Bökstedt, Marcel
2016-01-01
We study a novel type of braid groups on a closed orientable surface $\\Sigma$. These are fundamental groups of certain manifolds that are hybrids between symmetric products and configuration spaces of points on $\\Sigma$; a class of examples arises naturally in gauge theory, as moduli spaces of vortices in toric fibre bundles over $\\Sigma$. The elements of these braid groups, which we call divisor braids, have coloured strands that are allowed to intersect according to rules specified by a graph $\\Gamma$. In situations where there is more than one strand of each colour, we show that the corresponding braid group admits a metabelian presentation as a central extension of the free Abelian group $H_1(\\Sigma;\\mathbb{Z})^{\\oplus r}$, where $r$ is the number of colours, and describe its Abelian commutator. This computation relies crucially on producing a link invariant (of closed divisor braids) in the three-manifold $S^1 \\times \\Sigma $ for each graph $\\Gamma$. We also describe the von Neumann algebras associated t...
Braided Clifford algebras as braided quantum groups
Durdevic, M
1995-01-01
The paper deals with braided Clifford algebras, understood as Chevalley-Kahler deformations of braided exterior algebras. It is shown that Clifford algebras based on involutive braids can be naturally endowed with a braided quantum group structure. Basic group entities are constructed explicitly.
2002-01-01
On October 13, 2000, the Expedition 3 crew of the International Space Station, high over Tibet, took this interesting photo of the Brahmaputra River. This mighty Asian river carves a narrow west-east valley between the Tibetan Plateau to the north and the Himalaya Mountains to the south, as it rushes eastward for more than 1500 km in southwestern China. This 15-km stretch is situated about 35 km south of the ancient Tibetan capital of Lhasa where the river flow becomes intricately braided as it works and reworks its way through extensive deposits of erosional material. This pattern is indicative of a combination heavy sediment discharge from tributaries and reduction of the river's flow from either a change in gradient or perhaps even climate conditions over the watershed. The light color of the deposits and the milky color of the water is attributed to presence of glacial 'flour,' the fine material created by erosion from glaciers. Besides erosion by water and ice, this scene also depicts features created by wind. Note the delicate field of dunes on the alluvial fan toward the right edge of the image. The riverbed here is at an elevation of over 3,500 m, and with the long west-east extent of this barren valley, strong, persistent westerly winds also move and shape these deposits. Photos such as this one bring immediate visual understanding and appreciation of natural processes in some of the most remote locations on Earth. Image ISS003-E-6632, was provided by the Earth Sciences and Image Analysis Laboratory at Johnson Space Center. Additional images taken by astronauts and cosmonauts can be viewed at the NASA-JSC Gateway to Astronaut Photography of Earth.
Hamilton, Linus
2014-01-01
Braid is a 2008 puzzle game centered around the ability to reverse time. We show that Braid can simulate an arbitrary computation. Our construction makes no use of Braid's unique time mechanics, and therefore may apply to many other video games. We also show that a plausible "bounded" variant of Braid lies within 2-EXPSPACE. Our proof relies on a technical lemma about Turing machines which may be of independent interest. Namely, define a braidlike Turing machine to be a Turing machine that, w...
van den Berg, J. B.; Ghrist, R.; Vandervorst, R. C.; Wójcik, W.
2015-09-01
Area-preserving diffeomorphisms of a 2-disc can be regarded as time-1 maps of (non-autonomous) Hamiltonian flows on R / Z ×D2. The periodic flow-lines define braid (conjugacy) classes, up to full twists. We examine the dynamics relative to such braid classes and define a new invariant for such classes, the BRAID FLOER HOMOLOGY. This refinement of Floer homology, originally used for the Arnol'd Conjecture, yields a Morse-type forcing theory for periodic points of area-preserving diffeomorphisms of the 2-disc based on braiding. Contributions of this paper include (1) a monotonicity lemma for the behavior of the nonlinear Cauchy-Riemann equations with respect to algebraic lengths of braids; (2) establishment of the topological invariance of the resulting braid Floer homology; (3) a shift theorem describing the effect of twisting braids in terms of shifting the braid Floer homology; (4) computation of examples; and (5) a forcing theorem for the dynamics of Hamiltonian disc maps based on braid Floer homology.
Roy, Sutanu
2016-01-01
We propose a general theory of braided quantum groups in the C*-algebraic framework. More precisely, we construct braided quantum groups using manageable braided multiplicative unitaries over a regular C*-quantum group. We show that braided C*-quantum groups are equivalent to C*-quantum groups with projection.
Decoupling braided tensor factors
It is shown that the braided tensor product algebra of two module algebras A1, A2 of a quasitriangular Hopf algebra is equal to the ordinary tensor product algebra of A1 with a subalgebra isomorphic to A2 and commuting with A1. As applications of the theorem the braided tensor product algebras of two or more quantum group covariant quantum space or deformed Heisenberg algebras are considered
Free braided differential calculus, braided binomial theorem and the braided exponential map
Majid, S
1993-01-01
Braided differential operators $\\del^i$ are obtained by differentiating the addition law on the braided covector spaces introduced previously (such as the braided addition law on the quantum plane). These are affiliated to a Yang-Baxter matrix $R$. The quantum eigenfunctions $\\exp_R(\\vecx|\\vecv)$ of the $\\del^i$ (braided-plane waves) are introduced in the free case where the position components $x_i$ are totally non-commuting. We prove a braided $R$-binomial theorem and a braided-Taylors theorem $\\exp_R(\\veca|\\del)f(\\vecx)=f(\\veca+\\vecx)$. These various results precisely generalise to a generic $R$-matrix (and hence to $n$-dimensions) the well-known properties of the usual 1-dimensional $q$-differential and $q$-exponential. As a related application, we show that the q-Heisenberg algebra $px-qxp=1$ is a braided semidirect product $\\C[x]\\cocross \\C[p]$ of the braided line acting on itself (a braided Weyl algebra). Similarly for its generalization to an arbitrary $R$-matrix.
Gonzalez-Meneses, Juan
2010-01-01
These are Lecture Notes of a course given by the author at the French-Spanish School "Tresses in Pau", held in Pau (France) in October 2009. It is basically an introduction to distinct approaches and techniques that can be used to show results in braid groups. Using these techniques we provide several proofs of well known results in braid groups, namely the correctness of Artin's presentation, that the braid group is torsion free, or that its center is generated by the full twist. We also recall some solutions of the word and conjugacy problems, and that roots of a braid are always conjugate. We also describe the centralizer of a given braid. Most proofs are classical ones, using modern terminology. I have chosen those which I find simpler or more beautiful.
Reducible braids and Garside theory
Gonzalez-Meneses, Juan
2010-01-01
We show that reducible braids which are, in a Garside-theoretical sense, as simple as possible within their conjugacy class, are also as simple as possible in a geometric sense. More precisely, if a braid belongs to a certain subset of its conjugacy class which we call the stabilized set of sliding circuits, and if it is reducible, then its reducibility is geometrically obvious: it has a round or almost round reducing curve. Moreover, for any given braid, an element of its stabilized set of sliding circuits can be found using the well-known cyclic sliding operation. This leads to a polynomial time algorithm for deciding the Nielsen-Thurston type of any braid, modulo one well-known conjecture on the speed of convergence of the cyclic sliding operation.
Cable Braid Electromagnetic Penetration Model.
Warne, Larry K. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Langston, William L. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Basilio, Lorena I. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States); Johnson, W. A. [Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
2015-06-01
The model for penetration of a wire braid is rigorously formulated. Integral formulas are developed from energy principles and reciprocity for both self and transfer immittances in terms of potentials for the fields. The detailed boundary value problem for the wire braid is also setup in a very efficient manner; the braid wires act as sources for the potentials in the form of a sequence of line multipoles with unknown coefficients that are determined by means of conditions arising from the wire surface boundary conditions. Approximations are introduced to relate the local properties of the braid wires to a simplified infinite periodic planar geometry. This is used in a simplified application of reciprocity to be able to treat nonuniform coaxial geometries including eccentric interior coaxial arrangements and an exterior ground plane.
Presentations of Graph Braid Groups
Farley, Daniel; Sabalka, Lucas
2009-01-01
Let G be a graph. The (unlabeled) configuration space of n points on G is the space of all n-element subsets of G. The fundamental group of such a configuration space is called a graph braid group. We use a version of discrete Morse theory to compute presentations of all graph braid groups, for all finite connected graphs G and all natural numbers n.
Duality principle and braided geometry
Majid, S
1994-01-01
We give an overview of a new kind symmetry in physics which exists between observables and states and which is made possible by the language of Hopf algebras and quantum geometry. It has been proposed by the author as a feature of Planck scale physics. More recent work includes corresponding results at the semiclassical level of Poisson-Lie groups and at the level of braided groups and braided geometry.
Braided Field Quantization from Quantum Poincare Covariance
Lukierski, Jerzy
2012-01-01
We demonstrate that the covariance of the algebra of quantum NC fields under quantum-deformed Poincare symmetries implies the appearence of braided algebra of fields and the notion of braided locality in NC QFT. We briefly recall the historical development of NC QFT which was firstly formulated in the framework using classical relativistic symmetries but further it was described as generated by the quantum-deformed symmetries. We argue that consistent covariant quantum-deformed formalism requires "braiding all the way", in particular braided commutator of deformed field oscillators as well as the braid between the field oscillators and noncommutative Fourier exponentials. As example of braided quantum-deformed NC QFT we describe the NC scalar free fields on noncommutative canonical (Moyal-Weyl) space-time with braided c-number field commutator which implies braided locality.
Tensile properties of braided composite rods
Pereira, Cristiana Gonilho; Fangueiro, Raúl; Jalali, Said; Araújo, Mário Duarte de; Marques, P
2008-01-01
The current work is concerning the development of braided reinforced composite rods for civil engineering applications, namely for concrete internal reinforcement. The research study aims to understand the mechanical behaviour of braided reinforced composite rods produced from an innovative technique. Seven types of braided reinforced composite rods were produced, varying the type of fibres used as a core reinforcement of a polyester braided fabric. E-glass, carbon, HT polyethylene fibres ...
Simple braids for surface homeomorphisms
Parwani, Kamlesh
2005-01-01
Let S be a compact, oriented surface with negative Euler characteristic and let f be a homeomorphism of S that is isotopic to the identity. If there exists a periodic orbit with a non-zero rotation vector, then there exists a simple braid with the same rotation vector.
Permutation Analysis of Track and Column Braiding
李毓陵; 丁辛; 胡良剑
2004-01-01
The positions of braiding carrier in track and column braiding are represented by a diagrammatic braiding plan and a corresponding lattice-array is defined. A set is then formed so that the permutation analysis can be performed to represent the movement of carriers in a braiding process. The process of 4-step braiding is analyzed as an example to describe the application of the proposed method by expressing a braiding cycle as a product of disjoint cycles. As a result, a mapping relation between the disjoint cycles and the movement of carriers is deduced. Following the same analysis principles, a process of 8-step braiding and the corresponding initial state of the lattice-array is developed. A successful permutation analysis to the process manifests the general suitability of the proposed method.
The Picard crossed module of a braided tensor category
Davydov, Alexei; Nikshych, Dmitri
2012-01-01
For a finite braided tensor category we introduce its Picard crossed module consisting of the group of invertible module categories and the group of braided tensor autoequivalences. We describe the Picard crossed module in terms of braided autoequivalences of the Drinfeld center of the braided tensor category. As an illustration, we compute the Picard crossed module of a braided pointed fusion category.
Braided nodal lines in wave superpositions
Dennis, M R
2003-01-01
Nodal lines (phase singularities, optical vortices) are the generic interference fringes of complex scalar waves. Here, an exact complex solution of the time independent wave equation (Helmholtz equation) is considered, possessing nodal lines which are braided in the form of a borromean, or pig-tail braid. The braid field is a superposition of counterpropagating, counterrotating, non-coaxial order 3 Bessel beams, and a plane wave whose propagation is perpendicular to that of the beams. The construction is structurally stable, and can be generalized to a limited class of other braids.
Majorana Braiding with Thermal Noise
Pedrocchi, Fabio L.; DiVincenzo, David P.
2015-09-01
We investigate the self-correcting properties of a network of Majorana wires, in the form of a trijunction, in contact with a parity-preserving thermal environment. As opposed to the case where Majorana bound states are immobile, braiding Majorana bound states within a trijunction introduces dangerous error processes that we identify. Such errors prevent the lifetime of the memory from increasing with the size of the system. We confirm our predictions with Monte Carlo simulations. Our findings put a restriction on the degree of self-correction of this specific quantum computing architecture.
Emergent Braided Matter of Quantum Geometry
Sundance Bilson-Thompson
2012-03-01
Full Text Available We review and present a few new results of the program of emergent matter as braid excitations of quantum geometry that is represented by braided ribbon networks. These networks are a generalisation of the spin networks proposed by Penrose and those in models of background independent quantum gravity theories, such as Loop Quantum Gravity and Spin Foam models. This program has been developed in two parallel but complimentary schemes, namely the trivalent and tetravalent schemes. The former studies the braids on trivalent braided ribbon networks, while the latter investigates the braids on tetravalent braided ribbon networks. Both schemes have been fruitful. The trivalent scheme has been quite successful at establishing a correspondence between braids and Standard Model particles, whereas the tetravalent scheme has naturally substantiated a rich, dynamical theory of interactions and propagation of braids, which is ruled by topological conservation laws. Some recent advances in the program indicate that the two schemes may converge to yield a fundamental theory of matter in quantum spacetime.
Systematically generated two-qubit anyon braids
Carnahan, Caitlin; Zeuch, Daniel; Bonesteel, N. E.
2016-05-01
Fibonacci anyons are non-Abelian particles for which braiding is universal for quantum computation. Reichardt has shown how to systematically generate nontrivial braids for three Fibonacci anyons which yield unitary operations with off-diagonal matrix elements that can be made arbitrarily small in a particular natural basis through a simple and efficient iterative procedure. This procedure does not require brute force search, the Solovay-Kitaev method, or any other numerical technique, but the phases of the resulting diagonal matrix elements cannot be directly controlled. We show that despite this lack of control the resulting braids can be used to systematically construct entangling gates for two qubits encoded by Fibonacci anyons.
Enhance Production Rate of Braiding Machine Using Speed Reduction Technique
Manoj A. Kumbhalkar; Sachin V. Mate; Sushama Dhote; Mudra Gondane
2013-01-01
Textile designing is a technical process which includes different methods for production of textile, surface design and structural design of a textile. Braid is the textile product having various types like round and flat braid made by using textile threads or wires which are alternatively interwoven in braiding machine. A small scale industry in Nagpur produces each type of cotton braids using 16 spindle braiding machines on the single line shaft acquired power from 0.50 HP motor runs at 144...
Detecting coherent structures using braids
Allshouse, Michael R
2011-01-01
The detection of coherent structures is an important problem in fluid dynamics, particularly in geophysical applications. For instance, knowledge of how regions of fluid are isolated from each other allows prediction of the ultimate fate of oil spills. Existing methods detect Lagrangian coherent structures, which are barriers to transport, by examining the stretching field as given by finite-time Lyapunov exponents. These methods are very effective when the velocity field is well-determined, but in many applications only a small number of flow trajectories are known, for example when dealing with oceanic float data. We introduce a topological method for detecting invariant regions based on a small set of trajectories. In the method we regard the two-dimensional trajectory data as a braid in three dimensions, with time being the third coordinate. Invariant regions then correspond to trajectories that travel together and do not entangle other trajectories. We detect these regions by examining the growth of hypo...
Symmetric centres of braided monoidal categories
无
2000-01-01
This paper introduces the concept of‘symmetric centres' of braided monoidal categories. Let H be a Hopf algebra with bijective antipode over a field k. We address the symmetric centre of the Yetter-Drinfel'd module category HH(yD) and show that a left Yetter-Drinfel'd module M belongs to the symmetric centre of HH(yD) if and only if M is trivial. We also study the symmetric centres of categories of representations of quasitriangular Hopf algebras and give a sufficient and necessary condition for the braid of H(M) to induce the braid of (H(H)(A),(○)A,A,φ,l,r), or equivalently, the braid of (A#H(H),(○)A,A,φ,l,r), where A is a quantum commutative H-module algebra.
Infinitesimal 2-braidings and differential crossed modules
Cirio, Lucio S
2013-01-01
We categorify the notion of an infinitesimal braiding in a linear strict symmetric monoidal category, leading to the notion of a (strict) infinitesimal 2-braiding in a linear symmetric strict monoidal 2-category. We describe the associated categorification of the 4-term relation, leading to six categorified relations. We prove that any infinitesimal 2-braiding gives rise to a flat and fake flat 2-connection in the configuration space of $n$ undistinguishable particles in the complex plane, hence to a categorification of the Knizhnik-Zamolodchikov connection. We discuss infinitesimal 2-braidings in a category naturally assigned to every differential crossed module, leading to the notion of a quasi-invariant tensor in a differential crossed module. Finally we prove that quasi-invariant tensors exist in the differential crossed module associated to the string Lie-2-algebra.
Modelling planform changes of braided rivers
Jagers, Hendrik Reinhard Albert
2003-01-01
This study has focused on modelling techniques to predict planform changes of braided rivers and their relation with state-of-the-art knowledge on the physical processes and the availability of model input data
Braided magnetic fields: equilibria, relaxation and heating
Pontin, D I; Russell, A J B; Hornig, G
2015-01-01
We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling. The key results obtained from recent modelling efforts are summarised, in the context of testable predictions for the laboratory. We discuss the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity - as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We discuss the properties of this relaxation, and in particular the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor's hypo...
Braided magnetic fields: equilibria, relaxation and heating
Pontin, D. I.; Candelaresi, S.; Russell, A. J. B.; Hornig, G.
2016-05-01
We examine the dynamics of magnetic flux tubes containing non-trivial field line braiding (or linkage), using mathematical and computational modelling, in the context of testable predictions for the laboratory and their significance for solar coronal heating. We investigate the existence of braided force-free equilibria, and demonstrate that for a field anchored at perfectly-conducting plates, these equilibria exist and contain current sheets whose thickness scales inversely with the braid complexity—as measured for example by the topological entropy. By contrast, for a periodic domain braided exact equilibria typically do not exist, while approximate equilibria contain thin current sheets. In the presence of resistivity, reconnection is triggered at the current sheets and a turbulent relaxation ensues. We finish by discussing the properties of the turbulent relaxation and the existence of constraints that may mean that the final state is not the linear force-free field predicted by Taylor’s hypothesis.
Diagrammatics of braided group gauge theory
Majid, S
1996-01-01
We develop a gauge theory or theory of bundles and connections on them at the level of braids and tangles. Extending recent algebraic work, we provide now a fully diagrammatic treatment of principal bundles, a theory of global gauge transformations, associated braided fiber bundles and covariant derivatives on them. We describe the local structure for a concrete Z_3-graded or `anyonic' realization of the theory.
Self-diagnosing braided composite rod
Fangueiro, Raúl; Zdraveva, E.; Pereira, Cristiana Gonilho; Ferreira, A.; Lanceros-Méndez, S.
2010-01-01
This paper presents the development of a braided reinforced composite rod (BCR) able to both reinforce and monitor the stress state of concrete structures. Carbon fibers have been used as sensing and reinforcing materials along with glass fiber. Various composites rods have been produced using an author patented technique based on a modified conventional braiding machine. The materials investigated were prepared with different carbon fiber content as follows: BCR2 (77% glass/23...
Concrete reinforced by braided fibre composite rods
Fangueiro, Raúl; Sousa, Guilherme José Miranda de; Soutinho, Hélder Filipe Cunha; Jalali, Said; Araújo, Mário Duarte de
2005-01-01
One of the most serious problems affecting concrete is corrosion of the steel reinforcement. Corrosion may occur due to reaction of lime present in hydrated cement with carbon dioxide or to the action of chlorides. The braiding technique is probably the most ancient production process for textile structures. Normally used for ropes and cables, braided fabrics are also very interesting for composite reinforcements due to their characteristics: in-plane multiaxial ...
On braided Poisson and quantum inhomogeneous groups
Zakrzewski, S.
1997-01-01
The well known incompatibility between inhomogeneous quantum groups and the standard q-deformation is shown to disappear (at least in certain cases) when admitting the quantum group to be braided. Braided quantum ISO(p,N-p) containing SO_q(p,N-p) with |q|=1 are constructed for N=2p, 2p+1, 2p+2. Their Poisson analogues (obtained first) are presented as an introduction to the quantum case.
Fan deltas and braid deltas: conceptual problems
McPherson, J.G.; Shanmugam, G.; Moiola, R.J.
1986-05-01
The concept of fan deltas has been widely misinterpreted in the geologic literature. A true fan delta is defined as an alluvial fan deposited into a standing body of water. Such sequences are of limited areal extent and are, as expected, uncommon in the rock record. By contrast, braid deltas (herein defined), formed by progradation of a braided fluvial system into a standing body of water, are a common geomorphic feature in many modern settings, and their deposits are common in the geologic record. Braid-delta sequences are often identified as fan deltas, on the false premise that coarse-grained deposits in a deltaic setting are always part of an alluvial fan complex. The authors find that most published examples of so called fan deltas contain no direct evidence for the presence of an alluvial fan. Even in examples where an alluvial fan could be documented, the authors found that, in many cases, the alluvial fan complex was far removed from the shoreline, separated by an extensive braid plain. The authors suggest that such systems are better classified as braid deltas. They consider that it is essential to distinguish the environmental setting of true fan deltas from that of braid deltas. Misclassification will lead to incorrect interpretations of expected facies, sandstone geometry, reservoir quality, and tectonic settings. Criteria based on geometry, vertical and lateral lithofacies associations, and paleocurrent patterns should be used to correctly identify and distinguish these depositional systems.
In Vitro Degradation of Polyglycolide/Chitosan Hybrid Braids
YUAN Xiaoyan; ZHANG Qingwei; WANG Yonglin; YAO Kangde
2005-01-01
Hybrid braids of polyglycolide (PGA) and chitosan were prepared by the three-yarn braiding method from PGA and chitosan fiber bundles. These braids were in vitro degraded by incubating them in phosphate buffered saline (PBS) at pH 7.4 and 37 ℃ for 5 weeks. Results suggested that PGA/chitosan hybrid braids degraded significantly. Scanning electron micrographs showed that chitosan fibers in the PGA/chitosan hybrid braid with about 750% PGA in weight (PGA75/chitosan) were shaped into gel-like after 5 weeks, but those in the hybrid braid with about 250% PGA in weight (PGA25/chitosan) did not change. After 5 weeks, the ultimate tensile loads of PGA and PGA75/chitosan braids lost almost completely, but those of chitosan and PGA25/chitosan braids remained around 14 N. The PGA/chitosan hybrid braids with higher initial ultimate tensile load would have potential applications in tendon/ligament tissue reconstruction.
Geometrical deployment for braided stent.
Bouillot, Pierre; Brina, Olivier; Ouared, Rafik; Yilmaz, Hasan; Farhat, Mohamed; Erceg, Gorislav; Lovblad, Karl-Olof; Vargas, Maria Isabel; Kulcsar, Zsolt; Pereira, Vitor Mendes
2016-05-01
The prediction of flow diverter stent (FDS) implantation for the treatment of intracranial aneurysms (IAs) is being increasingly required for hemodynamic simulations and procedural planning. In this paper, a deployment model was developed based on geometrical properties of braided stents. The proposed mathematical description is first applied on idealized toroidal vessels demonstrating the stent shortening in curved vessels. It is subsequently generalized to patient specific vasculature predicting the position of the filaments along with the length and local porosity of the stent. In parallel, in-vitro and in-vivo FDS deployments were measured by contrast-enhanced cone beam CT (CBCT) in idealized and patient-specific geometries. These measurements showed a very good qualitative and quantitative agreement with the virtual deployments and provided experimental validations of the underlying geometrical assumptions. In particular, they highlighted the importance of the stent radius assessment in the accuracy of the deployment prediction. Thanks to its low computational cost, the proposed model is potentially implementable in clinical practice providing critical information for patient safety and treatment outcome assessment. PMID:26891065
Equilibrium theory for braided elastic filaments
van der Heijden, Gert
Motivated by supercoiling of DNA and other filamentous structures, we formulate a theory for equilibria of 2-braids, i.e., structures formed by two elastic rods winding around each other in continuous contact and subject to a local interstrand interaction. Unlike in previous work no assumption is made on the shape of the contact curve. Rather, this shape is found as part of the solution. The theory is developed in terms of a moving frame of directors attached to one of the strands with one of the directors pointing to the position of the other strand. The constant-distance constraint is automatically satisfied by the introduction of what we call braid strains. The price we pay is that the potential energy involves arclength derivatives of these strains, thus giving rise to a second-order variational problem. The Euler-Lagrange equations for this problem give balance equations for the overall braid force and moment referred to the moving frame as well as differential equations that can be interpreted as effective constitutive relations encoding the effect that the second strand has on the first as the braid deforms under the action of end loads. Simple analytical cases are discussed first and used as starting solutions in parameter continuation studies to compute classes of both open and closed (linked or knotted) braid solutions.
Braid My Hair - Randy Owen sings out for sick children
... Bar Home Current Issue Past Issues Braid My Hair - Randy Owen sings out for sick children Past ... debut performance of his latest song, "Braid My Hair," was the highlight during this year's Songwriter's Dinner ...
A Secure Key Agreement Protocol Using Braid Groups
Atul Chaturvedi; Shyam Sundar
2010-01-01
This paper presents an authenticated key agreement protocol based on a braid group. It is proved that the proposed protocol meets several security attributes under the assumption that the Root Problem (RP) in braid group is a hard problem.
Tensile performance of braided composite rods for concrete reinforcement
Pereira, Cristiana Gonilho; Fangueiro, Raúl; Jalali, Said; Araújo, Mário Duarte de; Marques, P.
2008-01-01
The current work is concerned with the development of braided composite rods for civil engineering applications, namely for concrete internal reinforcement, as a steel substitute. The research study aims at understanding the tensile behaviour of composite rods reinforced by a textile structure – braided structure with core reinforcement. Seven types of braided composite rods were produced, varying the type of fibres used as a core reinforcement of a polyester braided structure. Eglass, car...
Braided composite rods to reinforce concrete subjected to aggressive environments
Pereira, Cristiana Gonilho; Fangueiro, Raúl; Jalali, Said; Marques, P.; Araújo, Mário Duarte de
2008-01-01
The current work is concerned with the development of braided composite rods for civil engineering applications, namely for concrete internal reinforcement, as a steel substitute. The research study aims at understanding the tensile behaviour of composite rods reinforced by a textile structure – braided structure with core reinforcement. Seven types of braided composite rods were produced, varying the type of fibres used as a core reinforcement of a polyester braided structure. E-glass, ca...
Diffusive evolution of experimental braided rivers
Reitz, Meredith D.; Jerolmack, Douglas J.; Lajeunesse, Eric; Limare, Angela; Devauchelle, Olivier; Métivier, François
2014-05-01
Water flowing over a loose granular bed organizes into a braided river, a network of ephemeral and interacting channels. The temporal and spatial evolution of this network of braided channels is not yet quantitatively understood. In ˜1 m-scale experiments, we found that individual channels exhibit a self-similar geometry and near-threshold transport conditions. Measurements of the rate of growth of topographic correlation length scales, the time scale of system-slope establishment, and the random spatial decorrelation of channel locations indicate together that the evolution of the braided river system may be diffusive in nature. This diffusion is due to the separation of scales between channel formation and network evolution, and the random motion of interacting channels when viewed at a coarse-grained scale.
Integrated Design for Manufacturing of Braided Preforms for Advanced Composites Part I: 2D Braiding
Gao, Yan Tao; Ko, Frank K.; Hu, Hong
2013-12-01
This paper presents a 2D braiding design system for advanced textile structural composites was based on dynamic models. A software package to assist in the design of braided preform manufacturing has been developed. The package allows design parameters (machine speeds, fiber volume fraction, tightness factor, etc.) to be easily obtained and the relationships between said parameters to be demonstrated graphically. The fabirc geometry model (FGM) method was adopted to evaluate the mechanical properties of the composites. Experimental evidence demonstrates the success of the use of dynamic models in the design software for the manufacture of braided fabric preforms.
Effect of braiding process on the damage tolerance of 3-D braided graphite/epoxy composites
El-Shiekh, Aly; Li, Wei; Hammad, Mohamed
1989-01-01
One of the key advantages of three-dimensional braided composite materials is their high impact damage tolerance comparing with laminated composites, due to their fully integrated fibrous substrates. In this paper, the effect of different processing methods on the impact damage tolerance of braided graphite/epoxy composite is experimentally assessed. The test specimens are prepared using both of the two existing three-dimensional braiding techniques (the 4-step and the 2-step processes). After the specimens are impacted under controlled impact energy, the damage introduced is studied. Then a compression test is conducted to evaluate the compression strength of the specimens after impact.
