Stealth Amphiphiles: Self-Assembly of Polyhedral Boron Clusters.
Ďorďovič, Vladimír; Tošner, Zdeněk; Uchman, Mariusz; Zhigunov, Alexander; Reza, Mehedi; Ruokolainen, Janne; Pramanik, Goutam; Cígler, Petr; Kalíková, Květa; Gradzielski, Michael; Matějíček, Pavel
2016-07-01
This is the first experimental evidence that both self-assembly and surface activity are common features of all water-soluble boron cluster compounds. The solution behavior of anionic polyhedral boranes (sodium decaborate, sodium dodecaborate, and sodium mercaptododecaborate), carboranes (potassium 1-carba-dodecaborate), and metallacarboranes {sodium [cobalt bis(1,2-dicarbollide)]} was extensively studied, and it is evident that all the anionic boron clusters form multimolecular aggregates in water. However, the mechanism of aggregation is dependent on size and polarity. The series of studied clusters spans from a small hydrophilic decaborate-resembling hydrotrope to a bulky hydrophobic cobalt bis(dicarbollide) behaving like a classical surfactant. Despite their pristine structure resembling Platonic solids, the nature of anionic boron cluster compounds is inherently amphiphilic-they are stealth amphiphiles. PMID:27287067
Boron clusters in luminescent materials.
Mukherjee, Sanjoy; Thilagar, Pakkirisamy
2016-01-21
In recent times, luminescent materials with tunable emission properties have found applications in almost all aspects of modern material sciences. Any discussion on the recent developments in luminescent materials would be incomplete if one does not account for the versatile photophysical features of boron containing compounds. Apart from triarylboranes and tetra-coordinate borate dyes, luminescent materials consisting of boron clusters have also found immense interest in recent times. Recent studies have unveiled the opportunities hidden within boranes, carboranes and metalloboranes, etc. as active constituents of luminescent materials. From simple illustrations of luminescence, to advanced applications in LASERs, OLEDs and bioimaging, etc., the unique features of such compounds and their promising versatility have already been established. In this review, recent revelations about the excellent photophysical properties of such materials are discussed. PMID:26574714
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...
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.
Comparative study on the spectral properties of boron clusters Bn 0/−1(n = 38–40)
Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Sun, Guangyu; Qin, Shuijie
2016-01-01
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-...
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 Bn(0/-1)(n = 38-40).
Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Sun, Guangyu; Qin, Shuijie
2016-01-01
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 Bn(0/-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 Bn(0/-1) with different structures (cage structure or quasi-planar structure) and with different sizes (n = 38-40). PMID:27113504
Özdoğan, Cem; Kunstmann, Jens; Quandt, Alexander
2014-06-01
As a possible way of modifying the intrinsic properties of graphene, we study the doping of graphene by embedded boron clusters with density functional theory. Cluster doping is technologically relevant as the cluster implantation technique can be readily applied to graphene. We find that B? clusters embedded into graphene and graphene nanoribbons are structurally stable and locally metallize the system. This is done both by the reduction of the Fermi energy and by the introduction of boron states near the Fermi level. A linear chain of boron clusters forms a metallic "wire" inside the graphene matrix. In a zigzag edge graphene nanoribbon, the cluster-related states tend to hybridize with the edge and bulk states. The magnetism in boron-doped graphene systems is generally very weak. The presence of boron clusters weakens the edge magnetism in zigzag edge graphene nanoribbon, rather than making the system appropriate for spintronics. Thus, the doping of graphene with the cluster implantation technique might be a viable technique to locally metallize graphene without destroying its attractive bulk properties.
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-
Structure of boron clusters revisited, Bn with n = 14-20
Tai, Truong Ba; Tam, Nguyen Minh; Nguyen, Minh Tho
2012-03-01
We reinvestigate the structures of neutral boron clusters Bn, with n = 14-20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All Bn have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.
Nonadiabtic electron dynamics in densely quasidegenerate states in highly excited boron cluster.
Yonehara, Takehiro; Takatsuka, Kazuo
2016-04-28
Following the previous study on nonadiabatic reaction dynamics including boron clusters [T. Yonehara and K. Takatsuka, J. Chem. Phys. 137, 22A520 (2012)], we explore deep into highly excited electronic states of the singlet boron cluster (B12) to find the characteristic features of the densely quasi-degenerate electronic state manifold, which undergo very frequent nonadiabatic transitions and thereby intensive electronic state mixing among very many of the relevant states. So much so, isolating the individual adiabatic states and tracking the expected potential energy surfaces both lose the physical sense. This domain of molecular situation is far beyond the realm of the Born-Oppenheimer approximation. To survey such a violent electronic state-mixing, we apply a method of nonadiabatic electron wavepacket dynamics, the semiclassical Ehrenfest method. We have tracked those electron wavepackets and found the electronic state mixing looks like an ultrafast diffusion in the Hilbert space, which results in huge fluctuation. Furthermore, due to such a violent mixing, the quantum phases associated with the electronic states are swiftly randomized, and consequently the coherence among the electronic states are lost quickly. Besides, these highly excited states are mostly of highly poly-radical nature, even in the spin singlet manifold and the number of radicals amounts up to 10 electrons in the sense of unpaired electrons. Thus the electronic states are summarized to be poly-radical and decoherent with huge fluctuation in shorter time scales of vibrational motions. The present numerical study sets a theoretical foundation for unknown molecular properties and chemical reactivity of such densely quasi-degenerate chemical species. PMID:27131547
Space-filling polyhedral sorbents
Energy Technology Data Exchange (ETDEWEB)
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.
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.
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
Janczak, Slawomir; Olejniczak, Agnieszka; Balabańska, Sandra; Chmielewski, Marcin K; Lupu, Marius; Viñas, Clara; Lesnikowski, Zbigniew J
2015-10-19
A synthetic strategy for functionalization of the three vertices of o-carborane and the attachment of the obtained triped to the solid support was developed. Further functionalization of the triped with short DNA sequences by automated DNA synthesis was achieved. The proposed methodology is a first example of boron cluster chemistry on a solid support opening new perspectives in boron cluster functionalization. PMID:26346614
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...
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.
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.
Unstructured Polyhedral Mesh Thermal Radiation Diffusion
International Nuclear Information System (INIS)
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
Exploiting Polyhedral Symmetries in Social Choice
Schürmann, Achill
2011-01-01
A large amount of literature in social choice theory deals with quantifying the probability of certain election outcomes. One way of computing the probability of a specific voting situation under the impartial anonymous culture is via counting integral points in polyhedra. Here, Ehrhart theory can help, but unfortunately the dimension and complexity of the involved polyhedra grows rapidly with the number of candidates. However, if we exploit available polyhedral symmetries, some computations become possible that previously were infeasible. We show this in three well known examples: Condorcet's paradox, Condorcet efficiency of plurality voting and in Plurality voting vs Plurality Runoff.
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.
Synthesis of carbon-containing composite materials in burning mode
Directory of Open Access Journals (Sweden)
Roza Abdulkarimova
2012-03-01
Full Text Available The possibility of obtaining multicomponent refractory composition materials on the basis of quarts containing raw material by SHS method was studied. It is shown that a complex use of preliminary mechanochemicala ctivatin (MA and modification of the charge mixture with carbon containing additives contributes to formation of carbide and nitride phases in synthesis products.
Plasma processing of carbon-containing technical aggregations and wastes
Cherednichenko, V. S.; An'shakov, A. S.; Faleev, V. A.; Danilenko, A. A.
2008-12-01
The plasma gasification of technical aggregations is experimentally studied using the utilization of solid domestic wastes as an example. A shaft electric furnace is described, and the experimental and calculated data are analyzed and compared. The high-temperature gasification of carbon-containing wastes is shown to be a promising process.
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.
Gao, Zhenyu; Horiguchi, Yukichi; Nakai, Kei; Matsumura, Akira; Suzuki, Minoru; Ono, Koji; Nagasaki, Yukio
2016-10-01
A boron delivery system with high therapeutic efficiency and low adverse effects is crucial for a successful boron neutron capture therapy (BNCT). In this study, we developed boron cluster-containing redox nanoparticles (BNPs) via polyion complex (PIC) formation, using a newly synthesized poly(ethylene glycol)-polyanion (PEG-polyanion, possessing a (10)B-enriched boron cluster as a side chain of one of its segments) and PEG-polycation (possessing a reactive oxygen species (ROS) scavenger as a side chain of one of its segments). The BNPs exhibited high colloidal stability, selective uptake in tumor cells, specific accumulation, and long retention in tumor tissue and ROS scavenging ability. After thermal neutron irradiation, significant suppression of tumor growth was observed in the BNP-treated group, with only 5-ppm (10)B in tumor tissues, whereas at least 20-ppm (10)B is generally required for low molecular weight (LMW) (10)B agents. In addition, increased leukocyte levels were observed in the LMW (10)B agent-treated group after thermal neutron irradiation, and not in BNP-treated group, which might be attributed to its ROS scavenging ability. No visual metastasis of tumor cells to other organs was observed 1 month after irradiation in the BNP-treated group. These results suggest that BNPs are promising for enhancing the BNCT performance. PMID:27467416
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.
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.
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
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.
Parallelizing dynamic sequential programs using polyhedral process networks
Nadezhkin, Dmitry
2012-01-01
The Polyhedral Process Network (PPN) is a suitable parallel model of computation (MoC) used to specify embedded streaming applications in a parallel form facilitating the efficient mapping onto embedded parallel execution platforms. Unfortunately, specifying an application using a parallel MoC is a
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.
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.
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.
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.
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.
Final Project Report: A Polyhedral Transformation Framework for Compiler Optimization
Energy Technology Data Exchange (ETDEWEB)
Sadayappan, Ponnuswamy [The Ohio State University; Rountev, Atanas [The Ohio State University
2015-06-15
The project developed the polyhedral compiler transformation module PolyOpt/Fortran in the ROSE compiler framework. PolyOpt/Fortran performs automated transformation of affine loop nests within FORTRAN programs for enhanced data locality and parallel execution. A FORTAN version of the Polybench library was also developed by the project. A third development was a dynamic analysis approach to gauge vectorization potential within loops of programs; software (DDVec) for automated instrumentation and dynamic analysis of programs was developed.
Saturation points on faces of a rational polyhedral cone
Takemura, Akimichi; Yoshida, Ruriko
2006-01-01
Different commutative semigroups may have a common saturation. We consider distinguishing semigroups with a common saturation based on their ``sparsity''. We propose to qualitatively describe sparsity of a semigroup by considering which faces of the corresponding rational polyhedral cone have saturation points. For a commutative semigroup we give a necessary and sufficient condition for determining which faces have saturation points. We also show that we can construct a commutative semigroup ...
Highly uniform polyhedral colloids formed by colloidal crystal templating
Wang, Yifan; McGinley, James; Crocker, John; Crocker Research Group Team
2015-03-01
We seek to create polyhedral solid particles by trapping oil droplets in a colloidal crystal, and polymerizing them in situ, resulting in polyhedral particles containing spherical dimples in an ordered arrangement. Specifically, highly monodisperse, micron-sized droplets of 3-methacryloxypropyl trimethoxysilane (TPM) were first prepared through a poly condensation reaction, following well established methods. The droplets were mixed with an excess of polystyrene(PS) particles (diameter in 2.58 μm), which formed close packed (FCC or HCP) colloidal crystals by natural sedimentation and compression under partial drying to an extent, with TPM oil droplets trapped into their tetrahedral and octahedral interstitial sites and wet PS particles. Depending on the initial particle volume fraction and extent of drying, a high yield of dimpled particles having different shapes including tetrahedra and cubes were obtained after oil initiated polymerization and dissolution of the host PS particles, as seen under SEM. The effects of TPM to PS particles size ratio, drying time, and other factors in relation to the yield of tetrahedral and cubic dimpled particles will be presented. Finally, fractionation techniques were used to obtain suspensions of uniform polyhedral particles of high purity.
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.
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.
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.
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.
SALOME PLATFORM and TetGen for Polyhedral Mesh Generation
Energy Technology Data Exchange (ETDEWEB)
Lee, Sang Yong; Park, Chan Eok; Kim, Shin Whan [KEPCO E and C Company, Inc., Daejeon (Korea, Republic of)
2014-05-15
SPACE and CUPID use the unstructured mesh and they also require reliable mesh generation system. The combination of CAD system and mesh generation system is necessary to cope with a large number of cells and the complex fluid system with structural materials inside. In the past, a CAD system Pro/Engineer and mesh generator Pointwise were evaluated for this application. But, the cost of those commercial CAD and mesh generator is sometimes a great burden. Therefore, efforts have been made to set up a mesh generation system with open source programs. The evaluation of the TetGen has been made in focusing the application for the polyhedral mesh generation. In this paper, SALOME will be evaluated for the efforts in conjunction with TetGen. In section 2, review will be made on the CAD and mesh generation capability of SALOME. SALOME and TetGen codes are being integrated to construct robust polyhedral mesh generator. Edge removal on the flat surface and vertex reattachment to the solid are two challenging tasks. It is worthwhile to point out that the Python script capability of the SALOME should be fully utilized for the future investigation.
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.
Materials and Concepts for Full Ceramic SOFCs with Focus on Carbon Containing Fuels
DEFF Research Database (Denmark)
Holtappels, Peter; Sudireddy, Bhaskar Reddy; Veltzé, Sune;
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...
Energy Technology Data Exchange (ETDEWEB)
Bregadze, V., E-mail: bre@ineos.ac.ru [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Str. 28, Moscow 119991 (Russian Federation); Semioshkin, A.; Sivaev, I. [A.N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, Vavilov Str. 28, Moscow 119991 (Russian Federation)
2011-12-15
Recent achievements in design and synthesis of boronated acids, amino acids, glycerols as well as conjugates of polyhedral boron hydrides (ortho-carborane, closo-dodecaborate and cobalt bis(dicarbollide)) with natural porphyrins, carbohydrates and nucleosides are described.
Code Generation in the Polyhedral Model Is Easier Than You Think
Bastoul, Cédric
2004-01-01
Many advances in automatic parallelization and optimization have been achieved through the polyhedral model. It has been extensively shown that this computational model provides convenient abstractions to reason about and apply program transformations. Nevertheless, the complexity of code generation has long been a deterrent for using polyhedral representation in optimizing compilers. First, code generators have a hard time coping with generated code size and control overhead that may spoil t...
Mascon gravitation model using a shaped polyhedral source
Chanut, T. G. G.; Aljbaae, S.; Carruba, V.
2015-07-01
In the last two decades, new computational tools have been developed in order to aid space missions to orbit around irregular small bodies. One of the techniques consists in rebuilding their shape in tetrahedral polyhedron. This method is well suited to determine the shape and estimate certain physical features of asteroids. However, a large computational effort is necessary depending on the quantity of triangular faces chosen. Another method is based on a representation of the central body in terms of mascons (discrete spherical masses). The main advantage of the method is its simplicity which makes the calculation faster. Nevertheless, the errors are non-negligible when the attraction expressions are calculated near the surface of the body. In this work, we carry out a study to develop a new code that determines the centre of mass of each tetrahedron of a shaped polyhedral source and evaluates the gravitational potential function and its first- and second-order derivatives. We performed a series of tests and compared the results with the classical polyhedron method. We found good agreement between our determination of the attraction expressions close to the surface, and the same determination by the classical polyhedron method. However, this agreement does not occur inside the body. Our model appears to be more accurate in representing the potential very close to the body's surface when we divide the tetrahedron in three parts. Finally, we have found that in terms of CPU time requirements, the execution of our code is much faster compared with the polyhedron method.
Fast polyhedral cell sorting for interactive rendering of unstructured grids
Energy Technology Data Exchange (ETDEWEB)
Combra, J; Klosowski, J T; Max, N; Silva, C T; Williams, P L
1998-10-30
Direct volume rendering based on projective methods works by projecting, in visibility order, the polyhedral cells of a mesh onto the image plane, and incrementally compositing the cell's color and opacity into the final image. Crucial to this method is the computation of a visibility ordering of the cells. If the mesh is ''well-behaved'' (acyclic and convex), then the MPVO method of Williams provides a very fast sorting algorithm; however, this method only computes an approximate ordering in general datasets, resulting in visual artifacts when rendered. A recent method of Silva et al. removed the assumption that the mesh is convex, by means of a sweep algorithm used in conjunction with the MPVO method; their algorithm is substantially faster than previous exact methods for general meshes. In this paper we propose a new technique, which we call BSP-XMPVO, which is based on a fast and simple way of using binary space partitions on the boundary elements of the mesh to augment the ordering produced by MPVO. Our results are shown to be orders of magnitude better than previous exact methods of sorting cells.
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.
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.
Rhenium distribution at high temperature processing of some kinds of carbon-containing raw materials
International Nuclear Information System (INIS)
Rhenium distribution at high temperature processing of some kinds of non-conventional potential carbon-containing raw materials (such as shale oil, shungite-containing rocks, high viscosity oil and natural bitumen) is studied. Rhenium concentrating products in semicoking, oxidizing pyrolysis, bertinization and plasma chemical processing of Middle Asian shale oil are revealed. It is established that during semicoking of shale oil, rhenium is concentrating in a solid product (semicoke); during bertinization, oxidizing pyrolysis and plasma chemical processing - in bertinate pyrolysis coke, coke and adsorber nozzle material correspondingly
Fuel cell components and systems having carbon-containing electrically-conductive hollow fibers
Energy Technology Data Exchange (ETDEWEB)
Langry, Kevin C; Farmer, Joseph C
2015-04-28
A method, according to one embodiment, includes acquiring a structure having an ionically-conductive, electrically-resistive electrolyte/separator layer covering an inner or outer surface of a carbon-containing electrically-conductive hollow fiber and a catalyst along one side thereof, adding an anode that extends along at least part of a length of the structure, and adding a cathode that extends along at least part of the length of the structure, the cathode being on an opposite side of the hollow fiber as the anode.
DEFF Research Database (Denmark)
Mak, Vicky; Thomadsen, Tommy
2006-01-01
hard. The QSTSP and the QKP can be solved using branch-and-cut methods. Good bounds can be obtained if strong constraints are used. Hence it is important to identify strong or even facet-defining constraints. This paper studies the polyhedral combinatorics of the QSTSP and the QKP, i.e. amongst others...
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 membran...
Modeling IrisCode and its variants as convex polyhedral cones and its security implications.
Kong, Adams Wai-Kin
2013-03-01
IrisCode, developed by Daugman, in 1993, is the most influential iris recognition algorithm. A thorough understanding of IrisCode is essential, because over 100 million persons have been enrolled by this algorithm and many biometric personal identification and template protection methods have been developed based on IrisCode. This paper indicates that a template produced by IrisCode or its variants is a convex polyhedral cone in a hyperspace. Its central ray, being a rough representation of the original biometric signal, can be computed by a simple algorithm, which can often be implemented in one Matlab command line. The central ray is an expected ray and also an optimal ray of an objective function on a group of distributions. This algorithm is derived from geometric properties of a convex polyhedral cone but does not rely on any prior knowledge (e.g., iris images). The experimental results show that biometric templates, including iris and palmprint templates, produced by different recognition methods can be matched through the central rays in their convex polyhedral cones and that templates protected by a method extended from IrisCode can be broken into. These experimental results indicate that, without a thorough security analysis, convex polyhedral cone templates cannot be assumed secure. Additionally, the simplicity of the algorithm implies that even junior hackers without knowledge of advanced image processing and biometric databases can still break into protected templates and reveal relationships among templates produced by different recognition methods. PMID:23193454
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
International Nuclear Information System (INIS)
Novel monodispersed Fe5(PO4)4(OH)3·2H2O microspheres with the diameters of several micrometers were prepared by a facile one-step hydrothermal method without using any templates, only employing FeCl3·6H2O and NaNH4HPO4 as the initial materials. The obtained samples were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM), respectively. The characterizations revealed that the as-prepared microspheres are constructed by the polyhedral nanoparticles with an average diameter of 100 nm. The corresponding FePO4 microspheres assembled by mesoporous polyhedral nanocrystals can be easily obtained by calcining a sphere-like Fe5(PO4)4(OH)3·2H2O precursor. - Graphical abstract: Novel monodispersed Fe5(PO4)4(OH)3·H2O microspheres with a diameter of several micrometers were successfully obtained by a simple, template-free hydrothermal route. FePO4 microspheres constructed by mesoporous polyhedral FePO4 nanocrystals could be easily prepared by calcining an Fe5(PO4)4(OH)3·2H2O precursor. Display Omitted - Highlights: • Monodispersed Fe5(PO4)4(OH)3·2H2O microspheres were prepared by a facile hydrothermal method without using any templates • Fe5(PO4)4(OH)3·2H2O microspheres present a novel morphology, which was constructed by closely polyhedral nanoparticles. • The FePO4 microspheres assembled by mesoporous polyhedral nanocrystals obtained by calcining Fe5(PO4)4(OH)3·2H2O precursor
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
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.
Three-Dimensional Porous Metal-Metalloporphyrin Framework Consisting of Nanoscopic Polyhedral Cages
Energy Technology Data Exchange (ETDEWEB)
Wang, Xi-Sen; Meng, Le; Cheng, Qigan; Kim, Chungsik; Wojtas, Lukasz; Chrzanowski, Matthew; Chen, Yu-Sheng; Zhang, X Peter; Ma, Shengqian [USF; (UC)
2012-02-07
An unprecedented nanoscopic polyhedral cage-containing metal-metalloporphyrin framework, MMPF-1, has been constructed from a custom-designed porphyrin ligand, 5,15-bis(3,5-dicarboxyphenyl)porphine, that links Cu_{2}(carboxylate)_{4} moieties. A high density of 16 open copper sites confined within a nanoscopic polyhedral cage has been achieved, and the packing of the porphyrin cages via an 'ABAB' pattern affords MMPF-1 ultramicropores which render it selective toward adsorption of H_{2} and O_{2} over N_{2}, and CO_{2} over CH_{4}.
The set of realizations of a max-plus linear sequence is semi-polyhedral
Blondel, Vincent; Portier, Natacha
2010-01-01
We show that the set of realizations of a given dimension of a max-plus linear sequence is a finite union of polyhedral sets, which can be computed from any realization of the sequence. This yields an (expensive) algorithm to solve the max-plus minimal realization problem. These results are derived from general facts on rational expressions over idempotent commutative semirings: we show more generally that the set of values of the coefficients of a commutative rational expression in one letter that yield a given max-plus linear sequence is a semi-algebraic set in the max-plus sense. In particular, it is a finite union of polyhedral sets.
Stress analysis of 3D complex geometries using the scaled boundary polyhedral finite elements
Talebi, Hossein; Saputra, Albert; Song, Chongmin
2016-08-01
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.
Effect of photochemical self-action of carbon-containing aerosol: Wildfires
Konovalov, I. B.; Berezin, E. V.; Beekmann, M.
2016-05-01
It has been shown by numerical simulation that the rate of formation of secondary organic aerosols (SOAs) in smoke plumes caused by vegetation and peat fires under real conditions can significantly depend on the aerosol optical thickness (AOT). The AOT determines the photodissociation rate and hydroxyl radical concentration, which in turn determines the rate of SOA generation as a result of oxidation of semivolatile organic compounds. Quantitative analysis has been carried out for the situation that took place in European Russia during the 2010 Russian wildfires. The state-of-the-art 3D chemical transport model is used in this study; the simulations are optimized and validated using the data of monitoring of the particulate matter in the Moscow region and Finland. The findings indicate that it is important to allow for this effect in studies focused on the analysis and prediction of air pollution due to wildfires, as well as climate and weather studies, whose results may depend on the assumptions about the content and properties of atmospheric carbon-containing aerosol.
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)
Abay Molla Kassa
2014-07-01
Full Text Available In this paper, we developed a novel algorithmic approach for thesolution of multi-parametric non-convex programming problems withcontinuous decision variables. The basic idea of the proposedapproach is based on successive convex relaxation of each non-convexterms and sensitivity analysis theory. The proposed algorithm isimplemented using MATLAB software package and numericalexamples are presented to illustrate the effectiveness andapplicability of the proposed method on multi-parametric non-convexprogramming problems with polyhedral constraints.
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.
