A Polyakov action on Riemann surfaces

International Nuclear Information System (INIS)

Zucchini, R.

1991-02-01

A calculation of the effective action for induced conformal gravity on higher genus Riemann surfaces is presented. Our expression, generalizing Polyakov's formula, depends holomorphically on the Beltrami and integrates the diffeomorphism anomaly. A solution of the conformal Ward identity on an arbitrary compact Riemann surfaces without boundary is presented, and its remarkable properties are studied. (K.A.) 16 refs., 2 figs

Riemann quasi-invariants

International Nuclear Information System (INIS)

Pokhozhaev, Stanislav I

2011-01-01

The notion of Riemann quasi-invariants is introduced and their applications to several conservation laws are considered. The case of nonisentropic flow of an ideal polytropic gas is analysed in detail. Sufficient conditions for gradient catastrophes are obtained. Bibliography: 16 titles.

Derivative-Based Trapezoid Rule for the Riemann-Stieltjes Integral

Directory of Open Access Journals (Sweden)

Weijing Zhao

2014-01-01

Full Text Available The derivative-based trapezoid rule for the Riemann-Stieltjes integral is presented which uses 2 derivative values at the endpoints. This kind of quadrature rule obtains an increase of two orders of precision over the trapezoid rule for the Riemann-Stieltjes integral and the error term is investigated. At last, the rationality of the generalization of derivative-based trapezoid rule for Riemann-Stieltjes integral is demonstrated.

Quantum field theory on higher-genus Riemann surfaces

International Nuclear Information System (INIS)

Kubo, Reijiro; Yoshii, Hisahiro; Ojima, Shuichi; Paul, S.K.

1989-07-01

Quantum field theory for b-c systems is formulated on Riemann surfaces with arbitrary genus. We make use of the formalism recently developed by Krichever and Novikov. Hamiltonian is defined properly, and the Ward-Takahashi identities are derived on higher-genus Riemann surfaces. (author)

Solution of Riemann problem for ideal polytropic dusty gas

International Nuclear Information System (INIS)

Nath, Triloki; Gupta, R.K.; Singh, L.P.

2017-01-01

Highlights : • A direct approach is used to solve the Riemann problem for dusty ideal polytropic gas. • An analytical solution to the Riemann problem for dusty gas flow is obtained. • The existence and uniqueness of the solution in dusty gas is discussed. • Properties of elementary wave solutions of Riemann problem are discussed. • Effect of mass fraction of solid particles on the solution is presented. - Abstract: The Riemann problem for a quasilinear hyperbolic system of equations governing the one dimensional unsteady flow of an ideal polytropic gas with dust particles is solved analytically without any restriction on magnitude of the initial states. The elementary wave solutions of the Riemann problem, that is shock waves, rarefaction waves and contact discontinuities are derived explicitly and their properties are discussed, for a dusty gas. The existence and uniqueness of the solution for Riemann problem in dusty gas is discussed. Also the conditions leading to the existence of shock waves or simple waves for a 1-family and 3-family curves in the solution of the Riemann problem are discussed. It is observed that the presence of dust particles in an ideal polytropic gas leads to more complex expression as compared to the corresponding ideal case; however all the parallel results remain same. Also, the effect of variation of mass fraction of dust particles with fixed volume fraction (Z) and the ratio of specific heat of the solid particles and the specific heat of the gas at constant pressure on the variation of velocity and density across the shock wave, rarefaction wave and contact discontinuities are discussed.

Two-dimensional time dependent Riemann solvers for neutron transport

International Nuclear Information System (INIS)

Brunner, Thomas A.; Holloway, James Paul

2005-01-01

A two-dimensional Riemann solver is developed for the spherical harmonics approximation to the time dependent neutron transport equation. The eigenstructure of the resulting equations is explored, giving insight into both the spherical harmonics approximation and the Riemann solver. The classic Roe-type Riemann solver used here was developed for one-dimensional problems, but can be used in multidimensional problems by treating each face of a two-dimensional computation cell in a locally one-dimensional way. Several test problems are used to explore the capabilities of both the Riemann solver and the spherical harmonics approximation. The numerical solution for a simple line source problem is compared to the analytic solution to both the P 1 equation and the full transport solution. A lattice problem is used to test the method on a more challenging problem

Riemann solvers and undercompressive shocks of convex FPU chains

International Nuclear Information System (INIS)

Herrmann, Michael; Rademacher, Jens D M

2010-01-01

We consider FPU-type atomic chains with general convex potentials. The naive continuum limit in the hyperbolic space–time scaling is the p-system of mass and momentum conservation. We systematically compare Riemann solutions to the p-system with numerical solutions to discrete Riemann problems in FPU chains, and argue that the latter can be described by modified p-system Riemann solvers. We allow the flux to have a turning point, and observe a third type of elementary wave (conservative shocks) in the atomistic simulations. These waves are heteroclinic travelling waves and correspond to non-classical, undercompressive shocks of the p-system. We analyse such shocks for fluxes with one or more turning points. Depending on the convexity properties of the flux we propose FPU-Riemann solvers. Our numerical simulations confirm that Lax shocks are replaced by so-called dispersive shocks. For convex–concave flux we provide numerical evidence that convex FPU chains follow the p-system in generating conservative shocks that are supersonic. For concave–convex flux, however, the conservative shocks of the p-system are subsonic and do not appear in FPU-Riemann solutions

Formulation of dynamical theory of X-ray diffraction for perfect crystals in the Laue case using the Riemann surface.

Science.gov (United States)

Saka, Takashi

2016-05-01

The dynamical theory for perfect crystals in the Laue case was reformulated using the Riemann surface, as used in complex analysis. In the two-beam approximation, each branch of the dispersion surface is specified by one sheet of the Riemann surface. The characteristic features of the dispersion surface are analytically revealed using four parameters, which are the real and imaginary parts of two quantities specifying the degree of departure from the exact Bragg condition and the reflection strength. By representing these parameters on complex planes, these characteristics can be graphically depicted on the Riemann surface. In the conventional case, the absorption is small and the real part of the reflection strength is large, so the formulation is the same as the traditional analysis. However, when the real part of the reflection strength is small or zero, the two branches of the dispersion surface cross, and the dispersion relationship becomes similar to that of the Bragg case. This is because the geometrical relationships among the parameters are similar in both cases. The present analytical method is generally applicable, irrespective of the magnitudes of the parameters. Furthermore, the present method analytically revealed many characteristic features of the dispersion surface and will be quite instructive for further numerical calculations of rocking curves.

Non-abelian bosonization in higher genus Riemann surfaces

International Nuclear Information System (INIS)

Koh, I.G.; Yu, M.

1988-01-01

We propose a generalization of the character formulas of the SU(2) Kac-Moody algebra to higher genus Riemann surfaces. With this construction, we show that the modular invariant partition funciton of the SO(4) k = 1 Wess-Zumino model is equivalent, in arbitrary genus Riemann surfaces, to that of free fermion theory. (orig.)

A Riemann problem with small viscosity and dispersion

Directory of Open Access Journals (Sweden)

Kayyunnapara Thomas Joseph

2006-09-01

Full Text Available In this paper we prove existence of global solutions to a hyperbolic system in elastodynamics, with small viscosity and dispersion terms and derive estimates uniform in the viscosity-dispersion parameters. By passing to the limit, we prove the existence of solution the Riemann problem for the hyperbolic system with arbitrary Riemann data.

Integrability of Liouville system on high genus Riemann surface: Pt. 1

International Nuclear Information System (INIS)

Chen Yixin; Gao Hongbo

1992-01-01

By using the theory of uniformization of Riemann-surfaces, we study properties of the Liouville equation and its general solution on a Riemann surface of genus g>1. After obtaining Hamiltonian formalism in terms of free fields and calculating classical exchange matrices, we prove the classical integrability of Liouville system on high genus Riemann surface

Collisionless analogs of Riemann S ellipsoids with halo

International Nuclear Information System (INIS)

Abramyan, M.G.

1987-01-01

A spheroidal halo ensures equilibrium of the collisionless analogs of the Riemann S ellipsoids with oscillations of the particles along the direction of their rotation. Sequences of collisionless triaxial ellipsoids begin and end with dynamically stable members of collisionless embedded spheroids. Both liquid and collisionless Riemann S ellipsoids with weak halo have properties that resemble those of bars of SB galaxies

Fuzzy Riemann surfaces

International Nuclear Information System (INIS)

Arnlind, Joakim; Hofer, Laurent; Hoppe, Jens; Bordemann, Martin; Shimada, Hidehiko

2009-01-01

We introduce C-Algebras (quantum analogues of compact Riemann surfaces), defined by polynomial relations in non-commutative variables and containing a real parameter that, when taken to zero, provides a classical non-linear, Poisson-bracket, obtainable from a single polynomial C(onstraint) function. For a continuous class of quartic constraints, we explicitly work out finite dimensional representations of the corresponding C-Algebras.

Meromorphic functions and cohomology on a Riemann surface

International Nuclear Information System (INIS)

Gomez-Mont, X.

1989-01-01

The objective of this set of notes is to introduce a series of concepts of Complex Analytic Geometry on a Riemann Surface. We motivate the introduction of cohomology groups through the analysis of meromorphic functions. We finish by showing that the set of infinitesimal deformations of a Riemann surface (the tangent space to Teichmueller space) may be computed as a Cohomology group. (author). 6 refs

On the $a$-points of the derivatives of the Riemann zeta function

OpenAIRE

Onozuka, Tomokazu

2016-01-01

We prove three results on the $a$-points of the derivatives of the Riemann zeta function. The first result is a formula of the Riemann-von Mangoldt type; we estimate the number of the $a$-points of the derivatives of the Riemann zeta function. The second result is on certain exponential sum involving $a$-points. The third result is an analogue of the zero density theorem. We count the $a$-points of the derivatives of the Riemann zeta function in $1/2-(\\log\\log T)^2/\\log T

Riemann's and Helmholtz-Lie's problems of space from Weyl's relativistic perspective

Science.gov (United States)

Bernard, Julien

2018-02-01

I reconstruct Riemann's and Helmholtz-Lie's problems of space, from some perspectives that allow for a fruitful comparison with Weyl. In Part II. of his inaugural lecture, Riemann justifies that the infinitesimal metric is the square root of a quadratic form. Thanks to Finsler geometry, I clarify both the implicit and explicit hypotheses used for this justification. I explain that Riemann-Finsler's kind of method is also appropriate to deal with indefinite metrics. Nevertheless, Weyl shares with Helmholtz a strong commitment to the idea that the notion of group should be at the center of the foundations of geometry. Riemann missed this point, and that is why, according to Weyl, he dealt with the problem of space in a "too formal" way. As a consequence, to solve the problem of space, Weyl abandoned Riemann-Finsler's methods for group-theoretical ones. However, from a philosophical point of view, I show that Weyl and Helmholtz are in strong opposition. The meditation on Riemann's inaugural lecture, and its clear methodological separation between the infinitesimal and the finite parts of the problem of space, must have been crucial for Weyl, while searching for strong epistemological foundations for the group-theoretical methods, avoiding Helmholtz's unjustified transition from the finite to the infinitesimal.

Riemann zeta function from wave-packet dynamics

DEFF Research Database (Denmark)

Mack, R.; Dahl, Jens Peder; Moya-Cessa, H.

2010-01-01

We show that the time evolution of a thermal phase state of an anharmonic oscillator with logarithmic energy spectrum is intimately connected to the generalized Riemann zeta function zeta(s, a). Indeed, the autocorrelation function at a time t is determined by zeta (sigma + i tau, a), where sigma...... index of JWKB. We compare and contrast exact and approximate eigenvalues of purely logarithmic potentials. Moreover, we use a numerical method to find a potential which leads to exact logarithmic eigenvalues. We discuss possible realizations of Riemann zeta wave-packet dynamics using cold atoms...

Riemann-Theta Boltzmann Machine arXiv

CERN Document Server

Krefl, Daniel; Haghighat, Babak; Kahlen, Jens

A general Boltzmann machine with continuous visible and discrete integer valued hidden states is introduced. Under mild assumptions about the connection matrices, the probability density function of the visible units can be solved for analytically, yielding a novel parametric density function involving a ratio of Riemann-Theta functions. The conditional expectation of a hidden state for given visible states can also be calculated analytically, yielding a derivative of the logarithmic Riemann-Theta function. The conditional expectation can be used as activation function in a feedforward neural network, thereby increasing the modelling capacity of the network. Both the Boltzmann machine and the derived feedforward neural network can be successfully trained via standard gradient- and non-gradient-based optimization techniques.

Riemann surfaces, Clifford algebras and infinite dimensional groups

International Nuclear Information System (INIS)

Carey, A.L.; Eastwood, M.G.; Hannabuss, K.C.

1990-01-01

We introduce of class of Riemann surfaces which possess a fixed point free involution and line bundles over these surfaces with which we can associate an infinite dimensional Clifford algebra. Acting by automorphisms of this algebra is a 'gauge' group of meromorphic functions on the Riemann surface. There is a natural Fock representation of the Clifford algebra and an associated projective representation of this group of meromorphic functions in close analogy with the construction of the basic representation of Kac-Moody algebras via a Fock representation of the Fermion algebra. In the genus one case we find a form of vertex operator construction which allows us to prove a version of the Boson-Fermion correspondence. These results are motivated by the analysis of soliton solutions of the Landau-Lifshitz equation and are rather distinct from recent developments in quantum field theory on Riemann surfaces. (orig.)

BRST quantization of superconformal theories on higher genus Riemann surfaces

International Nuclear Information System (INIS)

Leman Kuang

1992-01-01

A complex contour integral method is constructed and applied to the Becchi-Rouet-Stora-Tyutin (BRST) quantization procedure of string theories on higher genus Riemann surfaces with N=0 and 1 Krichever-Novikov (KN) algebras. This method makes calculations very simple. It is shown that the critical spacetime dimension of the string theories on a genus-g Riemann surface equals that of the string theories on a genus-zero Riemann surface, and that the 'Regge intercepts' in the genus-g case are α(g)=1-3/4g-9/8g 2 and 1/2-3/4g-17/16g 2 for bosonic strings and superstrings, respectively. (orig.)

Exploring the Riemann zeta function 190 years from Riemann's birth

CERN Document Server

Nikeghbali, Ashkan; Rassias, Michael

2017-01-01

This book is concerned with the Riemann Zeta Function, its generalizations, and various applications to several scientific disciplines, including Analytic Number Theory, Harmonic Analysis, Complex Analysis and Probability Theory. Eminent experts in the field illustrate both old and new results towards the solution of long-standing problems and include key historical remarks. Offering a unified, self-contained treatment of broad and deep areas of research, this book will be an excellent tool for researchers and graduate students working in Mathematics, Mathematical Physics, Engineering and Cryptography.

Explicit solution of Riemann-Hilbert problems for the Ernst equation

Science.gov (United States)

Klein, C.; Richter, O.

1998-01-01

Riemann-Hilbert problems are an important solution technique for completely integrable differential equations. They are used to introduce a free function in the solutions which can be used at least in principle to solve initial or boundary value problems. But even if the initial or boundary data can be translated into a Riemann-Hilbert problem, it is in general impossible to obtain explicit solutions. In the case of the Ernst equation, however, this is possible for a large class because the matrix problem can be shown to be gauge equivalent to a scalar one on a hyperelliptic Riemann surface that can be solved in terms of theta functions. As an example we discuss the rigidly rotating dust disk.

Compact Riemann surfaces an introduction to contemporary mathematics

CERN Document Server

Jost, Jürgen

2006-01-01

Although Riemann surfaces are a time-honoured field, this book is novel in its broad perspective that systematically explores the connection with other fields of mathematics. It can serve as an introduction to contemporary mathematics as a whole as it develops background material from algebraic topology, differential geometry, the calculus of variations, elliptic PDE, and algebraic geometry. It is unique among textbooks on Riemann surfaces in including an introduction to Teichmüller theory. For this new edition, the author has expanded and rewritten several sections to include additional material and to improve the presentation.

On Lovelock analogs of the Riemann tensor

Science.gov (United States)

Camanho, Xián O.; Dadhich, Naresh

2016-03-01

It is possible to define an analog of the Riemann tensor for Nth order Lovelock gravity, its characterizing property being that the trace of its Bianchi derivative yields the corresponding analog of the Einstein tensor. Interestingly there exist two parallel but distinct such analogs and the main purpose of this note is to reconcile both formulations. In addition we will introduce a simple tensor identity and use it to show that any pure Lovelock vacuum in odd d=2N+1 dimensions is Lovelock flat, i.e. any vacuum solution of the theory has vanishing Lovelock-Riemann tensor. Further, in the presence of cosmological constant it is the Lovelock-Weyl tensor that vanishes.

Method of construction of the Riemann function for a second-order hyperbolic equation

Science.gov (United States)

Aksenov, A. V.

2017-12-01

A linear hyperbolic equation of the second order in two independent variables is considered. The Riemann function of the adjoint equation is shown to be invariant with respect to the fundamental solutions transformation group. Symmetries and symmetries of fundamental solutions of the Euler-Poisson-Darboux equation are found. The Riemann function is constructed with the aid of fundamental solutions symmetries. Examples of the application of the algorithm for constructing Riemann function are given.

SO(N) WZNW models on higher-genus Riemann surfaces

International Nuclear Information System (INIS)

Alimohammadi, M.; Arfaei, H.; Bonn Univ.

1993-08-01

With the help of the string functions and fusion rules of SO(2N) 1 , we show that the results on SU(N) 1 correlators on higher-genus Riemann surfaces (HGRS) can be extended to the SO(2N) 1 and other level-one simply-laced WZNW models. Using modular invariance and factorization properties of Green functions we find multipoint correlators of primary and descendant fields of SO(2N+1) 1 WZNW models on higher genus Riemann surfaces. (orig.)

The continuous determination of spacetime geometry by the Riemann curvature tensor

International Nuclear Information System (INIS)

Rendall, A.D.

1988-01-01

It is shown that generically the Riemann tensor of a Lorentz metric on an n-dimensional manifold (n ≥ 4) determines the metric up to a constant factor and hence determines the associated torsion-free connection uniquely. The resulting map from Riemann tensors to connections is continuous in the Whitney Csup(∞) topology but, at least for some manifolds, constant factors cannot be chosen so as to make the map from Riemann tensors to metrics continuous in that topology. The latter map is, however, continuous in the compact open Csup(∞) topology so that estimates of the metric and its derivatives on a compact set can be obtained from similar estimates on the curvature and its derivatives. (author)

On Riemann zeroes, lognormal multiplicative chaos, and Selberg integral

International Nuclear Information System (INIS)

Ostrovsky, Dmitry

2016-01-01

Rescaled Mellin-type transforms of the exponential functional of the Bourgade–Kuan–Rodgers statistic of Riemann zeroes are conjecturally related to the distribution of the total mass of the limit lognormal stochastic measure of Mandelbrot–Bacry–Muzy. The conjecture implies that a non-trivial, log-infinitely divisible probability distribution is associated with Riemann zeroes. For application, integral moments, covariance structure, multiscaling spectrum, and asymptotics associated with the exponential functional are computed in closed form using the known meromorphic extension of the Selberg integral. (paper)

Supermanifolds and super Riemann surfaces

International Nuclear Information System (INIS)

Rabin, J.M.

1986-09-01

The theory of super Riemann surfaces is rigorously developed using Rogers' theory of supermanifolds. The global structures of super Teichmueller space and super moduli space are determined. The super modular group is shown to be precisely the ordinary modular group. Super moduli space is shown to be the gauge-fixing slice for the fermionic string path integral

The Picard group of the moduli space of r-Spin Riemann surfaces

DEFF Research Database (Denmark)

Randal-Williams, Oscar

2012-01-01

An r-Spin Riemann surface is a Riemann surface equipped with a choice of rth root of the (co)tangent bundle. We give a careful construction of the moduli space (orbifold) of r-Spin Riemann surfaces, and explain how to establish a Madsen–Weiss theorem for it. This allows us to prove the “Mumford...... conjecture” for these moduli spaces, but more interestingly allows us to compute their algebraic Picard groups (for g≥10, or g≥9 in the 2-Spin case). We give a complete description of these Picard groups, in terms of explicitly constructed line bundles....

Colliding holes in Riemann surfaces and quantum cluster algebras

Science.gov (United States)

Chekhov, Leonid; Mazzocco, Marta

2018-01-01

In this paper, we describe a new type of surgery for non-compact Riemann surfaces that naturally appears when colliding two holes or two sides of the same hole in an orientable Riemann surface with boundary (and possibly orbifold points). As a result of this surgery, bordered cusps appear on the boundary components of the Riemann surface. In Poincaré uniformization, these bordered cusps correspond to ideal triangles in the fundamental domain. We introduce the notion of bordered cusped Teichmüller space and endow it with a Poisson structure, quantization of which is achieved with a canonical quantum ordering. We give a complete combinatorial description of the bordered cusped Teichmüller space by introducing the notion of maximal cusped lamination, a lamination consisting of geodesic arcs between bordered cusps and closed geodesics homotopic to the boundaries such that it triangulates the Riemann surface. We show that each bordered cusp carries a natural decoration, i.e. a choice of a horocycle, so that the lengths of the arcs in the maximal cusped lamination are defined as λ-lengths in Thurston-Penner terminology. We compute the Goldman bracket explicitly in terms of these λ-lengths and show that the groupoid of flip morphisms acts as a generalized cluster algebra mutation. From the physical point of view, our construction provides an explicit coordinatization of moduli spaces of open/closed string worldsheets and their quantization.

The exchange algebra for Liouville theory on punctured Riemann sphere

International Nuclear Information System (INIS)

Shen Jianmin; Sheng Zhengmao

1991-11-01

We consider in this paper the classical Liouville field theory on the Riemann sphere with n punctures. In terms of the uniformization theorem of Riemann surface, we show explicitly the classical exchange algebra (CEA) for the chiral components of the Liouville fields. We find that the matrice which dominate the CEA is related to the symmetry of the Lie group SL(n) in a nontrivial manner with n>3. (author). 10 refs

Essay on Fractional Riemann-Liouville Integral Operator versus Mikusinski’s

Directory of Open Access Journals (Sweden)

Ming Li

2013-01-01

Full Text Available This paper presents the representation of the fractional Riemann-Liouville integral by using the Mikusinski operators. The Mikusinski operators discussed in the paper may yet provide a new view to describe and study the fractional Riemann-Liouville integral operator. The present result may be useful for applying the Mikusinski operational calculus to the study of fractional calculus in mathematics and to the theory of filters of fractional order in engineering.

Conformal fields. From Riemann surfaces to integrable hierarchies

International Nuclear Information System (INIS)

Semikhatov, A.M.

1991-01-01

I discuss the idea of translating ingredients of conformal field theory into the language of hierarchies of integrable differential equations. Primary conformal fields are mapped into (differential or matrix) operators living on the phase space of the hierarchy, whereas operator insertions of, e.g., a current or the energy-momentum tensor, become certain vector fields on the phase space and thus acquire a meaning independent of a given Riemann surface. A number of similarities are observed between the structures arising on the hierarchy and those of the theory on the world-sheet. In particular, there is an analogue of the operator product algebra with the Cauchy kernel replaced by its 'off-shell' hierarchy version. Also, hierarchy analogues of certain operator insertions admit two (equivalent, but distinct) forms, resembling the 'bosonized' and 'fermionized' versions respectively. As an application, I obtain a useful reformulation of the Virasoro constraints of the type that arise in matrix models, as a system of equations on dressing (or Lax) operators (rather than correlation functions, i.e., residues or traces). This also suggests an interpretation in terms of a 2D topological field theory, which might be extended to a correspondence between Virasoro-constrained hierarchies and topological theories. (orig.)

Submaximal Riemann-Roch expected curves and symplectic packing.

Directory of Open Access Journals (Sweden)

Wioletta Syzdek

2007-06-01

Full Text Available We study Riemann-Roch expected curves on $mathbb{P}^1 imes mathbb{P}^1$ in the context of the Nagata-Biran conjecture. This conjecture predicts that for sufficiently large number of points multiple points Seshadri constants of an ample line bundle on algebraic surface are maximal. Biran gives an effective lower bound $N_0$. We construct examples verifying to the effect that the assertions of the Nagata-Biran conjecture can not hold for small number of points. We discuss cases where our construction fails. We observe also that there exists a strong relation between Riemann-Roch expected curves on $mathbb{P}^1 imes mathbb{P}^1$ and the symplectic packing problem. Biran relates the packing problem to the existence of solutions of certain Diophantine equations. We construct such solutions for any ample line bundle on $mathbb{P}^1 imes mathbb{P}^1$ and a relatively smallnumber of points. The solutions geometrically correspond to Riemann-Roch expected curves. Finally we discuss in how far the Biran number $N_0$ is optimal in the case of mathbb{P}^1 imes mathbb{P}^1. In fact we conjecture that it can be replaced by a lower number and we provide evidence justifying this conjecture.

The sewing technique and correlation functions on arbitrary Riemann surfaces

International Nuclear Information System (INIS)

Di Vecchia, P.

1989-01-01

We describe in the case of free bosonic and fermionic theories the sewing procedure, that is a very convenient way for constructing correlation functions of these theories on an arbitrary Riemann surface from their knowledge on the sphere. The fundamental object that results from this construction is the N-point g-loop vertex. It summarizes the information of all correlation functions of the theory on an arbitrary Riemann surface. We then check explicitly the bosonization rules and derive some useful formulas. (orig.)

Gaussian curvature on hyperelliptic Riemann surfaces

Indian Academy of Sciences (India)

Indian Acad. Sci. (Math. Sci.) Vol. 124, No. 2, May 2014, pp. 155–167. c Indian Academy of Sciences. Gaussian curvature on hyperelliptic Riemann surfaces. ABEL CASTORENA. Centro de Ciencias Matemáticas (Universidad Nacional Autónoma de México,. Campus Morelia) Apdo. Postal 61-3 Xangari, C.P. 58089 Morelia,.

Hysteresis rarefaction in the Riemann problem

Czech Academy of Sciences Publication Activity Database

Krejčí, Pavel

2008-01-01

Roč. 138, - (2008), s. 1-10 ISSN 1742-6588. [International Workshop on Multi-Rate Processes and Hysteresis. Cork , 31.03.2008-05.04.2008] Institutional research plan: CEZ:AV0Z10190503 Keywords : Preisach hysteresis * Riemann problem Subject RIV: BA - General Mathematics http://iopscience.iop.org/1742-6596/138/1/012010

A variational approach to closed bosonic strings on bordered Riemann surfaces

International Nuclear Information System (INIS)

Ohrndorf, T.

1987-01-01

Polyakov's path integral for bosonic closed strings defined on a bordered Riemann surface is investigated by variational methods. It is demonstrated that boundary variations are generated by the Virasoro operators. The investigation is performed for both, simply connected Riemann surfaces as well as ringlike domains. It is shown that the form of the variational operator is the same on both kinds of surfaces. The Virasoro algebra arises as a consistency condition for the variation. (orig.)

Line operators from M-branes on compact Riemann surfaces

Energy Technology Data Exchange (ETDEWEB)

Amariti, Antonio [Physics Department, The City College of the CUNY, 160 Convent Avenue, New York, NY 10031 (United States); Orlando, Domenico [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland); Reffert, Susanne, E-mail: sreffert@itp.unibe.ch [Albert Einstein Center for Fundamental Physics, Institute for Theoretical Physics, University of Bern, Sidlerstrasse 5, CH-3012 Bern (Switzerland)

2016-12-15

In this paper, we determine the charge lattice of mutually local Wilson and 't Hooft line operators for class S theories living on M5-branes wrapped on compact Riemann surfaces. The main ingredients of our analysis are the fundamental group of the N-cover of the Riemann surface, and a quantum constraint on the six-dimensional theory. The latter plays a central role in excluding some of the possible lattices and imposing consistency conditions on the charges. This construction gives a geometric explanation for the mutual locality among the lines, fixing their charge lattice and the structure of the four-dimensional gauge group.

Structural stability of Riemann solutions for strictly hyperbolic systems with three piecewise constant states

Directory of Open Access Journals (Sweden)

Xuefeng Wei

2016-12-01

Full Text Available This article concerns the wave interaction problem for a strictly hyperbolic system of conservation laws whose Riemann solutions involve delta shock waves. To cover all situations, the global solutions are constructed when the initial data are taken as three piecewise constant states. It is shown that the Riemann solutions are stable with respect to a specific small perturbation of the Riemann initial data. In addition, some interesting nonlinear phenomena are captured during the process of constructing the solutions, such as the generation and decomposition of delta shock waves.

Interpolating and sampling sequences in finite Riemann surfaces

OpenAIRE

Ortega-Cerda, Joaquim

2007-01-01

We provide a description of the interpolating and sampling sequences on a space of holomorphic functions on a finite Riemann surface, where a uniform growth restriction is imposed on the holomorphic functions.

Superconformal algebra on meromorphic vector fields with three poles on super-Riemann sphere

International Nuclear Information System (INIS)

Wang Shikun; Xu Kaiwen.

1989-07-01

Based upon the Riemann-Roch theorem, we construct superconformal algebra of meromorphic vector fields with three poles and the relevant abelian differential of the third kind on super Riemann sphere. The algebra includes two Ramond sectors as subalgebra, and implies a picture of interaction of three superstrings. (author). 14 refs

Chiral bosonization on a Riemann surface

International Nuclear Information System (INIS)

Eguchi, Tohru; Ooguri, Hirosi

1987-01-01

We point out that the basic addition theorem of θ-functions, Fay's identity, implies an equivalence between bosons and chiral fermions on Riemann surfaces with arbitrary genus. We present a rule for a bosonized calculation of correlation functions. We also discuss ghost systems of n and (1-n) tensors and derive formulas for their chiral determinants. (orig.)

Extended KN algebras and extended conformal field theories over higher genus Riemann surfaces

International Nuclear Information System (INIS)

Ceresole, A.; Huang Chaoshang

1990-01-01

A global operator formalism for extended conformal field theories over higher genus Riemann surfaces is introduced and extended KN algebra are obtained by means of the KN bases. The BBSS construction of the spin-3 operator is carried out for Kac-Moody algebra A 2 over a Riemann surface of arbitrary genus. (orig.)

Conformal scalar fields and chiral splitting on super Riemann surfaces

International Nuclear Information System (INIS)

D'Hoker, E.; Phong, D.H.

1989-01-01

We provide a complete description of correlation functions of scalar superfields on a super Riemann surface, taking into account zero modes and non-trivial topology. They are built out of chirally split correlation functions, or conformal blocks at fixed internal momenta. We formulate effective rules which determine these completely in terms of geometric invariants of the super Riemann surface. The chirally split correlation functions have non-trivial monodromy and produce single-valued amplitudes only upon integration over loop momenta. Our discussion covers the even spin structure as well as the odd spin structure case which had been the source of many difficulties in the past. Super analogues of Green's functions, holomorphic spinors, and prime forms emerge which should pave the way to function theory on super Riemann surfaces. In superstring theories, chirally split amplitudes for scalar superfields are crucial in enforcing the GSO projection required for consistency. However one really knew how to carry this out only in the operator formalism to one-loop order. Our results provide a way of enforcing the GSO projection to any loop. (orig.)

Pseudo-periodic maps and degeneration of Riemann surfaces

CERN Document Server

Matsumoto, Yukio

2011-01-01

The first part of the book studies pseudo-periodic maps of a closed surface of genus greater than or equal to two. This class of homeomorphisms was originally introduced by J. Nielsen in 1944 as an extension of periodic maps. In this book, the conjugacy classes of the (chiral) pseudo-periodic mapping classes are completely classified, and Nielsen’s incomplete classification is corrected. The second part applies the results of the first part to the topology of degeneration of Riemann surfaces. It is shown that the set of topological types of all the singular fibers appearing in one-parameter holomorphic families of Riemann surfaces is in a bijective correspondence with the set of conjugacy classes of the pseudo-periodic maps of negative twists. The correspondence is given by the topological monodromy.

Getting superstring amplitudes by degenerating Riemann surfaces

International Nuclear Information System (INIS)

Matone, Marco; Volpato, Roberto

2010-01-01

We explicitly show how the chiral superstring amplitudes can be obtained through factorisation of the higher genus chiral measure induced by suitable degenerations of Riemann surfaces. This powerful tool also allows to derive, at any genera, consistency relations involving the amplitudes and the measure. A key point concerns the choice of the local coordinate at the node on degenerate Riemann surfaces that greatly simplifies the computations. As a first application, starting from recent ansaetze for the chiral measure up to genus five, we compute the chiral two-point function for massless Neveu-Schwarz states at genus two, three and four. For genus higher than three, these computations include some new corrections to the conjectural formulae appeared so far in the literature. After GSO projection, the two-point function vanishes at genus two and three, as expected from space-time supersymmetry arguments, but not at genus four. This suggests that the ansatz for the superstring measure should be corrected for genus higher than four.

Generalized Riemann problem for reactive flows

International Nuclear Information System (INIS)

Ben-Artzi, M.

1989-01-01

A generalized Riemann problem is introduced for the equations of reactive non-viscous compressible flow in one space dimension. Initial data are assumed to be linearly distributed on both sides of a jump discontinuity. The resolution of the singularity is studied and the first-order variation (in time) of flow variables is given in exact form. copyright 1989 Academic Press, Inc

Superconformal structures and holomorphic 1/2-superdifferentials on N=1 super Riemann surfaces

International Nuclear Information System (INIS)

Kachkachi, H.; Kachkachi, M.

1992-07-01

Using the Super Riemann-Roch theorem we give a local expression for a holomorphic 1/2-superdifferential in a superconformal structure parametrized by special isothermal coordinates on an N=1 Super Riemann Surface (SRS). This construction is done by choosing a suitable origin for these coordinates. The holomorphy of the latter with respect to super Beltrami differentials is proven. (author). 26 refs

The beauty of the Riemann-Silberstein vector

International Nuclear Information System (INIS)

Bialynicki-Birula, I.

2005-01-01

Beams of light carrying angular momentum have recently been widely studied theoretically and experimentally. In my talk I will show that the description of these beams in terms of the Riemann-Silberstein vector offers many advantages. In particular, it provides a natural bridge between the classical and the quantum description. (author)

Quantized Dirac field in curved Riemann--Cartan background. I. Symmetry properties, Green's function

International Nuclear Information System (INIS)

Nieh, H.T.; Yan, M.L.

1982-01-01

In the present series of papers, we study the properties of quantized Dirac field in curved Riemann--Cartan space, with particular attention on the role played by torsion. In this paper, we give, in the spirit of the original work of Weyl, a systematic presentation of Dirac's theory in curved Riemann--Cartan space. We discuss symmetry properties of the system, and derive conservation laws as direct consequences of these symmetries. Also discussed is conformal gauge symmetry, with torsion effectively playing the role of a conformal gauge field. To obtain short-distance behavior, we calculate the spinor Green's function, in curved Riemann--Cartan background, using the Schwinger--DeWitt method of proper-time expansion. The calculation corresponds to a generalization of DeWitt's calculation for a Riemannian background

Local Extrema of the $\\Xi(t)$ Function and The Riemann Hypothesis

OpenAIRE

Kobayashi, Hisashi

2016-01-01

In the present paper we obtain a necessary and sufficient condition to prove the Riemann hypothesis in terms of certain properties of local extrema of the function $\\Xi(t)=\\xi(\\tfrac{1}{2}+it)$. First, we prove that positivity of all local maxima and negativity of all local minima of $\\Xi(t)$ form a necessary condition for the Riemann hypothesis to be true. After showing that any extremum point of $\\Xi(t)$ is a saddle point of the function $\\Re\\{\\xi(s)\\}$, we prove that the above properties o...

Toeplitz operators on higher Cauchy-Riemann spaces

Czech Academy of Sciences Publication Activity Database

Engliš, Miroslav; Zhang, G.

2017-01-01

Roč. 22, č. 22 (2017), s. 1081-1116 ISSN 1431-0643 Institutional support: RVO:67985840 Keywords : Toeplitz operator * Hankel operator * Cauchy-Riemann operators Subject RIV: BA - General Math ematics OBOR OECD: Pure math ematics Impact factor: 0.800, year: 2016 https://www. math .uni-bielefeld.de/documenta/vol-22/32.html

Study of the Riemann problem and construction of multidimensional Godunov-type schemes for two-phase flow models

International Nuclear Information System (INIS)

Toumi, I.

1990-04-01

This thesis is devoted to the study of the Riemann problem and the construction of Godunov type numerical schemes for one or two dimensional two-phase flow models. In the first part, we study the Riemann problem for the well-known Drift-Flux, model which has been widely used for the analysis of thermal hydraulics transients. Then we use this study to construct approximate Riemann solvers and we describe the corresponding Godunov type schemes for simplified equation of state. For computation of complex two-phase flows, a weak formulation of Roe's approximate Riemann solver, which gives a method to construct a Roe-averaged jacobian matrix with a general equation of state, is proposed. For two-dimensional flows, the developed methods are based upon an approximate solver for a two-dimensional Riemann problem, according to Harten-Lax-Van Leer principles. The numerical results for standard test problems show the good behaviour of these numerical schemes for a wide range of flow conditions [fr

Conformal deformation of Riemann space and torsion

International Nuclear Information System (INIS)

Pyzh, V.M.

1981-01-01

Method for investigating conformal deformations of Riemann spaces using torsion tensor, which permits to reduce the second ' order equations for Killing vectors to the system of the first order equations, is presented. The method is illustrated using conformal deformations of dimer sphere as an example. A possibility of its use when studying more complex deformations is discussed [ru

Study Paths, Riemann Surfaces, and Strebel Differentials

Science.gov (United States)

Buser, Peter; Semmler, Klaus-Dieter

2017-01-01

These pages aim to explain and interpret why the late Mika Seppälä, a conformal geometer, proposed to model student study behaviour using concepts from conformal geometry, such as Riemann surfaces and Strebel differentials. Over many years Mika Seppälä taught online calculus courses to students at Florida State University in the United States, as…

Approximate Riemann solver for the two-fluid plasma model

International Nuclear Information System (INIS)

Shumlak, U.; Loverich, J.

2003-01-01

An algorithm is presented for the simulation of plasma dynamics using the two-fluid plasma model. The two-fluid plasma model is more general than the magnetohydrodynamic (MHD) model often used for plasma dynamic simulations. The two-fluid equations are derived in divergence form and an approximate Riemann solver is developed to compute the fluxes of the electron and ion fluids at the computational cell interfaces and an upwind characteristic-based solver to compute the electromagnetic fields. The source terms that couple the fluids and fields are treated implicitly to relax the stiffness. The algorithm is validated with the coplanar Riemann problem, Langmuir plasma oscillations, and the electromagnetic shock problem that has been simulated with the MHD plasma model. A numerical dispersion relation is also presented that demonstrates agreement with analytical plasma waves

Riemann problems and their application to ultra-relativistic heavy ion collisions

International Nuclear Information System (INIS)

Plohr, B.J.; Sharp, D.H.

1986-07-01

Heavy ion collisions at sufficiently high energies to form quark-gluon plasma are considered. The phase transformation from a quark-gluon phase to hadrons as the nuclear matter cools is modeled as a hydrodynamical flow. Nonlinear waves are the predominant feature of this type of flow and the Riemann problem of a relativistic gas undergoing a phase transformation is explored as a method to numerically model this phase transition process in nuclear matter. The solution of the Riemann problem is outlined and results of preliminary numerical computations of the flow are presented. 10 refs., 2 figs

Multidimensional Riemann problem with self-similar internal structure. Part II - Application to hyperbolic conservation laws on unstructured meshes

Science.gov (United States)

Balsara, Dinshaw S.; Dumbser, Michael

2015-04-01

Multidimensional Riemann solvers that have internal sub-structure in the strongly-interacting state have been formulated recently (D.S. Balsara (2012, 2014) [5,16]). Any multidimensional Riemann solver operates at the grid vertices and takes as its input all the states from its surrounding elements. It yields as its output an approximation of the strongly interacting state, as well as the numerical fluxes. The multidimensional Riemann problem produces a self-similar strongly-interacting state which is the result of several one-dimensional Riemann problems interacting with each other. To compute this strongly interacting state and its higher order moments we propose the use of a Galerkin-type formulation to compute the strongly interacting state and its higher order moments in terms of similarity variables. The use of substructure in the Riemann problem reduces numerical dissipation and, therefore, allows a better preservation of flow structures, like contact and shear waves. In this second part of a series of papers we describe how this technique is extended to unstructured triangular meshes. All necessary details for a practical computer code implementation are discussed. In particular, we explicitly present all the issues related to computational geometry. Because these Riemann solvers are Multidimensional and have Self-similar strongly-Interacting states that are obtained by Consistency with the conservation law, we call them MuSIC Riemann solvers. (A video introduction to multidimensional Riemann solvers is available on http://www.elsevier.com/xml/linking-roles/text/html". The MuSIC framework is sufficiently general to handle general nonlinear systems of hyperbolic conservation laws in multiple space dimensions. It can also accommodate all self-similar one-dimensional Riemann solvers and subsequently produces a multidimensional version of the same. In this paper we focus on unstructured triangular meshes. As examples of different systems of conservation laws we

Two-Loop Scattering Amplitudes from the Riemann Sphere

CERN Document Server

Geyer, Yvonne; Monteiro, Ricardo; Tourkine, Piotr

2016-01-01

The scattering equations give striking formulae for massless scattering amplitudes at tree level and, as shown recently, at one loop. The progress at loop level was based on ambitwistor string theory, which naturally yields the scattering equations. We proposed that, for ambitwistor strings, the standard loop expansion in terms of the genus of the worldsheet is equivalent to an expansion in terms of nodes of a Riemann sphere, with the nodes carrying the loop momenta. In this paper, we show how to obtain two-loop scattering equations with the correct factorization properties. We adapt genus-two integrands from the ambitwistor string to the nodal Riemann sphere and show that these yield correct answers, by matching standard results for the four-point two-loop amplitudes of maximal supergravity and super-Yang-Mills theory. In the Yang-Mills case, this requires the loop analogue of the Parke-Taylor factor carrying the colour dependence, which includes non-planar contributions.

Functionals of finite Riemann surfaces

CERN Document Server

Schiffer, Menahem

1954-01-01

This advanced monograph on finite Riemann surfaces, based on the authors' 1949-50 lectures at Princeton University, remains a fundamental book for graduate students. The Bulletin of the American Mathematical Society hailed the self-contained treatment as the source of ""a plethora of ideas, each interesting in its own right,"" noting that ""the patient reader will be richly rewarded."" Suitable for graduate-level courses, the text begins with three chapters that offer a development of the classical theory along historical lines, examining geometrical and physical considerations, existence theo

Structural stability of solutions to the Riemann problem for a non-strictly hyperbolic system with flux approximation

Directory of Open Access Journals (Sweden)

Meina Sun

2016-05-01

Full Text Available We study the Riemann problem for a non-strictly hyperbolic system of conservation laws under the linear approximations of flux functions with three parameters. The approximated system also belongs to the type of triangular systems of conservation laws and this approximation does not change the structure of Riemann solutions to the original system. Furthermore, it is proven that the Riemann solutions to the approximated system converge to the corresponding ones to the original system as the perturbation parameter tends to zero.

Probability laws related to the Jacobi theta and Riemann zeta function and Brownian excursions

OpenAIRE

Biane, P.; Pitman, J.; Yor, M.

1999-01-01

This paper reviews known results which connect Riemann's integral representations of his zeta function, involving Jacobi's theta function and its derivatives, to some particular probability laws governing sums of independent exponential variables. These laws are related to one-dimensional Brownian motion and to higher dimensional Bessel processes. We present some characterizations of these probability laws, and some approximations of Riemann's zeta function which are related to these laws.

Reduction of 4-dim self dual super Yang-Mills onto super Riemann surfaces

International Nuclear Information System (INIS)

Mendoza, A.; Restuccia, A.; Martin, I.

1990-05-01

Recently self dual super Yang-Mills over a super Riemann surface was obtained as the zero set of a moment map on the space of superconnections to the dual of the super Lie algebra of gauge transformations. We present a new formulation of 4-dim Euclidean self dual super Yang-Mills in terms of constraints on the supercurvature. By dimensional reduction we obtain the same set of superconformal field equations which define self dual connections on a super Riemann surface. (author). 10 refs

The Differential-Algebraic Analysis of Symplectic and Lax Structures Related with New Riemann-Type Hydrodynamic Systems

Science.gov (United States)

Prykarpatsky, Yarema A.; Artemovych, Orest D.; Pavlov, Maxim V.; Prykarpatski, Anatolij K.

2013-06-01

A differential-algebraic approach to studying the Lax-type integrability of the generalized Riemann-type hydrodynamic hierarchy, proposed recently by O. D. Artemovych, M. V. Pavlov, Z. Popowicz and A. K. Prykarpatski, is developed. In addition to the Lax-type representation, found before by Z. Popowicz, a closely related representation is constructed in exact form by means of a new differential-functional technique. The bi-Hamiltonian integrability and compatible Poisson structures of the generalized Riemann type hierarchy are analyzed by means of the symplectic and gradient-holonomic methods. An application of the devised differential-algebraic approach to other Riemann and Vakhnenko type hydrodynamic systems is presented.

The KZB equations on Riemann surfaces

OpenAIRE

Felder, Giovanni

1996-01-01

In this paper, based on the author's lectures at the 1995 les Houches Summer school, explicit expressions for the Friedan--Shenker connection on the vector bundle of WZW conformal blocks on the moduli space of curves with tangent vectors at $n$ marked points are given. The covariant derivatives are expressed in terms of ``dynamical $r$-matrices'', a notion borrowed from integrable systems. The case of marked points moving on a fixed Riemann surface is studied more closely. We prove a universa...

Weyl and Riemann-Liouville multifractional Ornstein-Uhlenbeck processes

International Nuclear Information System (INIS)

Lim, S C; Teo, L P

2007-01-01

This paper considers two new multifractional stochastic processes, namely the Weyl multifractional Ornstein-Uhlenbeck process and the Riemann-Liouville multifractional Ornstein-Uhlenbeck process. Basic properties of these processes such as locally self-similar property and Hausdorff dimension are studied. The relationship between the multifractional Ornstein-Uhlenbeck processes and the corresponding multifractional Brownian motions is established

Moduli of Riemann surfaces, transcendental aspects

International Nuclear Information System (INIS)

Hain, R.

2000-01-01

These notes are an informal introduction to moduli spaces of compact Riemann surfaces via complex analysis, topology and Hodge Theory. The prerequisites for the first lecture are just basic complex variables, basic Riemann surface theory up to at least the Riemann-Roch formula, and some algebraic topology, especially covering space theory. The first lecture covers moduli in genus 0 and genus 1 as these can be understood using relatively elementary methods, but illustrate many of the points which arise in higher genus. The notes cover more material than was covered in the lectures, and sometimes the order of topics in the notes differs from that in the lectures. We have seen in genus 1 case that M 1 is the quotient Γ 1 /X 1 of a contractible complex manifold X 1 = H by a discrete group Γ 1 = SL 2 (Z). The action of Γ 1 on X 1 is said to be virtually free - that is, Γ 1 has a finite index subgroup which acts (fixed point) freely on X 1 . In this section we will generalize this to all g >= 1 - we will sketch a proof that there is a contractible complex manifold Xg, called Teichmueller space, and a group Γ g , called the mapping class group, which acts virtually freely on X g . The moduli space of genus g compact Riemann surfaces is the quotient: M g = Γ g /X g . This will imply that M g has the structure of a complex analytic variety with finite quotient singularities. Teichmueller theory is a difficult and technical subject. Because of this, it is only possible to give an overview. In this lecture, we compute the orbifold Picard group of M g for all g >= 1. Recall that an orbifold line bundle over M g is a holomorphic line bundle L over Teichmueller space X g together with an action of the mapping class group Γ g on it such that the projection L → X g is Γ g -equivariant. An orbifold section of this line bundle is a holomorphic Γ g -equivariant section X g → L of L. This is easily seen to be equivalent to fixing a level l>= 3 and considering holomorphic

Weyl transforms associated with the Riemann-Liouville operator

Directory of Open Access Journals (Sweden)

N. B. Hamadi

2006-01-01

Full Text Available For the Riemann-Liouville transform ℛα, α∈ℝ+, associated with singular partial differential operators, we define and study the Weyl transforms Wσ connected with ℛα, where σ is a symbol in Sm, m∈ℝ. We give criteria in terms of σ for boundedness and compactness of the transform Wσ.

Quantum Riemann surfaces. Pt. 2; The discrete series

Energy Technology Data Exchange (ETDEWEB)

Klimek, S. (Dept. of Mathematics, IUPUI, Indianapolis, IN (United States)); Lesniewski, A. (Dept. of Physics, Harvard Univ., Cambridge, MA (United States))

1992-02-01

We continue our study of noncommutative deformations of two-dimensional hyperbolic manifolds which we initiated in Part I. We construct a sequence of C{sup *}-algebras which are quantizations of a compact Riemann surface of genus g corresponding to special values of the Planck constant. These algebras are direct integrals of finite-dimensional C{sup *}-algebras. (orig.).

Poisson sigma model with branes and hyperelliptic Riemann surfaces

International Nuclear Information System (INIS)

Ferrario, Andrea

2008-01-01

We derive the explicit form of the superpropagators in the presence of general boundary conditions (coisotropic branes) for the Poisson sigma model. This generalizes the results presented by Cattaneo and Felder [''A path integral approach to the Kontsevich quantization formula,'' Commun. Math. Phys. 212, 591 (2000)] and Cattaneo and Felder ['Coisotropic submanifolds in Poisson geometry and branes in the Poisson sigma model', Lett. Math. Phys. 69, 157 (2004)] for Kontsevich's angle function [Kontsevich, M., 'Deformation quantization of Poisson manifolds I', e-print arXiv:hep.th/0101170] used in the deformation quantization program of Poisson manifolds. The relevant superpropagators for n branes are defined as gauge fixed homotopy operators of a complex of differential forms on n sided polygons P n with particular ''alternating'' boundary conditions. In the presence of more than three branes we use first order Riemann theta functions with odd singular characteristics on the Jacobian variety of a hyperelliptic Riemann surface (canonical setting). In genus g the superpropagators present g zero mode contributions

Riemann y los Números Primos

Directory of Open Access Journals (Sweden)

José Manuel Sánchez Muñoz

2011-10-01

Full Text Available En el mes de noviembre de 1859, durante la presentación mensual de losinformes de la Academia de Berlín, el alemán Bernhard Riemann presentóun trabajo que cambiaría los designios futuros de la ciencia matemática. El tema central de su informe se centraba en los números primos, presentando el que hoy día, una vez demostrada la Conjetura de Poincaré, puede ser considerado el problema matemático abierto más importante. El presente artículo muestra en su tercera sección una traducción al castellano de dicho trabajo.

On an isospectrality question over compact Riemann surfaces

International Nuclear Information System (INIS)

Srinivas Rau, S.

1990-01-01

It is proved that for a generic compact Riemann surface X of genus g>1,(i) there are at most 2 2g unitary characters of π 1 (X) whose associated line bundles have laplacians of identical spectrum, (ii) generating cycles for π 1 (X) can be chosen to be closed geodesics whose length multiplicity is 1. (author). 5 refs

Reassessing Riemann's paper on the number of primes less than a given magnitude

CERN Document Server

Dittrich, Walter

2018-01-01

In this book, the author pays tribute to Bernhard Riemann (1826–1866), mathematician with revolutionary ideas, whose work on the theory of integration, the Fourier transform, the hypergeometric differential equation, etc. contributed immensely to mathematical physics. This book concentrates in particular on Riemann’s only work on prime numbers, including such then new ideas as analytical continuation in the complex plane and the product formula for entire functions. A detailed analysis of the zeros of the Riemann zeta function is presented. The impact of Riemann’s ideas on regularizing infinite values in field theory is also emphasized.

Modular transformations of conformal blocks in WZW models on Riemann surfaces of higher genus

International Nuclear Information System (INIS)

Miao Li; Ming Yu.