Positive braid knots of maximal topological 4-genus
Liechti, Livio
2015-01-01
We show that a positive braid knot has maximal topological 4-genus exactly if it has maximal signature invariant. As an application, we determine all positive braid knots with maximal topological 4-genus and compute the topological 4-genus for all positive braid knots with up to 12 crossings.
Braiding operator via quantum cluster algebra
We construct a braiding operator in terms of the quantum dilogarithm function based on the quantum cluster algebra. We show that it is a q-deformation of the R-operator for which hyperbolic octahedron is assigned. Also shown is that, by taking q to be a root of unity, our braiding operator reduces to the Kashaev RK-matrix up to a simple gauge-transformation. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical devoted to ‘Cluster algebras in mathematical physics’. (paper)
Statistical Model of the 3-D Braided Composites Strength
XIAO Laiyuan; ZUO Weiwei; CAI Ganwei; LIAO Daoxun
2007-01-01
Based on the statistical model for the tensile statistical strength of unidirectional composite materials and the stress analysis of 3-D braided composites, a new method is proposed to calculate the tensile statistical strength of the 3-D braided composites. With this method, the strength of 3-D braided composites can be calculated with very large accuracy, and the statistical parameters of 3-D braided composites can be determined. The numerical result shows that the tensile statistical strength of 3-D braided composites can be predicted using this method.
Ferrofluids, complex particle dynamics and braid description
Finely divided magnetic matter is important in many areas of science and technology. A special sub-class of systems are made up of freely moving particles suspended in a carrier liquid where the magnetic interactions play an important role in the actual structure formation and dynamical behaviour. These include ferrofluids, which are colloids of magnetic particles dispersed in carrier fluids, magnetic micro-beads, which are micrometer sized plastic beads loaded with iron oxide, and nonmagnetic particles dispersed in ferrofluids, forming the so-called 'magnetic holes'. How, in a simple and forceful way, is it possible to characterise the dynamics of systems with several moving components like dispersed magnetic particles subjected to external magnetic fields? The methods based on the theory of braids may provide the answer. Braid theory is a sub-field of mathematics known as topology. It involves classifying different ways of tracing curves in space. The topological description of braids thus provides a simple and concise language for describing the dynamics of a system of moving particles as if they perform a complicated dance as they move about one another, and the braid encodes the choreography of this dance
Ferrofluids, complex particle dynamics and braid description
Skjeltorp, Arne T.; Clausen, Sigmund; Helgesen, Geir
2001-05-01
Finely divided magnetic matter is important in many areas of science and technology. A special sub-class of systems are made up of freely moving particles suspended in a carrier liquid where the magnetic interactions play an important role in the actual structure formation and dynamical behaviour. These include ferrofluids, which are colloids of magnetic particles dispersed in carrier fluids, magnetic micro-beads, which are micrometer sized plastic beads loaded with iron oxide, and nonmagnetic particles dispersed in ferrofluids, forming the so-called "magnetic holes". How, in a simple and forceful way, is it possible to characterise the dynamics of systems with several moving components like dispersed magnetic particles subjected to external magnetic fields? The methods based on the theory of braids may provide the answer. Braid theory is a sub-field of mathematics known as topology. It involves classifying different ways of tracing curves in space. The topological description of braids thus provides a simple and concise language for describing the dynamics of a system of moving particles as if they perform a complicated dance as they move about one another, and the braid encodes the choreography of this dance.
Quantum Lorentz and braided Poincare groups
Zakrzewski, S.
1997-01-01
Quantum Lorentz groups H admitting quantum Minkowski space V are selected. Natural structure of a quantum space G = V x H is introduced, defining a quantum group structure on G only for triangular H (q=1). We show that it defines a braided quantum group structure on G for |q|=1.
Burst Testing of Triaxial Braided Composite Tubes
Salem, J. A.; Bail, J. L.; Wilmoth, N. G.; Ghosn, L. J.; Kohlman, L. W.; Roberts, G. D.; Martin, R. E.
2014-01-01
Applications using triaxial braided composites are limited by the materials transverse strength which is determined by the delamination capacity of unconstrained, free-edge tows. However, structural applications such as cylindrical tubes can be designed to minimize free edge effects and thus the strength with and without edge stresses is relevant to the design process. The transverse strength of triaxial braided composites without edge effects was determined by internally pressurizing tubes. In the absence of edge effects, the axial and transverse strength were comparable. In addition, notched specimens, which minimize the effect of unconstrained tow ends, were tested in a variety of geometries. Although the commonly tested notch geometries exhibited similar axial and transverse net section failure strength, significant dependence on notch configuration was observed. In the absence of unconstrained tows, failure ensues as a result of bias tow rotation, splitting, and fracture at cross-over regions.
Iadecola, Thomas; Schuster, Thomas; Chamon, Claudio
2016-08-01
Many topological phenomena first proposed and observed in the context of electrons in solids have recently found counterparts in photonic and acoustic systems. In this work, we demonstrate that non-Abelian Berry phases can arise when coherent states of light are injected into "topological guided modes" in specially fabricated photonic waveguide arrays. These modes are photonic analogues of topological zero modes in electronic systems. Light traveling inside spatially well-separated topological guided modes can be braided, leading to the accumulation of non-Abelian phases, which depend on the order in which the guided beams are wound around one another. Notably, these effects survive the limit of large photon occupation, and can thus also be understood as wave phenomena arising directly from Maxwell's equations, without resorting to the quantization of light. We propose an optical interference experiment as a direct probe of this non-Abelian braiding of light.
Braid group representation on quantum computation
There are many studies about topological representation of quantum computation recently. One of diagram representation of quantum computation is by using ZX-Calculus. In this paper we will make a diagrammatical scheme of Dense Coding. We also proved that ZX-Calculus diagram of maximally entangle state satisfies Yang-Baxter Equation and therefore, we can construct a Braid Group representation of set of maximally entangle state
Braid group representation on quantum computation
Aziz, Ryan Kasyfil, E-mail: kasyfilryan@gmail.com [Department of Computational Sciences, Bandung Institute of Technology (Indonesia); Muchtadi-Alamsyah, Intan, E-mail: ntan@math.itb.ac.id [Algebra Research Group, Bandung Institute of Technology (Indonesia)
2015-09-30
There are many studies about topological representation of quantum computation recently. One of diagram representation of quantum computation is by using ZX-Calculus. In this paper we will make a diagrammatical scheme of Dense Coding. We also proved that ZX-Calculus diagram of maximally entangle state satisfies Yang-Baxter Equation and therefore, we can construct a Braid Group representation of set of maximally entangle state.
Geometric representations of the braid groups
Castel, Fabrice
2011-01-01
We show that the morphisms from the braid group with n strands in the mapping class group of a surface with a possible non empty boundary, assuming that its genus is smaller or equal to n/2 are either cyclic morphisms (their images are cyclic groups), or transvections of monodromy morphisms (up to multiplication by an element in the centralizer of the image, the image of a standard generator of the braid group is a Dehn twist, and the images of two consecutive standard generators are two Dehn twists along two curves intersecting in one point). As a corollary, we determine the endomorphisms, the injective endomorphisms, the automorphisms and the outer automorphism group of the following groups: the braid group with n strands where n is greater than or equal to 6, and the mapping class group of any surface of genus greater or equal than 2. For each statement involving the mapping class group, we study both cases: when the boundary is fixed pointwise, and when each boundary component is fixed setwise. We will al...
Imperfect dark energy from kinetic gravity braiding
We introduce a large class of scalar-tensor models with interactions containing the second derivatives of the scalar field but not leading to additional degrees of freedom. These models exhibit peculiar features, such as an essential mixing of scalar and tensor kinetic terms, which we have named kinetic braiding. This braiding causes the scalar stress tensor to deviate from the perfect-fluid form. Cosmology in these models possesses a rich phenomenology, even in the limit where the scalar is an exact Goldstone boson. Generically, there are attractor solutions where the scalar monitors the behaviour of external matter. Because of the kinetic braiding, the position of the attractor depends both on the form of the Lagrangian and on the external energy density. The late-time asymptotic of these cosmologies is a de Sitter state. The scalar can exhibit phantom behaviour and is able to cross the phantom divide with neither ghosts nor gradient instabilities. These features provide a new class of models for Dark Energy. As an example, we study in detail a simple one-parameter model. The possible observational signatures of this model include a sizeable Early Dark Energy and a specific equation of state evolving into the final de-Sitter state from a healthy phantom regime
Teleportation, Braid Group and Temperley--Lieb Algebra
Zhang, Yong
2006-01-01
We explore algebraic and topological structures underlying the quantum teleportation phenomena by applying the braid group and Temperley--Lieb algebra. We realize the braid teleportation configuration, teleportation swapping and virtual braid representation in the standard description of the teleportation. We devise diagrammatic rules for quantum circuits involving maximally entangled states and apply them to three sorts of descriptions of the teleportation: the transfer operator, quantum mea...
CAD/CAM of braided preforms for advanced composites
Yang, Gui; Pastore, Christopher; Tsai, Yung Jia; Soebroto, Heru; Ko, Frank
A CAD/CAM system for braiding to produce preforms for advanced textile structural composites is presented in this paper. The CAD and CAM systems are illustrated in detail. The CAD system identifies the fiber placement and orientation needed to fabricate a braided structure over a mandrel, for subsequent composite formation. The CAM system uses the design parameters generated by the CAD system to control the braiding machine. Experimental evidence demonstrating the success of combining these two technologies to form a unified CAD/CAM system for the manufacture of braided fabric preforms with complex structural shapes is presented.
Self-organized braiding in solar coronal loops
Berger, M. A.; Asgari-Targhi, M.; Deluca, E. E.
2015-08-01
In this paper, we investigate the evolution of braided solar coronal loops. We assume that coronal loops consist of several internal strands which twist and braid about each other. Reconnection between the strands leads to small flares and heating of the loop to x-ray temperatures. Using a method of generating and releasing braid structure similar to a forest fire model, we show that the reconnected field lines evolve to a self-organised critical state. In this state, the frequency distributions of coherent braid sequences as well as flare energies follow power law distributions. We demonstrate how the presence of net helicity in the loop alters the distribution laws.
A new algebra which transmutes to the braided algebra
Yildiz, A
1999-01-01
We find a new braided Hopf structure for the algebra satisfied by the entries of the braided matrix $BSL_q(2)$. A new nonbraided algebra whose coalgebra structure is the same as the braided one is found to be a two parameter deformed algebra. It is found that this algebra is not a comodule algebra under adjoint coaction. However, it is shown that for a certain value of one of the deformation parameters the braided algebra becomes a comodule algebra under the coaction of this nonbraided algebr...
Braiding in Conformal Field Theory and Solvable Lattice Models
Gepner, D; Gepner, Doron; Fuchs, Jurgen
1994-01-01
Braiding matrices in rational conformal field theory are considered. The braiding matrices for any two block four point function are computed, in general, using the holomorphic properties of the blocks and the holomorphic properties of rational conformal field theory. The braidings of $SU(N)_k$ with the fundamental are evaluated and are used as examples. Solvable interaction round the face lattice models are constructed from these braiding matrices, and their Boltzmann weights are given. This allows, in particular, for the derivation of the Boltzmann weights of such solvable height models.
Xianghua LI; Xiaohui LIU; Shenfang YUAN
2008-01-01
The experimental characterization of three-dimensional (3-D) braided composites is extremely important for their design and analysis. Because of their desirable attributes and outstanding performance, optical fiber sensors (OFSs) can be embedded to mon-itor mechanical properties of textile composites. This paper discusses two techniques to incorporate different OFSs into 3-D braided composite preforms. The oper-ating principle of various sensor systems is first con-ducted. Experiments using Michelson interferometers, FBG sensors, and micro-bend sensors are performed to verify the concept of the proposed method. Strain curves of various OFSs tests are finally compared, and they all exhibit good linearity.
A study of mixing in coherent vortices using braiding factors
This paper studies the use of braiding fluid particles to quantify the amount of mixing within a fluid flow. We analyze the pros and cons of braid methods by considering the motion of three or more fluid particles in a coherent vortex structure. The relative motions of the particles, as seen in a space-time diagram, produce a braid pattern, which is correlated with mixing and measured by the braiding factor. The flow we consider is a Gaussian vortex within a rotating strain field that generates cat's eyes in the vortex. We also consider a modified version of this strain field that contains a resonance frequency effect that produces multiple sets of cat's eyes at different radii. As the thickness of the cat's eyes increases, they interact with one another and produce complex Lagrangian motion in the flow that increases the braiding of particles, hence implying more mixing within the vortex. It is found that calculating the braiding factor using only three fluid particles gives useful information about the flow, but only if all three particles lie in the same region of the flow, i.e. this gives good local information. We find that we only require one of the three particles to trace a chaotic path to give an exponentially growing braiding factor. i.e. a non-zero 'braiding exponent'. A modified braiding exponent is also introduced which removes the spurious effects caused by the rotation of the fluid. This analysis is extended to a more global approach by using multiple fluid particles that span larger regions of the fluid. Using these global results, we compare the braiding within a viscously spreading Gaussian vortex in the above strain fields, where the flow is determined both kinematically and dynamically. We show that the dynamic feedback of the strain field onto the flow field reduces the overall amount of braiding of the fluid particles.
Braided Composite Technologies for Rotorcraft Structures
Jessie, Nathan
2015-01-01
A&P Technology has developed a braided material approach for fabricating lightweight, high-strength hybrid gears for aerospace drive systems. The conventional metallic web was replaced with a composite element made from A&P's quasi-isotropic braid. The 0deg, +/-60deg braid architecture was chosen so that inplane stiffness properties and strength would be nearly equal in all directions. The test results from the Phase I Small Spur Gear program demonstrated satisfactory endurance and strength while providing a 20 percent weight savings. (Greater weight savings is anticipated with structural optimization.) The hybrid gears were subjected to a proof-of-concept test of 1 billion cycles in a gearbox at 10,000 revolutions per minute and 490 in-lb torque with no detectable damage to the gears. After this test the maximum torque capability was also tested, and the static strength capability of the gears was 7x the maximum operating condition. Additional proof-of-concept tests are in progress using a higher oil temperature, and a loss-of-oil test is planned. The success of Phase I led to a Phase II program to develop, fabricate, and optimize full-scale gears, specifically Bull Gears. The design of these Bull Gears will be refined using topology optimization, and the full-scale Bull Gears will be tested in a full-scale gear rig. The testing will quantify benefits of weight savings, as well as noise and vibration reduction. The expectation is that vibration and noise will be reduced through the introduction of composite material in the vibration transmission path between the contacting gear teeth and the shaft-and-bearing system.
Unraveling "Braid": Puzzle Games and Storytelling in the Imperative Mood
Arnott, Luke
2012-01-01
"Unraveling Braid" analyzes how unconventional, non-linear narrative fiction can help explain the ways in which video games signify. Specifically, this essay looks at the links between the semiotic features of Jonathan Blow's 2008 puzzle-platform video game Braid and similar elements in Georges Perec's 1978 novel "Life A User's Manual," as well as…
Sharing the Arts of the Blue Ridge Mountains. Rug Braiding.
Holman, Martha; Gailey, Lamar
This module on rug braiding is one of eight modules designed to provide instruction on authentic Blue Ridge Mountain crafts to adult basic education students at low cost. Contents include notes on the history of rug braiding; process used, including equipment and materials, as well as method described narratively and graphically; and the followup,…
Braids as a representation space of SU(5)
Cartin, Daniel
2015-01-01
The Standard Model of particle physics provides very accurate predictions of phenomena occurring at the sub-atomic level, but the reason for the choice of symmetry group and the large number of particles considered elementary, is still unknown. Along the lines of previous preon models positing a substructure to explain these aspects, Bilson-Thompson showed how the first family of elementary particles is realized as the crossings of braids made of three strands, with charges resulting from twists of those strands with certain conditions; in this topological model, there are only two distinct neutrino states. Modeling the particles as braids implies these braids must be the representation space of a Lie algebra, giving the symmetries of the Standard Model. In this paper, this representation is made explicit, obtaining the raising operators associated with the Lie algebra of $SU(5)$, one of the earliest grand unified theories. Because the braids form a group, the action of these operators are braids themselves, ...
Approaches for Tensile Testing of Braided Composites
Roberts, Gary D.; Salem, Jonathan A.; Bail, Justin L.; Kohlman, Lee W.; Binienda, Wieslaw K.; Martin, Richard E.
2011-01-01
For angleply composites, lamina tension and compression strengths are commonly determined by applying classical lamination theory to test data obtained from testing of angleply composite specimens. For textile composites such as 2D triaxial braids, analysis is more complex and standard test methods do not always yield reliable strength measurements. This paper describes recent research focused on development of more reliable tensile test methods for braided composites and presents preliminary data for various approaches. The materials investigated in this work have 0deg+/-60 2D triaxial braid architecture with nearly equal fiber volume fraction in each of the three fiber directions. Flat composite panels are fabricated by resin transfer molding (RTM) using six layers of the braided preform aligned along the 0deg fiber direction. Various epoxy resins are used as matrix materials. Single layer panels are also fabricated in order to examine local variations in deformation related to the braid architecture. Specimens are cut from these panels in the shape of standard straight-sided coupons, an alternative bowtie geometry, and an alternative notched geometry. Axial tensile properties are measured using specimens loaded along the 0deg fiber direction. Transverse tensile properties are measured using specimens loaded perpendicular to the 0deg fibers. Composite tubes are also fabricated by RTM. These tubes are tested by internal pressurization using a soft rubbery material sealed between the inside diameter of the tube and the load fixtures. The ends of the tube are unconstrained, so the primary load is in the hoop direction. Tubes are fabricated with the 0deg fibers aligned along the tube axis by overbraiding the preform on a mandrel. Since the loading is in the hoop direction, testing of the overbraided tube provides a measure of transverse tensile strength. Previous work has indicated that straight-sided coupons yield a transverse tensile strength that is much lower
The braidings of mapping class groups and loop spaces
Song, Yongjin
2000-01-01
The disjoint union of mapping class groups forms a braided monoidal category. We give an explicit expression of braidings in terms of both their actions on the fundamental group of the surface and the standard Dehn twists. This braided monoidal category gives rise to a double loop space. We prove that the action of little 2-cube operad does not extend to the action of little 3-cube operad by showing that the Browder operation induced by 2-cube operad action is nontrivial. A rather simple expr...
Braiding surface links which are coverings over the standard torus
NAKAMURA, Inasa
2009-01-01
We consider a surface link in the 4-space which can be presented by a simple branched covering over the standard torus, which we call a torus-covering link. Torus-covering links include spun $T^2$-knots and turned spun $T^2$-knots. In this paper we braid a torus-covering link over the standard 2-sphere. This gives an upper estimate of the braid index of a torus-covering link. In particular we show that the turned spun $T^2$-knot of the torus $(2,\\,p)$-knot has the braid index four.
Quilts central extensions, braid actions, and finite groups
2000-01-01
Quilts are 2-complexes used to analyze actions and subgroups of the 3-string braid group and similar groups. This monograph establishes the fundamentals of quilts and discusses connections with central extensions, braid actions, and finite groups. Most results have not previously appeared in a widely available form, and many results appear in print for the first time. This monograph is accessible to graduate students, as a substantial amount of background material is included. The methods and results may be relevant to researchers interested in infinite groups, moonshine, central extensions, triangle groups, dessins d'enfants, and monodromy actions of braid groups.
Core reilforced braided composite armour as a substitute to steel in concrete reinforcement
Fangueiro, Raúl; Sousa, Guilherme José Miranda de; Araújo, Mário Duarte de; Pereira, C. Gonilho; Jalali, Said
2006-01-01
This paper presents the work that is being done at the University of Minho concerning the development of brainded rods concrete reinforcement. Several samples of core reinforced braided fabrics have been produced varying the type of braided fabric (core reinforced and hybrid), the linear density of the core reinforcing yarns and the type of braiding structure (with or without ribs). The tensile properties of braided fabrics has also been analysed. Core reinforced braided composites rods were ...
Failure analysis of woven and braided fabric reinforced composites
Naik, Rajiv A.
1994-01-01
A general purpose micromechanics analysis that discretely models the yarn architecture within the textile repeating unit cell was developed to predict overall, three dimensional, thermal and mechanical properties, damage initiation and progression, and strength. This analytical technique was implemented in a user-friendly, personal computer-based, menu-driven code called Textile Composite Analysis for Design (TEXCAD). TEXCAD was used to analyze plain weave and 2x2, 2-D triaxial braided composites. The calculated tension, compression, and shear strengths correlated well with available test data for both woven and braided composites. Parametric studies were performed on both woven and braided architectures to investigate the effects of parameters such as yarn size, yarn spacing, yarn crimp, braid angle, and overall fiber volume fraction on the strength properties of the textile composite.
Braided Tensor Categories and Extensions of Vertex Operator Algebras
Huang, Yi-Zhi; Kirillov, Alexander; Lepowsky, James
2015-08-01
Let V be a vertex operator algebra satisfying suitable conditions such that in particular its module category has a natural vertex tensor category structure, and consequently, a natural braided tensor category structure. We prove that the notions of extension (i.e., enlargement) of V and of commutative associative algebra, with uniqueness of unit and with trivial twist, in the braided tensor category of V-modules are equivalent.
Multifunctional braided composite rods for civil engineering applications
Fangueiro, Raúl; Zdraveva, Emilijia; Pereira, Cristiana Gonilho; Lanceros-Méndez, S.; Jalali, Said; Araújo, Mário Duarte de
2010-01-01
This paper presents the development of a braided reinforced composite rod (BCR) able to both reinforce and monitor the stress state of concrete elements. Carbon fibers have been used as sensing and reinforcing material along with glass fiber. Various composites rods have been produced using an author patented technique based on a modified conventional braiding machine. The materials investigated were prepared with different carbon fiber content as follows: BCR2 (77% glass/23% c...
Self-Sustained Magnetic Braiding in Toroidal Plasmas
Itoh, K; Fukuyama, A.; Itoh, S.-I.; Yagi, M.; Azumi, M.
1994-01-01
Theory for the magnetic braiding in toroidal plasmas, which is caused by microscopic pressure-gradient-driven turbulence, is developed. When the pressure gradient exceeds a threshold, the self-sustaining of the magnetic braiding and enhanced anomalous transport occur. The balance between the nonlinear destabilization and nonlinear stabilization, which determines the stationary turbulence, is solved analytically for the case of interchange mode. The enhanced thermal conductivity and magneti...
Braids as a representation space of SU(5)
Cartin, Daniel
2015-06-01
The standard model of particle physics provides very accurate predictions of phenomena occurring at the sub-atomic level, but the reason for the choice of symmetry group and the large number of particles considered elementary is still unknown. Along the lines of previous preon models positing a substructure to explain these aspects, Bilson-Thompson showed how the first family of elementary particles is realized as the crossings of braids made of three strands, with charges resulting from twists of those strands with certain conditions; in this topological model, there are only two distinct neutrino states. Modeling the particles as braids implies these braids must be the representation space of a Lie algebra, giving the symmetries of the standard model. In this paper, this representation is made explicit, obtaining the raising operators associated with the Lie algebra of SU(5), one of the earliest grand unified theories. Because the braids form a group, the action of these operators are braids themselves, leading to their identification as gauge bosons. Possible choices for the other two families are also given. Although this realization of particles as braids is lacking a dynamical framework, it is very suggestive, especially when considered as a natural method of adding matter to loop quantum gravity.
Braids as a representation space of SU(5)
The standard model of particle physics provides very accurate predictions of phenomena occurring at the sub-atomic level, but the reason for the choice of symmetry group and the large number of particles considered elementary is still unknown. Along the lines of previous preon models positing a substructure to explain these aspects, Bilson-Thompson showed how the first family of elementary particles is realized as the crossings of braids made of three strands, with charges resulting from twists of those strands with certain conditions; in this topological model, there are only two distinct neutrino states. Modeling the particles as braids implies these braids must be the representation space of a Lie algebra, giving the symmetries of the standard model. In this paper, this representation is made explicit, obtaining the raising operators associated with the Lie algebra of SU(5), one of the earliest grand unified theories. Because the braids form a group, the action of these operators are braids themselves, leading to their identification as gauge bosons. Possible choices for the other two families are also given. Although this realization of particles as braids is lacking a dynamical framework, it is very suggestive, especially when considered as a natural method of adding matter to loop quantum gravity
Mechanical properties of triaxially braided composites: Experimental and analytical results
Masters, John E.; Foye, Raymond L.; Pastore, Christopher M.; Gowayed, Yasser A.
1992-01-01
The unnotched tensile properties of 2-D triaxial braid reinforced composites from both an experimental and an analytical viewpoint are studied. The materials are graphite fibers in an epoxy matrix. Three different reinforcing fiber architectures were considered. Specimens were cut from resin transfer molded (RTM) composite panels made from each braid. There were considerable differences in the observed elastic constants from different size strain gage and extensometer reading. Larger strain gages gave more consistent results and correlated better with the extensometer reading. Experimental strains correlated reasonably well with analytical predictions in the longitudinal, 0 degrees, fiber direction but not in the transverse direction. Tensile strength results were not always predictable even in reinforcing directions. Minor changes in braid geometry led to disproportionate strength variations. The unit cell structure of the triaxial braid was discussed with the assistance of computer analysis of the microgeometry. Photomicrographs of braid geometry were used to improve upon the computer graphics representations of unit cells. These unit cells were used to predict the elastic moduli with various degrees of sophistication. The simple and the complex analyses were generally in agreement but none adequately matched the experimental results for all the braids.
Analysis of woven and braided fabric reinforced composites
Naik, Rajiv A.
1994-01-01
A general purpose micromechanics analysis that discretely models the yarn architecture within the textile repeating unit cell, was developed to predict overall, three dimensional, thermal and mechanical properties. This analytical technique was implemented in a user-friendly, personal computer-based, windows compatible code called Textile Composite Analysis for Design (TEXCAD). TEXCAD was used to analyze plain, 5-harness satin, and 8-harness satin weave composites along with 2-D braided and 2x2, 2-D triaxial braided composites. The calculated overall stiffnesses correlated well with available 3-D finite element results and test data for both the woven and the braided composites. Parametric studies were performed to investigate the effects of yarn size on the yarn crimp and the overall thermal and mechanical constants for plain weave composites. The effects of braid angle were investigated for the 2-D braided composites. Finally, the effects of fiber volume fraction on the yarn undulations and the thermal and mechanical properties of 2x2, 2-D triaxial braided composites were also investigated.
Topology and geometry of nematic braids
Čopar, Simon, E-mail: simon.copar@fmf.uni-lj.si
2014-05-01
Topological analysis of disclinations in nematic liquid crystals is an interesting and diverse topic that goes from strict mathematical theorems to applications in elaborate systems found in experiments and numerical simulations. The theory of nematic disclinations is shown from both the geometric and topological perspectives. Entangled disclination line networks are analyzed based on their shape and the behavior of their cross section. Methods of differential geometry are applied to derive topological results from reduced geometric information. For nematic braids, systems of −1/2 disclination loops, created by inclusion of homeotropic colloidal particles, a formalism of rewiring is constructed, allowing comparison and construction of an entire set of different conformations. The disclination lines are described as ribbons and a new topological invariant, the self-linking number, is introduced. The analysis is generalized from a constant −1/2 profile to general profile variations, while retaining the geometric treatment. The workings of presented topological statements are demonstrated on simple models of entangled nematic colloids, estimating the margins of theoretical assumptions made in the formal derivations, and reviewing the behavior of the disclinations not only under topological, but also under free-energy driven constraints.
Sorting out meandering and braiding: discriminating formative conditions and stratigraphy
Kleinhans, M. G.; van de Lageweg, W. I.; Schuurman, F.; Van Dijk, W. M.