Polygonal Prism Mesh in the Viscous Layers for the Polyhedral Mesh Generator, PolyGen
International Nuclear Information System (INIS)
Polyhedral mesh has been known to have some benefits over the tetrahedral mesh. Efforts have been made to set up a polyhedral mesh generation system with open source programs SALOME and TetGen. The evaluation has shown that the polyhedral mesh generation system is promising. But it is necessary to extend the capability of the system to handle the viscous layers to be a generalized mesh generator. A brief review to the previous works on the mesh generation for the viscous layers will be made in section 2. Several challenging issues for the polygonal prism mesh generation will be discussed as well. The procedure to generate a polygonal prism mesh will be discussed in detail in section 3. Conclusion will be followed in section 4. A procedure to generate meshes in the viscous layers with PolyGen has been successfully designed. But more efforts have to be exercised to find the best way for the generating meshes for viscous layers. Using the extrusion direction of the STL data will the first of the trials in the near future
Status of the Polyhedral Mesh Generator using SALOME PLATFORM and TetGen
Energy Technology Data Exchange (ETDEWEB)
Lee, Sang Yong; Park, Chan Eok; Kim, Shin Whan [KEPCO E-C Company, Daejeon (Korea, Republic of)
2014-10-15
Recently developed porous body approach codes such as SPACE and CUPID require a CAD system to estimate the porosity. Since they use the unstructured mesh and they also require reliable mesh generation system. The combination of CAD system and mesh generation system is necessary to cope with a large number of cells and the complex fluid system with structural materials inside. In the past, a CAD system Pro/Engineer and mesh generator Pointwise were evaluated for this application. But, the cost of those commercial CAD and mesh generator is sometimes a great burden. Therefore, efforts have been made to set up a mesh generation system with open source programs. The evaluation of the TetGen has been made in focusing the application for the polyhedral mesh generation. In this paper, SALOME will be described for the efforts to combine TetGen with it. In section 2, brief introduction will be made on the CAD and mesh generation capability of SALOME and Tetgen. SALOME and TetGen codes are being integrated to construct robust polyhedral mesh generator. Procedures to merge boundary faces and to cut concave cells are developed to remove concave cells to get final convex polyhedral mesh. Treating the internal boundary face, i.e. non-manifold face will be the next task in the future investigation.
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.
Energy Technology Data Exchange (ETDEWEB)
Henzie, Joel; Grunwald, Michael; Widmer-Cooper, Asaph; Geissler, Phillip L.; Yang, Peidong
2011-03-01
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.
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.
Wysokowski, Marcin; Materna, Katarzyna; Walter, Juliane; Petrenko, Iaroslav; Stelling, Allison L; Bazhenov, Vasilii V; Klapiszewski, Łukasz; Szatkowski, Tomasz; Lewandowska, Olga; Stawski, Dawid; Molodtsov, Serguei L; Maciejewski, Hieronim; Ehrlich, Hermann; Jesionowski, Teofil
2015-01-01
Chitinous scaffolds isolated from the skeleton of marine sponge Aplysina cauliformis were used as a template for the deposition of polyhedral oligomeric silsesquioxanes (POSS). These chitin-POSS based composites with hydrophobic properties were prepared for the first time using solvothermal synthesis (pH 3, temp 80 °C), and were thoroughly characterized. The resulting material was studied using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy and thermogravimetry. A mechanism for the chitin-POSS interaction after exposure to these solvothermal conditions is proposed and discussed. PMID:25889055
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Zhang, Liying; Xiong, Shanxin; Ma, Jan; Lu, Xuehong [School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)
2009-05-15
In this paper we report a high-contrast complementary electrochromic device based on polyaniline-tethered polyhedral oligomeric silsesquioxane (POSS-PANI) and tungsten oxide (WO{sub 3}). The electrochromic properties, cyclic voltammetry behavior and coloration efficiency of the device are studied. Due to the loosely packed structure of POSS-PANI, it possesses more accessible doping sites and hence gives rise to a significantly higher electrochromic contrast than polyaniline (PANI). Furthermore, the replacement of PANI with POSS-PANI as the complementary layer for WO{sub 3} leads to an enhanced complementary effect, for which the underneath mechanism is also discussed. (author)
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. PMID:26752650
International Nuclear Information System (INIS)
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)
International Nuclear Information System (INIS)
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
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.
Suzuki, Kohei; Omori, Takesi; Kajishima, Takeo
2014-11-01
Although the advantage of using arbitrarily-shaped polyhedral meshes for the industrial flow applications is clear, their employment to two-phase flows is rather limited due to the poor prediction accuracy of the existing numerical methods on such meshes. We present a numerical method based on VOF (Volume of Fluid) method which works on arbitrarily-shaped three-dimensional polyhedral meshes with little volume/shape error for the interface advection and with little curvature estimation error. To make the implementation in three-dimensional geometry feasible, we extend THINC (Tangent of Hyperbola Interface Capturing) method for polyhedral meshes which does not require laborious geometric arithmetics. In the oral presentation we will also show that the combination of RDF (Reconstructed Distance Function) algorithm and the carefully selected discretization procedure gives good performance in the interface curvature estimation.
Directory of Open Access Journals (Sweden)
Dalissier E.
2013-12-01
Full Text Available The objective of the ComPASS project is to develop a parallel multiphase Darcy flow simulator adapted to general unstructured polyhedral meshes (in a general sense with possibly non planar faces and to the parallelization of advanced finite volume discretizations with various choices of the degrees of freedom such as cell centres, vertices, or face centres. The main targeted applications are the simulation of CO2 geological storage, nuclear waste repository and reservoir simulations. The CEMRACS 2012 summer school devoted to high performance computing has been an ideal framework to start this collaborative project. This paper describes what has been achieved during the four weeks of the CEMRACS project which has been focusing on the implementation of basic features of the code such as the distributed unstructured polyhedral mesh, the synchronization of the degrees of freedom, and the connection to scientific libraries including the partitioner METIS, the visualization tool PARAVIEW, and the parallel linear solver library PETSc. The parallel efficiency of this first version of the ComPASS code has been validated on a toy parabolic problem using the Vertex Approximate Gradient finite volume spatial discretization with both cell and vertex degrees of freedom, combined with an Euler implicit time integration.
International Nuclear Information System (INIS)
The quaternary carbon-containing alcohols (1-6) were resolved enantioselectively by various lipases such as PFL (Pseudomonas fluorescens lipase), LAK (Pseudomonas fluorescens lipase), CRL (Candida rugosa lipase) and PCL (Pseudomonas cepacia lipase). The enzymatic resolution of racemic alcohol (±)-2 gave the excellent enantioselectivity in favor of (S)-2d in 99% ee, while those of the racemic alcohols (1, 3, 4, 5 and 6) gave the resolved alcohols with moderate to good enantioselectivity. Also, their absolute configurations were determined by chemical transformation to the known compounds
International Nuclear Information System (INIS)
The atomic structure of amorphous carbon-containing materials such as carbon glass, spectroscopically pure carbon, schungite and anthracite is investigated using X ray diffraction analysis and computerized simulation. In computerized simulation of model gratings packing into packets an interlayer distance and a number of layer in a packet varied and a gratings turn is predetermined randomly. The quantity of gratings in a packet is shown to vary between four for anthracite and six for spectroscopically pure coal. The interlayer distance for all amorphous carbonaceous materials is above 3.35 A which is typical for graphite
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.
Institute of Scientific and Technical Information of China (English)
ZHU Yu-fang; ZHAO Jun-feng; WANG Xi; LI Qi-fang
2008-01-01
Polyvinylcarbazole(PVK) composites containing organic-inorganic hybrid polyhedral oligomeric silsesquioxane(POSS) PVK-POSS were prepared by free radical polymerization.POSS monomers reacted with vinylcarbazole and were completely dispersed at molecular level in PVK matrix and PVK-POSS nanocomposites display higher glass transition temperature(Tg) in comparison with neat PVK.Optical properties of PVK/POSS nanocomposites were investigated by UV-spectrum and PL-spectrum and the results show that the PVK-POSS nanoparticles have a good interface effect and improve color purity effectively.The maximum absorption wavelength bathochromically shifts gradually with the increasing of the content of POSS.The luminescent intensity becomes higher and higher with the increase of POSS content,and reaches its maximum luminescent intensity when the POSS content is 3% (mass fraction),while some POSS-rich nanoparticles are present in matrix when contents of POSS are beyond 5%.
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).
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.
International Nuclear Information System (INIS)
We develop a piecewise linear (PWL) Galerkin finite element spatial discretization for the multi-dimensional radiation diffusion equation. It uses recently introduced 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 first demonstrate some analytical properties of the PWL method and perform a simple mode analysis to compare the PWL method with Palmer's vertex-centered finite-volume method and with a bilinear continuous finite element method. We then show that this new PWL method gives solutions comparable to those from Palmer's. 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
Lligadas, Gerard; Ronda, Joan C; Galià, Marina; Cádiz, Virginia
2006-12-01
This study is concerned with the preparation and properties of a new class of bionanocomposites from renewable resources. Epoxidized linseed oil (ELO) and 3-glycidylpropylheptaisobutyl-T8-polyhedral oligomeric silsesquioxane (G-POSS) (2, 5, and 10 wt %) were cross-linked, and Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were employed to characterize the POSS-reinforced oil-based polymer networks. No POSS aggregates were observed for the 2 wt % G-POSS nanocomposite by SEM. POSS-rich particles with diameters of several nanometers were observed in the nanocomposites with 5 and 10 wt % G-POSS. Enhanced glass transition temperatures and storage moduli of the networks in the glassy state and rubber plateau were observed to be higher than those of the POSS-free oil based polymer network, due to the reinforcement effect of POSS cages. PMID:17154483
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.
International Nuclear Information System (INIS)
Composite membranes based on poly(2,2′(m-phenylene)-5,5′bibenzimidazole) (PBI) and sulfonated polyhedral oligosilsesquioxane (S-POSS) with S-POSS contents of 5 and 10 wt.% were prepared by solution casting as base materials for high temperature polymer electrolyte membrane fuel cells. With membranes based on pure PBI as a reference point, the composite membranes were characterized with respect to spectroscopic and physicochemical properties. After doping with phosphoric acid, the composite membranes showed considerably improved ex situ proton conductivity under anhydrous as well as under fully 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
Compatible discrete operator schemes on polyhedral meshes for elliptic and Stokes equations
International Nuclear Information System (INIS)
This thesis presents a new class of spatial discretization schemes on polyhedral meshes, called Compatible Discrete Operator (CDO) schemes and their application to elliptic and Stokes equations In CDO schemes, preserving the structural properties of the continuous equations is the leading principle to design the discrete operators. De Rham maps define the degrees of freedom according to the physical nature of fields to discretize. CDO schemes operate a clear separation between topological relations (balance equations) and constitutive relations (closure laws). Topological relations are related to discrete differential operators, and constitutive relations to discrete Hodge operators. A feature of CDO schemes is the explicit use of a second mesh, called dual mesh, to build the discrete Hodge operator. Two families of CDO schemes are considered: vertex-based schemes where the potential is located at (primal) mesh vertices, and cell-based schemes where the potential is located at dual mesh vertices (dual vertices being in one-to-one correspondence with primal cells). The CDO schemes related to these two families are presented and their convergence is analyzed. A first analysis hinges on an algebraic definition of the discrete Hodge operator and allows one to identify three key properties: symmetry, stability, and P0-consistency. A second analysis hinges on a definition of the discrete Hodge operator using reconstruction operators, and the requirements on these reconstruction operators are identified. In addition, CDO schemes provide a unified vision on a broad class of schemes proposed in the literature (finite element, finite element, mimetic schemes... ). Finally, the reliability and the efficiency of CDO schemes are assessed on various test cases and several polyhedral meshes. (author)
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.
Forni, Fulvio; Teel, Andrew; Zaccarian, Luca
2011-01-01
In this paper we formulate the tracking problem of a translating mass in a polyhedral billiard as a stabilization problem for a suitable set. Due to the discontinuous dynamics arising from nonsmooth impacts, the tracking problem is formulated within a hybrid systems framework and a Lyapunov function is given, which decreases during flow (continuous motion) and remains constant across jumps (impacts of the masses). To guarantee non-increase of the Lyapunov function at jumps, we introduce a nov...
Dielectric properties of polyhedral oligomeric silsesquioxane (POSS)-based nanocomposites at 77k
Energy Technology Data Exchange (ETDEWEB)
Pan, Ming-Jen; Gorzkowski, Edward; McAllister, Kelly, E-mail: pan@anvil.nrl.navy.mi [Multifunctional Materials Branch, Code 6350 U.S. Naval Research Laboratory 4555 Overlook Avenue SW, Washington, DC 20375 (United States)
2011-10-29
The goal of this study is to develop dielectric nanocomposites for high energy density applications at liquid nitrogen temperature by utilizing a unique nano-material polyhedral oligomeric silsesquioxanes (POSS). A POSS molecule is consisted of a silica cage core with 8 silicon and 12 oxygen atoms and organic functional groups attached to the corners of the cage. In this study, we utilize POSS for the fabrication of nanocomposites both as a silica nanoparticle filler to enhance the breakdown strength and as a surfactant for effective dispersion of high permittivity ceramic nanoparticles in a polymer matrix. The matrix materials selected for the study are polyvinylidene fluoride (PVDF) and poly(methyl methacrylate) (PMMA). The ceramic nanoparticles are barium strontium titanate (BST 50/50) and strontium titanate. The dielectric properties of the solution-cast nanocomposites films were correlated to the composition and processing conditions. We determined that the addition of POSS did not provide enhanced dielectric performance in PVDF- and PMMA-based materials at either room temperature or 77K. In addition, we found that the dielectric breakdown strength of PMMA is lower at 77K than at room temperature, contradicting literature data.
International Nuclear Information System (INIS)
In the present study, spherical nanoparticles (NPs) containing polyhedral oligosilsesquioxane (POSS) as an inner hydrophobic core and poly(vinyl alcohol) PVA as a hydrophilic outer shell were prepared by dialysis approach. Preparation of amphiphilic POSS-grafted-PVA co-polymer was characterized by 1H NMR and FT-IR. The results indicated urethane linkage between monoisocyanate group of POSS macromer and the hydroxyl groups of PVA. The dynamic light scattering (DLS) and electrophoretic light scattering (ELS) of the NPs revealed that they have an average hydrodynamic diameter and negative zeta (ζ)-potential of 215 nm and - 161 mV, respectively. Atomic force microscopy (AFM) and bio-transmission electron microscope (BIO-TEM) have shown unagglomerated NPs within a diameter range of 60-90 nm. The prepared NPs were investigated to improve the control release of anticancer drug; paclitaxel as a model drug. Due to drug loading, the hydrodynamic diameter and negative zeta (ζ)-potential have changed to 325 nm and - 14 mV, respectively. In addition, in-vitro drug release experiments were conducted; the obtained results explicated continuous release for over 40 days. However, in case of using pure drug only, the drug completely released within 1 h.
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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.
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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.
Liquid crystal alignment by polyhedral oligomeric silsesquioxane (POSS)-polyimide nanocomposites
Liu, Han-Shiang; Jeng, Shie-Chang
2013-05-01
Polyimide (PI) films are widely used in the liquid crystal display (LCD) industry to align liquid crystal (LC) molecules in a specific orientation with a pretilt angle θp on the PI alignment films. It was observed that physical dispersion of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in commercial homogenous PIs decreases the surface energy of the PI alignment films and generates a controllable θp in the range 0° < θp < 90°, which is not easily achieved by complicate PI synthesis. Characteristics of POSS-PI nanocomposites were studied to investigate the influence of POSS nanoparticles on PIs. Increased absorption in the infrared spectra and decreased decomposition temperature and glass transition temperature with POSS doped concentration in PI were observed due to the increase in free volume of POSS-PI nanocomposites. Such nanoscale hybridization suggests a novel approach to tune the properties of PIs through modification of molecular interaction. A fast response no-bias optically-compensated bend (OCB) LCD with a pretilt angle of 68° was also demonstrated in this work.
Kim, Ho-Joong; Kwon, Younghwan; Kim, Chang Kee
2014-11-01
Polyurethane/polyhedral oligomeric silsesquioxane (PU/POSS) hybrid composites are prepared by a one-step PU reaction using hydroxyl-terminated polybutadiene (HTPB) prepolymer, isophorone diisocyanate (IPDI) and either non-reactive or reactive POSS molecule. The effect of incorporation of functionalized POSS molecules covalently bonded or physically blended into PU matrix is investigated in terms of mechanical reinforcement and thermal stability of these resulting PU/POSS hybrid composites. PU/POSS hybrid composites prepared with reactive POSS molecules exhibit the mechanical reinforcement while maintaining low glass transition temperataure (T(g)), probably due to the fact that reactive POSS molecules chemically incorporated in PU are aggregated to crystallize, effectively working as a physical crosslinking in PU/POSS hybrid composites. This can be advantageous in that mechanical reinforcement of PU/POSS hybrid composites can be achived without sacrificing the low temperature properties of these composites. However, the contribution of POSS molecules incorporated covalently into PU matrix is virtually absent on the thermal decomposition temperature (T(d,max)) measured using TGA/DTG. Thermal degradation behavior of these hybrid composites in the early stage rather appears to depend preferably on characteristics of POSS molecules incorporated. PMID:25958582
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.
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
Belikov, A. V.; Skrypnik, A. V.; Kurnyshev, V. Yu; Shatilova, K. V.
2016-06-01
We have studied carbon-containing optothermal fibre converters (COTFCs) that are located on the distal end of a quartz – quartz optical fibre for delivering laser radiation in medical laser surgery systems and differ in the thickness and structure of the layer of a material converting laser radiation into heat. The heating dynamics of 'thin-film' and '3D' converters have been investigated at average incident 980-nm semiconductor laser beam powers of 0.3, 1.0 and 4.0 W, with the converters placed freely in air. The results demonstrate that, before the instant of disintegration, the efficiency of laser heating of the converter surface can reach 3000 °C W-1 for thin-film converters, 1000 °C W-1 for spherical 3D converters and 55 °C W-1 for planar 3D converters. The thin-film converter breaks down at an average laser beam power as low as 0.30 +/- 0.05 W, which is accompanied by a considerable reduction in heating efficiency and is caused by the disintegration of the carbon film on its surface. The spherical 3D converter breaks down at an average power of 4.0 +/- 0.1 W, as a result of the disintegration of the carbon film on its surface and partial melting of a modified layer containing microbubbles. The carbon film on the surface of the planar 3D converter also disintegrates at an average power of 4.0 +/- 0.1 W, but the structure of the modified layer remains unchanged. We have constructed structural and optophysical models of the converters by simulating light absorption in carbon films on the surface of the COTFC and inside the microbubbles present in the modified layer of the converters. The proposed models of the COTFCs have been shown to adequately describe real converters.
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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.
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
Toyosawa, Yoshiko; Kawagoe, Yasushi; Matsushima, Ryo; Crofts, Naoko; Ogawa, Masahiro; Fukuda, Masako; Kumamaru, Toshihiro; Okazaki, Yozo; Kusano, Miyako; Saito, Kazuki; Toyooka, Kiminori; Sato, Mayuko; Ai, Yongfeng; Jane, Jay-Lin; Nakamura, Yasunori; Fujita, Naoko
2016-03-01
Starch granule morphology differs markedly among plant species. However, the mechanisms controlling starch granule morphology have not been elucidated. Rice (Oryza sativa) endosperm produces characteristic compound-type granules containing dozens of polyhedral starch granules within an amyloplast. Some other cereal species produce simple-type granules, in which only one starch granule is present per amyloplast. A double mutant rice deficient in the starch synthase (SS) genes SSIIIa and SSIVb (ss3a ss4b) produced spherical starch granules, whereas the parental single mutants produced polyhedral starch granules similar to the wild type. The ss3a ss4b amyloplasts contained compound-type starch granules during early developmental stages, and spherical granules were separated from each other during subsequent amyloplast development and seed dehydration. Analysis of glucan chain length distribution identified overlapping roles for SSIIIa and SSIVb in amylopectin chain synthesis, with a degree of polymerization of 42 or greater. Confocal fluorescence microscopy and immunoelectron microscopy of wild-type developing rice seeds revealed that the majority of SSIVb was localized between starch granules. Therefore, we propose that SSIIIa and SSIVb have crucial roles in determining starch granule morphology and in maintaining the amyloplast envelope structure. We present a model of spherical starch granule production. PMID:26747287
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. PMID:27433703
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.
Tan, Aaron; Farhatnia, Yasmin; Goh, Debbie; Natasha, G; de Mel, Achala; Lim, Jing; Teoh, Swee-Hin; Malkovskiy, Andrey V; Chawla, Reema; Rajadas, Jayakumar; Cousins, Brian G; Michael R Hamblin; Alavijeh, Mohammad S; Seifalian, Alexander M
2013-01-01
An unmet need exists for the development of next-generation multifunctional nanocomposite materials for biomedical applications, particularly in the field of cardiovascular regenerative biology. Herein, we describe the preparation and characterization of a novel polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) nanocomposite polymer with covalently attached anti-CD34 antibodies to enhance capture of circulating endothelial progenitor cells (EPC). This material may ...
Mujib Khan; Mahesh Hosur; Hassan Mahfuz; Richard Granata; Felicia Powell
2011-01-01
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 silsesqui...
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.
Pan, Haiyan; Zhang, Yuanyuan; Pu, Hongting; Chang, Zhihong
2014-10-01
A new series of organic-inorganic hybrid proton exchange membranes (PEMs) were prepared using sulfonated polyimides containing benzimidazole (SPIBIs) and glycidyl ether of polyhedral oligomeric silsesquioxanes (G-POSS). SPIBIs were synthesized using 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA), 5-amino-2-(4-aminophenyl) benzimidazole (APBIA) and 4,4‧-diaminodiphenyl ether-2,2‧-disulfonic acid (ODADS). The organic-inorganic cross-linked membranes can be prepared by SPIBIs with G-POSS by a thermal treatment process. The cross-linking density of the membranes was evaluated by gel fractions. The water uptake, swelling ratio, mechanical property, thermal behavior, proton conductivity, oxidative and hydrolytic stability of the cross-linked organic-inorganic membranes were intensively investigated. All the cross-linked membranes exhibit high cross-linking density for the gel fraction higher than 70%. Compared to pristine membranes (SPIBIs) and membranes without benzimidazole groups (SPI), the anti-free-radical oxidative and hydrolytic stabilities of cross-linked membranes are significantly higher. The anti-free-oxidative stability of SPIBI-100-P (cross-linked SPIBI membrane with 100% degree of sulfonation) is nearly four-fold higher than that of SPIBI-100. The proton conductivity of the cross-linked membranes ranges from 10-3 S cm-1 to 10-2 S cm-1 depending both on the degree of sulfonation (DS) of the SPIBI and temperature.
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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.
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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.
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.
International Nuclear Information System (INIS)
Highlights: ► The homogenously-mixed PCL/POSS nanocomposites were prepared by solution blending. ► The crosslinking of the nanocomposites was conducted by electron beam irradiation. ► The crosslinked nanocomposites showed the improved mechanical and thermal properties. ► This technique is useful to fabricate high-performance polymer nanocomposites. - Abstract: Crosslinked poly(ε-caprolactone)/polyhedral oligomeric silsesquioxane (PCL/POSS) nanocomposite films prepared by a solution casting were crosslinked by electron beam irradiation under various conditions. The results of the crosslinking degree measurement revealed that the crosslinking degree of the PCL/POSS nanocomposites reached to 74%, which depended on the POSS content and the absorbed dose. The results of the FE–SEM and EDX analyses revealed that the POSS was homogeneously dispersed in the PCL matrix. In comparison to the virgin PCL with a tensile strength of 20 MPa, the tensile strength of the crosslinked PCL/POSS nanocomposites increased to 25.8 MPa with an increasing POSS content and absorbed dose to 100 kGy, whereas their elongation-at-break was considerably reduced. The results of the dynamic mechanical analysis revealed that the crosslinked PCL/POSS nanocomposites had a higher heat resistance than the virgin PCL. Based on the results of the enzymatic degradation test, the biodegradability of the crosslinked PCL/POSS nanocomposites was significantly reduced in comparison to that of the virgin PCL.
International Nuclear Information System (INIS)
The electron beam-induced crosslinking of poly(butylene adipate-co-terephthalate) (PBAT)/polyhedral oligomeric silsesquioxane (POSS) nanocomposites was investigated in this study. PBAT/POSS nanocomposites prepared by a solution blending with various compositions were crosslinked by electron beam irradiation at various absorbed doses ranging from 20 to 200 kGy and their properties were characterized in terms of their degree of crosslinking, morphology, thermal and mechanical properties, and biodegradability. The results of the degree of crosslinking measurements revealed that PBAT/POSS nanocomposites were more effectively crosslinked than the pure PBAT and that the degree of crosslinking was dependent on the absorbed dose and POSS content. From the results of the FE-SEM and EDX analyses, the POSS was found to be uniformly dispersed in the PBAT matrix. Based on the results of the UTM, DMA, and TMA, the crosslinked PBAT/POSS nanocomposites exhibited much higher thermal and mechanical properties compared to those of the pure PBAT. - Highlights: ► Crosslinked PBAT/POSS nanocomposites were prepared by electron beam irradiation. ► The POSS as a nanofillers was homogeneously dispersed in the PBAT matrix. ► The crosslinked nanocomposites exhibited improved thermal and mechanical properties.