1989-05-01

We derive the modular transformations for conformal blocks in Wess-Zumino-Witten models on Riemann surfaces of higher genus. The basic ingredient consists of using the Chern-Simons theory developed by Witten. We find that the modular transformations generated by Dehn twists are linear combinations of Wilson line operators, which can be expressed in terms of braiding matrices. It can also be shown that modular transformation matrices for g > 0 Riemann surfaces depend only on those for g ≤ 3. (author). 13 refs, 15 figs

Riemann zeros and phase transitions via the spectral operator on fractal strings

International Nuclear Information System (INIS)

Herichi, Hafedh; Lapidus, Michel L

2012-01-01

The spectral operator was introduced by Lapidus and van Frankenhuijsen (2006 Fractal Geometry, Complex Dimensions and Zeta Functions: Geometry and Spectra of Fractal Strings) in their reinterpretation of the earlier work of Lapidus and Maier (1995 J. Lond. Math. Soc. 52 15–34) on inverse spectral problems and the Riemann hypothesis. In essence, it is a map that sends the geometry of a fractal string onto its spectrum. In this review, we present the rigorous functional analytic framework given by Herichi and Lapidus (2012) and within which to study the spectral operator. Furthermore, we give a necessary and sufficient condition for the invertibility of the spectral operator (in the critical strip) and therefore obtain a new spectral and operator-theoretic reformulation of the Riemann hypothesis. More specifically, we show that the spectral operator is quasi-invertible (or equivalently, that its truncations are invertible) if and only if the Riemann zeta function ζ(s) does not have any zeros on the vertical line Re(s) = c. Hence, it is not invertible in the mid-fractal case when c= 1/2 , and it is quasi-invertible everywhere else (i.e. for all c ∈ (0, 1) with c≠ 1/2 ) if and only if the Riemann hypothesis is true. We also show the existence of four types of (mathematical) phase transitions occurring for the spectral operator at the critical fractal dimension c= 1/2 and c = 1 concerning the shape of the spectrum, its boundedness, its invertibility as well as its quasi-invertibility. This article is part of a special issue of Journal of Physics A: Mathematical and Theoretical in honour of Stuart Dowker’s 75th birthday devoted to ‘Applications of zeta functions and other spectral functions in mathematics and physics’. (review)

Exploration and extension of an improved Riemann track fitting algorithm

Science.gov (United States)

Strandlie, A.; Frühwirth, R.

2017-09-01

Recently, a new Riemann track fit which operates on translated and scaled measurements has been proposed. This study shows that the new Riemann fit is virtually as precise as popular approaches such as the Kalman filter or an iterative non-linear track fitting procedure, and significantly more precise than other, non-iterative circular track fitting approaches over a large range of measurement uncertainties. The fit is then extended in two directions: first, the measurements are allowed to lie on plane sensors of arbitrary orientation; second, the full error propagation from the measurements to the estimated circle parameters is computed. The covariance matrix of the estimated track parameters can therefore be computed without recourse to asymptotic properties, and is consequently valid for any number of observation. It does, however, assume normally distributed measurement errors. The calculations are validated on a simulated track sample and show excellent agreement with the theoretical expectations.

A contribution to the great Riemann solver debate

Science.gov (United States)

Quirk, James J.

1992-01-01

The aims of this paper are threefold: to increase the level of awareness within the shock capturing community to the fact that many Godunov-type methods contain subtle flaws that can cause spurious solutions to be computed; to identify one mechanism that might thwart attempts to produce very high resolution simulations; and to proffer a simple strategy for overcoming the specific failings of individual Riemann solvers.

Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics

National Research Council Canada - National Science Library

Derbyshire, John

2003-01-01

.... Is the hypothesis true or false?Riemann's basic inquiry, the primary topic of his paper, concerned a straightforward but nevertheless important matter of arithmetic defining a precise formula to track and identify the occurrence...

Conformal algebra of Riemann surfaces

International Nuclear Information System (INIS)

Vafa, C.

1988-01-01

It has become clear over the last few years that 2-dimensional conformal field theories are a crucial ingredient of string theory. Conformal field theories correspond to vacuum solutions of strings; or more precisely we know how to compute string spectrum and scattering amplitudes by starting from a formal theory (with a proper value of central charge of the Virasoro algebra). Certain non-linear sigma models do give rise to conformal theories. A lot of progress has been made in the understanding of conformal theories. The author discusses a different view of conformal theories which was motivated by the development of operator formalism on Riemann surfaces. The author discusses an interesting recent work from this point of view

Fractal supersymmetric QM, Geometric Probability and the Riemann Hypothesis

CERN Document Server

Castro, C

2004-01-01

The Riemann's hypothesis (RH) states that the nontrivial zeros of the Riemann zeta-function are of the form $ s_n =1/2+i\\lambda_n $. Earlier work on the RH based on supersymmetric QM, whose potential was related to the Gauss-Jacobi theta series, allows to provide the proper framework to construct the well defined algorithm to compute the probability to find a zero (an infinity of zeros) in the critical line. Geometric probability theory furnishes the answer to the very difficult question whether the probability that the RH is true is indeed equal to unity or not. To test the validity of this geometric probabilistic framework to compute the probability if the RH is true, we apply it directly to the the hyperbolic sine function $ \\sinh (s) $ case which obeys a trivial analog of the RH (the HSRH). Its zeros are equally spaced in the imaginary axis $ s_n = 0 + i n \\pi $. The geometric probability to find a zero (and an infinity of zeros) in the imaginary axis is exactly unity. We proceed with a fractal supersymme...

The Riemann zeta-function theory and applications

CERN Document Server

Ivic, Aleksandar

2003-01-01

""A thorough and easily accessible account.""-MathSciNet, Mathematical Reviews on the Web, American Mathematical Society. This extensive survey presents a comprehensive and coherent account of Riemann zeta-function theory and applications. Starting with elementary theory, it examines exponential integrals and exponential sums, the Voronoi summation formula, the approximate functional equation, the fourth power moment, the zero-free region, mean value estimates over short intervals, higher power moments, and omega results. Additional topics include zeros on the critical line, zero-density estim

The concept of a Riemann surface

CERN Document Server

Weyl, Hermann

2009-01-01

This classic on the general history of functions was written by one of the twentieth century's best-known mathematicians. Hermann Weyl, who worked with Einstein at Princeton, combined function theory and geometry in this high-level landmark work, forming a new branch of mathematics and the basis of the modern approach to analysis, geometry, and topology.The author intended this book not only to develop the basic ideas of Riemann's theory of algebraic functions and their integrals but also to examine the related ideas and theorems with an unprecedented degree of rigor. Weyl's two-part treatment

Seeley-De Witt coefficients in a Riemann-Cartan manifold

International Nuclear Information System (INIS)

Cognola, G.; Zerbini, S.; Istituto Nazionale di Fisica Nucleare, Povo

1988-01-01

A new derivation of the first two coefficients of the heat kernel expansion for a second-order elliptic differential operator on a Riemann-Cartan manifold with arbitrary torsion is given. The expressions are presented in a very compact and tractable form useful for physical applications. Comparisons with other similar results that appeared in the literature are briefly discussed. (orig.)

Ship-induced solitary Riemann waves of depression in Venice Lagoon

Energy Technology Data Exchange (ETDEWEB)

Parnell, Kevin E. [College of Marine and Environmental Sciences and Centre for Tropical Environmental and Sustainability Sciences, James Cook University, Queensland 4811 (Australia); Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Soomere, Tarmo, E-mail: soomere@cs.ioc.ee [Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn (Estonia); Zaggia, Luca [Institute of Marine Sciences, National Research Council, Castello 2737/F, 30122 Venice (Italy); Rodin, Artem [Institute of Cybernetics at Tallinn University of Technology, Akadeemia tee 21, 12618 Tallinn (Estonia); Lorenzetti, Giuliano [Institute of Marine Sciences, National Research Council, Castello 2737/F, 30122 Venice (Italy); Rapaglia, John [Sacred Heart University Department of Biology, 5151 Park Avenue, Fairfield, CT 06825 (United States); Scarpa, Gian Marco [Università Ca' Foscari, Dorsoduro 3246, 30123 Venice (Italy)

2015-03-06

We demonstrate that ships of moderate size, sailing at low depth Froude numbers (0.37–0.5) in a navigation channel surrounded by shallow banks, produce depressions with depths up to 2.5 m. These depressions (Bernoulli wakes) propagate as long-living strongly nonlinear solitary Riemann waves of depression substantial distances into Venice Lagoon. They gradually become strongly asymmetric with the rear of the depression becoming extremely steep, similar to a bore. As they are dynamically similar, air pressure fluctuations moving over variable-depth coastal areas could generate meteorological tsunamis with a leading depression wave followed by a devastating bore-like feature. - Highlights: • Unprecedently deep long-living ship-induced waves of depression detected. • Such waves are generated in channels with side banks under low Froude numbers. • The propagation of these waves is replicated using Riemann waves. • Long-living waves of depression form bore-like features at rear slope.

Ship-induced solitary Riemann waves of depression in Venice Lagoon

International Nuclear Information System (INIS)

Parnell, Kevin E.; Soomere, Tarmo; Zaggia, Luca; Rodin, Artem; Lorenzetti, Giuliano; Rapaglia, John; Scarpa, Gian Marco

2015-01-01

We demonstrate that ships of moderate size, sailing at low depth Froude numbers (0.37–0.5) in a navigation channel surrounded by shallow banks, produce depressions with depths up to 2.5 m. These depressions (Bernoulli wakes) propagate as long-living strongly nonlinear solitary Riemann waves of depression substantial distances into Venice Lagoon. They gradually become strongly asymmetric with the rear of the depression becoming extremely steep, similar to a bore. As they are dynamically similar, air pressure fluctuations moving over variable-depth coastal areas could generate meteorological tsunamis with a leading depression wave followed by a devastating bore-like feature. - Highlights: • Unprecedently deep long-living ship-induced waves of depression detected. • Such waves are generated in channels with side banks under low Froude numbers. • The propagation of these waves is replicated using Riemann waves. • Long-living waves of depression form bore-like features at rear slope

From Euclidean to Minkowski space with the Cauchy-Riemann equations

International Nuclear Information System (INIS)

Gimeno-Segovia, Mercedes; Llanes-Estrada, Felipe J.

2008-01-01

We present an elementary method to obtain Green's functions in non-perturbative quantum field theory in Minkowski space from Green's functions calculated in Euclidean space. Since in non-perturbative field theory the analytical structure of amplitudes often is unknown, especially in the presence of confined fields, dispersive representations suffer from systematic uncertainties. Therefore, we suggest to use the Cauchy-Riemann equations, which perform the analytical continuation without assuming global information on the function in the entire complex plane, but only in the region through which the equations are solved. We use as example the quark propagator in Landau gauge quantum chromodynamics, which is known from lattice and Dyson-Schwinger studies in Euclidean space. The drawback of the method is the instability of the Cauchy-Riemann equations against high-frequency noise,which makes it difficult to achieve good accuracy. We also point out a few curious details related to the Wick rotation. (orig.)

A fast Cauchy-Riemann solver. [differential equation solution for boundary conditions by finite difference approximation

Science.gov (United States)

Ghil, M.; Balgovind, R.

1979-01-01

The inhomogeneous Cauchy-Riemann equations in a rectangle are discretized by a finite difference approximation. Several different boundary conditions are treated explicitly, leading to algorithms which have overall second-order accuracy. All boundary conditions with either u or v prescribed along a side of the rectangle can be treated by similar methods. The algorithms presented here have nearly minimal time and storage requirements and seem suitable for development into a general-purpose direct Cauchy-Riemann solver for arbitrary boundary conditions.

A Modified Groundwater Flow Model Using the Space Time Riemann-Liouville Fractional Derivatives Approximation

Directory of Open Access Journals (Sweden)

Abdon Atangana

2014-01-01

Full Text Available The notion of uncertainty in groundwater hydrology is of great importance as it is known to result in misleading output when neglected or not properly accounted for. In this paper we examine this effect in groundwater flow models. To achieve this, we first introduce the uncertainties functions u as function of time and space. The function u accounts for the lack of knowledge or variability of the geological formations in which flow occur (aquifer in time and space. We next make use of Riemann-Liouville fractional derivatives that were introduced by Kobelev and Romano in 2000 and its approximation to modify the standard version of groundwater flow equation. Some properties of the modified Riemann-Liouville fractional derivative approximation are presented. The classical model for groundwater flow, in the case of density-independent flow in a uniform homogeneous aquifer is reformulated by replacing the classical derivative by the Riemann-Liouville fractional derivatives approximations. The modified equation is solved via the technique of green function and the variational iteration method.

Nontrivial Solution of Fractional Differential System Involving Riemann-Stieltjes Integral Condition

Directory of Open Access Journals (Sweden)

Ge-Feng Yang

2012-01-01

differential system involving the Riemann-Stieltjes integral condition, by using the Leray-Schauder nonlinear alternative and the Banach contraction mapping principle, some sufficient conditions of the existence and uniqueness of a nontrivial solution of a system are obtained.

Riemann-Hilbert treatment of Liouville theory on the torus: the general case

International Nuclear Information System (INIS)

Menotti, Pietro

2011-01-01

We extend the previous treatment of Liouville theory on the torus to the general case in which the distribution of charges is not necessarily symmetric. This requires the concept of Fuchsian differential equation on Riemann surfaces. We show through a group theoretic argument that the Heun parameter and a weight constant are sufficient to satisfy all monodromy conditions. We then apply the technique of differential equations on a Riemann surface to the two-point function on the torus in which one source is arbitrary and the other small. As a byproduct, we give in terms of quadratures the exact Green function on the square and on the rhombus with opening angle 2π/6 in the background of the field generated by an arbitrary charge.

The Riemann problem for the relativistic full Euler system with generalized Chaplygin proper energy density-pressure relation

Science.gov (United States)

Shao, Zhiqiang

2018-04-01

The relativistic full Euler system with generalized Chaplygin proper energy density-pressure relation is studied. The Riemann problem is solved constructively. The delta shock wave arises in the Riemann solutions, provided that the initial data satisfy some certain conditions, although the system is strictly hyperbolic and the first and third characteristic fields are genuinely nonlinear, while the second one is linearly degenerate. There are five kinds of Riemann solutions, in which four only consist of a shock wave and a centered rarefaction wave or two shock waves or two centered rarefaction waves, and a contact discontinuity between the constant states (precisely speaking, the solutions consist in general of three waves), and the other involves delta shocks on which both the rest mass density and the proper energy density simultaneously contain the Dirac delta function. It is quite different from the previous ones on which only one state variable contains the Dirac delta function. The formation mechanism, generalized Rankine-Hugoniot relation and entropy condition are clarified for this type of delta shock wave. Under the generalized Rankine-Hugoniot relation and entropy condition, we establish the existence and uniqueness of solutions involving delta shocks for the Riemann problem.

Exact Riemann solutions of the Ripa model for flat and non-flat bottom topographies

Science.gov (United States)

Rehman, Asad; Ali, Ishtiaq; Qamar, Shamsul

2018-03-01

This article is concerned with the derivation of exact Riemann solutions for Ripa model considering flat and non-flat bottom topographies. The Ripa model is a system of shallow water equations accounting for horizontal temperature gradients. In the case of non-flat bottom topography, the mass, momentum and energy conservation principles are utilized to relate the left and right states across the step-type bottom topography. The resulting system of algebraic equations is solved iteratively. Different numerical case studies of physical interest are considered. The solutions obtained from developed exact Riemann solvers are compared with the approximate solutions of central upwind scheme.

Asymptotic analysis on a pseudo-Hermitian Riemann-zeta Hamiltonian

Science.gov (United States)

Bender, Carl M.; Brody, Dorje C.

2018-04-01

The differential-equation eigenvalue problem associated with a recently-introduced Hamiltonian, whose eigenvalues correspond to the zeros of the Riemann zeta function, is analyzed using Fourier and WKB analysis. The Fourier analysis leads to a challenging open problem concerning the formulation of the eigenvalue problem in the momentum space. The WKB analysis gives the exact asymptotic behavior of the eigenfunction.

Functional models for commutative systems of linear operators and de Branges spaces on a Riemann surface

International Nuclear Information System (INIS)

Zolotarev, Vladimir A

2009-01-01

Functional models are constructed for commutative systems {A 1 ,A 2 } of bounded linear non-self-adjoint operators which do not contain dissipative operators (which means that ξ 1 A 1 +ξ 2 A 2 is not a dissipative operator for any ξ 1 , ξ 2 element of R). A significant role is played here by the de Branges transform and the function classes occurring in this context. Classes of commutative systems of operators {A 1 ,A 2 } for which such a construction is possible are distinguished. Realizations of functional models in special spaces of meromorphic functions on Riemann surfaces are found, which lead to reasonable analogues of de Branges spaces on these Riemann surfaces. It turns out that the functions E(p) and E-tilde(p) determining the order of growth in de Branges spaces on Riemann surfaces coincide with the well-known Baker-Akhiezer functions. Bibliography: 11 titles.

An Exact, Compressible One-Dimensional Riemann Solver for General, Convex Equations of State

Energy Technology Data Exchange (ETDEWEB)

Kamm, James Russell [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2015-03-05

This note describes an algorithm with which to compute numerical solutions to the one- dimensional, Cartesian Riemann problem for compressible flow with general, convex equations of state. While high-level descriptions of this approach are to be found in the literature, this note contains most of the necessary details required to write software for this problem. This explanation corresponds to the approach used in the source code that evaluates solutions for the 1D, Cartesian Riemann problem with a JWL equation of state in the ExactPack package [16, 29]. Numerical examples are given with the proposed computational approach for a polytropic equation of state and for the JWL equation of state.

Averages of ratios of the Riemann zeta-function and correlations of divisor sums

Science.gov (United States)

Conrey, Brian; Keating, Jonathan P.

2017-10-01

Nonlinearity has published articles containing a significant number-theoretic component since the journal was first established. We examine one thread, concerning the statistics of the zeros of the Riemann zeta function. We extend this by establishing a connection between the ratios conjecture for the Riemann zeta-function and a conjecture concerning correlations of convolutions of Möbius and divisor functions. Specifically, we prove that the ratios conjecture and an arithmetic correlations conjecture imply the same result. This provides new support for the ratios conjecture, which previously had been motivated by analogy with formulae in random matrix theory and by a heuristic recipe. Our main theorem generalises a recent calculation pertaining to the special case of two-over-two ratios.

Bernhard Riemann 1826-1866 Turning Points in the Conception of Mathematics

CERN Document Server

Laugwitz, Detlef

2008-01-01

The name of Bernard Riemann is well known to mathematicians and physicists around the world. College students encounter the Riemann integral early in their studies. Real and complex function theories are founded on Riemann’s work. Einstein’s theory of gravitation would be unthinkable without Riemannian geometry. In number theory, Riemann’s famous conjecture stands as one of the classic challenges to the best mathematical minds and continues to stimulate deep mathematical research. The name is indelibly stamped on the literature of mathematics and physics. This book, originally written in German and presented here in an English-language translation, examines Riemann’s scientific work from a single unifying perspective. Laugwitz describes Riemann’s development of a conceptual approach to mathematics at a time when conventional algorithmic thinking dictated that formulas and figures, rigid constructs, and transformations of terms were the only legitimate means of studying mathematical objects. David Hi...

Large chiral diffeomorphisms on Riemann surfaces and W-algebras

International Nuclear Information System (INIS)

Bandelloni, G.; Lazzarini, S.

2006-01-01

The diffeomorphism action lifted on truncated (chiral) Taylor expansion of a complex scalar field over a Riemann surface is presented in the paper under the name of large diffeomorphisms. After an heuristic approach, we show how a linear truncation in the Taylor expansion can generate an algebra of symmetry characterized by some structure functions. Such a linear truncation is explicitly realized by introducing the notion of Forsyth frame over the Riemann surface with the help of a conformally covariant algebraic differential equation. The large chiral diffeomorphism action is then implemented through a Becchi-Rouet-Stora (BRS) formulation (for a given order of truncation) leading to a more algebraic setup. In this context the ghost fields behave as holomorphically covariant jets. Subsequently, the link with the so-called W-algebras is made explicit once the ghost parameters are turned from jets into tensorial ghost ones. We give a general solution with the help of the structure functions pertaining to all the possible truncations lower or equal to the given order. This provides another contribution to the relationship between Korteweg-de Vries (KdV) flows and W-diffeomorphims

Riemann type algebraic structures and their differential-algebraic integrability analysis

Directory of Open Access Journals (Sweden)

Prykarpatsky A.K.

2010-06-01

Full Text Available The differential-algebraic approach to studying the Lax type integrability of generalized Riemann type equations is devised. The differentiations and the associated invariant differential ideals are analyzed in detail. The approach is also applied to studying the Lax type integrability of the well known Korteweg-de Vries dynamical system.

Non-uniqueness of admissible weak solutions to the Riemann problem for isentropic Euler equations

Science.gov (United States)

Chiodaroli, Elisabetta; Kreml, Ondřej

2018-04-01

We study the Riemann problem for multidimensional compressible isentropic Euler equations. Using the framework developed in Chiodaroli et al (2015 Commun. Pure Appl. Math. 68 1157–90), and based on the techniques of De Lellis and Székelyhidi (2010 Arch. Ration. Mech. Anal. 195 225–60), we extend the results of Chiodaroli and Kreml (2014 Arch. Ration. Mech. Anal. 214 1019–49) and prove that it is possible to characterize a set of Riemann data, giving rise to a self-similar solution consisting of one admissible shock and one rarefaction wave, for which the problem also admits infinitely many admissible weak solutions.

Flux quantization and quantum mechanics on Riemann surfaces in an external magnetic field

International Nuclear Information System (INIS)

Bolte, J.; Steiner, F.

1990-10-01

We investigate the possibility to apply an external constant magnetic field to a quantum mechanical system consisting of a particle moving on a compact or non-compact two-dimensional manifold of constant negative Gaussian curvature and of finite volume. For the motion on compact Riemann surfaces we find that a consistent formulation is only possible if the magnetic flux is quantized, as it is proportional to the (integrated) first Chern class of a certain complex line bundle over the manifold. In the case of non-compact surfaces of finite volume we obtain the striking result that the magnetic flux has to vanish identically due to the theorem that any holomorphic line bundle over a non-compact Riemann surface is holomorphically trivial. (orig.)

E-string theory on Riemann surfaces

Energy Technology Data Exchange (ETDEWEB)

Kim, Hee-Cheol; Vafa, Cumrun [Jefferson Physical Laboratory, Harvard University, Cambridge, MA (United States); Razamat, Shlomo S. [Physics Department, Technion, Haifa (Israel); Zafrir, Gabi [Kavli IPMU (WPI), UTIAS, the University of Tokyo, Kashiwa, Chiba (Japan)

2018-01-15

We study compactifications of the 6d E-string theory, the theory of a small E{sub 8} instanton, to four dimensions. In particular we identify N = 1 field theories in four dimensions corresponding to compactifications on arbitrary Riemann surfaces with punctures and with arbitrary non-abelian flat connections as well as fluxes for the abelian sub-groups of the E{sub 8} flavor symmetry. This sheds light on emergent symmetries in a number of 4d N = 1 SCFTs (including the 'E7 surprise' theory) as well as leads to new predictions for a large number of 4-dimensional exceptional dualities and symmetries. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ice cream and orbifold Riemann-Roch

Science.gov (United States)

Buckley, Anita; Reid, Miles; Zhou, Shengtian

2013-06-01

We give an orbifold Riemann-Roch formula in closed form for the Hilbert series of a quasismooth polarized n-fold (X,D), under the assumption that X is projectively Gorenstein with only isolated orbifold points. Our formula is a sum of parts each of which is integral and Gorenstein symmetric of the same canonical weight; the orbifold parts are called ice cream functions. This form of the Hilbert series is particularly useful for computer algebra, and we illustrate it on examples of {K3} surfaces and Calabi-Yau 3-folds. These results apply also with higher dimensional orbifold strata (see [1] and [2]), although the precise statements are considerably trickier. We expect to return to this in future publications.

Ice cream and orbifold Riemann-Roch

International Nuclear Information System (INIS)

Buckley, Anita; Reid, Miles; Zhou Shengtian

2013-01-01

We give an orbifold Riemann-Roch formula in closed form for the Hilbert series of a quasismooth polarized n-fold (X,D), under the assumption that X is projectively Gorenstein with only isolated orbifold points. Our formula is a sum of parts each of which is integral and Gorenstein symmetric of the same canonical weight; the orbifold parts are called ice cream functions. This form of the Hilbert series is particularly useful for computer algebra, and we illustrate it on examples of K3 surfaces and Calabi-Yau 3-folds. These results apply also with higher dimensional orbifold strata (see [1] and [2]), although the precise statements are considerably trickier. We expect to return to this in future publications.

Quantum field theory on higher-genus Riemann surfaces, 2

International Nuclear Information System (INIS)

Kubo, Reijiro; Ojima, Shuichi.

1990-08-01

Quantum field theory for closed bosonic string systems is formulated on arbitrary higher-genus Riemann surfaces in global operator formalism. Canonical commutation relations between bosonic string field X μ and their conjugate momenta P ν are derived in the framework of conventional quantum field theory. Problems arising in quantizing bosonic systems are considered in detail. Applying the method exploited in the preceding paper we calculate Ward-Takahashi identities. (author)

AdS5 solutions from M5-branes on Riemann surface and D6-branes sources

Energy Technology Data Exchange (ETDEWEB)

Bah, Ibrahima [Department of Physics and Astronomy, University of Southern California,Los Angeles, CA 90089 (United States); Institut de Physique Théorique, CEA/Saclay,91191 Gif-sur-Yvette (France)

2015-09-24

We describe the gravity duals of four-dimensional N=1 superconformal field theories obtained by wrapping M5-branes on a punctured Riemann surface. The internal geometry, normal to the AdS{sub 5} factor, generically preserves two U(1)s, with generators (J{sup +},J{sup −}), that are fibered over the Riemann surface. The metric is governed by a single potential that satisfies a version of the Monge-Ampère equation. The spectrum of N=1 punctures is given by the set of supersymmetric sources of the potential that are localized on the Riemann surface and lead to regular metrics near a puncture. We use this system to study a class of punctures where the geometry near the sources corresponds to M-theory description of D6-branes. These carry a natural (p,q) label associated to the circle dual to the killing vector pJ{sup +}+qJ{sup −} which shrinks near the source. In the generic case the world volume of the D6-branes is AdS{sub 5}×S{sup 2} and they locally preserve N=2 supersymmetry. When p=−q, the shrinking circle is dual to a flavor U(1). The metric in this case is non-degenerate only when there are co-dimension one sources obtained by smearing M5-branes that wrap the AdS{sub 5} factor and the circle dual the superconformal R-symmetry. The D6-branes are extended along the AdS{sub 5} and on cups that end on the co-dimension one branes. In the special case when the shrinking circle is dual to the R-symmetry, the D6-branes are extended along the AdS{sub 5} and wrap an auxiliary Riemann surface with an arbitrary genus. When the Riemann surface is compact with constant curvature, the system is governed by a Monge-Ampère equation.

Infinite conformal symmetries and Riemann-Hilbert transformation in super principal chiral model

International Nuclear Information System (INIS)

Hao Sanru; Li Wei

1989-01-01

This paper shows a new symmetric transformation - C transformation in super principal chiral model and discover an infinite dimensional Lie algebra related to the Virasoro algebra without central extension. By using the Riemann-Hilbert transformation, the physical origination of C transformation is discussed

Selberg trace formula for bordered Riemann surfaces: Hyperbolic, elliptic and parabolic conjugacy classes, and determinants of Maass-Laplacians

International Nuclear Information System (INIS)

Bolte, J.

1992-08-01

The Selberg trace formula for automorphic forms of weight m ε- Z, on bordered Riemann surfaces is developed. The trace formula is formulated for arbitrary Fuchsian groups of the first kind which include hyperbolic, elliptic and parabolic conjugacy classes. In the case of compact bordered Riemann surfaces we can explicitly evaluate determinants of Maass-Laplacians for both Dirichlet and Neumann boundary-conditions, respectively. Some implications for the open bosonic string theory are mentioned. (orig.)

Integrable systems twistors, loop groups, and Riemann surfaces

CERN Document Server

Hitchin, NJ; Ward, RS

2013-01-01

This textbook is designed to give graduate students an understanding of integrable systems via the study of Riemann surfaces, loop groups, and twistors. The book has its origins in a series of lecture courses given by the authors, all of whom are internationally known mathematicians and renowned expositors. It is written in an accessible and informal style, and fills a gap in the existing literature. The introduction by Nigel Hitchin addresses the meaning of integrability: how do werecognize an integrable system? His own contribution then develops connections with algebraic geometry, and inclu

Bosonization in a two-dimensional Riemann Cartan geometry

International Nuclear Information System (INIS)

Denardo, G.; Spallucci, E.

1987-01-01

We study the vacuum functional for a Dirac field in a two dimensional Riemann-Cartan geometry. Torsion is treated as a quantum variable while the metric is considered as a classical background field. Decoupling spinors from the non-Riemannian part of the geometry introduces a chiral Jacobian into the vacuum generating functional. We compute this functional Jacobian determinant by means of the Alvarez method. Finally, we show that the effective action for the background geometry is of the Liouville type and does not preserve any memory of the initial torsion field. (author)

Representation of symmetric metric connection via Riemann-Christoffel curvature tensor

International Nuclear Information System (INIS)

Selikhov, A.V.

1989-01-01

Bivector σ-bar μ ν ' which is the Jacoby matrix of the transformation to the Riemanian coordinates is considered in the paper. Basing on the dual nature of σ-bar μ ν ' the representation of metric connection (Christoffel symbols) have been obtained at the Riemanian coordinates via Riemann-Christoffel curvature tensor; the covariant conserved four-momentum in the general theory of relativity have been constructed. 11 refs

Riemann-Roch Spaces and Linear Network Codes

DEFF Research Database (Denmark)

Hansen, Johan P.

We construct linear network codes utilizing algebraic curves over finite fields and certain associated Riemann-Roch spaces and present methods to obtain their parameters. In particular we treat the Hermitian curve and the curves associated with the Suzuki and Ree groups all having the maximal...... number of points for curves of their respective genera. Linear network coding transmits information in terms of a basis of a vector space and the information is received as a basis of a possibly altered vector space. Ralf Koetter and Frank R. Kschischang %\\cite{DBLP:journals/tit/KoetterK08} introduced...... in the above metric making them suitable for linear network coding....

Towards a theory of chaos explained as travel on Riemann surfaces

International Nuclear Information System (INIS)

Calogero, F; Santini, P M; Gomez-Ullate, D; Sommacal, M

2009-01-01

We investigate the dynamics defined by a set of three coupled first-order ODEs. It is shown that the system can be reduced to quadratures which can be expressed in terms of elementary functions. Despite the integrable character of the model, the general solution is a multiple-valued function of time (considered as a complex variable), and we investigate the position and nature of its branch points. In the semi-symmetric case (g 1 = g 2 ≠ g 3 ), for rational values of the coupling constants the system is isochronous and explicit formulae for the period of the solutions can be given. For irrational values, the motions are confined but feature aperiodic motion with sensitive dependence on initial conditions. The system shows a rich dynamical behaviour that can be understood in quantitative detail since a global description of the Riemann surface associated with the solutions can be achieved. The details of the description of the Riemann surface are postponed to a forthcoming publication. This toy model is meant to provide a paradigmatic first step towards understanding a certain novel kind of chaotic behaviour

Extended Riemann-Liouville type fractional derivative operator with applications

Directory of Open Access Journals (Sweden)

Agarwal P.

2017-12-01

Full Text Available The main purpose of this paper is to introduce a class of new extended forms of the beta function, Gauss hypergeometric function and Appell-Lauricella hypergeometric functions by means of the modified Bessel function of the third kind. Some typical generating relations for these extended hypergeometric functions are obtained by defining the extension of the Riemann-Liouville fractional derivative operator. Their connections with elementary functions and Fox’s H-function are also presented.

Modification of the Riemann problem and the application for the boundary conditions in computational fluid dynamics

Directory of Open Access Journals (Sweden)

Kyncl Martin

2017-01-01

Full Text Available We work with the system of partial differential equations describing the non-stationary compressible turbulent fluid flow. It is a characteristic feature of the hyperbolic equations, that there is a possible raise of discontinuities in solutions, even in the case when the initial conditions are smooth. The fundamental problem in this area is the solution of the so-called Riemann problem for the split Euler equations. It is the elementary problem of the one-dimensional conservation laws with the given initial conditions (LIC - left-hand side, and RIC - right-hand side. The solution of this problem is required in many numerical methods dealing with the 2D/3D fluid flow. The exact (entropy weak solution of this hyperbolical problem cannot be expressed in a closed form, and has to be computed by an iterative process (to given accuracy, therefore various approximations of this solution are being used. The complicated Riemann problem has to be further modified at the close vicinity of boundary, where the LIC is given, while the RIC is not known. Usually, this boundary problem is being linearized, or roughly approximated. The inaccuracies implied by these simplifications may be small, but these have a huge impact on the solution in the whole studied area, especially for the non-stationary flow. Using the thorough analysis of the Riemann problem we show, that the RIC for the local problem can be partially replaced by the suitable complementary conditions. We suggest such complementary conditions accordingly to the desired preference. This way it is possible to construct the boundary conditions by the preference of total values, by preference of pressure, velocity, mass flow, temperature. Further, using the suitable complementary conditions, it is possible to simulate the flow in the vicinity of the diffusible barrier. On the contrary to the initial-value Riemann problem, the solution of such modified problems can be written in the closed form for some

Physical and Geometric Interpretations of the Riemann Tensor, Ricci Tensor, and Scalar Curvature

OpenAIRE

Loveridge, Lee C.

2004-01-01

Various interpretations of the Riemann Curvature Tensor, Ricci Tensor, and Scalar Curvature are described. Also, the physical meanings of the Einstein Tensor and Einstein's Equations are discussed. Finally a derivation of Newtonian Gravity from Einstein's Equations is given.

Existence and Nonexistence of Positive Solutions for Coupled Riemann-Liouville Fractional Boundary Value Problems

Directory of Open Access Journals (Sweden)

Johnny Henderson

2016-01-01

Full Text Available We investigate the existence and nonexistence of positive solutions for a system of nonlinear Riemann-Liouville fractional differential equations with two parameters, subject to coupled integral boundary conditions.

Super-quasi-conformal transformation and Schiffer variation on super-Riemann surface

International Nuclear Information System (INIS)

Takahasi, Wataru

1990-01-01

A set of equations which characterizes the super-Teichmueller deformations is proposed. It is a supersymmetric extension of the Beltrami equation. Relations between the set of equations and the Schiffer variations with the KN bases are discussed. This application of the KN bases shows the powerfulness of the KN theory in the study of super-Riemann surfaces. (author)

A variational principle giving gravitational 'superpotentials', the affine connection, Riemann tensor, and Einstein field equations

International Nuclear Information System (INIS)

Stachel, J.

1977-01-01

A first-order Lagrangian is given, from which follow the definitions of the fully covariant form of the Riemann tensor Rsub(μνkappalambda) in terms of the affine connection and metric; the definition of the affine connection in terms of the metric; the Einstein field equations; and the definition of a set of gravitational 'superpotentials' closely connected with the Komar conservation laws (Phys. Rev.; 113:934 (1959)). Substitution of the definition of the affine connection into this Lagrangian results in a second-order Lagrangian, from which follow the definition of the fully covariant Riemann tensor in terms of the metric, the Einstein equations, and the definition of the gravitational 'superpotentials'. (author)

Vertex operators, non-abelian orbifolds and the Riemann-Hilbert problem

International Nuclear Information System (INIS)

Gato, B.; Massachusetts Inst. of Tech., Cambridge

1990-01-01

We show how to construct the oscillator part of vertex operators for the bosonic string moving on non-abelian orbifolds, using the conserved charges method. When the three-string vertices are twisted by non-commuting group elements, the construction of the conserved charges becomes the Riemann-Hilbert problem with monodromy matrices given by the twists. This is solvable for any given configuration and any non-abelian orbifold. (orig.)

Representation theory of current algebra and conformal field theory on Riemann surfaces

International Nuclear Information System (INIS)

Yamada, Yasuhiko

1989-01-01

We study conformal field theories with current algebra (WZW-model) on general Riemann surfaces based on the integrable representation theory of current algebra. The space of chiral conformal blocks defined as solutions of current and conformal Ward identities is shown to be finite dimensional and satisfies the factorization properties. (author)

Riemann solvers for multi-component gas mixtures with temperature dependent heat capacities; Solveurs de riemann pour des melanges de gaz parfaits avec capacites calorifiques dependant de la temperature

Energy Technology Data Exchange (ETDEWEB)

Beccantini, A

2001-07-01

This thesis represents a contribution to the development of upwind splitting schemes for the Euler equations for ideal gaseous mixtures and their investigation in computing multidimensional flows in irregular geometries. In the preliminary part we develop and investigate the parameterization of the shock and rarefaction curves in the phase space. Then, we apply them to perform some field-by-field decompositions of the Riemann problem: the entropy-respecting one, the one which supposes that genuinely-non-linear (GNL) waves are both shocks (shock-shock one) and the one which supposes that GNL waves are both rarefactions (rarefaction-rarefaction one). We emphasize that their analysis is fundamental in Riemann solvers developing: the simpler the field-by-field decomposition, the simpler the Riemann solver based on it. As the specific heat capacities of the gases depend on the temperature, the shock-shock field-by-field decomposition is the easiest to perform. Then, in the second part of the thesis, we develop an upwind splitting scheme based on such decomposition. Afterwards, we investigate its robustness, precision and CPU-time consumption, with respect to some of the most popular upwind splitting schemes for polytropic/non-polytropic ideal gases. 1-D test-cases show that this scheme is both precise (exact capturing of stationary shock and stationary contact) and robust in dealing with strong shock and rarefaction waves. Multidimensional test-cases show that it suffers from some of the typical deficiencies which affect the upwind splitting schemes capable of exact capturing stationary contact discontinuities i.e the developing of non-physical instabilities in computing strong shock waves. In the final part, we use the high-order multidimensional solver here developed to compute fully-developed detonation flows. (author)

Riemann monodromy problem and conformal field theories

International Nuclear Information System (INIS)

Blok, B.

1989-01-01

A systematic analysis of the use of the Riemann monodromy problem for determining correlators (conformal blocks) on the sphere is presented. The monodromy data is constructed in terms of the braid matrices and gives a constraint on the noninteger part of the conformal dimensions of the primary fields. To determine the conformal blocks we need to know the order of singularities. We establish a criterion which tells us when the knowledge of the conformal dimensions of primary fields suffice to determine the blocks. When zero modes of the extended algebra are present the analysis is more difficult. In this case we give a conjecture that works for the SU(2) WZW case. (orig.)

Fermions on a Riemann surface and the Kadomtsev-Petviashvili equation

International Nuclear Information System (INIS)

Zabrodin, A.V.

1989-01-01

It is shown that the S matrix of free massless fermions on a Riemann surface of finite genus generates quasiperiodic solutions of the Kadomtsev-Petviashvili equation. An operator that changes the genus of a solution is constructed, and the law of composition of such operators is discussed. The construction is a generalization of the well-known operator approach in the case of soliton solutions to the general case of quasiperiodic τ functions

Riemann solvers for multi-component gas mixtures with temperature dependent heat capacities

International Nuclear Information System (INIS)

Beccantini, A.

2001-01-01

This thesis represents a contribution to the development of upwind splitting schemes for the Euler equations for ideal gaseous mixtures and their investigation in computing multidimensional flows in irregular geometries. In the preliminary part we develop and investigate the parameterization of the shock and rarefaction curves in the phase space. Then, we apply them to perform some field-by-field decompositions of the Riemann problem: the entropy-respecting one, the one which supposes that genuinely-non-linear (GNL) waves are both shocks (shock-shock one) and the one which supposes that GNL waves are both rarefactions (rarefaction-rarefaction one). We emphasize that their analysis is fundamental in Riemann solvers developing: the simpler the field-by-field decomposition, the simpler the Riemann solver based on it. As the specific heat capacities of the gases depend on the temperature, the shock-shock field-by-field decomposition is the easiest to perform. Then, in the second part of the thesis, we develop an upwind splitting scheme based on such decomposition. Afterwards, we investigate its robustness, precision and CPU-time consumption, with respect to some of the most popular upwind splitting schemes for polytropic/non-polytropic ideal gases. 1-D test-cases show that this scheme is both precise (exact capturing of stationary shock and stationary contact) and robust in dealing with strong shock and rarefaction waves. Multidimensional test-cases show that it suffers from some of the typical deficiencies which affect the upwind splitting schemes capable of exact capturing stationary contact discontinuities i.e the developing of non-physical instabilities in computing strong shock waves. In the final part, we use the high-order multidimensional solver here developed to compute fully-developed detonation flows. (author)

Instanton calculus without equations of motion: semiclassics from monodromies of a Riemann surface

Science.gov (United States)

Gulden, Tobias; Janas, Michael; Kamenev, Alex

2015-02-01

Instanton calculations in semiclassical quantum mechanics rely on integration along trajectories which solve classical equations of motion. However in systems with higher dimensionality or complexified phase space these are rarely attainable. A prime example are spin-coherent states which are used e.g. to describe single molecule magnets (SMM). We use this example to develop instanton calculus which does not rely on explicit solutions of the classical equations of motion. Energy conservation restricts the complex phase space to a Riemann surface of complex dimension one, allowing to deform integration paths according to Cauchy’s integral theorem. As a result, the semiclassical actions can be evaluated without knowing actual classical paths. Furthermore we show that in many cases such actions may be solely derived from monodromy properties of the corresponding Riemann surface and residue values at its singular points. As an example, we consider quenching of tunneling processes in SMM by an applied magnetic field.

The Great Gorilla Jump: An Introduction to Riemann Sums and Definite Integrals

Science.gov (United States)

Sealey, Vicki; Engelke, Nicole

2012-01-01

The great gorilla jump is an activity designed to allow calculus students to construct an understanding of the structure of the Riemann sum and definite integral. The activity uses the ideas of position, velocity, and time to allow students to explore familiar ideas in a new way. Our research has shown that introducing the definite integral as…

From Riemann to differential geometry and relativity

CERN Document Server

Papadopoulos, Athanase; Yamada, Sumio

2017-01-01

This book explores the work of Bernhard Riemann and its impact on mathematics, philosophy and physics. It features contributions from a range of fields, historical expositions, and selected research articles that were motivated by Riemann’s ideas and demonstrate their timelessness. The editors are convinced of the tremendous value of going into Riemann’s work in depth, investigating his original ideas, integrating them into a broader perspective, and establishing ties with modern science and philosophy. Accordingly, the contributors to this volume are mathematicians, physicists, philosophers and historians of science. The book offers a unique resource for students and researchers in the fields of mathematics, physics and philosophy, historians of science, and more generally to a wide range of readers interested in the history of ideas.

Regular Riemann-Hilbert transforms, Baecklund transformations and hidden symmetry algebra for some linearization systems

International Nuclear Information System (INIS)

Chau Ling-Lie; Ge Mo-Lin; Teh, Rosy.

1984-09-01

The Baecklund Transformations and the hidden symmetry algebra for Self-Dual Yang-Mills Equations, Landau-Lifshitz equations and the Extended Super Yang-Mills fields (N>2) are discussed on the base of the Regular Riemann-Hilbert Transform and the linearization equations. (author)

Classical and quantum Liouville theory on the Riemann sphere with n>3 punctures (III)

International Nuclear Information System (INIS)

Shen Jianmin; Sheng Zhengmao; Wang Zhonghua

1992-02-01

We study the Classical and Quantum Liouville theory on the Riemann sphere with n>3 punctures. We get the quantum exchange algebra relations between the chiral components in the Liouville theory from our assumption on the principle of quantization. (author). 5 refs

Stability of the isentropic Riemann solutions of the full multidimensional Euler system

Czech Academy of Sciences Publication Activity Database

Feireisl, Eduard; Kreml, Ondřej; Vasseur, A.

2015-01-01

Roč. 47, č. 3 (2015), s. 2416-2425 ISSN 0036-1410 R&D Projects: GA ČR GA13-00522S EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : Euler system * isentropic solutions * Riemann problem * rarefaction wave Subject RIV: BA - General Mathematics Impact factor: 1.486, year: 2015 http://epubs.siam.org/doi/abs/10.1137/140999827

Fourier-Laplace transform of irreducible regular differential systems on the Riemann sphere

International Nuclear Information System (INIS)

Sabbah, C

2004-01-01

It is shown that the Fourier-Laplace transform of an irreducible regular differential system on the Riemann sphere underlies a polarizable regular twistor D-module if one considers only the part at finite distance. The associated holomorphic bundle defined away from the origin of the complex plane is therefore equipped with a natural harmonic metric having a tame behaviour near the origin

Integral relations for invariants constructed from three Riemann tensors and their applications in quantum gravity

International Nuclear Information System (INIS)

van Nieuwenhuizen, P.; Wu, C.C.

1977-01-01

The lowest order quantum corrections to pure gravitation are finite because there exists an integral relation between products of two Riemann tensors (the Gauss--Bonnet theorem). In this article several algebraic and integral relations are determined between products of three Riemann tensors in four- and six-dimensional spacetime. In both cases, one is left with only one invariant when R/sub μ//sub ν/=0, viz., ∫ (-g) 1 / 2 (R/sub b//sub β//sub μ//sub ν/R/sup μ//sup ν//sup rho//sup sigma/R/sub rho//sub sigma/ /sup α//sup β/).It is explicitly shown that this invariant does not vanish, even when R/sub μ//sub ν/=0. Consequently, the two-loop quantum corrections to pure gravitation will only be finite if, due to miraculous cancellation, the coefficient of this invariant vanishes

Jet Riemann-Lagrange Geometry Applied to Evolution DEs Systems from Economy

OpenAIRE

Neagu, Mircea

2007-01-01

The aim of this paper is to construct a natural Riemann-Lagrange differential geometry on 1-jet spaces, in the sense of nonlinear connections, generalized Cartan connections, d-torsions, d-curvatures, jet electromagnetic fields and jet Yang-Mills energies, starting from some given non-linear evolution DEs systems modelling economic phenomena, like the Kaldor model of the bussines cycle or the Tobin-Benhabib-Miyao model regarding the role of money on economic growth.

Codomains for the Cauchy-Riemann and Laplace operators in ℝ2

Directory of Open Access Journals (Sweden)

Lloyd Edgar S. Moyo

2008-01-01

Full Text Available A codomain for a nonzero constant-coefficient linear partial differential operator P(∂ with fundamental solution E is a space of distributions T for which it is possible to define the convolution E*T and thus solving the equation P(∂S=T. We identify codomains for the Cauchy-Riemann operator in ℝ2 and Laplace operator in ℝ2 . The convolution is understood in the sense of the S′-convolution.

Riemann-Hilbert approach to the time-dependent generalized sine kernel

Energy Technology Data Exchange (ETDEWEB)

Kozlowski, K.K.

2010-12-15

We derive the leading asymptotic behavior and build a new series representation for the Fredholm determinant of integrable integral operators appearing in the representation of the time and distance dependent correlation functions of integrable models described by a six-vertex R-matrix. This series representation opens a systematic way for the computation of the long-time, long-distance asymptotic expansion for the correlation functions of the aforementioned integrable models away from their free fermion point. Our method builds on a Riemann-Hilbert based analysis. (orig.)

Polynomials, Riemann surfaces, and reconstructing missing-energy events

CERN Document Server

Gripaios, Ben; Webber, Bryan

2011-01-01

We consider the problem of reconstructing energies, momenta, and masses in collider events with missing energy, along with the complications introduced by combinatorial ambiguities and measurement errors. Typically, one reconstructs more than one value and we show how the wrong values may be correlated with the right ones. The problem has a natural formulation in terms of the theory of Riemann surfaces. We discuss examples including top quark decays in the Standard Model (relevant for top quark mass measurements and tests of spin correlation), cascade decays in models of new physics containing dark matter candidates, decays of third-generation leptoquarks in composite models of electroweak symmetry breaking, and Higgs boson decay into two tau leptons.

Supersymmetric Dirac particles in Riemann-Cartan space-time

International Nuclear Information System (INIS)

Rumpf, H.

1981-01-01

A natural extension of the supersymmetric model of Di Vecchia and Ravndal yields a nontrivial coupling of classical spinning particles to torsion in a Riemann-Cartan geometry. The equations of motion implied by this model coincide with a consistent classical limit of the Heisenberg equations derived from the minimally coupled Dirac equation. Conversely, the latter equation is shown to arise from canonical quantization of the classical system. The Heisenberg equations are obtained exact in all powers of h/2π and thus complete the partial results of previous WKB calculations. The author also considers such matters of principle as the mathematical realization of anticommuting variables, the physical interpretation of supersymmetry transformations, and the effective variability of rest mass. (Auth.)

A novel supersymmetry in 2-dimensional Yang-Mills theory on Riemann surfaces

International Nuclear Information System (INIS)

Soda, Jiro

1991-02-01

We find a novel supersymmetry in 2-dimensional Maxwell and Yang-Mills theories. Using this supersymmetry, it is shown that the 2-dimensional Euclidean pure gauge theory on a closed Riemann surface Σ can be reduced to a topological field theory which is the 3-dimensional Chern-Simons gauge theory in the special space-time topology Σ x R. Related problems are also discussed. (author)

Differential-algebraic integrability analysis of the generalized Riemann type and Korteweg-de Vries hydrodynamical equations

Energy Technology Data Exchange (ETDEWEB)

Prykarpatsky, Anatoliy K [Department of Mining Geodesy, AGH University of Science and Technology, Cracow 30059 (Poland); Artemovych, Orest D [Department of Algebra and Topology, Faculty of Mathematics and Informatics of the Vasyl Stefanyk Pre-Carpathian National University, Ivano-Frankivsk (Ukraine); Popowicz, Ziemowit [Institute of Theoretical Physics, University of Wroclaw (Poland); Pavlov, Maxim V, E-mail: pryk.anat@ua.f, E-mail: artemo@usk.pk.edu.p, E-mail: ziemek@ift.uni.wroc.p, E-mail: M.V.Pavlov@lboro.ac.u [Department of Mathematical Physics, P.N. Lebedev Physical Institute, 53 Leninskij Prospekt, Moscow 119991 (Russian Federation)

2010-07-23

A differential-algebraic approach to studying the Lax-type integrability of the generalized Riemann-type hydrodynamic equations at N = 3, 4 is devised. The approach is also applied to studying the Lax-type integrability of the well-known Korteweg-de Vries dynamical system.

Differential-algebraic integrability analysis of the generalized Riemann type and Korteweg-de Vries hydrodynamical equations

International Nuclear Information System (INIS)

Prykarpatsky, Anatoliy K; Artemovych, Orest D; Popowicz, Ziemowit; Pavlov, Maxim V

2010-01-01

A differential-algebraic approach to studying the Lax-type integrability of the generalized Riemann-type hydrodynamic equations at N = 3, 4 is devised. The approach is also applied to studying the Lax-type integrability of the well-known Korteweg-de Vries dynamical system.

Superconformal algebra and central extension of meromorphic vector fields with multipoles on super-Riemann sphere

International Nuclear Information System (INIS)

Wang Shikun; Xu Kaiwen.