2011-12-01
For various river channel patterns, the necessary formative conditions differ, but how is not entirely understood. Furthermore, not only the morphology and dynamics differ, but also the resulting stratigraphy differs, of which understanding is required to infer past environmental conditions and predict reservoir behaviour. Our objective is to identify the necessary and sufficient conditions for forming dynamic meandering and braided rivers. We reproduced both patterns experimentally and with a physics-based numerical model, and produced synthetic stratification from bed elevation maps and control lacquer peels for the experiments. Experimental meandering was produced using a mixture of poorly sorted sediment and silt-sized silica flour and a transversely moving inflow boundary. Braiding was produced in exactly the same conditions but without the silica flour. These experiments represent gravel-bed rivers in nature, where both experimental meandering and braiding channels were close to the transition between the types. Onset meandering was also produced in the numerical model (Delft3D) with a similar transversely moving inflow boundary, whilst braided rivers formed with fixed inflow or some noise on the transverse discharge distribution at the inflow boundary. The silica flour deposited on crevasse splays and in chute channels, forming new floodplain. This caused much less chute cutoffs and stronger banks. The resulting meandering river formed multiple sets of scroll bars forming pointbars, overlain by splays and floodplain. The braided river, in contrast, showed mid-channel bars and multiple active channels, faster and more haphazard bar and channel migration, and frequent chute cutoffs. Apart from the floodplain, stratification in meandering rivers consisted of sigmoidally stratified units formed by scroll bars and channel fills, usually formed after chute cutoff. Braided rivers had similar units but much smaller and more. In both cases the highest preservation
Mechanical properties of triaxially braided composites - Experimental and analytical results
Masters, John E.; Foye, Raymond L.; Pastore, Christopher M.; Gowayed, Yasser A.
1993-01-01
This paper investigates the unnotched tensile properties of two-dimensional (2D) triaxial braid-reinforced composites both experimentally and analytically. The materials are graphite fibers in an epoxy matrix. Three different reinforcing fiber architectures were considered. There were considerable differences in the observed elastic constants from different size strain gage and extensometer readings. Larger strain gages gave more consistent results and correlated better with the extensometer readings. Experimental strains correlated reasonably well with analytical predictions in the longitudinal, 0 deg, fiber direction but not in the transverse direction. Tensile strength results were not always predictable even in reinforcing directions. Minor changes in braid geometry led to disproportionate strength variations. The unit cell structure of the triaxial braid was discussed with the assistance of computer analysis of the microgeometry. Photomicrographs of braid geometry were used to improve upon the computer graphics representations of unit cells. These unit cells were used to predict the elastic moduli with various degrees of sophistication. The simple and the complex analyses were generally in agreement, but none adequately matched the experimental results for all the braids.
An experimental study on mechanical properties of GFRP braid-pultruded composite rods
2009-09-01
Full Text Available In this work, a conventional textile braiding machine was modified and added to a pultrusion line in order to produce glass fiber reinforced composite rods by braiding-pultrusion technique. Braid-pultruded (BP rods were produced with three braid roving linear densities and also with three different braid angles. To study the influence of overbraiding on mechanical properties of pultruded rods, unidirectional (UD rods, without braided fabric, were produced, as well. All rod types were subjected to tensile, bending and torsion tests. The experimental results showed that BP rods have considerably higher shear modulus, but lower tensile modulus and flexural rigidity than those of UD pultruded rods, when fiber volume fraction is kept constant. Moreover, rods produced with higher braid roving linear densities had better torsional, but lower tensile and flexural properties. The highest shear modulus was observed in BP rods with braid angle of 45°.
On M\\"{u}ger's centralizer for a certain class of braided fusion categories
Burciu, S.
2014-01-01
We provide a general formula for Mueger's centralizer of any fusion subcategory of a braided fusion category containing a tannakian subcategory. This entails a description for Mueger's centralizer of all fusion subcategories of a group theoretical braided fusion category.
Non-Abelian braid statistics versus projective permutation statistics
Recent papers by Finkelstein, Galiautdinov, and co-workers [J. Math. Phys. 42, 1489 (2001); 42, 3299 (2001)] discuss a suggestion by Wilczek that non-Abelian projective representations of the permutation group can be used as a new type of particle statistics, valid in any dimension. Wilczek's suggestion was based in part on an analysis by Nayak and Wilczek (NW) of the non-Abelian representation of the braid group in a quantum Hall system. We point out that projective permutation statistics is not possible in a local quantum field theory as it violates locality, and show that the NW braid group representation is not equivalent to a projective representation of the permutation group. The structure of the finite image of the braid group in a 2n/2-1-dimensional representation is obtained
Teleportation, braid group and Temperley-Lieb algebra
We explore algebraic and topological structures underlying the quantum teleportation phenomena by applying the braid group and Temperley-Lieb algebra. We realize the braid teleportation configuration, teleportation swapping and virtual braid representation in the standard description of the teleportation. We devise diagrammatic rules for quantum circuits involving maximally entangled states and apply them to three sorts of descriptions of the teleportation: the transfer operator, quantum measurements and characteristic equations, and further propose the Temperley-Lieb algebra under local unitary transformations to be a mathematical structure underlying the teleportation. We compare our diagrammatical approach with two known recipes to the quantum information flow: the teleportation topology and strongly compact closed category, in order to explain our diagrammatic rules to be a natural diagrammatic language for the teleportation
The braided single-stage protocol for quantum secure communication
Darunkar, Bhagyashri; Verma, Pramode K.
2014-05-01
This paper presents the concept and implementation of a Braided Single-stage Protocol for quantum secure communication. The braided single-stage protocol is a multi-photon tolerant secure protocol. This multi-photon tolerant protocol has been implemented in the laboratory using free-space optics technology. The proposed protocol capitalizes on strengths of the three-stage protocol and extends it with a new concept of braiding. This protocol overcomes the limitations associated with the three-stage protocol in the following ways: It uses the transmission channel only once as opposed to three times in the three-stage protocol, and it is invulnerable to man-in-the-middle attack. This paper also presents the error analysis resulting from the misalignment of the devices in the implementation. The experimental results validate the efficient use of transmission resources and improvement in the data transfer rate.
Mechanical properties of braided commingled glass/polypropylene composites
Fibre reinforced plastics (Fr) are now widely used due to improved specific properties compared to more conventional materials. In particular the automotive and aerospace industries are turning towards these materials for weight reduction. Moreover the anti corrosion properties of FRP are also of interest to manufacturers as an alternative to metallic materials. The reinforcing fibres used in the composite materials can be assembled using a variety of textile processing techniques. Of these, 2-D braiding is particularly attractive for hollow components or sandwich laminates. In this study flat plaques were produced by braiding commingled yam at various angles on a cylindrical mandrel, after which the braids were slit and consolidated by non-isothermal compression moulding. Mechanical properties of the composites were measured and the results are discussed with reference to the arising fibre architecture and microstructure. The results obtained illustrate that there is a major influence of the fibre orientation on the final properties of the composite. (author)
Knots, Braids and BPS States in M-Theory
Grassi, Antonella; Guralnik, Zachary; Ovrut, Burt A.
2001-01-01
In previous work we considered M-theory five branes wrapped on elliptic Calabi-Yau threefold near the smooth part of the discriminant curve. In this paper, we extend that work to compute the light states on the worldvolume of five-branes wrapped on fibers near certain singular loci of the discriminant. We regulate the singular behavior near these loci by deforming the discriminant curve and expressing the singularity in terms of knots and their associated braids. There braids allow us to comp...
Self-sustained magnetic braiding in toroidal plasmas
Theory for the magnetic braiding in toroidal plasmas, which is caused by microscopic pressure-gradient-driven turbulence, is developed. When the pressure gradient exceeds a threshold, the self-sustaining of the magnetic braiding and enhanced anomalous transport occur. The balance between the nonlinear destabilization and nonlinear stabilization, which determines the stationary turbulence, is solved analytically for the case of interchange mode. The enhanced thermal conductivity and magnetic perturbation amplitude as well as the threshold pressure gradient are obtained. Cusp-type catastrophe is predicted, allowing the abrupt burst of magnetic perturbations. (author)
Dual mechanical braiding experiments provide a useful tool with which to investigate the nature of interactions between rod-like molecules, for instance actin and DNA. In conditions close to molecular condensation, one would expect an appearance of a local minimum in the interaction potential between the two molecules. We investigate this situation, introducing an attractive component into the interaction potential, using a model developed for describing such experiments. We consider both attractive interactions that do not depend on molecular structure and those which depend on a DNA-like helix structure. In braiding experiments, an attractive term may lead to certain effects. A local minimum may cause molecules to collapse from a loosely braided configuration into a tight one, occurring at a critical value of the moment applied about the axis of the braid. For a fixed number of braid pitches, this may lead to coexistence between the two braiding states, tight and loose. Coexistence implies certain proportions of the braid are in each state, their relative size depending on the number of braid pitches. This manifests itself as a linear dependence in numerically calculated quantities as functions of the number of braid pitches. Also, in the collapsed state, the braid radius stays roughly constant. Furthermore, if the attractive interaction is helix dependent, the left-right handed braid symmetry is broken. For a DNA like charge distribution, using the Kornyshev–Leikin interaction model, our results suggest that significant braid collapse and coexistence only occurs for left handed braids. Regardless of the interaction model, the study highlights the possible qualitative physics of braid collapse and coexistence; and the role helix specific forces might play, if important. The model could be used to connect other microscopic theories of interaction with braiding experiments. (paper)
Investigation on the Thermal Conductivity of 3-Dimensional and 4-Directional Braided Composites
Liu Zhenguo; Zhang Haiguo; Lu Zixing; Li Diansen
2007-01-01
It is vital to choose a factual and reasonable micro-structural model of braided composites for improving the calculating precision of thermal property of 3-D braided composites by finite element method (FEM). On the basis of new microstructure model of braided composites proposed recently, the model of FEM calculation for thermal conductivity of 3-dimennsional and 4-directional braided composites is set up in this paper. The curves of coefficient of effective thermal conductivity versus fiber volume ratio and interior braiding angle are obtained. Furthermore, comparing the results of FEM with the available experimental data, the reasonability and veracity of calculation are confirmed at the same time.
Relationship Between Compression Strength and Its Microstructure of 5 Axial-Braided Composite
Yang; Chaokun; Zhu; Jianxun; Jiang; Yun
2007-01-01
Compression performance of 5-axial braided composites is observed through compression tests.A mixed model of micro-buckling shear with braided tows web is set up to predict compression stress of braided composite through analyzing three broken modes.Using this mixed model,data from tests indicated that the main parameters effecting the compression properties of braided composite are fiber volume fraction,directional angle,axial-tow volume fraction and diameter of tow.Contributing rate of tows is proposed to describe the compression properties of fibre composites.Optimization geometrical structure of braids can optimize composite properties.
Processing and performance of nanophased braided carbon/epoxy composites
A systematic study has been carried out to investigate mechanical properties of 2D nanophased braided carbon/epoxy composites. SC-15 epoxy with three types of braided fabrics: ±45 deg., 0/±45 deg., and 0/±60 deg. was used to fabricate composite laminates using vacuum assisted resin infusion molding (VARIM) process. Low-velocity impact (LVI), ultrasonic nondestructive evaluation (NDE) and 3-point bend flexure studies were carried out on biaxial and triaxial braided samples. Impact parameters like peak load and absorbed energy were calculated. All the LVI tested samples were then subjected to ultrasonic c-scan testing to determine the damage size. From the results it was seen that laminates sustained the impact load without any damage at 10 J, a little damage at 20 J and more damage at 30 J. From the ultrasonic tests it was seen that the biaxial ±45 deg. laminates had lowest damage. Flexural test showed the highest flexural strength and stiffness for triaxial 0 deg./±45 deg. An investigation was also carried out to improve the properties of the braided laminates by introducing Nanomer I-28E nanoclay, a surface modified montmorillonite mineral, into SC-15 epoxy matrix. Different weight percentages of nanoclay were dispersed in SC-15 epoxy. Highest properties were obtained for samples with 1% by weight of nanoclay reinforcement.
Processing and performance of nanophased braided carbon/epoxy composites
Hosur, Mahesh V., E-mail: hosur@tuskegee.ed [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States); Islam, Md. Mazedul; Jeelani, Shaik [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States)
2010-04-15
A systematic study has been carried out to investigate mechanical properties of 2D nanophased braided carbon/epoxy composites. SC-15 epoxy with three types of braided fabrics: +-45 deg., 0/+-45 deg., and 0/+-60 deg. was used to fabricate composite laminates using vacuum assisted resin infusion molding (VARIM) process. Low-velocity impact (LVI), ultrasonic nondestructive evaluation (NDE) and 3-point bend flexure studies were carried out on biaxial and triaxial braided samples. Impact parameters like peak load and absorbed energy were calculated. All the LVI tested samples were then subjected to ultrasonic c-scan testing to determine the damage size. From the results it was seen that laminates sustained the impact load without any damage at 10 J, a little damage at 20 J and more damage at 30 J. From the ultrasonic tests it was seen that the biaxial +-45 deg. laminates had lowest damage. Flexural test showed the highest flexural strength and stiffness for triaxial 0 deg./+-45 deg. An investigation was also carried out to improve the properties of the braided laminates by introducing Nanomer I-28E nanoclay, a surface modified montmorillonite mineral, into SC-15 epoxy matrix. Different weight percentages of nanoclay were dispersed in SC-15 epoxy. Highest properties were obtained for samples with 1% by weight of nanoclay reinforcement.
Higher dimensional unitary braid matrices: Construction, associated structures and entanglements
We construct (2n)2 x (2n)2 unitary braid matrices R-circumflex for n ≥ 2 generalizing the class known for n = 1. A set of (2n) x (2n) matrices (I, J,K,L) are defined. R-circumflex is expressed in terms of their tensor products (such as K x J), leading to a canonical formulation for all n. Complex projectors P± provide a basis for our real, unitary R-circumflex. Baxterization is obtained. Diagonalizations and block- diagonalizations are presented. The loss of braid property when R-circumflex (n > 1) is block-diagonalized in terms of R-circumflex (n = 1) is pointed out and explained. For odd dimension (2n + 1)2 x (2n + 1)2, a previously constructed braid matrix is complexified to obtain unitarity. R-circumflexLL- and R-circumflexTT- algebras, chain Hamiltonians, potentials for factorizable S-matrices, complex non-commutative spaces are all studied briefly in the context of our unitary braid matrices. Turaev construction of link invariants is formulated for our case. We conclude with comments concerning entanglements. (author)
Mechanical Properties of Triaxial Braided Carbon/Epoxy Composites
Bowman, C. L.; Roberts, G. D.; Braley, M. S.; Xie, M.; Booker, M. J.
2003-01-01
In an on-going effort to increase the safety and efficiency of turbine engines, the National Aeronautics and Space Administration is exploring lightweight alternatives to the metal containment structures that currently encase commercial jet engines. Epoxy reinforced with braided carbon fibers is a candidate structural material which may be suitable for an engine case. This paper reports flat-coupon mechanical-property experiments performed to compliment previously reported subcomponent impact testing and analytical simulation of containment structures. Triaxial-braid T700/5208 epoxy and triaxial-braid T700h436 toughened epoxy composites were evaluated. Also, two triaxial-braid architectures (0 degrees plus or minus 60 degrees, and 0 degrees plus or minus 45 degrees) with the M36 resin were evaluated through tension, compression, and shear testing. Tensile behavior was compared between standard straight-sided specimens (ASTM D3039) and bow-tie specimens. Both double-notch shear (ASTM D3846) and Iosepescu (ASTM D5379) tests were performed as well. The M36/O degrees plus or minus 45 degrees configuration yield the best response when measurements were made parallel to the axial tows. Conversely, the M36/0 degrees plus or minus 60 degrees configuration was best when measurements were made perpendicular to the axial tows. The results were used to identify critical properties and to augment the analysis of impact experiments.
Nonlinear Deformation Behavior of New Braided Composites with Six-axis Yarn Orientations
The braiding technology is one of fabrication methods that can produce three-dimensional fiber preforms. Braided composites have many advantages over other two-dimensional composites such as no delamination, high impact and fatigue properties, near-net shape preform, etc. Due to the undulated yarns in the braided preforms, however, their axial stiffness is lower than that of uni-directional or woven composites. To improve the axial stiffness, the longitudinal axial yarns were already introduced along with the braiding axis (five-axis braiding technology). In this study, we developed a new braided structure using six-axis braiding technology. In addition to braiding and longitudinal axial yarns, transverse axial yarn was introduced. New braided composites, so called six-axis braiding composites, were manufactured using ultra high molecular weight polyethylene and epoxy resin and their mechanical properties were characterized. To investigate the mechanical performance of these braided composites according to their manufacturing conditions, a numerical analysis was performed using their unit-cell modeling and finite element analysis. In the analysis the nonlinear deformation behavior will be included.
Chiral braided and woven composites: design, fabrication, and electromagnetic characterization
Wheeland, Sara; Bayatpur, Farhad; Amirkhizi, Alireza V.; Nemat-Nasser, Sia
2011-04-01
This work presents a new chiral composite composed of copper wires braided with Kevlar and nylon to form conductive coils integrated among structural fiber. To create a fabric, these braids were woven with plain Kevlar fiber. This yielded a composite with all coils possessing the same handedness, producing a chiral material. The electromagnetic response of this fabric was first simulated using a finite element full-wave simulation. For the electromagnetic measurement, the sample was placed between two lens-horn antennas connected to a Vector Network Analyzer. The frequency response of the sample was scanned between 5.5 and 8GHz. The measured scattering parameters were then compared to those of the simulated model. The measured parameters agreed well with the simulation results, showing a considerable chirality within the measured frequency band. The new composite combines the strength and durability of traditional composites with an electromagnetic design to create a multifunctional material.
Changes of the hydrodynamic conditions in the braided river
Karol PLESIŃSKI
2014-11-01
Full Text Available The paper focuses on the understanding of the basic hydrodynamic conditions along the braided gravel-bed river. The measuring cross-section was located in the Ochotnica River, where its braided channel development was observed. Investigations take place from 2003 up to 2014. Measurements were performed for selected characteristic points. The study focused mostly on the measurements of water velocities under different flow conditions, and next on finding basic hydraulic parameters of flow: shear velocity, shear stresses, Reynolds number, Froude number. In addition, the gravel material from the river bed was examined, in order to find sedimentological characteristics of it.
Introduction to complex reflection groups and their braid groups
Broué, Michel
2010-01-01
Weyl groups are particular cases of complex reflection groups, i.e. finite subgroups of GLr(C) generated by (pseudo)reflections. These are groups whose polynomial ring of invariants is a polynomial algebra. It has recently been discovered that complex reflection groups play a key role in the theory of finite reductive groups, giving rise as they do to braid groups and generalized Hecke algebras which govern the representation theory of finite reductive groups. It is now also broadly agreed upon that many of the known properties of Weyl groups can be generalized to complex reflection groups. The purpose of this work is to present a fairly extensive treatment of many basic properties of complex reflection groups (characterization, Steinberg theorem, Gutkin-Opdam matrices, Solomon theorem and applications, etc.) including the basic findings of Springer theory on eigenspaces. In doing so, we also introduce basic definitions and properties of the associated braid groups, as well as a quick introduction to Bessis' ...
Electron beam processing of carbon fibre reinforced braided composites
The possibility of producing a new type carbon fibre reinforced composite profile has been examined by applying braiding, a well-known process of textile technology. Pipe and hollow profile composite products can be manufactured this way by applying Electron Beam curing. The fabric-like braided reinforcing structure was manufactured out of Hungarian-made carbon fibre roving of 48,000 elementary fibres. The mutual irradiation of the system impregnated with epoxy-acrylate oligomer by 8 MeV EB resulted in better mechanical properties then conventional chemical curing. Owing to its low density and high specific strength this new composite product can possibly be applied in dynamically loaded structures e.g. in the automotive industry
Braids as a representation space of SU(5)
Cartin, Daniel
2015-01-01
The Standard Model of particle physics provides very accurate predictions of phenomena occurring at the sub-atomic level, but the reason for the choice of symmetry group and the large number of particles considered elementary, is still unknown. Along the lines of previous preon models positing a substructure to explain these aspects, Bilson-Thompson showed how the first family of elementary particles is realized as the crossings of braids made of three strands, with charges resulting from twi...
Electron beam processing of carbon fibre reinforced braided composites beams
Complete text of publication follows. In this paper the possibility of producing a new type carbon fiber reinforced composite is examined by applying braiding, a well-known process of textile technology. The appearance of the new Hungarian carbon fiber with excellent mechanical properties in the market enables the development of newer type carbon fiber reinforced composites in the continuously widening range of engineering applications. Advanced hollow profiles, pipes and other composite products can be manufactured in continuous operation. A new way of composite production of this kind is the manufacturing of reinforcing structure by braiding technology producing a composite with sufficient mechanical properties from this cross directional fabric-like textile structure by impregnation. This manufacturing process can complete the variety of hollow products serving the same purpose as pultrusion or filament winding. This way a profile type framework element with a hollow cross section is manufactured having favorable mechanical properties. Owing to its small mass and high specific strength this product can be applied in dynamically loaded structures e.g. in the automotive industry. For crosslinking of the matrix the method of high-speed electron beam curing has been examined in order to reach continuous operation. The field of use and application of carbon fiber braided structures has a great chance especially in machine engineering and in the automotive industry. The main reason for this is that braiding processes are capable of producing structures having good mechanical properties at a low processing price. The mass of the composite load-bearing structure produced this way is one fifth of the steel product having similar geometry, and its specific mechanical properties are nearly as good as that of the most commonly applied semiproduct and structural component, the welded steel profile
Knots, Braids and Hedgehogs from the Eikonal Equation
Wereszczynski, A.
2005-01-01
The complex eikonal equation in the three space dimensions is considered. We show that apart from the recently found torus knots this equation can also generate other topological configurations with a non-trivial value of the $\\pi_2(S^2)$ index: braided open strings as well as hedgehogs. In particular, cylindric strings i.e. string solutions located on a cylinder with a constant radius are found. Moreover, solutions describing strings lying on an arbitrary surface topologically equivalent to ...
Duality Theorem and Drinfeld Double in Braided Tensor Categories
Shouchuan Zhang
2003-01-01
Let (C, ( ), I, C) be a braided tensor category. For a finite Hopf algebra H in c with CH, H = C-1 H,H, the duality theorem is shown, i.e.,(R#H)#H^* ≌ R( ) (H-( )H^*)as algebras in C. Also, it is proved that the Drinfeld double (D(H), [b]) is a quasi-triangular Hopf algebra in c.
Hurwitz equivalence of braid monodromies and extremal elliptic surfaces
Degtyarev, Alex
2009-01-01
We discuss the equivalence between the categories of certain ribbon graphs and subgroups of the modular group $\\Gamma$ and use it to construct exponentially large families of not Hurwitz equivalent simple braid monodromy factorizations of the same element. As an application, we also obtain exponentially large families of {\\it topologically} distinct algebraic objects such as extremal elliptic surfaces, real trigonal curves, and real elliptic surfaces.
Development of braided drug-loaded nanofiber sutures
The objectives of this work are twofold. Firstly, while most work on electrospinning is limited to the development of only functional materials, a structural application of electrospun nanofibers is explored. Secondly, a drug-loaded tissue suture is fabricated and its various properties are characterized. Braided drug-loaded nanofiber sutures are obtained by combining an electrospinning process with a braiding technique followed by a coating procedure. Two different electrospinning techniques, i.e. blend and coaxial electrospinning, to incorporate a model drug cefotaxime sodium (CFX-Na) into poly(L-lactic acid) (PLLA) nanofibers have been applied and compared with each other. Properties of the braided drug-loaded sutures are characterized through a variety of methods including SEM, TEM and tensile testing. The results show that the nanofibers had a preferable micromorphology. The drug was incorporated into the polymer nanofibers homogeneously, with no cross-linking. The nanofibers maintained their fibrous structures. An in vitro release study indicates that the drug-loaded nanofibers fabricated by blend electrospinning and coaxial electrospinning had a different drug release behavior. An inhibition zone experiment shows that both sutures obtained from the nanofibers of the different electrospinning techniques had favorable antibacterial properties. The drug-loaded sutures had preferable histological compatibility performance compared with commercial silk sutures in an in vivo comparative study.
Characterization of Triaxial Braided Composite Material Properties for Impact Simulation
Roberts, Gary D.; Goldberg, Robert K.; Biniendak, Wieslaw K.; Arnold, William A.; Littell, Justin D.; Kohlman, Lee W.
2009-01-01
The reliability of impact simulations for aircraft components made with triaxial braided carbon fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Improvements to standard quasi-static test methods are needed to account for the large unit cell size and localized damage within the unit cell. The deformation and damage of a triaxial braided composite material was examined using standard quasi-static in-plane tension, compression, and shear tests. Some modifications to standard test specimen geometries are suggested, and methods for measuring the local strain at the onset of failure within the braid unit cell are presented. Deformation and damage at higher strain rates is examined using ballistic impact tests on 61- by 61- by 3.2-mm (24- by 24- by 0.125-in.) composite panels. Digital image correlation techniques were used to examine full-field deformation and damage during both quasi-static and impact tests. An impact analysis method is presented that utilizes both local and global deformation and failure information from the quasi-static tests as input for impact simulations. Improvements that are needed in test and analysis methods for better predictive capability are examined.
Simulation of braiding anyons using matrix product states
Ayeni, Babatunde M.; Singh, Sukhwinder; Pfeifer, Robert N. C.; Brennen, Gavin K.
2016-04-01
Anyons exist as pointlike particles in two dimensions and carry braid statistics, which enable interactions that are independent of the distance between the particles. Except for a relatively few number of models, which are analytically tractable, much of the physics of anyons remains still unexplored. In this paper, we show how U(1) symmetry can be combined with the previously proposed anyonic matrix product states to simulate ground states and dynamics of anyonic systems on a lattice at any rational particle number density. We provide proof of principle by studying itinerant anyons on a one-dimensional chain where no natural notion of braiding arises and also on a two-leg ladder where the anyons hop between sites and possibly braid. We compare the result of the ground-state energies of Fibonacci anyons against hardcore bosons and spinless fermions. In addition, we report the entanglement entropies of the ground states of interacting Fibonacci anyons on a fully filled two-leg ladder at different interaction strength, identifying gapped or gapless points in the parameter space. As an outlook, our approach can also prove useful in studying the time dynamics of a finite number of non-Abelian anyons on a finite two-dimensional lattice.
Development of braided drug-loaded nanofiber sutures
Hu Wen [School of Materials Science and Engineering, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Huang Zhengming [School of Aerospace Engineering and Applied Mechanics, Tongji University, 1239 Siping Road, Shanghai 200092 (China); Liu Xiangyang, E-mail: huangzm@tongji.edu.cn [Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 (Singapore)
2010-08-06
The objectives of this work are twofold. Firstly, while most work on electrospinning is limited to the development of only functional materials, a structural application of electrospun nanofibers is explored. Secondly, a drug-loaded tissue suture is fabricated and its various properties are characterized. Braided drug-loaded nanofiber sutures are obtained by combining an electrospinning process with a braiding technique followed by a coating procedure. Two different electrospinning techniques, i.e. blend and coaxial electrospinning, to incorporate a model drug cefotaxime sodium (CFX-Na) into poly(L-lactic acid) (PLLA) nanofibers have been applied and compared with each other. Properties of the braided drug-loaded sutures are characterized through a variety of methods including SEM, TEM and tensile testing. The results show that the nanofibers had a preferable micromorphology. The drug was incorporated into the polymer nanofibers homogeneously, with no cross-linking. The nanofibers maintained their fibrous structures. An in vitro release study indicates that the drug-loaded nanofibers fabricated by blend electrospinning and coaxial electrospinning had a different drug release behavior. An inhibition zone experiment shows that both sutures obtained from the nanofibers of the different electrospinning techniques had favorable antibacterial properties. The drug-loaded sutures had preferable histological compatibility performance compared with commercial silk sutures in an in vivo comparative study.
Symmetry-protected non-Abelian braiding of Majorana Kramers' pairs
Gao, Pin; Liu, Xiong-Jun
2016-01-01
We show the complete symmetry conditions for non-Abelian braiding of Majorana Kramers' pairs (MKPs) in a time-reversal (TR) invariant topological superconductor. By introducing an effective Hamiltonian approach to describe the braiding of MKPs, we show that the non-Abelian braiding is protected when the effective Hamiltonian exhibits a new TR like anti-unitary symmetry, which is satisfied if the system is free of dynamical noise. Further, even the dynamical noise may not cause error in braidi...
DETERMINATION OF INTERNAL STRAIN IN 3-D BRAIDED COMPOSITES USING OPTIC FIBER STRAIN SENSORS
YuanShenfang; HuangRui; LiXianghua; LiuXiaohui
2004-01-01
A reliable understanding of the properties of 3-D braided composites is of primary importance for proper utilization of these materials. A new method is introduced to study the mechanical performance of braided composite materials using embedded optic fiber sensors. Experimental research is performed to devise a method of incorporating optic fibers into a 3-D braided composite structure. The efficacy of this new testing method is evaluated on two counts. First,the optical performance of optic fibers is studied before and after incorporated into 3-D braided composites, as well as after completion of the manufacturing process for 3-D braided composites,to validate the ability of the optic fiber to survive the manufacturing process. On the other hand,the influence of incorporated optic fiber on the original braided composite is also researched by tension and compression experiments. Second, two kinds of optic fiber sensors are co-embedded into 3-D braided composites to evaluate their respective ability to measure the internal strain.Experimental results show that multiple optic fiber sensors can be co-braided into 3-D braided composites to determine their internal strain which is difficult to be fulfilled by other current existing methods.