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.
东鞍山含碳酸盐赤铁矿石浮选试验%Flotation separation of Donganshan carbonates-containing hematite ore
Institute of Scientific and Technical Information of China (English)
邵安林
2013-01-01
For the mixed minerals which were prepared by pure martite, siderite and quartz, the iron grade, yield and recovery decrease rapidly with the increase of siderite content in iron ore, which indicates that the reverse flotation couldn't concentrate the carbonates-containing hematite ore. Stepped flotation was proposed which separates siderite first and then takes martite apart from quartz. Therefore, the mass fraction of the iron grade increases from 42.34% to 59.09% and iron recovery increases from 53.18% to 79.84% compared with routine reverse flotation. And for Donganshan carbonates-containing hematite ore, the mass fraction of iron grade of 66.34% and recovery of 71.6% are obtained in close-circle experiment of stepped flotation.%针对纯矿物配成的含赤铁矿、菱铁矿、石英的混合矿进行浮选试验.随着铁矿石中菱铁矿质量分数的提高,铁精矿TFe品位、产率和回收率等指标迅速下降,说明现有反浮选流程不能将含有菱铁矿的铁矿石有效分选.提出将菱铁矿预先分离、然后再将赤铁矿和石英分离的分步浮选流程,相比常规反浮选流程,铁精矿TFe质量分数由42.34％上升至59.09％,铁的回收率由53.18％提高到79.84％.而针对东鞍山含菱铁矿的赤铁矿石,采用分步浮选工艺闭路流程,可获得铁精矿TFe质量分数为66.34％,回收率为71.60％.
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.
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.
Ghanbari, Hossein; Radenkovic, Dina; Marashi, Sayed Mahdi; Parsno, Shirin; Roohpour, Nima; Burriesci, Gaetano; Seifalian, Alexander M
2016-06-01
In the cardiovascular system, the endothelial layer provides a natural antithrombogenic surface on the inner portion of the heart and associated vessels. For a synthetic material therefore, the ability to attract and retain endothelial or endothelial progenitor cells (EPCs), ultimately creating a single endothelial layer on its surface, is of prime importance. The authors have developed a nanocomposite polymer, based on a combination of polyhedral oligomeric silsesquioxane nanoparticles and polycarbonate urea urethane (POSS-PCU), which is biocompatible and has been used in human for the world's first synthetic trachea, tear duct, and bypass graft. In this study, the authors modified the surface of this casted nanocomposite by grafting fibronectin derived bioactive peptides [glycine-arginine-glycine-aspartic acid-glycine (GRGDG) and lauric acid conjugated GRGDG (GRGDG-LA)] to enhance the endothelialization for using heart valves leaflets from circulating EPCs. Human peripheral blood mononuclear cells were separated using Ficoll-Paque centrifugation, with harvested EPCs purified using CD34 microbead labeling and magnetic-activated cell sorting. Cells were seeded onto 96 well plates coated with POSS-PCU, GRGDG/GRGDG-LA modified POSS-PCU and PCU polymers, for a period of 21 days. Cells were studied under light, confocal, and scanning electron microscope (SEM). Fluorescence-activated cell sorting was used to analyze cell surface markers. Cell attachment and proliferation was observed in all POSS-PCU samples, significantly higher than the activity seen within the control PCU polymers (p < 0.05). Microscopic examination revealed clonal expansion and morphological changes in cells seeded on POSS-PCU. The cells expressed increasing levels of mature endothelial cell markers over time with a concurrent reduction in hematopoietic stem cell marker expression. SEM showed a mixed population of morphologically differentiated endothelial cells and EPCs. These results support
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)
Preparation of Polyhedral Oligomeric Silsesquioxane Modified Polyurethane%多面体低聚倍半硅氧烷改性PU的制备
Institute of Scientific and Technical Information of China (English)
田春蓉; 王建华; 孙杰; 梁书恩; 程克梅
2011-01-01
采用多面体低聚倍半硅氧烷(POSS)对聚氨酯(PU)进行改性,并对改性PU的性能进行研究.结果表明:采用超声波分散法可将POSS均匀分散在PU基体中；八乙烯基POSS对PU具有较好的补强和增韧作用,而八苯基POSS对PU的补强作用不明显.%Polyurethane(PU) was modified by polyhedral oligomeric silsesquioxane(POSS) , and the properties of modified PU were investigated. The results showed that,POSS was uniformly dispersed in PU matrix by using ultrasonic dispersion method; octavinylsilsesquioxane(OVS) possessed preferable reinforcing and toughening effects, but octaphenylsilsesquioxane (OPS) had no significant reinforcing effect.
DEFF Research Database (Denmark)
Johansen, Peter M.; Breinbjerg, Olav
1995-01-01
of the source and observation points can be almost arbitrary. The line integral representation yields the exact same result as the conventional surface radiation integral; however, it is potentially less time consuming and particularly useful when the physical optics field can be augmented by a fringe wave......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...... contribution as calculated from physical theory of diffraction equivalent edge currents. The final expression for the line integral representation is lengthy but involves only simple functions and is thus suited for numerical calculation. To illustrate the exactness of the line integral representation...
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
Watanabe, Kenta; Hirata, Michiko; Tominari, Tsukasa; Matsumoto, Chiho; Endo, Yasuyuki; Murphy, Gillian; Nagase, Hideaki; Inada, Masaki; Miyaura, Chisato
2016-09-01
Carboranes are a class of carbon-containing polyhedral boron cluster compounds with globular geometry and hydrophobic surface that interact with hormone receptors such as estrogen receptor (ER) and androgen receptor (AR). We have synthesized BA321, a novel carborane compound, which binds to AR. We found here that it also binds to ERs, ERα and ERβ. In orchidectomized (ORX) mice, femoral bone mass was markedly reduced due to androgen deficiency and BA321 restored bone loss in the male, whilst the decreased weight of seminal vesicle in ORX mice was not recovered by administration of BA321. In female mice, BA321 acts as a pure estrogen agonist, and restored both the loss of bone mass and uterine atrophy due to estrogen deficiency in ovariectomized (OVX) mice. In bone tissues, the trabecular bone loss occurred in both ORX and OVX mice, and BA321 completely restored the trabecular bone loss in both sexes. Cortical bone loss occurred in ORX mice but not in OVX mice, and BA321 clearly restored cortical bone loss due to androgen deficiency in ORX mice. Therefore, BA321 is a novel selective androgen receptor modulator (SARM) that may offer a new therapy option for osteoporosis in the male. PMID:27402268
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.
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.
International Nuclear Information System (INIS)
Environment perception is an important process which enables a robot to perform actions in an unknown scene. Although many sensors exist to 'give sight', the camera seems to play a leading part. This thesis deals with the reconstruction of scenes made of cylindrical and polyhedral objects from sequences of images provided by a moving camera. Two methods are presented. Both are based on the evolution of apparent contours of objects in a sequence. The first approach has been developed considering that camera motion is known. Despite the good results obtained by this method, the specific conditions it requires makes its use limited. In order to avoid an accurate evaluation of camera motion, we introduce another method allowing, at the same time, to estimate the object parameters and camera positions. In this approach, only is needed a 'poor' knowledge of camera displacements supplied by the control system of the robotic platform, in which the camera is embedded. An optimal integration of a priori information, as well as the dynamic feature of the state model to estimate, lead us to use the Kalman filter. Experiments conducted with synthetic and real images proved the reliability of these methods. Camera calibration set-up is also suggested to achieve the most accurate scene models resulting from reconstruction processes. (author)
Institute of Scientific and Technical Information of China (English)
邵安林
2011-01-01
东鞍山铁矿高碳酸盐矿石中的菱铁矿常使东鞍山烧结厂的反浮选工序“精尾不分”,导致这些高碳酸盐矿石不能入选.为此,采用纯矿物配成的人工混合矿研究了菱铁矿对假象赤铁矿与石 英常规反浮选的影响,并进行了人工混合矿及东鞍山高碳酸盐赤铁矿石磁选混合精矿的分步浮选试验.其中磁选混合精矿的分步浮选闭路试验在第1步正浮选时预先除去了占总量9.13％的菱铁矿,使第2步反浮选获得了铁精矿品位为66.34％、回收率为71.60％的良好分选指标,从而证明分步浮选是东鞍山高碳酸盐铁矿石的有效浮选工艺.%Siderite among Donganshan carbonates-contained iron ore usually makes the non-separation of concentrates and tailings in the reverse flotation of Donganshan Sinter Plant, resulting in the loss of the high carbonates ore. Therefore, artificial mixed minerals were adopted to investigate the effect of siderite on the reverse flotation of martite and quartz. Then, stepped flotation experiments of artificial mixed minerals and mixed magnetic concentrate of Donganshan high carbonates-contained hematite ores were carried out, where about 9. 13% of siderite are removed at the first step of direct flotation in the close-circuit tests of mixed magnetic concentrate, and good index with iron concentrate of Fe grade 66. 34% and recovery 71.60% was obtained in close-circuit experiment of the reverse flotation at the second step. All these approved that the stepped flotation is an effective flotation process for Donganshan high carbonates-contained hematite ore.
Directory of Open Access Journals (Sweden)
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.
Directory of Open Access Journals (Sweden)
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.
Jefferson, LaCrissia U; Netchaev, Anton D; Jefcoat, Jennifer A; Windham, Amber D; McFarland, Frederick M; Guo, Song; Buchanan, Randy K; Buchanan, J Paige
2015-06-17
Coatings prepared from titania-thiol-ene compositions were found to be both self-cleaning, as measured by changes in water contact angle, and photocatalytic toward the degradation of an organic dye. Stable titania-thiol-ene dispersions at approximately 2 wt % solids were prepared using a combination of high-shear mixing and sonication in acetone solvent from photocatalytic titania, trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS) dispersant, and select thiol-ene monomers, i.e., trimethylolpropane tris(3-mercaptopropionate) (TMPMP), pentaerythritol allyl ether (APE), and 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TTT). The dispersed particle compositions were characterized by DLS and TEM. The synthetic methods employed yield a strongly bound particle/POSS complex, supported by IR, 29Si NMR, and TGA. The factors of spray techniques, carrier solvent volatility, and particle size and size distributions, in combination, likely all contribute to the highly textured but uniform surfaces observed via SEM and AFM. Polymer composites possessed thermal transitions (e.g., Tg) consistent with composition. In general, the presence of polymer matrix provided mechanical integrity, without significantly compromising or prohibiting other critical performance characteristics, such as film processing, photocatalytic degradation of adsorbed contaminants, and the hydrophobic-hydrophilic transition. In all cases, coatings containing photocatalytic titania were converted from superhydrophobic to superhydrophilic, as defined by changes in the water contact angle. The superhydrophilic state of samples was considered persistent, since long time durations in complete darkness were required to observe any significant hydrophobic return. In a preliminary demonstration, the photocatalytic activity of prepared coatings was confirmed through the degradation of crystal violet dye. This work demonstrates that a scalable process can be found to prepare titania
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 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 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. PMID:27384590
Directory of Open Access Journals (Sweden)
V. G. Domiciano
2004-09-01
Full Text Available Os benefícios proporcionados pela adição de carbono em concretos refratários têm ampliado a utilização desses materiais em aplicações siderúrgicas. Contudo, um problema inerente à utilização de carbono em refratários é a sua susceptibilidade à oxidação a temperaturas superiores a 600 °C. Uma das alternativas empregada na tentativa de controlar a oxidação do carbono é o uso de antioxidantes. Dentre eles, o pó de alumínio tem mostrado bons resultados em tijolos refratários contendo carbono. Porém, sua aplicação em concretos refratários é limitada pela forte tendência que o pó de alumínio apresenta em se hidratar. Algumas técnicas de recobrimento baseadas no processo Sol-Gel têm sido empregadas como forma de impedir a reação de hidratação do pó de alumínio quando em água. Entretanto, a eficiência destes recobrimentos ainda não foi avaliada em concretos refratários. O presente trabalho se propõe a avaliar a eficiência de recobrimentos à base de SiO2 ou TiO2 em inibir a reação de hidratação do pó de alumínio em condições reais de aplicação. Estes recobrimentos foram obtidos a partir de alcóxidos metálicos e um polímero reativo fazendo uso do método Sol-Gel.The benefits promoted by the addition of carbon in refractory castables resulted the increase use of these materials in steel making industry. Nevertheless, carbon-containing refractory castables faces the problem of oxidation at temperatures above 600°C. One of the alternatives to overcome this drawback is the use of antioxidants. Among them, aluminum powder has shown good results in carbon containing refractory bricks. However, its application in refractory castables is restricted by the strong tendency of aluminum powder to react with water. Some surface treatments, based on Sol-Gel process, have been employed to generate an oxide coating in order to inhibit the hydration reaction when aluminum is exposed to water. However, the
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.
Directory of Open Access Journals (Sweden)
V. G. Domiciano
2006-09-01
Full Text Available Os benefícios proporcionados pela adição de carbono em concretos refratários têm ampliado a utilização destes materiais em aplicações siderúrgicas. Contudo, um dos problemas que ainda limita o emprego de concretos refratários contendo elevado teor de carbono é a corrosão de pós metálicos comumente empregados para conter a oxidação do carbono a altas temperaturas. Estudos preliminares mostraram que a corrosão das partículas metálicas é diretamente afetada pelas condições alcalinas promovidas pela presença de cimento. Diante disso, o objetivo deste trabalho foi avaliar o efeito da temperatura e a influência de diferentes agentes ligantes sobre a resistência à corrosão de pós metálicos (Al e Si em água e em concretos refratários contendo elevado teor de carbono. Para isso, foi empregada uma técnica capaz de detectar a liberação de gás H2 como produto da reação de corrosão dos metais. Os resultados obtidos revelaram a possibilidade de aplicação dos pós metálicos em concreto refratário através da escolha de um ligante apropriado.The benefits promoted by carbon addition in refractory castables have led to an increase in the use of such materials in the steel making industry. Nevertheless, one of the problems that still hinder the use of high-carbon-containing castables is the corrosion of metal powders commonly used to prevent carbon oxidation at high temperatures. Preliminary studies have pointed out that the metal powders corrosion within the castables is affected by the aggressive alkaline conditions promoted by cement hydration. The present work aimed to evaluate the effect of temperature as well as the influence of different binders on the corrosion resistance of Al and Si powders in water and in high-carbon containing castables. A technique able to detect the H2-gas release was used to identify the metal powders corrosion. The results revealed the possibility of applying Al or Si powders in these
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.
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.
Energy Technology Data Exchange (ETDEWEB)
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.
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...
Institute of Scientific and Technical Information of China (English)
宋保莹; 袁立宾; 韦思明
2015-01-01
对东鞍山含碳酸盐铁矿石的工艺矿物学进行了研究,提出了处理含碳酸盐铁矿石的分步浮选工艺流程:第一步,在中性环境中采用正浮选分离出碳酸盐;第二步,在强碱性环境中采用反浮选分选赤铁矿. 工业生产实践表明,分步浮选取得了较好的技术经济指标,对同类选矿厂具有较好的借鉴作用.%Based on the study on process mineralogy of carbonate-containing refractory iron ore in Donganshan Iron Mine, stepped flotation process was proposed for treating such kind of ore. At the first stage, siderite was separated by direct flotation with a neutral media, and at second stage, hematite could be separated by reverse flotation in a strong alkaline solution. The production practice showed a good performance was achieved by such stepped flotation process, which can be of reference for processing similar iron ore.
Polyhedral Techniques in Combinatorial Optimization
Aardal, K.I.; van Hoesel, S.
1995-01-01
Combinatorial optimization problems arise in several areas ranging from management to mathematics and graph theory. Most combinatorial optimization problems are compu- tationally hard due to the restriction that a subset of the variables have to take integral values. During the last two decades ther
Synthesis of boron-cluster containing amino acids and preparation of their polymers
Slepukhina, Irina
2006-01-01
The first aim of this work was to prepare water soluble [B12H12]2- containing amino acids. This task was reached by using the ability of dodecaborate derivatives such as ammonio-undecahydro-closo-dodecaborate BNH3, hydroxo-undecahydro-closo-dodecaborate BOH and S-(2-cyanoethyl)-thio-undecahydro-closo-dodecaborate(2-)CE-BSH to undergo alkylation reactions. With this idea we used halogen substituted monoalkylated educts such as:- 4-Bromobutylacetamidodiethylmalonate. Alkylation reactions with B...
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
Directory of Open Access Journals (Sweden)
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.
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.
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.
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。
Azaboranes (RNH2)B8H11NHR. A new type of boron cluster for possible use in BNCT
International Nuclear Information System (INIS)
This interesting group of novel, water-soluble (RNH2)B8H11NHR species can be regarded as new boron carriers with potential use in the synthesis of boron-rich compounds for application in BNCT. These azaboranes are synthesized by the reaction of B9H13(SMe2) with primary amines NH2R. (author)
Sublimation properties in carbon containing tungsten-rhenium single crystals
International Nuclear Information System (INIS)
Data on sublimation parameters of W-Re single crystals with Re contents varying from 0.1 to 4.2 at % and different quantity of C, are obtained by the Langmuir method at superhigh vacuum. It is shown that the rates of sublimation in specimens with lesser carbon content (4.6X10-2 % at) increase with Re concentration growth (from 2.6 to 3.8% at) and sublimation parameters in specimens with greater carbon content (1.2x10-1 - 1.5x10-1% at) decrease in comparison with W(C=1.5x10-2 % at). The anisotropy of rate and heat of sublimation is observed in equivalent crystallographic directions , one of them is perpendicular to the crystallization direction. Another one - parallel to it. The effects observed are explained by the increase of C solubility in Re and by its redistribution in W bcc - lattice with a temperature increase
Sublimation properties in carbon containing tungsten-rhenium single crystals
Energy Technology Data Exchange (ETDEWEB)
Dekhtyar, I.Ya.; Kolesnik, V.N.; Patoka, V.I.; Ovsienko, D.E.; Silant' ev, V.I.; Sosnina, E.I. (AN Ukrainskoj SSR, Kiev. Inst. Metallofiziki)
Data on sublimation parameters of W-Re single crystals with Re contents varying from 0.1 to 4.2 at % and different quantity of C, are obtained by the Langmuir method at superhigh vacuum. It is shown that the rates of sublimation in specimens with lesser carbon content (4.6X10/sup -2/ % at) increase with Re concentration growth (from 2.6 to 3.8% at) and sublimation parameters in specimens with greater carbon content (1.2x10/sup -1/ - 1.5x10/sup -1/% at) decrease in comparison with W(C=1.5x10/sup -2/ % at). The anisotropy of rate and heat of sublimation is observed in equivalent crystallographic directions <100>, one of them is perpendicular to the crystallization direction. Another one - parallel to it. The effects observed are explained by the increase of C solubility in Re and by its redistribution in W bcc - lattice with a temperature increase.
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...
Hygroscopicity of Black-Carbon-Containing Aerosol in Wildfire Plumes
Perring, A. E.; Schwarz, J. P.; Markovic, M. Z.; Fahey, D. W.; Yokelson, R. J.; Jimenez, J. L.; Campuzano Jost, P.; Day, D. A.; Palm, B. B.; Wisthaler, A.; Ziemba, L. D.; Anderson, B. E.; Diskin, G. S.; Huey, L. G.; Gao, R. S.
2015-12-01
Water uptake by black carbon (BC) containing aerosol has been quantified in wildfire plumes of varying age (from 1 to ~40 hr old) sampled in North America during the NASA SEAC4RS mission of 2013. Measurements were made in flight using parallel single-particle soot photometers (SP2) that simultaneously detected the BC component of the ambient aerosol ensemble under contrasting humidity conditions. The hygroscopicity parameter, κ, of material internally mixed with BC derived from this data set is consistent with previous estimates of bulk aerosol hygroscopicity from biomass burning sources. We explore the temporal evolution of κ during aging of the Yosemite Rim Fire plume to constrain the rate of conversion of BC-containing aerosol from hydrophobic to hydrophilic modes in these emissions. We also investigate the relationship between κ values for BC-containing particles and the oxidation state and hygroscopicity of the bulk aerosol. These observations have implications for BC transport and removal in biomass burning plumes and provide important constraints on model treatment of BC optical and microphysical properties from wildfire sources in ambient conditions.
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)
Gu Jian-Bing; Yang Xiang-Dong; Wang Huai-Qian; Li Hui-Fang
2012-01-01
The geometrical structures,relative stabilities,electronic and magnetic properties of small BnAlˉ (2 ≤ n ≤ 9) clusters are systematically investigated by using the first-principles density functional theory.The results show that the Al atom prefers to reside either on the outer-side or above the surface,but not in the centre of the clusters in all of the most stable BnAlˉ (2 ≤ n ≤ 9) isomers and the one excess electron is strong enough to modify the geometries of some specific sizes of the neutral clusters.All the results of the analysis for the fragmentation energies,the second-order difference of energies,and the highest occupied-lowest unoccupied molecular orbital energy gaps show that B4Alˉ and B8Alˉ clusters each have a higher relative stability.Especially,the B8Alˉ cluster has the most enhanced chemical stability.Furthermore,both the local magnetic moments and the total magnetic moments display a pronounced oddeven oscillation with the number of boron atoms,and the magnetic effects arise mainly from the boron atoms except for the B7Alˉ and B9Alˉ clusters.
Reconstruction of 3D morphology of polyhedral nanoparticles
International Nuclear Information System (INIS)
The three-dimensional (3D) faceting morphology of ceria nanoparticles is analysed using transmission electron microscopy (TEM)-based computed tomography on the nanometre scale. A novel tomography mode of electron energy loss spectroscopic imaging using a single energy window for inelastically scattered electrons is introduced and found to be reliable and fast for freestanding nanoparticles. To compare the new tomographic method with other methods, we provide the first comprehensive application of three complementary TEM-based imaging techniques, including bright field TEM and annular dark field specific TEM (STEM). Traditional bright-field TEM tomography is found to be applicable, in spite of obvious artefacts, for crystalline particles of constant composition. However, the safest interpretation is achieved by a combined recording of bright field and spectroscopic images
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...... and the overall performance of the branch-and-cut algorithm several computational experiments are conducted. We present some of the results of these experiments....
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.
CSG Feature Trees from Engineering Sketches of Polyhedral Shapes
Plumed Ferrer, Raquel; Varley, Peter Ashley Clifford; Company, Pedro
2014-01-01
We investigate the problem of determining design intent from engineering sketches: what did the designer have in mind when sketching a component? Specifically, we consider the unidirectional reverse mapping from form features, as determined from an input sketch, to design features, representing the design intent present in the designer’s mind. We introduce a list of com- mon engineering form features. For each, we list which geometrical cues may be helpful in identifying these features in des...
Polyhedral oligomeric silsesquioxanes as modifiers of polyoxymethylene structure
Czarnecka-Komorowska, Dorota; Sterzynski, Tomasz; Dutkiewicz, Michal
2015-12-01
In this paper the influence of silsesquioxanes (POSS) on crystallization behaviour of polyoxymethylene (POM) during non-isothermal crystallization was investigated by polarized light microscope (PLM) and differential scanning calorimetry (DSC). The study concerns polyoxymethylene (POM) and nanocomposites containing POSS's with different organic functional groups ePOSS, vPOSS and hPOSS (0.5% and 1% by weight). The nucleation effectiveness was assessed by DSC determination of crystallization temperature and by optical measurement of nucleation density and spherulites dimensions. An increase of crystallization temperature alone with a decrease of the average spherulites dimension deliver a proof of a nucleation - like activity of hPOSS. An additionally effect observed for POPSS modified POM was a higher homogeneity of the morphology.
The number of polyhedral (3-connected planar) graphs
Duijvestijn, A.J.W.; Federico, P.J.
1981-01-01
Data is presented on the number of 3-connected planar graphs, isomorphic to the graphs of convex polyhedra, with up to 22 edges. The numbers of such graphs having the same number of edges, and the same number of vertices and faces, are tabulated. Conjectured asymptotic formulas by W. T. Tutte and by
The number of polyhedral (3-Connected Planar) Graphs
Duijvestijn, A.J.W.
1996-01-01
Data is presented on the number of 3-connected planar graphs, isomorphic to the graphs of convex polyhedra, with up to 26 edges. Results have been checked with the the number of rooted c-nets of R.C. Mullin and P.J. Schellenberg and Liu Yanpei.
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
adsorption capacity per mass of carbon. Cases reporting increased residual carbon content due to low-NO, combustion are described, together with observations from a pilot scale experiment, where increased AEA adsorption capacity of carbon appeared to relate with firing at low-NO, conditions. Post-treatment...... 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...... 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....
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.
Features of the interaction of alumina and silica with carbon-containing reducing agents
Energy Technology Data Exchange (ETDEWEB)
Kondratenko, A.P.