1989-12-01

The superconformal algebras of meromorphic vector fields with multipoles, the central extension and the relevant abelian differential of the third kind on super Riemann sphere were constructed. The background of our theory is concerned with the interaction of closed superstrings. (author). 9 refs

Robinson manifolds and Cauchy-Riemann spaces

CERN Document Server

Trautman, A

2002-01-01

A Robinson manifold is defined as a Lorentz manifold (M, g) of dimension 2n >= 4 with a bundle N subset of C centre dot TM such that the fibres of N are maximal totally null and there holds the integrability condition [Sec N, Sec N] subset of Sec N. The real part of N intersection N-bar is a bundle of null directions tangent to a congruence of null geodesics. This generalizes the notion of a shear-free congruence of null geodesics (SNG) in dimension 4. Under a natural regularity assumption, the set M of all these geodesics has the structure of a Cauchy-Riemann manifold of dimension 2n - 1. Conversely, every such CR manifold lifts to many Robinson manifolds. Three definitions of a CR manifold are described here in considerable detail; they are equivalent under the assumption of real analyticity, but not in the smooth category. The distinctions between these definitions have a bearing on the validity of the Robinson theorem on the existence of null Maxwell fields associated with SNGs. This paper is largely a re...

Quadratic algebras and noncommutative integration of Klein-Gordon equations in non-steckel Riemann spaces

International Nuclear Information System (INIS)

Varaksin, O.L.; Firstov, V.V.; Shapovalov, A.V.; Shirokov, I.V.

1995-01-01

The method of noncommutative integration of linear partial differential equations is used to solve the Klein-Gordon equations in Riemann space, in the case when the set of noncommutating symmetry operators of this equation for a quadratic algebra consists of one second-order operator and several first-order operators. Solutions that do not permit variable separation are presented

Inverse Scattering, the Coupling Constant Spectrum, and the Riemann Hypothesis

International Nuclear Information System (INIS)

Khuri, N. N.

2002-01-01

It is well known that the s-wave Jost function for a potential, λV, is an entire function of λ with an infinite number of zeros extending to infinity. For a repulsive V, and at zero energy, these zeros of the 'coupling constant', λ, will all be real and negative, λ n (0) n n =1/2+iγ n . Thus, finding a repulsive V whose coupling constant spectrum coincides with the Riemann zeros will establish the Riemann hypothesis, but this will be a very difficult and unguided search.In this paper we make a significant enlargement of the class of potentials needed for a generalization of the above idea. We also make this new class amenable to construction via inverse scattering methods. We show that all one needs is a one parameter class of potentials, U(s;x), which are analytic in the strip, 0≤Res≤1, Ims>T 0 , and in addition have an asymptotic expansion in powers of [s(s-1)] -1 , i.e. U(s;x)=V 0 (x)+gV 1 (x)+g 2 V 2 (x)+...+O(g N ), with g=[s(s-1)] -1 . The potentials V n (x) are real and summable. Under suitable conditions on the V n 's and the O(g N ) term we show that the condition, ∫ 0 ∞ vertical bar f 0 (x) vertical bar 2 V 1 (x) dx≠0, where f 0 is the zero energy and g=0 Jost function for U, is sufficient to guarantee that the zeros g n are real and, hence, s n =1/2+iγ n , for γ n ≥T 0 .Starting with a judiciously chosen Jost function, M(s,k), which is constructed such that M(s,0) is Riemann's ξ(s) function, we have used inverse scattering methods to actually construct a U(s;x) with the above properties. By necessity, we had to generalize inverse methods to deal with complex potentials and a nonunitary S-matrix. This we have done at least for the special cases under consideration.For our specific example, ∫ 0 ∞ vertical bar f 0 (x) vertical bar 2 V 1 (x) dx=0 and, hence, we get no restriction on Img n or Res n . The reasons for the vanishing of the above integral are given, and they give us hints on what one needs to proceed further. The problem

A Theta lift representation for the Kawazumi-Zhang and Faltings invariants of genus-two Riemann surfaces

CERN Document Server

Pioline, Boris

2016-01-01

The Kawazumi-Zhang invariant $\\varphi$ for compact genus-two Riemann surfaces was recently shown to be a eigenmode of the Laplacian on the Siegel upper half-plane, away from the separating degeneration divisor. Using this fact and the known behavior of $\\varphi$ in the non-separating degeneration limit, it is shown that $\\varphi$ is equal to the Theta lift of the unique (up to normalization) weak Jacobi form of weight $-2$. This identification provides the complete Fourier-Jacobi expansion of $\\varphi$ near the non-separating node, gives full control on the asymptotics of $\\varphi$ in the various degeneration limits, and provides a efficient numerical procedure to evaluate $\\varphi$ to arbitrary accuracy. It also reveals a mock-type holomorphic Siegel modular form of weight $-2$ underlying $\\varphi$. From the general relation between the Faltings invariant, the Kawazumi-Zhang invariant and the discriminant for hyperelliptic Riemann surfaces, a Theta lift representation for the Faltings invariant in genus two ...

Riemann-Liouville integrals of fractional order and extended KP hierarchy

International Nuclear Information System (INIS)

Kamata, Masaru; Nakamula, Atsushi

2002-01-01

An attempt to formulate the extensions of the KP hierarchy by introducing fractional-order pseudo-differential operators is given. In the case of the extension with the half-order pseudo-differential operators, a system analogous to the supersymmetric extensions of the KP hierarchy is obtained. Unlike the supersymmetric extensions, no Grassmannian variable appears in the hierarchy considered here. More general hierarchies constructed by the 1/Nth-order pseudo-differential operators, their integrability and the reduction procedure are also investigated. In addition to finding the new extensions of the KP hierarchy, a brief introduction to the Riemann-Liouville integral is provided to yield a candidate for the fractional-order pseudo-differential operators

A New Riemann Type Hydrodynamical Hierarchy and its Integrability Analysis

International Nuclear Information System (INIS)

Golenia, Jolanta Jolanta; Bogolubov, Nikolai N. Jr.; Popowicz, Ziemowit; Pavlov, Maxim V.; Prykarpatsky, Anatoliy K.

2009-12-01

Short-wave perturbations in a relaxing medium, governed by a special reduction of the Ostrovsky evolution equation, and later derived by Whitham, are studied using the gradient-holonomic integrability algorithm. The bi-Hamiltonicity and complete integrability of the corresponding dynamical system is stated and an infinite hierarchy of commuting to each other conservation laws of dispersive type are found. The well defined regularization of the model is constructed and its Lax type integrability is discussed. A generalized hydrodynamical Riemann type system is considered, infinite hierarchies of conservation laws, related compatible co-symplectic structures and Lax type representations for the special cases N = 2, 3 and N = 4 are constructed. (author)

The Euler–Riemann gases, and partition identities

International Nuclear Information System (INIS)

Chair, Noureddine

2013-01-01

The Euler theorem in partition theory and its generalization are derived from a non-interacting quantum field theory in which each bosonic mode with a given frequency is equivalent to a sum of bosonic mode whose frequency is twice (s-times) as much, and a fermionic (parafermionic) mode with the same frequency. Explicit formulas for the graded parafermionic partition functions are obtained, and the inverse of the graded partition function (IGPPF), turns out to be bosonic (fermionic) partition function depending on the parity of the order s of the parafermions. It is also shown that these partition functions are generating functions of partitions of integers with restrictions, the Euler generating function is identified with the inverse of the graded parafermionic partition function of order 2. As a result we obtain new sequences of partitions of integers with given restrictions. If the parity of the order s is even, then mixing a system of parafermions with a system whose partition function is (IGPPF), results in a system of fermions and bosons. On the other hand, if the parity of s is odd, then, the system we obtain is still a mixture of fermions and bosons but the corresponding Fock space of states is truncated. It turns out that these partition functions are given in terms of the Jacobi theta function θ 4 , and generate sequences in partition theory. Our partition functions coincide with the overpartitions of Corteel and Lovejoy, and jagged partitions in conformal field theory. Also, the partition functions obtained are related to the Ramond characters of the superconformal minimal models, and in the counting of the Moore–Read edge spectra that appear in the fractional quantum Hall effect. The different partition functions for the Riemann gas that are the counter parts of the Euler gas are obtained by a simple change of variables. In particular the counter part of the Jacobi theta function is (ζ(2t))/(ζ(t) 2 ) . Finally, we propose two formulas which brings

Loss of hyperbolicity changes the number of wave groups in Riemann problems

OpenAIRE

Vítor Matos; Julio D. Silva; Dan Marchesin

2016-01-01

Themain goal of ourwork is to showthat there exists a class of 2×2 Riemann problems for which the solution comprises a singlewave group for an open set of initial conditions. This wave group comprises a 1-rarefaction joined to a 2-rarefaction, not by an intermediate state, but by a doubly characteristic shock, 1-left and 2-right characteristic. In order to ensure that perturbations of initial conditions do not destroy the adjacency of the waves, local transversality between a composite curve ...

Do extended objects move along the geodesics in the Riemann space-time

International Nuclear Information System (INIS)

Denisov, V.I.; Logunov, A.A.; Mestvirishvili, M.A.

1981-01-01

Movement of an extended self-gravitating body in the gravitational field of another distant body is studied in the postnewtonian approximation of arbitrary metrical gravitational theory. Comparison of the mass center acceleration of the extended body with the acceleration of a point body moving in the Riemann space-time, the metrics of which is formally equivalent to the metrics of two moving extended bodies, shows that in any metrical gravitation theory with conservation laws of energy and momentum of the matter and gravitational field taken together, the mass center of the extended body does not, in general case, move along the geodesics of the Riemann space-time. Application of the general formulas obtained to the system Sun-Earth combined with the experimental data of the lunar laser ranging, shows that the Earth in its orbital motion is oscillating with respect to reference geodesics, with the period about one hour and the amplitude not less than 10 -2 cm. This amplitude is of the postnewtonian magnitude and as a consequence, the deviation of the Earth movement from the geodesical movement can be observed in the experiment possessing the postnewtonian accuracy. The difference between the acceleration of the Earth mass center and that of a test body in the postnewtonian approximation is equal to 10 -7 part of the Earth acceleration. The ratio of the passive gravitational mass of the Earth (defined according to Will) and its inert mass differs from 1 by 10 -8 approximately [ru

Cálculo de áreas mediante la suma de Riemann con la TI-83

OpenAIRE

Lupiáñez, José Luis

2002-01-01

En este artículo presentamos una actividad para introducir el cálculo del área que encierra una curva, basada en la Suma de Riemann, y que puede realizarse con la calculadora TI-83. El planteamiento de la actividad permite estudiar varias funciones sin perder tiempo en tediosos cálculos, con idea de observar lo acertado de este método de aproximación.

Non-uniqueness of admissible weak solutions to the Riemann problem for the isentropic Euler equations

Czech Academy of Sciences Publication Activity Database

Chiodaroli, E.; Kreml, Ondřej

2018-01-01

Roč. 31, č. 4 (2018), s. 1441-1460 ISSN 0951-7715 R&D Projects: GA ČR(CZ) GJ17-01694Y Institutional support: RVO:67985840 Keywords : Riemann problem * non-uniqueness * weak solutions Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.767, year: 2016 http://iopscience.iop.org/ article /10.1088/1361-6544/aaa10d/meta

Non-uniqueness of admissible weak solutions to the Riemann problem for the isentropic Euler equations

Czech Academy of Sciences Publication Activity Database

Chiodaroli, E.; Kreml, Ondřej

2018-01-01

Roč. 31, č. 4 (2018), s. 1441-1460 ISSN 0951-7715 R&D Projects: GA ČR(CZ) GJ17-01694Y Institutional support: RVO:67985840 Keywords : Riemann problem * non-uniqueness * weak solutions Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 1.767, year: 2016 http://iopscience.iop.org/article/10.1088/1361-6544/aaa10d/meta

The Riemann zeros as energy levels of a Dirac fermion in a potential built from the prime numbers in Rindler spacetime

International Nuclear Information System (INIS)

Sierra, Germán

2014-01-01

We construct a Hamiltonian H R whose discrete spectrum contains, in a certain limit, the Riemann zeros. H R is derived from the action of a massless Dirac fermion living in a domain of Rindler spacetime, in 1 + 1 dimensions, which has a boundary given by the world line of a uniformly accelerated observer. The action contains a sum of delta function potentials that can be viewed as partially reflecting moving mirrors. An appropriate choice of the accelerations of the mirrors, provide primitive periodic orbits that are associated with the prime numbers p, whose periods, as measured by the observer's clock, are logp. Acting on the chiral components of the fermion χ ∓ , H R becomes the Berry–Keating Hamiltonian ±(x p-hat + p-hat x)/2, where x is identified with the Rindler spatial coordinate and p-hat with the conjugate momentum. The delta function potentials give the matching conditions of the fermion wave functions on both sides of the mirrors. There is also a phase shift e iϑ for the reflection of the fermions at the boundary where the observer sits. The eigenvalue problem is solved by transfer matrix methods in the limit where the reflection amplitudes become infinitesimally small. We find that, for generic values of ϑ, the spectrum is a continuum where the Riemann zeros are missing, as in the adelic Connes model. However, for some values of ϑ, related to the phase of the zeta function, the Riemann zeros appear as discrete eigenvalues that are immersed in the continuum. We generalize this result to the zeros of Dirichlet L-functions, which are associated to primitive characters, that are encoded in the reflection coefficients of the mirrors. Finally, we show that the Hamiltonian associated to the Riemann zeros belongs to class AIII, or chiral GUE, of the Random Matrix Theory. (paper)

Jacob's ladders, Riemann's oscillators, quotient of two oscillating multiforms and set of metamorphoses of this system

OpenAIRE

Moser, Jan

2015-01-01

In this paper we introduce complicated oscillating system, namely quotient of two multiforms based on Riemann-Siegel formula. We prove that there is an infinite set of metamorphoses of this system (=chrysalis) on critical line $\\sigma=\\frac 12$ into a butterfly (=infinite series of M\\" obius functions in the region of absolute convergence $\\sigma>1$).

Fractional parts and their relations to the values of the Riemann zeta function

KAUST Repository

Alabdulmohsin, Ibrahim

2017-09-06

A well-known result, due to Dirichlet and later generalized by de la Vallée–Poussin, expresses a relationship between the sum of fractional parts and the Euler–Mascheroni constant. In this paper, we prove an asymptotic relationship between the summation of the products of fractional parts with powers of integers on the one hand, and the values of the Riemann zeta function, on the other hand. Dirichlet’s classical result falls as a particular case of this more general theorem.

Fractional parts and their relations to the values of the Riemann zeta function

KAUST Repository

Alabdulmohsin, Ibrahim

2017-01-01

A well-known result, due to Dirichlet and later generalized by de la Vallée–Poussin, expresses a relationship between the sum of fractional parts and the Euler–Mascheroni constant. In this paper, we prove an asymptotic relationship between the summation of the products of fractional parts with powers of integers on the one hand, and the values of the Riemann zeta function, on the other hand. Dirichlet’s classical result falls as a particular case of this more general theorem.

The mass-damped Riemann problem and the aerodynamic surface force calculation for an accelerating body

International Nuclear Information System (INIS)

Tan, Zhiqiang; Wilson, D.; Varghese, P.L.

1997-01-01

We consider an extension of the ordinary Riemann problem and present an efficient approximate solution that can be used to improve the calculations of aerodynamic forces on an accelerating body. The method is demonstrated with one-dimensional examples where the Euler equations and the body motion are solved in the non-inertial co-ordinate frame fixed to the accelerating body. 8 refs., 6 figs

Ernst Equation and Riemann Surfaces: Analytical and Numerical Methods

International Nuclear Information System (INIS)

Ernst, Frederick J

2007-01-01

metric tensor components. The first two chapters of this book are devoted to some basic ideas: in the introductory chapter 1 the authors discuss the concept of integrability, comparing the integrability of the vacuum Ernst equation with the integrability of nonlinear equations of Korteweg-de Vries (KdV) type, while in chapter 2 they describe various circumstances in which the vacuum Ernst equation has been determined to be relevant, not only in connection with gravitation but also, for example, in the construction of solutions of the self-dual Yang-Mills equations. It is also in this chapter that one of several equivalent linear systems for the Ernst equation is described. The next two chapters are devoted to Dmitry Korotkin's concept of algebro-geometric solutions of a linear system: in chapter 3 the structure of such solutions of the vacuum Ernst equation, which involve Riemann theta functions of hyperelliptic algebraic curves of any genus, is contrasted with the periodic structure of such solutions of the KdV equation. How such solutions can be obtained, for example, by solving a matrix Riemann-Hilbert problem and how the metric tensor of the associated spacetime can be evaluated is described in detail. In chapter 4 the asymptotic behaviour and the similarity structure of the general algebro-geometric solutions of the Ernst equation are described, and the relationship of such solutions to the perhaps more familiar multi-soliton solutions is discussed. The next three chapters are based upon the authors' own published research: in chapter 5 it is shown that a problem involving counter-rotating infinitely thin disks of matter can be solved in terms of genus two Riemann theta functions, while in chapter 6 the authors describe numerical methods that facilitate the construction of such solutions, and in chapter 7 three-dimensional graphs are displayed that depict all metrical fields of the associated spacetime. Finally, in chapter 8, the difficulties associated with

On Riemann boundary value problems for null solutions of the two dimensional Helmholtz equation

Science.gov (United States)

Bory Reyes, Juan; Abreu Blaya, Ricardo; Rodríguez Dagnino, Ramón Martin; Kats, Boris Aleksandrovich

2018-01-01

The Riemann boundary value problem (RBVP to shorten notation) in the complex plane, for different classes of functions and curves, is still widely used in mathematical physics and engineering. For instance, in elasticity theory, hydro and aerodynamics, shell theory, quantum mechanics, theory of orthogonal polynomials, and so on. In this paper, we present an appropriate hyperholomorphic approach to the RBVP associated to the two dimensional Helmholtz equation in R^2 . Our analysis is based on a suitable operator calculus.

Efficient numerical simulation of non-integer-order space-fractional reaction-diffusion equation via the Riemann-Liouville operator

Science.gov (United States)

Owolabi, Kolade M.

2018-03-01

In this work, we are concerned with the solution of non-integer space-fractional reaction-diffusion equations with the Riemann-Liouville space-fractional derivative in high dimensions. We approximate the Riemann-Liouville derivative with the Fourier transform method and advance the resulting system in time with any time-stepping solver. In the numerical experiments, we expect the travelling wave to arise from the given initial condition on the computational domain (-∞, ∞), which we terminate in the numerical experiments with a large but truncated value of L. It is necessary to choose L large enough to allow the waves to have enough space to distribute. Experimental results in high dimensions on the space-fractional reaction-diffusion models with applications to biological models (Fisher and Allen-Cahn equations) are considered. Simulation results reveal that fractional reaction-diffusion equations can give rise to a range of physical phenomena when compared to non-integer-order cases. As a result, most meaningful and practical situations are found to be modelled with the concept of fractional calculus.

The transition from regular to irregular motions, explained as travel on Riemann surfaces

International Nuclear Information System (INIS)

Calogero, F; Santini, P M; Gomez-Ullate, D; Sommacal, M

2005-01-01

We introduce and discuss a simple Hamiltonian dynamical system, interpretable as a three-body problem in the (complex) plane and providing the prototype of a mechanism explaining the transition from regular to irregular motions as travel on Riemann surfaces. The interest of this phenomenology-illustrating the onset in a deterministic context of irregular motions-is underlined by its generality, suggesting its eventual relevance to understand natural phenomena and experimental investigations. Here only some of our main findings are reported, without detailing their proofs: a more complete presentation will be published elsewhere

Temperature duality on Riemann surface and cosmological solutions for genus g = 1 and 2

International Nuclear Information System (INIS)

Yan Jun; Wang Shunjin

1999-01-01

A bosonic string model at finite temperature on the gravitation g μν and the dilaton φ background field is examined. Moreover, the duality relation of energy momentum tensor on high genus Riemann surface is derived. At the same time, the temperature duality invariance for the action of string gas matter is proved in 4-D Robertson-Walker metric, the string cosmological solutions and temperature duality of the equations of motion for genus g = 1 and 2 are also investigated

Applications of Wirtinger Inequalities on the Distribution of Zeros of the Riemann Zeta-Function

Directory of Open Access Journals (Sweden)

Saker SamirH

2010-01-01

Full Text Available On the hypothesis that the th moments of the Hardy -function are correctly predicted by random matrix theory and the moments of the derivative of are correctly predicted by the derivative of the characteristic polynomials of unitary matrices, we establish new large spaces between the zeros of the Riemann zeta-function by employing some Wirtinger-type inequalities. In particular, it is obtained that which means that consecutive nontrivial zeros often differ by at least 6.1392 times the average spacing.

(Anti-) selfdual Riemann curvature tensor in four spacelike compactified dimensions, O5 isometry group and chiral fermion zero modes

International Nuclear Information System (INIS)

Minkowski, P.

1986-01-01

The metric and contorsion tensors are constructed which yield a combined Riemann curvature tensor of the form Rsup(+-)sub(μνsigmatau)=(1/2a 2 )(gsub(μsigma)gsub(νtau) - gsub(μtau)gsub(νsigma)+-√g epsilonsub(μνsigmatau)). The metric with euclidean signature (++++) describes a sphere S 4 with radius a, i.e. admits the isometry group O5. For selfdual (antiselfdual) curvature tensor the contorsion tensor is given by the antiselfdual (selfdual) instanton configuration with respect to the spin gauge group SU2sub(R) (SU2sub(L)). The selfdual (antiselfdual) Riemann tensor admits two covariantly constant right-handed (left-handed) spin 1/2 fermion zero modes, one J=1/2 and one J=3/2 right-handed (left-handed) multiplet corresponding to L=1, transforming as a pseudoreal representation of O4 (SU2sub(R(L))). The hermitean Dirac equation retains only the two constant chiral modes. (orig.)

Minimal models on Riemann surfaces: The partition functions

International Nuclear Information System (INIS)

Foda, O.

1990-01-01

The Coulomb gas representation of the A n series of c=1-6/[m(m+1)], m≥3, minimal models is extended to compact Riemann surfaces of genus g>1. An integral representation of the partition functions, for any m and g is obtained as the difference of two gaussian correlation functions of a background charge, (background charge on sphere) x (1-g), and screening charges integrated over the surface. The coupling constant x (compacitification radius) 2 of the gaussian expressions are, as on the torus, m(m+1), and m/(m+1). The partition functions obtained are modular invariant, have the correct conformal anomaly and - restricting the propagation of states to a single handle - one can verify explicitly the decoupling of the null states. On the other hand, they are given in terms of coupled surface integrals, and it remains to show how they degenerate consistently to those on lower-genus surfaces. In this work, this is clear only at the lattice level, where no screening charges appear. (orig.)

Minimal models on Riemann surfaces: The partition functions

Energy Technology Data Exchange (ETDEWEB)

Foda, O. (Katholieke Univ. Nijmegen (Netherlands). Inst. voor Theoretische Fysica)

1990-06-04

The Coulomb gas representation of the A{sub n} series of c=1-6/(m(m+1)), m{ge}3, minimal models is extended to compact Riemann surfaces of genus g>1. An integral representation of the partition functions, for any m and g is obtained as the difference of two gaussian correlation functions of a background charge, (background charge on sphere) x (1-g), and screening charges integrated over the surface. The coupling constant x (compacitification radius){sup 2} of the gaussian expressions are, as on the torus, m(m+1), and m/(m+1). The partition functions obtained are modular invariant, have the correct conformal anomaly and - restricting the propagation of states to a single handle - one can verify explicitly the decoupling of the null states. On the other hand, they are given in terms of coupled surface integrals, and it remains to show how they degenerate consistently to those on lower-genus surfaces. In this work, this is clear only at the lattice level, where no screening charges appear. (orig.).

The motion of a classical spinning point particle in a Riemann-Cartan space-time

International Nuclear Information System (INIS)

Amorim, R.

1983-01-01

A consistent set of equations of motion for classical charged point particles with spin and magnetic dipole moment in a Riemann-Cartan space-time is generated from a generalized Lagrangean formalism. The equations avoid the spurius free helicoidal solutions and at the same time conserve the canonical condition of normalization of the 4-velocity. The 4-velocity and the mechanical moment are paralell in this theory, where the condition of orthogonality between the spin and the 4-velocity is treated as a non-holonomic one. (Author) [pt

Existence and Solution-representation of IVP for LFDE with Generalized Riemann-Liouville fractional derivatives and $n$ terms

OpenAIRE

Kim, Myong-Ha; Ri, Guk-Chol; O, Hyong-Chol

2013-01-01

This paper provides the existence and representation of solution to an initial value problem for the general multi-term linear fractional differential equation with generalized Riemann-Liouville fractional derivatives and constant coefficients by using operational calculus of Mikusinski's type. We prove that the initial value problem has the solution of if and only if some initial values should be zero.

On the solutions of the dKP equation: the nonlinear Riemann Hilbert problem, longtime behaviour, implicit solutions and wave breaking

International Nuclear Information System (INIS)

Manakov, S V; Santini, P M

2008-01-01

We have recently solved the inverse scattering problem for one-parameter families of vector fields, and used this result to construct the formal solution of the Cauchy problem for a class of integrable nonlinear partial differential equations in multidimensions, including the second heavenly equation of Plebanski and the dispersionless Kadomtsev-Petviashvili (dKP) equation. We showed, in particular, that the associated inverse problems can be expressed in terms of nonlinear Riemann-Hilbert problems on the real axis. In this paper, we make use of the nonlinear Riemann-Hilbert problem of dKP (i) to construct the longtime behaviour of the solutions of its Cauchy problem; (ii) to characterize a class of implicit solutions; (iii) to elucidate the spectral mechanism causing the gradient catastrophe of localized solutions of dKP, at finite time as well as in the longtime regime, and the corresponding universal behaviours near breaking

On the solutions of the dKP equation: the nonlinear Riemann Hilbert problem, longtime behaviour, implicit solutions and wave breaking

Energy Technology Data Exchange (ETDEWEB)

Manakov, S V [Landau Institute for Theoretical Physics, Moscow (Russian Federation); Santini, P M [Dipartimento di Fisica, Universita di Roma ' La Sapienza' , and Istituto Nazionale di Fisica Nucleare, Sezione di Roma 1, Piazz.le Aldo Moro 2, I-00185 Rome (Italy)

2008-02-08

We have recently solved the inverse scattering problem for one-parameter families of vector fields, and used this result to construct the formal solution of the Cauchy problem for a class of integrable nonlinear partial differential equations in multidimensions, including the second heavenly equation of Plebanski and the dispersionless Kadomtsev-Petviashvili (dKP) equation. We showed, in particular, that the associated inverse problems can be expressed in terms of nonlinear Riemann-Hilbert problems on the real axis. In this paper, we make use of the nonlinear Riemann-Hilbert problem of dKP (i) to construct the longtime behaviour of the solutions of its Cauchy problem; (ii) to characterize a class of implicit solutions; (iii) to elucidate the spectral mechanism causing the gradient catastrophe of localized solutions of dKP, at finite time as well as in the longtime regime, and the corresponding universal behaviours near breaking.

Riemann surfaces of complex classical trajectories and tunnelling splitting in one-dimensional systems

Science.gov (United States)

Harada, Hiromitsu; Mouchet, Amaury; Shudo, Akira

2017-10-01

The topology of complex classical paths is investigated to discuss quantum tunnelling splittings in one-dimensional systems. Here the Hamiltonian is assumed to be given as polynomial functions, so the fundamental group for the Riemann surface provides complete information on the topology of complex paths, which allows us to enumerate all the possible candidates contributing to the semiclassical sum formula for tunnelling splittings. This naturally leads to action relations among classically disjoined regions, revealing entirely non-local nature in the quantization condition. The importance of the proper treatment of Stokes phenomena is also discussed in Hamiltonians in the normal form.

A Riemann-Hilbert formulation for the finite temperature Hubbard model

Energy Technology Data Exchange (ETDEWEB)

Cavaglià, Andrea [Dipartimento di Fisica and INFN, Università di Torino,Via P. Giuria 1, 10125 Torino (Italy); Cornagliotto, Martina [Dipartimento di Fisica and INFN, Università di Torino,Via P. Giuria 1, 10125 Torino (Italy); DESY Hamburg, Theory Group,Notkestrasse 85, D-22607 Hamburg (Germany); Mattelliano, Massimo; Tateo, Roberto [Dipartimento di Fisica and INFN, Università di Torino,Via P. Giuria 1, 10125 Torino (Italy)

2015-06-03

Inspired by recent results in the context of AdS/CFT integrability, we reconsider the Thermodynamic Bethe Ansatz equations describing the 1D fermionic Hubbard model at finite temperature. We prove that the infinite set of TBA equations are equivalent to a simple nonlinear Riemann-Hilbert problem for a finite number of unknown functions. The latter can be transformed into a set of three coupled nonlinear integral equations defined over a finite support, which can be easily solved numerically. We discuss the emergence of an exact Bethe Ansatz and the link between the TBA approach and the results by Jüttner, Klümper and Suzuki based on the Quantum Transfer Matrix method. We also comment on the analytic continuation mechanism leading to excited states and on the mirror equations describing the finite-size Hubbard model with twisted boundary conditions.

Divergence-free MHD on unstructured meshes using high order finite volume schemes based on multidimensional Riemann solvers

Science.gov (United States)

Balsara, Dinshaw S.; Dumbser, Michael

2015-10-01

Several advances have been reported in the recent literature on divergence-free finite volume schemes for Magnetohydrodynamics (MHD). Almost all of these advances are restricted to structured meshes. To retain full geometric versatility, however, it is also very important to make analogous advances in divergence-free schemes for MHD on unstructured meshes. Such schemes utilize a staggered Yee-type mesh, where all hydrodynamic quantities (mass, momentum and energy density) are cell-centered, while the magnetic fields are face-centered and the electric fields, which are so useful for the time update of the magnetic field, are centered at the edges. Three important advances are brought together in this paper in order to make it possible to have high order accurate finite volume schemes for the MHD equations on unstructured meshes. First, it is shown that a divergence-free WENO reconstruction of the magnetic field can be developed for unstructured meshes in two and three space dimensions using a classical cell-centered WENO algorithm, without the need to do a WENO reconstruction for the magnetic field on the faces. This is achieved via a novel constrained L2-projection operator that is used in each time step as a postprocessor of the cell-centered WENO reconstruction so that the magnetic field becomes locally and globally divergence free. Second, it is shown that recently-developed genuinely multidimensional Riemann solvers (called MuSIC Riemann solvers) can be used on unstructured meshes to obtain a multidimensionally upwinded representation of the electric field at each edge. Third, the above two innovations work well together with a high order accurate one-step ADER time stepping strategy, which requires the divergence-free nonlinear WENO reconstruction procedure to be carried out only once per time step. The resulting divergence-free ADER-WENO schemes with MuSIC Riemann solvers give us an efficient and easily-implemented strategy for divergence-free MHD on

Implicit approximate Riemann solver for two fluid two phase flow models

International Nuclear Information System (INIS)

Raymond, P.; Toumi, I.; Kumbaro, A.

1993-01-01

This paper is devoted to the description of new numerical methods developed for the numerical treatment of two phase flow models with two velocity fields which are now widely used in nuclear engineering for design or safety calculations. These methods are finite volumes numerical methods and are based on the use of Approximate Riemann Solver's concepts in order to define convective flux versus mean cell quantities. The first part of the communication will describe the numerical method for a three dimensional drift flux model and the extensions which were performed to make the numerical scheme implicit and to have fast running calculations of steady states. Such a scheme is now implemented in the FLICA-4 computer code devoted to 3-D steady state and transient core computations. We will present results obtained for a steady state flow with rod bow effect evaluation and for a Steam Line Break calculation were the 3-D core thermal computation was coupled with a 3-D kinetic calculation and a thermal-hydraulic transient calculation for the four loops of a Pressurized Water Reactor. The second part of the paper will detail the development of an equivalent numerical method based on an approximate Riemann Solver for a two fluid model with two momentum balance equations for the liquid and the gas phases. The main difficulty for these models is due to the existence of differential modelling terms such as added mass effects or interfacial pressure terms which make hyperbolic the model. These terms does not permit to write the balance equations system in a conservative form, and the classical theory for discontinuity propagation for non-linear systems cannot be applied. Meanwhile, the use of non-conservative products theory allows the study of discontinuity propagation for a non conservative model and this will permit the construction of a numerical scheme for two fluid two phase flow model. These different points will be detailed in that section which will be illustrated by

Scattering analysis of asymmetric metamaterial resonators by the Riemann-Hilbert approach

DEFF Research Database (Denmark)

Kaminski, Piotr Marek; Ziolkowski, Richard W.; Arslanagic, Samel

2016-01-01

This work presents an analytical treatment of an asymmetric metamaterial-based resonator excited by an electric line source, and explores its beam shaping capabilities. The resonator consists of two concentric cylindrical material layers covered with an infinitely thin conducting shell with an ap......This work presents an analytical treatment of an asymmetric metamaterial-based resonator excited by an electric line source, and explores its beam shaping capabilities. The resonator consists of two concentric cylindrical material layers covered with an infinitely thin conducting shell...... with an aperture. Exact analytical solution of the problem is derived; it is based on the n-series approach which is casted into the equivalent Riemann-Hilbert problem. The examined configuration leads to large enhancements of the radiated field and to steerable Huygens-like directivity patterns. Particularly...

Riemann surfaces and algebraic curves a first course in Hurwitz theory

CERN Document Server

Cavalieri, Renzo

2016-01-01

Hurwitz theory, the study of analytic functions among Riemann surfaces, is a classical field and active research area in algebraic geometry. The subject's interplay between algebra, geometry, topology and analysis is a beautiful example of the interconnectedness of mathematics. This book introduces students to this increasingly important field, covering key topics such as manifolds, monodromy representations and the Hurwitz potential. Designed for undergraduate study, this classroom-tested text includes over 100 exercises to provide motivation for the reader. Also included are short essays by guest writers on how they use Hurwitz theory in their work, which ranges from string theory to non-Archimedean geometry. Whether used in a course or as a self-contained reference for graduate students, this book will provide an exciting glimpse at mathematics beyond the standard university classes.

Numerical implication of Riemann problem theory for fluid dynamics

International Nuclear Information System (INIS)

Menikoff, R.

1988-01-01

The Riemann problem plays an important role in understanding the wave structure of fluid flow. It is also crucial step in some numerical algorithms for accurately and efficiently computing fluid flow; Godunov method, random choice method, and from tracking method. The standard wave structure consists of shock and rarefaction waves. Due to physical effects such as phase transitions, which often are indistinguishable from numerical errors in an equation of state, anomalkous waves may occur, ''rarefaction shocks'', split waves, and composites. The anomalous waves may appear in numerical calculations as waves smeared out by either too much artificial viscosity or insufficient resolution. In addition, the equation of state may lead to instabilities of fluid flow. Since these anomalous effects due to the equation of state occur for the continuum equations, they can be expected to occur for all computational algorithms. The equation of state may be characterized by three dimensionless variables: the adiabatic exponent γ, the Grueneisen coefficient Γ, and the fundamental derivative G. The fluid flow anomalies occur when inequalities relating these variables are violated. 18 refs

Deduction of Einstein equation from homogeneity of Riemann spacetime

Science.gov (United States)

Ni, Jun

2012-03-01

The symmetry of spacetime translation leads to the energy-momentum conservation. However, the Lagrange depends on spacetime coordinates, which makes the symmetry of spacetime translation different with other symmetry invariant explicitly under symmetry transformation. We need an equation to guarantee the symmetry of spacetime translation. In this talk, I will show that the Einstein equation can be deduced purely from the general covariant principle and the homogeneity of spacetime in the frame of quantum field theory. The Einstein equation is shown to be the equation to guarantee the symmetry of spacetime translation. Gravity is an apparent force due to the curvature of spacetime resulted from the conservation of energy-momentum. In the action of quantum field, only electroweak-strong interactions appear with curved spacetime metric determined by the Einstein equation.. The general covariant principle and the homogeneity of spacetime are merged into one basic principle: Any Riemann spacetime metric guaranteeing the energy-momentum conservation are equivalent, which can be called as the conserved general covariant principle. [4pt] [1] Jun Ni, Chin. Phys. Lett. 28, 110401 (2011).

Decontamination sheet

International Nuclear Information System (INIS)

Hirose, Emiko; Kanesaki, Ken.

1995-01-01

The decontamination sheet of the present invention is formed by applying an adhesive on one surface of a polymer sheet and releasably appending a plurality of curing sheets. In addition, perforated lines are formed on the sheet, and a decontaminating agent is incorporated in the adhesive. This can reduce the number of curing operation steps when a plurality steps of operations for radiation decontamination equipments are performed, and further, the amount of wastes of the cured sheets, and operator's exposure are reduced, as well as an efficiency of the curing operation can be improved, and propagation of contamination can be prevented. (T.M.)

Differential Galois theory through Riemann-Hilbert correspondence an elementary introduction

CERN Document Server

Sauloy, Jacques

2017-01-01

Differential Galois theory is an important, fast developing area which appears more and more in graduate courses since it mixes fundamental objects from many different areas of mathematics in a stimulating context. For a long time, the dominant approach, usually called Picard-Vessiot Theory, was purely algebraic. This approach has been extensively developed and is well covered in the literature. An alternative approach consists in tagging algebraic objects with transcendental information which enriches the understanding and brings not only new points of view but also new solutions. It is very powerful and can be applied in situations where the Picard-Vessiot approach is not easily extended. This book offers a hands-on transcendental approach to differential Galois theory, based on the Riemann-Hilbert correspondence. Along the way, it provides a smooth, down-to-earth introduction to algebraic geometry, category theory and tannakian duality. Since the book studies only complex analytic linear differential equat...

A boundary-fitted staggered difference method for incompressible flow using Riemann geometry

International Nuclear Information System (INIS)

Koshizuka, Seiichi; Kondo, Shunsuke; Oka, Yoshiaki.

1990-01-01

A boundary-fitted staggered difference method (BFSDM) is investigated for incompressible flow in nuclear plants. BFSDM employs control cells for scalars, staggered location of velocity components, and integrated formulation of div=0. Governing equations are written as coordinate-free forms using Riemann geometry. Flow velocity is represented with contravariant physical components in the present method. Connection terms emerge as source terms in the coordinate-free governing equations. These terms are studied from the viewpoints of physical meaning, numerical stability, and conservative property. Some flows on a round or slant boundary are solved using boundary-fitted curvilinear (BFC) grids and rectangular grids to compare the present method and the rectangular-type (R-type) staggered difference method (SDM). Supercomputing of the present method, including vector processing, is also discussed compared with the R-type method. (author)

A Riemann-Hilbert approach to the inverse problem for the Stark operator on the line

Science.gov (United States)

Its, A.; Sukhanov, V.

2016-05-01

The paper is concerned with the inverse scattering problem for the Stark operator on the line with a potential from the Schwartz class. In our study of the inverse problem, we use the Riemann-Hilbert formalism. This allows us to overcome the principal technical difficulties which arise in the more traditional approaches based on the Gel’fand-Levitan-Marchenko equations, and indeed solve the problem. We also produce a complete description of the relevant scattering data (which have not been obtained in the previous works on the Stark operator) and establish the bijection between the Schwartz class potentials and the scattering data.

Eigenfunctions and Eigenvalues for a Scalar Riemann-Hilbert Problem Associated to Inverse Scattering

Science.gov (United States)

Pelinovsky, Dmitry E.; Sulem, Catherine

A complete set of eigenfunctions is introduced within the Riemann-Hilbert formalism for spectral problems associated to some solvable nonlinear evolution equations. In particular, we consider the time-independent and time-dependent Schrödinger problems which are related to the KdV and KPI equations possessing solitons and lumps, respectively. Non-standard scalar products, orthogonality and completeness relations are derived for these problems. The complete set of eigenfunctions is used for perturbation theory and bifurcation analysis of eigenvalues supported by the potentials under perturbations. We classify two different types of bifurcations of new eigenvalues and analyze their characteristic features. One type corresponds to thresholdless generation of solitons in the KdV equation, while the other predicts a threshold for generation of lumps in the KPI equation.

Towards quantized number theory: spectral operators and an asymmetric criterion for the Riemann hypothesis.

Science.gov (United States)

Lapidus, Michel L

2015-08-06

This research expository article not only contains a survey of earlier work but also contains a main new result, which we first describe. Given c≥0, the spectral operator [Formula: see text] can be thought of intuitively as the operator which sends the geometry onto the spectrum of a fractal string of dimension not exceeding c. Rigorously, it turns out to coincide with a suitable quantization of the Riemann zeta function ζ=ζ(s): a=ζ(∂), where ∂=∂(c) is the infinitesimal shift of the real line acting on the weighted Hilbert space [Formula: see text]. In this paper, we establish a new asymmetric criterion for the Riemann hypothesis (RH), expressed in terms of the invertibility of the spectral operator for all values of the dimension parameter [Formula: see text] (i.e. for all c in the left half of the critical interval (0,1)). This corresponds (conditionally) to a mathematical (and perhaps also, physical) 'phase transition' occurring in the midfractal case when [Formula: see text]. Both the universality and the non-universality of ζ=ζ(s) in the right (resp., left) critical strip [Formula: see text] (resp., [Formula: see text]) play a key role in this context. These new results are presented here. We also briefly discuss earlier joint work on the complex dimensions of fractal strings, and we survey earlier related work of the author with Maier and with Herichi, respectively, in which were established symmetric criteria for the RH, expressed, respectively, in terms of a family of natural inverse spectral problems for fractal strings of Minkowski dimension D∈(0,1), with [Formula: see text], and of the quasi-invertibility of the family of spectral operators [Formula: see text] (with [Formula: see text]). © 2015 The Author(s) Published by the Royal Society. All rights reserved.

A geometric construction of the Riemann scalar curvature in Regge calculus

International Nuclear Information System (INIS)

McDonald, Jonathan R; Miller, Warner A

2008-01-01

The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas

A geometric construction of the Riemann scalar curvature in Regge calculus

Science.gov (United States)

McDonald, Jonathan R.; Miller, Warner A.

2008-10-01

The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas.

Efficient analytical implementation of the DOT Riemann solver for the de Saint Venant-Exner morphodynamic model

Science.gov (United States)

Carraro, F.; Valiani, A.; Caleffi, V.

2018-03-01

Within the framework of the de Saint Venant equations coupled with the Exner equation for morphodynamic evolution, this work presents a new efficient implementation of the Dumbser-Osher-Toro (DOT) scheme for non-conservative problems. The DOT path-conservative scheme is a robust upwind method based on a complete Riemann solver, but it has the drawback of requiring expensive numerical computations. Indeed, to compute the non-linear time evolution in each time step, the DOT scheme requires numerical computation of the flux matrix eigenstructure (the totality of eigenvalues and eigenvectors) several times at each cell edge. In this work, an analytical and compact formulation of the eigenstructure for the de Saint Venant-Exner (dSVE) model is introduced and tested in terms of numerical efficiency and stability. Using the original DOT and PRICE-C (a very efficient FORCE-type method) as reference methods, we present a convergence analysis (error against CPU time) to study the performance of the DOT method with our new analytical implementation of eigenstructure calculations (A-DOT). In particular, the numerical performance of the three methods is tested in three test cases: a movable bed Riemann problem with analytical solution; a problem with smooth analytical solution; a test in which the water flow is characterised by subcritical and supercritical regions. For a given target error, the A-DOT method is always the most efficient choice. Finally, two experimental data sets and different transport formulae are considered to test the A-DOT model in more practical case studies.

Dense sheet Z-pinches

International Nuclear Information System (INIS)

Tetsu, Miyamoto

1999-01-01

The steady state and quasi-steady processes of infinite- and finite-width sheet z-pinches are studied. The relations corresponding to the Bennett relation and Pease-Braginskii current of cylindrical fiber z-pinches depend on a geometrical factor in the sheet z-pinches. The finite-width sheet z-pinch is approximated by a segment of infinite-width sheet z-pinch, if it is wide enough, and corresponds to a number of (width/thickness) times fiber z-pinch plasmas of the diameter that equals the sheet thickness. If the sheet current equals this number times the fiber current, the plasma created in the sheet z-pinches is as dense as in the fiber z-pinches. The total energy of plasma and magnetic field per unit mass is approximately equal in both pinches. Quasi-static transient processes are different in several aspects from the fiber z-pinch. No radiation collapse occurs in the sheet z-pinch. The stability is improved in the sheet z-pinches. The fusion criterions and the experimental arrangements to produce the sheet z-pinches are also discussed. (author)

Zeros da função zeta de Riemann e o teorema dos números primos

OpenAIRE

Oliveira, Willian Diego [UNESP

2013-01-01

We studied various properties of the Riemann’s zeta function. Three proofs of the Prime Number Theorem were provides. Classical results on zero-free region of the zeta function, as well as their relation to the error term in the Prime Number Theorem, were studied in details Estudamos várias propriedades da função zeta de Riemann. Três provas do Teorema dos Números Primos foram fornecidas. Resultados clássicos sobre regiões livres de zeros da função zeta, bem como sua relação com o termo do...

Contribution of non integer integro-differential operators (NIDO) to the geometrical understanding of Riemann's conjecture-(II)

International Nuclear Information System (INIS)

Le Mehaute, Alain; El Kaabouchi, Abdelaziz; Nivanen, Laurent

2008-01-01

Advances in fractional analysis suggest a new way for the physics understanding of Riemann's conjecture. It asserts that, if s is a complex number, the non trivial zeros of zeta function 1/(ζ(s)) =Σ n=1 ∞ (μ(n))/(n s ) in the gap [0, 1], is characterized by s=1/2 (1+2iθ). This conjecture can be understood as a consequence of 1/2-order fractional differential characteristics of automorph dynamics upon opened punctuated torus with an angle at infinity equal to π/4. This physical interpretation suggests new opportunities for revisiting the cryptographic methodologies

On a Nonlocal Ostrovsky-Whitham Type Dynamical System, Its Riemann Type Inhomogeneous Regularizations and Their Integrability

Directory of Open Access Journals (Sweden)

Jolanta Golenia

2010-01-01

Full Text Available Short-wave perturbations in a relaxing medium, governed by a special reduction of the Ostrovsky evolution equation, and later derived by Whitham, are studied using the gradient-holonomic integrability algorithm. The bi-Hamiltonicity and complete integrability of the corresponding dynamical system is stated and an infinite hierarchy of commuting to each other conservation laws of dispersive type are found. The well defined regularization of the model is constructed and its Lax type integrability is discussed. A generalized hydrodynamical Riemann type system is considered, infinite hierarchies of conservation laws, related compatible Poisson structures and a Lax type representation for the special case N=3 are constructed.

Cylinder renormalization for Siegel disks and a constructive Measurable Riemann Mapping Theorem

CERN Document Server

Gaydashev, D G

2006-01-01

The boundary of the Siegel disk of a quadratic polynomial with an irrationally indifferent fixed point with the golden mean rotation number has been observed to be self-similar. The geometry of this self-similarity is universal for a large class of holomorphic maps. A renormalization explanation of this universality has been proposed in the literature. However, one of the ingredients of this explanation, the hyperbolicity of renormalization, has not been proved yet. The present work considers a cylinder renormalization - a novel type of renormalization for holomorphic maps with a Siegel disk which is better suited for a hyperbolicity proof. A key element of a cylinder renormalization of a holomorphic map is a conformal isomorphism of a dynamical quotient of a subset of $\\field{C}$ to a bi-infinite cylinder $\\field{C} / \\field{Z}$. A construction of this conformal isomorphism is an implicit procedure which can be performed using the Measurable Riemann Mapping Theorem. We present a constructive proof of the Mea...

Integral approximants for functions of higher monodromic dimension

Energy Technology Data Exchange (ETDEWEB)

Baker, G.A. Jr.

1987-01-01

In addition to the description of multiform, locally analytic functions as covering a many sheeted version of the complex plane, Riemann also introduced the notion of considering them as describing a space whose ''monodromic'' dimension is the number of linearly independent coverings by the monogenic analytic function at each point of the complex plane. I suggest that this latter concept is natural for integral approximants (sub-class of Hermite-Pade approximants) and discuss results for both ''horizontal'' and ''diagonal'' sequences of approximants. Some theorems are now available in both cases and make clear the natural domain of convergence of the horizontal sequences is a disk centered on the origin and that of the diagonal sequences is a suitably cut complex-plane together with its identically cut pendant Riemann sheets. Some numerical examples have also been computed.

Relation between current sheets and vortex sheets in stationary incompressible MHD

Directory of Open Access Journals (Sweden)

D. H. Nickeler

2012-03-01

Full Text Available Magnetohydrodynamic configurations with strong localized current concentrations and vortices play an important role in the dissipation of energy in space and astrophysical plasma. Within this work we investigate the relation between current sheets and vortex sheets in incompressible, stationary equilibria. For this approach it is helpful that the similar mathematical structure of magnetohydrostatics and stationary incompressible hydrodynamics allows us to transform static equilibria into stationary ones. The main control function for such a transformation is the profile of the Alfvén-Mach number MA, which is always constant along magnetic field lines, but can change from one field line to another. In the case of a global constant MA, vortices and electric current concentrations are parallel. More interesting is the nonlinear case, where MA varies perpendicular to the field lines. This is a typical situation at boundary layers like the magnetopause, heliopause, the solar wind flowing around helmet streamers and at the boundary of solar coronal holes. The corresponding current and vortex sheets show in some cases also an alignment, but not in every case. For special density distributions in 2-D, it is possible to have current but no vortex sheets. In 2-D, vortex sheets of field aligned-flows can also exist without strong current sheets, taking the limit of small Alfvén Mach numbers into account. The current sheet can vanish if the Alfvén Mach number is (almost constant and the density gradient is large across some boundary layer. It should be emphasized that the used theory is not only valid for small Alfvén Mach numbers MA MA ≲ 1. Connection to other theoretical approaches and observations and physical effects in space plasmas are presented. Differences in the various aspects of theoretical investigations of current sheets and vortex sheets are given.

An ice sheet model validation framework for the Greenland ice sheet

Science.gov (United States)

Price, Stephen F.; Hoffman, Matthew J.; Bonin, Jennifer A.; Howat, Ian M.; Neumann, Thomas; Saba, Jack; Tezaur, Irina; Guerber, Jeffrey; Chambers, Don P.; Evans, Katherine J.; Kennedy, Joseph H.; Lenaerts, Jan; Lipscomb, William H.; Perego, Mauro; Salinger, Andrew G.; Tuminaro, Raymond S.; van den Broeke, Michiel R.; Nowicki, Sophie M. J.

2017-01-01

We propose a new ice sheet model validation framework - the Cryospheric Model Comparison Tool (CmCt) - that takes advantage of ice sheet altimetry and gravimetry observations collected over the past several decades and is applied here to modeling of the Greenland ice sheet. We use realistic simulations performed with the Community Ice Sheet Model (CISM) along with two idealized, non-dynamic models to demonstrate the framework and its use. Dynamic simulations with CISM are forced from 1991 to 2013, using combinations of reanalysis-based surface mass balance and observations of outlet glacier flux change. We propose and demonstrate qualitative and quantitative metrics for use in evaluating the different model simulations against the observations. We find that the altimetry observations used here are largely ambiguous in terms of their ability to distinguish one simulation from another. Based on basin-scale and whole-ice-sheet-scale metrics, we find that simulations using both idealized conceptual models and dynamic, numerical models provide an equally reasonable representation of the ice sheet surface (mean elevation differences of framework demonstrates that our proposed metrics can distinguish relatively better from relatively worse simulations and that dynamic ice sheet models, when appropriately initialized and forced with the right boundary conditions, demonstrate a predictive skill with respect to observed dynamic changes that have occurred on Greenland over the past few decades. An extensible design will allow for continued use of the CmCt as future altimetry, gravimetry, and other remotely sensed data become available for use in ice sheet model validation.

Chlamydia - CDC Fact Sheet

Science.gov (United States)

... Archive STDs Home Page Bacterial Vaginosis (BV) Chlamydia Gonorrhea Genital Herpes Hepatitis HIV/AIDS & STDs Human Papillomavirus ( ... sheet Pelvic Inflammatory Disease (PID) – CDC fact sheet Gonorrhea – CDC fact sheet STDs Home Page Bacterial Vaginosis ( ...

