating higher thermal stability. Conversely, the values found for 2,4-difluoro derivatives were lower, in some cases even than those of neat PS. The results were discussed and interpreted.
Energy Technology Data Exchange (ETDEWEB)
Larsen, Randy W; Wojtas, Lukasz [USF
2012-10-25
The ability to confine photoactive catalysts within metal-organic framework (MOF) materials affords the opportunity to expand the functional diversity of these materials into solar based applications. Here, the confinement of Ru(II)tris(2,2'-bipyridine) (RuBpy) by a MOF material derived from Zn(II) ions and trimesic acid (hereafter, USF2) is examined. Although the encapsulated RuBpy could not be crystallographically resolved within the MOF framework, the photophysical properties of the complex are characteristic of confinement including extended triplet metal-to-ligand (^{3}MLCT) lifetime (τ_{ethanol} = 614 ns and {τ_{USF2} = 1.2 μs at 25 °C) and a slight hypsochromic shift in the steady-state emission spectrum relative to RuBpy in ethanol. The extended lifetime is attributed to a deactivation of a nonradiative ^{3}dd that is antibonding with respect to the Ru(II)-bipyridine due to a confined molecular environment. These results represent one of the first examples of RuBpy encapsulation and photophysical characterization within a polyhedral MOF material.
Hu, X. B.; Zhu, Y. L.; Sheng, N. C.; Ma, X. L.
2014-12-01
Ni-based single superalloys play a crucial role in the hottest parts of jet engines. However, due to the complex geometry and macro-segregation during the solidification process, the cast defect such as stray grains is inevitable. Therefore, the transient liquid phase (TLP) bonding which can join several small single crystalline castings together is gradually believed to be an effective method for improving the yields of production of the complex components. The melting point depressant element B is always added into the interlayer filler material. Consequently, borides including the M3B2 and M5B3 phase usually precipitate during the TLP bonding process. So a comprehensive knowledge of the fine structural characteristics of the borides is very critical for an accurate evaluation of the TLP bonding process. In this work, by means of the aberration-corrected transmission electron microscopy, we show, at an atomic scale, the Wyckoff positional order phenomenon of the metal atoms in the unit cell of M3B2- and M5B3-type boride. Meanwhile, the defect along the (001) plane of the above two types of boride are determined to be the polyhedral intergrowth with complex configurations.
Energy Technology Data Exchange (ETDEWEB)
Longhi, Marielen; Zini, Lucas Pandolphi; Birriel, Eliena Jonko; Kunst, Sandra Raquel; Zattera, Ademir Jose, E-mail: marielen_longhi@hotmail.com [Universidade de Caxias do Sul (LPOL/UCS), RS (Brazil). Laboratorio de Polimeros; Pistor, Vinicius [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)
2013-07-01
The incorporation of nanofiller in thermosetting like epoxy resin as has been studied in order to modify its properties. In this research, nanocomposites were obtained by incorporating 5% by weight of three polyhedral oligomeric silsesquioxane (POSS) with different number of functionalization: Glicidilisobutil-POSS, Triglicidilisobutil- POSS and Glicicil POSS in an epoxy matrix by sonification process. The nanocomposites were characterized by analysis of X-ray diffraction (DRX), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The DRX analysis showed the characteristic peak of POSS and TEM images showed that there is a difference in the dispersion of nanocages for the difference in the number of epoxy groups on the POSS. The incorporation of Glicidilisobutil-POSS showed a significant increase in the glass transition temperature (Tg) value, and also that the most effective from the viewpoint of the dispersion, on the other hand, the Glycidyl-POSS had a greater influence on the thermal stability demonstrating that the dispersion medium is an important characteristic to define the most desirable properties. (author)
CARBON-CONTAINING COMPOSITES BASED ON METALS
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VAGANOV V. E.
2015-10-01
Full Text Available Problem statement Among the developed technologies metal-composites production,a special place takes powder metallurgy, having fundamental differences from conventionally used foundry technologies. The main advantages of this technology are: the possibility of sensitive control, the structure and phase composition of the starting components, and ultimately the possibility of obtaining of bulk material in nanostructured state with a minimum of processing steps. The potential reinforcers metals include micro and nano-sized oxides, carbides, nitrides, whiskers. The special position is occupied with carbon nanostructures (CNS: С60 fullerenes, single-layer and multi-layer nanotubes, onions (spherical "bulbs", nano-diamonds and graphite,their properties are being intensively studied in recent years. These objects have a high thermal and electrical conductivity values, superelasticity, and have a strength approximate to the theoretical value, which can provide an obtaining composite nanomaterial with a unique set of physical and mechanical properties. In creation of a metal matrix composite nanomaterials (CM, reinforced by various CNS, a special attention should be given to mechanical activation processes (MA already at the stage of preparation of the starting components affecting the structure, phase composition and properties of aluminum-matrix composites. Purpose. To investigate the influence of mechanical activation on the structure and phase composition of aluminum-matrix composites. Conclusion. The results of the study of the structure and phase composition of the initial and mechanically activated powders and bulk-modified metal-composites are shown, depending on the type and concentration of modifying varieties CNS, regimes of MA and parameters of compaction. The study is conducted of tribological properties of Al-CNS OF nanostructured materials.
Chaves, Camilo; Alshomer, Feras; Palgrave, Robert G; Kalaskar, Deepak M
2016-07-27
This study present amino functionalization of biocompatible polymer polyhedral oligomeric silsequioxane-poly(carbonate-urea) urethane (POSS-PCU) using plasma polymerization process to induce osteogenic differentiation of adipose derived stem cells (ADSCs). Optimization of plasma polymerization process was carried out keeping cell culture application in mind. Thus, samples were rigorously tested for retention of amino groups under both dry and wet conditions. Physio-chemical characterization was carried out using ninhydrin test, X-ray photon spectroscopy, scanning electron microscopy, and static water contact analysis. Results from physio chemical characterization shows that functionalization of the amino group is not stable under wet conditions and optimization of plasma process is required for stable bonding of amino groups to the POSS-PCU polymer. Optimized samples were later tested in vitro in short and long-term culture to study differentiation of ADSCs on amino modified samples. Short-term cell culture shows that initial cell attachment was significantly (p < 0.001) improved on amine modified samples (NH2-POSS-PCU) compared to unmodified POSS-PCU. NH2-POSS-PCU samples also facilitates osteogenic differentiation of ADSCs as confirmed by immunological staining of cells for extracellular markers such as collagen Type I and osteopontin. Quantification of total collagen and ALP activity also shows significant (p < 0.001) increase on NH2-POSS-PCU samples compared to unmodified POSS-PCU. A pilot study also confirms that these optimized amino modified POSS-PCU samples can further be functionalized using bone inducing peptide such as KRSR using conventional wet chemistry. This further provides an opportunity for biofunctionalization of the polymer for various tissue specific applications.
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Mujib Khan
2011-09-01
Full Text Available Our continuing quest to improve the performance of polymer composites under moist and saltwater environments has gained momentum in recent years with the reinforcement of inorganic nanoparticles into the polymer. The key to mitigate degradation of composites under such environments is to maintain the integrity of the fiber/matrix (F/M interface. In this study, the F/M interface of carbon/vinyl ester composites has been modified by coating the carbon fiber with polyhedral oligomeric silsesquioxane (POSS. POSS is a nanostructured inorganic-organic hybrid particle with a cubic structure having silicon atoms at the core and linked to oxygen atoms. The advantage of using POSS is that the silicon atoms can be linked to a substituent that can be almost any chemical group known in organic chemistry. Cubic silica cores are ‘hard particles’ and are about 0.53 nm in diameter. The peripheral organic unit is a sphere of about 1–3 nm in diameter. Further, cubic structure of POSS remains intact during the polymerization process and therefore with appropriate functional groups, if installed on the fiber surface, would provide a stable and strong F/M interface. Two POSS systems with two different functional groups; namely, octaisobutyl and trisilanolphenyl have been investigated. A set of chemical and mechanical procedures has been developed to coat carbon fibers with POSS, and to fabricate layered composites with vinyl ester resin. Interlaminar shear and low velocity impact tests have indicated around 17–38% improvement in mechanical properties with respect to control samples made without the POSS coating. Saltwater and hygrothermal tests at various environmental conditions have revealed that coating with POSS reduces water absorption by 20–30% and retains the composite properties.
Penélope Hernández; José Vila Gisbert
2009-01-01
Una aproximació polièdrica al concepte microeconòmicA Polyhedral Approach to the Microeconomic ConceptEste artículo propone un enfoque tridimensional de cualquier concepto en Microeconomía y analiza las implicaciones de esta multidimensionalidad en el proceso de aprendizaje-enseñanza de la microeconomía en educación universitaria. Las tres facetas del aprendizaje presentadas son la experiencial-vivencial, la gráfico-geométrica y la matemático-formal. En cada una de ellas el lenguaje utilizado...
American Society for Testing and Materials. Philadelphia
2004-01-01
1.1 This test method covers determining the concentrations of refrigerant-114, other carbon-containing and fluorine-containing compounds, hydrocarbons, and partially or completely substituted halohydrocarbons that may be impurities in uranium hexafluoride. The two options are outlined for this test method. They are designated as Part A and Part B. 1.1.1 To provide instructions for performing Fourier-Transform Infrared (FTIR) spectroscopic analysis for the possible presence of Refrigerant-114 impurity in a gaseous sample of uranium hexafluoride, collected in a "2S" container or equivalent at room temperature. The all gas procedure applies to the analysis of possible Refrigerant-114 impurity in uranium hexafluoride, and to the gas manifold system used for FTIR applications. The pressure and temperatures must be controlled to maintain a gaseous sample. The concentration units are in mole percent. This is Part A. 1.2 Part B involves a high pressure liquid sample of uranium hexafluoride. This method can be appli...
The hydrogen storage properties of Na decorated small boron cluster B6Na8
Tang, Chunmei; Wang, Zhiguo; Zhang, Xue; Wen, Ninghua
2016-09-01
The binding energy of the Na atoms to the hollow sites of the B6 cage is larger than the experimental cohesive energy of bulk Na, so the clustering of Na atoms can be avoided. The polarization interaction dominates the adsorption of H2 by the B6Na8 cluster. The Na-coated B6Na8sbnd B8sbnd B6Na8 complex with the dispersive Na atoms and four H2 molecules adsorbed per Na can serve as better building blocks of polymers than the (B6Na8)2 dimer. These findings suggest a new route to design cluster-assembled hydrogen storage materials based on sp2-terminated boron chains.
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Iwata, Suehiro; Akase, Dai; Aida, Misako; Xantheas, Sotiris S.
2016-08-04
The relative stability and the characteristics of the hydrogen bond networks in the cubic cages of (H2O)8, dodecahedral cages of (H2O)20,and tetrakaidodecahedral cages of (H2O)24 are studied. The charge-transfer and dispersion interaction terms of every pair of the hydrogen bonds are evaluated by using the perturbation theory based on the locally-projected molecular orbital (LPMO PT). Every water molecule and every hydrogen-bonded pair in polyhedral clusters are classified by the types of the adjacent molecules and hydrogen bonds. The relative binding energies among the polyhedral clusters are grouped by these classifications. The necessary condition for the stable conformers and the rules of the ordering of the relative stability among the isomers are derived from the analysis. The O–O distances and the pair-wise charge-transfer terms are dependent not only on the types of the hydrogen donor and acceptor waters but also on the types of the adjacent waters. This dependence is analyzed with Mulliken’s charge-transfer theory. The work is partially supported by the Grant-in-Aid for Science Research of JSPS (SI, DA, MA). SSX was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences. Battelle operates the Pacific Northwest National Laboratory for the US Department of Energy.
多面体线框模型的表面识别技术%Identifying faces 0f polyhedral wireframe models
Institute of Scientific and Technical Information of China (English)
赵军; 高满屯; 王三民
2011-01-01
This paper presents an efficient algorithm for extracting faces from polyhedral wireframe models. The main features of the algorithm are using the topological and geometric information of wireframe models and its stronger adaptability. First, the wireframe model is projected to a plane, and the "invisible" edges which are obstructed by another edge in projection are hidden. And the edges which have a common vertex are arranged into a set in counterclockwise.Then search the minimal circle based on rule of the smallest rotation angle in clockwise. At the same time the Moebius rule are use to delete the illegal circle and remove the finished edges which are accurately contained by two circles. When a " visible" edge is removed, "invisible" edges blocked by it may be "visible" ones. So the new minimal circle can be searched. Repeat this course until all edge is removed and there are no illegal circle and illegal edge. Finally, the remaining circle are all true face of the model and all point to outside of the object by adjusting their direction. Several typical examples are given to demonstrate the widespread adaptability and high efficiency of the algorithm.%提出一种综合利用线框模型几何信息和拓扑信息的表面识别算法.首先利用平行投影法将3维线框模型投影到2维平面上,隐藏被遮挡边和悬边悬链;然后在可见投影边线图中,根据各个顶点的关联边序列,按照顺时针最小转角原则搜索最小回路;最后根据Moebius规则和二流形体的性质,及时删除不是表面投影的非法回路和图中的完备边,并调整回路的方向,使其均指向体外.通过各类典型立体的表面识别实验表明,算法具有广泛的立体适应能力和较高的效率.
Research Progress on Metal-containing Polyhedral Oligomeric Silsesquioxanes%含金属笼型倍半硅氧烷的研究进展
Institute of Scientific and Technical Information of China (English)
曾碧榕; 许一婷; 罗伟昂; 戴李宗
2012-01-01
倍半硅氧烷作为催化剂载体硅胶表面结构与性能研究的模型,可以通过表征其表面反应性质来直观认识硅胶负载型催化剂的作用机制。过去几十年来,倍半硅氧烷的研究呈现飞跃式的发展态势,开发出许多新化合物和新合成方法,并在一些催化过程中得到应用。将倍半硅氧烷作为金属化合物的配体,极大地丰富了元素化学的内容。本文重点介绍了合成含金属笼型倍半硅氧烷的相关进展,同时介绍了含金属笼型倍半硅氧烷在聚合物材料应用中的研究。%Polyhedral oligomeric silsesquioxancs （POSS） is a kind of organic and inorganic hybrids molecules with cage-like nanostructure. Study on POSS has gained great interest and becomes a hot spot in the field of catalytic materials over the past decade. New synthetic approaches have been developed, and new complexes based on elements throughout the periodic table have been synthesized. Researchers have also developed many methods to incorporate silsesquioxanes into new materials. It showed that the metal-containing POSS complexes were models of silica immobilized with metal complexes, and could provide us an intimate knowledge of the reactions on the surface of silica support. This review introduces the development of the synthesis of metallasilsesquioxanes of main group and transition metals, and also presents the recent applications of metal-containing POSS in flame retardant polymers, photoelectric material and so on. In the future, the research will focus on the synthesis and characterization of novel metal-containing POSS compounds as well as their applications in the field of catalysts and functional materials.
Polyhedral Scattering of Fundamental Monopoles
Battye, R; Rychenkova, P; Sutcliffe, P; Battye, Richard; Gibbons, Gary; Rychenkova, Paulina; Sutcliffe, Paul
2003-01-01
The dynamics of n slowly moving fundamental monopoles in the SU(n+1) BPS Yang-Mills-Higgs theory can be approximated by geodesic motion on the 4n-dimensional hyperkahler Lee-Weinberg-Yi manifold. In this paper we apply a variational method to construct some scaling geodesics on this manifold. These geodesics describe the scattering of n monopoles which lie on the vertices of a bouncing polyhedron; the polyhedron contracts from infinity to a point, representing the spherically symmetric n-monopole, and then expands back out to infinity. For different monopole masses the solutions generalize to form bouncing nested polyhedra. The relevance of these results to the dynamics of well separated SU(2) monopoles is also discussed.
Institute of Scientific and Technical Information of China (English)
姚敏; 王嘉骏; 顾雪萍; 冯连芳
2012-01-01
Dendrimer is one type of macromolecules with well-defined, highly-branched and nano-scaled architectures, composed of three distinct domains： core, branches and terminal groups. Its potential functions and applications are explored based on the unique physical and chemical features due to special molecular architecture. Using polyhedral oligomerie silsesquioxanes （POSS） as the core of dendrimers is an effective and facile way to simplify the tedious repetitive steps of preparation and separation. Since POSS allows eight branches to radiate from a silicon-oxygen rigid cubic core, the dendrimers can be constructed in a well-controlled globular, three- dimensional framework, and large numbers of peripheral groups can be obtained at relatively low generation numbers. As a kind of novel nano-hybrid supermolecules, POSS-based dendrimers have attracted considerable interest in materials science. In this review, we briefly introduce the synthetic approaches of some typical POSS- based dendrimers categorized by the different chemical composition of branching units, and then focus on the potential functions and applications of this nano-hybrid material in the fields of catalysis, gene and drug delivery, liquid crystals, light harvesting and energy transfer. The specific and excellent properties imparted by the incorporation of POSS into dendrimers are also presented. Finally, the advances of POSS-based dendrimers are prospected.%树枝状大分子（dendrimer）是一种高度支化、纳米尺度的人工合成大分子，具有独特的物理化学性能和重要的应用前景。利用具有8个可官能化顶点的多面体低聚倍半硅氧烷（POSS）作为树枝状大分子的核心，可在一定程度上简化树枝状大分子繁琐的合成与分离过程，在低代数时就可获得较大的表面官能团密度，并使树枝状分子呈现球形对称结构。POSS基树枝状大分子结合了POSS和树枝状分子结构与性能的优势，是一类
Institute of Scientific and Technical Information of China (English)
周伟; 王嘉骏; 顾雪萍; 冯连芳
2011-01-01
Wetting behavior of water on the surface of polyhedral oligomeric silsesquiones (H-POSS) was investigated by molecular dynamics simulation. Force fields of COMPASS and SPC were applied for H-POSS and water, respectively. It is found that simulated density of H-POSS substrate is 1.84 g/cm3, and apparent diffraction peaks come out, which indicate that the substrate is crystallizable to some extent. It suggests that COMPASS force field is adaptable to the construction and investigation of H-POSS. The surface of H-POSS is hydrophobic with the water contact angle as 104.9° in the simulation. In addition, H-POSS was synthesized from trichlorosilane (HSiCl3) with direct hydrolytic condensation. Through the characterization by FT-IR, adsorption peaks take place at the wavenumber of 2260, 1142 and 871 cm"1. The experimental contact angle is 109.3° on the surface of H-POSS. Compared with the simulated contact angle, the relative error is merely 4 %. It's validated that molecular dynamic simulation can be utilized to calculate the wettability of H-POSS monomer. Besides, the hydrophobicity is weakened when system temperature is increased.Keywords: Wettability, H-POSS, Contact angle, Molecular dynamics simulationFluent software was used to simulate the wind flow field around a new-type porous fence with a porosity of 0.4 to indicate the changes of velocity, pressure coefficient and turbulence kinetic energy around a triangular prism model located behind the porous fence under different deflector forms. The numerical predictions showed that the deflectors play a guiding role and makes the flow up to a certain angle to reduce the direct influence on the windward of the prism. In addition, it showed that the form of gradual angels had the better perfomance comparing to other forms due to eliminiting the velocity recirculation zone between the fence and the windward surface and making the flow field behind the porous fence stable.%采用分子动力学模拟方法研究了水滴
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C. S. Bitencourt
2013-03-01
.Due to their unique set of properties and characteristics, carbon containing refractories have been a key issue in order that the steelmaking industry could attain its current productivity levels. However, further development of these materials is still necessary, especially due to the increasing pressure on the steelmaking sector to make its processes safer and more sustainable, goals which directly depend on the performance of the refractories used for the iron and steel production chain. Thus, in order to identify opportunities not yet explored, as well as to examine the research lines that have been successful in increasing the carbon containing refractory performance, this paper presents an extensive review regarding likely components of these materials, such as binders, carbon sources and additives. Based on the innovations recently disclosed, it is pointed out the use of combined additions of antioxidants agents and TiO2 to promote the development of phases with special morphologies (such as whiskers, and novel additives that enable the graphitization of the carbon from the thermosetting resins. This latter advance is particularly significant, because it provides to the resins a capacity before exclusive of the coal tar pitch, binder which has been avoided due to the unhealthy conditions that it brings to the steelmaking industry workplaces, as well as to the refractories industry. Among the possibilities of innovation pointed out, it is highlighted the addition of coupling agents to the resin bonded refractories in order to optimize its processability. Such improvement would be particularly important for resin bonded castables, materials that currently have limited applications, but are attracting great interest due to their many advantages over preformed products, which make them an important target for new developments.
Bianchini, D; Butler, I S; Barsan, M M; Martens, W; Frost, R L; Galland, G B; dos Santos, J H Z
2008-11-01
Thermal decomposition studies of the free polyhedral oligomeric silsesquioxane, POSSh, and when this compound has been impregnated with Cp2ZrCl2 (Cp = eta5-C5H5) or immobilized on SiO2 were conducted using infrared emission spectroscopy (IES) over a 100-1000 degrees C temperature range and by thermogravimetric analysis (TGA). The organic groups in POSS(h) apparently decompose thermally into Si-CH3, Si-H and other fragments. Upon impregnation with Cp2ZrCl2, however, a different thermal decomposition pathway was followed and new infrared emission bands appeared in the 1000-900 cm(-1) region suggesting the formation of Si-O-Zr moieties. When immobilized on SiO2 and subjected to thermal decomposition, the POSSh compound lost its organic groups and the inorganic structure remaining was incorporated into the SiO2 framework.
Institute of Scientific and Technical Information of China (English)
薛燕鹏; 陈玉勇
2012-01-01
The induction furnace dipping experimental method is used to simulate the application condition on site.The phase composition,weight loss features under high temperatures and microstructure of carbon containing refractories after corroded by molten steel are investigated by means of analytical methods,such as XRD,SEM,TGA etc.The results show that in the stage of heating in the range from 20~1 300℃ the weight of MgO-C sample has been reduced all through,the total weight reduction is 1.142 7mg,occupying 16.93% of its total mass,while the weight loss of Al2O3-MgO-C sample is less,the total weight loss is 0.441 4mg,occupying 6.45% of its total mass.When heating temperatures range from 1 070~1 170℃,Al2O3-MgO-C sample has increased weight in small amount.The corrosion mechanisms of molten steel on MgO-C and Al2O3-MgO-C refractories are nearly same.Molten steel penetrates into the grain boundaries of major phases,generating many small holes at the boundaries and leaving intergranular and intragranular iron precipitation.%采用感应炉浸渍实验法模拟钢包现场使用情况,借助X-射线衍射仪（XRD）、扫描电子显微镜（SEM）和热重分析设备（TGA）等分析手段,研究了含碳耐火材料的相组成、高温失重特性以及被钢液侵蚀后的显微组织。结果表明,在20～1 300℃加热阶段,MgO-C试样一直在减重,减重共计1.142 7mg,占试样总质量的16.93%,而Al2O3-MgO-C试样减重较少,减重共计0.441 4mg,占试样总质量的6.45%。加热温度在1 070～1 170℃,Al2O3-MgO-C试样少量增重。钢液对MgO-C和Al2O3-MgO-C耐火材料的侵蚀机理基本相同,均沿主相晶界侵入,晶界处有许多小孔洞,且晶界和晶内分布有许多小铁珠。
Directory of Open Access Journals (Sweden)
Penélope Hernández
2009-12-01
Full Text Available Una aproximació polièdrica al concepte microeconòmicA Polyhedral Approach to the Microeconomic ConceptEste artículo propone un enfoque tridimensional de cualquier concepto en Microeconomía y analiza las implicaciones de esta multidimensionalidad en el proceso de aprendizaje-enseñanza de la microeconomía en educación universitaria. Las tres facetas del aprendizaje presentadas son la experiencial-vivencial, la gráfico-geométrica y la matemático-formal. En cada una de ellas el lenguaje utilizado es diferente y el paso entre las tres facetas conforman el camino apropiado para la adquisición profunda del concepto microeconómico a estudio. Se incorpora además dos casos donde se ilustra el método de la aproximación poliédrica de dos conceptos microeconómicos estándar en los programas de Introducción de la Microeconomía y Microeconomía Intermedia.
Institute of Scientific and Technical Information of China (English)
徐洪耀; 严正权; 张超; 苏新艳; 光善仪
2011-01-01
多面体笼型倍半硅氧烷( POSS)由O-Si-O链接的纳米尺寸的笼型无机芯[(SiO1.5)n]和外围有机取代基团(活性或惰性)组成,这种独特的结构为杂化功能材料的制备提供了重要的平台与基础.本文从低介电材料结构对其件能的影响以及低介电性能的形成机理等方面综述了低介电材料的制备方法,尤其是POSS在低介电材料控制制备的研究进展,为该领域新材料的设计提供借鉴.%Polyhedral oligosilsesquioixanes(POSS) is a nanosized organic-inorganic hybrid molecule, which consists of a well-defined cage-like nano inorganic core[ (SiO1.5) ? ] surrounded by organic corner groups. The unique structure of POSS molecules provide an important platform for controllable preparation of hybrid nano-composites in molecular level dispersion. In this paper, the influence of hybrid molecular structure on properties and forming mechanism of low dielectric constant, in particular, the research progress of POSS-based nanocomposite low dielectric constant materials were summarized.
不规则多面体高保温玻璃采光顶施工技术%Construction of Irregular Polyhedral Thermo-insulating Glass Daylighting Roof
Institute of Scientific and Technical Information of China (English)
胡龙伟; 田砾; 赵铁军
2014-01-01
The daylighting roof with high thermo-insulating glass is adopted increasingly in large-scale public building because of its great visual impact and artistic expressive force along with day lighting and heat preservation. However,if the construction precision is not enough, leakage of water, glass blowout and other question will stand out easily. The construction technology of S-G eco-park experience center were studied in this paper, corresponding technical measure of such an irregular polyhedral thermo-insulating and glass daylighting roof can ensure the installation accuracy of the glass within mm order of magnitude. Specialized construction technology can be summed up base on this engineering and can be utilized in similar projects.%高保温采光屋顶在大型公共建筑中越来越多地得到应用，因为其具有极强的视觉冲击力和艺术表现力的同时，具有采光、保温等诸多功能。但如果施工精度不高，则易引起渗漏水、玻璃爆裂等问题。针对国内某生态园的体验中心不规则多面体高保温采光屋顶的施工进行了研究，相应的施工工艺及技术措施可以保证高保温玻璃安装精度控制在mm数量级。在此基础上总结了不规则多面体玻璃采光顶专用施工技术，对保证类似工程的施工精度具有一定的参考价值。
Speciation of residual carbon contained in UO2
Ziouane, Yannis; Arab-Chapelet, Bénédicte; Tamain, Christelle; Lalleman, Sophie; Delahaye, Thibaud; Leturcq, Gilles
2016-12-01
UO2 powders were synthesized thanks to oxalic precipitation (platelet morphology) and sol-gel route and completely characterized. A secondary phase was found depending on the calcination atmospheres. This phase has been identified by Raman spectroscopy as graphitic material (i.e. carbon-based secondary compound) and quantified by thermogravimetric analyses. Its amount varies with the calcination atmosphere. The presence of this secondary phase has no significant effect on the lattice parameter and its specific surface area.
On the practical application of carbon-containing nanocomposites
Vaganov, V. Ye.
2015-01-01
Raising of problem. The ever increasing demand for low-quality packaging materials for the food and pharmaceutical industries has led to the creation of mnogotonazhnyh production of polyethylene terephthalate (PETF) and thus necessitated their subsequent disposal or recycling. One promising avenue is to provide utilization of recycled polymer fibers and the subsequent production of a nonwoven fabric having a tremendous prospects for use in construction, engineering and so on. The main problem...
Processing of carbon containing gamma titanium aluminide alloys
Energy Technology Data Exchange (ETDEWEB)
Paul, J.D.H.; Froebel, U.; Oehring, M.; Appel, F. [Inst. for Materials Research, GKSS Research Centre, Geesthacht (Germany)
2003-07-01
Gamma-based titanium aluminide alloys have received much attention over the last decade with the intention of being used in turbine applications. In the as-cast state these alloys are relatively brittle when compared with conventional materials. In order to meet property requirements, optimisation of both alloy composition and microstructure are necessary. Alloys based on Ti-45Al-(5-10)Nb (at.%) with carbon additions seems capable of meeting many of the properties necessary for application. This paper addresses the reasons behind the choice of this alloy composition and discusses a relevant processing route. (orig.)
Group field theories generating polyhedral complexes
Thürigen, Johannes
2015-01-01
Group field theories are a generalization of matrix models which provide both a second quantized reformulation of loop quantum gravity as well as generating functions for spin foam models. While states in canonical loop quantum gravity, in the traditional continuum setting, are based on graphs with vertices of arbitrary valence, group field theories have been defined so far in a simplicial setting such that states have support only on graphs of fixed valency. This has led to the question whether group field theory can indeed cover the whole state space of loop quantum gravity. In this contribution based on [1] I present two new classes of group field theories which satisfy this objective: i) a straightforward, but rather formal generalization to multiple fields, one for each valency and ii) a simplicial group field theory which effectively covers the larger state space through a dual weighting, a technique common in matrix and tensor models. To this end I will further discuss in some detail the combinatorial ...
Robust structural identification via polyhedral template matching
DEFF Research Database (Denmark)
Larsen, Peter Mahler; Schmidt, Søren; Schiøtz, Jakob
2016-01-01
Successful scientific applications of large-scale molecular dynamics often rely on automated methods for identifying the local crystalline structure of condensed phases. Many existing methods for structural identification, such as common neighbour analysis, rely on interatomic distances (or thres...... is made available under a Free and Open Source Software license....
Fluorinated Polyhedral Oligomeric Silsesquioxanes (F-POSS)
2008-01-01
spotlight. Preparative approaches are often inspired by naturally evolved biological systems.[1] Specifically, a leaf of the lotus plant exhibits an... plant exhibits an inherent self-cleaning mechanism resulting frommicron-sized waxy nodes protruding from its surface such that water is naturally... Planta 1997, 202, 1. [4] a) N. Takeshita, L. A. Paradis, D. Oner, T. J. McCarthy, W. Chen, Langmuir 2004, 20, 8131; b) J.-Y. Shiu, C.-W. Kuo, P
Some polyhedral results in combinatorial optimization
Xiao, Han; 肖汉
2016-01-01
Many combinatorial optimization problems can be conceived of as optimizing a linear function over a polyhedron. Investigating properties of the associated polyhedron has been evidenced to be a powerful schema for solving combinatorial optimization problems, especially for characterizing min-max relations. Three different topics in combinatorial optimization are explored in this thesis, which fall within a unified characterization: integrality of polyhedra. Various min-max relations in com...
A polyhedral approach to quadratic assignment problem
Köksaldı, Ahmet Sertaç Murat
1994-01-01
Ankara : Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent University, 1994. Thesis (Master's) -- Bilkent University, 1994. Includes bibliographical references. In this thesis, Quadratic Assignment Problem is considered. Since Quadratic Assignment Problem is JVP-bard, no polynomial time exact solution method exists. Proving optimality of solutions to Quadratic Assignment Problems has been limited to instances of small dimension. In...
Fluorinated Polyhedral Oligomeric Silsesquioxanes (F-POSS)
2010-02-01
oleophobicity ) of a material. The F-POSS series measured water contact angles are on average 50° higher than for hexadecane contact angles. As a... oleophobicities of FH, FO, and FD are the same. Distribution A: Approved for public release; distribution unlimited. 7 Table 1. Selected Properties of F...measured contact angle of 150° (c). 3.2 POSS Fluoropolymers Selected F-POSS compounds possessing the highest hydro- and oleophobicity were blended
Institute of Scientific and Technical Information of China (English)
欧俊杰; 林辉; 刘哲益; 张振宾; 董靖; 邹汉法
2013-01-01
Two kinds of hybrid monolithic capillary columns were prepared via free radical polymerization. First, the hybrid monolithic column was in situ fabricated by using two polyhedral oligomeric silsesquioxanes (POSS) , POSS-methacryl substituted ( cage mixture, n = 8 , 10, 12) (POSS-MA) and POSS-( 1-propylmethacrylate )-heptaisobutyl substituted ( Bu-POSS ) , as crosslinker and monomer, respectively, in the presence of porogenic solvents ( propanol/ PEG400) and initiator (azodisobutyronitrile). Second, the hybrid monolithic column was similarly prepared by using POSS-MA, as sole monomer under the same conditions. The resulting two kinds of hybrid monolithic columns, poly( Bu-POSS-co-POSS-MA) and poly ( POSS-MA) , were characterized and applied for the separation of alkylbenzenes by capillary liquid chroma-tography (cLC) , showing good mechanical stability and reproducibility. Additionally, the poly (POSS-MA) monolith could be easily modified with other organic monomers, such as stearyl methacrylate (SMA) and benzyl metacrylate (BeMA) , with the presence of methacryl groups on the surface of the poly( POSS-MA) monolith. Compared with the raw poly( POSS-MA) monolith, the post-modified poly (POSS-MA) monolith exhibited higher column efficiency and better selectivity. This simple process of using POSS reagents via free radical polymerization is providing a novel way for the preparation of the organic-silica hybrid monolithic columns.%本文采用自由基聚合法原位制备了两种杂化毛细管整体柱.首先以含有一个甲基丙烯酸基团的多面体低聚倍半硅氧烷(POSS)试剂(Bu-POSS)为单体、以含有多个甲基丙烯酸基团的POSS试剂(POSS-MA)为交联剂在二元致孔剂(正丙醇/聚乙二醇400)和引发剂(偶氮二异丁腈)存在下发生热引发聚合,在毛细管中形成聚(Bu-POSS-co-POSS-MA)杂化整体柱；另外仅以POSS-MA为单体在相同条件下制备聚(POSS-MA)杂化整体柱,并将这两种杂化整体柱应用于小
Directory of Open Access Journals (Sweden)
C. S. Bitencourt
2013-03-01
Full Text Available Por suas diversas vantagens em relação ao piche de alcatrão convencional, o uso das resinas termofixas fenólicas vem se expandindo na produção dos refratários contendo carbono. Contudo, apesar desta tendência, ainda se verificam poucos trabalhos publicados no meio acadêmico que se proponham a investigar como alterações nas características desses polímeros podem afetar e beneficiar o processamento e as propriedades dos refratários. Algumas pesquisas reportam os efeitos dessas alterações sobre a pirólise do termofixo isolado. Entretanto, empregar plenamente as suas conclusões nos estudos em refratários pode não ser adequado, visto que os demais componentes e os próprios métodos de processamento desses materiais podem ter uma importante influência sobre o comportamento do termofixo. Assim, procurando verificar os caminhos mais promissores para desenvolver resinas fenólicas que apresentem um desempenho otimizado para essa aplicação específica, este artigo faz uma revisão geral sobre a química desses termofixos e suas conseqüências para o processamento do refratário e para a geração de carbono. Também serão revisados alguns aditivos capazes de auxiliar a resina a alcançar tal desempenho superior, entre eles os chamados agentes grafitizantes, que teriam a função de induzir a cristalização do carbono produzido pelo termofixo, um fenômeno antes exclusivo de fontes de carbono grafitizáveis como os piches.Based on the many advantages over the conventional coal tar pitch, the application of thermosetting phenolic resins has been expanding for the production of carbon containing refractories. Nevertheless, despite this trend, it is noticeable that there are few published technical and scientific papers aiming to investigate how modifications in these polymers characteristics could affect and benefit the refractories processing and properties. There are studies in the literature analyzing the effects of these
Institute of Scientific and Technical Information of China (English)
周成飞; 曹巍; 翟彤; 曾心苗; 郭建梅
2013-01-01
以甲基丙烯酸β-羟乙酯和乙烯基多面体低聚倍半硅氧烷(POSS)为原料,采用一步法制得POSS/聚(氨酯-酰亚胺)纳米复合泡沫材料,研究了γ射线吸收剂量对纳米复合泡沫材料性能的影响.结果表明,在吸收剂量为50 kGy的条件下辐照,材料表现出最好的热稳定性；纳米复合泡沫材料玻璃态区的储能模量最高,损耗模量也遵循同样规律,但在75 kGy条件下损耗峰值最高.另外,吸声性能、阻燃性能和压缩强度都随着吸收剂量的增大而提高.%The polyhedral oligomeric silsesquioxane ( POSS)/poly( urethane-imide) ( PUI) was prepared by one-step method with 2-hydrooxyethyl methacrylate and vinyl-POSS as materials. The effect of absorbed dose of γ-ray on the properties of the nano-composite foam was investigated. The results showed that the thermal stability of radiation crosslinking POSS/PUI nano-composite foam was the best when absorbed dose was 50 kGy. The storage modulus in glassy zone of nano-composite foam was the hightest when absorbed dose was 50 kGy, while the loss modulus in glassy zone followed the same rule, but the loss peak value reached the maximun when absorbed dose was 75 kGy. Besides, the acoustic properties, flame retardance and compressive strength of nano-composite foam increased with the increase of absorbed dose.