1976-01-01
In the mining of Ekibastuz coals, a rock containing 35 to 49% of coal substance and 60 to 65% of mineral fractions, mainly silica and alumina, is sent to the waste dump. When this rock is heated in an inert atmosphere above 1500 C the alumina and silica are reduced by the carbon present, as a result of which, in prinicple, it is possible to obtain a number of valuable products. These reactions are discussed.
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.
Decontamination of carbonate containing process streams in a reprocessing plant by chromatography
International Nuclear Information System (INIS)
Results of a new procedure are presented to decontaminate carbonate process streams containing fission products and actinides occurring in burned up fuel elements combining a filtration and chromatographic step. First the unsoluble or hydrolysed plutonium and fission product species are separated by a filter mounted in front of a Bio-Rex 5 resin column which fixes all activities remaining in the filtrate. The solution passing the column is decontaminated greater than 99%. The recovery of the actinides and fission products from the resin and the filter is performed by 4 M nitric acid. (orig./PW)
Anisotropy of sublimation from equivalent crystal faces of carbon-containing tungsten monocrystals
Energy Technology Data Exchange (ETDEWEB)
Dekhtyar, I.Ya.; Kolesnik, V.N.; Ovsienko, D.E.; Patoka, V.I.; Silant' ev, V.I.; Sosnina, E.I. (AN Ukrainskoj SSR, Kiev. Inst. Metallofiziki)
1981-08-01
Anisotropy of sublimation parameters was found in equivalent faces (100) or (1O0) of W single crystals oriented perpendicular or parallel to the growth direction. The anisotropy value depends on C concentration in W single crystals.
Anisotropy of sublimation from equivalent crystal faces of carbon-containing tungsten monocrystals
International Nuclear Information System (INIS)
Anisotropy of sublimation parameters was found in equivalent faces (100) or (1O0) of W single crystals oriented perpendicular or parallel to the growth direction. The anisotropy value depends on C concentration in W single crystals
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.
Kinetic study of the reaction of uranium with various carbon-containing gases
International Nuclear Information System (INIS)
The kinetic study of the reaction U + CO2 and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO2 → UO2 + 2 CO U + CO2 → UO2 + C The reaction with carbon monoxide leads to a mixture of dioxide UO2, dicarbide UC2 and free carbon. The main reaction can be written. U + CO → 1/2 UO2 + 1/2 UC2 The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO2 and UC2 can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO2 and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author)
Experimental evaluation of biomass burning emissions: Nitrogen and carbon containing compounds
International Nuclear Information System (INIS)
Data are presented on the nitrogen and carbon emissions of biomass burning. The results of the authors' experiments enable them to calculate new source strengths for many compounds, considering different burning stages and fire conditions on the one hand, and different fuel types and properties, on the other hand. They also presented a method for balancing elemental budgets of fires, which had already been described for carbon compounds by other authors but which is new for the nitrogen inventory. Based on their measurements they show that biomass burning contributes significantly to the global budgets of HCN, CH3CN (possibly the major source), NOx (12%), CO(22%), C2 to C4 hydrocarbons (14%), CH3Cl(41%), and probably also to the global source of C1-C5 aliphatic amines. Further, pyrogenic CO2 amounts are likely to represent a substantial contribution to the global greenhouse warming. An important result, from the study is the identification of N2 emissions, which causes a significant loss of fixed nitrogen (pyro-denitrification) in tropical ecosystems in the order of 5% to 20% of the global nitrogen fixation rate. Because of an interesting interplay between an enhanced postfire nitrogen fixation and an enhanced postfire N2O emission, it is not yet known if losses due to pyro-denitrification are balanced by nitrogen fixation
Kwon, Nam Hee; Yin, Hui; Brodard, Pierre; Sugnaux, Claudia; Fromm, Katharina M.
2014-01-01
Cathodes in lithium ion batteries consist of an ionic conductor, an electronic conductor and a binder in order to make a composite that is both electronically and ionically conductive. The carbon coating on the cathode material plays a critical role for the electrochemical properties of lithium ion batteries due to the increased electronic conductivity. We explain the relationship between the electrochemical properties and the characteristics of composites prepared using the ball-milling proc...
Moteki, N.
2015-12-01
Black carbon (BC) is a light-absorbing carbonaceous aerosol emitted from combustions of fossil fuels and biomasses and is estimated as the second most important contributor to positive climate forcing after the carbon dioxide. In the atmosphere, the fractal aggregate of BC-spherules may be mixed with non-absorbing (or weakly absorbing) compounds that forms morphologically complex "BC-containing particle". A reliable scattering code for BC-containing particles is necessary for predicting mass absorption efficiency of BC and designing/evaluating optical techniques for estimating microphysical properties (i.e., size distribution, mixing state, shape, refractive index) of BC-containing particles. The computational methods that derived from the volume-integral form of the Maxwell equation, such as discrete dipole approximation (DDA), are method of choice for morphologically complex object like BC-containing particles. In ordinary DDA, the entire particle volume is approximated as a collection of tiny cubical dipoles (with side length d) placed on a 3D cubic lattice. For several model BC-containing particles, the comparisons with numerically exact T-matrix method reveals that the ordinary DDA suffered from persistent positive systematic error (up to +30%) in absorption even under d DDA error is identified to be the shape error in BC-spherules. To eliminate the shape error in BC-spherules, we propose a new DDA methodology which may be called hybrid DDA (h-DDA): each primary BC sphere is assumed as a spherical dipole, while remaining particle volume of coating material is approximated by a collection of tiny cubical dipoles on a 3D cubic lattice. Positive absorption bias up to +30% in ordinary DDA is suppressed to within 3% in h-DDA. In h-DDA code, an efficient FFT-based algorithm for solving the matrix equation has been implemented, by utilizing the multilevel block-Toeplitz property of the submatrix corresponding to inter-dipole interaction within coating material.
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.
Nano-twin mediated plasticity in carbon-containing FeNiCoCrMn high entropy alloys
Energy Technology Data Exchange (ETDEWEB)
Wu, Z. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Materials Science and Engineering Department, University of Tennessee, Knoxville, TN 37996 (United States); Parish, C.M. [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Bei, H., E-mail: beih@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States)
2015-10-25
Equiatomic FeNiCoCrMn alloy has been reported to exhibit promising strength and ductility at cryogenic temperature and deformation mediated by nano-twining appeared to be one of the main reasons. We use the FeNiCoCrMn alloy as a base alloy to seek further improvement of its mechanical properties by alloying additional elements, i.e., interstitial carbon. The effects of carbon on microstructures, mechanical properties and twinning activities were investigated in two different temperatures (77 and 293 K). With addition of 0.5 at% C, the high entropy alloy still remains entirely single phase face-centered cubic (FCC) crystal structure. The materials can be cold rolled and recrystallized to produce a microstructure with equiaxed grains. Both strain hardening rate and strength are enhanced while high uniform elongations to fracture (∼70% at 77 K and ∼40% at 293 K) are still maintained. The increased strain hardening and strength could be caused by the promptness of deformation twinning in C-containing high entropy alloys. - Highlights: • Interstitial atom C was successfully added into FeNiCoCrMn high entropy alloys. • The strain hardening rate and strength are enhanced in the C-containing alloy. • The increased strain-hardening and strength are caused by the nano-twinning.
Moteki, Nobuhiro
2016-07-01
An accurate and efficient simulation of light scattering by an atmospheric black carbon (BC)-containing aerosol-a fractal-like cluster of hundreds of carbon monomers that is internally mixed with other aerosol compounds such as sulfates, organics, and water-remains challenging owing to the enormous diversities of such aerosols' size, shape, and mixing state. Although the discrete dipole approximation (DDA) is theoretically an exact numerical method that is applicable to arbitrary non-spherical inhomogeneous targets, in practice, it suffers from severe granularity-induced error and degradation of computational efficiency for such extremely complex targets. To solve this drawback, we propose herein a hybrid DDA method designed for arbitrary BC-containing aerosols: the monomer-dipole assumption is applied to a cluster of carbon monomers, whereas the efficient cubic-lattice discretization is applied to the remaining particle volume consisting of other materials. The hybrid DDA is free from the error induced by the surface granularity of carbon monomers that occurs in conventional cubic-lattice DDA. In the hybrid DDA, we successfully mitigate the artifact of neglecting the higher-order multipoles in the monomer-dipole assumption by incorporating the magnetic dipole in addition to the electric dipole into our DDA formulations. Our numerical experiments show that the hybrid DDA method is an efficient light-scattering solver for BC-containing aerosols in arbitrary mixing states. The hybrid DDA could be also useful for a cluster of metallic nanospheres associated with other dielectric materials.
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.
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
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...
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.
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.
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.
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.
Croce, Gianluca; Carniato, Fabio; Milanesio, Marco; Boccaleri, Enrico; Paul, Geo; van Beek, Wouter; Marchese, Leonardo
2009-11-21
This work is focused on a multidisciplinary study of a completely condensed octaisobutyl-silsesquioxane (IBUPOSS) as a model of the alkyl POSS family. IBUPOSS is characterized by the presence of eight isobutyl groups bonded to the corners of the siliceous framework. Differential scanning calorimetric measurements and an innovative simultaneous in situ Raman/XRPD experiment suggested that IBUPOSS undergoes a solid phase transition around 330 K, and indicated that this transition is related to a change in the conformational freedom of the isobutyl chains. The X-ray powder diffraction (XRPD) pattern of the high temperature phase was indexed in the high symmetry [R3m] space group. The Raman data indicated a larger mobility of the aliphatic side chains at high temperature, thus inducing a disorder in the IBUPOSS moiety. Multidimensional heteronuclear solid-state NMR experiments were employed to probe the structural and motional features of the observed phase transition. The various conformations can be accounted for by a pseudo-D(3h) symmetry able to obey to the [R3m] space group. Simulations on molecular mechanics and dynamics, together with quantum-chemical calculations, confirmed this hypothesis and gave some hints on the conformational mobility and the energetic features of IBUPOSS, a base material with relevant applications in catalysis and polymer science. PMID:19865764
Construction of scalar and vector finite element families on polygonal and polyhedral meshes
Gillette, Andrew; Rand, Alexander; Bajaj, Chandrajit
2014-01-01
We combine theoretical results from polytope domain meshing, generalized barycentric coordinates, and finite element exterior calculus to construct scalar- and vector-valued basis functions for conforming finite element methods on generic convex polytope meshes in dimensions 2 and 3. Our construction recovers well-known bases for the lowest order N\\'ed\\'elec, Raviart-Thomas, and Brezzi-Douglas-Marini elements on simplicial meshes and generalizes the notion of Whitney forms to non-simplicial c...
Celso, Fabricio; Mikhailenko, Serguei D.; Rodrigues, Marco A. S.; Mauler, Raquel S.; Kaliaguine, Serge
2016-02-01
Composite proton exchange membranes (PEMs) intended for fuel cell applications were prepared by embedding of various amounts of dispersed tri-sulfonic acid ethyl POSS (S-Et-POSS) and tri-sulfonic acid butyl POSS (S-Bu-POSS) in thin films of sulfonated poly ether-ether ketone. The electrical properties of the PEMs were studied by Impedance spectroscopy and it was found that their conductivity σ changes with the filler content following a curve with a maximum. The water uptake of these PEMs showed the same dependence. The investigation of initial isolated S-POSS substances revealed the properties of typical electrolytes, which however in both cases possessed low conductivities of 1. 17 × 10-5 S cm-1 (S-Et-POSS) and 3.52 × 10-5 S cm-1 (S-Bu-POSS). At the same time, the insoluble in water S-POSS was found forming highly conductive interface layer when wetted with liquid water and hence producing a strong positive impact on the conductivity of the composite PEM. Electrical properties of the composites were analysed within the frameworks of effective medium theory and bounding models, allowing to evaluate analytically the range of possible conductivity values. It was found that these approaches produced quite good approximation of the experimental data and constituted a fair basis for interpretation of the observed relationship.
R Implementation of a Polyhedral Approximation to a 3D Set of Points Using the ?-Shape
Thomas Lafarge; Beatriz Pateiro-López; Antonio Possolo; Joy Dunkers
2014-01-01
This work has been partially supported by Spanish Grant MTM2008-03010 and the IAP research network grant no. P6/03 from the Belgian government (Beatriz Pateiro-L opez), and by the Shape Metrology Innovations in Measurement Science from the National Institute of Standards and Technology (all the authors). Since the work is a work product of the National Institute of Standards and Technology, an agency of the U.S. federal government, it is not subject to copyright in the United States. We...
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%.
International Nuclear Information System (INIS)
We describe a new technique for the fabrication of a thin strain relaxed buffer (TSRB). This method is based on the incorporation of carbon during the epitaxial growth of a thin constant composition Si0.78Ge0.22 layer. An annealing step is carried out after growth in order to increase the relaxation and therefore the stability of the buffer. This method allows to prepare smooth and defect free TSRBs with 91% relaxation. First Hall mobility measurements at 77 K of strained silicon on top of the TSRB (single side modulation doped structure) show promising electron mobility value of 18,500 cm2/(V s)
Energy Technology Data Exchange (ETDEWEB)
Feron, G. [Commissariat a l' Energie Atomique, Grenoble (France). Centre d' Etudes Nucleaires
1963-09-15
The kinetic study of the reaction U + CO{sub 2} and U + CO has been performed by a thermogravimetric method on a spherical uranium powder, in temperature ranges respectively from 460 to 690 deg. C and from 570 to 850 deg. C. The reaction with carbon dioxide leads to uranium dioxide. A carbon deposition takes place at the same time. The global reactions is the result of two reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C The reaction with carbon monoxide leads to a mixture of dioxide UO{sub 2}, dicarbide UC{sub 2} and free carbon. The main reaction can be written. U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} The free carbon results of the disproportionation of the carbon monoxide. A remarkable separation of the two phases UO{sub 2} and UC{sub 2} can be observed. A mechanism accounting for the phenomenon has been proposed. The two reactions U + CO{sub 2} and U + CO begin with a long germination period, after which, the reaction velocity seems to be limited in both cases by the ionic diffusion of oxygen through the uranium dioxide. (author) [French] L'etude cinetique des reactions U sol + CO{sub 2} gaz et U sol + CO gaz a ete effectuee par thermogravirnetrie sur une poudre d'uranium a grains spheriques, les domaines de temperature etudies s'etendant respectivement de 460 a 690 deg. C et de 570 a 850 deg. C. L'action du dioxyde de carbone conduit au dioxyde d'uranium UO{sub 2}; il se produit en meme temps un depot de carbone. La reaction globale resulte des deux reactions: U + 2 CO{sub 2} {yields} UO{sub 2} + 2 CO U + CO{sub 2} {yields} UO{sub 2} + C Le mono-oxyde de carbone conduit a un melange de dioxyde UO{sub 2}, de dicarbure UC{sub 2} et de carbone libre. La reaction principale s'ecrit: U + CO {yields} 1/2 UO{sub 2} + 1/2 UC{sub 2} Le carbone libre provient de la dismutation du mono-oxyde de carbone. On observe une separation remarquable des deux phases UO{sub 2} et UC{sub 2}; un mecanisme rendant compte de ce phenomene a ete propose. Les deux reactions U + CO{sub 2} et U + CO, debutent par une longue periode de germination, apres laquelle la vitesse de la reaction semble etre limitee dans les deux cas par la diffusion d'ions O{sup 2-} dans l'oxyde UO{sub 2} forme. (auteur)
Sezer, Ali Osman
The supersonic expansion of dilute aqueous solutions for the synthesis of new materials is a complex flow system. Flow prediction and modeling are, therefore, quite challenging. Electrokinetic streaming potentials generated during the supersonic nozzle expansion further complicate the nature of these flow processes. Flow-generated potentials are believed to significantly affect the electrochemical environment of the flow, and therefore, may influence the properties of the product. This dissertation research was an attempt to experimentally and theoretically investigate the significance of flow-generated electrochemical phenomena and their possible effect on the deposited thin carbon films. Brand's computer model was used to predict the physical properties of the expanding jet at the nozzle. The sensitivity of the predicted flow parameters to operating conditions was then analyzed. The results of this parametric flow modeling were used to identify deposition regions of flow space that have less sensitivity to fluctuations in process temperatures and pressures. Streaming currents were predicted from measured nozzle currents. The first high-temperature-pressure Pourbaix diagrams were constructed for the carbon-water system. Equilibrium Pourbaix diagrams together with predicted streaming currents suggested a possible CVD-like mechanism for the deposition of thin carbon films. Deposited carbon films were analyzed for morphology, composition and structure by vibrational spectroscopy and electron microscopy. IR and Raman analysis of carbon samples were not conclusive in revealing any measurable differences in samples. Although Raman spectra showed considerable shifts in peak positions, the lack of internal standard in the spectra made it difficult to draw any reliable conclusions. Significant variations in surface morphology were found for samples grown under different substrate bias. Electron diffraction analysis conclusively showed the presence of a cubic diamond and Lonsdaleite phase in a carbon sample, which supports the predicted CVD-like deposition mechanism in the process that enables the phase transition from hexagonal graphite to cubic diamond.
Schutzius, Thomas M; Bayer, Ilker S; Jursich, Gregory M; Das, Arindam; Megaridis, Constantine M
2012-09-01
Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ∼100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications. PMID:22820974
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.
Schutzius, Thomas M.; Bayer, Ilker S.; Jursich, Gregory M.; Das, Arindam; Megaridis, Constantine M.
2012-08-01
Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ~100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications.Surfaces patterned with alternating (binary) superhydrophobic-superhydrophilic regions can be found naturally, offering a bio-inspired template for efficient fluid collection and management technologies. We describe a simple wet-processing, thermal treatment method to produce such patterns, starting with inherently superhydrophobic polysilsesquioxane-silica composite coatings prepared by spray casting nanoparticle dispersions. Such coatings become superhydrophilic after localized thermal treatment by means of laser irradiation or open-air flame exposure. When laser processed, the films are patternable down to ~100 μm scales. The dispersions consist of hydrophobic fumed silica (HFS) and methylsilsesquioxane resin, which are dispersed in isopropanol and deposited onto various substrates (glass, quartz, aluminum, copper, and stainless steel). The coatings are characterized by advancing, receding, and sessile contact angle measurements before and after thermal treatment to delineate the effects of HFS filler concentration and thermal treatment on coating wettability. SEM, XPS and TGA measurements reveal the effects of thermal treatment on surface chemistry and texture. The thermally induced wettability shift from superhydrophobic to superhydrophilic is interpreted with the Cassie-Baxter wetting theory. Several micropatterned wettability surfaces demonstrate potential in pool boiling heat transfer enhancement, capillarity-driven liquid transport in open surface-tension-confined channels (e.g., lab-on-a-chip), and select surface coating applications relying on wettability gradients. Advantages of the present approach include the inherent stability and inertness of the organosilane-based coatings, which can be applied on many types of surfaces (glass, metals, etc.) with ease. The present method is also scalable to large areas, thus being attractive for industrial coating applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr30979c
Ruiz Abad, David
2009-01-01
The knowledge about the diffusion of products and educts into and out of porous materials is of high importance for the development of new porous sol-gel processed hybrid catalysts. Therefore the accessibility of active centers embedded in sol-gel materials was studied by luminescence spectroscopy. Modified tris(2,2’- bipyridine)ruthenium(II) and pyrenemethanol were co-condensed with tetramethoxysilane (TMOS) in a buffer system. The buffer enforces the pH to remain constant during the sol-gel...
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...
Kim, Ho-Joong; Kwon, Younghwan; Kim, Chang Kee
2013-01-01
Thermal and mechanical properties of PU/POSS nanocomposites plasticized with DOA were investigated. These hybrid materials were prepared using one-step method through the incorporation of flexible HTPB prepolymer, reactive or non-reactive POSS nanoparticle, and DOA plasticizer under IPDI curative system. The plasticizer added into PU/POSS composites decreased glass transition temperature, mechanical strength and modulus, while the change of thermal stability was modest. Thermal stability of these hybrid composites was found to depend preferably on characteristics of POSS molecules incorporated. PMID:23646777
Energy Technology Data Exchange (ETDEWEB)
Wang, Xi-Sen; Chrzanowski, Matthew; Wojtas, Lukasz; Chen, Yu-Sheng; Ma, Shengqian [USF; (UC)
2013-03-19
A change for the better: Exchange of Cd^{II} in the catalytically inactive framework MMPF-5 (see scheme) with Co^{II} afforded a metalloporphyrin-based nanoreactor, MMPF-5(Co). This framework, consisting of small cubicuboctahedral cages, demonstrated interesting performances in the catalytic epoxidation of trans-stilbene with tBuOOH.
Wang, Xi-Sen; Chrzanowski, Matthew; Wojtas, Lukasz; Chen, Yu-Sheng; Ma, Shengqian
2013-03-01
A change for the better: Exchange of Cd(II) in the catalytically inactive framework MMPF-5 (see scheme) with Co(II) afforded a metalloporphyrin-based nanoreactor, MMPF-5(Co). This framework, consisting of small cubicuboctahedral cages, demonstrated interesting performances in the catalytic epoxidation of trans-stilbene with tBuOOH. PMID:23386517
Directory of Open Access Journals (Sweden)
Vinícius Pistor
2013-01-01
Full Text Available In this study, epoxy nanocomposites containing different fractions of n-phenylaminopropyl (POSS were prepared. The nanocomposites were studied by transmission electron microscopy (TEM, gel content, dynamic-mechanical analysis (DMA and thermogravimetric analysis (TGA. The parameters for Avrami's equation were calculated from the degradation curves. The dispersions used to form the nanocomposites were effective above 5 wt % of POSS, and the gel content increased with the addition of POSS. The DMA analysis exhibited an increase in the storage modulus (E' and a shifting of Tg to higher temperatures upon POSS incorporation. The weight loss indicated that the POSS promoted an increase in thermal stability of the epoxy resin. The Avrami parameters demonstrated that the addition of POSS decreased the Avrami constant (k', increased the half-life (t1/2 of degradation and promoted changes in the Avrami exponent (n. These results suggest that the increase in the glass transition temperature and thermal stability depend on the reactive groups in the POSS nanoparticles.
Vinícius Pistor; Bluma Guenther Soares; Raquel Santos Mauler
2013-01-01
In this study, epoxy nanocomposites containing different fractions of n-phenylaminopropyl (POSS) were prepared. The nanocomposites were studied by transmission electron microscopy (TEM), gel content, dynamic-mechanical analysis (DMA) and thermogravimetric analysis (TGA). The parameters for Avrami's equation were calculated from the degradation curves. The dispersions used to form the nanocomposites were effective above 5 wt % of POSS, and the gel content increased with the addition of POSS. T...
Yang, Lei; Fan, Weiliu; Li, Yanlu; Sun, Honggang; Wei, Lei; Cheng, Xiufeng; Zhao, Xian
2012-06-18
In general, the presence of shared edges of polyhedra for high-valence low-coordinated small cations is rarely seen except under extreme conditions such as high pressure. However, the ambient-pressure synthesis of KZnB(3)O(6) built of edge-sharing BO(4) tetrahedra is contrary to this. By investigating the molecular dynamics, lattice dynamics, and electronic properties via density functional theory, we studied the origin of the phase stability of the edge-sharing (es) and "corner-sharing (cs)" KZnB(3)O(6). Lattice dynamics results show that there are no phonon anomalies that could lead to the instability of es-KZnB(3)O(6), which is consistent with molecular dynamics analysis. For "cs-KZnB(3)O(6)", a soft mode at the G point in the phonon dispersion is identified that reflects the dynamic instability with respect to small distortions. Eigenvector analysis of the soft mode of "cs-KZnB(3)O(6)" indicates that the instability comes from the linkage of ZnO(5) polyhedra rather than BO(x) polyhedra. Electronic property calculation indicates that the edge-sharing BO(4) polyhedra connected by the longest B-O σ bonds provide a solid framework for es-KZnB(3)O(6). In the case of "cs-KZnB(3)O(6)", the overlong Zn-O bond possesses the smallest covalent nature and the least orbital overlap among the bonds in a ZnO(5) polyhedron, and these two features of the electronic structure reduce the stability of "cs-KZnB(3)O(6)" compared to es-KZnB(3)O(6). The electronic property calculation further confirms the results obtained from lattice dynamics analysis. PMID:22667686
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.
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。
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.
A Photoelectron Spectroscopy and ab initio Study of B3- and B4- Anions and Their Neutrals
Energy Technology Data Exchange (ETDEWEB)
Zhai, Hua-Jin; Wang, Lai S.; Alexandrova, A N.; Boldyrev, Alexander I.; Zakrzewski, V G.
2003-11-06
The two smallest boron clusters (B3 and B4) in their neutral and anionic forms were studied by photoelectron spectroscopy and ab initio calculations. Vibrationally resolved photoelectron spectra were observed for B3- at three photon energies (355, 266, and 193 nm) and the electron affinity of B3 was measured to be+0.02 eV.