Approximate Riemann solvers and flux vector splitting schemes for two-phase flow; Solveurs de Riemann approches et schemas de decentrement de flux pour les ecoulements diphasiques

Energy Technology Data Exchange (ETDEWEB)

Toumi, I.; Kumbaro, A.; Paillere, H

1999-07-01

These course notes, presented at the 30. Von Karman Institute Lecture Series in Computational Fluid Dynamics, give a detailed and through review of upwind differencing methods for two-phase flow models. After recalling some fundamental aspects of two-phase flow modelling, from mixture model to two-fluid models, the mathematical properties of the general 6-equation model are analysed by examining the Eigen-structure of the system, and deriving conditions under which the model can be made hyperbolic. The following chapters are devoted to extensions of state-of-the-art upwind differencing schemes such as Roe's Approximate Riemann Solver or the Characteristic Flux Splitting method to two-phase flow. Non-trivial steps in the construction of such solvers include the linearization, the treatment of non-conservative terms and the construction of a Roe-type matrix on which the numerical dissipation of the schemes is based. Extension of the 1-D models to multi-dimensions in an unstructured finite volume formulation is also described; Finally, numerical results for a variety of test-cases are shown to illustrate the accuracy and robustness of the methods. (authors)

Extending the Riemann-Solver-Free High-Order Space-Time Discontinuous Galerkin Cell Vertex Scheme (DG-CVS) to Solve Compressible Magnetohydrodynamics Equations

Science.gov (United States)

2016-06-08

Ideal Magnetohydrodynamics,” J. Com- put. Phys., Vol. 153, No. 2, 1999, pp. 334–352. [14] Tang, H.-Z. and Xu, K., “A high-order gas -kinetic method for...notwithstanding any other provision of law , no person shall be subject to any penalty for failing to comply with a collection of information if it does...Riemann-solver-free spacetime discontinuous Galerkin method for general conservation laws to solve compressible magnetohydrodynamics (MHD) equations. The

Laminin-521 Promotes Rat Bone Marrow Mesenchymal Stem Cell Sheet Formation on Light-Induced Cell Sheet Technology

Directory of Open Access Journals (Sweden)

Zhiwei Jiang

2017-01-01

Full Text Available Rat bone marrow mesenchymal stem cell sheets (rBMSC sheets are attractive for cell-based tissue engineering. However, methods of culturing rBMSC sheets are critically limited. In order to obtain intact rBMSC sheets, a light-induced cell sheet method was used in this study. TiO2 nanodot films were coated with (TL or without (TN laminin-521. We investigated the effects of laminin-521 on rBMSCs during cell sheet culturing. The fabricated rBMSC sheets were subsequently assessed to study cell sheet viability, reattachment ability, cell sheet thickness, collagen type I deposition, and multilineage potential. The results showed that laminin-521 could promote the formation of rBMSC sheets with good viability under hyperconfluent conditions. Cell sheet thickness increased from an initial 26.7 ± 1.5 μm (day 5 up to 47.7 ± 3.0 μm (day 10. Moreover, rBMSC sheets maintained their potential of osteogenic, adipogenic, and chondrogenic differentiation. This study provides a new strategy to obtain rBMSC sheets using light-induced cell sheet technology.

The Equation Δ u + ∇φ· ∇u = 8πc(1-heu) on a Riemann Surface

International Nuclear Information System (INIS)

Wang Meng

2009-12-01

Let M be a compact Riemann surface, h(x) a positive smooth function on M, and φ(x) a smooth function on M which satisfies that ∫ M e φ dV g = 1. In this paper, we consider the functional J(u) = 2 1 ∫ M |∇u| 2 e φ dV g +8πc ∫ M ue φ dV g -8πclog ∫ M he u+φ dV g . We give a sufficient condition under which J achieves its minimum for c ≤ inf xelement ofM Φ(x). (author)

A family of high-order gas-kinetic schemes and its comparison with Riemann solver based high-order methods

Science.gov (United States)

Ji, Xing; Zhao, Fengxiang; Shyy, Wei; Xu, Kun

2018-03-01

Most high order computational fluid dynamics (CFD) methods for compressible flows are based on Riemann solver for the flux evaluation and Runge-Kutta (RK) time stepping technique for temporal accuracy. The advantage of this kind of space-time separation approach is the easy implementation and stability enhancement by introducing more middle stages. However, the nth-order time accuracy needs no less than n stages for the RK method, which can be very time and memory consuming due to the reconstruction at each stage for a high order method. On the other hand, the multi-stage multi-derivative (MSMD) method can be used to achieve the same order of time accuracy using less middle stages with the use of the time derivatives of the flux function. For traditional Riemann solver based CFD methods, the lack of time derivatives in the flux function prevents its direct implementation of the MSMD method. However, the gas kinetic scheme (GKS) provides such a time accurate evolution model. By combining the second-order or third-order GKS flux functions with the MSMD technique, a family of high order gas kinetic methods can be constructed. As an extension of the previous 2-stage 4th-order GKS, the 5th-order schemes with 2 and 3 stages will be developed in this paper. Based on the same 5th-order WENO reconstruction, the performance of gas kinetic schemes from the 2nd- to the 5th-order time accurate methods will be evaluated. The results show that the 5th-order scheme can achieve the theoretical order of accuracy for the Euler equations, and present accurate Navier-Stokes solutions as well due to the coupling of inviscid and viscous terms in the GKS formulation. In comparison with Riemann solver based 5th-order RK method, the high order GKS has advantages in terms of efficiency, accuracy, and robustness, for all test cases. The 4th- and 5th-order GKS have the same robustness as the 2nd-order scheme for the capturing of discontinuous solutions. The current high order MSMD GKS is a

Superfund fact sheet: The remedial program. Fact sheet

International Nuclear Information System (INIS)

1992-09-01

The fact sheet describes what various actions the EPA can take to clean up hazardous wastes sites. Explanations of how the criteria for environmental and public health risk assessment are determined and the role of state and local governments in site remediation are given. The fact sheet is one in a series providing reference information about Superfund issues and is intended for readers with no formal scientific training

Radiation protecting sheet

International Nuclear Information System (INIS)

Makiguchi, Hiroshi.

1989-01-01

As protection sheets used in radioactivity administration areas, a thermoplastic polyurethane composition sheet with a thickness of less 0.5 mm, solid content (ash) of less than 5% and a shore D hardness of less than 60 is used. A composite sheet with thickness of less than 0.5 mm laminated or coated with such a thermoplastic polyurethane composition as a surface layer and the thermoplastic polyurethane composition sheet applied with secondary fabrication are used. This can satisfy all of the required properties, such as draping property, abrasion resistance, high breaking strength, necking resistance, endurance strength, as well as chemical resistance and easy burnability in burning furnace. Further, by forming uneveness on the surface by means of embossing, etc. safety problems such as slippage during operation and walking can be overcome. (T.M.)

A new numerical approach for uniquely solvable exterior Riemann-Hilbert problem on region with corners

Science.gov (United States)

Zamzamir, Zamzana; Murid, Ali H. M.; Ismail, Munira

2014-06-01

Numerical solution for uniquely solvable exterior Riemann-Hilbert problem on region with corners at offcorner points has been explored by discretizing the related integral equation using Picard iteration method without any modifications to the left-hand side (LHS) and right-hand side (RHS) of the integral equation. Numerical errors for all iterations are converge to the required solution. However, for certain problems, it gives lower accuracy. Hence, this paper presents a new numerical approach for the problem by treating the generalized Neumann kernel at LHS and the function at RHS of the integral equation. Due to the existence of the corner points, Gaussian quadrature is employed which avoids the corner points during numerical integration. Numerical example on a test region is presented to demonstrate the effectiveness of this formulation.

Automobile sheet metal part production with incremental sheet forming

Directory of Open Access Journals (Sweden)

İsmail DURGUN

2016-02-01

Full Text Available Nowadays, effect of global warming is increasing drastically so it leads to increased interest on energy efficiency and sustainable production methods. As a result of adverse conditions, national and international project platforms, OEMs (Original Equipment Manufacturers, SMEs (Small and Mid-size Manufacturers perform many studies or improve existing methodologies in scope of advanced manufacturing techniques. In this study, advanced manufacturing and sustainable production method "Incremental Sheet Metal Forming (ISF" was used for sheet metal forming process. A vehicle fender was manufactured with or without die by using different toolpath strategies and die sets. At the end of the study, Results have been investigated under the influence of method and parameters used.Keywords: Template incremental sheet metal, Metal forming

Multichannel approach to studying scalar resonances

International Nuclear Information System (INIS)

Krupa, D.; Surovtsev, Yu.S.

1995-11-01

The multichannel approach to the investigation of resonances is given in order to determine their quantum chromodynamical nature. The formula for the analytic continuation of the N-channel S-matrix to the unphysical sheets of the Riemann surface is given, which is a solution of the N-channel problem in that it enables a prediction of the coupled-process amplitudes on the uniformization plane of the S-matrix. The resonance representations by pairs of complex-conjugate clusters of poles and zeros on the Riemann surface are discussed. The concept of standard clusters as model-independent characteristics of the resonance is developed. 32 refs, 5 figs, 4 tabs

Geometry of thin liquid sheet flows

Science.gov (United States)

Chubb, Donald L.; Calfo, Frederick D.; Mcconley, Marc W.; Mcmaster, Matthew S.; Afjeh, Abdollah A.

1994-01-01

Incompresible, thin sheet flows have been of research interest for many years. Those studies were mainly concerned with the stability of the flow in a surrounding gas. Squire was the first to carry out a linear, invicid stability analysis of sheet flow in air and compare the results with experiment. Dombrowski and Fraser did an experimental study of the disintegration of sheet flows using several viscous liquids. They also detected the formulation of holes in their sheet flows. Hagerty and Shea carried out an inviscid stability analysis and calculated growth rates with experimental values. They compared their calculated growth rates with experimental values. Taylor studied extensively the stability of thin liquid sheets both theoretically and experimentally. He showed that thin sheets in a vacuum are stable. Brown experimentally investigated thin liquid sheet flows as a method of application of thin films. Clark and Dumbrowski carried out second-order stability analysis for invicid sheet flows. Lin introduced viscosity into the linear stability analysis of thin sheet flows in a vacuum. Mansour and Chigier conducted an experimental study of the breakup of a sheet flow surrounded by high-speed air. Lin et al. did a linear stability analysis that included viscosity and a surrounding gas. Rangel and Sirignano carried out both a linear and nonlinear invisid stability analysis that applies for any density ratio between the sheet liquid and the surrounding gas. Now there is renewed interest in sheet flows because of their possible application as low mass radiating surfaces. The objective of this study is to investigate the fluid dynamics of sheet flows that are of interest for a space radiator system. Analytical expressions that govern the sheet geometry are compared with experimental results. Since a space radiator will operate in a vacuum, the analysis does not include any drag force on the sheet flow.

Orbifold Riemann surfaces: Teichmueller spaces and algebras of geodesic functions

Energy Technology Data Exchange (ETDEWEB)

Mazzocco, Marta [Loughborough University, Loughborough (United Kingdom); Chekhov, Leonid O [Institute for Theoretical and Experimental Physics (Russian Federation State Scientific Center), Moscow (Russian Federation)

2009-12-31

A fat graph description is given for Teichmueller spaces of Riemann surfaces with holes and with Z{sub 2}- and Z{sub 3}-orbifold points (conical singularities) in the Poincare uniformization. The corresponding mapping class group transformations are presented, geodesic functions are constructed, and the Poisson structure is introduced. The resulting Poisson algebras are then quantized. In the particular cases of surfaces with n Z{sub 2}-orbifold points and with one and two holes, the respective algebras A{sub n} and D{sub n} of geodesic functions (classical and quantum) are obtained. The infinite-dimensional Poisson algebra D{sub n}, which is the semiclassical limit of the twisted q-Yangian algebra Y'{sub q}(o{sub n}) for the orthogonal Lie algebra o{sub n}, is associated with the algebra of geodesic functions on an annulus with n Z{sub 2}-orbifold points, and the braid group action on this algebra is found. From this result the braid group actions are constructed on the finite-dimensional reductions of this algebra: the p-level reduction and the algebra D{sub n}. The central elements for these reductions are found. Also, the algebra D{sub n} is interpreted as the Poisson algebra of monodromy data of a Frobenius manifold in the vicinity of a non-semisimple point. Bibliography: 36 titles.

Best Management Practice, Fact Sheet 2. Sheet Flow to Open Space

OpenAIRE

Sample, David; Doumar, Lia

2013-01-01

This publication explains what sheet flow to open space is, where and how it is used, their limitations, routine and nonroutine maintenance, expected costs, and a glossary of terms. This fact sheet is one of a 15-part series on urban stormwater management practices.

Carbon sheet pumping

International Nuclear Information System (INIS)

Ohyabu, N.; Sagara, A.; Kawamura, T.; Motojima, O.; Ono, T.

1993-07-01

A new hydrogen pumping scheme has been proposed which controls recycling of the particles for significant improvement of the energy confinement in toroidal magnetic fusion devices. In this scheme, a part of the vacuum vessel surface near the divertor is covered with carbon sheets of a large surface area. Before discharge initiation, the sheets are baked up to 700 ∼ 1000degC to remove the previously trapped hydrogen atoms. After being cooled down to below ∼ 200degC, the unsaturated carbon sheets trap high energy charge exchange hydrogen atoms effectively during a discharge and overall pumping efficiency can be as high as ∼ 50 %. (author)

Things Fall Apart: Topology Change From Winding Tachyons

Energy Technology Data Exchange (ETDEWEB)

Adams, A.

2005-02-04

We argue that closed string tachyons drive two spacetime topology changing transitions--loss of genus in a Riemann surface and separation of a Riemann surface into two components. The tachyons of interest are localized versions of Scherk-Schwarz winding string tachyons arising on Riemann surfaces in regions of moduli space where string-scale tubes develop. Spacetime and world-sheet renormalization group analyses provide strong evidence that the decay of these tachyons removes a portion of the spacetime, splitting the tube into two pieces. We address the fate of the gauge fields and charges lost in the process, generalize it to situations with weak flux backgrounds, and use this process to study the type 0 tachyon, providing further evidence that its decay drives the theory sub-critical. Finally, we discuss the time-dependent dynamics of this topology-changing transition and find that it can occur more efficiently than analogous transitions on extended supersymmetric moduli spaces, which are limited by moduli trapping.

FDTD modeling of thin impedance sheets

Science.gov (United States)

Luebbers, Raymond J.; Kunz, Karl S.

1991-01-01

Thin sheets of resistive or dielectric material are commonly encountered in radar cross section calculations. Analysis of such sheets is simplified by using sheet impedances. In this paper it is shown that sheet impedances can be modeled easily and accurately using Finite Difference Time Domain (FDTD) methods.

Approximate Riemann solvers and flux vector splitting schemes for two-phase flow

International Nuclear Information System (INIS)

Toumi, I.; Kumbaro, A.; Paillere, H.

1999-01-01

These course notes, presented at the 30. Von Karman Institute Lecture Series in Computational Fluid Dynamics, give a detailed and through review of upwind differencing methods for two-phase flow models. After recalling some fundamental aspects of two-phase flow modelling, from mixture model to two-fluid models, the mathematical properties of the general 6-equation model are analysed by examining the Eigen-structure of the system, and deriving conditions under which the model can be made hyperbolic. The following chapters are devoted to extensions of state-of-the-art upwind differencing schemes such as Roe's Approximate Riemann Solver or the Characteristic Flux Splitting method to two-phase flow. Non-trivial steps in the construction of such solvers include the linearization, the treatment of non-conservative terms and the construction of a Roe-type matrix on which the numerical dissipation of the schemes is based. Extension of the 1-D models to multi-dimensions in an unstructured finite volume formulation is also described; Finally, numerical results for a variety of test-cases are shown to illustrate the accuracy and robustness of the methods. (authors)

Multi-Regge kinematics and the moduli space of Riemann spheres with marked points

Energy Technology Data Exchange (ETDEWEB)

Duca, Vittorio Del [Institute for Theoretical Physics, ETH Zürich,Hönggerberg, 8093 Zürich (Switzerland); Druc, Stefan; Drummond, James [School of Physics & Astronomy, University of Southampton,Highfield, Southampton, SO17 1BJ (United Kingdom); Duhr, Claude [Theoretical Physics Department, CERN,Route de Meyrin, CH-1211 Geneva 23 (Switzerland); Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium); Dulat, Falko [SLAC National Accelerator Laboratory, Stanford University,Stanford, CA 94309 (United States); Marzucca, Robin [Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium); Papathanasiou, Georgios [SLAC National Accelerator Laboratory, Stanford University,Stanford, CA 94309 (United States); Verbeek, Bram [Center for Cosmology, Particle Physics and Phenomenology (CP3),Université catholique de Louvain,Chemin du Cyclotron 2, 1348 Louvain-La-Neuve (Belgium)

2016-08-25

We show that scattering amplitudes in planar N=4 Super Yang-Mills in multi-Regge kinematics can naturally be expressed in terms of single-valued iterated integrals on the moduli space of Riemann spheres with marked points. As a consequence, scattering amplitudes in this limit can be expressed as convolutions that can easily be computed using Stokes’ theorem. We apply this framework to MHV amplitudes to leading-logarithmic accuracy (LLA), and we prove that at L loops all MHV amplitudes are determined by amplitudes with up to L+4 external legs. We also investigate non-MHV amplitudes, and we show that they can be obtained by convoluting the MHV results with a certain helicity flip kernel. We classify all leading singularities that appear at LLA in the Regge limit for arbitrary helicity configurations and any number of external legs. Finally, we use our new framework to obtain explicit analytic results at LLA for all MHV amplitudes up to five loops and all non-MHV amplitudes with up to eight external legs and four loops.

Plasma dynamics in current sheets

International Nuclear Information System (INIS)

Bogdanov, S.Yu.; Drejden, G.V.; Kirij, N.P.; AN SSSR, Leningrad

1992-01-01

Plasma dynamics in successive stages of current sheet evolution is investigated on the base of analysis of time-spatial variations of electron density and electrodynamic force fields. Current sheet formation is realized in a two-dimensional magnetic field with zero line under the action of relatively small initial disturbances (linear regimes). It is established that in the limits of the formed sheet is concentrated dense (N e ∼= 10 16 cm -3 ) (T i ≥ 100 eV, bar-Z i ≥ 2) hot pressure of which is balanced by the magnetic action of electrodynamic forces is carried out both plasma compression in the sheet limits and the acceleration along the sheet surface from a middle to narrow side edges

46 CFR 232.4 - Balance sheet accounts.

Science.gov (United States)

2010-10-01

... 46 Shipping 8 2010-10-01 2010-10-01 false Balance sheet accounts. 232.4 Section 232.4 Shipping... ACTIVITIES UNIFORM FINANCIAL REPORTING REQUIREMENTS Balance Sheet § 232.4 Balance sheet accounts. (a.... (b) Purpose of balance sheet accounts. The balance sheet accounts are intended to disclose the...

RELATIVISTIC MAGNETOHYDRODYNAMICS: RENORMALIZED EIGENVECTORS AND FULL WAVE DECOMPOSITION RIEMANN SOLVER

International Nuclear Information System (INIS)

Anton, Luis; MartI, Jose M; Ibanez, Jose M; Aloy, Miguel A.; Mimica, Petar; Miralles, Juan A.

2010-01-01

We obtain renormalized sets of right and left eigenvectors of the flux vector Jacobians of the relativistic MHD equations, which are regular and span a complete basis in any physical state including degenerate ones. The renormalization procedure relies on the characterization of the degeneracy types in terms of the normal and tangential components of the magnetic field to the wave front in the fluid rest frame. Proper expressions of the renormalized eigenvectors in conserved variables are obtained through the corresponding matrix transformations. Our work completes previous analysis that present different sets of right eigenvectors for non-degenerate and degenerate states, and can be seen as a relativistic generalization of earlier work performed in classical MHD. Based on the full wave decomposition (FWD) provided by the renormalized set of eigenvectors in conserved variables, we have also developed a linearized (Roe-type) Riemann solver. Extensive testing against one- and two-dimensional standard numerical problems allows us to conclude that our solver is very robust. When compared with a family of simpler solvers that avoid the knowledge of the full characteristic structure of the equations in the computation of the numerical fluxes, our solver turns out to be less diffusive than HLL and HLLC, and comparable in accuracy to the HLLD solver. The amount of operations needed by the FWD solver makes it less efficient computationally than those of the HLL family in one-dimensional problems. However, its relative efficiency increases in multidimensional simulations.

On the properties of torsions in Riemann-Cartan space-times

International Nuclear Information System (INIS)

Baker, W.M.; Atkins, W.K.; Davis, W.R.

1978-01-01

This paper is the first paper in a series of three papers dealing with the physical properties of torsions in Riemann-Cartan space-times (U 4 ). Paper one deals with the particular types of torsion that can be associated with the U 4 reinterpretation of a special class of null electromagnetic solutions of the standard form of Einstein's equations. In particular, for plane null electromagnetic solutions, three types of torsion solutions are associated with this type of reinterpretation. Two of these solutions, the trivector and semi-symmetric torsions, although rather special, serve as examples of what could be done to find the associated torsions in terms of simple requirements on identities in U 4 . The third class is obtained by relating the contorsion to the Lanczos ''spin'' tensor. Paper two, dealing with gravitational radiation, provides the proper background relating to the physical significance of the Lanczos tensor. This series of papers is primarily concerned with the question of the possible physical role of all types of torsion, compatible with an extension or an U 4 reinterpretation of Einstein's theory, consistent with the broadest possible interpretation of the present form of the Einstein-Cartan-Sciama-Kibble theory. However, in paper three some consideration will be given on theories with simpler metrical generalizations of U 4 and the related types of torsion. We emphasize that the content of paper one and two should be viewed mainly as special formal results that introduce the more general considerations of paper three

Global ice sheet modeling

International Nuclear Information System (INIS)

Hughes, T.J.; Fastook, J.L.

1994-05-01

The University of Maine conducted this study for Pacific Northwest Laboratory (PNL) as part of a global climate modeling task for site characterization of the potential nuclear waste respository site at Yucca Mountain, NV. The purpose of the study was to develop a global ice sheet dynamics model that will forecast the three-dimensional configuration of global ice sheets for specific climate change scenarios. The objective of the third (final) year of the work was to produce ice sheet data for glaciation scenarios covering the next 100,000 years. This was accomplished using both the map-plane and flowband solutions of our time-dependent, finite-element gridpoint model. The theory and equations used to develop the ice sheet models are presented. Three future scenarios were simulated by the model and results are discussed

Sheet production apparatus for removing a crystalline sheet from the surface of a melt using gas jets located above and below the crystalline sheet

Energy Technology Data Exchange (ETDEWEB)

Kellerman, Peter L.; Thronson, Gregory D.

2017-06-14

In one embodiment, a sheet production apparatus comprises a vessel configured to hold a melt of a material. A cooling plate is disposed proximate the melt and is configured to form a sheet of the material on the melt. A first gas jet is configured to direct a gas toward an edge of the vessel. A sheet of a material is translated horizontally on a surface of the melt and the sheet is removed from the melt. The first gas jet may be directed at the meniscus and may stabilize this meniscus or increase local pressure within the meniscus.

On the modular structure of the genus-one Type II superstring low energy expansion

International Nuclear Information System (INIS)

D’Hoker, Eric; Green, Michael B.; Vanhove, Pierre

2015-01-01

The analytic contribution to the low energy expansion of Type II string amplitudes at genus-one is a power series in space-time derivatives with coefficients that are determined by integrals of modular functions over the complex structure modulus of the world-sheet torus. These modular functions are associated with world-sheet vacuum Feynman diagrams and given by multiple sums over the discrete momenta on the torus. In this paper we exhibit exact differential and algebraic relations for a certain infinite class of such modular functions by showing that they satisfy Laplace eigenvalue equations with inhomogeneous terms that are polynomial in non-holomorphic Eisenstein series. Furthermore, we argue that the set of modular functions that contribute to the coefficients of interactions up to order D 10 R 4 are linear sums of functions in this class and quadratic polynomials in Eisenstein series and odd Riemann zeta values. Integration over the complex structure results in coefficients of the low energy expansion that are rational numbers multiplying monomials in odd Riemann zeta values.

On the modular structure of the genus-one Type II superstring low energy expansion

Energy Technology Data Exchange (ETDEWEB)

D’Hoker, Eric [Department of Physics and Astronomy,University of California, Los Angeles, CA 90095 (United States); Green, Michael B. [Department of Applied Mathematics and Theoretical Physics,Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Vanhove, Pierre [Institut des Hautes Études Scientifiques, Le Bois-Marie, 35 route de Chartres,F-91440 Bures-sur-Yvette (France); Institut de physique théorique, Université Paris Saclay, CEA, CNRS,F-91191 Gif-sur-Yvette (France)

2015-08-11

The analytic contribution to the low energy expansion of Type II string amplitudes at genus-one is a power series in space-time derivatives with coefficients that are determined by integrals of modular functions over the complex structure modulus of the world-sheet torus. These modular functions are associated with world-sheet vacuum Feynman diagrams and given by multiple sums over the discrete momenta on the torus. In this paper we exhibit exact differential and algebraic relations for a certain infinite class of such modular functions by showing that they satisfy Laplace eigenvalue equations with inhomogeneous terms that are polynomial in non-holomorphic Eisenstein series. Furthermore, we argue that the set of modular functions that contribute to the coefficients of interactions up to order D{sup 10}R{sup 4} are linear sums of functions in this class and quadratic polynomials in Eisenstein series and odd Riemann zeta values. Integration over the complex structure results in coefficients of the low energy expansion that are rational numbers multiplying monomials in odd Riemann zeta values.

Vitamin and Mineral Supplement Fact Sheets

Science.gov (United States)

... website Submit Search NIH Office of Dietary Supplements Vitamin and Mineral Supplement Fact Sheets Search the list ... Supplements: Background Information Botanical Dietary Supplements: Background Information Vitamin and Mineral Fact Sheets Botanical Supplement Fact Sheets ...

Dynamics of Radially Expanding Liquid Sheets

Science.gov (United States)

Majumdar, Nayanika; Tirumkudulu, Mahesh S.

2018-04-01

The process of atomization often involves ejecting thin liquid sheets at high speeds from a nozzle that causes the sheet to flap violently and break up into fine droplets. The flapping of the liquid sheet has long been attributed to the sheet's interaction with the surrounding gas phase. Here, we present experimental evidence to the contrary and show that the flapping is caused by the thinning of the liquid sheet as it spreads out from the nozzle exit. The measured growth rates of the waves agree remarkably well with the predictions of a recent theory that accounts for the sheet's thinning but ignores aerodynamic interactions. We anticipate these results to not only lead to more accurate predictions of the final drop-size distribution but also enable more efficient designs of atomizers.

On membrane interactions and a three-dimensional analog of Riemann surfaces

Energy Technology Data Exchange (ETDEWEB)

Kovacs, Stefano [Dublin Institute for Advanced Studies, 10 Burlington Road, Dublin 4 (Ireland); ICTP South American Institute for Fundamental Research, IFT-UNESP,São Paulo, SP 01440-070 (Brazil); Sato, Yuki [National Institute for Theoretical Physics, School of Physics and Mandelstam Institute for Theoretical Physics, University of the Witwartersrand,Wits 2050 (South Africa); Shimada, Hidehiko [Okayama Institute for Quantum Physics,Okayama (Japan)

2016-02-08

Membranes in M-theory are expected to interact via splitting and joining processes. We study these effects in the pp-wave matrix model, in which they are associated with transitions between states in sectors built on vacua with different numbers of membranes. Transition amplitudes between such states receive contributions from BPS instanton configurations interpolating between the different vacua. Various properties of the moduli space of BPS instantons are known, but there are very few known examples of explicit solutions. We present a new approach to the construction of instanton solutions interpolating between states containing arbitrary numbers of membranes, based on a continuum approximation valid for matrices of large size. The proposed scheme uses functions on a two-dimensional space to approximate matrices and it relies on the same ideas behind the matrix regularisation of membrane degrees of freedom in M-theory. We show that the BPS instanton equations have a continuum counterpart which can be mapped to the three-dimensional Laplace equation through a sequence of changes of variables. A description of configurations corresponding to membrane splitting/joining processes can be given in terms of solutions to the Laplace equation in a three-dimensional analog of a Riemann surface, consisting of multiple copies of ℝ{sup 3} connected via a generalisation of branch cuts. We discuss various general features of our proposal and we also present explicit analytic solutions.

On membrane interactions and a three-dimensional analog of Riemann surfaces

International Nuclear Information System (INIS)

Kovacs, Stefano; Sato, Yuki; Shimada, Hidehiko

2016-01-01

Membranes in M-theory are expected to interact via splitting and joining processes. We study these effects in the pp-wave matrix model, in which they are associated with transitions between states in sectors built on vacua with different numbers of membranes. Transition amplitudes between such states receive contributions from BPS instanton configurations interpolating between the different vacua. Various properties of the moduli space of BPS instantons are known, but there are very few known examples of explicit solutions. We present a new approach to the construction of instanton solutions interpolating between states containing arbitrary numbers of membranes, based on a continuum approximation valid for matrices of large size. The proposed scheme uses functions on a two-dimensional space to approximate matrices and it relies on the same ideas behind the matrix regularisation of membrane degrees of freedom in M-theory. We show that the BPS instanton equations have a continuum counterpart which can be mapped to the three-dimensional Laplace equation through a sequence of changes of variables. A description of configurations corresponding to membrane splitting/joining processes can be given in terms of solutions to the Laplace equation in a three-dimensional analog of a Riemann surface, consisting of multiple copies of ℝ"3 connected via a generalisation of branch cuts. We discuss various general features of our proposal and we also present explicit analytic solutions.

A global and stochastic analysis approach to bosonic strings and associated quantum fields

International Nuclear Information System (INIS)

Albeverio, S.; Hoeegh-Krohn, R.; Paycha, S.; Scarlatti, S.

1989-01-01

We construct a probability measure giving a mathematical realization of Polyakov's heuristic measure for bosonic strings in space-time dimensions 3 << d << 13, having as world sheet compact Riemann surfaces Λ of arbitrary genus. The measure involves the path space measures for scalar fields with exponential interaction on Λ and a measure on Teichmueller space. (orig.)

A global and stochastic analysis approach to bosonic strings and associated quantum fields

Energy Technology Data Exchange (ETDEWEB)

Albeverio, S.; Hoeegh-Krohn, R.; Paycha, S.; Scarlatti, S.

1989-01-01

We construct a probability measure giving a mathematical realization of Polyakov's heuristic measure for bosonic strings in space-time dimensions 3 << d << 13, having as world sheet compact Riemann surfaces /Lambda/ of arbitrary genus. The measure involves the path space measures for scalar fields with exponential interaction on /Lambda/ and a measure on Teichmueller space. (orig.).

A global and stochastic analysis approach to bosonic strings and associated quantum fields

International Nuclear Information System (INIS)

Albeverio, S.; Hoeegh-Krohn, R.; Paycha, S.; Scarlatti, S.

1989-01-01

We construct a probability measure giving a mathematical realization of Polyakov's heuristic measure for bosonic strings in space-time dimensions 3 ≤ d ≤ 13, having as world sheet compact Riemann surfaces Λ of arbitrary genus. The measure involves the path space measures for scalar fields with exponential interaction on Λ and a measure on Teichmueller space. (orig.)

Buckling and stretching of thin viscous sheets

Science.gov (United States)

O'Kiely, Doireann; Breward, Chris; Griffiths, Ian; Howell, Peter; Lange, Ulrich

2016-11-01

Thin glass sheets are used in smartphone, battery and semiconductor technology, and may be manufactured by producing a relatively thick glass slab and subsequently redrawing it to a required thickness. The resulting sheets commonly possess undesired centerline ripples and thick edges. We present a mathematical model in which a viscous sheet undergoes redraw in the direction of gravity, and show that, in a sufficiently strong gravitational field, buckling is driven by compression in a region near the bottom of the sheet, and limited by viscous resistance to stretching of the sheet. We use asymptotic analysis in the thin-sheet, low-Reynolds-number limit to determine the centerline profile and growth rate of such a viscous sheet.

Ohm's law for a current sheet

Science.gov (United States)

Lyons, L. R.; Speiser, T. W.

1985-01-01

The paper derives an Ohm's law for single-particle motion in a current sheet, where the magnetic field reverses in direction across the sheet. The result is considerably different from the resistive Ohm's law often used in MHD studies of the geomagnetic tail. Single-particle analysis is extended to obtain a self-consistency relation for a current sheet which agrees with previous results. The results are applicable to the concept of reconnection in that the electric field parallel to the current is obtained for a one-dimensional current sheet with constant normal magnetic field. Dissipated energy goes directly into accelerating particles within the current sheet.

Adjustable focus laser sheet module for generating constant maximum width sheets for use in optical flow diagnostics

International Nuclear Information System (INIS)

Hult, J; Mayer, S

2011-01-01

A general design of a laser light sheet module with adjustable focus is presented, where the maximum sheet width is preserved over a fixed region. In contrast, conventional focusing designs are associated with a variation in maximum sheet width with focal position. A four lens design is proposed here, where the first three lenses are employed for focusing, and the last for sheet expansion. A maximum sheet width of 1100 µm was maintained over a 50 mm long distance, for focal distances ranging from 75 to 500 mm, when a 532 nm laser beam with a beam quality factor M 2 = 29 was used for illumination

Riemann-Christoffel Tensor in Differential Geometry of Fractional Order Application to Fractal Space-Time

Science.gov (United States)

Jumarie, Guy

2013-04-01

By using fractional differences, one recently proposed an alternative to the formulation of fractional differential calculus, of which the main characteristics is a new fractional Taylor series and its companion Rolle's formula which apply to non-differentiable functions. The key is that now we have at hand a differential increment of fractional order which can be manipulated exactly like in the standard Leibniz differential calculus. Briefly the fractional derivative is the quotient of fractional increments. It has been proposed that this calculus can be used to construct a differential geometry on manifold of fractional order. The present paper, on the one hand, refines the framework, and on the other hand, contributes some new results related to arc length of fractional curves, area on fractional differentiable manifold, covariant fractal derivative, Riemann-Christoffel tensor of fractional order, fractional differential equations of fractional geodesic, strip modeling of fractal space time and its relation with Lorentz transformation. The relation with Nottale's fractal space-time theory then appears in quite a natural way.

Collisionless current sheet equilibria

Science.gov (United States)

Neukirch, T.; Wilson, F.; Allanson, O.

2018-01-01

Current sheets are important for the structure and dynamics of many plasma systems. In space and astrophysical plasmas they play a crucial role in activity processes, for example by facilitating the release of magnetic energy via processes such as magnetic reconnection. In this contribution we will focus on collisionless plasma systems. A sensible first step in any investigation of physical processes involving current sheets is to find appropriate equilibrium solutions. The theory of collisionless plasma equilibria is well established, but over the past few years there has been a renewed interest in finding equilibrium distribution functions for collisionless current sheets with particular properties, for example for cases where the current density is parallel to the magnetic field (force-free current sheets). This interest is due to a combination of scientific curiosity and potential applications to space and astrophysical plasmas. In this paper we will give an overview of some of the recent developments, discuss their potential applications and address a number of open questions.

17 CFR 210.6-04 - Balance sheets.

Science.gov (United States)

2010-04-01

... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Balance sheets. 210.6-04... sheets. This rule is applicable to balance sheets filed by registered investment companies except for... of this part. Balance sheets filed under this rule shall comply with the following provisions: Assets...

Ice sheet in peril

DEFF Research Database (Denmark)

Hvidberg, Christine Schøtt

2016-01-01

Earth's large ice sheets in Greenland and Antarctica are major contributors to sea level change. At present, the Greenland Ice Sheet (see the photo) is losing mass in response to climate warming in Greenland (1), but the present changes also include a long-term response to past climate transitions...

The transposition of the balance sheet to financial and functional balance sheet. Research and development

Directory of Open Access Journals (Sweden)

Liana GĂDĂU

2015-09-01

Full Text Available As the title suggests, through this paper we want to highlight the necessity of treating again the content and the form of the balance sheet in order to adapt it to a more efficient analysis, this way surpassing the informational valences of the classic balance sheet. The functional and the financial balance sheet will be taken into account. These models of balance sheet permit the complex analyses regarding the solvability or the bankruptcy risk of an enterprise to take place, and also other analyses, like the analysis of the structure and the financial/ functional equilibrium, the analysis of the company on operating cycles and their role in the functioning of the company. Through the particularities offered by each of these two models of balance sheet, we want to present the advantages of a superior informing. This content of this material is based on a vast investigation of the specialized literature.

Ice_Sheets_CCI: Essential Climate Variables for the Greenland Ice Sheet

Science.gov (United States)

Forsberg, R.; Sørensen, L. S.; Khan, A.; Aas, C.; Evansberget, D.; Adalsteinsdottir, G.; Mottram, R.; Andersen, S. B.; Ahlstrøm, A.; Dall, J.; Kusk, A.; Merryman, J.; Hvidberg, C.; Khvorostovsky, K.; Nagler, T.; Rott, H.; Scharrer, M.; Shepard, A.; Ticconi, F.; Engdahl, M.

2012-04-01

As part of the ESA Climate Change Initiative (www.esa-cci.org) a long-term project "ice_sheets_cci" started January 1, 2012, in addition to the existing 11 projects already generating Essential Climate Variables (ECV) for the Global Climate Observing System (GCOS). The "ice_sheets_cci" goal is to generate a consistent, long-term and timely set of key climate parameters for the Greenland ice sheet, to maximize the impact of European satellite data on climate research, from missions such as ERS, Envisat and the future Sentinel satellites. The climate parameters to be provided, at first in a research context, and in the longer perspective by a routine production system, would be grids of Greenland ice sheet elevation changes from radar altimetry, ice velocity from repeat-pass SAR data, as well as time series of marine-terminating glacier calving front locations and grounding lines for floating-front glaciers. The ice_sheets_cci project will involve a broad interaction of the relevant cryosphere and climate communities, first through user consultations and specifications, and later in 2012 optional participation in "best" algorithm selection activities, where prototype climate parameter variables for selected regions and time frames will be produced and validated using an objective set of criteria ("Round-Robin intercomparison"). This comparative algorithm selection activity will be completely open, and we invite all interested scientific groups with relevant experience to participate. The results of the "Round Robin" exercise will form the algorithmic basis for the future ECV production system. First prototype results will be generated and validated by early 2014. The poster will show the planned outline of the project and some early prototype results.

AI applications in sheet metal forming

CERN Document Server

Hussein, Hussein

2017-01-01

This book comprises chapters on research work done around the globe in the area of artificial intelligence (AI) applications in sheet metal forming. The first chapter offers an introduction to various AI techniques and sheet metal forming, while subsequent chapters describe traditional procedures/methods used in various sheet metal forming processes, and focus on the automation of those processes by means of AI techniques, such as KBS, ANN, GA, CBR, etc. Feature recognition and the manufacturability assessment of sheet metal parts, process planning, strip-layout design, selecting the type and size of die components, die modeling, and predicting die life are some of the most important aspects of sheet metal work. Traditionally, these activities are highly experience-based, tedious and time consuming. In response, researchers in several countries have applied various AI techniques to automate these activities, which are covered in this book. This book will be useful for engineers working in sheet metal industri...

Modelling the transition between fixed and mobile bed conditions in two-phase free-surface flows: The Composite Riemann Problem and its numerical solution

Science.gov (United States)

Rosatti, Giorgio; Zugliani, Daniel

2015-03-01

In a two-phase free-surface flow, the transition from a mobile-bed condition to a fixed-bed one (and vice versa) occurs at a sharp interface across which the relevant system of partial differential equations changes abruptly. This leads to the possibility of conceiving a new type of Riemann Problem (RP), which we have called Composite Riemann Problem (CRP), where not only the initial constant values of the variables but also the system of equations change from left to right of a discontinuity. In this paper, we present a strategy for solving a CRP by reducing it to a standard RP of a single, composite system of equations. This can be obtained by combining the two original systems by means of a suitable weighting function, namely the erodibility variable, and the introduction of an appropriate differential equation for this quantity. In this way, the CRP problem can be analyzed theoretically with standard methods, and the features of the solutions can be clearly identified. In particular, a stationary contact wave is able to correctly describe the sharp transition between mobile- and fixed-bed conditions. A finite volume scheme based on the Multiple Averages Generalized Roe approach (Rosatti and Begnudelli (2013) [22]) was used to numerically solve the fixed-mobile CRP. Several test cases demonstrate the effectiveness, exact well balanceness and high accuracy of the scheme when applied to problems that fall within the physical range of applicability of the relevant mathematical model.

Effect of Temperature and Sheet Temper on Isothermal Solidification Kinetics in Clad Aluminum Brazing Sheet

Science.gov (United States)

Benoit, Michael J.; Whitney, Mark A.; Wells, Mary A.; Winkler, Sooky

2016-09-01

Isothermal solidification (IS) is a phenomenon observed in clad aluminum brazing sheets, wherein the amount of liquid clad metal is reduced by penetration of the liquid clad into the core. The objective of the current investigation is to quantify the rate of IS through the use of a previously derived parameter, the Interface Rate Constant (IRC). The effect of peak temperature and initial sheet temper on IS kinetics were investigated. The results demonstrated that IS is due to the diffusion of silicon (Si) from the liquid clad layer into the solid core. Reduced amounts of liquid clad at long liquid duration times, a roughened sheet surface, and differences in resolidified clad layer morphology between sheet tempers were observed. Increased IS kinetics were predicted at higher temperatures by an IRC model as well as by experimentally determined IRC values; however, the magnitudes of these values are not in good agreement due to deficiencies in the model when applied to alloys. IS kinetics were found to be higher for sheets in the fully annealed condition when compared with work-hardened sheets, due to the influence of core grain boundaries providing high diffusivity pathways for Si diffusion, resulting in more rapid liquid clad penetration.

Energy information sheets

Energy Technology Data Exchange (ETDEWEB)

NONE

1995-07-01

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

Experiments on sheet metal shearing

OpenAIRE

Gustafsson, Emil

2013-01-01

Within the sheet metal industry, different shear cutting technologies are commonly used in several processing steps, e.g. in cut to length lines, slitting lines, end cropping etc. Shearing has speed and cost advantages over competing cutting methods like laser and plasma cutting, but involves large forces on the equipment and large strains in the sheet material.Numerical models to predict forces and sheared edge geometry for different sheet metal grades and different shear parameter set-ups a...

Predicting Pulsar Scintillation from Refractive Plasma Sheets

Science.gov (United States)

Simard, Dana; Pen, Ue-Li

2018-05-01

The dynamic and secondary spectra of many pulsars show evidence for long-lived, aligned images of the pulsar that are stationary on a thin scattering sheet. One explanation for this phenomenon considers the effects of wave crests along sheets in the ionized interstellar medium, such as those due to Alfvén waves propagating along current sheets. If these sheets are closely aligned to our line-of-sight to the pulsar, high bending angles arise at the wave crests and a selection effect causes alignment of images produced at different crests, similar to grazing reflection off of a lake. Using geometric optics, we develop a simple parameterized model of these corrugated sheets that can be constrained with a single observation and that makes observable predictions for variations in the scintillation of the pulsar over time and frequency. This model reveals qualitative differences between lensing from overdense and underdense corrugated sheets: Only if the sheet is overdense compared to the surrounding interstellar medium can the lensed images be brighter than the line-of-sight image to the pulsar, and the faint lensed images are closer to the pulsar at higher frequencies if the sheet is underdense, but at lower frequencies if the sheet is overdense.

Energized Oxygen : Speiser Current Sheet Bifurcation

Science.gov (United States)

George, D. E.; Jahn, J. M.

2017-12-01

A single population of energized Oxygen (O+) is shown to produce a cross-tail bifurcated current sheet in 2.5D PIC simulations of the magnetotail without the influence of magnetic reconnection. Treatment of oxygen in simulations of space plasmas, specifically a magnetotail current sheet, has been limited to thermal energies despite observations of and mechanisms which explain energized ions. We performed simulations of a homogeneous oxygen background, that has been energized in a physically appropriate manner, to study the behavior of current sheets and magnetic reconnection, specifically their bifurcation. This work uses a 2.5D explicit Particle-In-a-Cell (PIC) code to investigate the dynamics of energized heavy ions as they stream Dawn-to-Dusk in the magnetotail current sheet. We present a simulation study dealing with the response of a current sheet system to energized oxygen ions. We establish a, well known and studied, 2-species GEM Challenge Harris current sheet as a starting point. This system is known to eventually evolve and produce magnetic reconnection upon thinning of the current sheet. We added a uniform distribution of thermal O+ to the background. This 3-species system is also known to eventually evolve and produce magnetic reconnection. We add one additional variable to the system by providing an initial duskward velocity to energize the O+. We also traced individual particle motion within the PIC simulation. Three main results are shown. First, energized dawn- dusk streaming ions are clearly seen to exhibit sustained Speiser motion. Second, a single population of heavy ions clearly produces a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce the bifurcated current sheet. Finally a bifurcated current sheet is compatible with the Harris current sheet model. This work is the first step in a series of investigations aimed at studying the effects of energized heavy ions on magnetic reconnection. This work differs

Experimental formability analysis of bondal sandwich sheet

Science.gov (United States)

Kami, Abdolvahed; Banabic, Dorel

2018-05-01

Metal/polymer/metal sandwich sheets have recently attracted the interests of industries like automotive industry. These sandwich sheets have superior properties over single-layer metallic sheets including good sound and vibration damping and light weight. However, the formability of these sandwich sheets should be enhanced which requires more research. In this paper, the formability of Bondal sheet (DC06/viscoelastic polymer/DC06 sandwich sheet) was studied through different types of experiments. The mechanical properties of Bondal were determined by uniaxial tensile tests. Hemispherical punch stretching and hydraulic bulge tests were carried out to determine the forming limit diagram (FLD) of Bondal. Furthermore, cylindrical and square cup drawing tests were performed in dry and oil lubricated conditions. These tests were conducted at different blank holding forces (BHFs). An interesting observation about Bondal sheet deep drawing was obtaining of higher drawing depths at dry condition in comparison with oil-lubricated condition.

Ice sheet hydrology - a review

International Nuclear Information System (INIS)

Jansson, Peter; Naeslund, Jens-Ove; Rodhe, Lars

2007-03-01

This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

Ice sheet hydrology - a review

Energy Technology Data Exchange (ETDEWEB)

Jansson, Peter; Naeslund, Jens-Ove [Dept. of Physical Geography and Quaternary Geology, Stockholm Univ., Stockholm (Sweden); Rodhe, Lars [Geological Survey of Sweden, Uppsala (Sweden)

2007-03-15

This report summarizes the theoretical knowledge on water flow in and beneath glaciers and ice sheets and how these theories are applied in models to simulate the hydrology of ice sheets. The purpose is to present the state of knowledge and, perhaps more importantly, identify the gaps in our understanding of ice sheet hydrology. Many general concepts in hydrology and hydraulics are applicable to water flow in glaciers. However, the unique situation of having the liquid phase flowing in conduits of the solid phase of the same material, water, is not a commonly occurring phenomena. This situation means that the heat exchange between the phases and the resulting phase changes also have to be accounted for in the analysis. The fact that the solidus in the pressure-temperature dependent phase diagram of water has a negative slope provides further complications. Ice can thus melt or freeze from both temperature and pressure variations or variations in both. In order to provide details of the current understanding of water flow in conjunction with deforming ice and to provide understanding for the development of ideas and models, emphasis has been put on the mathematical treatments, which are reproduced in detail. Qualitative results corroborating theory or, perhaps more often, questioning the simplifications made in theory, are also given. The overarching problem with our knowledge of glacier hydrology is the gap between the local theories of processes and the general flow of water in glaciers and ice sheets. Water is often channelized in non-stationary conduits through the ice, features which due to their minute size relative to the size of glaciers and ice sheets are difficult to incorporate in spatially larger models. Since the dynamic response of ice sheets to global warming is becoming a key issue in, e.g. sea-level change studies, the problems of the coupling between the hydrology of an ice sheet and its dynamics is steadily gaining interest. New work is emerging

Disintegration of liquid sheets

Science.gov (United States)

Mansour, Adel; Chigier, Norman

1990-01-01

The development, stability, and disintegration of liquid sheets issuing from a two-dimensional air-assisted nozzle is studied. Detailed measurements of mean drop size and velocity are made using a phase Doppler particle analyzer. Without air flow the liquid sheet converges toward the axis as a result of surface tension forces. With airflow a quasi-two-dimensional expanding spray is formed. The air flow causes small variations in sheet thickness to develop into major disturbances with the result that disruption starts before the formation of the main break-up region. In the two-dimensional variable geometry air-blast atomizer, it is shown that the air flow is responsible for the formation of large, ordered, and small chaotic 'cell' structures.

Root-growth-inhibiting sheet

Science.gov (United States)

Burton, F.G.; Cataldo, D.A.; Cline, J.F.; Skiens, W.E.; Van Voris, P.

1993-01-26

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a geotextile'' and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

Root-growth-inhibiting sheet

Science.gov (United States)

Burton, Frederick G.; Cataldo, Dominic A.; Cline, John F.; Skiens, W. Eugene; Van Voris, Peter

1993-01-01

In accordance with this invention, a porous sheet material is provided at intervals with bodies of a polymer which contain a 2,6-dinitroaniline. The sheet material is made porous to permit free passage of water. It may be either a perforated sheet or a woven or non-woven textile material. A particularly desirable embodiment is a non-woven fabric of non-biodegradable material. This type of material is known as a "geotextile" and is used for weed control, prevention of erosion on slopes, and other landscaping purposes. In order to obtain a root repelling property, a dinitroaniline is blended with a polymer which is attached to the geotextile or other porous material.

Mobility Balance Sheet 2009

International Nuclear Information System (INIS)

Jorritsma, P.; Derriks, H.; Francke, J.; Gordijn, H.; Groot, W.; Harms, L.; Van der Loop, H.; Peer, S.; Savelberg, F.; Wouters, P.

2009-06-01

The Mobility Balance Sheet provides an overview of the state of the art of mobility in the Netherlands. In addition to describing the development of mobility this report also provides explanations for the growth of passenger and freight transport. Moreover, the Mobility Balance Sheet also focuses on a topical theme: the effects of economic crises on mobility. [nl

Safety advice sheets

CERN Multimedia

HSE Unit

2013-01-01

You never know when you might be faced with questions such as: when/how should I dispose of a gas canister? Where can I find an inspection report? How should I handle/store/dispose of a chemical substance…?   The SI section of the DGS/SEE Group is primarily responsible for safety inspections, evaluating the safety conditions of equipment items, premises and facilities. On top of this core task, it also regularly issues “Safety Advice Sheets” on various topics, designed to be of assistance to users but also to recall and reinforce safety rules and procedures. These clear and concise sheets, complete with illustrations, are easy to display in the appropriate areas. The following safety advice sheets have been issued so far: Other sheets will be published shortly. Suggestions are welcome and should be sent to the SI section of the DGS/SEE Group. Please send enquiries to general-safety-visits.service@cern.ch.

Manifold free multiple sheet superplastic forming

Science.gov (United States)

Elmer, John W.; Bridges, Robert L.

2004-01-13

Fluid-forming compositions in a container attached to enclosed adjacent sheets are heated to relatively high temperatures to generate fluids (gases) that effect inflation of the sheets. Fluid rates to the enclosed space between the sheets can be regulated by the canal from the container. Inflated articles can be produced by a continuous, rather than batch-type, process.

21 CFR 880.5180 - Burn sheet.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Burn sheet. 880.5180 Section 880.5180 Food and... Burn sheet. (a) Identification. A burn sheet is a device made of a porous material that is wrapped aroung a burn victim to retain body heat, to absorb wound exudate, and to serve as a barrier against...

Sheet-bulk metal forming – forming of functional components from sheet metals

Directory of Open Access Journals (Sweden)

Merklein Marion

2015-01-01

Full Text Available The paper gives an overview on the application of sheet-bulk metal forming operations in both scientific and industrial environment. Beginning with the need for an innovative forming technology, the definition of this new process class is introduced. The rising challenges of the application of bulk metal forming operations on sheet metals are presented and the demand on a holistic investigation of this topic is motivated. With the help of examples from established production processes, the latest state of technology and the lack on fundamental knowledge is shown. Furthermore, perspectives regarding new research topics within sheet-bulk metal forming are presented. These focus on processing strategies to improve the quality of functional components by the application of process-adapted semi-finished products as well as the local adaption of the tribological system.