Mesoscale studies of ionic closed membranes with polyhedral geometries
Olvera de la Cruz, Monica
2016-06-01
Large crystalline molecular shells buckle spontaneously into icosahedra while multicomponent shells buckle into various polyhedra. Continuum elastic theory explains the buckling of closed shells with one elastic component into icosahedra. A generalized elastic model, on the other hand, describes the spontaneous buckling of inhomogeneous shells into regular and irregular polyhedra. By co-assembling water-insoluble anionic (-1) amphiphiles with cationic (3+) amphiphiles, we realized ionic vesicles. Results revealed that surface crystalline domains and the unusual shell shapes observed arise from the competition of ionic correlations with charge-regulation. We explain here the mechanism by which these ionic membranes generate a mechanically heterogeneous vesicle.
Registering pointclouds of polyhedral buildings to 2D maps
Khoshelham, K.; Gorte, B.G.
2009-01-01
This paper presents a method for automated pointcloud-to-map registration using a plane matching technique. The registration is based on estimating a transformation between a set of planes inferred from the map and their corresponding planes extracted from the pointcloud. A plane matching algorithm
Polyhedral Computations for the Simple Graph Partitioning Problem
DEFF Research Database (Denmark)
Sørensen, Michael Malmros
The simple graph partitioning problem is to partition an edge-weighted graph into mutually disjoint subgraphs, each containing no more than b nodes, such that the sum of the weights of all edges in the subgraphs is maximal. In this paper we present a branch-and-cut algorithm for the problem that ...
Polyhedral Oligomeric Silsesquioxane (POSS) Polyimides as Space-Survivable Materials
2006-01-01
Survivable Materials 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Sandra J. Tomczak (AFRL/PRSM); Vandana Vij...measurements on each sample Multiple samples of Kapton H®, 8.75 % Si8O11 MC-POSS PI, and silica-coated Kapton HN® (provided by Astral Technology Unlimited...Figure 3. SEM images of results from a self-passivation experiment. (a.) Kapton H®, (b.) SiO2 coated Kapton HN® (Provided by Astral
Mesoscale studies of ionic closed membranes with polyhedral geometries
2016-07-25
Materials Science and Engineering, Northwestern University, Evanston, Illinois 60208, USA; Department of Physics and Astronomy, Northwestern University...National Academy of Sciences , USA. Eb = dS 2κ(r)(H − H0)2 + κG(r)G , where H is the mean curvature, and G is the Gaussian curvature, and the bending...the soft component is the boundary of the hard component but in the opposite direction . Given that in the discretized model9 used to generate Figure 1
DNA rendering of polyhedral meshes at the nanoscale
Benson, Erik; Mohammed, Abdulmelik; Gardell, Johan; Masich, Sergej; Czeizler, Eugen; Orponen, Pekka; Högberg, Björn
2015-07-01
It was suggested more than thirty years ago that Watson-Crick base pairing might be used for the rational design of nanometre-scale structures from nucleic acids. Since then, and especially since the introduction of the origami technique, DNA nanotechnology has enabled increasingly more complex structures. But although general approaches for creating DNA origami polygonal meshes and design software are available, there are still important constraints arising from DNA geometry and sense/antisense pairing, necessitating some manual adjustment during the design process. Here we present a general method of folding arbitrary polygonal digital meshes in DNA that readily produces structures that would be very difficult to realize using previous approaches. The design process is highly automated, using a routeing algorithm based on graph theory and a relaxation simulation that traces scaffold strands through the target structures. Moreover, unlike conventional origami designs built from close-packed helices, our structures have a more open conformation with one helix per edge and are therefore stable under the ionic conditions usually used in biological assays.
Polymerization of Fluoroalkyl Polyhedral Oligomeric Silsesquioxane (F-POSS) Macromers
2012-12-01
robust superhydrophobic/ oleophobic /omniphobic surfaces • Via covalently attached F-POSS to substrate (surface, nanoparticle, polymer matrix) – Effects...condition. • F-POSS compounds have a near limitless potential in producing a variety of new hydrophobic, oleophobic , or ominiphobic polymer composites
Functionalized Fluorinated Polyhedral Oligomeric Silsesquioxane (F-POSS)
2012-01-01
oligomeric silsesquioxane (F-POSS) possesses one of the lowest surface energies leading to the creation of superhydrophobic and oleophobic surfaces...material for low surface energy materials • Applications – Mechanical robust superhydrophobic/ oleophobic /omniphobic surfaces • Via covalently...F-POSS possesses one of the lowest surface energies leading to the creation of superhydrophobic and oleophobic surfaces. (a) Mabry, J. M
Ultrahydrophobic Fluorinated Polyhedral Oligomeric Silsesquioxanes (F-POSS) (Preprint)
2007-01-25
fluids such as a polar hydrocarbon (CH2I2) and nonpolar hydrocarbon (n-decane) were also measured to determine oleophobicity . The FD solid surface...degree of oleophobicity in addition to hydrophobicity. H2O CH2I2 n-Decane 0 20 40 60 80 100 120 140 160 PTFE FD POSS H2O 2I2 2 Figure 4. Graph
Lemloh, Marie-Louise; Marin, Frédéric; Herbst, Frédéric; Plasseraud, Laurent; Schweikert, Michael; Baier, Johannes; Bill, Joachim; Brümmer, Franz
2013-02-01
In the protist world, the ciliate Coleps hirtus (phylum Ciliophora, class Prostomatea) synthesizes a peculiar biomineralized test made of alveolar plates, structures located within alveolar vesicles at the cell cortex. Alveolar plates are arranged by overlapping like an armor and they are thought to protect and/or stiffen the cell. Although their morphology is species-specific and of complex architecture, so far almost nothing is known about their genesis, their structure and their elemental and mineral composition. We investigated the genesis of new alveolar plates after cell division and examined cells and isolated alveolar plates by electron microscopy, energy-dispersive X-ray spectroscopy, FTIR and X-ray diffraction. Our investigations revealed an organic mesh-like structure that guides the formation of new alveolar plates like a template and the role of vesicles transporting inorganic material. We further demonstrated that the inorganic part of the alveolar plates is composed out of amorphous calcium carbonate. For stabilization of the amorphous phase, the alveolar vesicles, the organic fraction and the element phosphorus may play a role.
Leroy, W. P.; Detavernier, C.; Van Meirhaeghe, R. L.; Lavoie, C.
2007-03-01
Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin films. The solid-state reaction was examined between 11 transition metals (W, Mo, Fe, Cr, V, Nb, Mn, Ti, Ta, Zr, and Hf) and an amorphous carbon layer. Capping layers (C or TiN) of different thicknesses were applied to prevent oxidation. Carbide formation is evidenced for nine metals and the phases formed have been identified (for a temperature ranging from 100to1100°C). W first forms W2C and then WC; Mo forms Mo2C; Fe forms Fe3C; Cr first forms metastable phases Cr2C and Cr3C2-x, and finally forms Cr3C2; V forms VCx; Nb transforms into Nb2C followed by NbC; Ti forms TiC; Ta first forms Ta2C and then TaC; and Hf transforms into HfC. The activation energy for the formation of the various carbide phases has been obtained by in situ x-ray diffraction.
Wear resistant composite structure of vitreous carbon containing convoluted fibers. Final report
Energy Technology Data Exchange (ETDEWEB)
Burton, R.G.; Burton, R.A.
1996-05-28
Energy Related Inventions Program Number 613 was a two year program to commercialize a unique new wear material, Metal Reinforced Carbon Composite, MRCC. The program was designed to manufacture sample components of MRCC for evaluation by potential users and manufacturers. As a result of the program Burton Technologies Inc. and Rotary Power International are forming a joint company to manufacture, market and license MRCC materials to a wide range of industries.
A review of the interference of carbon containing fly ash with air entrainment in concrete
DEFF Research Database (Denmark)
Pedersen, Kim Hougaard; Jensen, Anker Degn; Skjøth-Rasmussen, Martin Skov;
2008-01-01
Industrial utilization of fly ash from pulverized coal combustion plays an important role in environmentally clean and cost effective power generation. Today, the primary market for fly ash utilization is as pozzolanic additive in the production of concrete. However, the residual carbon in fly ash...... on the adsorption capacity of AEAs. The type of fuel used in the combustion process influences the amount and properties of the residual carbon. Fly ash derived from bituminous coal has generally higher carbon content compared with fly ash produced from subbituminous coal or lignite, but shows a lower AEA......-treatment methods applied to improve fly ash quality are described in the review. Ozonation, thermal treatment and physical cleaning of carbon have been found to improve the fly ash performance for concrete utilization. Ultimately, recommendations for further work are outlined in the discussion....
Synthesis and Explosive Consolidation of Titanium, Aluminium, Boron and Carbon Containing Powders
Chikhradze, Mikheil; Oniashvili, George; Chikhradze, Nikoloz; D. S Marquis, Fernand
2016-10-01
The development of modern technologies in the field of materials science has increased the interest towards the bulk materials with improved physical, chemical and mechanical properties. Composites, fabricated in Ti-Al-B-C systems are characterized by unique physical and mechanical properties. They are attractive for aerospace, power engineering, machine and chemical applications. The technologies to fabricate ultrafine grained powder and bulk materials in Ti-Al-B-C system are described in the paper. It includes results of theoretical and experimental investigation for selection of powders composition and determination of thermodynamic conditions for bland preparation, as well as optimal technological parameters for mechanical alloying and adiabatic compaction. The crystalline coarse Ti, Al, C powders and amorphous B were used as precursors and blends with different compositions of Ti-Al, Ti-Al-C, Ti-B-C and Ti-Al-B were prepared. Preliminary determination/selection of blend compositions was made on the basis of phase diagrams. The powders were mixed according to the selected ratios of components to produce the blend. Blends were processed in “Fritsch” Planetary premium line ball mill for mechanical alloying, syntheses of new phases, amorphization and ultrafine powder production. The blends processing time was variable: 1 to 20 hours. The optimal technological regimes of nano blend preparation were determined experimentally. Ball milled nano blends were placed in metallic tube and loaded by shock waves for realization of consolidation in adiabatic regime. The structure and properties of the obtained ultrafine grained materials depending on the processing parameters are investigated and discussed. For consolidation of the mixture, explosive compaction technology is applied at room temperatures. The prepared mixtures were located in low carbon steel tube and blast energies were used for explosive consolidation compositions. The relationship of ball milling technological parameters and explosive consolidation conditions on the structure/properties of the obtained samples are described in the paper.
Directory of Open Access Journals (Sweden)
Novoselova I.A.
2003-01-01
Full Text Available Features of the electroreduction of carbon dioxide dissolved in the equimolar melt of sodium and potassium chlorides under excessive pressure of up to 1.7 MPa have been studied by cyclic voltametry over a wide polarization rate range. It has been found that the electrode process occurs in two stages at sweep rates of ≤0.1 V s-1, and its mechanism has been suggested. The cathodic product is polycrystalline graphite. Systems and conditions for producing two- and three-component refractory metal carbides using CO2 as a synthesis component have been selected.
Mesoporous carbon-containing voltammetric biosensor for determination of tyramine in food products.
Kochana, Jolanta; Wapiennik, Karolina; Knihnicki, Paweł; Pollap, Aleksandra; Janus, Paula; Oszajca, Marcin; Kuśtrowski, Piotr
2016-07-01
A voltammetric biosensor based on tyrosinase (TYR) was developed for determination of tyramine. Carbon material (multi-walled carbon nanotubes or mesoporous carbon CMK-3-type), polycationic polymer-i.e., poly(diallyldimethylammonium chloride) (PDDA), and Nafion were incorporated into titania dioxide sol (TiO2) to create an immobilization matrix. The features of the formed matrix were studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The analytical performance of the developed biosensor was evaluated with respect to linear range, sensitivity, limit of detection, long-term stability, repeatability, and reproducibility. The biosensor exhibited electrocatalytic activity toward tyramine oxidation within a linear range from 6 to 130 μM, high sensitivity of 486 μA mM(-1) cm(-2), and limit of detection of 1.5 μM. The apparent Michaelis-Menten constant was calculated to be 66.0 μM indicating a high biological affinity of the developed biosensor for tyramine. Furthermore, its usefulness in determination of tyramine in food product samples was also verified. Graphical abstract Different food samples were analyzed to determine tyramine using biosensor based on tyrosinase.
Mesoporous carbon-containing voltammetric biosensor for determination of tyramine in food products
Kochana, Jolanta; Wapiennik, Karolina; Knihnicki, Paweł; Pollap, Aleksandra; Janus, Paula; Oszajca, Marcin; Kuśtrowski, Piotr
2016-01-01
A voltammetric biosensor based on tyrosinase (TYR) was developed for determination of tyramine. Carbon material (multi-walled carbon nanotubes or mesoporous carbon CMK-3-type), polycationic polymer—i.e., poly(diallyldimethylammonium chloride) (PDDA), and Nafion were incorporated into titania dioxide sol (TiO2) to create an immobilization matrix. The features of the formed matrix were studied by scanning electron microscopy (SEM) and cyclic voltammetry (CV). The analytical performance of the d...
Fujii, Shinya; Kano, Atsushi; Songkram, Chalermkiat; Masuno, Hiroyuki; Taoda, Yoshiyuki; Kawachi, Emiko; Hirano, Tomoya; Tanatani, Aya; Kagechika, Hiroyuki
2014-02-15
1α,25-Dihydroxyvitamin D3 [1α,25(OH)₂D₃: 1] is a specific modulator of nuclear vitamin D receptor (VDR), and novel vitamin D analogs are therapeutic candidates for multiple clinical applications. We recently developed non-secosteroidal VDR agonists bearing a p-carborane cage (a carbon-containing boron cluster) as a hydrophobic core structure. These carborane derivatives are structurally quite different from classical secosteroidal vitamin D analogs. Here, we report systematic synthesis and activity evaluation of carborane-based non-secosteroidal vitamin D analogs. The structure-activity relationships of carborane derivatives are different from those of secosteroidal vitamin D derivatives, and in particular, the length and the substituent position of the dihydroxylated side chain are rather flexible in carborane derivatives. The structure-activity relationships presented here should be helpful in development of non-secosteroidal vitamin D analogs for clinical applications.
Leroy, W. P.; Detavernier, C.; van Meirhaeghe, R. L.; Kellock, A. J.; Lavoie, C.
2006-03-01
Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin Ti or Mo films and C substrates. Titanium carbide (TiC) was previously reported as a contact material to diamond and carbon nanotubes. However, the present study shows two disadvantages for the solid-state reaction of Ti and C. First, because Ti reacts readily with oxygen, a capping layer should be included to enable carbide formation. Second, the TiC phase can exist over a wide range of composition (about 10%, i.e., from Ti0.5C0.5 to Ti0.6C0.4), leading to significant variations in the properties of the material formed. The study of the Mo-C system suggests that molybdenum carbide (Mo2C) is a promising alternative, since the phase shows a lower resistivity (about 45% lower than for TiC), the carbide forms below 900 °C, and its formation is less sensitive to oxidation as compared with the Ti-C system. The measured resistivity for Mo2C is ρ=59 μΩ cm, and from kinetic studies an activation energy for Mo2C formation of Ea=3.15+/-0.15 eV was obtained.
PAN, X.; Kanaya, Y.; Taketani, F.; Miyakawa, T.; Inomata, S.; Komazaki, Y.; Tanimoto, H.; Uno, I.; Wang, Z.
2014-12-01
Open biomass burning (OBB) experiments were performed in the laboratory environment to investigate the mixing state of refractory black carbon (rBC) in fresh smoke and its dependence on combustion state. A Single-Particle Soot Photometer (SP2) was adopted to measure variation of number size distribution of rBC-containing particles in high temporal resolution. General combustion state of each OBB case was indicated by modified combustion efficiency (MCE) using accumulated enhancement of mixing ratios of carbon dioxide and carbon monoxide during the experiments. We found that mass equivalent diameter (MED) of rBC increased apparently with increase of MCE values, indicating the flaming-dominant combustion tend to produce the rBC particles with relative larger size, probably because of coagulation processes in high concentration condition. Coating thickness of rBC-containing particle was calculated by leading edge only fitting (LEO-fitting) method. In the present study we defined the rBC-containing particles with shell/core (S/C) ratio larger than 2 as "thickly coated" and that less then 1.5 as "thinly coated". As a result, thickly coated rBC particles normally had a relatively small core (MED of rBC less than 150 nm) and its number fraction showed an evident decrease as a function of MCE value, whereas, larger rBC particles (MED larger than 150 nm) were normally thinly coated. Number fraction of both thinly coated and uncoated rBC particles had an positive correlation with MCE value. Substantial amount of light scattering particles (LSP) observed in the smoldering-dominant OBB plumes could partially explain the increase of number fraction of coated rBC particles. ∆rBC/∆CO ratio showed a good positive correlation with MCE with an average value of 16.8 (1.2 - 51.6) ng/m3/ppbv, and ∆rBC/∆CO2 ratio was found 628.7 ng/m3/ppmv, generally consistent with previous studies.
2006-05-31
temperature were performed in a Siemens 2D Small Angle Diffractometer configured in Wide Angle mode using a 12kW rotating anode; these samples (powders...Cp) Si O Si Si SiO O O Si O Si Si SiO O O O O O O R R R R R R R R CH3 R OO CH3 O CH3 O Si O Si Si Si O O O Si O Si Si Si O O O O O O O R R R R R R nx
The Software of Polyhedral Homotopy Continuation Method and Parallel Computation of its
郡司, 貴之
2008-01-01
A system of multi variables polynomial equations arises in many fields of science and engineering. The polyhedralhomotopy continuation method is one of the methods for finding all isolated complex solutions of systems of polynomialequations. First, the method constructs the homotopy systems adding the parameter for the systems of polynomial equations.Next, it finds the solutions of starting systems of them. It traces the homotopy curves which can be defined as oneof the solution set of homoto...
A Polyhedral Object's CSG-Rep Reconstruction From a Single 2D Line Drawing
Wang, Weidong; Grinstein, Georges G.
1990-03-01
The interpretation of a 2D line drawing as a 3D scene is an important area of study within the fields of artificial intelligence and machine vision. In the area of CAD/CAM, research has focused on the reconstruction of a 3D solid from its engineering drawings, either with two views or three views, or from its wireframe representation. We have been working on the problem of automatically reconstructing a 3D solid object's Constructive Solid Geometry (CSG) representation from a single 2D line drawing of the object. This paper describes our approach as well as some preliminary results. We validate our approach on a restricted set of objects consisting of simple rectilinear polyhedra. Using the Huffman-Clowes labeling scheme we are able to successfully identify the primitive blocks necessary for the CSG tree generation, as well as the set operations that must be applied to them. Extension to general polyhedra is also discussed.
1980-06-15
Fluorine gas, diluted with 5-15% nitrogen, is bubbled into the aqueous solution until it is present in excess. An aqueous solution of Nt^ PFe is then added...stirred and aqueous te’ramethylammonium hydroxide is added until the color changes abruptly to a light hue. At this point an audition :.] 5-10 g. of
Functionalization of Fluoroalkyl Polyhedral Oligomeric Silsesquioxanes (F-POSS) (Post Print)
2012-08-01
profilometer. Size exclusion chromatography (SEC) was performed with a high-pressure liquid chromatography ( HPLC , Agilent) system at a flow rate of 1.00 mL...fluoroalkyl chains, similar to compound 1, which are attached to the open Si-O frame-work via methylene groups. The structure confirms the Si...disorder. Thermal ellipsoids at 50%. Green F, Black C, Red O, Blue Si. (Hydrogen atoms and disordered segments are omitted for clarity). The crystal
Althaus, Ernst; Caprara, Alberto; Lenhof, Hans-Peter; Reinert, Knut
2002-01-01
Multiple sequence alignment is one of the dominant problems in computational molecular biology. Numerous scoring functions and methods have been proposed, most of which result in NP-hard problems. In this paper we propose for the first time a general formulation for multiple alignment with arbitrary gap-costs based on an integer linear program (ILP). In addition we describe a branch-and-cut algorithm to effectively solve the ILP to optimality. We evaluate the performances of our approach in terms of running time and quality of the alignments using the BAliBase database of reference alignments. The results show that our implementation ranks amongst the best programs developed so far.
Delay-dependent robust H∞ control of convex polyhedral uncertain fuzzy systems
Institute of Scientific and Technical Information of China (English)
无
2008-01-01
The robust H∞ control problem for a class of uncertain Takagi-Sugeno fuzzy systems with time-varying state delays is studied. The uncertain parameters are supposed to reside in a polytope. Based on the delay-dependent Lyapunov functional method, a new delay-dependent robust H∞ fuzzy controller, which depends on the size of the delays and the derivative of the delays, is presented in term of linear matrix inequalities (LMIs). For all admissible uncertainties and delays, the controller guarantees not only the asymptotic stability of the system but also the prescribed H∞ attenuation level. In addition, the effectiveness of the proposed design method is demonstrated by a numerical example.
Mixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment.
Yuvaraj, K; Roy, Dipak Kumar; Anju, V P; Mondal, Bijnaneswar; Varghese, Babu; Ghosh, Sundargopal
2014-12-07
The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp*Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp*Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp*Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and (1)H, (11)B and (13)C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6.
R Implementation of a Polyhedral Approximation to a 3D Set of Points Using the ?-Shape
Directory of Open Access Journals (Sweden)
Thomas Lafarge
2014-01-01
Full Text Available This work presents the implementation in R of the ?-shape of a finite set of points in the three-dimensional space R3. This geometric structure generalizes the convex hull and allows to recover the shape of non-convex and even non-connected sets in 3D, given a ran- dom sample of points taken into it. Besides the computation of the ?-shape, the R package alphashape3d provides users with tools to facilitate the three-dimensional graphical visu- alization of the estimated set as well as the computation of important characteristics such as the connected components or the volume, among others.
Directory of Open Access Journals (Sweden)
Qinghai He
2013-01-01
Full Text Available In general Banach spaces, we consider a vector optimization problem (SVOP in which the objective is a set-valued mapping whose graph is the union of finitely many polyhedra or the union of finitely many generalized polyhedra. Dropping the compactness assumption, we establish some results on structure of the weak Pareto solution set, Pareto solution set, weak Pareto optimal value set, and Pareto optimal value set of (SVOP and on connectedness of Pareto solution set and Pareto optimal value set of (SVOP. In particular, we improved and generalize, Arrow, Barankin, and Blackwell’s classical results in Euclidean spaces and Zheng and Yang’s results in general Banach spaces.
Dopierała, Katarzyna; Maciejewski, Hieronim; Prochaska, Krystyna
2016-04-01
Binary mixtures of cholesterol and fully-condensed octakis[{2-(3,4-epoxycyclohexyl) etyl}dimethyl-silyloxy]octasilsesquioxane (OE-POSS) were characterized using Langmuir trough for obtaining surface pressure-area isotherms. The most characteristic feature of the mixed films is the presence of two collapse points on the isotherms. The first one is attributed to the collapse of less stable OE-POSS and it occurs at similar surface pressures for all compositions, while the second one corresponds to cholesterol collapse. Brewster angle microscopy observations confirmed the collapse behavior of the mixed film. Strong condensing effect was observed for the mean molecular areas dependence on cholesterol content in the film. Moreover, formation of microdomains of each component in the matrix of the other one was confirmed by BAM images. For the reasons of molecular structures and interactions a true mixed and homogenous film did not form in the systems considered. Phase separation was observed for all the compositions experimented. The lack of the interactions of OE-POSS with biomembrane components represented by cholesterol is beneficial for applications of OE-POSS in biomedical devices.
DEFF Research Database (Denmark)
Mak, Vicky; Thomadsen, Tommy
2006-01-01
This paper considers the cardinality constrained quadratic knapsack problem (QKP) and the quadratic selective travelling salesman problem (QSTSP). The QKP is a generalization of the knapsack problem and the QSTSP is a generalization of the travelling salesman problem. Thus, both problems are NP...
2006-11-15
AFRL/PRSM); Vandana Vij (ERC); 5d. PROJECT NUMBER DARPA443 Timothy Minton & Amy Brunsvold (Montana State Univ.); Michael Wright, Brian Petteys...8.75 % Si8O11 MC-POSS PI, and silica-coated Kapton HN® (provided by Astral Technology Unlimited, Inc. Lot No. 00625-007, with a 130 nm SiO2 coating...images of results from a self-passivation experiment. (a.) Kapton H®, (b.) SiO2 coated Kapton HN® (Provided by Astral Industries Inc.), and (c.) 8.75 wt
Polyhedral Oligomeric Silsesquioxane (POSS) Polyimides as Space-Survivable Materials (Preprint)
2006-07-27
Survivable Materials (Preprint) 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER Sandra J. Tomczak (AFRL/PRSM...Multiple samples of Kapton H®, 8.75 % Si8O11 MC-POSS PI, and silica-coated Kapton HN® (provided by Astral Technology Unlimited, Inc. Lot No. 00625-007...self-passivation experiment. (a.) Kapton H®, (b.) SiO2 coated Kapton HN® (Provided by Astral Industries Inc.), and (c.) 8.75 wt % Si8O11 cage MC
Doping induced modification in polyhedral tilt in hexagonal Ho1-xYxMnO3
Kaushik, S. D.; Rayaprol, S.
2012-06-01
We have studied the effect of systematic doping of Y at Ho site on the crystal structure of hexagonal HoMnO3 We have carried out room temperature neutron diffraction (ND) study on Ho1-xYxMnO3 (x = 0, 0.25, 0.50, 0.75), and by analyzing this ND data we have determined the cell parameters, Mn-O bond length, O-Mn-O bond angle. The variation in certain M-O bond length and O-Mn-O bond angles has been understood in terms of modifications in tilt of the MnO5 polyhedra due to Ho site Y doping in hexagonal HoMnO3.
2012-05-01
anhydrous THF over a period of ½ h. The reaction mixture was stirred overnight followed by filtration . The filter cake was washed with distilled H2O...used in the production of Kapton-like polyimides, which were shown to exhibit excellent resistance to the atomic oxygen flux that plagues the use of...While each of these compounds has been shown to improve oxidation resistance in the host polyimide polymers, interest in materials with superior
Synthesis of polyhedral iron oxide nanocrystals bound by high-index facets
Institute of Scientific and Technical Information of China (English)
GAO Feng; LIU RongMei; YIN JingZhou; LU QingYi
2014-01-01
High surface energy of high-index facets endows nanocrystals with high activities and thus promotes potential applications such as highly efficient catalysts,special optical,electrical and magnetic devices.But the high surface energy of the high-index facets usually drives them to grow faster than the other facets and finally disappear during the crystal growth,which leads the synthesis of nanocrystals with high-indexed facets exposed to be a great challenge.Herein,we introduced two routes to control the synthesis of-Fe2O3polyhedrons with different sets of high-index facets,one using different metal ions（Ni2＋,Cu2＋or Zn2＋）as structure-directing agents and the other applying polymer surfactant sodium carboxymethyl cellulose（CMC）as additive.The growth process of high-index-Fe2O3polyhedrons was also discussed and possible growth mechanism was proposed.
Local analysis of hybrid systems on polyhedral sets with state-dependent switching
Directory of Open Access Journals (Sweden)
Leth John
2014-06-01
Full Text Available This paper deals with stability analysis of hybrid systems. Various stability concepts related to hybrid systems are introduced. The paper advocates a local analysis. It involves the equivalence relation generated by reset maps of a hybrid system. To establish a tangible method for stability analysis, we introduce the notion of a chart, which locally reduces the complexity of the hybrid system. In a chart, a hybrid system is particularly simple and can be analyzed with the use of methods borrowed from the theory of differential inclusions. Thus, the main contribution of this paper is to show how stability of a hybrid system can be reduced to a specialization of the well established stability theory of differential inclusions. A number of examples illustrate the concepts introduced in the paper.
Horn clause verification with convex polyhedral abstraction and tree automata-based refinement
DEFF Research Database (Denmark)
Kafle, Bishoksan; Gallagher, John Patrick
2017-01-01
underlying the Horn clauses. Experiments using linear constraint problems and the abstract domain of convex polyhedra show that the refinement technique is practical and that iteration of abstract interpretation with tree automata-based refinement solves many challenging Horn clause verification problems. We......In this paper we apply tree-automata techniques to refinement of abstract interpretation in Horn clause verification. We go beyond previous work on refining trace abstractions; firstly we handle tree automata rather than string automata and thereby can capture traces in any Horn clause derivations...... rather than just transition systems; secondly, we show how algorithms manipulating tree automata interact with abstract interpretations, establishing progress in refinement and generating refined clauses that eliminate causes of imprecision. We show how to derive a refined set of Horn clauses in which...
2005-10-11
Fluorodecyl8T8 and fluorooctyl8T8 increased the oleophobicity of PVDF – Unfilled PVDF samples yielded contact angles around 25° – Addition of...the oleophobicity of PVDF PVDF PVDF 5wt% Fluorooctyl8T8 19 DRAFT: Distribution A: Approved for public release; distribution unlimited Results and...fluoropolymers increased the water and organic contact angles – Addition of methyl8T8 to PVDF decreased the oleophobicity , but increased the hydrophobicity
Fluoroalkyl Polyhedral Oligomeric Silsesquioxane (F-POSS) Based Monomers and Polymers
2011-07-19
surface energies leading to the creation of superhydrophobic and oleophobic surfaces. (a) Mabry, J. M.; Vij, A.; Iacono, S. T.; Viers, b. D., Angew...for use a building block material for low surface energy materials • Applications – Mechanical robust superhydrophobic/ oleophobic /omniphobic surfaces...potential in producing a variety of new hydrophobic, oleophobic , or ominiphobic polymer composites. – Reaction mechanisms, polymer composites, block
de Boer, Ryan Sietze
Soy fibre and soybean oil were utilized to produce a bio-composite targeted as a substitute for conventional petroleum-based materials. The study was divided into two parts; the first was the development of a bio-epoxy that consisted of conventional epoxy, epoxidized soybean oil, and two types of functionalized POSS. The second part of the study involved blending of the bio-epoxy with titanate treated soy fibre. Combined incorporation of epoxide and amine functionalized POSS in the bio-epoxy matrix resulted in a 29% impact strength improvement compared to the petroleum-based epoxy. Incorporation of the epoxide functionalized POSS resulted in improvements in tensile strength by 8%, tensile modulus by 2%, and an increase in the glass transition temperature by 4% compared to the petroleum-based epoxy and epoxidized soybean oil hybrid. The coupling of titanate to soy fibre in comparison to the soy fibre without titanate treatment resulted in an impact strength improvement of 37%. Furthermore, the coupling of titanate increased the tensile strength and tensile modulus by 24% and 22% respectively, and reduced the water absorption by 70%.
Effects of Peripheral Architecture on the Properties of Aryl Polyhedral Oligomeric Silsesquioxanes
2012-07-26
be supported by this analysis. Further TGA analysis was performed on 2 to elucidate the effects of heating rate on the two distinct events witnessed...material exists in the char residue after the 700 °C soak. TGA analysis revealed that ∼25% of the char residue is organic in character. Analogous
Strain Gradient Solution for the Eshelby-Type Polyhedral Inclusion Problem
2012-01-01
and (2) reduce to the governing equations and the boundary conditions in terms of displacement in classical elasticity (e.g., Timoshenko and Goodier...v is Poisson’s ratio, which is related to the Lamé constants l and m through (e.g., Timoshenko and Goodier, 1970) l¼ Evð1þvÞð12vÞ , m¼ E 2ð1þvÞ...and polyhedra. J. Mech. Phys. Solids 44, 1977–1995. Rowlinson, J.S., 1989. The Yukawa potential. Physica A 156, 15–34. Timoshenko , S.P., Goodier, J.N
Khadilkar, Mihir R; Escobedo, Fernando A
2014-10-17
Sought-after ordered structures of mixtures of hard anisotropic nanoparticles can often be thermodynamically unfavorable due to the components' geometric incompatibility to densely pack into regular lattices. A simple compatibilization rule is identified wherein the particle sizes are chosen such that the order-disorder transition pressures of the pure components match (and the entropies of the ordered phases are similar). Using this rule with representative polyhedra from the truncated-cube family that form pure-component plastic crystals, Monte Carlo simulations show the formation of plastic-solid solutions for all compositions and for a wide range of volume fractions.
Energy Technology Data Exchange (ETDEWEB)
Silva, A.F. [Delft University of Technology, Faculty of Applied Sciences, DelftChemTech, Julianalaan 136, 2628 BL Delft (Netherlands); Universidade Federal de Santa Catarina, Departamento de Quimica, 88040-900 Florianopolis, SC (Brazil); Welz, B. [Universidade Federal de Santa Catarina, Departamento de Quimica, 88040-900 Florianopolis, SC (Brazil); Loos-Vollebregt, M.T.C. de [Delft University of Technology, Faculty of Applied Sciences, DelftChemTech, Julianalaan 136, 2628 BL Delft (Netherlands)], E-mail: m.t.c.deloos-vollebregt@tudelft.nl
2008-07-15
Pyrolysis curves in electrothermal atomic absorption spectrometry (ET AAS) and electrothermal vaporization inductively coupled plasma mass spectrometry (ETV-ICP-MS) have been compared for As, Se and Pb in lobster hepatopancreas certified reference material using Pd/Mg as the modifier. The ET AAS pyrolysis curves confirm that the analytes are not lost from the graphite furnace up to a pyrolysis temperature of 800 deg. C. Nevertheless, a downward slope of the pyrolysis curve was observed for these elements in the biological material using ETV-ICP-MS. This could be related to a gain of sensitivity at low pyrolysis temperatures due to the matrix, which can act as carrier and/or promote changes in the plasma ionization equilibrium. Experiments with the addition of ascorbic acid to the aqueous standards confirmed that the higher intensities obtained in ETV-ICP-MS are related to the presence of organic compounds in the slurry. Pyrolysis curves for As, Se and Pb in coal and coal fly ash were also investigated using the same Pd/Mg modifier. Carbon intensities were measured in all samples using different pyrolysis temperatures. It was observed that pyrolysis curves for the three analytes in all slurry samples were similar to the corresponding graphs that show the carbon intensity for the same slurries for pyrolysis temperatures from 200 deg. C up to 1000 deg. C.