Institute of Scientific and Technical Information of China (English)
王刚
2005-01-01
在60℃和100℃的水中放置36h,通过确定相和显微结构变化来研究未涂覆和涂覆无机-有机复合涂层的铝粉的水合性能,指明其抗水合性能得到显著改善.在空气气氛中于1250℃下放置1.5h,研究了与未涂覆和涂覆无机-有机复合涂层的铝粉共存的石墨的抗氧化性能.与有涂层的铝粉共存的石墨的氧化率相似于与无涂层的铝粉共存的石墨的氧化率,指明两种铝粉具有相似的抗氧化性.抗氧化性方面的极小变化以及抗水合性的显著改善,使得有涂层的铝粉作为潜在的抗氧化剂使用于含碳浇注料系统中.
Li, Zukui; Ding, Ran; Floudas, Christodoulos A
2011-01-01
Robust counterpart optimization techniques for linear optimization and mixed integer linear optimization problems are studied in this paper. Different uncertainty sets, including those studied in literature (i.e., interval set; combined interval and ellipsoidal set; combined interval and polyhedral set) and new ones (i.e., adjustable box; pure ellipsoidal; pure polyhedral; combined interval, ellipsoidal, and polyhedral set) are studied in this work and their geometric relationship is discusse...
The energy landscape of fullerene materials: a comparison between boron, boron-nitride and carbon
De, Sandip; Amsler, Maximilian; Pochet, Pascal; Genovese, Luigi; Goedecker, Stefan
2010-01-01
Using the minima hopping global geometry optimization method on the density functional potential energy surface we study medium size and large boron clusters. Even though for isolated medium size clusters the ground state is a cage like structure they are unstable against external perturbations such as contact with other clusters. The energy landscape of larger boron clusters is glass like and has a large number of structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers in our minima hopping runs. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found.
B28: the smallest all-boron cage from an ab initio global search
Zhao, Jijun; Huang, Xiaoming; Shi, Ruili; Liu, Hongsheng; Su, Yan; King, R. Bruce
2015-09-01
Our ab initio global searches reveal the lowest-energy cage for B28, which is built from two B12 units and prevails over the competing structural isomers such as planar, bowl, and tube. This smallest boron cage extends the scope of all-boron fullerene and provides a new structural motif of boron clusters and nanostructures.Our ab initio global searches reveal the lowest-energy cage for B28, which is built from two B12 units and prevails over the competing structural isomers such as planar, bowl, and tube. This smallest boron cage extends the scope of all-boron fullerene and provides a new structural motif of boron clusters and nanostructures. Electronic supplementary information (ESI) available: Planar isomer structures of B28 and spatial distributions of front molecular orbitals. See DOI: 10.1039/c5nr04034e
The B32 cluster has the most stable bowl structure with a remarkable heptagonal hole.
Tai, Truong Ba; Nguyen, Minh Tho
2015-05-01
The neutral B32 exhibits an aromatic bowl structure containing one heptagonal hole, while two anionic species, one having a bowl structure and the other a quasi-planar structure, are almost degenerate in energy. These findings not only give more insight into the structural features of boron clusters, but also present a key result explaining the presence of heptagonal holes in the fullerene B40. PMID:25845816
Warneke, Jonas; Jenne, Carsten; Bernarding, Johannes; Azov, Vladimir A; Plaumann, Markus
2016-05-01
A gas phase binding study revealed strong intrinsic intermolecular interactions between dianionic halogenated closo-dodecaborates [B12X12](2-) and several neutral organic receptors. Oxidation of a tetrathiafulvalene host allowed switching between two host-guest binding modes in a supramolecular complex. Complexes of β-cyclodextrin with [B12F12](2-) show remarkable stability in the gas phase and were successfully tested as carriers for the delivery of boron clusters into cancer cells. PMID:27087168
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
Convergence of hausdorff approximation methods for the Edgeworth-Pareto hull of a compact set
Efremov, R. V.
2015-11-01
The Hausdorff methods comprise an important class of polyhedral approximation methods for convex compact bodies, since they have an optimal convergence rate and possess other useful properties. The concept of Hausdorff methods is extended to a problem arising in multicriteria optimization, namely, to the polyhedral approximation of the Edgeworth-Pareto hull (EPH) of a convex compact set. It is shown that the sequences of polyhedral sets generated by Hausdorff methods converge to the EPH to be approximated. It is shown that the Estimate Refinement method, which is most frequently used to approximate the EPH of convex compact sets, is a Hausdorff method and, hence, generates sequences of sets converging to the EPH.
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.
Rubinstein, J Hyam
2009-01-01
This is a personal view of some problems on minimal surfaces, Ricci flow, polyhedral geometric structures, Haken 4-manifolds, contact structures and Heegaard splittings, singular incompressible surfaces after the Hamilton-Perelman revolution.
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.
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.
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
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.
International Nuclear Information System (INIS)
The monoclonal antibody against mercaptoundecahydrododecaborate (BSH) was prepared, which recognized specifically the icosahedral boron cluster moiety and named 'anti-BSH MAb'. The dissociation constant of anti-BSH MAb against BSH was determined, and the cross reactivity was also clarified by using the enzyme-linked immunosorbent assay (ELISA). In addition, the amino acid sequences of the antigen-binding site in the variable region of heavy and light chains were partly determined and characterized upon protein database. Furthermore, a highly specific, rapid and practical immunoassay for BSH including quantitative determination of the BSH concentrations in blood by the competitive ELISA system using anti-BSH MAb has been explored. (author)
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
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. PMID:26864511
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.
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 ...
Directory of Open Access Journals (Sweden)
Nadja Lima Pinheiro
1993-01-01
Full Text Available Trichogenes longipinnis (Britski & Ortega, 1983 is a leather fish restricted to the rivers on the shore in the southeast of Brazil. In this work, the oesophagous structure is being showed. The oesophagous appears itself short, dorsally inclinated toward pericardium and ventrally covered by liver lobe. By electron microscopy we can observe a mucosa layer formed by stratified squamous epithelium and lamina propria with stratum compactum. The epithelium is composed by three types of cells: superficial squamous cells; mucous cells, similar to the globet cells and polyhedric cells. The stratification of this epithelium provides a complete basal layer of proliferation polyhedric cells. The cells in the intermediate region of the epithelium are also polyhedric. These cells are just bellow the superficial squamous cells and packed among mucous cells.
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.
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.
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.
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.
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.
Carburizer process in electric arc furnaces
Karasev, V. P.; Babichevskii, G. V.; Prokopenko, Ya. Yu.
2015-06-01
The behavior of coke and carbon in heating and melting of steel scrap is considered. The efficiency of carbon assimilation in the period of metal melting is estimated for various versions of introduction of a lump carbon-containing material into an EAF charge. The use of a carbon-containing material as an alternative heat source in EAF is analyzed.
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.
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.
Folic acid derivatives for PET imaging and therapy addressing folate receptor positive tumors
International Nuclear Information System (INIS)
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 18F-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 18F-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 18F-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 18F-labeling, which could be accomplished using a microwave-assisted synthesis, a [K is contained in 2.2.2]+/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 conducted. The synthesis of the
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
Theory of Linear Optical Absorption in B_12 Clusters: Role of the geometry
Sahu, Sridhar
2009-01-01
Boron clusters have been widely studied theoretically for their geometrical properties and electronic structure using a variety of methodologies. An important cluster of boron is the B$_{12}$ cluster whose two main isomers have distinct geometries, namely, icosahedral ($I_{h}$) and quasi planar ($C_{3v}$). In this paper we investigate the linear optical absorption spectrum of these two B$_{12}$ structures with the aim of examining the role of geometry on the optical properties of clusters. The optical absorption calculations are performed using both the semi-empirical and the ab initio approaches. The semi-empirical approach uses a wave function methodology employing the INDO model Hamiltonian, coupled with large-scale configuration interaction (CI) calculations, to account for the electron-correlation effects. The \\emph{ab initio} calculations are performed within a time-dependent-density-functional-theory (TDDFT) methodology. The results for the two approaches are in very good qualitative agreement with eac...
Furue, Ryuhei; Nishimoto, Takuro; Park, In Seob; Lee, Jiyoung; Yasuda, Takuma
2016-06-13
Luminescent materials consisting of boron clusters, such as carboranes, have attracted immense interest in recent years. In this study, luminescent organic-inorganic conjugated systems based on o-carboranes directly bonded to electron-donating and electron-accepting π-conjugated units were elaborated as novel optoelectronic materials. These o-carborane derivatives simultaneously possessed aggregation-induced emission (AIE) and thermally activated delayed fluorescence (TADF) capabilities, and showed strong yellow-to-red emissions with high photoluminescence quantum efficiencies of up to 97 % in their aggregated states or in solid neat films. Organic light-emitting diodes utilizing these o-carborane derivatives as a nondoped emission layer exhibited maximum external electroluminescence quantum efficiencies as high as 11 %, originating from TADF. PMID:27145481
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.
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.
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.
Energy Technology Data Exchange (ETDEWEB)
Tandy, P.; Yu, Ming; Leahy, C.; Jayanthi, C. S.; Wu, S. Y. [Department of Physics and Astronomy, University of Louisville, Louisville, Kentucky 40292 (United States)
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 B{sub N} 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 B{sub 12} 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.
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...
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.
Convergency analysis of the high-order mimetic finite difference method
Energy Technology Data Exchange (ETDEWEB)
Lipnikov, Konstantin [Los Alamos National Laboratory; Veiga Da Beirao, L [UNIV DEGLI STUDI; Manzini, G [NON LANL
2008-01-01
We prove second-order convergence of the conservative variable and its flux in the high-order MFD method. The convergence results are proved for unstructured polyhedral meshes and full tensor diffusion coefficients. For the case of non-constant coefficients, we also develop a new family of high-order MFD methods. Theoretical result are confirmed through numerical experiments.
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.
The Generation of Curved Clathrin Coats from Flat Plaques
Otter, den Wouter K.; Briels, Wim J.
2011-01-01
Flat clathrin lattices or ‘plaques’ are commonly believed to be the precursors to clathrin-coated buds and vesicles. The sequence of steps carrying the flat hexagonal lattice into a highly curved polyhedral cage with exactly 12 pentagons remains elusive, however, and the large numbers of disrupted i
International Nuclear Information System (INIS)
A perspective view of the polyhedral representation in Sr exchanged titanosilicate with sitinakite topology. The eight ring tunnel along c-axis depicts a nine coordinated Sr complex. Dark and light gray spheres in the eight ring channel represent water molecules and Sr2+ cations respectively
Inequalities Representing Polyhedra
Bosse, H.; Grötschel, M.; Henk, M.
2005-01-01
Our main result is that every n-dimensional polytope can be described by at most 2n−1 polynomial inequalities and, moreover, these polynomials can explicitly be constructed. For an n-dimensional pointed polyhedral cone we prove the bound 2n−2 and for arbitrary polyhedra we get a construc
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.
Synthesis of o- and m-carborane derivatives of 5,10,15,20-tetra-(p-anionphenyl)porphyrin
International Nuclear Information System (INIS)
The data on synthesis of o- and m-carborane-containing porphyrins, which derivatives through boron atom of polyhedral nucleus are presented. The reaction of the porphyrin amino group acylation may be used for production of the porphyrin carborane derivative with high boron content (up to 30 %) with the purpose of applying them in boron neutron-capture cancer therapy
Polyhedra [LnOn]: coordination numbers, shape, interpolyhedral bonds, Zn-O distances
International Nuclear Information System (INIS)
Peculiarities of oxygen atoms positioning in the nearest surrounding of rare earth elements are studied. Main characteristics of coordination polyhedra (LnOn): shape, vertex number and interatomic distances. Peculiarities of their change in the rare earth elements series are revealed. It is shown by example of icosahedron and cube that fragmentation processes form in many case the basis of mechanisms of polyhedral transformations
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.)
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
Intelligent Biohybrid Neurotechnologies: Are They Really What They Claim?
Panuccio, Gabriella; Semprini, Marianna; Natale, Lorenzo; Chiappalone, Michela
2016-01-01
In the era of intelligent biohybrid neurotechnologies for brain repair, new fanciful terms are appearing in the scientific dictionary to define what has so far been unimaginable. As the emerging neurotechnologies are becoming increasingly polyhedral and sophisticated, should we talk about evolution and rank the intelligence of these devices?
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
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.
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.
Sub-Critical Closed String Field Theory in D Less Than 26
Kaku, M
1994-01-01
We construct the second quantized action for sub-critical closed string field theory with zero cosmological constant in dimensions $ 2 \\leq D < 26$, generalizing the non-polynomial closed string field theory action proposed by the author and the Kyoto and MIT groups for $D = 26$. The proof of gauge invariance is considerably complicated by the presence of the Liouville field $\\phi$ and the non-polynomial nature of the action. However, we explicitly show that the polyhedral vertex functions obey BRST invariance to all orders. By point splitting methods, we calculate the anomaly contribution due to the Liouville field, and show in detail that it cancels only if $D - 26 + 1 + 3 Q ^ 2 = 0 $, in both the bosonized and unbosonized polyhedral vertex functions. We also show explicitly that the four point function generated by this action reproduces the shifted Shapiro-Virasoro amplitude found from $c=1$ matrix models and Liouville theory in two dimensions. LATEX file.
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.
Estimating Small-Body Gravity Field from Shape Model and Navigation Data
Park, Ryan S.; Werner, Robert A.; Bhaskaran, Shyam
2008-01-01
This paper presents a method to model the external gravity field and to estimate the internal density variation of a small-body. We first discuss the modeling problem, where we assume the polyhedral shape and internal density distribution are given, and model the body interior using finite elements definitions, such as cubes and spheres. The gravitational attractions computed from these approaches are compared with the true uniform-density polyhedral attraction and the level of accuracies are presented. We then discuss the inverse problem where we assume the body shape, radiometric measurements, and a priori density constraints are given, and estimate the internal density variation by estimating the density of each finite element. The result shows that the accuracy of the estimated density variation can be significantly improved depending on the orbit altitude, finite-element resolution, and measurement accuracy.
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.
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.
Lattice engineering through nanoparticle-DNA frameworks
Tian, Ye; Zhang, Yugang; Wang, Tong; Xin, Huolin L.; Li, Huilin; Gang, Oleg
2016-06-01
Advances in self-assembly over the past decade have demonstrated that nano- and microscale particles can be organized into a large diversity of ordered three-dimensional (3D) lattices. However, the ability to generate different desired lattice types from the same set of particles remains challenging. Here, we show that nanoparticles can be assembled into crystalline and open 3D frameworks by connecting them through designed DNA-based polyhedral frames. The geometrical shapes of the frames, combined with the DNA-assisted binding properties of their vertices, facilitate the well-defined topological connections between particles in accordance with frame geometry. With this strategy, different crystallographic lattices using the same particles can be assembled by introduction of the corresponding DNA polyhedral frames. This approach should facilitate the rational assembly of nanoscale lattices through the design of the unit cell.
Na2TiGeO5: Crystal structure stability at low temperature and high pressure
DEFF Research Database (Denmark)
Waskowska, A.; Gerward, Leif; Olsen, J.S.;
2008-01-01
The temperature evolution of the lattice parameters measured from 295 to 125 K exhibits a small instability below T-c approximate to 278 K, indicating ferroelastic properties of Na2TiGeO5. The behavior is related to the specific crystal structure built of polyhedral layers with shared TiO5 pyramids...... and GeO4 tetrahedra, alternating with layers of Na+ cations. Antiparallel alignment of the short apical titanyl bond in adjacent rows of the polyhedral layer gives rise to spontaneous strain, when a distortion of the TiO5 groups occurs. Single-crystal structures determined at room temperature and 120 K......, presumably to an orthorhombic structure. The pressure effect on the transition temperature is given by Delta T-c/Delta P approximate to 1.76 K/GPa....
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.
Path inequalities for the vehicle routing problem with time windows
DEFF Research Database (Denmark)
Kallehauge, Brian; Boland, Natashia; Madsen, Oli B.G.
2007-01-01
the advantage of avoiding additional variables and linking constraints. In the new formulation, time windows are modeled using path inequalities that eliminate time and capacity infeasible paths. We present a new class of strengthened path inequalities based on the polyhedral results obtained by Mak (Ph.......D. Thesis, 2001) for a variant of the TSP. We study the VRPTW polytope and determine its dimension. We show that the lifted path inequalities are facet defining under certain assumptions. We also introduce precedence constraints in the context of the VRPTW. Computational experiments are performed...... is therefore that a polyhedral approach to the VRPTW is a viable alternative to the path formulation of Desrochers et al. (Oper Res 40 (1992), 342-354)....
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)
Parent’s perception about motor-sport activity in Italian primary school
Gomez-Paloma, Filippo; Agrillo, Filomena; D'anna, Cristiana
2013-01-01
The educational value of motor-sport activity in Italia Primary School had its full acknowledgement through a historical development that has seen the legislative evolution and scientific research to carry on together. This increase has inevitably conditioned the school that had to adapt its educational proposals to the new cultural changes. The child with his needs and his personal needs becomes the pivot around which all educational interventions. Participation in activities polyhedral inve...
Synthesis and characterization of a POSS-maleimide precursor for hybrid nanocomposites
Jothibasu, S; S. Premkumar; Alagar, M.; Hamerton, I
2008-01-01
Epoxy polyhedral oligomeric silsesquioxane (POSS)-based hybrid nanocomposites were prepared by in situ polymerization of a homogeneous blend of the diglycidylether of bisphenol-A and 4,4'diaminodiphenylmethane (DDM) in the presence of octa(maleimidophenyl)silsesquioxane. The reaction of a maleimido-functionalized POSS cube with the epoxy resin was studied by Fourier transform infrared analysis and the formation of nanocomposites was confirmed by wide-angle X-ray diffraction and scanning elect...
How effective is graphene nanopore geometry on DNA sequencing?
Satarifard, Vahid; Foroutan, Masumeh; 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 assesse...
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.
Sub-Critical Closed String Field Theory in D Less Than 26
Kaku, Michio
1993-01-01
We construct the second quantized action for sub-critical closed string field theory with zero cosmological constant in dimensions $ 2 \\leq D < 26$, generalizing the non-polynomial closed string field theory action proposed by the author and the Kyoto and MIT groups for $D = 26$. The proof of gauge invariance is considerably complicated by the presence of the Liouville field $\\phi$ and the non-polynomial nature of the action. However, we explicitly show that the polyhedral vertex functions ob...
Influence of rounds sub-grains in high burnup UO2 fuel
International Nuclear Information System (INIS)
In a recent paper, it has been shown that the so called 'rim structure' in high burnup UO2 fuel contains in fact two types of sub-grains: polyhedral and round ones. Polyhedral sub-grains have an average size of approximately 0.5 μm, and have been observed for more than ten years. The faceted porosity associated to these polyhedral sub-grains is characteristic of the rim effect. Round sub-grains have an average size of approximately 0.2 μm and are found to be formed on the free surface of initial grains or of polyhedral sub-grains. Round sub-grains can be observed in the rim area and also continuously from the periphery to the mid-pellet. This suggests that round sub-grains do not depend on rim effect, but are more likely to derive from a surface effect. In this contribution SEM photographs showing the evolution of the round sub-grains morphology will support a proposed mechanism for round sub-grains formation. This mechanism involves a surface modification due to stresses applied on a free surface using the Greenfeld formalism. These stresses could be due to segregation of fission products on some grain faces. This supposition is supported by EPMA experiments which show the segregation of some fission products on surfaces where round sub-grains are observed, while other surfaces with no round sub-grains have the same concentration in fission products as the bulk of the grains. Segregation of fission products on surface has also been observed in CANDU fuel by XPS. This specific behaviour of fission products gives a new insight in the chemistry of irradiated fuel and asks the question of the influence of round sub-grains formations on the release of fission products. (author)
Viglietta, Giovanni
2013-01-01
We study the Art Gallery Problem for face guards in polyhedral environments. The problem can be informally stated as: how many (not necessarily convex) windows should we place on the external walls of a dark building, in order to completely illuminate its interior? We consider both closed and open face guards (i.e., faces with or without their boundary), and we study several classes of polyhedra, including orthogonal polyhedra, 4-oriented polyhedra, and 2-reflex orthostacks. We give upper and...
An Efficient Inexact ABCD Method for Least Squares Semidefinite Programming
Sun, Defeng; Toh, Kim-Chuan; Yang, Liuqin
2015-01-01
We consider least squares semidefinite programming (LSSDP) where the primal matrix variable must satisfy given linear equality and inequality constraints, and must also lie in the intersection of the cone of symmetric positive semidefinite matrices and a simple polyhedral set. We propose an inexact accelerated block coordinate descent (ABCD) method for solving LSSDP via its dual, which can be reformulated as a convex composite minimization problem whose objective is the sum of a coupled quadr...
The mathematics of lecture hall partitions
Savage, Carla D.
2016-01-01
Over the past twenty years, lecture hall partitions have emerged as fundamental combinatorial structures, leading to new generalizations and interpretations of classical theorems and new results. In recent years, geometric approaches to lecture hall partitions have used polyhedral geometry to discover further properties of these rich combinatorial objects. In this paper we give an overview of some of the surprising connections that have surfaced in the process of trying to understand the lect...
Fanovarietäten mit Toruswirkung der Komplexität Eins
Huggenberger, Elaine
2013-01-01
The subject of this thesis are varieties with a torus action of complexity one, i.e. algebraic varieties X with an algebraic torus T acting effectively on them, where dim(T)=dim(X)-1. A combinatorial description for such varieties is provided which generalizes the convex geometrical description of toric varieties by lattice fans. The systematical construction of rational complexity-one T-varieties in terms of certain integral matrices and a collection of polyhedral cones is applied to classi...
Towards a topological fingerprint of music
Bergomi, Mattia G.; Baraté, Adriano; Di Fabio, Barbara
2016-01-01
Can music be represented as a meaningful geometric and topological object? In this paper, we propose a strategy to describe some music features as a polyhedral surface obtained by a simplicial interpretation of the \\textit{Tonnetz}. The \\textit{Tonnetz} is a graph largely used in computational musicology to describe the harmonic relationships of notes in equal tuning. In particular, we use persistent homology in order to describe the \\textit{persistent} properties of music encoded in the afor...
Effects of melt blended poss nanofillers on pom and ABS thermal stability
Vilà Ramírez, Narciso
2014-01-01
This PhD thesis investigated the incorporation of Polyhedral Oligomeric Silsesquioxanes (POSS) in thermoplastic base materials via melt-blending procedures. Particularly, a focus is taken on the enhancement of the thermal resistance through the addition of different types of POSS on two popular engineering plastics known by their low thermal stability, one being a semi-crystalline copolymer i.e. polyoxymethylene (POM) and the other an amorphous copolymer i.e. acrylonitrile butadiene styren...
Hybrid electrolytes with controlled network structures for lithium metal batteries.
Pan, Qiwei; Smith, Derrick M; Qi, Hao; Wang, Shijun; Li, Christopher Y
2015-10-21
Solid polymer electrolytes (SPEs) with tunable network structures are prepared by a facile one-pot reaction of polyhedral oligomeric silsesquioxane and poly(ethylene glycol). These SPEs, with high conductivity and high modulus, exhibit superior resistance to lithium dendrite growth even at high current densities. Measurements of lithium metal batteries with a LiFePO4 cathode show excellent cycling stability and rate capability. PMID:26316140
B. Harshavardhan; Mallikarjuna, J. M.
2013-01-01
In this investigation, a CFD analysis has been carried out on in-cylinder fluid flows and air-fuel interaction in Direct Injection Spark Ignition (DISI) engine by changing combustion chamber geometry during intake and compression stroke at an engine speed of 1500 rpm for four different types of piston profiles viz., flat piston, flat piston with centre bowl, dome piston with centre bowl and pentroof offset bowl piston. A polyhedral trimmed cell has been taken for meshing of the geometries usi...
Two-Layer Planarization in Graph Drawing
Mutzel, Petra; Weiskircher, René
1998-01-01
We study the \\tlpp s that have applications in Automatic Graph Drawing. We are searching for a two-layer planar subgraph of maximum weight in a given two-layer graph. Depending on the number of layers in which the vertices can be permuted freely, that is, zero, one or two, different versions of the problems arise. The latter problem was already investigated in \\cite{Mut97} using polyhedral combinatorics. Here, we study the remaining two cases and the relationships bet...
Ghoniem, Ahmed
2007-01-01
This dissertation addresses the development of enhanced formulations for minimax and mixed-integer programming models for certain industrial and logistical systems, along with the design and implementation of efficient algorithmic strategies. We first examine the general class of minimax mixed-integer 0-1 problems of the type that frequently arise in decomposition approaches and in a variety of location and scheduling problems. We conduct an extensive polyhedral analysis of this problem in o...