Reconstructing the last Irish Ice Sheet 2: a geomorphologically-driven model of ice sheet growth, retreat and dynamics

Science.gov (United States)

Greenwood, Sarah L.; Clark, Chris D.

2009-12-01

The ice sheet that once covered Ireland has a long history of investigation. Much prior work focussed on localised evidence-based reconstructions and ice-marginal dynamics and chronologies, with less attention paid to an ice sheet wide view of the first order properties of the ice sheet: centres of mass, ice divide structure, ice flow geometry and behaviour and changes thereof. In this paper we focus on the latter aspect and use our new, countrywide glacial geomorphological mapping of the Irish landscape (>39 000 landforms), and our analysis of the palaeo-glaciological significance of observed landform assemblages (article Part 1), to build an ice sheet reconstruction yielding these fundamental ice sheet properties. We present a seven stage model of ice sheet evolution, from initiation to demise, in the form of palaeo-geographic maps. An early incursion of ice from Scotland likely coalesced with local ice caps and spread in a south-westerly direction 200 km across Ireland. A semi-independent Irish Ice Sheet was then established during ice sheet growth, with a branching ice divide structure whose main axis migrated up to 140 km from the west coast towards the east. Ice stream systems converging on Donegal Bay in the west and funnelling through the North Channel and Irish Sea Basin in the east emerge as major flow components of the maximum stages of glaciation. Ice cover is reconstructed as extending to the continental shelf break. The Irish Ice Sheet became autonomous (i.e. separate from the British Ice Sheet) during deglaciation and fragmented into multiple ice masses, each decaying towards the west. Final sites of demise were likely over the mountains of Donegal, Leitrim and Connemara. Patterns of growth and decay of the ice sheet are shown to be radically different: asynchronous and asymmetric in both spatial and temporal domains. We implicate collapse of the ice stream system in the North Channel - Irish Sea Basin in driving such asymmetry, since rapid

Pre-LGM Northern Hemisphere ice sheet topography

Directory of Open Access Journals (Sweden)

J. Kleman

2013-10-01

Full Text Available We here reconstruct the paleotopography of Northern Hemisphere ice sheets during the glacial maxima of marine isotope stages (MIS 5b and 4.We employ a combined approach, blending geologically based reconstruction and numerical modeling, to arrive at probable ice sheet extents and topographies for each of these two time slices. For a physically based 3-D calculation based on geologically derived 2-D constraints, we use the University of Maine Ice Sheet Model (UMISM to calculate ice sheet thickness and topography. The approach and ice sheet modeling strategy is designed to provide robust data sets of sufficient resolution for atmospheric circulation experiments for these previously elusive time periods. Two tunable parameters, a temperature scaling function applied to a spliced Vostok–GRIP record, and spatial adjustment of the climatic pole position, were employed iteratively to achieve a good fit to geological constraints where such were available. The model credibly reproduces the first-order pattern of size and location of geologically indicated ice sheets during marine isotope stages (MIS 5b (86.2 kyr model age and 4 (64 kyr model age. From the interglacial state of two north–south obstacles to atmospheric circulation (Rocky Mountains and Greenland, by MIS 5b the emergence of combined Quebec–central Arctic and Scandinavian–Barents-Kara ice sheets had increased the number of such highland obstacles to four. The number of major ice sheets remained constant through MIS 4, but the merging of the Cordilleran and the proto-Laurentide Ice Sheet produced a single continent-wide North American ice sheet at the LGM.

Research on Al-alloy sheet forming formability during warm/hot sheet hydroforming based on elliptical warm bulging test

Science.gov (United States)

Cai, Gaoshen; Wu, Chuanyu; Gao, Zepu; Lang, Lihui; Alexandrov, Sergei

2018-05-01

An elliptical warm/hot sheet bulging test under different temperatures and pressure rates was carried out to predict Al-alloy sheet forming limit during warm/hot sheet hydroforming. Using relevant formulas of ultimate strain to calculate and dispose experimental data, forming limit curves (FLCS) in tension-tension state of strain (TTSS) area are obtained. Combining with the basic experimental data obtained by uniaxial tensile test under the equivalent condition with bulging test, complete forming limit diagrams (FLDS) of Al-alloy are established. Using a quadratic polynomial curve fitting method, material constants of fitting function are calculated and a prediction model equation for sheet metal forming limit is established, by which the corresponding forming limit curves in TTSS area can be obtained. The bulging test and fitting results indicated that the sheet metal FLCS obtained were very accurate. Also, the model equation can be used to instruct warm/hot sheet bulging test.

On Jovian plasma sheet structure

International Nuclear Information System (INIS)

Khurana, K.K.; Kivelson, M.G.

1989-01-01

The authors evaluate several models of Jovian plasma sheet structure by determining how well they organize several aspects of the observed Voyager 2 magnetic field characteristics as a function of Jovicentric radial distance. It is shown that in the local time sector of the Voyager 2 outbound pass (near 0300 LT) the published hinged-magnetodisc models with wave (i.e., models corrected for finite wave velocity effects) are more successful than the published magnetic anomaly model in predicting locations of current sheet crossings. They also consider the boundary between the plasma sheet and the magnetotail lobe which is expected to vary slowly with radial distance. They use this boundary location as a further test of the models of the magnetotail. They show that the compressional MHD waves have much smaller amplitude in the lobes than in the plasma sheet and use this criterion to refine the identification of the plasma-sheet-lobe boundary. When the locations of crossings into and out of the lobes are examined, it becomes evident that the magnetic-anomaly model yields a flaring plasma sheet with a halfwidth of ∼ 3 R J at a radial distance of 20 R J and ∼ 12 R J at a radial distance of 100 R J . The hinged-magnetodisc models with wave, on the other hand, predict a halfwidth of ∼ 3.5 R J independent of distance beyond 20 R J . New optimized versions of the two models locate both the current sheet crossings and lobe encounters equally successfully. The optimized hinged-magnetodisc model suggests that the wave velocity decreases with increasing radial distance. The optimized magnetic anomaly model yields lower velocity contrast than the model of Vasyliunas and Dessler (1981)

Rubella - Fact Sheet for Parents

Science.gov (United States)

... and 4 through 6 years Fact Sheet for Parents Color [2 pages] Español: Rubéola The best way ... according to the recommended schedule. Fact Sheets for Parents Diseases and the Vaccines that Prevent Them Chickenpox ...

Cell sheet technology and cell patterning for biofabrication

Energy Technology Data Exchange (ETDEWEB)

Hannachi, Imen Elloumi; Yamato, Masayuki; Okano, Teruo [Institute of Advanced Biomedical Engineering and Science, Tokyo Women' s Medical University, 8-1 Kawada-cho, Shinjuku, Tokyo (Japan)

2009-06-01

We have developed cell sheet technology as a modern method for the fabrication of functional tissue-like and organ-like structures. This technology allows for a sheet of interconnected cells and cells in full contact with their natural extracellular environment to be obtained. A cell sheet can be patterned and composed according to more than one cell type. The key technology of cell sheet engineering is that a fabricated cell sheet can be harvested and transplanted utilizing temperature-responsive surfaces. In this review, we summarize different aspects of cell sheet engineering and provide a survey of the application of cell sheets as a suitable material for biofabrication and clinics. Moreover, since cell micropatterning is a key tool for cell sheet engineering, in this review we focus on the introduction of our approaches to cell micropatterning and cell co-culture to the principles of automation and how they can be subjected to easy robotics programming. Finally, efforts towards making cell sheet technology suitable for biofabrication and robotic biofabrication are also summarized. (topical review)

Initial-value problem for the 1-D wave equation in an inhomogeneous medium

International Nuclear Information System (INIS)

Sedlacek, Z.; Roberts, B.; Adam, J.A.

1986-03-01

A complete mathematical analysis of oscillations of an inhomogeneous medium described by a wave equation with a space-dependent coefficient is given. The initial-value problem is solved both by the Laplace transform and by normal-mode analysis and the equivalency of both approaches is demonstrated. The Green function of the problem is a double-valued function of the complex frequency, analytic in the upper and lower halves of the complex frequency plane (the ''physical'' sheet of its Riemann surface) with discontinuity on the whole real axis, corresponding to the continuous frequency spectrum of the physical system in question. The Green function has complex poles on analytic continuation onto the ''unphysical'' sheet of its Riemann surface. This makes it possible, by inverting the Laplace transform, to interpret the solution of the initial-value problem in terms of ''damped'' eigenmodes. The continuum eigenmodes can be constructed directly and are also recovered by integrating the Green function in the complex frequency plane along a closed contour enclosing the spectrum. Their orthogonality and completeness is proved. The solution of the initial-value problem synthesized from the continuum eigenmodes can be interpreted in terms of travelling disturbances scattered by inhomogeneity. (author)

Energy information sheets

Energy Technology Data Exchange (ETDEWEB)

1993-12-02

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the general public. Written for the general public, the EIA publication Energy Information Sheets was developed to provide information on various aspects of fuel production, prices, consumption and capability. The information contained herein pertains to energy data as of December 1991. Additional information on related subject matter can be found in other EIA publications as referenced at the end of each sheet.

Weld Repair of Thin Aluminum Sheet

Science.gov (United States)

Beuyukian, C. S.; Mitchell, M. J.

1986-01-01

Weld repairing of thin aluminum sheets now possible, using niobium shield and copper heat sinks. Refractory niobium shield protects aluminum adjacent to hole, while copper heat sinks help conduct heat away from repair site. Technique limits tungsten/inert-gas (TIG) welding bombardment zone to melt area, leaving surrounding areas around weld unaffected. Used successfully to repair aluminum cold plates on Space Shuttle, Commercial applications, especially in sealing fractures, dents, and holes in thin aluminum face sheets or clad brazing sheet in cold plates, heat exchangers, coolers, and Solar panels. While particularly suited to thin aluminum sheet, this process also used in thicker aluminum material to prevent surface damage near weld area.

Modeling the Alzheimer Abeta17-42 fibril architecture: tight intermolecular sheet-sheet association and intramolecular hydrated cavities.

Science.gov (United States)

Zheng, Jie; Jang, Hyunbum; Ma, Buyong; Tsai, Chung-Jun; Nussinov, Ruth

2007-11-01

We investigate Abeta(17-42) protofibril structures in solution using molecular dynamics simulations. Recently, NMR and computations modeled the Abeta protofibril as a longitudinal stack of U-shaped molecules, creating an in-parallel beta-sheet and loop spine. Here we study the molecular architecture of the fibril formed by spine-spine association. We model in-register intermolecular beta-sheet-beta-sheet associations and study the consequences of Alzheimer's mutations (E22G, E22Q, E22K, and M35A) on the organization. We assess the structural stability and association force of Abeta oligomers with different sheet-sheet interfaces. Double-layered oligomers associating through the C-terminal-C-terminal interface are energetically more favorable than those with the N-terminal-N-terminal interface, although both interfaces exhibit high structural stability. The C-terminal-C-terminal interface is essentially stabilized by hydrophobic and van der Waals (shape complementarity via M35-M35 contacts) intermolecular interactions, whereas the N-terminal-N-terminal interface is stabilized by hydrophobic and electrostatic interactions. Hence, shape complementarity, or the "steric zipper" motif plays an important role in amyloid formation. On the other hand, the intramolecular Abeta beta-strand-loop-beta-strand U-shaped motif creates a hydrophobic cavity with a diameter of 6-7 A, allowing water molecules and ions to conduct through. The hydrated hydrophobic cavities may allow optimization of the sheet association and constitute a typical feature of fibrils, in addition to the tight sheet-sheet association. Thus, we propose that Abeta fiber architecture consists of alternating layers of tight packing and hydrated cavities running along the fibrillar axis, which might be possibly detected by high-resolution imaging.

Sheet pinch devices

International Nuclear Information System (INIS)

Anderson, O.A.; Baker, W.R.; Ise, J. Jr.; Kunkel, W.B.; Pyle, R.V.; Stone, J.M.

1958-01-01

Three types of sheet-like discharges are being studied at Berkeley. The first of these, which has been given the name 'Triax', consists of a cylindrical plasma sleeve contained between two coaxial conducting cylinders A theoretical analysis of the stability of the cylindrical sheet plasma predicts the existence of a 'sausage-mode' instability which is, however, expected to grow more slowly than in the case of the unstabilized linear pinch (by the ratio of the radial dimensions). The second pinch device employs a disk shaped discharge with radial current guided between flat metal plates, this configuration being identical to that of the flat hydromagnetic capacitor without external magnetic field. A significant feature of these configurations is the absence of a plasma edge, i.e., there are no regions of sharply curved magnetic field lines anywhere in these discharges. The importance of this fact for stability is not yet fully investigated theoretically. As a third configuration a rectangular, flat pinch tube has been constructed, and the behaviour of a flat plasma sheet with edges is being studied experimentally

Global and stochastic analysis approach to bosonic strings and associated quantum fields

Energy Technology Data Exchange (ETDEWEB)

Albeverio, S.; Hoeegh-Krohn, R.; Paycha, S.; Scarlatti, S.

1989-01-01

We construct a probability measure giving a mathematical realization of Polyakov's heuristic measure for bosonic strings in space-time dimensions 3 less than or equal to d less than or equal to 13, having as world sheet compact Riemann surfaces ..lambda.. of arbitrary genus. The measure involves the path space measures for scalar fields with exponential interaction on ..lambda.. and a measure on Teichmueller space.

A computational exploration of the McCoy-Tracy-Wu solutions of the third Painlevé equation

Science.gov (United States)

Fasondini, Marco; Fornberg, Bengt; Weideman, J. A. C.

2018-01-01

The method recently developed by the authors for the computation of the multivalued Painlevé transcendents on their Riemann surfaces (Fasondini et al., 2017) is used to explore families of solutions to the third Painlevé equation that were identified by McCoy et al. (1977) and which contain a pole-free sector. Limiting cases, in which the solutions are singular functions of the parameters, are also investigated and it is shown that a particular set of limiting solutions is expressible in terms of special functions. Solutions that are single-valued, logarithmically (infinitely) branched and algebraically branched, with any number of distinct sheets, are encountered. The algebraically branched solutions have multiple pole-free sectors on their Riemann surfaces that are accounted for by using asymptotic formulae and Bäcklund transformations.

Effect of Cell Sheet Manipulation Techniques on the Expression of Collagen Type II and Stress Fiber Formation in Human Chondrocyte Sheets.

Science.gov (United States)

Wongin, Sopita; Waikakul, Saranatra; Chotiyarnwong, Pojchong; Siriwatwechakul, Wanwipa; Viravaidya-Pasuwat, Kwanchanok

2018-03-01

Cell sheet technology is applied to human articular chondrocytes to construct a tissue-like structure as an alternative treatment for cartilage defect. The effect of a gelatin manipulator, as a cell sheet transfer system, on the quality of the chondrocyte sheets was investigated. The changes of important chondrogenic markers and stress fibers, resulting from the cell sheet manipulation, were also studied. The chondrocyte cell sheets were constructed with patient-derived chondrocytes using a temperature-responsive polymer and a gelatin manipulator as a transfer carrier. The properties of the cell sheets, including sizes, expression levels of collagen type II and I, and the localization of the stress fibers, were assessed and compared with those of the cell sheets harvested without the gelatin manipulator. Using the gelatin manipulator, the original size of the chondrocyte cell sheets was retained with abundant stress fibers, but with a decrease in the expression of collagen type II. Without the gelatin manipulator, although the cell shrinkage occurred, the cell sheet with suppressed stress fiber formation showed significantly higher levels of collagen type II. These results support our observations that stress fiber formation in chondrocyte cell sheets affected the production of chondrogenic markers. These densely packed tissue-like structures possessed a good chondrogenic activity, indicating their potential for use in autologous chondrocyte implantation to treat cartilage defects.

Settlement during vibratory sheet piling

NARCIS (Netherlands)

Meijers, P.

2007-01-01

During vibratory sheet piling quite often the soil near the sheet pile wall will settle. In many cases this is not a problem. For situations with houses, pipelines, roads or railroads at relative short distance these settlements may not be acceptable. The purpose of the research described in this

49 CFR 1243.2 - Condensed balance sheet.

Science.gov (United States)

2010-10-01

... 49 Transportation 9 2010-10-01 2010-10-01 false Condensed balance sheet. 1243.2 Section 1243.2... § 1243.2 Condensed balance sheet. Commencing with reports for the 3 months beginning January 1, 1972, and... hereby, required to compile and file quarterly reports of balance sheet items in accordance with...

Electron energization in the geomagnetic tail current sheet

International Nuclear Information System (INIS)

Lyons, L.R.

1984-01-01

Electron motion in the distant tail current sheet is evaluated and found to violate the guiding center approximation at energies > or approx. =100 eV. Most electrons within the energy range approx.10 -1 -10 2 keV that enter the current sheet become trapped within the magnetic field reversal region. These electrons then convect earthward and gain energy from the cross-tail electric field. If the energy spectrum of electrons entering the current sheet is similar to that of electrons from the boundary layer surrounding the magnetotail, the energy gain from the electric field produces electron energy spectra comparable to those observed in the earth's plasma sheet. Thus current sheet interactions can be a significant source of particles and energy for plasma sheet electrons as well as for plasma sheet ions. A small fraction of electrons within the current sheet has its pitch angles scattered so as to be ejected from the current sheet within the atmospheric loss cone. These electrons can account for the electron precipitation near the high-latitude boundary of energetic electrons, which is approximately isotropic in pitch angle up to at least several hundred keV. Current sheet interaction should cause approximately isotropic auroral precipitation up to several hundred keV energies, which extends to significantly lower latitudes for ions than for electrons in agreement with low-altitude satellite observations. Electron precipitation associated with diffuse aurora generally has a transition at 1-10 keV to anisotropic pitch angle distributions. Such electron precipitation cannot be explained by current sheet interactions, but it can be explained by pitch angle diffusion driven by plasma turbulence

Bessel light sheet structured illumination microscopy

Science.gov (United States)

Noshirvani Allahabadi, Golchehr

Biomedical study researchers using animals to model disease and treatment need fast, deep, noninvasive, and inexpensive multi-channel imaging methods. Traditional fluorescence microscopy meets those criteria to an extent. Specifically, two-photon and confocal microscopy, the two most commonly used methods, are limited in penetration depth, cost, resolution, and field of view. In addition, two-photon microscopy has limited ability in multi-channel imaging. Light sheet microscopy, a fast developing 3D fluorescence imaging method, offers attractive advantages over traditional two-photon and confocal microscopy. Light sheet microscopy is much more applicable for in vivo 3D time-lapsed imaging, owing to its selective illumination of tissue layer, superior speed, low light exposure, high penetration depth, and low levels of photobleaching. However, standard light sheet microscopy using Gaussian beam excitation has two main disadvantages: 1) the field of view (FOV) of light sheet microscopy is limited by the depth of focus of the Gaussian beam. 2) Light-sheet images can be degraded by scattering, which limits the penetration of the excitation beam and blurs emission images in deep tissue layers. While two-sided sheet illumination, which doubles the field of view by illuminating the sample from opposite sides, offers a potential solution, the technique adds complexity and cost to the imaging system. We investigate a new technique to address these limitations: Bessel light sheet microscopy in combination with incoherent nonlinear Structured Illumination Microscopy (SIM). Results demonstrate that, at visible wavelengths, Bessel excitation penetrates up to 250 microns deep in the scattering media with single-side illumination. Bessel light sheet microscope achieves confocal level resolution at a lateral resolution of 0.3 micron and an axial resolution of 1 micron. Incoherent nonlinear SIM further reduces the diffused background in Bessel light sheet images, resulting in

Magnetic configurations of the tilted current sheets in magnetotail

Directory of Open Access Journals (Sweden)

C. Shen

2008-11-01

Full Text Available In this research, the geometrical structures of tilted current sheet and tail flapping waves have been analysed based on multiple spacecraft measurements and some features of the tilted current sheets have been made clear for the first time. The geometrical features of the tilted current sheet revealed in this investigation are as follows: (1 The magnetic field lines (MFLs in the tilted current sheet are generally plane curves and the osculating planes in which the MFLs lie are about vertical to the equatorial plane, while the normal of the tilted current sheet leans severely to the dawn or dusk side. (2 The tilted current sheet may become very thin, the half thickness of its neutral sheet is generally much less than the minimum radius of the curvature of the MFLs. (3 In the neutral sheet, the field-aligned current density becomes very large and has a maximum value at the center of the current sheet. (4 In some cases, the current density is a bifurcated one, and the two humps of the current density often superpose two peaks in the gradient of magnetic strength, indicating that the magnetic gradient drift current is possibly responsible for the formation of the two humps of the current density in some tilted current sheets. Tilted current sheets often appear along with tail current sheet flapping waves. It is found that, in the tail flapping current sheets, the minimum curvature radius of the MFLs in the current sheet is rather large with values around 1 RE, while the neutral sheet may be very thin, with its half thickness being several tenths of RE. During the flapping waves, the current sheet is tilted substantially, and the maximum tilt angle is generally larger than 45°. The phase velocities of these flapping waves are several tens km/s, while their periods and wavelengths are several tens of minutes, and several earth radii, respectively. These tail flapping events generally last several hours and occur during quiet periods or periods of

Relativistic current sheets in electron-positron plasmas

International Nuclear Information System (INIS)

Zenitani, S.

2008-01-01

The current sheet structure with magnetic field reversal is one of the fundamental structure in space and astrophysical plasmas. It draws recent attention in high-energy astrophysical settings, where relativistic electron-positron plasmas are considered. In this talk we will review the recent progress of the physical processes in the relativistic current sheet. The kinetic stability of a single current sheet, the nonlinear behavior of these instabilities, and recent challenges on the multi current sheet systems are introduced. We will also introduce some problems of magnetic reconnection in these relativistic environments. (author)

Tube sheet design for PFBR steam generator

International Nuclear Information System (INIS)

Chellapandi, P.; Chetal, S.C.; Bhoje, S.B.

1991-01-01

Top and bottom tube sheets of PFBR Steam Generators have been analysed with 3D and axisymmetric models using CASTEM Programs. Analysis indicates that the effects of piping reactions at the inlet/outlet nozzles on the primary stresses in the tube sheets are negligible and the asymmetricity of the deformation pattern introduced in the tube sheet by the presence of inlet/outlet and manhole nozzles is insignificant. The minimum tube sheet thicknesses for evaporator and reheater are 135 mm and 75 mm respectively. Further analysis has indicated the minimum fillet radius at the junction of tube sheet and dished end should be 20 mm. Simplified methodology has been developed to arrive at the number of thermal baffles required to protect the tube sheet against fatigue damage due to thermal transient. This method has been applied to PFBR steam generators to determine the required number of thermal baffles. For protecting the bottom tube sheet of evaporator against the thermal shock due to feed water and secondary pump trip, one thermal shield is found to be sufficient. Further analysis is required to decide upon the actual number to take care of the severe thermal transient, following the event of sudden dumping of water/steam, immediately after the sodium-water reaction. (author)

17 CFR 210.5-02 - Balance sheets.

Science.gov (United States)

2010-04-01

... customers at the date of the balance sheet. Include a general description of the prerequisites for billing... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Balance sheets. 210.5-02... Balance sheets. The purpose of this rule is to indicate the various line items and certain additional...

Pressure balance between lobe and plasma sheet

International Nuclear Information System (INIS)

Baumjohann, W.; Paschmann, G.; Luehr, H.

1990-01-01

Using eight months of AMPTE/IRM plasma and magnetic field data, the authors have done a statistical survey on the balance of total (thermal and magnetic) pressure in the Earth's plasma sheet and tail lobe. About 300,000 measurements obtained in the plasma sheet and the lobe were compared for different levels of magnetic activity as well as different distances from the Earth. The data show that lobe and plasma sheet pressure balance very well. Even in the worst case they do not deviate by more than half of the variance in the data itself. Approximately constant total pressure was also seen during a quiet time pass when IRM traversed nearly the whole magnetotail in the vertical direction, from the southern hemisphere lobe through the neutral sheet and into the northern plasma sheet boundary layer

Thermomechanical processing of plasma sprayed intermetallic sheets

Science.gov (United States)

Hajaligol, Mohammad R.; Scorey, Clive; Sikka, Vinod K.; Deevi, Seetharama C.; Fleischhauer, Grier; Lilly, Jr., A. Clifton; German, Randall M.

2001-01-01

A powder metallurgical process of preparing a sheet from a powder having an intermetallic alloy composition such as an iron, nickel or titanium aluminide. The sheet can be manufactured into electrical resistance heating elements having improved room temperature ductility, electrical resistivity, cyclic fatigue resistance, high temperature oxidation resistance, low and high temperature strength, and/or resistance to high temperature sagging. The iron aluminide has an entirely ferritic microstructure which is free of austenite and can include, in weight %, 4 to 32% Al, and optional additions such as .ltoreq.1% Cr, .gtoreq.0.05% Zr .ltoreq.2% Ti, .ltoreq.2% Mo, .ltoreq.1% Ni, .ltoreq.0.75% C, .ltoreq.0.1% B, .ltoreq.1% submicron oxide particles and/or electrically insulating or electrically conductive covalent ceramic particles, .ltoreq.1% rare earth metal, and/or .ltoreq.3% Cu. The process includes forming a non-densified metal sheet by consolidating a powder having an intermetallic alloy composition such as by roll compaction, tape casting or plasma spraying, forming a cold rolled sheet by cold rolling the non-densified metal sheet so as to increase the density and reduce the thickness thereof and annealing the cold rolled sheet. The powder can be a water, polymer or gas atomized powder which is subjecting to sieving and/or blending with a binder prior to the consolidation step. After the consolidation step, the sheet can be partially sintered. The cold rolling and/or annealing steps can be repeated to achieve the desired sheet thickness and properties. The annealing can be carried out in a vacuum furnace with a vacuum or inert atmosphere. During final annealing, the cold rolled sheet recrystallizes to an average grain size of about 10 to 30 .mu.m. Final stress relief annealing can be carried out in the B2 phase temperature range.

17 CFR 210.7-03 - Balance sheets.

Science.gov (United States)

2010-04-01

... 17 Commodity and Securities Exchanges 2 2010-04-01 2010-04-01 false Balance sheets. 210.7-03... 1940, AND ENERGY POLICY AND CONSERVATION ACT OF 1975 Insurance Companies § 210.7-03 Balance sheets. (a... otherwise permitted by the Commission, should appear on the face of the balance sheets and in the notes...

Disposal sheet for preventing scattering of radioactive contaminated material

International Nuclear Information System (INIS)

Miyasaka, Shun-ichi; Kurioka, Hitoshi; Nakamura, Kenjiro.

1990-01-01

Upon disposal of vinyl sheets at the final stage of dismantling operation for nuclear buildings, etc., radioactive contaminated materials caused by cutting concretes, etc. remain on the sheets. In view of the above, members capable of restoring original shape due to the temperature difference are attached to the sheet main body so that the sheet main body may be folded into a bag-like shape. Since the members as described above are bent upon temperature elevation in the sheets, the sheet main body is pulled by the members and then spontaneously folded into a bag-like shape. As a result, the radioactive contaminated materials remaining on the sheets are wrapped into the sheet main body free from touch to operator's hands or without scattering to the surrounding. This can prevent operator's external and internal exposure. (T.M.)

Single Point Incremental Forming using a Dummy Sheet

DEFF Research Database (Denmark)

Skjødt, Martin; Silva, Beatriz; Bay, Niels

2007-01-01

A new version of single point incremental forming (SPIF) is presented. This version includes a dummy sheet on top of the work piece, thus forming two sheets instead of one. The dummy sheet, which is in contact with the rotating tool pin, is discarded after forming. The new set-up influences....... The possible influence of friction between the two sheets is furthermore investigated. The results show that the use of a dummy sheet reduces wear of the work piece to almost zero, but also causes a decrease in formability. Bulging of the planar sides of the pyramid is reduced and surface roughness...

Neutron spatial distribution measurement with 6Li-contained thermoluminescent sheets

International Nuclear Information System (INIS)

Konnai, A.; Odano, N.; Sawamura, H.; Ozasa, N.; Ishikawa, Y.

2006-01-01

We have been developing a thermoluminescent (TL) sheet for photon dosimetry (TL sheet) with thermoluminescent material of LiF:Mg, Cu, P and a co-polymer of ethylene and tetrafluoroethylene. For the purpose of a development of simple method for neutron spatial distribution measurement, TL sheet for neutron detection (NTL sheet) is made by adding 94.7% enriched 6 LiF to TL sheet. TL material in TL sheet is directly excited by ionizing radiation whereas, in the case of neutron detection, TL material in NTL sheet is indirectly excited by neutron capture reaction. That is neutron distribution can be obtained with TL caused by α particle from 6 Li(n, α) 3 H reaction. Responses of NTL sheets to neutrons were examined at the neutron beam irradiation facility for Boron Neutron Capture Therapy (BNCT) in JRR-4 research reactor in Japan Atomic Energy Agency. TL and NTL sheets were exposed to striped and roundly distributed neutron fields. Attenuations of neutron flux in air and water were also observed using NTL sheets. TL sheets were also exposed on the same conditions and compared with NTL sheets. TL intensity ratios of NTL sheet to TL sheet were consistent with the calculated value from 6 Li content. Thermal neutron attenuation observed by NTL sheet also corresponded with the result measured by Au wire radioactivation and TLD chips, which were currently used in BNCT at JRR-4. These results were analyzed with by Monte Carlo simulation. The present results indicated that NTL sheet is applicable to measurement of neutron spatial distribution. (author)

On the possible eigenoscillations of neutral sheets

International Nuclear Information System (INIS)

Almeida, W.A.; Costa, J.M. da; Aruquipa, E.G.; Sudano, J.P.

1974-12-01

A neutral sheet model with hyperbolic tangent equilibrium magnetic field and hyperbolic square secant density profiles is considered. It is shown that the equation for small oscillations takes the form of an eigenvalue oscillation problem. Computed eigenfrequencies of the geomagnetic neutral sheet were found to be in the range of the resonant frequencies of the geomagnetic plasma sheet computed by other authors

Uranium mining sites - Thematic sheets

International Nuclear Information System (INIS)

2009-01-01

A first sheet proposes comments, data and key numbers about uranium extraction in France: general overview of uranium mining sites, status of waste rock and tailings after exploitation, site rehabilitation. The second sheet addresses the sources of exposure to ionizing radiations due to ancient uranium mining sites: discussion on the identification of these sources associated with these sites, properly due to mining activities or to tailings, or due to the transfer of radioactive substances towards water and to the contamination of sediments, description of the practice and assessment of radiological control of mining sites. A third sheet addresses the radiological exposure of public to waste rocks, and the dose assessment according to exposure scenarios: main exposure ways to be considered, studied exposure scenarios (passage on backfilled path and grounds, stay in buildings built on waste rocks, keeping mineralogical samples at home). The fourth sheet addresses research programmes of the IRSN on uranium and radon: epidemiological studies (performed on mine workers; on French and on European cohorts, French and European studies on the risk of lung cancer associated with radon in housing), study of the biological effects of chronic exposures. The last sheet addresses studies and expertises performed by the IRSN on ancient uranium mining sites in France: studies commissioned by public authorities, radioactivity control studies performed by the IRSN about mining sites, participation of the IRSN to actions to promote openness to civil society

Sheet, ligament and droplet formation in swirling primary atomization

Directory of Open Access Journals (Sweden)

Changxiao Shao

2018-04-01

Full Text Available We report direct numerical simulations of swirling liquid atomization to understand the physical mechanism underlying the sheet breakup of a non-turbulent liquid swirling jet which lacks in-depth investigation. The volume-of-fluid (VOF method coupled with adapted mesh refinement (AMR technique in GERRIS code is employed in the present simulation. The mechanisms of sheet, ligament and droplet formation are investigated. It is observed that the olive-shape sheet structure is similar to the experimental result qualitatively. The numerical results show that surface tension, pressure difference and swirling effect contribute to the contraction and extension of liquid sheet. The ligament formation is partially at the sheet rim or attributed to the extension of liquid hole. Especially, the movement of hairpin vortex exerts by an anti-radial direction force to the sheet surface and leads to the sheet thinness. In addition, droplet formation is attributed to breakup of ligament and central sheet.

Sheet, ligament and droplet formation in swirling primary atomization

Science.gov (United States)

Shao, Changxiao; Luo, Kun; Chai, Min; Fan, Jianren

2018-04-01

We report direct numerical simulations of swirling liquid atomization to understand the physical mechanism underlying the sheet breakup of a non-turbulent liquid swirling jet which lacks in-depth investigation. The volume-of-fluid (VOF) method coupled with adapted mesh refinement (AMR) technique in GERRIS code is employed in the present simulation. The mechanisms of sheet, ligament and droplet formation are investigated. It is observed that the olive-shape sheet structure is similar to the experimental result qualitatively. The numerical results show that surface tension, pressure difference and swirling effect contribute to the contraction and extension of liquid sheet. The ligament formation is partially at the sheet rim or attributed to the extension of liquid hole. Especially, the movement of hairpin vortex exerts by an anti-radial direction force to the sheet surface and leads to the sheet thinness. In addition, droplet formation is attributed to breakup of ligament and central sheet.

Copper contamination in thin stainless steel sheet

International Nuclear Information System (INIS)

Holbert, R.K. Jr.; Dobbins, A.G.; Bennett, R.K. Jr.

1986-01-01

The standard welding technique used at Oak Ridge Y-12 Plant for joining thin stainless sheet is the gas tungsten arc (GTA) welding process. One of the reoccurring problems with the sheet welds is surface cracking in the heat-affected zone (HAZ). Metallography shows that the cracks are only about 0.05 mm (0.002 in.) deep which is significant in a 0.25 mm (0.01 in.) thick sheet. Thus, welding requirements do not permit any surfacing cracking as detected by a fluorescent dye penetrant test conducted on every part after welding. Surface cracks have been found in both of the two most common weld designs in the thin sheet fabricated at the Oak Ridge Y-12 Plant. These butt joints are welded between two 0.25 mm thick stainless steel sheets and a tube with eyelet welded to a 25 mm (0.98 in.) thick sheet. The weld between the two sheets is made on a semiautomatic seam welding unit, whereas the tube-to-eyelet-to-sheet welds are done manually. The quality of both welds is very dependent on the welding procedure and the way the parts are placed in the weld fixturing. Metallographic examination has indicated that some welded parts with surface cracking in the weld region had copper particles on the surface, and the question of copper contamination has been raised. With the aid of a scanning electron microscope and an electron microprobe, the existence of copper in an around the surface cracks has been verified. The copper is on the surface of the parts prior to welding in the form of small dust particles

World-sheet gauge fields in superstrings

International Nuclear Information System (INIS)

Porrati, M.; Tomboulis, E.T.

1989-01-01

We investigate the introduction of world-sheet 2-dimensional gauge fields in a manner consistent with world-sheet supersymmetry. We obtain the effective string action resulting from the exact integration over the world-sheet gauge fields to show that it generally describes string models with spontaneous breaking of gauge symmetries with continuous breaking parameters. We examine the question of spacetime supersymmetry spontaneous breaking, and show that breaking with continuous, in particular arbitrarily small breaking parameters does not occur; only breaking for discrete values of parameters is possible. (orig.)

Bifurcation of Jovian magnetotail current sheet

Directory of Open Access Journals (Sweden)

P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the Bx-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Environmental constraints on West Antarctic ice-sheet formation

Energy Technology Data Exchange (ETDEWEB)

Lindstrom, D R; MacAyeal, D R

1987-01-01

Small perturbations in Antarctic environmental conditions can culminate in the demise of the Antarctic ice sheet's western sector. This may have happened during the last interglacial period, and could recur within the next millennium due to atmospheric warming from trace gas and CO/sub 2/ increases. In this study, we investigate the importance of sea-level, accumulation rate, and ice influx from the East Antarctic ice sheet in the re-establishment of the West Antarctic ice sheet from a thin cover using a time-dependent numerical ice-shelf model. Our results show that a precursor to the West Antarctic ice sheet can form within 3000 years. Sea-level lowering caused by ice-sheet development in the Northern Hemisphere has the greatest environmental influence. Under favorable conditions, ice grounding occurs over all parts of the West Antarctic ice sheet except up-stream of Thwaites Glacier and in the Ross Sea region.

Hydrothermal growth of upright-standing ZnO sheet microcrystals

International Nuclear Information System (INIS)

Shi, Ruixia; Yang, Ping; Dong, Xiaobin; Jia, Changchao; Li, Jia

2014-01-01

Highlights: • Upright-standing ZnO sheet microcrystals were hydrothermally fabricated. • The ZnO sheets were prepared with sodium oxalate at 70 °C without any surfactant. • The preferable adsorption of oxalate anions causes the formation of ZnO sheet. • The continuous growth in six directions leads to the formation of hexagonal sheets. - Abstract: Large-scale upright-standing ZnO sheet microcrystals were fabricated on Zn substrate using sodium oxalate as structure-directing agent by a hydrothermal method at low temperature (70 °C) without any surfactant. The sheets are about 3–5 μm in dimension and 100–300 nm in thickness. The strong and narrow diffraction peaks of ZnO indicate that the sample has a good crystallinity and size. The morphology of sheet-like ZnO varied with the concentrations of sodium oxalate and reaction time. The sheet-like ZnO would transform into rod-like ones when sodium oxalate was substituted by equivalent sodium acetate. The formation of sheet-like ZnO is attributed to the preferable adsorption of oxalate anions on (0 0 0 1) face of ZnO, which inhibits the intrinsic growth of ZnO. Additionally, the continuous growth in six (0 1 −1 0) directions that have the lowest surface energy leads to the formation of hexagonal sheets

12 CFR 615.5211 - Risk categories-balance sheet assets.

Science.gov (United States)

2010-01-01

... 12 Banks and Banking 6 2010-01-01 2010-01-01 false Risk categories-balance sheet assets. 615.5211...—balance sheet assets. Section 615.5210(c) specifies certain balance sheet assets that are not assigned to the risk categories set forth below. All other balance sheet assets are assigned to the percentage...

The plasma sheet boundary and Ksub(p)

International Nuclear Information System (INIS)

Freeman, J.W.

1975-01-01

Freeman and Maguire (1967) first drew attention to the intrusion of energetic plasma from the tail to the geostationary orbit during geomagnetically disturbed times. Vasyliunas (1968) reported a correlation between the inward extension of the inner boundary of the plasma sheet and the Ksub(p) index and pointed out that the plasma sheet could occasionally reach the geostationary orbit distance. More recently McIlwain (1972) using the more refined detectors aboard the ATS-5 geostationary space-craft, has emphasized the correlation between the location of the plasma sheet boundary along the ATS orbit and geomagnetic activity. Using some older but unpublished data from the Suprathermal Ion Detector aboard the ATS-1 geostationary satellite, the relation between the local time occurrence of the plasma sheet at the geostationary orbit (6.6Rsub(E)) and Ksub(p) index is reported and then a relationship for the shift in the plasma sheet radial position is derived. (Auth.)

Surface elevation changes of the greenland ice sheet - results from ESA'S ice sheet CCI

DEFF Research Database (Denmark)

Fredenslund Levinsen, Joanna; Khvorostovky, Kirill; Meister, Rakia

2013-01-01

In order to ensure long-term climate data records for the Greenland Ice Sheet (GIS), ESA have launched the Climate Change Initiative (CCI). This work presents the preliminary steps towards the Ice Sheet CCI's surface elevation change (SEC) derivation using radar altimeter data. In order to find...... the most optimal method, a Round Robin exercise was conducted in which the scientific community was asked to provide their best SEC estimate over the Jakobshavn Isbr drainage basin. The participants used both repeat-track (RT), overlapping footprints, and the cross-over (XO) methods, and both ICESat laser...... and Envisat radar altimeter data were used. Based on this and feedback sheets describing their methods we found that a combination of the RT and XO techniques yielded the best results. In the following, the obtained results will be presented and discussed....

Probability based hydrologic catchments of the Greenland Ice Sheet

Science.gov (United States)

Hudson, B. D.

2015-12-01

Greenland Ice Sheet melt water impacts ice sheet flow dynamics, fjord and coastal circulation, and sediment and biogeochemical fluxes. Melt water exiting the ice sheet also is a key term in its mass balance. Because of this, knowledge of the area of the ice sheet that contributes melt water to a given outlet (its hydrologic catchment) is important to many ice sheet studies and is especially critical to methods using river runoff to assess ice sheet mass balance. Yet uncertainty in delineating ice sheet hydrologic catchments is a problem that is rarely acknowledged. Ice sheet catchments are delineated as a function of both basal and surface topography. While surface topography is well known, basal topography is less certain because it is dependent on radar surveys. Here, I a present a Monte Carlo based approach to delineating ice sheet catchments that quantifies the impact of uncertain basal topography. In this scheme, over many iterations I randomly vary the ice sheet bed elevation within published error bounds (using Morlighem et al., 2014 bed and bed error datasets). For each iteration of ice sheet bed elevation, I calculate the hydraulic potentiometric surface and route water over its path of 'steepest' descent to delineate the catchment. I then use all realizations of the catchment to arrive at a probability map of all major melt water outlets in Greenland. I often find that catchment size is uncertain, with small, random perturbations in basal topography leading to large variations in catchments size. While some catchments are well defined, others can double or halve in size within published basal topography error bars. While some uncertainty will likely always remain, this work points to locations where studies of ice sheet hydrology would be the most successful, allows reinterpretation of past results, and points to where future radar surveys would be most advantageous.

On the balance of stresses in the plasma sheet.

Science.gov (United States)

Rich, F. J.; Wolf, R. A.; Vasyliunas, V. M.

1972-01-01

The stress resulting from magnetic tension on the neutral sheet must, in a steady state, be balanced by any one or a combination of (1) a pressure gradient in the direction along the axis of the tail, (2) a similar gradient of plasma flow kinetic energy, and (3) the tension resulting from a pressure anisotropy within the plasma sheet. Stress balance in the first two cases requires that the ratios h/LX and BZ/BX be of the same order of magnitude, where h is the half-thickness of the neutral sheet, LX is the length scale for variations along the axis of the tail, and BZ and BX are the magnetic field components in the plasma sheet just outside the neutral sheet. The second case requires, in addition, that the plasma flow speed within the neutral sheet be of the order of or larger than the Alfven speed outside the neutral sheet. Stress balance in the third case requires that just outside the neutral sheet the plasma pressure obey the marginal firehose stability condition.

Thermal Transport Properties of Dry Spun Carbon Nanotube Sheets

Directory of Open Access Journals (Sweden)

Heath E. Misak

2016-01-01

Full Text Available The thermal properties of carbon nanotube- (CNT- sheet were explored and compared to copper in this study. The CNT-sheet was made from dry spinning CNTs into a nonwoven sheet. This nonwoven CNT-sheet has anisotropic properties in in-plane and out-of-plane directions. The in-plane direction has much higher thermal conductivity than the out-of-plane direction. The in-plane thermal conductivity was found by thermal flash analysis, and the out-of-plane thermal conductivity was found by a hot disk method. The thermal irradiative properties were examined and compared to thermal transport theory. The CNT-sheet was heated in the vacuum and the temperature was measured with an IR Camera. The heat flux of CNT-sheet was compared to that of copper, and it was found that the CNT-sheet has significantly higher specific heat transfer properties compared to those of copper. CNT-sheet is a potential candidate to replace copper in thermal transport applications where weight is a primary concern such as in the automobile, aircraft, and space industries.

Nonparaxial Bessel and Bessel–Gauss pincers light-sheets

Energy Technology Data Exchange (ETDEWEB)

Mitri, F.G., E-mail: F.G.Mitri@ieee.org

2017-01-23

Highlights: • Bessel and Bessel–Gauss autofocusing light sheets (i.e. beams in 2D) are developed. • The light-sheets are synthesized based on the angular spectrum decomposition method. • Computations of the scattering, radiation force and torque benefit from the solutions. - Abstract: Nonparaxial optical Bessel and Bessel–Gauss pincers optical-sheets are introduced based upon the angular spectrum decomposition in plane waves. The angular spectrum function and the beam-shape coefficients are expressed by means of improper integrals computed numerically. The radiated component of the electric field is also evaluated, displaying unique features of the nonparaxial Bessel pincers light-sheets. This new type of auto-focusing light-sheets finds potential applications in the development of novel methods in optical light-sheet tweezers for particle manipulation in opto-fluidics, particle sizing and imaging. Numerical predictions for the scattering, radiation force and torque, and particle dynamics also benefit from the developed beam solution.

Nonparaxial Bessel and Bessel–Gauss pincers light-sheets

International Nuclear Information System (INIS)

Mitri, F.G.

2017-01-01

Highlights: • Bessel and Bessel–Gauss autofocusing light sheets (i.e. beams in 2D) are developed. • The light-sheets are synthesized based on the angular spectrum decomposition method. • Computations of the scattering, radiation force and torque benefit from the solutions. - Abstract: Nonparaxial optical Bessel and Bessel–Gauss pincers optical-sheets are introduced based upon the angular spectrum decomposition in plane waves. The angular spectrum function and the beam-shape coefficients are expressed by means of improper integrals computed numerically. The radiated component of the electric field is also evaluated, displaying unique features of the nonparaxial Bessel pincers light-sheets. This new type of auto-focusing light-sheets finds potential applications in the development of novel methods in optical light-sheet tweezers for particle manipulation in opto-fluidics, particle sizing and imaging. Numerical predictions for the scattering, radiation force and torque, and particle dynamics also benefit from the developed beam solution.

Bifurcation of Jovian magnetotail current sheet

Directory of Open Access Journals (Sweden)

P. L. Israelevich

2006-07-01

Full Text Available Multiple crossings of the magnetotail current sheet by a single spacecraft give the possibility to distinguish between two types of electric current density distribution: single-peaked (Harris type current layer and double-peaked (bifurcated current sheet. Magnetic field measurements in the Jovian magnetic tail by Voyager-2 reveal bifurcation of the tail current sheet. The electric current density possesses a minimum at the point of the B_x-component reversal and two maxima at the distance where the magnetic field strength reaches 50% of its value in the tail lobe.

Buckling Behavior of Substrate Supported Graphene Sheets

Directory of Open Access Journals (Sweden)

Kuijian Yang

2016-01-01

Full Text Available The buckling of graphene sheets on substrates can significantly degrade their performance in materials and devices. Therefore, a systematic investigation on the buckling behavior of monolayer graphene sheet/substrate systems is carried out in this paper by both molecular mechanics simulations and theoretical analysis. From 70 simulation cases of simple-supported graphene sheets with different sizes under uniaxial compression, two different buckling modes are investigated and revealed to be dominated by the graphene size. Especially, for graphene sheets with length larger than 3 nm and width larger than 1.1 nm, the buckling mode depends only on the length/width ratio. Besides, it is revealed that the existence of graphene substrate can increase the critical buckling stress and strain to 4.39 N/m and 1.58%, respectively, which are about 10 times those for free-standing graphene sheets. Moreover, for graphene sheets with common size (longer than 20 nm, both theoretical and simulation results show that the critical buckling stress and strain are dominated only by the adhesive interactions with substrate and independent of the graphene size. Results in this work provide valuable insight and guidelines for the design and application of graphene-derived materials and nano-electromechanical systems.

Lateral dimension-dependent antibacterial activity of graphene oxide sheets.

Science.gov (United States)

Liu, Shaobin; Hu, Ming; Zeng, Tingying Helen; Wu, Ran; Jiang, Rongrong; Wei, Jun; Wang, Liang; Kong, Jing; Chen, Yuan

2012-08-21

Graphene oxide (GO) is a promising precursor to produce graphene-family nanomaterials for various applications. Their potential health and environmental impacts need a good understanding of their cellular interactions. Many factors may influence their biological interactions with cells, and the lateral dimension of GO sheets is one of the most relevant material properties. In this study, a model bacterium, Escherichia coli ( E. coli ), was used to evaluate the antibacterial activity of well-dispersed GO sheets, whose lateral size differs by more than 100 times. Our results show that the antibacterial activity of GO sheets toward E. coli cells is lateral size dependent. Larger GO sheets show stronger antibacterial activity than do smaller ones, and they have different time- and concentration-dependent antibacterial activities. Large GO sheets lead to most cell loss after 1 h incubation, and their concentration strongly influences antibacterial activity at relative low concentration (oxidation capacity toward glutathione is similar, consistent with X-ray photoelectron spectroscopy and ultraviolet-visible absorption spectroscopy results. This suggests the lateral size-dependent antibacterial activity of GO sheets is caused by neither their aggregation states, nor oxidation capacity. Atomic force microscope analysis of GO sheets and cells shows that GO sheets interact strongly with cells. Large GO sheets more easily cover cells, and cells cannot proliferate once fully covered, resulting in the cell viability loss observed in the followed colony counting test. In contrast, small GO sheets adhere to the bacterial surfaces, which cannot effectively isolate cells from environment. This study highlights the importance of tailoring the lateral dimension of GO sheets to optimize the application potential with minimal risks for environmental health and safety.

Fabrication of Carbon Nanotube Polymer Actuator Using Nanofiber Sheet

Science.gov (United States)

Kato, Hayato; Shimizu, Akikazu; Sato, Taiga; Kushida, Masahito

2017-11-01

Carbon nanotube polymer actuators were developed using composite nanofiber sheets fabricated by multi-walled carbon nanotubes(MWCNTs) and poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP). Nanofiber sheets were fabricated by electrospinning method. The effect of flow rate and polymer concentration on nanofiber formation were verified for optimum condition for fabricating nanofiber sheets. We examined the properties of MWCNT/PVDF-HFP nanofiber sheets, as follows. Electrical conductivity and mechanical strength increased as the MWCNT weight ratio increased. We fabricated carbon nanotube polymer actuators using MWCNT/PVDF-HFP nanofiber sheets and succeeded in operating of our actuators.

Global ice sheet/RSL simulations using the higher-order Ice Sheet System Model.

Science.gov (United States)

Larour, E. Y.; Ivins, E. R.; Adhikari, S.; Schlegel, N.; Seroussi, H. L.; Morlighem, M.

2017-12-01

Relative sea-level rise is driven by processes that are intimately linked to the evolution ofglacial areas and ice sheets in particular. So far, most Earth System models capable of projecting theevolution of RSL on decadal to centennial time scales have relied on offline interactions between RSL andice sheets. In particular, grounding line and calving front dynamics have not been modeled in a way that istightly coupled with Elasto-Static Adjustment (ESA) and/or Glacial-Isostatic Adjustment (GIA). Here, we presenta new simulation of the entire Earth System in which both Greenland and Antarctica ice sheets are tightly coupledto an RSL model that includes both ESA and GIA at resolutions and time scales compatible with processes suchas grounding line dynamics for Antarctica ice shelves and calving front dynamics for Greenland marine-terminatingglaciers. The simulations rely on the Ice Sheet System Model (ISSM) and show the impact of higher-orderice flow dynamics and coupling feedbacks between ice flow and RSL. We quantify the exact impact of ESA andGIA inclusion on grounding line evolution for large ice shelves such as the Ronne and Ross ice shelves, as well asthe Agasea Embayment ice streams, and demonstate how offline vs online RSL simulations diverge in the long run,and the consequences for predictions of sea-level rise.This work was performed at the California Institute of Technology's Jet Propulsion Laboratory undera contract with the National Aeronautics and Space Administration's Cryosphere Science Program.