Braiding a Flock: Winding Statistics of Interacting Flying Spins
Caussin, Jean-Baptiste; Bartolo, Denis
2015-06-01
When animal groups move coherently in the form of a flock, their trajectories are not all parallel, the individuals exchange their position in the group. In this Letter, we introduce a measure of this mixing dynamics, which we quantify as the winding of the braid formed from the particle trajectories. Building on a paradigmatic flocking model we numerically and theoretically explain the winding statistics and show that it is predominantly set by the global twist of the trajectories as a consequence of a spontaneous symmetry breaking.
Braided embeddings of contact 3-manifolds in the standard contact 5-sphere
Etnyre, John B.; Furukawa, Ryo
2015-01-01
In this paper we study embeddings of contact manifolds using braidings of one manifold about another. In particular we show how to embed many contact 3-manifolds into the standard contact 5-sphere. We also show how to obstruct braidings of one manifold about another using contact geometry.
Tablet-woven and tabby-woven braids from the Czech late medieval archaeological findings
Březinová, Helena
2010-01-01
Roč. 23, - (2010), s. 47-51. ISSN 0860-0007 Institutional research plan: CEZ:AV0Z80020508 Keywords : textile fragments * tablet-woven braids * tabby-woven braids * late medieval Subject RIV: AC - Archeology, Anthropology, Ethnology
On the cohomology of spaces of links and braids via configuration space integrals
Volic, Ismar
2010-01-01
We study the cohomology of spaces of string links and braids in $\\mathbb{R}^n$ for $n\\geq 3$ using configuration space integrals. For $n>3$, these integrals give a chain map from certain diagram complexes to the deRham algebra of differential forms on these spaces. For $n=3$, they produce all finite type invariants of string links and braids.
Complete braided adsorbent for marine testing to demonstrate 3g-U/kg-adsorbent
Janke, Chris [ORNL; Yatsandra, Oyola [ORNL; Mayes, Richard [ORNL; none,; Gill, Gary [PNNL; Li-Jung, Kuo [PNNL; Wood, Jordana [PNNL; Sadananda, Das [ORNL
2014-04-30
ORNL has manufactured four braided adsorbents that successfully demonstrated uranium adsorption capacities ranging from 3.0-3.6 g-U/kg-adsorbent in marine testing at PNNL. Four new braided and leno woven fabric adsorbents have also been prepared by ORNL and are currently undergoing marine testing at PNNL.
Theoretical studies on conformation comparison of braid-like and triplex DNA
Yang, Linjing; Bai, Chunli; Liu, Ciquan; Shi, Xiufan; Lee, Imshik
1999-03-01
Based on the experimental data of scanning tunneling microscopy (STM), models of three-stranded braid-like DNAs composed by three kinds of base triplets AAA, TAT and GCA were constructed. We investigated the braid-like DNAs and their comparative triplex DNAs using a molecular mechanics method. The three strands of braid-like DNAs are proven equivalent, while those of triplex DNAs are not. The conformational energies for braid-like DNAs were found to be higher than that for triplex DNAs. Each period in one strand of braid-like DNA has 18 nucleotides, half of which are right-handed, while the other half are left-handed. Additional discussions concerning sugar puckering modes and the H-bonds are also included.
Structure Design of the 3-D Braided Composite Based on a Hybrid Optimization Algorithm
Zhang, Ke
Three-dimensional braided composite has the better designable characteristic. Whereas wide application of hollow-rectangular-section three-dimensional braided composite in engineering, optimization design of the three-dimensional braided composite made by 4-step method were introduced. Firstly, the stiffness and damping characteristic analysis of the composite is presented. Then, the mathematical models for structure design of the three-dimensional braided composite were established. The objective functions are based on the specific damping capacity and stiffness of the composite. The design variables are the braiding parameters of the composites and sectional geometrical size of the composite. The optimization problem is solved by using ant colony optimization (ACO), contenting the determinate restriction. The results of numeral examples show that the better damping and stiffness characteristic could be obtained. The method proposed here is useful for the structure design of the kind of member and its engineering application.
A pseudo genetic model of coarse braided-river deposits
Pirot, Guillaume; Straubhaar, Julien; Renard, Philippe
2015-12-01
A new method is proposed to produce three-dimensional facies models of braided-river aquifers based on analog data. The algorithm consists of two steps. The first step involves building the main geological units. The production of the principal inner structures of the aquifer is achieved by stacking Multiple-Point-Statistics simulations of successive topographies, thus mimicking the major successive flooding events responsible for the erosion and deposition of sediments. The second step of the algorithm consists of generating fine scale heterogeneity within the main geological units. These smaller-scale structures are generated by mimicking the trough-filling process occurring in braided rivers; the imitation of the physical processes relies on the local topography and on a local approximation of the flow. This produces realistic cross-stratified sediments, comparable to what can be observed in outcrops. The three main input parameters of the algorithm offer control over the proportions, the continuity and the dimensions of the deposits. Calibration of these parameters does not require invasive field measurements and can rely partly on analog data.
High temperature braided rope seals for static sealing applications
Adams, Michael L.; Olsen, Andrew; Darolia, Ram; Steinetz, Bruce M.; Bartolotta, Paul A.
1996-01-01
Achieving efficiency and performance goals of advanced aircraft and industrial systems are leading designers to implement high temperature materials such as ceramics and intermetallics. Generally these advanced materials are applied selectively in the highest temperature sections of the engine system including the combustor and high pressure turbine, amongst others. Thermal strains that result in attaching the low expansion-rate components to high expansion rate superalloy structures can cause significant life reduction in the components. Seals are being designed to both seal and to serve as compliant mounts allowing for relative thermal growths between high temperature but brittle primary structures and the surrounding support structures. Designers require high temperature, low-leakage, compliant seals to mitigate thermal stresses and control parasitic and cooling airflow between structures. NASA is developing high temperature braided rope seals in a variety of configurations to help solve these problems. This paper will describe the types of seals being developed, describe unique test techniques used to assess seal performance, and present leakage flow data under representative pressure, temperature and scrubbing conditions. Feasibility of the braided rope seals for both an industrial tube seal and a turbine vane seal application is also demonstrated.
Braided affine geometry and q-analogs of wave operators
The main goal of this review is to compare different approaches to constructing the geometry associated with a Hecke type braiding (in particular, with that related to the quantum group Uq(sl(n))). We place emphasis on the affine braided geometry related to the so-called reflection equation algebra (REA). All objects of such a type of geometry are defined in the spirit of affine algebraic geometry via polynomial relations on generators. We begin by comparing the Poisson counterparts of 'quantum varieties' and describe different approaches to their quantization. Also, we exhibit two approaches to introducing q-analogs of vector bundles and defining the Chern-Connes index for them on quantum spheres. In accordance with the Serre-Swan approach, the q-vector bundles are treated as finitely generated projective modules over the corresponding quantum algebras. Besides, we describe the basic properties of the REA used in this construction and compare different ways of defining q-analogs of partial derivatives and differentials on the REA and algebras close to them. In particular, we present a way of introducing a q-differential calculus via Koszul type complexes. The elements of the q-calculus are applied to defining q-analogs of some relativistic wave operators. (topical review)
Shinyama, Y., E-mail: y083818@edu.imc.tut.ac.jp [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Yamaji, T.; Hatsukade, Y. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Takai, Y.; Aly-Hassan, M.S.; Nakai, A.; Hamada, H. [Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Tanaka, S. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)
2011-11-15
We applied a current-injection-based NDE method using a HTS-SQUID gradiometer to a braided CFRP with artificial cracks. Current distributions in the braided CFRP were estimated from measured field gradient distributions. A small crack, in which a few carbon-fiber bundles were cut, was well detected from the current distributions. A cross-section of the CFRP showed that a density of the bundles at edges is higher than the other part. The experimental results demonstrated the capability of the method to detect sub-mm cracks. Braided carbon fiber reinforced plastics (CFRPs) are one of multifunctional materials with superior properties such as mechanical strength to normal CFRPs since the braided CFRPs have continuous fiber bundles. In this paper, we applied the current-injection-based nondestructive evaluation (NDE) method using a HTS-SQUID gradiometer to the braided CFRP for the detection of the breakage of the bundles. We prepared planar braided CFRP samples with and without artificial cracks of 1 and 2 mm lengths, and measured the current density distribution above the samples using the NDE method. In the measurement results, not only a few completely-cut bundles but also the additional partially-cut bundles were detected from decrease in the measured current density along the cut bundle around the cracks. From these results, we showed that it is possible to inspect a few partially-cut bundles in the braided CFRPs by the NDE method.
Alterations in braided rivers' morphology: a typology for Curvature Subcarpathians (Romania)
Ioana-Toroimac, Gabriela; Zaharia, Liliana; Ciobotaru, Nicu
2015-04-01
The morphology of braided rivers was altered by human pressures in the last century in Europe. Rivers from Curvature Subcarpathians have the highest sediment charges in Romania, therefore it seems relevant to evaluate the status of their braided sectors. Therefore, the aim of this work is to carry out an inventory of river morphology alterations suffered by braided rivers in Curvature Subcarpathians and to establish a typology based on indicators for channel adjustments and artificiality. For channel adjustments, we calculated the length of the braided sectors, the width of the active-channels and the length of banks covered by a riparian forest for 1900-2011 interval, in GIS. For artificiality, we counted dams, weirs, bridges, as well as artificial banks length for 2011 time horizon. The results indicate a diminishing braiding activity: all the rivers narrowed their braided active-channel (30-70% of the mean width); the majority suffered fluvial metamorphosis, transforming partially into single channels (0-75% of the braided sector length in 1900); artificial banks vary from 0 to 40% of the initial braided sector. We distinguished three main types of braided rivers based on morphological alterations. Type 1 includes rivers with human interventions and important braiding retraction, both upstream and downstream; a sub-type characterises by riparian forest lining the downstream metamorphosed reach; most rivers are in the south-western part of the studied region; the most demonstrative examples are Prahova and Ialomiţa rivers. Type 2 corresponds to rivers with important retraction upstream, without important values of artificiality; most demonstrative is Râmna River. Type 3 regroups rivers with a low level of channel adjustments and artificiality; actually, they had and still have the highest braiding activity in the studied region; they are located in the north-eastern part; typical examples are Putna and Şuşiţa rivers. As a discussion, the variations of active
Hom-Hopf group coalgebras and braided T-categories obtained from Hom-Hopf algebras
You, Miman; Zhou, Nan; Wang, Shuanhong
2015-11-01
The main aim of this paper is to provide new examples of braided T-categories in the sense of Turaev [Arabian J. Sci. Eng., Sect. C 33(2C), 483-503 (2008)]. For this purpose, we first introduce a class of new twisted Yetter-Drinfeld modules categories. Then, we construct a new braided T-category, generalizing the main constructions by Panaite and Staic [Isr. J. Math. 158, 349-366 (2007)]. Finally, we show that the new braided T-category in some conditions coincides with the representations of a certain Hom-Hopf group-coalgebra that we construct.
Factorization of differential expansion for antiparallel double-braid knots
Morozov, A
2016-01-01
Continuing the quest for exclusive Racah matrices, which are needed for evaluation of colored arborescent-knot polynomials in Chern-Simons theory, we suggest to extract them from a new kind of a double-evolution -- that of the antiparallel double-braids, which is a simple two-parametric family of two-bridge knots, generalizing the one-parametric family of twist knots. In the case of rectangular representations $R=[r^s]$ we found an evidence that the corresponding differential expansion miraculously factorizes and can be obtained from that for the twist knots. This reduces the problem of rectangular exclusive Racah to constructing the answers for just a few twist knots. We develop a recent conjecture on the structure of differential expansion for the simplest members of this family -- the trefoil and the figure-eight knot,-- but manage to guess the full answer only for contributions of single-floor pyramids. One step still remains to be done.
S-duality wall of SQCD from Toda braiding
Floch, Bruno Le
2015-01-01
S-duality domain walls couple quarks of a four-dimensional $N=2$ theory on one side of the wall to monopoles on the other side. This paper describes the S-duality wall of SU(N) SQCD with 2N hypermultiplets in terms of fields on the defect, namely three-dimensional $N=2$ SQCD with gauge group U(N-1) and 2N fundamental and 2N antifundamental chiral multiplets. The theory is found through the AGT correspondence by computing the braiding kernel of two semi-degenerate vertex operators in the Toda CFT. This three-dimensional theory is a limit of a USp(2N-2) gauge theory whose four-dimensional lift is self-dual, a situation reminiscent of how the theory T[G] on the S-duality wall of $N=4$ super Yang-Mills is self-mirror.
Systematically Generated Two-Qubit Braids for Fibonacci Anyons
Zeuch, Daniel; Carnahan, Caitlin; Bonesteel, N. E.
We show how two-qubit Fibonacci anyon braids can be generated using a simple iterative procedure which, in contrast to previous methods, does not require brute force search. Our construction is closely related to that of, but with the new feature that it can be used for three-anyon qubits as well as four-anyon qubits. The iterative procedure we use, which was introduced by Reichardt, generates sequences of three-anyon weaves that asymptotically conserve the total charge of two of the three anyons, without control over the corresponding phase factors. The resulting two-qubit gates are independent of these factors and their length grows as log 1/ ɛ, where ɛ is the error, which is asymptotically better than the Solovay-Kitaev method.
Yarn carrier apparatus for braiding machines and the like
El-Shiekh, Aly (Inventor); Li, Wei (Inventor); Hammad, Mohamed (Inventor)
1992-01-01
A yarn carrier apparatus particularly suited for use in braiding machinery or the like due to its capability of continuous yarn feeding and retraction of long lengths of yarn. The yarn carrier apparatus comprises a yarn supply spool which is rotatably mounted within the housing, a spring motor also mounted within the housing and operatively connected to the yarn supply spool through a mechanical transmission assembly which is adapted to multiply rotational movement between the first element of the gear assembly operatively connected to the spring motor and the final element of the gear assembly operatively connected to the yarn supply spool. The spring motor is adapted to tension the yarn during both feeding and retraction thereof, and it is further adapted to periodically rotatably slip within the housing and partially unwind so as to allow for continuous withdrawal of a long length of yarn without the spring motor becoming fully wound and preventing further yarn retraction.
Two dimensional hydrodynamic modeling of a high latitude braided river
Humphries, E.; Pavelsky, T.; Bates, P. D.
2014-12-01
Rivers are a fundamental resource to physical, ecologic and human systems, yet quantification of river flow in high-latitude environments remains limited due to the prevalence of complex morphologies, remote locations and sparse in situ monitoring equipment. Advances in hydrodynamic modeling and remote sensing technology allow us to address questions such as: How well can two-dimensional models simulate a flood wave in a highly 3-dimensional braided river environment, and how does the structure of such a flood wave differ from flow down a similar-sized single-channel river? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate flood waves, discharge, water surface height, and velocity measurements over a ~70 km reach of the Tanana River in Alaska. In order to use LISFLOOD-FP a digital elevation model (DEM) fused with detailed bathymetric data is required. During summer 2013, we surveyed 220,000 bathymetric points along the study reach using an echo sounder system connected to a high-precision GPS unit. The measurements are interpolated to a smooth bathymetric surface, using Topo to Raster interpolation, and combined with an existing five meter DEM (Alaska IfSAR) to create a seamless river terrain model. Flood waves are simulated using varying complexities in model solvers, then compared to gauge records and water logger data to assess major sources of model uncertainty. Velocity and flow direction maps are also assessed and quantified for detailed analysis of braided channel flow. The most accurate model output occurs with using the full two-dimensional model structure, and major inaccuracies appear to be related to DEM quality and roughness values. Future work will intercompare model outputs with extensive ground measurements and new data from AirSWOT, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.
无
2008-01-01
Based on unit cell model,the 3D 4-directional braided composites can be simplified as unidirectional composites with different local axial coordinate system and the compliance matrix of unidirectional composites can be defined utilizing the bridge model.The total stiffness matrix of braided composites can be obtained by the volume average stiffness of unidirectional composites with different local axial coordinate system and the engineering elastic constants of braided composites were computed further.Based on the iso-strain assumption and the bridge model,the stress distribution of fiber bundle and matrix of different unidirectional composites can be determined and the tensile strength of 3D 4-directional braided composites was predicted by means of the Hoffman's failure criterion for the fiber bundle and Mises' failure criterion for the matrix.
Software for Computing, Archiving, and Querying Semisimple Braided Monoidal Category Data
2016-08-04
This software package collects various open source and freely available codes and algorithms to compute and archive the categorical data for certain semisimple braided monoidal categories. In particular, it computes the data for of group theoretical categories for academic research.
Evaluation of Braided Stiffener Concepts for Transport Aircraft Wing Structure Applications
Deaton, Jerry W.; Dexter, H. Benson (Editor); Markus, Alan; Rohwer, Kim
1995-01-01
Braided composite materials have potential for application in aircraft structures. Stiffeners, wing spars, floor beams, and fuselage frames are examples where braided composites could find application if cost effective processing and damage requirements are met. Braiding is an automated process for obtaining near-net shape preforms for fabrication of components for structural applications. Previous test results on braided composite materials obtained at NASA Langley indicate that damage tolerance requirements can be met for some applications. In addition, the braiding industry is taking steps to increase the material through-put to be more competitive with other preform fabrication processes. Data are presented on the compressive behavior of three braided stiffener preform fabric constructions as determined from individual stiffener crippling test and three stiffener wide panel tests. Stiffener and panel fabrication are described and compression data presented for specimens tested with and without impact damage. In addition, data are also presented on the compressive behavior of the stitched stiffener preform construction currently being used by McDonnell Douglas Aerospace in the NASA ACT wing development program.
Braided Multi-Electrode Probes (BMEPs) for Neural Interfaces
Kim, Tae Gyo
Although clinical use of invasive neural interfaces is very limited, due to safety and reliability concerns, the potential benefits of their use in brain machine interfaces (BMIs) seem promising and so they have been widely used in the research field. Microelectrodes as invasive neural interfaces are the core tool to record neural activities and their failure is a critical issue for BMI systems. Possible sources of this failure are neural tissue motions and their interactions with stiff electrode arrays or probes fixed to the skull. To overcome these tissue motion problems, we have developed novel braided multi-electrode probes (BMEPs). By interweaving ultra-fine wires into a tubular braid structure, we obtained a highly flexible multi-electrode probe. In this thesis we described BMEP designs and how to fabricate BMEPs, and explore experiments to show the advantages of BMEPs through a mechanical compliance comparison and a chronic immunohistological comparison with single 50microm nichrome wires used as a reference electrode type. Results from the mechanical compliance test showed that the bodies of BMEPs have 4 to 21 times higher compliance than the single 50microm wire and the tethers of BMEPs were 6 to 96 times higher compliance, depending on combinations of the wire size (9.6microm or 12.7microm), the wire numbers (12 or 24), and the length of tether (3, 5 or 10 mm). Results from the immunohistological comparison showed that both BMEPs and 50microm wires anchored to the skull caused stronger tissue reactions than unanchored BMEPs and 50microm wires, and 50microm wires caused stronger tissue reactions than BMEPs. In in-vivo tests with BMEPs, we succeeded in chronic recordings from the spinal cord of freely jumping frogs and in acute recordings from the spinal cord of decerebrate rats during air stepping which was evoked by mesencephalic locomotor region (MLR) stimulation. This technology may provide a stable and reliable neural interface to spinal cord
Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites
Goldberg, Robert K.; Littell, Justin D.; Binienda, Wieslaw K.
2010-01-01
In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process. A new analytical approach models triaxially braided carbon fiber composite materials within the environment of a transient dynamic finite-element code, specifically the commercially available transient dynamic finite-element code LS-DYNA. The geometry of the braided composites is approximated by a series of parallel laminated composites. The composite is modeled by using shell finite elements. The material property data are computed by examining test data from static tests on braided composites, where optical strain measurement techniques are used to examine the local strain variations within the material. These local strain data from the braided composite tests are used along with a judicious application of composite micromechanics- based methods to compute the stiffness properties of an equivalent unidirectional laminated composite required for the shell elements. The local strain data from the braided composite tests are also applied to back out strength and failure properties of the equivalent unidirectional composite. The properties utilized are geared towards the application of a continuum damage mechanics-based composite constitutive model available within LS-DYNA. The developed model can be applied to conduct impact simulations of structures composed of triaxially braided composites. The advantage of this technology is that it facilitates the analysis of the deformation and damage response of a triaxially braided polymer matrix
Lee, D J
2013-01-01
This is a technical document that outlines a calculation of an electrostatic interaction energy between two rods, with charge helices on them, forming a braid. We deal here with screened electrostatics. A general braid geometry is considered, though to obtain local expressions for the energy the curvature of the rods is considered to be small. Further approximations are made for small tilt angle. This is a generalization of the calculations given in the supplemental material of [R. Cortini et Al, Biophys. J. 101 875 (2011)] for a straight symmetric braid structure, using a different method of calculation where the braid geometry does not need to be supposed a priori.
Turkana Grits - a Cretaceous braided alluvial system in northern Kenya
Handford, C.R.
1987-05-01
Rather spotty but excellent exposures of the Cretaceous-age Turkana Grits occur near the western shore of Lake Turkana, northern Kenya. These very coarse to pebbly arkosic sandstones and sandy conglomerates were derived from and rest unconformably upon Precambrian metamorphic basement; they are overlain by late Tertiary basaltic flows that comprise much of the volcanics in the East African Rift Zone. The formation ranges up to 2000 ft thick in the Laburr Range. Several outcrops contain sauropod, crocodile, and tortoise remains as well as abundant trunks of petrified wood (Dryoxylon). Five major facies make up the Turkana Grits and record a major episode of continental fluvial deposition in basins flanked by Precambrian basement. Facies 1 is crudely stratified, cobble and boulder conglomerate (clast-supported); Facies 2 is crudely stratified pebble-cobble conglomerate and pebbly sandstone; Facies 3 is trough cross-bedded, very coarse sandstones containing fossils wood and vertebrate remains; Facies 4 is crudely stratified to massive sandstones with ironstone nodules; and Facies 5 is red, purple, and gray mudstone and mud shale with carbonate nodules. Facies 1 through 3 record deposition in proximal to medial braided-stream channel, longitudinal bar and dune complexes. Facies 4 is a lowland, hydromorphic paleosol, and Facies 5 represents overbank and abandoned channel-fill sedimentation in an alluvial plain.
TRIGGER MECHANISM OF SOLAR SUBFLARES IN A BRAIDED CORONAL MAGNETIC STRUCTURE
Tiwari, Sanjiv K.; Alexander, Caroline E.; Winebarger, Amy R.; Moore, Ronald L., E-mail: sanjiv.k.tiwari@nasa.gov [NASA Marshall Space Flight Center, Mail Code ZP 13, Huntsville, AL 35812 (United States)
2014-11-01
Fine-scale braiding of coronal magnetic loops by continuous footpoint motions may power coronal heating via nanoflares, which are spontaneous fine-scale bursts of internal reconnection. An initial nanoflare may trigger an avalanche of reconnection of the braids, making a microflare or larger subflare. In contrast to this internal triggering of subflares, we observe external triggering of subflares in a braided coronal magnetic field observed by the High-resolution Coronal Imager (Hi-C). We track the development of these subflares using 12 s cadence images acquired by SDO/AIA in 1600, 193, 94 Å, and registered magnetograms of SDO/HMI, over four hours centered on the Hi-C observing time. These data show numerous recurring small-scale brightenings in transition-region emission happening on polarity inversion lines where flux cancellation is occurring. We present in detail an example of an apparent burst of reconnection of two loops in the transition region under the braided coronal field which is appropriate for releasing a short reconnected loop downward and a longer reconnected loop upward. The short loop presumably submerges into the photosphere, participating in observed flux cancellation. A subflare in the overlying braided magnetic field is apparently triggered by the disturbance of the braided field by the reconnection-released upward loop. At least 10 subflares observed in this braided structure appear to be triggered this way. How common this external trigger mechanism for coronal subflares is in other active regions, and how important it is for coronal heating in general, remain to be seen.
Loop braiding statistics in exactly soluble three-dimensional lattice models
Lin, Chien-Hung; Levin, Michael
2015-07-01
We construct two exactly soluble lattice spin models that demonstrate the importance of three-loop braiding statistics for the classification of three-dimensional gapped quantum phases. The two models are superficially similar: both are gapped and both support particlelike and looplike excitations similar to those of charges and vortex lines in a Z2×Z2 gauge theory. Furthermore, in both models the particle excitations are bosons, and in both models the particle and loop excitations have the same mutual braiding statistics. The difference between the two models is only apparent when one considers the recently proposed three-loop braiding process in which one loop is braided around another while both are linked to a third loop. We find that the statistical phase associated with this process is different in the two models, thus proving that they belong to two distinct phases. An important feature of this work is that we derive our results using a concrete approach: we construct string and membrane operators that create and move the particle and loop excitations and then we extract the braiding statistics from the commutation algebra of these operators.
Cater, Christopher; Xiao, Xinran; Goldberg, Robert K.; Kohlman, Lee W.
2015-01-01
A combined experimental and analytical approach was performed for characterizing and modeling triaxially braided composites with a modified subcell modeling strategy. Tensile coupon tests were conducted on a [0deg/60deg/-60deg] braided composite at angles of 0deg, 30deg, 45deg, 60deg and 90deg relative to the axial tow of the braid. It was found that measured coupon strength varied significantly with the angle of the applied load and each coupon direction exhibited unique final failures. The subcell modeling approach implemented into the finite element software LS-DYNA was used to simulate the various tensile coupon test angles. The modeling approach was successful in predicting both the coupon strength and reported failure mode for the 0deg, 30deg and 60deg loading directions. The model over-predicted the strength in the 90deg direction; however, the experimental results show a strong influence of free edge effects on damage initiation and failure. In the absence of these local free edge effects, the subcell modeling approach showed promise as a viable and computationally efficient analysis tool for triaxially braided composite structures. Future work will focus on validation of the approach for predicting the impact response of the braided composite against flat panel impact tests.
Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads
Goldberg, Robert K.; Roberts, Gary D.; Blinzler, Brina J.; Kohlman, Lee W.; Binienda, Wieslaw K.
2012-01-01
In order to design impact resistant aerospace components made of triaxially-braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to material mechanisms such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat coupons have been examined to alleviate difficulties observed with standard test methods. The results from the coupon level tests have been used to characterize and validate a macro level finite element-based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid unit cell is approximated by using four parallel laminated composites, each with a different fiber layup, which roughly simulates the braid architecture. In the analysis, each of these laminated composites is modeled as a shell element. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the coupon level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model include the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.
Fusion and braiding in finite and affine Temperley-Lieb categories
Gainutdinov, A M
2016-01-01
Finite Temperley-Lieb (TL) algebras are diagram-algebra quotients of (the group algebra of) the famous Artin's braid group $B_N$, while the affine TL algebras arise as diagram algebras from a generalized version of the braid group. We study asymptotic `$N\\to\\infty$' representation theory of these quotients (parametrized by $q\\in\\mathbb{C}^{\\times}$) from a perspective of braided monoidal categories. Using certain idempotent subalgebras in the finite and affine algebras, we construct infinite `arc' towers of the diagram algebras and the corresponding direct system of representation categories, with terms labeled by $N\\in\\mathbb{N}$. The corresponding direct-limit category is our main object of studies. For the case of the finite TL algebras, we prove that the direct-limit category is abelian and highest-weight at any $q$ and endowed with braided monoidal structure. The most interesting result is when $q$ is a root of unity where the representation theory is non-semisimple. The resulting braided monoidal catego...
Finite Element Model for Failure Study of Two-Dimensional Triaxially Braided Composite
Li, Xuetao; Binienda, Wieslaw K.; Goldberg, Robert K.
2010-01-01
A new three-dimensional finite element model of two-dimensional triaxially braided composites is presented in this paper. This meso-scale modeling technique is used to examine and predict the deformation and damage observed in tests of straight sided specimens. A unit cell based approach is used to take into account the braiding architecture as well as the mechanical properties of the fiber tows, the matrix and the fiber tow-matrix interface. A 0 deg / plus or minus 60 deg. braiding configuration has been investigated by conducting static finite element analyses. Failure initiation and progressive degradation has been simulated in the fiber tows by use of the Hashin failure criteria and a damage evolution law. The fiber tow-matrix interface was modeled by using a cohesive zone approach to capture any fiber-matrix debonding. By comparing the analytical results to those obtained experimentally, the applicability of the developed model was assessed and the failure process was investigated.
Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.
Wu, Yue; Nan, Bo; Chen, Liang
2014-01-01
3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N. PMID:25121121
Network response to disturbances in large sand-bed braided rivers
Schuurman, F.; Kleinhans, M. G.; Middelkoop, H.
2016-01-01
The reach-scale effects of human-induced disturbances on the channel network in large braided rivers are a challenge to understand and to predict. In this study, we simulated different types of disturbances in a large braided river to get insight into the propagation of disturbances through a braided channel network. The results showed that the disturbances initiate an instability that propagates in the downstream direction by means of alteration of water and sediment division at bifurcations. These adjustments of the bifurcations change the migration and shape of bars, with a feedback to the upstream bifurcation and alteration of the approaching flow to the downstream bifurcation. This way, the morphological effect of a disturbance amplifies in the downstream direction. Thus, the interplay of bifurcation instability and asymmetrical reshaping of bars was found to be essential for propagation of the effects of a disturbance. The study also demonstrated that the large-scale bar statistics are hardly affected.
Numerical Modeling of Bifurcation Evolution in a Sand-bed Braided River
De Haas, T.; Schuurman, F.; Kleinhans, M. G.
2012-12-01
River bifurcations are key units in a braided river. Although simple bifurcations are well understood and can be analyzed by 1D models (e.g. Bolla Pittaluga et al., 2003 and Kleinhans et al., 2008), predicting the stability and dynamics of multiple interacting bifurcations in a braided river with migrating bars requires understanding of the interaction between braid bars, channel network and bifurcations, in particular the upstream curvature and downstream backwater effects. Our objective is to understand the evolution of bifurcations at migrating bars in a braided river and the effects on bar evolution. We used the 3D numerical morphodynamic model Delft3D to produce a dynamically braiding sand bed river. This model solves the 3D-flow and computes sediment transport and bed level change accounting for effects of transverse bed slope. It includes a simple bank erosion model to reactivate emerged areas. The morphology of mid-channel bars produced by the model was analyzed and the partitioning of water and sediment over the bifurcating channels are compared with a 1D model concept. Next, the evolution of bars is linked to that of the bifurcations, in order to infer relations between bar morphology and bifurcation evolution. We find that upstream bar dynamics have a major effect on the stability of bifurcations. Migration and elongation of bars can close the upstream entrance of a bifurcation channel, independent of the stability of the bifurcation. Moreover, bifurcation angle and upstream curvature can be affected by upstream bar migration and elongation, which steers flow and sediment partitioning at the bifurcation. At the same time, the partitioning of water and sediment over a bifurcation affects bar shape. Sediment eroded at one of the bar sides just downstream of the bifurcation deposits downstream of the braid bar in the form of tail bars. Hence bar shape as observable on imagery contains useful information about the evolution of the upstream bifurcation and
Observational Constraints on Kinetic Gravity Braiding from the Integrated Sachs-Wolfe Effect
Kimura, Rampei; Kobayashi, Tsutomu; Yamamoto, Kazuhiro
2011-01-01
The cross-correlation between the integrated Sachs-Wolfe (ISW) effect and the large scale structure (LSS) is a powerful tool to constrain dark energy and alternative theories of gravity. In this paper, we obtain observational constraints on kinetic gravity braiding from the ISW-LSS cross-correlation. We find that the late-time ISW effect in the kinetic gravity braiding model anti-correlates with large scale structures in a wide range of parameters, which clearly demonstrates how one can disti...
Flat connections on configuration spaces and formality of braid groups of surfaces
Enriquez, B
2011-01-01
We construct an explicit bundle with flat connection on the configuration space of n points of a complex curve. This enables one to recover the `formality' isomorphism between the Lie algebra of the prounipotent completion of the pure braid group of n points on a surface and an explicitly presented Lie algebra t_{g,n} (Bezrukavnikov), and to extend it to a morphism from the full braid group of the surface to the semidirect product exp(hat t_{g,n}) rtimes S_n.
The energy absorption of damaged braided and non-crimp fibre composite material structures
Bottome, Kristofer John
2006-01-01
The effects of pre-existing damage on the mode of failure and energy absorption characteristics of Non-Crimp Fabric (NCF) and biaxially braided tubular sections under axial loading were considered. Loading rate effects were incorporated by testing at quasi-static rates and impact rates up to 7ms-1 and the pre-existing damage was simulated through stress concentrations and out-of-plane impact damage. Circular and square geometries were tested, and a range of NCF and braided fibre architectures...
Grain sorting in the morphological active layer of a braided river physical model
Leduc, P.; Ashmore, P.; Gardner, J. T.
2015-07-01
A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morpho-dynamics and for measuring and predicting bed load transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to re-work the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three-dimensions. Normalizing active layer thickness and dividing into 10 sub-layers we show that all grain sizes occur with almost equal frequency in all sub-layers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bed load prediction a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.
Métivier, F.; Devauchelle, O.; Chauvet, H.; Lajeunesse, E.; Meunier, P.; Blanckaert, K.; Zhang, Z.; Fan, Y.; Liu, Y.; Dong, Z.; Ye, B.
2015-11-01
The Bayanbulak Grassland, Tianshan, China is located in an intramountane sedimentary basin where meandering and braided gravel-bed streams coexist under the same climatic and geological settings. We report on measurements of their discharge, width, depth, slope and grain size. Based on this data set, we compare the morphology of individual threads from braided and meandering streams. Both types of threads share statistically indistinguishable regime relations. Their depths and slopes compare well with the threshold theory, but they are wider than predicted by this theory. These findings are reminiscent of previous observations from similar gravel-bed streams. Using the scaling laws of the threshold theory, we detrend our data with respect to discharge to produce a homogeneous statistical ensemble of width, depth and slope measurements. The statistical distributions of these dimensionless quantities are similar for braided and meandering streams. This suggests that a braided river is a collection of intertwined channels, which individually resemble isolated streams. Given the environmental conditions in Bayanbulak, we furthermore hypothesize that bedload transport causes the channels to be wider than predicted by the threshold theory.
Littell, Justin D.; Binienda, Wieslaw K.; Goldberg, Robert K.; Roberts, Gary D.
2008-01-01
Quasi-static tests have been performed on triaxially braided carbon fiber composite materials with large unit cell sizes. The effects of different fibers and matrix materials on the failure mode were investigated. Simulations of the tests have been performed using the transient dynamic finite element code, LS-DYNA. However, the wide range of failure modes observed for the triaxial braided carbon fiber composites during tests could not be simulated using composite material models currently available within LS-DYNA. A macroscopic approach has been developed that provides better simulation of the material response in these materials. This approach uses full-field optical measurement techniques to measure local failures during quasi-static testing. Information from these experiments is then used along with the current material models available in LS-DYNA to simulate the influence of the braided architecture on the failure process. This method uses two-dimensional shell elements with integration points through the thickness of the elements to represent the different layers of braid along with a new analytical method for the import of material stiffness and failure data directly. The present method is being used to examine the effect of material properties on the failure process. The experimental approaches used to obtain the required data will be described, and preliminary results of the numerical analysis will be presented.
Trigger Mechanism of Solar Subflares in a Braided Coronal Magnetic Structure
Tiwari, Sanjiv K; Winebarger, Amy R; Moore, Ronald L
2014-01-01
Fine-scale braiding of coronal magnetic loops by continuous footpoint motions may power coronal heating via nanoflares, which are spontaneous fine-scale bursts of internal reconnection. An initial nanoflare may trigger an avalanche of reconnection of the braids, making a microflare or larger subflare. In contrast to this internal triggering of subflares, we observe external triggering of subflares in a braided coronal magnetic field observed by the {\\it High-resolution Coronal Imager (Hi-C)}. We track the development of these subflares using 12 s cadence images acquired by {\\it SDO}/AIA in 1600, 193, 94 \\AA, and registered magnetograms of {\\it SDO}/HMI, over four hours centered on the {\\it Hi-C} observing time. These data show numerous recurring small-scale brightenings in transition-region emission happening on polarity inversion lines where flux cancellation is occurring. We present in detail an example of an apparent burst of reconnection of two loops in the transition region under the braided coronal fiel...
(Re)braiding to Tell: Using "Trenzas" as a Metaphorical-Analytical Tool in Qualitative Research
Quiñones, Sandra
2016-01-01
Metaphors can be used in qualitative research to illuminate the meanings of participant experiences and examine phenomena from insightful and creative perspectives. The purpose of this paper is to illustrate how I utilized "trenzas" (braids) as a metaphorical and analytical tool for understanding the experiences and perspectives of…
Littell, Justin D.; Binienda, Wieslaw K.; Arnold, William A.; Roberts, Gary D.; Goldberg, Robert K.
2010-01-01
The reliability of impact simulations for aircraft components made with triaxial-braided carbon-fiber composites is currently limited by inadequate material property data and lack of validated material models for analysis. Methods to characterize the material properties used in the analytical models from a systematically obtained set of test data are also lacking. A macroscopic finite element based analytical model to analyze the impact response of these materials has been developed. The stiffness and strength properties utilized in the material model are obtained from a set of quasi-static in-plane tension, compression and shear coupon level tests. Full-field optical strain measurement techniques are applied in the testing, and the results are used to help in characterizing the model. The unit cell of the braided composite is modeled as a series of shell elements, where each element is modeled as a laminated composite. The braided architecture can thus be approximated within the analytical model. The transient dynamic finite element code LS-DYNA is utilized to conduct the finite element simulations, and an internal LS-DYNA constitutive model is utilized in the analysis. Methods to obtain the stiffness and strength properties required by the constitutive model from the available test data are developed. Simulations of quasi-static coupon tests and impact tests of a represented braided composite are conducted. Overall, the developed method shows promise, but improvements that are needed in test and analysis methods for better predictive capability are examined.
Investigation of a Macromechanical Approach to Analyzing Triaxially-Braided Polymer Composites
Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.
2010-01-01
A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The material stiffness and strength values required for the constitutive model are determined based on coupon level tests on the braided composite. Simulations of quasi-static coupon tests of a representative braided composite are conducted. Varying the strength values that are input to the material model is found to have a significant influence on the effective material response predicted by the finite element analysis, sometimes in ways that at first glance appear non-intuitive. A parametric study involving the input strength parameters provides guidance on how the analysis model can be improved.
Grain sorting in the morphological active layer of a braided river physical model
Leduc, P.; Ashmore, P.; Gardner, J. T.
2015-12-01
A physical scale model of a gravel-bed braided river was used to measure vertical grain size sorting in the morphological active layer aggregated over the width of the river. This vertical sorting is important for analyzing braided river sedimentology, for numerical modeling of braided river morphodynamics, and for measuring and predicting bedload transport rate. We define the morphological active layer as the bed material between the maximum and minimum bed elevations at a point over extended time periods sufficient for braiding processes to rework the river bed. The vertical extent of the active layer was measured using 40 hourly high-resolution DEMs (digital elevation models) of the model river bed. An image texture algorithm was used to map bed material grain size of each DEM. Analysis of the 40 DEMs and texture maps provides data on the geometry of the morphological active layer and variation in grain size in three dimensions. By normalizing active layer thickness and dividing into 10 sublayers, we show that all grain sizes occur with almost equal frequency in all sublayers. Occurrence of patches and strings of coarser (or finer) material relates to preservation of particular morpho-textural features within the active layer. For numerical modeling and bedload prediction, a morphological active layer that is fully mixed with respect to grain size is a reliable approximation.
Categorical action of the extended braid group of affine type A
Gadbled, Agnes; Thiel, Anne-Laure; Wagner, Emmanuel
2015-01-01
Using a quiver algebra of a cyclic quiver, we construct a faithful categorical action of the extended braid group of affine type A on its bounded homotopy category of finitely generated projective modules. The algebra is trigraded and we identify the trigraded dimensions of the space of morphisms of this category with intersection numbers coming from the topological origin of the group.
Analysis of the spatiotemporal planform dynamics of braided rivers: a novel laboratory investigation
Redolfi, Marco; Bertoldi, Walter; Tubino, Marco
2016-04-01
Braided rivers are highly dynamic, labile environments which experience significant morphological changes even during moderate flow events. Recent remote sensing techniques enable to monitor the river morphology with great detail. However, capturing the rapid morphological changes of a large river with sufficient temporal and spatial resolution is still very challenging. As a consequence, quantitative analysis of the braided channel dynamics is often limited to local processes (e.g. a single bifurcation or confluence) and short time periods (e.g. a single flood). This work aims at providing quantitative, statistical description of the channel network dynamics in a braided network at larger spatial and temporal scales, namely the reach scale and the multiple flood scale. This can be achieved using a new technique based on time lapse imagery that we recently developed at the University of Trento. This technique provides high frequency, two dimensional maps of the bed load transport in a large laboratory model, thus allowing to capture the spatiotemporal variability of the transport processes with unprecedented detail. We performed a set of laboratory experiments in a 23 m long, 3 m wide flume, sand bed load flume, where self-formed braided networks can be reproduced. We run several experiments with different discharges and channel widths, lasting for a long time (from 20 to 65 hours) to enable a robust statistical description of the equilibrium morphodynamics. High-resolution pictures were taken at 1 min interval from two SLR cameras, then rectified and merged in order to cover a 7 m long reach. We processed a large number of images to obtain maps of bed load transport, and we developed an algorithm to automatically identifies active (i.e. transporting) channels, bifurcations and confluences. The statistical analysis we performed includes two dimensional correlations, spatial and temporal scales, channel migration rate, avulsion frequency, bank erosion rate. This
Quantum field theory of particles with braid group statistics in 2+1 dimensions
Mund, J K H
1997-01-01
The present thesis is concerned with the local quantum physics of relativistic particles and fields in three space-time dimensions, whose statistics is to be described by a representation of the braid group -- so-called plektons or, if the representation is Abelian, anyons. In particular the issue of the existence of free anyonic fields is addressed. In our context, these are operators affiliated with the 'local' field algebras and creating only single particle vectors from the vacuum. (Localizability here refers to regions extending to infinity in some spacelike direction.) Under a mild regularity condition for these fields, we can derive commutation relations which are not compatible with braid group statistics. Further, model-independent results concerning the PCT operator and the connection of spin and statistics are obtained. Assuming the observable algebra to satisfy the Bisognano-Wichmann theorem, a PCT theorem for plektons is derived. For anyons it is shown that the Bisognano-Wichmann property of the ...
On some 3-point functions in the $W_4$ CFT and related braiding matrix
Furlan, P
2015-01-01
We construct a class of 3-point constants in the $sl(4)$ Toda conformal theory $W_4$, extending the examples in Fateev and Litvinov. Their knowledge allows to determine the braiding/fusing matrix transforming 4-point conformal blocks of one fundamental, labelled by the 6-dimensional $sl(4)$ representation, and three partially degenerate vertex operators. It is a $3 \\times 3$ submatrix of the generic $6 \\times 6$ fusing matrix consistent with the fusion rules for the particular class of representations. We check a braiding relation which has wider applications to conformal models with $sl(4)$ symmetry. The 3-point constants in dual regions of central charge are compared in preparation for a BPS like relation in the $\\hat{sl}(4)$ WZW model.
Yarn Architecture Analysis of Two-step 3D Braided Composites
SUN Ying; KANG Yi-lan; LI Jia-lu
2005-01-01
A comprehensive study of yarn architecture of two-step rectangle 3D braided composites is presented. Firstly, the braided surface, the shapes of yams and the intertwining between braider yarns and axial yarns are analyzed from experimentation. With the microstructure being defined, three levels of unit cell structure are identified, i.e. large unit cell, second unit cell and minimal unit cell. Secondly, based on the minimal unit cell in the interior and on the boundary of the entire cross-section, the deformations of axial yarns squashed by braider yams contribute to the increase of the fiber packing factors of axial yarns. Finally, the predicted fiber volume fraction of the composites decreases with the increase of linear density of the braider yarn and the pitch length. Favorable correlations between the predicted and the experimental results are found for six groups of the composites.
From representations of the braid group to solutions of the Yang-Baxter equation
A systematic method is developed for constructing solutions of the Yang-Baxter equation from given braid group representations, arising from such finite dimensional irreps of quantum groups that any irrep can be affinized and the tensor product of the irrep with itself is multiplicity-free. The main tool used in the construction is a tensor product graph, whose circuits give rise to consistency conditions. A maximal tree of this graph leads to an explicit formula for the quantum R-matrix when the consistency conditions are satisfied. As examples, new solutions of the Xang-Baxter equations are found, corresponding to braid group generators associated with the symmetric and antisymmetric tensor irreps of Uq[gl(m)], a spinor irrep of Uq[so(2n)], and the minimal irreps of Uq[E6] and Uq[E7]. (orig.)
Zhang, Chao; Binienda, Wieslaw K.; Morscher, Gregory; Martin, Richard E.
2012-01-01
The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55 C and 120 C. Transverse microcrack morphology was investigated using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied. Keywords: Thermal cycles; Microcrack; Finite Element Model; Braided Composite
The algebraic crossing number and the braid index of knots and links
Kawamuro, Keiko
2009-01-01
It has been conjectured that the algebraic crossing number of a link is uniquely determined in minimal braid representation. This conjecture is true for many classes of knots and links. The Morton-Franks-Williams inequality gives a lower bound for braid index. And sharpness of the inequality on a knot type implies the truth of the conjecture for the knot type. We prove that there are infinitely many examples of knots and links for which the inequality is not sharp but the conjecture is still true. We also show that if the conjecture is true for K and L, then it is also true for the (p,q)-cable of K and for the connect sum of K and L.
The Effects of Spatial Resolution and Dimensionality on Modeling Braided River Hydraulics
Altenau, E. H.; Pavelsky, T.; Bates, P. D.
2015-12-01
Braided rivers are challenging features to quantify due to their dynamic morphology and dominance in remote locations. Advances in hydrodynamic modeling and remote sensing over the past few decades offer opportunities to explore braided river processes at finer resolutions with increased efficiency. These methods allow us to address questions such as: What model structure is necessary to accurately reproduce inundation extent and water surface elevations in a braided river? What effects do the smaller channels within a braided river have on simulating wave propagation and slope? How much accuracy is lost as model resolution and dimension are decreased? Here, we use the raster-based hydrodynamic model LISFLOOD-FP to simulate water surface elevations, inundation extent, and slope at various resolutions and dimensions over a ~90 km reach of the Tanana River, Alaska. Model input and validation data were collected during two field campaigns in the summers of 2013 and 2015. Field data included water surface elevation, discharge, velocity, slope, and bathymetric measurements. Six models are run to simulate flood waves across the study reach over a two-month timespan. The model structures vary in complexity from a full 2D model at 10 m resolution to a coupled 1D/2D model at 100 m resolution where the channel is represented in 1D by an effective centerline within a 2D floodplain grid. Results from the different models are compared to assess the effects on inundation extent, wave celerity, water elevations and slope. Digital elevation model (DEM) quality and resolution have major effects on inundation extent and water surface elevations, while model dimensionality has a larger effect on wave celerity and slope. Future work will compare model outputs with AirSWOT data, an airborne analog for the Surface Water and Ocean Topography (SWOT) mission, which aims to provide high-resolution measurements of terrestrial and ocean water surface elevations globally.
3D flexible NiTi-braided elastomer composites for smart structure applications
Heller, Luděk; Vokoun, David; Šittner, Petr; Finckh, H.
2012-01-01
Roč. 21, č. 4 (2012), s. 1-13. ISSN 0964-1726 R&D Projects: GA ČR GAP108/10/1296 EU Projects: European Commission(XE) 46559 - CERINKA; European Commission(XE) 515813 - AVALON Grant ostatní: IP UPWIND(XE) 019945 Institutional research plan: CEZ:AV0Z10100520 Keywords : NiTi * braided structures * composites Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.024, year: 2012
A New approach to the construction of braided T-categories
Lu, Daowei; You, Miman; Wang, Shuanhong
2016-01-01
The aim of this paper is to construct a new braided $T$-category via the generalized Yetter-Drinfel'd modules and Drinfel'd codouble over Hopf algebra, an approach different from that proposed by Panaite and Staic \\cite{PS}. Moreover, in the case of finite dimensional, we will show that this category coincides with the corepresentation of a certain coquasitriangular Turaev group algebra that we construct. Finally we apply our theory to the case of group algebra.
The Processing Design of Jute Spun Yarn/PLA Braided Composite by Pultrusion Molding
Anin Memon; Asami Nakai
2013-01-01
Prevalently, the light has been shed on the green composite from the viewpoint of environmental protection. Jute fibers are natural fibers superior due to light weight, low cost, and being environmentally friendly corresponding to the green composite materials. Meticulously, fibers of polylactic acid (PLA) thermoplastic biopolymer were used as the resin fibers. In this study, the fabrication of tubular jute spun yarn/PLA braided composite by pultrusion molding was presented. The intermediate ...
Goldberg, Robert K.; Blinzler, Brina J.; Binienda, Wieslaw K.
2010-01-01
A macro level finite element-based model has been developed to simulate the mechanical and impact response of triaxially-braided polymer matrix composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. For the current analytical approach, each shell element is considered to be a smeared homogeneous material. The commercial transient dynamic finite element code LS-DYNA is used to conduct the simulations, and a continuum damage mechanics model internal to LS-DYNA is used as the material constitutive model. The constitutive model requires stiffness and strength properties of an equivalent unidirectional composite. Simplified micromechanics methods are used to determine the equivalent stiffness properties, and results from coupon level tests on the braided composite are utilized to back out the required strength properties. Simulations of quasi-static coupon tests of several representative braided composites are conducted to demonstrate the correlation of the model. Impact simulations of a represented braided composites are conducted to demonstrate the capability of the model to predict the penetration velocity and damage patterns obtained experimentally.
Feldspar-fluid interactions in braid microperthites: pleated rims and vein microperthites
Lee, Martin R.; Waldron, Kim A.; Parsons, I.; Brown, William L.
Braid microperthitic alkali feldspars in the Klokken, South Greenland and Coldwell, Ontario syenite intrusions have bulk-compositional variations along grain boundaries called pleated rims. These, together with vein microperthites in aplites which cross-cut the syenites, have been investigated by SEM and TEM. We distinguish two main types of pleated rims, ``arched '' and ``parallel-sided '', consisting of alternating Ab- and Or-rich areas on (001), which are 0.5-300 μm in length normal to (010) and 0.2-20 μm in width along (010). The smallest pleats, which occur on intracrystalline boundaries in Klokken feldspars, are fully coherent and composed of low albite and low microcline. Above the heads of some of the coarser pleats, braid microperthite grades into a film crypto- and micro-perthite and antiperthite microtexture called a ``transitional zone'' containing roughly planar lamellae of low albite and tweed orthoclase. During pleat development, local alternating volumes form in which the proportions of the phases differ ( phase separation) and the morphology of the intergrowths changes from braided to straight in response to this change in local bulk composition. Straightening is also accompanied by transformation of low microcline to tweed orthoclase. The coarsest pleats, which occur along grain boundaries in feldspars from the Coldwell syenite, are semi- or in-coherent and have a thick coherent and semicoherent transitional zone. Coarsening of pleats and development of the transitional zone has been facilitated by diffusion of ``water'' into grain interiors. In many cases, pleated rims have suffered deuteric alteration, by dissolution-reprecipitation processes, through the action of a water-rich fluid from the grain boundary, in which tweed orthoclase was transformed into irregular microcline and micropores developed. Vein microperthites in aplites from Klokken, and by extension the vein microperthites almost universal in most alkali granites, are interpreted
Template synthesis of braided gold nanowires with gemini surfactant-HAuCl{sub 4} aggregates
Wang Wentao; Han Yuchun; Gao Mingyuan, E-mail: gaomy@iccas.ac.cn; Wang Yilin, E-mail: yilinwang@iccas.ac.cn [Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Key Laboratory of Colloid and Interface Science (China)
2013-01-15
One-dimensional braided gold nanowires with 40-50 nm in width and several micrometers in length which were fabricated by using cationic gemini surfactant hexamethylene-1,6-bis (dodecyl dimethylammonium bromide) (C{sub 12}C{sub 6}C{sub 12}Br{sub 2}). Through simply regulating the mole ratio of C{sub 12}C{sub 6}C{sub 12}Br{sub 2} to HAuCl{sub 4}, the morphology of the gold products changed into nanoparticles and nanowires. The CryoTEM images indicated that the C{sub 12}C{sub 6}C{sub 12}Br{sub 2}/HAuCl{sub 4} mixture formed spherical or fibrillar aggregates depending on the mole ratio of C{sub 12}C{sub 6}C{sub 12}Br{sub 2} to HAuCl{sub 4}, which performed as the versatile templates for morphology-controlled synthesis of the multiple gold nanomaterials. The HRTEM and SAED results suggested the nanowires and braided nanowires were polycrystalline. The gold nanostructure displayed a time-dependent growth process, i.e., first the nanoparticles arranged in one dimension, and then assembled into nanowires. Therefore, a template-directed aggregation and fusion process of nanoparticles is proposed for the formation of the one-dimensional gold nanomaterials. The braided nanowires exhibited a higher catalytic activity in the reduction of p-nitroaniline than that of the nanowires. This gemini surfactant-based template provides a versatile strategy for the morphology-controlled synthesis of gold nanomaterials, and may be applied for the synthesis of other noble-metal nanomaterials.
Structure and properties of braided sleeve preforms for chemical vapor infiltration
Starr, T.L.; Fiadzo, O.G.; Hablutzel, N. [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Technology
1998-04-01
In all composites the properties and structure of the reinforcement strongly influence the performance of the material. For some composites, however, the reinforcement also affects the fabrication process itself exerting an additional, second order influence on performance. This is the case for the chemical vapor infiltration (CVI) process for fabrication of ceramic matrix composites. In this process the matrix forms progressively as a solid deposit, first onto the fiber surfaces, then onto the previous layer of deposit, ultimately growing to fill the inter-fiber porosity. The transport of reactants to the surfaces and the evolved morphology of the matrix depend on the initial reinforcement structure. This structure can vary greatly and is controlled by such factors as fiber size and cross-section, the number of filaments and amount of twist per tow or yarn, and the weave or braid architecture. Often the choice of reinforcement is based on mechanical performance analysis or on the cost and availability of the material or on the temperature stability of the fiber. Given this choice, the composite densification process--CVI--must be optimized to attain a successful material. Ceramic fiber in the form of cylindrical braided sleeve is an attractive choice for fabrication of tube-form ceramic matrix composites. Multiple, concentric layers of sleeve can be placed over a tubular mandrel, compressed and fixed with a binder to form a freestanding tube preform. This fiber architecture is different than that created by layup of plain weave cloth--the material used in most previous CVI development. This report presents the results of the investigation of CVI densification of braided sleeve preforms and the evolution of their structure and transport properties during processing.
Holistic and Consistent Design Process for Hollow Structures Based on Braided Textiles and RTM
Gnädinger, Florian; Karcher, Michael; Henning, Frank; Middendorf, Peter
2014-06-01
The present paper elaborates a holistic and consistent design process for 2D braided composites in conjunction with Resin Transfer Moulding (RTM). These technologies allow a cost-effective production of composites due to their high degree of automation. Literature can be found that deals with specific tasks of the respective technologies but there is no work available that embraces the complete process chain. Therefore, an overall design process is developed within the present paper. It is based on a correlated conduction of sub-design processes for the braided preform, RTM-injection, mandrel plus mould and manufacturing. For each sub-process both, individual tasks and reasonable methods to accomplish them are presented. The information flow within the design process is specified and interdependences are illustrated. Composite designers will be equipped with an efficient set of tools because the respective methods regard the complexity of the part. The design process is applied for a demonstrator in a case study. The individual sub-design processes are accomplished exemplarily to judge about the feasibility of the presented work. For validation reasons, predicted braiding angles and fibre volume fractions are compared with measured ones and a filling and curing simulation based on PAM-RTM is checked against mould filling studies. Tool concepts for a RTM mould and mandrels that realise undercuts are tested. The individual process parameters for manufacturing are derived from previous design steps. Furthermore, the compatibility of the chosen fibre and matrix system is investigated based on pictures of a scanning electron microscope (SEM). The annual production volume of the demonstrator part is estimated based on these findings.