Matching and Clustering: Two Steps Towards Automatic Model Generation in Computer Vision
Gros, Patrick
1993-01-01
International audience In this paper, we present a general frame for a system of automatic modelling and recognition of 3D polyhedral objects. Such a system has many applications for robotics : recognition, localization, grasping,...Here we focus upon one main aspect of the system : when many images of one 3D object are taken from different unknown viewpoints, how to recognize those of them which represent the same aspect of the object ? Briefly, it is possible to determine automatically i...
Granular Cell Tumor: An Uncommon Benign Neoplasm
Tirthankar Gayen; Anupam Das; Kaushik Shome; Debabrata Bandyopadhyay; Dipti Das; Abanti Saha
2015-01-01
Granular cell tumor is a distinctly rare neoplasm of neural sheath origin. It mainly presents as a solitary asymptomatic swelling in the oral cavity, skin, and rarely internal organs in the middle age. Histopathology is characteristic, showing polyhedral cells containing numerous fine eosinophilic granules with indistinct cell margins. We present a case of granular cell tumor on the back of a 48-year-old woman which was painful, mimicking an adnexal tumor.
Forni, Fulvio; Teel, Andrew
2011-01-01
Two control results are described: 1) local tracking control for convex billiards with piecewise locally Lipschitz boundary, and 2) global tracking control for special polyhedral billiards, including rectangles and equilateral triangles. The controllers are based on Lyapunov functions and a mirroring concept introduced in a companion paper. The local results require the impacts to satisfy an average dwell-time condition with parameters that depend on the Lipschitz constant of the function tha...
DNA Cages with Icosahedral Symmetry in Bionanotechnology
Jonoska, Nataša; Taormina, Anne; Twarock, Reidun
Blueprints for polyhedral cages with icosahedral symmetry made of circular DNA molecules are provided. The basic rule is that every edge of the cage is met twice in opposite directions by the DNA strand(s), and vertex junctions are realized by a set of admissible junction types. As nanocontainers for cargo storage and delivery, the icosidodecahedral cages are of special interest because they have the largest volume per surface ratio of all cages discussed here.
Inverse parametric convex programming problems via convex liftings
Nguyen, Ngoc Anh; Olaru, Sorin; Rodriguez-Ayerbe, Pedro; Hovd, Morten; Necoara, Ion
2014-01-01
The present paper introduces a procedure to recover an inverse parametric linear or quadratic programming problem from a given liftable polyhedral partition over which a continuous piecewise affine function is defined. The solution to the resulting parametric linear problem is exactly the initial piecewise affine function over the given original parameter space partition. We provide sufficient conditions for the existence of solutions for such inverse problems. Furthermore, the constructive p...
Granular cell tumor: An uncommon benign neoplasm
Directory of Open Access Journals (Sweden)
Tirthankar Gayen
2015-01-01
Full Text Available Granular cell tumor is a distinctly rare neoplasm of neural sheath origin. It mainly presents as a solitary asymptomatic swelling in the oral cavity, skin, and rarely internal organs in the middle age. Histopathology is characteristic, showing polyhedral cells containing numerous fine eosinophilic granules with indistinct cell margins. We present a case of granular cell tumor on the back of a 48-year-old woman which was painful, mimicking an adnexal tumor.
Tan Aaron; Madani Seyed; Rajadas Jayakumar; Pastorin Giorgia; Seifalian Alexander M
2012-01-01
Abstract Background The application of nanotechnology in biology and medicine represents a significant paradigm shift in the approach to the treatment of cancer. Evidence suggests that when exposed to near-infrared radiation (NIR), carbon nanotubes (CNTs) dissipate a substantial amount of heat energy. We have developed a novel nanocomposite polymer, polyhedral oligomeric silsesquioxane poly (carbonate-urea) urethane (POSS-PCU). POSS-PCU displays excellent biocompatibility and has been used in...
Design and development of a prosthetic implant for cardiovascular reconstructions
Ahmed, M.
2011-01-01
There is a significant worldwide demand for a small calibre vascular graft for use as a bypass or replacement conduit. Our lab has developed a novel nanocomposite poly- mer based on polyhedral oligomeric silsesquioxane and poly(carbonate-urea)urethane (POSS-PCU) which has displayed promising properties in vitro. In this thesis, POSS- PCU has been utilised to fabricate prosthetic small calibre conduits for use as arterial replacements. An important feature in determining the succes...
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...
Crowley, C.; Klanrit, P; C.R. Butler; Varanou, A; Platé, M.; Hynds, R. E.; Chambers, R. C.; Seifalian, A. M.; Birchall, M A; Janes, S M
2016-01-01
Polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) is a versatile nanocomposite biomaterial with growing applications as a bioscaffold for tissue engineering. Integration of synthetic implants with host tissue can be problematic but could be improved by topographical modifications. We describe optimization of POSS-PCU by dispersion of porogens (sodium bicarbonate (NaHCO3), sodium chloride (NaCl) and sucrose) onto the material surface, with the principle aim of incre...
Optimization of Acrylic Acid Grafting onto POSS-PCU Nanocomposite Using Response Surface Methodology
Solouk, A.; Solati-Hashjin, M.; S. Najarian; Mirzadeh, H.; Seifalian, A. M.
2011-01-01
The novel nanocomposite based on poly(carbonate-urea)urethane and polyhedral oligomeric silsesquioxanes (POSS) has been used in medicine especially in cardiovascular applications. It is also known that the cell affinity towards biomaterials can be promoted by immobilization of extracellular matrix proteins onto these materials surfaces. The inert surface of POSS-PCU nanocomposite is not directly suitable for immobilization of such biomolecules and therefore, its biocompatibility should be imp...
Effects of sterilization treatments on bulk and surface properties of nanocomposite biomaterials
Ahmed, Maqsood; Punshon, Geoffrey; Darbyshire, Arnold; Seifalian, Alexander M
2013-01-01
With the continuous and expanding use of implantable biomaterials in a clinical setting, this study aims to elucidate the influence of sterilization techniques on the material surface and bulk properties of two polyurethane nanocomposite biomaterials. Both solid samples and porous membranes of nondegradable polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU) and a biodegradable poly(caprolactone-urea) urethane (POSS-PCL) were examined. Sterilization techniques includ...
Neopolares de problemas de empaquetamiento sobre semigrupos
Aráoz Durand, Julián Arturo
1982-01-01
Los neopolares permiten caracterizar las caras de un poliedro combinatorio como vértices de poliedros altamente estructurados. Esto sirve para generar planos de cortes y para obtener propiedades duales en problemas de programación entera. Gomory caracterizó neopolares para problemas sobre grupos, Aráoz en "Polyhedral Neopolarities" extendió estos resultados a semigrupos de cubrimiento. En este trabajo se caracterizan neopolares importantes de semigrupos de empaquetamiento que incluyen los pro...
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.
The dynamic behaviour of a modified polyurethane resin
Appleby-Thomas, G. J.; Hazell, P.J.; Stennett, C; Cooper, G; Cleave, R.
2011-01-01
The dynamic response of both a pure and nano-reinforced polyurethane replacement resin (PRR) have been investigated using plate impact techniques. Similar U-P-U- S Hugoniot equations of state have been established for both materials, despite the altered cross-linking associated with the addition of inorganic polyhedral oligomeric silsesquioxane (POSS) blocks of c. 1.5 nm size to the resin matrix. At higher particle velocities a similar U-P-U-S response to that of polyurethane ...
Jeng, Shie-Chang; Hwang, Su-June; Chen, Tai-An; Liu, Han-Shiang; Chen, Mu-Zhe
2012-03-01
We have developed two approaches for controlling the pretilt angles of liquid crystal molecules by using conventional polyimide (PI) alignment materials either doping homogeneous PIs with Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles or treating homeotropic PIs with ultraviolet light. These techniques are very simple and are compatible with current methods familiar in the LCD industry. The characteristics of modified PI alignment films and their applications for photonic devices are demonstrated in this paper.
Bohannon, Kevin Patrick; Jun, Yonggun; Gross, Steven P.; Smith, Gregory Allan
2013-01-01
Neuroinvasive herpesviruses cause diseases in humans ranging from cold sores to central nervous system infections. Unlike most icosahedral viruses, herpesvirus capsids are surrounded by protein layers that lack polyhedral architecture. The outer layers are critical for herpesvirus infectivity. Although the disorganized layers are visible by electron microscopy, the protein topography of these layers remains unclear. We fused fluorophores to virus proteins and pinpointed their positions within...
DEFF Research Database (Denmark)
Schwerdtfeger, Peter; Wirz, Lukas; Avery, James Emil
2014-01-01
Fullerenes are carbon molecules that form polyhedral cages. Their bond structures are exactly the planar cubic graphs that have only pentagon and hexagon faces. Strikingly, a number of chemical properties of a fullerene can be derived from its graph structure. A rich mathematics of cubic planar g....... In this paper, we present a general overview of recent topological and graph theoretical developments in fullerene research over the past two decades, describing both solved and open problems....
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.
Justi, S.
1985-01-01
It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.
Golden Root Geometry Structuring the Polyhedra and Other Forms Via Plato’s Triangles
Panagiotis Chr. Stefanides
2014-01-01
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”...
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.
Coated vesicles participate in the receptor-mediated endocytosis of insulin
1983-01-01
We have purified coated vesicles from rat liver by differential ultracentrifugation. Electron micrographs of these preparations reveal only the polyhedral structures typical of coated vesicles. SDS PAGE of the coated vesicle preparation followed by Coomassie Blue staining of proteins reveals a protein composition also typical of coated vesicles. We determined that these rat liver coated vesicles possess a latent insulin binding capability. That is, little if any specific binding of 125I-insul...
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.
The Structure of the Set of Equilibria for Two Person Multicriteria Games
Borm, P.E.M.; Vermeulen, D.; Voorneveld, M.
1998-01-01
In this paper the structure of the set of equilibria for two person multicriteria games is analysed. It turns out that the classical result for the set of equilibria for bimatrix games, that it is a finite union of polytopes, is only valid for multicriteria games if one of the players only has two pure strategies. A full polyhedral description of these polytopes can be derived when the player with an arbitrary number of pure strategies has one criterion.
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....
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.
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.
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
The Planar CoB18 (-) Cluster as a Motif for Metallo-Borophenes.
Li, Wan-Lu; Jian, Tian; Chen, Xin; Chen, Teng-Teng; Lopez, Gary V; Li, Jun; Wang, Lai-Sheng
2016-06-20
Monolayer-boron (borophene) has been predicted with various atomic arrangements consisting of a triangular boron lattice with hexagonal vacancies. Its viability was confirmed by the observation of a planar hexagonal B36 cluster with a central six-membered ring. Here we report a planar boron cluster doped with a transition-metal atom in the boron network (CoB18 (-) ), suggesting the prospect of forming stable hetero-borophenes. The CoB18 (-) cluster was characterized by photoelectron spectroscopy and quantum chemistry calculations, showing that its most stable structure is planar with the Co atom as an integral part of a triangular boron lattice. Chemical bonding analyses show that the planar CoB18 (-) is aromatic with ten π-electrons and the Co atom has strong covalent interactions with the surrounding boron atoms. The current result suggests that transition metals can be doped into the planes of borophenes to create metallo-borophenes, opening vast opportunities to design hetero-borophenes with tunable chemical, magnetic, and optical properties. PMID:27094830
Proceedings of workshop on 'boron chemistry and boron neutron capture therapy'
International Nuclear Information System (INIS)
This volume contains the proceedings of the 4th Workshop on 'the Boron Chemistry and Boron Neutron Capture Therapy' held on February 24 in 1992. First, clinical experiences of BNCT in the Kyoto University Research Reactor in 1992 were briefly reported. Then, the killing effects of boron cluster-containing nucleic acid precursors on tumor cells were shown (Chap. 2). The various trials of the optical resolution of B-p-boronophenylalanine for neutron capture therapy were made (Chap. 3). The borate-dextran gel complexes were investigated by the nuclear magnetic resonance spectroscopy. The stability constants of borate complexes were listed, and are useful in the solution chemistry of boron compounds (Chap. 4). The interactions between boron compounds and biological materials were studied by the paper electrophoresis which had been developed by us (Chap. 5). Molecular design of boron-10 carriers and their organic synthesis were reported (Chap. 6). Carborane-containing aziridine boron carriers which were directed to the DNA alkylation were synthesized and their cancer cell killing efficacies were tested (Chap. 7). The solution chemistry of deuterium oxide which is a good neutron moderator was reported, relating to the BNCT (Chap. 8). (author)
Visible-Light-Induced Olefin Activation Using 3D Aromatic Boron-Rich Cluster Photooxidants.
Messina, Marco S; Axtell, Jonathan C; Wang, Yiqun; Chong, Paul; Wixtrom, Alex I; Kirlikovali, Kent O; Upton, Brianna M; Hunter, Bryan M; Shafaat, Oliver S; Khan, Saeed I; Winkler, Jay R; Gray, Harry B; Alexandrova, Anastassia N; Maynard, Heather D; Spokoyny, Alexander M
2016-06-01
We report a discovery that perfunctionalized icosahedral dodecaborate clusters of the type B12(OCH2Ar)12 (Ar = Ph or C6F5) can undergo photo-excitation with visible light, leading to a new class of metal-free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V and can participate in electron-transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron-deficient styrene monomers at cluster loadings as low as 0.005 mol%. Furthermore, photo-excitation of B12(OCH2C6F5)12 in the presence of a less activated olefin such as isobutylene results in the production of highly branched poly(isobutylene). This work introduces a new class of air-stable, metal-free photo-redox reagents capable of mediating chemical transformations. PMID:27186856
Sources and transport systems for low energy extreme of ion implantation
Energy Technology Data Exchange (ETDEWEB)
Hershcovitch, A.; Batalin, V.A.; Bugaev, A.S.; Gushenets, V.I.; Alexeyenko, O.; Gurkova, E.; Johnson, B.M.; Kolomiets, A.A.; Kropachev, G.N.; Kuibeda, R.P.; Kulevoy, T.V.; Masunov, E.S.; Oks, E.M.; Pershin, V.I.; Polozov, S.M.; Poole, H.J.; Seleznev, D.N.; Storozhenko, P.A.; Vizir, A.; Svarovski, A.Ya.; Yakushin, P.; Yushkov, G.Yu.
2010-06-06
For the past seven years a joint research and development effort focusing on the design of steady state, intense ion sources has been in progress with the ultimate goal being to meet the two, energy extreme range needs of mega-electron-volt and 100's of electron-volt ion implanters. However, since the last Fortier is low energy ion implantation, focus of the endeavor has shifted to low energy ion implantation. For boron cluster source development, we started with molecular ions of decaborane (B{sub 10}H{sub 14}), octadecaborane (B{sub 18}H{sub 22}), and presently our focus is on carborane (C{sub 2}B{sub 10}H{sub 12}) ions developing methods for mitigating graphite deposition. Simultaneously, we are developing a pure boron ion source (without a working gas) that can form the basis for a novel, more efficient, plasma immersion source. Our Calutron-Berna ion source was converted into a universal source capable of switching between generating molecular phosphorous P{sub 4}{sup +}, high charge state ions, as well as other types of ions. Additionally, we have developed transport systems capable of transporting a very large variety of ion species, and simulations of a novel gasless/plasmaless ion beam deceleration method were also performed.
Van Duong, Long; Nguyen, Minh Tho
2016-06-29
Geometric and electronic structures of the boron cluster B14 and its silicon derivatives B13Si(+), B13Si(-), and B12Si2 were determined using DFT calculations (TPSSh/6-311+G(d)). The B12Si2 fullerene, which is formed by substituting two B atoms at two apex positions of the B14 fullerene by two Si atoms, was also found as the global minimum structure. We demonstrated that the electronic structure and orbital configuration of these small fullerenes can be predicted by the wavefunctions of a particle on a cylinder. The early appearance of high angular node MOs in B14 and B12Si2 can be understood by this simple model. Replacement of one B atom at a top position of B14 by one Si atom, followed by the addition or removal of one electron does not lead to a global minimum fullerene structure for the anion B13Si(-) and cation B13Si(+). The early appearance of the 5σ1 orbital in B13Si(+) causes a lower stability for the fullerene-type structure. PMID:27306917
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. PMID:25594368
Makarova, E B; Kiselyova, N S; Smetankina, M A; Bliznets, D G; Rubstein, A P; Krokhina, N B
2011-08-01
We studied changes of microarchitectonics of lymph nodes in mature rabbits in response to introduction of bioimplants based on porous titanium with carbon-containing nanocoating or nanocoating with hydroxyapatite embedded into pores. Moderate local reactivity of the lymphoid system was observed in animals with implants coated with carbon-containing films within 30 days after surgery. In animals with nanocoated implants containing hydroxyapatite, the immune response was more pronounced. Introduction of implants led to activation of cellular and humoral mechanisms of immunity in animals of both groups. PMID:22448374
Mechanism of Additives in Blocking up Pore While Al2O3—C Material Being Oxidized
Institute of Scientific and Technical Information of China (English)
TIANShou－xin; CHENZhao－you
1996-01-01
This paper testifies that aluminium and silicon as well as their carbidex and nitrides can react with CO in carbon-containing zone to form Al2O3 and SiO gas through experiment and thermodyanmic analysis,The gases diffuse to oxidized zone and react with oxidizers such as CO2,As a result ,Al2O3 and SiO2 are deposited from the gases ,wihich block the pores,thus reduce the amount of gas diffusion and increase oxidation resistnace of carbon-containing materials.
Apparatus for producing carbon-coated nanoparticles and carbon nanospheres
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.
Formation of ZrB2 in MgO-C Composite Materials Using In-Situ Synthesis Method
Institute of Scientific and Technical Information of China (English)
LI Lin; HONG Yan-ruo; SUN Jia-lin; HE Zhi-yong; PENG Xiao-yan
2006-01-01
ZrB2 in MgO-C composite materials obtained by both microwave sintering synthesis and in-situ reaction at lower temperature was investigated. The test result shows that 66.67% of reactant changed into ZrB2, and the other form Al2O3, which could optimize the properties of carbon-containing materials. Therefore, the method of in-situ synthesizing ZrB2 acting as antioxidant in carbon-containing materials is considered as one of best ways to reduce the cost and ZrB2 as refractories is used on a large-scale.
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.
Energy Technology Data Exchange (ETDEWEB)
Petrov, Victor, E-mail: victor.petrov@psi.c [Laboratory for Reactor Physics and Systems Behaviour, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland); Manera, Annalisa, E-mail: annalisa.manera@psi.c [Laboratory for Reactor Physics and Systems Behaviour, Paul Scherrer Institute, 5232 Villigen PSI (Switzerland)
2011-05-15
Highlights: Two different types of meshes (hexahedral and polyhedral) were used. The calculations are performed with and without a flow swirl in the cold legs. CFD model has been validated on the basis of JULIETTE experimental facility data. - Abstract: A computational fluid dynamic (CFD) model for the pressure vessel of the evolutionary pressurized reactor (EPR{sup TM}) was developed and validated. The aim of this model is the simulation of transients where three-dimensional effects play a strong role, such as boron dilution and main steam line break (MSLB) scenarios. First, a full solid (CAD) model has been built, that includes all details of the reactor pressure vessel (RPV) and the internals which are important for fluid dynamic analyses. The solid model has then been used as basis for the generation of the computational mesh necessary to carry out CFD simulations. Both a hexahedral and a polyhedral mesh have been created. The CFD model has been validated against experimental results of the JULIETTE facility, a 1:5 scaled mock-up of the EPR{sup TM} reactor RPV built by AREVA and equipped with advanced instrumentation. The performances of the hexahedral and the polyhedral meshes are investigated in relation to the agreement with experimental data, convergence and CPU requirements. In addition, the effect of the cold-leg swirls on the velocity field inside the RPV is investigated. These swirls mimic the effects of the main coolant recirculation pumps on the flow field at the entrance of the RPV. It is shown that the CFD model is able to capture the shift of the maximum velocity in the downcomer annulus observed in the experimental results. Good qualitative as well as quantitative agreement with the experimental data is achieved.
Mechanism of ruthenium dioxide crystallization during high level waste vitrification
International Nuclear Information System (INIS)
Ruthenium, arising from the reprocessing of spent uranium oxide fuel, has a low solubility in glass melt. It crystallizes in the form of particles of RuO2 of acicular or polyhedral morphology dispersed in fission product and actinides waste containment glass. Since the morphology of these particles strongly influences the physico-chemical properties, the knowledge and the control of their mechanism of formation are of major importance. The goal of this work is to determine the chemical reactions responsible for the formation of RuO2 particles of acicular or polyhedral shape during glass synthesis. Using a simplification approach, the reactions between RuO2-NaNO3, and more complex calcine RuO2-Al2O3-Na2O and a sodium borosilicate glass are studied. In situ scanning electron microscopy and XANES at increasing temperatures are used to follow changes in composition, speciation and morphology of the ruthenium intermediate species. Those compounds are thoroughly characterised by SEM, XRD, HRTEM, and ruthenium K-edge X-ray absorption spectroscopy. This combined approach allows us to show that the ruthenium speciation modification during vitrification is the key of control of the morphology of RuO2 particles in the glass. In particular, the formation of a specific intermediate compound (Na3RuO4) is one of the main steps that lead to the precipitation of needle-shaped RuO2 particles in the melt. The formation of polyhedral particles, on the contrary, results from the direct incorporation of RuO2 crystals in the melt followed by an Ostwald ripening mechanism. (author)
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.
Nanotechnology and bio-functionalisation for peripheral nerve regeneration
Directory of Open Access Journals (Sweden)
Tina Sedaghati
2015-01-01
Full Text Available There is a high clinical demand for new smart biomaterials, which stimulate neuronal cell proliferation, migration and increase cell-material interaction to facilitate nerve regeneration across these critical-sized defects. This article briefly reviews several up-to-date published studies using Arginine-Glycine-Aspartic acid peptide sequence, nanocomposite based on polyhedral oligomeric silsesquioxane nanoparticle and nanofibrous scaffolds as promising strategies to enhance peripheral nerve regeneration by influencing 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.
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.
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...... defining inequalities in a branch-and-cut algorithm for the problem. We give a description of this algorithm, including some separation procedures, and present the computational results for different sets of test problems. The computation times that are obtained indicate that this algorithm is more...... efficient than previously described algorithms for the problem. Udgivelsesdato: APR 1...
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...... of facet defining inequalities in a branch-and-cut algorithm for the problem. We give a description of this algorithm, including some separation procedures, and present the computational results for different sets of test problems. The computation times that are obtained indicate that this algorithm...... is more efficient than previously described algorithms for the problem....
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.
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.
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.
DEFF Research Database (Denmark)
Jensen, Anders Nedergaard; Lauritzen, Niels; Fukuda, Komei;
2005-01-01
The Gröbner walk is an algorithm for conversion between Gröbner bases for different term orders. It is based on the polyhedral geometry of the Gröbner fan and involves tracking a line between cones representing the initial and target term order. An important parameter is explicit numerical...... perturbation of this line. This usually involves both time and space demanding arithmetic of integers much larger than the input numbers. In this paper we show how the explicit line may be replaced by a formal line using Robbiano's characterization of group orders on . This gives rise to the generic Gröbner...
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.
Surface-enhanced raman spectroscopy substrate for arsenic sensing in groundwater
Energy Technology Data Exchange (ETDEWEB)
Yang, Peidong; Mulvihill, Martin; Tao, Andrea R.; Sinsermsuksakul, Prasert; Arnold, John
2015-06-16
A surface-enhanced Raman spectroscopy (SERS) substrate formed from a plurality of monolayers of polyhedral silver nanocrystals, wherein at least one of the monolayers has polyvinypyrrolidone (PVP) on its surface, and thereby configured for sensing arsenic is described. Highly active SERS substrates are formed by assembling high density monolayers of differently shaped silver nanocrystals onto a solid support. SERS detection is performed directly on this substrate by placing a droplet of the analyte solution onto the nanocrystal monolayer. Adsorbed polymer, polyvinypyrrolidone (PVP), on the surface of the nanoparticles facilitates the binding of both arsenate and arsenite near the silver surface, allowing for highly accurate and sensitive detection capabilities.
Computational Methods Development at Ames
Kwak, Dochan; Smith, Charles A. (Technical Monitor)
1998-01-01
This viewgraph presentation outlines the development at Ames Research Center of advanced computational methods to provide appropriate fidelity computational analysis/design capabilities. Current thrusts of the Ames research include: 1) methods to enhance/accelerate viscous flow simulation procedures, and the development of hybrid/polyhedral-grid procedures for viscous flow; 2) the development of real time transonic flow simulation procedures for a production wind tunnel, and intelligent data management technology; and 3) the validation of methods and the flow physics study gives historical precedents to above research, and speculates on its future course.