A. Miguel Iznaga Benítez; I. Pérez Mallea
2000-01-01
El conocimiento de la estructura de datos de los modelos geométricos ha posibilitado el desarrollo de algoritmos parasolucionar problemas complejos. Estos algoritmos han facilitado a su vez, la automatización en las oficinas de diseño através de los medios computacionales.Por tal motivo, se presenta el desarrollo de un algoritmo para la obtención de cortes y secciones en cuerpos geométricospoliédricos, se plantean las etapas fundamentales del algoritmo y a través de un ejercicio se ejemplific...
Omrani, Abdollah; Yen, Ying-Chieh; Cheng, Chih-Chia; Chang, Feng-Chih
2014-01-01
A facile method was developed to prepare MWCNT/POSS nanocomposites by direct esterification between carboxylic acid functionalized MWCNT and octa(phenol) octasilsesquioxane. Completeness of the MWCNT surface modification was confirmed by FT-IR. The hybrid nano-MWCNT-OP-POSS composite structure and properties was characterized using DSC, TGA, optical microscopy, WAXD, and AFM. The results indicated the solubility and processability of MWCNT-COOH improved because of OP-POSS grafting on MWCNT surface. The Tg and thermal stability of the nanocomposites was higher than that of the OP-POSS as a result of the cross-linking reaction. AFM observations revealed that the nanocomponents were reacted in a homogeneous phase at nanoscale level.
Energy Technology Data Exchange (ETDEWEB)
Hernandez Pezzi, C.
2010-07-01
This article gives an overall view of the changes and challenges that have occurred in crisis and in the environment of 2010 to the new production model called the law of economy and sustainable. (Author)
Energy Technology Data Exchange (ETDEWEB)
Yang, Hongyu [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Department of Building and Construction, City University of Hong Kong and USTC-CityU Joint Advanced Research Centre, Suzhou (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute of University of Science and Technology of China, Suzhou (China); Wang, Xin; Yu, Bin; Song, Lei [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Hu, Yuan, E-mail: yuanhu@ustc.edu.cn [State Key Laboratory of Fire Science, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui 230026 (China); Suzhou Key Laboratory of Urban Public Safety, Suzhou Institute of University of Science and Technology of China, Suzhou (China); Yuen, Richard K.K. [Department of Building and Construction, City University of Hong Kong and USTC-CityU Joint Advanced Research Centre, Suzhou (China)
2012-05-10
Highlights: Black-Right-Pointing-Pointer Flame retarded epoxy resins with borates were prepared using POSS as a curing agent. Black-Right-Pointing-Pointer Borates and POSS exhibited a synergistic effect on flame retardancy of epoxy resins. Black-Right-Pointing-Pointer Incorporation of borates and POSS significantly reduced the heat release rate. - Abstract: A series of flame-retardant epoxy resins containing boron and silicon were obtained through a crosslinking reaction, using tris (2-hydroxypropyl) borate (THPB) together with octaaminophenyl POSS (OapPOSS) as the curing agents. The limiting oxygen index (LOI) reached 30.5% when the contents of boron and silicon in the cured system were 1.5% and 0.5%, respectively, indicating that THPB and OapPOSS exhibited good flame retardant effect on epoxy resins (EP). Microscale combustion calorimetry (MCC) results indicated that the peak heat release rate (PHRR) and total heat release (THR) of the cured systems were reduced by 69% and 46%, respectively, compared to those of pure EP. Moreover, the thermal degradation process and flame retardant mechanism of the composites were investigated by TGA, real time FTIR and TG-FTIR. The chemical components of the char residues were explored by XPS.
2007-01-01
TGA analysis of POSS PFCB copolymers showed step-wise decomposition of copolymers resulting from the initial degradation of the POSS cages at 297−355...fluorinated 2,2-bis(4-trifluorovinyloxybiphenyl)-1,1,1,3,3,3-hexafluoropropane monomer. TGA analysis of POSS PFCB copolymers showed step-wise decomposition of...hexafluorocyclobutene from the PFCB ring. This has been previously shown by Babb et al. based on the thermal degradation of PFCB polymers [10]. TGA analysis showed a
2007-10-17
the more fluorinated 2,2-bis(4- trifluorovinyloxybiphenyl)-1,1,1,3,3,3-hexafluoropropane monomer. TGA analysis of POSS PFCB copolymers showed step...1,1,1,3,3,3-hexafluoropropane monomer. TGA analysis of POSS PFCB copolymers showed step-wise decomposition of copolymers resulting from the initial...the PFCB ring. This has been previously shown by Babb based on the thermal degradation of PFCB polymers [10]. TGA analysis showed a significant
Institute of Scientific and Technical Information of China (English)
张铁民; 方建军; 蒋太国; 毛莹博
2014-01-01
The effects of oxidized copper ores which came from Lanping of Yunnan Province were studied using agitation leaching methods in laboratory in order to find out the optimum leaching conditions under normal temperature and pressure .Silver content of the ores was high .The ores belonged to typical carbonate minerals .The optimum conditions obtained were as follows:ammonia concentration 1.5 mol/L, granding fineness about 85% -0.074 mm, liquid -solid ratio 2.5∶1 and leching time 3 h.The leaching rate of this ore could reach 70%.%针对兰坪燕子洞碳酸盐型含银氧化铜矿石高碱性、高砷、高结合率的特点，进行了常温常压氨浸试验研究。研究表明：常温常压，在氨水浓度1．5 mol/L，碳酸氢铵浓度1．5 mol/L，磨矿细度-0．074 mm占85％，液固比2．5∶1，浸出时间3 h条件下，铜浸出率可达70％。氨浸液经萃取-电积可得到99．95％的电积铜，有效地实现了铜元素的回收利用。
Institute of Scientific and Technical Information of China (English)
秦洁
2012-01-01
介绍了国内外转底炉直接还原工艺发展现状,提出含碳球团造块技术、转底炉装料机设计、转底炉出料机设计、转底炉炉温、炉压及炉内气氛的控制以及金属化球团防氧化技术等是保障转底炉连续稳定顺行的关键技术。合理的水分、压力及粘结剂种类可以获得较好的压球效果;振动给料机和装有硬质耐磨合金的螺旋出料机是目前转底炉装、出料机的主流;根据原料的不同,各厂家已摸索出适宜的炉温、炉压等工艺参数,并对金属化球团采取冷却或隔绝空气的保护措施。%The current development of rotary hearth furnace (RHF) technologies for direct reduction is introduced in this paper. The cold-pressing technology, the design of charging and discharging machines of RHF, the controlling of temperature, pressure and atmosphere in the furnace, and the antioxidation of metallized pellet are the key technologies for ensuring stable and continuous operation of RHF. Reasonable water content, pressure and binder categories could obtain preferable briquetting results. Vibration feeder and spiral discharging machine with hard alloy on the surface of the blades are the major facilities in RHF system. According to the supply of raw materials in different plants, suitable technological parameters of RHF, such as temperature, pressure atmosphere in the furnace have been investigated. In addition, cooling or air isolation measures to protect metallized pellet are also developed.
Tlusty, Tsvi
2010-01-01
This note discusses a relation between the multiplicity m of the second eigenvalue {\\lambda}2 of a Laplacian on a graph G, tight mappings of G and a discrete analogue of Courant's nodal line theorem. For a certain class of graphs, we show that the m-dimensional eigenspace of {\\lambda}2 is tight and thus defines a tight mapping of G into an m-dimensional Euclidean space. The tightness of the mapping is shown to set Colin de Verdi\\`ere's upper bound on the maximal {\\lambda}2-multiplicity, where chr({\\gamma}(G)) is the chromatic number and {\\gamma}(G) is the genus of G.
Macías, Ramón; Bould, Jonathan; Holub, Josef; Kennedy, John D; Stíbr, Bohumil; Thornton-Pett, Mark
2007-07-21
Reaction between [RhCl(PPh(3))(3)] and the [nido-6-NB(9)H(11)](-) anion in CH(2)Cl(2) yields orange eleven-vertex [8,8-(PPh(3))(2)-nido-8,7-RhNB(9)H(11)]. Reaction of the [nido-6-CB(9)H(12)](-) anion with [cis-PtCl(2)(PMe(2)Ph)(2)] in methanol affords yellow eleven-vertex [9-(OMe)-8,8-(PMe(2)Ph)(2)-nido-8,7-PtCB(9)H(10)], which is also formed from the reaction of MeOH with [8,8-(PPh(3))(2)-nido-8,7-PtCB(9)H(10)]. Both compounds have been characterised by single-crystal X-ray diffraction analysis and examined by NMR spectroscopy and have structures based on eleven-vertex nido-type geometries, with the metal centre and the heteroatoms in the adjacent (8)- and (7)-positions on the pentagonal open face. The metal-to-heteroborane bonding sphere of is fluxional, with a DeltaG(double dagger) value of 48.4 kJ mol(-1). DFT calculations on the model compounds [8,8-(PH(3))(2)-nido-8,7-RhNB(9)H(11)] and [8,8-(PH(3))(2)-nido-8,7-RhSB(9)H(10)] have been carried out to define the fluxional process and the intermediates involved.
Xu, Juan; Li, Yuanyuan; Wang, Lei; Cai, Qifa; Li, Qingwei; Gao, Biao; Zhang, Xuming; Huo, Kaifu; Chu, Paul K
2016-09-22
A lithium-ion hybrid supercapacitor (Li-HSC) comprising a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode has attracted much interest because it accomplishes a large energy density without compromising the power density. In this work, hierarchical carbon coated WO3 (WO3/C) with a unique mesoporous structure and metal-organic framework derived nitrogen-doped carbon hollow polyhedra (MOF-NC) are prepared and adopted as the anode and the cathode for Li-HSCs. The hierarchical mesoporous WO3/C microspheres assembled by radially oriented WO3/C nanorods along the (001) plane enable effective Li(+) insertion, thus exhibit high capacity, excellent rate performance and a long cycling life due to their high Li(+) conductivity, electronic conductivity and structural robustness. The WO3/C structure shows a reversible specific capacity of 508 mA h g(-1) at a 0.1 C rate (1 C = 696 mA h g(-1)) after 160 discharging-charging cycles with excellent rate capability. The MOF-NC achieved the specific capacity of 269.9 F g(-1) at a current density of 0.2 A g(-1). At a high current density of 6 A g(-1), 92.4% of the initial capacity could be retained after 2000 discharging-charging cycles, suggesting excellent cycle stability. The Li-HSC comprising a WO3/C anode and a MOF-NC cathode boasts a large energy density of 159.97 W h kg(-1) at a power density of 173.6 W kg(-1) and 88.3% of the capacity is retained at a current density of 5 A g(-1) after 3000 charging-discharging cycles, which are better than those previously reported for Li-HSCs. The high energy and power densities of the Li-HSCs of WO3/C//MOF-NC render large potential in energy storage.
2012-10-01
door for use a building block material for low surface energy materials • Applications – Mechanical robust superhydrophobic/ oleophobic /omniphobic...polymers for F-POSS • F-POSS compounds have a near limitless potential in producing a variety of new hydrophobic, oleophobic , or ominiphobic polymer
Understanding boron through size-selected clusters: structure, chemical bonding, and fluxionality.
Sergeeva, Alina P; Popov, Ivan A; Piazza, Zachary A; Li, Wei-Li; Romanescu, Constantin; Wang, Lai-Sheng; Boldyrev, Alexander I
2014-04-15
Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center-two-electron (2c-2e) σ bonds on the periphery and delocalized multicenter-two-electron (nc-2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron's electron deficiency and leads to fluxional behavior, which has been observed in B13(+) and B19(-). A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B(-), formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B(-)/C analogy. It is
Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality
Energy Technology Data Exchange (ETDEWEB)
Sergeeva, Alina P.; Popov, Ivan A.; Piazza, Zachary A.; Li, Wei-Li; Romanescu, Constantin; Wang, Lai S.; Boldyrev, Alexander I.
2014-04-15
Conspectus Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center–two-electron (2c–2e) σ bonds on the periphery and delocalized multicenter–two-electron (nc–2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron’s electron deficiency and leads to fluxional behavior, which has been observed in B13+ and B19–. A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B–, formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B
New insight in boron chemistry: Application in two-photon absorption
Bolze, F.; Hayek, A.; Sun, X. H.; Baldeck, P. L.; Bourgogne, C.; Nicoud, J.-F.
2011-07-01
Two groups of one-dimensional (1D) boron containing two-photon absorbing fluorophores have been prepared and characterized. One group includes boron atoms incorporated in the conjugated or pseudo conjugated central core and the other contain a boron cluster as an acceptor group at one end of the fluorophores. Two boron containing central cores (with two boron atoms) have been explored: the cyclodiborazane and the pyrazabole moieties. The chosen boron cluster, p-carborane, contains 10 boron atoms. All the prepared fluorophores present high two-photon absorption cross-sections. Some water-soluble as well as lipophylic dyes have been prepared and used in bio-imaging.
Institute of Scientific and Technical Information of China (English)
刘玲; 周铮; 丁雪佳; 张立群
2007-01-01
采用溶液共混法制备了笼状硅氧烷低聚物(POSS)/硅橡胶复合材料,用差示扫描量热仪在不同降温速率下研究了POSS/硅橡胶复合材料的非等温结晶性能,考察了POSS质量分数分别为5%(试样P 5)、10%(试样P 10)争30%(试样P 30)时对复合材料非等温结晶参数和活化能的影响,并选用Ozawa及Ozawa-Avrami联合法对POSS/硅橡胶的非等温结晶性能进行了分析.结果表明,Ozawa-Avrami联合方法适合描述POSS/硅橡胶的非等温结晶现象;POSS/硅橡胶复合材料成核速率的大小依次为P 5、P 15和P 30,生长速率则相反,而结晶速率大小依次为P 30、P 5和P 15.
Azema, Émilien; Peyroux, R; Dubois, Frédéric; Saussine, G
2008-01-01
By means of tree-dimensional contact dynamics simulations, we analyze the vibrational dynamics of a confined granular layer in response to harmonic forcing. The sample is composed of polyedric grains with a shape derived from digitalized ballast. The system involves a jammed state separating passive (loading) and active (unloading) states. We show that an approximate expression of the packing resistance force as a function of the displacement of the free retaining wall from the jamming position provides a good description of the dynamics. We study in detail the scaling of displacements and velocities with loading parameters. In particular, we find that, for a wide range of frequencies, the data collapse by scaling the displacements with the inverse square of frequency, the inverse of the force amplitude and the square of gravity. We show that the mean compaction rate increases linearly with frequency up to a characteristic frequency of 10 Hz and then it declines in inverse proportion to frequency.
Yamanaka, Shoji; Komatsu, Masaya; Tanaka, Masashi; Sawa, Hiroshi; Inumaru, Kei
2014-05-28
Single crystals of sodium containing silicon clathrate compounds Na8Si46 (type I) and NaxSi136 (type II) were prepared from the mixtures of NaSi and Si under high-pressure and high-temperature conditions of 5 GPa at 600-1000 °C. The type II crystals were obtained at relatively low-temperature conditions of 700-800 °C, which were found to have a Na excess composition Na30.5Si136 in comparison with the compounds NaxSi136 (x ≤ 24) obtained by a thermal decomposition of NaSi under vacuum. The single crystal study revealed that the Na excess type II compound crystallizes in space group Fd3̅m with a lattice parameter of a = 14.796(1) Å, slightly larger than that of the ambient phase (Na24Si136), and the large silicon hexakaidecahedral cages (@Si28) are occupied by two sodium atoms disordered in the two 32e sites around the center of the @Si28 cages. At temperatures primitive cell with space group P213, and the Na atoms in the @Si28 cages are aligned as Na2 pairs. The temperature dependence of the magnetic susceptibility of Na30.5Si136 suggests that the two Na ions (2 Na(+)) in the cage are changed to a Na2 molecule. The Na atoms of Na30.5Si136 can be deintercalated from the cages topochemically by evacuation at elevated temperatures. The single crystal study of the deintercalated phases NaxSi136 (x = 25.5 and 5.5) revealed that only excess Na atoms have disordered arrangements.
Institute of Scientific and Technical Information of China (English)
朱树高; 朱群
2001-01-01
应用配合、沉淀反应,采取综合措施强化含铜、铅、汞、碳精矿的浸出、置换,采用常规一浸一洗氰化流程就能使金的回收率达到95%以上,该经验具有推广应用价值.
Institute of Scientific and Technical Information of China (English)
刁永发; 郝卫辉; 邹钺
2011-01-01
Absorption of gas-phase mercury （Hg0） in coal-fired flue gases by activated carbon fiber（ACF） cooperated with the filter bag with Polyimide （P84） and aramid 1313（NOMEX） polyphenylene sulfide （PPS）, glass fiber, polysulfonamide （PSA） and polytetrafluoroethene （PTFE）fiber were investigated in the fixed bed system. The ACF＋PPS doped fibers were modified respectively by adding 5%, 10%, 15% potassium bromide （KBr） and Potassium iodide （KI） solution. The results show that mercury removal efficiency of different properties of ACF-doped fibers vary widely, and the removal rate is between 39% and 71%, and adsorption efficiency of mercury （Hg0） by modified ACF＋PPS doped fibers with KBr and KI is above 80% and 90% separately when the inlet concentration of mercury is 30μg/m3 and the adsorption temperature is 160℃. The highest efficiency by non-modified ACF＋PPS doped fibers is just 70%. The results also indicated that ACF＋PPS doped fibers modified by KI had a better adsorption efficiency than doped fibers modified by KBr with the same mass fraction. And the higher the mass fraction of KI is, the better the adsorption efficiency of the Hg0 vapor. The adsorption efficiency is above 98% especially when using modified ACF＋PPS doped fibers by 15% KI after a certain time. So modified ACF＋PPS doped fibers can keep high Hg0 removal rate.%通过固定床实验系统的烟气脱除零价汞实验，研究了活性炭纤维协同滤袋用聚酰亚胺、芳纶1313、聚苯硫醚、玻璃纤维、芳砜纶以及聚四氟乙烯等常用纤维，对烟气中零价汞的脱除效果。研究了改性前不同性能掺炭纤维，以及用质量分数分别为5％、10％、15％的溴化钾、碘化钾溶液改性后的活性炭纤维（activatedcarbonfiber,ACF）和聚苯硫醚（polyphenylenesulfide，PPS）形成的掺炭纤维，对模拟燃煤烟气中零价汞（Hg0）的吸附性能。结果表明：在汞蒸气入口浓度为30μg／m^3，吸附温度为16
Directory of Open Access Journals (Sweden)
A. P. Luz
2011-06-01
Full Text Available In this work the sessile drop technique was used in order to evaluate the melting temperature of synthetic and industrial slags, and their contact angle as a function of time and temperature on substrates of an Al2O3-SiO2-SiC-C castable containing 10 wt.% of carbon or its matrix. The best experimental conditions for the evaluation of the wetting behavior of refractory castables were attained when 25 x 25 x 10 mm³ matrix substrates and cylindrical slag pellets of 3 mm diameter and 5 mm high were used. This substrate - slag set resulted in contact angle values with good reliability. Small differences between the contact angle behavior on ground and polished matrix surfaces for synthetic slags were also detected. Additionally, industrial slags containing various oxide components, showed high values of contact angles and lower liquid spreading when compared with synthetic slags. This difference can be associated to the interaction liquid-solid at the material interface. Besides that, the wetting experiments were presented as a good alternative for measuring the melting temperatures of slags, as their values are difficult to determine due to the high oxide variety in the industrial slag compositions and the interaction between the slag and the substrate.Neste trabalho a técnica da gota séssil foi usada na avaliação da temperatura de fusão de escórias sintéticas e industriais e de seus ângulos de contato, em função do tempo e da temperatura, sobre substratos de um concreto Al2O3-SiO2-SiC-C que contém 10%-p de carbono ou sobre somente sua matriz. As melhores condições experimentais para a avaliação do comportamento de molhamento dos concretos refratários foram obtidas quando utilizados substratos da matriz de 25 x 25 x 10 mm³ e cilindros das escórias com 3 mm de diâmetro e 5 mm de altura. O uso deste conjunto substrato-escória proporcionou a obtenção de valores de ângulo de contato com boa reprodutibilidade. Pequenas diferenças entre o comportamento do ângulo de contato de escórias sintéticas sobre amostras da matriz com superfície retificada ou polida também foram verificadas. Adicionalmente, as escórias industriais que continham diversos óxidos em suas composições mostraram maiores valores de ângulo de contato e menor espalhamento dos líquidos quando comparados com as escórias sintéticas. Esta diferença pode estar associada à interação entre o líquido-sólido na interface destes materiais. Além disso, os experimentos de molhabilidade foram apresentados como uma boa alternativa para medir a temperatura de fusão de escórias, uma vez que estes dados são difíceis de serem determinados devido à grande variedade de óxidos presentes nas composições das escórias industriais e a possível interação entre escória e substrato.
Glassy dynamics of convex polyhedra
Tasios, Nikos; Gantapara, Anjan Prasad; Dijkstra, Marjolein
2014-01-01
Self-assembly of polyhedral-shaped particles has attracted huge interest with the advent of new synthesis methods that realize these faceted particles in the lab. Recent studies have shown that polyhedral-shaped particles exhibit a rich phase behavior by excluded volume interactions alone; some of t
Adiabatic isometric mapping algorithm for embedding 2-surfaces in Euclidean 3-space
Ray, Shannon; Miller, Warner A.; Alsing, Paul M.; Yau, Shing-Tung
2015-12-01
Alexandrov proved that any simplicial complex homeomorphic to a sphere with strictly non-negative Gaussian curvature at each vertex can be isometrically embedded uniquely in {{{R}}}3 as a convex polyhedron. Due to the nonconstructive nature of his proof, there have yet to be any algorithms, that we know of, that realizes the Alexandrov embedding in polynomial time. Following his proof, we developed the adiabatic isometric mapping (AIM) algorithm. AIM uses a guided adiabatic pull-back procedure on a given polyhedral metric to produce an embedding that approximates the unique Alexandrov polyhedron. Tests of AIM applied to two different polyhedral metrics suggests that its run time is sub cubic with respect to the number of vertices. Although Alexandrov’s theorem specifically addresses the embedding of convex polyhedral metrics, we tested AIM on a broader class of polyhedral metrics that included regions of negative Gaussian curvature. One test was on a surface just outside the ergosphere of a Kerr black hole.
Synthesis and characterization of tantalum silsesquioxane complexes.
Guillo, Pascal; Fasulo, Meg E; Lipschutz, Michael I; Tilley, T Don
2013-02-14
Tantalum polyhedral oligosilsesquioxane (POSS) complexes have been synthesised and characterized. X-ray structures of these complexes revealed that the coordination number of the tantalum center greatly affects the cube-like silsesquioxane framework.
A non-linear constrained optimization technique for the mimetic finite difference method
Energy Technology Data Exchange (ETDEWEB)
Manzini, Gianmarco [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Svyatskiy, Daniil [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Bertolazzi, Enrico [Univ. of Trento (Italy); Frego, Marco [Univ. of Trento (Italy)
2014-09-30
This is a strategy for the construction of monotone schemes in the framework of the mimetic finite difference method for the approximation of diffusion problems on unstructured polygonal and polyhedral meshes.
Classification of eight dimensional perfect forms
Dutour Sikiric, M.; Schuermann, A.; Vallentin, F.
2007-01-01
In this paper, we classify the perfect lattices in dimension 8. There are 10916 of them. Our classification heavily relies on exploiting symmetry in polyhedral computations. Here we describe algorithms making the classification possible.
On Alternative Optimal Solutions to Linear Fractional Optimization Problems
Institute of Scientific and Technical Information of China (English)
ShengjiaXue
2004-01-01
The structure of the optimal solution set is derived for linear fractional optimization problems with the representation theorem of polyhedral sets．And the computational procedure in determining all optimal solutions is also given．
Hybrid polymer networks as ultra low `k` dielectric layers
Energy Technology Data Exchange (ETDEWEB)
Lewicki, James; Worsley, Marcus A.
2016-02-16
According to one embodiment, a polymeric material includes at least one polydimethylsiloxane (PDMS) polymer, and at least one polyhedral oligomericsilsequioxane (POSS) molecule. According to another embodiment, a method includes providing at least one polydimethylsiloxane (PDMS) polymer, providing at least one polyhedral oligomericsilsequioxane (POSS) molecule, and coupling the at least one PDSM polymer to the at least one POSS molecule to form a hybrid polymeric material.
Discrete Ricci Flow in Higher Dimensions
2015-02-01
Adiabatic Isometric Map- ping Algorithm for Embedding Polyhedral Metrics in Euclidean 3 Space,” to be submitted to Class. Quantum Grav. (2014). 5... Algorithm for Embedding Polyhedral Metrics in Euclidean 3 Space, to be submitted to Class. Quantum Grav. (2014). [15] P. M. Alsing, M. Corne, J. R. McDonald...Cleared: 24 FEB 2015 13. SUPPLEMENTARY NOTES 14. ABSTRACT The objective of this research to develop an efficient and justifiable algorithm to
Planar CoB18- Cluster: a New Motif for - and Metallo-Borophenes
Chen, Teng-Teng; Jian, Tian; Lopez, Gary; Li, Wan-Lu; Chen, Xin; Li, Jun; Wang, Lai-Sheng
2016-06-01
Combined Photoelectron Spectroscopy (PES) and theoretical calculations have found that anion boron clusters (Bn-) are planar and quasi-planar up to B25-. Recent works show that anion pure boron clusters continued to be planar at B27-,B30-,B35- and B36-. B35- and B36- provide the first experimental evidence for the viability of the two-dimensional (2D) boron sheets (Borophene). The 2D to three-dimensional (3D) transitions are shown to happen at B40-,B39- and B28-, which possess cage-like structures. These fullerene-like boron cage clusters are named as Borospherene. Recently, borophenes or similar structures are claimed to be synthesized by several groups. Following an electronic design principle, a series of transition-metal-doped boron clusters (M©Bn-, n=8-10) are found to possess the monocyclic wheel structures. Meanwhile, CoB12- and RhB12- are revealed to adopt half-sandwich-type structures with the quasi-planar B12 moiety similar to the B12- cluster. Very lately, we show that the CoB16- cluster possesses a highly symmetric Cobalt-centered drum-like structure, with a new record of coordination number at 16. Here we report the CoB18- cluster to possess a unique planar structure, in which the Co atom is doped into the network of a planar boron cluster. PES reveals that the CoB18- cluster is a highly stable electronic system with the first adiabatic detachment energy (ADE) at 4.0 eV. Global minimum searches along with high-level quantum calculations show the global minimum for CoB18- is perfectly planar and closed shell (1A1) with C2v symmetry. The Co atom is bonded with 7 boron atoms in the closest coordination shell and the other 11 boron atoms in the outer coordination shell. The calculated vertical detachment energy (VDE) values match quite well with our experimental results. Chemical bonding analysis by the Adaptive Natural Density Partitioning (AdNDP) method shows the CoB18- cluster is π-aromatic with four 4-centered-2-electron (4c-2e) π bonds and one 19
Hückel's Rule of Aromaticity Categorizes Aromatic Closo Boron Hydride Clusters
Poater i Teixidor, Jordi; Solà i Puig, Miquel; Viñas, Clara; Teixidor, Francesc
2016-01-01
A direct connection is established between tridimensional aromatic closo boron hydride clusters and planar aromatic [n]annulenes for medium and large size boron clusters. In particular, our results prove the existence of a link between the two-dimensional Hückel rule followed by aromatic [n]-annulenes and Wade-Mingos' rule of three-dimensional aromaticity applied to the aromatic [BnHn]2- closo boron hydride clusters. Our results show that closo boron hydride clusters can be categorized into d...
Beyond organic chemistry: aromaticity in atomic clusters.
Boldyrev, Alexander I; Wang, Lai-Sheng
2016-04-28
We describe joint experimental and theoretical studies carried out collaboratively in the authors' labs for understanding the structures and chemical bonding of novel atomic clusters, which exhibit aromaticity. The concept of aromaticity was first discovered to be useful in understanding the square-planar unit of Al4 in a series of MAl4(-) bimetallic clusters that led to discoveries of aromaticity in many metal cluster systems, including transition metals and similar cluster motifs in solid compounds. The concept of aromaticity has been found to be particularly powerful in understanding the stability and bonding in planar boron clusters, many of which have been shown to be analogous to polycyclic aromatic hydrocarbons in their π bonding. Stimulated by the multiple aromaticity in planar boron clusters, a design principle has been proposed for stable metal-cerntered aromatic molecular wheels of the general formula, M@Bn(k-). A series of such borometallic aromatic wheel complexes have been produced in supersonic cluster beams and characterized experimentally and theoretically, including Ta@B10(-) and Nb@B10(-), which exhibit the highest coordination number in two dimensions.
Adiabatic Isometric Mapping Algorithm for Embedding 2-Surfaces in Euclidean 3-Space
Ray, Shannon; Alsing, Paul M; Yau, Shing-Tung
2015-01-01
Alexandrov proved that any simplicial complex homeomorphic to a sphere with strictly non-negative Gaussian curvature at each vertex can be isometrically embedded uniquely in $\\mathbb{R}^3$ as a convex polyhedron. Due to the nonconstructive nature of his proof, there have yet to be any algorithms, that we know of, that realizes the Alexandrov embedding in polynomial time. Following his proof, we developed the adiabatic isometric mapping (AIM) algorithm. AIM uses a guided adiabatic pull-back procedure to produce "smooth" embeddings. Tests of AIM applied to two different polyhedral metrics suggests that its run time is sub cubic with respect to the number of vertices. Although Alexandrov's theorem specifically addresses the embedding of convex polyhedral metrics, we tested AIM on a broader class of polyhedral metrics that included regions of negative Gaussian curvature. One test was on a surface just outside the ergosphere of a Kerr black hole.
An Origami Approximation to the Cosmic Web
Neyrinck, Mark C
2014-01-01
The powerful Lagrangian view of structure formation was essentially introduced to cosmology by Zel'dovich. In the current cosmological paradigm, a dark-matter-sheet 3D manifold, inhabiting 6D position-velocity phase space, was flat (with vanishing velocity) at the big bang. Afterward, gravity stretched and bunched the sheet together in different places, forming a cosmic web when projected to the position coordinates. Here, I explain some properties of an origami approximation, in which the sheet does not stretch or contract (an assumption that is false in general), but is allowed to fold. Even without stretching, the sheet can form an idealized cosmic web, with convex polyhedral voids separated by straight walls and filaments, joined by convex polyhedral nodes. The nodes form in 'polygonal' or 'polyhedral' collapse, somewhat like spherical/ellipsoidal collapse, except incorporating simultaneous filament and wall formation. The origami approximation allows phase-space geometries of nodes, filaments, and walls ...
The Geometry of the Neighbor-Joining Algorithm for Small Trees
Eickmeyer, Kord
2009-01-01
In 2007, Eickmeyer et al. showed that the tree topologies outputted by the Neighbor-Joining (NJ) algorithm and the balanced minimum evolution (BME) method for phylogenetic reconstruction are each determined by a polyhedral subdivision of the space of dissimilarity maps ${\\R}^{n \\choose 2}$, where $n$ is the number of taxa. In this paper, we will analyze the behavior of the Neighbor-Joining algorithm on five and six taxa and study the geometry and combinatorics of the polyhedral subdivision of the space of dissimilarity maps for six taxa as well as hyperplane representations of each polyhedral subdivision. We also study simulations for one of the questions stated by Eickmeyer et al., that is, the robustness of the NJ algorithm to small perturbations of tree metrics, with tree models which are known to be hard to be reconstructed via the NJ algorithm.
Minkowski sum of HV-polytopes in Rn
Delos, Vincent
2014-01-01
Minkowski sums cover a wide range of applications in many different fields like algebra, morphing, robotics, mechanical CAD/CAM systems ... This paper deals with sums of polytopes in a n dimensional space provided that both H-representation and V-representation are available i.e. the polytopes are described by both their half-spaces and vertices. The first method uses the polytope normal fans and relies on the ability to intersect dual polyhedral cones. Then we introduce another way of considering Minkowski sums of polytopes based on the primal polyhedral cones attached to each vertex.
EVAPORATION FORM OF ICE CRYSTALS IN SUBSATURATED AIR AND THEIR EVAPORATION MECHANISM
ゴンダ, タケヒコ; セイ, タダノリ; Takehiko, Gonda; Tadanori, Sei
1987-01-01
The evaporation form and the evaporation mechanism of dendritic ice crystals grown in air of 1.0×(10)^5 Pa and at water saturation and polyhedral ice crystals grown in air of 4.0×10 Pa and at relatively low supersaturation are studied. In the case of dendritic ice crystals, the evaporation preferentially occurs in the convex parts of the crystal surfaces and in minute secondary branches. On the other hand, in the case of polyhedral ice crystals, the evaporation preferentially occurs in the pa...
Electrorheological fluids and methods
Energy Technology Data Exchange (ETDEWEB)
Green, Peter F.; McIntyre, Ernest C.
2015-06-02
Electrorheological fluids and methods include changes in liquid-like materials that can flow like milk and subsequently form solid-like structures under applied electric fields; e.g., about 1 kV/mm. Such fluids can be used in various ways as smart suspensions, including uses in automotive, defense, and civil engineering applications. Electrorheological fluids and methods include one or more polar molecule substituted polyhedral silsesquioxanes (e.g., sulfonated polyhedral silsesquioxanes) and one or more oils (e.g., silicone oil), where the fluid can be subjected to an electric field.
Stoer, Mechthild
1992-01-01
The problem of designing a cost-efficient network that survives the failure of one or more nodes or edges of the network is critical to modern telecommunications engineering. The method developed in this book is designed to solve such problems to optimality. In particular, a cutting plane approach is described, based on polyhedral combinatorics, that is ableto solve real-world problems of this type in short computation time. These results are of interest for practitioners in the area of communication network design. The book is addressed especially to the combinatorial optimization community, but also to those who want to learn polyhedral methods. In addition, interesting new research problemsare formulated.
Approche polyèdrale du problème de tournées de véhicules
1995-01-01
This thesis deals with the vehicle routing problem which is the problem of designing optimal routes of vehicles from a depot to a set of customers. Up to now, only heuristic methods have been used in practice. In this work, we focus on the polyhedral approach of the problem, it means on an exact method based on the polyhedral representation of the convex hull of feasible solutions. More precisely, we present a "Branch and Cut" algorithm for the classical vehicle routing problem with any unspl...
The Application of Spherical Harmonics for Describing a Cube-Shape Particle
Directory of Open Access Journals (Sweden)
Urtė Radvilaitė
2015-03-01
Full Text Available The paper disccusses various models for discrete element methods of modelling particle shapes. The multi-sphere method is most frequently used, though a polyhedral approach and a hybrid sphero-polyhedral model can also be introduced. All above mentioned methods precisely approximate particle shapes, and difficulties in modelling contact between particles arise. Thus, there is a need to have an universal method that gives the analytical expression of the shape. For this purpose, spherical harmonics have been introduced. The article presents the concept of the spherical harmonics model and experimental results describing the cube-shape particle.