Fang, Wen-Zhen; Zhang, Hu; Chen, Li; Tao, Wen-Quan
2015-01-01
In this paper, a multiple-relaxation-time lattice Boltzmann model with an off-diagonal collision matrix was adopted to predict the effective thermal conductivities of the anisotropic heterogeneous materials whose components are also anisotropic. The half lattice division scheme was adopted to deal with the internal boundaries to guarantee the heat flux continuity at the interfaces. Accuracy of the model was confirmed by comparisons with benchmark results and existing simulation data. The present method was then adopted to numerically predict the transverse and longitudinal effective thermal conductivities of three-dimensional (3D) four-directional braided composites. Some corresponding experiments based on the Hot Disk method were conducted to measure their transverse and longitudinal effective thermal conductivities. The predicted data fit the experiment data well. Influences of fiber volume fractions and interior braiding angles on the effective thermal conductivities of 3D four-directional braided composit...
Mixed Paraparticles, Colors, Braidings and a new class of Realizations for Lie superalgebras
Kanakoglou, K; Herrera-Aguilar, A
2009-01-01
A rigorous algebraic description of the notion of realization, specialized in the case of Lie superalgebras is given. The idea of the Relative Parabose set $P_{BF}$ is recalled together with some recent developments and its braided group structure is established together with an extended discussion of its ($\\mathbb{Z}_{2} \\times \\mathbb{Z}_{2}$)-grading. The final result of the paper employs $P_{BF}$ in order to realize an arbitrary Lie superalgebra. It is furthermore shown that the constructed realization is a $\\mathbb{Z}_{2}$-graded Hopf algebra homomorphism. Virtual applications in pure mathematics and theoretical physics as well are outlined.
The Calabi-Yau property of Hopf algebras and braided Hopf algebras
Yu, Xiaolan; Zhang, Yinhuo
2011-01-01
Let $H$ be a finite dimensional semisimple Hopf algebra and $R$ a braided Hopf algebra in the category of Yetter-Drinfeld modules over $H$. When $R$ is a Calabi-Yau algebra, a necessary and sufficient condition for $R#H$ to be a Calabi-Yau Hopf algebra is given. Conversely, when $H$ is the group algebra of a finite group and the smash product $R#H$ is a Calabi-Yau algebra, we give a necessary and sufficient condition for the algebra $R$ to be a Calabi-Yau algebra.
Quantum entanglement: the unitary 8-vertex braid matrix with imaginary rapidity
We study quantum entanglements induced on product states by the action of 8-vertex braid matrices, rendered unitary with purely imaginary spectral parameters (rapidity). The unitarity is displayed via the 'canonical factorization' of the coefficients of the projectors spanning the basis. This adds one more new facet to the famous and fascinating features of the 8-vertex model. The double periodicity and the analytic properties of the elliptic functions involved lead to a rich structure of the 3-tangle quantifying the entanglement. We thus explore the complex relationship between topological and quantum entanglement. (fast track communication)
EVOLUTION OF SPINNING AND BRAIDING HELICITY FLUXES IN SOLAR ACTIVE REGION NOAA 10930
The line-of-sight magnetograms from Solar Optical Telescope Narrowband Filter Imager observations of NOAA Active Region 10930 have been used to study the evolution of spinning and braiding helicities over a period of five days starting from 2006 December 9. The north (N) polarity sunspot was the follower and the south (S) polarity sunspot was the leader. The N-polarity sunspot in the active region was rotating in the counterclockwise direction. The rate of rotation was small during the first two days of observations and it increased up to 8° hr–1 on the third day of the observations. On the fourth and fifth days it remained at 4° hr–1 with small undulations in its magnitude. The sunspot rotated about 260° in the last three days. The S-polarity sunspot did not complete more than 20° in five days. However, it changed its direction of rotation five times over a period of five days and injected both the positive and negative type of spin helicity fluxes into the corona. Through the five days, both the positive and negative sunspot regions injected equal amounts of spin helicity. The total injected helicity is predominantly negative in sign. However, the sign of the spin and braiding helicity fluxes computed over all the regions were reversed from negative to positive five times during the five-day period of observations. The reversal in spinning helicity flux was found before the onset of the X3.4-class flare, too. Though, the rotating sunspot has been observed in this active region, the braiding helicity has contributed more to the total accumulated helicity than the spinning helicity. The accumulated helicity is in excess of –7 × 1043 Mx2 over a period of five days. Before the X3.4-class flare that occurred on 2006 December 13, the rotation speed and spin helicity flux increased in the S-polarity sunspot. Before the flare, the total injected helicity was larger than –6 × 1043 Mx2. The observed reversal in the sign of spinning and braiding helicity
Laboratory experimental investigations of braid theory using the rotor-oscillator flow
Filippi, Margaux; Atis, Séverine; Allshouse, Michael; Jacobs, Gustaaf; Budišić, Marko; Thiffeault, Jean-Luc; Peacock, Thomas
2015-11-01
Interpreting ocean surface dynamics is crucial to many areas of oceanography, ranging from marine ecology to pollution management. Motivated by this, we investigated the braid theory method to detect transport barriers bounding coherent structures in two-dimensional flows. Whereas most existing techniques rely on an extensive spatiotemporal knowledge of the flow field, we sought to identify these structures from sparse data sets involving trajectories of a few tracer particles in a two-dimensional flow. We present the results from our laboratory experiments, which were based on investigations using the rotor-oscillator flow, as a stepping stone towards oceanic applications.
Event-Scale Morphodynamics and Sediment Sorting in a Dynamic Braided River Revealed by TLS
Vericat, D.; Brasington, J.
2008-12-01
In the last decade, advances in topographic survey and digital elevation modelling have enabled a revolution in the study of fluvial morphodynamics. Despite this recent progress, our understanding of braided river dynamics remains limited by the time-space scale of studies. Hindered by high labour and flight costs, together with slow ground-based survey methods, studies to date have focused either on event-scale dynamics of morphological units (Ferguson and Ashworth, 1992; Lane et al., 1995; Milan et al., 2007) or seasonal-annual dynamics of larger system-scale reaches (sensu Lane, 2006; e.g., Brasington et al., 2003; Lane et al., 2003). Terrestrial Laser Scanning technology offers the potential to acquire rapidly, reach-scale datasets which record topographic information at the resolution of bed grain-scale upwards. However, as yet, no detailed 3d datasets exist that reveal the system-scale evolution of a braided river through a continuous sequence of floods. Such data are urgently required to address unresolved and fundamental questions concerning the controls and behaviour of braided rivers and are also needed to validate morphodynamic simulation models (Brasington and Richards, 2007). Our recent wok has demonstrated that TLS can be applied to recover centimetre-scale channel morphology, maps of particle size, sorting, packing and floodplain roughness (Brasington et al., 2007, 2008; Antonarakis, 2008a,b; Hodge et al., in review). This potential is illustrated by the results obtained in a field study conducted in January 2008. This used TLS to monitor the evolution of channel morphology and develop methods to derive models of bed roughness and facies in a small 500 x 300 m reach of the actively braided Rees River, New Zealand. Fieldwork comprised repeat surveys before and after 3 competent events, combining laser scans from eight positions with bathymetric data obtained by RTK GPS. The resulting point clouds incorporated between 48-110 million survey points, with
Development of a Progressive Failure Finite Element Analysis For a Braided Composite Fuselage Frame
Hart, Daniel Constantine
2002-01-01
Short, J-section columns fabricated from a textile composite are tested in axial compression to study the modes of failure with and without local buckling occuring.The textile preform architecture is a 2x2, 2-D triaxial braid with a yarn layup of [0 deg 18k/+-64 deg 6k] 39.7% axial. The preform was resin transfer molded with 3M PR500 epoxy resin. Finite element analyses (FEA) of the test specimens are conducted to assess intra- and inter- laminar progressive failure models. These progressive...
Application of braid groups in 2D hall system physics composite Fermion structure
Jacak, Janusz; Jacak, Lucjan
2012-01-01
In the present treatise progress in topological approach to Hall system physics is reported, including recent achievements in graphene. The homotopy methods of braid groups turn out to be of particular convenience in order to grasp peculiarity of 2D charged systems upon magnetic field resulting in Laughlin correlations. The real progress in understanding of structure and role of composite fermions in Hall system is provided. The crucial significance of carrier mobility apart from interaction in creation of the fractional quantum Hall effect (FQHE) is described and supported by recent graphene
TOPICAL REVIEW: Braided affine geometry and q-analogs of wave operators
Gurevich, Dimitri; Saponov, Pavel
2009-08-01
The main goal of this review is to compare different approaches to constructing the geometry associated with a Hecke type braiding (in particular, with that related to the quantum group Uq(sl(n))). We place emphasis on the affine braided geometry related to the so-called reflection equation algebra (REA). All objects of such a type of geometry are defined in the spirit of affine algebraic geometry via polynomial relations on generators. We begin by comparing the Poisson counterparts of 'quantum varieties' and describe different approaches to their quantization. Also, we exhibit two approaches to introducing q-analogs of vector bundles and defining the Chern-Connes index for them on quantum spheres. In accordance with the Serre-Swan approach, the q-vector bundles are treated as finitely generated projective modules over the corresponding quantum algebras. Besides, we describe the basic properties of the REA used in this construction and compare different ways of defining q-analogs of partial derivatives and differentials on the REA and algebras close to them. In particular, we present a way of introducing a q-differential calculus via Koszul type complexes. The elements of the q-calculus are applied to defining q-analogs of some relativistic wave operators.
Development of Hybrid Braided Composite Rods for Reinforcement and Health Monitoring of Structures
Sohel Rana
2014-01-01
Full Text Available In the present study, core-reinforced braided composite rods (BCRs were developed and characterized for strain sensing capability. A mixture of carbon and glass fibre was used in the core, which was surrounded by a braided cover of polyester fibres. Three compositions of core with different carbon fibre/glass fibre weight ratios (23/77, 47/53, and 100/0 were studied to find out the optimum composition for both strain sensitivity and mechanical performance. The influence of carbon fibre positioning in BCR cross-section on the strain sensing behaviour was also investigated. Strain sensing property of BCRs was characterized by measuring the change in electrical resistance with flexural strain. It was observed that BCRs exhibited increase (positive response or decrease (negative response in electrical resistance depending on carbon fibre positioning. The BCR with lowest amount of carbon fibre was found to give the best strain sensitivity as well as the highest tensile strength and breaking extension. The developed BCRs showed reversible strain sensing behaviour under cyclic flexural loading with a maximum gauge factor of 23.4 at very low strain level (0.55%. Concrete beams reinforced with the optimum BCR (23/77 also exhibited strain sensing under cyclic flexural strain, although the piezoresistive behaviour in this case was irreversible.
Development of hybrid braided composite rods for reinforcement and health monitoring of structures.
Rana, Sohel; Zdraveva, Emilija; Pereira, Cristiana; Fangueiro, Raul; Correia, A Gomes
2014-01-01
In the present study, core-reinforced braided composite rods (BCRs) were developed and characterized for strain sensing capability. A mixture of carbon and glass fibre was used in the core, which was surrounded by a braided cover of polyester fibres. Three compositions of core with different carbon fibre/glass fibre weight ratios (23/77, 47/53, and 100/0) were studied to find out the optimum composition for both strain sensitivity and mechanical performance. The influence of carbon fibre positioning in BCR cross-section on the strain sensing behaviour was also investigated. Strain sensing property of BCRs was characterized by measuring the change in electrical resistance with flexural strain. It was observed that BCRs exhibited increase (positive response) or decrease (negative response) in electrical resistance depending on carbon fibre positioning. The BCR with lowest amount of carbon fibre was found to give the best strain sensitivity as well as the highest tensile strength and breaking extension. The developed BCRs showed reversible strain sensing behaviour under cyclic flexural loading with a maximum gauge factor of 23.4 at very low strain level (0.55%). Concrete beams reinforced with the optimum BCR (23/77) also exhibited strain sensing under cyclic flexural strain, although the piezoresistive behaviour in this case was irreversible. PMID:24574867
Quantum field theory of particles with braid group statistics in 2+1 dimensions
The present thesis is concerned with the local quantum physics of relativistic particles and fields in three space-time dimensions, whose statistics is to be described by a representation of the braid group -- so-called plektons or, if the representation is Abelian, anyons. In particular the issue of the existence of free anyonic fields is addressed. In our context, these are operators affiliated with the 'local' field algebras and creating only single particle vectors from the vacuum. (Localizability here refers to regions extending to infinity in some spacelike direction.) Under a mild regularity condition for these fields, we can derive commutation relations which are not compatible with braid group statistics. Further, model-independent results concerning the PCT operator and the connection of spin and statistics are obtained. Assuming the observable algebra to satisfy the Bisognano-Wichmann theorem, a PCT theorem for plektons is derived. For anyons it is shown that the Bisognano-Wichmann property of the observable algebra lifts, in a 'twisted' version, to the field algebra. In particular, the PCT-operator coincides, up to a 'twist operator', with the modular conjugation of the field algebra associated to a standard wedge region. From this fact, the spin-statistics theorem for anyons is derived
In the paper we outline an approach to investigate multiplicative structures in K-theory of braiding-commutative algebras. We introduce quantizations of underlying monoidal categories which induce quantizations of the multiplicative structure on the corresponding K-theory. (author)
Métivier, François; Devauchelle, Olivier; Chauvet, Hugo; Lajeunesse, Eric; Meunier, Patrick; Blanckaert, Koen; Ashmore, Peter; Zhang, Zhi; Fan, Yuting; Liu, Youcun; Dong, Zhibao; Ye, Baisheng
2016-03-01
The Bayanbulak Grassland, Tianshan, P. R. China, is located in an intramontane sedimentary basin where meandering and braided gravel-bed rivers coexist under the same climatic and geological settings. We report and compare measurements of the discharge, width, depth, slope and grain size of individual threads from these braided and meandering rivers. Both types of threads share statistically indistinguishable regime relations. Their depths and slopes compare well with the threshold theory, but they are wider than predicted by this theory. These findings are reminiscent of previous observations from similar gravel-bed rivers. Using the scaling laws of the threshold theory, we detrend our data with respect to discharge to produce a homogeneous statistical ensemble of width, depth and slope measurements. The statistical distributions of these dimensionless quantities are similar for braided and meandering threads. This suggests that a braided river is a collection of intertwined threads, which individually resemble those of meandering rivers. Given the environmental conditions in Bayanbulak, we furthermore hypothesize that bedload transport causes the threads to be wider than predicted by the threshold theory.
Mohamed O. E. Altahir
2014-08-01
Full Text Available The aim of this study was to assess the effect of heat treatment and salt concentrations (0, 5, and 10% on the free amino acids (FAA composition of Sudanese braided cheese (BC ripened for up to 3 months at 5±2°C. Heat and salt concentration significantly affected the FAA of braided cheese. The free amino acids concentrations of BC ripened in 0%, 5%, and 10% salted whey (SW were significantly fluctuated. Under ripening conditions tested (salt level + time, braided cheese made from pasteurized milk (BCPM had consistently lower values of FAA than braided cheese made from raw milk (BCRM. In fresh cheese, the major FAA in BCRM were Glu (36.12 nmol/ml, Leu (26.77nmol/ml and Lys (14.51 nmol/ml while the major ones in BCPM were Lys (2.94 nmol/ml and Ala (2.45 nmol/ml. BCPM stored in 10% SW had shorter quality life compared to that stored in 5% salted whey.
Liu, Ziliang; Shen, Fang; Zhu, Xiaomin; Li, Fengjie; Tan, Mengqi
2015-01-01
A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km). The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front" character. PMID
McVeigh Elliot R
2009-08-01
Full Text Available Abstract Background Catheter visualization and tracking remains a challenge in interventional MR. Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance. Results The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability and antenna (signal attenuation properties. With this configuration, the temperature increase remained less than 2°C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo. Conclusion We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures.
Ziliang Liu
Full Text Available A large, shallow braided river delta sedimentary system developed in the Yanchang Formation during the Triassic in the southwest of the Ordos basin. In this braided delta system, abundant oil and gas resources have been observed, and the area is a hotspot for oil and gas resource exploration. Through extensive field work on outcrops and cores and analyses of geophysical data, it was determined that developments in the Late Triassic produced favorable geological conditions for the development of shallow water braided river deltas. Such conditions included a large basin, flat terrain, and wide and shallow water areas; wet and dry cyclical climate changes; ancient water turbulence; dramatic depth cycle changes; ancient uplift development; strong weathering of parent rock; and abundant supply. The shallow water braided river delta showed grain sediment granularity, plastic debris, and sediment with mature composition and structure that reflected the strong hydrodynamic environment of large tabular cross-bedding, wedge cross-bedding, and multiple positive rhythms superimposed to form a thick sand body layer. The branch river bifurcation developed underwater, and the thickness of the sand body increased further, indicating that the slope was slow and located in shallow water. The seismic responses of the braided river delta reflected strong shallow water performance, indicated by a progradation seismic reflection phase axis that was relatively flat; in addition, the seismic reflection amplitude was strong and continuous with a low angle and extended over considerable distances (up to 50 km. The sedimentary center was close to the provenance, the width of the river was large, and a shallow sedimentary structure and a sedimentary rhythm were developed. The development of the delta was primarily controlled by tectonic activity and changes in the lake level; as a result, the river delta sedimentary system eventually presented a "small plain, big front
Littell, Justin D.
2013-01-01
Increasingly, carbon composite structures are being used in aerospace applications. Their highstrength, high-stiffness, and low-weight properties make them good candidates for replacing many aerospace structures currently made of aluminum or steel. Recently, many of the aircraft engine manufacturers have developed new commercial jet engines that will use composite fan cases. Instead of using traditional composite layup techniques, these new fan cases will use a triaxially braided pattern, which improves case performance. The impact characteristics of composite materials for jet engine fan case applications have been an important research topic because Federal regulations require that an engine case be able to contain a blade and blade fragments during an engine blade-out event. Once the impact characteristics of these triaxial braided materials become known, computer models can be developed to simulate a jet engine blade-out event, thus reducing cost and time in the development of these composite jet engine cases. The two main problems that have arisen in this area of research are that the properties for these materials have not been fully determined and computationally efficient computer models, which incorporate much of the microscale deformation and failure mechanisms, are not available. The research reported herein addresses some of the deficiencies present in previous research regarding these triaxial braided composite materials. The current research develops new techniques to accurately quantify the material properties of the triaxial braided composite materials. New test methods are developed for the polymer resin composite constituent and representative composite coupons. These methods expand previous research by using novel specimen designs along with using a noncontact measuring system that is also capable of identifying and quantifying many of the microscale failure mechanisms present in the materials. Finally, using the data gathered, a new hybrid
The Brauer Group of Central Separable Monoids in a Braided Monoidal Category
J.M. Fernández Vilaboa; R. González Rodríguez; E. Villanueva Novoa
2002-01-01
For a braided monoidal category (C,(○×), K, c), in a previous paper, we construct a Brauer group B1,c(C) for the 1-Azumaya monoids in C. In this paper,we investigate separability and centrality properties for 1-Azumaya monoids when the coequalizers in C are stable. This leads to the notion of 2-Azumaya monoids,and to a new subgroup B2,c(C) of the Brauer group B1,c(C) that generalizes the analogous groups in the symmetric case. Finally, we prove that B2,c(C) and B1,c(C) are equal if the base object of the category is projective.
Mechanical behavior of a triaxially braided textile composite at high temperature
El Mourid, Amine
The work presented in this thesis aimed at understanding the influence of viscoelasticity, temperature and aging on the mechanical behaviour of a textile composite using experimental, analytical and numerical tools. The studied material was a triaxially braided composite with fibres in the 0°/+/-60° directions. The yarns were made of carbon fibres, embedded in an MVK10 temperature resistant polyimide matrix. The first step consisted in developing analytical and numerical frameworks to predict viscoelastic behaviour in textile composites. Simulations were performed for both braided and woven textile architectures, at different stiffness contrasts and yarns volume fractions. The analytical framework accuracy was verified with the help of the numerical simulations. An important finding of this study was that the analytical framework, combined with the Mori-Tanaka model, leads to relatively accurate predictions for both the permanent and transient parts. Therefore, the authors believe that the Mori-Tanaka model with an adjusted aspect ratio to take into account yarn curvature is reliable for predicting viscoelastic behaviour in textile composites. The textile composite that was studied in this project did not display viscoelastic behaviour, due to the high yarn volume fraction. However, the framework remains relevant for higher temperature applications or lower yarn volume fractions. The second step was to investigate the temperature effect on the tensile behavior of the carbon/MVK10 triaxially braided composite material studied in this project. To achieve this goal, a series of room and high temperature tensile tests on both matrix and composite samples were performed. The tests on composite samples were performed along two different material directions at the maximum service temperature allowed by the Federal Aviation Administration for aircraft components, and a dedicated replication technique was developed in order to track crack densities as a function of
Zhang Yujing
2016-01-01
Full Text Available This paper is aimed at analyzing the dynamic behavior of the gear transmission system in a braiding machine. In order to observe the nonlinear phenomenon and reveal the time-varying gear meshing mechanism, a mathematical model with five degrees-of-freedom gear system under internal and external random disturbance of gear system is established. With this model, bifurcation diagrams, Poincare maps, phase diagrams, power spectrum, time-process diagrams, and Lyapunov exponents are used to identify the chaotic status. Meanwhile, by these analytical methods, spur gear pair with or without random perturbation are compared. The numerical results suggest that the vibration behavior of the model is consistent with that of Clifford system. The chaotic system associated parameters are picked out, which can be helpful to the design and control of braiding machines.
Zhang Yujing; Meng Zhuo; Sun Yize
2016-01-01
This paper is aimed at analyzing the dynamic behavior of the gear transmission system in a braiding machine. In order to observe the nonlinear phenomenon and reveal the time-varying gear meshing mechanism, a mathematical model with five degrees-of-freedom gear system under internal and external random disturbance of gear system is established. With this model, bifurcation diagrams, Poincare maps, phase diagrams, power spectrum, time-process diagrams, and Lyapunov exponents are used to identif...
Kasprak, A.; Ashmore, P.; Peirce, S.; Wheaton, J. M.
2013-12-01
The travel distances of coarse sediment in gravel-bed rivers during floods, or their path-lengths, exhibit strong dependencies on the arrangement of geomorphic units they are sourced from, routed through or around, and finally deposited on. Despite previous research on both braiding and single-thread meandering streams, a coherent rule set which relates particle path lengths to morphology remains elusive; such a rule set has the potential to vastly simplify models which seek to predict sediment transport or morphodynamics in these channels. Here we seek to understand the sensitivity of particle path-length distributions to morphology via a physical model of a braided stream, by using fluorescent tracer particles to track sediment path-lengths. These flume experiments provide a rich dataset composed of before-and-after bed photogrammetry, along with high-resolution photography and high-speed video documentation of particle deposition and mobility. Initial analyses indicate a strong coupling between particle path-length and the spatial arrangement of in-channel geomorphic units, with bar heads and point bars frequently acting as sink locations for tracer particles. This is interesting as it suggests that morphodynamics are in part contingent on morphology with strong positive feedbacks on hydraulics, deposition and negative feedbacks on path-length. Several mechanisms of braiding were captured in the simulations as erosional source processes for the tracers, including chute cutoff of point bars, bank erosion, channel incision, and bar edge trimming. These results may help inform the development of morphodynamic models for braided rivers which rely on particle path-lengths to simplify sediment transport algorithms, and such relations between channel morphology and path-length hold the potential to benefit numerous other modeling efforts, as well as provide a heuristic framework with which to understand fluvial morphodynamics.
Williams, R. D.; J. Brasington; Hicks, M; Measures, R.; Rennie, C.D.; Vericat, D.
2013-01-01
Gravel-bed braided rivers are characterized by shallow, branching flow across low relief, complex, and mobile bed topography. These conditions present a major challenge for the application of higher dimensional hydraulic models, the predictions of which are nevertheless vital to inform flood risk and ecosystem management. This paper demonstrates how high-resolution topographic survey and hydraulic monitoring at a density commensurate with model discretization can be used to advance hydrodynam...
Wawrzyniak, V.; Piégay, H.; Allemand, P.; Grandjean, P.
2011-12-01
At the catchment scale water temperature is influenced by geographical factors, but at the reach scale superficial and groundwater hydrology and channel geometry strongly affect thermal patterns. During the last 30 years, studies have been pointed out the significance and complexity of water exchanges between the channel and the hyporheic and phreatic zones. These surface-subsurface water exchanges influence water temperature patterns. Braided rivers present particular thermal conditions with very high spatial water temperature variability. This high thermal variability is difficult to comprehend using only in situ measurements and so thermal infrared (TIR) remote sensing is particularly suited to assessing the thermal patterns associated with these rivers. The aims of this study are to evaluate temperature patterns of nine braided reaches at very high spatial resolution (~20 cm) and to link temperature and water-body types. We hypothesized that river type has an influence of the spatial patterns of water temperature and that the patterns change through the day. All reaches are located in France, in the Rhône catchment. The nine reaches were selected based on high aquatic habitat diversities and are located in three regional areas: the massif des Écrins, the Rhône valley, and south Alps. They are about 1 km long. We have three distinct temporal approaches. The first one is a multi-site approach which proposes one survey of each site during summers 2010 or 2011. Three reaches were selected for the second phase (a multi-annual analysis and were therefore imaged both in summers 2010 and 2011. The last phase is an intra-day survey of two reaches with several flights at different times of day. This presentation focuses on the last approach with two reaches of the Drôme and Drac Noir rivers. To observe the evolution of the thermal patterns of these two reaches through the day, four flights within a day were realized during summer 2011 for both sites. The Drôme reach
Ni, Xiao-Yu; Pan, Chang-Wang; Gangadhara Prusty, B
2015-08-01
This paper discusses various issues relating to the mechanical properties of a braided non-vascular stent made of a Ni-Ti alloy. The design of the stent is a major factor which determines its reliability after implantation into a stenosed non-vascular cavity. This paper presents the effect of the main structural parameters on the mechanical properties of braided stents. A parametric analysis of a commercial stent model is developed using the commercial finite element code ANSYS. As a consequence of the analytical results that the pitch of wire has a greater effect than other structural parameters, a new design of a variable pitch stent is presented to improve mechanical properties of these braided stents. The effect of structural parameters on mechanical properties is compared for both stent models: constant and variable pitches. When the pitches of the left and right quarters of the stent are 50% larger and 100% larger than that of the central portion, respectively, the radial stiffness in the central portion increases by 10% and 38.8%, while the radial stiffness at the end portions decreases by 128% and 164.7%, the axial elongation by 25.6% and 56.6% and the bending deflection by 3.96% and 10.15%. It has been demonstrated by finite element analysis that the variable pitch stent can better meet the clinical requirements. PMID:24867297
Podolak, Charles J.
2013-01-01
An ensemble of rule-based models was constructed to assess possible future braided river planform configurations for the Toklat River in Denali National Park and Preserve, Alaska. This approach combined an analysis of large-scale influences on stability with several reduced-complexity models to produce the predictions at a practical level for managers concerned about the persistence of bank erosion while acknowledging the great uncertainty in any landscape prediction. First, a model of confluence angles reproduced observed angles of a major confluence, but showed limited susceptibility to a major rearrangement of the channel planform downstream. Second, a probabilistic map of channel locations was created with a two-parameter channel avulsion model. The predicted channel belt location was concentrated in the same area as the current channel belt. Finally, a suite of valley-scale channel and braid plain characteristics were extracted from a light detection and ranging (LiDAR)-derived surface. The characteristics demonstrated large-scale stabilizing topographic influences on channel planform. The combination of independent analyses increased confidence in the conclusion that the Toklat River braided planform is a dynamically stable system due to large and persistent valley-scale influences, and that a range of avulsive perturbations are likely to result in a relatively unchanged planform configuration in the short term.
Magnetic Structure of Sites of Braiding in Hi-C Active Region
Tiwari, S. K.; Alexander, C. E.; Winebarger, A.; Moore, R. L.
2014-01-01
High-resolution Coronal Imager (Hi-C) observations of an active region (AR) corona, at a spatial resolution of 0.2 arcsec, have offered the first direct evidence of field lines braiding, which could deliver sufficient energy to heat the AR corona by current dissipation via magnetic reconnection, a proposal given by Parker three decades ago. The energy required to heat the corona must be transported from the photosphere along the field lines. The mechanism that drives the energy transport to the corona is not yet fully understood. To investigate simultaneous magnetic and intensity structure in and around the AR in detail, we use SDO/HMI+AIA data of + / - 2 hours around the 5 minute Hi-C flight. In the case of the QS, work done by convection/granulation on the inter-granular feet of the coronal field lines probably translates into the heat observed in the corona. In the case of the AR, as here, there could be flux emergence, cancellation/submergence, or shear flows generating large stress and tension in coronal field loops which is released as heat in the corona. However, to the best of our knowledge, there is no observational evidence available to these processes. We investigate the changes taking place in the photospheric feet of the magnetic field involved with brightenings in the Hi-C AR corona. Using HMI 45s magnetograms of four hours we find that, out of the two Hi-C sub-regions where the braiding of field lines were recently detected, flux emergence takes place in one region and flux cancellation in the other. The field in these sub-regions are highly sheared and have apparent high speed plasma flows at their feet. Therefore, shearing flows plausibly power much of the coronal and transition region heating in these areas of the AR. In addition, the presence of large flux emergence/cancellation strongly suggests that the work done by these processes on the pre-existing field also drives much of the observed heating.