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.
Kannan, Aravindaraj G.; McInnes, Steven J. P.; Choudhury, Namita R.; Dutta, Naba K.; Voelcker, Nicolas H.
2008-12-01
Here we describe a new class of near superhydrophobic surfaces formed using fluorinated polyhedral oligosilsesquioxane (FluoroPOSS) urethane hybrids and porous silicon gradients (pSi). We demonstrate that the surface segregation behavior of the hydrophobic fluoro component can be controlled by the type and nature of chain extender of the urethane and resultant hydrophobic association via intra or intermolecular aggregation. The surface film formed exhibits near superhydrophobicity. This work has significant potential for applications in antifouling and self-cleaning coatings, biomedical devices, microfluidic systems and tribological surfaces.
Feature - Based Approach to Automatic Fixturing System Planning ForUniform Polyhedra Workpiece
Directory of Open Access Journals (Sweden)
Amjad Barzan
2008-01-01
Full Text Available This paper demonstrates the design of an algorithm to represent the design stages of fixturing system that serve in increasing the flexibility and automation of fixturing system planning for uniform polyhedral part. This system requires building a manufacturing feature recognition algorithm to present or describe inputs such as (configuration of workpiece and built database system to represents (production plan and fixturing system exiting to this algorithm. Also knowledge base system was building or developed to find the best fixturing analysis (workpiece setup, constraints of workpiece and arrangement the contact on this workpiece to workpiece.
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.
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.
[Morphological diversity of Pandorina morum (Mull.) Vory (Volvocaceae) colonies].
Voĭtekhovskiĭ, Iu L
2001-01-01
Morphological variability of polyhedral colonies of green algae (Volvocaceae) were studied using some elements of combinative theory of polyhedron and the theory of diophantine equations. These colonies are considered as results of self-organization according to topological regularities of sphere dissection by convex polygons. It was shown that in three-dimensional Euclidean space for each colony of Pandorina morum (Müll.) Bory only three different forms are possible. One of them has no plane of symmetry and, thus, has two enantiomorphous varieties. It is suggested that frequency spectrum of forms can be used as potential indicator of environment pollution. PMID:11605552
Cooper, Martin
2010-01-01
The computer interpretation of line drawings is a classic problem in AI and has inspired the development of some fundamental AI tools. This novel approach to drawing interpretation combines new constraints with recent advances in soft constraint programming, Based on the author's considerable research experience, this book contains state-of-the-art reviews of work in drawing interpretation and discrete optimisation and is not just restricted to drawings of polyhedral objects, but also covers complex curved objects. The book will become a standard reference in the field with its coverage of man
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.
Matching and Clustering: Two Steps Towards Object Modelling in Computer Vision
Gros, Patrick
1995-01-01
International audience In this article, we present a general frame for a system of au tomatic modeling and recognition of 3D polyhedral objects. Such a system has many applications for robotics: e.g., recog nition, localization, and grasping. Here we focus on one main aspect of the system: when many images of one 3D object are taken from different unknown viewpoints, how to recognize those that represent the same aspect of the object? Briefly, is it possible to determine automatically if t...
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.
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.
Homotopy theory the mathematical works of J. H. C. whitehead
James, I M
1962-01-01
Homotopy Theory contains all the published mathematical work of J. H. C. Whitehead, written between 1947 and 1955. This volume considers the study of simple homotopy types, particularly the realization of problem for homotopy types. It describes Whitehead's version of homotopy theory in terms of CW-complexes.This book is composed of 21 chapters and begins with an overview of a theorem to Borsuk and the homotopy type of ANR. The subsequent chapters deal with four-dimensional polyhedral, the homotopy type of a special kind of polyhedron, and the combinatorial homotopy I and II. These topics are
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.
Directory of Open Access Journals (Sweden)
Xin Zuo
2016-01-01
Full Text Available Continuity (both lower and upper semicontinuities results of the Pareto/efficient solution mapping for a parametric vector variational inequality with a polyhedral constraint set are established via scalarization approaches, within the framework of strict pseudomonotonicity assumptions. As a direct application, the continuity of the solution mapping to a parametric weak Minty vector variational inequality is also discussed. Furthermore, error bounds for the weak vector variational inequality in terms of two known regularized gap functions are also obtained, under strong pseudomonotonicity assumptions.
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
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.
Discrete Element Method Simulation of a Boulder Extraction From an Asteroid
Kulchitsky, Anton K.; Johnson, Jerome B.; Reeves, David M.; Wilkinson, Allen
2014-01-01
The force required to pull 7t and 40t polyhedral boulders from the surface of an asteroid is simulated using the discrete element method considering the effects of microgravity, regolith cohesion and boulder acceleration. The connection between particle surface energy and regolith cohesion is estimated by simulating a cohesion sample tearing test. An optimal constant acceleration is found where the peak net force from inertia and cohesion is a minimum. Peak pulling forces can be further reduced by using linear and quadratic acceleration functions with up to a 40% reduction in force for quadratic acceleration.
Combinatorial topology of three-dimensional self-affine tiles
Bandt, Christoph
2010-01-01
We develop tools to study the topology and geometry of self-affine fractals in dimension three and higher. We use the self-affine structure and obtain rather detailed information about the connectedness of interior and boundary sets, and on the dimensions and intersections of boundary sets. As an application, we describe in algebraic terms the polyhedral structure of the six fractal three-dimensional twindragons. Only two of them can be homeomorphic to a ball but even these have faces which are not homeomorphic to a disk.
Tunable pretilt angles based on nanoparticles-doped planar liquid-crystal cells.
Jeng, Shie-Chang; Hwang, Shug-June; Yang, Chen-Yu
2009-02-15
The nanoparticles-induced vertical alignment technique was applied to generate variable liquid-crystal pretilt angles based on doping different concentrations of polyhedral oligomeric silsesquioxane (POSS) nanoparticles in the planar-aligned liquid crystal cells. Competition between the homogeneously aligned polyimide layer and POSS-induced spontaneous vertical alignment domain generated the variable pretilt angle. Experimental results demonstrated that the pretilt angle theta(p) is a function of the doped POSS concentration and can be controlled continuously over the range of 0 degrees
Controlled Assembly of Endohedrally-Functionalized Metal-Ligand Supramolecular Complexes
Johnson, Amber
2014-01-01
An area of supramolecular chemistry that has recently been growing in popularity is the synthesis of metal-ligand cages. These are most commonly comprised of organic ligands and transition metal ions. Cage complexes often take the form of geometric polyhedra such as tetrahedra and octahedra, where the ligands act as the edges or faces and the metals serve as the vertices. Because these complexes have a polyhedral design, there is a central cavity in the cage, and this has been exploited for g...
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
L’hyperterminotique, un modèle paradigmatique d’organisation du savoir
Surmont, Jean-Nicolas de
2012-01-01
La représentation linéaire de la connaissance ne peut rendre compte de la nature polyèdre du terme. Le néologisme hyperterminotique désigne les situations ou processus d’organisation et de gestion de termes et de terminologies par le biais d’outils hypertextuels à l’intérieur des réseaux. L’hyperterminotique débouche sur une définition éthique du concept de paradigme. A linear knowledge representation cannot assume the polyhedral nature of terms. What we call hyperterminotics includes situ...
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.
Institute of Scientific and Technical Information of China (English)
ZHENG Yu; QIAN Wenhan
2005-01-01
Currently, most efficient algorithms for force-closure analysis and dynamic force distribution utilize linear programming, but friction models are nonlinear. Substituting polyhedral cones for circular cones of Coulomb friction realizes the linearization of the frictional point contact constraint. So far, however, there is no approach to soft finger contact. This paper presents such an approach. Then the foregoing algorithms can be extended to grasping with soft finger contact. Herein an optimal force distribution algorithm for soft multifingered grasps is developed with an illustrative example.
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. PMID:26645985
Acoustic Echoes Reveal Room Shape
Dokmanic, Ivan; Parhizkar, Reza; Walther, Andreas; Lu, Yue M.; Vetterli, Martin
2013-01-01
Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room’s response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to “blindfoldedly” estimate the room geometry. This is achiev...
A robust optimization approach to energy and reserve dispatch in electricity markets
DEFF Research Database (Denmark)
Zugno, Marco; Conejo, Antonio J.
2015-01-01
at the balancing (real-time) stage, in the worst-case realization of the stochastic production within a specified uncertainty set. We propose a novel reformulation of the problem that allows considering general polyhedral uncertainty sets. In a case-study, we show that, in comparison to a risk-averse stochastic...... programming model, the robust optimization approach progressively trades off optimality in expectation with improved performance in terms of risk. These differences, however, gradually taper off as the level of risk-aversion increases for the stochastic programming approach. Computational studies show...
Model-based recognition of 3-D objects by geometric hashing technique
International Nuclear Information System (INIS)
A model-based object recognition system is developed for recognition of polyhedral objects. The system consists of feature extraction, modelling and matching stages. Linear features are used for object descriptions. Lines are obtained from edges using rotation transform. For modelling and recognition process, geometric hashing method is utilized. Each object is modelled using 2-D views taken from the viewpoints on the viewing sphere. A hidden line elimination algorithm is used to find these views from the wire frame model of the objects. The recognition experiments yielded satisfactory results. (author). 8 refs, 5 figs
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.
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.
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.
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.
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.
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
Studies on the sublimation of tungsten single crystal (110) face and the influence of carbon
International Nuclear Information System (INIS)
Evaporation of tungsten single crystals face (110) is studied in ultrahigh vacuum (better than 1x10-9 torr) by Langmuir method. Small admixtures of carbon are shown to markedly influence the process. Carbon hinders the evaporation and increases the sublimation energy by 25 kcal. The data obtained show that the reported parametres of tungsten evaporation refer to a carbon-containing material
40 CFR 98.113 - Calculating GHG emissions.
2010-07-01
... must calculate and report the annual process CO2 emissions from each EAF using the procedures in either... paragraphs (b)(2)(i) and (b)(2)(ii) of this section. (i) For each EAF, determine the annual mass of carbon in each carbon-containing input and output material for the EAF and estimate annual process CO2...
R-Matrix Calculations of Electron Molecule Collision Data
International Nuclear Information System (INIS)
Results for R-matrix calculations performed during the Coordinated Research Project (CRP) on Atomic and Molecular Data for Plasma Modelling are discussed. Electron collision problems studied include collisions with various carbon containing molecules including C2, HCCH, CH4, C2H6 and C3H8. (author)
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.
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.
Mei, Yu; Cheng, Zhuo-wei; Wang, Jia-de; Lu, Yin
2015-12-01
A pilot biotrickling filter (BTF) was set up for removal of a mixed waste gas containing toluene and ethanol. The packing material was composed of polyhedral sphere and polyhedral hollow column previously designed by our group. The results showed this BTF could successfully start up within only 8 d and the average eliminate capacities for toluene and ethanol were 97.14 and 113.10 g · (m³ · h)⁻¹, respectively. Empty bed residence time (EBRT) and the inlet concentration had effects on the removal of toluene. The maximum elimination capacity of toluene and ethanol was 123.34 and 206.36 g (m³ · h)⁻¹ under EBRT of 21.11 s, respectively. However, the effect of spray liquid density was not obvious, and the optimal value of solution and gas ratio was 6.82 L · m⁻³. The influence of unstable processing condition on its performance was also investigated. NaOH solution could effectively reduce the plugging of the filler layer, and the removal capability of pollutant could be recovered within 3 days. After the running was stopped for 10 d, the removal performance of this BTF could be quickly recovered. PMID:27011972
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.
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.
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。
Relevance of capsid structure in the buckling and maturation of spherical viruses
International Nuclear Information System (INIS)
The shape and mechanical properties of viral capsids play an important role in several biological processes during the virus life cycle. In particular, to become infective, many viruses require a maturation stage where the capsid undergoes a buckling transition, from an initial spherical procapsid into a final icosahedral faceted shell. Here we study, using a minimal physical model, how the capsid shape and the buckling transition depend on the triangulation number T and the icosahedral class P of the virus structure. We find that, for small shells, capsids with P = 1 are most likely to produce polyhedral shapes that minimize their energy and accumulated stress, whereas viruses with P = 3 prefer to remain spherical. For big capsids, all shells are more stable adopting an icosahedral shape, in agreement with continuum elastic theory. Moreover, spherical viruses show a buckling transition to polyhedral shells under expansion, in consonance with virus maturation. The resulting icosahedral shell is mechanically stiffer, tolerates larger expansions and withstands higher internal pressures before failing, which could explain why some dsDNA viruses, which rely on the pressurization of their genetic material to facilitate the infection, undergo a buckling transition. We emphasize that the results are general and could also be applied to non-biological systems. (paper)
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.
Farhatnia, Yasmin; Pang, Jun Hon; Darbyshire, Arnold; Dee, Ryan; Tan, Aaron; Seifalian, Alexander M
2016-01-01
Covered stents are stents wrapped with a thin polymeric membrane, and are typically used to treat vessel aneurysms and seal perforated arteries. Current covered stents suffer from restenosis due to limitations in material and fabrication methods which leaves metallic struts directly exposed to blood. We have developed a biocompatible and haemocompatible nanocomposite polymer, polyhedral oligomeric silsesquioxane poly(carbonate-urea) urethane (POSS-PCU). We devised a novel combination of ultrasonic spray atomisation system and dip-coating process to produce small calibre covered stents with metal struts fully embedded within the membrane, which also yields greater coating uniformity. Stent-polymer bonding was enhanced via silanisation and coating of reactive pre-polymer. Platelet studies supported the non-thrombogenicity of POSS-PCU. Biomechanical performances including diametrical compliance, bending strength, radial strength and recoil were evaluated and optimised. This proof-of-principle manufacturing technique could lead to the development of next-generation small calibre adult and paediatric covered stents. These stents are currently undergoing preclinical trial. From the Clinical Editor: The use of stents to treat vascular diseases is now the standard of care in the clinical setting. Nonetheless, a major problem of the current stents is the risk of restenosis and thrombosis. The authors developed a nanocomposite material using polyhedral oligomeric silsesquioxane and poly(carbonate-urea) urethane (POSS-PCU) and incorporated into metallic stents. Preliminary data have already shown promising results. It is envisaged that this would further lead to better stent technology in the future. PMID:26238080
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.
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.
Thickness and clearance visualization based on distance field of 3D objects
Directory of Open Access Journals (Sweden)
Masatomo Inui
2015-07-01
Full Text Available This paper proposes a novel method for visualizing the thickness and clearance of 3D objects in a polyhedral representation. The proposed method uses the distance field of the objects in the visualization. A parallel algorithm is developed for constructing the distance field of polyhedral objects using the GPU. The distance between a voxel and the surface polygons of the model is computed many times in the distance field construction. Similar sets of polygons are usually selected as close polygons for close voxels. By using this spatial coherence, a parallel algorithm is designed to compute the distances between a cluster of close voxels and the polygons selected by the culling operation so that the fast shared memory mechanism of the GPU can be fully utilized. The thickness/clearance of the objects is visualized by distributing points on the visible surfaces of the objects and painting them with a unique color corresponding to the thickness/clearance values at those points. A modified ray casting method is developed for computing the thickness/clearance using the distance field of the objects. A system based on these algorithms can compute the distance field of complex objects within a few minutes for most cases. After the distance field construction, thickness/clearance visualization at a near interactive rate is achieved.
Mimetic finite difference method
Lipnikov, Konstantin; Manzini, Gianmarco; Shashkov, Mikhail
2014-01-01
The mimetic finite difference (MFD) method mimics fundamental properties of mathematical and physical systems including conservation laws, symmetry and positivity of solutions, duality and self-adjointness of differential operators, and exact mathematical identities of the vector and tensor calculus. This article is the first comprehensive review of the 50-year long history of the mimetic methodology and describes in a systematic way the major mimetic ideas and their relevance to academic and real-life problems. The supporting applications include diffusion, electromagnetics, fluid flow, and Lagrangian hydrodynamics problems. The article provides enough details to build various discrete operators on unstructured polygonal and polyhedral meshes and summarizes the major convergence results for the mimetic approximations. Most of these theoretical results, which are presented here as lemmas, propositions and theorems, are either original or an extension of existing results to a more general formulation using polyhedral meshes. Finally, flexibility and extensibility of the mimetic methodology are shown by deriving higher-order approximations, enforcing discrete maximum principles for diffusion problems, and ensuring the numerical stability for saddle-point systems.
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.
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.
Acoustic echoes reveal room shape.
Dokmanic, Ivan; Parhizkar, Reza; Walther, Andreas; Lu, Yue M; Vetterli, Martin
2013-07-23
Imagine that you are blindfolded inside an unknown room. You snap your fingers and listen to the room's response. Can you hear the shape of the room? Some people can do it naturally, but can we design computer algorithms that hear rooms? We show how to compute the shape of a convex polyhedral room from its response to a known sound, recorded by a few microphones. Geometric relationships between the arrival times of echoes enable us to "blindfoldedly" estimate the room geometry. This is achieved by exploiting the properties of Euclidean distance matrices. Furthermore, we show that under mild conditions, first-order echoes provide a unique description of convex polyhedral rooms. Our algorithm starts from the recorded impulse responses and proceeds by learning the correct assignment of echoes to walls. In contrast to earlier methods, the proposed algorithm reconstructs the full 3D geometry of the room from a single sound emission, and with an arbitrary geometry of the microphone array. As long as the microphones can hear the echoes, we can position them as we want. Besides answering a basic question about the inverse problem of room acoustics, our results find applications in areas such as architectural acoustics, indoor localization, virtual reality, and audio forensics. PMID:23776236
Directory of Open Access Journals (Sweden)
Kavi H Patel
2013-12-01
Full Text Available Reconstruction of the human auricle remains a challenge to plastic surgeons, and current approaches are not ideal. Tissue engineering provides a promising alternative. This study aims to evaluate the chondrogenic potential of bone marrow–derived mesenchymal stem cells on a novel, auricular-shaped polymer. The proposed polyhedral oligomeric silsesquioxane-modified poly(hexanolactone/carbonateurethane/urea nanocomposite polymer has already been transplanted in patients as the world’s first synthetic trachea, tear duct and vascular bypass graft. The nanocomposite scaffold was fabricated via a coagulation/salt-leaching method and shaped into an auricle. Adult bone marrow–derived mesenchymal stem cells were isolated, cultured and seeded onto the scaffold. On day 21, samples were sent for scanning electron microscopy, histology and immunofluorescence to assess for neocartilage formation. Cell viability assay confirmed cytocompatability and normal patterns of cellular growth at 7, 14 and 21 days after culture. This study demonstrates the potential of a novel polyhedral oligomeric silsesquioxane-modified poly(hexanolactone/carbonateurethane/urea scaffold for culturing bone marrow–derived mesenchymal stem cells in chondrogenic medium to produce an auricular-shaped construct. This is supported by scanning electron microscopy, histological and immunofluorescence analysis revealing markers of chondrogenesis including collagen type II, SOX-9, glycosaminoglycan and elastin. To the best of our knowledge, this is the first report of stem cell application on an auricular-shaped scaffold for tissue engineering purposes. Although many obstacles remain in producing a functional auricle, this is a promising step forward.
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.
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 ...
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.
Operational damage of steel 12Kh1MF steam superheater tubes
International Nuclear Information System (INIS)
The structure and mechanical properties of steel 12Kh1MF specimens are investigated after cyclic tests under conditions simulating operational regime of steam superheater tubes. It is revealed that in thermal barocycling a decrease of steel strength and a transition from trans crystalline to intercrystalline feature take place due to precipitation of complex carbides along grain boundaries. Complex carbide formation is resulted from the appearance of free carbon of decomposed carbon-containing organic impurities in a water coolant
Catalytic carbon deposition on 3-dimensional carbon fibre supports
Thornton, Matthew James
2005-01-01
Catalytic carbon deposition reactions, using methane, ethane or synthetic natural gas (1.8 vol. % propane, 6.7 vol. % ethane and balance methane) as the carbon-containing gas feedstock with or without the addition of hydrogen, have been investigated over nickel, cobalt and iron catalysts supported on 3-dimensional carbon fibre supports, using both a horizontal tube furnace and an isothermal, isobaric induction furnace. The transition metal catalysts were prepared by impregnating 3-dimens...
Data on collisions of hydrogen atoms and ions with atoms and molecules, (1)
International Nuclear Information System (INIS)
This report presents a compilation of the experimental data on cross sections for charge transfer of H, H+ and H- with H2, N2, O2, H2O, C and carbon containing molecules. A survey has been made systematically of the literature up to the middle of 1982. The cross sections are given as a function of projectile energy in graphs and tables; a list of references is also attached. (author)
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.
Developemnt and Application of Al2O3—MgO Castable for Large Ladles in Con—casting System
Institute of Scientific and Technical Information of China (English)
MAXinwang; XUYanqing; 等
1998-01-01
Using Al2O3-MgO castable in large ladle can avoid containation of molten steel from carbon-containing refractories and increas ladle servic life remarkably,The addition of magnesia and fine powder,the effect of grain size on the proper-ties of the castable,especially linear change and structure spalling have been studied,Castable pro-dued for large ladle with small weare rate has got good applicatio result.
Sevilla Solís, Marta; Yu, Linghui; Fellinger, Tim Patrick; Fuertes Arias, Antonio Benito; Titirici, Maria-Magdalena
2013-01-01
[EN] N-doped mesoporous carbons containing small amounts of graphitic carbon have been successfully prepared using the nanocasting technique. Polypyrrole was used as N-dopant carbon precursor and SBA-15 or silica xerogel as templates. Graphitic carbon domains provide a good electronic conductivity of up to 0.33 S cm−1, a necessary property for electrochemical applications, while a mesoporous structure reduces mass transport limitations. These characteristics are further combined with a high N...
Composition, Property Characterization and Application of Agricultural and Forest Biomass Carbon
Lei, Chunsheng; Zhu, Xiaofeng; Zhou, Meicheng; Liang, Yuting; Zhang, Feng'e
2014-01-01
We analyzed the compositions and basic properties of agricultural and forest biomass carbon, and used the pot method to study the influence of such element on the remediation of contaminated soils and growth of crops. Results show that agricultural and forest biomass carbon contains various nutrients that are necessary for crop growth, high specific surface area, and pore structure development. Cotton stalk charcoal can reduce bioavailability of Cadmium (Cd) in soil. Under mild Cd pollution, ...
Spectroscopic characterisation of novel materials for semiconductor device applications
Reid, Ian
2007-01-01
The thesis uses surface science techniques to characterise the chemical composition and electronic properties of a range of carbon containing materials which have application in advanced semiconductor fabrication. The initial focus was on investigating the properties ofcarbon-doped oxide (CDO) which is a low dielectric constant material and a leading candidate to replace silicon dioxide (SiOz) as an interlayer dielectric (ILD) in microprocessor fabrication. The work then progresses to determi...
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.
Studies in sublimation of tungsten single crystal (110) face and the influence of carbon
Energy Technology Data Exchange (ETDEWEB)
Dekhtyar, I.Ya.; Kolesnik, V.M.; Patoka, V.I.; Silant' ev, V.I.
1975-12-01
Evaporation of the tungsten single crystal (110) face was studied in ultrahigh vacuum (better than 1.10/sup -9/ Torr) using the Langmuir method. The influence of carbon impurities on the evaporation parameters was found out and carbon is shown to increase the sublimation energy by 25 kcal. The data obtained show that the parameters of tungsten evaporation available in literature should be related to carbon-containing materials.
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.
Coral reef invertebrate microbiomes correlate with the presence of photosymbionts
Bourne, David G.; Dennis, Paul G.; Uthicke, Sven; Soo, Rochelle M; Tyson, Gene W; Nicole WEBSTER
2013-01-01
Coral reefs provide habitat for an array of marine invertebrates that host symbiotic microbiomes. Photosynthetic symbionts including Symbiodinium dinoflagellates and diatoms potentially influence the diversity of their host-associated microbiomes by releasing carbon-containing photosynthates and other organic compounds that fuel microbial metabolism. Here we used 16S ribosomal RNA (rRNA) gene amplicon pyrosequencing to characterise the microbiomes of 11 common Great Barrier Reef marine invert...
Combustion method for producing fullerenes
Howard, Jack B.; McKinnon, J. Thomas
1993-01-01
A method for synthesizing fullerenes in flames is provided. Fullerenes are prepared by burning carbon-containing compounds in a flame and collecting the condensibles. The condensibles contain the desired fullerenes. Fullerene yields can be optimized and fullerene composition can be selectively varied. Fullerene yields and compositions are determined by selectively controlling flame conditions and parameters such as C/O ratio, pressure, temperature, residence time, diluent concentration and gas velocity.
Golden Root Geometry Structuring the Polyhedra and Other Forms Via Plato’s Triangles
Directory of Open Access Journals (Sweden)
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.
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.
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).