Coupling of climate models and ice sheet models by surface mass balance gradients: application to the Greenland Ice Sheet

Directory of Open Access Journals (Sweden)

M. M. Helsen

2012-03-01

Full Text Available It is notoriously difficult to couple surface mass balance (SMB results from climate models to the changing geometry of an ice sheet model. This problem is traditionally avoided by using only accumulation from a climate model, and parameterizing the meltwater run-off as a function of temperature, which is often related to surface elevation (H_s. In this study, we propose a new strategy to calculate SMB, to allow a direct adjustment of SMB to a change in ice sheet topography and/or a change in climate forcing. This method is based on elevational gradients in the SMB field as computed by a regional climate model. Separate linear relations are derived for ablation and accumulation, using pairs of H_s and SMB within a minimum search radius. The continuously adjusting SMB forcing is consistent with climate model forcing fields, also for initially non-glaciated areas in the peripheral areas of an ice sheet. When applied to an asynchronous coupled ice sheet – climate model setup, this method circumvents traditional temperature lapse rate assumptions. Here we apply it to the Greenland Ice Sheet (GrIS. Experiments using both steady-state forcing and glacial-interglacial forcing result in realistic ice sheet reconstructions.

Joining of Aluminium Alloy Sheets by Rectangular Mechanical Clinching

International Nuclear Information System (INIS)

Abe, Y.; Mori, K.; Kato, T.

2011-01-01

A mechanical clinching has the advantage of low running costs. However, the joint strength is not high. To improve the maximum load of the joined sheets by a mechanical clinching, square and rectangular mechanical clinching were introduced. In the mechanical clinching, the two sheets are mechanically joined by forming an interlock between the lower and upper sheets by the punch and die. The joined length with the interlock was increased by the rectangular punch and die. The deforming behaviours of the sheets in the mechanical clinching were investigated, and then the interlock in the sheets had distribution in the circumference of the projection. Although the interlocks were formed in both projection side and diagonal, the interlock in the diagonal was smaller because of the long contact length between the lower sheet and the die cavity surface. The maximum load of the joined sheets by the rectangular mechanical clinching was two times larger than the load by the round mechanical clinching.

The properties of bioengineered chondrocyte sheets for cartilage regeneration

Directory of Open Access Journals (Sweden)

Ota Naoshi

2009-03-01

Full Text Available Abstract Background Although the clinical results of autologous chondrocyte implantation for articular cartilage defects have recently improved as a result of advanced techniques based on tissue engineering procedures, problems with cell handling and scaffold imperfections remain to be solved. A new cell-sheet technique has been developed, and is potentially able to overcome these obstacles. Chondrocyte sheets applicable to cartilage regeneration can be prepared with this cell-sheet technique using temperature-responsive culture dishes. However, for clinical application, it is necessary to evaluate the characteristics of the cells in these sheets and to identify their similarities to naive cartilage. Results The expression of SOX 9, collagen type 2, 27, integrin α10, and fibronectin genes in triple-layered chondrocyte sheets was significantly increased in comparison to those in conventional monolayer culture and in a single chondrocyte sheet, implying a nature similar to ordinary cartilage. In addition, immunohistochemistry demonstrated that collagen type II, fibronectin, and integrin α10 were present in the triple-layered chondrocyte sheets. Conclusion The results of this study indicate that these chondrocyte sheets with a consistent cartilaginous phenotype and adhesive properties may lead to a new strategy for cartilage regeneration.

Fatigue characteristics of dual-phase steel sheets

Energy Technology Data Exchange (ETDEWEB)

Onn, Irwan Herman; Ahmad, Norhayati; Tamin, Mohd Nasir [Universiti Teknologi Malaysia, Skudai (Malaysia)

2015-01-15

Fatigue characteristics of dual-phase steel sheets, commonly used in automobile body construction were established. For this purpose, a series of fatigue tests, each at constant stress amplitude were conducted on 1.2 mm-thick, dual-phase DP600 steel sheet specimens with two different load ratios of minimum-to-maximum stress, R = 0.1 and -1. The resulting fatigue behavior is expressed in terms of fatigue strength-life (S-N) curves. Fatigue behavior of the steel sheets in the high-cycle fatigue region can be represented by Basquin's equation with coefficient and exponent value of 921.2 and 0.093, respectively. An endurance limit of 255 MPa is observed. In addition, fatigue strengths of the dual-phase steel sheets display lower magnitude than their bulk counterparts. Effect of mean stress on fatigue behavior of the steel sheets is well predicted by Walker's model. Exponential calibration factor is introduced to the models by SWT, Goodman and Morrow with comparable prediction to the Walker's model.

Dynamics of a radially expanding liquid sheet: Experiments

Science.gov (United States)

Majumdar, Nayanika; Tirumkudulu, Mahesh

2017-11-01

A recent theory predicts that sinuous waves generated at the center of a radially expanding liquid sheet grow spatially even in absence of a surrounding gas phase. Unlike flat liquid sheets, the thickness of a radially expanding liquid sheet varies inversely with distance from the center of the sheet. To test the predictions of the theory, experiments were carried out on a horizontal, radially expanding liquid sheet formed by collision of a single jet on a solid impactor. The latter was placed on a speaker-vibrator with controlled amplitude and frequency. The growth of sinuous waves was determined by measuring the wave surface inclination angle using reflected laser light under both atmospheric and sub-atmospheric pressure conditions. It is shown that the measured growth rate matches with the predictions of the theory over a large range of Weber numbers for both pressure conditions suggesting that the thinning of the liquid sheet plays a dominant role in setting the growth rate of sinuous waves with minimal influence of the surrounding gas phase on its dynamics. IIT Bombay.

Optimal swimming of a sheet.

Science.gov (United States)

Montenegro-Johnson, Thomas D; Lauga, Eric

2014-06-01

Propulsion at microscopic scales is often achieved through propagating traveling waves along hairlike organelles called flagella. Taylor's two-dimensional swimming sheet model is frequently used to provide insight into problems of flagellar propulsion. We derive numerically the large-amplitude wave form of the two-dimensional swimming sheet that yields optimum hydrodynamic efficiency: the ratio of the squared swimming speed to the rate-of-working of the sheet against the fluid. Using the boundary element method, we show that the optimal wave form is a front-back symmetric regularized cusp that is 25% more efficient than the optimal sine wave. This optimal two-dimensional shape is smooth, qualitatively different from the kinked form of Lighthill's optimal three-dimensional flagellum, not predicted by small-amplitude theory, and different from the smooth circular-arc-like shape of active elastic filaments.

Balance of the West Antarctic Ice Sheet

Science.gov (United States)

2002-01-01

For several decades, measurements of the West Antarctic Ice Sheet showed it to be retreating rapidly. But new data derived from satellite-borne radar sensors show the ice sheet to be growing. Changing Antarctic ice sheets remains an area of high scientific interest, particularly in light of recent global warming concerns. These new findings are significant because scientists estimate that sea level would rise 5-6 meters (16-20 feet) if the ice sheet collapsed into the sea. Do these new measurements signal the end of the ice sheet's 10,000-year retreat? Or, are these new satellite data simply much more accurate than the sparse ice core and surface measurements that produced the previous estimates? Another possibility is that the ice accumulation may simply indicate that the ice sheet naturally expands and retreats in regular cycles. Cryologists will grapple with these questions, and many others, as they examine the new data. The image above depicts the region of West Antarctica where scientists measured ice speed. The fast-moving central ice streams are shown in red. Slower tributaries feeding the ice streams are shown in blue. Green areas depict slow-moving, stable areas. Thick black lines depict the areas that collect snowfall to feed their respective ice streams. Reference: Ian Joughin and Slawek Tulaczyk Science Jan 18 2002: 476-480. Image courtesy RADARSAT Antarctic Mapping Project

Spina Bifida: General Information. Fact Sheet Number 12 = La Espina Bifida: Informacion General. Fact Sheet Number 12.

Science.gov (United States)

National Information Center for Children and Youth with Disabilities, Washington, DC.

This fact sheet offers definitions of the three types of spina bifida, outlines their incidence, describes characteristics of individuals with spina bifida, and reviews educational implications. The fact sheet emphasizes that school programs should be flexible to accommodate these students' special needs and frequent absences, that children with…

Ice Sheets & Ice Cores

DEFF Research Database (Denmark)

Mikkelsen, Troels Bøgeholm

Since the discovery of the Ice Ages it has been evident that Earth’s climate is liable to undergo dramatic changes. The previous climatic period known as the Last Glacial saw large oscillations in the extent of ice sheets covering the Northern hemisphere. Understanding these oscillations known....... The first part concerns time series analysis of ice core data obtained from the Greenland Ice Sheet. We analyze parts of the time series where DO-events occur using the so-called transfer operator and compare the results with time series from a simple model capable of switching by either undergoing...

Microstructure evolution of a dissimilar junction interface between an Al sheet and a Ni-coated Cu sheet joined by magnetic pulse welding

Energy Technology Data Exchange (ETDEWEB)

Itoi, Takaomi, E-mail: itoi@faculty.chiba-u.jp [Department of Mechanical Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Mohamad, Azizan Bin; Suzuki, Ryo [Department of Mechanical Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Okagawa, Keigo [Department of Electrical and Electronics Engineering, Tokyo Metropolitan College of Industrial Technology, 1-10-40 Higashi ohi, Shinagawa-ku, Tokyo 140-0011 (Japan)

2016-08-15

An Al sheet and a Ni-coated Cu sheet were lap joined by using magnetic pulse welding (MPW). Tensile tests were performed on the joined sheets, and a good lap joint was achieved at a discharge energy of > 0.9 kJ. The weld interface exhibited a wavy morphology and an intermediate layer along the weld interface. Microstructure observations of the intermediate layer revealed that the Ni coating region consisted of a Ni–Al binary amorphous alloy and that the Al sheet region contained very fine Al nanograins. Ni fragments indicative of unmelted residual Ni from the coating were also observed in parts of the intermediate layer. Formation of these features can be attributed to localize melting and a subsequent high rate cooling of molten Al and Ni confined to the interface during the MPW process. In the absence of an oxide film, atomic-scale bonding was also achieved between the intermediate layer and the sheet surfaces after the collision. MPW utilises impact energy, which affects the sheet surfaces. From the obtained results, good lap joint is attributed to an increased contact area, the anchor effect, work hardening, the absence of an oxide film, and suppressed formation of intermetallic compounds at the interface. - Highlights: •Good lap joint of an Al sheet and a Ni-coated Cu sheet was achieved by using magnetic pulse welding. •A Ni–Al binary amorphous alloy was formed as an intermediate layer at weld interface. •Atomic-scale bonding was achieved between the intermediate layer and the sheet surfaces.

Synthesis of nanometre-thick MoO3 sheets

Science.gov (United States)

Kalantar-Zadeh, Kourosh; Tang, Jianshi; Wang, Minsheng; Wang, Kang L.; Shailos, Alexandros; Galatsis, Kosmas; Kojima, Robert; Strong, Veronica; Lech, Andrew; Wlodarski, Wojtek; Kaner, Richard B.

2010-03-01

The formation of MoO3 sheets of nanoscale thickness is described. They are made from several fundamental sheets of orthorhombic α-MoO3, which can be processed in large quantities via a low cost synthesis route that combines thermal evaporation and mechanical exfoliation. These fundamental sheets consist of double-layers of linked distorted MoO6 octahedra. Atomic force microscopy (AFM) measurements show that the minimum resolvable thickness of these sheets is 1.4 nm which is equivalent to the thickness of two double-layers within one unit cell of the α-MoO3 crystal.

Fact Sheets on Pesticides in Schools.

Science.gov (United States)

National Coalition against the Misuse of Pesticides, Washington, DC.

This document consists of a collection of fact sheets about the use of pesticides in schools and how to reduce it. The sheets are: (1) "Alternatives to Using Pesticides in Schools: What Is Integrated Pest Management?"; (2) "Health Effects of 48 Commonly Used Pesticides in Schools"; (3) "The Schooling of State Pesticide…

Single clay sheets inside electrospun polymer nanofibers

Science.gov (United States)

Sun, Zhaohui

2005-03-01

Nanofibers were prepared from polymer solution with clay sheets by electrospinning. Plasma etching, as a well controlled process, was used to supply electrically excited gas molecules from a glow discharge. To reveal the structure and arrangement of clay layers in the polymer matrix, plasma etching was used to remove the polymer by controlled gasification to expose the clay sheets due to the difference in reactivity. The shape, flexibility, and orientation of clay sheets were studied by transmission and scanning electron microscopy. Additional quantitative information on size distribution and degree of exfoliation of clay sheets were obtained by analyzing electron micrograph of sample after plasma etching. Samples in various forms including fiber, film and bulk, were thinned by plasma etching. Morphology and dispersion of inorganic fillers were studied by electron microscopy.

Complex world-sheets from N=2 strings

International Nuclear Information System (INIS)

Barbon, J.L.F.

1996-01-01

We study some properties of target space strings constructed from (2,1) heterotic strings. We argue that world-sheet complexification is a general property of the bosonic sector of such target world-sheets. We give a target space interpretation of this fact and relate it to the non-gaussian nature of free string field theory. We provide several one-loop calculations supporting the stringy construction of critical world-sheets in terms of (2,1) models. Using finite-temperature boundary conditions in the underlying (2,1) string we obtain non-chiral target space spin structures, and point out some of the problems arising for chiral spin structures, such as the heterotic world-sheet. To this end, we study the torus partition function of the corresponding asymmetric orbifold of the (2,1) string. (orig.)

Motion and shape of snowplough sheets in coaxial accelerators

International Nuclear Information System (INIS)

Tsagas, N.F.; Mair, G.L.R.; Prinn, A.E.

1978-01-01

A long coaxial accelerator is filled with helium at initial gas pressure between 0.2 and 4 Torr. When connected to a large capacitor at < - 10 kV a discharge is started at one end; the central electrode has negative polarity. The velocity of the plasma sheet, the snowplough, and its shape have been derived from streak photographs for terminal currents between about 100 and 300 kA. The motion of the sheet has been analysed by balancing the electromagnetic driving force against the inertia of the mass of the gas swept up by a plane sheet taken to be impenetrable to gas atoms. The calculated positions and average sheet velocities, which involve simplifying assumptions, have been found to be in good agreement with observations at different positions and pressures. Also the shape of the sheet has been derived by allowing for the sheet's curvature in the linear momentum equation while net radial motions causing variations in profile have, at first, been excluded. The calculated shape of the sheet is very nearly that photographically observed. The axial velocity of a sheet element is evaluated under the assumption that the plasma is azimuthally uniform, free of spikes and that the vessel's wall does not affect the shape. (author)

Corrosion Behavior of Brazed Zinc-Coated Structured Sheet Metal

Directory of Open Access Journals (Sweden)

A. Nikitin

2017-01-01

Full Text Available Arc brazing has, in comparison to arc welding, the advantage of less heat input while joining galvanized sheet metals. The evaporation of zinc is reduced in the areas adjacent to the joint and improved corrosion protection is achieved. In the automotive industry, lightweight design is a key technology against the background of the weight and environment protection. Structured sheet metals have higher stiffness compared to typical automobile sheet metals and therefore they can play an important role in lightweight structures. In the present paper, three arc brazing variants of galvanized structured sheet metals were validated in terms of the corrosion behavior. The standard gas metal arc brazing, the pulsed arc brazing, and the cold metal transfer (CMT® in combination with a pulsed cycle were investigated. In experimental climate change tests, the influence of the brazing processes on the corrosion behavior of galvanized structured sheet metals was investigated. After that, the corrosion behavior of brazed structured and flat sheet metals was compared. Because of the selected lap joint, the valuation of damage between sheet metals was conducted. The pulsed CMT brazing has been derived from the results as the best brazing method for the joining process of galvanized structured sheet metals.

Orientation and Morphology Effects in Rapid Silicon Sheet Solidification

Science.gov (United States)

Ciszek, T. F.

1984-01-01

Radial growth anisotropies and equilibrium forms of point nucleated, dislocation free silicon sheets spreading horizontally on the free surface of a silicon melt were measured for (100), (110), (111), and (112) sheet planes. The growth process was recorded. Qualitative Wulff surface free energy polar plots were deduced from the equilibrium shapes for each sheet plane. Predicted geometries for the tip shape of unidirectional, dislocation free, horizontally grown sheets growing in various directions within the planes were analyzed. Polycrystalline sheets and dendrite propagation were analyzed. For dendrites, growth rates on the order of 2.5 m/min and growth rate anisotropies of 25 are measured.

47 CFR 32.101 - Structure of the balance sheet accounts.

Science.gov (United States)

2010-10-01

... 47 Telecommunication 2 2010-10-01 2010-10-01 false Structure of the balance sheet accounts. 32.101... UNIFORM SYSTEM OF ACCOUNTS FOR TELECOMMUNICATIONS COMPANIES Instructions for Balance Sheet Accounts § 32.101 Structure of the balance sheet accounts. The Balance Sheet accounts shall be maintained as follows...

Molding cork sheets to complex shapes

Science.gov (United States)

Sharpe, M. H.; Simpson, W. G.; Walker, H. M.

1977-01-01

Partially cured cork sheet is easily formed to complex shapes and then final-cured. Temperature and pressure levels required for process depend upon resin system used and final density and strength desired. Sheet can be bonded to surface during final cure, or can be first-formed in mold and bonded to surface in separate step.

Whooping Cough (Pertussis) - Fact Sheet for Parents

Science.gov (United States)

... months 4 through 6 years Fact Sheet for Parents Color [2 pages] Español: Tosferina (pertussis) The best ... according to the recommended schedule. Fact Sheets for Parents Diseases and the Vaccines that Prevent Them Chickenpox ...

Characterization of Tensile Mechanical Behavior of MSCs/PLCL Hybrid Layered Sheet

Directory of Open Access Journals (Sweden)

Azizah Intan Pangesty

2016-06-01

Full Text Available A layered construct was developed by combining a porous polymer sheet and a cell sheet as a tissue engineered vascular patch. The primary objective of this study is to investigate the influence of mesenchymal stem cells (MSCs sheet on the tensile mechanical properties of porous poly-(l-lactide-co-ε-caprolactone (PLCL sheet. The porous PLCL sheet was fabricated by the solid-liquid phase separation method and the following freeze-drying method. The MSCs sheet, prepared by the temperature-responsive dish, was then layered on the top of the PLCL sheet and cultured for 2 weeks. During the in vitro study, cellular properties such as cell infiltration, spreading and proliferation were evaluated. Tensile test of the layered construct was performed periodically to characterize the tensile mechanical behavior. The tensile properties were then correlated with the cellular properties to understand the effect of MSCs sheet on the variation of the mechanical behavior during the in vitro study. It was found that MSCs from the cell sheet were able to migrate into the PLCL sheet and actively proliferated into the porous structure then formed a new layer of MSCs on the opposite surface of the PLCL sheet. Mechanical evaluation revealed that the PLCL sheet with MSCs showed enhancement of tensile strength and strain energy density at the first week of culture which is characterized as the effect of MSCs proliferation and its infiltration into the porous structure of the PLCL sheet. New technique was presented to develop tissue engineered patch by combining MSCs sheet and porous PLCL sheet, and it is expected that the layered patch may prolong biomechanical stability when implanted in vivo.

The storm time central plasma sheet

Directory of Open Access Journals (Sweden)

R. Schödel

2002-11-01

Full Text Available The plasma sheet plays a key role during magnetic storms because it is the bottleneck through which large amounts of magnetic flux that have been eroded from the dayside magnetopause have to be returned to the dayside magnetosphere. Using about five years of Geotail data we studied the average properties of the near- and midtail central plasma sheet (CPS in the 10–30 RE range during magnetic storms. The earthward flux transport rate is greatly enhanced during the storm main phase, but shows a significant earthward decrease. Hence, since the magnetic flux cannot be circulated at a sufficient rate, this leads to an average dipolarization of the central plasma sheet. An increase of the specific entropy of the CPS ion population by a factor of about two during the storm main phase provides evidence for nonadiabatic heating processes. The direction of flux transport during the main phase is consistent with the possible formation of a near-Earth neutral line beyond ~20 RE.Key words. Magnetospheric physics (plasma convection; plasma sheet; storms and substorms

New directions in the science and technology of advanced sheet explosive formulations and the key energetic materials used in the processing of sheet explosives: Emerging trends.

Science.gov (United States)

Talawar, M B; Jangid, S K; Nath, T; Sinha, R K; Asthana, S N

2015-12-30

This review presents the work carried out by the international community in the area of sheet explosive formulations and its applications in various systems. The sheet explosive is also named as PBXs and is a composite material in which solid explosive particles like RDX, HMX or PETN are dispersed in a polymeric matrix, forms a flexible material that can be rolled/cut into sheet form which can be applied to any complex contour. The designed sheet explosive must possess characteristic properties such as flexible, cuttable, water proof, easily initiable, and safe handling. The sheet explosives are being used for protecting tanks (ERA), light combat vehicle and futuristic infantry carrier vehicle from different attacking war heads etc. Besides, sheet explosives find wide applications in demolition of bridges, ships, cutting and metal cladding. This review also covers the aspects such as risks and hazard analysis during the processing of sheet explosive formulations, effect of ageing on sheet explosives, detection and analysis of sheet explosive ingredients and the R&D efforts of Indian researchers in the development of sheet explosive formulations. To the best of our knowledge, there has been no review article published in the literature in the area of sheet explosives. Copyright © 2015 Elsevier B.V. All rights reserved.

Australian Government Balance Sheet Management

OpenAIRE

Wilson Au-Yeung; Jason McDonald; Amanda Sayegh

2006-01-01

Since almost eliminating net debt, the Australian Government%u2019s attention has turned to the financing of broader balance sheet liabilities, such as public sector superannuation. Australia will be developing a significant financial asset portfolio in the %u2018Future Fund%u2019 to smooth the financing of expenses through time. This raises the significant policy question of how best to manage the government balance sheet to reduce risk. This paper provides a framework for optimal balance sh...

Energy information sheets, July 1998

Energy Technology Data Exchange (ETDEWEB)

NONE

1998-07-01

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

Energy information sheets, September 1996

Energy Technology Data Exchange (ETDEWEB)

NONE

1996-09-01

The National Energy Information Center (NEIC), as part of its mission, provides energy information and referral assistance to Federal, State, and local governments, the academic community, business and industrial organizations, and the public. The Energy Information Sheets was developed to provide general information on various aspects of fuel production, prices, consumption, and capability. Additional information on related subject matter can be found in other Energy Information Administration (EIA) publications as referenced at the end of each sheet.

Anesthesia Fact Sheet

Science.gov (United States)

... Education About NIGMS NIGMS Home > Science Education > Anesthesia Anesthesia Tagline (Optional) Middle/Main Content Area En español ... Version (464 KB) Other Fact Sheets What is anesthesia? Anesthesia is a medical treatment that prevents patients ...

Ice flow Modelling of the Greenland Ice Sheet

DEFF Research Database (Denmark)

Nielsen, Lisbeth Tangaa

Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others. In t...... a steady state with respect to the reference climate at the end of the simulation and that the mass balance of the ice sheet at this time was more sensitive to recent climate fluctuations than the temperature forcing in the early or mid-Holocene.......Models of ice flow have a range of application in glaciology, including investigating the large-scale response of ice sheets to changes in climate, assimilating data to estimate unknown conditions beneath the ice sheet, and in interpreting proxy records obtained from ice cores, among others....... In this PhD project, the use of ice flow models for the interpretation of the age-structure of the Greenland ice sheet, i.e. the depth within the ice, at which ice deposited at given times are found at present day. Two different observational data sets of this archive were investigated. Further, paleo...

Forced tearing of ductile and brittle thin sheets.

Science.gov (United States)

Tallinen, T; Mahadevan, L

2011-12-09

Tearing a thin sheet by forcing a rigid object through it leads to complex crack morphologies; a single oscillatory crack arises when a tool is driven laterally through a brittle sheet, while two diverging cracks and a series of concertinalike folds forms when a tool is forced laterally through a ductile sheet. On the other hand, forcing an object perpendicularly through the sheet leads to radial petallike tears in both ductile and brittle materials. To understand these different regimes we use a combination of experiments, simulations, and simple theories. In particular, we describe the transition from brittle oscillatory tearing via a single crack to ductile concertina tearing with two tears by deriving laws that describe the crack paths and wavelength of the concertina folds and provide a simple phase diagram for the morphologies in terms of the material properties of the sheet and the relative size of the tool.

Self-inhibiting growth of the Greenland Ice Sheet

DEFF Research Database (Denmark)

Langen, Peter Lang; Solgaard, Anne Munck; Hvidberg, Christine Schøtt

2012-01-01

The build-up of the Greenland Ice Sheet (GrIS) from ice-free conditions is studied in an ice sheet model (ISM) driven by fields from an atmospheric general circulation model (GCM) to demonstrate the importance of coupling between the two components. Experiments where the two are coupled off-line...... are augmented by one where an intermediate ice sheet configuration is coupled back to the GCM. Forcing the ISM with GCM fields corresponding to the ice-free state leads to extensive regrowth which, however, is halted when the intermediate recoupling step is included. This inhibition of further growth is due...... to a Föhn effect of moist air parcels being lifted over the intermediate ice sheet and arriving in the low-lying Greenland interior with high temperatures. This demonstrates that two-way coupling between the atmosphere and the ice sheet is essential for understanding the dynamics and that large scale...

Antibubbles and fine cylindrical sheets of air

KAUST Repository

Beilharz, D.

2015-08-14

Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air layers which can wrap around the entire drop to form repeatable antibubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread reaching all the way to the pinch-off nozzle. The air sheet can also wrap around this thread and remain stable over an extended period of time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these thin cylindrical air sheets is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer. We use interferometry to measure the air-layer thickness versus depth along the cylindrical air sheet and around the drop. The air film is thickest above the equator of the drop, but thinner below the drop and up along the air cylinder. Based on microbubble volumes, the thickness of the cylindrical air layer becomes less than 100 nm before it ruptures.

Antibubbles and fine cylindrical sheets of air

KAUST Repository

Beilharz, D.; Guyon, A.; Li, E.  Q.; Thoraval, M.-J.; Thoroddsen, Sigurdur T

2015-01-01

Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a higher-viscosity drop onto a lower-viscosity pool, we have explored new geometries of such air films. In this way we are able to maintain stable air layers which can wrap around the entire drop to form repeatable antibubbles, i.e. spherical air layers bounded by inner and outer liquid masses. Furthermore, for the most viscous drops they enter the pool trailing a viscous thread reaching all the way to the pinch-off nozzle. The air sheet can also wrap around this thread and remain stable over an extended period of time to form a cylindrical air sheet. We study the parameter regime where these structures appear and their subsequent breakup. The stability of these thin cylindrical air sheets is inconsistent with inviscid stability theory, suggesting stabilization by lubrication forces within the submicron air layer. We use interferometry to measure the air-layer thickness versus depth along the cylindrical air sheet and around the drop. The air film is thickest above the equator of the drop, but thinner below the drop and up along the air cylinder. Based on microbubble volumes, the thickness of the cylindrical air layer becomes less than 100 nm before it ruptures.

Nonparaxial Bessel and Bessel-Gauss pincers light-sheets

Science.gov (United States)

Mitri, F. G.

2017-01-01

Nonparaxial optical Bessel and Bessel-Gauss pincers optical-sheets are introduced based upon the angular spectrum decomposition in plane waves. The angular spectrum function and the beam-shape coefficients are expressed by means of improper integrals computed numerically. The radiated component of the electric field is also evaluated, displaying unique features of the nonparaxial Bessel pincers light-sheets. This new type of auto-focusing light-sheets finds potential applications in the development of novel methods in optical light-sheet tweezers for particle manipulation in opto-fluidics, particle sizing and imaging. Numerical predictions for the scattering, radiation force and torque, and particle dynamics also benefit from the developed beam solution.

Ice Sheet Roughness Estimation Based on Impulse Responses Acquired in the Global Ice Sheet Mapping Orbiter Mission

Science.gov (United States)

Niamsuwan, N.; Johnson, J. T.; Jezek, K. C.; Gogineni, P.

2008-12-01

The Global Ice Sheet Mapping Orbiter (GISMO) mission was developed to address scientific needs to understand the polar ice subsurface structure. This NASA Instrument Incubator Program project is a collaboration between Ohio State University, the University of Kansas, Vexcel Corporation and NASA. The GISMO design utilizes an interferometric SAR (InSAR) strategy in which ice sheet reflected signals received by a dual-antenna system are used to produce an interference pattern. The resulting interferogram can be used to filter out surface clutter so as to reveal the signals scattered from the base of the ice sheet. These signals are further processed to produce 3D-images representing basal topography of the ice sheet. In the past three years, the GISMO airborne field campaigns that have been conducted provide a set of useful data for studying geophysical properties of the Greenland ice sheet. While topography information can be obtained using interferometric SAR processing techniques, ice sheet roughness statistics can also be derived by a relatively simple procedure that involves analyzing power levels and the shape of the radar impulse response waveforms. An electromagnetic scattering model describing GISMO impulse responses has previously been proposed and validated. This model suggested that rms-heights and correlation lengths of the upper surface profile can be determined from the peak power and the decay rate of the pulse return waveform, respectively. This presentation will demonstrate a procedure for estimating the roughness of ice surfaces by fitting the GISMO impulse response model to retrieved waveforms from selected GISMO flights. Furthermore, an extension of this procedure to estimate the scattering coefficient of the glacier bed will be addressed as well. Planned future applications involving the classification of glacier bed conditions based on the derived scattering coefficients will also be described.

Protein unfolding versus β-sheet separation in spider silk nanocrystals

International Nuclear Information System (INIS)

Alam, Parvez

2014-01-01

In this communication a mechanism for spider silk strain hardening is proposed. Shear failure of β-sheet nanocrystals is the first failure mode that gives rise to the creation of smaller nanocrystals, which are of higher strength and stiffness. β-sheet unfolding requires more energy than nanocrystal separation in a shear mode of failure. As a result, unfolding occurs after the nanocrystals separate in shear. β-sheet unfolding yields a secondary strain hardening effect once the β-sheet conformation is geometrically stable and acts like a unidirectional fibre in a fibre reinforced composite. The mechanism suggested herein is based on molecular dynamics calculations of residual inter-β-sheet separation strengths against residual intra-β-sheet unfolding strengths. (paper)

Cerebral Palsy: General Information. Fact Sheet Number 2 = La Paralisis Cerebral: Informacion General. Fact Sheet Number 18.

Science.gov (United States)

Interstate Research Associates, McLean, VA.

This fact sheet on cerebral palsy is offered in both English and Spanish. First, it provides a definition and considers various causes (e.g., an insufficient amount of oxygen reaching the fetal or newborn brain). The fact sheet then offers incidence figures and explains characteristics of the three main types of cerebral palsy: spastic, athetoid,…

Film sheet cassette

International Nuclear Information System (INIS)

1981-01-01

A novel film sheet cassette is described for handling CAT photographic films under daylight conditions and facilitating their imaging. A detailed description of the design and operation of the cassette is given together with appropriate illustrations. The resulting cassette is a low-cost unit which is easily constructed and yet provides a sure light-tight seal for the interior contents of the cassette. The individual resilient fingers on the light-trap permit the ready removal of the slide plate for taking pictures. The stippled, non-electrostatic surface of the pressure plate ensures an air layer and free slidability of the film for removal and withdrawal of the film sheet. The advantage of the daylight system is that a darkroom need not be used for inserting and removing the film in and out of the cassette resulting in a considerable time saving. (U.K.)

An Adaptive Test Sheet Generation Mechanism Using Genetic Algorithm

Directory of Open Access Journals (Sweden)

Huan-Yu Lin

2012-01-01

Full Text Available For test-sheet composition systems, it is important to adaptively compose test sheets with diverse conceptual scopes, discrimination and difficulty degrees to meet various assessment requirements during real learning situations. Computation time and item exposure rate also influence performance and item bank security. Therefore, this study proposes an Adaptive Test Sheet Generation (ATSG mechanism, where a Candidate Item Selection Strategy adaptively determines candidate test items and conceptual granularities according to desired conceptual scopes, and an Aggregate Objective Function applies Genetic Algorithm (GA to figure out the approximate solution of mixed integer programming problem for the test-sheet composition. Experimental results show that the ATSG mechanism can efficiently, precisely generate test sheets to meet the various assessment requirements than existing ones. Furthermore, according to experimental finding, Fractal Time Series approach can be applied to analyze the self-similarity characteristics of GA’s fitness scores for improving the quality of the test-sheet composition in the near future.

Simulations of the Scandinavian ice sheet and its subsurface conditions

International Nuclear Information System (INIS)

Boulton, G.S.; Caban, P.; Hulton, N.

1999-12-01

An ice sheet model has been applied to an approximate flow line through the area of the Fennoscandian ice sheet. The modelled ice sheet fluctuations have been matched with stratigraphic evidence of Weichselian ice sheet fluctuation in order to simulate ice sheet attributes through time along the flowline. The model predicts extensive melting at the base of the ice sheet. This output has been used as an input to a simplified model of hydrogeology along the southern flank of the ice sheet so as to reconstruct patterns of subglacial groundwater flow. The output from the model is also used to estimate patterns of subglacial stress and strain. Results suggest that large scale subglacial groundwater catchment are formed which were quite different in extent from modern catchment; that fossil subglacial groundwaters should be found at sampling depths; and much fracturing in shallow bedrock in Sweden could be glacially generated

Simulations of the Scandinavian ice sheet and its subsurface conditions

Energy Technology Data Exchange (ETDEWEB)

Boulton, G.S.; Caban, P.; Hulton, N. [Edinburgh Univ. (United Kingdom). Dept of Geology and Geophysics

1999-12-01

An ice sheet model has been applied to an approximate flow line through the area of the Fennoscandian ice sheet. The modelled ice sheet fluctuations have been matched with stratigraphic evidence of Weichselian ice sheet fluctuation in order to simulate ice sheet attributes through time along the flowline. The model predicts extensive melting at the base of the ice sheet. This output has been used as an input to a simplified model of hydrogeology along the southern flank of the ice sheet so as to reconstruct patterns of subglacial groundwater flow. The output from the model is also used to estimate patterns of subglacial stress and strain. Results suggest that large scale subglacial groundwater catchment are formed which were quite differentin extent from modern catchment; that fossil subglacial groundwaters should be found at sampling depths; and much fracturing in shallow bedrock in Sweden could be glacially generated.

Synthesis, characterization and optical properties of sheet-like ZnO

International Nuclear Information System (INIS)

Liu, Changzhen; Meng, Dawei; Wu, Xiuling; Wang, Yongqian; Yu, Xiaohong; Zhang, Zhengjie; Liu, Xiaoyang

2011-01-01

Highlights: → Sheet-like ZnO with regular hexagon shape was synthesized with a two-step method. → Sheet-like ZnO predecessor was synthesized at low temperature in open system. → The diameter and thickness of ZnO sheet can be controlled conveniently. → This low-cost and environmentally benign approach is controllable and reproducible. → Sheet-like ZnO may have potential application in optical and electrical devices. -- Abstract: Sheet-like ZnO with regular hexagon shape and uniform diameter has been successfully synthesized through a two-step method without any metal catalyst. First, the sheet-like ZnO precursor was synthesized in a weak alkaline carbamide environment with stirring in a constant temperature water-bath by the homogeneous precipitation method, then sheet-like ZnO was obtained by calcining at 600 o C for 2 h. The structures and optical properties of sheet-like ZnO have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and UV-vis-NIR spectrophotometer. The results reveal that the product is highly crystalline with hexagonal wurtzite phase and has appearance of hexagon at (0 0 0 1) plane. The HRTEM images confirm that the individual sheet-like ZnO is single crystal. The PL spectrum exhibits a narrow ultraviolet emission at 397 nm and a broad visible emission centering at 502 nm. The band gap of sheet-like ZnO is about 3.15 eV.

Comparison of Corrosion Behavior of Electrochemically Deposited Nano-Cobalt-Coated Ni Sheet

Directory of Open Access Journals (Sweden)

Nasser Al-Aqeeli

2013-01-01

Full Text Available Corrosion behavior of nano-coblat-coated Ni sheet was compared with pure Ni and 20% Fe-Ni alloy sheet using potentiodynamic polarization and linear polarization technique in 0.1 M NaCl solution at room temperature. Results showed that corrosion resistance properties of nano-Co-coated Ni sheet were almost same as that of pure Ni sheet, however corrosion resistance of 20% Fe-Ni sheet was decreased significantly. Pitting potential of 20% Fe-Ni sheet was subsequently decreased as compared to pure Ni sheet as well as nano-cobalt-coated Ni sheet. SEM/EDS analysis of the corroded surfaces showed that both pure Ni and nano-coblat-coated Ni sheet did not show any appreciable corrosion however significant corrosion was observed in the case of 20% Fe-Ni sheet.

Comparison of the generalized Riemann solver and the gas-kinetic scheme for inviscid compressible flow simulations

International Nuclear Information System (INIS)

Li Jiequan; Li Qibing; Xu Kun

2011-01-01

The generalized Riemann problem (GRP) scheme for the Euler equations and gas-kinetic scheme (GKS) for the Boltzmann equation are two high resolution shock capturing schemes for fluid simulations. The difference is that one is based on the characteristics of the inviscid Euler equations and their wave interactions, and the other is based on the particle transport and collisions. The similarity between them is that both methods can use identical MUSCL-type initial reconstructions around a cell interface, and the spatial slopes on both sides of a cell interface involve in the gas evolution process and the construction of a time-dependent flux function. Although both methods have been applied successfully to the inviscid compressible flow computations, their performances have never been compared. Since both methods use the same initial reconstruction, any difference is solely coming from different underlying mechanism in their flux evaluation. Therefore, such a comparison is important to help us to understand the correspondence between physical modeling and numerical performances. Since GRP is so faithfully solving the inviscid Euler equations, the comparison can be also used to show the validity of solving the Euler equations itself. The numerical comparison shows that the GRP exhibits a slightly better computational efficiency, and has comparable accuracy with GKS for the Euler solutions in 1D case, but the GKS is more robust than GRP. For the 2D high Mach number flow simulations, the GKS is absent from the shock instability and converges to the steady state solutions faster than the GRP. The GRP has carbuncle phenomena, likes a cloud hanging over exact Riemann solvers. The GRP and GKS use different physical processes to describe the flow motion starting from a discontinuity. One is based on the assumption of equilibrium state with infinite number of particle collisions, and the other starts from the non-equilibrium free transport process to evolve into an

14 CFR Section 3 - Chart of Balance Sheet Accounts

Science.gov (United States)

2010-01-01

... 14 Aeronautics and Space 4 2010-01-01 2010-01-01 false Chart of Balance Sheet Accounts Section 3 Section 3 Aeronautics and Space OFFICE OF THE SECRETARY, DEPARTMENT OF TRANSPORTATION (AVIATION... Balance Sheet Classifications Section 3 Chart of Balance Sheet Accounts [See footnotes at end of table...

17 CFR 229.1001 - (Item 1001) Summary term sheet.

Science.gov (United States)

2010-04-01

... sheet that is written in plain English. The summary term sheet must briefly describe in bullet point format the most material terms of the proposed transaction. The summary term sheet must provide security... transaction. The bullet points must cross-reference a more detailed discussion contained in the disclosure...

Theoretical Predictions of Freestanding Honeycomb Sheets of Cadmium Chalcogenides

Energy Technology Data Exchange (ETDEWEB)

Zhou, Jia [ORNL; Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Kent, Paul R [ORNL; Xie, Yu [ORNL; Terrones Maldonado, Humberto [ORNL; Smith, Sean C [ORNL

2014-01-01

Two-dimensional (2D) nanocrystals of CdX (X = S, Se, Te) typically grown by colloidal synthesis are coated with organic ligands. Recent experimental work on ZnSe showed that the organic ligands can be removed at elevated temperature, giving a freestanding 2D sheet of ZnSe. In this theoretical work, freestanding single- to few-layer sheets of CdX, each possessing a pseudo honeycomb lattice, are considered by cutting along all possible lattice planes of the bulk zinc blende (ZB) and wurtzite (WZ) phases. Using density functional theory, we have systematically studied their geometric structures, energetics, and electronic properties. A strong surface distortion is found to occur for all of the layered sheets, and yet all of the pseudo honeycomb lattices are preserved, giving unique types of surface corrugations and different electronic properties. The energetics, in combination with phonon mode calculations and molecular dynamics simulations, indicate that the syntheses of these freestanding 2D sheets could be selective, with the single- to few-layer WZ110, WZ100, and ZB110 sheets being favored. Through the GW approximation, it is found that all single-layer sheets have large band gaps falling into the ultraviolet range, while thicker sheets in general have reduced band gaps in the visible and ultraviolet range. On the basis of the present work and the experimental studies on freestanding double-layer sheets of ZnSe, we envision that the freestanding 2D layered sheets of CdX predicted herein are potential synthesis targets, which may offer tunable band gaps depending on their structural features including surface corrugations, stacking motifs, and number of layers.

NTPR Fact Sheets

Science.gov (United States)

History Documents US Underground Nuclear Test History Reports NTPR Radiation Exposure Reports Enewetak Atoll Cleanup Documents TRAC About Who We Are Our Values History Locations Our Leadership Director Support Center Contact Us FAQ Sheet Links Success Stories Contracts Business Opportunities Current

The social balance sheet 2004

OpenAIRE

Ph. Delhez; P. Heuse

2005-01-01

Each year, in the 4th quarter’s Economic Review, the National Bank examines the provisional results of the social balance sheets. As all the social balance sheets are not yet available for 2004, the study is based on a limited population of enterprises, compiled according to the principle of a constant sample. This population is made up of 38,530 enterprises employing around 1,331,000 workers in 2004. The main results of the analysis, in terms of employment, working hours, labour cost and tra...

Analysis of Financial Position Based on the Balance Sheet

OpenAIRE

Spineanu-Georgescu Luciana

2011-01-01

Analysis of financial position based on the balance sheet is mainly aimed at assessing the extent to which financial structure chosen by the firm, namely, financial resources, covering the needs reflected in the balance sheet financed. This is done through an analysis known as horizontal analysis balance sheet financial imbalances.

Sense and readability: participant information sheets for research studies.

Science.gov (United States)

Ennis, Liam; Wykes, Til

2016-02-01

Informed consent in research is partly achieved through the use of information sheets. There is a perception however that these information sheets are long and complex. The recommended reading level for patient information is grade 6, or 11-12 years old. To investigate whether the readability of participant information sheets has changed over time, whether particular study characteristics are related to poorer readability and whether readability and other study characteristics are related to successful study recruitment. Method: We obtained 522 information sheets from the UK National Institute for Health Research Clinical Research Network: Mental Health portfolio database and study principal investigators. Readability was assessed with the Flesch reading index and the Grade level test. Information sheets increased in length over the study period. The mean grade level across all information sheets was 9.8, or 15-16 years old. A high level of patient involvement was associated with more recruitment success and studies involving pharmaceutical or device interventions were the least successful. The complexity of information sheets had little bearing on successful recruitment. Information sheets are far more complex than the recommended reading level of grade 6 for patient information. The disparity may be exacerbated by an increasing focus on legal content. Researchers would benefit from clear guidance from ethics committees on writing succinctly and accessibly and how to balance the competing legal issues with the ability of participants to understand what a study entails. © The Royal College of Psychiatrists 2016.

Advanced friction modeling for sheet metal forming

NARCIS (Netherlands)

Hol, J.; Cid Alfaro, M.V.; de Rooij, Matthias B.; Meinders, Vincent T.

2012-01-01

The Coulomb friction model is frequently used for sheet metal forming simulations. This model incorporates a constant coefficient of friction and does not take the influence of important parameters such as contact pressure or deformation of the sheet material into account. This article presents a

Advanced friction modeling in sheet metal forming

NARCIS (Netherlands)

Hol, J.; Cid Alfaro, M.V.; Meinders, Vincent T.; Huetink, Han

2011-01-01

The Coulomb friction model is frequently used for sheet metal forming simulations. This model incorporates a constant coefficient of friction and does not take the influence of important parameters such as contact pressure or deformation of the sheet material into account. This article presents a

Nonlinear dynamics of thin current sheets

International Nuclear Information System (INIS)

Daughton, William

2002-01-01

Observations indicate that the current sheet in the Earth's geomagnetic tail may compress to a thickness comparable to an ion gyro-radius prior to substorm onset. In recent years, there has been considerable controversy regarding the kinetic stability of these thin structures. In particular, the growth rate of the kink instability and its relevance to magnetotail dynamics is still being debated. In this work, a series of fully kinetic particle-in-cell simulations are performed for a thin Harris sheet. The ion to electron mass ratio is varied between m i /m e =4→400 and careful comparisons are made with a formally exact approach to the linear Vlasov theory. At low mass ratio m i /m e <64, the simulations are in excellent agreement with the linear theory, but at high mass ratio the kink instability is observed to grow more rapidly in the kinetic simulations than predicted by theory. The resolution to this apparent discrepancy involves the lower hybrid instability which is active on the edge of the sheet and rapidly produces nonlinear modifications to the initial equilibrium. The nature of this nonlinear deformation is characterized and a simple model is proposed to explain the physics. After the growth and saturation of the lower hybrid fluctuations, the deformed current sheet is similar in structure to a Harris equilibrium with an additional background population. This may explain the large growth rate of the kink instability at later times, since this type of modification to the Harris sheet has been shown to greatly enhance the growth rate of the kink mode

Ice Sheet Model Intercomparison Project (ISMIP6) contribution to CMIP6

Science.gov (United States)

Nowicki, Sophie M.J.; Payne, Tony; Larour, Eric; Seroussi, Helene; Goelzer, Heiko; Lipscomb, William; Gregory, Jonathan; Abe-Ouchi, Ayako; Shepherd, Andrew

2018-01-01

Reducing the uncertainty in the past, present and future contribution of ice sheets to sea-level change requires a coordinated effort between the climate and glaciology communities. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) is the primary activity within the Coupled Model Intercomparison Project – phase 6 (CMIP6) focusing on the Greenland and Antarctic Ice Sheets. In this paper, we describe the framework for ISMIP6 and its relationship to other activities within CMIP6. The ISMIP6 experimental design relies on CMIP6 climate models and includes, for the first time within CMIP, coupled ice sheet – climate models as well as standalone ice sheet models. To facilitate analysis of the multi-model ensemble and to generate a set of standard climate inputs for standalone ice sheet models, ISMIP6 defines a protocol for all variables related to ice sheets. ISMIP6 will provide a basis for investigating the feedbacks, impacts, and sea-level changes associated with dynamic ice sheets and for quantifying the uncertainty in ice-sheet-sourced global sea-level change. PMID:29697697

Production (information sheets)

NARCIS (Netherlands)

2007-01-01

Documentation sheets: Geo energy 2 Integrated System Approach Petroleum Production (ISAPP) The value of smartness 4 Reservoir permeability estimation from production data 6 Coupled modeling for reservoir application 8 Toward an integrated near-wellbore model 10 TNO conceptual framework for "E&P

Evolution of the MHD sheet pinch

International Nuclear Information System (INIS)

Matthaeus, W.H.; Montgomery, D.

1979-01-01

A magnetohydrodynamic (MHD) problem of recurrent interest for both astrophysical and laboratory plasmas is the evolution of the unstable sheet pinch, a current sheet across which a dc magnetic field reverses sign. The evolution of such a sheet pinch is followed with a spectral-method, incompressible, two-dimensional, MHD turbulence code. Spectral diagnostics are employed, as are contour plots of vector potential (magnetic field lines), electric current density, and velocity stream function (velocity streamlines). The nonlinear effect which seems most important is seen to be current filamentation: the concentration of the current density onto sets of small measure near a mgnetic X point. A great deal of turbulence is apparent in the current distribution, which, for high Reynolds numbers, requires large spatial grids (greater than or equal to (64) 2 ). 11 figures, 1 table

Dipole-sheet multipole magnets for accelerators

International Nuclear Information System (INIS)

Walstrom, P.L.

1993-01-01

The dipole-sheet formalism can be used to describe both cylindrical current-sheet multipole magnets and cylindrical-bore magnets made up of permanent magnet blocks. For current sheets, the formalism provides a natural way of finding a finite set of turns that approximate a continuous distribution. The formalism is especially useful In accelerator applications where large-bore, short, high-field-quality magnets that are dominated by fringe fields are needed. A further advantage of the approach is that in systems with either open or cylindrically symmetric magnetic boundaries, analytical expressions for the three-dimensional fields that are suitable for rapid numerical evaluation can be derived. This development is described in some detail. Also, recent developments in higher-order particle-beam optics codes based on the formalism are described briefly

Influence of temperature fluctuations on equilibrium ice sheet volume

Science.gov (United States)

Bøgeholm Mikkelsen, Troels; Grinsted, Aslak; Ditlevsen, Peter

2018-01-01

Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB) of the Greenland Ice Sheet (GrIS) has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent) smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr-1 (24-59 Gt yr-1, 95 % credibility) for a warming of 3 °C above preindustrial values, or 13 % (10-25, 95 % credibility) of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10-0.18 °C, 95 % credibility) for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.

Sheet Beam Klystron Instability Analysis

International Nuclear Information System (INIS)

Bane, K.

2009-01-01

Using the principle of energy balance we develop a 2D theory for calculating growth rates of instability in a two-cavity model of a sheet beam klystron. An important ingredient is a TE-like mode in the gap that also gives a longitudinal kick to the beam. When compared with a self-consistent particle-in-cell calculation, with sheet beam klystron-type parameters, agreement is quite good up to half the design current, 65 A; at full current, however, other, current-dependent effects come in and the results deviate significantly

Bi-directional electrons in the near-Earth plasma sheet

Directory of Open Access Journals (Sweden)

K. Shiokawa

2003-07-01

Full Text Available We have studied the occurrence characteristics of bi-directional electron pitch angle anisotropy (enhanced flux in field-aligned directions, F^ /F|| > 1.5 at energies of 0.1–30 keV using plasma and magnetic field data from the AMPTE/IRM satellite in the near-Earth plasma sheet. The occurrence rate increases in the tailward direction from XGSM = - 9 RE to - 19 RE . The occurrence rate is also enhanced in the midnight sector, and furthermore, whenever the elevation angle of the magnetic field is large while the magnetic field intensity is small, B ~ 15 nT. From these facts, we conclude that the bi-directional electrons in the central plasma sheet are produced mainly in the vicinity of the neutral sheet and that the contribution from ionospheric electrons is minor. A high occurrence is also found after earthward high-speed ion flows, suggesting Fermi-type field-aligned electron acceleration in the neutral sheet. Occurrence characteristics of bi-directional electrons in the plasma sheet boundary layer are also discussed.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet

Firm Investment and Balance-Sheet Problems in Japan

OpenAIRE

Toshitaka Sekine

1999-01-01

This paper investigates whether balance-sheet conditions of firms and their main banks matter for firm investment behavior using dynamic corporate panel data in Japan for the period 1985-95. It finds that smaller non-bond issuing firms were facing liquidity constraints; these firms’ balance-sheet conditions (the debt asset ratios) affected their investment from the midst of the bubble era by influencing main banks’ lending to them; and the deterioration of their main banks’ balance-sheet cond...

The quantitative inspection of iron aluminide green sheet using transient thermography

International Nuclear Information System (INIS)

Watkins, Michael L.; Hinders, Mark K.; Scorey, Clive; Winfree, William

1999-01-01

The recent development of manufacturing techniques for the fabrication of thin iron aluminide, FeAl, sheet requires advanced quantitative methods for on-line inspection. An understanding of the mechanisms responsible for flaws and the development of appropriate flaw detection methods are key elements in an effective quality management system. The first step in the fabrication of thin FeAl alloy sheet is the formation of a green sheet, either by cold rolling or tape casting FeAl powder mixed with organic binding agents. The finished sheet is obtained using a series of process steps involving binder elimination, densification, sintering, and annealing. Non-uniformities within the green sheet are the major contributor to material failure in subsequent sheet processing and the production of non-conforming finished sheet. Previous work has demonstrated the advantages of using active thermography to detect the flaws and heterogeneity within green powder composites (1)(2)(3). The production environment and physical characteristics of these composites provide for unique challenges in developing a rapid nondestructive inspection capability. Thermography is non-contact and minimizes the potential damage to the fragile green sheet. Limited access to the material also demands a one-sided inspection technique. In this paper, we will describe the application of thermography for 100% on-line inspection within an industrial process. This approach is cost competitive with alternative technologies, such as x-ray imaging systems, and provides the required sensitivity to the variations in material composition. The formation of green sheet flaws and their transformation into defects within intermediate and finished sheet products will be described. A green sheet conformance criterion will be presented which would significantly reduce the probability of processing poor quality green sheet which contributes to higher waste and inferior bulk alloy sheet

Antibubbles and fine cylindrical sheets of air

NARCIS (Netherlands)

Beilharz, D.; Guyon, A.; Li, E.Q.; Thoraval, Marie-Jean; Thoroddsen, S.T.