Toric degenerations of Bezier patches
Garcia-Puente, Luis David; Zhu, Chungang
2010-01-01
The control polygon of a Bezier curve is well-defined and meaningful---there is a sequence of weights under which the limiting position of the curve is the control polygon. For a Bezier surface patch, there are many possible polyhedral control structures, and none are canonical. We propose a not necessarily polyhedral control structure for surface patches, regular control surfaces, which are certain C^0 spline surfaces. While not unique, regular control surfaces are exactly the possible limiting positions of a Bezier patch when the weights are allowed to vary, but the control points are fixed.
Some results from a study of carbon minerals by the thermal method
Energy Technology Data Exchange (ETDEWEB)
Otakuziyev, E.; Kasymov, A.K.; Miralimova, N.M.
1979-01-01
Using the optimum technique of thermal analysis in carbon-containing shales and hornfels of ancient deposits of the Kyzylkum and Zirabulak-Ziaetdinsk mountains, four groups are revealed of mineral form of carbon, corresponding to the kerite-oxykeriteanthraxolite-shungite-graphite series. Interpretation of the thermograms obtained shows the varying degree of metamorphism of the carbon-containing rock of the areas studied.
40 CFR 98.183 - Calculating GHG emissions.
2010-07-01
... (metric tons). 44/12 = Ratio of molecular weights, CO2 to carbon. 2000/2205 = Conversion factor to convert... smelting furnace, determine the annual mass of carbon in each carbon-containing material, other than fuel... emissions using Equation R-1 of this section. Carbon-containing materials include carbonaceous...
Directory of Open Access Journals (Sweden)
W. Luo
2015-08-01
Full Text Available Soil pH buffering capacity (pHBC plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate containing soils and 1700 km sub-transect with non-carbonate containing soils across northern China. Soil pHBC was greater in the carbonate containing soils than in the non-carbonate containing soils. Acid addition decreased soil pH in the non-carbonate containing soils more markedly than in the carbonate containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC, carbonate content and exchangeable sodium (Na concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate containing soils and CEC was the main determinant of buffering capacity in the non-carbonate containing soils. Soil pHBC was positively related to aridity index and carbonate content across the carbonate containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate and non-carbonate containing soils, leading to different rates, risks, and impacts of acidification. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.
Study of Magnesium Diboride Clusters Using Hybrid Density Functional Theory
Directory of Open Access Journals (Sweden)
D. Rodríguez
2007-12-01
Full Text Available Using hybrid density functional theory and a relatively large basis set, the lowest energy equilibrium structure, vibrational spectrum, and natural orbital analysis were obtained for magnesium diboride clusters [(MgB2x for x=1,2, and 3]. For comparison, boron clusters [BxÃ‚Â forÃ‚Â x=2,4,Ã‚Â andÃ‚Â 6] were also considered. The MgB2 and (MgB22 showed equilibrium structures with the boron atoms in arrangements similar to what was obtained for pure boron atoms, whereas, for (MgB23 a different arrangement of boron was obtained. From the population analysis, large electron density in the boron atoms forming the clusters was observed.
Organic non-aqueous cation-based redox flow batteries
Energy Technology Data Exchange (ETDEWEB)
Jansen, Andrew N.; Vaughey, John T.; Chen, Zonghai; Zhang, Lu; Brushett, Fikile R.
2016-03-29
The present invention provides a non-aqueous redox flow battery comprising a negative electrode immersed in a non-aqueous liquid negative electrolyte, a positive electrode immersed in a non-aqueous liquid positive electrolyte, and a cation-permeable separator (e.g., a porous membrane, film, sheet, or panel) between the negative electrolyte from the positive electrolyte. During charging and discharging, the electrolytes are circulated over their respective electrodes. The electrolytes each comprise an electrolyte salt (e.g., a lithium or sodium salt), a transition-metal free redox reactant, and optionally an electrochemically stable organic solvent. Each redox reactant is selected from an organic compound comprising a conjugated unsaturated moiety, a boron cluster compound, and a combination thereof. The organic redox reactant of the positive electrolyte is selected to have a higher redox potential than the redox reactant of the negative electrolyte.
Synthesis of borophenes: Anisotropic, two-dimensional boron polymorphs
Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian; Wood, Joshua D.; Alducin, Diego; Myers, Benjamin D.; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel Jose; Ponce, Arturo; Oganov, Artem R.; Hersam, Mark C.; Guisinger, Nathan P.
2016-01-01
At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes.Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal. PMID:26680195
The dominant role of chalcogen bonding in the crystal packing of 2D/3D aromatics.
Fanfrlík, Jindřich; Přáda, Adam; Padělková, Zdeňka; Pecina, Adam; Macháček, Jan; Lepšík, Martin; Holub, Josef; Růžička, Aleš; Hnyk, Drahomír; Hobza, Pavel
2014-09-15
The chalcogen bond is a nonclassical σ-hole-based noncovalent interaction with emerging applications in medicinal chemistry and material science. It is found in organic compounds, including 2D aromatics, but has so far never been observed in 3D aromatic inorganic boron hydrides. Thiaboranes, harboring a sulfur heteroatom in the icosahedral cage, are candidates for the formation of chalcogen bonds. The phenyl-substituted thiaborane, synthesized and crystalized in this study, forms sulfur⋅⋅⋅π type chalcogen bonds. Quantum chemical analysis revealed that these interactions are considerably stronger than both in their organic counterparts and in the known halogen bond. The reason is the existence of a highly positive σ-hole on the positively charged sulfur atom. This discovery expands the possibilities of applying substituted boron clusters in crystal engineering and drug design.
Folic acid derivatives for PET imaging and therapy addressing folate receptor positive tumors
Energy Technology Data Exchange (ETDEWEB)
Schieferstein, Hanno
2013-07-01
Folic acid, also known as vitamin B9, is the oxidized form of 5,6,7,8-tetrahydrofolate, which serves as methyl- or methylene donor (C1-building blocks) during DNA synthesis. Under physiological conditions the required amount of 5,6,7,8-tetrahydrofolate for survival of the cell is accomplished through the reduced folate carrier (RFC). In contrast, the supply of 5,6,7,8-tetrahydrofolate is insufficient under pathophysiological conditions of tumors due to an increased proliferation rate. Consequently, many tumor cells exhibit an (over)expression of the folate receptor. This phenomenon has been applied to diagnostics (PET, SPECT, MR) to image FR-positive tumors and on the other hand to treat malignancies related to a FR (over)expression. Based on this concept, a new {sup 18}F-labeled folate for PET imaging has been developed and was evaluated in vivo using tumor-bearing mice. The incorporation of oligoethylene spacers into the molecular structure led to a significant enhancement of the pharmacokinetics in comparison to previously developed {sup 18}F-folates. The liver uptake could be reduced by one sixth by remaining a tumor uptake of 3%ID/g leading to better contrast ratios. Encouraged by these results, a clickable {sup 18}F-labeled serine-based prosthetic group has been synthesized, again with the idea to improve the metabolic and pharmacokinetic profile of hydrophilic radiotracers. Therefore, an alkyne-carrying azido-functionalized serine derivative for coupling to biomolecules was synthesized and a chlorine leaving group for {sup 18}F-labeling, which could be accomplished using a microwave-assisted synthesis, a [K is contained in 2.2.2]{sup +}/carbonate system in DMSO. Radiochemical yields of 77±6% could be achieved. The promising results obtained from the FR-targeting concept in the diagnostic field have been transferred to the boron neutron capture therapy. Therefore, a folate derivative was coupled to different boron clusters and cell uptake studies were
Tandy, P; Yu, Ming; Leahy, C; Jayanthi, C S; Wu, S Y
2015-03-28
An upgrade of the previous self-consistent and environment-dependent linear combination of atomic orbitals Hamiltonian (referred as SCED-LCAO) has been developed. This improved version of the semi-empirical SCED-LCAO Hamiltonian, in addition to the inclusion of self-consistent determination of charge redistribution, multi-center interactions, and modeling of electron-electron correlation, has taken into account the effect excited on the orbitals due to the atomic aggregation. This important upgrade has been subjected to a stringent test, the construction of the SCED-LCAO Hamiltonian for boron. It was shown that the Hamiltonian for boron has successfully characterized the electron deficiency of boron and captured the complex chemical bonding in various boron allotropes, including the planar and quasi-planar, the convex, the ring, the icosahedral, and the fullerene-like clusters, the two-dimensional monolayer sheets, and the bulk alpha boron, demonstrating its transferability, robustness, reliability, and predictive power. The molecular dynamics simulation scheme based on the Hamiltonian has been applied to explore the existence and the energetics of ∼230 compact boron clusters BN with N in the range from ∼100 to 768, including the random, the rhombohedral, and the spherical icosahedral structures. It was found that, energetically, clusters containing whole icosahedral B12 units are more stable for boron clusters of larger size (N > 200). The ease with which the simulations both at 0 K and finite temperatures were completed is a demonstration of the efficiency of the SCED-LCAO Hamiltonian.
Sensor Placement Design for Object Pose Determination with Three Light- Stripe Range Finders
1994-05-10
uncertainties in polyhedral object recognition. IEEE Transactions on Robotics and Automation, 7(3):361-371, June 1991. [6] R. E. Ellis. Planning...cell with multi-sensor capabilities. IEEE Transactions on Robotics and Automation, 5(6):765- 783, December 1989. [151 K. Ikeuchi and T. Kanade. Modeling
Forward Modeling of Gravity, Gravity Gradients,and Magnetic Anomalies due to Complex Bodies
Institute of Scientific and Technical Information of China (English)
Luo Yao; Yao Changli
2007-01-01
On the basis of the results of improved analytical expression of computation of gravity anomalies due to a homogeneous polyhedral body composed of polygonal facets, and applying the forward theory with the coordinate transformation of vectors and tensors, we deduced both the analytical expressions for gravity gradient tensors and for magnetic anomalies of a polygon, and obtained new analytical expressions for computing vertical gradients of gravity anomalies and vertical component of magnetic anomalies caused by a polyhedral body. And also we developed explicitly the complete unified expressions for the calculation of gravity anomalies, gravity gradient, and magnetic anomalies due to the homogeneous polyhedron. Furthermore, we deduced new analytical expressions for computing vertical gradients of gravity anomalies due to a finite rectangular prism by applying the newly obtained expressions for gravity gradient tensors due to a polyhedral target body. Comparison with forward calculation of models shows the correctness of these new expressions. It will reduce forward calculation time of gravity-magnetic anomalies and improve computational efficiency by applying our unified expressions for joint forward modeling of gravity-magnetic anomalies due to homogeneous polyhedral bodies.
Mirror Symmetry and Polar Duality of Polytopes
Directory of Open Access Journals (Sweden)
David A. Cox
2015-09-01
Full Text Available This expository article explores the connection between the polar duality from polyhedral geometry and mirror symmetry from mathematical physics and algebraic geometry. Topics discussed include duality of polytopes and cones as well as the famous quintic threefold and the toric variety of a reflexive polytope.
A Coverage Dominance Approach for Sensor Deployment Optimization
2011-07-01
Wireless Networks, 2003. [19] S. Kumar, T. H. Lai, and J. Balogh, On k-coverage in a mostly sleeping sensor network. Wireless Network, no. 14, pp. 277 – 294...Polyhedral Terrain in Polynomial Time. Image and Vision Computing, vol. 18, pp. 773 – 780, 2000. [22] S. Meguerdichian, F. Koushanfar, M. Potkonjak, and M
Convenient Model for Systems with Hystereses-Control
DEFF Research Database (Denmark)
Wisniewski, Rafal; Leth, John-Josef
2011-01-01
We establish a model of a system with hystereses, which allows for standard stability analysis of fixed points and closed orbits. To this end, we represent a system with hystereses as a piecewise-affine switched system that consists of a family of dynamical systems defined on disjoint polyhedral ...
Packing of non-spherical aggregate particles by DEM
Stroeven, P.; He, H.
2013-01-01
Loose random and dense random mono-size pacl
1988-12-01
Researchers have suggested other solution strategies, using ideas from nonlinear progamming for solving this general separable convex cost flow problems. Some...plane methods and branch and bound procedures of integer programming, primal-dual methods of linear and nonlinear programming, and polyhedral methods...Combinatorial Optimization: Networks and Matroids), Bazaraa and Jarvis [1978] (Linear Programming and Network Flows), Minieka [1978] (Optimization Algorithms for
Uniqueness in inverse elastic scattering with finitely many incident waves
Energy Technology Data Exchange (ETDEWEB)
Elschner, Johannes [Weierstrass-Institut fuer Angewandte Analysis und Stochastik (WIAS) im Forschungsverbund Berlin e.V. (Germany); Yamamoto, Masahiro [Tokyo Univ. (Japan). Dept. of Mathematical Sciences
2009-07-01
We consider the third and fourth exterior boundary value problems of linear isotropic elasticity and present uniqueness results for the corresponding inverse scattering problems with polyhedral-type obstacles and a finite number of incident plane elastic waves. Our approach is based on a reflection principle for the Navier equation. (orig.)
The high-pressure behavior of bloedite
DEFF Research Database (Denmark)
Comodi, Paola; Nazzareni, Sabrina; Balic Zunic, Tonci
2014-01-01
:bb:bc = 0.72:0.94:1. The evolution of crystal lattice and geometrical parameters indicates no phase transition up to 11 GPa. Sulfate polyhedra are incompressible, whereas the Mg polyhedral bulk modulus is 95 GPa. The sodium polyhedron is the softest part of the whole structure with a bulk modulus of 41 GPa...
Strategy-Proof Assignment Of Multiple Resources
DEFF Research Database (Denmark)
Erlanson, Albin; Szwagrzak, Karol
2015-01-01
by maximizing a separably concave function over a polyhedral extension of the set of Pareto-efficient allocations is strategy-proof. Moreover, these are the only strategy-proof, unanimous, consistent, and resource-monotonic mechanisms. These mechanisms generalize the parametric rationing mechanisms (Young, 1987...
Pospelov, A. I.
2016-08-01
Adaptive methods for the polyhedral approximation of the convex Edgeworth-Pareto hull in multiobjective monotone integer optimization problems are proposed and studied. For these methods, theoretical convergence rate estimates with respect to the number of vertices are obtained. The estimates coincide in order with those for filling and augmentation H-methods intended for the approximation of nonsmooth convex compact bodies.
Institute of Scientific and Technical Information of China (English)
Tong Kang; Zheng-peng Wu; De-hao Yu
2004-01-01
In this paper, we investigate the finite element A - φ method to approximate the eddy current equations with discontinuous coefficients in general three-dimensional Lipschitz polyhedral eddy current region. Nonmatching finite element meshes on the interface are considered and optimal error estimates are obtained.
Potsi, Georgia
2016-01-01
This thesis represents part of my research efforts aiming at the generation of new knowledge on the functionalization of carbon nanodiscs as well as the intercalation of graphene oxide and clays using a simple diamondoid derivative or polyhedral oligomeric silsesquioxanes (POSS). The thesis also con
Energy Technology Data Exchange (ETDEWEB)
Blanchini, F. [Universita di Udine (Italy); Carabelli, S. [Politecnico di Torino (Italy)
1994-12-31
We apply a technique recently proposed in literature for the robust stabilization of linear systems with time-varying uncertain parameters to a magnetic levitation system. This technique allows the construction of a polyhedral Lyapunov function and a linear variable-structure stabilizing controller.
DEFF Research Database (Denmark)
Speyer, D.; Jensen, Anders Nedergaard; Bogart, T.;
2005-01-01
The tropical variety of a d-dimensional prime ideal in a polynomial ring with complex coefficients is a pure d-dimensional polyhedral fan. This fan is shown to be connected in codimension one. We present algorithmic tools for computing the tropical variety, and we discuss our implementation...
Design of an Emergency Shelter
Kamerling, M.W.
2013-01-01
This paper presents the design of a light and robust temporary emergency shelter with a triangulated polyhedral grid to transfer the lateral and vertical loads efficiently. To simplify the construction the variety of the elements is minimized, only two sizes of elements are applied. For the structur
Quadratic elongation: A quantitative measure of distortion in coordination polyhedra
Robinson, Kelly F.; Gibbs, G.V.; Ribbe, P.H.
1971-01-01
Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrahedral coordination complexes, both of which show variations in bond length and bond angle. The quadratic elonga tion is dimensionless, giving a quantitative measure of polyhedral distortion which is independent of the effective size of the polyhedron.
松本, 信雄
1999-01-01
A comprehensive review, including some recent results, of the structures, properties and fablication methods of inorganic and organic silicon-based materials with backbone dimensions from 0 to 3 is presented. Quantum effects in low-dimensional silicon structures are discussed using organosilicon materials, such as polyhedral compounds and oligosilanes (quantum dots), polysilanes (quantum wires), heterocopolymers (one-dimensional superlattices), and polysilynes (quantum planes).
Binary Positive Semidefinite Matrices and Associated Integer Polytopes
DEFF Research Database (Denmark)
Letchford, Adam N.; Sørensen, Michael Malmros
2012-01-01
quadric, multicut and clique partitioning polytopes-are faces of binary psd polytopes. Finally, we present some implications of these polyhedral relationships. In particular, we answer an open question in the literature on the max-cut problem, by showing that the rounded psd inequalities define a polytope....
On monomial ideal rings and a theorem of Trevisan
Bahri, A; Cohen, F R; Gitler, S
2012-01-01
A direct proof is presented of a form of Alvise Trevisan's result, that every monomial ideal ring is represented by the cohomology of topological space. Certain of these rings are shown to be realized by polyhedral products indexed by simplicial complexes.
Molecular Modeling of Interfacial Behaviors of Nanomaterials
2007-05-01
15 L. Huang, and J. Kieffer, ’Molecular Dynamics Study of Cristobalite Silica Using a Charge Transfer Three- Body Potential Model,’ J. Chem. Phys...8217 Nano Letters in preparation (2006). 20 J. Zhou, and J. Kieffer, ’Simulation of Hexane-Functionalized Polyhedral Oligomeric Silses- quioxanes,’ J
Discrete Curvature Theories and Applications
Sun, Xiang
2016-08-25
Discrete Di erential Geometry (DDG) concerns discrete counterparts of notions and methods in di erential geometry. This thesis deals with a core subject in DDG, discrete curvature theories on various types of polyhedral surfaces that are practically important for free-form architecture, sunlight-redirecting shading systems, and face recognition. Modeled as polyhedral surfaces, the shapes of free-form structures may have to satisfy di erent geometric or physical constraints. We study a combination of geometry and physics { the discrete surfaces that can stand on their own, as well as having proper shapes for the manufacture. These proper shapes, known as circular and conical meshes, are closely related to discrete principal curvatures. We study curvature theories that make such surfaces possible. Shading systems of freeform building skins are new types of energy-saving structures that can re-direct the sunlight. From these systems, discrete line congruences across polyhedral surfaces can be abstracted. We develop a new curvature theory for polyhedral surfaces equipped with normal congruences { a particular type of congruences de ned by linear interpolation of vertex normals. The main results are a discussion of various de nitions of normality, a detailed study of the geometry of such congruences, and a concept of curvatures and shape operators associated with the faces of a triangle mesh. These curvatures are compatible with both normal congruences and the Steiner formula. In addition to architecture, we consider the role of discrete curvatures in face recognition. We use geometric measure theory to introduce the notion of asymptotic cones associated with a singular subspace of a Riemannian manifold, which is an extension of the classical notion of asymptotic directions. We get a simple expression of these cones for polyhedral surfaces, as well as convergence and approximation theorems. We use the asymptotic cones as facial descriptors and demonstrate the
Apparatus and process for the surface treatment of carbon fibers
Energy Technology Data Exchange (ETDEWEB)
Paulauskas, Felix Leonard; Ozcan, Soydan; Naskar, Amit K.
2016-05-17
A method for surface treating a carbon-containing material in which carbon-containing material is reacted with decomposing ozone in a reactor (e.g., a hollow tube reactor), wherein a concentration of ozone is maintained throughout the reactor by appropriate selection of at least processing temperature, gas stream flow rate, reactor dimensions, ozone concentration entering the reactor, and position of one or more ozone inlets (ports) in the reactor, wherein the method produces a surface-oxidized carbon or carbon-containing material, preferably having a surface atomic oxygen content of at least 15%. The resulting surface-oxidized carbon material and solid composites made therefrom are also described.
The Mechanism of Silicon and Silicon Carbide Making Carbon—containing Materials Antioxidize
Institute of Scientific and Technical Information of China (English)
TIANShouxin; SimThiamChee; 等
1996-01-01
The paper analyses redox reactions of an-tioxidants Si and SiC ete at different positions in the course of oxidation of carbon-containing materials,It is pointed out that redox reaction of antioxidants in oxidized-zone plays a very important part in antioxidation of carbon-con-taining materials,The reason why SiC can make carbon-containing material antioxide at thermodynamic temperature has been ex-plained,Experiment proves that antioxidants in oxidized zone can make carbon-containing materils antioxidize.
W. T. Luo; Nelson, P N; Li, M.-H.; J. P. Cai; Zhang, Y.Y.; Zhang, Y. G.; S. Yang; R. Z. Wang; Wang, Z. W.; Wu, Y. N.; X. G. Han; Y. Jiang
2015-01-01
Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate-containing soils and 1700 km sub-transect with non-carbonate-containing soils) across northern China. Soil pHBC was greater in the carbonate-containing soils ...
Recursively-regular subdivisions and applications
Directory of Open Access Journals (Sweden)
Rafel Jaume
2016-05-01
Full Text Available We generalize regular subdivisions (polyhedral complexes resulting from the projection of the lower faces of a polyhedron introducing the class of recursively-regular subdivisions. Informally speaking, a recursively-regular subdivision is a subdivision that can be obtained by splitting some faces of a regular subdivision by other regular subdivisions (and continue recursively. We also define the finest regular coarsening and the regularity tree of a polyhedral complex. We prove that recursively-regular subdivisions are not necessarily connected by flips and that they are acyclic with respect to the in-front relation. We show that the finest regular coarsening of a subdivision can be efficiently computed, and that whether a subdivision is recursively regular can be efficiently decided. As an application, we also extend a theorem known since 1981 on illuminating space by cones and present connections of recursive regularity to tensegrity theory and graph-embedding problems.
Steinitz theorems for simple orthogonal polyhedra
Directory of Open Access Journals (Sweden)
David Eppstein
2014-09-01
Full Text Available We define a simple orthogonal polyhedron to be a three-dimensional polyhedron with the topology of a sphere in which three mutually-perpendicular edges meet at each vertex.By analogy to Steinitz's theorem characterizing the graphs of convex polyhedra, we find graph-theoretic characterizations of three classes of simple orthogonal polyhedra: corner polyhedra, which can be drawn by isometric projection in the plane with only one hidden vertex, xyz polyhedra, in which each axis-parallel line through a vertex contains exactly one other vertex, and arbitrary simple orthogonal polyhedra. In particular, the graphs of xyz polyhedra are exactly the bipartite cubic polyhedral graphs, and every bipartite cubic polyhedral graph with a 4-connected dual graph is the graph of a corner polyhedron. Based on our characterizations we find efficient algorithms for constructing orthogonal polyhedra from their graphs.
Engineering the architectural diversity of heterogeneous metallic nanocrystals.
Yu, Yue; Zhang, Qingbo; Xie, Jianping; Lee, Jim Yang
2013-01-01
Similar to molecular engineering where structural diversity is used to create more property variations for application explorations, the architectural engineering of heterogeneous metallic nanocrystals (HMNCs) can likewise increase the versatility of metallic nanocrystals (NCs). Here we present a synthesis strategy capable of engineering the architectural diversity of HMNCs through rational and independent programming of every architecture-determining element, that is, the shape and size of the component NCs and their spatial arrangement. The strategy is based on the galvanic replacement reaction of a self-sustaining layer formed by underpotential deposition on a polyhedral NC. The selective deposition of satellite NCs on specific site of the central NC is realized by creating a geometry-dependent heterogeneous electron distribution. This site-selective deposition approach is applicable to central NCs in various polyhedral shapes and sizes. The satellite NCs can further develop their own shape and size through crystal growth kinetics control.
Hidden topological constellations and polyvalent charges in chiral nematic droplets
Posnjak, Gregor; Čopar, Simon; Muševič, Igor
2017-02-01
Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=-2, -3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules.
Earth Abundant Element Type I Clathrate Phases
Directory of Open Access Journals (Sweden)
Susan M. Kauzlarich
2016-08-01
Full Text Available Earth abundant element clathrate phases are of interest for a number of applications ranging from photovoltaics to thermoelectrics. Silicon-containing type I clathrate is a framework structure with the stoichiometry A8-xSi46 (A = guest atom such as alkali metal that can be tuned by alloying and doping with other elements. The type I clathrate framework can be described as being composed of two types of polyhedral cages made up of tetrahedrally coordinated Si: pentagonal dodecahedra with 20 atoms and tetrakaidecahedra with 24 atoms in the ratio of 2:6. The cation sites, A, are found in the center of each polyhedral cage. This review focuses on the newest discoveries in the group 13-silicon type I clathrate family: A8E8Si38 (A = alkali metal; E = Al, Ga and their properties. Possible approaches to new phases based on earth abundant elements and their potential applications will be discussed.
Theoretical study of aging effects on LaNi5 tritium storage
Institute of Scientific and Technical Information of China (English)
PING Feilin; JIANG Gang; ZHANG Lin; ZHU Zhenghe
2005-01-01
The electronic structure and energy of La2Ni10H12 and La2Ni10H11He (He is at tetrahedral, octahedral or twelve-face polyhedral interstitials) double cells have been calculated using the density functional theory. Their equilibrium structure, energy bands, electronic density of states (DOS) and X-ray diffraction are presented and discussed. The results indicate the helium-3 produced due to the decay of tritium is most possibly sited at twelve-face polyhedral and octahedral interstices and changes the thermodynamic properties of LaNi5 tritide system. The changes due to aging such as the reduction in the isotherm plateau pressure, increase of the isotherm plateau slope, and appearance of deeply trapped hydrogen are caused not only by the lattice expansion, but also by modification of the electronic structure due to the presence of He.
The mimetic finite difference method for elliptic problems
Veiga, Lourenço Beirão; Manzini, Gianmarco
2014-01-01
This book describes the theoretical and computational aspects of the mimetic finite difference method for a wide class of multidimensional elliptic problems, which includes diffusion, advection-diffusion, Stokes, elasticity, magnetostatics and plate bending problems. The modern mimetic discretization technology developed in part by the Authors allows one to solve these equations on unstructured polygonal, polyhedral and generalized polyhedral meshes. The book provides a practical guide for those scientists and engineers that are interested in the computational properties of the mimetic finite difference method such as the accuracy, stability, robustness, and efficiency. Many examples are provided to help the reader to understand and implement this method. This monograph also provides the essential background material and describes basic mathematical tools required to develop further the mimetic discretization technology and to extend it to various applications.
On intersection of two embedded spheres in 3-space (Russian version)
Rukhovich, Alexey
2011-01-01
We study intersection of two polyhedral spheres without self-intersections in 3-space. We find necessary and sufficient conditions on sequences x = x_1,x_2,...,x_n, y = y_1,y_2,...,y_n of positive integers, for existence of 2-dimensional polyhedra f,g in R^3 homeomorphic to the sphere and such that * f-g has n connected components, of which the i-th one has x_i neighbors in f and * g-f has n connected components, of which the i-th one has y_i neighbors in g. Analogously we study intersection of three polyhedral spheres without self-intersections in 3-space. Russian version is accessible to high-school teachers and students interested in mathematics.
Path planning algorithms for assembly sequence planning. [in robot kinematics
Krishnan, S. S.; Sanderson, Arthur C.
1991-01-01
Planning for manipulation in complex environments often requires reasoning about the geometric and mechanical constraints which are posed by the task. In planning assembly operations, the automatic generation of operations sequences depends on the geometric feasibility of paths which permit parts to be joined into subassemblies. Feasible locations and collision-free paths must be present for part motions, robot and grasping motions, and fixtures. This paper describes an approach to reasoning about the feasibility of straight-line paths among three-dimensional polyhedral parts using an algebra of polyhedral cones. A second method recasts the feasibility conditions as constraints in a nonlinear optimization framework. Both algorithms have been implemented and results are presented.
Superlattices assembled through shape-induced directional binding.
Lu, Fang; Yager, Kevin G; Zhang, Yugang; Xin, Huolin; Gang, Oleg
2015-01-01
Organization of spherical particles into lattices is typically driven by packing considerations. Although the addition of directional binding can significantly broaden structural diversity, nanoscale implementation remains challenging. Here we investigate the assembly of clusters and lattices in which anisotropic polyhedral blocks coordinate isotropic spherical nanoparticles via shape-induced directional interactions facilitated by DNA recognition. We show that these polyhedral blocks--cubes and octahedrons--when mixed with spheres, promote the assembly of clusters with architecture determined by polyhedron symmetry. Moreover, three-dimensional binary superlattices are formed when DNA shells accommodate the shape disparity between nanoparticle interfaces. The crystallographic symmetry of assembled lattices is determined by the spatial symmetry of the block's facets, while structural order depends on DNA-tuned interactions and particle size ratio. The presented lattice assembly strategy, exploiting shape for defining the global structure and DNA-mediation locally, opens novel possibilities for by-design fabrication of binary lattices.
The Building Game: From Enumerative Combinatorics to Conformational Diffusion
Johnson-Chyzhykov, Daniel; Menon, Govind
2016-08-01
We study a discrete attachment model for the self-assembly of polyhedra called the building game. We investigate two distinct aspects of the model: (i) enumerative combinatorics of the intermediate states and (ii) a notion of Brownian motion for the polyhedral linkage defined by each intermediate that we term conformational diffusion. The combinatorial configuration space of the model is computed for the Platonic, Archimedean, and Catalan solids of up to 30 faces, and several novel enumerative results are generated. These represent the most exhaustive computations of this nature to date. We further extend the building game to include geometric information. The combinatorial structure of each intermediate yields a systems of constraints specifying a polyhedral linkage and its moduli space. We use a random walk to simulate a reflected Brownian motion in each moduli space. Empirical statistics of the random walk may be used to define the rates of transition for a Markov process modeling the process of self-assembly.
Hidden topological constellations and polyvalent charges in chiral nematic droplets
Posnjak, Gregor; Čopar, Simon; Muševič, Igor
2017-01-01
Topology has an increasingly important role in the physics of condensed matter, quantum systems, material science, photonics and biology, with spectacular realizations of topological concepts in liquid crystals. Here we report on long-lived hidden topological states in thermally quenched, chiral nematic droplets, formed from string-like, triangular and polyhedral constellations of monovalent and polyvalent singular point defects. These topological defects are regularly packed into a spherical liquid volume and stabilized by the elastic energy barrier due to the helical structure and confinement of the liquid crystal in the micro-sphere. We observe, for the first time, topological three-dimensional point defects of the quantized hedgehog charge q=−2, −3. These higher-charge defects act as ideal polyvalent artificial atoms, binding the defects into polyhedral constellations representing topological molecules. PMID:28220770
Location Of A Vehicle With A Laser Range Finder
Zhao, C. J.; Monchaud, S.; Marce, L.; Julliere, M.
1984-02-01
Absolute location of a mobile robot is necessary to improve the autonomy of vehicle built for hostile environments. We are developing a scanning laser range finder based on triangulation to get range data about the edges of a cylindrical polyhedral world. From the matching between the measurements and data computed from a model of the a priori known environment, the position of the robot is deduced accurately.
Formulations and exact algorithms for the vehicle routing problem with time windows
DEFF Research Database (Denmark)
Kallehauge, Brian
2008-01-01
In this paper we review the exact algorithms proposed in the last three decades for the solution of the vehicle routing problem with time windows (VRPTW). The exact algorithms for the VRPTW are in many aspects inherited from work on the traveling salesman problem (TSP). In recognition of this fact...... with the analysis of the polyhedral structure of the VRPTW. We conclude by examining possible future lines of research in the area of the VRPTW....
Feireisl, Eduard; Hošek, Radim; Maltese, David; Novotný, Antonín
2015-01-01
We derive an a priori error estimate for the numerical solution obtained by time and space discretization by the finite volume/finite element method of the barotropic Navier--Stokes equations. The numerical solution on a convenient polyhedral domain approximating a sufficiently smooth bounded domain is compared with an exact solution of the barotropic Navier--Stokes equations with a bounded density. The result is unconditional in the sense that there are no assumed bounds on the numerical sol...
Ichiba, Tomoyuki; Banner, Adrian; Karatzas, Ioannis; Fernholz, Robert
2009-01-01
We study Atlas-type models of equity markets with local characteristics that depend on both name and rank, and in ways that induce a stability of the capital distribution. Ergodic properties and rankings of processes are examined with reference to the theory of reflected Brownian motions in polyhedral domains. In the context of such models, we discuss properties of various investment strategies, including the so-called growth-optimal and universal portfolios.
ON ALTERNATIVE OPTIMAL SOLUTIONS TO QUASIMONOTONIC PROGRAMMING WITH LINEAR CONSTRAINTS
Institute of Scientific and Technical Information of China (English)
Xue Shengjia
2007-01-01
In this paper, the nonlinear programming problem with quasimonotonic ( both quasiconvex and quasiconcave )objective function and linear constraints is considered. With the decomposition theorem of polyhedral sets, the structure of optimal solution set for the programming problem is depicted. Based on a simplified version of the convex simplex method,the uniqueness condition of optimal solution and the computational procedures to determine all optimal solutions are given, if the uniqueness condition is not satisfied. An illustrative example is also presented.
A compactification of the Bruhat-Tits building
Landvogt, Erasmus
1996-01-01
The aim of this work is the definition of the polyhedral compactification of the Bruhat-Tits building of a reductive group over a local field. In addition, an explicit description of the boundary is given. In order to make this work as self-contained as possible and also accessible to non-experts in Bruhat-Tits theory, the construction of the Bruhat-Tits building itself is given completely.
Energy Technology Data Exchange (ETDEWEB)
Flandrin, N.; Bennis, Ch. [Institut Francais du Petrole (IFP), 92 - Rueil-Malmaison (France); Borouchaki, H. [Universite de Technologie de Troyes, 10 (France)
2005-06-01
This paper presents a new frontal approach to generate a 3D hybrid mesh in reservoir flow simulation. The mesh follows the flow directions around each well and allows to increase the accuracy in numerical simulations. In the hexahedral structured reservoir mesh, a local radial structured mesh is inserted around each well. Unstructured polyhedral meshes based on power diagrams are used to connect the structured meshes together. (authors)
Probabilistic structural analysis by extremum methods
Nafday, Avinash M.
1990-01-01
The objective is to demonstrate discrete extremum methods of structural analysis as a tool for structural system reliability evaluation. Specifically, linear and multiobjective linear programming models for analysis of rigid plastic frames under proportional and multiparametric loadings, respectively, are considered. Kinematic and static approaches for analysis form a primal-dual pair in each of these models and have a polyhedral format. Duality relations link extreme points and hyperplanes of these polyhedra and lead naturally to dual methods for system reliability evaluation.
Viruses of eukaryotic green algae. Final technical report, June 1, 1989--February 1, 1992
Energy Technology Data Exchange (ETDEWEB)
Van Etten, J.L.
1992-12-31
We have isolated and partially characterized many large, polyhedral, DNA containing, plaque forming viruses which infect certain unicellular, eukaryotic, chlorella-like green algae. These viruses have several unique features, including the fact that they code for DNA site-specific endonucleases and DNA methyltransferases. The primary objectives of this study were to identify, clone, and characterize some of the virus-encoded DNA methyltransferases and DNA restriction endonucleases in order to understand their biological function.