International Nuclear Information System (INIS)
Preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. The ethanolamine ammonia-lyase microcompartment is composed of five different shell proteins that have been proposed to assemble into symmetrically shaped polyhedral particles of varying sizes. Here, preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. Cloning, overexpression and purification resulted in highly pure protein that crystallized readily under many different conditions. In all cases the protein forms thin hexagonal plate-shaped crystals belonging to space group P3 that are of unusually high stability against different solvent conditions. The crystals diffracted to a resolution of 2.0 Å using synchrotron radiation but proved to be radiation-sensitive. Preparations of heavy-atom-derivatized crystals for use in determining the three-dimensional structure are under way
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...
Incidence Geometry in a Weyl Chamber II: $SL_n$
Esole, Mboyo; Jagadeesan, Ravi; Noël, Alfred G
2016-01-01
We study the polyhedral geometry of the hyperplanes orthogonal to the weights of the first and the second fundamental representations of $sl_n$ inside the dual fundamental Weyl chamber. We obtain generating functions that enumerate the flats and the faces of a fixed dimension. In addition, we describe the extreme rays of the incidence geometry and classify simplicial faces. From the perspective of supersymmetric gauge theories with 8 supercharges in five dimensional spacetime, the poset of flats is isomorphic to the network of mixed Coulomb-Higgs branches. On the other hand, the poset of faces is conjectured to be isomorphic to the network of crepant partial resolutions of an elliptic fibration with gauge algebra $sl_n$ and "matter representation" given by the sum of the first two fundamental representations.
A non-linear von Neumann law for three-dimensional foam coarsening
Hilgenfeldt, Sascha; Kraynik, Andrew M.; Koehler, Stephan A.; Stone, Howard A.
2001-03-01
About 50 years ago, John von Neumann proved that the coarsening rate of individual bubbles in a 2-D dry foam is a linear function of the number of edges of the polygonal bubble. Soon afterwards it was conjectured that a statistical analog holds in three dimensions: polyhedral bubbles with a given number F of faces have an average growth rate that scales linearly in F. Using a theorem by Minkowski, we derive a parameter-free analytical expression for the average growth rates and show that it is non-linear, asymptoting to a square-root power in F. Experimental data and detailed foam simulations are in exceptionally good agreement with the analytical results. A refined model incorporates foam disorder to further improve the predictive power of the theory.
Foam coarsening: von Neumann's law in three dimensions is non-linear
Hilgenfeldt, Sascha; Kraynik, Andrew M.; Koehler, Stephan A.; Stone, Howard A.
2001-11-01
Fifty years ago, John von Neumann proved that the coarsening rate of individual bubbles in a 2-D dry foam is a linear function of the number of edges of the polygonal bubble. By analogy, it has been conjectured that the average growth rates of 3-D polyhedral bubbles scale linearly with the number F of faces. Using a theorem by Minkowski, we derive a parameter-free analytical expression for the average growth rates and show that the 3-D von Neumann law is non-linear, asymptoting to a square-root power in F. Detailed simulations are in exceptionally good agreement with the analytical formula. This result is important for the understanding of the geometrical structure and aging dynamics of many random cellular materials beyond foams, such as metal grains, spin glasses, or living cells.
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.
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.
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.
Anhydrous proton conducting composite membranes containing Nafion and triazole modified POSS
International Nuclear Information System (INIS)
Development of membrane electrolytes having reasonable proton conductivity and mechanical strength under anhydrous conditions is of great importance for proton exchange membrane fuel cells operated at elevated temperature. With the introduction of triazole modified polyhedral oligomeric silsesquioxanes (Tz-POSS) into Nafion membrane, the formed composite electrolytes exhibit improved mechanical properties compared to pristine Nafion membrane due to the well distribution of Tz-POSS inside the membrane. The anhydrous proton conductivity of the formed composite membranes increases initially with the increase in temperature, reaching about 0.02 Scm−1 at 140 °C. With further increase in temperature to about 150 °C, the composite membrane reaches its glass transition point above which the proton conductivity decreases dramatically. The performance of assembled single cell from composite membrane is slightly dependent on humidification conditions at 95 °C, reaching 0.45 V at 600 mAcm−2 using hydrogen and oxygen as reaction gases
Opposite face sensitivity of CeO₂ in hydrogenation and oxidation catalysis.
Vilé, Gianvito; Colussi, Sara; Krumeich, Frank; Trovarelli, Alessandro; Pérez-Ramírez, Javier
2014-11-01
The determination of structure-performance relationships of ceria in heterogeneous reactions is enabled by the control of the crystal shape and morphology. Whereas the (100) surface, predominantly exposed in nanocubes, is optimal for CO oxidation, the (111) surface, prevalent in conventional polyhedral CeO2 particles, dominates in C2H2 hydrogenation. This result is attributed to the different oxygen vacancy chemistry on these facets. In contrast to oxidations, hydrogenations on CeO2 are favored over low-vacancy surfaces owing to the key role of oxygen on the stabilization of reactive intermediates. The catalytic behavior after ageing at high temperature confirms the inverse face sensitivity of the two reaction families. PMID:25146728
The effect of substrate stretching on the thin-film distribution near an alveolar corner
Chini, Greg; Jensen, Oliver
2003-11-01
Because the lung contains an extensive and highly-curved air--liquid interface, surface tension forces play a central role in respiration. Anatomical studies have shown that the lung's liquid-film lining accumulates in the corners of polyhedral alveoli (the terminal airway units). We study the thin-film distribution near an alveolar corner by numerically integrating a model equation. In the absence of substrate stretching, the film attains a quasi-steady form in which a satellite drop drains slowly into a corner puddle. Canonical `Hammond draining' dynamics are observed, with the (perturbation) pressure varying rapidly and monotonically between the puddle and droplet. When the substrate is stretched, to mimic the effect of breathing, the pressure variation is no longer monotonic. We discuss the origin and implications of the modified pressure distribution and attempt to identify asymptotic scaling regimes.
Research on Spacecraft Illumination
Directory of Open Access Journals (Sweden)
Bo Cai
2011-07-01
Full Text Available Illumination analysis of spacecraft is very important. This paper firstly introduces the importance of spacecraft illumination analysis in aerospace fields and points out that illumination conditions will influence the design of shape of spacecraft body and the installation of spacecraft equipments. Then, it discusses two methods for analyzing spacecraft solar-panel shadow and illumination conditions: ray tracing illumination algorithm and polyhedral mesh contour edge projection algorithm and compares their efficiency and feasibility. Shadow area and solar area are computed of every cell on solar panels. We designed solar panel single-axis rotation experiment to validate the proposed algorithm. The experimental results show that contour edge projection algorithm has fine accuracy and costs less time. For detailed illumination information, we apply a practical segment clipping algorithm after some comparisons.
Zhang, Lei; Yang, Wenbin; Wu, Xiao-Yuan; Lu, Can-Zhong; Chen, Wen-Zhe
2016-08-01
Hydrophobic metal-organic frameworks (MOFs) not only have high water stability, but also exhibit high adsorption capacity towards organic molecules, in particular hydrocarbons. Herein we report a rare metal fluoride organic framework MFOF-1 with high hydrophobicity, which is constructed from unprecedented fluoride- and sulfate-bridged cubane-type tetranuclear cobalt clusters. MFOF-1 consists of three types of polyhedral cages with face-sharing configurations, and possesses a novel (3,9)-connected 3D+3D→3D self-interpenetrating array or the rare pyr topology. MFOF-1 shows high thermal stability and high stability in water and even acid/base aqueous solutions, and exhibits rather high H2 and CO2 storage capacities at ambient pressure. Remarkably, MFOF-1 shows little adsorption of water but considerably high uptakes of methanol, n-hexane, cyclohexane, and benzene, and exhibits a certain degree of adsorption selectivity of benzene over cyclohexane. PMID:27376623
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.
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.
Dumitriu, Ana-Maria-Corina; Balan, Mihaela; Bargan, Alexandra; Shova, Sergiu; Varganici, Cristian-Dragos; Cazacu, Maria
2016-04-01
During acid hydrolysis of 3-cyanopropyltriethoxysilane (CyTES) in a molar ratio HCl:CyTES - 4.6:1 in methanol, with the intention to prepare the properly polyhedral oligomeric silsesquioxane (POSSQ) or carboxyl derivative, the conversion of organic functional group occurred by replacing the CN group with Cl forming octakis(chloropropyl)octasilsesquioxane (Cl-POSSQ). The structure was determined through X-ray single crystal diffraction, spectral (FTIR and NMR) techniques and elemental analysis. The stepwise conversion of the CN group during the 3-cyanopropyltriethoxysilane hydrolysis was monitored through IR and 13C NMR spectroscopy. Thermal behavior was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moisture sorption capacity was evaluated by water vapor sorption in dynamic regime (DVS). The biological activity was in vitro tested against three fungi and two bacteria.
Nisse, Mounir
2011-01-01
A coamoeba is the image of a subvariety of a complex torus under the argument map to the real torus. Similarly, a non-archimedean coamoeba is the image of a subvariety of a torus over a non-archimedean field with complex residue field under an argument map. The phase tropical variety is the closure of the image under the pair of maps, tropicalization and argument. We describe the structure of non-archimedean coamoebae and phaseropical varieties in terms of complex coamoebae and their phase limit sets. The argument map depends upon a section of the valuation map, and we explain how this choice (mildly) affects the non-archimedean coamoeba. We also identify a class of varieties whose non-archimedean coamoebae and phase tropical varieties are objects from polyhedral combinatorics.
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.
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.
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}
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.
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...
Lan, Fujun; Bayraksan, Güzin; Lansey, Kevin
2016-03-01
A regional water supply system design problem that determines pipe and pump design parameters and water flows over a multi-year planning horizon is considered. A non-convex nonlinear model is formulated and solved by a branch-and-reduce global optimization approach. The lower bounding problem is constructed via a three-pronged effort that involves transforming the space of certain decision variables, polyhedral outer approximations, and the Reformulation Linearization Technique (RLT). Range reduction techniques are employed systematically to speed up convergence. Computational results demonstrate the efficiency of the proposed algorithm; in particular, the critical role range reduction techniques could play in RLT based branch-and-bound methods. Results also indicate using reclaimed water not only saves freshwater sources but is also a cost-effective non-potable water source in arid regions. Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/0305215X.2015.1016508.
Conforti, Michele; Zambelli, Giacomo
2014-01-01
This book is an elegant and rigorous presentation of integer programming, exposing the subject’s mathematical depth and broad applicability. Special attention is given to the theory behind the algorithms used in state-of-the-art solvers. An abundance of concrete examples and exercises of both theoretical and real-world interest explore the wide range of applications and ramifications of the theory. Each chapter is accompanied by an expertly informed guide to the literature and special topics, rounding out the reader’s understanding and serving as a gateway to deeper study. Key topics include: formulations polyhedral theory cutting planes decomposition enumeration semidefinite relaxations Written by renowned experts in integer programming and combinatorial optimization, Integer Programming is destined to become an essential text in the field.
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.
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.
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.
Bulk synthesis of polymer-inorganic colloidal clusters.
Perro, Adeline; Manoharan, Vinothan N
2010-12-21
We describe a procedure to synthesize colloidal clusters with polyhedral morphologies in high yield (liter quantities at up to 70% purity) using a combination of emulsion polymerization and inorganic surface chemistry. We show that the synthesis initially used for silica-polystyrene hybrid clusters can be generalized to create clusters from other inorganic and polymer particles. We also show that high yields of particular morphologies can be obtained by precise control of the inorganic seed particle size, a finding that can be explained using a hard-sphere packing model. These clusters can be further chemically modified for a variety of applications. Introducing a cross-linker leads to colloidal clusters that can be index matched in an appropriate solvent, allowing them to be used for particle tracking or optical studies of colloidal self-assembly. Also, depositing a thin silica layer on these colloids allows the surface properties to be controlled using silane chemistry. PMID:21080658
On the Nature of Bonding in Parallel Spins in Monovalent Metal Clusters.
Danovich, David; Shaik, Sason
2016-05-27
As we approach the Lewis model centennial, it may be timely to discuss novel bonding motifs. Accordingly, this review discusses no-pair ferromagnetic (NPFM) bonds that hold together monovalent metallic atoms using exclusively parallel spins. Thus, without any traditional electron-pair bonds, the bonding energy per atom in these clusters can reach 20 kcal mol(-1). This review describes the origins of NPFM bonding using a valence bond (VB) analysis, which shows that this bonding motif arises from bound triplet electron pairs that are delocalized over all the close neighbors of a given atom in the cluster. The VB model accounts for the tendency of NPFM clusters to assume polyhedral shapes with rather high symmetry and for the very steep rise of the bonding energy per atom. The advent of NPFM clusters offers new horizons in chemistry of highly magnetic species sensitive to magnetic and electric fields. PMID:27070320
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.
Influence of POSS modifier on NLO properties of the hybrid materials
Institute of Scientific and Technical Information of China (English)
CHEN Ping; WANG Wen-jun; LIU Yun-long; MA Yan; ZHANG Xing-wen; LU Zu-shun; SUN Ke-jun
2006-01-01
The nonlinear optical (NLO) active chromophore was prepared by a bridging agent, glycidyl ether(AGE), to connect disperse orange 3 ( DO3 ) and ( γ-Methacrylpropyl ) -silsesquioxane (MP-SSO). A freeradical polymerization was performed to fabricate the methacrylate/Silica hybrid NLO films. Different amounts(5-25 wt% ) of (γ-methacrylpropyl)-polyhedral oligomeric silsesquioxanes (POSS) were added as the modifier to improve the degree of cross-linking, density and structure of the NLO matrix. As a result, the modified material properties including coating transmittance, glass transition temperature ( Tg), absoption spectra before and after poling, Marker stripes, etc. were presented. The hybrid film containing 15 wt% POSS exhibits the highest Tg, nonresonant second-order nonlinearity (d33 = 92 pm/V) and temporal stability among the others.
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...
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...
Directory of Open Access Journals (Sweden)
Vinicius Pistor
2012-01-01
Full Text Available The synthesis of thermoplastic polyurethanes (TPU from the reaction of a NCO group-containing prepolymer and 0, 1.14, 1.71, and 2.28 wt% of trisilanol isobutyl polyhedral oligomeric silsesquioxane (POSS was carried out in an instrumented batch mixer. The samples were characterized by thermogravimetric analysis (TGA, differential scanning calorimetry (DSC, X-ray diffraction (XRD, and scanning electron microscopy (SEM. SEM analysis shows that the incorporation of POSS promoted strongly aggregation through physical interactions (formation of POSS-rich domains. Modifications in the TPU microstructure and the reduction in the crystal size were observed in the XRD diffractograms. The incorporation of POSS equally altered the TPU crystallization, and samples bearing higher concentrations of POSS formed two distinct types of crystalline structures. The kinetics of crystallization showed that nucleation strongly depends on the balance between TPU crystal formation and POSS-rich domains.
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.
Studii cu privire la soluţii de fundaţii utilizând plăci subţiri conice şi poliedrice
Directory of Open Access Journals (Sweden)
Alina Tirtea
2012-03-01
Full Text Available Theoretical and experimental studies have been performed in order to determine the possibility of using thin plates as foundation solutions for frame structures. It was studied three types of solutions regarding the realization of isolated footing under columns using two types of thin plates: a Conical plates with the top upward (element E1, respectively the top downward (element E2; b Trunk of pyramid type of polyhedral plates (element E3. These two types of thin plates have been considered for the following reasons: favorable stress distribution in the foundation soil; the stresses that occur within the thin plate are mainly compressive, which leads to a significant reduction of foundation reinforcement; reduced consumption of concrete and reinforcement.
Institute of Scientific and Technical Information of China (English)
张坚; 张明瑜; 赵媛媛; 陈保国; 孙家鍾
2005-01-01
对单个多面体硼烷(Polyhedral boranes)已有较多的理论研究，由多个多面体通过共用一个或多个顶点而构成的稠合型硼烷(Macropolyhedral borones)，具有多种多样的结构类型，并已被大量合成出来，目前对稠合型硼烷结构及成键特性的理论研究尚不充分，它们不能再以简单的closo，nido和arachno分类，Wade规则也不再适于解释其结构，理论上各种电子计数规则已有不少报道，对预言和发现新的分子十分重要。
Thermally stable single-atom platinum-on-ceria catalysts via atom trapping.
Jones, John; Xiong, Haifeng; DeLaRiva, Andrew T; Peterson, Eric J; Pham, Hien; Challa, Sivakumar R; Qi, Gongshin; Oh, Se; Wiebenga, Michelle H; Pereira Hernández, Xavier Isidro; Wang, Yong; Datye, Abhaya K
2016-07-01
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. PMID:27387946
An improved method to identify grain boundary creep cavitation in 316H austenitic stainless steel
Energy Technology Data Exchange (ETDEWEB)
Chen, B., E-mail: b.chen@bristol.ac.uk [Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR (United Kingdom); Flewitt, P.E.J. [Interface Analysis Centre, University of Bristol, 121 St. Michael' s Hill, Bristol BS2 8BS (United Kingdom); H.H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom); Smith, D.J. [Department of Mechanical Engineering, University of Bristol, Bristol BS8 1TR (United Kingdom); Jones, C.P. [Interface Analysis Centre, University of Bristol, 121 St. Michael' s Hill, Bristol BS2 8BS (United Kingdom)
2011-04-15
Inter-granular creep cavitation damage has been observed in an ex-service 316H austenitic stainless steel thick section weldment. Focused ion beam cross-section milling combined with ion channelling contrast imaging is used to identify the cavitation damage, which is usually associated with the grain boundary carbide precipitates in this material. The results demonstrate that this technique can identify, in particular, the early stage of grain boundary creep cavitation unambiguously in materials with complex phase constituents. -- Research highlights: {yields} FIB milling plus ion channelling contrast optimise the observation of cavity. {yields} Identification of the creep cavities unambiguously, using an FIB technique. {yields} The FIB technique can retain the polyhedral shape of cavity. {yields} Various stages of creep cavitation can be observed, using the FIB technique.
Epoxy Resin Composite Based on Functional Hybrid Fillers
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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.
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.
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.
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.
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-...
Inorganic materials synthesis in ionic liquids
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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.
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.
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.
Severcan, Isil; Geary, Cody; Chworos, Arkadiusz; Voss, Neil; Jacovetty, Erica; Jaeger, Luc
2010-09-01
Supramolecular assembly is a powerful strategy used by nature to build nanoscale architectures with predefined sizes and shapes. With synthetic systems, however, numerous challenges remain to be solved before precise control over the synthesis, folding and assembly of rationally designed three-dimensional nano-objects made of RNA can be achieved. Here, using the transfer RNA molecule as a structural building block, we report the design, efficient synthesis and structural characterization of stable, modular three-dimensional particles adopting the polyhedral geometry of a non-uniform square antiprism. The spatial control within the final architecture allows the precise positioning and encapsulation of proteins. This work demonstrates that a remarkable degree of structural control can be achieved with RNA structural motifs for the construction of thermostable three-dimensional nano-architectures that do not rely on helix bundles or tensegrity. RNA three-dimensional particles could potentially be used as carriers or scaffolds in nanomedicine and synthetic biology.
CFD Simulation Of Air-Flow Over A „Quarter-Circular” Object Valided By Experimental Measurement
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Králik Juraj
2015-12-01
Full Text Available A Computer-Fluid-Dynamic (CFD simulation of air-flow around quarter-circular object using commercial software ANSYS Fluent was used to study iteration of building to air-flow. Several, well know transient turbulence models were used and results were compared to experimental measurement of this object in Boundary Layer Wind Tunnel (BLWT of Slovak University of Technology (SUT in Bratislava. Main focus of this article is to compare pressure values from CFD in three different elevations, which were obtained from experimental measurement. Polyhedral mesh type was used in the simulation. Best results on the windward face elevations were obtained using LES turbulence model, where the averaged difference was around 7.71 %. On the leeward face elevations it was SAS turbulence model and averaged differences from was 15.91 %. On the circular face it was SAS turbulence model and averaged differences from all elevations was 12.93 %.
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JinJoo Kim
2015-06-01
Full Text Available Diatoms are a major component of the biological community, serving as the principal primary producers in the food web and sustaining oxygen levels in aquatic environments. Among marine planktonic diatoms, the cosmopolitan Skeletonema costatum is one of the most abundant and widespread species in the world’s oceans. Here, we report the basic characteristics of a new diatom-infecting S. costatum virus (ScosV isolated from Jaran Bay, Korea, in June 2008. ScosV is a polyhedral virus (45–50 nm in diameter that propagates in the cytoplasm of host cells and causes lysis of S. costatum cultures. The infectivity of ScosV was determined to be strain- rather than species-specific, similar to other algal viruses. The burst size and latent period were roughly estimated at 90–250 infectious units/cell and <48 h, respectively.
Kim, JinJoo; Kim, Chang-Hoon; Youn, Seok-Hyun; Choi, Tae-Jin
2015-06-01
Diatoms are a major component of the biological community, serving as the principal primary producers in the food web and sustaining oxygen levels in aquatic environments. Among marine planktonic diatoms, the cosmopolitan Skeletonema costatum is one of the most abundant and widespread species in the world's oceans. Here, we report the basic characteristics of a new diatom-infecting S. costatum virus (ScosV) isolated from Jaran Bay, Korea, in June 2008. ScosV is a polyhedral virus (45-50 nm in diameter) that propagates in the cytoplasm of host cells and causes lysis of S. costatum cultures. The infectivity of ScosV was determined to be strain- rather than species-specific, similar to other algal viruses. The burst size and latent period were roughly estimated at 90-250 infectious units/cell and <48 h, respectively. PMID:26060438
Experimental Insight into the Radiation Resistance of Zirconia-Based Americium Ceramics
International Nuclear Information System (INIS)
Our works shows that the americium pyrochlore 241Am2Zr2O7 undergoes a phase transition to a defect-fluorite structure along with an unusual volume contraction when subjected to internal radiation from α-emitting actinides. Disorder relaxation proceeds through the simultaneous formation of cation anti sites and oxygen Frenkel pairs. X-ray absorption spectroscopy at the Am-LII and the Zr-K edges reveals that Am-O polyhedra show an increasing disorder with increasing exposure. In contrast, the Zr-O polyhedral units remain highly ordered, while rotating along edges and corners, thereby reducing the structural strain imposed by the growing disorder around americium. We believe it is this particular property of the compound that provides the remarkable resistance to radiation (≥9.4 * 1018) α-decay events g-1 or 0.80 dpa). (authors)
Geometry of polycrystals and microstructure
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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.
Nanoparticle-doped polyimide for controlling the pretilt angle of liquid crystals devices.
Hwang, Shug-June; Jeng, Shie-Chang; Hsieh, I-Ming
2010-08-01
The pretilt angles of liquid crystal molecules can be controlled by using conventional polyimide (PI) alignment material doped with different concentrations of Polyhedral Oligomeric Silsequioxanes (POSS) nanoparticles, which have been observed to spontaneously induce vertical alignment. The addition of POSS in the homogenous PI changes the surface energy of the alignment layer and generates a variable pretilt angle. Experimental results demonstrate that the pretilt angle thetap is a function of the POSS concentration, and can be tuned continuously over the range of 0 degrees
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...
On the Geometric Interpretation of the Nonnegative Rank
Gillis, Nicolas
2010-01-01
The nonnegative rank of a nonnegative matrix is the minimum number of nonnegative rank-one factors needed to reconstruct it exactly. The problem of determining this rank and computing the corresponding nonnegative factors is difficult; however it has many potential applications, e.g., in data mining, graph theory and computational geometry. In particular, it can be used to characterize the minimal size of any extended reformulation of a given combinatorial optimization program. In this paper, we introduce and study a related quantity, called the restricted nonnegative rank. We show that computing this quantity is equivalent to a problem in polyhedral combinatorics, and fully characterize its computational complexity. This in turn sheds new light on the nonnegative rank problem, and in particular allows us to provide new improved lower bounds based on its geometric interpretation. We apply these results to slack matrices and linear Euclidean distance matrices and obtain counter-examples to two conjectures of B...
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Nadja Lima Pinheiro
1993-01-01
Full Text Available The observations made about the stomach of Trichogenes longipinnis (Britski & Ortega, 1983 showed a rounded organ which has in its dorsal side an accessory structure - a cul de sac - that comunicates with it. The distal part of this dorsal accessory presents characteristic of an organ that exercise respiratory functions: reduction in the thickness of the mucosa and arrangement of an intrincate continuous capilar net in close contact with the superficial cells of the epithelium. In this portion there are no glands in the lamina propria. The epithelium shows a superficial squamous cels; they are very slim, and sometimes, with the capillary endothelium form a single barrier between the organ lumen and the blood. Polyhedric cells are also present in this epithelium; they are located under the squamous cells, sheltered between capillaries and basal cells.