2015-01-01

Drops impacting at low velocities onto a pool surface can stretch out thin hemispherical sheets of air between the drop and the pool. These air sheets can remain intact until they reach submicron thicknesses, at which point they rupture to form a myriad of microbubbles. By impacting a

Reducing Test Anxiety while Increasing Learning: The Cheat Sheet

Science.gov (United States)

Erbe, Brigitte

2007-01-01

Student learning is greatly enhanced by studying prior to an exam. Allowing students to prepare a cheat sheet for the exam helps structure this study time and deepens learning. The crib sheet is well defined: one double-sided page of notes. An award for the best and most creative cheat sheet allows the instructor to appreciate the students'…

Ice sheet hydrology from observations

Energy Technology Data Exchange (ETDEWEB)

Jansson, Peter [Dept. of Physical Geography and Quaternary Geology, Stockholm Univ-, Stockholm (Sweden)

2010-11-15

The hydrological systems of ice sheets are complex. Our view of the system is split, largely due to the complexity of observing the systems. Our basic knowledge of processes have been obtained from smaller glaciers and although applicable in general to the larger scales of the ice sheets, ice sheets contain features not observable on smaller glaciers due to their size. The generation of water on the ice sheet surface is well understood and can be satisfactorily modeled. The routing of water from the surface down through the ice is not complicated in terms of procat has been problematic is the way in which the couplings between surface and bed has been accomplished through a kilometer of cold ice, but with the studies on crack propagation and lake drainage on Greenland we are beginning to understand also this process and we know water can be routed through thick cold ice. Water generation at the bed is also well understood but the main problem preventing realistic estimates of water generation is lack of detailed information about geothermal heat fluxes and their geographical distribution beneath the ice. Although some average value for geothermal heat flux may suffice, for many purposes it is important that such values are not applied to sub-regions of significantly higher fluxes. Water generated by geothermal heat constitutes a constant supply and will likely maintain a steady system beneath the ice sheet. Such a system may include subglacial lakes as steady features and reconfiguration of the system is tied to time scales on which the ice sheet geometry changes so as to change pressure gradients in the basal system itself. Large scale re-organization of subglacial drainage systems have been observed beneath ice streams. The stability of an entirely subglacially fed drainage system may hence be perturbed by rapid ice flow. In the case of Antarctic ice streams where such behavior has been observed, the ice streams are underlain by deformable sediments. It is

Ice sheet hydrology from observations

International Nuclear Information System (INIS)

Jansson, Peter

2010-11-01

The hydrological systems of ice sheets are complex. Our view of the system is split, largely due to the complexity of observing the systems. Our basic knowledge of processes have been obtained from smaller glaciers and although applicable in general to the larger scales of the ice sheets, ice sheets contain features not observable on smaller glaciers due to their size. The generation of water on the ice sheet surface is well understood and can be satisfactorily modeled. The routing of water from the surface down through the ice is not complicated in terms of procat has been problematic is the way in which the couplings between surface and bed has been accomplished through a kilometer of cold ice, but with the studies on crack propagation and lake drainage on Greenland we are beginning to understand also this process and we know water can be routed through thick cold ice. Water generation at the bed is also well understood but the main problem preventing realistic estimates of water generation is lack of detailed information about geothermal heat fluxes and their geographical distribution beneath the ice. Although some average value for geothermal heat flux may suffice, for many purposes it is important that such values are not applied to sub-regions of significantly higher fluxes. Water generated by geothermal heat constitutes a constant supply and will likely maintain a steady system beneath the ice sheet. Such a system may include subglacial lakes as steady features and reconfiguration of the system is tied to time scales on which the ice sheet geometry changes so as to change pressure gradients in the basal system itself. Large scale re-organization of subglacial drainage systems have been observed beneath ice streams. The stability of an entirely subglacially fed drainage system may hence be perturbed by rapid ice flow. In the case of Antarctic ice streams where such behavior has been observed, the ice streams are underlain by deformable sediments. It is

3D staggered Lagrangian hydrodynamics scheme with cell-centered Riemann solver-based artificial viscosity

International Nuclear Information System (INIS)

Loubere, Raphael; Maire, Pierre-Henri; Vachal, Pavel

2013-01-01

The aim of the present work is the 3D extension of a general formalism to derive a staggered discretization for Lagrangian hydrodynamics on unstructured grids. The classical compatible discretization is used; namely, momentum equation is discretized using the fundamental concept of subcell forces. Specific internal energy equation is obtained using total energy conservation. The subcell force is derived by invoking the Galilean invariance and thermodynamic consistency. A general form of the subcell force is provided so that a cell entropy inequality is satisfied. The subcell force consists of a classical pressure term plus a tensorial viscous contribution proportional to the difference between the node velocity and the cell-centered velocity. This cell-centered velocity is an extra degree of freedom solved with a cell-centered approximate Riemann solver. The second law of thermodynamics is satisfied by construction of the local positive definite subcell tensor involved in the viscous term. A particular expression of this tensor is proposed. A more accurate extension of this discretization both in time and space is also provided using a piecewise linear reconstruction of the velocity field and a predictor-corrector time discretization. Numerical tests are presented in order to assess the efficiency of this approach in 3D. Sanity checks show that the 3D extension of the 2D approach reproduces 1D and 2D results. Finally, 3D problems such as Sedov, Noh, and Saltzman are simulated. (authors)

Laser Indirect Shock Welding of Fine Wire to Metal Sheet.

Science.gov (United States)

Wang, Xiao; Huang, Tao; Luo, Yapeng; Liu, Huixia

2017-09-12

The purpose of this paper is to present an advanced method for welding fine wire to metal sheet, namely laser indirect shock welding (LISW). This process uses silica gel as driver sheet to accelerate the metal sheet toward the wire to obtain metallurgical bonding. A series of experiments were implemented to validate the welding ability of Al sheet/Cu wire and Al sheet/Ag wire. It was found that the use of a driver sheet can maintain high surface quality of the metal sheet. With the increase of laser pulse energy, the bonding area of the sheet/wire increased and the welding interfaces were nearly flat. Energy dispersive spectroscopy (EDS) results show that the intermetallic phases were absent and a short element diffusion layer which would limit the formation of the intermetallic phases emerging at the welding interface. A tensile shear test was used to measure the mechanical strength of the welding joints. The influence of laser pulse energy on the tensile failure modes was investigated, and two failure modes, including interfacial failure and failure through the wire, were observed. The nanoindentation test results indicate that as the distance to the welding interface decreased, the microhardness increased due to the plastic deformation becoming more violent.

Large patternable metal nanoparticle sheets by photo/e-beam lithography

Science.gov (United States)

Saito, Noboru; Wang, Pangpang; Okamoto, Koichi; Ryuzaki, Sou; Tamada, Kaoru

2017-10-01

Techniques for micro/nano-scale patterning of large metal nanoparticle sheets can potentially be used to realize high-performance photoelectronic devices because the sheets provide greatly enhanced electrical fields around the nanoparticles due to localized surface plasmon resonances. However, no single metal nanoparticle sheet currently exists with sufficient durability for conventional lithographical processes. Here, we report large photo and/or e-beam lithographic patternable metal nanoparticle sheets with improved durability by incorporating molecular cross-linked structures between nanoparticles. The cross-linked structures were easily formed by a one-step chemical reaction; immersing a single nanoparticle sheet consisting of core metals, to which capping molecules ionically bond, in a dithiol ethanol solution. The ligand exchange reaction processes were discussed in detail, and we demonstrated 20 μm wide line and space patterns, and a 170 nm wide line of the silver nanoparticle sheets.

Optimal Design of Sheet Pile Wall Embedded in Clay

Science.gov (United States)

Das, Manas Ranjan; Das, Sarat Kumar

2015-09-01

Sheet pile wall is a type of flexible earth retaining structure used in waterfront offshore structures, river protection work and temporary supports in foundations and excavations. Economy is an essential part of a good engineering design and needs to be considered explicitly in obtaining an optimum section. By considering appropriate embedment depth and sheet pile section it may be possible to achieve better economy. This paper describes optimum design of both cantilever and anchored sheet pile wall penetrating clay using a simple optimization tool Microsoft Excel ® Solver. The detail methodology and its application with examples are presented for cantilever and anchored sheet piles. The effects of soil properties, depth of penetration and variation of ground water table on the optimum design are also discussed. Such a study will help professional while designing the sheet pile wall penetrating clay.

How might the North American ice sheet influence the northwestern Eurasian climate?

Science.gov (United States)

Beghin, P.; Charbit, S.; Dumas, C.; Kageyama, M.; Ritz, C.

2015-10-01

It is now widely acknowledged that past Northern Hemisphere ice sheets covering Canada and northern Europe at the Last Glacial Maximum (LGM) exerted a strong influence on climate by causing changes in atmospheric and oceanic circulations. In turn, these changes may have impacted the development of the ice sheets themselves through a combination of different feedback mechanisms. The present study is designed to investigate the potential impact of the North American ice sheet on the surface mass balance (SMB) of the Eurasian ice sheet driven by simulated changes in the past glacial atmospheric circulation. Using the LMDZ5 atmospheric circulation model, we carried out 12 experiments under constant LGM conditions for insolation, greenhouse gases and ocean. In these experiments, the Eurasian ice sheet is removed. The 12 experiments differ in the North American ice-sheet topography, ranging from a white and flat (present-day topography) ice sheet to a full-size LGM ice sheet. This experimental design allows the albedo and the topographic impacts of the North American ice sheet onto the climate to be disentangled. The results are compared to our baseline experiment where both the North American and the Eurasian ice sheets have been removed. In summer, the sole albedo effect of the American ice sheet modifies the pattern of planetary waves with respect to the no-ice-sheet case, resulting in a cooling of the northwestern Eurasian region. By contrast, the atmospheric circulation changes induced by the topography of the North American ice sheet lead to a strong decrease of this cooling. In winter, the Scandinavian and the Barents-Kara regions respond differently to the American ice-sheet albedo effect: in response to atmospheric circulation changes, Scandinavia becomes warmer and total precipitation is more abundant, whereas the Barents-Kara area becomes cooler with a decrease of convective processes, causing a decrease of total precipitation. The gradual increase of the

Breakup characteristics of power-law liquid sheets formed by two impinging jets

International Nuclear Information System (INIS)

Bai, Fuqiang; Diao, Hai; Chang, Qing; Wang, Endong; Du, Qing; Zhang, Mengzheng

2014-01-01

The breakup characteristics of the shear-thinning power-law liquid sheets formed by two impinging jets have been investigated with the shadowgraph technique. This paper focuses on the effects of spray parameters (jet velocity), physical parameters (viscosity) and geometry parameters (impinging angle and nozzle cross-sectional shape) on the breakup behaviors of liquid sheets. The breakup mode, sheet length and expansion angle of the sheet are extracted from the spray images obtained by a high speed camera. Impinging angle and Weber number play the similar roles in promoting the breakup of liquid sheets. With the increase of jet velocity, five different breakup modes are observed and the expansion angle increases consistently after the closed-rim mode while the sheet length first increases and then decreases. But there exists a concave consisting of a fierce drop and a second rising process on the sheet length curve for the fluid with smaller viscosity. Different nozzle cross-sectional shapes emphasize significant effects on the sheet length and expansion angle of liquid sheets. At a fixed Weber number, the liquid sheet with greater viscosity has a greater sheet length and a smaller expansion angle due to the damping effect of viscosity. (papers)

Fatigue analysis of a PWR steam generator tube sheet

International Nuclear Information System (INIS)

Billon, F.; Buchalet, C.; Poudroux, G.

1985-01-01

The fatigue analysis of a PWR steam generator (S.G) tube sheet is threefold. First, the flow, pressure and temperature variations during the design transients are defined for both the primary fluid and the normal and auxiliary feedwater. Second, the flow, velocities, pressure and temperature variations of the secondary fluid at the bottom of the downcomer and above the tube sheet are determined for the transients considered. Finally, the corresponding temperatures and stresses in the tube sheet are calculated and the usage factors determined at various locations in the tube sheet. The currently available standard design transients for the primary fluid and the feedwater are too conservative to be utilized as such in the fatigue analysis of the S.G. tube sheets. Thus, a detailed examination and reappraisal of each operating transient was performed. The revised design conditions are used as inputs to the calculation model TEMPTRON. TEMPTRON determines the mixing conditions between the feedwater and the recirculation fluid from the S.G. feedwater nozzles to the center of the tube sheet via the downcomer. The fluid parameters, flow rate and velocity, temperature and pressure variations, as a function of the time during the transients are obtained. Finally, the usage factors at various locations on the tube sheet are derived using the standard ASME section III method

Grounding line transient response in marine ice sheet models

Directory of Open Access Journals (Sweden)

A. S. Drouet

2013-03-01

Full Text Available Marine ice-sheet stability is mostly controlled by the dynamics of the grounding line, i.e. the junction between the grounded ice sheet and the floating ice shelf. Grounding line migration has been investigated within the framework of MISMIP (Marine Ice Sheet Model Intercomparison Project, which mainly aimed at investigating steady state solutions. Here we focus on transient behaviour, executing short-term simulations (200 yr of a steady ice sheet perturbed by the release of the buttressing restraint exerted by the ice shelf on the grounded ice upstream. The transient grounding line behaviour of four different flowline ice-sheet models has been compared. The models differ in the physics implemented (full Stokes and shallow shelf approximation, the numerical approach, as well as the grounding line treatment. Their overall response to the loss of buttressing is found to be broadly consistent in terms of grounding line position, rate of surface elevation change and surface velocity. However, still small differences appear for these latter variables, and they can lead to large discrepancies (> 100% observed in terms of ice sheet contribution to sea level when cumulated over time. Despite the recent important improvements of marine ice-sheet models in their ability to compute steady state configurations, our results question the capacity of these models to compute short-term reliable sea-level rise projections.

A laser sheet self-calibration method for scanning PIV

Science.gov (United States)

Knutsen, Anna N.; Lawson, John M.; Dawson, James R.; Worth, Nicholas A.

2017-10-01

Knowledge of laser sheet position, orientation, and thickness is a fundamental requirement of scanning PIV and other laser-scanning methods. This paper describes the development and evaluation of a new laser sheet self-calibration method for stereoscopic scanning PIV, which allows the measurement of these properties from particle images themselves. The approach is to fit a laser sheet model by treating particles as randomly distributed probes of the laser sheet profile, whose position is obtained via a triangulation procedure enhanced by matching particle images according to their variation in brightness over a scan. Numerical simulations and tests with experimental data were used to quantify the sensitivity of the method to typical experimental error sources and validate its performance in practice. The numerical simulations demonstrate the accurate recovery of the laser sheet parameters over range of different seeding densities and sheet thicknesses. Furthermore, they show that the method is robust to significant image noise and camera misalignment. Tests with experimental data confirm that the laser sheet model can be accurately reconstructed with no impairment to PIV measurement accuracy. The new method is more efficient and robust in comparison with the standard (self-) calibration approach, which requires an involved, separate calibration step that is sensitive to experimental misalignments. The method significantly improves the practicality of making accurate scanning PIV measurements and broadens its potential applicability to scanning systems with significant vibrations.

16 CFR 460.15 - How installers must handle fact sheets.

Science.gov (United States)

2010-01-01

... ADVERTISING OF HOME INSULATION § 460.15 How installers must handle fact sheets. If you are an installer, you... from you, you must show them the fact sheet(s) for the type(s) of insulation they want. You can decide...

Ice sheets on plastically-yielding beds

Science.gov (United States)

Hewitt, Ian

2016-11-01

Many fast flowing regions of ice sheets are underlain by a layer of water-saturated sediments, or till. The rheology of the till has been the subject of some controversy, with laboratory tests suggesting almost perfectly plastic behaviour (stress independent of strain rate), but many models adopting a pseudo-viscous description. In this work, we consider the behaviour of glaciers underlain by a plastic bed. The ice is treated as a viscous gravity current, on a bed that allows unconstrained slip above a critical yield stress. This simplified description allows rapid sliding, and aims to investigate 'worst-case' scenarios of possible ice-sheet disintegration. The plastic bed results in an approximate ice-sheet geometry that is primarily controlled by force balance, whilst ice velocity is determined from mass conservation (rather than the other way around, as standard models would hold). The stability of various states is considered, and particular attention is given to the pace at which transitions between unstable states can occur. Finally, we observe that the strength of basal tills depends strongly on pore pressure, and combine the model with a description of subglacial hydrology. Implications for the present-day ice sheets in Greenland and Antarctica will be discussed. Funding: ERC Marie Curie FP7 Career Integration Grant.

Pseudomonas - Fact Sheet

OpenAIRE

Public Health Agency

2012-01-01

Fact sheet on Pseudomonas, including:What is Pseudomonas?What infections does it cause?Who is susceptible to pseudomonas infection?How will I know if I have pseudomonas infection?How can Pseudomonas be prevented from spreading?How can I protect myself from Pseudomonas?How is Pseudomonas infection treated?

Adaptive spacetime method using Riemann jump conditions for coupled atomistic-continuum dynamics

International Nuclear Information System (INIS)

Kraczek, B.; Miller, S.T.; Haber, R.B.; Johnson, D.D.

2010-01-01

We combine the Spacetime Discontinuous Galerkin (SDG) method for elastodynamics with the mathematically consistent Atomistic Discontinuous Galerkin (ADG) method in a new scheme that concurrently couples continuum and atomistic models of dynamic response in solids. The formulation couples non-overlapping continuum and atomistic models across sharp interfaces by weakly enforcing jump conditions, for both momentum balance and kinematic compatibility, using Riemann values to preserve the characteristic structure of the underlying hyperbolic system. Momentum balances to within machine-precision accuracy over every element, on each atom, and over the coupled system, with small, controllable energy dissipation in the continuum region that ensures numerical stability. When implemented on suitable unstructured spacetime grids, the continuum SDG model offers linear computational complexity in the number of elements and powerful adaptive analysis capabilities that readily bridge between atomic and continuum scales in both space and time. A special trace operator for the atomic velocities and an associated atomistic traction field enter the jump conditions at the coupling interface. The trace operator depends on parameters that specify, at the scale of the atomic spacing, the position of the coupling interface relative to the atoms. In a key finding, we demonstrate that optimizing these parameters suppresses spurious reflections at the coupling interface without the use of non-physical damping or special boundary conditions. We formulate the implicit SDG-ADG coupling scheme in up to three spatial dimensions, and describe an efficient iterative solution scheme that outperforms common explicit schemes, such as the Velocity Verlet integrator. Numerical examples, in 1dxtime and employing both linear and nonlinear potentials, demonstrate the performance of the SDG-ADG method and show how adaptive spacetime meshing reconciles disparate time steps and resolves atomic-scale signals in

Inverse scattering transform for the vector nonlinear Schroedinger equation with nonvanishing boundary conditions

International Nuclear Information System (INIS)

Prinari, Barbara; Ablowitz, Mark J.; Biondini, Gino

2006-01-01

The inverse scattering transform for the vector defocusing nonlinear Schroedinger (NLS) equation with nonvanishing boundary values at infinity is constructed. The direct scattering problem is formulated on a two-sheeted covering of the complex plane. Two out of the six Jost eigenfunctions, however, do not admit an analytic extension on either sheet of the Riemann surface. Therefore, a suitable modification of both the direct and the inverse problem formulations is necessary. On the direct side, this is accomplished by constructing two additional analytic eigenfunctions which are expressed in terms of the adjoint eigenfunctions. The discrete spectrum, bound states and symmetries of the direct problem are then discussed. In the most general situation, a discrete eigenvalue corresponds to a quartet of zeros (poles) of certain scattering data. The inverse scattering problem is formulated in terms of a generalized Riemann-Hilbert (RH) problem in the upper/lower half planes of a suitable uniformization variable. Special soliton solutions are constructed from the poles in the RH problem, and include dark-dark soliton solutions, which have dark solitonic behavior in both components, as well as dark-bright soliton solutions, which have one dark and one bright component. The linear limit is obtained from the RH problem and is shown to correspond to the Fourier transform solution obtained from the linearized vector NLS system

Continuous development of current sheets near and away from magnetic nulls

International Nuclear Information System (INIS)

Kumar, Sanjay; Bhattacharyya, R.

2016-01-01

The presented computations compare the strength of current sheets which develop near and away from the magnetic nulls. To ensure the spontaneous generation of current sheets, the computations are performed congruently with Parker's magnetostatic theorem. The simulations evince current sheets near two dimensional and three dimensional magnetic nulls as well as away from them. An important finding of this work is in the demonstration of comparative scaling of peak current density with numerical resolution, for these different types of current sheets. The results document current sheets near two dimensional magnetic nulls to have larger strength while exhibiting a stronger scaling than the current sheets close to three dimensional magnetic nulls or away from any magnetic null. The comparative scaling points to a scenario where the magnetic topology near a developing current sheet is important for energetics of the subsequent reconnection.

Dynamic Antarctic ice sheet during the early to mid-Miocene

Science.gov (United States)

Gasson, Edward; DeConto, Robert M.; Pollard, David; Levy, Richard H.

2016-03-01

Geological data indicate that there were major variations in Antarctic ice sheet volume and extent during the early to mid-Miocene. Simulating such large-scale changes is problematic because of a strong hysteresis effect, which results in stability once the ice sheets have reached continental size. A relatively narrow range of atmospheric CO2 concentrations indicated by proxy records exacerbates this problem. Here, we are able to simulate large-scale variability of the early to mid-Miocene Antarctic ice sheet because of three developments in our modeling approach. (i) We use a climate-ice sheet coupling method utilizing a high-resolution atmospheric component to account for ice sheet-climate feedbacks. (ii) The ice sheet model includes recently proposed mechanisms for retreat into deep subglacial basins caused by ice-cliff failure and ice-shelf hydrofracture. (iii) We account for changes in the oxygen isotopic composition of the ice sheet by using isotope-enabled climate and ice sheet models. We compare our modeling results with ice-proximal records emerging from a sedimentological drill core from the Ross Sea (Andrill-2A) that is presented in a companion article. The variability in Antarctic ice volume that we simulate is equivalent to a seawater oxygen isotope signal of 0.52-0.66‰, or a sea level equivalent change of 30-36 m, for a range of atmospheric CO2 between 280 and 500 ppm and a changing astronomical configuration. This result represents a substantial advance in resolving the long-standing model data conflict of Miocene Antarctic ice sheet and sea level variability.

Ice Sheet Model Intercomparison Project (ISMIP6) Contribution to CMIP6

Science.gov (United States)

Nowicki, Sophie M. J.; Payne, Tony; Larour, Eric; Seroussi, Helene; Goelzer, Heiko; Lipscomb, William; Gregory, Jonathan; Abe-Ouchi, Ayako; Shepherd, Andrew

2016-01-01

Reducing the uncertainty in the past, present, and future contribution of ice sheets to sea-level change requires a coordinated effort between the climate and glaciology communities. The Ice Sheet Model Intercomparison Project for CMIP6 (ISMIP6) is the primary activity within the Coupled Model Intercomparison Project phase 6 (CMIP6) focusing on the Greenland and Antarctic ice sheets. In this paper, we describe the framework for ISMIP6 and its relationship with other activities within CMIP6. The ISMIP6 experimental design relies on CMIP6 climate models and includes, for the first time within CMIP, coupled ice-sheetclimate models as well as standalone ice-sheet models. To facilitate analysis of the multi-model ensemble and to generate a set of standard climate inputs for standalone ice-sheet models, ISMIP6 defines a protocol for all variables related to ice sheets. ISMIP6 will provide a basis for investigating the feedbacks, impacts, and sea-level changes associated with dynamic ice sheets and for quantifying the uncertainty in ice-sheet-sourced global sea-level change.

Microstructural Changes in Brazing Sheet due to Solid-Liquid Interaction

NARCIS (Netherlands)

Wittebrood, A.J.

2009-01-01

Aluminium brazing sheet is the material of choice to produce automotive heat exchangers. Although in Dutch the official translation of aluminium brazing sheet is “aluminium hardsoldeerplaat” the English name is used in the industry. Aluminium brazing sheet is basically a sandwich material and

Transfer of fibroblast sheets cultured on thermoresponsive dishes with membranes.

Science.gov (United States)

Kawecki, Marek; Kraut, Małgorzata; Klama-Baryła, Agnieszka; Łabuś, Wojciech; Kitala, Diana; Nowak, Mariusz; Glik, Justyna; Sieroń, Aleksander L; Utrata-Wesołek, Alicja; Trzebicka, Barbara; Dworak, Andrzej; Szweda, Dawid

2016-06-01

In cell or tissue engineering, it is essential to develop a support for cell-to-cell adhesion, which leads to the generation of cell sheets connected by extracellular matrix. Such supports must be hydrophobic and should result in a detachable cell sheet. A thermoresponsive support that enables the cultured cell sheet to detach using only a change in temperature could be an interesting alternative in regenerative medicine. The aim of this study was to evaluate plates covered with thermoresponsive polymers as supports for the formation of fibroblast sheets and to develop a damage-free procedure for cell sheet transfer with the use of membranes as transfer tools. Human skin fibroblasts were seeded on supports coated with a thermoresponsive polymer: commercial UpCell™ dishes (NUNC™) coated with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) and dishes coated with thermoresponsive poly(tri(ethylene glycol) monoethyl ether methacrylate) (P(TEGMA-EE)). Confluent fibroblast sheets were effectively cultured and harvested from both commercial PNIPAM-coated dishes and laboratory P(TEGMA-EE)-coated dishes. To transfer a detached cell sheet, two membranes, Immobilon-P(®) and SUPRATHEL(®), were examined. The use of SUPRATHEL for relocating the cell sheets opens a new possibility for the clinical treatment of wounds. This study established the background for implementing thermoresponsive supports for transplanting in vitro cultured fibroblasts.

Endogenous Sheet-Averaged Tension Within a Large Epithelial Cell Colony.

Science.gov (United States)

Dumbali, Sandeep P; Mei, Lanju; Qian, Shizhi; Maruthamuthu, Venkat

2017-10-01

Epithelial cells form quasi-two-dimensional sheets that function as contractile media to effect tissue shape changes during development and homeostasis. Endogenously generated intrasheet tension is a driver of such changes, but has predominantly been measured in the presence of directional migration. The nature of epithelial cell-generated forces transmitted over supracellular distances, in the absence of directional migration, is thus largely unclear. In this report, we consider large epithelial cell colonies which are archetypical multicell collectives with extensive cell-cell contacts but with a symmetric (circular) boundary. Using the traction force imbalance method (TFIM) (traction force microscopy combined with physical force balance), we first show that one can determine the colony-level endogenous sheet forces exerted at the midline by one half of the colony on the other half with no prior assumptions on the uniformity of the mechanical properties of the cell sheet. Importantly, we find that this colony-level sheet force exhibits large variations with orientation-the difference between the maximum and minimum sheet force is comparable to the average sheet force itself. Furthermore, the sheet force at the colony midline is largely tensile but the shear component exhibits significantly more variation with orientation. We thus show that even an unperturbed epithelial colony with a symmetric boundary shows significant directional variation in the endogenous sheet tension and shear forces that subsist at the colony level.

Influence of temperature fluctuations on equilibrium ice sheet volume

Directory of Open Access Journals (Sweden)

T. B. Mikkelsen

2018-01-01

Full Text Available Forecasting the future sea level relies on accurate modeling of the response of the Greenland and Antarctic ice sheets to changing temperatures. The surface mass balance (SMB of the Greenland Ice Sheet (GrIS has a nonlinear response to warming. Cold and warm anomalies of equal size do not cancel out and it is therefore important to consider the effect of interannual fluctuations in temperature. We find that the steady-state volume of an ice sheet is biased toward larger size if interannual temperature fluctuations are not taken into account in numerical modeling of the ice sheet. We illustrate this in a simple ice sheet model and find that the equilibrium ice volume is approximately 1 m SLE (meters sea level equivalent smaller when the simple model is forced with fluctuating temperatures as opposed to a stable climate. It is therefore important to consider the effect of interannual temperature fluctuations when designing long experiments such as paleo-spin-ups. We show how the magnitude of the potential bias can be quantified statistically. For recent simulations of the Greenland Ice Sheet, we estimate the bias to be 30 Gt yr−1 (24–59 Gt yr−1, 95 % credibility for a warming of 3 °C above preindustrial values, or 13 % (10–25, 95 % credibility of the present-day rate of ice loss. Models of the Greenland Ice Sheet show a collapse threshold beyond which the ice sheet becomes unsustainable. The proximity of the threshold will be underestimated if temperature fluctuations are not taken into account. We estimate the bias to be 0.12 °C (0.10–0.18 °C, 95 % credibility for a recent estimate of the threshold. In light of our findings it is important to gauge the extent to which this increased variability will influence the mass balance of the ice sheets.

Continuous liquid sheet generator for ion stripping

International Nuclear Information System (INIS)

Gavin, B.; Batson, P.; Leemann, B.; Rude, B.

1984-10-01

Many of the technical problems of generating a large thin liquid sheet from 0.02 to 0.20 μm thick (3 to 40 μgm/cm 2 ) have been solved. It is shown that this perennial sheet is stable and consonant in dimension. Several ion beam species from the SuperHILAC have been used for evaluation; at 0.11 MeV/n. In one of three modes this sheet serves as an equivalent substitute for a carbon foil. The second mode is characterized by a solid-like charge state distribution but with a varying fraction of unstripped ions. The third mode gives stripping performance akin to a vapor stripping medium. 9 references, 7 figures

Simulation spread sheet of Angra-1 secondary circuit

International Nuclear Information System (INIS)

Futuro, F.L.; Rucos, J.; Ogando, A.; Maprelian, E.; Bassel, W.S.; Baptista Filho, B.D.

2000-01-01

The efficient operation of a Nuclear Power Plant (NPP) requires the continuous identification of derivations in the main operating parameters. The identification and analysis of those derivations allow someone to detect the degradation of instruments or even of any equipment. In order to study this problem the group of thermal generation of Angra 1 NPP, devised the use of a Microsoft Excel spread sheet for the automation of Angra 1 thermal balance. In the set of simulation spread sheets, measured values of the secondary system main parameters were compared with project values for a given reactor power level and condenser pressure. The spread sheets provide the turbines power and efficiency and do the plant thermal balance. This work presents a general description of the spread sheets set and a real case analysis of Angra 1 NPP, showing its precision and use easiness. (author)

The Potsdam Parallel Ice Sheet Model (PISM-PIK) - Part 2: Dynamic equilibrium simulation of the Antarctic ice sheet

Science.gov (United States)

Martin, M. A.; Winkelmann, R.; Haseloff, M.; Albrecht, T.; Bueler, E.; Khroulev, C.; Levermann, A.

2011-09-01

We present a dynamic equilibrium simulation of the ice sheet-shelf system on Antarctica with the Potsdam Parallel Ice Sheet Model (PISM-PIK). The simulation is initialized with present-day conditions for bed topography and ice thickness and then run to steady state with constant present-day surface mass balance. Surface temperature and sub-shelf basal melt distribution are parameterized. Grounding lines and calving fronts are free to evolve, and their modeled equilibrium state is compared to observational data. A physically-motivated calving law based on horizontal spreading rates allows for realistic calving fronts for various types of shelves. Steady-state dynamics including surface velocity and ice flux are analyzed for whole Antarctica and the Ronne-Filchner and Ross ice shelf areas in particular. The results show that the different flow regimes in sheet and shelves, and the transition zone between them, are captured reasonably well, supporting the approach of superposition of SIA and SSA for the representation of fast motion of grounded ice. This approach also leads to a natural emergence of sliding-dominated flow in stream-like features in this new 3-D marine ice sheet model.

Extension of the root-locus method to a certain class of fractional-order systems.

Science.gov (United States)

Merrikh-Bayat, Farshad; Afshar, Mahdi; Karimi-Ghartemani, Masoud

2009-01-01

In this paper, the well-known root-locus method is developed for the special subset of linear time-invariant systems commonly known as fractional-order systems. Transfer functions of these systems are rational functions with polynomials of rational powers of the Laplace variable s. Such systems are defined on a Riemann surface because of their multi-valued nature. A set of rules for plotting the root loci on the first Riemann sheet is presented. The important features of the classical root-locus method such as asymptotes, roots condition on the real axis and breakaway points are extended to the fractional case. It is also shown that the proposed method can assess the closed-loop stability of fractional-order systems in the presence of a varying gain in the loop. Moreover, the effect of perturbation on the root loci is discussed. Three illustrative examples are presented to confirm the effectiveness of the proposed algorithm.

75 FR 55340 - Recovery Fact Sheet 9580.100, Mold Remediation

Science.gov (United States)

2010-09-10

...] Recovery Fact Sheet 9580.100, Mold Remediation AGENCY: Federal Emergency Management Agency, DHS. ACTION... accepting comments on Recovery Fact Sheet RP9580.100, Mold Remediation. DATES: Comments must be received by... 20472-3100. II. Background The Recovery Fact Sheet RP9580.100, Mold Remediation, identifies the expenses...

Balance velocities of the Greenland ice sheet

DEFF Research Database (Denmark)

Joughin, I.; Fahnestock, M.; Ekholm, Simon

1997-01-01

We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetery data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail......, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning....

Cholera Fact Sheet

Science.gov (United States)

... news-room/fact-sheets/detail/cholera","@context":"http://schema.org","@type":"Article"}; العربية 中文 français русский español ... that includes feedback at the local level and information-sharing at the global level. Cholera cases are ...

Magneto-hydrodynamics of coupled fluid–sheet interface with mass suction and blowing

International Nuclear Information System (INIS)

Ahmad, R.

2016-01-01

There are large number of studies which prescribe the kinematics of the sheet and ignore the sheet's mechanics. However, the current boundary layer analysis investigates the mechanics of both the electrically conducting fluid and a permeable sheet, which makes it distinct from the other studies in the literature. One of the objectives of the current study is to (i) examine the behaviour of magnetic field effect for both the surface and the electrically conducting fluid (ii) investigate the heat and mass transfer between a permeable sheet and the surrounding electrically conducting fluid across the hydro, thermal and mass boundary layers. Self-similar solutions are obtained by considering the RK45 technique. Analytical solution is also found for the stretching sheet case. The skin friction dual solutions are presented for various types of sheet. The influence of pertinent parameters on the dimensionless velocity, shear stress, temperature, mass concentration, heat and mass transfer rates on the fluid–sheet interface is presented graphically as well as numerically. The obtained results are of potential benefit for studying the electrically conducting flow over various soft surfaces such as synthetic plastics, soft silicone sheet and soft synthetic rubber sheet. These surfaces are easily deformed by thermal fluctuations or thermal stresses. - Highlights: • The momentum equation is modelled for both the surrounding MHD fluid and the sheet with the effects of mass suction and blowing. • The current study further investigates the heat and mass transfer characteristics between a permeable sheet and the surrounding electrically conducting fluid across the thermal and mass boundary layers. • Both the approximated and analytical techniques have been included for the purpose of comparison, and the perfect numerical agreements have been established with the previous studies. • Dual solutions for the skin friction coefficients are found for various categories of

Composite cell sheet for periodontal regeneration: crosstalk between different types of MSCs in cell sheet facilitates complex periodontal-like tissue regeneration.

Science.gov (United States)

Zhang, Hao; Liu, Shiyu; Zhu, Bin; Xu, Qiu; Ding, Yin; Jin, Yan

2016-11-14

Tissue-engineering strategies based on mesenchymal stem cells (MSCs) and cell sheets have been widely used for periodontal tissue regeneration. However, given the complexity in periodontal structure, the regeneration methods using a single species of MSC could not fulfill the requirement for periodontal regeneration. We researched the interaction between the periodontal ligament stem cells (PDLSCs) and jaw bone marrow-derived mesenchymal stem cells (JBMMSCs), and constructed a composite cell sheet comprising both of the above MSCs to regenerate complex periodontium-like structures in nude mice. Our results show that by co-culturing PDLSCs and JBMMSCs, the expressions of bone and extracellular matrix (ECM)-related genes and proteins were significantly improved in both MSCs. Further investigations showed that, compared to the cell sheet using PDLSCs or JBMMSCs, the composite stem cell sheet (CSCS), which comprises these two MSCs, expressed higher levels of bone- and ECM-related genes and proteins, and generated a composite structure more similar to the native periodontal tissue physiologically in vivo. In conclusion, our results demonstrate that the crosstalk between PDLSCs and JBMMSCs in cell sheets facilitate regeneration of complex periodontium-like structures, providing a promising new strategy for physiological and functional regeneration of periodontal tissue.

Effects of electron pressure anisotropy on current sheet configuration

Energy Technology Data Exchange (ETDEWEB)

Artemyev, A. V., E-mail: aartemyev@igpp.ucla.edu; Angelopoulos, V.; Runov, A. [Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California 90095 (United States); Vasko, I. Y. [Space Research Institute, RAS, Moscow (Russian Federation)

2016-09-15

Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

Effects of electron pressure anisotropy on current sheet configuration

International Nuclear Information System (INIS)

Artemyev, A. V.; Angelopoulos, V.; Runov, A.; Vasko, I. Y.

2016-01-01

Recent spacecraft observations in the Earth's magnetosphere have demonstrated that the magnetotail current sheet can be supported by currents of anisotropic electron population. Strong electron currents are responsible for the formation of very thin (intense) current sheets playing the crucial role in stability of the Earth's magnetotail. We explore the properties of such thin current sheets with hot isotropic ions and cold anisotropic electrons. Decoupling of the motions of ions and electrons results in the generation of a polarization electric field. The distribution of the corresponding scalar potential is derived from the electron pressure balance and the quasi-neutrality condition. We find that electron pressure anisotropy is partially balanced by a field-aligned component of this polarization electric field. We propose a 2D model that describes a thin current sheet supported by currents of anisotropic electrons embedded in an ion-dominated current sheet. Current density profiles in our model agree well with THEMIS observations in the Earth's magnetotail.

Structural Biology Fact Sheet

Science.gov (United States)

... NIGMS NIGMS Home > Science Education > Structural Biology Structural Biology Tagline (Optional) Middle/Main Content Area PDF Version (688 KB) Other Fact Sheets What is structural biology? Structural biology is the study of how biological ...

Friction and lubrication modelling in sheet metal forming: Influence of lubrication amount, tool roughness and sheet coating on product quality

Science.gov (United States)

Hol, J.; Wiebenga, J. H.; Carleer, B.

2017-09-01

In the stamping of automotive parts, friction and lubrication play a key role in achieving high quality products. In the development process of new automotive parts, it is therefore crucial to accurately account for these effects in sheet metal forming simulations. This paper presents a selection of results considering friction and lubrication modelling in sheet metal forming simulations of a front fender product. For varying lubrication conditions, the front fender can either show wrinkling or fractures. The front fender is modelled using different lubrication amounts, tool roughness’s and sheet coatings to show the strong influence of friction on both part quality and the overall production stability. For this purpose, the TriboForm software is used in combination with the AutoForm software. The results demonstrate that the TriboForm software enables the simulation of friction behaviour for varying lubrication conditions, i.e. resulting in a generally applicable approach for friction characterization under industrial sheet metal forming process conditions.

The electrostatics of charged insulating sheets peeled from grounded conductors

International Nuclear Information System (INIS)

Datta, M J; Horenstein, M N

2008-01-01

The physics of a charged, insulating sheet peeled from a ground-plane conductor is examined. Contact charging is ensured by charging a sheet to 10-12 kV with corona to establish intimate electrostatic contact with the underlying conductor. The surface potential is next forced to zero by sweeping the sheet with a stainless-steel brush, and the surface recharged to a new potential between 0 and 11 kV. The sheet is then peeled from the ground plane and its residual charge density is measured. Results show that the residual charge equals the breakdown-limiting value, but its polarity depends on the surface potential acquired just prior to peeling. The results have relevance to studies of industrial webs and insulating sheets.

Behavior of protruding lateral plane graphene sheets in liquid dodecane: molecular dynamics simulations

Energy Technology Data Exchange (ETDEWEB)

Chen, Shenghui; Sun, Shuangqing, E-mail: sunshuangqing@upc.edu.cn; Li, Chunling [China University of Petroleum (East China), College of Science (China); Pittman, Charles U. [Mississippi State University, Department of Chemistry (United States); Lacy, Thomas E. [Mississippi State University, Department of Aerospace Engineering (United States); Hu, Songqing, E-mail: songqinghu@upc.edu.cn [China University of Petroleum (East China), College of Science (China); Gwaltney, Steven R. [Mississippi State University, Department of Chemistry (United States)

2016-11-15

Molecular dynamics simulations are used to investigate the behavior of two parallel graphene sheets fixed on one edge (lateral plane) in liquid dodecane. The interactions of these sheets and dodecane molecules are studied with different starting inter-sheet distances. The structure of the dodecane solvent is also analyzed. The results show that when the distance between the two graphene sheets is short (less than 6.8 Å), the sheets will expel the dodecane molecules between them and stack together. However, when the distance between two sheets is large (greater than 10.2 Å), the two sheets do not come together, and the dodecane molecules will form ordered layers in the interlayer spacing. The equilibrium distance between the graphene sheets can only take on specific discrete values (3.4, 7.8, and 12.1 Å), because only an integer number of dodecane layers forms between the two sheets. Once the graphene sheets are in contact, they remain in contact; the sheets do not separate to allow dodecane into the interlayer spacing.

Continental Ice Sheets and the Planetary Radiation Budget

NARCIS (Netherlands)

Oerlemans, J.

1980-01-01

The interaction between continental ice sheets and the planetary radiation budget is potentially important in climate-sensitivity studies. A simple ice-sheet model incorporated in an energybalance climate model provides a tool for studying this interaction in a quantitative way. Experiments in which

Best Management Practice Fact Sheet. 12, Filtering Practices

OpenAIRE

Sample, David; Barlow, Stefani

2013-01-01

This fact sheet is one of a 15-part series on urban stormwater management practices. This fact sheet discusses filtering practices, what they are, where they are used, how they work, maintenance, limitations, performance, expected costs and includes a glossary of terms.

Best Management Practice Fact Sheet. 10, Dry Swale

OpenAIRE

Sample, David; Doumar, Lia

2013-01-01

This fact sheet is one of a 15-part series on urban stormwater management practices. This fact sheet discusses dry swales, what they are, where they are used, how they work, maintenance, limitations, performance, expected costs and includes a glossary of terms.

Best Management Practice Fact Sheet. 11, Wet Swale

OpenAIRE

Sample, David; Doumar, Lia

2013-01-01

This fact sheet is one of a 15-part series on urban stormwater management practices. This fact sheet discusses wet swales, what they are, where they are used, how they work, maintenance, limitations, performance, expected costs and includes a glossary of terms.

Vortices on the string and superstring world sheets

International Nuclear Information System (INIS)

Abrikosov, A.A.; Kogan, Ya.I.

1989-01-01

The world-sheet dynamics of the first quantized string propagating in non-simply connected space is considered. Presence of the vortices on the world sheet lead to Berezinsky-Kosterlitz-Thouless(BKT) phase transition. Bosonic and superstring cases are discussed. 20 refs.; 2 figs

Characterization of Platinum Nanoparticles Deposited on Functionalized Graphene Sheets

Directory of Open Access Journals (Sweden)

Yu-Chun Chiang

2015-09-01

Full Text Available Due to its special electronic and ballistic transport properties, graphene has attracted much interest from researchers. In this study, platinum (Pt nanoparticles were deposited on oxidized graphene sheets (cG. The graphene sheets were applied to overcome the corrosion problems of carbon black at operating conditions of proton exchange membrane fuel cells. To enhance the interfacial interactions between the graphene sheets and the Pt nanoparticles, the oxygen-containing functional groups were introduced onto the surface of graphene sheets. The results showed the Pt nanoparticles were uniformly dispersed on the surface of graphene sheets with a mean Pt particle size of 2.08 nm. The Pt nanoparticles deposited on graphene sheets exhibited better crystallinity and higher oxygen resistance. The metal Pt was the predominant Pt chemical state on Pt/cG (60.4%. The results from the cyclic voltammetry analysis showed the value of the electrochemical surface area (ECSA was 88 m2/g (Pt/cG, much higher than that of Pt/C (46 m2/g. The long-term test illustrated the degradation in ECSA exhibited the order of Pt/C (33% > Pt/cG (7%. The values of the utilization efficiency were calculated to be 64% for Pt/cG and 32% for Pt/C.

The Response of Ice Sheets to Climate Variability

Science.gov (United States)

Snow, K.; Goldberg, D. N.; Holland, P. R.; Jordan, J. R.; Arthern, R. J.; Jenkins, A.

2017-12-01

West Antarctic Ice Sheet loss is a significant contributor to sea level rise. While the ice loss is thought to be triggered by fluctuations in oceanic heat at the ice shelf bases, ice sheet response to ocean variability remains poorly understood. Using a synchronously coupled ice-ocean model permitting grounding line migration, this study evaluates the response of an ice sheet to periodic variations in ocean forcing. Resulting oscillations in grounded ice volume amplitude is shown to grow as a nonlinear function of ocean forcing period. This implies that slower oscillations in climatic forcing are disproportionately important to ice sheets. The ice shelf residence time offers a critical time scale, above which the ice response amplitude is a linear function of ocean forcing period and below which it is quadratic. These results highlight the sensitivity of West Antarctic ice streams to perturbations in heat fluxes occurring at decadal time scales.

Hibernia fact sheet

International Nuclear Information System (INIS)

Anon.

1994-01-01

This fact sheet gives details of the Hibernia oil field including its location, discovery date, oil company's interests in the project, the recoverable reserves of the two reservoirs, the production system used, capital costs of the project, and overall targets for Canadian benefit. Significant dates for the Hibernia project are listed. (UK)

A simple holistic hypothesis for the self-destruction of ice sheets

Science.gov (United States)

Hughes, T.

2011-07-01

Ice sheets are the only components of Earth's climate system that can self-destruct. This paper presents the quantitative force balance for bottom-up modeling of ice sheets, as first presented qualitatively in this journal as a way to quantify ice-bed uncoupling leading to self-destruction of ice sheets ( Hughes, 2009a). Rapid changes in sea level and climate can result if a large ice-sheet self-destructs quickly, as did the former Laurentide Ice Sheet of North America between 8100 and 7900 BP, thereby terminating the last cycle of Quaternary glaciation. Ice streams discharge up to 90 percent of ice from past and present ice sheets. A hypothesis is presented in which self-destruction of an ice sheet begins when ubiquitous ice-bed decoupling, quantified as a floating fraction of ice, proceeds along ice streams. This causes ice streams to surge and reduce thickness by some 90 percent, and height above sea level by up to 99 percent for floating ice, so the ice sheet undergoes gravitational collapse. Ice collapsing over marine embayments becomes floating ice shelves that may then disintegrate rapidly. This floods the world ocean with icebergs that reduce the ocean-to-atmosphere heat exchange, thereby triggering climate change. Calving bays migrate up low stagnating ice streams and carve out the accumulation zone of the collapsed ice sheet, which prevents its recovery, decreases Earth's albedo, and terminates the glaciation cycle. This sequence of events may coincide with a proposed life cycle of ice streams that drain the ice sheet. A first-order treatment of these life cycles is presented that depends on the longitudinal force balance along the flowbands of ice streams and gives a first approximation to ice-bed uncoupling at snapshots during gravitational collapse into ice shelves that disintegrate, thereby removing the ice sheet. The stability of the Antarctic Ice Sheet is assessed using this bottom-up approach.

Balance sheet capacity and endogenous risk

OpenAIRE

Jon Danielsson; Hyun Song Shin; Jean-Pierre Zigrand

2011-01-01

Banks operating under Value-at-Risk constraints give rise to a well-defined aggregate balance sheet capacity for the banking sector as a whole that depends on total bank capital. Equilibrium risk and market risk premiums can be solved in closed form as functions of aggregate bank capital. We explore the empirical properties of the model in light of recent experience in the financial crisis and highlight the importance of balance sheet capacity as the driver of the financial cycle and market r...

Symmetry breaking bifurcations of a current sheet

International Nuclear Information System (INIS)

Parker, R.D.; Dewar, R.L.; Johnson, J.L.

1990-01-01

Using a time evolution code with periodic boundary conditions, the viscoresistive hydromagnetic equations describing an initially static, planar current sheet with large Lundquist number have been evolved for times long enough to reach a steady state. A cosh 2 x resistivity model was used. For long periodicity lengths L p , the resistivity gradient drives flows that cause forced reconnection at X point current sheets. Using L p as a bifurcation parameter, two new symmetry breaking bifurcations were found: a transition to an asymmetric island chain with nonzero, positive, or negative phase velocity, and a transition to a static state with alternating large and small islands. These states are reached after a complex transient behavior, which involves a competition between secondary current sheet instability and coalescence

Tuning the mechanical properties of vertical graphene sheets through atomic layer deposition

International Nuclear Information System (INIS)

Davami, Keivan; Jiang, Yijie; Cortes, John; Lin, Chen; Turner, Kevin T; Bargatin, Igor; Shaygan, Mehrdad

2016-01-01

We report the fabrication and characterization of graphene nanostructures with mechanical properties that are tuned by conformal deposition of alumina. Vertical graphene (VG) sheets, also called carbon nanowalls (CNWs), were grown on copper foil substrates using a radio-frequency plasma-enhanced chemical vapor deposition (RF-PECVD) technique and conformally coated with different thicknesses of alumina (Al_2O_3) using atomic layer deposition (ALD). Nanoindentation was used to characterize the mechanical properties of pristine and alumina-coated VG sheets. Results show a significant increase in the effective Young’s modulus of the VG sheets with increasing thickness of deposited alumina. Deposition of only a 5 nm thick alumina layer on the VG sheets nearly triples the effective Young’s modulus of the VG structures. Both energy absorption and strain recovery were lower in VG sheets coated with alumina than in pure VG sheets (for the same peak force). This may be attributed to the increase in bending stiffness of the VG sheets and the creation of connections between the sheets after ALD deposition. These results demonstrate that the mechanical properties of VG sheets can be tuned over a wide range through conformal atomic layer deposition, facilitating the use of VG sheets in applications where specific mechanical properties are needed. (paper)

Principles for designing proteins with cavities formed by curved β sheets

Energy Technology Data Exchange (ETDEWEB)

Marcos, Enrique; Basanta, Benjamin; Chidyausiku, Tamuka M.; Tang, Yuefeng; Oberdorfer, Gustav; Liu, Gaohua; Swapna, G. V. T.; Guan, Rongjin; Silva, Daniel-Adriano; Dou, Jiayi; Pereira, Jose Henrique; Xiao, Rong; Sankaran, Banumathi; Zwart, Peter H.; Montelione, Gaetano T.; Baker, David

2017-01-12

Active sites and ligand-binding cavities in native proteins are often formed by curved β sheets, and the ability to control β-sheet curvature would allow design of binding proteins with cavities customized to specific ligands. Toward this end, we investigated the mechanisms controlling β-sheet curvature by studying the geometry of β sheets in naturally occurring protein structures and folding simulations. The principles emerging from this analysis were used to design, de novo, a series of proteins with curved β sheets topped with α helices. Nuclear magnetic resonance and crystal structures of the designs closely match the computational models, showing that β-sheet curvature can be controlled with atomic-level accuracy. Our approach enables the design of proteins with cavities and provides a route to custom design ligand-binding and catalytic sites.

Modelling the Antarctic Ice Sheet

DEFF Research Database (Denmark)

Pedersen, Jens Olaf Pepke; Holm, A.