Tan, A. J. K.
2014-01-01
The 2 main unresolved issues inherent in coronary stents are in-stent restenosis (ISR) and late stent thrombosis (ST). ISR is largely due to vascular smooth muscle cell (VSMC) proliferation, and ST is attributed to a lack of re-endothelialization. This thesis describes the conceptualization and development of a biofunctionalized polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) platform, for the express purpose of circumventing ISR and ST. A bare-metal stent is emb...
Multiple optimal solutions to a sort of nonlinear optimization problem
Institute of Scientific and Technical Information of China (English)
Xue Shengjia
2007-01-01
The optimization problem is considered in which the objective function is pseudolinear(both pseudoconvex and pseudoconcave) and the constraints are linear. The general expression for the optimal solutions to the problem is derived with the representation theorem of polyhedral sets, and the uniqueness condition of the optimal solution and the computational procedures to determine all optimal solutions ( ifthe uniqueness condition is not satisfied ) are provided. Finally, an illustrative example is also given.
Stabilization of fuzzy systems with constrained controls by using positively invariant sets
Directory of Open Access Journals (Sweden)
A. El Hajjaji
2006-01-01
Full Text Available We deal with the extension of the positive invariance approach to nonlinear systems modeled by Takagi-Sugeno fuzzy systems. The saturations on the control are taken into account during the design phase. Sufficient conditions of asymptotic stability are given ensuring at the same time that the control is always admissible inside the corresponding polyhedral set. Both a common Lyapunov function and piecewise Lyapunov function are used.
Aquaporin-Based Biomimetic Polymeric Membranes: Approaches and Challenges
DEFF Research Database (Denmark)
Habel, Joachim Erich Otto; Hansen, Michael; Kynde, Søren;
2015-01-01
In recent years, aquaporin biomimetic membranes (ABMs) for water separation have gained considerable interest. Although the first ABMs are commercially available, there are still many challenges associated with further ABM development. Here, we discuss the interplay of the main components of ABMs...... thin film interfacial polymerization techniques. Finally, we describe some new developments in interfacial polymerization using polyhedral oligomeric silsesquioxane cages for increasing the physical and chemical durability of thin film composite membranes....
Photoelectron Spectroscopy Study of [Ta2B6]-: a Hexagonal Bipyramdial Cluster
Jian, Tian; Li, Weili; Romanescu, Constantin; Wang, Lai-Sheng
2014-06-01
It has been a long-sought goal in cluster science to discover stable atomic clusters as building blocks for cluster-assembled nanomaterials, as exemplified by the fullerenes and their subsequent bulk syntheses.[1,2] Clusters have also been considered as models to understand bulk properties, providing a bridge between molecular and solid-state chemistry.[3] Herein we report a joint photoelectron spectroscopy and theoretical study on the [Ta2B6]- and [Ta2B6] clusters.[4] The photoelectron spectrum of [Ta2B6]- displays a simple spectral pattern and a large HOMO-LUMO gap, suggesting its high symmetry. Theoretical calculations show that both the neutral and anion are D6h pyramidal. The chemical bonding analyses for [Ta2B6] revealed the nature of the B6 and Ta interactions and uncovered strong covalent bonding between B6 and Ta. The D6h-[TaB6Ta] gaseous cluster is reminiscent of the structural pattern in the ReB6X6Re core in the [(Cp*Re)2B6H4Cl2] and the TiB6Ti motif in the newly synthesized Ti7Rh4Ir2B8 solid-state compound.[5,6] The current work provides an intrinsic link between a gaseous cluster and motifs for solid materials. Continued investigations of the transition-metal boron clusters may lead to the discovery of new structural motifs involving pure boron clusters for the design of novel boride materials. Reference [1] H.W. Kroto, J. R. Heath, S. C. OBrien, R. F. Curl, R. E. Smalley, Nature 1985, 318, 162 - 163. [2] W. Krtschmer, L. D. Lamb, K. Fostiropoulos, D. R. Huffman, Nature 1990, 347, 354 - 358. [3] T. P. Fehlner, J.-F. Halet, J.-Y. Saillard, Molecular Clusters: A Bridge to Solid-State Chemitry, Cambridge University Press, UK, 2007. [4] W. L. Li, L. Xie, T. Jian, C. Romanescu, X. Huang, L.-S. Wang, Angew. Chem. Int. Ed. 2014, 126, 1312 - 1316. [5] B. Le Guennic, H. Jiao, S. Kahlal, J.-Y. Saillard, J.-F. Halet, S. Ghosh, M. Shang, A. M. Beatty, A. L. Rheingold, T. P. Fehlner, J. Am. Chem. Soc. 2004, 126, 3203 - 3217. [6] B. P. T. Fokwa, M. Hermus, Angew
An Origami Approximation to the Cosmic Web
Neyrinck, Mark C.
2016-10-01
The powerful Lagrangian view of structure formation was essentially introduced to cosmology by Zel'dovich. In the current cosmological paradigm, a dark-matter-sheet 3D manifold, inhabiting 6D position-velocity phase space, was flat (with vanishing velocity) at the big bang. Afterward, gravity stretched and bunched the sheet together in different places, forming a cosmic web when projected to the position coordinates. Here, I explain some properties of an origami approximation, in which the sheet does not stretch or contract (an assumption that is false in general), but is allowed to fold. Even without stretching, the sheet can form an idealized cosmic web, with convex polyhedral voids separated by straight walls and filaments, joined by convex polyhedral nodes. The nodes form in `polygonal' or `polyhedral' collapse, somewhat like spherical/ellipsoidal collapse, except incorporating simultaneous filament and wall formation. The origami approximation allows phase-space geometries of nodes, filaments, and walls to be more easily understood, and may aid in understanding spin correlations between nearby galaxies. This contribution explores kinematic origami-approximation models giving velocity fields for the first time.
Morphology transformation of Cu2O by adding TEOA and their antibacterial activity
Duan, Weijia; Zheng, Min; Li, Rong; Wang, Yuyuan
2016-11-01
Cu2O polyhedral particles and hollow spheres were successfully synthesized by adjusting the concentration of triethanolamine (TEOA). The as-prepared samples were structurally characterized by the scanning electron microscope (SEM), X-ray powder diffraction (XRD), and transmission electron microscopy (TEM). The results revealed that the solid polyhedral Cu2O with sizes ranging from 70 to 150 nm was in good crystallization. The diameter of the hollow Cu2O spheres increased to 350-450 nm. It was found that the sizes and morphologies of the products could be significantly affected by the concentration of TEOA. And the morphology of Cu2O transformed from solid polyhedrons to hollow spheres with the further enrichment of TEOA concentration. A possible mechanism was proposed to explain the formation of the hollow Cu2O spheres. In addition, we investigated the antibacterial activities of the samples. It was demonstrated that the hollow Cu2O sphere exhibited better antibacterial activities for Escherichia coli ( E. coli) and Staphylococcus aureus ( S. aureus) compared with the solid polyhedral Cu2O.
A Novel Virtual Node Hexahedral Element with Exact Integration and Octree Meshing
Directory of Open Access Journals (Sweden)
Logah Perumal
2016-01-01
Full Text Available The method presented in this work is a 3-dimensional polyhedral finite element (3D PFEM based on virtual node method. Novel virtual node polyhedral elements (termed as VPHE are developed here, particularly virtual node hexahedral element (termed as VHE. Stiffness matrices of these polyhedral elements consist of simple polynomials. Thus, a new algorithm is introduced in this paper, which enables exact integration of monomials without a need for high number of integration points and weights. The number of nodes for VHE elements is not restricted, as opposed to the conventional hexahedral elements. This feature enables formulation of transition elements (termed as T-VHE which are useful to adaptive computation. Performances of the new VHE elements in solid mechanics and conductive heat transfer phenomena are examined through numerical simulations. The new T-VHE elements are utilized in octree mesh. The VHE elements are found to produce good results and T-VHE elements help to reduce number of global nodes for the analysis.
Singh, H.; Gokhale, A. M.; Mao, Y.; Tewari, A.; Sachdev, A. K.
2009-12-01
The serial sectioning technique is well known for the reconstruction of three-dimensional (3D) microstructures of opaque materials. In recent years, techniques also have been developed for the reconstruction of high-fidelity, large-volume segments of 3D microstructures that use montage serial sections and robot-assisted automated acquisitions of montage serial sections. This article reports the reconstruction of the multiphase, multiscale 3D microstructure of a permanent mold cast unmodified Al-12 wt pct Si-1 wt pct Ni base alloy that contains eutectic Si platelets, coarse primary polyhedral Si particles, Fe-rich script intermetallic particles, and pores. These constituents are segmented, reconstructed, rendered, and characterized in three dimensions. The estimated 3D microstrucutral attributes include the distribution of eutectic platelet thickness; the mean volume, mean surface area, and mean thickness of the eutectic Si platelets; the mean volume and the mean surface area of the polyhedral primary Si particles; and the mean number of faces, edges, and corners on the polyhedral primary Si particles.
Mechanism of RuO2 crystallization in borosilicate glass: an original in situ ESEM approach.
Boucetta, Hassiba; Podor, Renaud; Stievano, Lorenzo; Ravaux, Johann; Carrier, Xavier; Casale, Sandra; Gossé, Stéphane; Monteiro, Amélie; Schuller, Sophie
2012-03-19
Ruthenium, a fission product arising from the reprocessing of spent uranium oxide (UOX) fuel, crystallizes in the form of acicular RuO(2) particles in high-level waste containment glass matrices. These particles are responsible for significant modifications in the physicochemical behavior of the glass in the liquid state, and their formation mechanisms are a subject of investigation. The chemical reactions responsible for the crystallization of RuO(2) particles with acicular or polyhedral shape in simplified radioactive waste containment glass are described. In situ high-temperature environmental scanning electron microscopy (ESEM) is used to follow changes in morphology and composition of the ruthenium compounds formed by reactions at high temperature between a simplified RuO(2)-NaNO(3) precursor and a sodium borosilicate glass (SiO(2)-B(2)O(3)-Na(2)O). The key parameter in the formation of acicular or polyhedral RuO(2) crystals is the chemistry of the ruthenium compound under oxidized conditions (Ru(IV), Ru(V)). The precipitation of needle-shaped RuO(2) crystals in the melt might be associated with the formation of an intermediate Ru compound (Na(3)Ru(V)O(4)) before dissolution in the melt, allowing Ru concentration gradients. The formation of polyhedral crystals is the result of the direct incorporation of RuO(2) crystals in the melt followed by an Ostwald ripening mechanism.
Chemistry by Way of Density Functional Theory
Bauschlicher, Charles W., Jr.; Ricca, Alessandra; Partridge, Harry; Langohff, Stephen R.; Arnold, James O. (Technical Monitor)
1996-01-01
In this work we demonstrate that density functional theory (DFT) methods make an important contribution to understanding chemical systems and are an important additional method for the computational chemist. We report calibration calculations obtained with different functionals for the 55 G2 molecules to justify our selection of the B3LYP functional. We show that accurate geometries and vibrational frequencies obtained at the B3LYP level can be combined with traditional methods to simplify the calculation of accurate heats of formation. We illustrate the application of the B3LYP approach to a variety of chemical problems from the vibrational frequencies of polycyclic aromatic hydrocarbons to transition metal systems. We show that the B3LYP method typically performs better than the MP2 method at a significantly lower computational cost. Thus the B3LYP method allows us to extend our studies to much larger systems while maintaining a high degree of accuracy. We show that for transition metal systems, the B3LYP bond energies are typically of sufficient accuracy that they can be used to explain experimental trends and even differentiate between different experimental values. We show that for boron clusters the B3LYP energetics are not as good as for many of the other systems presented, but even in this case the B3LYP approach is able to help understand the experimental trends.
Energy Technology Data Exchange (ETDEWEB)
Tamat, S.R.; Moore, D.E.; Patwardhan, A.; Hersey, P. (Univ. of Sydney (Australia))
1989-07-01
The concept of conjugating boron cluster compounds to monoclonal antibodies has been examined by several groups of research workers in boron neutron capture therapy (BNCT). The procedures reported to date for boronation of monoclonal antibodies resulted in either an inadequate level of boron incorporation, the precipitation of the conjugates, or a loss of immunological activity. The present report describes the conjugation of dicesium-mercapto-undecahydrododecaborate (Cs2B12H11SH) to 225.28S monoclonal antibody directed against high molecular weight melanoma-associated antigens (HMW-MAA), using poly-L-ornithine as a bridge to increase the carrying capacity of the antibody and to minimize change in the conformational structure of antibody. The method produces a boron content of 1,300 to 1,700 B atoms per molecule 225.28S while retaining the immunoreactivity. Characterization in terms of the homogeneity of the conjugation of the boron-monoclonal antibody conjugates has been studied by gel electrophoresis and ion-exchange HPLC.
Wang, Weihua; Zhang, Xiaoxiao; Li, Ping; Sun, Qiao; Li, Zhen; Ren, Cong; Guo, Chao
2015-01-29
The discovery of advanced materials with high selectivity and efficiency is essential to realize practical carbon capture and sequestration. Here, we have investigated the interactions of the Co@B8/Co@B8(-) and M@B9/M@B9(-) (M = Ir, Rh, Ru) clusters with CO2, N2, and CH4 gas molecules theoretically. We found that neutral boron clusters have weak interaction with CO2, N2, and CH4 molecules. Similarly, the clusters with their negative charge states have also weak interaction with N2 and CH4 molecules. However, anionic clusters have a strong interaction with CO2, which can be explained by the Lewis acid-base interaction as CO2 (Lewis acid) can gain electron easily from the electron-rich anionic clusters. Moreover, the kinetic stability of the formed complexes after CO2 capture has been validated by ab initio molecular dynamics. In all, the present study demonstrates, for the first time, that the anionic boron wheel ring clusters can be used as potential advanced materials for CO2 capture and separation from flue gas and natural gas mixtures.
Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Qin, Shuijie
2017-01-01
Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to study the stabilities, photoelectron, infrared, Raman and electronic absorption spectra of borospherene B44‑ and metalloborospherenes MB440/‑ (M = Li, Na, and K). It is found that all atoms can form stable exohedral metalloborospherenes M&B440/‑, whereas only Na and K atoms can be stably encapsulated inside B440/‑ cage. In addition, relative energies of these metalloborospherenes suggest that Na and K atoms favor exohedral configuration. Importantly, doping of metal atom can modify the stabilities of B44 with different structures, which provides a possible route to produce stable boron clusters or metalloborospherenes. The calculated results suggest that B44 tends to get electrons from the doped metal. Metalloborospherenes MB44‑ are characterized as charge-transfer complexes (M2+B442‑), where B44 tends to get two electrons from the extra electron and the doped metal, resulting in similar features with anionic B442‑. In addition, doping of metal atom can change the spectral features, such as blueshift or redshift and weakening or strengthening of characteristic peaks, since the extra metal atom can modify the electronic structure. The calculated spectra are readily compared with future spectroscopy measurements and can be used as fingerprints to identify B44‑ and metalloborospherenes.
Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Qin, Shuijie
2017-01-01
Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to study the stabilities, photoelectron, infrared, Raman and electronic absorption spectra of borospherene B44− and metalloborospherenes MB440/− (M = Li, Na, and K). It is found that all atoms can form stable exohedral metalloborospherenes M&B440/−, whereas only Na and K atoms can be stably encapsulated inside B440/− cage. In addition, relative energies of these metalloborospherenes suggest that Na and K atoms favor exohedral configuration. Importantly, doping of metal atom can modify the stabilities of B44 with different structures, which provides a possible route to produce stable boron clusters or metalloborospherenes. The calculated results suggest that B44 tends to get electrons from the doped metal. Metalloborospherenes MB44− are characterized as charge-transfer complexes (M2+B442−), where B44 tends to get two electrons from the extra electron and the doped metal, resulting in similar features with anionic B442−. In addition, doping of metal atom can change the spectral features, such as blueshift or redshift and weakening or strengthening of characteristic peaks, since the extra metal atom can modify the electronic structure. The calculated spectra are readily compared with future spectroscopy measurements and can be used as fingerprints to identify B44− and metalloborospherenes. PMID:28071694
Apparatus for producing carbon-coated nanoparticles and carbon nanospheres
Energy Technology Data Exchange (ETDEWEB)
Perry, W. Lee; Weigle, John C.; Phillips, Jonathan
2015-10-20
An apparatus for producing carbon-coated nano- or micron-scale particles comprising a container for entraining particles in an aerosol gas, providing an inlet for carbon-containing gas, providing an inlet for plasma gas, a proximate torch for mixing the aerosol gas, the carbon-containing gas, and the plasma gas, bombarding the mixed gases with microwaves, and providing a collection device for gathering the resulting carbon-coated nano- or micron-scale particles. Also disclosed is a method and apparatus for making hollow carbon nano- or micro-scale spheres.
Tai, Yu-Chong (Inventor); Liger, Matthieu (Inventor); Harder, Theodore (Inventor); Konishi, Satoshi (Inventor); Miserendino, Scott (Inventor)
2010-01-01
A method of making carbon thin films comprises depositing a catalyst on a substrate, depositing a hydrocarbon in contact with the catalyst and pyrolyzing the hydrocarbon. A method of controlling a carbon thin film density comprises etching a cavity into a substrate, depositing a hydrocarbon into the cavity, and pyrolyzing the hydrocarbon while in the cavity to form a carbon thin film. Controlling a carbon thin film density is achieved by changing the volume of the cavity. Methods of making carbon containing patterned structures are also provided. Carbon thin films and carbon containing patterned structures can be used in NEMS, MEMS, liquid chromatography, and sensor devices.
Facile synthesis and regeneration of Mg(BH4)2 by high energy reactive ball milling of MgB2.
Gupta, Shalabh; Hlova, Ihor Z; Kobayashi, Takeshi; Denys, Roman V; Chen, Fu; Zavaliy, Ihor Y; Pruski, Marek; Pecharsky, Vitalij K
2013-01-28
We report direct hydrogenation of MgB(2) in a planetary ball mill. Magnesium borohydride, Mg(BH(4))(2), and various polyhedral borane anion salts have been synthesized at pressures between 50 and 350 bar H(2) without the need for subsequent isothermal hydrogenation at elevated temperature and pressure. The obtained products release ∼4 wt% H(2) below 390 °C, and a major portion of Mg(BH(4))(2) transforms back to MgB(2) at around 300 °C, demonstrating the possibility of reversible hydrogen storage in an Mg(BH(4))(2)-MgB(2) system.
Immersed surfaces in the modular orbifold
Calegari, Danny
2010-01-01
A hyperbolic conjugacy class in the modular group PSL(2,Z) corresponds to a closed geodesic in the modular orbifold. Some of these geodesics virtually bound immersed surfaces, and some do not; the distinction is related to the polyhedral structure in the unit ball of the stable commutator length norm. We prove the following stability theorem: for every hyperbolic element of the modular group, the product of this element with a sufficiently large power of a parabolic element is represented by a geodesic that virtually bounds an immersed surface.
Jiang, Caigui
2014-09-01
This paper builds on recent progress in computing with geometric constraints, which is particularly relevant to architectural geometry. Not only do various kinds of meshes with additional properties (like planar faces, or with equilibrium forces in their edges) become available for interactive geometric modeling, but so do other arrangements of geometric primitives, like honeycomb structures. The latter constitute an important class of geometric objects, with relations to “Lobel” meshes, and to freeform polyhedral patterns. Such patterns are particularly interesting and pose research problems which go beyond what is known for meshes, e.g. with regard to their computing, their flexibility, and the assessment of their fairness.
Algebraic Systems Biology: A Case Study for the Wnt Pathway.
Gross, Elizabeth; Harrington, Heather A; Rosen, Zvi; Sturmfels, Bernd
2016-01-01
Steady-state analysis of dynamical systems for biological networks gives rise to algebraic varieties in high-dimensional spaces whose study is of interest in their own right. We demonstrate this for the shuttle model of the Wnt signaling pathway. Here, the variety is described by a polynomial system in 19 unknowns and 36 parameters. It has degree 9 over the parameter space. This case study explores multistationarity, model comparison, dynamics within regions of the state space, identifiability, and parameter estimation, from a geometric point of view. We employ current methods from computational algebraic geometry, polyhedral geometry, and combinatorics.
Recovering an electromagnetic obstacle by a few phaseless backscattering measurements
Li, Jingzhi; Liu, Hongyu; Wang, Yuliang
2017-03-01
We consider the electromagnetic scattering from a convex polyhedral PEC or PMC obstacle due to a time-harmonic incident plane wave. It is shown that the modulus of the far-field pattern in the backscattering aperture possesses a certain local maximum behavior. Using the local maximum indicating phenomena, one can determine the exterior unit normal directions, as well as the face areas, of the front faces of the obstacle. Then we propose a recovery scheme of reconstructing the obstacle by phaseless backscattering measurements. This work significantly extends our recent study in Li and Liu (2014 preprint) from two dimensions and acoustic scattering to the more challenging three dimensions and electromagnetic scattering.
da Silva, A Cannas; Pires, A R
2009-01-01
An origami manifold is a manifold equipped with a closed 2-form which is symplectic except on a hypersurface where it is like the pullback of a symplectic form by a folding map and its kernel defines a circle fibration. We can move back and forth between origami and symplectic manifolds using cutting (unfolding) and radial blow-up (folding), modulo compatibility conditions. We prove an origami convexity theorem for hamiltonian torus actions, classify toric origami manifolds by polyhedral objects resembling paper origami and discuss examples. We also prove a cobordism result and some of its classical consequences, and compute the cohomology of a special class of origami manifolds.
Solouk, Atefeh; Cousins, Brian G; Mirzadeh, Hamid; Seifalian, Alexander M
2011-01-01
Surface modification using plasma processing can significantly change the chemical and physical characteristics of biomaterial surfaces. When used in combination with additional modification techniques such as direct chemical or biochemical methods, it can produce novel biomaterial surfaces, which are anticoagulant, bioactive, and biomimetic in nature. This article reviews recent advances in improving hemocompatibility of biomaterials by plasma surface modification (PSM). The focus of this review is on PSM of the most commonly used polymers for vascular prostheses such as expanded polytetrafluoroethylene (PTFE), polyethylene terephthalate (Dacron(®) ), and next generation of biomaterials, including polyhedral oligomeric silsesquioxane nanocomposite.
Chitsazi, Mohammad Reza; Korbekandi, Hassan; Asghari, Gholamreza; Bahri Najafi, Rahim; Badii, Akbar; Iravani, Siavash
2016-01-01
The objectives were to study the potential of Pulicaria gnaphalodes (Vent.) Boiss. aerial parts in production of nanoparticles and the effect of the extraction solvent on the produced nanoparticles. Methanol and dichloromethane extracts were prepared by percolation of the plant powder. Both the extracts of P. gnaphalodes (Vent.) Boiss. successfully produced small and polydispersed nanoparticles with low aggregates in early hours of the biotransformation. Methanol extract produced spherical and many single nanoparticles, whereas dichloromethane produced porous polyhedral and more aggregated nanoparticles. Methanol extract of this plant seems to be quiet useful for industrial scale production of nanoparticles.
On the convex hull of 3-cycles of the complete graph
Directory of Open Access Journals (Sweden)
Kovalev Michel
2003-01-01
Full Text Available Let Kn be the complete undirected graph with n vertices. A 3-cycle is a cycle consisting of 3 edges. The 3-cycle polytope is defined as the convex hull of the incidence vectors of all 3-cycles in Kn. In this paper, we present a polyhedral analysis of the 3-cycle polytope. In particular, we give several classes of facet defining inequalities of this polytope and we prove that the separation problem associated to one of these classes of inequalities is NP-complete. Finally, it is proved that the 3-cycle polytope is a 2-neighborly polytope.
Heckbert, Paul S
1994-01-01
Graphics Gems IV contains practical techniques for 2D and 3D modeling, animation, rendering, and image processing. The book presents articles on polygons and polyhedral; a mix of formulas, optimized algorithms, and tutorial information on the geometry of 2D, 3D, and n-D space; transformations; and parametric curves and surfaces. The text also includes articles on ray tracing; shading 3D models; and frame buffer techniques. Articles on image processing; algorithms for graphical layout; basic interpolation methods; and subroutine libraries for vector and matrix algebra are also demonstrated. Com
One cutting plane algorithm using auxiliary functions
Zabotin, I. Ya; Kazaeva, K. E.
2016-11-01
We propose an algorithm for solving a convex programming problem from the class of cutting methods. The algorithm is characterized by the construction of approximations using some auxiliary functions, instead of the objective function. Each auxiliary function bases on the exterior penalty function. In proposed algorithm the admissible set and the epigraph of each auxiliary function are embedded into polyhedral sets. In connection with the above, the iteration points are found by solving linear programming problems. We discuss the implementation of the algorithm and prove its convergence.
LDRD final report on polyphosphaacetylenes, new hybrid conducting organic-inorganic materials
Energy Technology Data Exchange (ETDEWEB)
Jamison, G.M.; Loy, D.A.; Saunders, R.S.; Alam, T.M. [Sandia National Labs., Albuquerque, NM (United States). Properties of Organic Materials Dept.
1996-06-01
Thermal, electrochemical and transition metal mediated reactions of phosphaacetylene monomers were conducted in attempts to form novel polyphosphaacetylenes as a new class of potentially electrically conducting polymers. Molecular modeling was used to simulate the molecular conformations of optimized, isolated oligomers to identify the proper monomeric repeat units for highly conjugated molecules. Electrodeposition of suitable monomers led to low molecular weight oligomers. Thermal polymerization of phosphaacetylene monomers bearing aromatic substituents ed to the formation of polyhedral cage oligomers. Under metathesis polymerization conditions the phosphaacetylene monomers form unique complexes via an unprecedented sequence of intermediates which suggest that metathesis to linear oligomers is achievable. Conductivity measurements on electrodeposited oligomers indicate modest electrical conductivity.
Differential thermal analysis of Al[sub 8]FeMnSi[sub 2] intermetallic phase particles
Energy Technology Data Exchange (ETDEWEB)
Flores-Valdes, A.; Pech-Canul, M.I.; Mendez-Nonell, M.; Sukiennik, M. (Unidad Saltillo (Mexico). Centro de Investigacion y de Estudios Avanzados del IPN)
1994-02-15
This paper is concerned with the use of differential thermal analysis to determine melting point, enthalpy and entropy of fusion of the Al[sub 8]FeMnSi[sub 2] intermetallic phase, currently present in Al-Si-Fe-Mn alloys as polyhedral precipitates. The procedure includes the evaluation of the enthalpy from measurements of the area under the peak of transformation on melting. The particular of this phase were obtained through preferential chemical dissolution of the matrix from several Al-Si-Fe-Mn alloys, as was discussed in a previous work.
Mimetic Finite Differences for Flow in Fractures from Microseismic Data
Al-Hinai, Omar
2015-01-01
We present a method for porous media flow in the presence of complex fracture networks. The approach uses the Mimetic Finite Difference method (MFD) and takes advantage of MFD\\'s ability to solve over a general set of polyhedral cells. This flexibility is used to mesh fracture intersections in two and three-dimensional settings without creating small cells at the intersection point. We also demonstrate how to use general polyhedra for embedding fracture boundaries in the reservoir domain. The target application is representing fracture networks inferred from microseismic analysis.
Self-folding devices and materials for biomedical applications.
Randall, Christina L; Gultepe, Evin; Gracias, David H
2012-03-01
Because the native cellular environment is 3D, there is a need to extend planar, micro- and nanostructured biomedical devices to the third dimension. Self-folding methods can extend the precision of planar lithographic patterning into the third dimension and create reconfigurable structures that fold or unfold in response to specific environmental cues. Here, we review the use of hinge-based self-folding methods in the creation of functional 3D biomedical devices including precisely patterned nano- to centimeter scale polyhedral containers, scaffolds for cell culture and reconfigurable surgical tools such as grippers that respond autonomously to specific chemicals.
Parallel and distributed computation for fault-tolerant object recognition
Wechsler, Harry
1988-01-01
The distributed associative memory (DAM) model is suggested for distributed and fault-tolerant computation as it relates to object recognition tasks. The fault-tolerance is with respect to geometrical distortions (scale and rotation), noisy inputs, occulsion/overlap, and memory faults. An experimental system was developed for fault-tolerant structure recognition which shows the feasibility of such an approach. The approach is futher extended to the problem of multisensory data integration and applied successfully to the recognition of colored polyhedral objects.
Strategy-Proof Assignment Of Multiple Resources
DEFF Research Database (Denmark)
Erlanson, Albin; Szwagrzak, Karol
2015-01-01
We examine the strategy-proof allocation of multiple resources; an application is the assignment of packages of tasks, workloads, and compensations among the members of an organization. In the domain of multidimensional single-peaked preferences, we find that any allocation mechanism obtained...... by maximizing a separably concave function over a polyhedral extension of the set of Pareto-efficient allocations is strategy-proof. Moreover, these are the only strategy-proof, unanimous, consistent, and resource-monotonic mechanisms. These mechanisms generalize the parametric rationing mechanisms (Young, 1987...
Directory of Open Access Journals (Sweden)
Jícha M.
2013-04-01
Full Text Available The paper deals with instigation of influence of air duct geometry on air jet direction in aircraft cabin ventilated by mixing ventilation. CFD approach was used for investigation and model geometry was based on small aircraft cabin mock-up geometry. Model was also equipped by nine seats and five manikins that represent passengers. The air jet direction was observed for selected ambient environment parameters and several types of air duct geometry and influence of main air duct geometry on jets direction is discussed. The model was created in StarCCM+ ver. 6.04.014 software and polyhedral mesh was used.
Fišer, J.; Jícha, M.
2013-04-01
The paper deals with instigation of influence of air duct geometry on air jet direction in aircraft cabin ventilated by mixing ventilation. CFD approach was used for investigation and model geometry was based on small aircraft cabin mock-up geometry. Model was also equipped by nine seats and five manikins that represent passengers. The air jet direction was observed for selected ambient environment parameters and several types of air duct geometry and influence of main air duct geometry on jets direction is discussed. The model was created in StarCCM+ ver. 6.04.014 software and polyhedral mesh was used.
Feedback control of time-delay systems with bounded control and state
Directory of Open Access Journals (Sweden)
M. Dambrine
1995-01-01
Full Text Available This paper is concerned with the problem of stabilizing linear time-delay systems under state and control linear constraints. For this, necessary and sufficient conditions for a given non-symmetrical polyhedral set to be positively invariant are obtained. Then existence conditions of linear state feedback control law respecting the constraints are established, and a procedure is given in order to calculate such a controller. The paper concerns memoryless controlled systems but the results can be applied to cases of delayed controlled systems. An example is given.
Energy Technology Data Exchange (ETDEWEB)
La Iglesia, A.
2009-07-01
Using the polyhedral units model of Hazen and employing a method of least-squares, the contribution of nineteen constituent units to the free energy and fifteen units to the enthalpy, at 298 K and 1 bar of pressure, have been calculated for mineral phosphates. The contribution of these constituent units to the free energy at higher temperatures has also been calculated. From these data we can estimate the thermodynamic properties of phosphates by summing the contribution of the distinct units, with more accuracy than the methods published up until now. (Author) 36 refs.
Energy Technology Data Exchange (ETDEWEB)
Vilches, J.; Lopez, A.; Martinez, M.C.; Gomez, J.; Barbera, J.
This paper discusses the value of scanning electron microscopy (SEM) and x-ray microanalysis in the classification of craniopharyngiomas. This neoplasm shows epithelial nest, cords of cuboid cells, foci of squamous metaplasia, and microcystic degeneration. SEM reveals that the epithelial cysts are lined with elongated cells that possess numerous microvilli and blebs and that some cysts are lined with polyhedral cells. The microvilli are interpreted as characteristic of the fast growing craniopharyngiomas. A microanalytical study of the calcified areas reveals the presence of magnesium, phosphorus, and calcium.
New Facets and a Branch-and-Cut Algorithm for the Weighted Clique Problem
DEFF Research Database (Denmark)
Sørensen, Michael Malmros
2001-01-01
We consider a polyhedral approach to the weighted maximal b-clique problem. Given a node- and edge-weighted complete graph the problem is to find a complete subgraph (clique) with no more than b nodes such that the sum of the weights of all nodes and edges in the clique is maximal. We introduce...... four new classes of facet defining inequalities for the associated b-clique polytope. One of these inequality classes constitutes a generalization of the well known tree inequalities; the other classes are associated with multistars. We utilize these inequality classes together with other classes...
New facets and a branch-and-cut algorithm for the weighted clique problem
DEFF Research Database (Denmark)
Sørensen, Michael Malmros
2004-01-01
We consider a polyhedral approach to the weighted maximal b-clique problem. Given a node- and edge-weighted complete graph the problem is to find a complete subgraph (clique) with no more than b nodes such that the sum of the weights of all nodes and edges in the clique is maximal. We introduce...... four new classes of facet defining inequalities for the associated b-clique polytope. One of these inequality classes constitutes a generalization of the well known tree inequalities; the other classes are associated with multistars. We use these inequalities together with other classes of facet...
Design of Cu8Zr5-based bulk metallic glasses
DEFF Research Database (Denmark)
Yang, L.; Xia, J.H.; Wang, Q.;
2006-01-01
Basic polyhedral clusters have been derived from intermetallic compounds at near-eutectic composition by considering a dense packing and random arrangement of atoms at shell sites. Using such building units, bulk metallic glasses can be formed. This strategy was verified in the Cu-Zr binary syste.......382)(100-x)Nb-x, where x=1.5 and 2.5 at. %, and (Cu0.618Zr0.382)(98)Sn-2. The present results may open a route to prepare amorphous alloys with improved glass forming ability....
Zhao, Liang; Mak, Thomas C W
2005-11-01
New Agn subset C2-R-C2 supersetAgn (R = p-, m-, o-C6H4; n = 4, 5) supramolecular synthons have been explored in the coordination network assembly of silver(I) complexes of the isomeric phenylenediethynides. An unprecedented mu5-eta1-coordination mode for the ethynide moiety and a mixed mu4,mu5-coordination mode for the o-phenylenediethynide group are observed, providing a rationale for the abundant occurrence of C2@Agn (n polyhedral cages in double and multiple salts of silver acetylenediide.
Harmonics on the factored three-sphere and the Hopf map
Dowker, J S
2009-01-01
Laplacian eigenmodes on homogeneous Clifford-Klein factors of the three-sphere are obtained as pullbacks of harmonics on the orbifolded two-sphere using the Hopf map. A method of obtaining these polyhedral harmonics using binary invariants is presented which has computational advantages over those based on projection techniques, or those using invariants constructed in terms of Cartesian coordinates. In addition, modes transforming according to the irreps of the deck group are found in easy fashion using the covariants already conveniently calculated by Desmier and Sharp.
Production of carbon nanotubes
Journet, C.; Bernier, P.
Carbon nanostructures such as single-walled and multi-walled nanotubes (SWNTs and MWNTs) or graphitic polyhedral nanoparticles can be produced using various methods. Most of them are based on the sublimation of carbon under an inert atmosphere, such as the electric arc discharge process, the laser ablation method, or the solar technique. But chemical methods can also be used to synthesize these kinds of carbon materials: the catalytic decomposition of hydrocarbons, the production by electrolysis, the heat treatment of a polymer, the low temperature solid pyrolysis, or the in situ catalysis.