Braid bar and island dynamics of the multi-threaded Rio Paraná, Argentina
Nicholas, A.; Ashworth, P.; Sandbach, S.; Amsler, M.; Best, J.; Hardy, R.; Lane, S.; Orfeo, O.; Parsons, D.; Reesink, A.; Sambrook Smith, G.; Szupiany, R.
2012-04-01
Here we report results from a three year study of channel dynamics and bar evolution in one of the World's largest rivers, the multi-threaded Rio Paraná, Argentina. The Rio Paraná is a sand-bed river (D50 ~ 0.35 mm) with a channel pattern that is characterised by stable vegetated islands, dynamic sandy braid bars, partially-coupled floodplain wetlands and, in many reaches, a dominant meandering thalweg. Mean channel width and depth at bankfull conditions are ~2-3 km and ~7-8 m, respectively. Thalweg scour depths are up to 25-30 m. Channel and bar morphodynamics were monitored during this study using a range of techniques including repeat bathymetric surveys, using single- and multi-beam echo sounding, acoustic Doppler current profiler surveys of flow structure and suspended sediment concentration, and analysis of historic bathymetric maps and satellite imagery. Channel hydrodynamics and morphodynamics were also investigated using a range of numerical modelling strategies. These included a 3D Computational Fluid Dynamics model, a 2D physically-based morphodynamic model that solves the shallow water form of the Navier-Stokes equations, and a reduced-complexity model that neglects much of the physics governing fluvial processes. Here we focus on a comparison of numerical model results and field evidence in order to evaluate which modelling strategies have the greatest potential for elucidating process-form relationships within the World's largest multi-threaded rivers. We show that all three modelling approaches are capable of predicting observed depth-mean flow structures within a 30 km study reach of the Rio Paraná. However, we conclude that models of intermediate complexity, based on the depth-averaged shallow water equations, may provide the most effective tools for simulating bar formation and river evolution over time periods of decades to centuries. Results from our morphodynamic model simulations and field data analysis provide insight into mechanisms of
Using Remote-sensing to Survey Topography and Morphologic Change on Large Braided River Beds
Maurice, D.; Hicks, M.; Shankar, U.
2007-12-01
Since 1999 we have made extensive use of a variety of remote-sensing technologies to survey bed topography over reaches of large braided gravel-bed rivers on the east coast of New Zealand's South Island. The motivations have been (i) to collect input and validation data for 2-d hydrodynamic models for quantifying in-stream physical habitat and for predicting flood levels and (ii) to survey spatially-distributed riverbed erosion and deposition in order to estimate bedload fluxes by the 'morphological' method. Typical applications have been to river reaches 3-4 km long and 1 km wide, with grid cells from 1-5 m. We use different techniques to survey dry and wet areas of braided riverbed. For dry areas, we have used digital photogrammetry and infra-red airborne LiDAR. For wetted channels, we have generally used ortho-rectified colour imagery or multi-spectral scanning to map water depth, then we map bed topography by subtracting the water depth from a DEM of the water surface obtained from photogrammetry or LiDAR. The imagery is calibrated to water depth using field measurements on the day of imagery acquisition. Surveys are undertaken during low flows to maximise bed exposure. We use ground-based RTK-GPS and echo-sounding to collect calibration and validation data, and sometimes simply use these methods to survey the wetted areas. Orthoimagery at multiple river flows is used to validate 2-d model results. We have been able to achieve elevation accuracies at interpolated points of the order of 10-15 cm for dry areas. This accuracy typically degrades to 20-30 cm for wetted areas. Our experience has exposed a number of issues relating to survey accuracy and practicality at large river scales. These include: changing geoidal models between surveys; local systematic error with photogrammetric model mosaics; geospatial synchronisation of multi-platform data; time-synchronisation of LiDAR and imagery- collecting aeroplanes and suitable weather and river conditions
Demissie, Biadgilgn; Frankl, Amaury; Haile, Mitiku; Nyssen, Jan
2014-05-01
Braided rivers have received relatively little attention in research and development activities in drylands. However, they strongly impact agroecology and agricultural activities and thereby local livelihoods. The Raya Graben (3750 km² including the escarpment) is a marginal graben of the Ethiopian Rift Valley located in North Ethiopia. In order to study the dynamics of braided rivers and the relationship with biophysical controls, 20 representative catchments were selected, ranging between 15 and 311 km². First, the 2005 morphology (length, area) of the braided rivers was related to biophysical controls (vegetation cover, catchment area and slope gradient in the steep upper catchments and gradient in the graben bottom). Second, the changes in length of the braided rivers were related to vegetation cover changes in the upper catchments since 1972. Landsat imagery was used to calculate the Normalized Difference Vegetation Index (NDVI), and to map vegetation cover and the total length of the braided rivers. Spot CNES imagery available from Google Earth was used to identify the total area of the braided rivers in 2005. A linear regression analysis revealed that the length of braided rivers was positively related to the catchment area (R²=0.32, p<0.01), but insignificantly related to vegetation cover in the upper catchments. However, there is an indication that it is an important factor in the relationship calculated for 2005 (R²=0.2, p=0.064). Similarly, the area occupied by the braided rivers was related to NDVI (R²=0.24, p<0.05) and upper catchment area (R²=0.447, p<0.01). Slope gradient is not an important explanatory factor. This is related to the fact that slope gradients are steep (average of 38.1%) in all upper and gentle (average of 3.4%) in graben bottom catchments. The vegetation cover in the upper catchments shows a statistically insignificant increasing trend (R²=0.73, p=0.067) over the last 40 years, whereas length of rivers in the graben bottom
Evaluation of Test Methods for Triaxially Braided Composites using a Meso-Scale Finite Element Model
Zhang, Chao
2015-10-01
The characterization of triaxially braided composite is complicate due to the nonuniformity of deformation within the unit cell as well as the possibility of the freeedge effect related to the large size of the unit cell. Extensive experimental investigation has been conducted to develop more accurate test approaches in characterizing the actual mechanical properties of the material we are studying. In this work, a meso-scale finite element model is utilized to simulate two complex specimens: notched tensile specimen and tube tensile specimen, which are designed to avoid the free-edge effect and free-edge effect induced premature edge damage. The full field strain data is predicted numerically and compared with experimental data obtained by Digit Image Correlation. The numerically predicted tensile strength values are compared with experimentally measured results. The discrepancy between numerically predicted and experimentally measured data, the capability of different test approaches are analyzed and discussed. The presented numerical model could serve as assistance to the evaluation of different test methods, and is especially useful in identifying potential local damage events.
The classification of the virtually cyclic subgroups of the sphere braid groups
Gonçalves, Daciberg Lima
2011-01-01
We study the problem of determining the isomorphism classes of the virtually cyclic subgroups of the n-string braid groups B_n(S^2) of the 2-sphere S^2. If n is odd, or if n is even and sufficiently large, we obtain the complete classification. For small even values of n, the classification is complete up to an explicit finite number of open cases. In order to prove our main theorem, we obtain a number of other results of independent interest, notably the characterisation of the centralisers and normalisers of the finite cyclic and dicyclic subgroups of B_n(S^2), a result concerning conjugate powers of finite order elements, an analysis of the isomorphism classes of the amalgamated products that occur as subgroups of B_n(S^2), as well as an alternative proof of the fact that the universal covering space of the n-th configuration space of S^2 has the homotopy type of S^3 if n is greater than or equal to three.
3D flexible NiTi-braided elastomer composites for smart structure applications
While outstanding functional properties of thin NiTi wires are nowadays well recognized and beneficially utilized in medical NiTi devices, development of 2D/3D wire structures made out of these NiTi wires remains challenging and mostly unexplored. The research is driven by the idea of creating novel 2D/3D smart structures which inherit the functional properties of NiTi wires and actively utilize geometrical deformations within the structure to create new/improved functional properties. Generally, textile technology provides attractive processing methods for manufacturing 2D/3D smart structures made out of NiTi wires. Such structures may be beneficially combined with soft elastomers to create smart deformable composites. Following this route, we carried out experimental work focused on development of 3D flexible NiTi-braided elastomer composites involving their design, laboratory manufacture and thermomechanical testing. We describe the manufacturing technology and structural properties of these composites; and perform thermomechanical tests on the composites, focusing particularly on quasistatic tensile properties, energy absorption, damping and actuation under tensile loading. Functional thermomechanical properties of the composites are discussed with regard to the mechanical properties of the components and architecture of the composites. It is found that the composites indeed inherit all important features of the thermomechanical behavior of NiTi wires but, due to their internal architecture, outperform single NiTi wires in some features such as the magnitude of recoverable strain, superelastic damping capacity and thermally induced actuation strain. (paper)
BRAID: A Unifying Paradigm for the Analysis of Combined Drug Action.
Twarog, Nathaniel R; Stewart, Elizabeth; Hammill, Courtney Vowell; A Shelat, Anang
2016-01-01
With combination therapies becoming increasingly vital to understanding and combatting disease, a reliable method for analyzing combined dose response is essential. The importance of combination studies both in basic and translational research necessitates a method that can be applied to a wide range of experimental and analytical conditions. However, despite increasing demand, no such unified method has materialized. Here we introduce the Bivariate Response to Additive Interacting Doses (BRAID) model, a response surface model that combines the simplicity and intuitiveness needed for basic interaction classifications with the versatility and depth needed to analyze a combined response in the context of pharmacological and toxicological constraints. We evaluate the model in a series of simulated combination experiments, a public combination dataset, and several experiments on Ewing's Sarcoma. The resulting interaction classifications are more consistent than those produced by traditional index methods, and show a strong relationship between compound mechanisms and nature of interaction. Furthermore, analysis of fitted response surfaces in the context of pharmacological constraints yields a more concrete prediction of combination efficacy that better agrees with in vivo evaluations. PMID:27160857
On the use of airborne LiDAR for braided river monitoring and water surface delineation
Vetter, M.; Höfle, B.; Pfeifer, N.; Rutzinger, M.; Stötter, J.
2009-04-01
Airborne LiDAR is an established technology for Earth surface surveying. With LiDAR data sets it is possible to derive maps with different land use classes, which are important for hydraulic simulations. We present a 3D point cloud based method for automatic water surface delineation using single as well as multitemporal LiDAR data sets. With the developed method it is possible to detect the location of the water surface with high planimetric accuracy. The multitemporal analysis of different LiDAR data sets makes it possible to visualize, monitor and quantify the changes of the flow path of braided rivers as well as derived water surface land use classes. The reflection properties from laser beams (1064 nm wavelength) on water surfaces are characterized by strong absorption or specular reflection resulting in a dominance of low signal amplitude values and a high number of laser shot dropouts (i.e. non-recorded laser echoes). The occurrence of dropouts is driven by (i) the incidence angle, (ii) the surface reflectance and (iii) the roughness of the water body. The input data of the presented delineation method are the modeled dropouts and the point cloud attributes of geometry and signal amplitude. A terrestrial orthophoto is used to explore the point cloud in order to find proper information about the geometry and amplitude attributes that are characteristic for water surfaces. The delineation method is divided into five major steps. (a) We compute calibrated amplitude values by reducing the atmospheric, topographic influences and the scan geometry for each laser echo. (b) Then, the dropouts are modeled by using the information from the time stamps, the pulse repetition frequency, the inertial measurement unit and the GPS information of the laser shots and the airplane. The next step is to calculate the standard deviation of the heights for all reflections and all modeled dropouts (c) in a specific radius around the points. (d) We compute the amplitude ratio
Highlights: • The stability of materials under extreme conditions is an important issue for the safety of nuclear reactors. • To improve zircaloys’ thermal stability in off-normal conditions, coating of SiC filaments is considered because silicon carbide possesses remarkable inertness at high temperatures. • Mathematical morphology was used for automatic defect identification in Zircaloy-4 rods braided with the layer of SiC filament. • The original mathematical morphology algorithms allowing solving the problem of quality assurance were developed. • In nuclear industry, such algorithms are used for the first time. - Abstract: In the after-Fukushima world, the stability of materials under extreme conditions is an important issue for the safety of nuclear reactors. Among the methods explored currently to improve zircaloys’ thermal stability in off-normal conditions, using a protective coat of the SiC filaments is considered because silicon carbide is well known for its remarkable chemical inertness at high temperatures. A typical SiC fiber contains ∼50,000 individual filaments of 5–10 μm in diameter. In this paper, an effort was made to develop and apply mathematical morphology to the process of automatic defect identification in Zircaloy-4 rods braided with the protective layer of the silicon carbide filament. However, the issues of the braiding quality have to be addressed to ensure its full protective potential. We present the original mathematical morphology algorithms that allow solving this problem of quality assurance successfully. In nuclear industry, such algorithms are used for the first time, and could be easily generalized to the case of automated continuous monitoring for defect identification in the future
Gran, K. B.; Michal, T.
2014-12-01
Increased bank stability by riparian vegetation in braided rivers can decrease bed reworking rates and focus the flow. The magnitude of influence and resulting channel morphology are functions of vegetation strength vs. channel dynamics, a concept encapsulated in a dimensionless ratio between timescales for vegetation growth and channel reworking known as T*. We investigate this relationship in an aggrading braided river at Mount Pinatubo, Philippines, and compare results to numerical and physical models. Gradual reductions in post-eruption sediment loads have reduced bed reworking rates, allowing vegetation to persist year-round and impact channel dynamics on the Pasig-Potrero and Sacobia Rivers. From 2009-2011, we collected data detailing vegetation extent, type, density, and root strength. Incorporating these data into RipRoot and BSTEM models shows cohesion due to roots increased from zero in unvegetated conditions to >10.2 kPa in densely-growing grasses. Field-based parameters were incorporated into a cellular model comparing vegetation growth and sediment mobility effects on braided channel dynamics. The model shows that both low sediment mobility and high vegetation strength lead to less active systems, reflecting trends observed in the field. An estimated T* between 0.8 - 2.3 for the Pasig-Potrero River suggests channels were mobile enough to maintain the braidplain width clear of vegetation and even experience slight gains in area through annual removal of existing vegetation. However, persistent vegetation focused flow and thus aggradation over the unvegetated fraction of braidplain, leading to an aggradational imbalance and transition to a more avulsive state. While physical models predict continued narrowing of the active braidplain as T* declines, the future trajectory of channel-vegetation interactions at Pinatubo as sedimentation rates decline appears more complicated due to strong seasonal variability in precipitation and sediment loads. By 2011
Desbois, Jean; Nechaev, Sergei
1997-01-01
We study numerically and analytically the average length of reduced (primitive) words in so-called locally free and braid groups. We consider the situations when the letters in the initial words are drawn either without or with correlations. In the latter case we show that the average length of the reduced word can be increased or lowered depending on the type of correlation. The ideas developed are used for analytical computation of the average number of peaks of the surface appearing in som...
Jules Fleury, Thomas; Pothin, Virginie; Vella, Claude; Dussouillez, Philippe; Izem, Abdelkoddouss
2015-04-01
Low-altitude aerial photogrammetry offers new opportunities for geomorphology and other fields requiring very high-resolution topographic data. It combines the advantages of the reproducibility of GPS topographic surveys with the high accuracy of LIDAR, but at relatively low-cost, easy-to-deploy and with the synaptic advantage of remote sensing. In order to evaluate the potential of photogrammetry on river systems and to assess river-bed changes and erosion-accretion processes, we conducted several surveys over the period of one year on the Buech river, a gravel-bed braided river located in the French Southern Alps. The study area is located directly upstream of a gravel pit and there is an interest in evaluating its effects on the riverbed. Our field protocol was comprised of vertical aerial photographs taken from a microlight aircraft flying approximately 300 ft above the ground. The equipment used was a full-frame DSLR with a wide angle lense, synchronised with a DGPS onboard. Fourty 40cm wide targets were placed on the ground and georeferenced by RTK DGPS with an accuracy of 2cm. In addition, close to one thousand Ground Control Points (GCPs) were measured within the different types of ground surfaces (vegetated, water, gravels) in order to assess the Digital Terrain Model (DTM) accuracy. We operated the production of the 3D model and its derived products: Digital Surface Model (DSM) and orthophotography, with user-friendly Agisoft (c) Photoscan Professional software. The processing of several hundred pictures with 2.5 cm ground resolution resulted in a DSM with a resolution of 10 cm and a vertical accuracy within 5 cm. As is expected, accuracy was best on bare bars and decreased with increasing vegetation density. To complement the DSM in the wetted channels, we used the orthophotos to establish a relationship between water color and flow depth using statistical multivariate regressions. Merging the bathymetric model and the DSM produced a DTM with a vertical
Projective ribbon permutation statistics: A remnant of non-Abelian braiding in higher dimensions
Freedman, Michael; Hastings, Matthew B.; Nayak, Chetan; Qi, Xiao-Liang; Walker, Kevin; Wang, Zhenghan
2011-03-01
In a recent paper, Teo and Kane [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.104.046401 104, 046401 (2010)] proposed a three-dimensional (3D) model in which the defects support Majorana fermion zero modes. They argued that exchanging and twisting these defects would implement a set R of unitary transformations on the zero-mode Hilbert space which is a “ghostly” recollection of the action of the braid group on Ising anyons in two dimensions. In this paper, we find the group T2n, which governs the statistics of these defects by analyzing the topology of the space K2n of configurations of 2n defects in a slowly spatially varying gapped free-fermion Hamiltonian: T2n≡π1(K2n). We find that the group T2n=Z×T2nr, where the “ribbon permutation group” T2nr is a mild enhancement of the permutation group S2n: T2nr≡Z2×E((Z2)2n⋊S2n). Here, E((Z2)2n⋊S2n) is the “even part” of (Z2)2n⋊S2n, namely, those elements for which the total parity of the element in (Z2)2n added to the parity of the permutation is even. Surprisingly, R is only a projective representation of T2n, a possibility proposed by Wilczek [e-print arXiv:hep-th/9806228]. Thus, Teo and Kane’s defects realize projective ribbon permutation statistics,” which we show to be consistent with locality. We extend this phenomenon to other dimensions, codimensions, and symmetry classes. We note that our analysis applies to 3D networks of quantum wires supporting Majorana fermions; thus, these networks are not required to be planar. Because it is an essential input for our calculation, we review the topological classification of gapped free-fermion systems and its relation to Bott periodicity.
A radio frequency tracing experiment of bedload transport in a small braided mountain stream
Liebault, F.; Chapuis, M.; Bellot, H.; Deschatres, M.
2009-04-01
Radio frequency identification technology is used for monitoring the displacement of coarse particles in streams since the beginning of the 2000s. Passive integrated transponders (PIT tags) are small, cheap and long-lasting electronic tags that can be programmed with their own identification code. Initially used in environmental research for animal tracking, they have been deployed successfully in a variety of fluvial environments for coarse sediment tracing. Pioneering studies conducted in both semiarid and humid small upland streams with low intensity bedload transport gave recovery rates above 85% (Nichols 2004; Lamarre et al. 2005). Here we present an experiment of radio frequency sediment tracing implemented on a small braided mountain stream with a high intensity bedload transport and a wide active channel (mean active channel width: about 20 m). The study site is the Bouinenc Torrent, a tributary to the Bléone River in SE France that drains a 39 km² mountainous drainage basin of the Southern Prealps. In spring 2008, we deployed 451 tracers with b-axis ranging from 23 to 520 mm. Tracers were deployed along 8 cross sections located in the upstream part of the lowest 2.3 km of the stream. We developed a RFID detection system composed of an antenna and a reader unit; this system is characterized by a range of detection of 80 cm in optimal configuration. Two small intensity flow events occurred in June 2008 and entrained the tracers deployed in the most active part of the active channel. We mapped the position of the displaced tracers with a dGPS in July 2008. We obtained an overall recovery rate of 88%. The recovery rate calculated for the active tracers (those that were displaced after the flow events) was 76%. The projection of the tracer dispersion cloud on high resolution aerial photographs obtained with a drone allows us to calculate the distance of transport for each tracer. Mean and maximal distances of transport were respectively 796 m (+/- 53 m) and 2
QU Zhaoming; WANG Qingguo; LEI Yisan; ZHANG Ruigang
2013-01-01
To develop electromagnetic protection composites with integrated structure-function properties,the three-dimension (3D) braided nickel plated carbon fiber/epoxy resin (Ni-CF3D/EP) composites were prepared based on 3D five-directional braiding,unitary nickel plating and mold compression shaping.The electromagnetic protection properties of Ni-CF3D/EP composites including shielding effectiveness (SE) and reflection loss against plane electromagnetic wave,shielding properties against electromagnetic pulse (EMP) were investigated.The test results show that the novel composites have good electromagnetic protection properties in a wide frequency range of 14 kHz～ 18 GHz with SE of 42 dB～95 dB,the absorption bandwidth of-5 dB in 2 GHz～ 18 GHz can reach 10 GHz and the pulse peak SE against EMP is 43.7 dB which can reduce the electromagnetic energy greatly.Meanwhile,the mechanic properties were also investigated and the results indicate that the Ni-CF3D/EP composites can replace metal materials for loading-bearing structural applications because of their excellent mechanic properties.
Pedrocchi, Fabio L.; Bonesteel, N. E.; DiVincenzo, David P.
2015-09-01
The Majorana code is an example of a stabilizer code where the quantum information is stored in a system supporting well-separated Majorana bound states (MBSs). We focus on one-dimensional realizations of the Majorana code, as well as networks of such structures, and investigate their lifetime when coupled to a parity-preserving thermal environment. We apply the Davies prescription, a standard method that describes the basic aspects of a thermal environment, and derive a master equation in the Born-Markov limit. We first focus on a single wire with immobile MBSs and perform error correction to annihilate thermal excitations. In the high-temperature limit, we show both analytically and numerically that the lifetime of the Majorana qubit grows logarithmically with the size of the wire. We then study a trijunction with four MBSs when braiding is executed. We study the occurrence of dangerous error processes that prevent the lifetime of the Majorana code from growing with the size of the trijunction. The origin of the dangerous processes is the braiding itself, which separates pairs of excitations and renders the noise nonlocal; these processes arise from the basic constraints of moving MBSs in one-dimensional (1D) structures. We confirm our predictions with Monte Carlo simulations in the low-temperature regime, i.e., the regime of practical relevance. Our results put a restriction on the degree of self-correction of this particular 1D topological quantum computing architecture.
CSO BOLOCAM 1.1 mm CONTINUUM MAPPING OF THE BRAID NEBULA STAR FORMATION REGION IN CYGNUS OB7
We present a 1.1 mm map of the Braid Nebula star formation region in Cygnus OB7 taken using Bolocam on the Caltech Submillimeter Observatory. Within the 1 deg2 covered by the map, we have detected 55 cold dust clumps all of which are new detections. A number of these clumps are coincident with IRAS point sources although the majority are not. Some of the previously studied optical/near-IR sources are detected at 1.1 mm. We estimate total dust/gas masses for the 55 clumps together with peak visual extinctions. We conclude that over the whole region, approximately 20% of the clumps are associated with IRAS sources suggesting that these are protostellar objects. The remaining 80% are classed as starless clumps. In addition, both FU Orionis (FUor) like objects in the field, the Braid Star and HH 381 IRS, are associated with strong millimeter emission. This implies that FUor eruptions can occur at very early stages of pre-main-sequence life. Finally, we determine that the cumulative clump mass function for the region is very similar to that found in both the Perseus and ρ Ophiuchus star-forming regions.
Hatsukade, Y., E-mail: hatukade@ens.tut.ac.jp [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Shinyama, Y.; Yoshida, K. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan); Takai, Y. [Osaka Sangyo University, 3-1-1 Nakagaito, Daito, Osaka 574-8530 (Japan); Aly-Hassan, M.S.; Nakai, A.; Hamada, H. [Advanced Fibro-Science Division, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto 606-8585 (Japan); Adachi, S.; Tanabe, K. [International Superconductivity Technology Center, Superconductivity Research Laboratory, 10-13, Shinonome 1-chome, Koto-ku, Tokyo 135-0062 (Japan); Tanaka, S. [Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku-cho, Toyohashi, Aichi 441-8580 (Japan)
2013-01-15
Highlights: ► Tensile load was applied to braided CFRPs with and without CNFs and cutting edges. ► Visualization method using SQUID gradiometer was also applied to the braided CFRPs. ► Different destructive mechanisms and current distributions were obtained. ► Dispersed CNFs enhanced mechanical and electrical properties of the braided CFRPs. -- Abstract: Step-by-step tensile tests were applied to flat-braided carbon-fiber-reinforced polymers with and without added dispersions of carbon nanofibers (CNFs) and with and without sample sides cut off to study their mechanical properties and destructive mechanisms by means of in situ observation and stress–strain measurements. An ex situ nondestructive evaluation technique, using a high-temperature superconductor superconducting quantum interference device gradiometer, was also applied to the samples to study their electrical properties; the relationships between the mechanical and electrical properties by visualizing current maps in the samples during ac current injection was also studied. Clear differences were observed in the mechanical and electrical properties and the destructive mechanisms between the samples with and without CNFs and with and without cut off sides. These differences were mainly attributed to the addition of CNFs, which enhanced the mechanical and electrical connections between the carbon fiber bundles.
Highlights: ► Tensile load was applied to braided CFRPs with and without CNFs and cutting edges. ► Visualization method using SQUID gradiometer was also applied to the braided CFRPs. ► Different destructive mechanisms and current distributions were obtained. ► Dispersed CNFs enhanced mechanical and electrical properties of the braided CFRPs. -- Abstract: Step-by-step tensile tests were applied to flat-braided carbon-fiber-reinforced polymers with and without added dispersions of carbon nanofibers (CNFs) and with and without sample sides cut off to study their mechanical properties and destructive mechanisms by means of in situ observation and stress–strain measurements. An ex situ nondestructive evaluation technique, using a high-temperature superconductor superconducting quantum interference device gradiometer, was also applied to the samples to study their electrical properties; the relationships between the mechanical and electrical properties by visualizing current maps in the samples during ac current injection was also studied. Clear differences were observed in the mechanical and electrical properties and the destructive mechanisms between the samples with and without CNFs and with and without cut off sides. These differences were mainly attributed to the addition of CNFs, which enhanced the mechanical and electrical connections between the carbon fiber bundles
Janke, Christopher James [ORNL; Das, Sadananda [ORNL; Oyola, Yatsandra [ORNL; Mayes, Richard T [ORNL; Gill, Gary [Pacific Northwest National Laboratory (PNNL); Kuo, Li-Jung [Pacific Northwest National Laboratory (PNNL); Wood, Jordana [Pacific Northwest National Laboratory (PNNL)
2015-01-01
This report describes work on the successful completion of Milestone M2FT-15OR0310041 (1/30/2015) entitled, Demonstrate braided material with 3.5 g U/kg sorption capacity under seawater testing condition . This effort is part of the Seawater Uranium Recovery Program, sponsored by the U.S. Department of Energy, Office of Nuclear Energy, and involved the development of new adsorbent braided materials at the Oak Ridge National Laboratory (ORNL) and marine testing at the Pacific Northwest National Laboratory (PNNL). ORNL has recently developed four braided fiber adsorbents that have demonstrated uranium adsorption capacities greater than 3.5 g U/kg adsorbent after marine testing at PNNL. The braided adsorbents were synthesized by braiding or leno weaving high surface area polyethylene fibers and conducting radiation-induced graft polymerization of itaconic acid and acrylonitrile monomers onto the braided materials followed by amidoximation and base conditioning. The four braided adsorbents demonstrated capacity values ranging from 3.7 to 4.2 g U/kg adsorbent after 56 days of exposure in natural coastal seawater at 20 oC. All data are normalized to a salinity of 35 psu.