2015-01-01

to sea level high stands during past interglacial periods. A number of AIS models have been developed and applied to try to understand the workings of the AIS and to form a robust basis for future projections of the AIS contribution to sea level change. The recent DCESS (Danish Center for Earth System......The Antarctic ice sheet is a major player in the Earth’s climate system and is by far the largest depository of fresh water on the planet. Ice stored in the Antarctic ice sheet (AIS) contains enough water to raise sea level by about 58 m, and ice loss from Antarctica contributed significantly...

Silicon Sheet Quality is Improved By Meniscus Control

Science.gov (United States)

Yates, D. A.; Hatch, A. E.; Goldsmith, J. M.

1983-01-01

Better quality silicon crystals for solar cells are possible with instrument that monitors position of meniscus as sheet of solid silicon is drawn from melt. Using information on meniscus height, instrument generates feedback signal to control melt temperature. Automatic control ensures more uniform silicon sheets.

Oscillations of spherical fullerenes interacting with graphene sheet

Energy Technology Data Exchange (ETDEWEB)

Ghavanloo, Esmaeal, E-mail: ghavanloo@shirazu.ac.ir; Fazelzadeh, S. Ahmad

2017-01-01

In the present study, the oscillations of spherical fullerenes in the vicinity of a fully constrained graphene sheet are investigated. Using the continuous approximation and Lennard-Jones potential, the van der Waals (vdW) potential energy and interaction forces are obtained. The equation of motion is derived and directly solved based on the actual force distribution between the fullerene molecules and the graphene sheet. Numerical results are obtained and shown that the oscillation is sensitive to the size of the fullerene as well as the distance between the center of the fullerene and the graphene sheet.

Magma transport in sheet intrusions of the Alnö carbonatite complex, central Sweden.

Science.gov (United States)

Andersson, Magnus; Almqvist, Bjarne S G; Burchardt, Steffi; Troll, Valentin R; Malehmir, Alireza; Snowball, Ian; Kübler, Lutz

2016-06-10

Magma transport through the Earth's crust occurs dominantly via sheet intrusions, such as dykes and cone-sheets, and is fundamental to crustal evolution, volcanic eruptions and geochemical element cycling. However, reliable methods to reconstruct flow direction in solidified sheet intrusions have proved elusive. Anisotropy of magnetic susceptibility (AMS) in magmatic sheets is often interpreted as primary magma flow, but magnetic fabrics can be modified by post-emplacement processes, making interpretation of AMS data ambiguous. Here we present AMS data from cone-sheets in the Alnö carbonatite complex, central Sweden. We discuss six scenarios of syn- and post-emplacement processes that can modify AMS fabrics and offer a conceptual framework for systematic interpretation of magma movements in sheet intrusions. The AMS fabrics in the Alnö cone-sheets are dominantly oblate with magnetic foliations parallel to sheet orientations. These fabrics may result from primary lateral flow or from sheet closure at the terminal stage of magma transport. As the cone-sheets are discontinuous along their strike direction, sheet closure is the most probable process to explain the observed AMS fabrics. We argue that these fabrics may be common to cone-sheets and an integrated geology, petrology and AMS approach can be used to distinguish them from primary flow fabrics.

Should Cheat Sheets be Used as Study Aids in Economics Tests?

OpenAIRE

Yoav Wachsman

2002-01-01

This paper reports an experiment that investigates the effectiveness of cheat sheets as study aids for economics tests. A cheat sheet is a piece of paper that students can write anything they want on and use during a test. I find that both preparing and using a cheat sheet improves students' test performance. Additionally, there is no evidence that students become over dependent on their cheat sheets for answers.

Bamboo Fibre Reinforced Cement Used as a Roofing Sheet | Alade ...

African Journals Online (AJOL)

Bamboo fibre roofing sheet was able to withstand an average load of 51Kg, which is above the minimum required strength of 50kg. Comparatively, Asbestos roofing sheets and coconut fibre roofing sheets of similar dimensions had failure loads of 104.65Kg and 79Kg respectively. When immersed in water, bamboo fibre ...

Solar wind and substorm excitation of the wavy current sheet

Directory of Open Access Journals (Sweden)

C. Forsyth

2009-06-01

Full Text Available Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the ZGSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −YGSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002. We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005 and Erkaev et al. (2008. We find that the Erkaev et al. (2008 model gives the best fit to the observations.

Tearing resistance of some co-polyester sheets

International Nuclear Information System (INIS)

Kim, Ho Sung; Karger-Kocsis, Jozsef

2004-01-01

A three-zone model consisting of initial, evolutionary and stabilised plastic zones for tearing resistance was proposed for polymer sheets. An analysis with the model, based on the essential work of fracture (EWF) approach, was demonstrated to be capable for predicting specific total work of fracture along the tear path across all the plastic zones although accuracy of specific essential work of fracture is subject to improvement. Photo-elastic images were used for identification of plastic deformation sizes and profiles. Fracture mode change during loading was described in relation with the three zones. Tearing fracture behaviour of extruded mono- and bi-layer sheets of different types of amorphous co-polyesters and different thicknesses was investigated. Thick material exhibited higher specific total work of tear fracture than thin mono-layer sheet in the case of amorphous polyethylene terephthalate (PET). This finding was explained in terms of plastic zone size formed along the tear path, i.e., thick material underwent larger plastic deformation than thin material. When PET and polyethylene terephthalate glycol (PETG) were laminated with each other, specific total work of fracture of the bi-layer sheets was not noticeably improved over that of the constituent materials

Annual Energy Balance Sheets 2001-2002

International Nuclear Information System (INIS)

2004-01-01

During the year 2002 the primary supply of energy reached 629 TWh, which is 7.7 TWh less than 2001. The decrease originates mainly from the reduced electricity production from water power. Also the electricity production in nuclear power plants decreased by 4.5 TWh. If we were to look at the supplied energy for final consumption we will find a slightly rise by 1.8 TWh. The year 2002 was warmer than a 'normal' year and that consequently brings lower energy needs. Compared with 2001, 2002 was not warmer and a net electricity import of 5.4 TWh covered the energy needs. The energy use increased by 3.3 TWh between 2002 and 2001. The industry sector shows the largest rise by 2.9 TWh, nearly 2 per cent. Within that sector, energy from biomass fuel had a rise by 6.7 per cent. The household sector decreases its energy use by 2.7 per cent, and oil and electricity show the largest decrease. The proportionately high electricity price probably had a slowing down effect on the electricity use. The balance sheets of energy sources are showing the total supply and consumption of energy sources expressed in original units, i.e. units recorded in the primary statistics - mainly commercial units. The production of derived energy commodities is recorded on the supply - side of the balance sheets of energy sources, which is not the case in the energy balance sheets. The balance sheets of energy sources also include specifications of input--output and energy consumption in energy conversion industries. The energy balance sheets are based on primary data recorded in the balance sheets of energy sources, here expressed in a common energy unit, TJ. The production of derived energy is recorded in a second flow-step comprising energy turnover in energy conversion and is also specified in complementary input - output tables for energy conversion industries. The following items are shown in the energy balance sheets. 1.1 Inland supply of primary energy; 1.3 Import; 1.4 Export; 1.5 Changes in

Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release

Science.gov (United States)

van As, Dirk; Mikkelsen, Andreas Bech; Holtegaard Nielsen, Morten; Box, Jason E.; Claesson Liljedahl, Lillemor; Lindbäck, Katrin; Pitcher, Lincoln; Hasholt, Bent

2017-06-01

Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, well-constrained river discharge time series from the Watson River in southwest Greenland, with an accurate, observation-based ice sheet surface mass balance model of the ˜ 12 000 km2 ice sheet area feeding the river. For the 2006-2015 decade, we find a large range of a factor of 3 in interannual variability in discharge. The amount of discharge is amplified ˜ 56 % by the ice sheet's hypsometry, i.e., area increase with elevation. A good match between river discharge and ice sheet surface meltwater production is found after introducing elevation-dependent transit delays that moderate diurnal variability in meltwater release by a factor of 10-20. The routing lag time increases with ice sheet elevation and attains values in excess of 1 week for the upper reaches of the runoff area at ˜ 1800 m above sea level. These multi-day routing delays ensure that the highest proglacial discharge levels and thus overbank flooding events are more likely to occur after multi-day melt episodes. Finally, for the Watson River ice sheet catchment, we find no evidence of meltwater storage in or release from the en- and subglacial environments in quantities exceeding our methodological uncertainty, based on the good match between ice sheet runoff and proglacial discharge.

Active current sheets near the earth's bow shock

International Nuclear Information System (INIS)

Schwartz, S.J.; Kessel, R.L.; Brown, C.C.; Woolliscroft, L.J.C.; Dunlop, M.W.; Farrugia, C.J.; Hall, D.S.

1988-01-01

The authors present here an investigation of active current sheets observed by the AMPTE UK spacecraft near the Earth's bow shock, concentrating on their macroscopic features and geometry. Events selected primarily by flow directions which deviate substantially from the Sun-Earth line show similar characteristics, including their association with an underlying macroscopic current sheet and a hot central region whose flow direction is organized, at least in part, by location relative to the inferred initial intersection point between the current sheet and the bow shock. This region is flanked by edges which, according to a Rankine-Hugoniot analysis, are often fast shocks whose orientation is consistent with that expected if a bulge on the bow shock convected past the spacecraft. They have found the magnetosheath manifestations of these events which they study in detail. They suggest that these events are the direct result of the disruption and reformation of the bow shock by the passage of an interplanetary current sheet, most probably a tangential discontinuity

Financing gas plants using off balance sheet structures

International Nuclear Information System (INIS)

Best, R.J.; Malcolm, V.

1999-01-01

A means by which to finance oil and gas facilities using off balance sheet structures was presented. Off balance sheet facility financing means the sale by an oil and gas producer of a processing and/or transportation facility to a financial intermediary, who under a Management Agreement, appoints the producer as the operator of the facility. The financial intermediary charges a fixed processing fee to the producer and all the benefits and upside of ownership are retained by the producer. This paper deals specifically with a flexible off balance sheet facility financing structure that can be used to make effective use of discretionary capital which is committed to gas processing and to the construction of new gas processing facilities. Off balance sheet financing is an attractive alternative method of ownership that frees up capital that is locked into the facilities while allowing the producer to retain strategic control of the processing facility

Fast imaging of live organisms with sculpted light sheets

Science.gov (United States)

Chmielewski, Aleksander K.; Kyrsting, Anders; Mahou, Pierre; Wayland, Matthew T.; Muresan, Leila; Evers, Jan Felix; Kaminski, Clemens F.

2015-04-01

Light-sheet microscopy is an increasingly popular technique in the life sciences due to its fast 3D imaging capability of fluorescent samples with low photo toxicity compared to confocal methods. In this work we present a new, fast, flexible and simple to implement method to optimize the illumination light-sheet to the requirement at hand. A telescope composed of two electrically tuneable lenses enables us to define thickness and position of the light-sheet independently but accurately within milliseconds, and therefore optimize image quality of the features of interest interactively. We demonstrated the practical benefit of this technique by 1) assembling large field of views from tiled single exposure each with individually optimized illumination settings; 2) sculpting the light-sheet to trace complex sample shapes within single exposures. This technique proved compatible with confocal line scanning detection, further improving image contrast and resolution. Finally, we determined the effect of light-sheet optimization in the context of scattering tissue, devising procedures for balancing image quality, field of view and acquisition speed.

Heat Exchanger Tube to Tube Sheet Joints Corrosion Behavior

Directory of Open Access Journals (Sweden)

M. Iancu

2013-03-01

Full Text Available Paper presents the studies made by the authors above the tube to tube sheet fittings of heat exchanger with fixed covers from hydrofining oil reforming unit. Tube fittings are critical zones for heat exchangers failures. On a device made from material tube and tube sheet at real joints dimensions were establish axial compression force and traction force at which tube is extracted from expanded joint. Were used two shapes joints with two types of fittings surfaces, one with smooth hole of tube sheet and other in which on boring surface we made a groove. From extracted expanded tube zones were made samples for corrosion tests in order to establish the corrosion rate, corrosion potential and corrosion current in working mediums such as hydrofining oil and industrial water at different temperatures. The corrosion rate values and the temperature influence are important to evaluate joints durability and also the results obtained shows that the boring tube sheet shape with a groove on hole tube shape presents a better corrosion behavior then the shape with smooth hole tube sheet.

Interaction of a charge with a thin plasma sheet

International Nuclear Information System (INIS)

Bordag, M.

2007-01-01

The interaction of the electromagnetic field with a two-dimensional plasma sheet intended to describe the pi-electrons of a carbon nanotube or a C 60 molecule is investigated. By first integrating out the displacement field of the plasma or the electromagnetic field, different representations for quantities like the Casimir energy are derived which are shown to be consistent with one another. Starting from the covariant gauge for the electromagnetic field, it is shown that the matching conditions to which the presence of the plasma sheet can be reduced are different from the commonly used ones. The difference in the treatments does not show up in the Casimir force between two parallel sheets, but it is present in the Casimir-Polder force between a charge or a neutral atom and a sheet. At once, since the plasma sheet is a regularization of the conductor boundary conditions, this sheds light on the difference in physics found earlier in the realization of conductor boundary conditions as 'thin' or 'thick' boundary conditions in Phys. Rev. D 70, 085010 (2004)

A Case Study and Balance Sheet Approach to Unemployment.

Science.gov (United States)

Hesketh, Beryl; And Others

1987-01-01

Describes positive and negative aspects of employment and unemployment in a balance sheet framework. Discusses the value of the balance sheet approach in understanding individual differences in reactions to unemployment. (Author/KS)

The Potsdam Parallel Ice Sheet Model (PISM-PIK – Part 2: Dynamic equilibrium simulation of the Antarctic ice sheet

Directory of Open Access Journals (Sweden)

M. A. Martin

2011-09-01

Full Text Available We present a dynamic equilibrium simulation of the ice sheet-shelf system on Antarctica with the Potsdam Parallel Ice Sheet Model (PISM-PIK. The simulation is initialized with present-day conditions for bed topography and ice thickness and then run to steady state with constant present-day surface mass balance. Surface temperature and sub-shelf basal melt distribution are parameterized. Grounding lines and calving fronts are free to evolve, and their modeled equilibrium state is compared to observational data. A physically-motivated calving law based on horizontal spreading rates allows for realistic calving fronts for various types of shelves. Steady-state dynamics including surface velocity and ice flux are analyzed for whole Antarctica and the Ronne-Filchner and Ross ice shelf areas in particular. The results show that the different flow regimes in sheet and shelves, and the transition zone between them, are captured reasonably well, supporting the approach of superposition of SIA and SSA for the representation of fast motion of grounded ice. This approach also leads to a natural emergence of sliding-dominated flow in stream-like features in this new 3-D marine ice sheet model.

BRITICE-CHRONO: Constraining rates and style of marine-influenced ice sheet decay to provide a data-rich playground for ice sheet modellers

Science.gov (United States)

Clark, Chris

2014-05-01

Uncertainty exists regarding the fate of the Antarctic and Greenland ice sheets and how they will respond to forcings from sea level and atmospheric and ocean temperatures. If we want to know more about the mechanisms and rate of change of shrinking ice sheets, then why not examine an ice sheet that has fully disappeared and track its retreat through time? If achieved in enough detail such information could become a data-rich playground for improving the next breed of numerical ice sheet models to be used in ice and sea level forecasting. We regard that the last British-Irish Ice Sheet is a good target for this work, on account of its small size, density of information and with its numerous researchers already investigating it. BRITICE-CHRONO is a large (>45 researchers) NERC-funded consortium project comprising Quaternary scientists and glaciologists who will search the seafloor around Britain and Ireland and parts of the landmass in order to find and extract samples of sand, rock and organic matter that can be dated (OSL; Cosmogenic; 14C) to reveal the timing and rate of change of the collapsing British-Irish Ice Sheet. The purpose is to produce a high resolution dataset on the demise on an ice sheet - from the continental shelf edge and across the marine to terrestrial transition. Some 800 new date assessments will be added to those that already exist. This poster reports on the hypotheses that underpin the work. Data on retreat will be collected by focusing on 8 transects running from the continental shelf edge to a short distance (10s km) onshore and acquiring marine and terrestrial samples for geochronometric dating. The project includes funding for 587 radiocarbon, 140 OSL and 158 TCN samples for surface exposure dating; with sampling accomplished by two research cruises and 16 fieldwork campaigns. Results will reveal the timing and rate of change of ice margin recession for each transect, and combined with existing landform and dating databases, will be

Mountain building and the initiation of the Greenland Ice Sheet

DEFF Research Database (Denmark)

Solgaard, Anne Munck; Bonow, Johan; Langen, Peter Lang

2013-01-01

The effects of a new hypothesis about mountain building in Greenland on ice sheet initiation are investigated using an ice sheet model in combination with a climate model. According to this hypothesis, low-relief landscapes near sea level characterised Greenland in Miocene times until two phases...... superimposed by cold and warm excursions. The modelling results show that no ice initiates in the case of the low-lying and almost flat topography prior to the uplifts. However, the results demonstrate a significant ice sheet growth in response to the orographically induced increase in precipitation....... Under conditions that are colder than the present, the ice can overcome the Föhn effect, flow into the interior and form a coherent ice sheet. The results thus indicate that the Greenland Ice Sheet of today is a relict formed under colder conditions. The modelling results are consistent...

Two-and-one-half-dimensional magnetohydrodynamic simulations of the plasma sheet in the presence of oxygen ions: The plasma sheet oscillation and compressional Pc 5 waves

International Nuclear Information System (INIS)

Lu Li; Liu Zhenxing; Cao Jinbin

2002-01-01

Two-and-one-half-dimensional magnetohydrodynamic simulations of the multicomponent plasma sheet with the velocity curl term in the magnetic equation are represented. The simulation results can be summarized as follows: (1) There is an oscillation of the plasma sheet with the period on the order of 400 s (Pc 5 range); (2) the magnetic equator is a node of the magnetic field disturbance; (3) the magnetic energy integral varies antiphase with the internal energy integral; (4) disturbed waves have a propagating speed on the order of 10 km/s earthward; (5) the abundance of oxygen ions influences amplitude, period, and dissipation of the plasma sheet oscillation. It is suggested that the compressional Pc 5 waves, which are observed in the plasma sheet close to the magnetic equator, may be caused by the plasma sheet oscillation, or may be generated from the resonance of the plasma sheet oscillation with some Pc 5 perturbation waves coming from the outer magnetosphere

Mirage effect from thermally modulated transparent carbon nanotube sheets.

Science.gov (United States)

Aliev, Ali E; Gartstein, Yuri N; Baughman, Ray H

2011-10-28

The single-beam mirage effect, also known as photothermal deflection, is studied using a free-standing, highly aligned carbon nanotube aerogel sheet as the heat source. The extremely low thermal capacitance and high heat transfer ability of these transparent forest-drawn carbon nanotube sheets enables high frequency modulation of sheet temperature over an enormous temperature range, thereby providing a sharp, rapidly changing gradient of refractive index in the surrounding liquid or gas. The advantages of temperature modulation using carbon nanotube sheets are multiple: in inert gases the temperature can reach > 2500 K; the obtained frequency range for photothermal modulation is ~100 kHz in gases and over 100 Hz in high refractive index liquids; and the heat source is transparent for optical and acoustical waves. Unlike for conventional heat sources for photothermal deflection, the intensity and phase of the thermally modulated beam component linearly depends upon the beam-to-sheet separation over a wide range of distances. This aspect enables convenient measurements of accurate values for thermal diffusivity and the temperature dependence of refractive index for both liquids and gases. The remarkable performance of nanotube sheets suggests possible applications as photo-deflectors and for switchable invisibility cloaks, and provides useful insights into their use as thermoacoustic projectors and sonar. Visibility cloaking is demonstrated in a liquid.

Hanford Site Treated Effluent Disposal Facility process flow sheet

International Nuclear Information System (INIS)

Bendixsen, R.B.

1993-04-01

This report presents a novel method of using precipitation, destruction and recycle factors to prepare a process flow sheet. The 300 Area Treated Effluent Disposal Facility (TEDF) will treat process sewer waste water from the 300 Area of the Hanford Site, located near Richland, Washington, and discharge a permittable effluent flow into the Columbia River. When completed and operating, the TEDF effluent water flow will meet or exceed water quality standards for the 300 Area process sewer effluents. A preliminary safety analysis document (PSAD), a preconstruction requirement, needed a process flow sheet detailing the concentrations of radionuclides, inorganics and organics throughout the process, including the effluents, and providing estimates of stream flow quantities, activities, composition, and properties (i.e. temperature, pressure, specific gravity, pH and heat transfer rates). As the facility begins to operate, data from process samples can be used to provide better estimates of the factors, the factors can be entered into the flow sheet and the flow sheet will estimate more accurate steady state concentrations for the components. This report shows how the factors were developed and how they were used in developing a flow sheet to estimate component concentrations for the process flows. The report concludes with how TEDF sample data can improve the ability of the flow sheet to accurately predict concentrations of components in the process

Symmetry breaking bifurcations of a current sheet

International Nuclear Information System (INIS)

Parker, R.D.; Dewar, R.L.; Johnson, J.L.

1988-08-01

Using a time evolution code with periodic boundary conditions, the viscoresistive hydromagnetic equations describing an initially static, planar current sheet with large Lundquist number have been evolved for times long enough to reach a steady state. A cosh 2 x resistivity model was used. For long periodicity lengths, L p , the resistivity gradient drives flows which cause forced reconnection at X point current sheets. Using L p as a bifurcation parameter, two new symmetry breaking bifurcations were found - a transition to an asymmetric island chain with nonzero, positive or negative phase velocity, and a transition to a static state with alternating large and small islands. These states are reached after a complex transient behavior which involves a competition between secondary current sheet instability and coalescence. 31 refs., 6 figs

Flat-plate solar array project. Volume 3: Silicon sheet: Wafers and ribbons

Science.gov (United States)

Briglio, A.; Dumas, K.; Leipold, M.; Morrison, A.

1986-01-01

The primary objective of the Silicon Sheet Task of the Flat-Plate Solar Array (FSA) Project was the development of one or more low cost technologies for producing silicon sheet suitable for processing into cost-competitive solar cells. Silicon sheet refers to high purity crystalline silicon of size and thickness for fabrication into solar cells. Areas covered in the project were ingot growth and casting, wafering, ribbon growth, and other sheet technologies. The task made and fostered significant improvements in silicon sheet including processing of both ingot and ribbon technologies. An additional important outcome was the vastly improved understanding of the characteristics associated with high quality sheet, and the control of the parameters required for higher efficiency solar cells. Although significant sheet cost reductions were made, the technology advancements required to meet the task cost goals were not achieved.

Machine Shop Suggested Job and Task Sheets. Part I. 25 Elementary Jobs.

Science.gov (United States)

Texas A and M Univ., College Station. Vocational Instructional Services.

This volume consists of elementary job and task sheets adaptable for use in the regular vocational industrial education programs for the training of machinists and machine shop operators. Twenty-five simple machine shop job sheets are included. Some or all of this material is provided for each job sheet: an introductory sheet with aim, checking…

Current state and future perspectives on coupled ice-sheet - sea-level modelling

Science.gov (United States)

de Boer, Bas; Stocchi, Paolo; Whitehouse, Pippa L.; van de Wal, Roderik S. W.

2017-08-01

The interaction between ice-sheet growth and retreat and sea-level change has been an established field of research for many years. However, recent advances in numerical modelling have shed new light on the precise interaction of marine ice sheets with the change in near-field sea level, and the related stability of the grounding line position. Studies using fully coupled ice-sheet - sea-level models have shown that accounting for gravitationally self-consistent sea-level change will act to slow down the retreat and advance of marine ice-sheet grounding lines. Moreover, by simultaneously solving the 'sea-level equation' and modelling ice-sheet flow, coupled models provide a global field of relative sea-level change that is consistent with dynamic changes in ice-sheet extent. In this paper we present an overview of recent advances, possible caveats, methodologies and challenges involved in coupled ice-sheet - sea-level modelling. We conclude by presenting a first-order comparison between a suite of relative sea-level data and output from a coupled ice-sheet - sea-level model.

On the structure of the magnetotail current sheet

International Nuclear Information System (INIS)

Ashour-Abdalla, M.; Peroomian, V.; Richard, R.L.; Zelenyi, L.M.

1993-01-01

Results from modeling ion distribution functions in a two-dimensional reduction of the Tsyganenko magnetic field model have enabled the authors to calculate the full ion pressure tensor inside the model magnetotail. A thin current sheet is formed in the distant tail and the pressure tensor within this sheet has significant off-diagonal terms. These terms resulting from quasiadiabatic ion trajectories create azimuthally asymmetric distribution functions which are capable of maintaining stress-balance. Outside the current sheet the off-diagonal terms disappear and moderate anisotropy builds up with P perpendicular/P parallel ∼ 0.8. Closer to the Earth rapid isotropization of the distribution occurs

Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

Science.gov (United States)

Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

2007-01-01

Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

Research Status on the Heterogeneous Sheet Connection Forming Technology

Directory of Open Access Journals (Sweden)

SHI Wen-yong

2017-04-01

Full Text Available The heterogeneous sheet connection forming is one of the effective ways to realize lightweight in many fields，such as equipment manufacturing and transportation. However, there are obvious differences in the material properties，when using the traditional connection methods，there is a certain technical bottlenecks. In this paper, the technological characteristics and research status of the welding method and mechanical connection method are discussed in detail，such as the TIC welding and the laser welding. The advantages and development potential of the technology are introduced in the field of the heterogeneous sheet connection，in combination with the industry development and the use demand，the development of the heterogeneous sheet connection technology is expected，to provide the technical support for the research and development of new heterogeneous sheet connection technology.

1998 energy balance sheet of France

International Nuclear Information System (INIS)

Anon.

1999-01-01

This paper summarizes the results of the energy balance sheet of France for the year 1998 according to the data published by the energy observatory from the general direction of energy and raw materials (DGEMP) and according to the press communication given by C. Pierret, French state secretary of the industry. The following points are commented: the energy balance sheet (national production and energy independence, the energy shares in the consumption), the decay of the energy bill, and the details of the bill by energy type. (J.S.)

Physics of the magnetotail current sheet

International Nuclear Information System (INIS)

Chen, J.

1993-01-01

The Earth's magnetotail plays an important role in the solar-wind--magnetosphere coupling. At the midplane of the magnetotail is a current sheet where the dominant magnetic field component reverses sign. The charged particle motion in and near the current sheet is collisionless and nonintegrable, exhibiting chaotic scattering. The current understanding of the dynamical properties of the charged particle motion is discussed. In particular, the relationships between particle dynamics and global attributes of the system are elucidated. Geometrical properties of the phase space determine important physical observables on both micro- and macroscales

Periodic folding of viscous sheets

Science.gov (United States)

Ribe, Neil M.

2003-09-01

The periodic folding of a sheet of viscous fluid falling upon a rigid surface is a common fluid mechanical instability that occurs in contexts ranging from food processing to geophysics. Asymptotic thin-layer equations for the combined stretching-bending deformation of a two-dimensional sheet are solved numerically to determine the folding frequency as a function of the sheet’s initial thickness, the pouring speed, the height of fall, and the fluid properties. As the buoyancy increases, the system bifurcates from “forced” folding driven kinematically by fluid extrusion to “free” folding in which viscous resistance to bending is balanced by buoyancy. The systematics of the numerically predicted folding frequency are in good agreement with laboratory experiments.

Modelling of aluminium sheet forming at elevated temperatures

NARCIS (Netherlands)

van den Boogaard, Antonius H.; Huetink, Han

2004-01-01

The formability of Al–Mg sheet can be improved considerably, by increasing the temperature. By heating the sheet in areas with large shear strains, but cooling it on places where the risk of necking is high, the limiting drawing ratio can be increased to values above 2.5. At elevated temperatures,

On normal modes of gas sheets and discs

International Nuclear Information System (INIS)

Drury, L.O'C.

1980-01-01

A method is described for calculating the reflection and transmission coefficients characterizing normal modes of the Goldreich-Lynden-Bell gas sheet. Two families of gas discs without self-gravity for which the normal modes can be found analytically are given and used to illustrate the validity of the sheet approximation. (author)

Hypsometric amplification and routing moderation of Greenland ice sheet meltwater release

Directory of Open Access Journals (Sweden)

D. van As

2017-06-01

Full Text Available Concurrent ice sheet surface runoff and proglacial discharge monitoring are essential for understanding Greenland ice sheet meltwater release. We use an updated, well-constrained river discharge time series from the Watson River in southwest Greenland, with an accurate, observation-based ice sheet surface mass balance model of the  ∼  12 000 km2 ice sheet area feeding the river. For the 2006–2015 decade, we find a large range of a factor of 3 in interannual variability in discharge. The amount of discharge is amplified  ∼  56 % by the ice sheet's hypsometry, i.e., area increase with elevation. A good match between river discharge and ice sheet surface meltwater production is found after introducing elevation-dependent transit delays that moderate diurnal variability in meltwater release by a factor of 10–20. The routing lag time increases with ice sheet elevation and attains values in excess of 1 week for the upper reaches of the runoff area at  ∼  1800 m above sea level. These multi-day routing delays ensure that the highest proglacial discharge levels and thus overbank flooding events are more likely to occur after multi-day melt episodes. Finally, for the Watson River ice sheet catchment, we find no evidence of meltwater storage in or release from the en- and subglacial environments in quantities exceeding our methodological uncertainty, based on the good match between ice sheet runoff and proglacial discharge.

Nonlinear Dynamics of Non-uniform Current-Vortex Sheets in Magnetohydrodynamic Flows

Science.gov (United States)

Matsuoka, C.; Nishihara, K.; Sano, T.

2017-04-01

A theoretical model is proposed to describe fully nonlinear dynamics of interfaces in two-dimensional MHD flows based on an idea of non-uniform current-vortex sheet. Application of vortex sheet model to MHD flows has a crucial difficulty because of non-conservative nature of magnetic tension. However, it is shown that when a magnetic field is initially parallel to an interface, the concept of vortex sheet can be extended to MHD flows (current-vortex sheet). Two-dimensional MHD flows are then described only by a one-dimensional Lagrange parameter on the sheet. It is also shown that bulk magnetic field and velocity can be calculated from their values on the sheet. The model is tested by MHD Richtmyer-Meshkov instability with sinusoidal vortex sheet strength. Two-dimensional ideal MHD simulations show that the nonlinear dynamics of a shocked interface with density stratification agrees fairly well with that for its corresponding potential flow. Numerical solutions of the model reproduce properly the results of the ideal MHD simulations, such as the roll-up of spike, exponential growth of magnetic field, and its saturation and oscillation. Nonlinear evolution of the interface is found to be determined by the Alfvén and Atwood numbers. Some of their dependence on the sheet dynamics and magnetic field amplification are discussed. It is shown by the model that the magnetic field amplification occurs locally associated with the nonlinear dynamics of the current-vortex sheet. We expect that our model can be applicable to a wide variety of MHD shear flows.

Window-dressing in German interwar balance sheets

OpenAIRE

Mark Spoerer

1998-01-01

German accounting rules value assets and liabilities asymmetrically and thus lead to grossly distorted balance sheets. In the interwar debate on a reform of disclosure regulation, financial experts considered the (undisclosed) tax balance sheet, which had to be drawn up separately for the corporate tax assessment, as a paradigm for adequate financial disclosure. However, due to tax secrecy thay were barred from analyzing tax documents. Using archival evidence, we analyz...

Geometry task & drill sheets : grades 6-8

CERN Document Server

Rosenberg, Mary

2011-01-01

For grades 6-8, our Common Core State Standards-based combined resource meets the geometry concepts addressed by the NCTM standards and encourages the students to review the concepts in unique ways. The task sheets introduce the mathematical concepts to the students around a central problem taken from real-life experiences, while the drill sheets provide warm-up and timed practice questions for the students to strengthen their procedural proficiency skills.

Estimating the future ice sheet hydropower potential in Paakitsoq, Ilulissat, West Greenland

DEFF Research Database (Denmark)

Ahlstrøm, Andreas P.; Mottram, R.H.; Nielsen, C.

2008-01-01

sheet has emphasized the risk of sudden changes in catchment supply. In this study, we present a thorough investigation of hydropower feasibility at the Paakitsoq basin, near Ilulissat in West Greenland. The catchment is completely dominated by the Greenland ice sheet which provides large quantities...... of meltwater during the summer season. However, geometrical changes in the ice sheet, for example due to a retreat or an advance of the ice sheet margin, could change the hydrological catchment within the ice sheet. Such a change would have a devastating economical impact as a hydropower plant is a significant...... long-term investment for an Arctic community of modest population. Here we present a new bedrock and surface map of the Paakitsoq/Swiss Camp part of the Greenland ice sheet and a prediction of the future discharge up to 2080 AD using regional climate model output, dynamic ice sheet modelling...

Solar wind and substorm excitation of the wavy current sheet

Directory of Open Access Journals (Sweden)

C. Forsyth

2009-06-01

Full Text Available Following a solar wind pressure pulse on 3 August 2001, GOES 8, GOES 10, Cluster and Polar observed dipolarizations of the magnetic field, accompanied by an eastward expansion of the aurora observed by IMAGE, indicating the occurrence of two substorms. Prior to the first substorm, the motion of the plasma sheet with respect to Cluster was in the Z_GSM direction. Observations following the substorms show the occurrence of current sheet waves moving predominantly in the −Y_GSM direction. Following the second substorm, the current sheet waves caused multiple current sheet crossings of the Cluster spacecraft, previously studied by Zhang et al. (2002. We further this study to show that the velocity of the current sheet waves was similar to the expansion velocity of the substorm aurora and the expansion of the dipolarization regions in the magnetotail. Furthermore, we compare these results with the current sheet wave models of Golovchanskaya and Maltsev (2005 and Erkaev et al. (2008. We find that the Erkaev et al. (2008 model gives the best fit to the observations.

The Efficacy of a Silicone Sheet in Postoperative Scar Management.

Science.gov (United States)

Kim, Jin Sam; Hong, Joon Pio; Choi, Jong Woo; Seo, Dong Kyo; Lee, Eun Sook; Lee, Ho Seong

2016-09-01

Silicone gel sheeting has been introduced to prevent scarring, but objective evidence for its usefulness in scar healing is limited. Therefore, the authors' objective was to examine the effectiveness of silicone gel sheeting by randomly applying it to only unilateral scars from a bilateral hallux valgus surgery with symmetrical closure. In a prospective randomized, blinded, intraindividual comparison study, the silicone gel sheeting was applied to 1 foot of a hallux valgus incision scar (an experiment group) for 12 weeks upon removal of the stitches, whereas the symmetrical scar from the other foot was left untreated (a control group). The scars were evaluated at 4 and 12 weeks after the silicon sheet application. The Vancouver Scar Scale was used to measure the vascularity, pigmentation, pliability, height, and length of the scars. Adverse effects were also evaluated, and they included pain, itchiness, rash, erythema, and skin softening. At weeks 4 and 12, the experiment group scored significantly better on the Vancouver Scar Scale in all items, except length (P sheet does not cause adverse effects (P sheet application did show a significant improvement in prevention of postoperative scarring.

1970-1997 energy balance-sheets

International Nuclear Information System (INIS)

1998-01-01

The aim of this document is to bring together a consistent and harmonized set of statistical data on energy economics in the French territory. The information is based on the global and structural approach of the different energy balance-sheets published between 1970 and 1997. The first chapter gives a general idea of the energy situation of the passed year and outlines the evolution of the main aggregates (production, primary and final consumption etc..) comparatively to those of the general economy. The second chapter is devoted to the history of energy economics. Time series of indicators and diagrams allow to precise the structural modifications that occurred during the last decades. The main transformations in the national energy production and the development of the different energy sources in the industry, the residential and tertiary sectors and in the transportation sector are described too. The third chapter gives numerical data on energy for the last 28 years using the common Mtpe unit (million of tons of petroleum equivalent). These balance sheets are based on new energy keeping methods and use identical equivalence coefficients. The last chapter presents the energy balance sheets for the last three years, using the proper units for coal, petroleum, gas and electricity. (J.S.)

Effect of Fe, Co, Si and Ge impurities on optical properties of graphene sheet

International Nuclear Information System (INIS)

Kheyri, A.; Nourbakhsh, Z.; Darabi, E.

2016-01-01

The electronic and linear optical properties of pure graphene and impurity-graphene (with Fe, Co, Si and Ge impurities) sheets are investigated by using the full potential linear augmented plane wave plus local orbital (FPLAPW + lo) in the framework of the density functional theory (DFT). The calculated results are obtained within the generalized gradient approximation using the Perdew–Burke–Ernzerhof scheme in the presence of spin-orbit interaction. The band structure, partial electron density of states, dielectric function, absorption coefficient, optical conductivity, extinction index, energy loss function, reflectivity and the refraction index of these sheets for parallel and perpendicular electromagnetic wave polarization to sheet are investigated. The optical conductivity of Si-graphene and Ge-graphene sheets for the parallel electromagnetic wave polarization to the sheet starts with a gap about 0.4 eV confirms that these sheets have semiconductor behavior. Also the optical spectra of these sheets are anisotropic along these two wave polarizations. The dielectric function in the static limit of pure graphene sheet for perpendicular electromagnetic wave polarization to sheet does not significant change in the presence of Si, Ge, Fe and Co impurities. The static refractive index of Fe-graphene and Co-graphene sheets for parallel electromagnetic wave polarization to sheet is much larger than the corresponding value of pure graphene sheet. - Highlights: • Graphene sheet with Fe and Co impurities is metal. • Graphene sheet with Si and Ge impurities is semiconductor with 0.2 eV energy band gap. • These sheets optical spectra have metallic behavior for perpendicular polarization. • These sheets optical spectra have semiconductor behavior for parallel polarization. • Graphene sheet with Si and Ge impurities can use for optoelectronic devices.

Effect of Fe, Co, Si and Ge impurities on optical properties of graphene sheet

Energy Technology Data Exchange (ETDEWEB)

Kheyri, A. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Nourbakhsh, Z., E-mail: z.nourbakhsh@sci.ui.ac.ir [Physics Department, Faculty of Science, University of Isfahan, Isfahan (Iran, Islamic Republic of); Darabi, E. [Plasma Physics Research Center, Science and Research Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of)

2016-08-01

The electronic and linear optical properties of pure graphene and impurity-graphene (with Fe, Co, Si and Ge impurities) sheets are investigated by using the full potential linear augmented plane wave plus local orbital (FPLAPW + lo) in the framework of the density functional theory (DFT). The calculated results are obtained within the generalized gradient approximation using the Perdew–Burke–Ernzerhof scheme in the presence of spin-orbit interaction. The band structure, partial electron density of states, dielectric function, absorption coefficient, optical conductivity, extinction index, energy loss function, reflectivity and the refraction index of these sheets for parallel and perpendicular electromagnetic wave polarization to sheet are investigated. The optical conductivity of Si-graphene and Ge-graphene sheets for the parallel electromagnetic wave polarization to the sheet starts with a gap about 0.4 eV confirms that these sheets have semiconductor behavior. Also the optical spectra of these sheets are anisotropic along these two wave polarizations. The dielectric function in the static limit of pure graphene sheet for perpendicular electromagnetic wave polarization to sheet does not significant change in the presence of Si, Ge, Fe and Co impurities. The static refractive index of Fe-graphene and Co-graphene sheets for parallel electromagnetic wave polarization to sheet is much larger than the corresponding value of pure graphene sheet. - Highlights: • Graphene sheet with Fe and Co impurities is metal. • Graphene sheet with Si and Ge impurities is semiconductor with 0.2 eV energy band gap. • These sheets optical spectra have metallic behavior for perpendicular polarization. • These sheets optical spectra have semiconductor behavior for parallel polarization. • Graphene sheet with Si and Ge impurities can use for optoelectronic devices.

Bracing system of the reflecting sheets making up an insulating pile

International Nuclear Information System (INIS)

Carr, R.W.

1976-01-01

In order to reduce heat and radiation losses, the body of nuclear reactors and the connected pipe work are encased in reflecting and insulating piles of thin spaced sheets of aluminium or stainless steel. These spaced sheets are then encased in thicker and more solid internal and external shells. The piles and shells are generally shaped to follow the contour of the reactor and connected piping. It is therefore necessary to have available a study bracing system to keep the pile intact during the various handling and assembly operations. The fastening system must also exert an effect on the edge of the pile to prevent the sheets making it up from shifting in relation to each other. The description is given of a fastening system that includes an oblong section to be fitted along the edges of the piles up sheets; bracing substantially perpendicular to the oblong section, to space the sheets of the stack in pairs; and a maintaining system, normally perpendicular to the oblong section, to enable the fastener to be clipped to the edge of the sheets by bending it around the edge of each sheet of the pile [fr

Biobeam—Multiplexed wave-optical simulations of light-sheet microscopy

Science.gov (United States)

Weigert, Martin; Bundschuh, Sebastian T.

2018-01-01

Sample-induced image-degradation remains an intricate wave-optical problem in light-sheet microscopy. Here we present biobeam, an open-source software package that enables simulation of operational light-sheet microscopes by combining data from 105–106 multiplexed and GPU-accelerated point-spread-function calculations. The wave-optical nature of these simulations leads to the faithful reproduction of spatially varying aberrations, diffraction artifacts, geometric image distortions, adaptive optics, and emergent wave-optical phenomena, and renders image-formation in light-sheet microscopy computationally tractable. PMID:29652879

Bringing Sheet Music to Life: My Experiences with OMR

Directory of Open Access Journals (Sweden)

Andrew Bullen

2008-06-01

Full Text Available This article describes the process of digitizing sheet music celebrating Pullman porters and rail travel from the 1870s-1920s. The process involves 1 digitizing sheet music, 2 running the digitized sheet music through an Optical Musical Recognition (OMR software package, 3cleaning up the resulting file, 4 converting it into an .mp3/MIDI file, and 5 tweaking it to use the voices/instruments of a music editing software program. The pros and cons of some popular OMR programs are discussed.

Interactions between two beta-sheets. Energetics of beta/beta packing in proteins.

Science.gov (United States)

Chou, K C; Némethy, G; Rumsey, S; Tuttle, R W; Scheraga, H A

1986-04-20

The analysis of the interactions between regularly folded segments of the polypeptide chain contributes to an understanding of the energetics of protein folding. Conformational energy-minimization calculations have been carried out to determine the favorable ways of packing two right-twisted beta-sheets. The packing of two five-stranded beta-sheets was investigated, with the strands having the composition CH3CO-(L-Ile)6-NHCH3 in one beta-sheet and CH3CO-(L-Val)6-NHCH3 in the other. Two distinct classes of low-energy packing arrangements were found. In the class with lowest energies, the strands of the two beta-sheets are aligned nearly parallel (or antiparallel) with each other, with a preference for a negative orientation angle, because this arrangement corresponds to the best complementary packing of the two twisted saddle-shaped beta-sheets. In the second class, with higher interaction energies, the strands of the two beta-sheets are oriented nearly perpendicular to each other. While the surfaces of the two beta-sheets are not complementary in this arrangement, there is good packing between the corner of one beta-sheet and the interior part of the surface of the other, resulting in a favorable energy of packing. Both classes correspond to frequently observed orientations of beta-sheets in proteins. In proteins, the second class of packing is usually observed when the two beta-sheets are covalently linked, i.e. when a polypeptide strand passes from one beta-sheet to the other, but we have shown here that a large contribution to the stabilization of this packing arrangement arises from noncovalent interactions.

Using REE tracers to measure sheet erosion changing to rill erosion

International Nuclear Information System (INIS)

Liu Puling; Xue Yazhou; Song Wei; Wang Mingyi; Ju Tongjun

2004-01-01

Rare Earth Elements (REE) tracer method was used to study sheet erosion changing to rill erosion on slope land. By placing different rare earth elements of different soil depth across a slope in an indoor plot, two simulated rainfalls were applied to study the change of erosion type and the rill erosion process. The results indicate that the main erosion type is sheet erosion at the beginning of the rainfalls, and serious erosion happens after rill erosion appears. Accumulated sheet and rill erosion amounts increase with the rainfalls time. The percentage of sheet erosion amount decreases and rill erosion percentage increases with time. At the end of the rainfalls, the total rill erosion amounts are 4-5 times more than sheet erosion. In this paper, a new REE tracer method was used to quantitatively distinguish sheet and rill erosion amounts. The new REE tracer method should be useful to future studying of erosion processes on slope lands. (authors)

Description and classification of uranium oxide hydrate sheet topologies

International Nuclear Information System (INIS)

Miller, M.L.; Burns, P.C.; Ewing, R.C.; Finch, R.J.

1996-01-01

The uranyl oxide hydrates (UOH) are important corrosion products of uraninite and UO 2 in spent nuclear fuel under oxidizing conditions. However, the systematics of the crystal chemistry, thermodynamic parameters, and solubilities of this mineral group are poorly understood. With the exception of the synthetic UO 2 (OH) 2 polymorphs, all UOH crystal structures are based on sheets of edge-sharing 5 and 4-coordinated uranyl dipyramids. This structural similarity suggests that it is possible to develop a model by which to estimate the thermodynamic behavior of UOHs from data on structural endmember phases. Toward this end, a method of quantitatively describing all known UOH sheets has been developed. Only four structural unit chains are required to construct the uranyl oxide hydrate sheets (as well as the structurally similar U 3 O 8 sheets). The H-chain is restricted to α-UO 2 (OH) 2 and is made up of hexagonally coordinated uranyl ions sharing opposing edges. The arrowhead chain composed of pentagonal dipyramids sharing edges and alternating with trigonal vacancies is present in all other UOH sheets. These arrowhead chains are directed and can occur in both an Up-arrow and Down-arrow sense within a single sheet. The P-chain consists of edge-sharing pentagonal dipyramids forming a zigzag chain. The P-chain is flanked on both sides by arrowhead chains of the same sense. The remaining structural unit is a discontinuous chain of rhombic dipyramids. This R-chain is produced when nested adjacent Up-arrow and Down-arrow arrowhead chains are translated by a diagonal shift. This chain occurs in sheets which contain only 4-coordinate uranyl ion and those containing both 4- and 5-coordinate uranyl ions

Patterns through elastic instabilities, from thin sheets to twisted ribbons

Science.gov (United States)

Damman, Pascal

Sheets embedded in a given shape by external forces store the exerted work in elastic deformations. For pure tensile forces, the work is stored as stretching energy. When the forces are compressive, several ways to store the exerted work, combining stretching and bending deformations can be explored. For large deflections, the ratio of bending, Eh3ζ2 /L4 and stretching, Ehζ4 /L4 energies, suggests that strain-free solutions should be favored for thin sheets, provided ζ2 >>h2 (where E , ζ , Land h are the elastic modulus, the deflection, a characteristic sheet size and its thickness). For uniaxially constrained sheets deriving from the Elastica, strain-free solutions are obvious, i.e., buckles, folds or wrinkles grow to absorb the stress of compression. In contrast, crumpled sheets exhibit ``origami-like'' solutions usually described as an assembly of flat polygonal facets delimitated by ridges focusing strains are observed. This type of solutions is particularly interesting since a faceted morphology is isometric to the undeformed sheet, except at those narrow ridges. In some cases however, the geometric constraints imposed by the external forces do not allow solutions with negligible strain in the deformed state. For instance, considering a circular sheet on a small drop, so thin that bending becomes negligible, i.e., Eh3 / γL2 geometry and a competition between various energy terms, involving stretching and bending modes.

Ni-Flash-Coated Galvannealed Steel Sheet with Improved Properties

Science.gov (United States)

Pradhan, D.; Dutta, M.; Venugopalan, T.

2016-11-01

In the last several years, automobile industries have increasingly focused on galvannealed (GA) steel sheet due to their superior properties such as weldability, paintability and corrosion protection. To improve the properties further, different coatings on GA have been reported. In this context, an electroplating process (flash coating) of bright and adherent Ni plating was developed on GA steel sheet for covering the GA defects and enhancing the performances such as weldability, frictional behavior, corrosion resistance and phosphatability. For better illustration, a comparative study with bare GA steel sheet has also been carried out. The maximum electroplating current density of 700 A/m2 yielded higher cathode current efficiency of 95-98%. The performances showed that Ni-coated (coating time 5-7 s) GA steel sheet has better spot weldability, lower dynamic coefficient of friction (0.07 in lubrication) and three times more corrosion resistance compared to bare GA steel sheet. Plate-like crystal of phosphate coating with size of 10-25 µm was obtained on the Ni-coated GA. The main phase in the phosphate compound was identified as hopeite (63.4 wt.%) along with other phases such as spencerite (28.3 wt.%) and phosphophyllite (8.3 wt.%).

Low cost light-sheet microscopy for whole brain imaging

Science.gov (United States)

Kumar, Manish; Nasenbeny, Jordan; Kozorovitskiy, Yevgenia

2018-02-01

Light-sheet microscopy has evolved as an indispensable tool in imaging biological samples. It can image 3D samples at fast speed, with high-resolution optical sectioning, and with reduced photobleaching effects. These properties make light-sheet microscopy ideal for imaging fluorophores in a variety of biological samples and organisms, e.g. zebrafish, drosophila, cleared mouse brains, etc. While most commercial turnkey light-sheet systems are expensive, the existing lower cost implementations, e.g. OpenSPIM, are focused on achieving high-resolution imaging of small samples or organisms like zebrafish. In this work, we substantially reduce the cost of light-sheet microscope system while targeting to image much larger samples, i.e. cleared mouse brains, at single-cell resolution. The expensive components of a lightsheet system - excitation laser, water-immersion objectives, and translation stage - are replaced with an incoherent laser diode, dry objectives, and a custom-built Arduino-controlled translation stage. A low-cost CUBIC protocol is used to clear fixed mouse brain samples. The open-source platforms of μManager and Fiji support image acquisition, processing, and visualization. Our system can easily be extended to multi-color light-sheet microscopy.

Research on Computer Integrated Manufacturing of Sheet Metal Parts for Lithium Battery

Directory of Open Access Journals (Sweden)

Pan Wei-Min

2016-01-01

Full Text Available Lithium battery has been widely used as the main driving force of the new energy vehicle in recent years. Sheet metal parts are formed by means of pressure forming techniques with the characteristics of light weight, small size and high structural strength. The sheet metal forming has higher productivity and material utilization than the mechanical cutting, therefore sheet metal parts are widely used in many fields, such as modern automotive industry, aviation, aerospace, machine tools, instruments and household appliances. In this paper, taking a complex lithium battery box as an example, the integrated manufacturing of sheet metal parts is studied, and the digital integrated design and manufacturing process system is proposed. The technology is studied such as sheet metal design, unfolding, sheet nesting and laser cutting, CNC turret punch stamping programming, CNC bending etc. The feasibility of the method is verified through the examples of products and the integrated manufacturing of sheet metal box is completed.

Enhanced ice sheet melting driven by volcanic eruptions during the last deglaciation.

Science.gov (United States)

Muschitiello, Francesco; Pausata, Francesco S R; Lea, James M; Mair, Douglas W F; Wohlfarth, Barbara

2017-10-24

Volcanic eruptions can impact the mass balance of ice sheets through changes in climate and the radiative properties of the ice. Yet, empirical evidence highlighting the sensitivity of ancient ice sheets to volcanism is scarce. Here we present an exceptionally well-dated annual glacial varve chronology recording the melting history of the Fennoscandian Ice Sheet at the end of the last deglaciation (∼13,200-12,000 years ago). Our data indicate that abrupt ice melting events coincide with volcanogenic aerosol emissions recorded in Greenland ice cores. We suggest that enhanced ice sheet runoff is primarily associated with albedo effects due to deposition of ash sourced from high-latitude volcanic eruptions. Climate and snowpack mass-balance simulations show evidence for enhanced ice sheet runoff under volcanically forced conditions despite atmospheric cooling. The sensitivity of past ice sheets to volcanic ashfall highlights the need for an accurate coupling between atmosphere and ice sheet components in climate models.