Central Configurations of the Five-Body Problem with Equal Masses
Lee, Tsung-Lin
2009-01-01
In this paper we present a complete classification of the isolated central configurations of the five-body problem with equal masses. This is accomplished by using the polyhedral homotopy method to approximate all the isolated solutions of the Albouy-Chenciner equations. The existence of exact solutions, in a neighborhood of the approximated ones, is then verified using the Krawczyk method. Although the Albouy-Chenciner equations for the five-body problem are huge, it is possible to solve them in a reasonable amount of time.
Shape reconstruction and object recognition using angles in an image
Fukada, Youji
1991-02-01
This paper describes an algorithm which recovers 6 degrees of freedom ( that is rotational and translational matrices R and T ) of polyhedral objects using L-corners in a monocular image. First the gradients of the cirtain object''s faces are determined using the constraints derived from angles of L-corners. R accompanied by the object is then determined. Second a constraint concerning T is derived from a junction point of a Lcorner. After that T is determined using a set of constraints derived from the L-corners that contributed to the determination of R. By assembling only those L-corners the cirtain object is recognized.
Nanotechnology and bio-functionalisation for peripheral nerve regeneration
Institute of Scientific and Technical Information of China (English)
Tina Sedaghati; Alexander M Seifalian
2015-01-01
There is a high clinical demand for new smart biomaterials, which stimulate neuronal cell pro-liferation, migration and increase cell-material interaction to facilitate nerve regeneration across these critical-sized defects. This article brielfy reviews several up-to-date published studies using Arginine-Glycine-Aspartic acid peptide sequence, nanocomposite based on polyhedral oligo-meric silsesquioxane nanoparticle and nanoifbrous scaffolds as promising strategies to enhance peripheral nerve regeneration by inlfuencing cellular behaviour such as attachment, spreading and proliferation. The aim is to establish the potent manipulations, which are simple and easy to employ in the clinical conditions for nerve regeneration and repair.
Diagonalization of the symmetrized discrete i th right shift operator
Fuentes, Marc
2007-01-01
In this paper, we consider the symmetric part of the so-called ith right shift operator. We determine its eigenvalues as also the associated eigenvectors in a complete and closed form. The proposed proof is elementary, using only basical skills such as Trigonometry, Arithmetic and Linear algebra. The first section is devoted to the introduction of the tackled problem. Second and third parts contain almost all the ?technical? stuff of the proofE Afterwards, we continue with the end of the proof, provide a graphical illustration of the results, as well as an application on the polyhedral ?sandwiching? of a special compact of arising in Signal theory.
The Galerkin finite element method for a multi-term time-fractional diffusion equation
Jin, Bangti
2015-01-01
© 2014 The Authors. We consider the initial/boundary value problem for a diffusion equation involving multiple time-fractional derivatives on a bounded convex polyhedral domain. We analyze a space semidiscrete scheme based on the standard Galerkin finite element method using continuous piecewise linear functions. Nearly optimal error estimates for both cases of initial data and inhomogeneous term are derived, which cover both smooth and nonsmooth data. Further we develop a fully discrete scheme based on a finite difference discretization of the time-fractional derivatives, and discuss its stability and error estimate. Extensive numerical experiments for one- and two-dimensional problems confirm the theoretical convergence rates.
Tóth, L Fejes; Ulam, S; Stark, M
1964-01-01
Regular Figures concerns the systematology and genetics of regular figures. The first part of the book deals with the classical theory of the regular figures. This topic includes description of plane ornaments, spherical arrangements, hyperbolic tessellations, polyhedral, and regular polytopes. The problem of geometry of the sphere and the two-dimensional hyperbolic space are considered. Classical theory is explained as describing all possible symmetrical groupings in different spaces of constant curvature. The second part deals with the genetics of the regular figures and the inequalities fo
Rawn, C.J.; Rondinone, A.J.; Chakoumakos, B.C.; Circone, S.; Stern, L.A.; Kirby, S.H.; Ishii, Y.
2003-01-01
Neutron powder diffraction data confirm that hydrate samples synthesized with propane crystallize as structure type II hydrate. The structure has been modeled using rigid-body constraints to describe C3H8 molecules located in the eight larger polyhedral cavities of a deuterated host lattice. Data were collected at 12, 40, 100, 130, 160, 190, 220, and 250 K and used to calculate the thermal expansivity from the temperature dependence of the lattice parameters. The data collected allowed for full structural refinement of atomic coordinates and the atomic-displacement parameters.
Ovarian interstitial cell tumor in a South American sea lion (Otaria flavescens).
Biancani, Barbara; Lacave, Geraldine; Magi, Gian Enrico; Rossi, Giacomo
2010-07-01
A case of an ovarian tumor is reported in an 8-yr-old South American sea lion (Otaria flavescens) kept in a marine park in Malta (35.57 degrees N, 14.25 degrees E). The neoplasm was a solid mass of dense sheets and nests of round to polyhedral, irregularly shaped cells with abundant, finely vacuolated cytoplasm. The nuclei were uniformly small and round to oval. The supporting stroma contained thecal cells. The tumor cells were positive for positive inhibin and vimentin and focally positive for cytokeratin by immunohistochemistry. The neoplasm was diagnosed as an ovarian sex cord-stromal tumor, specifically an interstitial cell tumor.
Geometrical Inverse Preconditioning for Symmetric Positive Definite Matrices
Directory of Open Access Journals (Sweden)
Jean-Paul Chehab
2016-07-01
Full Text Available We focus on inverse preconditioners based on minimizing F ( X = 1 − cos ( X A , I , where X A is the preconditioned matrix and A is symmetric and positive definite. We present and analyze gradient-type methods to minimize F ( X on a suitable compact set. For this, we use the geometrical properties of the non-polyhedral cone of symmetric and positive definite matrices, and also the special properties of F ( X on the feasible set. Preliminary and encouraging numerical results are also presented in which dense and sparse approximations are included.
A Simplex-Like Algorithm for Fisher Markets
Adsul, Bharat; Babu, Ch. Sobhan; Garg, Jugal; Mehta, Ruta; Sohoni, Milind
We propose a new convex optimization formulation for the Fisher market problem with linear utilities. Like the Eisenberg-Gale formulation, the set of feasible points is a polyhedral convex set while the cost function is non-linear; however, unlike that, the optimum is always attained at a vertex of this polytope. The convex cost function depends only on the initial endowments of the buyers. This formulation yields an easy simplex-like pivoting algorithm which is provably strongly polynomial for many special cases.
Mobile robots III; Proceedings of the Meeting, Cambridge, MA, Nov. 10, 11, 1988
Energy Technology Data Exchange (ETDEWEB)
Wolfe, W.J.
1989-01-01
Topics discussed include path planning, terrain classification, planetary rovers, navigation, architecture and control, three-dimensional sensing, and behavior specification. Particular papers are presented on a minimum path algorithm among three-dimensional polyhedral objects, parallel off-road perception processing on the autonomous land vehicle, hazard avoidance for a Mars rover, color vision for road following, a pipeline architecture for near real-time stereo range detection, a computational structure for enforcing reactive behavior in a mobile robot, and homeostatic control for a mobile robot.
Lee, Hye-In; Kim, Young-Jin
2016-06-01
Protoporphyrin IX (PpIX) has wide applications in photodynamic diagnosis and photodynamic therapy (PDT) in many human diseases. However, poor water solubility and cancer cell localization limit its direct application for PDT. We improved the water-solubility and cellular internalization of PpIX to enhance PDT efficacy by developing biocompatible PpIX/linolenic acid-conjugated polyhedral oligomeric silsesquioxane (PPLA) nanohybrids. The resulting PPLA nanohybrids exhibited a quasi-spherical shape with a size of gastric cancer cells. These results imply that the PPLA nanohybrid system may be applicable in PDT.
Bioenergy Plants: Hopes, Concerns and Prospectives
Institute of Scientific and Technical Information of China (English)
Martin A.J.Parry; Hai-Chun Jing
2011-01-01
@@ There are major concerns over both the security of energy supplies (declining supplies and political control) and the en-vironmental costs associated with energy generation and use.The global consumption of carbon-containing fossil fuels for heat, electricity, transport and the manufacture of chemicals is not sustainable.
Lithographically defined microporous carbon-composite structures
Energy Technology Data Exchange (ETDEWEB)
Burckel, David Bruce; Washburn, Cody M.; Lambert, Timothy N.; Finnegan, Patrick Sean; Wheeler, David R.
2016-12-06
A microporous carbon scaffold is produced by lithographically patterning a carbon-containing photoresist, followed by pyrolysis of the developed resist structure. Prior to exposure, the photoresist is loaded with a nanoparticulate material. After pyrolysis, the nanonparticulate material is dispersed in, and intimately mixed with, the carbonaceous material of the scaffold, thereby yielding a carbon composite structure.
MPPA-SSI12 automated module facility for "liquid" carburizing
Syropyatov, V. Ya.
2011-10-01
An automated module facility of model MPPA-SSi12 for making controlled endothermic furnace atmospheres based on carbon-containing liquids is described. The facility is used for batching and feeding process liquids into carburizing shaft electric furnaces with automatic control of the carbon potential by changing the flow of added air.
Coe, Jotham W; Vetelino, Michael G; Bashore, Crystal G; Wirtz, Michael C; Brooks, Paige R; Arnold, Eric P; Lebel, Lorraine A; Fox, Carol B; Sands, Steven B; Davis, Thomas I; Schulz, David W; Rollema, Hans; Tingley, F David; O'Neill, Brian T
2005-06-15
The preparation and biological activity of analogs of (-)-cytisine, an alpha4beta2 nicotinic receptor partial agonist, are discussed. All-carbon-containing phenyl ring replacements of the pyridone ring system, generated via Heck cyclization protocols, exhibited weaker affinity and lower efficacy partial agonist profiles relative to (-)-cytisine. In vivo, selected compounds exhibit lower efficacy partial agonist profiles than that of (-)-cytisine.
Carbon nanofibers: catalytic synthesis and applications
Jong, K.P. de; Geus, John W.
2001-01-01
Carbon nanofibers (diameter range, 3-100 nm; length range, 1.1-1000 µm) have been known for a long time as a nuisance that often merges during catalythic conversion of carbon-containing gases. The recent outburst of interest in these graphitic materials originates from their potential for unique app
Assessment of full ceramic solid oxide fuel cells based on modified strontium titanates
DEFF Research Database (Denmark)
Holtappels, Peter; Ramos, Tania; Sudireddy, Bhaskar Reddy;
2014-01-01
stimulated the development for full ceramic anodes based on strontium titanates. Furthermore, the Ni-cermet is primarily a hydrogen oxidation electrode and efficiency losses might occur when operating on carbon containing fuels. In the European project SCOTAS-SOFC full ceramic cells comprising CGO...
Micelotta, Elisabetta Rita
2009-01-01
Polycyclic Aromatic Hydrocarbons (PAHs) are one of the most common chemical compounds on Earth. These big molecules are naturally present in crude oil and coal deposits, and are also formed by incomplete combustion of carbon-containing fuels, hence they are found in car exhaust, cigarette smoke and
Protection of porous carbon fuel particles from boudouard corrosion
Energy Technology Data Exchange (ETDEWEB)
Cooper, John F.
2015-05-26
A system for producing energy that includes infusing porous carbon particles produced by pyrolysis of carbon-containing materials with an off-eutectic salt composition thus producing pore-free carbon particles, and reacting the carbon particles with oxygen in a fuel cell according to the reaction C+O.sub.2=CO.sub.2 to produce electrical energy.
40 CFR 98.210 - Definition of the source category.
2010-07-01
... that uses carbonates or carbonate containing minerals that are consumed in the production of cement... technology used to control emissions from stationary fuel combustion equipment. Emissions from carbonates used in sorbent technology are reported under 40 CFR 98, subpart C (Stationary Fuel Combustion Sources)....
Energy Technology Data Exchange (ETDEWEB)
Pool, K.H.; Brimhall, J.L.; Raney, P.J.; Hart, P.E.
1987-01-01
Purpose of this study was to measure the initial wear rates of TiB/sub 2/ carbon-containing cathode materials (TiB/sub 2/-G) under electrolytic conditions. Parameters evaluated included bath ratio, current density, and aluminum pad thickness. In order to measure initial wear rates, the tests were limited to 8 h.
2013-11-01
Carbon-Type Amorphous Material with Metalic and Non-Metalic Constituents Analysis of “Brown Goo” HP Pump Filter Elt . Line Intensity (c/s) Error...Pump Filter FINDING Carbon-containing amorphous material with metals and non-metals contamination Elt . Line Intensity (c/s) Error 2-sig Conc Units...6 4.1 Materials
Morphologically and size uniform monodisperse particles and their shape-directed self-assembly
Collins, Joshua E.; Bell, Howard Y.; Ye, Xingchen; Murray, Christopher Bruce
2015-11-17
Monodisperse particles having: a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology are disclosed. Due to their uniform size and shape, the monodisperse particles self assemble into superlattices. The particles may be luminescent particles such as down-converting phosphor particles and up-converting phosphors. The monodisperse particles of the invention have a rare earth-containing lattice which in one embodiment may be an yttrium-containing lattice or in another may be a lanthanide-containing lattice. The monodisperse particles may have different optical properties based on their composition, their size, and/or their morphology (or shape). Also disclosed is a combination of at least two types of monodisperse particles, where each type is a plurality of monodisperse particles having a single pure crystalline phase of a rare earth-containing lattice, a uniform three-dimensional size, and a uniform polyhedral morphology; and where the types of monodisperse particles differ from one another by composition, by size, or by morphology. In a preferred embodiment, the types of monodisperse particles have the same composition but different morphologies. Methods of making and methods of using the monodisperse particles are disclosed.
Distance-Based Phylogenetic Methods Around a Polytomy.
Davidson, Ruth; Sullivant, Seth
2014-01-01
Distance-based phylogenetic algorithms attempt to solve the NP-hard least-squares phylogeny problem by mapping an arbitrary dissimilarity map representing biological data to a tree metric. The set of all dissimilarity maps is a Euclidean space properly containing the space of all tree metrics as a polyhedral fan. Outputs of distance-based tree reconstruction algorithms such as UPGMA and neighbor-joining are points in the maximal cones in the fan. Tree metrics with polytomies lie at the intersections of maximal cones. A phylogenetic algorithm divides the space of all dissimilarity maps into regions based upon which combinatorial tree is reconstructed by the algorithm. Comparison of phylogenetic methods can be done by comparing the geometry of these regions. We use polyhedral geometry to compare the local nature of the subdivisions induced by least-squares phylogeny, UPGMA, and neighbor-joining when the true tree has a single polytomy with exactly four neighbors. Our results suggest that in some circumstances, UPGMA and neighbor-joining poorly match least-squares phylogeny.
Toxicity effects of water extracts of Holothuria atra Jaeger in mice
Institute of Scientific and Technical Information of China (English)
Ridzwan Bin Hashim; Nurul Alia Azizan; Zaitunnatakin Zamli; Farah Hanis Zulkipli; Nurzafirah Mazlan; Osama Yousef Althunibat
2014-01-01
Objective:To determine lethal median dose (LD50) and histopathological toxicity of water extract of Holothuria atra (H. atra) in mice. Methods: The behavioral changes, mortality and histopathology examination on liver were assessed in mice 14 d after the administration (i.p.) of H. atra water extract. Seven doses (10, 20, 30, 50, 100, 150 and 200 mg/kg) of H. atra were used. The control group was treated with normal saline. Results:In the acute study in mice, the water extracts of H. atra caused dose-dependent general behavior adverse affects and mortality. The main behavioral sign of toxicity was hypoactivity, noticed immediately after administration of the extract which was more obvious at the higher doses and persisted until death. Mortality increased with increasing doses, the calculated LD50 was 41 mg/kg in mice. The liver toxicity was confirmed by histopathological examination, which indicated the presence of abnormal hepatocytes with a distorted shape and undefined cell lining as well as enlarged nuclei in low doses groups. High doses groups indicated a more prominent distortion of the polyhedral hepatocytes with undefined cell lining, massive cytoplasm, pyknotic, karyorhexis and karyolytic nuclei (necrosis of hepatocytes). Control group showed polyhedral hepatocytes with defined cell lining arranged in cords and normal round nuclei, with granular cytoplasm. Conclusions: Because of the relatively low LD50 value in the acute study in mice, it may be concluded that the H. atra water extract is toxic.
Pottmann, Helmut
2015-03-03
This paper is an overview of architectural structures which are either composed of polyhedral cells or closely related to them. We introduce the concept of a support structure of such a polyhedral cell packing. It is formed by planar quads and obtained by connecting corresponding vertices in two combinatorially equivalent meshes whose corresponding edges are coplanar and thus determine planar quads. Since corresponding triangle meshes only yield trivial structures, we focus on support structures associated with quad meshes or hex-dominant meshes. For the quadrilateral case, we provide a short survey of recent research which reveals beautiful relations to discrete differential geometry. Those are essential for successfully initializing numerical optimization schemes for the computation of quad-based support structures. Hex-dominant structures may be designed via Voronoi tessellations, power diagrams, sphere packings and various extensions of these concepts. Apart from the obvious application as load-bearing structures, we illustrate here a new application to shading and indirect lighting. On a higher level, our work emphasizes the interplay between geometry, optimization, statics, and manufacturing, with the overall aim of combining form, function and fabrication into novel integrated design tools.
Ideal structure of icosahedral Al-Cu-Li quasicrystals
Yamamoto, Akiji
1992-03-01
A structure model for the icosahedral Al-Cu-Li quasicrystal has been derived. This is described in six-dimensional space as a six-dimensional crystal, having four kinds of occupation domains with complicated polyhedral shape. A general structure-factor formula is derived for such polyhedral domains, and a simple description of the structure using the site symmetry is proposed. The model gives R factors of 0.076 and 0.085 for recent x-ray and neutron-single-crystal-diffraction data [Boissieu, Janot, Dubois, Audier, and Dubost, J. Phys. 3, 1 (1991)]. The structure consists of a large number of icosahedral clusters and linking atoms joining them. It leads to an ideal cubic R-Al-Cu-Li structure and a large number of other cubic crystals when appropriate phason strains are taken into account. Two structures, the ideal R-Al-Cu-Li structure and a fictitious structure with a period (1+ √5 )/2 times longer, are shown.
Engineered protein nano-compartments for targeted enzyme localization.
Directory of Open Access Journals (Sweden)
Swati Choudhary
Full Text Available Compartmentalized co-localization of enzymes and their substrates represents an attractive approach for multi-enzymatic synthesis in engineered cells and biocatalysis. Sequestration of enzymes and substrates would greatly increase reaction efficiency while also protecting engineered host cells from potentially toxic reaction intermediates. Several bacteria form protein-based polyhedral microcompartments which sequester functionally related enzymes and regulate their access to substrates and other small metabolites. Such bacterial microcompartments may be engineered into protein-based nano-bioreactors, provided that they can be assembled in a non-native host cell, and that heterologous enzymes and substrates can be targeted into the engineered compartments. Here, we report that recombinant expression of Salmonella enterica ethanolamine utilization (eut bacterial microcompartment shell proteins in E. coli results in the formation of polyhedral protein shells. Purified recombinant shells are morphologically similar to the native Eut microcompartments purified from S. enterica. Surprisingly, recombinant expression of only one of the shell proteins (EutS is sufficient and necessary for creating properly delimited compartments. Co-expression with EutS also facilitates the encapsulation of EGFP fused with a putative Eut shell-targeting signal sequence. We also demonstrate the functional localization of a heterologous enzyme (β-galactosidase targeted to the recombinant shells. Together our results provide proof-of-concept for the engineering of protein nano-compartments for biosynthesis and biocatalysis.
Yu, Yue; Zhang, Qingbo; Liu, Bo; Lee, Jim Yang
2010-12-29
The shape-controlled synthesis of noble metal nanocrystals (NCs) bounded by high-index facets is a current research interest because the products have the potential of significantly improving the catalytic performance of NCs in industrially important reactions. This study reports a versatile method for synthesizing polyhedral NCs enclosed by a variety of high-index Pd facets. The method is based on the heteroepitaxial growth of Pd layers on concave trisoctahedral (TOH) gold NC seeds under careful control of the growth kinetics. Polyhedral Au@Pd NCs with three different classes of high-index facets, including concave TOH NCs with {hhl} facets, concave hexoctahedral (HOH) NCs with {hkl} facets, and tetrahexahedral (THH) NCs with {hk0} facets, can be formed in high yield. The Miller indices of NCs are also modifiable, and we have used the THH NCs as a demonstrative example. The catalytic activities of these NCs were evaluated by the structure-sensitive reaction of formic acid electro-oxidation. The results showed that the high-index facets are generally more active than the low-index facets. In summary, a seeded growth process based on concave high-index faceted monometallic TOH NC templates and careful control of the growth kinetics is a simple and effective strategy for the synthesis of noble metal NCs with high-index facets. It also offers tailorability of the surface structure in shape-controlled synthesis.
Endogenous growth of a Miocene submarine dacite cryptodome, Rebun Island, Hokkaido, Japan
Goto, Yoshihiko; McPhie, Jocelyn
1998-09-01
Momo-iwa, Rebun Island, Hokkaido, Japan, is a dacite cryptodome 200-300 m across and 190 m high. The dome is inferred to have intruded wet, poorly consolidated sediment in a shallow marine environment. The internal structure of the dome is concentric, with a massive core, banded rim, and narrow brecciated border, all of which are composed of compositionally uniform feldspar-phyric dacite. Boundaries between each of the zones are distinct but gradational. The massive core consists of homogeneous coherent (unfractured) dacite and is characterized by radial columnar joints 60-200 cm across. The banded rim encircles the massive core and is 40 m wide. It is characterized by large-scale flow banding parallel to the dome surface. The flow banding comprises alternating partly crystalline and more glassy bands 80-150 cm thick. The outermost brecciated border is up to 80 cm thick, and consists of in situ breccia and blocky peperite. The in situ breccia comprises polyhedral dacite clasts 5-20 cm across and a cogenetic granular matrix. The blocky peperite consists of polyhedral dacite clasts 0.5-2 cm across separated by the host sediment (mudstone). The internal structures of the dome suggest endogenous growth involving a continuous magma supply during a single intrusive phase and simple expansion from the interior. Although much larger, the internal structures of Momo-iwa closely resemble those of lobes in subaqueous felsic lobe-hyaloclastite lavas.
Hikosaka, Ryouichi; Nagata, Fukue; Tomita, Masahiro; Kato, Katsuya
2016-10-01
Antibodies have received significant attention for use as antibody drugs, because they bind the objective protein (antigen) via antigen-antibody reactions. Recently, many reports have appeared on various monoclonal antibodies that recognize a single antigen. In this study, monoclonal antibodies are used as adsorbates on mesoporous silica (MPS) for affinity chromatography. MPS has high surface area and large pore volume; moreover, pore diameter, pore structure, and particle morphology are relatively easy to tune by adjusting the conditions of synthesis. The pore structure (two-dimensional (2D) hexagonal and three-dimensional cubic) and particle morphology (spherical and polyhedral) of MPS are optimized for use in a monoclonal antibody/MPS composite. When anti-IgG (one of the monoclonal antibodies) adsorbs on the MPS material and IgG (antigen) binds to anti-IgG/MPS composites, MCM-41p with a 2D-hexagonal pore structure and polyhedral particle morphology has the highest IgG binding efficiency. In addition, the antibody/MPS composites remain stable in chaotropic and low-pH solutions and can be cycled at least five times without decreasing IgG elution. In purification and removal tests, the use of the antibody/MPS composites allows only the objective protein from protein mixtures to be bound and eluted.
Assembly of a 3D Cellular Computer Using Folded E-Blocks
Directory of Open Access Journals (Sweden)
Shivendra Pandey
2016-04-01
Full Text Available The assembly of integrated circuits in three dimensions (3D provides a possible solution to address the ever-increasing demands of modern day electronic devices. It has been suggested that by using the third dimension, devices with high density, defect tolerance, short interconnects and small overall form factors could be created. However, apart from pseudo 3D architecture, such as monolithic integration, die, or wafer stacking, the creation of paradigms to integrate electronic low-complexity cellular building blocks in architecture that has tile space in all three dimensions has remained elusive. Here, we present software and hardware foundations for a truly 3D cellular computational devices that could be realized in practice. The computing architecture relies on the scalable, self-configurable and defect-tolerant cell matrix. The hardware is based on a scalable and manufacturable approach for 3D assembly using folded polyhedral electronic blocks (E-blocks. We created monomers, dimers and 2 × 2 × 2 assemblies of polyhedral E-blocks and verified the computational capabilities by implementing simple logic functions. We further show that 63.2% more compact 3D circuits can be obtained with our design automation tools compared to a 2D architecture. Our results provide a proof-of-concept for a scalable and manufacture-ready process for constructing massive-scale 3D computational devices.
Nguyen, Hoai-Nam
2014-01-01
A comprehensive development of interpolating control, this monograph demonstrates the reduced computational complexity of a ground-breaking technique compared with the established model predictive control. The text deals with the regulation problem for linear, time-invariant, discrete-time uncertain dynamical systems having polyhedral state and control constraints, with and without disturbances, and under state or output feedback. For output feedback a non-minimal state-space representation is used with old inputs and outputs as state variables. Constrained Control of Uncertain, Time-Varying, Discrete-time Systems details interpolating control in both its implicit and explicit forms. In the former at most two linear-programming or one quadratic-programming problem are solved on-line at each sampling instant to yield the value of the control variable. In the latter the control law is shown to be piecewise affine in the state, and so the state space is partitioned into polyhedral cells so that at each sampling ...
Directory of Open Access Journals (Sweden)
Stan Schein
2016-08-01
Full Text Available The Goldberg construction of symmetric cages involves pasting a patch cut out of a regular tiling onto the faces of a Platonic host polyhedron, resulting in a cage with the same symmetry as the host. For example, cutting equilateral triangular patches from a 6.6.6 tiling of hexagons and pasting them onto the full triangular faces of an icosahedron produces icosahedral fullerene cages. Here we show that pasting cutouts from a 6.6.6 tiling onto the full hexagonal and triangular faces of an Archimedean host polyhedron, the truncated tetrahedron, produces two series of tetrahedral (Td fullerene cages. Cages in the first series have 28n2 vertices (n ≥ 1. Cages in the second (leapfrog series have 3 × 28n2. We can transform all of the cages of the first series and the smallest cage of the second series into geometrically convex equilateral polyhedra. With tetrahedral (Td symmetry, these new polyhedra constitute a new class of “convex equilateral polyhedra with polyhedral symmetry”. We also show that none of the other Archimedean polyhedra, six with octahedral symmetry and six with icosahedral, can host full-face cutouts from regular tilings to produce cages with the host’s polyhedral symmetry.
Structure constraints and instability leading to the post-perovskite phase transition of MgSiO 3
Martin, C. David; Parise, John B.
2008-01-01
Recent experience with Rietveld refinement of structural analogues and literature surveys, suggests anion-anion repulsion limits the stability of the perovskite phase, including in the MgSiO 3 perovskite to post-perovskite transition. Assuming rigid octahedral coordination, still to be tested experimentally, the critical point where intra- and inter-octahedral anion-anion distances are equal provides a useful metric for predicting the pressure of the perovskite/post-perovskite transition and the Clapeyron slope of the phase boundary, once pressure and temperature derivatives of relevant structure parameters are known. The inter-octahedral anion-anion distances and the polyhedral volume ratio are rigorously formulated as a function of octahedral rotation in this work, assuming the orthorhombic ( Pbnm) perovskite structure, where regular octahedra share each corner and conform to the in- and anti-phase rotation schemes designated by space group symmetry. These mathematical expressions are consistent with structure data from 70 perovskite-structured materials surveyed in the literature at ambient as well as extreme conditions and define structure constraints, such as the minimum polyhedral volume ratio, which must be reached before the phase transition to the post-perovskite structure-type can proceed. The formalism we present is general for perovskite ( Pbnm) and dependent on the accuracy with which structures can be determined from, sometimes compromised, high pressure diffraction data.
POMSS配位化合物%Synthesis and Application of POMSS
Institute of Scientific and Technical Information of China (English)
李昂; 张春玲; 孙国恩; 牟建新
2012-01-01
The synthesis strategies, physical and chemical properties, as well as applications of polyhedral oligometallasilsesquioxanes（POMSS） have taken a remarkable leap in recent 20 years. It is still one of the research focuses at present. A rich chemistry of POMSS has developed with elements throughout the periodic table, that used widely as catalysts or silica-supported catalyst models and some other functional materials. In this paper, the developments and applications of POMSS are summarized and reviewed, especially for the status quo of incompletely condensed polyhedral oligomeric silsesquioxanes coordination chemistry.%近20年来,聚倍半硅氧烷金属配合物（POMSS）的合成、物理和化学性质以及应用,取得了飞跃式的发展,是当前的研究热点之一。其所包含的配位元素的种类几乎遍布整个元素周期表,并被广泛地应用于催化剂领域和其他功能材料领域。本文根据配位元素的特点对POMSS配合物进行了分类,并对其合成方法、发展及应用情况做了简单总结,最后对POMSS未来的研究前景进行了展望。
Electrochemical Corrosion of Carbon—Containing Refractories
Institute of Scientific and Technical Information of China (English)
CHENZhao－you
1994-01-01
The electrochemical examination on the cor-rosion of carbon or carbon containing refractiories at molten slag-liquid interface has been carried out.The electromotive force(E.M.F)of cells with different molten slags:C|molten slag | Fe at elevated temperatures has been measured by means of potentiometer and it is in the range from 250 to 450mV .It is found that the carbon electrode in these cells is anode and whn a counter E.M.F.is applied externally to the cel,the corrosion of carbon electrode will be sup-pressed entirely.Test results show that the local corrosion of carbon containing refractories at slag-metal interface is mainly caused by the mechanism of electrochemical corrosion.
Directory of Open Access Journals (Sweden)
Alexandr Ivanovich Khanchuk
2016-12-01
Full Text Available The results of the research interaction between ash and slag samples from Vladivostok TPP’s landfills saturated with underburning and ammonium hydrodifluoride were given. It was found out that the reactions of the main components of a concentrate with NH4HF2 are flowing with creation of complex ammonium fluoro-metalate. It is shown that the distribution of REM (rare earth metals between foam and heavier products is going during the flotation process of carbon-containing ash and slag samples without significant concentrating. It is shown that the water leaching of fluoridated product lets transfer silicone, aluminum and iron salts into solution and concentrate rare earth elements in insoluble residue in the form of complex salts of NaLnF4 general formula. We propose a schematic diagram of hydrodifluoride recycling of carbon-containing sample, which provides concentrating of REM with incomplete separation of macro-components.
The discovery of fullerenes in the 1.85 billion-year-old Sudbury meteorite crater
Energy Technology Data Exchange (ETDEWEB)
Becker, L.; Bada, J.L. [Scripps Institution of Oceanography, La Jolla, CA (United States); Winans, R.E.; Hunt, J.E. [Argonne National Lab., IL (United States); Bunch, T.E. [National Aeronautics and Space Administration, Moffett Field, CA (United States). Ames Research Center; French, B.M. [National Aeronautics and Space Administration, Washington, DC (United States)
1996-02-01
Fullerenes (C{sub 60}, C{sub 70}) have been identified by laser time-of-flight and electron-ionization mass spectroscopy in rock samples (black tuff in the Onaping formation) from the crater. They were likely synthesized within the impact plume from carbon contained in the meteorite. The isotopic ratios suggest {sup 13}C enrichment. They are associated with sulfur which may have protected them. This is the largest known deposit of naturally occurring fullerenes.
Formation of a Composite Based on Polyurethane with Carbon Nanotubes and Shungite
Komarov, F. F.; Krivosheev, R. M.; Ksenofontov, M. A.; Koltunovich, T.; Abdullin, Kh. A.; Ostrovskaya, L. E.; Togambaeva, A. K.
2015-03-01
Physicomechanical and electrophysical characteristics of a polyurethane composite doped with carbon-containing materials have been investigated. It has been found that the roughness of the sample's surface and also the porosity increase with the concentration of the dopant. Volt-ampere characteristics of composite materials point to the activated type of conductivity in these materials; however, at a temperature of nearly 340 K, the type of conductivity is changed. Also, the frequency dependence of the conductivity has been established.
A New 5-Phase Equation of State for Carbon
Energy Technology Data Exchange (ETDEWEB)
Coe, Joshua Damon [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division; Gammel, J. Tinka [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Theoretical Division
2016-09-06
We describe the development of SESAME 7835, a new tabular equation of state (EOS) for carbon containing the diamond, bc8, simple cubic, simple hexagonal, and liquid/plasma phases. We compare the EOS against a wide variety of experimental data and simulation results, including static compression, dynamic compression, specific heat, and thermal expansion. To the extent that the reference data agree amongst themselves, the results are satisfactory in all cases.
Impurity-defect structure of anodic aluminum oxide produced by two-sided anodizing in tartaric acid
Chernyakova, K. V.; Vrublevsky, I. A.; Ivanovskaya, M. I.; Kotsikau, D. A.
2012-03-01
Porous aluminum oxide is prepared in a 0.4 M aqueous solution of tartaric acid by two-sided anodizing. Fourier Transform IR spectroscopy (FTIR) data reveal the presence, in the alumina, of unoxidized tartarate ions, as well as products of their partial (radical organic products and CO) and complete (CO2) oxidation. Carboxylate ions and elemental carbon contained in the anodic oxide impart a gray color to the films.
A Nonequilibrium Finite-Rate Carbon Ablation Model for Radiating Earth Re-entry Flows
2015-09-17
for carbon containing environments like Mars and Titan . The CN violet bands were the only atomic or molecular systems considered for the NEQAIR...range of surface pressures and temperatures [78, 124, 83, 82, 58, 100, 77]. Additionally, MacLean [63] developed a tool to compute the composition of an...Intensity Measurements in Simulated Titan Atmospheres. Journal of Thermophysics and Heat Transfer, 24(2):291300, April 2010. 22. Candler, G. V. The
Surface Chemistry and Tribology of Copper Surfaces in Carbon Dioxide and Water Vapor Environments
2011-02-23
progress). Simultaneous XAS and cyclic voltammetry of Cu in bicarbonate solutions under potentiostatic control at the Berkeley Synchrotron facility (Figure...bicarbonate ions that mimic the conditions of the wet brush-rotor contact. Electrochemical control of the surface by cyclic voltammetry makes it...the electrochemical modifications of Cu under potentiostat control and solution pH 3) Determine the loss of mass of Cu when in carbonate containing
A Better Method for Evaluating Heavy Metal Water Pollution
Hering, Janet
2002-01-01
High concentrations of heavy metals, and even trace amounts of some, can be harmful to both plants and animals. The toxicity of heavy metal contamination, however, is highly dependent on the chemical form of the metal in question. Metals that are bound in particles or to organic (carbon-containing) compounds are less toxic than dissolved free ions, less toxic meaning that the metals are less readily available for uptake by marine organisms.
Bioorganic Chemistry. A Natural Reunion of the Physical and Life Sciences
Poulter, C. Dale
2009-01-01
Organic substances were conceived as those found in living organisms. Although the definition was soon broadened to include all carbon-containing compounds, naturally occurring molecules have always held a special fascination for organic chemists. From these beginnings, molecules from nature were indespensible tools as generations of organic chemists developed new techniques for determining structures, analyzed the mechanisms of reactions, explored the effects conformation and stereochemistry...