Wang, Juven C.; Wen, Xiao-Gang
2015-01-01
String and particle braiding statistics are examined in a class of topological orders described by discrete gauge theories with a gauge group G and a 4-cocycle twist ω4 of G 's cohomology group H4(G ,R /Z ) in three-dimensional space and one-dimensional time (3 +1 D ) . We establish the topological spin and the spin-statistics relation for the closed strings and their multistring braiding statistics. The 3 +1 D twisted gauge theory can be characterized by a representation of a modular transformation group, SL (3 ,Z ) . We express the SL (3 ,Z ) generators Sx y z and Tx y in terms of the gauge group G and the 4-cocycle ω4. As we compactify one of the spatial directions z into a compact circle with a gauge flux b inserted, we can use the generators Sx y and Tx y of an SL (2 ,Z ) subgroup to study the dimensional reduction of the 3D topological order C3 D to a direct sum of degenerate states of 2D topological orders Cb2 D in different flux b sectors: C3 D=⊕bCb2 D . The 2D topological orders Cb2 D are described by 2D gauge theories of the group G twisted by the 3-cocycle ω3 (b ), dimensionally reduced from the 4-cocycle ω4. We show that the SL (2 ,Z ) generators, Sx y and Tx y, fully encode a particular type of three-string braiding statistics with a pattern that is the connected sum of two Hopf links. With certain 4-cocycle twists, we discover that, by threading a third string through two-string unlink into a three-string Hopf-link configuration, Abelian two-string braiding statistics is promoted to non-Abelian three-string braiding statistics.
Lin, Jia-Horng; Chen, Chih-Kuang; Wen, Shih-Peng; Lou, Ching-Wen
2015-01-01
Bone scaffolds require a three-dimensional structure, high porosity, interconnected pores, adequate mechanical strengths, and non-toxicity. A high porosity is incongruent with mechanical strengths. Therefore, this study combines a braiding method and microsphere solution to create bone scaffolds with a high porosity and sufficient mechanical strengths. First, poly-L-lactide (PLLA) plied yarns are braided into 5-, 10-, 15-, 20-, and 25-layer hollow braids, and then thermally treated at 165 °C for various durations. Next, sodium alginate (SA) microspheres, cross-linked with CaCl2 solution with various concentrations, are combined with PLLA porous braided bone scaffolds to form PLLA/SA/CS microsphere hybrid scaffolds, which are then observed for surface observation, and tested for porosity, water contact angle, compressive strength, MTT assay, bioactivity, alkaline phosphatase (ALP) assay, cell attachment, and statistical analyses. The test results show that the layer amount of the bone scaffold is proportional to the compressive strength. With the same number of layers, the compressive strength is inversely proportional to the concentration of the CaCl2 solution. The results of surface observation, porosity, and water contact angle tests show that PLLA/SA/CS microsphere hybrid scaffolds possess a high porosity and good hydrophilicity; as a result, the braiding manufacture and the bonding technique effectively solve the confliction between porosity and mechanical strength. The concentration of CaCl2 does not pertain to cell activity and ALP results, exemplified by good cell attachment on bone scaffolds for each specification. PMID:25953547
Dow, Marvin B.; Dexter, H. Benson
1997-01-01
Summary results are presented from the research conducted on woven, braided, knitted and stitched (textile) composites at the Langley Research Center and under the NASA Advanced Composites Technology (ACT) Program in the period from 1985 to 1997. The report also includes an annotated bibliography of 270 U.S. publications on textile composites (with their abstracts). Two major research areas are discussed: (1) the general research in textile composites performed throughout the period under the direction of the Langley Research Center and (2) the development of textile composite aircraft structures by industry under the NASA ACT Program. The annotated bibliography is organized in three subsections: (1) general textiles R&D under the auspices of Langley, (2) ACT Program development of textile structural components, and (3) textiles research by individuals and organizations not associated with the ACT Program. An author index is provided for the reports and documents.
Brasington, J.; Williams, R. D.; Vericat, D.; Hicks, M.; Goodsell, B.
2011-12-01
The last decade has witnessed a technological revolution in the acquisition of geospatial data. These developments have profound implications for the practice of river science, creating a step-change in the dimensionality, resolution and precision of measurement of fluvial forms and processes. The pace of change has been remarkable; typical datasets of channel geometry have grown from cross-sections containing a few hundred survey observations, to airborne lidar surveys incorporating millions of points. With wide-area terrestrial laser scans comprising tens of billions observations now set to emerge, our data perspectives have been expanded by seven orders of magnitude. Such rapid modernization brings with it new challenges and necessitates the development of novel data management strategies, original algorithms to process dense 3d data, higher dimensional spatial metrics and innovative simulation methods to make optimal use of this rich vein of information. In this paper we describe a field-to-product methodology which aims to address these challenges and has been used to generate an unparalleled dataset capturing the morphological evolution of a labile gravel-bed braided river through a continuous sequence of floods between Oct 2009 and May 2010. These data were generated using a data-fusion approach that combines close-range terrestrial laser scanning with bathymetric data derived from non-metric aerial photography. Surveys were acquired over a 2.5 x 0.7 km reach of the Rees River; a piedmont braided system draining a highland catchment of Southern Alps of NZ. During a 10 month field campaign through the summer flood season, this study reach was resurveyed systematically after each competent flood event. Multi-scale DEMs were derived that capture the spatial distribution of facies and morphological changes at high precision. Results indicate that over 80% of the reach was subject to significant erosion or deposition, with a complex pattern of response to the
Sorini, Chris; Chattopadhyay, Aditi; Goldberg, Robert K.; Kohlman, Lee W.
2016-01-01
Understanding the high velocity impact response of polymer matrix composites with complex architectures is critical to many aerospace applications, including engine fan blade containment systems where the structure must be able to completely contain fan blades in the event of a blade-out. Despite the benefits offered by these materials, the complex nature of textile composites presents a significant challenge for the prediction of deformation and damage under both quasi-static and impact loading conditions. The relatively large mesoscale repeating unit cell (in comparison to the size of structural components) causes the material to behave like a structure rather than a homogeneous material. Impact experiments conducted at NASA Glenn Research Center have shown the damage patterns to be a function of the underlying material architecture. Traditional computational techniques that involve modeling these materials using smeared homogeneous, orthotropic material properties at the macroscale result in simulated damage patterns that are a function of the structural geometry, but not the material architecture. In order to preserve heterogeneity at the highest length scale in a robust yet computationally efficient manner, and capture the architecturally dependent damage patterns, a previously-developed subcell modeling approach where the braided composite unit cell is approximated as a series of four adjacent laminated composites is utilized. This work discusses the implementation of the subcell methodology into the commercial transient dynamic finite element code LS-DYNA (Livermore Software Technology Corp.). Verification and validation studies are also presented, including simulation of the tensile response of straight-sided and notched quasi-static coupons composed of a T700/PR520 triaxially braided [0deg/60deg/-60deg] composite. Based on the results of the verification and validation studies, advantages and limitations of the methodology as well as plans for future work
Medvedev, Vladimir K.
1995-01-01
In this paper we indicate one method of construction of linear representations of groups and algebras with translation invariant (except, maybe , finite number) defining relationships. As an illustration of this method, we give one approach to the construction of linear representations of braid group and derive some series of such representations. Some invariants of oriented knots and links are constructed. The author is grateful to Yuri Drozd, Sergey Ovsienko and other members of algebraic s...
Foek, Dave Lie Sam; Yetkiner, Enver; Ozcan, Mutlu
2013-01-01
OBJECTIVE: To analyze the fatigue resistance, debonding force, and failure type of fiber-reinforced composite, polyethylene ribbon-reinforced, and braided stainless steel wire lingual retainers in vitro. METHODS: Roots of human mandibular central incisors were covered with silicone, mimicking the periodontal ligament, and embedded in polymethylmethacrylate. The specimens (N = 50), with two teeth each, were randomly divided into five groups (n = 10/group) according to the retainer materials...
Zhang, Chao; Xu, Xiwu; Chen, Kang
2013-10-01
As new lightweight textile material, 3D five directional and full five directional braided composites (5DBC and F5DBC) have tremendous potential applications in the aerospace industry. Before they are used in primary loading-bearing structures, a rational characterization of their mechanical properties is essential. In this paper, three types of unit-cell models corresponding to the interior, surface and corner regions of 5DBC and F5DBC are proposed. By introducing the reasonable boundary conditions, the effective stiffness properties of these two materials are predicted and compared by the three unit-cells models. The detailed mechanical response characteristic of the three unit-cell models is presented and analyzed in various loading cases. Numerical results show good agreement with experiment data, thus validates the proposed simulation method. Moreover, a parametric study is carried out for analyzing the effects of braiding angle and fiber volume fraction on the elastic properties of 5DBC and F5DBC. The obtained results can help designers to optimize the braided composite structures.
De Vincenzo, Annamaria; Brancati, Francesco; Pannone, Marilena
2016-08-01
Laboratory experiments were performed with nearly uniform fluvial gravel (D50=9 mm, D10=5 mm and D90=13 mm) to analyse the relationship between stream power and bed load transport rate in gravel-bed braided rivers at high grain Reynolds numbers. The values of the unit-width dimensionless bed-load rate qb* and unit-width dimensionless stream power ω* were evaluated in equilibrium conditions based on ten different experimental runs. Then, they were plotted along with values obtained during particularly representative field studies documented in the literature, and a regression law was derived. For comparison, a regression analysis was performed using the data obtained from laboratory experiments characterized by smaller grain sizes and, therefore, referring to relatively low grain Reynolds numbers. A numerical integration of Exner's equation was performed to reconstruct the local and time-dependent functional dependence of qb* and ω*. The results led to the following conclusions: 1) At equilibrium, the reach-averaged bed load transport rate is related to the reach-averaged stream power by different regression laws at high and low grain Reynolds numbers. Additionally, the transition from bed to suspended load transport is accelerated by low Re*, with the corresponding bed load discharge increasing with stream power at a lower, linear rate. 2) When tested against the gravel laboratory measurements, the high Re* power law derived in the present study performs considerably better than do previous formulas. 3) The longitudinal variability of the section-averaged equilibrium stream power is much more pronounced than that characterizing the bed load rate, at least for high Re*. Thus, the stream power and its local-scale heterogeneity seem to be directly responsible for transverse sediment re-distribution and, ultimately, for the determination of the spatial and temporal scales that characterize the gravel bedforms. 4) Finally, the stochastic interpretation of the wetted
Picco, L.; Mao, L.; Cavalli, M.; Buzzi, E.; Rainato, R.; Lenzi, M. A.
2013-11-01
Braided rivers are dynamic and complex environments shaped by the balance of the flow and sediment regimes and by the influence of the riparian vegetation and disturbances such as floods. In particular, the balance between sediment supply and transport capacity can determine the morphological evolution of a river. For instance, aggrading and widening trends are distinctive of reaches where sediment supply is higher than transport capacity. In contrast, incising and narrowing tendencies are dominant. The aim of the present study is to analyze the short-term morphological dynamics and the processes of erosion and sediment deposition along a small reach of a relatively unimpacted gravel-bed braided river (Tagliamento River, northeast Italy) using a terrestrial laser scanner (TLS). The study area is around 23 ha and has been surveyed before after two periods with relevant flood events, two of which were higher than the bankfull level and occurred between September 2010 and September 2011. The very high point clouds density allowed us to derive three high resolution digital elevation models (DEMs) with 0.125 × 0.125 m pixel size. Scan data cloud merging was achieved with an overall high degree of accuracy and resolution (subcentimeter). Topographic data were more accurate for exposed surfaces than those collected in wet areas. A detailed net of dGPS control points allowed us to verify the high quality of the DEMs derived from the surveys (RMSE of about 5 cm). Two DEMs of difference (DoD) were computed, revealing different and consistent episodes of erosion and deposition within the analyzed area, and changes in morphology of channel and bars could also be detected, such as bar edge accretion and bank erosion demonstrating a strong dynamicity of the Tagliamento River. Moreover, a very detailed estimation of the surface roughness in the study area has been carried out, permitting a large-scale analysis of the roughness values distribution. The results of the analysis on
Jochen eSchubert
2015-11-01
Full Text Available Metric resolution digital terrain models (DTMs of rivers now make it possible for multi-dimensional fluid mechanics models to be applied to characterize flow at fine scales that are relevant to studies of river morphology and ecological habitat, or microscales. These developments are important for managing rivers because of the potential to better understand system dynamics, anthropogenic impacts, and the consequences of proposed interventions. However, the data volumes and computational demands of microscale river modeling have largely constrained applications to small multiples of the channel width, or the mesoscale. This report presents computational methods to extend a microscale river model beyond the mesoscale to the macroscale, defined as large multiples of the channel width. A method of automated unstructured grid generation is presented that automatically clusters fine resolution cells in areas of curvature (e.g., channel banks, and places relatively coarse cells in areas lacking topographic variability. This overcomes the need to manually generate breaklines to constrain the grid, which is painstaking at the mesoscale and virtually impossible at the macroscale. The method is applied to a braided river with an extremely complex channel network configuration and shown to yield an efficient fine resolution model. The sensitivity of model output to grid design and resistance parameters is also examined as it relates to analysis of hydrology, hydraulic geometry and river habitats and the findings reiterate the importance of model calibration and validation.
Pereira, J. Michael; Roberts, Gary D.; Ruggeri, Charles R.; Gilat, Amos; Matrka, Thomas
2010-01-01
An experimental program is underway to measure the impact and high strain rate properties of triaxial braided composite materials and to quantify any degradation in properties as a result of thermal and hygroscopic aging typically encountered during service. Impact tests are being conducted on flat panels using a projectile designed to induce high rate deformation similar to that experienced in a jet engine fan case during a fan blade-out event. The tests are being conducted on as-fabricated panels and panels subjected to various numbers of aging cycles. High strain rate properties are being measured using a unique Hopkinson bar apparatus that has a larger diameter than conventional Hopkinson bars. This larger diameter is needed to measure representative material properties because of the large unit cell size of the materials examined in this work. In this paper the experimental techniques used for impact and high strain rate testing are described and some preliminary results are presented for both as-fabricated and aged composites.
Leake, S.A.; Lilly, M.R.
1995-01-01
The Fairbanks, Alaska, area has many contaminated sites in a shallow alluvial aquifer. A ground-water flow model is being developed using the MODFLOW finite-difference ground-water flow model program with the River Package. The modeled area is discretized in the horizontal dimensions into 118 rows and 158 columns of approximately 150-meter square cells. The fine grid spacing has the advantage of providing needed detail at the contaminated sites and surface-water features that bound the aquifer. However, the fine spacing of cells adds difficulty to simulating interaction between the aquifer and the large, braided Tanana River. In particular, the assignment of a river head is difficult if cells are much smaller than the river width. This was solved by developing a procedure for interpolating and extrapolating river head using a river distance function. Another problem is that future transient simulations would require excessive numbers of input records using the current version of the River Package. The proposed solution to this problem is to modify the River Package to linearly interpolate river head for time steps within each stress period, thereby reducing the number of stress periods required.
Ioana-Toroimac, Gabriela
2016-07-01
The inventory of long-term braiding activity is a useful tool for detecting alterations in a rivers' hydromorphological state and for a river's management in the context of the Water Framework Directive on integrated river basin management for Europe. Our study focuses on braided sectors of rivers in South-Eastern Subcarpathians (Romania). The inventory evaluates types of alterations based on the spatial analysis of fluvial morphology indicators (i.e., length of the river sector forming a braided pattern; width of the braided active channel), and vegetation cover (i.e., length of banks covered by forest and shrubs; area of in-stream patches of shrubs) accumulated over the last century. Furthermore, we performed a regional scale hierarchical cluster analysis to estimate the degree of alteration when compared to an historical baseline. In South-Eastern Subcarpathians, the studied rivers experienced a decrease of braiding activity revealed by the shortening and narrowing of their braided sectors, expansion of riparian forests, and the diminishment of vegetated islands' areas. We separated three types of river clusters, corresponding to low (cluster 1), moderate (cluster 2), and high (cluster 3) degree of alteration. Moreover, the clusters demonstrate the evolutionary path of the braided pattern alterations until the functioning of another channel pattern. The inventory is relevant for differing types and levels of alterations. Additionally, this tool may serve as a first step toward the restoration of altered sectors by identifying rivers in cluster 1 as potential candidates of present-day reference sites for altered rivers with similar natural conditions as in cluster 3.
Gleason, C. J.; Smith, L. C.; Finnegan, D. C.; LeWinter, A. L.; Pitcher, L. H.; Chu, V. W.
2015-06-01
River systems in remote environments are often challenging to monitor and understand where traditional gauging apparatus are difficult to install or where safety concerns prohibit field measurements. In such cases, remote sensing, especially terrestrial time-lapse imaging platforms, offer a means to better understand these fluvial systems. One such environment is found at the proglacial Isortoq River in southwestern Greenland, a river with a constantly shifting floodplain and remote Arctic location that make gauging and in situ measurements all but impossible. In order to derive relevant hydraulic parameters for this river, two true color (RGB) cameras were installed in July 2011, and these cameras collected over 10 000 half hourly time-lapse images of the river by September of 2012. Existing approaches for extracting hydraulic parameters from RGB imagery require manual or supervised classification of images into water and non-water areas, a task that was impractical for the volume of data in this study. As such, automated image filters were developed that removed images with environmental obstacles (e.g., shadows, sun glint, snow) from the processing stream. Further image filtering was accomplished via a novel automated histogram similarity filtering process. This similarity filtering allowed successful (mean accuracy 79.6 %) supervised classification of filtered images from training data collected from just 10 % of those images. Effective width, a hydraulic parameter highly correlated with discharge in braided rivers, was extracted from these classified images, producing a hydrograph proxy for the Isortoq River between 2011 and 2012. This hydrograph proxy shows agreement with historic flooding observed in other parts of Greenland in July 2012 and offers promise that the imaging platform and processing methodology presented here will be useful for future monitoring studies of remote rivers.
Boerner, Audrey R.; Gates, John B.
2015-05-01
Impacts of environmental changes on groundwater carbon cycling are poorly understood despite their potentially high relevance to terrestrial carbon budgets. This study focuses on streambed groundwater chemistry during a period of drought-induced river drying and consequent disconnection between surface water and groundwater. Shallow groundwater underlying vegetated and bare portions of a braided streambed in the Platte River (Nebraska, USA) was monitored during drought conditions in summer 2012. Water temperature and dissolved inorganic carbon (dominated by HCO3-) in streambed groundwater were correlated over a 3 month period coinciding with a decline in river discharge from 35 to 0 m3 s-1. Physical, chemical, and isotopic parameters were monitored to investigate mechanisms affecting the HCO3- trend. Equilibrium thermodynamic modeling suggests that an increase of pCO2 near the water table, coupled with carbonate mineral weathering, can explain the trend. Stronger temporal trends in Ca2+ and Mg2+ compared to Cl- are consistent with carbonate mineral reequilibria rather than evaporative concentration as the primary mechanism of the increased HCO3-. Stable isotope trends are not apparent, providing further evidence of thermodynamic controls rather than evaporation from the water table. A combination of increased temperature and O2 in the dewatered portion of the streambed is the most likely driver of increased pCO2 near the water table. Results of this study highlight potential linkages between surface environmental changes and groundwater chemistry and underscore the need for high-resolution chemical monitoring of alluvial groundwater in order to identify environmental change impacts.
Hufenbach, W.; Gude, M.; Czulak, A.; Kretschmann, Martin
2014-04-01
Increasing economic, political and ecological pressure leads to steadily rising percentage of modern processing and manufacturing processes for fibre reinforced polymers in industrial batch production. Component weights beneath a level achievable by classic construction materials, which lead to a reduced energy and cost balance during product lifetime, justify the higher fabrication costs. However, complex quality control and failure prediction slow down the substitution by composite materials. High-resolution fibre-optic sensors (FOS), due their low diameter, high measuring point density and simple handling, show a high applicability potential for an automated sensor-integration in manufacturing processes, and therefore the online monitoring of composite products manufactured in industrial scale. Integrated sensors can be used to monitor manufacturing processes, part tests as well as the component structure during product life cycle, which simplifies allows quality control during production and the optimization of single manufacturing processes.[1;2] Furthermore, detailed failure analyses lead to a enhanced understanding of failure processes appearing in composite materials. This leads to a lower wastrel number and products of a higher value and longer product life cycle, whereby costs, material and energy are saved. This work shows an automation approach for FOS-integration in the braiding process. For that purpose a braiding wheel has been supplemented with an appliance for automatic sensor application, which has been used to manufacture preforms of high-pressure composite vessels with FOS-networks integrated between the fibre layers. All following manufacturing processes (vacuum infiltration, curing) and component tests (quasi-static pressure test, programmed delamination) were monitored with the help of the integrated sensor networks. Keywords: SHM, high-pressure composite vessel, braiding, automated sensor integration, pressure test, quality control, optic
Medvedev, V K
1995-01-01
In this paper we indicate one method of construction of linear representations of groups and algebras with translation invariant (except, maybe , finite number) defining relationships. As an illustration of this method, we give one approach to the construction of linear representations of braid group and derive some series of such representations. Some invariants of oriented knots and links are constructed. The author is grateful to Yuri Drozd, Sergey Ovsienko and other members of algebraic seminar at Kiev University for the creative atmosphere without which this work could hardly appear.
Bertoldi, W.; Gurnell, A. M.; Welber, M.
2013-01-01
This paper investigates wood recruitment and deposition dynamics in a large gravel-bed, braided river (Tagliamento River, Italy). We used a combination of field measurements, automatically repeated ground images, and remotely sensed surveys to quantify wood input through bank erosion and associated downstream deposition. Two sites were investigated where floods caused the erosion of vegetated island edges. A lidar survey preceding the erosion events provided data on the morphology and vegetation structure of the eroded areas, allowing estimation of the number of trees that were uprooted. Sequences of ground-based images acquired automatically (and supported by field measurements) showed the time, number, and location of deposited trees. Results show that the complex morphology of braided rivers induces specific deposition patterns. We observed wide dispersal of wood on gravel bars, with jams characterised by a small number of logs (on average 2-3) and, in many cases, only a single log. A large proportion of the eroded trees (up to 40%) were deposited on the nearest downstream bar. This illustrates significant wood retention close to the recruitment site, with the remaining wood dispersed widely downstream. Differences in the observed level of local wood retention were associated with the proximity of the erosion site to the main channel and differences were also observed in retention between the peak and the falling limb of flood events, confirming that water depth and probably flow velocity are the crucial parameters controlling wood deposition.
The cranial cruciate ligament rupture is one of the main orthopaedic diseases which affect dogs. Many surgical techniques have been described and they aim to relief the pain, restore stifle biomechanical stability and prevent the progression of osteoarthritis. Fascia lata, braided polyester and polyamida were used in lateral fabellar suture to stifle stabilization after induced cranial cruciate ligament rupture in dogs that were submitted to radiographic and macroscopic evaluation of joint. In this study 18 dogs weighting more than 15kg were used (middleweight - 19.67kg), distributed in three groups corresponding to each technique, evaluated during 30 and 60 days. In the radiographic exam, the dogs had evidence of moderate to severe joint effusion, capsular distension and, in most cases, lacking of degenerative articular disease features. At the macroscopic exam of the stifle joint thickening of the joint capsule and periarticular soft tissues, erosion of the femoral condyles cartilage in all groups and loosening of the suture were observed in dogs submitted to extra-articular stabilization techniques employing braided polyester and polyamida
Lallias-Tacon, S.; Liébault, F.; Piégay, H.; Leduc, P.
2012-04-01
The recent development of innovative topographic survey technologies offers new opportunities for investigating spatial and temporal patterns of gravel-bed rivers morphological responses to flood events. In this study, multidate airborne LiDAR surveys were used to reconstruct reach-scale morphological changes of a gravel-bed braided river following a channel-forming flood event. LiDAR surveys were acquired in October 2008 and June 2010 for a 7-km reach of the Bès River, a very active aggrading braided channel, which is a tributary to the Bléone River in the Southern French Prealps (drainage area: 234 km2). Between these two dates, a 15-year flood occurred in December 2009, with a peakflow discharge of 171 m3 s-1. A DEM of difference (DoD) was produced by subtraction of LiDAR-derived DTM pair. Spatially distributed error in Dod was accounted with dGPS field measurement by sampling of different types of terrains (exposed gravel bars, spares and dense vegetated areas). The scour and fill maps allowed reconstructing erosion and deposition of bedforms and provide a volume estimate for calculating a sediment budget. These bedforms were described by different factors like their geometry (width, shape), their position and elevation relative to the main low-flow channel and their vegetation cover. Bed morphology was also studied by extracting different metrics at regularly-spaced cross-sections to infer information about sediment transfer in the braided channel. Final aim is to link bedform characteristics with their morphological response. Morphological changes were also studied in a historical context with a series of aerial photographs (1948-2010) to link the present-day morphology of the river with longer term channel changes. Active channel and island area were measured at reach and sub-reach scales (50 m), as well as active channel and island widths for cross-sections (every 10 m along). These variables were coupled with landscape changes and hydrological events in
Frost, Miroslav; Sedlák, Petr; Kruisová, Alena; Landa, Michal
2014-01-01
Roč. 23, č. 7 (2014), s. 2584-2590. ISSN 1059-9495 R&D Projects: GA ČR GA14-15264S; GA ČR(CZ) GP14-28306P; GA ČR GA13-13616S Grant ostatní: Rada Programu interní podpory projektů mezinárodní spolupráce AV ČR(CZ) M100761203 Institutional support: RVO:61388998 Keywords : braided stent * numerical simulation * R-phase * shape memory alloys Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.998, year: 2014 http://link.springer.com/article/10.1007/s11665-014-0966-z
JIANG Yiming; ZHANG Jinliang
2008-01-01
During the early Silurian, a transgressive and vast shallow sea with flat sea-floor covered the central Tarim Basin (the Tazhong area). The depositional environment of the middle member of the Kalpingtag Formation is controversial. In order to provide a basis for the prediction of reservoir sand, the sedimentary facies are recognized according to abundant core observations and de-scriptions combined with well-log analysis, isograms, seismic interpretations and regional sedimentary background. The middle member of the Kalpingtag Formation, which shows a retrograding sequence, is interpreted as braid-delta deposits influenced by mi-nor tidal reworking. The sources of clasts are from the southern uplift. The subaqueous braid-delta deposits in the study area have some characteristics quite different from the common deltas that generally deposit in marginal seas. Four facies grouped to a delta front association are recognized, ranging from distributary-channel (Facies A), front bar (Facies B), sand sheet (Facies C) and inter-distributary bay (Facies D). The distributary channels construct the sandbody framework of the delta front. Front bar deposits, which are fine-grained with low depositionai dips, display a near-continuous sand strip around the entire periphery of the delta. Sand sheet deposits are mainly found in front of Facies B, gradationally contacting with the prodelta. The interdistributary bay is essentially the uppermost unit capping the channel sequence and generally made up of laminated and massive mudstones. The delta front deposits display extensive sheet-like bodies contrasting with the characteristic wedge shapes of common subaqueous delta bodies. The bi-modal cross-stratification and mud drapes in the fine-to medium-grained sandstone in the distal area are inferred to reflect high-energy tidal processes.
王瑞; 肖长发; 刘美甜; 张旭良
2013-01-01
利用二维编织技术将聚丙烯腈(PAN)纤维编织成中空编织管,以聚丙烯腈为成膜聚合物,以聚乙二醇为成孔剂,配制铸膜液,采用同心圆纺丝法制备同质编织管增强型聚丙烯腈中空纤维膜.研究结果表明,所得同质编织管增强型聚丙烯腈中空纤维膜的表面分离层具有类似于非对称膜的结构,铸膜液可渗入编织管纤维束中；随着编织管编织节距的增大,同质编织管增强型聚丙烯腈中空纤维膜表面分离层厚度减小,同时膜的平均孔径增大,膜的纯水通量随之增大；铸膜液渗入编织管纤维束的现象未影响膜的通透性能；编织管的断裂强度最大可达100 MPa以上.通过水浴振荡、超声波水浴振荡及等力拉伸3种方法测试了同质编织管增强型中空纤维膜和异质编织管增强型中空纤维膜中编织管与表面分离层之间的界面结合性能,结果表明前者的界面结合性能优于后者.%Homogeneous braided tube reinforced polyacrylonitrile ( PAN) hollow fiber membranes which contained hollow braided tube and separation surface were prepared by concentric circles spinning method. The braided tube was prepared by the two-dimensional braided technique using PAN fibers. While the separation surface was obtained by non-solvent induced phase separation method with PAN as the polymer matrix, dimethyl sulfoxide (DMSO) as the solvent,and polyethylene glycol (PEG) as the pore-forming agent. Results showed that the structure of separation surface was similar to asymmetric membrane. The casting solution would penetrate into the voids among fiber bundles of the braided tube. As the braided pitch increasing, the thickness of separation surface decreased, which induced the promotion of the membrane water flux. There was no obvious influence of casting solution penetration on the membrane permeability. The breaking strength of braided tube was up to 100 MPa. Water bath vibration, ultrasonic vibration and