Gihm, Yong Sik; Kwon, Chang Woo
2017-02-01
Multiple exposures of peperite within the Cretaceous Buan Volcanics, southwest Korea, have been examined in order to determine variations in their textural characteristics and to investigate their mode of formation. Along undulating boundaries between rhyolite (lava flow) and deformed host sediment expressed as a series of load and flame structures, exposures commonly contain two distinct types of peperite. Type-1 peperites are composed mostly of rounded juvenile clasts at their base and polyhedral juvenile clasts at their upper levels, interpreted to have formed via a two-stage process. Firstly, abrasion of juvenile clasts occurred after their fragmentation due to shear stress imparted by the overlying and still-moving lava flow, forming rounded juvenile clasts. Subsequent in situ quenching fragmentation of the lava flow produced clasts with platy to polyhedral shapes immediately after emplacement of the lava flow. Type-2 peperites laterally extend into the interior of featureless rhyolite as layers that decrease in thickness with increasing distance away from the flame zone. These layers exhibit horizontal textural variations, ranging from poorly sorted mixtures of ash- to block-sized angular juvenile clasts in the proximal zone, to closely packed polyhedral and tabular juvenile clasts with jigsaw-crack textures in the middle and distal zones. Type-2 peperite are inferred to have formed due to internal steam explosions that resulted from an expansion of heated pore water (leading to an increase in pore fluid pressure) that had been vertically injected into the interior of the rhyolite from the flame zone. The proximal zone, composed mainly of poorly sorted mixtures of juvenile clasts, represents the explosion sites. Juvenile clasts in the middle and distal zones are interpreted to have formed due to three separate processes: the development of fractures in the rhyolite during the internal steam explosions, injection of the host sediment through the fractures, and
On the optimality of the neighbor-joining algorithm
Directory of Open Access Journals (Sweden)
Pachter Lior
2008-04-01
Full Text Available Abstract The popular neighbor-joining (NJ algorithm used in phylogenetics is a greedy algorithm for finding the balanced minimum evolution (BME tree associated to a dissimilarity map. From this point of view, NJ is "optimal" when the algorithm outputs the tree which minimizes the balanced minimum evolution criterion. We use the fact that the NJ tree topology and the BME tree topology are determined by polyhedral subdivisions of the spaces of dissimilarity maps R+(n2 MathType@MTEF@5@5@+=feaafiart1ev1aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacPC6xNi=xH8viVGI8Gi=hEeeu0xXdbba9frFj0xb9qqpG0dXdb9aspeI8k8fiI+fsY=rqGqVepae9pg0db9vqaiVgFr0xfr=xfr=xc9adbaqaaeGaciGaaiaabeqaaeqabiWaaaGcbaWenfgDOvwBHrxAJfwnHbqeg0uy0HwzTfgDPnwy1aaceaGae83gHi1aa0baaSqaaiabgUcaRaqaamaabmaabaqbaeqabiqaaaqaaiabd6gaUbqaaiabikdaYaaaaiaawIcacaGLPaaaaaaaaa@3BA1@ to study the optimality of the neighbor-joining algorithm. In particular, we investigate and compare the polyhedral subdivisions for n ≤ 8. This requires the measurement of volumes of spherical polytopes in high dimension, which we obtain using a combination of Monte Carlo methods and polyhedral algorithms. Our results include a demonstration that highly unrelated trees can be co-optimal in BME reconstruction, and that NJ regions are not convex. We obtain the l2 radius for neighbor-joining for n = 5 and we conjecture that the ability of the neighbor-joining algorithm to recover the BME tree depends on the diameter of the BME tree.
Effect of Mg substitution on electromagnetic properties of NiCuZn ferrite
Sujatha, Ch.; Venugopal Reddy, K.; Sowri Babu, K.; RamaChandra Reddy, A.; Buchi Suresh, M.; Rao, K. H.
2013-08-01
Mg substituted NiCuZn ferrites were prepared through sol-gel method using polyvinyl alcohol (PVA) as a chelating agent. The samples after annealing at 500 °C to remove PVA were sintered at 950 °C for 1 h. The structural and electromagnetic properties of the samples were investigated. All the samples showed single phase spinel structure with increased lattice constant as a function of Mg concentration. The morphology reveals polyhedral shaped grains with increased grain size as a function of Mg composition. Dielectric parameters showed low values at higher frequencies. The initial permeability increased with Mg substitution in place of Ni in accordance with the microstructure. The samples sintered at low temperature having low dielectric losses and improved permeability along with the high frequency stability of permeability find applications in multilayer chip inductors.
Rotational Brownian Dynamics simulations of clathrin cage formation
Energy Technology Data Exchange (ETDEWEB)
Ilie, Ioana M.; Briels, Wim J. [Computational BioPhysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Otter, Wouter K. den, E-mail: w.k.denotter@utwente.nl [Computational BioPhysics, Faculty of Science and Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Multi Scale Mechanics, Faculty of Engineering Technology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)
2014-08-14
The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assembly dynamics. However, Brownian Dynamics of rotating anisotropic particles gives rise to a number of complications not encountered in translational Brownian Dynamics. We thoroughly test the Rotational Brownian Dynamics scheme proposed by Naess and Elsgaeter [Macromol. Theory Simul. 13, 419 (2004); Naess and Elsgaeter Macromol. Theory Simul. 14, 300 (2005)], confirming its validity. We then apply the algorithm to simulate a patchy particle model of clathrin, a three-legged protein involved in vesicle production from lipid membranes during endocytosis. Using this algorithm we recover time scales for cage assembly comparable to those from experiments. We also briefly discuss the undulatory dynamics of the polyhedral cage.
da Rosa, Marize Raquel Diniz; de Oliveira, James Maxwell Souza; Dias-Ribeiro, Eduardo; Ferreira-Rocha, Julierme; de Barros, Iolanda Maria Cariry Carvalho Lacet; Lopes, Patricia de Medeiros Loureiro
2011-01-01
Calcifying epithelial odontogenic tumor (CEOT) is a rare, locally invasive neoplasm characterized by the presence of amyloid material that can become calcified. It often is found in the posterior region of the mandible. Such tumors in the maxilla and those that invade the maxillary sinus are extremely rare. This article presents the sixth reported clinical case of a CEOT that invaded the maxillary sinus and extended to the interior of the nasal cavity. The tumor had grown toward the sinus roof, but there was no association with an impacted tooth. Histopathologically, the tumor was composed of plates of polyhedral epithelial cells with highly eosinoplilic cytoplasm, nuclear polymorphism, clear-cell contours, and intercellular bridges in fibrous conjunctive tissue. Amorphous eosinophilic material and diverse calcifications permeated the epithelial cells.
Proof Compression and the Mobius PCC Architecture for Embedded Devices
Jensen, Thomas
2009-01-01
The EU Mobius project has been concerned with the security of Java applications, and of mobile devices such as smart phones that execute such applications. In this talk, I'll give a brief overview of the results obtained on on-device checking of various security-related program properties. I'll then describe in more detail how the concept of certified abstract interpretation and abstraction-carrying code can be applied to polyhedral-based analysis of Java byte code in order to verify properties pertaining to the usage of resources of a down-loaded application. Particular emphasis has been on finding ways of reducing the size of the certificates that accompany a piece of code.
Peripheral dentinogenic ghost cell tumor
Directory of Open Access Journals (Sweden)
Sushant S Kamat
2013-01-01
Full Text Available Dentinogenic ghost cell tumors (DGCT are uncommon lesions mainly with rare peripheral types. This report presents a case of peripheral DGCT on the left side of the mandibular alveolar ridge of a heavy smoker, a 68-year-old man, with main presenting feature as a mild pain. Submandibular lymphadenopathy and radiological "saucerization" were evident. Differential diagnosis included fibroma, neurofibroma, peripheral ameloblastoma, peripheral odontogenic fibroma, and peripheral giant cell granuloma. Histologically, ameloblastoma-like epithelial elements were seen in association with grouped ghost cells. Proliferating polyhedral cells and stellate reticulum-like cells with various densities were spread over a wide range of the field. The lesion was curetted and after 2 years of follow up, it did not recur.
Boron-Based (Nano-Materials: Fundamentals and Applications
Directory of Open Access Journals (Sweden)
Umit B. Demirci
2016-09-01
Full Text Available The boron (Z = 5 element is unique. Boron-based (nano-materials are equally unique. Accordingly, the present special issue is dedicated to crystalline boron-based (nano-materials and gathers a series of nine review and research articles dealing with different boron-based compounds. Boranes, borohydrides, polyhedral boranes and carboranes, boronate anions/ligands, boron nitride (hexagonal structure, and elemental boron are considered. Importantly, large sections are dedicated to fundamentals, with a special focus on crystal structures. The application potentials are widely discussed on the basis of the materials’ physical and chemical properties. It stands out that crystalline boron-based (nano-materials have many technological opportunities in fields such as energy storage, gas sorption (depollution, medicine, and optical and electronic devices. The present special issue is further evidence of the wealth of boron science, especially in terms of crystalline (nano-materials.
Three-Dimensional TIN Algorithm for Digital Terrain Modeling%数字地形建模的真三维TIN算法研究
Institute of Scientific and Technical Information of China (English)
朱庆; 张叶廷; 李逢春
2008-01-01
The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrain surface modeling, a new algorithm for the automatic generation of three dimensional triangulated irregular network from a point cloud is proposed. Based on the local topological consistency test, a combined algorithm of constrained 3D Delaunay triangulation and region-growing is extended to ensure topologically correct reconstruction. This paper also introduced an efficient neighboring triangle location method by making full use of the surface normal information. Experimental results prove that this algorithm can efficiently obtain the most reasonable reconstructed mesh surface with arbitrary topology, wherein the automatically reconstructed surface has only small topological difference from the true surface. This algorithm has potential applications to virtual environments, computer vision, and so on.
Thermally stable single-atom platinum-on-ceria catalysts via atom trapping
Energy Technology Data Exchange (ETDEWEB)
Jones, John; Xiong, Haifeng; DelaRiva, Andrew; Peterson, Eric J.; Pham, Hien; Challa, Sivakumar R.; Qi, Gongshin; Oh, Se H.; Wiebenga, Michelle H.; Pereira Hernandez, Xavier I.; Wang, Yong; Datye, Abhaya K.
2016-07-08
Catalysts based on single atoms of scarce precious metals can lead to more efficient use through enhanced reactivity and selectivity. However, single atoms on catalyst supports can be mobile and aggregate into nanoparticles when heated at elevated temperatures. High temperatures are detrimental to catalyst performance unless these mobile atoms can be trapped. We used ceria powders having similar surface areas but different exposed surface facets. When mixed with a platinum/ aluminum oxide catalyst and aged in air at 800°C, the platinum transferred to the ceria and was trapped. Polyhedral ceria and nanorods were more effective than ceria cubes at anchoring the platinum. Performing synthesis at high temperatures ensures that only the most stable binding sites are occupied, yielding a sinter-resistant, atomically dispersed catalyst.
Deza, Michel Marie
2014-01-01
This updated and revised third edition of the leading reference volume on distance metrics includes new items from very active research areas in the use of distances and metrics such as geometry, graph theory, probability theory and analysis. Among the new topics included are, for example, polyhedral metric space, nearness matrix problems, distances between belief assignments, distance-related animal settings, diamond-cutting distances, natural units of length, Heidegger’s de-severance distance, and brain distances. The publication of this volume coincides with intensifying research efforts into metric spaces and especially distance design for applications. Accurate metrics have become a crucial goal in computational biology, image analysis, speech recognition and information retrieval. Leaving aside the practical questions that arise during the selection of a ‘good’ distance function, this work focuses on providing the research community with an invaluable comprehensive listing of the main available di...
Energy Technology Data Exchange (ETDEWEB)
Gomis, O.; Lavina, B.; Rodríguez-Hernández, P.; Muñoz, A.; Errandonea, R.; Errandonea, D.; Bettinelli, M.
2017-01-20
Zircon-type holmium phosphate (HoPO_{4}) and thulium phosphate (TmPO_{4}) have been studied by single-crystal x-ray diffraction and ab initio calculations. We report on the influence of pressure on the crystal structure, and on the elastic and thermodynamic properties. The equation of state for both compounds is accurately determined. We have also obtained information on the polyhedral compressibility which is used to explain the anisotropic axial compressibility and the bulk compressibility. Both compounds are ductile and more resistive to volume compression than to shear deformation at all pressures. Furthermore, the elastic anisotropy is enhanced upon compression. Finally, the calculations indicate that the possible causes that make the zircon structure unstable are mechanical instabilities and the softening of a silent B_{ 1u} mode.
Constructing Extended Formulations from Reflection Relations
Kaibel, Volker
2010-01-01
There are many examples of optimization problems whose associated polyhedra can be described much nicer, and with way less inequalities, by projections of higher dimensional polyhedra than this would be possible in the original space. However, currently not many general tools to construct such extended formulations are available. In this paper, we develop a framework of polyhedral relations that generalizes inductive constructions of extended formulations via projections, and we particularly elaborate on the special case of reflection relations. The latter ones provide polynomial size extended formulations for several polytopes that can be constructed as convex hulls of the unions of (exponentially) many copies of an input polytope obtained via sequences of reflections at hyperplanes. We demonstrate the use of the framework by deriving small extended formulations for the G-permutahedra of all finite reflection groups G (generalizing both Goeman's extended formulation of the permutahedron of size O(n log n) an...
Development of TiO2 and TiO2/Fe-based polymeric nanocomposites by single-step laser pyrolysis
Alexandrescu, R.; Morjan, I.; Dumitrache, F.; Scarisoreanu, M.; Fleaca, C. T.; Morjan, I. P.; Barbut, A. D.; Birjega, R.; Prodan, G.
2013-08-01
Polymer-based nanocomposites provided with inorganic cores were simultaneously manufactured by the single-step laser pyrolysis. A comparative study was performed on two types of nanocomposites, starting from two different systems: TiO2/methyl methacrylate (MMA) and TiO2/Fe/hexamethyl disiloxane (HMDSO) polymer. The reactive mixture contained TiCl4 as Ti precursor and alternatively, Fe(CO)5 (in case of TiO2/Fe mixture). The analytical techniques used for the characterization indicate distinct morphologies for the obtained nanostructures. Polyhedral and almost spherical nanoparticles in a coalescent matrix and very rare individual core-shell particles are noticed for the TiO2/MMA nanocomposites. Instead, nanoparticles presenting core-shell structures were often present in the TiO2/Fe/HMDSO polymeric nanocomposites.
Wu, Yu-Ning; Huang, Rao; Zeng, Xiang-Ming; Wen, Yu-Hua
2016-02-01
Fe nanoparticles have attracted great interest due to their potent magnetic and catalytic properties which strongly depend on the structures and morphologies. In this article, molecular dynamic simulations were employed to investigate structural and thermal stabilities of body-centered cubic Fe nanoparticles with octadecahedral, dodecahedral and spherical shapes. Size-dependent structural stability was firstly examined. Subsequently, computer simulations on the heating process of octadecahedral Fe nanoparticle discovered that {100} facets premelt earlier than {110} ones. As a result, the dodecahedral nanoparticle enclosed by {110} facets exhibited a better thermal stability than the octadecahedral one terminated by both {110} and {100} facets. Nevertheless, it was found that the octadecahedron presented a better shape stability than the dodecahedron by monitoring the shape factor and statistical radius during continuous heating. This study provides a significant insight not only into the experimental preparation of polyhedral Fe nanoparticles but also into their utilization in high-temperature environments.
Indian Academy of Sciences (India)
Anand P Gokula; Rambhatla G Sastry
2015-12-01
In 3D gravity modelling, right rectangular vertical prism model with linear and nonlinear density and polyhedral bodies with linear density variation exist in geophysical literature. Here, we propose a vertical pyramid model with depth-wise parabolic density contrast variation. Initially, we validate our analytic expression against the gravity effect of a right rectangular parallelepiped of constant density contrast. We provide two synthetic examples and a case study for illustrating the effectiveness of our pyramid model in gravity modelling. The included case study of Los Angeles basin, California demonstrates the comparative advantages of our pyramid model over a conventional right rectangular vertical prism model. Our pyramid model could be quite effective as a building block for evaluating the gravity effect of an arbitrarily-shaped 3D or 2.5-D source(s).
Using the Schur Complement to Reduce Runtime in KULL's Magnetic Diffusion Package
Energy Technology Data Exchange (ETDEWEB)
Brunner, T A; Kolev, T V
2010-12-15
Recently a Resistive Magnetohydrodynamics (MHD) package has been added to the KULL code. In order to be compatible with the underlying hydrodynamics algorithm, a new sub-zonal magnetics discretization was developed that supports arbitrary polygonal and polyhedral zones. This flexibility comes at the cost of many more unknowns per zone - approximately ten times more for a hexahedral mesh. We can eliminate some (or all, depending on the dimensionality) of the extra unknowns from the global matrix during assembly by using a Schur complement approach. This trades expensive global work for cache-friendly local work, while still allowing solution for the full system. Significant improvements in the solution time are observed for several test problems.
Using a two-step matrix solution to reduce the run time in KULL's magnetic diffusion package
Energy Technology Data Exchange (ETDEWEB)
Brunner, T A; Kolev, T V
2010-12-17
Recently a Resistive Magnetohydrodynamics (MHD) package has been added to the KULL code. In order to be compatible with the underlying hydrodynamics algorithm, a new sub-zonal magnetics discretization was developed that supports arbitrary polygonal and polyhedral zones. This flexibility comes at the cost of many more unknowns per zone - approximately ten times more for a hexahedral mesh. We can eliminate some (or all, depending on the dimensionality) of the extra unknowns from the global matrix during assembly by using a Schur complement approach. This trades expensive global work for cache-friendly local work, while still allowing solution for the full system. Significant improvements in the solution time are observed for several test problems.
How effective is graphene nanopore geometry on DNA sequencing?
Satarifard, Vahid; Ejtehadi, Mohammad Reza
2015-01-01
In this paper we investigate the effects of graphene nanopore geometry on homopolymer ssDNA pulling process through nanopore using steered molecular dynamic (SMD) simulations. Different graphene nanopores are examined including axially symmetric and asymmetric monolayer graphene nanopores as well as five layer graphene polyhedral crystals (GPC). The pulling force profile, moving fashion of ssDNA, work done in irreversible DNA pulling and orientations of DNA bases near the nanopore are assessed. Simulation results demonstrate the strong effect of the pore shape as well as geometrical symmetry on free energy barrier, orientations and dynamic of DNA translocation through graphene nanopore. Our study proposes that the symmetric circular geometry of monolayer graphene nanopore with high pulling velocity can be used for DNA sequencing.
A Leydig Cell Tumour in a Cat: Histological and Immunohistochemical Findings
Directory of Open Access Journals (Sweden)
Pietro Asproni
2013-01-01
Full Text Available A 13-year-old intact male cat was submitted to castration after the finding of the enlargement of the right testis during the clinical visit. Macroscopically, a nodule of 2 cm of diameter was observed on the cut surface of the enlarged testis. Histologically, the nodule was composed by polyhedral to elongated cells with a large, eosinophilic, and vacuolated cytoplasm and small, round, and dark nuclei. These cells were arranged in acinar structures and solid sheets. The tumour was diagnosed as a Leydig cell tumour. Immunohistochemical analysis revealed that neoplastic cells were vimentin, calretinin, and melan-A positive, whereas a lack of immunoreactivity to cytokeratins confirmed the diagnosis. To our knowledge, this is the first description of a feline Leydig cells tumour without any concurrent testicular neoplasm or in a nonretained testis.
2002-01-01
The experiment is designed to search for highly ionizing particles such as the monopole and the dyon. On the assumption that monopole-antimonopole pairs are produced via a virtual photon intermediate state, and have a mass in the range 0-100~GeV, a direct search for Dirac monopoles using e$^+$e$^-$ annihilation carries a distinct cross-sectional advantage over a search using hadron colliders.\\\\ \\\\ The MODAL detector is formed from Lexan/CR-39 dielectric track detector modules arranged in a polyhedral configuration outside of the vacuum pipe and around the intersection region, as shown on the opposite page. Etchable track detectors are more sensitive to particles at normal incidence, the shape of the detector was chosen with this fact in mind to allow for maximum acceptance of monopoles which leave the beam pipe. These dielectric track detectors will enable us to detect particles with magnetic charge: 20e$<$g$ _{d}
Homotopy theory in toric topology
Grbić, J.; Theriault, S.
2016-04-01
In toric topology one associates with each simplicial complex K on m vertices two key spaces, the Davis-Januszkiewicz space DJK and the moment-angle complex \\mathscr{Z}K, which are related by a homotopy fibration \\mathscr{Z}K\\xrightarrow{\\tilde{w}}DJ_K\\to \\prodi=1m{C}P∞. A great deal of work has been done to study the properties of DJK and \\mathscr{Z}K, their generalizations to polyhedral products, and applications to algebra, combinatorics, and geometry. Chap. 1 surveys some of the main results in the homotopy theory of these spaces. Chap. 2 breaks new ground by initiating a study of the map \\tilde{w}. It is shown that, for a certain family of simplicial complexes K, the map \\tilde{w} is a sum of higher and iterated Whitehead products. Bibliography: 49 titles.
Inorganic materials synthesis in ionic liquids
Directory of Open Access Journals (Sweden)
Christoph Janiak
2014-01-01
Full Text Available The field of "inorganic materials from ionic liquids" (ILs is a young and dynamically growing research area for less than 10 years. The ionothermal synthesis in ILs is often connected with the preparation of nanomaterials, the use of microwave heating and in part also ultrasound. Inorganic material synthesis in ILs allows obtaining phases which are not accessible in conventional organic or aqueous solvents or with standard methods of solid-state chemistry or under such mild conditions. Cases at hand include "ligand-free" metal nanoparticles without added stabilizing capping ligands, inorganic or inorganic-organic hybrid solid-state compounds, large polyhedral clusters and exfoliated graphene from low-temperature synthesis. There are great expectations that ILs open routes towards new, possibly unknown, inorganic materials with advantageous properties that cannot (or only with great difficulty be made via conventional processes.
CFD modeling of pulsatile hemodynamics in the total cavopulmonary connection
Zobaer, S. M. Tareq; Hasan, A. B. M. Toufique
2016-07-01
Total cavopulmonary connection is a blood flow pathway which is created surgically by an operation known as Fontan procedure, performed on children with single ventricle heart defects. Recent studies have shown that the hemodynamics in the connection can be strongly influenced by the presence of pulsatile flow. The aim of this paper is model the pulsatile flow patterns, and to calculate the vorticity field and power losses in an idealized 1.5D offset model of Total Cavopulmonary Connection. A three-dimensional polyhedral mesh was constructed for the numerical simulation. The rheological properties of blood were considered as Newtonian, and flow in the connection was assumed to be laminar. The results demonstrated complex flow patterns in the connection. The outcomes of the simulation showed reasonable agreement with the results available in the literature for a similar model.
Neyrinck, Mark C
2014-01-01
In the current cosmological paradigm, an initially flat three-dimensional manifold that pervades space (the `dark-matter sheet') folds up to build concentrations of mass (galaxies), and a cosmic web between them. Galaxies are nodes, connected by a network of filaments and walls. The folding is in six-dimensional (3D position, plus 3D velocity) phase space. The positions of creases, or caustics, mark the edges of structures. Here, I introduce an origami approximation to cosmological structure formation, in which the dark-matter sheet is not allowed to stretch. But it still produces an idealized cosmic web, with nodes, filaments, walls and voids. In 2D, nodes form in `polygonal collapse' (a twist-fold in origami), necessarily generating filaments simultaneously. In 3D, nodes form in `polyhedral collapse,' simultaneously generating filaments and walls. The masses, spatial arrangement, and angular momenta of nodes and filaments are related in the model. I describe some `tetrahedral collapse', or tetrahedral twist...
Nonlinear programming for classification problems in machine learning
Astorino, Annabella; Fuduli, Antonio; Gaudioso, Manlio
2016-10-01
We survey some nonlinear models for classification problems arising in machine learning. In the last years this field has become more and more relevant due to a lot of practical applications, such as text and web classification, object recognition in machine vision, gene expression profile analysis, DNA and protein analysis, medical diagnosis, customer profiling etc. Classification deals with separation of sets by means of appropriate separation surfaces, which is generally obtained by solving a numerical optimization model. While linear separability is the basis of the most popular approach to classification, the Support Vector Machine (SVM), in the recent years using nonlinear separating surfaces has received some attention. The objective of this work is to recall some of such proposals, mainly in terms of the numerical optimization models. In particular we tackle the polyhedral, ellipsoidal, spherical and conical separation approaches and, for some of them, we also consider the semisupervised versions.
Performance measurement of autonomous grasping software in a simulated orbital environment
Norsworthy, Robert S.
1993-12-01
The EVAHR (extravehicular activity helper/retriever) robot is being developed to perform a variety of navigation and manipulation tasks under astronaut supervision. The EVAHR is equipped with a manipulator and dexterous end-effector for capture and a laser range imager with pan/tilt for target perception. Perception software has been developed to perform target pose estimation, tracking, and motion estimation for rigid, freely rotating, polyhedral objects. Manipulator grasp planning and trajectory control software has also been developed to grasp targets while avoiding collisions. A software simulation of the EVAHR hardware, orbital dynamics, collision detection, and grasp impact dynamics has been developed to test and measure the performance of the integrated software. Performance measurements include grasp success/failure % and time-to-grasp for a variety of targets, initial target states, and simulated pose estimation computing resources.
Crystal Frameworks, Matrix-valued Functions and Rigidity Operators
Power, S C
2011-01-01
An introduction and survey is given of some recent work on the infinitesimal dynamics of \\textit{crystal frameworks}, that is, of translationally periodic discrete bond-node structures in $\\mathbb{R}^d$, for $ d=2,3,...$. We discuss the rigidity matrix, a fundamental object from finite bar-joint framework theory, rigidity operators, matrix-function representations and low energy phonons. These phonons in material crystals, such as quartz and zeolites, are known as rigid unit modes, or RUMs, and are associated with the relative motions of rigid units, such as ~SiO$_4$ tetrahedra in the tetrahedral polyhedral bond-node model for quartz. We also introduce semi-infinite crystal frameworks, bi-crystal frameworks and associated multi-variable Toeplitz operators.
Cobalt Borate Phosphate, Co 3[BPO 7], Synthesis and Characterization
Yilmaz, Aysen; Bu, Xianhui; Kizilyalli, Meral; Kniep, Rudiger; Stucky, Galen D.
2001-02-01
Single crystals of Co3[BPO7] were obtained by boron flux method and characterized by single-crystal diffraction data. The compound crystallizes in the monoclinic space group Cm with a=9.774(2), b=12.688(2), c=4.9057(8) Å, β=119.749(2)°; V=528.20(15) Å3; Z=4. The structure consists of Co in trigonal bipyramids, square pyramids, and distorted octahedra. Polyhedral Co centers, triangular B centers, and tetrahedral P centers are joined together to form a three-dimensional network. The temperature dependence of the magnetic susceptibility of the compound follows the Curie-Weiss law to 30 K. Below this temperature, the magnetic behavior displayed first antiferromagnetic ordering followed by ferrimagnetic coupling at 25 K.
Tribological Performance of Green Lubricant Enhanced by Sulfidation IF-MoS2
Directory of Open Access Journals (Sweden)
Shih-Chen Shi
2016-10-01
Full Text Available Biopolymers reinforced with nanoparticle (NP additives are widely used in tribological applications. In this study, the effect of NP additives on the tribological properties of a green lubricant hydroxypropyl methylcellulose (HPMC composite was investigated. The IF-MoS2 NPs were prepared using the newly developed gas phase sulfidation method to form a multilayered, polyhedral structure. The number of layers and crystallinity of IF-MoS2 increased with sulfidation time and temperature. The dispersity of NPs in the HPMC was investigated using Raman and EDS mapping and showed great uniformity. The use of NPs with HPMC enhanced the tribological performance of the composites as expected. The analysis of the worn surface shows that the friction behavior of the HPMC composite with added NPs is very sensitive to the NP structure. The wear mechanisms vary with NP structure and depend on their lubricating behaviors.
Galerkin FEM for Fractional Order Parabolic Equations with Initial Data in H − s , 0 ≤ s ≤ 1
Jin, Bangti
2013-01-01
We investigate semi-discrete numerical schemes based on the standard Galerkin and lumped mass Galerkin finite element methods for an initial-boundary value problem for homogeneous fractional diffusion problems with non-smooth initial data. We assume that Ω ⊂ ℝd , d = 1,2,3 is a convex polygonal (polyhedral) domain. We theoretically justify optimal order error estimates in L2- and H1-norms for initial data in H-s (Ω), 0 ≤ s ≤ 1. We confirm our theoretical findings with a number of numerical tests that include initial data v being a Dirac δ-function supported on a (d-1)-dimensional manifold. © 2013 Springer-Verlag.
Fabritz, Sebastian; Hörner, Sebastian; Könning, Doreen; Empting, Martin; Reinwarth, Michael; Dietz, Christian; Glotzbach, Bernhard; Frauendorf, Holm; Kolmar, Harald; Avrutina, Olga
2012-08-21
Polyhedral silsesquioxanes are considered valuable conjugation scaffolds. Nevertheless, only a few examples of silsesquioxane-assembled peptide oligomers have been reported to date. We developed a new bioorthogonal cube-octameric silsesquioxane (COSS) scaffold bearing eight aminooxy coupling sites allowing for the conjugation of diverse peptides via oxime ligation. We found that the coupling efficacy depends on the ligand in view of steric hindrance and electrostatic repulsion. For the first time scaffold-based conjugation of cystine-knot miniproteins having a backbone of about thirty amino acids was successfully accomplished without loss of bioactivity. Atomic force microscopy (AFM) provided further knowledge on the size of COSS verifying them as picoscaffolds growing upon bioconjugation to nano-dimension.
Combination of acoustical radiosity and the image source method
DEFF Research Database (Denmark)
Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho;
2013-01-01
A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part....... The model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated...... allows for a dynamic control of the image source production, so that no fixed maximum reflection order is required. The model is optimized for energy impulse response predictions in arbitrary polyhedral rooms. The predictions are validated by comparison with published measured data for a real music...
catena-Poly[bis(μ3-2-methyl-3,5-dinitrobenzoatodisilver(I
Directory of Open Access Journals (Sweden)
Muhammad Danish
2011-07-01
Full Text Available In the title coordination polymer, [Ag2(C8H5N2O62]n, the silver ion is coordinated to three O atoms from three different anions in an approximate T-shape with one bond much longer than the other two. The polyhedral connectivity leads to [100] chains containing alternating centrosymmetric four-rings and eight-rings, with a short d10...d10 Ag...Ag interaction [2.8846 (4 Å] across the latter. The nitro groups are oriented at dihedral angles of 21.2 (5 and 64.3 (3° with respect to the aromatic ring of the ligand. A C—H...O interaction occurs in the crystal.
New Evidence of the Existence of Associative Elements of Water (Clusters
Directory of Open Access Journals (Sweden)
Ignat Ignatov
2016-06-01
Full Text Available In this review it is reported about new data on the structure of water cyclic associates (clusters with general formula (Н2Оn and their charged ionic clusters [(Н2Оn]+ and [(Н2Оn]- by means of computer modelling and spectroscopy methods as 1Н-NMR, IR-spectroscopy, DNES, EXAFS-spectroscopy, X-Ray and neurons diffraction. The computer calculation of polyhedral nanoclusters (Н2Оn, where n = 3–20 are carried out. Based on this data the main structural mathematical models describing water structure (quasicrystalline, continious, fractal, fractal-clathrate have been examined and some important physical characteristics were obtained.
Geometry of polycrystals and microstructure
Directory of Open Access Journals (Sweden)
Ball John M.
2015-01-01
Full Text Available We investigate the geometry of polycrystals, showing that for polycrystals formed of convex grains the interior grains are polyhedral, while for polycrystals with general grain geometry the set of triple points is small. Then we investigate possible martensitic morphologies resulting from intergrain contact. For cubic-totetragonal transformations we show that homogeneous zero-energy microstructures matching a pure dilatation on a grain boundary necessarily involve more than four deformation gradients. We discuss the relevance of this result for observations of microstructures involving second and third-order laminates in various materials. Finally we consider the more specialized situation of bicrystals formed from materials having two martensitic energy wells (such as for orthorhombic to monoclinic transformations, but without any restrictions on the possible microstructure, showing how a generalization of the Hadamard jump condition can be applied at the intergrain boundary to show that a pure phase in either grain is impossible at minimum energy.
New light on Bergman complexes by decomposing matroid types
Dlugosch, Martin
2011-01-01
Bergman complexes are polyhedral complexes associated to matroids. Faces of these complexes are certain matroids, called matroid types, too. In order to understand the structure of these faces we decompose matroid types into direct summands. Ardila/Klivans proved that the Bergman Complex of a matroid can be subdivided into the order complex of the proper part of its lattice of flats. Beyond that Feichtner/Sturmfels showed that the Bergman complex can even be subdivided to the even coarser nested set complex. We will give a much shorter and more general proof of this fact. Generalizing formulas proposed by Ardila/Klivans and Feichtner/Sturmfels for special cases, we present a decomposition into direct sums working for faces of any of these complexes. Additionally we show that it is the finest possible decomposition for faces of the Bergman complex.
Preparation of spherical cobalt carbonate powder with high tap density
Institute of Scientific and Technical Information of China (English)
XIAO Jin; WANG Jian-feng; LIU Yong-dong; LI Jie; LIU Ye-xiang
2006-01-01
Spherical cobalt carbonate with high tap density, good crystallization and uniform particle size was prepared by controlled chemical crystal method using cobalt chloride and ammonium bicarbonate as cobalt source and precipitator. The effects of pH value and reaction time on crystallization and physical properties of cobalt carbonate were studied. The results show that the key factors influencing the preparation process of spherical cobalt carbonate with high tap density and good crystallization are how to control pH value (7.25 ± 0.05) and keep some reaction time (about 10 h). Co4O3 was prepared by sintering spherical morphology CoCO3 samples at varied temperatures. The results show that as the decomposition temperature increases, the as-obtained Co4O3 products with porous structure transform into polyhedral structure with glazed surface, and simultaneously the cobalt content and tap density increase. However, the specific surface area shows a trend of decrease.
Rotational Brownian dynamics simulations of clathrin cage formation.
Ilie, Ioana M; den Otter, Wouter K; Briels, Wim J
2014-08-14
The self-assembly of nearly rigid proteins into ordered aggregates is well suited for modeling by the patchy particle approach. Patchy particles are traditionally simulated using Monte Carlo methods, to study the phase diagram, while Brownian Dynamics simulations would reveal insights into the assembly dynamics. However, Brownian Dynamics of rotating anisotropic particles gives rise to a number of complications not encountered in translational Brownian Dynamics. We thoroughly test the Rotational Brownian Dynamics scheme proposed by Naess and Elsgaeter [Macromol. Theory Simul. 13, 419 (2004); Naess and Elsgaeter Macromol. Theory Simul. 14, 300 (2005)], confirming its validity. We then apply the algorithm to simulate a patchy particle model of clathrin, a three-legged protein involved in vesicle production from lipid membranes during endocytosis. Using this algorithm we recover time scales for cage assembly comparable to those from experiments. We also briefly discuss the undulatory dynamics of the polyhedral cage.
Golden Root Geometry Structuring the Polyhedra and Other Forms Via Plato’s Triangles
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Panagiotis Chr. Stefanides
2014-11-01
Full Text Available Under Golden Root Geometry Structuring the Polyhedra and other Forms Via Plato’s Triangles, we refer to the basic geometric configurations which, as this theory contemplates, are necessary for the progressive mode of formation of the five polyhedral and the geometries involved in their sections and related circles and further to logarithms, via lines, areas and volumes. Basis of all these structures is a very special Scalene Orthogonal Triangle “Plato’s Most Beautiful” [F25], together with his Orthogonal Isosceles one. Structural Forms are identified bearing in common these triangular identities. The particular angle of the Scalene Orthogonal is that whose ArcTan[Θ]=Τ and T = SQR ((SQR. (5 + 1/2.
Self-assembly of molecule-like nanoparticle clusters directed by DNA nanocages.
Li, Yulin; Liu, Zhiyu; Yu, Guimei; Jiang, Wen; Mao, Chengde
2015-04-01
Analogous to the atom-molecule relationship, nanoparticle (NP) clusters (or NP-molecules) with defined compositions and directional bonds could potentially integrate the properties of the component individual NPs, leading to emergent properties. Despite extensive efforts in this direction, no general approach is available for assembly of such NP-molecules. Here we report a general method for building this type of structures by encapsulating NPs into self-assembled DNA polyhedral wireframe nanocages, which serve as guiding agents for further assembly. As a demonstration, a series of NP-molecules have been assembled and validated. Such NP-molecules will, we believe, pave a way to explore new nanomaterials with emergent functions/properties that are related to, but do not belong to the individual component nanoparticles.
Allen, James
2013-01-01
We discuss the construction of ADHM data for Yang-Mills instantons with the symmetries of the regular polytopes in four dimensions. We show that the case of the pentatope can be studied using a simple modification of the approach previously developed for platonic data. For the remaining polytopes, we describe a framework in which the building blocks of the ADHM data correspond to the edges in the extended Dynkin diagram that arises via the McKay correspondence. These building blocks are then assembled into ADHM data through the identification of pairs of commuting representations of the associated binary polyhedral group. We illustrate our procedure by the construction of ADHM data associated with the pentatope, the hyperoctahedron and the 24-cell, with instanton charges 4, 7 and 23, respectively. Furthermore, we show that within our framework these are the lowest possible charges with these symmetries. Plots of topological charge densities are presented that confirm the polytope structure and the relation to...
Platonic topology and CMB fluctuations: Homotopy, anisotropy, and multipole selection rules
Kramer, Peter
2009-01-01
The Cosmic Microwave Background CMB originates from an early stage in the history of the universe. Observed low multipole contributions of CMB fluctuations have motivated the search for selection rules from the underlying topology of 3-space. Everitt (2004) has generated all homotopies for Platonic spherical 3-manifolds by face gluings. We transform the glue generators into isomorphic deck transformations. The deck transformations act on a spherical Platonic 3-manifold as prototile and tile the 3-sphere by its images. A complete set of orthonormal functions on the 3-sphere is spanned by the Wigner harmonic polynomials. For a tetrahedral, two cubic and three octahedral manifolds we construct algebraically linear combinations of Wigner polynomials, invariant under deck transformations and with domain the manifold. We prove boundary conditions on polyhedral faces from homotopy. By algebraic means we pass to a multipole expansion. Assuming random models of the CMB radiation, we derive multipole selection rules, d...
2002-01-01
Discrete geometry investigates combinatorial properties of configurations of geometric objects. To a working mathematician or computer scientist, it offers sophisticated results and techniques of great diversity and it is a foundation for fields such as computational geometry or combinatorial optimization. This book is primarily a textbook introduction to various areas of discrete geometry. In each area, it explains several key results and methods, in an accessible and concrete manner. It also contains more advanced material in separate sections and thus it can serve as a collection of surveys in several narrower subfields. The main topics include: basics on convex sets, convex polytopes, and hyperplane arrangements; combinatorial complexity of geometric configurations; intersection patterns and transversals of convex sets; geometric Ramsey-type results; polyhedral combinatorics and high-dimensional convexity; and lastly, embeddings of finite metric spaces into normed spaces. Jiri Matousek is Professor of Com...
A new method for the size- and shape-controlled synthesis of lead nanostructures
Energy Technology Data Exchange (ETDEWEB)
Nabais, Catarina [Laboratoire de Chimie du Solide Mineral, Nancy University, CNRS, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France); Schneider, Raphael [Departement de Chimie Physique des Reactions, Nancy University, CNRS, 1 Rue Grandville, BP 20451, 54001 Nancy Cedex (France); Bellouard, Christine [Laboratoire de Physique des Materiaux, Nancy University, CNRS, 54506 Vandoeuvre-les-Nancy Cedex (France); Lambert, Jacques [Laboratoire de Chimie Physique et Microbiologie pour l' Environnement, Nancy University, CNRS, 405 Rue de Vandoeuvre, 54506 Villers-les-Nancy Cedex (France); Willmann, Patrick [CNES, 18 avenue E. Belin, 31055 Toulouse Cedex (France); Billaud, Denis, E-mail: denis.billaud@lcsm.uhp-nancy.fr [Laboratoire de Chimie du Solide Mineral, Nancy University, CNRS, BP 239, 54506 Vandoeuvre-les-Nancy Cedex (France)
2009-09-15
Lead(0) nano-/microcrystals with multiform crystal morphologies (separated nanoparticles, elongated nanoparticles, aggregated nanoparticles, polyhedral microcrystals and plate-like whiskers) were successfully synthesized by a facile and effective solution-phase method using lithium or sodium tert-butoxide-activated hydride as reducing and stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy were used to characterize the samples. The experimental results indicated that the weaker t-BuOLi ligand was the more efficient for the growth/nucleation of spherical nanoparticles initially formed into larger particles. The possible mechanisms of Pb(0) microcrystals formation during ligand removal are presented. Additionally, we have investigated the magnetic properties and found that the nanoparticles exhibit a superconducting transition at 7.1 {+-} 0.1 K in agreement with the transition temperature measured in bulk Pb.
Epoxy Resin Composite Based on Functional Hybrid Fillers
Directory of Open Access Journals (Sweden)
Mariusz Oleksy
2014-08-01
Full Text Available A study was carried out involving the filling of epoxy resin (EP with bentonites and silica modified with polyhedral oligomeric silsesquioxane (POSS. The method of homogenization and the type of filler affect the functional and canceling properties of the composites was determined. The filler content ranged from 1.5% to 4.5% by mass. The basic mechanical properties of the hybrid composites were found to improve, and, in particular, there was an increase in tensile strength by 44%, and in Charpy impact strength by 93%. The developed hybrid composites had characteristics typical of polymer nanocomposites modified by clays, with a fine plate morphology of brittle fractures observed by SEM, absence of a plate separation peak in Wide Angles X-ray Scattering (WAXS curves, and an exfoliated structure observed by TEM.
Guts of surfaces and the colored Jones polynomial
Futer, David; Purcell, Jessica
2013-01-01
This monograph derives direct and concrete relations between colored Jones polynomials and the topology of incompressible spanning surfaces in knot and link complements. Under mild diagrammatic hypotheses, we prove that the growth of the degree of the colored Jones polynomials is a boundary slope of an essential surface in the knot complement. We show that certain coefficients of the polynomial measure how far this surface is from being a fiber for the knot; in particular, the surface is a fiber if and only if a particular coefficient vanishes. We also relate hyperbolic volume to colored Jones polynomials. Our method is to generalize the checkerboard decompositions of alternating knots. Under mild diagrammatic hypotheses, we show that these surfaces are essential, and obtain an ideal polyhedral decomposition of their complement. We use normal surface theory to relate the pieces of the JSJ decomposition of the complement to the combinatorics of certain surface spines (state graphs). Since state graphs have p...
Design of self-supporting surfaces
Vouga, Etienne
2012-07-01
Self-supporting masonry is one of the most ancient and elegant techniques for building curved shapes. Because of the very geometric nature of their failure, analyzing and modeling such strutures is more a geometry processing problem than one of classical continuum mechanics. This paper uses the thrust network method of analysis and presents an iterative nonlinear optimization algorithm for efficiently approximating freeform shapes by self-supporting ones. The rich geometry of thrust networks leads us to close connections between diverse topics in discrete differential geometry, such as a finite-element discretization of the Airy stress potential, perfect graph Laplacians, and computing admissible loads via curvatures of polyhedral surfaces. This geometric viewpoint allows us, in particular, to remesh self-supporting shapes by self-supporting quad meshes with planar faces, and leads to another application of the theory: steel/glass constructions with low moments in nodes. © 2012 ACM 0730-0301/2012/08-ART87.
Jiang, Caigui
2014-07-01
Motivated by requirements of freeform architecture, and inspired by the geometry of hexagonal combs in beehives, this paper addresses torsion-free structures aligned with hexagonal meshes. Since repetitive geometry is a very important contribution to the reduction of production costs, we study in detail “honeycomb structures”, which are defined as torsion-free structures where the walls of cells meet at 120 degrees. Interestingly, the Gauss-Bonnet theorem is useful in deriving information on the global distribution of node axes in such honeycombs. This paper discusses the computation and modeling of honeycomb structures as well as applications, e.g. for shading systems, or for quad meshing. We consider this paper as a contribution to the wider topic of freeform patterns, polyhedral or otherwise. Such patterns require new approaches on the technical level, e.g. in the treatment of smoothness, but they also extend our view of what constitutes aesthetic freeform geometry.
CFD Simulation of Air Flow Over an Object with Gable Roof, Revised with Y+ Approach
Directory of Open Access Journals (Sweden)
Králik Juraj
2016-12-01
Full Text Available Aim of this contribution is to provide insight view into analysis focused on obtaining external pressure coefficients on isolated two storey low-rise building with 15° elevation gable roof using Computer Fluid Dynamics simulation and these are compared to values that offering Eurocodes. Final Volume Model consisting of polyhedral mesh will be used for analysis with two different turbulence models. Mesh was created with respect to y+ parameter, where desired value was below one which leads us to fine mesh type. Secondary aim of this contribution is to compare performance of selected turbulence models. For this purpose were chosen Detached Eddy Simulation and Large Eddy Simulation which are part of the Scale Resolving Simulation turbulence models.
Liquid Crystal Microlens Using Nanoparticle-Induced Vertical Alignment
Directory of Open Access Journals (Sweden)
Shug-June Hwang
2015-01-01
Full Text Available The nanoparticle-induced vertical alignment (NIVA of the nematic liquid crystals (LC is applied to achieve an adaptive flat LC microlens with hybrid-aligned nematic (HAN mode by dropping polyhedral oligomeric silsesquioxane (POSS nanoparticle solution on a homogeneous alignment layer. The vertical alignment induced by the POSS nanoparticles resulted in the formation of a hybrid-aligned LC layer with concentric nonuniform distribution of the refractive index in the planar LC cell, which subsequently played the role of the lens, even in the absence of any applied voltages. The dimensions of the concentric HAN structure significantly depend on the volume of the microdroplet and the POSS concentration. The focus effect of this flat microlens was observed while electrically controlling its focal length using the applied voltages from −50 mm to −90 mm.
Selective assemblies of giant tetrahedra via precisely controlled positional interactions
Huang, Mingjun; Hsu, Chih-Hao; Wang, Jing; Mei, Shan; Dong, Xuehui; Li, Yiwen; Li, Mingxuan; Liu, Hao; Zhang, Wei; Aida, Takuzo; Zhang, Wen-Bin; Yue, Kan; Cheng, Stephen Z. D.
2015-04-01
Self-assembly of rigid building blocks with explicit shape and symmetry is substantially influenced by the geometric factors and remains largely unexplored. We report the selective assembly behaviors of a class of precisely defined, nanosized giant tetrahedra constructed by placing different polyhedral oligomeric silsesquioxane (POSS) molecular nanoparticles at the vertices of a rigid tetrahedral framework. Designed symmetry breaking of these giant tetrahedra introduces precise positional interactions and results in diverse selectively assembled, highly ordered supramolecular lattices including a Frank-Kasper A15 phase, which resembles the essential structural features of certain metal alloys but at a larger length scale. These results demonstrate the power of persistent molecular geometry with balanced enthalpy and entropy in creating thermodynamically stable supramolecular lattices with properties distinct from those of other self-assembling soft materials.
Synthèse et étude structurale de Na9Cr(MoO46
Directory of Open Access Journals (Sweden)
Wassim Dridi
2015-05-01
Full Text Available The title compound, nonasodium chromium(III hexakis[molybdate(VI], Na9Cr(MoO46 was prepared by solid-state reactions. The basic structure units are isolated polyhedral clusters composed of a central CrO6 octahedron sharing vertices with six MoO4 tetrahedra to form an open framework in which the Na+ cations are bound to the free vertices of the MoO4 tetrahedra. The Cr3+ cation has site symmetry of 32 (6a, one Na atom sits on a twofold axis (18e, and all other atoms are at general positions. The bond-valance-sum model confirms the expected values of ion charges. The title compound is isotypic with Na9Sc(MoO46 and Na9Fe(MoO46. It is compared and discussed with similar structures.
Liu, Yizhi; Sun, Yi; Zeng, Fanlin; Xie, Weili; Liu, Yang; Geng, Lin
2014-12-01
Nanocomposite dental resins composed of polyhedral oligomeric silsesquioxane nanocomposite matrix and 0, 0.5,1, 1.5 and 2 wt% nano SiO2 as filler were prepared by light curing method. The nanocomposite resins were characterized by performing compressive, three-point flexure, nanoindentation and nanoscratch testings as well as optical microscopy and scanning electron microscope analysis. The effects of different nano SiO2 contents were studied on compressive strength, flexural strength, hardness and resistance of composite resin. From the mechanical results, it was found that nano SiO2 effectively enhanced the mechanical properties of the composite resins at low content. With the increase of the nano SiO2 content, the mechanical properties decreased. It was attributed to the content of nano SiO2 and dispersion of nanoparticles in matrix.
Energy Technology Data Exchange (ETDEWEB)
Liu, Yizhi; Sun, Yi, E-mail: sunyi@hit.edu.cn; Zeng, Fanlin [Harbin Institute of Technology, Department of Astronautic Science and Mechanics (China); Xie, Weili, E-mail: xwl811@126.com [Harbin Medical University, Department of Stomatology (China); Liu, Yang [Harbin Stomatology Hospital (China); Geng, Lin [Harbin Institute of Technology, School of Materials Science and Engineering (China)
2014-12-15
Nanocomposite dental resins composed of polyhedral oligomeric silsesquioxane nanocomposite matrix and 0, 0.5,1, 1.5 and 2 wt% nano SiO{sub 2} as filler were prepared by light curing method. The nanocomposite resins were characterized by performing compressive, three-point flexure, nanoindentation and nanoscratch testings as well as optical microscopy and scanning electron microscope analysis. The effects of different nano SiO{sub 2} contents were studied on compressive strength, flexural strength, hardness and resistance of composite resin. From the mechanical results, it was found that nano SiO{sub 2} effectively enhanced the mechanical properties of the composite resins at low content. With the increase of the nano SiO{sub 2} content, the mechanical properties decreased. It was attributed to the content of nano SiO{sub 2} and dispersion of nanoparticles in matrix.
Directory of Open Access Journals (Sweden)
Simge Gencalp Irizalp
2014-06-01
Full Text Available The effect of α-Fe and β-Fe intermetallics concentration and morphology as well as α-Al morphology on the microstructure and mechanical properties of thixoformed and gravity cast A380 alloy was reported. The α-Al15Si2(Fe,Mn3 intermetallic particle was observed polyhedral morphology in thixoforming while it was observed Chinese script morphology in conventional gravity casting. The β-Al5FeSi particle was solidified in the form of small plate in thixoforming while it was solidified in the form of needle-like in gravity casting at the grain boundaries of α-Al. The mechanical properties of the alloys have been enhanced by thixoforming compared with the conventional cast condition.
Modification effect of lanthanum on primary phase Mg2Si in Mg-Si alloys
Institute of Scientific and Technical Information of China (English)
WANG Liping; GUO Erjun; MA Baoxia
2008-01-01
The modifying effect of La addition on primary phase Mg2Si in Mg-5Si alloys was investigated. The results showed that a proper amount of La could effectively modify the primary phase Mg2Si. Based on the present experiment, the optimal modification effect was obtained with an addition of about 0.5 wt.% La. The size of the primary phase Mg2Si was considerably reduced to 25 μm or less and the morphology was modified from a coarse dendritic shape to a polyhedral shape. However, when the addition of La increased to 0.8 wt.% or higher, the primary Mg2Si grew into a coarse dendritic morphology again. Moreover, it was found that some LaSi2 compounds were formed during solidification and the amount of the compounds appeared to increase gradually with increasing La content.
Directory of Open Access Journals (Sweden)
Amit Shankar Singh
2013-01-01
Full Text Available Malignant peripheral nerve sheath tumor (MPNST is a rare variety of soft-tissue sarcoma of ecto-mesenchymal origin. Various sites have been mentioned, but it is rare in cauda equina. Only five cases of MPNST of cauda equina are reported till date. A 42-year-old male presented with complaints of weakness in lower limbs for last 5 months with bladder and bowel dysfunction. On magnetic resonance imaging, an isointense lesion on T1 and a hyperintense on T2 imaging was found at terminal spinal cord level. The lesion was excised following laminectomy and showed varied cellularity with thin oval, polyhedral and spindle-shaped cells arranged in bundles on microscopic examination suggesting MPNST. MPNST of cauda equina is rare and is associated with Neurofibromatosis Type-1 or radiation exposure, but is rarer without these risk factors. Prognosis is favorable in these cases.
Ellipsoidal analysis of coordination polyhedra
Cumby, James; Attfield, J. Paul
2017-02-01
The idea of the coordination polyhedron is essential to understanding chemical structure. Simple polyhedra in crystalline compounds are often deformed due to structural complexity or electronic instabilities so distortion analysis methods are useful. Here we demonstrate that analysis of the minimum bounding ellipsoid of a coordination polyhedron provides a general method for studying distortion, yielding parameters that are sensitive to various orders in metal oxide examples. Ellipsoidal analysis leads to discovery of a general switching of polyhedral distortions at symmetry-disallowed transitions in perovskites that may evidence underlying coordination bistability, and reveals a weak off-centre `d5 effect' for Fe3+ ions that could be exploited in multiferroics. Separating electronic distortions from intrinsic deformations within the low temperature superstructure of magnetite provides new insights into the charge and trimeron orders. Ellipsoidal analysis can be useful for exploring local structure in many materials such as coordination complexes and frameworks, organometallics and organic molecules.
Viruses of eukaryotic green algae; Progress report, June 20, 1990--July 1, 1991
Energy Technology Data Exchange (ETDEWEB)
Van Etten, J.L.
1991-12-31
Many large polyhedral, dsDNA containing (ca. 330 kb), plaque forming viruses which infect a unicellular, eukaryotic, chlorella-like green alga have been isolated and characterized. The plaque assay, the ability to synchronously infect the host, the short life cycle, and the ability of the viruses to undergo homologous recombination make them excellent model systems for studying many plant cell functions in the manner that bacterial and animal viruses have been used to study bacterial and animal cell functions. These viruses have several unique features including: (1) coding for DNA methyltransferase and site-specific (restriction) endonucleases and (2) unlike other viruses, these viruses appear to code for the enzymes involved in the glycosylation of their glycoproteins.
Energy Technology Data Exchange (ETDEWEB)
Lisitsa, Vadim, E-mail: lisitsavv@ipgg.sbras.ru [Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk (Russian Federation); Novosibirsk State University, Novosibirsk (Russian Federation); Tcheverda, Vladimir [Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk (Russian Federation); Kazakh–British Technical University, Alma-Ata (Kazakhstan); Botter, Charlotte [University of Stavanger (Norway)
2016-04-15
We present an algorithm for the numerical simulation of seismic wave propagation in models with a complex near surface part and free surface topography. The approach is based on the combination of finite differences with the discontinuous Galerkin method. The discontinuous Galerkin method can be used on polyhedral meshes; thus, it is easy to handle the complex surfaces in the models. However, this approach is computationally intense in comparison with finite differences. Finite differences are computationally efficient, but in general, they require rectangular grids, leading to the stair-step approximation of the interfaces, which causes strong diffraction of the wavefield. In this research we present a hybrid algorithm where the discontinuous Galerkin method is used in a relatively small upper part of the model and finite differences are applied to the main part of the model.
Gupta, S.; Fischer, J. K. H.; Lunkenheimer, P.; Loidl, A.; Novak, E.; Jalarvo, N.; Ohl, M.
2016-10-01
We present the relaxation dynamics of glass-forming glycerol mixed with 1.1 nm sized polyhedral oligomeric silsesquioxane (POSS) molecules using dielectric spectroscopy (DS) and two different neutron scattering (NS) techniques. Both, the reorientational dynamics as measured by DS and the density fluctuations detected by NS reveal a broadening of the α relaxation when POSS molecules are added. Moreover, we find a significant slowing down of the α-relaxation time. These effects are in accord with the heterogeneity scenario considered for the dynamics of glasses and supercooled liquids. The addition of POSS also affects the excess wing in glycerol arising from a secondary relaxation process, which seems to exhibit a dramatic increase in relative strength compared to the α relaxation.
Jagged Tiling for Intra-tile Parallelism and Fine-Grain Multithreading
Energy Technology Data Exchange (ETDEWEB)
Shrestha, Sunil; Manzano Franco, Joseph B.; Marquez, Andres; Feo, John T.; Gao, Guang R.
2015-05-01
In this paper, we have developed a novel methodology that takes into consideration multithreaded many-core designs to better utilize memory/processing resources and improve memory residence on tileable applications. It takes advantage of polyhedral analysis and transformation in the form of PLUTO, combined with a highly optimized finegrain tile runtime to exploit parallelism at all levels. The main contributions of this paper include the introduction of multi-hierarchical tiling techniques that increases intra tile parallelism; and a data-flow inspired runtime library that allows the expression of parallel tiles with an efficient synchronization registry. Our current implementation shows performance improvements on an Intel Xeon Phi board up to 32.25% against instances produced by state-of-the-art compiler frameworks for selected stencil applications.
Controlled growth of silver nanoparticles in a hydrothermal process
Institute of Scientific and Technical Information of China (English)
Juan Zou; Yao Xu; Bo Hou; Dong Wu; Yuhan Sun
2007-01-01
A two-step synthesis was used to control the shape of silver nanoparticles. First, a few spherical silver nanoparticles, ～10 nm in size, were prepared via reduction of Ag+ ions in aqueous Ag(NH3)2NO3 by poly(N-vinyl-2-pyrrolidone) (PVP). Then, in a subsequent hydrothermal treatment,the remaining Ag+ ions were reduced by PVP into polyhedral nanoparticles, or larger spherical nanoparticles formed from the small spherical seed silver nanoparticles in the first step. The morphology and size of the resultant particles depend on the hydrothermal temperature, PVP/Ag molar ratio and concentration of Ag+ ions. By using UV-visible spectroscopy (UV-vis), transmission electron microscopy (TEM) and powder X-ray diffraction (XRD), the possible growth mechanism of the silver nanoparticles was discussed.
Lambert, Cédric; Thoeni, Klaus; Giacomini, Anna; Casagrande, Davide; Sloan, Scott
2012-09-01
Developing an accurate representation of the rock mass fabric is a key element in rock fall hazard analysis. The orientation, persistence and density of fractures control the volume and shape of unstable blocks or compartments. In this study, the discrete fracture modelling technique and digital photogrammetry were used to accurately depict the fabric. A volume distribution of unstable blocks was derived combining polyhedral modelling and kinematic analyses. For each block size, probabilities of failure and probabilities of propagation were calculated. A complete energy distribution was obtained by considering, for each block size, its occurrence in the rock mass, its probability of falling, its probability to reach a given location, and the resulting distribution of energies at each location. This distribution was then used with an energy-frequency diagram to assess the hazard.
Light sensitive polymer obtained by dispersion of azo-functionalized POSS nanoparticles
Miniewicz, A.; Tomkowicz, M.; Karpinski, P.; Sznitko, L.; Mossety-Leszczak, B.; Dutkiewicz, M.
2015-07-01
Hybrid inorganic-organic nanoparticles based on cubic siloxane cage (RSiO3/2)8, known as polyhedral oligosilsesquioxane (POSS), have been functionalized by eight groups of azo-benzene mesogens and dispersed in poly(methyl methacrylate) PMMA matrix. Presence of azo-benzene units adds an important light-driven functionality to the system due to their photoisomerization resulting in refractive index and/or absorption changes of the whole system. The polymer films containing various concentrations of azo-POSS nanoparticles show remarkable changes of surface morphology being either transparent (at low POSS concentration) or highly scattering (at high POSS concentration) for visible light. Surface structures were examined by optical microscopy as well as by atomic force microscopy (AFM). Results of photoinduced alignment are discussed in the framework of light-induced modification of the aliphatic chains containing azo-benzene photoisomerizing moieties and self-organization process.
Mir, Shabir Ahmad; Bosco, Sowriappan John Don
2014-08-15
Starch and flour of seven temperate rice cultivars grown in Himalayan region were evaluated for composition, granule structure, crystallinity, Raman spectrometry, turbidity, swelling power, solubility, pasting properties and textural properties. The rice cultivars showed medium to high amylose content for starch (24.69-32.76%) and flour (17.78-24.86%). SKAU-382 showed the highest amount of amylose (32.76%). Rice starch showed polyhedral granule shapes and differences in their mean granule size (2.3-6.5 μm) were noted among the samples. The starch and flour samples showed type A-pattern with strong reflection at 15, 18, and 23. Pasting profile and textural analysis of rice starch and flour showed that all the cultivars differences, probably due to variation in amylose content. The present study can be used for identifying differences between rice genotypes for starch and flour quality and could provide guidance to possible industries for their end use.
Topological Logics with Connectedness over Euclidean Spaces
Kontchakov, Roman; Pratt-Hartmann, Ian; Zakharyaschev, Michael
2011-01-01
We consider the quantifier-free languages, Bc and Bc0, obtained by augmenting the signature of Boolean algebras with a unary predicate representing, respectively, the property of being connected, and the property of having a connected interior. These languages are interpreted over the regular closed sets of n-dimensional Euclidean space (n greater than 1) and, additionally, over the regular closed polyhedral sets of n-dimensional Euclidean space. The resulting logics are examples of formalisms that have recently been proposed in the Artificial Intelligence literature under the rubric "Qualitative Spatial Reasoning." We prove that the satisfiability problem for Bc is undecidable over the regular closed polyhedra in all dimensions greater than 1, and that the satisfiability problem for both languages is undecidable over both the regular closed sets and the regular closed polyhedra in the Euclidean plane. However, we also prove that the satisfiability problem for Bc0 is NP-complete over the regular closed sets i...
Error analysis of semidiscrete finite element methods for inhomogeneous time-fractional diffusion
Jin, B.
2014-05-30
© 2014 Published by Oxford University Press on behalf of the Institute of Mathematics and its Applications. All rights reserved. We consider the initial-boundary value problem for an inhomogeneous time-fractional diffusion equation with a homogeneous Dirichlet boundary condition, a vanishing initial data and a nonsmooth right-hand side in a bounded convex polyhedral domain. We analyse two semidiscrete schemes based on the standard Galerkin and lumped mass finite element methods. Almost optimal error estimates are obtained for right-hand side data f (x, t) ε L∞ (0, T; Hq(ω)), ≤1≥ 1, for both semidiscrete schemes. For the lumped mass method, the optimal L2(ω)-norm error estimate requires symmetric meshes. Finally, twodimensional numerical experiments are presented to verify our theoretical results.
Baghdadi, Riyadh; Bastoul, Cedric; Pouchet, Louis-Noel; Rauchwerger, Lawrence
2011-01-01
Research in automatic parallelization of loop-centric programs started with static analysis, then broadened its arsenal to include dynamic inspection-execution and speculative execution, the best results involving hybrid static-dynamic schemes. Beyond the detection of parallelism in a sequential program, scalable parallelization on many-core processors involves hard and interesting parallelism adaptation and mapping challenges. These challenges include tailoring data locality to the memory hierarchy, structuring independent tasks hierarchically to exploit multiple levels of parallelism, tuning the synchronization grain, balancing the execution load, decoupling the execution into thread-level pipelines, and leveraging heterogeneous hardware with specialized accelerators. The polyhedral framework allows to model, construct and apply very complex loop nest transformations addressing most of the parallelism adaptation and mapping challenges. But apart from hardware-specific, back-end oriented transformations (if-...
Compressibility and Structural Properties of Jadeite, NaAlSi2O6 at High Pressure
Institute of Scientific and Technical Information of China (English)
Xiuling Wu; Xiaoyu Fan; Fei Qin; Dawei Meng; Xiaoling Zhang; Long Chen; Weiping Liu; Jianping Zheng
2013-01-01
The structural properties of jadeite at high pressures (0.000 1-30 GPa) are investigated using plane-wave pseudopotential density functional theory method.As a function of pressure,the monoclinic cell parameters were calculated and the compressibility coefficients are 0.0026,0.0023 and 0.0026 GPa-1,respectively.The bond length,bond angle and distortion variation were studied in order to obtain the information of polyhedral compression.The pressure-volume equation of state was considered in order to obtain the bulk modulus K0.Comparison between the calculated K0 values and the experimental data suggested that the model provides reasonable insights into crystallographic and physical properties of jadeite.
Valiant load-balanced robust routing under hose model for WDM mesh networks
Zhang, Xiaoning; Li, Lemin; Wang, Sheng
2006-09-01
In this paper, we propose Valiant Load-Balanced robust routing scheme for WDM mesh networks under the model of polyhedral uncertainty (i.e., hose model), and the proposed routing scheme is implemented with traffic grooming approach. Our Objective is to maximize the hose model throughput. A mathematic formulation of Valiant Load-Balanced robust routing is presented and three fast heuristic algorithms are also proposed. When implementing Valiant Load-Balanced robust routing scheme to WDM mesh networks, a novel traffic-grooming algorithm called MHF (minimizing hop first) is proposed. We compare the three heuristic algorithms with the VPN tree under the hose model. Finally we demonstrate in the simulation results that MHF with Valiant Load-Balanced robust routing scheme outperforms the traditional traffic-grooming algorithm in terms of the throughput for the uniform/non-uniform traffic matrix under the hose model.
a Continuous-Time Positive Linear System
Directory of Open Access Journals (Sweden)
Kyungsup Kim
2013-01-01
Full Text Available This paper discusses a computational method to construct positive realizations with sparse matrices for continuous-time positive linear systems with multiple complex poles. To construct a positive realization of a continuous-time system, we use a Markov sequence similar to the impulse response sequence that is used in the discrete-time case. The existence of the proposed positive realization can be analyzed with the concept of a polyhedral convex cone. We provide a constructive algorithm to compute positive realizations with sparse matrices of some positive systems under certain conditions. A sufficient condition for the existence of a positive realization, under which the proposed constructive algorithm works well, is analyzed.
Final report, DOE Grant DE-FG02-98ER25352, Computational semidefinite programming
Energy Technology Data Exchange (ETDEWEB)
Overton, Michael L.
2002-09-05
Semidefinite programming (SDP) is an extension of linear programming, with vector variables replaced by matrix variables and component wise nonnegativity replaced by positive semidefiniteness. SDP's are convex, but not polyhedral, optimization problems. SDP is well on its way to becoming an established paradigm in optimization, with many current potential applications. Consequently, efficient methods and software for solving SDP's are of great importance. During the award period, attention was primarily focused on three aspects of computational semidefinite programming: General-purpose methods for semidefinite and quadratic cone programming; Specific applications (LMI problems arising in control, minimizing a sum of Euclidean norms, a quantum mechanics application of SDP); and Optimizing matrix stability.
Crystallization in Zr60Al15Ni25 bulk metallic glass subjected to rolling at room temperature
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
The microstructure evolution of Zr60Al15Ni25 bulk metallic glass during rolling at room temperature is investigated by differential scanning calorimetry(DSC),high-resolution transmission electron microscopy(HRTEM) and selected area electronic diffraction(SAED).The HRTEM images show that shear bands are produced in the rolled specimens,indicating the essence of inhomogeneous deformation due to rolling,and that there exist nanocrystals with size of about 5-10 nm in the transition regions between the shear bands and the undeformed matrix in the rolled specimens with deformation degrees of 80% and 95%.Based on the polyhedral structure model and the shear transformation zone(STZ) theory,the influence of viscous flow,free volume,viscosity and the stress situation on the crystallization behaviors in the metallic glass during rolling is discussed.
Sherali-Adams Relaxations of Graph Isomorphism Polytopes
Malkin, Peter N
2011-01-01
We investigate the Sherali-Adams lift & project hierarchy applied to a graph isomorphism polytope whose integer points encode the isomorphisms between two graphs. In particular, the Sherali-Adams relaxations characterize a new vertex classification algorithm for graph isomorphism, which we call the generalized vertex classification algorithm. This algorithm generalizes the classic vertex classification algorithm and generalizes the work of Tinhofer on polyhedral methods for graph automorphism testing. We establish that the Sherali-Adams lift & project hierarchy when applied to a graph isomorphism polytope needs Omega(n) iterations in the worst case before converging to the convex hull of integer points. We also show that this generalized vertex classification algorithm is also strongly related to the well-known Weisfeiler-Lehman algorithm, which we show can also be characterized in terms of the Sherali-Adams relaxations of a semi-algebraic set whose integer points encode graph isomorphisms.
Task-Level Data Model for Hardware Synthesis Based on Concurrent Collections
Directory of Open Access Journals (Sweden)
Jason Cong
2012-01-01
Full Text Available The ever-increasing design complexity of modern digital systems makes it necessary to develop electronic system-level (ESL methodologies with automation and optimization in the higher abstraction level. How the concurrency is modeled in the application specification plays a significant role in ESL design frameworks. The state-of-art concurrent specification models are not suitable for modeling task-level concurrent behavior for the hardware synthesis design flow. Based on the concurrent collection (CnC model, which provides the maximum freedom of task rescheduling, we propose task-level data model (TLDM, targeted at the task-level optimization in hardware synthesis for data processing applications. Polyhedral models are embedded in TLDM for concise expression of task instances, array accesses, and dependencies. Examples are shown to illustrate the advantages of our TLDM specification compared to other widely used concurrency specifications.
Energy Technology Data Exchange (ETDEWEB)
He Fuan; Zhang Liming [Laboratory for Polymer Composite and Functional Materials, Institute of Optoelectronic and Functional Composite Materials, School of Chemistry and Chemical Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou 510275 (China)
2006-12-28
A new strategy was developed for in situ formation of polyethylene nanocomposites, in which synthetic laponite clay was first modified by octaaminopropyl polyhedral oligometric silsesquioxane (OapPOSS) and then used to support a nickel {alpha}-diimine late-transition-metal catalyst for ethylene polymerization. The resulting polyethylene nanocomposites were investigated with respect to their structure and properties by x-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), dynamic mechanical analysis (DMA) and thermogravimetric analysis (TGA). It was found that the layered silicates could be exfoliated effectively in the polyethylene matrix. In comparison with pure polyethylene, the polyethylene in the nanocomposites has a lower branching degree. The combination of OapPOSS with the laponite clay particles results in a remarkable increase in storage modulus and thermal decomposition temperature.